PT91598B - PROCESS FOR THE PREPARATION OF DEGRADABLE LACTIDE THERMOPLASTICS - Google Patents

Abstract

The invention relates to a process for the preparation of an environmentally biodegradable composition of polylactic acid which comprises the stages of: a. preparing a lactide monomer and a catalyst, b. polymerizing the monomer from stage a to form a polymer at a sufficiently low temperature to permit the reaction to be stopped before polymerization is complete, c. monitoring the level of monomer in stage b, determining the quantity of remaining monomer, and d. stopping the polymerization in stage b before the reaction is completed for a quantity of monomer determined in stage c so that the monomer is fixed in association with the polymer in order to react with a predetermined quantity.

Description

DESCRIPTION This application derives and claims priority from the following eight United States patent applications: The application entitled Biodegreeable and Malleable Lactide Packaging Thermoplastics. having Serial No. 07 / 229,896, filed on August 8, 1988; the application entitled Biodegradable Replacement of Polystyrene Crystal, having the n? Serie 07 / 229,939, filed on August 8, 1988; the application entitled Mixtures of Polylactic Acid, having Series Ne 07 / 229,894, filed on August 8, 1988; the application entitled Impact Modified Degradable Polylactides, with Serial Numbers 07 / 317,391, filed on March 1, 1989; the Biodegradable and Malleable Lactid Packaging Thermoplastics application, with the legal deposit number PE 2767-1, filed on July 31, 1989; the application entitled Biodegradable Substitution of Polystyrene Crystal, having the legal deposit number PF 2771-1, filed on July 31, 1989; the application entitled Polylactic acid mixtures. having the legal deposit number PF 2772-1, filed on July 31, 1989; and the application entitled Impact Modified Degradable Polylactides, with the legal deposit number FF 2781-1, filed on July 31, 1989 »All the referred applications have the Memorial Battelle Institute as attorney.

FIELD OF THE INVENTION

In a first embodiment, the present invention relates to plasticized polymers of 1-lactide, D-Lactide, D, L-lactide and respective mixtures suitable for packaging applications, where non-gradable plastics (p eg polyethylene) <> In addition, the first embodiment refers to a method for the production of malleable films and other packaging products and the respective product. The invention is useful for the production of a product that has the characteristics of normal plastics, yet is biodegradable.

In a second embodiment, the invention reveals a material and a process for preparing it, which is an alternative, that is, a replacement for crystal polystyrene, sometimes known as orientable polystyrene or OPS. The material is an alternative to OPS, but is composed of a polyester capable of being biodegraded in the environment after approximately a period of one year. The material is a polyester, consisting of polymerized lactic acid, prepared either from D-lactic acid or from 1-lactic acid or from D, 1-lactic acid. The proportion between the two polymerized monomer units, the treatment process and, in some cases, certain auxiliary ingredients, determine the precise physical properties necessary for the exact requirements of an alternative to OPS. Thus, in a proportion of approximately 90/10 of l-lactic acid / D, 1-lactic acid, poly2 merized lactic acid (PLA) is a thermoplastic with a good behavior, which is clear, colorless and very rigid »As as such, it is very suitable for preparing films, foams and other thermo-formed products of disposable or one-time use plastic. Having served its purpose as a packaging plastic, PIA slowly biodegrades into the environment giving rise to innocuous products when left in the environment. This harmless depletion can help to alleviate the growing problems of plastic pollution in the environment »

In a third embodiment, the invention relates to the mixing of conventional thermoplastics with polylactic acid. This mixture provides new environmentally degradable thermoplastics »Environmentally degradable thermoplastics are useful in a wide variety of applications.

The third embodiment further relates to a method for producing pliable films and other packaging products and the respective product. The invention is useful in the production of a product that has the characteristics of normal plastics, yet is degradable in the environment »

A fourth embodiment of the invention relates to the mixture of elastomers compatible with polylactides. This mixture provides impact resistance modified polylactides that are useful in a wide variety of applications, including those where impact modified polystyrene would be used.

The fourth embodiment further refers to a method for preparing packaging products and the respective product. The invention is useful in the production of a product that has the characteristics of normal impact and resistant plastics, yet is degradable in the environment.

BACKGROUND OF THE INVENTION

There is a need for a biodegradable packaging thermoplastic in the environment as a response to the tremendous amounts of discarded plastic packaging materials. Plastic sales in the United States in 1987 were 24.4 million metric tons, of which 5.7 million were recorded as packaging plastics. A significant amount of this plastic is discarded and becomes a plastic pollution, which constitutes a stain on the landscape and a threat to marine life. Mortality estimates reach as high as 1 to 2 million sea birds and 100 000 marine mammals per year.

Another problem with the waste of plastic packaging is the concern caused by the scarcity of land for landfills. 'It is estimated that most large cities will have exhausted land available for the disposal of solid waste in the early 1990s. Plastics make up approximately 5 percent of the weight and 6 percent of the volume of solid waste.

Another disadvantage of conventional plastics is that they are ultimately derived from petroleum, which makes plastics dependent on the uncertainties of importing foreign crude oil. A better source of raw material would be one that derives from renewable domestic resources.

However, there are good reasons for using plastics in packaging. They provide attractive aesthetic quality in the form of attractive packaging, which can be manufactured quickly and filled with specific product units. The packaging maintains hygiene, storage stability and useful qualities, such as transparency for inspection of the contents. These packages are known for their low production cost and chemical stability.

This stability leads, however, to a very long life of the plastic so that, when its function ends, the discarded packages remain in the environment for an incalculable time.

Lactic acid polymers and copolymers have been known for some time as materials with unique properties, as they are biodegradable, biocompatible and have moplastics. These polymers are thermoplastics that work well, 100 percent, truly biodegradable in an animal body through hydrolysis over a period of time ranging from several months to a year »In a humid environment they start to show degradation after several weeks and disappear in a period of about a year when left on or in the ground or in seawater. The degradation products are lactic acid, carbon dioxide and water, all of which are harmless.

In practice, the acid is converted into its lactide, which is a cyclic dimer, which constitutes the monomer for polymerization. Lactic acid is potentially available from cheap raw materials, such as corn starch or corn syrup, by fermentation, or from petrochemical raw materials, such as ethylene. resin lactide through catalyzed fusion polymerization, a common process well known to plastics producers. When polymerizing an intermediate monomer, versatility in resin composition is allowed. Molecular weight can be easily controlled. The compositions can be changed to introduce specific properties.

Homopolymers and copolymers of various cyclic esters, such as glycolide, lactide, and lactones have been described in numerous patents and scientific publications. Previous patents have disclosed processes for polymerizing lactic acid, lactide, or both, and have failed to polymerize

high molecular weight merers with good physical properties, and polymeric products were often sticky and viscous materials without good physical properties, see, for example, U.S. Patents 1,995,970; 2,362,511; and 2,683,136. The lowe patent, U.S. Patent 2,668,162, teaches first of all the use of pure glycolide and lactide to obtain high molecular weight lactide polymers and copolymers. The lactide is the lactic acid dilactone and is an internal ester of lactic acid. When the lactide is formed, water is eliminated as a by-product, subsequently allowing the lactide to be polymerized by opening the ring giving a high weight linear polyester. molecular without tiring condensation methods. The copolymerization of lactide and glycolide conferred rigidity and improved the processing of thermoplastic, compared to homopolymers. Polymers and copolymers of excellent physical properties were obtained using the intermediate lactide to form PLA. The Lowe patent discloses copolymers of lactide and glycolide which are hard, clear, cold-stretching, elastic and capable of converting at 210 ° C into consistent films.

Similar disclosures in the patent and other literature have developed lactide polymerization and copolymerization processes to produce very strong, crystalline, orientable and hard polymers, which have been transformed into fibers and prosthetic devices that were biodegradable and biocompatible, sometimes called absorbable. The polymers slowly sap through hydrolysis. See, for example, U.S. Patents 2,703,316; 2,758,987; 3,297,033; 3,463,178;

531 561; 3,620,218; 3,636,956; 3,736,646; 3,797,499; 3 839 297 3 982 543; 4,243,775; 4,438,253; 4,496,446; European Patent Application 0146398. International Application W0 86/00533, and Offenlegundsschrift 2 118 127.

Other patents teach the use of these polymers as hard surgical elements for clasps, screws, nails, pins and prostheses for biomedical bones. See ·· 6 ··

for example, U.S. Patents 3,739,773: 4,060,089; and 4,279,249.

Controlled release devices have been developed using mixtures of bioactive substances with lactide and / or glycolide polymers and copolymers. See, for example, U.S. Patents 3,773,919; 3 887 699; 4,273,920; 4,419,340 4,471,077; 4,578,384; 4,728,721; R.G. Sinclair, Environmental Science & Technology, 7 (10), 955 (1973). R.G. Sinclair, Actas, 55 International Symposium on Controlled Release of Bioactive Materials, 5 «12 and 8.2, Akron University Editorial, 1978«. These applications of polymers and copolymers of lace required rigid or glassy materials, which were grindable and did not reveal physical properties for evident use in thermoplastic packaging materials.

References have been found in the prior art for the use of lactide copolymers for obvious packaging applications. Thus, in the aforementioned Lowe's patent, clear and consistent films of a lactose and glycolide copolymer are referred to. _The US Patent 2,703,316 describes lactide polymers as film formers which are tough and orientable. A "rubble" fabric was described, which was stiff, flexible and strong, brittle or malleable. However, to obtain malleability, the polylactide must be wetted with a volatile solvent, otherwise brittle and hard polymers were obtained. It is specified that the lactide monomer has a melting point above 12090 ′, the number of 1-lactide melts at 95 ° C and the D, E-lactide melts at 1282C _O This is an example of the prior art which teaches special modifications of lactide polymers in order to obtain malleability. Thus, in US Patent 3,021,309, lactides are copolymerized with delta-valerolactone and caprolactone in order to modify lactide polymers and obtain hard, white, crystalline solids. Solid and soft copolymer compositions are mentioned only with the copolymer of caprolactone and lactoria of 2,4-dimethyl-4-methoxymethyl-5-hydroxypentanoic acid, not with lactide compositions. US Patent 3,284,417 concerns the production of polyethers

- 7 useful esters as plasticizers and intermediates for the preparation of elastomers and foams. This patent excludes lactides and uses lactone ring based compositions with 7 to 9 memos, such as epsilon-caprolactone, in order to obtain the desired intermediates. Some data are not provided on the tensile strength, modulus or percentage of elongation. US Patent 3,297,033 teaches the use of glycolide-lactide copolymers to prepare ductile materials, orientable in fibers suitable for suturing. Plasticizers are said to interfere with crystallinity, but are useful for sponges and films ”o It is evident in these disclosures that the lactide polymers and copolymers are hard except when plasticized. This is also true in US Patent 3,736,646, where lactide-glycolide copolymers are softened through the use of solvents, such as methylene chloride, xylene or toluene. In U S. Patent 3,797,499 are mentioned copolymers of 1-lactide and D, L-lactide as possessing greater flexibility in elongated fibers for absorbable sutures. These fibers have tensile strengths greater than 50,000 psi (3,450 bar) with elongation percentages of approximately 20 percent. The modules are about one million psi (70,000 bar). These are still very hard compositions compared to most flexible packaging compositions, reflecting their use for sutures. US Patent 3 844 987 discloses the use of grafts and mixtures of biodegradable polymers with naturally occurring biodegradable products, such as cellulosic materials, soybean seed powder, rice husks and beer yeasts, for manufactured articles such as a container to hold a medium for germinating and growing seeds or sprouts. These invoiced items are not suitable for packaging applications. US Patent 4 620 999 discloses a composition in the form of a single biodegradable bag composed of polymers of copolymer of 3-hydroxybutyrate and 3-hydroxybutyrate / 3-hydroxyvalerate.

lactic acid, for comparison, is 2-hydroxy-propionic acid. U.S. Patent 3,982,543 teaches the use of volatile solvents as plasticizers with lactide copolymers in order to obtain malleability. U.S. Patents 4,045,418 and 4,057,537

they are based on the copolymerization of caprolactone with lactides be either l-lactide or D-l-lactide, in order to obtain malleability. U.S. Patent 4,052,988 teaches the use of poly- (p-dioxanone) in order to obtain better knot ligation and knot security for absorbable sutures. U.S. Patents 4,558? 769 and 4,526,695 disclose the use of deformable glycolide and lactide polymers and polymers, but only at elevated temperatures. European patent application 0108933 uses a modification of glycolide copolymers with polyethylene glycol in order to obtain triple block copolymers, which are referred to as suture materials. As previously mentioned, there is a strong consensus that malleability is obtained in lactide polymers only through plasticizers that are volatile and fugitive solvents, or other comonomer materials.

Copolymers of L-lactide and D, l-lactide had been known in the prior art, but references note that malleability is not an intrinsic physical property. U.S. Patent 2,758,987 discloses homopolymers of 1- or D-L-lactide, which are described as being pressable by melting into orientable, strong and clear films. The properties of pç> li-L-lactide are given as: tensile strength, 29,000 psi (2000 bar); elongation percentage, 23 percent; elasticity module 710,000 psi (50,000 bar). The properties of poly-D, 1-lactide were: 26,000 psi (1,800 bar) of tensile strength; 48 percent stretching; and a modulus of elasticity of 260,000 psi (18,000 bar). Copolymers of 1- and D, L-lactide, i.e., copolymers of 1- and D, 1-lactide, are disclosed only for a 50/50 by weight mixture. They offer only stickiness properties (Example 3). Rei. An antipodal monomer species (optically active, for example, l-lactide) is preferred as the preferred source for the development of high resistance to traction. Exemplary are the homopolymers of e'D, l-lactide, and the weight ratio 75/25, 50/50 and 25/75 of 1- / D, 1-lactide copolymers in US Patent 2 951 828, a which shows the polymerization by drops of alpha-hydroxy-carboxylic acids. The copolí.

mers have softening points of 110 to 135 ^ 0. No further physical property data is provided for the hardness and flexibility, except for physical properties which refer to the drop size and softening points in the range of 110 to 135 ^and C. The weight ratios 95/5, 92.5 / 7.5 90/10 and 85/15 copolymers of l-lactide / D, L-lactide are referred to in US Patents 3,636,956 and 3,797,499 · They are evaluated as elongated fiber filaments and have resistance to traction greater than 50,000 psi (3,450 bar), modules of about one milliac (70,000 bar), and elongation percentage of approximately 20 percent. Plasticizers, in the same way as in US Patent 3,636,956 above, were used to give malleability _{and an} Off-white crystalline polymer consisting of a l-lactide / D, L-lactide copolymer refers to Offenlegundsschrift 2 118 127 in a ratio of 90/10 ', no physical properties were provided for this copolymer. The patent teaches the use of surgical elements.

All U.S. Patents 3,297,033; 3 463 158}

531 561; 3,636,956; 3,736,646; 3,739,773 and 3,797,499 disclose lactide polymers and copolymers which are orientable, crystalline and strong polymers suitable for fibers and suture materials. These disclosures teach the use of highly crystalline materials, which are oriented by elongation and annealed in order to obtain tensile strength and modulus, characteristically greater than 50,000 psi and 1 000 000 psi (3,450 and 70,000 bar), respectively. Although the possibility of molding is mentioned on a variety of articles in various forms, the physical properties of extruded and non-oriented molded products are not mentioned. For example, the U.S Patent »

636 956 teaches the preparation of a 90 / l0 weight ratio of L-lactide / Djl-lactide and refers to oriented and elongated fibers. However, it is preferable in this disclosure to use pure L-lactide monomer for greater crystallinity and traction of the elongated fiber.

The U.S Patent

797 499 teaches the glass-

lyering a 95/5 weight ratio of L-lactide, D, L-lactide (Example V); however, the material is turned into filaments. In column 5, row 1, Schneider, in contrast, teaches marked properties in the range provided in the present invention. Plasticizers are used, such as glyceryl triacetate, ethyl benzoate and diethyl phthalate.

US patents 3 736 646, 3 773 919, 3 887 699, 4 273 920, 4 471 077 and 4 578 384 teach the use of lactide polymers and copolymers as delayed release matrices for pharmaceutical products, which are biodegradable and biocompatible. Again, the physical properties of the polymers obtained by usual thermoforming methods, such as film extrusion or molding, are not mentioned.

. Of particular interest, the U. S. Patent

719 246 teaches the combination of homopolymers of l-lactide, D-lactide, polymers or mixtures thereof} and copolymers of l-lactide or D-lactide with at least one non-lactide comonomer. The mixture is aimed at producing compositions that have interactive segments of poly- (L-lactide) and poly- (D-lactide).

Canadian Patent 808,731 discloses copolymers of L- and D, L-lactide in which a bivalent metal of Group II forms part of the structure. The L- / D, L-lactide copolymer in a 90/100 ratio (Example 2) and the L-lactide homopolymer have been described as being suitable for films and fibers. The 9θ / 9θ copolymer is described as a white copolymer and the L-lactide homopolymer can be molded into transparent films. (The most crystalline polymer should be the white or opaque material, which is the homopolymer.) The patent reveals that the fact that the new polylactides of the present invention contain the metallic component of the catalyst in the form of a lactate appears to be significant. In addition, polylactides find use in the manufacture of films and fibers, which are prepared by conventional methods of manufacturing thermoplastic resin ”. Some of the physical properties data on the strength and flexibility of the films are not provided.

Canadian Patent 865 673 discloses copolymer compositions of l-lactide and D, l-lactide in the proportions of 1- / D, L-lactide of 97/3, 95/5, 92.5 / 7.5 90/10 and 85/15, respectively. These were all characterized as elongated filaments for surgical applications. The tensile strength, approximately 100 Ό00 psi, (6 9θθ bar), was high, the elongation was approximately 20 percent and plasticizers were mentioned to achieve malleability. D, L-lactide bodies of less than 15 weight percent are claimed.

Canadian Patent 923 245 discloses the copolymers of L- and D, l-lactide (Example 15) · The copolymer with a 90/10 ratio is described as being a white polylactide. It is stated that polylactides prepared by the methods of the patent are useful in the manufacture of films or fibers prepared by conventional thermoplastic resin manufacturing methods.

US Patent 4,719,246 teaches the use and simple mixing of polymers of poly-1- and poly- (D-lactide), referred to as poly- (S-lactide) and poly- (R-lactide), of respective mixtures ; and copolymers of l-lactide or D-lactide with at least one non-lactide comonomer. The examples are all physical mixtures. The special interconnecting properties ”are derived from the formation of newborn compounds (cf. Stereochemistry of Carbon Compounds, Ε. 1. Eliel, McGraw-Hill, 1962, p. 45). The newly formed compounds are constituted by enanciomeros fittings, that is to say, the forms D and 1 (or R and S) are connected to each other by polar forces. This fact can cause a decrease, or an increase, in the crystalline melting points, depending on whether the D to D (or 1 to '1) forces are less, or greater, than the D to 1 forces. 12 riches needed to accentuate the effect (as stated in US Patent 4,719,246, Column 4, line 48) are homopolymers, or lengths of long chains, both D and 1. The great symmetry or regularity of these structures allows them to adapt to each other, or to hook, using very regular polar forces, either because they are the same or reflected images. This leads to considerable crystallinity. The racemic compound technique has a long history that goes back to classical chemistry.

U.S. Patent 4,661 550 discloses mixtures of a poly- (L-lactic) acid and / or poly- (D, L-lactic) acid with a segmented polyester-urethane or polyester-urethane. Biodegradable materials are formed that are useful in synthetic replacements of tissues and biological organs in reconstructive surgery.

Nowhere in the prior art is it revealed that lactide polymers are capable of highly extensible and malleable compositions, through the use of lactide monomers, lactic acid or lactic acid oligomers such as plasticizer None of the above compositions is suitable for the needs of hem packaging defined by the thermoplastic polymer industry.

It will be appreciated by those skilled in the art that duplicating the characteristics of one thermoplastic with another is not predictable. Thus, with crystal polystyrene, or OPS, there are exact requirements for satisfactory performance of polystyrene, which has been developed for many years to meet the specifications of manufacture and end use of grades of OPS.

BRIEF DESCRIPTION OF THE INVENTION general teaching of the invention, and first embodiment, is that homopolymers of L-lactide, D-13

-lactide and DL-lactide and copolymers of the respective mixtures that have been plasticized with lactide monomer (s), lactic acid or lactide or lactic acid oligomers are useful as well-functioning thermoplastics, which can mimic characteristics of common non-plastics -degradable in the environment (for example the properties of polyethylene and the like). This composition has the formula:

CH, 0

I II

4- Q _ Q

Ί

H e is fully plasticized with a plasticizer selected from the group consisting of lactide, lactic acid, lactic acid oligomers and mixtures thereof. In addition, lactic acid oligomers are preferably represented by Formula II, in which an integer: 2 4 n 10. Preferably, the plasticizer contains from 2 to 60 weight percent of the polymer. The polymers can be derived from lactide monomers selected from the group consisting of 1-lactide, D-lactide, meso-D, 1-lactide and mixtures thereof. Preferably n is 150 <n 20,000.

CH, 0

I I

C - 0 - 0 -) - ^{11 1} α, m lactide monomer can be present in an amount of 5 to 40 weight percent of the polymer, whereas the lactide oligomer or lactic acid and its oligomers may be present in an amount of 2 to 60 per cent of weight. This composition allows many of the characteristics

desirable characteristics of polyethylene, such as malleability, transparency and rigidity.

Additionally, a process for preparing the biodegradable composition is provided. The process includes the mixing, heating and melting phases of one or more lactide monomers and catalyst; polymerization of the solution monomers to form a polymer at a sufficiently low temperature to allow the polymerization reaction to be stopped before completing the polymerization; control of the monomer level; and stopping the reaction before completing the polymerization in an amount of monomer determined by the control; so that the unreacted monomer is trapped together with the polymer.

Additionally, a process for the preparation of a plasticized polymer of polylactic acid is proposed which comprises mixing, heating and melting one or more lactide manomers and a catalyst; polymerize the manomers of the solution to form a polymer without stopping the reaction; and incorporate a plasticizer in the polymer, the plasticizer being selected from the group consisting of D-lactide, 1-lactide, meso-D, 1-lactide, lactic acid, lactic acid oligomers and mixtures thereof

A second embodiment of the invention includes a process for preparing a biodegradable composition in the environment and a biodegradable composition in the environment useful as a substance for polystyrene comprising polylactic acid units of formula I, where n is an integer between 75 and 10 000 and alpha carbon and a mixture of configurations 1 and D with a preponderance of D or 1 units, in which the polymer is prepared from L-lactide or D-lactide, in 35 to 95 parts by weight, and D, 1-lactide in 15 to 5 parts by weight, where the non-oriented polymer has a tensile strength of at least 5,000 psi (340 bar) and a module

tangent of at least 200,000 psi (13,800 bar) and plasticizer of 0.1 to 5 weight percent.

A third embodiment of the invention teaches the process for producing a degradable composition in the environment and a degradable composition in the environment comprising mixtures of a physical mixture of polylactic acid; and one or more polymers selected from the group consisting of a polymer of ethylene terephthalate, a polymer or copolymer of ethylene, ethylene, propylene, vinyl chloride, vinyl acetate, alkyl methacrylate, alkyl acrylate and respective physical mixtures.

A fourth embodiment teaches the process for producing an environmentally degradable composition and is found to be an environmentally degradable composition comprising combinations of a physical mixture of polylactic acid and compatible elastomers in the mixture that provide improved impact resistance to the combined composition. An elastomer such as this can be, for example, a Hytrel ¹ , a segmented polyester, which is a copolymer of the block of crystalline segments of polybutylene terephthalate and long chain segments of polyether glycol. An example of a mole is known by the commercial name segmented polyester Hytrel ^ 4056 (Du Pont).

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is a graph showing the relationship between the percentage of lactide in the composition as a plasticizer and the tensile strength.

Figure 2 is a graph showing the relationship between the percentage of lactide in the composition as a plasticizer and the elastic modulus.

Figure 3 is a graph showing the relationship 16 -

between the percentage of oligomers in the composition as a plasticizer and the tensile strength, where curve A refers to a 90/10 copolymer and curve B refers to a 92.5 / 7.5 copolymer »

Figure 4 is a graph showing the relationship between the percentage of oligomer in the composition as plasticizer and the elastic modulus, where curve A refers to a copolymer of 90/10 ratio θ and curve B refers to a copolymer of proportion 92.5 / 7.5 ·

Figure 5 illustrates the graphical representation of the differential scanning calorimetry (DSC) of L- / D, L-lactide copolymer in the 90/10 unheated proportion of Example 5 B.

Figure 6 illustrates the DSC of Example 5 B material after remaining at 70 ° C for 100 minutes.

Figure 7 illustrates the DSC of Example 5 B material after annealing I852F (852C) overnight.

Figure 8 illustrates the DSC of the material of Example 5 B that was combined with 5 percent calcium lactate

Figure 9 compares the melt viscosity in relation to the shear index characteristics of polystyrene and lactide polymer prepared in the same way as in example 8 B.

Figure 10 illustrates a DSC for the copolymer of Example 8 B.

Figure 11 illustrates a DSC for the L-lactide homopolymer which is added to the copolymer of Example 8 B.

Figure 12 illustrates a DSC for the composition

combination of Example 23 of the copolymer of Example 8 B and a homopolymer of 1-lactide.

Figure 13 illustrates a graphical representation of the differential scanning calorimetry (DSC) of L- / D, L-lactide copolymer in the proportion of 9θ / ΐ0 combined with 5 percent polystyrene.

DETAILED DESCRIPTION OF THE INVENTION AND FORMS

PREFERRED ACCOMPLISHMENTS

FIRST FORM OF GENERAL CONCRETIZATION

The biodegradable compositions in the environment disclosed here are completely degradable giving compatible materials in the environment. The intermediate products of degradation: lactic acid and short chain oligomers of lactide or lactic acid are naturally occurring substances and widely distributed in nature that are easily metabolized by a wide variety of organisms. Its natural products of ultimate degradation are carbon dioxide and water. The studied equivalents of these compositions, such as those containing lesser amounts of other materials, fillers or expanders, can be completely degradable in the environment through the proper choice of materials. Those with positions presented here provide environmentally acceptable materials, because their deterioration and physical degradation is much faster and more complete than that of conventional non-degradable plastics that they replace. In addition, as all or almost the entire composition will be polylactic acid, and / or a lactide or oligomer derived from lactic acid, there will be no residue left, or only a small portion of the more time consuming degradation residue will remain. This residue will have an exposed surface higher than that of the starting product and a predictably rapid rate of degradation.

The general application of the invention results in the first and general embodiment of this. All homopolymers of D-lactide, L-lactide, D, L-lactide, as well as copolymers of D-lactide, l-lactide; D-lactide, D, l-lactide l-lactide, D, l-lactide; and D-lactide, l-lactide and D, l-lactide produce materials useful in the invention when plasticized by lactide monomers, lactic acid, lactide oligomers, lactic acid oligomers and their mixtures »The plasticizer can be produced by stopping the reaction before polymerization is complete. The additional plasticizer polymer, consisting of lactide monomers (D-lactide, l-lactide, D, l-lactide or respective mixtures), lactic acid, lactide oligomers or lactic acid oligomers and respective mixtures can be optionally added. The polymer is defined by the formula:

Γ ⁵ ϊ <- at ^C ~ ⁰

-fem that n is the degree of polymerization (number of repeated units) and is plasticized with a plasticizer derived from the incomplete polymerization of the monomers used to produce the polymer. The more closely integrated the plasticizer with the pulp is, the better its characteristics are. If desired, additional monomer or oligomer can be added to any residual monomer or oligomer that remains in the composition. The lactic acid oligomers useful as plasticizers are defined by formula II, in which a whole number:

75 m, however, the preferable range is: 2 m 10

H

II c

I IM

BKi.

The proportions of L-lactide, D-lactide and D, L-lactide are not crucial to obtain flexible thermoplastics. The parts of L-lactide, D-lactide and D, L-lactide can vary, in a wide proportion by weight to form a homopolymer or copolymer. The lactide monomers employed according to the invention are commercially obtainable so that neither the monomeric reagent itself nor the method by which it is prepared form part of the present invention.

D-lactide and a dilactone, or a cyclic dimer, of D-lactic acid. Similarly, L-lactide is a cyclic dimer of L-lactic acid. The meso-D, L-lactide is a cyclic dimer of D- and L-lactic acid, 0 D, L-racemic lactide is made up of a mixture of D- and L-lactide. When used alone in this specification, the term D-L-lactide includes meso-D, L-lactide or D, racemic l-lactide.

One of the methods reported in the literature to prepare a lactide is to dehydrate lactic acid under high vacuum. The product is distilled at an elevated temperature and a low pressure. Lactids and their preparation are discussed by W.H.Carothers, G.l. Dorough and M.J. Johnson (J.Am.Chem.

Soc. 54, 761-762 / 1932 /); J.Gay-Lussac and J. Pelouse (Ann.7, / 18327); C.A. Bischoff and P. Walden (Chem. Ber. 26, 263/19027; Ann. 279, 171/1984 /); θ Heinrich Byk (German Pat. 267 826/1912 through Chem.Abstr. 8,554, 2054 / ~ 1914 /) ·

Active acids can be prepared optically by direct fermentation of almost any non-toxic carbohydrate product, by-product or waste, using numerous strains of the bacterial genus Lactobacillus. for example Lactobacillus desbruckii, L.salivarius. L.casei, etc. Optically active acids can also be obtained by resolving the racemic mixture through the ammonium and zinc salt, or dosed with alkaloids, such as morphine. The L-lactide is a white powder with a molecular weight of 144. If a commercially obtainable product is used according to the present invention,

impure, it is preferable to purify it by recrystallization from anhydrous methyl isobutyl ketone. The white crystals of l-lactide melt between 96 and 9850, D, L-lactic acid used in the preparation of D, l-lactide is commercially obtainable. D, l-lactic acid can be prepared synthetically by means of lactonitrile hydrolysis (acetaldehyde cyanohydrin) or by direct fermentation of almost any product, by-product or waste of non-toxic carbohydrate, using numerous strains of the bacterial genus lactobacillus. D, L-lactide is a white powder with a molecular weight of 144. If a commercially impure product is used according to the present invention, it is preferable to purify it by recrystallization from anhydrous methyl isobutyl ketone . A commercially obtainable product like this, comprising a semi-solid melt with softening between 90 and 130 ° C, was recrystallized from methyl isobutyl ketone and decolorized using charcoal. After three ** z recrystallizations like this, the product was vacuum-dried in a rotating drum with nitrogen purge for 8 to 24 hours at room temperature. The white crystals thus obtained are constituted by a D, L-lactide mixture that melts from 115 to 1282C.

In preparing the compositions according to the invention, it is preferable to carry out the reaction in the liquid phase in a closed container under vacuum in the presence of a tin ester of a carboxylic acid containing up to 18 carbon atoms. However, the compositions can also be prepared at atmospheric pressure with a polymerization system covered by an inert gas such as, for example, nitrogen. If the polymerization is carried out in the presence of oxygen or air, some discoloration occurs with a consequent decrease in the molecular weight and in the tensile strength. The process can be carried out at temperatures where the polymerization is slow in its last stages in order to fix residual monomer in the melt of viscous polymer. Preferred temperatures for this purpose are generally between the melting points of pure 1-lactide and pure D, L-lactide, or between 95 and 127 ° C. While not wishing in any way to limit the scope of the invention, it is presently believed that below about 129 ° C the following occurs:

1. The lactide monomer mixture of Le D, L-lactide monomers melts to form a eutectic mixture, which melts to form a mobile fluid that is an intimate solution of one, two or three monomers.

2. The molten fluid is polymerized by a catalyst in order to form a viscous solution in an increasing way and possibly the unreacted monomer is fixed in association with the polymer in the form of a solution and not with a distinct heterogeneous phase. The monomer can no longer react, as the reaction is extremely limited by diffusion and cannot contact the low concentration of active end groups of the polymer.

3 · Polymerization stops or slows down considerably so that, at room temperature, the combination of monomer and polymer appears in the form of a solid solution which gives plasticization, clarity and flexibility to the composition.

4. The catalyst is deactivated so that subsequent melt transformation does not cause polymerization to resume.

5. The plasticized composition is quite stable since the residual monomer has a high boiling point, for example, the boiling point of the lactide is from 142 ° C to 8 Torr, and is closely associated with its open chain tautomer polylactide.

Alternatively, the process can be carried out at any temperature between the melting point of L-lactide and 200 ° C and the lactide or lactide acid is subsequently22 -

cast or combined in solvent in the polymer as an additional process step. Temperatures above 20020 are undesirable due to the copolymer's tendency to degrade.

Increasing the temperature within the range of 95 to 200 ° C generally increases the rate of polymerization. Such results are obtained by heating a mixture of L-lactide and D, l-lactide to a temperature between about HOsC and 16020.

The catalysts employed according to the invention are tin esters of carboxylic acids containing up to 18 carbon atoms. Examples of these acids are formic, acetic, propionic, butyric, valeric, capric, caprylic, pelargonic, capric, lauric, myristic, palmitic, stearic and benzoic acids. Good results have been obtained with divalent tin acetate and divalent tin caprylate.

The catalyst is used in normal catalytic amounts. In general, a concentration of catalysadpr in the range of about 0.001 to 2 weight percent, based on the total weight of the 1-lactide and D, 1-lactide, is suitable. A concentration of the catalyst in the range of about 0.01 to about 1.0 weight percent is preferred. Good results are obtained when the concentration of the catalyst ranges from about 0.02 to about 0.5 weight percent. The exact amount of the catalyst in either case depends largely on the catalyst employed and the operational variables, including time and temperature. The exact conditions can be easily determined by those skilled in the art.

The reaction time of the polymerization phase itself is guided by the other reaction variables, including the reaction temperature, the particular catalyst, the amount of catalyst and whether or not a liquid carrier is employed. The reaction time can vary from a few minutes to a period of hours, or days, depending on the particular set of conditions that is employed. Heating of the

CTT monomers until the desired level of polymerization is detected. The level of polymerization can be determined by analyzing the residual monomers »As previously discussed, the reaction temperature can be chosen to enhance the incorporation of the monomer and provide plasticized compositions directly at the outlet of the polymerization reactor» reaction at the time the composition has achieved the conversion of monomer to polymer which is desired to achieve the desired plasticization »In the preferred embodiment of the invention, approximately 2 to 3 percent lactide is left to react, depending on the plasticization to be achieved.

In general, it is preferable to conduct polymerization in the absence of impurities containing hydrogen, active, as the presence of such impurities tends to deactivate the catalyst and / or to increase the induction time. It is also preferable to conduct the polymerization under substantially anhydrous conditions »

The copolymers of the invention can be prepared by mass polymerization, suspension polymerization or solution polymerization. The polymerization can be carried out in the presence of a normally liquid organic inert vehicle such as aromatic hydrocarbons, for example, benzene, toluene, xylene, ethylbenzene and the like; oxygenated organic compounds such as anisole, ethylene glycol diethyl and dimethyl esters; saturated hydrocarbons, usually liquid, including cyclic and cyclic substituted saturated hydrocarbons, such as hexane, heptane, cyclohexane, alkyl cyclohexane, decahydronaphthalene and the like.

/ polymerization process can be conducted in a discontinuous, semi-continuous or continuous manner. In the preparation of the monomeric lactide and catalyst reagents for subsequent polymerization, these can be mixed

by any order, according to known polymerization techniques. In this way, the catalyst can be added to any of the monomeric reagents. Thereafter, the monomer containing the catalyst can be mixed with another monomer. Alternatively, the monomorphic reagents can be mixed with each other. The catalyst can then be added to the reaction mixture. If desired, the catalyst can be dissolved or suspended in a normally liquid organic inert vehicle. If desired, monomeric reagents can be added to the catalyst, catalyst solution or catalyst suspension, either in the form of a solution or as a suspension in an inert organic vehicle. In addition, monomorphic reagents and the catalyst are also added to a reactor simultaneously. The reactor can be equipped with a conventional heat exchanger and / or a mixing device. The reactor can be any equipment normally employed in the polymer preparation technique. A suitable container is, for example, a stainless steel reactor.

The biodegradable compositions in the environment produced according to the present invention, depending on the proportions of L-lactide, D-lactide and meso-D, L-lactide, find use in manufactured articles, such as films, fibers and molded and laminated products, which are prepared by conventional manufacturing methods. These manufactured articles are suitable for non-medical use, that is, outside the body where they can replace ordinary plastics that are not degradable in the environment.

For example, filaments are prepared by extruding the molten copolymer through a die. Films are formed by forming a flat deposit of solutions of the biodegradable compositions and then removing the solvent, pressing solid biodegradable compositions in a hydraulic press with the heated press members, or by extrusion through a slit.

Various techniques, including slow cooling and rapid cooling, can be used in the preparation of molded forms of the copolymers of the invention.

Studied equivalents of the compositions of the invention are those that contain minor amounts of other materials. Copolymers produced according to the present invention can be modified, if desired, by the addition of an agent that promotes the formation of cross-links, other plasticizers, a coloring agent, a filler and the like.

Crosslinking can be carried out by combining the compositions with free radical initiators, such as cumene hydroperoxide, and then molding them at elevated temperatures. This technique can improve the resistance to heat and solvents »Curing can also be carried out by combining copolymers with multifunctional compounds, such as polyhydric alcohols and molding, or by heating and vacuum molding. Multilayer extrusion reactions to cure polyesters are an obvious method of forming cross-links and elongating copolymer chains.

When preparing molded forms, a filler can be incorporated into the compositions before curing. A filler has the function of modifying the properties of a molded product, including strength, durability, temperature resistance, etc. Known fillers include aluminum foot, powdered calcium carbonate, silica, kaolinite (kaolin), magnesium silicate and the like. Of particular advantage is starch, which combines well with the compositions giving rise to a combination that is completely biodegradable in the environment.

Other changes can be made to

properties combined by melting compositions with other polymers and copolymers of lactides, glycolides and caprolactone

The compositions prepared according to the present invention can be used in the production of reinforced laminated plastic material according to known processes. In general, the laminated plastic materials are made from a fibrous tangle or by joining a multiplicity of sheets of material to form a matrix, which is consolidated into a unitary structure by letting precursor or composition fuse through the fibrous material and proceeding to cure while All found in a mold or hydraulic press to form the matrix include natural and synthetic fibers, such as cellulose derived from wood, cotton, linen, hemp and the like, glass, nylon, cellulose acetate and the like.

The compositions of the invention and their preparation are further illustrated by the following specific examples:

EXAMPLE 1

L-lactide / D, racemic L-lactide 80/20

160 grams of 1-lactide and 40 grams of racemic D, L-lactide, both of high purity (Purao, Inc. triple recrystallized), were poured into a 500 ml round bottom flask and purged with dry nitrogen for one day. To the other. 10 ml of divalent tin octanoate are dissolved in 60 ml of anhydrous toluene and 10 ml of solvent is distilled into a Dean-Stark siphon in order to dry this catalyst solution by azeotropic distillation. From the 10 ml of bivalent tin octanoate in the 50 ml of dry toluene, a 0.20 ml portion is removed with a syringe and injected into the lactides in the reaction flask. The nitrogen purging is continuous through a connection with a syringe needle that enters the reaction vial through a rubber septum and an outlet through

of a piece of pipe that connects to a water guard bottle. The nitrogen stream is maintained between 1 and 3 bubbles per second. The flask was heated in an oil bath maintained between 123 and 1272 ° C.

During the first part of the heating the lactides melt and are completely mixed by swirling. Then, the products become quite viscous. After 20 hours of heating, the flask and the colorless transparent products are removed from the heating bath, cooled, the flask is broken and subjected to a temperature shock with liquid nitrogen to separate the product glasses. The copolymer was molded in a heated hydraulic press. It was possible to carry out compression molding for films between 5 and 10 mil (125 to 250 µm) at 20000 lb (1400 bar) of pressure, at 170 ° C, in a time period of 2 minutes. The tensile properties of the films were studied in an Instron test apparatus, and the results are reported in Table I. Samples of 1/3-inch (approximately 3.2 mm) thickness were also molded for strength testing. impact. A thermal gravimetric analysis (TGA) of the product was performed, recording the weight loss during heating the sample to 150 ° C in 4 minutes and maintaining the temperature at 1505 ° C for 60 minutes. The weight loss of the sample was 19.5 percent and almost complete in 60 minutes. Weight loss is attributed to the loss of lactide monomer. Differential scanning calorimetry (DSC) results reveal that the composition has a heat absorption starting at around 110 ° C, becoming more pronounced as the temperature increases to 200 ° C. No melting point was observed. Test I852F (8590) was annealed overnight and examined again. They remained transparent, colorless and malleable. It was possible to reshape samples of the copolymer 6 times without any discoloration or evident loss of strength. The thin films were clear, transparent, colorless and very flexible, despite repeated molding.

TABLE 1

PROPERTIES OF OCPOLYLERS (a) OF L-LACTIDE AND D, L-LAO TYPE WHEN PLASTIFIED BY LACTIDE

EXAMPLE No. 1 2 3 Film thickness, one 200 200 250 (thousand) (8) (8) (10) Tensile strength, bar 270 117 545 ASTM D638 (1OOO psi) (3.9) (1.7) (7.9) Elongation, percentage 28 806 5.5 100 percent module, bar (1000 psi) 51 (0.74) _M - 200 percent module, bar (1000 psi) 83 (120) - - Tangent module, bar (1000 psi) 2520 (36.6) - - 19 900 289 Impact resistance of Izod, ft-lb / in (b) 0.63 - 0.4 PM (χ 10 ³ ) 540 281 341 M _n (χ 10 ³ ) 270 118 97.5 ff C) Residual lactide, ^v percent 19 <> 5 27.8 2.7 a) 80/20, weight percentage of L- / D, L- Racemic lactide b) 1/8 inch (approximately 3.2 mm) samples with chamfer

c) Weight loss isothermal TGA at I5O2C.

EXAMPLE 2

1.84 kg of L-lactide, 0.46 kg of D, racemic L-lactide and 2.3 ml of the divalent tin solution were placed in a 3 liter round bottom flask, in the same way as in Example 1. The mixture was purged with argon for 3 hours and then heated isothermally in an oil bath at 125 ° C. The mixture melted, was thoroughly mixed by swirling, and formed a colorless, transparent and homogeneous fluid, whose viscosity increases substantially. After several hours. After 64 hours the flask was removed from the heating bath, cooled and the glass was separated from the clear, transparent and solid product. The rubber-like composition was sliced and sliced in a dry ice mill until pieces of 1/8 inch or smaller (about 3.2 mm) were obtained. Was the ground substance dried in an oven with 1002 ° C air circulation? for several hours, then dried under vacuum overnight at room temperature. Compression-molded films were prepared as described in Example 1 and the films were examined to determine their tensile strength and weight loss properties by TGA as shown in Table Ί.

EXAMPLE 3

79.98 g of L-lactide, 20.04% D, racemic L-lactide and 0.20 ml of divalent tin octanoate solution, similar to Example 1, were placed in a 250 ml round-bottom flask. The flask was purged with nitrogen through inlets and outlets and heated in a 1252G oil bath. The mixture was melted in a colorless, flowing liquid which was mixed thoroughly by turning the flask. After 2 hours, increase the temperature of the oil bath ² to 147 C, and after 14 hours total heating time, the temperature dropped to 131 ^ 0. The total warm-up time was 18 hours. The product is transparent, colorless and glassy. It was considered similar to the previous examples and the results are recorded in the

- 30 Table 1.

Examples 1 to 3 show the effect of the reaction temperature on the properties of the copolymers as originated by the resulting composition »

EXAMPLE 4

The copolymers of Examples 1 and 3 were immersed in water for several months. After 3 weeks, the copolymer of Example 1 became milky, while that of Example 3 remained clear for approximately 2 months; after 3 months the film of Example 3 became visibly milky and the film of Example 1 white and opaque.

The water that had been in contact with the film of Example 1 acquired an acidic sabot, while that of Example 3 remained tasteless.

Inspection of the data in Table 1 reveals that the copolymer of Example 1 is a biodegradable substitute in the environment for polyethylene. Those skilled in the art will recognize that the physical properties of the copolymer are excellent with useful combination for many packaging applications. Its resistance to traction and its initial tangent module resembles favorably with polyethylene compositions used, for example, in plastic trash bags, in film for common packaging, in plastic shopping bags, sandwich packaging, packaging for eggs and the like. The shape of the stress-tension curves is approximately the same for both the copolymer as a linear low density polyethylene composition normally used in waste bag compositions. Table 2 presents a comparison of properties.

COMPARISON OF POLYETHYLENE WITH POLYMERS OF POLYLAOTIC ACID

TABLE 2_ ..

PROPERTY LDPE NA 272 PELBD ^) COPOLYMER OF LACTIDE (c Tensile strength Pub 150 200 269 ASTM C Standard (1000 psi) (2.18) (2.9) (3.90) Stretching % 2 61 500 230 Tangent module Pub 3780 3520 2524 (1000 psi) (54.9) (51.0) (36.6) Module at 100 λ Pub 122 - 51 (1000 psi) (1.77) - (0.74) Module at 200 / Pub 125 - 83 (1000 psi) (1.82) - (1.20) RDT, 18 bar ° G 35 37 50 (264 psi) ° F (95) (99) (122) a) Linear polyethylene low den age, 5-10 thousand, (125 to 250 µm), 2-in / min. (5 cm / min); determination own b) Linear polyethylene low den sity, data > file

computer

c) L-lactide / D copolymer, racemic L-lactide, Example 1

d) Heat distortion temperature.

The lactide polymerization can be stopped, with conversion of the monomer to incomplete polymer, in a controllable way. This is illustrated in Examples 1 and 2. The lactide monomer binds very closely with loop polymer. Alternatively, the compositions can be derived by mixing lactide with preformed polymer. In that case the added lactide can be the same or different with respect to stereochemistry, for example, L-, D-, or D, L-lactide, to that used to make the polymer.

The composition can be completed by combining the fused polymer with lactide monomer in conventional process equipment, such as a roller mill or twin screw mixer _o The lactide polymers, normally hard and glassy, become flexible by means of lactide and remain transparent, colorless and almost odorless. The lactide is not very fugitive, requiring heating and a nitrogen purge, usually between 170 and 200 ° C for 20 to 60 minutes to remove the lactide in a gravimetric analysis. Neither is the lactide seen in films under an optical microscope. The lactide domains are submicrometric in size. This easing of polylactic acid suggests its use as a biodegradable substitute in the environment for single-use polyolefin packaging films.

EXAMPLES 5 TO 16

A series of experiments were carried out in which copolymers of L- and D, L-lactide were prepared, combined by fusion with varying amounts of lactide and studied the physical properties of the combinations as a function of dc. lactide composition. The monomer content in the lactide was determined by a previously developed thermo-gravimetric gravimetric analysis (TGA). The lactide contents were measured before and after composing and molding on films.

It was observed that the milling by open roll or double roll tended to volatilize the lactide at temperatures required by very high molecular weight lactide copolymers. These losses could be minimized using premixtures (master batches) or using lower molecular weight lactide copolymers (with their lower preservative mixing temperatures). A better method of combining and mixing was by conventional twin screw extrusion, which minimized volatilization losses. Some results are shown in Table 3 «The combinations of polylactide and lactide plasticizer are very malleable, becoming more and more with increasing lactide content. They are colorless and transparent. Only a very mild pleasant smell of lactide is detectable and there is no noticeable lactide flavor. The plastic film samples in Table 3 are tear resistant, easily foldable and can be punctured without breaking or tearing. These samples stiffen slightly when placed in a cold chamber (5 ² C, 4OsE), but remain flexible and foldable without breaking. These films are remarkably soft to the touch, indicating a glass transition temperature below 37 ^? C. When the lactide content is less than 20 percent, the films will make a typical polyolefin film noise when they are rotated. With larger lactide content the films have a drop and the warm touch of a PUC.

As shown in Table 3, the elastic modules (initial tangent modules) can be relatively high, similar to those of a low density linear polyethylene (PELBD). This is an indication of potential stability. The lower modules and tensile strength are similar to those of low density polyethylene (LDPE). Figures 1 and 2 show a graph of physical properties as a function of the volume of mactid. With reference to Table 3, at approximately 17 to 20 percent lactide volume, the traction properties are similar to those of polyethylene used in garbage and shopping bags.

At lower lactide volumes, the combinations have a similarity to polypropylene. Some data can be compared in Table 3 ·

Table 4 defines the conventional plastics used in the comparisons.

Table 3 reveals some data for mixtures of lactides and polylactides.

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TABLE 3

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The results do not differ greatly from similar compositions of examples 1 and 2, prepared by other means. However, those skilled in the art will recognize that the physical properties found varied slightly, depending on the homogeneity of the mixture, the tensile test conditions and the manufacturing technique for preparing the films. The comparisons in Table 3 reveal that lactide polymer blends have a wide range of controllable compositions that mimic many types of conventional non-degradable plastic.

EXAMPLE 17

An oligometric polylactic acid (OPLA) was prepared by mixing with polylactides as follows. An 88 percent solution of lactic acid (956 g) was poured into a three-pipe (1 liter) flask equipped with a mechanical stirrer and a thermometer probe. The reaction mixture was concentrated under a nitrogen leak between 150 and 190 ° C at 200 mm Hg for one hour until the theoretical amount of dilution water was eliminated. No catalyst was used, except lactic acid and its oligomers. This temperature and vacuum was maintained and distillation was continued for two hours until 73 percent of the theoretical amount of dewatering water was removed.

total time required was three hours. At this point, the reaction was stopped. The water samples and the flask oligomer were titrated with 0.5N NaOH. Some lactic acid, 26.2g, was found in the water distillate. The balloon oliromer (OPLA) was also refluxed with an excess of 0.5N NaOH and then the excess was diluted with standard H2 SO4.

The data are recorded in Table 5 · OPLA flows well when hot, and shows some cold flow. It has a polymerization grade of 3.4. It was used in Example 20 in which it was combined by melting with the polymer of Example 19 °

TABLE 5

OPLA CHARACTERIZATION OF EXAMPLE 1

Percentage of theoretical dehydrate

Percentage of titratable acid

Percentage Total expression of sterility as per-polymetallic Hactic acid rization percentage

34.4 82.4 116.8 3.4

EXAMPLE 18 i ^Γ I

Example 17 was repeated, with the difference that distillation was carried out more slowly. After eight hours of heating, during which the temperature was slowly increased from 63 to 175 ° C to 200 mm Hg, a balloon sample was titrated and 62.2 percent of theoretical water removal was determined.

The titration revealed a degree of polymerization of 4.3 '. The molecular weight of OPLA was further increased during! 2 hours, heating to 179 ^Q C and using a vacuum pump. The OPLA was no longer soluble in NaOH O, 1N, white as water and did not flow cold. This material is a second example of preparing '! OPLA with a slightly higher degree of polymerization compared to Example 1. It was mixed with polylactide nos! Examples 22 and 25. The degree of polymerization was estimated to be about 6 to 10.

EXAMPLE 19

A lactide polymer was prepared by methods similar to Example 3 · Polymerized by fume

Ί i

i

they are a L-lactide / D, racemic L-lactide copolymer with a weight percentage of 9θ / ΐ0, using 0.02 parts percent of starch bivalent tin octanoate catalyst. In a similar manner, a 100% L-lactide monopoly (1- PIA) was prepared. The ccpolymer was combined with the raonopolymer at 350 ° E (177 ° C) in a twin screw extruder at a 90/10 copolymer / homopolymer weight ratio.

By gel permeation chromatography (GPC) of the combination, a weight average molecular weight (PM) of 182000 and a weight average molecular weight (Ma) of 83000 were determined. TGA) was 1.7 weight percent.

This combination was mixed with the oligomeric polylactic acid of (OPLA) from Example 17 to provide Example 20. The tensile strength properties are reported in Table 6.

EXAMPLE 20 The polymer of Example 19 was combined by melting with the OPLA of Example 17 in an open two-roller mill for 20 minutes at 325 ° E (163 ° C). The mixture was molded by film compression and was tested as shown in Table 6. The molecular weights by GPC were mono, modal homogeneous distributions (P? L / M = 2.6) with PM = 192000 and M = '73000.

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EXAMPLE 21 - 25 copolymer of example 19 was combined by melting with 20 percent of the L - PLA described in Example 19. The combination is recorded as Example 21 in Table 6, where its analyzes and tensile properties are recorded. Example 21 was, in turn, combined by fusion with various amounts of the QPLA of Example 18 and these were tested as before and recorded in Table 6, Examples 22 and 25.

Table 7 records the molecular weights per GPG of these compositions. Tensile strengths and modules are compared with the CPLA weight percentages in figures 3 and 4 (lower curves).

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Examples 26 to 30

A second series of copolymers was combined with OPLA. A set of 92.5 / / 7.5 L / D, I - lactide was prepared using methods similar to those of Examples 19 and 21. This is Example 26 of Tables 8 and 9 · It was combined by fusion as ΟΡΙΑ of Example 18 in a two-roller mill open at 325 ² F (163 ^S C) for approximately twenty minutes. The combinations were molded by compression into films of thickness 3 to 5 ml: (125 to 250 mm) and their tensile properties and molecular weights were measured by GPC. The properties are recorded in Tables 8 and 9 and represented graphically in figures 3 θ 4 ·

The second series of combinations revealed significantly higher values for the tensile properties, although the molecular weights were lower »This may be due to the lower residual lactide monomer and / or the change in the composition of higher polymers. All OPLA polylactide combinations could be easily molded into transparent films without adhesion »

All D, L-Lactids are racemic

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PROPERTIES OF POLYLACTIDE FUSION MIXTURES AND OLYGOMERIC POLYLAGIC ACID 92.5 / 7.5 οι οι -4 οι cn cn cn ro H io i-9 ^Ω Cte

TABLE 9

MOLECULAR WEIGHTS OF COPOLYMERS OF L- / D, L - RACEMIC LACTIDE AT 92.5 / 7.5

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Examples 51 and 32

Film samples, with and without plasticizer, were exposed to seawater in Daytona, Florida, from March until

May. The pH of the water varied between 7.3 and 7.6 and the salinity between

33.2 and 38.4 pp. The water gradually warmed up in the test from 15 to 2790. The test pieces were cut into strips and their tensile behavior was tested before and after periodic intervals in sea water. The results are shown in Table 10. All samples showed physical degradation and whitening progressively over time. Without plasticizer the samples showed bleaching and degradation after six weeks in seawater. The OPLA polylactide combination de1 graduated more quickly, showing evidence of degradation after three weeks. The incorporation of lactide in a percentage of 20 caused immediate bleaching and evident degradation after one week of exposure.

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TABLE 10 (continued)

Jl

The foregoing examples state that a composition entirely of lactic acid can be a malleable thermoplastic useful for flexible plastic containers. By comparison, unplasticized homopoli- (L-lactide) is a highly crystalline polymer with a tensile strength of about 7000 psi (480 bar), with an elongation of 1 percent and an initial modulus of 500 000 psi (135 000 bar). It is very brittle, opaque and easily cracks. It is neither a thermoplastic that works well, nor is it transparent. The poly - (D, I - racemic lactide) is a non-crystalline glassy polymer, with a glass transition temperature of approximately 50 ° C, a tensile strength of about 6 300 psi (430, bar), an enlargement of approximately 12 percent and an initial 160,000 psi (11,000 bar) module. It is also brittle, although it is transparent. In. full contrast, a copolymer polymer of

1- lactide / D, l - racemic lactide that is plasticized with lactide monomer, is remarkably different. For example, plasticized polymers can have a tensile strength of approximately 3,900 psi (270 bar), an elongation of 431 percent and an initial modulus of 56,000 psi (13,000 bar). The plasticized polymer is clear and colorless and the combination has to be heated to more than ΙΟΟθΟ to remove the plasticizer.

Although the theory predicted a less crystalline structure, as a result of plasticization, what is surprising is the stable, transparent and malleable compositions that can arise and, secondly, the almost exhausted agreement. properties required by certain packaging applications, such as polyethylene. This invention comes at a time when there is a need for such initial properties in a material that is slowly biodegradable in the environment, as it could alleviate plastic pollution problems.

It will be apparent to those skilled in the art that extremely intimate combinations of high polymers with plasticizers are a rarity. The plasticization allows a great extension in the initial physical properties and in the time by tiodegradation in the environment.

The amount of plasticizers in the polymer depends on the characteristics of the desired compositions »If lactide is used as a plasticizer, the range is preferably 5 to 40 weight percent, whereas if only lactide or lactic acid oligomers are used the range could be 2 to 60 weight percent »Surprisingly, up to 30 percent oligomer can be added without substantially affecting the tensile strength or modulus» See figures 3 θ 4. Adding 30 to 60 weight percent oligomers produces plasticization significant and an affirmation of the physical properties This fact contributes to a great economy of the composition, since the oligomeric lactic acid is cheaper than the high polymeric lactic acid. Lactic acid oligomer or any lactide can be prepared. It is important to note that the lactic acid oligomer normally contains significant amounts of lactic acid, unless removed. This is an important consideration in custom made compositions with specific properties. Those skilled in the art and knowing the teachings of this invention will be able to select reaction conditions in order to obtain appropriate chain lengths for the polymer, and the proportions of polymer and plasticizers in order to obtain compositions manufactured having physical properties similar to packaging thermoplastics. used normally and, however, degrade relatively quickly »For example, higher amounts of plasticizer result in polymers having increased flexibility and increasing physical stiffness properties, however also obtaining a rate of increasing degradation. In addition, shorter chain lengths for the polymer will require less plasticizer as they obtain the same properties as those obtained with longer lengths »

Also provided by the first embodiment of the invention is a process for producing a biodegradable composition in the environment which is a plasticized polymer of polylactic acid with formula (I). The process comprises the preparation of one or more lactide monomers and a catalyst; polymerizing the monomers to give rise to a polymer at a temperature sufficiently low to allow the polymerization reaction to be stopped before completing the polymerization; monitoring the monomer level to determine the amount of the remaining monomer; and stopping the reaction before completing the polymerization to a specified amount of monomer, in order to effect the monomer, which did not react in a predetermined amount in the polymer. The process lactide monomers are selected from the group consisting of D - lactide, 1 - lactide, meso - D, L - lactide, D, L - racemic lactide and their mixtures. Optionally, additional plasticizer can be incorporated in the polymer, the plasticizer being also selected from the group consisting of 1 - lactide, D - lactide, D, 1 - racemic lactide, meso D, L-lactide, lactic acid, lactic acid oligomers, oligomers lactide and mixtures thereof.

Preferably, the polymerisation of the monomers is carried out at a temperature below 129 ^° C. In addition, the processing of the plasticized polymer to obtain a final product is preferably carried out at a temperature sufficiently low to retain the plasticizer in the polymer. This temperature can be over 129 ° C. If the additional monomer and / or oligomer is added, the monomer retention will not naturally be as critical.

Also provided by the first embodiment of the invention is a process for the preparation of a polymer of formula I, comprising the preparation of one or more lactide monomers and a catalyst; polymerization to monomers to form a polymer; and the integration of plas52 -

tifier in a separate phase in the polymer, the plasticizer being selected from the group consisting of D - lactide, 1 - lactide, D, L - lactide, lactic acid oligomers and their mixture

The compositions of the invention should have a tensile strength of 300 to 20,000 psi (20 to 1,400 bar), an enlargement to break of 50 to 1,000 percent and a tangent modulus of 20,000 to 250,000 psi (1,400 at 17 200 bar).

Preferably, by replacing polio lefins, the compositions have a tensile strength of at least 3,000 psi (200 bar), an elongation to break of at least 250 percent and a tangent modulus of at least 50 000 psi (3,500 bar) o

The homopolymers and copolymers of the present invention are insoluble in water, but in constant contact with them; are slowly degradable. However, degradation is rapid when compared to polyolefin compositions that are replaced by the invention. In this way, rejected objects made from polymers are environmentally acceptable as they slowly degrade into harmless substances. If objects made of polymers of the invention are set on fire, they burn with a clean, blue flame.

In addition to the foregoing, a method is additionally provided by the first embodiment of the invention to replace a thermoplastic composition with the biodegradable composition of the invention in which the thermoplastic composition comprises first orientable polymer units, replacing the first polymer units with a second orientable polymer having a non-oriented tensile strength of 300 to 20,000 psi (20 to 1,400 bar), an elongation to break of 50 to 1,000 percent and a tangent modulus of 20,000 to 25,000 psi (l 400 to 17,000 bar); the second polymer comprising units of polylactic acid having the structure in formula I, in which n is the number of units and n is an integer,

150 u <20 OCO and is plasticized with a plasticizer selected from the group consisting of lactide, lactic acid oligomers, lactide oligomers and mixtures thereof. polyvinyl and polyethylene terephthalate. In addition to the above list, the method is useful for replacing polymers of styrene, vinyl acetate, alkyl metracrylate and alkyl acrylate. It should be understood that copolymers made of mixtures of monomers in the said group and of physical mixtures of the polymers and copolymers of the group described above are also substitutable SECOND FORM OF GENERAL CONCRETIZATION

- The biodegradable compositions in the environment disclosed here as a second embodiment are completely degradable giving environmentally friendly and acceptable materials. The intermediate products of degradation: lactic acid is a naturally occurring substance, widely distributed, which is easily metabolized by a wide variety of organisms- Its natural end products of degradation are carbon dioxide and water- Equivalents studied of these compositions, such as those containing minor amounts of other substantial filling or diluting materials, can also be completely degradable in the environment through the right choice of materials- The present compositions provide environmentally acceptable materials because their deterioration and physical degradation is much faster and complete than conventional plastic degradables that they replace. In addition, since all or a large portion of the composition will be polylactic acid, and / or a lactide or oligomer derived from lactic acid, there will be no residue or only a small portion of slower degradation residue will remain. This residue will have an exposed area higher than the total product and an expected faster degradation speed.

The preferred composition of the present invention comprises polylactic acid units polymerized with the said unit of formula I, in which n is an integer between 75 and 10,000 and the alpha carbon is a random mixture D and 1 (or R and S) with a preponderance of one of the pure enaciomers. When η is low, polylactic acid, PIA, is easily processed but is considerably weaker than when n is higher. When n is quite large, for example 7000 or greater, PLA is quite strong but difficult to mold by injection. Preferably, n is approximately 500 to 3,000 for a better balance of physical properties of final utility and melt processing. Monomers are selected in portions of 1 (or D) / D, L of polymerized lactic acid or its cyclic dimer, lactide, as discussed further below. Both the lactic acid and the lactide allow to obtain the repetition PIA unit, presented above, but the lactide is preferable, since it allows to obtain more easily the highest molecular weights necessary for good physical properties. Once the lactide, which has the structure:

CH.,

I ³ - C - H / \ = CC = 0 \ z

H - C-0

I

CH ₅ has two alpha carbons that are asymmetric, there are three types of lactide, which are, D, D - (or D); L, L - (or 1 and even D, L - lactide.

D - lactide is a dilactide, or cyclic dimer, of D - lactic acid. Similarly, L - lactide is a cyclic dimer of lactic acid. The meso D, L - lactide is a cyclic dimer of D - and L - lactic acid. The racemic D, L - lactide comprises a 50/50 mixture of D and L - lactide. When used alone in this specification, the term D, L - lactide is intended to include meso - E, L lactide cu D, L - racemic lactide. The term dispersed as used in this specification means that the material is homogeneous and even mixed with the polymer.

L - Pure PLA has poor processing characteristics, easily cracks and becomes opaque.

D, L - PLA works easily but is not rigid enough to be an adequate replacement for OPS.

The proportion of the L - lactide / D, L - lactide copolymer of between 65/15 to 95/5 and preferably 9θ / ΐ0, is a preferred embodiment of the invention. At proportions higher than 95/5, the copolymer is difficult to form by thermoforming without cracking and is easily opaque at room temperature. At ratios lower than 85/15, lactide copolymers exhibit modules lower than 0 desirable for OPS replacement. Among these limits, copolymers are obtained by abrupt cooling from the melt in manufacturing equipment / process typical of plastics technology to achieve films and molded shapes that are clear, colorless and extremely rigid. The properties of the molten products as described are very close to the properties of an OPS.

Another advantage of this invention is that the isolated lactic acid copolymer can be obtained from cheap raw materials. Corn syrup can be fermented using starch and corn to obtain racemic L- and D-lactic acid, depending on the microorganism. Racemic D, L-lactic acid is inexpensively obtainable from ethylene, which can be oxidized to acetaldehyde, which is reacted with hydrogen cyanide to form lactonitrile, which is hydrolyzed to acid D , L - racemic lactic acid. Lactate is obtained simply by distilling lactic acid. There is no change in the asymmetric carbon stereochemistry

by transforming lactic acid with lactide by common distillation / condensation methods.

Although the present specification discusses the reaction of L - lactide and D, L - lactide, it should be understood that reactions specifying L - lactide can also use D - lactide. In this way the reaction of D - lactide and D, L - lactide, according to the method described here, will give an equivalent product, the only difference being that the light rotates in a different direction.

Preferably, the copolymers of the present invention are formed by heating the monomer mixture to form a homogeneous melt and adding a catalyst to cause lactide to polymerize with the opening of the ring. The polymerization is preferably carried out in an anhydrous atmosphere. inert, such as argon nitrogen, or under vacuum. Suitable catalysts include bivalent metal oxides and organometallic compounds, such as bivalent tin octanoate, zinc acetate, cadmium acetate, aluminum acetate or butanoate, tin chloride, tin benzoate and antimenium oxide. The divalent tin octanoate is the preferred catalyst because of its high solubility in monomers, ease of preparation in anhydrous form and low toxicity. The amount of catalyst required can vary between approximately 0.02 and 2 weight percent, based on the monomers and is preferably about 0.2 percent. The molecular weight and melt viscosities of the copolymers are controllable by the amount of catalyst and / or chain transfer agents such as glycolic acid. The polymerization reaction temperature is between approximately 100 and 200 ° C. The lowest color formation Occurs below 14020 and the polymerization rate is better above 135 ° C. Since the racemic D, 1 - lactide melts at 127 ° C it is best for converting monomer into polymerizing polymer at a temperature above 127 ° C.

When clarity and transparency are required, as for OPS replacement, the copolymers of this invention are polymerized in an inert atmosphere above their melting points which are generally in the range of 125 to 150 ° C. The molten lactide copolymer can be extruded at the exit of the polymerizer on rods and bars, cooled, palletized and stored in bags for use in subsequent molding and extrusion operations.

Similarly, the clarity of packaging films formed by thermoforming and molded articles is achieved by molding and extruding above the melting points of the copolymers and rapidly cooling the manufactured product »After this operation, the copolymers remain transparent, unless that are heated for several hours above their glass transition temperature, Tg, and below the melting point, Tm. The slow cooling of sheets, plates, films and thermoformed products can induce spherolite crystallinity in the copolymers, which causes an improvement in the heat stability of the manufactured product, but causes some loss of transparency »Nucleating agents, such as sodium benzoate , calcium lactate and the like can also induce substantial and rapid crystallinity »A slight copolymer traction effort between its Tg and Tm induces the orientation of the polymer molecules and can substantially improve the physical properties in loss of transparency. As an approximate measure, copolymers have a conservation period under storage conditions of several months, but disappear within about a year when fully moistened.

The following examples are only illustrative of the present invention »In Examples 15 and '73, a series of compositions was prepared and evaluated» It was found, in contrast to the prior art, that there are distinct differences in procedural behavior and in physical properties of 1 - lactide / D, l - lactide copolymers »

- 58 ~

EXAMPLE 1B

They were placed in a 500 ml dry round bottom halao l60g of L - lactide (grade three stars Purac, Inc.) and 40g of D, L - racemic lactide (grade three stars, Purac, Inc / This mixture was heated for approximately one hour at a temperature of 123 to 1292C with a continuous nitrogen purge through a stopper provided with an outlet.The monomers form a clear melt which is completely mixed by stirring the melt. catalyst and dried by azeotropic distillation, i.e. 10 ml of divalent tin octanoate (Polyscienes, Inc.)

The mixture of different types of polymers or lactide copolymer can substantially modify the physical properties. As an example, mixing by melting the high melting lactide polymer with a lower melting lactide copolymer can provide a transparent material, which has a sufficient amount and a type of Christianity to remain transparent. Those skilled in the art will recognize that such transparency in molded films, high stiffness, high temperature of heat distortion, thermo-processability and hydrodegradability in the environment are a rare combination of properties. In this way, the polymers can be mixed as well as nucleated, oriented and controlled by molecular weight to provide a considerable range of processing possibilities and final properties in the final composite thermoplastic.

The copolymers of the present invention hydrolyze with formation of lactic acid again in the presence of moisture. In the presence of ambient air and humidity, hydrolysis becomes evident in a period of about 12 to 13 months. The ccpolymers then become sticky, slightly opaque and very brittle. When immersed in water, copolymers show

hydrolysis effects evident in a period of 1 to 4 months, depending on the composition, the molecular weights of the ambient temperature, its quotient between surface and volume and the particular aqueous environment in which the copolymers are placed. Microorganisms can further reduce lactic acid giving rise to carbon dioxide and water, in 60 ml of toluene; 10 ml of toluene was distilled with residual water into a Dean-Stark siphon communicating with the atmosphere through a drying tube. An amount of 0.20 ml of the divalent tin octonoate solution was poured into the melt using a pipette and mixed thoroughly. The nitrogen purge continues and the melt becomes more and more viscous over the next three hours. Heating continues at 123 to 127 ° C for 20 to 24 hours. The mixture was allowed to cool to room temperature and the flask was further cooled with liquid nitrogen behind and behind a protective barrier. The glass shatters and is tapped out of the polymer. The copolymer is clear and colorless and is evaluated in a series of tests shown in Table 13. Compression films are molded at 170 ° C in a heated hydraulic press for future tensile tests. 1/8-inch thick (approximately 3.2 mm) t plates are molded

for Izod impact tests with ASTM notch, D 256 and heat deformation temperature, ASTM, D648. Differential scanning calorimetry (DSC) evaluated the glass transition temperature (Tg) and the melting point (Tm, center of the endotherm).

EXAMPLES 2b to 7B

The procedures of Example 1B were repeated, except that the ratio of L- and D, racemic L-lactide was changed as shown in Table 1 B with the test results. The pure L-lactide polymer, Example 7 B, did not always mold well at a temperature of 17O-2CO2C, as it cracked frequently while cooling in the mold. It was often made opaque by cooling.

(1000 psi) (289) (221) (694) (210) (268) (748)

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PROPERTIES OF L / LACTIDE COPOLYMERS0 / D, RACEMIC L-LACTIDE

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TABLE 1B (Continued)

In a similar manner to Examples 43 and 53 3, a copolymer was prepared in a weight ratio 9θ / ΐ0 of L-lactide / D, racemic L-lactide. They were placed in a 2 liter flask with a dry nitrogen purge 1045.5 g of L-lactide and 116.4 g of D, racemic L-lactide. An amount of 1.0 ml of anhydrous bivalent tin octanoate solution (0.2 ml per ml of toluene) was added. The flask was purged with nitrogen overnight, then heated in an oil bath at 141 ° C until the monomers were melted and well mixed and the heating was slowly lowered to 125 ° C, continuing to that temperature for 72 hours. The polymer slowly becomes whitish while cooling. After removing the glass, the colorless and cloudy glassy copolymer was evaluated. Gel permeation chromatography gives an average weight molecular weight (M.M.) of 522,500 and an average number molecular weight (Mn) of 149,000.

A DSC of the lactide polymer reveals a strong Tm at 145 ° C, see Figure 10. The lactide polymer was melted, cooled rapidly and examined again by DSC, without detecting melting or crystallization points. However, a Tg appears at approximately 50-55 ° C. The results show that the polymer can be crystalline or amorphous, depending on its thermal history.

EXAMPLES 9B and 12B

The series of compositions was expanded, using the procedures of Example 1 B, except that other proportions of L- and D, racemic L-lactide were used and heating was 2 hours at 125 ° O and 14 hours at 125-147 ° C, then 2 hours at 147-131 C. The results are shown in Table 2 B.

TRACTION PROPERTIES AND COPOLYMER MODULE OF L-LACTIDEO AND D, L-LACTIDE

Composition, weight ratio, L-lactide / D, L-lactide

(Racemic) 70/30 60/40 20/80 0/100 Example No. 9B 103 11B 123 Color / transparency Colorless clear Film thickness, jum (thousand) 150-230 (6 - 9) 100-150 (4 - 6) 100-125 (4 - 5) 125-180 (5 -7) Tensile strength (a) bar, ASTM D 638 (1000 psi) 476 (6 - 9) 462 (6 - 7) 400 (5 - 8) 386 (5 -6) Stretching, % 3.2 3.0 2-7 2-8 Tangent module Pub (1000 psi) / ;and 19800 (287) 20200 (293) 19000 (275) I92OO (278) a) Subtract films from 0.2 / min- (50 mm / min) tweezers and 5 / min (1,27mm / min) film. with a separation speed of The results of í examples previous reveal

that only certain compositions have the properties required for

- 64 for a replacement of the CPS. The main requirements for an OPS-like material are clarity and colorlessness, tensile strength greater than 7,000 psi (480 bar), tangent modulus (a measure of stiffness) greater than 400,000 psi (27,600 bar) and thermoplasticity with good behavior. Table 5® records some side-by-side comparisons of a crystalline polystyrene (OPS) and a random copolymer of l-lactide in a percentage by weight of 87.5 and of racemic D, L-lactide in a percentage by weight of 12.5.

TABLE 3

COMPARISON OF PHYSICAL PROPERTIES

Properties ' Poly- (lactic acid) Example 3 B Polystyrene Crystal Impact resistance pact, Izod with en cut ft - lb / in 0.4 0.4 Tensile strength final section, bar 572 510 (psi) 8300 7400 Stretching, 6.0 4.0 Elastic module, bar 47900 31000 (psi) 694,000 450,000

Deviation temperature.20

under load, (264 psi) 18bar (The) 93 (2F) (200) Specific weight 1.25 1.05 Rockwell Hardness (B) M 75 Softening point Vicat, sC (ç) 107 (2?) (225)

TABLE 5B (Continued)

Fusion Gaudal,

D 1238 (G) 40-46

1.7 2 / lC min / ^e ) 1.6 2/10 min / ^f ) (a) Depends on thermal history (h) Support D = 97 (c) DSC, Tm = 1252C (257 F) at 10 degrees / min (d) The flow rate decreases at lower temperatures (e) According to the manufacturer's information.

(f) From our experience.

EXAMPLE 13 B

The copolymer of Example 2 B was molded and reshaped several times to determine whether color would develop in the films and whether the molecular weights remained high. Through this experience it is determined whether the copolymer can be recycled, an important consideration for manufacturing practices. The results in Table 43 show that the copolymer remains completely clear and colorless after repeated heating and molding, despite the fact that the copolymer has been exposed to air at high temperatures repeatedly.

- 66 QUESTION 4 5

EFFECT OF MCLDA G-EM ON COPOLYMER AND AND MILK

Example ) At the. History Appearance PM χ 10 ³ Mn xlO ⁵ P.M / / Mn Example 2 B ⁽ >) Unframed, Complete 926 218 - - directly mind gives transparent polymerization close and (The) colorless Example 13 B Example 2 B after molding (B) II 301 135 2.22 (The) Example 13 3 Example 2 B after molding , (B) gem 6 times '' ff 137 56.7 2.42

(a) Copolymer of L-lactide / D, racemic L-lactide in an 85/15 ratio (b) Compression molding at 167 ° O (333 ° E) for 7 minutes per 5-mil film (125 µm)

EXAMPLE 14B to 18B

The copolymers of Examples 2B, 3B and 6B were compressed into films of approximately 20 to 30 mil thickness (500 to 760 µm) and placed in a heated Ins tron apparatus where the films were stretched 5 times their length at 83 ° C at a rate of 0.5 inches (12.7 mm) per minute. The films were quickly cooled after withdrawing from Instron, and were found to have approximately

- one thousand (125 µm) thick. They were clear and colorless.

Resistance properties were evaluated and recorded in Table 5 B. When stretched 8 to 10 times their length, the films show evidence of crystallinity formation due to the development of turbidity and some loss of transparency.

The results show that very thin films with adequate rigidity and transparency can be prepared for OPS replacement. Thus, despite the higher density of the delactide copolymers compared to that of the powder. liestyrene, trenos material can be used for hard OPS replacements.

TABLE 5 B

PROPERTIES OF L-LACTIDE COPOLYMERS / D, RACEMIC L-LACTIDE AFTER ORIENTATION (a)

Composition, weight ratio L-Lactide /

D, L-lactide (racemic) 65/15 65/15 S5 / 15 87.5 / 12.5 95/5

Example number 14B 153 16B 173 18B Film thickness cell jim 140 125 165 125 100 thousand (5.5 ) (5.0) (6.5) (5.0) (4.0) Resistance to bar pull 965 101c 1030 900 1100 (1000 psi) (14, 0) (14.7) (15.0) (13.0) (16.0) Stretching / 31.5 15.4 30.0 23.8 37.4

TABLE 5 3 (Continued)

Tangent bar module (1000 psi)

38900 23900 30000 35400 (564) (419) (02) (513)

a) 5 X oriented at 83 ° C using a downward stretching speed of 0.5 in./min. in Instron (12.7 mm / min).

EXAMPLE 19 B

Films of the lactide copolymers of Table 1 B were immersed in water for a period of several months.

The copolymers remained clear for approximately 2 months; after 3 months a slight haze developed. After being placed on a shelf in moist air and with frequent handling, the films remained virtually unchanged for approximately one year, although the Instron data show a small decrease in strength and elongation after several months. In a landfill, the buried films appear in a period of 6 months to 2 years, depending on the humidity of the pH, the temperature, the composition, the quotient between the surface and the volume, and the biological activity of the landfill. All films burn with a clean blue flame.

EXAMPLE 20 B

DSC examined the lactide copolymer of Example 53 (film obtained by rapid cooling and compression molded) and found to have less than 2 percent crystallinity, see Figure 5, in the vicinity of 130 ° C. A 1/8 inch (approximately 3.2 mm) thick sample of the copolymer of Example 5 B was annealed in an oven at 185 ° F (85 ° C) for 16 hours.

The sample became cloudy and the DSC of the sample, see Pigure 7, revealed a pronounced increase in crystallinity. The sample had a heat deformation temperature at 264 psi (18 bar) (HDT) from 90 to 95-03. A similar sample without annealing showed a heat deformation temperature of 50 to 55 ° C, which corresponds to its Tg.

EXAMPLE 21 B

Calcium lactate in a weight percentage of 5 was combined in a heated roller mill with the lactide copolymer of Example 5 B at 17 ° C for approximately 5 minutes. The roll combination in the form of a plate was removed and examined. It was tough, strong and cloudy. By 82X optical microscopy heterogeneous domains were detected in the size range from a few microns to 30 microns. By DSC there is a substantial increase in crystallinity in the vicinity of 145 ⁹ O, see Figure 8, which remains after rapid cooling and re-cementing. The above-mentioned results, comparing Examples 8 B, 20 3 and 21 B, show that the nucleating agents are faster and more effective in inducing crystallinity in lactide copolymers. Nucleating agents such as salts of carboxylic acids can be used, with lactic acid salts being preferred. EXAMPLES 22 B

They were placed in a 500-ml three-necked round-bottom flask, equipped with a mechanical stirrer and a nitrogen inlet and outlet, 180.7 g of L-lactide and 40.2 g of D, racemic L-lactide ( both from Boehringer and Ingelheim, grade The contents of the flask were heated to 110 ° C under a nitrogen purge to melt the lactides and 20.1 g of polyethylene polyols (Amoco 23, melt index 3.5 g / The polystyrene swelled a lot and partially dissolved with stirring overnight, while heating up to 185 ° C. The temperature was lowered to 1415 ° C and 0.2 ml of octanoate solution was added. anhydrous divalent tin (0.2 ml / ml of t) luene). The stirrer was turned off and the po70 lactides were allowed -

limerize to 141 ° C over a period of 3 days. The very swollen polystyrene floats to the surface after the agitator is turned off. The lower polylactide phase was cooled and examined by DSC. The sample has a low Tg, approximately 35-C, and on the other hand, it has no apparent temperature transitions. Compression-molded films are clear, colorless and very malleable. These results indicate that polystyrene completely stops the formation of crystallinity,

EXSMPLO 23 B

The lactide copolymer of Example 8 B was combined with a roller mill with 20 weight percent of the L-lactide homopolymer produced in Example 7 B. A sample of the homopolymer was analyzed by DSC, see Figure 11. Exa the combined sample was mined by DSC and found to have a Tg of 59 to 63 ² C and strong Tm's at 150 and I662C, see Eigure 12. The films were clear tending to slightly cloudy, depending on the cooling speed after pressing. Rapidly cooled samples crystallize easily by heating to approximately 80 to 90 ° C. As a result, the heat deformation temperature of the combination is now quite high. The combination becomes cloudy at 80 to 90 ° C but does not deform with heat, as 0 does the 90/10 copolymer of unmatched proportion. Tensile data, as shown in Table 6 B, were obtained in non-oriented compression molded films and compared to similar data obtained for polystyrene.

TABLE 6 Β

COMPARISON OF POLYLACTIDE COMBINATION OF EXAMPLE 23 3 WITH CRYSTAL POLYSTYRENE

Example 23 B ( ^a ) Crystal polystyrene ( ^a > B) Film thickness, μπι 200 355 (thousand) (8) (14) Tensile strength, ASTM D882, bar 530 414 (1000 psi) (7.7) (6.0) Elongation, ^, in yield 6.5 3.2 Tangent module, bar 22300 18400 (1000 psi) (323) (267)

a) Thin films, non-oriented compression molded test pieces.

b) melting index 1.7

This example shows that a melt combination is an excellent way to improve the properties of the copolymer, so that advantageous properties similar to those of polystyrene are realized. The greater the amount of homopolymer based on L-lactide (or D-lactide) combined with the polymer, the higher the heat deformation temperature, however, the turbidity will also increase. In this way, the addition of homopolymer can be combined with other methods of increasing properties similar to those of polystyrene while still maintaining clarity.

As an additional example, orien films

produced from the polymer increase the tensile properties. With eight to ten times elongation the physical properties continue to increase, but the material becomes cloudy. The degree of orientation will therefore need to be controlled or combined with the other methods of changing properties to obtain optimal characteristics similar to those of polystyrene.

EXAMPLES 24 B to 27 3

Examples 24B to 273 refer to polymerization of lactide with controlled amounts of chain transfer agents, demonstrating that molecular weights can be controlled using transfer agents, such as glycolic acid. The results are shown in Table 7 3. There is an almost linear relationship between the amount of transfer agent and the inverse of the average weight molecular weight.

A preferred chain transfer agent is lactic acid.

TABLE 7 B

MOLECULAR WEIGHT CONTROL USING AGENTS

CHAIN TRANSFER

Example No. ^ ^3- ) CTA PPH M _n (b) P.M. PM / M _n 24 3 0.22 13,500 107,300 8.0 25 B 0.45 12,800 66,700 5.2 26 3 0.90 7,300 29.9OC 4.1 27 B 1.80 4,7OO I3,9OO 2.9

a) Parts of the glycolic acid chain transfer agent (CTA) per hundred parts of lactide in the polymerization recipe.

b) Gel permeation chromatography in the tetrahydrofuran solvent, 232C, with columns of 10θ, 10 ^ _} 10 ^ and 10 ^ anhstrom The molecular weights of number average, Mn, and weight average, PM are calculated by compared to monodisperse polystyrene standards.

EXAMPLE 23 B

A 4.0 ml (100 µm) compression molded particle of the lactide copolymer of Example 2 B was evaluated as a barrier film by ASTM methods. The results are shown in Table 8 B, the lactide copolymer constitutes a much better barrier to carbon dioxide and oxygen than polystyrene. By comparison with some other polymer barrier films, the lactide copolymer is a barrier film suitable for many packaging applications.

TABLE 8 3

EXAMPLE 28 B GAS PERMEABILITY

Units Lactide copolymer, Example 2 B Polystyrene cri_s tal <»> Tereftala to Vinylidene chloride-vinyl chloride copolymer ^(b) cnP / lOC sq. in / 24 h / atm co ₂ 32.1 900 15-25 3.8-44 (cn // 100 cm ^ 24 h. atm) (4.98) (140) (2.3-3.9) (0.59-6.8) ° 2 19.9 350 6-8 0.8-6.9 (cm ^ / 100cm ^ 24 h. atm) (3.08) (54) (0.9-1.2) (0.12-1.1)

- 74 a) ASTM D1434-75, Example 2 B was a compression molded film of 100 µm (4.0 mil)

b) Values of Modern Plastic Encyclopedia

EXAMPLE 29 3

Over 1/8 inch (approx. 3.2 mm) thick sheets of the lactide copolymers of Examples 13-6B were immersed overnight in a mixture of petroleum ether and methylene chloride. At proportions of 70/30 to 60/40 petroleum ether / methylene chloride, the copolymers form foam when placed in boiling water. Irregular but well-expanded foams are formed.

EXAMPLE 30 3

The melting viscosities of a commercial crystal polystyrene (type 201, Huntsman Chemical Corp.) and the lactide polymer of Example 8 B were compared. The melt index, ASTM D1238 (G), of polystyrene was 1, 6 g / l0 min. at 200 ° C using the standard weight of 5 kg. The melt index of the lactide polymer was 40 to 468/10 min. Under the same conditions, however, at 160 ° C the value was 8.0 g / 10 min.

A more detailed comparison of the melting viscosities was obtained by observing the melting viscosities of the six polymers in an Instron Capillary Viscometer. The comparative results are shown in Figure 9 «

The cutting rates normally found during extrusion and injection molding range from approximately 100 to 1,000 s ¹ . The inspection of the data in Figure 9 shows that the melt viscosity of the lactide polymer at 160 ° C is very similar to that of polystyrene at 2005C.

The above results show that lactide polymers can be processed by melting, at lower temperatures than polystyrene, using very similar methods.

EXAMPLES 31 B and 34 B · ^r ··· '- · ..............

Small test polymerizations of purified mesolactide (meso-D, L-lactide) (recrystallized and dried) in the form of homopolymer and copolymer were performed. The molecular weights were evaluated using G-PC and compared to analogues of D, L-lactide, The results are shown in Table 9 B _{o The} polymers were pressed by melting in films and their physical properties were evaluated and compared, as shown in Table 10 B. Experimental differences in plate thickness and molecular weights, copolymers are similar within experimental error. The mesolactide polymer homope is somewhat weaker.

TABLE 9 B

MOLECULAR WEIGHT COMPARISON OF GPC POLYMERS AND COPOLYMERS OF MESO AND RACJEMIC LACTID

Example Composition Mon. GPC x 10

31 3 D, L - PLA - - 97.5 341 757 3.49 32 B Meso PLA 2.76 62.5 152 264 2.42 33 3 90 / l0, L- / Meso 1.67 29 142 301 1.67 34 3 90/10, L- / D, L - - 91.3 201 350 2.20

- 76 (a) Compression molded films

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An overall description of the composition of the second embodiment of the invention includes a biodegradable polymer in the environment, comprising polymerized lactic acid units of the structure of formula I, wherein n is an integer between 75 and 10,000 and the alpha carbon atom and one mixture of L and D configurations, with a preponderance of either D units or L units, the polymer being suitable for replacing polystyrene. Preferably, De 1 units of the polymer can be prepared from L-lactide or D-lactide, at 35 to 95 parts by weight, and D, L-lactide from 15 to 5 by weight. A biodegradable composition in the environment with improved properties, more similar to those of polystyrene, it comprises combinations of a physical mixture of acid units. of the polymerized lactic acid of the structure of formula I, where n is an integer between 75 and 10,000 and the alpha carbon atom and a random mixture of L and D configurations with a preponderance of either D units or L units, a homopolymer of D-lactide or L-lactide- Compositions that have n equal to an integer between 150 and 10,000 have a good balance between melting processability and strength. A general description of the process for producing the composition of the second embodiment comprises mix with a catalyst, heat and melt the L-lactide or D-lactide monomer and the D, L-lactide monomer with the l-lactide monomer or the D-lactide monomer in an amount of 85 to 95 parts by weight and the monomer of D, L-lactide in an amount of 15 to 5 parts by weight, to form an intimate solution; polymerize the solution; and treating the polymer in order to modify its properties so as to make the polymer suitable as a substitute for polystyrene. The properties of the composition can be adjusted by adding a maleation agent; adding a D-lactide or L-lactide homopolymer by mixing to produce a physical mixture; orienting the polymer;

adding a nucleating agent and a D-lactide or L-lactide polymer per mixture, adding a nucleating agent and a D-lactide or L-lactide polymer by mixing θ orienting the polymer; adding chain transfer agents to the polymerization phase in order to adjust the characteristics for a polystyrene substitution, annealing at a high temperature, and adding additional plasticizer, the plasticizer being selected from the group consisting of D-lactide, L-lactide, meso-D, l-lactide, lactic acid, lactide oligomer, lactic acid oligomer and mixtures thereof. If a monomer is selected as a plasticizer, a unique composition can be obtained by adding a monomer that is stereochemically different from that used to obtain the polylactide in the composition. Similarly, the addition of oligomer stereochemically different from what can be obtained during polymerization of the polymer gives a unique product. Colored bodies can be excluded by carrying out polymerization in an inert atmosphere and at reaction temperatures preferably at 140 ° C or below. Various combinations of the previous treatments can be employed to obtain the optimal characteristics, as those skilled in the art will calculate, once they know the teachings of the invention. As can be seen in the first embodiment mentioned above, a greater amount of monomer or oligomer can have a significant effect. In the present second embodiment, lower amounts of monomer and oligomer 'are preferred to give rigidity. It is preferred that the plasticizer is present in an amount of 0.1 to 5 percent. The composition normally contains plasticizer in an amount that depends on the polymerization conditions or the amount added after polymerization. One can select the additional monomer used as a plasticizer from the group: D-lactide, L-lactide, meso-D, racemic L-lactide and respective mixtures. Lactid or lactic acid oligomers can also be added. Unique compositions can be obtained by adding monomer or oligomer stereochemically different from those selected for the polymers in the composition.

In addition, by the second embodiment of the invention, a method for replacing a thermoplastic composition with the biodegradable composition of the invention is provided, the thermoplastic composition comprising first orientable polystyrene units, replacing the first polymer units with a second orientable polymer , having a non-oriented tensile strength of at least 5,000 and a tangent spike of at least 200,000; in which the second polymer comprises polylactic acid units of the structure in formula I, where n is the number of repeating units and n is an integer, 75 <n 10 000, and the alpha carbon atom is a mixture of configurations 1 and D with a preponderance of either D units or L units, in which the polymer is prepared from lactide 1 cu D of 85 to 95 parts by weight, and D, l-lactide of 15 to 5 parts by weight and is plasticized with a plasticizer selected from the group consisting of lactide, lactic acid oligomers, lactide oligomers and mixtures between 0.1 and 5.0 weight percent.

Studied equivalents of the compositions of the invention are those that contain minor amounts of other materials. The compositions produced according to the present invention can be modified, if desired, by the addition of a crosslinking agent, other plasticizers, a filler dye and the like.

The compositions of the present invention can be processed by melt transformation into useful manufactured articles, being a self-contained structure, such as disposable containers, cutlery, trays, plates, cups, single-use trays, syringes, medical trays, packaging films and the like. The compositions are useful in that they can have the characteristics of normal polystyrenes and therefore replace them, but nonetheless degrade in the environment. The compositions are especially useful for owls and for use only for a short period of time

in use before discarding.

THIRD FORM OF GENERAL CONCRETIZATION

A third embodiment reveals the combination of polylactic acid (PLA) with polystyrene (PS), polyethylene (PE), polyethylene terephthalate (PET) and polypropylene (PP). The embodiment reveals that polylactic acid is compatible by melting with these conventional thermoplastics and the effect on their physical properties.

The environmentally degradable compositions disclosed herein are at least partially degradable. That is, the polylactic acid portion of the composition will decompose relatively quickly compared to the more stable portions of the combination and will cause physical deterioration of the combined material. For example, when the compositions are intimate and homogeneous mixtures with sizes of small extensions the physical deterioration will destroy the product originally formed. The compositions of the present invention provide environmentally acceptable materials, because their deterioration and physical degradation is much faster than that of conventional non-degradable plastics. In addition, as a significant portion of the composition may be polylactic acid and / or a lactide or oligomer derived from lactic acid, only a small portion of the slower degrading thermoplastic residue will remain (eg polystyrene). This residue will have a large exposed surface and is supposed to decompose more quickly than a block-formed product.

D-lactide is a dilactone, or cyclic dimer, of B-lactic acid. Similarly, L-lactide is a cyclic dimer of L-lactic acid. The meso-D, 1-lactide is a cyclic dimer of D- and L-lactic acids. The racemic D, 1-lactide comprises a 50/50 mixture of D- and L-lactides. When used alone in this specification, the term "D, l-lactide" is intended to include meso-D, L-lactide or D, L «" racemic lactide. Polylactic acid can be prepared from one or more of the aforementioned intermediates

EXAMPLE 1 C

Polystyrene was combined with polylactic acid in a solvent and poured from the solvent using CKgOLp to determine optimal compatibility. The films cast from the solvent were translucent and apparently not curdled. A sample has a homogeneous appearance with the naked eye and resists folding and handling without tearing. The 310 X optical microscope reveals heterogeneous extensions of 3 microns and smaller. The combination is apparently very compatible. It does not show any alteration for 2 years with regard to the flowering of fugitive material, nor does its physical properties show evidence of degradation.

EXAMPLE 2 0

It was combined by melting similarly polypropylene 8525, from Herantes, in Brabender with polylactic acid at 400 ° E (200 ° C). The proportions of PP / PLA prepared were 100/0 for the comparison sample, 90/10 θ 75/25 »

EXAMPLES 3 C to 5 0

Compositions were prepared by melting polylactic acid with polystyrene. A high molecular weight polystyrene (Piccolastic, E-125, Hercules) and a low molecular weight polystyrene (Piccolastic, D-100) were investigated.

A general-purpose polystyrene (Huntsman, polystyrene 208), a crystal polystyrene, is also used. These were mixed in a Brabender at 3252E (I632C) in different proportions with polylactic acid.

The proportions of polystyrene / polylactic acid used were 100 / O for the comparison sample, s of 90/10; and 75/25 for Huntsman 203 general purpose polystyrene.

Two types of polyethylene terephthalate (Clearstuff from Goodyear and Kodapak TN-0148 from Eastman) were used. These were dried overnight at 90 ° C and were combined by melting at 525 °? (275 ° C) in a Brabender with polylactic acid for just a few minutes. The polylactic acid reduced the melt viscosity.

EXAMPLES 8 C to 16 C

The comparison samples and those combined with polypropylene, general purpose polystyrene and polyethylene terephthalate (from Eastman) of Examples 20 to 7 C were ground in an Abbey mill and molded by compression into small particles of approximately 5,000 (125 um). Polylactic acid-polypropylene films were molded at about 400 °? (200 ° C); polylactic acid-polystyrene films were obtained at 25G-300 ° E (12C-150 ° O); films of polylactic acid-polyethylene terephthalate were molded at about 525 °? (275 ° C).

After conditioning them to an h.r. 50 percent and 23 ° C for 24 hours were tested on Instron. Comparison samples were treated similarly. Samples of the compression-molded film were placed on an Atlas Aeatner-0-Meter to assess resistance to weather conditions (cycles of 1C2 minutes of sun and 18 minutes of rain). The results for these Examples are shown in Table 1 C.

EXAMPLES 17 0 to 19 C

Three samples of 100 percent polylactic acid are prepared using poly- (E, L-lactic acid) as described above, but the film thickness is 10 to 15 mil (250 to 380 µm). Tests were carried out as in Examples 20 0 at

C, below, except that the second sample is tested after 82 hours of exposure to 50 percent relative humidity at 72 ° F (22 ° C).

EXAMPLES 20 0 to 27 0

High density polyethylene, HDPE (0.960 g / cm ^), was combined with polylactic acid in the Brabender Plasticorder at 1519C for 10 minutes. Combination ratios of 137 high density polyethylene of polylactic acid were used from 100 / O to the comparison samples, 9θ / ΐθ, 80/20 and 50/50 ° Two samples of each are prepared. The combinations were ground in an Abbey mill and compressed into 10 to 15 mil films (250 to 3θ0 µm) _o The films were tested in an Atlas Weather-O-Meter prepared for 51 minutes of arc light - carbon and 9 minutes of water spray. It was possible to vary the temperature from room temperature to 140 ° ΐ (60 ° C) _o Tensile strength and extension tests were carried out until yield and traction break classification for the samples, as shown in Table 2 0.

EXAMPLES 28 C to 35 0

Low density polyethylene, PE3D (0.917 g / cnr), was combined with polylactic acid in Brabender Plasticorder at 151 ° C for 10 minutes. Proportions of combinations of low density polyethylene / polylactic acid of 100 / O were used for comparison samples 90/10 and 50/50. Two samples of each were prepared. The samples were treated and evaluated as in the case of Examples 20 0 to 27 C _o The results are shown in Table 2 C „

EXAMPLE 34 0

They were placed in a 500 ml three-necked round-bottom flask, equipped with a mechanical stirrer and a nitrogen inlet and outlet, 180.7 g of L-lactide and 40.2 g

of D, racemic L-lactide (both from Boehringer and Ingelheim, grade S).

The contents of the flask were heated to 110 ° C under a nitrogen purge to melt the lactides and 20.1 g of polystyrene (amoco 23, melt index 3.5 g / 10 min) was added. 0 polietireno swelled enough and partially dissolved while stirring an overnight and warming to increased I852O ₀ up lowered the temperature to 141 ^ 0 and added to 0.2 ml of bivalent tin octoate solution anhydrous (0.2 ml / ml toluene) »The shaker was turned off and the lactides were allowed to polymerize at 1413 ° C for a period of 3 days. The highly swollen polystyrene floated to the surface after the agitator was turned off. The lower polylactic phase was cooled and examined using differential scanning calorimetry (DSC). The sample has a low Tg, approximately 35-θ, and on the other hand, it lacks apparent temperature transitions. Compression-molded films are clear, colorless and very flexible. These results indicate that polystyrene completely stops the formation of crystallinity under these conditions.

EXAMPLE 35 C

It was combined in a polylactic acid roller mill with crystal polystyrene. The combination revealed excellent compatibility of polystyrene dispersed in polylactic acid. In this way, 5 weight percent polystyrene was dispersed in a 90/10 ratio of racemic L- / D, L-lactide copolymer in a two-roll mill at 170 ° C. The material became cloudy and exhibited considerable crystallinity by thermal analysis.

This example demonstrates that under these conditions polystyrene easily induces crystallinity in polylactic acid. A thermal analysis of the material, see Eigura 13, reveals that it remains crystalline, even when heated and cooled.

Examples 34 C and 35 C illustrate that acid - 85

polylactic combined with the non-degradable plastics referred to above can produce final properties in the mixture, depending on the mixing technique or combinations used.

Fusion combinations of all types in Brabender exhibited small heterogeneous particles 10 microns in size or less. Tensile strengths were determined before and after aging by exposure to simulated weather conditions. After 1248 hours (52 days) in the Atlas Weather-O-Meter, all polypropylene samples were whitish and extremely brittle and it was not possible to test them. The polypropylene samples were re-tested at smaller intervals, as shown in Table 1 C. At approximately 300 hours of aging in the Atlas Weather-O-Meter, the samples showed significant environmental degradation.

The combinations of polystyrene with polylactic acid showed environmental degradation that was evident after 300 hours of simulated aging. The polyethylene terephthalate combinations were also visibly degraded environmentally in approximately 300 hours

TABLE 1 Q

RESISTANCE TO FILM TRACTION BEFORE, AND AFTER ACCELERATED AGING (a)

Combination ratio and Material ' Resistance traction ( °) /% elongation Then h Before 310 400 yo / o pp / pla (°) 1665/61 585 / 1.6 494 / 1.7 90/10, PP / PLA 1568/51 954 / 3.2 346 / - 75/25, PP / PLA 1124/14 370 / 1.1 254 / 1.0 100/0 PP / PLA ( 3200 / 2.0 1066 / 1.0 - M

TABLE 1 O (Continued)

90/10, PS / PLA 2350 / 2.0 532 / 1.0 - - 75/25. FS / PLA / 1493 / 1.6 434 / 1.0 - - 100/0 PET / PLA ^{<e /} 3036 / - 3509 / 3.0 - - 90/10, pet / pla 2147 / - 1378 / 3.0 - - 75/25, PET / PLA 2743 / - 2041 / 3.0

(a) Weather-C-Meter, 102 minutes of sunshine, 18 minutes of rain (b) 0.05 in / min. (1.27 mm / min), Instron (o) Polypropylene Hercules 825 (d) Huntsman 208 (e) Tennessee Eastman, Kodapak T.N 0143

Polylactic acid, high density polyethylene, low density polyethylene and their combinations were evaluated to determine physical strength before and after simulated aging, and the results are shown in Table 20.

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TABLE 2 C

PHYSICAL PROPERTIES OF POLYETHYLENE (PE), POLYLACTIC ACID (PLA) AND THEIR MIXTURES BEFORE AND AFTER EXPOSURE TO WEATHER-0-METER

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TABLE 2 Q (ONGOING PAOBS!

S®35 polylactic acid and its combinations were much more degradable in the environment than pure low or high density polyethylene. High density polyethylene samples degraded substantially without weight loss, while high density polylactic acid-polyethylene combinations showed weight loss, particularly in cases where the microscope revealed that polylactic acid was exposed on the surface of the films. The high density polyethylene was graduated by exposure to actinic light, as seen under a microscope.

With all samples, the increase in the percentage of polylactic acid lowered the tensile strength before and after simulated aging. The incorporation of polylactic acid introduced introduced rapid degradation in the combinations of polypropylene, polystyrene, polyethylene taraphthalate and high and low density polyethylene. Presumably, actinic light, like polyester hydrolysis, degrades the polymer. The small spherical microheterogeneous extensions of the combination are undoubtedly of polylactic acid, which is almost iritically covered. Consequently, hydrolysis of polylactic acid is slow. Faster degradation can be achieved through hydrolysis by controlling the position of polylactic acid. This fact, in contrast, is related to the combination rheology during melt combinations.

small size of the dispersed heterogeneous extensions indicates good compatibility of the mixed polymers.

In a simulated landfill, where light is excluded, comparison samples and combinations show much lower rates of degradation. Only with hydrolysis will the samples of polylactic acid slowly turn white, while combinations remain qualitatively unchanged during the test period.

Conversely, the addition of smaller amounts of non-degradable thermoplastics to polylactic acid to form compatible combinations, using, for example, polypropylene, polystyrene, polyethylene terephthalate and high or low density polyethylene, will delay the rate of polylactic acid degradation, A preferred composition range is 80-99 per cent by weight polylactic acid.

A general description of the degradable composition in the environment comprises combinations of a physical mixture of polylactic acid (polylactide) and a polymer selected from the group consisting of an ethylene terephthalate polymer, a polymer or copolymer of styrene, ethylene, propylene, vinyl chloride, vinyl acetate, alkyl methacrylate, acrylate, and mixtures thereof. Other possible combinations of composition are referred to below in the discussion of embodiments of the process of the invention.

. The combinations preferably use a physical mixture of polylactic acid of formula I, where n is an integer between 75 and 10,000; and a polymer selected from the group consisting of polystyrene, polyethylene, polyethylene terephthalate and polypropylene and other compositions discussed below. A preferred composition is one in which polylactic acid constitutes 5 to 50 weight percent of the composition. A preferred composition has a polylactic acid content of 10 to 20 weight percent.

The polymers selected from the previous group, considered the added polymer, can be used alone or in combination. The group is not restricted to those mentioned above, since other types of polymers are said to be compatible with polylactic acid. These include polymers and copolymers made from the group of ethylene, propylene, styrene, vinyl chloride, vinyl acetate, alkyl methacrylates and alkyl acrylates. It should be understood that the

The term copolymers in the sense given in the present specification includes polymers made from mixtures of the monomers of the said group. Physical mixtures of the polymers and copolymers of the above group are also useful in the invention.

The third embodiment further provides a process for preparing a composition that includes: providing a polylactic acid; selecting a polymer from the group consisting of a polymer of ethylene terephthalate, a polymer or copolymer of styrene, ethylene, propylene, vinyl chloride, vinyl acetate, alkyl methacrylate, alkyl acrylate and respective physical mixtures; and combine the polymers. The combination can be made by mixing by melting in a roller mill or by composition in an extruder or by any other mechanical means. The polylactic acid provided preferably has formula I.

This embodiment further provides a process for the composition of the invention which includes providing a lactide selected from the group consisting of D-lactide, 1-lactide, meso-D, L-lactide, D, racemic L-lactide, and mixtures thereof. ; selecting a polymer from the group consisting of polymers or copolymers of styrene, ethylene, ethylene terephthalate, propylene, vinyl chloride, vinyl acetate, alkyl methacrylate; alkyl acrylate and respective physical mixtures.

The selected lactide and polymer are mixed and heated to melt the lactide and at least partially dissolve the polymer. Finally, the lactide is at least partially polymerized in order to obtain a combination of polylactide, non-polymerized lactide monomer and the selected polymer. Preferably, the polymerization is controlled by regulating the amount of lactide remaining and stopping the polymerization at the desired level. If desired, the polymerization can be carried out until the end. Monomeo can be added

- 92 of additional lactide, lactic acid, lactide oligomer, lactic acid oligomer and mixtures thereof, in quantities which provide flexibility, as plasticizers in order to obtain desired characteristics, as taught in the first general embodiment.

It will be apparent to those skilled in the art that the proportions of polylactic acid and added polymer can vary widely, depending on their mutual solubilities, The solubilities, on the other hand, vary with the effectiveness of the mixture and its temperature. While placing the polylactic acid and the added polymer in a mutual solvent solution will result in homogeneity, the use of solvent is not practical for many commercial processes »Physical mixing, such as melting in a roller mill or in an extruder, it is more practical, but it must be controlled to achieve homogeneity, that is, high cutting effort is required to achieve the desired homogeneity »Even with intimate mixing, different polymers may not be compatible, that is, they may continue to separate * if in relatively large heterogeneous extensions with a dimension, for example, 10 to 100 microns, or larger. Consequently, a curd mixture or a combination with weak properties is obtained »What is surprising is that polylactic acid is easily compatible by combining with a wide variety of other polymers, including polar and non-polar polymers»

The temperature of the combination can be varied by melting the polylactic acid with other polymers to adjust the proportions of the polylactic acid with one or more additional polymers »At lower temperatures, the solubilities may not be suitable, while a very high temperature will cause the mixture to decompose _o A normal temperature range is 100 to 220 ° C, the preferred range is 130 to 1802 «,

The viscosities are also significant in melting the different polymer components »The viscosities increase rapidly with increasing molecular weight. By controlling the proportions of the polylactic acid and the polymer, or polymers, added, the temperature, the type and the mixing time and the molecular weight, a wide range of mixtures can be obtained.

In this way, for example, polylactic acid can be dispersed in the added polymer or polymers, or vice versa, and the size and geometry of the dispersed phase can vary widely, ranging from discrete spheres to fibers of different diameters or lengths .

This results in a wide variety of physical properties and degradation time in the environment. The weight percentage ratio between the polylactic acid and the selected polymer can be between 99 ^; 1 and 1 = 99 ·

When the lactide monomer is used to dissolve the added polymer and the lactide is subsequently polymerized, the mixing and polymerization temperature must be balanced between the mutual solubilities and the lactide reactivity. Higher temperatures normally produce lower molecular weight polylactic acid. Another embodiment of the invention consists of mixing at one temperature and polymerizing at another temperature to achieve variations in the geometry of the dispersed phase, as discussed above.

The compositions inserted here can be processed by melt-making into useful articles of manufacture having a self-contained structure, such as disposable containers, cutlery, trays, plates, cups, single-use trays, syringes, medical trays, packaging films and the like. The compositions are useful in that they can have the characteristics of normal plastics and, therefore, replace them, however degrading in the environment. Compositions are especially useful for single-use articles or those with a short shelf life before being discarded

FOURTH FORM OF GENERAL OGNCRETIZATION

Within the other form cR: oneretization of the invention are included;

elastomers is what they are <

imue or sac modifiers compatible with fuses with polylactic acid. By melting compatible, it is intended to mean all polymers that can be intimately mixed with polylactic acid, as discussed in the third general embodiment. The mixing results in a substantially homogeneous combination.

The environmentally degradable compositions disclosed herein are, at least, partially degradable. That is, the polylactic acid portion of the composition will decompose relatively quickly compared to the combination portions and will cause

M3.C The most stable and homogeneous physical composition of the material in this example, when the compositions are intimate mixtures with small dimensions, the physical deterioration will destroy the product originally formed. The compositions inserted here provide environmentally acceptable materials, because their deterioration and physical degradation is much faster than that of conventional non-degradable plastics.

In addition, since a large portion of the composition will be polylactic acid, and / or a lactic acid-derived milk or oligomer, only a small portion of the slower degrading elastomer residue (e.g. segmented polyester) will remain. This residue will be an extensive exposed surface and is supposed to decompose more quickly than a block-formed product.

The examples below show the combination of polylactic acid (PLA) with a Hy-trel ^-1 · *, a segmented polyester that is a block copolymer of hard crystalline segments of polybutylene terephthalate and soft chain segments.

long polyether glycol. Polylactic acid is shown to be compatible in fusion with this elastomer and the effect on its physical properties is shown.

D-lactide is a dilactide, or cyclic dimer, of D-lactic acid. Similarly, l-lactide is a cyclic dimer of L-lactic acid. The meso-B 'L-lactide is a cyclic dimer of D- and 1-lactic acid. The comical D, L-lactide comprises a 50/50 mixture of D- and L-lactide. When used alone in this specification, the term D, L-lactide is intended to include the meso-D, L-lactide or the racemic D, l-lactide. Polylactic acid can be prepared from one or more of the mentioned intermediates.

SXEMFLO 1 D

A polylactic copolymer without segmented polyester Rytrel ^{x was} prepared using the procedure of Example 1 B of the second general embodiment of Serial No. 229 939 and tested for Izod impact strength. The results are shown in Table 1 D. For a more complete comparison, Table 1 B of the second general embodiment records Izod's impact resistance of other proportions between the L-lactide and the DL lactide.

EXAMPLE 2 D

Weigh into a 250 ml 3-neck round-bottom flask 10.96 g of D, L-lactide, 108.86 g of L-lactide and 5.27 g of segmented polyester Hytrel ™ 4056 (Du Pont, a thermoplastic elastomer). Kytrel 40 * 56 segmented polyester and a polyester elastomer with a low Shore D durometer flexure module, a high melt viscosity, a melt index of 7, a density of 1.17, a m.p. 3342? (16820), a Vicat softening temperature of 2342? (1122C) and an extrusion temperature of 3402? at 4002? (170 ° C to 20020). The balloon is equipped with a mechanical stirrer and

a nitrogen inlet and outlet. The contents are heated through an oil bath. 0 segmented polyester Hytrel ^T ^ dissolves in the molten lactide at 170 ^ ^2. A catalyst solution is prepared by dissolving 10 ml of divalent tin octanoate in 60 ml of toluene and distilling 10 ml in toluene. A 100 microliter portion of the catalyst solution is injected into the lactated and segmented polyester solution Hytrel Agit O. ™ if the mixture is mixed under nitrogen at 155 ° C for approximately 64 hours.

The viscosity increases rapidly and the mixture becomes cloudy. The product is hard and opaque. They are shaped by compressing films 8 to 9 mil (200-230 æm) in thickness at 155 ^ ⁵ and measured tensile properties are as shown in Table 1 D.

1/8 inch (approximately 3.2 mm) thick plates were molded by compression and their Izod impact strength was measured using a 2-pound (0.907 kg) pendulum. The results are recorded in Table 1 D , which compares the data with a polylactide copolymer semez lar ^m m D of Example 1 without polyester, and Hytrel segmented data to the called medium impact polystyrene, Example 7D.

EXAMPLE 3 D

800.0 g of L-lactide and 202.3 g of D, racemic L-lactide are copolymerized using 1.0 ml of the catalyst solution using methods similar to those of Example 2 D,

ΤΤΊ f / omitting Hytrel segmented polyester. The lactide copolymer is clear and colorless. In a separate polymerization, 104.0 g of L-lactide are polymerized by melting, using 100 microliters of catalyst. The polymer (L-PLA) is white, crystalline and breaks easily when struck.

A 375 ² ^ (19O ² C) electrically heated two-roller mill was heated, then

- 97 lac-

the roll 8.4 g of polyester, segmented Hytrel ¹ and 19.2 g of L-PLA. To this mixture was added 172.4 of the tide copolymer <> The mixture becomes easily homogeneous and is removed from the rolls, molded and tested, as in Example 2 D. The data are recorded in Table 1 D.

EXAMPLE 4 D lactide copolymer of Example 3 D, 80 g the L-PLA of Example 3 D, 10 g, and 10 g of segmented polyester TM

4056 Hytrel are combined in a two-roller mill, as described previously in Example 3 D. The combination was tested as before. The data are recorded in Table 1 D.

EXAMPLE 5 D

100 g of the combination of Example 3 D was combined with an additional 20 g of 4056 Hytrel segmented polyester. The combination easily mixed on the roll and was apparently quite compatible. Physical properties were measured as described above and recorded in Table 1 D.

EXAMPLES 6 D and 7 D

Typical crystal polystyrene and medium tax polystyrene were tested and used for comparative controls.

The above-mentioned results clearly indicate that they can modify polylactides for impact resistance. The combinations provided Izod's impact strengths significantly higher than the control of crystal polystyrene and gave slightly lower or equivalent impact strengths compared to medium impact polystyrene. Those skilled in the art will recognize that the impact resistance data in Table 1 D can be further improved by optimizing the amount and type of impact modifier.

- 98 Since polylactides were previously shown in the third general embodiment described above to be compatible in combination with numerous other components and thermoplastics, the process of modifying polylactides to provide impact resistance is generic for polylactide mixtures and elastomers that are compatible in fusion. Likewise, those skilled in the art will recognize that the data in Table 1 D will improve when the combinations are injection molded, as opposed to compression molding, since the former often induces orientations of the species and, consequently, a profound improvement in impact resistance.

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Compositions are useful thermoplastics that can be melted by conventional processes, such as extrusion and molding »

The combinations preferably use a physical mixture of polylactic acid of formula I, where n is an integer between 75 and 10,000; and a polymer comprising a segmented polyester. A useful composition is one in which polylactic acid constitutes 50 to 95 weight percent of the composition. A preferred composition has a polylactic acid content of 70 to 80 weight percent.

Two embodiments of the general process for producing the composition include (l) melt combination of PDA with a compatible melt polymer that provides improved impact resistance, such as a segmented polyester, and (2) solution combination during polymerization of PIA as in Example 2 D, in which segmented Hytrel polyester is dissolved in PLA _The polylactic acid provided preferably has the formula I »If desired, plasticizer can be added in quantities that give malleability to the combination that is selected from the group consisting of lactide monomers, lactic acid oligomer, lactic acid, and mixtures thereof. The addition of the plasticizer will provide additional unique physical properties, as previously described in the first, second and third general embodiments »microscopic examination of the Hytrel segmented polyester / polylactic acid mixture revealed that the dispersed segmented Hytrel polyester is present in small spherical extensions , a few microns in size or less. These extension dimensions can be adjusted through mixing conditions such as time, mixing speed and temperature.

-, 102 -

Consequently, for example, the polymer or polymers added to the polylactic acid should generally be small in size, heterogeneous in length, less than 10 microns, and may be submicroscopic or dissolved in the acid of the polylactic. In addition, this impact modifier must be elastomeric.

Although it is not intended to be restricted to any particular theory, it is believed that the present invention provides a continuous matrix of polylactic acid containing microscopic extensions intimately mixed of Hytrel segmented TM polyester that act as crack arresters, since the latter is a thermoplastic elastomer compatible with polylactic acid.

To this end, the impact modifier must be elastomeric and must be closely linked to polylactic acid in the form of a discrete heterogeneous phase. The added polymer, the impact modifier, can be a thermoplastic elastomer, or a crosslinked rubber, to achieve this elastic behavior. Suitable examples are natural rubber and styrene-butadiene copolymers.

In a test of material placed in water for five months, the material became brittle compared to a material not exposed to water _o Additionally, the water became acidic indicating a chemical decomposition of the polylactic acid giving lactic acid. It was also evident that the isolated polylactic acid degraded more quickly than the Hytrel segmented polyester / polylactic acid mixture. In this way, Hytrel segmented polyester can also be used to delay the degradation rate of polylactic acid.

A third component can be added that is compatible with the other components mentioned above.

earlier to achieve improved compatibility. Thus, when polylactic acid and impact modifier have poor compatibility, a third component can be added to improve compatibility. This third component is usually added when it is compatible with the other two individually, and when the other two, the polylactic acid and the impact modifier, are not very compatible. The desired effect is achieved by increasing the interfacial bond between polylactic acid and the elastomeric impact modifier. However, what is surprising is the vast extent of compatibility of polylactic acid with other types of polymers, both polar and non-polar. This circumstance can be referred to in the third general embodiment.

The compositions inserted here can be processed by melt transformation into articles of manufacture such as containers, cutlery, trays, plates, cups, single-use trays, syringes, medical trays and the like. The compositions are particularly useful for articles of single use or with a short period of useful life before being discarded.

Although the invention has been described above with reference to several specific examples and embodiments, it should be understood that the invention is not limited to such illustrated examples and embodiments and can be practiced in various ways within the scope of the claims set out below .

Claims (3)

- 1§ Process for the preparation of a biodegradable composition in the environment of polylactic acid characterized by comprising the phases of: 104 a. Prepare a lactide monomer and a catalyst; b „polymerize the monomer from phase (a) to form a polymer at a temperature sufficiently below 3 - 3 × X * 3. ρΘ3? [ΓΪ1 · allow the reaction to be stopped before complete polymerization; ç. monitor the level of the monomer in step (b); determining the amount of the remaining monomer; and d. stop the polymerization of step (b) before completing the reaction for an amount of monomer determined in step (c) so that the unreacted monomer in a predetermined amount is fixed in association with the polymer. 2. A process according to claim 1, characterized in that the obtained composition, useful as a substitute for thermoplastic polymer compositions, contains a polymer of the formula: -t— c - G - 0 -) · I H that is plasticized with a plasticizer selected from the group consisting of lactide, lactic acid oligomers, lactide oligomers and mixtures thereof, in which the number of repeated units and a whole number, 150 <n <20 000, and composition not oriented has a tensile strength of 300 to 20,000 psi (21 to 1400 kg / cm), a breaking strength of 50 to 1000 percent and a tangent modulus of 20,000 to 250,000 psi (1400 to 17580 k ^ cm ² ). Process according to claim 1, ca · - 105 - characterized by the polymer being derived from lactide monomer selected from the group consisting of l-lactide, D-lactide, meso-D, L-lactide and mixtures thereof. Process according to claim 1, characterized in that the lactic acid or lactide oligomers have the formula: CH, 0 I ⁵ I + - 0 - o - o -}. _m H where m ó an integer: 2 S m S 75. - ₅ ã _ Process according to claim 1, characterized in that the composition obtained additionally contains one; plasticizer dispersed among the composition that is selected from the monomer group consisting of D-lactide, L-lactide, meso-D, l-lactide, D, racemic L-lactide and their mixtures in such a way that at least part of the dispersed monomer and stereochemically different from that used in the preparation of the polymer. 6. A process according to claim 1, characterized in that the composition obtained additionally contains an oligomer dispersed among the composition which is not produced during polymerization of the polymer. - 7th „ Process according to claim 1, 106 characterized by additionally understanding the phase of: and. additonally incorporate a plasticizer in the composition, the plasticizer being further selected from the group consisting of L-lactide, D-lactide, meso-D, L-lactide, lactic acid, lactide oligomers, lactic acid oligomers and mixtures thereof. 83. The method of claim 7, further comprising the step of selecting a monomer that is stereochemically different from that selected to prepare the polymer. - 9a Process for the preparation of a biodegradable composition of pclilactic acid characterized by comprising the phases of: The. preparing the lactide monomer and catalyst; B. polymerizing the monomer of the solution from step (a) to form a polymer; and ç. incorporate a plasticizer in the polymer of step (b), being plasticizer selected from the group consisting of D-lactide, L-lactide, D, L-lactide, lactic acid oligomers, lactide oligomers and mixtures thereof. - 103 Process for, in a thermoplastic polymer composition that contains orientable units of a first polymer, to make the composition biodegradable in the environment characterized by comprising the phases of: replace the first polymer units with a second orientable polymer that has a resistance to - 10 7 non-oriented traction from 300 to 20,000 psi (21 to 1400 hg / cm), a break length of 50 to 1000 percent and a tangent modulus from 20,000 to 250,000 psi (1400 to 17 580 kg / cm ² ); the second polymer containing polylactic acid units of the formula: CH, 0 i ⁵ il - c - o-4 _n H where η ό the number of repeated units and η ó an integer, 150 - n - 20 OCO and ó plasticized with a plasticizer selected from the group consisting of lactide, lactic acid oligomers, oligomers lactide and mixtures » - 11 ^ Process for, in a polyolefin composition containing orientable units of a first polymer, to make the biodegradable composition in the environment characterized by comprising the phases of: replace the first polymer units with a second orientable polymer that has a non-oriented tensile strength of 300 to 20,000 psi (21 to 1400 kg / cm), a breaking strength of 50 to 1000 percent and a tangent module from 20 COO to 250,000 psi (1400 to 17 580 kg / cm ² ); containing the second polylactic acid unit polymer of the formula: CH0 il o 108 where n is the number of repetition units and n is an integer number, 150 í n C. 20 000 e and plasticized with a plasticizer selected from the group consisting of lactide, lactic acid oligomers, lactide oligomers and mixtures thereof - 12 & Process for the preparation of a biodegradable composition in the environment useful as a polystyrene substitute that contains polylactic acid units of the formula; II where n is an integer between 75 θ 10,000 and carbon al fa ó a mixture of configurations 1 and D with a preponderance of either L or D units, the polymer being prepared from L-lactide or of D-lactide at 85 to 95 parts by weight, and D, L-lactide at 15 to 5 parts by weight, with the non-oriented polymer having a tensile strength of at least 5000 psi '(350 kg / crn) and a modulus tangent of at least 200,000 psi (14,000 kg / cm) and plasticizer dispersed from 0.1 to 5% by weight, characterized by comprising the phases of: The. mix with a catalyst, heat and melt L-lactide or D-lactide monomer and D, l-lactide monomer, with the proportion of L-lactide monomer or D-lactide monomer from 85 to 95 parts by weight 15 to 5 parts by weight of the monomer of D, L-lactide, in order to form an intimate solution; B. polymerize the solution of step (a); and O. treating the polymer of step (b) to improve its properties. Process according to claim 12, characterized in that the obtained composition additionally contains monomer dispersed in the composition selected from the group consisting of D-lactide, L-lactide, 'meso-D, L-lactide, D, L-lactide racemic and mixtures thereof such that at least part of the dispersed monomer is stereochemically different from the monomer used to prepare the polymer. 14. A process according to claim 12, characterized in that the composition obtained additionally contains oli · genera stereochemically different from that obtained during the polymerization of the polymer. - 15 & Process for the preparation of a biodegradable composition in the environment useful as a polystyrene substitute characterized by physically mixing: The. a first polymer that has polylactic acid units of the formula: ch ₇ 0 r ii - (- 0-0-0 -> I H where n is an integer between 75 θ 10 COO and alpha carbon is a mixture of L and D configurations with a preponderance of both D units and L units; and B. a lactide homopolymer of D-lactide or L-slab; and where the non-oriented composition has a 110 - tensile strength of at least 5000 psi (350 kg / 2 z / cm) and a tangent modulus of at least 200,000 psi (14,000 kg / cnT) and dispersed plasticizer. The process according to claim 15, characterized in that the composition obtained additionally contains plasticizer dispersed in a weight percentage of 0.1 to 5%. 176. The method of claim 15, wherein the polymerized lactic acid in the composition obtained is present in an amount of 93 to 75 weight percent and the lactide homopolymer is present in an amount of 2 to 25 weight percent. . - Process according to claim 15, characterized in that the composition obtained additionally contains a pesticide, which is selected from the group consisting of D-lactide, L-lactide, meso-D, L-lactide, lactic acid, oligomer of lactide, lactic acid oligomer and their mixtures. - Process according to claim 15, characterized in that the composition obtained additionally contains plasticizer, which is selected from the monomer group consisting of D-lactide, L-lactide, meso-L, L-lactide, D, L- racemic lactide and mixtures thereof such that at least part of the dispersed monomer is stereochemically different from that used to prepare the first polymer and the homopolymer. 111 - Process according to claim 12, characterized in that the treatment comprises the addition step by mixing a copolymer of D-lactide or L-lactide. 21. The method of claim 12, wherein the treatment comprises the addition step by mixing a nucleating agent and a polymer of D-lactide or L-lactide. - 22 * „ Process according to claim 12, characterized in that the treatment additionally comprises the stages of: The. controlling the polymerization of step (b) by adding chain transfer agents; and B. add nucleating agents and a homopolymer of D-lactide or L-lactide per mixture. 23. The method of claim 12, further comprising the treatment step by adding additional plasticizer to the composition, the plasticizer being selected from the group consisting of D-lactide, -U-lactide, meso-D, L -lactide, lactic acid, lactide oligopolymer, lactic acid oligopolymer and mixtures thereof. - Process according to claim 12, characterization per, when at least one monomer is selected 112 - a monomer is stereochemically different from the micromer (s) selected in step (a). - 25- Process for making a moplastic polymer composition containing orientable units of a first polystyrene, making the composition biodegradable in the environment characterized by comprising the phase of: replace the polystyrene units with a second orientable polymer that has a non-oriented tensile strength of at least 5,000 psi (550 kg / cm), and a tangent modulus of at least 200,000 psi (14,000 kg / cm) and plasticizer dispersed in a weight percentage of 0.1 to 5 ^: comprising the second polymer, polylactic acid units of the formula: 3- c - Q - oT _n T i ^_ l where n is an integer between 75 θ 10 000 and alpha carbon is a mixture of configurations 1 and D with a preponderance of either D units or L units, the polymer being prepared from L-lactide or D-lactide at 85 to 95 parts by weight and D, L-lactide at 15 to 5 parts by weight. - 26 »Process for the preparation of a biodegradable composition in the environment that contains a physical mixture of: to «a polylactic acid; and B. a polymer selected from the group consisting of an ethylene terephthalate polymer, a polymer or copolymer of styrene, ethylene or propylene, vinyl chloride, vinyl acetate, alkyl methacrylate, alkyl acrylate and their physical mixtures; - 113 characterized by comprising the phases of: The. taking a polylactic acid; B. selecting a polymer from the group consisting of a polymer of ethylene terephthalate, a polymer or copolymer of styrene, ethylene or propylene, vinyl chloride, vinyl acetate, alkyl methacrylate, alkyl acrylate and their physical mixtures; and O. mixing the polymers of steps a and b. 27. The method of claim 26, wherein the weight percent ratio of polylactic acid to the selected polymer is a ratio of 99 ^: 1 to 1:99. 28. The process according to claim 26, characterized in that the composition obtained additionally contains a plasticizer which is selected from the group consisting of D-lactide, L-lactide, meso-D, l-lactide, lactic acid, lactide oligomer, lactic acid oligornerc and mixtures thereof. - 29- Process for the preparation of a biodegradable composition in the environment characterized by comprising 'the phases of: The. take a lactide monomer selected from the group consisting of D-lactide, L-lactide, meso-D, L-lactide, D, L-racemic lactide and mixtures thereof; bo select a polymer from a group consisting of an ethylene terephthalate polymer, a polymer or copolymer of styrene, ethylene or propylene, vinyl chloride, vinyl acetate, alkyl methacrylate, alkyl acrylate and their physical mixtures; ç. mixing and heating the lactide selected in (a) and the polymer selected in (b) under conditions suitable for melting the lactide and at least partially dissolving the polymer; and d. polymerize the lactide in the mixture of step (c) to obtain a mixture of polylactide and polymer. 30. The method of claim 29, further comprising the step of: and. form a self-supporting structure with the mixture. Process according to claim 29, characterized in that it further comprises monitoring the amount of monomer remaining and controlling the polymerization of step (d) to obtain a mixture containing residual monomer. 32. The method of claim 29, further comprising the step of: and. add plasticizer selected from the group consisting of lactide monomer, lactide oligomer, lactic acid oligomer, lactic acid and their mixtures, to the mixture after polymerization. - 33§ Process for the preparation of an environmentally degradable composition that contains a physical mixture of: - 115 - The. a polylactic acid; and b „a polymer compatible with the mixture that provides improved impact resistance to polylactic acid, characterized by comprising the phases of: The. taking a polylactic acid; B. selecting a polymer compatible with the mixture that provides improved impact resistance to polylactic acid; and ç. mix the polymers of phases (a) and (b) _the 34. The method of claim 33, wherein -6 polylactic acid constitutes 50 to 99 weight percent of the composition. 35. The method of claim 33, wherein the polymer compatible with the mixture is a segmented polyester. 365. The method of claim 35, characterized in that the polymer compatible with the mixture is a block copolymer of hard crystalline segments of polybutylene terephthalate and soft segments in long chain of polyether glycol. 37. The method of claim 53, wherein a segmented polyester is selected. 385 Process according to claim 33, characterized in that a block copolymer of hard crystalline segments of polybutylene tereitalate and soft segments in long chain of polyether glycols or natural rubber and styrene-butadiene copolymers is selected. . - 39- Process for the preparation of an environmentally degradable composition that contains a physical mixture of: The. a polylactic acid; and B. a polymer compatible with the mixture that gives improved resistance to impact to polylactic acid, characterized by comprising the phases of: The. mixing one or more lactides selected from the group consisting of D-lactide, L-lactide, D, L-lactide and their mixtures with a polymer compatible with the mixture which gives the composition improved impact resistance; B. heating and dissolving the polymer compatible with the mixture in the lactide (s) of step (a) to form a solution; and ç. polymerize the lactide (s) in the solution. 40. The method of claim 39, further comprising the step of forming useful forms from the composition obtained by melting. - Process according to claim 59, characterized in that it further comprises: selecting a piece of limestone compatible with the mixture containing a polyester segmented A process according to claim 39, characterized in that it further comprises the selection of a polymer compatible with the mixture consisting of a block copolymer of hard crystalline segments of polybutylene terephthalate and soft long chain segments of polyether glycols and natural rubber and styrene-butadiene copolymers or a mixture of these components. 43. The method of claim 35, further comprising the phase of: and. addition of plasticizer to the mixture selected from the group consisting of lactide monomer, lactide oligomer, lactic acid oligomer, lactic acid and mixtures thereof.