HK1118845B - Biodegradable aliphatic-aromatic polyesters - Google Patents

Description

Biodegradable aliphatic-aromatic polyesters

The present invention relates to biodegradable aliphatic-aromatic polyesters (AAPE) obtained from long-chain aliphatic dicarboxylic acids, polyfunctional aromatic acids and diols, and mixtures of said polyesters with other biodegradable polymers of natural or synthetic origin.

Biodegradable aliphatic-aromatic polyesters obtained from dicarboxylic acids and diols are known in the literature and are commercially available. The presence of aromatic components in the polyester chain is important to obtain a polymer with a sufficiently high melting point and an acceptable crystallization rate.

Although such polyesters are currently commercially available, the amount of aromatic acids in the chain is generally below 49% because above the threshold the percentage of biodegradation of the polyester is significantly reduced. It is reported (Muller et al, Angew. chem., int., Ed. (1999), 38, pp.1438-1441) that copolymers with a mole fraction of 42 mol% of terephthalate of the polybutylene adipate-co-terephthalate type biodegrade completely to compost after twelve weeks, whereas products with a mole fraction of 51 mol% of terephthalate show a percentage biodegradation of less than 40%. This different behavior is attributed to the formation of a higher number of butylene terephthalate sequences greater than or equal to 3 in length, which are less biodegradable. However, if it is possible to maintain suitable biodegradability properties, an increase in the percentage of aromatic acids in the chain is desirable, since this will cause an increase in the melting point of the polyester, an increase or at least maintenance of important mechanical properties (such as ultimate strength and elastic modulus), and will also cause an increase in the crystallization rate of the polyester, thereby improving its industrial processability.

Another drawback of the currently commercially available biodegradable aliphatic-aromatic polyesters is represented by the fact that: the monomers that constitute them are derived from non-renewable sources, thus maintaining the significant environmental impact associated with the preparation of such polyesters, despite their biodegradability. They have much more energy content than LDPE and HDPE, especially in the presence of adipic acid. On the other hand, the use of monomers of plant origin will contribute to the reduction of CO₂Emissions in the atmosphere, and reduced use of monomers derived from non-renewable resources.

U.S. patent 4,966,959 discloses certain copolyesters comprising 60 to 75 mole percent terephthalic acid, 25 to 40 mole percent aliphatic or cycloaliphatic carboxylic acid, and a diol component. Such polyesters have an intrinsic viscosity (intrinsic viscosity) of about 0.4 to about 0.6, making the polyesters useful as adhesives but unsuitable for many other applications.

U.S. Pat. No. 4,398,022 discloses copolyesters comprising terephthalic acid and 1, 12-dodecanedioic acid and a glycol component comprising 1, 4-cyclohexanedimethanol. The acid component may optionally include one or more acids commonly used in the preparation of polyesters, but the examples show that 1, 12-dodecanedioic acid must be present in order for the polyester to have the desired melt strength.

U.S. Pat. No. 5,559,171 discloses binary blends of cellulose esters and aliphatic-aromatic copolyesters. The AAPE component of such blends comprises a blend derived from C₂-C₁₄The aliphatic diacid moiety, and the aromatic acid-derived moiety, the former moiety may constitute 30 to 95 mol% of the copolymer and the latter moiety may constitute 70 to 5 mol% of the copolymer. Certain AAPEs disclosed in this document do not require blending and are useful in film applications. They comprise a compound derived from C₂-C₁₀Structural part of aliphatic diacidAnd moieties derived from aromatic acids, the former moieties may constitute from 95 to 35 mol% of the copolymer and the latter moieties may constitute from 5 to 65 mol% of the copolymer.

DE-A-19508737 discloses biodegradable AAPE comprising terephthalic acid, an aliphatic diacid and a diol component. The weight-average molecular weights Mw of such AAPEs are always very low (max 51000g/mol), so that their industrial applicability is limited.

Accordingly, it is a general object of the present invention to disclose improved AAPEs and blends comprising the same.

In fact, the present invention relates to a biodegradable aliphatic/aromatic copolyester (AAPE) comprising:

A) an acid component comprising the following repeating units:

1)50-60 mol% of an aromatic polyfunctional acid;

2)40-50 mol% of an aliphatic acid, at least 90% of which is a Long Chain Dicarboxylic Acid (LCDA) of natural origin selected from azelaic acid, sebacic acid, brassylic acid or mixtures thereof;

B) at least one diol component;

the aliphatic Long Chain Dicarboxylic Acid (LCDA) and the diol component (B) have a number of carbon atoms according to the following general formula:

(C_LCDA·y_LCDA)/2+C_B·y_B＞7.5

wherein:

-C_LCDAis the number of carbon atoms of the LCDA and can be 9, 10 or 13;

-y_LCDAis the mole fraction of each LCDA based on the total moles of LCDA;

-C_Bis the number of carbon atoms of each diol component;

-y_Bis the mole fraction of each diol based on the total moles of diol component (B)；

The AAPE has:

-a biodegradation rate after 90 days higher than 70% with respect to pure cellulose according to standard ISO 14855 amino 1;

-a density equal to or less than 1.2 g/cc;

a number average molecular weight Mn of 40,000 and 140,000;

-an intrinsic viscosity of 0.8-1.5.

Preferably, the biodegradation rate after 90 days as defined above is higher than 80%.

The AAPE according to the invention is rapidly crystallizable.

Preferably, the biodegradable polyester of the present invention is characterized in that said aliphatic Long Chain Dicarboxylic Acid (LCDA) and said diol component (B) have a number of carbon atoms according to the following general formula:

(C_LCDA·y_LCDA/2)+C_B·y_B＞8

"polyfunctional aromatic acids" for the purposes of the present invention preferably mean aromatic dicarboxylic compounds of the phthalic acid type and their esters, preferably terephthalic acid.

The content of aromatic dicarboxylic acids in the biodegradable polyester according to the invention is from 50 mol% to 60 mol% with respect to the total molar content of dicarboxylic acids.

The number average molecular weight Mn of the polyesters according to the invention is 40,000-140,000. The polydispersity index Mw/Mn, determined by Gel Permeation Chromatography (GPC), is between 1.7 and 2.6, preferably between 1.8 and 2.5.

Examples of diols according to the invention are 1, 2-ethanediol, 1, 2-propanediol, 1, 3-propanediol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, 1, 7-heptanediol, 1, 8-octanediol, 1, 9-nonanediol, 1, 10-decanediol, 1, 11-undecanediol, 1, 12-dodecanediol, 1, 13-tridecanediol, 1, 4-cyclohexanedimethanolPropylene glycol, neopentyl glycol, 2-methyl-1, 3-propanediol, dianhydrosorbitol, dianhydromannitol, dianhydroiditol, cyclohexanediol, and cyclohexanemethylene glycol. Particularly preferred is C₂-C₁₀A diol of the type (I). Even more particularly preferred is C₂-C₄A diol. Butanediol is most preferred.

The polyester according to the invention has an intrinsic viscosity (for CHCl at 25 ℃) ranging from 0.8dl/g to 1.5dl/g, preferably from 0.83dl/g to 1.3dl/g, even more preferably from 0.85dl/g to 1.2dl/g₃0.2g/dl solution in (1) was measured using an Ubbelhode viscometer).

In the case of typical applications for plastic materials (e.g., bubble films, injection molded materials, foams, etc.), the Melt Flow Rate (MFR) of the polyester according to the invention is from 0.5 to 100g/10 min, preferably from 1.5 to 70g/10 min, more preferably from 2.0 to 50g/10 min (measured at 190 ℃/2.16kg according to ASTM D1238 standard).

The polyesters according to the invention have a crystallization temperature T of more than 25 ℃, preferably more than 30 ℃, most preferably more than 40 ℃_c。

The polyester has a weight of 1.20g/cm or less as measured by a Mohr-Westphal weighing machine³The density of (c).

The aliphatic acid a2, which may be different from LCDA, may comprise or consist of at least one hydroxy acid, in an amount of up to 10 mol% relative to the total molar content of aliphatic acids. Examples of suitable hydroxy acids are glycolic acid, hydroxybutyric acid, hydroxyhexanoic acid, hydroxyvaleric acid, 7-hydroxyheptanoic acid, 8-hydroxyhexanoic acid, 9-hydroxynonanoic acid, lactic acid or lactide. The hydroxy acid may be inserted into the chain as it is, or may be prepared beforehand to be reacted with a diacid or a diol. The hydroxy acid units may be randomly inserted in the chain or may form blocks of adjacent units.

In the preparation of the copolyesters according to the invention, one or more polyfunctional molecules may advantageously be added in an amount of 0.02 to 3.0 mol%, preferably 0.1 mol% to 2.5 mol%, relative to the amount of dicarboxylic acid (and possibly hydroxy acid), in order to obtain a branched product. Examples of such molecules are glycerol, pentaerythritol, trimethylolpropane, citric acid, dipentaerythritol, sorbitan mono-hydrate, monohydro-mannitol, epoxidized oils such as epoxidized soybean oil, epoxidized linseed oil, etc., dihydroxystearic acid, itaconic acid, etc.

Although the polymers according to the invention can achieve a high level of performance without the need to add chain extenders such as di-and/or polyisocyanates and isocyanurates, di-and/or polyepoxides, bisoxazolines, polycarbodiimides or divinyl ethers, the addition of these chain extenders in any case may improve their performance when the situation requires.

In general, these additives are used in percentages of 0.05 to 2.5%, preferably 0.1 to 2.0%. In order to improve the reactivity of these additives, specific catalysts such as zinc stearate (metal salts of fatty acids) can be used for the polyepoxides.

For example, the increase in molecular weight of the polyester can be advantageously achieved by adding various organic peroxides during the extrusion process. The increase in molecular weight of the biodegradable polyester can be easily detected by observing the increase in viscosity value following treatment of the polyester with peroxide.

In the case of films prepared using the polyester according to the invention, the addition of the above chain extenders according to the teaching of EP 1497370 results in a gel fraction of less than 4.5% (w/w) relative to the polyester. In this respect, the content of EP 1497370 must be incorporated by reference in the present specification. By suitably adjusting the molecular weight, the polyesters according to the invention have properties and viscosity values which make them suitable for many practical applications, such as films, injection molded articles, extrusion-coated articles, fibers, foams, thermoformed articles, extruded profiles and sheets, extrusion blow molding, injection blow molding, rotational molding, stretch blow molding, and the like.

In the case of films, production techniques such as film blowing, casting and coextrusion can be used. In addition, such films may be biaxially oriented either on-line or after film preparation. The film may also be oriented by stretching in one direction, wherein the stretch ratio is from 1: 2 up to 1: 15, more preferably from 1: 2.2 up to 1: 8. It is also possible to carry out the stretching in the presence of a highly filled material containing inorganic fillers. In this case, stretching produces micropores and the film thus obtained may be particularly suitable for hygiene applications.

In particular, the polyesters according to the invention are suitable for the preparation of:

-unidirectional or bidirectional films, and multilayer films containing other polymeric materials;

-films for agricultural use, such as mulching films;

-clinfilm (extensible film) for food, for wrapping in agricultural applications and for trash packaging;

shrink films, for example for pallets, mineral water, six-pack bails, etc.;

-bags and liners for collecting organic matter, such as food waste, and for collecting cut grass and yard waste;

single-and multilayer thermoformed packaging for food products, such as containers for milk, yoghurt, meat, beverages and the like;

-coatings obtained with the extrusion-surfacing technique;

-a multilayer laminate comprising layers of paper, plastic material, aluminium, metallized film;

-expanded or expandable beads for the preparation of parts formed by sintering;

-foamed and semi-foamed articles comprising foamed blocks made of pre-foamed particles;

-foamed sheets, thermoformed foamed sheets and containers obtained therefrom for packaging food products;

containers for fruits and vegetables in general;

-composites containing gelatinized, destructurized and/or complexed starch, native starch, flour, other fillers of natural, vegetable or inorganic origin;

fibers, microfibers, composite fibers having a core consisting of a rigid polymer (such as PLA, PET, PTT, etc.) and an outer shell made of the material according to the invention, composite fibers, fibers having various cross sections (round to lobed), lamellar fibers, fabrics and non-woven fabrics or spun-bonded or thermobonded fabrics for cleaning, hygiene, agricultural, georemediation, environmental beautification and clothing applications.

Furthermore, the polyesters according to the invention can be used in the form of blends (also obtained by reactive extrusion) with: polyesters of the same type (e.g., aliphatic/aromatic copolyesters such as polybutylene adipate terephthalate PBTA, polybutylene succinate terephthalate PBTS, and polybutylene glutarate terephthalate PBTG), or other biodegradable polyesters (e.g., polylactic acid, poly-e-caprolactone, polyhydroxybutyrates such as poly-3-hydroxybutyrate, poly-4-hydroxybutyrate, polyhydroxybutyrate valerate, polyhydroxybutyrate propionate, polyhydroxybutyrate hexanoate, polyhydroxybutyrate decanoate, polyhydroxybutyrate dodecanoate, polyhydroxybutyrate hexadecanoate, polyhydroxybutyrate octadecanoate, and polyalkylene succinates and their copolymers with adipic acid, lactic acid, or lactide and caprolactone, and combinations thereof), or other polymers other than polyesters.

Mixtures of polyesters with polylactic acid are particularly preferred.

According to another object of the invention, the polyesters according to the invention can also be used in the form of blends with polymers of natural origin, such as starch, cellulose, chitosan, alginates, natural rubber or natural fibres (for example jute, kenaf, hemp). The starch and cellulose may be modified, and among these, mention may be made, for example, of starches or cellulose esters having a degree of substitution of from 0.2 to 2.5, hydroxypropylated starches, and modified starches containing fatty chains. Preferred esters are acetates, propionates, butyrates and combinations thereof. Furthermore, the starch may be used in its destructurized form, in its gelatinized form or as a filler.

Mixtures of polyester and starch are particularly preferred.

Mixtures of starch with the polyesters according to the invention can form biodegradable polymer compositions having good resistance to aging and moisture. In these compositions comprising thermoplastic starch and a thermoplastic polymer that is not compatible with starch, the starch constitutes the dispersed phase and the thermoplastic polymer constitutes the continuous phase. In this respect, the content of EP 947559 must be incorporated by reference in the present specification.

The polymer composition can maintain high tear strength even under low humidity conditions. This property is obtained when the starch is present in the form of a dispersed phase having an average size of less than 1 μm. The preferred number average size of the starch granules is 0.1-0.5 microns, and more than 80% of the granules have a size less than 1 micron.

These characteristics are obtained when the water content of the composition is preferably maintained between 1 and 15% during the mixing of the components. However, it is also possible to operate at a content of less than 1% by weight, in which case starting with pre-dried and pre-plasticized starch.

It is also useful to degrade the starch to a low molecular weight prior to or during compounding with the polyester of the present invention in order to have an intrinsic viscosity of the starch in the final material or product of 1 to 0.2dl/g, preferably 0.6 to 0.25dl/g, more preferably 0.55 to 0.3 dl/g.

The destructured starch may be added to the polyester of the invention before or during mixing with plasticizers such as water, glycerol, di-and polyglycerols, ethylene or propylene glycol, ethylene and propylene diglycol, polyethylene glycol, polypropylene glycol, 1, 2-propanediol, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, sorbitol, eryritol, xylitol, mannitol, sucrose, 1, 3-propanediol, 1, 2-, 1, 3-, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-, 1, 5-hexanediol, 1, 2, 6-, 1, 3, 5-hexanetriol, neopentyl glycol, and polyvinyl alcohol prepolymers and polymers, polyol acetates, ethoxylates and propoxylates, especially sorbitol ethoxylates, sorbitol acetates, and pentaerythritol acetate. The amount of high-boiling plasticizer (plasticizer other than water) used is 0 to 50% by weight, preferably 10 to 30% by weight, relative to the starch.

The water may be combined with the high boiling point plasticizer or used separately as a plasticizer during the plasticizing stage of the starch prior to or during mixing of the composition, and may be removed at a desired level by degassing in one or more steps during the extrusion process. After the plasticization and mixing of the components is complete, the water is removed by degassing to obtain a final content of about 0.2-3% by weight.

Water, as well as high boiling plasticizers, alter the viscosity of the starch phase and affect the rheology of the starch/polymer system, thereby helping to determine the size of the dispersed particles. A compatibilizer may also be added to the mixture. They may belong to the following categories:

-additives such as esters obtained from a polyol and a mono-or polycarboxylic acid having a dissociation constant pK of less than 4.5 (in the case of polycarboxylic acids, this value refers to the pK of the first carboxyl group), with a hydrophilic/lipophilic balance index value (HLB) greater than 8.

-esters with HLB value ranging from 5.5 to 8, obtained from polyols and mono-or polycarboxylic acids with less than 12 carbon atoms and with pK value greater than 4.5 (in the case of polycarboxylic acids, this value refers to the pK of the first carboxyl group).

-esters with HLB value less than 5.5, obtained from polyols and fatty acids containing from 12 to 22 carbon atoms.

These compatibilizers may be used in amounts of 0.2 to 40% by weight, preferably 1 to 20% by weight, relative to the starch. The starch blend may also contain a polymeric compatibilizer having two components: one component compatible or soluble with starch and a second component soluble or compatible with polyester.

Examples are starch/polyester copolymers obtained by transesterification catalysts. Such polymers may be produced by reactive blending during compounding or may be prepared in a separate process and then added during extrusion. In general, block copolymers of hydrophilic and hydrophobic units are particularly suitable. Additives such as di-and polyepoxides, di-and polyisocyanates, isocyanurates, polycarbodiimides and peroxides may also be added. They can be used as stabilizers and chain extenders.

All of the above products can help create the desired microstructure. It is also possible to promote in situ reactions to create bonds between the starch and the polymer matrix. Furthermore, aliphatic-aromatic polymers with an intrinsic viscosity (intrinsic viscosity) higher than 1dl/g, chain extended with aliphatic or aromatic diisocyanates or di-and polyepoxides or isocyanurates or oxazolines, or aliphatic-aromatic polyesters in any case with a ratio between Mn and MFI (190 ℃, 2.16kg) higher than 10,000, preferably higher than 12,500, more preferably higher than 15,000, can also be used to obtain the desired microstructure.

Another way to improve the microstructure is to obtain starch complexation (complexation) in the starch-polyester mixture.

In this respect, the content of EP 965615 must be incorporated by reference in the present specification. In this case, in the X-ray spectrum of the composition comprising the polyester according to the invention, the Hc/Ha ratio between the peak height (Hc) of the complex in the range from 13 to 14 ℃ and the peak height (Ha) of the amorphous starch occurring at about 20.5 ℃ where the distribution of the peaks in the amorphous phase has been reconstructed is less than 2 and greater than 0.02.

The starch/polyester ratio is 5/95 wt% to 60/40 wt%, more preferably 10/90 wt% to 45/55 wt%.

In these starch-based blends in combination with the polyesters of the invention, it is possible to add: polyolefins, high and low hydrolysis polyvinyl alcohols, ethylene-vinyl alcohol copolymers and ethylene-vinyl acetate copolymers and combinations thereof, and also aliphatic polyesters such as polybutylene succinate, polybutylene adipate succinate caprolactate, polybutylene lactate succinate, polycaprolactone polymers and copolymers, PBT, PET, PTT, polyamides, polybutylene adipate terephthalate (which contains 40-70% terephthalic acid, with and without sulfonate groups, with or without branching, and possibly chain extended with diisocyanates or isocyanurates), polyurethanes, polyamide-urethanes, cellulose and starch esters such as acetates, propionates and butyrates with a degree of substitution of 1 to 3, preferably 1.5 to 2.5, polyhydroxyalkanoates, poly L-lactic acid, poly D-lactic acid and lactide, mixtures and copolymers thereof.

The starch blends of the polyesters of the invention hold better crystallization ability than compostable starch blends, where the copolyester is polybutylene terephthalate adipate with a terephthalic acid content of 45-49% (range of products with industrial properties), and which can be easily processed in film blowing even at an MFI of 7g/10 min (170 ℃, 5kg), due to the high crystallization rate of the matrix. Furthermore, they have a value higher than 20kj/m²Preferably higher than 30kj/m²Most preferably higher than 45kj/m²Impact strength (measured on a blown film 30 μm thick at 10 ℃ and a relative humidity of less than 5%).

Composites having exceptional resistance and easy processability comprise destructured starch and polylactic acid polymers in combination with the polyesters of the invention and copolymers, with and without additives such as polyepoxides, carbodiimides and/or peroxides.

In the case of starch nanoparticles having a size of less than 500 μm, preferably less than 300 μm, the starch-based film may even be transparent.

It is also possible to start from the dispersion of starch in the form of small droplets to dispersions in which two co-continuous phases coexist and the blend is characterized by allowing a higher water content during processing.

In general, in order to obtain a co-continuous structure, it is possible to select a starch with a high amylopectin content and/or to add to the starch-polyester composition a block copolymer with hydrophobic and hydrophilic units. Possible examples are polyvinyl acetate/polyvinyl alcohol and polyester/polyether copolymers, wherein the block length used, the balance between hydrophilicity and hydrophobicity of the block and the quality of the compatibilizer can be suitably varied to fine-tune the microstructure of the starch-polyester composition.

The polyesters according to the invention can also be used in the form of blends with the polymers of synthetic origin and with polymers of natural origin mentioned above. Mixtures of polyesters with starch and polylactic acid are particularly preferred.

Blends of polyesters according to the invention with PLA are of particular benefit, since the high crystallization rate of the aliphatic-aromatic polyesters of the invention and their high compatibility with PLA polymers and copolymers allows the covering of materials with a wide range of rigidity and high crystallization rates, which makes these blends particularly suitable for injection molding and extrusion.

Furthermore, blends of such polyesters with poly-L-and poly-D-lactic acid or poly-L-and poly-D-lactide, wherein the ratio between poly-L-lactic acid or lactide and poly-D-lactic acid or lactide is from 10/90 to 90/10, preferably from 20/80 to 80/20, and the ratio between aliphatic-aromatic polyester and poly-lactic acid or PLA blend is from 5/95 to 95/5, preferably from 10/90 to 90/10, are of particular interest due to the high crystallization rate and high heat resistance. The polylactic acid or lactide polymer or copolymer typically has a molecular weight Mn of 30,000-300,000, more preferably 50,000-250,000.

To improve the transparency and toughness of such blends and to reduce or avoid the lamellar structure of polylactide polymers, other polymers may be incorporated as compatibilizers or toughening agents: polybutylene succinate and copolymers thereof with adipic acid and/or lactic acid and/or hydroxycaproic acid, polycaprolactone, C₂-C₁₃Diols and C₄-C₁₃Aliphatic polymers of diacids, polyhydroxyalkanoates, polyvinyl alcohol with a degree of hydrolysis of 75 to 99% and copolymers thereof, polyethylene with a degree of hydrolysis of 0 to 70%, preferably 0 to 60%Vinyl esters of acids. Particularly preferred as diols are ethylene glycol, propylene glycol, butylene glycol, and particularly preferred as acids are azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid and combinations thereof.

In order to maximize the compatibility between the polyester of the present invention and polylactic acid, it is very useful to introduce a copolymer having a block having high affinity for the aliphatic-aromatic copolyester of the present invention and a block having affinity for the lactic acid polymer or copolymer. An especially preferred example is a block copolymer of the aliphatic aromatic copolymer of the present invention and polylactic acid. Such block copolymers can be obtained as follows: both starting polymers are end-capped with hydroxyl groups and then these polymers are reacted with chain extenders capable of reacting with hydroxyl groups, such as diisocyanates. Examples are 1, 6-esametylene diisocyanate, isophorone diisocyanate, methylene diphenyl diisocyanate, toluene diisocyanate and the like. Chain extenders capable of reacting with acid groups such as di-and polyepoxide (e.g., bisphenol diglycidyl ether, glycerol diglycidyl ether) divinyl derivatives may also be used if the polymers of the blend are end-capped with acid groups. Carbodiimide, bisoxazoline, isocyanurate, or the like may also be used as the chain extender.

The intrinsic viscosity of such block copolymers may be in the range of 0.3 to 1.5dl/g, more preferably 0.45 to 1.2 dl/g. The amount of compatibilizer in the blend of aliphatic-aromatic copolyester and polylactic acid may be 0.5 to 50 wt%, more preferably 1 to 30 wt%, more preferably 2 to 20 wt%.

The polyesters according to the invention can also be advantageously blended with fillers of organic and inorganic nature. The fillers are preferably used in amounts of from 0.5 to 70% by weight, preferably from 5 to 50% by weight.

As organic fillers, mention may be made of wood powders, proteins, cellulose powders, grape residues, bran, corn husks, compost, other natural fibers, cereal grits, with and without plasticizers such as polyols.

As inorganic filler, mention may be made of substances capable of being dispersed and/or reduced to flakes having submicron dimensions, preferably less than 500nm, more preferably less than 300nm, even more preferably less than 50 nm. Particularly preferred are various zeolites and silicates such as wollastonite, montmorillonite, hydrotalcite which are also functionalized by molecules capable of interacting with starch and/or the specific polyester. The use of these fillers can improve stiffness, water and air permeability, dimensional stability and maintain transparency.

The process for the preparation of the polyesters according to the invention can be carried out according to any process known in the art. In particular, the polyester can be advantageously obtained by polycondensation. Advantageously, the polymerization process of the copolyester may be carried out in the presence of a suitable catalyst. As suitable catalysts, mention may be made, for example, of tin organometallic compounds, such as derivatives of stannic acid; titanium compounds such as orthobutyl titanate; and aluminum compounds such as triisopropylaluminum; antimony compounds and zinc compounds.

Examples

In the examples provided below, the following test methods were employed:

-measuring MFR at 150 ℃ and 5kg or 190 ℃ and 2.16kg according to the conditions specified in ASTM D1238-89 standard;

-melting and crystallization temperatures and enthalpies were measured with a differential scanning calorimeter Perkin Elmer DSC7 under the following heating regime:

the first scan is performed at 20 deg.C/min from-30 deg.C to 200 deg.C

A second scan at 10 deg.C/min from 200 deg.C to-30 deg.C

A third scan at 20 deg.C/min from-30 deg.C to 200 deg.C

-T_m1Measured as the endothermic peak, T, of the first scan_m2Measured as the peak endotherm of the third scan; t is_cMeasured as the peak exotherm for the second scan.

-density

Density measurements according to the Mohr Westphal method were carried out using an analytical balance, Sartorius AC 120S, equipped with Sartorius Kit YDK 01. The Kit is equipped with two small baskets. Once the Kit has been installed, ethanol is introduced into the crystallizer. The balance was maintained at room temperature. Each run was run at approximately 2g of polymer (pellet or pellets).

The density d is determined according to the following formula:

D＝(W_a/G)d_fl

wherein

W_a: weight of sample in air

W_fl: weight of sample in alcohol

G＝W_a-W_fl

d_flEthanol density at room temperature (values read from the table provided by Sartorius company using Kit)

Experimental error of density value is + -2.5X 10^-3Within the range.

-η_inHas been determined according to ASTM 2857-87 method

Mn has been determined on an Agilent 1100 series GPC system with chloroform as eluent and polystyrene standards for the calibration curve.

Example 1

To a 25-1 steel reactor equipped with a mechanical stirrer, nitrogen flow inlet, condenser and a connection to a vacuum pump were added:

2890g of terephthalic acid (17.4mol),

3000g of sebacic acid (14.8mol),

3500g of butanediol (38.9mol),

6.1g of butylstannoic acid.

The molar percentage of terephthalic acid with respect to the sum of the moles of the acid component was 54.0 mol%.

The temperature of the reactor was then increased to 200 ℃ and a nitrogen stream was applied. After about 90% of the theoretical amount of water has been distilled off, the pressure is gradually reduced to a value of less than 3mmHg and the temperature is increased to 240 ℃.

After about 3 hours, the molten product was poured out of the reactor, cooled in a water bath and granulated. During the latter operation, it can be observed how the product starts to solidify rapidly and can be granulated easily. The product obtained had an intrinsic viscosity (c ═ 0.2g/dl, measured in chloroform at 25 ℃) η_in0.93(dl/g), MFR (190 ℃; 2.16kg) 20g/10 min, Mn 52103, density 1.18g/cm³。

From the H-NMR analysis, the percentage of aromatic units was found to be 53.5. + -. 0.5%.

Example 1A

To a reactor according to example 1 the same ingredients of example 1 were added:

2890g of terephthalic acid (17.4mol),

3000g of sebacic acid (14.8mol),

3500g of butanediol (38.9mol),

6.1g of butylstannoic acid.

The molar percentage of terephthalic acid with respect to the sum of the moles of the acid component was 54.0 mol%.

The reaction is carried out for the necessary time to obtain a product having the following characteristics: intrinsic viscosity (measured in chloroform at 25 ℃ C., c ═ 0.2g/dl) η_in1.03(dl/g), 14.8g/10 min MFR (190 ℃; 2.16kg), 58097 Mn, 1.18g/cm density³。

Example 2 (comparative)

To a reactor according to example 1 were added:

2480g of terephthalic acid (14.9mol),

3400g of sebacic acid (16.8mol),

3430g of butanediol (38.1mol),

6.1g of butylstannoic acid.

The molar percentage of terephthalic acid with respect to the sum of the moles of the acid component was 47 mol%.

The temperature of the reactor was then increased to 200 ℃ and a nitrogen stream was applied. After about 90% of the theoretical amount of water has been distilled off, the pressure is gradually reduced until a value of less than 3mmHg is reached and the temperature is increased to 240 ℃.

After about 3 hours, an intrinsic viscosity (. eta.) (. 0.2g/dl as measured in chloroform at 25 ℃) was obtained_in1.00(dl/g) and MFR (190 ℃; 2.16kg) 13g/10 min.

From the H-NMR analysis, the percentage of aromatic units was found to be 47.0. + -. 0.5%.

Example 3 (comparative)

To a reactor according to example 1 were added:

2770g of dimethyl terephthalate (14.3mol),

3030g of dimethyl adipate (17.4mol),

3710g of butanediol (41.2mol),

0.7g of tetraisopropyl orthotitanate (in n-butanol)

The molar percentage of the aromatic content relative to the sum of the moles of the acid component was 45 mol%.

The temperature of the reactor was then increased to 200-210 ℃. After at least 95% of the theoretical amount of methanol has been distilled off, the pressure is gradually reduced until a value of less than 2mmHg is reached and the temperature is increased to 250-260 ℃.

After about 4 hours, an intrinsic viscosity (. eta.) (. 0.2g/dl as measured in chloroform at 25 ℃) was obtained_in0.92(dl/g) and an MFR (190 ℃; 2.16kg) of 20g/10 min.

From the H-NMR analysis, the percentage of aromatic units was found to be 47.0. + -. 0.5%.

Example 4 (comparative)

The procedure of example 1 was repeated, using the following:

3623.9g of dimethyl terephthalate (18.68mol),

3582.5g of butanediol (39.81mol),

2244.7g azelaic acid (11.94 mol).

The molar percentage of the aromatic content relative to the sum of the moles of the acid component was 61 mol%.

The intrinsic viscosity (. eta.) (. 0.2g/dl as measured in chloroform at 25 ℃ C.) was obtained_in0.95(dl/g), 1.21g/cc density and 5.5g/10 min MFR (190 ℃; 2.16 kg).

Example 5

The procedure of example 1 was repeated, using the following:

3476.48g of dimethyl terephthalate (17.92mol),

3493.80g of butanediol (38.82mol),

2411g of sebacic acid (11.94 mol).

The molar percentage of the aromatic content relative to the sum of the moles of the acid component was 60 mol%.

Mn is 56613, Mw/Mn-2.0364, intrinsic viscosity (measured in chloroform at 25 ℃, c-0.2 g/dl) η_in0.97(dl/g), density 120g/cc and MFR (190 ℃; 2.16kg) 7.8g/10 min.

Example 6

The procedure of example 1 was repeated, using the following:

3187.4g of dimethyl terephthalate (16.43mol),

3559.1g of butanediol (39.55mol),

2630.1g of azelaic acid (14.00 mol).

The molar percentage of the aromatic content relative to the sum of the moles of the acid component was 54 mol%. The intrinsic viscosity (. eta.) (. 0.2g/dl as measured in chloroform at 25 ℃ C.) was obtained_in1.04(dl/g), 1.2g/cc density and 7.12g/10 min MFR (190 ℃; 2.16 kg).

Example 7

The procedure of example 1 was repeated, using the following:

2865.4g of dimethyl terephthalate (14.77mol),

3201.1g of butanediol (35.57mol),

3072g brassylic acid (12.6 mol).

The molar percentage of the aromatic content relative to the sum of the moles of the acid component was 54 mol%.

The intrinsic viscosity (. eta.) (. 0.2g/dl as measured in chloroform at 25 ℃ C.) was obtained_in0.90(dl/g), 1.16g/cc density and MFR (190 ℃; 2.16kg) g/10 min.

The samples of the above examples were then formed into films by blown film technology on a Formac Polyfilm 20 apparatus equipped with a metering screw 20C13 (L/D25, RC 1.3; air gap 1 mm; 30-50 RPM; T140-. The obtained film had a thickness of about 30 μm.

After film formation, and one week after conditioning at 23 (.

Table 1 lists the thermal properties of the products of the examples and Table 2 lists the mechanical properties of the films obtained from these products.

TABLE 1 thermal Properties

Examples	Aromatic hydrocarbons	Tm1	ΔHm1	Tc	ΔHc	Tm2
							1	53.5％	133	28	58	20	130
1A	53.5	-	-	46	19	129
							2 (comparison)	47％	112	19	22	19	113
3 (comparison)	47％	120	19	16	18	114
							4 (comparison)	61％	-	-	104	21	154
5	60％	-	-	82	23	145
							6	54％	-	-	42	24	130
7	54％	-	-	76	16	133

TABLE 2 mechanical Properties

Examples	1	2 (comparison)	3 (comparison)	4 (comparison)	5	6	7*
								Tensile Property-longitudinal
Yield point (MPa)	11	6.5	9	11.5	12	9	6
								Ultimate strength (MPa)	40	28	40	40.0	45	33.5	23.5
Modulus of elasticity(MPa)	90	65	105	170	130	120	70
								Breaking energy (MJ/M)3)	143	135	170	150	154	169	155

Mechanical properties of the product of example 7 were tested on compression molded samples having a thickness of about 100 μm.

Biodegradation test

For the products of table 3, biodegradation tests were carried out according to standard ISO 14855 amino 1 with controlled composting treatment.

The test was carried out on 30 micron films milled in liquid nitrogen until they broke down to a size of less than 2mm, or on pellets milled to particles with a diameter < 250 μm. As a positive reference microcrystalline cellulose, Avicel No. K29865731202 for column chromatography was used. Powder particle size: 80% is 20 μm-160 μm; 20% is less than 20 μm.

TABLE 3 biodegradation

Examples	Aromatic content	LCDA/diol	Granules milled from	Relative biodegradability after 90 days
					1	53.5％	Sebacic acid butanediol	Film(s)	107.44
2 (comparison)	47％	Sebacic acid butanediol	Film(s)	99.6
					3 (comparison)	47％	Adipic acid butanediol	Film(s)	80.71
Cellulose, process for producing the same, and process for producing the same	-	-	Film/pellet	100
					4 (comparison)	61％	Azelaic acid butanediol	Granular material	10.39 (end of test: 49 days)
5	60％	Sebacic acid butanediol	Granular material	104
					6	54％	Azelaic acid butanediol	Granular material	82
7	54％	Brassylic acid butanediol	Granular material	73

TABLE 4 Density

Examples	Aromatic content	LCDA/diol	Density g/cc
				1	53.5％	Sebacic acid butanediol	1.18
2 (comparison)	47％	Sebacic acid butanediol	1.17
				3 (comparison)	47％	Adipic acid butanediol	1.23
4 (comparison)	61％	Azelaic acid butanediol	1.21
				5	60％	Sebacic acid butanediol	1.20
6	54％	Azelaic acid butanediol	1.20
				7	54％	Brassylic acid butanediol	1.15

It was found from the above examples that selecting an AAPE according to the invention provides a product with an excellent balance between biodegradability and mechanical properties.

Example 8

28 parts by weight of the polymer of example 6 was blended with 58 parts of a poly L-lactide polymer having a Mn of 180000, an MFR (190 ℃, 2.16kg) of 3.5g/10 min, a lactide residue of less than 0.2% and a D content of about 6%, and 14 parts talc. The extruder used was a twin screw extruder, Haake Rheocord 90 RheomexTW-100. The heat distribution was 120-190 ℃.

The pellets obtained have been dried at 60 ℃ for 1 hour. In a capillary rheometer Goettfert Rheotest 1000 equipped with a 1mm capillary rheometer at 190 ℃ and 100sec^-1The melt viscosity measured at the shear rate of (a) was 600Pa s. The pellets were injection molded in a Sandretto press 60 series 7 where a dumbbell mold was used to prepare the samples for mechanical testing and a 12 cavity clipper mold was used to test the industrial moldability.

The mechanical properties obtained for the dumbbell specimens according to ASTM specification D638 after conditioning at 23 ℃ and 55% RH are reported below:

stress at break (MPa)42

Elongation at break (%) 271

Young's modulus (MPa)2103

Energy to break (Kj/m)²)1642

Dumbbell samples were tested in biodegradation under a controlled composting treatment, achieving 100% biodegradation after 50 days.

The processing cycle is comparable to polypropylene and is 14 seconds and the molding system is fully automated.

One blend differs from the blend described in this example only in that the aromatic-aliphatic polyester, specifically the polymer of example 6, was coated with polybutylene terephthalate adipate (MFR at 190 ℃, 2.16kg of 3.4, 47 mol% terephthalic acid, density of 1.23 g/cm)³) Instead, the molded part cannot be automatically demolded.

Example 9

Blends were prepared by mixing 70 wt% of the polymer of example 5 and 30 wt% of the same PLA as described in example 8. The blend was prepared in the twin screw extruder of example 8 under the same thermal profile. The pellets were dried and film blown as reported in the previous examples.

The film showed the following tensile properties in the film direction:

stress at break (MPa)25

Elongation at break (%) 400

Young's modulus (MPa)590

Energy to break (Kj/m)²)3600

The film has good transparency. The tear strength differs in the two directions of film blowing, indicating significant orientation.

Addition of 10% of a block copolymer of PLA with a viscosity of 0.85dl/g and an aliphatic aromatic block consisting of butanediol with sebacic acid and 46-54 mol% terephthalic acid gave similar and better tensile properties (stress at break (MPa)28, elongation at break (%) 380, Young's modulus (MPa)840, energy at break (Kj/m) than the samples without compatibilizer²)3600) but the tear strength is more balanced in both directions.

Claims (28)

1. Biodegradable aliphatic/aromatic copolyester comprising:

A) a unit of an acid component comprising the following repeating units:

1)50-60 mol% of an aromatic polyfunctional acid;

2)40-50 mol% of an aliphatic acid, at least 90 mol% of which is a long chain dicarboxylic acid of natural origin selected from azelaic acid, sebacic acid, brassylic acid or mixtures thereof;

B) units of at least one diol component;

the aliphatic long-chain dicarboxylic acid and the diol component (B) have a number of carbon atoms according to the following general formula:

(C_LCDA·y_LCDA)/2+C_B·y_B＞7.5

wherein:

-C_LCDAis the number of carbon atoms of the aliphatic long chain dicarboxylic acid and is 9, 10 or 13;

-y_LCDAis the mole fraction of each aliphatic long chain dicarboxylic acid based on the total moles of the aliphatic long chain dicarboxylic acids;

-C_Bis the number of carbon atoms of each diol component;

-y_Bis the mole fraction of each diol based on the total moles of diol component (B);

the aliphatic/aromatic copolyester has:

-a biodegradation rate after 90 days higher than 70% with respect to pure cellulose according to standard ISO 14855 amino 1;

-a density equal to or less than 1.2 g/cc;

a number average molecular weight Mn of 40,000 and 140,000;

-an intrinsic viscosity of 0.8-1.5.

2. Biodegradable polyester according to claim 1, characterized in that said aromatic polyfunctional acid is selected from phthalic acids.

3. Biodegradable polyester according to claim 2, characterized in that said aromatic polyfunctional acid is terephthalic acid.

4. Biodegradable polyester according to claim 1, characterized in that the polydispersity index Mw/Mn of said biodegradable aliphatic/aromatic copolyester is comprised between 1.7 and 2.6.

5. Biodegradable polyester according to claim 4, characterized in that said polydispersity index Mw/Mn ranges from 1.8 to 2.5.

6. Biodegradable polyester according to claim 1, characterized in that said diol is selected from: 1, 2-ethanediol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, 1, 7-heptanediol, 1, 8-octanediol, 1, 9-nonanediol, 1, 10-decanediol, 1, 11-undecanediol, 1, 12-dodecanediol, 1, 13-tridecanediol, 1, 4-cyclohexanedimethanol, propylene glycol, neopentyl glycol, 2-methyl-1, 3-propanediol, dianhydrosorbitol, dianhydromannitol, dianhydroiditol, cyclohexanediol, and cyclohexanemethylene glycol.

7. Biodegradable polyester according to claim 6, characterized in that said propylene glycol is 1, 2-propylene glycol.

8. Biodegradable polyester according to claim 6, characterized in that said propylene glycol is 1, 3-propanediol.

9. Biodegradable polyester according to claim 6, characterized in that said diol contains from 2 to 10 carbon atoms.

10. Biodegradable polyester according to claim 9, characterized in that said diol contains 2 to 4 carbon atoms.

11. Biodegradable polyester according to claim 1, characterized in that said aliphatic long chain dicarboxylic acid and said diol component (B) have a number of carbon atoms according to the following general formula:

(C_LCDA·y_LCDA/2)+C_B·y_B＞8

12. biodegradable polyester according to claim 1, characterized in that said biodegradation rate is higher than 80% after 90 days.

13. The peanut of claim 1Biodegradable polyesters, characterised by a crystallization temperature T_cAbove 25 ℃.

14. Biodegradable polyester according to claim 13, characterized in that said crystallization temperature T_cAbove 30 ℃.

15. Biodegradable polyester according to claim 14, characterized in that said crystallization temperature T_cAbove 40 ℃.

16. Biodegradable polyester according to claim 1, characterized in that said aliphatic acid comprises at least one hydroxy acid in an amount of at most 10 mol% with respect to the total molar content of said aliphatic acid.

17. Blend comprising a biodegradable polyester according to any one of the preceding claims, characterized by containing both a biodegradable polyester according to any one of the preceding claims and other biodegradable polymers of natural or synthetic origin.

18. Blends of biodegradable polyesters according to claim 17, obtained by reactive extrusion.

19. Blend of biodegradable polyesters according to claim 17, characterized in that the polymer of synthetic origin is chosen from polylactic acid, poly-e-caprolactone, polyhydroxybutyrate, and polyalkylene succinate.

20. Blend of biodegradable polyesters according to claim 19, characterized in that the polyhydroxybutyrate is selected from polyhydroxybutyrate valerate, polyhydroxybutyrate propionate, polyhydroxybutyrate hexanoate, polyhydroxybutyrate decanoate, polyhydroxybutyrate dodecanoate, polyhydroxybutyrate hexadecanoate and polyhydroxybutyrate octadecanoate.

21. Blend of biodegradable polyesters according to claim 17, characterized in that the polymers of natural origin are chosen from starches, celluloses, chitosans, alginates or natural rubbers.

22. Blend of biodegradable polyesters according to claim 21, characterized in that the starch or cellulose is modified.

23. Blend of biodegradable polyesters according to claim 22, characterized in that the modified starch or cellulose is a starch or cellulose ester with a degree of substitution of 0.2 to 2.5, hydroxypropylated starch, and modified starch containing fatty chains.

24. Blend of biodegradable polyesters according to claim 21, characterized in that the starch is present in destructurized or gelatinized form or in the form of fillers.

25. Blend of biodegradable polyesters according to claim 17, in which the polymer of synthetic origin is polylactic acid and the polymer of natural origin is starch.

26. Use of a biodegradable polyester according to any of the preceding claims 1 to 16 for the production of:

-unidirectional or bidirectional films, and multilayer films containing other polymeric materials;

-films for agricultural use;

-a bag and a hood for collecting organic matter;

single-and multi-layer packaging for food products, including containers for milk, yoghurt, meat, beverages;

-coatings obtained with the extrusion-surfacing technique;

-a multilayer laminate comprising layers of paper, plastic material, aluminium, metallized film;

-expanded or expandable beads for the preparation of parts formed by sintering;

-foamed and semi-foamed articles comprising foamed blocks made of pre-foamed particles;

-foamed sheets, thermoformed sheets and containers for packaging food products obtained therefrom;

containers for fruits and vegetables in general;

-composites containing gelatinized, destructurized and/or complexed starch, native starch, flour, other fillers of natural, vegetable or inorganic origin;

fibers, fabrics and non-woven fabrics for use in the health, hygiene and hygiene sectors.

27. Use of a blend of biodegradable polyesters according to any of the preceding claims 17 to 25 for the production of:

-unidirectional or bidirectional films, and multilayer films containing other polymeric materials;

-films for agricultural use;

-a bag and a hood for collecting organic matter;

single-and multi-layer packaging for food products, including containers for milk, yoghurt, meat, beverages;

-coatings obtained with the extrusion-surfacing technique;

-a multilayer laminate comprising layers of paper, plastic material, aluminium, metallized film;

-expanded or expandable beads for the preparation of parts formed by sintering;

-foamed and semi-foamed articles comprising foamed blocks made of pre-foamed particles;

-foamed sheets, thermoformed sheets and containers for packaging food products obtained therefrom;

containers for fruits and vegetables in general;

-composites containing gelatinized, destructurized and/or complexed starch, native starch, flour, other fillers of natural, vegetable or inorganic origin;

fibers, fabrics and non-woven fabrics for use in the health, hygiene and hygiene sectors.

28. Use according to claim 26 or 27, wherein the film for agricultural use is a mulch film.