FR3028520A1 - COMPOSITION BASED ON A MIXTURE OF POLYESTERS AND THERMOPLASTIC STARCH WITH IMPROVED FILMABILITY. - Google Patents

Abstract

The invention relates to a thermoplastic composition comprising at least one mixture of polyesters (A) comprising at least one polylactic acid (A1) and at least one aliphatic polyester (A2) or a semi-aliphatic polyester other than the polymer (A1), at least one starch (B), at least one organic starch softener (C) characterized in that: • the mass percentage of (A1) relative to the mass of (A1) and (A2), expressed by mass dry, ranges from 2 to 70%, advantageously from 10 to 50%, preferably from 18 to 30%; At least 50% of the mass of polylactic acid (A1) consists of semi-crystalline polylactic acid; And in that the mass ratio starch (B) / organic plasticizer (C), expressed in dry mass, ranges from 85/15 to 40/60.

Description

Field of the invention The invention relates to a thermoplastic composition comprising thermoplastic starch, a semi-crystalline polylactic acid and at least one aliphatic polyester other than said polylactic acid or a semi-aliphatic polyester. The subject of the invention is also a process for the manufacture of this composition as well as a process for the manufacture of film by sheath blowing using this composition. BACKGROUND OF THE INVENTION Because of their many advantages, plastics have become essential for the mass production of objects. Indeed, because of their thermoplastic nature, one can manufacture at high rates all kinds of objects from these polymers. To manufacture these objects, small pieces of these thermoplastic polymers are used, generally in the form of granules, which are melted by the supply of heat and mechanical stresses in shaping machines. For example, film can be made by introducing these granules into a jacket extruder or flat extruder, or making bottles by introducing them into a blowing extruder. These objects are generally made from non-biodegradable thermoplastics, such as polyolefins or polyamides. However, these plastics are still little recycled today. Thus, this poses environmental problems because they are generally incinerated and this incineration can cause the release of toxic gases. Thus, one of the important concerns today in the field of polymers is to provide biodegradable or at least compostable polymers. Among the biodegradable and / or compostable polymers, mention may be made of aliphatic polyesters or semi-aliphatic polyesters such as poly (butylene succinate) (PBS), poly (butylene succinate-co-adipate) (PBSA), poly -E-caprolactone (pCAPA), polylactic acid (PLA) or poly (butylene adipate-co-terephthalate) (PBAT) as well as polyhydroxyalkanoates of the polyhydroxybutyrate (PHB) or poly (hydroxy butyrate-co-valerate) type (PHVB). The aliphatic and semi-aliphatic polyesters generally have melting temperatures close to those of the polyolefins, which allows, inter alia, their application in the fields of films and packaging, the biodegradability of which is an obvious advantage for single-use applications. uses.

However, one of the problems with these polyesters is that they are relatively expensive. One of the solutions envisaged to provide more economical biodegradable compositions is to manufacture thermoplastic starch-based compositions, which consist of starch and plasticizer of this starch such as glycerol. Indeed, the manufacture of these compositions is advantageous because starch is one of the biobased polymers that is naturally most common in the environment. However, these thermoplastic starches have insufficient properties, especially in terms of water resistance. In addition, the transformation of starch into thermoplastic starch is not easy because it requires the use of stresses and / or high temperatures during thermomechanical mixing, which tends to degrade the thermoplastic starch thus formed. To counteract these drawbacks, compositions based on aliphatic or semi-aliphatic polyesters and on plasticized starch have been developed. In these compositions, the thermoplastic starch phase is generally dispersed in the polyester phase. These compositions have numerous advantages, such as being able to be compostable and / or biodegradable and to have a very improved resistance to water compared with thermoplastic starch. These compositions are generally manufactured by extrusion. An intimate mixing rod of the two polymers is then obtained, this rod then being passed through a granulator to form granules. The Applicant has found that one of the problems of compositions based on thermoplastic starch and aliphatic polyester such as PBS or PBSA is that these compositions can be transformed into a film by blowing the sheath at rates very reduced compared, for example, to polyethylenes. This phenomenon is particularly important when the mass quantity of organic plasticizer in thermoplastic starch is high, ie when the organic plasticizer / starch mass ratio, expressed as dry weight, is equal to or greater than 15/85. In the context of industrial processes, this leads to unsatisfactory productivity and therefore to excessive production costs. The application WO 2013/073402 describes a composition comprising a starch (a1), a biodegradable resin (a2) other than a polylactic acid and an amorphous polylactic acid (b), in which the mass ratio (b) / (a2) ) ranges from 20/80 to 50/50 and the mass ratio (components other than (b)) / (b) is between 95/5 and 50/50. This composition is transformed by blowing sheath. It has improved tensile, elongation, impact resistance, heat seal strength and tear resistance properties. However, the Applicant has found that these compositions do not allow high speed production of films by extrusion blowing sheath.

As part of its research, the Applicant has managed to provide new compositions to overcome these problems. SUMMARY OF THE INVENTION The invention thus relates to a thermoplastic composition comprising at least one polyester blend (A) comprising at least one polylactic acid (A1) and at least one aliphatic polyester (A2) or a semi-aliphatic polyester other than the polymer (A1), at least one starch (B), at least one organic softener of the starch (C) characterized in that: - the mass percentage of (A1) with respect to the mass of (A1) and (A2), expressed as dry weight, is from 2 to 70%; At least 50% of the mass of polylactic acid (A1) consists of semi-crystalline polylactic acid; - And in that the mass ratio starch (B) / organic plasticizer (C), expressed in dry mass, ranges from 85/15 to 40/60. The Applicant has found that these compositions are easily filmable by extrusion blowing jacket, despite the large amount of organic plasticizer used in the thermoplastic starch. The invention will now be detailed in the description below. DETAILED DESCRIPTION OF THE INVENTION The subject of the invention is a thermoplastic composition based on a mixture of polyesters (A) comprising at least one polylactic acid (A1) and at least one aliphatic polyester (A2) other than (A1). or a semi-aliphatic polyester, starch (B) and plasticizer (C). A thermoplastic composition is a composition that reversibly softens under the action of heat and hardens on cooling to room temperature. It has at least one glass transition temperature (Tg) below which the amorphous fraction of the composition is in the brittle glassy state, and above which the composition can undergo reversible plastic deformations. The glass transition temperature or at least one of the glass transition temperatures of the starch-based thermoplastic composition of the present invention is preferably from -150 ° C to 40 ° C. This starch-based composition can, of course, be shaped by the processes traditionally used in plastics, such as extrusion, injection, molding, blowing and calendering. Its viscosity, measured at a temperature of 100 ° C. to 200 ° C., is generally between 10 and 106 Pa.s.

The composition according to the invention is based on a polyester mixture which comprises polylactic acid (A1), said polylactic acid being at least 50% semi-crystalline polylactic acid. Polylactic acid is generally obtained by polymerization of lactide, by ring opening. Lactide can be in the form of D-lactide, L-lactide or in the form of meso-lactide. The crystallinity of the polylactic acid is mainly controlled by the amounts of D-lactide and L-lactide and to a lesser extent by the type of catalyst used. Thus, the polymerization of a racemic mixture of L-lactide and D-lactide generally leads to the synthesis of an amorphous polylactic acid, whereas the polymerization of pure D-lactide or pure L-lactide leads to the synthesis of a semi-crystalline polylactic acid. A synthetic method using a racemic mixture can also lead to a heterotactic PLA having crystallinity using stereospecific catalysts. Preferably, the polylactic acid has a crystallinity (or degree of crystallinity) ranging from 30 to 75%, most preferably from 40 to 60%. The degree of crystallinity of the PLA can be determined by differential scanning calorimetry analysis on the basis of the calculation of the ratio of the jump values of Cp to Tg of the semicrystalline product which is to be characterized and of the same product rendered totally amorphous. . For example, a sample of about 10 mg of the material to be characterized is subjected to a heating ramp from -20 ° C to 200 ° C at a rate of 10 ° C / min. The value of the jump from Cp to Tg of this sample (called ACn r-sample) is measured on this cycle. At the end of this first heating, the sample is completely melted. It is then subjected to rapid cooling at a rate of 30 ° C / min to -20 ° C. The purpose of this second step is to make the sample totally amorphous. It is possible to ensure the non-recrystallization of the sample during cooling by following the signal measured by the device. Finally, once the sample is 100% amorphous, it is reheated to 200 ° C. at a rate of 10 ° C. per minute. The value of the jump from Cp to Tg of this 100% amorphous sample (called 4On-amorph) is measured on this third cycle. The degree of crystallinity (x) is determined as follows: x = (1 - 4Ch sample / ACPamorph) * 1 00.

According to a variant of the invention, the polylactic acid (A1) comprises an amorphous polylactic acid, that is to say that (A1) is a mixture of amorphous polylactic acid and semi-crystalline polylactic acid. According to this variant, the amount of amorphous polylactic acid, relative to the totality of the polylactic acid, does not exceed 50%, advantageously does not exceed 20%, preferably does not exceed 10%. More particularly, the polylactic acid may advantageously consist of a mixture of 55 to 90% of semicrystalline polylactic acid and 10 to 45% of amorphous polylactic acid, the quantities being expressed as dry mass of acid. polylactic. The composition according to the invention also comprises an aliphatic polyester other than polylactic acid (A1) or a semi-aliphatic polyester.

An aliphatic polyester is a polyester which comprises nonaromatic monomers exclusively. By "understanding monomers" is meant that the polyester is capable of being obtained by polycondensation of these monomers. For example, if the polyester comprises succinic acid and 1,4-butanediol, it means that the polyester is capable of being obtained by polycondensation of monomers comprising succinic acid and 1,4-butanediol. It is also stated that when the polyester comprises x% of a monomer (X), this means that it can be obtained from a monomer mixture comprising, with respect to the total mass of the monomers, x % of monomer (X). An aliphatic polyester is a polyester capable of being obtained using non-aromatic monomers, said monomers being chosen from polyols, polyacids and monomers bearing at least one carboxylic acid function and at least one alcohol function. These non-aromatic monomers may be linear, cycloaliphatic or branched. It is also possible to obtain these polyesters by enzymatic or fermentation routes, as in the case of polyhydroxyalkanoates. These polyols are generally aliphatic diols, preferably saturated linear aliphatic diols. As linear aliphatic diol, there may be mentioned ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 3028520 Or a mixture of aliphatic diol units comprising at least one of these units, preferentially ethylene glycol, 1,4-butanediol or a mixture of these diols, most preferably 1,4-butanediol. The polyacids are generally aliphatic diacids, preferably saturated aliphatic diacids. By way of example, these diacids may be succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid or a mixture of these. diacids. Preferably, the aliphatic diacid is selected from succinic acid and adipic acid or a mixture of these acids. The polyesters can also be obtained from the esters, anhydrides or chlorides of these polyacids. Monomers bearing at least one carboxylic acid function and at least one alcohol function are generally hydroxy acids. By way of example, the hydroxy acids may be glycolic acid, hydroxybutyric acid, hydroxycaproic acid, hydroxyvaleric acid, 7-hydroxyheptanoic acid, 8-hydroxyoctanoic acid, 9-hydroxyoctanoic acid, Hydroxynonanoic acid or a mixture of these hydroxy acids. The polyesters can also be obtained from dilactone such as glycolide or lactone such as caprolactone. A semi-aliphatic polyester comprises, in addition to the aliphatic monomers mentioned above, at least one aromatic monomer which may be a polyol, a polyacid or a monomer carrying at least one carboxylic acid function and at least one alcohol function. This may especially be an aromatic polyacid, advantageously an aromatic diacid, terephthalic acid or furanic acid, preferably terephthalic acid. The polyesters can also be obtained from the esters or chlorides of these polyacids. It is generally considered that a semi-aliphatic polyester comprises, based on all the monomers, from 50.1 to 99.9 mol% of aliphatic monomers. The semi-aliphatic polyester may especially be a copolymer comprising butanediol-1,4, adipic acid and terephthalic acid (PBAT). Preferably, the polyester (A2) is an aliphatic polyester, preferably chosen from polymers (A2) for condensing ethylene glycol and / or butanediol-1,4 and succinic acid and / or adipic acid.

With respect to the total weight of the polyester, the total weight of ethylene glycol, 1,4-butanediol, succinic acid and adipic acid is advantageously greater than 90%.

Preferably, the aliphatic polyester (A2) comprises 1,4-butanediol and succinic acid and / or adipic acid. The polyester (A2) is most preferably selected from PBS and PBSA. The invention is particularly advantageous when the aliphatic polyester (A2) is amorphous.

According to the invention, the mass percentage of (A1) with respect to the weight of (A1) and (A2), expressed in dry mass, ranges from 2 to 70%. Preferably, this mass percentage ranges from 10 to 50%, most preferably from 18 to 30%. In these preferred embodiments, the compositions can be converted into a film by extrusion blowing at a faster rate, these films further having mechanical properties quite suitable for use in a bag. It is possible to manufacture films from this composition by sheath extrusion blasting, using particularly high production rates and this especially in the preferred range above. It is specified that, according to the invention, the mass proportions in each constituent are expressed in dry mass. Thus, when one gives the proportions of a component relative to the total mass of the composition, the dry mass of this component is understood to refer to the dry mass of the composition. Preferably, the polyesters (A) have a melt index ranging from 0.1 to 50 g / 10 min, advantageously from 0.5 to 15 g / 10 min (1S01133, 190 ° C, 2.16 kg).

The composition according to the invention further comprises starch (B) and an organic starch plasticizer (C), both forming thermoplastic starch. As regards starch (B), it can be of any type. If it is desired to obtain a composition of lower cost, the starch preferentially used for the manufacture of the composition is a granular starch, preferably a native starch.

The term "granular starch" is used herein to mean a starch which is native or physically, chemically or enzymatically modified, and which has retained, within the starch granules, a semicrystalline structure similar to that evidenced in the grains of starch. starch naturally occurring in reserve organs and tissues of higher plants, particularly in cereal seeds, legume seeds, potato or cassava tubers, roots, bulbs, stems and fruits. In the native state, the starch grains generally have a degree of crystallinity which varies from 15 to 45%, and which depends essentially on the botanical origin of the starch and the possible treatment which it has undergone. Granular starch, placed under polarized light, has a characteristic black cross, so-called Maltese cross, typical of the granular state.

According to the invention, the granular starch can come from all botanical origins, including a granular starch rich in amylose or conversely, rich in amylopectin (in English "waxy"). It may be starch native to cereals such as wheat, maize, barley, triticale, sorghum or rice, tubers such as potato or cassava, or legumes such as peas and soybeans, and mixtures of such starches.

The starch can also be modified, chemically or physically. The organic plasticizer of the starch (C) has the function of rendering the starch thermoplastic. It may be an organic plasticizer selected from diols and polyols such as glycerol, polyglycerols, sorbitans, sorbitol, mannitol, and hydrogenated glucose syrups, urea, polyols of molar mass less than 800 g / mol and any mixtures of these products, preferably glycerol, sorbitol or a mixture of glycerol and sorbitol. According to the invention, the composition comprises relatively large amounts of plasticizer, that is to say that the mass ratio starch (B) / organic plasticizer (C), expressed in dry mass, is less than or equal to 85/15. . More specifically, the weight ratio of starch (B) / organic plasticizer (C), expressed in dry mass, ranges from 85/15 to 40/60, advantageously from 85/15 to 50/50, preferably from 80/20 to 60/40. Even when the amounts of plasticizer are important, the composition according to the invention can be converted into films by extrusion blowing sheath, this even using high production rates. According to the invention, the composition may comprise relatively large amounts of thermoplastic starch. The composition according to the invention may thus comprise a total mass quantity of polyester (A) in the range from 35 to 75 parts, for example in the range from 40 to 70 parts, advantageously ranging from 45 to 60 parts, preferably ranging from 48 to 58 parts, these mass quantities being expressed relative to 100 parts of the total dry mass of the constituents (A1), (A2), (B) and (C).

Preferably, the composition according to the invention is characterized by a morphology which is in the form of co-continuous domains of thermoplastic starch and polyester. The morphology of the composition can be observed by scanning electron microscopy. Even when the amounts of thermoplastic starch are large, the composition according to the invention can be shaped into granules, without these forming rosaries. In certain proportions such as those defined above, the morphology of the composition has co-continuous domains of polyester and thermoplastic starch. These compositions exhibit improved biodegradability compared to compositions in which the thermoplastic starch is dispersed in a continuous polyester phase.

The composition according to the invention may also comprise additional additives or polymers, referred to as additional components, or a mixture thereof. The composition according to the invention may thus also comprise a binding agent carrying a plurality of functions capable of reacting with the polyester and / or the starch and / or the organic plasticizer of the starch, this function possibly being chosen from the functions carboxylic acid, carboxylic acid ester, isocyanate or epoxy. This binding agent, in particular citric acid, may be present in a mass quantity ranging from 0.01 to 0.45 parts, these mass quantities being expressed relative to 100 parts of the dry mass of the various constituents of (A1), (A2), (B) and (C). Advantageously, the composition comprises from 0.05 to 0.3 parts of citric acid, preferably from 0.06 to 0.20 parts, most preferably from 0.07 to 0.15 parts, relative to 100 parts of the mass. of the various constituents of (A1), (A2), (B) and (C). The presence of citric acid in the composition makes it possible to improve the homogeneity thereof and thus to improve the properties of the composition. In the proportions of citric acid selected and particularly preferred, the composition is easy to granulate, in comparison with polyester and thermoplastic starch compositions comprising larger amounts of citric acid. The composition according to the present invention may also comprise, as other additive or additional component, fillers or fibers of organic or inorganic nature, nanoscale or not, functionalized or not. They may be silicas, zeolites, fibers or glass beads, clays, mica, titanates, silicates, graphite, calcium carbonate, talc, carbon nanotubes, wood fibers, carbon fibers, polymer fibers, proteins, cellulosic fibers, lignocellulosic fibers and undestracted granular starch. These fillers or fibers can improve the hardness, rigidity or permeability to water or gases. Preferably, the composition comprises from 0.1 to 200 parts of fillers and / or fibers, for example from 0.5 to 50 parts, this amount being expressed relative to 100 parts of the total dry matter of the constituents (A1), (A2) (B) and (C). The composition may also be of the composite type, i.e., include large amounts of these fillers and / or fibers. The additive useful for the composition according to the invention may also be chosen from opacifying agents, dyes and pigments. They can be selected from cobalt acetate and the following compounds: HS-325 Sandoplast® RED BB (which is a compound carrying an azo function also known as Solvent Red 195), HS-510 Sandoplast® Blue 2B which is an anthraquinone, Polysynthren® Blue R, and Clariant® RSB Violet. The composition may also include as an additive a process agent, or processing aid, to reduce the pressure in the processing tool. These agents may also function as mold release agents to reduce adhesion to the forming materials of the composition, such as molds or calender rolls. These agents can be selected from esters and fatty acid amides, metal salts, soaps, paraffins or hydrocarbon waxes. Specific examples of these agents are zinc stearate, calcium stearate, aluminum stearate, stearamides, erucamide, behenamide, beeswax or candelilla waxes. Preferably, the composition further comprises a fatty acid and glycerol monoester, for example glycerol monostearate. According to this preferred variant, this composition makes it possible to produce films which are less tacky than compositions which are free of this constituent. Preferably, the amount by weight of the process agent, and in particular fatty acid monoester and glycerol, ranges from 0.05 to 1.7 parts, for example from 0.3 to 1.65 parts, advantageously from 0, 5 to 1.5 parts, preferably from 0.65 to 1.3 parts, these quantities being expressed relative to 100 parts of the dry mass of the various constituents (A1), (A2), (B) and (C) . The composition according to the invention may also comprise other additives such as stabilizing agents, for example light stabilizing agents, UV stabilizing agents and heat stabilizing agents, fluidifying agents, flame retardants and antistatic agents. . It may also include primary and / or secondary antioxidants. The primary antioxidant may be a sterically hindered phenol selected from the compounds Hostanox® 0 3, Hostanox® 010, Hostanox® 016, Ultranox® 210, Ultranox®276, 3028520 11 Dovernox® 10, Dovernox® 76, Dovernox ® 3114, Irganox® 1010, Irganox® 1076. The secondary antioxidant may be selected from trivalent phosphorus compounds such as Ultranox® 626, Doverphos® S-9228, Hostanox® P-EPQ, or Irgafos® 168. The composition may further comprise an additional polymer, different from the polyester according to the invention. This polymer may be chosen from polyamides, polystyrene, styrene copolymers, styrene-acrylonitrile copolymers, styrene-acrylonitrilebutadiene copolymers, polymethyl methacrylates, acrylic copolymers, poly (ether-imides), polyphenylene oxides. such as (2,6-dimethylphenylene) polyoxide, phenylene polysulfate, polyestercarbonates, polycarbonates, polysulfones, polysulfone ethers, polyetherketones and mixtures of these polymers. The composition may also comprise, as additional polymer, a polymer making it possible to improve the impact properties of the polymer, in particular functional polyolefins such as functionalized ethylene or propylene polymers and copolymers, core-shell copolymers or block copolymers.

The compositions according to the invention may also comprise polymers of natural origin, such as cellulose, chitosans, alginates, carrageenans, agar-agar, proteins such as gluten, pea proteins, casein, collagen, gelatin, lignin, these polymers of natural origin may or may not be physically or chemically modified.

According to a variant of the invention, the composition comprises in dry mass: from 1 to 55 parts of at least one polyester (A1); from 5 to 65 parts of at least one polyester (A2); from 5 to 50 parts of at least one starch (B), preferably from 20 to 40 parts; from 5 to 50 parts at least one organic plasticizer (C) of the starch, preferably from 10 to 25 parts; the sum of the quantities of the constituents (A1), (A2), (B) and (C) making 100 parts and in which: the mass percentage of (A1) with respect to the mass of (A1) and (A2), expressed in dry mass, ranges from 2 to 70%; At least 50% of the polylactic acid (A1) mass consists of semicrystalline polylactic acid; - And the mass ratio starch (B) / organic plasticizer (C), expressed in dry mass, ranges from 85/15 to 40/60; the composition may also comprise from 0.01 to 200 parts of additional constituent (s) chosen from additives and polymers other than (A1), (A2), (B), (C). The composition according to the invention can be manufactured using a manufacturing method characterized in that it comprises: an introduction step a) in a component mixing system comprising a polyester mixture (A) comprising at least one polylactic acid (A1) and at least one aliphatic polyester (A2) or a semi-aliphatic polyester other than the polymer (A1), at least one starch (B), at least one organic starch softener (C) and optionally some water ; a mixing step b) in which the constituents are thermomechanically mixed to obtain the thermoplastic composition; a recovery step c) of the thermoplastic composition. Obviously, the amounts of the various constituents can be varied so as to obtain the compositions described above. In the case where constituents comprising moisture are used, the person skilled in the art can easily, in order to carry out the method, determine the mass quantities of the various wet-mass constituents to be introduced into the mixing system, by measuring in advance the moisture in each component, for example by performing an assay using the Karl-Fisher method, in order to obtain the compositions in the proportions described above. By way of illustration, in the Examples section, the description of compositions expressed in dry mass, with the amounts of each of the constituents used in the process which are in turn expressed in wet mass, is described. As for the mixing system, it may be internal bladed or rotor mixers, external mixers, co-rotating or counter-rotating twin-screw extruders. However, it is preferred to carry out this mixture by extrusion, in particular by using an extruder. 3028520 13 bi-screw co-rotating. In the case of an extruder, the various constituents of the composition can be introduced by means of introducing hoppers located along the extruder. In order to prepare the composition, use may especially be made of the process described in document WO 2010/0102822 A1.

The mixing system may comprise a drying system, for example a volatile extraction system such as a vacuum pump. In this case, it is possible to reduce the moisture content of the composition at the end of the process, compared with the total humidity in the constituents introduced in step a). Preferably, the humidity of the composition is adjusted so as to be between 2.5 and 10 9% relative to the total (thus wet) mass of the constituents introduced in step a). Advantageously, the process comprises at least one drying step, so that the humidity of the composition is between 0.2 and 1.4%. Preferably, the mixture of step b) is carried out simultaneously with the drying step, for example by connecting a vacuum pump to the reactor. The process may also include a separate drying step, later taking up the recovery step c). According to the invention, the mixing temperature during step b) is advantageously from 90 to 210 ° C., preferably from 110 to 190 ° C. The mixture of the constituents of the composition can be carried out under an inert atmosphere. As for the mixing system, they may be blade or rotor internal mixers, external mixers, co-rotating or counter-rotating twin-screw, twin-screw extruders. Preferably, the mixing step b) is carried out in an extruder, in particular by using a co-rotating twin-screw extruder. By extrusion, the introduction step a) of the various constituents of the composition can be done using feed hoppers located along the extruder. When extrusion mixing is performed, the composition recovered in step c) is in the form of a polymer rod. Preferably, the manufacturing method further comprises a granulation step d) of the composition recovered in step c). At the end of this granulation step d) granules of composition are obtained.

This granulation step can be done by any type of granulator, for example under a water ring, under water or rushes. The recovered composition can be granulated very easily, without forming rosaries. The invention also relates to granules of the composition according to the invention. The invention also relates to an article comprising the composition according to the invention. This article can be of any type and be obtained using conventional transformation techniques. This may be, for example, fibers or yarns useful for the textile industry or other industries. These fibers or yarns can be woven to form fabrics or nonwovens.

The article according to the invention can also be a film, a sheet. These films or sheets can be manufactured by calendering techniques, flat film extrusion, extrusion blow molding. In particular, the invention relates to a sheath blown film manufacturing method comprising: - a step of extruding the composition or granules according to the invention to form a melted composition; a step of forming a sheath by blowing the molten composition obtained in the next step; A pulling step of the sheath; and a step of recovering a film. The composition according to the invention may have, when it is in the form of a film with a thickness of 50 μm, a Young's modulus greater than 100 MPa, advantageously ranging from 200 to 1000 MPa, preferably ranging from 300 to 550 MPa. In these ranges, and particularly in the preferred ranges, these films make it possible to be advantageously used in bags. The film thus obtained may have a thickness ranging from 5 to 200 μm, preferably from 10 to 100 μm. Advantageously, the drawing speed is greater than 5 m / s, preferably greater than 10 m / s. The compositions according to the invention, in particular in the preferred embodiments, make it possible to maintain excellent production rates and to obtain high draw speeds. The article according to the invention may also be a container for transporting gases, liquids and / or solids. It may be bottles, for example bottles of sparkling water or not, bottles of juice, bottles of soda, bottles, bottles of alcoholic beverages, vials, for example bottles of medicine, bottles of cosmetic products, dishes, for example for ready meals, microwave dishes or lids. These containers can be of any size. They can be manufactured by extrusion blow molding, thermoforming or injection blow molding.

The articles may also be multilayer articles, of which at least one layer comprises the composition according to the invention. These articles can be manufactured by a process comprising a coextrusion step in the case where the materials of the different layers are brought into contact in the molten state. By way of example, mention may be made of tube coextrusion, coextrusion of profile, coextrusion blow molding (blowmolding) techniques of a bottle, a bottle or a reservoir, generally grouped together under the term of coextrusion blow molding of hollow body, co-extrusion inflation also called blowing of sheath (in English "film blowing") and co-extrusion flat ("in English" cast coextrusion "). They may also be manufactured by a method comprising a step of applying a melt composition layer to a layer of organic polymer, paper, metal or solid state adhesive composition. This step may be carried out by pressing, overmolding, lamination or lamination, extrusion-rolling, coating, extrusion-coating or coating. The invention will now be illustrated in the examples below. It is specified that these examples do not limit the present invention.

Manufacture of Compositions According to the Invention and Comparative Constituents The constituents of the various exemplified compositions are shown below. Aliphatic polyester - - A2: Aliphatic condensation polyester of succinic acid, adipic acid and 1,4-butanediol (PBSA), melting point of 95 ° C., having a melt index of 1.2 g / 10 min 5 - Al: Semi-crystalline polylactic acid (PLA) produced by Natureworks LLC L-Lactic acid content: 95.7 mol. %, D-Lactic acid content: 4.3 mol. % Melting point = 150 ° C; Melt flow rate MFR = 2.6 g / 10 min; crystallinity = 51% Amorphous polylactic acid (PLA) produced by Natureworks LLC L-Lactic acid content: 88 mol. %, D-Lactic acid content: 12 mol. % Melting point = no melting; Flow rate MFR = 6.0 g / 10 min 15 - LBJ Starch. Wheat starch (containing 12.5% water) - Plasticizer LC12 = Glycerol - Additives Compatibilizer = Citric acid (AC) Process aid = Glycerol monostearate (GMA) 25 Method of making the composition Examples of this method The invention was carried out on a Leistritz brand extruder, ZSE27MAXX60D, Diameter 28, Length L / D = 60, for a flow rate of: 20 kg / hr - Temperature profile (fifteen heating zones Z1 to Z15, temperature in ° C. ): 20/60/60/80/90/110/130/130/180/160/180/150/130/130/130 with a variable screw speed from 200 rpm to 400 rpm.

Physical mixing of the polyester granules is carried out prior to introduction into the extruder. As part of this process, the extruder is introduced into the extruder: the mixture of the polyesters in the main hopper of the extruder, whereupon said mixture passes through all the heating zones of the extruder; plasticizer of the starch at the zone Z3 (9 to 12 D), - the starch, the compatibilizer as well as possibly process aids at the zone Z4 (13 to 16 D) - the Degassing is achieved by applying a partial vacuum in Z 9 (33-36 D) and in zone 11 (41-44 10 D) (vacuum of 100 mbar) to remove volatile compounds such as water. The granules are obtained by a conventional underwater granulation system. Details of the compositions The compositions (Examples 1 to 9) were made using the method described above. The amounts of the various constituents of the compositions are shown in Table 1. The proportions of all the constituents are given in relation to the wet weight of the sum of the constituents (A1), (A2), (B) and (C) Table 1: Proportion of the constituents of the compositions in wet mass introduced into the extruder Composition PBSA PLA (B) (C) MGS AC (A2) (A1) Example 1 45.89 0 35.17 18.94 0.95 0.1 Example 2 44.74 1.15 35.17 18.94 0.95 0.1 Example 3 43.6 2.29 35.17 18.94 0.95 0.1 Example 4 41.3 4.59 35.17 18 , 94 0.95 0.1 Example 5 39.01 6.88 35.17 18.94 0.95 0.1 Example 6 36.71 9.18 35.17 18.94 0.95 0.1 Example 7 32.12 13.77 35.17 18.94 0.95 0.1 Example 8 36.71 9.18 * 35.17 18.94 0.95 0.1 Example 9 32.12 13.77 * 35 18.94 0.95 0.1 *: amorphous PLA 3028520 The resulting compositions were granulated and these granules were dried for 2 hours at 80 ° C. In Table 2 are given the weight proportions of the various constituents of the composition recovered in the form of dried granules, these amounts being expressed relative to 100 parts of the total dry matter of (A1), (A2), (B) and (C). Table 2: Proportion of the constituents of the dry compositions Composition PBSA PLA (B) (C) MGS AC% (A1) / (A2 + A1) (A2) (A1) Example 1 48 0 32.19 19.81 0.1 0.1 0 Example 2 46.80 1.20 32.19 19.81 1 0.1 2.5 Example 3 45.6 2.4 32.19 19.81 1 0.1 5 Example 4 43.20 4.8 32 , 19 19.81 1 0.1 10 Example 5 40.80 7.20 32.19 19.81 1 0.1 Example 6 38.40 9.60 32.19 19.81 1 0.1 Example 7 33.6 14.4 32.19 19.81 1 0.1 25 Example 8 38.40 9.6 * 32.19 19.81 1 0.1 0 Example 9 33.6 14.4 * 32.19 19 , 81 1 0.1 0 *: amorphous PLA The granules of the compositions were converted into 50 micron thick films on a COLLIN brand blow mold extruder (Diameter 20, Length L / D = 18, five Z1 heating zones). to Z5) using the following temperature profile (160CC / 160 ° C / 160 ° C / 160 ° C / 160 ° C) and screw speed of 60 rpm.

Characterization of the compositions and films obtained from compositions 1 to 9: Examples 1 to 9 demonstrate the benefits of the composition according to the invention: the different compositions, which differ only in the choice of the amount and type of acid 3028520 19 polylactic employed, are thus compared. The properties were obtained for a thickness of 50 lm.

Table 3. Effect of Amount and Type of Polylactic Acid (A1) on the Properties of Compositions Composition Speed Speed Overall Filmability Modulus Elongation Constraint (MPa) at Break at Work Work (% ) (MPa) (m / min) (% max speed of the blowing extruder) Example 1 (CP) Not filmable Example 2 (EX) 3.5 27 + 61 623 14.4 Example 3 (EX) 4 31 + 67 558 13.6 Example 4 (EX) 4 31 + 100 461 15.6 Example 5 (EX) 7.5 58 + 148 326 16.3 Example 6 (EX) 13 100 ++ 173 257 14.4 Example 7 (EX Example 8 (CP) 4.8 37 + 104 288 10.5 Example 9 (CP) 2.4 18 + 195 284 12.5 Notation of filmability ++: No problem of stability of bubble +: No problem of stability after reduction of the speed of implementation It is found that when the amount of plasticizer in the thermoplastic starch is important (as is the case in Example 1), It is not possible to transform this film into a film extrusion molding inflation. The use of semi-crystalline PLA (Examples 2 to 7 according to the invention) makes it possible to obtain a filmable composition, while the amount of plasticizer in the thermoplastic starch is identical to that of Example 1.

It is found that the Young's modulus increases proportionally with the PLA level and is accompanied by a decrease in elongation at break. The rate of use becomes maximal for compositions comprising 20% or more of semi-crystalline PLA, this amount being expressed in dry weight of the total amount of polyester (A1) and (A2). In addition, the appearance of the films is much better in these proportions (no micro-holes). On the other hand, the use of amorphous PLA is not favorable: whatever the rate used, the film breaks, even when the drawing speed is low. In addition, the addition of this polymer does not make it possible to improve the print speeds in the same proportions as the addition of the semicrystalline PLA that is useful for the invention. 10

Claims (16)

REVENDICATIONS1. Thermoplastic composition comprising at least one mixture of polyesters (A) comprising at least one polylactic acid (A1) and at least one aliphatic polyester (A2) or a semi-aliphatic polyester other than the polymer (A1), at least one starch (B) ), at least one organic softener of the starch (C) characterized in that: - the mass percentage of (A1) relative to the mass of (A1) and (A2), expressed in dry mass, ranges from 2 to 70%, advantageously from 10 to 50%, preferably from 18 to 30%; at least 50% of the mass of polylactic acid (A1) is composed of semi-crystalline polylactic acid, and in that the weight ratio of starch (B) / organic plasticizer (C), expressed in dry mass, ranges from 85/15 to 40/60. 2. Composition according to claim 1, characterized in that it comprises a mass quantity of polyester (A) in the range from 35 to 75 parts, for example in the range from 40 to 70 parts, advantageously from 45 to 60 parts, preferably ranging from 48 to 58 parts, these mass quantities being expressed relative to 100 parts of the total dry mass of the constituents (A1), (A2), (B) and (C). 3. Composition according to one of the preceding claims, characterized in that the degree of crystallinity of the semi-crystalline polylactic acid is in the range of 20 to 75%. 4. Composition according to one of the preceding claims, characterized in that the polylactic acid consists of a mixture of 55 to 90% of semicrystalline polylactic acid and 10 to 45% of amorphous polylactic acid, the amounts being expressed as dry mass of polylactic acid. 25 5. Composition according to one of the preceding claims, characterized in that the mass ratio starch / plasticizer, expressed in dry mass, ranges from 85/15 to 50/50, preferably from 80/20 to 60/40. 6. Composition according to one of the preceding claims, characterized in that it further comprises a binding agent carrying a plurality of functions capable of reacting with the polyester and the starch, this function possibly being chosen from carboxylic acid functions. for example citric acid, carboxylic acid ester, isocyanate or epoxy. 3028520 22 7. Composition according to one of the preceding claims, characterized in that it further comprises a process agent, especially monoesters of fatty acid and glycerol, for example glycerol monostearate. 8. Composition according to one of the preceding claims, characterized in that the organic plasticizer is chosen from diols and polyols such as glycerol, polyglycerols, sorbitans, sorbitol, mannitol, and hydrogenated glucose syrups. , urea, polyethers with a molar mass of less than 800 g / mol, and any mixtures of these products, preferably glycerol, sorbitol or a mixture of glycerol and sorbitol. 10 9. Composition according to one of the preceding claims, characterized in that the polyester (A2) is aliphatic and is a condensation polymer of ethylene glycol and / or butanediol-1,4 and succinic acid and / or adipic acid. 10. A method of manufacturing a composition according to one of the preceding claims, characterized in that it comprises: 15 ^ an introduction step a) in a mixing system of constituents comprising a mixture of polyesters (A) comprising at least minus a polylactic acid (A1) and at least one aliphatic polyester (A2) or a semi-aliphatic polyester other than the polymer (A1), at least one starch (B), at least one organic starch plasticizer (C) and possibly water; a mixing step b) in which the constituents are thermomechanically mixed to obtain the thermoplastic composition; a recovery step c) of the thermoplastic composition. 11. The method of claim 10, characterized in that: - the amount of water is adjusted so that the moisture of the constituents introduced in step a) is between 2.5 and 9%; - The mixture of step b) is carried out simultaneously with drying, so that the moisture of the composition recovered in step c) is between 0.2 and 1.4%. 12. Method according to one of claims 10 or 11, characterized in that the mixing temperature during step b) ranges from 90 to 210 ° C, preferably from 110 to 190 ° C. 3028520 23 13. Method according to one of claims 10 to 12, characterized in that the mixing system is a twin-screw extruder. 14. Method according to one of claims 10 to 13, characterized in that the polyester (A) introduced in step a) has a melt index ranging from 0.1 to 50 g / 10 min, advantageously from 0 5 to 15 g / 10 min (IS01133, 190 ° C, 2.16 kg). 15. A method of manufacturing film by blowing the sheath, characterized in that it comprises - a step of extruding the composition according to one of claims 1 to 9 to form a molten composition; A step of forming a sheath by blowing the molten composition obtained in the next step; a pulling step of the sheath; and a step of recovering a film. 16. Method according to the preceding claim, characterized in that it has the drawing speed is greater than 5 m / s, preferably greater than 10 m / s.