BE1020028A3 - POLYMERIC MATERIAL BASED ON POLY (LACTIC ACID). - Google Patents

Abstract

A polymeric material comprising a blend of a base polylactic acid (PLA) polymer of from 60% to 85% by weight of L units and from 15% to 40% by weight of D units or 60% by weight. % to 85% by weight D units and 15% to 40% L units, and a plasticizer selected from the group consisting of citric acid esters, glycerine esters and derivatives, polyalkylene ethers) , oligomers of lactide or lactic acid derivatives, fatty acid esters and epoxidized oils, the content of which is between 10% and 40% by weight, relative to the total weight of the polymer material.

Description

Polymeric material based on poly (lactic acid)

The present invention relates to the field of biopolymers based on poly (lactic acid) derivatives, biosourced and biodegradable, and their use in the glass field, in particular as an interlayer film in laminated glasses.

Poly (lactic acid) and polylactic acid polymer, as used in the claims, (PLA) is a well-known biobased and biodegradable polyester.

The PLA can be obtained by ring-opening polymerization of lactide, itself obtained by controlled depolymerization of oligomers of lactic acid derived, via chemical and biotechnological processes, from corn starch or beet sugar, for example .

Lactic acid, the basic unit of PLA, is a chiral molecule that has two L and D enantiomers. The ratio of opposite configuration units in PLA, that is, D units in PLLA or patterns L in PDLA, defines its optical purity. A PLLA will be all the more optically pure that its rate of D motifs will be low. Many properties of PLA are directly or indirectly related to their optical purity, for example PLA of high optical purity crystallize more easily than PLA of low optical purity.

PLA has been the subject of intense studies and chemical modifications in order to favorably substitute it for polymers from the petrochemical industry, which pose environmental problems and are likely to cause toxicity to humans. Among these, we can mention the slow degradation of these polymers and the toxicity of residues from their incineration that is found in the food chain.

Also, PLA and modified PLA are preferred over other biopolymers, such as starch or cellulose derivatives having lower mechanical performance and low UV resistance.

Applications of PLA or PLA modified polymers are mainly for food packaging and in the medical field (gloves) for which properties of transparency, resistance to impact, heat and humidity are sought.

In the glass industry, laminated glass is commonly used as security glass in architecture and also as windshield in cars and others. The interlayer film between two glass sheets conventionally used is a polymer of the EVA (ethylene-vinyl acetate), polyurethane or PVB (polyvinyl butyral) type. In view of the environmental problems caused by such polymers and their ever increasing costs, it has been envisaged to replace them in laminates with films or films of PLA or modified PLA. However, it is necessary that the latter biopolymers have sufficient thermomechanical properties to meet the requirements of transparency in time, mechanical strength, namely elastic deformation, glass transition temperature (Tg), elongation at break, energy d impact and fragility, and good adhesion to glass.

The unmodified PLA films do not achieve these objectives because of their low flexibility and adhesive properties at temperatures below 60 ° C on the one hand and secondly because they present at temperatures above 60 ° C undesirable flexibilities making their use limited.

To overcome these drawbacks and to obtain the desired thermomechanical properties for these polymers, it has been proposed to use PLA grades characterized by low optical purity, that is to say by a high level of D units in a PLLA. or, respectively, L-patterns in a PDLA. Indeed, studies have shown that a fraction of D units in a PLLA or, respectively, of L units in a PDLA, greater than 10% had a beneficial influence on the crystallization of PLA by decreasing it, which avoids the production of materials with undesirable opacity.

Another means is a plasticization optionally coupled to a crosslinking of the base PLA.

Said base PLA having a high Young's modulus (about 2500 MPa - ISO 527), but on the other hand having low elongations at break, of a few percent, and a low resistance to impact, it can not be used as such as for example in laminated glasses to restore the performance of the PVB. This disadvantage can be avoided, according to embodiments, by the incorporation, in the basic PLA, of a suitable plasticizer in order to increase the mobility of the PLA chains, resulting in a decrease of Tg up to typically ambient temperature, and an increase in elongation at break. However, the chosen plasticizer must also be easily miscible with the PLA, have stability over time and not exude out of the mixture. The nature, the rate of incorporation as well as the molecular weight of the plasticizer influences these effects. The choice of the plasticizer therefore lies in a compromise between the properties sought.

Generally, plasticizers suitable for PLA are those of the chemical class of triesters, such as citrates, acetyl citrates and glycerol esters, polyalkylene ethers, such as polyethylene glycol (PEG) and its derivatives, oligomers of lactide or lactic acid derivatives. Some studies have shown that fatty acid esters and epoxidized oils may also be suitable, for example based on soybean oil, palm oil or linseed oil. The level incorporated in the PLA varies between 3 and 30% by weight.

In summary, a suitable plasticizer in a PLA composition allows a joint decrease in Tg, melting and crystallization temperatures, resulting in that of Young's modulus and tensile stress, but also the increase in elongation at breaking.

Patent Application KR 2008-0043041 discloses a composition comprising a PLA resin and a plasticizer selected from the group consisting of an acetyl monoglyceride, a citrate derivative, such as tributyl citrate, and mixtures thereof. This provides a modified PLA having increased impact resistance and elongation and being biocompatible. However, this document does not mention any influence of the relative level of D-lactic acid or L-lactic acid units in PLA on these properties.

The application US 2008/0213209 discloses reticulated and plasticized PLA rosin, which is based on organic acids of the family of diterpenes called resin acids. However, a possible influence of the optical purity of PLA is not indicated.

The presence of plasticizer is therefore necessary to improve the properties of PLA, but two other factors which must be satisfied as to their desired properties are the stability of the PLA / plasticizer compositions, in particular avoiding the exudation of the plasticizer, and the absence of crystallization of PLA because it induces opacification or even an increase in the stiffness of the material, both undesirable. Now, the crystallization could be favored by the lowering of the Tg induced by the addition of the plasticizer.

In order to provide a PLA material which can advantageously be substituted for the polymers originating from the petroleum industry while presenting the mechanical properties listed above, the Applicant has found a new formulation of plasticized PLA which also overcomes the drawbacks of the prior art.

The invention thus relates to a polymeric material comprising a blend of a base polylactic acid (PLA) polymer of 60% to 85% by weight of L units and 15% to 40% by weight of D units or 60% to 85% by weight D units and 15% to 40% L units, and a plasticizer selected from the group consisting of citric acid esters, glycerine esters and derivatives, polyalkylene ethers ), oligomers of lactide or lactic acid derivatives, fatty acid esters and epoxidized oils, the content of which is between 10% and 40% by weight, relative to the total weight of the polymeric material.

The Applicant has oriented his research towards formulations that make it possible to obtain physical properties (Tg, Young's modulus, deformation behavior) close to those of the dividers that can currently be found on the market for laminated glasses (polyvinyl butyral). ) -PVB), ethylene vinyl acetate (EVA), thermoplastic polyurethane (TPU), ionomeric resin, ...), which makes a film obtained from this material very advantageously usable as an intermediate film in a laminated glass. The properties of interest are in particular:

Tg, which is advantageously between 0 ° C and 35 ° C, in particular between 5 ° C and 25 ° C, that is to say close to the ambient temperature,

Deformation behavior exhibiting a plastic or elastic character,

Young's modulus (E) (measured according to ISO 527), between 0.1 and 300 MPa; preferably between 1 and 300 MPa,

An elongation at break (ε), advantageously between 50% and 800%, preferably between 200% and 600%;

A breaking stress (o) of between 5 and 70 MPa, in particular between 15 and 50 MPa,

Transparency, and

Thermal stability or aging.

The Applicant has shown that the chemical nature of the plasticizer, its rate of incorporation as well as its molecular weight can adversely affect the desired properties of the polymeric material if not judiciously chosen. Thus, it has been shown that it is preferable to use an incorporation rate of not more than 40%, preferably not more than 25%, to prevent its exudation out of the material, exudation which can also be observed if the others conditions are not respected. It must also not be volatile at the manufacturing temperatures of the material. Preference is given to plasticizers derived from citric acid.

Advantageously, the plasticizer is selected from the group consisting of esters of citric acid, esters of glycerin, and polyalkylene ethers, their corresponding derivatives and mixtures thereof. It is of course preferable that the plasticizer is also biodegradable.

The esters of citric acid are preferably the alkyl derivatives of these esters, such as triethyl citrate, n-tributyl citrate (TbC), n-hexyl citrate, and acetyl derivatives of these esters, such as acetyl-citrate, acetyl-triethyl-citrate, acetyl-n-tributyl-citrate and acetyl-n-trihexyl-citrate.

The glycerol esters and their derivatives are advantageously mono-, di-, tri-glycerides, as well as their acetylated and / or alkylated derivatives and their mixtures, such as glyceryl triacetate (TAC),

The poly (alkylene ethers) are preferably polyethylene glycol (PEG) or polypropylene glycol (PPG) and their derivatives.

Epoxidized oils may also be suitable, such as soybean oil, palm oil or linseed oil.

Very advantageously, the plasticizers are citric acid esters, in particular n-tributyl citrate (TbC), glycerol esters and their respective derivatives and mixtures.

Preferably, the content of plasticizer is between 15 and 30% by weight, more preferably between 20 and 25% by weight, relative to the total weight of the polymer.

The number-average molecular masses (Mn) of the basic PLA are preferably between 50000 and 200000, more preferably between 70000 and 180000, advantageously between 70000 and 150 000. The Applicant has shown that such basic PLA Mn are those that provide the best results in terms of properties sought. The PLA Mn values can be measured by CES whose molecular weight calibration is performed with polystyrene (PS) standards.

The basic PLA that can be used are first and foremost commercially available.

By way of example, in two PLA samples whose D units are respectively 11% and 12.1%, TbC and TAC contents of between 10 and 30% have been added. For these ranges of values, the Tg is between 18 ° C and 34 ° C and these Tg values remain generally stable during aging tests greater than 12 months at room temperature.

They can also be synthesized in particular from a mixture of monomers L-lactide and D-lactide with a catalyst / initiator system consisting of an organotin, such as tin ethylhexanoate, triphenylphosphine and an alcohol, such as octanol, in the presence of an organic phenyl solvent, such as toluene. The mixture is refluxed at high temperature, typically at 190 ° C, for 0.5-1 hr. The residual lactide and the low oligomers are removed by precipitation in methanol. The proportion of each L-lactide and D-lactide monomer determines the rate of D units in the basic PLA.

In the polymeric material, the base PLA consists of 60% to 85% by weight of L units and 15% to 40% by weight of D units or 60% to 85% by weight of D units and 15% by weight. at 40% of L units, advantageously 15% and 30% of L units or D units and, respectively, of 70% to 85% by weight of D units or L units. One of the important aspects of the invention lies in the relative content of one of the isomers with respect to the other. It is therefore the relative proportion that contributes to the desired effects. These levels make it possible to obtain good transparency of PLA by reducing its crystallinity. The Applicant has also, surprisingly, shown that the plasticizer content and the ratio of units of opposite configuration must be within the aforementioned ranges, since, outside of these, the desired technical effect is not achieved, especially because of too high values of E (Young's modulus), typically greater than 300 MPa, which results in unacceptable stiffness of the material for the desired applications.

Moreover, to overcome the possible problems of exudation of the plasticizer and achieve the desired properties, such as the absence of crystallization or obtaining a deformation behavior of elastic type, even more easily, the basic PLA in the polymeric material is advantageously modified by crosslinking of its chains. The polymeric material, comprising the cross-linked PLA and the plasticizer above, makes it possible in particular to avoid total exudation of the plasticizer from the material, which retains its flexibility.

The crosslinking agent of the basic PLA chains is usually chosen from methacrylic and acrylic copolymers, optionally containing glycidyl functions, such as joncryl (formula c)); isocyanurate derivatives, preferably allylic derivatives, such as triallyl isocyanurates (TAIC - - Formula a)); organic peroxides, such as dicumyl peroxide (DCP - Formula b)); and their mixtures, or any other multifunctional molecule capable of driving, by radical reaction along the PLA chain or by reaction with the ends of the PLA chains, for example, at a partial crosslinking of PLA, as well as mixtures of the molecules cited together or with other multifunctional molecules.

In the compound of formula c), R 1 to R 5 preferably independently represent H or C 1 -C 3 alkyl or their combination, R 6 is preferably C 1 -C 3 alkyl; x, y and z are from 1 to 20. An example of such a compound is available commercially as Joncryl ADR 4368-CS from BASF.

Preferably, the crosslinking content is at most 5% by weight, relative to the total weight of the modified PLA, and advantageously in the range 0.1% -5%, in particular between 0.5 and 4%.

The thermal stability of the polymeric material must also be ensured, since the plasticization and, where appropriate, the crosslinking are carried out at temperatures greater than 150 ° C., or even of the order of 180 ° C.-200 ° C., in order to be effective, in an internal mixer or kneader, or in an extruder. The plastification and the crosslinking can be carried out concomitantly, or in a sequenced manner.

The invention also relates to a film or film made of a polymeric material as defined above.

Preferably, the thickness of the film is between 0.1 and 3 mm.

For the production of this film, the polymer material advantageously also includes additives chosen from the group consisting of anti-blocking agents intended in particular to reduce contact adhesion phenomena, stabilizing agents, especially with respect to radiation. UV, absorbent agents (UV and infrared radiation), anti-static agents.

Anti-blocking agents are typically compounds which prevent the contact adhesion of films based on the polymer material of the invention, especially when they are wound for storage or transport. These are typically talc, silica, mica, kaolin, pertite, wollastonite, titanium dioxide and diatomaceous earth which are in the form of very finely ground powder, or organic molecules such as for example erucamide. It is typically added so that the content is from 0.1 to 4% by weight based on the total weight of the polymeric material. This agent, when it is used, advantageously makes it possible to solve the problems of contact adhesion of the film on itself during storage, for example in a roll, while maintaining the transparency of the polymeric material.

The stabilizing agents are used to prevent any oxidative or thermo-oxidative degradation of the polymer material during its manufacture, if this is the case. The agents are those conventionally used, such as phosphite derivatives.

The preparation of the polymer material is preferably carried out by mixing the PLA, the plasticizer and, depending on the case, the crosslinking agent, at temperatures above 150 ° C., or even in the order of 180 ° C. to 200 ° C. to be effective, in an internal mixer or kneader, for example Brabender brand, or else by extrusion, according to known technologies and devices. The material is for example a resin in the form of granules. Crosslinking is possible because of the high temperature, for example by generating radical systems both by the crosslinking agent and those of the PLA, which induces the crosslinking.

According to embodiments, when the crosslinking step is implemented, it is carried out concomitantly with the plasticizer addition step. The plasticization and the crosslinking can therefore be carried out concomitantly, or in a sequenced manner.

As well as the interleaves currently used in laminated glasses, the films of this polymeric material can be obtained by means of methods well known in the technical field of the manufacture of plastic films, for example by cast extrusion, by extrusion blowing of sheath or else by thermopressing.

The thermomechanical parameters and advantages of the polymeric materials of the invention are characterized by the following measurements and tests.

- DMA ("Dynamic Mechanical Analysis") tests according to ASTM D4065, D4440 and D5279 standards. These tests are carried out by raising the temperature from -40 ° C to 170 ° C at 3 ° C / min, at 1 Hz and at 0.04% tension deformation of specimens 0.5 mm thick.

- The DSC ("Differential Scanning Calorimeter") tests according to the ISO 11357 standard which make it possible to determine the Tg and to highlight the absence of undesirable phenomena of crystallization. They are carried out by raising the temperature from -40 ° C. to 220 ° C. at 10 ° C./min; cooling from 220 ° C to -40 ° C to 20 ° C / min; isothermal 2 minutes; temperature rise from -40 ° C to 220 ° C at 10 ° C / min.

- The tensile tests, according to the ISO 527 standard, which make it possible to measure the Young's modulus (E), the elongation at break (ε) and the stress at break (σ) were carried out on samples cut to size punch in heat-treated plates with a crosshead speed of 10 mm / min.

Steric Exclusion Chromatography (CES) which makes it possible to determine the various number average molecular weights (Mn) and weight (Mw), in particular for synthetic polymer materials. Internal standards are polystyrene.

The invention also relates to a substrate coated with the film consisting essentially of the polymer material of the invention.

In the context of the invention, the substrate preferably represents a glass substrate which is very advantageously transparent, a transparent glass substrate coated with at least one functional layer, such as antireflective layers, of low emissivity ("Low-E "), Solar control, sodium ion barrier and color neutralization in reflection. The substrate can also represent mirrors, glass substrates coated with layers of lacquer for decorative applications. The substrate, preferably transparent, may be a polymeric material based on polycarbonate or poly (methylmethacrylate).

Another aspect of the invention is a laminated assembly comprising at least two substrates, which assembly comprises, between the at least two substrates, at least one interlayer film of impact-resistant and tear-resistant polymeric material, comprising a mixture ( i) a base polylactic acid (PLA) polymer consisting of 60% to 85% by weight of L units and 15% to 40% by weight of D units or 60% to 85% by weight of units D and 15% to 40% of L units and (ii) a plasticizer, the content of which is between 10 and 40% by weight, relative to the total weight of the polymer material.

Thanks to the thermomechanical properties of this film, very close to those of the PVB in particular, it is possible to consider in particular a laminated glass as being of "safety glazing" quality, that is to say for which, in case of breakage of the glazing, the debris remains fixed on the film and therefore not likely to hurt people handling it or who find themselves nearby. Such glazings are advantageously used as windshields of motor cars or in any other known application.

Preferably, the plasticizers used are those mentioned above.

It is also advantageous to incorporate in the polymer material crosslinkers and various other additives, such as those described above, in order to implement the film of the invention and the laminated assembly comprising it.

Preferably, at least one of the substrates of the laminated assembly is a glass substrate. The glass substrate is not limited in itself, and typically represents clear floated glass, extra clear, colored, or borosilicate, which are transparent, whose thicknesses are typically between about 1 mm and 8 mm. By extra-clear glass is meant a glass comprising a maximum iron content, expressed as FeaCh, of less than 0.04% by weight, in particular less than 0.02% by weight. By clear glass is meant a glass comprising a maximum iron content, expressed as Fe 2 O 3, ranging from 0.04 to 0.4% by weight. It can also be tempered or hardened glass.

According to embodiments, at least one of the substrates of the laminated assembly is made of polymer, typically polycarbonate or poly (methylmethacrylate). According to other embodiments, one of the substrates is a glass substrate and the other is a polymer substrate above.

It may be envisaged to use this film in laminated glasses based on three glass substrates, the film then being an interlayer between the three substrates, the intermediate substrate having on each of its faces the film of the invention.

The outer faces of the glass substrates may also comprise at least one functional layer deposit, such as antireflective, low emissivity, antifouling or adapted to photovoltaic devices, such as doped metal oxide layers (SnO2: F), TiO 2, layers preventing the migration of sodium ions from the glass, such as layers of oxycarbides, oxynitrides or silicon oxides.

Laminated glasses are manufactured by techniques known per se, in particular by analogy with laminated glasses based on PVB film.

The examples which follow illustrate the invention without limiting its scope. Examples

In all the examples which follow, the polymeric materials with the base PLA in which plasticizers, crosslinking agents and other additives are incorporated, are prepared in the following manner.

The basic PLA is introduced into an internal brand mixer

Brabender (volume of the mixing chamber = 55 cm3) at a temperature of 190 ° C. After a mixture of 5-10 min, the plasticizer is incorporated at contents ranging from 10 to 40% by weight, based on the total weight of the base PLA polymer. The whole is mixed at this temperature for 10 minutes to obtain a homogeneous polymer material. This is then thermopressed at 190 ° C. under a pressure of 130 bars to obtain discs 10 cm in diameter and 0.5 mm thick.

The polymeric materials which incorporate, in addition to the plasticizer, a crosslinking agent are prepared in the following manner.

Prior to the addition of the plasticizer and after introduction of the basic PLA as above, is incorporated 3% by weight of crosslinking agents (or crosslinkers) respectively Joncryl ADR 4368-CS, from BASF, and DCP. The mixture is mixed for about 5 minutes and the plasticizer is then incorporated. The later stages are those described above. In the case of addition of two different crosslinking agents, 1.5% by weight of the first crosslinking agent is incorporated and 5 min and 1.5% of the second crosslinking agent are mixed, followed by mixing for 5 min.

The synthesis of basic PLA having a PDLA isomer level of between 15% and 40% by weight is carried out with two samples of lactide grade polymerization, one being a dimer of lactic acid, L isomers, the other being a racemic mixture of lactic acid dimers, L and D isomers. Depending on the respective amount in each sample, the contents are obtained varying between 15 and 40% by weight of D units. A catalyst / initiator system is used. consisting of tin ethylhexanoate, triphenylphosphine and octanol, (lactide / ethylhexanoate tin = 4500, lactide / octanol = 420, ethylhexanoate tin / triphenylphosphine = 1) in the presence of toluene. The mixture is refluxed at 190 ° C for 35 minutes. Residual lactide and lower oligomers are removed by precipitation in methanol, the base PLA being then dried under vacuum at 60 ° C for complete removal of the solvent. The relative proportion of L-lactide and D-lactide determines the optical purity of the base PLA.

For each formulation mentioned in the examples below, the amounts of additives added are expressed as percentage by weight of the total. Example 1

A polylactic acid (PLA) formulation to which a plasticizer, n-tri-butyl citrate (TbC), whose content is 20% (Sample A) was added. It has a pattern ratio D of 30%.

By way of comparison, a Sample B characterized by a D-unit rate of 12% and comprising a TbC content of 5% was considered.

Table 1 shows the evolution of the Tg of the formulations and the mechanical properties thus obtained.

By way of example, Table 1 also includes the values of these properties for the PVB.

The results of Table 1 clearly indicate that the optical purity of the PLA and the plasticizer content according to the invention makes it possible to reduce the Tg, and it is observed that for the sample B (comparative), the composition of which is outside the invention, values are too high in terms of Young's modulus (E) and too low for elongation at break (ε).

Example 2

A poly (lactic acid) (PLA) formulation to which a plasticizer is added, n-tributyl citrate (TbC), the base PLA having been cross-linked (J = joncryl ADR 4368-CS) is considered.

The following Table 2 presents the characteristics of the polymeric materials: plasticizer content, rate of D units, crosslinker content, as well as data on the mechanical properties of these materials.

Table 2

The results in Table 2 indicate that, for the samples C to F according to the invention, the properties desired for these materials are obtained contrary to the sample G, outside the invention, for which the properties are not satisfactory.

Example 3

Aging tests make it possible to characterize the stability of the formulations produced. A series of tensile specimens were thus aged at 100 ° C overnight and the thermomechanical properties were re-evaluated.

A poly (lactic acid) formulation (PLA) to which a plasticizer has been added, n-tri-butyl citrate (TbC), the base PLA having optionally been cross-linked (J = joncryl ADR 4368-CS) is considered. .

The following Table 3 presents the characteristics of the polymer materials: plasticizer content, D-ratio, crosslinker content, as well as data on the mechanical properties of these materials before and after the aging step (in italics) and also informs if a melting peak was observed during the DSC measurement, which indicates the presence of a crystalline phase in the polymer material.

Table 3

Samples A and C have satisfactory properties before and after aging.

On the other hand, for the samples H to K, outside the invention, the appearance of a crystalline phase is observed during the aging at high temperature, which generates unsatisfactory thermomechanical properties but also a clouding of the material which makes it unsuitable for them. targeted applications.

Claims (13)

A polymeric material comprising a blend of a base polylactic acid (PLA) polymer of 60% to 85% by weight of L units and 15% to 40% by weight of D units or 60% to 85% by weight of % by weight D units and from 15% to 40% of L units, and a plasticizer selected from the group consisting of citric acid esters, glycerine esters and derivatives, polyalkylene ethers, oligomers of lactide or lactic acid derivatives, fatty acid esters and epoxidized oils, the content of which is between 10% and 40% by weight, relative to the total weight of the polymer material. 2. Material according to claim 1, in which the citric acid esters are the alkyl esters, in particular n-tributyl citrate (TbC). 3. Material according to claim 1 or 2, wherein the glycerin esters and their derivatives are mono-, di-, tri-glycerides, and their acetylated and / or alkylated derivatives and mixtures thereof, such as glyceryl triacetate. (TAC). 4. Material according to one of claims 1 to 3, wherein the plasticizer content is between 15 and 30% by weight, more preferably between 20% and 25% by weight, relative to the total weight of the polymer material. . 5. Material according to one of claims 1 to 4, wherein the base polylactic acid polymer (PLA) consists of 15% to 30% of L or D units and, respectively, of 70% to 85% by weight. pattern weight D or L. 6. Material according to one of claims 1 to 5, wherein the base PLA is modified by crosslinking its chains by means of a crosslinking agent. 7. The material according to claim 6, wherein the crosslinking agent of the basic PLA chains is chosen from methacrylic and acrylic copolymers, optionally containing glycidyl functions, such as joncryl; isocyanurate derivatives, preferably allylic derivatives, such as triallyl isocyanurates (TAIC); organic peroxides, such as dicumyl peroxide (DCP); and their mixtures. 8. Material according to claim 6 or 7, wherein the crosslinking content is at most 5% by weight, relative to the total weight of the modified PLA, and advantageously in the range 0.1% -5%, in between 0.5 and 4%. 9. Film of polymeric material, consisting of a polymeric material according to one of claims 1 to 8. A laminated assembly comprising at least two substrates, which assembly comprises, between the at least two substrates, at least one interlayer film of impact and tear resistant polymeric material, comprising a mixture of (i) a polymer of base polylactic acid (PLA) consisting of 60% to 85% by weight of L units and 15% to 40% by weight of D units or 60% to 85% by weight of D units and 15% to 40% by weight of L units and (ii) a plasticizer, the content of which is between 10 and 40% by weight, relative to the total weight of the polymer material. The laminated assembly of claim 10, wherein the plasticizer is as defined in any one of claims 1 to 4. Laminated assembly according to claim 10 or 11, wherein the basic PLA is defined according to one of claims 6 to 8. 13. Laminated assembly according to one of claims 10 to 12, wherein at least one of the substrates is a glass substrate.