EP2094767A1

EP2094767A1 - Copolymer grafted with polyamide, material comprising it, preparation process and uses

Info

Publication number: EP2094767A1
Application number: EP06842082A
Authority: EP
Inventors: Mathilde Weber; Ilias Iliopoulos; Ludwik Leibler; Pierre Gerard
Original assignee: Centre National de la Recherche Scientifique CNRS; Arkema France SA
Current assignee: Centre National de la Recherche Scientifique CNRS; Arkema France SA
Priority date: 2006-12-01
Filing date: 2006-12-01
Publication date: 2009-09-02
Also published as: US20100063223A1; WO2008065259A1; JP2010511088A

Abstract

The invention relates to a graft copolymer composed of a backbone formed of a block copolymer of general formula B-(A)n in which A is a rigid block polymer with a glass transition temperature of more than 0°C, B is a flexible block polymer with a glass transition temperature of less than 0°C, and n is 1 or is a natural integer greater than 1, it being possible for the blocks A, when n is 2 or more, to be identical or different; and of polyamide (PA) grafts which are carried by the rigid polymer block or blocks, the resulting graft copolymer being represented by the formula (Ag)m-B-(A)p, in which A and B are as defined above, Ag is the block A carrying at least one graft (PA), and m and p are natural integers whose sum is equal to n, but p being able to be equal to 0.

Description

POLYAMIDE GRAFT COPOLYMER, MATERIAL CONTAINING SAME, METHOD OF MANUFACTURE AND USES.

The present invention relates to a graft copolymer comprising a flexible polymer block (which can also be called a soft block) and at least one rigid polymer block (which may also be called a hard block), the rigid polymer block or blocks. carrying polyamide grafts (PA). Such a graft copolymer is obtained by the reaction with an amine or acid-terminated polyamide of a copolymer comprising the flexible polymer block and the rigid polymer block or blocks, this or these rigid polymer blocks being functionalized. Advantageously, the graft copolymer is a hard-soft-hard type copolymer whose end blocks, in particular based on methyl methacrylate (MMA), carry the grafts of PA.

According to the present invention, a material is obtained which has good thermomechanical properties and good chemical resistance, as well as, under particular conditions, good transparency.

Polymethylmethacrylate (PMMA) is a material that is valued for its excellent optical properties. However, it is limited in terms of thermomechanical behavior because its glass transition temperature (denoted T _g ) is 105 ^° C.

(for a PMMA obtained by radical polymerization).

It is also limited in terms of resistance to stress cracking. The search has found a number of solutions to improve these performances. Thus, the copolymerization of methyl methacrylate (MMA) with methacrylic acid (MAA) can result in copolymers having higher thermomechanical strengths; he This is for example the Oroglas HT121 grade of the Applicant. It is also possible to mention the process for imidizing PMMA by reactive extrusion with an amine to give the materials known under the name KAMAX® from Rohm and Haas. These solutions, however, have limitations that exclude these methacrylic materials of particularly demanding applications from a chemical and / or thermal point of view.

[Prior State of the Technique]

EP 0 500 361 A2 describes the PMMA / PA alloys made using a graft copolymer obtained by melt reaction of a PMMA carrying glutaric anhydride functions and an amine-terminated polyamide as a compatibilizer of a mixture. PMMA and PA. The graft copolymer can be prepared in situ during the manufacture of the alloy.

EP 0 438 239 A2 describes the use as a compatibilizing agent of a graft copolymer obtained by melt reaction of a PMMA bearing glutaric anhydride functions and a polyamide.

EP 0 537 767 A1 describes a material obtained by the reaction of a PMMA carrying glutaric anhydride functions, a thermoplastic resin which may be a polyamide and a copolymer bearing epoxide functional groups.

FR 2 868 785 A discloses a graft copolymer consisting of a PMMA trunk and polyamide grafts having a number-average molecular mass of between 1000 and 10,000 g / mol, and a material comprising this graft polymer, which material has both transparency and thermomechanical and chemical resistance.

The Applicant has now discovered that materials having an excellent compromise of the properties indicated above can be obtained by grafting polyamide onto a block copolymer, having a soft block and at least one hard block, in particular a soft diblock copolymer. hard-hard or hard-hard triblock or a star copolymer having a soft block as a core and at least three hard blocks as arms, the hard blocks being functionalized as indicated in the following.

In particular, it has been found that copolymers used for grafting and having nanostructuring retain their nanostructuration after grafting. This is the case of the examples of hard-soft-hard copolymers illustrating the present invention. By "nanostructured copolymers", or "nanostructured materials" is meant stable and dispersed polymer mixtures in domains of size generally less than 100 nm, preferably a few tens of nanometers. The consequence of this phenomenon is to obtain graft copolymers that are resistant to solvents and have improved thermomechanical behavior at high temperatures. It is also remarkable that the length of the grafts has no influence on the conservation of nanostructuration as was the case in FR 2 868 785 A. On the contrary, it appears that the properties are better for longer grafts. [Brief Description of the Invention]

A first object of the present invention is a graft copolymer consisting of a trunk formed of a block copolymer of general formula:

B- (A) _n

in which :

A is a rigid polymer block with a glass transition temperature greater than 0 ^° C .; B is a flexible polymer block of glass transition temperature below 0 ^° C; and n is 1 or is a natural number greater than 1, the blocks A, when n is 2 or more, which may be the same or different, and polyamide graft (PA) carried by the rigid polymer block or blocks, the graft copolymer obtained being represented by the general formula:

(A _g ) _m -B- (A) _p wherein: A and B are as defined above;

Ag is block A carrying at least one graft (PA); and m and p are natural whole numbers whose sum is equal to n, p being able to be equal to 0, however.

By "identical A blocks" is meant identical blocks of identical chemical nature since they are obtained from the same starting monomer composition. In fact, as is well known to those skilled in the art, the composition and the molar mass of the blocks A indicated as identical may vary from one block A to the other. Another subject of the invention relates to the process for preparing the graft copolymer as defined above, characterized in that it consists in reacting with a polyamide terminated with a primary or acid amine function a copolymer of formula general B- (A) _n , A, B and n being as defined above and the block or A bearing functionalities capable of reacting with primary amine or acid functions of the polyamide.

Another subject of the invention relates to a material comprising the graft copolymer according to the invention.

Yet another subject of the invention relates to the use of the graft copolymer according to the invention or of the material comprising it.

[Figures]

In the description of these figures and in the "Examples" part below, the index "f" associated with the notation of a polymer block means that this block is functionalized, allowing it to react with the graft polyamide.

Figures la. and Ib are TEM microscopy pictures of a functionalized triblock copolymer material P (MMAf-b-BA-b-MMAf) prior to polyamide grafting; FIGS. 2a to 2c are TEM micrographs of the grafted triblock copolymer material obtained in Example 2; Figures 3, 5 and 7 each show DMA conservation modulus curves for different samples of triblock copolymer material grafted with the invention and for the functionalized triblock copolymer before the grafting of the polyamide, FIG. 7 also containing the curve for a polyamide which has been used for the grafting; - Figures 4a. at 4d are TEM micrographs of grafted triblock copolymer materials Examples 2, 4 and 5 respectively and the material consisting of a PMMAf grafted with a polyamide; Figures 6a. at 6d are TEM micrographs of grafted triblock copolymer materials Examples 6, 5, 7 and 8, respectively.

[Detailed description]

With regard to the trunk copolymer of formula B- (A) _n , it is in particular a copolymer whose A blocks have a T _g greater than 0 ^° C., in particular greater than or equal to 50 ^° C., advantageously greater than or equal to 80 ^° C., and the block B has a T _g lower than 0 ^° C., in particular less than or equal to -1 ^{0 °} C., advantageously less than or equal to -30 ^° C.

The monomers composing blocks A and B can be chosen from vinyl, vinylidene, diene, olefinic and alkylic monomers, the person skilled in the art knowing how to combine them to obtain the desired T _g for each of them.

By vinyl monomers is meant acrylic acid or its alkali or alkaline earth metal salts, such as sodium, potassium or calcium, (meth) acrylates, vinylaromatic monomers, vinyl esters, (meth) acrylonitrile, (meth) acrylamide and mono- and di- (C1-18 alkyl) - (meth) acrylamides, and monoesters and diesters of maleic anhydride and maleic acid.

The (meth) acrylates are in particular those of the formulas respectively:

CH ₂ = C (CH ₃ ) -COOR ° and CH ₂ = CH-COO-R ⁰

in which R ⁰ is chosen from alkyl radicals comprising from 1 to 18 carbon atoms, linear or branched, primary, secondary or tertiary, cycloalkyl comprising from 5 to 18 carbon atoms, (alkoxy with 1 to 18 carbon atoms) - alkyl with 1 to 18 carbon atoms, (alkylthio with 1 to 18 carbon atoms) -alkyl with 1 to 18 carbon atoms, aryl and arylalkyl, these radicals being optionally substituted by at least one halogen atom (such as fluorine) and / or at least one hydroxyl group after protecting this hydroxyl group, the above alkyl groups being linear or branched; and (meth) acrylates of glycidyl, norbornyl, isobornyl.

Examples of methacrylates that may be mentioned are methyl, ethyl, 2,2,2-trifluoroethyl, n-propyl, isopropyl, n-butyl, sec-butyl and tertiary methacrylates. butyl, n-amyl, i-amyl, n-hexyl, 2-ethylhexyl, cyclohexyl, octyl, i-octyl, nonyl, decyl, lauryl, stearyl, phenyl, benzyl, β-hydroxyethyl, isobornyl, hydroxypropyl, hydroxybutyl.

As examples of acrylates of the above formula, mention may be made of methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl and tert. -butyl hexyl, 2-ethylhexyl, isooctyl, 3,3,5-trimethylhexyl, nonyl, isodecyl, lauryl, octadecyl, cyclohexyl, phenyl, methoxymethyl, methoxyethyl, ethoxymethyl, ethoxyethyl, perfluorooctyl.

For the purposes of the present invention, the term "vinylaromatic monomer" means an ethylenically unsaturated aromatic monomer such as styrene, vinyltoluene, alpha-methylstyrene, methyl-4-styrene, methyl-3-styrene or methoxy-4-styrene. hydroxymethyl-2-styrene, ethyl-4-styrene, ethoxy-4-styrene, dimethyl-3,4-styrene, chloro-2-styrene, chloro-3-styrene, chloro 4-methyl-3-styrene, tert. 3-butyl-styrene, 2,4-dichloro-styrene, 2,6-dichloro-styrene and 1-vinyl-naphthalene.

Vinyl esters include vinyl acetate, vinyl propionate, vinyl chloride and vinyl fluoride.

As the vinylidene monomer, vinylidene fluoride is mentioned.

By diene monomer is meant a diene chosen from linear or cyclic dienes, conjugated or non-conjugated, such as butadiene, 2,3-dimethyl-butadiene, isoprene, 1,3-pentadiene, 1, 4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 1,9-decadiene, 5-methylene-2-norbornene, 5-vinyl-2-norbornene, 2-alkyl-2, 5-norbonadienes, 5-ethylene-2-norbornene, 5-

(2-propenyl = -2-norbornene, 5- (5-hexenyl) -2-norbornene, 1,5-cyclooctadiene, bicyclo [2,2,2] octa-2,5-diene, cyclopendatiene, 4, 7, 8, 9-tetrahydroindene and 1-isopropylidene tetrahydroindene.

Olefinic monomers include ethylene, butene, hexene and 1-octene. The fluorinated olefinic monomers can also be mentioned. Moreover, n is 1 or is advantageously a natural number from 2 to 20.

According to a particular embodiment, in the case where n is at least 2, all the blocks A are identical and / or all the blocks A _g are identical. Advantageously, P = O.

Particularly mentioned are triblock triblock copolymers ABA giving the graft copolymers A _g -B-

A _g .

With regard to the blocks A, according to the present invention, it is, in the starting copolymer (before grafting), functionalized blocks to allow the grafting.

The preparation of starting block copolymers is well known to those skilled in the art and will not be repeated here. In this regard, reference may be made to patent documents WO 2004 087796, WO 2003 062293 and FR 2 807 439. The method of polymerization consisting in preparing block B by a conventional recipe by mixing the monomer (s) with an alkoxyamine of Function n, then to dilute the block B in the monomer mixture intended to form the block or blocks A (controlled radical polymerization).

In particular, the blocks A are methacrylic functional blocks, predominantly comprising methyl methacrylate (MMA) units. The or each methacrylic block A may thus comprise from 70 to 99.5%, advantageously from 80 to 99.5%, and preferably from 85 to 99.5%, by weight, of MMA units.

The or each block A thus comprises at least one unit carrying at least one function that has allowed the grafting and selected from acid, acid salt, anhydride or epoxide functions, advantageously from the acid and anhydride functions.

The or each unit carrying at least one functional group chosen from acid, acid salt, anhydride and epoxide functions is especially chosen from:

The units resulting from at least one monomer comprising a C = C double bond, copolymerizable with the main monomer forming the block A concerned and bearing at least one functional group chosen from acid, acid salt, anhydride and epoxide functions; ; and the glutaric anhydride units of formula:

in which R ₃ and R 4 denote H or a methyl radical.

In particular, the or each block A comprises at least one glutaric anhydride unit and / or at least one acrylic acid unit and / or at least one methacrylic acid unit.

The or each block A can thus comprise, by weight, from 0.5 to 30%, advantageously from 0.5 to 20%, preferably from 0.5 to

15%, of the pattern or patterns carrying at least one function acid, acid salt, anhydride or epoxide, advantageously at least one acid and / or anhydride function.

In the case where said units are derived from a monomer comprising a C = C double bond, copolymerizable with MMA and carrying at least one acid function, acid salt, anhydride or epoxide, it copolymerizes with MMA by a radical mechanism.

By way of example of a monomer carrying at least one acid function, mention may be made of 2-acrylamido-2-methylpropanesulphonic acid, vinylsulphonic acid, styrene sulphonic acid and l-allyloxy acid. 2-hydroxypropane sulfonic acid, alkyl allyl sulfosuccinic acid, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid.

Preferably, it is acrylic acid or methacrylic acid because these two monomers copolymerize very well with MMA. Methacrylic acid is particularly preferred. Indeed, when the copolymerization is conducted in an aqueous dispersed medium, the acrylic acid remains largely solubilized in water, which is not the case with methacrylic acid. The groups carrying an acid function are then as follows:

ΛΛflΛΛΛCIÏ9-CH ^<nΛft ^'w irtΛΛΛΛΛCIÎ9-C ^<nftΛΛΛ' '

I I

C = O C = O

OH OH

From an acid function, the acid salt function can be obtained by known techniques. A monomer carrying at least one acid salt function is therefore of a monomer carrying at least one acid function by a neutralization reaction. A monomer carrying at least one acid salt function is derived from a monomer carrying at least one acid function from the preceding list. The cation of the acid salt can be for example Li ⁺ , Na ⁺ , K ⁺ , a quaternary ammonium salt.

By way of example of monomer bearing at least one anhydride functional group, mention may be made of maleic anhydride, itaconic anhydride and citraconic anhydride.

By way of example of monomer carrying at least one epoxide functional group, mention may be made of aliphatic glycidyl esters or aliphatic glycidyl ethers, such as allyl glycidyl ether, vinyl glycidyl ether, maleate and glycidyl itaconate, and acrylate and glycidyl methacrylate, alicyclic glycidyl esters or alicyclic glycidyl ethers such as 2-cyclohexene-1-glycidyl ether, cyclohexene-4,5-diglycidylcarboxylate, cyclohexene-4-glycidyl carboxylate, 5-norbornene 2-methyl-2-glycidyl carboxylate and endocis-bicyclo (2,2,1) -5-heptene-2,3-diglycidyl dicarboxylate. Glycidyl methacrylate is a preferred monomer because, like MMA, it is a methacrylic ester and therefore effectively copolymerizes with MMA.

Moreover, the or each block A can also comprise at least one unit of a comonomer (a) having at least one C = C double bond, copolymerizable with the main monomer forming said block and which does not carry a acid function, acid salt, anhydride or epoxide. The comonomer (a) may be chosen for example from the following monomers:

• acrylic monomers of formula CH ₂ = CH-C (= 0) -O-R wherein R denotes an alkyl group C1-C4 ₀ linear, cyclic or branched optionally substituted by a halogen atom, hydroxy, alkoxy cyano, such as, for example, methyl, ethyl, propyl, n-butyl, isobutyl, tert-butyl, 2-ethylhexyl acrylate, hydroxyalkyl acrylates, acrylonitrile;

Methacrylic monomers of formula CH ₂ = C (CH ₃ ) -C (= O) -O-R _{2 in} which R ₂ denotes a linear, cyclic or branched C ₂ -C ₄ 0 alkyl group optionally substituted by a halogen atom; , a hydroxy, alkoxy, cyano, amino or epoxy group, such as, for example, ethyl, propyl, n-butyl, isobutyl, tert-butyl, 2-ethylhexyl methacrylate, hydroxyalkyl methacrylates, methacrylonitrile; and vinylaromatic monomers such as for example styrene, substituted styrenes such as alpha-methylstyrene, monochlorostyrene or tertbutyl styrene.

Advantageously, the comonomer (a) contains only one C = C double bond. Preferably, the comonomer (a) is an acrylic monomer CH ₂ = CH-C (= O) -O-R 1 in which R 1 is a C 1 -C 6 alkyl such as, for example, the acrylate of methyl, ethyl, propyl, butyl, 2-ethyl hexyl or a methacrylic monomer CH ₂ = C (CH ₃ ) -C (= O) -O-R2 in which R ₂ is a C ₂ alkyl -Cg such as ethyl methacrylate, propyl, butyl, 2-ethyl hexyl.

The or each block A may be based on MMA and include, by weight:

• 70 to 99.5% MMA; From 0 to 20% of a comonomer (a) having at least one C = C double bond, copolymerizable with MMA and which does not carry an acid function, acid salt, anhydride or epoxide;

• from 0.5 to 30% of at least one group carrying at least one acid function, acid salt, anhydride or epoxide.

In particular, the or each block A may be based on MMA and comprise, by weight: • from 80 to 99.5% of MMA;

• from 0 to 10% of a comonomer (a) having at least one C = C double bond, copolymerizable with MMA and which does not carry an acid function, acid salt, anhydride or epoxide; From 0.5 to 20% of at least one group carrying at least one acid, acid salt, anhydride or epoxide function.

More particularly, the or each MMA-based block A may comprise, by weight:

• 85 to 99.5% MMA; • from 0 to 5% of a comonomer (a) having at least one C = C double bond, copolymerizable with MMA and which does not carry an acid function, acid salt, anhydride or epoxide; and from 0.5 to 15% of at least one group carrying at least one acid, acid salt, anhydride or epoxide function.

A methacrylic functional block A is generally obtained by the copolymerization of MMA with at least one monomer carrying at least one acid function, acid salt, anhydride or epoxide, optionally in the presence of a comonomer A having at least one double bond C = C, copolymerizable with MMA and which does not carry an acid, anhydride or epoxide function. The copolymerization can take place in bulk, in solution in a solvent, or in a dispersed medium (suspension, emulsion, miniemulsion).

A methacrylic functional block A may also comprise glutaric anhydride groups represented by the formula:

in which R ₃ and R 4 denote H or a methyl radical. These are obtained by an intramolecular reaction between two fused functions, for example between two acid functions, between an acid function and an ester function or between two ester functions. This type of group is particularly appreciated because of their high reactivity vis-à-vis the primary amine functions of the polyamide.

When a methacrylic functional block A comprising glutaric anhydride groups is prepared from acrylic or methacrylic acid, the conversion of acid functions to glutaric anhydride functions is often incomplete. The methacrylic functional block therefore comprises both glutaric anhydride groups and acrylic or methacrylic acid groups (which have not reacted to give glutaric anhydride functions). This type of methacrylic functional block is very particularly preferred because the glutaric anhydride groups are very reactive, especially with the primary amine functions. In addition, the glutaric anhydride groups are introduced more easily into the methacrylic functional block than by the direct copolymerization of MMA with maleic anhydride or with another monomer carrying an anhydride group.

The relative proportion of acid functions and glutaric anhydride functions depends on the content of initial acid functions and the conditions of the dehydration (temperature, reaction time, pressure, presence or absence of a catalyst, etc.). The overall content of the acid functions and glutaric anhydride functions is between 0.5 and 30%, advantageously between 0.5 and 20%, preferably between 0.5 and 15%. The relative proportion (by weight) of the glutaric anhydride functions with respect to the glutaric anhydride functions and the acid functions (ie the weight percentage of glutaric anhydride functions / (glutaric anhydride functions + acid functions)) is as for it between 1 and 100%, preferably between 10 and 90%, more preferably between 50 and 90%.

In order to obtain a methacrylic functional block bearing glutaric anhydride groups, one of the methods described in the documents EP 0318197 B1, Japanese Kokai 60/231756, Japanese Kokai 61/254608 or Japanese Kokai 61/43604 may be used, GB 1437176, US 4789709. The reaction making it possible to obtain the glutaric anhydride groups is conducted at a temperature greater than 15O ⁰ C, preferably between 200 and 28O ⁰ C, optionally in the presence of a reduced pressure of less than 1 bar and possibly in the presence of an acidic or basic catalyst. It can be carried out in an extruder having a degassing well or in a devolatilizer. A secondary amine can be used in a manner similar to that described in EP 0 318 197.

As regards block B, according to the invention, it advantageously comprises butyl acrylate units or mainly butyl acrylate units.

The average molecular weight (M _w) of the block copolymer B (A) _n is generally between 10 000 and 500 000 g / mol. Preferably, M _w is between 50000 and 200000 g / mol because on the one hand the very small masses may affect the glass transition temperature (T _g ) of the polymer while the very high masses affect its fluidity and make its transformation in the molten state difficult. The person skilled in the art knows how to adjust the average molecular weight by weight, for example by introducing a transfer agent and / or using the parameter polymerization temperature. As regards the polyamide, this may be a homopolyamide or a copolyamide terminated by a primary amine function or an acid function. Preferably, it is a primary amine function, which has a good reactivity with respect to acid, acid, anhydride or epoxide functions. The primary amine function is very reactive with respect to the acid or anhydride functions.

Advantageously, in order to provide the thermomechanical resistance to the material according to the invention, the polyamide has a melting temperature of between 100 and 300 ^° C., preferably between 140 and 250 ^° C.

By homopolyamide is meant the condensation products of a lactam (or the corresponding amino acid) or a diacid with a diamine (or their salts). It does not take into account the chain limiter which can be a diacid, a monoacid, a diamine or a monoamine in the case of lactams and another diacid or another diamine in the case of polyamides resulting from the condensation of a diamine with a diacid. By copolyamide is meant the precedents in which there is at least one monomer more than necessary, for example two lactams or a diamine and two acids or a diamine, a diacid and a lactam.

The polyamide is chosen from PA 6, PA 6-6, PA 11, PA 12 and their copolymers. Preferably, it is PA 6 because this polyamide provides a good resistance to the solvent by its crystallinity and a good thermomechanical resistance. According to a first type, the copolyamide results from the condensation of at least two alpha-omega aminocarboxylic acids or of at least two lactams having from 6 to 12 carbon atoms or a lactam and an aminocarboxylic acid which do not have the same number of carbon atoms. The copolyamide of this first type may also include units which are residues of diamines and dicarboxylic acids.

By way of example of a dicarboxylic acid, mention may be made of diacids such as isophthalic, terephthalic, adipic, azelaic, suberic, sebacic, nonanedioic and dodecanedioic acids.

By way of example of a diamine, mention may be made of hexamethylenediamine, dodecamethylenediamine, metaxylylenediamine, bis-p-aminocyclohexylmethane and trimethylhexamethylenediamine.

As an example of alpha-omega-aminocarboxylic acid, mention may be made of aminocaproic acid, aminoundecanoic acid and aminododecanoic acid.

Examples of lactam include caprolactam, oenantholactam and laurolactam.

According to a second type, the copolyamide results from the condensation of at least one alpha-omega-aminocarboxylic acid (or a lactam), at least one diamine and at least one dicarboxylic acid. The alpha-omega-aminocarboxylic acid, the lactam and the dicarboxylic acid can be chosen from those mentioned above. The diamine may be a branched aliphatic diamine, linear or cyclic or arylic. By way of examples, mention may be made of hexamethylenediamine, piperazine, isophorone diamine (IPD), methyl pentamethylenediamine (MPDM), bis (aminocyclohexyl) methane (BACM), bis (3-methyl-4-aminocyclohexyl) methane

(BMACM).

In order for the polyamide to be terminated by a primary amine function, it is possible to use a chain limiter of formula:

R ₅ NH

^R 6

in which R ₅ is hydrogen or a linear or branched alkyl group containing up to 20 carbon atoms, Re is a group having up to 20 carbon atoms linear or branched alkyl or alkenyl, a cycloaliphatic radical limiting may be by for example, laurylamine or oleylamine.

The polyamide terminated with a primary amine or acid function has a number-average molecular weight (M _n ) of between 1000 and 50000 g / mol, more preferably between 1000 and 40 000 g / mol, advantageously between 1000 and 30 000 g / mol, preferably between 1000 and 20000 g / mol. This average molecular weight is determined using size exclusion chromatography calibrated using PMMA samples. M _n is therefore given in PMMA equivalents.

The preferred monofunctional polymerization limiters are laurylamine and oleylamine. The polyamides can be manufactured according to methods known to man of the art, for example by polycondensation in an autoclave. The polycondensation is carried out at a temperature generally between 200 and 300 ⁰ C, under vacuum or under an inert atmosphere, with stirring of the reaction mixture. The average chain length of the polyamide is determined by the initial molar ratio between the polycondensable monomer or the lactam and the chain limiter. For the calculation of the average chain length, there are usually a chain limiter molecule to a chain of ^f oligomer.

Graft copolymer:

The graft copolymer according to the invention may especially comprise the following characteristics: the number-average molecular mass of one or each A block is between 5000 and 100,000 g / mol, more preferably between 10,000 and 70,000 g / mol advantageously between 15,000 and 50,000 g / mol; the number-average molecular mass of block B is between 5000 and 100,000 g / mol, more preferably between 5000 and 60,000 g / mol, advantageously between 5,000 and 40,000 g / mol, preferably between 10,000 and 40 000 g / mol; and the number-average molecular mass of the polyamide grafts is between 1000 and 50 000 g / mol, more preferably between 1000 and 40 000 g / mol, advantageously between 1000 and 30 000 g / mol, preferably between 1000 and 20,000 g / mol. The weight ratio of the copolymer B- (A) _n as defined above to the polyamide (PA) grafts is in particular from 10:90 to 95: 5, advantageously from 50:50 to 90:10, preferably from 60: 40 to 80:20.

The graft copolymer according to the invention is obtained by the reaction of the copolymer B- (A) _n (with the functionalized block or blocks A) and the polyamide terminated by a primary or acidic amine function. If the polyamide is terminated by a primary amine function, the A blocks are preferably carrying acid functions, acid salts, anhydride or epoxide. If the polyamide is terminated by an acid function, the A blocks are preferably carrying epoxide functions.

During the reaction of the copolymer and the finished polyamide with a primary or acidic amine function, a graft copolymer consisting of a trunk and polyamide grafts is formed (for more details on the graft copolymers, reference may be made to Kirk-Othmer, Encyclopaedia of Chemical Technology, 3 ^rd edition, Volume 6, page 798). Depending on the nature of the methacrylic functional blocks preferably forming the A blocks, the amounts of functional PMMA and polyamide that are introduced, as well as the conditions of the reaction, a graft copolymer that is more or less rich in grafts can be obtained.

On average, there is generally, in block A _g , from 1 to 100, preferably from 1 to 50, polyamide grafts (PA).

The reaction can be carried out in solution in a solvent or in a molten state. Preferably, the reaction is conducted in the molten state because it avoids the use of solvent which must then be eliminated once the reaction is complete. The molten state also makes it possible to accelerate the speed of the reaction. Any mixing tool suitable for thermoplastics may be used. A twin-screw extruder, in particular a corotating twin-screw, is entirely suitable because it makes it possible to carry out the mixing in the molten state, can operate continuously and ensures good homogenization of the starting copolymer and the polyamide. The reaction is conducted at a temperature between 180 and 32O ⁰ C, preferably between 180 and 28O ⁰ C. The average residence time of the melt in the extruder ^f may be between 1 second and 15 minutes, rather between 1 second and 10 minutes. If an extruder is used, granules are recovered at the outlet of the extruder. These granules can then be put into the desired form (film, injected part, molded part, plate, ...) using a thermoplastic transformation tool known to those skilled in the art, for example an extruder.

For the reaction, from 5 to 90%, preferably from 10 to 50%, advantageously from 20 to 40%, of polyamide terminated with a primary or acidic amine function are used for 10 to 95%, respectively, of 50 to 90%. preferably from 60 to 80% of starting copolymer. The reaction of 20 to 40% of polyamide terminated with a primary or acidic amine function and 60 to 80% of starting copolymer makes it possible to obtain a material having a good transparency, A being based on MMA.

Depending on the initial amounts of B- (A) _n and polyamide copolymer, as well as reaction conditions (by example contact time, temperature), it may remain the starting copolymer and / or the unreacted polyamide. The reaction therefore leads to a material consisting of: the graft copolymer of the invention; unreacted copolymer B- (A) _n , or the A blocks carrying functional groups capable of reacting with primary or acidic amine functions; of polyamide terminated by a primary amine or unreacted acid function.

More specifically, the material consists, by weight: from 10 to 98% graft copolymer of the invention; from 1 to 50% of said unreacted (functional) copolymer B- (A) _n ; from 1 to 50% of polyamide terminated by a primary amine or unreacted acid function; the total making 100%.

Preferably, the material consists of, by weight: 20 to 80% graft copolymer of the invention; from 5 to 50% of said unreacted (functional) copolymer B- (A) _n ; from 5 to 50% of polyamide terminated with a primary amine or unreacted acid function; the total making 100%.

The presence of starting copolymer and / or unreacted polyamide is not necessarily detrimental to the final properties of the material, it may even improve some of its properties. The unreacted starting copolymer has a high affinity with the trunk of the graft copolymer, the unreacted polyamide has a high affinity with graft copolymer grafts. We can thus observe a phenomenon of swelling of the trunk and grafts of the graft copolymer which has already been observed for other types of graft copolymers (see in this regard the following article: H. Pernot et al., Nature Mater. Vol.l, p. 54).

The Applicant has found that, in the case in particular where A is based on MMA, the graft copolymer, like the starting functionalized copolymer, is organized in nanodomains, that is to say in domains whose average size is less than 100 nm. This organization makes it possible to obtain a homogeneous material having all the properties described above.

Shock additives:

A core-shell shock modifier (more commonly known as core-shell) can be added to the material to improve its impact resistance. This impact modifier is in the form of fine particles having an elastomer core and at least one thermoplastic shell, the size of the particles being generally less than 1 μm and advantageously between 50 and 300 nm. The impact modifier is prepared using emulsion polymerization. From 0 to 60%, preferably from 0 to 30% by weight, of the core-shell impact modifier with respect to the material is added to the material.

The heart can be constituted for example:

• a homopolymer of isoprene or butadiene or

Copolymers of isoprene with at most 30 mol% of a vinyl monomer or Copolymers of butadiene with at most 30 mol% of a vinyl monomer.

The vinyl monomer may be styrene, alkylstyrene, acrylonitrile or alkyl (meth) acrylate.

The heart can be made up of:

A homopolymer of an alkyl (meth) acrylate or

Copolymers of an alkyl (meth) acrylate with at most 30 mol% of a monomer chosen from another alkyl (meth) acrylate and a vinyl monomer.

The alkyl (meth) acrylate is advantageously butyl acrylate. The vinyl monomer may be styrene, alkylstyrene, acrylonitrile, butadiene or isoprene.

The heart may be advantageously crosslinked in whole or in part. It suffices to add at least difunctional monomers during the preparation of the core, these monomers may be chosen from poly (meth) acrylic esters of polyols such as butylene di (meth) acrylate and trimethylolpropane trimethacrylate. Other difunctional monomers are, for example, divinylbenzene, trivinylbenzene, vinyl acrylate and vinyl methacrylate. The core may also be cross-linked by grafting or as a comonomer during the polymerization, unsaturated functional monomers such as unsaturated carboxylic acid anhydrides, unsaturated carboxylic acids and unsaturated epoxides. Mention may be made, for example, of maleic anhydride, (meth) acrylic acid and glycidyl methacrylate. The bark or bark consists of a homopolymer of styrene, an alkylstyrene or methyl methacrylate or copolymers comprising at least 70 mol% of one of these monomers and at least one comonomer chosen from other previous monomers, another alkyl (meth) acrylate, vinyl acetate and acrylonitrile. The bark may be functionalized by introducing, by grafting or as comonomer during the polymerization, unsaturated functional monomers such as unsaturated carboxylic acid anhydrides, unsaturated carboxylic acids and unsaturated epoxides. Mention may be made, for example, of maleic anhydride, (meth) acrylic acid and glycidyl methacrylate.

Examples of impact modifiers include core-shell copolymers having polystyrene bark and core-bark copolymers having a PMMA bark. There are also core - shell copolymers with two barks, one made of polystyrene and the other outside PMMA. Examples of impact modifiers, as well as their method of preparation, are described in the following patents: US 4,180,494, US 3,808,180, US 4,096,202, US 4,260,693, US 3,287,443, US 3,657,391, US 4,299,928, US 3,985,704, US 5,773,520.

Advantageously, the core represents, by weight, 70 to 90% of the impact modifier and the bark of 30 to 10%.

The impact modifier can be soft / hard type. By way of example of an impact modifier of the soft / hard type, mention may be made of the one consisting of: (i) from 75 to 80 parts of a core comprising in moles at least 93% of butadiene, 5% of styrene and 0.5 to 1% of divinylbenzene and

(ii) from 25 to 20 parts of two barks of essentially the same weight, one of polystyrene and the other of PMMA.

Another example of a soft / hard impact modifier is the one having a core made of polybutyl acrylate or a butyl acrylate / butadiene copolymer and a PMMA bark.

The impact modifier can also be of the hard / soft / hard type, that is to say that it contains in the order a hard heart, a soft bark and a hard bark. The hard parts may consist of the above soft / hard shell polymers and the soft part may consist of the above soft core polymers.

An example of hard / soft / hard impact modifier is that consisting of:

(i) a copolymer core of methyl methacrylate and ethyl acrylate,

(ii) a copolymer layer of butyl acrylate and styrene,

(iii) a bark copolymer of methyl methacrylate and ethyl acrylate.

The shock modifier can also be hard (heart) / soft / medium hard. In this case, the outer shell "half hard" consists of two barks: one intermediate and one outer. The intermediate bark is a copolymer of methyl methacrylate, styrene and at least one monomer selected from alkyl acrylates, butadiene and isoprene. The outer bark is a PMMA homopolymer or copolymer.

An example of a hard / soft / half-hard shock modifier is that made in this order:

(i) a copolymer core of methyl methacrylate and ethyl acrylate,

(ii) a bark copolymer of butyl acrylate and styrene,

(iii) a bark copolymer of methyl methacrylate, butyl acrylate and styrene, (iv) a bark copolymer of methyl methacrylate and ethyl acrylate.

The impact modifier and the material according to the invention are mixed using a mixing tool suitable for thermoplastics, for example an extruder.

Other additives:

Other additives can also be added to the material. It can be anti-UV additive (s), antioxidant (s), release agent (s), lubricating agents (s) ... As an example of anti-UV additives Examples are those described in US Pat. No. 5,256,472. Benzotriazoles and benzophenones are advantageously used. By way of example, Tinuvin® 213 or Tinuvin® 109 and preferably Tinuvin® 234 or Tinuvin P® or Tinuvin 770® from Ciba Specialty Chemicals can be used.

Uses of the graft copolymer and the material containing it: The graft copolymer and the material containing it according to the invention can be used in the form of films, extruded parts blown, injected parts. It can also be in the form of extruded plates that are used for sanitary applications (manufacture of bathtubs, washbasins, shower tubs ...). In the sanitary field, the chemical resistance and the crack resistance of the material are two appreciated properties.

The graft copolymer and the material containing it according to the invention can also be converted into organic panes, window frames, pipes, air ducts, seals, etc. In the field of transport, for example, it can be used to manufacture decorative panels in automobiles, trucks, trains and planes. In the field of sport, it can be used as injected parts in the sports shoe, golf clubs ... It can also find applications in the fibers for example as fiber optic coatings, but also in parts medical use, in the field of electrical and electronic applications, and more generally as technical polymers without excluding applications in the packaging.

The graft copolymer and the material containing it according to the invention can also serve as a compatibilizing agent for obtaining an alloy based on a polyamide and a polymer chosen from PMMA, PVDF and PVC. and acrylic polymers. For example, it is possible to use a corotative extruder to carry out the mixing. Preferably, the polymer of the alloy is PMMA or PVDF. The polyamide may be a PA 6, PA 6-6, PA 11 or PA 12. The polyamide of the alloy is of the same nature as the polyamide terminated by a primary amine or acid function which serves to obtain the grafts. Thus, for example, for the compatibilization of a polyamide 12 with PMMA, the grafts are made of polyamide 12.

PMMA denotes a homo- or copolymer of MMA comprising more than 50% by weight of MMA. In the case where the PMMA is a copolymer, the MMA is copolymerized with at least one comonomer chosen from: acrylic monomers of formula CH ₂ = CH-C (= O) -O-Ri where R 1 denotes a C 1 -C 6 alkyl group C4 ₀ linear, cyclic or branched optionally substituted by a halogen atom, a hydroxy, alkoxy, cyano group, such as for example methyl acrylate, ethyl, propyl, n-butyl, isobutyl, tert-butyl, 2-ethylhexyl, hydroxyalkyl acrylates, acrylonitrile; methacrylic monomers of formula CH ₂ = C (CH ₃ ) -C (= O) -O-R2 where R ₂ denotes a linear, cyclic or branched C ₂ -C ₄ 0 alkyl group optionally substituted by a halogen atom, a hydroxy, alkoxy, cyano, amino or epoxy groups such as, for example, ethyl, propyl, n-butyl, isobutyl, tert-butyl, 2-ethylhexyl methacrylate, hydroxyalkyl methacrylates, methacrylonitrile; vinylaromatic monomers such as, for example, styrene, substituted styrenes such as alpha-methylstyrene, monochlorostyrene, tertbutyl styrene. PVDF denotes a homo- or copolymer of vinylidene fluoride (VF ₂ ) comprising more than 50% by weight of VF ₂ . In the case where the PVDF is a copolymer, the VF ₂ is copolymerized with at least one comonomer chosen from compounds containing a vinyl group capable of opening to polymerize and which contains, directly attached to this vinyl group, at least one fluorine atom, a fluoroalkyl group or a fluoroalkoxy group. As an example of a comonomer, mention may be made of vinyl fluoride; trifluoroethylene; chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); Hexafluoropropylene (HFP); perfluoro (alkyl vinyl) ethers such as perfluoro (methyl vinyl) ether (PMVE), perfluoro (ethyl vinyl) ether (PEVE) and perfluoro (propyl vinyl) ether (PPVE); perfluoro (1,3-dioxole); perfluoro (2,2-dimethyl-1,3-dioxole) (PDD); the product of formula CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ X in which X is SO ₂ F, CO ₂ H, CH ₂ OH, CH ₂ OCN or CH ₂ OPO ₃ H; the product of formula CF ₂ = CFOCF ₂ CF ₂ SO ₂ F; the product of formula F (CF ₂ ) _n CH ₂ OCF = CF ₂ in which n is 1, 2, 3, 4 or 5; the product of formula R ₇ CH ₂ OCF = CF ₂ in which R ₇ is hydrogen or F (CF ₂ ) _z and z is 1, 2, 3 or 4; the product of formula RsOCF = CH ₂ wherein R ₈ is F (CF ₂ ) _z - and z is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); 3,3,3-trifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene.

The alloy comprises:

From 2 to 20% of the graft copolymer or of the material containing it according to the invention;

From 10 to 90% of a polyamide that may be chosen from PA 6, PA 6-6, PA 11 or PA 12; From 10 to 90% of a polymer chosen from PMMA, PVDF, PVC and acrylic polymers.

The graft copolymer or the material containing it, according to the invention, can also serve as a coextrusion binder in a polyamide-based multilayer structure and a polymer chosen from PMMA, PVDF, PVC and acrylic polymers. The multilayer structure is thus composed in the order of the following layers: a layer of polyamide; a layer c2 of the material according to the invention; a layer c3 of a polymer chosen from PMMA, PVDF, PVC and acrylic polymers; the layers adhering to each other.

The definitions of the terms polyamide, PMMA and PVDF have been given previously.

The multilayer structure may be for example in the form of a film, a plate, a tube or a hollow body. In the case of a multilayer structure in the form of a film, each layer c1, c2 and c3 may have a thickness of between 2 and 300 microns, advantageously between 5 and 200 microns, preferably between 10 and 100 microns. In the case of a multilayer structure in the form of a plate, a tube or a hollow body, the layer c 2 of the material according to the invention has a thickness of between 2 and 300 μm, preferably between 2 and 300 μm. and 100 μm. The other cl and c3 layers have a thickness greater than 100 microns, rather between 0.1 and 100 mm. [Examples]

The following examples illustrate the invention without, however, limiting its scope.

In these examples, the following abbreviations have been used:

MMA methyl methacrylate;

BA butyl acrylate; MAA methacrylic acid;

THF tetrahydrofuran;

PTA phosphotungstic acid;

BzOH benzyl alcohol;

CDCl ₃ deuterated chloroform; PA polyamide;

_F PMMA block copolymer of MMA and MAA containing anhydride groups dimethylglutaric;

P (MMA _f -b-BA-b-MMAf): triblock copolymer whose end blocks are PMMAf blocks and the central block is a block of polybutyl acrylate, the methacrylic acid and dimethylglutaric anhydride groups constituting reactive sites;

P (MMA _f -b-BA-b-MMAf) -g-PA: graft triblock copolymers of the invention; R weight ratio P (MMAf-b-BA-b-MMAf): PA of the two polymers (trunk and grafts) used in the examples illustrating the present invention;

SEC steric exclusion chromatography; IRTF Fourier transform infrared spectroscopy; TEM electron microscopy in transmission;

¹ H NMR proton nuclear magnetic resonance;

DSC differential scanning calorimetry;

DMA differential dynamic analysis; Mn: number average molecular weight; Ip: polymolecularity index (ratio of the weight average molar mass to the number average molar mass); Tf: melting temperature.

GENERAL CONDITIONS FOR THE PREPARATION OF COPOLYMER MATERIALS TRIBLOC GRAFTED OF THE INVENTION

Grafted triblock copolymer materials were prepared by reactive extrusion of P (MMA _f -b-BA-b-MMA _f) and a PA terminal primary amine function on a micro-extruder DACA 3 g capacity to 25O ⁰ C for 6 minutes at a rotation speed of 200 rpm under a nitrogen atmosphere.

To observe the stability of the materials, the samples were subjected to thermal annealing at 235 ^° C. for 1 hour under vacuum.

The characteristics of the copolymer P (MMAF-b-BA-b-MMAF) are as follows: Mn and I _p, determined by SEC with PMMA as a standard, are respectively 70,000 g / mol and 2.1; the molar percentage of BA is 34%, evaluated by ¹ H NMR; the molar percentages of MMA, MAA and dimethylglutaric anhydride are respectively 58%, 6% and 2%, evaluated by FTIR in solution in chloroform.

The morphology of the copolymer P (MMAf-b-BA-b-MMAf) was studied by MET; two complementary markings were tested, namely: the ruthenium marking in the liquid phase which makes it possible to densify the butyl acrylate which appears in black in FIG. ; and

labeling with PTA in aqueous solution with BzOH as marking promoter which makes it possible to mark the PMMA (in gray in FIG. 1b).

The copolymer P (MMAf-b-BA-b-MMAf) has a lamellar morphology corrugated and interconnected without order at great distance, which can be described as labyrinth lamellar phase.

PA with terminal primary amine function

Different PAs with terminal primary amine function were used. These polyamides were characterized by their Mn determined by ¹ H NMR in CDCl ₃ with trifluoroacetic anhydride and their Tf, measured by DSC.

PAl: it is a monoamine PA6 of Mn 2550 g / mol having a T _f of 218 ^° C.

PA2: it is a monoamine PA6 of Mn 5320 g / mol having a T _f of 219 ^° C.

PA3: it is a monoamine PA6 of Mn 16500 g / mol having a T _f of 222 ⁰ C.

CHARACTERIZATION OF THE GRAFTED TRIBLOC COPOLYMER MATERIALS OF THE INVENTION

Thermomechanical behavior:

The thermomechanical behavior of the samples obtained was followed by DMA. The rods were pressed at 25O ⁰ C in the form of rectangular bars, then subjected to a bending deformation of 20 microns amplitude at a frequency of 1 Hz, between -80 and 25O ⁰ C with a ramp of 3 ° C / min.

The storage module (E ') is measured using the TA Instrument DMA 9980 apparatus. The conservation modules obtained are given in MPa units.

Chemical resistance:

The test consists of observing the resistance of a rod placed in chloroform for three days at ambient temperature (the ring represents 3% by weight relative to chloroform). The assessment of the resistance is qualitative and consists in seeing if the ring keeps its shape or disintegrates in contact with the solvent. If the ring disintegrates, the chemical resistance is very bad, whereas if the ring keeps its shape, the chemical resistance is very good.

Transparency:

Transparency is appreciated qualitatively.

Microscopic analysis:

The morphology was studied by MET at the extruder outlet or after annealing (1 hour at 235 ^° C. under vacuum). The samples were microtomed at room temperature and then labeled: - or with ruthenium: the domains formed by the blocks of poly (butyl acrylate), of poly (methyl methacrylate) and the polyamide grafts appear respectively in black, white and gray ;

or to PTA in the presence of BzOH: the domains formed by the polyamide (free or in the form of grafts), and the blocks of poly (methyl methacrylate) and of poly (butyl acrylate) appear in black, gray and white respectively.

EXAMPLES 1 to 3:

Preparation by reactive extrusion of copolymeric materials P (MMA _f -b-BA-b-MMA _f ): PAl

Grafted triblock copolymers of the title were prepared with an R ratio of 80: 20 (Example 1);

70: 30 (Example 2) and 60: 40 (Example 3) under the conditions indicated above.

Figures 2a and 2b show the morphology of the material of Example 2 at the extruder outlet, observed by MET: ruthenium labeling (Figure 2a) and PTA / BzOH labeling (Figure 2b).

The same annealed material 1 hour did not evolve, as can be seen in Figure 2c (PTA / BzOH labeling).

The graft material is therefore stable and the residual homopolymers are incorporated into the graft copolymer structure.

The morphologies of the materials of Examples 1 and 3 were also very thin and stable to annealing.

In order to check the stability of the materials, the rods of the extrudates annealed at 235 ^° C. under vacuum for 1 hour could be dissolved in benzyl alcohol at 130 ^° C., which shows that the P (MMA _f -b-BA -b-MMA _f ) has not undergone irreversible crosslinking.

In FIG. 3, the conservation modulus curves obtained by DMA for the samples of Examples 1 to 3 and for a sample of P (MMA _f -b-BA-b-MMAf) as a function of temperature:

- P (MMA _f -b-BA-b-MMA _f ): solid line - graft copolymer material of Example 1: ++++++++++++

graft copolymer material of Example 2: dotted line

graft copolymer material of Example 3: succession of "-" signs

In Table 1 below, the value of the storage module was given at 20 ^° C.

In FIG. 3, all the transitions of the components of the mixture can be observed:

glass transition of polybutyl acrylate at -50 ^° C .;

glass transition of the polyamide at approximately 30 ^° C. and

glass transition of poly (methyl methacrylate) at 130 ^° C .; and finally the melting of the crystalline part of PA6 at 22O ⁰ C.

In the systems of Examples 1 to 3, the module at ambient temperature (20 ^° C.) is slightly greater than the reference.

A module tray appears above the transition temperature of the poly (methyl methacrylate) block from 30% PA-I in the material. The plateau results from the crystallinity of PA-I in the mixtures. The grafting has therefore taken place.

EXAMPLES 4 and 5:

Preparation by reactive extrusion of copolymers P (MMA _f -b-BA-b-MMA _f ): PA2 and PA3 Copolymers of the title grafted with PA2 (Example 4) and PA3 (Example 5) were prepared in a ratio R = 70: 30 under the conditions indicated above.

It has been observed that the increase in the size of the graft does not significantly deteriorate the transparency of the samples, whereas a ring of PMMAf / PA3 with R = 70: 30, produced under the same conditions, is white.

The morphology of the materials of Examples 2, 4, 5 and of said PMMAf / PA3 is also illustrated by Figures 4a, 4b, 4c and 4d, respectively, where the images of the different samples are presented, observed by TEM after annealing for 1 hour at 235. ⁰ C under vacuum and PTA labeling (the domain formed by the polyamide appears in black).

It can be seen that as the size of the graft increases in the P (MMA _f -b-BA-b-MMA _f ) / PA systems, the dispersion remains very fine and homogeneous. This result is very different from that obtained in the absence of the poly (butyl acrylate) central block and suggests that it plays a major role in the grafting reaction. In all systems there is graft copolymer and any residual polymers P (MMAf-b-BA-b-MMAf) and PA are very well incorporated into the structure.

The evolution curves of the storage modulus as a function of temperature, obtained by DMA, are given in FIG. 5 for the samples of Examples 2, 4 and 5 and for a sample of P (MMA _f -b-BA-b). -MMA _f ):

- P (MMA _f -b-BA-b-MMA _f ): solid line

- graft copolymer of Example 2: dotted line - graft copolymer of Example 4: +++++++++++++++

graft copolymer of Example 5: ooooooooooooooooo In Table 1 below, the value of the storage module was given at 20 ^° C.

The material of Example 4 behaves like the material of Example 2. The material of Example 5 has an interesting behavior since it does not flow significantly beyond the glass transition of blocks of poly (methyl methacrylate). In addition, the value of the module tray above the Tg of poly (methyl methacrylate) blocks is much higher than in the other mixtures of the same composition.

The solvent resistance of these extruded R = 70: 30 samples was tested by immersing pieces from chloroform extrudates for several days. Chloroform resistance increases with the size of AP grafts used: the shape of the specimen persists and swelling decreases. This is characteristic of good AP connectivity through the sample. These observations can be correlated with thermomechanical analysis results (Figure 5).

Materials with PA6 of greater mass (PA3) have thus made it possible to obtain materials in which the PA is very finely dispersed and which have interesting properties.

EXAMPLES 6 to 8:

Preparation by reactive extrusion of copolymers P (MMA _f -b-BA-b-MMA _f ) PA3

The copolymers of the title were prepared with R = 80: 20 (Example 6), R = 50: 50 (Example 7) and R = 30: 70 (Example 8) under the conditions indicated above. The materials (extrudates) obtained are relatively transparent with the exception of the material of Example 8.

The TEM images of the materials of Examples 6, 5, 7 and 8, annealed for 1 hour at 235 ^° C. under vacuum, are given in FIGS 6a respectively. at 6d (PTA labeling).

As the PA content increases in the mixture, the morphology remains very thin and homogeneous. Morphology also changes with PA content. For 70% PA, there is indeed a tendency to disperse P (MMA _f -b-BA-b-MMA _f ) in PA (Figure 6d); as a result, the product obtained is white. In contrast, when AP represents only 20% of the mixture, PA nodules can be observed (Figure 6a).

The evolution curves of the storage module as a function of temperature are given in FIG. 7 for P (MMAf-b-BA-b-MMAf), the materials of Examples 5, 7, 8 and PA3:

- P (MMA _f -b-BA-b-MMA _f ): solid line

graft copolymer material of Example 5: oooooooooooo

graft copolymer material of Example 7: ++++++++++++ - graft copolymer material of Example 8: xxxxxxxxxxxx

- PA3: dotted line

In Table 1 below, the values of the storage modulus were given at 20 ^° C. and at 18 ^° C. for these five materials. The module at room temperature and the tray at 18O ⁰ C increases with the content of PA.

Also, it appears from Figure 7 that the behavior of the PA at 80 ^° C. is improved. CONCLUSION:

The grafted triblock materials of the invention have fine and homogeneous morphologies, whatever the size of the PA chains used. The graft triblock copolymer content is high and the residual polymers P (MMAf-b-BA-b-MMAf) and PA are well incorporated into the structure. In addition, the morphology of the mixtures hardly changed during the annealing (1 h at 235 ^° C. under vacuum). These results differ from those obtained in the absence of the PBA central block. The structuring of P (MMA _f -b-BA-b-MMA _f ) therefore plays an important role on the grafting process and on the stability of the mixtures obtained.

The properties of these mixtures were studied by DMA and immersing the rods in a good solvent of the triblock. The best thermomechanical properties and solvent resistance are observed in the case of mixtures extruded with PA6 of large mass (15000 g / mol). This translates into DMA by a higher modulus at room temperature, a stable material up to Tg PMMA blocks and a high modulus up to PA melting for blends with 70% PA content. mass.

Table 1

Value of the storage modulus (E ') at 20 ^° C. or 18 ^° C.

Example (E ') at 20 ^° C. (E') at 18 ^° C. (in MPa) (in MPa)

Reference P (MMA _f -b-BA-b-MMAf) 1105

1 (PA = PAI, R = 80 = 80) 1105

2 (PA = PAI, R = 70%) 1260

3 (PA = PAI; R = 60 40) 1315

4 (PA = PA2, R = = 70) 1105

(PA = PA3, R = = 70) 1270 6

7 (PA = PA3, R = 50 50) 1770

8 (PA = PA3, R = = 30 70) 2055 105

PA3 2265 200

Claims

1 - graft copolymer consisting of a trunk formed of a block copolymer of general formula:

B- (A) _n

in which: A is a rigid polymer block having a glass transition temperature greater than 0 ^° C .; B is a flexible polymer block of glass transition temperature below 0 ^° C; and n is 1 or is a natural number greater than 1, the blocks A, when n is 2 or more, which may be identical or different, and polyamide grafts (PA) carried by the rigid polymer block or blocks, the graft copolymer obtained being represented by the general formula:

(A _g ) _m -B- (A) _p in which:

A and B are as defined above; Ag is block A carrying at least one graft (PA); and m and p are natural integers whose sum is equal to n, p being able, however, to be equal to 0.

2 - graft copolymer according to claim 1, characterized in that n is 1 or is a natural number of 2 to

20.

3 - graft copolymer according to one of claims 1 and 2, characterized in that, in the case where n is at least 2, all A blocks are identical and / or all Ag blocks are identical. 4 - graft copolymer according to one of claims 1 to 3, characterized in that: the number-average molecular weight of one or each block A is between 5000 and 100,000 g / mol, rather between 10,000 and 70,000 g / mol, advantageously between 15,000 and 50,000 g / mol; the number-average molecular mass of block B is between 5000 and 100,000 g / mol, more preferably between 5000 and 60,000 g / mol, advantageously between 5,000 and 40,000 g / mol, preferably between 10,000 and 40 000 g / mol; and the number-average molecular mass of the polyamide grafts is between 1000 and 50 000 g / mol, preferably between 1000 and 40 000 g / mol, advantageously between 1000 and 30 000 g / mol, preferably between 1000 and and 20,000 g / mol.

5 - graft copolymer according to one of claims 1 to 4, characterized in that the mass ratio of the copolymer B- (A) _n as defined in claim 1 to polyamide grafts (PA) is from 10:90 to 95: 5, preferably 50:50 to 90:10, preferably 60:40 to 80:20.

6 - graft copolymer according to one of claims 1 to 5, characterized in that the or each block A is a polymer block having a glass transition temperature greater than or equal to 50 ^° C., advantageously greater than or equal to 80 ^° C. vs. 7 - graft copolymer according to one of claims 1 to 6, characterized in that the block B is a polymer block having a glass transition temperature less than or equal to -1O ⁰ C, preferably less than or equal to -30 ⁰ vs.

8 - graft copolymer according to one of claims 1 to 7, characterized in that the or each block A is a methacrylic block, comprising predominantly methyl methacrylate units (MMA).

9 - graft copolymer according to claim 8, characterized in that the or each block A comprises from 70 to 99.5%, advantageously from 80 to 99.5%, preferably from 85 to 99.5%, by weight, of MMA motifs.

10 - graft copolymer according to one of claims 1 to 9, characterized in that the or each block A comprises at least one unit carrying at least one function that has allowed the grafting and selected from the acid functions, salt of acid, anhydride or epoxide, advantageously among the acid and anhydride functions.

11 - graft copolymer according to claim 10, characterized in that the or each unit carrying at least one function selected from acid, acid salt, anhydride and epoxide functions is chosen from:

The units resulting from at least one monomer comprising a C = C double bond, copolymerizable with the main monomer forming the block A concerned and bearing at least one functional group chosen from acid, acid salt, anhydride and epoxide functions; ; and

Glutaric anhydride units of formula: in which R ₃ and R 4 denote H or a methyl radical.

12 - graft copolymer according to claim 11, characterized in that the or each block A comprises at least one glutaric anhydride unit and / or at least one acrylic acid unit and / or at least one methacrylic acid unit.

13 - graft copolymer according to one of claims 10 to 12, characterized in that the or each block A comprises, by weight, from 0.5 to 30%, preferably from 0.5 to 20%, preferably from 0 to , 5 to 15%, of the unit or units bearing at least one acid function, acid salt, anhydride or epoxide, advantageously at least one acid and / or anhydride function.

14 - graft copolymer according to one of claims 1 to 13, characterized in that the or each block A comprises at least one unit of a comonomer (a) having at least one C = C double bond, copolymerizable with the monomer main forming said block and which does not carry an acid function, acid salt, anhydride or epoxide.

15 - graft copolymer according to claim 14, characterized in that the comonomer (a) is chosen from the following monomers: • acrylic monomers of formula

CH ₂ = CH-C (= O) -O-Ri where R 1 is a alkyl C1-C4 ₀ linear, cyclic or branched optionally substituted by a halogen atom, hydroxy, alkoxy, cyano; Methacrylic monomers of formula

CH ₂ = C (CH ₃ ) -C (= O) -O-R ₂ where R ₂ denotes a linear, cyclic or branched C ₂ -C ₄ 0 alkyl group optionally substituted with a halogen atom, a hydroxy group or an alkoxy group cyano, amino or epoxy; and vinylaromatic monomers.

16 - graft copolymer according to one of claims 1 to 15, characterized in that the or each block A is based on MMA and comprises, by weight:

• 70 to 99.5% MMA;

From 0 to 20% of a comonomer (a) having at least one C = C double bond, copolymerizable with MMA and which does not carry an acid function, acid salt, anhydride or epoxide;

17 - graft copolymer according to claim 16, characterized in that the or each block A is based on MMA and comprises, by weight:

• 80 to 99.5% MMA; From 0 to 10% of a comonomer (a) having at least one C = C double bond, copolymerizable with MMA and which does not carry an acid function, acid salt, anhydride or epoxide;

From 0.5 to 20% of at least one group carrying at least one acid, acid salt, anhydride or epoxide function.

18 - Graft copolymer according to claim 17, characterized in that the or each MMA-based block A comprises, by weight: • from 85 to 99.5% of MMA;

• from 0 to 5% of a comonomer (a) having at least one C = C double bond, copolymerizable with MMA and which does not carry an acid function, acid salt, anhydride or epoxide; and from 0.5 to 15% of at least one group carrying at least one acid, acid salt, anhydride or epoxide function.

19 - graft copolymer according to one of claims 1 to 18, characterized in that the block B comprises butyl acrylate units or mainly butyl acrylate units.

20 - graft copolymer according to one of claims 1 to 19, characterized in that the polyamide forming the grafts is selected from PA 6, PA 6-6, PA 11, PA 12 and their copolymers.

21 - graft copolymer according to claim 20, characterized in that the polyamide has a melting temperature between 100 and 400 ⁰ C, preferably between 120 and 300 ⁰ C, preferably between 140 and 25O ⁰ C. 22 - graft copolymer according to one of claims 1 to

21, characterized in that there is, per block A _g , on average from 1 to 100, preferably from 1 to 50, polyamide grafts (PA).

23 - graft copolymer according to one of claims 1 to

22, characterized in that it consists of a triblock copolymer A _g -BA _g .

24 - Process for preparing a graft copolymer as defined in one of claims 1 to 23, characterized in that it consists in reacting with a polyamide terminated with a primary amine or acidic function a copolymer of general formula B- (A) _n , A, B and n being as defined in claim 1 and the block or blocks having functionalities capable of reacting with primary amine or acid functional groups of the polyamide.

25 - Process according to claim 24, characterized in that it is carried out by reactive extrusion at a temperature of 180 to 32O ⁰ C, preferably 180 to 28O ⁰ C, for a period of time of 1 second to 15 minutes , rather from 1 second to 10 minutes.

25 - Material consisting of: graft copolymer (A _g ) _m -B- (A) _P as defined in one of claims 1 to 23, in particular from 10 to 98% by weight; of copolymer B- (A) _{n which has} not reacted, B- (A) _n being as defined in claim 1, the block or blocks A carrying functionalities capable of react with primary amine or acid functions, in particular from 1 to 50% by weight; from 1 to 50% by weight of polyamide terminated with a primary amine function or unreacted acid, in particular from 1 to 50% by weight; the total being 100% by weight.

27 - Material according to Claim 26, characterized in that from 0 to 60% by weight, preferably from 0 to 30% by weight, of impact modifiers of the core-shell type relative to the material have been added.

28 - Use of the graft copolymer as defined in one of claims 1 to 23 or the material as defined in one of claims 26 and 27 in the form of films, extruded parts blown, parts injected or plates extruded.

29 - Use of the graft copolymer as defined in one of claims 1 to 23 or the material as defined in one of claims 26 and 27 as a compatibilizing agent for obtaining an alloy based on a polyamide and a polymer selected from PMMA, PVDF, PVC and acrylic polymers.

30 - Use of the graft copolymer as defined in one of claims 1 to 23 or the material as defined in one of claims 26 and 27 as a coextrusion binder of a polyamide-based multilayer structure and a polymer chosen from PMMA, PVDF, PVC and acrylic polymers, having the order of the following layers: a polyamide layer; a layer c2 of the material; a layer c3 of a polymer chosen from PMMA, PVDF, PVC and acrylic polymers; the layers adhering to each other.