FR2617173A1 - DIAMINE-FREE IMIDE GROUP POLYMERS AND PROCESS FOR THEIR PREPARATION - Google Patents

Abstract

New thermally stable polymers containing imide groups. More precisely, these polymers are obtained by reaction, at a temperature ranging from 50 DEG C to 300 DEG C, between: (a) an N,N'-bismaleimide, (b) an acrylate reactant consisting especially of a novolac epoxy (meth)acrylate, and (c) an imidazole compound. These polymers are advantageously employed for the production of laminates.

Description

DIAMINE-FREE IMIDE GROUP POLYMERS
AND THEIR PREPARATION PROCESS
The subject of the present invention is new thermostable polymers, the production of which involves bis-imides. It also relates to processes for the preparation of these polymers.

Polymers obtained by reaction between a
N, N'-bis-imide of unsaturated dicarboxylic acid such as for example a
N, N'-bis-maleimide with a biprimary diamine (French Patent No. 1,555,564). The amounts of N, N'-bis-imide and diamine are chosen so that the ratio
number of moles of bis-imide
number of moles of diamine is at least equal to 1; moreover, it is generally preferred for it to be less than 50. Thermostable resins are obtained which remarkably withstand severe thermal stresses.

 it is generally indicated in the aforementioned French patent that the preparation of these resins can be carried out in bulk by heating the reagents previously subjected to an intimate mixture or else within an inert polar diluent such as dimethylformamide, N-methylpyrrolidone, dimethylacetamide, the latter process can be used for example when the implementation of the polymer requires the use of a solution.

 Finally, it is mentioned that for many jobs, it is advantageous to operate in two stages; in a first stage, a prepolymer is prepared by heating the intimate mixture of the two reactants at a twisting temperature of 100 to 2500 C. The prepolymer obtained can be used in the form of a solution, suspension, powder or else still shaped by simple hot casting. In a second stage, it is possible to cause a coating of the prepolymer by heating to temperatures of the order of 3000 C, possibly under pressure.

 These polymers can be converted into films or multicellular materials. They are of very particular interest for the preparation either of molded articles possibly in association with fibrous or pulverulent fillers, or of laminates based on mineral fibers (simple fibers, fabric or non-woven of fibers) such as for example carbon, boron or glass fibers. However, the preparation and use of these polymers necessitate taking hygienic precautions when the biprimary diamine used is of aromatic nature due to the toxicity which some of them may exhibit.

 To overcome this drawback, the Applicant is interested in the development of new polymers with imide groups which do not use diamines for their preparation.

We have already described in the European patent application
EP-A-0.167.304 polymers with imide groups which can be obtained without using diamines for their preparation. Such polyamides are obtained for example from - a combination of several N, N'-bis-maleimides, and - a (meth) acrylic ester consisting in the reaction product of (meth) acrylic acid with an epoxy resin such as a glycidic ether of poly (hydroxyphenyl) alkane or of a phenol / formaldehyde polycondensate of the novolak type.

Continuing work in this technical field, the
Applicant has noted that the teaching of the aforementioned patent application does not allow, starting from a reagent generating imide groups consisting of a single and unique
N, N'-bis-maleimide, to produce homogeneous prepolymers and polymers for which the bis-maleimide and the (meth) acrylic ester are involved in a common copolymerization reaction. It has also been found that the prepolymers which can be prepared do not lend themselves well to the production of prepreg intermediate articles (used for the preparation of laminates) and using the technique of impregnation with solvent due to the very low solubility of these prepolymers. in commonly used solvents.

 It has now been found, and this is what constitutes the object of the present invention, polymers with imide groups obtained from a single N, N'-bis-maleimide and an ester (meth ) acrylic epoxy resin which are homogeneous and perfectly suitable, when they appear as prepolymers, for an implementation requiring the use of a solution in a solvent. To achieve this result, an additional reagent consisting of an imidazole compound should be added to the preparation medium of the desired polyimides.

dans laquelle
les symboles Y, identiques ou différents, représentent chacun un atome d'hydrogène, un radical méthyle ou un atome de chlore
le symbole A représente un radical divalent choisi dans le groupe constitué par les radicaux : cyclohexylènes ; phénylènes; méthyl-4 phénylène-1,3 ; méthyl-2 phénylène-i,3 ; méthyl-5 phenylène-1,3 ; diéthyl-2,5 méthyl-3 phénylène-1,4 ; et les radicaux de formule

dans laquelle T représente un lien valentiel simple ou un groupement

More specifically, the present invention relates to polymers with imide groups, characterized in that they comprise the reaction product, at a temperature ranging from 500 ° C. to 3000 ° C., between
- (a) an N, N'-bis-maleimide of formula

in which
the symbols Y, which are identical or different, each represent a hydrogen atom, a methyl radical or a chlorine atom
the symbol A represents a divalent radical chosen from the group consisting of radicals: cyclohexylenes; phenylenes; 4-methyl-1,3-phenylene; 2-methylphenylene-1,3; 5-methyl-1,3-phenylene; 2,5-diethyl-3-methyl-1,4-phenylene; and the radicals of formula

in which T represents a simple valential link or a grouping

et les symboles X, identiques ou différents, représentent chacun un atome d'hydrogène, un radical méthyle, éthyle ou isopropyle
- (b) un réactif acrylate consistant
* soit (bl) dans un (méth)acrylate d'époxy novolaque répondant à la formule générale

dans laquelle
les symboles R1 et R2, identiques ou différents, représentent chacun un atome d'hydrogène ou un radical méthyle
n est un nombre positif se situant dans l'intervalle allant de 0,1 à8;
* soit dans le mélange du composé (bl) précité avec au plus 30 t en poids, par rapport au poids au mélange (bol) + (b2), d'un composé (b2) de formule générale ::
(CH2 = CR3 - CO - O)3--- B (III) dans laquelle
le symbole R3 représente un atome d'hydrogène ou un radical méthyle;
le symbole B représente un radical organique trivalent dérivé d'un hydrocarbure aliphatique saturé linéaire ou ramifié ayant de 1 à 20 atomes de carbone et pouvant renfermer un ou plusieurs ponts oxygène et une ou plusieurs fonctions hydroxyles
et (c) un composé imidazole.

and the symbols X, identical or different, each represent a hydrogen atom, a methyl, ethyl or isopropyl radical
- (b) a consistent acrylate reagent
* or (bl) in a (meth) acrylate novolak corresponding to the general formula

in which
the symbols R1 and R2, identical or different, each represent a hydrogen atom or a methyl radical
n is a positive number in the range of 0.1 to 8;
* either in the mixture of the abovementioned compound (bl) with at most 30 t by weight, relative to the weight in the mixture (bowl) + (b2), of a compound (b2) of general formula:
(CH2 = CR3 - CO - O) 3 --- B (III) in which
the symbol R3 represents a hydrogen atom or a methyl radical;
the symbol B represents a trivalent organic radical derived from a linear or branched saturated aliphatic hydrocarbon having from 1 to 20 carbon atoms and which may contain one or more oxygen bridges and one or more hydroxyl functions
and (c) an imidazole compound.

As specific examples of bis-imides (a) of formula (I), there may be mentioned in particular - N, N '-metaphenylene-bis-maleimide, - N, N'-paraphenylene-bis-maleimide, - N, N'-4,4 '-diphenylmethane-bis-maleimide, - N, N'-4,4'-diphenylether-bis-maleimide, - N, N'-4,4'-diphenylsulphone-bis -maleimide, - N, N'-cyclohexylene-1,4-bis-maleimide, - N, N '-4,4' -diphenyl-1 i cyclohexane-bis-maleimide, - N, N'-4 , 4'-diphenyl-2,2 propane-bis-maleimide, - N, N'-4,4 '-triphenylmethane-bis-maleimide, - N, N'-N'-methyl-2-phenylene-1,3-bis -maleimide, - N, N'-methyl-4-phenylene-1,3-bis-maleimide, - N, N'-methyl-5-phenylene-1,3-bis-maleimide,
These bis-maleimides can be prepared according to the methods described in American patent US-A-3,018,290 and English patent GB-A-1,137,290. Preferably, for the implementation of the present invention, the N, N-4,4'-diphenylmethane-bis-maleimide.

 Novolak (bi) epoxy (meth) acrylates of formula (II) are known products, some of which are commercially available.

They can be prepared by reacting (meth) acrylic acid with an epoxy resin of the novolak type, the latter being the reaction product of epichlorohydrin and of phenol / formaldehyde polycondensates (in formula (II) given above. R2 is then a hydrogen atom) or cresol / formaldehyde polycondensates (in formula (II) R2 is then a methyl radical). These oligomeric polyacrylates (b1) of formula (II) and a process for preparing them are described, for example, in American patent US-A-3,535,403.

 As specific examples of compounds (b2) of formula (III) which can be used alongside the (meth) acrylate novolak (bl), mention may be made in particular of the (meth) acrylic esters of polyols such as 1,2,3-butanetriol tri (meth) acrylate, 1,2,6-hexanetriol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaeryl thritol tri (meth) acrylate.

 Preferably used for the implementation of the present invention, the (meth) acrylates of novolak epoxy (bl) of formula (II) in which R1 and R2 represent a hydrogen atom and n is a positive number se lying in the range from 0.1 to 5, these compounds being taken alone or as a mixture with at most 25% by weight, relative to the weight of the mixture (bl) + (b2), of a compound (b2 ) consisting of trimethylolpropane triacrylate.

The quantities of N, N'-bis-imide (a) and of acrylate reagent (b) are chosen so that the ratio r
number of maleimide groups provided by bis-imide (a)
number of acrylic double bonds provided by the reagent (b) is in the range from 1.7 / 1 to 10/1 and preferably ranging from 2/1 to 8/1. It should be clearly understood that the expression "acrylic double bonds provided by the reagent (b)" designates all of the groups CH2 = CR1 provided by the compound (bl) more optionally all of the groups CH2 = CR3 provided by the compound (b2).

dans laquelle R4, R5i R6 et R7 identique ou différents, représentent chacun : un atome d'hydrogène, un radical alkyle ou alcoxy ayant de 1 à 20 atomes de carbone, vinyle, phényle, nitro, R6 pouvant former avec
R7 et les atomes de carbone auxquels sont liés ces radicaux un cycle unique comme par exemple benzénique.The imidazole compound (c) corresponds to the general formula

in which R4, R5i R6 and R7, identical or different, each represent: a hydrogen atom, an alkyl or alkoxy radical having from 1 to 20 carbon atoms, vinyl, phenyl, nitro, R6 can form with
R7 and the carbon atoms to which these radicals are linked a single ring such as, for example, benzene.

 As specific examples of imidazole compounds, there may be mentioned in particular: imidazole or glyoxaline, 1-methylimidazole, 2-methylimidazole, 1,2-dimethylimidazole, 1-vinylimidazole, 2-methyl vinyl imidazole, benzimidazole.

 The imidazole compound is used in catalytic amounts. Depending on the nature of the imidazole compound and according to the desired polymerization rate at the implementation stage, the imidazole compound is used at a rate, expressed in number of moles of compound (c) per 100 g of bis-imide (a) , lying in the range from 0.15.10 a to 6.10 3 and preferably ranging from 0.3.10 to 4.10.

 The polymers according to the invention can be prepared in bulk by direct heating of the bis-imide (a), of the acrylate reagent (b) and of the imidazole compound (c) at least until a homogeneous liquid mixture is obtained. The temperature may vary depending on the physical state of the compounds present, but it is generally between 500 ° C. and 3000 ° C. It is advantageous to bring and maintain the starting compounds in a state of intimate mixing before and during the heating using, for example, good agitation. Preferably, the imidazole compound (c) is added initially to the well-stirred mixture of reagents (a) and (b) so as to allow its rapid dispersion. When this compound is particularly active, to avoid its encapsulation in the polymer network generated, it is desirable to add it to a solvent compatible with the reaction medium; it has been found that it could be advantageous to use one of the polar organic liquids which is discussed below as the solvent.

 The preparation of the polymers according to the invention can also be carried out by heating the mixture of reactants within an organic diluent which liquidates in at least part of the range 50 ° C. to 3000 C. Among these diluents, mention may be made in particular aromatic hydrocarbons such as xylenes and toluene, halogenated hydrocarbons such as chlorobenzenes, polar solvents such as dioxane, tetrahydrofuran, dibutyl oxide, dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone, dimethylacetamide, methylglycol, methyl ethyl ketone and cyclohexanone. Polymer solutions or suspensions can be used as they are for many uses; the polymers can also be isolated, for example by filtration, optionally after precipitation using an appropriate non-solvent.

 It should be understood that the properties of the polymers according to the invention can vary to a large extent depending in particular on the exact nature of the reagents used, the proportions of reagents chosen and the precise temperature conditions adopted in the range mentioned above. As regards the polymers obtained, these can be hardened polymers, insoluble in the usual polar solvents such as for example the liquids mentioned in the preceding paragraph and which do not exhibit any significant softening below the temperature at which they - begin to degrade.

 However, these polymers can also be in the form of prepolymers (P) soluble in polar organic solvents such as, for example, those mentioned above and having a softening point at a temperature below 2000 ° C. (in general this point of softening is between 500 and 1500 C). These prepolymers can be obtained in bulk by heating the mixture of reactants until a homogeneous or pasty product is obtained at a temperature generally between 500 and 1800 ° C. for a period which can range from a few minutes to a few hours, this the duration being shorter the higher the temperature adopted.

Before subjecting the mixture of reagents to heating, it is also advantageous to effect it by stirring a prior intimate mixture. There is also a preferred method of using the imidazole compound - (c) and this is the cell indicated above in connection with the direct preparation of cured polymers. The prepolymers can also be prepared in suspension or in solution in a diluent which is liquid in at least part of the range 500 - 1800C.

 The prepolymers (P) can be used in the liquid mass state, a simple hot casting sufficient for the shaping and the production of molded objects. It is also possible, after cooling and grinding, to use them in the form of powders which are remarkably suitable for compression molding operations, possibly in the presence of fillers in the form of powders, spheres, granules, fibers or flakes. . In the form of solutions, the prepolymers (P) can be used for the production of prepreg intermediate articles, the reinforcement of which can be constituted by fibrous materials (in the form of single fibers, woven or nonwoven webs) - å base silicate or aluminum or zirconium oxide, carbon, graphite, boron, asbestos or glass. These prepolymers (P) can also be used for the production of cellular materials after incorporation of a blowing agent such as for example azodicarbonamide.

 In a second stage, the prepolymers (P) can be hardened by heating to temperatures of the order of 3000 C, generally between 1500 and 2500 C; additional shaping can be carried out during hardening, possibly under vacuum or under super-atmospheric pressure, these operations can also be consecutive.

 According to a preferred embodiment of the present invention, the operation is carried out in two stages, the first stage consisting in heating the mixture of the reactants between 50 ° C. and 1800 ° C. to form a prepolymer (P), the second stage consisting in hardening the prepolymer (P), after having given it the desired shape, by heating to temperatures of the order of 3000 C.

 However, in accordance with an even more preferred embodiment of the present invention, the operation is carried out in two stages, but using in the first stage a process for the continuous preparation of the prepolymer (P) consisting in introducing the bis-imide (a ) in the divided solid state, the acrylate reagent (b) in the liquid or molten state and the imidazole compound (c) in the solid state or in solution in a kneader with extruder screw.

The expression "screw extruder mixer" is intended to denote an apparatus which does not have a dead zone during the progression of the material. Devices of this kind which may include one or more screws are described in the work of EG FISHER-Extrusion of
Plastics (Interscience Publisher 1964) pages 104 to 108. These mixers can comprise two worms which mesh intimately with each other and rotate in the same direction; an apparatus of this type more particularly equipped for the preparation of alkaline terephthalates is described in French patent FR-A-1 462 935. Another variety of mixers which can be used is constituted by apparatus comprising an endless screw with interrupted thread simultaneously performing rotational movement and an oscillatory movement in the direction of the axis, housed in an envelope comprising teeth which cooperate with the interrupted fins of the screw. Devices of this type are described in French patents FR-A-1 184 392, 1 184 393, 1 307 106 and 1 369 283.

 For reasons of convenience of implementation, it is preferred to use bis-imide (a) in the form of particles whose dimensions range from 0.1 to 5 mm. Their introduction into the mixer can be regulated by devices known for this use, such as vits or dosing scales.

 The acrylate reagent (b) is fed in the liquid state into the mixing area. Its introduction can be carried out by means of a metering pump. The supply of the reagent (b) can be carried out at one or more points located preferably downstream of the supply zone of the bis-imide (a).

 The imidazole compound (c) can be incorporated in the solid state with the acrylate reagent (b). However, it is preferred to incorporate the imidazole compound (c) in the form of a solution in a polar solvent such as those which have been mentioned above; in this preferred case, the imidazole compound (c) can be very well incorporated with the acrylate reagent (b), but its introduction into the mixer can also be carried out at any other point in the mixing zone, preferably downstream of the acrylate reagent supply zone (b).

 Maintaining the mixing zone at the chosen temperature of between 500 ° C. and 1800 ° C. and preferably between 1300 ° C. and 1600 ° C. is generally obtained by controlled heating of the envelope of the screw or of the worms of the apparatus. With regard to the envelope, the heating can be exerted in a uniform manner over its entire length, but it is also possible to have several contiguous heating zones ensuring the temperature of the mixing zone, for example increasing in the direction of progression of the material. Upstream of the first point of introduction of the reagent (b), it is preferred that the temperature be situated in the range 20 - 1300 C.

The residence time of the products in the mixing zone can vary to a certain extent depending on the bis-imides (a) used, the temperature adopted and the quantities of reagents used. Generally, it is of the order of 1 to 30 minutes. At the outlet of the mixer, it is possible to adjust the softening point of the prepolymer (P) by heating the latter in an oven under specified temperature and duration conditions. For example, when the reagent (a) is the
N, N'-4,4'-diphenylmethane-bis-maleimide and the ratio r is close to 5/1, prepolymers are obtained having softening points of the order of 500 C to 600 C for a prepolymerization temperature 1550 C and a residence time in the range 5-10 minutes.

 The polymers according to the invention interest the fields of industry which require materials endowed with good mechanical and electrical properties as well as a great chemical inertness at temperatures from 2000 to 3000 C. By way of examples, they are particularly suitable good for the manufacture of intermediate prepreg articles. The prepreg articles can be used for the production of parts having various shapes and functions in many industries such as aeronautics. These parts, called laminates, which can be parts of revolution, are obtained by plating several layers of prepreg on a form or a support. Prepregs can also be used as reinforcements or as a means of repairing damaged parts.

 The following examples are given by way of illustration, but not limitation.

EXAMPLE 1
Example which describes a polymer according to the invention prepared by a batch process.

- 320 parts by weight of N, N'-4,4'-diphenylmethane bis-maleimide (0.558 maleimide groups per 100 g) are introduced into a reactor equipped with an agitator and placed in an oil bath thermostatically controlled at 1600 ° C. bis-imide), having a softening point of 1570 C, and - 78 parts by weight of acrylate reagent consisting in the mixture based on approximately 80% by weight of an epoxy novolak diacrylate of formula (II) in which R1 = R2 = H and n is a number between 2 and 4 and 20% by weight of trimethylolpropane triacrylate this reagent is commercially available under the registered trademark
EBECRYL 629 from the company UCB and it has approximately 0.5 free acrylic double bonds per 100 g of reagent.

The mixture is stirred for 40 minutes until a homogeneous mass is obtained. 0.20 parts by weight of imidazole are then added in the form of a 10% by weight solution in the
N-methylpyrrolidone.

Stirring of the reaction medium is continued for 20 minutes at 1600 ° C., then the mixture is poured onto a tray. After cooling, the prepolymer obtained is ground and a yellow powder is obtained which is soluble in solvents such as for example
N-methylpyrrolidone, cyclohexanone and dimethylformamide. The prepolymer obtained has a softening point of 830 C; n viscosity, measured in 50% by weight solution in cyclohexanone, is 0.35 Pa.s.

A 50 t weight prepolymer solution is used in the
N-methylpyrrolidone to coat a glass fabric made by the
PORCHER company under the reference 7628 whose grammage is 200 g / m and having undergone a treatment with gamma-aminopropyltriethoxysilane (silane A 1100 from UNION CARBIDE). The impregnated fabric contains 35 g of prepolymer per 65 g of fabric; it is dried in a ventilated atmosphere at 1300 C for 5 minutes. Then cut 6 squares (15 x 15 cm) which are stacked with a copper foil 35 µm thick placed on one of the outer faces of the stack and the assembly is placed between the trays of a press under the following conditions: - pressure: 40.105 Pa, - heating of the press plates: 15 minutes at 1500 C, then 45 minutes at 2000 C.

 During the lamination operation, a creep rate of the polymer is observed of around 20% by weight. After an additional heat treatment at 2350 C for 6 hours, the adhesion of copper is examined on the prepared 6-ply laminate: this adhesion, measured with a dynamometer by pulling copper at 900 angles (according to MIL P 55 617 standard B with a traction speed of 55 mm / min), is of the order of 15 N / cm; this value is maintained after aging for 1000 hours at 2000 C.

 By way of comparative test, the preceding Example 1 was reproduced, but in the absence of imidazole. The reaction mixture heated to 160 ° C. solidifies after 1 hour 30 minutes of mixing. After cooling and grinding, the powder obtained has a softening point of 700 C; it is very sparingly soluble in the aforementioned solvents. Analysis shows that the bis-maleimide was little or not engaged in a reaction with the acrylate reagent. The prepolymer thus obtained is not suitable for the applications described, in particular for the preparation of laminates.

EXAMPLE 2
Example which describes a polymer according to the invention prepared by a continuous process.

 The apparatus used is a BUSS laboratory kneader known under the name "KO-kneader" type PR 46. This kneader comprises an endless screw formed of a shaft comprising interrupted helical threads, the interruptions forming separate fins; it is driven by an appropriate mechanism. The screw is housed in a body comprising three contiguous double-walled coaxial cylindrical envelopes; the inner wall of the kneading body has teeth-shaped projections. The screw is subjected to a rotational movement and simultaneously to an oscillatory movement in the direction of its axis, which creates an exchange of material in two directions.

 In the first envelope, water at 200 ° C. is circulated and in the other two, a fluid heated to 1550 ° C. The speed of rotation of the screw is 60 revolutions / minute.

 In the first part of the mixer (corresponding to the first envelope), N, N'-4,4'-diphenylmethane-bis-maleimide is introduced via a metering balance at the rate of 1200 g / h; bis-maleimide is introduced in the form of grains whose average size is of the order of 0.25 mm.

In the second part of the mixer (corresponding to the second envelope), the assembly is introduced: acrylate reagent according to Example 1 + imidazole solution at 20 t by weight in the
N-methylpyrrolidone, at a rate of 300 g / h.

 The dosage of reagents is such that the bis-maleimide represents 79.9 t of the weight of the bis-maleimide + acrylate reagent and the imidazole 0.05 t of the weight of the same set.

 The average residence time of the material in the. mixer is around 6 minutes 30 seconds. At the outlet of the apparatus, a prepolymer is collected whose softening point is of the order of 550 C. This prepolymer brought to 1700 C for 17 minutes has a softening point of 800 C. It is soluble in solvents such as for example N-methylpyrrolidone, cyclohexanone and dimethylformamide and it has a viscosity (measured as indicated in example 1) of 0.35 Pa.s.

With the prepolymer thus obtained, prepregs and laminates comprising 18 plies (18 layers of prepregs) are prepared under the conditions described above in Example 1 (note that no copper foil is used here). After annealing at 2350 C for 6 hours, the laminates have the following mechanical characteristics - flexural strength measured at 2000 C (according to the standard
NF T 51 001): 350 MPa, - inflection module: 28,000 MPa.

The prepolymer obtained is also subjected to measurements in
TMA ("Thermal Mechanical Analysis" or Thermal Mechanical Analysis standard ASTM E 831-81 with a temperature rise rate of 50 C / min). On the product annealed at 2350 C, it is observed that the average coefficient of expansion between 400 C and 3000 C is 40 ym / m / C and that the glass transition temperature is 3400 C.

Claims (13)

1) Polymers with imide groups characterized in that they comprise the reaction product, at a temperature ranging from 500 C to 3000 C, between  - (a) an N, N'-bis-maleimide of formula

 in which  the symbols Y, which may be identical or different, each represent a hydrogen atom, a methyl radical or a chlorine atom;  the symbol A represents a divalent radical chosen from the group consisting of radicals: cyclohexylenes; phenylenes; 4-methyl-1,3-phenylene; 2-methyl-1,3-phenylene; 5-methyl-1,3-phenylene; 2,5-diethyl-3-methyl-1,4-phenylene; and the radicals of formula

 in which T represents a simple valential link or a grouping

 and (c) an imidazole compound.  the symbol B represents a trivalent organic radical derived from a linear or ratified saturated aliphatic hydrocarbon having 1 & 20 carbon atones and which can contain one or more oxygen bridges and one or more bydroxyl functions  the symbol R3 represents. a hydrogen atom or a methyl radical;  * either in the mixture of the above-mentioned compound (bowl) with at most 30 t by weight, relative to the weight of the mixture (bl) + (b2), of a compound (b2) of general formula (CH2 = CR3 - CO - O) --- 3 B (III) in which:  . n is a positive number in the range of 0.1 to 8;  the symbols R1 and R2, identical or different, each represent a hydrogen atom or a methyl radical;  in which

 * either (bi) in a (meth) acrylate novolak corresponding to the general formula  - (b) a consistent acrylate reagent  and the symbols X, identical or different, each represent a hydrogen atom, a methyl, ethyl or isopropyl radical;

2) Polymers according to claim 1, characterized in that the bis-maleimide (a) of formula (I) is N, N'-4,4'-diphenylmethane-bis-maleimide. 3) Polymers according to any one of claims 1 or 2 characterized in that the acrylate reagent (b) is chosen from the group formed by novolak epoxy (neth) acrylates (bl) of formula (II) in which R1 and R2 represent a hydrogen atom and n is a positive number lying in the range from 1 to 5, these compounds being taken alone or in a mixture with at most 25 t by weight, relative to the weight of the mixture (bowl ) + (b2), of a compound (b2) consisting of trimethylolpropane triacrylate. 4) Polymers according to any one of claims 1 to 3, characterized in that the imidazole compound (c) corresponds to the general formula

  in which R4, R5, -R6 and R7, identical or different, each represent: a hydrogen atom, an alkyl or alkoxy radical having from 1 to 20 carbon atoms, vinyl, phenyl, nitro, R6 can form with R7 and the carbon atoms to which these radicals are linked a single ring such as for example a benzene ring.  5) Polymer according to claim 4, characterized in that the imidazole compound (c) is chosen from the group formed by imidazole or glyoxaline, 1-methylimidazole, 2-methylimidazole, 1,2-dimethylimidazole , vinyl-imidazole, 2-methyl vinyl imidazole and benzimidazole.  6) Polymers according to any one of claims 1 to 5, characterized in that on the one hand the amounts of N, N'-bis-imide (a) of acrylate reagent (b) are chosen so that the report  number of maleimide groups provided by bis-imide (a)  number of acrylic double bonds provided by the acrylate (b) is in the range from l, V l to 10/1, and on the other hand the level of imidazole compound (c), expressed in number of moles of compound (c) per 100 g of bis-imide (a), lies in the range from 0.15.10-3 to 6.10 7) Polymers according to any one of claims 1 to 6, characterized in that they are in the form of hardened polymers, insoluble in the usual polar organic solvents and having no significant softening below the temperature at which they begin to degrade. 8) Polymers according to any one of claims 1 to 6, characterized in that they are in the form of thermosetting prepolymers (P) soluble in the usual polar organic solvents and have a softening point at a temperature below 2000 C . 9) Process for the preparation of cured polymers according to claims 1 to 7, characterized in that it consists in heating the mixture of reagents between 500 C and 1800 C to initially form a prepolymers (P), then caused the hardening of the prepolymers (P) by heating at a temperature between 1500 C and 2500 C. 10) A method of preparing thermosetting polymers (P) according to claims 1 9 6 and 8, characterized in that the mixture of reactants is directly heated to a temperature between 500 C and 1800 C until obtaining d '' a homogeneous liquid or pasty product. 11) Preparation process according to claim 9 or 10, characterized in that one uses a continuous preparation process of the prepolymer (P) consisting in introducing the bis-imide (a) in isolation in the divided solid state, the acrylate reagent (b) in the liquid or molten state and the imidazole compound (c) in the solid state or in solution in a kneader with extruder screw. 12) A method of preparation according to claim 11, characterized in that one uses a mixer comprising an endless screw with interrupted thread performing simultaneously a rotary movement and an oscillatory movement in the direction of the axis, housed in a envelope comprising teeth which cooperate with the interrupted fins of the screw. 13) Method according to one of claims il and 12, characterized in that the acrylate reagent (b) and the imidazole compound (c) are fed downstream of the feed zone of the imide reagent (a).