NO875222L - POLYMERS WITH IMID GROUPS AND PROCEDURES FOR THEIR PREPARATION. - Google Patents

Abstract

Heat-stable polymers containing imide groups. These polymers are obtained by reaction between: - (a) one or more N,N'-bismaleimides, - (b) one or more hindered diprimary diamines of the 4,4'-diamino- 3,3',5,5'-tetraalkyldiphenylmethane or 1,3- or 1,4-diamino- trialkylbenzene type, - (c) optionally one or more monomers other than a bisimide and containing one or more polymerisable carbon-carbon double bonds, - (d) and optionally a compound of the imidazole type. These polymers are employed especially for the production of moulded articles, laminates and articles with a cellular structure.

Description

The present invention relates to new thermostable polymers which are produced using bis-imides and hindered diamines. The invention also relates to the production of these polymers.

Polymers obtained by reaction between an N,N'-bis-imide of an unsaturated dicarboxylic acid have previously been described, such as e.g.

an N,N'-bis-maleimide with a biprimary diamine (French Patent 1,555,564). The amounts of N,N'-bis-imide and diamine are chosen so that the ratio:

is at least equal to 1. Furthermore, it is generally preferred that this should be less than 50. Thermostable resins are obtained which remarkably resist strong thermal stresses. It is also indicated in the aforementioned patent that the production of these resins can be carried out in a melt while heating the reaction components which have previously been subjected to an intimate mixture, or also in a mixture with an inert polar diluent such as e.g. dimethylformamide, N-methylpyrrolidone, dimethylacetamide, the last method can be used e.g. when the use of the polymer necessitates the use of a solution.

Finally, it is mentioned that for numerous applications it is advantageous to work in two stages. In a first step, a prepolymer is prepared by heating the intimate mixture of the two reaction components at a temperature of approximately 100 to 250°C. The obtained prepolymer can be used in the state of solution, suspension, powder or also by simple pouring in a hot state. In another step, the curing of the prepolymer can be brought about by heating up to temperatures of approximately 300°C, possibly under pressure.

These polymers can be converted into films or multicellular materials. They are of particular interest for the production of molded objects, possibly in association with fibrous or powdered fillers or layered structures based on inorganic fibers (simple fibres, weaves or non-woody fiber structures) such as e.g. carbon fibres, boron fibers or glass fibres. However, the production and use of these polymers necessitates that precautions be taken on a hygienic level, as the biprimary diamine used is of an aromatic nature and some of them can be toxic.

In order to remedy this disadvantage, new polymers with imide groups have been developed which for their production use aromatic diarnins which do not pose a risk of the above-mentioned toxicity.

More particularly, the present invention relates to polymers with imide groups and they are characterized in that they are formed by the reaction product, at a temperature from 50 to 300°C, between:

- (a) an N,N'-bis-imide or an association of several bis-imides of formula:

in which :

. the symbols Y are the same or different, and each stands for

H, CH3 or Cl,

. the symbol A stands for a divalent radical selected from the group consisting of 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 radicals with formula:

where T represents a single valence bond or group:

and the symbols X, which are the same or different, each represent a hydrogen atom, methyl, ethyl or isopropyl. - (b) one or more hindered biprimary diamines from the group of:

(i) the type corresponding to the general formula:

in which:

. the symbols , R^, R-^ and R^ are the same or different

equal and each stand for methyl, ethyl, propyl or isopropyl, . the symbols Z are the same or different, and each represents a hydrogen atom or a chlorine atom,

(ii) and the types corresponding to the general formula:

. the amino radicals are in the méta or para position in relation to each other, . the symbols R^ are the same or different and represent each methyl, ethyl, propyl or isopropyl, and - (c) optionally one or more monomers other than the bis-imide of formula (I) and containing one or more polymerisable carbon-carbon double bonds, and

- (d) optionally a compound of the imidazole type.

As specific examples of bis-imides with formula (I) the following can be mentioned in particular:

- N,N'-metaphenylene-bis-maleimide,

- N,N'-paraphenylene-bis-maleimide,

- N,N1 -4,4'-diphenylmethane-bis-maleimide,

- N,N'-4,4-diphenyl ether-bis-maleimide,

- N,N'-4,4'-diphenylsulfone-bis-maleimide,

- N,N'-cyclohexylene-1,4-bis-maleimide,

- N,N'-4,4'-diphenyl-1,1-cyclohexane-bis-maleimide,

- N,N'-4,4'-diphenyl-2,2-propane-bis-maleimide,

- N,N'-4,4'-triphenylmethane-bis-maleimide,

- N,N'-2-methylphenylene-1,3-bis-maleimide,

- N,N'-4-methylphenylene-1,3-bis-malediimide,

- N,N'-5-methylphenylene-1,3-bis-maleimide.

These bis-maleimides can be prepared according to the methods described in US Patent 3,018,290 and British Patent 1,127,290. N,N'-4,4'-diphenylmethane-bis-maleimide is preferably used in the practice of the present invention either alone or in a mixture with N,N'-2-methylphenylene-1,3-bis-maleimide, N,N '-4-methylphenylene-1,3-bis-maleimide and/or N,N 1-5-methylphenylene-1,3-bis-maleimide.

As specific examples of hindered diamines with formulas (II) and (III) the following can be mentioned in particular:

- 4,4'-diamino-3,3',5,5'-tetramethyldiphenylmethane,

- 4,4'-diamino-3,3',5,5'-tetraethyldiphenylmethane,

- 4,4'-diamino-3,5-dimethyl-3',5'-diethyldiphenylmethane,

- 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane,

- 4,4'-diamino-3,3',5,5'-tetraisopropyldiphenylmethane,

- 4,4'-diamino-3,3'-diisopropyl-5,5'-dimethyldiphenylmethane,

- 4,4'-diamino-2,2'-dichloro-3,3',5,5'-tetraethyldiphenylmethane,

- 1,3-diamino-2,4-diethyl-6-methylbenzene,

- 1,3-diamino-2-methyl-4,6-diethylbenzene, and

- their mixtures.

These hindered diamines can be prepared according to the method described in British patent specification 852,651 and US patent specification 3,481,900. 4,4'-diamino-3,3',5,5'-tetraethyldiphenylmethane, 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane, and their mixtures are preferably used in the practice of the invention .

The amount of N,N'-bis-imide or imides (a) and hindered diamine or diamines (b) is chosen so that the ratio r:

is in the range from 1.1/1 to 20/1 and preferably from 2/1 to 5/1.

The steric hindrance of the diamines according to the invention leads to a low reactivity of the constituents of the polymerization mixture, and this allows the achievement of gelation of the prepolymers and complete curing of resins during much longer periods of time than those observed with the polyimides according to French patent 1,555 .564, especially those obtained from N,N'-4,4'-diphenylmethane-bis-maleimide and 4,4'-diamino-diphenyl-methane. This lower reactivity of the components in the polymerization mixture in accordance with the invention may be of particular interest for the production of cast objects by pouring the prepolymers, for the formation of workpieces by the method of filament wrapping and finally for the use of the impregnation method by hot melting. The achieved viscosities for the prepolymers in the molten state are fully acceptable for transformers and the development of their properties over time is small.

With regard to the polyimides obtained according to French patent document 1,555,564 by heating, in particular of N,N1 -4,4'-diphenylmethane-bis-maleimide and 4,4<1->diamino-diphenylmethane, it is determined that the choice of hindered diamines in accordance with the present invention unexpectedly allows obtaining cured polymers that exhibit a retention of flexural modulus in the heat that is

very good and even possibly superior.

It may be advantageous in some cases to modify the polymers in accordance with the invention by using a copolymerizable reaction component (c). Possible reaction component (c) can be mentioned in particular:<*>When, for example, want to reduce the fluidity of the polymerization mixture: ;() either one or more monomers with formula:; ; in which the allyloxy or metallyloxy radical is in position ortho, méta or para in relation to the carbon atom in the benzene ring linked to the nitrogen, ;(C2) or a composition comprising:;- a mixture of a monomer with the formula:; ; in which the allyloxy or metallyloxy radical is in position ortho, méta or para in relation to the carbon atom in the benzene ring linked to the nitrogen, ;- with:;. at least one monosubstituted derivative of formula:; . and possibly one or more disubstituted derivatives with ; In the aforementioned composition which serves as reaction component (C2), the quantity ratio between the various components in the mixture of products with formulas (IV), (V) and optionally (VI) can vary within wide limits. In general, the quantity ratio between the components is chosen within the following limits (expressed as a weight percentage for each of the components in the mixture): - at least 30%, and preferably 50 to 80% of the N-methylyloxy-phenylmelamide of formula (IV), - 5 to 50%, and preferably 10 to 35% of monometallyl-substituted derivative or derivatives of formula (V), - 0 to 20%, and preferably 0 to 15% of dimetallyl-substituted derivative or derivatives of formula (VI), as the sum of the components included in each case is 100% by weight. <*>When you want, e.g. to improve the advantages of the bending properties at high temperature: (c^) one or more substituted heterocyclic compounds.

With regard to the possible reaction component (c^), this is chosen from among:

- N-(2-allyloxyphenyl)maleimide,

- N-(3-allycoxyphenyl)maleimide,

- N-(4-allycoxyphenyl)maleimide,

- N-(2-metalyloxyphenyl)maleimide,

- N-(3-metalyloxyphenyl)maleimide,

- N-(4-metalyloxyphenyl)maleimide,

- and their mixtures.

The maleimides of formula (IV) are new products which can be prepared in particular from aminophenols (ortho, méta or para), by means of a Claisen reaction.

One can e.g. react the aminophenol, where the amine function is previously blocked by reaction with acetic anhydride to form the acetamidophenol, in the individual case with an allyl halide (most often the bromide) or methallyl halide in solution in acetone and in the presence of dipotassium carbonate. The amine function is then regenerated by hydrolysis.

The corresponding maleimide is then prepared in the classical manner by reacting the allyloxyaniline or metallyloxyaniline obtained in the preceding in solution with maleic anhydride, in the presence of acetic anhydride, triethylamine and a nickel salt (especially nickel acetate).

N-(allyloxyphenyl)maleimide or N-(metallyloxyphenyl)maleimide is then obtained.

N-(4-allyloxy enyl') maleimide is a mustard yellow solid with a melting point of approximately 103°C.

The NMR analysis is consistent with the following structure:

1H NMR; solvent: DMSO d6; reference: hexamethyldisiloxane

(HMDS)

7.16 (2H,m) : H 3.5

7.10 (2H,s) : maleimide

6.98 (2H,m) : H 2.6

5.99 (1H,m) : -CH=

5.35 and 5.22 (2H,dd) : =CH 2

4.55 (2H,d) : OCH 2

The N-(3-allyloxyphenyl)maleimide is a yellow-orange viscous liquid which crystallizes slowly at ordinary temperature and which boils at about 150°C under a pressure of 20 Pa.

The NMR analysis is consistent with the following structure:

1H NMR; solvent: DMSO d6 ; reference: HMDS

6.85, 6.89 and 6.93 (3H,m) : H4, H2 and H6

7.10 (2H,s) : maleimide

7.32 (1H,t) : H5

5.99 (1H,m) : -CH=

5.35 and 5.21 (2H,dd) : =CH 2

4.51 (2H,d) : OCH 2

The N-(2-allyloxyphenyl)maleimide is a pale yellow crystallized solid with a melting point of 82°C and a boiling point of 148 to 155°C under a pressure of 20 Pa.

The NMR analysis is consistent with the following structure:

1H NMR; solvent: DMSO d6; reference: HMDS

7.38 (lH.dt) : H5

7.20 (lH.dd) : H3

7.15 (2H,s) : maleimide

7.09 (1H,dd) : H6

6.99 (lH,dt) : H4

5.83 (1H,m) : -CH=

5.18 and 5.11 (2H,dd) : =CH 2

4.50 (2H,d) : OCH 2

The N-(4-methyloxyphenyl)maleimide is a beige colored solid with a melting point of 64°C.

The NMR analysis is consistent with the following structure:

1H NMR; solvent: DMSO d6; reference: HMDS 7.16 (2H,d) : H 3.5

7.09 (2H,s) : maleimide 6.97 (2H,d) : H 2.6

4.90 and 5.00 (1H,s) : CH2=

4.45 (2H,s) : 0CH2

1.71 (3H,s) : CH 3

The N-(3-metaloxyphenyl)maleimide is a beige colored solid with a melting point of 39°C.

The NMR analysis is consistent with the following structure:

1H NMR; solvent: DMSO d6; reference: HMDS

7.32 (1H,t) : H5

7.10 (2H,s) : maleimide 6.94 (1H,d) : H6

6.89 (1H,s) : H2

6.84 (1H,d) : H4

4.90 and 5.00 (1H,1) : CH2=

4.42 (2H,s) : 0CH2

1.70 (3H,s) : CH 3

The N-(2-methyloxyphenyl)maleimide is a beige colored solid with a melting point of 96°C.

The NMR analysis is consistent with the following structure:

1H NMR; solvent: DMSO d6; reference: HMDS

7.36 (1H,t) : H5

7.20 (1H,d) : H3

7.14 (2H,s) : maleimide

7.07 (1H,d) : H6

6.98 (1H,t) : H4

4.82 and 4.88 (1H,s) : CH 2 =

4.39 (2H,s) : OCH 2

1.59 (3H,s) : CH 3

With regard to the possible reaction component (c^), preferably used as a composition, which comprises a mixture of N-(meth)allyloxyphenylmaleimide of formula (IV) with one or more (meth)allyl substituted derivatives of formula or formulas (V) and optionally (VI), the crude product obtained by applying the original method defined in the following: This method is characterized by carrying out three subsequent steps in one and the same reactor: - the first step consists in converting an aminophenol in a solvent mixture with maleic anhydride by working at a temperature from 20 to 200°C for a time which, depending on the chosen temperature, is from 30 minutes to two hours and leads to a first reaction mixture containing an N-(hydroxyphenyl)maleamic acid, - the second step consists in carrying out a (meth)allylation reaction of the aforementioned acid by reacting the above-mentioned first reaction mixture with a (meth)allyhalide by working at a pH which is set and maintained ldes at a constant value between 7 and 14 upon addition of a specific amount of an aqueous alkaline solution and at a temperature from 40 to 150°C, and which after acidification and removal of the aqueous phase leads to another organic reaction mixture containing a N -((meth)allyloxyphenyl)maleamic acid, one or more N-((meth)allyloxy, (met)allylphenyl)maleamic acids and optionally one or more N-((meth)allyloxy, di(met)allylphenyl) maleamic acids, — it . third step consists in carrying out a ring closure reaction of the mentioned maleamic acids by reacting the above-mentioned second reaction mixture with a lower carboxylic acid anhydride, in the presence of a tertiary amine and optionally a catalyst, after which the solvent for the reaction is removed and this leads to a reaction crude product which is a composition containing a mixture consisting of at least 30% by weight and preferably 50 to 80% by weight of N-(meth)allyloxyphenyl maleimide, 5 to 50% and preferably 10 to 35% by weight of one or more N-((met ) allyloxy, (meth)allylphenyl)maleimides, and 0 to 20% by weight and preferably 0 to 15% by weight of one or more N-((meth)allyloxy, di(meth)allylphenyl)maleimides.

The three steps to be described in more detail are carried out in a single solvent for the highest possible simplicity of the process, but it is possible to work with a change of solvent during one or the other step, without disadvantages. The choice of solvent is liberal, but as the second step is carried out in a water-organic two-phase environment, it may be desirable to use an organic solvent that is not miscible with water, as this considerably simplifies the treatment of the reaction mixture. Among solvents which are possibly miscible with water and which can be used, those which, under the temperature conditions used for the synthesis, dissolve the starting aminophenol are mentioned as preferred. Among these solvents can e.g. mention is made of alcohols such as methanol, ethanol, butanol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone; nitrides, e.g. as benzonitrile, propionitrile, acetonitrile 1; esters such as ethyl acetate, butyl acetate; aromatic solvents such as e.g. anisole, chlorobenzene; halogenated hydrocarbons such as chloroform, dichloromethane, dichloroethane.

With regard to the first step in the process, it can be said that the concentration of the initial reaction components in the solvent used is not critical. It is nevertheless not interesting to dilute too strongly for reasons of productivity, nor to concentrate too strongly in order to retain good stirrability. In this first step, the maleic anhydride is used in amounts that at least correspond to 1 mol per moles of aminophenol. Generally, larger amounts of the order of 1.01 to 1.5 mol per moles of aminophenol. Furthermore, the temperature is preferably kept between 40 and 60°C.

With regard to the second step, one begins by adding to the reaction mixture the quantity of an aqueous alkaline solution, e.g. an aqueous solution of NaOH, necessary to, on the one hand, convert the N-(hydroxyphenyl)maleic acid into a salt and, on the other hand, to achieve the desired pH. The pH is maintained constant during the reaction by adding sodium hydroxide. The pH is preferably set and maintained at a constant value between 10 and 12. The allylation reaction is preferably carried out with (meth)allyl bromide or (meth)allyl chloride. The amount of (meth)allyl halide is about 1.5 to 10 moles per molar phenolic OH group and preferably about 2 to 4. Excess of this reaction component can be recovered at the end of the operation and recycled in a subsequent operation. The addition time for the (meth)allyl halide is not critical and can be in the range from one hour to five hours, and preferably from two to four hours. In this second step, the temperature is preferably between 60 and 100°C. It is noted that at the end of the step the aqueous phase is acidified to a pH of approximately 1 using common acids, preferably oxyacids or inorganic hydrogen acids. The aqueous layer is removed and the organic layer is left in the reactor.

With regard to the third step in the process, acetic anhydride is advantageously used as the anhydride of a lower carboxylic acid in amounts at least corresponding to 1 mol per molar group HOOC-CH=CH-CO-NH- to be ring-closed. Larger quantities of approximately 1.05 to 1.5 mol per maleamic acid group.

Among suitable tertiary amines, mention may be made in particular of the trialkyl amines such as the N,N-dialkylanilines in which the alkyl radicals have 1 to 12 carbon atoms. Triethylamine and N,N-dimethylamine are advantageously used. Amounts of tertiary amine are between 0.05 and 2 mol per molar group HOOC-CH=CH-CO-NH-.

As catalysts, e.g. nickel salts of carboxylic acids, optionally hydrated, as well as chelated forms of this metal are used. Acetate and acetylacetonate are particularly suitable. These catalysts are used in very small quantities, approximately 0.05 to 1.5 g per molar group HOOC-CH= CH-CO-NH-, and preferably about 0.1 to 0.8 g.

In this third step, the temperature is not critical and only affects the reaction kinetics. This temperature can e.g. be between 40 and 150°C and preferably between 60 and 80°C. At the end of this step, the solvent is removed by distillation under vacuum and a crude reaction product with the appearance of an oil is obtained.

In accordance with a highly preferred embodiment of the invention, the aforementioned method is well suited for, starting from metaaminophenol, to produce the following compositions of mixtures based on: N-(3-(meth)allyloxyphenyl)maleimide + N-(3-( met)allyloxy-4-(met)allylphenyl)maleimide + N-(3-(met)allyloxy-6-(met)allyl-phenyl)maleimide + optionally N-(3-(met)allyloxy-4,6-di (meth)allylphenyl)maleimide.

From orthoaminophenol, the following compositions have been prepared containing mixtures based on: N-(2-(meth)allyloxyphenyl)maleimide + N-(2-(meth)allyloxy-3-(meth)allylphenyl)maleimide + N-(-2- (meth)allyl-5-(meth)allyl-phenyl)maleimide + optionally N-(2-(meth)allyloxy-3,5-di(meth)allylphenyl)maleimide.

From paraaminophenol, compositions comprising mixtures based on: N-(4-(meth)allyloxyphenyl)maleimide + N-(-4-(meth)allyloxy-3-(meth)allylphenyl)maleimide + optionally N-(4- (meth)allyloxy-3,5-di(meth)allylphenyl)maleimide.

With regard to the possible reaction component (c-^), this is chosen from among vinylpyridines, N-vinylpyrrolidone, allyl isocyanurate and vinyltetrahydrofuran.

With regard to the amount of possible reaction component (c), this can generally amount to less than 60% by weight, and preferably from 5 to 50% by weight of the total amount of reaction component is (a) and (b).

The reactivity of the components (a), (b) and possibly (c) in the polymerization mixture in accordance with the invention can be increased, e.g. when the intended applications require the execution of molding operations by injection into a machine, by adding a catalyst (d) of the imidazole type.

The possible imidazole compound (d) corresponds to the gene-

real formula:

wherein Rg, R7-, Rg and R^ are the same or different, and each represents a hydrogen atom, alkyl or alkoxy of 1 to 20 carbon atoms, vinyl, phenyl, nitro, wherein Rg together with Rg and the carbon atoms to which they are attached may form a call such as a benzene ring, with Rg possibly representing a carbonyl group attached to another imidazole ring.

As specific examples of imidazole compounds (d) can be mentioned in particular imidazole or glyoxaline, 1-methylimidazole, 2-methylimidazole, 1,2-dimethylimidazole, 1-vinylimidazole, 1-vinyl-2-methylimidazole, benzimidazole, carbonyldiimidazole.

The possible imidazole compound is used in catalytic amounts. Depending on the nature of the imidazole compound and the desired reaction rate at the application step, the imidazole compound is used in an amount from 0.01 to 1% by weight in relation to the total amount of the reaction components (a) + (b) + optionally (c), and preferably in amounts from 0.05 to 0.5%.

The polymers according to the invention can be prepared by directly heating the bis-imide or imides (a), the amine reaction component (b) and optionally the reaction component (c) optionally with the imidazole compound (d) at least until a liquid homogeneous mixture is obtained. The temperature can vary as a function of the physical state of the compounds present but is generally between 50 and 300°C. It is advantageous to bring and maintain the starting compounds in an intimately mixed state before and during the heating by means of e.g. a good stir. When imidazole compound (d) is used, this is preferably added initially to the stirred reaction mixture containing the reaction component (a) and/or (b). When this compound is particularly active, in order to avoid its encapsulation in the developed polymer lattice, it is desirable to add it in a solvent or diluent which is compatible with the reaction mixture. It has been found that it can be interesting that one of the polar organic liquids mentioned below is used as a solvent or diluent.

The production of polymers in accordance with the invention can also be carried out by heating the mixture of reaction components in an organic solvent which is liquid, at least in part of the range 50 to 250°C. Among these diluents, aromatic hydrocarbons such as xylenes and toluene, halogenated hydrocarbons such as chlorobenzenes, polar solvents such as dioxane, tetrahydrofuran and dibutyl oxide, dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone, dimethylacetamide, cyclohexanone, methylglycol and methylethylketone can be mentioned in particular. Solutions or suspensions of polymers can be used as is for numerous applications. One can also isolate the polymers, e.g. by filtration, possibly precipitation using an organic diluent which is miscible with the solvent used. In this connection, a hydrocarbon with a boiling point that does not particularly exceed 120°C can advantageously be used.

It is clear that the properties of the polymers according to the invention can vary greatly as a function, in particular, of the exact nature of the reaction components used, the quantity ratio of selected reaction components, and further conditions for the temperature adapted in the previously mentioned area. With regard to the polymers obtained, these can be hardened polymers, insoluble in common solvents such as e.g. the compounds mentioned in the preceding paragraph which do not show any particular softening below the temperature at which they begin to decompose.

However, the polymers can also exist in the form of prepolymers (P) soluble in polar organic solvents, and which have a softening point at a temperature below 200°C (usually this softening point is between 50 and 150°C). These prepolymers can be obtained in a melt by heating the mixture of reaction components until a homogeneous or pasty product is obtained at a temperature generally between 50 and 180°C for a duration which can be from a few minutes to a few hours, this duration being shorter depending on the temperature used is higher. Before the mixture of reaction components is subjected to heating, it is also advantageous to carry out an intimate mixture by prior stirring. There is also a preferred embodiment using imidazole compound (d) and it is the one indicated above with regard to the direct production of cured polymers. The production of polymers can also be carried out in suspension or in solution in a diluent which is liquid in at least part of the range 50 to 180°C.

When one chooses to use the possible reaction component (c), it is noted that the prepolymers (P) can also be obtained by forming a prepolymer (PP) from the bis-imide or imides (a) and the reaction component (c) which is then reacted with the amine reaction component ( b) and, if desired, the imidazole compound (d). A prepolymer (P'P') can also be prepared in advance by heating the mixture of the amine reaction component (b), the reaction component (c) and, if desired, the imidazole compound (d), after which this is reacted with the bis-imide or imides (a) to obtain of the prepolymer (P). The temperature condition and duration used for the production of the prepolymers (PP) or (P'P') and for their conversion to prepolymers (P) are as stated above in connection with the production of the prepolymers (P) by direct mixing of the reaction components (a) , (b) and optionally (c) and, if necessary, the imidazole compound (d).

The prepolymers (P) can be used in a liquid state where a simple pouring in a hot state is sufficient for shaping and forming molded objects. You can also, after cooling and painting, use them in the form of powders which are particularly suitable for pressure casting operations, possibly in the presence of fillers in the form of powders, balls, granules, fibers or flakes. In the form of suspensions or solutions, the prepolymers (P) can be used to form coatings and pre-impregnated intermediate product articles where the reinforcement can be made up of fiber materials based on silicate or oxide of aluminum or zirconium, carbon, graphite, boron, asbestos or glass.

One can also use these prepolymers (P) for the formation of cell-shaped materials after incorporating a pore-forming agent such as e.g. azodicarbonamide.

In another step, the prepolymers (P) can be cured by heating to temperatures of approximately 300°C, generally between 150 and 300°C. A variation can be carried out during this curing, possibly under vacuum or under a super-atmospheric pressure, as these operations can also be carried out in sequence.

When you want to use the possible reaction component (c), you do not go outside the scope of the invention if you prepare the polymers according to the invention that do not exist in the form of the prepolymers (P), by using an intimate mixture of the prepolymer (PP), amine reaction component ( b), and as needed imidazole compound (d), or an intimate mixture of the prepolymer (P'P') and the bis-imide or imides (a) which is heated in melt under the previously described conditions.

The polymers according to the invention are of interest for the industrial areas that require materials with good mechanical and electrical properties as well as a large degree of chemical inertness at temperatures of 200 to 300°C. As examples, they are suitable for the production of insulating materials in the form of sheets or tubes for electrical transformers, carriers for printed circuits, gears, sacks, etc. The pre-impregnated objects can be used for the production of workpieces with varied shapes and functions within numerous industries such as e.g. the airline industry. These workpieces, referred to as layer structures, can be bodies of revolution and are obtained by placing several layers of pre-impregnated structures on a form or carrier. The pre-impregnated structures can also be used as reinforcements or as repair agents for damaged objects. It is also possible to produce workpieces by the methods of filament winding with or without a carrier. It is also possible to carry out injection molding or pultrusion. It is recalled that for the production of e.g. molded objects are possible either starting from a mixture of reaction components or a prepolymer (P). When proceeding directly from the mixture of reaction components, this mixture is given the shape of the desired object and curing is then carried out by heating. When starting from prepolymer (P), casting can be done by simple pouring in the heat or by injection and hardening is then produced by heating.

The following examples illustrate the invention.

EXAMPLE 1.

In a glass reactor equipped with side tubes and an anchor-type stirrer, introduce at normal temperature:

- 76 g (0.212 mol) N,N'-4,4'-diphenylmethane-bis-maleimide, and

- 24 g (0.085 mol) 4,4'-diamino-3,31-diethyl-5,5'-dimethyl-diphenylmethane (the ratio r is equal to 2.5/1).

The reactor is placed in an oil bath preheated to

160°C and allowed to react for 45 minutes, where the last five minutes are carried out under a reduced pressure of 13.3.10 2 Pa.

The reaction mixture is then poured into a mold preheated to 150°C. You can then produce plates with dimensions 140 x 100 x 4 mm which are subjected to the following heating cycle:

. 100 minutes between 150 and 250°C,

. 18 hours at 250°C, and

. 2 hours between 250 and 25°C.

After removal from the mold, the sheets based on hardened polymer are cut up to obtain test pieces with dimensions 30 x 7 x 4 mm, on which the breaking strength (Rf) and bending modulus (Mf) are measured (Instron apparatus with distance between the supports 25.4 etc.).

As a comparison test, the operations described above are repeated but using the following reaction components: - 147.4 g (0.412 mol) N,N'-4,4'-diphenylmethane-bis-maleimide, and 32.6 g (0.165 mol) 4 ,41-diaminodiphenylmethane (the ratio r

is equal to 2.5/1).

These reaction components are introduced within four minutes into the reactor preheated to 160°C. The obtained mass is homogeneous. The gas is then degassed for one minute, after which the mixture is allowed to react at 160°C for a further nine minutes.

The values for the bending properties are collected in the following table:

The gel formation time for the prepolymers has been measured in accordance with example 1 and the comparison experiment. The gel formation time is measured in each case with 10 g of a mixture of powders of bis-imide and diamine, using a Sunshine apparatus. Time 0 is defined by immersing the tube containing the powder blend in a thermostatically controlled bath at the measurement temperature. The results are the following: - Gel formation time at 160°C of the prepolymer according to example 1: 100 minutes. - Gel formation time at 160°C of the prepolymer according to the comparison test: 15 minutes.

EXAMPLES 2 to 5.

In a glass reactor equipped with an anchor-type stirrer, 1.83 g (0.006 mol) of 4,4<1->diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane and varying amounts of imidazole are introduced at ordinary temperature. Thus absence of imidazole in example 2, 0.005 g in example 3, 0.010 g in example 4 and 0.015 g in example 5.

The reaction mixture is homogenized for 30 seconds at 160°C. It is cooled and 8.17 g (0.022 mol) of N,N<1->4,4'-diphenylmethane-bis-maleimide are introduced (the ratio r is equal to 3.6/1). The reactor is immersed again in a bath at 160°C and the time required from this point for the reaction mixture to gel is determined on the Sunshine apparatus.

It turns out that the prepolymers according to the present invention, depending on the content of catalyst, produce a large margin of reactivity and it is possible that this reactivity is easily set to the desired value depending on the intended applications. One can thus also use the obtained prepolymers for applications that require very short reaction times (e.g. machine injection) as well as for applications that require agents for long reaction times (e.g. hot melt impregnation, injection into compact reinforcement materials consisting of fibers that are arranged in different directions).

EXAMPLE 6.

Into the reactor in example 1, 19.9 g (0.064 mol) of 4,4'-diamino-3,3',5,5'-tetraethyldiphenylmethane and 0.15 g of imidazole are introduced at normal temperature.

The reactor is placed in an oil bath preheated at 160°C and the reaction mixture is homogenised for four minutes.

80.1 g (0.224 mol) of N,N'-4,4'-diphenylmethane-bis-maleimide are then introduced over the course of three minutes (the ratio r is equal to 3.5/1). A reduced pressure of 2600 Pa is then applied for three minutes. The reaction mixture is allowed to react for a further five minutes. The obtained prepolymer is then poured, cast, cured and tested as indicated above in Example 1.

Results of bending tests with hardened polymer test pieces:

- at 25°C: Rf = 140 MPa

Mf = 3100 MPa

- at 250°C: Rf = 53 MPa

Mf = 2000 MPa

Claims (10)

1. Polymers with imide groups, characterized in that they comprise the reaction product at a temperature from 50 to 300°C between:- (a) an N,N'-bis-imide or an association of several bis-imides with formula: in which: . the symbols Y are the same or different and each stand for H, CH3 or Cl, . the symbol A represents a divalent radical selected from 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 radicals with formula: where T represents a single valence bond or group: and the symbols X are the same or different, each representing a hydrogen atom, methyl, ethyl or isopropyl, - (b) one or more hindered biprimary diamines selected from the group of: (i) Compound types corresponding to the general formula: in which: . the symbols R 1 , R 2 , R 1 and R 2 are the same or different, each representing methyl, ethyl, propyl or isopropyl, . the symbols Z are the same or different and each represent a hydrogen atom or chlorine atom, (ii) and compound types corresponding to the general formula: in which: . the amino radicals are in position méta or para in relation to each other, . the symbols R,, are the same or different and represent each methyl, ethyl, propyl or isopropyl, and - (c) optionally one or more monomers other than the bis-imide of formula (I) and containing one or more polymerisable carbon-carbon double bonds, and - (d) optionally a compound of the imidazole type. 2. Polymers as specified in claim 1, characterized in that reaction component (c) when such is used, consists of the following compound types: () one or more monomers with formula: in which the allyloxy or metallyloxy radical is in position ortho, meta or para in relation to the carbon atom in the benzene ring linked to the nitrogen atom, (c^) a compound containing:- a mixture of a monomer of formula: in which the allyloxy or metallyloxy radical is in position ortho, meta or para in relation to the carbon atom in the benzene ring linked to the nitrogen atom, - with:. at least one monosubstituted derivative of formula: . and optionally one or more disubstituted derivatives with formula: (c^ ) one or more substituted heterocyclic compounds. 3. Polymers as specified in claim 1 or 2, characterized in that the imidazole derivative (d), when used, corresponds to the general formula: wherein Rg, R^, Rg and Rg are the same or different, and each represents a hydrogen atom, alkyl or alkoxy of 1 to 20 carbon atoms, vinyl, phenyl, nitro, Rg together with Rg and the carbon atoms to which they are attached may form a ring like for example. a benzene ring, Rg can also represent a carbonyl group attached to another imidazole ring. 4. Polymers as specified in one or more of claims 1-3, characterized in that the amount of N,N'-bis-imide or imides (a) and hindered diamine or diamines (b) is chosen so that the ratio r: is in the range from 1.1/1 to 20/1 and preferably from 2/1 to 5/1, the amount of any reaction component (c), when this is used, is generally less than 60% by weight and preferably 5 to 50% by weight % of the total weight of the reaction components (a) and (b), and the amount of the imidazole compound, when used, is in the range from 0.01 to 1% by weight in relation to the total amount of the reaction component (a) + (b) and optionally (c), and preferably from 0.05 to 0.5% by weight. 5. Polymers as set forth in which as. preferably from claims 1-4, characterized in that they are in the form of hardened polymers, insoluble in common solvents, and which do not show any particular softening at temperatures lower than those at which they begin to break down. 6. Polymers as specified in any of claims 1-4, characterized in that they are in the form of thermosetting prepolymers (P) soluble in polar organic solvents and which have a softening point at a temperature below 200°C. 7. Process for the production of cured polymers as specified in claims 1-5, characterized in that the mixture of reaction components is heated directly at a temperature between 50 and 300°C. 8. Method as stated in claim 7, characterized in that the mixture of reaction components is heated between 50 and 180°C to first form a prepolymer (P) after which hardening of the prepolymer (P) is brought about by heating at a temperature between 150 and 300° C. 9. Process for the production of thermosetting polymers (P) as stated in any of claims 1-4, and 6, characterized in that the mixture of reaction components is heated directly at a temperature between 50 and 180°C until a liquid homogeneous or paste-shaped product. 10. Use of polymers as specified in claims 1-6 for the production of molded objects, coatings, objects with cellular structure and reinforced and impregnated composite materials.