PT98872A - PROCESS FOR THE PREPARATION OF THERMOENDURABLE COMPOSITIONS BASED ON CIANATE ESTER COMPOUNDS AND POLYMID COMPOUNDS WITH GROUP (S) DIORGANOPOLYSYLOXANE - Google Patents

Description

" PROCESS FOR THE PREPARATION OF THERMOENDURABLE COMPOSITIONS BASED ON CYANATE ESTERS AND POLYMID COMPOUNDS WITH GROUP (S) DIORGANOPOLYSYLOXANO " The present invention relates to thermosetting compositions comprising: A) at least one cyanate ester compound consisting essentially of a polyfunctional aromatic cyanic ester having at least two cyanate groups (-O-C = N) attached to a in a prepolymer derived from said organic ester and in a copolymer prepolymer derived from said cyanic acid ester and from a polyamide; and B) at least one elastomer consisting essentially of a polyimide compound comprising in its structure one or more diorganopolysiloxane groups. The invention further relates to the hardened resins prepared from said thermosetting compositions. The thermosetting compositions according to the present invention may further contain a suitable catalyst and one or more additional polymerizable compounds which include -2-

namely a conventional bis-maleimide, an optionally halogenated epoxy resin, an acrylate reagent or an alkyl phenol, and may be further associated with known reinforcing fillers.

Polyfunctional aromatic cyan esters are known products which are prepared by reaction between a cyanogen halide and a polyhydroxylated phenol (see U.S. Pat. No. 3,553,244). These cyanic acid esters can give rise to hardened resins by a cyclotrimerization reaction of the cyanate groups which yields substituted triazine rings which are organized according to a three-dimensional polycyanurate network.

Such polycyanurate resins, which have found numerous uses in various application domains, have interesting electrical properties (in particular dielectric characteristics), but have the disadvantage of having levels of other properties still insufficient, in particular in the matter of toughness (levels of values shock resistance CHARPY, GIC and KIC have to be improved) and adhesion to metallic substrates.

In order to obtain tenacious resins, it has been proposed, in the prior art, to modify the polycyaractone resins by adding to the respective preparation medium: high boiling point-containing propellants containing ester groups (see patent US-A-4 094 852); an acrylonitrile / butadiene copolymer (see U.S. Patent 3,649,714); an elastomer such as natural rubbers, polymers derived from conjugated dienes (such as butadiene and isoprene), polychloroprene (see U.S. Patent 4,396,745); or an amorphous thermoplastic polymer, such as a polysulfone, a polyarylate, a polyether sulfone (see European Patent Application EP-A-0 311 341). However, such polymer blends are of such a nature that they exhibit a serious lack of thermostability at application temperatures as high as 220 ° C to 300 ° C. The inventor has now discovered that it is possible to obtain, from of polyfunctional aromatic cyanic acid esters, resins having in the hardened state an excellent compromise of properties in particular in terms of toughness, thermostability and adhesion, employing a modifying agent consisting essentially of a polyimide compound which comprises in its structure one or more diorganopolysiloxane groups.

More precisely, the present invention relates to thermosetting compositions comprising:

Α) - at least one cyanate ester compound selected from the group consisting of: 1) - a monomeric polyfunctional aromatic cyanic acid ester having the formula R 1 - ) in which n is an integer from 2 to 5 and R is an aromatic organic radical of the same value having six to thirty carbon atoms, wherein the cyanate groups are attached to the nucleus or nuclei aromatics of R; 2) a pre-polymer of 1); and 3) a co-prepolymer of 1) and an aromatic primary polyamine; B) - at least one elastomeric compound; and optionally: C) an appropriate catalyst; Said compositions being characterized in that the constituent B) consists of at least one compound selected from the group consisting of: a) N, N'-bis-maleimide having a diorganopolysiloxane group essentially having the following general formula

in which the symbol X, which is in the ortho, meta or para position with respect to the carbon atom of -6-

benzene group attached to the nitrogen atom, represents a single valence bond or an atom or one of the following groupings of formulas:

II or I! s

R 2, R 3, R 5, R 5, R 9, R 9 and R 9, which may be the same or different, each represent a monovalent hydrocarbon radical selected from linear or branched alkyl radicals having from one to twelve carbon atoms , which radicals may be substituted by one or more chlorine, bromine or fluorine atoms or by a -CN group; a phenyl radical optionally substituted by one or more alkyl and / or alkoxy radicals having one to four carbon atoms and one or more chlorine atoms; x is an integer in the range of 2 to 8; the symbols y and z represent numbers, equal or different, integers or fractions, the sum of which is in the range of 0 to 100; -7-

5) - a prepolymer of 4), and 6) a co-prepolymer of 4) and an aromatic bipyridine diamine. With respect to constituent A, the R symbol of the cyanate ester of formula (I) may represent: i) a valence radical which is the same as that derived from an aromatic hydrocarbon having six to sixteen carbon atoms, , benzene, naphthalene, anthracene or pyrene; ii) a valence radical which is the same as that derived from a group having several aromatic nuclei linked together by means of a single valence bond or an inert atom or an inert bivalent group such as, for example, the group of formula general (III)

(III) wherein R 'is a single valence bond or a bivalent inert atom or group,

such as: -O-; -S-; a linear or branched alkylene radical having one to ten carbon atoms, optionally substituted by one or more chlorine, bromine or fluorine atoms and optionally interrupted by one or more oxygen atoms; -CO-; -NR " - wherein the symbol R " represents a hydrogen atom, an alkyl radical having one to three carbon atoms, phenyl or cyclohexyl;

In addition, the various aromatic groups mentioned above in paragraphs i) and ii) may be substituted by one or more linear or branched alkyl or alkoxy radicals having one to four carbon atoms or by one or more halogen atoms.

Preferably, the cyanate esters (1) of general formula (I) which are used consist of bifunctional compounds corresponding to the general formula: -N-C-O.

O-C-N (R ") a / (IV) (R "";

in which the symbol R '" represents a single valence bond or an atom or one of the following groupings of formulas:

the R " " , the same or different, each represents a substituent selected from chlorine, bromine or fluorine atoms or methyl, ethyl, propyl or isopropyl radicals, two R " neighbors located in the same nucleus together represent a hexagonal aromatic nucleus; M is an integer of 0 or 1; a is an integer equal to 0, 1 or 2, the symbols a being, when two of them are present, being identical or different from each other. By way of specific examples of preferred bifunctional cyanate esters (1) of general formula (IV), there may be mentioned in particular: 1,3-dicyanato-benzene; 1,4-dicyanato-benzene; 1,3-dicyanato-naphthalene; 1,4-dicyanato-naphthalene; 1,6-dicyanato-naphthalene; 1,8-dicyanato-naphthalene; 2,6-dicyanato-naphthalene; 2,7-dicyanato-naphthalene; 4,4'-dicyanato-biphenyl; bis- (4-cyanato-phenyl) -methane; bis- (3,5-dimethyl-4-cyanato-phenyl) -methane; -11-

. 2,2-bis- (4-cyanato-phenyl) -propane; . 2,2-bis- (4-cyanato-phenyl) -hexafluoropropane; . 1,1-bis- (4-cyanato-phenyl) ethane; . bis- (4-cyanato-phenyl) ether; thioether bis- (4-cyanato-phenyl); bis- (4-cyanato-phenyl) -sulfone; . bis- (4-cyanato-phenyl) -tetrahydro-dicyclopentadiene.

For the practice of the present invention, bis- (4-cyanato-phenyl) -methane, bis- (3,5-dimethyl-4-cyanato-phenyl) - methane, 2,2-bis (4-cyanato-phenyl) -propane or mixtures of these cyanates.

The cyanate esters (1) can also be used in the form of a prepolymer (2), which comprises symmetrical triazine cycles, which is preferred by partial cyclotrimerization of the cyanate groups by heating the cyanate ester monomer (1) to a temperature in the range of 130 ° C to 220 ° C for a sufficient time to cyclotrify 5% to 75% of the total number of the cyanate groups and preferably 15% to 50% of the functional cyanate groups. Prepolymers of this type (2) have a weight average molecular weight of from 400 to 12,000 -

preparing in the presence of a catalyst of either the acid type, for example a mineral protonic acid or a Lewis acid, or the basic type, such as, for example, an alkali metal hydroxide, an alkali metal or a tertiary amine.

The cyanate esters (1) may further be used in the form of a copolymer (3) derived from (1) and an aromatic primary polyamine, such as, preferably, an aromatic biprimary diamine selected from the group formed per : * , . (3.1) the chemical species corresponding to the general formula (V) in which A is a bivalent radical selected from the group consisting of cyclohexylene radicals; phenylene; 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 general formula:

And in which B is a single valence bond or a grouping of one of the formulas: - ch 2

0

II I S -; H-C 0

- 0 02 (3.2) chemical species having the general formula (VI)

Wherein: the same or different R9, R10, R11 and R12 'are each methyl, ethyl, propyl or isopropyl; T, the same or different, are each a hydrogen atom or a chlorine atom; and E is a bivalent radical selected from the group consisting of the radicals of formulas

and (3) the chemical species corresponding to the general formula (VII):

in which: the amino radicals are in the meta or para position in relation to one another; the same or different symbols each represent a methyl, ethyl, propyl or isopropyl radical. Examples of diamines (3.1) of general formula (V) include, in particular: paraphenylene diamine, metaphenylene diamine, 4,4'-diaminodiphenylmethane, 2,2-bis - (4-aminophenyl) propane, benzidine, bis- (4-aminophenyl) oxide, and 4,4'-diaminodiphenylsulfone. -16-

For the practice of the present invention, use. Preferably, 4,4'-diaminodiphenylmethane is added. By way of specific examples of hindered diamines (3.2) and (3.3) of general formulas (VI) and (VII), the following may be mentioned in particular: 4,4'-diamino-3,3 ', 5,5 '-tetramethyl-diphenylmethane, 4,4'-diamino-3,3', 5,5'-tetraethyl-diphenylmethane, 4,4'-diamino-3,5-dimethyl-3 ', 5'- 4,4'-diamino-3,3'-diethyl-5,5'-dimethyl-diphenylmethane, 4,4'-diamino-3,3 ', 5,5'-tetraisopropyl- diphenylmethane, 4,4'-diamino-3,3'-diisopropyl-5,5'-dimethyl-diphenylmethane, bis- (4-amino-3,5-dimethyl-alpha, alpha-dimethylbenzyl ) 1,4-benzene, bis- (4-amino-3,5-dimethyl-alpha, alpha-dimethyl-benzyl) -1,3-benzene, 1,3-diamino-2,4- 6-methyl-benzene and 1,3-diamino-2-methyl-4,6-benzene. -17-

These sterically hindered diamines can be prepared according to the processes described in GB-A-852 651 and in U.S. Patent 3,481,900. For the practice of the present invention, it uses 4,4'-diamino-3,3 ', 5,5'-tetramethyl-diphenylmethane, 4,4'-diamino-3,3', 5,5'-tetraethyl-diphenyl- methane, 4,4'-diamino-3,3'-diethyl-5,5'-dimethyl-diphenyl-methane and mixtures thereof. The co-prepolymers (3) are obtained by reacting the cyanate ester monomer (1) with the diamine, operating in a homogeneous liquid medium, optionally using a suitable solvent, such as a ketone, at temperatures ranging from 0 ° C to 100 ° C ° C, for a time between one minute and one hour. The proportions of cyanate and diamine ester are chosen such that the ratio of the number of cyanate groups -QC = N number of N ^ groups is in the range of 1.1 / 1 to 10/1 and preferably between 1.5 / 1 and 5/1.

Most particularly, for the practice of the present invention, a constituent (A), consisting of a (2) prepolymer derived from the bifunctional (1) cyanate esters of the general formula (IV) is used. -18-

The constituent (B) of the curable compositions according to the present invention consists, as indicated above, of at least one compound selected from the group consisting of N, N'-bis-maleimido-siloxane (4), a pre- polymer (5) derived from (4) and a co-prepolymer (6) derived from (4) and an aromatic biprimary diamine. In the case of the siloxane bis-maleimides (4) of formula (II), when e and / or z are greater than 1, there is a compound having polymeric structures and rarely has a single compound, but most of the time there is a mixture of compounds with the same chemical structure that differ from one another by the number of repeating units of their molecule; this gives an average value of y and / or z which may be an integer or fractional number.

When the preparation of the compositions according to the present invention is carried out as described above in an organic solvent or diluent, any of the compounds (4) of formula (II) may be used.

Suitable bis-maleimides which are especially suitable are those corresponding to the general formula (II), in which: R 1 = R 2 = R 2 = Rg = linear alkyl radical having one to three carbon atoms; the symbols x = 2, 3 or 4; the sum y + z is in the range of 0 to 100 and preferably 4 to 70; 2) the symbols X = -0-; R 2 = R 2 = R 2 = R 6 = linear alkyl radical having one to three carbon atoms; R 2 = R 2 = phenyl radical; x = 2, 3 or 4; the sum y + z is in the range of 0 to 100 and preferably 4 to 70; 3) the symbols X = -O-; R2 = Ry = Rg = linear alkyl radical having one to three carbon atoms; R 2 = R 2 = phenyl radical; x = 2, 3 or 4; the sum y + z is in the range of 0 to 100 and preferably 4 to 70; 4) the symbols X = -0-; R1 = R2 = R2 = R5 = Ry = Rg = = linear alkyl radical having one to three carbon atoms; R 2 = R 2 = phenyl radical; x = 2, 3 or 4; the sum y + z is in the range of 0 to 100 and preferably 4 to 70; 5) the symbols X = -0-; R 2 = R 5 = R 5 = Ry = linear alkyl radical having one to three carbon atoms; R 2 = R 2 = R 2 = phenyl radical? x = 2, 3 or 4; the sum y + z is in the range of 0 to 100, and preferably 4 to 70.

Specific examples of especially suitable bis-maleimido siloxanes (4) include, in particular, compounds of the following formulas: - - CH 2) 3 CH 3 J 4 T 70 /

9 I N 15

co 1 CH

C0 1 XH

CO-CH 3 Si CH 3

I CH3 CH3

ch3 I

(CH 2) 3 with y + z-4 T 70

CH3 0 '(CH2) 3 -Si-O-CH3

CH3 - Si - (CH2) 3 CH3 4 T 70 - 0

C0 I CH

V

co 1 CH

CO-CH 2 -CH

When the preparation of the polymers according to the invention is carried out in bulk, bis-maleimides (4) of general formula (II) are preferably used in those in which the diorganopolysiloxane group contains a plurality of Si-phenyl or Si substituted phenyl. Bis-maleimides of this type which are very especially suitable are those belonging to the following groups, in order of increasing preference: bis-maleimides nos. 2, 3, 4 and 5, bis-maleimides nos. 7, 8 and 9. -23 -

The bis-maleimido siloxanes of formula (II) are compounds which are obtained by reacting maleic anhydride in the presence of a dehydrating agent, a tertiary amine, an organic diluent and a catalyst, a diamine with a diorganopolysiloxane of the general formula > -

in which X, R 2, R 3, R 4, R 5, R 5, R 6, R 9, R 4, R 5, x, y and z are as defined above for general formula (II) -siloxanes and on the preparation process thereof, in particular relates to the contents of the French patent application FR-A-2 611 728.

The bis-maleimido siloxanes (4) may also be used in the form of a prepolymer (5), which is prepared by heating the bis-maleimido-siloxane (4) by working in mass or in a liquid diluent, which may be a solvent, at temperatures between 50 ° C and 180 ° C, preferably between -24-

80 ° C and 170 ° C, for a time interval of between five minutes and two hours or more, this time interval being the shorter the higher the temperature being used.

The bis-maleimido siloxanes (4) may further be used in the form of a copolymer (6) derived from (4) and an aromatic biprimary diamine selected from the group consisting of the chemical species (3.1), (3.2 ) and (3.3) discussed above with regard to the definition of the co-prepolymer (3) of the compound (A). The copolymer (6) may be prepared by reacting the bis-maleimido-siloxane (4) and the diamine by operating in bulk or in a liquid diluent, which may be a solvent, at temperatures ranging from 50 ° C and 180Â ° C, preferably 80Â ° C to 170Â ° C, for a time between five minutes and two hours or more, so as to obtain a homogenous liquid medium. The proportions of bisimide and diamine are chosen in such a way that the ratio of moles of bisimide to the number of moles of diamine is in the range of 1.2 / 1 to 10/1 and preferably between 2/1 and 5/1. --R.

Particularly preferably, for the practice of the present invention, a constituent (B), consisting of a bis-maleimido-siloxane (4) selected from the bis-maleimides numbers 1 to 9 is used. The reactivity of the constituents of the compositions (C), which may be chosen from compounds which accelerate and / or regulate the reactivity of the cyanate groups both during the performance of the cyclotrimerization reaction as during the carrying out of the subsequent cross-linking reaction; as examples of compounds of this nature, the following may be mentioned in particular: compounds with a free hydrogen atom, such as, for example, alcohols, phenols, carboxylic acids and primary and secondary amines; compounds which consist of metal carboxylates, optionally dissolved in non-volatile functional liquids, such as, for example, an alkyl phenol or a monoalcohol (see US Pat. Nos. 4,604,452 and US-A-4 608 434, the disclosure of which is hereby incorporated by reference); -26-

compounds which consist of chelates, such as metallic acetyl acetonates, optionally dissolved in an alkyl phenol (see US-A-4 785 075, the contents of which are also incorporated herein by reference. the present specification for reference).

Preferred catalysts consist of metal acetyl acetonates and, in particular, of the zinc, copper, manganese or cobalt acetyl acetonates.

In the thermosetting compositions which have just been defined, the amounts of constituents (A) and (B) are chosen to have, by weight with respect to the weight of the (A) + (B) set: 50% to 98% and , preferably 1 to 95% constituent (A) and 2% to 50% and preferably 5% to 25% of elastomeric constituent (B).

In the case of the optional catalyst (C), according to its nature and according to the crosslinking speed desired in the practical operation of the process, when used, a -27% - which is between 0.005% and 10% and preferably between 0.01% and 5%, based on the weight of the overall composition, which includes (A) + (B) + optionally one or more polymerizable compounds which will be referred to hereinafter.

In fact, the compositions according to the present invention may further comprise an additive (D), consisting of one or more additional polymerizable compounds selected from: 7) a N, N'-bis-maleimide of (VIII) wherein: Z, the same or different, each represents a hydrogen atom or a chlorine atom or a radical CH3; and . G may represent one of the radicals A is represented by general formula (V) corresponding to the chemical species (3.1) of aromatic primary diamines; 8) a chlorinated or brominated epoxide resin; 9) a non-halogenated epoxide resin; 10) an alkyl phenol of the general formula:

R15O

Wherein: H is a single valence bond or a bivalent radical selected from the group consisting of the radicals of the formulas CH 1 -CH 2 -; - CH2 - CH2 -; - C -; - S -; - S0-; e-S < > 2 and R 3, the same or different, are each a hydrogen atom or a methyl radical; and R4, which may be the same or different, are each a hydrogen atom or a linear or branched alkyl radical having one to six carbon atoms, or a phenyl radical; an acrylate of formula (X)

< CH 2 = CR 16 -CO-O-L P (X) in which: the symbol represents a hydrogen atom or a methyl radical; p is an integer or fractional number of at least 1 and at most 8; and . L is an organic radical of valence p derived from a linear or branched saturated aliphatic radical having one to thirty carbon atoms and which may contain one or more oxygen bridges and / or one or more free hydroxyl functions of a (of the aryl or aliphatic aryl type) having six to one hundred and fifty carbon atoms, consisting of a benzene ring which may be substituted by one to three alkyl radicals having one to five carbon atoms or by several benzene nuclei, optionally substituted as indicated above, bonded together by a single valence bond, an inert grouping or an alkylene radical having one to three carbon atoms, said aromatic radical possibly containing at several sites of its structure one or more oxygen bridges and / or one or more free hydroxyl functions, the valence or free valences of the aromatic radical L being contained by a carbon atom of an aliphatic chain and / or a carbon atom of a benzene nucleus.

When a compound (D) (or a mixture of compounds D) is used in the performance of the compositions according to the present invention, it constitutes 2% to 35% by weight, preferably 5% to 30%, of the overall composition (A ) + (B) + (D) + optionally (C). By way of specific examples of bis-maleimides (7) of general formula (VIII), the following compounds may be mentioned in particular: N, N'-metaphenylene-bis-maleimide, N, N'-paraphenylene-bis maleimide, â € ‡ â € ‡ â € ‡ â € ‡ â € ‡ â € ‡ â € ‡ â € ‡ â € ‡ â € ‡ â € ‡ â € ‡ â € ‡ â € ‡ â € ‡ â € ‡ â € ‡ â € ‡ â € ‡ â € ‡ â € ‡ â € ‡ â € ‡ -4,4'-diphenylsulfone-bis-maleimide, Ν'-cyclohexylene-1,4-bis-maleimide, Ν, Ν'-4,4'-diphenyl-1,1-cyclohexane -bis-maleimide, Ν, Ν'-4,4'-diphenyl-2,2-propane bis-maleimide, Ν, Ν'-4,4'-triphenyl-methane-bis-maleimide, Ν, Ν ' 2-methyl-1,3-phenylene-bis-maleimide, 4-N, Î ± -methyl-1,3-phenylene-bis-maleimide, and 5β, Î ± -methyl-1,3-phenylene-bis -maleimide.

These bis-maleimides can be prepared according to the processes described in U.S.-A-3 018 290 and in GB-A-1 137 290. In the practice of the present invention, Î'-4,4'-diphenyl-methane-bis-maleimide, alone or in admixture with Î ±, Î ± -methyl-2-phenylene-1,3-bis-maleimide, N, N-methyl-4-phenylene-1,3-bis-maleimide and / or with Ν, Ν'-methyl-5-phenylene-1,3-bis-maleimide. -32-

It has been found that the amount of chlorine or bromine which may be present in the compositions according to the present invention due to the additive (8) is capable of influencing certain properties of the obtained hardened compositions, namely the thermal stability properties and in terms of adhesion to metals, such as copper, for example. In this table, the best results are obtained when this amount of chlorine or bromine from the additive (8), expressed as a percentage by weight of elemental chlorine or of elemental bromine in relation to the weight of the overall mixture (A) + (B) + optional compound (C) + optional compound (D), constitutes 81 at most; this amount of chlorine or bromine is preferably in the range of 1% to 6%. The amount of chlorine or bromine may be readily adjusted to have the desired value using, for example, epoxy resins of (8) with a more or less important chlorine or bromine content and starting from mixtures of epoxide (8) with non-halogenated epoxy resins (9).

By " chlorinated or brominated epoxide resin " " it is intended to define an epoxide resin having an epoxide equivalent weight of 200-2000 and consisting of a glycidyl ether obtained by reacting with epichlorohydrin a chlorinated or brominated derivative in the aromatic nucleus or nuclei obtained from a polyphenol selected from the group consisting of

The group of bis (hydroxyphenyl) alkanes, such as bis-2,2- (4-hydroxy-phenyl) -propane, bis- (4-hydroxyphenyl) -methane, bis- (4- dihydro-xy-phenyl) -methyl-phenyl-methane, bis- (4-hydroxy-phenyl) -thiolyl meta, resorcinol, hydroquinone, pyrocatechol, 4,4'-dihydroxy-diphenyl and the condensation products of the above-mentioned phenols with an aldehyde. The term " epoxy equivalent weight ", which appeared before, can be defined as the weight of the resin (in grams) containing an epoxide-C-C- function. 0

Preferably, a chlorinated or brominated epoxide resin having an epoxide equivalent weight of from 250 to 500 is chosen. More particularly, an epoxy resin (8) is used in the present invention, which consists of a resin belonging to (hydroxy-phenyl) -alkanes, brominated in the aromatic nuclei, discussed above with respect to the detailed definition of the resin (8).

By " non-halogenated epoxide resin " " it is intended to define an epoxide resin having an epoxide equivalent weight of from 100 to 1000 and consisting of a glycidyl ether obtained by reacting with epichlorohydrin- -34-

a non-chlorinated or non-brominated polyphenol in the aromatic nucleus (s) selected from the group of phenols discussed above with respect to the detailed definition of the resin (8).

Preferably, a non-halogenated epoxy resin having an epoxide equivalent weight of from 150 to 300 is chosen. Most preferably, an epoxy resin (9) is used which consists of a resin belonging to the family of the bis - (hydroxy-phenyl) -alkanes in the aromatic nuclei discussed above with respect to the detailed definition of the resin (8). Specific examples of alkyl phenols (10) of formula (IX) include, in particular: 4,4'-dihydroxy-3,3'-diallyl bisphenyl, bis (4- hydroxy-3-allyl-phenyl) -methane, bis- (4-hydroxy-3-allyl-phenyl) ether,

bis-2,2- (4-hydroxy-3-allyl-phenyl) -propane or 0,0'-diallyl bisphenol A and the methyl ether corresponding to one or other of the above-mentioned alkenyl phenols.

Alkenyl phenols were prepared, as is well known, by thermal transposition (Claisen) of allyl ethers of phenols, which are obtained in a known manner by reacting, for example, phenols and allyl chloride in the presence of a alkali metal hydroxide and solvents. As the reacting acrylate (11) which is especially convenient, there may be mentioned: (11.1) - the mono (meth) acrylates having the general formula (X), in which: p is 1; and L is a monovalent organic radical of the general formula (XI) in which the symbol represents a linear or branched alkyl radical having one to six carbon atoms, or a radical phenyl, and q is an integer of 0, 1, 2, 3, 4 or 5; di (meth) acrylates corresponding to the general formula (X) in which : p is 2, and L is a divalent organic radical of the general formula (XII) < -CH2CH20 > j:

(XII) wherein L2 is a linear or branched bivalent alkylene radical having two to nine carbon atoms and which may contain one or more oxygen bridges or a radical of general formula

in which U is a single valence bond or a group of formula

CH 2 -CH 2 -, -CH 2 -CH 2 -, -CH (CH 3) CH 2 -f -C-, -O-, -S-; " and the symbols r and s, the same or different, each represent an integer equal to 0, 1, 2, 3, 4 or 5; (11.3) - tri (meth) acrylates and tetra (meth) acrylates corresponding to the general formula (X) in which: p is 3 or 4; and . L is a trivalent or tetravalent organic radical derived from a linear or branched saturated aliphatic radical having from three to twenty carbon atoms and which may contain one or more oxygen bridges and / or one or more free hydroxyl functions; (11.4) the novolak epoxide (meth) acrylates which, corresponding to the general formula (X), are represented by the following general formula (XIII):

in which : . R1 is as defined above for the general formula (X); . the symbol is hydrogen or a methyl radical; and t is an integer or fractional number comprised between 0.1 and 7; Mixtures of various acrylates and / or methacrylates of the same type (11.1), (11.2), (11.3) or (11.4) J together or mixtures of one or more acrylates and / or methacrylates of the same the same type with one or more acrylates and / or methacrylates of another type. By way of specific examples of acrylate reagent (11.1) which are especially suitable, mention may be made in particular of: methyl mono (meth) acrylates; phenol- (mono-oxyethylated) mono (meth) acrylates; phenol mono (meth) acrylates (dioxethylated). By way of specific examples of acrylate reagent (11.2) which are suitable, there may be mentioned: ethylene glycol di (meth) acrylates; 1,4-butanediol di (meth) acrylates; hexanediol di (meth) acrylates; di- (monoxyethylated or polyoxyethylated) di (meth) acrylates, triphenylphenoxyglycol di (meth) acrylates, 4,4'-dihydroxy-diphenylmethane, bisphenol A, 4'-dihydroxy-diphenyl di (meth) acrylates in particular di (di-oxyethylated) bisphenol A di (monooxyethylated) di (meth) acrylates or di general formula (XII), wherein L 2 represents the radical of the formula -40-

and the symbols r = s = 1 or 2}. By way of specific examples of acrylate reagent (11.3) which are especially suitable, mention may be made in particular of butanetriol-1,2,4-tri (meth) acrylates; hexanetriol-1,2,6-tri (meth) acrylates; trimethylolpropane tri (meth) acrylates; pentaerythritol tri (meth) acrylates; pentaerythritol tetra (meth) acrylates.

The novolak epoxide (meth) acrylates (11.4) are known products, some of which are commercially available. They may be prepared by reacting (meth) acrylic acids with an epoxide resin of the novolak type, the latter being the reaction product of epichlorohydrin and phenol / formaldehyde polycondensates in the general formula (XIII) above, then represents a hydrogen atom or of cresol / formaldehyde polycondensates in the general formula (XIII), R 4 is then a methyl radical. These oligomeric polyacrylates (11.4) and a process for their preparation are described, for example, in U.S. Patent 3,335,403. Specific examples of the acrylate reagent ( 11.4), which are especially suitable, mention may be made in particular of novolak epoxide acrylates of the general formula (XIII) in which R 16 and R 16 are each hydrogen and t represents an integer or a fractional number in the range of 0.1 to 5. By way of specific examples of the acrylate reagent (11.5) which are especially convenient, there may be mentioned the mixtures of the epoxide (meth) acrylates (11.4) with a maximum of 30% by weight relative to the weight of the mixture (11.4) + (11.3), of a triacrylate and / or a trimethacrylate corresponding to the definitions given above with respect to the acrylate reagent (11.3) ) and, in particular, mixtures of acri These are especially convenient, precisely mentioned above, with a maximum of 25% by weight, based on the weight of the blend, of a triacrylate and / or trimethacrylate, which is conveniently selected from those just cited before. The acrylate reagent (11) which is used in an especially preferred manner is selected from the group consisting of di- (mono-oxyethylated) bisphenol A di (meth) acrylates; di- (di-oxyethylated) bisphenol A di (meth) acrylates; acrylates of the general formula (XIII) in which the symbols and R4a each represent a hydrogen atom,

and t is an integer or fractional number ranging from 0.1 to 5, these compounds being used alone or in admixture with not more than 25% by weight of the mixture of trimethylolpropane triacrylate.

In the compositions according to the present invention, various adjuvants may also be incorporated. Such adjuvants, commonly used and well known to those skilled in the art, may be, for example, stabilizers or degradation inhibitors, lubricants or demoulding agents, dyes or pigments, powder or particulate fillers such as silicates, carbonates, kaolin, chalk, quartz, curling powder, mica or glass microspheres. It is also possible for agents to incorporate adjuvants which modify the physical structure of the product obtained, for example, porogenic agents or fibrous reinforcing agents, such as, in particular, carbon fibrils, polyimide, aromatic polyamides, " whiskers ".

The curable compositions according to the present invention may be the result of a simple direct mixing at room temperature (23 ° C) of the constituent (A) with the constituent (B) and optionally of the additive (D) with the catalyst (C), if necessary. -43- ✓

Preferably, however, the curable compositions according to the present invention are the result of a preliminary reaction, carried out with the different constituents used, obtained by heating and giving a homogeneous liquid material. The hardenable compositions according to the present invention thus obtained will be described in the following paragraphs by the expression: " preferred compositions ".

More precisely, said preferred compositions may be prepared by directly heating the constituent (A), the constituent (B) and optionally the additive (D), with the catalyst (C), if necessary, over a range of sufficient time to obtain a homogeneous liquid mixture. The temperature may vary depending on the physical state of the compounds, but is generally between 40 ° C and 120 ° C, and preferably between 50 ° C and 100 ° C. The reaction time is in the range of five minutes to one hour or more.

According to an advantageous operating method used to prepare the preferred compositions, in a first step, the constituent consisting of the cyanate ester (A) is heated at temperatures between 40Â ° C and 120Â ° C, preferably between 50Â ° C and 100 ° C, to which it is in a homogeneous liquid state, operating in the absence of the optional catalyst (C). Then, in a second step, it is added to the liquid medium, which is stirred and held at a temperature equal to or equal to 40%

different from that used in the foregoing step, the polyimide-siloxane constituent (B), also comprising from 40 ° C to 120 ° C, preferably from 50 ° C to 100 ° C, the temperature for a sufficient time to obtain a homogeneous liquid medium (duration in the range of five minutes to one hour or more). In the case where the optional catalyst (C) is chosen, it is introduced into the second operation, preferably as a solution in the constituent (B) to which a filler has been added. If the additive (D) is used, it can be introduced at any time, either during the first operation or during the second operation. The melt viscosity of the thus obtained preferred compositions, measured at 80 ° C, can easily be adjusted to have the desired value, ranging from 0.1 to 50 Pa.s, in particular by choosing the nature and the respective proportions of the constituents used, as well as acting on the temperature and the duration of the heating.

The operations just described may be carried out not only in the melt but still in the presence of varying amounts of a polar liquid, such as, for example, cresol, dimethylformamide, N-methylpyrrolidone, dimethylacetamide, methyl ethyl ketone, dioxane and cyclohexanone. -4-

In the homogeneous liquid state, the preferred compositions may be used directly, for example, either for impregnating conductors or for making moldings by simple hot or injection casting, or for forming adhesives. After cooling and milling, it is also possible to employ such compositions in the form of powders, for example to obtain compression molded articles, optionally in combination with fibrous or powdery fillers. Preferred compositions may also be used in solution in the preparation of coatings, collagens, laminate materials whose backbone may be in the form of woven or nonwoven fabrics, unidirectional elements or natural or synthetic staple fibers, such as, for example, filaments or glass, boron, carbon, tungsten, silicon, polyamide-imide or aromatic polyamide fibers.

Preferred compositions have a very particular interest in obtaining pre-impregnated intermediate articles without solvent. The impregnation of the fibrous material can be carried out by the usual techniques such as immersion, scraper impregnation or mesh or transfer impregnation. The transferable film and the pre-impregnated articles may be used directly or be stored for further use; they remarkably retain their properties during cold storage at temperatures ranging from 0 ° C to 10 ° C. Preferred compositions used in this application preferably have a melt viscosity of from 2 to 50 Pa. s.

The prepreg materials are usable in the realization of parts having varied shapes and functions in numerous industries, such as in the aeronautical industry. These pieces, which may be pieces of revolution, are obtained by plating several layers of prepregs on a mold or a support. Prepregs can also be used as reinforcements or as means of repairing deteriorated parts.

However, it is also possible to design parts according to the winding technique in filaments with or without a carrier, for the production of parts of revolution, a technique used in particular in the manufacture of parts which are of interest in the automobile and aeronautical industries. Preferred compositions used in this art preferably have a melt viscosity of from 0.1 to 2 Pa.s.

The curable compositions according to the present invention may be cured (or cross-linked) by heating at temperatures comprised between 100 ° C and 250 ° C, for ten minutes to twenty-five hours, optionally under pressure. Before crosslinking, in the case of the preparation of the preferred compositions,

the latter are in the form of a prepolymer consisting of a single phase; the products obtained from the polyimide-siloxane constituent (B) and optionally the additive (D) are, in effect, soluble in the product obtained from the polyfunctional cyanate ester (A) constituent. In the course of the cross-linking, as reactions taking place where the still free -fO-C = N groups take part, a phase separation phenomenon develops and finally a cured composition having a biphasic structure consisting of a and a discontinuous phase formed of particles in the order of magnitude of 0.01 to 1 micrometer, rich in product from the starting elastomeric constituent (B).

The following Examples illustrate, in a non-limiting manner, how the present invention may be practiced.

In these Examples, a number of controls were performed. Also, several properties were measured. The operating procedures and / or the standards under which these controls and measures were carried out shall be set out below. -4-

VISCOSITY OF THE HARDNESS STURDEN COMPOSITION The melt viscosity referred to herein is the dynamic viscosity of the composition obtained at the time of the pour at the end of the bulk preparation process by heating the constituents is measured at 80 ° C +/- 0.1 ° C with a RHEOMAT 30 viscometer from the company CONTRAVES, equipped with a rotor running on a gradient of 13 secs S its value is expressed in Pa.s.

ENDURING COMPOSITION GRAVELING POINT

It is called a softening point at the approximate temperature where a glass rod of 6 millimeters in diameter can easily penetrate a few millimeters into the material.

The glass transition temperature (Tg) corresponds to the brutal fall of the modulus of elasticity as a function of temperature. It can be determined in the graph that represents the variations of the modulus of elasticity (E) as a function of temperature, variations that are measured by dynamic mechanical analysis with the aid of a DUPONT Model 982 DMA apparatus with the rate of rise of temperature equal to 30 ° C per minute. The beakers are conditioned to EHO, ie they are placed in a desiccator containing silica gel and dried for twenty four hours at room temperature under 0.66-1.33.10 Pa before performing the determinations.

HARDENING COMPOSITION TENACITY The CHARPY shock resistance is determined at 20 ° C with barrette type probes with 80 x 10 x 4 mm that have no notch, conditioned to EHO, according to ASTM D 256. The propagation energy of the crack GIC and the critical coefficient of deformation concentration K1C are determined with CT test tubes (CT = compact tensile stress) in accordance with ASTM E 399.

TEST OF ADHERENCE OF HARDENED COMPOSITION OF STAINLESS STEEL

This test is performed by simple shearing according to ASTM D 1002. The curable composition is deposited as a 200 micron thick film on the metal substrate and is then cross-linked under pressure. The deformation value is measured at shear rupture (6R). -6-

EXAMPLE 1 1. Embodiment of the Invention

100 grams of a 2,2-bis- (4-cyanato-phenyl) -propane prepolymer is introduced into a glass reactor equipped with an anchor type stirrer, in which 30% of the cyanate groups were cyclotrimerized; this product is marketed by Société HI-TEK POLYMERS under the trade name AROCY B30.

Step 1: The reactor is immersed in an oil bath preheated to 80 ° C and its contents are stirred until the complete melting of the charged constituent is achieved and a homogeneous liquid mass is obtained. The duration of this operation is five minutes and then proceeds under reduced pressure.

Operation 2: The liquid mass thus obtained is cooled to 60øC and 18 grams of bis-maleimide-siloxane, which is described in the following paragraph 2, is added and 0.025 grams of copper acetylacetonate [Cu (C Hy02) 2I * previously dissolved in the bis-5α-α-maleimido siloxane. The reaction mass is maintained at 60 ° C under stirring until a homogenous liquid medium is obtained. The duration of this operation is 10 minutes. Thereafter, the liquid reaction mass thus obtained is poured into a preheated mold at 170øC. The thermosetting composition thus obtained is soft and viscous at room temperature (20øC). It has a softening point near 0 ° C. Its viscosity at 80 ° C equals 1 Pa.s and its gelation time at 170 ° C equals eight minutes.

With this composition, it is possible to impregnate the Hot-Melt type (with molten material without solvent) from fibrous base materials, for example from woven fabrics of carbon fibers, to make pre-printed intermediate articles, in the temperature range of 50 ° C to 100 ° C.

By immediately stripping the thermosetting composition in a mold as indicated above, plates having the dimensions of 140 x 100 x 4 mm, which are subjected to the following cooking cycle, can be prepared. 60 minutes at 170 ° C. 55 minutes between 170 ° C and 225 ° C,. 16 hours at 225 ° C e.g. 2 hours between 225 ° C and 25 ° C.

After demolding, the plates at the base of the hardened composition are cut to obtain appropriate sized beakers, in which the glass transition temperature (Tg), the modulus of elasticity (E), the Charpy (Rc) without notch and the values of G1C and K1C.

The values found are as follows:

Tg: 235 ° EC: * at 20 ° C: * at 200 ° C: 0.3 GPa 1.75 GPa Rc: 22kJ / m2 G1C: 160 J / m2 KCl: 0.66 Mpa Vm For comparison, the operations described above but without the use of bis-maleimide-siloxane.

The Rc and G1C values are decreased by 50%: the moduli of elasticity E at 20 ° C and 200 ° C are increased by 10%. -53-

Stainless steel adhesion tests were also carried out. The curable composition according to the Example is crosslinked under a pressure of 10æ Pa, according to the cooking cycle recited above. The values determined for the shear burst load (6R) are as follows: 6R: * at 20 ° C: 16 MPa * at 200 ° C: 18 MPa.

These values are substantially unchanged after the tested samples were subjected to 1000 hour aging at 180øC. In the absence of bis-maleimide-siloxane, shear burst values are 10 MPa to 20 ° C and 12 MPa at 200 ° C. 2. Description of the Preparation Process of Bis-Maleimide with Groups Diorganopolysiloxane Used in Example

This bis-maleimide has the following formula:

2.1 Preparation of Diamine with Diorganopolysloxane Group from which this Bis-Maleimide is derived

In a glass reactor equipped with a central stirrer, a charge ampoule and an upstream coolant in which a slight overpressure of dry nitrogen is established, 369 grams (0.46 mol) of an alpha, omega-bis- (hydrogen) - diorganopolysiloxane of formula CH3 H-Si-O-4-

4

A v CH3

Having a reaction mass of the order of 802 grams.

The reactor is then introduced into an oil bath preheated to 55øC and then the catalyst is added. The latter is the Karsted catalyst (elemental platinum-based complex and 1,3-divinyl-1 , 1,3,3-tetramethyl-disiloxane); is in the form of a solution in toluene (concentration equal to 3.5% by weight) and 1.49 cubic centimeters of this catalyst solution is introduced through a syringe; the quotient between the weight of elemental platinum used / weight of the reaction mass is equal to 91.10 '.

Into the reactor, 137 grams (0.92 mole) of methoxy-aniline is then gradually drained for a time interval of sixty minutes, so as to control the exothermicity of the reaction. Thirty minutes after the end of the introduction, the temperature is allowed to reach room temperature. The product obtained, weighing 506 grams, is a clear, orange-brown viscous oil having a proton nuclear magnetic resonance spectrum according to the following structure formula:

The molecular mass is of the order of 1100 grams. Under these conditions, the conversion rate of the reactants employed is equal to 100% (by nuclear magnetic resonance and infrared analysis, the presence of neither amine nor the hydrogenated siloxane oligomer was not detected) and the desired diamine yield by weight is equal to 100%. 2.2 Preparation of Bis-Maleimido-DiorRano-Polysiloxane

In a glass reactor equipped with a central stirrer and rising coolant in which a slight overpressure of dry nitrogen has been established and which is placed in an oil bath preheated to 55øC, are introduced simultaneously for ten minutes using of two 28-gram flasks of acetone solution of 28 grams (0.025 mole and 0.02 N-function) of the diamino siloxane prepared in paragraph 2.1; and 15 cubic centimeters of an acetone solution of 6.4 grams (0.055 mole) of maleic anhydride.

After the introduction is completed, each ampoule is charged with 5 cubic centimeters of acetone, which are then added to the stirred reaction mass for a further fifteen minutes.

6.1 grams (0.06 mole) of acetic anhydride is charged into the loading ampoule containing the maleic anhydride, and in the other ampoule, 1.67 grams (0.0165 mole) of triethylamine are charged.

These two compounds are then introduced into the reactor and then 0.3 cc of an aqueous solution containing 0.0528 mole of nickel acetate per 100 cc of solution is added.

The reaction mixture is refluxed under stirring for two hours and thirty minutes. Then, the temperature drops to 20 ° C.

The reaction mixture is diluted with 80 cubic centimeters of ice water (5øC) under vigorous stirring, and then the oily product present is extracted with 80 cubic centimeters of ethyl acetate. The organic phase thus obtained is washed with 3 times 80 cubic centimeters of water to reach pH 6 in the washing waters and then dried over two hours on anhydrous sodium sulfate. After filtration, the ethyl acetate is removed from the organic phase by evaporation, quenching this under reduced pressure (about 70 Pa) at 60øC and collecting 30.3 grams (i.e., an equivalent yield by weight at 96% relative to the theoretical value) of an orange-brown viscous product, the nuclear magnetic resonance spectrum of which is according to the structure of the desired bis-maleimide as defined at the beginning of this Example. The molecular mass is of the order of 1,200 grams. EXAMPLE 2

It is operated exactly as described in Example 1, but without introducing catalyst (acetyl acetonate of copper) in step 2.

At the end of step 2, the liquid reaction mass is poured into a mold preheated to 200 ° C.

The thermosetting composition thus obtained is soft and sticky at room temperature (20 ° C). It has a softening point of about 0 ° C. Its viscosity at 80 ° C equals 1 Pa.s and its gelation time at 200 ° C is equal to thirty-five minutes.

With this composition, a Hot Melt type impregnation (with non-solvent melt) of fibrous materials based, for example, of woven carbon fiber tarps, can be made to make pre-printed intermediate articles in temperature range of 50 ° C to 100 ° C.

By immediately stripping the thermosetting composition in a mold, plates having the dimensions of 140 x 100 x 4 mm, which will be subjected to the following cooking cycle, can be prepared:. 60 minutes at 200 ° C. 50 minutes between 200 ° C and 250 ° C,. 5 hours at 250 ° C. 2 hours between 250 ° C and 25 ° C. -60- /

After demolding, the hardened composite base plates are cut to obtain appropriate sized beakers, with which the glass transition temperature (Tg), the modulus of elasticity (E), the Charpy impact resistance (Rc ) without notch and the values of G1C and K1C.

The determined values are as follows:

Tg: 230 ° C E: * at 20 ° C: 3.0 GPa * at 200 ° C: 1.75 GPa

Rc: 23 kJ / m2 G1C: 165 J / m2 K1C: 0.64 Mpa Vm " EXAMPLE 3

In a glass reactor provided with an anchor type stirrer, 75 grams of a 2,2-bis- (4-cyanato-phenyl) -propane prepolymer are introduced at room temperature, in which 307 of the functional cyanate groups were cyclotrimerized; this product is marketed by Sociéti HI-TEK POLYMERS under the name AROCY B30. -6-

Step 1: The reactor is immersed in an oil bath preheated to 80 ° C and its contents are stirred until the complete melting of the charged constituent is achieved and a homogeneous liquid mass is obtained. The duration of this operation is five minutes and is followed by degassing under reduced pressure. Step 2: The liquid mass thus obtained is cooled to 60øC and 18 grams of the bis-maleimido-siloxane described in Example 1 is added, 0.025 grams of copper acetylacetonate previously dissolved in the bis-maleimido siloxane and 25 grams di (di-oxyethylated) bisphenol A diacrylate (commercially available under the trade mark ABECRYL 150 from Societe UCB). The reaction mass is maintained at 60 ° C under stirring until a homogenous liquid medium is obtained. The duration of this operation is ten minutes. The liquid reaction mixture thus obtained is then poured into a preheated mold at 170øC. The thermosetting composition thus obtained is soft and sticky at room temperature (20øC). It has a softening point near -10 ° C. Its viscosity at 80 ° C is 0.5 Pa.s and its gelation time at 170 ° C is equal to ten minutes. Tf.

With this composition, it is possible to impregnate the Hot-Melt type (with molten material without solvent) from fibrous materials based, for example, from woven carbon fiber tarps, to make pre-impregnated intermediate articles with ranges of temperatures between 50 ° C and 100 ° C.

By immediately pouring the thermosetting composition into a mold, sheets having the dimensions of 140 x 100 x 4 mm, which will be subjected to the following cooking cycle: 60 minutes at 170 ° C, 55 minutes at 170 ° C and 225 ° C, 16 hours at 225 ° C. 2 hours between 225 ° C and 25 ° C.

After demolding, the plates at the base of the hardened composition are cut to obtain appropriately sized beakers, in which the glass transition temperature (Tg), the modulus of elasticity (E), the Charpy (Rc) without notch and the values of G1C and K1C.

The determined values are as follows:

Tg: 210øC E *: at 20øC: 3.0 GPa * at 200øC: 1.0 GPa Rc: 26 kJ / m2 G1C: 305 J / m2 K1C: 0.79 Mpa Vm-

Claims (8)

A process for the preparation of thermosetting compositions comprising: A) at least one cyanate ester compound selected from the group consisting of: 1) a monomeric cyclic monofunctional aromatic ester of the formula R - (- 0-C = N) n (I) wherein n is an integer from 2 to 2 to; and R represents an aromatic organic radical having a valence of n with 6 to 30 carbon atoms, the cyanate groups being attached to the aromatic number or to the aromatic nuclei of R; 2) a prepolymer of 1); and 3) a copolymer of 1) and an aromatic primary polyamine; 3) at least one elastomeric compound; and optionally C) an appropriate catalyst, component B) consisting of at least one compound and is selected from the group consisting of: (a) a Ν, Ν'-bis-maleimide with a group of diorganopolysiloxane corresponding essentially the general formula 3 / in which X is a substituent which is in the ortho, meta or para position with respect to the carbon atom of the benzene ring attached to the nitrogen atom chosen from the group consisting of a single valence bond and one of the following atoms and groups 0 b - 0 -; - S -; - S -; R 2, R 4, R 6, R 6, R 7 and R 6, are the same or different, each represents a monovalent hydrocarbon radical selected from: the straight chain or branched alkyl of 1 to 12 carbon atoms which may be substituted with one or more chlorine, bromine or fluorine atoms or a -CN group; a phenyl radical optionally substituted with one or more alkyl and / or alkoxy radicals having 1 to 4 carbon atoms or one or more chlorine atoms; x is an integer of from 2 to 8; and the symbols y and z represent numbers, equal or different, integers or fractions, the sum of which is comprised between 0 and 100; 4 5) a prepolymer of 4); and 6) a copolymer of 4) and an aromatic biprimary diamine; the weight ratios of components A) and B), relative to the total weight of A) B) being: 50 to 98%, preferably 75 to 95%, of component A); and 2 to 50%, preferably 5 to 25%, of elastomer component B); characterized in that, in a first step, the component (A) formed by the cyanate ester is heated to a temperature of from 40 ° to 120 ° C and preferably from 50 ° to 100 ° C, which is in a homogeneous liquid state, operating in the absence of the catalyst C) eventually; then in a second step is added to the liquid medium which is stirred and maintained at the same or different temperature from the one used in the previous step, also comprised between 40 ° and 120 ° C, and preferably between 50 ° and 100 ° C, component B) is formed by the polyimidazoxane, the stirring and the temperature being maintained for a sufficient time to obtain a homogenous liquid medium; in such a way that, if an optional catalyst C) is used, the latter is introduced in the second step, preferably in the form of a solution in the loaded component B). D 2. A process according to claim 1, wherein in R 1 and R 2 the cyanate ester of formula (I) may represent: i) a valence radical n derived from an aromatic hydrocarbon having Such as, for example, benzene, naphthalene, anthracene or pyrene; ii) a valence radical n derived from a group having several aromatic nuclei linked together by a single valence bond or an inert atom or by an inert bivalent group such as, for example, a group of formula in which R 'is a single valence bond or an inert bivalent atom or group, such as, for example, -O- or -S-; a straight or branched chain alkylene radical having 1 to 10 carbon atoms which optionally bears as substituents one or more chlorine, bromine or fluorine atoms and is optionally interrupted by one or more oxygen atom (s); or a -CO- group; or a group of formula 6 -NR " - in which the symbol R " represents a hydrogen atom, a C 1 -C 3 -alkyl, phenyl or cyclohexyl radical; a -COO- group; the various aromatic groups mentioned in paragraphs (i) and (ii) may be substituted with one or more C -C-C alquilo straight or branched chain alkyl or alkoxy radicals or one or more halogen atom (s). 3. A process as claimed in claim 2, wherein the cyanate esters (1) of formula (I) used are bifunctional compounds of general formula wherein R '" represents a valence bond or one of the following atoms and groups â € ƒâ € ƒâ € ƒâ € ƒâ € ƒâ € ƒâ € ƒâ € ƒR22quot ;, â € ƒâ € ƒâ € ƒâ € ƒâ € ƒâ € ƒâ € ƒâ € ƒR11quot ;, the same or different R7quot; symbols each represent a substituent selected from a chlorine, bromine or fluorine atom or a methyl, ethyl, propyl or isopropyl radical, neighbors in the same nucleus together represent an aromatic hexagonal nucleus; n is an integer equal to 0 or 1; and a is an integer of 0, 1 or 2, the symbols being the same or different from each other when there are two. 4. A process as claimed in any one of claims 1 to 3, wherein in component B) the bis-maleimide-siloxane 4) is selected from the group consisting of bis-maleimino-8,8- of the formula (II) in which: 1) X is -O-; R4, R4, R 2, R 2, R 2, R 3, R 4, R 5, R 9 and R 9 are the same and each represents a straight chain alkyl radical having 1 to 3 carbon atoms; x is one of the numbers 2, 3 or 4; the sum y + z is comprised between 0 and 100 and preferably between 4 and 70; 2) x is -O-; R 2, R 2, R 3, R 4, R 9 and R 9 are the same and each represents a straight-chain alkyl radical having 1 to 3 carbon atoms; R 1 and R 2 are the same and are each a phenyl radical; x is one of the numbers 2, 3 or 4; and the sum y + z is comprised between 0 and 100 and preferably between 4 and 70; 3) X is -O-; R 2, R 2 and R 3 are the same and each represents a straight chain alkyl radical having 1 to 3 carbon atoms; R 2, R 2, R 2 and R 2 are the same and each represents a phenyl radical; x is one of the numbers 2, 3 or 4; and the sum v + z is from 0 to 100 and preferably from 4 to 70; 4) X is -O-; R 2, R 2, R 2, R 2, R 2 and R 3 are the same and are each a straight-chain alkyl radical having 1 to 3 carbon atoms; R 2 and R 3 are the same and each represents a phenyl radical; x is one of the numbers 2, 3 or 4; and the sum y -r z is from 0 to 100 and preferably from 4 to 70; or 3) X is -O-; R1, R2 and R3 are the same and are each a straight-chain alkyl radical having 1 to 3 carbon atoms; R 2, R 2, R 2 and R 2 are the same and are each a phenyl radical; x is one of the numbers 2, 3 or 4; and the sum y + z is comprised between 0 and 100 and preferably between 4 and 70. 5. A process as claimed in any one of claims 1 to 4, wherein the catalyst (C) when a catalyst is used is selected from the group consisting of: compounds having a labile hydrogen atom consisting of alcohols, phenols, carboxylic acids and primary or secondary amines; compounds which consist of metal carboxylates optionally dissolved in an alkylphenol or a monoalcohol; and - compounds consisting of metal acetylacetonates, optionally dissolved in an alkylphenol. 10 A composition according to any one of claims 1 to 5, characterized in that the compositions also comprise an additive (D) consisting of one or more additional polymerizable preservatives selected from: 7) a N, N'-bis -Maleimide of the general formula ZC-CO-CO-CZ; N-G-N | (VIII): wherein the same or different symbols are each a hydrogen, halogen or methyl group; G is a bivalent radical selected from the group consisting of the radicals: cyclohexylenes, phenylenes; 4-methyl-phenylene-1,3; 2-methyl-phenylene-1,3; 5-methyl-phenylene-1,3,2,5-diethyl-3-methyl-phenylene-1,4; and the radicals of general formula in which B is a single valence bond or a group 11 CH3-CH. C = O, CH = O = silane 8) a chlorinated or brominated epoxy resin; 9) a non-halogenated epoxy resin; 10) an alkylphenol of general formula in which H is a single valence bond or a bivalent radical chosen from the group consisting of the radicals CH 2 --CH 2 --CH 2 S - ; - SO-; and -S02 -; the same or different symbols each represent a hydrogen atom or a methyl radical; yl; and the same or different Râ,,, are each a hydrogen atom or a straight or branched chain alkyl radical having 1 to 6 carbon atoms or a phenyl radical; 11) an acrylate of the general formula (CH 2 = CR 15 -CO-O-) - L (X) P wherein the symbol represents a hydrogen atom or a methyl radical; p is an integer or fraction thereof at least equal to 1 and at most equal to 8; and L is an organic radical of valence p which is derived from a saturated, straight or branched chain aliphatic radical having 1 to 30 carbon atoms and which may contain one or more oxygen bridges and / or one or more free hydroxyl functions of an aromatic (aryl or arylaliphatic) radical having 6 to 150 carbon atoms consisting of a benzene ring which may be substituted by one to three C1 -C4 alkyl radicals or various benzene ring nuclei optionally substituted as above, an inert group or an alkylene radical having 1 to 3 carbon atoms, said aromatic moiety being able to contain at various positions of its structure one or more oxygen bridges and / or one or more functions hydroxyl groups and the free valence (s) of the aromatic radical L may be located on a carbon atom of an aliphatic chain and / or on a carbon atom of a benzene ring. 7. A process according to any one of claims 1 to 7, wherein the catalyst (C) when used is employed in a proportion of from 0.005 to 10%, preferably from 0.01 to 5% by weight. relative to the weight of the overall composition containing A) + B) + if appropriate the polymerizable additional compound (s) D). 8. A process for the preparation of adhesives, structural parts and pre-impregnated intermediate articles, characterized in that, by using a thermosetting composition prepared by the process according to any one of Claims 1 to 7, there is carried out: a) a molding by simple hot or injection casting or filament winding; or (b) a solvent-free impregnation of various raaas :: aroscs. The Official Agent of Industrial Property i 15 The present invention relates to a method for the preparation of thermoconditional compositions of cystayl compounds and compounds of the general formula (I): wherein R 1 and R 2 are as defined in formula (I). A process for the preparation of thermosetting compositions containing: A) at least one cyanate ester compound consisting essentially of a polyfunctional aromatic cyan ester having at least two cyanate groups (-O-C = N) attached to a core a prepolymer derived from said organic ester or a co-prepolymer derived from said cyano ester and from a polyamine; and 3) at least one elastomer consisting essentially of a N, Ν'-bis-maleimide with a diorganopolysiloxane group, a prepolymer derived from said bis-maleimide or a copolymer derived from said bis-maleimide and a diamine; and optionally C) a suitable catalyst and optionally D) one or more additional polymerizable compounds; 16 i i i i which consists of: in a first step heating the component A) at a temperature in the range of 40 ° and 120 ° C, which is in a homogeneous state of the product, operating in the absence of the catalyst C) optionally; then, in a second step, adding to the liquid medium which is stirred and held at a temperature, the same or different from that used in the previous step, also comprised between 40 ° and 120 ° C, component 3), stirring being maintained and the temperature for a sufficient time to obtain a homogeneous liquid medium; in such a way that, if an optional catalyst C) is used, the latter is introduced in the second step, preferably in the form of a solution in the loaded component B). 0'Affect Industrial Property Otto