CA1270592A - Heat-curable polymers which contain imide groups and process - Google Patents

Abstract

HEAT-CURABLE POLYMERS WHICH CONTAIN
IMIDE GROUPS AND PROCESS
ABSTRACT
Heat curable compositions comprise (a) a bismaleimide, e.g., bismaleimidodiphenylmethane, and (b) a heat activat-able curing agent therefor comprising in combination (i) a polyamine and (ii) an alkenylphenol or alkenylphenol ether.
After reaction, preferably at temperatures of 100° to 250°C., optionally in admixture with polymerization cata-lysts, shaped articles, laminates, adhesive bonds and foams are produced. These have superior mechanical properties, especially hot/wet properties and improved resistance to thermal aging.

Description

~27~

29,825 HEAT CURABLE POLYMERS WHIC~ CONTAIN
IMIDE GROUPS AND PROCESS

The present invention relates to new heat-stable resins based on three-dimensional polyimides.

BACKGROUND OF THE INVENTION

Polyimide resins are particularly useful as aerospace adhesives and composites because of their remarkable mechanical strength, high service temperature, low moisture sensitivity, and enhanced processability.
Polyimides are used as components in the man-!. ufacture of polyaddition products and polymerization products. Thus, for example, the polyaddition reaction of bis-maleimides with primary diamines and the curing of these pre-adducts by polymerization by the action of heat are described in French Patent Number 1,555,564.
However, this process is not easily used in the production o ~ 2'7~5~
of composites because they are inherently brittle mater-ials and have less than optimum handling characteristics because tapes and fabrics impregnated with them have poor tack and drape characteristics.
Polyaddition products of bis-maleimides and alkenylphenols and/or alkenylphenol ethers are claimed in U.S. Patent No. 4,100,1~0. Such materials, however, while stable at ordinary temperatures, produce molded articles somewhat deficient in hot/wet strength and resistance to thermal aging.
Heat-curable three-dimensional compositions of bis-maleimides, polyamines and allyl esters are disclosed in German Published Patent Specification 2,131,735. But these have short processing times, making them unsuitable for the manufacture of composites and adhesives. Other heat-curable three-dimensional polyimides are known, e.g., from U.S. 4,454,283, which discloses bis-maleimides, polyamines and polyvinylaromatics. These compositions are toxic, and the ultimate impact resistance is poor, as is resistance to edge delamination.
It has now been discovered that polymers which contain imide groups and are based on polymaleimides, can be provided and that these do not exhibit the dis-advantages of the polyadducts based on polymaleimide, in the present state of the art. Moreover, these new compositions can be manuEactured without difficulty, they have long pot lives, and they produce heat cured articles with superior physical properties, particular-ly impact resistance, and strength retention after hot/
wet exposure, resistance to edge delamination and to the a~ver.se effects of therma~ aging.

SU~I~AI'Y 0~ V~ 0 According to the present invention, there are provided compositions which are stable on storage and can be cured by the action of heat, said compositions comprising (a) a heat curable polyimide resin containing, per average molecule, at least two groups of the formula ~C~
D \ / N - -CO
directly attached to carbon atoms, wherein D is CH C - CH = C - CH -3 11 2 1 ll CH- CH- CH -or a mixture thereof; and (b) a heat-activated curing agent for said polyimide resin comprising, in combination, (i) a polyamine of the formulae:

G (NH2) or NH NH NH

~-- R ~ R-wherein G denotes a y-valent organic radical having 2 to 40 carbon atoms and y is an integer of 2 to 4, each R
represents a divalent hydrocarbon radical obtained by 3S removing the oxygen atom of an aldehyde or ketone having ~z~
o 1 to 8 carbon atoms, and m is a number of from 0.1 to 2 and (ii) an alkenylphenol or an ether thereof, in amounts such that if N represents the number of moles of polyimide employed, N represents the number of moles of polyamine employed and N represents the number of moles of alkenylphenol or ether thereof employed, the ratio Nl Nl or

2 3 2(m + 2)N2 + N3 is greater than 0.3,-preferably from 0.3 to 10, y or m being defined as above.
In a preferred aspect, component (a) comprises a mixture of heat curable polyimide resins of the formula / CO~ / CO
D ~ ~ N Z - N ~ / D
CO CO

wherein D is CE~ - C - 2 1 or ICH -CH- CH- CH-or a mixture thereof, and Z is the residue of at least one aromatic diamine and in the minor proportion of the mixture, Z is the residue of an aliphatic diamine.
In another principal aspect, the present in-vention provides a process for the preparation of a cross-linked polymer which is stable on storage and can be cured by the action of heat which comprises o ~ 5~
(a) a polyimide of the formula R CO CO / R
S \C \ / \C
N-A-N ll / \ / CH
CO CO

wherein R is hydrogen or methyl, and A is a divalent radical of the formula ~ (R ) ~

in which R is selected from the group consisting of -CH -, C
CH

-SO2-, -SO-, -S- and -O-, and n is 0 or 1; or a poly-imide selected from the N,N'-bis-maleimide of 4,4'-diaminotriphenyl phosphate, the N,N'-bis-maleimide of 4,4'-diamino-triphenyl thiophosphate, the N,N',N'-tris-. 30 maleimide of tris-(4-aminophenyl) phosphate, the N,N',N"-tris-maleimide of tris-(4-aminophenyl) thiophosphate; or a mixture of said polyimides;
and, (b) a heat-activated curing agent for said polyimide (a) comprising, in combination, ~2~3~

(i) an arylene polyamine compound of the formula S Q (NH2) , or N~ ~ ~

wherein X is selected from hydrogen, lower alkyl, halogen, or mixtures thereof, and Q is a divalent radical com-prising at least two aryl radicals atached directly to each other or through a member selected from an.alkylene radical, straight chain or branched, of from 2 to 12 carbon atoms, -S-, -SO2-, -CO-, -O-, -CO2-(CH2) -CO2-wherein p is from 2 to 12, or a mixture of any of the foregoing members, and y' is 2, R each are divalent hydrocarbon radicals obtained by removing the oxygen atom of an aldehyde or ketone having 1 to 8 carbon atoms, and m is a number of from 0.1 to 2; and (ii) an alkenylphenol selected from o,o'-diallyl-bisphenol A, 4,4'-dihydroxy--3,3'-diallyldiphenyl, ~5 bis-(4-hydroxy-3-allylphenyl) methane, 2,2-bis-(4-hydroxy-

3,5-diallylphenyl)propane, eugenol, o,o'-dimethallyl-bisphenol A, 4,4'-dihydroxy-3,3'-dimethylallyldiphenyl, bis-(4-hydroxy-3-methallylphenyl)methane, 2,2-bis-(4-hydroxy-3,5-dimethallylphenyl)propane or 4-methallyl-2-methoxyphenol; or an alkenylphenol ether selected from 2~2-bis(4-methoxy-3-allylphenyl) propane, 2,2-bis(4-methoxy-3-methallyphenyl)propane, 4,4'-dimethoxy-3,3' diallyldiphenyl, 4,4'-dimethoxy-3,3'-dimethallyldiphenyl, bis(4-methoxy-3-allylphenyl)methane, bis(4-methoxy-3-35 methallylphenyl)methane, 2,2-bis(4-methoxy-3,5-diallyl-o ~ 27~ 3~
phenyl)propane, 2,2-bis-(4-methoxy-3,5-dimethallyl-phenyl)propane, 4-allylveratrole or 4-methallylveratrole;
or a mixture of said alkenylphenols, a mixture of said alkenylphenol ethers or a mixture of said alkenyl-phenols and said alkenylphenol ethers;
in amounts such that if N represents the number of moles of polyimide employed, N represents the number of moles of polyamine employed and N represents the number of moles of alkenylphenol or ether thereoE
employed, the ratio Nl Nl or 152 3 2(m -~ 2)N + N

is from 0.3 to 10, y' or m being defined as above.

DETAILED DESCRIPTION OF THE INVENTION

Useful polyimides for component (a) contain, per molecule, at least two radicals of the general formula:

25/ CO \
D \ / N-CO

in which D denotes a divalent radical containing a carbon-carbon double bond.
The polyimides are known, and can be prepared, for example, as described in U.S. 3,010,290, by reacting the corresponding diamines with unsaturated dicarboxylic acid anhydrides. It is contemplated to employ any of the polyimides which are listed in the above-mentioned 3L27~
~rench Pat. No. 1,555,564, and in U.S. 4,100,140.
Maleimides of the above general formula in which D
denotes divalent radicals of the formulae:

R - C - CH = C -ll or 2 in which R is hydrogen or methyl, are particularly suitable.
The reaction with polyimides which contain, per molecule, two or three radicals represented by D, and thus, in particular, the reaction with bis-maleimides and tris-maleimides, is a preferred embodiment of the invention.
As has been mentioned, especially suitable compositions are those wherein component (a) comprises a mixture of heat curable polyimide resins of the formula CO ~CO
D / N Z - N \ D
CO CO

wherein D is CH C - CH - C - or CIH -or a mixture thereof, and Z is the residue of at least one aromatic diamine and in the minor proportion of the mixture, Z is the residue of an aliphatic diamine.
In such compositions preferably from 75 to 95 parts by weight of 100 parts of the mixture consists of bis-imides derived from aromatic diamines. Illustrative - ~.2~15~?~
o of the preferred maleimides are those derived from at least one diamine selected from ethylene diamine, hexa-methylene diamine, phenylene diamine, trimethylhexa-methylene diamine, methylene dianiline, toluene diamine,

4,4'-diphenylmethane diamine, 4,4'-diphenyl-ether diamine, 4,4'-diphenylsulfone diamine, 4,4'-dicyclohexanemethane diamine, metaxylene diamine, 4,4'-diphenylcyclohexane diamine, 3,3'-diphenylsulfone diamine or a mixture of any of the foregoing. The best mixture of polyimides will be those having a melting point from 70 to 125C.
Special mention is made of the eutectic-like mixture known in the art and described in U.S. 4,454,283, which is a bismaleimide mixt~re derived from diamines consisting essentially of 50 to 80% methylene dianiline, 5 to 30~
toluene diamine and 5 to 25~ of trimethyl hexamethylene-diamine, by weight.
Other illustrative bis-maleimides are compounds of the formula:

C / \ / `C

II N-A-N

\C~ CO

in which R is hydrogen or lower alkyl (i.e., C -C6 alkyl), preferably, hydrogen or methyl, and A denotes a divalent organic radical with 2 to 40 carbon atoms.
In the above formula, A is especially preferably Of the formula:

~ (R

. .

wherein R represents one of the radicals -CH -, C

SO -, -SO-, -S- and -O- and n is 0 or 1.
Illustrative examples of suitable polyimides are: N,N'-ethylene-bis-maleimide, N,N'-hexamethylene-bismaleimide, N,N'-m-phenylene-bis-maleimide, N,N'-p-phenylene-bis-maleimide, N,N'-4,4'-diphenylmethane-bis-maleimide, N,N'-4,4'-3,3'dichloro-diphenylmethane-bis-maleimide, N,N'-4,4'(diphenyl ether)-bis-maleimide, N,N'-4,4'-diphenylsulphone-bis-maleimide, N,N'-4,4'-dicyclohexylmethanebis-maleimide, N,N'-alpha,alpha'-4,4'-dimethylenecyclohexanebis-maleimide, N,N'-m-xylylene-bis-maleimide, N,N'-p-xylylene-bis-maleimide, N,N'-4,4'-diphenylcyclohexanebis-maleimide, N,N'-m-phenylene-bis-citraconimide, N,N'-4,4'-diphenylmethane-bis-citraconimide, N,N'-4,4',2,2-diphenylpropane-bis-maleimide, ~,N'-alpha,alpha'-1,3-dipropylene-5,5-dimethyl-hydantoin-bis-maleimide, N,N'4,4'-diphenyl-methane-bis-itaconimide, N.N'-p-phenylenebis-itaconimide, N,N'-4,4'-diphenylmethane-bis-dimethylmaleimide, N,N'-4,4'-2,2-diphenylpropane-bis-dimethylmaleimide, ~,N'-hexamethylene-bis-dimethylmaleimide, N,N'-4,4'-(diphenyl èther)-bis-dimethylmaleimide and N,N'-4,4'-diphenyl-sulphone-bis-dimethylmaleimide. Special mention is made of N,N'-4,4'-diphenylmethane-bis-maleimide, also known as 4,4'-bismaleimidodiphenylmethane.
In harmony with the teachings of U.S. 4,100,140, bis-imides and tris-imides containing phosphorus can also be ~sed:

- :~2~5~

(O -A') O
~ (- A N \ / D)3_q wherein A' and A" are optionally substituted aromatic radicals or aromatic radicals which are interrupted by an oxygen atom, an alkylene group or a sulfonyl group, D
is as defined above, Z is oxygen or sulfur, q is 1 or 0.
These are described in German Published Patent Applica-tion No. 2,350,471.
Illustrative examples of these are: the N,N'-bis-maleimide of 4,4'-diamino-triphenyl phosphate, the N ,N ' -bis-maleimide of 4,4'-diamino-triphenyl thiophosphate, the N,N',N'-tris-maleimide of tris-(4-aminophenyl) phosphate and the N,N',N"-tris-maleimide of tris-(4-aminophenyl) thiophosphate.
As mentioned, the invention contemplates the use also of mixtures of two or more of all of the above-mentioned polyimides. In addition, mixtures of polymides with monoimides containing the radical D above defined can also be employed according to the invention.
The polyamines used as component (b)(i) will be oE the general formulae:

~-(NH2) or ~ r ~ ~ ~
- R~ -35 wherein G is a y-valent organic radical having 2 to 40 ~L 27~
12 . 61109-7449 carbon atoms and y is an inte~er from 2 to 4, and each R is a divalent hydrocarbon radical obtained by removing the oxygen a~om o~ an aldehyde ~rketone having 1 to 8 carbon atoms, and m represents a number from 0.1 to 2.
The polyamines of the formulae are known compounds. If the polyamine is a diprimary polyamine, G has the same meaning as A above and y denotes 2.
A preferred family of amines are arylene polyamine compounds of the formulae:
. Q ~N~l2)y or ~ R ~ R

wherein Q is a divalent radical comprising at least two aryl radicals attached directly to each other or through a member selected from an alkylene radical, straight chain or branched, of from 2 to 12 carbon atoms, -S-, -S02-, -C0-, -0-, -C02-(CH2)p-C02-wherein p ls from 2 to 12, or Q is a divalent radical comprising an aliphatic or cycloaliphatic radlcal, straight chain or ~ranched, o~ from 2 to 12 carbon atoms, which may also contaln ~ O O
Il 11 -S-, -S02-, -C-, -O-, -C-0-, and the like, or a mixture of any of ~Q~
12a 61109-7449 the foregoing members, and y' is 2, R each are divalent hydrocarbon radicals obtained by removing the oxygen atom of an aldehyde or ketone having 1 to 8 carbon atoms, and m is a number of from 0.1 to 2. Preferably R i5 CH2 and m has an average value sufficient to provide an equivalent ~7eight of about 50 to 53.
Illustrat,ive of diamines are: ~,4'diaminodicyclo-hexylmethane, 1,4-diaminocyclohexane, m-phenylene-I

~Z~ 3~
o diamine, p-phenylenediamine, 4,4'-diamino-diphenylmethane, bis-(4-aminophenyl)-2,2-propane, 4,4'-diamino-diphenyl ether, 4,4'-diaminodiphenylsulfone, 1,5-diaminoz?htha-lene, m-xylylenediamine, p-xylylenediamine, ethylene-diamine, hexamethylenediamine, bis-(gamma-aminopropyl)

-5,5-dimethyl-hydantoin and 4,4'-diaminotriphenyl phosphate, and the like. m-Phenylenediamine, 4,4'-di-aminodiphenylmethane, 4,4'diami.no-diphenyl ether, hexamethylenediamine, 4,4'diamino-triphenyl phos?hate or 4,4'-diamino-triphenyl thiophosphate are preferred.
Polyamines different from the diprimary poly-amines include those which have less than 40 car~on atoms and contain 3 or 4 NH groups per molecule. The ~H groups can be substitutents on a benzene ri.ng which is optionally substituted by methyl groups, or a naph-thalene ring, on a pyridine ri.ng or on a triazine ring.
They can also be substitutents on several benzen- rings which are linked to one another via a single valency bond, an atom or an inert group which have already been mentioned under the diprimary polyamines, or by one of the following groups O S
-N- , -CH~, -O-P-O- , -O-P-O- and -O-P-O-O O O
l l l Such polyamines include: 1,2,4-triaminoben-zene, 1,3,5-triaminobenzene, 2,4,6-triaminotoluene, 2,4,6-triamino-1,3,5-trimethylbenzene, 1,3,7-tri-amino-30 naphthalene, 2,4,4'-triaminophenyl, 3,4,6-triamino-pyridine, 2,4,4'-triaminophenyl ether, 2,4,4'-triamino-diphenylmethane, 2,4,4'-triaminodiphenyl-sulfone, 2,4,4'-triaminobenzophenone, 2,4,4'-triamino-3-methyl-diphenylmethane, N,N,N-tri(4-aminophenyl)-amine, tri-(4-aminophenyl)-methane, tri-(4-aminophenyl) 5 ~ ~ ;~

o phosphate, tri-t4-aminophenyl) phosphite, tri-(4-amino-phenyl) thiophosphate, 3,5,4'-triaminobenzanilide, melamine, 3,5,3,5'-tetraaminobenzophenone, 1,2,4,5--tetraaminoben'zene, 2,3,6,7-tetraaminoaphthalene, 3,3'-diaminobenzidine, 3,3',4,4'-tetraaminophenyl ether, 3,3',4,~'-tetraaminodiphenylmethane, 3,3',4,4'-tetra-aminodiphenylsulfone and 3,3-bis-(3,3'-diamino-phenyl)-py~idine.
The polyamines of the second formula are known compounds and can be obtained in accordance with the processes described in French Patent Specifications 1,430,977 and 1,481,935 by reacting primary aromatic amines with aldehydes or ketones. Examples of aldehydes or ketones used are formaldehyde, acetaldehyde, benzaldehyde, oenanthaldehyde, acetone, methyl ethyl ketone, cyclohexanone and acetophenone.
Mixtures of 2 or more polyamines of the formulae can also be reacted with the polyimides and/or allyl-phenols and/or all'yl-phenolethers.
The allylphenols and methallylphenols, or the ethers thereof, used as component (b)(ii) herein are preferably employed as the alkenylphenols or alkenylphenol ethers. Both mononuclear and polynuclear, preferably binuclear, alkenylphenols and alkenylphenol ethers can be employed. Preferably, at least one nucleus contains both an alkenyl group and a phenolic, optionally etherified, OH group.
Alkenylphenols can be made by rearrangement of the alkenyl ethers of phenols (for example oE the allyl ether of phenol) by the action of heat (Claisen rearrange-ment). These alkenyl ethers are also obtained according to known processes by reacting phenols and, for example, allyl chloride in the presence of an alkali meta~ hydroxide and solvents. By so doing, a condensation reaction takes place with elimination of alkali metal chloride.

~7~

Typical binuclear alkenylphenols are of the formula:
CH -CH = CH2 HO ~ -(R ) 2 ~ ~ ~ OH

CH =C~ - CH2 in which R and n have the meanings set forth above.
The use of mixtures of polynuclear alkenyl-phenols and/or alkenylphenol ethers with mononuclear alkenylphenols and/or alkenylphenol ethers is also with-in the invention. The alkenylphenol ethers preferably employed are those substances which contain one or more molecular radicals of the formula:

O - R

wherein R is an alkyl radical of 1 to 10 carbon atoms, an aryl radical or an alkenyl radical, preferably allyl or methallyl~ the O atom in the formula representing the phenolic ether bridge.
A further feature of the invention comprises using mixtures of those substances which contain only one OH group and only one alkenyl group on the aromatic nucleus with substances which contain several OH groups and/or several alkenyl groups on the aromatic nucleus, or of mixtures of the corresponding phenol ethers of these substances.
Illustrative of alkenylphenols useful in the invention are: o,o'-diallyl-bisphenol A, 4,4'-hydroxy-3,3'-allyldiphenyl, bis-(4-hydroxy-3-allylphenyl)-methane, 2,2-bis-(4-hydroxy-3,5-diallyl-phenyl)-propane and _ 16-eugenol. The corresponding methallyl compounds can also be used. In place of the said alkenylphenols it is also possible to use the corresponding ethers of these phenols, especially the methyl ëthers.
As has been mentioned above, in the present compositions, if N represents the number of moles of bisimide (a) employed, N represents the number of moles of polyamine employed, and N represents the number of moles of allylphenol and/or allylphenol ether employed, and y or m represents the valence of the amine or amines, then the ratios Nl _ - or 2 3 2(m + l)N2 + N3 are greater than 0.3. Preferably, the amounts of reactants are chosen so that the ratio is between 1.3 and 10, especially preferably between 1.5 and lO. The amounts of polyamine (b)(i) and allylphenol and/or allylphenol ether (b)(ii) are generally so chosen that y N

is between 0.05 and 20, preferably between 0.1 and lO.
As has been mentioned above, in the process of the present invention, the maleimides in which D contains a carbon-carbon double bond, are reacted with a combina-tion of a polyamine and an alkenylphenol and/or alkenyl-phenol ether, optionally in the presence of polymerisation catalysts.
In most cases the reaction according to the invention is carried out at temperatures of 20 to ?

250C. and preferably of 100 to 250C.
Also according to the invention, the reaction can be carried out in the presence of phenols, such as, for example, carbolic acid, cresol and bisphenol A.
That is to say commercial alkenylphenols, and the corresponding ethers, which still contain residues of the phenols used as the starting materials, can also be employed for the reaction according to the invention.
Polymerisation catalysts useful in the inven-tion are ionic and free-radical catalysts. They may be present in the reaction mixture in a concentration of 0.1 to 10% by weight, preferably of 0.1 to 5% by weight, based on the total amount of the reactants.
As ionic catalysts, there can be used tertiary or secondary amines or amines which contain several amino groups of different types (for example mixed tertiary/secondary amines) and quaternary ammonium compounds. The amine catalysts can be monoamines or polyamines. When secondary amines are used, monoamines are preferred~ Illustrative are: diethylamine, tri-butylamine, triethylamine, triamylamine, benzylmethyl-amine, tetramethyldiaminodiphenylmethane, N,N-diisobutyl-aminoacetonitrile, N,N-dibutylaminoacetonitrile, hetero-cyclic bases, such as quinoline, N~methylpyrrolidine, imidazole, 2-phenyl imidazole, benzimidazole and their homologues, and also mercaptobenzothiazole. Also suitable are benzyltrimethylammonium hydroxide and benzyltri-methylammonium methoxide, and the like.
Also suitable as ionic catalysts are alkali metal compounds, such as alkali metal alcoholates and alkali metal hydroxides. Sodium methylate is preferred.
As free-radical polymerization catalysts can be employed organic peroxides and hydroperoxides as well as azoisobutyronitrile. In this case also, the preferred 35 concentration is 0.1 to 5.0% by weight.

5~Z

Further polymerisation catalysts which can be employed for the process according to the invention are acetyl-acetonates, especially the acetyl-acetonates of the transistion metals. Special mention is made of the corresponding vanadium compound.
The reaction according to the invention is preferably carried out in the melt, or partly in the melt and partly in the solid phase. However, it can also be carried out in solution. In most cases, however, the addition of solvents can be dispensed with because the starting mixtures as such are already of sufficiently low viscosity even at medium temperatures (for example at 120C.). When the process is carried out in the melt, temperatures of 100 to 250C. are particularly suitable.
The following substances can be listed as examples of suitable solvents: chloroform, methylene chloride, methyl cellosolve, dioxane, tetrahydrofuran, dimethylformamide, tetramethylurea and N-methyl-pyrrolidone.
The process according to the invention canalso be carried out in two stages, in the following manner. After all of the starting materials have been mixed, and optionally after subsequent grinding of the mixture, the powder or the liquid is first heated for a limited time to, preferably, 120-170C. A product which can still be molded by the action of heat and, in some cases, is soluble is formed. If necessary, this prepolymer must be ground again to give a powder which can be processed, before it is finally cured during rinal processing. The pre-polymerisation can also be carried out by heating a solution or suspension of the starting materials.
As a rule, the preparation, according to the invention, of the crosslinked polymers containing imide ~ ~7 ~

groups is carried out with simultaneous shaping to give shaped articles~ sheet-like structures, laminates, adhesive bonds or foams. The additives customary in the technology of curable plastics, such as fillers, plasticizers, pigments, dyestuffs, mold-release agents and flame-retarding substances, can be added to the curable compositionsl Examples of fillers which can be used are glass fibers, mica, graphite fiber, quartz fiber, polyaramid fiber (KEVLAR~), kaolin, colloidal silica or metal powders and examples of mold-release agents which can be used are silicone oil, various waxes, zinc stearate or calcium stearate and the like.
Shaping of the product which can be manufactured by the process according to the invention can be effected in an extremely simple manner by a casting process using a casting mold. Shaping can also be carried out by hot molding using a press. Usually it suffices when the product is heated only briefly to temperatures of 170 to 250~C. under a pressure of 1 to 200 kg/cm and the molding, thus obtained, is fully cured outside the press.
The process according to the invention and the polyaddition products which can be produced by this pro-cess can be used in manufacturing castings, surface protection, electrical engineering, laminating processes, adhesives, in the manufacture of foams and in the building trades.

DESCRIPTION OF THE PREFERRED EI~BODI~ENTS
The following non-limiting examples illustrate the compositions and methods of the present invention and its advantages over compositions representative of the state of the art. All parts and percentages are by weight.

~ ~7 ~ !
_ 20 -EXA~PLES 1-3 ~ eighed amounts of the bismaleimide of 4,4'--diaminodiphenylmethane, o,o'-diallyl bisphenol A (~.S.
4,100,140, Cols. 6-7) and the respective polyamines are heated to 120 to 150C. and the melt is degassed and poured into molds preheated to 150C. The mixtures are heated in an oven, in a first stage to 177C~ for four hours and in a second stage to 232C. for four hours.
After cooling slowly, castings are obtained and physical, and flexural properties are determined by the following procedures: The flexural test is described in ASTM
D-790, Method I. Dynamic mechanical analysis was performed on a Dupont 981 Dynamic Mechanical Analyzer, and T was defined as the temperature at which the loss tangent, tan ~ , is a maximum. ASTM D4065 test method covers this type oE T measurement. Conditionihg before testing is described g~y the phrases "wet" and "dry".
"Wet" refers to conditioning for two weeks at 71C.;
"Dry" means testing a sample, as prepared, at 23C.
For comparison purposes, a two component polyimide/allylphenol mixture according to the prior art (U.S. 4,100,140) is prepared and tested. The formulations used and the results obtained are set forth in Table 1:

~LZ7~5~

~ o ,~
o ~ u~ ~ o 1 o ~ ~ ~ ~

,_ ~ ~1 --~ ~r I I ~ o~ o o ' ~ ~ ~ ~ er c~
10 E~
~ .
O u~
~1 u~ .
z æ ~ o ~
O o ~o ~r ~ . . . ~ 1-- ~ ~ ~1 ~ ~
H ~ O o o ~1 ~1 ~ U~ ~r O ~
~0 ~ V ~ ~ ~ V ~ ~ ~
~ s Z ~~ ~ ~ ~ ~ ~ ~ ~,~ C~ ~1 ~ C) ~
~ --~ 3 ~ ~ 3 ":1 ~ 3 ~ ~ 3 ~ ":1 3 '1:5 ~: :~
a ~:V V ra~ ~ -~s e ~ e ~
3 ~ ~ ~
a ~ c ,1; ~ c O
u~ ~ ~ ~ c ~
o ~ x a) s ~ ~ o ~ ~ ~ O S ~ E~
~ ~ ~ 0 ~ E s ~ c ~ ~ o c ~ ~ ~ ~ o C~O ~ ~ C .r~ O ~ m ~ c .. ~ ~ ~ c _1 1 _~
..~ u~ ~ o ~3 ._~ .~ 1 ~ 1 ~ ~ L~ ~ ~
u~ ~ ~ I ra. c ~ ~ v ~ o w ~ ~ ! ! , l ,, a) ~ n 3 o c ~ ~ e ~ o ~ o ~ ~, 3 5 ~: x ~ ~ o ~ ~" b ~u 3 E~

-The foregoing data demonstrate that the compositions accordin~ to this invention are unexpectedly superior in heat resis-tance, (higher Tg's), hot/wet properties, and/or resistance to thermal decomposition (properties retained after thermal aging).
The following Examples 4-6 illustrate the inventionO
They represent work done by applicant~' co-worker, Bruce Allen Stern, and they form the subject matter of United States Patent 4,608,426 and of Canadian Application 500,393.

lo One hundred parts of a mixture of the bis-maleimides of methylene dianiline (64 percent), trimethylhexamethylene diamine (15 percent) and toluene diamine (21 percent) (KERIMID ~ 353, Rhone-Poulenc) were mixed with 10 parts by weight of 3,3'-aiamino-diphenyl sulfone, 25 parts of o,o'-diallyl-bis-phenol A (CIBA-Geigy) and 0.25 parts of 2-ethyl-5-methylimidazole. Five parts of a fine-ly divided silica (CABOSIL ~ M 5) was added as a thixotrope. The composition gelled at a temperature of 350F. in 12 minutes. The bis-maleimide without 2-ethyl-4-methylimidazole required more than 20 minutes at a temperature of 350F. to gel.
The composition is used to impregnate graphite and carbon fibrous reinforcements in the form of tapes. The resin contents range from to 28 parts to 42 parts per 100 parts of resin plus fiber. The tapes are assembled into layers and consolidated under heat (350-400F.) and moderate pressure (40-100 psi) into lamina~ed panels. Good panels are obtained, with low shrinkage, - 22a - 61109-7449 ~:7~
well controlled, low flow, no blistering, having good thermal stability and excellent impact strength. The properties obtained will be tabulated hereafter for comparison with state of the art - systems~ Example 4 comprises inter-5~3~
-23 ~

mediate modulus carbon fibers (Hercules IM-6); Example 5 comprises high strength fibers (Celanese, CELION~ 6000).

The resin composition of Examples 4 and 5 is used to impregnate glass and quartz fibrous reinforcements in the form of fabric. The resin contents range from 25 to 40 parts per 100 parts of resin plus fiber. The impregnated fabric material is consolidated under heat and pressure into laminated shapes which are suitable for radomes. Good panels are obtained with low flow, low shrinkage, no blistering, good thermal stability and excellent impact strength.

PROCEDURE A
For comparison purposes, a state-of-the-art bis-maleimide system (U.S. 4,454,283) was formulated, and laminates comprising unidirectional graphite fiber tapes were impregnated with it and tested. 85 parts of the mixture of bis-maleimides used in Example 4 herein, 27 parts of 55 percent divinyl benzene, 5 parts of the trifunctional curing agent, triallyl isocyanurate and 1 part of the oxidation inhibitor, hydroquinone. During preparation and use as an impregnant for the graphite tapes, toxic odors and poor handleability were encoun-tered. The resin contents ranged from 25 to 40 percent.
The tapes were consolidated under heat and pressure into laminated panels. Good appearing panels were obtained but the impact performance was poor, and edge delamina-tion, especially, was found to be a problem. The proper-ties obtained will be tabulated hereafter for comparison with the compositions of this invention and that of another state-of-the-art system~

3~

PROCEDURE B
For comparison purposes, a second and different bis-maleimide system (U.S. 4,100,140) was formulated, and l'aminates comprising'unidirectional graphite fiber tapes were impregnated with it and tested. One hundred parts of N,N'-4,4'-diphenylmethane-bis-maleimide (CIBA-Geigy XU-292A) and 75 parts of o,o'-diallyl~bisphenol-A (CIBA-Geigy XU-292B) are melted at 70-100C. and 5 parts of a finely divided fumed colloidal silica (CABOSIL~ M 5) are added as a thixotrope. The melt is used to impregnate graphite or carbon fibrous reinforcements in the form of tapes. The resin contents range from 25 to 40 parts per 100 parts of resin plus fiber. The tapes are assembled into layers and consolidated under heat and pressure into laminated panels. Good panels were obtained with no blistering. The toughness as measured by impact testing was good, but properties measured on the hot panels were not as good and when measured on hot panels after exposure to moisture, they were much worse.
Flexural modulus, as a specific example, when measured on a dry panel at 450F~ was poor, and could not even be measure~ after the panel had been exposed to moisture.
The data obtained after measuring important physical properties are summarized in Table 2:

~7~)5~

TABLE 2: PROPERTIES OF COMPOSITES COMPRISING GRAPHITE
BIS-MALEIMIDE RESINS

Composition-(parts by weight?
Bis-maleimide/m-DDS/
o,o'-diallyl BPA 28-42 -- -- 28-42 Bis-maleimide/DVB -- 25-40 -- --Bis-maleimide/o,o'~
diallyl BPA -- -- 25-40 --Reinforcing graphite fibers Balance* Balance* Balance** Balance**
Pro~erties Impact Strength, peel apart mode, G , in.lbs./in 0.98 0.79 -- --Impact Strength, shear mode, 2 G , in.lbs./in 2.04 1.13 -- --Incipient Impact Energy, IIE, ft.lbs./mil. 4.49 1.80 -- ~-Impact damage area, 10 ft.-lbs. (in ) 1.02 3.73 -- --Edge Delamination Resistance Stress at first crack, ksi 26 14-16 41 40.9 Stress at failure, ksi 76 -- 98 68.6 Flexural modulus Dry 30 Room temp.,psi x 10 18.6 -- 19.6 17.9 450F., psi x 10 18.6 -- 10.3 16~7 Wet -6 too poor 450F., psi x 10 _ 13.5 ~ to measure 10.6 _ * Intermediate Modulus, IM6 ** High Strength, CELION

o From the foregoing results it is evident that the resin compositions according to this invention (Examples 4 and 5) provides good laminated panels with excellent toughness as represented by impact testing and by resistance to edge delamination, making it substan-tially superior to the first state-of-the-art system tA), and demonstrating thermal and moisture resistance, as represented by flexural modulus test results, substantially superior to the second state-of-the-art system (B).

~ r The general procedure of Examples 1 and 2 was repeated, making modifications in the formulations and neat resin castings are made and tested. The formulations used and the results obtained are set forth in Table 3:

~;~7~592 o cn H
10 ~
O ~r o ~r u~ a~ o r~
o ~ u~ ~ cn ~ o Ln o Lf I o ~ o~ o c,o c~ I / ~1 ~ ~ I o o o o ~ ~ ~ u~ ~r In CO ~n u~
z O O ~ ~ ~
1 c H ~1 ~ ~ Ln O Lt~ t--L ~ ~ ~ O O ~O
H O I r-l I a:~ ~ Il 1-- ~1 f~l U~ ~ 00 0 0 ~ ~1 O , O ~ ~ V V ~ ~ V V
C_~ * O O O O O O O O
a) ~u ~ c s s .c s s 5::
O C >~, ~ ~ ~,~, ~ ~ .,, ~ ~ ~ ~ ~ :~
Z v 2 0 x ~ ~:s ro 3 ~ ") 3 ~ ~:1 3 ~ ~ 3 ~ e ~ ~
u~
QJ ~ ~ ~ _ c ~ ~ ~ ~r a ~ c la 'JJ aJ ~
v ~ s r~ s: a e ~ ~ Q
z tJ e ,~ c ~ e H ~1 ~ ) Oa) 1~
2 ~ ~: ~ ~ ~~ x c c ~, ~ o a~
s s ~ I a~
a ~ Ql Q~ O 'r ~ ":5 C
H ~ ~--IC I ~ ~1 '~I U~
~ U~ '1~ _ H ~) O O.C X ~J ~1 H 4 1.~ ~ ~Ql O .C~
-l 1~ ~ >1 H K a~ u~
~: ~ e E~ S u~ ~_, ~
:~: ~_ U~ ~ l Ql O O ,~: I v~
H C ~ O C e ~ v ~ o m o ~1 . u, u, ~ c JJ
.~, e e ~ ~ e er a) ~ c ,~
.. ~) u~ E ~ I ~ ,~ H
r~ ~ ~_1 ~1 V ~ :~
1:¦ u~ .~ ~ v v o ~ H
CL1 P~ O I II t~l I .C ~J O' U~ U~ 3 ~
~:1 5~ 1~ _ _ _ I - .IJ Q ~ ~1 m ~ e ~r ~ o ~ o ~ ~
O ~ 1 ~ w G
E~ ~ ~) ~ ~r O Q t~ ~Ll 3 E-l ~

iq3~

o,o'-Diallylbisphenol A, 1963 g. was heated to 200F., then 3505 g. of the bismaleimide of methylene dianiline was added. After the bismaleimide was thorough-ly mixed, meta-diamine diphenylsulfone, 427 g., and fumed colloidal silica (CABOSIL), 105 9. were added and mixing was continued for 10 minutes. This mixture was - coated onto unidirectional graphite (CELION~ 6000).
This unidirectional tape was cut and laid up and cured 4 hours at 350F. and 4 hours at 440F. to give a laminate with the properties set foth in Table 4 (supra).

' EXAMPLE 10 To 1913 g. of o,o'-diallylbisphenol A which has been heated to 200F. was added 741 g. of KERIMID~
353 (see Example 4) and 2966 g. of the bismaleimide of methylene dianilini after 10 min., 111 g. of fumed colloidal silica, 260 g. of meta-diaminodiphenyl sulfone, and 9.3 g. of 2-ethyl-4-methylimidazole were added.
This mixture was coated onto unidirectional graphite fibers (to make ~graphite tape" prepreg). The prepreg was laid up and cured for 4 hours at 350F. and 4 hours at 440F. to give a high'quality laminate with proper-ties set forth in Table 4:

~Z7~5~3;~:

TABLE 4: PROPERTIES OF COMPOSITES COMPRISING GRAPHITE
AND BIS-MALEIMIDE RESINS

S ~_ Bis-maleimide/m-DDS/o,o'-diallyl BPA 28-42 --Bis-maleimide mixture/o,o'-diallyl BPA/m-DDS -- 28-42 Reinforcing graphite fibers, CELION~ Balance ~alance Edge Delamination Resistance Stress at first crack, ksi 42.2 27.1 Stress at failure, ksi 101.8 79.0 Flexural modulus 15 ~Y -6 Room temp., psi x 10 20.1 14.4 Wet 6 350F., psi x 10 18.2 13.0 -` ~27Ç~
- 30 - 61109-74~9 From the foregoing results it i5 evident that the resin compositions according to this invention (Examples 9 and 10) pro-vide good laminated panels with excellent toughness as represented by resistance to edge delamination and demonstrating thermal and moisture resistance, as represented by flexural modulus test results.
Many variations in the present invention will suggest themselves to those skilled in this art in light of the above detailed description. For example, instead of a bis-maleimide derived from maleic acid, one derived from citraconic or tetra-hydrophthalic acid can be used. Instead of 3,3'-diaminodiphenyl sulfone, 4,4'-di(3,3'-aminophenoxydiphenyl)sulfone can be used.
Instead of o,o'-diallyl bisphenol A, 4,4'-hydroxy-3,3'-allyldi-phenyl can be used. Instead of 2-ethyl-4-methylimidazole, 2-phenyl imidazole can be used. Instead of fibrous graphite or car-bon, glass or quartz reinforcements, ceramic fibers, such as 3M
Company's NEXTEL ~ fibers, and DuPont Company's KEVLAR ~ aramid fibers can be used. All such obvious modifications are within the full intended scope of the appended claims.

Claims (37)

29,825 WHAT IS CLAIMED IS:
.

1. A composition which is stable on storage and can be cured by the action of heat, said composition comprising (a) a heat curable polyimide resin containing, per average molecule, at least two groups of the formula directly attached to carbon atoms, wherein D is , , or or a mixture thereof; and (b) a heat-activated curing agent for said polyimide resin comprising, in combination, (i) a polyamine of the formulae:

or wherein G denotes a y-valent organic radical having 2 to 40 carbon atoms and y is an integer of 2 to 4, each R
represents a divalent hydrocarbon radical obtained by removing the oxygen atom of an aldehyde or ketone having 1 to 8 carbon atoms, and m is a number of from 0.1 to 2 and (ii) an alkenylphenol or an ether thereof in amounts such that if N1 represents the number of moles of polyimide employed, N2 represents the number of moles of polyamine employed and N3 represents the number of moles of alkenylphenol or ether thereof employed, the ratio or being greater than 0.3, y or m being defined as above.

2. A composition as defined in Claim 1 wherein component (a) comprises a mixture of heat curable poly-imide resins of the formula wherein D is or a mixture thereof, and Z is the residue of at least one aromatic diamine and in the minor proportion of the mixture, Z is the residue of an aliphatic diamine.

3. A composition as defined in Claim 2 wherein from 75 to 95 parts by weight of 100 parts of the mixture consists of bis-imides derived from aromatic diamines.

4. A composition as defined in Claim 2 wherein the polyimide is a bis-maleimide derived from at least one diamine selected from ethylene diamine, hexamethylene diamine, phenylene diamine, trimethylhexamethylene diamine, methylene dianiline, toluene diamine, 4,4'-diphenylmethane diamine, 4,4'-diphenyl-ether diamine, 4,4'-diphenylsulfone diamine, 4,4'-dicyclohexanemethane diamine, metaxylene diamine, 4,4'-diphenylcyclohexane diamine, 3,3'-diphenylsulfone diamine or a mixture of any of the foregoing.

5. A composition as defined in Claim 2 wherein the mixture of polyimides has a melting point between 70° and 125°C.

6. A composition as defined in Claim 4 wherein the mixture of bis-maleimides is derived from diamines consisting essentially of 50 to 80% methylene dianiline, 5 to 30% toluene diamine and 5 to 25% of trimethyl hexamethylene diamine.

7. A composition which is stable on storage and can be cured by the action of heat which comprises (a) a polyimide of the formula wherein R1 is hydrogen or methyl, and A is a divalent radical of the formula in which R2 is selected from the group consisting of -CH2-, -SO2-, -SO-, -S- and -O-, and n is 0 or 1; or a poly-imide selected from the N,N'bis-maleimide of 4,4'-diaminotriphenyl phosphate, the N,N' bis-maleimide of 4,4'-diamino-triphenyl thiophosphate, the N,N',N'-tris-maleimide of tris-(4-aminophenyl) phosphate, the N,N',N"-tris-maleimide of tris-(4-aminophenyl) thiophosphate; or a mixture of said polyimides;
and, (b) a heat-activated curing agent for said polyimide (a) comprising, in combination, (i) an arylene polyamine compound of the formula , or wherein X is selected from hydrogen, lower alkyl, halogen, or mixtures thereof, and Q is a divalent radical comprising at least two aryl radicals atached directly to each other or through a member selected from an alkylene radical, straight chain or branched, of from 2 to 12 carbon atoms, -S-, -SO2-, -CO-, -O-, -CO2-(CH2) -CO2- wherein p is from 2 to 12, or a mixture of any of the foregoing members, and y' is 2, R each are divalent hydrocarbon radicals obtained by removing the oxygen atom of an aldehyde or ketone having 1 to 8 carbon atoms, and m is a number of from 0.1 to 2; and (ii) an alkenylphenol selected from o,o'-diallyl-bisphenol A, 4,4'-dihydroxy-3,3'-diallyldiphenyl, bis-(4-hydroxy-3-allylphenyl) methane, 2,2-bis-(4-hydroxy-3,5-diallylphenyl)propane, eugenol, o,o'-dimethallyl-bisphenol A, 4,4'-dihydroxy-3,3'-dimethylallyldiphenyl, bis-(4-hydroxy-3-methallylphenyl)methane, 2,2-bis-(4-hydroxy-3,5-dimethallylphenyl)propane or 4-methallyl-2-methoxyphenol; or an alkenylphenol ether selected from 2,2-bis(4-methoxy-3-allylphenyl) propane, 2,2-bis(4-methoxy-3-methallyphenyl)propane, 4,4'-dimethoxy-3,3'-diallyldiphenyl, 4,4'-dimethoxy-3,3'-dimethallyldiphenyl, bis(4-methoxy-3-allylphenyl)methane, bis(4-methoxy-3-methallylphenyl)methane, 2,2-bis(4-methoxy-3,5-diallyl-phenyl)propane, 2,2-bis-(4-methoxy-3,5-dimethallyl-phenyl)propane, 4-allylveratrole or 4-methallylveratrole;
or a mixture of said alkenylphenols, a mixture of said alkenylphenol ethers or a mixture of said alkenyl-phenols and said alkenylphenol ethers;
in amounts such that if N1 represents the number of moles of polyimide employed, N2 represents the number of moles of polyamine employed and N3 represents the number of moles of alkenylphenol or ether thereof employed, the ratio or being from 0.3 to 10, y' or m being defined as above.

8. A composition as defined in Claim 7 wherein polyimide (a) comprises 4,4'-bismaleimidodiphenylmethane.

9. A composition as defined in Claim 7 wherein said arylenepolyamine compound (b)(i) is of the formula

10. A composition as defined in Claim 7 wherein said arylenepolyamine compound (b)(i) is of the formula

11. A composition as defined in Claim 7 wherein said arylenepolyamine (b)(i) is of the formula m having an average value sufficient to provide an equivalent weight of about 50 to 53.

12. A composition as defined in Claim 7 wherein component (b)(ii) comprises o,o'-diallylbisphenol-A, a compound of the formula

13. A composition as defined in Claim 7 wherein (a) said polyimide comprises-4,4'-bis-maleimidodiphenyl methane;
(b)(i) said arylenepolyamine compound is of the formula ; and (b)(ii) said alkenylphenol comprises o,o'-diallyl-bisphenol A.

14. A composition as defined in Claim 7 wherein (a) said polyimide comprises 4,4'-bismaleimido-diphenylmethane;
(b)(i) said arylenepolyamine compound is of the formula ; and (b)(ii) said alkenylphenol comprises o,o'-diallyl-bisphenol A.

15. A composition as defined in Claim 7 wherein (a) said polyimide comprises 4,4'-bismaleimido-diphenylmethane;
(b)(i) said arylenepolyamine compound is of the formula m having an average value sufficient to provide an equivalent weight of about 53; and (b) (ii) said alkenylphenol comprises o,o'-diallyl-bisphenol A.

16. A composition as defined in Claim 7 which additionally contains, in a concentration of 0.1 to 10%
by weight, based on the total amount of the reactants, a polymerization catalyst selected from an ionic catalyst, a free-radical polymerization catalyst or a transition metal acetylacetonate.

17. A composition as defined in Claim 16 wherein said polymerisation catalyst is present in a concentration of 0.1 to 5.0% by weight, based on the total amount of the reactants.

18. A composition as defined in Claim 1, con-taining polyimide (a), the arylenepolyamine (b)(i) and the alkenylphenol or alkenylphenol ether (b)(ii) in the form of a prepolymer.

19. A process for the preparation of a cross-linked polymer containing imide groups comprising reacting at a temperature of 20° to 250°C., (a) a heat curable polyimide resin containing, per average molecule, at least two groups of the formula directly attached to carbon atoms, wherein D is , , or or a mixture thereof; and (b) a heat-activated curing agent for said polyimide resin comprising, in combination, (i) a polyamine of the formulae:

or wherein G denote a y-valent organic radical having 2 to 40 carbon atoms and y is an integer of 2 to 4, each R
represents a divalent hydrocarbon radical obtained by removing the oxygen atom of an aldehyde or ketone having 1 to 8 carbon atoms, and m is a number of from 0.1 to 2 and (ii) an alkenylphenol or an ether thereof, in amounts such that if N1 represents the number of moles of polyimide employed, N2 represents the number of moles of polyamine employed and N3 represents the number of moles of alkenylphenol or ether thereof employed, the ratio or being greater than 0.3, y or m being defined as above.

20. A process as defined in Claim 19 wherein component a comprises a mixture of heat curable polyimide resins of the formula wherein D is or or a mixture thereof, and Z is the residue of at least one aromatic diamine and in the minor proportion of the mixture, Z is the residue of an aliphatic diamine.

21. A process as defined in Claim 20 wherein from 75 to 95 parts by weight of 100 parts of the mixture consists of bis-imides derived from aromatic diamines.

22. A process as defined in Claim 19 wherein the polyimide is a bis-maleimide derived from at least one diamine selected from ethylene diamine, hexa-methylene diamine, phenylene diamine, trimethylhexamethy-lene diamine, methylene dianiline, toluene diamine, 4,4'-diphenylmethane diamine, 4,4'-diphenyl-ether diamine, 4,4'-diphenylsulfone diamine, 4,4'-dicyclohexanemethane diamine, metaxylene diamine, 4,4'-diphenylcyclohexane diamine, 3,3'-diphenylsulfone diamine or a mixture of any of the foregoing.

23. A process as defined in Claim 20 wherein the mixture of polyimides has a melting point between 70° and 125°C.

24. A process as defined in Claim 20 wherein the mixture of bis-maleimidesis derived from diamines consisting essentially of 50 to 80% methylene dianiline, 5 to 30% toluene diamine and 5 to 25% of trimethyl hexamethylene diamine.

25. A process for the manufacture of a cross-linked polymer containing imide groups comprising reacting at a temperature of 20° to 250°C.
(a) a polyimide of the formula wherein R1 is hydrogen or methyl, and A is a divalent radical of the formula in which R2 is selected from the group consisting of -CH2-, -SO2-, -SO-, -S- and -O-, and n is 0 or 1; or a polyimide selected 41a 61109-7449 from the N,N'bis-maleimide of 4,4' diaminotriphenyl phosphate, the N,N'-bis-maleimide of 4,4'-diaminotriphenyl thiophosphate, the N,N',N'-tris-maleimide of tris-(4-aminophenyl) phosphate, the N,N',N"-tris-maleimide of tris-(4-aminophenyl) thiophosphate; or a mixture of said polyimides; and, (b) a heat-activated curing agent for said polyimide (a) comprising, in combination, (i) an arylene polyamine compound of the formula or wherein X is selected from hydrogen, lower alkyl, halogen, or mixtures thereof, and Q is a divalent radical com-prising at least two aryl radicals attached directly to each other or through a member selected from an alkylene radical, straight chain or branched, of from 2 to 12 carbon atoms, -S-, -SO2-, -CO-, -O-, -CO2-(CH2)p-CO2-wherein p is from 2 to 12, or a mixture of any of the foregoing members, and y' is 2, R each are divalent hydrocarbon radicals obtained by removing the oxygen atom of an aldehyde or ketone having 1 to 8 carbon atoms, and m is a number of from 0.1 to 2; and (ii) an alkenylphenol selected from o,o'-diallyl-bisphenol A, 4,4'-dihydroxy-3,3'-diallyldiphenyl, bis-(4-hydroxy-3-allylphenyl) methane, 2,2-bis-(4-hydroxy-3,5-diallylphenyl)propane, eugenol, o,o'-dimethallyl-bisphenol A, 4,4'-dihydroxy-3,3'-dimethylallyldiphenyl, bis-(4-hydroxy-3-methallylphenyl)methane, 2,2-bis-(4-hydroxy-3,5-dimethallylphenyl)propane or 4-methallyl-2-methoxyphenol; or an alkenylphenol ether selected from 2,2-bis(4-methoxy-3-allylphenyl) propane, 2,2-bis(4-methoxy-3-methallyphenyl)propane, 4,4'-dimethoxy-3,3'-diallyldiphenyl, 4,4'-dimethoxy-3,3'-dimethallyldiphenyl, bis(4-methoxy-3-allylphenyl)methane, bis(4-methoxy-3-methallylphenyl)methane, 2,2-bis(4-methoxy-3,5-diallyl-phenyl)propane, 2,2-bis-(4-methoxy-3,5-dimethallyl-phenyl)propane, 4-allylveratrole or 4-methallylveratrole;
or a mixture of said alkenylphenols, a mixture of said alkenylphenol ethers or a mixture of said alkenyl-phenols and said alkenylphenol ethers;
in amounts such that if N1 represents the number of moles of polyimide employed, N2 represents the number of moles of polyamine employed and N3 represents the number of moles of alkenylphenol or ether thereof employed, the ratio or is from 0.3 to 10, y' or m being defined as above.

26. A process as defined in Claim 19, wherein the reaction is allowed to proceed at a temperature of 100° to 250°C.

27. A process as defined in Claim 25, wherein polyimide (a) comprises 4,4'-bismaleimidodiphenylmethane.

28. A process as defined in Claim 25, wherein said arylenepolyamine compound (b)(i) is of the formula

29, A process as defined in Claim 25 wherein said arylenepolyamine compound (b)(i) is of the formula

30. A process as defind in Claim 25 wherein said arylenepolyamine (b)(i) is of the formula m having an average value sufficient to provide an equivalent weight of about 53.

31. A process as defined in Claim 25 wherein component (b)(ii) comprises o,o'-diallyl bisphenol-A, a compound of the formula

32. A process as defined in Claim 25 wherein (a) said polyimide comprises 4,4'-bis-maleimidodiphenylmethane;
(b)(i) said arylenepolyamine compound is of the formula ; and (b)(ii) said alkenylphenol comprises o,o'-diallyl-bisphenol A.

33. A process as defined in Claim 25 wherein (a) said polyimide comprises 4,4'-bis-maleimidodiphenylmethane;
(b)(i) said arylenepolyamine compound is of the formula ; and (b)(ii) said alkenylphenol comprises o,o'-diallyl-bisphenol A.

34. A process as defined in Claim 25 wherein (a) said polyimide comprises 4,4'-bis-maleimidodiphenylmethane (b)(i) said arylenepolyamine compound is of the formula m having an average value sufficient to provide on equivalent weight of about 53; and (b)(ii) said alkenylphenol comprises o,o'-diallyl-bisphenol A.

35. A process according to Claim 25 wherein the reaction of the polyimide component (a) and the alkenylphenol, alkenylphenol ether or mixture thereof component (b) is carried out in the presence of a poly-merization catalyst selected from the group consisting of an ionic catalyst, a free-radical polymerization catalyst and a transition metal acetylacetonate, said catalyst being in a concentration of 0.1 to 10% by weight, based on the total amount of reactants.

36. A process as defined in Claim 35, charac-terised in that a polymerisation catalyst is employed in a concentration of 0.1 to 5.0% by weight, based on the total amount of the reactants.

37. A crosslinked polymer prepared by the process of Claim 19.