Process for preparing thermosetting prepolymer from mixture of polyfunctional maleimide and bis-maleimide

A process for preparing a thermosetting maleimide prepolymer, which comprises heating, at a temperature of 100.degree. to 150.degree. C. for 10 to 60 minutes,

• (A) a polyfunctional maleimide compound obtained by the dehydration reaction of an amide acid formed from maleic anhydride and a polyamine prepared by the condensation of aniline with formaldehyde and represented by the formula (1):
• ##STR12## wherein n is in the range of from 0.1 to 3.0;
• (B) a bis-maleimide selected from the group consisting of N,N'-4,4'-diphenylmethane-bis-maleimide, N,N'-methylenebis-(3-chloro-p-phenylene)-bis-maleimide, N,N'-4,4'-diphenyl-sulfone-bis-maleimide, N,N'-4,4'-diphenyl-ether-bis-maleimide, N,N'-ethylene-bis-maleimide, N,N'-hexamethylene-bis-maleimide and combinations thereof;
• and
• (C) a diamine selected from the group consisting of 4,4'-diaminodicyclohexylmethane, 1,4-diaminocyclohexane, 2,6-diaminopyridine, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylmethane, 2,2'-bis(4-aminophenyl)propane, benzidine, 4,4'-diaminodiphenylsulfone, bis(4-aminophenyl) methylphosphine oxide, bis(4-aminophenyl)phenylphosphine oxide, bis(4-aminophenyl)methylamine, 1,5-diaminonaphthalene, m-xylylenediamine, p-xylylenediamine, hexamethylenediamine, 6,6'-diamino-2,2'-dipyridyl, 4,4'-diaminobenzophenone, 4,4'-diaminoazobenzene, bis(4-aminophenyl)phenylmethane, 1,1-bis(4-aminophenyl)cyclohexane, 1,1-bis(4-amino-3-methylphenyl)cyclohexane, 2,5-bis(m-aminophenyl)-1,3,4-oxadiazole, 2,5-bis(p-aminophenyl)-1,3,4-oxadiazole, 2,5-bis(m-aminophenyl)thialoro(4,5-d)thiazole, 5,5'-di(m-aminophenyl)-2,2'-bis(1,3,4-oxadiazolyl), 4,4'-diaminodiphenyl ether, 4,4'-bis(p-aminophenyl)-2,2'-dithiazole, m-bis(4-p-aminophenyl-2-thiazolyl)benzene, 4,4'-diaminobenzanilide, 4,4'-diaminophenyl benzoate, N,N'-bis(4-aminobenzyl)-p-phenylenediamine, 4,4'-methylenebis(2-chloroaniline) and combinations thereof;
• the weight proportion of the polyfunctional maleimide compound (A) relative to the total of the polyfunctional maleimide compound (A) and the bis-maleimide (B) being 10 to 80% and the molar ratio of the total of the polyfunctional maleimide compound (A) and the bis-maleimide (B) to the diamine (C) being 1:1 to 1:0.3.