Composition and method for making polyimide resin-reinforced fabric

Claim 2

In a composition of matter comprising a solution, in an organic solvent, of the following compounds: (a) a polyfunctional ester having the formula: ##STR4## wherein R 1 is a tetravalent acryl radical and R 2 is alkyl or hydrogen, at least two R 2 groups being alkyl; (b) a polyfunctional amine having the formula: H.sub.2 N-R.sub.3 -NH.sub.2 wherein R 3 is a divalent aryl radical; and (c) an end-capping agent having the formula: ##STR5## wherein R 2 is alkyl or hydrogen, at least one R 2 group being alkyl and R 4 is a divalent radical of the formula: ##STR6## wherein R 5 is hydrogen or lower alkyl; the molar ratio of a:b:c being n:n+1:2 wherein n has a value of 1-20, said compounds being present in an amount of 30 to 70% by weight of the solution, the improvement wherein said solution further comprises a copolymerizable, liquid, olefinic monomer compatible with the ingredients, said olefinic monomer having a boiling point of about 50° to 150° C., and being soluble in said solvent, the amount of said olefinic monomer dissolved in said solution being from 1 to 20% by weight based on the total weight of said polyfunctional ester, said polyfunctional amine, said end-capping agent, and said olefinic monomer.

Claim 3

An improved composition according to claim 1 wherein said olefinic monomer is selected from the group consisting of N-vinyl-2-pyrollidone; 5-vinyl-2-norbornene; 2,5-norbornadiene; and vinylbenzene.

Claim 4

In a method of forming a polyimide resin-reinforced fiber which comprises impregnating a fiber with a solution, in organic solvent, containing the following compounds: (a) a polyfunctional ester having the formula: ##STR7## wherein R 1 is a tetravalent aryl radical and R 2 is alkyl or hydrogen, at least two R 2 groups being alkyl; (b) a polyfunctional amine having the formula: H.sub.2 N-R.sub.3 -NH.sub.2 wherein R 3 is a divalent aryl radical; and (c) an end-capping agent having the formula: ##STR8## wherein R 2 is alkyl or hydrogen, at least one R 2 group being alkyl and R 4 is a divalent radical of the formula: ##STR9## wherein R 5 is hydrogen or lower alkyl; the molar ratio of a:b:c being n:n1:2 wherein n has a value of 1-20, said compounds being present in an amount of 30 to 70% by weight of the solution, in which the impregnated fabric is heated at an elevated temperature to form a prepreg material comprising polyimide prepolymer in said fabric and in which the prepreg material is heated at a higher elevated temperature to form a polyimide resin reinforcing said fabric; the improvement wherein the tack retention properties of said prepreg material are enhanced by including, in said solution, a copolymerizable, liquid, olefinic monomer compatible with the ingredients, said olefinic monomer having a boiling point of about 50° to 150° C., and being soluble in said solvent, the amount of said olefinic monomer dissolved in said solution being from 1 to 20% by weight based on the total weight of said polyfunctional ester, said polyfunctional amine, said end-capping agent, and said olefinic monomer, removing said solvent by heating said impregnated fibers at a temperature in the range of about 50° to 120° C., forming a prepolymer by heating said impregnated fiber at a temperature in the range of about 125° to 210° C., and heating the prepreg material at a temperature in the range of about 275° to 350° C. to form said polyimide resin.

Claim 5

In a method of forming a polyimide resin-reinforced fiber which comprises impregnating a fiber with a solution, in organic solvent, containing the following compounds: (a) a polyfunctional ester having the formula: ##STR7## wherein R 1 is a tetravalent aryl radical and R 2 is alkyl or hydrogen, at least two R 2 groups being alkyl; (b) a polyfunctional amine having the formula: H.sub.2 N-R.sub.3 -NH.sub.2 wherein R 3 is a divalent aryl radical; and (c) an end-capping agent having the formula: ##STR8## wherein R 2 is alkyl or hydrogen, at least one R 2 group being alkyl and R 4 is a divalent radical of the formula: ##STR9## wherein R 5 is hydrogen or lower alkyl; the molar ratio of a:b:c being n:n1:2 wherein n has a value of 1-20, said compounds being present in an amount of 30 to 70% by weight of the solution, in which the impregnated fabric is heated at an elevated temperature to form a prepreg material comprising polyimide prepolymer in said fabric and in which the prepreg material is heated at a higher elevated temperature to form a polyimide resin reinforcing said fabric; the improvement wherein the tack retention properties of said prepreg material are enhanced by including, in said solution, a copolymerizable, liquid, olefinic monomer compatible with the ingredients, said olefinic monomer having a boiling point of about 50° to 150° C., and being soluble in said solvent, the amount of said olefinic monomer dissolved in said solution being from 1 to 20% by weight based on the total weight of said polyfunctional ester, said polyfunctional amine, said end-capping agent, and said olefinic monomer, removing said solvent by heating said impregnated fibers at a temperature in the range of about 50° to 120° C., forming a prepolymer by heating said impregnated fiber at a temperature in the range of about 125° to 210° C., and heating the prepreg material at a temperature in the range of about 275° to 350° C. to form said polyimide resin.

Claim 6

An improved method according to claim 3 wherein said olefinic monomer is selected from the group consisting of N-vinyl-2-pyrollidone; 5-vinyl-2-norbornene; 2,5-norbornadiene; and vinylbenzene.