30 to 90 minutes then the non reactive solvent is added the molar ratio of oxoimine to dianhydride should be in the 0 1 1 to 10 1 range for best results the ratio of oxoimine should be from about 1 1 to 3 1 optimum results are obtained where this ratio is about 2 1 the bisimide produced by the preferred reaction of caprolactam and btca has the following general formula str4 any suitable non reactive solvent may be used as the diluant for the bisimide typical solvents include n methyl pyrrolidone dimethyl formamide dimethyl acetamide dimethyl sulfoxide and mixtures thereof as pointed out in example x of our u s pat no 4 442 283 where a reactive esterifying solvent is used higher proportions of btca when mixed with smaller proportions of btda tended to lower the thermal stability of the coating with the non reactive solvents of this invention and the processing conditions described below an excellent adhesive and fiber reinforced composited matrix material can be produced even with 100 btca once the solvent and bisimide are mixed or the solvent with the bisimide producing reactants the selected aromatic diamine or diamines are added to the solution preferrably an approximately stoichiometric quantity of diamine is used any suitable aromatic diamine may be used typical aromatic diamines include 4 4 39 diamino diphenyl ether 4 4 39 p phenylenediisopropylidene bisaniline 4 4 39 diaminodiphenyl oxide 4 4 39 diaminodiphenyl methane m phenylene diamine p phenylene.