PURPOSE: To prepare a high-quality titled prepreg free from bubbles and residual solvent, by impregnating a substrate with an epoxy resin composition varnish containing a cure assistant such as an organic acid Sn salt and a curing agent such as poly-p-vinylphenol, etc., and drying the varnish.
CONSTITUTION: A substrate is impregnated with a varnish obtained by dissolving (A) an epoxy resin composition containing (i) one or more compounds selected from an organic acid Sn salt (e.g. di-n-butyltin dimalate, etc.), an aluminate of formulaI(R is alkyl or aryl; n is 1W5) (e.g. Al isopropoxide) and an alkoxy group-containing silane compound of formula II (R is alkyl; R' is alkyl or aryl; n is 0W4) (e.g. tetramethoxysilane, etc.) and (ii) a poly-p-vinylphenol (halide) in (B) a mixed solvent composed of 15W30pts.wt. of a ketone solvent having a boiling point of 50W90°C, 6W15pts.wt. of a cellosolve solvent having a boiling point of 110W140°C, and 2W6pts.wt. of a cellosolve acetate solvent having a boiling point of 140W160°C and/or a polar solvent. The varnish is dried to obtain the objective epoxy resin prepreg.
MATSUMURA MASAHIRO
KITSUTA YOSHIHIRO
