Abstract

In one aspect, thermosetting liquid resinous polyepoxides are upgraded or advanced in molecular weight by a process including (A) providing a catalyst-free mixture of a dihydric phenol, preferably bisphenol-A and a liquid resinous polyepoxide containing 1,2-epoxy groups, preferably a low molecular weight epoxy resin consisting essentially of the diglycidyl ether of bisphenol-A, at a temperature above about a minimum reaction temperature for a catalytic liquid upgrade reaction between the dihydric phenol and the polyepoxide; and (B) subsequently introducing the catlyst, preferably an organic phosphine and most preferably triphenylphosphine, into the mixture of the dihydric phenol and polyepoxide at reaction temperature and maintaining the mixture containing the catalyst at reaction temperature for a time sufficient to produce the upgraded version of the thermosetting resinous polyepoxide. In another aspect, multiple catalyst additions are featured wherein, for example, after a first catalytic amount of a catalyst is introduced into the mixture of dihydric phenol and polyepoxide and the reaction has been maintained for a first period of time, a second catalytic amount of the catalyst is introduced into the mixture while at reaction temperature to upgrade further the polyepoxide. In yet another aspect of the disclosure, thermosetting resinous polyepoxides of improved molecular weight distribution are obtained by a process, preferably a continuous process, which involves (A) providing a catalyst-free mixture of bisphenol-A and a liquid resinous polyepoxide consisting essentially of an aromatic polyepoxide of the structural formula: ##STR1## to a temperature between 120° C. and about 200° C.; and (B) subsequently introducing triphenylphosphine into the mixture of the dihydric phenol and aromatic polyepoxide at a reaction temperature above 120° C. and maintaining the mixture containing the catalyst at reaction temperature for a time between about 5 and about 30 minutes.