Examples of the nonionic vinyl monomer are those having the general formula of ##STR4## wherein R2 is hydrogen or methyl group and R3 is an alkyl group having 1 to 8 carbon atoms, glycidyl group or a hydroxyalkyl group having 2 to 4 carbon atoms, such as methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, 2-ethylhexyl methacrylate, glycidyl methacrylate or hydroxyethyl methacryla