phenyl group or phenyl group substituted with an alkyl group having about 1-18 carbon atoms or an alkyl group having about 8-20 carbon atoms, and R4 is a phenyl group or a phenyl group substituted with an alkyl group having about 1-18 carbon atoms or an alkyl group having about 8-20, and preferably 12-18 carbon atoms;(2) radicals wherein R1, R2 and R3 are lower alkyl, and R4 is an alkyl or phenyl-