wherein R1 is selected from the group consisting of alkyl groups having from 1 to about 30 carbon atoms, cycloalkyl groups having 5 or 6 carbon atoms, C1 -C4 alkyl substituted cycloalkyl groups, phenyl, alkyl substituted phenyl of the general formula (R3)a Ph-- wherein Ph is phenyl, R3 is an alkyl group having from 1 to about 18 carbon atoms and a is an integer of from 1 to 3, and phenyl-alkyl gro