wherein R2 is an alkyl or alkyl benzyl group having from about 8 to about 18 carbon atoms in the alkyl chain; each R3 is selected from the group consisting of ???CH2CH2???, ???CH2CH(CH3)???, ???CH2CH(CH2OH)???, ???CH2CH2CH2???, and mixtures thereof; each R4 is selected from the group consisting of C1-4 alkyl, C1-4 hydroxyalkyl, benzyl, ring structures formed by joining the two R4 groups, ???CH2 CH