R2 is an alkylene or hydroxyalkylene group having from approx. 2 to 3 carbon atoms or mixtures thereof, each radical R1 is an alkyl or hydroxyalkyl group having from approx. 1 to approx. 3 carbon atoms or a polyethylene oxide group having about 1 to about 3 ethylene oxide units, and x is a number from 0 to about 10.