Improvement of hydrolytic stability of borate esters used as lubricant additives

Borate esters possess friction-reducing, antiwear and antioxidant characteristics when blended in lubricating oils. However, they are susceptible to hydrolysis. Eleven borate ester compounds were synthesized and their hydrolytic stabilities were compared. The results indicated that the hydrolysis problem of borate esters can be better solved by introducing N, N-dialkylamino-ethyl with alkyl radicals containing more than three carbon atoms. It is believed that the formation of a stable five-member ring structure in molecules involving coordination of nitrogen with boron substantially contributes to the resistance to hydrolysis of such type compounds. 7 refs., 2 figs., 2 tabs.