Elastomer compatible seal swell additive for automatic transmission fluids, power transmission fluids and hydraulic steering applications

摘要

A fluid having a mineral lubricating oil base and containing the combination of an oil-soluble tris (C.sub.8 -C.sub.24 hydrocarbyl) phosphite ester and an oil-soluble C.sub.8 -C.sub.24 hydrocarbyl substituted phenol, the weight ratio of said phosphite to said phenol ranging from about 4:1 to 1:4, preferably 3:1 to 1:3 whereby elastomer compatibility of said fluid is enhanced. The phosphite ester-substituted phenol combination imparts to the fluid the property of maintaining the chemical and physical properties of seals under oxidizing condition in automatic transmissions, power transmissions and power steering systems and thereby improves retention of the fluid in these mechanical structures; preferably when at least an inhibitory amount of an anti- oxidant capable of trapping free radicals at temperatures above 65 C. , preferably 80 to 200 C. is present.