Oxidation-resistant cyclophosphazene fluid including triarylphosphine or phosphine oxide

Abstract

The oxidation resistance of a cyclophosphazene-based fluid (such as a lubricant or a hydraulic fluid) can be improved by the addition to the fluid of an oxidation-inhibiting amount of an aryl phosphine or phosphine oxide. The aryl phosphine or phosphine oxide is preferably present in an amount of about 0.01 to about 5 percent by weight. The aryl phosphine or phosphine oxide can be (a) a symmetric triarylphosphine of formula R.sub.3 P, wherein R is 4-trifluoromethyl phenyl, 3-trifluoromethyl phenyl, 3-trifluoromethoxy phenyl, 3-(3-trifluoromethylphenoxy) phenyl, 3-(perfluoro-2, 5-dimethyl-3, 6-dioxanonyl) phenyl or 1-naphthyl; (b) an oxide of any of these symmetric triarylphosphines; or (c) 1, 3-bis(diphenylphosphino) benzene. The cyclophosphazene fluid component is preferably a (fluorinated phenoxy) (3-perfluoroalkylphenoxy)-cyclic phosphazene of the general formula (I): ##STR1## wherein n is 3 to 7, inclusive; wherein R is individually in each occurrence fluorinated phenoxy or 3-perfluoroalkylphenoxy; and wherein the ratio of fluorinated phenoxy to 3-perfluoroalkylphenoxy is about 1:5 to 1:1 inclusive. Although useful as antioxidants in other fluids such as polyphenyl ethers, perfluorinated aliphatic polyethers and polyol esters, the antioxidant activity of the defined aryl phosphines and phosphine oxides in cyclophosphazene fluids is unexpected because of the significant difference in the pathways of oxidative degradation between the cyclophosphazenes and these other fluids.

Dependencies are inferred from the claim text.