Perfluorinated polyether lubricant compositions

Abstract

A lubricant composition comprises a perfluorinated polyalkylether base fluid (PFPAE) and an oxidation-corrosion inhibiting amount of a perfluoro-substituted benzothiazole or bis-benzothiazole. The benzothiazole compound additive exhibits excellent solubility in the base fluid and possesses outstanding low volatility characteristics. As a result, the lubricant composition functions as a noncorrosive, stable material suitable for long term applications over a wide temperature range (-65° F. to >600° F.) in an oxidative environment. The perfluoro-substituted benzothiazoles and bis-benzothiazoles have the formula: Q--R f or Q--R f '--Q, wherein Q is ##STR1## wherein R f is a linear or branched perfluoroalkylether group containing at least one ether linkage and R f ' is a linear or branched perfluoroalkyleneeher group containing at least one ether linkage. In formulating the lubricant composition of this invention, an oxidation-corrosion inhibiting amount of the substituted benzothiazole is dissolved in the PFPAE base fluid. The amount of the benzothiazole employed generally ranges from about 0.05 to 5.0 weight percent, preferably about 0.5 to 2.0 weight percent, based on the weight of the base fluid. This provides a lubricant containing an amount of oxidation-corrosion inhibiting additive that is adequate for long term applications at elevated temperatures while maintaining excellent formulation stability after storage at low temperatures for long periods of time.

We claim: 
     
       1. A lubricant composition comprising a perfluorinated polyalkylether base fluid and an oxidation-corrosion inhibiting amount of a perfluoro-substituted benzothiazole. 
     
     
       2. The composition of claim 1 wherein said perfluoro-substituted benzothiazole has the formula Q--R f , wherein Q is ##STR11## and wherein R f  is a linear or branched perfluoroalkylether group containing at least one ether linkage. 
     
     
       3. The composition of claim 1 wherein the amount of said substituted benzothiazole is about 0.05 to 5.0 weight percent. 
     
     
       4. The composition of claim 1 wherein the amount of said substituted benzothiazole is about 0.5 to 2.0 weight percent. 
     
     
       5. The composition of claim 2 wherein R f  is ##STR12## wherein x has a value of 1 to 20. 
     
     
       6. The composition of claim 2 wherein R f  is   C.sub.2 F.sub.5 O(C.sub.2 F.sub.4 O).sub.x CF.sub.2 --     wherein x has a value of 1 to 20.   
     
     
       7. The composition of claim 5 wherein said base fluid has the general formula F(CF 2  CF 2  O) r  (CF 2  O) q  R f , wherein R f  is a perfluoroalkyl group having 1 or 2 carbon atoms, and q and r are integers such that the fluid has a kinematic viscosity of 17.56 cSt. at 100° F. and wherein said x has a value of 3. 
     
     
       8. The composition of claim 5 wherein said base fluid has the general formula ##STR13## wherein R f  is a perfluoroalkyl group having 1 or 2 carbon atoms, and s is an integer such that the fluid has a kinematic viscosity of 282 cSt. at 100° F. and wherein said x has a value of 3. 
     
     
       9. A lubricant composition comprising a perfluorinated polyalkylether base fluid and an oxidation-corrosion inhibiting amount of a perfluoro-substituted bis-benzothiazole. 
     
     
       10. The composition of claim 9 wherein said perfluoro-substituted bis-benzothiazole has the formula Q--R f  '--Q, wherein Q is ##STR14## and wherein R f  ' is a linear or branched perfluoroalkyleneether group containing at least one ether linkage. 
     
     
       11. The composition of claim 9 wherein the amount of said substituted bis-benzothiazole is about 0.05 to 5.0 weight percent. 
     
     
       12. The composition of claim 9 wherein the amount of said substituted bis-benzothiazole is about 0.5 to 2.0 weight percent. 
     
     
       13. The composition of claim 10 wherein R f  ' is ##STR15## wherein y+z is 3. 
     
     
       14. The composition of claim 9 wherein said base fluid has the general formula F(CF 2  CF 2  O) r  (CF 2  O) q  R f , wherein R f  is a perfluoroalkyl group having 1 or 2 carbon atoms, and q and r are integers such that the fluid has a kinematic viscosity of 17.56 cSt. at 100° F. and wherein R f  ' is ##STR16## wherein y+z is 3.