Lubricating composition with good oxidative stability and reduced deposit formation
A lubricant composition that is particularly suited for use in steam and gas turbine oils and in circulating oils has a balance of excellent oxidative stability and reduced sludge formation and comprises a blended mixture of alkylated phenyl-α-naphthylamine and at least oil soluble triazole or triazole derivative in an oil of lubricating viscosity, such compositions being capable of a residual RPVOT of 25% after at least 500 hours test duration test duration 120° C. in Dry TOST test or, alternatively 50% after 700 hours or 25% after 1000 hours.
1. A composition consisting essentially of an oil of lubricating viscosity selected from API Group II, III and IV base stocks, an alkylated phenyl-α-naphthyl amine as the sole antioxidant, said alkylated phenyl-α-naphthyl amine having an alkyl group having from 8 to 12 carbon atoms and being present in an amount of 0.19-0.26 wt %; and 0.01-0.04 wt % of dimethylaminomethyltolytriazole as the sole metal deactivator, wherein said composition is free of diphenylamine and alkylated derivatives thereof.
2. The composition of claim 1 , having a residual RPVOT of 25% after at least 500 hours test duration at 120° C. in the modified MHI Dry TOST test.
3. The composition of claim 1 , further comprising an additive selected from an antirust agent, a demulsifier, a diluent oil, and combinations thereof.
4. The composition of claim 1 having less than 65 mg/Kg of sludge after 500 hours test duration at 120° C. in the modified MHI Dry TOST test.
5. The composition of claim 1 having a residual RPVOT of at least 25% after 800 hours test duration at 120° C. in the modified MHI Dry TOST test.
6. A method of lubricating a turbine, comprising the step of lubricating a turbine with a lubricant composition consisting essentially of an oil of lubricating viscosity selected from API Group II, III and IV base stocks, an alkylated phenyl-α-naphthylamine as the sole antioxidant, said alkylated phenyl-α-naphthyl amine having an alkyl group having from 8 to 12 carbon atoms and being present in an amount of 0.19-0.26 wt %; and 0.01-0.04 wt % of dimethylaminomethyltolytriazole as the sole metal deactivator, wherein said composition is free of diphenylamine and alkylated derivatives thereof
7. The method of claim 6 , wherein said alkylated phenyl-α-naphthyl amine is octylated phenyl-alpha-naphthylamine.
8. The lubricating composition of claim 1 , said composition requiring at least 500 hours test duration at 120° C. to reach a residual RPVOT of 25% in the modified MHI Dry TOST test.
9. The lubricating composition of claim 1 , said composition requiring at least 700 hours test duration at 120° C. to reach a residual RPVOT of 50% in the modified MHI Dry TOST test.
10. The lubricating composition of claim 1 , said composition requiring at least 1000 hours test duration at 120° C. to reach a residual RPVOT of 25% in the modified MHI Dry TOST test.
11. A lubricating composition consisting of:
a) an oil of lubricating viscosity and selected from API Groups II, III, and IV;
b) 0.19-0.26 wt % of an alkylated phenyl-α-naphthylamine as the sole antioxidant, said alkylated phenyl-α-naphthyl amine having an alkyl group having from 8 to 12 carbon atoms;
c) 0.01-0.04 wt % of dimethylaminomethyltolytriazole as the sole metal deactivator; and
d) at least one additive selected from rust inhibitors, demulsifiers, antifoam agents, dispersants, detergents, diluent oil, succinated polyolefins, viscosity modifiers, pour point depressants, antistatic agents, antirust agents, extreme pressure/antiwear agents, and seal swell agents.