Method for improving antiwear performance and demulsibility performance

Abstract

A method for improving antiwear performance and demulsibility performance in an engine lubricated with a lubricating oil by using as the lubricating oil a formulated oil. The formulated oil has a composition including a lubricating oil base stock as a major component, and an antiwear additive as a minor component. The antiwear additive includes a zinc dialkyl dithiophosphate compound represented by the formula Zn[SP(S)(OR 1 )(OR 2 )] 2 wherein R 1 and R 2 are independently primary or secondary C 1 to C 8 alkyl groups. The R 1 and R 2 primary or secondary alkyl groups of the zinc dialkyl dithiophosphate compound, and the amount of the zinc dialkyl dithiophosphate compound in the lubricating oil, are sufficient for the lubricating oil to exhibit improved antiwear performance and demulsibility performance. The lubricating oils of this disclosure are suitable for use in marine system oils for two-stroke marine diesel engines.

What is claimed is: 
     
         1 . A method for improving antiwear performance and demulsibility performance in an engine lubricated with a lubricating oil by using as the lubricating oil a formulated oil, said formulated oil having a composition comprising a lubricating oil base stock as a major component; and an antiwear additive as a minor component; wherein the antiwear additive comprises a zinc dialkyl dithiophosphate compound represented by the formula
   Zn[SP(S)(OR 1 )(OR 2 )] 2      
       wherein R 1  and R 2  are independently primary or secondary C 1  to C 8  alkyl groups; and 
       wherein the R 1  and R 2  primary or secondary alkyl groups of the zinc dialkyl dithiophosphate compound, and the amount of the zinc dialkyl dithiophosphate compound having the R 1  and R 2  primary or secondary alkyl groups in the lubricating oil, are sufficient for the lubricating oil to exhibit improved antiwear performance and demulsibility performance as compared to antiwear performance and demulsibility performance achieved using a lubricating oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R 1  and R 2  primary or secondary alkyl groups, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R 1  and R 2  primary or secondary alkyl groups in the lubricating oil. 
     
     
         2 . The method of  claim 1  wherein the lubricating oil base stock comprises a Group I or Group II base oil. 
     
     
         3 . The method of  claim 1  wherein the primary or secondary C 1  to C 8  alkyl groups of the zinc dialkyl dithiophosphate compound are derived from an alcohol selected from the group consisting of: 2-propanol, 1-butanol, 1-isobutanol, 2-butanol, 1-pentanol, 3-methyl-1-butanol, 2-pentanol, 3-pentanol, 3-methyl-2-butanol, 1-hexanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, and 2-ethyl-1-hexanol, and mixtures thereof. 
     
     
         4 . The method of  claim 1  wherein the zinc dialkyl dithiophosphate compound having the R 1  and R 2  primary or secondary alkyl groups, is present in an amount of from 0.1 weight percent to 1.2 weight percent, based on the total weight of the lubricating oil. 
     
     
         5 . The method of  claim 1  wherein the zinc dialkyl dithiophosphate compound having the R 1  and R 2  primary or secondary alkyl groups, in which the R 1  and R 2  primary or secondary alkyl groups are derived from 2-ethyl-1-hexanol, is present in an amount of from 0.1 weight percent to 0.8 weight percent, based on the total weight of the lubricating oil. 
     
     
         6 . The method of  claim 1  wherein the zinc dialkyl dithiophosphate compound having the R 1  and R 2  primary or secondary alkyl groups, in which the R 1  and R 2  primary or secondary alkyl groups are derived from 4-methyl-2-pentanol, is present in an amount of from 0.1 weight percent to 0.8 weight percent, based on the total weight of the lubricating oil. 
     
     
         7 . The method of  claim 1  wherein the zinc dialkyl dithiophosphate compound having the R 1  and R 2  primary or secondary alkyl groups, in which the R 1  and R 2  primary or secondary alkyl groups are derived from 2-propanol, 2-butanol, 1-iso-butanol, or n-pentanol, is present in an amount of from 0.3 weight percent to 0.8 weight percent, based on the total weight of the lubricating oil. 
     
     
         8 . The method of  claim 1  wherein the lubricating oil is a marine lubricating oil. 
     
     
         9 . The method of  claim 1  wherein, in antiwear measurements of the lubricating oil as measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG, the lubricating oil achieves at least a FZG Failure Load Stage 11 or 12 rating. 
     
     
         10 . The method of  claim 1  wherein, in demulsibility measurements of the lubricating oil as measured by High Shear Demulsibility Test, the lubricating oil achieves at least 3.8 mL free water, less than 1 mL emulsion, and less than 1 weight percent water in oil. 
     
     
         11 . The method of  claim 1  wherein the lubricating oil further comprises one or more of a viscosity index improver, antioxidant, detergent, dispersant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, anti-rust additive, and friction modifier. 
     
     
         12 . The method of  claim 1  wherein, in antiwear measurements of the lubricating oil as measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG, the antiwear performance of the lubricating oil is improved as compared to the antiwear performance of a lubricating oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R 1  and R 2  primary or secondary alkyl groups, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R 1  and R 2  primary or secondary alkyl groups in the lubricating oil; and wherein, in demulsibility measurements of the lubricating oil as measured by High Shear Demulsibility Test, the demulsibility performance is improved as compared to the demulsibility performance of a lubricating oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R 1  and R 2  primary or secondary alkyl groups, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R 1  and R 2  primary or secondary alkyl groups in the lubricating oil. 
     
     
         13 . A lubricating engine oil having a composition comprising a lubricating oil base stock as a major component; and an antiwear additive as a minor component; wherein the antiwear additive comprises a zinc dialkyl dithiophosphate compound represented by the formula
   Zn[SP(S)(OR 1 )(OR 2 )] 2      
       wherein R 1  and R 2  are independently primary or secondary C 1  to C 8  alkyl groups; and 
       wherein the R 1  and R 2  primary or secondary alkyl groups of the zinc dialkyl dithiophosphate compound, and the amount of the zinc dialkyl dithiophosphate compound having the R 1  and R 2  primary or secondary alkyl groups in the lubricating engine oil, are sufficient for the lubricating engine oil to exhibit improved antiwear performance and demulsibility performance as compared to antiwear performance and demulsibility performance achieved using a lubricating engine oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R 1  and R 2  primary or secondary alkyl groups, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R 1  and R 2  primary or secondary alkyl groups in the lubricating engine oil. 
     
     
         14 . The lubricating engine oil of  claim 13  wherein the lubricating oil base stock comprises a Group I or Group II base oil. 
     
     
         15 . The lubricating engine oil of  claim 13  wherein the primary or secondary C 1  to C 8  alkyl groups of the zinc dialkyl dithiophosphate compound are derived from an alcohol selected from the group consisting of: 2-propanol, 1-butanol, 1-isobutanol, 2-butanol, 1-pentanol, 3-methyl-1-butanol, 2-pentanol, 3-pentanol, 3-methyl-2-butanol, 1-hexanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, and 2-ethyl-1-hexanol, and mixtures thereof. 
     
     
         16 . The lubricating engine oil of  claim 13  wherein the zinc dialkyl dithiophosphate compound having the R 1  and R 2  primary or secondary alkyl groups, is present in an amount of from 0.1 weight percent to 1.2 weight percent, based on the total weight of the lubricating engine oil. 
     
     
         17 . The lubricating engine oil of  claim 13  wherein the zinc dialkyl dithiophosphate compound having the R 1  and R 2  primary or secondary alkyl groups, in which the R 1  and R 2  primary or secondary alkyl groups are derived from 2-ethyl-1-hexanol, is present in an amount of from 0.1 weight percent to 0.8 weight percent, based on the total weight of the lubricating engine oil. 
     
     
         18 . The lubricating engine oil of  claim 13  wherein the zinc dialkyl dithiophosphate compound having the R 1  and R 2  primary or secondary alkyl groups, in which the R 1  and R 2  primary or secondary alkyl groups are derived from 4-methyl-2-pentanol, is present in an amount of from 0.1 weight percent to 0.8 weight percent, based on the total weight of the lubricating engine oil. 
     
     
         19 . The lubricating engine oil of  claim 13  wherein the zinc dialkyl dithiophosphate compound having the R 1  and R 2  primary or secondary alkyl groups, in which the R 1  and R 2  primary or secondary alkyl groups are derived from 2-propanol, 2-butanol, 1-iso-butanol, or n-pentanol, is present in an amount of from 0.3 weight percent to 0.8 weight percent, based on the total weight of the lubricating engine oil. 
     
     
         20 . The lubricating engine oil of  claim 13  wherein the lubricating engine oil is a marine lubricating oil. 
     
     
         21 . The lubricating engine oil of  claim 13  wherein, in antiwear measurements of the lubricating engine oil as measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG, the lubricating engine oil achieves at least a FZG Failure Load Stage 11 or 12 rating. 
     
     
         22 . The lubricating engine oil of  claim 13  wherein, in demulsibility measurements of the lubricating oil as measured by High Shear Demulsibility Test, the lubricating oil achieves at least 3.8 mL free water, less than 1 mL emulsion, and less than 1 weight percent water in oil. 
     
     
         23 . The lubricating engine oil of  claim 13  wherein the lubricating engine oil further comprises one or more of a viscosity index improver, antioxidant, detergent, dispersant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, anti-rust additive, and friction modifier. 
     
     
         24 . The lubricating engine oil of  claim 13  wherein, in antiwear measurements of the lubricating engine oil as measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG, the antiwear performance of the lubricating engine oil is improved as compared to the antiwear performance of a lubricating engine oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R 1  and R 2  primary or secondary alkyl groups, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R 1  and R 2  primary or secondary alkyl groups in the lubricating engine oil; and wherein, in demulsibility measurements of the lubricating engine oil as measured by High Shear Demulsibility Test, the demulsibility performance is improved as compared to the demulsibility performance of a lubricating engine oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R 1  and R 2  primary or secondary alkyl groups, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R 1  and R 2  primary or secondary alkyl groups in the lubricating engine oil. 
     
     
         25 . A gear component of a marine engine lubricated with the lubricating engine oil of  claim 13 .