Lubricant composition comprising alkali metal borate and polyalkylene succinic anhydride

Abstract

Disclosed are lubricant compositions comprising a dispersed hydrated alkali metal borate and a polyalkylene succinic anhydride, a mixture of polyalkylene succinic anhydrides or derivatives thereof. Also disclosed are methods for improving the water tolerance of a lubricant composition comprising an alkali metal borate. Such methods employ compositions comprising a dispersed hydrated alkali metal borate and a polyalkylene succinic anhydride, a mixture of polyalkylene succinic anhydrides or derivatives thereof.

What is claimed is:  
     
         1 . A lubricant composition which comprises: 
 a) a base oil of lubricating viscosity,    b) a dispersed hydrated alkali metal borate, and    c) a dispersant that is selected from the group consisting of a polyalkylene succinic anhydride, a non-nitrogen containing derivative of the polyalkylene succinic anhydride, mixtures of polyalkylene succinic anhydrides, mixtures of non-nitrogen containing derivatives of the polyalkylene succinic anhydride and mixtures of both polyalkylene succinic anhydrides and non-nitrogen containing derivatives of the polyalkylene succinic anhydride.    
     
     
         2 . The lubricant composition according to  claim 1 , wherein the dispersed hydrated alkali metal borate is a dispersed hydrated sodium borate.  
     
     
         3 . The lubricant composition according to  claim 2 , wherein the dispersed hydrated sodium borate has a sodium to boron metal ratio of from about 1:2.5 to about 1:4.5.  
     
     
         4 . The lubricant composition according to  claim 1 , wherein the dispersant is a mixture of polyalkylene succinic anhydrides.  
     
     
         5 . The lubricant composition according to  claim 4 , wherein the mixture of polyalkylene succinic anhydrides is a mixture of polyisobutenyl succinic anhydrides.  
     
     
         6 . The lubricant composition according to  claim 5 , wherein the mixture of polyisobutenyl succinic anhydrides comprises a low molecular weight polyisobutenyl succinic anhydride component and a high molecular weight polyisobutenyl succinic anhydride component.  
     
     
         7 . The lubricant composition according to  claim 6 , wherein the low molecular weight polyisobutenyl succinic anhydride component has a number average molecular weight of from about 500 to below 1000 and the high molecular weight polyisobutenyl succinic anhydride component has a number average molecular weight of from 1000 to about 3000.  
     
     
         8 . The lubricant composition according to  claim 1 , wherein the dispersed hydrated alkali metal borate has a ratio of at least 2:1 relative to the dispersant.  
     
     
         9 . The lubricant composition according to  claim 8 , wherein the dispersed hydrated alkali metal borate has a ratio of from 2:1 to 10:1 relative to the dispersant.  
     
     
         10 . The lubricant composition according to  claim 8 , wherein the dispersed hydrated alkali metal borate has a ratio of at least 5:2 relative to the dispersant.  
     
     
         11 . The lubricant composition according to  claim 1 , which further comprises a metal sulfonate.  
     
     
         12 . The lubricant composition according to  claim 11 , wherein said metal sulfonate is a calcium alkyl aromatic sulfonate.  
     
     
         13 . The lubricant composition according to  claim 1 , which further comprises from about 0.001 moles to about 0.11 moles of a water soluble oxo anion per mole of boron.  
     
     
         14 . The lubricant composition according to  claim 13 , wherein said oxo anion is selected from the group consisting of nitrate, sulfate, carbonate, phosphate, pyrophosphate, silicate, aluminate, germanate, stannate, zincate, plumbate, titanate, molybdate, tungstate, vanadate, niobate, tantalate, uranate, isopolymolybdate, isopolytungstate, heteropolymolybdate, heteropolytungstates, and mixtures thereof.  
     
     
         15 . A method for enhancing the water tolerance of lubricant compositions comprising alkali metal borate which method comprises adding an anti-wear effective amount of a dispersed hydrated alkali metal borate to a base oil of lubricating viscosity in combination with a dispersant effective amount of a dispersant selected from the group consisting of a polyalkylene succinic anhydride, a non-nitrogen containing derivative of the polyalkylene succinic anhydride, mixtures of polyalkylene succinic anhydrides, mixtures of non-nitrogen containing derivatives of the polyalkylene succinic anhydride and mixtures of both polyalkylene succinic anhydrides and non-nitrogen containing derivatives of the polyalkylene succinic anhydride.  
     
     
         16 . The lubricant composition according to  claim 1 , wherein the dispersed hydrated alkali metal borate is a dispersed hydrated sodium borate having a hydroxyl to boron ratio of from about 0.8:1 to 1.6:1.