Lubricating oil composition for cellulose base wet friction material

Abstract

There is disclosed a lubricating oil composition for cellulose base wet friction material which comprises a base oil blended with (A) a boron-containing imide base dispersant (e.g. boron treated polyalkenyl succinimide) having a weight-average molecular weight in the range of 500 to 3000 and having a ratio by weight of boron to nitrogen (B/N) in the range of 0.1 to 1.5 in such a blending amount that the boron content and the nitrogen content each derived from the component (A) are made to be at least 60 ppm by weight and at least 100 ppm by weight, respectively based on the base oil. The above lubricating oil composition enhances peeling resistant durability for a friction material, especially a cellulose base friction material without impairing the wear resistance or scoring resistance of a steel material element, and is well suited for use in a cellulose base friction material for a starting and running device and a transmission clutch that are used in an automatic transmission of an automobile.

What is claimed is:  
     
         1 . A lubricating oil composition for cellulose base wet friction material which comprises a base oil blended with (A) a boron-containing imide base dispersant having a weight-average molecular weight in the range of 500 to 3000 and having a ratio by weight of boron to nitrogen (B/N) in the range of 0.1 to 1.5 in such a blending amount that the boron content and the nitrogen content each derived from the component (A) are made to be at least 60 ppm by weight and at least 100 ppm by weight, respectively based on said base oil.  
     
     
         2 . The lubricating oil composition according to  claim 1 , wherein the boron-containing imide base dispersant as the component (A) has a ratio by weight of boron to nitrogen (B/N) in the range of 0.2 to 1.0.  
     
     
         3 . The lubricating oil composition according to  claim 1 , wherein the boron-containing imide base dispersant as the component (A) is produced by treating polyalkenyl succinimide with a boron compound.  
     
     
         4 . The lubricating oil composition according to  claim 3 , wherein the polyalkenyl succinimide is polybutenyl succinimide.  
     
     
         5 . The lubricating oil composition according to  claim 1 , wherein the boron content derived from the component (A) is in the range of 60 to 300 ppm based on said base oil.  
     
     
         6 . The lubricating oil composition according to  claim 1 , wherein the nitrogen content derived from the component (A) is in the range of 100 to 1200 ppm based on said bade oil.  
     
     
         7 . The lubricating oil composition according to  claim 1 , which further comprises (B) at least one member selected from the group consisting of an active phosphorus base compound and an active sulfur base compound.  
     
     
         8 . The lubricating oil composition according to  claim 7 , wherein the active phosphorus base compound is at least one member selected from the group consisting of the acidic phosphate esters and phosphite esters represented by the general formula (III):  
       
         
           
           
               
               
           
         
       
       wherein A is hydrogen atom or hydroxyl group; k is 0 or 1 with the proviso that A is hydroxyl group when k is 0, and A is hydrogen atom or hydroxyl group when k is 1; and R 7  and R 8  are each hydrogen atom or a hydrocarbon group which has 1 to 18 carbon atoms, and which may contain at least one member selected from the group consisting of oxygen atom and sulfur atom with the proviso that R 7  and R 8  may be the same as or different from each other, but are not simultaneously hydrogen atom.