Use of polyclycerin esters as friction modifiers in lubricant formulations

Abstract

The present invention relates to a lubricating oil composition comprising polyglycerol partial esters of polyfunctional carboxylic acids and saturated or unsaturated, linear or branched fatty acids and/or poly(hydroxystearic acid) and the use thereof to lubricate an engine and reduce friction.

1 . A lubricating oil composition comprising
 (a) 0.2 to 5% by weight of one or more polyglycerol partial esters, based on a total weight of the lubricating oil composition, wherein the polyglycerol partial esters are obtained by esterification of a polyglycerol mixture with   (i) one or more polyfunctional carboxylic acids and   (ii) one or more saturated or unsaturated, linear or branched fatty acids and/or   (ii) poly(hydroxystearic acid),   wherein a degree of esterification of the poly-glycerol mixture is between 30 and 75% of the OH goups;   (b) 85 to 99.8% by weight of an apolar base stock selected from the group consisting of API Group II, III and IV and mixtures thereof, based on the total weight of the lubricating oil composition; and   (c) 0 to 10% by weight of a polar ester oil of API Group V, based on the total weight of the lubricating oil composition.   
     
     
         2 . The lubricating oil composition according to  claim 1 , wherein the polyglycerol has a mean degree of condensation of from 3 to 6. 
     
     
         3 . The lubricating oil composition according to  claim 1 , wherein the fatty acids are saturated or unsaturated, linear or branched having 8 to 22 carbon atoms. 
     
     
         4 . The lubricating oil composition according to  claim 1 , wherein the saturated fatty acids are one or more selected from the group consisting of caprylic acid, capric acid, lauric acid, tridecanoic acid, myristic acid, palmitic acid, margaric acid, stearic acid, isostearic acid, arachidic acid, behenic acid, and 12-hydroxy stearic acid. 
     
     
         5 . The lubricating oil composition according to  claim 1 , wherein the unsaturated fatty acids are one or more selected from the group consisting of hexadecenoic acids, octadecenoic acids, eicosenoic docosenoic acids, octadecadienoic acids, octadecatrienoic acids, and ricinoleic acid. 
     
     
         6 . The lubricating oil composition according to  claim 1 , wherein the polyfunctional carboxylic: acids have 4 to 54 carbon atoms, and a mean functionality of from 2 to 2.5. 
     
     
         7 . The lubricating oil composition according to  claim 1 , wherein the polyfunctional carboxylic acids are aliphatic dicarboxylic acids which are selected from the group consisting of malonic acid, succinic acid, furmaric acid, maleic acid, dimethylgiutaric acid, adipic acid, trimethyladipic acid, azelaic acid, sebacic acid, dodecanedioic acid and their anhydrides. 
     
     
         8 . The lubricating oil composition according to  claim 1 , wherein the polyglycerol partial esters have HLB values of from 3 to 7. 
     
     
         9 . The lubricating oil composition according to  claim 1 , wherein the polyglycerol partial esters have an OH-number in the range of 50 to 180 mg KOH/g. 
     
     
         10 . The lubricating oil composition according to  claim 1 , further comprising an additive. 
     
     
         11 . The lubricating oil composition according to  claim 10 , wherein the additive is at least one selected from the group consisting of viscosity index (VI) improvers, pour point depressants, dispersants, detergents, defoamers, corrosion inhibitors, antioxidants, antiwear and extreme pressure additives and fiction modifiers. 
     
     
         12 . The lubricating oil composition according to  claim 1 , wherein the polyglycerol partial esters have a weight-average molecular weight of 2,000 to 15,000 g/mol. 
     
     
         13 . A method of lubricating an engine, comprising adding the lubricating oil composition according to  claim 1  to the engine. 
     
     
         14 . A method of reducing friction in an engine, comprising applying the lubricating oil composition according to  claim 1  to the engine.