Dispersant

Abstract

A novel ashless polymeric dispersant is claimed which is suitable for use in an automotive lubricant composition. The ashless polymeric dispersant has a number average molecular weight of between 200 and 15,000 and derived from the reaction of a polar head group, which comprises a polar moiety having more than one amine, alcohol, acid or halogen functionality with two or more polar tail groups where each polar tail group comprises a polymeric backbone of 2 to 30 monomeric repeat units, each repeat unit comprising a hydrocarbon chain functionalised by the presence of at least one electronegative element or moiety. The dispersant has good dispersancy properties, when used as a sole dispersant or in combination with other dispersants. It provides enhanced seal resistance and has good oxidative stability in automotive applications as compared to current commercial products. Furthermore the low temperature viscosity of an automotive lubricant composition containing the dispersant is superior to that of a composition with current commercial dispersants.

1 . An ashless polymeric dispersant suitable for use in an automotive lubricant composition having a number average molecular weight of between 200 and 15,000, wherein the dispersant is derived from the reaction of a polar head group, which comprises a polar moiety having more than one amine, alcohol, acid or halogen functionality with two or more polar tail groups where each polar tail group comprises a polymeric backbone of 2 to 30 monomeric repeat units, each repeat unit comprising a hydrocarbon chain functionalised by the presence of at least one electronegative element or moiety. 
     
     
         2 . An ashless polymeric dispersant as claimed in  claim 1  wherein the dispersant has a number average molecular weight of between 500 and 10,000, more preferably 500 and 7,000. 
     
     
         3 . An ashless polymeric dispersant as claimed in  claim 1  wherein the polar moiety of the polar head group has more than one amine or alcohol functionality. 
     
     
         4 . An ashless polymeric dispersant as claimed in  claim 3  wherein the polar moiety of the polar head group has two to four amine functionalities. 
     
     
         5 . An ashless polymeric dispersant as claimed in  claim 1  wherein each of the two or more polar tail groups has the same chemistry. 
     
     
         6 . An ashless polymeric dispersant as claimed in  claim 1  wherein the hydrocarbon chain of the two or more polar tail groups is a divalent radical which may be straight chained or branched and contains from 8 to 35 carbon atoms. 
     
     
         7 . An ashless polymeric dispersant as claimed in  claim 6  wherein the hydrocarbon chain is CH 3 —(CH 2 ) 5 —CH—(CH 2 ) 10 —. 
     
     
         8 . An ashless polymeric dispersant as claimed in  claim 1  wherein the electronegative element or moiety of the hydrocarbon chain is chosen from oxygen, ester and amide and is positioned either in the backbone or is a pendant group to the monomeric repeat unit. 
     
     
         9 . An ashless polymeric dispersant as claimed in  claim 8  wherein the electronegative element or moiety of the hydrocarbon chain is an ester which is positioned in the backbone of the monomelic repeat unit. 
     
     
         10 . An ashless polymeric dispersant as claimed in  claim 1  wherein the number of monomeric repeat units ranges from 2 to 30, preferably 2 to 20, more preferably 3 to 15. 
     
     
         11 . An ashless polymeric dispersant as claimed in  claim 1  wherein the polymeric ashless dispersant is derived from the polyesterification of a hydroxyalkyl acid where the alkyl group has 8 to 35 carbon atoms. 
     
     
         12 . An ashless polymeric dispersant as claimed in  claim 11  wherein the hydroxyalkyl acid is 12-hydroxystearic acid. 
     
     
         13 . An ashless polymeric dispersant as claimed in  claim 1  wherein the polymeric ashless dispersant has a number average molecular weight of between 500 and 10,000, preferably between 500 and 7,000, more preferably 500 and 5,000, especially 500 and 3,000. 
     
     
         14 . An automotive lubricant composition comprising a base fluid and an ashless polymeric dispersant having a number average molecular weight of between 200 and 15,000, wherein the dispersant is derived from the reaction of a polar head group, which comprises a polar moiety having more than one amine, alcohol, acid or halogen functionality with two or more polar tail groups where each polar tail group comprises a polymeric backbone of 2 to 30 monomeric repeat units, each repeat unit comprising a hydrocarbon chain functionalised by the presence of at least one electronegative element or moiety. 
     
     
         15 . An automotive lubricant composition as claimed in  claim 14 , which further comprises 0.1 to 20% by weight of a surfactant additive with respect to the weight of the ashless polymeric dispersant. 
     
     
         16 . An automotive lubricant composition as claimed in  claim 14 , which further comprises other dispersants present at a level of up to 20% by weight. 
     
     
         17 . Use of an automotive lubricant composition comprising a base fluid and 0.001 to 20% by weight of a polymeric ashless dispersant having a number average molecular weight of between 200 and 15,000 wherein the dispersant is derived from the reaction of a polar head group, which comprises a polar moiety having more than one amine, alcohol, acid or halogen functionality with two or more polar tail groups where each polar tail group comprises a polymeric backbone of 2 to 30 monomeric repeat units, each repeat unit comprising a hydrocarbon chain functionalised by the presence of at least one electronegative element or moiety in an engine or a transmission or a fuel supply line. 
     
     
         18 . Use of an ashless polymeric dispersant having a number average molecular weight of between 200 and 15,000, wherein the dispersant is derived from the o reaction of a polar head group, which comprises a polar moiety having more than one amine, alcohol, acid or halogen functionality with two or more polar tail groups where each polar tail group comprises a polymeric backbone of 2 to 30 monomeric repeat units, each repeat unit comprising a hydrocarbon chain functionalised by the presence of at least one electronegative element or moiety in an engine or transmission oil or a 5 fuel.