Fuel compositions

Abstract

A fuel composition comprising a base fuel and at least one viscosity index (VI) improving additive, wherein the viscosity index (VI) improving additive is a star-shaped polyisoprene-based polymer. The viscosity index improving additive can be used in a fuel composition to provide improved lubricity as well as providing improved power output and/or acceleration characteristics.

1 . A fuel composition comprising a base fuel and at least one viscosity index (VI) improving additive, wherein the viscosity index (VI) improving additive is a star-shaped polyisoprene-based polymer. 
     
     
         2 . The fuel composition according to  claim 1  wherein the star-shaped polyisoprene-based polymer is characterized by the formula:
   (D′-PA-D″) n -X;
 
 wherein D′ represents a block derived from at least one diene; PA represents a block derived from monoalkenyl arene; D″ represents a block derived from diene; n represents the average number of arms per star polymer formed by the reaction of 2 or more moles of a polyalkenyl coupling agent per mole of arms; and X represents a nucleus of a polyalkenyl coupling agent; 
 wherein at least one of diene blocks D′ and D″ is a copolymer block derived from mixed diene monomer, in which from about 65 wt % to about 95 wt % of the incorporated monomer units are from isoprene and from about 5 wt % up to about 35 wt % of the incorporated monomer units are from butadiene, and wherein at least about 80 wt % of the butadiene is incorporated in a 1,4-configuration; and 
 wherein D′ has a number average molecular weight of from about 10,000 to about 120,000 daltons; PA has a number average molecular weight of from about 10,000 to about 50,000 daltons; and D″ has a number average molecular weight of from about 5,000 to about 60,000 daltons. 
 
     
     
         3 . The fuel composition according to  claim 1  wherein the star-shaped polyisoprene-based polymer comprises a crosslinked polystyrene core with arms of hydrogenated polyisoprene or poly(alternated ethylene-propylene). 
     
     
         4 . The fuel composition according to  claim 1  wherein the fuel composition is a diesel fuel composition. 
     
     
         5 . The fuel composition according to  claim 1  wherein the concentration of the VI improving additive in the fuel composition is from 0.001 to 0.5% w/w, preferably from 0.05 to 0.25% w/w. 
     
     
         6 . A use of a viscosity index (VI) improving additive in an automotive fuel composition, for the purpose of improving the lubricity of the fuel composition, wherein the viscosity index (VI) improving additive is a star-shaped polyisoprene-based polymer. 
     
     
         7 . A use of a viscosity index (VI) improving additive in an automotive fuel composition, for the purpose of improving the power output of an internal combustion engine into which the viscosity index (VI) improving additive, or an automotive fuel composition containing the viscosity index (VI) improving additive, is or is intended to be introduced or of a vehicle powered by such an engine, wherein the viscosity index (VI) improving additive is a star-shaped polyisoprene-based polymer. 
     
     
         8 . A use of a viscosity index (VI) improving additive in an automotive fuel composition, for the purpose of improving the lubricity of the fuel composition at the same time as improving the power output of an internal combustion engine into which the viscosity index (VI) improving additive, or an automotive fuel composition containing the viscosity index (VI) improving additive, is or is intended to be introduced or of a vehicle powered by such an engine, wherein the viscosity index (VI) improving additive is a star-shaped polyisoprene-based polymer. 
     
     
         9 . The use according to  claim 7 , wherein the VI improving additive is pre-dissolved in a solvent or fuel component. 
     
     
         10 . (canceled) 
     
     
         11 . The use according to  claim 8 , wherein the VI improving additive is pre-dissolved in a solvent or fuel component.