Lubricating Composition and Method of Lubricating a Transmission

Abstract

The present invention relates to a lubricating composition comprising: (a) an oil of lubricating viscosity having a kinematic viscosity at 100° C. of 2.8 to 3.6 cSt (mm2/s) and a viscosity index of 104 to 130; (b) 1.2 to 5.0 wt % of at least one borated dispersant, wherein at least one borated dispersant is further functionalised with a sulphur or phosphorus moiety; (c) a calcium-containing detergent present in an amount to deliver at least 110 ppm to 700 ppm of calcium; (d) at least two phosphorus-containing compounds present in an amount to deliver 360 to 950 ppm of phosphorus; and (e) 0.1 wt % to 5 wt % of a linear polymer viscosity modifier having dispersant functionality. The invention further provides a method of lubricating a transmission with the lubricating composition disclosed wherein.

1 . A lubricating composition comprising:
 (a) an oil of lubricating viscosity having a kinematic viscosity at 100° C. of 2.8 to 3.6 cSt (mm 2 /s) and a viscosity index of 104 to 130;   (b) 1.2 to 5.0 wt % of at least one borated dispersant, wherein at least one borated dispersant is further functionalised with a sulphur or phosphorus moiety;   (c) a calcium-containing detergent, wherein the detergent is present in an amount to deliver at least 110 ppm to 700 ppm of calcium;   (d) a at least two phosphorus-containing compounds, wherein the phosphorus-containing compounds are present in an amount to deliver 360 to 950 ppm of phosphorus to the lubricating composition, wherein at least 150 ppm of the phosphorus is delivered by a C 4-6  hydrocarbyl phosphite; and   (e) 0.1 wt % to 5 wt % of a linear polymer viscosity modifier having dispersant functionality, wherein the linear polymer has a weight average molecular weight of 5,000 to 25,000.   
     
     
         2 . The composition of  claim 1 , wherein the calcium-containing detergent is present in an amount to deliver 130 ppm to 600 ppm of calcium. 
     
     
         3 . The composition of  claim 1  wherein the C 4-6  hydrocarbyl phosphite is a C 4  alkyl phosphite. 
     
     
         4 . The composition of  claim 1  wherein the borated dispersant is a borated polyisobutylene succinimide dispersant, wherein the polyisobutylene of the borated polyisobutylene succinimide has a number average molecular weight of 750 to 2200. 
     
     
         5 . The composition of  claim 1  further comprising a second borated dispersant wherein the borated dispersant is a borated polyisobutylene succinimide dispersant, wherein the polyisobutylene of the borated polyisobutylene succinimide has a number average molecular weight of 750 to 2200. 
     
     
         6 . The composition of  claim 1  further comprising a non-borated dispersant. 
     
     
         7 . The composition of  claim 6 , wherein the non-borated dispersant is a polyisobutylene succinimide wherein the polyisobutylene of the borated polyisobutylene succinimide has a number average molecular weight of 750 to 2200. 
     
     
         8 . The composition of  claim 1  wherein the borated dispersant has a N:CO ratio of 0.9:1 to 1.6:1. 
     
     
         9 . The composition of  claim 1 , wherein the composition further comprises 0.1 wt % to 4 wt % of a linear (meth)acrylic polymer viscosity modifier having dispersant functionality, wherein the linear polymer has a weight average molecular weight of greater than 25,000 to 400,000. 
     
     
         10 . The composition of  claim 1 , wherein the linear polymer viscosity modifier having dispersant functionality comprises:
 0.1 wt % to 4 wt % of a linear (meth)acrylic polymer viscosity modifier having dispersant functionality, wherein the linear polymer has a weight average molecular weight of 10,000 to 20,000; and   0.1 wt % to 4 wt % of a linear (meth)acrylic polymer viscosity modifier having dispersant functionality, wherein the linear polymer has a weight average molecular weight of greater than 20,000 to 250,000.   
     
     
         11 . The composition of  claim 1 , wherein the linear polymer viscosity modifier having dispersant functionality comprises
 0.1 wt % to 4 wt % of a linear (meth)acrylic polymer having dispersant functionality wherein the linear polymer has a weight average molecular weight of 5,000 to 25,000,   and the composition further comprises   0.1 wt % to 4 wt % of a (meth)acrylic polymer having star architecture.   
     
     
         12 . The composition of  claim 11 , wherein the (meth)acrylic polymer having star architecture has three or more arms that comprise a poly(meth)acrylate polymer is derived from a monomer composition comprising:
 (a) 50 wt % to 100 wt % of an alkyl (meth)acrylate, wherein the alkyl group of the (meth)acrylate has 12 to 15 carbon atoms;   (b) 0 wt % to 40 wt % of an alkyl (meth)acrylate, wherein the alkyl group of the (meth)acrylate has 1 to 9 carbon atoms;   (c) 0 wt % to 10 wt % of a dispersant monomer,   (d) 0 wt % to 5 wt % of a vinyl aromatic monomer; and   (e) 0 wt % to 20 wt % of an alkyl (meth)acrylate, wherein the alkyl group of the (meth)acrylate has 16 to 18 carbon atoms.   
     
     
         13 . The composition of  claim 11 , wherein the (meth)acrylic polymer having star architecture has three or more arms that comprise a poly(meth)acrylate polymer is derived from a monomer composition comprising:
 (a) 60 wt % to 95 wt % of an alkyl (meth)acrylate, wherein the alkyl group of the (meth)acrylate has 12 to 15 carbon atoms;   (b) 5 wt % to 30 wt % of an alkyl (meth)acrylate, wherein the alkyl group of the (meth)acrylate has 1 to 9 carbon atoms;   (c) 0 wt % to 10 wt % of a dispersant monomer,   (d) 0 wt % to 5 wt % of a vinyl aromatic monomer; and   (e) 0 wt % to 20 wt % of an alkyl (meth)acrylate, wherein the alkyl group of the (meth)acrylate has 16 to 18 carbon atoms.   
     
     
         14 . The composition of  claim 1 , wherein the linear polymer viscosity modifier having dispersant functionality
 is a sole dispersant viscosity modifier present at 0.5 wt % to 4 wt % of a linear (meth)acrylic polymer viscosity modifier having dispersant functionality, wherein the linear polymer has a weight average molecular weight of 5,000 to 25,000 and   wherein oil the of lubricating viscosity has a kinematic viscosity at 100° C. of 2.8 to 3.1 cSt (mm 2 /s) and a viscosity index of 104 to 130.   
     
     
         15 . The composition of  claim 1 , wherein the composition further comprises a C 8-20  hydrocarbyl phosphite. 
     
     
         16 . The composition of  claim 1  wherein the calcium-containing detergent is a calcium sulphonate or a calcium phenate. 
     
     
         17 . The composition of  claim 1 , wherein the calcium-containing detergent is a calcium sulphonate. 
     
     
         18 . The composition of  claim 1 , wherein the oil of lubricating viscosity has a kinematic viscosity at 100° C. of 2.8 to 3.6 cSt (mm 2 /s) and a viscosity index of 110 to less than 120. 
     
     
         19 . A method of lubricating an automatic transmission comprising supplying to the automatic transmission a composition of  claim 1 .