Lubricant composition with an improved viscosity characteristic at low operating temperature

Abstract

A lubricant composition with a comb polymer and a synthetic base oil has improved viscosity characteristics at low operating temperatures. In addition, a comb polymer can be used for producing a lubricant having an R-factor of less than or equal to 8, wherein the R-factor is defined as the ratio of the kinematic viscosity at −20° C. and the kinematic viscosity at +20° C.

1 : A lubricant composition, comprising:
 (A) 20 to 90% by weight of a synthetic base oil; and   (B) 10 to 80% by weight of a comb polymer, comprising the following monomers:
 (a) 20 to 35% by weight of esters of (meth)acrylic acid and a hydroxylated hydrogenated polybutadiene; and 
 (b) 0.2 to 15% by weight of styrene, 
 (c) 0.2 to 20% by weight of alkyl methacrylates comprising 12 to 15 carbon atoms in the alkyl chain, 
   (d) 50 to 70% by weight of alkyl (meth)acrylates comprising 1 to 4 carbon atoms in the alkyl chain,   based on the total weight of the comb polymer.   
     
     
         2 : The lubricant composition according to  claim 1 , wherein a ratio of the kinematic viscosity of the lubricant composition at −20° C. (KV −20 ) to the kinematic viscosity at +20° C. (KV +20 ), KV −20 /KV +20 , is 8 less, wherein the kinematic viscosities are measured according to ASTM D445. 
     
     
         3 : The lubricant composition according to  claim 1 , wherein the synthetic base oil (A) is a polyalphaolefin having a kinematic viscosity at 100° C. according to ASTM D445 of 1 to 20 mm 2 /s. 
     
     
         4 : The lubricant composition according to  claim 1 , wherein the synthetic base oil (A) is a polyalphaolefin having a kinematic viscosity at 100° C. according to ASTM D445 of 1 to 10 mm 2 /s. 
     
     
         5 : The lubricant composition according to  claim 1 , wherein the synthetic base oil (A) is a polyalphaolefin having a kinematic viscosity at 100° C. according to ASTM D445 of 1 to 5 mm 2 /s. 
     
     
         6 : The lubricant composition according to  claim 1 , wherein the synthetic base oil (A) is a polyalphaolefin having a kinematic viscosity at 100° C. according to ASTM D445 of 2 to 3 mm 2 /s. 
     
     
         7 : The lubricant composition according to  claim 1 , wherein the lubricant composition comprises 30 to 80% by weight of the synthetic base oil (A) and 20 to 70% by weight of the comb polymer (B), based on the total weight of the lubricant composition. 
     
     
         8 : The lubricant composition according to  claim 1 , wherein the hydroxylated hydrogenated polybutadiene of component (a) has a number-average molecular weight M n  to DIN 55672-1 of 4.000 to 5.000 g/mol. 
     
     
         9 : The lubricant composition according to  claim 1 , wherein the comb polymer (B) comprises:
 (a) 25 to 30% by weight of esters of (meth)acrylic acid and a hydroxylated hydrogenated polybutadiene,   (b) 0.2 to 15% by weight of styrene,   (c) 0.2 to 15% by weight of alkyl methacrylates comprising 12 to 14 carbon atoms in the alkyl chain,   (d) 50 to 65% by weight of butylmethacrylate, and   (e) 0.1 to 0.2% by weight of methylmethacrylate,   based on the total weight of the comb polymer.   
     
     
         10 : A method of producing a lubricant composition, comprising:
 adding a comb polymer as an additive to a base oil, said comb polymer comprising:
 (a) 20 to 35% by weight of esters of (meth)acrylic acid and a hydroxylated hydrogenated polybutadiene, 
 (b) 0.2 to 15% by weight of styrene, 
 (c) 0.2 to 20% by weight of alkyl methacrylates comprising 12 to 15 carbon atoms in the alkyl chain, 
 (d) 50 to 65% by weight of alkyl (meth)acrylates comprising 1 to 4 carbon atoms in the alkyl chain, 
 based on the total weight of the comb polymer, 
   said lubricant composition having an R-factor of less than or equal to 8, wherein the R-factor is defined as the ratio of the kinematic viscosity of the lubricant composition at −20° C. to the kinematic viscosity at +20° C. measured according to ASTM D445.   
     
     
         11 : The method according to  claim 10 , wherein the base oil is a polyalphaolefin base oil having a kinematic viscosity at 100° C. according to ASTM D445 of 1 mm 2 /s to 20 mm 2 /s. 
     
     
         12 : The method according to  claim 10 , wherein the base oil is a polyalphaolefin base oil having a kinematic viscosity at 100° C. according to ASTM D445 of 1 to 10 mm 2 /s. 
     
     
         13 : The method according to  claim 10 , wherein the base oil is a polyalphaolefin base oil having a kinematic viscosity at 100° C. according to ASTM D445 of 1 to 5 mm 2 /s. 
     
     
         14 : The method according to  claim 10 , wherein the base oil is a polyalphaolefin base oil having a kinematic viscosity at 100° C. according to ASTM D445 of 2 to 3 mm 2 /s. 
     
     
         15 : The method according to  claim 10 , wherein the lubricant composition has the R-factor of 1 to 8. 
     
     
         16 : The method use according to  claim 10 , wherein the comb polymer (B) comprises:
 (a) 25 to 30% by weight of esters of (meth)acrylic acid and a hydroxylated hydrogenated polybutadiene,   (b) 0.2 to 15% by weight of styrene,   (c) 0.2 to 15% by weight of alkyl methacrylates comprising 12 to 14 carbon atoms in the alkyl chain,   (d) 50 to 65% by weight of butylmethacrylate, and   (e) 0.1 to 0.2% by weight of methylmethacrylate,   based on the total weight of the comb polymer.   
     
     
         17 : The lubricant composition of  claim 1 , wherein the synthetic base oil (A) and the comb polymer (B) are present in a content of 100%, in total, of the lubricant composition.