An object is to provide a viscosity index improver composition that is capable of properly regulating the HTHS viscosity in the effective temperature range of a lubricating oil composition to a lower range, and a lubricating oil composition containing the viscosity index improver composition, and the viscosity index improver composition contains a comb-shaped polymer (A) containing a structural unit derived from a macromonomer (α) and a structural unit derived from a particular monomer (A1), the macromonomer (α) having a (meth)acryloyl group at one end, and having a structural unit derived from a monomer (α1) selected from butadiene and hydrogenated butadiene.

An object is to provide a viscosity index improver composition that is capable of properly regulating the HTHS viscosity in the effective temperature range of a lubricating oil composition to a lower range, and a lubricating oil composition containing the viscosity index improver composition, and the viscosity index improver composition contains a comb-shaped polymer (A) containing a structural unit derived from a macromonomer (α) and a structural unit derived from a particular monomer (A1), the macromonomer (α) having a (meth)acryloyl group at one end, and having a structural unit derived from a monomer (α1) selected from butadiene and hydrogenated butadiene.

The present invention aims to provide a viscosity index improver composition and a lubricating oil composition having a low HTHS viscosity at 100° C., an excellent shear stability, and an excellent low temperature viscosity. The present invention relates to, for example, a viscosity index improver composition (C), containing: a copolymer (A) containing a polyolefin-based monomer (a) represented by the following formula (1) as a constituent monomer; a copolymer (B) containing a (meth)acrylic acid alkyl ester (c) having a C12-C15 straight-chain or branched alkyl group and a (meth)acrylic acid alkyl ester (d) having a C16-C20 straight-chain or branched alkyl group as constituent monomers; and a base oil, wherein a weight average molecular weight ratio {(A)/(B)} of the copolymer (A) to the copolymer (B) is 2 to 55, and a weight ratio (A/B) of the copolymer (A) to the copolymer (B) constituting the viscosity index improver composition (C) is 5 to 100:

##STR00001##

The present invention aims to provide a viscosity index improver composition and a lubricating oil composition having a low HTHS viscosity at 100° C., an excellent shear stability, and an excellent low temperature viscosity. The present invention relates to, for example, a viscosity index improver composition (C), containing: a copolymer (A) containing a polyolefin-based monomer (a) represented by the following formula (1) as a constituent monomer; a copolymer (B) containing a (meth)acrylic acid alkyl ester (c) having a C12-C15 straight-chain or branched alkyl group and a (meth)acrylic acid alkyl ester (d) having a C16-C20 straight-chain or branched alkyl group as constituent monomers; and a base oil, wherein a weight average molecular weight ratio {(A)/(B)} of the copolymer (A) to the copolymer (B) is 2 to 55, and a weight ratio (A/B) of the copolymer (A) to the copolymer (B) constituting the viscosity index improver composition (C) is 5 to 100:

##STR00001##

A lubricant composition that comprises a hydrocarbon base oil, a polar viscosity improver; and an esterified polyalkylene glycol: R.sup.1[O(R.sup.2O).sub.n(R.sup.3O).sub.m(C═O)R.sup.4].sub.p, wherein R.sup.1 is a linear alkyl having 1 to 18 carbon atoms, a branched alkyl having 4 to 18 carbon atoms or an aryl with 6 to 30 carbon atoms; R.sup.2O is an oxypropylene moiety derived from 1, 2-propylene oxide; R.sup.3O is an oxybutylene moiety derived from butylene oxide, wherein R.sup.2O and R.sup.3O are in a block or a random distribution; R.sup.4 is a linear alkyl with 1 to 18 carbon atoms, a branched alkyl with 4 to 18 carbon atoms or an aryl with 6 to 18 carbon atoms; n and m are each independently integers ranging from 0 to 20 wherein n+m is greater than 0, and p is an integer from 1 to 4. The lubricant composition may have a viscosity index of at least 150, a kinematic viscosity at 100° C. from 2 to 5 centistokes and a kinematic viscosity at −20° C. of at most 600 centistokes.

A lubricant composition that comprises a hydrocarbon base oil, a polar viscosity improver; and an esterified polyalkylene glycol: R.sup.1[O(R.sup.2O).sub.n(R.sup.3O).sub.m(C═O)R.sup.4].sub.p, wherein R.sup.1 is a linear alkyl having 1 to 18 carbon atoms, a branched alkyl having 4 to 18 carbon atoms or an aryl with 6 to 30 carbon atoms; R.sup.2O is an oxypropylene moiety derived from 1, 2-propylene oxide; R.sup.3O is an oxybutylene moiety derived from butylene oxide, wherein R.sup.2O and R.sup.3O are in a block or a random distribution; R.sup.4 is a linear alkyl with 1 to 18 carbon atoms, a branched alkyl with 4 to 18 carbon atoms or an aryl with 6 to 18 carbon atoms; n and m are each independently integers ranging from 0 to 20 wherein n+m is greater than 0, and p is an integer from 1 to 4. The lubricant composition may have a viscosity index of at least 150, a kinematic viscosity at 100° C. from 2 to 5 centistokes and a kinematic viscosity at −20° C. of at most 600 centistokes.

The present invention relates to a continuous high-pressure polymerization process for the preparation of a liquid ethylene copolymer which comprises in polymerized form 20 to 60 wt % of ethylene; and at least 20 wt % of an acrylate, which is selected from C.sub.1-C.sub.22 alkyl (meth)acrylate, where a monomer feed comprising the ethylene and the acrylate is polymerized in the presence of at least 2 wt % of a chain transfer agent. The invention further relates to the liquid ethylene copolymer obtainable by the polymerization process; and to a lubricant comprising the liquid ethylene copolymer obtainable by the polymerization process; and to a method for reducing friction between moving surfaces comprising the step of contacting the surfaces with the lubricant or with the ethylene copolymer.

A low friction coated article includes a first structure that has a first lubricated surface coated with a first polyelectrolyte coating. A second structure has a second lubricated surface with a second polyelectrolyte coating opposite the first lubricated surface. The first and second polyelectrolyte coatings include alternating layers of positively charged polyelectrolyte layers and negatively charged polyelectrolyte layers hydrated with a lubricant.

A low friction coated article includes a first structure that has a first lubricated surface coated with a first polyelectrolyte coating. A second structure has a second lubricated surface with a second polyelectrolyte coating opposite the first lubricated surface. The first and second polyelectrolyte coatings include alternating layers of positively charged polyelectrolyte layers and negatively charged polyelectrolyte layers hydrated with a lubricant.

A lubricating oil composition may include a base oil (A), an olefin copolymer (B), and a poly(alkyl(meth)acrylate) (C), in which a weight average molecular weight of the olefin copolymer (B) is 10,000 to 80,000, a content of the olefin copolymer (B) is 0.01% to 0.23% by mass based on the total amount of the lubricating oil composition, and a content of the poly(alkyl(meth)acrylate) (C) is 0.02% to 0.40% by mass based on the total amount of the lubricating oil composition.