A viscosity index improver containing a copolymer (A) whose essential constituent monomer is a monomer (a) having a number average molecular weight of 800 to 4,000 represented by the following formula (1), the copolymer (A) having a solubility parameter in the range of 9.00 to 9.40:

##STR00001##

wherein R.sup.1 is a hydrogen atom or a methyl group; X.sup.1 is a group represented by O, O(AO).sub.m, or NH, AO is a C2-C4 alkyleneoxy group, m is an integer of 1 to 10, each AO may be the same or different when m is 2 or more, and the (AO).sub.m moieties may be randomly bonded or block-bonded; R.sup.2 is a residue after removal of one hydrogen atom from a hydrocarbon polymer whose essential constituent monomer is butadiene in which the butadiene is present in a proportion of 50% by weight or more based on the weight of R.sup.2, or after removal of one hydrogen atom from a polymer formed by partial hydrogenation of the hydrocarbon polymer; and p represents a number of 0 or 1.

A viscosity index improver containing a copolymer (A) whose essential constituent monomer is a monomer (a) having a number average molecular weight of 800 to 4,000 represented by the following formula (1), the copolymer (A) having a solubility parameter in the range of 9.00 to 9.40:

##STR00001##

wherein R.sup.1 is a hydrogen atom or a methyl group; X.sup.1 is a group represented by O, O(AO).sub.m, or NH, AO is a C2-C4 alkyleneoxy group, m is an integer of 1 to 10, each AO may be the same or different when m is 2 or more, and the (AO).sub.m moieties may be randomly bonded or block-bonded; R.sup.2 is a residue after removal of one hydrogen atom from a hydrocarbon polymer whose essential constituent monomer is butadiene in which the butadiene is present in a proportion of 50% by weight or more based on the weight of R.sup.2, or after removal of one hydrogen atom from a polymer formed by partial hydrogenation of the hydrocarbon polymer; and p represents a number of 0 or 1.

Provided is a lubricity-imparting agent that can impart durable lubricity (in particular, lubricity at the time of wetting) to a substrate. It has been found that a lubricity-imparting agent including a copolymer containing a constitutional unit (A) based on 2-methacryloyloxyethyl phosphorylcholine and a constitutional unit (B) based on a photoreactive functional group-containing monomer, or a copolymer containing a constitutional unit (A) based on 2-methacryloyloxyethyl phosphorylcholine, a constitutional unit (B) based on a photoreactive functional group-containing monomer, and a constitutional unit (C) based on a hydrophobic group-containing monomer can impart durable lubricity to a substrate surface through a simple approach called photoirradiation.

The present invention relates to a lubricant composition comprising at least one polyalkyl(meth)acrylate including repeating units derived from (meth)acrylates having 6 to 22 carbon atoms in the alcohol radical, wherein the polyalkyl(meth)acrylate includes repeating units derived from ethylenically unsaturated monomers having at least one covalently bonded phosphorus atom. The present invention further relates to a polyalkyl(meth)acrylate suitable for such a lubricant composition and to the use of a polyalkyl(meth)acrylate having repeating units derived from ethylenically unsaturated monomers having at least one covalently bonded phosphorus atom for reducing friction.

The present invention relates to a lubricant composition comprising at least one polyalkyl(meth)acrylate including repeating units derived from (meth)acrylates having 6 to 22 carbon atoms in the alcohol radical, wherein the polyalkyl(meth)acrylate includes repeating units derived from ethylenically unsaturated monomers having at least one covalently bonded phosphorus atom. The present invention further relates to a polyalkyl(meth)acrylate suitable for such a lubricant composition and to the use of a polyalkyl(meth)acrylate having repeating units derived from ethylenically unsaturated monomers having at least one covalently bonded phosphorus atom for reducing friction.

The invention provides a lubricating composition containing an oil of lubricating viscosity and a block copolymer. The block copolymer may contain (a) a hydrophobic first block having C.sub.1-30 alkyl (meth)acrylic units, wherein at least 50 wt % of the C.sub.1-30 alkyl (meth)acrylic units are C.sub.12-15 alkyl (meth)acrylic units, and up to 50 wt % of the C.sub.1-30 alkyl (meth)acrylic units are C.sub.16-20 alkyl (meth)acrylic units, with the proviso that alkyl groups of the C.sub.1-30 alkyl (meth)acrylic units have an average total number of carbon atoms of at least 8; and (b) a second block having (meth)acrylic units further having a heteroatom-containing group providing a polar group. The invention further relates to a method of lubricating an internal combustion engine by lubricating the engine with the lubricating composition. The invention further relates to the use of the block copolymer as an emulsifier and/or pour point depressant.

The invention provides a lubricating composition containing an oil of lubricating viscosity and a block copolymer. The block copolymer may contain (a) a hydrophobic first block having C.sub.1-30 alkyl (meth)acrylic units, wherein at least 50 wt % of the C.sub.1-30 alkyl (meth)acrylic units are C.sub.12-15 alkyl (meth)acrylic units, and up to 50 wt % of the C.sub.1-30 alkyl (meth)acrylic units are C.sub.16-20 alkyl (meth)acrylic units, with the proviso that alkyl groups of the C.sub.1-30 alkyl (meth)acrylic units have an average total number of carbon atoms of at least 8; and (b) a second block having (meth)acrylic units further having a heteroatom-containing group providing a polar group. The invention further relates to a method of lubricating an internal combustion engine by lubricating the engine with the lubricating composition. The invention further relates to the use of the block copolymer as an emulsifier and/or pour point depressant.

A lubricating oil additive composition that is suitable as a load bearing additive, and is excellent in wear resistance, extreme pressure property, and thermal stability, and a lubricating oil composition containing the lubricating oil additive composition. A lubricating oil additive composition containing a poly(meth)acrylate-based copolymer (X) containing a structural unit (a) derived from a particular alkyl (meth)acrylate (A), a structural unit (b) derived from a particular hydroxy group containing (meth)acrylate (B), and a structural unit (c) derived from a particular phosphorus-containing (meth)acrylate (C).

A lubricating oil additive composition that is suitable as a load bearing additive, and is excellent in wear resistance, extreme pressure property, and thermal stability, and a lubricating oil composition containing the lubricating oil additive composition. A lubricating oil additive composition containing a poly(meth)acrylate-based copolymer (X) containing a structural unit (a) derived from a particular alkyl (meth)acrylate (A), a structural unit (b) derived from a particular hydroxy group containing (meth)acrylate (B), and a structural unit (c) derived from a particular phosphorus-containing (meth)acrylate (C).

The present invention aims to provide a viscosity index improver excellent in shear stability and having a low HTHS viscosity and a high viscosity index. The viscosity index improver of the present invention contains a (co)polymer (A) containing a polyolefin-based monomer as an essential monomer unit, and a base oil, wherein the absolute value of difference in solubility parameter between the (co)polymer (A) and the base oil is 0.8 to 2.0 (cal/cm.sup.3).sup.1/2.