A lubricating oil composition for a transmission, the composition including: (A) a lubricant base oil comprising a mineral base oil and/or a synthetic base oil; and (B) a poly(meth)acrylate having a weight average molecular weight of no more than 25,000, wherein the composition has a kinematic viscosity at 100° C. of 2.5 to 4.9 mm.sup.2/s.

The present invention aims to provide a viscosity index improver composition capable of providing a lubricant composition that has an excellent viscosity index improving effect, excellent antifoaming properties, and excellent persistence of the antifoaming properties. The present invention relates to a viscosity index improver composition, containing: a (co)polymer (A) containing a monomer (a) represented by the following formula (1) as an essential monomer; a C18-C40 chain aliphatic alcohol (B); and a base oil,

##STR00001##

wherein R.sup.1 is a hydrogen atom or a methyl group; -X.sup.1- is a group represented by —O— or —NH—; R.sup.2 is a C2-C4 alkylene group; R.sup.3 and R.sup.4 are each independently a C8-C24 linear or branched alkyl group; and p is an integer of 0 to 20, with each R.sup.2 being optionally the same as or different from each other when p is 2 or greater.

The present invention aims to provide a viscosity index improver composition capable of providing a lubricant composition that has an excellent viscosity index improving effect, excellent antifoaming properties, and excellent persistence of the antifoaming properties. The present invention relates to a viscosity index improver composition, containing: a (co)polymer (A) containing a monomer (a) represented by the following formula (1) as an essential monomer; a C18-C40 chain aliphatic alcohol (B); and a base oil,

##STR00001##

wherein R.sup.1 is a hydrogen atom or a methyl group; -X.sup.1- is a group represented by —O— or —NH—; R.sup.2 is a C2-C4 alkylene group; R.sup.3 and R.sup.4 are each independently a C8-C24 linear or branched alkyl group; and p is an integer of 0 to 20, with each R.sup.2 being optionally the same as or different from each other when p is 2 or greater.

Acrylate-olefin copolymers and a method for the preparation of these copolymers are provided. Lubricant compositions can contain the aforementioned copolymers. The copolymers are useful as a lubricant additive or a synthetic base fluid in a lubricating oil composition, preferably in a gear oil composition, a transmission oil composition, a hydraulic oil composition, an engine oil composition, a marine oil composition, an industrial lubricating oil composition or in grease.

Acrylate-olefin copolymers and a method for the preparation of these copolymers are provided. Lubricant compositions can contain the aforementioned copolymers. The copolymers are useful as a lubricant additive or a synthetic base fluid in a lubricating oil composition, preferably in a gear oil composition, a transmission oil composition, a hydraulic oil composition, an engine oil composition, a marine oil composition, an industrial lubricating oil composition or in grease.

Polyalkyl(meth)acrylates contain specified amounts of long-chain alkyl (meth)acrylates and functional monomers. Lubricant compositions can contain such polyalkyl(meth)acrylates, and the polyalkyl(meth)acrylates can be used as viscosity index (VI) improvers with good fuel economy as well as soot-dispersant function. The polyalkyl(meth)acrylates can provide equal or even unproved deposits in lubricant compositions, especially in engine oil (EO) compositions.

Polyalkyl(meth)acrylates contain specified amounts of long-chain alkyl (meth)acrylates and functional monomers. Lubricant compositions can contain such polyalkyl(meth)acrylates, and the polyalkyl(meth)acrylates can be used as viscosity index (VI) improvers with good fuel economy as well as soot-dispersant function. The polyalkyl(meth)acrylates can provide equal or even unproved deposits in lubricant compositions, especially in engine oil (EO) compositions.

A lipophilic copolymer including polar multi-blocks having general formula (I):

[(B.sub.yA.sub.k).sub.s].sub.t(A.sub.jC.sub.m)  (I)

wherein: B represents at least one monomer unit deriving from a lipophilic monomer having general formula (II):

##STR00001## wherein: X represents a hydrogen atom; or a methyl group; R is selected from C.sub.1-C.sub.50 alkyl groups, linear or branched; A represents at least one monomer unit deriving from a polar monomer selected from: (a) compounds having general formula (III):

##STR00002## wherein X represents a hydrogen atom or a methyl group and n represents an integer comprised between 0 and 4; (b) (meth)acrylamide or (meth)acrylamides substituted on the nitrogen atom with one or two C.sub.1-C.sub.4 alkyl groups linear or branched; (c) di-(C.sub.1-C.sub.4)-alkylamino-(C.sub.1-C.sub.4)-alkyl (meth)acrylates; C represents at least one monomer unit deriving from a polar polyfunctional monomer having general formula (IV):

Z—(W).sub.p  (IV) wherein: Z represents a group containing carbon, hydrogen and, optionally, oxygen; and W represents a function able to react covalently with an alkyl radical.

A lipophilic copolymer including polar multi-blocks having general formula (I):

[(B.sub.yA.sub.k).sub.s].sub.t(A.sub.jC.sub.m)  (I)

wherein: B represents at least one monomer unit deriving from a lipophilic monomer having general formula (II):

##STR00001## wherein: X represents a hydrogen atom; or a methyl group; R is selected from C.sub.1-C.sub.50 alkyl groups, linear or branched; A represents at least one monomer unit deriving from a polar monomer selected from: (a) compounds having general formula (III):

##STR00002## wherein X represents a hydrogen atom or a methyl group and n represents an integer comprised between 0 and 4; (b) (meth)acrylamide or (meth)acrylamides substituted on the nitrogen atom with one or two C.sub.1-C.sub.4 alkyl groups linear or branched; (c) di-(C.sub.1-C.sub.4)-alkylamino-(C.sub.1-C.sub.4)-alkyl (meth)acrylates; C represents at least one monomer unit deriving from a polar polyfunctional monomer having general formula (IV):

Z—(W).sub.p  (IV) wherein: Z represents a group containing carbon, hydrogen and, optionally, oxygen; and W represents a function able to react covalently with an alkyl radical.

Anaerobic sealant lubricant compositions and uses are disclosed. The anaerobic sealant lubricant compositions cure anaerobically but have lubricity for easy disassembly, making the compositions well suited for fasteners and threaded components.