Acrylate-based copolymer, method for producing said copolymer, friction reducer using said copolymer, and lubricating composition containing said friction reducer

A method of inhibiting friction of a base oil, comprising adding an acrylate-based copolymer to the base oil wherein the acrylate-based copolymer is obtained by polymerizing monomers containing a polymerizable monomer (a) consisting of an alkyl acrylate-based monomer represented by the following general formula (1) in an amount of from 10 mol % to 95 mol % with respect to a total number of moles of the constituent monomers, a polymerizable monomer (b) consisting of an alkylene glycol acrylate-based monomer represented by the following general formula (2) in an amount of from 5 mol % to 50 mol % with respect to the total number of moles of the constituent monomers, and at least one kind of polymerizable monomer (c) selected from the group consisting of an aromatic vinyl-based monomer (c-1) and a short-chain alkyl acrylate-based monomer (c-2) represented by the following general formula (3) in an amount of from 0 mol % to 60 mol % with respect to the total number of moles of the constituent monomers:

• wherein R1 represents an alkyl group having 4 to 18 carbon atoms, and A1 represents a hydrogen atom;
• wherein R2 represents an alkylene group having 2 to 4 carbon atoms, R3 represents a hydrogen atom or an alkyl group having 1 to 30 carbon atoms, A2 represents a hydrogen atom, and “n” represents a number from 2 to 20;
• and
• wherein R4 represents an alkyl group having 1 to 3 carbon atoms, and A3 represents a hydrogen atom.

A lubricating oil composition, comprising:

• a friction reducer consisting of an acrylate-based copolymer;
• and
• a base oil wherein the acrylate-based copolymer is obtained by polymerizing constituent monomers containing a polymerizable monomer (a) consisting of an alkyl acrylate-based monomer represented by the following general formula (1) in an amount of from 30 mol % to 95 mol % with respect to a total number of moles of the constituent monomers, and a polymerizable monomer (b) consisting of an alkylene glycol acrylate-based monomer represented by the following general formula (2) in an amount of from 5 mol % to 70 mol % with respect to the total number of moles of the constituent monomers:
• wherein R1 represents an alkyl group having 4 to 18 carbon atoms, and A1 represents a hydrogen atom;
• and
• wherein R2 represents an alkylene group having 2 to 4 carbon atoms, R3 represents a hydrogen atom or an alkyl group having 1 to 30 carbon atoms, A2 represents a hydrogen atom, and “n” represents a number from 2 to 20.