Polymer, friction reducer for lubricating oil, and lubricating oil composition

Abstract

A polymer having a main-chain polymeric structure and a side-chain polymeric structure, wherein the side-chain polymeric structure comprises a constituent unit derived from an alkyl (meth)acrylate (a) in which the alkyl group has 11-30 carbon atoms. The polymer has a mass-average molecular weight of 90,000 or lower.

Description

[Technical field]

[0001] The present invention relates to a polymer for use in a lubricating oil, a friction reducer for a lubricating oil, and a lubricating oil composition. This application claims priority based on Japanese Patent Application No. 2022-143800, filed on September 9, 2022, the contents of which are incorporated herein by reference. [Background technology]

[0002] Lubricating oils, such as automobile engine oils and driveline oils, contain various friction reducers to reduce energy loss due to friction and to extend the life of equipment by preventing seizure. In recent years, the viscosity of lubricating oils has been reduced in order to reduce fuel consumption, and the load on the contact surfaces between metals has become more severe, making the role of friction reducers even more important. Examples of friction reducers include oiliness improvers such as long-chain fatty acid esters and fatty acid amides, antiwear agents such as phosphate esters and zinc dithiophosphates, extreme pressure agents such as organic sulfur compounds and organic halogen compounds, and friction modifiers such as organic molybdenum compounds. However, depending on the conditions and environments of use, these additives alone may not be sufficient to reduce friction. In order to overcome this problem, studies are being conducted on the use of polymer materials as friction reducers. For example, Patent Document 1 discloses that a (meth)acrylic graft copolymer can be suitably used as a friction modifier. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-113676 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the method of Patent Document 1 is insufficient in reducing friction, and the viscosity of the lubricating oil composition is high, which increases energy loss due to stirring resistance, thereby deteriorating fuel efficiency.

[0005] An object of the present invention is to provide a polymer, and to provide a polymer that can be used to provide a polymer lubricating oil additive, a friction reducer for lubricating oil, and a lubricating oil composition that have a high friction reducing effect and a low viscosity. [Means for solving the problem]

[0006] The present invention has the following aspects. [1] A polymer having a main chain structure and a side chain polymer structure, the side chain polymer structure contains a structural unit derived from an alkyl(meth)acrylate (a) having an alkyl group with 11 to 30 carbon atoms, A polymer having a mass average molecular weight of 90,000 or less. [2] A base oil solution containing 2% by mass of the polymer is prepared, and the kinematic viscosity at 40°C measured in accordance with ASTM D7279 (D445) is 22.4 cSt or less; 2. The polymer of claim 1, wherein the base oil is API Group III plus. [3] A polymer having a main chain structure and a side chain polymer structure, the side chain polymer structure contains a structural unit derived from an alkyl(meth)acrylate (a) having an alkyl group with 11 to 30 carbon atoms, A base oil solution containing 2% by mass of the polymer is prepared, and the kinematic viscosity at 40°C measured in accordance with ASTM D7279 (D445) is 22.4 cSt or less; The base oil is a polymer that meets API Group III plus standards. [4] The polymer according to [3], wherein the mass average molecular weight is less than 50,000. [5] The polymer according to any one of [1] to [4], further comprising a structural unit derived from an alkyl(meth)acrylate (b) having an alkyl group with 1 to 10 carbon atoms. [6] The polymer according to any one of [1] to [5], which contains a structural unit derived from a vinyl radically polymerizable monomer (m1). [7] The polymer according to any one of [1] to [6], wherein the proportion of the main chain polymer structure is preferably 5 to 98 mass%, more preferably 10 to 95 mass%, and still more preferably 20 to 90 mass%, based on the total mass of the polymer. [8] The polymer according to any one of [1] to [7], wherein the proportion of the side chain polymer structure is preferably from 2 to 95 mass%, more preferably from 5 to 90 mass%, and still more preferably from 10 to 80 mass%, based on the total mass of the polymer. [9] The copolymer according to any one of [1] to [8], wherein the alkyl(meth)acrylate (a) is preferably an alkyl(meth)acrylate having an alkyl group with 11 to 20 carbon atoms, more preferably an alkyl(meth)acrylate having an alkyl group with 11 to 18 carbon atoms, and even more preferably an alkyl(meth)acrylate having an alkyl group with 11 to 14 carbon atoms.

[10] The polymer according to any one of [1] to [9], wherein the content of the structural unit derived from the alkyl (meth)acrylate (a) is preferably 50 to 100 mass%, more preferably 60 to 100 mass%, further preferably 70 to 99 mass%, and particularly preferably 80 to 98 mass%, based on the total mass of the side chain polymer structure.

[11] The polymer according to any one of [1] to

[10] , wherein the content of the structural unit derived from the alkyl (meth)acrylate (a) is preferably 20 to 98 mass%, more preferably 25 to 95 mass%, and further preferably 30 to 90 mass%, based on the total mass of the polymer.

[12] The polymer according to any one of [1] to

[11] , further comprising a structural unit derived from an alkyl (meth)acrylate (b) having an alkyl group with 1 to 10 carbon atoms, wherein the (meth)acrylate (b) is preferably a (meth)acrylate having a linear or branched alkyl group, more preferably an alkyl acrylate having an alkyl group with 2 to 8 carbon atoms, still more preferably an alkyl acrylate having an alkyl group with 2 to 4 carbon atoms, and particularly preferably n-butyl acrylate.

[13] The copolymer according to any one of [1] to

[12] , further comprising a structural unit derived from an alkyl (meth)acrylate (b) having an alkyl group with 1 to 10 carbon atoms, wherein the content of the structural unit derived from the (meth)acrylate (b) is preferably 3 to 80 mass%, more preferably 5 to 75 mass%, and even more preferably 10 to 70 mass%, relative to the total mass of the polymer.

[14] The copolymer according to any one of [1] to

[13] , further comprising a structural unit derived from another radically polymerizable vinyl compound (c) which does not belong to any of the structural units derived from the alkyl(meth)acrylate (a) and the structural units derived from the alkyl(meth)acrylate (b) having an alkyl group with 1 to 10 carbon atoms, wherein the radically polymerizable vinyl compound (c) is preferably an alkyl(meth)acrylate having a polar group, more preferably an alkyl(meth)acrylate having a hydroxyl group, a carboxy group, an amino group or an amide group, and even more preferably an alkyl(meth)acrylate having a hydroxyl group.

[15] The copolymer according to any one of [1] to

[14] , further comprising a structural unit derived from another radically polymerizable vinyl compound (c) which does not belong to any of the structural units derived from the alkyl (meth)acrylate (a) and the structural units derived from the alkyl (meth)acrylate (b) having an alkyl group with 1 to 10 carbon atoms, wherein the content of the structural units derived from the other radically polymerizable vinyl compound (c) is preferably 0 to 20 mass%, more preferably 0 to 10 mass%, and even more preferably 0 to 5 mass%, relative to the total mass of the polymer.

[16] The polymer according to any one of [1] to

[15] , which contains a structural unit derived from a macromonomer (M).

[17] The polymer according to

[16] , wherein the macromonomer (M) contains a structural unit derived from an alkyl(meth)acrylate (a) having 11 to 30 carbon atoms in the alkyl group.

[18] The polymer according to

[16] , wherein the macromonomer (M) has a structure represented by the following formula (1): (In the formula, X 1 ~Xn-1 each independently represents a hydrogen atom, a methyl group, or CHOH; Y 1 ~Y n each independently represents X bonded to a vinyl group of the vinyl radical polymerizable monomer (m2) which is a monomer constituent unit of the macromonomer (M). 1 ~X n-1 Z represents a terminal group, and n represents an integer of 2 to 10,000. [ka]

[19] The polymer according to

[18] , wherein the vinyl radical polymerizable monomer (m2) contains the alkyl (meth)acrylate (a).

[20] The polymer according to any one of

[16] to

[19] , wherein the content of the structural unit derived from the alkyl (meth)acrylate (a) is preferably 50 to 100 mass%, more preferably 60 to 100 mass%, further preferably 70 to 99 mass%, and particularly preferably 80 to 98 mass%, based on the total mass of the macromonomer (M).

[21] The polymer according to any one of

[16] to

[20] , wherein the macromonomer (M) contains a structural unit derived from an alkyl (meth)acrylate (b) having an alkyl group with 1 to 10 carbon atoms, and the content of the structural unit derived from the (meth)acrylate (b) is more preferably 0.5 to 40 mass%, further preferably 1 to 30 mass%, and particularly preferably 1.5 to 20 mass%, relative to the total mass of the macromonomer (M).

[22] The polymer according to any one of [1] to

[21] , wherein the ratio of [the content of the structural units derived from the alkyl (meth)acrylate (b) having a carbon number of 1 to 10 in the alkyl group] / [the content of the structural units derived from the alkyl (meth)acrylate (a)] in the macromonomer (M) is preferably 0.001 to 0.1, more preferably 0.005 to 0.05, and even more preferably 0.01 to 0.03.

[23] The polymer according to any one of

[16] to

[22] , wherein the content of the constitutional unit derived from the macromonomer (M) is preferably 1 to 70 mass%, more preferably 2 to 60 mass%, and still more preferably 5 to 50 mass%, based on the total mass of the polymer.

[24] The polymer according to any one of

[16] to

[23] , wherein the mass average molecular weight (Mw) of the macromonomer (M) measured by gel permeation chromatography is preferably 5,000 or more and 50,000 or less, more preferably 8,000 or more and 40,000 or less, and even more preferably 10,000 or more and 30,000 or less.

[25] The polymer according to any one of

[16] to

[24] , wherein the macromonomer (M) has a number average molecular weight (Mn) measured by gel permeation chromatography (GPC) of preferably 500 to 30,000, more preferably 1,000 to 25,000, and particularly preferably 2,000 to 20,000.

[26] The polymer according to any one of

[16] to

[25] , wherein the molecular weight distribution (Mw / Mn) of the macromonomer (M) as measured by gel permeation chromatography is preferably 1.0 or more and 10 or less, more preferably 1.2 or more and 8 or less, and even more preferably 1.5 or more and 5 or less.

[27] The polymer according to any one of [1] to

[26] , wherein the mass average molecular weight (Mw) of the polymer measured by GPC is preferably 90,000 or less, more preferably 10,000 or more and 90,000 or less, further preferably 12,000 to 85,000, particularly preferably 15,000 to 80,000, and most preferably 20,000 to 75,000.

[28] The polymer according to any one of [1] to

[27] , wherein the number average molecular weight (Mn) of the polymer measured by gel permeation chromatography (GPC) is preferably 5,000 or more and 50,000 or less, more preferably 7,000 or more and 40,000 or less, and even more preferably 10,000 or more and 30,000 or less.

[29] The polymer according to any one of [1] to

[28] , wherein the molecular weight distribution (Mw / Mn) of the polymer as measured by gel permeation chromatography (GPC) is preferably 1.0 or more and 20 or less, more preferably 1.5 or more and 15 or less, and even more preferably 2.0 or more and 10 or less.

[30] The polymer according to any one of [1] to

[29] , wherein a friction coefficient measured at 40°C using an SRV5 testing machine (manufactured by Optimol Instruments Pruftechnik GmbH) in a base oil solution containing 2 mass% of the polymer is preferably 0.16 or less, more preferably less than 0.138, and even more preferably 0.135 or less.

[31] A base oil solution containing 2% by mass of the polymer is prepared, and the kinematic viscosity at 40°C measured in accordance with ASTM D7279 (D445) is preferably 0 to 22.4 cSt, more preferably 5 cSt or more but less than 22.25 cSt, even more preferably 10 cSt or more but less than 22.00 cSt, and particularly preferably 15 to 21.50 cSt; The polymer according to any one of [1] to

[30] , wherein the base oil is API Group III plus.

[32] A lubricating oil additive comprising the polymer according to any one of [1] to

[31] .

[33] A friction reducer for lubricating oil, comprising the polymer according to any one of [1] to

[31] and a base oil.

[34] The friction reducer for lubricating oils according to

[33] , wherein the base oil is an API Group III base oil, an API Group III plus base oil, or an API Group IV base oil.

[35] The friction reducer for lubricating oil according to

[33] or

[34] , wherein the content of the polymer is preferably 10 to 80 mass%, more preferably 15 to 70 mass%, and even more preferably 20 to 60 mass%, when the total mass of the lubricating oil additive is 100 mass%.

[36] A lubricating oil composition comprising the friction reducer for lubricating oil according to any one of

[33] to

[35] .

[37] The lubricating oil composition according to

[36] , wherein the content of the polymer is preferably 0.01 to 30 mass%, more preferably 0.05 to 25 mass%, and even more preferably 0.1 to 20 mass%, when the total mass of the lubricating oil composition is 100 mass%.

[38] Use of the polymer according to any one of [1] to

[31] for producing a lubricating oil composition.

[39] Use of the polymer according to any one of [1] to

[31] for reducing friction.

[40] Use of the polymer according to any one of [1] to

[31] for improving lubricity.

[41] Use of a composition comprising the polymer according to any one of [1] to

[31] for reducing friction.

[42] Use of a composition containing the polymer according to any one of [1] to

[31] for improving lubricity.

[43] The use described in

[41] or

[42] , wherein the composition contains a solvent.

[44] The use according to

[43] , wherein the solvent is a base oil.

[45] The use according to

[44] , wherein the base oil is an API Group III base oil, an API Group III plus base oil, or an API Group IV base oil.

[46] The use according to any one of

[41] to

[45] , wherein the content of the polymer is preferably 0.01 to 30 mass%, more preferably 0.05 to 25 mass%, and even more preferably 0.1 to 20 mass%, when the total mass of the composition is 100 mass%.

[0007] In addition, the present invention has the following aspects. [1] A friction reducer for lubricating oils, comprising a (meth)acrylic graft copolymer A having a main chain polymer structure and a side chain polymer structure, A friction reducer for lubricating oil, wherein the (meth)acrylic graft copolymer A contains a structural unit derived from an alkyl (meth)acrylate (a) having an alkyl group with 11 to 30 carbon atoms in the side chain polymer structure, and has a mass average molecular weight of 10,000 to 90,000. [2] The friction reducer for lubricating oils according to [1], wherein the (meth)acrylic graft copolymer A further contains a structural unit derived from an alkyl (meth)acrylate (b) having an alkyl group having 1 to 10 carbon atoms. [3] The friction reducer for lubricating oils according to [1], wherein the (meth)acrylic graft copolymer A contains a constituent unit derived from a vinyl radically polymerizable monomer (m1) and a constituent unit derived from a macromonomer (M). [4] The friction reducer for lubricating oils according to [3], wherein the macromonomer (M) contains a structural unit derived from an alkyl (meth)acrylate (a) having 11 to 30 carbon atoms in the alkyl group. [5] The friction reducer for lubricating oil according to [3], wherein the macromonomer (M) has a structure represented by the following formula (1):

[0008] [ka]

[0009] (In the formula, X 1 ~X n-1 each independently represents a hydrogen atom, a methyl group, or CHOH; Y 1 ~Y n each independently represents X bonded to a vinyl group of the vinyl radical polymerizable monomer (m2) which is a monomer constituent unit of the macromonomer (M). 1 ~X n-1 Z represents a terminal group, and n represents an integer of 2 to 10,000. [6] A lubricating oil composition comprising the friction reducer for lubricating oil according to any one of [1] to [5]. Effect of the Invention

[0010] According to the polymer of the present invention, it is possible to provide a polymer that has a high friction reducing effect and is capable of providing a low-viscosity polymer lubricant additive, a friction reducer for lubricating oil, and a lubricant oil composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described in detail below. The following embodiments are merely examples for explaining the present invention, and are not intended to limit the present invention to these embodiments. The present invention can be implemented in various forms without departing from the spirit of the present invention.

[0012] In the present invention, "(meth)acrylic" is a general term for "acrylic" and "methacrylic". "(meth)acrylate" is a general term for "acrylate" and "methacrylate". "(meth)acryloyl group" is a general term for "acryloyl group" and "methacryloyl group", and is a group represented by CH2=C(R)-C(=O)- (R is a hydrogen atom or a methyl group). "Macromonomer" means a polymer having a radical polymerizable group or an addition-reactive functional group. "Vinyl radical polymerizable monomer" means a monomer having an ethylenically unsaturated bond that is not a macromonomer.

[0013] The polymer in the first aspect of the present invention has a main chain polymer structure and a side chain polymer structure, the side chain polymer structure contains a structural unit derived from an alkyl (meth)acrylate (a) having an alkyl group with 11 to 30 carbon atoms, and has a mass average molecular weight of 90,000 or less. The polymer in a second aspect of the present invention has a main chain polymer structure and a side chain polymer structure, the side chain polymer structure contains a structural unit derived from an alkyl (meth)acrylate (a) having an alkyl group with 11 to 30 carbon atoms, a base oil solution containing 2 mass % of the polymer is prepared, and the kinetic viscosity at 40°C measured in accordance with ASTM D7279 (D445) is 22.4 cSt or less, and the base oil is API Group III plus. The polymer is preferably a graft copolymer in which at least a part of the constituent units is derived from a (meth)acrylic monomer. The polymer may further contain a constituent unit derived from a monomer other than the (meth)acrylic monomer (e.g., styrene, etc.).

[0014] The polymer is preferably a graft copolymer composed of a main chain polymer structure and a side chain polymer structure (branch polymer structure) chemically bonded to the main chain polymer structure (trunk polymer structure). In this specification, the graft copolymer is a polymer having one or more types of blocks connected as a side chain polymer structure to the main chain polymer structure. The structures of the main chain polymer and the side chain polymer may be different or the same. There is no particular limitation on the method for producing the graft copolymer, but examples thereof include a method of producing a macromonomer having a radically polymerizable double bond at its end as a side chain polymer structure, and then radically polymerizing it with a monomer that will be a constituent unit of the main chain polymer, a method of producing a main chain polymer having a reactive site and a macromonomer having a reactive site in advance, and then reacting them, and a method of producing a side chain polymer structure by generating radicals on the main chain polymer using an initiator having hydrogen abstraction ability after producing the main chain polymer, and reacting a monomer that will be a constituent unit of the side chain polymer.

[0015] The polymer preferably contains a structural unit derived from an alkyl(meth)acrylate (a) (hereinafter also referred to as "component (a)") having an alkyl group with 11 to 30 carbon atoms in its side chain polymer structure, and has a mass average molecular weight of 10,000 to 90,000. It may further contain a structural unit derived from an alkyl(meth)acrylate (b) (hereinafter also referred to as "component (b)") having an alkyl group with 1 to 10 carbon atoms.

[0016] The total content of the (a) component and the (b) component as structural units is preferably 70 mass% or more, more preferably 75 mass% or more, and even more preferably 80 mass% or more, of the total mass of the polymer. The polymer contains a constitutional unit derived from the component (a) in a side chain polymer structure, and may contain a constitutional unit derived from the component (a) in both the side chain polymer structure and the main chain polymer structure. Examples of the (a) component include n-undecyl (meth)acrylate, i-undecyl (meth)acrylate, n-dodecyl (meth)acrylate, i-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, i-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, i-tetradecyl (meth)acrylate, n-cetyl (meth)acrylate, i-cetyl (meth)acrylate, n-stearyl (meth)acrylate, i-stearyl (meth)acrylate, n-octadecyl (meth)acrylate, i-octadecyl (meth)acrylate, n-behenyl (meth)acrylate, i-behenyl (meth)acrylate, etc. Two or more of these may be used in combination.

[0017] From the viewpoint of reducing the viscosity of the lubricating oil composition, component (a) is preferably an alkyl (meth)acrylate having an alkyl group with 11 to 20 carbon atoms, more preferably an alkyl (meth)acrylate having an alkyl group with 11 to 18 carbon atoms, and even more preferably an alkyl (meth)acrylate having an alkyl group with 11 to 14 carbon atoms. From the viewpoint of increasing the solubility of the polymer in the base oil, the component (a) is preferably an alkyl (meth)acrylate having an alkyl group with 11 to 20 carbon atoms, more preferably an alkyl methacrylate having an alkyl group with 11 to 20 carbon atoms, still more preferably an alkyl methacrylate having an alkyl group with 11 to 18 carbon atoms, and particularly preferably an alkyl methacrylate having an alkyl group with 11 to 14 carbon atoms.

[0018] From the viewpoint of enhancing the friction-reducing effect and enabling the lubricating oil composition to have a low viscosity, the content of structural units derived from component (a) relative to the total mass of the polymer is preferably 20 to 98 mass%, more preferably 25 to 95 mass%, and even more preferably 30 to 90 mass%.

[0019] Examples of the component (b) include alkyl (meth)acrylates having a linear alkyl group, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, and n-nonyl (meth)acrylate; i-propyl (meth)acrylate, i-butyl (meth)acrylate, and t-butyl (meth)acrylate; acrylate, i-nonyl(meth)acrylate, n-decyl(meth)acrylate, i-decyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, etc.; alkyl(meth)acrylates having a cyclic alkyl group such as cyclopentyl(meth)acrylate, cyclohexyl(meth)acrylate, dicyclopentanyl(meth)acrylate, isobornyl(meth)acrylate, 4-t-butylcyclohexyl(meth)acrylate, etc. These may be used in combination of two or more kinds.

[0020] From the viewpoint of enhancing the friction-reducing effect, the component (b) is preferably a (meth)acrylate having a linear or branched alkyl group, more preferably an alkyl acrylate having an alkyl group with 2 to 8 carbon atoms, even more preferably an alkyl acrylate having an alkyl group with 2 to 4 carbon atoms, and particularly preferably n-butyl acrylate.

[0021] From the viewpoint of enhancing the friction-reducing effect and enabling the lubricating oil composition to have a low viscosity, the content of structural units derived from component (b) relative to the total mass of the polymer is preferably 3 to 80 mass%, more preferably 5 to 75 mass%, and even more preferably 10 to 70 mass%.

[0022] In order to improve the solubility of the polymer in the base oil, it is preferable that the polymer contains a structural unit derived from the component (a) as a structural unit in a side chain polymer structure, and it is more preferable that the polymer contains the structural unit in both the side chain polymer structure and the main chain polymer structure. The polymer preferably contains a structural unit derived from the component (b) as a structural unit in a side chain polymer structure, and more preferably in both the side chain polymer structure and the main chain polymer structure.

[0023] The mass average molecular weight (Mw) of the polymer is preferably 90,000 or less. From the viewpoint of reducing the viscosity of the lubricating oil composition, the mass average molecular weight of the polymer is more preferably from 10,000 to 90,000, even more preferably from 12,000 to 85,000, particularly preferably from 15,000 to 80,000, and most preferably from 20,000 to 75,000.

[0024] The polymer may contain a structural unit derived from a radically polymerizable vinyl compound other than the components (a) and (b) (hereinafter also referred to as "component (c)"). Examples of the other radically polymerizable vinyl compounds include styrene, α-methylstyrene, pt-butylstyrene, vinyl toluene, vinyl acetate, and (meth)acrylate compounds other than the components (a) and (b). Examples of the (meth)acrylate compound other than the components (a) and (b) include alkyl (meth)acrylates having a hydroxyl group, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, glycerin mono(meth)acrylate, ethylene glycol mono(meth)acrylate, and propylene glycol mono(meth)acrylate; alkyl (meth)acrylates containing a carboxy group, such as (meth)acrylic acid, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, 2-(meth)acryloyloxyethyl phthalate, and 2-(meth)acryloyloxyethyl hexahydrophthalate; phenyl (meth)acrylate, benzyl (meth)acrylate, and phenoxyethyl (meth)acrylate. alkyl (meth)acrylates having an aromatic ring structure such as phenoxydiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, nonylphenoxypolyethylene glycol (meth)acrylate, phenoxypolypropylene glycol (meth)acrylate, phenylphenyl (meth)acrylate, phenylphenoxyethyl (meth)acrylate, phenoxybenzyl (meth)acrylate, phenylbenzyl (meth)acrylate, naphthyl (meth)acrylate, and (1-naphthyl)methyl (meth)acrylate; alkyl (meth)acrylates having a heterocyclic structure such as tetrahydrofurfuryl (meth)acrylate, glycidyl (meth)acrylate, and (meth)acryloylmorpholine; alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, and butoxyethyl (meth)acrylate;Examples of the silane include 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 2-(meth)acryloyloxyethyl acid phosphate, trifluoroethyl (meth)acrylate, heptadecafluorodecyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, and (meth)acrylamide. Two or more of these may be used in combination.

[0025] From the viewpoint of enhancing the friction-reducing effect and enabling the lubricating oil composition to have a low viscosity, the content of structural units derived from component (c) relative to the total mass of the polymer is preferably 0 to 20 mass%, more preferably 0 to 10 mass%, and even more preferably 0 to 5 mass%. The total amount of the structural units derived from the components (a) to (c) does not exceed 100% by mass based on the total mass of the polymer.

[0026] The polymer may contain a constituent unit derived from a vinyl radically polymerizable monomer (m1) (hereinafter also referred to as "component (m1)") and a constituent unit derived from a macromonomer (M) (hereinafter also referred to as "component (M)").

[0027] Examples of the (m1) component include styrene, vinyl acetate, and (meth)acrylate compounds. Examples of the (meth)acrylate compounds include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, and n-undecyl (meth)acrylate. alkyl (meth)acrylates having a linear alkyl group, such as n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, n-cetyl (meth)acrylate, n-stearyl (meth)acrylate, and n-behenyl (meth)acrylate; i-propyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, and s-butyl (meth)acrylate. alkyl (meth)acrylates having a branched alkyl group such as isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, i-nonyl (meth)acrylate, i-decyl (meth)acrylate, 3-i-propylheptyl (meth)acrylate, i-undecyl (meth)acrylate, 2-t-butylheptyl (meth)acrylate, i-dodecyl (meth)acrylate, i-tridecyl (meth)acrylate, i-tetradecyl (meth)acrylate, and i-behenyl (meth)acrylate; alkyl (meth)acrylates having a cyclic alkyl group such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenoxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and adamantyl (meth)acrylate;Alkyl (meth)acrylates having a hydroxyl group, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, glycerin mono(meth)acrylate, ethylene glycol mono(meth)acrylate, and propylene glycol mono(meth)acrylate; alkyl (meth)acrylates containing a carboxy group, such as (meth)acrylic acid, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, 2-(meth)acryloyloxyethyl phthalate, and 2-(meth)acryloyloxyethyl hexahydrophthalate; phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, and phenoxydiethylene glycol. alkyl (meth)acrylates having an aromatic ring structure such as phenyl (meth)acrylate, phenoxy polyethylene glycol (meth)acrylate, nonyl phenoxy polyethylene glycol (meth)acrylate, phenoxy polypropylene glycol (meth)acrylate, phenyl phenyl (meth)acrylate, phenyl phenoxy ethyl (meth)acrylate, phenoxy benzyl (meth)acrylate, phenyl benzyl (meth)acrylate, naphthyl (meth)acrylate, and (1-naphthyl) methyl (meth)acrylate; alkyl (meth)acrylates having a heterocyclic structure such as tetrahydrofurfuryl (meth)acrylate, glycidyl (meth)acrylate, and (meth)acryloyl morpholine; alkoxy alkyl (meth)acrylates such as methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, and butoxyethyl (meth)acrylate;Examples of such acrylates include allyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 2-(meth)acryloyloxyethyl acid phosphate, trifluoroethyl (meth)acrylate, heptadecafluorodecyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, and (meth)acrylamide. These may be used in combination of two or more kinds.

[0028] From the viewpoint of enhancing the friction-reducing effect, it is preferable that the (m1) component contains the (b) component, more preferably an alkyl acrylate having an alkyl group with 2 to 8 carbon atoms, even more preferably an alkyl acrylate having an alkyl group with 2 to 4 carbon atoms, and particularly preferably n-butyl acrylate. From the viewpoint of increasing the solubility of the polymer in the base oil, it is preferable that the component (m1) contains the component (a), and an alkyl (meth)acrylate having an alkyl group with 11 to 20 carbon atoms is more preferable, an alkyl (meth)acrylate having an alkyl group with 11 to 18 carbon atoms is even more preferable, and an alkyl (meth)acrylate having an alkyl group with 11 to 14 carbon atoms is particularly preferable.

[0029] The (M) component is a compound containing two or more structural units derived from a monomer (m2) (hereinafter also referred to as "(m2) component") having a vinyl radical polymerizable group and having a radical polymerizable group at the end, and contains the (a) component as the (m2) component. Examples of the (m2) component other than the (a) component include the compounds listed as the (m1) component. In terms of increasing the solubility of the polymer in the base oil, the (m2) component is preferably an alkyl (meth)acrylate having an alkyl group with 11 to 20 carbon atoms, more preferably an alkyl methacrylate having an alkyl group with 11 to 20 carbon atoms, even more preferably an alkyl methacrylate having an alkyl group with 11 to 18 carbon atoms, and particularly preferably an alkyl methacrylate having an alkyl group with 11 to 14 carbon atoms. In addition, it is preferable that the (m2) component contains the (b) component. From the viewpoint of increasing the solubility of the polymer in the base oil, the component (m2) is preferably a (meth)acrylate having a linear or branched alkyl group, more preferably an alkyl methacrylate having an alkyl group with 1 to 8 carbon atoms, even more preferably an alkyl methacrylate having an alkyl group with 1 to 4 carbon atoms, and particularly preferably methyl methacrylate.

[0030] In order to increase the solubility of the polymer in the base oil, the structural units derived from the component (a) are preferably contained in an amount of 50 mass % or more, more preferably 60 mass % or more, even more preferably 70 mass % or more, and particularly preferably 80 mass % or more, based on the total mass of the component (M). Furthermore, from the viewpoint of radical polymerizability, the component (M) preferably has a structure represented by the following formula (1).

[0031] [ka]

[0032] (In the formula, X 1 ~X n-1 each independently represents a hydrogen atom, a methyl group, or CHOH; Y 1 ~Y neach independently represents X bonded to a vinyl group of the component (m2) which is a monomer structural unit of the macromonomer (M). 1 ~X n-1 Z represents a terminal group, and n represents an integer of 2 to 10,000.

[0033] X 1 ~X n-1 and Y 1 ~Y n are each independently a substituent bonded to the vinyl group of the component (m2). Y 1 ~Y n For example, OR 1 , halogen atom, COR 2 , COOR 3 , C.N., C.O.N. 4 R 5 , N.H.C.O.R. 6 , or R 7 R 1 ~R 7 each independently represents a hydrogen atom, an alkyl group, an aryl group, a heteroaryl group, or the like.

[0034] The terminal group Z may be a hydrogen atom or a group derived from a radical polymerization initiator, as in the terminal groups of polymers obtained by known radical polymerization.

[0035] In addition, from the viewpoints of increasing the solubility of the polymer in the base oil and increasing the friction reducing effect, the content of the structural units derived from the (M) component is preferably 1 to 70 mass%, more preferably 2 to 60 mass%, and even more preferably 5 to 50 mass%, relative to the total mass of the polymer. The polymer may contain two or more types of structural units derived from the component (M).

[0036] In order to increase the solubility of the polymer in the base oil, the structural units derived from the component (b) are preferably contained in an amount of more than 0 mass% and not more than 50 mass%, more preferably 0.5 to 40 mass%, even more preferably 1 to 30 mass%, and particularly preferably 1.5 to 20 mass%, relative to the total mass of the component (M). In order to increase the solubility of the polymer in the base oil, the ratio of [the content of the structural units derived from the component (b)] / [the content of the structural units derived from the component (a)] in the component (M) is preferably from 0.001 to 0.1, more preferably from 0.005 to 0.05, and even more preferably from 0.01 to 0.03.

[0037] From the viewpoints of increasing the solubility of the polymer in the base oil and increasing the friction reducing effect, the mass average molecular weight (Mw) of the macromonomer (M) measured by gel permeation chromatography (GPC) is preferably 5,000 or more and 50,000 or less, more preferably 8,000 or more and 40,000 or less, and even more preferably 10,000 or more and 30,000 or less.

[0038] From the viewpoints of increasing the solubility of the polymer in the base oil and increasing the friction reducing effect, the number average molecular weight (Mn) of the (M) component measured by gel permeation chromatography is preferably 500 to 30,000, more preferably 1,000 to 25,000, and particularly preferably 2,000 to 20,000.

[0039] From the viewpoints of increasing the solubility of the polymer in the base oil and increasing the friction reducing effect, the molecular weight distribution (Mw / Mn) of the macromonomer (M) measured by gel permeation chromatography (GPC) is preferably 1.0 or more and 10 or less, more preferably 1.2 or more and 8 or less, and even more preferably 1.5 or more and 5 or less.

[0040] The (M) component may be produced by a known method or may be commercially available. Examples of the method for producing the M component include a method using a cobalt chain transfer agent (U.S. Pat. No. 4,680,352), a method using an α-substituted unsaturated compound such as α-bromomethylstyrene as a chain transfer agent (WO 88 / 04304), a method of chemically bonding a polymerizable group (JP-A-60-133007 and U.S. Pat. No. 5,147,952), and a method using thermal decomposition (JP-A-11-240854).

[0041] The method using a cobalt chain transfer agent is preferred in terms of the number of production steps and the use of a catalyst with a high chain transfer constant. Because the cobalt chain transfer agent has a high chain transfer constant, a macromonomer with a controlled molecular weight can be obtained by adding a small amount of the agent.

[0042] As the cobalt chain transfer agent, a known cobalt complex can be used. The amount of the cobalt chain transfer agent is preferably 0.00001 to 0.1 parts by mass, more preferably 0.00005 to 0.05 parts by mass, and particularly preferably 0.0001 to 0.02 parts by mass, relative to 100 parts by mass of the component (m2).

[0043] The number average molecular weight (Mn) of the polymer contained in the friction reducer for lubricating oil of the present invention, as measured by gel permeation chromatography (GPC), is preferably from 5,000 to 50,000, more preferably from 7,000 to 40,000, and even more preferably from 10,000 to 30,000, in order to increase the solubility of the polymer in the base oil and to enhance the friction reducing effect.

[0044] The molecular weight distribution (Mw / Mn) of the polymer contained in the friction reducer for lubricating oil of the present invention, as measured by gel permeation chromatography (GPC), is preferably 1.0 or more and 20 or less, more preferably 1.5 or more and 15 or less, and even more preferably 2.0 or more and 10 or less, from the viewpoints of increasing the solubility of the polymer in the base oil and increasing the friction reducing effect.

[0045] Next, an example of the method for producing the friction reducer for lubricating oil of the present invention will be described. The friction reducer for lubricating oil of the present invention can be produced by polymerizing a monomer mixture containing the component (m1) and the component (M) in a base oil by a known method. The base oil is not particularly limited, but examples thereof include API Group III base oils such as YUBASE3 manufactured by SK Lubricants, API Group III plus base oils such as YUBASE4 manufactured by SK Lubricants, and API Group IV base oils such as polyalphaolefins.

[0046] The (M) component is preferably a macromonomer obtained by polymerizing a monomer mixture containing a vinyl radical polymerizable monomer in the base oil using a cobalt chain transfer agent. The cobalt chain transfer agent has a high chain transfer constant, so that a macromonomer with a controlled molecular weight can be obtained by adding a small amount of the cobalt chain transfer agent.

[0047] The polymerization may be carried out under known conditions, but it is preferable to use α-methylstyrene dimer as a chain transfer agent because it is particularly effective in suppressing heat generation during polymerization.

[0048] The friction reducer for lubricating oils containing the polymer of the present invention can be used as a friction reducer for lubricating oils to be added to lubricating oils such as engine oils, drive system oils (gear oils, transmission oils), hydraulic oils, and metal processing oils used in mobility such as automobiles and ships, industrial machinery, robots, etc.

[0049] Examples of the base oil for the lubricating oil include mineral base oils refined from crude oil and chemically synthesized synthetic oils. For example, API Group III base oils such as YUBASE3 manufactured by SK Lubricants, API Group III plus base oils such as YUBASE4 manufactured by SK Lubricants, and API Group IV base oils such as polyalphaolefins.

[0050] The lubricating oil composition of the present invention contains the friction reducer for lubricating oil of the present invention. The lubricating oil composition of the present invention may contain other additives other than the friction reducer for lubricating oil of the present invention. Examples of other additives include antioxidants, viscosity index improvers, pour point depressants, detergents and dispersants, corrosion inhibitors, rust inhibitors, antifoaming agents, emulsifiers, fungicides, and antiemulsifiers. In addition, the lubricating oil composition of the present invention may contain oiliness improvers such as long-chain fatty acid esters and fatty acid amides, antiwear agents such as phosphate esters and zinc dithiophosphates, extreme pressure agents such as organic sulfur compounds and organic halogen compounds, and friction modifiers such as organic molybdenum compounds, as friction reducers other than those of the present invention. The lubricating oil composition of the present invention may be a grease containing a thickener, such as a soap-based thickener (lithium soap, calcium soap, sodium soap, aluminum soap, etc.), an inorganic-based thickener (bentonite, silica gel, etc.), or an organic-based thickener (polyurea, polyurethane, etc.).

[0051] The content of the polymer of the present invention contained in the lubricating oil composition is preferably 0.01 to 30 mass%, more preferably 0.05 to 25 mass%, and even more preferably 0.1 to 20 mass%, based on 100 mass% of the lubricating oil composition. By making the content of the friction reducer for lubricating oil 0.01 mass% or more, the friction reducing effect can be increased. By making it 30 mass% or less, the viscosity of the lubricating oil composition can be reduced.

[0052] A base oil solution containing 2% by mass of the polymer is prepared, and the friction coefficient measured at 40°C using an SRV5 testing machine (manufactured by Optimol Instruments Pruftechnik GmbH) is preferably 0.16 or less, more preferably less than 0.138, and even more preferably 0.135 or less.

[0053] A base oil solution containing 2% by mass of the polymer is prepared, and the kinematic viscosity at 40°C measured in accordance with ASTM D7279 (D445) is preferably 0 to 22.4 cSt, more preferably 5 to 22.25 cSt, even more preferably 10 to 22.00 cSt, and particularly preferably 15 to 21.50 cSt. The base oil is API Group III plus. EXAMPLES

[0054] The present invention will be described in more detail below with reference to examples and comparative examples. In the examples, "parts" refers to "parts by mass". Evaluations were performed by the following methods. In Tables 1 to 6, the content of the structural unit derived from each monomer is shown in mass%. The content of each structural unit was calculated from the mass of the monomer relative to the total mass of the monomers used in the polymerization reaction.

[0055] <Molecular weight of macromonomer (M)> Measurement was performed using gel permeation chromatography (GPC) (HLC-8320 manufactured by Tosoh Corporation). After preparing a 0.2% by mass solution of the macromonomer (M) in tetrahydrofuran, 10 μl of the above solution was injected into an apparatus equipped with columns manufactured by Tosoh Corporation (TSKgel SuperHZM-M (inner diameter 4.6 mm, length 15 cm), HZM-M (inner diameter 4.6 mm, length 15 cm), HZ-2000 (inner diameter 4.6 mm, length 15 cm), TSKguardcolumn SuperHZ-L (inner diameter 4.6 mm, length 3.5 cm), and measurement was performed under the conditions of flow rate: 0.35 ml / min, eluent: tetrahydrofuran (stabilizer BHT), column temperature: 40° C., and Mw, Mn, and Mw / Mn were calculated in terms of standard polystyrene.

[0056] <Molecular weight of polymer> Measurement was performed using gel permeation chromatography (GPC) (HLC-8320 manufactured by Tosoh Corporation). After preparing a 0.2% by mass solution of the polymer obtained in the examples in tetrahydrofuran, 10 μl of the above solution was injected into an apparatus equipped with columns manufactured by Tosoh Corporation (2 TSKgel SuperHZM-H (inner diameter 6.0 mm, length 15 cm) and TSKguard column SuperHZ-H (inner diameter 4.6 mm, length 3.5 cm), and measurement was performed under the conditions of a flow rate of 0.5 ml / min, eluent: tetrahydrofuran (stabilizer BHT), and column temperature: 40° C., and the mass average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw / Mn) were calculated in terms of standard polystyrene.

[0057] <Kinematic viscosity at 40℃> A YUBASE4 solution containing 2% by mass of the obtained polymer was prepared, and the kinetic viscosity at 40° C. was evaluated using a fully automatic simplified kinetic viscometer (manufactured by Cannon, product name: Simple-VIS type) in accordance with the ASTM D7279 (D445) method.

[0058] <Friction coefficient at 40℃> A YUBASE4 solution containing 2% by mass of the obtained polymer was prepared, and the friction coefficient was measured at 40° C. using an SRV5 tester (manufactured by Optimol Instruments Pruftechnik GmbH). The measurement conditions were as follows, and the friction coefficient was evaluated 60 minutes after the start of the measurement. Test method: Ball-on-disc (ball diameter: 10mm, ball and disc material: SUJ2) Test mode: round trip (50Hz, stroke 1mm) Load capacity: 200N

[0059] [Production Example 1] (Synthesis of Co complex (cobalt chain transfer agent)) In a synthesis apparatus equipped with a stirrer, 2.00 g (8.03 mmol) of cobalt (II) acetate tetrahydrate (Wako Pure Chemical Industries, Ltd., Wako special grade), 3.86 g (16.1 mmol) of diphenylglyoxime (Tokyo Chemical Industry Co., Ltd., EP grade), and 100 ml of diethyl ether that had been deoxygenated in advance by nitrogen bubbling were placed under a nitrogen atmosphere, and the mixture was stirred at 25°C for 2 hours. Next, 20 ml of boron trifluoride diethyl ether complex (Tokyo Chemical Industry Co., Ltd., EP grade) was added and stirred for another 6 hours. The obtained product was filtered, and the solid was washed with diethyl ether and dried at 100 MPa or less at 20°C for 12 hours to obtain 5.02 g (7.93 mmol, yield 99% by mass) of a brown solid Co complex.

[0060] [Production Example 2] (Synthesis of Macromonomer M1) In a reaction vessel equipped with a stirrer, a cooling tube, and a thermometer, 58 parts of YUBASE4, 98 parts of Acryester SL (manufactured by Mitsubishi Chemical Corporation, trade name: Acryester SL, a mixture of an alkyl methacrylate with 12 carbon atoms in the alkyl group and an alkyl methacrylate with 13 carbon atoms in the alkyl group), 2 parts of methyl methacrylate (MMA), and 0.005 parts of the Co complex prepared in Production Example 1 were added, and the liquid temperature was raised to 40°C, and nitrogen was bubbled for 2 hours while stirring to remove dissolved oxygen. A mixture of YUBASE4 (2 parts) and 0.1 parts of t-butylperoxy-2-ethylhexanoate (manufactured by Arkema Yoshitomi Co., Ltd., trade name: Luperox 26) as a polymerization initiator was added, and the liquid temperature was raised to 90°C. After stirring for 2.5 hours, a mixture of YUBASE4 (10 parts) and Luperox 26 (0.7 parts) was added dropwise over 1 hour. After the dropwise addition, the temperature was raised to 105° C. and maintained for 1.5 hours, after which 20 parts of YUBASE4 was added and cooled to obtain a YUBASE4 solution containing 52.6% by mass of macromonomer M1. The results of GPC of the obtained macromonomer M1 are shown in Table 1.

[0061] [Production Example 3] (Synthesis of macromonomer M2) A reaction vessel equipped with a stirrer, a cooling tube and a thermometer was charged with 58 parts of YUBASE4, 98 parts of Acrylate SL, 2 parts of MMA and 0.005 parts of the Co complex prepared in Production Example 1, and the liquid temperature was raised to 40°C. Nitrogen was bubbled for 2 hours while stirring to remove dissolved oxygen. A mixture of YUBASE4 (2 parts) and 0.1 parts of t-amylperoxy-2-ethylhexanoate (manufactured by Arkema Yoshitomi Co., Ltd., trade name: Luperox 575) as a polymerization initiator was added, the liquid temperature was raised to 90°C, and after stirring for 2.5 hours, a mixture of YUBASE4 (10 parts) and Luperox 26 (0.7 parts) was added dropwise over 1 hour. After dropping, the temperature was raised to 105°C and held for 1.5 hours, and then 20 parts of YUBASE4 was added and cooled to obtain a YUBASE4 solution containing 52.6% by mass of macromonomer M2. The results of GPC of the obtained macromonomer M2 are shown in Table 1.

[0062] [Production Example 4] (Synthesis of macromonomer M3) In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 58 parts of YUBASE4, 98 parts of n-stearyl methacrylate (manufactured by Kyoeisha Chemical Co., Ltd., product name: Light Ester S), 2 parts of methyl methacrylate (MMA), and 0.005 parts of the Co complex prepared in Production Example 1 were added, and the liquid temperature was raised to 40 ° C. and nitrogen was bubbled for 2 hours while stirring to remove dissolved oxygen. A mixture of YUBASE4 (2 parts) and polymerization initiator Luperox 26 (0.2 parts) was added, the liquid temperature was raised to 90 ° C., and after stirring for 2.5 hours, a mixture of YUBASE4 (10 parts) and Luperox 26 (0.7 parts) was dropped over 1 hour. After dropping, the temperature was raised to 105 ° C. and held for 1.5 hours, and then 20 parts of YUBASE4 was added and cooled to obtain a YUBASE4 solution containing 52.6 mass% of macromonomer M3. The results of GPC of the obtained macromonomer M3 are shown in Table 1.

[0063] [Production Example 5] (Synthesis of macromonomer M4) In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 58 parts of YUBASE4, 98 parts of lauryl methacrylate (manufactured by Mitsubishi Chemical Corporation, trade name: Acryester L), 2 parts of methyl methacrylate (MMA), and 0.005 parts of the Co complex prepared in Production Example 1 were added, and the liquid temperature was raised to 40 ° C. and nitrogen was bubbled for 2 hours while stirring to remove dissolved oxygen. A mixture of YUBASE4 (2 parts) and polymerization initiator Luperox 26 (0.4 parts) was added, the liquid temperature was raised to 90 ° C., and after stirring for 2.5 hours, a mixture of YUBASE4 (10 parts) and Luperox 26 (0.7 parts) was dropped over 1 hour. After dropping, the temperature was raised to 105 ° C. and held for 1.5 hours, and then 20 parts of YUBASE4 were added and cooled to obtain a YUBASE4 solution containing 52.6 mass% of macromonomer M4. The results of GPC of the obtained macromonomer M4 are shown in Table 1.

[0064] [Production Example 6] (Synthesis of macromonomer M5) A reaction vessel equipped with a stirrer, a cooling tube and a thermometer was charged with 58 parts of YUBASE4, 98 parts of Acrylate SL, 2 parts of MMA and 0.0075 parts of the Co complex prepared in Production Example 1, and the liquid temperature was raised to 40°C. Nitrogen was bubbled for 2 hours while stirring to remove dissolved oxygen. A mixture consisting of YUBASE4 (2 parts) and 0.1 parts of t-amylperoxy-2-ethylhexanoate (manufactured by Arkema Yoshitomi Co., Ltd., trade name: Luperox 575) as a polymerization initiator was added, the liquid temperature was raised to 90°C, and after stirring for 2.5 hours, a mixture consisting of YUBASE4 (10 parts) and Luperox 26 (0.7 parts) was added dropwise over 1 hour. After dropping, the temperature was raised to 105°C and held for 1.5 hours, and then 20 parts of YUBASE4 was added and cooled to obtain a YUBASE4 solution containing 52.6% by mass of macromonomer M2. The results of GPC of the obtained macromonomer M5 are shown in Table 1.

[0065] [Production Example 7] (Synthesis of macromonomer M6) In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 58 parts of YUBASE4, 100 parts of 2-ethylhexyl methacrylate and 0.003 parts of the Co complex prepared in Production Example 1 were added, the liquid temperature was raised to 40°C, and nitrogen was bubbled for 2 hours while stirring to remove dissolved oxygen. A mixture consisting of YUBASE4 (2 parts) and 0.1 parts of t-amylperoxy-2-ethylhexanoate (manufactured by Arkema Yoshitomi Co., Ltd., trade name: Luperox 575) as a polymerization initiator was added, the liquid temperature was raised to 90°C, and after stirring for 2.5 hours, a mixture consisting of YUBASE4 (10 parts) and Luperox 575 (0.7 parts) was added dropwise over 1 hour. After dropping, the temperature was raised to 105°C and held for 1.5 hours, and then 20 parts of YUBASE4 were added and cooled to obtain a YUBASE4 solution containing 52.6% by mass of macromonomer M6. The results of GPC of the obtained macromonomer M6 are shown in Table 1.

[0066] <Example 1> In a reaction vessel equipped with a stirrer, a cooling tube, and a thermometer, 30 parts of YUBASE4 and 47.6 parts of the YUBASE4 solution of macromonomer M1 obtained in Production Example 2 were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C, and a mixture consisting of 25 parts of YUBASE4, 56 parts of n-butyl acrylate, 19 parts of lauryl acrylate, 0.1 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (0.9 parts) as a chain transfer agent was dropped over 4 hours. After maintaining at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110°C and maintaining it for 1 hour, YUBASE4 (58.1 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducers for lubricating oil are shown in Table 2. In Tables 2 to 6, the polymer compositions also include the constituent units in the macromonomer (M).

[0067] <Example 2> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 30 parts of YUBASE4 and 47.6 parts of the YUBASE4 solution of macromonomer M2 obtained in Production Example 3 were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C, and a mixture consisting of 25 parts of YUBASE4, 56 parts of n-butyl acrylate, 19 parts of lauryl acrylate, 0.1 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (0.9 parts) as a chain transfer agent was dropped over 4 hours. After maintaining at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110°C and maintaining it for 1 hour, YUBASE4 (58.1 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducers for lubricating oil are shown in Table 2.

[0068] <Example 3> In a reaction vessel equipped with a stirrer, a cooling tube, and a thermometer, 30 parts of YUBASE4 and 9.5 parts of the YUBASE4 solution of macromonomer M1 obtained in Production Example 2 were added, and nitrogen was bubbled while stirring to remove dissolved oxygen. The liquid temperature was raised to 85°C, and a mixture consisting of 25 parts of YUBASE4, 71 parts of n-butyl acrylate, 24 parts of lauryl acrylate, 0.1 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (0.9 parts) as a chain transfer agent was dropped over 4 hours. After maintaining at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110°C and maintaining it for 1 hour, YUBASE4 (56.1 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducers for lubricating oil are shown in Table 2.

[0069] <Example 4> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 40 parts of YUBASE4, 66.7 parts of the YUBASE4 solution of macromonomer M2 obtained in Production Example 3, 49 parts of n-butyl acrylate, 16 parts of lauryl acrylate, 0.03 parts of Luperox 26 as a polymerization initiator, and 0.7 parts of α-methylstyrene dimer as a chain transfer agent were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C and held for 3.5 hours, after which a mixture of YUBASE4 (42 parts) and Luperox 26 (0.015 parts) was added dropwise over 2 hours. Furthermore, after holding at 85°C for 1 hour, a mixture of YUBASE4 (30 parts) and Perocta O (0.5 parts) was added dropwise over 1 hour. The temperature was then raised to 110°C and held for 1 hour, after which 42 parts of YUBASE4 was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducer for lubricating oil are shown in Table 2.

[0070] <Example 5> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 50 parts of YUBASE4, 47.6 parts of the YUBASE4 solution of macromonomer M1 obtained in Production Example 2, 45 parts of n-butyl acrylate, 30 parts of lauryl acrylate, 0.03 parts of Luperox 26 as a polymerization initiator, and 0.9 parts of α-methylstyrene dimer as a chain transfer agent were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C and held for 3.5 hours, after which a mixture of YUBASE4 (42 parts) and Luperox 26 (0.015 parts) was added dropwise over 2 hours. Furthermore, after holding at 85°C for 1 hour, a mixture of YUBASE4 (30 parts) and Perocta O (0.5 parts) was added dropwise over 1 hour. The temperature was then raised to 110°C and held for 1 hour, after which 41.1 parts of YUBASE4 was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducer for lubricating oil are shown in Table 2.

[0071] <Example 6> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 50 parts of YUBASE4, 47.6 parts of the YUBASE4 solution of macromonomer M1 obtained in Production Example 2, 30 parts of n-butyl acrylate, 45 parts of lauryl acrylate, 0.03 parts of Luperox 26 as a polymerization initiator, and 0.9 parts of α-methylstyrene dimer as a chain transfer agent were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C and held for 3.5 hours, after which a mixture consisting of YUBASE4 (42 parts) and Luperox 26 (0.015 parts) was added dropwise over 2 hours. Furthermore, after holding at 85°C for 1 hour, a mixture consisting of YUBASE4 (30 parts) and Perocta O (0.5 parts) was added dropwise over 1 hour. The temperature was then raised to 110°C and held for 1 hour, after which 41.1 parts of YUBASE4 was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducer for lubricating oil are shown in Table 2.

[0072] <Example 7> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 50 parts of YUBASE4, 47.6 parts of the YUBASE4 solution of macromonomer M1 obtained in Production Example 2, 20 parts of n-butyl acrylate, 55 parts of lauryl acrylate, 0.03 parts of Luperox 26 as a polymerization initiator, and 0.9 parts of α-methylstyrene dimer as a chain transfer agent were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C and held for 3.5 hours, after which a mixture consisting of YUBASE4 (42 parts) and Luperox 26 (0.015 parts) was added dropwise over 2 hours. Furthermore, after holding at 85°C for 1 hour, a mixture consisting of YUBASE4 (30 parts) and Perocta O (0.5 parts) was added dropwise over 1 hour. The temperature was then raised to 110°C and held for 1 hour, after which 41.1 parts of YUBASE4 was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducer for lubricating oil are shown in Table 2.

[0073] <Example 8> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 50 parts of YUBASE4, 47.6 parts of the YUBASE4 solution of macromonomer M1 obtained in Production Example 2, 30 parts of ethyl acrylate (manufactured by Mitsubishi Chemical Corporation), 45 parts of lauryl acrylate, 0.03 parts of Luperox 26 as a polymerization initiator, and 0.9 parts of α-methylstyrene dimer (manufactured by NOF Corporation, trade name: Nofumer MSD) as a chain transfer agent were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C and held for 3.5 hours, after which a mixture consisting of YUBASE4 (42 parts) and Luperox 26 (0.015 parts) was added dropwise over 2 hours. Furthermore, after holding at 85°C for 1 hour, a mixture consisting of YUBASE4 (30 parts) and Perocta O (0.5 parts) was added dropwise over 1 hour. The temperature was then raised to 110°C and held for 1 hour, after which 41.1 parts of YUBASE4 was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducer for lubricating oil are shown in Table 2.

[0074] <Example 9> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 50 parts of YUBASE4, 47.6 parts of the YUBASE4 solution of macromonomer M3 obtained in Production Example 4, 56 parts of n-butyl acrylate, 19 parts of lauryl acrylate, 0.03 parts of Luperox 26 as a polymerization initiator, and 0.9 parts of α-methylstyrene dimer as a chain transfer agent were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C and held for 3.5 hours, after which a mixture consisting of YUBASE4 (42 parts) and Luperox 26 (0.015 parts) was added dropwise over 2 hours. Furthermore, after holding at 85°C for 1 hour, a mixture consisting of YUBASE4 (30 parts) and Perocta O (0.5 parts) was added dropwise over 1 hour. The temperature was then raised to 110°C and held for 1 hour, after which 41.1 parts of YUBASE4 was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducer for lubricating oil are shown in Table 2.

[0075] <Example 10> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 50 parts of YUBASE4, 47.6 parts of the YUBASE4 solution of macromonomer M4 obtained in Production Example 5, 56 parts of n-butyl acrylate, 19 parts of lauryl acrylate, 0.03 parts of Luperox 26 as a polymerization initiator, and 0.9 parts of α-methylstyrene dimer (manufactured by NOF Corporation, trade name: Nofumer MSD) as a chain transfer agent were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C and held for 3.5 hours, after which a mixture consisting of YUBASE4 (42 parts) and Luperox 26 (0.015 parts) was added dropwise over 2 hours. Furthermore, after holding at 85°C for 1 hour, a mixture consisting of YUBASE4 (30 parts) and Perocta O (0.5 parts) was added dropwise over 1 hour. The temperature was then raised to 110°C and held for 1 hour, after which 41.1 parts of YUBASE4 was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducer for lubricating oil are shown in Table 2.

[0076] <Example 11> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 30 parts of YUBASE4 and 47.6 parts of the YUBASE4 solution of macromonomer M2 obtained in Production Example 3 were added, and nitrogen was bubbled while stirring to remove dissolved oxygen. The liquid temperature was raised to 85°C, and a mixture consisting of 25 parts of YUBASE4, 56 parts of n-butyl acrylate, 19 parts of lauryl acrylate, 0.1 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (1.2 parts) as a chain transfer agent was dropped over 4 hours. After maintaining at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110°C and maintaining it for 1 hour, YUBASE4 (58.1 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducers for lubricating oil are shown in Table 3.

[0077] <Example 12> In a reaction vessel equipped with a stirrer, a cooling tube, and a thermometer, 30 parts of YUBASE4 and 47.6 parts of the YUBASE4 solution of macromonomer M2 obtained in Production Example 3 were added, and nitrogen was bubbled while stirring to remove dissolved oxygen. The liquid temperature was raised to 85°C, and a mixture consisting of 25 parts of YUBASE4, 50 parts of n-butyl acrylate, 25 parts of lauryl acrylate, 0.1 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (0.9 parts) as a chain transfer agent was dropped over 4 hours. After maintaining at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110°C and maintaining it for 1 hour, YUBASE4 (58.1 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducers for lubricating oil are shown in Table 3.

[0078] <Example 13> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 30 parts of YUBASE4 and 47.6 parts of the YUBASE4 solution of macromonomer M2 obtained in Production Example 3 were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C, and a mixture consisting of 25 parts of YUBASE4, 20 parts of n-butyl acrylate, 25 parts of lauryl acrylate, 30 parts of n-butyl methacrylate (manufactured by Mitsubishi Chemical Corporation, trade name: Acryester B), 0.1 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (0.9 parts) as a chain transfer agent was added dropwise over 4 hours. After maintaining at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was added dropwise over 1.5 hours. After heating to 110°C and holding for 1 hour, YUBASE4 (58.1 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducer for lubricating oil are shown in Table 3.

[0079] <Example 14> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 30 parts of YUBASE4 and 47.6 parts of the YUBASE4 solution of macromonomer M1 obtained in Production Example 2 were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85 ° C., and a mixture consisting of 25 parts of YUBASE4, 20 parts of n-butyl acrylate, 25 parts of lauryl acrylate, 30 parts of Acrylate B, 0.1 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (0.9 parts) as a chain transfer agent was added dropwise over 4 hours. After maintaining at 85 ° C. for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was added dropwise over 1.5 hours. After heating to 110°C and holding for 1 hour, YUBASE4 (58.1 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducer for lubricating oil are shown in Table 3.

[0080] <Example 15> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 30 parts of YUBASE4 and 47.6 parts of the YUBASE4 solution of macromonomer M2 obtained in Production Example 3 were added, and nitrogen was bubbled while stirring to remove dissolved oxygen. The liquid temperature was raised to 85°C, and a mixture consisting of 25 parts of YUBASE4, 45 parts of n-butyl acrylate, 30 parts of lauryl acrylate, 0.1 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (0.9 parts) as a chain transfer agent was dropped over 4 hours. After maintaining at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110°C and maintaining it for 1 hour, YUBASE4 (58.1 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducers for lubricating oil are shown in Table 3.

[0081] <Example 16> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 30 parts of YUBASE4 and 47.6 parts of the YUBASE4 solution of macromonomer M2 obtained in Production Example 3 were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C, and a mixture consisting of 25 parts of YUBASE4, 60 parts of n-butyl acrylate, 15 parts of lauryl acrylate, 0.1 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (1.2 parts) as a chain transfer agent was dropped over 4 hours. After maintaining at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110°C and maintaining it for 1 hour, YUBASE4 (58.1 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducers for lubricating oil are shown in Table 3.

[0082] <Example 17> In a reaction vessel equipped with a stirrer, a cooling tube, and a thermometer, 30 parts of YUBASE4 and 47.6 parts of the YUBASE4 solution of macromonomer M2 obtained in Production Example 3 were added, and nitrogen was bubbled while stirring to remove dissolved oxygen. The liquid temperature was raised to 85°C, and a mixture consisting of 25 parts of YUBASE4, 64 parts of n-butyl acrylate, 11 parts of lauryl acrylate, 0.1 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (1.2 parts) as a chain transfer agent was dropped over 4 hours. After maintaining at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110°C and maintaining it for 1 hour, YUBASE4 (58.1 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducers for lubricating oil are shown in Table 3.

[0083] <Example 18> In a reaction vessel equipped with a stirrer, a cooling tube, and a thermometer, 30 parts of YUBASE4 and 95.2 parts of the YUBASE4 solution of macromonomer M2 obtained in Production Example 3 were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85 ° C., and a mixed liquid consisting of 25 parts of YUBASE4, 50 parts of n-butyl acrylate, 0.1 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (1.2 parts) as a chain transfer agent was dropped over 4 hours. After holding at 85 ° C. for 1 hour, a mixed liquid of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110 ° C. and holding for 1 hour, YUBASE4 (35.4 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducer for lubricating oil are shown in Table 3.

[0084] <Example 19> In a reaction vessel equipped with a stirrer, a cooling tube, and a thermometer, 30 parts of YUBASE4 and 38.1 parts of the YUBASE4 solution of macromonomer M2 obtained in Production Example 3 were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C, and a mixture consisting of 25 parts of YUBASE4, 60 parts of n-butyl acrylate, 20 parts of lauryl acrylate, 0.1 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (0.9 parts) as a chain transfer agent was dropped over 4 hours. After maintaining at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110°C and maintaining it for 1 hour, YUBASE4 (62.5 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducers for lubricating oil are shown in Table 3.

[0085] <Example 20> In a reaction vessel equipped with a stirrer, a cooling tube, and a thermometer, 30 parts of YUBASE4 and 19 parts of the YUBASE4 solution of macromonomer M2 obtained in Production Example 3 were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C, and a mixture consisting of 25 parts of YUBASE4, 67 parts of n-butyl acrylate, 23 parts of lauryl acrylate, 0.1 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (0.9 parts) as a chain transfer agent was dropped over 4 hours. After maintaining at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110°C and maintaining it for 1 hour, YUBASE4 (71.6 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducers for lubricating oil are shown in Table 3.

[0086] <Example 21> In a reaction vessel equipped with a stirrer, a cooling tube, and a thermometer, 50 parts of YUBASE4 and 9.5 parts of the YUBASE4 solution of macromonomer M2 obtained in Production Example 3 were added, and nitrogen was bubbled while stirring to remove dissolved oxygen. The liquid temperature was raised to 85°C, and a mixture consisting of 25 parts of YUBASE4, 71 parts of n-butyl acrylate, 24 parts of lauryl acrylate, 0.1 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (0.9 parts) as a chain transfer agent was dropped over 4 hours. After maintaining at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110°C and maintaining it for 1 hour, YUBASE4 (56.1 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducers for lubricating oil are shown in Table 4.

[0087] <Example 22> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 30 parts of YUBASE4 and 47.6 parts of the YUBASE4 solution of macromonomer M5 obtained in Production Example 6 were added, and nitrogen was bubbled while stirring to remove dissolved oxygen. The liquid temperature was raised to 85°C, and a mixture consisting of 25 parts of YUBASE4, 56 parts of n-butyl acrylate, 19 parts of lauryl acrylate, 0.1 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (1.2 parts) as a chain transfer agent was dropped over 4 hours. After maintaining at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110°C and maintaining it for 1 hour, YUBASE4 (58.1 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducers for lubricating oil are shown in Table 4.

[0088] <Example 23> In a reaction vessel equipped with a stirrer, a cooling tube, and a thermometer, 30 parts of YUBASE4 and 47.6 parts of the YUBASE4 solution of macromonomer M5 obtained in Production Example 6 were added, and nitrogen was bubbled while stirring to remove dissolved oxygen. The liquid temperature was raised to 85°C, and a mixture consisting of 25 parts of YUBASE4, 45 parts of n-butyl acrylate, 30 parts of lauryl acrylate, 0.1 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (0.9 parts) as a chain transfer agent was dropped over 4 hours. After maintaining at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110°C and maintaining it for 1 hour, YUBASE4 (58.1 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducers for lubricating oil are shown in Table 4.

[0089] <Example 24> In a reaction vessel equipped with a stirrer, a cooling tube, and a thermometer, 30 parts of YUBASE4 and 47.6 parts of the YUBASE4 solution of macromonomer M5 obtained in Production Example 6 were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C, and a mixture consisting of 25 parts of YUBASE4, 64 parts of n-butyl acrylate, 11 parts of lauryl acrylate, 0.1 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (1.2 parts) as a chain transfer agent was dropped over 4 hours. After maintaining at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110°C and maintaining it for 1 hour, YUBASE4 (58.1 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducers for lubricating oil are shown in Table 4.

[0090] <Example 25> In a reaction vessel equipped with a stirrer, a cooling tube, and a thermometer, 30 parts of YUBASE4 and 95.2 parts of the YUBASE4 solution of macromonomer M5 obtained in Production Example 6 were added, and nitrogen was bubbled while stirring to remove dissolved oxygen. The liquid temperature was raised to 85°C, and a mixture consisting of 25 parts of YUBASE4, 50 parts of n-butyl acrylate, 0.1 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (1.2 parts) as a chain transfer agent was dropped over 4 hours. After holding at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110°C and holding for 1 hour, YUBASE4 (35.4 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducer for lubricating oil are shown in Table 4.

[0091] <Example 26> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 50 parts of YUBASE4, 47.6 parts of the YUBASE4 solution of macromonomer M2 obtained in Production Example 3, 56 parts of 2-ethylhexyl acrylate (manufactured by Mitsubishi Chemical Corporation), 19 parts of lauryl acrylate, 0.03 parts of Luperox 26 as a polymerization initiator, and 1.2 parts of α-methylstyrene dimer as a chain transfer agent were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C and held for 3.5 hours, after which a mixture consisting of YUBASE4 (42 parts) and Luperox 26 (0.015 parts) was added dropwise over 2 hours. Furthermore, after holding at 85°C for 1 hour, a mixture consisting of YUBASE4 (30 parts) and Perocta O (0.5 parts) was added dropwise over 1 hour. The temperature was then raised to 110°C and held for 1 hour, after which 41.1 parts of YUBASE4 was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducer for lubricating oil are shown in Table 4.

[0092] <Example 27> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 30 parts of YUBASE4 and 47.6 parts of the YUBASE4 solution of macromonomer M2 obtained in Production Example 3 were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C, and a mixture consisting of 25 parts of YUBASE4, 56 parts of n-butyl acrylate, 19 parts of lauryl acrylate, 1 part of Luperox 575 as a polymerization initiator, and Nofumer MSD (1.9 parts) as a chain transfer agent was dropped over 4 hours. After maintaining at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110°C and maintaining it for 1 hour, YUBASE4 (58.1 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducers for lubricating oil are shown in Table 4.

[0093] <Example 28> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 30 parts of YUBASE4 and 47.6 parts of the YUBASE4 solution of macromonomer M1 obtained in Production Example 2 were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C, and a mixture consisting of 25 parts of YUBASE4, 56 parts of n-butyl acrylate, 18 parts of lauryl acrylate, 4-hydroxybutyl acrylate (manufactured by Mitsubishi Chemical Corporation, trade name: 4HBA) (1 part), 0.1 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (1.9 parts) as a chain transfer agent was added dropwise over 4 hours. After maintaining at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was added dropwise over 1.5 hours. After heating to 110°C and holding for 1 hour, YUBASE4 (58.1 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducer for lubricating oil are shown in Table 4.

[0094] <Example 29> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 30 parts of YUBASE4 and 47.6 parts of the YUBASE4 solution of macromonomer M1 obtained in Production Example 2 were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C, and a mixture consisting of 25 parts of YUBASE4, 54 parts of n-butyl acrylate, 18 parts of lauryl acrylate, 4-hydroxybutyl acrylate (manufactured by Mitsubishi Chemical Corporation, trade name: 4HBA) (3 parts), 3 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (4 parts) as a chain transfer agent was added dropwise over 4 hours. After maintaining at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was added dropwise over 1.5 hours. After heating to 110°C and holding for 1 hour, YUBASE4 (58.1 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducer for lubricating oil are shown in Table 4.

[0095] <Example 30> In a reaction vessel equipped with a stirrer, a cooling tube, and a thermometer, 30 parts of YUBASE4 and 95.2 parts of the YUBASE4 solution of macromonomer M2 obtained in Production Example 3 were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85 ° C., and a mixed liquid consisting of 25 parts of YUBASE4, 50 parts of n-butyl acrylate, 1 part of Luperox 575 as a polymerization initiator, and Nofumer MSD (1.9 parts) as a chain transfer agent was dropped over 4 hours. After holding at 85 ° C. for 1 hour, a mixed liquid of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110 ° C. and holding for 1 hour, YUBASE4 (58.1 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducer for lubricating oil are shown in Table 5.

[0096] <Example 31> In a reaction vessel equipped with a stirrer, a cooling tube, and a thermometer, 30 parts of YUBASE4 and 95.2 parts of the YUBASE4 solution of macromonomer M1 obtained in Production Example 2 were added, and nitrogen was bubbled while stirring to remove dissolved oxygen. The liquid temperature was raised to 85°C, and a mixture consisting of 25 parts of YUBASE4, 47 parts of n-butyl acrylate, 3 parts of 4-hydroxybutyl acrylate, 0.5 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (0.9 parts) as a chain transfer agent was dropped over 4 hours. After maintaining at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110°C and maintaining it for 1 hour, YUBASE4 (58.1 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducers for lubricating oil are shown in Table 5.

[0097] <Example 32> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 30 parts of YUBASE4 and 95.2 parts of the YUBASE4 solution of macromonomer M2 obtained in Production Example 3 were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C, and a mixture consisting of 25 parts of YUBASE4, 47 parts of n-butyl acrylate, 3 parts of 4-hydroxybutyl acrylate, 0.1 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (1.3 parts) as a chain transfer agent was dropped over 4 hours. After maintaining at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110°C and maintaining it for 1 hour, YUBASE4 (58.1 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducers for lubricating oil are shown in Table 5.

[0098] <Example 33> In a reaction vessel equipped with a stirrer, a cooling tube, and a thermometer, 30 parts of YUBASE4 and 133.1 parts of the YUBASE4 solution of macromonomer M2 obtained in Production Example 3 were added, and nitrogen was bubbled while stirring to remove dissolved oxygen. The liquid temperature was raised to 85 ° C., and a mixture consisting of 30 parts of YUBASE4, 30 parts of n-butyl acrylate, 0.5 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (0.9 parts) as a chain transfer agent was dropped over 4 hours. After holding at 85 ° C. for 1 hour, a mixture of YUBASE4 (20 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110 ° C. and holding for 1 hour, YUBASE4 (44.5 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducer for lubricating oil are shown in Table 5.

[0099] <Example 34> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 30 parts of YUBASE4 and 133.1 parts of the YUBASE4 solution of macromonomer M2 obtained in Production Example 3 were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C, and a mixture consisting of 30 parts of YUBASE4, 27 parts of n-butyl acrylate, 3 parts of 4-hydroxybutyl acrylate, 1 part of Luperox 575 as a polymerization initiator, and Nofumer MSD (0.9 parts) as a chain transfer agent was dropped over 4 hours. After maintaining at 85°C for 1 hour, a mixture of YUBASE4 (20 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110°C and maintaining it for 1 hour, YUBASE4 (44.5 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducers for lubricating oil are shown in Table 5.

[0100] <Example 35> In a reaction vessel equipped with a stirrer, a cooling tube, and a thermometer, 10 parts of YUBASE4 and 171.0 parts of the YUBASE4 solution of macromonomer M2 obtained in Production Example 3 were added, and nitrogen was bubbled while stirring to remove dissolved oxygen. The liquid temperature was raised to 85 ° C., and a mixed liquid consisting of 30 parts of YUBASE4, 10 parts of n-butyl acrylate, and 0.3 parts of Luperox 575 as a polymerization initiator was dropped over 4 hours. After holding at 85 ° C. for 1 hour, a mixed liquid of YUBASE4 (45 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110 ° C. and holding for 1 hour, YUBASE4 (22.5 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducer for lubricating oil are shown in Table 5.

[0101] <Comparative Example 1> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 50 parts of YUBASE4, 47.6 parts of the YUBASE4 solution of macromonomer M1 obtained in Production Example 2, 56 parts of n-butyl acrylate, 19 parts of lauryl acrylate, 0.03 parts of Luperox 26 as a polymerization initiator, and 0.1 parts of α-methylstyrene dimer as a chain transfer agent were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C and held for 3.5 hours, after which a mixture of YUBASE4 (42 parts) and Luperox 26 (0.015 parts) was added dropwise over 2 hours. Furthermore, after holding at 85°C for 1 hour, a mixture of YUBASE4 (30 parts) and 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (manufactured by NOF Corp., trade name: Perocta O) (0.5 parts) was added dropwise over 1 hour. The temperature was then raised to 110°C and held for 1 hour, after which 41.1 parts of YUBASE4 was added and cooled to obtain a YUBASE4 solution containing 35% by mass of polymer. The evaluation results of the obtained friction reducer for lubricating oil are shown in Table 6.

[0102] <Comparative Example 2> In a reaction vessel equipped with a stirrer, a cooling tube, and a thermometer, 30 parts of YUBASE4 and 47.6 parts of the YUBASE4 solution of macromonomer M1 obtained in Production Example 2 were added, and nitrogen was bubbled while stirring to remove dissolved oxygen. The liquid temperature was raised to 85 ° C., and a mixture consisting of 25 parts of YUBASE4, 13 parts of n-butyl acrylate, 62 parts of lauryl acrylate, 0.1 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (0.9 parts) as a chain transfer agent was dropped over 4 hours. After holding at 85 ° C. for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110 ° C. and holding for 1 hour, YUBASE4 (58.1 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of polymer. The evaluation results of the obtained friction reducer for lubricating oil are shown in Table 6.

[0103] <Comparative Example 3> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 72.6 parts of YUBASE4, 45 parts of n-butyl acrylate, 30 parts of lauryl acrylate, 24.5 parts of Acryester SL, 0.5 parts of MMA, 0.03 parts of Luperox 26 as a polymerization initiator, and 0.15 parts of α-methylstyrene dimer as a chain transfer agent were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C and held for 3.5 hours, after which a mixture of YUBASE4 (42 parts) and Luperox 26 (0.015 parts) was added dropwise over 2 hours. Furthermore, after holding at 85°C for 1 hour, a mixture of YUBASE4 (60 parts) and 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (manufactured by NOF Corp., trade name: Perocta O) (0.5 parts) was added dropwise over 1 hour. The temperature was then raised to 110°C and held for 1 hour, after which 11.1 parts of YUBASE4 was added and cooled to obtain a YUBASE4 solution containing 35% by mass of polymer. The evaluation results of the obtained friction reducer for lubricating oil are shown in Table 6.

[0104] <Comparative Example 4> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 6.9 parts of YUBASE4, 47.6 parts of the YUBASE4 solution of macromonomer M1 obtained in Production Example 2, 45 parts of n-butyl methacrylate (manufactured by Mitsubishi Chemical Corporation, trade name: Acryester B), 30 parts of lauryl acrylate, 0.15 parts of Luperox 26 as a polymerization initiator, and 0.025 parts of α-methylstyrene dimer as a chain transfer agent were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C and held for 3.5 hours, after which a mixture consisting of YUBASE4 (42 parts) and Luperox 26 (0.015 parts) was added dropwise over 2 hours. Furthermore, after holding at 85°C for 1 hour, a mixture consisting of YUBASE4 (67.5 parts) and Perocta O (0.5 parts) was added dropwise over 1 hour. The temperature was then raised to 110°C and held for 1 hour, after which 46.7 parts of YUBASE4 was added and cooled to obtain a YUBASE4 solution containing 35% by mass of polymer. The evaluation results of the obtained friction reducer for lubricating oil are shown in Table 6.

[0105] <Comparative Example 5> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 6.9 parts of YUBASE4, 47.6 parts of the YUBASE4 solution of macromonomer M1 obtained in Production Example 2, 35 parts of n-butyl methacrylate (manufactured by Mitsubishi Chemical Corporation, trade name: Acryester B), 40 parts of lauryl acrylate, 0.15 parts of Luperox 26 as a polymerization initiator, and 0.025 parts of α-methylstyrene dimer as a chain transfer agent were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The liquid temperature was raised to 85°C and held for 3.5 hours, after which a mixture consisting of YUBASE4 (42 parts) and Luperox 26 (0.015 parts) was added dropwise over 2 hours. Furthermore, after holding at 85°C for 1 hour, a mixture consisting of YUBASE4 (67.5 parts) and Perocta O (0.5 parts) was added dropwise over 1 hour. The temperature was then raised to 110°C and held for 1 hour, after which 46.7 parts of YUBASE4 was added and cooled to obtain a YUBASE4 solution containing 35% by mass of polymer. The evaluation results of the obtained friction reducer for lubricating oil are shown in Table 6.

[0106] <Comparative Example 6> In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 30 parts of YUBASE4 and 47.6 parts of the YUBASE4 solution of macromonomer M6 obtained in Production Example 7 were added, and nitrogen was bubbled while stirring to remove dissolved oxygen. The liquid temperature was raised to 85°C, and a mixture consisting of 25 parts of YUBASE4, 56 parts of n-butyl acrylate, 19 parts of lauryl acrylate, 0.5 parts of Luperox 575 as a polymerization initiator, and Nofumer MSD (1.9 parts) as a chain transfer agent was dropped over 4 hours. After maintaining at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was dropped over 1.5 hours. After raising the temperature to 110°C and maintaining it for 1 hour, YUBASE4 (58.1 parts) was added and cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic graft copolymer. The evaluation results of the obtained friction reducers for lubricating oil are shown in Table 6.

[0107] [Table 1]

[0108] [Table 2]

[0109] [Table 3]

[0110] [Table 4]

[0111] [Table 5]

[0112] [Table 6]

[0113] The abbreviations in Tables 1 to 6 are as follows. SLMA: A mixture of an alkyl methacrylate with an alkyl group having 12 carbon atoms and an alkyl methacrylate with an alkyl group having 13 carbon atoms (manufactured by Mitsubishi Chemical Corporation, product name: Acryester SL) SMA: n-Stearyl methacrylate (Kyoeisha Chemical Co., Ltd., product name: Light Ester S) LMA: Lauryl methacrylate (Mitsubishi Chemical Corporation, product name: Acryester L) MMA: Methyl methacrylate (Mitsubishi Chemical Corporation, product name: Acryester M) EHMA: 2-Ethylhexyl methacrylate (manufactured by Mitsubishi Chemical Corporation, product name "Acryester EH") M1: Macromonomer synthesized in Example 2 M2: Macromonomer synthesized in Example 3 M3: Macromonomer synthesized in Example 4 M4: Macromonomer synthesized in Example 5 M5: Macromonomer synthesized in Example 6 M6: Macromonomer synthesized in Example 7 LA: Lauryl acrylate (Osaka Organic Chemical Industry Co., Ltd., product name: LA) EHA: 2-Ethylhexyl acrylate (Mitsubishi Chemical) BA: n-Butyl acrylate (Mitsubishi Chemical) EA: Ethyl acrylate (Mitsubishi Chemical) BMA: n-Butyl methacrylate (Mitsubishi Chemical Corporation, product name: Acryester B)

[0114] As is clear from Tables 2 to 6, the friction reducers for lubricating oil obtained in each Example had low kinetic viscosity and were highly effective in reducing the friction coefficient, whereas the friction reducers for lubricating oil obtained in each Comparative Example had high kinetic viscosity and were less effective in reducing the friction coefficient. [Industrial Applicability]

[0115] According to the present invention, it is possible to provide a polymer that can provide a polymer lubricating oil additive, a friction reducer for lubricating oil, and a lubricating oil composition having a high friction reducing effect and a low viscosity.

Claims

1. The composition includes a polymer having a main chain polymer structure and a side chain polymer structure, and a base oil, The polymer comprises a structural unit derived from an alkyl(meth)acrylate (a) having an alkyl group with 11 to 30 carbon atoms, and a structural unit derived from an alkyl(meth)acrylate (b) having an alkyl group with 1 to 10 carbon atoms, the main chain polymer structure includes at least one structural unit selected from the group consisting of a structural unit derived from an alkyl(meth)acrylate (a) having an alkyl group with 11 to 30 carbon atoms and a structural unit derived from an alkyl(meth)acrylate (b) having an alkyl group with 1 to 10 carbon atoms, the side chain polymer structure contains a structural unit derived from an alkyl (meth)acrylate (a) having an alkyl group with 11 to 30 carbon atoms, The polymer has a mass average molecular weight of 90,000 or less, the total content of the structural units derived from the alkyl (meth)acrylate (a) having 11 to 30 carbon atoms in the alkyl group and the structural units derived from the alkyl (meth)acrylate (b) having 1 to 10 carbon atoms in the alkyl group is 70 mass% or more relative to 100 mass% of the total mass of the polymer; Friction reducer for lubricating oils.

2. The composition includes a polymer having a main chain polymer structure and a side chain polymer structure, and a base oil, the side chain polymer structure contains a structural unit derived from an alkyl (meth)acrylate (a) having an alkyl group with 11 to 30 carbon atoms, the main chain polymer structure contains a structural unit derived from an alkyl(meth)acrylate (b) having 1 to 10 carbon atoms, The polymer has a mass average molecular weight of 90,000 or less. Friction reducer for lubricating oils.

3. The composition includes a polymer having a main chain polymer structure and a side chain polymer structure, and a base oil, The polymer contains a constitutional unit derived from a macromonomer (M), The polymer comprises a structural unit derived from an alkyl(meth)acrylate (a) having an alkyl group with 11 to 30 carbon atoms, and a structural unit derived from an alkyl(meth)acrylate (b) having an alkyl group with 1 to 10 carbon atoms, the main chain polymer structure includes at least one structural unit selected from the group consisting of a structural unit derived from an alkyl(meth)acrylate (a) having an alkyl group with 11 to 30 carbon atoms and a structural unit derived from an alkyl(meth)acrylate (b) having an alkyl group with 1 to 10 carbon atoms, the side chain polymer structure contains a structural unit derived from an alkyl (meth)acrylate (a) having an alkyl group having 11 to 30 carbon atoms, The polymer has a mass average molecular weight of 90,000 or less. Friction reducer for lubricating oils.

4. A base oil solution containing 2% by mass of the polymer is prepared, and the kinematic viscosity at 40° C. measured in accordance with ASTM D7279 (D445) is 22.4 cSt or less; The friction reducer for lubricating oil according to any one of claims 1 to 3, wherein the base oil is API Group III plus.

5. The friction reducer for lubricating oil according to any one of claims 1 to 3, wherein the mass average molecular weight is less than 50,000.

6. The friction reducer for lubricating oil according to any one of claims 1 to 3, comprising a structural unit derived from a vinyl radically polymerizable monomer (m1).

7. 3. The friction reducer for lubricating oil according to claim 1, comprising a structural unit derived from a macromonomer (M).

8. 8. The friction reducer for lubricating oil according to claim 7, wherein the macromonomer (M) contains a structural unit derived from an alkyl (meth)acrylate (a) in which the alkyl group has 11 to 30 carbon atoms.

9. 4. The friction reducer for lubricating oil according to claim 3, wherein the macromonomer (M) contains a structural unit derived from an alkyl (meth)acrylate (a) having an alkyl group having 11 to 30 carbon atoms.

10. The friction reducer for lubricating oil according to claim 8, wherein the macromonomer (M) has a structure represented by the following formula (1): (In the formula, X １ ~X ｎ－１ are each independently a hydrogen atom, a methyl group, or CH ２ OH, Y １ ~Y ｎ each independently represents X bonded to a vinyl group of the vinyl radical polymerizable monomer (m2) which is a monomer constituent unit of the macromonomer (M). １ ~X ｎ－１ Z represents a terminal group, and n represents an integer of 2 to 10,000. 【Chemistry 1】

11. The friction reducer for lubricating oil according to claim 9 , wherein the macromonomer (M) has a structure represented by the following formula (1): (In the formula, X １ ~X ｎ－１ are each independently a hydrogen atom, a methyl group, or CH ２ OH, Y １ ~Y ｎ each independently represents X bonded to a vinyl group of the vinyl radical polymerizable monomer (m2) which is a monomer constituent unit of the macromonomer (M). １ ~X ｎ－１ Z represents a terminal group, and n represents an integer of 2 to 10,000. 【Chemistry 2】

12. A lubricating oil composition comprising the friction reducer for lubricating oil according to any one of claims 1 to 3.

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