Composition and lubricant composition

Abstract

To provide a composition and a lubricant composition having an excellent friction reduction effect.SOLUTION: A composition comprises a (meth)acrylic copolymer (A), a zinc-containing compound, and a base oil, wherein the (meth)acrylic copolymer (A) comprises a polymer block (I) and a polymer block (II) having a composition different from that of the polymer block (I), the polymer block (I) comprises structural units derived from a monomer represented by general formula (1), the polymer block (II) comprises structural units derived from a monomer represented by general formula (2), and the zinc-containing compound is contained in an amount of 0.01 to 10 pts.mass per 1 pts.mass of the (meth)acrylic copolymer (A). R1 is a hydrogen atom or a methyl group, R2 is a straight-chain or branched-chain alkyl group having 11 to 30 carbon atoms, R3 is a hydrogen atom or a methyl group, and R4 is a straight-chain or branched-chain alkyl group having 1 to 30 carbon atoms.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to compositions and lubricant compositions used in engine oils, drive system oils (gear oils, transmission oils), hydraulic oils, metalworking oils, greases, etc. [Background technology]

[0002] Lubricants such as automobile engine oils and drivetrain oils contain various friction reducers to reduce energy loss due to friction and to extend the life of equipment by preventing seizure.With the recent trend toward lower viscosity lubricants aimed at fuel economy, the load on metal-to-metal contact surfaces has become increasingly severe, making the role of friction reducers even more important.

[0003] 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 usage conditions and environment, these additives alone may not be sufficient to reduce friction. To overcome this problem, studies are underway to use polymer materials as friction reducers. For example, Patent Document 1 discloses that comb polymers containing repeating units derived from polyolefin-based macromonomers and repeating units derived from low-molecular-weight monomers can be suitably used as friction modifiers (friction improvers). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2007 / 003238 Summary of the Invention [Problem to be solved by the invention]

[0005] However, lubricant compositions containing conventional friction reducers are insufficient in reducing friction. An object of the present invention is to provide a composition and a lubricant composition that have an excellent friction-reducing effect. [Means for solving the problem]

[0006] As a result of extensive research, the present inventors have found that the use of a specific (meth)acrylic copolymer (A) in combination with a zinc-containing compound in a composition containing a base oil can produce an excellent friction-reducing effect, and have thus completed the present invention.

[0007] That is, the present invention has the following aspects. [1] A (meth)acrylic copolymer (A), a zinc-containing compound, and a base oil, the (meth)acrylic copolymer (A) has a polymer block (I) and a polymer block (II) having a composition different from that of the polymer block (I), The polymer block (I) contains a structural unit derived from a monomer represented by the following general formula (1): The polymer block (II) contains a structural unit derived from a monomer represented by the following general formula (2): The composition, wherein the content of the zinc-containing compound is 0.01 to 10 parts by mass per 1 part by mass of the (meth)acrylic copolymer (A).

[0008] [ka]

[0009] In formula (1), R 1 is a hydrogen atom or a methyl group, and R 2 is a straight or branched chain alkyl group having 11 to 30 carbon atoms.

[0010] [ka]

[0011] In formula (2), R3 is a hydrogen atom or a methyl group, and R 4 is a straight or branched alkyl group having 1 to 30 carbon atoms.

[0012] [2] The composition according to [1] above, wherein the (meth)acrylic copolymer (A) is a graft copolymer. [3] The composition according to [1] or [2], wherein the (meth)acrylic copolymer (A) contains a structural unit derived from a macromonomer. [4] The composition according to any one of [1] to [3], wherein the zinc-containing compound is one or more compounds selected from the group consisting of zinc dialkyldithiophosphate, zinc dithiocarbamate, and zinc phosphate. [5] The composition according to any one of [1] to [4] above, wherein the content of the (meth)acrylic copolymer (A) is 0.1 to 10 mass % relative to the total mass of the composition. [6] The composition according to any one of the above [1] to [5], wherein the (meth)acrylic copolymer (A) contains a structural unit derived from an alkyl acrylate. [7] The composition according to any one of the above [1] to [6], which contains a friction reducer containing the (meth)acrylic copolymer (A). [8] A lubricant composition comprising the composition according to any one of [1] to [7]. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a composition and a lubricant composition that have an excellent friction-reducing effect. DETAILED DESCRIPTION OF THE INVENTION

[0014] 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. In this specification and claims, a numerical range expressed by "to" means a numerical range that includes the numbers before and after "to" as the lower and upper limits. For example, A to B is equivalent to A or more and B or less. The numerical ranges of the contents, various physical property values, and property values ​​disclosed in this specification can be arbitrarily combined with the lower and upper limits to form new numerical ranges.

[0015] In addition, in the present invention and this specification, the following terms have the following meanings. "(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). The term "macromonomer" refers to a polymer having a radically polymerizable group or an addition-reactive functional group. Examples of the radically polymerizable group include a (meth)acryloyl group, a vinyl group, and a terminally polymerizable functional group represented by the formula (3) described below. Examples of the addition-reactive functional group include a hydroxy group, a carboxy group, an isocyanate group, and a glycidyl group. The term "vinyl radical polymerizable monomer" refers to a monomer that has an ethylenically unsaturated bond and is not a macromonomer. The term "structural unit" refers to a unit that constitutes a polymer derived from a monomer, i.e., a structural unit formed by polymerization of a monomer, or a structural unit in which a portion of the structural unit has been converted into a different structure by modifying a polymer.

[0016] [Composition] The composition of the present invention (hereinafter also referred to as "composition (X)") contains the (meth)acrylic copolymer (A), a zinc-containing compound, and a base oil shown below. The composition (X) may further contain, in addition to the (meth)acrylic copolymer (A), the zinc-containing compound, and the base oil, other components (hereinafter also referred to as "optional components"), as necessary, within a range that does not impair the effects of the present invention.

[0017] <(Meth)acrylic copolymer (A)> The (meth)acrylic copolymer (A) (hereinafter also simply referred to as "copolymer (A)") functions as a friction reducer. That is, the copolymer (A) is preferably contained in the composition (X) as a friction reducer. The friction reducer may consist of only the copolymer (A), or may contain components other than the copolymer (A) as long as the effects of the present invention are not impaired. When the composition (X) contains the copolymer (A), it can exhibit an excellent friction-reducing effect.

[0018] The copolymer (A) is a copolymer having a polymer block (I) and a polymer block (II) having a composition different from that of the polymer block (I). The copolymer (A) refers to a copolymer in which at least a portion of the constituent units are derived from a (meth)acrylic monomer. It is preferable that the polymer block (I) contains repeating units derived from a (meth)acrylic monomer. It is also preferable that both the polymer block (I) and the polymer block (II) contain repeating units derived from a (meth)acrylic monomer. The copolymer (A) may further contain a structural unit derived from a monomer other than the (meth)acrylic monomer (for example, styrene).

[0019] The copolymer (A) may have the polymer block (I) and the polymer block (II). As the copolymer (A), a diblock copolymer consisting of polymer block (I) and polymer block (II); a triblock copolymer in which polymer block (I) and polymer block (II) are in the (I)-(II)-(I) or (II)-(I)-(II) configuration; a star copolymer having polymer block (I) as a side chain and polymer block (II) as a core portion; a graft copolymer having polymer block (I) as a side chain and polymer block (II) as a main chain; or a graft copolymer having polymer block (II) as a side chain and polymer block (I) as a main chain is preferred, a graft copolymer having polymer block (I) as a side chain and polymer block (II) as a main chain or a graft copolymer having polymer block (II) as a side chain and polymer block (I) as a main chain is more preferred, and a graft copolymer having polymer block (I) as a side chain and polymer block (II) as a main chain is even more preferred. In the present invention, a graft copolymer is a polymer having one or more types of block chains connected as side chain polymer structures to a main chain polymer structure.

[0020] The method for producing the graft copolymer is not particularly limited, and examples thereof include a method in which a macromonomer having a radically polymerizable double bond at its terminal is produced as a side chain polymer structure, and then radically polymerized with a monomer that will become a structural unit of the main chain polymer; a method in which a main chain polymer having a reactive site and a macromonomer having a reactive site are produced in advance, and then these are reacted; a method in which, after producing the main chain polymer, a radical is generated on the main chain polymer using an initiator having hydrogen abstraction ability, and then a monomer that will become a structural unit of the side chain polymer is reacted to produce a side chain polymer structure. From the viewpoints of simple reaction and easy control of the structure, a method in which a macromonomer having a radically polymerizable double bond is produced as a side chain polymer structure, and then radically polymerized with a monomer that will become a structural unit of the main chain polymer is preferred.

[0021] (Polymer block (I)) The polymer block (I) contains a constituent unit derived from a monomer represented by the following general formula (1) (hereinafter also referred to as "monomer (a)"). The polymer block (I) preferably contains a structural unit derived from the monomer (a) as a repeating unit.

[0022] [ka]

[0023] In formula (1), R 1 is a hydrogen atom or a methyl group, and R 2 is a straight or branched chain alkyl group having 11 to 30 carbon atoms. R 2 R has 11 to 30 carbon atoms, preferably 11 to 20, more preferably 11 to 18, and even more preferably 12 to 14. 2 If the number of carbon atoms in R is equal to or greater than the lower limit, the solubility in the base oil is good. 2 When the number of carbon atoms is equal to or less than the upper limit, the friction reducing performance is improved.

[0024] The monomer (a) is a (meth)acrylic monomer having an alkyl group, that is, an alkyl(meth)acrylate. Examples of the monomer (a) include (meth)acrylates having a linear alkyl group such as n-undecyl(meth)acrylate, n-dodecyl(meth)acrylate, n-tridecyl(meth)acrylate, n-tetradecyl(meth)acrylate, n-cetyl(meth)acrylate, n-stearyl(meth)acrylate, n-octadecyl(meth)acrylate, and n-behenyl(meth)acrylate; and (meth)acrylates having a branched alkyl group such as i-undecyl(meth)acrylate, i-dodecyl(meth)acrylate, i-tridecyl(meth)acrylate, i-tetradecyl(meth)acrylate, i-cetyl(meth)acrylate, i-stearyl(meth)acrylate, i-octadecyl(meth)acrylate, i-behenyl(meth)acrylate, and 2-t-butylheptyl(meth)acrylate. The polymer block (I) may contain structural units derived from only one type of monomer (a), or may contain structural units derived from two or more types of monomer (a).

[0025] As the monomer (a), a linear or branched alkyl (meth)acrylate having 11 to 30 carbon atoms is preferred, a linear or branched alkyl methacrylate having 11 to 30 carbon atoms is more preferred, a linear or branched alkyl methacrylate having 11 to 20 carbon atoms is even more preferred, a linear or branched alkyl methacrylate having 11 to 18 carbon atoms is particularly preferred, and a linear or branched alkyl methacrylate having 12 to 14 carbon atoms is most preferred, because they have better solubility in the base oil described below and a better friction-reducing effect.

[0026] The content of the structural units derived from monomer (a) is preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 80% by mass or more, relative to the total mass of all structural units constituting polymer block (I), and may be 100% by mass, but is preferably less than 100% by mass, since this can improve the solubility in base oil and the friction-reducing performance, and can improve fuel economy by reducing the viscosity of composition (X).

[0027] The content of the structural units derived from monomer (a) is preferably 20 to 90 mass%, more preferably 25 to 85 mass%, and even more preferably 30 to 80 mass%, based on the total mass of all structural units constituting copolymer (A), because this can improve the solubility in base oil and the friction-reducing performance, and can improve fuel economy by lowering the viscosity of composition (X).

[0028] The polymer block (I) may further contain, in addition to the structural units derived from the monomer (a), structural units derived from a monomer other than the monomer (a) (hereinafter also referred to as "monomer (m1)"). The monomer (m1) is not particularly limited as long as it is copolymerizable with the monomer (a), and examples thereof include alkenes and / or alkadienes, styrene, α-methylstyrene, pt-butylstyrene, vinyltoluene, vinyl acetate, and (meth)acrylic monomers other than the monomer (a) (hereinafter also referred to as "other (meth)acrylic monomers"). Other (meth)acrylic monomers include, for example, (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, n-nonyl (meth)acrylate, and n-decyl (meth)acrylate; i-propyl (meth)acrylate, i-butyl (meth)acrylate, and t-butyl (meth)acrylate; (meth)acrylates having a branched alkyl group, such as butyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, i-nonyl (meth)acrylate, i-decyl (meth)acrylate, and 3-i-propylheptyl (meth)acrylate; cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenoxyethyl (meth)acrylate, and dicyclopentanyl (meth)acrylate; (Meth)acrylates having a cyclic alkyl group such as phenyl (meth)acrylate, adamantyl (meth)acrylate, etc.; phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, nonylphenoxypolyethylene glycol (meth)acrylate, phenoxypolypropylene glycol (meth)acrylate, phenylphenyl (meth)acrylate, phenylphenoxyethyl (meth)acrylate (meth)acrylates having an aromatic ring structure such as tetrahydrofurfuryl (meth)acrylate, phenoxybenzyl (meth)acrylate, phenylbenzyl (meth)acrylate, naphthyl (meth)acrylate, and (1-naphthyl)methyl (meth)acrylate; (meth)acrylates having a heterocyclic structure such as tetrahydrofurfuryl (meth)acrylate, glycidyl (meth)acrylate, and (meth)acryloylmorpholine; alkoxy (meth)acrylates such as methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, and butoxyethyl (meth)acrylate;(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, polyethylene glycol mono(meth)acrylate, propylene glycol mono(meth)acrylate, and polypropylene glycol mono(meth)acrylate; (meth)acrylic acid, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, and 2-(meth)acryloyl phthalate. (Meth)acrylates containing a carboxy group such as 2-(meth)acryloyloxyethyl hexahydrophthalate; 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, (meth)acrylamide, and the like; The polymer block (I) may contain structural units derived from only one type of monomer (m1), or may contain structural units derived from two or more types of monomer (m1).

[0029] From the viewpoint of achieving a higher friction-reducing effect, the monomer (m1) is preferably the following monomer (b), monomer (c), or monomer (d), with monomer (b) and monomer (c) being more preferred. That is, the polymer block (I) preferably contains, in addition to the structural unit derived from monomer (a), one or more structural units selected from the group consisting of structural units derived from monomer (b), structural units derived from monomer (c), and structural units derived from monomer (d), and more preferably contains one or more structural units selected from the group consisting of structural units derived from monomer (b) and structural units derived from monomer (c). The monomer (b) is one or more monomers selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, and n-butyl (meth)acrylate. Monomer (c) is one or more monomers selected from the group consisting of (meth)acrylates having a hydroxyl group and (meth)acrylates having a carboxyl group, i.e., 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, polyethylene glycol mono(meth)acrylate, propylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, (meth)acrylic acid, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, 2-(meth)acryloyloxyethyl phthalate, and 2-(meth)acryloyloxyethyl hexahydrophthalate. The monomer (d) is one or more monomers selected from the group consisting of (meth)acrylates having an aromatic ring structure, alkoxy(meth)acrylates, trifluoroethyl(meth)acrylate, and heptadecafluorodecyl(meth)acrylate. That is, one or more monomers selected from the group consisting of phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, 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, (1-naphthyl)methyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, trifluoroethyl (meth)acrylate, and heptadecafluorodecyl (meth)acrylate.

[0030] The content of the structural units derived from the monomer (m1) is preferably 0 to 70 mass%, more preferably more than 0 mass% and 50 mass% or less, and even more preferably more than 0 mass% and 20 mass% or less, relative to the total mass of all structural units constituting the polymer block (I), because this can improve the solubility in the base oil and the friction-reducing performance, and can improve fuel economy by reducing the viscosity of the composition (X).

[0031] In order to increase the solubility of the copolymer (A) in the base oil, the content of the structural units derived from the monomer (b) is preferably more than 0% by mass and not more than 20% by mass, more preferably 0.1 to 15% by mass, even more preferably 0.2 to 10% by mass, and particularly preferably 0.5 to 5% by mass, relative to the total mass of all structural units constituting the polymer block (I).

[0032] In order to increase the solubility of the copolymer (A) in the base oil, the content of the structural units derived from the monomer (c) is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, particularly preferably 5% by mass or less, and may be 0% by mass, relative to the total mass of all structural units constituting the polymer block (I).

[0033] The polymer block (I) preferably contains two or more structural units derived from a monomer having a vinyl radical polymerizable group (hereinafter also referred to as "monomer (m2)") and is a polymer block derived from a macromonomer having a radical polymerizable group at its terminal. Examples of the monomer (m2) include the above-mentioned monomer (a) and monomer (m1). The polymer block (I) preferably contains a structural unit derived from the monomer (a) as the monomer (m2).

[0034] Furthermore, when the polymer block (I) is a polymer block derived from a macromonomer, it is preferable that the polymer block (I) has a structure represented by the following general formula (3) from the viewpoint of radical polymerizability.

[0035] [ka]

[0036] In formula (3), X 1 ~X n-1 are each independently a hydrogen atom, a methyl group, or CHOH, and Y 1 ~Y n are each independently X bonded to the vinyl group of the monomer (m2), which is a monomer structural unit. 1 ~X n-1 is a substituent other than the group represented by the formula (I), Z is a terminal group, and n is an integer of 2 to 10,000.

[0037] X 1 ~X n-1 and Y 1 ~Y n are each independently a substituent bonded to the vinyl group of the monomer (m2).1 ~Y n For example, OR 5 , halogen atoms, COR 6 , COOR 7 ,CN,CONR 8 R 9 , NHCOR 10 , or R 11 Examples include: R 5 ~R 11 are each independently a hydrogen atom, an alkyl group, an aryl group, a heteroaryl group, or the like. The terminal group Z may be a hydrogen atom or a group derived from a radical polymerization initiator, similar to the terminal groups of polymers obtained by known radical polymerization.

[0038] The mass average molecular weight (Mw) of the polymer block (I) measured by gel permeation chromatography (GPC) is preferably 2,000 to 100,000, more preferably 3,000 to 80,000, even more preferably 4,000 to 50,000, and particularly preferably 5,000 to 30,000, because this can improve the solubility in the base oil and the friction-reducing performance, and can improve fuel economy by lowering the viscosity of the composition (X).

[0039] The number average molecular weight (Mn) of the polymer block (I) measured by gel permeation chromatography is preferably 500 to 30,000, more preferably 1,000 to 25,000, even more preferably 2,000 to 20,000, and particularly preferably 3,000 to 16,000, because this can improve the solubility in the base oil and the friction-reducing performance, and can improve fuel economy by lowering the viscosity of the composition (X).

[0040] The molecular weight distribution (Mw / Mn) of the polymer block (I) measured by gel permeation chromatography is preferably 1.0 to 5.0, more preferably 1.3 to 3.0, and even more preferably 1.5 to 2.5, because this can improve the solubility in the base oil and the friction-reducing performance, and can improve fuel economy by lowering the viscosity of the composition (X). The mass average molecular weight (Mw) of the polymer block (I) means the mass average molecular weight in terms of standard polystyrene, and the number average molecular weight (Mn) means the number average molecular weight in terms of standard polystyrene.

[0041] When the polymer block (I) is a polymer block derived from a macromonomer, the macromonomer may be one produced by a known method or a commercially available one. Examples of methods for producing the macromonomer 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 / 004304), 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).

[0042] Among these, the method using a cobalt chain transfer agent is preferred because it requires fewer production steps and uses 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. As the cobalt chain transfer agent, known cobalt complexes can be used. The amount of the cobalt chain transfer agent used is preferably 0.00001 to 0.1 parts by mass, more preferably 0.00005 to 0.05 parts by mass, and even more preferably 0.0001 to 0.02 parts by mass, relative to 100 parts by mass of the monomer (m2).

[0043] In order to increase the solubility of the copolymer (A) in the base oil and to further enhance the friction-reducing effect, the content of the polymer block (I) is preferably 1 to 70 mass%, more preferably 2 to 60 mass%, and even more preferably 5 to 50 mass%, based on the total mass of the copolymer (A).

[0044] (Polymer block (II)) The polymer block (II) is a polymer block having a different composition from the polymer block (I). The polymer block (II) contains a constituent unit derived from a monomer represented by the following general formula (2) (hereinafter also referred to as "monomer (e)"). The polymer block (II) preferably contains a structural unit derived from the monomer (e) as a repeating unit.

[0045] [ka]

[0046] In formula (2), R 3 is a hydrogen atom or a methyl group, and R 4 is a straight or branched alkyl group having 1 to 30 carbon atoms. R 4 R has 1 to 30 carbon atoms, preferably 1 to 20, more preferably 1 to 18, still more preferably 1 to 10, particularly preferably 1 to 8, and most preferably 1 to 4. 4 If the number of carbon atoms in R is equal to or greater than the lower limit, the solubility in the base oil is good. 4 When the number of carbon atoms is equal to or less than the upper limit, the friction reducing performance is improved.

[0047] The monomer (e) is an alkyl-containing (meth)acrylic monomer, that is, an alkyl(meth)acrylate. Examples of the monomer (e) include (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, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, n-undecyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, n-cetyl (meth)acrylate, n-stearyl (meth)acrylate, n-octadecyl (meth)acrylate, and n-behenyl (meth)acrylate; and (meth)acrylates having a branched alkyl group such as i-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, s-butyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, i-nonyl (meth)acrylate, i-decyl (meth)acrylate, 3-i-propylheptyl (meth)acrylate, i-undecyl (meth)acrylate, i-dodecyl (meth)acrylate, i-tridecyl (meth)acrylate, i-tetradecyl (meth)acrylate, i-cetyl (meth)acrylate, i-stearyl (meth)acrylate, i-octadecyl (meth)acrylate, i-behenyl (meth)acrylate, and 2-t-butylheptyl (meth)acrylate. The polymer block (II) may contain structural units derived from only one type of monomer (e), or may contain structural units derived from two or more types of monomer (e).

[0048] As the monomer (e), a linear or branched alkyl (meth)acrylate having 1 to 4 carbon atoms is preferred, a linear or branched alkyl acrylate having 1 to 4 carbon atoms is more preferred, a linear alkyl acrylate having 1 to 4 carbon atoms is even more preferred, and n-butyl acrylate is particularly preferred, because it has a more excellent friction-reducing effect.

[0049] The content of the structural units derived from the monomer (e) is preferably 20 to 100 mass%, more preferably 30 to 99.5 mass%, and even more preferably 45 to 99 mass%, based on the total mass of all structural units constituting the polymer block (II), because this can improve the solubility in the base oil and the friction-reducing performance, and can improve fuel economy by lowering the viscosity of the composition (X).

[0050] The content of the structural units derived from monomer (e) is preferably 10 to 90 mass%, more preferably 15 to 85 mass%, and even more preferably 20 to 70 mass%, based on the total mass of all structural units constituting copolymer (A), because this can improve the solubility in base oil and the friction-reducing performance, and can improve fuel economy by lowering the viscosity of composition (X).

[0051] The polymer block (II) may further contain, in addition to the structural units derived from the monomer (e), structural units derived from a monomer other than the monomer (e) (hereinafter also referred to as "monomer (m3)"). Examples of the monomer (m3) include the monomer (m1) exemplified above in the description of the polymer block (I) (excluding the monomer (e)). The polymer block (II) may contain structural units derived from only one type of monomer (m3), or may contain structural units derived from two or more types of monomer (m3).

[0052] From the viewpoint of achieving a higher friction-reducing effect, the monomer (m3) is preferably the monomer (f) shown below. That is, the polymer block (II) preferably contains a constituent unit derived from the monomer (f) in addition to a constituent unit derived from the monomer (e). The monomer (f) is a monomer represented by the following general formula (4).

[0053] [ka]

[0054] In formula (4), R 12 is a hydrogen atom or a methyl group, and R13 is an organic group containing a hydrogen atom or a polar group (excluding alkoxyalkyl groups). Examples of polar groups include a hydroxyl group, a carboxyl group, a heterocyclic structure (for example, an aliphatic heterocyclic ring having 2 to 6 carbon atoms, or an aromatic heterocyclic ring having 4 to 10 carbon atoms), an alkoxysilyl group, a trialkoxysilyl group having 3 to 9 carbon atoms, a phosphate group, an amino group, a primary amino group having 1 to 6 carbon atoms, and a secondary amino group having 2 to 6 carbon atoms.

[0055] Examples of the monomer (f) include (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, polyethylene glycol mono(meth)acrylate, propylene glycol mono(meth)acrylate, and polypropylene glycol mono(meth)acrylate; (meth)acrylic acid, 2-(meth)acryloyloxyethyl succinate, and 2-(meth)acryloyl maleate. (meth)acrylates containing a carboxy group such as 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl hexahydrophthalate; (meth)acrylates having a heterocyclic structure such as tetrahydrofurfuryl (meth)acrylate, glycidyl (meth)acrylate, (meth)acryloylmorpholine; 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 2-(meth)acryloyloxyethyl acid phosphate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, (meth)acrylamide, and the like. The polymer block (II) may contain structural units derived from only one type of monomer (f), or may contain structural units derived from two or more types of monomer (f).

[0056] As the monomer (f), a (meth)acrylate having a hydroxyl group or a carboxyl group is preferred, a (meth)acrylate having a hydroxyl group is more preferred, and an acrylate having a hydroxyl group is even more preferred. The total number of carbon atoms in the monomer (f) is preferably 3 to 10, more preferably 3 to 9, and even more preferably 3 to 8.

[0057] The content of the structural units derived from the monomer (m3) is preferably 0 to 80 mass%, more preferably 0.5 to 70 mass%, and even more preferably 1 to 55 mass%, relative to the total mass of all structural units constituting the polymer block (II), because this can improve the solubility in the base oil and the friction-reducing performance, and can improve fuel economy by lowering the viscosity of the composition (X).

[0058] The content of the structural units derived from the monomer (f) is preferably 0 to 20 mass%, more preferably 0.1 to 15 mass%, even more preferably 0.5 to 5 mass%, and particularly preferably 0.5 to 3 mass%, relative to the total mass of all structural units constituting the polymer block (II), because this can improve the solubility in the base oil and the friction-reducing performance, and can improve fuel economy by lowering the viscosity of the composition (X).

[0059] In order to improve the friction-reducing performance, the total content of the structural units derived from monomer (a), the structural units derived from monomer (b), the structural units derived from monomer (c), the structural units derived from monomer (e), and the structural units derived from monomer (f) is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, based on the total mass of all the structural units constituting copolymer (A). Note that the total content does not exceed 100% by mass.

[0060] The copolymer (A) may contain, as structural units, a structural unit derived from the monomer (a), a structural unit derived from the monomer (m1), a structural unit derived from the monomer (e), and a structural unit derived from the monomer (m3) in either the main chain polymer structure or the side chain polymer structure.

[0061] Copolymer (A) preferably contains structural units derived from alkyl acrylate, as this improves compatibility with composition (X), and it is more preferable that at least polymer block (II) contains structural units derived from alkyl acrylate. The content of the alkyl acrylate-derived structural units contained in the polymer block (II) is preferably 20% by mass or more, more preferably 50% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and may be 100% by mass, based on the total mass of all structural units constituting the polymer block (II).

[0062] In order to increase the solubility of the copolymer (A) in the base oil and to further enhance the friction-reducing effect, the content of the polymer block (II) is preferably 30 to 99 mass%, more preferably 40 to 98 mass%, and even more preferably 50 to 95 mass%, based on the total mass of the copolymer (A).

[0063] (molecular weight) The mass average molecular weight (Mw) of the copolymer (A) measured by gel permeation chromatography (GPC) is preferably 5,000 to 1,000,000, more preferably 15,000 to 500,000, even more preferably 20,000 to 200,000, and particularly preferably 30,000 to 100,000, because this can improve the solubility in the base oil and the friction-reducing performance, and can improve fuel economy by lowering the viscosity of the composition (X).

[0064] The number average molecular weight (Mn) of the copolymer (A) measured by gel permeation chromatography is preferably 500 to 800,000, more preferably 1,000 to 500,000, even more preferably 10,000 to 250,000, and particularly preferably 20,000 to 100,000, because this can improve the solubility in the base oil and the friction-reducing performance, and can improve fuel economy by lowering the viscosity of the composition (X).

[0065] The molecular weight distribution (Mw / Mn) of the copolymer (A) measured by gel permeation chromatography is preferably 1.0 to 15, more preferably 2.0 to 10, and even more preferably 3.0 to 8.0, because this can improve the solubility in the base oil and the friction-reducing performance, and can improve fuel economy by lowering the viscosity of the composition (X). The mass average molecular weight (Mw) of the copolymer (A) means the mass average molecular weight in terms of standard polystyrene, and the number average molecular weight (Mn) means the number average molecular weight in terms of standard polystyrene.

[0066] (Manufacturing method) The copolymer (A) can be produced by, for example, a method of polymerizing a monomer mixture containing a (meth)acrylic monomer in a base oil; a method of polymerizing a monomer mixture containing a (meth)acrylic monomer in a volatile organic solvent and dissolving it in a base oil by solvent substitution; a method of polymerizing a monomer mixture containing a (meth)acrylic monomer without a solvent and then dissolving it in a base oil, etc. Among these, the method of polymerizing a monomer mixture containing a (meth)acrylic monomer in a base oil is preferred from the viewpoint of solubility in the base oil. Examples of the (meth)acrylic monomer include other (meth)acrylic monomers among the above-mentioned monomer (a), monomer (e) and monomer (m1). The base oil will be described later.

[0067] The polymerization may be carried out under known conditions, but it is preferable to use a cobalt chain transfer agent, α-methylstyrene dimer, or the like as the chain transfer agent because they are particularly effective in suppressing heat generation during polymerization.

[0068] Copolymer (A) can be obtained, for example, by polymerizing a monomer mixture containing monomer (a) and, if necessary, monomer (m1) in a base oil in the presence of a chain transfer agent and a polymerization initiator to produce polymer block (I), which is a macromonomer-derived polymer block, and then polymerizing a monomer mixture containing monomer (e) and, if necessary, monomer (m3) in a base oil in the presence of the resulting polymer block (I). The polymerization of the monomer mixture containing monomer (e) may be carried out in the presence of at least one of a chain transfer agent and a polymerization initiator.

[0069] <Zinc-containing compounds> Examples of zinc-containing compounds include zinc dithiophosphate, zinc dithiocarbamate, and zinc phosphate. The zinc-containing compounds may be used alone or in combination of two or more. Among these, zinc dithiophosphate is preferred as the zinc-containing compound because of its excellent friction-reducing performance, and among these, zinc dialkyldithiophosphate is more preferred. As the zinc dialkyldithiophosphate, a compound represented by the following general formula (5) is even more preferred.

[0070] [ka]

[0071] In formula (5), R 14 ~R 16 are each independently a hydrocarbon group having 1 to 20 carbon atoms. Examples of hydrocarbon groups having 1 to 20 carbon atoms include primary alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, and icosyl groups; secondary propyl, secondary butyl, secondary pentyl, secondary hexyl, secondary heptyl, and secondary octyl groups; secondary alkyl groups such as a secondary nonyl group, a secondary decyl group, a secondary undecyl group, a secondary dodecyl group, a secondary tridecyl group, a secondary tetradecyl group, a secondary pentadecyl group, a secondary hexadecyl group, a secondary heptadecyl group, a secondary octadecyl group, a secondary nonadecyl group, and a secondary icosyl group; a tertiary butyl group, a tertiary pentyl group, a tertiary hexyl group, a tertiary heptyl group, a tertiary octyl group, a tertiary nonyl group, a tertiary decyl group, a tertiary undecyl group, a tertiary dodecyl group, a tertiary tridecyl group, and a tertiary tetradecyl group; tertiary alkyl groups such as a tertiary pentadecyl group, a tertiary hexadecyl group, a tertiary heptadecyl group, a tertiary octadecyl group, a tertiary nonadecyl group, and a tertiary icosyl group; branched butyl groups (such as an isobutyl group), branched pentyl groups (such as an isopentyl group), branched hexyl groups (such as an isohexyl group), branched heptyl groups (such as an isoheptyl group), branched octyl groups (such as an isooctyl group, a 2-ethylhexyl group), branched nonyl groups (such as an isononyl group), branched decyl groups (such as an isodecyl group), and branched undecyl groups. branched alkyl groups such as a branched alkyl group (such as an isoundecyl group), a branched dodecyl group (such as an isododecyl group), a branched tridecyl group (such as an isotridecyl group), a branched tetradecyl group (such as an isotetradecyl group), a branched pentadecyl group (such as an isopentadecyl group), a branched hexadecyl group (such as an isohexadecyl group), a branched heptadecyl group (such as an isoheptadecyl group), a branched octadecyl group (such as an isooctadecyl group), a branched nonadecyl group (such as an isononadecyl group), and a branched icosyl group (such as an isoicosyl group);Examples of suitable aryl groups include phenyl, toluyl, xylyl, cumenyl, mesityl, benzyl, phenethyl, styryl, cinnamyl, benzhydryl, trityl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl, hexylphenyl, heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, undecylphenyl, dodecylphenyl, styrenated phenyl, p-cumylphenyl, phenylphenyl, and benzylphenyl. Among these, primary alkyl groups, secondary alkyl groups, and aryl groups are preferred.

[0072] <Base oil> Examples of base oils include mineral base oils (hereinafter also referred to as "mineral oils") refined from crude oil, and chemically synthesized synthetic oils (hereinafter also referred to as "synthetic chemical oils"). Examples of base oils 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 poly-α-olefins. The base oil may be used alone or in combination of two or more.

[0073] <Optional ingredients> Examples of optional components contained in composition (X) include antioxidants, viscosity index improvers, pour point depressants, detergent-dispersants, corrosion inhibitors, rust inhibitors, antifoaming agents, emulsifiers, mildew inhibitors, anti-emulsifiers, colorants, and metal deactivators. Furthermore, the composition (X) may contain, as a friction reducer other than the copolymer (A), an oiliness improver such as a long-chain fatty acid ester or a fatty acid amide, an anti-wear agent such as a phosphate ester, an extreme pressure agent such as an organic sulfur compound or an organic halogen compound, or a friction modifier such as an organic molybdenum compound. Composition (X) may also be a grease containing a thickener, such as a soap-based thickener (lithium soap, calcium soap, sodium soap, aluminum soap, etc.), an inorganic thickener (bentonite, silica gel, etc.), or an organic thickener (polyurea, polyurethane, etc.). The optional components may be used alone or in combination of two or more.

[0074] <Content> The content of copolymer (A) is preferably 0.01 to 30 mass%, more preferably 0.05 to 25 mass%, even more preferably 0.1 to 15 mass%, and particularly preferably 0.2 to 5 mass%, relative to the total mass of composition (X). When the content of copolymer (A) is equal to or greater than the above lower limit, the friction-reducing effect of composition (X) is further improved. When the content of copolymer (A) is equal to or less than the above upper limit, the kinematic viscosity of composition (X) is reduced, improving fuel economy.

[0075] The content of the zinc-containing compound relative to 1 part by mass of copolymer (A) is 0.01 to 10 parts by mass, preferably 0.1 to 5 parts by mass, and more preferably 0.5 to 3 parts by mass. When the content of the zinc-containing compound is within the above range, the combined effect of copolymer (A) and zinc-containing compound is fully exhibited.

[0076] The content of the base oil is preferably 10 to 99.98 mass%, more preferably 30 to 90 mass%, and even more preferably 50 to 85 mass%, relative to the total mass of the composition (X). When the content of the base oil is within the above range, the kinematic viscosity is reduced and fuel economy is improved.

[0077] The total content of the copolymer (A), the zinc-containing compound, and the base oil is preferably 10% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass or more, relative to the total mass of the composition (X), and may be 100% by mass.

[0078] <Manufacturing method> The composition (X) can be obtained by mixing the copolymer (A), a zinc-containing compound, a base oil, and, if necessary, optional components. When copolymer (A) is produced in a base oil, copolymer (A) is obtained in a dissolved or dispersed state in the base oil. A zinc-containing compound and, if necessary, optional components may be added to a solution containing copolymer (A) (hereinafter also referred to as a "base oil solution of copolymer (A)") to be used as composition (X). The base oil solution of copolymer (A) may be diluted with base oil before use.

[0079] <Action and effect> The composition (X) contains the copolymer (A), a specific amount of a zinc-containing compound, and a base oil, and therefore has an excellent friction-reducing effect.

[0080] <Application> Composition (X) can be used as a lubricant such as an engine oil, a drive system oil (gear oil, transmission oil), a hydraulic oil, a metal processing oil, or a grease, which is used in mobility such as automobiles and ships, industrial machinery, robots, etc.

[0081] [Lubricant composition] The lubricant composition of the present invention (hereinafter also referred to as "lubricant composition (Y)") contains the above-mentioned composition (X). The lubricant composition (Y) may consist solely of the composition (X), or may further contain components other than the composition (X) (hereinafter also referred to as "optional components"), as necessary.

[0082] The content of composition (X) is preferably 10% by mass or more, more preferably 50% by mass or more, and even more preferably 80% by mass or more, relative to the total mass of lubricant composition (Y), and may be 100% by mass.

[0083] Examples of optional components contained in the lubricant composition (Y) include the optional components exemplified above in the description of the composition (X). The optional components may be used alone or in combination of two or more.

[0084] The lubricant composition (Y) can be obtained, for example, by mixing the composition (X) with optional components. Alternatively, the composition (X) may be used as it is as the lubricant composition (Y). [Example]

[0085] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples as long as it does not deviate from the gist of the present invention, and various modifications are possible as long as they do not deviate from the gist of the present invention. In the examples, "parts" refers to "parts by mass." In Table 1, the contents of the macromonomer and the structural units derived from each monomer are shown in mass%. The contents of the macromonomer and each structural unit were calculated from the mass (amount used) of the macromonomer or monomer relative to the total mass of the macromonomer and monomer used in the polymerization reaction. The measurement and evaluation methods are described below.

[0086] <Measurement of molecular weight of macromonomer (M1)> The molecular weight of macromonomer (M1) was measured using gel permeation chromatography (GPC) (Tosoh Corporation, product name "HLC-8320"). After preparing a 0.2% by mass solution of macromonomer (M1) in tetrahydrofuran, 10 μL of the solution was injected into an apparatus equipped with columns (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)) manufactured by Tosoh Corporation. Measurement was performed under the following conditions: flow rate: 0.35 mL / min, eluent: tetrahydrofuran (stabilizer: BHT), column temperature: 40°C, and the mass average molecular weight (Mw), number average molecular weight (Mn), and Mw / Mn were calculated in terms of standard polystyrene.

[0087] <Measurement of Molecular Weight of (Meth)acrylic Copolymer (A) and Random Copolymer> (Meth)acrylic copolymer (A) and the random copolymer were measured using gel permeation chromatography (GPC) (manufactured by Tosoh Corporation, product name "HLC-8320"). After preparing a 0.2% by mass tetrahydrofuran solution of (meth)acrylic copolymer (A) or the random copolymer, 10 μl of the above solution was injected into an apparatus equipped with columns manufactured by Tosoh Corporation (TSKgel SuperHZM-H 2 pieces (inner diameter 6.0 mm, length 15 cm), TSKguardcolumn SuperHZ-H (inner diameter 4.6 mm, length 3.5 cm)), and measured under the conditions of a flow rate of 0.5 ml / min, eluent: tetrahydrofuran (stabilizer BHT), and column temperature: 40 °C. The mass average molecular weight (Mw), number average molecular weight (Mn), and Mw / Mn were calculated in terms of standard polystyrene conversion.

[0088] <Measurement of coefficient of friction> Using a UMT TriboLab tester (manufactured by Brukbr), the coefficient of friction of composition (X) at 80 °C was measured. The measurement conditions were as follows, and the coefficient of friction 1000 seconds after the start of measurement was evaluated. (Measurement conditions) · Test method: Ball on disk (ball diameter: 10 mm, ball and disk materials: SUJ2). · Test mode: Rotation (200 mm / s). · Load: 20 N.

[0089] [[ID=I7]] "Production Example 1" <Synthesis of Co complex (cobalt chain transfer agent)> Into a synthesis apparatus equipped with a stirring device, under a nitrogen atmosphere, 2.00 g (8.03 mmol) of cobalt(II) acetate tetrahydrate (manufactured by Fujifilm Wako Pure Chemical Corporation, Wako special grade), 3.86 g (16.1 mmol) of diphenylglyoxime (manufactured by Tokyo Chemical Industry Co., Ltd., EP grade), and 100 ml of diethyl ether previously deoxygenated by nitrogen bubbling were added and stirred at 25 °C for 2 hours. Next, 20 ml of boron trifluoride diethyl ether complex (EP grade, manufactured by Tokyo Chemical Industry Co., Ltd.) was added, and the mixture was stirred for another 6 hours. The obtained mixture was filtered, and the solid was washed with diethyl ether and dried at 20°C under 100 MPa or less for 12 hours to obtain 5.02 g (7.93 mmol, yield 99% by mass) of a brown solid Co complex.

[0090] "Manufacturing Example 2" <Synthesis of macromonomer (M1)> A reaction vessel equipped with a stirrer, a condenser, and a thermometer was charged with 58 parts of base oil (SK Lubricants, trade name "YUBASE4"), 98 parts of Acrylatester SL (Mitsubishi Chemical Corporation, trade name "Acrylatester SL", a mixture of an alkyl methacrylate having 12 carbon atoms in the alkyl group and an alkyl methacrylate having 13 carbon atoms in the alkyl group), 2 parts of methyl methacrylate (MMA) (Mitsubishi Chemical Corporation, trade name "Acrylatester M"), and 0.005 parts of the Co complex prepared in Production Example 1. The liquid temperature was raised to 40°C, and nitrogen was bubbled through the liquid for 2 hours while stirring to remove dissolved oxygen. A mixture of 2 parts YUBASE4 and 0.1 parts t-butylperoxy-2-ethylhexanoate (Arkema Yoshitomi Co., Ltd., trade name "Luperox 26") as a polymerization initiator was added, and the temperature was raised to 90°C. After stirring for 2.5 hours, a mixture of 10 parts YUBASE4 and 0.7 parts Luperox 26 was added dropwise over 1 hour. After the dropwise addition, the temperature was raised to 105°C and maintained for 1.5 hours. 20 parts YUBASE4 was added and cooled to obtain a YUBASE4 solution containing 52.6% by mass of macromonomer (M1) (hereinafter also referred to as "macromonomer (M1) base oil solution"). The molecular weight of the resulting macromonomer (M1) was measured, revealing an Mw of 22,000, an Mn of 9,700, and an Mw / Mn ratio of 2.3.

[0091] "Manufacturing Example 3" <Synthesis of (meth)acrylic copolymer (A-1)> A reactor equipped with a stirrer, condenser, and thermometer was charged with 30 parts of base oil (SK Lubricants, trade name "YUBASE4") and 47.6 parts of the base oil solution of macromonomer (M1) obtained in Production Example 2 (25 parts of macromonomer (M1)). Dissolved oxygen was removed by bubbling nitrogen through the mixture 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 (Mitsubishi Chemical Corporation, trade name "nBA"), 19 parts of lauryl acrylate (Osaka Organic Chemical Industry Ltd., trade name "LA"), 0.1 parts of t-amylperoxy-2-ethylhexanoate (Arkema Yoshitomi Co., Ltd., trade name "Luperox 575") as a polymerization initiator, and 0.7 parts of α-methylstyrene dimer (NOF Corporation, trade name "Nofumer MSD") as a chain transfer agent was added dropwise to the reactor over 4 hours. After the dropwise addition was completed, the mixture was held for 1 hour, and then a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was added dropwise over 90 minutes. The temperature was then raised to 110°C and held for 1 hour. After that, 58.1 parts of YUBASE4 was added and the mixture was cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic copolymer (A-1) (hereinafter also referred to as "base oil solution of copolymer (A-1)"). The obtained (meth)acrylic copolymer (A-1) is a (meth)acrylic copolymer having the macromonomer (M1) synthesized in Production Example 2 as the polymer block (I) and a polymer block (II) containing structural units derived from n-butyl acrylate and structural units derived from lauryl acrylate. The molecular weight of the (meth)acrylic copolymer (A-1) was measured to find that Mw was 133,000, Mn was 28,000, and Mw / Mn was 4.8. The results are shown in Table 1.

[0092] "Manufacturing Example 4" <Synthesis of (meth)acrylic copolymer (A-2)> To a reaction vessel equipped with a stirrer, a condenser, and a thermometer, 30 parts of base oil (manufactured by SK Lubricants Co., Ltd., product name "YUBASE4") and 47.6 parts of the base oil solution of macromonomer (M1) obtained in Production Example 2 (25 parts as macromonomer (M1)) were added, and nitrogen was bubbled through the mixture with 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 (manufactured by Mitsubishi Chemical Corporation, trade name "nBA"), 18 parts of lauryl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name "LA"), 1 part of 4-hydroxybutyl acrylate (manufactured by Mitsubishi Chemical Corporation, trade name "4HBA"), 0.1 parts of t-amylperoxy-2-ethylhexanoate (manufactured by Arkema Yoshitomi Co., Ltd., trade name "Luperox 575") 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 was added dropwise to the reaction vessel over 4 hours. After the addition was completed, the mixture was held for 1 hour, and then a mixture consisting of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was added dropwise over 90 minutes. The mixture was then heated to 110°C and maintained for 1 hour. After this, 58.1 parts of YUBASE4 was added and the mixture was cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic copolymer (A-2) (hereinafter also referred to as "base oil solution of copolymer (A-2)"). The resulting (meth)acrylic copolymer (A-2) was a (meth)acrylic copolymer having the macromonomer (M1) synthesized in Production Example 2 as polymer block (I) and a polymer block (II) containing structural units derived from n-butyl acrylate, structural units derived from lauryl acrylate, and structural units derived from 4-hydroxybutyl acrylate. The molecular weight of the resulting (meth)acrylic copolymer (A-2) was measured to find that Mw was 118,000, Mn was 26,000, and Mw / Mn was 4.5. The results are shown in Table 1.

[0093] "Manufacturing Example 5" <Synthesis of random copolymers> A reactor equipped with a stirrer, condenser, and thermometer was charged with 50 parts of base oil (SK Lubricants, trade name "YUBASE4"). Dissolved oxygen was removed by bubbling nitrogen through the mixture while stirring. The liquid temperature was raised to 85°C, and a mixture of 15 parts of YUBASE4, 95 parts of lauryl acrylate (Osaka Organic Chemical Industry, trade name "LA"), 5 parts of caprolactone-modified hydroxyalkyl (meth)acrylate (Daicel Corporation, trade name "Placcel FM3"), 0.1 parts of t-amylperoxy-2-ethylhexanoate (Arkema Yoshitomi Co., Ltd., trade name "Luperox 575") as a polymerization initiator, and 0.5 parts of α-methylstyrene dimer (NOF Corporation, trade name "Nofumer MSD") as a chain transfer agent was added dropwise to the reactor over 4 hours. After the dropwise addition was completed, the mixture was held for 1 hour, and then a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was added dropwise over 90 minutes. The temperature was then raised to 110°C and held for 1 hour, after which 70.6 parts of YUBASE4 was added and the mixture was cooled to obtain a YUBASE4 solution containing 35% by mass of random copolymer (A-3) (hereinafter also referred to as "base oil solution of copolymer (A-3)"). The molecular weight of the resulting random copolymer (A-3) was measured to find that Mw was 98,000, Mn was 21,000, and Mw / Mn was 4.7. The results are shown in Table 1.

[0094] [Table 1]

[0095] "Example 1" 1.43 g of the base oil solution of copolymer (A-1) obtained in Production Example 3 (containing 0.5 g of copolymer (A-1)), 0.25 g of zinc di-2-ethylhexyldithiophosphate (manufactured by Kemipex, trade name "LUBIMAX AW1188N"), and 23.32 g of base oil (manufactured by SK Lubricants, trade name "YUBASE4") were mixed, and the resulting mixture was stirred and mixed for 10 minutes while heated to 65°C, to obtain composition (X-1) of Example 1. The coefficient of friction of the resulting composition (X-1) was measured, and the results are shown in Table 2.

[0096] "Example 2, Comparative Examples 1 to 4" Composition (X-2) of Example 2, Composition (X-3) of Comparative Example 1, Composition (X-4) of Comparative Example 2, Composition (X-5) of Comparative Example 3, and Composition (X-6) of Comparative Example 4 were obtained in the same manner as in Example 1, except that the blending amounts of each component were changed as shown in Table 2. The friction coefficients of the resulting compositions (X-2) to (X-6) were measured, and the results are shown in Table 2.

[0097] [Table 2]

[0098] As is clear from Table 2, the composition (X-1) obtained in Example 1 and the composition (X-2) obtained in Example 2 had low coefficients of friction. In contrast, the composition (X-3) obtained in Comparative Example 1, which did not contain the (meth)acrylic copolymer (A), the composition (X-4) and the composition (X-5) obtained in Comparative Example 2, which did not contain the zinc-containing compound, and the composition (X-6) obtained in Comparative Example 4, which contained the random copolymer (A-3), all had high coefficients of friction. These results demonstrate that a significant friction-reducing effect can be obtained by using the (meth)acrylic copolymer (A), the zinc-containing compound, and the base oil in combination.

Claims

1. Contains a (meth)acrylic copolymer (A), a zinc-containing compound, and a base oil, the (meth)acrylic copolymer (A) has a polymer block (I) and a polymer block (II) having a composition different from that of the polymer block (I), The polymer block (I) contains a structural unit derived from a monomer represented by the following general formula (1): The polymer block (II) contains a structural unit derived from a monomer represented by the following general formula (2): The content of the zinc-containing compound is 0.01 to 10 parts by mass per 1 part by mass of the (meth)acrylic copolymer (A). 【Chemistry 1】 (In formula (1), R １ is a hydrogen atom or a methyl group, and R ２ is a straight or branched chain alkyl group having 11 to 30 carbon atoms. 【Chemistry 2】 (In formula (2), R ３ is a hydrogen atom or a methyl group, and R ４ is a straight or branched chain alkyl group having 1 to 30 carbon atoms.

2. The composition according to claim 1 , wherein the (meth)acrylic copolymer (A) is a graft copolymer.

3. The composition according to claim 1 or 2, wherein the (meth)acrylic copolymer (A) contains a structural unit derived from a macromonomer.

4. 3. The composition according to claim 1, wherein the zinc-containing compound is one or more compounds selected from the group consisting of zinc dialkyldithiophosphate, zinc dithiocarbamate, and zinc phosphate.

5. 3. The composition according to claim 1, wherein the content of the (meth)acrylic copolymer (A) is 0.1 to 10% by mass based on the total mass of the composition.

6. The composition according to claim 1 or 2, wherein the (meth)acrylic copolymer (A) contains a structural unit derived from an alkyl acrylate.

7. The composition according to claim 1 or 2, further comprising a friction reducer containing the (meth)acrylic copolymer (A).

8. A lubricant composition comprising the composition of claim 1 or 2.

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