JP2017125090A - Method for producing copolymer of maleimide monomer, and viscosity index improver, and method for producing lubricant composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a maleimide copolymer having a high viscosity index and excellent shear stability and showing sufficient solubility to a lubricant base oil, at a high polymer rate and in a small number of steps.SOLUTION: A method for producing a copolymer has the step for polymerization of a monomer comprising a maleimide monomer as an essential component in a lubricant base oil.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a copolymer having a specific structure, and a method for producing a viscosity index improver containing the copolymer. In particular, the present invention relates to a method for producing a viscosity index improver having a high viscosity index and good shear stability, and exhibiting sufficient solubility in a lubricating oil.

  In recent years, lubricating oil for internal combustion engines has been strongly required to improve fuel-saving characteristics, and one means is to reduce viscosity resistance by reducing the viscosity of the lubricating oil. However, simply reducing the viscosity causes problems such as liquid leakage and seizure. Therefore, it is effective to add a viscosity index improver having an effect of keeping the viscosity at a low temperature while keeping the viscosity at a high temperature high.

Viscosity index improvers are known to contain polymers, and there are various types. Especially, the viscosity index improver which consists of an alkyl (meth) acrylate polymer shows a high viscosity index improvement effect. On the other hand, the viscosity index improver made of alkyl (meth) acrylate polymer has poor shear stability, so there is a problem that the fuel-saving property is lowered during long-term use (long life property is poor). Examples of means for improving include reducing the molecular weight of the viscosity index improver. In general, the lower the molecular weight, the less the influence of shearing, and the lower the molecular weight reduction range. Therefore, by using a low molecular weight viscosity index improver, it is possible to suppress the viscosity reduction after shearing (Patent Document 1 and Non-Patent Document 1). Patent Document 1).

  From the viewpoint of improving shear stability and thermal stability, a method of introducing a specific amount of maleimide monomer into the main chain skeleton of a polymethacrylate viscosity index improver has been proposed (Patent Document 2).

JP 2013-104032 A JP2015-86314A JP 2001-233919 A Sanyo Chemical News 2013 New Year No. 476

  The present invention provides a maleimide copolymer having a high viscosity index and good shear stability and sufficient solubility in a lubricating base oil with a high polymerization rate and a small number of steps. The purpose is to do.

  As described above, the polymethacrylate viscosity index improver is a polymer and therefore undergoes a decrease in molecular weight due to shearing, resulting in a decrease in the viscosity of the lubricating oil composition and a reduction in fuel economy. Sex improves. On the other hand, generally, the lower the molecular weight, the lower the viscosity index improving effect tends to be low. Therefore, when a low molecular weight viscosity index improver is used, there arises a problem that the viscosity index decreases. Furthermore, in order to adjust to a desired viscosity, it is necessary to increase the usage-amount of a viscosity index improver, and it tends to be disadvantageous in cost.

  In addition, a polymethacrylate viscosity index improver in which a specific amount of maleimide monomer is introduced into the main chain skeleton has a high viscosity index and good shear stability. In the polymerization of maleimide copolymers, it is known that the addition of an acid component is effective for improving the polymerization rate of maleimide monomers (Patent Document 3). However, when the above method is used, an odor derived from an acid component may be generated at the time of production, which causes a problem in workability. There was also concern about corrosion of the equipment due to acid components.

  The copolymer can be obtained by a method such as bulk polymerization, solution polymerization, suspension polymerization, or emulsion polymerization. When a solvent is used, if a solvent that is insoluble in the lubricating base oil is used, solvent replacement after polymerization is required, which increases the number of steps.

  As a result of intensive studies, the present inventors have found that a monomer containing a maleimide monomer is copolymerized in a lubricating base oil, and have reached the present invention.

  That is, the present invention comprises a step of polymerizing a monomer containing a maleimide monomer (hereinafter referred to as “component (a)”) as an essential component in a lubricating base oil. It is a manufacturing method.

In addition to the component (a), the monomer includes (b) an alkyl (meth) acrylate having an aliphatic hydrocarbon group having 1 to 5 carbon atoms (hereinafter referred to as “component (b)”), (c) It is preferably a monomer containing an alkyl (meth) acrylate having an aliphatic hydrocarbon group having 6 to 40 carbon atoms (hereinafter referred to as “component (c)”).
The copolymer is preferably obtained in a step of polymerizing the monomer in a lubricating base oil in the presence of a trifunctional or higher polyvalent mercaptan and / or a trifunctional or higher polyfunctional initiator.
This invention is also a manufacturing method of the viscosity index improver containing the copolymer obtained by the said manufacturing method.
The present invention is also a method for producing a lubricating oil composition containing the viscosity index improver.

  By using the production method of the present invention, the polymerization rate of the maleimide monomer can be improved without using an acid component, shear stability suitable as a viscosity index improver, a copolymer exhibiting a high viscosity index, and A lubricating oil composition can be obtained without a solvent replacement step.

The present invention is described in detail below. In the following description, “part” means “part by mass” and “%” means “mass%” unless otherwise specified. In addition, “A to B” indicating a range indicates that the range is A or more and B or less.
This invention is a manufacturing method of the copolymer characterized by having the process of superposing | polymerizing the monomer which contains a monomer (a) component as an essential component in lubricating oil base oil.

  The monomer (a) component used in the present invention is a maleimide monomer represented by the following general formula (1).

(Wherein R ¹ and R ² are each independently a hydrogen atom or an alkyl group, and X is a hydrogen atom, a linear, branched or cyclic alkyl group, a substituted alkyl group, an aryl group or a substituted aryl group. is there.)
As the monomer (a) component, among the above X, the branched alkyl group may have an alkyl group having an aromatic ring. The cyclic alkyl group is preferably an alkyl group having an aromatic ring such as a benzyl group or a cycloalkyl group such as a cyclohexyl group. The aryl group is preferably a phenyl group, a naphthyl group, or an aryl group substituted with an aromatic ring hydrogen.

Specific examples of the monomer (a) component include maleimide, N-methylmaleimide, N-ethylmaleimide, N-isopropylmaleimide, N-butylmaleimide, N-isobutylmaleimide, N-tertiarybutylmaleimide, N-cyclohexyl Maleimide, N-laurylmaleimide, N-stearylmaleimide, N-phenylmaleimide, N-benzylmaleimide, N-chlorophenylmaleimide, N-methylphenylmaleimide, N-naphthylmaleimide, N-hydroxylethylmaleimide, N-hydroxylphenylmaleimide, N-methoxyphenylmaleimide, N-carboxyphenylmaleimide, N-nitrophenylmaleimide, N-tribromophenylmaleimide and the like can be mentioned, and one or more of these compounds are used. . Of these, N-phenylmaleimide, N-cyclohexylmaleimide, N-isopropylmaleimide, N-benzylmaleimide, N-laurylmaleimide, N-stearyl are highly available and economical and have high solubility in base oils. Maleimide is preferable, N-phenylmaleimide, N-cyclohexylmaleimide, and N-benzylmaleimide are more preferable, and N-cyclohexylmaleimide is further preferable. In addition, the said monomer (a) may be used independently and may use 2 or more types together.
The content of the monomer (a) component is 0.5 to 35 parts by mass, preferably 2 to 35 parts by mass, based on 100 parts by mass of all monomer components. Preferably they are 5 mass parts or more and 35 mass parts or less, Especially preferably, they are 5 mass parts or more and 30 mass parts or less. The viscosity index improver containing the polymer using the monomer (a) component in the above numerical range can enhance the shear stability while ensuring the solubility in the base oil. Furthermore, effects such as improvement in clean dispersibility of sludge and the like and suppression of wear on the metal surface are expected.

  In addition to the component (a), the monomer used in the present invention is (b) an alkyl (meth) acrylate having an aliphatic hydrocarbon group having 1 to 5 carbon atoms (hereinafter referred to as “component (b)”). (C) A monomer containing an alkyl (meth) acrylate having an aliphatic hydrocarbon group having 6 to 40 carbon atoms (hereinafter referred to as “component (c)”) is preferable.

As the component (b), specifically, it has a structure represented by the following general formula (2), R ^{3 in} the formula is a hydrogen atom or a methyl group, and R ⁴ is the number of carbon atoms. (Meth) acrylates which are 1 to 5 aliphatic hydrocarbon groups. R ⁴ may be linear, cyclic or branched, and may have a substituent.

The monomer (b) component may be such that R ³ and R ⁴ are each a single monomer, or a mixture of two or more monomers in which R ³ and / or R ⁴ are different. Good. From the viewpoint of reactivity, R ³ is preferably a hydrogen atom or a methyl group. In view of improving the viscosity index, R ⁴ is preferably linear or branched.

  Specific examples of the monomer (b) component include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, and n-butyl (meth) acrylate. , Iso-butyl (meth) acrylate, t-butyl (meth) acrylate, n-amyl (meth) acrylate, iso-amyl (meth) acrylate, t-amyl (meth) acrylate, neopentyl (meth) acrylate, and the like. . Among these, it is preferable that at least methyl (meth) acrylate is included as the monomer (b) component. When the component (b) contains methyl (meth) acrylate, the viscosity index improving effect is large, and the viscosity index improver has high heat resistance and high shear stability. In addition, the said monomer (b) may be used independently and may use 2 or more types together.

    The content of the monomer (b) component is preferably 2 to 40 parts by mass, more preferably 5 to 35 parts by mass, particularly preferably 100 parts by mass in total of all monomer components. Is 5 parts by mass or more and 30 parts by mass or less. When the content of the monomer (b) component is in the above range, the copolymerization with other components is good, the polymerization rate is good, the polymerization rate is high, and the productivity is good. Moreover, the shear stability and base oil solubility of the viscosity index improver obtained by copolymerization become better.

The monomer (c) component used in the present invention has a structure represented by the following general formula (3), and R ^{5 in} the formula is a hydrogen atom or a methyl group, and R ⁶ is carbon. Examples thereof include (meth) acrylates having an alkyl group of 6 to 40, preferably 6 to 24, particularly preferably 12 to 24. R ⁶ may be linear, cyclic or branched, and may have a substituent.

Monomer component (c) may be a mixture of R ⁵ and R ⁶ each may be a single monomer, R ⁵ and / or R ⁶ are different 2 or more monomers Good. From the viewpoint of reactivity, R ⁵ is preferably a hydrogen atom or a methyl group.
Specific examples of the monomer (c) component include n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (Meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) ) Acrylate, nonadecyl (meth) acrylate, eicosyl (meth) acrylate, behenyl (meth) acrylate, tetracosyl (meth) acrylate, 2-decyltetradecyl (meth) acrylate, Hexyl (meth) acrylate, menthyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, adamantyl (meth) acrylate. Among these, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, eicosyl (meta) from the viewpoint of availability and economy and high solubility in base oils. ) Acrylate, behenyl (meth) acrylate, tetracosyl (meth) acrylate, 2-decyltetradecyl (meth) acrylate, and cyclohexyl (meth) acrylate are preferred. In addition, the said monomer (b) may be used independently and may use 2 or more types together.

  The content of the monomer (c) component is preferably 20 parts by mass or more and less than 95 parts by mass, more preferably 25 parts by mass or more and 85 parts by mass or less, particularly preferably 100 parts by mass of the total monomer components. Is 30 parts by mass or more and 75 parts by mass or less. A viscosity index improver containing a polymer using the monomer (c) component in the above numerical range has good solubility in base oils of various compositions.

  By using the component (c) having a long-chain alkyl group with low polarity, a polymer having high oil solubility can be obtained. The component (a) is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, relative to 100 parts by mass of the polymer. The upper limit is preferably 33 parts by mass or less, particularly preferably 30 parts by mass or less. When the component (a) is less than 0.5 parts by mass, the effect of introducing the component (a) is not sufficiently obtained, and the shear stability is not sufficiently improved. Furthermore, the clean dispersibility of sludge or the like derived from the highly polar structure of the component (a) may be reduced, or the metal surface may be worn or the fatigue life may be reduced. If it exceeds 35 parts by mass, the solubility in the lubricating base oil tends to be reduced or the viscosity index tends to be reduced. In addition, when the weight average molecular weight is less than 200,000, not only the viscosity index of the lubricating oil composition is lowered, but it is necessary to increase the amount of the viscosity index improver used to adjust to a desired viscosity. Is disadvantageous.

  Moreover, as a monomer component which synthesize | combines the polymer of this invention, radically polymerizable monomers (d) other than an essential component (a), (b), (c) component can be contained. The monomer (d) can be classified into a monofunctional monomer having one radical polymerizable group in the same molecule and a polyfunctional monomer having two or more radical polymerizable groups in the same molecule. .

  Examples of monofunctional monomers include (b), (meth) acrylates other than components (c), unsaturated mono- or dicarboxylic esters, unsaturated carboxylic acids, vinyl aromatics, vinyl esters, vinyl ethers, olefins, Examples include vinyl cyanide, N-vinyl compound, (meth) acrylamide, and the like. These monofunctional monomers may be used alone or in combination of two or more.

  Examples of (meth) acrylates other than the components (b) and (c) include benzyl (meth) acrylate, phenyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3 -Hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meta ) Acrylate, 2-phenoxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, morpholinoalkylene (meth) acrylate, α-hydroxymethylacrylic Methyl, polyethylene glycol mono (meth) acrylate.

  Examples of unsaturated mono- or dicarboxylic acid esters include butyl crotonate, octyl crotonate, dodecyl crotonate, dibutyl maleate, dilauryl maleate, dioctyl fumarate, distearyl fumarate, dilauryl itaconate and the like. .

  Examples of unsaturated carboxylic acids include (meth) acrylic acid, crotonic acid, cinnamic acid, vinyl benzoic acid, maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, and the like.

  Examples of the vinyl aromatic compound include styrene monomers such as styrene, α-methylstyrene, vinyltoluene, and methoxystyrene, 2-vinylpyridine, 4-vinylpyridine, and the like.

  Examples of the vinyl ester include vinyl acetate, vinyl propionate, vinyl octylate and the like.

  Examples of the vinyl ether include methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, octyl vinyl ether, decyl vinyl ether, dodecyl vinyl ether, octadecyl vinyl ether and the like.

  Examples of olefins include ethylene, propylene, 1-butene, isobutene, 1-hexene, 1-decene, 1-tetradecene, 1-octadecene, diisobutene and the like.

  Examples of vinyl cyanide include acrylonitrile and methacrylonitrile.

  Examples of the N-vinyl compound include N-vinyl pyrrolidone, N-vinyl caprolactam, N-vinyl imidazole, N-vinyl morpholine, N-vinyl acetamide and the like.

Examples of (meth) acrylamide include N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyl (meth) acrylamide, N, N-dibutyl (meth) acrylamide, N -Methylol (meth) acrylamide, acryloyl morpholine, etc. are mentioned.
Among these monofunctional monomers, 2-hydroxyethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, methyl α-hydroxymethyl acrylate, N-vinylpyrrolidone, N, N-dimethyl ( Meth) acrylamide and acryloylmorpholine are preferred.

  The unit derived from the monofunctional monomer contained in the radical polymerizable monomer (d) other than the essential components (a), (b) and (c) is 0 part by mass with respect to 100 parts by mass of the polymer. It is 30 parts by mass or less, preferably 0 parts by mass or more and 25 parts by mass or less, and more preferably 0 parts by mass or more and 20 parts by mass or less.

  However, when using a styrene-type monomer, the unit derived from a styrene-type monomer is 2 mass parts or less with respect to 100 mass parts of polymers, and it is more preferable that it is 1 mass part or less. If the unit derived from the styrene monomer exceeds 2 parts by mass, the solubility and viscosity index of the viscosity index improver containing the polymer in the base oil tend to decrease.

  When using olefin as a monomer, it is preferable that the unit derived from olefin is 5 mass parts or less with respect to 100 mass parts of polymers, and it is more preferable that it is 3 mass parts or less. When the unit derived from olefins exceeds 5 parts by mass, the viscosity index of the viscosity index improver containing the polymer tends to decrease.

  Examples of polyfunctional monomers include polyfunctional (meth) acrylates, vinyl ether group-containing (meth) acrylates, allyl group-containing (meth) acrylates, polyfunctional (meth) acryloyl group-containing isocyanurates, polyfunctional urethanes (meth). Examples include polyfunctional (meth) acrylic compounds such as acrylates, polyfunctional maleimide compounds, polyfunctional vinyl ethers, polyfunctional allyl compounds, polyfunctional aromatic vinyls, and the like. In addition, the said polyfunctional monomer may be used independently and may use 2 or more types together.

  Examples of the polyfunctional (meth) acrylate include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, Hexanediol di (meth) acrylate, cyclohexanedimethanol di (meth) acrylate, bisphenol A alkylene oxide di (meth) acrylate, bisphenol F alkylene oxide di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tetra (Meth) acrylate, glycerin tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaeryth Tall penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 2,2 ′-[oxybis (methylene)] bisacrylate, dialkyl-2,2 ′-[oxybis (methylene)] bis-2-propenoate, etc. Can be mentioned.

  Examples of the vinyl ether group-containing (meth) acrylate include 2-vinyloxyethyl (meth) acrylate, 4-vinyloxybutyl (meth) acrylate, 4-vinyloxycyclohexyl (meth) acrylate, and 2- (vinyloxyethoxy) ethyl (meth) acrylate. , 2- (vinyloxyethoxyethoxyethoxy) ethyl (meth) acrylate and the like.

  Examples of the allyl group-containing (meth) acrylate include allyl (meth) acrylate, methyl-α-allyloxymethyl (meth) acrylate, stearyl-α-allyloxymethyl (meth) acrylate, 2-decyltetradecyl-α- And allyloxymethyl (meth) acrylate.

  Examples of the polyfunctional (meth) acryloyl group-containing isocyanurate include tri (acryloyloxyethyl) isocyanurate, tri (methacryloyloxyethyl) isocyanurate, and the like.

  Examples of the polyfunctional urethane (meth) acrylate include polyfunctional isocyanates such as tolylene diisocyanate, isophorone diisocyanate, and xylylene diisocyanate, and hydroxyl groups such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate ( Polyfunctional urethane (meth) acrylate obtained by reaction with (meth) acrylate, etc. are mentioned.

  Examples of the polyfunctional maleimide compound include 4,4′-diphenylmethane bismaleimide, m-phenylene bismaleimide, bisphenol A diphenyl ether bismaleimide, 3,3′-dimethyl-5,5′-diethyl-4,4′-. Examples include diphenylmethane bismaleimide, 4-methyl-1,3-phenylenebismaleimide, 1,6-bismaleimide- (2,2,4-trimethyl) hexane, and the like.

  Examples of the polyfunctional vinyl ether include ethylene glycol divinyl ether, diethylene glycol divinyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, butylene glycol divinyl ether, hexanediol divinyl ether, bisphenol A alkylene oxide divinyl ether, bisphenol F alkylene oxide divinyl ether. , Trimethylolpropane trivinyl ether, ditrimethylolpropane tetravinyl ether, glycerin trivinyl ether, pentaerythritol tetravinyl ether, dipentaerythritol pentavinyl ether, dipentaerythritol hexavinyl ether, and the like.

  Examples of polyfunctional allyl compounds include ethylene glycol diallyl ether, diethylene glycol diallyl ether, polyethylene glycol diallyl ether, propylene glycol diallyl ether, butylene glycol diallyl ether, hexanediol diallyl ether, bisphenol A alkylene oxide diallyl ether, and bisphenol F alkylene oxide. Polyfunctional allyl ethers such as diallyl ether, trimethylolpropane triallyl ether, ditrimethylolpropane tetraallyl ether, glyceryl triallyl ether, pentaerythritol tetraallyl ether, dipentaerythritol pentaallyl ether, dipentaerythritol hexaallyl ether; triallyl Isocyanurate Polyfunctional allyl group-containing isocyanurate; diallyl phthalate, polyfunctional allyl ester such as diphenic diallyl like; bis-allyl-nadi-imide compound; bis-allyl-nadi-imide compound and the like.

Examples of the polyfunctional aromatic vinyl include divinylbenzene.
The unit derived from the polyfunctional monomer contained in the radical polymerizable monomer (d) other than the essential components (a), (b) and (c) is 0 part by mass with respect to 100 parts by mass of the polymer. It is preferably 5 parts by mass or less, more preferably 0 parts by mass or more and 3 parts by mass or less, and still more preferably 0 parts by mass or more and 2 parts by mass or less. In this case, when the polymer has a star structure or a crosslinked structure, the shear stability of the viscosity index improver containing the polymer can be improved without significantly impairing the solubility in the base oil.

  However, 2,2 ′-[oxybis (methylene)] bisacrylic acid, dialkyl-2,2 ′-[oxybis (methylene)] bis-2-propenoate, methyl α-allyloxymethyl acrylate, α-allyloxymethyl In the case of a polyfunctional monomer in which polymerization proceeds while cyclizing, such as stearyl acrylate and α-allyloxymethyl acrylate 2-decyltetradecyl, 0 to 30 parts by mass with respect to 100 parts by mass of the polymer It is preferable that it is below, More preferably, it is 0 to 25 mass parts, More preferably, it is 0 to 20 mass parts. In this case, due to the effect of the ring structure introduced into the main chain, the heat resistance of the viscosity index improver containing the polymer is improved, and the shear stability can be improved.

  If the unit derived from the polyfunctional monomer exceeds the above range, gelation may proceed during polymerization, or the solubility of the viscosity index improver containing the polymer in the base oil may decrease.

  When the monomer component is polymerized by a radical polymerization mechanism, it is industrially advantageous to use a radical polymerization initiator in combination. The radical polymerization initiator includes a thermal radical polymerization initiator that generates a polymerization initiating radical by heating and a photo radical polymerization initiator that generates a polymerization initiating radical by irradiation with an active energy ray. Or 2 or more types can be used. It is also preferable to add one or more conventionally known thermal radical polymerization accelerators, photosensitizers, photoradical polymerization accelerators, and the like as necessary.

  Specific examples of the thermal radical polymerization initiator include methyl ethyl ketone peroxide, cyclohexanone peroxide, methylcyclohexanone peroxide, methyl acetoacetate peroxide, acetyl acetate peroxide, 1,1-bis (t-hexyl peroxide). Oxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-hexylperoxy) cyclohexane, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1, 1-bis (t-butylperoxy) -2-methylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, 1,1-bis (t-butylperoxy) cyclododecane, 1,1-bis (T-Butylperoxy) butane, p-menthan high Loperoxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, t-hexyl hydroperoxide, t-butyl hydroperoxide, α, α'-bis (T-butylperoxy) diisopropylbenzene, dicumyl peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, t-butylcumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexyne-3, isobutyryl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide Oxide, sc Acid peroxide, m-toluoylbenzoyl peroxide, benzoyl peroxide, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, bis (4-t-butylcyclohexyl) peroxydicarbonate, di-2 -Ethoxyethyl peroxydicarbonate, di-2-ethoxyhexyl peroxydicarbonate, di-3-methoxybutyl peroxydicarbonate, di-s-butyl peroxydicarbonate, di (3-methyl-3-methoxybutyl ) Peroxydicarbonate, α, α′-bis (neodecanoylperoxy) diisopropylbenzene, cumylperoxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, 1 -Cyclohexyl-1- Tylethyl peroxyneodecanoate, t-hexylperoxyneodecanoate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t-butylperoxypivalate, 1,1,3 , 3-tetramethylbutylperoxy-2-ethylhexanoate, 2,5-dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexanoate, 1-cyclohexyl-1-methylethylperoxy-2 -Ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-hexylperoxyisopropylmonocarbonate, t-butylperoxyisobutyrate, t-butyl peroxymalate, t-butyl peroxy-3,5,5-tri Tylhexanoate, t-butyl peroxylaurate, t-butyl peroxyisopropyl monocarbonate, t-butyl peroxy-2-ethylhexyl monocarbonate, t-butyl peroxyacetate, t-butyl peroxy-m-toluyl Benzoate, t-butylperoxybenzoate, bis (t-butylperoxy) isophthalate, 2,5-dimethyl-2,5-bis (m-toluylperoxy) hexane, t-hexylperoxybenzoate, 2,5 -Dimethyl-2,5-bis (benzoylperoxy) hexane, t-butylperoxyallyl monocarbonate, t-butyltrimethylsilyl peroxide, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) Propane, 3,3 ', 4,4'-teto La (t-butylperoxycarbonyl) benzophenone, t-amylperoxyisonanoate, t-amylperoxy-2-ethylhexanoate, sodium persulfate, potassium persulfate, ammonium persulfate, hydrogen peroxide, etc. Oxide-based initiator; 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 1-[(1-cyano-1-methylethyl) azo] formamide, 1,1′-azobis (cyclohexane-1- Carbonitrile), 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2 '-Azobis (2,4-dimethyl-4-methoxyvaleronitrile), 2,2'-azobis (2-methylpropionamidine) dihydride Chloride, 2,2′-azobis (2-methyl-N-phenylpropionamidine) dihydrochloride, 2,2′-azobis [N- (4-chlorophenyl) -2-methylpropionamidine] dihydrochloride, 2,2 ′ -Azobis [N- (4-hydrophenyl) -2-methylpropionamidine] dihydrochloride, 2,2'-azobis [2-methyl-N- (phenylmethyl) propionamidine] dihydrochloride, 2,2'-azobis [2-Methyl-N- (2-propenyl) propionamidine] dihydrochloride, 2,2′-azobis [N- (2-hydroxyethyl) -2-methylpropionamidine] dihydrochloride, 2,2′-azobis [ 2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2, '-Azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis [2- (4,5,6,7-tetrahydro-1H-1,3-diazepine-2- Yl) propane] dihydrochloride, 2,2′-azobis [2- (3,4,5,6-tetrahydropyrimidin-2-yl) propane] dihydrochloride, 2,2′-azobis [2- (5-hydroxy) -3,4,5,6-tetrahydropyrimidin-2-yl) propane] dihydrochloride, 2,2'-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] propane} Dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane], 2,2′-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) ) -2-Hydroxyethyl] propionamide}, 2,2′-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) ethyl] propionamide}, 2,2′-azobis [2-methyl -N- (2-hydroxyethyl) propionamide], 2,2'-azobis (2-methylpropionamide), 2,2'-azobis (2,4,4-trimethylpentane), 2,2'-azobis (2-methylpropane), dimethyl-2,2-azobis (2-methylpropionate), 4,4′-azobis (4-cyanopentanoic acid), 2,2′-azobis [2- (hydroxymethyl) Azo initiators such as propionitrile], 2,3-dimethyl-2,3-diphenylbutane, and the like.

  Examples of the thermal radical polymerization accelerator that can be used together with the thermal radical polymerization initiator include metal soaps such as cobalt, copper, tin, zinc, manganese, iron, zirconium, chromium, vanadium, calcium, and potassium; Quaternary ammonium salts; thiourea compounds; ketone compounds, etc., specifically, for example, cobalt octylate, cobalt naphthenate, copper octylate, copper naphthenate, manganese octylate, naphthenic acid Manganese, dimethylaniline, triethanolamine, triethylbenzylammonium chloride, di (2-hydroxyethyl) p-toluidine, ethylenethiourea, acetylacetone, methyl acetoacetate and the like can be mentioned.

  Specific examples of the radical photopolymerization initiator include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1 -Phenylpropan-1-one, 1- [4- (2-hydroxyethoxy) phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1- {4- [4- ( 2-hydroxy-2-methylpropionyl) benzyl] phenyl} -2-methylpropan-1-one, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, 2-benzyl-2 -Dimethylamino-1- (4-morpholinophenyl) -butanone-1,2- (dimethylamino) -2-[(4-methyl Alkylphenone compounds such as phenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone; benzophenones such as benzophenone, 4,4′-bis (dimethylamino) benzophenone and 2-carboxybenzophenone Compound: Benzoin compounds such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether; thioxanthone, 2-ethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4 -Thioxanthone compounds such as diethylthioxanthone; 2- (4-methoxyphenyl) -4,6-bis (trichloromethyl) -s-triazine, 2- (4-methoxynaphthyl) -4,6 Bis (trichloromethyl) -s-triazine, 2- (4-ethoxynaphthyl) -4,6-bis (trichloromethyl) -s-triazine, 2- (4-ethoxycarboquinylnaphthyl) -4,6-bis ( Halomethylated triazine compounds such as trichloromethyl) -s-triazine; 2-trichloromethyl-5- (2′-benzofuryl) -1,3,4-oxadiazole, 2-trichloromethyl-5- [β- ( 2'-benzofuryl) vinyl] -1,3,4-oxadiazole, 4-oxadiazole, 2-trichloromethyl-5-furyl-1,3,4-oxadiazole and the like halomethylated oxadiazoles Compound; 2,2′-bis (2-chlorophenyl) -4,4 ′, 5,5′-tetraphenyl-1,2′-biimidazole, 2,2′-bis (2 4-dichlorophenyl) -4,4 ′, 5,5′-tetraphenyl-1,2′-biimidazole, 2,2′-bis (2,4,6-trichlorophenyl) -4,4 ′, 5 Biimidazole compounds such as 5′-tetraphenyl-1,2′-biimidazole; 1,2-octanedione, 1- [4- (phenylthio)-, 2- (O-benzoyloxime)], ethanone, 1 Oxime ester compounds such as [9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl]-, 1- (O-acetyloxime); bis (η5-2,4-cyclopentadiene -1-yl) -bis (2,6-difluoro-3- (1H-pyrrol-1-yl) -phenyl) titanium compounds such as titanium; p-dimethylaminobenzoic acid, p-diethylamino Benzoic acid ester compounds such as benzoic acid; acridine compounds such as 9-phenyl acridine; and the like.

  When the monomer component is polymerized by a radical polymerization mechanism, a known chain transfer agent may be used as necessary, and it is more preferable to use in combination with a radical polymerization initiator. Specific examples of such chain transfer agents include mercaptocarboxylic acids such as mercaptoacetic acid and 3-mercaptopropionic acid; methyl mercaptoacetate, methyl 3-mercaptopropionate, 2-ethylhexyl 3-mercaptopropionate, N-octyl 3-mercaptopropionate, methoxybutyl 3-mercaptopropionate, stearyl 3-mercaptopropionate, trimethylolpropane tris (3-mercaptopropionate), pentaerythritol tetrakis (3-mercaptopropionate), di Mercaptocarboxylic esters such as pentaerythritol hexakis (3-mercaptopropionate); ethyl mercaptan, t-butyl mercaptan, n-dodecyl mercaptan, 1,2-dimercaptoethane, etc. Alkyl mercaptans; mercaptoalcohols such as 2-mercaptoethanol and 4-mercapto-1-butanol; aromatic mercaptans such as benzenethiol, m-toluenethiol, p-toluenethiol and 2-naphthalenethiol; tris [(3 -Mercaptopropionyloxy) -ethyl] mercaptoisocyanurates such as isocyanurate; disulfides such as 2-hydroxyethyl disulfide and tetraethylthiuram disulfide; dithiocarbamates such as benzyldiethyldithiocarbamate; simple units such as α-methylstyrene dimer Monomeric dimers; alkyl halides such as carbon tetrabromide; Among these, mercaptocarboxylic acids, mercaptocarboxylic esters, alkyl mercaptans, mercaptoalcohols, aromatic mercaptans; mercaptoisocyanurates in terms of availability, ability to prevent crosslinking, and low degree of polymerization rate reduction. Compounds having a mercapto group, such as catechol, are preferred. These may be used alone or in combination of two or more.

  When the monomer component is polymerized by a radical polymerization mechanism, it is more preferable to perform radical polymerization in the presence of a trifunctional or higher polyvalent mercaptan and / or a trifunctional or higher polyfunctional initiator.

  Examples of the trifunctional or higher polyvalent mercaptan include trimethylolpropane trimercaptoacetate, trimethylolpropane tri (3-mercaptopropionate), pentaerythritol tetrakismercaptoacetate, pentaerythritol tetrakis (3-mercaptopropionate), Dipentaerythritol hexakis mercaptoacetate, dipentaerythritol hexakis (3-mercaptopropionate) and other compounds having three or more hydroxyl groups and carboxyl group-containing mercaptans polyester compounds, triazine polyvalent thiols, polyvalent epoxy compounds A compound obtained by adding hydrogen sulfide to a plurality of epoxy groups and introducing three or more mercapto groups per molecule, a plurality of carboxyl groups and mercapto of polyvalent carboxylic acid Ethanol to can be such compounds include having esterified three or more mercapto groups per molecule comprising. The trifunctional or higher polyvalent mercaptan can be used alone or in combination (for example, mixed).

  The amount (total amount added) of the trifunctional or higher polyvalent mercaptan is appropriately determined according to the type and amount of the monomer used, the polymerization conditions such as polymerization temperature and polymerization concentration, the molecular weight of the target polymer, and the like. What is necessary is just to set, and it does not specifically limit. From the viewpoint of obtaining a viscosity index improver containing a polymer having a high base oil solubility and a weight average molecular weight of 100,000 or more, the amount of trifunctional or higher polyvalent mercaptan used is 100 parts by mass of the monomer component. On the other hand, 0.01 mass part or more is preferable, 0.05 mass part or more is more preferable, 5 mass part or less is preferable, 3 mass part or less is more preferable, and 2 mass part or less is further more preferable. By setting it as this range, molecular weight distribution becomes narrow and shear stability can be improved.

  Examples of the trifunctional or higher polyfunctional initiator include 2,2-bis (4,4-t-butylperoxycyclohexyl) propane, tris (t-butylperoxy) triazine, 3,3 ′, 4,4. Trifunctional or higher functional organic peroxides such as' -tetra (t-butylperoxycarbonyl) benzophenone are exemplified, but not particularly limited.

  The usage amount (addition amount total amount) of the trifunctional or higher polyfunctional initiator is not particularly limited, and may be appropriately set according to the purpose and application. From the viewpoint of obtaining a viscosity index improver containing a polymer having a weight average molecular weight of 100,000 or more, which has high viscosity index and base oil solubility, taking into consideration the balance between polymerizability, adverse effects of degradation products, and economic efficiency. The amount of the trifunctional or higher polyfunctional initiator is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, and 0.05 parts by mass or more with respect to 100 parts by mass of the monomer component. More preferably, it is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and further preferably 2 parts by mass or less.

  A polymer obtained by radical polymerization of a monomer component in the presence of a trifunctional or higher polyvalent mercaptan and / or a trifunctional or higher polyfunctional initiator has a structure in which a polymer chain is branched from the center. It will have. That is, the polymer contained in the viscosity index improver of the present invention has a branch unit derived from a trifunctional or higher polyvalent mercaptan and / or a branch unit derived from a trifunctional or higher polyfunctional initiator. When the polymer contained in the viscosity index improver has such a structure, the shear stability of the viscosity index improver containing the polymer can be improved without greatly impairing the solubility in the base oil. it can.

When the polymer contained in the viscosity index improver has a branched unit derived from a trifunctional or higher polyvalent mercaptan, the polymer has a branched unit (chain transfer agent residue) represented by the following formula (4). Is preferred. In the following formula (4), L _T represents an m-valent organic residue, m represents a number of 0 or more. m is preferably 0-5.

When the polymer contained in the viscosity index improver has a branch unit derived from a trifunctional or higher polyfunctional initiator, the polymer preferably has a branch unit derived from a trifunctional or higher functional peroxide. Preferably has a branch unit represented by the following formula (5). In the following formula (5), L _S represents an n-valent organic residue (initiator residue), and n represents a number of 0 or more. n is preferably 0 to 5.

  The polymer contained in the viscosity index improver may contain only one or both of a branched unit derived from a polyfunctional mercaptan having a functionality of 3 or more and a branched unit derived from a polyfunctional initiator having a functionality of 3 or more. Also good. Only one type of trifunctional or higher polyvalent mercaptan-derived branch unit may be contained, or two or more types may be contained. Only one type of branch unit derived from a trifunctional or higher polyfunctional initiator may be contained, or two or more types may be contained.

  The content of the trifunctional or higher polyfunctional mercaptan-derived branch unit in the polymer is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and 5 parts by mass with respect to 100 parts by mass of the polymer. Part or less, preferably 3 parts by weight or less, more preferably 2 parts by weight or less. By setting it as this range, the molecular weight distribution of the polymer becomes narrow, and the shear stability can be improved. The content of the branch unit derived from the trifunctional or higher polyvalent mercaptan is obtained by dividing the amount of the trifunctional or higher polyvalent mercaptan used by the polymer mass.

  The content of the branch unit derived from the trifunctional or higher polyfunctional initiator in the polymer is a viscosity index and a viscosity index improver containing a polymer having a high base oil solubility and a weight average molecular weight of 100,000 or more. From 100 parts by mass of the polymer, 0.01 parts by mass or more is preferable, 0.02 parts by mass or more is more preferable, 0.05 parts by mass or more is more preferable, and 10 parts by mass or less is preferable, and 5 parts by mass is preferable. The following is more preferable, and 2 parts by mass or less is more preferable. The content of the branch unit derived from the trifunctional or higher polyfunctional initiator is obtained by dividing the amount of the trifunctional or higher polyfunctional initiator used by the polymer mass.

  In the case of using a trifunctional or higher polyvalent mercaptan and / or a trifunctional or higher polyfunctional initiator in the polymerization step, suitable conditions such as the type and amount of use thereof are as described above. In the polymerization, the trifunctional or higher polyvalent mercaptan and / or the trifunctional or higher polyfunctional initiator may be added all at once or in divided portions. Further, a bifunctional or lower functional mercaptan or a bifunctional or lower functional initiator may be used in combination.

Since narrowing the molecular weight distribution of the copolymer obtained by the present invention is very advantageous from the viewpoint of improving the viscosity index and improving the shear stability, Living Radical Polymerization can also be used as a polymerization method. As specific methods, RAFT method, NMP method, ATRP method and the like are well known. Details are outlined in Aldrich Material Matters Volume 5, Number 1, 2010. For example, in the case of the RAFT method, 2,2′-azobisisobutyronitrile is used as a polymerization initiator and cumyl dithiobenzoate is used as a polymerization catalyst in JP2012-197399A.
The polymerization temperature at the time of polymerizing the monomer component may be appropriately set according to the polymerization mechanism, the type and amount of the monomer used, the type and amount of the polymerization initiator / polymerization catalyst, and the like. Although it is not, 0 to 200 degreeC is preferable and 25 to 150 degreeC is especially preferable. If the polymerization temperature is less than 0 ° C., the polymerization reaction is very slow, and if it exceeds 200 ° C., the reaction is so intense that it is difficult to control.

  The monomer component is polymerized by a solution polymerization method. The solvent used for the polymerization is a lubricating base oil.

    As the lubricating base oil, known lubricating base oils can be used without particular limitation, and mineral oil base oils and synthetic base oils can be preferably mentioned. Examples of the mineral oil base oil include paraffinic and naphthenic base oils. Mineral base oils include those obtained by subjecting raw material base oils to solvent refining, hydrocracking or hydroisomerization. Examples of synthetic base oils include hydrocarbon, ester, ether, silicon, and fluorine base oils. As described above, the lubricating base oil is used as a polymerization reaction solvent for the polymer.

As a preferred specific example of the mineral oil base oil, the following base oils (1) to (7) are used as raw materials, and the raw oil and / or a lubricating oil fraction recovered from the raw oil is used as a predetermined refining method. And base oils obtained by recovering the lubricating oil fraction. Further, the following base oil (8) or (9) obtained by performing a predetermined treatment on a base oil selected from (1) to (7) or a lubricating oil fraction recovered from the base oil is particularly preferable.
(1) Distilled oil (WVGO) by distillation under reduced pressure of paraffin base crude oil and / or mixed base crude oil at atmospheric distillation residue
(2) Wax (such as slack wax) obtained by the lubricant dewaxing process and / or synthetic wax (Fischer-Tropsch wax, GTL wax, etc.) obtained by the gas-liquid (GTL) process, etc.
(3) One or two or more mixed oils selected from base oils (1) to (2) and / or mild hydrocracked oils of the mixed oils (4) selected from base oils (1) to (3) 2 or more kinds of mixed oils (5) Base oils (1) to (4)
(6) Mild hydrocracking treatment oil (MHC) of base oil (5)
(7) Two or more mixed oils selected from base oils (1) to (6).
(8) Hydrocracking a base oil selected from the base oils (1) to (7) or a lubricating oil fraction recovered from the base oil, and recovering the product or the product by distillation or the like Hydrocracked mineral oil obtained by performing dewaxing treatment such as solvent dewaxing or catalytic dewaxing on the lubricating oil fraction, or by performing distillation after the dewaxing treatment.
(9) A base oil selected from the base oils (1) to (7) or a lubricating oil fraction recovered from the base oil is hydroisomerized and recovered from the product or the product by distillation or the like. Hydroisomerized mineral oil obtained by subjecting a lubricating oil fraction to dewaxing treatment such as solvent dewaxing or catalytic dewaxing, or distillation after the dewaxing treatment.
Specific examples of synthetic base oils include poly α-olefins or hydrides thereof, isobutene oligomers or hydrides thereof, isoparaffins, alkylbenzenes, alkylnaphthalenes, diesters (ditridecyl glutarate, di-2-ethylhexyl adipate). , Diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate, etc.), polyol ester (trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol 2-ethylhexanoate, pentaerythritol pelargonate, etc.), poly Examples thereof include oxyalkylene glycol, dialkyl diphenyl ether, polyphenyl ether, and the like, and poly α-olefin is particularly preferable. As the poly α-olefin, typically, an oligomer or co-oligomer (1-octene oligomer, decene oligomer, ethylene-propylene co-oligomer, etc.) having 2 to 32 carbon atoms, preferably 6 to 16 carbon atoms, and those. Of the hydrides. The kinematic viscosity at 100 ° C. of the synthetic base oil is preferably 1 to ²⁰ mm ² / sec.

The base oil selected from the above base oils (1) to (7) or the above base oil (1) to (7) is used as a lubricating base oil to be blended when the copolymer obtained by the present invention is used as a viscosity index improver. The base oil (8) or (9) obtained by performing the above-described treatment on the lubricating oil fraction recovered from the base oil is particularly preferred. It is also preferred to use a base oil belonging to Group III based on classification by the American Petroleum Institute (API). As the lubricating base oil blended in the lubricating oil composition, the above-described synthetic base oil may be used.
The lubricating base oil used in the present invention preferably has a paraffin content of 60 to 90 parts by mass, more preferably 65 to 85 parts by mass, out of 100 parts by mass of the lubricating base oil. It is particularly preferable that it is 70 parts by weight or more and 80 parts by weight or less. Moreover, it is preferable that content of naphthene is 15 to 40 mass parts among 100 mass parts of lubricating base oil, More preferably, it is 20 to 35 mass parts, More preferably, it is 25 to 30 mass parts. It is particularly preferable that the amount is not more than part by mass. When the composition of the lubricating base oil is within these ranges, not only is it excellent in thermal stability and light stability, but also adjustment to a desired viscosity is easy. Further, the balance between the viscosity index and the low temperature characteristics of the lubricating base oil is good.

  In the lubricating oil composition obtained by the present invention, the above lubricating base oil may be used alone, or may be used in combination with one or more other base oils. In addition, when using together lubricating base oil and another base oil, it is preferable that the said mixed base oil contains the said lubricating base oil (8) or (9) at least. The ratio of the lubricating base oil (8) or (9) in the mixed base oil is preferably 30% by mass or more, more preferably 50% by mass or more, and 70% by mass or more. Further preferred.

  The viscosity index of the lubricating base oil is preferably 100 or more, more preferably 120 or more, and preferably 160 or less. When the viscosity index is less than 100, not only the viscosity-temperature characteristics, thermal / oxidative stability, and volatilization prevention properties deteriorate, but also the friction coefficient tends to increase, and the wear prevention properties tend to decrease. . On the other hand, when the viscosity index exceeds 160, the low-temperature viscosity characteristics tend to deteriorate. In addition, the viscosity index as used in the field of this invention means the viscosity index measured based on JISK2283.

  The pour point of the lubricating base oil is preferably 0 ° C. or lower, more preferably −5 ° C. or lower, and more preferably −10 ° C. or lower. In addition, the pour point as used in the field of this invention means the viscosity index measured based on JISK2269.

  The polymer obtained by the present invention preferably has a weight average molecular weight (Mw) of 100,000 or more, more preferably 200,000 or more and 600,000 or less, more preferably more than 250,000 and 600,000 or less, and still more preferably. 270,000 to 550,000. When the weight average molecular weight of the polymer is less than the above lower limit, not only the viscosity index of the lubricating oil composition is lowered, but it is necessary to increase the amount of the viscosity index improver used to adjust to the desired viscosity. This is disadvantageous in terms of cost. When the weight average molecular weight of the polymer is excessively large, the solubility of the viscosity index improver in the base oil tends to be insufficient or the shear stability of the lubricating oil composition tends to decrease. Further, the molecular weight distribution of the polymer obtained by the present invention is preferably 4.0 or less, more preferably 3.0 or less, and even more preferably 2.8 or less from the viewpoint of improving the viscosity index and shear stability. . In addition, the weight average molecular weight in this invention and molecular weight distribution (Mw / Mn) are the values measured by the method as described in the below-mentioned Example.

  The degree of branching of the polymer obtained by the present invention is preferably 1.0 or more, more preferably 1.4 or more, and preferably 10.0 or less, more preferably 6.0 or less, and further preferably 4.0 or less. preferable. When the degree of branching is less than 1.0, the branched structure of the polymer is not sufficient, and improvement in shear stability cannot be expected. The degree of branching in the present invention corresponds to the average number of branch points per molecule of the polymer, and logically, for example, the degree of branching of a straight-chain polymer without branching is 0, and the only branching From the point, the degree of branching of the polymer in which three polymer chains are extended is 1, the degree of branching of the polymer in which four polymer chains are extended is 2, and the degree of branching of the polymer in which five polymer chains are extended The degree of branching is 3.

  The SP value (solubility parameter) of the polymer obtained by the present invention is preferably 8.8 or more, more preferably 8.9 or more, further preferably 9.0 or more, and more preferably 9.6 or less, 9.5 The following is more preferable, and 9.4 or less is more preferable. The SP value of the base oil generally shows a value of about 8.0 to 8.5. However, if the SP value of the polymer is 8.8 or more, the viscosity index of the lubricating oil composition is easily increased, and the SP of the polymer is increased. If the value is 9.6 or less, it becomes easy to ensure the solubility of the viscosity index improver in the base oil. The SP value can be measured using a known method.

  The copolymer obtained by the present invention can achieve both a high viscosity index improvement effect and shear stability at a high level. As specific numerical values of shear stability, PSSI (Permanent Cystability Index: ASTM D 6022) or decomposition start temperature is an index. The viscosity index improver according to this embodiment contains the above-mentioned polymer as a main component, preferably 70% by mass or more, more preferably 90% by mass or more, particularly preferably 95%, based on the viscosity index improver of the present invention. It is contained as a mass% or more, most preferably 99 mass% or more and 100 mass% or less. The PSSI of this viscosity index improver is preferably 50 or less, more preferably 45 or less, and particularly preferably 40 or less. The PSSI is preferably 0.1 or more, more preferably 0.5 or more, still more preferably 2 or more, and particularly preferably 5 or more. When PSSI is less than 0.1, the effect of improving the viscosity index is small and the cost may increase. When PSSI exceeds 50, the shear stability and storage stability may be deteriorated. In addition, PSSI in this invention is the value measured by the method as described in the below-mentioned Example.

  The viscosity index improver according to the present invention contains the above-mentioned polymer as a main component, and preferably, in 100% by mass of the viscosity index improver, the polymer is 70% by mass or more, more preferably 90% by mass or more, and further preferably. The content is 95% by mass or more, particularly preferably 99% by mass or more and 100% by mass or less.

  This invention is also a manufacturing method of a lubricating oil composition containing the viscosity index improver obtained by the above. The lubricating oil composition of the present invention can be obtained by adding the above-mentioned lubricating base oil or the additives described below to the viscosity index improver of the present invention. The viscosity index of the lubricating oil composition obtained according to the present invention is preferably 200 or more and 400 or less, and more preferably 230 or more and 300 or less. When the viscosity index is within the above range, the fuel economy, heat / oxidation stability, and storage stability are excellent.

  In the lubricating oil composition according to the present embodiment, the content of the viscosity index improver of the present invention described above is preferably 0.01% by mass or more and 20% by mass or less, more preferably, based on the total amount of the lubricating oil composition. Is 0.1 mass% or more and 15 mass% or less, More preferably, it is 0.5 mass% or more and 10 mass% or less.

  The lubricating oil composition obtained by the present invention contains the above-described copolymer obtained by the present invention as an essential component. More preferably, it contains at least one additive selected from a pour point depressant, an antiwear agent, a metal-based detergent dispersant, an ashless detergent dispersant, an antioxidant, a corrosion inhibitor, a defoamer, and a friction modifier. It is preferable to do.

  As the pour point depressant, any pour point depressant used for lubricating oil can be used. Examples include polymethacrylates, naphthalene-chlorinated paraffin condensation products, phenol-chlorinated paraffin condensation products, and the like. Among these, addition of polymethacrylates is preferable.

  As the antiwear agent (or extreme pressure agent), any antiwear agent / extreme pressure agent used for lubricating oil can be used. For example, sulfur-based, phosphorus-based, sulfur-phosphorus extreme pressure agents and the like can be used. Specifically, zinc dialkyldithiophosphate (ZnDTP), phosphites, thiophosphites, dithiophosphites Acid esters, trithiophosphites, phosphate esters, thiophosphate esters, dithiophosphate esters, trithiophosphate esters, amine salts thereof, metal salts thereof, derivatives thereof, dithiocarbamate, zinc dithio Carbamate, MoDTC, disulfides, polysulfides, sulfurized olefins, sulfurized fats and oils, and the like can be given. Among these, addition of a sulfur-based extreme pressure agent is preferable, and sulfurized fats and oils are particularly preferable.

  Examples of the metal detergent / dispersant include normal salts or basic salts such as alkali metal / alkaline earth metal sulfonate, alkali metal / alkaline earth metal phenate, and alkali metal / alkaline earth metal salicylate. Examples of the alkali metal include sodium and potassium, and examples of the alkaline earth metal include magnesium, calcium and barium. Magnesium or calcium is preferable, and calcium is more preferable.

  As the ashless detergent / dispersant, any ashless detergent / dispersant used in lubricating oils can be used. For example, at least one linear or branched alkyl group or alkenyl group having 40 to 400 carbon atoms is contained in the molecule. Mono- or bissuccinimide having one, benzylamine having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, or at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule Examples include polyamines or modified products of these boron compounds, carboxylic acids, phosphoric acids, and the like. In use, one kind or two or more kinds arbitrarily selected from these can be blended.

  Examples of the antioxidant include ashless antioxidants such as phenols and amines, and metal antioxidants such as copper and molybdenum. Specifically, for example, as a phenol-based ashless antioxidant, 4,4′-methylenebis (2,6-di-tert-butylphenol), 4,4′-bis (2,6-di-tert- Butylphenol) and the like are amine-based ashless antioxidants such as phenyl-α-naphthylamine, alkylphenyl-α-naphthylamine, and dialkyldiphenylamine.

  Examples of the corrosion inhibitor include benzotriazole, tolyltriazole, thiadiazole, or imidazole compounds.

  Examples of the defoaming agent include silicone oil, fluorosilicone oil, alkenyl succinic acid derivative having a kinematic viscosity at 25 ° C. of 1000 to 100,000 mm 2 / s, ester of polyhydroxy aliphatic alcohol and long chain fatty acid, methyl salicylate And o-hydroxybenzyl alcohol.

  As friction modifiers, in addition to organic molybdenum compounds such as succinimide molybdenum complexes such as molybdenum dithiocarbamate and molybdenum dithiophosphate, and amine salts of organic molybdic acid, linear alkyl and metal having 8 to 30 carbon atoms as a basic structure. And having a polar group that can be adsorbed on the same molecule in the same molecule. Examples of polar groups include amines, polyamines, amides, urea compounds and alkenyls such as amine compounds, fatty acid esters, fatty acid amides, fatty acids, fatty alcohols, aliphatic ethers, urea compounds, hydrazide compounds having these simultaneously in the molecule. Examples thereof include succinimide type, ester, alcohol and diol, or monoalkyl glycerol ester having ester and hydroxyl group at the same time. In addition, there are various types such as an alkylamine afucosyl alcohol having an amine and a hydroxyl group in the same molecule.

  The lubricating oil composition according to the present embodiment is a pour point depressant, an antiwear agent, a metallic detergent / dispersant, an ashless detergent / dispersant, an antioxidant, a corrosion inhibitor, a defoamer, and a friction modifier, or When it contains 2 or more types, it is preferable that each content is 0.01 mass% or more and 10 mass% or less on the basis of the whole quantity of a lubricating oil composition. Moreover, when the lubricating oil composition according to the present embodiment contains an antifoaming agent, the content is preferably 0.0001% by mass or more and 0.01% by mass or less.

  The lubricating oil composition according to the present embodiment further contains a viscosity index improver, rust inhibitor, demulsifier, metal deactivator, etc. other than the polymer of the present invention, in addition to the above components. Can do.

  The viscosity index improver other than the polymer of the present invention according to the previous embodiment is specifically a non-dispersed or dispersed ester group-containing viscosity index improver, for example, a non-dispersed or dispersed poly (meta ) Acrylic viscosity index improver, non-dispersed or dispersed olefin- (meth) acrylate copolymer viscosity index improver, styrene-maleic anhydride copolymer viscosity index improver, and mixtures thereof. Among these, non-dispersed or dispersed poly (meth) acrylate viscosity index improvers are preferable. A non-dispersed or dispersed polymethacrylate viscosity index improver is particularly preferable. In addition, a non-dispersed or dispersed ethylene-α-olefin copolymer or a hydrogenated product thereof, polyisobutylene or a hydrogenated product thereof, a styrene-diene hydrogenated copolymer, a polyalkylstyrene, and the like can be given.

  Examples of the rust inhibitor include petroleum sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenyl succinic acid ester, and polyhydric alcohol ester.

  Examples of the demulsifier include polyalkylene glycol nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, or polyoxyethylene alkyl naphthyl ether.

  Examples of metal deactivators include imidazoline, pyrimidine derivatives, alkylthiadiazoles, mercaptobenzothiazoles, benzotriazoles or derivatives thereof, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bis. Examples thereof include dialkyldithiocarbamate, 2- (alkyldithio) benzimidazole, and β- (o-carboxybenzylthio) propiononitrile.

The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. In addition,% and part in an Example and a comparative example represent the mass% and a mass part.
Analysis and evaluation on the polymer were performed by the following methods.
(Maleimide monomer polymerization rate)
For the measurement of the polymerization rate, gas chromatography (manufactured by Shimadzu Corporation, GC2010) was used. The measurement conditions are as follows.

Column: Inert CapR 1 (inner diameter 0.25 mm, length 30 m)
temperature:
Inlet temperature: 200 ° C
Detector temperature: 350 ° C
Carrier gas: helium (column flow rate 1.39 mL / min)
Injection volume: 0.5 μL
Internal standard sample: tridecane Diluent solvent: p-xylene Specifically, a calibration curve solution in which each monomer used for polymerization and tridecane were dissolved in p-xylene in advance was prepared, and the solution was subjected to the above measurement conditions. A calibration curve was prepared from the peak area obtained by measurement by gas chromatography. Next, a measurement sample is prepared by dissolving a polymerization solution, which is a measurement object, and tridecane in p-xylene, the sample is measured by gas chromatography under the above measurement conditions, and an internal calibration curve using the prepared calibration curve is used. The content ratio of the residual monomer in the polymerization solution was determined by a standard method, and the polymerization ratio was calculated from the ratio to the monomer content ratio before the start of polymerization.
(Weight average molecular weight)
System: Tosoh GPC system HLC-8220
Measurement side column configuration:
Guard column: manufactured by Tosoh Corporation, TSK guard column Super HZ-L
Separation column: Tosoh TSKgel SuperHZM-M
Reference side column configuration and reference column: Tosoh TSKgel SuperH-RC
Developing solvent: Chloroform (Wako Pure Chemical Industries, special grade)
Flow rate of developing solvent: 0.6 mL / min Standard sample: TSK standard polystyrene (manufactured by Tosoh, PS-oligomer kit)
Column temperature: 40 ° C
(Viscosity index)
The polymer was diluted with a base oil (YUBASE 4 manufactured by SK) so that the kinematic viscosity at 100 ° C. was 7.0 mm ² / s, and measured by the method of JIS K2283.
(Shear stability)
The polymer was diluted in a base oil (YUBASE 4 manufactured by SK) so that the kinematic viscosity at 100 ° C. was 7.0 mm ² / s, and ultrasonic waves were irradiated under the following conditions.
Equipment: UP400S manufactured by Hielscher Ultrasonics
Setting: Amplitude = 70%, Cycle = 1
Time: 5 minutes Temperature: 100 ° C
The kinematic viscosity before and after shearing and at 100 ° C. of the base oil was measured, and SSI = {1− (kinematic viscosity after shearing−kinematic viscosity of base oil) / (kinematic viscosity before shearing−dynamic viscosity of base oil)} * 100 It was calculated by the following formula.
(Odor)
Take 10g of the liquid after completion of polymerization in a 100ml screw tube, cover and heat at 120 ° C for 1 hour, check the odor by removing the lid, and if there is an odor derived from the acid component, no odor The case was marked with ○.
(SP value)
The SP value (solubility parameter) of the polymer was measured using Materials Studio (registered trademark) Ver. 6.1 Calculated using the MS-Synthia module. First, a monomer structure was created and a repeating structure was defined. Polymer physical properties (solubility parameters, etc.) were calculated with the MS-Synthia module using the defined monomer structure. The MS-Synthia module is a software that can calculate the physical properties of polymers by using Quantitative Structure Property Relationships (QSPR). Physical properties can be calculated. The detailed theory is described in the following literature, which is incorporated herein by reference: Published by Josef Bicerano, “Prediction of Polymer Properties, 3rd Edition”, published by Marcel Dekker. This time, the value of the Fedors method was used among SP values (solubility parameters) of the Fedors method and van Krevelen method improved by Bicerano, which can be calculated by MS-Synthia.
Example 1
In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, a nitrogen introduction pipe, and a dropping funnel, 20 parts by mass of methyl methacrylate (MMA), 30 parts by mass of stearyl methacrylate (StMA), 10 parts by mass of N-phenylmaleimide (PMI) Part, mixture of lauryl methacrylate / tridecyl methacrylate = 54/46 (mass ratio) (SLMA) 40 parts by mass, base oil (YUBASE 4 made by SK) 143.6 parts by mass, pentaerythritol tetrakis (mercaptoacetate) 0.05 mass The contents were heated to 105 ° C. while introducing nitrogen gas. A solution obtained by mixing 0.0774 parts by mass of t-amyl peroxyisononanoate (manufactured by Arkema Yoshitomi, Luperox (registered trademark) 570) and 1.38 parts by mass of a base oil (YUBASE 4 manufactured by SK) as a polymerization initiator. While adding, a solution prepared by dissolving 0.034 parts by mass of the polymerization initiator in 3.40 parts by mass of base oil (YUBASE 4 manufactured by SK) was added dropwise over 2 hours, and the solution polymerization proceeded for another 4 hours. Aged.

  Subsequently, the cooling pipe was replaced with a U-shaped pipe connected to the cooling pipe and a distillate receiver, and 83.3 parts by mass of base oil (YUBASE 4 manufactured by SK) was charged into the reaction vessel. After raising the bath temperature to 150 ° C., the pressure was gradually reduced using a vacuum pump to remove volatile components. 30 minutes after the internal temperature reached 142 ° C., the pressure was released and cooled to obtain a polymer base oil solution (polymer concentration 30% by mass). The results are shown in Table 1.

(Example 2)
In Example 1, the same operation was carried out except that 10 parts by mass of PMI was changed to 10 parts by mass of cyclohexylmaleimide (CHMI), 25 parts by mass of MMA, and 35 parts by mass of SLMA. A coalescence concentration of 30% by mass was obtained. The results are shown in Table 1.
(Example 3)
In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, a nitrogen introduction pipe, and a dropping funnel, 20 parts by mass of MMA, 30 parts by mass of StMA, 10 parts by mass of PMI, 40 parts by mass of SLMA, base oil (YUBASE 4 manufactured by SK) 61.2 Part by mass and 0.05 part by mass of pentaerythritol tetrakis (mercaptoacetate) were charged, and the content was heated to 105 ° C. while introducing nitrogen gas. A solution obtained by mixing 0.0258 parts by mass of t-amyl peroxyisononanoate (manufactured by Arkema Yoshitomi, Luperox (registered trademark) 570) and 0.46 parts by mass of a base oil (YUBASE 4 manufactured by SK) as a polymerization initiator. While adding, a solution in which 0.205 parts by mass of the polymerization initiator was dissolved in 10.3 parts by mass of the base oil was dropped over 4 hours, and the solution polymerization was allowed to proceed, followed by aging for 4 hours.

  Subsequently, the cooling pipe was replaced with a U-shaped pipe connected to the cooling pipe and a distillate receiver, and 166.6 parts by mass of base oil (YUBASE 4 manufactured by SK) was charged into the reaction vessel. After raising the bath temperature to 150 ° C., the pressure was gradually reduced using a vacuum pump to remove volatile components. 30 minutes after the internal temperature reached 142 ° C., the pressure was released and cooled to obtain a polymer base oil solution (polymer concentration 30% by mass). The results are shown in Table 1.

(Comparative Example 1)
In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, a nitrogen introduction pipe, and a dropping funnel, 20 parts by mass of MMA, 30 parts by mass of StMA, 10 parts by mass of PMI, 40 parts by mass of SLMA, an antioxidant (ADK STAB (registered trademark) 2112, ADEKA) 0.05 parts by weight, acetic anhydride 0.40 parts by weight, pentaerythritol tetrakis (mercaptoacetate) 0.05 parts by weight, and toluene 60.8 parts by weight, while introducing nitrogen gas into this, The contents were heated to 105 ° C. As a polymerization initiator, a solution prepared by mixing 0.0258 parts by mass of t-amylperoxyisononanoate (manufactured by Arkema Yoshitomi Corp., Luperox (registered trademark) 570) and 0.46 parts by mass of toluene was added, and the polymerization was started. The solution polymerization was advanced while dropping a solution prepared by dissolving 0.205 parts by mass of the agent in 20.5 parts by mass of toluene over 4 hours, and further aging was performed for 4 hours.

  Subsequently, the cooling pipe was replaced with a U-shaped pipe connected to the cooling pipe and the distillate receiver, and 233 parts by mass of base oil (YUBASE 4 manufactured by SK) was charged into the reaction vessel. After raising the bath temperature to 150 ° C., the pressure was gradually reduced using a vacuum pump to remove toluene. 30 minutes after the internal temperature reached 142 ° C., the pressure was released and cooled to obtain a polymer base oil solution (polymer concentration 30% by mass). The results are shown in Table 1.

(Comparative Example 2)
In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, a nitrogen introduction pipe, and a dropping funnel, MMA 25 parts by mass, StMA 40 parts by mass, PMI 10 parts by mass, SLMA 25 parts by mass, antioxidant (ADK STAB (registered trademark) 2112, ADEKA)) 0.05 parts by mass, acetic anhydride 0.40 parts by mass, n-dodecyl mercaptan 0.05 parts by mass, and toluene 27.4 parts by mass, while introducing nitrogen gas to the contents, The temperature was raised to 105 ° C. As a polymerization initiator, a solution prepared by mixing 0.0258 parts by mass of t-amylperoxyisononanoate (manufactured by Arkema Yoshitomi Corp., Luperox (registered trademark) 570) and 0.46 parts by mass of toluene was added, and the polymerization was started. The solution polymerization was allowed to proceed while dropwise adding a solution prepared by dissolving 0.103 parts by mass of the agent in 10.3 parts by mass of toluene over 4 hours, followed by further aging for 4 hours.

  Subsequently, the cooling pipe was replaced with a U-shaped pipe connected to the cooling pipe and the distillate receiver, and 233 parts by mass of base oil (YUBASE 4 manufactured by SK) was charged into the reaction vessel. After raising the bath temperature to 150 ° C., the pressure was gradually reduced using a vacuum pump to remove toluene. 30 minutes after the internal temperature reached 142 ° C., the pressure was released and cooled to obtain a polymer base oil solution (polymer concentration 30% by mass). The results are shown in Table 1.

(Comparative Example 3)
In Comparative Example 2, the same operation was performed except that acetic anhydride was not added to obtain a polymer base oil solution (polymer concentration: 30% by mass). The results are shown in Table 1.

  When polymerization was carried out in the examples, it showed a high polymerization rate without using an acid component, and when the obtained copolymer was used as a viscosity index improver, a high viscosity index and sufficient shear stability. showed that.

  By using the production method of the present invention, a maleimide copolymer can be obtained at a high polymerization rate without fear of odor and corrosion. The lubricating oil composition using the obtained viscosity index improver containing the copolymer exhibits a high viscosity index and sufficient shear stability, and can meet the future demands for fuel economy and long life of automobiles. Therefore, it can be suitably used for drive system lubricating oil, hydraulic oil, and engine oil.

Claims (5)

A method for producing a copolymer, comprising a step of polymerizing a monomer containing a maleimide monomer (hereinafter referred to as “component (a)”) as an essential component in a lubricating base oil. In addition to the component (a), (b) an alkyl (meth) acrylate having an aliphatic hydrocarbon group having 1 to 5 carbon atoms, (c) an alkyl having an aliphatic hydrocarbon group having 6 to 40 carbon atoms ( The manufacturing method of the copolymer characterized by having the process of superposing | polymerizing the monomer containing a meth) acrylate in lubricating oil base oil. 3. The method according to claim 1, further comprising a step of polymerizing the monomer in a lubricating base oil in the presence of a trifunctional or higher polyvalent mercaptan and / or a trifunctional or higher polyfunctional initiator. A method for producing a copolymer of The manufacturing method of the viscosity index improver containing the copolymer obtained by the manufacturing method in any one of Claims 1-3. The manufacturing method of the lubricating oil composition containing the viscosity index improver of Claim 4.