JP6498084B2 - Viscosity index improver and lubricating oil composition - Google Patents

Description

  The present invention relates to a viscosity index improver having a specific structure, and a lubricating oil composition containing the same. In particular, the present invention relates to a viscosity index improver that has a high viscosity index and good shear stability and exhibits sufficient solubility in a lubricating oil.

  In recent years, lubricating oils for internal combustion engines have been strongly required to improve fuel saving characteristics, and one means is to reduce friction loss 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.

  There are various types of viscosity index improvers. Among them, a viscosity index improver composed of an alkyl (meth) acrylate polymer (hereinafter also referred to as a polymethacrylate viscosity index improver) exhibits a high viscosity index improving effect. On the other hand, since the polymethacrylate viscosity index improver has poor shear stability, there has been a problem in that fuel-saving characteristics are deteriorated (long life property is poor) during long-term use.

  Examples of means for improving shear stability 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).

  On the other hand, from the viewpoint of improving thermal stability, a method of introducing a specific amount of styrene into the main chain skeleton of the polymethacrylate viscosity index improver has been proposed (Patent Document 2).

JP 2013-104032 A JP-A-8-176576 Sanyo Chemical News 2013 New Year No. 476

  The present invention relates to a viscosity index improver containing a polymethacrylate polymer having a high viscosity index and good shear stability and exhibiting sufficient solubility in a lubricating base oil, and a polymethacrylate viscosity. A lubricating oil composition using an index improver is provided.

  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 terms of cost.

  In addition, the thermal stability and shear stability of a polymethacrylate viscosity index improver having a specific amount of styrene introduced into the main chain skeleton are not sufficient, and further, there are disadvantages in that the solubility in the base oil and the viscosity index decrease. It was.

  As a result of intensive studies, the present inventors have found a viscosity index improver containing a specific polymethacrylate polymer having a ring structure in the main chain, and further a lubricating oil composition, and have reached the present invention.

  That is, the present invention provides (a) an alkyl (meth) acrylate having an aliphatic hydrocarbon group having 1 to 5 carbon atoms (hereinafter referred to as “component (a)”), (b) having 6 to 40 carbon atoms. An alkyl (meth) acrylate having an aliphatic hydrocarbon group (hereinafter referred to as “component (b)”), and (c) a maleimide monomer represented by the following general formula (1) (hereinafter referred to as “(c)”) A viscosity index improver containing a polymer obtained by polymerizing as an essential component), and the unit derived from component (c) is 0.5 parts by mass or more with respect to 100 parts by mass of the polymer. It is a viscosity index improver containing a polymer of 35 parts by mass or less, a styrene monomer-derived unit of 2 parts by mass or less, and a weight average molecular weight (Mw) of 100,000 or more.

(Wherein R ¹ and R ² are each independently a hydrogen atom or an alkyl group, and X is a hydrogen atom, a linear, cyclic or branched alkyl group (including an alkyl group having an aromatic ring) or aryl. Group.)
Moreover, this invention is a lubricating oil composition containing the said viscosity index improver.

  By using the viscosity index improver of the present invention, shear stability and heat resistance can be improved as compared with conventional lubricating oil compositions. Further, the viscosity index improver of the present invention can provide a lubricating oil composition having a high viscosity index in order to exhibit sufficient solubility in a base oil while having a high molecular weight.

  The viscosity index improver of the present invention comprises (a) an alkyl (meth) acrylate having an aliphatic hydrocarbon group having 1 to 5 carbon atoms (hereinafter referred to as “component (a)”), and (b) a carbon number. An alkyl (meth) acrylate having 6 to 40 aliphatic hydrocarbon groups (hereinafter referred to as “component (b)”), and (c) a maleimide monomer represented by the following general formula (1) (hereinafter, A viscosity index improver containing a polymer obtained by polymerizing “(c) component” as an essential component, and the unit derived from the component (c) is 0.1% relative to 100 parts by mass of the polymer. It is a viscosity index improver containing a polymer which is 5 parts by mass or more and 35 parts by mass or less, a unit derived from a styrene monomer is 2 parts by mass or less, and a weight average molecular weight (Mw) is 100,000 or more. .

  By using the component (b) having a long-chain alkyl group with low polarity, a polymer having high oil solubility can be obtained. Further, the component (c) is preferably 2 parts by mass or more, more preferably 5 parts by mass or more with respect 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 (c) is less than 0.5 parts by mass, the effect of introducing the component (c) is not sufficiently obtained, and the shear stability is not sufficiently improved. Furthermore, there are cases where the clean dispersibility of sludge and the like derived from the highly polar structure of the component (c) is reduced, or the metal surface is worn and the fatigue life is 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 100,000, not only the viscosity index of the lubricating oil composition is lowered, but also it is necessary to increase the amount of use of the viscosity index improver in order to adjust to a desired viscosity. Is disadvantageous.

  Hereinafter, each monomer component will be described in detail.

Among the monomer components used for the synthesis of the polymer contained in the viscosity index improver of the present invention, the component (a) specifically has a structure represented by the following general formula (2). And (meth) acrylates in which R ³ in the formula is a hydrogen atom or a methyl group, and R ⁴ is an aliphatic hydrocarbon group having 1 to 5 carbon atoms. R ⁴ may be linear, cyclic or branched, and may have a substituent.

The monomer (a) 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 (a) 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 them, it is preferable that at least methyl (meth) acrylate is included as the monomer (a) component. When the component (a) 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 (a) may be used independently and may use 2 or more types together.

  The content of the monomer (a) 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 (a) 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 (b) component used in the present invention has a structure represented by the above general formula (2), and R ^{3 in} the formula is a hydrogen atom or a methyl group, and R ⁴ 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 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.
Specific examples of the monomer (b) 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, stearyl (meth) acrylate, nonadecyl (meta) ) Acrylate, eicosyl (meth) acrylate, behenyl (meth) acrylate, tetracosyl (meth) acrylate, 2-decyltetradecyl (meth) acrylate, cyclohexyl (meth) acrylate Menthyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, adamantyl (meth) acrylate. Among these, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, eicosyl (meth) acrylate, behenyl (meta) from the viewpoints of availability and economy and high solubility in base oils. ) 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 (b) component is preferably 50 parts by weight or more and less than 95 parts by weight, more preferably 55 parts by weight or more and 93 parts by weight or less, particularly preferably 100 parts by weight of the total of all monomer components. Is 60 parts by mass or more and 90 parts by mass or less. The viscosity index improver containing a polymer using the monomer (b) component in the above numerical range has good solubility in base oils having various compositions.

  The monomer (c) 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, cyclic or branched alkyl group (including an alkyl group having an aromatic ring) or aryl. Group.)
As the monomer (c) component, among the above X, 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 (c) 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 (c) may be used independently and may use 2 or more types together.
The content of the monomer (c) component is 0.5 parts by mass or more and 35 parts by mass or less, preferably 2 parts by mass or more and 35 parts by mass or less, with respect to 100 parts by mass of the total 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 (c) 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.

  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 (meth) acrylates other than component (a), unsaturated mono- or dicarboxylic esters, unsaturated carboxylic acids, vinyl aromatics, vinyl esters, vinyl ethers, olefins, vinyl cyanide, N-vinyl compound, (meth) acrylamide, etc. are mentioned. These monofunctional monomers may be used alone or in combination of two or more.

  Examples of (meth) acrylates other than the component (a) include benzyl (meth) acrylate, phenyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 3-hydroxypropyl ( (Meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 2 -Phenoxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, morpholinoalkylene (meth) acrylate, methyl α-hydroxymethyl acrylate 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) acrylic acid ester include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, and 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, ditrimethylol Propane tetra (meth) acrylate, glycerin tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipenta Rithritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 2,2 '-[oxybis (methylene)] bisacrylic acid, dialkyl-2,2'-[oxybis (methylene)] bis-2-propenoate Etc.

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

  Examples of allyl group-containing (meth) acrylic acid esters include allyl (meth) acrylate, methyl α-allyloxymethyl acrylate, stearyl α-allyloxymethyl acrylate, α-allyloxymethyl acrylate 2-decyltetra Examples include decyl.

  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. The polyfunctional urethane (meth) acrylate obtained by reaction with containing (meth) acrylic acid ester, 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.

  The polymerization method of the monomer component may be any of bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization and the like, but is not particularly limited. When using a dispersion medium, an emulsifier, a dispersant, etc., there is no particular limitation and a known one can be used.

  A known method can be used as a method for controlling the molecular weight. For example, it can be controlled by adjusting the amount and type of the polymerization initiator / polymerization catalyst, the polymerization temperature, and the type and amount of the chain transfer agent.

  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.

  Sensitivity and reactivity can be improved by using a photosensitizer and a photoradical polymerization accelerator together with the photoradical initiator. Examples of such photosensitizers and photoradical polymerization accelerators include dye compounds such as xanthene dyes, coumarin dyes, 3-ketocoumarin compounds, and pyromethene dyes; ethyl 4-dimethylaminobenzoate, 4-dimethylamino Examples include dialkylaminobenzene compounds such as 2-ethylhexyl benzoate; mercaptan hydrogen donors such as 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, and 2-mercaptobenzimidazole.

  Among the above radical polymerization initiators, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane and 3,3 ′, 4,4′-tetra (t-butylperoxycarbonyl) benzophenone When such a polyfunctional initiator is used, since the polymer takes a star structure or a crosslinked structure, the shear stability of the viscosity index improver containing the polymer can be improved.

  The total amount of the radical polymerization initiator added may be appropriately set depending on the purpose and application, and is not particularly limited. However, considering the balance between the polymerization property, the adverse effect of the decomposition product, and the economy, the base oil solubility is further improved. In order to obtain a viscosity index improver containing a polymer having a high weight average molecular weight of 100,000 or more, 0.01 parts by mass or more and 10 parts by mass or less, preferably 0.1 parts by mass with respect to 100 parts by mass of the monomer component. 02 parts by mass or more and 5 parts by mass or less, more preferably 0.05 parts by mass or more and 2 parts by mass or less.

  The total amount of the thermal radical polymerization accelerator, photosensitizer, and photoradical polymerization accelerator added may be appropriately set according to the purpose and application, and is not particularly limited. From the viewpoint of balance between adverse effects and economics, 0.02 to 10 parts by mass, preferably 0.05 to 5 parts by mass, and more preferably 0.1 to 100 parts by mass of the monomer component. It is not less than 3 parts by mass.

  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.

  Among the chain transfer agents, multifunctional such as trimethylolpropane tris (3-mercaptopropionate), pentaerythritol tetrakis (3-mercaptopropionate), dipentaerythritol hexakis (3-mercaptopropionate) When a chain transfer agent is used, since the polymer takes a star structure or a crosslinked structure, the shear stability of the viscosity index improver containing the polymer can be improved.

  The amount of the chain transfer agent used in the radical polymerization mechanism may be appropriately set according to the type and amount of the monomer used, the polymerization conditions such as the polymerization temperature and the polymerization concentration, the molecular weight of the target polymer, Although not particularly limited, in order to obtain a viscosity index improver containing a polymer having a high base oil solubility and a weight average molecular weight of 100,000 or more, 0.01 parts by mass or more with respect to 100 parts by mass of the monomer component 5 mass parts or less are preferable, 0.05 mass parts or more and 3 mass parts or less are more preferable, 0.05 mass parts or more and 2 mass parts or less are more preferable. By setting it as this range, molecular weight distribution becomes narrow and shear stability can be improved.

Since narrowing the molecular weight distribution is very advantageous from the viewpoint of improving the viscosity index and improving the shear stability, Living Radical Polymerization can also be used as the 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 may be polymerized by a bulk polymerization method, but when polymerized by a solution polymerization method, an emulsion polymerization method, or a suspension polymerization method, the solvent used for the polymerization is inert to the polymerization reaction. If it is, it will not specifically limit, What is necessary is just to set suitably according to polymerization conditions, such as a polymerization mechanism, the kind and quantity of the monomer to be used, and the kind and quantity of a polymerization initiator and a polymerization catalyst.

  Examples of such solvents include monoalcohols such as methanol, ethanol, isopropanol, n-butanol, and s-butanol; glycols such as ethylene glycol and propylene glycol; cyclic ethers such as tetrahydrofuran and dioxane; ethylene glycol monomethyl Glycol monomers such as ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, 3-methoxybutanol Ethers; ethylene glycol dimethyl Ether, ethylene glycol diethyl ether, ethylene glycol ethyl methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, and other glycol ethers; ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether Acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol Esters of glycol monoethers such as monoethyl ether acetate, propylene glycol monobutyl ether acetate, dipropylene glycol monomethyl ether acetate, dipropylene glycol monoethyl ether acetate, dipropylene glycol monobutyl ether acetate, 3-methoxybutyl acetate; methyl acetate, Ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, methyl propionate, ethyl propionate, butyl propionate, methyl lactate, ethyl lactate, butyl lactate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, 3-ethoxy Alkyl esters such as methyl propionate, ethyl 3-ethoxypropionate, methyl acetoacetate and ethyl acetoacetate; acetone, Ketones such as butyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene; aliphatic hydrocarbons such as hexane, cyclohexane and octane; dimethylformamide, dimethylacetamide, N- Amides such as methylpyrrolidone, water and the like can be mentioned. Among these, toluene, xylene, hexane, cyclohexane, methyl ethyl ketone, and tetrahydrofuran are preferable from the viewpoints of ensuring the solubility of the polymer and easy replacement of the solvent with the base oil after polymerization. Further, a lubricating base oil described later can also be suitably used as the solvent. In this case, solvent replacement after polymerization is unnecessary, and the process is simplified, which is more preferable. These solvents may be used alone or in combination of two or more. The amount of the solvent used is not particularly limited, but from the viewpoint of obtaining a polymer having a weight average molecular weight of 100,000 or more, the concentration of the total amount of the monomer component, the polymerization initiator and other components is 40% by mass of the whole. A degree of 100% by mass or less is preferable.

As said lubricating base oil, a mineral base oil or a synthetic base oil can be mentioned preferably. As a preferred specific example of the base oil, the following base oils (1) to (7) are used as raw materials, and the raw oil and / or lubricating oil fraction recovered from the raw oil is refined by a predetermined refining method. And a base oil obtained by recovering the lubricating oil fraction. Moreover, the following base oil (8) obtained by performing a predetermined | prescribed process about the base oil selected from (7) or the lubricating oil fraction collect | recovered from the said base oil is especially 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) Two or more kinds of mixed oils (5) Paraffin-based crude oil and / or degassed oil (DAO) of vacuum-distilled residue oil of atmospheric distillation residue oil of mixed-base crude oil
(6) Mild hydrocracking treatment oil (MHC) of base oil (5)
(7) Two or more mixed oils selected from base oils (1) to (6).
The product or the lubricating oil fraction recovered from the product by distillation or the like is subjected to dewaxing treatment such as solvent dewaxing or catalytic dewaxing, or the dewaxing treatment is performed and then distilled. Hydrocracked mineral oil obtained by the above (8) Hydroisomerization of a base oil selected from the above base oils (1) to (7) or a lubricating oil fraction recovered from the base oil, and its product or its production Hydroisomerized mineral oil obtained by performing dewaxing treatment such as solvent dewaxing or catalytic dewaxing on the lubricating oil fraction recovered from the product by distillation or the like, or by distilling after the dewaxing treatment.

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, ditridec Decyl adipate, di-2-ethylhexyl sebacate, etc.), polyol ester (trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol 2-ethylhexanoate, pentaerythritol pelargonate, etc.), polyoxyalkylene glycol, dialkyl Examples thereof include diphenyl ether and polyphenyl ether, and among them, poly α-olefin is 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 / s.

  The polymer contained in the viscosity index improver of the present invention has a weight average molecular weight (Mw) of 100,000 or more. Preferably it is 200,000 or more and 600,000 or less, More preferably, it is more than 250,000 and 600,000 or less, More preferably, it is 270,000 or more and 550,000 or less. 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. In addition, the weight average molecular weight in this invention is the value measured by the method as described in the below-mentioned Example.

  The viscosity index improver of the present invention can achieve both a viscosity index improving 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 40 or less, more preferably 35 or less, still more preferably 30 or less, and particularly preferably 25 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 40, shear stability and storage stability may be deteriorated.

  The decomposition start temperature of the viscosity index improver is preferably 290 ° C. or higher and 500 ° C. or lower, more preferably 295 ° C. or higher and 450 ° C. or lower, further preferably 300 ° C. or higher and 400 ° C. or lower, and particularly preferably 310 ° C. It is 380 degreeC or more. By improving the heat resistance, thermal decomposition stability and shear stability are improved. On the other hand, when the heat resistance is excessively improved, the solubility in the base oil tends to be insufficient or the viscosity index tends to decrease.

  The present invention is also a lubricating oil composition containing the viscosity index improver of the present invention. The viscosity index of the lubricating oil composition of 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.

  The lubricating oil composition of the present invention contains a lubricating base oil and the above-described viscosity index improver of the present invention as essential components. 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 lubricating base oil according to the present embodiment, the base oil selected from the base oils (1) to (7) described as the above-described polymer reaction solvent or the lubricating oil fraction recovered from the base oil is described above. The base oil (8) obtained by performing the treatment is particularly preferable.

Further, the above-described synthetic base oil may be used as the lubricating base oil according to the present embodiment.
The viscosity index of the lubricating base oil according to the present embodiment is preferably 100 or more, more preferably 120 to 160. When the viscosity index is less than the above lower limit, 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 decrease. There is a tendency. On the other hand, when the viscosity index exceeds the above upper limit, 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.

  In the lubricating oil composition according to the present embodiment, the lubricating base oil according to the present embodiment may be used alone, and the lubricating base oil according to the present embodiment may be one of other base oils or You may use together with 2 or more types. In addition, when using together the lubricating base oil which concerns on this embodiment, and another base oil, the ratio of the said lubricating base oil (8) which occupies in those mixed base oils is 30 mass% or more. Preferably, it is 50 mass% or more, and more preferably 70 mass% or more.

  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.

  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, polyhydroxy aliphatic alcohol and long chain fatty acid ester, methyl salicylate having a kinematic viscosity at 25 ° C. of 1000 to 100,000 mm 2 / s 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 metal-based detergent dispersant, an ashless detergent dispersant, an antioxidant, a rust 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.

  In addition to the above components, the lubricating oil composition according to the present embodiment includes a viscosity index improver other than the polymer of the present invention, a pour point depressant, a cleaning dispersant, a rust inhibitor, a demulsifier, a metal emulsifier. An activator and the like can further be contained.

  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.
Example 1
In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, a nitrogen introduction pipe, and a dropping funnel, 35 parts by mass of methyl methacrylate (MMA), 60 parts by mass of stearyl methacrylate (StMA), 5 parts by mass of N-phenylmaleimide (PMI) Parts, antioxidant (ADK STAB 2112, manufactured by ADEKA) 0.05 parts by mass, n-dodecyl mercaptan (DM) 0.1 parts by mass as a chain transfer agent, and 0.46 parts by mass of toluene are charged with nitrogen gas. While being introduced, the contents were heated to 105 ° C. Next, solution polymerization was allowed to proceed while dropwise adding a solution of 0.205 parts by mass of t-amylperoxyisononanoate (manufactured by Arkema Yoshitomi, Luperox 570) to 10.5 parts by mass of toluene over 4 hours. . 30 minutes after the completion of dropping, 13.5 parts by mass of toluene was added, and aging was further performed for 2.5 hours.
Subsequently, the cooling pipe was replaced with a toroidal pipe connected to the cooling pipe and the distillate receiver, and 233 parts by mass of base oil (viscosity index 130) 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).
Analysis and evaluation on the polymer were performed by the following methods. The results are shown in Table 1.
(Weight average molecular weight)
System: Tosoh GPC system HLC-8220
Measurement 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
(Base oil solubility)
The base oil solution having a polymer concentration of 30% by mass was evaluated as ◯ or × according to the following criteria.
○: At 25 ° C., it is completely dissolved visually and the solution becomes transparent.
X: Undissolved residue is visually confirmed at 25 ° C., or the solution becomes cloudy.
(Viscosity index)
The polymer was diluted in a base oil (viscosity index: 130) so that the kinematic viscosity at 100 ° C. was 7.0 mm ² / s, and measured by the method of JIS K2283. The case where the viscosity index was 230 or more was evaluated as ◯, the case where it was 200 or more and less than 230 was evaluated as Δ, and the case where it was less than 200 was evaluated as ×.
(Decomposition start temperature)
The decomposition start temperature (Td) was determined from dynamic TG measurement on the polymer. Specifically, it is as follows. About 1 g of the polymerization solution in the reaction vessel before adding the base oil was collected, diluted with toluene, further dropped into methanol for reprecipitation, and then heated at 100 ° C. for 1 hour under vacuum. The obtained polymer was heated from a normal temperature to 500 ° C. in a nitrogen gas atmosphere using a differential type differential thermal balance apparatus (Rigaku, Thermo Plus2 TG-8120). At this time, when the sample mass reduction rate is 0.005% by mass / second or less, the rate of temperature increase is 10 ° C./min. When the sample mass decrease rate during temperature increase exceeds 0.005% by mass / second The temperature was increased by using stepwise isothermal control so that the speed was maintained at 0.005 mass% / second or less. The temperature at which stepwise isothermal control was first performed in order to maintain the mass reduction rate (the lowest temperature at which stepwise isothermal control was performed) was defined as Td of the resin composition.
(Shear stability)
The polymer was diluted in a base oil (viscosity index: 130) 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 The case where the value calculated by the above formula was less than 25 was marked with ◯, and the case where it was 25 or more was marked with ×.
(Example 2)
The same operation as in Example 1 was performed except that 35 parts by mass of MMA was changed to 20 parts by mass, 60 parts by mass of StMA was changed to 70 parts by mass, and 5 parts by mass of PMI was changed to 10 parts by mass. The results are shown in Table 1.
(Example 3)
MMA 15 parts by mass, StMA 70 parts by mass, N-cyclohexylmaleimide (CMI) 15 parts by mass, antioxidant (ADK STAB 2112, ADEKA) 0.05 parts by weight, n-dodecyl mercaptan (DM) 0.1 part by weight as a chain transfer agent, and 16.6 parts by weight of toluene, while introducing nitrogen gas to this, the content is increased to 105 ° C. The temperature was raised. Next, solution polymerization was allowed to proceed while dropwise adding a solution of 0.205 parts by mass of t-amylperoxyisononanoate (Arkema Yoshitomi, Luperox 570) to 20.5 parts by mass of toluene over 4 hours. . After completion of the dropping, aging was further performed for 3 hours.

  Subsequently, the cooling pipe was replaced with a toroidal pipe connected to the cooling pipe and the distillate receiver, and 233 parts by mass of base oil (viscosity index 130) 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).

Analysis and evaluation on the polymer were carried out in the same manner as in Example 1. The results are shown in Table 1.
Example 4
The same operation as in Example 3 was performed except that MMA 15 parts by mass was changed to 5 parts by mass, StMA 70 parts by mass to 65 parts by mass, and CMI 15 parts by mass to 30 parts by mass. The results are shown in Table 1.
(Example 5)
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 StMA and 40 parts by mass of lauryl methacrylate (LMA), N-phenylmaleimide ( PMI) 10 parts by mass, toluene 52.8 parts by mass, antioxidant (Adeka Stub 2112, made by ADEKA) 0.05 part by mass, pentaerythritol tetrakis (mercaptoacetate) 0.05 part by mass, and nitrogen gas was introduced into this However, 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, Luperox 570) and 0.46 parts by mass of toluene was added, and the polymerization initiator was 0.205 parts by mass. The solution polymerization was allowed to proceed while adding a solution obtained by dissolving 2 parts by mass of toluene in 20.5 parts by mass over 4 hours, followed by further aging for 2 hours.
Subsequently, the cooling pipe was replaced with a toroidal pipe connected to the cooling pipe and the distillate receiver, and 233 parts by mass of base oil (viscosity index 130) 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.
(Example 6)
In Example 5, the same operation was carried out except that 0.05 parts by mass of pentaerythritol tetrakis (mercaptoacetate) was changed to 0.06 parts by mass of hexakis (3-mercaptopropionic acid) dipentaerythritol. An oil solution (polymer concentration 30% by mass) was obtained. The results are shown in Table 1.
(Comparative Example 1)
The same operation as in Example 1 was performed except that 35 parts by mass of MMA was changed to 40 parts by mass, and 5 parts by mass of PMI was changed to 0 parts 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, 35 parts by mass of methyl methacrylate (MMA), 60 parts by mass of stearyl methacrylate (StMA), 5 parts by mass of N-phenylmaleimide (PMI) Part, antioxidant (ADK STAB 2112, manufactured by ADEKA) 0.05 part by mass, n-dodecyl mercaptan (DM) 0.2 part by mass as a chain transfer agent, and toluene 149 part by mass, nitrogen gas was introduced into this While the contents were heated to 105 ° C. Next, solution polymerization was allowed to proceed while dropwise adding a solution of 0.205 parts by mass of t-amylperoxyisononanoate (Arkema Yoshitomi, Luperox 570) to 20.5 parts by mass of toluene over 4 hours. . At the end of the dropping, aging was performed for 3 hours.

  Subsequently, the cooling pipe was replaced with a toroidal pipe connected to the cooling pipe and the distillate receiver, and 233 parts by mass of base oil (viscosity index 130) 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).

Analysis and evaluation on the polymer were carried out in the same manner as in Example 1. The results are shown in Table 1.
(Comparative Example 3)
The same operation as in Example 4 was performed except that 5 parts by mass of MMA was changed to 0 parts by mass, 65 parts by mass of StMA was changed to 60 parts by mass, and 30 parts by mass of CMI was changed to 40 parts by mass of PMI. Since the whole base oil solution was cloudy, evaluation of viscosity index and shear stability could not be performed. The results are shown in Table 1.
(Comparative Example 4)
MMA 32 parts by mass, StMA 60 parts by mass, PMI 5 parts by mass, antioxidant (ADK STAB 2112, manufactured by ADEKA) 0.05 part by mass in a reaction vessel equipped with a stirrer, temperature sensor, cooling pipe, nitrogen introduction pipe, and dropping funnel Then, 0.1 part by mass of n-dodecyl mercaptan (DM) and 0.46 part by mass of toluene were charged as chain transfer agents, and the contents were heated to 105 ° C. while introducing nitrogen gas. Next, a solution obtained by dissolving 0.205 parts by mass of t-amylperoxyisononanoate (manufactured by Arkema Yoshitomi, Luperox 570) and 1 part by mass of styrene (ST) over 4 hours in 10.5 parts by mass of toluene Solution polymerization was allowed to proceed while dropping. 30 minutes after the completion of dropping, 13.5 g of toluene was added, and aging was further performed for 2.5 hours.

  Subsequently, the cooling pipe was replaced with a toroidal pipe connected to the cooling pipe and the distillate receiver, and 233 parts by mass of base oil (viscosity index 130) 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).

  Analysis and evaluation on the polymer were carried out in the same manner as in Example 1. In addition, although the whole base oil solution was thin and cloudy, it was used for evaluation as it was. The results are shown in Table 1.

  Since the polymers obtained in the examples all have a high molecular weight, the viscosity index was high when used as a viscosity index improver. In addition, by using a specific amount of maleimide monomer during polymerization, heat resistance can be improved without sacrificing base oil solubility and viscosity index improvement ability compared to the case of using a large amount of styrene monomer. Thus, a viscosity index improver having high molecular weight and high shear stability was obtained.

  The lubricating oil composition using the viscosity index improver containing the polymer of the present invention can improve the shear stability without sacrificing the base oil solubility as compared with the conventional lubricating oil composition, and Since the viscosity index is as high as possible, it can meet future demands for fuel economy and long life of automobiles, and therefore can be suitably used for drive system lubricating oil, hydraulic oil, and engine oil.

Claims (5)

(A) an alkyl (meth) acrylate having an aliphatic hydrocarbon group having 1 to 5 carbon atoms (hereinafter referred to as “component (a)”), (b) an aliphatic hydrocarbon group having 6 to 40 carbon atoms Alkyl (meth) acrylate (hereinafter referred to as “component (b)”), and (c) a maleimide monomer represented by the following general formula (1) (hereinafter referred to as “component (c)”) Is a viscosity index improver containing a polymer obtained by polymerizing as an essential component, and the unit derived from component (c) is 0.5 parts by mass or more and 35 parts by mass or less with respect to 100 parts by mass of the polymer. Yes, a viscosity index improver containing a polymer having a styrene monomer-derived unit of 2 parts by mass or less and a weight average molecular weight (Mw) of 100,000 or more.

(Wherein R ¹ and R ² are each independently a hydrogen atom or an alkyl group, and X is a hydrogen atom, a linear, cyclic or branched alkyl group (including an alkyl group having an aromatic ring) or aryl. Group.) The viscosity index improver according to claim 1, wherein the unit derived from the component (c) is 5 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the polymer. The viscosity index improver according to claim 1 or 2, wherein the unit derived from component (b) is 50 parts by mass or more and less than 95 parts by mass with respect to 100 parts by mass of the polymer. The viscosity index improver according to any one of claims 1 to 3, wherein Mw of the polymer is 200,000 or more and 600,000 or less. A lubricating oil composition comprising a lubricating base oil and a viscosity index improver according to any one of claims 1 to 4.