JP2017101211A - Lubricant composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lubricant composition in which a cloudiness is not easily to occur even after long-term use.SOLUTION: Provided is a lubricant composition containing a lubricant base oil and a viscosity index improver, and in which the viscosity index improver contains a comb-type polymer having a trunk part and 2 or more branch parts bonded to the trunk part, the trunk contains a constitutional unit derived from styrene and a constitutional unit derived from (meth)acrylate, the 2 or more branch parts may be the same or different from each other and each contains a constitutional unit derived from (meth)acrylate, and each of the branch parts is bonded to the benzene ring of the constitutional unit derived from the styrene via a linking group at different positions of the trunk part.SELECTED DRAWING: None

Description

  The present invention relates to a lubricating oil composition.

In recent years, fuel consumption has been reduced in the automobile industry to reduce CO ₂ emissions. As one of the means, high performance of the lubricating oil is expected. For example, lubricating oil (also referred to as engine oil) used in an internal combustion engine such as an automobile engine is used in a temperature range from a low temperature to a high temperature. However, the fuel efficiency decreases due to the change in viscosity depending on the temperature. In order to reduce this reduction in fuel efficiency, a method of adding a viscosity index improver to the lubricating base oil is generally used. By adding a viscosity index improver, the viscosity index of the lubricating base oil is improved, and while maintaining the viscosity of the lubricating oil in the high temperature range, the increase in viscosity in the low temperature range is suppressed and fuel efficiency is improved. . The greater the effect of improving the viscosity index, the better the fuel economy.

  A typical example of the viscosity index improver is a linear poly (meth) acrylate as described in Patent Document 1.

  In addition, as a viscosity index improver that is more fuel-efficient than linear poly (meth) acrylate, Patent Document 2 discloses that 8 to 10 repeating units derived from a polyolefin-based macromonomer in the main chain. A styrene monomer having 1 to 10 carbon atoms, an alkyl (meth) acrylate having 1 to 10 carbon atoms in an alcohol group, a vinyl ester having 1 to 11 carbon atoms in an acyl group, and 1 to 10 in an alcohol group Repeating units derived from low molecular weight monomers selected from the group consisting of vinyl ethers having 1 carbon atom, (di) alkyl maleates having 1 to 10 carbon atoms in the alcohol group, and mixtures of these monomers; A comb polymer is disclosed.

JP 2008-88215 A Special table 2010-532805 gazette

  However, even the comb polymer disclosed in Patent Document 2 has a problem that turbidity tends to occur with the use of the lubricating oil composition, and there is still room for improvement as it can be put to practical use.

  This invention is made | formed in view of such a situation, and it aims at providing the lubricating oil composition which does not produce turbidity even if it uses it for a long period of time.

In order to solve the above problems, the present invention provides the lubricating oil composition described in the following [1] to [4].
[1] A lubricating oil composition containing a lubricating base oil and a viscosity index improver, wherein the viscosity index improver has a trunk and two or more branches bonded to the trunk. Including the polymer, the trunk includes a structural unit derived from styrene and a structural unit derived from (meth) acrylate, and two or more branches may be the same or different from each other, each derived from (meth) acrylate A lubricating oil composition in which each of the branches is bonded to a benzene ring of a structural unit derived from styrene via a linking group at a different position of the trunk.
[2] The ratio of the structural unit derived from the methyl methacrylate monomer is 30% by mass to 50% by mass based on the total amount of the structural unit derived from (meth) acrylate contained in the trunk and the two or more branches. The ratio of the structural unit derived from the dodecyl methacrylate monomer is 0% by mass to 70% by mass, and the ratio of the structural unit derived from the octadecyl methacrylate monomer is 0% by mass to 60% by mass. Lubricating oil composition.
[3] The lubricating oil composition according to [1] or [2], wherein the weight average molecular weight Mw measured by gel permeation chromatography is 20,000 to 2,000,000.
[4] The ratio Mw / Mn of the weight average molecular weight Mw and the number average molecular weight Mn measured by gel permeation chromatography is 1.0 to 8.0, [1] to [3] The lubricating oil composition described.

  According to the present invention, it is possible to provide a lubricating oil composition that hardly causes turbidity even when used for a long period of time.

  Hereinafter, preferred embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

  The lubricating oil composition according to this embodiment is a lubricating oil composition containing a lubricating base oil and a viscosity index improver, wherein the viscosity index improver includes a trunk and two or more bonded to the trunk. And a trunk includes a structural unit derived from styrene and a structural unit derived from (meth) acrylate, and the two or more branches may be the same as or different from each other. , Each of which includes a structural unit derived from (meth) acrylate, and each of the branches is bonded to a benzene ring of a structural unit derived from styrene via a linking group at a different position of the trunk.

The present inventors infer the reason why turbidity hardly occurs even when the lubricating oil composition is used for a long period of time.
That is, first, in the case of a conventional comb polymer (comb polymer having a repeating unit derived from a polyolefin-based macromonomer in a branch part), with long-term use, a bond is cleaved at a predetermined position of the comb polymer, It is thought that the hydrocarbon which is a branch part or a part thereof is liberated to cause turbidity. Further, it is considered that as a result of liberation of the hydrocarbons, turbidity occurs due to the formation of a portion where the polarity balance of the polymer is lost and the polymer cannot be dissolved in the base oil.
On the other hand, the comb polymer included in the lubricating oil composition according to the present invention includes a structural unit in which both the trunk and the plurality of branches are derived from (meth) acrylate, and the trunk has a trunk at a predetermined position. In order to connect the branches, structural units derived from styrene are introduced. Therefore, even if the bond at a predetermined position of the comb polymer is cleaved with long-term use, the branch portion or a part thereof includes a structural unit derived from (meth) acrylate, so that it is considered that turbidity hardly occurs.

  Furthermore, like a linear poly (meth) acrylate disclosed in Patent Document 1, a polymer having a high proportion of structural units derived from (meth) acrylate is a comb polymer disclosed in Patent Document 2. In comparison, since the glass transition temperature (Tg) of the polymer is high and the viscosity temperature characteristic is poor, the fuel economy tends to be poor. Surprisingly, however, in the case of the comb polymer contained in the lubricating oil composition according to the present invention, sufficient savings can be achieved despite the inclusion of structural units derived from (meth) acrylate in both the trunk and the branch. Fuel efficiency can be achieved.

  The trunk part of the comb polymer according to the present embodiment includes a structural unit derived from styrene and a structural unit derived from (meth) acrylate.

  The (meth) acrylate composing such a trunk is not particularly limited, and one (meth) acrylate can be used alone or in combination of two or more (meth) acrylates. Examples of such (meth) acrylate include alkyl (meth) acrylate. Examples of the alkyl (meth) acrylate include alkyl (meth) acrylates having 1 to 6 carbon atoms in the alkyl group, alkyl (meth) acrylates having 7 to 16 carbon atoms in the alkyl group, and carbon numbers in the alkyl group. Alkyl (meth) acrylate etc. which are 17-40 are mentioned.

  Examples of the alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl. (Meth) acrylate, tert-butyl (meth) acrylate, n-hexyl (meth) acrylate and the like can be mentioned. Examples of the alkyl (meth) acrylate having an alkyl group having 7 to 16 carbon atoms include heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) ) Acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, cetyl (meth) acrylate and the like. Examples of the alkyl (meth) acrylate having an alkyl group having 17 to 40 carbon atoms include octadecyl (meth) acrylate, icosyl (meth) acrylate, docosyl (meth) acrylate, hexatriacontyl (meth) acrylate, and the like. It is done.

（一般式（１）中、Ｒ^１及びＲ^２は、それぞれ独立に、水素原子又は炭素数１〜１８のアルキル基を示す。） The structural unit derived from styrene constituting the trunk is not particularly limited, but the benzene ring of the structural unit derived from styrene has a linking group for bonding to a branch part described later, and The group is preferably a divalent organic group. In particular, the branch part and the benzene ring are preferably bonded to the same carbon atom contained in the linking group. Examples of such a structural unit include a compound represented by the following general formula (1). The structural unit which originates is mentioned, These can be used individually by 1 type or in combination of 2 or more types.

(In General Formula (1), R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 18 carbon atoms.)

  Among these, a structural unit derived from 4-methylstyrene is preferable from the viewpoint of availability and / or ease of manufacturing a comb polymer.

  In addition, the executive has a carbon number of alkyl group from the viewpoint of obtaining a lubricating oil composition that more effectively maintains the level of the original fuel-saving properties and does not deteriorate the fuel-saving properties even when used for a long time. A structural unit derived from an alkyl (meth) acrylate that is 1-6, a structural unit derived from an alkyl (meth) acrylate having an alkyl group having 7 to 16 carbon atoms, and an alkyl having an alkyl group having 17 to 40 carbon atoms It is preferable to include at least one selected from the group consisting of structural units derived from (meth) acrylate and structural units derived from styrene, derived from methyl (meth) acrylate, derived from dodecyl (meth) acrylate And at least one selected from the group consisting of structural units derived from octadecyl (meth) acrylate and More preferably contains a structural unit derived from emissions.

  The content of the structural unit constituting the trunk is not particularly limited, but in particular, from the viewpoint of ensuring sufficient solubility in the lubricating oil, the alkyl group has 1 to 6 carbon atoms based on the total amount of the trunk. The structural unit derived from a certain alkyl (meth) acrylate is 0 to 50% by mass, the structural unit derived from the alkyl (meth) acrylate having an alkyl group having 7 to 16 carbon atoms is 10 to 90% by mass, and the carbon of the alkyl group It is preferable that the structural unit derived from the alkyl (meth) acrylate whose number is 17-40 is 0-90 mass%, the structural unit derived from styrene is 1-30 mass%, and carbon number of an alkyl group is 1 10 to 40% by mass of structural units derived from alkyl (meth) acrylate being 6, and derived from alkyl (meth) acrylate having 7 to 16 carbon atoms in the alkyl group The structural unit is 20 to 60% by mass, the structural unit derived from alkyl (meth) acrylate having an alkyl group having 17 to 40 carbon atoms is 10 to 50% by mass, and the structural unit derived from styrene is 2 to 10% by mass. It is more preferable that

  In the comb polymer according to this embodiment, the trunk preferably has a weight average molecular weight Mw measured by gel permeation chromatography of 10,000 to 200,000, more preferably 35,000 to 90,000, and 48000 to 90,000. More preferably it is. When the Mw of the trunk is within the above range, the molecular weight balance between the trunk and the branch can be secured, and particularly sufficient solubility in the lubricating oil can be secured.

  The branch part of the comb polymer according to the present embodiment includes a structural unit derived from (meth) acrylate.

  The (meth) acrylate constituting such a branch is not particularly limited, and one (meth) acrylate can be used alone or in combination of two or more (meth) acrylates. . Examples of such (meth) acrylate include alkyl (meth) acrylate. Examples of the alkyl (meth) acrylate include alkyl (meth) acrylates having 1 to 6 carbon atoms in the alkyl group, alkyl (meth) acrylates having 7 to 16 carbon atoms in the alkyl group, and carbon numbers in the alkyl group. Alkyl (meth) acrylate etc. which are 17-40 are mentioned.

  Examples of the alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl. (Meth) acrylate, tert-butyl (meth) acrylate, n-hexyl (meth) acrylate and the like can be mentioned. Examples of the alkyl (meth) acrylate having an alkyl group having 7 to 16 carbon atoms include heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) ) Acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, cetyl (meth) acrylate and the like. Examples of the alkyl (meth) acrylate having an alkyl group having 17 to 40 carbon atoms include octadecyl (meth) acrylate, icosyl (meth) acrylate, docosyl (meth) acrylate, hexatriacontyl (meth) acrylate, and the like. It is done.

  Among these, from the viewpoint of obtaining a lubricating oil composition that is more effective in maintaining the original level of fuel-saving properties and is less likely to become turbid even when used for a long period of time, the branch portion has a carbon number of an alkyl group. Is a structural unit derived from an alkyl (meth) acrylate having 1 to 6 carbon atoms, a structural unit derived from an alkyl (meth) acrylate having an alkyl group having 7 to 16 carbon atoms, and an alkyl group having 17 to 40 carbon atoms. It is preferable to include at least one selected from the group consisting of structural units derived from alkyl (meth) acrylates, structural units derived from methyl (meth) acrylate, structural units derived from dodecyl (meth) acrylate, and octadecyl ( More preferably, it contains at least one selected from the group consisting of structural units derived from (meth) acrylates.

  The content of the structural unit derived from each of the above alkyl (meth) acrylates constituting the branch is not particularly limited, but from the viewpoint of ensuring sufficient fuel saving characteristics and solubility in lubricating oil, Based on the total amount, the structural unit derived from an alkyl (meth) acrylate having 1 to 6 carbon atoms in the alkyl group is 30 to 50% by mass, and the alkyl (meth) acrylate having 7 to 16 carbon atoms in the alkyl group is used. The structural unit derived from 40 to 70% by mass, the structural unit derived from alkyl (meth) acrylate having 17 to 40 carbon atoms in the alkyl group is preferably 0 to 30% by mass, and the carbon number of the alkyl group is 1 to 6 alkyl (meth) acrylate structural unit derived from 35 to 45% by mass, alkyl group having 7 to 16 carbon atoms is alkyl (meth) a Structural units 45 to 65 mass% derived from Relate a structural unit number of carbon atoms in the alkyl group is derived from an alkyl (meth) acrylate is 17 to 40 is more preferably 0 to 10 mass%. When the alkyl (meth) acrylate having 1 to 6 carbon atoms in the alkyl group is 30% by mass or more, the fuel-saving characteristics can be more effectively exhibited, and on the other hand, the lubricating oil is 50% by mass or less. Sufficient solubility can be ensured. When the alkyl (meth) acrylate having 7 to 16 carbon atoms in the alkyl group is 40% by mass or more, solubility in the lubricating oil and low temperature fluidity can be sufficiently secured, while 70% by mass or less. As a result, fuel saving characteristics can be more effectively exhibited. When the alkyl (meth) acrylate having 17 to 40 carbon atoms in the alkyl group is 30% by mass or less, the low-temperature fluidity can be sufficiently secured while sufficiently securing the solubility in the lubricating oil.

  The comb polymer according to the present embodiment includes the above-described trunk portion and two or more branch portions described above coupled to the trunk portion, and each of the branch portions is derived from styrene at different positions of the trunk portion. It is bonded to the unit's benzene ring via a linking group.

  The linking group is a divalent organic group, and the branch and the benzene ring are preferably bonded to the same carbon atom contained in the linking group.

  The content ratio of the structural units constituting the comb polymer according to the present embodiment is not particularly limited, but from the viewpoint of ensuring sufficient fuel saving characteristics and solubility in lubricating oil in long-term use, the executive And the structural unit derived from the alkyl (meth) acrylate whose carbon number of an alkyl group is 1-6 is 30 mass% on the basis of the whole quantity of the structural unit derived from the (meth) acrylate contained in two or more branch parts. ˜50 mass%, alkyl (meth) whose structural unit derived from alkyl (meth) acrylate having an alkyl group with 7 to 16 carbon atoms is 0 mass% to 70 mass%, and alkyl group with 17 to 40 carbon atoms It is preferable that the structural unit derived from an acrylate is 0 mass%-60 mass%, and the structural unit derived from the alkyl (meth) acrylate whose carbon number of an alkyl group is 1-6. 30% to 50% by mass, 35% to 70% by mass of a structural unit derived from an alkyl (meth) acrylate having an alkyl group having 7 to 16 carbon atoms, and an alkyl group having 17 to 40 carbon atoms The structural unit derived from (meth) acrylate is more preferably 0% by mass to 30% by mass. The structural unit derived from an alkyl (meth) acrylate having 1 to 6 carbon atoms in the alkyl group is a structural unit derived from a methyl methacrylate monomer, and the alkyl group having 7 to 16 carbon atoms in the alkyl group. The structural unit derived from (meth) acrylate is a structural unit derived from dodecyl methacrylate monomer, and the structural unit derived from alkyl (meth) acrylate having an alkyl group having 17 to 40 carbon atoms is octadecyl methacrylate monomer. A structural unit derived from is preferable.

  In the comb polymer according to this embodiment, the upper limit value of the weight average molecular weight Mw measured by gel permeation chromatography is preferably 200000 or less, more preferably 1300000 or less, and 1200000 or less. Is more preferably 1000000 or less, even more preferably 600000 or less, and most preferably 500000 or less. On the other hand, the lower limit of the weight average molecular weight Mw is preferably 20,000 or more, more preferably 50,000 or more, further preferably 100,000 or more, and particularly preferably 300,000 or more. Further, the weight average molecular weight Mw is preferably 20000 to 2000000, more preferably 50000 to 1300000, still more preferably 100000 to 1200000, and particularly preferably 300000 to 1200000. When the Mw of the comb polymer is within the above range, the lubricating oil composition is more effective in maintaining the level of the original fuel-saving properties of the lubricating oil composition and less likely to become turbid even when used for a longer period of time. Can be obtained.

  The comb polymer according to this embodiment has a molecular weight distribution (Mw / Mn) expressed as a ratio of the weight average molecular weight Mw and the number average molecular weight Mn measured by gel permeation chromatography of 1.0 to 8.0. Preferably, it is 1.0 to 5.0, more preferably 1.5 to 3.0. When Mw / Mn is 1.0 or more, it is possible to obtain a lubricating oil composition that hardly causes turbidity even when used for a longer period of time. The level of fuel saving characteristics can be more effectively maintained.

  The method for producing a comb polymer according to the present embodiment includes a first step of performing free radical polymerization of styrene having a structure in which a halogen group is bonded to a benzene ring via a linking group and (meth) acrylate, And a second step of performing controlled radical polymerization of (meth) acrylate starting from the halogen group of the polymer obtained in the step.

(First step)
The first step is a step of performing free radical polymerization of styrene having a structure in which a halogen group is bonded to a benzene ring via a linking group and (meth) acrylate. A polymer serving as a trunk of the comb polymer according to the first embodiment described above by the first step, that is, a structural unit derived from styrene having a structure in which a halogen group is bonded to a benzene ring via a linking group; A polymer having a structural unit derived from (meth) acrylate can be obtained. Polymerization can be performed by adding the said (meth) acrylate, the said styrene, a radical initiator, a chain transfer agent, etc. in a solution, and making it react in the temperature range of 50-150 degreeC, for example.

（一般式（２）中、Ｒ^１及びＲ^２は、それぞれ独立に、水素原子又は炭素数１〜１８のアルキル基を示し、ＸはＣｌ、Ｂｒ及びＩからなる群より選択されるハロゲン原子を示す。） Examples of styrene having a structure in which a halogen group is bonded to a benzene ring via a linking group include compounds represented by the following general formula (2). Among these, from the viewpoint of availability and reactivity, 4- (chloromethyl) styrene is preferable as the styrene used for polymerization.

(In General Formula (2), R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, and X represents a halogen atom selected from the group consisting of Cl, Br and I. Show.)

  Examples of the radical initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 4,4′-azobis (4-cyanovaleric) acid, Azo initiators such as 1,1′-azobis (1-cyclohexanecarbonitrile), azobisisobutyric acid amidine hydrochloride, 2,2′-azobis (2,4-dimethylvaleronitrile), benzoyl peroxide, di-peroxide Examples thereof include organic peroxide initiators such as tert-butyl. Among these, an azo-based initiator is preferable from the viewpoint that it is not affected by the solvent used for the polymerization and has a low risk of explosion or the like.

  Examples of the chain transfer agent include n-dodecyl mercaptan, tert-dodecyl mercaptan, lauryl mercaptan, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropyltriethoxysilane, and γ-mercaptopropylmethyl. Examples include mercaptans such as diethoxysilane and halogen-containing compounds.

  The polymerization can be performed without a solvent, but may be performed in a solvent. When polymerization is performed in a solvent, the solvent to be used is not particularly limited. For example, high polarity such as dimethyl sulfoxide (DMSO), dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), N-methylpyrrolidone, etc. Aprotic solvents, carbonate solvents such as ethylene carbonate and propylene carbonate, alcohol solvents such as methanol, ethanol, propanol, isopropanol, n-butyl alcohol and tert-butyl alcohol, nitriles such as acetonitrile, propionitrile and benzonitrile Solvents, ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone, ether solvents such as diethyl ether and tetrahydrofuran, halogenated hydrocarbon solvents such as methylene chloride and chloroform Ethyl acetate, ester solvents such as butyl acetate, pentane, hexane, heptane, cyclohexane, octane, decane, benzene, toluene, hydrocarbon solvents such as xylene, mineral oil, and the like base oil synthetic oil. As mineral oil, for example, a lubricating oil fraction obtained by distillation under reduced pressure of atmospheric residual oil obtained by atmospheric distillation of crude oil can be removed by solvent, solvent extraction, hydrocracking, solvent dewaxing, hydrogenation Examples thereof include those refined by performing one or more treatments such as refining, wax isomerized mineral oil, and base oils produced by a method of isomerizing GTL wax (gas-tuly wax). Synthetic oils include, for example, polybutene or hydrides thereof, poly-α-olefins such as 1-octene oligomers and 1-decene oligomers or hydrides thereof, ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditrile. Diesters such as decyl adipate, di-2-ethylhexyl sebacate, polyol esters such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate, alkylnaphthalene, alkylbenzene, etc. Aromatic synthetic oils or mixtures thereof. These solvents can be used alone or in combination of two or more.

  The polymer formed in this step preferably has a weight average molecular weight Mw measured by gel permeation chromatography of 10,000 to 200,000, more preferably 35,000 to 90,000, and further preferably 48,000 to 90,000. preferable. When Mw is within the above range, the molecular weight balance between the trunk portion and the branch portion in the finally obtained comb polymer can be secured, and particularly sufficient solubility in the lubricating oil can be secured.

(Second step)
The second step is a step of performing controlled radical polymerization of (meth) acrylate using the halogen group of the polymer obtained in the first step as a starting point. By the second step, the comb-shaped polymer according to the first embodiment, that is, the trunk, and the two or more branches coupled to the trunk, the trunk is a structural unit derived from styrene and (meta) Including a structural unit derived from acrylate, two or more branches may be the same as or different from each other, each including a structural unit derived from (meth) acrylate, and each of the branches is at a different position of the trunk A comb polymer bonded to a benzene ring of a structural unit derived from styrene via a linking group can be obtained. The controlled radical polymerization (controlled polymerization) in the second step can be carried out using a halogen group present in a structural unit derived from styrene as a starting point as a starting point as an initiator. Hereinafter, the controlled polymerization method will be described.

  Controlled polymerization methods include atom transfer radical polymerization (ATRP (J. Am. Chem. Soc. 1995, 117, 5614, Macromolecules. 1995, 28, 1721)), single electron transfer polymerization (Simple Electron Transfer). Polymerization: SET-LRP (J. Am. Chem. Soc. 2006, 128, 14156, JPS Chem 2007, 45, 1607)) and reversible transfer catalytic polymerization (Reversible Chain Transfer Catalyzed Polymerized RAT) Controlling Living Radical Polymerization Polymer Transactions 68,223-231 (2011), Japanese Patent Application Laid-Open No. 2014-111798)), living radical polymerization using organic tellurium (Organo Tellurium Mediated Living Radical Polymerization; TERP method (WO2004014848)) and the like.

  The above atom transfer radical polymerization (ATRP) and one electron transfer polymerization (SET-LRP) are living radical polymerization methods for vinyl monomers using a transition metal complex containing a transition metal or a transition metal compound and a ligand as a polymerization catalyst. The reversible transfer catalytic polymerization (RTCP) is a living radical polymerization method in which these transition metals or transition metal complexes are not used as a polymerization catalyst.

  In atom transfer radical polymerization, for example, a copper complex can be used as the transition metal complex. The atom transfer radical polymerization in the case of using a copper complex is, for example, as follows. That is, the monovalent copper complex pulls out the halogen atom at the end of the polymer to generate radicals to form a divalent copper complex. The divalent copper complex returns to the monovalent copper complex by returning the halogen atom to the radical at the polymerization end. Living radical polymerization including these equilibrium is atom transfer radical polymerization.

  In the one-electron transfer polymerization, as the transition metal or transition metal complex, for example, metallic copper or copper complex can be used. One-electron transfer polymerization in the case of using metallic copper or a copper complex is, for example, as follows. That is, zero-valent metal copper or a copper complex pulls out a halogen atom at the end of the polymer to generate a radical to form a divalent copper complex. The divalent copper complex returns a halogen atom to the radical at the polymerization end to become a zero-valent copper complex. The monovalent copper complex is disproportionated to become zero-valent and divalent copper complexes. Living radical polymerization including these equilibria is one-electron transfer polymerization.

  In addition, by reducing the antioxidant transition metal complex that causes polymerization delay and termination using a reducing agent, the polymerization reaction can be rapidly advanced to a high reaction rate even under low catalyst conditions with few transition metal complexes. Activators Regenerated by Electron Transfer: ARGET (Macromolecules. 2006, 39, 39) has been reported as an improved formulation of the above atom transfer radical polymerization.

  In the second step of the method for producing a comb polymer according to this embodiment, any of the above polymerization methods can be used.

In the case of using atom transfer radical polymerization, as the polymerization catalyst, for example, a metal complex having a central metal of Group 7, Group 8, Group 9, Group 11, or Group 11 of the periodic table can be used. In particular, monovalent or divalent copper, divalent ruthenium, or divalent iron is preferable. Specifically, cuprous chloride, cupric chloride, cuprous bromide, cuprous iodide, cuprous cyanide, cuprous oxide, cuprous acetate, cuprous perchlorate, etc. Is mentioned. When using a copper compound, an amine ligand may be added in order to increase the catalytic activity. A tristriphenylphosphine complex of divalent ruthenium chloride (RuCl ₂ (PPh ₃ ) ₃ ) is also suitable as a catalyst. When using a tristriphenylphosphine complex of divalent ruthenium chloride, an aluminum compound such as trialkoxyaluminum may be added in order to increase the catalytic activity. Further, a tristriphenylphosphine complex of divalent iron chloride (FeCl ₂ (PPh ₃ ) ₃ ) is also suitable as a catalyst. Among these, it is preferable to use a copper catalyst because it can be obtained at a low cost.

  Moreover, you may use a polydentate amine in combination with the said polymerization catalyst from a viewpoint of raising catalyst activity, raising a polymerization rate, and improving productivity.

The polydentate amine used as the ligand is not particularly limited, and examples thereof include 2,2-bipyridine, 4,4′-di- (5-nonyl) -2,2′-bipyridine, N- (n-propyl) pyridylmethanimine, N- (n-octyl) pyridylmethanimine and other bidentate polydentate amines, N, N, N ′, N ″, N ″ -pentamethyldiethylenetriamine , N-propyl-N, N-di (2-pyridylmethyl) amine and other tridentate polydentate amines, hexamethyltris (2-aminoethyl) amine (often abbreviated as Me ₆ TREN) N, N-bis (2-dimethylaminoethyl) -N, N′-dimethylethylenediamine, 2,5,9,12-tetramethyl-2,5,9,12-tetraazatetradecane, 2,6,9 , 13-Tetramethyl-2,6 , 9,13-tetraazatetradecane, 4,11-dimethyl-1,4,8,11-tetraazabicyclohexadecane, N ′, N ″ -dimethyl-N ′, N ″ -bis ((pyridine-2 -Yl) methyl) ethane-1,2-diamine, tris [(2-pyridyl) methyl] amine (TPMA), 2,5,8,12-tetramethyl-2,5,8,12-tetraazatetradecane, etc. A multidentate polydentate amine such as N, N, N ′, N ″, N ′ ″, N ″ ″, N ″ ″-heptamethyltetraethylenetetramine Examples thereof include bidentate amines, hexadentate polydentate amines such as N, N, N ′, N′-tetrakis (2-pyridylmethyl) ethylenediamine, and polyamines such as polyethyleneimine.

  A base may be added to neutralize the acid present in the polymerization system or the acid generated and suppress acid accumulation. Although it does not restrict | limit especially as a base, For example, a monoamine base, a polyamine base, an inorganic base etc. are mentioned. A monoamine base is a compound having one site acting as a base in one molecule, for example, a primary amine such as methylamine, aniline or lysine, a secondary amine such as dimethylamine or piperidine, trimethylamine, triethylamine, etc. And tertiary amines, aromatics such as pyridine and pyrrole, and ammonia. Examples of the polyamine base include diamines such as ethylenediamine and tetramethylethylenediamine, triamines such as diethylenetriamine and pentamethyldiethylenetriamine, tetramines such as triethylenetetramine, hexamethyltriethylenetetramine and hexamethylenetetramine, and polyethyleneimine. The inorganic base is a compound containing a simple substance of Group 1 or 2 of the periodic table or an element of Group 1 or 2 of the periodic table, and is not particularly limited. For example, lithium, sodium, calcium Group 1 or 2 of the periodic table such as sodium methoxide, potassium ethoxide, methyl lithium, sodium hydroxide, potassium hydroxide, potassium carbonate, sodium bicarbonate, ammonium bicarbonate, trisodium phosphate, Periodic table of disodium hydrogen phosphate, tripotassium phosphate, dipotassium hydrogen phosphate, sodium acetate, potassium acetate, sodium oxalate, potassium oxalate, phenoxy sodium, phenoxy potassium, sodium ascorbate, potassium ascorbate, etc. Compounds containing Group 1 or Group 2 elements, ammonium hydroxide, etc. Such as salt of an acid and a strong base and the like. These bases can be used individually by 1 type or in combination of 2 or more types. The base may be added directly to the reaction system or may be generated in the reaction system.

  When using a copper complex as a polymerization catalyst, you may use a reducing agent from a viewpoint of improving polymerization activity as mentioned above. By using a reducing agent, it is possible to reduce the amount of transition metal catalyst normally required from several hundred to several thousand ppm to several tens to several hundred ppm. As the reducing agent, a reducing agent that does not generate an acid when reducing a copper complex, a reducing agent that generates an acid when reducing a copper complex (hydride reducing agent), or the like can be used.

  Examples of the reducing agent that does not generate an acid when reducing a copper complex include metals, metal compounds, organotin compounds, phosphorus or phosphorus compounds, sulfur or sulfur compounds, and the like.

  Examples of metals include alkali metals such as lithium, sodium and potassium, alkaline earth metals such as beryllium, magnesium, calcium and barium, typical metals such as aluminum and zinc, transitions such as copper, nickel, ruthenium and iron A metal etc. are mentioned, These metals may be in the state of an alloy (amalgam) with mercury.

Examples of the metal compound include complexes in which a typical metal or a transition metal or a salt thereof, carbon monoxide, an olefin, a nitrogen-containing compound, an oxygen-containing compound, a phosphorus-containing compound, a sulfur-containing compound, and the like are coordinated. Specifically, compounds of metal and ammonia / amine, titanium trichloride, titanium alkoxide, chromium chloride, chromium sulfate, chromium acetate, iron chloride, copper chloride, copper bromide, tin chloride, zinc acetate, zinc hydroxide, Carbonyl complexes such as Ni (CO) ₄ and Co ₂ CO ₈ and olefin complexes such as [Ni (cod) ₂ ], [RuCl ₂ (cod)] and [PtCl ₂ (cod)] (where cod is cyclooctadiene) ), [RhCl (P (C ₆ H ₅ ) ₃ ) ₃ ], [RuCl ₂ (P (C ₆ H ₅ ) ₃ ) ₂ ], [PtCl ₂ (P (C ₆ H ₅ ) ₃ ) ₂ ] And phosphine complexes.

  Examples of the organic tin compound include tin octylate, tin 2-ethylhexylate, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin mercaptide, dibutyltin thiocarboxylate, dibutyltin dimaleate, and dioctyltin thiocarboxylate.

  Examples of phosphorus or phosphorus compounds include phosphorus, trimethylphosphine, triethylphosphine, triphenylphosphine, trimethylphosphite, triethylphosphite, triphenylphosphite, hexamethylphosphorustriamide, hexaethylphosphorustriamide, and the like. It is done.

Examples of sulfur or sulfur compounds include sulfur, Rongalite, hydrosulfite, and thiourea dioxide. Rongalite is a formaldehyde derivative of sulfoxylate and is represented by MSO ₂ · CH ₂ O (M represents Na or Zn). Specific examples include sodium formaldehyde sulfoxylate and zinc formaldehyde sulfoxylate. Hydrosulfite is a general term for sodium hyposulfite and formaldehyde derivatives of sodium hyposulfite.

  As a reducing agent (hydride reducing agent) that generates an acid when reducing a copper complex, metal hydride, silicon hydride, boron hydride, nitrogen hydride, organic compounds exhibiting a reducing action, hydrogen sulfide, etc. Etc.

  Examples of metal hydrides include aluminum hydrides such as diisobutylaluminum hydride, lithium aluminum hydride, sodium aluminum hydride, sodium triethoxyaluminum hydride, sodium bis (2-methoxyethoxy) aluminum hydride, and triphenyl hydride. Organic tin hydrides such as tin, hydrogenated tri-n-butyltin, diphenyltin hydride, di-n-butyltin hydride, triethyltin hydride, trimethyltin hydride, sodium hydride, germanium hydride, tungsten hydride, etc. Is mentioned.

  Examples of the silicon hydride include trichlorosilane, trimethylsilane, triethylsilane, diphenylsilane, phenylsilane, polymethylhydrosiloxane, and the like.

  Examples of the boron hydride include borane, diborane, sodium borohydride, sodium trimethoxyborate, sodium borohydride, sodium cyanide borohydride, lithium cyanoborohydride, lithium borohydride, triethylboron hydride. Examples include lithium, lithium tri-s-butylborohydride, lithium tri-t-butylborohydride, calcium borohydride, potassium borohydride, zinc borohydride, tetra-n-butylammonium borohydride, and the like. .

  Examples of the nitrogen hydride include hydrazine and diimide.

  Examples of the organic compound exhibiting a reducing action include alcohols, aldehydes, phenols, organic acid compounds, and the like. Examples of the alcohol include methanol, ethanol, propanol, and isopropanol. Examples of the aldehyde include formaldehyde, acetaldehyde, benzaldehyde, formic acid and the like. Examples of phenols include phenol, hydroquinone, dibutylhydroxytoluene, tocopherol and the like. Examples of the organic acid compound include citric acid, oxalic acid, ascorbic acid, ascorbate, ascorbate ester and the like.

  These reducing agents can be used singly or in combination of two or more. These reducing agents may be added directly to the reaction system or may be generated in the reaction system. In the latter case, electrolytic reduction is also included. In electrolytic reduction, it is known that electrons generated at the cathode exhibit a reducing action immediately or once after solvation. That is, a reducing agent produced by electrolysis can also be used.

  The polymerization in the second step can be performed without a solvent, but may be performed in a solvent. When the polymerization is performed in a solvent, the solvent to be used is not particularly limited. For example, the solvent, mineral oil, and synthetic oil exemplified in the first step can be preferably used, and ionic liquid, water, super A critical fluid or the like can also be used. These can be used individually by 1 type or in combination of 2 or more types. In atom transfer radical polymerization (ARGET) using a reducing agent, the transition metal or transition metal complex, polydentate amine, base, reducing agent, monomer and initiator are uniform in the reaction system. Since it is preferable from the viewpoint of reaction rate, ease of preparation, and reduction in scale-up risk, it is preferable to select a solvent that dissolves them.

  In addition, the method for manufacturing a comb polymer according to the present embodiment may further include a removal step of removing unreacted monomers and the like between the first step and the second step. It is preferable to perform 1 process and 2nd process continuously. By continuously performing the first step and the second step, the comb polymer according to the present embodiment can be obtained by a simpler manufacturing process, which is economically effective.

  The viscosity index improver according to this embodiment includes the comb polymer according to this embodiment described above.

  The viscosity index improver according to this embodiment can be contained in the lubricating oil composition together with the lubricating base oil. The lubricating oil composition contains at least the base oil and the viscosity index improver according to this embodiment, but may contain other additives.

  Other additives include viscosity index improvers other than the above comb polymers, antioxidants, antiwear agents (or extreme pressure agents), corrosion inhibitors, rust inhibitors, pour point depressants, demulsifiers, metal emulsifiers. Activators, antifoaming agents, (ashless) friction modifiers, metallic detergents, ashless dispersants and the like can be mentioned. These additives can be used alone or in combination of two or more.

  Viscosity index improvers other than the above comb polymers include polymethacrylate viscosity index improver, polyisobutene viscosity index improver, ethylene-propion copolymer viscosity index improver, styrene-butadiene hydrogenated copolymer viscosity index improve Agents and the like.

  Examples of the antioxidant include phenolic antioxidants and amine antioxidants.

  Examples of amine-based antioxidants include 4,4′-methylenebis (2,6-di-tert-butylphenol), 4,4′-bis (2,6-di-tert-butylphenol), 4,4- Bis (2-methyl-6-tert-butylphenol), 2,2-methylenebis (4-ethyl-6-tert-butylphenol), 2,2-methylenebis (4-methyl-6-tert-butylphenol), 4,4 -Butylidenebis (3-methyl-6-tert-butylphenol), 4,4-isopropylidenebis (2,6-di-tert-butylphenol), 2,2-methylenebis (4-methyl-6-nonylphenol), 2, 2-isobutylidenebis (4,6-dimethylphenol), 2,2-methylenebis (4-methyl-6-cyclohexyl) Enol), 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,4-dimethyl-6-tert-butylphenol, 2,6-di -Tert-α-dimethylamino-p-cresol, 2,6-di-tert-butyl-4- (N, N-dimethylaminomethylphenol), 4,4'-thiobis (2-methyl-6-tert- Butylphenol), 4,4′-thiobis (3-methyl-6-tert-butylphenol), 2,2′-thiobis (4-methyl-6-tert-butylphenol), bis (3-methyl-4-hydroxy-5) -Tert-butylbenzyl) sulfide, bis (3,5-di-tert-butyl-4-hydroxybenzyl) sulfide, 2,2'-thio-di Ethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], tridecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, pentaerythrityl- Tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, stearyl-3- ( 3,5-di-tert-butyl-4-hydroxyphenyl) propionate, octyl-3- (3-methyl-5-di-tert-butyl-4-hydroxyphenyl) propionate, and the like.

  As the amine-based antioxidant, for example, known amine-based antioxidants generally used for lubricating oils such as aromatic amine compounds, alkyldiphenylamines, alkylnaphthylamines, phenyl-α-naphthylamines, alkylphenyl-α-naphthylamines, etc. Agents.

  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 corrosion inhibitor include benzotriazole, tolyltriazole, thiadiazole, and imidazole compounds.

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

  Examples of the pour point depressant include polyalkyl (meth) acrylates different from the viscosity index improver.

  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 and 2- (alkyldithio) propiononitrile.

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

  As the ashless friction modifier, any compound usually used as an ashless friction modifier for lubricating oil can be used. For example, an alkyl group or alkenyl group having 6 to 30 carbon atoms, particularly 6 carbon atoms. Ashless friction modifiers such as amine compounds, fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, aliphatic ethers having at least one linear alkyl group or linear alkenyl group of ˜30 in the molecule. . Further, nitrogen-containing compounds and acid-modified derivatives thereof described in JP-A-2009-286831, various ashless friction modifiers exemplified in International Publication No. 2005/037967 pamphlet, and the like can also be used.

  Examples of the metal detergent 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 dispersant, any ashless dispersant used in lubricating oils can be used. For example, a mono- or mono-chain having at least one linear or branched alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule. Bisuccinimide, benzylamine having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, polyamine having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, or these And modified products of 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.

  Moreover, these additives may further contain a solvent. As the solvent, highly refined mineral oil, solvent refined mineral oil, synthetic oil and the like can be used. Among these, highly refined mineral oil and solvent refined mineral oil are preferably used. When the additive contains a solvent, the content of the solvent is preferably 5 to 75% by mass, more preferably 30 to 60% by mass, based on the total amount of the additive.

  When the lubricating oil composition contains one or more of the above-mentioned other additives, each content is preferably 0.01 to 10% by mass based on the total amount of the lubricating oil composition. . Moreover, when the lubricating oil composition which concerns on this embodiment contains an antifoamer, the content becomes like this. Preferably it is 0.0001-0.01 mass%.

  The lubricating base oil contained in the lubricating oil composition is not particularly limited, and a lubricating base oil used for ordinary lubricating oils can be used. Specifically, a mineral oil base oil, a synthetic oil base oil, or a mixture of two or more kinds of lubricant base oils selected from these can be used.

  Examples of mineral oil base oils include, for example, solvent oil removal, solvent extraction, hydrocracking, solvent removal of lubricating oil fractions obtained by distillation under reduced pressure of atmospheric residual oil obtained by atmospheric distillation of crude oil. Examples include those refined by performing one or more treatments such as dewaxing and hydrorefining, wax isomerized mineral oil, base oils produced by a method of isomerizing GTL wax (gas-tuly wax), and the like.

  Synthetic lubricating oils include, for example, polybutene or hydrides thereof, poly-α-olefins such as 1-octene oligomers and 1-decene oligomers or hydrides thereof, ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate Diesters such as ditridecyl adipate, di-2-ethylhexyl sebacate, polyol esters such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate, alkylnaphthalene, An aromatic synthetic oil such as alkylbenzene or a mixture thereof can be exemplified.

The kinematic viscosity of the lubricating base oil at 100 ° C. is preferably 2.5 to 10.0 mm ² / s, more preferably 3.0 to 8.0 mm ² / s, still more preferably 3.5 to 6.0 mm ^2. / S. The viscosity index of the lubricating base oil is preferably 90 to 165, more preferably 100 to 155, and still more preferably 120 to 150.

  The saturated content of the lubricating base oil by chromatographic analysis is preferably 80% or more, more preferably 85% or more, still more preferably 90% or more, and most preferably, in order to easily exert the effect of adding the viscosity index improver and the like. Is 95% or more.

  The content of the viscosity index improver according to the present embodiment is preferably 0.1 to 20.0% by mass, more preferably 0.5 to 15.0% by mass, further based on the total amount of the lubricating oil composition. Preferably it is 1.0-10.0 mass%.

The kinematic viscosity at 100 ° C. of the lubricating oil composition is preferably 3.0 to 8.5 mm ² / s, more preferably 4.0 to 8.0 mm ² / s, still more preferably 5.6 to 7.5 mm. ² / s. When the kinematic viscosity at 100 ° C. of the lubricating oil composition is not less than the above lower limit value, it becomes easy to ensure lubricity. On the other hand, when the kinematic viscosity at 100 ° C. is not more than the above upper limit value, more fuel-saving characteristics are maintained. It tends to be easy. In the present specification, the kinematic viscosity at 100 ° C. means the kinematic viscosity at 100 ° C. defined by ASTM D-445.

  The viscosity index of the lubricating oil composition is preferably 150 to 250, more preferably 160 to 240, and still more preferably 170 to 230. When the viscosity index is equal to or higher than the above lower limit, the fuel-saving characteristics can be more effectively maintained while maintaining the HTHS viscosity, and the low-temperature viscosity is easily lowered. On the other hand, when the viscosity index is less than or equal to the above upper limit, low temperature fluidity, solubility of additives, and compatibility with sealing materials can be ensured. In the present specification, the viscosity index means a viscosity index defined in JIS K 2283-1993.

  Whether the lubricating oil composition is less likely to become turbid even when used for a long period of time is determined by conducting a JPI-5S-29-88 ultrasonic shear stability test (10 kHz, 10 h) on the lubricating oil composition, After storing the sample oil after the test at 0 ° C. for 30 days, it can be evaluated by whether or not the lubricating oil composition is turbid.

  The fuel-saving characteristics of the lubricating oil composition are evaluated by the HTHS viscosity at 150 ° C. and 100 ° C. specified in ASTM D-4683. The HTHS viscosity means a high shear viscosity at the same temperature. The HTHS viscosity at 150 ° C. of the present invention is preferably 1.4 mPa · s or more, more preferably 2.0 mPa · s or more, still more preferably 2.3 mPa · s or more, and most preferably 2.6 mPa · s or more. When the HTHS viscosity at 150 ° C. is equal to or higher than the lower limit, evaporation of the lubricating oil composition can be suppressed, and lubricity can be ensured. The HTHS viscosity at 100 ° C. of the lubricating oil composition is preferably 5.4 mPa · s or less, more preferably 5.3 mPa · s or less, still more preferably 5.2 mPa · s or less, and particularly preferably 5.1 mPa · s. s or less, more preferably 5.0 mPa · s or less. When the HTHS viscosity at 100 ° C. is not more than the above upper limit value, higher fuel saving characteristics can be obtained.

  The shear stability of the lubricating oil composition is evaluated by the Sonic method defined in ASTM D-6278. The value was calculated by dividing the kinematic viscosity after the test by the kinematic viscosity before the test. The shear stability in the present invention is preferably 10% or less, more preferably 5% or less.

  The low temperature fluidity of the lubricating oil composition in the present invention is evaluated by the MRV viscosity at −40 ° C. specified in ASTM D-4684. In the present invention, the MRV viscosity at −40 ° C. is preferably 60000 mPa · s or less, more preferably 40000 mPa · s or less, and further preferably 30000 mPa · s or less. When the MRV viscosity at −40 ° C. is not more than the above upper limit value, the pumping characteristics at low temperature are excellent.

  As described above, the lubricating oil composition according to the present embodiment can be used in a wide range of fields such as a lubricating oil for an internal combustion engine, a drive system lubricating oil (for example, an automatic transmission oil, a manual transmission oil, a final reduction gear oil, etc.). However, it is particularly useful in the field of lubricating oil for internal combustion engines. In this case, the fuel of the internal combustion engine may be either gasoline or diesel fuel.

  Specific examples of the present invention are shown below, but the present invention is not limited to the following examples. In the following Examples and Comparative Examples, “number average molecular weight”, “weight average molecular weight”, and “molecular weight distribution (ratio between weight average molecular weight and number average molecular weight)” are standards using gel permeation chromatography (GPC). It was calculated by the polystyrene conversion method. However, as for the trunk portion, a GPC column filled with polystyrene cross-linked gel (shodex GPC K-804; manufactured by Showa Denko KK, trade name) was measured using chloroform as a GPC solvent. The comb polymer was measured using a GPC column filled with polystyrene cross-linked gel (TSK guard column Super HZ-H; trade name, manufactured by Tosoh Corporation) and tetrahydrofuran as a GPC solvent.

[Production of comb polymer]
(Production Example 1)
A separable flask (1) equipped with a stirrer and a reflux condenser was charged with 49.7 g of mineral oil as a polymerization solvent and subjected to nitrogen bubbling for 30 minutes at room temperature. In a three-necked flask (2) equipped with a stirrer, 8.2 g of methyl methacrylate (MMA; manufactured by Wako Pure Chemical Industries, Ltd.) as a monomer for the trunk, 8.2 g of dodecyl methacrylate (LMA; manufactured by Wako Pure Chemical Industries, Ltd.), 10.9 g of octadecyl methacrylate (SMA; manufactured by Tokyo Chemical Industry Co., Ltd.), 1.2 g of 4- (chloromethyl) styrene (CMSt; manufactured by Tokyo Chemical Industry Co., Ltd.) and 28.4 g of toluene as a solvent for dissolving monomers are charged. Nitrogen bubbling was performed for 30 minutes after stirring and mixing to obtain a uniform solution. Also, 0.07 g of 2,2-azobis (2-methylbutyronitrile) (V-59; manufactured by Wako Pure Chemical Industries, Ltd., trade name) was added to the two-necked flask (3) as an initiator, and the initiator was dissolved. After stirring and mixing with 16.6 g of isopropyl acetate as a working solvent, a homogeneous solution was made, and nitrogen bubbling was performed for 30 minutes. After adding the total amount of (3) to (2), nitrogen bubbling was further performed for 15 minutes. When (1) was heated in an oil bath and the internal temperature reached 105 ° C., (2) was added dropwise to initiate polymerization. The total amount of (2) was dropped in about 90 minutes. After the completion of dropping (2), the mixture was continuously stirred for about 5 hours and then cooled to obtain a polymer for forming a trunk. The weight average molecular weight (Mw) obtained by GPC of the polymer was 69000, the number average molecular weight (Mn) was 37000, and the molecular weight distribution was 1.9. Subsequently, 14 mg of cupric chloride (CuCl ₂ ) as a polymerization catalyst and 0.18 g of tris [(2-pyridyl) methyl] amine (TPMA; manufactured by Aldrich) as a polydentate amine were catalyzed in a separable flask (1) containing the above polymer A solution dissolved in 1.0 g of ethanol as a solvent for dissolution was charged and mixed with stirring. Further, 52.2 g of methyl methacrylate and 77.8 g of dodecyl methacrylate as a monomer for branches and 267.1 g of mineral oil as a polymerization solvent were added to obtain a homogeneous solution by stirring and mixing, and then nitrogen bubbling was performed for 30 minutes. When the internal temperature reached 80 ° C. in an oil bath, 0.057 ml of tin octylate as a reducing agent was added to initiate polymerization. While maintaining the internal temperature of 80 ° C., tin octylate was added twice every 30 minutes, and then added twice every hour (0.28 ml in total). After stirring for about 4 hours after the addition of tin octylate, the internal temperature was set to 120 ° C., and unreacted monomers and toluene were removed under reduced pressure to obtain a comb polymer 1. The weight average molecular weight (Mw) obtained by GPC of comb polymer 1 was 388000, the number average molecular weight (Mn) was 192000, and the molecular weight distribution (Mw / Mn) was 2.0. Solvent for dissolving initiator used for forming trunk, monomer for trunk, polymerization solvent, solvent for dissolving monomer and solvent for dissolving initiator, monomer for branch used for forming branch, polymerization solvent, polymerization catalyst, Table 1 shows the composition of the bident amine, the solvent for dissolving the catalyst, and the reducing agent. The monomer composition (% by mass) of the trunk and the branch in the obtained comb polymer 1, the number average molecular weight of the trunk and the comb polymer 1 (Mn ), Weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn), and composition of constituent unit monomers derived from each (meth) acrylate based on the total amount of constituent units derived from (meth) acrylate of comb polymer 1 Table 3 shows (mass%).

(Production Examples 2 to 17)
Solvent for dissolving initiator used for forming trunk, monomer for trunk, polymerization solvent, solvent for dissolving monomer and solvent for dissolving initiator, monomer for branch used for forming branch, polymerization solvent, polymerization catalyst, Comb polymers 2 to 17 were synthesized in the same manner as in Production Example 1 except that the composition of the bident amine, the solvent for dissolving the catalyst and the reducing agent was changed as shown in Tables 1 and 2. Monomer composition (mass%) of trunk and branch in the obtained comb polymers 2 to 17, number average molecular weight (Mn), weight average molecular weight (Mw) and molecular weight distribution (Mw / m) of the trunk and comb polymers 2 to 17 Tables 3 and 4 show the composition (mass%) of constituent unit monomers derived from each (meth) acrylate based on the total amount of constituent units derived from (Mn) and the (meth) acrylates of comb polymers 2 to 17. In the table, Nyper BW represents benzoyl peroxide (manufactured by NOF Corporation).

[Preparation of lubricating oil composition]
(Examples 1-17)
Lubricating oil base oil (API Group III base oil, kinematic viscosity at 100 ° C .: 4.2 mm ² //) using the comb polymers 1 to 17 prepared in Production Examples 1 to 17 as viscosity index improvers based on the total amount of the lubricating oil composition s, viscosity index: 125) and additives (MoDTC friction modifier (Mo content 10 mass%, S content 11 mass%) 0.5 mass%, succinimide ashless dispersant 4.0 mass%, ZnDTP antiwear agent (P content 6.5% by mass) 1% by mass, amine antioxidant 0.8% by mass, and overbased calcium sulfonate (base number 170 mg KOH / g, Ca content 6.3 mass) %) Package type performance additive consisting of 2.5% by mass) was blended as shown in Tables 5 and 6 to prepare lubricating oil compositions of Examples 1 to 17, respectively.

(Comparative Example 1)
A conventional comb polymer C1 (comb polymer having a repeating unit derived from a polyolefin-based macromonomer at a branch portion) was synthesized according to Example 4 of Patent Document 2. The obtained comb polymer C1 had a weight average molecular weight of 300,000. Using this comb polymer C1 as a viscosity index improver, a lubricant base oil (API Group III base oil, kinematic viscosity at 100 ° C .: 4.2 mm ² / s, viscosity index: 125) and additives (MoDTC friction modifier ( Mo content 10 mass%, S content 11 mass%) 0.5 mass%, succinimide-based ashless dispersant 4.0 mass%, ZnDTP-based antiwear agent (P content 6.5 mass%) 1 mass %, Amine-based antioxidant 0.8% by mass, and overbased calcium sulfonate (base value 170 mg KOH / g, Ca content 6.3% by mass) 2.5% by mass package type performance additive) The lubricating oil composition of Comparative Example 1 was prepared by blending as shown in FIG.

[Evaluation of lubricating oil composition]
Tables 5 and 6 show various properties (kinematic viscosity at 100 ° C., HTHS viscosity at 100 ° C. and 150 ° C., shear stability, and MRV viscosity at −40 ° C.) of the obtained lubricating oil composition. In addition, the turbidity test and the solubility test in the base oil of the comb polymer were evaluated according to the following methods. The evaluation results are shown in Tables 5 and 6. In Tables 5 and 6, “YS” means Yield Stress. If the yield stress is present, it means a deviation from the standard.

(Turbidity test)
The obtained lubricating oil composition was subjected to a JPI-5S-29-88 ultrasonic shear stability test (10 kHz, 10 h), and the sample oil after the test was stored at 0 ° C. for 30 days. It was evaluated whether turbidity was recognized in the thing. The evaluation results are shown in Tables 5 and 6. In Tables 5 and 6, Y is indicated when turbidity is observed, and N is indicated when turbidity is not observed.

(Solubility test of comb polymer in base oil)
The comb polymer was mixed at 3.3% by mass with respect to the base oil, heated and stirred at 120 ° C. for 2 hours, cooled to room temperature, and the appearance of the solution was visually evaluated. The judgment was as follows.
○: Uniform solution state.
X: A state in which the polymer is precipitated and separated from the base oil.

Claims (4)

A lubricating oil composition comprising a lubricating base oil and a viscosity index improver,
The viscosity index improver comprises a comb polymer having a trunk and two or more branches bonded to the trunk,
The trunk includes a structural unit derived from styrene and a structural unit derived from (meth) acrylate,
The two or more branches may be the same as or different from each other, each including a structural unit derived from (meth) acrylate,
Each of the branch parts is a lubricating oil composition in which a benzene ring of a structural unit derived from the styrene is bonded via a linking group at a different position of the trunk part.   Based on the total amount of structural units derived from (meth) acrylate contained in the trunk and the two or more branches, the proportion of structural units derived from methyl methacrylate monomer is 30% by mass to 50% by mass, The ratio of the structural unit derived from a dodecyl methacrylate monomer is 0 mass%-70 mass%, The ratio of the structural unit derived from an octadecyl methacrylate monomer is 0 mass%-60 mass%. Lubricating oil composition.   The lubricating oil composition according to claim 1 or 2, wherein the weight average molecular weight Mw measured by gel permeation chromatography is 20,000 to 2,000,000.   Lubricating oil composition as described in any one of Claims 1-3 whose ratio Mw / Mn of the weight average molecular weight Mw measured by gel permeation chromatography and the number average molecular weight Mn is 1.0-8.0. object.