JP2018095861A - Viscosity index improver for lubricant and lubricant composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lubricant additive having high base oil solubility, viscosity index improver property, and shear stability, and a lubricant composition having viscosity index and shear stability in excellent balance.SOLUTION: In a viscosity index improver for a lubricant containing a solid matter (S), the viscosity index improver for a lubricant is characterized by that the solid matter (S) satisfies the following condition (I) and contains a graft copolymer (C), the graft copolymer (C) being composed of a precursor polymer (A) and a graft part derived from a polymer (B) which is different from the polymer (A). Condition (I): in an infrared absorption spectroscopy measurement of a cross-section passing a central part (x) of the solid matter (S) to one point (z) on its surface which gives the shortest distance to the surface, and a middle point (y) thereof, an absorbance (Abs) of each point satisfies the following relations: X≥0.01Y≥0.01Z≥0.01, and X<Y<Z, wherein X is a value of Abs(key band of B)/Abs(key band of A) at (x), Y is a value of Abs(key band of B)/Abs(key band of A) at (y), and Z is a value of Abs(key band of B)/Abs(key band of A) at (z).SELECTED DRAWING: None

Description

  The present invention relates to a viscosity index improver for a lubricating oil having high viscosity index improving ability and shear stability, and a lubricating oil composition to which the same is added.

  Petroleum products generally have viscosities that vary greatly with changes in temperature, and the so-called viscosity depends on temperature. Lubricating oils used as engine oil, gear oil, hydraulic oil, etc. for automobiles range from low to high temperatures. It is practically desirable that the viscosity does not change as much as possible over a wide range. Viscosity index is used as this scale, and the greater the viscosity index, the higher the stability against temperature change. Therefore, for the purpose of reducing the temperature dependence of the viscosity, a certain polymer that is soluble in a lubricating base oil such as mineral oil is used as a viscosity index improver for the lubricating oil. As such a polymer, for example, polymethacrylate (PMA) (see Patent Document 1), olefin copolymer (OCP) (see Patent Document 2), polyisobutylene (PIB) and the like are used.

  Each lubricating oil to which these polymers are added has its characteristics. For example, PMA is excellent in improving the viscosity index and has a pour point depressing action, but has a thickening effect and low shear stability. In order to improve the thickening effect, there is a method of increasing the molecular weight of PMA. However, in this case, stability against shearing force is extremely deteriorated, and a decrease in viscosity at the time of driving becomes a problem. PIB has a large thickening effect but is inferior in viscosity index improvement. OCP is inferior in viscosity index to PMA, but has a large thickening effect and excellent shear stability.

  Methods for improving the physical properties of OCP include adjusting monomer types, molar ratio, etc., changing monomer sequence such as random, block, etc., blending polymers with different compositions, ethylene / α-olefin copolymer There are methods for graft copolymerization of polar monomers, and various methods have been tried.

  For example, Patent Document 3 discloses a blend of ethylene / α-olefin copolymers having different ethylene contents, and shows that when used as a viscosity index improver of a lubricating oil, excellent low temperature characteristics can be obtained. Has been. On the other hand, other devices utilizing the characteristics of living polymerization have been made. For example, in Patent Document 4, a random copolymer of ethylene and α-olefin having a narrow molecular weight distribution and a different composition in the molecule, block copolymer Coalescence is disclosed. These copolymers have shear stability and thickening, and excellent low temperature properties, and have been shown to be suitable as viscosity index improvers.

  In this way, various attempts have been made to improve the performance. In recent years, however, the service life has been improved to improve the temperature-viscosity characteristics for the purpose of energy saving and to reduce waste lubricant (shear stability, heat-resistant oxidation). Stability) is increasing, and further improvement in performance balance is demanded for viscosity index improvers.

  As a measure for further improving the performance balance, it is conceivable to combine an ethylene / α-olefin copolymer having excellent viscosity and heat resistance and a poly (meth) acrylate having excellent temperature / viscosity characteristics. A graft copolymer obtained by reacting (meth) acrylate in the presence of a radical initiator is disclosed. However, it is difficult to obtain a sufficient reaction rate in the radical grafting reaction, and the resulting graft product contains a large amount of unmodified polyolefin and (meth) acrylate homopolymers, so the amount of active ingredients is small and significant. No performance improvement can be expected.

  As a method for increasing the content of the graft copolymer, a method is conceivable in which a graft copolymer is obtained by copolymerizing a macromonomer having a functional group having radical polymerizability to a polyolefin chain with (meth) acrylate. As a method for producing a polyolefin macromonomer for synthesizing such a graft copolymer, for example, Patent Document 6 discloses that a polymerized acryloyl group or methacryloyl group is attached to the end of polyethylene synthesized by using a living polymerization method. The method of introducing is described.

  In the above-described method using living polymerization, only one polymer can be obtained from one catalytic activity point. However, from the viewpoint of productivity, it is preferable that the number of polymers obtained from one catalytic activity point is larger. Accordingly, it is difficult to say that the use of living polymerization is economically satisfactory in view of industrial mass production. Moreover, since the method described in Patent Document 6 uses an anionic polymerization method using alkyl lithium, the polyolefin that can be produced as a macromonomer is a polyethylene having a relatively low molecular weight of about 1000 mer at the maximum, and a lubricating oil. It is difficult to apply to an ethylene / α-olefin copolymer having a molecular weight of 500 to 20,000 useful as an additive.

JP-A-7-62372 Japanese Patent Publication No.46-34508 U.S. Pat. No. 3,697,429 JP 60-35209 A JP 61-181528 A JP-A-6-329720

  The problem to be solved by the present invention is that it has a high viscosity index from the viewpoint of low fuel consumption and energy saving of automobiles and industrial machines, and is excellent in shear stability from the viewpoint of reducing waste lubricant, It is to provide a high viscosity index improver for lubricating oil.

As a result of intensive studies to solve the above problems, it has been found that a specific copolymer has excellent viscosity index improving ability and shear stability as a viscosity index improver for lubricating oil.
That is, the present invention is specified by the following [1] to [7].

[1] A viscosity index improver for lubricating oil containing a solid (S), wherein the solid (S) satisfies the following requirement (I) and contains a graft copolymer (C), C) is a viscosity index improver for lubricating oils having a precursor polymer (A) and a graft part derived from a polymer (B) different from (A).
Requirement (I): In the infrared absorption spectroscopic measurement of the cross section passing through one point (z) and the middle point (y) of the surface that is the shortest distance from the center (x) to the surface of the solid (S), Absorbance (Abs) at a point satisfies the following relationship.
X ≧ 0.01
Y ≧ 0.01
Z ≧ 0.01
and,
X <Y <Z
However,
X is the value of Abs (B key band) / Abs (A key band) in (x) Y is the value of Abs (B key band) / Abs (A key band) in (y) Z is Value of Abs (B key band) / Abs (A key band) in (z)

[2] The viscosity index improver for lubricating oil according to [1], wherein the solid (S) is particles having an average particle diameter of 0.0001 mm to 1000 mm.
[3] Graft, wherein the precursor polymer (A) constituting the graft copolymer (C) is a polymer composed of one or more α-olefins selected from α-olefins having 2 to 18 carbon atoms. The viscosity index improver for lubricating oils according to [1] or [2], which is a copolymer (C).
[4] The solid (S) is obtained by graft-polymerizing a monomer having an ethylenically unsaturated group and a polar functional group in the same molecule from the surface of the precursor polymer (A) particles. The viscosity index improver for lubricating oils according to any one of [1] to [3].
[5] The viscosity index for lubricating oil according to any one of [1] to [4], wherein the polymer (B) includes a polymer of a monomer having an ethylenically unsaturated group and a polar functional group in the same molecule. Improver.
[6] Improvement in viscosity index for lubricating oil according to any one of [1] to [5], wherein the grafting rate (%) represented by the following formula is 1% or more and 150% or less Agent.
Grafting rate (%) = [mass of (B) / mass of (A)] × 100
[7] (i) 0.2 to 50 parts by mass of the viscosity index improver for lubricating oils according to any one of [1] to [6];
(Ii) 50 to 99.8 parts by mass of a base oil consisting of at least one selected from mineral oil, synthetic hydrocarbon oil and ester oil and having a kinematic viscosity at 100 ° C. in the range of 1 to ²⁰ mm ² / s; As needed (iii) from detergent dispersants, viscosity index improvers, antioxidants, corrosion inhibitors, antiwear agents, friction modifiers, pour point depressants, rust inhibitors, antifoaming agents and extreme pressure agents A lubricating oil composition comprising: at least one additive selected from the group consisting of:

  The viscosity index improver for lubricating oils of the present invention has superior viscosity temperature characteristics and shear stability compared to conventional viscosity index improvers for lubricating oils. Therefore, by blending with lubricating base oil and other additives such as mineral oil and α-olefin oligomer, the lubricating oil composition has high viscosity temperature characteristics, shear stability, and excellent fuel efficiency and durability. Things can be provided.

Hereinafter, the present invention will be described in detail.
The viscosity index improver for lubricating oils of the present invention comprises a solid (including a precursor polymer (A) and a graft copolymer (C) having a graft part derived from a polymer (B) different from (A) ( S) is contained. Preferably, in the viscosity index improver for lubricating oil, the solid (S) accounts for 80% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more.

  The viscosity index improver for lubricating oil of the present invention may contain components other than the solid (S) as long as the effects of the present invention are not impaired. Examples thereof include polymers conventionally used as viscosity index improvers for lubricating oils and various additives such as antioxidants.

<Solid matter (S)>
The solid (S) satisfies the following requirement (I).
Requirement (I): In the infrared absorption spectroscopic measurement of the cross section passing through one point (z) and the middle point (y) of the surface that is the shortest distance from the center (x) to the surface of the solid (S), Absorbance (Abs) at a point satisfies the following relationship.
X ≧ 0.01
Y ≧ 0.01
Z ≧ 0.01
and,
X <Y <Z
However,
X is the value of Abs (B key band) / Abs (A key band) in (x) Y is the value of Abs (B key band) / Abs (A key band) in (y) Z is Value of Abs (B key band) / Abs (A key band) in (z)

This is because the polymer (B) exists not only in (z) but also in (x) and (y).
That is, the solid (S) indicates that the polymer (B) is grafted to the central portion of the precursor polymer (A). This improves the solubility of the viscosity index improver for lubricating oil in the base oil (base oil) used for the preparation of the lubricating oil composition, which is preferable in the appearance of the resulting lubricating oil composition.
The solid (S) is preferably X ≧ 0.1, Y ≧ 0.1, Z ≧ 0.2, more preferably X ≧ 0.2, Y ≧ 0.2, Z ≧ 0.5. .

Solid (S) Shape The solid (S) is preferably in the form of particles, usually 0.0001 mm to 1000 mm, preferably 0.0001 mm to 800 mm, more preferably 0.0001 mm to 100 mm, The average particle size is particularly preferably 0.0001 mm or more and 10 mm or less.

Here, in the present invention, the average particle size of the solid (S) is determined by a laser diffraction diffraction method (when the average particle size is less than 1 mm) or a classification method using a sieve (when the average particle size is 1 mm or more). Mean average particle size. By having the above average particle diameter, workability when producing a lubricating oil composition or the like is improved.
The solid (S) may be in the form of various molded products such as a bale, a film, a sheet, or a fiber in addition to a particle shape such as a powder or a pellet.

Precursor polymer (A)
The precursor polymer (A) constituting the graft copolymer (C) according to the present invention is preferably a polyolefin, and specifically, one or more kinds of α selected from α-olefins having 2 to 18 carbon atoms. -A polymer comprising an olefin is employed. In the present specification, a polymer composed of one or more α-olefins selected from α-olefins having 2 to 18 carbon atoms is referred to as “polyolefin resin” or simply “polyolefin”. There is.

  Examples of the polymer consisting of one or more α-olefins selected from α-olefins having 2 to 18 carbon atoms include ethylene, propylene, butene-1, pentene-1, 2-methylbutene-1, 3 -Methylbutene-1, hexene-1, 3-methylpentene-1, 4-methylpentene-1, 3,3-dimethylbutene-1, heptene-1, methylhexene-1, dimethylpentene-1, trimethylbutene-1 Ethylpentene-1, octene-1, methylpentene-1, dimethylhexene-1, trimethylpentene-1, ethylhexene-1, methylethylpentene-1, diethylbutene-1, propylpentene-1, decene-1, Methylnonene-1, dimethyloctene-1, trimethylheptene-1, ethyloctene-1, methylethylhept Mention may be made of homopolymers or copolymers of α-olefins such as ten-1, diethylhexene-1, dodecene-1, and hexadodecene-1.

  Among these, as a preferred polymer, a polymer having ethylene as a main component, a polymer having propylene as a main component, a polymer having butene as a main component, a polymer having 4-methylpentene-1 as a main component, Ethylene / propylene random copolymer, ethylene / butene random copolymer, propylene / butene random copolymer, ethylene / propylene / butene random copolymer, 4-methylpentene-1 and propylene random copolymer, 4- Random copolymer of methylpentene-1 and hexene-1, random copolymer of 4-methylpentene-1 and decene-1, random copolymer of 4-methylpentene-1 and tetradecene, 4-methylpentene -1 and hexadecene-1 random copolymer, 4-methylpentene-1 and octadecene-1 random copolymer Body, and a random copolymer of 4-methylpentene-1 and hexadecene-1 and octadecene-1, and the like.

  The polymer may be a polymer mainly composed of a cyclic olefin, a non-conjugated diene, and an aromatic olefin. These olefins may be used alone or in combination of two or more. The content of the olefin is usually 50 mol% or less, preferably 40 mol% or less, more preferably 30 mol% or less. In the present invention, in addition to ethylene, propylene, 1-butene, 4-methyl-1-pentene, 3-methyl-1-butene, 1-hexene, 1-octene, etc., tetracyclododecene, norbornene, styrene A homopolymer or a copolymer can be preferably used. As the third component, for example, an ethylene / propylene / nonconjugated diene copolymer using a nonconjugated diene such as 5-ethylidene norbornene, 5-methylnorbornene, 5-vinylnorbornene, dicyclopentadiene, 1,4-pentadiene, etc. Rubber (EPDM) or the like is also preferably used. These can be used singly or in combination of several kinds.

The polymer according to the present invention can be used for both an isotactic structure and a syndiotactic structure, and there is no particular limitation on stereoregularity.
When using polyolefin as a precursor polymer (A), as long as the property is not impaired, well-known materials other than polyolefin can be contained arbitrarily. In this case, the blending amount of the known material is usually 20% by mass or less, preferably 10% by mass or less.

  Examples of resins other than polyolefin that can be used as the precursor polymer (A) include ethylene / polar group-containing vinyl copolymers, polystyrene, polyamide, acrylic resins, polyphenylene sulfide resins, polyether ether ketone resins, polyester resins, polysulfones, Examples include polyphenylene oxide, polyimide, polyetherimide, acrylonitrile / butadiene / styrene copolymer (ABS), conjugated diene rubber, styrene rubber, phenol resin, melamine resin, silicone resin, and epoxy resin. These resins may contain one kind or two or more kinds, and are preferably styrene-based rubbers, specifically, styrene-butadiene-styrene-based SBS rubber, styrene-butadiene-butylene-styrene-based SBBS rubber. Styrene / ethylene / butylene / styrene-based SEBS rubber, and the like.

Precursor polymer (A) shape The precursor polymer (A) according to the present invention is preferably in the form of particles, usually 0.0001 mm to 1000 mm, preferably 0.0001 mm to 800 mm, more preferably 0. The average particle diameter is 0.0001 mm to 100 mm, particularly preferably 0.0001 mm to 10 mm.

Here, in the present invention, the average particle diameter of the precursor polymer (A) can be measured by the method described in the section “Shape of Solid (S)”.
The precursor polymer (A) according to the present invention may be in the form of particles such as powder and pellets, but also in the form of veils, films, sheets, fibers, and the like, and polymers having shapes obtained from various molding processes can be used. . Among these, pellets and veils are preferable from the viewpoint of work efficiency.
The shape of the precursor polymer (A) is usually maintained in the solid (S) containing the graft copolymer (C).

  When the precursor polymer (A) according to the present invention is a molded product, it is usually 0.0001 mm to 1000 mm, preferably 0.0001 mm to 800 mm, more preferably 0.0001 mm to 100 mm, and particularly preferably 0.00. It has an average thickness or diameter of 0001 mm to 10 mm. As the molding method, any known method can be used. Specifically, it can be produced by injection molding, blow molding, press molding, calendar molding, extrusion molding, stamping molding, or the like. In extrusion molding, a sheet or film (unstretched), a pipe, a tube, an electric wire and the like can be formed. In particular, an injection molding method, a press molding method, and an extrusion molding method are preferable.

  For the stretched film, an extruded sheet or an extruded film (unstretched) as described above can be produced, for example, a tenter method (longitudinal and transverse stretching or transverse and longitudinal stretching), simultaneous biaxial stretching method, or uniaxial stretching method.

  Examples of the fibers include polyolefin fibers, wholly aromatic polyamide fibers, aliphatic polyamide fibers, polyester fibers, cellulose fibers, and carbon fibers. Furthermore, what decomposed | disassembled the plant into the fiber form is mentioned.

Polymer (B)
The polymer (B) constituting the graft part of the graft copolymer (C) contained in the solid (S) according to the present invention is a polymer different from the precursor polymer (A). The graft copolymer (C) according to the present invention is obtained by graft polymerization of a monomer having an ethylenically unsaturated group and a polar functional group in the same molecule from the surface of the precursor polymer (A). That is, the polymer (B) preferably contains a polymer of a monomer having an ethylenically unsaturated group and a polar functional group in the same molecule.

  Examples of the monomer having an ethylenically unsaturated group and a polar functional group in the same molecule according to the present invention include a hydroxyl group-containing ethylenically unsaturated compound, an amino group-containing ethylenically unsaturated compound, and an epoxy group-containing ethylenically unsaturated compound. , Nitrogen-containing aromatic vinyl compounds, lactam structure-containing ethylenically unsaturated compounds, unsaturated carboxylic acids and derivatives thereof, vinyl ester compounds, nitrile group-containing unsaturated compounds, vinyl chloride and vinylsilane compounds. These can be used singly or in combination of two or more.

  Among these, specific examples of the hydroxyl group-containing ethylenically unsaturated compound include hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxy- Propyl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate, glycerin mono (meth) acrylate, pentaerythritol mono (meth) acrylate, trimethylolpropane mono (meth) acrylate, tetramethylol ethane mono (meth) (Meth) acrylic acid esters such as acrylate, butanediol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, 2- (6-hydroxyhexanoyloxy) ethyl acrylate; 0-undecen-1-ol, 1-octen-3-ol, 2-methanol norbornene, hydroxystyrene, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, N-methylol acrylamide, 2- (meth) acryloyloxyethyl acid phosphate, Examples include glycerin monoallyl ether, allyl alcohol, allyloxyethanol, 2-butene-1,4-diol, and glycerin monoalcohol. Among these, hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate are preferable.

  The amino group-containing ethylenically unsaturated compound is a compound having an ethylenic double bond and an amino group, and as such a compound, a vinyl-based compound having at least one amino group and a substituted amino group represented by the following formula: A monomer can be mentioned.

上記式中、Ｒ⁶は水素原子、メチル基またはエチル基を示し、Ｒ⁷は、水素原子、炭素原子数が１〜１２、好ましくは１〜８のアルキル基または炭素原子数が６〜１２、好ましくは６〜８のシクロアルキル基である。なお上記のアルキル基、シクロアルキル基は、さらに置換基を有してもよい。

In the above formula, R ⁶ represents a hydrogen atom, a methyl group or an ethyl group, and R ⁷ represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms or 6 to 12 carbon atoms, Preferably it is a 6-8 cycloalkyl group. The above alkyl group and cycloalkyl group may further have a substituent.

  Specific examples of such amino group-containing ethylenically unsaturated compounds include aminoethyl (meth) acrylate, propylaminoethyl (meth) acrylate, 2- (dimethylamino) ethyl methacrylate, and aminopropyl (meth) acrylate. Alkyl ester derivatives of acrylic acid or methacrylic acid such as phenylaminoethyl methacrylate and cyclohexylaminoethyl methacrylate; vinylamine derivatives such as N-vinyldiethylamine and N-acetylvinylamine; allylamine, methacrylamine, N- Allylamine derivatives such as methyl (meth) acrylamine; (meth) acrylamide, N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, and N, N-dimethylaminopropyl (meth) Aminostyrene such as p- aminostyrene; acrylamide derivatives such as acrylamide 6-aminohexyl succinimide and 2-aminoethyl succinimide and the like. Among these, aminoethyl (meth) acrylate, propylaminoethyl (meth) acrylate, (meth) acrylamide, and N, N-dimethyl (meth) acrylamide are preferable.

The epoxy group-containing ethylenically unsaturated compound is a monomer having at least one polymerizable unsaturated bond and epoxy group in one molecule. Specific examples of such epoxy group-containing ethylenically unsaturated compounds include glycidyl acrylate, glycidyl methacrylate, mono and diglycidyl esters of maleic acid, mono and diglycidyl esters of fumaric acid, mono and diglycidyl esters of crotonic acid, tetrahydro Mono and diglycidyl esters of phthalic acid, mono and glycidyl esters of itaconic acid, mono and diglycidyl esters of butenetricarboxylic acid, mono and diglycidyl esters of citraconic acid, endo-cis-bicyclo [2.2.1] hept- Mono- and diglycidyl esters of 5-ene-2,3-dicarboxylic acid (Nadic acid ^™ ), endo-cis-bicyclo [2.2.1] hept-5-en-2-methyl-2,3-dicarboxylic acid (Methyl nadic acid ^{T M} ) mono- and diglycidyl esters, mono- and glycidyl esters of dicarboxylic acids such as mono- and glycidyl esters of allyl succinic acid (1 to 12 carbon atoms of the alkyl group in the case of mono-glycidyl esters), alkyls of p-styrene carboxylic acid Glycidyl ester, allyl glycidyl ether, 2-methylallyl glycidyl ether, styrene-p-glycidyl ether, 3,4-epoxy-1-butene, 3,4-epoxy-3-methyl-1-butene, 3,4-epoxy Examples include -1-pentene, 3,4-epoxy-3-methyl-1-pentene, 5,6-epoxy-1-hexene, and vinylcyclohexene monoxide. Among these, glycidyl (meth) acrylate and allyl glycidyl ether are preferable.

  Specific examples of the nitrogen-containing aromatic vinyl compound include 4-vinylpyridine, 2-vinylpyridine, 5-ethyl-2-vinylpyridine, 2-methyl-5-vinylpyridine, 2-isopropenylpyridine, and 2-vinylquinoline. , 3-vinylisoquinoline, N-vinylcarbazole and the like.

Specific examples of the lactam structure-containing ethylenically unsaturated compound include N-vinylpyrrolidone.
Specific examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, nadic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, norbornene dicarboxylic acid, bicyclo [2,2 , 1] Various unsaturated carboxylic acids such as hept-2-ene-5,6-dicarboxylic acid.

  Examples of the unsaturated carboxylic acid derivative include —C (═O) —X (where X is an atom selected from Group 15 to 17 elements) such as acid anhydrides, acid halides, amides, imides, and esters of the above unsaturated carboxylic acids. ), And specific examples thereof include maleenyl chloride, maleenylimide, maleic anhydride, itaconic anhydride, citraconic anhydride, tetrahydrophthalic anhydride, bicyclo [2,2,1] hept-2 -Ene-5,6-dicarboxylic anhydride, dimethyl maleate, monomethyl maleate, diethyl maleate, diethyl fumarate, dimethyl itaconate, diethyl citraconic acid, dimethyl tetrahydrophthalate, bicyclo [2,2,1] hept 2-ene-5,6-dicarboxylate dimethyl, acrylic acid, methyl acrylate, ethyl acrylate Propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, acryloyl chloride, acrylamide, maleenylimide, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, glycidyl acrylate, aminoethyl acrylate, aminopropyl acrylate, tetrahydrofurfuryl acrylate , Methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, methacryloyl chloride, methacrylamide, hydroxyethyl methacrylate, hydroxypropyl methacrylate, glycidyl methacrylate, aminoethyl methacrylate, methacryl Aminopropyl acid, tetrahydrofurfuryl methacrylate, etc. Door can be.

  Among the unsaturated carboxylic acids and derivatives thereof, acrylic acid, methyl acrylate, ethyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, acrylamide, methacrylamide, maleic anhydride, hydroxyethyl acrylate, hydroxyethyl methacrylate Glycidyl methacrylate, aminopropyl methacrylate, tetrahydrofurfuryl acrylate, and tetrahydrofurfuryl methacrylate are preferred. Among these, (meth) acrylic acid, maleic anhydride, methyl (meth) acrylate, ethyl (meth) acrylate, and tetrahydrofurfuryl (meth) acrylate are particularly preferable.

  Examples of vinyl ester compounds include vinyl acetate, vinyl propionate, vinyl n-butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caproate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate, p -(T-butyl) vinyl benzoate, vinyl salicylate, vinyl cyclohexanecarboxylate, etc. can be mentioned.

  Examples of the nitrile group-containing unsaturated compound include (meth) acrylonitrile, fumaronitrile, allyl cyanide, cyanoethyl acrylate and the like. Among these, (meth) acrylonitrile is preferable.

In addition to these compounds, epoxy group-containing ethylenically unsaturated compounds such as allyl glycidyl ether, and vinyl silane compounds are also preferred.
In the present specification, hereinafter, a monomer having an ethylenically unsaturated group and a polar functional group in the same molecule may be referred to as “graft monomer” or simply “monomer”.

  In the graft copolymer (C), the grafting rate of the monomer having a grafted ethylenically unsaturated group and a polar functional group in the same molecule is 1% or more, preferably 3% or more, more preferably 5% or more, More preferably, it is 8% or more. There is no upper limit to the amount of the monomer having a grafted ethylenically unsaturated group and a polar functional group in the same molecule, but even if grafting exceeds 150%, there is no corresponding effect, while the shape of the particles Therefore, it is preferable not to exceed 150%, more preferably not to exceed 100%, and still more preferably not to exceed 50%.

  Here, when two or more of the above-mentioned “monomers having an ethylenically unsaturated group and a polar functional group in the same molecule” are used, the total grafting rate is preferably 1% or more. It is more preferable that the total grafting ratio is within the above preferable range.

The grafting rate can be determined by the following formula. In addition, when a mass increase is slight, it can obtain | require by < ¹ > H-NMR measurement.
Grafting rate (%) = [mass of (B) / mass of (A)] × 100
Here, the mass of (B) is obtained as [mass of (C) −mass of (A)].

The other monomer graft copolymer (C) includes a monomer having an ethylenically unsaturated group in addition to a monomer having an ethylenically unsaturated group and a polar functional group in the same molecule. A monomer other than “a monomer having an ethylenically unsaturated group and a polar functional group in the same molecule” (hereinafter “other monomer”) may be further included in a grafted state. In this embodiment, the graft copolymer (C) includes a repeating unit derived from a monomer having an ethylenically unsaturated group and a polar functional group in the same molecule with respect to the precursor polymer, and derived from “other monomers”. It has a structure in which a repeating unit is introduced.

  Here, examples of “other monomers” that can be optionally grafted to the precursor polymer include aromatic vinyl compounds other than the “nitrogen-containing aromatic vinyl compound”.

  Here, examples of the aromatic vinyl compound other than the “nitrogen-containing aromatic vinyl compound” include compounds represented by the following formulae.

上記式において、Ｒ⁸ およびＲ⁹ は、互いに同一でも異なっていてもよく、水素原子または炭素原子数が１〜３のアルキル基を示し、具体的には、メチル基、エチル基、プロピル基およびイソプロピル基を挙げることができる。また、Ｒ¹⁰はそれぞれ独立に炭素原子数が１〜３の炭化水素基またはハロゲン原子を示し、具体的には、メチル基、エチル基、プロピル基およびイソプロピル基並びに塩素原子、臭素原子およびヨウ素原子などを挙げることができる。また、ｎは通常は０〜５、好ましくは１〜５の整数を表す。

In the above formula, R ⁸ and R ⁹ may be the same or different from each other, and represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, specifically, a methyl group, an ethyl group, a propyl group, and Mention may be made of the isopropyl group. R ¹⁰ independently represents a hydrocarbon group having 1 to 3 carbon atoms or a halogen atom, and specifically includes a methyl group, an ethyl group, a propyl group, an isopropyl group, a chlorine atom, a bromine atom, and an iodine atom. And so on. N represents an integer of usually 0 to 5, preferably 1 to 5.

  Specific examples of such aromatic vinyl compounds include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, p-chlorostyrene, m-chlorostyrene and p-chloro. Examples include methylstyrene, and among these, styrene is preferable.

<Method for producing solid (S)>
The production method for obtaining the solid (S) according to the present invention is not particularly limited as long as the obtained solid (S) satisfies the above-described requirements.

  As a suitable production method for obtaining the solid (S) containing the graft copolymer (C), as described in Patent Document 2 and Non-Patent Documents 1 and 2, an alkyl boron is reacted with oxygen to form a peroxide. And graft polymerization to a polymer utilizing the initiator.

Solvents used for the grafting reaction include water, aromatic hydrocarbon solvents such as benzene, toluene and xylene, aliphatic hydrocarbon solvents such as pentane, hexane, heptane, octane, nonane and decane, cyclohexane and methyl. Cycloaliphatic hydrocarbon solvents such as cyclohexane and decahydronaphthalene, chlorinated hydrocarbon solvents such as chlorobenzene, dichlorobenzene, trichlorobenzene, methylene chloride, chloroform, carbon tetrachloride, tetrachloroethylene, 1-methyl- 2-pyrrolidone, ethylene carbonate, propylene carbonate, γ-butyrolactone, N-methyl-2-pyrrolidone, propylene glycol monomethyl ether acetate, tributyl acetylcitrate, 2,4-pentadiene, dimethyl sulfoxide, n-alkyl azides , Ketones such as 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, 3-methoxy-3-methyl-1-butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, acetophenone, benzophenone, cyclohexanone Benzyl alcohol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-ethyl-1-hexanol, normal propyl alcohol, isopropyl alcohol, ethanol, methanol, etc. And alcohols such as ethyl ether, ethylene glycol monomethyl ether, anisole, phenyl ether, dioxane, and tetrahydrofuran; and esters such as ethyl acetate and butyl acetate. Of these, water is preferred.
The above solvents may be used alone or in combination of two or more.

  Moreover, there is no restriction | limiting in particular about the contact method and contact order of a precursor polymer (A), the said graft monomer, and the said alkyl boron, A various method is employable. Further, the precursor polymer may be impregnated with a graft monomer or alkyl boron in advance. Furthermore, in order to adjust the molecular weight of the graft polymer, a known chain transfer agent can be used in combination.

  On the other hand, regarding the order of contact with oxygen, since it is a reaction starting point, a method in which alkyl boron is introduced and then contacted with oxygen is preferable. Moreover, it is preferable that the grafting monomer to be used is previously purged with oxygen by a nitrogen aeration treatment.

  In addition, known additives, for example, antioxidants such as hindered phenol compounds, process stabilizers, heat stabilizers, heat aging agents, weather stabilizers, antistatic agents, slips as long as they do not interfere with the object of the present invention Radical scavengers represented by nitroxy radicals such as anti-blocking agents, anti-blocking agents, anti-fogging agents, lubricants, pigments, dyes, nucleating agents, plasticizers, hydrochloric acid absorbents, flame retardants, anti-blooming agents, piperidines, Various additives such as known softeners, tackifiers, processing aids, adhesion promoters, fillers such as carbon fibers, glass fibers and whiskers can be used in combination. Also, other polymer compounds can be blended in small amounts without departing from the spirit of the present invention.

  The graft reaction as described above can be used without particular limitation as long as it is an apparatus capable of mixing and heating. For example, both vertical and horizontal reactors can be used. Specific examples include a fluidized bed, a moving bed, a loop reactor, a horizontal reactor with a stirring blade, a vertical reactor with a stirring blade, a rotating drum, and the like. Also, a multi-shaft / spinning / revolution combined mixer such as a planetary mixer, a kneader, a paddle dryer, a Henschel mixer, a static mixer, a V blender, a tumbler, and a nauter mixer can be used.

  As defined in the present invention, the graft copolymer (C) is washed with a solvent capable of dissolving a monomer or homopolymer having an unreacted ethylenically unsaturated group and a polar functional group in the same molecule. It is possible to fit within the range.

Examples of such solvents include water, aliphatic hydrocarbons such as hexane, heptane, decane, and cyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene; acetone, methyl ethyl ketone, methyl isobutyl ketone, acetophenone, benzophenone, Ketones such as cyclohexanone; benzyl alcohol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-ethyl-1-hexanol, normal propyl alcohol, isopropyl alcohol, Alcohols such as ethanol and methanol; ethers such as ethyl ether, ethylene glycol monomethyl ether, anisole, phenyl ether, dioxane and tetrahydrofuran; esthetics such as ethyl acetate and butyl acetate And a mixed solvent composed of two or more of these. Preferred are ketones and alcohols, and acetone and methanol are particularly preferred. The washing temperature can be a temperature of room temperature or higher as long as the graft copolymer (C) after the grafting reaction is maintained, and preferably room temperature to 110 ° C, more preferably 40 to 100 ° C. More preferably, it is 50-80 degreeC.
Here, when the cleaning temperature is set higher than the boiling point of the cleaning solvent at atmospheric pressure, it is preferably performed in a sealed state in order to prevent volatilization of the cleaning solvent.

<Lubricating oil composition>
The lubricating oil composition of the present invention comprises:
(I) Viscosity index improver for lubricating oil containing the solid (S) 0.2 to 50 parts by weight, preferably 0.2 to 25 parts by weight, more preferably 0.25 to 10 parts by weight, particularly preferably Is 0.25 to 5 parts by mass, more preferably 0.3 to 2.5 parts by mass,
(Ii) 50 to 99.8 parts by mass of a base oil consisting of at least one selected from mineral oil, synthetic hydrocarbon oil and ester oil and having a kinematic viscosity at 100 ° C. in the range of 1 to ²⁰ mm ² / s; As needed (iii) from detergent dispersants, viscosity index improvers, antioxidants, corrosion inhibitors, antiwear agents, friction modifiers, pour point depressants, rust inhibitors, antifoaming agents and extreme pressure agents And at least one additive selected from the group consisting of:

The base oil used in the lubricating oil composition of the present invention is at least one selected from conventionally known mineral oils, synthetic hydrocarbon oils, and ester oils having a kinematic viscosity at 100 ° C. in the range of 1 to ²⁰ mm ² / s. A seed base oil is used.

  Mineral oils generally have several grades depending on the method of refining, but generally mineral oils containing 0.5 to 10% wax are used. For example, a highly refined oil having a composition mainly composed of isoparaffin having a low pour point and a high viscosity index produced by a hydrogenolysis refining method can be used.

  Examples of the synthetic hydrocarbon oil include α-olefin oligomers, alkylbenzenes, alkylnaphthalenes, and the like, and these can be used alone or in combination of two or more. Among these, as the α-olefin oligomer, a low molecular weight oligomer of at least one olefin selected from olefins having 8 to 12 carbon atoms can be used. Such an α-olefin oligomer can be produced by cationic polymerization, thermal polymerization, or radical polymerization using a Ziegler catalyst or a Lewis acid as a catalyst.

  Alkylbenzenes and alkylnaphthalenes are usually mostly dialkylbenzene or dialkylnaphthalene having an alkyl chain length of 6 to 14 carbon atoms. Such alkylbenzenes or alkylnaphthalenes are Friedel of benzene or naphthalene and olefin. Produced by kraft alkylation reaction. The alkylated olefin used in the production of alkylbenzenes or alkylnaphthalenes may be a linear or branched olefin or a combination thereof. These production methods are described, for example, in US Pat. No. 3,909,432.

  As ester oils, monoesters produced from monobasic acids and alcohols; diesters produced from dibasic acids and alcohols or diols and monobasic acids or acid mixtures; diols, triols (eg trimethylolpropane) And polyol esters produced by reacting tetraols (for example, pentaerythritol), hexaols (for example, dipentaerythritol) and the like with monobasic acids or acid mixtures. Examples of these esters include tridecyl pelargonate, di-2-ethylhexyl adipate, di-2-ethylhexyl azelate, trimethylolpropane triheptanoate, pentaerythritol tetraheptanoate and the like.

The following can be illustrated as an additive used for the lubricating oil composition of this invention, These can be used individually or in combination of 2 or more types.
Detergent / dispersant: metal sulfonate, metal phenate, metal phosphonate, succinimide and the like can be exemplified, and usually used in the range of 0 to 15% by mass.
Pour point depressant: Polymethacrylate, alkylnaphthalene and the like can be exemplified, and usually used in the range of 0 to 3% by mass.
Extreme pressure agent: Sulfur-based extreme pressure agent such as sulfides, sulfoxides, sulfones, thiophosphinates, thiocarbonates, sulfurized fats and oils, sulfurized olefins; phosphate ester, phosphite ester, phosphate ester amine salt, Illustrative are phosphoric acids such as phosphite amines; halogen compounds such as chlorinated hydrocarbons. The extreme pressure agent is used in the range of 0 to 15% by mass as necessary.
Antiwear agents: inorganic or organic molybdenum compounds such as molybdenum disulfide, organoboron compounds such as alkyl mercaptyl borate; graphite, antimony sulfide, boron compounds, polytetrafluoroethylene, and the like. An antiwear agent is used in 0-3 mass% as needed.
Antioxidant: Phenol compounds and amine compounds such as 2,6-di-tert-butyl-4-methylphenol are exemplified. An antioxidant is used in 0-3 mass% as needed.
Rust preventive agent: Various amine compounds, carboxylic acid metal salts, polyhydric alcohol esters, phosphorus compounds, sulfonates and the like. A rust preventive agent is used in 0-3 mass% as needed.
Antifoaming agents: Examples include silicone compounds such as dimethylsiloxane and silica gel dispersion, alcohol compounds and ester compounds. An antifoamer is used in 0-0.2 mass% as needed.
In addition to the above additives, a demulsifier, a colorant, an oily agent (oiliness improver), and the like can be used in the lubricating oil composition according to the present invention as necessary.

EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these. The following examples and comparative examples were evaluated by the following methods.
In the case of a sample having an infrared absorption spectroscopic measurement particle size and thickness of 0.05 mm or more, a cross-section passing through a point on the surface that is the shortest distance from the center of the sample to the surface is prepared, and then a micro infrared is manufactured by VARIAN. Using a spectroscopic method (FTS-7000 / UMA600), each measurement point was measured by a total reflection (ATR) method using a Ge crystal. The measurement range was 4000 cm ⁻¹ to 600 cm ⁻¹ , the resolution was 4 cm ⁻¹ , and the number of integrations was 128 times. From the obtained absorption spectrum, the ratio between the absorbance in the key band derived from the graft polymer and the key band derived from the precursor polymer, and the value of Abs (B key band) / Abs (A key band) were calculated.

On the other hand, in the case of a sample having a particle size and thickness of less than 0.05 mm, a cross section thin section passing through a point on the surface that is the shortest distance from the center of the sample to the surface is prepared using a microtome, and then the section is formed on a substrate. It collect | recovered on (ZnS) and measured each measurement location by AFM-IR method using the nano scale infrared spectroscopy (nanoIR2) made from ANASYS INSTRUMENTS. The measurement range was 2000 cm ⁻¹ to 900 cm ⁻¹ and the resolution was 4 cm ⁻¹ . From the obtained absorption spectrum, the ratio between the absorbance in the key band derived from the graft polymer and the key band derived from the precursor polymer, and the value of Abs (B key band) / Abs (A key band) were calculated.

Grafting rate The grafting rate was determined by the following formula.
Grafting ratio (%) = [(mass of graft copolymer−mass of precursor polymer) / (mass of precursor polymer)] × 100

MFR (g / 10 min)
In accordance with JIS K 7210, measurement was performed at a load of 10 kg and a temperature of 190 ° C.

Density was measured according to JIS K 7112.
Adjustment of Polymer Concentrate A 10 mass percent polymer solution (polymer concentrate) was prepared using Yubase-4 (manufactured by SK Lubricants).

Adjustment of blended oil Yubase-4 (manufactured by SK Lubricants) was used as a base oil, and after adding a pour point depressant (Leblanc 165, manufactured by Toho Chemical Co., Ltd.), the blending amount of the polymer concentrate was adjusted at 100 ° C. A blended sample was prepared so as to have a constant viscosity (10 mm ² / s).

The solubility of the soluble polymer in the base oil was evaluated as follows. After adjusting the polymer concentrate, the polymer was allowed to stand at room temperature for one week, and the appearance was observed.
○: No sediment or suspended matter ×: There is a sediment or suspended matter

Viscosity characteristics Kinematic viscosity and viscosity index were determined by measuring the kinematic viscosity at 100 ° C. and 40 ° C. according to the method described in JIS K2283.

Cold Cranking Simulator (CCS)
Measurements were made according to ASTM D 5293. The CCS viscosity is used for evaluation of low-temperature / starting slidability of the crankshaft. The smaller the value, the better the low-temperature characteristics of the lubricating oil.

Mini-Rotary Viscocity (MRV)
Measurements were made based on ASTM D D4684. The MR viscosity is used for evaluation for pumping the oil pump at a low temperature, and the smaller the value, the better the low temperature characteristic of the lubricating oil.

Shear Stability Index (SSI)
Measurement was performed based on JPI-5S-29-88. SSI is a measure of the loss of kinematic viscosity due to the breakage of the molecular chain of the copolymer in the lubricating oil under high shear conditions. The larger the SSI, the greater the loss of kinematic viscosity.

[Polymerization Example 1] Ethylene / propylene copolymer A 2 liter volume autoclave with a stirring blade (manufactured by SUS) sufficiently purged with nitrogen was charged with 900 ml of heptane at 23 ° C. To this autoclave, 4.5 Nl of propylene and 200 Nml of hydrogen were introduced while rotating a stirring blade and cooling with ice. Next, the autoclave was heated to 70 ° C. and further pressurized with ethylene so that the total pressure was 0.6 MPa (6 kg / cm ² ). When the internal pressure of the autoclave reached 0.6 MPa (6 kg / cm ² ), 0.3 ml of a 1.0 mmol / ml hexane solution of triisobutylaluminum was injected with nitrogen. Subsequently, 0.016 mmol of triphenylcarbenium (tetrakispentafluorophenyl) borate prepared in advance, [dimethyl (t-butyramide) (tetramethyl-η ⁵ -cyclopentadienyl) silane, in terms of B Polymerization was initiated by injecting 3 ml of a toluene solution containing 0.004 mmol of titanium dichloride into an autoclave with nitrogen. Thereafter, the temperature of the autoclave was adjusted to an internal temperature of 70 ° C. for 5 minutes, and ethylene was directly supplied so that the pressure was 0.6 MPa (6 kg / cm ² ). Five minutes after the start of polymerization, 5 ml of methanol was charged into the autoclave by a pump to stop the polymerization, and the autoclave was depressurized to atmospheric pressure. 3 liters of methanol was poured into the reaction solution with stirring. The obtained polymer containing the solvent was dried at 130 ° C. for 13 hours at 80 kPa (600 torr) to obtain 32 g of an ethylene / propylene copolymer. The same polymerization operation was performed several times to ensure the required amount. As a result of polymer analysis, MFR = 56 (g / 10 min, 190 ° C.), density 862 kg / m ³ , average particle size 4.5 mm, Mw = 7,4600, Mn = 34,700, Mw / Mn = 2 .15. The obtained ethylene / propylene copolymer was pelletized using an extruder and a pelletizer. The pellet physical properties were MFR = 56 (g / 10 min, 190 ° C.), density 862 kg / m ³ , and average particle size 4.5 mm.

[Example 1 (polymerization example 2)]
As the precursor polymer, the pellet-shaped ethylene / propylene copolymer obtained in Polymerization Example 1 was used. The obtained pellet shape was also used, and methyl methacrylate (MMA) was used as a graft monomer.

  First, 100 g of ethylene / propylene copolymer pellets were immersed in a tributyl boron (TBB) / n-butanol solution prepared in advance at a concentration of 5 wt% under a nitrogen atmosphere for one day, and then filtered TBB-impregnated pellets were prepared. . The equivalent amount of impregnated TBB was 1.4 g.

In a nitrogen atmosphere, 500 g of pure water was charged into a 2 L separable flask, and nitrogen was bubbled through the solution (nitrogen bubbling) at a rate of 2 L per minute for 30 minutes with stirring, and then the TBB-impregnated pellets prepared above The liquid temperature was adjusted to 40 ° C. Subsequently, 30 mL of air was bubbled into the liquid using a syringe under a nitrogen atmosphere with stirring. After 30 minutes, 24.7 g of MMA and 0.26 g of 3-mercaptopropionic acid as a chain transfer agent were charged and reacted for 2 hours. After completion of the reaction, air was bubbled into the liquid at a rate of 2 L / min for 5 minutes. Thereafter, the polymer was filtered with a glass filter, sufficiently washed with acetone, and vacuum-dried at 60 ° C. for 8 hours. A pellet-shaped graft copolymer similar to the precursor polymer was obtained.
Table 1 summarizes the amount of each raw material charged, the grafting conditions, and the properties of the graft copolymer.

[Comparative Example 1 (Polymerization Example 3)]
The pellet-shaped ethylene / propylene copolymer obtained in Polymerization Example 1 was used as the precursor polymer. Further, methyl methacrylate (MMA) was used as a graft monomer.
Under a nitrogen atmosphere, 1000 g of pure water and 100 g of ethylene / propylene copolymer pellets were charged into a 2 L separable flask, and the liquid temperature was adjusted to 40 ° C. Thereafter, nitrogen was bubbled through the solution (nitrogen bubbling) at a rate of 2 L / min for 30 minutes with stirring, and then 0.2 g of tributylboron (TBB) was charged. Subsequently, 120 mL of air was bubbled into the liquid using a syringe under a nitrogen atmosphere with stirring. After 30 minutes, 25.7 g of MMA was charged and reacted for 2 hours. After completion of the reaction, air was bubbled into the liquid at a rate of 2 L / min for 5 minutes. Thereafter, the polymer was filtered with a glass filter, sufficiently washed with acetone, and vacuum-dried at 60 ° C. for 8 hours. A pellet-shaped graft copolymer similar to the precursor polymer was obtained.

[Comparative Example 2 (Polymerization Example 4)]
The pellet-shaped ethylene / propylene copolymer obtained in Polymerization Example 1 was used as the precursor polymer. Further, MMA was used as a graft monomer.

  First, 100 g of ethylene / propylene copolymer pellets were immersed in MMA for 6 hours under a nitrogen atmosphere, and then filtered MMA-impregnated pellets were prepared. The equivalent amount of MMA impregnated was 24.9 g.

  Under a nitrogen atmosphere, 500 g of pure water and the MMA-impregnated pellet prepared above were charged into a 2 L separable flask, and the liquid temperature was adjusted to 40 ° C. Thereafter, nitrogen was bubbled through the liquid (nitrogen bubbling) at a rate of 2 L / min for 30 minutes with stirring, and 0.053 g of tributylboron (TBB) was charged. Subsequently, under a nitrogen atmosphere with stirring, 30 mL of air was bubbled into the liquid using a syringe and reacted for 2 hours. After completion of the reaction, air was bubbled into the liquid at a rate of 2 L / min for 5 minutes.

Thereafter, the polymer was filtered with a glass filter, sufficiently washed with acetone, and vacuum-dried at 60 ° C. for 8 hours. A pellet-shaped graft copolymer similar to the precursor polymer was obtained.
Table 1 summarizes the amount of each raw material charged, the grafting conditions, and the properties of the graft copolymer.

[Example 2]
After using Yubase-4 (manufactured by SK Lubricants) as a base oil and preparing a 10 mass percent solution (polymer concentrate) of the graft copolymer (C) in the form of pellets obtained in Polymerization Example 2, Yubase-4 and flow A point depressant (Lebran 165, manufactured by Toho Chemical Co., Ltd.) was blended to prepare a lubricating oil. The performance of the obtained lubricating oil was evaluated. Table 2 shows the blending ratio and the evaluation results.

[Comparative Example 3]
A lubricating oil composition was prepared and evaluated in the same manner as in Example 1 except that the graft copolymer in pellet form obtained in Polymerization Example 3 was used. Table 2 shows the blending ratio and the evaluation results.

[Comparative Example 4]
A lubricating oil composition was prepared and evaluated in the same manner as in Example 1 except that the ethylene / propylene copolymer pellet polymer obtained in Polymerization Example 1 was used. Table 2 shows the blending ratio and the evaluation results.

[Comparative Example 5]
A lubricating oil composition was prepared and evaluated in the same manner as in Example 1 except that the graft copolymer in pellet form obtained in Polymerization Example 4 was used. Table 2 shows the blending ratio and the evaluation results.

[Contrast between Example and Comparative Example]
The lubricating oil composition of Example 2 using the graft copolymer obtained in Example 1 was 40 ° C. compared to the lubricating oil composition [Comparative Example 3] using an ethylene / propylene copolymer (Polymerization Example 1). It has excellent properties of low kinematic viscosity and high viscosity index. In addition, the lubricating oil composition using the graft copolymer (Polymer 3 and Polymer 4) that does not satisfy the absorbance (Abs) requirement of the graft copolymer (C) has an evaluation of x (precipitate or float). ) Was inferior. It is suggested that the polymers 3 and 4 have poor solubility in the base oil.

  The viscosity index improver for lubricating oils of the present invention is superior in the balance between viscosity index improving ability and shear stability compared to conventional viscosity indexes, and as a lubricant additive suitable for fuel saving and long drain interval. Is available.

Claims (7)

A viscosity index improver for lubricating oil containing a solid (S), wherein the solid (S) satisfies the following requirement (I) and contains a graft copolymer (C), the graft copolymer (C) being Viscosity index improver for lubricating oil, comprising: a precursor polymer (A); and a graft part derived from a polymer (B) different from (A).
Requirement (I)
In the infrared absorption spectroscopic measurement of the cross-section passing through one point (z) and the middle point (y) of the surface having the shortest distance from the center (x) to the surface of the solid (S), the absorbance (Abs) at each of the above points ) Satisfies the following relationship.
X ≧ 0.01
Y ≧ 0.01
Z ≧ 0.01
and,
X <Y <Z
However,
X is the value of Abs (B key band) / Abs (A key band) in (x) Y is the value of Abs (B key band) / Abs (A key band) in (y) Z is Value of Abs (B key band) / Abs (A key band) in (z)   The viscosity index improver for lubricating oil according to claim 1, wherein the solid (S) is a particle having an average particle size of 0.0001 mm to 1000 mm.   The precursor polymer (A) constituting the graft copolymer (C) is a polymer composed of one or more α-olefins selected from α-olefins having 2 to 18 carbon atoms. The viscosity index improver for lubricating oil according to claim 1 or 2.   The solid (S) is obtained by graft-polymerizing a monomer having an ethylenically unsaturated group and a polar functional group in the same molecule from the surface of the precursor polymer (A), which is a solid, from one or more types. The viscosity index improver for lubricating oil according to any one of claims 1 to 3.   The viscosity index improver for lubricating oil according to any one of claims 1 to 4, wherein the polymer (B) contains a polymer of a monomer having an ethylenically unsaturated group and a polar functional group in the same molecule. The viscosity index improver for lubricating oil according to any one of claims 1 to 5, wherein a grafting rate (%) represented by the following formula is 1% or more and 150% or less.
Grafting rate (%) = [mass of (B) / mass of (A)] × 100 (I) 0.2 to 50 parts by mass of the viscosity index improver for lubricating oil according to any one of claims 1 to 6;
(Ii) 50 to 99.8 parts by mass of a base oil consisting of at least one selected from mineral oil, synthetic hydrocarbon oil and ester oil and having a kinematic viscosity at 100 ° C. in the range of 1 to ²⁰ mm ² / s; As needed (iii) from detergent dispersants, viscosity index improvers, antioxidants, corrosion inhibitors, antiwear agents, friction modifiers, pour point depressants, rust inhibitors, antifoaming agents and extreme pressure agents A lubricating oil composition comprising: at least one additive selected from the group consisting of: