Viscosity index improving agent composition and lubricating oil composition

Abstract

The present invention provides a lubricating oil composition that is highly effective in suppressing the amount of coking deposits and has excellent fuel efficiency, making it suitable for use in internal combustion engines. [Solution] A viscosity index improver composition comprising a copolymer (A) containing, as essential constituent monomers, a polyolefin monomer (a) represented by general formula (1), an alkyl (meth)acrylate (b) having a linear alkyl group having 1 to 4 carbon atoms, and an alkyl (meth)acrylate (c2) having a linear or branched alkyl group having 5 to 10 carbon atoms, wherein the proportion of monomer (c) in the monomers constituting copolymer (A) is 60% by weight or less, based on the total weight of the monomers constituting copolymer (A).

Description

[Technical Field]

[0001] The present invention relates to viscosity index improving agent compositions and lubricating oil compositions. [Background technology]

[0002] In recent years, with global warming becoming a worldwide problem, there has been a strong demand to reduce CO2 emissions from automobile exhaust. To reduce automobile CO2 emissions, it is increasingly important to enable longer driving distances with limited fuel, in other words, to improve the fuel efficiency of automobiles. It is known that improving the fuel efficiency of automobiles is greatly influenced not only by improvements to the hardware of the internal combustion engine, but also by improvements to the engine oil that lubricates it. Known technologies for improving fuel efficiency in engine oil include the use of viscosity index improvers having a specific structure, combined in specific amounts (see, for example, Patent Document 1), and the use of polymethacrylate (PMA)-based viscosity index improvers (see, for example, Patent Document 2).

[0003] Furthermore, exhaust gas regulations for internal combustion engines are becoming stricter year by year, and technologies capable of meeting these demands are being considered for lubricating oil compositions used in internal combustion engines. In general, internal combustion engines have seen improvements in fuel injection technology and the introduction of exhaust gas purification devices called DPFs (Diesel Particulate Filters) or GPFs (Gasoline Particulate Filters) to purify soot and ash contained in exhaust gases in order to meet exhaust gas regulations. However, if fuel injection technology is not optimized, exhaust gases will not be purified. Furthermore, even if filters such as DPFs are installed, problems such as filter clogging can occur due to the emission of soot and particulate matter (PM) contained in the exhaust gas. It is believed that components derived from lubricating oil contribute to the emission of PM, which is one of the causes of such filter clogging (approximately 30% of emitted PM is due to components derived from lubricating oil), and lubricating oils that comply with exhaust gas regulations are required. A known technology for reducing particulate matter emissions from engine oil involves blending the engine oil with a specific amount of metal components (see, for example, Patent Document 3). However, this technology does not provide sufficient fuel efficiency. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6223231 [Patent Document 2] Japanese Patent Publication No. 2016-65222 [Patent Document 3] Japanese Patent Publication No. 2023-174583 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Generally, engine oils using polymethacrylate (PMA) viscosity index improvers offer excellent fuel efficiency. However, conventional PMA-based viscosity index improvers can increase coking deposits, which can lead to filter clogging and malfunctions in equipment, thus increasing the amount of particulate matter in exhaust gases. For these reasons, there are restrictions on their usage. Restricting the amount of engine oil used can sometimes lead to insufficient fuel efficiency, so improvements are needed. The object of the present invention is to provide a lubricating oil composition that is highly effective in suppressing the amount of coking deposits and has excellent fuel efficiency, and is suitable for use in internal combustion engines. [Means for solving the problem]

[0006] The inventors arrived at the present invention after diligent research. In other words, the present invention relates to a viscosity index improving agent composition comprising a copolymer (A) containing a polyolefin monomer (a) represented by the following general formula (1), an alkyl (meth)acrylate having a linear alkyl group having 1 to 4 carbon atoms (b), and an alkyl (meth)acrylate monomer (c) having a linear or branched alkyl group having 5 to 10 carbon atoms as essential constituent monomers, wherein the proportion of monomer (c) in the monomers constituting the copolymer (A) is 60% by weight or less based on the total weight of the monomers constituting the copolymer (A); and a lubricating oil composition comprising the viscosity index improving agent composition and at least one additive selected from the group consisting of detergents, dispersants, antioxidants, oiliness improvers, pour point depressants, friction and wear modifiers, extreme pressure agents, defoamers, anti-emulsifiers, metal deactivators, and corrosion inhibitors.

[0007] [ka] [In general formula (1), R 1 is a hydrogen atom or a methyl group; -X 1 - is -O-, -O(AO) m A group represented by - or -NH-, where A is an alkylene group having 2 to 4 carbon atoms, m is an integer from 1 to 10, and when m is 2 or greater, A may be the same or different; R 2 [p is a residue obtained by removing one hydrogen atom from a hydrocarbon polymer containing a 1,2-butylene group as a constituent unit; p is a number, either 0 or 1.] [Effects of the Invention]

[0008] The viscosity index improving agent composition of the present invention provides a lubricating oil composition that is highly effective in suppressing the amount of caulking deposits (amount of deposits on panels in panel caulking tests), has excellent fuel efficiency, and is suitable for use in internal combustion engines. [Modes for carrying out the invention]

[0009] The viscosity index improving agent composition of the present invention comprises a copolymer (A) containing a polyolefin monomer (a) represented by general formula (1), an alkyl (meth)acrylate monomer (b) having a linear alkyl group having 1 to 4 carbon atoms, and an alkyl (meth)acrylate monomer (c) having a linear or branched alkyl group having 5 to 10 carbon atoms as essential constituent monomers. In the viscosity index improving agent composition of the present invention, the proportion of monomer (c) in the monomers constituting copolymer (A) is 60% by weight or less, based on the total weight of the monomers constituting copolymer (A).

[0010] [ka] [In general formula (1), R 1 is a hydrogen atom or a methyl group; -X 1 - is -O-, -O(AO) m A group represented by - or -NH-, where A is an alkylene group having 2 to 4 carbon atoms, m is an integer from 1 to 10, and when m is 2 or greater, A may be the same or different; R 2 [p is a residue obtained by removing one hydrogen atom from a hydrocarbon polymer containing a 1,2-butylene group as a constituent unit; p is a number, either 0 or 1.]

[0011] The present inventors have found that by using a viscosity index improver composition comprising a copolymer (A) containing monomer (a), the alkyl (meth)acrylate (b), and monomer (c) as essential constituent monomers, wherein the proportion of monomer (c) is 60% by weight or less based on the total weight of the monomers constituting copolymer (A), it is possible to provide a lubricating oil composition that is excellent in fuel efficiency and has a high effect in suppressing the amount of coking deposits. If copolymer (A) lacks one or more essential monomers, the viscosity index improvement effect may be insufficient, or the fuel efficiency and coking deposit suppression effect of a lubricating oil composition using a viscosity index improver containing copolymer (A) may be insufficient. For example, when the copolymer (A) does not contain a polyolefin monomer (a) as a constituent monomer, the viscosity index may decrease and the deposit amount may increase. Also, when the copolymer (A) does not contain an alkyl (meth)acrylate (b) as a constituent monomer, the viscosity index may decrease. When the copolymer (A) does not contain a monomer (c) as a constituent monomer, the deposit amount may increase. Furthermore, when the amount of the monomer (c) exceeds 60% by weight based on the total weight of the monomers constituting the copolymer (A), the fuel efficiency may decrease.

[0012] <Copolymer (A)> In the present invention, the copolymer (A) is a polymer containing, as essential constituent monomers, a polyolefin monomer (a) represented by the above general formula (1), an alkyl (meth)acrylate (b) having a linear alkyl group with 1 to 4 carbon atoms, and an alkyl (meth)acrylate monomer (c) having a linear or branched alkyl group with 5 to 10 carbon atoms. The constituent monomers constituting the copolymer (A) include the above monomer (a), the above alkyl (meth)acrylate (b), and the above monomer (c) as essential constituent monomers.

[0013] In the present invention, the polyolefin monomer (a) is a monomer obtained by modifying a hydrocarbon polymer described later and reacting it with (meth)acrylic acid. Note that "(meth)acrylic" means methacrylic and / or acrylic.

[0014] R in the general formula (1) 1 is a hydrogen atom or a methyl group. Among these, from the viewpoint of the viscosity index improvement effect, a methyl group is preferable.

[0015] -X in the general formula (1) 1 - is a group represented by -O-, -O(AO) m - or -NH-. A in the general formula (1) is an alkylene group having 2 to 4 carbon atoms. Examples of the alkylene group having 2 to 4 carbon atoms include an ethylene group, a 1,2- or 1,3-propylene group, and a 1,2-, 1,3- or 1,4-butylene group. m is an integer between 1 and 10, and is preferably an integer between 1 and 4, and more preferably an integer between 1 and 2, from the viewpoint of HTHS viscosity in the effective temperature range (e.g., 80 to 150°C). When m is 2 or greater, A may be the same or different, (AO) m The parts can be either random joins or block joins. -X 1 Of these, -O- and -O(AO) are preferred from the viewpoint of HTHS viscosity in the effective temperature range. m The group is represented by -, and more preferably by -O- and -O(CH2CH2O)-.

[0016] p is a number that is either 0 or 1.

[0017] R in general formula (1) 2 This is a residue obtained by removing one hydrogen atom from a hydrocarbon polymer that contains a 1,2-butylene group (-CH2CH(CH2CH3)- or -CH(CH2CH3)CH2-) as a constituent unit. Examples of hydrocarbon polymers with a 1,2-butylene group as a constituent unit include polymers with 1-butene as a constituent monomer, and polymers in which the terminal double bond of a 1,2-adduct obtained by polymerizing 1,3-butadiene is hydrogenated. Hydrocarbon polymers may be block polymers or random polymers. A hydrocarbon polymer containing a 1,2-butylene group as a constituent unit may also be a hydrocarbon polymer further containing constituent units other than the 1,2-butylene group. Examples of constituent monomers for hydrocarbon polymers include (1) aliphatic unsaturated hydrocarbons, (2) alicyclic unsaturated hydrocarbons, and (3) aromatic group-containing unsaturated hydrocarbons. If the hydrocarbon polymer has double bonds, some or all of the double bonds may be hydrogenated by hydrogenation.

[0018] The constituent monomers that make up hydrocarbon polymers are: (1) Aliphatic unsaturated hydrocarbons [olefins with 2 to 36 carbon atoms (e.g., ethylene, propylene, isobutene, 1-butene, 2-butene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, triacocene and hexatriacose, etc.), dienes with 2 to 36 carbon atoms (e.g., 1,2-butadiene, 1,3-butadiene, isoprene, 1,4-pentadiene, 1,5-hexadiene and 1,7-octadiene, etc.)] (2) Alicyclic unsaturated hydrocarbons [e.g., cyclohexene, (di)cyclopentadiene, pinene, limonene, indene, vinylcyclohexene, and ethylidenebicycloheptene, etc.] (3) Aromatic group-containing unsaturated hydrocarbons (for example, styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, ethylstyrene, isopropylstyrene, butylstyrene, phenylstyrene, cyclohexylstyrene, benzylstyrene, clotylbenzene, vinylnaphthalene, divinylbenzene, divinyltoluene, divinylxylene and trivinylbenzene, etc.) are examples. If the constituent monomers of a hydrocarbon polymer have two or more double bonds, some or all of the double bonds originating from the constituent monomers may be hydrogenated in the hydrocarbon polymer.

[0019] In one embodiment, R 2 The hydrocarbon polymer in this invention may be a hydrocarbon polymer using only C4 monomers as constituent monomers, and the C4 monomer may be at least one selected from the group consisting of 1-butene and 1,3-butadiene, or a combination of isobutene and at least one selected from the group consisting of 1-butene and 1,3-butadiene. When 1,3-butadiene is used as a constituent monomer, the terminal double bond of the 1,2-adduct of 1,3-butadiene in the hydrocarbon polymer may be hydrogenated.

[0020] The number average molecular weight of monomer (a) (hereinafter abbreviated as Mn) is preferably 800 to 10,000, more preferably 1,000 to 9,500, still more preferably 1,200 to 9,000, and particularly preferably 2,000 to 8,700. When Mn of monomer (a) is 800 or more, the solubility in the base oil tends to be good, and when it is 10,000 or less, the copolymerizability with other monomers tends to be good.

[0021] In the present invention, the weight average molecular weight (hereinafter abbreviated as Mw) and Mn can be measured by gel permeation chromatography (hereinafter abbreviated as GPC) under the following conditions. <Measurement conditions for Mw and Mn> Apparatus: "HLC-8320GPC" [manufactured by Tosoh Corporation] Columns: Two "TSKgel GMHXL" [manufactured by Tosoh Corporation] 「TSKgel Multipore H XL -M」 One Measurement temperature: 40 °C Sample solution: 0.25 wt% tetrahydrofuran solution Solution injection volume: 10.0 μl Detector: Refractive index detector Reference substance: Standard polystyrene (TS Reference substance: TSKstandard POLYSTYRENE) 12 points (Molecular weights: 589, 1,050, 2,630, 9,100, 19,500, 37,900, 96,400, 190,000, 355,000, 1,090,000, 2,110,000, 4,480,000) [manufactured by Tosoh Corporation]

[0022] Monomer (a) can be obtained by an esterification reaction of a polymer (Y) having a hydroxyl group at one end, which is obtained by introducing a hydroxyl group to one end of a hydrocarbon polymer, and (meth) acrylic acid. Alternatively, it can be obtained by a transesterification reaction of a polymer (Y) having a hydroxyl group at one end and an alkyl (meth) acrylate (preferably having 1 to 4 carbon atoms) such as methyl (meth) acrylate.

[0023] Specific examples of polymers (Y) containing a hydroxyl group at one end include (Y1) to (Y4) below. Alkylene oxide adducts (Y1); obtained by adding alkylene oxides (ethylene oxide and propylene oxide, etc.) to hydrocarbon polymers obtained by polymerizing unsaturated hydrocarbons (x) in the presence of an ionic polymerization catalyst (such as a sodium catalyst) (in this case, monomer (a) is -X in general formula (1)). 1 -ga-(AO) m (A compound where p=0) Hydroborated products (Y2); hydroboration reaction products of hydrocarbon polymers of unsaturated hydrocarbons (x) having a double bond at one end (e.g., those described in U.S. Patent No. 4,316,973), etc. (In this case, monomer (a) is -X in general formula (1)) 1 (A compound in which - is -O- and p=0) Maleic anhydride-ene-amino alcohol adduct (Y3); obtained by imidizing the reaction product obtained by the ene reaction of a hydrocarbon polymer of an unsaturated hydrocarbon (x) having a double bond at one end with maleic anhydride with an amino alcohol, etc. (In this case, monomer (a) is -X in general formula (1)) 1 (A compound in which - is -O- and p=1) Hydroformyl-hydride (Y4); obtained by hydroformylation of a hydrocarbon polymer of an unsaturated hydrocarbon (x) having a double bond at one end, followed by a hydrogenation reaction (for example, as described in Japanese Patent Publication No. 63-175096) (in this case, monomer (a) is -X in general formula (1)). 1 (A compound in which - is -O- and p=0) Among these polymers (Y) containing a hydroxyl group at one end, alkylene oxide adducts (Y1) and hydroborates (Y2) are preferred from the viewpoint of viscosity index improvement, and alkylene oxide adducts (Y1) are more preferred.

[0024] R in general formula (1) 2The proportion of butadiene among the total monomers constituting the polymer (the weight percentage of 1,3-butadiene in the total constituent monomers in a hydrocarbon polymer containing a 1,2-butylene group as a constituent unit) is preferably 50% by weight or more, more preferably 75% by weight or more, even more preferably 85% by weight or more, and particularly preferably 90% by weight or more, from the viewpoint of improving viscosity index.

[0025] In a hydrocarbon polymer containing a 1,2-butylene group as a constituent unit in general formula (1), an isobutylene group may be present from the viewpoint of improving viscosity index. From the viewpoint of improving viscosity index, the total amount of isobutylene groups and 1,2-butylene groups is preferably 30 mol% or more, more preferably 40 mol% or more, and even more preferably 50 mol% or more, based on the total number of moles of constituent monomers of the hydrocarbon polymer. As a method to increase the total ratio of isobutylene groups to 1,2-butylene groups in a hydrocarbon polymer, the following methods can be employed, for example. In the case of the alkylene oxide adduct (Y1) described above, for example, in anionic polymerization using 1,3-butadiene, the total ratio of isobutylene groups to 1,2-butylene groups in the hydrocarbon polymer can be increased by lowering the reaction temperature {for example, below the boiling point of 1,3-butadiene (-4.4°C)} and reducing the amount of polymerization initiator added relative to 1,3-butadiene. In the case of the hydroborides (Y2), maleic anhydride-ene-amino alcohol adducts (Y3), and hydroformyl-hydrides (Y4) described above, the above ratio can be increased by increasing the degree of polymerization of the hydrocarbon polymer having a double bond at one end.

[0026] Regarding the structure of the hydrocarbon polymer in general formula (1) derived from 1-butene and / or 1,3-butadiene, the ratio of 1,2-butylene groups (number of moles of 1,2-butylene groups / total number of moles of constituent monomers × 100), based on the total number of moles of constituent monomers of the hydrocarbon polymer, is preferably 30 mol% or more, and more preferably 30 to 70 mol%, from the viewpoint of viscosity index improvement effect and copolymerizability with other monomers. The ratio of 1,2-butylene groups is, 13 It can be measured by 1C-NMR. Specifically, for example, if only monomers with 4 carbon atoms are used, the hydrocarbon polymer can be measured. 13 By analyzing with 1C-NMR, the mole percentage of 1,2-butylene groups can be calculated and determined based on the total number of moles of constituent units of the hydrocarbon polymer using the following formula (1). 13 In 1C-NMR, a peak originating from the tertiary carbon atom (-CH2CH(CH2CH3)-) of the 1,2-butylene group appears at an integral value of 26-27 ppm (integral value B). This can be determined from the integral value of the above peak and the integral value related to the peak of all carbon atoms in the hydrocarbon polymer (integral value C). Ratio of 1,2-butylene groups (mol%) = {(integral value B) × 4} / (integral value C) × 100 (1) To increase the proportion of 1,2-butylene groups, for example, in anionic polymerization using 1,3-butadiene, the reaction temperature should be set below the boiling point of 1,3-butadiene (-4.4°C), and the amount of polymerization initiator added should be reduced relative to the amount of 1,3-butadiene. To decrease the proportion of 1,2-butylene groups, the reaction temperature should be set above the boiling point of 1,3-butadiene, and the amount of initiator should be increased.

[0027] In a hydrocarbon polymer containing a 1,2-butylene group as a constituent unit in general formula (1), the total amount of isobutylene groups and 1,2-butylene groups is: 13 It can be measured by 1C-NMR. Specifically, for example, if only monomers with 4 carbon atoms are used, the hydrocarbon polymer can be measured. 13 By analyzing with 1C-NMR and calculating using the following formula (2), the total mole percentage of isobutylene groups and 1,2-butylene groups based on the total number of moles of constituent units of the hydrocarbon polymer can be determined. 13In 1C-NMR, a peak originating from the methyl group of the isobutylene group appears at an integral value of 30-32 ppm (integral value A), and a peak originating from the branched methylene group (-CH2CH(CH2CH3)- or -CH(CH2CH3)CH2-) of the 1,2-butylene group appears at an integral value of 26-27 ppm (integral value B). The total mole percentage of isobutylene groups and 1,2-butylene groups, based on the total number of moles of constituent units of the hydrocarbon polymer, can be determined from the integral values ​​of the above peaks and the integral value of the peak for all carbon in the hydrocarbon polymer (integral value C). Total amount of isobutylene group and 1,2-butylene group (mol%) = 100 × {(integral value A) × 2 + (integral value B) × 4} / (integral value C) (2)

[0028] R 2 If the hydrocarbon polymer in the above contains butadiene, or butadiene and 1-butene as constituent monomers, then R in general formula (1) 2 In a structure comprising part or all of butadiene, or a structure derived from butadiene and 1-butene, the molar ratio of the 1,2-adduct to the 1,4-adduct (1,2-adduct / 1,4-adduct) is preferably 5 / 95 to 95 / 5, more preferably 20 / 80 to 80 / 20, and even more preferably 30 / 70 to 70 / 30, from the viewpoint of viscosity index improvement effect and copolymerizability with other monomers.

[0029] R 2 If the hydrocarbon polymer in contains 1,3-butadiene, or 1,3-butadiene and 1-butene as constituent monomers, then R in general formula (1) 2 The molar ratio of the 1,2-adduct / 1,4-adduct in the structure, which is part or all of the 1,3-butadiene or derived from 1,3-butadiene and 1-butene, is 1 H-NMR and 13 It can be measured using methods such as 13C-NMR and Raman spectroscopy.

[0030] The solubility parameter (hereinafter abbreviated as SP value) of the constituent units derived from monomer (a) (structures in which the (meth)acryloyl groups of monomer (a) react to form single bonds) is preferably 7.0 to 9.0 (cal / cm³) from the viewpoint of making the SP value of copolymer (A) appropriate and from the viewpoint of solubility in the base oil. 3 ) 1 / 2 More preferably 7.3 to 8.5 (cal / cm²) 3 ) 1 / 2 That is the case. SPvalue, for example, R 2 The degree of branching and the number of carbon atoms tend to be larger, while the degree of branching and the number of carbon atoms tend to be larger.

[0031] In this invention, the SP value refers to the value calculated using formula (28) on page 153 of the Fedors method (Polymer Engineering and Science, February, 1974, Vol. 14, No. 2, pp. 147-154), using the numerical values ​​(heat of vaporization and molar volume of atoms or functional groups at 25°C) listed on page 152 (Table 5). Specifically, it refers to the Δe parameter of the Fedors method, as listed in Table 1 below. i and v i The values ​​can be used to calculate the following formula by applying the values ​​corresponding to the types of atoms and atomic groups within the molecular structure. SP value = (ΣΔe i / Σv i ) 1 / 2

[0032] [Table 1]

[0033] The SP value of the constituent unit derived from monomer (a) can be calculated using the above parameters based on the molecular structure of the constituent unit derived from monomer (a), and can be set to a desired range by appropriately adjusting the weight fraction of the monomer (unsaturated hydrocarbon (x)) used. Furthermore, when the copolymer (A) uses two or more monomers (a), the SP value can be calculated by calculating the SP value of each of the multiple constituent units that make up monomer (a) using the method described above, and then weighting the SP values ​​of the constituent units derived from each monomer (a) based on the weight fraction of the constituent monomer units. In the present invention, it is preferable that the SP value calculated by weighting the values ​​satisfies the range of SP values ​​of the constituent units derived from the monomer (a). The method for calculating the SP value of the copolymer will be described later.

[0034] In the present invention, copolymer (A) contains an alkyl (meth)acrylate (b) having a linear alkyl group having 1 to 4 carbon atoms as a constituent monomer.

[0035] Examples of alkyl (meth)acrylate esters (b) having a linear alkyl group with 1 to 4 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, and n-butyl (meth)acrylate. Of these, ethyl (meth)acrylate and n-butyl (meth)acrylate are preferred from the viewpoint of HTHS viscosity and viscosity index, and n-butyl (meth)acrylate is more preferred.

[0036] In the present invention, copolymer (A) is a copolymer containing an alkyl (meth)acrylate monomer (c) having a linear or branched alkyl group with 5 to 10 carbon atoms as a constituent monomer.

[0037] Examples of alkyl (meth)acrylate monomers (c) having a linear or branched alkyl group with 5 to 10 carbon atoms include pentyl (meth)acrylate, hexyl (meth)acrylate, 2-methylpentyl (meth)acrylate, 2-ethylbutyl (meth)acrylate, heptyl (meth)acrylate, 2-methylhexyl (meth)acrylate, 2-ethylpentyl (meth)acrylate, 2-propylbutyl (meth)acrylate, octyl (meth)acrylate, 2-methylheptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and 2-propylpentyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, and isodecyl (meth)acrylate. As monomer (c), hexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isodecyl (meth)acrylate are preferred from the viewpoint of HTHS viscosity, viscosity index, and deposit amount suppression, and more preferably hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isodecyl (meth)acrylate.

[0038] In the present invention, copolymer (A) is preferably a copolymer that contains a monomer (d) represented by the following general formula (2) and / or a (meth)acryloyl monomer (e) having an alkyl group having 11 to 36 carbon atoms, from the viewpoint of HTHS viscosity and viscosity index and deposit amount suppression.

[0039] [ka] [In general formula (2), R 3 is a hydrogen atom or a methyl group; -X 2 - represents a group represented by -O- or -NH-; R 4 R is an alkylene group having 2 to 4 carbon atoms; 5 R is an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms; q is an integer from 1 to 20, and when q is 2 or greater, R 4 They may be the same or different.

[0040] R in general formula (2) 3 This is either a hydrogen atom or a methyl group. Of these, the methyl group is preferred from the viewpoint of viscosity index.

[0041] -X in general formula (2) 2 - represents a group represented by -O- or -NH-. Of these, the group represented by -O- is preferred from the viewpoint of viscosity index.

[0042] R in general formula (2) 4 This refers to an alkylene group having 2 to 4 carbon atoms. Examples of alkylene groups having 2 to 4 carbon atoms include ethylene, isopropylene, 1,2- or 1,3-propylene, isobutylene, and 1,2-, 1,3- or 1,4-butylene.

[0043] In general formula (2), q is an integer from 1 to 20, and from the viewpoint of viscosity index and low-temperature viscosity, it is preferably an integer from 1 to 5, and more preferably an integer from 1 to 2. R when q is 2 or greater 4 They may be the same or different, (R 4 O) q The structure of the parts can be either random joins or block joins.

[0044] R in general formula (2) 5 These are alkyl groups having 1 to 10 carbon atoms. Specifically, these include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, n-heptyl, isoheptyl, n-hexyl, 2-ethylhexyl, n-pentyl, and n-octyl groups. Among alkyl groups having 1 to 10 carbon atoms, alkyl groups having 1 to 8 carbon atoms are preferred from the viewpoint of HTHS viscosity, viscosity index, and deposit amount suppression; more preferably alkyl groups having 2 to 8 carbon atoms; particularly preferred alkyl groups having 2 to 6 carbon atoms; and most preferably alkyl groups having 4 to 6 carbon atoms.

[0045] Specific examples of monomer (d) include methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate {e.g., 2-(n-butyloxy)ethyl (meth)acrylate, 2-(tert-butyloxy)ethyl (meth)acrylate, 2-(sec-butyloxy)ethyl (meth)acrylate, 2-(isobutyloxy)ethyl (meth)acrylate, etc.}, hexyloxyethyl (meth)acrylate {e.g., 2-(n-hexyloxy)ethyl (meth)acrylate, 2-(isohexyloxy)ethyl (meth)acrylate, etc.}, octyloxyethyl (meth)acrylate {e.g., 2-(n-2-ethylhexyl)ethyl (meth)acrylate, etc.}, methoxypropyl (meth)acrylate, ethoxy Examples include propyl (meth)acrylate, propoxypropyl (meth)acrylate, butoxypropyl (meth)acrylate {for example, 2-(n-butyloxy)propyl (meth)acrylate, 2-(tert-butyloxy)propyl (meth)acrylate, 2-(sec-butyloxy)propyl (meth)acrylate, 2-(isobutyloxy)propyl (meth)acrylate, etc.}, methoxybutyl (meth)acrylate, ethoxybutyl (meth)acrylate, propoxybutyl (meth)acrylate, and butoxybutyl (meth)acrylate, as well as esters of (meth)acrylic acid with at least 2 to 20 moles of a linear or branched alkyl alcohol having 1 to 4 carbon atoms, selected from the group consisting of ethylene oxide, propylene oxide, and butylene oxide. Of these, butoxyethyl (meth)acrylate and 2-hexyloxyethyl (meth)acrylate are preferred from the viewpoint of viscosity index and deposit amount suppression.

[0046] Examples of (meth)acryloyl monomers (e) having an alkyl group with 11 to 36 carbon atoms include alkyl (meth)acrylates having a linear alkyl group {e.g., n-undecyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, n-pentadecyl (meth)acrylate, n-hexadecyl (meth)acrylate, n-heptadecyl (meth)acrylate, n-octadecyl (meth)acrylate, n-icosyl (meth)acrylate, n-dodecyl (meth)acrylate}. (meth)acrylamides having linear alkyl groups {e.g., N-nonyl(meth)acrylamide, N-decyl(meth)acrylamide, N-dodecyl(meth)acrylamide, N-tridecyl(meth)acrylamide, N-tetradecyl(meth)acrylamide, N-pentadecyl(meth)acrylamide, N-hexadecyl(meth)acrylamide, etc.}, (meth)acrylamides having branched alkyl groups Alkyl acrylate {e.g., 2-methylundecyl (meth)acrylate, isododecyl (meth)acrylate, 2-methyldodecyl (meth)acrylate, isotridecyl (meth)acrylate, 2-methyltridecyl (meth)acrylate, isotetradecyl (meth)acrylate, 2-methyltetradecyl (meth)acrylate, isopentadecyl (meth)acrylate, 2-methylpentadecyl (meth)acrylate, isohexadecyl (meth)acrylate, 2-octyldecyl (meth)acrylate, ethylene glycol mono-2-octylpenta Esterilized products of decyl ether and (meth)acrylic acid, 2-n-octyldodecyl (meth)acrylic acid, 2-n-decyltetradecyl (meth)acrylic acid, 2-n-dodecylhexadecyl (meth)acrylic acid, 2-n-tetradecyloctadecyl (meth)acrylic acid, 2-n-dodecylpentadecyl (meth)acrylic acid, 2-n-tetradecylheptadecyl (meth)acrylic acid, 2-n-hexadecylheptadecyl (meth)acrylic acid, 2-n-heptadecylicosyl (meth)acrylic acid, 2-n-hexadecyldocosyl (meth)acrylic acid,Examples include (meth)acrylic acid 2-n-eicosyldocosyl, (meth)acrylic acid 2-n-tetracosylhexacosyl, etc., (meth)acrylamides having branched alkyl groups {e.g., N-2-methylundecyl(meth)acrylamide, N-isododecyl(meth)acrylamide, N-2-methyldodecyl(meth)acrylamide, N-isotridecyl(meth)acrylamide, N-2-methyltridecyl(meth)acrylamide, N-isotetradecyl(meth)acrylamide, N-2-methyltetradecyl(meth)acrylamide, N-isopentadecyl(meth)acrylamide, N-2-methylpentadecyl(meth)acrylamide, N-isohexadecyl(meth)acrylamide, etc.}, and esters of alkylene oxides (2-4 carbon atoms) of alkyl alcohols having 9-36 carbon atoms in 1-20 molar amounts with (meth)acrylic acid. As monomer (e), linear alkyl (meth)acrylate (alkyl ester of (meth)acrylate having a linear alkyl group) and branched alkyl (meth)acrylate (alkyl ester of (meth)acrylate having a branched alkyl group) are preferred from the viewpoint of improving HTHS viscosity and viscosity index. As monomer (e), (meth)acrylic acid esters of alkyl alcohol mixtures such as Neodol® 23 (a mixture of linear and branched alkyl alcohols having 12 to 15 carbon atoms, manufactured by SHELL) and Neodol® 45 (a mixture of linear and branched alkyl alcohols having 14 to 16 carbon atoms, manufactured by SHELL) may be used.

[0047] In addition to the monomers (a) to (e) described above, copolymer (A) in the present invention may also contain other monomers as constituent monomers, such as nitrogen atom-containing monomer (f), hydroxyl group-containing monomer (g), phosphorus atom-containing monomer (h), aromatic ring-containing vinyl monomer (i), monomers (j) to monomers (n), etc. Monomers (f) to (n) may be used individually or in combination of two or more.

[0048] Examples of nitrogen atom-containing monomers (f) include the following monomers (f1) to (f4), excluding monomers (a) to (e). Amide group-containing monomer (f1): (meth)acrylamide, N-(N'-monoalkylaminoalkyl)(meth)acrylamide [having an aminoalkyl group (2-6 carbon atoms) with one C1-4 alkyl group bonded to the nitrogen atom; for example, N-(N'-methylaminoethyl)(meth)acrylamide, N-(N'-ethylaminoethyl)(meth)acrylamide, N-(N'-isopropylamino-n-butyl)(meth)acrylamide and N-(N'-n- or isobutylamino-n-butyl)(meth)acrylamide, etc.], dialkyl(meth)acrylamide [having two C1-4 alkyl groups bonded to the nitrogen atom; for example, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide and N, Examples include N-di-n-butyl(meth)acrylamide, N-(N',N'-dialkylaminoalkyl)(meth)acrylamide [those having an aminoalkyl group (with 2 to 6 carbon atoms) in which two alkyl groups with 1 to 4 carbon atoms are bonded to the nitrogen atom of the aminoalkyl group; for example, N-(N',N'-dimethylaminoethyl)(meth)acrylamide, N-(N',N'-diethylaminoethyl)(meth)acrylamide, N-(N',N'-dimethylaminopropyl)(meth)acrylamide, and N-(N',N'-di-n-butylaminobutyl)(meth)acrylamide, etc.]; and N-vinyl carboxylic acid amides [N-vinylformamide, N-vinylacetamide, N-vinyl-n- or isopropionic acid amide, and N-vinylhydroxyacetamide, etc.].

[0049] Nitro group-containing monomer (f2): Examples include 4-nitrostyrene.

[0050] Monomers containing primary to tertiary amino groups (f3): Primary amino group-containing monomers {alkenylamines with 3-6 carbon atoms [(meth)allylamine and clotylamine, etc.], aminoalkyl (2-6 carbon atoms) (meth)acrylates [aminoethyl (meth)acrylate, etc.]}; Secondary amino group-containing monomers {monoalkylaminoalkyl (meth)acrylates [those having an aminoalkyl group (2-6 carbon atoms) with one C1-6 alkyl group bonded to the nitrogen atom; for example, Nt-butylaminoethyl (meth)acrylate and N-methylaminoethyl (meth)acrylate, etc.], dialkenylamines with 6-12 carbon atoms [di(meth)allylamine, etc.]}; Tertiary amino group-containing monomers {dialkylaminoalkyl (meth)acrylates [a group with 1-6 carbon atoms bonded to the nitrogen atom Examples include aminoalkyl groups (with 2 to 6 carbon atoms) with two hydroxyl groups bonded to them; for example, N,N-dimethylaminoethyl (meth)acrylate and N,N-diethylaminoethyl (meth)acrylate, etc., alicyclic (meth)acrylates having a nitrogen atom [such as morpholinoethyl (meth)acrylate], aromatic monomers [such as N-(N',N'-diphenylaminoethyl)(meth)acrylamide, N,N-dimethylaminostyrene, 4-vinylpyridine, 2-vinylpyridine, N-vinylpyrrole, N-vinylpyrrolidone and N-vinylthiopyrrolidone], and their hydrochloride salts, sulfates, phosphates, or lower alkyl (with 1 to 8 carbon atoms) monocarboxylic acid (such as acetic acid and propionic acid) salts.

[0051] Nitrile group-containing monomer (f4): Examples include (meth)acrylonitrile.

[0052] Of the monomers (f), (f1) and (f3) are preferred, and more preferably are N-(N',N'-diphenylaminoethyl)(meth)acrylamide, N-(N',N'-dimethylaminoethyl)(meth)acrylamide, N-(N',N'-diethylaminoethyl)(meth)acrylamide, N-(N',N'-dimethylaminopropyl)(meth)acrylamide, N,N-dimethylaminoethyl(meth)acrylate, and N,N-diethylaminoethyl(meth)acrylate.

[0053] Hydroxyl group-containing monomer (g): Hydroxyl group-containing aromatic monomers (e.g., p-hydroxystyrene), hydroxyalkyl (C2-C6) (meth)acrylates [e.g., 2-hydroxyethyl (meth)acrylate and 2- or 3-hydroxypropyl (meth)acrylate], mono- or bis-hydroxyalkyl (C1-C4) substituted (meth)acrylamides [N,N-bis(hydroxymethyl)(meth)acrylamide, N,N-bis(hydroxypropyl)(meth)acrylamide, N,N-bis(2-hydroxybutyl)(meth)acrylamide] Etc., vinyl alcohol, C3-C12 alkenols [(meth)allyl alcohol, clotyl alcohol, isoclotyl alcohol, 1-octenol and 1-undecenol, etc.], C4-C12 alkene monools or alkene diols [1-buten-3-ol, 2-buten-1-ol and 2-buten-1,4-diol, etc.], hydroxyalkyl (C1-C6) alkenyl (C3-C10) ethers (2-hydroxyethylpropenyl ether, etc.), polyhydric (3-8 hydric) alcohols (glycerides) Alkenyl (3-10 carbon atoms) ethers or (meth)acrylates [such as sucrose (meth)allyl ether] of alcohols (such as pentaerythritol, sorbitol, sorbitan, diglycerin, sugars, and sucrose), polyoxyalkylene glycol (2-4 carbon atoms in the alkylene group, degree of polymerization 2-50), polyoxyalkylene polyol [polyoxyalkylene ethers of the above 3-8 valent alcohols (2-4 carbon atoms in the alkylene group, degree of polymerization 2-100)], polyoxyalkylene glycol or polyoxyalkylene polyol Examples include alkyl (1-4 carbon atoms) ether mono(meth)acrylates [polyethylene glycol (Mn: 100-300) mono(meth)acrylate, polypropylene glycol (Mn: 130-500) mono(meth)acrylate, methoxypolyethylene glycol (Mn: 110-310) (meth)acrylate, lauryl alcohol ethylene oxide adduct (2-30 mol) (meth)acrylate, and polyoxyethylene (Mn: 150-230) sorbitan mono(meth)acrylate, etc.].

[0054] Examples of phosphorus atom-containing monomers (h) include the following monomers (h1) to (h2).

[0055] Phosphate ester group-containing monomer (h1): Examples include (meth)acryloyloxyalkyl (C2-C4) phosphate esters [(meth)acryloyloxyethyl phosphate and (meth)acryloyloxyisopropyl phosphate] and alkenyl phosphate esters [vinyl phosphate, allyl phosphate, propenyl phosphate, isopropenyl phosphate, butenyl phosphate, pentenyl phosphate, octenyl phosphate, decenyl phosphate, and dodecenyl phosphate, etc.]. Note that "(meth)acryloyloxy" means acryloyloxy or methacryloyloxy.

[0056] Phosphono group-containing monomer (H2): Examples include (meth)acryloyloxyalkyl (C2-C4) phosphonic acids [(meth)acryloyloxyethylphosphonic acid, etc.] and alkenyl (C2-C12) phosphonic acids [vinylphosphonic acid, allylphosphonic acid, octenylphosphonic acid, etc.].

[0057] Of the monomers (h), (h1) is preferred, (meth)acryloyloxyalkyl (2-4 carbon atoms) phosphate esters are preferred, and (meth)acryloyloxyethyl phosphate is particularly preferred.

[0058] Aromatic ring-containing vinyl monomer (i): Examples include styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, 4-ethylstyrene, 4-isopropylstyrene, 4-butylstyrene, 4-phenylstyrene, 4-cyclohexylstyrene, 4-benzylstyrene, 4-clotylbenzene, indene, and 2-vinylnaphthalene.

[0059] Of the monomers (i), styrene and α-methylstyrene are preferred, and styrene is even more preferred.

[0060] Monomers (j) include those having two or more unsaturated groups, such as divinylbenzene, C4-C12 alkadienes (butadiene, isoprene, 1,4-pentadiene, 1,6-heptadiene, and 1,7-octadiene, etc.), (di)cyclopentadiene, vinylcyclohexene and ethylidenebicycloheptene, limonene, ethylene di(meth)acrylate, polyalkylene oxide glycol di(meth)acrylate, pentaerythritol trialyl ether, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, trimethylolpropane tri(meth)acrylate, and esters of unsaturated carboxylic acids with Mn of 500 or more and glycols, and esters of unsaturated alcohols and carboxylic acids, as described in International Publication WO01 / 009242.

[0061] Vinyl esters, vinyl ethers, vinyl ketones (k) (sometimes abbreviated as monomer (k)): Examples include vinyl esters of saturated fatty acids having 2 to 12 carbon atoms (vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl octanoate, etc.), alkyl, aryl, or alkoxyalkyl vinyl ethers having 1 to 12 carbon atoms (methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, 2-ethylhexyl vinyl ether, phenyl vinyl ether, vinyl-2-methoxyethyl ether, and vinyl-2-butoxyethyl ether, etc.), and alkyl or aryl vinyl ketones having 1 to 8 carbon atoms (methyl vinyl ketone, ethyl vinyl ketone, and phenyl vinyl ketone, etc.).

[0062] Epoxy group-containing monomer(l) (sometimes abbreviated as monomer(l)): Examples include glycidyl (meth)acrylate and glycidyl (meth)allyl ether.

[0063] Halogen-containing monomers (m) (sometimes abbreviated as monomer(m)): Examples include vinyl chloride, vinyl bromide, vinylidene chloride, (meth)allyl chloride, and halogenated styrenes (such as dichlorostyrene).

[0064] Esters (n) of unsaturated polycarboxylic acids (sometimes abbreviated as monomer(n)): Examples include alkyl, cycloalkyl, or aralkyl esters of unsaturated polycarboxylic acids [alkyl diesters of unsaturated dicarboxylic acids (maleic acid, fumaric acid, and itaconic acid, etc.) having 1 to 8 carbon atoms (dimethyl maleate, dimethyl fumarate, diethyl maleate, and dioctyl maleate)].

[0065] The weight percentage of monomer (a) among the constituent monomers of copolymer (A) is preferably 1 to 50% by weight, more preferably 5 to 40% by weight, particularly preferably 8 to 40% by weight, and most preferably 10 to 30% by weight, based on the total weight of the monomers constituting copolymer (A), from the viewpoint of reducing HTHS viscosity and improving viscosity index at 100°C.

[0066] The weight percentage of monomer (b) among the constituent monomers of copolymer (A) is preferably 1 to 80% by weight, and more preferably 3 to 70% by weight, based on the total weight of the monomers constituting copolymer (A), from the viewpoint of reducing HTHS viscosity and improving viscosity index at 100°C.

[0067] The weight percentage of monomer (c) among the constituent monomers of copolymer (A) is 60% by weight or less. From the viewpoint of reducing HTHS viscosity and improving viscosity index at 100°C, and suppressing deposit amount, it is preferably 1 to 60% by weight, more preferably 5 to 50% by weight, and particularly preferably 5 to 40% by weight, based on the total weight of the monomers constituting copolymer (A).

[0068] When the constituent monomers of copolymer (A) include monomer (d), the weight percentage of monomer (d) is preferably 1 to 50% by weight, more preferably 1 to 40% by weight, and particularly preferably 5 to 30% by weight, based on the total weight of the monomers constituting copolymer (A), from the viewpoint of reducing HTHS viscosity and improving viscosity index at 100°C and suppressing the amount of deposits.

[0069] When the constituent monomers of copolymer (A) include monomer (d), the weight ratio (d / c) of monomer (d) to monomer (c) is preferably 0.4 to 3.6, and more preferably 0.4 to 3.4, based on the total weight of the monomers constituting copolymer (A) from the viewpoint of shear stability and deposit suppression.

[0070] When the constituent monomers of copolymer (A) include monomer (e), the weight percentage of monomer (e) is preferably 0.1 to 60% by weight, more preferably 0.1 to 40% by weight, and particularly preferably 0.1 to 30% by weight, based on the total weight of the monomers constituting copolymer (A), from the viewpoint of reducing HTHS viscosity, improving viscosity index, and suppressing deposit amount.

[0071] The total weight percentage of monomers (f) to (n) among the constituent monomers of copolymer (A) is preferably 5% by weight or less, and more preferably 1% by weight or less, based on the total weight of the monomers constituting copolymer (A), from the viewpoint of reducing HTHS viscosity and improving viscosity index at 100°C.

[0072] Copolymer (A) may be a copolymer containing 1 to 50% by weight of monomer (a) and 1 to 80% by weight of monomer (b), based on the total weight of the monomers constituting copolymer (A).

[0073] The Mw of copolymer (A) is preferably 5,000 to 2,000,000 from the viewpoint of HTHS viscosity in the effective temperature range and low-temperature viscosity, and a more preferred range is shown in Table 2, depending on the application of the viscosity index improver composition and the lubricating oil composition containing the viscosity index improver composition.

[0074] [Table 2] * : Automatic transmission oil ** : Belt-Continuously Valuable Transmission Oil ***: Manual transmission oil

[0075] The molecular weight distribution (Mw / Mn) of copolymer (A) is preferably 1.0 to 4.0, and more preferably 1.5 to 3.5, from the viewpoint of shear stability. The measurement conditions for Mw and molecular weight distribution (Mw / Mn) of copolymer (A) are the same as those for Mw and Mn of monomer (a) described above.

[0076] The SP value of copolymer (A) is 8.0 to 10.0 (cal / cm²) from the viewpoint of solubility in the base oil and viscosity index improvement effect. 3 ) 1 / 2 Preferably, and more preferably, 9.0 to 9.5 (cal / cm²). 3 ) 1 / 2 That is the case.

[0077] In this specification, the SP value of copolymer (A) refers to the weighted average of the SP values ​​of constituent units (structures in which vinyl groups have been single-bonded by polymerization reactions) derived from each monomer constituting copolymer (A) using the SP value calculation method described above, based on the weight fraction of each constituent monomer at the time of preparation. The method for calculating the SP value of a copolymer will be explained with a specific example (an example in which the copolymer is a polymer of 50% by weight of methyl methacrylate and 50% by weight of ethyl methacrylate), but the present invention is not limited thereto. (1) Calculate the SP value of each constituent unit derived from the constituent monomers. The constituent unit derived from methyl methacrylate consists of two CH3 atoms, one CH2 atom, one C atom, and one CO2 atom. Therefore, according to the following formula, the SP value of the constituent unit derived from methyl methacrylate is 9.933 (cal / cm³). 3 ) 1 / 2 It can be seen that this is the case. ΣΔei =1125×2+1180+350+4300=8080 Σv i =33.5 × 2 + 16.1 - 19.2 + 18.0 = 81.9 δ = (8080 / 81.9) 1 / 2 = 9.933 (cal / cm 3 ) 1 / 2 The SP value of the constituent unit derived from ethyl methacrylate is calculated in the same way as the SP value of the constituent unit derived from methyl methacrylate, resulting in 9.721 (cal / cm³). 3 ) 1 / 2 It can be seen that this is the case. (2) Calculate the SP value of the copolymer. Since the copolymer is a polymer of 50% by weight methyl methacrylate and 50% by weight ethyl methacrylate, the SP value of the copolymer is calculated by weighting and averaging the SP values ​​of the constituent units derived from each monomer, as shown below. SP value of copolymer = (9.933 × 50 + 9.721 × 50) / 100 = 9.827

[0078] The SP value of copolymer (A) can be set to a desired range by appropriately adjusting the monomers and their weight fractions used. Specifically, the SP value can be reduced by using a large amount of monomers with long alkyl groups, and increased by using a large amount of monomers with short alkyl groups.

[0079] The viscosity index improving agent composition of the present invention can be obtained by known manufacturing methods, specifically by solution polymerization of the above monomer in a base oil in the presence of a polymerization catalyst. Examples of polymerization catalysts include azo catalysts (such as 2,2'-azobis(2-methylbutyronitrile) and 2,2'-azobis(2,4-dimethylvaleronitrile)), peroxide catalysts (such as benzoyl peroxide, cumyl peroxide, and lauryl peroxide), and redox catalysts (such as mixtures of benzoyl peroxide and tertiary amines). Furthermore, known chain transfer agents (such as alkyl mercaptans with 2 to 20 carbon atoms) can be used as needed to adjust the molecular weight. The polymerization temperature is preferably 25 to 140°C, and more preferably 50 to 120°C. In addition to solution polymerization in the base oil as described above, copolymer (A) can be obtained by bulk polymerization, emulsion polymerization, or suspension polymerization, and then dissolved in the base oil. The copolymer (A) contained in the viscosity index improver composition may be either a random addition copolymer or an alternating copolymer, and may also be either a graft copolymer or a block copolymer.

[0080] From the viewpoint of handling properties, the content of copolymer (A) in the viscosity index improving agent composition of the present invention is preferably 10 to 50% by weight, and more preferably 20 to 30% by weight, based on the weight of the viscosity index improving agent composition.

[0081] The viscosity index improving agent composition of the present invention may also contain the above copolymer (A) and a base oil [for example, hydrocarbon oil {mineral oil (solvent-refined oil, paraffin oil, high viscosity index oil containing isoparaffin, high viscosity index oil obtained by hydrocracking of isoparaffin and naphthenic oil, etc.), poly-α-olefin synthetic lubricant, hydrocarbon-based synthetic base oil such as GTL oil or Fischer-Tropsch synthetic base oil such as CTL}, ester oil, etc.], an alkyl (meth)acrylate copolymer (B) other than the above copolymer (A) (details will be described later), etc. As for the base oils mentioned above, base oils belonging to Groups I to V of the API (American Petroleum Institute) classification are preferred from the viewpoint of the solubility of copolymer (A).

[0082] Kinematic viscosity of base oil at 100°C (measured according to JIS-K2283 (2000)) (Unit: mm)2 The viscosity index ( / s, hereafter abbreviated) is preferably 1.0 to 15, and more preferably 1.0 to 5.0, from the viewpoint of viscosity index and HTHS viscosity at effective temperature. The viscosity index of the base oil (measured according to JIS-K2283 (2000)) is preferably 100 or higher, and more preferably 110 or higher, from the viewpoint of HTHS viscosity in the effective temperature range.

[0083] From the viewpoint of handling, the base oil content in the viscosity index improving agent composition of the present invention is preferably 5% by weight or more, more preferably 25% by weight or more, and particularly preferably 50% by weight or more, based on the weight of the viscosity index improving agent composition.

[0084] The viscosity index improving agent composition of the present invention may contain two or more of the base oils described above.

[0085] <Copolymer (B)> The viscosity index improving agent composition of the present invention may contain an alkyl (meth)acrylate copolymer (B) other than copolymer (A).

[0086] Copolymer (B) includes copolymers that do not contain monomer (a), such as copolymers in which an alkyl (meth)acrylate having an alkyl group with 9 to 36 carbon atoms is an essential constituent monomer. Specifically, examples include (meth)acrylic acid n-dodecyl, (meth)acrylic acid n-tetradecyl, (meth)acrylic acid n-hexadecyl and (meth)acrylic acid n-octadecyl copolymers, (meth)acrylic acid n-octadecyl / (meth)acrylic acid n-dodecyl (molar ratio 10-30 / 90-70) copolymers, (meth)acrylic acid n-tetradecyl / (meth)acrylic acid n-dodecyl (molar ratio 10-30 / 90-70) copolymers, (meth)acrylic acid n-hexadecyl / (meth)acrylic acid n-dodecyl / (meth)acrylic acid methyl (molar ratio 20-40 / 55-75 / 0-10) copolymers, and acrylic acid n-dodecyl / methacrylate n-dodecyl (molar ratio 10-40 / 90-60) copolymers, which may be used individually or in combination of two or more.

[0087] The Mw of copolymer (B) is preferably 5,000 to 100,000, and more preferably 10,000 to 80,000, from the viewpoint of reducing the pour point temperature. The SP value of copolymer (B) is preferably 7.0 to 10, and more preferably 8.0 to 9.5, from the viewpoint of solubility in the base oil. The measurement conditions for the Mw of copolymer (B) are the same as those for the Mw of monomer (a) described above.

[0088] From the viewpoint of reducing low-temperature viscosity, the content of copolymer (B) in the viscosity index improving agent composition of the present invention is preferably 0.01 to 30% by weight, and more preferably 0.01 to 10% by weight, based on the weight of copolymer (A).

[0089] The viscosity index improving agent composition of the present invention exhibits excellent handling properties. Furthermore, lubricating oil compositions containing the viscosity index improving agent composition of the present invention can be suitably used in gear oils (differential oils and industrial gear oils, etc.), MTFs, transmission oils [ATFs, DCTFs, and belt-CVTFs, etc.], traction oils (toroidal-CVTFs, etc.), shock absorber oils, power steering oils, hydraulic oils (hydraulic oils for construction machinery and industrial hydraulic oils, etc.), and engine oils for hybrid vehicles. In particular, it can be suitably used as a lubricating oil composition for internal combustion engines, and especially as engine oil (for gasoline and diesel engines).

[0090] <Lubricating oil composition> The lubricating oil composition of the present invention comprises the viscosity index improving agent composition of the present invention and at least one additive selected from the group consisting of detergents, dispersants, antioxidants, oiliness improvers, pour point depressants, friction and wear modifiers, extreme pressure agents, defoamers, anti-emulsifiers, metal deactivators, and corrosion inhibitors.

[0091] The content of the viscosity index improving agent composition in the lubricating oil composition is preferably 1.5 to 30% by weight, and more preferably 2 to 20% by weight, based on the weight of the lubricating oil composition, from the viewpoint of viscosity index and HTHS viscosity. The content of copolymer (A) in the lubricating oil composition of the present invention is preferably 0.1% by weight or more and less than 10% by weight, and more preferably 0.5% to 3% by weight, based on the weight of the lubricating oil composition, from the viewpoint of viscosity index improvement effect and cost. From the viewpoint of reducing low-temperature viscosity, the content of copolymer (B) in the lubricating oil composition of the present invention is preferably 0.01 to 5% by weight based on the weight of the lubricating oil composition. From the viewpoint of reducing fuel consumption and reducing costs, the base oil content in the lubricating oil composition of the present invention is preferably 43 to 98% by weight, and more preferably 57 to 93% by weight, based on the weight of the lubricating oil composition.

[0092] Examples of additives in the present invention include the following: (1) Cleaning agent: Basic, overbasic, or neutral metal salts [overbasic sulfonates (petroleum sulfonates, alkylbenzene sulfonates, alkylnaphthalene sulfonates, etc.) or alkaline earth metal salts, etc.], salicylates, phenates, naphthenates, carbonates, phosphonates, and mixtures thereof; (2) Dispersant: Succinimides (bis- or mono-polybutenyl succinimides), Mannich condensates, borates, etc.; (3) Antioxidants: Hindered phenols and aromatic secondary amines, etc. (4) Oiliness improvers: Long-chain fatty acids and their esters (oleic acid and oleic acid esters, etc.), long-chain amines and their amides (oleylamine and oleylamide, etc.), etc. (5) Pour point depressants: Polyalkyl methacrylate, ethylene-vinyl acetate copolymer, etc. (6) Friction and wear modifiers: Molybdenum-based and zinc-based compounds (such as molybdenum dithiophosphate, molybdenum dithiocarbamate, and zinc dialkyldithiophosphate); (7) Extreme pressure agents: Sulfur compounds (mono- or disulfide, sulfoxide, and sulfur phosphide compounds), phosphide compounds, and chlorine compounds (such as chlorinated paraffins); (8) Antifoaming agent: Silicone oils, metal soaps, fatty acid esters, and phosphate compounds, etc. (9) Antiemulsifiers: Quaternary ammonium salts (such as tetraalkylammonium salts), sulfated oils and phosphates (such as phosphates of polyoxyethylene-containing nonionic surfactants), hydrocarbon solvents (toluene, xylene, ethylbenzene), etc.; (10) Metal deactivators: Nitrogen-containing compounds (such as benzotriazole), nitrogen-containing chelate compounds (such as N,N'-disalithidene-1,2-diaminopropane), nitrogen and sulfur-containing compounds (such as 2-(n-dodecylthio)benzimidazole), etc. (11) Corrosion inhibitors: Nitrogen atom-containing compounds (such as benzotriazole and 1,3,4-thiodiazolyl-2,5-bisdialkyldithiocarbamate), etc.

[0093] These additives may be added individually, or two or more may be added as needed. A mixture of these additives may also be called a performance additive or packaging additive, and this may also be added. The content of each of these additives is preferably 0.1 to 15% by weight based on the total amount of the lubricating oil composition. Furthermore, the total content of each additive is preferably 0.1 to 30% by weight, more preferably 0.3 to 20% by weight, and then even more preferably 3 to 10% by weight, based on the total amount of the lubricating oil composition.

[0094] As mentioned above, from the perspective of compatibility with the latest engines (especially diesel engines), engine oil compositions (an example of a lubricating oil composition) are required to have coking resistance (high effectiveness in suppressing the amount of coking deposits). The coking resistance of engine oil compositions is generally evaluated by the panel coking test (Federal Test Method Std. 791-3462). The panel coking test can be performed by measuring the weight (mg) of the deposits adhering to a panel under predetermined conditions such as panel temperature, oil temperature, and test time. Not all oil scattered in the engine transforms into a caulking agent; the weight of the resulting panel deposits varies depending on the combination of additives contained in the oil. From this perspective, panel caulking tests of engine oil compositions are generally conducted under the following measurement conditions, taking into account the actual conditions inside the engine: panel temperature of 300°C, oil temperature of 100°C, and test duration of 3 hours (15 seconds on / 45 seconds off). Conventional engine oils using viscosity index improvers containing poly(meth)acrylate (PMA), while exhibiting excellent fuel efficiency, sometimes showed panel deposits exceeding 150 mg when performing panel coking tests under the above measurement conditions. From this perspective, in engine oil compositions using viscosity index improvers containing PMA, it is preferable that the amount of panel deposits in the panel coking test be 150 mg or less, and more preferably 140 mg or less. Specific test methods will be described in detail in the examples.

[0095] The lubricating oil composition of the present invention is suitably used in gear oils (differential oils and industrial gear oils, etc.), MTFs, transmission fluids [ATFs, DCTFs, and belt-CVTFs, etc.], traction oils (toroidal-CVTFs, etc.), shock absorber oils, power steering oils, hydraulic fluids (hydraulic fluids for construction machinery and industrial hydraulic fluids, etc.), and lubricating oil compositions for hybrid vehicles. In particular, it is suitably used as a lubricating oil composition for internal combustion engines, and especially as engine oil (for gasoline and diesel engines).

[0096] This specification discloses the following:

[0097] The present disclosure (1) is a viscosity index improver composition comprising a copolymer (A) containing a polyolefin monomer (a) represented by the following general formula (1), an alkyl (meth)acrylate monomer (b) having a linear alkyl group having 1 to 4 carbon atoms, and an alkyl (meth)acrylate monomer (c) having a linear or branched alkyl group having 5 to 10 carbon atoms as essential constituent monomers, wherein the proportion of monomer (c) in the monomers constituting the copolymer (A) is 60% by weight or less based on the total weight of the monomers constituting the copolymer (A).

[0098] [ka] [In general formula (1), R 1 is a hydrogen atom or a methyl group; -X 1 - is -O-, -O(AO) m A group represented by - or -NH-, where A is an alkylene group having 2 to 4 carbon atoms, m is an integer from 1 to 10, and when m is 2 or greater, A may be the same or different; R 2 [p is a residue obtained by removing one hydrogen atom from a hydrocarbon polymer containing a 1,2-butylene group as a constituent unit; p is a number, either 0 or 1.]

[0099] Disclosure (2) is the viscosity index improver composition according to Disclosure (1) above, wherein the monomer constituting the copolymer (A) further comprises a monomer (d) represented by the following general formula (2), and / or a (meth)acryloyl monomer (e) having an alkyl group having 11 to 36 carbon atoms.

[0100] [ka] [In general formula (2), R 3 is a hydrogen atom or a methyl group; -X 2 - represents a group represented by -O- or -NH-; R 4 R is an alkylene group having 2 to 4 carbon atoms; 5 R is an alkyl group with 1 to 10 carbon atoms, or an aryl group with 6 to 20 carbon atoms; q is an integer from 1 to 20, and when q is 2 or greater, R 4They may be the same or different.

[0101] Disclosure (3) is a viscosity index improving agent composition according to Disclosure (1) or (2) above, wherein the monomers constituting the copolymer (A) are copolymers containing 1 to 80% by weight of the alkyl (meth)acrylate (b) and 1 to 60% by weight of the alkyl (meth)acrylate (c), based on the total weight of the monomers constituting the copolymer (A). Disclosure (4) further comprises a viscosity index improver composition according to any one of disclosures (1) to (3) above, wherein the base oil is a base oil of API classification Group I to V. Disclosure (5) is a lubricating oil composition comprising a viscosity index improving agent composition described in any one of Disclosures (1) to (4) above, and at least one additive selected from the group consisting of detergents, dispersants, antioxidants, oiliness improvers, pour point depressants, friction and wear modifiers, extreme pressure agents, defoamers, anti-emulsifiers, metal deactivators, and corrosion inhibitors. [Examples]

[0102] The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0103] <Manufacturing Example 1> In a pressure-resistant reaction vessel made of stainless steel equipped with a temperature control device and a stirrer, 400 parts by weight of degassed and dehydrated hexane, 1 part by weight of tetrahydrofuran, 75 parts by weight of 1,3-butadiene, and 2 parts by weight of n-butyllithium were charged, and polymerization was carried out at a polymerization temperature of 70°C. After the polymerization rate reached approximately 100%, 2 parts by weight of ethylene oxide was added, and the reaction was carried out at 50°C for 3 hours. To stop the reaction, 50 parts by weight of water and 25 parts by weight of 1N hydrochloric acid aqueous solution were added, and the mixture was stirred at 80°C for 1 hour. The organic phase of the reaction solution was collected using a separatory funnel, and after raising the temperature to 70°C, the solvent was removed over 2 hours under reduced pressure of 0.027 to 0.040 MPa. The obtained polybutadiene containing a hydroxyl group at one end was transferred to a reaction vessel equipped with a temperature control device, a stirrer, and a hydrogen inlet tube, and 150 parts by weight of tetrahydrofuran was added and dissolved uniformly. A suspension of 10 parts by weight of palladium carbon and 50 parts by weight of tetrahydrofuran, which had been pre-mixed, was poured in, and the reaction was carried out at room temperature for 8 hours while supplying hydrogen to the liquid at a flow rate of 30 mL / min through the hydrogen inlet tube. After that, the palladium carbon was removed by filtration, and the obtained filtrate was heated to 70°C and the tetrahydrofuran was removed under reduced pressure of 0.027~0.040 MPa to obtain a hydrogenated polybutadiene polymer containing a hydroxyl group at one end (Y1-1) (total ratio of isobutylene group and 1,2-butylene group: 45 mol%, 1,2-adduct / 1,4-adduct (molar ratio): 45 / 55, hydroxyl value: 8.0 mg KOH / g, crystallization temperature: -60°C or below). 245 parts by weight of a hydrogenated polybutadiene polymer containing a hydroxyl group at one end (Y1-1), 245 parts by weight of methacrylic acid, and 98 parts by weight of an inorganic porous material supported by sulfonic acid groups (acid value 45 mg KOH / g, particle size 240 μm) were added, and esterification was carried out at 120°C. Next, the inorganic porous material supported by sulfonic acid groups was removed by filtration, and excess methacrylic acid was removed from the reaction solution under reduced pressure (0.027~0.040 MPa) to obtain monomer (a-1). The molecular weight of the obtained monomer (a-1) was measured by GPC, and the ratio of 1,2-butylene groups was determined. 13 Measurements were taken by 13C-NMR. The results were Mw=6,900, Mn=6,800, 1,2-butylene group ratio=45 mol%, and -X in general formula (1). 1 - represents the group -O(CH2CH2O)1-, and p=0.

[0104] <Manufacturing Example 2> In a 1 L stainless steel pressure-resistant reaction vessel equipped with a temperature control device and a stirrer, 400 parts by weight of degassed and dehydrated hexane, 1 part by weight of tetrahydrofuran, and 0.4 parts by weight of n-butyllithium were charged and then cooled to -40°C. 90 parts by weight of 1,3-butadiene liquefied at -40°C were added, and polymerization was carried out at a polymerization temperature of -40°C. The process was then carried out in the same manner as in Production Example 1 to obtain a hydrogenated polybutadiene polymer containing a hydroxyl group at one end (Y1-2) (total ratio of isobutylene group and 1,2-butylene group: 65 mol%, 1,2-adduct / 1,4-adduct (molar ratio): 65 / 35, hydroxyl value: 13.1 mg KOH / g, crystallization temperature: -60°C or below). Furthermore, (Y1-2) was esterified with methacrylic acid to obtain monomer (a-2). The molecular weight of the obtained monomer (a-2) was measured by GPC, and the ratio of 1,2-butylene groups was determined. 13 Measurements were taken by 13C-NMR. The results were Mw=6,900, Mn=6,800, 1,2-butylene group ratio=65 mol%, and -X in general formula (1). 1 - represents the group -O(CH2CH2O)1-, and p=0.

[0105] <Example 1> A reaction vessel equipped with a stirring device, a heating and cooling device, a thermometer, and a nitrogen inlet tube is used as the base oil during polymerization. Hydrocarbon oil-1 (SP value: 8.3 (cal / cm³) 3 ) 1 / 2 kinematic viscosity at 100℃: 4.2 mm 2 200 parts by weight of copolymer (A) / s, viscosity index: 128, and 100 parts by weight of monomer formulations for producing copolymer (A) as described in Table 3 were added, followed by nitrogen purging (gas phase oxygen concentration 100 ppm). After heating to 76°C under a sealed container with stirring, the polymerization catalyst (2,2-azobis(2-methylbutyronitrile)) as described in Table 3 was added, and the polymerization reaction was carried out at the same temperature for 4 hours. The temperature was raised to 90°C and the reaction was allowed to proceed for 2 hours, then the temperature was raised to 120-130°C, and 33 parts by weight of hydrocarbon oil-1 as a dilution base oil was added to obtain the viscosity index improver composition (R-1) of Example 1 containing 30% by weight of copolymer (A-1). The SP value of the obtained copolymer (A-1) was calculated by the method described above, and Mw was measured by the method described above. The results are shown in Table 3.

[0106] <Examples 2 to 15, Comparative Examples 1 to 2> Except for using the monomers of the types described in Table 3 in the proportions described in Table 3 as the monomer complex, in the same manner as in Example 1, viscosity index improver compositions (R-2) to (R-15) of Examples 2 to 15 containing 30.0% by weight of copolymers (A-2) to (A-15) and copolymer (A'-1), and 22% by weight of copolymer (A'-2), and viscosity index improver compositions (S-1) to (S-2) of Comparative Examples 1 to 2 were obtained.

[0107] The compositions of the monomers (a) to (d) described in Table 3 are as described below. The SP value is the value rounded off to three decimal places. <Monomer (a)> (a-1): Methacrylic acid ester of (Y1-1) [Mn: 6800, SP value 8.41 (cal / cm 3 ) 1 / 2 (a-2): Methacrylic acid ester of (Y1-2) [Mn: 6800, SP value 8.33 (cal / cm 3 ) 1 / 2 <Monomer (b)> (b-1): n-Butyl methacrylate (butyl methacrylate) (SP value 9.45 (cal / cm 3 ) 1 / 2 ) <Monomer (c)> (c-1) Hexyl methacrylate (hexyl methacrylate) (SP value 9.28 (cal / cm 3 ) 1 / 2 ) (c-2) 2-Ethylhexyl methacrylate (2-ethylhexyl methacrylate) (SP value 8.77 (cal / cm 3 ) 1 / 2 ) (c-3): Isodecyl methacrylate (isodecyl methacrylate) (SP value 8.97 (cal / cm 3 ) 1 / 2 ) <Monomer (d)> (d-1): 2-Butoxyethyl methacrylate (2-butoxyethyl methacrylate) (SP value 9.43 (cal / cm 3 ​​) 1 / 2 ) (d-2): 2-hexyloxyethyl methacrylate (2-hexyloxyethyl methacrylate) (SP value 9.30 (cal / cm³) 3 ) 1 / 2 ) <monomer(e)> (e-1): Methacrylic acid ester of Neodol 23 {Ester of a mixture of linear and branched alkyl methacrylates with 12-15 carbon atoms [SHELL's "Neodol 23" (weight ratio = linear C12:branched C12:linear C13:branched C13 = 40:10:40:10 mixture) and methacrylic acid], SP value 8.99 (cal / cm²) 3 ) 1 / 2 )} (e-2): Methacrylic acid ester of Neodol 45 {Ester of a mixture of linear and branched alkyl methacrylates with 14-16 carbon atoms [SHELL's "Neodol 45" (weight ratio = linear C14:branched C14:linear C15:branched C15 = 40:10:40:10 mixture) and methacrylic acid], SP value 8.94 (cal / cm²) 3 ) 1 / 2 )}

[0108] The SP values ​​of the constituent units (structures in which carbon-carbon double bonds react to form single bonds) derived from each monomer (a-1), monomer (a-2), monomer (e-1), and monomer (e-2) were calculated based on the following formula. Constituent units derived from monomer (a-1) ΣΔe i =1125(CH3)+1180(CH2)+350(C)+4300(CO2)=6955 Σv i =33.5(CH3)+16.1(CH2)-19.2(C)+18.0(CO2)=48.4 ΣΔe i =1180(CH2)×2+800(O)=3160 Σv i = 16.1(CH2) × 2 + 3.8(O) = 36 ΣΔe i =1180(CH2)×2+1125(CH3)+820(CH)=4305 Σv i =16.1(CH2)×2+33.5(CH3)-1.0(CH)=64.7 ΣΔe i =1180(CH2)×4=4720 Σv i = 16.1(CH2) × 4 = 64.4 Here, the total number of 1,2-butylene groups and 1,4-butylene groups is as follows: Total number of 1,2-butylene groups and 1,4-butylene groups = (6800 - 85 - 44) / 56 = 119.125 Therefore, the parameters of the constituent unit derived from (a-1) are as follows: ΣΔe i =6955+3160+4305×119.125×0.45+4720×119.125×0.55=550138.4 Σv i =48.4 + 36 + 64.7 × 119.125 × 0.45 + 64.4 × 119.125 × 0.55 = 7772.132 SP value of the constituent unit derived from (a-1) = (ΣΔe i / Σv i ) 1 / 2 =(550138.4 / 7772.132) 1 / 2 =8.413

[0109] Constituent units derived from monomer (a-2) Total number of 1,2-butylene groups and 1,4-butylene groups = (6800 - 85 - 44) / 56 = 119.125 ΣΔe i =6955+3160+4305×119.125×0.65+4720×119.125×0.35=540251 Σv i =48.4+36+64.7×119.125×0.65+64.4×119.125×0.35=7779.279 SP value of the constituent unit derived from (a-2) = (ΣΔe i / Σv i ) 1 / 2 =(540251 / 7779.279) 1 / 2 =8.334

[0110] Constituent units derived from monomers (e-1) Straight-chain C12 ΣΔe i =6955+1180×11+1125=21060 Σv i = 48.4 + 16.1 × 11 + 33.5 = 259 SP value = (ΣΔe i / Σv i ) 1 / 2 =(21060 / 259) 1 / 2 =9.017 Branch C12 ΣΔe i =6955+1180×9+1125×2+820=20645 Σv i = 48.4 + 16.1 × 9 + 33.5 × 2 - 1.0 = 259.3 SP value = (ΣΔe i / Σv i ) 1 / 2 =(20645 / 259.3) 1 / 2 =8.923 Straight-chain C13 ΣΔe i =6955+1180×12+1125=22240 Σv i = 48.4 + 16.1 × 12 + 33.5 = 275.1 SP value = (ΣΔe i / Σv i ) 1 / 2 =(22240 / 275.1) 1 / 2 =8.991 Branch C13 ΣΔe i =6955+1180×10+1125×2+820=21825 Σv i = 48.4 + 16.1 × 10 + 33.5 × 2 - 1.0 = 275.4 SP value = (ΣΔe i / Σv i ) 1 / 2 =(21825 / 275.4) 1 / 2 =8.902 SP value of the constituent unit derived from (e-1) = (9.017 × 40 + 8.923 × 10 + 8.991 × 40 + 8.902 × 10) / 100 = 8.986

[0111] Constituent units derived from monomers (e-2) Straight-chain C14 ΣΔe i =6955+1180×13+1125=23420 Σv i = 48.4 + 16.1 × 13 + 33.5 = 291.2 SP value = (ΣΔe i / Σv i ) 1 / 2 =(23420 / 291.2) 1 / 2 =8.968 Branch C14 ΣΔe i =6955+1180×11+1125×2+820=23005 Σv i = 48.4 + 16.1 × 11 + 33.5 × 2 - 1.0 = 291.5 SP value = (ΣΔe i / Σv i ) 1 / 2 =(23005 / 291.5) 1 / 2 =8.884 Straight chain C15 ΣΔe i =6955+1180×14+1125=24600 Σv i = 48.4 + 16.1 × 14 + 33.5 = 307.3 SP value = (ΣΔe i / Σv i ) 1 / 2 =(24600 / 307.3) 1 / 2 =8.947 Branch C15 ΣΔe i =6955+1180×12+1125×2+820=24185 Σv i = 48.4 + 16.1 × 12 + 33.5 × 2 - 1.0 = 307.6 SP value = (ΣΔe i / Σv i ) 1 / 2=(24185 / 307.6) 1 / 2 =8.867 SP value of the constituent unit derived from (e-2) = (8.968 × 40 + 8.884 × 10 + 8.947 × 40 + 8.867 × 10) / 100 = 8.941

[0112] The base oil used in the examples and comparative examples was a hydrocarbon base oil [SK Lubricants Co., Ltd., product name "Yubase4", API classification Group III (kinematic viscosity at 100°C: 4.2 mm)]. 2 kinematic viscosity at 40°C ( / s): 19.12 mm² 2 ( / s)

[0113] <Method for measuring the viscosity of base oil> The kinematic viscosity at 40°C and 100°C was measured using the JIS-K2283 (2000) method. The viscosity index was also calculated using the JIS-K2283 (2000) method.

[0114] <Examples 16-30, Comparative Examples 3-4> Evaluation of viscosity index improver compositions of Examples 1-15 and Comparative Examples 1-2 (evaluated as SAE 30 grade) (Preparation of base oil containing additives) In a stainless steel container equipped with a stirring device, the base oil [Yubase4 (kinematic viscosity at 100℃: 4.2mm)] 2 A base oil containing additives was prepared by adding (viscosity index: 128) and a packaged engine oil additive. The amount of additive added was set to 15% by weight based on the weight of the additive-containing base oil. (Preparation of lubricating oil composition) To obtain the lubricating oil compositions with an HTHS viscosity of 3.3 mPa·s at 150°C, viscosity index improving compositions (R-1) to (R-15) or (S-1) to (S-2) were added to the additive-containing base oil, respectively, to obtain the lubricating oil compositions (V-1) to (V-15) of Examples 16 to 30 and the lubricating oil compositions (W-1) to (W-2) of Comparative Examples 3 and 4. The HTHS viscosity (100°C), kinematic viscosity (40°C, 100°C), viscosity index, panel deposit amount, and shear stability of each example's lubricating oil composition (V-1) to (V-15) and (W-1), (W-2) were measured by the following method. The results are shown in Table 3.

[0115] <Method for measuring the HTHS viscosity of lubricating oil compositions> The HTHS viscosity was measured according to the method specified in ASTM D 5481. Measurements were taken at 150°C and 100°C. An HTHS viscosity of 5.8 to 6.3 (mPa·s) at 100°C is preferable because it indicates excellent fuel efficiency.

[0116] <Method for measuring the viscosity of lubricating oil compositions and calculating the viscosity index (VI)> The kinematic viscosity at 40°C and 100°C was measured according to the method specified in JIS-K2283 (2000), and the viscosity index was calculated according to the method specified in JIS-K2283 (2000). A higher viscosity index value indicates a greater viscosity index improvement effect. A viscosity index of 250 or higher is preferable.

[0117] <Measurement of amount of material adhering to the panel (mg)> For each example of lubricating oil composition, the amount of material adhering to the panel was measured by performing a panel caulking test (measurement conditions: panel temperature 300°C, oil temperature 100°C, test time 3 hours (on 15 seconds / off 45 seconds)). The measurement method is as follows. A test machine equipped with a splasher (PANEL COKING TESTER, manufactured by Rigosha Co., Ltd.) was filled with 300 mL of the oil to be measured (engine oil composition), and an aluminum panel was attached to the top. The oil was heated to 100°C and the panel to 300°C. Once these temperatures were reached, the splasher was rotated at 1000 rpm to splash the oil onto the panel. This cycle of splashing oil for 15 seconds and stopping for 45 seconds was repeated for 3 hours. After that, the weight (mg) of the components adhering to the aluminum panel was measured. A smaller amount of material adhering to the panel indicates a higher suppression effect on the amount of caulking deposit. The amount of material adhering to the panel is preferably 150 mg or less, and more preferably 140 mg or less.

[0118] <Method for measuring and calculating the shear stability (SSI) of lubricating oil compositions> Shear stability was measured according to the method specified in ASTM D 6278 and calculated according to the method specified in ASTM D 6022. A smaller value indicates higher shear stability. From the perspective of product life, a shear stability of 40 or less is preferable.

[0119] [Table 3]

[0120] From the evaluation results of the lubricating oil compositions of the examples and comparative examples, which were prepared to have an HTHS viscosity of approximately 3.3 mPa·s at 150°C, it can be seen that the compositions of the examples have a better balance of HTHS viscosity at 100°C, viscosity index, fuel efficiency, and panel deposit amount compared to the compositions of the comparative examples. [Industrial applicability]

[0121] The viscosity index improving agent composition of the present invention, when used as a lubricating oil composition, exhibits a high viscosity index improving effect, excellent fuel efficiency, and can reduce the amount of deposits adhering to panels (high effectiveness in suppressing the amount of coking deposits). Therefore, it is suitably used in gear oils (differential oils and industrial gear oils, etc.), MTFs, transmission oils [ATFs, DCTFs, and belt-CVTFs, etc.], traction oils (toroidal-CVTFs, etc.), shock absorber oils, power steering oils, hydraulic oils (hydraulic oils for construction machinery and industrial hydraulic oils, etc.), and engine oils (for gasoline and diesel engines), and is particularly suitable for use as a lubricating oil composition for internal combustion engines.

Claims

1. The copolymer (A) comprises a polyolefin monomer (a) represented by the following general formula (1), an alkyl (meth)acrylate monomer having a linear alkyl group having 1 to 4 carbon atoms (b), and an alkyl (meth)acrylate monomer having a linear or branched alkyl group having 5 to 10 carbon atoms (c), as essential constituent monomers. A viscosity index improving agent composition wherein the proportion of monomer (c) in the monomers constituting the copolymer (A) is 60% by weight or less, based on the total weight of the monomers constituting the copolymer (A). 【Chemistry 1】 [In general formula (1), R １ is a hydrogen atom or a methyl group; -X １ - is -O-, -O (AO) ｍ A group represented by - or -NH-, where A is an alkylene group having 2 to 4 carbon atoms, m is an integer from 1 to 10, and when m is 2 or greater, A may be the same or different; R ２ [where p is a residue obtained by removing one hydrogen atom from a hydrocarbon polymer containing a 1,2-butylene group as a constituent unit; p is a number of 0 or 1.]

2. The viscosity index improving agent composition according to claim 1, wherein the monomer constituting the copolymer (A) further comprises a monomer (d) represented by the following general formula (2) and / or a (meth)acryloyl monomer (e) having an alkyl group having 11 to 36 carbon atoms. 【Chemistry 2】 [In general formula (2), R ３ is a hydrogen atom or a methyl group; -X ２ - is a group represented by -O- or -NH-; R ４ is an alkylene group having 2 to 4 carbon atoms; R ５ is an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 20 carbon atoms; q is an integer of 1 to 20, and when q is 2 or more, R ４ may be the same or different. ]

3. The viscosity index improving agent composition according to claim 1, wherein the monomer constituting the copolymer (A) is a copolymer containing 1 to 80% by weight of the alkyl (meth)acrylate (b) and 1 to 60% by weight of the alkyl (meth)acrylate (c), based on the total weight of the monomers constituting the copolymer (A).

4. Furthermore, the viscosity index improving agent composition according to claim 1, comprising a base oil of API classification Group I to V as the base oil.

5. A lubricating oil composition comprising a viscosity index improving agent composition according to any one of claims 1 to 4, and at least one additive selected from the group consisting of a detergent, a dispersant, an antioxidant, an oiliness improving agent, a pour point depressant, a friction and wear modifier, an extreme pressure agent, an antifoaming agent, an anti-emulsifier, a metal deactivator, and a corrosion inhibitor.

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