Lubricating oil composition

Abstract

To provide a lubricant composition capable of achieving both cooling performance (heat transfer coefficient) and lubricating performance.SOLUTION: A lubricant composition comprises: a polymer (A) having a monomer (a) represented by a general formula (1) and / or a monomer (b) represented by a general formula (2) as essential constituent monomers; and an ester compound (B) represented by a general formula (3). Weight average molecular weight of the polymer (A) is preferably 100,000 to 2,000,000, and a solubility parameter of the polymer (A) is preferably 9.0 to 11.5 (cal / cm3)1 / 2.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a lubricating oil composition. [Background technology]

[0002] In recent years, in order to improve fuel efficiency, there has been a demand for improved power transmission efficiency and smaller size and lighter weight in automotive transmissions. As a result, transmission mechanisms have evolved from manual transmissions to automatic transmissions, and more recently, continuously variable transmissions are being installed in some vehicles. Meanwhile, electric vehicles equipped with lead-acid batteries, nickel-metal hydride batteries, lithium-ion batteries, fuel cells, etc., and fitted with electric motors, or hybrid vehicles that use these batteries in combination with internal combustion engines, are being developed, and in these vehicles, transmission oil and electric motor oil are used separately.

[0003] Recently, in electric vehicles and hybrid vehicles, there has been a growing demand for the standardization of these oils and for miniaturization and weight reduction by packaging the transmission and electric motor. As a result, there has been a need for a new oil that possesses not only the lubrication performance of a manual transmission oil, automatic transmission oil, or continuously variable transmission oil, but also the insulating and cooling properties of an electric motor oil.

[0004] Transmission fluids require thermal and oxidative stability, detergent and dispersive properties, wear prevention, and seizure prevention. To meet these requirements, transmission fluids generally use mineral oil-based or synthetic base oils with various additives (antioxidants, detergent and dispersant agents, wear inhibitors, rust inhibitors, metal deactivators, friction modifiers, antiperspirants, colorants, seal expanders, viscosity index improvers, etc.). Such transmission fluids have low volume resistivity and insufficient insulation, which can lead to problems such as short circuits in electric motors when used as electric motor fluid, as well as poor cooling and power loss due to high kinematic viscosity.

[0005] On the other hand, electric motor oil requires insulating and cooling properties, but not lubrication, so it contains very few additives. Therefore, when electric motor oil is used in a transmission, there is a problem of significant wear on bearings, gears, etc. Furthermore, with the progress of miniaturization and high rotation speeds in electric motors, there is a growing expectation for the cooling properties of lubricating oil. In other words, in electric motor-equipped vehicles such as electric vehicles or hybrid vehicles, there is a need for an automotive transmission oil composition that has anti-seize performance, wear prevention performance, and low-temperature flow performance as a transmission oil, while also possessing insulating and cooling properties that are superior to those of conventional products.

[0006] It is known that ester-based synthetic oils with high thermal conductivity, such as esters of monohydric alcohols and monobasic acids and / or esters of monohydric alcohols and polybasic acids, are used as automotive transmission fluid compositions that also possess cooling properties (Patent Documents 1 and 2).

[0007] However, the ester compounds specifically disclosed are esters of azelaic acid and isooctanolic acid, esters of neopentyl glycol and isooctanoic acid, and esters of oleic acid and isooctanolic acid. However, these have the problem of insufficient cooling performance (heat transfer coefficient) for use as transmission fluid in electric vehicles or hybrid vehicles. Furthermore, they have the problem of thin oil film thickness and poor lubrication. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2009-242547 [Patent Document 2] Japanese Patent Publication No. 2014-25081 [Overview of the project] [Problems that the invention aims to solve]

[0009] The object of the present invention is to provide a lubricating oil composition that can achieve both cooling performance (heat transfer coefficient) and lubricity.

Means for Solving the Problems

[0010] As a result of intensive studies, the present inventors have arrived at the present invention. That is, the present invention is a lubricating oil composition comprising a polymer (A) having a monomer (a) represented by the following general formula (1) and / or a monomer (b) represented by the following general formula (2) as an essential constituent monomer, and an ester compound (B) represented by the following general formula (3).

[0011]

Chemical formula

[0012]

Chemical formula

[0013]

Chemical formula

[0014] The lubricating oil composition of the present invention can achieve both cooling performance (heat transfer coefficient) and lubrication performance.

[0015] In this invention, "excellent cooling performance" means that the heat transfer coefficient at 40°C is high (2.10 W / (m²). 2 (Above / K), high heat transfer coefficient at 80°C (2.30 W / (m²) 2 / K) means above, and "excellent lubricity" means that the oil film thickness (nm) at 10 mm / s is 3.0 or higher. [Modes for carrying out the invention]

[0016] The lubricating oil composition of the present invention is a polymer (A) having monomer (a) represented by the following general formula (1) and / or monomer (b) represented by the following general formula (2) as essential constituent monomers, and an ester compound (B) represented by the following general formula (3).

[0017] [ka] [In general formula (1), R 1 is a hydrogen atom or a methyl group; -X 1 - represents a group represented by -O- or -NH-; R 2 O is a linear or branched alkylene oxy group having 2 to 4 carbon atoms, and if p is 2 or more, there are multiple R 2 They may be the same or different. p is an integer from 0 to 20; R 3 This represents a linear or branched alkyl group having 25 to 44 carbon atoms.

[0018] [ka] [In general formula (2), R 4 is a hydrogen atom or a methyl group; -X 2 - 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 0 to 10, and when m is 2 or greater, A may be the same or different; R 5 [where isobutylene and / or 1,2-butylene groups are essential constituent units, and one hydrogen atom has been removed from a hydrocarbon polymer with 43 or more carbon atoms; q represents the number 0 or 1.]

[0019] [ka] [In general formula (3), R 6 Each of these is an alkyl group having 1 to 12 carbon atoms, which may each have substituents, and R 7 Each of these is an alkylene group having 2 to 6 carbon atoms, which may independently have substituents, and R 8 [x] is a residue obtained by removing two carboxyl groups from a chain-like aliphatic divalent carboxylic acid (x) having 4 to 12 carbon atoms, and n independently represents an integer from 1 to 3. <Polymer (A)> In the present invention, the polymer (A) has monomer (a) represented by the general formula (1) and / or monomer (b) represented by the general formula (2) as essential constituent monomers.

[0020] R in general formula (1) 1 This is either a hydrogen atom or a methyl group, and from the viewpoint of lubricity, a methyl group is preferred.

[0021] -X in general formula (1) 1 - is a group represented by -O- or -NH-, and from the viewpoint of lubricity, -O- is preferred.

[0022] R in general formula (1) 2 O is a linear or branched alkylene oxy group having 2 to 4 carbon atoms, and R2 Examples of alkylene groups represented by include ethylene groups, 1,2- or 1,3-propylene groups, and 1,2-, 1,3- or 1,4-butylene groups.

[0023] In general formula (1), p is the number of moles of alkylene oxide added, and is an integer from 0 to 20. From the viewpoint of solubility in the base oil, it is preferably an integer from 0 to 4, and more preferably an integer from 0 to 2. When p is 2 or more, R 2 They may be the same or different, R 2 (R) 2 O) p The parts can be either random joins or block joins.

[0024] R in general formula (1) 3This represents linear or branched alkyl groups having 25 to 44 carbon atoms. Specifically, it includes linear alkyl groups (e.g., n-pentacosyl group, n-hexacosyl group, n-octacosyl group, n-triacontyl group, n-dotriacontyl group, n-tetratriacontyl group, n-hexatriacontyl group, n-tetracontyl group, n-dotetracontyl group, n-tetratetracontyl group, etc.), branched alkyl groups {e.g., those with a branch at position 2 [2-dodecyltridecyl group, 2-alkyl (alkyl group with 11 to 13 carbon atoms) tetradecyl group {e.g., 2-dodecyltetradecyl group, etc.}, 2-alkyl (alkyl group with 9 to 15 carbon atoms) hexadecyl group {e.g., 2-dodecylhexadecyl group, 2-tetradecylhexadecyl group, etc.}, 2-alkyl (alkyl group with 7 to 17 carbon atoms) octadecyl group {e.g., 2-tetra Examples include residues obtained by removing hydroxyl groups from oxo alcohols obtained from olefins [e.g., decyloctadecyl group, 2-hexadecyloctadecyl group, etc.], 2-alkyl (alkyl group with 5-19 carbon atoms) icosyl group [e.g., 2-hexadecylicosyl group, etc.], 2-alkyl (alkyl group with 3-21 carbon atoms) docosyl group, 2-alkyl (alkyl group with 1-20 carbon atoms) tetracosyl group, 2-alkyl (alkyl group with 1-18 carbon atoms) hexacosyl group, 2-alkyl (alkyl group with 1-16 carbon atoms) octacosyl group, 2-alkyl (alkyl group with 1-14 carbon atoms) triacontyl group, etc.], etc.

[0025] R 3 From the viewpoint of lubricity, cooling properties, and solubility in base oil, preferred are branched alkyl groups having 25 to 36 carbon atoms, more preferably branched alkyl groups having 28 to 36 carbon atoms, particularly preferred are branched alkyl groups having 28 to 32 carbon atoms, and most preferably are 2-dodecylhexadecyl groups and 2-tetradecyloctadecyl groups.

[0026] Specifically, monomer (a) is alkyl (meth)acrylate having a linear alkyl group with 25 to 44 carbon atoms {e.g., n-pentacosyl(meth)acrylate, n-hexacosyl(meth)acrylate, n-octacosyl(meth)acrylate, n-triacontyl(meth)acrylate, n-dotriacontyl(meth)acrylate, n-tetratriacontyl(meth)acrylate, n-hexatriacontyl(meth)acrylate, n-tetracontyl(meth)acrylate, n-dotetracontyl(meth)acrylate, n-tetratetra Contyl (meth)acrylate, etc.; alkyl (meth)acrylates having branched alkyl groups with 25 to 44 carbon atoms [for example, those with branching at the 2-position [for example, 2-dodecyltridecyl (meth)acrylate, 2-alkyl (alkyl group with 11 to 13 carbon atoms) tetradecyl (meth)acrylate {for example, 2-dodecyltetradecyl (meth)acrylate, etc.}; 2-alkyl (alkyl group with 9 to 15 carbon atoms) hexadecyl (meth)acrylate {for example, 2-dodecylhexadecyl (meth)acrylate, 2-tetradecylhexadecyl (meth)acrylate 2-alkyl(alkyl group with 7-17 carbon atoms) octadecyl(meth)acrylate {e.g., 2-tetradecyloctadecyl(meth)acrylate, 2-hexadecyloctadecyl(meth)acrylate, etc.}, 2-alkyl(alkyl group with 5-19 carbon atoms) icosyl(meth)acrylate {e.g., 2-hexadecylicosyl(meth)acrylate, etc.}, 2-alkyl(alkyl group with 3-21 carbon atoms) docosyl(meth)acrylate, 2-alkyl(alkyl group with 1-20 carbon atoms) tetracosyl(meth)acrylate, 2-alkyl(alkyl [e.g., hexacosyl (meth)acrylate (C1-18 C1 group), octacosyl (meth)acrylate (2-alkyl (C1-16 C1 alkyl group)), triacontyl (meth)acrylate (2-alkyl (C1-14 C1 alkyl group)), (meth)acrylate esters of alkylene oxide (1-20 moles added) adducts (1-20 moles added) of aliphatic alcohols having a linear alkyl group with 25-44 C1 groups {e.g., n-pentacosyl alcohol}, aliphatic alcohols having a branched alkyl group with 25-44 C1 groups {e.g.,Examples include (meth)acrylic acid esters of alkylene oxide adducts (1 to 20 moles added) of 2-dodecyltetradecyl alcohol, etc., (meth)acrylic acid esters of the oxo alcohol of the olefin, and (meth)acrylic acid esters of alkylene oxide adducts (1 to 20 moles added) of the oxo alcohol of the olefin.

[0027] As monomer (a), from the viewpoint of lubricity, cooling properties and solubility in base oil, (meth)acrylate having a branched alkyl group with 25 to 42 carbon atoms is preferred, more preferably (meth)acrylate having a branched alkyl group with 25 to 42 carbon atoms, even more preferably (meth)acrylate having a branched alkyl group with 28 to 38 carbon atoms, particularly preferably (meth)acrylate having a branched alkyl group with 28 to 36 carbon atoms, and most preferably 2-dodecylhexadecyl(meth)acrylate, 2-tetradecyloctadecyl(meth)acrylate, and 2-hexadecylicosyl(meth)acrylate.

[0028] The solubility parameter (hereinafter abbreviated as SP value) of the constituent unit of (A) derived from monomer (a) (the structure in which the carbon-carbon double bond of (a) reacts to form a single bond) is preferably 8.0 to 9.0 (cal / cm³) from the viewpoint of copolymerization with other monomers and adjusting the SP value of (A) to an appropriate level. 3 ) 1 / 2 And more preferably 8.5 to 8.8 (cal / cm²). 3 ) 1 / 2 The SP value is, for example, R 3 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.

[0029] 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

[0030] [Table 1] Furthermore, if the polymer (A) uses two or more monomers (a), it is preferable to calculate the SP value of each of the multiple monomers (a) constituting (A) using the method described above, and to obtain an arithmetic mean of the SP values ​​of each monomer (a) based on the weight fraction of the constituent units, so that the value satisfies the range of SP values ​​of the monomers (a).

[0031] R in general formula (2) 4 The atom is either a hydrogen atom or a methyl group, and from the viewpoint of lubricity, a methyl group is preferred.

[0032] -X in general formula (2) 2 - is -O-, -O(AO) m It is a group represented by - or -NH-.

[0033] A is an alkylene group with 2 to 4 carbon atoms.

[0034] Examples of alkylene groups having 2 to 4 carbon atoms include ethylene groups, 1,2- or 1,3-propylene groups, and 1,2-, 1,3- or 1,4-butylene groups.

[0035] m is an integer from 0 to 10, and is preferably an integer from 0 to 4, and more preferably an integer from 0 to 2, from the viewpoint of solubility in the base oil (ester compound (B), etc., the same applies hereinafter).

[0036] 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.

[0037] -X 2 -From the standpoint of lubricity, -O- and -O(AO) m A group represented by - is preferred, and more preferably -O- and -O(CH2CH2O) m It is a base represented by -.

[0038] In general formula (2), q is a number of 0 or 1, and from the viewpoint of solubility in the base oil, 0 is preferred.

[0039] R in general formula (2) 5 This is a residue obtained by removing one hydrogen atom from a hydrocarbon polymer having 43 or more carbon atoms that contains an isobutylene group and / or a 1,2-butylene group as constituent units.

[0040] The isobutylene group is represented by -CH2C(CH3)2- or -C(CH3)2CH2-, and the 1,2-butylene group is represented by -CH2CH(CH2CH3)- or -CH(CH2CH3)CH2-.

[0041] Examples of hydrocarbon polymers having isobutylene groups and / or 1,2-butylene groups as constituent units include polymers using isobutene and 1-butene as constituent monomers (unsaturated hydrocarbons (x)), and polymers in which the double bond of a 1,2-adduct obtained by polymerizing 1,3-butadiene is hydrogenated.

[0042] Furthermore, in addition to isobutene, 1-butene, and 1,3-butadiene, the hydrocarbon polymer may also contain one or more of the following unsaturated hydrocarbons (x) as constituent monomers.

[0043] (1) Aliphatic unsaturated hydrocarbons [olefins with 2 to 36 carbon atoms (e.g., ethylene, propylene, 2-butene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, triacocene, and hexatriacosene, etc.) and dienes with 4 to 36 carbon atoms (e.g., 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 (e.g., styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, ethylstyrene, isopropylstyrene, butylstyrene, phenylstyrene, cyclohexylstyrene, benzylstyrene, clotylbenzene, vinylnaphthalene, divinylbenzene, divinyltoluene, divinylxylene, and trivinylbenzene, etc.) The hydrocarbon polymer composed of these may be a block polymer or a random polymer. Furthermore, if the hydrocarbon polymer has double bonds, some or all of the double bonds may be hydrogenated by hydrogenation. In one embodiment, R 5 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 isobutene, 1-butene, and 1,3-butadiene.

[0044] The number-average molecular weight (hereinafter abbreviated as Mn) of monomer (b) is preferably 800 to 10,000, more preferably 1,000 to 9,000, and even more preferably 1,200 to 8,500. When the Mn of monomer (b) is 800 or higher, it tends to have good lubricity, and when it is 10,000 or lower, it tends to have good copolymerization with other monomers.

[0045] 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 piece 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] The monomer (b) can be obtained by an esterification reaction of a polymer (Y) containing 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, or an ester exchange reaction with an alkyl (meth)acrylate (preferably having 1 to 4 carbon atoms) such as methyl (meth)acrylate. Here, "(meth)acrylic" means "acrylic and / or methacrylic".

[0046] Specific examples of the polymer (Y) containing a hydroxyl group at one end include the following (Y1) to (Y4).

[0047] Alkylene oxide adduct (Y1); obtained by adding an alkylene oxide (such as ethylene oxide and propylene oxide) to a hydrocarbon polymer obtained by polymerizing an unsaturated hydrocarbon (x) in the presence of an ionic polymerization catalyst (such as a sodium catalyst), etc. (in this case, in the general formula (2), the monomer (b) is -X2 -ga-(AO) m (A compound where - and q=0)

[0048] Hydroborate (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 (b) is -X in general formula (2) 2 (A compound where - is -O- and q=0)

[0049] 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 (b) is -X in general formula (2) 2 (A compound in which - is -O- and q=1)

[0050] 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 (b) is -X in general formula (2)). 2 (A compound where - is -O- and q=0)

[0051] Among these polymers (Y) containing a hydroxyl group at one end, from the viewpoint of lubricity, alkylene oxide adducts (Y1), hydroborates (Y2), and maleic anhydride-ene-amino alcohol adducts (Y3) are preferred, and alkylene oxide adducts (Y1) are more preferred.

[0052] R in general formula (2) 5The proportion of butadiene among the total monomers constituting the polymer (the weight percentage of 1,2-butadiene in the total constituent monomers in a hydrocarbon polymer containing isobutylene groups and / or 1,2-butylene groups as constituent units) 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 lubricity.

[0053] In a hydrocarbon polymer containing isobutylene groups and / or 1,2-butylene groups as constituent units in general formula (2), 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 units of the hydrocarbon polymer, from the viewpoint of lubricity.

[0054] As a method to increase the total ratio of isobutylene groups to 1,2-butylene groups in hydrocarbon polymers, for example, the following methods can be employed. 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 setting the reaction temperature 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.

[0055] In a hydrocarbon polymer containing isobutylene groups and / or 1,2-butylene groups as constituent units in general formula (2), 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. 13By analyzing with 1C-NMR and calculating using the following formula (1), 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. 13 In 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).

[0056] Total amount of isobutylene group and 1,2-butylene group (mol%) = 100 × {(integral value A) × 2 + (integral value B) × 4} / (integral value C) (1) R 5 If the hydrocarbon polymer in the above contains butadiene, or butadiene and 1-butene as constituent monomers, then R in general formula (2) 5 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 lubricity and copolymerizability with other monomers.

[0057] R 5 If the hydrocarbon polymer in the above contains butadiene, or butadiene and 1-butene as constituent monomers, then R in general formula (2) 5 The molar ratio of the butadiene, which constitutes part or all of the structure, or the 1,2-adduct / 1,4-adduct in the structure derived from butadiene and 1-butene is 1 H-NMR and 13 It can be measured using methods such as 13C-NMR and Raman spectroscopy.

[0058] The SP value of the constituent units derived from monomer (b) is preferably 7.0 to 9.0 (cal / cm³) from the viewpoint of making the SP value of (A) appropriate and solubility in the base oil. 3 ) 1 / 2 More preferably 7.3 to 8.5 (cal / cm²) 3 ) 1 / 2 That is the case.

[0059] The SP value of the constituent unit derived from monomer (b) can be calculated using the above parameters based on the molecular structure of the constituent unit derived from monomer (b), and can be set to a desired range by appropriately adjusting the monomer (unsaturated hydrocarbon (x)) and the weight fraction of monomer (unsaturated hydrocarbon (x)) used.

[0060] Furthermore, if the polymer (A) uses two or more monomers (b), it is preferable to calculate the SP value of each of the multiple constituent units derived from (b) using the method described above, and to obtain an arithmetic mean of the SP values ​​of the constituent units derived from each monomer (b) based on the weight fraction of the constituent units, so that the value satisfies the range of SP values ​​of the constituent units derived from the monomer (b).

[0061] Polymer (A) may be a copolymer in which, in addition to monomers (a) and (b), one or more monomers selected from the group consisting of alkyl (meth)acrylates having alkyl groups with 1 to 4 carbon atoms (c), alkyl (meth)acrylates having alkyl groups with 5 to 24 carbon atoms (d), hydroxyl group-containing monomers (e), phosphorus atom-containing monomers (f), and nitrogen atom-containing monomers (g) (excluding monomers (a) and monomer (b)) are constituent monomers.

[0062] When an alkyl (meth)acrylate (c) having an alkyl group with 1 to 4 carbon atoms is used as a constituent monomer, the SP value of polymer (A) can be made moderately high without inhibiting the effects of the side chains of the constituent units derived from monomers (a) and (b). This allows for a large difference in SP values ​​between (A) and the ester compound (B), reducing the ratio (kinematic viscosity at 40°C / kinematic viscosity at 80°C) and tending to result in superior lubricity and cooling effects.

[0063] Examples of C1-C4 alkyl(meth)acrylates (c) include alkyl(meth)acrylates having a linear alkyl group with C1-C4 {e.g., methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate, n-butyl(meth)acrylate, etc.} and alkyl(meth)acrylates having a branched alkyl group with C3-C4 {e.g., isopropyl(meth)acrylate, isobutyl(meth)acrylate, tert-butyl(meth)acrylate, sec-butyl(meth)acrylate, etc.}.

[0064] Of these, alkyl methacrylates having a linear alkyl group with 1 to 4 carbon atoms are preferred from the viewpoint of cooling properties, and methyl (meth)acrylate and n-butyl (meth)acrylate are more preferred.

[0065] Alkyl (meth)acrylates (d) having C5-C24 alkyl groups include alkyl (meth)acrylates having linear alkyl groups with C5-C24 {for example, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, 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 -Nonadecyl (meth)acrylate, n-icosyl (meth)acrylate, n-docosyl (meth)acrylate, n-tetracosyl (meth)acrylate, etc.}, alkyl (meth)acrylates having branched alkyl groups with 5 to 24 carbon atoms {e.g., isopentyl (meth)acrylate, 2,2-dimethylpropyl (meth)acrylate, tert-pentyl (meth)acrylate, 1-ethylpropyl (meth)acrylate, sec-pentyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isononyl (meth)acrylate, 3,5,5-trimethylhexyl (meth)acrylate, 2,4,6-Trimethylheptyl (meth)acrylate, 2-Methylnonyl (meth)acrylate, Isodecyl (meth)acrylate, 2-Ethylnonyl (meth)acrylate, Isoundecyl (meth)acrylate, Isododecyl (meth)acrylate, Isotetradecyl (meth)acrylate, 2-Ethyldodecyl (meth)acrylate, Isopentadecyl (meth)acrylate, 2-Ethyltridecyl (meth)acrylate, 2-Methyltetradecyl (meth)acrylate, Isohexadecyl (meth)acrylate Examples include isoheptadecyl (meth)acrylate, 2-octylnonyl (meth)acrylate, 2-hexylundecyl (meth)acrylate, 2-ethylpentadecyl (meth)acrylate, 2-(3-methylhexyl)-7-methylnonyl (meth)acrylate, isooctadecyl (meth)acrylate, 1-hexyltridecyl (meth)acrylate, 2-ethylheptadecyl (meth)acrylate, isoicosyl (meth)acrylate, 2-decyltetradecyl (meth)acrylate, etc.

[0066] Of these, from the viewpoint of low-temperature fluidity, n-dodecyl(meth)acrylate, n-tridecyl(meth)acrylate, n-tetradecyl(meth)acrylate, n-pentadecyl(meth)acrylate, n-hexadecyl(meth)acrylate, n-octadecyl(meth)acrylate, and 2-decyltetradecyl(meth)acrylate are preferred, and 2-decyltetradecyl(meth)acrylate is more preferred.

[0067] Examples of hydroxyl group-containing monomers (e) include the following:

[0068] 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 di-hydroxyalkyl (C1-C4) substituted (meth)acrylamides [e.g., N,N-dihydroxymethyl (meth)acrylamide, N,N-dihydroxypropyl (meth)acrylamide, N,N-di-2-hydroxybutyl (meth)acrylamide], vinyl alcohol, C3-C12 alkenols [e.g., (meth)aryl alcohol, clotyl alcohol, isocyl alcohol] Examples include rotyl 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.), and alkenyl (C3-C10) ethers or (meth)acrylates of polyhydric (3-8 hydric) alcohols (glycerin, pentaerythritol, sorbitol, sorbitan, diglycerin, sugars and sucrose, etc.) [sucrose (meth)allyl ether, etc.]. Of these, hydroxyalkyl (C2-C6) (meth)acrylates are preferred from the viewpoint of coolability and copolymerizability with other monomers, and hydroxyethyl (meth)acrylates are more preferred.

[0069] Examples of phosphorus atom-containing monomers (f) used in combination with monomers (a) and (b) include the following monomers (f1) to (f2).

[0070] Phosphate ester group-containing monomer (f1): 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.].

[0071] Phosphono group-containing monomer (f2): 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.].

[0072] Among the phosphorus atom-containing monomers (f), (f1) is preferred from the viewpoint of copolymerizability with other monomers and solubility in base oils, (meth)acryloyloxyalkyl (2-4 carbon atoms) phosphate esters are more preferred, and (meth)acryloyloxyethyl phosphate is particularly preferred.

[0073] Examples of nitrogen atom-containing monomers (g) [excluding monomers (a) and monomer (b)] include the following monomers (g1) to (g4).

[0074] Amide group-containing monomer (g1): (meth)acrylamide, monoalkylamino(meth)acrylamide [a nitrogen atom to which one C1-C4 alkyl group is bonded; for example, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, and Nn- or isobutyl(meth)acrylamide, etc.], monoalkylaminoalkyl(meth)acrylamide [having an aminoalkyl group (C2-C6) to which one C1-C4 alkyl group is bonded to a nitrogen atom; for example, N-methylaminoethyl(meth)acrylamide, N-ethylaminoethyl(meth)acrylamide, N-isopropylamino-n-butyl(meth)acrylamide, and Nn- or isobutylamino-n-butyl(meth)acrylamide, etc.], dialkylamino(meth)acrylamide [a nitrogen atom to which two C1-C4 alkyl groups are bonded; for example, N Examples include those having a nitrogen atom only in the amide group, such as N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, and N,N-di-n-butyl(meth)acrylamide, dialkylaminoalkyl(meth)acrylamide [those having an aminoalkyl group (2-6 carbon atoms) in which two alkyl groups with 1-4 carbon atoms are bonded to the nitrogen atom; for example, N,N-dimethylaminoethyl(meth)acrylamide, N,N-diethylaminoethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, and N,N-di-n-butylaminobutyl(meth)acrylamide, etc.], and N-vinyl carboxylic acid amide [N-vinylformamide, N-vinylacetamide, N-vinyl-n- or isopropionylamide, and N-vinylhydroxyacetamide, etc.].

[0075] Nitro group-containing monomer (g2): Examples include 4-nitrostyrene.

[0076] Monomers containing primary to tertiary amino groups (g3): Primary amino group-containing vinyl 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 vinyl monomers {monoalkylaminoalkyl (meth)acrylates [those having an aminoalkyl group (2-6 carbon atoms) in which one alkyl group with 1-6 carbon atoms is bonded to a nitrogen atom; for example, t-butylaminoethyl (meth)acrylate and methylaminoethyl (meth)acrylate, etc.], dialkenylamines with 6-12 carbon atoms [di(meth)allylamine, etc.]}; Tertiary amino group-containing vinyl monomers {dialkylaminoalkyl (meth)acrylates [nitrogen atom Examples include aminoalkyl groups (with 2 to 6 carbon atoms) to which two alkyl groups with 1 to 6 carbon atoms are bonded; for example, dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate, etc., alicyclic (meth)acrylates having a nitrogen atom [morpholinoethyl (meth)acrylate, etc.], aromatic vinyl monomers [N,N-diphenylaminoethyl (meth)acrylamide, N,N-dimethylaminostyrene, 4-vinylpyridine, 2-vinylpyridine, N-vinylpyrrole, N-vinylpyrrolidone and N-vinylthiopyrrolidone, etc.], and their hydrochloride salts, sulfates, phosphates, or lower alkyl (1 to 8 carbon atoms) monocarboxylic acid (acetic acid and propionic acid, etc.) salts.

[0077] Nitrile group-containing monomer (g4): Examples include (meth)acrylonitrile.

[0078] Among the nitrogen atom-containing vinyl monomers (g), (g1) and (g3) are preferred from the viewpoint of copolymerizability with other monomers, and N,N-diphenylaminoethyl(meth)acrylamide, dimethylaminoethyl(meth)acrylamide, diethylaminoethyl(meth)acrylamide, dimethylaminopropyl(meth)acrylamide, dimethylaminoethyl(meth)acrylate, and diethylaminoethyl(meth)acrylate.

[0079] Polymer (A) may also consist of the following monomers (h) to (o).

[0080] Aliphatic hydrocarbon monomers (h): Examples include alkenes with 2 to 20 carbon atoms (ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, and octadecene, etc.) and alkadienes with 4 to 12 carbon atoms (butadiene, isoprene, 1,4-pentadiene, 1,6-heptadiene, and 1,7-octadiene, etc.).

[0081] Alicyclic hydrocarbon monomers (i): Examples include cyclohexene, (di)cyclopentadiene, pinene, limonene, vinylcyclohexene, and ethylidene bicycloheptene.

[0082] Aromatic hydrocarbon monomers (j): Examples include styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, 4-ethylstyrene, 4-isopropylstyrene, 4-butylstyrene, 4-phenylstyrene, 4-cyclohexylstyrene, 4-benzylstyrene, indene, 4-clotylbenzene, and 2-vinylnaphthalene.

[0083] Vinyl esters, vinyl ethers, vinyl ketones (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.).

[0084] Epoxy group-containing monomer (l): Examples include glycidyl (meth)acrylate and glycidyl (meth)allyl ether.

[0085] Halogen element-containing monomer (m): Examples include vinyl chloride, vinyl bromide, vinylidene chloride, (meth)allyl chloride, and halogenated styrenes (such as dichlorostyrene).

[0086] Esters (n) of unsaturated polycarboxylic acids: 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)].

[0087] Alkoxyalkyl ether monomer (o); Methoxyethyl (meth)acrylate, methoxypropyl (meth)acrylate, methoxybutyl (meth)acrylate, methoxyheptyl (meth)acrylate, methoxyhexyl (meth)acrylate, methoxypentyl (meth)acrylate, methoxyoctyl (meth)acrylate, ethoxyethyl (meth)acrylate, ethoxypropyl (meth)acrylate, ethoxybutyl (meth)acrylate, ethoxyheptyl (meth)acrylate, ethoxyhexyl (meth)acrylate, ethoxypentyl (meth)acrylate, ethoxyoctyl (meth)acrylate, propoxymethyl (meth)acrylate, propoxyethyl Examples include propoxypropyl (meth)acrylate, propoxybutyl (meth)acrylate, propoxyheptyl (meth)acrylate, propoxyhexyl (meth)acrylate, propoxypentyl (meth)acrylate, propoxyoctyl (meth)acrylate, butoxymethyl (meth)acrylate, butoxyethyl (meth)acrylate, butoxypropyl (meth)acrylate, butoxybutyl (meth)acrylate, butoxyheptyl (meth)acrylate, butoxyhexyl (meth)acrylate, butoxypentyl (meth)acrylate, butoxyoctyl (meth)acrylate, etc.

[0088] Among the monomers (o), preferred are methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, and butoxyethyl (meth)acrylate.

[0089] The proportion of monomer (a) constituting polymer (A) is preferably 9 to 50% by weight, more preferably 10 to 45% by weight, and most preferably 10 to 40% by weight, based on the total weight of constituent monomers of (A), from the viewpoint of lubricity, cooling properties, and low-temperature fluidity.

[0090] The proportion of monomer (b) constituting (A) is preferably 1 to 30% by weight, more preferably 2 to 25% by weight, even more preferably 3 to 20% by weight, and particularly preferably 5 to 20% by weight, based on the total weight of the constituent monomers of (A), from the viewpoint of lubricity and low-temperature fluidity.

[0091] The total proportion of monomers (a) and (b) constituting (A) is preferably 1 to 60% by weight, more preferably 10 to 60% by weight, even more preferably 10 to 55% by weight, and particularly preferably 10 to 40% by weight, based on the total weight of the constituent monomers of (A), from the viewpoint of cooling performance.

[0092] From the viewpoint of cooling performance, the proportion of monomer (c) constituting (A) is preferably 40 to 90% by weight, more preferably 45 to 90% by weight, even more preferably 46 to 90% by weight, and particularly preferably 50 to 85% by weight, based on the total weight of the constituent monomers of (A).

[0093] The proportion of monomer (d) constituting (A) is preferably 20% by weight or less, and more preferably 5-10% by weight, based on the total weight of the constituent monomers of (A), from the viewpoint of solubility in the base oil.

[0094] The total content of monomers (e) to (g) constituting (A) is preferably 20% by weight or less, more preferably 1 to 15% by weight, and particularly preferably 2 to 10% by weight, based on the weight of (A), from the viewpoint of solubility in the base oil.

[0095] The total content of (h) to (o) that constitute (A) is preferably 10% by weight or less, more preferably 1 to 7% by weight, and particularly preferably 2 to 5% by weight, based on the weight of (A), from the viewpoint of solubility in the base oil.

[0096] The SP value of (A) is 9.0 to 11.5 (cal / cm²) from the viewpoint of cooling and lubrication. 3 ) 1 / 2 Preferably, and more preferably, 9.3 to 9.9 (cal / cm²). 3 ) 1 / 2, more preferably 9.35 to 9.8 (cal / cm 3 ) 1 / 2 and particularly preferably 9.4 to 9.7 (cal / cm 3 ) 1 / 2 .

[0097] The SP value of (A) means a value obtained by calculating the SP values of the constituent units (structures in which vinyl groups have become single bonds by a polymerization reaction) derived from each monomer constituting (A) using the above-described method for calculating the SP value, and performing a weighted average based on the weight fraction of each monomer at the time of charging. For example, when the monomer is methyl methacrylate, the constituent unit derived from methyl methacrylate has, as atomic groups, two CH3s, one CH2, one C, and one CO2. Therefore, from the following mathematical formula, the SP value of the constituent unit derived from methyl methacrylate is 9.933 (cal / cm 3 ). 1 / 2 It can be understood that it is. Similarly, by calculation, the SP value of the constituent unit derived from ethyl methacrylate is 9.721 (cal / cm 3 ). 1 / 2 It can be understood that it is. ΣΔe i = 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 When the polymer is a polymer of 50% by weight of methyl methacrylate and 50% by weight of ethyl methacrylate, the SP value of the polymer is calculated by performing a weighted average based on the weight fraction of the SP values of the constituent units derived from each monomer as follows. SP value of polymer = (9.933×50 + 9.721×50) / 100 = 9.827 The SP value of polymer (A) can be adjusted to a desired range by appropriately adjusting the monomers and weight fractions used. Specifically, the SP value can be decreased by using more monomers having a longer carbon number of the alkyl group, and the SP value can be increased by using more monomers having a shorter carbon number of the alkyl group.

[0098] The weight-average molecular weight (hereinafter abbreviated as Mw) of (A) is preferably 50,000 to 2,000,000, more preferably 100,000 to 2,000,000, even more preferably 100,000 to 1,000,000, particularly preferably 100,000 to 600,000, and most preferably 100,000 to 500,000, from the viewpoint of cooling and lubricity.

[0099] (A) can be obtained by known manufacturing methods, specifically by solution polymerization of the monomer in a solvent in the presence of a polymerization catalyst.

[0100] Examples of solvents include toluene, xylene, alkylbenzenes having 9 to 10 carbon atoms, methyl ethyl ketone, ethyl acetate, 2-propanol, and ester oils (for example, ester compound (B) described later).

[0101] Polymerization catalysts include azo catalysts (such as azobisisobutyronitrile and azobisvaleronitrile), peroxide catalysts (such as benzoyl peroxide, cumyl peroxide, and lauryl peroxide), and redox catalysts (such as a mixture of benzoyl peroxide and a tertiary amine). Furthermore, known chain transfer agents (such as alkyl mercaptans with 2 to 20 carbon atoms) can be used as needed.

[0102] The polymerization temperature is preferably 25 to 140°C, and more preferably 50 to 120°C. In addition to the solution polymerization described above, (A) can also be obtained by bulk polymerization, emulsion polymerization, or suspension polymerization.

[0103] When (A) is a copolymer, the polymerization form may be either a random addition copolymer or an alternating copolymer, and it may also be either a graft copolymer or a block copolymer.

[0104] <Ester compound (B)> The lubricating oil composition of the present invention contains an ester compound (B) represented by the following general formula (3). [Chemical formula] [In general formula (3), R 6 is each independently an alkyl group having 1 to 12 carbon atoms which may have a substituent, R 7 is each independently an alkylene group having 2 to 6 carbon atoms which may have a substituent, R 8 is a residue obtained by removing two carboxyl groups from a chain aliphatic dicarboxylic acid (x) having 4 to 12 carbon atoms, and n each independently represents an integer of 1 to 3.] In general formula (3), R 6 is each independently an alkyl group having 1 to 12 carbon atoms which may have a substituent. Specifically, a methyl group, an ethyl group, a linear alkyl group having 3 to 12 carbon atoms {for example, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, etc.}, a branched alkyl group having 3 to 12 carbon atoms {for example, isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, sec-pentyl group, neopentyl group, 3-pentyl group, tert-pentyl group, 2-ethylhexyl group, etc.} and the like can be mentioned. Among these, from the viewpoints of thermal conductivity and insulation, 1 to 10 carbon atoms are preferable, more preferably 1 to 8 carbon atoms, and particularly preferably 5 to 6 carbon atoms from the viewpoint of friction reduction. Also, from the viewpoint of thermal conductivity, a linear alkyl group is preferable.

[0105] The heat transfer rate is a value calculated by the following formula from density, thermal conductivity, kinematic viscosity, etc. It tends to increase as the thermal conductivity is higher and the kinematic viscosity is lower.

[0106] R 6 Examples of the substituent which may be possessed include a hydroxyl group, a substituted or unsubstituted amino group, a halogen group, a nitro group, a nitrile group, a carbonyl group, an imino group and the like. From the viewpoint of thermal conductivity, R 6 is preferably an alkyl group having no substituent.

[0107] In general formula (3), R 7 Each of these is independently a C2-C3 alkylene group which may have substituents, and specifically includes ethylene group, trimethylene group, 1,2-propylene group (-CH(CH3)CH2- or -CH2CH(CH3)-), 1,2-, 1,3- or 1,4-butylene group, isobutylene group, 1,2-, 1,3-, 1,4- or 1,5-pentylene group, 1,2-, 1,3-, 1,4-, 1,5- or 1,6-hexylene group, etc. Of these, the ethylene group is preferred from the viewpoint of thermal conductivity.

[0108] In general formula (3), n represents an integer from 1 to 3 independently, and 1 is preferred from the viewpoint of thermal conductivity, friction reduction, and thermal stability.

[0109] R 8 (x) is a residue obtained by removing two carboxyl groups from a linear aliphatic dicarboxylic acid (x) having 4 to 12 carbon atoms. Specifically, (x) can be a linear aliphatic dicarboxylic acid {e.g., succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanediic acid, dodecanediic acid, etc.}, a branched aliphatic dicarboxylic acid {e.g., methylsuccinic acid, 2-methylglutaric acid, 2-methyladipic acid, 3-methyladipic acid, 2,4-dimethylpimelic acid, 2,6-dimethylpimelic acid, etc.}, or aliphatic dicarboxylic acid with substituents {e.g., malic acid, tartaric acid, etc.}.

[0110] Of these, from the viewpoint of thermal conductivity and friction reduction, a linear aliphatic dicarboxylic acid having 6 to 10 carbon atoms is preferred, more preferably a linear aliphatic dicarboxylic acid having 6 to 10 carbon atoms, and particularly preferably adipic acid.

[0111] The ester compound (B) may be a diester compound of a monohydric alcohol (y) represented by the following general formula (4) and the chain-like aliphatic divalent carboxylic acid (x). R 6 -(OR 7 )n-OH (4) In general formula (4), R 6 , R 7 and n are R in the general formula (3) above, respectively. 6 , R 7 And is synonymous with n, and the same applies to preferred terms.

[0112] Specifically, as a monohydric alcohol (y), R 7 Those with 2 carbon atoms; Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monopentyl ether, ethylene glycol monohexyl ether, ethylene glycol monoheptyl ether, ethylene glycol monooctyl ether, ethylene glycol monononyl ether, ethylene glycol monodecyl ether, ethylene glycol monoundecyl ether, ethylene glycol monododecyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monopentyl ether, diethylene glycol monohexyl ether, diethylene glycol monoheptyl Examples include ethers, diethylene glycol monooctyl ether, diethylene glycol monononyl ether, diethylene glycol monodecyl ether, diethylene glycol monoundecyl ether, diethylene glycol monododecyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, triethylene glycol monopentyl ether, triethylene glycol monohexyl ether, triethylene glycol monoheptyl ether, triethylene glycol monooctyl ether, triethylene glycol monononyl ether, triethylene glycol monodecyl ether, triethylene glycol monoundecyl ether, triethylene glycol monododecyl ether, and the like.

[0113] R 7 Those with 3 carbon atoms; Propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol monopentyl ether, propylene glycol monohexyl ether, propylene glycol monoheptyl ether, propylene glycol monooctyl ether, propylene glycol monononyl ether, propylene glycol monodecyl ether, propylene glycol monoundecyl ether, propylene glycol monododecyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, dipropylene glycol monopentyl ether, dipropylene glycol monohexyl ether, dipropylene glycol monoheptyl Examples include dipropylene glycol monooctyl ether, dipropylene glycol monononyl ether, dipropylene glycol monodecyl ether, dipropylene glycol monoundecyl ether, dipropylene glycol monododecyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, tripropylene glycol monobutyl ether, tripropylene glycol monopentyl ether, tripropylene glycol monohexyl ether, tripropylene glycol monoheptyl ether, tripropylene glycol monooctyl ether, tripropylene glycol monononyl ether, tripropylene glycol monodecyl ether, tripropylene glycol monoundecyl ether, and tripropylene glycol monododecyl ether.

[0114] R 7 Those with 4 carbon atoms; Butylene glycol monomethyl ether, butylene glycol monoethyl ether, butylene glycol monopropyl ether, butylene glycol monobutyl ether, butylene glycol monopentyl ether, butylene glycol monohexyl ether, butylene glycol monoheptyl ether, butylene glycol monooctyl ether, butylene glycol monononyl ether, butylene glycol monodecyl ether, butylene glycol monoundecyl ether, butylene glycol monododecyl ether, dibutylene glycol monomethyl ether, dibutylene glycol monoethyl ether, dibutylene glycol monopropyl ether, dibutylene glycol monobutyl ether, dibutylene glycol monopentyl ether, dibutylene glycol monohexyl ether, dibutylene glycol monoheptyl Examples include ethers, dibutylene glycol monooctyl ether, dibutylene glycol monononyl ether, dibutylene glycol monodecyl ether, dibutylene glycol monoundecyl ether, dibutylene glycol monododecyl ether, tributylene glycol monomethyl ether, tributylene glycol monoethyl ether, tributylene glycol monopropyl ether, tributylene glycol monobutyl ether, tributylene glycol monopentyl ether, tributylene glycol monohexyl ether, tributylene glycol monoheptyl ether, tributylene glycol monooctyl ether, tributylene glycol monononyl ether, tributylene glycol monodecyl ether, tributylene glycol monoundecyl ether, tributylene glycol monododecyl ether, and the like.

[0115] R 7 Those with 5 carbon atoms; Pentylene glycol monomethyl ether, pentylene glycol monoethyl ether, pentylene glycol monopropyl ether, pentylene glycol monobutyl ether, pentylene glycol monopentyl ether, pentylene glycol monohexyl ether, pentylene glycol monoheptyl ether, pentylene glycol monooctyl ether, pentylene glycol monononyl ether, pentylene glycol monodecyl ether, pentylene glycol monoundecyl ether, pentylene glycol monododecyl ether, dipentylene glycol monomethyl ether, dipentylene glycol monoethyl ether, dipentylene glycol monopropyl ether, dipentylene glycol monobutyl ether, dipentylene glycol monopentyl ether, dipentylene glycol monohexyl ether, dipentylene glycol monoheptyl Examples include tripentylene glycol monooctyl ether, dipentylene glycol monononyl ether, dipentylene glycol monodecyl ether, dipentylene glycol monoundecyl ether, dipentylene glycol monododecyl ether, tripentylene glycol monomethyl ether, tripentylene glycol monoethyl ether, tripentylene glycol monopropyl ether, tripentylene glycol monobutyl ether, tripentylene glycol monopentyl ether, tripentylene glycol monohexyl ether, tripentylene glycol monoheptyl ether, tripentylene glycol monooctyl ether, tripentylene glycol monononyl ether, tripentylene glycol monodecyl ether, tripentylene glycol monoundecyl ether, tripentylene glycol monododecyl ether, and the like.

[0116] R 7 Those with 6 carbon atoms; Hexylene glycol monomethyl ether, hexylene glycol monoethyl ether, hexylene glycol monopropyl ether, hexylene glycol monobutyl ether, hexylene glycol monopentyl ether, hexylene glycol monohexyl ether, hexylene glycol monoheptyl ether, propylene glycol monooctyl ether, hexylene glycol monononyl ether, hexylene glycol monodecyl ether, hexylene glycol monoundecyl ether, hexylene glycol monododecyl ether, dihexylene glycol monomethyl ether, dihexylene glycol monoethyl ether, dihexylene glycol monopropyl ether, dihexylene glycol monobutyl ether, dihexylene glycol monopentyl ether, dihexylene glycol monohexyl ether, dihexylene glycol monoheptyl Examples include dihexylene glycol monooctyl ether, dihexylene glycol monononyl ether, dihexylene glycol monodecyl ether, dihexylene glycol monoundecyl ether, dihexylene glycol monododecyl ether, trihexylene glycol monomethyl ether, trihexylene glycol monoethyl ether, trihexylene glycol monopropyl ether, trihexylene glycol monobutyl ether, trihexylene glycol monopentyl ether, trihexylene glycol monohexyl ether, trihexylene glycol monoheptyl ether, trihexylene glycol monooctyl ether, trihexylene glycol monononyl ether, trihexylene glycol monodecyl ether, trihexylene glycol monoundecyl ether, trihexylene glycol monododecyl ether, and the like.

[0117] Of these, from the viewpoint of thermal conductivity, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monopentyl ether, ethylene glycol monohexyl ether, ethylene glycol monoheptyl ether, ethylene glycol monooctyl ether, ethylene glycol monononyl ether, and ethylene glycol monodecyl ether are preferred, and more preferably ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monopentyl ether, ethylene glycol monohexyl ether, ethylene glycol monoheptyl ether, and ethylene glycol monooctyl ether are preferred, and from the viewpoint of lubricity, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monopentyl ether, and ethylene glycol monohexyl ether are particularly preferred.

[0118] As for the ester compound (B), from the viewpoint of thermal conductivity, it is preferable to have 2 to 4 methyl groups, more preferably 2 to 3, and particularly preferably 2.

[0119] As an ester compound (B) having two methyl groups, in general formula (3), R 6 is a linear alkyl group, and R 7 is an ethylene group or a trimethylene group, R 8 Examples include compounds in which two carboxyl groups have been removed from a linear aliphatic divalent carboxylic acid.

[0120] In ester compound (B), the total number of terminal methyl groups (-CH3), methylene groups (-CH2-), carbonyl groups (-C(=O)-), and ether groups (-O-) in the main chain (main chain length) is preferably 16 to 30, and more preferably 22 to 30, from the viewpoint of thermal conductivity and friction coefficient.

[0121] The SP value of ester compound (B) is 8.8-9.6 (cal / cm³) from the viewpoint of the solubility of (A). 3 ) 1 / 2 Preferably, and more preferably, 9.0 to 9.6 (cal / cm²). 3 ) 1 / 2 That is the case.

[0122] Kinematic viscosity of ester compound (B) at 40°C (measured according to JIS-K2283) (unit: mm) 2 From the viewpoint of cooling performance, the value of / s (hereinafter abbreviated) is preferably 5.0 to 20.0, and more preferably 5.0 to 10.0.

[0123] A value of 5.0 or higher indicates good lubrication, while a value of 20.0 or lower indicates good cooling.

[0124] The kinematic viscosity of ester compound (B) at 40°C can be adjusted by the number of carbon atoms in the carboxylic acid and alcohol used in the synthesis. For example, using compounds with fewer carbon atoms tends to result in lower kinematic viscosity, while using compounds with more carbon atoms tends to result in higher kinematic viscosity.

[0125] Kinematic viscosity of ester compound (B) at 100°C (measured according to JIS-K2283) (unit: mm) 2 From the viewpoint of lubricity, the value of / s (hereinafter abbreviated) is preferably 1.0 to 10.0, and more preferably 1.0 to 5.0.

[0126] The kinematic viscosity of ester compound (B) at 100°C can be adjusted by the number of carbon atoms in the carboxylic acid and alcohol used in the synthesis. For example, using compounds with fewer carbon atoms tends to result in lower kinematic viscosity, while using compounds with more carbon atoms tends to result in higher kinematic viscosity.

[0127] The volume resistivity of ester compound (B) at 25°C (measured in accordance with JIS C2101 24 (Volume resistivity test, room temperature 25°C)) is, from the viewpoint of insulating properties, 10 as the lower limit. 8Preferably Ω·cm or more, and more preferably 10 9 Ω·cm or more, particularly preferably 10 10 It is greater than or equal to Ω·cm.

[0128] The volume resistivity of ester compound (B) can be adjusted by the number of carbon atoms in the carboxylic acid and alcohol used during synthesis. For example, using compounds with fewer carbon atoms tends to result in lower volume resistivity, while using compounds with more carbon atoms tends to result in higher volume resistivity.

[0129] The heat transfer coefficient of ester compound (B) at 40°C (calculated under the conditions described below) is 2.15 W / (m²) from the viewpoint of cooling performance. 2 A value of 2.20 W / (m²) or higher is preferred, and more preferably 2.20 W / (m²). 2 / K) is greater than or equal to this.

[0130] The heat transfer coefficient of ester compound (B) at 40°C tends to decrease when a compound with a small number of carbon atoms is used, as the thermal conductivity decreases and the heat transfer coefficient tends to decrease, while it tends to increase when a compound with a large number of carbon atoms is used, as the thermal conductivity increases and the heat transfer coefficient tends to increase.

[0131] In the present invention, the method for producing the ester compound (B) is not particularly limited and can be produced by known methods. For example, it can be synthesized by esterification condensation or transesterification reaction between the monohydric alcohol (y) and at least one selected from the group consisting of the linear aliphatic divalent carboxylic acid (x), the lower alcohol ester of (x), and the acid anhydride of (x).

[0132] The reaction temperature is preferably 120 to 160°C.

[0133] Examples of catalysts include sodium hydroxide, p-toluenesulfonic acid, boron trifluoride, hydrogen fluoride, tin chloride, zinc, titanium, potassium hydroxide, mineral acids (sulfuric acid, hydrochloric acid, etc.), zinc chloride, hypophosphorous acid, and dibutyltin oxide, with p-toluenesulfonic acid and hypophosphorous acid being preferred. The process can also be carried out without a catalyst.

[0134] Suitable reaction solvents include benzene, toluene, and xylene, with toluene and xylene being preferred. The reaction can also be carried out without a solvent.

[0135] The molar ratio (OH / COOH) of the hydroxyl group of the monohydric alcohol (y) to the carboxyl group of the linear aliphatic dicarboxylic acid (x) is preferably 2.0 / 1.0 to 3.0 / 1.0, and more preferably 2.2 / 1.0 to 2.8 / 1.0, from the viewpoint of heat resistance.

[0136] The ester condensation reaction can be carried out using, for example, the acid value as an indicator, and the acid value of the ester compound (B) is preferably 3 mg KOH / g or less, more preferably 1 mg KOH / g or less.

[0137] The ester condensation reaction can be carried out using, for example, the hydroxyl value as an indicator, and the hydroxyl value of the ester compound (B) is preferably 3 mg KOH / g or less, more preferably 1 mg KOH / g or less.

[0138] <Lubricating oil composition> The lubricating oil composition of the present invention is a lubricating oil composition comprising the polymer (A) and the ester compound (B), and may also contain other base oils, additives, etc., in addition to (A) and (B). Other base oils include mineral oils (solvent-refined oils, paraffin oils, high viscosity index oils containing isoparaffins, high viscosity index oils obtained by hydrocracking of isoparaffins, and naphthenic oils, etc.), synthetic lubricants [GTL oils (Gas to Liquid), hydrocarbon-based synthetic lubricants (poly-α-olefin-based synthetic lubricants, etc.)]. Of these, mineral oils and synthetic lubricants are preferred from the viewpoint of insulation, and mineral oils are more preferred.

[0139] Other base oils are preferred, from the viewpoint of cooling properties, to have a kinematic viscosity of 6 to 20 at 40°C, and more preferably 6 to 15.

[0140] Examples of additives include at least one additive selected from the group consisting of detergents, dispersants, antioxidants, oiliness improvers, friction and wear modifiers, extreme pressure agents, defoamers, anti-emulsifiers, corrosion inhibitors, and pour point depressants. (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) Friction and wear modifiers: Molybdenum-based and zinc-based compounds (such as molybdenum dithiophosphate, molybdenum dithiocarbamate, and zinc dialkyldithiophosphate); (6) Extreme pressure agents: Sulfur compounds (mono- or disulfide, sulfoxide, and sulfur phosphide compounds), phosphide compounds, and chlorine compounds (such as chlorinated paraffins); (7) Antifoaming agent: Silicone oils, metallic soaps, fatty acid esters, and phosphate compounds, etc. (8) Antiemulsifiers: Quaternary ammonium salts (such as tetraalkylammonium salts), sulfated oils, and phosphates (such as phosphates of polyoxyethylene-containing nonionic surfactants), etc. (9) Corrosion inhibitors: Nitrogen atom-containing compounds (such as benzotriazole and 1,3,4-thiodiazolyl-2,5-bisdialkyldithiocarbamate), etc. (10) Pour point effectors: Polyalkyl methacrylate, polyalkyl acrylate, polyalkylstyrene, polyvinyl acetate, etc.

[0141] Kinematic viscosity of lubricating oil composition at 100°C (measured according to JIS-K2283) (unit: mm) 2 The value of / s (hereinafter abbreviated) is preferably 2.0 to 6.0, and more preferably 2.5 to 5.5, from the viewpoint of cooling performance and lubrication performance.

[0142] If the kinematic viscosity of the lubricating oil composition at 100°C is 2.0 or higher, it exhibits good lubrication, and if it is 6.0 or lower, it exhibits good cooling performance.

[0143] Kinematic viscosity of lubricating oil composition at 40°C (measured according to JIS-K2283) (unit: mm) 2 From the viewpoint of lubrication, the value of / s (hereinafter abbreviated) is preferably 5 to 18, and more preferably 8 to 15.

[0144] Kinematic viscosity of lubricating oil composition at 80°C (measured according to JIS-K2283) (unit: mm) 2 The value of / s (hereinafter abbreviated) is preferably 2 to 9, and more preferably 3 to 8, from the viewpoint of cooling and lubrication.

[0145] From the viewpoint of cooling and lubrication, the ratio of the kinematic viscosity at 40°C to the kinematic viscosity at 80°C (40°C / 80°C) of the lubricating oil composition is preferably 1.40 or higher at the lower limit, more preferably 1.50 or higher, and particularly preferably 1.60 or higher, and preferably 2.00 or lower at the upper limit, more preferably 1.95 or lower, and particularly preferably 1.92 or lower.

[0146] When the ratio is 1.40 or higher, lubrication tends to be good, and when it is 2.00 or lower, cooling tends to be good.

[0147] From the viewpoint of lubricity and cooling properties, the content of polymer (A) in the lubricating oil composition is preferably 0.1% by weight or more, more preferably 0.2% by weight or more, and preferably 30% by weight or less, more preferably 20% by weight or less, and particularly preferably 10% by weight or less, based on the weight of the lubricating oil composition.

[0148] From the viewpoint of cooling performance, the content of ester compound (B) in the lubricating oil composition is preferably 10% by weight or more, more preferably 30% by weight or more, particularly preferably 50% by weight or more, most preferably 70% by weight or more, and preferably 100% by weight or less, based on the weight of the lubricating oil composition.

[0149] From the viewpoint of cooling performance, the content of other base oils in the lubricating oil composition is preferably 90% by weight or less, more preferably 70% by weight or less, particularly preferably 50% by weight or less, and most preferably 30% by weight or less, based on the weight of the lubricating oil composition.

[0150] The amount of additives in the lubricating oil composition (total amount if multiple types are included) may include various additives as needed, as long as the cooling performance is not impaired.

[0151] The weight ratio ((A) / (B)) of polymer (A) to ester compound (B) in the lubricating oil composition is preferably 0.1 / 99.9 to 30.0 / 70.0, more preferably 0.2 / 99.8 to 20.0 / 80.0, and most preferably 0.2 / 99.8 to 10.0 / 90.0, from the viewpoint of lubricity and cooling properties.

[0152] The weight ratio of the ester compound (B) to the base oil other than (B) in the lubricating oil composition ((B) / base oil other than (B)) is preferably 10 / 90 to 100 / 0, more preferably 30 / 70 to 100 / 0, particularly preferably 50 / 50 to 100 / 0, and most preferably 70 / 30 to 100 / 0, from the viewpoint of cooling and insulating properties.

[0153] The weight ratio ((B) / mineral oil) of the ester compound (B) to the mineral oil in the lubricating oil composition is preferably 10 / 90 to 100 / 0, more preferably 30 / 70 to 100 / 0, particularly preferably 50 / 50 to 100 / 0, and most preferably 70 / 30 to 100 / 0, from the viewpoint of cooling and insulating properties.

[0154] The absolute difference between the SP value of polymer (A) and the SP value of ester compound (B) in the lubricating oil composition is 2.0 (cal / cm³) from the viewpoint of solubility. 3 ) 1 / 2 The following is preferred, and more preferably 1.0 (cal / cm³). 3 ) 1 / 2 The following applies:

[0155] If (A) and (B) each contain multiple types, it is preferable that the arithmetic mean value based on weight fraction satisfies the above relationship.

[0156] The thermal conductivity of the lubricating oil composition at 25°C (measured with a thermal characteristic meter under the conditions described below) is preferably 0.143 W / (m·K) or higher, and more preferably 0.145 W / (m·K) or higher, from the viewpoint of cooling performance.

[0157] The lubricating oil composition may contain a monohydric alcohol (y) and / or a linear aliphatic dicarboxylic acid (x).

[0158] The content of monohydric alcohol (y) in the lubricating oil composition is preferably 0.01 to 0.30% by weight, and more preferably 0.01 to 0.10% by weight, based on the weight of the lubricating oil composition.

[0159] The content of the linear aliphatic dicarboxylic acid (x) in the lubricating oil composition is preferably 0.01 to 0.30% by weight, and more preferably 0.01 to 0.10% by weight, based on the weight of the lubricating oil composition.

[0160] The hydroxyl value of the lubricating oil composition (measured in accordance with JIS K0070) is preferably 1.0 mg KOH / g or less from the viewpoint of heat resistance. The hydroxyl value can be adjusted by sufficiently reducing the remaining hydroxyl groups during the reaction process.

[0161] The acid value of the lubricating oil composition (measured in accordance with JIS K 2501) is preferably 1.0 mg KOH / g or less from the viewpoint of heat resistance. The acid value can be adjusted by neutralizing the carboxylic acid contained in the lubricating oil composition.

[0162] The lubricating oil composition of the present invention has excellent cooling properties (heat transfer coefficient) and oil film thickness, and is therefore suitably used in gear oil (differential oil and industrial gear oil, etc.), MTF, transmission oil [ATF and belt-CVTF, etc.], traction oil (toroidal-CVTF, etc.), shock absorber oil, power steering oil, hydraulic oil (hydraulic oil for construction machinery and industrial hydraulic oil, etc.), and engine oil. From the viewpoint of easily exhibiting cooling properties and friction reduction effects, it is preferably used as transmission oil, electric motor oil, or dual-purpose oil for transmissions and electric motors in electric vehicles or hybrid vehicles, and is particularly preferably used as dual-purpose oil for transmissions and electric motors in electric vehicles or hybrid vehicles. [Examples]

[0163] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0164] <Manufacturing Example 1> 277.6 g (2.1 mol) of ethylene glycol monopentyl ether, 146.1 g (1.0 mol) of adipic acid, and sulfuric acid (0.2 wt% of the total amount of acid and alcohol) as a catalyst were charged into a 500 ml four-necked flask equipped with a stirrer, thermometer, and water distillation receiver with condenser, and the temperature was raised to 150 °C. The esterification reaction was carried out for approximately 5 hours while removing the generated water. After the reaction was completed, the mixture was neutralized with an excess of caustic soda aqueous solution relative to the total acid value, and then washed with water until neutral. Distillation was then carried out at 180 °C and 2 kPa to obtain 337.5 g (90% yield) of ester oil (B-1) as ester compound (B). The kinematic viscosity (40 °C, 100 °C), thermal conductivity, heat transfer coefficient, and MTM (mini-traction) friction coefficient (100 mm / s, 10 mm / s) of the obtained ester oil were evaluated. The results are shown in Table 2.

[0165] <Manufacturing Examples 2-10, Comparative Manufacturing Examples 1-4> Ester compounds (B) were obtained as ester oils (B-2) to (B-10) and (B'-1) to (B'-4) in the same manner as in Example 1, except that 2.1 moles of monohydric alcohol (y) or other monohydric alcohol (y') listed in Table 2 were used instead of ethylene glycol monopentyl ether, and 1.0 mole of dibasic acid (x) listed in Table 2 was used instead of adipic acid. The kinematic viscosity (40°C, 100°C), thermal conductivity, heat transfer coefficient, and MTM friction coefficient (100 mm / s, 10 mm / s) of the obtained ester oils were evaluated. The results are shown in Table 2.

[0166] [Table 2]

[0167] <Manufacturing Example 11> Production of polymer solution (R-1) In a reaction vessel equipped with a stirring device, a heating / cooling device, a thermometer and a nitrogen inlet tube, 100 parts by weight of monomer formulation {monomer (a-1) [2-dodecylhexadecyl methacrylate (esterified product of ISOFOL28 manufactured by Sasol and methacrylic acid)] 17.5 parts by weight, monomer (a-2) [2-tetradecyloctadecyl methacrylate (esterified product of ISOFOL32 manufactured by Sasol and methacrylic acid)] 17.5 parts by weight, monomer (c-1) [methyl methacrylate] 65 parts by weight} is added, and as a polymerization base oil, ester compound (B-1) [E 400 parts by weight of a diester of ethylene glycol monohexyl ether and adipic acid, and 0.2 parts by weight of 1,1'-di(t-butylperoxy)cyclohexane were added, and the mixture was purged with nitrogen (gas phase oxygen concentration 100 ppm). The mixture was heated to 100°C under a sealed container with stirring, and the polymerization reaction was carried out at the same temperature for 4 hours. After raising the temperature to 110°C, the mixture was aged for 2 hours, and then raised to 130°C. Unreacted monomers were removed over 1 hour under reduced pressure (0.027~0.040 MPa) at the same temperature to obtain polymer solution (R-1) containing polymer (A-1).

[0168] <Manufacturing Example 12> Production of polymer solution (R-2) In Production Example 11, 0.1 parts by weight of dodecyl mercaptan was added to the reaction vessel, and the other operations were carried out in the same manner to obtain polymer solution (R-2) containing polymer (A-2).

[0169] <Manufacturing Example 13> Production of polymer solution (R-3) In Production Example 11, 1.0 part by weight of dodecyl mercaptan was added to the reaction vessel, and the other operations were carried out in the same manner to obtain polymer solution (R-3) containing polymer (A-3).

[0170] <Manufacturing Examples 14-22, Comparative Manufacturing Examples 11-15> Preparation of polymer solutions (R-4) to (R-12) and (R'-1) to (R'-5) The reaction was carried out in the same manner as in Production Example 11, except that the polymerized base oil was changed to one of those listed in Table 3, to obtain polymer solutions (R-4) to (R-12) and (R'-1) to (R'-5) containing the polymer, respectively.

[0171] <Manufacturing Examples 23-29, Comparative Manufacturing Example 16> Preparation of polymer solutions (R-13) to (R-19) and (R'-6) In Production Example 11, the reaction was carried out similarly except that the monomer formulation and polymer base oil were changed to those listed in Table 3 or 4, yielding polymer solutions (R-13) to (R-19) and (R'-6) containing polymers, respectively.

[0172] [Table 3]

[0173] [Table 4]

[0174] The compositions of monomers (a) to (g) listed in Tables 3 and 4 are as follows. (a-1): 2-dodecylhexadecyl methacrylate (esterified product of ISOFOL28 manufactured by Sasol and methacrylic acid) (a-2): 2-tetradecyloctadecyl methacrylate (esterified product of ISOFOL32 manufactured by Sasol and methacrylic acid) (a-3): 2-Hexadecylicosyl methacrylate (esterified product of ISOFOL36 manufactured by Sasol and methacrylate) (b-1): Polybutadiene macromonomer (esterified product of Kuraray's L-1203 [1,2-adduct / 1,4-adduct = 45 / 55] and methacrylic acid, Mn = 6960) (b-2): Polybutadiene macromonomer (esterified product of Kuraray's L-3203 [1,2-adduct / 1,4-adduct = 65 / 35] and methacrylic acid, Mn = 6960) (b-3): Polybutadiene macromonomer (esterified with methacrylic acid from HLBH-1500M [1,2-adduct / 1,4-adduct = 65 / 35] manufactured by Cray Valley, Mn = 2700) (c-1): Methyl methacrylate (c-2): n-butyl methacrylate (d-1): n-dodecyl methacrylate (d-2): n-tetradecyl methacrylate (d-3): n-hexadecyl methacrylate (d-4): n-octadecyl methacrylate (d-5): Decyltetradecyl methacrylate (e-1): Hydroxyethyl methacrylate (f-1): Methacryloyloxyethyl phosphate (g-1): N,N-dimethylaminoethyl methacrylate

[0175] Furthermore, the ester oil (B'-5) and mineral oil (C-1) used in Tables 3-8 are as follows. (B'-5): Diester of neopentyl glycol and octanoic acid (kinematic viscosity at 40°C: 7.00 mm) 2 / s, 100℃ kinematic viscosity: 2.20mm 2 ( / s, SP value: 8.93) (C-1): Mineral oil (SK Lubricants YUBASE3, kinematic viscosity at 40°C: 12.43 mm) 2 / s, 100℃ kinematic viscosity: 3.12mm 2 ( / s, SP value: 8.30)

[0176] <Examples 1-25, Comparative Examples 1-6> Manufacturing and evaluation of lubricating oil compositions (V-1) to (V-25) and (V'-1) to (V'-6) In a stainless steel container equipped with a stirring device, polymer solutions (R-1) to (R-19) and (R'-1) to (R'-6) were blended with base oil in the amounts shown in Tables 5 to 8 to obtain lubricating oil compositions (V-1) to (V-25) and (V'-1) to (V'-6).

[0177] [Table 5]

[0178] [Table 6]

[0179] [Table 7]

[0180] [Table 8]

[0181] The kinematic viscosity, viscosity index, oil film thickness, thermal conductivity, heat transfer coefficient, and volume resistivity of lubricating oil compositions (V-1) to (V-25) and (V'-1) to (V'-7) at each temperature were measured using the following method.

[0182] The following commercially available ATF oil was used in Comparative Example 7. Manufactured by Toyota, product name "TOYOTA AUTO FLUID WS"

[0183] <Method for measuring the kinematic viscosity of a lubricating oil composition and method for calculating the viscosity index> The kinematic viscosity was measured at 100°C and 40°C according to the JIS-K2283 method, and the viscosity index was calculated.

[0184] <Measurement of thermal conductivity> The measurements were taken using a Decagon KD2pro thermal characteristics meter with a single needle sensor at room temperature of 25°C.

[0185] <Method for calculating heat transfer coefficient> The heat transfer coefficient at 40°C and 80°C was calculated using the following formulas based on the kinematic viscosity, thermal conductivity, density, and constant-pressure specific heat of the lubricating oil composition at each temperature (40°C or 80°C). Heat transfer coefficient (W / m 2 K)=(density[kg / m 3 ]) 0.33 × (Specific heat at constant pressure [kJ / kgK]) 0.33 × (Thermal conductivity [W / mK]) 0.67 / (Kinematic viscosity [mm 2 / s]) 0.17 The density was measured by DA-645 manufactured by Kyoto Electronics Industry Co., Ltd. The specific heat at constant pressure was measured by Q-20 manufactured by TA Instruments.

[0186] <MTM (Mini Traction) Friction Coefficient> Using an MTM (Mini Traction) tester, measurements were taken under the following measurement conditions to obtain a Stribeck curve, and the friction coefficients at speeds of 10 mm / s and 100 mm / s were used as results. Equipment: PCS Instruments MTM-2 Disk: MTM polished disc (standard) (0.01 micron) Ball: Drilled 3 / 4 AISI52100 precision steel ball Speed: 10 mm / s to 3,000 mm / s Temperature: 100 °C Sliding / Rolling Ratio: 50% Load: 30 N

[0187] <Measurement of Oil Film Thickness> Using the optical interference method with an EHD tester (manufactured by PCS Instruments), the oil film thickness (nm) at a constant load and slip ratio was calculated to evaluate the oil film thickness forming ability of each lubricating oil composition. The test conditions of the EHD tester are shown below. Disk: EHD Silica Spacer Layer Disc Ball: 3 / 4’’ Plain Steel Ball Load: 30 N Ball Speed: 10 mm to 3,000 mm / s Temperature: 100 °C Slip Ratio: 0% The oil film thickness (nm) at 10 mm / s was used as the measurement result. The measured oil film thickness (nm) was evaluated according to the following criteria. ☆: 5.0 nm or more ◎: 4.0 nm or more and less than 5.0 nm ○: 3.0 nm or more and less than 4.0 nm △: 2.0nm or more and less than 3.0nm ×: Less than 2.0nm

[0188] The results in Tables 5-8 show that the lubricating oil composition of the present invention has a high heat transfer coefficient, a thick oil film, and can achieve both cooling and lubrication properties. On the other hand, the lubricating oil compositions of Comparative Examples 1 to 6 have a low heat transfer coefficient of 2.23 or less, a thin oil film thickness, and inferior cooling and lubrication properties. [Industrial applicability]

[0189] The lubricating oil composition of the present invention has excellent cooling and lubrication properties and is therefore suitably used in gear oil (differential oil and industrial gear oil, etc.), MTF, transmission oil [ATF and belt-CVTF, etc.], traction oil (toroidal-CVTF, etc.), shock absorber oil, power steering oil, hydraulic oil (hydraulic oil for construction machinery and industrial hydraulic oil, etc.), and engine oil. In particular, it is useful as transmission oil, electric motor oil, and dual-purpose oil for transmissions and electric motors in electric vehicles or hybrid vehicles, and is extremely useful as a dual-purpose oil for transmissions and electric motors in electric vehicles or hybrid vehicles.

Claims

1. A lubricating oil composition comprising a polymer (A) having monomer (a) represented by the following general formula (1) and / or monomer (b) represented by the following general formula (2) as essential constituent monomers, and an ester compound (B) represented by the following general formula (3). 【Chemistry 1】 [In general formula (1), R １ is a hydrogen atom or a methyl group; -X １ - represents a group represented by -O- or -NH-; R ２ O is a linear or branched alkylene oxy group having 2 to 4 carbon atoms, and if p is 2 or more, there are multiple R ２ They may be the same or different. p is an integer from 0 to 20; R ３ [This represents a linear or branched alkyl group having 25 to 44 carbon atoms.] 【Chemistry 2】 [In general formula (2), R ４ is a hydrogen atom or a methyl group; -X ２ - is a group represented by -O-, -O(AO) ｍ - or -NH-, A is an alkylene group having 2 to 4 carbon atoms, m is an integer of 0 to 10, and when m is 2 or more, A may be the same or different; R ５ is a residue obtained by removing one hydrogen atom from a hydrocarbon polymer having 43 or more carbon atoms having an isobutylene group and / or a 1,2-butylene group as an essential constituent unit; q represents a number of 0 or 1.] 【Transformation 3】 [In general formula (3), R ６ Each of these is an alkyl group having 1 to 12 carbon atoms, which may each have substituents, and R ７ Each of these is an alkylene group having 2 to 6 carbon atoms, which may independently have substituents, and R ８ [x] is a residue obtained by removing two carboxyl groups from a chain-like aliphatic divalent carboxylic acid (x) having 4 to 12 carbon atoms, and n independently represents an integer from 1 to 3.

2. The lubricating oil composition according to claim 1, wherein the weight-average molecular weight of the polymer (A) is 100,000 to 2,000,000.

3. The solubility parameter of the polymer (A) is 9.0 to 11.5 (cal / cm³). ３ ) １／２ The lubricating oil composition according to claim 1.

4. The kinematic viscosity of the ester compound (B) at 100°C is 1.0 to 5.0 mm. ２ The lubricating oil composition according to claim 1, wherein the value is / s.

5. The solubility parameter of the ester compound (B) is 8.8 to 9.6 (cal / cm³). ３ ) １／２ The lubricating oil composition according to claim 1.

6. The lubricating oil composition according to claim 1, wherein the content of the polymer (A) is 0.1 to 30% by weight.

7. The absolute value of the difference between the solubility parameter of polymer (A) and the solubility parameter of ester compound (B) is 2.0 (cal / cm³). ３ ) １／２ The lubricating oil composition according to claim 1, wherein the following applies:

8. The lubricating oil composition according to claim 1, wherein the polymer (A) contains an alkyl (meth)acrylate (c) having an alkyl group having 1 to 4 carbon atoms as a constituent monomer.

9. The lubricating oil composition according to claim 8, wherein the polymer (A) is a polymer comprising, based on the weight of polymer (A), monomers (a) and (b) in total at 10 to 60% by weight and alkyl (meth)acrylate (c) at 40 to 90% by weight.

10. The lubricating oil composition according to claim 1, used as transmission fluid for a hybrid vehicle.

11. The lubricating oil composition according to claim 1, which is used as a dual-purpose oil for the transmission and electric motor in an electric vehicle or hybrid vehicle.

12. The lubricating oil composition according to claim 1, comprising one or more additives selected from the group consisting of dispersants, detergents, antioxidants, oiliness improvers, pour point depressants, friction and wear modifiers, extreme pressure agents, defoamers, anti-emulsifiers, and corrosion inhibitors.

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