Lubricant agent composition and lubricant agent additive

Abstract

To provide a novel lubricant agent additive and a novel lubricant agent composition that can reduce friction of a sliding part.SOLUTION: A lubricant agent additive comprises a polymer containing an olefin compound as a monomer unit or a modified polymer obtained by modifying a hydrogenated polymer with maleic acid or maleic anhydride. A lubricant agent composition comprises: a base oil; and a polymer containing an olefin compound as a monomer unit or a modified polymer obtained by modifying a hydrogenated polymer with maleic acid or maleic anhydride.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to lubricating oil compositions and lubricating oil additives. [Background technology]

[0002] Lubricating oil compositions are used in the sliding parts of mechanical systems to lubricate the sliding parts. Lubricating oil compositions generally contain base oils and additives selected according to desired properties. Reducing friction in sliding parts is essential for saving energy and power in mechanical systems. To reduce friction in sliding parts, for example, friction reducers are used as additives. As friction reducers, for example, Patent Document 1 discloses alkanolamines having a specific chemical structure, and Patent Document 2 discloses glycerol monooleate. Such friction reducers are required to be able to handle a wide range of lubrication conditions (speed range, load, temperature, sliding material). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-199665 [Patent Document 2] Patent No. 5442784 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of one aspect of the present invention is to provide a novel lubricating additive and lubricating oil composition that can reduce friction in sliding parts. [Means for solving the problem]

[0005] The present inventors have found that a modified polymer obtained by modifying a polymer containing an olefin compound as a monomer unit or a hydrogenated product thereof with maleic acid or maleic anhydride can function as an additive for reducing friction in sliding parts.

[0006] One aspect of the present invention is a lubricating oil composition containing a base oil and a modified polymer obtained by modifying a polymer containing an olefin compound as a monomer unit or a hydrogenated product thereof with maleic acid or maleic anhydride.

[0007] The olefin compound may contain a conjugated diene compound. The polymer or its hydrogenated product may be a block copolymer or its hydrogenated product containing a block containing a conjugated diene compound as a monomer unit and a block containing an aromatic vinyl compound as a monomer unit. The polymer or its hydrogenated product may be a homopolymer or its hydrogenated product containing only one type of conjugated diene compound as a monomer unit. The content of the modified polymer may be 0.001 mass % or more and 50 mass % or less, based on the total mass of the lubricating oil composition. The lubricating oil composition may further contain a crosslinking agent having active hydrogen.

[0008] Another aspect of the present invention is a lubricating oil additive containing a modified polymer obtained by modifying a polymer containing an olefin compound as a monomer unit or a hydrogenated polymer thereof with maleic acid or maleic anhydride.

[0009] The olefin compound may contain a conjugated diene compound. The polymer or its hydrogenated product may be a block copolymer or its hydrogenated product containing a block containing a conjugated diene compound as a monomer unit and a block containing an aromatic vinyl compound as a monomer unit. The polymer or its hydrogenated product may be a homopolymer or its hydrogenated product containing only one type of conjugated diene compound as a monomer unit. The lubricating oil additive may further contain a crosslinking agent having active hydrogen. [Effects of the Invention]

[0010] According to one aspect of the present invention, it is possible to provide a novel lubricating additive and lubricating oil composition that can reduce friction in sliding parts. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present invention is a lubricating oil composition containing a base oil and a modified polymer obtained by modifying a polymer containing an olefin compound as a monomer unit or a hydrogenated product thereof with maleic acid or maleic anhydride.

[0012] Examples of base oils include hydrocarbon oils and oxygenated oils. Examples of hydrocarbon oils include mineral hydrocarbon oils and synthetic hydrocarbon oils. Examples of oxygenated oils include esters, ethers, carbonates, ketones, and silicones. One type of base oil may be used alone, or two or more types may be used in combination.

[0013] Examples of mineral hydrocarbon oils include paraffinic mineral oils (normal paraffin, isoparaffin, etc.), naphthenic mineral oils, aromatic mineral oils, etc., which are obtained by refining a lubricating oil fraction obtained by atmospheric distillation and / or vacuum distillation of crude oil using a refining process such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, clay treatment, etc., either alone or in combination.

[0014] Examples of synthetic hydrocarbon oils include alkylbenzene, alkylnaphthalene, polyα-olefin (PAO), polybutene, and ethylene-α-olefin copolymer.

[0015] Examples of the ester include polyol ester, complex ester, etc. Examples of the ether include polyvinyl ether, polyalkylene glycol, etc.

[0016] The kinematic viscosity of the base oil at 40°C is, for example, 1 mm 2 / s or more, 5mm 2 / s or more, or 10 mm 2 / s or more, and 2 / s or less, 500mm 2 / s or less, 200mm 2 / s or less, 100mm 2 / s or less, or 50 mm2 / s or less. In this specification, the kinematic viscosity refers to the kinematic viscosity measured in accordance with JIS K 2283:2000.

[0017] The content of the base oil may be, for example, 50 mass% or more, 60 mass% or more, 70 mass% or more, 80 mass% or more, 90 mass% or more, 95 mass% or more, or 97 mass% or more based on the total amount of the lubricating oil composition.

[0018] The polymer or its hydrogenated product contains one or more olefin compounds as monomer units. The polymer or its hydrogenated product may contain only one or more olefin compounds as monomer units, or may contain one or more olefin compounds and another compound copolymerizable with the olefin compounds. The other compound may be, for example, a vinyl compound having a vinyl group. The polymer may be a homopolymer or a copolymer.

[0019] An olefin compound is a hydrocarbon compound having at least one carbon-carbon double bond. The number of carbon atoms in the olefin compound may be, for example, 1 or more and 6 or less. The olefin compound may be, for example, an alkene compound having one carbon-carbon double bond, specifically, ethylene, propylene, butylene, etc.

[0020] The olefin compound may be, for example, a diene compound having two carbon-carbon double bonds, or a conjugated diene compound having a pair of conjugated double bonds (carbon-carbon double bonds). Examples of conjugated diene compounds include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. The conjugated diene compound is preferably at least one selected from the group consisting of 1,3-butadiene and isoprene.

[0021] The polymer may contain only alkene compounds as monomer units of the olefin compound, such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-acrylic copolymer, ethylene-butene copolymer, and chlorosulfonated polyethylene.

[0022] The polymer may contain only a conjugated diene compound as a monomer unit of the olefin compound. Such a polymer may be a homopolymer containing only one type of conjugated diene compound as a monomer unit, such as polybutadiene (poly-1,3-butadiene), polyisoprene, etc., preferably polyisoprene. Such a polymer may be a copolymer containing a conjugated diene compound as a monomer unit, such as a styrene-diene copolymer, an acrylonitrile-diene copolymer, etc.

[0023] The polymer may contain, for example, an olefin compound, an alkene compound, and a conjugated diene compound as monomer units, and such a polymer may be, for example, an ethylene-propylene-diene copolymer.

[0024] In one embodiment, the polymer may be a block copolymer, preferably a block copolymer including a block A containing a conjugated diene compound as a monomer unit and a block B containing an aromatic vinyl compound as a monomer unit. The aromatic vinyl compound has an aromatic ring and a vinyl group. Examples of aromatic vinyl compounds include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, and vinylanthracene. The aromatic vinyl compound is preferably styrene.

[0025] Block A is a polymer block containing more than 50 mass%, 60 mass% or more, 70 mass% or more, 80 mass% or more, 90 mass% or more, or 95 mass% or more of a conjugated diene compound as a monomer unit, based on the total amount of monomer units contained in block A. Block A may be a homopolymer block containing only a conjugated diene compound as a monomer unit, or may be a copolymer block containing a conjugated diene compound and an aromatic vinyl compound as monomer units.

[0026] Block B is a polymer block containing, as monomer units, more than 50% by mass, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more of an aromatic vinyl compound, based on the total amount of monomer units contained in block B. Block B may be a homopolymer block containing only an aromatic vinyl compound as a monomer unit, or may be a copolymer block containing, as monomer units, an aromatic vinyl compound and a conjugated diene compound.

[0027] The block copolymer may have, for example, a structure represented by any one of the following formulas (1) to (3). B-(AB) m …(1) B-(AB) n -A …(2) A-(BA) m …(3) In the formula, A represents block A, B represents block B, m represents an integer of 1 to 5, and n represents an integer of 0 to 5. m may be 1.

[0028] The block copolymer is preferably a block copolymer having a structure represented by formula (1), in which block A is preferably a block containing 1,3-butadiene or isoprene as a monomer unit, more preferably a homopolymer block containing only 1,3-butadiene or isoprene as a monomer unit, and block B is preferably a block containing styrene as a monomer unit, more preferably a homopolymer block containing only styrene as a monomer unit.

[0029] The modified polymer may be a modified polymer obtained by modifying a polymer containing one or more olefin compounds as monomer units or a hydrogenated product thereof with maleic acid or maleic anhydride, preferably a modified polymer of a polymer in which the olefin compound is a conjugated diene compound or a hydrogenated product thereof, more preferably a block copolymer containing a block containing a conjugated diene compound as a monomer unit and a block containing an aromatic vinyl compound as a monomer unit, or a modified polymer of a hydrogenated product thereof. The modified polymer is preferably a modified polymer obtained by modifying a homopolymer (polyisoprene) containing only isoprene as a monomer unit with maleic anhydride, more preferably a modified polymer obtained by modifying a styrene-butadiene-styrene block copolymer (SBS), its hydrogenated products styrene-ethylene / butylene-styrene block copolymer (SEBS), styrene-isoprene-styrene block copolymer (SIS), or its hydrogenated product styrene-ethylene / propylene-styrene block copolymer (SEPS) with maleic acid or maleic anhydride.

[0030] The number average molecular weight Mn of the modified polymer may be 1,000 or more, 5,000 or more, 10,000 or more, 30,000 or more, or 50,000 or more, and may be 500,000 or less, 200,000 or less, 100,000 or less, or 80,000 or less.The weight average molecular weight Mw of the modified polymer may be 2,000 or more, 10,000 or more, 20,000 or more, 50,000 or more, or 70,000 or more, and may be 750,000 or less, 300,000 or less, 200,000 or less, or 150,000 or less. The z-average molecular weight Mz of the modified polymer may be 50,000 or more, 70,000 or more, or 100,000 or more, and may be 400,000 or less, 350,000 or less, or 320,000 or less. The Mw / Mn of the modified polymer may be 1 or more, 1.1 or more, or 1.2 or more, and may be 2.5 or less, 2.2 or less, or 2 or less. These average molecular weights are measured by a conventionally known GPC (gel permeation chromatography) analysis method (polystyrene equivalent value).

[0031] The maleination ratio of the modified polymer may be 0.1% by mass or more, 0.5% by mass or more, 0.7% by mass or more, or 1% by mass or more, and may be 5% by mass or less, 4% by mass or less, or 3% by mass or less. The maleination ratio is measured by a conventionally known acid value measurement method.

[0032] The modified polymers described above can be obtained by modifying the above polymers or hydrogenated products thereof with maleic acid or maleic anhydride by known methods. Alternatively, the modified polymers can be purchased commercially.

[0033] The content of the modified polymer may be 0.001% by mass or more, 0.005% by mass or more, 0.01% by mass or more, 0.02% by mass or more, 0.03% by mass or more, 0.04% by mass or more, 0.05% by mass or more, 0.1% by mass or more, 0.2% by mass or more, 0.3% by mass or more, or 0.4% by mass or more, and may be 50% by mass or less, 20% by mass or less, 5% by mass or less, 4% by mass or less, 3% by mass or less, 2% by mass or less, or 1% by mass or less, based on the total amount of the lubricating oil composition.

[0034] The lubricating oil composition may further contain a crosslinking agent capable of crosslinking the modified polymers to each other, from the viewpoint of further reducing friction at sliding parts. The crosslinking agent may be present in the lubricating oil composition in a state in which the modified polymers are crosslinked to each other, or may be present in the lubricating oil composition in a simple form without crosslinking the modified polymers to each other.

[0035] Examples of such crosslinking agents include crosslinking agents having active hydrogen. The crosslinking agent may have, for example, a hydroxyl group, an amino group, or a thiol group as a functional group having active hydrogen. Preferably, the crosslinking agent may further have a nitrogen-containing heterocycle in addition to the functional group having active hydrogen. Examples of nitrogen-containing heterocycles include a triazole ring, a pyridine ring, a thiadiazole ring, an imidazole ring, an isocyanurate ring, a triazine ring, and a hydantoin ring. The crosslinking agent preferably has a hydroxyl group or an amino group and a triazole ring, an isocyanurate ring, or a triazine ring, and more preferably has a hydroxyl group or an amino group and a triazole ring or an isocyanurate ring. Examples of such crosslinking agents include 4H-3-amino-1,2,4-triazole, 2-aminopyridine, aminoimidazole, 2-amino-1,3,5-triazine, aminoisocyanurate, hydroxypyridine, and tris(2-hydroxyethyl)isocyanurate.

[0036] The content of the crosslinking agent may be 0.001 equivalents or more, 0.01 equivalents or more, 0.1 equivalents or more, or 0.5 equivalents or more, and may be 5 equivalents or less, 3 equivalents or less, or 2 equivalents or less, relative to the amount of the modifying functional group in the modified polymer.

[0037] In addition to the base oil and modified polymer, the lubricating oil composition may further contain other additives depending on the desired properties and the intended use of the lubricating oil composition. Examples of other additives include antiwear agents, antioxidants, oiliness agents, antifoaming agents, metal deactivators, viscosity index improvers, pour point depressants, detergent-dispersants, acid scavengers, rust inhibitors, and thickeners (particularly when the lubricating oil composition is used as a grease). The content of the other additives may be, for example, 0.1% by mass or more and 20% by mass or less, based on the total amount of the lubricating oil composition.

[0038] The lubricating oil compositions described above contain, in addition to a base oil, a modified polymer obtained by modifying a polymer containing a conjugated diene compound as a monomer unit or a hydrogenated version thereof with maleic acid or maleic anhydride, thereby reducing friction in sliding parts compared to lubricating oil compositions that do not contain the modified polymer or lubricating oil compositions that contain a polymer containing a conjugated diene compound as a monomer unit (not modified with maleic acid or maleic anhydride) or a hydrogenated version thereof. Furthermore, in one embodiment, a lubricating oil composition containing the modified polymer can improve the wear resistance of sliding parts compared to a lubricating oil composition that does not contain the modified polymer.

[0039] In other words, the modified polymer is suitable as an additive for lubricating oils. Another embodiment of the present invention is an additive for lubricating oils containing the modified polymer. This additive for lubricating oils can also be called a friction reducer (for lubricating oils), an anti-wear agent (for lubricating oils), a lubricity improver (for lubricating oils), or the like. The additive for lubricating oils may further contain the above-mentioned crosslinking agent. Another embodiment of the present invention can also be called a method for lubricating sliding parts using the modified polymer (a method for reducing friction of sliding parts, a method for improving the wear resistance of sliding parts, or a method for improving the lubricity of sliding parts).

[0040] Examples of applications of lubricants include lubricating oils and thin-film coating oils. Examples of lubricating oils include engine oils, two-cycle engine oils, automatic transmission oils, differential gear oils, tri-axial CVT oils, shock absorber oils, hydraulic oils, turbine oils, compressor oils, sliding surface oils, machine tool oils, bearing oils, sintered oil-impregnated bearing oils, metal processing oils, chain oils, chainsaw oils, precision machinery oils, robot joint sliding oils, drone bearing oils, refrigeration oils, automotive greases, EPS greases, high-speed bearing greases, industrial greases, industrial gear oils, centralized fuel supply machine greases, propeller shaft greases, hub bearing greases, CVJ greases, and wheel bearing greases. Examples of thin-film coating oils include household quick-drying lubricating oils, industrial assembly oils, and industrial rust-preventive coating oils. [Example]

[0041] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0042] (Example 1-1) A lubricating oil composition with the composition shown in Table 1 (mass % based on the total weight of the lubricating oil composition) was prepared using a commercially available hydraulic oil (trade name: Super Highland SE32 (manufactured by ENEOS Corporation)) as test oil 1 and a modified polymer obtained by modifying a styrene-ethylene / butylene-styrene block copolymer (SEBS) with maleic anhydride (hereinafter also referred to as "maleic anhydride-modified SEBS"; trade name: FG1924 (manufactured by Kraton Corporation) with Mn: 68,500, Mw: 12,300, Mz: 215,700, Mw / Mn: 1.859, maleation rate: 1% by mass). Specifically, 99.9 g of test oil 1 and 0.1 g of the maleic anhydride-modified SEBS were placed in an eggplant-shaped flask, and the gas phase was replaced with nitrogen. The contents of the eggplant-shaped flask were then stirred in an oil bath at 130°C for 3 hours to completely dissolve the maleic anhydride-modified SEBS, yielding a lubricating oil composition.

[0043] (Example 1-2) A lubricating oil composition was prepared in the same manner as in Example 1-1, except that, after dissolving the maleic anhydride-modified SEBS, 1 equivalent of a crosslinking agent (4H-3-amino-1,2,4-triazole (ATA)) relative to the amount of maleic acid-modified functional groups in the maleic anhydride-modified SEBS was further added, and the mixture was stirred in an eggplant-shaped flask at 180°C in an oil bath for 30 minutes.

[0044] (Examples 1-3) A lubricating oil composition was prepared in the same manner as in Example 1-2, except that tris(2-hydroxyethyl)isocyanurate (TIC) was used as the crosslinking agent instead of ATA.

[0045] (Examples 1-4) A lubricating oil composition was prepared in the same manner as in Example 1-2, except that a modified polymer obtained by modifying polyisoprene with maleic anhydride (hereinafter also referred to as "maleic anhydride-modified isoprene"; trade name: LIR-403, molecular weight: 34,000, modified polymer in which three molecules of maleic anhydride are added per molecule of the modified polymer) was used instead of the maleic anhydride-modified SEBS.

[0046] (Comparative Example 1-1) Test oil 1 was used as it was as a lubricating oil composition.

[0047] (Comparative Example 1-2) A lubricating oil composition was prepared in the same manner as in Example 1-1, except that SEBS not modified with maleic anhydride was used instead of the maleic anhydride-modified SEBS.

[0048] (Measurement of coefficient of friction) For each of the lubricating oil compositions of the above Examples and Comparative Examples, the friction coefficient (μ) was measured under the following conditions using an MTM (Mini Traction Machine) testing machine (manufactured by PCS Instruments). Ball: 3 / 4 inch steel ball Disc: Steel Load: 20N Slip rate (SRR): 50% Average speed: 0~3000mm / s Oil temperature: 40℃ Table 1 shows the friction coefficients at average speeds of 5 mm / s and 10 mm / s.

[0049] [Table 1]

[0050] (Examples 2-1 to 2-4 and Comparative Examples 2-1 to 2-2) Instead of test oil 1, mineral oil (kinematic viscosity at 40°C: 20 mm 2Lubricating oil compositions having the compositions shown in Table 2 (mass % based on the total amount of the lubricating oil composition) were prepared in the same manner as in Example 1-1 or 1-2, except that test oil 2, a mixture of 99 parts by mass of methylparaben (MSA) and 1 part by mass of tricresyl phosphate, was used. Glycerol monooleate, a known friction reducer, was added to Comparative Example 2-2. The coefficient of friction of each of the obtained lubricating oil compositions was measured in the same manner as in Example 1-1. The coefficients of friction at average speeds of 5 mm / s and 10 mm / s are shown in Table 2.

[0051] [Table 2]

[0052] (Examples 3-1 to 3-2 and Comparative Example 3-1) Lubricating oil compositions were prepared in the same manner as in Example 2-1, etc., except that the components of the lubricating oil compositions (mass % based on the total amount of the lubricating oil composition) were changed as shown in Table 3.

[0053] (Measurement of friction coefficient and wear scar width) For each of the obtained lubricating oil compositions, the friction coefficient and wear scar width were measured under the following conditions using a ball-on-disk reciprocating sliding lubrication tester. Ball: 1 / 4 inch steel ball (SUJ-2) Disk: Steel plate (SUJ-2) or copper plate (pure copper: 99.9%) Oil amount: 0.5mL Load: 2000g (if the disc is steel plate) 250g (if the disc is copper plate) Sliding amplitude: ±20mm Sliding speed: 10mm / s Sliding: 150 times for 10 minutes (if the disc is steel plate) 15 round trips, 1 minute (if the disc is copper plate) Temperature: room temperature Table 3 shows the average friction coefficient for the five strokes before the end of the friction test and the width of the disc wear mark after the test.

[0054] [Table 3]

[0055] (Example 4-1 and Comparative Example 4-1) Lubricating oil compositions were prepared in the same manner as in Example 2-1, etc., except that the components of the lubricating oil compositions (mass % based on the total amount of the lubricating oil composition) were changed as shown in Table 4.

[0056] (Measurement of coefficient of friction) For each of the obtained lubricating oil compositions, the friction coefficient was measured in the same manner as in Example 1-1, except that a fluororubber plate was used as the disk and the load was changed to 10 N. The friction coefficients at average speeds of 100 mm / s and 1000 mm / s are shown in Table 4. Furthermore, the friction coefficient of each of the obtained lubricating oil compositions was measured by performing a test using an MTM tester in the same manner as in Example 1-1, etc., except that a polyether ether ketone (PEEK) plate was used as the disk and the load was changed to 10 N. The friction coefficients at average speeds of 10 mm / s and 100 mm / s are shown in Table 4.

[0057] [Table 4]

[0058] (Example 5-1 and Comparative Example 5-1) Lubricating oil compositions having the compositions shown in Table 5 (mass % based on the total amount of the lubricating oil composition) were prepared in the same manner as in Example 1-2, except that Test Oil 3, a polyol ester of pentaerythritol and a mixed acid of 2-hexanoic acid and 3,5,5-trimethylhexanoic acid (1 / 1 (molar ratio)), was used instead of Test Oil 1. The friction coefficients of each of the obtained lubricating oil compositions were measured in the same manner as in Example 1-1, etc. Table 5 shows the friction coefficients at average speeds of 2 mm / s and 5 mm / s.

[0059] [Table 5]

[0060] (Examples 6-1 to 6-2 and Comparative Example 6-1) Instead of test oil 1, a paraffinic mineral oil (kinematic viscosity at 40°C: 2 mm 2 Lubricating oil compositions having the compositions (mass % based on the total amount of the lubricating oil composition) shown in Table 6 were prepared in the same manner as in Example 1-1 or 1-2, except that test oil 4, a mixture of 99 parts by mass of hydroxybenzoates (hydroxybenzoates / s) and 1 part by mass of tricresyl phosphate, was used. The coefficient of friction of each of the obtained lubricating oil compositions was measured in the same manner as in Example 1-1, etc., except that the load was changed to 10 N. The friction coefficients at average speeds of 10 mm / s and 100 mm / s are shown in Table 6.

[0061] [Table 6]

Claims

1. A base oil, a modified polymer obtained by modifying a polymer containing an olefin compound as a monomer unit or a hydrogenated polymer thereof with maleic acid or maleic anhydride; A lubricating oil composition comprising:

2. The lubricating oil composition of claim 1, wherein the olefin compound comprises a conjugated diene compound.

3. 3. The lubricating oil composition according to claim 2, wherein the polymer or hydrogenated product thereof is a block copolymer or hydrogenated product thereof, which comprises a block containing the conjugated diene compound as a monomer unit and a block containing an aromatic vinyl compound as a monomer unit.

4. 3. The lubricating oil composition according to claim 2, wherein the polymer or hydrogenated product thereof is a homopolymer containing only one type of the conjugated diene compound as a monomer unit, or a hydrogenated product thereof.

5. The lubricating oil composition according to any one of claims 1 to 4, wherein the content of the modified polymer is from 0.001 to 50 mass% based on the total amount of the lubricating oil composition.

6. The lubricating oil composition according to any one of claims 1 to 5, further comprising a crosslinking agent having active hydrogen.

7. A lubricating oil additive comprising a polymer containing an olefin compound as a monomer unit or a modified polymer obtained by modifying a hydrogenated polymer thereof with maleic acid or maleic anhydride.

8. 8. The lubricating oil additive of claim 7, wherein the olefin compound comprises a conjugated diene compound.

9. 9. The lubricating oil additive according to claim 8, wherein the polymer or the hydrogenated product thereof is a block copolymer or a hydrogenated product thereof, the block copolymer including a block containing the conjugated diene compound as a monomer unit and a block containing an aromatic vinyl compound as a monomer unit.

10. The lubricating oil additive according to claim 8, wherein the polymer or hydrogenated product thereof is a homopolymer containing the conjugated diene compound as a monomer unit or a hydrogenated product thereof.

11. The lubricating oil additive according to any one of claims 7 to 10, further comprising a crosslinking agent having active hydrogen.

Images