Viscosity index improver and lubricating oil composition

Abstract

The present invention aims to provide a viscosity index improver and a lubricating oil composition containing the viscosity index improver. The lubricating oil composition containing the viscosity index improver has a good gel index and can obtain a lubricating oil composition with excellent HTHS viscosity at 100°C and kinematic viscosity at 40°C. The present invention relates to a viscosity index improver, etc., which contains a copolymer (A) and an ester oil (Z), wherein the copolymer (A) comprises a polyolefin monomer (a) represented by the following general formula (1) and a monomer represented by the following general formula (2) and R 4 The monomer (b) is an alkyl group having 4 carbon atoms as a constituent monomer, and further contains a monomer (c) represented by the following general formula (3) and / or a monomer represented by the following general formula (2) with R 4 A monomer (d) which is an alkyl group having 2 to 3 carbon atoms is used as a constituent monomer. [In the general formula (1), R 1 is a hydrogen atom or a methyl group; 1 ‑is‑O‑,‑O(AO) m A is an alkylene group having 2 to 4 carbon atoms, m is an integer of 1 to 10, and when m is 2 or more, A may be the same or different; R 2 is a residue obtained by removing one hydrogen atom from a hydrocarbon polymer containing a 1,2-butylene group as a structural unit; p is a number of 0 or 1. [In the general formula (2), R 3 is a hydrogen atom or a methyl group; 2 - is a group represented by -O- or -NH-; R 4 is an alkyl group having 2 to 4 carbon atoms. 5 is a hydrogen atom or a methyl group; 3 - is a group represented by -O- or -NH-; R 6 is an alkylene group having 2 to 4 carbon atoms; R 7 is an alkyl group having 1 to 8 carbon atoms; r is an integer of 1 to 20, and when r is 2 or more, R 6 Can be the same or different.]

Description

Technical Field

[0001] The present invention relates to viscosity index improvers and lubricating oil compositions. Background Art

[0002] In recent years, in order to achieve CO 2 The reduction of emissions and the protection of oil resources have further demanded the fuel-saving of automobiles. As one of the measures to save fuel, it is possible to reduce the viscosity of the engine oil to reduce the viscous resistance. However, if the viscosity is reduced, problems such as leakage and burning of the bearings will occur. In response to this problem, the minimum guaranteed viscosity is stipulated in the viscosity standard for engine oils (SAEJ300) of the SAE in the United States. In the 0W-20 grade, as the viscosity under high temperature and high shear (HTHS viscosity), the 150°C HTHS viscosity (ASTM D4683 or D5481) is stipulated to be 2.6 mPa·s or more. In addition, in the 0W-16 grade, the 150°C HTHS viscosity is stipulated to be 2.3 mPa·s or more. In addition, in order to ensure the starting performance in cold areas, the viscosity characteristic at low temperature, called the gel index, is stipulated to be 12 or less in this grade. If the value of the gel index is high, the engine oil is easy to gel at low temperatures, and the starting performance of the engine will deteriorate. Regarding fuel economy, in addition to satisfying the above standards, an engine oil having a lower HTHS viscosity in the effective temperature range of 100°C and a lower kinematic viscosity in the low temperature range, especially at 40°C, is required. As such viscosity index improvers, methacrylate copolymers (Patent Documents 1 to 4), olefin copolymers (Patent Document 5), comb-type copolymers (Patent Documents 6 to 8), etc. are known.

[0003] However, the above-mentioned viscosity index improvers have the following problems: when added to an engine oil composition, the HTHS viscosity at 100° C. is still insufficient, and the kinematic viscosity at 40° C. is poor.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 6060311

[0007] Patent Document 2: Japanese Patent No. 2732187

[0008] Patent Document 3: Japanese Patent No. 2754343

[0009] Patent Document 4: Japanese Patent No. 3831203

[0010] Patent Document 5: Japanese Patent No. 3999307

[0011] Patent Document 6: Japanese Patent No. 3474918

[0012] Patent Document 7: Japanese Patent Application No. 2008-546894

[0013] Patent Document 8: Japanese Patent Application No. 2010-532805 Summary of the invention

[0014] Problems to be solved by the invention

[0015] An object of the present invention is to provide a viscosity index improver and a lubricating oil composition containing the viscosity index improver, wherein the lubricating oil composition containing the viscosity index improver has a good gel index and can obtain a lubricating oil composition excellent in HTHS viscosity at 100°C and kinematic viscosity at 40°C.

[0016] Means for solving problems

[0017] The present inventors have conducted studies to achieve the above-mentioned object and have thus achieved the present invention.

[0018] That is, the present invention relates to a viscosity index improver comprising a copolymer (A) and an ester oil (Z), wherein the copolymer (A) comprises a polyolefin monomer (a) represented by the following general formula (1) and a monomer represented by the following general formula (2) and R 4 The monomer (b) is an alkyl group having 4 carbon atoms as a constituent monomer, and further contains a monomer (c) represented by the following general formula (3) and / or a monomer represented by the following general formula (2) and R 4 A monomer (d) which is an alkyl group having 2 to 3 carbon atoms as a constituent monomer; a lubricating oil composition comprising the viscosity index improver and at least one additive selected from the group consisting of a detergent, a dispersant, an antioxidant, an oiliness improver, a pour point depressant, a friction and wear modifier, an extreme pressure agent, a defoamer, an anti-emulsifier, a metal passivator and a corrosion inhibitor.

[0019] [Chemistry 1]

[0020]

[0021] [In the general formula (1), R 1 is a hydrogen atom or a methyl group; -X 1 - is -O-, -O(AO) m - or -NH-, A is an alkylene group having 2 to 4 carbon atoms, m is an integer of 1 to 10, and when m is 2 or more, A may be the same or different; R 2 A residue obtained by removing one hydrogen atom from a hydrocarbon polymer containing a 1,2-butylene group as a structural unit; p is a number of 0 or 1.]

[0022] [Chemistry 2]

[0023]

[0024] [In general formula (2), R 3 is a hydrogen atom or a methyl group; -X 2 - is a group represented by -O- or -NH-; R 4 It is an alkyl group having 2 to 4 carbon atoms.]

[0025] [Chemistry 3]

[0026]

[0027] [In general formula (3), R 5 is a hydrogen atom or a methyl group; -X 3 - is a group represented by -O- or -NH-; R 6 is an alkylene group having 2 to 4 carbon atoms; R 7 is an alkyl group having 1 to 8 carbon atoms; r is an integer of 1 to 20, and when r is 2 or more, R 6 Can be the same or different.]

[0028] Effects of the Invention

[0029] The lubricating oil composition containing the viscosity index improver of the present invention can exhibit the effects of having a good gel index and having a low HTHS viscosity at 100° C. and a low kinematic viscosity at 40° C. DETAILED DESCRIPTION

[0030] The viscosity index improver of the present invention comprises a copolymer (A) and an ester oil (Z). The copolymer (A) comprises a polyolefin monomer (a) represented by the following general formula (1) and a monomer represented by the following general formula (2) with R 4 The monomer (b) is an alkyl group having 4 carbon atoms as a constituent monomer, and further contains a monomer (c) represented by the following general formula (3) and / or a monomer represented by the following general formula (2) and R 4 The monomer (d) is an alkyl group having 2 to 3 carbon atoms as a constituent monomer.

[0031] [Chemistry 4]

[0032]

[0033] [In the general formula (1), R 1 is a hydrogen atom or a methyl group; -X 1 - is -O-, -O(AO) m - or -NH-, A is an alkylene group having 2 to 4 carbon atoms, m is an integer of 1 to 10, and when m is 2 or more, A may be the same or different; R 2A residue obtained by removing one hydrogen atom from a hydrocarbon polymer containing a 1,2-butylene group as a structural unit; p is a number of 0 or 1.]

[0034] [Chemistry 5]

[0035]

[0036] [In general formula (2), R 3 is a hydrogen atom or a methyl group; -X 2 - is a group represented by -O- or -NH-; R 4 It is an alkyl group having 2 to 4 carbon atoms.]

[0037] [Chemistry 6]

[0038]

[0039] [In general formula (3), R 5 is a hydrogen atom or a methyl group; -X 3 - is a group represented by -O- or -NH-; R 6 is an alkylene group having 2 to 4 carbon atoms; R 7 is an alkyl group having 1 to 8 carbon atoms; r is an integer of 1 to 20, and when r is 2 or more, R 6 Can be the same or different.]

[0040] <Copolymer (A)>

[0041] The viscosity index improver of the present invention comprises a copolymer (A) comprising a polyolefin monomer (a) represented by the following general formula (1) and a monomer represented by the following general formula (2) wherein R 4 The monomer (b) is an alkyl group having 4 carbon atoms as a constituent monomer, and further contains a monomer (c) represented by the following general formula (3) and / or a monomer represented by the following general formula (2) and R 4 The monomer (d) is an alkyl group having 2 to 3 carbon atoms. The monomers (a) to (d) may be used alone or in combination of two or more.

[0042] The polyolefin monomer (a) represented by the above general formula (1) is described.

[0043] R in the general formula (1) 1 It is a hydrogen atom or a methyl group. Among these, a methyl group is preferred from the viewpoint of the viscosity index improving effect.

[0044] -X in the general formula (1) 1 - is -O-, -O(AO) m - or -NH-.

[0045] A is an alkylene group having 2 to 4 carbon atoms, and examples thereof include ethylene, 1,2-propylene or 1,3-propylene, isobutylene, and 1,2-butylene, 1,3-butylene or 1,4-butylene.

[0046] AO is an alkyleneoxy group having 2 to 4 carbon atoms, and examples thereof include ethyleneoxy, 1,2-propyleneoxy or 1,3-propyleneoxy, isobutyleneoxy, and 1,2-butyleneoxy, 1,3-butyleneoxy or 1,4-butyleneoxy.

[0047] m is the number of moles of the alkylene oxide added, and is an integer of 1 to 10, and is preferably an integer of 1 to 4, and more preferably an integer of 1 to 2, from the viewpoint of the viscosity index improvement effect.

[0048] When m is 2 or more, A may be the same or different, (AO) m The bonding form of the parts may be random or block-like.

[0049] In-X 1 -, from the aspect of viscosity index improvement effect, -O- and -O(AO) are preferred. m -, more preferably -O- and -O(CH 2 CH 2 O) 1 - represents a group.

[0050] p is a number of 0 or 1.

[0051] R in the general formula (1) 2 It is composed of 1,2-butylene (-CH 2 CH(CH 2 CH 3 )- or -CH(CH 2 CH 3 )CH 2 -) A residue obtained by removing one hydrogen atom from a hydrocarbon polymer as a structural unit.

[0052] In the hydrocarbon polymer containing a 1,2-butylene group as a structural unit, the ratio of the 1,2-butylene group in all structural units is preferably 10 to 90 mol %, more preferably 20 to 80 mol %, from the viewpoint of HTHS viscosity at 100°C.

[0053] When two polymers having different 1,2-butylene group ratios are used in combination in a hydrocarbon polymer containing 1,2-butylene groups as structural units, the absolute value of the difference between the two 1,2-butylene group ratios is preferably 10 to 80 mol %, more preferably 20 to 70 mol %, from the viewpoint of low temperature viscosity.

[0054] As the hydrocarbon polymer containing a 1,2-butylene group as a structural unit, a polymer having 37 or more carbon atoms is preferred, and examples thereof include a polymer obtained by hydrogenating the carbon-carbon double bond of a 1,2-addition product of a polymer obtained by using 1-butene as a constituent monomer (unsaturated hydrocarbon (x)) and a polymer obtained by using 1,3-butadiene.

[0055] Regarding the structure derived from 1-butene and / or 1,3-butadiene of the hydrocarbon polymer in the general formula (1), the proportion of 1,2-butylene groups in all structural units can be determined by 13 Specifically, for example, when only a substance with 4 carbon atoms is used as a monomer, 13 The hydrocarbon polymer was analyzed by C-NMR and determined by calculation using the following mathematical formula (1). 13 In C-NMR, the tertiary carbon atom (-CH 2 CH(CH 2 CH 3 The peak of )-) appears at an integrated value of 26 to 27 ppm (integral value B). The proportion of 1,2-butylene groups can be determined from the integrated value of the above peak and the integrated value of all carbon peaks of the hydrocarbon polymer (integral value C).

[0056] Ratio of 1,2-butylene group (mol%) = {(integral value B) × 4} / (integral value C) × 100 (1)

[0057] It should be noted that in order to increase the proportion of 1,2-butylene groups, for example, in anionic polymerization using 1,3-butadiene, the reaction temperature is lowered to a temperature below the boiling point of 1,3-butadiene (-4.4°C), and the amount of polymerization initiator added is less than that of 1,3-butadiene; in order to reduce the proportion of 1,2-butylene groups, the reaction temperature is increased to a temperature above the boiling point of 1,3-butadiene, and the amount of polymerization initiator added is more than that of 1,3-butadiene.

[0058] Regarding R in the general formula (1) 2 The ratio of 1,3-butadiene in all monomers (the weight ratio of 1,3-butadiene in all constituent monomers in a hydrocarbon polymer containing a 1,2-butylene group as a structural unit) is preferably 50% by weight or more, more preferably 75% by weight or more, particularly preferably 85% by weight or more, and most preferably 90% by weight or more, from the perspective of the viscosity index improvement effect.

[0059] In the general formula (1), the 2In the structure of a part or all of 1,3-butadiene, the molar ratio of 1,2-butylene (1,2-adduct) to 1,4-butylene (1,4-adduct) (1,2-adduct / 1,4-adduct) is preferably 1 / 99 to 99 / 1, more preferably 10 / 90 to 90 / 10, and particularly preferably 20 / 80 to 80 / 20, from the viewpoint of the viscosity index improvement effect and low-temperature viscosity.

[0060] In addition, as the monomer (a), it is preferred to use a monomer having a molar ratio (1,2-adduct / 1,4-adduct) of 1 / 99 to 50 / 50 and a monomer having a molar ratio of 51 / 49 to 99 / 1, and it is more preferred to use a monomer having a molar ratio of 10 / 90 to 50 / 50 and a monomer having a molar ratio of 55 / 45 to 90 / 10.

[0061] In the general formula (1), the 2 The molar ratio of 1,2-adduct / 1,4-adduct in the structure of part or all of 1,3-butadiene can be determined by 1 H-NMR, 13 C-NMR, Raman spectroscopy, etc.

[0062] From the perspective of low temperature viscosity, R in the general formula (1) 2 Preferably, it is a residue obtained by removing one hydrogen atom from a hydrocarbon polymer containing an isobutylene group as a structural unit in addition to a 1,2-butylene group. As a method for producing a hydrocarbon polymer containing an isobutylene group as a structural unit, there can be mentioned a method using isobutylene as a constituent monomer (unsaturated hydrocarbon (x)).

[0063] Regarding the total ratio of isobutylene groups to 1,2-butylene groups in the hydrocarbon polymer, from the perspective of low-temperature viscosity, the total molar number of structural units based on the hydrocarbon polymer is preferably 30 mol% or more, more preferably 40 mol% or more, particularly preferably 50 mol% or more, and most preferably 60 mol% or more.

[0064] The total ratio of isobutylene groups to 1,2-butylene groups based on the total number of structural units of the hydrocarbon polymer can be determined by 13 The hydrocarbon polymer is analyzed by C-NMR spectroscopy and determined by calculation using the following mathematical formula (2). Specifically, for example, when only monomers having 4 carbon atoms are used as monomers, 13In the C-NMR spectrum, the peak of the methyl group derived from the isobutylene group appears at an integrated value of 30-32 ppm (integral value A), and the peak of the tertiary carbon atom derived from the branched methylene group of the 1,2-butylene group appears at an integrated value of 26-27 ppm (integral value B). The total ratio can be calculated from the integrated value of the above peaks and the integrated value of all carbon peaks of the hydrocarbon polymer (integral value C).

[0065] Total ratio of isobutylene group and 1,2-butylene group (mol %) = {(integral value A) × 2 + (integral value B) × 4} / (integral value C) × 100 (2)

[0066] The hydrocarbon polymer containing a 1,2-butylene group as a structural unit may contain the following (1) to (3) as a constituent monomer as the unsaturated hydrocarbon (x) in addition to 1-butene and 1,3-butadiene.

[0067] (1) Aliphatic unsaturated hydrocarbons [olefins having 2 to 36 carbon atoms (e.g., ethylene, propylene, 2-butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, tricosene, and hexacosene) and dienes having 4 to 36 carbon atoms (e.g., isoprene, 1,4-pentadiene, 1,5-hexadiene, and 1,7-octadiene)]

[0068] (2) Alicyclic unsaturated hydrocarbons [e.g. cyclohexene, (di)cyclopentadiene, pinene, limonene, indene, vinylcyclohexene and ethylidene bicycloheptene]

[0069] (3) Unsaturated hydrocarbons containing aromatic groups (e.g., styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, ethylstyrene, isopropylstyrene, butylstyrene, phenylstyrene, cyclohexylstyrene, benzylstyrene, crotylbenzene, vinylnaphthalene, divinylbenzene, divinyltoluene, divinylxylene, trivinylbenzene, etc.)

[0070] The hydrocarbon polymer composed of these may be a block polymer or a random polymer. In addition, when the hydrocarbon polymer has carbon-carbon double bonds, part or all of the double bonds may be hydrogenated by hydrogenation. 2 The hydrocarbon polymer may be a hydrocarbon polymer using only monomers having 4 carbon atoms as constituent monomers, and the monomers having 4 carbon atoms may be 1-butene and / or 1,3-butadiene, and may contain isobutylene as necessary.

[0071] The weight proportion of unsaturated hydrocarbons other than 1-butene, 1,3-butadiene and isobutylene in the monomer (a) is preferably 50% by weight or less, more preferably 25% by weight or less, further preferably 15% by weight or less, particularly preferably 10% by weight or less.

[0072] The weight average molecular weight (hereinafter abbreviated as Mw) and number average molecular weight (hereinafter abbreviated as Mn) of the monomer (a) can be measured by gel permeation chromatography (hereinafter abbreviated as GPC) under the following conditions.

[0073] <Measurement Conditions for Mw and Mn of Monomer (a)>

[0074] Device: "HLC-8320GPC" [manufactured by Tosoh Corporation]

[0075] Column: "TSKgel GMHXL" [manufactured by Tosoh Corporation] 2 pieces

[0076] "TSKgel Multipore H XL-M" [manufactured by Tosoh Corporation] 1 piece

[0077] Measurement temperature: 40℃

[0078] Sample solution: 0.25 wt% tetrahydrofuran solution

[0079] Solution injection volume: 10.0μl

[0080] Detection device: Refractive index detector

[0081] Reference material: Standard polystyrene (TS Reference material: Standard polystyrene (TSKstandardPOLYSTYRENE))

[0082] 12 types (molecular weight: 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]

[0083] The Mn of the monomer (a) is preferably 800 to 10,000, more preferably 1,000 to 9,000, particularly preferably 1,200 to 8,500.

[0084] When the Mn of the monomer (a) is 800 or more, the viscosity index improving effect tends to be good, and when it is 10,000 or less, the shear stability during long-term use tends to be good.

[0085] From the viewpoint of low temperature viscosity, the Mw of the monomer (a) is preferably 900 to 13,000, more preferably 1,200 to 12,000, and particularly preferably 1,500 to 11,000.

[0086] The monomer (a) can be obtained by an esterification reaction between a polymer (Y) having a hydroxyl group at one end obtained by introducing a hydroxyl group into one end of a hydrocarbon polymer and (meth)acrylic acid, or an ester exchange reaction between the polymer (Y) and an alkyl (meth)acrylate (preferably the alkyl group has 1 to 4 carbon atoms) such as methyl (meth)acrylate.

[0087] In addition, "(meth)acrylic acid" means "acrylic acid and / or methacrylic acid".

[0088] From the viewpoint of solubility in lubricating oil, the solubility parameter (hereinafter also referred to as SP value) of the structural unit derived from the monomer (a) (a structure in which the vinyl portion of the monomer (a) reacts to form a single bond) is preferably 7.0 to 9.0 (cal / cm 3 ) 1 / 2 , more preferably 7.3 to 8.5 (cal / cm 3 ) 1 / 2 .

[0089] It should be noted that the SP value in the present invention is a value calculated by the method described in the mathematical formula (28) on page 153 of the Fedors method (Polymer Engineering and Science, February, 1974, Vol. 14, No. 2 P. 147-154) using the numerical values ​​(heat of vaporization and molar volume of an atom or functional group at 25° C.) described on page 152 (Table 5). Specifically, the SP value can be calculated based on the Δe described in the following Table 1 as a parameter of the Fedors method. i and Δv i The numerical value of is calculated by substituting the numerical values ​​corresponding to the types of atoms and atomic groups in the molecular structure into the following mathematical formula.

[0090] SP value = (ΣΔe i / ΣΔv i ) 1 / 2

[0091] [Table 1]

[0092]

[0093] The SP value of the structural unit derived from the monomer (a) can be calculated using the above parameters based on the molecular structure of the structural unit derived from the monomer (a), and can be within a desired range by appropriately adjusting the monomer (unsaturated hydrocarbon (x)) and weight fraction used.

[0094] Specific examples of the polymer (Y) containing a hydroxyl group at one end include the following (Y1) to (Y4).

[0095] Alkylene oxide adduct (Y1): a product obtained by adding alkylene oxide (ethylene oxide, propylene oxide, etc.) to a polymer obtained by polymerizing an unsaturated hydrocarbon (x) in the presence of an ionic polymerization catalyst (lithium catalyst, sodium catalyst, etc.) (in the general formula (1), -X 1 -for-(AO) m -, p=0).

[0096] Borohydride (Y2): a borohydride reaction product of a polymer of an unsaturated hydrocarbon (x) having a double bond at one end (e.g., a substance described in U.S. Patent No. 4,316,973) etc. (In the general formula (1), -X 1 - is -O-, p=0).

[0097] Maleic anhydride-ene-amino alcohol adduct (Y3): a product obtained by imidizing a reaction product obtained by reacting a polymer of an unsaturated hydrocarbon (x) having a double bond at one end with an ene of maleic anhydride with an amino alcohol (in the general formula (1), -X 1 - is -O-, p=1).

[0098] Hydroformylation-hydrogenation product (Y4): a product obtained by hydroformylating a polymer of an unsaturated hydrocarbon (x) having a double bond at one end, followed by hydrogenation (e.g., the product described in Japanese Unexamined Patent Publication No. 175096-63) (in the general formula (1), -X 1 - is -O-, p=0).

[0099] Among these polymers (Y) containing a hydroxyl group at one end, alkylene oxide adducts (Y1), borohydrides (Y2) and maleic anhydride-ene-amino alcohol adducts (Y3) are preferred from the viewpoint of the HTHS viscosity and viscosity index improvement effect, and alkylene oxide adducts (Y1) are more preferred.

[0100] The monomer (b) represented by the above general formula (2) is described.

[0101] In the monomer (b), R in the general formula (2) 3 It is a hydrogen atom or a methyl group. Among these, a methyl group is preferred from the viewpoint of the viscosity index improvement effect.

[0102] Monomer (b) is R in the general formula (2) 4 A monomer having an alkyl group having 4 carbon atoms.

[0103] Examples of the alkyl group having 4 carbon atoms include n-butyl, isobutyl, sec-butyl and tert-butyl.

[0104] Specific examples of the monomer (b) include butyl (meth)acrylate (for example, n-butyl (meth)acrylate, isobutyl (meth)acrylate, and the like) and N-butyl (meth)acrylamide.

[0105] As the monomer (b), from the viewpoint of the viscosity index improving effect, butyl (meth)acrylate is preferred, and n-butyl (meth)acrylate is more preferred.

[0106] The monomer (c) represented by the above general formula (3) is described.

[0107] R in the general formula (3) 5 It is a hydrogen atom or a methyl group. Among these, a methyl group is preferred from the viewpoint of the viscosity index improvement effect.

[0108] -X in the general formula (3) 3 - is a group represented by -O- or -NH-. Among these, a group represented by -O- is preferred from the viewpoint of the viscosity index improvement effect.

[0109] R in the general formula (3) 6 It is an alkylene group having 2 to 4 carbon atoms.

[0110] Examples of the alkylene group having 2 to 4 carbon atoms include ethylene, 1,2-propylene or 1,3-propylene, isobutylene, and 1,2-butylene, 1,3-butylene or 1,4-butylene.

[0111] R 6 O is an alkyleneoxy group having 2 to 4 carbon atoms, and examples thereof include ethyleneoxy, 1,2-propyleneoxy or 1,3-propyleneoxy, isobutyleneoxy, and 1,2-butyleneoxy, 1,3-butyleneoxy or 1,4-butyleneoxy.

[0112] In the general formula (3), r is an integer of 1 to 20, and is preferably an integer of 1 to 5, and more preferably an integer of 1 to 2, from the viewpoint of the viscosity index improvement effect and the low-temperature viscosity.

[0113] When r is 2 or more, R 6 O can be the same or different, (R 6 O) r The bonding form of the parts may be random or block-like.

[0114] R in the general formula (3) 7 It is an alkyl group having 1 to 8 carbon atoms, including straight-chain or branched-chain alkyl groups, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-heptyl, isoheptyl, n-hexyl, 2-ethylhexyl, n-pentyl and n-octyl.

[0115] Among the alkyl groups having 1 to 8 carbon atoms, an alkyl group having 1 to 7 carbon atoms is preferred from the viewpoint of the viscosity index improvement effect, an alkyl group having 1 to 6 carbon atoms is more preferred, an alkyl group having 1 to 5 carbon atoms is particularly preferred, and an alkyl group having 2 or 4 carbon atoms is most preferred.

[0116] Specific examples of the monomer (c) include methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, pentyloxyethyl (meth)acrylate, hexyloxyethyl (meth)acrylate, heptyloxyethyl (meth)acrylate, octyloxyethyl (meth)acrylate, methoxypropyl (meth)acrylate, ethoxypropyl (meth)acrylate, propoxypropyl (meth)acrylate, butoxypropyl (meth)acrylate, pentyloxypropyl (meth)acrylate, hexyloxypropyl (meth)acrylate, and octyloxyethyl (meth)acrylate. esters of (meth)acrylic acid and the like.

[0117] Among the monomers (c), ethoxyethyl (meth)acrylate and butoxyethyl (meth)acrylate are preferred from the viewpoint of the viscosity index improving effect.

[0118] The monomer (d) represented by the above general formula (2) is described.

[0119] In the monomer (d), R in the general formula (2) 3 It is a hydrogen atom or a methyl group. Among these, a methyl group is preferred from the viewpoint of the viscosity index improvement effect.

[0120] Monomer (d) is R in the general formula (2) 4 A monomer which is an alkyl group having 2 to 3 carbon atoms.

[0121] Examples of the alkyl group having 2 to 3 carbon atoms include ethyl group, n-propyl group, isopropyl group and the like.

[0122] Specific examples of the monomer (d) include ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, N-ethyl (meth)acrylamide, and N-propyl (meth)acrylamide.

[0123] As the monomer (d), ethyl (meth)acrylate is preferred from the viewpoint of the viscosity index improving effect.

[0124] In the copolymer (A), the weight proportion of the monomer (a) in the monomers constituting the copolymer (A) is preferably 1 to 50% by weight, more preferably 2 to 30% by weight, based on the total weight of the monomers constituting the copolymer (A), from the viewpoints of the HTHS viscosity at 100°C, the kinematic viscosity at 40°C, the shear stability and the viscosity index improvement effect.

[0125] In the copolymer (A), the weight proportion of the monomer (b) in the monomers constituting the copolymer (A) is preferably 1 to 80% by weight, more preferably 3 to 70% by weight, based on the total weight of the monomers constituting the copolymer (A), from the viewpoints of the HTHS viscosity at 100°C, the kinematic viscosity at 40°C, the shear stability and the viscosity index improvement effect.

[0126] In the copolymer (A), the weight proportion of the monomer (c) in the monomers constituting the copolymer (A) is preferably 1 to 60% by weight, more preferably 2 to 40% by weight, based on the total weight of the monomers constituting the copolymer (A), from the viewpoints of the HTHS viscosity at 100°C, the kinematic viscosity at 40°C, the shear stability and the viscosity index improvement effect.

[0127] In the copolymer (A), from the viewpoint of shear stability and viscosity index improvement effect, the total weight ratio of the monomer (c) and the monomer (d) in the constituent monomers of the copolymer (A) is preferably 1 to 60% by weight, more preferably 2 to 40% by weight based on the total weight of the monomers constituting the copolymer (A).

[0128] In the copolymer (A), the weight proportion of the monomer (d) in the monomers constituting the copolymer (A) is preferably 1 to 60% by weight, more preferably 2 to 40% by weight, based on the total weight of the monomers constituting the copolymer (A), from the viewpoints of the HTHS viscosity at 100°C, the kinematic viscosity at 40°C, the shear stability and the viscosity index improvement effect.

[0129] In the copolymer (A), the weight ratio {(c+d) / b} of the total weight of the monomer (c) and the monomer (d) in the constituent monomers of the copolymer (A) to the weight of the monomer (b) is preferably 0.01 to 20, more preferably 0.03 to 5, and further preferably 0.05 to 2. When the weight ratio {(c+d) / b} is 0.01 or more, the gel index and viscosity index tend to be good; when it is 20 or less, the gel index tends to be good.

[0130] In the copolymer (A), the weight ratio (c / b) of the weight of the monomer (c) to the weight of the monomer (b) in the constituent monomers of the copolymer (A) is preferably 0.01 to 20, more preferably 0.03 to 5, and further preferably 0.05 to 2. When the weight ratio (c / b) is 0.01 or more, the gel index and viscosity index tend to be good; when it is 20 or less, the gel index tends to be good.

[0131] In the present invention, the copolymer (A) is preferably a copolymer containing a (meth)acryloyl monomer (e) having a linear or branched alkyl group having 9 to 36 carbon atoms as a constituent monomer from the viewpoint of solubility in the base oil.

[0132] The monomer (e) includes a (meth)acryloyl monomer (e1) having a linear alkyl group having 9 to 36 carbon atoms and a (meth)acryloyl monomer (e2) having a branched alkyl group having 9 to 36 carbon atoms represented by the following general formula (4).

[0133] In addition, the monomer (e) may be used alone or in combination of two or more.

[0134] [Chemistry 7]

[0135]

[0136] [In general formula (4), R 8 is a hydrogen atom or a methyl group; -X 4 - is a group represented by -O- or -NH-; R 9 O is an alkyleneoxy group having 2 to 4 carbon atoms; R 10 and R 11 are each independently a linear alkyl group having 1 to 24 carbon atoms, R 10 and R 11 The total number of carbon atoms is 7 to 34; s is an integer of 0 to 20, and when s is 2 or more, R 9 O may be the same or different.]

[0137] Examples of the (meth)acryloyl monomer (e1) having a linear alkyl group having 9 to 36 carbon atoms (hereinafter sometimes referred to as monomer (e1)) include (meth)acrylic acid alkyl esters {esters of linear alkyl alcohols having 9 to 36 carbon atoms and (meth)acrylic acid, such as 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-hexadec ... (meth)acrylate, alkyl esters, n-hexadecyl (meth)acrylate, n-octadecyl (meth)acrylate, n-eicosyl (meth)acrylate, n-tetracosyl (meth)acrylate, n-triacontyl (meth)acrylate and n-hexadecyl (meth)acrylate}, esters of 1 to 20 mol addition products of alkylene oxide (2 to 4 carbon atoms) to straight-chain alkyl alcohols having 9 to 36 carbon atoms and (meth)acrylic acid, and (meth)acrylic acid alkylamides {amides of straight-chain alkylamines having 9 to 36 carbon atoms and acrylic acid}, etc.

[0138] Among the monomers (e1), from the viewpoint of the viscosity index improving effect, an alkyl (meth)acrylate having a linear alkyl group having 12 to 28 carbon atoms is preferred, an alkyl (meth)acrylate having a linear alkyl group having 12 to 24 carbon atoms is more preferred, and an alkyl (meth)acrylate having a linear alkyl group having 12 to 20 carbon atoms is particularly preferred.

[0139] The monomer (e1) may be used alone or in combination of two or more.

[0140] In the monomer (e2), R in the general formula (4) 8 It is a hydrogen atom or a methyl group. Among these, a methyl group is preferred from the viewpoint of the viscosity index improvement effect.

[0141] -X in the general formula (4) 4 - is a group represented by -O- or -NH-. Among these, a group represented by -O- is preferred from the viewpoint of the viscosity index improvement effect.

[0142] R in the general formula (4) 9 It is an alkylene group having 2 to 4 carbon atoms. Examples of the alkylene group having 2 to 4 carbon atoms include ethylene, 1,2-propylene or 1,3-propylene, isobutylene, and 1,2-butylene, 1,3-butylene or 1,4-butylene.

[0143] R 9 O is an alkyleneoxy group having 2 to 4 carbon atoms, and examples thereof include ethyleneoxy, 1,2-propyleneoxy or 1,3-propyleneoxy, isobutyleneoxy, and 1,2-butyleneoxy, 1,3-butyleneoxy or 1,4-butyleneoxy.

[0144] s in the general formula (4) is an integer of 0 to 20, preferably an integer of 0 to 5, more preferably an integer of 0 to 2, from the viewpoint of the viscosity index improvement effect.

[0145] When s is 2 or more, R 9 O can be the same or different, (R 9 O) s The moieties may be randomly bonded and may be block bonded.

[0146] R in the general formula (4) 10 and R 11 Each is independently a straight-chain alkyl group having 1 to 24 carbon atoms. Specifically, methyl, ethyl, n-propyl, n-butyl, n-heptyl, n-hexyl, n-pentyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tetradecyl, n-hexadecyl, n-octadecyl, n-eicosyl and n-tetracosyl can be mentioned. Among the straight-chain alkyl groups having 1 to 24 carbon atoms, R is preferably selected from the group consisting of: 10 or R 11 At least one of them is a linear alkyl group having 6 to 24 carbon atoms, and more preferably R 10 or R 11 At least one of them is a linear alkyl group having 6 to 20 carbon atoms, and R 10 or R 11 At least one of them is a straight-chain alkyl group having 8 to 16 carbon atoms.

[0147] R 10 and R 11 The total number of carbon atoms is 7 to 34, preferably 12 to 30, more preferably 14 to 26 from the viewpoint of the viscosity index improving effect.

[0148] Contains R 10 and R 11 The carbon chain consists of R 10 and R 11 One of the branched alkyl groups has a carbon number of 9 to 36. The branched alkyl group has a carbon number of 9 to 36, preferably 14 to 32, and more preferably 16 to 28 from the viewpoint of the viscosity index improving effect.

[0149] Specific examples of the monomer (e2) include 2-octyldecyl (meth)acrylate, an ester of ethylene glycol mono-2-octylpentadecyl ether and (meth)acrylic acid, 2-n-octyldodecyl (meth)acrylate, 2-n-decyltetradecyl (meth)acrylate, 2-n-dodecylhexadecyl (meth)acrylate, 2-n-tetradecyloctadecyl (meth)acrylate, 2-n-dodecylpentadecyl (meth)acrylate, 2-n-tetradecylheptadecyl (meth)acrylate, 2-n-hexadecylheptadecyl (meth)acrylate, 2-n-hexadecylhexadecyl (meth)acrylate, 2-n-hexadecyleicosyl (meth)acrylate, 2-n-hexadecylbehenyl (meth)acrylate, 2-n-tetracosylhexacosyl (meth)acrylate, and N-2-octyldecyl (meth)acrylamide.

[0150] The monomer (e2) may be used alone or in combination of two or more.

[0151] Among the monomers (e), from the viewpoint of solubility in the base oil and low-temperature viscosity, the (meth)acryloyl monomer (e2) having a branched alkyl group having 9 to 36 carbon atoms represented by the above-mentioned general formula (4) is preferred, and the (meth)acryloyl monomer having a branched alkyl group having 14 to 32 carbon atoms among the monomers (e2) is more preferred, and the (meth)acryloyl monomer having a branched alkyl group having 16 to 28 carbon atoms among the monomers (e2) is particularly preferred.

[0152] In the copolymer (A), from the viewpoint of the viscosity index improvement effect and the preferred SP value of the copolymer (A), the weight ratio of the monomer (e) in the monomers constituting the copolymer (A) is preferably 1 to 60% by weight, more preferably 5 to 35% by weight based on the total weight of the monomers constituting the copolymer (A).

[0153] The copolymer (A) in the present invention may further contain, in addition to the above-mentioned monomers (a) to (e), a nitrogen atom-containing monomer (f), a hydroxyl group-containing monomer (g), a phosphorus atom-containing monomer (h), an aromatic ring-containing vinyl monomer (i), and monomers (j) to (n) as constituent monomers.

[0154] The monomers (f) to (n) may be used alone or in combination of two or more.

[0155] Examples of the nitrogen atom-containing monomer (f) include the following monomers (f1) to (f4) other than the monomers (a) to (e).

[0156] Amide group-containing monomer (f1):

[0157] Examples include (meth)acrylamide, N-methyl (meth)acrylamide, N-(N'-monoalkylaminoalkyl) (meth)acrylamide [(meth)acrylamide having an aminoalkyl group (having 2 to 6 carbon atoms) bonded to a nitrogen atom, such as N-(N'-methylaminoethyl) (meth)acrylamide, N-(N'-ethylaminoethyl) (meth)acrylamide, N-(N'-isopropylamino-n-butyl) (meth)acrylamide, and N-(N'-n- or isobutylamino-n-butyl) (meth)acrylamide], and dialkyl (meth)acrylamide [(meth)acrylamide having two alkyl groups having 1 to 4 carbon atoms bonded to a nitrogen atom, such as N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N , N-diisopropyl(meth)acrylamide and N,N-di-n-butyl(meth)acrylamide, etc.], N-(N',N'-dialkylaminoalkyl)(meth)acrylamide [(meth)acrylamide having an aminoalkyl group (having 2 to 6 carbon atoms) bonded to the nitrogen atom of the aminoalkyl group with two alkyl groups having 1 to 4 carbon atoms; for example, N-(N',N'-dimethylaminoethyl)(meth)acrylamide, N-(N',N'-diethylaminoethyl)(meth)acrylamide, N-(N',N'-dimethylaminopropyl)(meth)acrylamide and N-(N',N'-di-n-butylaminobutyl)(meth)acrylamide, etc.]; N-vinylcarboxylic acid amides [N-vinylformamide, N-vinylacetamide, N-vinylpropionamide and N-vinylhydroxyacetamide, etc.], etc.

[0158] Nitro-containing monomers (f2):

[0159] Examples thereof include 4-nitrostyrene.

[0160] Monomers containing primary to tertiary amino groups (f3):

[0161] Examples include primary amino group-containing monomers {alkenylamines having 3 to 6 carbon atoms [(meth)allylamine and crotylamine, etc.], aminoalkyl(meth)acrylates (having 2 to 6 carbon atoms) [aminoethyl(meth)acrylate, etc.]}; secondary amino group-containing monomers {monoalkylaminoalkyl(meth)acrylates [(meth)acrylates having aminoalkyl(2 to 6 carbon atoms) groups having one alkyl group having 1 to 6 carbon atoms bonded to a nitrogen atom; for example, N-tert-butylaminoethyl(meth)acrylate and N-methylaminoethyl(meth)acrylate, etc.], dienylamines having 6 to 12 carbon atoms [di(meth)allylamine, etc.]}; tertiary amino group-containing monomers {dialkylaminoalkyl(meth)acrylates [having aminoalkyl(2 to 6 carbon atoms) groups having two alkyl ... (Meth)acrylates of aminoalkyl (carbon number 2 to 6) of an alkyl group having 1 to 6 carbon atoms; for example, N,N-dimethylaminoethyl (meth)acrylate and N,N-diethylaminoethyl (meth)acrylate, etc.], alicyclic (meth)acrylates having nitrogen atoms [morpholinoethyl (meth)acrylate, etc.], aromatic monomers [N-(N',N'-diphenylaminoethyl) (meth)acrylamide, N,N-dimethylaminostyrene, 4-vinylpyridine, 2-vinylpyridine, N-vinylpyrrole, N-vinylpyrrolidone and N-vinylthiopyrrolidone, etc.]}, and their hydrochlorides, sulfates, phosphates or lower alkyl (carbon number 1 to 8) monocarboxylic acid (acetic acid, propionic acid, etc.) salts, etc.

[0162] Nitrile-containing monomers (f4):

[0163] (Meth)acrylonitrile and the like are mentioned.

[0164] Among the monomers (f), preferred are amide group-containing monomers (f1) and primary to tertiary amino group-containing monomers (f3), and more preferred are N-(N',N'-diphenylaminoethyl)(meth)acrylamide, N-(N',N'-dimethylaminoethyl)(meth)acrylamide, N-(N',N'-diethylaminoethyl)(meth)acrylamide, N-(N',N'-dimethylaminopropyl)(meth)acrylamide, N,N-dimethylaminoethyl(meth)acrylate and N,N-diethylaminoethyl(meth)acrylate.

[0165] Hydroxyl-containing monomers (g):

[0166] Examples include hydroxyl-containing aromatic monomers (p-hydroxystyrene, etc.), hydroxyalkyl (meth)acrylates (carbon number 2 to 6) [2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate or -3-hydroxypropyl (meth)acrylate, etc.], monohydroxyalkyl or bishydroxyalkyl (carbon number 1 to 4) substituted (meth)acrylamides [N,N-bis(hydroxymethyl) (meth)acrylamide, N,N-bis(hydroxypropyl) (meth)acrylamide, N,N-bis(2-hydroxybutyl) (meth)acrylamide, etc.], vinyl alcohol, enols having 3 to 12 carbon atoms [(meth) Allyl alcohol, crotyl alcohol, isocrotyl alcohol, 1-octenol and 1-undecenol, etc.], olefin monoalcohols or olefin diols having 4 to 12 carbon atoms [1-butene-3-ol, 2-butene-1-ol and 2-butene-1,4-diol, etc.], hydroxyalkyl (carbon number 1 to 6) alkenyl (carbon number 3 to 10) ethers (2-hydroxyethyl propenyl ether, etc.), alkenyl (carbon number 3 to 10) ethers of polyols (3 to 8 hydration) (glycerol, pentaerythritol, sorbitol, sorbitan, diglycerol, sugars and sucrose, etc.) or (meth) acrylates [sucrose (meth) allyl ether, etc.], etc.;

[0167] Polyoxyalkylene glycol (alkylene group having 2 to 4 carbon atoms and a degree of polymerization of 2 to 50), polyoxyalkylene polyol [polyoxyalkylene ethers of the above trivalent to octavalent alcohols (alkylene group having 2 to 4 carbon atoms and a degree of polymerization of 2 to 100), etc.], mono(meth)acrylates of alkyl (carbon number 1 to 4) ethers of polyoxyalkylene glycol or polyoxyalkylene polyol [polyethylene glycol (Mn: 100 to 300) mono(meth)acrylate, polypropylene glycol (Mn: 130 to 500) mono(meth)acrylate, methoxypolyethylene glycol (Mn: 110 to 310) (meth)acrylate, lauryl alcohol ethylene oxide adduct (2 to 30 mol) (meth)acrylate, and polyoxyethylene mono(meth)acrylate (Mn: 150 to 230) sorbitan, etc.], etc.

[0168] Examples of the phosphorus atom-containing monomer (h) include the following monomers (h1) to (h2).

[0169] Monomers containing phosphate groups (h1):

[0170] Examples include (meth)acryloyloxyalkyl (carbon number 2 to 4) phosphates [(meth)acryloyloxyethyl phosphate and (meth)acryloyloxyisopropyl phosphate] and alkenyl phosphates [vinyl phosphate, allyl phosphate, propylene phosphate, isopropylene phosphate, butyl phosphate, pentyl phosphate, octenyl phosphate, decenyl phosphate, and dodecenyl phosphate, etc.]. It should be noted that "(meth)acryloyloxy" means an acryloyloxy group or a methacryloyloxy group.

[0171] Phosphonyl-containing monomers (h2):

[0172] Examples thereof include (meth)acryloyloxyalkyl (carbon number 2-4)phosphonic acid [such as (meth)acryloyloxyethylphosphonic acid] and alkenyl (carbon number 2-12)phosphonic acid [such as vinylphosphonic acid, allylphosphonic acid and octenylphosphonic acid].

[0173] Among the monomers (h), the phosphoric acid ester group-containing monomer (h1) is preferred, (meth)acryloyloxyalkyl (carbon number 2 to 4) phosphoric acid ester is more preferred, and (meth)acryloyloxyethyl phosphoric acid ester is particularly preferred.

[0174] Aromatic ring-containing vinyl monomer (i):

[0175] Examples thereof include styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, 4-ethylstyrene, 4-isopropylstyrene, 4-butylstyrene, 4-phenylstyrene, 4-cyclohexylstyrene, 4-benzylstyrene, 4-crotylbenzene, indene, and 2-vinylnaphthalene.

[0176] Among the monomers (i), styrene and α-methylstyrene are preferred, and styrene is more preferred.

[0177] Examples of the monomer (j) having two or more unsaturated groups include divinylbenzene, dienes having 4 to 12 carbon atoms (such as butadiene, isoprene, 1,4-pentadiene, 1,6-heptadiene and 1,7-octadiene), (di)cyclopentadiene, vinylcyclohexene and ethylidene bicycloheptene, limonene, ethylene di(meth)acrylate, polyoxyalkylene glycol di(meth)acrylate, pentaerythritol triallyl ether, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, trimethylolpropane tri(meth)acrylate, esters of unsaturated carboxylic acids and diols having an Mn of 500 or more as described in International Publication No. WO01 / 009242, and esters of unsaturated alcohols and carboxylic acids.

[0178] Vinyl esters, vinyl ethers, vinyl ketones (k) (sometimes referred to as monomers (k)):

[0179] Examples include vinyl esters of saturated fatty acids having 2 to 12 carbon atoms (vinyl acetate, vinyl propionate, vinyl butyrate, 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, vinyl-2-butoxyethyl ether, etc.), and alkyl or aryl vinyl ketones having 1 to 8 carbon atoms (methyl vinyl ketone, ethyl vinyl ketone, phenyl vinyl ketone, etc.).

[0180] Epoxy-containing monomer (1) (sometimes simply referred to as monomer (1)):

[0181] Examples thereof include glycidyl (meth)acrylate and glycidyl (meth)allyl ether.

[0182] Monomer (m) containing a halogen element (sometimes referred to as monomer (m)):

[0183] Examples thereof include vinyl chloride, vinyl bromide, vinylidene chloride, (meth)allyl chloride, and halogenated styrene (such as dichlorostyrene).

[0184] Ester of unsaturated polycarboxylic acid (n) (sometimes referred to simply as monomer (n)):

[0185] Examples include alkyl, cycloalkyl or aralkyl esters of unsaturated polycarboxylic acids [alkyl diesters of unsaturated dicarboxylic acids (such as maleic acid, fumaric acid and itaconic acid) having 1 to 8 carbon atoms (such as dimethyl maleate, dimethyl fumarate, diethyl maleate and dioctyl maleate)] and the like.

[0186] In the copolymer (A), from the viewpoint of the HTHS viscosity at the effective temperature and the viscosity index improvement effect, the weight proportion of the monomer (f) in the constituent monomers of the copolymer (A) is preferably 50% by weight or less, more preferably 1 to 40% by weight, based on the total weight of the monomers constituting the copolymer (A).

[0187] In the copolymer (A), from the viewpoint of the HTHS viscosity at the effective temperature and the viscosity index improvement effect, the weight proportion of the monomer (g) in the constituent monomers of the copolymer (A) is preferably 40 wt % or less, more preferably 1 to 30 wt % based on the total weight of the monomers constituting the copolymer (A).

[0188] In the copolymer (A), from the viewpoint of the HTHS viscosity at the effective temperature and the viscosity index improvement effect, the weight proportion of the monomer (h) in the constituent monomers of the copolymer (A) is preferably 30% by weight or less, more preferably 1 to 20% by weight, based on the total weight of the monomers constituting the copolymer (A).

[0189] In the copolymer (A), from the viewpoint of the HTHS viscosity at the effective temperature and the viscosity index improvement effect, the weight proportion of the monomer (i) in the constituent monomers of the copolymer (A) is preferably 20% by weight or less, more preferably 1 to 15% by weight, based on the total weight of the monomers constituting the copolymer (A).

[0190] In the copolymer (A), the weight proportion of the monomer (j) in the monomers constituting the copolymer (A) is preferably 10 wt % or less, more preferably 1 to 5 wt % based on the total weight of the monomers constituting the copolymer (A), from the viewpoint of HTHS viscosity at the effective temperature.

[0191] In the copolymer (A), the weight ratio of the monomer (k) in the monomers constituting the copolymer (A) is preferably 5% by weight or less, more preferably 0.5 to 2% by weight, based on the total weight of the monomers constituting the copolymer (A), from the viewpoint of the viscosity index improvement effect.

[0192] In the copolymer (A), from the viewpoint of the viscosity index improvement effect, the weight ratio of the monomer (1) in the monomers constituting the copolymer (A) is preferably 20 wt % or less, more preferably 1 to 10 wt % based on the total weight of the monomers constituting the copolymer (A).

[0193] In the copolymer (A), the weight ratio of the monomer (m) in the monomers constituting the copolymer (A) is preferably 5% by weight or less, more preferably 0.1 to 2% by weight, based on the total weight of the monomers constituting the copolymer (A), from the viewpoint of the viscosity index improvement effect.

[0194] In the copolymer (A), the weight ratio of the monomer (n) in the monomers constituting the copolymer (A) is preferably 1 wt% or less, more preferably 0.01 to 0.5 wt% based on the total weight of the monomers constituting the copolymer (A), from the viewpoint of the viscosity index improvement effect.

[0195] The Mw of the copolymer (A) is preferably 5,000 to 2,000,000, more preferably 5,000 to 1,000,000, particularly preferably 10,000 to 800,000, most preferably 15,000 to 700,000, and most preferably 30,000 to 600,000. When the Mw of the copolymer (A) is 5,000 or more, the viscosity-temperature characteristics tend to be improved and the viscosity index is improved. In addition, the amount of viscosity index improver added will not be too much, which is also advantageous in terms of cost. When the Mw is 2,000,000 or less, the shear stability tends to be good.

[0196] The more preferred range of Mw of the copolymer (A) varies depending on the use of the viscosity index improver and the lubricating oil composition, but is the range described in Table 2.

[0197] [Table 2]

[0198]

[0199] *: Automatic transmission oil

[0200] **: Belt type continuously variable transmission oil

[0201] ***: Manual transmission fluid

[0202] The Mn of the copolymer (A) is preferably 2,500 or more, more preferably 5,000 or more, particularly preferably 7,500 or more, and most preferably 15,000 or more. It is preferably 300,000 or less, more preferably 150,000 or less, and particularly preferably 100,000 or less.

[0203] When Mn is 2,500 or more, the viscosity-temperature characteristics are improved and the viscosity index is improved. In addition, the amount of viscosity index improver added is not too much, which is also advantageous in terms of cost. When Mn is 300,000 or less, the shear stability is good.

[0204] The molecular weight distribution (Mw / Mn) of the copolymer (A) is preferably 1.0 to 4.0, more preferably 1.5 to 3.5, from the viewpoint of shear stability.

[0205] The measurement conditions of Mw, Mn and molecular weight distribution of the copolymer (A) are the same as the measurement conditions of Mw and Mn of the above-mentioned monomer (a).

[0206] The copolymer (A) can be obtained by a known production method. Specifically, there can be mentioned a method of obtaining the copolymer by solution polymerization of the above-mentioned monomers in a solvent in the presence of a polymerization catalyst.

[0207] Examples of the solvent include toluene, xylene, alkylbenzenes having 9 to 10 carbon atoms, methyl ethyl ketone, mineral oil, synthetic oil, and mixtures thereof.

[0208] Examples of the polymerization catalyst include azo catalysts (2,2'-azobis(2-methylbutyronitrile) and 2,2'-azobis(2,4-dimethylvaleronitrile)), peroxide catalysts (benzoyl peroxide, cumyl peroxide, and lauryl peroxide), and redox catalysts (a mixture of benzoyl peroxide and a tertiary amine).

[0209] Furthermore, in order to adjust the molecular weight, a known chain transfer agent (such as an alkyl mercaptan having 2 to 20 carbon atoms) may be used as necessary.

[0210] The polymerization temperature is preferably 25 to 140° C., more preferably 50 to 120° C. In addition to the above-mentioned solution polymerization, the copolymer (A) can also be obtained by bulk polymerization, emulsion polymerization or suspension polymerization.

[0211] The copolymer (A) may be in the form of a random addition polymer or an alternating copolymer, or may be in the form of a graft copolymer or a block copolymer.

[0212] From the viewpoint of solubility in the base oil, the SP value calculated based on the weight fraction of the monomers constituting the copolymer (A) is preferably 8.0 to 10.0 (cal / cm 3 ) 1 / 2 , more preferably 8.5 to 9.5 (cal / cm 3 ) 1 / 2 .

[0213] The SP value calculated based on the weight fraction of the monomers constituting the copolymer (A) (sometimes referred to simply as the SP value of the copolymer (A)) is a value obtained by calculating the SP value of the structural unit (a structure in which the vinyl group becomes a single bond by polymerization reaction) derived from each monomer constituting the copolymer (A) using the above-mentioned SP value calculation method, and arithmetically averaging the SP value based on the weight fraction of each constituent monomer at the time of charging. For example, when the monomer is methyl methacrylate, in the structural unit derived from methyl methacrylate, CH 3 2, CH 2 is 1, C is 1, CO 2 Therefore, the SP value of the structural unit derived from methyl methacrylate is 9.933 (cal / cm 3 ) 1 / 2 The same calculation shows that the SP value of the structural unit derived from ethyl methacrylate is 9.721 (cal / cm 3 ) 1 / 2 .

[0214] ΣΔe i =1125×2+1180+350+4300=8080

[0215] ΣΔv i =33.5×2+16.1-19.2+18.0=81.9

[0216] δ=(8080 / 81.9) 1 / 2 =9.933(cal / cm 3 ) 1 / 2

[0217] When the copolymer is a polymer of 50% by weight of methyl methacrylate and 50% by weight of ethyl methacrylate, the SP value of the copolymer is calculated by taking the arithmetic mean based on the weight fraction of the SP value of the structural unit derived from each monomer as follows.

[0218] SP value of copolymer = (9.933 × 50 + 9.721 × 50) / 100 = 9.827

[0219] The SP value calculated based on the weight fraction of the monomers constituting the copolymer (A) can be adjusted to a desired range by appropriately adjusting the monomers used and the weight fraction of each monomer used. Specifically, the SP value can be reduced by using more monomers having a large number of carbon atoms in the alkyl group, and the SP value can be increased by using more monomers having a small number of carbon atoms in the alkyl group.

[0220] The shear stability index (SSI) of the copolymer (A) is preferably 70 or less, more preferably 60 or less, from the viewpoint of the service life of the lubricating oil composition.

[0221] In the present invention, the SSI of the copolymer (A) is a value representing the viscosity reduction of the copolymer (A) due to shearing as a percentage, and is a value measured in accordance with ASTM D6278. More specifically, it is a value calculated by the following mathematical formula (3).

[0222] SSI=(Kν 0 -Kν 1 ) / (Kν 0 -Kν oil ) (3)

[0223] In the above mathematical formula (3), Kν 0 Kν is the value of the kinematic viscosity at 100°C of a sample oil obtained by diluting the viscosity index improver containing the copolymer (A) in mineral oil. 1 It is the kinematic viscosity at 100°C after diluting the viscosity index improver containing the copolymer (A) in mineral oil and passing the obtained sample oil through a high shear Bosch diesel injector for 30 cycles according to the procedure of ASTM D6278. oil It is a value of the kinematic viscosity at 100° C. of the mineral oil used when diluting the viscosity index improver.

[0224] The viscosity index improver of the present invention may contain, in addition to the above-mentioned copolymer (A), an alkyl (meth)acrylate (co)polymer (B) other than the copolymer (A), and containing the (co)polymer (B) is preferred from the perspective of low-temperature viscosity.

[0225] The (co)polymer (B) includes a (co)polymer that does not contain the monomer (a), and examples thereof include a (co)polymer that contains a (meth)acryloyl monomer (e) having a linear or branched alkyl group having 9 to 36 carbon atoms as a constituent monomer. Specifically, there can be mentioned copolymers of n-dodecyl (meth)acrylate, n-tetradecyl (meth)acrylate, n-hexadecyl (meth)acrylate and n-octadecyl (meth)acrylate, copolymers of n-octadecyl (meth)acrylate / n-dodecyl (meth)acrylate (molar ratio of 10 to 30 / 90 to 70), copolymers of n-tetradecyl (meth)acrylate / n-dodecyl (meth)acrylate (molar ratio of 10 to 30 / 90 to 70), copolymers of n-hexadecyl (meth)acrylate / n-dodecyl (meth)acrylate / methyl (meth)acrylate (molar ratio of 20 to 40 / 55 to 75 / 0 to 10), and copolymers of n-dodecyl acrylate / n-dodecyl methacrylate (molar ratio of 10 to 40 / 90 to 60). These may be used alone or in combination of two or more.

[0226] In the viscosity index improver of the present invention, the content of the (co)polymer (B) is preferably 0.01 to 30% by weight, more preferably 0.01 to 10% by weight, based on the weight of the copolymer (A), from the viewpoint of low-temperature viscosity.

[0227] From the viewpoint of lowering the pour point temperature, the Mw of the (co)polymer (B) is preferably 5,000 to 100,000, more preferably 10,000 to 80,000.

[0228] From the viewpoint of solubility in the base oil, the SP value calculated based on the weight fraction of the monomer constituting the (co)polymer (B) is preferably 7.0 to 10, more preferably 8.0 to 9.5.

[0229] The measurement conditions of Mw of the (co)polymer (B) are the same as those of the above-mentioned monomer (a), and the calculation method of the SP value is the same as that of the copolymer (A).

[0230] In the viscosity index improver of the present invention, the copolymer (A) is preferably contained in an amount of 10% by weight or more and 40% by weight or less based on the weight of the viscosity index improver from the viewpoint of the viscosity index improvement effect and low-temperature viscosity.

[0231] In the viscosity index improver of the present invention, the (co)polymer (B) is preferably contained in an amount of 0.01 to 5% by weight based on the weight of the viscosity index improver from the viewpoint of low temperature viscosity.

[0232] <Ester oil (Z)>

[0233] The viscosity index improver of the present invention contains the above-mentioned copolymer (A) and ester oil (Z). The ester oil may be used alone or in combination of two or more. The viscosity index improver of the present invention contains the copolymer (A) containing the above-mentioned monomer (a) and monomer (b) as constituent monomers and further containing monomer (c) and / or monomer (d) as constituent monomers and the ester oil (Z). Therefore, even when the copolymer (A) having a high molecular weight is contained at a high concentration, the viscosity is low, and the viscosity index improver tends to have good handling properties. It is easy to take out from the reaction tank after the viscosity index improver is produced. In addition, when the viscosity index improver of the present invention is diluted to prepare a lubricating oil composition, by making the viscosity index improver contain ester oil (Z), it is estimated that compared with the case where the oil component contained in the lubricating oil composition is only hydrocarbon oil, the molecules are easily diffused at high temperature, and the molecules are easily aggregated when the temperature is lowered. The molecular behavior of the copolymer (A) is good, the HTHS viscosity at 100°C and the kinematic viscosity at 40°C are excellent, and the gel index is good.

[0234] The ester oil (Z) is not particularly limited as long as it is an ester compound having a lubricating function that has been used as a lubricating oil in the past. Examples thereof include esters formed from dicarboxylic acids and alcohols as described in Japanese Patent Application Laid-Open No. 11-172267, esters formed from monocarboxylic acids and diols as described in Japanese Patent Application Laid-Open No. 2003-321691, and phosphoric acid esters as described in Japanese Patent Application Laid-Open No. 10-77494.

[0235] Among these, preferred are ester oils (z1) which are esters of aliphatic saturated dicarboxylic acids having 4 to 16 carbon atoms and aliphatic saturated monohydric alcohols having 6 to 24 carbon atoms, and ester oils (z2) which are esters of aliphatic saturated monocarboxylic acids having 6 to 24 carbon atoms and aliphatic saturated dihydric alcohols having 4 to 16 carbon atoms, from the perspective of low-temperature viscosity.

[0236] As the ester oil (Z), from the viewpoint of the kinematic viscosity at 40° C., an esterified product having a total of 10 to 40 carbon atoms is preferred, and an esterified product having a total of 15 to 35 carbon atoms is more preferred.

[0237] In the ester oil (z1) which is an esterification product of an aliphatic saturated dicarboxylic acid having 4 to 16 carbon atoms and an aliphatic saturated monohydric alcohol having 6 to 24 carbon atoms, examples of the aliphatic saturated dicarboxylic acid having 4 to 16 carbon atoms include straight-chain saturated alkyl dicarboxylic acids {for example, n-succinic acid (succinic acid), n-glutaric acid (glutaric acid), n-hexanedioic acid (adipic acid), n-pimelic acid, n-octanedioic acid, n-nonanedioic acid, n-decanedioic acid (sebacic acid), n-undecanedicarboxylic acid, n-dodecanedioic acid, n-tridecanedioic acid, n-tetradecanedioic acid, n-pentadecanedioic acid and n-hexadecanedioic acid}, branched-chain saturated alkyl dicarboxylic acids {for example, 3-methyladipic acid}, and alicyclic saturated dicarboxylic acids {for example, 1,2-cyclopentanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid or 1,4-cyclohexanedicarboxylic acid}, etc.

[0238] In the ester oil (z1), examples of the aliphatic saturated monohydric alcohol having 6 to 24 carbon atoms include straight-chain saturated alkyl monoalcohols {e.g., n-hexanol, n-heptanol, n-octanol, n-nonanol, n-decanol, n-undecanol, n-dodecanol, n-tridecanol, n-tetradecanol, n-pentadecanol, n-hexadecanol, n-heptadecanol, n-octadecanol, n-nonadecanol, n-eicosanol, n-heneicosanol, n-docosanol and n-tetracosanol}, branched-chain saturated alkyl monoalcohols {for example, 2-ethylhexanol, isononanol, isodecanol, isoundecanol, isoundecanol, isododecanol, isotridecanol, isotetradecanol, isopentadecyl alcohol, isohexadecanol, isohexadecanol, isoheptadecanol, isooctadecanol and isonadecanol, etc.}, alicyclic monoalcohols {for example, cyclohexanol, 2-tert-butylcyclohexanol, 3-tert-butylcyclohexanol or 4-tert-butylcyclohexanol, menthol, cyclohexaneethanol, 2-isopropylcyclohexanol, 3-isopropylcyclohexanol or 4-isopropylcyclohexanol, etc.}, etc.

[0239] Specific examples of the ester oil (z1) include di(2-ethylhexyl) hexanediol ester {sometimes described as bis(2-ethylhexyl) adipate}, diisodecyl hexanediol ester {sometimes described as diisodecyl adipate}, didecyl heptanediol ester, didecyl heptanediol ester, didecyl heptanediol ester, diisodecyl heptanediol ester, diisodecyl heptanediol ester, diisoundecyl heptanediol ester, diisododecyl heptanediol ester, di(2-ethylhexyl) heptanediol ester, dinonyl octanedioate, didecyl octanedioate, and didecyl octanedioate. Di(undecanedioic acid) ester, diisononyl octanedioate, diisodecyl octanedioate, di(2-ethylhexyl) octanedioate, di(isoundecanedioate) decanedicarboxylate, dioctyl nonanedioate, dinonyl nonanedioate, didecyl nonanedioate, diisooctyl nonanedioate, diisononyl nonanedioate, diisodecyl nonanedioate, di(2-ethylhexyl) nonanedioate, dioctyl decanedicarboxylate, di(2-ethylhexyl) decanedicarboxylate {sometimes described as bis(2-ethylhexyl) sebacate}, dinonyl decanedicarboxylate, and didecyl decanedicarboxylate, etc.

[0240] Among the ester oils (z1), from the viewpoint of low-temperature viscosity, the esterification product of a straight-chain saturated alkyl dicarboxylic acid having 4 to 16 carbon atoms and an aliphatic saturated monohydric alcohol having 6 to 24 carbon atoms is preferred, the esterification product of a straight-chain saturated alkyl dicarboxylic acid having 4 to 16 carbon atoms and a branched saturated alkyl monoalcohol having 6 to 24 carbon atoms is further preferred, and the esterification product of a straight-chain saturated alkyl dicarboxylic acid having 4 to 10 carbon atoms and a branched saturated alkyl monoalcohol having 6 to 20 carbon atoms is particularly preferred.

[0241] In the ester oil (z2), examples of the aliphatic saturated monocarboxylic acid having 6 to 24 carbon atoms include straight-chain saturated alkyl monocarboxylic acids {for example, n-hexanoic acid, n-heptanoic acid, n-octanoic acid, n-nonanoic acid, n-decanoic acid, n-undecanoic acid, n-dodecanoic acid, n-tridecanoic acid, n-tetradecanoic acid, n-pentadecanoic acid, n-hexadecanoic acid, n-heptadecanoic acid, n-octadecanoic acid, n-nonadecanoic acid, n-eicosanoic acid, n-docosanoic acid and n-tetracosanoic acid}, branched-chain saturated alkyl monocarboxylic acids {for example, 2-ethylhexanoic acid, isononanoic acid, isodecanoic acid, isoundecanoic acid, isododecanoic acid, isotridecanoic acid, isotetradecanoic acid, isopentadecanoic acid, isohexadecanoic acid, isoheptadecanoic acid, isooctadecanoic acid and isonadecanoic acid}, and alicyclic monocarboxylic acids {for example, cyclohexanecarboxylic acid}.

[0242] In the ester oil (z2), examples of the aliphatic saturated diol having 4 to 16 carbon atoms include straight-chain saturated alkyl diols {e.g., 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,15-pentadecandiol, and 1,16-hexadecanediol}, branched-chain saturated alkyl diols {e.g., 2-methyl-1,3-propanediol, 2-methyl-1,4-butanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2-octanediol, 1,2-nonanediol, 1,2-decanediol, 1,2-undecanediol, 1,2-dodecanediol, 1,2-tridecanediol, 1,2-tetradecanediol, 1,2-pentadecandiol, 1,2-hexadecanediol, etc.}, alicyclic diols {for example, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, etc.}, etc.

[0243] Among the ester oils (z2), from the aspect of low-temperature viscosity, preferred are esters of aliphatic saturated monocarboxylic acids having 6 to 24 carbon atoms and straight-chain saturated alkyl diols having 4 to 16 carbon atoms, further preferred are esters of branched saturated alkyl monocarboxylic acids having 6 to 24 carbon atoms and straight-chain saturated alkyl diols having 4 to 16 carbon atoms, and particularly preferred are esters of branched saturated alkyl monocarboxylic acids having 6 to 20 carbon atoms and straight-chain saturated alkyl diols having 4 to 12 carbon atoms.

[0244] The ester oil (Z) preferably has a kinematic viscosity at 100° C. (measured in accordance with JIS-K2283) of 1 to 4 mm 2 / s, more preferably 1.5 to 3.6 mm 2 / s.

[0245] The kinematic viscosity of the ester oil (Z) at 100° C. can be adjusted by changing the carbon number of the carboxylic acid and the alkyl alcohol in synthesizing the ester oil (Z). Specifically, when a substance with a large carbon number is used, the kinematic viscosity at 100° C. increases.

[0246] The viscosity index of the ester oil (Z) (measured in accordance with JIS-K2283) is preferably 100 or more, more preferably 105 to 180, from the viewpoint of the viscosity index of the lubricating oil composition.

[0247] The viscosity index of the ester oil (Z) can be adjusted by changing the carbon number of the carboxylic acid and the alkyl alcohol when synthesizing the ester oil. Specifically, when a substance with a large carbon number is used, the viscosity index increases.

[0248] From the viewpoint of solubility of various additives, the SP value of the ester oil (Z) is preferably 8.0 to 10.0 (cal / cm 3 ) 1 / 2 , more preferably 8.5 to 9.5 (cal / cm 3 ) 1 / 2 .

[0249] From the viewpoint of compatibility, the absolute value of the difference between the SP value calculated based on the weight fraction of the monomers constituting the copolymer (A) and the SP value of the ester oil (Z) is preferably 0.1 to 2.0 (cal / cm 3 ) 1 / 2 , more preferably 0.1 to 1.5 (cal / cm 3 ) 1 / 2 , particularly preferably 0.1 to 1.0 (cal / cm 3 ) 1 / 2 .

[0250] The weight ratio ((A) / (Z)) of the copolymer (A) and the ester oil (Z) contained in the viscosity index improver of the present invention is preferably 10 / 90 to 70 / 30, more preferably 10 / 90 to 60 / 40, and particularly preferably 25 / 75 to 45 / 55 from the viewpoints of the handling property of the viscosity index improver, the gel index of the lubricating oil composition, and the volatility at 250°C. When the weight ratio is within this range, the viscosity of the viscosity index improver (for example, the viscosity at 90°C) is low, and the handling property tends to be good. In addition, when a lubricating oil composition is produced using a hydrocarbon oil as a base oil, the weight ratio ((A) / (Z)) in the lubricating oil composition is the above ratio, and the gel index and the volatility at 250°C of the lubricating oil composition tend to be good.

[0251] In the viscosity index improver of the present invention, the ester oil (Z) is preferably contained in an amount of 30 to 90% by weight, more preferably 40 to 89% by weight, and particularly preferably 50 to 87% by weight, based on the weight of the viscosity index improver, from the viewpoints of the handling properties of the viscosity index improver, the reduction in HTHS viscosity of the obtained lubricating oil composition, and the low-temperature viscosity. Within this range, when a lubricating oil composition is produced using a hydrocarbon oil as a base oil, the content of the ester oil in the lubricating oil composition is appropriate, and there is a tendency that a lubricating oil composition having a low HTHS viscosity and excellent low-temperature viscosity can be obtained.

[0252] In the viscosity index improver of the present invention, the copolymer (A) is preferably contained in an amount of 10 to 70% by weight, more preferably 10 to 40% by weight, and particularly preferably 12 to 40% by weight, based on the weight of the viscosity index improver, from the viewpoints of the handling properties of the viscosity index improver, the gel index of the lubricating oil composition, and the volatility at 250°C.

[0253] From the viewpoint of the handling property of the viscosity index improver, the kinematic viscosity of the viscosity index improver at 90° C. (measured in accordance with JIS-K2283) is preferably 100 to 20,000 mm 2 / s, more preferably 300 to 12000 mm 2 / s.

[0254] The viscosity index improver of the present invention may further contain a base oil other than the ester oil (Z). It is preferred to contain a base oil other than the ester oil (Z) from the viewpoint of the oxidation stability of the viscosity index improver and the oxidation stability and volatility at 250° C. of the lubricating oil composition.

[0255] Examples of the base oil other than the ester oil (Z) include hydrocarbon oils, and specific examples thereof include hydrocarbon oils of groups I to IV of the API classification.

[0256] From the viewpoint of solubility of various additives, the SP value of the hydrocarbon oil is preferably 7.8 to 9.5 (cal / cm 3 ) 1 / 2 , more preferably 8.0 to 9.0 (cal / cm 3 ) 1 / 2 .

[0257] It should be noted that, when a mixture of various hydrocarbon compounds such as mineral oil is used as the hydrocarbon oil, the molecular weight can be determined by GPC, 1 H-NMR and 13 The constituent components and their molecular structures can be roughly known from molecular structure analysis such as C-NMR, and the SP value of the hydrocarbon oil can be calculated by arithmetic mean based on the mole fraction.

[0258] In the viscosity index improver of the present invention, the absolute value of the difference between the SP values ​​of the ester oil (Z) and the hydrocarbon oil is preferably 0.1 to 2.0 (cal / cm 3 ) 1 / 2 , more preferably 0.2 to 1.5 (cal / cm 3 ) 1 / 2 , particularly preferably 0.3 to 1.0 (cal / cm 3 ) 1 / 2 .

[0259] In the viscosity index improver of the present invention, the absolute value of the difference between the SP value calculated based on the weight fraction of the monomers constituting the copolymer (A) and the SP value of the hydrocarbon oil is preferably 0.8 to 2.0 (cal / cm 3 ) 1 / 2 , more preferably 0.8 to 1.3 (cal / cm 3 ) 1 / 2 , particularly preferably 0.9 to 1.2 (cal / cm 3 ) 1 / 2 .

[0260] The absolute value of the difference between the SP value calculated based on the weight fraction of the monomers constituting the copolymer (A) and the SP value of the hydrocarbon oil can be set to a desired range by appropriately adjusting the type and weight fraction of the monomers used to produce the copolymer (A) relative to the base oil.

[0261] The kinematic viscosity of the hydrocarbon oil at 100° C. (measured according to JIS-K2283) is preferably 1 to 15 mm 2 / s, more preferably 2 to 5 mm 2 / s.

[0262] The viscosity index (measured in accordance with JIS-K2283) of the hydrocarbon oil is preferably 100 or more from the viewpoint of the viscosity index and low-temperature fluidity of the lubricating oil composition.

[0263] The weight ratio of the ester oil (Z) to the hydrocarbon oil in the viscosity index improver ((Z) / hydrocarbon oil) is preferably 40 / 60 to 100 / 0, more preferably 50 / 50 to 95 / 5, from the viewpoints of the oxidation stability of the viscosity index improver and the oxidation stability, volatility at 250°C and low-temperature viscosity when a lubricating oil composition is produced using a hydrocarbon oil as a base oil.

[0264] From the viewpoint of HTHS viscosity, the weight ratio of the copolymer (A) to the hydrocarbon oil in the viscosity index improver ((A) / hydrocarbon oil) is preferably 10 / 90 to 100 / 0, more preferably 20 / 80 to 90 / 10.

[0265] The viscosity index improver of the present invention preferably contains 1 to 35% by weight of hydrocarbon oil based on the weight of the viscosity index improver from the viewpoint of oxidation stability of the viscosity index improver and oxidation stability and volatility at 250° C. of the lubricating oil composition.

[0266] The cloud point of the hydrocarbon oil (measured according to JIS-K2269) is preferably -5°C or lower, more preferably -15°C or lower. When the cloud point of the hydrocarbon oil is within this range, the low-temperature viscosity of the lubricating oil composition tends to be good.

[0267] <Lubricating Oil Composition>

[0268] The lubricating oil composition of the present invention contains the viscosity index improver of the present invention and at least one additive selected from the group consisting of a detergent, a dispersant, an antioxidant, an oiliness improver, a pour point depressant, a friction and wear modifier, an extreme pressure agent, a defoamer, an anti-emulsifier, a metal deactivator and a corrosion inhibitor.

[0269] The lubricating oil composition of the present invention preferably contains the copolymer (A) in an amount of 0.1 wt % to less than 10 wt %, more preferably 0.5 wt % to less than 10 wt %, based on the weight of the lubricating oil composition, from the viewpoint of fuel efficiency.

[0270] The lubricating oil composition of the present invention preferably contains the (co)polymer (B) in an amount of 0.01 to 2% by weight based on the weight of the lubricating oil composition, from the viewpoint of low-temperature viscosity.

[0271] The lubricating oil composition of the present invention preferably contains the ester oil (Z) in an amount of 1 to 99.9% by weight, more preferably 1 to 30% by weight, based on the weight of the lubricating oil composition, from the viewpoints of gel index, low temperature viscosity, HTHS viscosity at 100°C and kinematic viscosity at 40°C.

[0272] The lubricating oil composition of the present invention preferably contains the hydrocarbon oil in an amount of 98.89% by weight or less, more preferably 50 to 90% by weight, based on the weight of the lubricating oil composition, from the viewpoint of oxidation stability.

[0273] When the lubricating oil composition is used as an engine oil, it is preferred that the kinematic viscosity at 100° C. be 2 to 10 mm 2 A lubricating oil composition containing 1 wt% or more and less than 10 wt% of the copolymer (A) in a base oil (ester oil (Z) or a mixture of ester oil (Z) and hydrocarbon oil) having a viscosity of 100 μm / s.

[0274] When the lubricating oil composition is used as a gear oil, it is preferred that the kinematic viscosity at 100° C. be 2 to 10 mm 2 A lubricating oil composition containing 3 to 20 wt% of the copolymer (A) in a base oil (ester oil (Z) or a mixture of ester oil (Z) and hydrocarbon oil) having a viscosity of 1000 μm / s.

[0275] When the lubricating oil composition is used as an automatic transmission oil (ATF, belt-type CVTF, etc.), the kinematic viscosity at 100° C. is preferably 2 to 6 mm 2 A lubricating oil composition containing 3 to 20 wt% of the copolymer (A) in a base oil (ester oil (Z) or a mixture of ester oil (Z) and hydrocarbon oil) having a viscosity of 1000 μm / s.

[0276] When the lubricating oil composition is used as traction oil, it is preferred that the kinematic viscosity at 100° C. be 1 to 5 mm 2 A lubricating oil composition containing 0.5 to 10 wt% of the copolymer (A) in a base oil (ester oil (Z) or a mixture of ester oil (Z) and hydrocarbon oil) having a viscosity of 100 μm / s.

[0277] The weight ratio ((A) / (Z)) of the copolymer (A) to the ester oil (Z) contained in the lubricating oil composition of the present invention is preferably 10 / 90 to 70 / 30, more preferably 10 / 90 to 60 / 40, and particularly preferably 25 / 75 to 45 / 55, from the viewpoints of gel index, low temperature viscosity, HTHS viscosity at 100°C and kinematic viscosity at 40°C.

[0278] The weight ratio of the ester oil (Z) to the hydrocarbon oil ((Z) / hydrocarbon oil) contained in the lubricating oil composition is preferably 1 / 99 to 20 / 80, more preferably 2 / 98 to 9 / 91, from the viewpoints of gel index, low temperature viscosity, HTHS viscosity at 100°C, kinematic viscosity at 40°C, oxidation stability, and volatility at 250°C. Within this range, the gel index, low temperature viscosity, HTHS viscosity at 100°C, and kinematic viscosity at 40°C tend to be improved without reducing the oxidation stability and volatility at 250°C of the lubricating oil composition.

[0279] From the viewpoint of HTHS viscosity, the weight ratio of the copolymer (A) to the hydrocarbon oil ((A) / hydrocarbon oil) contained in the lubricating oil composition is preferably 99.9 / 0.1 to 1 / 99, more preferably 99 / 1 to 10 / 90.

[0280] The lubricating oil composition of the present invention contains various additives. Examples of the additives include the following.

[0281] (1) Cleaning agent:

[0282] Basic, overbased or neutral metal salts [overbased or alkaline earth metal salts of sulfonates (petroleum sulfonates, alkylbenzene sulfonates and alkylnaphthalene sulfonates, etc.)], salicylates, phenates, naphthenates, carbonates, phosphonates and mixtures thereof;

[0283] (2) Dispersant:

[0284] Succinimides (bis- or mono-polybutenyl succinimides), Mannich condensates and borates, etc.;

[0285] (3) Antioxidants:

[0286] Hindered phenols and aromatic secondary amines, etc.;

[0287] (4) Oiliness enhancer:

[0288] 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.;

[0289] (5) Pour point depressant

[0290] Polyalkyl methacrylate, ethylene-vinyl acetate copolymer, etc.;

[0291] (6) Friction and wear regulator:

[0292] Molybdenum and zinc compounds (molybdenum dithiophosphate, molybdenum dithiocarbamate and zinc dialkyl dithiophosphate, etc.);

[0293] (7) Extreme pressure agent:

[0294] Sulfur compounds (monosulfide or disulfide, sulfoxide and sulfur-phosphorus compounds), phosphorus compounds and chlorine compounds (chlorinated paraffins, etc.);

[0295] (8) Defoaming agent:

[0296] Silicone oil, metal soap, fatty acid ester and phosphate compounds, etc.;

[0297] (9) Anti-emulsifier:

[0298] Quaternary ammonium salts (tetraalkylammonium salts, etc.), sulfated oils and phosphate esters (phosphate esters of nonionic surfactants containing polyoxyethylene, etc.), hydrocarbon solvents (toluene, xylene, ethylbenzene), etc.;

[0299] (10) Metal passivator

[0300] Nitrogen atom-containing compounds (benzotriazole, etc.), nitrogen atom-containing chelate compounds (N,N'-disalicylidene-1,2-diaminopropane, etc.), nitrogen / sulfur-containing compounds (2-(n-dodecylthio)benzimidazole, etc.), etc.;

[0301] (11) Anticorrosive agents:

[0302] Compounds containing nitrogen atoms (benzotriazole and 1,3,4-thiadiazolyl-2,5-bisdialkyldithiocarbamate, etc.)

[0303] Only one of these additives may be added, or two or more additives may be added as needed. In addition, additives obtained by mixing these additives are sometimes referred to as performance additives or package additives, and such additives may also be added.

[0304] The content of each of these additives is preferably 0.1 to 15% by weight based on the total weight of the lubricating oil composition, and the total content of the additives is preferably 0.1 to 30% by weight, more preferably 0.3 to 20% by weight, based on the total weight of the lubricating oil composition.

[0305] The lubricating oil composition of the present invention is suitable for use in gear oil (differential oil and industrial gear oil, etc.), MTF, transmission oil [ATF, DCTF and belt CVTF, etc.], traction oil (annular CVTF, etc.), shock absorber oil, power steering oil, hydraulic oil (hydraulic oil for construction machinery and industrial hydraulic oil, etc.) and engine oil (for gasoline engines and diesel engines).

[0306] Example

[0307] The present invention is further described below by way of examples and comparative examples, but the present invention is not limited thereto.

[0308] The ratio of 1,2-butylene groups in the structural units of hydrocarbon polymers is given by 13 The polymer was analyzed by C-NMR and the molecular weight was determined by the above method using the above mathematical formula (1).

[0309] The molar ratio of 1,2-adduct / 1,4-adduct in the hydrocarbon polymer (molar ratio in the structure derived from butadiene) is given by 13 The polymer was analyzed by C-NMR, and the value of the integrated value B and the integrated value C used in the above-mentioned mathematical formula (1) were determined by the following mathematical formula (3).

[0310] Molar ratio of 1,2-adduct / 1,4-adduct = {100×integral value B×4 / integral value C} / {100-(100×integral value B×4 / integral value C)} (3)

[0311] <Production Example 1>

[0312] Into a 1 L SUS pressure-resistant reaction vessel equipped with a temperature control device and a stirrer, 400 parts by weight of degassed and dehydrated hexane, 0.5 parts by weight of tetrahydrofuran, 90 parts by weight of 1,3-butadiene, and 0.9 parts by weight of n-butyllithium were charged, and polymerization was then carried out at a polymerization temperature of 50°C.

[0313] After the polymerization rate reached approximately 100%, 2 parts by weight of ethylene oxide was added and the reaction was further carried out at 50°C for 3 hours. To stop the reaction, 50 parts by weight of water and 25 parts by weight of 1N-hydrochloric acid aqueous solution were added and stirred at 80°C for 1 hour. The organic phase of the reaction solution was recovered with a separatory funnel, heated to 70°C, and the solvent was removed under a reduced pressure of 0.027 to 0.040 MPa for 2 hours.

[0314] The obtained polybutadiene containing a hydroxyl group at one end is transferred to a reaction vessel equipped with a temperature regulating device, a stirrer, and a hydrogen introduction tube, and 150 parts by weight of tetrahydrofuran is added to make it uniformly dissolved. After injecting a suspension prepared by premixing 10 parts by weight of palladium carbon and 50 parts by weight of tetrahydrofuran, hydrogen is supplied to the liquid at a flow rate of 30 mL / min through the hydrogen introduction tube, and the reaction is carried out at room temperature for 8 hours. After that, the palladium carbon is removed by filtration, the obtained filtrate is heated to 70°C, and tetrahydrofuran is removed under a reduced pressure of 0.027 to 0.040 MPa to obtain a polymer (Y-1) containing a hydroxyl group at one end of hydrogenated polybutadiene.

[0315] The molecular weight of (Y-1) obtained was measured by GPC. 13 The ratio of 1,2-butylene groups was measured by C-NMR. As a result, Mw=7,000, Mn=6,500, the ratio of 1,2-butylene groups=45 mol%, and the molar ratio (1,2-adduct / 1,4-adduct)=45 / 55.

[0316] <Production Example 2>

[0317] Into a 1 L SUS pressure-resistant reaction vessel equipped with a temperature control device and a stirrer, 400 parts by weight of degassed and dehydrated hexane, 2 parts by weight of tetrahydrofuran, 90 parts by weight of 1,3-butadiene, and 0.9 parts by weight of n-butyl lithium were charged, and then polymerization was carried out at a polymerization temperature of -0°C.

[0318] After the polymerization rate reached approximately 100%, 2 parts by weight of ethylene oxide was added and the mixture was reacted at 50°C for 3 hours. To stop the reaction, 50 parts by weight of water and 25 parts by weight of a 1N hydrochloric acid aqueous solution were added and stirred at 80°C for 1 hour. The organic phase of the reaction solution was recovered with a separatory funnel, heated to 70°C, and the solvent was removed under a reduced pressure of 0.027 to 0.040 MPa for 2 hours.

[0319] The obtained polybutadiene containing a hydroxyl group at one end is transferred to a reaction vessel equipped with a temperature regulating device, a stirrer, and a hydrogen introduction tube, and 150 parts by weight of tetrahydrofuran is added to make it uniformly dissolved. After injecting a suspension prepared by premixing 10 parts by weight of palladium carbon and 50 parts by weight of tetrahydrofuran, hydrogen is supplied to the liquid at a flow rate of 30 mL / min through the hydrogen introduction tube, and the reaction is carried out at room temperature for 8 hours. After that, the palladium carbon is removed by filtration, the obtained filtrate is heated to 70°C, and tetrahydrofuran is removed under a reduced pressure of 0.027 to 0.040 MPa to obtain a polymer (Y-2) containing a hydroxyl group at one end of hydrogenated polybutadiene.

[0320] The molecular weight of (Y-2) obtained was measured by GPC. 13 The ratio of 1,2-butylene groups was measured by C-NMR. As a result, Mw=7,000, Mn=6,500, the ratio of 1,2-butylene groups=65 mol%, and the molar ratio (1,2-adduct / 1,4-adduct)=65 / 35.

[0321] <Production Example 3: Production of Copolymer Composition (B-1)>

[0322] A hydrocarbon oil 1 (kinematic viscosity at 100° C.: 4.2 mm) was added to a reaction vessel equipped with a stirring device, a heating and cooling device, a thermometer, a dropping funnel, a nitrogen blowing tube, and a pressure reducing device. 2 / s, viscosity index: 122), 75 parts by weight of n-dodecyl methacrylate, 24 parts by weight of n-tetradecyl methacrylate, 41 parts by weight of n-hexadecyl methacrylate, 16 parts by weight of n-octadecyl methacrylate, 0.6 parts by weight of dodecyl mercaptan as a chain transfer agent, 0.5 parts by weight of 2,2-azobis(2,4-dimethylvaleronitrile) and 0.2 parts by weight of 2,2-azobis(2-methylbutyronitrile) were added to another glass beaker, stirred and mixed at 20°C to prepare a monomer solution, which was then added to a dropping funnel.

[0323] After nitrogen substitution of the gas phase of the reaction vessel (gas phase oxygen concentration: 100 ppm or less), the monomer solution was added dropwise over 2 hours while the temperature in the system was kept at 70 to 85°C in a sealed manner. After the addition was completed, the temperature was raised to 120 to 130°C after aging at 85°C for 2 hours, and then the unreacted monomers were removed at the same temperature under reduced pressure (0.027 to 0.040 MPa) for 2 hours to obtain a copolymer composition (B-1) containing 65% by weight of the copolymer (B) in hydrocarbon oil. The obtained copolymer (B) had an Mw of 53,000 and an SP value of 9.0.

[0324] <Production Example 4: Production of Copolymer Composition (B-2)>

[0325] Ester oil (Z-1) (bis(2-ethylhexyl) adipate, kinematic viscosity at 100°C: 2.3 mm) was added to a reaction vessel equipped with a stirring device, a heating and cooling device, a thermometer, a dropping funnel, a nitrogen blowing tube, and a decompression device. 2 / s, viscosity index: 118), 75 parts by weight of n-dodecyl methacrylate, 24 parts by weight of n-tetradecyl methacrylate, 41 parts by weight of n-hexadecyl methacrylate, 16 parts by weight of n-octadecyl methacrylate, 0.6 parts by weight of dodecyl mercaptan as a chain transfer agent, 0.5 parts by weight of 2,2-azobis(2,4-dimethylvaleronitrile) and 0.2 parts by weight of 2,2-azobis(2-methylbutyronitrile) were added to another glass beaker, stirred and mixed at 20°C to prepare a monomer solution, which was then added to a dropping funnel.

[0326] After nitrogen substitution of the gas phase of the reaction vessel (gas phase oxygen concentration: 100 ppm or less), the monomer solution was added dropwise over 2 hours while the temperature in the system was kept at 70 to 85°C in a sealed manner. After completion of the addition, the mixture was aged at 85°C for 2 hours, and then the temperature was raised to 120 to 130°C. Unreacted monomers were removed at the same temperature under reduced pressure (0.027 to 0.040 MPa) for 2 hours to obtain a copolymer composition (B-2) containing 65% by weight of the copolymer (B) in the ester oil. The obtained copolymer (B) had an Mw of 53,000 and an SP value of 9.0.

[0327] <Examples 1 to 28, Comparative Examples 1 to 4>

[0328] The base oil, monomer blend, and catalyst listed in Table 3-1, Table 3-2, or Table 4 were added to a reaction vessel equipped with a stirring device, a heating and cooling device, a thermometer, and a nitrogen inlet pipe in the amounts listed in Table 3-1, Table 3-2, or Table 4, and after nitrogen substitution (gas phase oxygen concentration 100 ppm), the temperature was raised to 76° C. under stirring in a sealed state, and a polymerization reaction was carried out at this temperature for 4 hours. After the temperature was raised to 120 to 130° C., unreacted monomers were removed at this temperature under reduced pressure (0.027 to 0.040 MPa) for 2 hours. The copolymer composition (B-1) obtained in Preparation Example 3 or the copolymer composition (B-2) obtained in Preparation Example 4 was further added in the amounts listed in Table 3-1, Table 3-2, or Table 4 to obtain viscosity index improvers (R-1) to (R-28) and (S-1) to (S-4). The SP values ​​of copolymers (A-1) to (A-18) and (A'-1) to (A'-3) were calculated by the above method, and Mw and Mn were measured by the above method. In addition, the base oil solubility of copolymer (A) was evaluated by the following method. In addition, the oxidation stability of the viscosity index improver was evaluated by the following method. In addition, the kinematic viscosity of the viscosity index improver at 90°C was measured by the following method. The results are shown in Table 3-1, Table 3-2 or Table 4.

[0329] <Method for evaluating base oil solubility of copolymer (A)>

[0330] The appearance of the viscosity index improvers (R-1) to (R-28) and (S-1) to (S-4) which had been temperature-controlled at 25°C for one day was visually observed under a fluorescent white light at room temperature of 25°C, and the solubility of the copolymer (A) in the base oil was evaluated according to the following evaluation criteria.

[0331] [Evaluation criteria]

[0332] ○: Uniform appearance, no insoluble copolymer

[0333] ×: The appearance is uneven, and insoluble matter of the copolymer is observed

[0334] <Determination method of oxidation stability>

[0335] According to JIS-K2514, an oxidation stability test was conducted at 165.5°C ± 0.5°C for 120 hours, and the increase in the total acid value (mgKOH / g) of the viscosity index improver and the lubricating oil composition before and after the test was measured. The smaller the value, the better the oxidation stability.

[0336] [Evaluation criteria: Viscosity index improver]

[0337] ◎: The increase in the total acid value of the lubricating oil composition before and after the test is 30 mgKOH / g or less

[0338] ○: The increase in the total acid value of the lubricating oil composition before and after the test is greater than 30 mgKOH / g and less than 50 mgKOH / g

[0339] △: The increase in the total acid value of the lubricating oil composition before and after the test is greater than 50 mgKOH / g and less than 70 mgKOH / g

[0340] <Method for measuring kinematic viscosity of viscosity index improver>

[0341] The kinematic viscosity at 90° C. is measured by the method of JIS-K2283. A lower value means a lower viscosity and better handling properties.

[0342] [Table 3-1]

[0343]

[0344] [Table 3-2]

[0345]

[0346] [Table 4]

[0347]

[0348] The base oils and the compositions of monomers (a) to (f) and the base oils described in Table 3-1, Table 3-2 or Table 4 are as follows.

[0349] (a-1): a methacrylated product of a polymer containing a hydroxyl group at one end of hydrogenated polybutadiene (ratio of 1,2-butylene group = 45 mol %) (Y-1) obtained in Production Example 1 [Mn: 6,600]

[0350] (a-2): Methacrylated product of the polymer containing a hydroxyl group at one end of the hydrogenated polybutadiene obtained in Production Example 2 (ratio of 1,2-butylene group = 65 mol %) (Y-2) [Mn: 6,600]

[0351] (b-1): n-Butyl methacrylate

[0352] (b-2): Isobutyl methacrylate

[0353] (c-1): Ethoxyethyl methacrylate

[0354] (c-2): Butoxyethyl methacrylate

[0355] (d-1): Ethyl methacrylate

[0356] (d-2): Isopropyl methacrylate

[0357] (e-1): n-dodecyl methacrylate (esterified product of Neodol 25 (manufactured by Shell Chemicals) and methacrylic acid)

[0358] (e-2): A mixture of linear and branched alkyl methacrylates having 12 to 13 carbon atoms (esterified product of Neodol 23 (manufactured by Shell Chemicals) and methacrylic acid)

[0359] (e-3): A mixture of linear and branched alkyl methacrylates having 14 to 15 carbon atoms (esterified product of Neodol 45 (manufactured by Shell Chemicals) and methacrylic acid)

[0360] (e-4): n-Hexadecyl methacrylate

[0361] (e-5): n-octadecyl methacrylate

[0362] (e-6): 2-n-decyltetradecyl methacrylate

[0363] (e-7): 2-n-dodecylhexadecyl methacrylate

[0364] (e-8): 2-n-Tetradecyloctadecyl methacrylate

[0365] (f-1): N,N-dimethylaminoethyl methacrylate

[0366] Ester oil (Z-1): bis(2-ethylhexyl) adipate (SP value = 8.93 (cal / cm 3 ) 1 / 2 , Kinematic viscosity at 100℃=2.3mm 2 / s, viscosity index = 118)

[0367] Ester oil (Z-2): bis(2-ethylhexyl) sebacate (SP value: 8.87 (cal / cm 3 ) 1 / 2 , Kinematic viscosity at 100℃: 3.2mm 2 / s, viscosity index: 151)

[0368] Ester oil (Z-3): diisodecyl adipate (SP value: 8.97 (cal / cm 3 ) 1 / 2 , Kinematic viscosity at 100℃: 3.6mm 2 / s, viscosity index: 141)

[0369] Hydrocarbon oil 1: SP value = 8.3-8.4 (cal / cm 3 ) 1 / 2 , Kinematic viscosity at 100℃ = 4.2mm 2 / s, viscosity index = 122 hydrocarbon oil 2: SP value = 8.2 ~ 8.3 (cal / cm 3 ) 1 / 2 , Kinematic viscosity at 100°C = 3.1 mm 2 / s, viscosity index = 106 From the results of Table 3-1, Table 3-2 and Table 4, it can be seen that the viscosity index improver of the present invention has a low kinematic viscosity at 90°C and excellent handling properties. In particular, by comparing Comparative Example 1 with Example 1, which has substantially the same Mw, type and amount of base oil, etc. except that the monomer (a) is not contained as a constituent monomer; by comparing Comparative Example 2 with Example 26, which has substantially the same Mw, type and amount of base oil, etc. except that the monomer (b) is not contained as a constituent monomer; by comparing Comparative Example 3 with Example 25, which has substantially the same Mw, type and amount of base oil, etc. except that the monomer (c) and the monomer (d) are not contained as constituent monomers; and by comparing Comparative Example 4 with Example 1, which does not contain an ester oil but contains the same copolymer (A), it can be seen that the viscosity index improver of the present invention has a further reduced viscosity and excellent handling properties by containing the copolymer (A) containing the monomer (a) and the monomer (b) as constituent monomers and further containing the monomer (c) and / or the monomer (d) as constituent monomers and the ester oil.

[0370] <Examples 29 to 56 and Comparative Examples 5 to 8: 0W-20 Evaluation>

[0371] Hydrocarbon oil (SP value: 8.3 to 8.4 (cal / cm 3 ) 1 / 2 , Kinematic viscosity at 100℃: 4.2mm 2 / s, viscosity index: 128) 90 parts by weight of a package additive "Infineum P5741" (base number = 84 mgKOH / g, calcium content = 2.49%, nitrogen content = 0.68%, phosphorus content = 0.78%, sulfated ash = 9.76%, zinc content = 0.86%), and viscosity index improvers (R-1) to (R-28) or (S-1) to (S-4) were added respectively so that the HTHS viscosity of the obtained lubricating oil composition at 150°C was 2.60±0.05 (mPa·s), thereby obtaining lubricating oil compositions (V-1) to (V-28) and (W-1) to (W-4).

[0372] The lubricating oil compositions (V-1) to (V-28) and (W-1) to (W-4) were measured for shear stability (BOSCH SSI, Sonic SSI), HTHS viscosity (150°C, 100°C, 80°C), kinematic viscosity (100°C, 40°C), viscosity index, gel index, low temperature viscosity (-40°C), volatility at 250°C, and oxidation stability by the following methods. The results are shown in Table 5 or Table 6.

[0373] [Table 5]

[0374]

[0375] [Table 6]

[0376]

[0377] <Examples 57 to 84 and Comparative Examples 9 to 12: Evaluation of 0W-16>

[0378] Hydrocarbon oil (SP value: 8.3 to 8.4 (cal / cm 3 ) 1 / 2 , Kinematic viscosity at 100℃: 4.2mm 2 / s, viscosity index: 128) 90 parts by weight and 10 parts by weight of a package additive (Infineum P5741), viscosity index improvers (R-1) to (R-28) or (S-1) to (S-4) were added respectively so that the HTHS viscosity of the obtained lubricating oil composition at 150°C was 2.30±0.05 (mPa·s), to obtain lubricating oil compositions (V-29) to (V-56) and (W-5) to (W-8). The shear stability (BOSCH SSI, Sonic SSI), HTHS viscosity (150°C, 100°C, 80°C), kinematic viscosity (100°C, 40°C), viscosity index, gel index, low temperature viscosity (-40°C), volatility at 250°C, and oxidation stability of the lubricating oil compositions (V-29) to (V-56) and (W-5) to (W-8) were measured by the following methods. The results are shown in Table 7 or Table 8.

[0379] [Table 7]

[0380]

[0381] [Table 8]

[0382]

[0383] <Method for measuring HTHS viscosity of lubricating oil composition>

[0384] The measurement is performed by the method of ASTM D 4683 at 80° C., 100° C., and 150° C. The lower the HTHS viscosity at 80° C. and 100° C., the better it means.

[0385] <Method for measuring kinematic viscosity of lubricating oil composition and method for calculating viscosity index>

[0386] The kinematic viscosity at 40° C. and 100° C. was measured by the method of JIS-K2283, and the viscosity index was calculated by the method of JIS-K2283. A larger value of the viscosity index means a higher viscosity index improvement effect.

[0387] <Method for measuring and calculating shear stability (BOSCH SSI) of lubricating oil composition>

[0388] The shear stability is measured by the method of ASTM D 6278 and calculated by the method of ASTM D 6022. The smaller the value, the higher the shear stability.

[0389] <Method for measuring and calculating shear stability (Sonic SSI) of lubricating oil composition>

[0390] The shear stability is measured by using an ultrasonic shearing device according to the method of JPI-5S-29-2006 and calculated by the method of ASTM D 6022. The smaller the value, the higher the shear stability.

[0391] <Method for measuring low temperature viscosity of lubricating oil composition>

[0392] The viscosity at -40°C was measured by the method of JPI-5S-42-2004. The smaller the value, the lower the low-temperature viscosity.

[0393] <Method for measuring gel index>

[0394] The gel index was measured by operating a scanning Brookfield viscometer according to ASTM D 5133. Specifically, about 20 ml of the lubricating oil composition was injected into a glass stator to the filling line, and after preheating at 90°C for 1.5 hours, a temperature gradient program was set, and the gel index was measured by cooling to -5°C to -40°C at a scanning rate of 1°C / hour. It should be noted that the smaller the value, the better the viscosity characteristics at low temperatures, and the better the engine oil.

[0395] <Determination method of evaporation>

[0396] The evaporation rate at 250° C. is measured by the method of ASTM D 5800. The smaller the value, the lower the evaporation rate of the lubricating oil, and the better it is as a motor oil.

[0397] <Determination method of oxidation stability>

[0398] According to JIS-K2514, an oxidation stability test was conducted at 165.5°C ± 0.5°C for 120 hours, and the increase in the total acid value (mgKOH / g) of the viscosity index improver and the lubricating oil composition before and after the test was measured. The smaller the value, the better the oxidation stability.

[0399] [Evaluation criteria: Lubricating oil composition]

[0400] ◎: The increase in the total acid value of the lubricating oil composition before and after the test is 3.0 mgKOH / g or less

[0401] ○: The increase in the total acid value of the lubricating oil composition before and after the test is greater than 3.0 mgKOH / g and less than 5.0 mgKOH / g

[0402] △: The increase in the total acid value of the lubricating oil composition before and after the test is greater than 5.0 mgKOH / g and less than 7.0 mgKOH / g

[0403] The results in Tables 5 to 8 show that the lubricating oil composition containing the viscosity index improver of the present invention has a good gel index, excellent HTHS viscosity at 100°C and kinematic viscosity at 40°C, and also excellent viscosity index, shear stability and low-temperature viscosity.

[0404] The lubricating oil compositions of Comparative Examples 5 to 7 and 9 to 11 used the viscosity index improver of Comparative Example 1 comprising a copolymer (A') not containing the monomer (a) as a constituent monomer, Comparative Example 2 comprising a copolymer (A') not containing the monomer (b) as a constituent monomer, or Comparative Example 3 comprising a copolymer (A') not containing the monomer (c) and the monomer (d) as constituent monomers.

[0405] The lubricating oil compositions of these comparative examples are compared with the lubricating oil compositions of Examples 29, 54, 53, 57, 82 and 81 using the viscosity index improver of Example 1, 26 or 25 (containing a copolymer (A) having substantially the same SP value and Mw, containing monomers (a) and (b) as constituent monomers, and further containing monomers (c) and / or monomers (d) as constituent monomers), and it is found that the gel index, HTHS viscosity at 100°C and kinematic viscosity at 40°C are inferior. In addition, it is found that the viscosity index, shear stability, low-temperature viscosity, oxidation stability and volatility at 250°C are also inferior. In addition, the lubricating oil compositions of Comparative Examples 8 and 12 using the viscosity index improver of Comparative Example 4 containing no ester oil are compared with Examples 29 and 57 containing the same copolymer (A), and it is found that the gel index, HTHS viscosity at 100°C and kinematic viscosity at 40°C are inferior. In addition, it is found that the viscosity index and low-temperature viscosity are also inferior.

[0406] Industrial Applicability

[0407] The lubricating oil composition containing the viscosity index improver of the present invention has a good gel index, and is excellent in HTHS viscosity at 100° C. and kinematic viscosity at 40° C., and is therefore suitable for use in gear oils (differential oils and industrial gear oils, etc.), MTFs, transmission oils [ATFs, DCTFs, belt-type CVTFs, etc.], traction oils (annular CVTFs, etc.), shock absorber oils, power steering oils, hydraulic oils (construction machinery hydraulic oils and industrial hydraulic oils, etc.), and engine oils (for gasoline engines and diesel engines).

Claims

1. A viscosity index improver comprising a copolymer (A) and an ester oil (Z), wherein the copolymer (A) comprises a polyolefin monomer (a) represented by the following general formula (1) and a monomer represented by the following general formula (2) and R 4 The monomer (b) is an alkyl group having 4 carbon atoms as a constituent monomer, and further contains a monomer (c) represented by the following general formula (3) and / or a monomer represented by the following general formula (2) and R 4 A monomer (d) which is an alkyl group having 2 to 3 carbon atoms as a constituent monomer, [Chemistry 1] In the general formula (1), R 1 is a hydrogen atom or a methyl group; -X 1 - is -O-, -O(AO) m - or -NH-, A is an alkylene group having 2 to 4 carbon atoms, m is an integer of 1 to 10, and when m is 2 or more, A is the same or different; R 2 A residue obtained by removing one hydrogen atom from a hydrocarbon polymer containing a 1,2-butylene group as a structural unit; p is a number of 0 or 1; [Chemistry 2] In the general formula (2), R 3 is a hydrogen atom or a methyl group; -X 2 - is a group represented by -O- or -NH-; R 4 An alkyl group having 2 to 4 carbon atoms; [Chemistry 3] In the general formula (3), R 5 is a hydrogen atom or a methyl group; -X 3 - is a group represented by -O- or -NH-; R 6 is an alkylene group having 2 to 4 carbon atoms; R 7 is an alkyl group having 1 to 8 carbon atoms; r is an integer of 1 to 20, and when r is 2 or more, R 6 Same or different.

2. The viscosity index improver according to claim 1, wherein The weight ratio (A) / (Z) of the copolymer (A) and the ester oil (Z) contained in the viscosity index improver is 10 / 90 to 70 / 30.

3. The viscosity index improver according to claim 1 or 2, wherein In the general formula (1), R 2 The present invention is a residue obtained by removing one hydrogen atom from a hydrocarbon polymer further comprising an isobutylene group as a structural unit in addition to a 1,2-butylene group, and is a residue obtained by removing one hydrogen atom from a hydrocarbon polymer in which the total proportion of the isobutylene group and the 1,2-butylene group is 30 mol% or more based on the total molar number of the structural units of the hydrocarbon polymer.

4. The viscosity index improver according to claim 1 or 2, wherein The solubility parameter calculated based on the weight fraction of the monomers constituting the copolymer (A) was 8.0 (cal / cm 3 ) 1 / 2 ~10.0(cal / cm 3 ) 1 / 2 .

5. The viscosity index improver according to claim 1 or 2, wherein The kinematic viscosity of the ester oil at 100°C is 1 mm 2 / s~4mm 2 / s, and the viscosity index is above 100.

6. The viscosity index improver according to claim 1 or 2, wherein In the monomers constituting the copolymer (A), a weight ratio (c+d) / b of the total weight of the monomer (c) and the monomer (d) to the weight of the monomer (b) is 0.01 to 20.

7. The viscosity index improver according to claim 1 or 2, wherein The copolymer (A) is a copolymer containing a (meth)acryloyl monomer (e) having a linear or branched alkyl group having 9 to 36 carbon atoms as a constituent monomer.

8. The viscosity index improver according to claim 7, wherein The copolymer (A) is a copolymer containing the following monomers as constituent monomers: based on the total weight of the monomers constituting the copolymer (A), it contains 1% by weight to 50% by weight of the monomer (a), 1% by weight to 80% by weight of the monomer (b), 1% by weight to 60% by weight in total of the monomer (c) and the monomer (d), and 1% by weight to 60% by weight of the (meth)acryloyl monomer (e).

9. The viscosity index improver according to claim 1 or 2, wherein The weight average molecular weight of the copolymer (A) is 5,000 to 2,000,000.

10. The viscosity index improver according to claim 1 or 2, wherein The viscosity index improver contains 0.01% by weight to 30% by weight of an alkyl (meth)acrylate (co)polymer (B) other than the copolymer (A), based on the weight of the copolymer (A).

11. The viscosity index improver according to claim 1 or 2, wherein The absolute value of the difference between the solubility parameter of the copolymer (A) and the solubility parameter of the ester oil (Z) is 0.1 (cal / cm 3 ) 1 / 2 ~2.0(cal / cm 3 ) 1 / 2 .

12. The viscosity index improver according to claim 1 or 2, wherein The polyol further contains hydrocarbon oil.

13. A lubricating oil composition comprising the viscosity index improver according to any one of claims 1 to 12, and at least one additive selected from the group consisting of a detergent, a dispersant, an antioxidant, an oiliness improver, a pour point depressant, a friction and wear modifier, an extreme pressure agent, a defoamer, an anti-emulsifier, a metal deactivator and a corrosion inhibitor.

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