Viscosity index improvers and lubricating oil compositions

Abstract

The object of the present invention is to provide a viscosity index improver that, in a lubricating oil composition using ester oil, exhibits excellent viscosity-enhancing effect at 100°C, can lower the kinematic viscosity at 40°C, and has a high viscosity index-enhancing effect while considering the environment, such as biodegradability and environmental toxicity. [Solution] A viscosity index improver containing a poly(meth)acrylate polymer (A), an ester oil (B), and an ester oil (C), wherein the solubility parameter (SP value) of the poly(meth)acrylate polymer (A) is 8.95 to 9.15 (cal / cm³). 3 ) 1 / 2 The ester oil (B) is a diesterified product, and the solubility parameter (SP value) of the ester oil (B) is 8.80-8.95 (cal / cm³). 3 ) 1 / 2 The ester oil (C) is a glycerol triester, and the solubility parameter of the ester oil (C) is 8.90-9.00 (cal / cm³). 3 ) 1 / 2 A viscosity index improver.

Description

Technical Field

[0001] The present invention relates to a viscosity index improver and a lubricating oil composition.

Background Art

[0002] In recent years, due to environmental regulations, the applications using lubricating oils with ester oils as the lubricating oil base oil have been increasing. Also, these lubricating oils require items such as biodegradability and environmental toxicity regarding lubricating oil additives. However, many of the current viscosity index improvers (for example, Patent Documents 1 and 2) exhibit effects on lubricating oil compositions using mineral oil as the lubricating oil base oil, and it is difficult to say that they exhibit excellent effects on lubricating oil compositions using ester oil. Viscosity index improvers that are also considered from the viewpoints of biodegradability and environmental toxicity are not common.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a viscosity index improver that is excellent in the thickening effect at 100°C of a lubricating oil composition, can lower the kinematic viscosity at 40°C, and has a high viscosity index improving effect considering the environment such as biodegradability and environmental toxicity in a lubricating oil composition using ester oil.

Means for Solving the Problems

[0005] As a result of intensive studies, the present inventors have arrived at the present invention. That is, the present invention is a viscosity index improver containing a poly(meth)acrylate polymer (A), an ester oil (B), and an ester oil (C), wherein the solubility parameter (SP value) of the poly(meth)acrylate polymer (A) is 8.95 to 9.15 (cal / cm 3 ) 1 / 2 , the ester oil (B) is a diesterified product, and the solubility parameter (SP value) of the ester oil (B) is 8.80 to 8.95 (cal / cm 3 ) 1 / 2 , the ester oil (C) is a glycerin triesterified product, and the solubility parameter of the ester oil (C) is 8.90 to 9.00 (cal / cm 3 ) 1 / 2 ; a lubricating oil composition containing the viscosity index improver.

Effect of the Invention

[0006] When the viscosity index improver of the present invention is used, in a lubricating oil composition using an ester oil, the thickening effect at 100°C of the lubricating oil composition is excellent, the kinematic viscosity at 40°C can be lowered, and the viscosity index improving effect is high.

Mode for Carrying Out the Invention

[0007] The viscosity index improver of the present invention is a viscosity index improver containing a poly(meth)acrylate polymer (A), an ester oil (B), and an ester oil (C), wherein the solubility parameter (SP value) of the poly(meth)acrylate polymer (A) is 8.95 to 9.15 (cal / cm 3 ) 1 / 2 , the ester oil (B) is a diesterified product, and the solubility parameter (SP value) of the ester oil (B) is 8.80 to 8.95 (cal / cm 3 ) 1 / 2 , the ester oil (C) is a glycerin triesterified product, and the solubility parameter of the ester oil (C) is 8.90 to 9.00 (cal / cm 3 ) 1 / 2 . Although ester oils (B) and (C) are highly biodegradable and have a low environmental impact, their high polarity makes it difficult to improve their viscosity index. However, in this invention, we have found that by using a poly(meth)acrylate polymer (A) having a specific solubility parameter (SP value), it is possible to create a viscosity index improver that exhibits excellent thickening effect at 100°C and lowers the kinematic viscosity at 40°C.

[0008] In the present invention, it is preferable from the viewpoint of viscosity index improvement effect that the poly(meth)acrylate polymer (A) contains an alkyl(meth)acrylate (a) (hereinafter sometimes abbreviated as monomer (a)) having a linear or branched alkyl group having 10 to 18 carbon atoms as a constituent monomer. Examples of linear or branched alkyl groups having 10 to 18 carbon atoms include linear alkyl groups (n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, etc.) and branched alkyl groups (isodecyl group, isoundecyl group, isododecyl group, isotridecyl group, isotetradecyl group, isopentadecyl group, isohexadecyl group, isoheptadecyl group, isooctadecyl group, 2-ethyloctyl group, 2-ethyldecyl group, 2-octyldecyl, etc.).

[0009] Examples of alkyl (meth)acrylates (a) include (meth)acrylates having a linear alkyl group {n-decyl(meth)acrylate, n-undecyl(meth)acrylate, n-dodecyl(meth)acrylate, n-tridecyl(meth)acrylate, n-tetradecyl(meth)acrylate, n-pentadecyl(meth)acrylate, n-hexadecyl(meth)acrylate, n-heptadecyl(meth)acrylate, n-octadecyl(meth)acrylate, etc.} and (meth)acrylates having a branched alkyl group. Examples include {isodecyl (meth)acrylate, isoundecyl (meth)acrylate, isododecyl (meth)acrylate, isotridecyl (meth)acrylate, isotetradecyl (meth)acrylate, isopentadecyl (meth)acrylate, isohexadecyl (meth)acrylate, isoheptadecyl (meth)acrylate, isooctadecyl (meth)acrylate, 2-ethyloctyl (meth)acrylate, 2-ethyldecyl (meth)acrylate, 2-octyldecyl (meth)acrylate, etc.}.

[0010] Alternatively, a mixture of the aforementioned alcohols may be used. For example, primary alcohol mixtures sold by Shell Company under the trade name NEODOL (e.g., NEODOL 23, NEODOL 25, NEODOL 45, etc.) are commercially available and can be obtained. Of these, linear alkyl (meth)acrylates having 10 to 18 carbon atoms are preferred from the viewpoint of improving viscosity index, and linear alkyl (meth)acrylates having 10 to 16 carbon atoms are more preferred.

[0011] In the present invention, it is preferable from the viewpoint of viscosity index improvement effect that the poly(meth)acrylate polymer (A) contains an alkyl(meth)acrylate (b) having a C1 alkyl group (hereinafter sometimes abbreviated as monomer (b)) as a constituent monomer. Examples of alkyl (meth)acrylate (b) include methyl (meth)acrylate.

[0012] In the present invention, the poly(meth)acrylate polymer (A) may contain as a constituent monomer at least one selected from the group consisting of alkyl(meth)acrylate (c) having a linear or branched alkyl group having 2 to 9 carbon atoms (hereinafter sometimes abbreviated as monomer (c)), alkyl(meth)acrylate (d) having an alkyl group having 19 to 36 carbon atoms (hereinafter sometimes abbreviated as monomer (d)), nitrogen atom-containing monomer (e), hydroxyl group-containing monomer (f), phosphorus atom-containing monomer (g), aliphatic hydrocarbon monomer (h), alicyclic hydrocarbon monomer (i), aromatic hydrocarbon monomer (j), vinyl compound (k), epoxy group-containing monomer (l), halogen element-containing monomer (m), and ester of unsaturated polycarboxylic acid (n).

[0013] In alkyl(meth)acrylate(c) having a linear or branched alkyl group with 2 to 9 carbon atoms, examples of the linear or branched alkyl group with 2 to 9 carbon atoms include ethyl group, linear alkyl group {n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-pentyl group, n-octyl group, n-nonyl group, etc.}, and branched alkyl group {isopropyl group, sec-butyl group, isobutyl group, tert-butyl group, isopentyl group, isohexyl group, isoheptyl group, isooctyl group, isononyl group, 2-ethylhexyl group, etc.}.

[0014] Examples of alkyl (meth)acrylate (c) include ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, and nonyl (meth)acrylate. Of these, linear (meth)acrylates with 2 to 4 carbon atoms are preferred from the viewpoint of improving viscosity index.

[0015] In alkyl(meth)acrylates (d) having an alkyl group with 19 to 36 carbon atoms, the alkyl group with 19 to 46 carbon atoms includes linear alkyl groups {n-icosyl(meth)acrylate, n-docosyl(meth)acrylate, n-tetracosyl(meth)acrylate, n-triacontyl(meth)acrylate, n-hexatriacontyl(meth)acrylate, etc.} and branched alkyl groups {2-n-decyltetradecyl(meth)acrylate, 2-n-dodecylhexadecyl(meth)acrylate}. Examples include 2-n-tetradecyloctadecyl(meth)acrylate, 2-n-dodecylpentadecyl(meth)acrylate, 2-n-tetradecylheptadecyl(meth)acrylate, 2-n-hexadecylheptadecyl(meth)acrylate, 2-n-heptadecylicosyl(meth)acrylate, 2-n-hexadecyldocosyl(meth)acrylate, 2-n-eicosyldocosyl(meth)acrylate, 2-n-tetracosylhexacosyl(meth)acrylate, etc.

[0016] Examples of nitrogen atom-containing monomers (e) include the following monomers (e1) to (e4). Amide group-containing monomer (e1): (meth)acrylamide, monoalkylamino(meth)acrylamide [a nitrogen atom to which one C1-C4 alkyl group is bonded; for example, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, and Nn- or isobutyl(meth)acrylamide, etc.], monoalkylaminoalkyl(meth)acrylamide [having an aminoalkyl group (C2-C6) to which one C1-C4 alkyl group is bonded to a nitrogen atom; for example, N-methylaminoethyl(meth)acrylamide, N-ethylaminoethyl(meth)acrylamide, N-isopropylamino-n-butyl(meth)acrylamide, and Nn- or isobutylamino-n-butyl(meth)acrylamide, etc.], dialkylamino(meth)acrylamide [a nitrogen atom to which two C1-C4 alkyl groups are bonded; for example, N Examples include those having a nitrogen atom only in the amide group, such as N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, and N,N-di-n-butyl(meth)acrylamide, dialkylaminoalkyl(meth)acrylamide [those having an aminoalkyl group (2-6 carbon atoms) in which two alkyl groups with 1-4 carbon atoms are bonded to the nitrogen atom; for example, N,N-dimethylaminoethyl(meth)acrylamide, N,N-diethylaminoethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, and N,N-di-n-butylaminobutyl(meth)acrylamide, etc.], and N-vinyl carboxylic acid amide [N-vinylformamide, N-vinylacetamide, N-vinyl-n- or isopropionylamide, and N-vinylhydroxyacetamide, etc.].

[0017] Nitro group-containing monomer (e2): Examples include 4-nitrostyrene.

[0018] Monomers containing primary to tertiary amino groups (e3): Primary amino group-containing monomers {alkenylamines with 3-6 carbon atoms [(meth)allylamine and clotylamine, etc.], aminoalkyl (2-6 carbon atoms) (meth)acrylates [aminoethyl (meth)acrylate, etc.]}; Secondary amino group-containing monomers {monoalkylaminoalkyl (meth)acrylates [those having an aminoalkyl group (2-6 carbon atoms) with one C1-6 alkyl group bonded to the nitrogen atom; for example, Nt-butylaminoethyl (meth)acrylate and N-methylaminoethyl (meth)acrylate, etc.], dialkenylamines with 6-12 carbon atoms [di(meth)allylamine, etc.]}; Tertiary amino group-containing monomers {dialkylaminoalkyl (meth)acrylates [a group with 1-6 carbon atoms bonded to the nitrogen atom Examples include aminoalkyl groups (with 2 to 6 carbon atoms) with two hydroxyl groups bonded to them; for example, N,N-dimethylaminoethyl (meth)acrylate and N,N-diethylaminoethyl (meth)acrylate, etc., alicyclic (meth)acrylates having a nitrogen atom [such as morpholinoethyl (meth)acrylate], aromatic monomers [such as N-(N',N'-diphenylaminoethyl)(meth)acrylamide, N,N-dimethylaminostyrene, 4-vinylpyridine, 2-vinylpyridine, N-vinylpyrrole, N-vinylpyrrolidone and N-vinylthiopyrrolidone], and their hydrochloride salts, sulfates, phosphates, or lower alkyl (with 1 to 8 carbon atoms) monocarboxylic acid (such as acetic acid and propionic acid) salts.

[0019] Nitrile group-containing monomer (e4): Examples include (meth)acrylonitrile.

[0020] Of the monomers (e), (e1) and (e3) are preferred, and more preferably are N-(N',N'-diphenylaminoethyl)(meth)acrylamide, N-(N',N'-dimethylaminoethyl)(meth)acrylamide, N-(N',N'-diethylaminoethyl)(meth)acrylamide, N-(N',N'-dimethylaminopropyl)(meth)acrylamide, N,N-dimethylaminoethyl(meth)acrylate, and N,N-diethylaminoethyl(meth)acrylate.

[0021] Hydroxyl group-containing monomer (f): Hydroxyl group-containing aromatic monomers (e.g., p-hydroxystyrene), hydroxyalkyl (C2-C6) (meth)acrylates [e.g., 2-hydroxyethyl (meth)acrylate and 2- or 3-hydroxypropyl (meth)acrylate], mono- or bis-hydroxyalkyl (C1-C4) substituted (meth)acrylamides [e.g., N,N-bis(hydroxymethyl)(meth)acrylamide, N,N-bis(hydroxypropyl)(meth)acrylamide, N,N-bis(2-hydroxybutyl)(meth)acrylamide], vinyl alcohol, C3-C12 alkenols [(meth)allyl alcohol, clotilamine] Alcohols, isoclotyl alcohol, 1-octenol and 1-undecenol, etc.; 4-12 carbon atom alkene monools or alkene diols [1-buten-3-ol, 2-buten-1-ol and 2-buten-1,4-diol, etc.]; hydroxyalkyl (1-6 carbon atoms) alkenyl (3-10 carbon atoms) ethers (2-hydroxyethylpropenyl ether, etc.); alkenyl (3-10 carbon atoms) ethers or (meth)acrylates of polyhydric (3-8 hydric) alcohols (glycerin, pentaerythritol, sorbitol, sorbitan, diglycerin, sugars and sucrose, etc.) [sucrose (meth)allyl ether, etc.]; Examples include polyoxyalkylene glycols (alkylene group with 2-4 carbon atoms, degree of polymerization 2-50), polyoxyalkylene polyols [polyoxyalkylene ethers of the above 3-8 valent alcohols (alkylene group with 2-4 carbon atoms, degree of polymerization 2-100)], and mono(meth)acrylates of alkyl (1-4 carbon atoms) ethers of polyoxyalkylene glycols or polyoxyalkylene polyols [polyethylene glycol (Mn: 100-300) mono(meth)acrylate, polypropylene glycol (Mn: 130-500) mono(meth)acrylate, methoxypolyethylene glycol (Mn: 110-310) (meth)acrylate, lauryl alcohol ethylene oxide adduct (2-30 mol) (meth)acrylate, and polyoxyethylene (Mn: 150-230) sorbitan mono(meth)acrylate, etc.].

[0022] Examples of phosphorus atom-containing monomers (g) include the following monomers (g1) to (g2).

[0023] Phosphate ester group-containing monomer (g1): Examples include (meth)acryloyloxyalkyl (C2-C4) phosphate esters [(meth)acryloyloxyethyl phosphate and (meth)acryloyloxyisopropyl phosphate] and alkenyl phosphate esters [vinyl phosphate, allyl phosphate, propenyl phosphate, isopropenyl phosphate, butenyl phosphate, pentenyl phosphate, octenyl phosphate, decenyl phosphate and dodecenyl phosphate, etc.].

[0024] Phosphono group-containing monomer (g2): (meth)acryloyloxyalkyl (2-4 carbon atoms) phosphonic acids [(meth)acryloyloxyethylphosphonic acid, etc.] and alkenyl (2-12 carbon atoms) phosphonic acids [vinyl Examples include phosphonic acid, allylphosphonic acid, and octenylphosphonic acid.

[0025] Among the phosphorus atom-containing monomers (g), (g1) is preferred from the viewpoint of copolymerizability with other monomers and solubility in base oil, (meth)acryloyloxyalkyl (2-4 carbon atoms) phosphate esters are more preferred, and (meth)acryloyloxyethyl phosphate is particularly preferred.

[0026] Aliphatic hydrocarbon monomers (h): Examples include alkenes with 2 to 20 carbon atoms (ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, and octadecene, etc.) and alkadienes with 4 to 12 carbon atoms (butadiene, isoprene, 1,4-pentadiene, 1,6-heptadiene, and 1,7-octadiene, etc.).

[0027] Alicyclic hydrocarbon monomers (i): Examples include cyclohexene, (di)cyclopentadiene, pinene, limonene, vinylcyclohexene, and ethylidene bicycloheptene.

[0028] Aromatic hydrocarbon monomers (j): Examples include styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, 4-ethylstyrene, 4-isopropylstyrene, 4-butylstyrene, 4-phenylstyrene, 4-cyclohexylstyrene, 4-benzylstyrene, indene, 4-clotylbenzene, and 2-vinylnaphthalene.

[0029] Vinyl compounds (vinyl esters, vinyl ethers, vinyl ketones) (k): Examples include vinyl esters of saturated fatty acids having 2 to 12 carbon atoms (vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl octanoate, etc.), alkyl, aryl, or alkoxyalkyl vinyl ethers having 1 to 12 carbon atoms (methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, 2-ethylhexyl vinyl ether, phenyl vinyl ether, vinyl-2-methoxyethyl ether, and vinyl-2-butoxyethyl ether, etc.), and alkyl or aryl vinyl ketones having 1 to 8 carbon atoms (methyl vinyl ketone, ethyl vinyl ketone, and phenyl vinyl ketone, etc.).

[0030] Epoxy group-containing monomer (l): Examples include glycidyl (meth)acrylate and glycidyl (meth)allyl ether.

[0031] Halogen element-containing monomer (m): Examples include vinyl chloride, vinyl bromide, vinylidene chloride, (meth)allyl chloride, and halogenated styrenes (such as dichlorostyrene).

[0032] Esters (n) of unsaturated polycarboxylic acids: Examples include alkyl, cycloalkyl, or aralkyl esters of unsaturated polycarboxylic acids [alkyl diesters of unsaturated dicarboxylic acids (maleic acid, fumaric acid, and itaconic acid, etc.) having 1 to 8 carbon atoms (dimethyl maleate, dimethyl fumarate, diethyl maleate, and dioctyl maleate)].

[0033] From the viewpoint of improving viscosity index, the weight percentage of monomer (a) constituting the poly(meth)acrylate polymer (A) is preferably 80% by weight or more, more preferably 85% by weight or more, and particularly preferably 90% by weight or more, based on the total weight of the monomers constituting (A). From the viewpoint of improving viscosity index, the weight percentage of monomers (b) constituting the poly(meth)acrylate polymer (A) is preferably 20% by weight or less, more preferably 15% by weight or less, and particularly preferably 5-10% by weight, based on the total weight of the monomers constituting (A). From an economic standpoint, the total weight ratio of monomers (a) and (b) constituting the poly(meth)acrylate polymer (A) is preferably 90% by weight or more, more preferably 95% by weight or more, and particularly preferably 99% by weight or more, based on the total weight of the monomers constituting (A). The total weight ratio of monomers (c) to (n) constituting the poly(meth)acrylate polymer (A) is preferably 10% by weight or less, more preferably 5% by weight or less, and particularly preferably 1% by weight or less, based on the total weight of the monomers constituting (A), from the viewpoint of improving viscosity index.

[0034] In the present invention, the solubility parameter (SP value) of the poly(meth)acrylate polymer (A) is 8.95 to 9.15 (cal / cm³). 3 ) 1 / 2 Therefore, from the viewpoint of viscosity index and thickening properties, it is preferably 9.00 to 9.12 (cal / cm²). 3 ) 1 / 2 That is the case. SP value is 8.95 (cal / cm³) 3 ) 1 / 2 If it is less than 9.15 (cal / cm³), the viscosity index improvement effect is low. 3 )1 / 2 Beyond a certain point, the kinematic viscosity (Kv40) at 40°C tends to decrease. In this invention, the SP value refers to the value calculated using the numerical values ​​(heat of vaporization and molar volume of atoms or functional groups at 25°C) described on page 152 (Table 5) of the Fedors method (Polymer Engineering and Science, February, 1974, Vol. 14, No. 2, pp. 147-154), and formula (28) on page 153 of the same paper. Specifically, based on the structure in which the carbon-carbon double bond of the monomer reacts to form a single bond, the Δe parameter of the Fedors method, as shown in Table 1 below, is used. i and v i By using the values ​​corresponding to the types of atoms and atomic groups within the molecular structure, the SP value of each monomer can be calculated by applying these values ​​to the following formula. SP value = (ΣΔe i / Σv i ) 1 / 2

[0035] [Table 1]

[0036] When polymer (A) is a copolymer composed of two or more monomers, the SP value of polymer (A) is calculated by determining the SP value of each monomer (constituent unit in which a carbon-carbon double bond has been replaced with a single bond) that makes up (A) using the method described above, and then calculating the arithmetic mean of the SP values ​​of each monomer (constituent unit in which a carbon-carbon double bond has been replaced with a single bond) based on the weight fraction of the constituent monomer units. The SP value of (A) can be adjusted by appropriately adjusting the SP values ​​and weight fractions of the monomers (constituent units in which a carbon-carbon double bond has been replaced with a single bond) used. For example, if the monomer is methyl methacrylate, the constituent units derived from methyl methacrylate consist of two CH3 atoms, one CH2 atom, one C atom, and one CO2 atom. Therefore, according to the following formula, the SP value of the constituent units derived from methyl methacrylate is 9.933 (cal / cm³). 3 ) 1 / 2It can be understood that it is so. Calculating in the same way, the SP value of the structural unit derived from ethyl methacrylate is 9.721 (cal / cm 3 ) 1 / 2 It can be understood that it is so. ΣΔe i =1125×2 + 1180 + 350 + 4300 = 8080 Σv i =33.5×2 + 16.1 - 19.2 + 18.0 = 81.9 δ=(8080 / 81.9) 1 / 2 =9.933 (cal / cm 3 ) 1 / 2 When the 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 additive averaging based on the weight fraction of the SP value of the structural unit derived from each monomer as follows. SP value of copolymer=(9.933×50 + 9.721×50) / 100 = 9.827 Also, when using two or more kinds of polymer (A), it is preferable that the value obtained by calculating the weight fraction based on the SP value of each polymer (A) and performing additive averaging satisfies the above SP value.

[0037] The weight average molecular weight of polymer (A)(hereinafter sometimes abbreviated as Mw) is preferably 300,000 to 1,000,000, more preferably 400,000 to 900,000, particularly preferably 500,000 to 800,000, and most preferably from the viewpoints of thickening property and viscosity index improving effect, 600,000 to 700,000. In the present invention, Mw, number average molecular weight (hereinafter sometimes abbreviated as Mn) and molecular weight distribution can be measured by gel permeation chromatography (hereinafter abbreviated as GPC) under the following conditions. <Measurement conditions for Mw, Mn and molecular weight distribution><The Apparatus: "HLC - 8320GPC" [manufactured by Tosoh Corporation] Column: "TSKgel GMHXL" [manufactured by Tosoh Corporation] 2 columns "TSKgel Multipore H XL -M 1 column Measurement temperature: 40°C Sample solution: 0.25% by weight tetrahydrofuran solution Solution injection volume: 10.0μl Detection device: Refractive index detector Reference material: Standard polystyrene (TSK standard POLYSTYRENE) 12 points (Molecular weights: 589, 1,050, 2,630, 9,100, 19,500, 37,900, 96,400, 190,000, 355,000, 1,090,000, 2,110,000, 4,480,000) [Manufactured by Tosoh Corporation]

[0038] Polymer (A) can be obtained by known manufacturing methods, specifically by solution polymerization of the monomer in a solvent in the presence of a polymerization catalyst. Examples of solvents include toluene, xylene, alkylbenzenes with 9 to 10 carbon atoms, methyl ethyl ketone, ethyl acetate, 2-propanol, and base oils (ester oils, mineral oils, etc.). Polymerization catalysts include azo catalysts (such as azobisisobutyronitrile and azobisvaleronitrile), peroxide catalysts (such as benzoyl peroxide, cumyl peroxide, and lauryl peroxide), and redox catalysts (such as a mixture of benzoyl peroxide and a tertiary amine). Furthermore, known chain transfer agents (such as alkyl mercaptans with 2 to 20 carbon atoms) can be used as needed. The polymerization temperature is preferably 25 to 140°C, and more preferably 50 to 120°C. In addition to the solution polymerization described above, (A) can also be obtained by bulk polymerization, emulsion polymerization, or suspension polymerization. When (A) is a copolymer, the polymerization form may be either a random addition copolymer or an alternating copolymer, and it may also be either a graft copolymer or a block copolymer.

[0039] In this invention, ester oil (B) is a diester compound with an SP value of 8.80 to 8.95 (cal / cm³). 3 ) 1 / 2 That is the case. Examples of ester oils (B) include diesters of a dihydric alcohol and a monohydric carboxylic acid (B1) and diesters of a monohydric alcohol and a dihydric carboxylic acid (B2).

[0040] Dihydric alcohols include dihydric alcohols with 2 to 24 carbon atoms, for example, aliphatic dihydric alcohols with 2 to 24 carbon atoms [linear saturated aliphatic diols {e.g., ethylene glycol, 1,3-propylene glycol, 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-pentadecanediol and 1,16-hexadecanediol, etc.}, branched saturated aliphatic diols {e.g., 2-methyl-1,3-propanediol Examples include: 2-methyl-1,4-butanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 3-methyl-1,5-pentanediol, 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-pentadecanediol, and 1,2-hexadecanediol, etc.; alicyclic diols {e.g., 1,2-, 1,3-, or 1,4-cyclohexanediol, etc.}; and dihydric alcohols containing aromatic rings with 8 to 24 carbon atoms {e.g., ethylene oxide adducts of dihydroxybenzene, etc.}. Of these, linear saturated aliphatic diols having 2 to 24 carbon atoms are preferred from the viewpoint of thickening properties and improving viscosity index, and linear saturated aliphatic diols having 4 to 10 carbon atoms are more preferred.

[0041] Monovalent carboxylic acids include aliphatic monovalent carboxylic acids having 2 to 25 carbon atoms [linear saturated aliphatic monovalent carboxylic acids {e.g., n-propanoic acid, n-butanoic acid, n-pentanoic acid, 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, eicosanoic acid, docosanoic acid and tetracosanoic acid, etc.}, linear unsaturated aliphatic monovalent carboxylic acids {e.g., pal Examples include mitoleic acid, oleic acid, linoleic acid, arachidic acid, linolenic acid, erucic acid, etc.; branched saturated aliphatic monocarboxylic acids having 2 to 25 carbon atoms {e.g., 2-ethylhexanoic acid, isononanoic acid, isodecanoic acid, isoundecanoic acid, isododecanoic acid, isotridecanoic acid, isotetradecanoic acid, isopentadecanoic acid, isohexadecanoic acid, isoheptadecanoic acid, isooctadecanoic acid, and isononadecanoic acid, etc.}; alicyclic monocarboxylic acids {e.g., cyclohexanecarboxylic acid, etc.}; and aromatic ring-containing monocarboxylic acids {e.g., benzoic acid, etc.}. Furthermore, as monocarboxylic acids, mixtures of carboxylic acids obtained from natural oils {for example, vegetable oils such as rapeseed oil, sesame oil, soybean oil, corn oil, sunflower oil, palm oil, palm kernel oil, coconut oil, safflower oil, rice oil, coconut oil, tuni oil, castor oil, safflower oil, peanut oil, cottonseed oil, linseed oil, mustard oil, etc., and animal oils such as beef oil, oak oil, whale oil, fish oil, etc.} may also be used. Of these, branched-chain saturated aliphatic monocarboxylic acids having 2 to 25 carbon atoms are preferred from the viewpoint of thickening properties and improving viscosity index, and more preferably branched-chain saturated aliphatic monocarboxylic acids having 5 to 20 carbon atoms.

[0042] Monohydric alcohols include monohydric alcohols with 1 to 24 carbon atoms, specifically aliphatic monoalcohols with 1 to 24 carbon atoms [linear saturated aliphatic monoalcohols {e.g., methanol, ethanol, n-propanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonanol, n-decanol, n-undecyl alcohol, n-dodecyl alcohol, n-tridecyl alcohol, n-tetradecyl alcohol, n-pentadecyl alcohol, n-hexadecyl alcohol, n-heptadecyl alcohol, n-octadecyl alcohol, n-nonadecyl alcohol, n-icosanol, n-heneicosanol, n-docosanol, and n-tetracosanol, etc. Examples include branched-chain saturated aliphatic monoalcohols {e.g., 2-ethylhexanol, isononyl alcohol, isodecyl alcohol, isoundecyl alcohol, isododecyl alcohol, isotridecyl alcohol, isotetradecyl alcohol, isopentadecyl alcohol, isohexadecyl alcohol, isoheptadecyl alcohol, isooctadecyl alcohol, and isononadecyl alcohol}, alicyclic monoalcohols {e.g., cyclohexanol, 2-, 3- or 4-t-butylcyclohexanol, menthol, cyclohexaneethanol, 2-, 3- or 4-isopropylcyclohexanol}, and monoalcohols containing aromatic rings with 7 to 24 carbon atoms {e.g., benzyl alcohol}. Of these, monohydric alcohols having 8 to 12 carbon atoms are preferred from the viewpoint of thickening properties and improving viscosity index, and more preferably branched-chain saturated aliphatic monoalcohols having 8 to 12 carbon atoms.

[0043] Divalent carboxylic acids include aliphatic divalent carboxylic acids with 2 to 24 carbon atoms [linear saturated aliphatic divalent carboxylic acids {e.g., ethanedioic acid (oxalic acid), propanedioic acid (malonic acid), n-butanedioic acid (succinic acid), n-heptanedioic acid (glutaric acid), n-hexanedioic acid (adipic acid), n-heptanedioic acid, n-octanedioic acid, n-nonanedioic acid (azelaic acid), n-decanedioic acid (sebacic acid), n-undecanedioic acid, n-dodecanedioic acid, n-tridecanedioic acid, n-tetradecanedioic acid, n-pe Examples include: nitratecanedioic acid and n-hexadecanedioic acid, branched-chain saturated aliphatic dicarboxylic acids (e.g., 3-methyladipic acid), unsaturated aliphatic dicarboxylic acids (e.g., maleic acid, fumaric acid), alicyclic saturated dicarboxylic acids (e.g., 1,2- or 1,3-cyclopentanedicarboxylic acid, 1,2-, 1,3- or 1,4-cyclohexanedicarboxylic acid, etc.), and aromatic ring-containing dicarboxylic acids with 8 to 24 carbon atoms (e.g., phthalic acid, isophthalic acid, terephthalic acid, etc.). Of these, linear saturated aliphatic dicarboxylic acids having 2 to 24 carbon atoms are preferred from the viewpoint of thickening properties and viscosity index improvement, linear saturated aliphatic dicarboxylic acids having 6 to 15 carbon atoms are preferred, and adipic acid and sebacic acid are particularly preferred.

[0044] As for the ester oil (B), from the viewpoint of thickening properties and improvement of viscosity index, a diester product of a monohydric alcohol having 8 to 12 carbon atoms and a dihydric carboxylic acid having 6 to 15 carbon atoms is preferred, more preferably a diester product of a monohydric alcohol having 8 to 12 carbon atoms (preferably a branched-chain saturated aliphatic monoalcohol) and a dihydric carboxylic acid having 6 to 8 carbon atoms, and particularly preferred a diester product of a monohydric alcohol having 8 to 12 carbon atoms (preferably a branched-chain saturated aliphatic monoalcohol) and adipic acid.

[0045] In this invention, the SP value of ester oil (B) is 8.80 to 8.95 (cal / cm³). 3 ) 1 / 2 Preferably 8.85-8.90 (cal / cm³) 3 ) 1 / 2 That is the case. If the SP value is less than 8.80, the product viscosity at 40°C will be high, making it less economical, and if it exceeds 8.95, the viscosity index will deteriorate. SP value of ester oil (B) (units below are (cal / cm) 3 ) 1 / 2 (The details are omitted.) Specifically, examples include diisononyl adipate (SP value = 8.89), isodecyl adipate (SP value = 8.87), and di(2-ethylhexyl) sebacate (SP value = 8.89).

[0046] The kinematic viscosity of ester oil (B) at 100°C (measured according to JIS-K2283) is 2.5 to 3.5 mm, from the perspective of economic efficiency (allowing for a higher product concentration at 100°C). 2 / s is preferred, and more preferably 2.9 to 3.3 mm 2 It is / s. The kinematic viscosity of ester oil (B) at 100°C (units below are in mm²). 2 (The / s is omitted) Specifically, examples include diisononyl adipate (3.1), bis(2-ethylhexyl) sebacate (3.2), bis(2-ethylhexyl) azelaate (3.0), and 2-ethylhexyl-n-octyl azelaate (3.1).

[0047] In the present invention, ester oil (C) is a glycerol triesterized product with an SP value of 8.90 to 9.00. The monocarboxylic acid constituting the ester oil (C) includes the aforementioned monocarboxylic acid, and from the viewpoint of reducing the burden on the environment, it is preferably a carboxylic acid mixture derived from vegetable oil, and more preferably a carboxylic acid mixture derived from rapeseed oil. As for the ester oil, vegetable oil is preferred from the viewpoint of reducing the burden on the environment, and rapeseed oil is more preferred.

[0048] The SP value of ester oil (C) is 8.90-9.00 (cal / cm³). 3 ) 1 / 2 It is 8.90-8.95 (cal / cm³). 3 ) 1 / 2 It is preferable. If the SP value is less than 8.90, the product viscosity at 40°C will be high, making it less economical, and if it exceeds 9.00, the viscosity index will deteriorate. If the carboxylic acid and / or alcohol constituting ester oil (B) or (C) is a mixture, the SP values ​​of ester oils (B) and (C) shall be the arithmetic mean of the SP values ​​based on the mole fractions of each esterified substance constituting each ester oil.

[0049] The kinematic viscosity of ester oil (C) at 100°C (measured according to JIS-K2283) is 6.0 to 11.0 mm², from the perspective of economic efficiency (allowing for higher product concentration at 100°C). 2 / s is preferred, and more preferably 7.0 to 10.0 mm 2 It is / s. The kinematic viscosity of ester oils (C) at 100°C tends to be higher when using monocarboxylic acids with a large number of carbon atoms, and lower when using monocarboxylic acids with a large number of carbon atoms. Furthermore, those with a small degree of branching tend to have high kinematic viscosity, while those with a large degree of branching tend to have low kinematic viscosity.

[0050] The viscosity index improver of the present invention contains the poly(meth)acrylate polymer (A), ester oil (B), and ester oil (C). The content of poly(meth)acrylate polymer (A) in the viscosity index improver is preferably 20 to 40% by weight, and more preferably 25 to 35% by weight, based on the weight of the viscosity index improver, from the viewpoint of thickening properties and viscosity index improvement. From an economic standpoint, the content of ester oil (B) in the viscosity index improver is preferably 10 to 30% by weight, and more preferably 15 to 25% by weight, based on the weight of the viscosity index improver. From the viewpoint of reducing environmental impact, the content of ester oil (C) in the viscosity index improver is preferably 40 to 60% by weight, and more preferably 45 to 55% by weight, based on the weight of the viscosity index improver.

[0051] The viscosity index improver of the present invention has high viscosity index improving effects in addition to being non-accumulative, non-environmentally toxic, and biodegradable, which are derived from ester oils. Therefore, it can be used in lubricating oils for applications where environmental leakage is a concern, and is particularly suitable as a viscosity index improver for lubricating oils for stern tube bearings.

[0052] The lubricating oil composition of the present invention may contain the viscosity index improver, and may also contain other base oils other than ester oils (B) and (C), additives, etc.

[0053] Other base oils include hydrocarbon oils {mineral oils (solvent-refined oils, paraffin oils, high viscosity index oils containing isoparaffins, high viscosity index oils obtained by hydrocracking of isoparaffins, naphthenic oils, etc.), hydrocarbon-based synthetic lubricants (poly-α-olefin-based synthetic lubricants, GTL base oils, etc.)}, and non-hydrocarbon-based synthetic oils (ester-based synthetic lubricants other than ester oils (B) and (C), ether-based synthetic lubricants, silicone-based synthetic lubricants, etc.). Of these, ester-based synthetic lubricants are preferred from the viewpoint of non-accumulative, non-environmentally toxic, and biodegradable properties.

[0054] Examples of additives include detergents, dispersants, antioxidants, oiliness improvers, pour point depressants, friction and wear modifiers, extreme pressure agents, defoamers, anti-emulsifiers, metal deactivators, and corrosion inhibitors. Examples of individual components of these additives are listed below. (1) Cleaning agent: Basic, overbasic, or neutral metal salts [overbasic sulfonates (petroleum sulfonates, alkylbenzene sulfonates, alkylnaphthalene sulfonates, etc.) or alkaline earth metal salts, etc.], salicylates, phenates, naphthenates, carbonates, phosphonates, and mixtures thereof; (2) Dispersant: Succinimides (bis- or mono-polybutenyl succinimides), Mannich condensates, borates, etc.; (3) Antioxidants: Hindered phenols and aromatic secondary amines, etc. (4) Oiliness improvers: Long-chain fatty acids and their esters (oleic acid and oleic acid esters, etc.), long-chain amines and their amides (oleylamine and oleylamide, etc.), etc. (5) Pour point depressants Polyalkyl methacrylate, ethylene-vinyl acetate copolymer, etc. (6) Friction and wear modifiers: Molybdenum-based and zinc-based compounds (such as molybdenum dithiophosphate, molybdenum dithiocarbamate, and zinc dialkyldithiophosphate); (7) Extreme pressure agents: Sulfur compounds (mono- or disulfide, sulfoxide, and sulfur phosphide compounds), phosphide compounds, and chlorine compounds (such as chlorinated paraffins); (8) Antifoaming agent: Silicone oils, metallic soaps, fatty acid esters, and phosphate compounds, etc. (9) Antiemulsifiers: Quaternary ammonium salts (such as tetraalkylammonium salts), sulfated oils and phosphates (such as phosphates of polyoxyethylene-containing nonionic surfactants), hydrocarbon solvents (toluene, xylene, ethylbenzene), etc.; (10) Metal deactivators Nitrogen-containing compounds (such as benzotriazole), nitrogen-containing chelate compounds (such as N,N'-disalithidene-1,2-diaminopropane), nitrogen and sulfur-containing compounds (such as 2-(n-dodecylthio)benzimidazole), etc. (11) Corrosion inhibitors: Nitrogen atom-containing compounds (such as benzotriazole and 1,3,4-thiodiazolyl-2,5-bisdialkyldithiocarbamate), etc. The additive may be included in the lubricating oil composition as a packaged additive for lubricating oil containing multiple additives.

[0055] The content of poly(meth)acrylate polymer (A) in the lubricating oil composition is preferably 1 to 5% by weight, and more preferably 1.2 to 2.1% by weight, based on the weight of the lubricating oil composition, from the viewpoint of improving viscosity and viscosity index. From the viewpoint of improving viscosity and viscosity index, the content of ester oil (B) in the lubricating oil composition is preferably 0.2 to 2% by weight, and more preferably 0.8 to 1.4% by weight, based on the weight of the lubricating oil composition. From the viewpoint of reducing environmental impact, the content of ester oil (C) in the lubricating oil composition is preferably 0.5 to 5.0% by weight, and more preferably 2 to 3.5% by weight, based on the weight of the lubricating oil composition. From the viewpoint of improving viscosity and viscosity index, the content of other base oils in the lubricating oil composition is preferably 97% by weight or less, and more preferably 80-90% by weight, based on the weight of the lubricating oil composition. The content of additives in the lubricating oil composition is preferably 3 to 17% by weight, and more preferably 6 to 14% by weight, based on the weight of the lubricating oil composition, from the viewpoint of other functions necessary for lubricating oils, such as oxidation prevention and wear prevention.

[0056] The lubricating oil composition of the present invention has high viscosity index in addition to being non-accumulative, non-environmentally toxic, and biodegradable, which are derived from ester oils. Therefore, it can be used as a lubricant in applications where environmental leakage is a concern, and is particularly suitable for use as a lubricant for stern tube bearings. [Examples]

[0057] The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0058] The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited thereto. Unless otherwise specified, % refers to weight percent and parts refers to parts by weight.

[0059] <Examples 1-10, Comparative Examples 1-3> In a reaction vessel equipped with a stirring device, a heating and cooling device, a thermometer, a dropping funnel, a nitrogen blowing tube, and a vacuum device, diisononyl adipate (SP value: 8.89, kinematic viscosity at 100°C: 3.1 mm) was added as ester oil (B). 2 / s, 40℃ kinematic viscosity: 10.8mm 2The amount of 0.04 / s (viscosity index: 149) listed in Table 2 was added, and in a separate glass beaker, the monomer mixture listed in Table 2 (total weight 100 parts), 0.04 parts of dodecyl mercaptan as a chain transfer agent per 100 parts total monomers, and 0.2 parts of 1,1-di(tert-butylperoxy)cyclohexane as an initiator per 100 parts total monomers were added, and the mixture was stirred and mixed at 20°C to prepare the monomer solution, which was then added to a dropping funnel. After purging the gas phase of the reaction vessel with nitrogen (gas phase oxygen concentration: 100 ppm or less), the monomer solution was added dropwise over 3 hours while maintaining the internal temperature of the sealed system at 85-98°C, and after 2 hours of aging at 110°C for 1 hour, the temperature was raised to 120-130°C, and unreacted monomers were removed over 2 hours under reduced pressure (0.027-0.040 MPa) at the same temperature. In addition, rapeseed oil (SP value: 8.94, kinematic viscosity at 100°C: 8.0 mm) is used as the ester oil (C). 2 The amount of ( / s) listed in Table 2 was added to obtain viscosity index improvers (R1) to (R10) and (S1) to (S3), respectively, which consist of copolymers (A-1) to (A-10) and (H-1) to (H-3). The SP values ​​of the obtained copolymers (A-1) to (A-10) and (H-1) to (H-3) were calculated using the method described above, and the Mw was measured using the method described above. The handling properties of the obtained viscosity index improvers were measured using the following method. The results are shown in Table 2.

[0060] [Table 2]

[0061] The monomer compositions listed in Table 2 are as follows: (a-1): Ester of a mixture of C12-C13 alcohols (Sasol Lial123, 12 / C13 = 44 / 56%, 55% of which have branching at the 2nd carbon) and methacrylic acid. (a-2): Ester of a mixture of C14-C15 alcohols (Sasol Lial 145, C14 / C15 = 60 / 40%, 60% having branching at the 2nd carbon) and methacrylic acid. (a-3): Ester of a mixture of C16-C18 alcohols (Kao KALCOL6870S, C16 / C18 = 76 / 24%) and methacrylic acid (a-4): Octadecyl methacrylate (b): Methyl methacrylate

[0062] <Examples 11-20, Comparative Examples 4-6> In a stainless steel container equipped with a stirring device, base oil I (pentaerythritol tetraester, kinematic viscosity at 100°C: 8.3 mm) 2 / s, 40℃ kinematic viscosity: 67.4mm 2 A lubricant (viscosity index: 90) is added, and the kinematic viscosity of the resulting lubricating oil composition at 40°C is 125.0±3 (mm²). 2 Viscosity index improvers (R1) to (R10) and (S1) to (S3) were added to obtain lubricating oil compositions (V1) to (V10) and (W1) to (W3), respectively, so that the viscosity index would be ( / s). The viscosity indices of lubricating oil compositions (V1) to (V10) and (W1) to (W3) were measured by the following method. The results are shown in Table 2.

[0063] <Viscosity index of lubricating oil composition> The measurements were taken according to the method of JIS-K2283.

[0064] As is clear from the results in Table 2, the viscosity index improver and lubricating oil composition of the present invention exhibit excellent viscosity index improving effects, and furthermore, they demonstrate excellent viscosity index improving ability with a small amount added to the lubricating oil. [Industrial applicability]

[0065] The lubricating oil composition of the present invention has high viscosity index in addition to being non-accumulative, non-environmentally toxic, and biodegradable, which are derived from ester oils. Therefore, it can be used as a lubricant in applications where environmental leakage is a concern, and is particularly suitable for use as a lubricant for stern tube bearings.

Claims

1. A viscosity index improver containing a poly(meth)acrylate polymer (A), an ester oil (B), and an ester oil (C), wherein the solubility parameter (SP value) of the poly(meth)acrylate polymer (A) is 8.95 to 9.15 (cal / cm³). ３ ) １／２ The ester oil (B) is a diesterified product, and the solubility parameter (SP value) of the ester oil (B) is 8.80 to 8.95 (cal / cm³). ３ ) １／２ The ester oil (C) is a glycerol triester, and the solubility parameter of the ester oil (C) is 8.90 to 9.00 (cal / cm³). ３ ) １／２ A viscosity index improver.

2. The viscosity index improver according to claim 1, wherein the weight percentage of alkyl (meth)acrylate (a) having a linear or branched alkyl group having 10 to 18 carbon atoms is 80% by weight or more, and the weight percentage of alkyl (meth)acrylate (b) having an alkyl group having 1 carbon atom is 20% by weight or less, based on the total weight of monomers constituting the poly(meth)acrylate polymer (A).

3. The viscosity index improver according to claim 1, wherein the ester oil (B) is a diesterified product of a monohydric alcohol having 8 to 12 carbon atoms and adipic acid.

4. The kinematic viscosity of ester oil (B) at 100°C is 2.9 to 3.3 mm. ２ / s, the kinematic viscosity of ester oil (C) at 100°C is 7.0 to 10.0 mm ２ A viscosity index improver according to claim 1, wherein the viscosity index improver is / s.

5. A lubricating oil composition comprising a viscosity index improver according to any one of claims 1 to 4.

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