JP5524500B2 - Viscosity index improver and lubricating oil composition - Google Patents

Description

  The present invention relates to a viscosity index improver, a viscosity index improver composition, and a lubricating oil composition containing a viscosity index improver.

In general, the viscosity of lubricating oil and hydraulic oil used in automobiles and the like decreases as the temperature increases. However, in practice, it is desirable that the viscosity does not change as much as possible over a wide range from low temperature to high temperature. Therefore, a method for improving the temperature dependence of viscosity by adding a polymer compound called a viscosity index improver to lubricating oil is widely used. As such a polymer compound, for example, a methacrylic acid ester copolymer (see Patent Literatures 1 to 3) and an olefin copolymer (see Patent Literature 4) are known.
In recent years, there has been a growing demand for protecting the global environment, and the fuel efficiency of automobiles has been further demanded. Reducing the viscosity of lubricating oil is one of the effective means of fuel saving by reducing viscous resistance, and there is a method of adding a viscosity index improver to a low-viscosity base oil as a method for realizing low viscosity. When the conventional viscosity index improver is used, the viscosity index can be secured at a high level, but there is a problem that the lubricity is lowered due to the low viscosity, particularly the metal fatigue property is deteriorated.

Japanese Patent No. 2732187 JP-A-8-53683 JP 2004-307551 A JP 2005-200454 A

In order to improve the metal fatigue property while keeping the viscosity of the lubricating oil low, a method of locally thickening only the vicinity of the sliding portion of the metal is conceivable, and a polymer with excellent metal adsorptivity is used. It is effective to increase the polymer concentration in the vicinity of the metal sliding part.
That is, the subject of this invention is providing the viscosity index improver excellent in the adsorptivity to a metal, keeping the viscosity index improvement effect high.

  As a result of intensive investigations to achieve the above object, the present inventors have found that a polymer composed of a specific monomer is excellent in adsorbability to metal while keeping the viscosity index improving ability high. And found the present invention. That is, this invention is from the group which consists of a structural unit which consists of an alkyl (meth) acrylate which has a C8-C17 alkyl group, and an alkyl (meth) acrylate which has a C18-C24 linear alkyl group. Oil-soluble copolymer containing one or more structural units (b) selected from the group consisting of one or more selected structural units (a) and a thiol group-containing structural unit (b1) and a carboxyl group-containing structural unit (b2) A viscosity index improver comprising a combination (A), wherein the copolymer (A) has a weight average molecular weight of 3,000 to 1,000,000, and the copolymer (A) Viscosity index improver containing 50 to 99.5% by weight of the structural unit (a) and 0.5 to 50% by weight of the structural unit (b) based on weight; 20 to 90% by weight The viscosity of A viscosity index improver composition comprising a number improver and a 10 to 80% by weight diluent; and a base oil and the viscosity index improver or the viscosity index improver composition. A lubricating oil composition containing from 0.01 to 45% by weight based on the weight of the product.

  The viscosity index improver of the present invention is excellent in adsorptivity to metal, and has the effect of locally thickening the vicinity of the metal surface, so that it has an excellent effect of hardly causing metal fatigue, In addition, the effect of improving the viscosity index is high.

The structural unit (a) of the oil-soluble copolymer (A) in the present invention is an alkyl (meth) acrylate having an alkyl group of C _8-17 (meaning _{8 to 17} carbon atoms, the same shall apply hereinafter) and C. It is obtained by copolymerizing one or more alkyl (meth) acrylates selected from the group consisting of alkyl (meth) acrylates having _18-24 linear alkyl groups.

_Examples of the alkyl (meth) acrylate having a C _8-17 alkyl group include linear C _8-17 alkyl (meth) acrylate, branched C _8-17 alkyl (meth) acrylate, and mixtures thereof.

As linear _C8-17 alkyl (meth) acrylate, n-octyl (meth) acrylate, n-nonyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, n-tridecyl ( Examples include alkyl (meth) acrylates such as (meth) acrylate, n-tetradecyl (meth) acrylate, n-pentadecyl (meth) acrylate and n-hexadecyl (meth) acrylate, and (meth) acrylates of C _8-17 Ziegler alcohol. It is done.

As branched C _8-17 alkyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isononyl (meth) acrylate, isodecyl (meth) acrylate, isododecyl (meth) acrylate, 2-methylundecyl (Meth) acrylate, isotridecyl (meth) acrylate, 2-methyldodecyl (meth) acrylate, isotetradecyl (meth) acrylate, 2-methyltridecyl (meth) acrylate, isopentadecyl (meth) acrylate and 2-methyltetra A decyl (meth) acrylate is mentioned.

The mixture of straight chain C _8-17 alkyl (meth) acrylate and branched C _8-17 alkyl (meth) acrylate includes (meth) acrylate of oxo alcohol, which includes “Neodol 23” and “Neodol”. 45 ”(manufactured by Shell Chemical Co., Ltd.),“ Dobanol 23 ”and“ Dobanol 45 ”(manufactured by Mitsubishi Chemical Corporation),“ oxocol 1213 ”and“ oxocol 1415 ”(manufactured by Nissan Chemical Co., Ltd.) and the like.

Among the alkyl (meth) acrylates having a C _8-17 alkyl group, C _12-17 (further C _12-16 ) alkyl (meth) acrylates, particularly linear _chains are preferred from the viewpoint of viscosity index and low temperature viscosity. C _12-17 (further C _12-16 ) alkyl (meth) acrylate.

Examples of the alkyl (meth) acrylate having a C _18-24 linear alkyl group include n-octadecyl (meth) acrylate, n-nonadecyl (meth) acrylate, n-eicosyl (meth) acrylate, and n-docosyl (meth). An acrylate, n-tetracosyl (meth) acrylate, etc. are mentioned. Among these, n-octadecyl (meth) acrylate is preferable from the viewpoint of viscosity index and low temperature viscosity.

  The oil-soluble copolymer (A) in the present invention includes one or more structural units (b) selected from the group consisting of the thiol group-containing structural unit (b1) and the carboxyl group-containing structural unit (b2). Adsorbability to metal is improved.

In the case where the oil-soluble copolymer (A) is an oil-soluble copolymer containing the thiol group-containing structural unit (b1), the following two methods are exemplified as the method for introducing a thiol group.
(1) A method of copolymerizing a thiol group-containing monomer.
(2) A method in which the functional group in the precursor copolymer having a functional group that can be derived to a thiol group is derived to a thiol group.
Of the methods (1) and (2), the method (2) is preferable from the viewpoint of stability during the production process.

  Examples of the thiol group-containing monomer in the method (1) include allyl mercaptan and 2-mercaptoethyl (meth) acrylate.

  Examples of the functional group that can be derived from the thiol group in the method (2) include a primary amino group, a hydroxyl group, and a carboxyl group. Of the functional groups, a primary amino group and a hydroxyl group, particularly a primary amino group, are preferable from the viewpoint of reactivity. The precursor copolymer in the method (2) is a method of copolymerizing a monomer containing a primary amino group-containing monomer, a hydroxyl group-containing monomer or a carboxyl group-containing monomer, or 1 In the case of a primary amino group, it is obtained by a method of copolymerizing a ketimine group-containing monomer and hydrolyzing the ketimine group. Thereafter, by reacting the primary amino group, hydroxyl group or carboxyl group in the obtained copolymer with a compound that reacts with these groups to form a thiol group, the target thiol group-containing structural unit is obtained. An oil-soluble copolymer containing is obtained.

  A copolymer having a ketimine group as a functional group is usually obtained by copolymerizing a ketimine group-containing monomer as one of the copolymerization components. The ketimine group-containing monomer is preferably used because it is relatively hydrophobic and has high stability even in the copolymerization step and hardly causes side reactions.

  Examples of the ketimine-containing monomer include monomers represented by the following general formula (1). When the monomer is used, the obtained copolymer is hydrolyzed with alkali or neutrality. The ketimine group can be converted to a primary amino group.

In the formula, R ¹ is a hydrogen atom or a methyl group, Q is a carbonyl group or a C _1-8 alkylene group, Z is —O— or —NH—, and A ¹ is a C _2-4 alkylene group (for example, an ethylene group, 1,2- or 1,3-propylene group and 1,2-, 1,3- or 1,4-butylene group), n is an integer of 0 to 50, and when Q is a carbonyl group, n is 1 It is an integer of ~ 50. R ² and R ³ are each independently a hydrogen atom, a C _1-8 alkyl group, an _optionally substituted phenyl group, or a C _4-12 cycloalkylene group in which R ² and R ³ are bonded to each other. R ² and R ³ are not hydrogen atoms at the same time.

Among the monomers represented by the general formula (1), examples of the method for producing a monomer in which Q is a carbonyl group and Z is —O— include the following methods. For example, primary amino group-containing alcohol [2
-Aminoethanol, 2-aminopropanol, 3-aminopropanol, 2-aminobutanol, 3-aminobutanol, 4-aminobutanol and 2- (2-aminoethoxy) ethanol, etc.] and ketones (cyclopentanone, cyclohexanone, acetone) , Methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl isopropyl ketone, diisopropyl ketone, and diisobutyl ketone) or aldehyde (benzaldehyde and methoxybenzaldehyde, etc.) or a solvent that azeotropes with water (toluene, benzene, xylene, etc.) if necessary After distilling water at a temperature of 100 ° C. or higher to react to obtain a ketiminated alcohol, the obtained ketiminated alcohol and (meth) acrylic acid, methyl (meth) acrylate or ( Monomers data) by dehydration esterification reaction or transesterification reaction between ethyl acrylate and the like represented by the general formula (1) is synthesized.

  Among the monomers represented by the general formula (1), those in which Q is an alkylene group include (meth) allylamine, aminoethyl (meth) allyl ether, aminoethoxyethyl (meth) allyl ether, etc. It is obtained by the reaction.

  Specific examples of the monomer represented by the general formula (1) include esters of (meth) acrylic acid and N-isopropylidene-2-hydroxyethylamine, (meth) acrylic acid and N- (1-methylisopenty Ridene) -2-hydroxyethylamine ester, (meth) acrylic acid and N-1-isobutylisopentylidene-2- (2-hydroxyethoxy) ethylamine ester, (meth) acrylic acid and N-isopropylidene- Examples include amides with 2-aminoethylamine and amides of (meth) acrylic acid with N-1-methylisopentylidene-2-aminoethylamine.

As primary amino group-containing monomers, aminoalkyl (C _1-8 ) (meth) acrylate or (meth) acrylamide [aminoethyl (meth) acrylate, aminopropyl (meth) acrylate and N-aminoethyl (meth) Acrylamide etc.] and monoalkenylamine [monoallylamine etc.].

As the hydroxyl group-containing monomer, C _5-8 (meth) acrylate containing one hydroxyl group [for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) Acrylate and 2-hydroxyethoxyethyl (meth) acrylate]; (meth) acrylate containing 2 to 8 hydroxyl groups [for example, glycerin, trimethylolpropane, pentaerythritol, sorbitol, sorbitan, diglycerin, sucrose and methylglucoside (meta Acrylates]; C _2-6 alkenols [eg vinyl alcohol (formed by hydrolysis of vinyl acetate units), (meth) allyl alcohol, (iso) propenyl alcohol and polyvalents containing 3-8 hydroxyl groups of alcohol C _3-6 alkenyl Ethers {trimethylolpropane mono- - or di - (meth) allyl ether}]; hydroxyl group-containing aromatic monomers (o-, m-or p- hydroxystyrene); and C ₂ of the hydroxyl group-containing monomer _-4 alkylene oxide (for example, ethylene oxide, 1,2- or 1,3-propylene oxide and 1,2-, 1,3- or 1,4-butylene oxide) adduct (addition mole number 1 to 20), etc. Is mentioned.

Examples of the carboxyl group-containing monomer include unsaturated monocarboxylic acids [methacrylic acid, acrylic acid, (iso) crotonic acid, cinnamic acid, etc.], unsaturated dicarboxylic acids (maleic acid, itaconic acid, citraconic acid, mesaconic acid, etc.) ) And mono-C _1-8 alkyl esters of unsaturated dicarboxylic acids (such as monoalkyl malates, monoalkyl fumarate and monoalkyl itaconates).

  Examples of the compound that reacts with a primary amino group, a hydroxyl group, or a carboxyl group to generate a thiol group include, for example, thiol group-containing carboxylic acids (such as thioglycolic acid and 3-mercaptopropionic acid), thiol group-containing carboxylic acid esters (thioglycols). And cyclic compounds having a dithioester group or a trithioester group represented by the general formula (2) (for example, ethylene dithiocarbonate, ethylene trithiocarbonate, C3-C22) Intramolecular cyclic ester of mercaptocarboxylic acid and intramolecular cyclic ester of mercaptothione carboxylic acid having 3 to 22 carbon atoms), and from the viewpoint of difficulty in side reactions, a dithioester group or a trithioester group is preferred. It is a cyclic compound having.

In the formula, R ⁴ is a linear or branched alkylene group having 1 to 20 carbon atoms or a linear or branched alkoxyalkylene group having 2 to 20 carbon atoms, X is an oxygen atom or sulfur atom, Y is a sulfur atom or methylene. It is a group.

  As a thiol group induced | guided | derived by the method of inducing | guiding | deriving the functional group which can be induced | guided | derived to a thiol group to the thiol group, group shown by following General formula (3) is mentioned.

In the general formula (3), R ¹ , Q, Z and A ¹ are the same groups corresponding to the R ¹ , Q, Z and A ¹ in the general formula (1), respectively, and n is each the general formula (1) And the same number corresponding to n.

Of the groups represented by the general formula (3), the following groups are preferable from the viewpoint of adsorptivity to metal.
(1): In general formula (3), R ¹ = methyl group, Q = carbonyl group, Z = oxygen atom, A ¹ = ethylene group, n = 2, in group (2): in general formula (3) R ¹ = methyl group, Q = carbonyl group, Z = oxygen atom, A ¹ = ethylene group, n = 1, group (3): in general formula (3), R ¹ = methyl group, Q = carbonyl A group wherein Z = —NH—, A ¹ = ethylene group, n = 1

Examples of the method for introducing the carboxyl group-containing structural unit (b2) into the oil-soluble copolymer (A) include a method of copolymerizing a carboxyl group-containing monomer.
Examples of the carboxyl group-containing monomer (b2) include the same as the carboxyl group-containing monomer. Of these, methacrylic acid and acrylic acid are preferred from the viewpoints of polymerizability and metal adsorption, and methacrylic acid is more preferred.

  The oil-soluble copolymer (A) in the present invention may further contain a structural unit (c) composed of an alkyl (meth) acrylate having an alkyl group having 1 to 4 carbon atoms. Examples of the structural unit (c) include methyl, ethyl, n- or isopropyl, or n-, iso-, sec-, or t-butyl (meth) acrylate. Of these, methyl methacrylate is preferred from the viewpoint of the ability to improve the viscosity index.

The oil-soluble copolymer (A) contains, in terms of the viscosity index and the adsorptivity to metal, based on the weight of (A), the structural units in weight% shown in Table 1 below.
In the above and the following, “%” means “% by weight” unless otherwise specified.

  The adsorptivity to the metal of the oil-soluble copolymer (A) can be evaluated by adsorption INDEX in the adsorption test of (A) to iron oxide.

The adsorption INDEX defined by the following mathematical formula (1) represents the adsorption property of the oil-soluble copolymer (A) to iron oxide. Since (A) is a polymer, it can be used as a measure of the amount of (A) adsorbed on the metal surface due to the change in viscosity of the solution (A) before and after adsorption. The larger the adsorption INDEX, the closer to the metal surface. It is thought that the metal fatigue property is improved because the polymer concentration in the region becomes higher and the viscosity increases locally.
The adsorption INDEX of (A) is preferably 2 or more, more preferably 2.5 or more. When the adsorption INDEX is 2 or more, the adsorptivity to metal is good.

The kinematic viscosity at 40 ° C. before and after the adsorption test is measured by the following method.
(1) 180 parts of base oil (“Diana Fresia W-8” manufactured by Idemitsu Kosan Co., Ltd., kinematic viscosity at 100 ° C .: 2.3 mm 2 / s. Kinematic viscosity at 40 ° C .: 8.06 mm 2 / s) An oil to be evaluated is prepared by adding 20 parts of the oil-soluble copolymer (A) and stirring and dissolving at 80 ° C. for 1 hour.
(2) The kinematic viscosity at 40 ° C. of the evaluation oil (kinematic viscosity at 40 ° C. before the adsorption test) is measured by the method of JIS-K-2283.
(3) Add 10 parts of iron oxide (divalent and trivalent mixture) (Aldrich reagent, particle size: 5 microns or less) to 100 parts of the evaluation oil, stir at 25 ° C. for 2 hours, and filter through filter paper Then, the kinematic viscosity at 40 ° C. (kinematic viscosity at 40 ° C. after the adsorption test) of the filtrate is measured.
(4) The adsorption INDEX is calculated to one decimal place by the above formula.

<Calculation example>
Kinematic viscosity at 40 ° C. before adsorption = 10.68 mm ² / s,
Kinematic viscosity at 40 ° C. after adsorption = 10.61 mm ² / s,
Kinematic viscosity at 40 ° C. of base oil [“Diana Fresia W-8” manufactured by Idemitsu Kosan Co., Ltd.] = 8.06 mm ² / s;

  The adsorption INDEX can be increased by increasing the ratio of the monomers (b) and / or (c) constituting (A), and can be decreased by decreasing the ratio.

  The oil-soluble copolymer (A) is usually dissolved in at least 0.5 parts, preferably at least 2 parts, more preferably at least 30 parts, particularly preferably at least 70 parts in 100 parts of mineral oil at 25 ° C.

The weight average molecular weight (hereinafter abbreviated as Mw) of (A) measured by gel permeation chromatography (GPC) using polystyrene as a standard is usually 3,000 to 1,000,000. If the Mw is less than 3,000, the viscosity index is low, and if it exceeds 1,000,000, the shear stability is poor.
Although the preferable range of Mw of (A) varies depending on the use of the lubricating oil composition containing (A), it is preferably in the range shown in Table 2 below from the viewpoint of shear stability. The Mw of (A) can be adjusted by the temperature at the time of polymerization, the monomer concentration (solvent concentration), the catalyst amount, the chain transfer agent amount, or the like.

*: Automatic transmission oil
**: Belt-Continuously variable transmission oil
***: Manual transmission oil

  (A) can be obtained by a known production method. For example, it can be obtained by radical polymerization of the above monomer in a solvent in the presence of a polymerization catalyst.

Examples of the solvent include aromatic solvents such as toluene, xylene or C _9-10 alkylbenzene, aliphatic C _6-18 hydrocarbons such as hexane, heptane, cyclohexane and octane, 2-propanol, 1-butanol and 2- C _3-8 alcohol solvents such as butanol, ketone solvents such as methyl ethyl ketone, and mineral oil can be used. Among these solvents, preferred are alcohol solvents from the viewpoint of solubility, and more preferred is 2-propanol.

Examples of the polymerization catalyst include azo catalysts [for example, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2,4-dimethyl). Valeronitrile) (hereinafter abbreviated as ADVN) and dimethyl 2,2-azobisisobutyrate], peroxide catalysts [for example, t-butyl peroxypivalate, t-hexyl peroxypivalate, t-butyl. Peroxyneoheptanoate, t-butylperoxyneodecanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-amylperoxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy 2-ethylhexanoate, dibutylperoxytrimethyladipate, benzoyl peroxide De, cumyl peroxide and lauryl peroxide] can be used. Furthermore, a chain transfer agent (for example, a C _2-20 alkyl mercaptan) can be used if necessary.

  The reaction temperature is usually 50 to 140 ° C, preferably 60 to 120 ° C. In addition to the above solution polymerization, it can also be obtained by bulk polymerization, emulsion polymerization or suspension polymerization. Furthermore, the polymerization mode of the copolymer may be either random addition polymerization or alternating copolymerization, and may be either graft copolymerization or block copolymerization.

  The viscosity index improver of the present invention usually comprises only the oil-soluble copolymer (A).

The viscosity index improver composition of the present invention contains 20 to 90% viscosity index improver and 10 to 80% diluent.
Rather than adding the viscosity index improver as it is to the base oil, it is preferable to add the viscosity index improver composition because it is easier to dissolve in the base oil.

  The viscosity index improver composition is obtained by dissolving the oil-soluble copolymer (A) in a solution and a diluent obtained by producing the oil-soluble copolymer (A) by solution polymerization. Things.

Diluents include aliphatic solvents [C _6-18 aliphatic hydrocarbons (hexane, heptane, cyclohexane, octane, decalin, kerosene, etc.)], aromatic solvents [C _7-15 aromatic solvents {toluene, xylene , Ethylbenzene, C ₉ aromatic mixed solvent (a mixture of trimethylbenzene and ethyl toluene, etc.) and C _10-11 aromatic mixed solvent}], mineral oil [eg, solvent refined oil, paraffin oil, isoparaffin] High viscosity index oil, high viscosity index oil by hydrocracking and naphthenic oil] and synthetic lubricating oils (hydrocarbon synthetic lubricating oil (poly α-olefin synthetic lubricating oil) and ester synthetic lubricating oil, etc.). . Of these, preferred are mineral oils and synthetic lubricating oils, and more preferred are mineral oils.

  The proportion of the oil-soluble copolymer (A) in the viscosity index improver composition is preferably 20 to 90%, more preferably 30 to 85%, from the viewpoint of handling properties, based on the weight of the viscosity index improver composition. In particular, it is 40 to 80%, and the ratio of the diluent is preferably 10 to 80%, more preferably 15 to 70%, particularly preferably 20 to 60% based on the weight of the viscosity index improver composition. .

The lubricating oil composition of the present invention comprises a base oil and the viscosity index improver or the viscosity index improver composition, and the viscosity index improver is usually at a concentration of 0.8 based on the weight of the lubricating oil composition. Contains 01-45%.
Base oils include mineral oils [for example, solvent refined oil, paraffin oil, high viscosity index oil containing isoparaffin, high viscosity index oil by hydrocracking and naphthenic oil] and synthetic lubricating oil [hydrocarbon synthetic lubricating oil ( Poly α-olefin-based synthetic lubricating oil, etc.) and ester-based synthetic lubricating oil, etc.] and mixtures thereof.

  The preferable content of the viscosity index improver in the lubricating oil composition based on the use of the lubricating oil composition is in the range shown in Table 3 below.

Kinematic viscosity at 100 ° C. of the base oil, from the viewpoint of low viscosity, preferably 1 to 6 mm ² / s, more preferably from 1 to 5 mm ² / s.
The viscosity index of the base oil is preferably 60 or more, more preferably 100 or more, particularly preferably 105 or more, preferably 180 or less, more preferably 175 or less, and particularly preferably 170 or less.
A lubricating oil composition in which the viscosity index improver or the viscosity index improver composition of the present invention is blended with such a base oil has a higher viscosity index and better fuel economy.

  Moreover, the pour point (JIS K2269-1993) of the base oil is preferably −5 ° C. or lower, more preferably −10 ° C. to −70 ° C. When the pour point of the base oil is within this range, the amount of precipitated wax is small and the low temperature viscosity is good.

The kinematic viscosity at 100 of the lubricating oil composition is preferably 1 to 12 mm ² / s from the viewpoint of lowering the viscosity, and more preferable ranges are described in Table 4 below based on the use of the lubricating oil composition. Range.

  The lubricating oil composition of the present invention includes gear oil such as differential oil and industrial gear oil, manual transmission oil (hereinafter abbreviated as MTF), automatic transmission oil (hereinafter abbreviated as ATF), and transmission oil such as belt-CVTF. It is suitably used for traction oil such as Toroidal-CVT oil, shock absorber oil, power steering oil, hydraulic fluid for construction machinery, industrial hydraulic fluid, and engine oil. Of these, preferred are differential oil, ATF, belt-CVT oil, engine oil and MTF, and more preferred are differential oil, ATF, belt-CVT oil and MTF.

  The lubricating oil composition of the present invention can further contain any one or more additives.

The following can be used as an additive.
(1) Detergent:
Basic, overbased or neutral metal salts [overbased or alkaline earth metal salts of sulfonates (such as petroleum sulfonates, alkylbenzene sulfonates and alkylnaphthalene sulfonates)], salicylates, phenates, naphthenates , Carbonates, phosphonates and mixtures thereof;
(2) Dispersant:
Succinimides (bis- or mono-polybutenyl succinimides), Mannich condensation products, borates and the like;
(3) Antioxidants:
Hindered phenols and aromatic secondary amines, etc .;
(4) Oiliness improver:
Long chain fatty acids and their esters (such as oleic acid and oleic acid esters), long chain amines and their amides (such as oleylamine and oleylamide), etc .;
(5) Friction and wear modifier:
Molybdenum and zinc compounds (such as molybdenum dithiophosphate, molybdenum dithiocarbamate and zinc dialkyldithiophosphate);
(6) Extreme pressure agent:
Sulfur compounds (mono- and disulfides, sulfoxides and sulfur phosphide compounds), phosphide compounds and chlorinated compounds (chlorinated paraffins, etc.);
(7) Antifoaming agent:
Silicon oil, metal soap, fatty acid ester and phosphate compound, etc .;
(8) Demulsifier:
Quaternary ammonium salts (tetraalkylammonium salts, etc.), sulfated oils and phosphates (polyoxyethylene-containing nonionic surfactant phosphates, etc.);
(9) Corrosion inhibitor:
Nitrogen atom-containing compounds (such as benzotriazole and 1,3,4-thiodiazolyl-2,5-bisdialkyldithiocarbamate) and the like.

These additives can be used in the amounts shown in Table 5 below based on the weight of the lubricating oil composition.

  The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. Below, a part represents a weight part.

The measurement methods and test methods used in the examples are as follows.
(Method for measuring weight average molecular weight by GPC)
Apparatus: HLC-802A manufactured by Toyo Soda
Column: TSK gel GMH6 2 Measurement temperature: 40 ° C
Sample solution: 0.5% tetrahydrofuran solution solution injection amount: 200 μl
Detector: Refractive index detector Standard: Polystyrene

(Test method for low temperature viscosity)
The viscosity at −40 ° C. was measured by the method of JPI-5S-26-85.
(Density measurement method)
This was performed by the vibration method of JIS-K-2249.
(Test method for kinematic viscosity and viscosity index)
It was carried out by the method of JIS-K-2283.
(Shear stability test method)
The test time was 20 hours according to the method of CEC L45-45-A-99.

<Production Example 1> (Synthesis of ketimine group-containing monomer)
Into a reaction vessel equipped with a stirrer, heating / cooling device, thermometer, dropping funnel, nitrogen blowing tube and decompression device, 90 parts of toluene, 200 parts of diisobutylketone and 50 parts of 2- (2-aminoethoxy) ethanol were charged, 130 After reacting at reflux for 4 hours, toluene and unreacted isobutyl ketone were removed under reduced pressure (pressure 6 mmHg). After cooling to 30 ° C., 75 parts of methyl methacrylate, 2.0 parts of sodium methoxide, 2.5 parts of phenothiazine and 200 parts of toluene were charged and reacted at 80 ° C. for 6 hours while refluxing (pressure 500 mmHg). Then, toluene and methyl methacrylate were removed under reduced pressure (pressure 6 mmHg), and an ester of methacrylic acid having the following structural formula and N-1-isobutylisopentylidene-2- (2-hydroxyethoxy) ethylamine (hereinafter, , Abbreviated as IBIPMA).

<Example 1>
In a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, a dropping funnel, a nitrogen blowing tube and a decompression device, 25 parts of toluene was charged, and in another glass beaker, 60 parts of n-dodecyl methacrylate and Production Example 1 62.5 parts of the obtained IBIPMA, 1.5 parts of dodecyl mercaptan as a chain transfer agent, 0.5 parts of ADVN as a radical polymerization initiator and 6 parts of toluene were charged and stirred and mixed at 20 ° C. to obtain a monomer solution. Prepared and charged into dropping funnel. After replacing the nitrogen in the gas phase part of the reaction vessel, the monomer solution was added dropwise over 2 hours while maintaining the system temperature at 70 to 85 ° C, and aging was carried out at 85 ° C for 2 hours from the end of the addition. Thereafter, 20 parts of water was added and hydrolyzed by heating and stirring at 85 ° C. for 2 hours. Next, the temperature was raised to 120 ° C., water and toluene were distilled off under reduced pressure (pressure 6 mmHg), the obtained polymer was reprecipitated with 500 parts of methanol, washed twice with 200 parts of methanol, and then at 100 ° C. It was dried under reduced pressure at a pressure of 6 mmHg for 4 hours to obtain a primary amino group-containing copolymer. Furthermore, 100 parts of the obtained copolymer, 20 parts of ethylene trithiocarbonate and 500 parts of tetrahydrofuran were charged, and the mixture was heated and stirred while refluxing at 85 ° C. for 2 hours to cause a ring-opening reaction. Thereafter, tetrahydrofuran was removed at 85 ° C. under reduced pressure (pressure 6 mmHg). Next, it was reprecipitated with 500 parts of methanol, washed twice with 200 parts of methanol, and then dried under reduced pressure at 100 ° C. for 4 hours at a pressure of 6 mmHg to obtain a thiol group-containing viscosity index improver (A1). Table 6 shows Mw of (A1).

<Example 2>
A thiol group-containing viscosity index improver (A2) was obtained in the same manner as in Example 1 except that 60 parts of n-dodecyl methacrylate was changed to 60 parts of 2-ethylhexyl acrylate. Table 6 shows the Mw of (A2).

<Example 3>
A thiol group-containing viscosity index improver (A3) was obtained in the same manner as in Example 1 except that 60 parts of n-dodecyl methacrylate was changed to 60 parts of n-hexadecyl methacrylate. Table 6 shows the Mw of (A3).

<Example 4>
A thiol group-containing viscosity index improver (A4) was obtained in the same manner as in Example 1 except that 60 parts of n-dodecyl methacrylate was changed to 60 parts of n-octadecyl methacrylate. Table 6 shows Mw of (A4).

<Example 5>
A thiol group-containing viscosity index improver (A5) was obtained in the same manner as in Example 1 except that 60 parts of n-dodecyl methacrylate was changed to 60 parts of n-tetracosyl methacrylate. Table 6 shows Mw of (A5).

<Example 6>
A thiol group-containing viscosity index improver (A6) was obtained in the same manner as in Example 1 except that 60 parts of n-dodecyl methacrylate were changed to 30 parts of n-dodecyl methacrylate and 30 parts of n-octadecyl methacrylate. Table 6 shows Mw of (A6).

<Example 7>
Thiol group-containing viscosity index improver (A7) in the same manner as in Example 1 except that 60 parts of n-dodecyl methacrylate was changed to 99.5 parts and 62.5 parts of IBIPMA were changed to 0.8 parts. Got. Table 6 shows Mw of (A7).

<Example 8>
A thiol group-containing viscosity index improver (A8) was obtained in the same manner as in Example 1 except that 60 parts of n-dodecyl methacrylate was changed to 50 parts and 62.5 parts of IBIPMA were changed to 78.1 parts. It was. Table 6 shows the Mw of (A8).

<Example 9>
A thiol group-containing viscosity index improver (A9) was obtained in the same manner as in Example 1 except that 60 parts of n-dodecyl methacrylate was changed to 80 parts and 62.5 parts of IBIPMA were changed to 31.3 parts. It was. Table 6 shows Mw of (A9).

<Example 10>
In a reaction vessel equipped with a stirrer, heating / cooling device, thermometer, dropping funnel, nitrogen blowing tube and decompression device, 25 parts of toluene was charged, and in another glass beaker, 75 parts of n-dodecyl methacrylate and 25 parts of methacrylic acid. , 1.5 parts of dodecyl mercaptan as a chain transfer agent, 0.5 parts of ADVN as a radical polymerization initiator and 6 parts of toluene were prepared, and stirred and mixed at 20 ° C. to prepare a monomer solution. Prepared. After replacing the nitrogen in the gas phase part of the reaction vessel, the monomer solution was added dropwise over 2 hours while maintaining the system temperature at 70 to 85 ° C, and aging was carried out at 85 ° C for 2 hours from the end of the addition. Thereafter, water and toluene were distilled off under reduced pressure (pressure 6 mmHg) at 120 ° C. to obtain a carboxyl group-containing viscosity index improver (A10). Table 6 shows Mw of (A10).

<Example 11>
A carboxyl group-containing viscosity index improver (A11) is obtained in the same manner as in Example 10 except that 75 parts of n-dodecyl methacrylate are changed to 30 parts of n-dodecyl methacrylate, 30 parts of n-octadecyl methacrylate and 15 parts of methyl methacrylate. It was. Table 6 shows Mw of (A11).

<Example 12>
Carboxyl group-containing viscosity index improver (A12) in the same manner as in Example 10 except that 75 parts of n-dodecyl methacrylate were changed to 30 parts of n-dodecyl methacrylate, 30 parts of n-octadecyl methacrylate and 15 parts of n-butyl methacrylate. Got. Table 6 shows Mw of (A12).

<Comparative Example 1>
A comparative viscosity index improver (B1) was obtained in the same manner as in Example 10 except that 75 parts of n-dodecyl methacrylate was changed to 100 parts and 25 parts of methacrylic acid was not used. Table 6 shows the Mw of (B1).

<Comparative example 2>
A comparative viscosity index improver (B2) was obtained in the same manner as in Example 10 except that 75 parts of n-dodecyl methacrylate was changed to 40 parts of n-dodecyl methacrylate, 30 parts of n-octadecyl methacrylate and 30 parts of methyl methacrylate. . Table 6 shows the Mw of (B2).

<Comparative Example 3>
Comparison was made in the same manner as in Example 1 except that 60 parts of n-dodecyl methacrylate was changed to 69.8 parts of n-dodecyl methacrylate and 30 parts of n-octadecyl methacrylate, and 62.5 parts of IBIPMA was changed to 0.3 part. Viscosity index improver (B3) was obtained. Table 6 shows the Mw of (B3).

<Comparative Example 4>
Comparative viscosity in the same manner as in Example 1 except that 60 parts of n-dodecyl methacrylate was changed to 20 parts of n-dodecyl methacrylate and 20 parts of n-octadecyl methacrylate, and 62.5 parts of IBIPMA was changed to 93.8 parts. An index improver (B4) was obtained. Table 6 shows the Mw of (B4).

In addition, each structural unit of (a)-(c) of Table 6 is as follows.
(A1): n-dodecyl methacrylate (a2): 2-ethylhexyl acrylate (a3): n-hexadecyl methacrylate (a4): n-octadecyl methacrylate (a5): n-tetracosyl acrylate (b1): 2- ( 2-mercaptoethoxy) ethyl methacrylate (b2): methacrylic acid (c1): methyl methacrylate (c2): n-butyl methacrylate

<Examples 13 to 24 and Comparative Examples 5 to 8> (Production and Evaluation of Lubricating Oil Composition)
In a stainless steel container equipped with a stirring and mixing device, the resulting lubricating oil composition has a kinematic viscosity at 100 ° C. of 5.2 ± 0.2 (mm ² / s), and the total lubricating oil composition is 100. Base oil (high viscosity index oil; kinematic viscosity at 100 ° C. = 4.6 mm ² / s, viscosity index = 118, pour point = −17.5 ° C.) and (A1) to (A12) or (B1) to (B4) were charged and mixed at 80 ° C. for 1 hour to prepare the lubricating oil compositions (C1) to (C12) of the present invention and comparative lubricating oil compositions (D1) to (D4). .
Table 7 shows the kinematic viscosity at 100 ° C., the viscosity index, the low temperature viscosity at −40 ° C., the shear stability, and the adsorption INDEX of the viscosity index improver of the resulting lubricating oil composition.

  Since the lubricating oil composition using the viscosity index improver of the present invention is superior to the lubricating oil composition using the conventional viscosity index improver, the viscosity index improving effect and the adsorptivity to metal are excellent. Drive system lubricants for transportation equipment and various machine tools [gear oil (manual transmission oil, differential oil, etc.) and automatic transmission oil (automatic transmission oil, belt CVT oil, toroidal CVT oil, etc.)], hydraulic oil It can be suitably used for machine hydraulic oil, power steering oil, shock absorber oil, etc. and engine oil (gasoline, diesel, etc.).

Claims (7)

1 or more types chosen from the group which consists of a structural unit which consists of an alkyl (meth) acrylate which has a C8-C17 alkyl group and an alkyl (meth) acrylate which has a C18-C24 linear alkyl group Structural unit (a) and thiol group-containing structural unit (b1) Consist of A viscosity index improver comprising an oil-soluble copolymer (A) containing a structural unit (b), wherein the copolymer (A) has a weight average molecular weight of 3,000 to 1,000,000. And 50 to 99.5% by weight of the structural unit (a) and 0.5 to 50% by weight of the structural unit (b) based on the total weight of the copolymer (A). Viscosity index improver.   2. The oil-soluble copolymer (A) is an oil-soluble copolymer obtained by derivatizing a functional group in a precursor copolymer having a functional group that can be derived into a thiol group into a thiol group. The viscosity index improver described.   The oil-soluble copolymer (A) further contains a structural unit (c) composed of an alkyl (meth) acrylate having an alkyl group having 1 to 4 carbon atoms, and is based on the total weight of the copolymer (A). The structural unit (a) is 60 to 94.5% by weight, the structural unit (b) is 0.5 to 30% by weight, and the structural unit (c) is 5 to 30% by weight. 2. The viscosity index improver according to 2. The oil-soluble copolymer (A) comprises only the structural unit (a), the structural unit (b), and the structural unit (c). 3 The viscosity index improver described.   A viscosity index improver composition comprising 20 to 90% by weight of the viscosity index improver according to any one of claims 1 to 4 and 10 to 80% by weight of a diluent.   A base oil and the viscosity index improver according to any one of claims 1 to 4 or the viscosity index improver composition according to claim 5, wherein the viscosity index improver is 0.01 based on the weight of the lubricating oil composition. A lubricating oil composition containing ˜45 wt%.   The lubricating oil composition according to claim 6, which is used for gear oil, transmission oil, traction oil, hydraulic oil or engine oil.