JP2009074068A - Viscosity index improver and lubricant composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a viscosity index improver excellent in viscosity improving effect, and also excellent in shear stability. <P>SOLUTION: The viscosity index improver comprises a (meth)acrylate copolymer (A) which has a syndiotacticity of 65-100% determined by a triad expression of (meth)acrylate unit enchainment according to<SP>13</SP>C-NMR method, wherein constituting monomers of the copolymer (A) are a 1-4C alkyl (meth)acrylate (a1) and a 12-32C alkyl (meth)acrylate (a3), and each of (a1) and (a3) are preferably 5-50 mass% and 50-95 mass% with respect to the total weight of the monomers, respectively. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a viscosity index improver and a lubricating oil composition. Specifically, the present invention relates to a viscosity index improver comprising a specific copolymer and a lubricating oil composition containing the viscosity index improver.

In recent years, from the viewpoint of protecting the global environment, there has been a further demand for improvements in fuel economy and long life of automobiles. Further improvement in viscosity index and actual use of lubricants and hydraulic oils used in automobiles. Suppression of permanent viscosity reduction due to shearing is required. Conventionally, as a method for improving the shear stability of a viscosity index improver, a method using a polymer compound having a relatively low molecular weight has been proposed (Patent Document 1). However, this method has a problem that although the shear stability is improved, the effect of improving the viscosity index is lowered.
JP 2002-302687 A

  This invention is made | formed in view of the said problem, and is providing the viscosity index improver which is excellent in the viscosity index improvement effect and excellent in shear stability.

As a result of intensive studies by the inventor in order to solve the above-mentioned problems, the inventors have found that a compound having a specific chemical structure exhibits an excellent effect as a viscosity index improver, and reached the present invention. That is, the present invention provides a (meth) acrylic acid ester copolymer (A) having a syndiotacticity of 65 to 100% by triad display of a (meth) acrylic acid ester unit chain portion determined by a ¹³ C-NMR method. A viscosity index improver comprising the viscosity index improver and a solvent, and a viscosity index improver concentrate having a viscosity index improver / solvent mass ratio of 10/90 to 95/5; and improving the viscosity index A lubricating oil composition comprising an agent or viscosity index improver concentrate and a base oil.

  The viscosity index improver of the present invention and the lubricating oil composition containing the viscosity index improver have better viscosity index improvement effect and shear stability than conventional ones, and can save fuel and long life of automobiles. Can greatly contribute to the improvement of

Hereinafter, the present invention will be described in detail. Generally, tacticity is used as an index representing the degree of stereoregularity in a polymer. Tacticity includes those in which the three-dimensional structure of the side chain is regularly controlled, and one having a three-dimensional structure in which the side chain is alternately positioned in the opposite direction with respect to the main chain formed from the carbon-carbon bond. It is called a syndiotactic structure, and one in which the side chains are located in the same direction is called isotactic. Also, syndiotacticity is used as an index representing the degree of syndiotactic structure. Syndiotacticity can be determined by a method described in known literature using ¹³ C-NMR (nuclear magnetic resonance spectrum by isotope carbon). The tacticity determined by NMR is the abundance ratio of a plurality of consecutive structural units (that is, the abundance ratio of the relative conformational relationship of the continuous structural units), for example, dyad in the case of two, The syndiotacticity in the present invention refers to that represented by the triad, and can be represented by a triad, and is the second unit of the 3 chain-linked (meth) acrylate ester-linked (meth) acrylate ester in ¹³ C-NMR. The peak area (intensity) ratio of the main chain carbon atom to which the ester group is bonded is determined by the following general formula.
Syndiotacticity (%) = [rr / (mm + mr + rr)] × 100
Here, mm is an integral value derived from an isotactic (meth) acrylate ester (δ45.4 to 46.0), and mr is an integral value derived from an atactic (meth) acrylate ester (δ44.8 to 45.45). 3) and rr are integral values (δ44.2 to 44.79) derived from syndiotactic (meth) acrylate.

The highly syndiotactic (meth) acrylic acid ester copolymer (A) in the present invention is syndiotacticity by triad display of a (meth) acrylic acid alkyl ester unit chain portion determined by ¹³ C-NMR method. Is 65 to 100%, preferably 80 to 100%, more preferably 90 to 100%, and particularly preferably 95 to 100%. Highly syndiotactic (meth) acrylic acid ester copolymer (A) solutions can be obtained from highly atactic (meth) acrylic acid ester copolymers or highly isotactic (meth) acrylic acid ester copolymers. Compared to the solution of coalescence, the viscosity is less affected by temperature change, and in particular, it has been found that the viscosity is not easily increased even at a low temperature, and the viscosity is not easily decreased even at a high temperature. . The reason why the temperature dependence of the viscosity of the copolymer (A) is low is not clear, but these highly syndiotactic copolymers are used as a solution between carbon-carbon bonds in a solution. It is presumed to be due to the fact that the change in the dissolution radius of the polymer is easy due to the temperature change.

The copolymer (A) in the present invention is composed of the following monomers.
(A): (meth) acrylic acid alkyl ester (b): (meth) acrylic acid ester other than (meth) acrylic acid alkyl ester (c): other monomer

(A): The (meth) acrylic acid alkyl ester is classified into the following (a1) to (a3) depending on the carbon number of the alkyl group.

(A1): (meth) acrylic acid alkyl ester having an alkyl group having 1 to 4 carbon atoms;
Alkyl groups having 3 and 4 carbon atoms include linear or branched ones. Specifically, (meth) acrylic acid methyl ester, (meth) acrylic acid ethyl ester, (meth) acrylic acid n-propyl ester, (meth) acrylic acid isopropyl ester, (meth) acrylic acid n-butyl ester and ( And (meth) acrylic acid t-butyl ester. Of the (a1), (meth) acrylic acid methyl ester is preferred.

(A2): (meth) acrylic acid alkyl ester having an alkyl group having 5 to 11 carbon atoms;
Alkyl groups include linear or branched ones. Specific examples include (meth) acrylic acid 2-ethylhexyl ester, (meth) acrylic acid n-decyl ester, and the like.

(A3): (meth) acrylic acid alkyl ester having an alkyl group having 12 to 32 carbon atoms;
Alkyl groups include linear or branched ones. Specifically, (meth) acrylic acid n-dodecyl ester, (meth) acrylic acid 2-methylundecyl ester, (meth) acrylic acid n-tridecyl ester, (meth) acrylic acid n-tetradecyl ester, ( (Meth) acrylic acid n-pentadecyl ester, (meth) acrylic acid n-hexadecyl ester, (meth) acrylic acid 2-methylpentadecyl ester, (meth) acrylic acid n-octadecyl ester, (meth) acrylic acid n- Examples include eicosyl ester, (meth) acrylic acid 2-octyldodecyl ester, (meth) acrylic acid 2-decyl tetradecyl ester, (meth) acrylic acid 2-tetradecyl octadecyl ester, and the like. Of (a3), a linear or branched alkyl group having 12, 13, 14, 15, 16, 18, 20, 24 and 32 carbon atoms, and a combination of two or more of these are preferable.

The following (b1) to (b5) may be mentioned as the (meth) acrylic acid ester (b) other than the (meth) acrylic acid alkyl ester.

(B1): (meth) acrylic acid alkenyl ester;
The alkenyl group includes a linear or branched alkenyl group having 1 to 30 carbon atoms. Specific examples include (meth) acrylic acid dodecenyl ester and (meth) acrylic acid oleyl ester.

(B2): (poly) alkylene glycol or mono (meth) acrylic acid ester of monoalkyl ether thereof;
Examples of the alkylene group constituting the (poly) alkylene glycol or its monoalkyl ether include alkylene groups having 2 to 20 carbon atoms, such as an ethylene group, a propylene group, and a butylene group. Preferably, it is a C2-C4 alkylene group. Moreover, as an alkyl group which comprises monoalkyl ether, a C1-C20 linear or branched alkyl group is mentioned, Preferably it is a C1-C18 alkyl group. The number of alkylene glycol units in the (poly) alkylene glycol is preferably 1-50, more preferably 1-20. Specific examples include polyethylene glycol (ethylene glycol unit number 9) monomethacrylate, polypropylene glycol (propylene glycol unit number 3) monomethacrylate, polyethylene glycol (ethylene glycol unit number 6) monomethyl ether monomethacrylate, and the like.

(B3): (meth) acrylic acid cycloalkyl ester;
Specific examples include cyclohexyl (meth) acrylate.

(B4): nitrogen-containing (meth) acrylic acid ester;
For example, dialkyl (1 to 4 carbon atoms) aminoalkyl (2 to 6 carbon atoms) (meth) acrylic acid ester [specifically, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate), morpholinoethyl ( And (meth) acrylic acid esters.

(B5): hydroxyl group-containing (meth) acrylic acid ester;
For example, hydroxyalkyl (2 to 6 carbon atoms) (meth) acrylic acid ester [specifically, 2-hydroxyethyl (meth) acrylate, 2 or 3-hydroxypropyl (meth) acrylate, etc.) can be mentioned.

Of these, (b) is preferably (b2) and (b5), more preferably (b5) from the viewpoint of the effect of improving the viscosity index.

Examples of the other monomer (c) include the following (c1) to (c6).

(C1): a carboxyl group-containing monomer;
For example, unsaturated monocarboxylic acids [specifically, (meth) acrylic acid, α-methyl (meth) acrylic acid, crotonic acid, cinnamic acid, etc.], unsaturated dicarboxylic acids [specifically, maleic acid, fumaric acid, etc. Acid] and the like.

(C2): ester of unsaturated carboxylic acid other than (meth) acrylic acid;
For example, C1-C30 alkyl ester of crotonic acid, C1-C24 alkyl diester of maleic acid, etc. are mentioned.

(C3); Aliphatic vinyl hydrocarbons such as alkenes having 2 to 30 carbon atoms [ethylene, propylene, 1-butene, α-olefin and the like], alkadienes having 4 to 18 carbon atoms, and the like.

(C4); alkyl alkenyl ethers Alkyl vinyl ethers having a linear or branched alkyl group having 1 to 30 carbon atoms, alkyl (meth) allyl ethers, etc.

(C5); Examples of the fatty acid vinyl ester fatty acid include fatty acids having a linear, branched or alicyclic group having 1 to 30 carbon atoms, and may be either saturated or unsaturated. Specific examples include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl hexanoate, and vinyl 2-ethylhexanoate.
(C6); aromatic vinyl hydrocarbons such as styrene, other substituted styrenes (substituents having 1 to 18 carbon atoms) [specifically, α-methylstyrene, vinyltoluene, etc.], divinyl substituted aromatic hydrocarbons [ Specific examples include divinylbenzene].

Among (c), from the viewpoint of the effect of improving the viscosity index, (c1), (c2), (c6) and a combination of two or more thereof are preferred, and (c1) is more preferred.

Of the monomers constituting the copolymer (A), from the viewpoint of the effect of improving the viscosity index, preferred is (a) and a combination of two or more thereof, and (b) and / or (c) if necessary. May be used in combination. When two or more of (a) are used in combination, the combination of (a1) and (a3) is more preferable.

The copolymer (A) comprises a (meth) acrylic acid alkyl ester (a1) having an alkyl group having 1 to 4 carbon atoms and a (meth) acrylic acid alkyl ester (a3) having an alkyl group having 12 to 32 carbon atoms. When the monomer is used and (b) and (c) are not used, (a1) is 5 to 50% by mass and (a3) is 50 to 95% by mass based on the mass of all monomers. Is preferred. More preferably, (a1) is 20 to 40% by mass, (a3) is 60 to 80% by mass, particularly preferably (a1) is 30 to 40% by mass and (a3) is 60 to 70% by mass.

Copolymer (A) is (a1), (a3), and (meth) acrylic acid ester (b) other than (meth) acrylic acid alkyl ester [especially hydroxyl group-containing (meth) acrylic acid ester (b5)] and When the other monomer (c) is used as a constituent monomer, each preferred mass ratio based on the mass of all monomers (total is 100% by mass) is from the viewpoint of the effect of improving the viscosity index, It is preferable that (a1) is 5 to 40% by mass, (a3) is 60 to 95% by mass, (b) [particularly (b5)] is 0 to 10% by mass, and (c) is 0 to 10% by mass. . More preferably, (a1) is 10 to 25% by mass, (a3) is 75 to 90% by mass, (b) [particularly (b5)] is 0 to 5% by mass, and (c) is 0 to 5% by mass. . If (b) and / or (c) are 10 mass% or less, since the fluidity | liquidity in low temperature is favorable, it is preferable. When (c) is used in combination, the syndiotacticity in the present invention targets only the tacticity derived from other than (c).

Although the manufacturing method of the highly syndiotactic copolymer (A) in this invention is not specifically limited, For example, the following method is mentioned. A method using a catalyst system composed of tetraalkoxytitanium and organoaluminum (Japanese Patent Publication No. 45-9749), a method using an organic magnesium compound catalyst (Japanese Patent Publication No. 45-40061 and Japanese Patent Publication No. 63-172709), two types Using a catalyst system comprising a combination of lithium compounds (Japanese Patent Publication No. 46-2830), polymerizing using a catalyst system comprising a titanium compound and a lithium aluminum compound (Japanese Patent Application Laid-Open No. 1-193312), organic lanthanides Polymerization using a compound catalyst system (Japanese Patent Laid-Open No. 3-263212), Polymerization using a catalyst system comprising an organoaluminum compound, a phenol and a bisoxazoline compound (Japanese Patent Laid-Open No. 10-139822), fluoro Polymerization in an alcohol solvent (Isobe et al. Journal of Polymer Science: Part A: Polymer Chemistry, 38, 4693-4703, 2000). In the production of the copolymer (A), the lower the polymerization temperature, the better the stereoregularity control. Therefore, the polymerization temperature is preferably 40 ° C. or less, more preferably 25 ° C. or less, particularly preferably 0 ° C. or less. It is.

As the initiator, an initiator selected from the group consisting of an azo-based initiator, a peroxide-based initiator, a redox-based initiator, an organic halogen compound initiator, and a trialkylborane can be used. In addition to this method, a method of initiating polymerization by irradiating with radiation, electron beam, ultraviolet ray or the like can also be adopted. Particularly for polymerization at low temperatures, redox initiators and trialkylborane initiators are preferred. Redox catalysts include alkali metal sulfites or bisulfites (eg, ammonium sulfite, ammonium bisulfite, etc.), ferrous chloride, ferrous sulfate, ascorbic acid and other reducing agents and alkali metal persulfates. , Ammonium persulfate, hydrogen peroxide, organic peroxides and the like in combination with an oxidizing agent. Examples of the trialkylborane include tri-n-butylborane and triethylborane, which act as an initiator by blowing a small amount of air. Examples of the azo initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), and the like. Is mentioned. Examples of peroxide initiators include inorganic peroxides [hydrogen peroxide, ammonium persulfate, etc.] and organic peroxides [t-butyl peroxypivalate, t-hexyl peroxypivalate, etc.].

For the polymerization, a chain transfer agent may be used in combination, and examples thereof include thiocarboxylic acids (such as n-lauryl mercaptan and mercaptoethanol), thiolic acids (such as thioglycolic acid and thiomalic acid), and secondary alcohols. (Isopropanol, etc.), amines (dibutylamine, etc.), hypophosphites (sodium hypophosphite, etc.) and the like, and the amount of chain transfer agent is preferably relative to the amount of all vinyl monomers. Is 0.001 to 10%. More preferably, it is 0.5 to 5%.

  The mode of copolymerization may be random copolymerization or alternating copolymerization, and may be either graft copolymerization or block copolymerization.

The weight average molecular weight of the copolymer (A) obtained by the above production method (hereinafter abbreviated as Mw. Mw is the weight average molecular weight determined by conversion to polystyrene by gel permeation chromatography). However, it is preferably 5,000 to 500,000, more preferably 10,000 to 500,000, and particularly preferably 10,000 to 250,000. If Mw is 10,000 or more, it is preferable in terms of the effect of improving the viscosity index, and if Mw is 500,000 or less, it is preferable in terms of shear stability. Further, when used for transmission oil, since shearing force is strongly applied, Mw is preferably 10,000 to 35,000, and more preferably 15,000 to 30,000.

  The copolymer (A) has a solubility parameter of preferably 9.0 to 9.3, more preferably 9.10 to 9.25, and particularly preferably 9.18 to 9.23. Is within the above range, the solubility in oil or organic solvent is good, and the effect of improving the viscosity index is high. In addition, the solubility parameter in this invention is Fedors method [Poym. Eng. Sci. 14 (2) 147-154, (1974)].

The crystallization start temperature of the copolymer (A) measured by a differential scanning calorimeter is preferably −10 ° C. or lower, more preferably −15 ° C. or lower, and particularly preferably −20 ° C. or lower. If it is -10 degrees C or less, it will be hard to thicken at low temperature and it will have little bad influence on a low-temperature characteristic. The crystallization start temperature of the copolymer (A) of the present invention by differential scanning calorimetry is “DSC7” manufactured by PERKIN-ELMER, using 5 mg of viscosity index improver as a sample at an isothermal rate of 10 ° C./min. This is the crystallization start temperature observed when cooling from 100 ° C. to −40 ° C.

  The HLB value of the copolymer (A) is preferably 0.5 to 6.0. When the HLB is within this range, the demulsibility is particularly good. More preferably, the HLB value is 1.0 to 5.5. Particularly preferably, the HLB value is 1.5 to 5.0. The HLB value of the present invention is a value calculated by the concept of organic inorganic HLB (“New Surfactant Introductory”, published by Sanyo Chemical Industries, P.197-198).

  The viscosity index improver of the present invention consists only of the copolymer (A). However, it is preferable that the viscosity index improver be further diluted with a solvent and used as a concentrated viscosity index improver because the handling property is good. In the case of dilution, the mass ratio of the viscosity index improver / solvent is preferably 10/90 to 95/5, more preferably 30/70 to 85/15. If it is this range, handling property will be still more favorable. Diluting solvents include solvent refined oils, isoparaffins and / or hydrocracked high viscosity index oils, hydrocarbon synthetic lubricating oils, ester synthetic lubricating oils, naphthenic oils, single composition organic solvents, and mixtures thereof. Can be mentioned. In addition, when a solvent is used in the above-described polymerization step, the solvent in the case where the solvent is left as it is is also included in a part of the dilution solvent. Examples of the organic solvent having a single composition include hydrocarbon solvents (pentane, hexane, etc.), aromatic solvents (toluene, xylene, etc.), alcohol solvents (octal, butanol, etc.), ketone solvents (methyl isobutyl ketone, Methyl ethyl ketone and the like), amide solvents (N, N-dimethylformamide, N-methylpyrrolidone and the like), and sulfoxide solvents (dimethyl sulfoxide and the like). Of these, solvent refined oils, isoparaffins and / or hydrocracked high viscosity index oils, hydrocarbon synthetic oils, ester synthetic oils, and naphthenic oils are preferred. Particularly preferred are solvent refined oils having a flash point (COC) of 120 ° C. or higher, isoparaffins and / or hydrocracked high viscosity index oils, hydrocarbon synthetic oils, ester synthetic oils, and naphthenic oils. In this range, the viscosity index improver is highly safe against fire. Moreover, these may mix 2 or more types.

  The viscosity index improver of the present invention is usually used for engine oil, transmission oil [gear oil (for industrial and automobile use), automatic transmission oil (automatic transmission oil, toroidal CVT oil and belt CVT oil), power steering oil and shock absorber. Used for oil, etc., but especially for transmission oils [gear oil (for automobiles), automatic transmission oils (automatic transmission oil, toroidal CVT oil and belt CVT oil)] that are severely sheared. It is. Most preferably, it is used for lubricating oil of an automatic transmission having a slip control mechanism with excellent fuel economy, and both fuel economy and long life are effective (does not adversely affect the shudder performance).

In the lubricating oil composition comprising the viscosity index improver and the viscosity index improver concentrate and base oil of the present invention, the base oil used preferably has a kinematic viscosity at 100 ° C. of ² to 5 mm ² / s. Further, the viscosity index of the base oil is preferably 95 or more, more preferably 100 or more. A lubricating oil composition in which the viscosity index improver and the viscosity index improver concentrate of the present invention are blended with such a base oil has a high viscosity index and good fuel economy. Further, the pour point (JIS K2269) of the base oil used is preferably −20 ° C. or lower. More preferably, it is -25 degrees C or less. If 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. Base oils include solvent refined oils, isoparaffins and / or hydrocracked high viscosity index oils, hydrocarbon synthetic lubricating oils, ester synthetic lubricating oils, naphthenic oils and mixtures of two or more thereof. .

  The viscosity index improver or the viscosity index improver concentrated liquid of the present invention is preferably used in the lubricating oil composition of the present invention by adding 1 to 30% as a copolymer (A) component to the base oil. . 2-10% when the lubricating oil composition of the present invention is engine oil, 2-25% when transmission oil (gear oil or automatic transmission oil), preferably 3-10%, and traction oil Particularly favorable results are obtained when 0.5 to 10% is added.

  The lubricating oil composition of the present invention comprises other optional components such as detergents (sulfonate, salicylate, phenate, naphthenate-based Mg and Ca salts), dispersants [(alkenyl (isobutenyl) succinimides] , Boronated alkenyl succinimides, Mannich condensation products, etc.)], antioxidants (zinc dithiophosphate, amines, hindered phenols, etc.), oil improvers [fatty acids (oleic acid), fatty acid esters, Alkylamines (oleylamine), alcohols (oleyl alcohol), amides (oleamide), etc.], friction wear modifiers (molybdenum dithiophosphate, molybdenum carbamate, etc.), extreme pressure agents (sulfur phosphorus, chlor, etc.), and Phosphorus additives (phosphoric acid alkyl ester, dialkyl phosphite, etc.) It may be added. The addition amount of these other optional components is preferably 0 to 15% with respect to the lubricating oil composition.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, this invention is not limited to these. Unless otherwise specified, “parts” means “parts by mass”.

[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 wt% THF solution solution injection amount: 200 μl
Detector: Refractive index detector Standard: Polystyrene

[Method for measuring syndiotacticity by ¹³ C-NMR]
Apparatus: Bruker A-300
Measuring solvent: CDCL ₃
Measurement sample solution: 100 mg sample dissolved in 0.5 mL CDCL ₃ Sample tube diameter: 5 mm
Integration count: 5120 calculations:
mm: Isotactic carbon integrated value (δ45.4-46.0)
mr: atactic carbon integral value (δ44.8-45.3)
rr: Syndiotactic carbon integral value (δ 44.2 to 44.79)
Syndiotacticity (%) = [rr / (mm + mr + rr)] × 100

[Shear stability test method]
In accordance with JASO M347-95, the test time was 10 hours.

[Test method for viscosity index]
Evaluation was performed according to JIS-K-2283.

Example 1
The inside of the glass reaction vessel with a stirrer and a three-way cock was degassed and replaced with argon. Then, 132 parts of 2,6-di-tert-butylphenol and 300 parts of toluene as a solvent were added, and trimethylaluminum was stirred while stirring. 15,000 parts of 2M hexane solution was added. After removing the solvent in the system at a reduced pressure of 20 mmHg, 27 parts of 2,2′-methylenebis [(4S) -4-tert-butyl-2-oxazoline] and 500 parts of toluene were added. The solution was stirred at 65 ° C. for 15 minutes, then cooled to 25 ° C., 4,000 parts of toluene was added, and 100 parts of the monomer mixture shown in Table 1 was added at the same temperature to initiate polymerization. After 3 hours, the polymerization reaction was stopped by adding 10,000 parts of 0.2 M hydrochloric acid methanol solution. The solution was poured into 500,000 parts of methanol to precipitate the polymer. The precipitated polymer was separated by filtration, washed with methanol, and dried at 60 ° C. under reduced pressure to obtain 70 parts of copolymer (A1), which was used as the viscosity index improver (V1) of Example 1. The syndiotacticity of (A1) was 95%. Thereafter, 50 parts of a viscosity index improver (V1) and 50 parts of solvent refined oil (flash point 160 ° C.) were added at 120 ° C. in a reaction vessel equipped with a stirrer, heating device, cooling device, thermometer and nitrogen blowing tube. The solution was uniformly dissolved and diluted with time to obtain 100 parts of the viscosity index improver concentrated liquid (B1) of the present invention.

Examples 2-5
In the same manner as in Example 1, the viscosity index improvers (V2) to (V5) of the present invention comprising the copolymers (A2) to (A5) were obtained. The syndiotacticity of (A2) to (A5) is shown in Table 2. Thereafter, similarly to Example 1, 50 parts of each of the copolymers (A2) to (A5) was diluted with 50 parts of solvent refined oil, and the viscosity index improver concentrated liquids (B2) to (B5) of the present invention were respectively obtained. 100 parts were obtained.

Example 6
A glass reaction vessel equipped with a stirrer and a cooling device was charged with 100 parts of the monomer mixture shown in Table 1, 1.5 parts of n-lauryl mercaptan, 300 parts of toluene and 200 parts of perfluoro-tert-butanol, and further polymerized. 10 parts of tributylborane was added as an initiator, air was introduced into the reaction system, and the reaction was carried out at −98 ° C. for 480 hours. The obtained product was precipitated in 10,000 parts of methanol in the same manner as in Example 1, filtered, washed, dried, and dried to obtain the viscosity index improver (V6) of the present invention comprising the copolymer (A6). Obtained. The syndiotacticity of (A6) was 92%. Thereafter, in the same manner as in Example 1, 100 parts of a viscosity index improver concentrated liquid (B6) was obtained.

Example 7
In the same manner as in Example 6, a viscosity index improver (V7) of the present invention comprising a copolymer (A7) was obtained. The syndiotacticity of (A7) was 92%. Thereafter, in the same manner as in Example 6, 100 parts of a viscosity index improver concentrated liquid (B7) was obtained.

Example 8
In a reaction vessel equipped with a stirrer and a cooling device, 100 parts of the monomer mixture of Table 1, 2 parts of n-lauryl mercaptan, 300 parts of toluene, 880 parts of perfluoro-tert-butanol were added 18 parts of tributylborane as a polymerization initiator. Part was added, air was introduced into the reaction system, and the reaction was carried out at -78 ° C for 168 hours. In the same manner as in Example 1, it was precipitated in methanol, filtered, washed, and dried to obtain a viscosity index improver (V8) comprising the copolymer (A8) of the present invention. The syndiotacticity of (A8) was 88%. Thereafter, in the same manner as in Example 1, 100 parts of a viscosity index improver concentrated liquid (B8) was obtained.

Example 9
In the same manner as in Example 8, a viscosity index improver (V9) of the present invention comprising a copolymer (A9) was obtained. The syndiotacticity of (A9) was 88%. Thereafter, in the same manner as in Example 8, 100 parts of a viscosity index improver concentrated liquid (B9) was obtained.

Comparative Example 1
In a reaction vessel equipped with a stirrer, a heating device, a cooling device, a thermometer, and a nitrogen blowing tube, 150 parts of toluene, 100 parts of a monomer mixture shown in Table 1, and 2,2′-azobis ( 2,4-Dimethylvaleronitrile) 0.5 part, 1 part of n-lauryl mercaptan was charged as a chain transfer agent, and after nitrogen substitution, a polymerization reaction was carried out at 90 ° C. for 6 hours in a sealed state. In the same manner as in Example 1, it was precipitated in methanol, filtered, washed, and dried to obtain a viscosity index improver (W1) comprising a comparative copolymer (H1). The syndiotacticity of (H1) was 60%. Thereafter, in the same manner as in Example 1, 100 parts of a viscosity index improver concentrated liquid (X1) was obtained.

Comparative Examples 2 and 3
In the same manner as in Comparative Example 1, comparative viscosity index improvers (W2) and (W3) comprising copolymers (H2) and (H3) were obtained. The syndiotacticity of (H2) and (H3) was 59% and 58%, respectively. Thereafter, in the same manner as in Comparative Example 1, 100 parts of each of the viscosity index improver concentrates (X2) and (X3) were obtained.

The abbreviations in Table 1 mean the following monomers.
MMA: Methyl methacrylate M04: Methacrylic acid n-butyl ester M12: Methacrylic acid n-dodecyl ester M14: Methacrylic acid n-tetradecyl ester M16: Methacrylic acid n-hexadecyl ester M24: Methacrylic acid 2-decyltetradecyl ester M32 : Methacrylic acid 2-tetradecyloctadecyl ester MOH: Methacrylic acid 2-hydroxyethyl ester MAA: Methacrylic acid

Table 2 shows physical property values and the like of the copolymers (A1) to (A9) and (H1) to (H3).

Examples 10-18, Comparative Examples 4-6
(B1) to (B9) and (X1) to (X3) are high viscosity index oils (pour point: -22.5 ° C,
(Kinematic viscosity at 100 ° C .: 3.0 mm ² / s) to prepare a lubricating oil composition. Then, the blending amount of the viscosity index improver concentrated liquid was adjusted so that the kinematic viscosity at 100 ° C. of the lubricating oil composition was 6.1 mm ² / s to obtain a test oil, and the shear stability and the viscosity index were evaluated. The obtained evaluation results are shown in Table 3.
The lubricating oil composition according to the present invention has a large viscosity index and a low viscosity reduction rate (%) in a shear stability test.

  Since the viscosity index improver of the present invention has a good viscosity index improving effect and shear stability, it can be used for automobile engine oil, transmission oil [gear oil (for industrial and automobile use), automatic transmission oil (automatic transmission oil, toroidal). CVT oil and belt CVT oil)], power steering oil, shock absorber oil, and the like.

Claims (4)

Viscosity index improver comprising (meth) acrylic acid ester copolymer (A) having a syndiotacticity of 65 to 100% by triad display of the (meth) acrylic acid ester unit chain portion determined by ¹³ C-NMR method .   The copolymer (A) comprises a (meth) acrylic acid alkyl ester (a1) having an alkyl group having 1 to 4 carbon atoms and a (meth) acrylic acid alkyl ester (a3) having an alkyl group having 12 to 32 carbon atoms. The viscosity index improver according to claim 1, wherein the monomer is a monomer, and (a1) is 5 to 50% by mass and (a3) is 50 to 95% by mass based on the mass of all monomers.   A viscosity index improver concentrate comprising the viscosity index improver according to claim 1 or 2 and a solvent, wherein the viscosity index improver / solvent mass ratio is 10/90 to 95/5.   A lubricating oil composition comprising the viscosity index improver or viscosity index improver concentrate according to claim 1 and a base oil.