JP2021014578A - Viscosity index improver and lubricant composition - Google Patents

Abstract

To provide a viscosity index improver and a lubricant composition containing the same, wherein the viscosity index improver has a high viscosity index and good solubility in an engine oil to which an essential additive is added, and a lubricating oil supplemented with the viscosity index improver has an excellent low temperature viscosity at -40°C.SOLUTION: The viscosity index improver comprises a copolymer (A) and a base oil, wherein the copolymer (A) contains a polyolefin-based monomer (a1) represented by a general formula (1) and a polyolefin-based monomer (a2) represented by a general formula (2) as constituent monomers, the copolymer (A) contains 1 to 14 wt.% of (a1) and 1 to 14 wt.% of (a2) based on total weight of the monomers constituting (A) as constituent monomers, and an absolute value of difference in solubility parameter between the copolymer (A) and the base oil is 0.8 to 2.0 (cal/cm3)1/2.SELECTED DRAWING: None

Description

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

In recent years, in order to reduce CO ₂ emissions and protect petroleum resources, fuel efficiency of automobiles has been further demanded. One of the fuel efficiency reductions is the reduction of viscous resistance by reducing the viscosity of engine oil. However, when the viscosity is lowered, problems such as liquid leakage and seizure occur. Therefore, engine oil contains various additives such as detergents, dispersants, antioxidants, oiliness improvers, friction and wear modifiers, extreme pressure agents, defoamers, anti-emulsifiers and corrosion inhibitors as essential components. ing. In cold regions, low temperature startability is required. This problem is stipulated in the US SAE engine oil viscosity standard (SAE J300), and in the 0W-20 grade, the viscosity under high temperature and high shear (HTHS viscosity) is 150 ° C. HTHS viscosity (THHS viscosity). ASTM D4683 or D5481) is specified to be 2.6 mPa · s or more. In addition, the same grade is specified to have a low temperature viscosity of 60,000 mPa · s or less at -40 ° C and no yield stress (ASTM D4684) in order to guarantee startability in cold regions. In order to reduce fuel consumption, an engine oil having a lower HTHS viscosity in an effective temperature range of 100 ° C. after satisfying the above standards is required, and various viscosity index improvers have been conventionally proposed. Known examples of such a viscosity index improver include methacrylate copolymers (Patent Documents 1 to 4), olefin copolymers (Patent Document 5), comb-type copolymers (Patent Documents 6 to 8), and the like. ing.
However, when the above-mentioned viscosity index improver is added to the engine oil composition, the reduction of the low-temperature viscosity at −40 ° C. is still insufficient and the fluidity is lost. Further, there is a problem that the solubility in the engine oil to which the essential additive is added to the engine oil is poor.

Japanese Patent No. 6060311 Japanese Patent No. 2732187 Japanese Patent No. 2754343 Japanese Patent No. 3831203 Japanese Patent No. 3999307 Japanese Patent No. 3474918 Japanese Patent Publication No. 2008-546894 Special Table 2010-532805

In the present invention, the lubricating oil to which the viscosity index improver is added has excellent low-temperature viscosity at −40 ° C., the solubility in the engine oil to which the essential additive for the engine oil is added is good, and the viscosity index is improved. An object of the present invention is to provide an agent and a lubricating oil composition containing the same.

The present inventors have arrived at the present invention as a result of studies for achieving the above object.
That is, the present invention is a copolymer containing a polyolefin-based monomer (a1) represented by the following general formula (1) and a polyolefin-based monomer (a2) represented by the following general formula (2) as constituent monomers. A viscosity index improver containing (A) and a base oil, wherein (A) is the above-mentioned (a1) based on the total weight of the monomers constituting (A) as constituent monomers. It is a copolymer containing 1 to 14% by weight of the above (a2) and 1 to 14% by weight of the above (a2), and the absolute value of the difference between the dissolution parameters of the (A) and the base oil is 0.8 to 2.0. (Cal / cm ³ ) ^1/2 viscosity index improver; the viscosity index improver, a cleaning agent, a dispersant, an antioxidant, an oiliness improver, a flow point lowering agent, a friction wear adjuster, and an extreme pressure agent. , A lubricating oil composition containing at least one additive selected from the group consisting of antifoaming agents, anti-emulsifying agents, metal inactivating agents and corrosion inhibitors.

［Ｒ^１は水素原子又はメチル基；−Ｘ^１−は−Ｏ−、−Ｏ（ＡＯ）_ｍ−又は−ＮＨ−で表される基であって、Ａは炭素数２〜４のアルキレン基であり、ｍは１〜１０の整数であり、ｍが２以上の場合のＡは同一でも異なっていてもよい；Ｒ^２は１，２−ブチレン基を構成単位として含む炭化水素重合体から水素原子を１つ除いた残基であり、１，２−ブチレン基を構成単位として含む炭化水素重合体において、全構成単位中の１，２−ブチレン基の比率は１〜５５モル％；ｐは０又は１の数。］

[R ¹ is a hydrogen atom or a methyl group; -X ^1- is a group represented by -O-, -O (AO) _m- or -NH-, and A is an alkylene group having 2 to 4 carbon atoms. Yes, m is an integer of 1-10, and A when m is 2 or more may be the same or different; R ² is a hydrogen atom from a hydrocarbon polymer containing a 1,2-butylene group as a constituent unit. In the hydrocarbon polymer containing 1,2-butylene group as a constituent unit, the ratio of 1,2-butylene group to all the constituent units is 1 to 55 mol%; p is 0. Or the number of 1. ]

［Ｒ^３は水素原子又はメチル基；−Ｘ^２−は−Ｏ−、−Ｏ（ＡＯ）_ｎ−又は−ＮＨ−で表される基であって、Ａは炭素数２〜４のアルキレン基であり、ｎは１〜１０の整数であり、ｎが２以上の場合のＡは同一でも異なっていてもよい；Ｒ^４は１，２−ブチレン基を構成単位として含む炭化水素重合体から水素原子を１つ除いた残基であり、１，２−ブチレン基を構成単位として含む炭化水素重合体において、全構成単位中の１，２−ブチレン基の比率は５６〜１００モル％；ｑは０又は１の数。］

[R ³ is a hydrogen atom or a methyl group; -X ^2- is a group represented by -O-, -O (AO) _n- or -NH-, and A is an alkylene group having 2 to 4 carbon atoms. There, n is an integer of 1 to 10, n is 2 or more a case may be the same or different; a hydrogen atom from a hydrocarbon polymer containing R ⁴ is 1,2-butylene group as the structural unit In the hydrocarbon polymer containing 1,2-butylene group as a constituent unit, the ratio of 1,2-butylene group to all the constituent units is 56 to 100 mol%; q is 0. Or the number of 1. ]

The viscosity index improver of the present invention and the lubricating oil composition containing the same have a low low-temperature viscosity at −40 ° C. and have good solubility in an engine oil to which an essential additive is added to the engine oil. , Has the effect of having a high viscosity index.

The present invention relates to a polyolefin-based monomer (a1) represented by the following general formula (1) (hereinafter, may be abbreviated as the monomer (a1)) and a polyolefin-based monomer represented by the following general formula (2). A viscosity index improver containing a copolymer (A) containing a monomer (a2) (hereinafter sometimes abbreviated as a monomer (a2)) as a constituent monomer and a base oil. The (A) contains 1 to 14% by weight of the (a1) and 1 to 14% by weight of the (a2) based on the total weight of the monomers constituting the (A) as the constituent monomers. It is a copolymer and is a viscosity index improver in which the absolute value of the difference between the dissolution parameters of the (A) and the base oil is 0.8 to 2.0 (cal / cm ³ ) ^1/2 .

［Ｒ^１は水素原子又はメチル基；−Ｘ^１−は−Ｏ−、−Ｏ（ＡＯ）_ｍ−又は−ＮＨ−で表される基であって、Ａは炭素数２〜４のアルキレン基であり、ｍは１〜１０の整数であり、ｍが２以上の場合のＡは同一でも異なっていてもよい；Ｒ^２は１，２−ブチレン基を構成単位として含む炭化水素重合体から水素原子を１つ除いた残基であり、１，２−ブチレン基を構成単位として含む炭化水素重合体において、全構成単位中の１，２−ブチレン基の比率は１〜５５モル％；ｐは０又は１の数。］

[R ¹ is a hydrogen atom or a methyl group; -X ^1- is a group represented by -O-, -O (AO) _m- or -NH-, and A is an alkylene group having 2 to 4 carbon atoms. Yes, m is an integer of 1-10, and A when m is 2 or more may be the same or different; R ² is a hydrogen atom from a hydrocarbon polymer containing a 1,2-butylene group as a constituent unit. In the hydrocarbon polymer containing 1,2-butylene group as a constituent unit, the ratio of 1,2-butylene group to all the constituent units is 1 to 55 mol%; p is 0. Or the number of 1. ]

［Ｒ^３は水素原子又はメチル基；−Ｘ^２−は−Ｏ−、−Ｏ（ＡＯ）_ｎ−又は−ＮＨ−で表される基であって、Ａは炭素数２〜４のアルキレン基であり、ｎは１〜１０の整数であり、ｎが２以上の場合のＡは同一でも異なっていてもよい；Ｒ^４は１，２−ブチレン基を構成単位として含む炭化水素重合体から水素原子を１つ除いた残基であり、１，２−ブチレン基を構成単位として含む炭化水素重合体において、全構成単位中の１，２−ブチレン基の比率は５６〜１００モル％；ｑは０又は１の数。］

[R ³ is a hydrogen atom or a methyl group; -X ^2- is a group represented by -O-, -O (AO) _n- or -NH-, and A is an alkylene group having 2 to 4 carbon atoms. There, n is an integer of 1 to 10, n is 2 or more a case may be the same or different; a hydrogen atom from a hydrocarbon polymer containing R ⁴ is 1,2-butylene group as the structural unit In the hydrocarbon polymer containing 1,2-butylene group as a constituent unit, the ratio of 1,2-butylene group to all the constituent units is 56 to 100 mol%; q is 0. Or the number of 1. ]

<Viscosity index improver>
The viscosity index improver of the present invention contains the polyolefin-based monomer (a1) represented by the general formula (1) and the polyolefin-based monomer (a2) represented by the general formula (2) as constituent monomers. Contains the copolymer (A) containing. In the following, the monomers (a1) and (a2) may be collectively abbreviated as the monomer (a).

<Copolymer (A)>
The monomer (a1) constituting the copolymer (A) is represented by the above general formula (1), and the monomer (a2) is represented by the above general formula (2).
One type of each of the monomers (a1) and (a2) may be used, or two or more types may be used in combination.

R ¹ in the general formula (1) is a hydrogen atom or a methyl group. Of these, a methyl group is preferable from the viewpoint of the effect of improving the viscosity index.
-X ^1- in the general formula (1) is a group represented by -O-, -O (AO) _m- or NH-.
A is an alkylene group having 2 to 4 carbon atoms, and examples thereof include an ethylene group, a 1,2- or 1,3-propylene group, and a 1,2-, 1,3- or 1,4-butylene group.
AO is an alkyleneoxy group having 2 to 4 carbon atoms, such as an ethyleneoxy group, a 1,2- or 1,3-propyleneoxy group, and a 1,2-, 1,3- or 1,4-butyleneoxy group. Can be mentioned.
m is the number of moles of alkylene oxide added, and is an integer of 1 to 10, preferably an integer of 1 to 4, and more preferably an integer of 1 to 2 from the viewpoint of the effect of improving the viscosity index.
When m is 2 or more, A may be the same or different, and the binding form of the (AO) _m portion may be random or block.
Of −X ^{1−, the} group represented by −O− or −O (AO) _m− is preferable from the viewpoint of the effect of improving the viscosity index, and more preferably −O− or −O (CH ₂ CH). ₂ O) It is a group represented by ₁ −.
p is a number of 0s or 1s.

R ³ in the general formula (2) is a hydrogen atom or a methyl group. Of these, a methyl group is preferable from the viewpoint of the effect of improving the viscosity index.
-X ^2- in the general formula (2) is a group represented by -O-, -O (AO) _n- or NH-.
A is an alkylene group having 2 to 4 carbon atoms, and examples thereof include an ethylene group, a 1,2- or 1,3-propylene group, and a 1,2-, 1,3- or 1,4-butylene group. AO is an alkyleneoxy group having 2 to 4 carbon atoms, such as an ethyleneoxy group, a 1,2- or 1,3-propyleneoxy group, and a 1,2-, 1,3- or 1,4-butyleneoxy group. Can be mentioned.
n is the number of moles of alkylene oxide added, and is an integer of 1 to 10, preferably an integer of 1 to 4, and more preferably an integer of 1 to 2 from the viewpoint of the effect of improving the viscosity index.
When n is 2 or more, A may be the same or different, and the binding form of the (AO) _n portion may be random or block.
-X ² - among the preferred from the viewpoint of the viscosity index improving effect, -O- or -O _{(AO) n} - is a group represented by even more preferably -O- or -O _(CH 2 CH ₂ O) It is a group represented by ₁ −.
q is a number of 0s or 1s.

R ² in the general formula (1) is a residue obtained by removing one hydrogen atom from a hydrocarbon polymer having a number average molecular weight of 1,000 or more containing a 1,2-butylene group as an essential constituent unit.
The 1,2-butylene group is a group represented by −CH ₂ CH (CH ₂ CH ₃ ) − or −CH (CH ₂ CH ₃ ) CH ₂ −.
In the hydrocarbon polymer containing 1,2-butylene group as a constituent unit, the ratio of 1,2-butylene group in all the constituent units is 1 to 55 mol%, and the low temperature viscosity, gelation index and viscosity index improver. From the viewpoint of solubility in the lubricating oil to which various additives other than the above are added, 10 to 53 mol% is preferable, and more preferably 20 to 50 mol%.

R ⁴ in the general formula (2) is a residue obtained by removing one hydrogen atom from a hydrocarbon polymer having a number average molecular weight of 1,000 or more containing a 1,2-butylene group as an essential constituent unit. In the hydrocarbon polymer containing 1,2-butylene group as a constituent unit, the ratio of 1,2-butylene group in all the constituent units is 56 to 100 mol%, which is 58 from the viewpoint of low temperature viscosity and gelation index. It is preferably ~ 90 mol%, more preferably 60-80 mol%.

Hydrocarbon polymers containing a 1,2-butylene group as a constituent unit include those having 37 or more carbon atoms, and a polymer using 1-butene as a constituent monomer (unsaturated hydrocarbon (x)). And a polymer obtained by hydrocarbonizing the double bond of the 1,2-additive obtained by polymerizing 1,3-butadiene.

In the hydrocarbon polymer containing 1,2-butylene group as a constituent unit in the general formula (1) and the general formula (2), the ratio of 1,2-butylene group in all the constituent units is measured by ¹³ C-NMR. can do. Specifically, assuming that only a monomer having 4 carbon atoms is used, the hydrocarbon polymer can be analyzed by ¹³ C-NMR and calculated and determined using the following mathematical formula (1). .. ^{In 13} C-NMR, a peak derived from the tertiary carbon atom of the 1,2-butylene group appears in the integrated value (integrated value A) of 26 to 27 ppm. It can be obtained from the integrated value of the above peaks and the integrated value (integrated value B) relating to the peak of all carbon of the hydrocarbon polymer.
Ratio of 1,2-butylene groups (mol%) = {(integral value A) x 4} / (integral value B) x 100 (1)
To increase the ratio of 1,2-butylene groups, for example, in anionic polymerization using 1,3-butadiene, the reaction temperature should be below the boiling point of 1,3-butadiene (-4.4 ° C). It suffices to lower the amount of the polymerization initiator added to 1,3-butadiene, and to reduce the ratio of 1,2-butylene groups, the reaction temperature should be above the boiling point of 1,3-butadiene. The temperature may be increased and the amount of the initiator may be increased.

In the general formula (1) hydrocarbon polymer containing a constitutional unit ratio (1,2-butylene group among 1,3-butadiene and 1-butene of the total monomers constituting the R ² in the total structure single The weight ratio of 1,3-butadiene and 1-butene in the polymer) is preferably 50% by weight or more, more preferably 75% by weight or more, and further preferably 85% by weight from the viewpoint of the effect of improving the viscosity index. As mentioned above, it is particularly preferably 90% by weight or more.
In the general formula (2) a hydrocarbon polymer containing a constitutional unit ratio (1,2-butylene group among 1,3-butadiene and 1-butene of the total monomers constituting the R ⁴ in the entire configuration single The weight ratio of 1,3-butadiene and 1-butene in the polymer) is preferably 50% by weight or more, more preferably 75% by weight or more, and further preferably 85% by weight from the viewpoint of the effect of improving the viscosity index. As mentioned above, it is particularly preferably 90% by weight or more.

In the structure derived from 1,3-butadiene and 1-butene constituting a part or all of R ^{2 in} the general formula (1), the molar ratio of 1,2-butylene group and 1,4-butylene group (1, The 2-butylene group / 1,4-butylene group) is preferably 1/99 to 55/45, more preferably 10/90 to 53/47, and particularly preferably 20 /, from the viewpoint of the viscosity index improving effect and the low temperature viscosity. It is 80 to 50/50.
In the general formula (2) constitutes a part or all of ^{R 4} in 1,3-butadiene and 1-butene-derived structure, 1,2-butylene and 1,4-butylene group molar ratio (1, 2-butylene group / 1,4-butylene group) is preferably 56/44 to 100/0, more preferably 58/46 to 90/10, particularly from the viewpoint of viscosity index improving effect, low temperature viscosity, and gelation index. It is preferably 60/40 to 80/20.

The molar ratio of 1,2-butylene group / 1,4-butylene group in the structure derived from 1,3-butadiene and 1-butene constituting a part or all of R ^{2 in} the general formula (1) is ¹ H-. It can be measured by NMR, ¹³ C-NMR, Raman spectroscopy, or the like. Formula (2) the molar ratio of 1,2-butylene group and 1,4-butylene group in the 1,3-butadiene and 1-butene-derived structure constituting a part or all of ^{R 4} in (1 The same applies to −butylene group / 1,4-butylene group).
To increase the ratio of 1,2-butylene groups, for example, in anionic polymerization using 1,3-butadiene, the reaction temperature should be below the boiling point of 1,3-butadiene (-4.4 ° C). It suffices to lower the amount of the polymerization initiator added to 1,3-butadiene, and to reduce the ratio of 1,2-butylene groups, the reaction temperature should be above the boiling point of 1,3-butadiene. The temperature may be increased and the amount of the initiator may be increased.

The hydrocarbon polymer containing a 1,2-butylene group as a constituent unit contains the following (1) to (3) as an unsaturated hydrocarbon (x) in addition to 1-butene and 1,3-butadiene. It may be a body.
(1) Aliphatic unsaturated hydrocarbons [olefins having 2-36 carbon atoms (for example, ethylene, propylene, 2-butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, triacene, hexatriacene, etc.) and Dienes having 4 to 36 carbon atoms (for example, isoprene, 1,4-pentadiene, 1,5-hexadiene, 1,7-octadiene, etc.)]
(2) Alicyclic unsaturated hydrocarbons [for example, cyclohexene, (di) cyclopentadiene, pinene, limonene, indene, vinylcyclohexene, etylidene bicycloheptene, etc.]
(3) Aromatic group-containing unsaturated hydrocarbons (for example, styrene, α-methylstyrene, vinyltorene, 2,4-dimethylstyrene, ethylstyrene, isopropylstyrene, butylstyrene, phenylstyrene, cyclohexylstyrene, benzylstyrene, crotyl) Styrene, vinylnaphthalene, divinylbenzene, divinyltoluene, divinylxylene, trivinylbenzene, etc.) and the like can be mentioned.
The hydrocarbon polymer composed of these may be a block polymer or a random polymer. When the hydrocarbon polymer has a double bond, a part or all of the double bond may be hydrogenated by hydrogenation.
The weight ratio of the constituent monomers derived from unsaturated hydrocarbons other than 1-butene and 1,3-butadiene in the monomers (a1) and (a2) is preferably 50% by weight or less, more preferably 25% by weight. Next, it is more preferably 15% by weight or less, and particularly preferably 10% by weight or less.

The monomers (a1) and (a2) are esterified with (meth) acrylic acid from the polymer (Y) having a hydroxyl group introduced at one end of the above-mentioned hydrocarbon polymer and containing a hydroxyl group at one end. , Or it can be obtained by an ester exchange reaction with an alkyl (meth) acrylate (preferably having 1 to 4 carbon atoms) such as methyl (meth) acrylate.
In addition, "(meth) acrylic" means "acrylic and / or methacrylic".

Specific examples of the polymer (Y) containing a hydroxyl group at one end include the following (Y1) to (Y4).
An alkylene oxide adduct (Y1); an alkylene oxide (ethylene oxide, propylene oxide, etc.) is added to a polymer obtained by polymerizing an unsaturated hydrocarbon (x) in the presence of an ion polymerization catalyst (lithium catalyst, sodium catalyst, etc.). (In the general formula (1), -X ¹ -is − (AO) _m − and p = 0; in the general formula (2), −X ² − is − (AO) _n − and q = 0).
Hydroboration product (Y2); hydroboration reaction product of a polymer of unsaturated hydrocarbon (x) having a double bond at one end (for example, as described in US Pat. No. 4,316,973), etc. (In the general formula (1), -X ^1- is -O- and p = 0; in the general formula (2), -X ^2- is -O- and q = 0. ).
Maleic anhydride-ene-aminoalcohol adduct (Y3); Amino alcohol is a reaction product obtained by an ene reaction between a polymer of unsaturated hydrocarbon (x) having a double bond at one end and maleic anhydride. (In the general formula (1), -X ^1- is -O- and p = 1; in the general formula (2), -X ^2- is -O-. And q = 1).
Hydroformyl-hydride (Y4); obtained by hydroformylating a polymer of unsaturated hydrocarbon (x) having a double bond at one end and then hydrogenating (for example, JP-A-63-175096). (In the general formula (1), -X ^1- is -O- and p = 0; in the general formula (2), -X ^2- is -O-, Q = 0).
Among these polymers (Y) containing a hydroxyl group at one end, from the viewpoint of improving the HTHS viscosity and viscosity index, the alkylene oxide adduct (Y1), the hydroborohydride (Y2) and the maleic anhydride are preferable. An en-aminoalcohol adduct (Y3), more preferably an alkylene oxide adduct (Y1).

The polymer (Y) preferably has a specific solubility parameter (hereinafter, may be abbreviated as SP value) from the viewpoint of solubility in lubricating oil. The range of the SP value is preferably 7.0 to 9.0 (cal / cm ³ ) ^1/2 , and more preferably 7.3 to 8.5 (cal / cm ³ ) ^1/2 .
The SP value in the present invention is determined by the mole fraction of the monomer (unsaturated hydrocarbon (x)) used in the Fedors method (Polymer Engineering and Science, February, 1974, Vol. 14, No. 2 P. et al. It is a value calculated by the method described in 147 to 154).
The SP value of the polymer (Y) can be set in a desired range by appropriately adjusting the SP value and mole fraction of the monomer (unsaturated hydrocarbon (x)) to be used.

The weight average molecular weight (hereinafter abbreviated as Mw) and the number average molecular weight (hereinafter abbreviated as Mn) of the monomers (a1) and (a2) are determined by gel permeation chromatography (hereinafter abbreviated as GPC) under the following conditions. Can be measured.
<Measurement conditions for Mw and Mn of monomers (a1) and (a2)>
Equipment: "HLC-8320GPC" [manufactured by Tosoh Corporation]
Column: 2 "TSKgel GMHXL" [manufactured by Tosoh Corporation]
"TSKgel Multipore H _XL- M 1 measurement temperature: 40 ° C
Sample solution: 0.25 wt% tetrahydrofuran solution Injection volume: 10.0 μl
Detection device: Refractive index detector Reference material: Standard polystyrene (TS reference material: Standard polystyrene (TSK standard POLYSTYRENE)
12 points (molecular weight: 589, 1,050, 2,630, 9,100, 19,500, 37,900, 96, 400, 190,000, 355,000, 1,090,000, 2,110,000 , 4,480,000) [manufactured by Tosoh Corporation]

The Mn of the monomers (a1) and (a2) is preferably 800 to 10,000, more preferably 1,000 to 9,000, and particularly preferably 1,200 to 8,500, respectively. When the Mn of the monomers (a1) and (a2) is 800 or more, the viscosity index improving effect tends to be good, and when it is 10,000 or less, the shear stability during long-term use tends to be good. There is.

In the copolymer (A), the weight ratio of the monomer (a1) to the constituent monomers of (A) is 1 to 14% by weight based on the total weight of the monomers constituting (A). From the viewpoint of the effect of improving the viscosity index, 2 to 12% by weight is preferable, and 5 to 10% by weight is more preferable.
When it is 1% by weight or more, the low temperature viscosity, viscosity index and shear stability are good. Further, when it is 14% by weight or less, the low temperature viscosity is good.

In the copolymer (A), the weight ratio of the monomer (a2) to the constituent monomers of (A) is 1 to 14% by weight based on the total weight of the monomers constituting (A). From the viewpoint of the effect of improving the viscosity index, 2 to 12% by weight is preferable, and 5 to 10% by weight is more preferable.
When it is 1% by weight or more, the viscosity index is good. Further, when it is 14% by weight or less, the solubility in the additive-containing base oil and the low temperature viscosity are good.

In the copolymer (A), the ratio of 1,2-butylene groups in all the constituent units in the hydrocarbon polymer constituting the monomer (a1) and the hydrocarbon polymer constituting the monomer (a2). The difference from the ratio of 1,2-butylene groups in all the constituent units in [{(a2) 1,2-butylene group ratio}-{(a1) 1,2-butylene group ratio}] is the low temperature viscosity. And from the viewpoint of gelation index, it is preferably 10 to 60.

［Ｒ^５は水素原子又はメチル基；−Ｘ^３−は−Ｏ−又は−ＮＨ−で表される基；Ｒ^６は炭素数２〜４のアルキレン基；Ｒ^７は炭素数１〜８のアルキル基；ｒは１〜２０の整数であり、ｒが２以上の場合のＲ^６は同一でも異なっていてもよい。］ In the present invention, the copolymer (A) has a copolymer weight of the monomer (b) represented by the following general formula (3) as a constituent monomer in addition to the above-mentioned monomers (a1) and (a2). The coalescence is preferable from the viewpoint of shear stability and viscosity index.
As the monomer (b), one type may be used, or two or more types may be used in combination.

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

R ⁵ in the general formula (3) is a hydrogen atom or a methyl group. Of these, a methyl group is preferable from the viewpoint of the effect of improving the viscosity index.
-X ^3- in the general formula (3) is a group represented by -O- or -NH-. Of these, from the viewpoint of the effect of improving the viscosity index, the group represented by −O− is preferable.
R ⁶ in the general formula (3) is an alkylene group having 2 to 4 carbon atoms. The alkylene group having 2 to 4 carbon atoms includes an ethylene group, an isopropylene group, a 1,2- or 1,3-propylene group, an isobutylene group, and a 1,2-, 1,3- or 1,4-butylene group. And so on.
R in the general formula (3) is an integer of 1 to 20, preferably an integer of 1 to 5, and more preferably an integer of 1 to 2 from the viewpoint of the viscosity index improving effect and the low temperature viscosity.
When r is 2 or more, R ⁶ O may be the same or different, and the binding form of the (R ⁶ O) _r portion may be random or block.

R ⁷ in the general formula (3) is an alkyl group having 1 to 8 carbon atoms. Specifically, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, n-heptyl group, isoheptyl group, n-hexyl group, 2-ethylhexyl group, Examples thereof include an n-pentyl group and an n-octyl group.
Among the alkyl groups having 1 to 8 carbon atoms, the alkyl group having 1 to 7 carbon atoms is preferable from the viewpoint of the effect of improving the viscosity index, and the alkyl group having 1 to 6 carbon atoms is particularly preferable. Alkyl groups having 1 to 5 carbon atoms, most preferably alkyl groups having 2 or 4 carbon atoms.

Specifically, as the monomer (b), methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, pentyloxyethyl (meth) acrylate, and hexyloxy. Ethyl (meth) acrylate, heptyloxyethyl (meth) acrylate, octyloxyethyl (meth) acrylate, methoxypropyl (meth) acrylate, ethoxypropyl (meth) acrylate, propoxypropyl (meth) acrylate, butoxypropyl (meth) acrylate, Pentyloxypropyl (meth) acrylate, hexyloxypropyl (meth) acrylate, heptyloxypropyl (meth) acrylate, octyloxypropyl (meth) acrylate, methoxybutyl (meth) acrylate, ethoxybutyl (meth) acrylate, propoxybutyl (meth) ) Acrylate, butoxybutyl (meth) acrylate, pentyloxybutyl (meth) acrylate, hexyloxybutyl (meth) acrylate, heptyloxybutyl (meth) acrylate and octyloxybutyl (meth) acrylate, and alcohols having 1 to 8 carbon atoms. Examples thereof include an esterified product with (meth) acrylic acid added with 2 to 20 mol of at least one selected from the group consisting of ethylene oxide, propylene oxide and butylene oxide.
Among the monomers (b), ethoxyethyl (meth) acrylate and butoxyethyl (meth) acrylate are preferable from the viewpoint of the effect of improving the viscosity index.
In addition, "(meth) acrylate" means "acrylate and / or methacrylate".

In the copolymer (A), the weight ratio of the monomer (b) among the constituent monomers of (A) is the monomer constituting (A) from the viewpoint of shear stability and viscosity index improving effect. From 3 to 65% by weight, more preferably 3 to 50% by weight, based on the total weight of.

In the present invention, the copolymer (A) further has a (meth) acrylic acid alkyl ester (c) having an alkyl group having 1 to 4 carbon atoms other than the monomer (b) (hereinafter, the monomer (c)). (May be abbreviated as) and / or (meth) acrylic acid alkyl ester (d) having a linear or branched alkyl group having 9 to 36 carbon atoms (hereinafter, may be abbreviated as monomer (d)). It is preferable that the copolymer contains the above as a constituent monomer from the viewpoint of the effect of improving the viscosity index.
One type of each of the monomers (c) and (d) may be used, or two or more types may be used in combination.

Specific examples of the (meth) acrylic acid alkyl ester (c) having an alkyl group having 1 to 4 carbon atoms include an esterified product of a linear or branched alcohol having 1 to 4 carbon atoms and (meth) acrylic acid. Examples include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl (meth) acrylate. Can be mentioned.
Of (c), methyl (meth) acrylate, ethyl (meth) acrylate and n-butyl (meth) acrylate are preferable from the viewpoint of the effect of improving the viscosity index, and (meth) acrylic is more preferable. Ethyl acrylate and n-butyl (meth) acrylate.

In the copolymer (A), the weight ratio of the monomer (c) to the constituent monomers of (A) is the total weight of the monomers constituting (A) from the viewpoint of the effect of improving the viscosity index. Based on this, it is preferably 1 to 80% by weight, more preferably 2 to 70% by weight.

［Ｒ^８は水素原子又はメチル基；−Ｘ^４−は−Ｏ−又は−ＮＨ−で表される基；Ｒ^９Ｏは炭素数２〜４のアルキレンオキシ基；Ｒ^１０及びＲ^１１はそれぞれ独立に炭素数１〜２４の直鎖アルキル基であり、Ｒ^１０及びＲ^１１の合計炭素数は７〜３４；ｓは０〜２０の整数であり、ｓが２以上の場合のＲ^９Ｏは同一でも異なっていてもよい。］ In the present invention, the copolymer (A) is preferably a copolymer containing the monomer (d) as a constituent monomer from the viewpoint of solubility in the base oil.
The monomer (d) is other than (a1) and (a2), and has a (meth) acrylic acid alkyl ester (d1) having a linear alkyl group having 9 to 36 carbon atoms and the following general formula (4). ) Includes a (meth) acrylic acid alkyl ester (d2) having a branched alkyl group having 9 to 36 carbon atoms.
As the monomer (d), one type may be used, or two or more types may be used in combination.

^{[R 8} is a hydrogen atom or a methyl group; -X ⁴ - is -O- or -NH- with a group represented; ^{R 9} O alkyleneoxy group having 2 to 4 carbon ^atoms; each independently are ^{R 10} and ^{R 11} Is a linear alkyl group having 1 to 24 carbon atoms, and the total carbon number of R ¹⁰ and R ¹¹ is 7 to 34; s is an integer of 0 to 20, and R ⁹ O is the same when s is 2 or more. But it can be different. ]

Examples of the (meth) acrylic acid alkyl ester (d1) having a linear alkyl group having 9 to 36 carbon atoms (hereinafter, may be abbreviated as monomer (d1)) include n-nonyl (meth) acrylic acid. N-decyl (meth) acrylate, n-undecyl (meth) acrylate, n-dodecyl (meth) acrylate, n-tridecyl (meth) acrylate, n-tetradecyl (meth) acrylate, (meth) acrylate n-pentadecyl, n-hexadecyl (meth) acrylate, n-octadecyl (meth) acrylate, n-icosyl (meth) acrylate, n-tetracosyl (meth) acrylate, n-triacontyl (meth) acrylate, ( Examples thereof include esterified products of n-hexatriacontyl acrylate and alkylene oxide (2-4 carbon atoms) of linear alcohol having 9 to 36 carbon atoms and (meth) acrylic acid. ..
Among the monomers (d1), from the viewpoint of the effect of improving the viscosity index, a (meth) acrylic acid alkyl ester having a linear alkyl group having 12 to 28 carbon atoms is preferable, and a (meth) acrylic acid alkyl ester having 12 to 28 carbon atoms is more preferable. A (meth) acrylic acid ester having 24 linear alkyl groups is particularly preferable, and a (meth) acrylic acid ester having a linear alkyl group having 12 to 20 carbon atoms is particularly preferable.
One type of monomer (d1) may be used, or two or more types may be used in combination.

In the monomer (d2), R ⁸ in the general formula (4) is a hydrogen atom or a methyl group. Of these, a methyl group is preferable from the viewpoint of the effect of improving the viscosity index.
-X ⁴ in the general formula (4) - is a group represented by -O- or -NH-. Of these, from the viewpoint of the effect of improving the viscosity index, the group represented by −O− is preferable.
R ⁹ in the general formula (4) is an alkylene group having 2 to 4 carbon atoms. Examples of the alkylene group having 2 to 4 carbon atoms include an ethylene group, an isopropylene group, a 1,2- or 1,3-propylene group, an isobutylene group and a 1,2-1,3- or 1,4-butylene group. Can be mentioned.
In the general formula (4), s is an integer of 0 to 20, and from the viewpoint of the effect of improving the viscosity index, an integer of 0 to 5 is preferable, and an integer of 0 to 2 is more preferable.
When s is 2 or more, R ⁹ O may be the same or different, and the (R ⁹ O) _s portion may be a random bond or a block bond.
R ¹⁰ and R ¹¹ in the general formula (4) are independently linear alkyl groups having 1 to 24 carbon atoms. Specifically, methyl group, ethyl group, n-propyl group, n-butyl group, n-heptyl group, n-hexyl group, n-pentyl group, n-octyl group, n-nonyl group, n-decyl group. , N-Undecyl group, n-dodecyl group, n-tetradecyl group, n-hexadecyl group, n-octadecyl group, n-eicosyl group, n-tetracosyl group and the like. Among the linear alkyl groups having 1 to 24 carbon atoms, the linear alkyl groups having 6 to 24 carbon atoms are preferable from the viewpoint of the effect of improving the viscosity index, and the linear alkyl groups having 6 to 20 carbon atoms are more preferable. Alkyl groups, particularly preferably linear alkyl groups having 8 to 16 carbon atoms.
The total number of carbon atoms of R ¹⁰ and R ¹¹ is 7 to 34, preferably 12 to 30 from the viewpoint of the effect of improving the viscosity index, and more preferably 14 to 26.

Specifically, as the monomer (d2), 2-octyldecyl (meth) acrylic acid, an esterified product of ethylene glycol mono-2-octylpentadecyl ether and (meth) acrylic acid, 2-octyl (meth) acrylic acid. n-octyldodecyl, 2-n-decyltetradecyl (meth) acrylate, 2-n-dodecylhexadecyl (meth) acrylate, 2-n-tetradecyl octadecyl (meth) acrylate, 2 (meth) acrylic acid -N-dodecyl pentadecyl, 2-n-tetradecyl heptadecyl (meth) acrylate, 2-n-hexadecyl heptadecyl (meth) acrylate, 2-n-heptadecyl icosyl (meth) acrylate, ( 2-n-Hexadecyldocosyl (meth) acrylate, 2-n-eicosyldocosyl (meth) acrylate, 2-n-tetracosylhexacosyl (meth) acrylate and N-2-octyldecyl (meth) Meta) Acrylic acid and the like can be mentioned.
One type of monomer (d2) may be used, or two or more types may be used in combination.

Among the monomer (d), (meth) acrylic having a branched alkyl group having 9 to 36 carbon atoms represented by the above general formula (4) is preferable from the viewpoint of solubility in base oil and low temperature viscosity. The acid alkyl ester (d2) is more preferable, and a (meth) acrylic acid alkyl ester having a branched alkyl group having 14 to 32 carbon atoms in (d2) is particularly preferable, and 16 to 16 carbon atoms in (d2) are particularly preferable. It is a (meth) acrylic acid alkyl ester having 28 branched alkyl groups.

In the copolymer (A), the weight ratio of the monomer (d) among the constituent monomers of (A) is determined by (A) from the viewpoint of setting the viscosity index and the copolymer (A) to a preferable SP value. It is preferably 1 to 60% by weight, more preferably 5 to 35% by weight, based on the total weight of the monomers constituting the above.

In addition to the above-mentioned monomers (a) to (d), the copolymer (A) in the present invention includes a nitrogen atom-containing monomer (e), a hydroxyl group-containing monomer (f), and a phosphorus atom-containing monomer. At least one monomer selected from the group consisting of (g) and the aromatic ring-containing vinyl monomer (h) may be used as the constituent monomer.
One type of each of the monomers (e) to (h) may be used, or two or more types may be used in combination.
Examples of the nitrogen atom-containing monomer (e) include the following monomers (e1) to (e4) excluding the monomer (a), the monomer (b) and the monomer (d). ..

Amide group-containing monomer (e1):
(Meta) acrylamide, monoalkyl (meth) acrylamide [For example, one in which one alkyl group having 1 to 4 carbon atoms is bonded to a nitrogen atom; specifically, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide. ) Amide, N-isopropyl (meth) acrylamide and Nn- or isobutyl (meth) acrylamide, etc.], N- (N'-monoalkylaminoalkyl) (meth) acrylamide [for example, the nitrogen atom has 1 to 4 carbon atoms. Has an aminoalkyl group (2 to 6 carbon atoms) to which one alkyl group is bonded; specifically, N- (N'-methylaminoethyl) (meth) acrylamide, N- (N'-ethylamino). Ethyl) (meth) acrylamide, N- (N'-isopropylamino-n-butyl) (meth) acrylamide and N- (N'-n- or isobutylamino-n-butyl) (meth) acrylamide, etc.], Dialkyl ( Meta) acrylamide [For example, a nitrogen atom to which two alkyl groups having 1 to 4 carbon atoms are bonded; specifically, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N. , N-diisopropyl (meth) acrylamide and N, N-di-n-butyl (meth) acrylamide, etc.], N- (N', N'-dialkylaminoalkyl) (meth) acrylamide [for example, nitrogen of aminoalkyl group Those having an aminoalkyl group (2 to 6 carbon atoms) in which two alkyl groups having 1 to 4 carbon atoms are bonded to an atom; specifically, N- (N', N'-dimethylaminoethyl) (meth). Acrylamide, N- (N', N'-diethylaminoethyl) (meth) acrylamide, N- (N', N'-dimethylaminopropyl) (meth) acrylamide and N- (N', N'-di-n- Butylaminobutyl) (meth) acrylamide, etc.]; N-vinylcarboxylic acid amide [eg, N-vinylformamide, N-vinylacetamide, N-vinyl-n- or isopropionic acid amide, N-vinylhydroxyacetamide, etc.] and the like. Can be mentioned.

Nitro group-containing monomer (e2):
4-Nitrostyrene and the like can be mentioned.

1-3-class amino group-containing monomer (e3):
Primary amino group-containing monomers {for example, alkenylamines having 3 to 6 carbon atoms [specifically, (meth) allylamines and crotylamines, etc.], aminoalkyl (2 to 6 carbon atoms) (meth) acrylates [for example, Aminoethyl (meth) acrylate, etc.]}; Secondary amino group-containing monomer {monoalkylaminoalkyl (meth) acrylate [for example, an aminoalkyl group in which one alkyl group having 1 to 6 carbon atoms is bonded to a nitrogen atom (for example, Those having 2 to 6 carbon atoms; specifically, N-t-butylaminoethyl (meth) acrylate, N-methylaminoethyl (meth) acrylate, etc.], dialkenylamines having 6 to 12 carbon atoms [dialkenylamine] (Meta) allylamine, etc.]}; Tertiary amino group-containing monomer {dialkylaminoalkyl (meth) acrylate [For example, an aminoalkyl group in which two alkyl groups having 1 to 6 carbon atoms are bonded to a nitrogen atom (2 carbon atoms). Those having ~ 6); specifically, N, N-dimethylaminoethyl (meth) acrylate and N, N-diethylaminoethyl (meth) acrylate, etc.], alicyclic (meth) acrylate having a nitrogen atom [for example. , Morphorinoethyl (meth) acrylate, etc.], aromatic monomers [eg, N- (N', N'-diphenylaminoethyl) (meth) acrylamide, N, N-dimethylaminostyrene, 4-vinylpyridine, 2-Vinylpyridine, N-vinylpyrrole, N-vinylpyrrolidone, N-vinylthiopyrrolidone, etc.]}, and these hydrochlorides, sulfates, phosphates or lower alkyl (1-8 carbon atoms) monocarboxylic acids (1-8 carbon atoms). Acetic acid, propionic acid, etc.) salts and the like can be mentioned.

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

Of the monomers (e), (e1) and (e3) are preferable, and N- (N', N'-diphenylaminoethyl) (meth) acrylamide and N- (N'are more preferable. , 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.

Hydroxy group-containing monomer (f):
Hydroxyl-containing aromatic monomers (such as p-hydroxystyrene), hydroxyalkyl (2-6 carbon atoms) (meth) acrylates [eg, 2-hydroxyethyl (meth) acrylate, and 2- or 3-hydroxypropyl (meth). ) Acrylic, etc.], mono- or bis-hydroxyalkyl (1 to 4 carbon atoms) substituted (meth) acrylamide [eg, N, N-bis (hydroxymethyl) (meth) acrylamide, N, N-bis (hydroxypropyl) (Meta) acrylamide, N, N-bis (2-hydroxybutyl) (meth) acrylamide, etc.], vinyl alcohol, alkenol with 3 to 12 carbon atoms [for example, (meth) allyl alcohol, crotyl alcohol, isocrotyl alcohol , 1-octenol and 1-undecenol, etc.], alkenemonool or alkenediol having 4 to 12 carbon atoms [for example, 1-buten-3-ol, 2-buten-1-ol and 2-butene-1,4- Diol, etc.], hydroxyalkyl (1 to 6 carbon atoms) alkenyl (3 to 10 carbon atoms) ether (eg, 2-hydroxyethylpropenyl ether, etc.), polyvalent (3 to 8 valent) alcohol (eg, glycerin, pentaerythritol) , Sorbitol, sorbitan, diglycerin, saccharides, sucrose, etc.) alkenyl (3 to 10 carbon atoms) ether or (meth) acrylate [for example, sucrose (meth) allyl ether, etc.];
Polyoxyalkylene glycol (2-4 carbon atoms of alkylene group, degree of polymerization 2-50), polyoxyalkylene polyol [Polyoxyalkylene ether of the above 3-8 valent alcohol (2-4 carbon atoms of alkylene group, degree of polymerization) 2 to 100) etc.], mono (meth) acrylate of alkyl (carbon number 1 to 4) ether of polyoxyalkylene glycol or polyoxyalkylene polyol [for example, polyethylene glycol (Mn: 100 to 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 mono (meth) ) Polyoxyethylene acrylate (Mn: 150 to 230) sorbitan, etc.] and the like;

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

Phosphate ester group-containing monomer (g1):
(Meta) acryloyloxyalkyl (2-4 carbon atoms) phosphate ester [eg, (meth) acryloyloxyethyl phosphate and (meth) acryloyloxyisopropyl phosphate] and alkenyl phosphate ester [eg vinyl phosphate, Allyl phosphate, propenyl phosphate, isopropenyl phosphate, butenyl phosphate, pentenyl phosphate, octenyl phosphate, decenyl phosphate, dodecenyl phosphate, etc.] and the like. In addition, "(meth) acryloyloxy" means acryloyloxy or methacryloyloxy.

Phosphono group-containing monomer (g2):
(Meta) acryloyloxyalkyl (2-4 carbon atoms) phosphonic acid [eg, (meth) acryloyloxyethyl phosphonic acid, etc.] and alkenyl (2-12 carbon atoms) phosphonic acid [eg, vinylphosphonic acid, allylphosphone, etc.] Acids and octenylphosphonic acids, etc.] and the like.

Of the monomers (g), (g1) is preferable, (meth) acryloyloxyalkyl (2-4 carbon atoms) phosphate ester is more preferable, and (meth) acryloy is particularly preferable. It is a loxyethyl phosphate.

Aromatic ring-containing vinyl monomer (h):
Styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, 4-ethylstyrene, 4-isopropylstyrene, 4-butylstyrene, 4-phenylstyrene, 4-cyclohexylstyrene, 4-benzylstyrene, 4-chrome Examples thereof include tylbenzene, inden and 2-vinylnaphthalene.

Of the monomer (h), styrene and α-methylstyrene are preferable, and styrene is more preferable.

In the copolymer (A), the weight ratio of the monomer (e) among the constituent monomers of (A) is a single amount constituting (A) from the viewpoint of HTHS viscosity and viscosity index at the execution temperature. Based on the total weight of the body, it is preferably 0 to 50% by weight, more preferably 1 to 40% by weight.
In the copolymer (A), the weight ratio of the monomer (f) to the constituent monomers of (A) is the total weight of the monomers constituting (A) from the viewpoint of HTHS viscosity and viscosity index. From 0 to 40% by weight, more preferably 1 to 30% by weight.
In the copolymer (A), the weight ratio of the monomer (g) to the constituent monomers of (A) is the total weight of the monomers constituting (A) from the viewpoint of HTHS viscosity and viscosity index. From 0 to 30% by weight, more preferably 1 to 20% by weight.
In the copolymer (A), the weight ratio of the monomer (h) to the constituent monomers of (A) is the total weight of the monomers constituting (A) from the viewpoint of HTHS viscosity and viscosity index. From 0 to 20% by weight, more preferably 1 to 15% by weight.

The copolymer (A) may be a copolymer having a monomer (i) having two or more unsaturated groups in addition to the monomers (a) to (h) as a constituent monomer. Good.
One type of monomer (i) may be used, or two or more types may be used in combination.

Examples of the monomer (i) having two or more unsaturated groups include divinylbenzene, alkaziene having 4 to 12 carbon atoms (butadiene, isoprene, 1,4-pentadiene, 1,6-heptadiene and 1,7-). Octadiene, etc.), (di) cyclopentadiene, vinylcyclohexene and etylidene bicycloheptene, limonene, ethylenedi (meth) acrylate, polyalkylene oxide glycol di (meth) acrylate, pentaerythritol triallyl ether, pentaerythritol tri (meth) acrylate, Pentaerythritol tetra (meth) acrylate, trimethylpropantri (meth) acrylate, ester of unsaturated carboxylic acid with Mn of 500 or more and glycol, and unsaturated alcohol and carboxylic acid described in WO01 / 009242. Examples include esters.

In the copolymer (A), the weight ratio of the monomer (i) to the constituent monomers of (A) is preferably 0 to 10% by weight, more preferably 0 to 10% by weight, from the viewpoint of HTHS viscosity at the effective temperature. It is 1 to 5% by weight.

In addition to the monomers (a), (b) and (e) to (i), the copolymer (A) may contain the following monomers (j) to (m) as constituent monomers.
One type of each of the monomers (j) to (m) may be used, or two or more types may be used in combination.

Vinyl esters, vinyl ethers, vinyl ketones (j) (sometimes abbreviated as monomer (j)):
Vinyl esters of saturated fatty acids with 2 to 12 carbon atoms (vinyl acetate, vinyl propionate, vinyl butyrate, vinyl octanate, etc.), alkyl, aryl or alkoxyalkyl vinyl ethers with 1 to 12 carbon atoms (methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, etc.) , 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 ketone with 1 to 8 carbon atoms (methyl vinyl ketone, ethyl vinyl ketone and Phenyl vinyl ketone, etc.) and the like.

Epoxy group-containing monomer (k) (may be abbreviated as monomer (k)):
Examples thereof include glycidyl (meth) acrylate and glycidyl (meth) allyl ether.

Halogen element-containing monomer (l) (may be abbreviated as monomer (l)):
Examples thereof include vinyl chloride, vinyl bromide, vinylidene chloride, allyl chloride (meth) and styrene halide (dichlorostyrene and the like).

Ester (m) of unsaturated polycarboxylic acid (sometimes abbreviated as monomer (m)):
Alkyl, cycloalkyl or aralkyl esters of unsaturated polycarboxylic acids [alkyl diesters of unsaturated dicarboxylic acids (maleic acid, fumaric acid, itaconic acid, etc.) with 1 to 8 carbon atoms (dimethyl maleate, dimethyl fumarate, diethyl maleate, etc.) And dioctyl maleate)] and the like.

In the copolymer (A), the weight ratio of the monomer (j) to the constituent monomers of (A) is the total weight of the monomers constituting (A) from the viewpoint of the effect of improving the viscosity index. Based on this, it is preferably 0 to 5% by weight, more preferably 0.5 to 2% by weight.
In the copolymer (A), the weight ratio of the monomer (k) to the constituent monomers of (A) is the total weight of the monomers constituting (A) from the viewpoint of the effect of improving the viscosity index. Based on this, it is preferably 0 to 20% by weight, more preferably 1 to 10% by weight.
In the copolymer (A), the weight ratio of the monomer (l) to the constituent monomers of (A) is the total weight of the monomers constituting (A) from the viewpoint of the effect of improving the viscosity index. Based on this, it is preferably 0 to 5% by weight, more preferably 0.1 to 2% by weight.
In the copolymer (A), the weight ratio of the monomer (m) to the constituent monomers of (A) is the total weight of the monomers constituting (A) from the viewpoint of the effect of improving the viscosity index. Based on this, it is preferably 0 to 1% by weight, more preferably 0.01 to 0.5% by weight.

The Mw of the copolymer (A) is preferably 5,000 to 2,000,000, more preferably 5,000 to 300,000, particularly preferably 10,000 to 250,000, and even more preferably. It is 15,000 to 220,000, most preferably 30,000 to 200,000. When the Mw of the copolymer (A) is 5,000 or more, the effect of improving the viscosity-temperature characteristics and the effect of improving the viscosity index tend to be good. In addition, the amount of the viscosity index improver added is not too large, which is advantageous in terms of cost. When it is 2,000,000 or less, the shear stability tends to be good.
The Mn of the copolymer (A) is preferably 2,500 or more, more preferably 5,000 or more, particularly preferably 7,500 or more, and most preferably 15,000 or more. Further, it is preferably 150,000 or less, more preferably 125,000 or less, and particularly preferably 100,000 or less.
When Mn is 2,500 or more, the effect of improving the viscosity-temperature characteristics and the effect of improving the viscosity index tend to be good. In addition, the amount of the viscosity index improver added is not too large, which is advantageous in terms of cost. When Mn is 150,000 or less, the shear stability tends to be good.
The molecular weight distribution (Mw / Mn) of the copolymer (A) is preferably 1.0 to 4.0, more preferably 1.5 to 3.5, from the viewpoint of shear stability.
The measurement conditions for the Mw, Mn and molecular weight distribution of the copolymer (A) are the same as the measurement conditions for the Mw and Mn of the monomers (a1) and (a2).

The copolymer (A) can be obtained by a known production method, and specific examples thereof include a method obtained by solution-polymerizing the above-mentioned monomer in a solvent in the presence of a polymerization catalyst.
Examples of the solvent include toluene, xylene, alkylbenzene having 9 to 10 carbon atoms, methyl ethyl ketone, mineral oil, synthetic oil and the like, and mixtures thereof.
Examples of the polymerization catalyst include azo catalysts (2,2'-azobis (2-methylbutyronitrile) and 2,2'-azobis (2,4-dimethylvaleronitrile)) and peroxide catalysts (benzoylper). Oxides, cumyl peroxides, lauryl peroxides, etc.) and redox catalysts (mixtures of benzoyl peroxide and tertiary amines, etc.) can be mentioned. Further, if necessary for adjusting the molecular weight, a known chain transfer agent (alkyl mercaptan having 2 to 20 carbon atoms, etc.) can also be used.
The polymerization temperature is preferably 25 to 140 ° C, more preferably 50 to 120 ° C. In addition to the above solution polymerization, the copolymer (A) can be obtained by bulk polymerization, emulsion polymerization or suspension polymerization.
The polymerization form of the copolymer (A) may be either a random addition polymer or an alternate copolymer, or may be a graft copolymer or a block copolymer.

The solubility parameter (sometimes abbreviated as SP value) of the copolymer (A) is preferably 7.0 to 10.0 (cal / cm ³ ) ^1/2 from the viewpoint of solubility in the base oil. More preferably, it is 8.0 to 9.5 (cal / cm ³ ) ^1/2 .
The SP value of the copolymer (A) can be set in a desired range by appropriately adjusting the SP value and mole fraction of the monomer used. Specifically, the SP value can be reduced by using a large number of monomers having a long carbon number of an alkyl group, and the SP value can be increased by using a large number of monomers having a short carbon number of an alkyl group. can do.

The viscosity index improver of the present invention may further contain a (meth) acrylic acid alkyl ester (co) polymer (B) other than the copolymer (A) in addition to the above copolymer (A). , (Co) polymer (B) is preferably contained from the viewpoint of low temperature viscosity.
The (co) polymer (B) includes a (co) polymer that does not contain the monomer (a), for example, an alkyl (meth) acrylate having a linear or branched alkyl group having 9 to 36 carbon atoms. Examples thereof include a (co) polymer having an ester (d) as a constituent monomer. Specifically, n-dodecyl (meth) acrylate, n-tetradecyl (meth) acrylate, n-hexadecyl (meth) acrylate and n-octadecyl (meth) acrylate copolymer, n (meth) acrylate. -Octadecyl / n-dodecyl (meth) acrylate (molar ratio 10-30 / 90-70) copolymer, n-tetradecyl (meth) acrylate / n-dodecyl (meth) acrylate (molar ratio 10-30 / 90-70) Copolymer, n-hexadecyl (meth) acrylate / n-dodecyl (meth) acrylate / methyl (meth) acrylate (molar ratio 20-40 / 55-75 / 0-10) And n-dodecyl acrylate / n-dodecyl methacrylate (molar ratio 10 to 40/90 to 60) copolymers and the like, and these may be used alone or in combination of two or more.

The content of the (co) polymer (B) is preferably 0.01 to 30% by weight, more preferably 0.01 to 10% by weight, based on the weight of the copolymer (A) from the viewpoint of low temperature viscosity. %.

The Mw of the (co) polymer (B) is preferably 5,000 to 100,000, more preferably 10,000 to 80,000 from the viewpoint of lowering the pour point temperature.
The value of the solubility parameter of the (co) polymer (B) is preferably 7.0 to 10 and more preferably 8.0 to 9.5 from the viewpoint of solubility in the base oil.
The measurement conditions for Mw of the (co) polymer (B) are the same as the measurement conditions for Mw of the monomers (a1) and (a2).

The viscosity index improver of the present invention preferably contains the copolymer (A) in an amount of 0.1 to 20% by weight based on the weight of the viscosity index improver.
In the viscosity index improver of the present invention, it is preferable to contain the (co) polymer (B) in an amount of 0.01 to 5% by weight based on the weight of the viscosity index improver.

<Base oil>
The viscosity index improver of the present invention contains a copolymer (A) and a base oil. Examples of the base oil include one or more base oils selected from the group consisting of group I to IV base oils of the API classification, GTL base oils and synthetic lubricating oil base oils (ester synthetic base oils, etc.). Of these, Group III mineral oils and GTL base oils are preferred.
(Measured by JIS-K2283) kinematic viscosity at 100 ° C. of the base oil is preferably from the viewpoint of viscosity index and low temperature fluidity is 1 to 15 mm ² / s, more preferably is 2 to 5 mm ² / s ..
The solubility parameter of the base oil is preferably 7.8 to 9.5 (cal / cm ³ ) ^1/2 , more preferably 8.0 to 9.0 (cal / cm), from the viewpoint of solubility of various additives. ³ ) It is ^1/2 .

In the viscosity index improver of the present invention, the absolute value of the difference between the dissolution parameters of the copolymer (A) and the base oil is 0.8 to 2.0 (cal / cm ³ ) ^1/2 , and (A) From the viewpoint of solubility in the base oil and low-temperature viscosity, 0.8 to 1.3 (cal / cm ³ ) ^1/2 is preferable, and 0.9 to 1.2 (cal / cm ³ ) ¹ is more preferable. It is ^{/ 2} . The absolute value of the difference in solubility parameter between the copolymer (A) and the base oil is the SP value and mole fraction of the monomer used to produce the copolymer (A) with respect to the base oil. The desired range can be obtained by adjusting as appropriate.

The viscosity index of the base oil (measured by JIS-K2283) is preferably 100 or more from the viewpoint of the viscosity index of the lubricating oil composition and the low temperature fluidity.

The cloudiness point of the base oil (measured by JIS-K2269) is preferably −5 ° C. or lower, and more preferably −15 ° C. or lower. When the cloudiness point of the base oil is within this range, the low temperature viscosity of the lubricating oil composition tends to be good.

<Lubricating oil composition>
The lubricating oil composition of the present invention comprises the viscosity index improver of the present invention, a cleaning agent, a dispersant, an antioxidant, an oiliness improver, a pour point lowering agent, a friction and wear adjusting agent, an extreme pressure agent, a defoaming agent, and the like. It contains one or more additives selected from the group consisting of anti-emulsifiers, metal deactants and corrosion inhibitors.
The lubricating oil composition of the present invention preferably contains the copolymer (A) in an amount of 0.1 to 20% by weight based on the weight of the lubricating oil composition.
In the lubricating oil composition of the present invention, it is preferable that the (co) polymer (B) is contained in an amount of 0.01 to 5% by weight based on the weight of the lubricating oil composition.

The lubricating oil composition of the present invention contains various additives. Examples of the additive include the following.
(1) Cleaner:
Basic, hyperbasic or neutral metal salts [superbasic or alkaline earth metal salts of sulfonates (petroleum sulfonates, alkylbenzenesulfonates, alkylnaphthalensulfonates, etc.)], salicylates, phenates, naphthenates, etc. Classes, carbonates, phosphonates and mixtures thereof;
(2) Dispersant:
Imides succinate (bis- or mono-polybutenyl succinate imides), Mannich condensates, borates, etc .;
(3) Antioxidant:
Hindered phenols and aromatic secondary amines, etc .;
(4) Oiliness improver:
Long chain fatty acids and their esters (oleic acid and oleic acid esters, etc.), long chain amines and their amides (oleylamine, oleylamide, etc.), etc .;
(5) Pour point lowering agent Polyalkyl methacrylate, ethylene-vinyl acetate copolymer, etc.;
(6) Friction wear modifier:
Molybdenum-based and zinc-based compounds (molybdenum dithiophosphate, molybdenum dithiocarbamate, zinc dialkyldithiophosphate, etc.), etc.;
(7) Extreme pressure agent:
Sulfur compounds (mono or disulfide, sulfoxide and sulfur phosphide compounds), phosphide compounds and chlorinated compounds (chlorinated paraffin, etc.), etc.;
(8) Defoamer:
Silicone oil, metal soap, fatty acid ester, phosphate compound, etc .;
(9) Anti-emulsifier:
Quaternary ammonium salts (tetraalkylammonium salts, etc.), sulfated oils and phosphates (polyoxyethylene-containing nonionic surfactant phosphates, etc.), hydrocarbon solvents (toluene, xylene, ethylbenzene, etc.), etc.;
(10) Metal inactivator Nitrogen atom-containing compound (benzotriazole, etc.), nitrogen atom-containing chelate compound (N, N'-disalitidene-1,2-diaminopropane, etc.), nitrogen / sulfur atom-containing compound (2- (n) -Dodecylthio) benzimidazole, etc.);
(11) Corrosion inhibitor:
Nitrogen atom-containing compounds (benzotriazole and 1,3,4-thiodiazolyl-2,5-bisdialkyldithiocarbamate, etc.) and the like.

Only one of these additives may be added, or two or more of these additives may be added as required. Further, a compound containing these additives may be referred to as a performance additive or a package additive, and may be added.
The content of each of these additives is preferably 0.1 to 15% by weight based on the total amount of the lubricating oil composition. The total content of each additive is preferably 0.1 to 30% by weight, more preferably 0.3 to 20% by weight, based on the total amount of the lubricating oil composition.

The lubricating oil composition of the present invention includes gear oils (differential oils, industrial gear oils, etc.), MTFs, transmission oils [ATF, DCTF, belt-CVTF, etc.], traction oils (toroidal-CVTF, etc.), shock absorber oils, etc. It is suitably used for power steering oil, hydraulic oil (hydraulic for construction machinery, industrial hydraulic oil, etc.) and engine oil (for gasoline and diesel).

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

The ratio (mol%) of 1,2-butylene groups in all the constituent units of the hydrocarbon polymer was determined by analyzing the polymer by ¹³ C-NMR and using the above formula (1) by the above method.

<Manufacturing example 1>
400 parts by weight of degassed and dehydrated hexane, 1 part by weight of tetrahydrofuran, 90 parts by weight of 1,3-butadiene, 2 parts by weight of n-butyllithium in a 1 L SUS pressure resistant reaction vessel equipped with a temperature controller and a stirrer. Was charged, and then the polymerization temperature was set to 70 ° C. for polymerization.
After the polymerization rate became almost 100%, 2 parts by weight of ethylene oxide was added, and the mixture was reacted at 50 ° C. for 3 hours. To stop the reaction, 50 parts by weight of water and 25 parts by weight of a 1N-hydrochloric acid aqueous solution were added, and the mixture was stirred at 80 ° C. for 1 hour. The organic phase of the reaction solution was recovered by a separating funnel, the temperature was raised to 70 ° C., and the solvent was removed under a reduced pressure of 10 to 20 Torr over 2 hours.
The obtained polybutadiene containing a hydroxyl group at one end was transferred to a reaction vessel equipped with a temperature controller, a stirrer, and a hydrogen introduction tube, and 150 parts by weight of tetrahydrofuran was added to uniformly dissolve the polybutadiene. After pouring a suspension in which 10 parts by weight of palladium carbon and 50 parts by weight of tetrahydrofuran are mixed in advance, hydrogen is supplied to the liquid at a flow rate of 30 mL / min from a hydrogen introduction tube and reacted at room temperature for 8 hours. It was. After that, palladium carbon was removed by filtration, the temperature of the obtained filtrate was raised to 70 ° C., and tetrahydrofuran was removed under a reduced pressure of 10 to 20 Torr to obtain a one-terminal hydroxyl group-containing polymer (Y1-1) of hydrogenated polybutadiene. It was.
The molecular weight of the obtained (Y1-1) was measured by GPC, and the 1,2-butylene group ratio was measured by ¹³ C-NMR. The results were Mw = 6,900, Mn = 6,700, 1,2-butylene group ratio = 45 mol%.

<Manufacturing example 2>
400 parts by weight of degassed and dehydrated hexane, 1 part by weight of tetrahydrofuran, 122 parts by weight of 1,3-butadiene, 2 parts by weight of n-butyllithium in a 1 L SUS pressure resistant reaction vessel equipped with a temperature controller and a stirrer. Was charged, and then the polymerization temperature was set to 70 ° C. for polymerization. After that, the same procedure as in Production Example 1 was carried out to obtain a single-terminal hydroxyl group-containing polymer (Y1-2) of hydrogenated polybutadiene.
The obtained molecular weight of (Y1-2) was measured by GPC, and the 1,2-butylene group ratio was measured by ¹³ C-NMR. The results were Mw = 9,300, Mn = 9,000, and 1,2-butylene group ratio = 45 mol%.

<Manufacturing example 3>
400 parts by weight of degassed and dehydrated hexane, 1 part by weight of tetrahydrofuran, 90 parts by weight of 1,3-butadiene, 2 parts by weight of n-butyllithium in a 1 L SUS pressure resistant reaction vessel equipped with a temperature controller and a stirrer. Was charged, and then the polymerization temperature was set to 100 ° C. for polymerization. After that, the same procedure as in Production Example 1 was carried out to obtain a single-terminal hydroxyl group-containing polymer (Y1-3) of hydrogenated polybutadiene.
The molecular weight of the obtained (Y1-3) was measured by GPC, and the 1,2-butylene group ratio was measured by ¹³ C-NMR. The results were Mw = 6,900, Mn = 6,700, 1,2-butylene group ratio = 25 mol%.

<Manufacturing example 4>
400 parts by weight of degassed and dehydrated hexane, 1 part by weight of tetrahydrofuran, and 0.4 parts by weight of n-butyllithium were charged in a 1 L SUS pressure resistant reaction vessel equipped with a temperature controller and a stirrer, and then -40. Cooled to ° C. 90 parts by weight of 1,3-butadiene liquefied at −40 ° C. was added thereto, and the polymerization was carried out at a polymerization temperature of −40 ° C.
After the polymerization rate became almost 100%, 2 parts by weight of ethylene oxide was added, the temperature was raised to 50 ° C., and the reaction was carried out for 3 hours. To stop the reaction, 50 parts by weight of water and 25 parts by weight of a 1N-hydrochloric acid aqueous solution were added, and the mixture was stirred at 80 ° C. for 1 hour. The organic phase of the reaction solution was recovered by a separating funnel, the temperature was raised to 70 ° C., and the solvent was removed under a reduced pressure of 10 to 20 Torr over 2 hours.
The obtained polybutadiene containing a hydroxyl group at one end was transferred to a reaction vessel equipped with a temperature controller, a stirrer, and a hydrogen introduction tube, and 150 parts by weight of tetrahydrofuran was added to uniformly dissolve the polybutadiene. After pouring a suspension in which 10 parts by weight of palladium carbon and 50 parts by weight of tetrahydrofuran are mixed in advance, hydrogen is supplied to the liquid at a flow rate of 30 mL / min from a hydrogen introduction tube and reacted at room temperature for 8 hours. It was. After that, palladium carbon was removed by filtration, the temperature of the obtained filtrate was raised to 70 ° C., and tetrahydrofuran was removed under a reduced pressure of 10 to 20 Torr to obtain a one-terminal hydroxyl group-containing polymer (Y1-4) of hydrogenated polybutadiene. It was.
The molecular weight of the obtained (Y1-4) was measured by GPC, and the 1,2-butylene group ratio was measured by ¹³ C-NMR. The results were Mw = 6,700, Mn = 6,500, 1,2-butylene group ratio = 66 mol%.

<Manufacturing example 5>
400 parts by weight of degassed and dehydrated hexane, 1 part by weight of tetrahydrofuran, and 0.4 parts by weight of n-butyllithium were charged in a 1 L SUS pressure resistant reaction vessel equipped with a temperature controller and a stirrer, and then -40. Cooled to ° C. To this, 18 parts by weight of 1,3-butadiene liquefied at −40 ° C. was added, and the polymerization temperature was set to −40 ° C. for polymerization. After that, the same procedure as in Production Example 4 was carried out to obtain a single-terminal hydroxyl group-containing polymer (Y1-5) of hydrogenated polybutadiene.
The obtained molecular weight of (Y1-5) was measured by GPC, and the 1,2-butylene group ratio was measured by ¹³ C-NMR. The results were Mw = 1,550, Mn = 1,500, and 1,2-butylene group ratio = 66 mol%.

<Manufacturing example 6>
In a 1 L SUS pressure resistant reaction vessel equipped with a temperature controller and a stirrer, 400 parts by weight of degassed and dehydrated hexane, 1 part by weight of tetrahydrofuran, and 0.4 parts by weight of n-butyllithium were charged, and then -55. Cooled to ° C. 90 parts by weight of 1,3-butadiene liquefied at −55 ° C. was added thereto, and the polymerization was carried out at a polymerization temperature of −55 ° C. After that, the same procedure as in Production Example 4 was carried out to obtain a single-terminal hydroxyl group-containing polymer (Y1-6) of hydrogenated polybutadiene.
The obtained molecular weight of (Y1-6) was measured by GPC, and the 1,2-butylene group ratio was measured by ¹³ C-NMR. The results were Mw = 6,900, Mn = 6,700, 1,2-butylene group ratio = 85 mol%.

<Manufacturing example 7>
400 parts by weight of degassed and dehydrated hexane, 1 part by weight of tetrahydrofuran, 90 parts by weight of 1,3-butadiene, 2 parts by weight of n-butyllithium in a 1 L SUS pressure resistant reaction vessel equipped with a temperature controller and a stirrer. Was charged, and then polymerized at a polymerization temperature of 115 ° C. After that, the same procedure as in Production Example 1 was carried out to obtain a single-terminal hydroxyl group-containing polymer (Y1-7) of hydrogenated polybutadiene.
The obtained molecular weight of (Y1-7) was measured by GPC, and the 1,2-butylene group ratio was measured by ¹³ C-NMR. The results were Mw = 6,900, Mn = 6,700, and 1,2-butylene group ratio = 1 mol%.

<Manufacturing example 8>
400 parts by weight of degassed and dehydrated hexane, 1 part by weight of tetrahydrofuran, 90 parts by weight of 1,3-butadiene, 2 parts by weight of n-butyllithium in a 1 L SUS pressure resistant reaction vessel equipped with a temperature controller and a stirrer. Was charged, and then the polymerization temperature was set to 0 ° C. for polymerization. After that, the same procedure as in Production Example 1 was carried out to obtain a single-terminal hydroxyl group-containing polymer (Y1-8) of hydrogenated polybutadiene.
The obtained molecular weight of (Y1-8) was measured by GPC, and the 1,2-butylene group ratio was measured by ¹³ C-NMR. The results were Mw = 6,900, Mn = 6,700, 1,2-butylene group ratio = 55 mol%.

<Manufacturing example 9>
400 parts by weight of degassed and dehydrated hexane, 1 part by weight of tetrahydrofuran, 90 parts by weight of 1,3-butadiene, 2 parts by weight of n-butyllithium in a 1 L SUS pressure resistant reaction vessel equipped with a temperature controller and a stirrer. Was charged, and then the polymerization temperature was set to −5 ° C. for polymerization. After that, the same procedure as in Production Example 1 was carried out to obtain a single-terminal hydroxyl group-containing polymer (Y1-9) of hydrogenated polybutadiene.
The obtained molecular weight of (Y1-9) was measured by GPC, and the 1,2-butylene group ratio was measured by ¹³ C-NMR. The results were Mw = 6,900, Mn = 6,700, 1,2-butylene group ratio = 56 mol%.
<Manufacturing example 10>
400 parts by weight of degassed and dehydrated hexane, 1 part by weight of tetrahydrofuran, 90 parts by weight of 1,3-butadiene, 2 parts by weight of n-butyllithium in a 1 L SUS pressure resistant reaction vessel equipped with a temperature controller and a stirrer. Was charged, and then the polymerization temperature was set to −65 ° C. for polymerization. After that, the same procedure as in Production Example 1 was carried out to obtain a single-terminal hydroxyl group-containing polymer (Y1-10) of hydrogenated polybutadiene.
The molecular weight of the obtained (Y1-10) was measured by GPC, and the 1,2-butylene group ratio was measured by ¹³ C-NMR. The results were Mw = 6,900, Mn = 6,700, 1,2-butylene group ratio = 100 mol%.

<Production Example 11: Production of copolymer (B)>
Base oil A (SP value: 8.3 (cal / cm ³ ) ^1/2 , 100 ° C. operation in a reaction vessel equipped with a stirrer, heating / cooling device, thermometer, dropping funnel, nitrogen blowing tube and depressurizing device. Viscosity: 4.2 mm ² / s, Viscosity index: 128) 75 parts by weight was put into another glass beaker, and 244 parts by weight of n-dodecyl methacrylate, 24 parts by weight of n-tetradecyl methacrylate, n-methacrylate. 21 parts by weight of hexadecyl, 37 parts by weight of n-octadecyl methacrylate, 0.6 parts by weight of dodecyl mercaptan as a chain transfer agent, 0.5 parts by weight of 2,2-azobis (2,4-dimethylvaleronitrile) and 2,2 parts by weight. -Azobis (2-methylbutyronitrile) was charged in an amount of 0.2 parts by weight, stirred and mixed at 20 ° C. to prepare a monomer solution, and the mixture was charged into a dropping funnel.
After performing nitrogen substitution in the gas phase part of the reaction vessel (gas phase oxygen concentration: 100 ppm or less), the monomer solution was added dropwise over 2 hours while maintaining the temperature inside the closed system at 70 to 85 ° C. After aging at 85 ° C. for 2 hours from the end, the temperature was raised to 120 to 130 ° C., and the unreacted monomer was removed under reduced pressure (0.027 to 0.040 MPa) at the same temperature over 2 hours. A copolymer composition (B-1) containing 65% by weight of the copolymer (B) in oil was obtained. The Mw of the obtained copolymer (B) was 53,000, and the SP value was 9.0.

<Examples 1 to 11>
Base oil A (SP value: 8.3 (cal / cm ³ ) ^1/2 , kinematic viscosity at 100 ° C. shown in Table 1 in a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer and a nitrogen introduction tube. : 4.2 mm ² / s, viscosity index: 128) or base oil B (SP value: 8.4 (cal / cm ³ ) ^1/2 , kinematic viscosity at 100 ° C: 4.1 mm ² / s, viscosity index: 124) 384.76 parts by weight, 110 parts by weight of the monomer formulation shown in Table 1, 0.5 parts by weight of 2,2'-azobis (2,4-dimethylvaleronitrile) and 2,2'-azobis (2,2'-azobis). 2-Methylbutyronitrile) 0.2 parts by weight was added, nitrogen substitution (gas phase oxygen concentration 100 ppm) was performed, and then the temperature was raised to 76 ° C. with stirring under sealing, and the polymerization reaction was carried out at the same temperature for 4 hours. Was done. After raising the temperature to 120 to 130 ° C., unreacted monomers were removed under reduced pressure (0.027 to 0.040 MPa) at the same temperature over 2 hours. The SP values of the obtained copolymers (A-1) to (A-9) were calculated by the above method, and Mw and Mn were measured by the above method. The results of Mw and molecular weight distribution (Mw / Mn) are shown in Table 1.
Further, 5.24 parts by weight of the copolymer composition (B-1) obtained in Production Example 11 was added, and 22% by weight of the copolymers (A-1) to (A-9) were added, respectively. A viscosity index improver containing 0.68% by weight of (B) and 77.32% by weight of base oil was obtained. Moreover, the base oil solubility of the copolymer (A) was evaluated by the following method. The results are shown in Table 1.

<Examples 12 to 23 and Comparative Examples 1 to 5>
Base oil A (SP value: 8.3 (cal / cm ³ ) ^1/2 , kinematic viscosity at 100 ° C. shown in Table 1 in a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer and a nitrogen introduction tube. : 4.2 mm ² / s, viscosity index: 128) or base oil B (SP value: 8.4 (cal / cm ³ ) ^1/2 , kinematic viscosity at 100 ° C: 4.1 mm ² / s, viscosity index: 124) 390 parts by weight, 110 parts by weight of the monomer formulation shown in Table 1, 0.5 parts by weight of 2,2'-azobis (2,4-dimethylvaleronitrile) and 2,2'-azobis (2-). 0.2 part by weight of methylbutyronitrile) was added, and after nitrogen substitution (gas phase oxygen concentration 100 ppm), the temperature was raised to 76 ° C. with stirring under sealing, and the polymerization reaction was carried out at the same temperature for 4 hours. It was. After raising the temperature to 120 to 130 ° C., the unreacted monomers were removed under reduced pressure (0.027 to 0.040 MPa) over 2 hours at the same temperature, and the copolymers (A-10) to (A-) were removed, respectively. 23) or Viscosity index improvers (R-10) to (R-23) and (S-1) containing 20% by weight of (A'-1) to (A'-5) and 80% by weight of base oil. -(S-5) was obtained. The SP values of the obtained copolymers (A-10) to (A-23) or (A'-1) to (A'-5) were calculated by the above method, and Mw was calculated by the above method (measurement conditions). Measured in 1). Moreover, the base oil solubility of the copolymer (A) was evaluated by the following method. The results are shown in Table 1.

<Evaluation method of base oil solubility of copolymer (A)>
Visually observe the appearance of the viscosity index improvers (R-1) to (R-23) and (S-1) to (S-5), and use the following evaluation criteria as the base oil for the copolymer (A). Solubility was evaluated.
[Evaluation criteria]
◯: Uniform appearance, no insoluble material of copolymer ×: Non-uniform appearance, insoluble material of copolymer is observed

The compositions of the monomers (a) to (g) shown in Table 1 are as described below.
(Y1-1): Hydride of one-terminal hydroxyl group-containing polybutadiene of Production Example 1 (1,2-butylene group ratio = 45 mol%)
(Y1-2): Hydride of one-terminal hydroxyl group-containing polybutadiene of Production Example 2 (1,2-butylene group ratio = 45 mol%)
(Y1-3): Hydride of one-terminal hydroxyl group-containing polybutadiene of Production Example 3 (1,2-butylene group ratio = 25 mol%)
(Y1-4): Hydride of one-terminal hydroxyl group-containing polybutadiene of Production Example 4 (1,2-butylene group ratio = 66 mol%)
(Y1-5): Hydride of one-terminal hydroxyl group-containing polybutadiene of Production Example 5 (1,2-butylene group ratio = 66 mol%)
(Y1-6): Hydride of one-terminal hydroxyl group-containing polybutadiene of Production Example 6 (1,2-butylene group ratio = 85 mol%)
(Y1-7): Hydride of one-terminal hydroxyl group-containing polybutadiene of Production Example 7 (1,2-butylene group ratio = 1 mol%)
(Y1-8): Hydride of one-terminal hydroxyl group-containing polybutadiene of Production Example 8 (1,2-butylene group ratio = 55 mol%)
(Y1-9): Hydride of one-terminal hydroxyl group-containing polybutadiene of Production Example 9 (1,2-butylene group ratio = 56 mol%)
(Y1-10): Hydride of one-terminal hydroxyl group-containing polybutadiene of Production Example 10 (1,2-butylene group ratio = 100 mol%)
(A1-1): Methacrylic acid esterified product of (Y1-1) [Mn: 6,800]
(A1-2): Methacrylic acid esterified product of (Y1-2) [Mn: 9,100]
(A1-3): Methacrylic acid esterified product of (Y1-3) [Mn: 6,800]
(A1-4): Methacrylic acid esterified product of (Y1-7) [Mn: 6,800]
(A1-5): Methacrylic acid esterified product of (Y1-8) [Mn: 6,800]
(A2-1): Methacrylic acid esterified product of (Y1-4) [Mn: 6,700]
(A2-2): Methacrylic acid esterified product of (Y1-5) [Mn: 1,600]
(A2-3): Methacrylic acid esterified product of (Y1-6) [Mn: 6,800]
(A2-4): Methacrylic acid esterified product of (Y1-9) [Mn: 6,800]
(A2-5): Methacrylic acid esterified product of (Y1-10) [Mn: 6,800]
(B-1): methoxyethyl methacrylate (b-2): ethoxyethyl methacrylate (b-3): butoxyethyl methacrylate (b-4): hexyloxyethyl methacrylate (c-1): methyl methacrylate (c-2) ): N-Butyl methacrylate (d-1): n-dodecyl methacrylate (Neodor25 (manufactured by Shell Chemicals))
And methacrylic acid esterified product)
(D-2): Linear and branched alkyl methacrylate mixture having 12 to 15 carbon atoms (esterified product of Neodol23 (manufactured by Shell Chemicals) and methacrylic acid).
(D-3): Linear and branched alkyl methacrylate mixture having 14 to 16 carbon atoms (esterified product of Neodol 45 (manufactured by Shell Chemicals) and methacrylic acid).
(D-4): n-tetradecyl methacrylate (d-5): n-hexadecyl methacrylate (d-6): 2-n-decyltetradecyl methacrylate (d-7): 2-n-dodecyl methacrylate Hexadecyl (d-8): 2-n-tetradecyl octadecyl methacrylate (e-1): N, N-dimethylaminoethyl methacrylate (f-1): 2-hydroxyethyl methacrylate (g-1): methacrylic acid Roxyethyl phosphate

<Evaluation of Examples 24 to 46 and Comparative Examples 6 to 10: 0W-20>
Base oil A (SP value: 8.3 (cal / cm ³ ) ^1/2 , kinematic viscosity at 100 ° C: 4.2 mm ² / s, viscosity index: 128) or base in a stainless steel container equipped with a stirrer. Oil B (SP value: 8.4 (cal / cm ³ ) ^1/2 , kinematic viscosity at 100 ° C: 4.1 mm ² / s, viscosity index: 124) 90 parts by weight and package additive (Infineum P5741) 10 weight Viscosity index improvers (R-1) to (R-) so that the HTHS viscosity at 150 ° C. of the obtained lubricating oil composition is 2.60 ± 0.05 (mm ² / s). 23) or (S-1) to (S-5) was added to obtain lubricating oil compositions (V-1) to (V-23) and (W-1) to (W-5).
Shear stability, HTHS viscosity (150 ° C, 100 ° C), 100 ° C kinematic viscosity, gelation index of lubricating oil compositions (V-1) to (V-23) and (W-1) to (W-5). , Viscosity index and low temperature viscosity (-40 ° C) were measured by the following methods. The results are shown in Table 2. In addition, the solubility when the package additive was added was evaluated by the following method.
Since Comparative Examples 7 and 9 had insoluble copolymers, shear stability, HTHS viscosity (150 ° C., 100 ° C.), 100 ° C. kinematic viscosity, gelation index, viscosity index and low temperature viscosity (-40 ° C.) ℃) was not measured.

<Evaluation of Examples 47 to 69 and Comparative Examples 11 to 15: 0 W-16>
Base oil A (SP value: 8.3 (cal / cm ³ ) ^1/2 , kinematic viscosity at 100 ° C: 4.2 mm ² / s, viscosity index: 128) or base in a stainless steel container equipped with a stirrer. Oil B (SP value: 8.4 (cal / cm ³ ) ^1/2 , kinematic viscosity at 100 ° C: 4.1 mm ² / s, viscosity index: 124) 90 parts by weight and package additive (Infineum P5741) 10 weight Viscosity index improvers (R-1) to (R-) so that the HTHS viscosity at 150 ° C. of the obtained lubricating oil composition is 2.30 ± 0.05 (mm ² / s). 23) or (S-1) to (S-5) was added to obtain lubricating oil compositions (V-24) to (V-46) and (W-6) to (W-10). Shear stability of lubricating oil compositions (V-24) to (V-46), (W-6) to (W-10), HTHS viscosity (150 ° C, 100 ° C), 100 ° C kinematic viscosity, gelation index , Viscosity index and low temperature viscosity (-40 ° C) were measured by the following methods. The results are shown in Table 3. In addition, the solubility when the package additive was added was evaluated by the following method.
In Comparative Examples 12 and 14, since there was an insoluble product of the copolymer, shear stability, HTHS viscosity (150 ° C., 100 ° C.), 100 ° C. kinematic viscosity, gelation index, viscosity index and low temperature viscosity (-40 ° C.) ℃) was not measured.

<Measuring method of HTHS viscosity of lubricating oil composition>
Measured at 100 ° C. and 150 ° C. by the method of ASTM D 5484. The lower the HTHS viscosity at 100 ° C., the better.

<Method of measuring kinematic viscosity of lubricating oil composition and method of calculating viscosity index>
The kinematic viscosities of 40 ° C and 100 ° C were measured by the method of ASTM D 445, and ASTM D 2
It was calculated by the method of 270. The larger the value of the viscosity index, the higher the effect of improving the viscosity index.

<Measurement method and calculation method of shear stability of lubricating oil composition>
It was measured by the method of ASTM D 6278 and calculated by the method of ASTM D 6022. The smaller the value, the higher the shear stability.

<Measuring method of low temperature viscosity of lubricating oil composition>
The viscosity at −40 ° C. was measured by the method of JPI-5S-42-2004. The smaller the value, the lower the low temperature viscosity.

<Method for measuring gelled index of lubricating oil composition>
A scanning Brookfield viscometer was operated by the method of ASTM D 5133 to measure the gelation index. Specifically, about 20 ml of the lubricating oil composition is poured into the glass stator to the fill line, preheated at 90 ° C. for 1.5 hours, and then a temperature gradient program is set at a scanning speed of 1 ° C./hour. The mixture was cooled to −5 ° C. to −40 ° C. and the gelation index was measured. The smaller the value, the better the viscosity characteristic at low temperature, which means that the oil is good as an engine oil.

<Method of evaluating solubility of copolymer in additive-containing base oil>
Visually observe the appearance of the lubricating oil compositions (V-1) to (V-46) and (W-1) to (W-10), and use the following evaluation criteria as a copolymer for the base oil containing the additive. The solubility of the polymer was evaluated.
[Evaluation criteria]
◯: Uniform appearance, no insoluble material of copolymer ×: Non-uniform appearance, insoluble material of copolymer is observed

As is clear from the results in Tables 2 and 3, the lubricating oil composition containing the viscosity index improver of the present invention has good solubility in the lubricating oil base oil to which various additives have been added. It can be seen that the low-temperature viscosity at −40 ° C. is excellent, the HTHS viscosity in the effective temperature range is low, and the viscosity index is high.
On the other hand, the lubricating oil compositions of Comparative Examples 6 to 15 are among the solubility in the lubricating oil base oil to which various additives are added, low temperature viscosity, shear stability, HTHS viscosity in the effective temperature range, and viscosity index. , At least one is inferior. Furthermore, the value of the gelation index is also high, indicating that gelation is likely to occur. In particular, from the comparison of the results of Comparative Examples 9 and 14 and Examples 43 and 66, the absolute value of the difference in the solubility parameter between the base oil and the copolymer was 2.0 even though the types of the monomers used were the same. If it exceeds, the solubility of the copolymer in the base oil becomes low, and it can be seen that the solubility in the base oil to which the additive is added is low even in the case of making a lubricating oil composition. Further, from the comparison of the results of Comparative Examples 10 and 15 and Examples 28 and 51, the absolute value of the difference in the solubility parameter between the base oil and the copolymer is less than 0.8 even if the type of the monomer used is the same. In the case of a lubricating oil composition, it can be seen that the HTHS viscosity at 100 ° C. is high, the shear stability is poor, and the low temperature viscosity is also high. Further, from the comparison of the results of Comparative Examples 6 and 11 and Examples 24 and 47, the viscosity obtained by containing the copolymer (A') containing the monomers (a1) and (a2) as constituent monomers. In the lubricating oil composition of the comparative example obtained by using the index improver, even if the absolute value of the difference between the dissolution parameters of the copolymer (A') and the base oil is 0.8 to 2.0. , Viscosity index, shear stability and low temperature viscosity are found to be inferior. Further, from the comparison of the results of Comparative Examples 7 and 12 and Examples 28 and 51, the copolymer (A') containing only (a2) as a constituent monomer was used instead of the combined use of (a1) and (a2). It can be seen that the lubricating oil composition of the comparative example obtained by using the viscosity index improver contained therein has low solubility of the copolymer in the base oil to which the additive is added. Further, from the comparison of the results of Comparative Examples 8 and 13 and Examples 29 and 52, the copolymer (A') containing the monomers (a1) and (a2) in an amount exceeding 14% by weight, respectively. The lubricating oil composition of the comparative example obtained by using the viscosity index improver containing) is inferior in HTHS viscosity at 100 ° C., kinematic viscosity at 100 ° C., viscosity index, shear stability and low temperature viscosity. I understand.

By using the viscosity index improver of the present invention, a lubricating oil composition having excellent low-temperature viscosity at −40 ° C., good solubility in engine oil to which an essential additive for engine oil is added, and a high viscosity index can be obtained. Therefore, the lubricating oil composition containing the viscosity index improver of the present invention includes gear oil (differential oil, industrial gear oil, etc.), MTF, transmission oil [ATF, DCTF, belt-CVTF, etc.], traction. It is suitably used for oils (toroidal-CVTF, etc.), shock absorber oils, power steering oils, hydraulic oils (hydraulics for construction machinery, industrial hydraulic oils, etc.) and engine oils (for gasoline and diesel).

Claims (9)

A copolymer (A) containing a polyolefin-based monomer (a1) represented by the following general formula (1) and a polyolefin-based monomer (a2) represented by the following general formula (2) as constituent monomers. A viscosity index improver containing oil, wherein (a1) is 1 to 14% by weight based on the total weight of the monomers constituting (A) as a constituent monomer. , A copolymer containing 1 to 14% by weight of the above (a2), and the absolute value of the difference between the dissolution parameters of the (A) and the base oil is 0.8 to 2.0 (cal / cm ³ ). A viscosity index improver that is ^1/2 .

[R ¹ is a hydrogen atom or a methyl group; -X ^1- is a group represented by -O-, -O (AO) _m- or -NH-, and A is an alkylene group having 2 to 4 carbon atoms. Yes, m is an integer of 1-10, and A when m is 2 or more may be the same or different; R ² is a hydrogen atom from a hydrocarbon polymer containing a 1,2-butylene group as a constituent unit. In the hydrocarbon polymer containing 1,2-butylene group as a constituent unit, the ratio of 1,2-butylene group to all the constituent units is 1 to 55 mol%; p is 0. Or the number of 1. ]

[R ³ is a hydrogen atom or a methyl group; -X ^2- is a group represented by -O-, -O (AO) _n- or -NH-, and A is an alkylene group having 2 to 4 carbon atoms. There, n is an integer of 1 to 10, n is 2 or more a case may be the same or different; a hydrogen atom from a hydrocarbon polymer containing R ⁴ is 1,2-butylene group as the structural unit In the hydrocarbon polymer containing 1,2-butylene group as a constituent unit, the ratio of 1,2-butylene group to all the constituent units is 56 to 100 mol%; q is 0. Or the number of 1. ] The viscosity index improver according to claim 1, wherein the copolymer (A) is a copolymer further containing a monomer (b) represented by the following general formula (3) as a constituent monomer.

[R ⁵ is a hydrogen atom or a methyl group; -X ^3- is a group represented by -O- or -NH-; R ⁶ is an alkylene group having 2 to 4 carbon atoms; R ⁷ is an alkyl having 1 to 8 carbon atoms. Group; r is an integer of 1 to 20, and when r is 2 or more, R ⁶ may be the same or different. ] The viscosity index improver according to claim 1 or 2, wherein the solubility parameter of the base oil is 7.8 to 9.5 (cal / cm ³ ) ^1/2 . The copolymer (A) further has a (meth) acrylic acid alkyl ester (c) having an alkyl group having 1 to 4 carbon atoms and / or a linear or branched alkyl group having 9 to 36 carbon atoms (meth). The viscosity index improver according to any one of claims 1 to 3, which is a copolymer containing an acrylic acid alkyl ester (d) as a constituent monomer. The copolymer (A) is 3 to 65% by weight of the (b) and 1 to 80% by weight of the (c) based on the total weight of the monomers constituting the (A) as a constituent monomer. The viscosity index improver according to claim 4, which is a copolymer containing 1 to 60% by weight of the above (d). The viscosity index improver according to any one of claims 1 to 5, wherein the copolymer (A) has a weight average molecular weight of 5,000 to 2,000,000. Further, claim 1 comprises 0.01 to 30% by weight of a (meth) acrylic acid alkyl ester (co) polymer (B) other than the copolymer (A) based on the weight of (A). The viscosity index improver according to any one of 1 to 6. The viscosity index improver according to any one of claims 1 to 7, wherein the base oil has a kinematic viscosity of 1 to 15 mm ² / s at 100 ° C. and the viscosity index of the base oil is 100 or more. The viscosity index improver according to any one of claims 1 to 8, a cleaning agent, a dispersant, an antioxidant, an oiliness improver, a pour point lowering agent, a friction wear adjusting agent, an extreme pressure agent, and a defoaming agent. A lubricating oil composition containing at least one additive selected from the group consisting of an anti-emulsifier, a metal defoaming agent and an antioxidant.