JPH0853686A - Viscosity index improver - Google Patents

Abstract

PURPOSE:To lower the low-temp. viscosity of a high-viscosity-index oil contg. an isomerized paraffin by using a specific alkyl acrylate-alkyl methacrylate copolymer as the main component. CONSTITUTION:A viscosity index improver comprising a copolymer having a wt. average mol.wt. of 10,000-500,000 is obtd. by subjecting 20-70wt.% alkyl acrylate component comprising an alkyl acrylate having a 5-10C alkyl group and, if necessary, an alkyl acrylate having a 1-4C alkyl group and 80-30wt.% alkyl methacrylate having a 1-22C alkyl group to free-radical polymn. in the presence of an azoic or peroxide polymn. catalyst in a mineral oil or other solvent.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a viscosity index improver. More specifically, it relates to a viscosity index improver for high viscosity index mineral oils containing isomerized paraffin.

[0002]

2. Description of the Related Art Due to social demands for fuel efficiency in recent years, it has been strongly desired that lubricating oils and hydraulic oils have low viscosity at low temperatures. As one of the means for solving this, high viscosity index oil containing isomerized paraffin, or the combination thereof with ordinary solvent refined mineral oil, synthetic lubricating oil, and MLDW oil is being used. On the other hand, attempts have been made to improve the low temperature viscosity by using a pour point depressant. An example of this is found in JP-A-54-70305, and there is a demand for a viscosity index improver suitable for the present high viscosity index oil. On the other hand, a viscosity index improver in which acrylate is positively copolymerized with methacrylate is known. An example of this is JP-A 47-12982. However, the publication describes that it is used for an engine oil using a normal solvent-refined mineral oil having a viscosity index of about 100, but it is not disclosed to use it for a high-viscosity index oil containing isomerized paraffin. Furthermore, there is no disclosure of using a high viscosity index oil to provide a lubricating oil or hydraulic oil having a low viscosity at low temperature. It is a matter of course that no high viscosity index oil was used at the time of filing of the publication and no mention was made of making the low temperature viscosity extremely low.

[0003]

DISCLOSURE OF THE INVENTION The present invention has a significantly different composition from ordinary mineral oils, and when used in a high viscosity index oil having a high viscosity index, it provides an excellent low temperature viscosity and an improved viscosity index. Develop agents.

[0004]

Means for Solving the Problems As a result of intensive studies, the present inventors have unexpectedly found that when a conventionally known polymer is used in a high viscosity index oil which is being used in recent years, an extremely low low temperature viscosity is obtained. The present invention was found out by giving it, and it came to the present invention. The present invention comprises a polymer (A) containing 20 to 70% by weight of an alkyl acrylate (a1) and 80 to 30% by weight of an alkyl methacrylate (b1) as a constituent unit, and has a high viscosity index oil containing isomerized paraffin. Is a viscosity index improver for.

The alkyl acrylate (a1) used in the present invention is an acrylate having an alkyl group having a linear or / and branched alkyl group having 1 to 22 carbon atoms. Examples of these are methyl acrylate, ethyl acrylate, isopropyl acrylate,
n-butyl acrylate, s-butyl acrylate, t
-Butyl acrylate, pentyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, i
-Decyl acrylate, dodecyl acrylate, tetradecyl acrylate, pentadecyl acrylate, cetyl acrylate, octadecyl acrylate and the like. Among these various acrylates, those having an alkyl group having 10 or less carbon atoms are preferable from the viewpoint of giving a lubricating oil having a low temperature viscosity, and particularly, an acrylate having an alkyl group having 1 to 4 carbon atoms and 5 to 5 carbon atoms. It is preferable to use an acrylate having 10 alkyl groups in combination, or to use only an acrylate having an alkyl group having 5 to 10 carbon atoms. More preferred are octyl acrylate and 2-ethylhexyl acrylate having an alkyl group having 8 carbon atoms.

The alkyl methacrylate (b1) used in the present invention is usually one having 1 to 22 carbon atoms, and examples thereof are methacrylates having the same alkyl group as the acrylate. Among these various methacrylates, preferred are methacrylates having an alkyl group having 10 or more carbon atoms, and particularly preferably 0 to 30 those having an alkyl group having 1 to 4 carbon atoms based on the total amount of methacrylate. % By weight, alkyl groups having 12 to 13 carbon atoms are 10 to 65% by weight, alkyl groups having 14 to 15 carbon atoms are 10 to 65% by weight, and alkyl groups having 16 to 18 carbon atoms are 0 to This is the case of 30% by weight.

There is a preferred range for the copolymerization ratio of the alkyl acrylate (a1) and the alkyl methacrylate (b1). From the viewpoint of low temperature viscosity characteristics (a1):
(B1) is generally preferred in the range of 20 to 70:80 to 30, and particularly preferred in the range of 30 to 60:70 to 40.

The viscosity index improver of the present invention has a preferred molecular weight. Usually, the weight average molecular weight (Mw) is required to be in the range of 1 to 500,000. If it is less than 10,000, the thickening effect is insufficient, and if it exceeds 500,000, the shear stability becomes poor.
When used as drive system lubricating oil (manual transmission oil, differential gear oil, automatic transmission oil, etc.), Mw is preferably 2
When used as a working oil (working oil for construction machinery, power steering oil, shock absorber oil, etc.), Mw is preferably in the range of 30,000 to 200,000, and engine oil (for gasoline, When it is used for diesel engines, etc., the Mw is in the range of 1300 to 500,000. In addition, this molecular weight is a value by GPC using polystyrene as a calibration curve.

The viscosity index improver of the present invention is a copolymer composed of an alkyl acrylate and an alkyl methacrylate, and if necessary, a monomer having at least one atom selected from a nitrogen atom, an oxygen atom and a sulfur atom. It may be a polymer containing one or more kinds of monomers. Examples of the introduction method include random copolymerization, graft copolymerization, and graft addition.
In this case, it is preferable that the viscosity index improver can be imparted with clean dispersibility and antioxidant property. An example of this is USP50
13468, USP5013470, EP50801
2, USP 4606834, USP 4036766, U
SP4036768, USP4904404, USP4
812261, USP4686812, USP4790
948, USP 4795577, JP-A-60-1107.
90, JP-A-61-247719, JP-A-63-514.
97, JP-A-63-179999, JP-A-01-193.
308, JP-A-01-284593, JP-A-62-14
1096, JP-A-02-296811, JP-A-04-2
Those described in 11498 and the like can be used. Specific examples thereof include N-vinylpyrrolidone, N-vinylpyrrolidone and N-vinylpyrrolidone.
Vinylthiopyrrolidone, vinylpyridine, N, N-dialkylaminoalkylene (meth) acrylate (the carbon number of the alkyl group is usually 1 to 4), N, N-dialkylaminoalkylene (meth) acrylamide (the carbon number of the alkyl group is Usually 1 to 4), vinylimidazole, morpholinoalkylene (meth) acrylate, etc., aminophenothiazine, N-arylphenylenediamine, aminocarbazole, aminothiazole, aminoindole,
Aminopyrrole, aminoimidazoline, aminomercaptothiazole, having aminopiperidine residue (meta)
Various types such as acrylate derivatives can be used. Also,
As an example of the compound to be graft-added, a small amount (for example, 0.5 to 5% by weight) of a carboxylic acid compound (maleic anhydride, methacrylic acid, crotonic acid, itaconic acid, etc.) is copolymerized during the copolymerization of acrylate and methacrylate. Examples thereof include those that are amidated or imidized with (poly) amines, and those that are Mannich condensed with formaldehyde and (poly) amines. Furthermore, a non-vinyl compound (for example, phenothiazines, imidazoles, thiazoles, benzothiazoles, triazoles, thiazolinedins, pyrimidines, piperazines, pyrrolidinones) is used for the copolymer (A) by using a radical catalyst or the like. , Oxazoles, thiomorpholines, etc.) and the like. The amount of these various compounds in the polymer (A) is usually 20% by weight or less, preferably 10% by weight or less, particularly preferably 5% by weight or less.
% By weight or less.

In the present invention, the polymer (A) is a constituent unit in the range of less than 30% by weight, preferably less than 20% by weight, in addition to (a1) and (b1), a polymerizable double bond. Other compounds having Examples of these include unsaturated mono- and / or polycarboxylic acid esters having an alkyl group with 1 to 30 carbon atoms (butyl crotonate, octyl crotonate, dodecyl crotonate, dibutyl maleate, dioctyl fumarate, dilauryl). Maleate, distearyl fumarate, dioctyl itaconate, dilauryl itaconate, etc.), vinyl aromatic compounds (styrene, vinyltoluene, etc.), vinyl ethers (methyl vinyl ether, butyl vinyl ether, etc.), vinyl esters (vinyl acetate, Vinyl propionate etc.), alpha olefins (decene, dodecene etc.) and the like.

The viscosity index improver of the present invention can be easily obtained by a conventional method. For example, it can be obtained by radically polymerizing the above-mentioned monomers in mineral oil or a solvent. In this case, as a polymerization catalyst, an azo type (for example, azobisisobutyronitrile, azobisvaleronitrile, etc.) or a peroxide type (for example, benzoyl peroxide,
Cumyl peroxide, lauryl peroxide, etc.) are used.

The viscosity index improver of the present invention preferably further contains a pour point depressant. As the pour point depressant, conventionally known polymethacrylates are used. For example, a methacrylate-based one having an alkyl group having 10 to 20 carbon atoms, or a combination of these methacrylate-based ones having two or more different compositions and molecular weights (for example, described in JP-A-54-70305). Of very high molecular weight (eg US
P5229021, etc.) and the like. When the pour point depressant is contained in this way, the polymer (A) 1
The pour point depressant is usually 30 parts by weight or less with respect to 00 parts by weight,
Preferably it is 20 parts by weight or less.

The isomerized paraffin-containing high viscosity index oil to which the viscosity index improver of the present invention is added is significantly different in performance and composition from those produced by ordinary solvent refining. is there. This high viscosity index oil is disclosed in Dutch Patent Application No. 7613854 and Japanese Patent Laid-Open No. 5-2143.
49 and the like. That is, it contains a component obtained by hydrocracking n-paraffin using a catalyst to isomerize i-paraffin. At this time, a noble metal catalyst or the like is usually used as the hydrocracking catalyst. It should be noted that the i-paraffin-containing isomerized mineral oil produced in this manner is further subjected to solvent refining and is also included in the target mineral oil of the present invention. Such an isomerized paraffin-containing mineral oil has a large viscosity index because it has a composition greatly different from that of a usual solvent-refined mineral oil. (Ordinary mineral oil has a viscosity index of 90-10
5). The viscosity index improver of the present invention is, of course, used only for isomerized paraffin-containing high viscosity index oils, but it also includes ordinary mineral oils and synthetic lubricating oils, and further MLDW.
It is also included in the present invention when mixed with oil or the like. Here, ordinary mineral oil means toluene / after removing the aromatic components with a solvent such as vacuum distillation oil and deasphalted oil with furfural.
Dewaxed with methyl ethyl ketone mixed solvent or propane solvent. Synthetic lubricating oils include those of ester type (esters of alcohols such as trimethylolpropane, pentaerythritol, and hexamethylenediol and fatty acids, esters of adipic acid and aliphatic alcohols) and polyolefin type. (For example, PAO-based ones such as decene oligomer). Further, MLDW oil is produced by a process called mobile lube dewaxing, and specifically, is wax obtained by decomposing and removing wax with a synthetic zeolite catalyst or the like. The present invention also includes the case where the high viscosity index oil and other substances are used in combination, and in this case, the content of the high viscosity index oil is about 100 to 30% by volume.

The viscosity index improver of the present invention is used together with a high viscosity index oil, and is most suitable for engine oils, drive system lubricating oils and hydraulic oils. Of these, when used in drive system lubricating oil or hydraulic oil, which is strongly required to have low temperature viscosity,
The excellent effect is further exhibited, which is preferable.

The viscosity index improver of the present invention contains other optional components such as detergents (sulfonate, salicylate, phenate, naphthenate, etc.), dispersants (isobutenyl succinimide, Mannich condensation). Substances, etc.), antioxidants (zinc dithiophosphate, amines, hindered phenols, etc.), oily agents (fatty acids,
A fatty acid ester-based agent), a friction / wear modifier (molybdenum dithiophosphate, molybdenum carbamate, etc.), and an extreme pressure agent (sulfur-phosphorus-based, chloro-based, etc.) may be contained.

[0016]

The present invention is described in detail below with reference to examples, but the present invention is not limited thereto. Unless otherwise specified,% means% by weight.

Example 1 300 g of mineral oil was placed in a glassy 1 liter reactor equipped with a stirrer, a thermometer, and a condenser, and the air in the reactor was replaced with nitrogen, and then the temperature was raised to 70 ° C. While flowing a small amount of nitrogen, 90 g of 2-ethylhexyl acrylate as a monomer, 210 g of a mixture of dodecyl methacrylate and tridecyl methacrylate (produced from dovanol, hereinafter abbreviated as 12 / 13MA) 210 g, and azobisvaleronitrile as a catalyst 0. A mixed solution of 9 g and 1.4 g of lauryl mercaptan as a chain transfer agent was added dropwise over 4 hours, and kept at the same temperature for 3 hours to complete the polymerization.
As a result, a polymer having a Mw of 380000 and a Mw / Mn of 1.9 and a polymer concentration of 49% was obtained.

Example 2 135 As a monomer, 2-ethylhexyl acrylate was used.
Polymerization was carried out in the same manner as in Example 1 except that 165 g of a mixture of tetradecyl methacrylate and pentadecyl methacrylate (produced from dovanol, hereinafter abbreviated as 14 / 15MA) was used, and Mw 39,000, Mw.
A polymer having a polymer concentration of /Mn1.9 of 49% was obtained.

Example 3 As a monomer, 2-ethylhexyl acrylate was used as 18
Polymerization was carried out in the same manner as in Example 1 except that 0 g and tetradecyl methacrylate 120 g were used, and Mw 4.0.
A polymer having a Mw / Mn of 2.0 and a polymer concentration of 49% was obtained.

Example 4 As a monomer, 2-ethylhexyl acrylate 135
g, 41 g of dodecyl methacrylate, 105 g of tetradecyl methacrylate, 7: 3 mixture of cetyl methacrylate and octadecyl methacrylate (16 / 18M below)
Polymerization was carried out in the same manner as in Example 1 except that 19 g (abbreviated to A) was used to obtain a polymer having a Mw of 370000 and a Mw / Mn of 1.8 and a polymer concentration of 49%.

Example 5 Polymerization was performed in the same manner as in Example 4 except that 30 g of butyl acrylate and 105 g of 2-ethylhexyl acrylate were used instead of 135 g of 2-ethylhexyl acrylate in the monomer, and Mw was 380000, Mw. A polymer having a polymer concentration of /Mn1.9 of 49% was obtained.

Example 6 Polymerization was carried out in the same manner as in Example 4 except that 135 g of dodecyl acrylate was used instead of 135 g of 2-ethylhexyl acrylate, and Mw was 370000, Mw / Mn.
A polymer having a polymer concentration of 1.7 and 49% was obtained.

Example 7 N-vinylpyrrolidone 3 was added to 200 g of the polymer of Example 4.
g, dicumyl peroxide 1.8 g, and mineral oil 3 g were put in a glass 1 liter reactor, the air in the reactor was replaced with nitrogen, and the mixture was reacted at 150 C for 4 hours with stirring. Polymerized Mw 43,000, M
A polymer having a w / Mn of 2.4 and a polymer concentration of 50% was obtained.

Example 8 Example 4 except that no lauryl mercaptan was used.
Polymerization is performed in the same manner as in Mw 220,000, Mw / Mn
A polymer of 2.9 having a polymer concentration of 50% was obtained.

Comparative Example 1 Methylmethacrylate (hereinafter abbreviated as MMA) 50 g, 12/13 MA 200 g, 16/18 MA as a monomer
Polymerization was performed in the same manner as in Example 1 except that 50 g was used, and the polymer concentration of Mw 38,000 and Mw / Mn 1.9 was 4
9% polymer was obtained.

Comparative Example 2 MMA as a monomer 15 g, 14/15 MA 200 g,
Polymerization was carried out in the same manner as in Example 1 except that 50 g of 16/18 MA was used to obtain a polymer having a Mw of 380000 and a Mw / Mn of 1.9 and a polymer concentration of 49%.

Comparative Example 3 MMA 50 g, 12/13 MA 95 g, 1 as a monomer
Polymerization was carried out in the same manner as in Example 1 except that 93 g of 4 / 15MA and 62 g of 16 / 18MA were used, and Mw 3.9.
A polymer having a Mw / Mn of 1.8 and a polymer concentration of 49% was obtained.

Comparative Example 4 MMA 50 g, 12/13 MA 75 g, 1 as a monomer
Polymerization was carried out in the same manner as in Example 1 except that 113 g of 4 / 15MA and 62 g of 16 / 18MA were used, and Mw of 3.9.
A polymer having a Mw / Mn of 1.8 and a polymer concentration of 49% was obtained.

Comparative Example 5 Comparative Example 3 except that lauryl mercaptan was not used.
Polymerized in the same manner as above, Mw 220,000, Mw / Mn3.0
A polymer having a polymer concentration of 50% was obtained.

(Use Examples 1 to 7 and Comparative Use Examples 1 to 4) The polymers of Examples 1 to 7 and the polymers of Comparative Examples 1 to 4 were used in 16 to 1
7%, as a pour point depressant, ACLUBE 122 (manufactured by Sanyo Kasei Co., Ltd.) 1%, high viscosity index oil A (viscosity index 1
23 (100 neutral oil) and high viscosity index oil B (100 neutral oil with viscosity index 138) respectively,
100 ℃ required for automatic transmission oil
The kinematic viscosity was adjusted to 7.4 to 7.6 cSt. The viscosities at -40 ° C were measured and the results shown in Table 1 were obtained. As is clear from Table 1, the viscosity of the present invention at low temperature is low.

[0031]

[Table 1] ------------- Viscosity index improver | High viscosity index oil A | High Viscosity index oil B −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− | 1 | of Example 1 | 21600 cps | 26500 cps | 2 | Example 2 | 16100 | 20200 | 3 | Example 3 | 18400 | 21000 Example of use | 4 | Example 4 | 14300 | 18600 | 5 | Example 5 | 15200 | 19900 | 6 | of Example 6 | 24700 | 27100 | 7 | of Example 7 | 16200 | 19700 −−−−−−−−−−−−−−−−−−−−−−−−−−− −−−−−−−− Comparison | 1 | In Comparative Example 1 | 52200 | 35500 Example | 2 | Thing of Comparative Example 2 | 37700 | 36000 | 3 | Thing of Comparative Example 3 | 37500 | 42400 | 4 | Thing of Comparative Example 4 | 34400 | 38200 ------------------ −−−−−−−−−−−−−−−−−−−−−−

(Comparative Use Examples 5 to 15) Instead of the high viscosity index oil, a conventional solvent refined mineral oil A (viscosity index 10 of 10) was used.
0 neutral oil), solvent refined mineral oil B (viscosity index 98)
100 neutral oil of Examples 1 to 7 and Comparative Examples 1 to
No. 4 was added in the same manner as in Use Examples 1 to 7 and Comparative Use Examples 1 to 4, the viscosity at −40 ° C. was measured, and the results in Table 2 were obtained.
As can be seen from Table 2, when ordinary mineral oil is used,
In each of Examples 1 to 7 and Comparative Examples 1 to 4, the low temperature viscosity does not change much. This indicates that the high viscosity index oil and the ordinary mineral oil have considerably different effects on the low temperature viscosity even when the same viscosity index improver is used.

[0033]

[Table 2] ------------- Viscosity index improver | High viscosity index oil A | High Viscosity index oil B −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− │ 5 │ of Example 1 ｜ 52200 cps | 47600 cps │ 6 │ Example 2 ｜ 51000 ｜ 48800 ｜ 7 ｜ Example 3 ｜ 52500 ｜ 49000 Comparison ｜ 8 ｜ Example 4 ｜ 46200 ｜ 44500 Usage Example ｜ 9 ｜ Example 5 ｜ 41300 ｜ 42700 | 10 | Example 6 | 39800 | 38400 | 11 | Example 7 | 44600 | 41500 | 12 | Comparative Example 1 | 33200 | 32100 | 13 | Comparative Example 2 | 55200 | 58800 | 14 | Comparative example | 45300 | 44100 | 15 | Comparative Example 4's | 51000 | 53200 ----------------------------------------------------------------------------------------------------------------------------------------------- −−

(Use Example 8 and Comparative Use Example 16) Use Example 1
-7 and the high-viscosity index oils A and B used in Comparative Use Examples 1-4, 3% of the polymer of Example 8 and Comparative Example 5 and ACLUVE 133 (manufactured by Sanyo Chemical Industry Co., Ltd.) as a pour point depressant.
0.5% is added to adjust the 100C viscosity required for 10W / 30 engine oil to 10.2-10.6cSt, and -2.
The CCS viscosity at 0 ° C. was measured and the results shown in Table 3 were obtained.

[0035]

[Table 3] ------------- Viscosity index improver | High viscosity index oil A | High Viscosity index oil B −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− 3130 cps | 3030cps −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−

(Comparative use examples 17 to 18) Comparative use examples 5 to 5
Lubricating oils were prepared in the same manner as in Use Example 8 and Comparative Use Example 16 using the usual solvent refined mineral oils A and B used in Table 15.
Was obtained.

[0037]

[Table 4] ------------- Viscosity index improver | High viscosity index oil A | High Viscosity index oil B −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− Comparative use example 17 | of Example 8 | 3820 cps | 3610 cps Comparative usage example 18 | Comparative example 5 | 4020 | 4160 --------------------------------------------------------------------------------------------------------------------------------------------------

(Use Example 9 and Comparative Use Example 19) Same as Use Examples 1 to 7 and Comparative Use Examples 1 to 4 except that those of Example 5 and Comparative Example 3 were used and no pour point depressant was used. Then, the viscosity at -40 ° C was measured and the results shown in Table 5 were obtained.

[0039]

[Table 5] ------------- Viscosity index improver | High viscosity index oil A | High Viscosity index oil B −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− Use example 9 | 51000cps −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− 100,000 or more -----------------------------------------

(Use Examples 10 to 12 and Comparative Use Example 20)
Using those of Examples 2, 4, 5, and Comparative Example 3, a high viscosity index oil A as a base oil: normal mineral oil A = 50:
Example 1 and Comparative Example 1 except that 50 (vol%, abbreviated as base oil A), high viscosity index oil B: normal mineral oil B = 50: 50 (vol%, abbreviated as base oil B) were used. Similarly, the viscosity at -40 ° C was measured and the results shown in Table 6 were obtained.

[0041]

[Table 6] ------------------------------------------- Viscosity index improver | Base oil A | Base oil B −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− | 10 | Example 2 | 21000cps | 27200cps Usage Example | 11 | Example 4 | 16800 | 20100 | 12 | Example 5 | 17300 | 21100 --21 ---------------------------------------------------------------------------------------------------------------------------------------- -------- Comparative use example | 20 | The thing of the comparative example 3 | 31700 | 36200 ------------------------------------------------------------------------------------------------------------------ −−−−−

[0042]

As is clear from the above Examples and Comparative Examples, it is found that when the improver of the present invention is used in a high viscosity index oil, a very low viscosity at low temperature (-40 ° C) is given.

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[Procedure amendment]

[Submission date] August 9, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0033

[Correction method] Change

[Correction content]

[0033]

[Table 2]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0037

[Correction method] Change

[Correction content]

[0037]

[Table 4]

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C10M 109: 00 145: 14) C10N 30:02 40:08 40:25

Claims (6)

[Claims] 1. A high viscosity isomerized paraffin containing a polymer (A) containing 20 to 70% by weight of an alkyl acrylate (a1) and 80 to 30% by weight of an alkyl methacrylate (b1) as a constituent unit. Viscosity index improver for index oils. 2. The improver according to claim 1, wherein (a1) is an alkyl acrylate having an alkyl group having 10 or less carbon atoms. 3. (a1) is an alkyl acrylate (a1-1) having an alkyl group having 1 to 4 carbon atoms, and an acrylate (a1-) having an alkyl group having 5 to 10 carbon atoms.
The improving agent according to claim 1 or 2, which is used in combination with 2) or is only (a1-2). 4. The improver according to claim 3, wherein (a1-2) is an alkyl acrylate having an alkyl group having 8 carbon atoms. 5. The improver according to claim 1, further comprising a pour point depressant (B). 6. The improver according to claim 1, which is for engine oil, drive system lubricating oil, or hydraulic oil.