JP2000239687A - Viscosity index improver and lubricating oil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a viscosity index improver giving an excellent low- temperature viscosity and having good oxidation stability and to provide a lubricating oil containing the same. SOLUTION: This improver comprises a random copolymer (A) essentially consisting of (a1) alkyl acrylate monomer with a 10C or lower alkyl and (a2) at least one monomer selected from the group consisting of a conjugated diene, acetylene, a substituted acetylene, an alkyl vinyl ether, and an alkyl allyl ether, wherein the amount of component (a) is above 70 wt.%, and that of (a2) is 0.05-3 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a viscosity index improver and a lubricating oil useful for an engine oil, a gear oil, a hydraulic oil and the like. More specifically, the present invention relates to a viscosity index improver having excellent low-temperature viscosity, low coking amount at high temperature, and good oxidation stability, and a lubricating oil containing the same.

[0002]

2. Description of the Related Art Various viscosity index improvers have been used to improve the viscosity index of lubricating oils. For example, hydrogenated poly (meth) acrylates, ethylene / propylene copolymers, and styrene / diene copolymers are known. However, in recent years, there has been a strong demand for lubricating oils used in automobiles and the like to have low low-temperature viscosity from the viewpoint of fuel saving and to improve oxidation stability from the viewpoint of long life. Agents are no longer able to satisfy this need.

[0003]

SUMMARY OF THE INVENTION In response to such a demand, the present invention develops a viscosity index improver which gives an excellent low-temperature viscosity and has good oxidation stability, and a lubricating oil containing the same. .

[0004]

Means for Solving the Problems As a result of diligent studies, the present inventors have found that a random copolymer comprising an alkyl acrylate and a specific amount of a second monomer component has an extremely low low-temperature viscosity and has a low The inventors have found that the stability is good, and have reached the present invention. The present invention has a carbon unit of 10
An alkyl acrylate monomer (a1) having the following alkyl group and a conjugated diene, acetylene, substituted acetylene,
It comprises a random copolymer (A) containing, as an essential component, at least one monomer (a2) selected from the group consisting of alkyl vinyl ethers and alkyl allyl ethers, wherein the content of (a1) exceeds 70% by weight. And (a2)
Is a viscosity index improver having a content of 0.05 to 3% by weight.

The alkyl acrylate having an alkyl group having 10 or less carbon atoms (a1) used in the present invention includes methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, s-butyl acrylate, and t-butyl acrylate. , Pentyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, n-decyl acrylate, i-decyl acrylate and the like. Among these various acrylates, when an alkyl acrylate having an alkyl group having 1 to 4 carbon atoms and an acrylate having an alkyl group having 5 to 10 carbon atoms are used in combination in terms of providing a lubricating oil having a low temperature viscosity, or 5 carbon atoms
The case of only an acrylate having 10 alkyl groups is preferred. More preferred are octyl acrylate and 2-ethylhexyl acrylate having an alkyl group having 8 carbon atoms.

The monomer (a2) used in the present invention
Is at least one member selected from the group consisting of conjugated dienes, acetylenes, substituted acetylenes, alkyl vinyl ethers and alkyl allyl ethers. Examples of the monomer (a2) used in the present invention include conjugated dienes having 4 to 12 carbon atoms (such as butadiene, isoprene, and chloroprene);
Acetylene; a substituted acetylene having 3 to 12 carbon atoms [alkyl acetylene (propyne, 1-butyne, 1-pentyne,
1-hexyne), arylacetylene having 8 to 16 carbon atoms (phenylacetylene, p-methylphenylacetylene, etc.)]; alkyl vinyl ether [usually alkyl vinyl ether having a linear or branched alkyl group having 1 to 18 carbon atoms (methyl Vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, amyl vinyl ether, hexyl vinyl ether, heptyl vinyl ether, octyl vinyl ether, nonyl vinyl ether, decyl vinyl ether, dodecyl vinyl ether, tridecyl vinyl ether, tetradecyl vinyl ether, pentadecyl vinyl ether, hexadecyl vinyl ether, octadecyl vinyl ether Etc.]; alkyl allyl ethers [usually, linear or Alkyl allyl ethers having a branched alkyl group (methyl allyl ether, ethyl allyl ether, propyl allyl ether, butyl allyl ether, amyl allyl ether, hexyl allyl ether, heptyl allyl ether, octyl allyl ether, nonyl allyl ether, decyl allyl ether, dodecyl Allyl ether, tridecyl allyl ether, tetradecyl allyl ether, pentadecyl allyl ether, hexadecyl allyl ether, octadecyl allyl ether, etc.], butadiene, isoprene, carbon number 8
An arylacetylene having 10 to 10 carbon atoms; an alkyl vinyl ether having an alkyl group having 1 to 8 carbon atoms; and an alkyl allyl ether having an alkyl group having 1 to 8 carbon atoms.

In the present invention, in addition to (a1) and (a2), the random copolymer (A) is an alkyl methacrylate monomer (b1) having an alkyl group having 1 to 20 carbon atoms. An alkyl acrylate monomer (b2) having an alkyl group having 11 or more carbon atoms can be contained. Examples of the monomer (b1) include methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, isodecyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, hexadecyl methacrylate, and octadecyl methacrylate. Can be Among these, preferred are methyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, and isodecyl methacrylate. Examples of the monomer (b2) include decyl acrylate, isodecyl acrylate, dodecyl acrylate, tridecyl acrylate, tetradecyl acrylate, hexadecyl acrylate, and octadecyl acrylate. Of these, decyl acrylate and isodecyl acrylate are preferred. Further, in the present invention, the copolymer (A) may contain another radical polymerizable monomer (c) as a constitutional unit. As the monomer (c), alkyl-unsaturated mono- and / or polycarboxylic acid esters having 1 to 30 carbon atoms (butyl crotonate, octyl crotonate, dodecyl crotonate, dibutyl maleate, dioctyl fumarate, dilauryl) Maleate, distearyl fumarate, dioctyl itaconate, dilauryl itaconate, alkyl acrylate having 11 to 30 carbon atoms, alkyl methacrylate having 21 to 30 carbon atoms); vinyl aromatic compound (styrene, vinyl toluene, etc.); vinyl Esters (vinyl acetate, vinyl propionate, etc.); carboxylic acid compounds (maleic anhydride, methacrylic acid, crotonic acid, itaconic acid, etc.); acrolein, containing one or more of these monomers can do. Of these, preferred are vinyl aromatic compounds, and particularly preferred is styrene.

Further, in the present invention, the random copolymer (A) may comprise, as a constitutional unit, a monomer (d) having at least one atom selected from a nitrogen atom, an oxygen atom and a sulfur atom, if necessary. ) May be contained. In this case, the viscosity index improver is preferable because it can impart clean dispersibility, antioxidant property, and the like. Examples include N-vinylpyrrolidone, N-vinylthiopyrrolidone, vinylpyridine, N,
N-dialkylaminoalkyl (meth) acrylate (the alkyl group usually has 1 to 4 carbon atoms), N, N-dialkylaminoalkyl (meth) acrylamide (the alkyl group usually has 1 to 4 carbon atoms), vinylimidazole, Morpholinoalkylene (meth) acrylate, etc., aminophenothiazine, N-arylphenylenediamine,
Examples thereof include aminocarbazole, aminothiazole, aminoindole, aminopyrrole, aminoimidazoline, aminomercaptothiazole, and a (meth) acrylate derivative having an aminopiperidine residue. Of these, preferred are N-vinylpyrrolidone, N, N
-Dialkylaminoalkyl (meth) acrylate (alkyl group usually has 1 to 4 carbon atoms), N, N-dialkylaminoalkyl (meth) acrylamide (alkyl group usually has 1 to 4 carbon atoms) and N-arylphenylene It is a (meth) acrylate derivative having a diamine residue.

The random copolymer (A) in the present invention
Can be easily obtained by an ordinary method. For example, it can be obtained by radical polymerization of the above monomers in mineral oil or a solvent. In this case, an azo type (eg, azobisisobutyronitrile, azobisvaleronitrile, etc.) or a peroxide type (eg, benzoyl peroxide, cumyl peroxide, lauryl peroxide, etc.) can be used as the polymerization catalyst. .

The copolymer (A) is a monomer (a1)
And (a2) a polymer obtained by polymerizing the monomers (b) and / or (c) and / or (d), if necessary, further adding the monomer (d) to a peroxide-based polymerization catalyst The graft polymer (A ′) can be obtained by performing the graft polymerization with

Further, the random polymer (A) is obtained by polymerizing the monomers (b) and / or (c) and / or (d) with the monomers (a1) and (a2) if necessary. When the monomer (c) is a carboxylic acid compound (maleic anhydride, methacrylic acid, crotonic acid, itaconic acid, etc.) in the polymer obtained, amidation or imidation with (poly) amines is performed. Alternatively, when the monomer (c) is acrolein, it can be obtained by performing Mannich condensation with (poly) amines. Further, the random copolymer (A) contains the monomers (a1) and (a)
If necessary, the polymer obtained by polymerizing the monomers (b), (c) and / or (d) in 2) may be added with a non-vinyl compound (for example, phenothiazines, imidazoles) by using a peroxide polymerization catalyst. , Thiazoles, benzothiazoles, triazoles, thiazolindins, pyrimidines, piperazines, pyrrolidinones, oxazoles,
Thiomorpholines, etc.).

The weight average molecular weight (Mw) of the random polymer (A) is usually from 100,000 to 500,000 from the viewpoints of the thickening effect and the shear stability. When used as a drive system lubricating oil (manual transmission oil, differential gear oil, automatic transmission oil, etc.), Mw is preferably 20,000 to 150,000, and hydraulic oil (hydraulic oil of construction machinery, power steering oil, shock oil) Mw is preferably in the range of 30,000 to 200,000 when used in an engine oil (for gasoline, diesel, etc.).
It is preferable to be in the range of 500,000. The weight average molecular weight is a molecular weight converted into polystyrene by gel permeation chromatography.

The amount of the monomer (a1) used in the present invention usually exceeds 70% by weight based on the random copolymer (A). Preferably, 72 to 95% by weight
And more preferably 75 to 90% by weight.
When the use amount of (a1) is 70% by weight or less, the effect of reducing the low-temperature viscosity is reduced. Monomer (a2) in the present invention
Is usually 0.05 to 3 based on the polymer (A).
% By weight. Preferably, it is 0.1 to 1% by weight.
If the amount of (a2) used is less than 0.05% by weight, the amount of coking increases sharply, and there is a possibility that the piston and cylinder of the engine may be damaged. On the other hand, if it exceeds 3% by weight, excellent oxidation stability cannot be maintained, which is insufficient for future demands for long life of lubricating oil. The amount of the monomer (b) used in the present invention is usually 29% by weight or less based on the polymer (A), and preferably 15 to
25% by weight. The amount of (c) used is usually 10% by weight or less, preferably 5% by weight or less. The amount of the monomer (d) used in the present invention is usually 5% by weight or less, preferably 3% by weight. (D) is preferably used in an amount of 0.5% by weight or more for improving cleanliness.

The viscosity index improver of the present invention preferably further contains a pour point depressant. Examples of the pour point depressant include polymethacrylate, polyacrylate,
Conventionally known compounds such as an alkylated aromatic compound and a fumarate-vinyl acetate copolymer are used. For example,
Methacrylates having 10 to 20 carbon atoms in the alkyl group, or combinations of two or more of these methacrylates having different compositions and molecular weights (for example, those described in JP-A-54-70305 and the like) Stuff),
Furthermore, those having a very high molecular weight (for example, USP 52290)
21 and the like). When the pour point depressant is thus contained, the pour point depressant is usually 30 parts by weight or less, preferably 1 part by weight, per 100 parts by weight of the polymer (A).
-20 parts by weight.

The viscosity index improver of the present invention is blended with a lubricating base oil to have a desired viscosity, melted and used as the lubricating oil of the present invention. The base oil generally has a viscosity in the range of 50 to 300 neutral oils. Specific examples include ordinary mineral oils, high viscosity index oils containing isomerized paraffins obtained by hydrocracking paraffins or polycyclic aromatics with a hydrogenation catalyst, and hydrocarbon-based synthesis comprising α-olefin oligomers. Lubricating oils, dioctyl adipates, ester-based synthetic lubricating oils such as fatty acids and trimethylol can be used. Among these, high viscosity index oils containing isomerized paraffin have a different composition from ordinary solvent-refined mineral oils, have large viscosity indices, and vary depending on the production method, isomerized paraffin content, etc.
It is about 0 to 160 (normal mineral oil has a viscosity index of about 90 to 105). Also, high viscosity index oils have a low content of aromatic compounds (for example, 1% by weight or less) and are therefore excellent in oxidative stability, and are preferred as base oils. The viscosity index improver of the present invention is usually added to the lubricating base oil in an amount of from 0.5 to 3
0% by weight is added and used as the lubricating oil of the present invention. 2 to 10% by weight when the lubricating oil of the present invention is an engine oil,
In the case of gear oil or automatic transmission oil, favorable results are obtained when 7 to 25% by weight is added.

The lubricating oil of the present invention also has a feature that when the viscosity index improver of the present invention and a molybdenum-based friction reducing agent are used in combination, the effect can be maximized. The molybdenum-based friction reducing agent includes a thiophosphate-based one and a carbamate-based one. The ratio of these molybdenum-based friction reducing agents in lubricating oil is usually 0.05
And the viscosity index improver is 0.5 to 30% by weight.
% By weight, lube base oil is 99.45 to 65% by weight.

The lubricating oil of the present invention may contain other known additives. These known components include, for example, viscosity index improvers (for example, hydrogenated products of ethylene / propylene copolymer and polyisoprene), detergents (sulfonate, salicylate, phenate, naphthenate and the like), Dispersant (isobutenyl succinimide type, Mannich condensation product type, etc.), antioxidant (zinc dithiophosphate, amine type, hindered phenol type, etc.), oil agent (fatty acid type, fatty acid ester type, etc.), A pressure agent (sulfur-phosphorous, chlorinated, etc.) may be included.

The intended uses of the lubricating oil of the present invention are gasoline engine oil, diesel engine oil, gear oil, automatic transmission oil, hydraulic oil, tractor oil, power steering oil,
Examples include shock absorber oil and compressor oil. Preferably, it is an engine oil.

[0019]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

Example 1 In a reactor equipped with a stirrer, a heating device, a thermometer, and a nitrogen blowing tube, 150 g of mineral oil, 80 g of 2-ethylhexyl acrylate as a monomer, and methyl methacrylate 5
g, 15 g of isodecyl methacrylate and 0.5 g of isoprene, 0.2 g of azobisvaleronitrile as a catalyst
After charging and purging with nitrogen, a polymerization reaction was carried out at 70 ° C. for 4 hours in a sealed state. As a result, a copolymer having a weight average molecular weight (M1) of 310,000 was obtained. This was designated as viscosity index improver 1 of the present invention.

Example 2 Polymerization was carried out in the same manner as in Example 1 except that 0.5 g of isoprene was changed to 0.5 g of n-butyl vinyl ether as a monomer, and a copolymer having a weight average molecular weight (M1) of 320,000 was used. A polymer was obtained. This was designated as viscosity index improver 2 of the present invention.

Example 3 75 g of 2-ethylhexyl acrylate as a monomer
5 g of butyl acrylate, isodecyl methacrylate 2
Example 1 except that 0 g and 0.5 g of isoprene were used.
Polymerization was carried out in the same manner as described above to obtain a polymer having a weight average molecular weight (M1) of 270,000. This was designated as viscosity index improver 3 of the present invention.

Example 4 75 g of 2-ethylhexyl acrylate as a monomer
Polymerization was carried out in the same manner as in Example 1 except that 5 g of styrene, 20 g of dodecyl methacrylate and 0.5 g of isoprene were used, to obtain a polymer having a weight average molecular weight (M1) of 340,000. This was designated as viscosity index improver 4 of the present invention.

Example 5 75 g of 2-ethylhexyl acrylate as a monomer
Polymerization was carried out in the same manner as in Example 1, except that 5 g of dimethylaminoethyl methacrylate, 20 g of dodecyl methacrylate, and 0.5 g of butyl allyl ether were used.
A polymer having a weight average molecular weight (M1) of 290,000 was obtained. This was designated as viscosity index improver 5 of the present invention.

Example 6 In a reactor equipped with a stirrer, a heating device, a thermometer and a nitrogen blowing tube, 150 g of mineral oil, 80 g of 2-ethylhexyl acrylate as a monomer, 20 g of dodecyl methacrylate and 0.5 g of isoprene, a catalyst were used. Was charged with 0.2 g of azobisvaleronitrile, purged with nitrogen, and then subjected to a polymerization reaction at 70 ° C. for 4 hours in a sealed state. Further, t
0.2 g of -butyl perbenzoate and 2 g of N-vinylpyrrolidone were charged, and graft polymerization was performed at 130 ° C for 2 hours. As a result, a polymer having a weight average molecular weight (M1) of 330,000 was obtained. This was designated as viscosity index improver 6 of the present invention.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 except that 0.5 g of isoprene was not used as a monomer to obtain a polymer having a weight average molecular weight (M1) of 320,000. This was designated as viscosity index improver ratio 1.

Comparative Example 2 80 g of 2-ethylhexyl acrylate as a monomer
Polymerization was carried out in the same manner as in Example 2 except that 5 g of methyl methacrylate, 15 g of isodecyl methacrylate and 3 g of n-butyl vinyl ether were used, to obtain a polymer having a weight average molecular weight (M1) of 310,000. This was designated as viscosity index improver ratio 2.

Comparative Example 3 OCP-based viscosity index improver comprising ethylene / propylene copolymer (Orfuse M-12, manufactured by Mitsui Petrochemical Industries, Ltd.)
10) was set as the viscosity index improver ratio 3.

Examples 7 to 12 and Comparative Examples 4 to 6 SJ-grade gasoline engines with the viscosity index improvers 1 to 6 of the present invention of Examples 1 to 6 and the viscosity index improver ratios 1 to 3 of Comparative Examples 1 to 3 Oil DI package 10% by weight, solvent refined oil A (200 neutral oil with viscosity index 100) 50
Wt% and high viscosity index oil B (100 with a viscosity index of 125
Neutral oil) 40% by weight of a viscosity index improver-free oil was added to a 100 ° C. kinematic viscosity of 10.5 mm ² / s, and the lubricating oils 1 to 6 and lubricating oil ratios 1 to 3 of the present invention were added. Created. These engine oils were subjected to a panel coking test and an oxidation stability test by the following methods. The results are shown in Table 1. Further, TBS viscosity (150 ° C., shear rate 10 ⁶ / sec) and CCS viscosity (−25 ° C., shear rate 10 ⁵ / sec) related to fuel economy were measured. The results are shown in Table 2.

(Method of Panel Coking Test) According to the panel coking test method Fed-791B, the lubricating oils 1 to 6 and the lubricating oil ratios 1 to 3 were subjected to a panel coking test at a panel temperature of 250 ° C. and an engine oil temperature of 100 ° C. for 4 hours. Carried out. After the test, the panel was washed with pentane, and the amount of coking was measured by a gravimetric method.

(Method of Oxidation Stability Test)
6 and lubricating oil ratios 1 to 3 according to JIS-K2514,
An oxidation stability test was performed at 165.5 ° C. for 120 hours.
The increase in the total acid value of the engine oil before and after the test was measured.

[0032]

[Table 1]

As can be seen from Table 1, lubricating oils 1 to 6 using the viscosity index improver of the present invention (Examples 7 to 12)
Has a significantly reduced coking amount as compared with lubricating oil ratio 1 (Comparative Example 4) using a viscosity index improver composed of a methacrylate-based polymer into which conjugated diene, substituted acetylene, alkyl vinyl ether or alkyl allyl ether is not introduced. Thus, the coking amount was equal to or less than the lubricating oil ratio 3 (Comparative Example 6) using the OCP-based viscosity index improver, which is conventionally said to have a small coking amount. Also,
A lubricating oil ratio of 2 (Comparative Example 5) using a viscosity index improver ratio of 2 containing 3% by weight of n-butyl vinyl ether as an alkyl vinyl ether had insufficient oxidation stability.

[0034]

[Table 2]

As can be seen from Table 2, the lubricating oils 1 to 6 using the viscosity index improver of the present invention (Examples 7 to 12)
Compared with the lubricating oil ratio 3 using the OCP viscosity index improver of Comparative Example 6, the TBS viscosity was lower and the CCS index was lower,
Good fuel economy can be expected.

[0036]

As is clear from the above examples, the lubricating oil using the viscosity index improver of the present invention is a
Since the coking amount can be reduced to the same level or less as compared with the engine oil to which the system viscosity index improver is added, and the TBS viscosity is lower and the CCS viscosity is lower than the case where the OCP system viscosity index improver is used. It is possible to provide an excellent lubricating oil that can meet the demand for fuel economy of automobiles.

Continued on the front page F term (reference) 4H104 BG10C BH07C CB08C CE01C CE03C CE05C CG01C DA02A EA02A EB02 EB05 FA06 LA01 LA02 LA04 LA05 PA02 PA03 PA04 PA05 PA20 PA42 PA44

Claims (8)

[Claims] 1. An alkyl acrylate monomer (a1) having an alkyl group having 10 or less carbon atoms as a constitutional unit and at least one kind selected from the group consisting of conjugated dienes, acetylenes, substituted acetylenes, alkyl vinyl ethers and alkyl allyl ethers. And (a2) as an essential component, the content of (a1) exceeds 70% by weight, and the content of (a2) is 0.0%.
A viscosity index improver that is 5 to 3% by weight. 2. An alkyl acrylate monomer (a1) having an alkyl group having 10 or less carbon atoms as a constitutional unit, and at least one monomer selected from the group consisting of conjugated dienes, acetylenes, substituted acetylenes, alkyl vinyl ethers and alkyl allyl ethers. Obtained by graft-polymerizing a monomer (d) having at least one atom selected from a nitrogen atom, an oxygen atom and a sulfur atom to a random copolymer (A) containing the monomer (a2) as an essential component. It comprises a polymer (A '), the content of (a1) exceeds 70% by weight, and (a2)
Is 0.05 to 3% by weight and the content of (d) is 5% by weight or less. 3. An alkyl acrylate (a1-1) having an alkyl group having 1 to 4 carbon atoms, wherein (a1) is an alkyl acrylate (a1-1) having 5 carbon atoms.
Alkyl acrylate having an alkyl group of 10 to 10 (a
The viscosity index improver according to claim 1 or 2, which is used in combination with (1-2) or (a1-2) alone. 4. A random copolymer further comprising (A) an alkyl methacrylate monomer (b) having an alkyl group having 1 to 20 carbon atoms as a constituent unit,
The viscosity index improver according to any one of claims 1 to 3, wherein the content of (b) is 29% by weight or less. 5. The viscosity index improver according to claim 1, which is used for a high viscosity index oil having a viscosity index of 110 to 160. 6. The viscosity index improver according to claim 1, further comprising a pour point depressant (C). 7. A lubricating oil to which the viscosity index improver according to claim 1 is added. 8. A high viscosity index of 0.5 to 30% by weight of a viscosity index improver according to claim 1, a 0.05 to 5% by weight of a molybdenum-based friction reducing agent, and a viscosity index of 110 to 160. A lubricating oil comprising 99.45 to 65% by weight of an oil as an essential component.