JPH0948988A - Viscosity index improver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a viscosity index improver which can heighten viscosity even when added in a small amount, is excellent in oxidation resistance and shear stability, and has a reduced temp. dependence of viscosity by polymerizing a free radical-polymerizable monomer using a specific chain transfer agent. SOLUTION: The improver comprises a (co)polymer obtained by polymerizing a free radical-polymerizable monomer using a free radical-polymerization initiator and a chain transfer agent free radical polymerization represented by the formula (wherein Q is a polyvalent organic group; A is a 1-8C alkylene; Z is a chain transfer group; p and q each is 0 or 1, provided that at least either is not 1; m is 2-100; and the groups in the respective [ ]s may be the same or different). This improver is reduced in sludge formation and is capable of increasing viscosity even when added in a small amount. It is excellent in oxidation resistance and shear stability and has a reduced temp. dependence of viscosity.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a viscosity index improver. More specifically, it relates to a low sludge viscosity index improver.

[0002]

2. Description of the Related Art As an important characteristic of a lubricating oil composition, it is required that the viscosity change is as small as possible in the operating temperature range. Viscosity index improvers are known as additives to enhance this property. Among them, polymethacrylates have the highest level of viscosity index improvement ability, so they are suitable for working oils such as gears and ATFs and engine oils. in use.

[0003]

However, the polymethacrylate type viscosity index improver has a problem that it has a large amount of sludge as compared with other types (for example, ethylene-propylene copolymer type) viscosity index improvers.

[0004]

Means for Solving the Problems The present inventors have improved the viscosity index of low sludge property by using a polymer having a narrow molecular weight distribution by using a specific chain transfer agent as a radical polymerizable monomer. The inventors have found that an agent can be obtained and reached the present invention. That is, the present invention provides a (co) polymer (A) obtained by polymerizing a radical polymerizable monomer using a radical polymerization initiator and a radical transfer chain transfer agent represented by the following general formula (1). ) Is a viscosity index improver. General formula In the formula, Q is a polyvalent organic group, A is an alkylene group having 1 to 8 carbon atoms, Z is a chain transfer group, p and q are 0 or 1, and p and q are not 1 at the same time, and m Is 2 to 100
The integers in [] may be the same or different.

The radically polymerizable monomers used in the present invention include the following. (A) Alkyl (meth) acrylate having an alkyl group having 1 to 22 carbon atoms: methyl (meth) acrylate,
Ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, eicosyl (meth) acrylate, etc. , (B) aromatic ethylenically unsaturated monomer: styrene, α-
Styrenes such as methylstyrene, vinyltoluene and hydroxystyrene, vinylnaphthalene and the like, (c) Aliphatic ethylenically unsaturated monomer: ethylene, propylene, butene, isobutylene, pentene, heptene,
Diisobutylene, octene, dodecene, octadecene,
Butadiene, isoprene, etc., (d) alicyclic ethylenically unsaturated monomer: cyclopentadiene, pinene, limonene, indene, bicyclopentadiene, ethylidene norbornene, etc.

(E) Hydroxyl group-containing (meth) acrylate: hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, etc. (f) Amide-containing ethylenically unsaturated monomer: (meth) acrylamide, N-methylol (G) Ethylenically unsaturated monomer having a polyalkylene glycol chain such as (meth) acrylamide: polyethylene glycol (molecular weight 30
0) Mono (meth) acrylate, polypropylene glycol (molecular weight 500) monoacrylate, methyl alcohol ethylene oxide 10 mol adduct (meth) acrylate, lauryl alcohol ethylene oxide 30 mol adduct (meth) acrylate, etc. (h) (meth) Acrylamide, etc .:

Of these, preferred are (a) and (b), and more preferred is (a).

In the general formula (1), Q is a residue obtained by removing OH from polyhydric alcohol or polyhydric phenol,
Examples thereof include a residue obtained by removing COOH from a polycarboxylic acid. As the polyhydric alcohol, alkylene glycol having 2 to 8 carbon atoms (ethylene glycol, propylene glycol, 1,3- and 1,4-butanediol, 1,6
-Hexanediol, neopentyl glycol, etc.),
Dihydric alcohols such as diols having a cyclic group and having 5 to 10 carbon atoms; 3 carbon atoms such as glycerin, trimethylolpropane, trimethylolethane and hexanetriol
~ 12 trihydric alcohol; 4 to 20 carbon atoms such as pentaerythritol, methylglycoside, diglycerin, etc.
Alcohols having a higher number of functional groups, such as pentitols (adnitol, arabitol, xylitol, etc.), hexitols (sorbitol, mannitol, iditol, taritol, dulcitol, etc.), sugars [sucrose, monosaccharides (glucose, mannose, etc.). , Fructose, sorbose, etc.), oligosaccharides (crehalose, lactose, raffinose, etc.)]; glucosides [eg polyols (glycol,
Glucosides of glycerin, trimethylolpropane, alkanepolyols such as hexanetriol); polyalkanepolyols [eg polyglycerin such as triglycerin, tetraglycerin]; polypentaerythritol (dipentaerythritol, tripentaerythritol, etc.); cycloalkanepolyols [Tetrakis (hydroxymethyl) cyclohexanol etc.] and the like can be mentioned. Further, polyvinyl alcohol having a degree of polymerization of up to 100 can be used.

Further, di- and triethanolamine; alkylamines having 2 to 20 carbon atoms, 2 to 6 carbon atoms
Alkylenediamines such as ethylenediamine, propylenediamine, hexamethylenediamine, polyalkylenepolyamines such as aliphatic amines such as diethylenetriamine, triethylenetetramine, aniline, phenylenediamine, diaminotoluene, xylylenediamine, methylenedianiline, diphenyletherdiamine, etc. Examples thereof include alicyclic amines such as group amines, isophoronediamine, cyclohexylenediamine, and dicyclohexylmethanediamine, and alkylene oxide adducts such as aminoethylpiperazine.

Examples of polyphenols include monocyclic polyphenols such as pyrogallol, hydroquinone and phloroglucin; bisphenols such as bisphenol A and bisphenol sulfone; condensation products of phenol and formaldehyde (novolak) and polyphenols.

As the polyvalent carboxylic acid, divalent carboxylic acid [(1) aliphatic dicarboxylic acid having 2 to 20 carbon atoms (maleic acid, fumaric acid, succinic acid, adipic acid, sebacic acid, malonic acid, azelaic acid, Mesaconic acid, citraconic acid, glutaconic acid, etc.); (2) Alicyclic dicarboxylic acid having 8 to 20 carbon atoms (cyclohexanedicarboxylic acid, methylmedic acid, etc.); (3) Aromatic dicarboxylic acid having 8 to 20 carbon atoms (phthalate) Acid, isophthalic acid, terephthalic acid, toluenedicarboxylic acid, naphthalenedicarboxylic acid, etc.);
(4) Alkyl or alkenyl succinic acid having a hydrocarbon group having 4 to 35 carbon atoms in the side chain (isododecenyl succinic acid, n-dodecenyl succinic acid, etc.), trivalent or higher carboxylic acids [(1) carbon number 7 to 20 aliphatic polycarboxylic acids (1,2,4-butanetricarboxylic acid, 1,2,5
-Hexanetricarboxylic acid, 1,3-dicarboxylic acid-
2-methyl-2-methylenecarboxypropane, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, etc.); (2) carbon number 9-20
Alicyclic polycarboxylic acids (e.g., 1,2,4-cyclohexanetricarboxylic acid); (3) aromatic polycarboxylic acids having 9 to 20 carbon atoms (1,2,4-benzenetricarboxylic acid, 1,2,5 -Benzenetricarboxylic acid, 2,5,7
-Naphthalene tricarboxylic acid and 1,2,4-naphthalene tricarboxylic acid, pyromellitic acid, benzophenone tetracarboxylic acid, etc.)] and the like. Further, an unsaturated polycarboxylic acid polymer having a degree of polymerization of up to 100 can be mentioned.

In the general formula (1), Z is SH,
SR, SSR, CX ₃ (R is an alkyl, aryl, aralkyl, alkoxy, aryloxy or cycloalkyl group having 1 to 20 carbon atoms, which may be substituted with a halogen atom, an alkyl group, a cyano group or a nitro group. Is a chlorine atom, a bromine atom.) And the like. Of these, SH is preferred.

In the general formula (1), p is 0 when Q is a polyhydric alcohol or polyhydric phenol residue, and p is 1 when Q is a polyhydric carboxylic acid residue. In the general formula (1), m is preferably 2-8. It is also preferable that p and q are 0 at the same time.

The chain transfer agent represented by the general formula (1) is Z
When is SH, it can be manufactured by the following method, for example. Chain Transfer Agent 1 (when p is 0 and q is 0) The alkylene glycol ether of a polyhydric alcohol is chlorinated at its terminal with thionyl chloride or the like, and then reacted with alkali hydrosulfide. Further, the ω-mercapto-alkyl alcohol and the polyhydric alcohol are etherified. Specific chain transfer agents include ethylene glycol-di-2-mercaptoethyl ether, trimethylolpropane-tri-2-mercaptoethyl ether, pentaerythritol-tetra-2-mercaptoethyl ether and the like.

Chain Transfer Agent 2 (when p is 1 and q is 0) The ω-mercapto-alkyl alcohol and the polyvalent carboxylic acid are esterified. Specific chain transfer agents include maleic acid-di-2-mercaptoethyl ester, fumaric acid-di-2-mercaptoethyl ester, adipic acid-di-2-mercaptoethyl ester, terephthalic acid-di-
2-mercaptoethyl ester and the like can be mentioned.

In the production of the above compound, for example, it is possible to co-add a cyclic ether and a cyclic lactone,
When co-adding, either random co-adding or block co-adding may be used.

In the above compounds, the cyclic ethers include ethylene oxide, propylene oxide, butylene oxide, epichlorohydrin, styrene oxide, etc., the cyclic thioethers include episulfide, etc., and the cyclic imines include ethyleneimine, etc. . These may be co-added, and when co-added, either random co-addition or block co-addition may be performed. Of these, preferred are cyclic ethers, and more preferred are ethylene oxide, propylene oxide and mixtures thereof.

In the above compound, the cyclic lactone includes ε-caprolactone, δ-valerolactone and the like, and the cyclic lactam includes ε-caprolactam and the like. These may be co-added, and when co-added, either random co-addition or block co-addition may be performed.

For example, in the case of the chain transfer agent 1, the cyclic ether to be added is preferably propylene oxide in order to obtain a polymer of alkyl (meth) acrylate or aromatic unsaturated monomer.

The amount of the chain transfer agent used in the present invention is usually 0.001 to 50 relative to the radical polymerizable monomer.
%, Preferably 0.01 to 30% by weight, particularly preferably 0.1 to 15% by weight.

The polymerization initiator used in the present invention is of a type that produces free radicals to initiate polymerization,
For example, 2,2'-azobisisobutyronitrile, 2,
2′-azobis (2,4-dimethylvaleronitrile),
2,2′-azobis (2-methylbutyronitrile),
1,1′-azobis (cyclohexane-1-arbonitrile), 2,2′-azobis (2,4,4-trimethylpentane), dimethyl 2,2′-azobis (2-methylpropionate), 2, Azo compounds such as 2′-azobis [2- (hydroxymethyl) propionitrile] and 1,1′-azobis (1-acetoxy-1-phenylethane); dibenzoyl peroxide, dicumyl peroxide, bis (4 Organic peroxides such as -t-butylcyclohexyl) peroxydicarbonate, benzoyl peroxide, lauroyl peroxide, and persuccinic acid can be used. These may be used in combination of two or more. The amount of the polymerization initiator is usually 0.01 to 10% by weight, preferably 0.05 to 10% by weight based on the radical polymerizable monomer.
5% by weight.

In the present invention, the polymerization method may be any of solution polymerization, emulsion polymerization and bulk polymerization, but solution polymerization is preferred in order to obtain a polymer having a narrow molecular weight distribution. Examples of the solvent in the case of solution polymerization include aliphatic hydrocarbons (hexane, heptane, mineral oil, etc.), aromatic hydrocarbons (toluene, xylene, etc.), and mixtures thereof.

The polymerization temperature is usually 30 to 200 ° C.,
It is preferably 50 to 150 ° C. Further, when a dispersion medium, an emulsifier, a dispersant, etc. are used, there is no particular limitation and known ones can be used.

The weight average molecular weight of the obtained (co) polymer is usually 10,000 to 1,000,000, preferably 30,000 to 500,000. When the weight average molecular weight is 10,000 to 100,000, the molecular weight distribution is usually 1.2 to 1.7, preferably 1.2 to 1.5. Weight average molecular weight of 100,000 to 1,000,
In the case of 000, the molecular weight distribution is usually 1.7 to 2.5, preferably 1.7 to 2.3. Although the molecular weight distribution varies depending on the polymerization system, it is much narrower than that when the chain transfer agent of the present invention is not used. Here, the molecular weight distribution means (weight average molecular weight / number average molecular weight).

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. In Examples and Comparative Examples,% and parts represent% by weight and parts by weight. The method for measuring the weight average molecular weight and the molecular weight distribution by GPC is as follows. Apparatus: Toyo Soda HLC-802A column: TSK gel GMH6 2 measuring temperature: 40 ° C. sample solution: 0.5 wt% THF solution solution injection amount: 200 μl Detector: Refractive index detector standard: polystyrene

[0026]

【Example】

(Production of Chain Transfer Agent) Production Example 1 150 parts of triethylene glycol was charged into a reaction vessel,
With stirring, 262 parts of thionyl chloride was added dropwise at 80 ° C. over 2 hours. After maintaining the same temperature for 1 hour, 500 parts of a 30% sodium hydrosulfide aqueous solution was added dropwise over 3 hours.
After holding at the same temperature for 1 hour, the temperature was returned to room temperature, liquid separation was performed, and ethylene glycol-di-2-mercaptoethyl ether 18
0 parts were obtained. This is designated as chain transfer agent A.

Production Example 2 Isophthalic acid was reacted with 2-mercaptoethanol,
Isophthalic acid-di-2-mercaptoethanol ester was obtained. This is designated as chain transfer agent B.

Examples 1 to 6 and Comparative Examples 1 to 3 In a reaction vessel equipped with a stirrer, a thermometer, and a condenser, the amount of mineral oil shown in Table 1 was put, and after nitrogen substitution, the temperature was raised to 70 ° C. and a small amount of nitrogen was added. The mixture of the monomer, the initiator, and the chain transfer agent shown in Table 1 was added dropwise over 4 hours while flowing. The same temperature was maintained for 3 hours to complete the polymerization, and a viscosity index improver as a copolymer was obtained.

[0029]

Table 1 MMA C1213 C1415 St HEMA2EHA Initiator Chain transfer agent ------------------------------------- -Example 1 30 135 135 0 0 0 0.9 A: 2.1 Example 2 30 135 135 0 0 0 0.9 B: 1.0 Example 3 30 105 135 30 0 0 0.9 A: 2.1 Example 4 30 125 135 0 10 0 0.9 A: 2.1 Example 5 30 0 135 0 0 135 0.9 A: 2.1 Example 6 30 135 135 0 0 0 0.3 A: 0.7 −−−−−−−−−−−−−−−−−−−−−− −−−−−−−−−−−−−−− Comparative Example 1 30 135 135 0 0 0 0.9 LSH: 1.4 Comparative Example 2 30 105 135 30 0 0 0.9 LSH: 1.4 Comparative Example 3 30 135 135 0 0 0 0.3 LSH: 0.3

The symbols in the table are as follows. MMA: methyl methacrylate C1213: a mixture of dodecyl methacrylate and tridecyl methacrylate. Manufactured from Dobanol 23 (manufactured by Mitsubishi Chemical). C1415: A mixture of tetradecyl methacrylate and pentadecyl methacrylate. Manufactured from banban 45 (manufactured by Mitsubishi Chemical). St: Styrene HEMA: Hydroxyethyl methacrylate 2EHA: 2-Ethylhexyl acrylate Initiator: Azobisvaleronitrile LSH: Lauryl mercaptan

Evaluation as Viscosity Index Improver One of the viscosity index improvers of Examples 1-5 and Comparative Examples 1 and 2 was used.
The amounts shown in Table 2 were adjusted so that the kinematic viscosity at 00 ° C. was 7.5 cSt and the viscosity index improvers of Example 6 and Comparative Example 3 were 10.2 cSt at 100 ° C. Uniformly blended with solvent refined oil (100 neutral oil with viscosity index 98), and according to JIS-K2514, at 95.5 at 165.5 ° C.
The oxidation stability test was conducted for 8 hours, and the amount of sludge according to the B method was measured. Here, the B method is a method in which a sludge flocculant is added to the blended oil after the test, and the amount of sludge settled by centrifugation is measured. The smaller the amount, the better the oxidation resistance. The results are shown in Table 2 together with the weight average molecular weight and molecular weight distribution of the viscosity index improver.

[0032]

[Table 2] Weight average molecular weight Molecular weight distribution Addition amount (%) Sludge amount (%) -------------------------------- ----- Example 1 50,000 1.4 10.7 1.5 Example 2 52,000 1.4 10.2 1.3 Example 3 48,000 1.5 10.9 1.7 Example 4 53,000 1.5 10.8 1.5 Example 5 51,000 1.4 10.9 1.2 Comparative Example 1 51,000 2.0 12.1 3.1 Comparative Example 2 53, 000 2.1 12.3 3.2 −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− Example 6 220 2,000 2.0 4.4 0.6 Comparative Example 3 210,000 2.9 5.2 1.2

As shown in Table 2, the viscosity index improver of the present invention was used as an operating oil (Examples 1 to 5 and Comparative Examples 1 and 2) for gears, ATF, etc. Also in Examples 6 and Comparative Example 3), it can be seen that a lubricating oil composition having the same viscosity can be obtained by adding a small amount, and the amount of sludge is small and the antioxidant property is excellent.

[0034]

INDUSTRIAL APPLICABILITY The viscosity index improver of the present invention is capable of increasing the viscosity even when added in a small amount and is excellent in antioxidant property. Further, the viscosity change with temperature is small, and the shear stability is also excellent.

Front page continuation (72) Inventor Nobuo Hisada 1-11, Hitotsubashi-honcho, Higashiyama-ku, Kyoto Sanyo Chemical Industry Co., Ltd. In the company

Claims (4)

[Claims] 1. A (co) polymer (A) obtained by polymerizing a radical polymerizable monomer using a radical polymerization initiator and a chain transfer agent for radical polymerization represented by the following general formula (1). ) A viscosity index improver. General formula In the formula, Q is a polyvalent organic group, A is an alkylene group having 1 to 8 carbon atoms, Z is a chain transfer group, p and q are 0 or 1, and p and q are not 1 at the same time, and m Is 2 to 100
The integers in [] may be the same or different. 2. The viscosity index improver according to claim 1, wherein Z in the general formula (1) is SH. 3. The viscosity index improver according to claim 1, wherein p and q are 0 in the general formula (1). 4. The radically polymerizable monomer has 1 to 2 carbon atoms.
The viscosity index improver according to any one of claims 1 to 3, comprising an alkyl (meth) acrylate having 2 alkyl groups.