JPH0948987A - 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 polymeizing a free radical-polymerizable monomer using a free radical-polymerization initiator and a chain transfer agent for free radical polymerization represented by the formula (wherein Q is a polyvalent organic group; X<1> is carbonyl or -CONH-; A<1> and A<2> each is a 1-8C alkylene; X<2> is O, S, or NH; Z is a chain transfer group; p, q, r, and x each is 0 or 1; m is 1-50; n is 2-100; and when the number of []s and m each is 2 to 50, then 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, X ¹ is a carbonyl group or -C
ONH-, A ¹ and A ² are alkylene groups having 1 to 8 carbon atoms, X
² is an oxygen atom, a sulfur atom or an NH group, Z is a chain transfer group, p, q, r and x are 0 or 1 respectively, and m is 1 to 5
An integer of 0 and n are integers of 2 to 100, and may be the same or different in [] and in {} when m is 2 to 50.

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. If p is 0,
x and q are 0 or 1, and r is 0. When p is 1, x is 0 and q and r are 0 or 1, respectively.

In the general formula (1), n is preferably 2 to 8 and m is preferably 1 to 30.

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, x is 0, q is 0 and r is 0) After the cyclic ether is added to the ω-mercapto-alkyl alcohol, it is etherified with the polyhydric alcohol. Alternatively, a cyclic ether is added to a polyhydric alcohol, the terminal is chlorinated with thionyl chloride or the like, and then reacted with an alkali hydrosulfide. Specific examples of chain transfer agents include polyoxyethylene glycol-di-2-mercaptoethyl ether.

Chain transfer agent 2 (p is 1, x is 0, q is 0,
When r is 0) A cyclic ether (cyclic sulfide, cyclic imine) is added to ω-mercapto-alkyl alcohol, and then esterified with a polyvalent carboxylic acid.

Chain transfer agent 3 (p is 0, x is 1, q is 1,
When r is 0) A cyclic lactone (cyclic lactam) is added to the polyhydric alcohol, and then esterified (amidated) with ω-mercapto-carboxylic acid. Specific examples of chain transfer agents include triethanolamine-ε-caprolactone adduct-tri-3-mercaptopropionic acid ester.

Chain transfer agent 4 (p is 0, x is 1, q is 0,
When r is 0) After adding a cyclic lactone (cyclic lactam) to the polyhydric alcohol, etherification (amination) is carried out with ω-mercapto-halogenide. Specific chain transfer agents include triethanolamine-ε-caprolactone adduct-tri-2
-Mercaptoethyl ether and the like.

Chain transfer agent 5 (p is 0, x is 0, q is 1,
When r is 0) After adding a cyclic ether (cyclic sulfide, cyclic imine) to the polyhydric alcohol, esterification (thioesterification, amidation) is carried out with ω-mercapto-carboxylic acid. Specific examples of chain transfer agents that can be produced by this method include the following. (1) 1-10 alkylene oxides (ethylene glycol, propylene glycol, etc.) in alkylene glycols (ethylene glycol, propylene glycol, etc.)
A product obtained by adding 0 mol and forming a diester with 3-mercaptopropionic acid at the end. Polyoxyethylene glycol (number average molecular weight 630) di-3-mercaptopropionic acid ester, polyoxypropylene glycol (number average molecular weight 600) di-3-mercaptopropionic acid ester and the like. (2) A compound in which 1 to 150 mol of alkylene oxide is added to a trihydric or higher polyhydric alcohol (glycerin, pentaerythritol, sho, etc.), and the end is formed into a diester with 3-mercaptopropionic acid. Tetra-3-mercaptopropionic acid ester of pentaerythritol ethylene oxide 20 mol adduct and the like. (3) Polyvinyl acetate (weight average molecular weight 50,000,
Esterified with 2-mercaptoacetic acid (saponification degree 10%).

Chain transfer agent 6 (p is 1, x is 0, q is 1,
When r is 0) After adding a cyclic ether (cyclic sulfide, cyclic imine) to the polycarboxylic acid, esterification (thioesterification, amidation) is carried out with ω-mercapto-carboxylic acid. Specific examples of the chain transfer agent include propylene oxide adipate 4 mol adduct-di-2-mercaptoacetic acid ester.

Chain transfer agent 7 (p is 1, x is 0, q is 0,
When r is 1) A cyclic lactone (cyclic lactam) is added to the polycarboxylic acid, and then esterified with ω-mercapto-alcohol.

Of these chain transfer agents, preferred are chain transfer agents 1 to 4, more preferred are chain transfer agents 1 and 2, and particularly preferred is chain transfer agent 1.

In the production of the above compound, it is also 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. Examples of cyclic ethers include ethylene oxide, propylene oxide, butylene oxide, epichlorohydrin, and styrene oxide, examples of cyclic thioethers include episulfide, and examples of cyclic imines include ethyleneimine. 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. Examples of the cyclic lactone include ε-caprolactone and δ-valerolactone, and examples of the cyclic lactam include ε-caprolactam. These may be co-added, and when co-added, either random co-addition or block co-addition may be performed.

The object of the chain transfer agent of the present invention is that a plurality of chain transfer groups are mutually at least 4 functional groups (ether,
(Ester, amide, etc.) are present apart from each other, which makes it possible to produce a polymer having a narrow molecular weight distribution.

As long as the above conditions are satisfied, the structure can be arbitrarily selected depending on the properties of the polymer to be obtained. For example, the cyclic ether added in the case of the chain transfer agent 1 is preferably propylene oxide in order to obtain a polymer of alkyl (meth) acrylate or an aromatic unsaturated monomer.

The amount of the chain transfer agent used in the present invention is usually 0.001 to 50 with respect 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).

[0031]

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

[0032]

【Example】

(Production of Chain Transfer Agent) Production Example 1 A pressure resistant reactor was charged with 760 parts of propylene glycol and 12 parts of potassium hydroxide, and the temperature was raised to 100 ° C. after purging with nitrogen. Propylene oxide 5,30 at 100-115 ° C
0 part was charged and reacted for 8 hours. After aging at the same temperature for 2 hours, the mixture was cooled to 50 to 70 ° C., 150 parts of water and 60 parts of synthetic magnesium silicate were added, and the mixture was stirred for 2 hours and filtered.
Then, it was dehydrated to obtain 5,900 parts of polyoxypropylene glycol having a number average molecular weight of 600. Next, 600 parts of this polyoxypropylene glycol was charged into a reaction vessel, and while stirring, 2 parts of 260 parts of thionyl chloride were added at 80 ° C.
It dripped over time. After keeping the same temperature for 1 hour, 30
% 500% aqueous sodium hydrosulfide solution was added dropwise over 3 hours. After maintaining at the same temperature for 1 hour, the temperature was returned to room temperature and liquid separation was performed to obtain 580 parts of polyoxypropylene glycol-di-2-mercaptopropyl ether which is the chain transfer agent of the present invention. This is designated as chain transfer agent A.

Production Example 2 680 parts of pentaerythritol and 5 parts of potassium hydroxide were charged into a pressure resistant reactor, and the temperature was raised to 130 ° C. after purging with nitrogen. Propylene oxide 5,85 at 130-160 ° C
0 part was charged and reacted for 5 hours. After aging at the same temperature for 1 hour, the mixture was cooled to 50 to 70 ° C., 160 parts of water and 60 parts of synthetic magnesium silicate were added, and the mixture was stirred for 2 hours and then filtered.
Then, the product was dehydrated to obtain 6,400 parts of a 20-mole propylene oxide adduct of pentaerythritol. Then
650 parts of this adduct was placed in a reaction vessel, and 520 parts of thionyl chloride was added dropwise at 80 ° C. over 4 hours while stirring. After maintaining the same temperature for 1.5 hours, 1,000 parts of a 30% sodium hydrosulfide aqueous solution was added dropwise over 5 hours. After holding at the same temperature for 2 hours, the temperature was returned to room temperature, and liquid separation was performed to obtain pentaerythritol propylene oxide adduct tetra-2-mercaptopropyl ether which is the chain transfer agent of the present invention. 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.

[0035]

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 to 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.

[0038]

[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 can be used as a working oil (Examples 1 to 5 and Comparative Examples 1 and 2) such as gears and ATFs as compared with Comparative Examples. Also in Example 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 sludge amount is small and the antioxidant property is excellent.

[0040]

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.

Continuation of front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication C10N 40:25 70:00 (72) Inventor Nobuo Hisada 1 Sanyo Kasei Kogyo Co., Ltd. 11-11 Hitotino-honcho, Higashiyama-ku, Kyoto-shi In-company (72) Inventor Taiko Saito 1-11, Hitotsubashi-honmachi, Higashiyama-ku, Kyoto Sanyo Kasei Kogyo

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, X ¹ is a carbonyl group or -C
ONH-, A ¹ and A ² are alkylene groups having 1 to 8 carbon atoms, X
² is an oxygen atom, a sulfur atom or an NH group, Z is a chain transfer group, p, q, r and x are 0 or 1 respectively, and m is 1 to 5
An integer of 0 and n are integers of 2 to 100, and may be the same or different in [] and in {} when m is 2 to 50. 2. The viscosity index improver according to claim 1, wherein Z in the general formula (1) is SH. 3. In the general formula (1), p, q, r, x
Are 0 and X ² is an oxygen atom, respectively.
The viscosity index improver described. 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.