JPH02274796A - Additive for lubricating oil - Google Patents

Abstract

PURPOSE:To produce the subject additive which exhibits, for example, an effect of improving the viscosity index of a lubricating oil by copolymerizing a specific alkyl (meth)acrylate with a specific polar monomer in the presence of a siloxane-bond-containing polymeric azo compound. CONSTITUTION:The subject additive is produced by copolymerizing a monomer mixture comprising 10 to 98 pts.wt. (hereinafter merely pts.) (meth)acrylate of a 7 to 30C saturated aliphatic alcohol, 0 to 50 pts. (meth)acrylate of a 1 to 6C saturated aliphatic alcohol, 0.2 to 10 pts. vinyl monomer having an N atom in the molecule (e.g. N-vinylpyrrolidone), and 0 to 30 pts. other vinyl monomer copolymerizable with each of the monomers (e.g. styrene) in the presence of 2 to 70 pts. siloxane-bond-containing polymeric azo compound of formula I (wherein R1 is (cyano)alkyl; R2 is a polyester diol residue or a polyether diol residue having siloxane bonds represented by formula II in the main chain; and (m) is 1 to 20) which has one or more diazo bonds in the molecule and a number-average molecule weight of 1,500 to 40,000.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to novel and useful lubricating oil additives. More specifically, the present invention provides siloxane bonds obtained by copolymerizing 41 alkyl (meth)acrylates and a specific polar monomer as main components in the presence of a specific polymeric azo thread compound having siloxane bonds. It relates to a block copolymer lubricant additive introduced into the main chain of an acrylic copolymer, and particularly has the effect of improving the viscosity index of lubricating oil, the effect of cleaning and dispersion, and the effect of thermal stabilization (improving heat resistance). It is an object of the present invention to provide a viscosity index improver for lubricating oils that has the following effects.

[Conventional technology]

Viscosity index improvers are important as additives to fully adjust the viscosity characteristics of lubricating oils, and are added to engine oils in order to maintain the lubricating effect by maintaining the viscosity of lubricating oils even at high temperatures. It has become absolutely essential.

By the way, oil-soluble polyacrylates, polyacrylates,
Polyisobutylene and ethylene-propylene copolymers are known, but among them, polyatarylate and polymetharylate have the best effect of improving the viscosity index, and they themselves have the ability to lower the pour point. It is one of the most frequently used types at present because it has both of these characteristics.

In the first place, lubricating oils such as gasoline engine oil and diesel engine oil are required to have a high degree of stability against heat and oxidation because they come into direct contact with the engine, which is at temperatures as high as 200 to 300 degrees Celsius. There is.

Under such severe conditions, it is inevitable that sludge is generated due to various additives, and in particular, sludge is likely to be generated due to thermal decomposition of polymers.

This sludge causes deposits on the inner walls of the engine and, in severe cases, can cause piston rings to stick.

To this end, various cleaning and dispersing agents have been developed and are in actual use to disperse such sludge in lubricating oil and prevent it from depositing on the inner walls of the engine.

In recent years, attempts have also been made to add this cleaning and dispersion effect to the viscosity index improver itself. Although it has been developed as a viscosity index improver, in reality, its effectiveness is still insufficient.
The reality is that inert types are still the mainstream.

For example, Special Publication No. 34-4992, Special Publication No. 44-57
As disclosed in No. 07 Oyohi Special Publication No. 51-40883, polar monomers and alkyl (meth)
Some products are simply copolymerized with acrylate, but in practice, sludge often adheres to the inner wall of the engine, and neither the cleaning dispersion effect nor the thermal stabilization effect is sufficiently achieved. We can say that it is.

On the other hand, Special Publication No. 51-20237 and Special Publication No. 53
As disclosed in Publication No. 2883, etc., attempts are made to improve cleaning dispersibility using a so-called graft structure in which a polar monomer is secondarily introduced into a base polymer of alkyl (meth)arylate. Attempts have also been made.

It is true that if such a method is followed, the clean dispersibility improves, but the drawback that the thermal stability of the alkyl (meth)acrylate is insufficient still remains unsolved.

Furthermore, it has been proposed to introduce styrene to improve thermal stability from a compositional perspective, but this method not only impairs the ability to improve the viscosity index but also leads to extreme oil solubility. As a result, the thickening effect cannot be expected, and even the ability to lower the pour point is lost.

As described above, the reality is that as long as the conventional techniques are followed, no one with satisfactory performance has been found.

[Problem to be solved by the invention]

However, in view of the various shortcomings or problems in the prior art as described above, the present inventors, in particular,
As a result of intensive studies aimed at resolving unresolved issues in conventional technology, we have developed a method based on a specific alkyl (meth)acrylate and a specific polar monomer in the presence of a specific siloxane-bonded gold-polymer azo compound. By using a specific block copolymer in which a siloxane bond is introduced into the main chain of an acrylic copolymer, which is obtained by polymerizing the acrylic copolymer as a The present invention was completed by discovering that an extremely useful targeted viscosity index improver having excellent properties (both properties and properties) can be obtained.

Therefore, the problem M to be solved by the present invention is to provide an extremely useful viscosity index improver that has both a detergent dispersion effect and a heat stabilization effect (heat resistance improvement effect), that is, a lubricating oil additive. Another problem to be solved by the present invention is to provide a highly effective agent which eliminates all of the various drawbacks mentioned above and makes maximum use of the %4E of alkyl (meth)arylate. It is an object of the present invention to provide a complete set of viscosity index improvers that are useful lubricating oil additives.

[Means to solve the problem]

The present invention, which is equipped with the following solution means, has been achieved in line with such problems to be solved.

That is, the present invention is directed to a compound represented by the general formula, which has at least one diazo bond in the molecule and has a number average molecular weight of 1,500 to 40.000.
In the presence of 2 to 70 parts by weight of the compound (a), 10 of the acrylic ester and/or methacrylic ester (b) of a saturated aliphatic alcohol having 7 to 30 carbon atoms.
~98 parts by weight, 0 to 50 parts by weight of an acrylic ester and/or methacrylic ester (C) of a saturated aliphatic alcohol having 1 to 6 carbon atoms, a vinyl monomer having a nitrogen atom in the molecule (d) and 0.2 to 10 parts by weight of another vinyl monomer (e) copolymerizable with each of the above monomers (b) to (d). It is an object of the present invention to provide a lubricating oil additive which is an extremely useful viscosity index improver and is obtained by copolymerizing a mixture.

Here, it has at least one diazo bond in one molecule as described above, and has a number average molecular weight of 1.500 to 4.
0,000 compound (a) is the general formula (1) shown above.
Compound (a) is the most important and most characteristic raw material component in the lubricating oil additive of the present invention, but the compound (a) itself has already been described as follows. This is as disclosed in Japanese Patent Application No. 80440/1983.

The compound (a) includes, for example, an acid chloride compound such as 4,4'-azobiscyanobentanoic acid chloride, and a compound having a hydroxyl group at both ends and having a dialkyl-diphenyl- or monoalkylmonophenylsiloxane bond. It is a compound obtained by the condensation reaction of and is a type of typical siloxane-bonded gold-containing polymer azo initiator.

Among these reaction components, rX-22 is a particularly representative compound having a siloxane bond at both ends, which is a compound having a hydroxyl group at both ends of a so-called silicone oil. −
160AS J, rX-22-160AJ, rX-22
-160B J, r X-22-160CJ, rX-2
2-1603AJ or r X-20-170DJ [
The above is a hydroxyl group-containing silicone compound manufactured by Shin-Etsu Chemical Co., Ltd. Nashi. ], Saitaka rBY-16-848'', r
BX-16-003J, r BX-16-001J,
r BX-16-004J, r 5F-8428J, r
SH-3771j, r BY-11-9534, r B
Y-11-954J, r BY-16-018J, r
BY-16-801J or r BY-16-817
J [The above are hydroxyl group-containing silicone compounds manufactured by Tone Silicone Co., Ltd. ] etc., or,
Polyester diols obtained by self-condensation or co-condensation of these various hydroxyl group-containing silicone compounds, or polyester diols obtained by condensing long chain dibasic acids of C4 or more with various hydroxyl group-containing silicone compounds (siloxane bond-containing diols). polyester diol, etc.

That is, the compound obtained by the above general formula (I) (
A) l-1: It is obtained by the addition condensation reaction of these various hydroxyl group-containing silicone compounds (siloxane bond-containing diols) and diazo-bonded gold acid chloride compounds. It is carried out in a solvent and in the presence of a tertiary amine such as triethylamine as a scavenger or catcher for the generated hydrogen chloride gas at a temperature of 30°C or less while cooling. .

Next, by filtering the quaternary ammonium salt thus produced as a by-product, and removing the solvent by drying under reduced pressure, the desired compound (a) can be obtained. The number average molecular weight of the compound (a) is preferably in the range of 1,500 to 40,000.

If it exceeds 40,000, the solubility in mineral oil will be extremely reduced, which is not preferable.

The amount of compound (a) to be used is 2 to 70
A range of 5 to 50 parts by weight is appropriate for 1 part by weight of the heavy part, and if it is less than 2 parts by weight, the amount of siloxane bonds introduced into the acrylic copolymer will be reduced, This is not preferable because it will not be possible to obtain a block copolymer, which is the desired viscosity index improver, and has a high heat resistance.On the other hand, if it exceeds 70 parts by weight, the molecular weight of the main chain portion of the acrylic copolymer will increase. I like it because I can't do it anymore.
It's not right.

Further, as the (meth)acrylic acid esters (b) of saturated aliphatic alcohols 07 to 30 mentioned above, only representative examples are listed; hezotyl (meth)acrylate, otatyl (meth)acrylate, 2- Ethylhexyl (meth)acrylate, nonyl (meth)acrylate, tethyl (meth)acrylate, lauryl (meth)acrylate or stearyl (meth)acrylate, among others, linear and 7-dimensional C12-C18 It is desirable to use an alkyl methacrylate having a branched mixed alkyl group.

The amount of the (meth)acrylic acid ester (b) used is 10 to 98 parts by weight, preferably 10 to 80 parts by weight, based on 2 to 70 parts by weight of the compound (a). A range within the range is appropriate.

Further, as the (meth)acrylic acid ester (c) of the saturated aliphatic alcohol 01 to C6 mentioned above, only representative ones are listed: methyl (meth)acrylate, ethyl (meth)acrylate, n -propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate or halohexyl (meth)arylate, among others, The use of methacrylic acid esters of saturated aliphatic alcohols @C1-C4, such as methyl methacrylate or n-1 methyl methacrylate, is preferred.

The amount of the (meth)acrylic acid ester (e) to be used is similarly within the range of 0 to 50 parts by weight, preferably 0 to 20 parts by weight, based on 2 to 70 parts by weight of the compound (IL). It is appropriate that the proportion be within the range so that the proportion is in parts by weight. If it exceeds 50 parts by weight, even if a siloxane bond is introduced into the main chain, problems such as loss of oil solubility or turbidity of the resulting block copolymer will occur, so this is not preferred. It doesn't look like a cave.

(]4) Furthermore, only representative examples of the vinyl monomer (d) having a nitrogen atom content in the molecule mentioned above are listed; N-vinylpyrrolidone, N-vinyl-5-furkyl N-vinyl cyclic amides;
Sialgyl(meth)acrylamides such as dimethylacrylamide or 1-IN,N-diethermethatalylamide; dialkylaminoalkyl(meth) such as dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylamine ethyl methacrylate or dimethylaminopropyl acrylate; Atarylates: '-! or dialkylaminoalkyl (meth) such as dimethylaminozorobyl (meth)acrylamide
Acrylamides, among others, N-vinyl-2
- The use of pyrrolidone is particularly preferred.

The vinyl monomer (d) is used in an amount of 2 to 10 parts by weight, preferably 3 to 5 parts by weight, based on 2 to 70 parts by weight of the compound (a). A range of proportions is appropriate.

If the amount is less than 2 parts by weight, it will be difficult to give the resulting block copolymer a sufficient cleaning and dispersion effect, and
On the other hand, if it exceeds 10 parts by weight, the resulting block copolymer itself will have a total decrease in oil solubility, and the amount of shredded and residual monomer will increase, so in either case, it is not practical. I don't like it because I can no longer say that.

Next, as the other vinyl monomer (e) copolymerizable with each monomer (h) to (d) described above, any monomer (olicomer) can be used as long as it has copolymerizability. Of course, it is also possible to use
Among them, to mention only the representative ones, aromatic vinyl monomers such as styrene; diesters of unsaturated dibasic acids such as dimethyl maleate or non-n-butyl fumarate; and vinyl acetate as well. In particular, fatty acid vinyl esters such as vinyl laurate are used, but styrene is particularly useful.

The amount of the vinyl monomer (e) to be used is within the range of 0 to 30 parts by weight, preferably 0 to 20 parts by weight, based on 2 to 70 parts by weight of the compound (a). An appropriate ratio range is such that .

The lubricating oil additive of the present invention, that is, the siloxane bond-containing block copolymer (silicone-acrylic), which is a viscosity index improver, is prepared using the various raw materials listed below.
Plotter copolymer) can be prepared by making full use of known and commonly used copolymerization reactions, and such reactions are usually carried out at a temperature of 60 to 140°C and a reaction time of 6 to 140°C.
It can be completed in about 24 hours, but of course it can be carried out under wall pressure conditions if necessary.

For sonosa, the reaction may be carried out in an oil-soluble solvent such as toluene or hexane, or the entire polymerization reaction may be carried out directly in mineral oil to form a base polymer of 10 to 70 polymers.
Of course, it may also be obtained as a mineral oil solution containing %.

The thus obtained silicone-acrylic 10 ivy copolymer viscosity index improver has polysiloxane chains and poly(meth)acrylate copolymer chains distributed in a block shape, and contains nitrogen atoms in the side chains. Vinyl monomers are provided in a distributed form within this poly(meth)arylate chain.

The block copolymer viscosity index improver has a weight average molecular weight (Mw) of 10,000 to 500,000, and a weight average molecular weight (Mw) of 10,000 to 500,000.
It is appropriate that the degree of molecular weight distribution (dispersion ratio) expressed by the ratio MW ) /number average molecular weight (Mn) is 10 or less, preferably 6 or less.

The lubricating oil additive of the present invention, i.e., the viscosity index-h agent, is
Applicable to natural or synthetic lubricating oils and therefore used as an additive to various lubricating oils such as gasoline engine oils, easel engine oils, gear oils, torque converter oils or odomatic transmission fluid (ATF) hydraulic oils. However, this amount is usually within the range of 1 to 30% by weight based on the lubricating oil.

There is no problem in adding a known and commonly used detergent dispersant, ashless detergent dispersant, antioxidant or extreme pressure (additive) agent to this Glock copolymer viscosity index improver.

Thus, the block copolymer viscosity index improver of the present invention satisfies all of the above-mentioned minimum essential conditions required for this type of lubricating oil additive, but its mechanism of action is not necessarily clear. However, silicone-acrylic block copolymers with siloxane-bonded gold main chains have
Firstly, the effect of improving heat resistance is supported by the fact that such siloxane bonds have much better heat resistance than C-C bonds. The block copolymer also has a small surface energy and also has polar groups, so adsorption to the sludge progresses, and the entropy of the silicone portion increases, resulting in sludge dispersion. This is the reason why the particles are amplified and expanded, which in turn supports the effect of improving cleaning and dispersion.

Furthermore, the ability to improve the viscosity index, which is the most important feature of this block copolymer, is generally determined by the oil solubility and flexibility of the polymer itself, This effect of improving the viscosity index is expressed by the expansion and contraction of the block copolymer, but this is because the siloxane bonds present in this block copolymer are particularly excellent in terms of flexibility. Presumed.

〔Effect of the invention〕

The silicone-acrylic block copolymer viscosity index improver of the present invention is characterized by a linkage between the poly(meth)acrylate main chain portion of the copolymer and the siloxane bonding portion introduced therein, that is, the polysiloxane chain. First of all, it has a unique structure in which a polar monomer is graft-polymerized by hydrogen abstraction into a block copolymer with a poly(meth)acrylate copolymer chain. It has excellent cleaning and dispersion properties due to the introduction of poly(meth)acrylate in the main chain.Secondly, the ability to improve the viscosity index and lower the pour point based on the main chain poly(meth)acrylate portion is taken advantage of. It has excellent performance, and thirdly, it has excellent thermal stability (heat resistance) due to the introduction of a siloxane bond into the main chain poly(meth)acrylate portion.

As described above, the lubricating oil additive which is the silicone-acrylic plotter copolymer viscosity index improver of the present invention has all the required characteristics of viscosity index improvement effect, detergent dispersion effect, and heat resistance. Because it is extremely useful, it exhibits all its distinctive effects as a lubricant for various engine oils such as gasoline engine oil and diesel engine oil.

〔Example〕

Next, the present invention will be explained by reference examples, examples, and comparative examples.
Explain the layers, specifics, and physical details. In the following, all parts and percentages are based on weight unless otherwise specified.

Reference Example 1 [Siloxane-bonded gold-containing polymeric azo initiator (a)
Preparation example] In a four-tube flask equipped with a stirrer, a thermometer, a reflux vessel and an inert gas introduction hole, 300 parts of chloroform, 9 parts of triethylamine and [X-22-160B J
(dimethylpolysiloxanediol), and at 20°C, 28.2 parts of 4,4'-azobiscyanobentanoic acid chloride and 70 parts of chloroform were charged.
A solution consisting of 50% was added dropwise under stirring over a period of 2 hours while the system was being completely cooled.

After the dropwise addition, the temperature was kept at the same temperature for 2 hours to allow the reaction to proceed completely, and then the by-produced triethylamine hydrochloride was removed by washing with water, filtered, and vacuum dried to obtain a product with a number average molecular weight of 13,500. , and a target compound having an average number of diazo bonds in the molecule of 3 was obtained. Hereinafter, this will be referred to as the compound (a
-1).

Reference Example 2 (same as above) 100 parts of rX-22-160AS J, [Plaxel 208J [lactone diol manufactured by Daicel Industries, Ltd.]
203 parts of chloroform, 112 parts of chloroform, and 19.3 parts of toluethylamine were charged, and the temperature was set at 20°C. 2 of the solution
The mixture was added dropwise with stirring and cooling over a period of time.

Thereafter, post-treatment was performed in the same manner as in Reference Example 1 to obtain all target compounds having a number average molecular weight of 12,000 and an average number of diazo bonds in the -molecule of 13. Hereinafter, this will be abbreviated as compound (a-2).

Example 1 10 parts of methyl methacrylate, 56 parts of alkyl methacrylate having a C12 to C18 mixed linear and branched alkyl group, and 30 parts of the compound (a-1) obtained in Reference Example 1 were dissolved. 8.
It was added dropwise into 100 parts of mineral oil (150% neat oil) at 0°C over a period of 3 hours, and the polymerization reaction was continued for an additional 5 hours. - dropwise addition of a mixture with 0.5 part of butylno-4-benzoate at 110° C. over a period of 1 hour;
Thereafter, the polymerization reaction was continued at the same temperature for 28 hours to obtain a yellow viscous and transparent liquid block copolymer.

Next, this liquid block copolymer was mixed with a viscosity index of 10.
The polymer content was adjusted to 5% by diluting with neat natural oil having a temperature of 0°C and a pour point of -12.5°C.

The viscosity index of this diluted solution was measured and was found to be 190, which showed an excellent ability to improve the viscosity index.

Further, good results were obtained in that the pour point of this diluted solution was -40°C or less.

Furthermore, this diluted solution was evaluated for both its clean dispersion performance and thermal stability using a panel caulking test as described below, and the clean dispersion performance received a score of 9.5. It had sufficient performance, and in terms of thermal stability, the amount of 7' points was only 20.
mfl, very good results were obtained.

Example 2 10 parts of n-butyl methacrylate, 37 parts of alkyl methacrylate having a linear mixed alkyl group of C1□ to C18, 10 parts of styrene, and the compound (a-2) obtained in Reference Example 2 A mixture consisting of 40 parts of
The polymerization reaction was carried out in mineral oil at 80°C for 5 hours.

Next, a mixture of 3 parts of N-vinyl-2-pyrrolidone and 0.5 parts of tert-butyl benzoate was added dropwise to the polymer solution thus obtained at 110°C over 2 hours, and thereafter at the same temperature. The mixture was kept for 8 hours to allow the entire polymerization reaction to proceed, yielding the desired plotter copolymer in the form of a yellow viscous and transparent liquid.

Thereafter, the viscosity index was measured in the same manner as in Example 1.
It was found that this block copolymer has a very good ability to improve the viscosity index, and the pour point of a diluted solution of this block copolymer in neutral oil is 14.
The temperature was below 2°C, and furthermore, the temperature of this diluted solution was below 2°C.
The results of the 9-channel coking test conducted showed that the cleaning dispersion ability was rated 9.0, and the thermal stability and deposit amount were extremely small at 15 ml, both of which were excellent.

Example 3 The amount of compound (a-1) obtained in Reference Example 1 was changed to 25 parts, and at the same time, the amount of compound (a-1) obtained in Reference Example 2 was changed to 25 parts.
2) to also use part 25, and C12~
A solution of the desired block copolymer was obtained in the same manner as in Example 1, except that the amount of C18 alkyl methacrylate having a linear and branched mixed alkyl base was changed to t-36 parts.

The viscosity index of this copolymer was measured in the same manner as in Example 1 and was 192! In addition, the pour point is -45°C or less, and i'? The results of the flannel caulking test showed that the cleanliness and dispersibility rating was 9.5, and the thermal stability evaluation showed that the amount of deposit was as small as 23 mji, indicating that the product was excellent in all respects.

Comparative Example 1 8 parts of butyl methacrylate, 88 parts of alkyl methacrylate having linear and branched mixed alkyl groups from C42 to C18, and 4 parts of N-vinyl-2-pyrrolidone were mixed in mineral oil (15o neutral oil). 100
In addition, a polymerization reaction was carried out for 8 hours at 80° C. using azobisisobutyronitrile as a polymerization initiator to obtain a solution of a control vinyl copolymer in the form of a yellow viscous liquid.

The viscosity index of this product was measured in the same manner as in Example 1, and it was found to have an excellent ability to improve the viscosity index of 182, and the pour point was 135°C.
Although it was good as below, the panel caulking test result showed that the cleanliness and dispersion rating was poor at 5.5.
In terms of thermal stability, the deposit amount was extremely high at 120 mjp, and therefore, both the cleaning dispersibility and thermal stability were insufficient, and were not of a level that could be put to practical use.

Comparative Example 2 The procedure was carried out except that the use of N-vinyl-2-pyrrolidone was completely omitted and the amount used was changed to 60 parts of alkyl methacrylate having a C42 to C48 linear and branched mixed alkyl group. In the same manner as in Example 1, a viscous liquid solution of a control vinyl copolymer was obtained.

The results of measuring the viscosity index of this product showed that it had an excellent ability to improve the viscosity index, which was 187, and it was also found that the pour point was good at -35°C or less. The results of the panel caulking test were extremely poor, with a rating of 5.5 for detergent dispersibility, and on the other hand, the evaluation of thermal stability also showed that the amount of digits was extremely high at 140 mg. Both of these were insufficient and could not be put to practical use.

Panel coking test Various viscosity index improvers obtained in each example and comparative example were diluted with mineral oil at a concentration of 1 for normal engine oil.
Then, the cleaning dispersibility and thermal stability of each viscosity index improver were evaluated using a non-N flannel coking tester.

The test conditions are as follows.

(1) Evaluation of cleaning and dispersibility 1. Panel temperature: 250°C 2. Oil temperature: 100°C 3. Test method: 1 part time continuous splashing 4. Blended oil formulation: 3. Test method = 15 seconds of splashing , a continuous cycle of 3 hours 4, with a stop of 45 seconds as one cycle, blended oil formulation: The i+nel rating is 1 rlo point if the aluminum test panel is unchanged from before the test, and the entire surface of this panel is covered with sludge adhesion. ``0 points'' if the case is met. This is done in increments of 0.5.

5. Sample weight: 250g

Claims (1)

[Claims] 1. General formula ▲ Numerical formula, chemical formula, table, etc. ▼... (I) However, in the formula, R_1 is an alkyl group or an alkyl group having a cyano group, and R_2 is an alkyl group in the main chain. Formula ▲ There are numerical formulas, chemical formulas, tables, etc. ▼ However, R_3 and R_4 in the formula each represent an alkyl group or phenyl group having 1 to 5 carbon atoms, which may be the same or different. It represents a polyester diol residue or a polyether diol residue having a siloxane bond shown in the following, and m is an integer from 1 to 20. has at least one diazo bond in one molecule, and has a number average molecular weight of 1,500 to 40,000
In the presence of 2 to 70 parts by weight of compound (a), 10 of acrylic ester and/or methacrylic ester (b) of a saturated aliphatic alcohol having 7 to 30 carbon atoms is added.
~98 parts by weight, 0 to 50 parts by weight of acrylic ester and/or methacrylic ester of saturated aliphatic alcohol having 1 to 6 carbon atoms (c), vinyl monomer having a nitrogen atom in the molecule (d) A monomer mixture consisting of 0.2 to 10 parts by weight of , and 0 to 30 parts by weight of another vinyl monomer (e) copolymerizable with each of the above-mentioned monomers (b) to (d). A lubricating oil additive obtained by copolymerizing.