Friction modifier and lubricating oil composition

Abstract

The purpose of the present invention is to provide: a friction modifier capable of achieving both an antifriction effect and storage stability; and a lubricating oil composition containing the friction modifier, the lubricating oil composition having a high antifriction effect and high high-temperature stability. The present invention pertains to a friction modifier containing a copolymer (A) having, as essential constituent monomers, a monomer (a) represented by general formula (1) and a monomer (b) represented by general formula (2), the average value of p per mole of the monomer (a) among the monomers constituting the copolymer (A) being 1-4, the weight-average molecular weight of the copolymer (A) being 50,000-380,000, and the average value of p per mole of the monomer (a) being 1-4. The copolymer (A) contains, as a constituent monomer, 10-60 wt% of the monomer (a) based on the total weight of the monomers constituting the copolymer (A). [In general formula (1), A1 represents a polymerizable group; -X < 1->,-X < 2-> and-X < 3-> are each independently a group represented by-O-or-NH-; r1 represents an alkylene group having 1 to 4 carbon atoms; r2 is an alkylene group having 2 to 20 carbon atoms; r3 is a hydrogen atom; and p is an integer from 1 to 100, and when p is 2 or more, the plurality of R2 and X3 are the same or different. ] [In general formula (2), R4 is a hydrogen atom or a methyl group; -X4 <-> is a group represented by-O <-> or-NH <->; and R5 is a straight chain or branched chain alkyl group with 5-44 carbon atoms. ]. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to a friction modifier and a lubricating oil composition. Background Art

[0002] In recent years, in order to improve fuel economy performance, automotive transmissions are required to improve power transmission efficiency and be smaller and lighter. The transmission mechanism has also changed from a manual transmission to an automatic transmission, and recently, continuously variable transmissions have been installed in some vehicles. On the other hand, electric vehicles equipped with lead-acid batteries, nickel-metal hydride batteries, lithium-ion batteries, fuel cells, etc. and equipped with electric motors, or hybrid vehicles that combine these batteries with internal combustion engines have been developed, and transmission oil and motor oil are used respectively in these vehicles.

[0003] Recently, in electric vehicles or hybrid vehicles, generalization of these oils and miniaturization and weight reduction achieved by encapsulating the transmission and the motor are required, and a new type of oil is desired that has insulation and copper compatibility as a motor oil in addition to anti-wear properties as a manual transmission oil, an automatic transmission oil, or a continuously variable transmission oil.

[0004] In order to meet requirements such as anti-wear properties and seizure prevention properties, friction modifiers are used, and usually phosphates, zinc dithiophosphates, organic sulfur compounds, etc. are added to mineral oil-based or synthetic base oils. However, transmission oils containing these friction modifiers have the effect of corroding copper, and in addition, the insulation is insufficient. Therefore, when used as motor oil, there are problems such as copper wire breakage and motor short circuit. Therefore, in electric vehicles or hybrid vehicles, a friction modifier that can balance copper compatibility, insulation, and anti-wear properties is required.

[0005] As friction modifiers that do not deteriorate copper compatibility and insulation, polymer-type friction modifiers that do not contain sulfur or phosphorus in their constituent elements can be cited. Specifically, copolymers composed of α-olefins and fumarate esters (Patent Document 1), acrylate copolymers having hydroxyl groups (Patent Document 2), polyesters having hydrophilic polymer units and polyolefin units (Patent Document 3), methacrylate copolymers having a block structure composed of polar segment units and hydrophobic segment units (Patent Document 4), etc. are known. However, the above polymer friction modifiers have the problem of insufficient friction reduction effect.

[0006] As friction modifiers for solving the above problems, (meth)acrylate copolymers having a monomer with a specific structure as an essential constituent monomer are known (Patent Documents 5 and 6). However, although the above friction modifiers have a high friction reduction effect, there are problems with storage stability. In addition, when the lubricating oil composition containing the above friction modifier is used at high temperature for a long time, there is a problem of generating precipitates.

[0007] Prior art documents

[0008] Patent documents

[0009] Patent document 1: Japanese Patent Publication No. 3730660

[0010] Patent document 2: Japanese Patent Publication No. 5822706

[0011] Patent document 3: Japanese Patent Publication No. 5684832

[0012] Patent document 4: Japanese Unexamined Patent Application Publication No. 4686444

[0013] Patent document 5: Japanese Unexamined Patent Application Publication No. 2022-151618

[0014] Patent document 6: Japanese Patent Publication No. 6582021 Summary of the invention

[0015] Problems to be solved by the invention

[0016] An object of the present invention is to provide a friction modifier and a lubricating oil composition containing the friction modifier, which can achieve both anti-friction effect and storage stability, and the lubricating oil composition has a high anti-friction effect and high high-temperature stability.

[0017] Means for solving the problems

[0018] The present inventors have conducted in-depth research and as a result, completed the present invention.

[0019] That is, the present invention relates to a friction modifier which is a copolymer (A) containing monomer (a) represented by the following general formula (1) and monomer (b) represented by the following general formula (2) as essential constituent monomers, wherein, in monomer (a) among the monomers constituting the copolymer (A), the average value of p per 1 mole of monomer (a) is 1 to 4, the weight-average molecular weight of the copolymer (A) is 0.5×10⁴ to 3.8×10⁴, and the copolymer (A) contains 10 to 60% by weight of the monomer (a) based on the total weight of the monomers constituting the copolymer (A) as a constituent monomer; and a lubricating oil composition containing the friction modifier and a base oil.

[0020] [Chemical formula 1]

[0021]

[0022] [In general formula (1), A 1 is a polymerizable group; -X 1 -, -X 2 - and -X 3 - are each independently a group represented by -O- or -NH-; R1 is an alkylene group having 1 to 4 carbon atoms; R 2 is an alkylene group having 2 to 20 carbon atoms; R 3 is a hydrogen atom; p is an integer of 1 to 100, and when p is 2 or more, multiple Rs 2 and X 3 are each the same or different.]

[0023] [Chemical formula 2]

[0024]

[0025] [In general formula (2), R 4 is a hydrogen atom or a methyl group; -X 4 - is a group represented by -O- or -NH-; R 5 is a linear or branched alkyl group having 5 to 44 carbon atoms.]

[0026] Effects of the Invention

[0027] The friction modifier of the present invention can balance the friction reduction effect and storage stability, and the lubricating oil composition containing the friction modifier of the present invention exhibits a high friction reduction effect and excellent high-temperature stability. Detailed Embodiments

[0028] <Friction Modifier>

[0029] The friction modifier of the present invention is a friction modifier comprising a copolymer (A) containing a monomer (a) represented by the following general formula (1) and a monomer (b) represented by the following general formula (2) as essential constituent monomers. In the monomer (a) among the monomers constituting the copolymer (A), the average value of p per 1 mole of the monomer (a) is 1 to 4, the weight average molecular weight of the copolymer (A) is 0.5×10⁴ to 3.8×10⁴, and the copolymer (A) contains 10 to 60% by weight of the monomer (a) based on the total weight of the monomers constituting the copolymer (A).

[0030] [Chemical formula 3]

[0031]

[0032] [In general formula (1), A 1 is a polymerizable group; -X 1 -, -X 2 - and -X 3 - are each independently a group represented by -O- or -NH-; R 1 is an alkylene group having 1 to 4 carbon atoms; R 2 is an alkylene group having 2 to 20 carbon atoms; R 3 is a hydrogen atom; p is an integer of 1 to 100, and when p is 2 or more, multiple Rs2 and X 3 are each the same or different.]

[0033] [Chemical Formula 4]

[0034]

[0035] [In General Formula (2), R 4 is a hydrogen atom or a methyl group; -X 4 - is a group represented by -O- or -NH-; R 5 is a linear or branched alkyl group having 5 to 44 carbon atoms.]

[0036] It should be noted that in the present invention, the high storage stability of the friction modifier means that, for example, even if the friction modifier is stored in an environment of 25°C for 30 days, no precipitate will be generated. In addition, the high high-temperature stability of the lubricating oil composition means that, for example, even if the lubricating oil composition is stored in an environment of 120°C for 2 hours, no precipitate will be generated.

[0037] <Copolymer (A)>

[0038] In the present invention, the copolymer (A) is a copolymer having the monomer (a) represented by the above General Formula (1) and the monomer (b) represented by the above General Formula (2) as essential constituent monomers. In the monomer (a) among the monomers constituting the copolymer (A), the average value of p per 1 mole of the monomer (a) is 1 to 4, the weight-average molecular weight of the copolymer (A) is 0.5×10^4 to 3.8×10^4, and the copolymer (A) contains 10 to 60% by weight of the monomer (a) based on the total weight of the monomers constituting the copolymer (A) as a constituent monomer.

[0039] In the present invention, the copolymer (A) contains the monomer (a) represented by the above General Formula (1) as an essential constituent monomer.

[0040] A in General Formula (1) 1 is a monovalent polymerizable group. A polymerizable group refers to a functional group capable of undergoing a polymerization reaction. Specifically, a radical polymerizable group or a cationic polymerizable group can be cited. As the polymerizable group, specifically, for example, a vinyl group, a (meth)acryloyl group, etc. can be cited.

[0041] From the aspect of the friction reduction effect, A 1 is preferably a vinyl group and a (meth)acryloyl group, and more preferably a (meth)acryloyl group.

[0042] It should be noted that in the present invention, "(meth)acryloyl group" means "acryloyl group and / or methacryloyl group", and "(meth)acrylate" means "acrylate and / or methacrylate".

[0043] -X in General Formula (1) 1 -, -X 2 -, and -X 3 - are each independently a group represented by -O- or -NH-.

[0044] As -X 1 -, -X 2 -, and -X 3 -, from the aspect of the antifriction effect, -O- is preferred.

[0045] R in General Formula (1) 1 is an alkylene group having 1 to 4 carbon atoms.

[0046] As the alkylene group having 1 to 4 carbon atoms, methylene, ethylene, 1,2-propylene or 1,3-propylene, 1,2-butylene, 1,3-butylene or 1,4-butylene, etc. can be cited. Among them, from the aspect of the antifriction effect, ethylene and 1,2-propylene or 1,3-propylene are preferred, and ethylene is more preferred.

[0047] p in General Formula (1) represents the addition mole number of the lactam and / or lactone described later. When p in General Formula (1) is 2 or more, multiple Rs 2 and X 3 are each the same or different.

[0048] In monomer (a) among the monomers constituting copolymer (A), from the aspects of the antifriction effect and storage stability, the average value of p per 1 mole of monomer (a) (average addition mole number, hereinafter also referred to as the molar average value of p) is 1 to 4, more preferably 1.5 to 3.5, and particularly preferably 2.0 to 3.5.

[0049] When the average value of p per 1 mole of monomer (a) exceeds 4, the antifriction effect and storage stability may deteriorate.

[0050] The reason for the deterioration of the storage stability of the friction modifier has not been determined yet, but it is speculated that if the molar average value of p exceeds 4, the ester group and / or amide group in copolymer (A) becomes more, and molecules are likely to aggregate with each other during long-term storage, and thus are likely to precipitate. Furthermore, due to the easy precipitation, monomer (a) cannot be used in a large amount as a constituent monomer of copolymer (A), so the antifriction effect is reduced.

[0051] When there are two or more kinds of monomer (a) constituting copolymer (A), the value obtained by weighted-averaging p of each monomer in monomer (a) based on the molar fraction of each monomer is the molar average value of p in General Formula (1).

[0052] The mole fraction of each monomer with a different number of p in the monomer (a) can be calculated by analyzing the chemical formula and content of each monomer (a) constituting the copolymer (A) using methods such as pyrolysis GC / MS.

[0053] Alternatively, when measuring p of the monomer (a) before it is introduced into the copolymer (A), the molar average value of p can be determined based on the 1 1H-NMR (nuclear magnetic resonance) spectrometry spectrum of the monomer (a). As an example, when the "lactam and / or lactone" is ε-caprolactone, the molar average value of p can be calculated by dividing half of the integral value of the peak around 1.4 ppm (the peak of the γ-hydrogen from the carbonyl carbon of ε-caprolactone) by the integral value of the peak around 6.4 ppm or 6.1 ppm (one of the peaks of the hydrogen atoms bonded to the unsaturated double bond of the acryloyl or methacryloyl group).

[0054] The γ-hydrogen from the carbonyl carbon of ε-caprolactone refers to the hydrogen atom bonded to the carbon atom with * in the structural formula (-CO-CH2-CH2-C * H2-CH2-CH2-O-) of ε-caprolactone.

[0055] The hydrogen atom bonded to the unsaturated double bond of the acryloyl group refers to the hydrogen atom bonded to the carbon atom with * in the structural formula H2C * =CH-CO-. The hydrogen atom bonded to the unsaturated double bond of the methacryloyl group refers to the hydrogen atom bonded to the carbon atom with * in the structural formula H2C * =C(CH3)-CO-.

[0056] Specifically, the molar average value of p can be calculated by the following formula.

[0057] (When A in the general formula (1) 1 is the acryloyl group)

[0058] Molar average value of p = (Integral value of the peak of the γ-hydrogen from the carbonyl carbon of ε-caprolactone / 2) / (Integral value of one of the peaks of the hydrogen atoms bonded to the unsaturated double bond of the acryloyl group)

[0059] (When A in the general formula (1) 1 is the methacryloyl group)

[0060] Molar average value of p = (Integral value of the peak of the γ-hydrogen from the carbonyl carbon of ε-caprolactone / 2) / (Integral value of one of the peaks of the hydrogen atoms bonded to the unsaturated double bond of the methacryloyl group)

[0061] R in the general formula (1) 2Represents an alkylene group having 2 to 20 carbon atoms. Specifically, examples of the alkylene group having 2 to 20 carbon atoms include ethylene, isopropylidene, 1,2-propylene or 1,3-propylene, isobutylidene, 1,2-butylene, 1,3-butylene or 1,4-butylene, isopentylidene, 1,2-pentylene, 1,3-pentylene, 1,4-pentylene or 1,5-pentylene, isohexylidene, 1,2-hexylene, 1,3-hexylene, 1,4-hexylene, 1,5-hexylene or 1,6-hexylene, isoheptylidene, 1,2-heptylene, 1,3-heptylene, 1,4-heptylene, 1,5-heptylene, 1,6-heptylene or 1,7-heptylene, isooctylidene, 1,8-octylene, isononylidene, 1,9-nonylene, isodecylidene, 1,10-decylene, isoundecylidene, 1,11-undecylene, isododecylidene, 1,12-dodecylene, isotridecylidene, 1,13-tridecylene, isotetradecylidene, 1,14-tetradecylene, isopentadecylidene, 1,15-pentadecylene, isohexadecylidene, 1,16-hexadecylene, isoheptadecylidene, 1,17-heptadecylene, isooctadecylidene, 1,18-isooctadecylene, isononadecylidene, 1,19-isononadecylene, isoeicosylidene, 1,20-eicosylene, etc.

[0062] As R 2 , from the aspects of anti-friction effect, storage stability and high-temperature stability, it is preferably an alkylene group having 2 to 17 carbon atoms, more preferably an alkylene group having 2 to 15 carbon atoms, particularly preferably an alkylene group having 2 to 13 carbon atoms, and most preferably an alkylene group having 2 to 10 carbon atoms.

[0063] R in the general formula (1) 3 represents a hydrogen atom.

[0064] As the monomer (a), from the aspect of anti-friction effect, preferably, examples include 1 to 4 molar addition products of lactones of hydroxyalkyl (meth) acryloyl monomers, 1 to 4 molar addition products of lactams of hydroxyalkyl (meth) acryloyl monomers, 1 to 4 molar addition products of lactones of aminoalkyl (meth) acryloyl monomers, 1 to 4 molar addition products of lactams of aminoalkyl (meth) acryloyl monomers, etc., and more preferably 1 to 4 molar addition products of lactones of hydroxyalkyl (meth) acryloyl monomers.

[0065] The number of moles of addition of the lactone or lactam in the above examples refers to the average number of moles of addition.

[0066] Examples of the hydroxyalkyl(meth)acryloyl monomer include hydroxyalkyl (meth)acrylate{(hydroxy methyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, etc.}, hydroxyalkyl (meth)acrylamide{hydroxymethyl (meth)acrylamide, hydroxyethyl (meth)acrylamide, hydroxypropyl (meth)acrylamide, hydroxybutyl (meth)acrylamide, etc.} and the like.

[0067] Examples of the aminoalkyl(meth)acryloyl monomer include aminoalkyl (meth)acrylate{(amino methyl (meth)acrylate, aminoethyl (meth)acrylate, aminopropyl (meth)acrylate, aminobutyl (meth)acrylate, etc.}, aminoalkyl (meth)acrylamide{aminomethyl (meth)acrylamide, aminoethyl (meth)acrylamide, aminopropyl (meth)acrylamide, aminobutyl (meth)acrylamide, etc.} and the like.

[0068] Examples of the lactone include lactones having 3 to 21 carbon atoms, such as β-propiolactone, γ-butyrolactone, δ-valerolactone, ε-caprolactone and the like.

[0069] Examples of the lactam include lactams having 3 to 21 carbon atoms, such as β-lactam, γ-lactam, δ-lactam and the like.

[0070] The 1 to 4 molar addition product of the hydroxyalkyl(meth)acryloyl monomer or the aminoalkyl(meth)acryloyl monomer and the lactone can be obtained, for example, by ring-opening addition of the lactone to the hydroxyalkyl(meth)acryloyl monomer or the aminoalkyl(meth)acryloyl monomer.

[0071] From the aspect of reaction time, the reaction temperature for the ring-opening addition reaction is preferably 80 to 150 °C, more preferably 100 to 140 °C.

[0072] The reaction time is preferably 2 to 24 hours, more preferably 3 to 10 hours.

[0073] The reaction can be carried out in the presence of a catalyst.

[0074] Examples of the catalyst for the above reaction include known catalysts, such as p-toluenesulfonic acid, tetrapropyl titanate, stannous octanoate and the like.

[0075] The amount of the catalyst used is preferably 0.01 to 5% by mass, more preferably 0.03 to 0.5% by mass, based on the amount of the reaction product.

[0076] After the ring-opening addition reaction is completed, the catalyst is preferably treated by a method of adsorbing / filtering using an adsorbent, a method of neutralizing to deactivate the catalyst, etc.

[0077] A 1-4 molar adduct of a lactam with a hydroxyalkyl(meth)acryloyl monomer or an aminoalkyl(meth)acryloyl monomer can be obtained, for example, by ring-opening addition of a lactam to a hydroxyalkyl(meth)acryloyl monomer or an aminoalkyl(meth)acryloyl monomer.

[0078] From the aspect of reaction time, the reaction temperature during the ring-opening addition reaction of the lactam is preferably 80 - 150 °C, more preferably 100 °C - 140 °C.

[0079] The reaction time is preferably 2 - 24 hours, more preferably 3 - 10 hours.

[0080] The reaction can be carried out in the presence of a catalyst.

[0081] As the catalyst for the above reaction, known catalysts can be used, such as tetrapropyl titanate, stannous octanoate, etc.

[0082] The amount of the catalyst is preferably 0.01 - 5% by mass, more preferably 0.03 - 0.5% by mass, based on the amount of the reaction product.

[0083] After the ring-opening addition reaction is completed, the catalyst is preferably removed by a method of adsorption / filtration using an adsorbent, a method of neutralization to deactivate the catalyst, etc.

[0084] As monomer (a), from the aspect of anti-friction property, a 1 - 4 molar adduct of a lactone with a hydroxyalkyl(meth)acrylate (where the hydroxyalkyl has 1 - 4 carbon atoms) is preferred, more preferably a 1 - 4 molar adduct of a lactone with a hydroxyalkyl(meth)acrylate (where the hydroxyalkyl has 2 - 4 carbon atoms), further preferably a 1 - 4 molar adduct of ε-caprolactone with a hydroxyalkyl(meth)acrylate (where the hydroxyalkyl has 2 - 3 carbon atoms), particularly preferably a 1 - 4 molar adduct of ε-caprolactone with hydroxyethyl (meth)acrylate, and most preferably a 1 - 3 molar adduct of ε-caprolactone with hydroxyethyl (meth)acrylate.

[0085] From the aspect of solubility in a lubricating oil base oil, the structural unit derived from monomer (a) (the structure formed by the reaction of the polymerizable group (such as vinyl) in monomer (a) to become a single bond) preferably has a specific solubility parameter (hereinafter sometimes abbreviated as SP value).

[0086] The SP value of the structural unit derived from monomer (a) is preferably 10.0 - 12.5 (cal / cm 3 ) 1 / 2 , more preferably 10.3 - 12.3 (cal / cm 3 ) 1 / 2 , particularly preferably 10.5 - 12.0 (cal / cm3 ) 1 / 2 。

[0087] It should be noted that the SP value in the present invention refers to the value calculated by the mathematical formula (28) on page 153 through the values (the heat of vaporization and molar volume of atoms or functional groups at 25 °C) recorded on page 152 (Table 5) of the Fedors method (Polymer Engineering and Science, February, 1974, Vol. 14, No. 2, P147-154). Specifically, according to the values of Δe i and v i recorded in Table 1 below, which are parameters of the Fedors method, and using the values corresponding to the types of atoms and atomic groups in the molecular structure, the value can be calculated by substituting them into the following mathematical formula.

[0088] SP value = (ΣΔe i / Σv i ) 1 / 2

[0089] [Table 1]

[0090] Parameters of the Fedors method

[0091] Atom or atomic group <![CDATA[Δe i [cal / mol]]]> <![CDATA[v i [cm 3 / mol]]]> <![CDATA[CH3]]> 1125 33.5 <![CDATA[CH2]]> 1180 16.1 CH 820 -1.0 C 350 -19.2 <![CDATA[H2C=]]> 1030 28.5 -CH= 1030 13.5 C＝ 1030 -5.5 HC≡ 920 27.4 -C≡ 1690 65 Phenyl 7630 71.4 Phenylene (ortho, meta, para) 7630 52.4 Phenyl (trisubstituted) 7630 33.4 Phenyl (tetrasubstituted) 7630 14.4 Phenyl (pentasubstituted) 7630 -4.6 Phenyl (hexasubstituted) 7630 -23.6 Closed loop of 5 or more atoms 250 16 Closed loop of 3 or 4 atoms 750 18 <![CDATA[CO3 (Carbonate)]]> 4200 22.0 COOH 6600 28.5 <![CDATA[CO2]]> 4300 18.0 CO 4150 10.8 CHO (aldehyde) 5100 22.3 <![CDATA[CO2CO2 (oxalate)]]> 6400 37.3 <![CDATA[C2O3 (anhydrous)]]> 7300 30.0 HCOO (formate) 4300 32.5 <![CDATA[CONH2]]> 10000 17.5 CONH 8000 9.5 CON 7050 -7.7 HCON 6600 11.3 HCONH 10500 27.0 COCl 5000 38.0 <![CDATA[NH2]]> 3000 19.2 NH 2000 4.5 N 1000 -9.0 -N＝ 2800 5.0 CN 6100 24.0 <![CDATA[NO2 (aliphatic)]]> 7000 24.0 <![CDATA[NO2 (aromatic)]]> 3670 32.0 <![CDATA[NO3]]> 5000 33.5 <![CDATA[NO2 (Nitrite)]]> 2800 33.5 CSN 4800 37.0 NCO 6800 35.0 <![CDATA[NF2]]> 1830 33.1 <![CDATA[NF2]]> 1210 24.5 O 800 3.8 OH 7120 10.0 OH (disubstituted or on adjacent carbon atoms) 5220 13.0

[0092] It should be noted that when two or more monomers (a) are used as monomers in the copolymer (A), regarding the SP value of the monomer (a), preferably, the SP values of the multiple monomers (a) constituting the copolymer (A) are calculated by the above method, and the value obtained by arithmetically averaging the SP values of each monomer (a) based on the weight fraction is within the above range.

[0093] In the present invention, the copolymer (A) contains the monomer (b) represented by the above general formula (2) as an essential constituent monomer.

[0094] R 4 in the general formula (2) is a hydrogen atom or a methyl group, and among them, from the aspects of antifriction property and the effect of improving the viscosity index, a methyl group is preferred.

[0095] -X 4 - in the general formula (2) is a group represented by -O- or NH-, and among them, from the aspect of antifriction property, -O- is preferred.

[0096] R 5is a linear or branched alkyl group having 5 to 44 carbon atoms, and examples thereof include pentyl, hexyl, n-octyl, 2-ethylhexyl, n-nonyl, isononyl, n-decyl, isodecyl, n-undecyl, isoundecyl, n-dodecyl, isododecyl, n-tridecyl, isotridecyl, n-tetradecyl, 2-ethyldodecyl, n-pentadecyl, 2-methyltetradecyl, n-hexadecyl, isohexadecyl, n-heptadecyl, isoheptadecyl, 2-ethylpentadecyl, 2-octylnonyl, 2-(3-methylhexyl)-7-methylnonyl, n-octadecyl, isooctadecyl, 2-hexylundecyl, 2-ethylheptadecyl, 1-hexyltridecyl, n-eicosyl, 2-octylundecyl, isoeicosyl, 1-undecyldodecyl, 1-octylpentadecyl, 2-decyltridecyl, n-tetracosyl, 2-decyltetradecyl, 2-dodecylpentadecyl, 2-heptylicosyl, 2-dodecylhexadecyl, n-triacontyl, 2-tetradecyloctadecyl, n-hexatriacontyl, n-tetracontyl, 2-ethyltetracontyl, and olefins [such as propylene oligomers (2 to 14 mers), ethylene / propylene oligomers (2 to 20 mers), and isobutylene oligomers (2 to 10 mers), etc.].

[0097] R 5 Among them, from the aspect of base oil solubility, it is preferably a linear or branched alkyl group having 10 to 34 carbon atoms, more preferably a linear or branched alkyl group having 12 to 32 carbon atoms, particularly preferably a linear or branched alkyl group having 16 to 32 carbon atoms, and most preferably a linear alkyl group having 16 to 22 carbon atoms and a branched alkyl group having 18 to 32 carbon atoms.

[0098] As the monomer (b), for example, pentyl (meth)acrylate, hexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-undecyl (meth)acrylate, isoundecyl (meth)acrylate, n-dodecyl (meth)acrylate, isododecyl (meth)acrylate, n-tridecyl (meth)acrylate, isotridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, 2-ethyldodecyl (meth)acrylate, n-pentadecyl (meth)acrylate, 2-methyltetradecyl (meth)acrylate, n-hexadecyl (meth)acrylate, isohexadecyl (meth)acrylate, n-heptadecyl (meth)acrylate, isoheptadecyl (meth)acrylate, 2-ethylpentadecyl (meth)acrylate, 2-octylnonyl (meth)acrylate, 2-(3-methylhexyl)-7-methylnonyl (meth)acrylate, n-octadecyl (meth)acrylate, isooctadecyl (meth)acrylate, 2-hexylundecyl (meth)acrylate, 2-ethylheptadecyl (meth)acrylate, 1-hexyltridecyl (meth)acrylate, n-eicosyl (meth)acrylate, 2-octylundecyl (meth)acrylate, isoeicosyl (meth)acrylate, 1-undecyldodecyl (meth)acrylate, 1-octylpentadecyl (meth)acrylate, 2-decyltridecyl (meth)acrylate, n-tetracosyl (meth)acrylate, 2-decyltetradecyl (meth)acrylate, 2-dodecylpentadecyl (meth)acrylate, 2-heptyleicosyl (meth)acrylate, 2-dodecylhexadecyl (meth)acrylate, n-triacontyl (meth)acrylate, 2-tetradecyloctadecyl (meth)acrylate, n-hexatriacontyl (meth)acrylate, n-tetracontyl (meth)acrylate, 2-ethyltetracontyl (meth)acrylate, etc. can be cited.

[0099] As the monomer (b), it is preferably selected from at least one of n-dodecyl (meth)acrylate (also referred to as dodecyl (meth)acrylate), (meth)acrylate of a linear or branched alkyl alcohol having 12 to 13 carbon atoms, n-hexadecyl (meth)acrylate (also referred to as hexadecyl (meth)acrylate), n-octadecyl (meth)acrylate (also referred to as octadecyl (meth)acrylate), 2-decyltetradecyl (meth)acrylate (also referred to as 2-decyltetradecyl (meth)acrylate), 2-dodecylhexadecyl (meth)acrylate (also referred to as 2-dodecylhexadecyl (meth)acrylate), and 2-tetradecyloctadecyl (meth)acrylate (also referred to as 2-tetradecyloctadecyl (meth)acrylate).

[0100] The copolymer (A) in the present invention may contain a (meth)acryloyl monomer (c) having an alkyl group with 1 to 4 carbon atoms. Examples of the (meth)acryloyl monomer (c) having an alkyl group with 1 to 4 carbon atoms include (meth)acrylic acid esters having an alkyl group with 1 to 4 carbon atoms and (meth)acrylamides having an alkyl group with 1 to 4 carbon atoms.

[0101] Examples of the (meth)acryloyl monomer (c) having an alkyl group with 1 to 4 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, sec-butyl (meth)acrylate, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-butyl(meth)acrylamide, etc.

[0102] As the monomer (c), from the viewpoints of antifriction property and viscosity index improvement effect, (meth)acrylic acid esters having an alkyl group with 1 to 4 carbon atoms are preferred, (meth)acrylic acid esters having a linear alkyl group with 1 to 4 carbon atoms are more preferred, and methyl (meth)acrylate and butyl (meth)acrylate are particularly preferred.

[0103] The copolymer (A) may contain monomers other than the above as constituent monomers. For example, it may be a copolymer having, as constituent monomers, one or more selected from the group consisting of a nitrogen atom-containing monomer (d) other than the above monomers (a), (b), and (c), a hydroxyl group-containing monomer (e) other than the above monomer (a), and a phosphorus atom-containing monomer (f).

[0104] Examples of the nitrogen atom-containing monomer (d) include the following monomers (d1) to (d4).

[0105] Amide group-containing monomer (d1):

[0106] Examples of monomers having only a nitrogen atom in the amide group include (meth)acrylamide, monoalkylaminoalkyl (meth)acrylamides [such as (meth)acrylamides having an aminoalkyl group (with 2 to 6 carbon atoms) in which one alkyl group having 1 to 4 carbon atoms is bonded to the nitrogen atom; for example, N-methylaminoethyl (meth)acrylamide, N-ethylaminoethyl (meth)acrylamide, N-isopropylaminobutyl (meth)acrylamide, and N-n-butyl or isobutylaminobutyl (meth)acrylamide, etc.], dialkylamino (meth)acrylamides [such as (meth)acrylamides having two alkyl groups having 1 to 4 carbon atoms bonded to the nitrogen atom; for example, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N,N-diisopropyl (meth)acrylamide, and N,N-dibutyl (meth)acrylamide, etc.], dialkylaminoalkyl (meth)acrylamides [such as (meth)acrylamides having an aminoalkyl group (with 2 to 6 carbon atoms) in which two alkyl groups having 1 to 4 carbon atoms are bonded to the nitrogen atom; for example, N,N-dimethylaminoethyl (meth)acrylamide, N,N-diethylaminoethyl (meth)acrylamide, N,N-dimethylaminopropyl (meth)acrylamide, and N,N-dibutylaminobutyl (meth)acrylamide, etc.], N-vinyl carboxamides [such as N-vinylformamide, N-vinylacetamide, N-vinylpropionamide or N-vinylisopropionamide, and N-vinylhydroxyacetamide, etc.].

[0107] Monomers containing nitro groups (d2):

[0108] Examples include 4-nitrostyrene.

[0109] Monomers containing primary to tertiary amino groups (d3):

[0110] Vinyl monomers containing a primary amino group can be exemplified by {alkenylamines having 3 to 6 carbon atoms in the carbon chain [(meth)allylamine, crotonamine, etc.], (meth)acrylic acid aminoalkyl esters having 2 to 6 carbon atoms in the carbon chain [(meth)acrylic acid aminoethyl ester, etc.]}; vinyl monomers containing a secondary amino group {(meth)acrylic acid monoalkylaminoalkyl esters [esters of (meth)acrylic acid having an aminoalkyl group (with 2 to 6 carbon atoms) formed by bonding one alkyl group having 1 to 6 carbon atoms to the nitrogen atom; for example, (meth)acrylic acid tert-butylaminoethyl ester, (meth)acrylic acid methylaminoethyl ester, etc.], alkenylamines having 6 to 12 carbon atoms in the carbon chain [di(meth)allylamine, etc.]}; vinyl monomers containing a tertiary amino group {(meth)acrylic acid dialkylaminoalkyl esters [esters of (meth)acrylic acid having an aminoalkyl group (with 2 to 6 carbon atoms) formed by bonding two alkyl groups having 1 to 6 carbon atoms to the nitrogen atom; for example, (meth)acrylic acid -N,N-dimethylaminoethyl ester, (meth)acrylic acid -N,N-diethylaminoethyl ester, etc.], alicyclic (meth)acrylic acid esters having a nitrogen atom [(meth)acrylic acid morpholinoethyl ester, etc.], aromatic vinyl monomers [N,N-diphenylaminoethyl (meth)acrylamide, N,N-dimethylaminostyrene, 4-vinylpyridine, 2-vinylpyridine, N-vinylpyrrole, N-vinylpyrrolidone, N-vinylthiopyrrolidone, etc.]}, and their hydrochloride salts, sulfate salts, phosphate salts, or salts with lower alkyl (having 1 to 8 carbon atoms) monocarboxylic acids (acetic acid, propionic acid, etc.).

[0111] Monomers containing a nitrile group (d4):

[0112] (Meth)acrylonitrile, etc., can be exemplified.

[0113] Among the vinyl monomers containing a nitrogen atom (d), the preferred ones are the monomers containing an amide group (d1) and the monomers containing a primary amino group to a tertiary amino group (d3), and more preferably N,N-diphenylaminoethyl (meth)acrylamide, dimethylaminoethyl (meth)acrylamide, diethylaminoethyl (meth)acrylamide, dimethylaminopropyl (meth)acrylamide, (meth)acrylic acid -N,N-dimethylaminoethyl ester, and (meth)acrylic acid -N,N-diethylaminoethyl ester.

[0114] As the monomers containing a hydroxyl group (e), the following monomers can be specifically exemplified.

[0115] Examples thereof include aromatic monomers having a hydroxyl group (such as p-hydroxystyrene), (meth)acrylic acid hydroxyalkyl (having 2 to 6 carbon atoms) esters [such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 2-hydroxy-2-methylpropyl (meth)acrylate], mono- or di-hydroxyalkyl (having 1 to 4 carbon atoms) substituted (meth)acrylamides [such as N,N-dihydroxymethyl (meth)acrylamide, N,N-dihydroxypropyl (meth)acrylamide, and N,N-di-2-hydroxybutyl (meth)acrylamide], vinyl alcohol, enols having 3 to 12 carbon atoms [(meth)allyl alcohol, crotyl alcohol, isocrotyl alcohol, 1-octenol, and 1-undecenol, etc.], olefin monohydric alcohols or olefin dihydric alcohols having 4 to 12 carbon atoms [such as 1-butene-3-ol, 2-butene-1-ol, and 2-butene-1,4-diol, etc.], hydroxyalkyl (having 1 to 6 carbon atoms) alkenyl (having 3 to 10 carbon atoms) ethers (such as 2-hydroxyethyl allyl ether), alkenyl (having 3 to 10 carbon atoms) ethers or (meth)acrylic acid esters of polyhydric (3- to 8-valent) alcohols [such as glycerol, pentaerythritol, sorbitol, sorbitan, diglycerol, saccharides, and sucrose, etc.] (such as sucrose (meth)allyl ether, etc.).

[0116] As the monomer (f) containing a phosphorus atom, the following monomers (f1) to (f2) can be cited.

[0117] Monomer (f1) containing a phosphate group:

[0118] (Meth)acryloyloxyalkyl (having 2 to 4 carbon atoms) phosphates [(meth)acryloyloxyethyl phosphate and (meth)acryloyloxyisopropyl phosphate] and vinyl phosphates [vinyl phosphate, allyl phosphate, propenyl phosphate, isopropenyl phosphate, butenyl phosphate, pentenyl phosphate, octenyl phosphate, decenyl phosphate, and dodecenyl phosphate, etc.].

[0119] Monomer (f2) containing a phosphonyl group:

[0120] (Meth)acryloyloxyalkyl (having 2 to 4 carbon atoms) phosphonic acids [(meth)acryloyloxyethyl phosphonic acid, etc.] and alkenyl (having 2 to 12 carbon atoms) phosphonic acids [vinyl phosphonic acid, allyl phosphonic acid, and octenyl phosphonic acid, etc.].

[0121] Among the monomers (f) containing a phosphorus atom, the monomer (f1) containing a phosphate group is preferred, the (meth)acryloyloxyalkyl (having 2 to 4 carbon atoms) phosphate is more preferred, and the (meth)acryloyloxyethyl phosphate is particularly preferred.

[0122] In addition to the monomers (a) to (f), the copolymer (A) may further contain the following monomers (g) to (n) as constituent monomers.

[0123] Alkoxyalkyl ether monomer (g):

[0124] (Meth)acrylic acid methoxyethyl ester, (meth)acrylic acid methoxypropyl ester, (meth)acrylic acid methoxybutyl ester, (meth)acrylic acid methoxyheptyl ester, (meth)acrylic acid methoxyhexyl ester, (meth)acrylic acid methoxypentyl ester, (meth)acrylic acid methoxyoctyl ester, (meth)acrylic acid ethoxyethyl ester, (meth)acrylic acid ethoxypropyl ester, (meth)acrylic acid ethoxybutyl ester, (meth)acrylic acid ethoxyheptyl ester, (meth)acrylic acid ethoxyhexyl ester, (meth)acrylic acid ethoxypentyl ester, (meth)acrylic acid ethoxyoctyl ester, (meth)acrylic acid propoxy methyl ester, (meth)acrylic acid propoxyethyl ester, (meth)acrylic acid propoxypropyl ester, (meth)acrylic acid propoxybutyl ester, (meth)acrylic acid propoxyheptyl ester, (meth)acrylic acid propoxyhexyl ester, (meth)acrylic acid propoxypentyl ester, (meth)acrylic acid propoxyoctyl ester, (meth)acrylic acid butoxy methyl ester, (meth)acrylic acid butoxyethyl ester, (meth)acrylic acid butoxypropyl ester, (meth)acrylic acid butoxybutyl ester, (meth)acrylic acid butoxyheptyl ester, (meth)acrylic acid butoxyhexyl ester, (meth)acrylic acid butoxypentyl ester, (meth)acrylic acid butoxyoctyl ester, etc.

[0125] Among the monomers (g), preferably (meth)acrylic acid methoxyethyl ester, (meth)acrylic acid ethoxyethyl ester, (meth)acrylic acid butoxyethyl ester.

[0126] Aliphatic hydrocarbon monomer (h):

[0127] Examples include olefins having 2 to 20 carbon atoms (such as ethylene, propylene, butene, isobutene, pentene, heptene, diisobutene, octene, dodecene, and octadecene) and diolefins having 4 to 12 carbon atoms (such as butadiene, isoprene, 1,4-pentadiene, 1,6-heptadiene, and 1,7-octadiene).

[0128] Cycloaliphatic hydrocarbon monomer (i):

[0129] Examples include cyclohexene, (bi)cyclopentadiene, pinene, limonene, vinylcyclohexene, and ethylidene bicycloheptene.

[0130] Aromatic hydrocarbon-based monomer (j):

[0131] Examples include styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, 4-ethylstyrene, 4-isopropylstyrene, 4-butylstyrene, 4-phenylstyrene, 4-cyclohexylstyrene, 4-benzylstyrene, indene, 4-crotylbenzene, and 2-vinylnaphthalene.

[0132] Vinyl esters, vinyl ethers, vinyl ketones (k):

[0133] Examples include vinyl esters of saturated fatty acids having 2 to 12 carbon atoms (such as vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl octanoate), alkyl, aryl, or alkoxyalkyl vinyl ethers having 1 to 12 carbon atoms (such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, 2-ethylhexyl vinyl ether, phenyl vinyl ether, vinyl-2-methoxyethyl ether, and vinyl-2-butoxyethyl ether), and alkyl or aryl vinyl ketones having 1 to 8 carbon atoms (such as methyl vinyl ketone, ethyl vinyl ketone, and phenyl vinyl ketone).

[0134] Monomer (l) containing an epoxy group:

[0135] Examples include glycidyl (meth)acrylate and glycidyl (meth)allyl ether.

[0136] Monomer (m) containing a halogen element:

[0137] Examples include vinyl chloride, vinyl bromide, vinylidene chloride, (meth)allyl chloride, and halogenated styrenes (such as dichlorostyrene).

[0138] Esters (n) of unsaturated polycarboxylic acids:

[0139] Examples include alkyl, cycloalkyl, or aralkyl esters of unsaturated polycarboxylic acids [dialkyl esters having 1 to 8 carbon atoms of unsaturated dicarboxylic acids (such as maleic acid, fumaric acid, and itaconic acid) (dimethyl maleate, dimethyl fumarate, diethyl maleate, and dioctyl maleate)].

[0140] Based on the total weight of the monomers constituting the copolymer (A), the weight ratio of monomer (a) in the monomers constituting the copolymer (A) is 10 to 60% by weight, preferably 15 to 50% by weight, more preferably 20 to 45% by weight, and particularly preferably 25 to 40% by weight.

[0141] When the weight ratio of monomer (a) is less than 10% by weight, the antifriction effect is low, and when it exceeds 60% by weight, the storage stability and high-temperature stability decrease.

[0142] From the aspect of solubility in base oil, based on the total weight of the monomers constituting the copolymer (A), the weight ratio of monomer (b) in the monomers constituting the copolymer (A) is preferably 40 to 90% by weight, more preferably 45 to 85% by weight, further preferably 50 to 80% by weight, and particularly preferably 55 to 75% by weight.

[0143] From the aspect of antifriction property, based on the total weight of the monomers constituting the copolymer (A), the total weight ratio of the monomer (a) and the monomer (b) in the monomers constituting the copolymer (A) is preferably 70% by weight or more, more preferably 75% by weight or more, and particularly preferably 75 to 95% by weight.

[0144] From the aspects of antifriction property and base oil solubility, the weight ratio (b / a) of the weight of the monomer (a) to the weight of the monomer (b) in the monomers constituting the copolymer (A) is preferably 0.8 to 5.0, more preferably 1.0 to 3.5, and particularly preferably 1.2 to 2.6.

[0145] From the aspect of antifriction property, based on the total weight of the monomers constituting the copolymer (A), the weight ratio of the monomer (c) in the monomers constituting the copolymer (A) is preferably 30% by weight or less, more preferably 25% by weight or less, and particularly preferably 5 to 25% by weight.

[0146] From the aspect of antifriction property, based on the total weight of the monomers constituting the copolymer (A), the total weight ratio of the monomers (d) to (f) in the monomers constituting the copolymer (A) is preferably 20% by weight or less, more preferably 10% by weight or less.

[0147] From the aspect of antifriction property, based on the total weight of the monomers constituting the copolymer (A), the weight ratio of the monomer (d) is preferably 5% by weight or less, more preferably 3% by weight or less, and particularly preferably 1% by weight or less.

[0148] From the aspect of antifriction property, based on the total weight of the monomers constituting the copolymer (A), the weight ratio of the monomer (e) is preferably 10% by weight or less, more preferably 5% by weight or less.

[0149] From the aspect of antifriction property, based on the total weight of the monomers constituting the copolymer (A), the total weight ratio of the monomers (g) to (n) in the monomers constituting the copolymer (A) is preferably 10% by weight or less, more preferably 5% by weight or less.

[0150] The respective weight ratios of the monomers (a) to (n) in the copolymer (A) can be measured by methods such as pyrolysis GC / MS. In addition, the weight ratios of the respective constituent monomers at the time of charging in the production of the copolymer (A) can also be used as the respective weight ratios of the monomers (a) to (n) in the copolymer (A).

[0151] From the aspects of antifriction property and storage stability, the ratio (a / b) of the side-chain length of monomer (a) constituting copolymer (A) to the side-chain length of monomer (b) [relative to the molar average number of carbon atoms of the alkyl group possessed by monomer (b) constituting copolymer (A) (for monomer (b), when R in general formula (2) 5 is a straight-chain, it is the number of carbon atoms of R 5 , and when R 5 is a branched alkyl group, it is the number of carbon atoms of the longest alkyl group) of the side-chain of monomer (a) {the length of the -R 1 -X 2 -(C(=O)R 2 -X 3 -)p part in general formula (1)} is preferably 0.5 to 2.1, and more preferably 0.9 to 1.8.

[0152] When within the above range, there is a tendency that the hydroxyl group or amino group possessed by monomer (a) is easily adsorbed on the metal, thus easily exerting an antifriction effect. In addition, there is a tendency that the aggregation of molecules with each other is suppressed and the storage stability is also good.

[0153] In addition, regarding the side-chain of monomer (a), for example, when monomer (a) is the ε-caprolactone 1-mole adduct of 2-hydroxyethyl methacrylate, the length of the side-chain is the number of C and O bonded in a chain in the side-chain part [-CH2CH2O(CCH2CH2CH2CH2CH2O)], which is 10.

[0154] In addition, when the alkyl group of monomer (b) is a branched alkyl group, the number of carbon atoms of the longer chain is taken as the number of carbon atoms of the alkyl group possessed by this monomer (b). For example, when R 5 is 2-tetradecyloctadecyl, the number of carbon atoms of the alkyl group possessed by monomer (b) is 18.

[0155] For example, when monomer (b) constituting copolymer (A) is 0.5 mole part of 2-tetradecyloctadecyl methacrylate and 0.5 mole part of dodecyl methacrylate, according to the following mathematical formula, the molar average number of carbon atoms of the alkyl group possessed by monomer (b) constituting copolymer (A) is 15.

[0156] Molar average number of carbon atoms = (18×0.5 + 12×0.5) / (0.5 + 0.5) = 15

[0157] From the aspects of base oil solubility and viscosity index improvement effect, the SP value of copolymer (A) is preferably 8.5 to 11.5 (cal / cm 3 ) 1 / 2 , and more preferably 8.7 to 11.0 (cal / cm3 ) 1 / 2 , further preferably 8.9 to 10.5 (cal / cm 3 ) 1 / 2 , particularly preferably 9.2 to 10.2 (cal / cm 3 ) 1 / 2 。

[0158] The SP value of copolymer (A) refers to the value obtained by arithmetically averaging the SP values of the structural units from each monomer constituting copolymer (A) (the structure in which the polymerizable groups (such as vinyl groups) contained in each monomer constituting copolymer (A) have become single bonds through polymerization reaction) using the above calculation method for the SP value. For example, in the case where the monomer is methyl methacrylate, in the structural unit from methyl methacrylate, in terms of atomic groups, there are 2 CH3, 1 CH2, 1 C, and 1 CO2. Therefore, it can be seen from the following mathematical formula that the SP value of the structural unit from methyl methacrylate is 9.933 (cal / cm 3 ) 1 / 2 . Similarly, by calculation, it can be known that the SP value of the structural unit from ethyl methacrylate is 9.721 (cal / cm 3 ) 1 / 2 。

[0159] ΣΔe i =1125×2 + 1180 + 350 + 4300 = 8080

[0160] Σv i =33.5×2 + 16.1 - 19.2 + 18.0 = 81.9

[0161] δ = (8080 / 81.9) 1 / 2 =9.933 (cal / cm 3 ) 1 / 2

[0162] In the case where the polymer is a polymer of 50% by weight of methyl methacrylate and 50% by weight of ethyl methacrylate, the SP value of the polymer is calculated as follows by arithmetically averaging based on the weight fractions of the SP values of the structural units from each monomer.

[0163] Polymer SP value = (9.933×50 + 9.721×50) / 100 = 9.827

[0164] The SP value of the copolymer (A) can be adjusted to the desired range by appropriately adjusting the monomers used and the weight fractions. Specifically, by using more monomers with a larger number of carbon atoms in the alkyl group, the SP value can be decreased, and by using more monomers with a smaller number of carbon atoms in the alkyl group, the SP value can be increased.

[0165] The weight-average molecular weight of the copolymer (A) (hereinafter simply referred to as Mw) is 0.5×10^4 to 3.8×10^4, preferably 1.0×10^4 to 3.5×10^4, and more preferably 1.5×10^4 to 3.0×10^4.

[0166] When Mw is less than 0.5×10^4, the friction-reducing property is low, and when it exceeds 3.8×10^4, the high-temperature stability decreases.

[0167] The reason for the deterioration of the high-temperature stability of the lubricating oil composition when the weight-average molecular weight exceeds 3.8×10^4 has not been determined yet, but it is speculated that: when the temperature of the lubricating oil composition is low, the copolymer (A) exists in a coiled state hiding the polar groups, but when the temperature becomes high, the molecules unfold. If the weight-average molecular weight exceeds 3.8×10^4, the side chains (-C(=O)-R 2 -X 3 -R 3 ) from the highly polar monomer (a) cannot be hidden in the side chains (R in the general formula (2)) from the monomer (b) and are likely to precipitate. 5 )

[0168] It should be noted that Mw can be measured by gel permeation chromatography under the following conditions.

[0169] <Measurement conditions for Mw of copolymer (A)>

[0170] Apparatus: "HLC-8320GPC" [manufactured by Tosoh Corporation]

[0171] Columns: 1 "Guardcolumn Super HZM-M" [manufactured by Tosoh Corporation] and 3 "TSKgel Super HZM-M" [manufactured by Tosoh Corporation]

[0172] Measurement temperature: 40 °C

[0173] Sample solution: 0.25 wt% solution in tetrahydrofuran

[0174] Solution injection volume: 100 μl

[0175] Detection device: Refractive index detector G

[0176] Reference substance: 12 kinds of standard polystyrene (TSK standard POLYSTYRENE) (molecular weights: 500, 1,050, 2,800, 5,970, 9,100, 18,100, 37,900, 96,400, 190,000, 355,000, 1,090,000, 2,890,000) [manufactured by Tosoh Corporation]

[0177] The copolymer (A) can be obtained by a known production method. Specifically, a method of solution polymerization of the above monomers in a solvent in the presence of a polymerization catalyst can be cited.

[0178] Examples of the solvent include toluene, xylene, alkylbenzenes having 9 to 10 carbon atoms, methyl ethyl ketone, ethyl acetate, 2-propanol, and the base oil described later.

[0179] Examples of the polymerization catalyst include azo catalysts (such as azobisisobutyronitrile and azodipentanenitrile), peroxide catalysts (such as benzoyl peroxide, cumyl peroxide, and lauryl peroxide), and redox catalysts (such as a mixture of benzoyl peroxide and tertiary amine). A known chain transfer agent (such as alkyl mercaptans having 2 to 20 carbon atoms) can also be further used as needed.

[0180] The polymerization temperature is preferably 25 to 140 °C, more preferably 50 to 120 °C. In addition to the above solution polymerization, the copolymer (A) can also be obtained by bulk polymerization, emulsion polymerization, or suspension polymerization.

[0181] As the polymerization form when the copolymer (A) is a copolymer, it can be either a random addition polymer or an alternating copolymer, and can also be either a graft copolymer or a block copolymer.

[0182] The friction modifier of the present invention only needs to contain the above copolymer (A). From the aspect of operability (such as ease of addition to the lubricating oil composition), a base oil can be further contained.

[0183] Examples of the base oil include mineral oils (such as solvent-refined oils, paraffinic oils, high-viscosity index oils containing isoparaffins, high-viscosity index oils obtained by hydrocracking based on isoparaffins, and naphthenic oils), synthetic lubricating oils [hydrocarbon-based synthetic lubricating oils (such as poly-α-olefin-based synthetic lubricating oils) and ester-based synthetic lubricating oils], and mixtures thereof. Among them, mineral oils are preferred from the aspect of insulation.

[0184] From the aspect of operability (such as ease of addition to the lubricating oil composition), based on the weight of the friction modifier, the content of the copolymer (A) in the friction modifier is preferably 20 to 90% by weight, more preferably 30 to 80% by weight.

[0185] From the viewpoint of operability (such as ease of addition to the lubricating oil composition), based on the weight of the friction modifier, the content of the base oil in the friction modifier is preferably 10 to 80% by weight, more preferably 20 to 70% by weight.

[0186] The friction modifier of the present invention can balance the friction reduction effect and storage stability, and is therefore suitable for use in gear oils (differential oils and industrial gear oils, etc.), MTFs, transmission oils [ATFs and belt-type CVTFs, etc.], traction oils (ring-type CVTFs, etc.), shock absorber oils, power steering oils, hydraulic oils (hydraulic oils for construction machinery and industrial hydraulic oils, etc.) and engine oils, etc. It is preferably used as a friction modifier for transmission oils, motor oils, and transmission / motor combined oils in electric vehicles or hybrid vehicles, and is particularly preferably used as a friction modifier for transmission / motor combined oils in electric vehicles or hybrid vehicles.

[0187] <Lubricating oil composition>

[0188] The lubricating oil composition of the present invention contains the above-mentioned friction modifier of the present invention and a base oil. As the base oil, when the base oil is contained in the friction modifier, the same base oil as the base oil in the friction modifier can be used, or a different one can be used.

[0189] Examples of the base oil used in the lubricating oil composition include mineral oils (solvent-refined oils, paraffinic oils, high-viscosity-index oils containing isoparaffins, high-viscosity-index oils obtained by hydrocracking of isoparaffins, naphthenic oils, etc.), synthetic lubricating oils [hydrocarbon-based synthetic lubricating oils (poly-α-olefin-based synthetic lubricating oils, etc.) and ester-based synthetic lubricating oils, etc.] and mixtures thereof. Among them, from the viewpoint of insulation, mineral oils are preferred.

[0190] From the viewpoint of the solubility of the copolymer (A), the kinematic viscosity of the base oil at 100 °C (kinematic viscosity measured in accordance with JIS-K2283 (2000)) is preferably 1 to 10 mm 2 / s, more preferably 1 to 4 mm 2 / s.

[0191] From the viewpoint of the viscosity index improvement effect, the viscosity index of the base oil (viscosity index measured in accordance with JIS-K2283 (2000)) is preferably 100 or more, more preferably 110 or more.

[0192] The cloud point of the base oil (cloud point measured in accordance with JIS-K2269 (1987)) is preferably -5 °C or lower, more preferably -15 °C or lower. If the cloud point of the base oil is within this range, the low-temperature viscosity of the lubricating oil composition is good.

[0193] In terms of compatibility, the absolute value (ΔSP) of the difference between the SP value of the copolymer (A) in the lubricating oil composition and the SP value of the base oil is preferably 0.5 to 3.2 (cal / cm 3 ) 1 / 2 , more preferably 0.6 to 2.5 (cal / cm 3 ) 1 / 2 , particularly preferably 0.6 to 2.1 (cal / cm 3 ) 1 / 2 , most preferably 0.7 to 1.7 (cal / cm 3 ) 1 / 2 .

[0194] In terms of the antifriction effect, the content of the copolymer (A) in the lubricating oil composition of the present invention is preferably 0.1 to 30% by weight, more preferably 0.1 to 20% by weight, particularly preferably 0.1 to 10% by weight based on the weight of the lubricating oil composition.

[0195] The lubricating oil composition of the present invention is suitable for use in gear oils (differential oils and industrial gear oils, etc.), MTF, transmission oils [ATF and belt-type CVTF, etc.], traction oils (ring-type CVTF, etc.), shock absorber oils, power steering oils, hydraulic oils (hydraulic oils for construction machinery and industrial hydraulic oils, etc.) and engine oils, etc., and is preferably useful as a transmission oil, an electric motor oil, an oil for both transmission and electric motor in an electric vehicle or a hybrid vehicle, and particularly preferably useful as an oil for both transmission and electric motor in an electric vehicle or a hybrid vehicle.

[0196] The lubricating oil composition of the present invention may contain various additives. As additives, the following additives can be mentioned.

[0197] (1) Viscosity index improver:

[0198] (Meth)acrylic acid (alkyl group with 1 to 7 carbon atoms (hereinafter sometimes simply referred to as C)) alkyl ester / (meth)acrylic acid (C8 to 40) linear or branched alkyl ester copolymer, dispersing monomer (amine monomer, etc.) / (meth)acrylic acid (C1 to 7) alkyl ester / (meth)acrylic acid (C8 to 40) linear or branched alkyl ester copolymer, hydroxyl group-containing monomer / (meth)acrylic acid (C1 to 7) alkyl ester / (meth)acrylic acid (C8 to 40) linear or branched alkyl ester copolymer, comb-shaped polymer [(meth)acrylic acid (C1 to 7) alkyl ester / (meth)acrylic acid (C8 to 40) linear or branched alkyl ester / polyolefin macromonomer], ethylene / (meth)acrylic acid (C1 to 18) alkyl ester copolymer, (meth)acrylic acid alkoxyalkyl ester / polybutene copolymer macromonomer / (meth)acrylic acid (C1 to 32) linear or branched alkyl ester copolymer, polyisobutene, polyalkylstyrene, ethylene / propylene copolymer, styrene / maleate copolymer, styrene / isoprene hydrogenated copolymer, etc.;

[0199] (2) Detergent:

[0200] Alkaline, highly alkaline or neutral metal salts [highly alkaline or alkaline earth metal salts of sulfonates (such as petroleum sulfonates, alkylbenzene sulfonates, and alkylnaphthalene sulfonates, etc.)], salicylates, phenates, naphthenates, carbonates, phosphonates, and their mixtures;

[0201] (3) Dispersant:

[0202] Succinimides (bis- or mono-polybutenyl succinimides), Mannich condensates, borates, etc.;

[0203] (4) Antioxidant:

[0204] Hindered phenols, aromatic secondary amines, etc.;

[0205] (5) Oiliness improver:

[0206] Long-chain fatty acids and their esters (such as oleic acid and oleic acid esters), long-chain amines and their amides (such as oleylamine and oleamide), etc.;

[0207] (6) Metal-based friction and wear modifier:

[0208] Molybdenum-based and zinc-based compounds (such as molybdenum dithiophosphate, molybdenum dithiocarbamate, and zinc dialkyldithiophosphate, etc.);

[0209] (7) Extreme pressure agent:

[0210] Sulfur-based compounds (such as monosulfide or disulfide, sulfoxide, and sulfur-phosphorus compounds), phosphorus compounds, and chlorine-based compounds (such as chlorinated alkanes, etc.);

[0211] (8) Defoamer:

[0212] Silicone oil, metal soaps, fatty acid esters, phosphate ester compounds, etc.;

[0213] (9) Demulsifier:

[0214] Quaternary ammonium salts (tetraalkylammonium salts, etc.), sulfated oils, and phosphate esters (phosphate esters of nonionic surfactants containing polyoxyethylene, etc.);

[0215] (10) Corrosion inhibitor:

[0216] Compounds containing nitrogen atoms (benzotriazole, 1,3,4-thiadiazolyl-2,5-bis(dialkyldithiocarbamate), etc.);

[0217] (11) Pour point depressant:

[0218] Alkyl polymethacrylates, alkyl polyacrylates, polyalkylstyrenes, polyvinyl acetates, etc.

[0219] The lubricating oil composition of the present invention preferably contains at least 1 kind selected from the group consisting of a viscosity index improver, a detergent, a dispersant, an antioxidant, an oiliness improver, a metal-based friction and wear modifier, an extreme pressure agent, a defoamer, a demulsifier, a corrosion inhibitor, and a pour point depressant. The lubricating oil composition may contain only 1 kind of these additives, or may contain 2 or more kinds of additives as needed.

[0220] Based on the total amount of the lubricating oil composition, the content of each of these additives is preferably 0.1 to 15% by weight. In addition, based on the total amount of the lubricating oil composition, the total content of the additives is preferably 0.1 to 30% by weight, more preferably 0.3 to 20% by weight, and further preferably 3 to 10% by weight.

[0221] The following matters are disclosed in this specification.

[0222] This disclosure (1) relates to a friction modifier which is a copolymer (A) containing the monomer (a) represented by the following general formula (1) and the monomer (b) represented by the following general formula (2) as essential constituent monomers. Among the monomers constituting the copolymer (A), the average value of p in 1 mole of the monomer (a) is 1 to 4, the weight average molecular weight of the copolymer (A) is 0.5×10⁴ to 3.8×10⁴, and the copolymer (A) contains 10 to 60% by weight of the monomer (a) based on the total weight of the monomers constituting the copolymer (A) as a constituent monomer.

[0223] [Chemical formula 5]

[0224]

[0225] [In general formula (1), A 1 is a polymerizable group; -X 1 -, -X 2 -, and -X 3 - are each independently a group represented by -O- or -NH-; R 1 is an alkylene group having 1 to 4 carbon atoms; R 2 is an alkylene group having 2 to 20 carbon atoms; R 3 is a hydrogen atom; p is an integer of 1 to 100, and when p is 2 or more, multiple R 2 and X 3 are each the same or different.]

[0226] [Chemical Formula 6]

[0227]

[0228] [In general formula (2), R 4 is a hydrogen atom or a methyl group; -X 4 - is a group represented by -O- or -NH-; R 5 is a linear or branched alkyl group having 5 to 44 carbon atoms.]

[0229] The present disclosure (2) relates to the friction modifier described in the present disclosure (1), wherein the ratio (b / a) of the weight of the monomer (a) to the weight of the monomer (b) in the monomers constituting the copolymer (A) is 0.8 to 5.0.

[0230] The present disclosure (3) relates to a lubricating oil composition comprising the friction modifier described in the present disclosure (1) or (2) and a base oil.

[0231] The present disclosure (4) relates to the lubricating oil composition described in the present disclosure (3), wherein the kinematic viscosity of the base oil at 100 °C is 1 mm 2 / s to 4 mm 2 / s.

[0232] The present disclosure (5) relates to the lubricating oil composition described in the present disclosure (3) or (4), which further contains at least one selected from the group consisting of a viscosity index improver, a detergent, a dispersant, an antioxidant, an oiliness improver, a metal-based friction and wear modifier, an extreme pressure agent, an antifoaming agent, an anti-emulsifier, a corrosion inhibitor, and a pour point depressant.

[0233] Examples

[0234] The present invention will be described in detail below by way of examples, but the present invention is not limited to these examples.

[0235] <Production Example 1> [Production of monomer (a-1)]

[0236] In a reaction vessel equipped with a temperature regulator, stirring blades, a decompression device, a serpentine condenser, a fractionating tube, a flask for receiving distillate, a nitrogen gas inlet, and an outlet, 260.3 parts by weight (2.0 mol parts) of 2-hydroxyethyl methacrylate (hereinafter abbreviated as HEMA), 684.8 parts by weight (6.0 mol parts) of ε-caprolactone, 3.7 parts by weight (0.03 mol parts) of hydroquinone monomethyl ether, and 0.27 parts by weight of butyltris(2-ethylhexanoyloxy)tin were charged, and the temperature was raised to 115 °C with stirring while introducing air. Subsequently, the reaction was carried out at 115 °C for 8 hours, and the distilled water was separated. It was further cooled to 25 °C, and the esterification reaction product (yield 100 mol%) was confirmed by 1 1H-NMR.

[0237] Monomer (a-1) is A in the general formula (1) 1 being methacryloyl, -X 1 -, -X 2 -, and -X 3 - being a group represented by -O-, R 1 being ethylene, the molar average value of p = 3, R 2 = pentamethylene, R 3 being a monomer represented by a hydrogen atom, and the SP value being 11.04.

[0238] <Production Example 2> [Production of monomer (a-2)]

[0239] In a reaction vessel equipped with a temperature regulator, stirring blades, a decompression device, a serpentine condenser, a fractionating tube, a flask for receiving distillate, a nitrogen gas inlet, and an outlet, 260.3 parts by weight (2.0 mol parts) of 2-hydroxyethyl methacrylate (HEMA), 913.2 parts by weight (8.0 mol parts) of ε-caprolactone, 3.7 parts by weight (0.03 mol parts) of hydroquinone monomethyl ether, and 0.27 parts by weight of butyltris(2-ethylhexanoyloxy)tin were charged, and the temperature was raised to 115 °C with stirring while introducing air. Subsequently, the reaction was carried out at 115 °C for 8 hours, and the distilled water was separated. It was further cooled to 25 °C, and the esterification reaction product (yield 100 mol%) was confirmed by 1 1H-NMR.

[0240] Monomer (a-2) is A in the general formula (1) 1 being methacryloyl, -X 1 -, -X 2 -, and -X 3 - being a group represented by -O-, R 1 being ethylene, the molar average value of p = 4, R 2 = pentamethylene, R 3 being a monomer represented by a hydrogen atom, and the SP value being 10.87.

[0241] <Production Example 3> [Production of Monomer (a-3)]

[0242] Into a reaction vessel equipped with a temperature regulator, stirring blades, a decompression device, a serpentine condenser, a fractionating column, a distillate receiving flask, a nitrogen gas inlet, and an outlet, 260.3 parts by weight (2.0 mol parts) of 2-hydroxyethyl methacrylate (HEMA), 228.3 parts by weight (2.0 mol parts) of ε-caprolactone, 3.7 parts by weight (0.03 mol parts) of hydroquinone monomethyl ether, and 0.27 parts by weight of butyltris(2-ethylhexanoyloxy)tin were charged, and the mixture was heated to 115°C with stirring while introducing air. Then, the reaction was carried out at 115°C for 8 hours to separate the distilled water. Further cooled to 25°C, and confirmed by 1 1H-NMR for the esterification reaction product (yield 53 mol%). Then, 2-hydroxyethyl methacrylate (HEMA) remaining as an impurity in 47 mol% was removed by silica gel column chromatography.

[0243] Monomer (a-3) has A in the general formula (1) 1 as a methacryloyl group, -X 1 -, -X 2 -, and -X 3 - being a group represented by -O-, R 1 being an ethylene group, the molar average value of p = 1.9, R 2 = a pentamethylene group, R 3 being a monomer represented by a hydrogen atom, and the SP value being 11.36.

[0244] <Production Example 4> [Production of Monomer (a-4)]

[0245] Into a reaction vessel equipped with a temperature regulator, stirring blades, a decompression device, a serpentine condenser, a fractionating column, a distillate receiving flask, a nitrogen gas inlet, and an outlet, 232.2 parts by weight (2.0 mol parts) of 2-hydroxyethyl acrylate (hereinafter abbreviated as HEA), 456.6 parts by weight (4.0 mol parts) of ε-caprolactone, 3.7 parts by weight (0.03 mol parts) of hydroquinone monomethyl ether, and 0.27 parts by weight of butyltris(2-ethylhexanoyloxy)tin were charged, and the mixture was heated to 115°C with stirring while introducing air. Then, the reaction was carried out at 115°C for 8 hours to separate the distilled water. Further cooled to 25°C, and confirmed by 1 1H-NMR for the esterification reaction product (yield 76 mol%). Then, 2-hydroxyethyl acrylate (HEA) remaining as an impurity in 24 mol% was removed by silica gel column chromatography.

[0246] Monomer (a-4) has A in the general formula (1) 1 as an acryloyl group, -X 1 -, -X 2 -, and -X3 - is a group represented by -O-, R 1 is ethylene, the molar average value of p = 2.6, R 2 = pentamethylene, R 3 is a monomer representing a hydrogen atom, and the SP value is 11.30.

[0247] <Production Example 5> [Production of monomer (a'-1)]

[0248] Into a reaction vessel equipped with a temperature regulator, stirring blades, a decompression device, a serpentine condenser, a fractionating tube, a distillate receiving flask, a nitrogen gas inlet and an outlet, 260.3 parts by weight (2.0 mol parts) of 2-hydroxyethyl methacrylate (HEMA), 1141.5 parts by weight (10.0 mol parts) of ε-caprolactone, 3.7 parts by weight (0.03 mol parts) of hydroquinone monomethyl ether, and 0.27 parts by weight of butyltris(2-ethylhexanoyloxy)tin were charged. While introducing air, the temperature was raised to 115 °C with stirring. Then, the reaction was carried out at 115 °C for 8 hours, and the distilled water was separated. It was further cooled to 25 °C, and the 1 esterification reaction product (yield 100 mol%) was confirmed by 1H-NMR.

[0249] Monomer (a'-1) is A in the general formula (1) 1 is methacryloyl, -X 1 -, -X 2 -, and -X 3 - is a group represented by -O-, R 1 is ethylene, the molar average value of p = 5, R 2 = pentamethylene, R 3 is a monomer represented by a hydrogen atom, and the SP value is 10.75.

[0250] <Production Example 6> [Production of monomer (a'-2)]

[0251] A mixture of 60.6 parts by weight (10 mol parts) of monomer (a-2) obtained by the method described in Production Example 2, 9.1 parts by weight (10 mol parts) of n-butyric acid, and 350 parts by weight of dichloromethane was stirred at 0 °C. Then, 6.3 parts by weight (5 mol parts) of 4-dimethylaminopyridine and 24.0 parts by weight (15 mol parts) of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide were added, and the mixture was heated to room temperature and stirred overnight. The reaction solution was washed with 1N hydrochloric acid, an aqueous sodium bicarbonate solution, and brine, and then the organic layer was dried over magnesium sulfate. Then, the solvent was removed, and the product was further dried under vacuum to obtain monomer (a'-2).

[0252] Monomer (a'-2) is A in the general formula (1) 1 is methacryloyl, -X1 -, -X 2 - and -X 3 - is the group represented by -O-, R 1 is ethylene, the molar average value of p = 4, R 2 = pentamethylene, R 3 The monomer represented by butyryl group has an SP value of 9.96.

[0253] <Examples 1 to 21, Comparative Examples 1 to 5>

[0254] 185 parts by weight of ethyl acetate, a total of 100 parts by weight of a mixture of various monomers described in Tables 2 to 3, dodecyl mercaptan in the amounts described in Tables 2 to 3 as a chain transfer agent, and 2,2'-azobis(2-methylbutyronitrile) were charged into a reaction vessel equipped with a stirring device, a heating and cooling device, a thermometer, and a nitrogen inlet tube. After nitrogen replacement (gas-phase oxygen concentration 100 ppm), the temperature was raised to 76°C with stirring under closed conditions, and a polymerization reaction was carried out at this temperature for 6 hours.

[0255] Mineral oil [SP value: 8.3 (cal / cm 3 ) 1 / 2 , kinematic viscosity at 100°C: 2.4 mm 2 / s, viscosity index: 96] 66.7 parts by weight was added, and after raising the temperature to 120°C, unreacted monomers and ethyl acetate were removed at this temperature under reduced pressure (0.027 to 0.040 MPa) for 2 hours to obtain the friction modifiers (A-1) to (A-21) of the present invention containing 60% by weight of the copolymer or the friction modifiers (B-1) to (B5) for comparison.

[0256]

[0257]

[0258]

[0259]

[0260]

[0261]

[0262] The various monomers described in Tables 2 to 3 are as follows.

[0263] (a'-1): 5-mole adduct of ε-caprolactone to HEMA

[0264] (a'-2): terminal butyl ester of 4-mole adduct of ε-caprolactone to HEMA

[0265] (b-1): n-Dodecyl methacrylate

[0266] (b-2): Methacrylate of Neodol 23 (a mixture of linear or branched alkyl alcohols with 12 to 13 carbon atoms (weight ratio = linear C12: branched C12: linear C13: branched C13 = 40:10:40:10) manufactured by Shell Chemical Company)

[0267] (b-3): n-Hexadecyl methacrylate

[0268] (b-4): n-Octadecyl methacrylate

[0269] (b-5): 2-Decyltetradecyl methacrylate

[0270] (b-6): 2-Dodecylhexadecyl methacrylate

[0271] (b-7): 2-Tetradecyloctadecyl methacrylate

[0272] (b-8): n-Dodecyl acrylate

[0273] (b-9): n-Octadecyl acrylate

[0274] (c-1): Methyl methacrylate

[0275] (c-2): n-Butyl methacrylate

[0276] (d-1): 2-(Dimethylamino)ethyl methacrylate

[0277] (e-1): 2-Hydroxyethyl acrylate

[0278] (e-2): 2-Hydroxyethyl methacrylate

[0279] (e-3): 2-Hydroxy-2-methylpropyl methacrylate

[0280] <Mw of the copolymer>

[0281] The Mw (weight average molecular weight) of the copolymer contained in the friction modifiers of Examples 1 to 21 and Comparative Examples 1 to 5 was measured under the conditions described in <Measurement conditions of Mw of copolymer (A)>.

[0282] <Weight ratio of monomers (b / a)>

[0283] Based on the blended weights of monomers (a-1) to (a-4) and monomers (b-1) to (b-9), the weight ratio of monomer (a) to monomer (b) in the monomers constituting copolymer (A) was calculated.

[0284] <Side chain length of monomer (a)>

[0285] Based on the mixing molar ratios of monomers (a-1) to (a-4) and monomers (a'-1) to (a'-2) and the lengths of the side chains of each monomer, the side chain length of monomer (a) is calculated. Additionally, monomers (a'-1) to (a'-2) are monomers not included in monomer (a), but in Table 3, the calculated values of the side chain length of monomer (a) are shown assuming that monomers (a'-1) to (a'-2) are included in monomer (a).

[0286] <Side chain length of monomer (b)>

[0287] Based on the mixing molar ratios of monomers (b-1) to (b-9) and the lengths of the side chains of each monomer, the side chain length of monomer (b) is calculated.

[0288] <Ratio of the side chain length from (a) to the side chain length from (b)>

[0289] By dividing the side chain length of monomer (a) by the side chain length of monomer (b), the ratio of the side chain length of monomer (a) to the side chain length of monomer (b) is calculated.

[0290] The side chain lengths of monomers (a-1) to (a-4), monomers (a'-1) to (a'-2), and monomers (b-1) to (b-9) are as follows.

[0291] (a-1): 24

[0292] (a-2): 31

[0293] (a-3): 16.3

[0294] (a-4): 21.2

[0295] (a'-1): 38

[0296] (a'-2): 35

[0297] (b-1): 12

[0298] (b-2): 13.5

[0299] (b-3): 16

[0300] (b-4): 18

[0301] (b-5): 14

[0302] (b-6): 16

[0303] (b-7): 18

[0304] (b-8): 12

[0305] (b-9): 18

[0306] <SP value of the copolymer>

[0307] Based on the weight fractions of the respective constituent monomers at the time of feeding, the SP value of the copolymer is calculated.

[0308] <Evaluation of the storage stability of the friction modifier>

[0309] For the friction modifiers (A-1) to (A-21), (B-1) to (B-5) obtained in Examples 1 to 21 and Comparative Examples 1 to 5, they were stored in a container at 25°C, and the presence or absence of precipitates was confirmed after 10 days, 20 days, 30 days, and 60 days. The storage stability was evaluated according to the following criteria.

[0310] [Evaluation criteria]

[0311] ☆: No precipitates are generated even after 60 days from the start of the test

[0312] ◎: Precipitates are generated after 60 days from the start of the test

[0313] 〇: Precipitates are generated after 30 days from the start of the test

[0314] △: Precipitates are generated after 20 days from the start of the test

[0315] ×: Precipitates are generated after 10 days from the start of the test

[0316] <Examples 22 to 42, Comparative Examples 6 to 10>

[0317] The friction modifiers (A-1) to (A-21) obtained in Examples 1 to 21 and the friction modifiers (B-1) to (B-5) obtained in Comparative Examples 1 to 5 were added to the following base oil 1 at a rate of 2% by weight based on the weight of the base oil (the addition amount is converted to solids), that is, the content of the copolymer (A) in the lubricating oil composition was 2% by weight, to obtain lubricating oil compositions (V-1) to (V-21), (W-1) to (W-5).

[0318] (1) Base oil 1: Mineral oil [SP value: 8.3 (cal / cm 3 ) 1 / 2 , kinematic viscosity at 100°C: 3.1 mm 2 / s, viscosity index: 107]

[0319] <Added kinematic viscosity>

[0320] The kinematic viscosity at 100 °C and the kinematic viscosity at 40 °C of the lubricating oil compositions (V-1) to (V-21), (W-1) to (W-5) were measured by the method described in JIS-K2283 (2000), and the results were shown as the added kinematic viscosity (mm 2 / s) in Tables 2 and 3.

[0321] <Viscosity Index>

[0322] The viscosity index of the lubricating oil compositions (V-1) to (V-21), (W-1) to (W-5) was measured by the method described in JIS-K2283 (2000), and the results were shown as the viscosity index in Tables 2 and 3.

[0323] <Evaluation of High-Temperature Stability of Lubricating Oil Composition>

[0324] The lubricating oil compositions (V-1) to (V-21), (W-1) to (W-5) were placed in a container and stirred at 120 °C, and the time until solid matter precipitated was measured, and the high-temperature stability was judged according to the following criteria.

[0325] [Evaluation Criteria]

[0326] ◎: Even after 5 hours or more from the start of the test, no solid matter precipitates

[0327] 〇: Solid matter precipitates after 2 hours or more and less than 5 hours from the start of the test

[0328] △: Solid matter precipitates after 1 hour or more and less than 2 hours from the start of the test

[0329] ×: Solid matter precipitates less than 1 hour from the start of the test

[0330] <Evaluation of MTM Friction Characteristics>

[0331] The friction reduction effect of the lubricating oil compositions (V-1) to (V-21), (W-1) to (W-5) was measured under the following conditions using an MTM (Micro Traction Machine) tester to obtain a Stribeck curve. The friction coefficients at 10 mm / s, 100 mm / s, and 1,000 mm / s immediately after the tester started to slide and 2 hours after sliding were shown as the MTM friction characteristics in Tables 2 to 3. The lower the MTM friction characteristics, the higher the friction reduction effect.

[0332] <Friction Evaluation>

[0333] Equipment: PCS Instruments MTM-2

[0334] Disk: MTM Grinding Disk (Standard) (0.01 μm)

[0335] Ball: Drilled 3 / 4 AISI 52100 precision steel ball

[0336] Speed: 10 mm / s to 3,000 mm / s

[0337] Temperature: 100 °C

[0338] Sliding / rolling ratio: 50%

[0339] Load: 30 N

[0340] From the results in Tables 2 to 3, it can be seen that the friction modifiers (Examples 1 to 21) of the present invention do not produce precipitates even when stored at 25 °C for more than 30 days, so the storage stability is excellent. In addition, it can be seen that the lubricating oil compositions (Examples 22 to 42) containing the friction modifiers of the present invention do not produce precipitates even when stored at 120 °C for more than 2 hours, so the high-temperature stability is excellent. Furthermore, it can be seen that due to the excellent high-temperature stability, a high friction-reducing effect is exhibited not only immediately after the start of sliding but also after 2 hours of sliding.

[0341] Industrial applicability

[0342] The lubricating oil composition containing the friction modifier of the present invention is suitable as drive train lubricating oil (MTF, differential gear oil, ATF, belt-type CVTF, etc.), hydraulic oil (mechanical hydraulic oil, power steering oil, shock absorber oil, etc.), engine oil (for gasoline engines and diesel engines, etc.) and traction oil, and is preferably useful as transmission oil, motor oil, and oil for both transmission and motor in electric vehicles or hybrid vehicles, and is particularly preferably useful as oil for both transmission and motor in electric vehicles or hybrid vehicles.

Claims

1. A friction modifier, which is a friction modifier of a copolymer (A) containing monomer (a) represented by the following general formula (1) and monomer (b) represented by the following general formula (2) as essential constituent monomers, wherein, In the monomer (a) among the monomers constituting the copolymer (A), the average value of p per 1 mol of the monomer (a) is 1 to 4, the weight-average molecular weight of the copolymer (A) is 0.5×10⁴ to 3.8×10⁴, and the copolymer (A) contains 10% by weight to 60% by weight of the monomer (a) based on the total weight of the monomers constituting the copolymer (A) as a constituent monomer. [Chemical formula 1] In general formula (1), A 1 is a polymerizable group; -X 1 -, -X 2 -, and -X 3 - are each independently a group represented by -O- or -NH-; R 1 is an alkylene group having 1 to 4 carbon atoms; R 2 is an alkylene group having 2 to 20 carbon atoms; R 3 is a hydrogen atom; p is an integer from 1 to 100, and when p is 2 or more, multiple R 2 and X 3 are each the same or different; [Chemical formula 2] In general formula (2), R 4 is a hydrogen atom or a methyl group; -X 4 - is a group represented by -O- or -NH-; R 5 is a linear or branched alkyl group having 5 to 44 carbon atoms.

2. The friction modifier according to claim 1, wherein, The ratio b / a of the weight of the monomer (a) to the weight of the monomer (b) among the monomers constituting the copolymer (A) is 0.8 to 5.

0.

3. A lubricating oil composition comprising the friction modifier according to claim 1 or 2 and a base oil.

4. The lubricating oil composition according to claim 3, wherein The kinematic viscosity of the base oil at 100 °C is 1 mm 2 / s to 4 mm 2 / s.

5. The lubricating oil composition according to claim 3, wherein, It further contains at least one selected from the group consisting of a viscosity index improver, a detergent, a dispersant, an antioxidant, an oiliness improver, a metal-based friction and wear modifier, an extreme pressure agent, an antifoaming agent, an anti-emulsifier, a corrosion inhibitor, and a pour point depressant.

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