Antifoaming agent, lubricating oil composition containing antifoaming agent, and machine using lubricating oil composition

Abstract

Provided is an antifoaming agent which exhibits excellent antifoaming properties even in a high-temperature environment.　This antifoaming agent is a polymer having, as polymerization components, at least (1) a polymerizable monomer having a functional group represented by -Si[OSi(R)3]n[R']3-n (n is an integer in the range of 1-3. R is each independently an alkyl group having 1-3 carbon atoms. R' is each independently an alkyl group having 1-3 carbon atoms), and one polymerizable unsaturated group, and (2) a polymerizable monomer having two or more polymerizable unsaturated groups.

Description

Antifoaming agent, lubricating oil composition containing antifoaming agent, and machine using the lubricating oil composition

[0001] The present invention relates to an antifoaming agent, a lubricating oil composition containing the antifoaming agent, and a machine using the lubricating oil composition.

[0002] Reducing carbon dioxide emissions has become an important theme in the industrial world in recent years. Carbon dioxide emissions from transportation equipment, including automobiles, account for nearly 20% of the total, and as one measure to reduce this, countries around the world have announced policies to switch from gasoline-powered vehicles to electric vehicles (EVs).

[0003] The most important issue for EVs is improving fuel efficiency, and to that end, research is being conducted at a rapid pace to reduce the size of the vehicle body and improve the efficiency of the drivetrain. One of the challenges in improving the efficiency of the drivetrain is foaming of lubricating oil. Lubricating oils are becoming less viscous to reduce frictional resistance, but this lower viscosity makes them more prone to foaming.

[0004] When high-load operation or high-speed driving is performed continuously, foaming increases in the low-viscosity lubricating oil, which can cause problems such as reduced lubrication performance and cooling efficiency; wear and seizure due to rupture of the oil film at friction points; and accelerated deterioration of the lubricating oil due to increased oil temperature.

[0005] For this reason, lubricating oils with high defoaming properties are required to suppress foaming from the initial stage of operation over a long period of time, and lubricating oils contain defoamers to prevent foaming. Polysiloxane-based defoamers are known as such defoamers, and various polysiloxane-based defoamers have been proposed (for example, Patent Document 1).

[0006] JP 2017-039924 A

[0007] Conventional polysiloxane-based defoaming agents have the problem that their defoaming properties decrease significantly as the temperature rises. For example, there has been a problem in that sufficient defoaming properties cannot be obtained in automotive applications where defoaming properties at high temperatures are required.

[0008] The problem to be solved by the present invention is to provide an antifoaming agent that exhibits excellent antifoaming properties even in a high-temperature environment. Another problem to be solved by the present invention is to provide a lubricating oil composition that can exhibit excellent lubricating performance even in a high-temperature environment.

[0009] The present inventors have conducted extensive research to solve the above problems and have found that a polymer containing, as polymerization components, a polymerizable monomer having a specific silicone functional group and one polymerizable unsaturated group, and a polymerizable monomer having two or more polymerizable unsaturated groups is a defoaming agent that exhibits excellent defoaming properties even in high-temperature environments, thereby completing the present invention.

[0010] That is, the present invention relates to the following defoaming agents, etc.: 1. —Si[OSi(R) ３ ] ｎ [R'] ３－ｎ (n is an integer ranging from 1 to 3; each R is independently an alkyl group having 1 to 3 carbon atoms; each R' is independently an alkyl group having 1 to 3 carbon atoms), and containing as polymerization components at least a polymerizable monomer (1) having one polymerizable unsaturated group and a polymerizable monomer (2) having two or more polymerizable unsaturated groups. 2. The defoaming agent according to 1, wherein the polymerizable monomer (1) is a compound represented by the following general formula (1-1): (In the general formula (1-1), R is independently an alkyl group having 1 to 3 carbon atoms, and R' is independently an alkyl group having 1 to 3 carbon atoms. L １１ is a divalent organic group or a single bond. n is an integer ranging from 1 to 3. P is a polymerizable group represented by general formula (P-1), a polymerizable group represented by general formula (P-2), or a polymerizable group represented by general formula (P-3). In general formula (P-1), general formula (P-2), and general formula (P-3), R １１ is a hydrogen atom or a methyl group. １２ is a hydrogen atom or an organic group. １３ is a hydrogen atom or a methyl group. * is L １１3. The defoaming agent according to 1 or 2, wherein the content of the polymerizable monomer (1) in the polymerization components is in the range of 10 mass% or more. 4. The defoaming agent according to any one of 1 to 3, wherein the polymerizable monomer (2) is a compound represented by the following general formula (2-1): (In the general formula (2-1), R ２１ is a hydrogen atom or a methyl group; x is an integer of 2 or more; ２１ is an organic group having a valence of x.) 5. The defoaming agent according to any one of 1 to 4, wherein the content of the polymerizable monomer (2) in the polymerization components is in the range of 1 to 75% by mass. 6. The defoaming agent according to any one of 1 to 5, wherein the polymerization components contain a polymerizable monomer (3) having one or more selected from the group consisting of an alkyl group having 1 to 18 carbon atoms, an aromatic group having 6 to 18 carbon atoms, a group containing a polyoxyalkylene chain, and a group containing a polyester chain. 7. The defoaming agent according to 6, wherein the polymerizable monomer (3) is one or more selected from the group consisting of a compound represented by the following general formula (3-1), a compound represented by the following general formula (3-2), a compound represented by the following general formula (3-3), a compound represented by the following general formula (3-4), and a compound represented by the following general formula (3-5): (In the general formulae (3-1), (3-2), (3-3), (3-4) and (3-5), R ３１ is a hydrogen atom or a methyl group, R ３２ is an alkyl group having 1 to 18 carbon atoms; R ３３ is a hydrogen atom or a methyl group, R ３４ is a hydrogen atom or an alkyl group having 1 to 18 carbon atoms; R ３５ is a hydrogen atom or a methyl group, R ３６ is an alkyl group having 1 to 18 carbon atoms, an alkyl group having 1 to 18 carbon atoms and an ether bond, or a hydrogen atom; R ３７ is a hydrogen atom or a methyl group, R ３８ is an alkyl group having 1 to 18 carbon atoms, an alkyl group having 1 to 18 carbon atoms and an ether bond, or a hydrogen atom; L ３ is a divalent organic group or a single bond, R ３９ is a hydrogen atom or a methyl group, R４０ are each independently an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, n is an integer ranging from 1 to 4, m is the number of repetitions, and the number average value of m is in the range of 1 to 200, p is an integer ranging from 1 to 10, q is the number of repetitions, and the number average value of q is in the range of 1 to 100, and l is an integer ranging from 0 to 5. 8. The defoaming agent according to 6 or 7, wherein the polymerizable monomer (3) comprises a compound represented by general formula (3-2). 9. The defoaming agent according to any one of 6 to 8, wherein the content of the polymerizable monomer (3) in the polymerization component is in the range of 0 to 75 mass%. 10. The defoaming agent according to any one of 1 to 9, wherein the weight average molecular weight is in the range of 2,000 to 200,000. 11. A lubricating oil composition containing a lubricating base oil and the defoaming agent according to any one of claims 1 to 10. 12. 12. The lubricating oil composition according to 11, which is used to lubricate the driving parts of a machine equipped with an internal combustion engine or an electric motor. 13. The lubricating oil composition according to 11, which is used to lubricate the driving parts of a vehicle equipped with an internal combustion engine or an electric motor. 14. A machine using the lubricating oil composition according to 11 in its driving parts.

[0011] The present invention can provide an antifoaming agent that exhibits excellent antifoaming properties even in a high-temperature environment, and a lubricating oil composition that can exhibit excellent lubricating performance even in a high-temperature environment.

[0012] An embodiment of the present invention will be described below. The present invention is not limited to the following embodiment, and can be carried out by making appropriate modifications within the scope that does not impair the effects of the present invention. In this specification, "(meth)acrylate" refers to either or both of acrylate and methacrylate.

[0013] [Antifoaming agent] The antifoaming agent of the present invention is —Si[OSi(R) ３ ] ｎ [R'] ３－ｎ(n is an integer of 1 to 3. Each R is independently an alkyl group having 1 to 3 carbon atoms. Each R' is independently an alkyl group having 1 to 3 carbon atoms), and the polymer contains as polymerization components at least a polymerizable monomer (1) having one polymerizable unsaturated group and a polymerizable monomer (2) having two or more polymerizable unsaturated groups. Here, the term "polymerization component" means a component that constitutes the polymer, and does not include solvents, polymerization initiators, etc. that do not constitute the polymer.

[0014] In the present invention, the term "polymerizable monomer" means a compound having a polymerizable unsaturated group, and examples of the polymerizable unsaturated group that the polymerizable monomer (1) and the polymerizable monomer (2) have include a (meth)acryloyl group, a (meth)acryloyloxy group, a (meth)acryloylamide group, a vinyl ether group, an allyl group, a styryl group, a (meth)acryloylamino group, and a maleimide group.

[0015] A polymer having at least the polymerizable monomer (1) and the polymerizable monomer (2) as polymerization components, which is the defoaming agent of the present invention, may be referred to as the "polymer of the present invention." Hereinafter, each component constituting the polymer of the present invention will be described.

[0016] The —Si[OSi(R) ３ ] ｎ [R'] ３－ｎ The functional group represented by is preferably —Si[OSi(R) ３ ] ３ is a functional group represented by the formula: ３ ) ３ ] ３ is.

[0017] The polymerizable monomer (1) is preferably a compound represented by the following general formula (1-1).

[0018] (In the general formula (1-1), R is independently an alkyl group having 1 to 3 carbon atoms, and R' is independently an alkyl group having 1 to 3 carbon atoms. L １１is a divalent organic group or a single bond. n is an integer ranging from 1 to 3. P is a polymerizable group represented by general formula (P-1), a polymerizable group represented by general formula (P-2), or a polymerizable group represented by general formula (P-3). In general formula (P-1), general formula (P-2), and general formula (P-3), R １１ is a hydrogen atom or a methyl group. １２ is a hydrogen atom or an organic group. １３ is a hydrogen atom or a methyl group. * is L １１ is the bond that bonds with

[0019] L １１ The "single bond" in the formula (I) means that O and Si are directly bonded to each other. １１ The divalent organic group is preferably an alkylene group having 1 to 50 carbon atoms or an alkyleneoxy group having 1 to 50 carbon atoms.

[0020] L １１ Examples of the alkylene group having 1 to 50 carbon atoms include a methylene group, an ethylene group, an n-propylene group, an n-butylene group, an n-pentylene group, an n-hexylene group, an n-heptylene group, an n-octylene group, an n-nonylene group, an n-decylene group, an n-dodecylene group, an isopropylene group, a 2-methylpropylene group, a 2-methylhexylene group, and a tetramethylethylene group.

[0021] L １１ The alkylene group having 1 to 50 carbon atoms is preferably an alkylene group having 1 to 15 carbon atoms, more preferably an alkylene group having 1 to 5 carbon atoms, and even more preferably a methylene group, an ethylene group, an n-propylene group, or an isopropylene group.

[0022] L １１ The alkyleneoxy group having 1 to 50 carbon atoms may be, for example, one or more —CH ２ - is a group in which - is substituted with -O-. １１The alkyleneoxy group having 1 to 50 carbon atoms is preferably an alkyleneoxy group having 1 to 15 carbon atoms, more preferably an alkyleneoxy group having 1 to 8 carbon atoms, and even more preferably a methyleneoxy group, an ethyleneoxy group, a propyleneoxy group, an oxytrimethylene group, a butyleneoxy group, an oxytetramethylene group, a pentyleneoxy group, a heptyleneoxy group, or an octyleneoxy group.

[0023] L １１ When the divalent organic group is an alkylene group having 1 to 50 carbon atoms or an alkyleneoxy group having 1 to 50 carbon atoms, these divalent organic groups are -CH ２ A part of the - may be replaced with a carbonyl group (-C(=O)-), a phenylene group, an amide bond or a urethane bond (-NHC(=O)-).

[0024] L １１ When the divalent organic group is an alkylene group having 1 to 50 carbon atoms or an alkyleneoxy group having 1 to 50 carbon atoms, a carbon atom of these groups may further be substituted with a substituent such as a hydroxyl group.

[0025] R １２ Examples of the organic group include alkyl groups having 1 to 18 carbon atoms. １２ Examples of the alkylene group having 1 to 18 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-dodecyl group, an isopropyl group, a 2-methylpropyl group, a 2-methylhexyl group, and a tetramethylethyl group.

[0026] n is preferably 2 or 3, and more preferably 3. The compound represented by the general formula (1-1) is preferably a compound represented by the following general formula (1-2) (n=3) or a compound represented by the following general formula (1-3) (n=2), and more preferably a compound represented by the following general formula (1-2).

[0027] (In the general formulas (1-2) and (1-3), P, R′, R １１ , and L １１are P, R', and R in the general formula (1-1). １１ and L １１ is the same as

[0028] The polymerizable monomer (1) as a polymerization component may be one type alone or two or more types of polymerizable monomer (1) having different structures.

[0029] The polymerizable monomer (1) can be produced by a known method, or a commercially available product such as 3-(methacryloyloxy)propyltris(trimethylsiloxy)silane may be used.

[0030] As the polymerizable monomer (1), in addition to the above-mentioned 3-(methacryloyloxy)propyltris(trimethylsiloxy)silane, for example, the following compounds can also be used.

[0031]

[0032] In the polymer of the present invention, the lower limit of the content of polymerizable monomer (1) is, for example, 10% by mass or more, 20% by mass or more, 25% by mass or more, 30% by mass or more, or 35% by mass or more, based on the total amount of polymerization components of the polymer. The upper limit of the content of polymerizable monomer (1) is not particularly limited, but is, for example, 99% by mass or less, 90% by mass or less, 80% by mass or less, 70% by mass or less, or 60% by mass or less, based on the total amount of polymerization components of the polymer. The combination of the upper and lower limits of the content of polymerizable monomer (1) can be, for example, in the range of 10% by mass to 99% by mass of the total amount of polymerization components of the polymer, and preferably in the range of 25% by mass to 80% by mass of the total amount of polymerization components of the polymer. The content of polymerizable monomer (1) can be adjusted by the raw material charge ratio of polymerizable monomer (1) when producing the polymer of the present invention.

[0033] The polymerizable monomer (2) is a polymerizable monomer having two or more polymerizable unsaturated groups, and may have two or more of one type of polymerizable unsaturated group, or may have two or more types of polymerizable unsaturated groups. The polymerizable monomer (2) is preferably a polymerizable monomer having two or more (meth)acryloyl groups or a polymerizable monomer having two or more (meth)acryloyloxy groups.

[0034] The polymerizable monomer (2) is preferably a compound represented by the following general formula (2-1).

[0035] (In the general formula (2-1), R ２１ is a hydrogen atom or a methyl group; n2 is an integer of 2 or more; L ２１ is an n2-valent organic group.

[0036] n2 may be an integer of 2 or more, for example, an integer in the range of 2 to 12, preferably an integer in the range of 2 to 8, more preferably an integer in the range of 2 to 6, and even more preferably an integer in the range of 2 to 4.

[0037] L ２１ The n2-valent organic group is an organic group having a valence corresponding to the value of n2. For example, when n2 is 2, it is a divalent organic group, and when n2 is 6, it is a hexavalent organic group.

[0038] L ２１ is preferably an alkylene group having 1 to 50 carbon atoms or an alkyleneoxy group having 1 to 50 carbon atoms, and is an organic group in which a hydrogen atom bonded to a carbon atom of the alkylene group or the alkyleneoxy group is replaced with a bond so as to have a valence corresponding to the value of n2. ２１ When L is a divalent organic group, ２１ is preferably an alkylene group having 1 to 50 carbon atoms or an alkyleneoxy group having 1 to 50 carbon atoms.

[0039] L ２１ Examples of the alkylene group having 1 to 50 carbon atoms include a methylene group, an ethylene group, an n-propylene group, an n-butylene group, an n-pentylene group, an n-hexylene group, an n-heptylene group, an n-octylene group, an n-nonylene group, an n-decylene group, an n-dodecylene group, an isopropylene group, a 2-methylpropylene group, a 2-methylhexylene group, and a tetramethylethylene group.

[0040] L ２１The alkylene group having 1 to 50 carbon atoms is preferably an alkylene group having 1 to 15 carbon atoms, more preferably an alkylene group having 1 to 5 carbon atoms, and even more preferably a methylene group, an ethylene group, an n-propylene group, or an isopropylene group.

[0041] L ２１ The alkyleneoxy group having 1 to 50 carbon atoms may be, for example, one or more —CH ２ - is a group in which - is substituted with -O-. ２１ The alkyleneoxy group having 1 to 50 carbon atoms is preferably an alkyleneoxy group having 1 to 15 carbon atoms, more preferably an alkyleneoxy group having 1 to 8 carbon atoms, and even more preferably a methyleneoxy group, an ethyleneoxy group, a propyleneoxy group, an oxytrimethylene group, a butyleneoxy group, an oxytetramethylene group, a pentyleneoxy group, a heptyleneoxy group, or an octyleneoxy group.

[0042] L ２１ When the divalent organic group is an alkylene group having 1 to 50 carbon atoms or an alkyleneoxy group having 1 to 50 carbon atoms, these divalent organic groups are -CH ２ A part of the - may be replaced by a carbonyl group (-C(=O)-), a phenylene group, a sulfide bond (-S-), an amide bond or a urethane bond.

[0043] L ２１ When the divalent organic group is an alkylene group having 1 to 50 carbon atoms or an alkyleneoxy group having 1 to 50 carbon atoms, a carbon atom of these groups may further be substituted with a substituent such as a hydroxyl group.

[0044] Specific examples of the polymerizable monomer (2) include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, butanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 2-hydroxy-3-methacrylpropyl acrylate, 2-hydroxy-1,3-dimethacryloxypropane, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, and ethoxylated bisphenol A. Examples of the acrylate include Nol A di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, tris-(2-acryloxyethyl)isocyanurate, bis-(2-acryloxyethyl)isocyanurate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and polypentaerythritol poly(meth)acrylate.

[0045] The polymerizable monomer (2) as a polymerization component may be one type alone or two or more types of polymerizable monomers (2) having different structures.

[0046] The polymerizable monomer (2) can be produced by a known method, and a commercially available product may also be used.

[0047] In the polymer of the present invention, the content of the polymerizable monomer (2) is, for example, in the range of 0.1 to 900 parts by mass relative to 100 parts by mass of the polymerizable monomer (1), preferably in the range of 1 to 500 parts by mass relative to 100 parts by mass of the polymerizable monomer (1), more preferably in the range of 3 to 300 parts by mass relative to 100 parts by mass of the polymerizable monomer (1). It is even more preferably in the range of 5 to 200 parts by mass relative to 100 parts by mass of the polymerizable monomer (1). The content of the polymerizable monomer (2) can be adjusted by the raw material charge ratio of the polymerizable monomer (2) when producing the polymer of the present invention.

[0048] In the polymer of the present invention, the content of the polymerizable monomer (2) is, for example, in the range of 0.1 to 90 mass %, preferably in the range of 1 to 75 mass %, more preferably in the range of 3 to 60 mass %, and even more preferably in the range of 5 to 50 mass %, based on the total amount of polymerization components of the polymer.

[0049] The polymerization components of the polymer of the present invention preferably include, in addition to the polymerizable monomer (1) and the polymerizable monomer (2), a polymerizable monomer (3) having one or more selected from the group consisting of an alkyl group having 1 to 18 carbon atoms, an aromatic group having 6 to 18 carbon atoms, a group containing a polyoxyalkylene chain, and a group containing a polyester chain. By further including the polymerizable monomer (3) as a polymerization component, for example, when the antifoaming agent of the present invention is added to a lubricating oil composition, high compatibility of the antifoaming agent with the lubricating base oil can be ensured.

[0050] The alkyl group having 1 to 18 carbon atoms contained in the polymerizable monomer (3) may be any of a linear alkyl group, a branched alkyl group, and a cyclic alkyl group, and specific examples thereof include a methyl group, an ethyl group, a normal propyl group, an isopropyl group, an n-butyl group, a t-butyl group, an n-hexyl group, a cyclohexyl group, an n-octyl group, a hexadecyl group, etc. The alkyl group having 1 to 18 carbon atoms contained in the polymerizable monomer (3) is preferably an alkyl group having 1 to 6 carbon atoms.

[0051] Examples of the aromatic group having 6 to 18 carbon atoms contained in the polymerizable monomer (3) include a phenyl group, a naphthyl group, an anthracen-1-yl group, and a phenanthrene-1-yl group.

[0052] The group containing a (poly)oxyalkylene chain contained in the polymerizable monomer (3) is a monovalent group containing a repeating oxyalkylene moiety or a divalent linking group containing a repeating oxyalkylene moiety.

[0053] The group containing a polyester chain contained in the polymerizable monomer (3) is a monovalent group containing a repeating ester bond moiety or a divalent linking group containing a repeating ester bond moiety.

[0054] The alkyl group having 1 to 18 carbon atoms contained in the polymerizable monomer (3) may further have a substituent, and examples of the substituent include a hydroxyl group, an aryl group, etc. The aromatic group having 6 to 18 carbon atoms contained in the polymerizable monomer (3) may further have a substituent, and examples of the substituent include a hydroxyl group, an alkyl group, etc.

[0055] Examples of the polymerizable monomer (3) having an alkyl group having 1 to 18 carbon atoms and in which the polymerizable unsaturated group is a (meth)acryloyl group include methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate, isopropyl(meth)acrylate, n-butyl(meth)acrylate, s-butyl(meth)acrylate, isobutyl(meth)acrylate, t-butyl(meth)acrylate, n-pentyl(meth)acrylate, n-hexyl(meth)acrylate, n-heptyl(meth)acrylate, n-octyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, decyl(meth)acrylate, and methyl(meth)acrylate. (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, and other alkyl esters of (meth)acrylic acid having 1 to 18 carbon atoms; and bridged cyclic alkyl esters of (meth)acrylic acid having 1 to 18 carbon atoms, such as dicyclopentanyloxylethyl (meth)acrylate, isobornyloxylethyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, dimethyladamantyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and dicyclopentenyl (meth)acrylate. In this application, "(meth)acrylate" refers to both methacrylate and acrylate.

[0056] Examples of the polymerizable monomer (3) having a phenylalkyl group having 7 to 18 carbon atoms or a phenoxyalkyl group having 7 to 18 carbon atoms and in which the polymerizable unsaturated group is a (meth)acryloyl group include benzyl (meth)acrylate, phenoxymethyl (meth)acrylate, and 2-phenoxyethyl (meth)acrylate.

[0057] Examples of the polymerizable monomer (3) having an alkyl group having 1 to 18 carbon atoms and in which the polymerizable unsaturated group is a vinyl ether group include alkyl vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tert-butyl vinyl ether, n-pentyl vinyl ether, n-hexyl vinyl ether, n-octyl vinyl ether, n-dodecyl vinyl ether, 2-ethylhexyl vinyl ether, and cyclohexyl vinyl ether; and cycloalkyl vinyl ethers.

[0058] Examples of the polymerizable monomer (3) having an aromatic group having 6 to 18 carbon atoms include styrene, α-methylstyrene, p-methylstyrene, and p-methoxystyrene.

[0059] Examples of the polymerizable monomer (3) having an alkyl group having 1 to 18 carbon atoms and in which the polymerizable unsaturated group is a (meth)acryloylamino group include N,N-dimethylacrylamide, N,N-diethylacrylamide, N-isopropylacrylamide, diacetoneacrylamide, and acroylmorpholine.

[0060] Examples of the polymerizable monomer (B) having an alkyl group having 1 to 18 carbon atoms and in which the polymerizable unsaturated group is a maleimide group include methylmaleimide, ethylmaleimide, propylmaleimide, butylmaleimide, hexylmaleimide, octylmaleimide, dodecylmaleimide, stearylmaleimide, and cyclohexylmaleimide.

[0061] Examples of the polymerizable monomer (3) having a group containing a polyoxyalkylene chain and in which the polymerizable unsaturated group is a (meth)acryloyl group include polypropylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, polytrimethylene glycol mono(meth)acrylate, polytetramethylene glycol mono(meth)acrylate, poly(ethylene glycol.propylene glycol) mono(meth)acrylate, polyethylene glycol.polypropylene glycol mono(meth)acrylate, poly(ethylene glycol.tetramethylene glycol) mono(meth)acrylate, polyethylene glycol.polytetramethylene glycol mono(meth)acrylate, poly(propylene glycol.tetramethylene glycol) mono(meth)acrylate, polypropylene glycol.polytetramethylene glycol mono(meth)acrylate, poly(propylene glycol.1,2-butylene glycol) mono(meth)acrylate, polypropylene glycol.poly1,2-butylene glycol mono(meth)acrylate, Poly(ethylene glycol·1,2-butylene glycol) mono(meth)acrylate, polyethylene glycol·poly 1,2-butylene glycol mono(meth)acrylate, poly(tetraethylene glycol·1,2-butylene glycol) mono(meth)acrylate, polytetraethylene glycol·poly 1,2-butylene glycol mono(meth)acrylate, poly 1,2-butylene glycol mono(meth)acrylate, poly(ethylene glycol·trimethylene glycol) mono(meth)acrylate, polyethylene Glycol / polytrimethylene glycol mono(meth)acrylate, poly(propylene glycol / trimethylene glycol) mono(meth)acrylate, polypropylene glycol / polytrimethylene glycol mono(meth)acrylate, poly(trimethylene glycol / tetramethylene glycol) mono(meth)acrylate, polytrimethylene glycol / polytetramethylene glycol mono(meth)acrylate, poly(1,2-butylene glycol / trimethylene glycol) mono(meth)acrylate, poly 1,Examples include 2-butylene glycol-polytrimethylene glycol mono(meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, poly(1,2-butylene glycol-tetramethylene glycol) mono(meth)acrylate, and poly(1,2-butylene glycol-polytetramethylene glycol mono(meth)acrylate). The above "poly(ethylene glycol-propylene glycol)" refers to a random copolymer of ethylene glycol and propylene glycol, and "polyethylene glycol-polypropylene glycol" refers to a block copolymer of ethylene glycol and propylene glycol.

[0062] The polymerizable monomer (3) is preferably at least one selected from the group consisting of a compound represented by the following general formula (3-1), a compound represented by the following general formula (3-2), a compound represented by the following general formula (3-3), and a compound represented by the following general formula (3-4):

[0063] (In the general formulae (3-1), (3-2), (3-3), (3-4) and (3-5), R ３１ is a hydrogen atom or a methyl group, R ３２ is an alkyl group having 1 to 18 carbon atoms; R ３３ is a hydrogen atom or a methyl group, R ３４ is a hydrogen atom or an alkyl group having 1 to 18 carbon atoms; R ３５ is a hydrogen atom or a methyl group, R ３６ is an alkyl group having 1 to 18 carbon atoms, an alkyl group having 1 to 18 carbon atoms and an ether bond, or a hydrogen atom; R ３７ is a hydrogen atom or a methyl group, R ３８ is an alkyl group having 1 to 18 carbon atoms, an alkyl group having 1 to 18 carbon atoms and an ether bond, or a hydrogen atom; L ３ is a divalent organic group or a single bond, R ３９ is a hydrogen atom or a methyl group, R ４０are each independently an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, n is an integer ranging from 1 to 4, m is the number of repetitions, the number average value of m being in the range of 1 to 200, p is an integer ranging from 1 to 10, q is the number of repetitions, the number average value of q being in the range of 1 to 100, and 1 is an integer ranging from 0 to 5.

[0064] In the formula (3-2), the m n's in the parentheses may be the same or different from each other. In the formula (3-3), the q p's in the parentheses may be the same or different from each other. In the formula (3-4), the q p's in the parentheses may be the same or different from each other.

[0065] R ３２ , R ３４ , R ３６ and R ３８ The alkyl group having 1 to 18 carbon atoms may further have a substituent, and examples of the substituent include a hydroxyl group and an aryl group. ３６ and R ３８ The alkyl group having 1 to 18 carbon atoms and an ether bond may further have a substituent, and examples of the substituent include a hydroxyl group and an aryl group. ３０ The alkyl group having 1 to 6 carbon atoms may further have a substituent, and examples of the substituent include a hydroxyl group and an aryl group. ４０ The alkoxy group having 1 to 6 carbon atoms may further have a substituent, and examples of the substituent include a hydroxyl group and an aryl group.

[0066] L in the formulas (3-3) and (3-4) ３ The divalent organic group is L １１ The divalent organic groups are the same as those mentioned above.

[0067] In the general formula (3-2), m represents the number of repetitions, and may be, for example, an integer of 1 or greater. The number average of m is, for example, in the range of 1 to 200, preferably in the range of 1 to 100, and more preferably in the range of 1 to 50. The number average of m can be confirmed by measuring the number average molecular weight of the polymerizable monomer (3) by the method described in the examples.

[0068] In the general formulas (3-3) and (3-4), q represents the number of repetitions, and may be, for example, an integer of 1 or greater. The number average of q is, for example, in the range of 1 to 100, preferably in the range of 1 to 80, and more preferably in the range of 1 to 50.

[0069] The polymerizable monomer (3) preferably contains one or more selected from the group consisting of the compound represented by the formula (3-2), the compound represented by the formula (3-3), and the compound represented by the formula (3-4). When the polymerizable monomer (3) contains one or more selected from the group consisting of the compound represented by the formula (3-2), the compound represented by the formula (3-3), and the compound represented by the formula (3-4), it is preferable that the total amount of the compound represented by the formula (3-2), the compound represented by the formula (3-3), and the compound represented by the formula (3-4) is 50 mass% or more relative to the total amount of the polymerizable monomer (3).

[0070] The polymerizable monomer (3) as a polymerization component may be one type alone or two or more types of polymerizable monomers (3) having different structures from each other.

[0071] The polymerizable monomer (3) can be produced by a known method. Alternatively, a commercially available product may be used as the polymerizable monomer (3). For example, commercially available products of the polymerizable monomer (3) having a group containing a polyoxyalkylene chain and in which the polymerizable unsaturated group is a (meth)acryloyl group include "NK ESTER M-20G", "NK ESTER M-40G", "NK ESTER M-90G", "NK ESTER M-230G", "NK ESTER AM-90G", "NK ESTER AMP-10G", "NK ESTER AMP-20G", and "NK ESTER AMP-60G" manufactured by Shin-Nakamura Chemical Co., Ltd., and "BLEMMER PE-90", "BLEMMER PE-200", "BLEMMER PE-350", and "BLEMMER PME-100" manufactured by NOF Corporation. Examples of such polymers include "Blenmer PME-200," "Blenmer PME-400," "Blenmer PME-4000," "Blenmer PP-1000," "Blenmer PP-500," "Blenmer PP-800," "Blenmer 70PEP-350B," "Blenmer 55PET-800," "Blenmer 50POEP-800B," "Blenmer 10PPB-500B," "Blenmer NKH-5050," "Blenmer AP-400," "Blenmer AE-350," the Plaxel F series manufactured by Daicel Corporation, and the Viscoat series manufactured by Osaka Organic Chemical Industry Ltd.

[0072] When the polymerizable monomer (3) is contained as a polymerization component, the content of the polymerizable monomer (3) is, for example, in the range of 0 to 200 parts by mass relative to 100 parts by mass of the polymerizable monomer (1), preferably in the range of 20 to 200 parts by mass relative to 100 parts by mass of the polymerizable monomer (1), more preferably in the range of 40 to 150 parts by mass relative to 100 parts by mass of the polymerizable monomer (1), and even more preferably in the range of 70 to 120 parts by mass relative to 100 parts by mass of the polymerizable monomer (1). The content of the polymerizable monomer (3) can be adjusted by the raw material charge ratio of the polymerizable monomer (3) when producing the polymer of the present invention.

[0073] In the polymer of the present invention, the content of the polymerizable monomer (3) is, for example, in the range of 0 to 90 mass %, preferably in the range of 1 to 80 mass %, more preferably in the range of 3 to 75 mass %, and even more preferably in the range of 5 to 70 mass %, based on the total amount of polymerization components of the polymer.

[0074] The polymer of the present invention may be any polymer containing polymerizable monomer (1), polymerizable monomer (2), and optional polymerizable monomer (3) as polymerization components, and may contain other polymerizable monomers as polymerization components as long as the effects of the present invention are not impaired. The polymer of the present invention is preferably a polymer whose polymerization components are essentially composed of polymerizable monomer (1), polymerizable monomer (2), and optional polymerizable monomer (3), and more preferably a copolymer whose polymerization components are solely composed of polymerizable monomer (1), polymerizable monomer (2), and optional polymerizable monomer (3). Here, "essentially composed" refers to a case where the total content of polymerizable monomer (1), polymerizable monomer (2), and optional polymerizable monomer (3) in the polymerization components of the polymer of the present invention is 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more.

[0075] The polymerization mode of the polymer of the present invention is not particularly limited. The polymer of the present invention may be a random polymer of polymerizable monomer (1), polymerizable monomer (2), and optional polymerizable monomer (3). Furthermore, the polymer of the present invention may be a block polymer having one or more polymer blocks of polymerizable monomer (1), polymerizable monomer (2), and optional polymerizable monomer (3).

[0076] The polymer of the present invention preferably does not contain fluorine atoms.

[0077] The number average molecular weight (Mn) of the polymer of the present invention is preferably in the range of 1,000 to 50,000, more preferably in the range of 1,000 to 30,000, and even more preferably in the range of 1,500 to 10,000. The weight average molecular weight (Mw) of the polymer of the present invention is preferably in the range of 1,000 to 300,000, more preferably in the range of 1,500 to 250,000, even more preferably in the range of 2,000 to 200,000, and particularly preferably in the range of 3,000 to 150,000.

[0078] In the present invention, the weight average molecular weight (Mw) and number average molecular weight (Mn) are values ​​measured by gel permeation chromatography (GPC) and converted into polystyrene equivalents. The number average molecular weight (Mn) and weight average molecular weight (Mw) values ​​of the polymer of the present invention are measured by the method described in the examples.

[0079] The defoaming agent of the present invention may contain a defoaming agent other than the polymer of the present invention, as long as it contains the polymer of the present invention. Furthermore, the defoaming agent of the present invention may be the polymer of the present invention.

[0080] [Method for Producing Polymer] The method for producing the polymer of the present invention is not particularly limited, and the polymer can be produced by a known method. The polymer of the present invention can be produced by a solution polymerization method, a bulk polymerization method, an emulsion polymerization method, or the like, based on a polymerization mechanism such as a radical polymerization method, a cationic polymerization method, or an anionic polymerization method. For example, in the case of a radical polymerization method, the polymer of the present invention can be produced by charging a polymerizable monomer mixture into an organic solvent and adding a general-purpose radical polymerization initiator.

[0081] As the polymerization initiator, various types can be used, for example, peroxides such as t-butylperoxy-2-ethylhexanoate, benzoyl peroxide, and diacyl peroxide, azo compounds such as azobisisobutyronitrile, dimethyl azobisisobutyrate, and phenylazotriphenylmethane, Mn(acac) ３If necessary, a chain transfer agent such as lauryl mercaptan, 2-mercaptoethanol, ethyl thioglycolic acid, or octyl thioglycolic acid, or a thiol compound having a coupling group such as γ-mercaptopropyltrimethoxysilane may be used as an additive such as a chain transfer agent.

[0082] Examples of the organic solvent include alcohols such as ethanol, isopropyl alcohol, n-butanol, iso-butanol, and tert-butanol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and methyl amyl ketone; esters such as methyl acetate, ethyl acetate, butyl acetate, methyl lactate, ethyl lactate, and butyl lactate; monocarboxylic acid esters such as methyl 2-oxypropionate, ethyl 2-oxypropionate, propyl 2-oxypropionate, butyl 2-oxypropionate, methyl 2-methoxypropionate, ethyl 2-methoxypropionate, propyl 2-methoxypropionate, and butyl 2-methoxypropionate; dimethylformamide, dimethyl sulfoxide, N-methyl Examples of the solvent include polar solvents such as pyrrolidone, ethers such as methyl cellosolve, cellosolve, butyl cellosolve, butyl carbitol, and ethyl cellosolve acetate, propylene glycols and esters thereof such as propylene glycol, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and propylene glycol monobutyl ether acetate, halogenated solvents such as 1,1,1-trichloroethane and chloroform, ethers such as tetrahydrofuran and dioxane, aromatic solvents such as benzene, toluene, and xylene, and fluorinated inert liquids such as perfluorooctane and perfluorotri-n-butylamine. These solvents can be used alone or in combination of two or more.

[0083] The polymer of the present invention can also be produced by living polymerization such as living radical polymerization or living anionic polymerization.

[0084] In living radical polymerization, a dormant species, whose active polymerization terminal is protected by an atom or atomic group, reversibly generates radicals and reacts with a monomer, thereby causing a propagation reaction. Even when a first monomer is consumed, the propagating terminal does not lose its activity and continues to react with a second monomer that is added sequentially to produce a block polymer. Examples of such living radical polymerization include atom transfer radical polymerization (ATRP), reversible addition-fragmentation radical polymerization (RAFT), nitroxide-mediated radical polymerization (NMP), and organotellurium radical polymerization (TERP). While there are no particular restrictions on which of these methods is used, ATRP is preferred due to its ease of control. ATRP uses an organic halide or a sulfonyl halide compound as a polymerization initiator and a metal complex composed of a transition metal compound and a ligand as a catalyst.

[0085] Specific examples of polymerization initiators that can be used in ATRP include 1-phenylethyl chloride, 1-phenylethyl bromide, chloroform, carbon tetrachloride, 2-chloropropionitrile, α,α'-dichloroxylene, α,α'-dibromoxylene, hexakis(α-bromomethyl)benzene, and C1-6 alkyl esters of C2-halogenated carboxylic acids (e.g., 2-chloropropionic acid, 2-bromopropionic acid, 2-chloroisobutyric acid, 2-bromoisobutyric acid, etc.). More specific examples of C1-6 alkyl esters of C2-halogenated carboxylic acids include, for example, methyl 2-chloropropionate, ethyl 2-chloropropionate, methyl 2-bromopropionate, and ethyl 2-bromoisobutyrate.

[0086] The transition metal compounds that can be used in ATRP are M ｎ＋ X ｎ It is expressed as follows: M ｎ＋ X ｎ The transition metal M of the transition metal compound represented by ｎ＋ As the ＋ , Cu ２＋ , Fe ２＋ , Fe ３＋ , Ru ２＋ , Ru ３＋, Cr ２＋ , Cr ３＋ , Mo ０ , Mo ＋ , Mo ２＋ , Mo ３＋ , W ２＋ , W ３＋ , Rh ３＋ , Rh ４＋ , Co ＋ , Co ２＋ , Re ２＋ , Re ３＋ , Ni ０ , Ni ＋ , Mn ３＋ , Mn ４＋ , V ２＋ , V ３＋ , Zn ＋ , Zn ２＋ , Au ＋ , Au ２＋ , Ag ＋ and Ag ２＋ M ｎ＋ X ｎ X in the transition metal compound represented by the formula (I) is a halogen atom, an alkoxyl group having 1 to 6 carbon atoms, (SO ４ ) １／２ , (PO ４ ) １／３ , (HPO ４ ) １／２ , (H ２ P.O. ４ ), triflate, hexafluorophosphate, methanesulfonate, arylsulfonate (preferably benzenesulfonate or toluenesulfonate), SeR １１ , CN and R １２ COO, where R １１ represents an aryl group or a linear or branched alkyl group having 1 to 20 carbon atoms (preferably 1 to 10 carbon atoms), R １２ represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms (preferably a methyl group) which may be substituted 1 to 5 times with halogen (preferably 1 to 3 times with fluorine or chlorine). ｎ＋ X ｎ In the transition metal compound represented by the formula (I), n represents the formal charge on the metal and is an integer of 0 to 7.

[0087] Examples of the ligand compound capable of forming a coordinate bond to the transition metal of the transition metal compound include a compound having a ligand containing one or more nitrogen atoms, oxygen atoms, phosphorus atoms, or sulfur atoms that can be coordinated to the transition metal via a σ bond, a compound having a ligand containing two or more carbon atoms that can be coordinated to the transition metal via a π bond, and a compound having a ligand that can be coordinated to the transition metal via a μ bond or an η bond.

[0088] The transition metal complex is not particularly limited, but preferred examples include complexes of transition metals of Groups 7, 8, 9, 10, and 11, and more preferred examples include complexes of zero-valent copper, monovalent copper, divalent ruthenium, divalent iron, or divalent nickel.

[0089] Specific examples of catalysts that can be used in ATRP include complexes with ligands such as 2,2'-bipyridyl and its derivatives, 1,10-phenanthroline and its derivatives, and polyamines such as tetramethylethylenediamine, pentamethyldiethylenetriamine, and hexamethyltris(2-aminoethyl)amine when the central metal is copper. Examples of divalent ruthenium complexes include dichlorotris(triphenylphosphine)ruthenium, dichlorotris(tributylphosphine)ruthenium, dichloro(cyclooctadiene)ruthenium, dichlorobenzeneruthenium, dichloro-p-cymeneruthenium, dichloro(norbornadiene)ruthenium, cis-dichlorobis(2,2'-bipyridine)ruthenium, dichlorotris(1,10-phenanthroline)ruthenium, and carbonylchlorohydridotris(triphenylphosphine)ruthenium. Examples of divalent iron complexes include bistriphenylphosphine complexes and triazacyclononane complexes.

[0090] In living radical polymerization, it is preferable to use a solvent. Examples of solvents used in living radical polymerization include ester solvents such as ethyl acetate, butyl acetate, and propylene glycol monomethyl ether acetate; ether solvents such as diisopropyl ether, dimethoxyethane, and diethylene glycol dimethyl ether; halogenated solvents such as dichloromethane and dichloroethane; aromatic solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohol solvents such as methanol, ethanol, and isopropanol; and aprotic polar solvents such as dimethylformamide and dimethyl sulfoxide. The above solvents may be used alone or in combination of two or more.

[0091] The polymerization temperature during the living radical polymerization is preferably in the range of room temperature to 120°C.

[0092] When the polymer of the present invention is produced by living radical polymerization, metals resulting from the transition metal compound used in the polymerization may remain in the resulting polymer. The metals remaining in the resulting polymer may be removed using activated alumina or the like after the polymerization is completed.

[0093] [Lubricating Oil Composition] The antifoaming agent of the present invention can be suitably used as an antifoaming agent for lubricating oil compositions, and the lubricating oil compositions of the present invention contain the antifoaming agent of the present invention.

[0094] The defoaming agent of the present invention is a polymer having a crosslinked structure by using a polymerizable monomer (2) having two or more polymerizable unsaturated groups as a polymerization component, and can suppress molecular spreading of the defoaming agent even in a high-temperature environment, thereby maintaining low solubility in a lubricating base oil. As a result, the defoaming agent of the present invention can exhibit high defoaming performance even in a high-temperature environment. Furthermore, in machines equipped with internal combustion engines or electric motors, high shear forces are applied to the drive units of the machines, but the defoaming agent of the present invention suppresses molecular weight reduction due to its crosslinked structure, thereby suppressing a decrease in defoaming performance.

[0095] As described above, the antifoaming agent of the present invention has high antifoaming performance and can be used without restriction in lubricating oil compositions for drive system devices such as shock absorbers, transmissions, and power steering systems of automobiles.

[0096] The content of the antifoaming agent of the present invention in the lubricating oil composition of the present invention is not particularly limited, and is, for example, in the range of 1 to 1,000 ppm by mass, preferably in the range of 5 to 700 ppm by mass, and more preferably in the range of 10 to 400 ppm by mass, of the total amount of the lubricating oil composition.

[0097] The lubricating base oil for the lubricating oil composition of the present invention may be any known oil, and may be a mineral oil, a synthetic oil, or a mixture of a mineral oil and a synthetic oil.

[0098] Examples of mineral oils include those obtained by subjecting lubricating oil fractions obtained by vacuum distillation of atmospheric residue obtained by atmospheric distillation of crude oil to one or more of solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, etc., and examples of such mineral oils include paraffinic mineral oils and naphthenic mineral oils.Further examples include mineral oils produced by isomerizing mineral oil waxes and waxes produced by the Fischer-Tropsch process (GTL waxes).

[0099] Examples of synthetic oils include polyolefins such as polybutene, α-olefin homopolymers and copolymers (e.g., ethylene-α-olefin copolymers), various esters such as polyol esters, dibasic acid esters, and phosphate esters, various ethers such as polyphenyl ether, polyglycols, alkylbenzenes, and alkylnaphthalenes.

[0100] The lubricating base oil may be used alone or in combination of two or more.

[0101] The kinematic viscosity of the lubricating base oil at 100°C is preferably 1 to 20 mm ２ / s, more preferably 2 to 15 mm ２ / s, and more preferably 2 to 10 mm ２When the kinematic viscosity at 100°C of the lubricating base oil is in the above range, evaporation loss is small and power loss due to viscous resistance is not so large, so that the fuel economy improvement effect is easily obtained.

[0102] The lubricating base oil preferably has a paraffin content (sometimes referred to as %Cp) determined by ndM ring analysis of 70% or more, more preferably 75% or more, and even more preferably 80% or more. When the paraffin content is in the above range, the lubricating base oil has good oxidation stability and the like.

[0103] The content of the lubricating base oil in the lubricating oil composition is, for example, in the range of 65 to 95 mass %, preferably 70 to 95 mass %, and more preferably 70 to 90 mass %, of the total amount of the lubricating oil composition.

[0104] The lubricating oil composition of the present invention may contain the antifoam agent of the present invention and a lubricating base oil, and may further contain other additives. Examples of other additives include ashless detergents, ashless friction modifiers, antiwear agents, extreme pressure agents, viscosity index improvers, metal deactivators, pour point depressants, and rust inhibitors. These additives may be used alone or in combination.

[0105] The content of each of the other additives can be adjusted as appropriate within a range that does not impair the effects of the present invention, and is typically 0.001 to 25 mass%, preferably 0.005 to 20 mass%, more preferably 0.01 to 15 mass%, based on the total amount of the lubricating oil composition. The total content of the other additives is preferably 25 mass% or less, more preferably 20 mass% or less, and even more preferably 15 mass% or less, based on the total amount of the lubricating oil composition.

[0106] Examples of ashless detergents include alkenyl succinimides such as alkenyl succinic acid monoimide and alkenyl succinic acid bisimide, and boron-modified alkenyl succinimide.

[0107] Examples of ashless friction modifiers include aliphatic amines, fatty acid esters, fatty acid amides, fatty acids, fatty alcohols, and aliphatic ethers, each of which has at least one alkyl or alkenyl group having 6 to 30 carbon atoms in the molecule.

[0108] Examples of anti-wear agents or extreme pressure agents include sulfur-containing compounds such as zinc dithiophosphate; phosphorus-containing compounds such as phosphites, phosphate esters, phosphonate esters, and their amine salts or metal salts; and sulfur- and phosphorus-containing anti-wear agents such as thiophosphites, thiophosphate esters, thiophosphonate esters, and their amine salts or metal salts.

[0109] Examples of viscosity index improvers include polymethacrylate, disperse polymethacrylate, olefin copolymers (e.g., ethylene-propylene copolymers), disperse olefin copolymers, and styrene copolymers (e.g., styrene-diene copolymers, styrene-isoprene copolymers).

[0110] Examples of metal deactivators include benzotriazole-based compounds, tolyltriazole-based compounds, imidazole-based compounds, and pyrimidine-based compounds.

[0111] Examples of pour point depressants include ethylene-vinyl acetate copolymers, condensates of chlorinated paraffin and naphthalene, condensates of chlorinated paraffin and phenol, polymethacrylates, and polyalkylstyrenes.

[0112] Examples of the rust inhibitor include petroleum sulfonates, alkylbenzene sulfonates, dinonylnaphthalene sulfonates, alkenyl succinates, polyhydric alcohol esters, and the like.

[0113] The lubricating oil composition of the present invention is suitable for use in lubricating the drive parts of machines equipped with an internal combustion engine or an electric motor. Regarding the lubrication of the drive parts, for example, in an electric vehicle, the drive part generally integrates a motor, an inverter, and a gearbox, and the drive parts can be lubricated by filling the gearbox with the lubricating oil composition of the present invention. Furthermore, in the case of a gasoline-powered vehicle, the drive part, which is the internal combustion engine, the lubricating oil composition of the present invention is stored in an oil pan and supplied to the cylinder via an oil pump, thereby lubricating the starting parts. The lubrication of the drive parts is not limited to these forms, and the drive parts can be lubricated by filling or supplying the lubricating oil composition of the present invention to parts where metals come into contact with each other.

[0114] The lubricating oil composition of the present invention can be used in any machine equipped with an internal combustion engine or an electric motor, including automobiles (gasoline-powered vehicles, electric vehicles), robots (industrial robots, entertainment robots), aircraft (airplanes, helicopters), ships, and various home appliances.

[0115] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0116] In the examples and comparative examples, the weight average molecular weight (Mw) and number average molecular weight (Mn) are values ​​calculated in terms of polystyrene based on gel permeation chromatography (GPC) measurements. The GPC measurement conditions are as follows:

[0117] [GPC measurement conditions] Measurement apparatus: High-speed GPC apparatus "HLC-8320GPC" manufactured by Tosoh Corporation Column: "TSK GUARDCOLUMN SuperHZ-L" manufactured by Tosoh Corporation + "TSK gel SuperHZM-N" manufactured by Tosoh Corporation + "TSK gel SuperHZM-N" manufactured by Tosoh Corporation + "TSK gel SuperHZM-N" manufactured by Tosoh Corporation + "TSK gel SuperHZM-N" manufactured by Tosoh Corporation Detector: RI (differential refractometer) Data processing: "EcoSEC Data Analysis Version 1.07" manufactured by Tosoh Corporation Column temperature: 40°C Developing solvent: tetrahydrofuran Flow rate: 0.35 mL / min Measurement sample: 7.5 mg of sample was dissolved in 10 ml of tetrahydrofuran, and the resulting solution was filtered through a microfilter to prepare the measurement sample. Sample injection amount: 20 μL Standard sample: The following monodisperse polystyrene with known molecular weight was used in accordance with the measurement manual for the "HLC-8320GPC".

[0118] (Monodisperse polystyrene) "A-300" manufactured by Tosoh Corporation "A-500" manufactured by Tosoh Corporation "A-1000" manufactured by Tosoh Corporation "A-2500" manufactured by Tosoh Corporation "A-5000" manufactured by Tosoh Corporation "F-1" manufactured by Tosoh Corporation "F-2" manufactured by Tosoh Corporation "F-4" manufactured by Tosoh Corporation "F-10" manufactured by Tosoh Corporation "F-20" manufactured by Tosoh Corporation "F-40" manufactured by Tosoh Corporation "F-80" manufactured by Tosoh Corporation "F-128" manufactured by Tosoh Corporation "F-288" manufactured by Tosoh Corporation

[0119] Synthesis Example 1 Synthesis of Defoamer (1) A glass flask equipped with a stirrer, a thermometer, a condenser, and a dropping device was charged with 30 parts by mass of dipropylene glycol monomethyl ether acetate as a solvent, and the temperature was raised to 95°C while stirring under a nitrogen stream. Next, two types of dropping liquids were placed in different dropping devices: a monomer solution obtained by dissolving 15 parts by mass of 3-(methacryloyloxy)propyltris(trimethylsiloxy)silane, 13.8 parts by mass of methoxypolyethylene glycol acrylate (the number of repeating ethylene oxide chains is about 9), and 4.5 parts by mass of polyethylene glycol dimethacrylate (the number of repeating ethylene oxide chains is about 4) in 37.7 parts by mass of dipropylene glycol monomethyl ether acetate; and a polymerization initiator solution obtained by dissolving 1 part by mass of t-butylperoxy-2-ethylhexanoate as a radical polymerization initiator in 10 parts by mass of dipropylene glycol monomethyl ether acetate. The monomer solution and the polymerization initiator solution were simultaneously added dropwise while maintaining the temperature inside the flask at 95° C. The monomer solution was added dropwise over 2 hours, and the polymerization initiator solution was added dropwise over 2.5 hours. After completion of the addition of the polymerization initiator solution, the mixture was stirred at 95° C. for 3 hours, then heated to 110° C. and stirred for 1 hour to obtain a solution of defoaming agent (1).

[0120] The molecular weight of the obtained defoaming agent (1) was measured by GPC and found to be a weight average molecular weight (Mw) of 33,000.

[0121] Synthesis Example 2 Synthesis of Defoamer (2) A glass flask equipped with a stirrer, a thermometer, a condenser, and a dropping device was charged with 30 parts by mass of dipropylene glycol monomethyl ether acetate as a solvent, and the temperature was raised to 100°C while stirring under a nitrogen stream. Next, two types of dropping liquids were placed in different dropping devices: a monomer solution obtained by dissolving 15 parts by mass of 3-(methacryloyloxy)propyltris(trimethylsiloxy)silane, 13.8 parts by mass of methoxypolyethylene glycol acrylate (the number of repeating ethylene oxide chains is approximately 9), and 4.5 parts by mass of trimethylolpropane triacrylate in 93.2 parts by mass of dipropylene glycol monomethyl ether acetate; and a polymerization initiator solution obtained by dissolving 1.67 parts by mass of t-butylperoxy-2-ethylhexanoate as a radical polymerization initiator in 10 parts by mass of dipropylene glycol monomethyl ether acetate. While the temperature inside the flask was kept at 100° C., the monomer solution and the polymerization initiator solution were simultaneously added dropwise, over 2 hours for the monomer solution and over 2.5 hours for the polymerization initiator solution. After completion of the dropwise addition of the polymerization initiator solution, the mixture was stirred at 100° C. for 4 hours to obtain a solution of defoaming agent (2).

[0122] The molecular weight of the obtained defoaming agent (2) was measured by GPC and found to be a weight average molecular weight (Mw) of 20,000.

[0123] Synthesis Example 3 Synthesis of Defoamer (3) A glass flask equipped with a stirrer, a thermometer, a condenser, and a dropping device was charged with 30 parts by mass of dipropylene glycol monomethyl ether acetate as a solvent, and the temperature was raised to 105°C while stirring under a nitrogen stream. Next, two types of dropping liquids were placed in different dropping devices: a monomer solution obtained by dissolving 15 parts by mass of 3-(methacryloyloxy)propyltris(trimethylsiloxy)silane, 13.8 parts by mass of methoxypolyethylene glycol acrylate (the number of repeating ethylene oxide chains is approximately 9), and 4.5 parts by mass of pentaerythritol tetraacrylate in 93.2 parts by mass of dipropylene glycol monomethyl ether acetate; and a polymerization initiator solution obtained by dissolving 1.67 parts by mass of t-butylperoxy-2-ethylhexanoate as a radical polymerization initiator in 10 parts by mass of dipropylene glycol monomethyl ether acetate. While maintaining the temperature inside the flask at 105° C., the monomer solution and the polymerization initiator solution were simultaneously added dropwise, over 2 hours for the monomer solution and over 2.5 hours for the polymerization initiator solution. After completion of the dropwise addition of the polymerization initiator solution, the mixture was stirred at 105° C. for 4 hours to obtain a solution of defoaming agent (3).

[0124] The molecular weight of the obtained defoaming agent (3) was measured by GPC and found to be a weight average molecular weight (Mw) of 26,000.

[0125] Synthesis Example 4 Synthesis of Defoamer (4) A glass flask equipped with a stirrer, a thermometer, a condenser, and a dropping device was charged with 30 parts by mass of dipropylene glycol monomethyl ether acetate as a solvent, and the temperature was raised to 110°C while stirring under a nitrogen stream. Next, two types of dropping liquids were placed in different dropping devices: a monomer solution obtained by dissolving 15 parts by mass of 3-(methacryloyloxy)propyltris(trimethylsiloxy)silane, 13.8 parts by mass of methoxypolyethylene glycol acrylate (the number of repeating ethylene oxide chains is approximately 9), and 4.5 parts by mass of dipentaerythritol hexaacrylate in 93.2 parts by mass of dipropylene glycol monomethyl ether acetate; and a polymerization initiator solution obtained by dissolving 6.66 parts by mass of t-butylperoxy-2-ethylhexanoate as a radical polymerization initiator in 10 parts by mass of dipropylene glycol monomethyl ether acetate. While maintaining the temperature inside the flask at 110° C., the monomer solution and the polymerization initiator solution were simultaneously added dropwise, over 2 hours for the monomer solution and over 2.5 hours for the polymerization initiator solution. After completion of the dropwise addition of the polymerization initiator solution, the mixture was stirred at 110° C. for 4 hours to obtain a solution of defoaming agent (4).

[0126] The molecular weight of the obtained defoaming agent (4) was measured by GPC and found to be a weight average molecular weight (Mw) of 13,000.

[0127] Synthesis Example 5 Synthesis of Defoamer (5) A glass flask equipped with a stirrer, a thermometer, a condenser, and a dropping device was charged with 30 parts by mass of n-butyl acetate as a solvent, and the temperature was raised to 100°C while stirring under a nitrogen stream. Next, two types of dropping liquids were placed in different dropping devices: a monomer solution obtained by dissolving 15 parts by mass of 3-(methacryloyloxy)propyltris(trimethylsiloxy)silane, 13.8 parts by mass of methoxypolyethylene glycol acrylate (the number of repeating ethylene oxide chains is approximately 9), and 4.5 parts by mass of tris(2-acryloyloxyethyl)isocyanurate in 78.1 parts by mass of n-butyl acetate; and a polymerization initiator solution obtained by dissolving 1.67 parts by mass of t-butylperoxy-2-ethylhexanoate as a radical polymerization initiator in 10 parts by mass of n-butyl acetate. The monomer solution and the polymerization initiator solution were simultaneously added dropwise while maintaining the temperature inside the flask at 100° C. The monomer solution was added dropwise over 2 hours, and the polymerization initiator solution was added dropwise over 2.5 hours. After completion of the addition of the polymerization initiator solution, the mixture was stirred at 100° C. for 3 hours, then heated to 110° C. and stirred for an additional 1 hour to obtain a solution of defoaming agent (5).

[0128] The molecular weight of the obtained defoaming agent (5) was measured by GPC and found to be a weight average molecular weight (Mw) of 14,000.

[0129] Synthesis Example 6 Synthesis of Defoamer (6) A glass flask equipped with a stirrer, a thermometer, a condenser, and a dropping device was charged with 30 parts by mass of dipropylene glycol monomethyl ether acetate as a solvent, and the temperature was raised to 110°C while stirring under a nitrogen stream. Next, two types of dropping liquids were placed in different dropping devices: a monomer solution prepared by dissolving 12.5 parts by mass of 3-(methacryloyloxy)propyltris(trimethylsiloxy)silane and 12.5 parts by mass of polyethylene glycol dimethacrylate (the number of repeating ethylene oxide chains is approximately 9) in 60 parts by mass of dipropylene glycol monomethyl ether acetate, and a polymerization initiator solution prepared by dissolving 7.5 parts by mass of t-butylperoxy-2-ethylhexanoate as a radical polymerization initiator in 10 parts by mass of dipropylene glycol monomethyl ether acetate. While maintaining the temperature inside the flask at 110° C., the monomer solution and the polymerization initiator solution were simultaneously added dropwise, over 2 hours for the monomer solution and over 2.5 hours for the polymerization initiator solution. After completion of the dropwise addition of the polymerization initiator solution, the mixture was stirred at 110° C. for 2 hours to obtain a solution of defoaming agent (5).

[0130] The molecular weight of the obtained defoaming agent (5) was measured by GPC and found to be a weight average molecular weight (Mw) of 15,000.

[0131] (Synthesis Comparative Example 1: Synthesis of Defoamer (1')) A glass flask equipped with a stirrer, thermometer, condenser, and dropping device was charged with 52 parts by mass of n-butyl acetate as a solvent, and the temperature was raised to 85°C while stirring under a nitrogen stream. Next, 30 parts by mass of 3-(methacryloyloxy)propyltris(trimethylsiloxy)silane dissolved in 50 parts by mass of n-butyl acetate, 20 parts by mass of methoxypolyethylene glycol methacrylate (the number of repeating ethylene oxide chains is approximately 9), and two types of dropping liquids were placed in separate dropping devices: a polymerization initiator solution in which 3 parts by mass of t-butylperoxy-2-ethylhexanoate as a radical polymerization initiator was dissolved in 15 parts by mass of n-butyl acetate. While maintaining the temperature inside the flask at 85°C, the monomer solution and the polymerization initiator solution were simultaneously added dropwise over 2 hours. After completion of the dropping, the mixture was stirred at 85°C for 4 hours, then the temperature was raised to 110°C, and further stirred for 1 hour to obtain a solution of defoamer (1').

[0132] The molecular weight of the resulting antifoaming agent (1') was measured by GPC and found to be 40,000 in weight average molecular weight (Mw).

[0133] (Synthesis Comparative Example 2: Synthesis of Antifoaming Agent (2')) A solution of antifoaming agent (2') was obtained in the same manner as in Synthesis Comparative Example 1, except that 30 parts by mass of a compound represented by the following formula (1') was used instead of 3-methacryloyloxypropyltris(trimethylsiloxy)silane.

[0134] (The repeating portion of n is approximately 65.)

[0135] The molecular weight of the resulting antifoaming agent (2') was measured by GPC and found to be a weight average molecular weight (Mw) of 25,000.

[0136] Comparative Example 3 A commercially available dimethyl silicone ("KF-96-50000cs" manufactured by Shin-Etsu Silicones Co., Ltd.) shown below was separately prepared as an antifoaming agent (3').

[0137]

[0138] The defoaming performance of the defoaming agent was evaluated by carrying out the following foaming test using the defoaming agent produced above. The results are shown in Table 1.

[0139] (Preparation of Lubricating Oil Compositions) Lubricating oil compositions were prepared by adding the amounts of antifoaming agents shown in Table 1 diluted with kerosene shown in Table 1 to 100 parts by mass of a base lubricating oil containing a lubricating base oil (paraffinic mineral oil) as the main component and small amounts of various additives (viscosity index improver, phosphite ester compound, thiadiazole compound, calcium-based detergent, metal deactivator, ashless dispersant, antioxidant, etc.).

[0140] The resulting lubricating oil composition was subjected to the following foaming test. The results are shown in Table 1. (Foaming Test) The foaming test was conducted in accordance with the homogenizer method disclosed in JP 2008-120880 A. Using a homogenizer ("T.K. Robomix" manufactured by Primix Corporation) equipped with a generator shaft ("Mini Mixer" manufactured by Primix Corporation), the lubricating oil composition was stirred under the following conditions, and the foam volume (mL) was determined by subtracting the oil surface reading (mL) before stirring from the foam surface reading (mL) 3 seconds after stirring was completed. A smaller foam volume indicates better defoaming properties. Rotation speed: 16,000 rpm Oil temperature: 80°C or 120°C Oil volume: 80 ml Container: 200 ml measuring cylinder (inner diameter φ36 mm) Stirring time: 1 minute

[0141]

[0142] The results in Table 1 confirm that the defoaming agents (1) to (6) exhibit excellent defoaming properties in both 80°C and 120°C temperature environments. On the other hand, the defoaming agent (1') that does not contain the "polymerizable monomer (2) having two or more polymerizable unsaturated groups" does not exhibit sufficient defoaming properties. The defoaming agent (2') exhibits defoaming properties at 80°C by introducing a polysiloxane structure, but does not exhibit sufficient defoaming properties at 120°C.

Claims

1. -Si[OSi(R) ３ ] ｎ [R'] ３－ｎ (n is an integer in the range of 1 to 3; each R is independently an alkyl group having 1 to 3 carbon atoms; each R' is independently an alkyl group having 1 to 3 carbon atoms), and contains as polymerization components at least a polymerizable monomer (1) having one polymerizable unsaturated group and a polymerizable monomer (2) having two or more polymerizable unsaturated groups.

2. The defoaming agent according to claim 1, wherein the polymerizable monomer (1) is a compound represented by the following general formula (1-1): (In the general formula (1-1), R is independently an alkyl group having 1 to 3 carbon atoms, and R' is independently an alkyl group having 1 to 3 carbon atoms. L １１ is a divalent organic group or a single bond. n is an integer ranging from 1 to 3. P is a polymerizable group represented by general formula (P-1), a polymerizable group represented by general formula (P-2), or a polymerizable group represented by general formula (P-3). In the general formulas (P-1), (P-2), and (P-3), R １１ is a hydrogen atom or a methyl group. １２ is a hydrogen atom or an organic group. １３ is a hydrogen atom or a methyl group. １１ is the bond that bonds to 3. The defoaming agent according to claim 1 or 2, wherein the content of the polymerizable monomer (1) in the polymerization components is in the range of 10 mass% or more.

4. The defoaming agent according to claim 1 or 2, wherein the polymerizable monomer (2) is a compound represented by the following general formula (2-1): (In the above general formula (2-1), R ２１ is a hydrogen atom or a methyl group; x is an integer of 2 or more; L ２１ is an organic group having a valence of x.

5. The defoaming agent according to claim 1 or 2, wherein the content of the polymerizable monomer (2) in the polymerization component is in the range of 1 to 75 mass %.

6. The defoaming agent according to claim 1 or 2, wherein the polymerization component comprises a polymerizable monomer (3) having one or more selected from the group consisting of an alkyl group having 1 to 18 carbon atoms, an aromatic group having 6 to 18 carbon atoms, a group containing a polyoxyalkylene chain, and a group containing a polyester chain.

7. The defoaming agent according to claim 6, wherein the polymerizable monomer (3) is one or more selected from the group consisting of a compound represented by the following general formula (3-1), a compound represented by the following general formula (3-2), a compound represented by the following general formula (3-3), a compound represented by the following general formula (3-4), and a compound represented by the following general formula (3-5): (In the above general formulae (3-1), (3-2), (3-3), (3-4) and (3-5), R ３１ is a hydrogen atom or a methyl group; R ３２ is an alkyl group having 1 to 18 carbon atoms; R ３３ is a hydrogen atom or a methyl group; R ３４ is a hydrogen atom or an alkyl group having 1 to 18 carbon atoms; R ３５ is a hydrogen atom or a methyl group; R ３６ is an alkyl group having 1 to 18 carbon atoms, an alkyl group having 1 to 18 carbon atoms and an ether bond, or a hydrogen atom; R ３７ is a hydrogen atom or a methyl group; R ３８ is an alkyl group having 1 to 18 carbon atoms, an alkyl group having 1 to 18 carbon atoms and an ether bond, or a hydrogen atom; ３ is a divalent organic group or a single bond; R ３９ is a hydrogen atom or a methyl group; R ４０ are each independently an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, n is an integer ranging from 1 to 4, m is the number of repetitions, the number average value of m is in the range of 1 to 200, p is an integer ranging from 1 to 10, q is the number of repetitions, the number average value of q is in the range of 1 to 100, and l is an integer ranging from 0 to 5.

8. The defoaming agent according to claim 7, wherein the polymerizable monomer (3) contains a compound represented by the general formula (3-2).

9. The defoaming agent according to claim 6, wherein the content of the polymerizable monomer (3) in the polymerization components is in the range of 0 to 75 mass %.

10. The defoaming agent according to claim 1 or 2, having a weight average molecular weight in the range of 2,000 to 200,000.

11. A lubricating oil composition comprising a lubricating base oil and the antifoaming agent according to claim 1.

12. The lubricating oil composition according to claim 11, which is used to lubricate the driving parts of a machine equipped with an internal combustion engine or an electric motor.

13. The lubricating oil composition according to claim 11, for use in lubricating the driving parts of a motor vehicle having an internal combustion engine or an electric motor.

14. A machine in which the lubricating oil composition according to claim 11 is used in a driving part.

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