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

Abstract

Provided is an antifoaming agent which exhibits excellent antifoaming properties even in a high-temperature environment. Specifically, the antifoaming agent is a polymer formed from one or more polymerizing ingredients at least including a polymerizable monomer (A) having two or more groups represented by general formula (a) (the R11 moieties are each independently a C1-C6 alkyl group, a phenyl group, or a group represented by -OSi(R14)3 (the R14 moieties are each independently a C1-C6 alkyl group or a phenyl group); the R12 moieties are each independently a C1-C6 alkyl group or a phenyl group; R13 is a C1-C6 alkyl group or a phenyl group; and x indicates the number of repetitions).

Description

[Technical field]

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

[0002] In recent years, reducing carbon dioxide emissions has become an important theme in the industrial world. In particular, carbon dioxide emissions from transportation equipment, including automobiles, account for nearly 20% of the total, and as one measure to reduce this, a switch from gasoline-powered automobiles to electric vehicles (EVs) has been put forward as a policy in various countries.

[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 drive system. One of the issues in improving the efficiency of the drive system is foaming of lubricants. Lubricants are becoming less viscous to reduce frictional resistance, but this lower viscosity makes them more susceptible to foaming. In addition, because the drive system of EVs is smaller, there are fewer voids, and the tolerance for foaming is also lower.

[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 lubricating performance and cooling efficiency due to foaming; wear and seizure caused by rupture of the oil film at friction points; and accelerated deterioration of the lubricating oil due to rising oil temperature.

[0005] For this reason, lubricating oils with high defoaming properties are required, and defoamers are added to lubricating oils to prevent foaming. Polysiloxane-based defoamers are known as such defoamers, and various polysiloxane-based defoamers have been proposed (e.g., Patent Documents 1-4). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2014-62259 A [Patent Document 2] WO2015 / 087628 publication [Patent Document 3] Special Publication No. 2008-542462 [Patent Document 4] Special Publication No. 2008-542010 Summary of the Invention [Problem to be solved by the invention]

[0007] Conventional polysiloxane-based defoamers have a problem in that their defoaming properties decrease significantly as the temperature increases. For example, there is 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 a defoaming agent that exhibits excellent defoaming properties even in a high-temperature environment. Another problem to be solved by the present invention is to provide a lubricating oil composition that is capable of exhibiting excellent lubricating performance even in a high-temperature environment. [Means for solving the problem]

[0009] Means for Solving the Problems The present inventors have conducted intensive research to solve the above problems, and as a result have found that a polymer having as at least a polymerization component a polymerizable monomer having two or more specific silicone chain-containing functional 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 a defoaming agent which is a polymer having, as at least a polymerization component, a polymerizable monomer (A) having two or more groups represented by the following general formula (a). [ka] (In the general formula (a), R 11 each independently represents an alkyl group having 1 to 6 carbon atoms, a phenyl group, or -OSi(R 14 A group represented by (R 14each independently represents an alkyl group having 1 to 6 carbon atoms or a phenyl group, R 12 each independently represents an alkyl group having 1 to 6 carbon atoms or a phenyl group, R 13 is an alkyl group having 1 to 6 carbon atoms or a phenyl group, x indicates the number of repetitions.) Effect of the Invention

[0011] The present invention provides a defoaming agent that exhibits excellent defoaming properties even in a high-temperature environment. The present invention can provide a lubricating oil composition that exhibits excellent lubricating performance even in a high-temperature environment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] An embodiment of the present invention will be described below. The present invention is not limited to the following embodiment, and can be implemented by making appropriate modifications within the scope that does not impair the effects of the present invention.

[0013] [Antifoaming agent] The defoaming agent of the present invention is a polymer having as at least a polymerization component a polymerizable monomer (A) having two or more groups represented by the following general formula (a). [ka] (In the general formula (a), R 11 each independently represents an alkyl group having 1 to 6 carbon atoms, a phenyl group, or -OSi(R 14 A group represented by (R 14 each independently represents an alkyl group having 1 to 6 carbon atoms or a phenyl group, R 12 each independently represents an alkyl group having 1 to 6 carbon atoms or a phenyl group, R 13 is an alkyl group having 1 to 6 carbon atoms or a phenyl group, x indicates the number of repetitions.)

[0014] In the defoaming agent of the present invention, one polymerizable monomer has two or more silicone chain-containing functional groups represented by the general formula (a), thereby increasing the density of the silicone chain-containing functional groups in the polymer. As a result, the surface tension reducing ability is improved, and the defoaming agent can be efficiently transferred to the air interface, thereby providing high defoaming properties even in high temperature environments.

[0015] In the present invention, the term "polymerization component" refers to a component that constitutes a polymer, and does not include a solvent, a polymerization initiator, and the like that do not constitute a polymer.

[0016] In the present invention, the term "polymerizable monomer" means a compound having a polymerizable unsaturated group, and examples of the polymerizable unsaturated group possessed by the polymerizable monomer (A) include C=C-containing groups such as (meth)acryloyl group, (meth)acryloyloxy group, (meth)acryloylamino group, vinyl ether group, allyl group, styryl group, maleimide group, etc. Among these, (meth)acryloyl group and (meth)acryloyloxy group are preferred because of the availability of raw materials and good polymerization reactivity. The number of polymerizable unsaturated groups contained in the polymerizable monomer may be one or two or more.

[0017] In the general formula (a), R 11 is preferably a methyl group or a trimethylsiloxy group, R 12 and R 13 is preferably a methyl group.

[0018] R 11 , R 12 , R 13 and R 14 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. R 11 , R 12 , R 13 and R 14 The phenyl group may further have a substituent, and examples of the substituent include a hydroxyl group and an alkyl group.

[0019] In the general formula (a), x represents the number of repetitions, and may be, for example, an integer of 1 or more. The number average of x is, for example, in the range of 1 to 150, preferably in the range of 1 to 100, more preferably in the range of 1 to 45, and further preferably in the range of 1 to 35. The number average value of x can be confirmed by measuring the number average molecular weight of the polymerizable monomer (A) by the method described in the Examples.

[0020] In the general formula (a), a plurality of R 11 may be the same or different. Similarly, multiple R 12 may be the same or different from each other.

[0021] The polymerizable monomer (A) is preferably a compound represented by the following general formula (a-1).

[0022] [ka] (In the general formula (a-1), R 11 , R 12 , R 13 and x are each R in the general formula (a). 11 , R 12 , R 13 and x is the same, R 15 is a hydrogen atom or a methyl group, L 11 and L 13 each independently represents a divalent organic group or a single bond, y is an integer ranging from 2 to 5; L 12 is an organic group with a valence of y+1.

[0023] L 11 and L 13 is preferably a single bond, an alkylene group having 1 to 50 carbon atoms, or an alkyleneoxy group having 1 to 50 carbon atoms.

[0024] L11 and L 13 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.

[0025] L 11 and L 13 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 further preferably a methylene group, an ethylene group, an n-propylene group or an isopropylene group.

[0026] L 11 and L 13 The alkyleneoxy group having 1 to 50 carbon atoms is, for example, a group in which one -CH2- in the alkylene group is replaced with -O-. L 11 and L 13 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.

[0027] L 11 and L 13 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, in these divalent organic groups, a part of the -CH2- may be replaced by a carbonyl group (-C(=O)-), a phenylene group, a sulfide bond (-S-), an amide bond or a urethane bond, and further, a hydroxyl group or the like may be substituted on the carbon atom.

[0028] L12 The organic group having a valence of y+1 includes, for example, a carbon atom and a benzene ring.

[0029] The polymerizable monomer (A) can be produced, for example, by reacting a polymerizable monomer having one silicone chain-containing functional group with an alcohol having two or more mercapto groups to synthesize a precursor having two or more silicone chain-containing functional groups and a hydroxyl group, and then reacting the precursor with a polymerizable monomer having an isocyanate group.

[0030] The following chemical formula is an example of a synthetic route when carrying out the above-mentioned production method, and a compound represented by general formula (a-1-1) can be produced as the polymerizable monomer (A).

[0031] [ka] (In the formula, R 16 is a hydrogen atom or a methyl group.

[0032] [ka] (In the formula, R 17 is a hydrogen atom or a methyl group, L 14 is a divalent organic group or a single bond.

[0033] In the general formula (a-1-1), L 14 As the divalent organic group, L 11 The divalent organic groups are the same as those mentioned above.

[0034] The polymerizable monomer (A) constituting the polymer that is the defoaming agent of the present invention (hereinafter sometimes simply referred to as the "polymer of the present invention") may be one type alone or two or more types.

[0035] The weight average molecular weight of the polymerizable monomer (A) is preferably in the range of 100 to 4,000. The "weight average molecular weight" herein is a value measured by the method described in the Examples.

[0036] In the polymer of the present invention, the lower limit of the content of the polymerizable monomer (A) in the polymerization components (hereinafter simply referred to as the "content of the polymerizable monomer (A)") is, for example, 5 mass% or more, and is preferably 10 mass% or more, 15 mass% or more, 20 mass% or more, 30 mass% or more, and 40 mass% or more in that order. The upper limit of the content of the polymerizable monomer (A) is not particularly limited, but is preferably, for example, 95 mass % or less, 90 mass % or less, 85 mass % or less, 80 mass % or less, 75 mass % or less, and 70 mass % or less, in that order. The content of the polymerizable monomer (A) can be adjusted by the charge ratio of the polymerizable monomer (A) when producing the polymer of the present invention.

[0037] The proportion of the polymerizable monomer (A) in the total amount of the polymerization components is preferably in the range of 20 to 80 mass %.

[0038] The polymer of the present invention preferably further comprises as a polymerization component a polymerizable monomer (B) having one or more groups 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.

[0039] The alkyl group having 1 to 18 carbon atoms contained in the polymerizable monomer (B) 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, a n-butyl group, a t-butyl group, a n-hexyl group, a cyclohexyl group, a n-octyl group, and a hexadecyl group. The alkyl group having 1 to 18 carbon atoms contained in the polymerizable monomer (B) is preferably an alkyl group having 1 to 6 carbon atoms.

[0040] Examples of the aromatic group having 6 to 18 carbon atoms contained in the polymerizable monomer (B) include a phenyl group, a naphthyl group, an anthracen-1-yl group, and a phenanthren-1-yl group.

[0041] The group containing a (poly)oxyalkylene chain contained in the polymerizable monomer (B) is a monovalent group containing a repeating oxyalkylene moiety or a divalent linking group containing a repeating oxyalkylene moiety.

[0042] The group containing a polyester chain contained in the polymerizable monomer (B) is a monovalent group containing a repeating ester bond portion or a divalent linking group containing a repeating ester bond portion.

[0043] The alkyl group having 1 to 18 carbon atoms contained in the polymerizable monomer (B) may further have a substituent, and examples of the substituent include a hydroxyl group and an aryl group. The aromatic group having 6 to 18 carbon atoms contained in the polymerizable monomer (B) may further have a substituent, and examples of the substituent include a hydroxyl group and an alkyl group.

[0044] 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 (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 ethyl (meth)acrylate. (meth)acrylic acid alkyl esters 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, dicyclopentenyl (meth)acrylate, and the like; and (meth)acrylic acid bridged cyclic alkyl esters 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, dicyclopentenyl (meth)acrylate, and the like. In the present application, "(meth)acrylate" means both methacrylate and acrylate.

[0045] Examples of the polymerizable monomer (B) 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.

[0046] 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 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.

[0047] Examples of the polymerizable monomer (B) having an aromatic group having 6 to 18 carbon atoms include styrene, α-methylstyrene, p-methylstyrene, and p-methoxystyrene.

[0048] 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 (meth)acryloylamino group include N,N-dimethylacrylamide, N,N-diethylacrylamide, N-isopropylacrylamide, diacetoneacrylamide, and acroylmorpholine.

[0049] 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.

[0050] Examples of the polymerizable monomer (B) 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, poly(1,2-butylene glycol polytetramethylene glycol mono(meth)acrylate, etc. In addition, the above "poly(ethylene glycol-propylene glycol)" means a random copolymer of ethylene glycol and propylene glycol, and "polyethylene glycol-polypropylene glycol" means a block copolymer of ethylene glycol and propylene glycol.

[0051] The polymerizable monomer (B) is preferably at least one selected from the group consisting of a compound represented by the following general formula (b-1), a compound represented by the following general formula (b-2), a compound represented by the following general formula (b-3), a compound represented by the following general formula (b-4), and a compound represented by the following general formula (b-5).

[0052] [ka] (In the general formulae (b-1), (b-2), (b-3), (b-4) and (b-5), R 21 is a hydrogen atom or a methyl group, R 22 is an alkyl group having 1 to 18 carbon atoms or a phenyl group, R 23 is a hydrogen atom or a methyl group, R 24 is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or a phenyl group, R 25 is a hydrogen atom or a methyl group, R 26 is an alkyl group having 1 to 18 carbon atoms or an alkyl group having 1 to 18 carbon atoms and an ether bond, R27 is a hydrogen atom or a methyl group, R 28 is an alkyl group having 1 to 18 carbon atoms or an alkyl group having 1 to 18 carbon atoms and an ether bond, R 29 is a hydrogen atom or a methyl group, R 30 each independently represents an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, L 2 is a divalent organic group or a single bond, n is an integer ranging from 1 to 4; m indicates the number of repetitions, p is an integer ranging from 1 to 10; q indicates the number of repetitions, l is an integer ranging from 0 to 5.

[0053] In the general formula (b-2), the m n's in the parentheses may be the same or different. In the general formula (b-3), the q p's in the parentheses may be the same or different. In the general formula (b-4), the q p's in the parentheses may be the same or different.

[0054] R 22 , R 24 , R 26 and R 28 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. R 22 and R 24 The phenyl group may further have a substituent, and examples of the substituent include a hydroxyl group and an alkyl group. R 26 and R 28 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. R 30The 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. R 30 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.

[0055] L in the general formulae (b-3) and (b-4) 2 The divalent organic group is L 1 The divalent organic groups are the same as those mentioned above.

[0056] In the general formula (b-2), m represents the number of repetitions, and may be, for example, an integer of 1 or more. The number average of m is, for example, in the range of 1 to 200, preferably in the range of 1 to 150, and more preferably in the range of 1 to 100. The number average value of m can be confirmed by measuring the number average molecular weight of the polymerizable monomer (B) by the method described in the Examples.

[0057] In the general formulae (b-3) and (b-4), q represents the number of repetitions, and may be, for example, an integer of 1 or more. 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. The number average value of q can be confirmed by measuring the number average molecular weight of the polymerizable monomer (B) by the method described in the Examples.

[0058] The polymerizable monomer (B) preferably contains at least the compound represented by the above general formula (b-2). By using the compound represented by the general formula (b-2) as a polymerization component, excellent compatibility with the lubricating base oil described below can be obtained.

[0059] The polymerizable monomer (B) can be produced by a known method. Commercially available products may be used as the polymerizable monomer (B). For example, commercially available products of the polymerizable monomer (B) 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 "Blenmer PE-90", "Blenmer PE-200", "Blenmer PE-350", and "Blenmer PME-100" manufactured by NOF Corporation. Examples of such products include "Blenmer PME-200", "Blenmer PME-400", "Blenmer PME-4000", "Blenmer PP-1000", "Blenmer PP-500", "Blenmer PP-800", "Blenmer 70 PEP-350B", "Blenmer 55 PET-800", "Blenmer 50 POEP-800B", "Blenmer 10 PPB-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 Co., Ltd.

[0060] The polymerizable monomer (B) constituting the polymer of the present invention may be one type alone or two or more types.

[0061] In the defoaming agent of the present invention, the mass ratio of the polymerizable monomer (A) to the polymerizable monomer (B) satisfies, for example, polymerizable monomer (A):polymerizable monomer (B)=5:95 to 95:5, preferably polymerizable monomer (A):polymerizable monomer (B)=20:80 to 90:10, more preferably polymerizable monomer (A):polymerizable monomer (B)=30:70 to 80:20, and further preferably polymerizable monomer (A):polymerizable monomer (B)=30:70 to 70:30.

[0062] The polymer of the present invention preferably further contains a polymerizable monomer (C) having one group represented by the above general formula (a) as a polymerization component. The defoaming properties of the defoaming agent can be further improved by combining a polymerizable monomer (A) having two or more silicone chain-containing functional groups with a polymerizable monomer (C) having one silicone chain-containing functional group.

[0063] The polymerizable monomer (C) is preferably a compound represented by the following general formula (c-1). [ka] (In the general formula (c-1), R 11 , R 12 , R 13 and x are each R in the general formula (a). 11 , R 12 , R 13 and x is the same, R 35 is a hydrogen atom or a methyl group, L 3 is a divalent organic group or a single bond.

[0064] L 3 The divalent organic group is the same as L 11 and L 13 The same applies to the divalent organic group.

[0065] In the polymer of the present invention, the content of the polymerizable monomer (C) in the polymerization components is, for example, in the range of 0 to 50 mass %, preferably in the range of 3 to 30 mass %, and more preferably in the range of 5 to 20 mass %. The content of the polymerizable monomer (C) can be adjusted by the raw material charge ratio of the polymerizable monomer (C) when producing the defoaming agent of the present invention.

[0066] The defoaming agent of the present invention may be a polymer containing at least the polymerizable monomer (A) as a polymerization component, and the polymerization form is not particularly limited. For example, when the defoaming agent of the present invention is a copolymer containing at least the polymerizable monomer (A) and the polymerizable monomer (B) and / or the polymerizable monomer (C) as polymerization components, the copolymer may be a random copolymer or a block copolymer.

[0067] The polymer of the present invention may contain at least the polymerizable monomer (A), the optional polymerizable monomer (B), and the optional polymerizable monomer (C) as polymerization components, and may contain other polymerizable monomers as polymerization components other than the polymerizable monomer (A), the polymerizable monomer (B), and the polymerizable monomer (C) within a range that does not impair the effects of the present invention. The polymer of the present invention is preferably a copolymer substantially composed of a polymerizable monomer (A), an optional polymerizable monomer (B), and an optional polymerizable monomer (C), and more preferably a copolymer composed only of a polymerizable monomer (A), an optional polymerizable monomer (B), and an optional polymerizable monomer (C). Here, "substantially composed" refers to a case where the total content of the polymerizable monomer (A), the optional polymerizable monomer (B), and the optional polymerizable monomer (C) in the polymerization components is 75% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more.

[0068] The polymer of the present invention preferably does not contain fluorine atoms.

[0069] 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 further 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, further preferably in the range of 2,000 to 200,000, and particularly preferably in the range of 3,000 to 15,000.

[0070] In the present invention, 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 number average molecular weight (Mn) and weight average molecular weight (Mw) of the polymer of the present invention are measured by the method described in the Examples.

[0071] [Polymer manufacturing method] 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, etc. based on a polymerization mechanism such as a radical polymerization method, a cationic polymerization method, an anionic polymerization method, etc. 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 in an organic solvent and adding a general-purpose radical polymerization initiator.

[0072] As the polymerization initiator, various types of initiators can be used, and examples thereof include peroxides such as t-butylperoxy-2-ethylhexanoate, benzoyl peroxide, and diacyl peroxide, azo compounds such as azobisisobutyronitrile, dimethyl azobisisobutyrate, and phenylazotriphenylmethane, and metal chelate compounds such as Mn(acac)3, and the like. If 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.

[0073] 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, aromatics 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.

[0074] The polymer of the present invention can also be produced by living polymerization such as living radical polymerization or living anionic polymerization.

[0075] In living radical polymerization, a dormant species whose active polymerization terminal is protected by an atom or atomic group reversibly generates a radical and reacts with a monomer, and a propagation reaction proceeds. Even if the first monomer is consumed, the propagation terminal does not lose activity, and reacts with the second monomer that is added sequentially to obtain 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 radical polymerization using organotellurium (TERP). Of these, there is no particular restriction on which method to use, but ATRP is preferred because of ease of control. In ATRP, polymerization is carried out using an organic halide or a sulfonyl halide compound as a polymerization initiator and a metal complex consisting of a transition metal compound and a ligand as a catalyst.

[0076] 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 alkyl esters having 1 to 6 carbon atoms of 2-halogenated carboxylic acids having 1 to 6 carbon atoms (e.g., 2-chloropropionic acid, 2-bromopropionic acid, 2-chloroisobutyric acid, 2-bromoisobutyric acid, etc.). More specific examples of the alkyl ester having 1 to 6 carbon atoms of a 2-halogenated carboxylic acid having 1 to 6 carbon atoms include methyl 2-chloropropionate, ethyl 2-chloropropionate, methyl 2-bromopropionate, and ethyl 2-bromoisobutyrate.

[0077] 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 for the + , Cu 2+ , Fe 2+ , Fe3+ , 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+ The compound may be selected from the group consisting of: M n+ X n X in the transition metal compound represented by the formula (1) is a halogen atom, an alkoxyl group having 1 to 6 carbon atoms, (SO4) 1 / 2 , (PO4) 1 / 3 , (HPO4) 1 / 2 , (H2PO4), 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 having 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). M n+ X n In the transition metal compound represented by the formula (I), n represents a formal charge on the metal and is an integer of 0 to 7.

[0078] Examples of the ligand compound capable of forming a coordinate bond with the transition metal of the above-mentioned transition metal compound include a compound having a ligand containing one or more nitrogen atoms, oxygen atoms, phosphorus atoms, or sulfur atoms capable of coordinating with the transition metal via a σ bond, a compound having a ligand containing two or more carbon atoms capable of coordinating with the transition metal via a π bond, and a compound having a ligand capable of coordinating with the transition metal via a μ bond or η bond.

[0079] 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.

[0080] 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, dichlorop-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.

[0081] In the living radical polymerization, it is preferable to use a solvent. Examples of solvents used in living radical polymerization include ester-based solvents such as ethyl acetate, butyl acetate, and propylene glycol monomethyl ether acetate; ether-based solvents such as diisopropyl ether, dimethoxyethane, and diethylene glycol dimethyl ether; halogen-based solvents such as dichloromethane and dichloroethane; aromatic solvents such as toluene and xylene; ketone-based solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohol-based 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 kinds.

[0082] The polymerization temperature during the living radical polymerization is preferably in the range of room temperature to 120°C.

[0083] When the polymer of the present invention is produced by living radical polymerization, the resulting polymer may contain residual metals resulting from the transition metal compound used in the polymerization. The residual metals in the resulting polymer may be removed using activated alumina or the like after the polymerization is completed.

[0084] [Lubricating oil composition] The antifoam agent of the present invention can be suitably used as an antifoam agent for lubricating oil compositions, and the lubricating oil compositions of the present invention contain the antifoam agent of the present invention. The defoaming agent of the present invention has high defoaming 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.

[0085] The content of the antifoam 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.

[0086] 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.

[0087] Examples of mineral oils include mineral oils obtained by subjecting lubricating oil fractions obtained by vacuum distillation of atmospheric residual oil obtained by atmospheric distillation of crude oil, and then refining the fraction by one or more of the following processes: solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, etc. Examples of mineral oils include paraffinic mineral oils and naphthenic mineral oils. Other examples include mineral oils produced by isomerizing mineral oil waxes and waxes produced by the Fischer-Tropsch process or the like (GTL wax).

[0088] 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.

[0089] The lubricating base oil may be used alone or in combination of two or more kinds.

[0090] The kinematic viscosity of the lubricating base oil at 100°C is preferably 2 to 20 mm 2 / s, more preferably 2 to 15 mm 2 / s, and more preferably 3 to 10 mm 2 / s range. When the kinetic viscosity at 100° C. of the lubricating base oil is within the above range, evaporation loss is small and power loss due to viscous resistance is not so large, making it easier to obtain an improvement in fuel economy.

[0091] The lubricating base oil preferably has a paraffin content (sometimes referred to as %Cp) by ndM ring analysis of 70% or more, more preferably 75% or more, and even more preferably 80% or more. The lubricating base oil has good oxidation stability and the like when the paraffin content is within the above range.

[0092] 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.

[0093] The lubricating oil composition of the present invention only needs to contain the antifoam agent of the present invention and a lubricating base oil, and may further contain other additives. Other additives may be added, such as ashless detergents, ashless friction modifiers, anti-wear agents, extreme pressure agents, viscosity index improvers, metal deactivators, pour point depressants, rust inhibitors, etc. These additives may be used alone or in combination of two or more.

[0094] The content of each of the other additives can be appropriately adjusted within a range that does not impair the effects of the present invention, and is usually 0.001 to 25 mass%, preferably 0.005 to 20 mass%, and 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.

[0095] Examples of the ashless detergent include alkenyl succinimides such as alkenyl succinic acid monoimides and alkenyl succinic acid bisimides, and boron-modified alkenyl succinimides.

[0096] Examples of ashless friction modifiers include aliphatic amines, fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, and aliphatic ethers, each of which has at least one alkyl or alkenyl group having 6 to 30 carbon atoms in the molecule.

[0097] Examples of anti-wear agents or extreme pressure agents include sulfur-containing compounds such as zinc dithiophosphate; phosphorus-containing compounds such as phosphites, phosphates, phosphonates, and their amine salts or metal salts; and sulfur- and phosphorus-containing anti-wear agents such as thiophosphites, thiophosphates, thiophosphonates, and their amine salts or metal salts.

[0098] Examples of viscosity index improvers include polymethacrylates, dispersion-type polymethacrylates, olefin copolymers (e.g., ethylene-propylene copolymers, etc.), dispersion-type olefin copolymers, and styrene copolymers (e.g., styrene-diene copolymers, styrene-isoprene copolymers, etc.).

[0099] Examples of the metal deactivator include benzotriazole-based compounds, tolyltriazole-based compounds, imidazole-based compounds, and pyrimidine-based compounds.

[0100] 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.

[0101] Examples of the rust inhibitor include petroleum sulfonates, alkylbenzene sulfonates, dinonylnaphthalene sulfonates, alkenyl succinic acid esters, polyhydric alcohol esters, and the like.

[0102] The lubricating oil composition of the present invention is suitable for use in lubricating the driving parts of machines equipped with an internal combustion engine or an electric motor. The lubricating oil composition of the present invention can be used with 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), and various home appliances. EXAMPLES

[0103] The present invention will be specifically described below with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

[0104] 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.

[0105] [GPC measurement conditions] Measurement equipment: Tosoh Corporation's high-speed GPC equipment "HLC-8320GPC" 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: Tosoh Corporation "EcoSEC Data Analysis Version 1.07" Column temperature: 40℃ Developing solvent: Tetrahydrofuran Flow rate: 0.35mL / min Measurement sample: 7.5 mg of the sample was dissolved in 10 ml of tetrahydrofuran, and the resulting solution was filtered through a microfilter to prepare a measurement sample. Sample injection volume: 20 μL Standard sample: In accordance with the measurement manual for the above-mentioned "HLC-8320GPC," the following monodisperse polystyrene with known molecular weight was used.

[0106] (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

[0107] (Synthesis Example 1: Synthesis of Defoamer (1)) A glass flask equipped with a stirrer, a thermometer, a cooling tube, and a dropping device was charged with 30 parts by mass of 1,3-dimercapto-2-propanol, 215 parts by mass of 3-methacryloxypropyltris(trimethylsiloxy)silane, 200 parts by mass of methyl ethyl ketone, and 0.1 parts by mass of NaH. Then, stirring was started under a nitrogen atmosphere, the temperature inside the flask was raised to 60°C, and stirring was continued for 1.5 hours to obtain a double-chain silicone monomer precursor (aa1) via the following synthesis route.

[0108] [ka]

[0109] In a glass flask equipped with a stirrer, a thermometer, a cooling tube, and a dropping device, 17.6 parts by mass of double-chain silicone monomer precursor (aa1), 20 parts by mass of n-butyl acetate, and 0.02 parts by mass of stannous octylate were charged. Then, stirring was started under an air stream, the temperature in the flask was raised to 75°C, and 3 parts by mass of 2-isocyanatoethyl methacrylate was dropped over 15 minutes. After the dropwise addition, the reaction was carried out by raising the temperature to 80°C and stirring for 1 hour, and the disappearance of the absorption peak of the isocyanate group was confirmed by IR spectrum measurement. As a result, a double-chain silicone monomer (a1) represented by the following formula was obtained.

[0110] [ka]

[0111] A glass flask equipped with a stirrer, a thermometer, a cooling tube, and a 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, two types of dropping liquids, namely 30 parts by mass of double-chain silicone monomer (a1) and 20 parts by mass of methoxypolyethylene glycol methacrylate (the number of repeating ethylene oxide chains is about 9) dissolved in 50 parts by mass of n-butyl acetate, and a polymerization initiator solution in which 3 parts by mass of t-butylperoxy-2-ethylhexanoate were dissolved in 15 parts by mass of n-butyl acetate as a radical polymerization initiator, were set in separate dropping devices, and were dropped simultaneously over 2 hours while keeping the inside of the flask at 85°C. After the dropping was completed, the mixture was stirred at 85°C for 4 hours, then heated to 110°C and stirred for another hour to obtain a defoaming agent (1) which is a polymer having a double-chain silicone monomer and a monomer having a group containing a polyoxyalkylene chain as a polymerization component.

[0112] The molecular weight of the obtained defoaming agent (1) was measured by GPC, and as a result, the weight average molecular weight (Mw) was 30,400.

[0113] (Synthesis Example 2: Synthesis of Defoamer (2)) A glass flask equipped with a stirrer, a thermometer, a cooling tube, and a 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, 25 parts by mass of double-chain silicone monomer (a1) dissolved in 50 parts by mass of n-butyl acetate, 25 parts by mass of methoxypolyethylene glycol methacrylate (the number of repeating ethylene oxide chains is about 9), and 5 parts by mass of methyl methacrylate, and two types of dropping liquids, namely, 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, were set in separate dropping devices, and were dropped simultaneously over 2 hours while keeping the inside of the flask at 85°C. After the dropping was completed, the mixture was stirred at 85°C for 4 hours, then heated to 110°C and stirred for another hour to obtain a defoaming agent (2) which is a polymer having a double-chain silicone monomer and a monomer having a group containing a polyoxyalkylene chain as a polymerization component.

[0114] The molecular weight of the obtained defoaming agent (2) was measured by GPC, and as a result, the weight average molecular weight (Mw) was 71,700.

[0115] (Synthesis Example 3: Synthesis of Defoamer (3)) A glass flask equipped with a stirring device, a thermometer, a cooling tube, and a 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, 20 parts by mass of a double-chain silicone monomer (a1), 4 parts by mass of 3-methacryloxypropyltris(trimethylsiloxy)silane, 22 parts by mass of methoxypolyethylene glycol methacrylate (the number of repeating ethylene oxide chains is about 9), and 4 parts by mass of methyl methacrylate dissolved in 50 parts by mass of n-butyl acetate, and two types of dropping liquids, namely, 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, were set in separate dropping devices, and were dropped simultaneously over 2 hours while maintaining the temperature inside the flask at 85° C. After the dropwise addition was completed, the mixture was stirred at 85°C for 4 hours, then the temperature was raised to 110°C and stirred for an additional hour to obtain a defoaming agent (3), which is a polymer having as polymerization components a double-chain silicone monomer, 3-methacryloxypropyltris(trimethylsiloxy)silane, methyl methacrylate, and a monomer having a group containing a polyoxyalkylene chain.

[0116] The molecular weight of the obtained defoaming agent (3) was measured by GPC, and as a result, the weight average molecular weight (Mw) was 50,700.

[0117] (Synthesis Example 4: Synthesis of Defoamer (4)) A glass flask equipped with a stirring device, a thermometer, a cooling tube, and a dropping device was charged with 52 parts by mass of n-butyl acetate as a solvent, and the temperature was raised to 95° C. while stirring under a nitrogen stream. Next, 39 parts by mass of a double-chain silicone monomer (a1), 8.5 parts by mass of 3-methacryloxypropyltris(trimethylsiloxy)silane, 45 parts by mass of methoxypolyethylene glycol acrylate (the number of repeating ethylene oxide chains is about 9), and 16.7 parts by mass of benzyl methacrylate dissolved in 133 parts by mass of n-butyl acetate, and two types of dropping liquids, namely, a polymerization initiator solution in which 11 parts by mass of t-butylperoxy-2-ethylhexanoate were dissolved in 30 parts by mass of n-butyl acetate as a radical polymerization initiator, were set in separate dropping devices, and the flask was simultaneously dropped over 2 hours while maintaining the temperature at 95° C. inside. After the dropwise addition was completed, the mixture was stirred at 95°C for 3 hours, then the temperature was raised to 110°C and stirred for an additional hour to obtain a defoaming agent (4), which is a polymer having as polymerization components a double-chain silicone monomer, 3-methacryloxypropyltris(trimethylsiloxy)silane, methyl methacrylate, and a monomer having a group containing a polyoxyalkylene chain.

[0118] The molecular weight of the obtained defoaming agent (4) was measured by GPC, and as a result, the weight average molecular weight (Mw) was 27,000.

[0119] (Synthesis Example 5: Synthesis of Defoamer (5)) In a glass flask equipped with a stirrer, a thermometer, a cooling tube, and a dropping device, 50 parts by mass of the double-chain silicone monomer precursor (aa1), 22 parts by mass of n-heptane, and 10.5 parts by mass of triethylamine were charged. Then, stirring was started under an air stream, the temperature inside the flask was raised to 40°C, and 5.2 parts by mass of acrylic acid chloride were dropped over 15 minutes. After the dropwise addition, the mixture was stirred for 3 hours to react, and then water was added to inactivate the excess acrylic acid chloride. Then, extraction was performed with citric acid to obtain the double-chain silicone monomer (a2) represented by the following formula.

[0120] [ka]

[0121] A glass flask equipped with a stirring device, a thermometer, a cooling tube, and a dropping device was charged with 52 parts by mass of n-butyl acetate as a solvent, and the temperature was raised to 95° C. while stirring under a nitrogen stream. Next, 20 parts by mass of a double-chain silicone monomer (a2), 4 parts by mass of 3-methacryloxypropyltris(trimethylsiloxy)silane, 22 parts by mass of methoxypolyethylene glycol methacrylate (the number of repeating ethylene oxide chains is about 9), and 4 parts by mass of methyl methacrylate dissolved in 50 parts by mass of n-butyl acetate, and two types of dropping liquids, namely, 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, were set in separate dropping devices, and were dropped simultaneously over 2 hours while maintaining the temperature inside the flask at 95° C. After the dropwise addition was completed, the mixture was stirred at 85°C for 4 hours, then the temperature was raised to 110°C and stirred for an additional hour to obtain a defoaming agent (5), which is a polymer having as polymerization components a double-chain silicone monomer, 3-methacryloxypropyltris(trimethylsiloxy)silane, methyl methacrylate, and a monomer having a group containing a polyoxyalkylene chain.

[0122] The molecular weight of the obtained defoaming agent (5) was measured by GPC, and as a result, the weight average molecular weight (Mw) was 17,000.

[0123] (Synthesis Example 6: Synthesis of Defoamer (6)) Into a glass flask equipped with a stirrer, a thermometer, a cooling tube, and a dropping device, 200 parts by mass of a commercially available silicone compound represented by the following formula, 100 parts by mass of n-butyl acetate as a solvent, and 0.05 parts by mass of stannous octylate as a catalyst were charged. Then, stirring was started under an air stream, the temperature inside the flask was raised to 75°C, 30 parts by mass of 2-isocyanatoethyl acrylate was dropped over 30 minutes, and after the dropwise addition, the temperature was raised to 80°C and the mixture was stirred for 3 hours to carry out a reaction. The resulting reaction product was subjected to IR spectroscopy, and it was confirmed that the absorption peak of the isocyanate group had disappeared. This gave a single-chain silicone monomer represented by the following formula.

[0124] [ka] (In the formula, n represents the number of repetitions, and the number average value of n is 10.)

[0125] In a glass flask equipped with a stirrer, a thermometer, a cooling tube, and a dropping device, 7.5 parts by mass of 1,3-dimercapto-2-propanol, 138 parts by mass of the single-chain silicone monomer obtained above, 100 parts by mass of n-butyl acetate, and 2.0 parts by mass of triethylamine were charged. Then, stirring was started under a nitrogen atmosphere, the temperature inside the flask was raised to 80°C, and stirring was continued for 10 hours to obtain a double-chain silicone monomer precursor (aa3) via the following synthesis route.

[0126] [ka]

[0127] In a glass flask equipped with a stirrer, a thermometer, a cooling tube, and a dropping device, 60 parts by mass of the double-chain silicone monomer precursor (aa3), 40 parts by mass of n-butyl acetate, and 0.02 parts by mass of stannous octylate were charged. Then, stirring was started under an air stream, the temperature in the flask was raised to 75°C, and 4.1 parts by mass of 2-isocyanatoethyl methacrylate was dropped over 15 minutes. After the dropwise addition, the reaction was carried out by raising the temperature to 80°C and stirring for 3 hours, and the disappearance of the absorption peak of the isocyanate group was confirmed by IR spectrum measurement. As a result, a double-chain silicone monomer (a3) ​​represented by the following formula was obtained.

[0128] [ka]

[0129] A glass flask equipped with a stirring device, a thermometer, a cooling tube, and a dropping device was charged with 34 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, two types of dropping liquids, namely 13 parts by mass of double-chain silicone monomer (a3), 15 parts by mass of methoxypolyethylene glycol methacrylate (the number of repeating ethylene oxide chains is about 9), 3 parts by mass of methyl methacrylate, and 3 parts by mass of 3-methacryloxypropyltris(trimethylsiloxy)silane dissolved in 33 parts by mass of n-butyl acetate, and a polymerization initiator solution in which 2 parts by mass of t-butylperoxy-2-ethylhexanoate were dissolved in 10 parts by mass of n-butyl acetate as a radical polymerization initiator, were set in separate dropping devices, and were dropped simultaneously over 2 hours while maintaining the temperature inside the flask at 85° C. After the dropwise addition was completed, the mixture was stirred at 85°C for 4 hours, then the temperature was raised to 110°C and stirred for an additional hour to obtain a defoaming agent (6), which is a polymer having as polymerization components a double-chain silicone monomer and a monomer having a group containing a polyoxyalkylene chain.

[0130] The molecular weight of the obtained defoaming agent (6) was measured by GPC, and as a result, the weight average molecular weight (Mw) was 25,000.

[0131] (Synthesis Example 7: Synthesis of Defoamer (7)) A glass flask equipped with a stirring device, a thermometer, a cooling tube, and a dropping device was charged with 52 parts by mass of n-butyl acetate as a solvent, and the temperature was raised to 90 ° C. while stirring under a nitrogen stream. Next, 20 parts by mass of a commercially available three-chain silicone compound (a4) (Mw 570-620) represented by the following formula dissolved in 50 parts by mass of n-butyl acetate, 4 parts by mass of 3-methacryloxypropyltris (trimethylsiloxy) silane, 22 parts by mass of methoxypolyethylene glycol methacrylate (the number of repeating ethylene oxide chains is about 9), and 4 parts by mass of methyl methacrylate, and two types of dropping liquids, namely, a polymerization initiator solution in which 5 parts by mass of t-butylperoxy-2-ethylhexanoate as a radical polymerization initiator was dissolved in 15 parts by mass of n-butyl acetate, were set in separate dropping devices, and the flask was kept at 90 ° C. while dropping them simultaneously over 2 hours. After the dropwise addition was completed, the mixture was stirred at 90°C for 2 hours, then the temperature was raised to 110°C and stirred for an additional 1.5 hours to obtain a defoaming agent (7), which is a polymer having as polymerization components a triple-chain silicone monomer, 3-methacryloxypropyltris(trimethylsiloxy)silane, methyl methacrylate, and a monomer having a group containing a polyoxyalkylene chain.

[0132] [ka]

[0133] The molecular weight of the obtained defoaming agent (7) was measured by GPC, and as a result, the weight average molecular weight (Mw) was 44,200.

[0134] (Comparative Synthesis Example 1: Synthesis of Defoamer (1')) A polymerization reaction was carried out in the same manner as in Synthesis Example 1, except that 20 parts by mass of 3-methacryloxypropyltris(trimethylsiloxy)silane represented by the following formula was used instead of the double-chain silicone monomer (a1), to obtain a defoaming agent (1') which is a polymer having as polymerization components a single-chain silicone monomer and a monomer having a group containing a polyoxyalkylene chain.

[0135] [ka]

[0136] The molecular weight of the resulting defoaming agent (1') was measured by GPC, and the weight average molecular weight (Mw) was 40,900.

[0137] (Comparative Synthesis Example 2: Synthesis of Defoamer (2')) A polymerization reaction was carried out in the same manner as in Synthesis Example 1, except that 20 parts by mass of a single-chain silicone monomer represented by the following formula was used instead of the double-chain silicone monomer (a1), to obtain a defoaming agent (2') which is a polymer having as polymerization components the single-chain silicone monomer and a monomer having a group containing a polyoxyalkylene chain.

[0138] [ka] (n represents the number of repetitions, and the number average value of n is 10.)

[0139] The molecular weight of the resulting defoaming agent (2') was measured by GPC, and the weight average molecular weight (Mw) was found to be 24,500.

[0140] A commercially available dimethyl silicone represented below ("KF-96-60,000cs" manufactured by Shin-Etsu Silicones Co., Ltd.) was separately prepared as an antifoaming agent (3').

[0141] [ka]

[0142] The defoaming performance of the defoaming agent produced above was evaluated by carrying out the following foaming test. The results are shown in Table 1.

[0143] (Preparation of Lubricating Oil Composition) Lubricating oil compositions were prepared by adding the antifoaming agent shown in Table 1 in the amount shown in Table 1 to 100 parts by mass of a base lubricating oil containing a lubricating oil 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.) using the dilution solvent shown in Table 1.

[0144] (Foaming test) The obtained lubricating oil composition was subjected to a foaming test at 80°C and 120°C according to the homogenizer method disclosed in JP 2008 120880 A. Specifically, the lubricating oil composition was stirred under the following conditions using a homogenizer ("TK Robomix" manufactured by Primix Corporation) equipped with a generator shaft ("Mini Mixer" manufactured by Primix Corporation), and the foaming amount (mL) was calculated by subtracting the oil surface reading (mL) before stirring from the foaming surface reading (mL) 3 seconds after stirring was stopped. The smaller the foaming amount, the better the defoaming ability. [Foaming test measurement conditions] Revolution speed: 16,000 rpm Oil temperature: 80℃ and 120℃ Oil amount: 80ml Container: 200ml measuring cylinder (inner diameter φ36mm) Mixing time: 1 minute

[0145] [Table 1]

[0146] The evaluation results in Table 1 show that defoamers using double-chain silicone monomers exhibit excellent defoaming properties even in high-temperature environments. On the other hand, defoamers that do not use double-chain silicone monomers (use single-chain silicone monomers) do not provide sufficient defoaming properties in high-temperature environments.

Claims

1. A defoaming agent which is a fluorine atom-free polymer having, as at least a polymerization component, a polymerizable monomer (A) having two or more groups represented by the following general formula (a), wherein the polymerizable monomer (A) is a compound represented by the following general formula (a-1): 【Chemistry 1】 (In the general formula (a), R １１ each independently represents an alkyl group having 1 to 6 carbon atoms, a phenyl group, or -OSi(R １４ ) ３ A group represented by R １４ each independently represents an alkyl group having 1 to 6 carbon atoms or a phenyl group, R １２ are each independently an alkyl group having 1 to 6 carbon atoms or a phenyl group, R １３ is an alkyl group having 1 to 6 carbon atoms or a phenyl group, x indicates the number of repetitions.) 【Chemistry 2】 (In the general formula (a-1), R １１ , R １２ , R １３ and x are each R in the general formula (a). １１ , R １２ , R １３ and x, R １５ is a hydrogen atom or a methyl group, L １１ and L １３ each independently represents a divalent organic group or a single bond, y is an integer ranging from 2 to 5; L １２ is an organic group having a valence of y+1.

2. The defoaming agent according to claim 1, wherein the polymerization component comprises a polymerizable monomer (B) having one or more groups 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.

3. The defoaming agent according to claim 2, wherein the polymerizable monomer (B) is at least one selected from the group consisting of a compound represented by the following general formula (b-1), a compound represented by the following general formula (b-2), a compound represented by the following general formula (b-3), and a compound represented by the following general formula (b-4): 【Chemistry 3】 (In the general formulae (b-1), (b-2), (b-3) and (b-4), R ２１ is a hydrogen atom or a methyl group, R ２２ is an alkyl group having 1 to 18 carbon atoms or a phenyl group, R ２３ is a hydrogen atom or a methyl group, R ２４ is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or a phenyl group, R ２５ is a hydrogen atom or a methyl group, R ２６ is an alkyl group having 1 to 18 carbon atoms or an alkyl group having 1 to 18 carbon atoms and an ether bond, R ２７ is a hydrogen atom or a methyl group, R ２８ is an alkyl group having 1 to 18 carbon atoms or an alkyl group having 1 to 18 carbon atoms and an ether bond, L ２ is a divalent organic group or a single bond, n is an integer ranging from 1 to 4; m indicates the number of repetitions, p is an integer ranging from 1 to 10; q indicates the number of repetitions.)

4. 3. The defoaming agent according to claim 1, wherein the polymerization component comprises a polymerizable monomer (C) having one group represented by the general formula (a).

5. The defoaming agent according to claim 4, wherein the polymerizable monomer (C) is a compound represented by the following general formula (c-1): 【Chemistry 4】 (In the general formula (c-1), R １１ , R １２ , R １３ and x are each R in the general formula (a). １１ , R １２ , R １３ and x, R ３５ is a hydrogen atom or a methyl group, L ３ is a divalent organic group or a single bond.

6. The defoaming agent according to claim 1 or 2, wherein the proportion of the polymerizable monomer (A) in the total amount of the polymerization components is in the range of 20 to 80 mass %.

7. The defoaming agent according to claim 1 or 2, having a weight average molecular weight in the range of 3,000 to 150,000.

8. A lubricating oil composition comprising a lubricating base oil and the antifoaming agent according to claim 1 or 2.

9. 9. The lubricating oil composition according to claim 8, which is used to lubricate the driving parts of a machine equipped with an internal combustion engine or an electric motor.

10. 9. The lubricating oil composition of claim 8, wherein the lubricating oil composition is used in a motor vehicle having an internal combustion engine or an electric motor to lubricate the driving parts of said motor vehicle.

11. A machine using the lubricating oil composition according to claim 8 in a driving part.

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