Friction reducing agent for lubricating oil, and lubricating oil composition

Abstract

To provide a friction reducing agent for a lubricant and a lubricant composition that have an excellent friction reducing effect.SOLUTION: A friction reducing agent for a lubricant comprises a (meth)acrylic copolymer A containing a structural unit derived from (meth)acrylate (a) represented by a general formula (1). In the general formula (1), R1 is a hydrogen atom or a methyl group, -X- is -O- or -NH-, -Y- is an alkylene group having 1 to 4 carbon atoms, p is 0 or 1, and R2 to R4 are each independently selected from an alkyl group having 1 to 4 carbon atoms, a trialkylsiloxy group having 3 to 12 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogen atom, a hydrogen atom, and a hydroxyl group, and at least one of R2 to R4 is either the alkyl group having 1 to 4 carbon atoms or the trialkylsiloxy group having 3 to 12 carbon atoms.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a friction reducer for lubricating oils and a lubricating oil composition used in lubricating oils. [Background technology]

[0002] Lubricants, such as those used in automobile engines and drivetrains, contain various friction-reducing agents to reduce energy loss due to friction and extend the lifespan of equipment by preventing seizing. In recent years, with the trend towards lower viscosity lubricants aimed at improving fuel efficiency, the load on metal-to-metal contact surfaces has become more severe, making the role of friction-reducing agents even more important. Examples of friction-reducing agents include oiliness enhancers such as long-chain fatty acid esters and fatty acid amides, anti-wear agents such as phosphate esters and zinc dithiophosphate, extreme pressure agents such as organic sulfur compounds and organic halogen compounds, and friction modifiers such as organic molybdenum compounds. However, depending on the usage conditions and environment, these additives alone may not provide sufficient friction reduction. To overcome this challenge, research is underway to use polymer materials as friction-reducing agents. For example, Patent Document 1 discloses that a viscosity index improver containing a copolymer having an alkoxysilane structure (meth)acrylate as a constituent monomer enhances the metal friction reduction ability of a lubricating oil composition. Furthermore, Patent Document 2 discloses that copolymers having alkyl acrylates and hydroxyalkyl acrylates as constituent monomers are effective as friction and wear reducers for lubricating oils. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2016-28138 [Patent Document 2] Japanese Patent Publication No. 2013-124266 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, in the methods of Patent Document 1 and Patent Document 2, the friction reduction effect is insufficient. An object of the present invention is to provide a friction reducing agent for lubricating oil and a lubricating oil composition having an excellent friction reduction effect.

Means for Solving the Problems

[0005] The present invention has the following aspects. [1] A friction reducing agent for lubricating oil containing a (meth)acrylic copolymer A containing a structural unit derived from the following general formula (1). ru ( a )component (wherein, R

[0006]

Chemical Formula

[0007] (In the formula, R )component , , 2 , 2 ,

[0007] , , , , , Note( , 4 , 4 , , 1 , , is a hydrogen atom or a methyl group, -X- is -O- or -NH-, -Y- is an alkylene group having 1 to 4 carbon atoms, p is 0 or 1, and R 2 ~R 4 are each independently any one selected from an alkyl group having 1 to 4 carbon atoms, a trialkylsiloxy group having 3 to 12 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogen atom, a hydrogen atom, and a hydroxyl group, and at least one of R 2 ~R 4 is either an alkyl group having 1 to 4 carbon atoms or a trialkylsiloxy group having 3 to 12 carbon atoms.) [2] The friction reducing agent for lubricating oil according to [1], wherein a Note( is a (meth)acrylate having a trialkylsilyl group or a tris(trialkylsiloxy)silyl group. )component [3] The friction reducing agent for lubricating oil according to [1] or [2], wherein the (meth)acrylic copolymer A further contains a structural unit derived from an alkyl (meth)acrylate (b) having a linear or branched alkyl group. ​[4] The lubricant friction reducer according to [3], wherein the alkyl group of the alkyl (meth) acrylate (b) has 1 to 20 carbon atoms. [5] The lubricant friction reducer according to any one of [1] to [4], wherein the (meth) acrylic copolymer A is a graft copolymer. [6] The lubricant friction reducer according to [5], wherein the (meth) acrylic copolymer A contains a structural unit derived from a vinyl-based radically polymerizable monomer (m1) and a structural unit derived from a macromonomer (M). [7] The lubricant friction reducer according to [6], wherein the macromonomer (M) contains a structural unit derived from a vinyl-based radically polymerizable monomer (m2). [8] The lubricant friction reducer according to [6], wherein the macromonomer (M) has the structure of the following formula (2).

[0008]

Chemical formula

[0009] (In the formula, X 1 ~X n-1 each independently represents a hydrogen atom, a methyl group or CH2OH, and Y 1 ~Y n each independently represents a substituent other than X 1 ~X n-1 that binds to the vinyl group of the vinyl-based radically polymerizable monomer (m2) which is the structural unit of the macromonomer (M). Z represents a terminal group, and n represents an integer of 2 to 10000.) [9] The lubricant friction reducer according to any one of [1] to [8], wherein the mass average molecular weight of the (meth) acrylic copolymer A is 5000 to 200000.

[10] A lubricant composition containing the lubricant friction reducer according to any one of [1] to [9].

Advantages of the Invention

[0010] According to the present invention, a lubricant friction reducer and a lubricant composition excellent in friction reduction effect can be provided.

Embodiments for Carrying Out the Invention

[0011] The present invention will now be described in detail. The following embodiments are merely illustrative for illustrating the present invention and are not intended to limit the present invention to these embodiments. The present invention can be implemented in various forms without departing from its spirit.

[0012] In this invention, "(meth)acrylic" is a general term for "acrylic" and "methacrylic". "(meth)acrylate" is a general term for "acrylate" and "methacrylate". "(meth)acryloyl group" is a general term for "acryloyl group" and "methacryloyl group", and is a group represented by CH2=C(R)-C(=O)-(R is a hydrogen atom or a methyl group). "Macromonomer" means a polymer having a radical polymerizable group or an addition-reactive functional group. "Vinyl radical polymerizable monomer" means a monomer having an ethylenically unsaturated bond that is not a macromonomer.

[0013] The friction reducing agent for lubricating oils of the present invention comprises (meth)acrylic copolymer A. (Meth)acrylic copolymer A is a (meth)acrylate represented by the following general formula (1). or (meth)acrylamide (a) (hereinafter also referred to as "component (a)") contains constituent units derived from (a). It may also contain constituent units derived from alkyl (meth)acrylate (b) (hereinafter also referred to as "component (b)") having linear or branched alkyl groups. It is preferable that the total mass of the (meth)acrylic copolymer A contains 70% by mass or more of component (a) and component (b) as constituent units, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0014] [ka]

[0015] In the above general formula (1), "R 1" is a hydrogen atom or a methyl group, "p" is 0 or 1, and "-X-" is "-O-" or "-NH-". "-Y-" is an alkylene group having 1 to 4 carbon atoms. Specific examples of such alkylene groups with 1 to 4 carbon atoms include methylene, ethylene, propylene, and butylene groups. These alkylene groups may be linear or branched.

[0016] "R 2 ~R 4 Each of these is independently selected from an alkyl group having 1 to 4 carbon atoms, a trialkylsiloxy group having 3 to 12 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogen atom, a hydrogen atom, or a hydroxyl group, and R 2 ~R 4 At least one of these is either an alkyl group having 1 to 4 carbon atoms or a trialkylsiloxy group having 3 to 12 carbon atoms. Specific examples of the C1-C4 alkyl group include methyl, ethyl, propyl, and butyl groups. These alkyl groups may be linear or branched. Specific examples of the C3-C12 trialkylsiloxy group include trimethylsiloxy, triethylsiloxy, tripropylsiloxy, and tributylsiloxy groups. The alkyl groups contained in these trialkylsiloxy groups may be linear or branched. Specific examples of the C1-C4 alkoxy group include methoxy, ethoxy, propoxy, and butoxy groups. These alkoxy groups may be linear or branched. Specific examples of the halogen atom include fluorine, chlorine, and bromine atoms.

[0017] (a) As for the component, R is chosen because it can provide a high friction reduction effect. 2 ~R 4 (Meth)acrylate having trialkylsilyl groups in which all are alkyl groups, or R 2 ~R 4(Meth)acrylates having tris(trialkylsiloxy)silyl groups, where all of the groups are trialkylsiloxy groups, are preferred, and (meth)acrylates having tris(trialkylsiloxy)silyl groups are particularly preferred.

[0018] (a) Specific examples of components include: [Dimethoxy(methyl)silyl](meth)acrylate, [diethoxy(methyl)silyl](meth)acrylate, [dimethoxy(methyl)silyl]methyl(meth)acrylate, [diethoxy(methyl)silyl]methyl(meth)acrylate, 2-[dimethoxy(methyl)silyl]ethyl(meth)acrylate, 2-[diethoxy(methyl)silyl]ethyl(meth)acrylate, 3-[dimethoxy(methyl)silyl]propyl(meth)acrylate, 3-[diethoxy(methyl)silyl]propyl(meth)acrylate, [dimethoxy(ethyl)silyl](meth)acrylate, [diethoxy(ethyl)silyl](meth)acrylate, (Meth)acrylates having a monoalkylsilane group, such as [dimethoxy(ethyl)silyl]methyl (meth)acrylate, [diethoxy(ethyl)silyl]methyl (meth)acrylate, 2-[dimethoxy(ethyl)silyl]ethyl (meth)acrylate, 2-[diethoxy(ethyl)silyl]ethyl (meth)acrylate, 3-[dimethoxy(ethyl)silyl]propyl (meth)acrylate, 3-[diethoxy(ethyl)silyl]propyl (meth)acrylate, dichloromethylsilyl (meth)acrylate, 2-(dichloromethylsilyl)ethyl (meth)acrylate, 3-(dichloromethylsilyl)propyl (meth)acrylate, etc.;

[0019] [Methoxydi(methyl)silyl](meth)acrylate, [Ethoxydi(methyl)silyl](meth)acrylate, [Methoxydi(methyl)silyl]methyl(meth)acrylate, [Ethoxydi(methyl)silyl]methyl(meth)acrylate, 2-[Methoxydi(methyl)silyl]ethyl(meth)acrylate, 2-[Ethoxydi(methyl)silyl]ethyl(meth)acrylate, 3-[Methoxydi(methyl)silyl]propyl(meth)acrylate, 3-[Ethoxydi(methyl)silyl]propyl(meth)acrylate, [Methoxydi(ethyl)silyl](meth)acrylate, (Meth)acrylates having a dialkylsilane group, such as [ethoxydi(ethyl)silyl](meth)acrylate, [methoxydi(ethyl)silyl]methyl(meth)acrylate, [ethoxydi(ethyl)silyl]methyl(meth)acrylate, 2-[methoxydi(ethyl)silyl]ethyl(meth)acrylate, 2-[ethoxydi(ethyl)silyl]ethyl(meth)acrylate, 3-[methoxydi(ethyl)silyl]propyl(meth)acrylate, 3-[ethoxydi(ethyl)silyl]propyl(meth)acrylate, chlorodimethylsilyl(meth)acrylate, 2-(chlorodimethylsilyl)ethyl(meth)acrylate, 3-(chlorodimethylsilyl)propyl(meth)acrylate, (meth)acryloxypropylbis(trimethylsiloxy)silanol, etc.;

[0020] Trimethylsilyl (meth)acrylate, triethylsilyl (meth)acrylate, tripropylsilyl (meth)acrylate, tributylsilyl (meth)acrylate, (trimethylsilyl)methyl (meth)acrylate, (triethylsilyl)methyl (meth)acrylate, (tripropylsilyl)methyl (meth)acrylate, (tributylsilyl)methyl (meth)acrylate, 2-(trimethylsilyl)ethyl (meth)acrylate, 2-(triethylsilyl)ethyl (meth)acrylate, 2-(tripropylsilyl)ethyl (meth)acrylate , 2-(tributylsilyl)ethyl (meth)acrylate, 3-(trimethylsilyl)propyl (meth)acrylate, 3-(triethylsilyl)propyl (meth)acrylate, 3-(tripropylsilyl)propyl (meth)acrylate, 3-(tributylsilyl)propyl (meth)acrylate, 4-(trimethylsilyl)butyl (meth)acrylate, 4-(triethylsilyl)butyl (meth)acrylate, 4-(tripropylsilyl)butyl (meth)acrylate, 4-(tributylsilyl)butyl (meth)acrylate, trimethylsilyl (meth) acrylic Amide, (trimethylsilyl)methyl(meth) acrylic Amide, 2-(trimethylsilyl)ethyl(meth) acrylic Amide, 3-(trimethylsilyl)propyl(meth) acrylicAmides, 4-(trimethylsilyl)butyl(meth)acrylamide, (trimethylsiloxy)methyl(meth)acrylate, (triethylsiloxy)methyl(meth)acrylate, (tripropylsiloxy)methyl(meth)acrylate, (tributylsiloxy)methyl(meth)acrylate, 2-(trimethylsiloxy)ethyl(meth)acrylate, 2-(triethylsiloxy)ethyl(meth)acrylate, 2-(tripropylsiloxy)ethyl(meth)acrylate, 2-(tributylsiloxy)ethyl(meth)acrylate , 3-(trimethylsiloxy)propyl (meth)acrylate, 3-(triethylsiloxy)propyl (meth)acrylate, 3-(tripropylsiloxy)propyl (meth)acrylate, 3-(tributylsiloxy)propyl (meth)acrylate, 4-(trimethylsiloxy)butyl (meth)acrylate, 4-(triethylsiloxy)butyl (meth)acrylate, 4-(tripropylsiloxy)butyl (meth)acrylate, 4-(tributylsiloxy)butyl (meth)acrylate, (trimethylsiloxy)methyl (meth) acrylic Amide, 2-(trimethylsiloxy)ethyl(meth) acrylic Amide, 3-(trimethylsiloxy)propyl(meth) acrylic (Meth)acrylates having a trialkylsilyl group, such as amides and 4-(trimethylsiloxy)butyl(meth)acrylamide. or (meth)acrylamide ;

[0021] Tris(trimethylsiloxy)silyl (meth)acrylate, Tris(triethylsiloxy)silyl (meth)acrylate, Tris(tripropylsiloxy)silyl (meth)acrylate, Tris(tributylsiloxy)silyl (meth)acrylate, [Tris(trimethylsiloxy)silyl]methyl (meth)acrylate, [Tris(triethylsiloxy)silyl]methyl (meth)acrylate, [Tris(tripropylsiloxy)silyl]methyl (meth)acrylate, [Tris(tributylsiloxy)silyl]methyl (meth)acrylate, 2-[Tris(trimethylsiloxy)silyl]ethyl (meth)acrylate, 2-[Tris(triethylsiloxy)silyl]ethyl (meth) acrylate, 2-[tris(tributylsiloxy)silyl]ethyl (meth)acrylate, 3-[tris(trimethylsiloxy)silyl]propyl (meth)acrylate, 3-[tris(triethylsiloxy)silyl]propyl (meth)acrylate, 3-[tris(tripropylsiloxy)silyl]propyl (meth)acrylate, 3-[tris(tributylsiloxy)silyl]propyl (meth)acrylate, 4-[tris(trimethylsiloxy)silyl]butyl (meth)acrylate, 4-[tris(triethylsiloxy)silyl]butyl (meth)acrylate, 4-[tris(tripropylsiloxy)silyl]butyl (meth)acrylate, 4-[tris(tributylsiloxy)silyl]butyl (meth)acrylate, tris(trimethylsiloxy)silyl (meth) acrylic amide, [tris(trimethylsiloxy)silyl]methyl(meth) acrylic Amide, 2-[tris(trimethylsiloxy)silyl]ethyl(meth) acrylic Amide, 3-[tris(trimethylsiloxy)silyl]propyl(meth) acrylic Amide, 4-[tris(trimethylsiloxy)silyl]butyl(meth) acrylic (Meth)acrylates having a tris(trialkylsiloxy)silyl group, such as amides. or (meth)acrylamide These are some examples.

[0022] (a) The constituent units derived from component (meth)acrylic copolymer A are preferably in an amount of 0.1 to 70% by mass, more preferably 0.2 to 60% by mass, and even more preferably 0.3 to 50% by mass, based on the total mass of the (meth)acrylic copolymer A, in order to enhance the friction reduction effect.

[0023] Specific examples of component (b) include alkyl(meth)acrylates having linear alkyl groups such as methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate, n-butyl(meth)acrylate, n-pentyl(meth)acrylate, n-hexyl(meth)acrylate, n-heptyl(meth)acrylate, n-octyl(meth)acrylate, n-nonyl(meth)acrylate, n-decyl(meth)acrylate, n-undecyl(meth)acrylate, n-dodecyl(meth)acrylate, n-tridecyl(meth)acrylate, n-tetradecyl(meth)acrylate, n-pentadecyl(meth)acrylate, n-cetyl(meth)acrylate, n-heptadecyl(meth)acrylate, and n-stearyl(meth)acrylate; Examples include branched alkyl(meth)acrylates such as i-propyl(meth)acrylate, i-butyl(meth)acrylate, t-butyl(meth)acrylate, i-nonyl(meth)acrylate, i-decyl(meth)acrylate, i-undecyl(meth)acrylate, i-dodecyl(meth)acrylate, i-tridecyl(meth)acrylate, i-tetradecyl(meth)acrylate, i-pentadecyl(meth)acrylate, i-cetyl(meth)acrylate, i-heptadecyl(meth)acrylate, i-stearyl(meth)acrylate, and 2-ethylhexyl(meth)acrylate.

[0024] (b) As for component (b), alkyl(meth)acrylates with 1 to 20 carbon atoms in the alkyl group are preferred, alkyl(meth)acrylates with 2 to 18 carbon atoms in the alkyl group are more preferred, and alkyl(meth)acrylates with 4 to 14 carbon atoms in the alkyl group are particularly preferred, in order to improve solubility in the base oil.

[0025] (b) The constituent units derived from component (meth)acrylic copolymer A are preferably in an amount of 30 to 99.9% by mass, more preferably 40 to 99.8% by mass, and even more preferably 50 to 99.7% by mass, based on the total mass of the (meth)acrylic copolymer A, in order to increase their solubility in the base oil.

[0026] The (meth)acrylic copolymer A may contain constituent units derived from other radical polymerizable vinyl compounds other than components (a) and (b) (hereinafter also referred to as "component (c)"). Examples of component (c) include styrene, α-methylstyrene, pt-butylstyrene, vinyltoluene, vinyl acetate, and (meth)acrylate compounds other than components (a) and (b).

[0027] (a) Other (meth)acrylate compounds include cyclic alkyl group (meth)acrylates such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, isobornyl (meth)acrylate, and 4-t-butylcyclohexyl (meth)acrylate; 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-t-butyl (meth)acrylate. (meth)acrylates having hydroxyl groups such as acrylate, 6-hydroxyhexyl (meth)acrylate, glycerin mono(meth)acrylate, ethylene glycol mono(meth)acrylate, propylene glycol mono(meth)acrylate; (meth)acrylic acid, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl hexahydrophthalate, etc. (meth)acrylate; phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, nonylphenoxypolyethylene glycol (meth)acrylate, phenoxypolypropylene glycol (meth)acrylate, phenylphenyl (meth)acrylate, phenylphenoxyethyl (meth)acrylate, phenoxybenzyl (meth)acrylate (meth)acrylates having an aromatic ring structure such as phenylbenzyl (meth)acrylate, naphthyl (meth)acrylate, and (1-naphthyl)methyl (meth)acrylate; (meth)acrylates having a heterocyclic structure such as tetrahydrofurfuryl (meth)acrylate, glycidyl (meth)acrylate, and (meth)acrylate oil morpholine; alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, and butoxyethyl (meth)acrylate;Examples include 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 2-(meth)acryloyloxyethyl acid phosphate, trifluoroethyl (meth)acrylate, heptadecafluorodecyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, and (meth)acrylamide. Two or more of these may be used in combination.

[0028] From the standpoint of achieving a higher friction reduction effect, the content of constituent units derived from component (c) relative to the total mass of (meth)acrylic copolymer A is preferably 0.01 to 30% by mass, more preferably 0.03 to 20% by mass, and even more preferably 0.5 to 10% by mass. Note that (meth)acrylic copolymer A does not necessarily have to contain constituent units derived from component (c). The total amount of constituent units derived from components (a) to (c) above shall not exceed 100% by mass of the total mass of the (meth)acrylic copolymer A.

[0029] The (meth)acrylic copolymer A may be a graft copolymer because it can enhance the friction reduction effect. In this specification, a graft copolymer is a polymer having one or more blocks chemically bonded to a main chain polymer structure (stem polymer structure) as side chain polymer structures (branch polymer structures). The structures of the main chain polymer and the side chain polymer may be different or the same. There are no particular limitations on the method for producing a graft copolymer, but examples include a method in which a macromonomer having a radically polymerizable double bond at its terminal is produced as a side chain polymer structure, and then radically polymerized with monomers that will become the constituent units of the main chain polymer; a method in which a main chain polymer having a reaction site and a macromonomer having a reaction site are produced in advance and then reacted; and a method in which, after producing the main chain polymer, a hydrogen abstraction initiator is used to generate radicals on the main chain polymer, and then monomers that will become the constituent units of the side chain polymer are reacted to produce the side chain polymer structure.

[0030] The graft copolymer (meth)acrylic copolymer A may contain the constituent units derived from components (a) to (c) in both the main chain polymer structure and the side chain polymer structure. (a) The friction reduction effect can be enhanced by incorporating the component into the side chain polymer structure or the main chain polymer structure. To further enhance the friction reduction effect, it is preferable to include alkyl (meth)acrylate with 1 to 4 carbon atoms in the alkyl group as a constituent unit of the main chain polymer structure, more preferably alkyl (meth)acrylate with 2 to 4 carbon atoms in the alkyl group, and even more preferably alkyl (meth)acrylate with 4 carbon atoms in the alkyl group. In order to enhance solubility in base oils, it is preferable to include alkyl (meth)acrylates with 5 to 20 carbon atoms in the alkyl group as constituent units of the side chain polymer structure, more preferably alkyl (meth)acrylates with 8 to 18 carbon atoms in the alkyl group, and even more preferably alkyl (meth)acrylates with 10 to 14 carbon atoms in the alkyl group.

[0031] The (meth)acrylic copolymer A, which is a graft copolymer, may contain constituent units derived from a vinyl radical polymerizable monomer (m1) (hereinafter also referred to as "(m1) component") and constituent units derived from a macromonomer (M) (hereinafter also referred to as "(M) component"). By copolymerizing the (m1) component and the (M) component, a graft copolymer having a main chain polymer structure with the (m1) component as a constituent unit and a side chain polymer structure consisting of the (M) component can be obtained.

[0032] The (m1) component can be any of the compounds listed as components (a) to (c) above. It is preferable that the (m1) component contains a (meth)acrylate compound due to its excellent radical polymerization properties. From the standpoint of further enhancing the friction reduction effect, it is preferable that component (m1) contains an alkyl (meth)acrylate with 1 to 4 carbon atoms in the alkyl group, more preferably an alkyl (meth)acrylate with 2 to 4 carbon atoms in the alkyl group, and even more preferably an alkyl (meth)acrylate with 4 carbon atoms in the alkyl group.

[0033] The (M) component is not particularly limited as long as it is a compound having a radical polymerizable group and a repeating structure. Examples include compounds obtained by modifying the terminals of polyisobutylene or hydrogenated polybutadiene with vinyl-based radical polymerizable groups, and compounds containing two or more constituent units derived from a monomer (m2) having a vinyl-based radical polymerizable group (hereinafter also referred to as "(m2) component") and having a radical polymerizable group at its terminal. Due to the high degree of design required for solubility in base oils, it is preferable that the compound contains two or more constituent units of the (m2) component and has a radical polymerizable group at its terminal.

[0034] Examples of component (m2) include the compounds listed as components (a) to (c) above. It is preferable that component (m2) contains a (meth)acrylate compound due to its excellent radical polymerization properties. From the standpoint of improving solubility in base oils, it is preferable that component (m2) contains an alkyl (meth)acrylate with 5 to 20 carbon atoms in the alkyl group, more preferably an alkyl (meth)acrylate with 8 to 18 carbon atoms in the alkyl group, and even more preferably an alkyl (meth)acrylate with 10 to 14 carbon atoms in the alkyl group.

[0035] Furthermore, from the viewpoint of radical polymerization, the (M) component is preferably structured as shown in the following formula (2).

[0036] [ka]

[0037] (In the formula, X 1 ~X n-1Each of these independently represents a hydrogen atom, a methyl group, or CH2OH, and Y 1 ~Y n Each of these independently bonds to the vinyl group of the vinyl radical polymerizable monomer (m2), which is a constituent unit of the macromonomer (M), X 1 ~X n-1 This shows substituents other than the specified ones. Z represents a terminal group, and n represents an integer from 2 to 10000.

[0038] X 1 ~X n-1 and Y 1 ~Y n These are substituents that independently bond to the vinyl group of component (m2). 1 ~Y n For example, OR 11 , halogen atom, COR 12 COOR 13 , CN, CONR 14 R 15 , NHCOR 16 , or R 17 Show, R 11 ~R 17 Each of these independently represents a hydrogen atom, an alkyl group, an aryl group, a heteroaryl group, etc.

[0039] The Z terminal group can be derived from a hydrogen atom or a radical polymerization initiator, similar to the terminal groups of polymers obtained by known radical polymerization.

[0040] Furthermore, in order to increase the solubility of (meth)acrylic copolymer A in the base oil and to enhance the friction reduction effect, the content of the constituent units derived from component (M) relative to the total mass of (meth)acrylic copolymer A is preferably 1 to 70% by mass, more preferably 2 to 60% by mass, and even more preferably 5 to 50% by mass.

[0041] In order to increase the solubility of (meth)acrylic copolymer A in the base oil, it is preferable that the (M) component contains 50% by mass or more of alkyl (meth)acrylate having 5 to 20 carbon atoms in the alkyl group, more preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferably 80% by mass or more, based on the total mass of component (M).

[0042] In order to improve the solubility of the (meth)acrylic graft copolymer A in the base oil and to improve the friction reduction effect, the mass-average molecular weight (Mw) of the macromonomer (M), as measured by gel permeation chromatography (GPC), is preferably 1,000 to 50,000, more preferably 2,000 to 40,000, and even more preferably 3,000 to 30,000.

[0043] In order to improve the solubility of (meth)acrylic copolymer A in the base oil and to improve the friction reduction effect, the number average molecular weight (Mn) of component (M) measured by gel permeation chromatography is preferably 500 to 30000, more preferably 1000 to 25000, and particularly preferably 2000 to 20000.

[0044] In order to improve the solubility of the (meth)acrylic copolymer A in the base oil and to improve the friction reduction effect, the molecular weight distribution (Mw / Mn) of the macromonomer (M) measured by gel permeation chromatography (GPC) is preferably 1.0 or more and 10 or less, more preferably 1.2 or more and 8 or less, and even more preferably 1.5 or more and 5 or less.

[0045] The aforementioned (M) component may be one that has been manufactured by a known method or one that is commercially available. Examples of methods for manufacturing the aforementioned M component include a method using a cobalt chain transfer agent (U.S. Patent No. 4,680,352), a method using an α-substituted unsaturated compound such as α-bromomethylstyrene as a chain transfer agent (International Publication No. 88 / 04304), a method of chemically bonding polymerizable groups (Japanese Patent Publication No. 60-133007 and U.S. Patent No. 5,147,952), and a method of thermal decomposition (Japanese Patent Publication No. 11-240,854).

[0046] The method using a cobalt chain transfer agent is preferred because it involves fewer manufacturing steps and utilizes a catalyst with a high chain transfer constant. Because cobalt chain transfer agents have a high chain transfer constant, macromonomers with controlled molecular weights can be obtained with only a small amount of addition.

[0047] Known cobalt complexes can be used as cobalt chain transfer agents. The amount of the cobalt chain transfer agent is preferably 0.00001 to 0.1 parts by mass, more preferably 0.00005 to 0.05 parts by mass, and particularly preferably 0.0001 to 0.02 parts by mass, per 100 parts by mass of the (m2) component.

[0048] The mass-average molecular weight (Mw) of the (meth)acrylic copolymer A contained in the friction-reducing agent for lubricating oil of the present invention, as measured by GPC, is preferably 5,000 to 200,000, more preferably 10,000 to 150,000, and even more preferably 15,000 to 100,000, from the standpoint of being able to enhance the friction-reducing effect and improve fuel efficiency by lowering the viscosity of the lubricating oil composition.

[0049] Furthermore, the number-average molecular weight (Mn) of the (meth)acrylic copolymer A contained in the friction-reducing agent for lubricating oil of the present invention, as measured by gel permeation chromatography (GPC), is preferably 2,000 to 100,000, more preferably 3,000 to 80,000, and even more preferably 5,000 to 50,000, in order to increase the solubility of the (meth)acrylic copolymer A in the base oil and to increase the friction-reducing effect.

[0050] Furthermore, the molecular weight distribution (Mw / Mn) of the (meth)acrylic copolymer A contained in the friction reducing agent for lubricating oil of the present invention, as measured by gel permeation chromatography (GPC), is preferably 1.0 to 30, more preferably 1.2 to 20, and even more preferably 1.5 to 10, in order to increase the solubility of the (meth)acrylic copolymer A in the base oil and to increase the friction reducing effect.

[0051] Next, an example of a method for producing the friction-reducing agent for lubricating oil of the present invention is shown. The friction reducing agent for lubricating oils of the present invention can be produced by polymerizing a monomer mixture containing component (a), and optionally components (b) and (c), in a base oil using a known method. Alternatively, it can be produced by polymerizing a monomer mixture containing component (m1) and component (M) in a base oil using a known method. Polymerization can be carried out under known conditions, but it is preferable to use α-methylstyrene dimer as a chain transfer agent because it has a particularly excellent effect in suppressing heat generation during polymerization.

[0052] The aforementioned base oils are not particularly limited, but examples include API Group III base oils such as YUBASE3 manufactured by SK Lubricants, API Group III Plus base oils such as YUBASE4 manufactured by SK Lubricants, and API Group IV base oils such as polyalphaolefins.

[0053] Furthermore, the (M) component is preferably a macromonomer obtained by polymerizing a monomer mixture containing a vinyl-based radical polymerizable monomer in the base oil using a cobalt chain transfer agent. Because the cobalt chain transfer agent has a high chain transfer constant, a macromonomer with a controlled molecular weight can be obtained by adding only a small amount.

[0054] The friction reducing agent for lubricating oils containing the (meth)acrylic copolymer A of the present invention can be used as a friction reducing agent for lubricating oils such as engine oil, drive system oil (gear oil, transmission oil), hydraulic oil, and metalworking oil used in mobility such as automobiles and ships, as well as industrial machinery and robots.

[0055] Examples of base oils for the aforementioned lubricating oils include mineral-based base oils refined from crude oil and chemically synthesized synthetic oils. Examples include API Group III base oils such as YUBASE3 manufactured by SK Lubricants, API Group III Plus base oils such as YUBASE4 manufactured by SK Lubricants, and API Group IV base oils such as polyalphaolefins.

[0056] The lubricating oil composition of the present invention is obtained by blending the friction reducing agent for lubricating oil of the present invention with a base oil. The lubricating oil composition of the present invention may contain other additives besides the friction reducing agent for lubricating oil of the present invention. Examples of other additives include antioxidants, viscosity index improvers, pour point depressants, detergent dispersants, corrosion inhibitors, rust inhibitors, defoamers, emulsifiers, antifungal agents, and anti-emulsifiers. In addition, other friction reducing agents may include oiliness improvers such as long-chain fatty acid esters and fatty acid amides, anti-wear agents such as phosphate esters and zinc dithiophosphate, extreme pressure agents such as organic sulfur compounds and organic halogen compounds, and friction modifiers such as organic molybdenum compounds. Furthermore, the lubricating oil composition of the present invention may also be a grease containing a thickener. Examples of thickeners include soap-based (lithium soap, calcium soap, sodium soap, aluminum soap, etc.), inorganic (bentonite, silica gel, etc.), and organic (polyurea, polyurethane, etc.).

[0057] The content of the friction reducing agent for lubricating oil of the present invention in the lubricating oil composition is preferably 0.01 to 30% by mass, more preferably 0.05 to 25% by mass, and even more preferably 0.1 to 20% by mass, based on 100% by mass of the lubricating oil composition. The friction reduction effect can be enhanced by setting the content of the friction reducing agent for lubricating oil to 0.01% by mass or more. The viscosity of the lubricating oil composition can be reduced by setting the content to 30% by mass or less. [Examples]

[0058] The present invention will be described in more detail below with reference to examples and comparative examples. In the examples, "parts" refers to "parts by mass." In Tables 1 and 2, the content of constituent units derived from each monomer is shown in mass percent. The content of each constituent unit was calculated from the mass of the monomer relative to the total mass of the monomers used in the polymerization reaction. The evaluation was performed by the following method.

[0059] <Molecular weight of macromonomer (M)> Measurements were performed using gel permeation chromatography (GPC) (HLC-8320, manufactured by Tosoh Corporation). After preparing a 0.2% by mass solution of macromonomer (M) in tetrahydrofuran, 10 μl of the solution was injected into an apparatus equipped with Tosoh Corporation columns (TSKgel SuperHZM-M (inner diameter 4.6 mm, length 15 cm), HZM-M (inner diameter 4.6 mm, length 15 cm), HZ-2000 (inner diameter 4.6 mm, length 15 cm), TSKguardcolumn SuperHZ-L (inner diameter 4.6 mm, length 3.5 cm)). Measurements were performed under the following conditions: flow rate: 0.35 ml / min, eluent: tetrahydrofuran (stabilizer BHT), column temperature: 40°C, and Mw, Mn, and Mw / Mn were calculated in terms of standard polystyrene.

[0060] <Molecular weight of (meth)acrylic copolymer> The measurements were performed using gel permeation chromatography (GPC) (HLC-8320, manufactured by Tosoh Corporation). After preparing a 0.2% by mass solution of the (meth)acrylic copolymer obtained in the examples using tetrahydrofuran, 10 μl of the above solution was injected into an apparatus equipped with two Tosoh columns (TSKgelSuperHZM-H (inner diameter 6.0 mm, length 15 cm) and a TSKguardcolumn SuperHZ-H (inner diameter 4.6 mm, length 3.5 cm)). Measurements were performed under the conditions of a flow rate of 0.5 ml / min, eluent: tetrahydrofuran (stabilizer BHT), and column temperature: 40°C. The mass-average molecular weight (Mw), number-average molecular weight (Mn), and molecular weight distribution (Mw / Mn) were calculated in terms of standard polystyrene.

[0061] <Coefficient of friction at 40℃> A YUBASE4 solution containing 2% by mass of the obtained (meth)acrylic copolymer was prepared, and the coefficient of friction at 40°C was measured using an SRV5 tester (manufactured by Optimol Instruments Pruftechnik GmbH). The measurement conditions were as follows, and the coefficient of friction was evaluated 30 minutes after the start of measurement. • Test method: Ball on disc (Ball diameter: 10mm, Ball and disc material: SUJ2) • Test mode: Reciprocating (50Hz, 1mm stroke) • Load: 200N

[0062] [Manufacturing Example 1] (Synthesis of Co complexes (cobalt chain transfer agents)) In a synthesis apparatus equipped with a stirring device, 2.00 g (8.03 mmol) of cobalt(II) acetate tetrahydrate (manufactured by Wako Pure Chemical Industries, Ltd., Wako Special Grade), 3.86 g (16.1 mmol) of diphenylglyoxime (manufactured by Tokyo Chemical Industry Co., Ltd., EP Grade), and 100 ml of diethyl ether that had been deoxygenated beforehand by nitrogen bubbling were added under a nitrogen atmosphere, and the mixture was stirred at 25°C for 2 hours. Next, 20 ml of boron trifluoride diethyl ether complex (Tokyo Chemical Industries, Ltd., EP grade) was added, and the mixture was stirred for a further 6 hours. The resulting solution was filtered, the solid was washed with diethyl ether, and dried at 20°C under pressure of 100 MPa or less for 12 hours to obtain 5.02 g (7.93 mmol, yield 99% by mass) of the brownish solid Co complex.

[0063] [Manufacturing Example 2] (Synthesis of macromonomer M1) In a reaction vessel equipped with a stirrer, condenser, and thermometer, 58 parts of YUBASE4, 98 parts of Acryester SL (manufactured by Mitsubishi Chemical Corporation, trade name: Acryester SL, a mixture of alkyl methacrylate with 12 C12 alkyl groups and alkyl methacrylate with 13 C13 alkyl groups), 2 parts of methyl methacrylate (MMA), and 0.005 parts of the Co complex prepared in Production Example 1 were added. The temperature was raised to 40°C, and dissolved oxygen was removed by bubbling nitrogen over the mixture for 2 hours while stirring. A mixture of YUBASE4 (2 parts) and t-amyl peroxy-2-ethylhexanoate (manufactured by Arkema Yoshitomi Co., Ltd., trade name: Luperox 575), a polymerization initiator, was added, and the temperature was raised to 90°C. After stirring for 2.5 hours, a mixture of YUBASE4 (10 parts) and Luperox 26 (0.7 parts) was added dropwise over 1 hour. After dropwise addition, the temperature was raised to 105°C and maintained for 1.5 hours. Then, 20 parts of YUBASE4 were added and the mixture was cooled to obtain a YUBASE4 solution containing 52.6% by mass of macromonomer M1. The GPC results of the obtained macromonomer M1 are shown in Table 1.

[0064] [Manufacturing Example 3] (Synthesis of macromonomer M2) In a reaction vessel equipped with a stirrer, condenser, and thermometer, 58 parts of YUBASE4, 78 parts of acrylic ester SL, and as component (a), 20 parts of 3-[tris(trimethylsiloxy)silyl]propyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.), 2 parts of methyl methacrylate (MMA), and 0.005 parts of the Co complex prepared in Production Example 1 were added. The liquid temperature was raised to 40°C, and dissolved oxygen was removed by bubbling nitrogen over the mixture for 2 hours while stirring. A mixture of YUBASE4 (2 parts) and the polymerization initiator Luperox 575 (0.1 parts) was added, and the liquid temperature was raised to 90°C. After stirring for 2.5 hours, a mixture of YUBASE4 (10 parts) and Luperox 26 (0.7 parts) was added dropwise over 1 hour. After dropwise addition, the temperature was raised to 105°C and maintained for 1.5 hours. Then, 20 parts of YUBASE4 were added and the mixture was cooled to obtain a YUBASE4 solution containing 52.6% by mass of macromonomer M2. The GPC results of the obtained macromonomer M2 are shown in Table 1.

[0065] <Example 1> In a reaction vessel equipped with a stirrer, condenser, and thermometer, 900 parts of YUBASE4 as the base oil, 5 parts of 3-[tris(trimethylsiloxy)silyl]propyl methacrylate (Tokyo Chemical Industries, Ltd.) as component (a), 75 parts of lauryl acrylate (Osaka Organic Chemicals Co., Ltd., trade name: LA) and 20 parts of n-butyl acrylate (Mitsubishi Chemical Corporation) as component (b), and 2 parts of 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate (NOF Corporation, trade name: Perocta-O) as a polymerization initiator were added. Dissolved oxygen in the reaction solution was removed by blowing nitrogen into the mixture for 1 hour while stirring at room temperature. Then, the temperature of the solution was raised to 80°C and stirred for 4 hours, and then raised to 95°C. After stirring for a further 2 hours, the mixture was cooled to obtain a YUBASE4 solution containing 10% by mass of (meth)acrylic copolymer. Table 2 shows the GPC results for the obtained (meth)acrylic copolymers. The evaluation results of the obtained friction reducers for lubricating oils are shown in Table 2.

[0066] <Examples 2-7, Comparative Examples 1-3> Except for changing the components (a) to (c) used to those shown in Table 2, (meth)acrylic copolymers were manufactured and evaluated using the same method as in Example 1.

[0067] <Example 8> In a reaction vessel equipped with a stirrer, condenser, and thermometer, 30 parts of YUBASE4 and 47.6 parts of a YUBASE4 solution of macromonomer M1 obtained in Production Example 2 were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The temperature of the solution was raised to 85°C, and a mixture of 25 parts of YUBASE4, 5 parts of 3-[tris(trimethylsiloxy)silyl]propyl methacrylate as component (a), 56 parts of n-butyl acrylate and 14 parts of lauryl acrylate as component (b), 0.1 part of Luperox 575 as a polymerization initiator, and 0.9 parts of α-methylstyrene dimer (manufactured by NOF Corporation, trade name: Nofmer MSD) as a chain transfer agent was added dropwise over 4 hours. After holding at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was added dropwise over 1.5 hours. The mixture was heated to 110°C and held for 1 hour, then 58.1 parts of YUBASE4 were added and the mixture was cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic copolymer. Table 2 shows the GPC results for the obtained (meth)acrylic copolymers. The evaluation results of the obtained friction reducers for lubricating oils are shown in Table 2. The monomer composition in Table 2 indicates that the macromonomer M1 contains 25% by mass, and the monomers constituting the macromonomer M1 are 24.5% by mass of SLMA and 0.5% by mass of MMA, and that the constituent units derived from (a-1) are present in the main chain of the graft copolymer.

[0068] <Example 9> In a reaction vessel equipped with a stirrer, condenser, and thermometer, 30 parts of YUBASE4 and 47.6 parts of a YUBASE4 solution of macromonomer M2 (a macromonomer containing 20% ​​by mass of constituent units derived from 3-[tris(trimethylsiloxy)silyl]propyl methacrylate) obtained in Production Example 3 were added, and dissolved oxygen was removed by bubbling nitrogen while stirring. The temperature of the solution was raised to 85°C, and a mixture of 25 parts of YUBASE4, 56 parts of n-butyl acrylate, 19 parts of lauryl acrylate as component (b), 0.1 part of Luperox 575 as a polymerization initiator, and 0.9 parts of Nofmer MSD as a chain transfer agent was added dropwise over 4 hours. After holding at 85°C for 1 hour, a mixture of YUBASE4 (50 parts) and Luperox 575 (0.5 parts) was added dropwise over 1.5 hours. The mixture was heated to 110°C and held for 1 hour, then 58.1 parts of YUBASE4 were added and the mixture was cooled to obtain a YUBASE4 solution containing 35% by mass of (meth)acrylic copolymer. Table 2 shows the GPC results for the obtained (meth)acrylic copolymers. The evaluation results of the obtained friction reducers for lubricating oils are shown in Table 2. The monomer composition in Table 2 contains 25% by mass of macromonomer M2, and the monomers constituting macromonomer M2 are 5% by mass of (a-1), 19.5% by mass of SLMA, and 0.5% by mass of MMA, indicating that the constituent units derived from (a-1) are present in the side chains of the graft copolymer.

[0069] [Table 1]

[0070] [Table 2]

[0071] The abbreviations in Tables 1 and 2 are as follows:

[0072] • (a-1): 3-[tris(trimethylsiloxy)silyl]propyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) • (a-2): 2-(trimethylsiloxy)ethyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) • M1: Macromonomer synthesized in Manufacturing Example 2 • M2: Macromonomer synthesized in Manufacturing Example 3 • SLMA: A mixture of alkyl methacrylate with 12 carbon atoms in the alkyl group and alkyl methacrylate with 13 carbon atoms in the alkyl group (manufactured by Mitsubishi Chemical Corporation, product name: Acryester SL) • MMA: Methyl methacrylate (manufactured by Mitsubishi Chemical Corporation, product name: Acryester M) • LA: Lauryl acrylate (manufactured by Osaka Organic Chemical Co., Ltd., product name: LA) nBA: n-butyl acrylate (manufactured by Mitsubishi Chemical Corporation) • KBM-503: 3-Methacryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBM-503) • 2HEA: 2-hydroxyethyl acrylate (manufactured by Osaka Organic Chemical Co., Ltd., product name: HEA)

[0073] As is clear from Table 1, the friction reducing agents for lubricating oil obtained in each example had a high effect in reducing the coefficient of friction. On the other hand, the friction reducing agents for lubricating oil obtained in each comparative example had a low effect in reducing the coefficient of friction.

Claims

1. A friction reducer for lubricating oils containing a (meth)acrylic copolymer A that includes constituent units derived from component (a) shown in the following general formula (1). 【Chemistry 1】 (In the formula, R １ is a hydrogen atom or a methyl group, -X- is -O- or -NH-, -Y- is an alkylene group having 1 to 4 carbon atoms, p is 0 or 1, R ２ ~R ４ Each of these is independently selected from an alkyl group having 1 to 4 carbon atoms, a trialkylsiloxy group having 3 to 12 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogen atom, a hydrogen atom, and a hydroxyl group, R ２ ~R ４ At least one of these is either an alkyl group having 1 to 4 carbon atoms or a trialkylsiloxy group having 3 to 12 carbon atoms.

2. The friction reducer for lubricating oil according to claim 1, wherein component (a) is a (meth)acrylate having a trialkylsilyl group or a tris(trialkylsiloxy)silyl group.

3. The friction reducer for lubricating oil according to claim 1, wherein the (meth)acrylic copolymer A further comprises a constituent unit derived from alkyl (meth)acrylate (b) having a linear or branched alkyl group.

4. The friction reducing agent for lubricating oil according to claim 3, wherein the alkyl (meth)acrylate (b) has 1 to 20 carbon atoms in the alkyl group.

5. The friction reducing agent for lubricating oil according to claim 1, wherein the (meth)acrylic copolymer A is a graft copolymer.

6. The friction reducer for lubricating oil according to claim 5, wherein the (meth)acrylic copolymer A comprises a constituent unit derived from a vinyl radical polymerizable monomer (m1) and a constituent unit derived from a macromonomer (M).

7. The friction reducer for lubricating oil according to claim 6, wherein the macromonomer (M) includes a constituent unit derived from a vinyl-based radical polymerizable monomer (m2).

8. The friction reducer for lubricating oil according to claim 6, wherein the macromonomer (M) has the structure of the following formula (2). 【Chemistry 2】 (In the formula, X １ to X ｎ－１ each independently represents a hydrogen atom, a methyl group, or CH ２ OH, Y １ to Y ｎ each independently represents a substituent other than X １ to X ｎ－１ bonded to the vinyl group of the vinyl radical-polymerizable monomer (m2) which is a constituent unit of the macromonomer (M). Z represents a terminal group, and n represents an integer of 2 to 10000.)

9. The friction reducing agent for lubricating oil according to claim 1, wherein the mass-average molecular weight of the (meth)acrylic copolymer A is 5,000 to 200,000.

10. A lubricating oil composition comprising a friction reducing agent for lubricating oil according to any one of claims 1 to 9.

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