Lubricant additives, viscosity index improvers, friction modifiers, and lubricant compositions

Abstract

To provide lubricating oil additives, viscosity index improvers, friction modifiers, and lubricating oil compositions that exhibit excellent solubility when added to oil and achieve both excellent shear stability and viscosity index. [Solution] A lubricating oil additive comprising a polymer and a solvent, wherein the polymer comprises a constituent unit (A) derived from a compound represented by the following general formula (1), the content of the constituent unit (A) is 15% by mass or more relative to the total mass of all constituent units constituting the polymer, at least a portion of the polymer is dissolved in the solvent, and the solvent contains a bio-based base oil. [C1] TIFF2026123474000006.tif28170(R 1 is C n H 2n+m The base is represented by , where n is an integer from 1 to 30, m is one of -3, -1, or 1, and 2n+m is an integer greater than or equal to 3.

Description

[Technical Field]

[0001] The present invention relates to lubricating oil additives, viscosity index improvers, friction modifiers, and lubricating oil compositions. [Background technology]

[0002] Traditionally, lubricating oils have been used in internal combustion engines, automatic transmissions, and other mechanical devices to ensure smooth operation. In recent years, from the perspective of protecting the global environment, the fuel efficiency performance required of lubricating oils has become increasingly important, and further improvements in viscosity index, one of the indicators of this performance, are needed. For example, Patent Document 1 discloses the use of a polymer of a selectively hydrogenated conjugated diene as a viscosity index improver.

[0003] However, conventional lubricant additives such as viscosity index improvers generally contain petroleum-derived base oils, which do not meet recent societal demands. Therefore, as a viscosity index improver containing a plant-derived base oil, for example, Patent Document 2 discloses a viscosity index improver concentrate containing a bio-based base oil having a specific molecular structure and a viscosity index improver selected from olefin copolymers, diene copolymers, and the like. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Special Publication No. 2002-521537 [Patent Document 2] Special Publication No. 2023-520938 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, the viscosity index improvers described in Patent Documents 1 and 2 do not necessarily satisfy the requirement of solubility in oil. In addition, Patent Documents 1 and 2 do not discuss the compatibility of shear stability and viscosity index when a lubricant additive is added to oil.

[0006] An object of the present invention is to provide a lubricant additive, a viscosity index improver, a friction modifier, and a lubricant composition that are excellent in solubility when added to oil and can achieve both excellent shear stability and viscosity index.

Means for Solving the Problems

[0007] The present invention has the following aspects. [1] A lubricant additive containing a polymer and a solvent, The polymer contains a structural unit (A) derived from a compound represented by the following general formula (1), The content of the structural unit (A) is 15% by mass or more based on the total mass of all the structural units constituting the polymer, At least a part of the polymer is present in a dissolved state in the solvent, The solvent contains a bio-based base oil, and the lubricant additive.

[0008]

Chemical formula

[0009] In the general formula (1), R is a group represented by C n H 2n+m n is an integer from 1 to 30, m is any one of -3, -1, and 1, and 2n + m is an integer of 3 or more.

[0010] [2] The lubricant additive according to [1], wherein the content of the bio-based base oil is 10% by mass or more based on the total mass of the solvent. [3] The lubricant additive according to [1] or [2], wherein the weight average molecular weight of the polymer is 1000 or more. [4] The lubricating oil additive according to any of [1] to [3] above, wherein in the general formula (1), n ​​is an integer from 2 to 11, m is -3 or -1, and 2n+m is an integer from 3 to 19. [5] The lubricating oil additive according to [4], wherein n is an integer from 6 to 11 and m is -3 or -1 in the general formula (1). [6] In the above general formula (1), R 1 is C6H 11 The lubricating oil additive described in [5] above, which is a group represented by . [7] The lubricating oil additive according to any one of [1] to [6], wherein the constituent unit (A) is at least one constituent unit selected from the group consisting of a structural unit derived from isoprene, a structural unit derived from myrcene, and a constituent unit derived from β-farnesene. [8] The lubricating oil additive according to any one of [1] to [7], wherein the polymer further comprises a constituent unit (B) derived from a (meth)acryloyl group-containing compound. [9] A viscosity index improver comprising any of the lubricating oil additives described in [1] to [8] above.

[10] A friction modifier comprising any of the lubricating oil additives described in [1] to [8] above.

[11] A lubricating oil composition comprising any of the lubricating oil additives described in [1] to [8] above. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a lubricating oil additive, viscosity index improver, friction modifier, and lubricating oil composition that exhibit excellent solubility when added to oil and achieve both excellent shear stability and viscosity index. [Modes for carrying out the invention]

[0012] The embodiments of the present invention will be described in detail below, but the present invention is not limited to the embodiments described below and can be implemented with various modifications within the scope of its gist. In this specification and in the claims, a numerical range represented by "~" means a numerical range that includes the numbers before and after "~" as the lower and upper limits, respectively. For example, A~B is synonymous with A or greater and B or less. The numerical ranges of content, various physical properties, and characteristic values ​​disclosed herein can be modified by arbitrarily combining their lower and upper limits to create new numerical ranges.

[0013] Furthermore, in the present invention and claims, the following terms have the following meanings: "Constituent unit" refers to the unit that makes up a polymer derived from monomers, that is, a constituent unit formed by the polymerization of monomers, or a constituent unit in which a part of the constituent unit has been converted to a different structure by a modification treatment of the polymer. The term "(meth)acryloyl group" is a general term encompassing both "acryloyl group" and "methacryloyl group," and the same applies to "(meth)acrylate" and "(meth)acrylic." "Weight-average molecular weight" and "number-average molecular weight" refer to the weight-average molecular weight or number-average molecular weight on a standard polystyrene basis, measured by gel permeation chromatography (GPC), respectively.

[0014] [Lubricant additive] The lubricating oil additive according to the present invention comprises the polymer (X) and solvent (Y) shown below. In addition to the polymer (X) and solvent (Y), the lubricating oil additive may further contain components other than the polymer (X) and solvent (Y) (hereinafter also referred to as "optional components (Z)") as needed, as long as they do not impair the effects of the present invention.

[0015] <Polymer (X)> At least a portion of the polymer (X) in the lubricating oil additive exists dissolved in the solvent (Y) described later. In lubricating oil additives, it is preferable that all of the polymer (X) is dissolved in the solvent (Y). The presence of at least a portion of the polymer (X) dissolved in the solvent (Y) results in excellent viscosity index improvement. Furthermore, "the entire polymer (X) is dissolved in the solvent (Y)" means that the polymer (X) and solvent (Y) are not separated under room temperature conditions (for example, 25°C), and whether or not separation has occurred can be determined visually.

[0016] The polymer (X) contains the following constituent units (A). The polymer (X) preferably further comprises the constituent unit (B) shown below, in addition to the constituent unit (A). In addition to the constituent unit (A), the polymer (X) may further contain, as necessary, constituent units other than constituent units (A) and (B) (hereinafter also referred to as "constituent unit (C)"), as long as they do not impair the effects of the present invention.

[0017] (Constituent unit (A)) The constituent unit (A) is a constituent unit derived from the compound represented by the following general formula (1) (hereinafter also referred to as "compound (A)"). The constituent unit (A) is preferably derived from a monomer obtained from a plant. That is, compound (A) is preferably a monomer derived from a plant. The plant-derived monomer can be confirmed by measuring its radiocarbon concentration.

[0018] [ka]

[0019] In general formula (1), R 1 is C n H 2n+m The base is represented by , where n is an integer from 1 to 30, m is one of -3, -1, or 1, and 2n+m is an integer greater than or equal to 3.

[0020] n is an integer between 1 and 30, preferably between 2 and 11, more preferably between 6 and 11, even more preferably between 6 and 10, particularly preferably between 6 and 8, and most preferably 6. If n is below the above upper limit, it has excellent solubility in oil (hereinafter also referred to as "oil solubility"). m is any one of -3, -1, and 1, -3 or -1 is preferred, and -1 is more preferred. 2n + m is an integer of 3 or more, an integer of 3 to 61 is preferred, an integer of 3 to 21 is more preferred, an integer of 3 to 19 is further preferred, 11 to 19 is particularly preferred, and 11 is most preferred.

[0021] In particular, n is an integer of 2 to 11, and m is preferably -3 or -1. In this case, 2n + m is preferably an integer of 3 to 21, and more preferably an integer of 3 to 19. Among them, particularly, n is an integer of 6 to 11, and m is preferably -3 or -1. More preferably, n is an integer of 6 to 10, and m is -3 or -1. Further preferably, n is an integer of 6 to 8, and m is -1. Particularly preferably, n is 6, and m is -1.

[0022] R 1 Examples of R include a group represented by CH3, a group represented by C6H 11 a group represented by C6H 13 a group represented by C 11 H 19 a group represented by C 11 H 21 a group represented by C 11 H 23 a group represented by C6H 11 a group represented by C 11 H 19 a group represented by C6H 11 a group represented by C6H R 1 When R is a group represented by CH3, examples of the compound (A) include isoprene. R 1 When R is a group represented by C6H 11 examples of the compound (A) include myrcene. R 1 When R is a group represented by C 11 H 19 examples of the compound (A) include β-farnesene.

[0023] The constituent unit (A) is preferably at least one constituent unit selected from the group consisting of structural units derived from isoprene, structural units derived from myrcene, and constituent units derived from β-farnesene. In particular, since both myrcene and β-farnesene are available as plant-derived monomers, it is more preferable from the viewpoint of building a carbon-recycling society that at least one of the structural units derived from myrcene and the constituent unit derived from β-farnesene is used. From the viewpoint of raw material price, the constituent unit derived from myrcene is preferred. The polymer (X) may contain only one type of constituent unit (A), or it may contain two or more types of constituent units (A).

[0024] The content of constituent unit (A) is 15% by mass or more, preferably 20% by mass or more, more preferably 40% by mass or more, even more preferably 60% by mass or more, and particularly preferably 80% by mass or more, and may also be 100% by mass, 99.9% by mass or less, 99.5% by mass or less, or 99% by mass or less. The above upper and lower limits can be combined arbitrarily. For example, the content of constituent unit (A) is 15% by mass or more, preferably 15 to 100% by mass, more preferably 20 to 99.9% by mass, even more preferably 40 to 99.5% by mass, particularly preferably 60 to 99.5% by mass, and most preferably 80 to 99% by mass. If the content of constituent unit (A) is above the above lower limit, the solubility in oil is further improved. In addition, the polymer (X) is less likely to gel. If the content of constituent unit (A) is below the above upper limit, the viscosity index improvement ability is further enhanced. The content of constituent unit (A) can be calculated from the amount of compound (A), which is the monomer used to introduce constituent unit (A) as a raw material monomer for polymer (X).

[0025] (Constituent unit (B)) The constituent unit (B) is a constituent unit derived from a (meth)acryloyl group-containing compound (hereinafter also referred to as "compound (B)"). The inclusion of constituent units (B) in the polymer (X) further enhances its viscosity index improvement ability.

[0026] Compound (B) has a (meth)acryloyl group in its molecule. Compound (B) may be a monofunctional monomer having one (meth)acryloyl group, or a polyfunctional monomer having two or more (meth)acryloyl groups. Among these, a monofunctional monomer having one (meth)acryloyl group is preferred because it tends to easily achieve both excellent shear stability and viscosity index.

[0027] The carbon number of compound (B) is preferably 3 to 65, more preferably 4 to 62, and even more preferably 4 to 60. If the carbon number of compound (B) is above the lower limit, the friction reduction ability is improved. If the carbon number of compound (B) is below the upper limit, the solubility in oil is further improved.

[0028] Examples of compounds (B) having one (meth)acryloyl group in the molecule include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, i-pentyl (meth)acrylate, 2-methylbutyl (meth)acrylate, n-hexyl (meth)acrylate, and n-octyl (meth)acrylate. , linear or branched alkyl-containing (meth)acrylates such as 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate; alicyclic (meth)acrylates such as cyclohexyl (meth)acrylate, 4-t-butylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, tricyclodecanyl (meth)acrylate, dicyclopentadienyl (meth)acrylate, dicyclopentanyl (meth)acrylate; 2-hydroxyethyl (meth)acrylate Relate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 1,2-dihydroxyethyl (meth)acrylate, 1,2-dihydroxypropyl (meth)acrylate, 1,2-dihydroxybutyl (meth)acrylate, 1,2-dihydroxy5-ethylhexyl (meth)acrylate, 1,1-dihydroxyethyl (meth)acrylate Hydroxyl group-containing (meth)acrylates such as rilate, 1,1-dihydroxypropyl (meth)acrylate, 1,1-dihydroxybutyl (meth)acrylate, 1,2,3-trihydroxypropyl (meth)acrylate, 1,2,3-trihydroxybutyl (meth)acrylate, 1,1,2-trihydroxypropyl (meth)acrylate, 1,1,2-trihydroxybutyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, and polypropylene glycol mono(meth)acrylate;Examples include epoxy group-containing (meth)acrylates such as glycidyl (meth)acrylate, glycidyl α-ethylacrylate, and 3,4-epoxybutyl (meth)acrylate; amino group-containing (meth)acrylates such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate; amide group-containing (meth)acrylates such as Nt-butyl (meth)acrylamide, N-methylol (meth)acrylamide, N-isopropylacrylamide, hydroxyethylacrylamide, N-methoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, and diacetone acrylamide.

[0029] Compound (B) having two or more (meth)acryloyl groups includes a difunctional monomer having two (meth)acryloyl groups, a trifunctional monomer having three (meth)acryloyl groups, and a tetrafunctional or higher monomer having four or more (meth)acryloyl groups.

[0030] Examples of bifunctional monomers include compounds represented by the following general formula (2). CH2=CR 2 -COO-(R 3 O) p -COCR 4 =CH2···(2) (In general formula (2), R 2 and R 4 Each is independently a hydrogen atom or a methyl group, and R 3 (where p is an alkylene group with 1 to 10 carbon atoms, and p is an integer greater than or equal to 1.)

[0031] R 3 The alkylene group has 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, and even more preferably 2 to 4 carbon atoms. p is an integer greater than or equal to 1, preferably between 1 and 30, more preferably between 1 and 20, even more preferably between 1 and 16, particularly preferably between 1 and 14, and most preferably between 1 and 12. If p is 2 or greater, multiple R3 O can be the same or different.

[0032] Examples of compounds represented by general formula (2) include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,5-pentanediol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, and polybutylene glycol di(meth)acrylate.

[0033] Examples of trifunctional monomers include pentaerythritol tri(meth)acrylate and trimethylolpropane tri(meth)acrylate. Examples of monomers with four or more functionalities include dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, ditrimethylolpropanetetraacrylate, and tetramethylolmethanetetra(meth)acrylate.

[0034] Compound (B) is preferably a compound having one (meth)acryloyl group in its molecule, and among these, hydroxy-containing (meth)acrylates are particularly preferred, 4-hydroxybutyl (meth)acrylate and polypropylene glycol mono(meth)acrylate are more preferred, and polypropylene glycol mono(meth)acrylate is even more preferred. In other words, the constituent unit (B) is preferably a constituent unit derived from a (meth)acrylate having one (meth)acryloyl group and one hydroxyl group within the molecule.

[0035] Among the compounds (B) having two or more (meth)acryloyl groups, compounds represented by general formula (2) are preferred, and among these, 1,3-butanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and polypropylene glycol di(meth)acrylate are more preferred, with 1,3-butanediol di(meth)acrylate being even more preferred. The polymer (X) may contain only one type of constituent unit (B), or it may contain two or more types of constituent units (B).

[0036] The content of constituent unit (B) is preferably 85% by mass or less, more preferably 80% by mass or less, even more preferably 60% by mass or less, particularly preferably 40% by mass or less, and most preferably 20% by mass or more, relative to the total mass of all constituent units constituting the polymer (X). It may also be 0% by mass, 0.1% by mass or more, 0.5% by mass or more, or 1% by mass or more. The above upper and lower limits can be combined arbitrarily. For example, the content of constituent unit (B) is preferably 0 to 85% by mass, more preferably 0.1 to 80% by mass, even more preferably 0.5 to 60% by mass, particularly preferably 0.5 to 40% by mass, and most preferably 1 to 20% by mass. If the content of constituent unit (B) is above the lower limit, the viscosity index improvement ability is further enhanced. If the content of constituent unit (B) is below the upper limit, the solubility in oil is further enhanced. In addition, the polymer (X) is less likely to gel. The content of constituent unit (B) can be calculated from the amount of compound (B), which is the monomer used to introduce constituent unit (B) as a raw material monomer for polymer (X).

[0037] (Constituent unit (C)) Constituent unit (C) is a constituent unit other than constituent unit (A) and constituent unit (B). In other words, constituent unit (C) is a constituent unit derived from a compound other than compound (A) and compound (B) (hereinafter also referred to as "compound (C)").

[0038] Compound (C) is not particularly limited as long as it can copolymerize with at least one of compound (A) and compound (B). Examples of compound (C) include vinyl cyanide monomers such as acrylonitrile and methacrylonitrile; aromatic vinyl monomers such as styrene, α-methylstyrene, and α-ethylstyrene; vinyl ether monomers such as vinyl methyl ether and vinyl ethyl ether; carboxylic acid vinyl monomers such as vinyl acetate and vinyl butyrate; olefin monomers such as ethylene, propylene, and isobutylene; vinyl halogenated monomers such as vinyl chloride and vinylidene chloride; maleimide monomers such as maleimide, N-phenylmaleimide, N-cyclohexylmaleimide, and N-methylmaleimide; and carboxyl group-containing monomers such as itaconic acid, crotonic acid, maleic acid, and fumaric acid. The polymer (X) may contain only one type of constituent unit (C) or may contain two or more types of constituent units (B).

[0039] The content of constituent unit (C) is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, particularly preferably 8% by mass or less, and may also be 0% by mass, based on the total mass of all constituent units that make up the polymer (X). If the content of constituent unit (C) is below the above upper limit, the solubility in oil is further improved. The content of constituent unit (C) can be calculated from the amount of compound (C), which is a monomer used to introduce constituent unit (C) as a raw material monomer for polymer (X).

[0040] (Physical properties of polymer (X)) The weight-average molecular weight of polymer (X) is preferably 1000 or more, more preferably 1000 to 100000, even more preferably 5000 to 50000, even more preferably 10000 to 45000, especially preferably 15000 to 40000, particularly preferably 18000 to 35000, and most preferably 20000 to 30000. If the weight-average molecular weight of polymer (X) is above the lower limit, the viscosity index improvement ability is further enhanced. If the weight-average molecular weight of polymer (X) is below the upper limit, the oil solubility and shear stability are further enhanced.

[0041] The number-average molecular weight of polymer (X) is preferably 5,000 to 50,000, more preferably 7,000 to 40,000, even more preferably 8,000 to 30,000, particularly preferably 9,000 to 25,000, and even more preferably 10,000 to 20,000. If the weight-average molecular weight of polymer (X) is above the lower limit, the viscosity index improvement ability is further enhanced. If the weight-average molecular weight of polymer (X) is below the upper limit, the solubility in oil and shear stability are further enhanced.

[0042] (Method for manufacturing polymer (X)) Polymer (X) is obtained by polymerizing compound (A). Polymer (X) is preferably produced by polymerizing compound (A), compound (B), and optionally compound (C). The polymerization method is not particularly limited, and known methods can be used, such as solution polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization. Among these, solution polymerization is preferred from the viewpoint of compatibility with lubricating oil additives. That is, it is preferable to produce the polymer (X) in a polymerization solvent. The polymer (X) obtained by solution polymerization is obtained in the form of a polymer solution dissolved in the polymerization solvent. The following describes in detail an example of a method for producing polymer (X) by solution polymerization.

[0043] Polymer (X) can be produced by polymerizing monomer components (M) containing compound (A) in a polymerization solvent using a known solution polymerization method. The monomer component (M) preferably contains at least one selected from the group consisting of isoprene, myrcene, and β-farnesene, more preferably contains at least one of myrcene and β-farnesene, and even more preferably contains myrcene. Preferably, the monomer component (M) further comprises compound (B) in addition to compound (A). The monomer component (M) may further contain compound (C) in addition to compound (A), if necessary.

[0044] The content of compound (A) is preferably 15 to 100% by mass, more preferably 20 to 99.9% by mass, even more preferably 40 to 99.5% by mass, particularly preferably 60 to 99.5% by mass, and most preferably 80 to 99% by mass, relative to the total mass of monomer component (M). The content of compound (B) is preferably 0 to 85% by mass, more preferably 0.1 to 80% by mass, even more preferably 0.5 to 60% by mass, particularly preferably 0.5 to 40% by mass, and most preferably 1 to 20% by mass, relative to the total mass of monomer component (M). The content of compound (C) is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, particularly preferably 8% by mass or less, and may also be 0% by mass, based on the total mass of monomer component (M).

[0045] As the polymerization solvent, known solvents used in solution polymerization can be used, but from the viewpoint of compatibility with lubricating oil additives, it is preferable to use a base oil. When a base oil is used as the polymerization solvent in the production of polymer (X), the polymer (X) produced in the base oil and the base oil can be used as lubricating oil additives.

[0046] Examples of base oils include bio-based base oils synthesized from vegetable oils, mineral-based base oils refined from crude oil (hereinafter also simply referred to as "mineral oil"), and chemically synthesized synthetic oils (hereinafter also referred to as "synthetic chemical oil").

[0047] Bio-based base oil is a base oil containing biomass-derived carbon, preferably containing 30% by mass or more of biomass-derived carbon relative to the total mass of the base oil, more preferably 50% by mass or more, even more preferably 80% by mass or more, and even more preferably 95% by mass or more. Bio-based base oil containing biomass-derived carbon is also called "biomass base oil". Examples of vegetable oils used as raw materials for bio-based base oils include palm oil, coconut oil, soybean oil, rapeseed oil, and mixtures thereof. Commercially available bio-based base oils can be used. Examples include API Group III base oils such as Novvi's "SynNova4" and "SynNova9". Bio-based base oils may be used individually or in combination of two or more types.

[0048] Examples of mineral-based base oils include paraffinic oils, naphthenic oils, and aromatic oils. Commercially available mineral-based base oils can be used. Examples include API Group III base oils such as "YUBASE3" manufactured by SK Lubricants, and API Group III Plus base oils such as "YUBASE4" manufactured by SK Lubricants. Mineral-based base oils may be used individually or in combination of two or more types.

[0049] Examples of synthetic oils include aliphatic hydrocarbon oils such as polyalphaolefins (PAO) and polybutene; aromatic hydrocarbon oils such as alkylbenzenes and alkylnaphthalenes; ester oils such as polyol esters and phosphate esters; ether oils such as polyphenyl ethers; polyalkylene glycol oils; and silicone oils. Commercially available synthetic oils can be used. For example, "DURASYN170" manufactured by INEOS Oligomers is one such product. Synthetic oils may be used individually or in combination of two or more types.

[0050] The polymerization solvent may be used alone or in combination of two or more types. From the perspective of reducing environmental impact and building a carbon-recycling society, bio-based base oils are preferred as polymerization solvents. In other words, it is preferable that the polymerization solvent contains bio-based base oils. As a polymerization solvent, in addition to bio-based base oil, at least one of mineral-based base oil and synthetic oil may be used in combination. As mineral-based base oil or synthetic oil, paraffin-based oils such as YUBASE4 and DURASYN170 are preferred from the viewpoint of improving viscosity index.

[0051] For polymerization of the monomer component (M), it is preferable to use a radical polymerization initiator. Examples of radical polymerization initiators include organic peroxides such as t-butyl peroxypivalate, o-methylbenzoyl peroxide, bis-3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, cyclohexanone peroxide, benzoyl peroxide, methyl ethyl ketone peroxide, dicumyl peroxide, lauroyl peroxide, diisopropylbenzene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, t-butyl peroxy-2-ethylhexanoate, and 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate; and azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile). Among these, organic peroxides are preferred, and among them, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate is particularly preferred. Radical polymerization initiators may be used individually or in combination of two or more.

[0052] The polymerization temperature is preferably 40 to 150°C, and more preferably 80 to 130°C. The polymerization time is preferably 1 to 24 hours, and more preferably 5 to 15 hours.

[0053] <Solvent (Y)> The solvent (Y) contains a bio-based base oil. In addition to the bio-based base oil, solvent (Y) may further contain solvents other than the bio-based base oil (hereinafter also referred to as "other solvents"), as long as they do not impair the effects of the present invention.

[0054] Examples of bio-based base oils include the bio-based base oils mentioned earlier in the description of the manufacturing method of Polymer(X). Other solvents include base oils other than bio-based base oils, such as mineral base oils and synthetic oils. Examples of mineral base oils and synthetic oils include the mineral base oils and synthetic oils that were previously exemplified in the description of the method for producing polymer (X), respectively.

[0055] The content of bio-based oil in solvent (Y) is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, particularly preferably 25% by mass or more, and may also be 100% by mass, 90% by mass or less, 80% by mass or less, 70% by mass or less, or 60% by mass or less. The above upper and lower limits can be combined arbitrarily. For example, the content of bio-based oil may be 10-100% by mass, 15-100% by mass, 20-100% by mass, 25-100% by mass, 25-90% by mass, 25-80% by mass, 25-70% by mass, or 25-60% by mass. If the content of bio-based oil is above the above lower limit, the viscosity index improvement ability will be further enhanced. In addition, it can reduce the environmental burden and tends to facilitate the construction of a carbon-recycling society.

[0056] The content of other solvents in solvent (Y) is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, and particularly preferably 75% by mass or less, and may also be 0% by mass, 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more. The above upper and lower limits can be combined arbitrarily. For example, the content of other solvents may be 0 to 90% by mass, 0 to 85% by mass, 0 to 80% by mass, 0 to 75% by mass, 10 to 75% by mass, 20 to 75% by mass, 30 to 75% by mass, or 40 to 75% by mass.

[0057] <Arbitrary component (Z)> Examples of optional components (Z) include detergents, dispersants, antioxidants, oiliness improvers, friction and wear modifiers, extreme pressure agents, defoamers, anti-emulsifiers, corrosion inhibitors, pour point depressants, rust inhibitors, emulsifiers, and antifungal agents. The optional component (Z) may be used alone or in combination of two or more types.

[0058] <Content> The polymer (X) content is preferably 0.1 to 99.9% by mass, more preferably 1 to 90% by mass, and even more preferably 2 to 70% by mass, relative to the total mass of the lubricating oil additive. If the polymer (X) content is above the lower limit, the viscosity index improvement ability is further enhanced. If the polymer (X) content is below the upper limit, a significant increase in the viscosity of the lubricating oil can be suppressed.

[0059] The solvent (Y) content is preferably 0.1 to 99.9% by mass, more preferably 10 to 99% by mass, and even more preferably 30 to 98% by mass, relative to the total mass of the lubricating oil additive. If the solvent (Y) content is above the lower limit, a significant increase in the viscosity of the lubricating oil can be suppressed. If the solvent (Y) content is below the upper limit, the viscosity index improvement ability is further enhanced.

[0060] The total content of polymer (X) and solvent (Y) is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may also be 100% by mass, based on the total mass of the lubricating oil additive.

[0061] <Method for manufacturing lubricating oil additives> Lubricating oil additives are obtained by mixing a polymer (X), a solvent (Y), and optionally an optional component (Z). For example, when a polymer (X) is produced by solution polymerization using a base oil as the polymerization solvent, the polymer (X) produced in the polymerization solvent can be used together with the polymerization solvent as a lubricating oil additive. Therefore, it is preferable to obtain the lubricating oil additive by producing the polymer (X) in the polymerization solvent. In other words, it is preferable that the method for producing the lubricating oil additive includes a step of producing the polymer (X) in the polymerization solvent.

[0062] Furthermore, when at least a bio-based base oil is used as the polymerization solvent, the polymer solution obtained by solution polymerization, in which the polymer (X) is dissolved in a polymerization solvent containing the bio-based base oil, may be used directly as a lubricating oil additive. In this case, the polymerization solvent corresponds to the solvent (Y) in the lubricating oil additive. Alternatively, the polymer solution may be further diluted with solvent (Y) as needed before being used as a lubricating oil additive. The solvent (Y) used for dilution may be a bio-based base oil or another solvent. In this case, the polymerization solvent and the solvent (Y) used for dilution correspond to the solvent (Y) in the lubricating oil additive. Furthermore, when using a base oil other than a bio-based base oil as the polymerization solvent, the lubricating oil additive can be produced by mixing the polymer solution obtained by solution polymerization with the bio-based base oil. In this case, the polymerization solvent and the bio-based base oil correspond to the solvent (Y) in the lubricating oil additive.

[0063] <Application> Lubricant additives are suitable as additives for various lubricants used in industrial machinery, robots, automobiles, and other mobility applications, such as engine oil, gear oil, hydraulic fluid, drivetrain lubricant, and automatic transmission fluid. Specific examples of additives added to lubricating oil include friction reducers such as oiliness improvers, extreme pressure agents, anti-wear agents, and friction modifiers, as well as antioxidants, viscosity index improvers, pour point depressants, detergent dispersants, corrosion inhibitors, rust inhibitors, defoamers, emulsifiers, antifungal agents, and anti-emulsifiers. Because the lubricating oil additive of the present invention has a high viscosity index improving effect, it is particularly suitable as a viscosity index improver for lubricating oils. Furthermore, the lubricating oil additive of the present invention can also be suitably used as a friction reducing agent, such as a friction modifier.

[0064] [Viscosity index improver] The viscosity index improver according to the present invention includes the lubricating oil additive of the present invention described above. In addition to the lubricating oil additive of the present invention, the viscosity index improver may further contain, if necessary, components other than the lubricating oil additive of the present invention (hereinafter also referred to as "optional components"), as long as they do not impair the effects of the present invention. Optional components include the optional component (Z) mentioned earlier in the explanation of lubricating oil additives. The optional components may be used individually or in combination of two or more.

[0065] Viscosity index improvers are desirable if their kinematic viscosity increase is greater at high temperatures and smaller at low temperatures. Generally, viscosity index improvers made of (meth)acrylate polymers are known to form a fine particulate structure without completely dissolving at low temperatures, and as the temperature rises, their solubility improves, causing the polymer chains to expand and exhibit the aforementioned functions. The viscosity index, calculated from the kinematic viscosity at low temperatures (e.g., 40°C) and high temperatures (e.g., 100°C), is used as an indicator of the performance of viscosity index improvers.

[0066] The viscosity index is a value measured in accordance with JIS K 2283:2000, and a higher value indicates less viscosity change with temperature. Furthermore, in recent years, viscosity index improvers are required to have even higher viscosity values ​​under high temperature (150°C) and high shear conditions (HTHS150°C viscosity). Therefore, it is preferable that the viscosity improver does not completely dissolve even at 100°C and is expected to continue to improve viscosity at higher temperatures. The dissolution state at 100°C can be evaluated, for example, by small-angle X-ray scattering (SAXS) measurement.

[0067] The viscosity index improver contains the lubricating oil additive of the present invention and therefore exhibits excellent viscosity index improvement capabilities. Specifically, the viscosity index measured by the method described in the examples below tends to be 165 or higher. If the viscosity index is above the above lower limit, fuel consumption of vehicles and the like can be reduced.

[0068] The content of the lubricating oil additive is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may also be 100% by mass, relative to the total mass of the viscosity index improver. Furthermore, the total content of polymer (X) and solvent (Y) in the viscosity index improver is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may also be 100% by mass, based on the total mass of the viscosity index improver.

[0069] [Friction modifier] The friction modifier according to the present invention includes the lubricating oil additive of the present invention described above. In addition to the lubricating oil additive of the present invention, the friction modifier may further contain, if necessary, components other than the lubricating oil additive of the present invention (hereinafter also referred to as "optional components"), as long as they do not impair the effects of the present invention. Optional components include the optional component (Z) mentioned earlier in the explanation of lubricating oil additives. The optional components may be used individually or in combination of two or more.

[0070] The content of the lubricating oil additive is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may also be 100% by mass, relative to the total mass of the friction modifier. Furthermore, the total content of polymer (X) and solvent (Y) in the friction modifier is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may also be 100% by mass, based on the total mass of the viscosity index improver.

[0071] [Lubricating oil composition] The lubricating oil composition according to the present invention contains the above-mentioned lubricating oil additive of the present invention. The lubricating oil composition may further contain lubricating oil in addition to the lubricating oil additive of the present invention. In addition to the lubricating oil additive of the present invention, the lubricating oil composition may further contain, if necessary, components other than the lubricating oil additive of the present invention (hereinafter also referred to as "optional components"), as long as they do not impair the effects of the present invention.

[0072] Examples of lubricants include the base oils mentioned earlier in the description of the method for producing polymer (X). Lubricating oil may be used individually or in combination of two or more types.

[0073] Optional components include the optional component (Z) mentioned earlier in the explanation of lubricating oil additives. Furthermore, the lubricating oil composition may optionally contain viscosity index improvers and friction reducers other than the lubricating oil additive of the present invention, as long as they do not impair the effects of the present invention. For example, friction reducers other than the lubricating oil additive of the present invention 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 molybdenum dithiocarbamate. The optional components may be used individually or in combination of two or more.

[0074] The lubricating oil composition may 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.).

[0075] The content of polymer (X) 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 the total mass of the lubricating oil composition. If the content of polymer (X) is above the lower limit, the viscosity index of the lubricating oil composition is sufficiently improved. In addition, there is a tendency for the friction reduction effect to be more easily obtained. If the content of polymer (X) is below the upper limit, the kinematic viscosity of the lubricating oil composition at low temperatures is suppressed, and fuel efficiency is improved.

[0076] The lubricating oil composition is suitable for use as various lubricants, such as engine oil, gear oil, hydraulic oil, drivetrain lubricant, and automatic transmission oil, in industrial machinery, robots, automobiles, and other mobility applications. [Examples]

[0077] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not exceed the spirit of the invention, and various modifications are possible as long as they do not depart from the spirit of the invention. The measurement and evaluation methods are shown below.

[0078] <Calculation of the content of constituent units> The content of each constituent unit in polymer (X) was calculated from the amount of monomer used. The content of constituent unit (A) relative to the total mass of polymer (X) was calculated from the amount of myrcene equivalent to compound (A) charged. The content of constituent unit (B) relative to the total mass of polymer (X) was calculated from the amount of polypropylene glycol monomethacrylate equivalent to compound (B) charged.

[0079] <Measurement of weight-average molecular weight (Mw) and number-average molecular weight (Mn)> The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of polymer (X) were determined by GPC (gel permeation chromatography) in terms of molecular weight on a standard polystyrene basis. Specifically, a tetrahydrofuran solution of the polymer solution was prepared, injected into an apparatus equipped with the separation column shown below, and the molecular weight of polymer (X) was measured under the measurement conditions shown below. The weight-average molecular weight (Mw) and number-average molecular weight (Mn) were then calculated in terms of standard polystyrene basis. • Device: Product name "HLC-8220" manufactured by Tosoh Corporation. • Separation column: Product name "TSK-GEL SUPER HM-H" manufactured by Tosoh Corporation, exclusion limit molecular weight = 4 × 10⁻⁶ 8 Inner diameter 6.0 mm, length 150 mm, • Detectors: RI (differential refractometer), UV, • Eluent: Tetrahydrofuran (THF) ·Flow rate: 0.600ml / min, • Sample concentration: 0.02 g / 10 mL Column temperature: 40°C.

[0080] <Evaluation of solubility> The polymer solution was further diluted with a base oil (SK Lubricants Co., Ltd., product name "YUBASE4", API standard Group III plus mineral base oil) to a polymer (X) concentration of 5% by mass. The transparency of the diluted solution was visually confirmed, and the solubility of polymer (X) in the base oil was evaluated according to the following evaluation criteria. ○: It is transparent. ×: Opaque or insoluble precipitates are present.

[0081] <Measurement of Shear Stability Index (SSI)> The kinematic viscosity (Vk40) at 40°C and (Vk100) at 100°C of the polymer solution was measured in accordance with JIS K 2283:2000. Subsequently, the sample was subjected to shearing for 60 minutes in accordance with the ultrasonic shear stability JASO method (JASO M347), and the kinematic viscosity (Vk40) at 40°C and (Vk100) at 100°C was measured again. The shear stability index (SSI) at 40°C and 100°C was calculated using the following formulas, with A being the kinematic viscosity before the shear test, B being the kinematic viscosity after the test, and C being the kinematic viscosity of the base oil alone. Shear Stability Index (SSI) = (AB) / (AC) × 100

[0082] <Measurement of Viscosity Index (VI)> The kinematic viscosity (Vk40) at 40°C and (Vk100) at 100°C were measured for the polymer solution in accordance with JIS K 2283:2000. Using the obtained "Vk40" and "Vk100," the viscosity index (VI) was calculated in accordance with JIS K 2283:2000. The viscosity index is a physical property that represents the temperature dependence of the viscosity of the lubricating oil.

[0083] <Measurement of the coefficient of friction (COF)> A lubricating oil additive was applied to a φ24 × 7.9 mm SUJ-2 disc, and the coefficient of friction was measured using a φ10 mm SUJ-2 ball with a vibration friction and wear tester (SRV tester) under the conditions of a test temperature of 40°C, an amplitude of 1 mm, and a frequency of 50 Hz. For the first 30 seconds of the test, the coefficient of friction was measured with a load of 50 N, and after 30 seconds, the load was changed to 200 N and the coefficient of friction was measured again. The average value of the coefficient of friction measured during the test period of 50 to 60 minutes was calculated and defined as the COF (Coefficient of Friction). If the disc wore down rapidly and the coefficient of friction increased sharply immediately after the start of the test, causing the test to stop, it was classified as "burnout."

[0084] [Example 1] In a dried Schlenk tube, bio-based base oil (manufactured by Novvi, trade name "SynNova4"), 98 parts by mass of myrcene (manufactured by Yasuhara Chemical Co., Ltd.), and 2 parts by mass of polypropylene glycol monomethacrylate (manufactured by NOF Corporation, trade name "PP-800") were charged as base oils. After thoroughly purging the Schlenk tube with nitrogen, the liquid temperature was raised to 100°C. Next, 10.0 parts by mass of 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate (manufactured by NOF Corporation, trade name "Perocta O") was added as a radical polymerization initiator, and the mixture was reacted for 10 hours to obtain a polymer solution containing 7% by mass of polymer (X), which was used as a lubricating oil additive. The molecular weight, shear stability index, viscosity index, and friction coefficient of the polymer (X) were measured for the obtained polymer solution. Furthermore, the solubility of the polymer solution was evaluated by diluting it with a base oil. The results are shown in Table 1.

[0085] [Examples 2-10, Comparative Examples 1-2] A polymer solution was prepared in the same manner as in Example 1, except that the amounts of myrcene and polypropylene glycol monomethacrylate were changed, and the composition (type and proportion) of the base oil was changed as shown in Tables 1 and 2, so that the content of constituent units (A) and (B) constituting polymer (X) was as shown in Tables 1 and 2. Various measurements and evaluations were then performed. The results are shown in Tables 1 and 2.

[0086] [Comparative Example 3] We used "YUBASE4," a product manufactured by SK Lubricants, as a lubricant additive and measured its shear stability index, viscosity index, and friction coefficient. We also diluted YUBASE4 with a base oil and evaluated its solubility. The results are shown in Table 2.

[0087] [Table 1]

[0088] [Table 2]

[0089] The abbreviations used in Tables 1 and 2 are as follows: PP-800: Polypropylene glycol monomethacrylate (manufactured by NOF Corporation). • SynNova4: A hydrocarbon-based bio-based oil (manufactured by Novvi) conforming to API Group III standards. • SynNova9: A hydrocarbon-based bio-based oil (manufactured by Novvi) conforming to API Group III standards. • YUBASE4: Mineral-based base oil conforming to API Group III Plus standards (manufactured by SK Lubricants). Note that the base oil compositions in Tables 1 and 2 are values ​​(mass%) when the total base oil is considered to be 100% by mass. Also, "polymer addition amount" refers to the content (mass%) of polymer (X) relative to the total mass of the polymer solution.

[0090] As is clear from Tables 1 and 2, the polymer solutions obtained in each example, which are lubricating oil additives, exhibited excellent solubility in the base oil, as well as good shear stability and viscosity index. Furthermore, in the lubricating oil additives obtained in each example, it was confirmed that the polymer (X) was dissolved in the base oil and not separated by visual inspection. On the other hand, the lubricating oil additive, which is a polymer solution obtained in Comparative Example 1 that does not contain a bio-based base oil, and YUBASE4 used in Comparative Example 3, had lower viscosity indices compared to the lubricating oil additives obtained in each example. In Comparative Example 2, where the content of constituent unit (A) was less than 15% by mass relative to the total mass of all constituent units of polymer (X), the polymer solution obtained had low solubility of polymer (X) in the base oil, and precipitate formed in the base oil, making it impossible to measure the shear stability index, viscosity index, and friction coefficient. [Industrial applicability]

[0091] The lubricating oil additive of the present invention exhibits excellent shear stability index, viscosity index improvement ability, and oil solubility, making it suitable as an additive for various lubricating oils such as engine oil, gear oil, hydraulic oil, drivetrain lubricating oil, and automatic transmission oil used in industrial machinery, robots, automobiles, and other mobility applications.

Claims

1. A lubricating oil additive comprising a maintenance agent and a solvent, The polymer includes a constituent unit (A) derived from a compound represented by the following general formula (1), The content of the constituent unit (A) is 15% by mass or more with respect to the total mass of all constituent units that make up the polymer. At least a portion of the polymer is dissolved in the solvent, A lubricating oil additive comprising the aforementioned solvent, which contains a bio-based base oil. 【Chemistry 1】 (In general formula (1), R １ is C ｎ H ２ｎ＋ｍ The base is represented by , where n is an integer from 1 to 30, m is one of -3, -1, or 1, and 2n + m is an integer greater than or equal to 3.

2. The lubricating oil additive according to claim 1, wherein the content of the bio-based base oil is 10% by mass or more relative to the total mass of the solvent.

3. The lubricating oil additive according to claim 1, wherein the weight-average molecular weight of the polymer is 1000 or more.

4. The lubricating oil additive according to claim 1, wherein in the general formula (1), n ​​is an integer from 2 to 11, m is -3 or -1, and 2n + m is an integer from 3 to 19.

5. The lubricating oil additive according to claim 4, wherein in the general formula (1), n ​​is an integer from 6 to 11 and m is -3 or -1.

6. In the above general formula (1), R １ is C ６ H １１ The lubricating oil additive according to claim 5, wherein the group is represented by .

7. The lubricating oil additive according to claim 1, wherein the constituent unit (A) is at least one constituent unit selected from the group consisting of a structural unit derived from isoprene, a structural unit derived from myrcene, and a constituent unit derived from β-farnesene.

8. The lubricating oil additive according to claim 1, wherein the polymer further comprises a constituent unit (B) derived from a (meth)acryloyl group-containing compound.

9. A viscosity index improver comprising the lubricating oil additive described in any one of claims 1 to 8.

10. A friction modifier comprising the lubricating oil additive described in any one of claims 1 to 8.

11. A lubricating oil composition comprising the lubricating oil additive according to any one of claims 1 to 8.

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