Lubricant additives

Abstract

To provide a lubricant additive that has a constitutional unit derived from a plant-derived monomer and, when added to oil, shows excellent abilities to improve viscosity indexes and dissolve in oil.SOLUTION: A lubricant additive contains a copolymer containing a constitutional unit (a) derived from a compound represented by the formula (1) and a constitutional unit (b) derived from alkyl (meth)acrylate. (In the formula (1), R1 is a C1-26 hydrocarbon group).SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a lubricating oil additive. [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.

[0003] The copolymer disclosed in Patent Document 1, which consists of structural units derived from a conjugated diene and structural units derived from an aromatic vinyl compound, is used as a viscosity index improver for lubricating oils. The alkyl (meth)acrylate copolymer disclosed in Patent Document 2 is also used as a viscosity index improver for lubricating oils. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2014 / 142001 [Patent Document 2] Japanese Patent Publication No. 2017-197728 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The viscosity index improver disclosed in Patent Document 1 has the problem that its solubility in oil decreases when it contains a large amount of constituent units derived from aromatic vinyl compounds. The copolymer disclosed in Patent Document 2 is excellent at improving the viscosity index of lubricating oils, but it uses petroleum-derived monomers as raw materials, which does not meet recent societal demands. In order to build a carbon-recycling society, there is a need for the development of different types of viscosity index improvers that use plant-derived monomers and have excellent effects in this regard.

[0006] The present invention aims to provide a lubricating oil additive that has constituent units derived from plant-derived monomers and, when added to oil, exhibits excellent viscosity index improvement and oil solubility. The plant-derived monomer can be confirmed by measuring the radiocarbon concentration. [Means for solving the problem]

[0007] To solve the above problems, the present invention encompasses the following embodiments.

[0008] [1]: A lubricating oil additive containing a copolymer comprising a constituent unit a derived from a compound represented by the following formula (1) and a constituent unit b derived from an alkyl (meth)acrylate.

[0009] [ka]

[0010] (In formula (1), R 1 (A hydrocarbon group has 1 to 26 carbon atoms.)

[0011] [2]: The lubricating oil additive according to [1], wherein the alkyl group in the constituent unit b derived from the alkyl (meth)acrylate has 2 to 32 carbon atoms.

[0012] [3]: The lubricating oil additive according to [1] or [2], wherein the constituent unit a comprises at least one of a structural unit derived from isoprene, a structural unit derived from myrcene, and a constituent unit derived from farnesene.

[0013] [4]: The lubricating oil additive according to [3], wherein the constituent unit a is at least one of a constituent unit derived from myrcene and a constituent unit derived from farnesene.

[0014] [5]: The lubricating oil additive according to [4], wherein the constituent unit a is a constituent unit derived from myrcene.

[0015] [6]: The lubricant additive according to any one of [1] to [5], wherein the content of the structural unit a in 100% by mass of all the structural units of the copolymer is 1 to 50% by mass, and the content of the structural unit b is 50 to 99% by mass.

[0016] [7]: The lubricant additive according to any one of [1] to [6], wherein the weight average molecular weight of the copolymer is 5,000 to 200,000. [Advantages of the Invention]

[0017] The copolymer contained in the lubricant additive of the present invention can be produced from plant-derived monomers, and the lubricant additive of the present invention containing this copolymer exhibits excellent viscosity index improvement ability and oil solubility when added to lubricating oil. [Embodiments for Carrying Out the Invention]

[0018] Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is an example of the embodiments of the present invention, and the present invention is not limited to these contents, and various modifications can be made and implemented within the scope of the gist.

[0019] [Explanation of Terms] In this specification, the following definitions of terms are adopted. The "structural unit" means a unit that constitutes a polymer derived from a monomer, that is, a structural unit formed by polymerization of a monomer, or a structural unit in which a part of the structural unit is converted into another structure by modifying the polymer. The "copolymer" according to the present invention means a polymer containing the structural unit a and the structural unit b derived from an alkyl (meth) acrylate. Here, "(meth) acrylate" means one or both of acrylate and methacrylate. In this specification, the "weight average molecular weight" and the "number average molecular weight" mean the weight average molecular weight and the number average molecular weight in terms of standard polystyrene measured by gel permeation chromatography (GPC) method.

[0020] The lubricant additive of the present invention is a lubricant additive containing a copolymer (hereinafter, may be referred to as "the copolymer of the present invention") containing a structural unit a derived from a compound represented by the following formula (1) and a structural unit b derived from an alkyl (meth) acrylate. The structural unit a derived from the compound represented by the following formula (1) is preferably derived from a monomer obtained from a plant.

[0021]

Chemical formula

[0022] In formula (1), R 1 is a hydrocarbon group having 1 to 26 carbon atoms. The hydrocarbon group preferably contains no heteroatom. The hydrocarbon group is preferably a group represented by at least one selected from C n H 2n+1 , C n H 2n-1 and C n H 2n-3 (n is an integer of 1 to 26). More preferably, the hydrocarbon group is at least one selected from CH3, C6H 11 , C 11 H 19 .

[0023] The copolymer of the present invention contains the structural unit a and the structural unit b as essential structural units, but may also contain other structural units (hereinafter, may be referred to as "other structural units c") other than the structural unit a and the structural unit b.

[0024] [Structural units of the copolymer] Hereinafter, the structural unit a, the structural unit b, and the other structural unit c constituting the copolymer of the present invention will be described in detail.

[0025] [Structural unit a] The copolymer of the present invention contains a constituent unit a derived from the compound represented by formula (1) above. Preferably, the constituent unit a is derived from at least one of isoprene, myrcene, and farnesene. The copolymer of the present invention may contain only one type of constituent unit a, or it may contain two or more types. From the viewpoint of handling during polymerization, constituent unit a is preferably a constituent unit derived from at least one of myrcene and farnesene, and from the viewpoint of raw material cost, it is more preferably a constituent unit derived from myrcene. Both of these are available as plant-derived monomers, which is preferable from the viewpoint of building a carbon-recycling society.

[0026] Assuming the total amount of all constituent units of the copolymer of the present invention is 100% by mass, the lower limit of the content of constituent unit a is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more, from the viewpoint of solubility in oil and from the viewpoint of including plant-derived raw materials. The upper limit of the content of constituent unit a is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, from the viewpoint of improving the viscosity index. The ratio of constituent unit a to the total amount of all constituent units of the copolymer (100% by mass) can be calculated from the amount of monomer used to introduce constituent unit a as a raw material monomer for the copolymer of the present invention.

[0027] <Constituent unit b> The copolymer of the present invention contains a constituent unit b derived from alkyl (meth)acrylate. Examples of this alkyl (meth)acrylate-derived constituent unit b include (meth)acrylates of linear or branched alkyl alcohols such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, propyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, dodecyl (meth)acrylate, and tridecyl (meth)acrylate; and (meth)acrylates of cyclic alkyl alcohols such as cyclohexyl (meth)acrylate.

[0028] In particular, from the viewpoint of improving the viscosity index and solubility in oil of the oil, it is preferable that the lower limit of the number of carbon atoms of the alkyl group in the constituent unit b derived from alkyl (meth)acrylate is 2 or more, more preferably 4 or more, even more preferably 6 or more, and especially preferably 8 or more. The upper limit of the number of carbon atoms of the alkyl group in the constituent unit b derived from alkyl (meth)acrylate is preferably 32 or less, more preferably 20 or less, and even more preferably 15 or less. The copolymer of the present invention may contain only one of these alkyl (meth)acrylate-derived constituent unit b, or it may contain two or more.

[0029] Assuming the total amount of all constituent units of the copolymer of the present invention is 100% by mass, the lower limit of the content of constituent unit b derived from alkyl (meth)acrylate is preferably 50% by mass or more, more preferably 60% by mass, and even more preferably 70% by mass or more, from the viewpoint of improving the viscosity index. The upper limit of the content of constituent unit b derived from alkyl (meth)acrylate is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 97% by mass or less. The ratio of constituent unit b to the total amount of all constituent units of the copolymer (100% by mass) can be calculated from the amount of alkyl (meth)acrylate used as a raw material monomer for introducing constituent unit b into the copolymer of the present invention.

[0030] <Other constituent units c> Constituent unit c is a constituent unit other than constituent units a and b described above. Other raw material monomers used to introduce the constituent unit c into the copolymer of the present invention include, for example, vinyl cyanide monomers such as acrylonitrile and methacrylonitrile; 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 halogenate monomers such as vinyl chloride and vinylidene chloride; and maleimide monomers such as maleimide, N-phenylmaleimide, N-cyclohexylmaleimide, and N-methylmaleimide. These may be used individually or in combination of two or more.

[0031] The content of constituent unit c is preferably 60% by mass or less, and more preferably 50% by mass or less, based on 100% by mass of the total constituent units of the copolymer of the present invention. This is because a content of 60% by mass or less of constituent unit c improves the solubility in oil when added to oil.

[0032] [Weight-average molecular weight (Mw) of copolymers] From the viewpoint of improving the viscosity index of oil, the lower limit of the weight-average molecular weight of the copolymer of the present invention is preferably 5,000 or more, and more preferably 10,000 or more. On the other hand, from the viewpoint of solubility in oil, the upper limit of the weight-average molecular weight of the copolymer of the present invention is preferably 200,000 or less, and more preferably 150,000 or less.

[0033] [Number-average molecular weight (Mn) of copolymers] From the viewpoint of improving the viscosity index of oil, the lower limit of the number-average molecular weight of the copolymer of the present invention is preferably 5,000 or more, and more preferably 10,000 or more. On the other hand, from the viewpoint of solubility in oil, the upper limit of the number-average molecular weight of the copolymer of the present invention is preferably 150,000 or less, and more preferably 100,000 or less.

[0034] [Method for producing polymers] There are no particular limitations on the method for producing the copolymer of the present invention. It can be produced by polymerizing the compound represented by formula (1) for introducing constituent unit a, the alkyl (meth)acrylate for introducing constituent unit b, and other monomers for introducing constituent unit c as needed, in the above-mentioned preferred proportions, using known polymerization methods 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. The following describes in detail the method for producing the copolymer of the present invention by solution polymerization.

[0035] <Polymerization initiator> The copolymer of the present invention can be manufactured using known radical polymerization initiators and by known methods. Examples of radical polymerization initiators include organic peroxides and azo compounds. One radical polymerization initiator can be used alone, or two or more can be used in combination.

[0036] Specific examples of suitable organic peroxides used as radical polymerization initiators include 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. Specific examples of azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile). Among these, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate is preferred.

[0037] (Polymerization solvent) In producing the copolymer of the present invention, a general organic solvent can be used as the polymerization solvent, but paraffin oil is preferred from the viewpoint of compatibility with lubricating oil additives. In this case, the copolymer in the paraffin oil used as the polymerization solvent can be used as the lubricating oil additive of the present invention.

[0038] [Lubricant additive] The lubricating oil additive of the present invention may contain, together with the copolymer of the present invention, one or more oil components such as paraffinic, naphthenic, and aromatic oils as a base oil. Furthermore, the lubricating oil additive of the present invention may contain only one type of copolymer of the present invention, or it may contain two or more copolymers with different types and compositions of constituent units a and b.

[0039] The lubricating oil additive of the present invention may contain various additives in addition to the copolymer and base oil of the present invention. Examples of additives other than the copolymer of the present invention include detergents, dispersants, antioxidants, oiliness improvers, friction and wear modifiers, extreme pressure agents, defoamers, anti-emulsifiers, corrosion inhibitors, and the like. The proportion of the copolymer of the present invention in the lubricating oil additive of the present invention is preferably 0.1 to 100% by mass relative to 100% by mass of the total components of the lubricating oil additive. However, when a base oil is included, it is generally preferable to include 0.1 to 50 parts by mass of the copolymer of the present invention per 100 parts by mass of the base oil.

[0040] When the lubricating oil additive of the present invention is used in various lubricating oils such as drivetrain lubricants, automatic transmission fluids, hydraulic fluids, and engine oils, the viscosity index measured by the method described in the Examples section below is preferably in the range of 140 to 250, and more preferably in the range of 150 to 200. When it is within this range, the fuel consumption of vehicles and the like can be reduced when used in the above applications. [Examples]

[0041] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following description.

[0042] <Percentage of constituent units> The proportion of each constituent unit in the copolymer was calculated from the amount of monomer used. The proportion of constituent unit a to 100% by mass of the total constituent units of the copolymer was calculated from the amount of compound represented by formula (1) used. The proportion of constituent unit b to 100% by mass of the total constituent units of the copolymer was calculated from the amount of alkyl (meth)acrylate used.

[0043] <Weight-average molecular weight (Mw) and number-average molecular weight (Mn)> The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the copolymer were determined by GPC (gel permeation chromatography) using molecular weights equivalent to standard polystyrene. The measurement equipment and conditions were as follows: • Equipment: HLC-8420GPC, manufactured by Tosoh Corporation • Separation column: TSK-GEL SUPER HM-H (exclusion limit molecular weight = 4 × 10) 8 ) 6.0mmφ×150mm • Detectors: RI (differential refractometer), UV • Eluent: Tetrahydrofuran (THF) ·Flow rate: 0.600mL / min • Sample concentration: 0.02g / 10mL Column temperature: 40°C

[0044] <Solution state> The transparency of the polymerization solution was visually inspected and evaluated as follows. 〇:Transparent ×: Opaque or containing precipitated insoluble matter.

[0045] <Kinematic viscosity> The kinematic viscosity of the polymerization solution was measured at 40°C and 100°C in accordance with JIS K2283. In Table 1 below, Vk40 represents the kinematic viscosity at 40°C, and Vk100 represents the kinematic viscosity at 100°C.

[0046] <Viscosity index (VI)> The viscosity index of the polymerization solution was measured in accordance with JIS K2283. The viscosity index is a physical property that represents the temperature dependence of the viscosity of a lubricating oil.

[0047] [Example 1] In a dried Schlenk tube, 33.3 parts by mass of lubricating oil base oil (manufactured by SK Lubricants Co., Ltd., trade name: YUBASE4), 80 parts by mass of alkyl methacrylate (manufactured by Mitsubishi Chemical Corporation, trade name: Acryester SL, alkyl group carbon number: 12-13), and 20 parts by mass of myrcene (manufactured by Yasuhara Chemical Co., Ltd.) were charged. After thoroughly purging the Schlenk tube with nitrogen, the temperature was raised to 100°C. Next, 2.2 parts by mass of 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, trade name: Perocta O) was added as a polymerization initiator, and the reaction was allowed to proceed for 10 hours. The resulting polymerization solution was used as a lubricating oil additive, and the various evaluations described above were performed. The results are shown in Table 1.

[0048] [Examples 2-6 and Comparative Examples 1-2] The polymerization solution was obtained in the same manner as in Example 1, using the amounts shown in Table 1. Various evaluations were then performed using the obtained polymerization solution. The results are shown in Table 1.

[0049] [Comparative Example 3] Various evaluations were conducted using only lubricating base oil (manufactured by SK Lubricants Co., Ltd., product name: YUBASE4). The results are shown in Table 1.

[0050] In Table 1, the abbreviations for the raw material monomers are as follows: SLMA: Acryester SL (manufactured by Mitsubishi Chemical Corporation, alkyl group carbon number: 12-13) BMA: Acryester B (manufactured by Mitsubishi Chemical Corporation, n-butyl methacrylate) St: Styrene monomer (manufactured by Nacalai Tesque Co., Ltd.)

[0051] [Table 1]

[0052] As shown in Table 1, Examples 1 to 6, which used the copolymer of the present invention having constituent units a and b, all showed good solubility in the base oil, while Comparative Examples 1 and 2, which did not contain constituent unit b, were insoluble in the base oil. Furthermore, Examples 1 to 6 all showed better kinematic viscosity and viscosity index (VI) compared to Comparative Example 3, which did not use the copolymer. [Industrial applicability]

[0053] The lubricating oil additive of the present invention has excellent viscosity index improvement ability and oil solubility, and is suitable for various lubricating oils such as drivetrain lubricants, automatic transmission fluids, hydraulic fluids, and engine oils.

Claims

1. A lubricating oil additive containing a copolymer comprising a structural unit a derived from a compound represented by the following formula (1) and a structural unit b derived from an alkyl (meth)acrylate, A lubricating oil additive in which the constituent unit a is at least one of a constituent unit derived from myrcene and a constituent unit derived from farnesene. 【Chemistry 1】 (In formula (1), R １ (This refers to a hydrocarbon group with 1 to 26 carbon atoms.)

2. The lubricating oil additive according to claim 1, wherein the number of carbon atoms in the alkyl group in the constituent unit b derived from the alkyl (meth)acrylate is 2 to 32.

3. The lubricating oil additive according to claim 1 or 2, wherein the constituent unit a is a constituent unit derived from myrcene.

4. The lubricating oil additive according to any one of claims 1 to 3, wherein the content of component a is 1 to 50% by mass and the content of component b is 50 to 99% by mass in 100% by mass of the total number of all component units of the copolymer.

5. The lubricating oil additive according to any one of claims 1 to 4, wherein the weight-average molecular weight of the copolymer is 5,000 to 200,000.

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