Oil composition and use of said oil composition

Abstract

The present disclosure relates to an oil composition comprising a base oil and a conjugated-diene-based polymer, wherein the conjugated-diene-based polymer has a number-average molecular weight of 11,000-74,000 and contains butadiene-derived structural units in an amount of 50 mass% or larger with respect to the whole mass of the conjugated-diene-based polymer. The oil composition has a dynamic viscosity at 100°C of 24.0 mm2 / s or less.

Description

Oil compositions and uses of said oil compositions

[0001] The present disclosure relates to an oil composition comprising a base oil and a conjugated diene-based polymer.

[0002] Lubricating oils used as engine oils and automatic transmission fluids contain additives, commonly called viscosity index improvers, to improve their viscosity characteristics. Various polymers, such as olefin copolymers, polymethacrylates, and styrene / hydrogenated diene block polymers, have been investigated as viscosity index improvers.

[0003] Patent Documents 1 and 2 disclose lubricating oils containing low molecular weight 1,4-polybutadiene as a viscosity index improver. Patent Document 3 discloses lubricating oils containing high molecular weight 1,4-polybutadiene mainly composed of cis-1,4 bond units.

[0004] JP 2018-141153 A U.S. Pat. No. 3,312,621 U.S. Pat. No. 3,329,613

[0005] Oil compositions such as lubricating oils are required to have a high viscosity index from the viewpoint of fuel economy. Furthermore, because oil compositions such as lubricating oils are used in environments where they are subject to various influences such as shear stress and oxidation, they are required to have stability against shear stress (hereinafter also referred to as shear stability) and oxidation (hereinafter also referred to as oxidation stability). Furthermore, they are required to have low viscosity at low temperatures so that they can function properly even in low-temperature environments. Although attempts have been made to improve the viscosity index and shear stability, it cannot be said that oil compositions with good oxidation stability and low-temperature viscosity have been sufficiently investigated.

[0006] Therefore, an object of the present disclosure is to provide an oil composition that has good viscosity index and shear stability as well as oxidation stability and low temperature viscosity.

[0007] The present inventors have conducted extensive research to solve the above problems and have completed the present invention. That is, the present disclosure includes the following preferred embodiments: [1] An oil composition comprising a base oil and a conjugated diene polymer, wherein the conjugated diene polymer has a number average molecular weight of 11,000 to 74,000 and contains structural units derived from butadiene in an amount of 50 mass % or more relative to the total amount of the conjugated diene polymer, and the kinematic viscosity of the oil composition at 100°C is 24.0 mm ２ / s or less. [2] The oil composition according to [1], wherein the vinyl content of the conjugated diene polymer is 0 to 30 mol %. [3] The oil composition according to [1] or [2], wherein the iodine value of the conjugated diene polymer is 200 g / 100 g to 500 g / 100 g. [4] The oil composition according to any one of [1] to [3], wherein the conjugated diene polymer is an unmodified polymer. [5] The oil composition according to any one of [1] to [4], wherein the conjugated diene polymer has a molecular weight distribution of 1.0 to 1.5. [6] The oil composition according to any one of [1] to [5], wherein the content of the conjugated diene polymer is 0.1 to 20 mass % based on the total amount of the oil composition. [7] The oil composition has a kinematic viscosity at 100°C of 6.8 mm ２ / s or more. [8] The oil composition according to any one of [1] to [7], wherein the ratio of cis-1,4-bond units to the total amount of 1,4-bond units in the structural units derived from butadiene is 70 mol % or less. [9] The oil composition according to any one of [1] to [8], wherein the base oil is at least one selected from the group consisting of base oils belonging to Groups I, II, III, and IV of the API (American Petroleum Institute) classification.

[10] The oil composition according to any one of [1] to [9], further comprising at least one additive selected from the group consisting of rust inhibitors, antioxidants, surfactants, pour point depressants, detergents / dispersants, metal deactivators, antifoam agents, friction modifiers, extreme pressure agents, and antiwear agents.

[11] The oil composition according to any one of [1] to

[10] , wherein the oil composition is a lubricating oil.

[12] The oil composition according to

[11] , wherein the lubricating oil is a transmission fluid or a hydraulic fluid.

[13] Use of the oil composition according to any one of [1] to

[12] as a lubricating oil.

[0008] The present disclosure also includes the following preferred embodiments:

[14] An oil composition comprising a base oil and a conjugated diene polymer, wherein the conjugated diene polymer contains structural units derived from butadiene in an amount of 50 mass% or more relative to the total amount of the conjugated diene polymer, the conjugated diene polymer has an iodine value of 200 g / 100 g to 500 g / 100 g, the proportion of cis-1,4-bond units relative to the total amount of 1,4-bond units in the structural units derived from butadiene is 70 mol% or less, and the kinematic viscosity of the oil composition at 100°C is 24.0 mm ２ / s or less.

[0009] The oil composition of the present disclosure can provide an oil composition that not only has a good viscosity index and shear stability, but also has good oxidation stability and low-temperature viscosity.

[0010] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the scope of the present disclosure is not limited to the embodiments described herein, and various modifications can be made without departing from the spirit of the present disclosure. Furthermore, in this specification, the expression "x to y" (x and y each represent a number) representing a numerical range means "not less than x and not more than y." Furthermore, when multiple upper and lower limit values ​​are described for a specific parameter, any upper and lower limit values ​​may be combined to form a suitable numerical range. Note that the following explanations regarding the oil compositions of the above embodiments [1] to

[13] also apply to the oil composition of the above embodiment

[14] , unless inconsistent.

[0011] The oil composition of the present disclosure is an oil composition comprising a base oil and a conjugated diene polymer, wherein the conjugated diene polymer has a number average molecular weight of 11,000 to 74,000 and contains structural units derived from butadiene in an amount of 50 mass% or more relative to the total amount of the conjugated diene polymer, and the kinematic viscosity of the oil composition at 100°C is 24.0 mm ２ / s or less.

[0012] (Conjugated Diene Polymer) The conjugated diene polymer contained in the oil composition has a number average molecular weight of 11,000 to 74,000. When the number average molecular weight is 11,000 or more, the thickening property, viscosity index, and low-temperature viscosity are sufficient. When the number average molecular weight is 74,000 or less, the shear stability, oxidation stability, and low-temperature viscosity are sufficient. From the viewpoints of thickening property, viscosity index, shear stability, oxidation stability, and low-temperature viscosity, the number average molecular weight of the conjugated diene polymer is preferably 14,000 to 60,000, more preferably 17,000 to 45,000, even more preferably 20,000 to 35,000, 20,000 to 33,000, 22,000 to 33,000, or 22,000 to 30,000. Note that the number average molecular weight in this specification refers to the number average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

[0013] From the viewpoints of thickening property, shear stability, and oxidation stability, the conjugated diene polymer preferably has a weight average molecular weight of 15,000 to 63,000, more preferably 18,000 to 47,000, and even more preferably 21,000 to 37,000, 21,000 to 35,000, 23,000 to 35,000, or 23,000 to 32,000. Note that the weight average molecular weight in this specification refers to a weight average molecular weight calculated in terms of polystyrene obtained by measurement using gel permeation chromatography (GPC).

[0014] From the viewpoints of thickening property, viscosity index, shear stability, oxidation stability, and low-temperature viscosity, the conjugated diene polymer preferably has a molecular weight distribution of 1.0 to 1.5, more preferably 1.0 to 1.3, even more preferably 1.0 to 1.2, still more preferably 1.0 to 1.1, and particularly preferably 1.0 to 1.07. The molecular weight distribution (Mw / Mn) means the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) in terms of standard polystyrene, determined by GPC measurement.

[0015] The conjugated diene polymer contained in the oil composition contains structural units derived from butadiene in an amount of 50% by mass or more relative to the total amount of the conjugated diene polymer. In other words, the conjugated diene polymer contained in the oil composition contains structural units derived from butadiene in an amount of 50% by mass or more relative to the total amount, which is the sum of the masses of all structural units of the conjugated diene polymer. Here, the conjugated diene polymer is a polymer containing structural units derived from a conjugated diene monomer. Examples of the conjugated diene monomer include at least one selected from the group consisting of butadiene, isoprene, and β-farnesene. The conjugated diene polymer is not particularly limited as long as it contains structural units derived from butadiene in an amount of 50% by mass or more. The conjugated diene polymer may be a homopolymer of butadiene, or a copolymer of butadiene and one or more other conjugated diene monomers. The amount of structural units derived from conjugated diene monomers in the conjugated diene polymer is preferably 80 to 100% by mass, more preferably 90 to 100% by mass, and even more preferably 95 to 100% by mass, based on the total amount of the conjugated diene polymer, from the viewpoints of thickening property, shear stability, and oxidation stability.

[0016] The conjugated diene polymer may have only structural units derived from butadiene, or may have structural units derived from butadiene and one or more structural units derived from other conjugated diene monomers, or may have structural units derived from butadiene and, optionally, other conjugated diene monomers and further other structural units derived from aromatic vinyl compounds, etc. When the conjugated diene polymer is a copolymer, it may be a random copolymer or a block copolymer.

[0017] The amount of the structural units derived from butadiene in the conjugated diene polymer is 50 to 100% by mass, preferably 70 to 100% by mass, more preferably 90 to 100% by mass, even more preferably 95 to 100% by mass, particularly preferably 98 to 100% by mass, and especially preferably 100% by mass, based on the total amount of the conjugated diene polymer, from the viewpoints of viscosity index, shear stability, oxidation stability, and low-temperature viscosity.

[0018] The amount of structural units derived from butadiene in the conjugated diene polymer and the amount of structural units derived from other conjugated diene monomers are １ H-NMR and １３ It can be calculated from the amount of butadiene monomer or conjugated diene monomer in the monomer mixture used in producing the conjugated diene polymer by C-NMR measurement or from the amount of butadiene monomer or conjugated diene monomer in the monomer mixture used in producing the conjugated diene polymer.

[0019] The structural unit derived from butadiene is not particularly limited as long as it is a structural unit derived from the monomer 1,3-butadiene. Examples include 1,2-bond units, 1,4-bond units (cis-1,4-bond units and trans-1,4-bond units), and structural units in which a modifying group is bonded to these. The 1,2-bond units have a vinyl group in the structural unit derived from butadiene. The cis-1,4-bond units and trans-1,4-bond units each have a carbon-carbon double bond moiety in the structural unit derived from butadiene. Furthermore, examples of structural units in which a modifying group is bonded to these include structural units obtained by bonding a modifying group to a moiety derived from a vinyl group in a 1,2-bond unit, and such structural units do not have a vinyl group.

[0020] From the viewpoints of thickening property, viscosity index, shear stability, oxidation stability, low-temperature viscosity, and handleability, the vinyl content of the conjugated diene polymer is preferably 0 to 30 mol%, more preferably 0.5 to 20 mol%, even more preferably 1 to 15 mol%, even more preferably 1 to 12 mol%, and particularly preferably 1 to 10 mol%, relative to the total amount of the conjugated diene polymer. The vinyl content refers to the total mol% of conjugated diene units bonded via 1,2-bonds, 3,4-bonds (in the case of other than farnesene), and 3,13-bonds (in the case of farnesene) (conjugated diene units bonded via bonds other than 1,4-bonds (in the case of other than farnesene) and 1,13-bonds (in the case of farnesene)) relative to 100 mol% of the total of conjugated diene polymer units. When the conjugated diene polymer is polybutadiene, the vinyl content may be the ratio of 1,2-bond units to the total amount of the polybutadiene (the total amount of 1,4-bond units and 1,2-bond units). "Vinyl content" is measured by infrared absorption spectroscopy, １It can be determined by H-NMR measurement or the like, for example, by the method described in the Examples.

[0021] In a preferred embodiment of the present disclosure, the ratio of the amount of 1,4-bond units to the total amount of structural units derived from conjugated diene monomers in the conjugated diene polymer is preferably 30 to 100 mol %, more preferably 50 to 100 mol %, and even more preferably 60 to 100 mol %, based on the total amount of structural units derived from conjugated diene monomers, from the viewpoints of thickening property, viscosity index, shear stability, oxidation stability, low-temperature viscosity, and handleability. The amounts of 1,4-bond units, cis-1,4-bond units, and trans-1,4-bond units are, respectively, １ It can be measured by H-NMR and infrared absorption spectroscopy, specifically by the method described in the Examples.

[0022] In a preferred embodiment of the present disclosure, the ratio of the amount of 1,4-bond units to the total amount of structural units derived from butadiene in the conjugated diene-based polymer is preferably 30 to 100 mol %, more preferably 50 to 100 mol %, and even more preferably 60 to 100 mol %, based on the total amount of structural units derived from butadiene, from the viewpoints of thickening property, viscosity index, shear stability, oxidation stability, low-temperature viscosity, and handleability. The amounts of 1,4-bond units, cis-1,4-bond units, and trans-1,4-bond units are, respectively, １ It can be measured by H-NMR and infrared absorption spectroscopy, specifically by the method described in the Examples.

[0023] In a preferred embodiment of the present disclosure, in the structural units derived from conjugated diene monomers of the conjugated diene polymer, the amount of cis-1,4-bond units relative to the total amount of 1,4-bond units is preferably 70 mol% or less, more preferably 0 to 70 mol%, even more preferably 0.1 to 60 mol%, even more preferably 10 to 50 mol%, and particularly preferably 30 to 45 mol%, from the viewpoints of thickening property, shear stability, and oxidative stability. Furthermore, the amount of trans-1,4-bond units relative to the total amount of 1,4-bond units is preferably 30 mol% or more, more preferably 30 to 100 mol%, even more preferably 40 to 99.9 mol%, even more preferably 50 to 95 mol%, particularly preferably 55 to 80 mol%, and particularly preferably 55 to 70 mol%.

[0024] In a preferred embodiment of the present disclosure, in the butadiene-derived structural units of the conjugated diene polymer, the amount of cis-1,4-bond units relative to the total amount of 1,4-bond units is preferably 70 mol% or less, more preferably 0 to 70 mol%, even more preferably 0.1 to 60 mol%, even more preferably 10 to 50 mol%, and particularly preferably 30 to 45 mol%. Also, the amount of trans-1,4-bond units relative to the total amount of 1,4-bond units is preferably 30 mol% or more, more preferably 30 to 100 mol%, even more preferably 40 to 99.9 mol%, even more preferably 50 to 95 mol%, particularly preferably 55 to 80 mol%, and particularly preferably 55 to 70 mol%.

[0025] In a preferred embodiment of the present disclosure, the amount of 1,2-bond units relative to the total amount of 1,4-bond units and 1,2-bond units in the butadiene-derived structural units of the conjugated diene-based polymer is, from the viewpoint of handleability (viscosity), preferably 0 to 30 mol %, more preferably 0.5 to 20 mol %, even more preferably 1 to 15 mol %, even more preferably 1 to 12 mol %, and particularly preferably 1 to 10 mol %. The amount of 1,2-bond units corresponds to, for example, the amount of vinyl groups in the butadiene-derived structural units. The amount can be determined by measuring the proportion of 1,2-bond units contained in the butadiene structural units by infrared absorption spectroscopy, １It can be calculated by H-NMR measurement or the like, and can be measured, for example, by the method described in the Examples.

[0026] The conjugated diene polymer is preferably an unmodified polymer. In this specification, the term "unmodified polymer" means that the diene polymer does not have any detectable functional groups bonded thereto, such as functional groups selected from the group consisting of carboxylic acid groups (e.g., maleic anhydride, maleic acid, succinic anhydride, succinic acid, etc.), hydroxyl groups, sulfonic acid groups, alkoxysilyl groups, amino groups, imide groups, nitrile groups, and mercapto groups. Whether a polymer is unmodified or not is determined depending on the functional groups, and can be determined by methods such as acid value titration, infrared absorption spectroscopy, １ This can be confirmed by H-NMR measurement, etc. The conjugated diene polymer preferably consists of only carbon and hydrogen.

[0027] In a preferred embodiment, the conjugated diene polymer preferably does not have a terminal hydroxyl group. Whether or not the polymer has a terminal hydroxyl group can be determined by the neutralization titration method of the hydroxyl value according to JIS K 0070-1992, infrared absorption spectroscopy (IR), １ This can be confirmed by H-NMR.

[0028] From the viewpoint of viscosity index and low-temperature viscosity, the conjugated diene polymer is preferably a conjugated diene polymer having a low hydrogenation rate or not being hydrogenated. The hydrogenation rate of the conjugated diene polymer is preferably 0 to 50 mol%, more preferably 0 to 40 mol%, even more preferably 0 to 20 mol%, still more preferably 0 to 10 mol%, particularly preferably 0 to 5 mol%, and especially preferably 0 mol%. The hydrogenation rate of the conjugated diene polymer is determined by calculating the content of carbon-carbon double bonds derived from the conjugated diene compound in the conjugated diene polymer as follows: １ It is a value measured by H-NMR measurement.

[0029] In a preferred embodiment of the present disclosure, the iodine value of the conjugated diene polymer is, from the viewpoint of viscosity index and low-temperature viscosity, preferably 200 g / 100 g to 500 g / 100 g, more preferably 250 g / 100 g to 500 g / 100 g, even more preferably 350 g / 100 g to 500 g / 100 g, still more preferably 400 g / 100 g to 500 g / 100 g, particularly preferably 420 g / 100 g to 500 g / 100 g, and especially preferably 450 g / 100 g to 500 g / 100 g. The iodine value is a value that can be determined in accordance with JIS K 0070:1992, and more specifically, is a value measured according to the method described in the Examples.

[0030] The content of the conjugated diene polymer in the oil composition may be determined depending on the properties such as viscosity required of the oil composition, and is not particularly limited, but is preferably 0.1 to 20 mass%, more preferably more than 0.1 to 20 mass%, even more preferably 0.3 to 20 mass%, still more preferably 0.5 to 15 mass%, and particularly preferably 1.0 to 10 mass%, based on the total amount of the oil composition. If the content of the conjugated diene polymer is not less than the above lower limit, it is preferred from the viewpoint of the viscosity index and low-temperature viscosity of the oil composition, and if it is not more than the above upper limit, it is preferred from the viewpoint of the production cost of the oil composition.

[0031] (Method for Producing Conjugated Diene Polymer) The method for producing the conjugated diene polymer is not particularly limited. For example, it is preferable to produce the conjugated diene polymer by polymerizing butadiene and, if necessary, other monomers copolymerizable with butadiene, for example, by a solution polymerization method.

[0032] As the solution polymerization method, a known method or a method equivalent to a known method can be applied. For example, a butadiene-containing monomer is polymerized in a solvent using a Ziegler catalyst, a metallocene catalyst, or an anionically polymerizable active metal or active metal compound, optionally in the presence of a polar compound.

[0033] Examples of the solvent include aliphatic hydrocarbons such as n-butane, n-pentane, isopentane, n-hexane, n-heptane, and isooctane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, and methylcyclopentane; and aromatic hydrocarbons such as benzene, toluene, and xylene.

[0034] Examples of the anionically polymerizable active metal include alkali metals such as lithium, sodium, and potassium; alkaline earth metals such as beryllium, magnesium, calcium, strontium, and barium; and lanthanoid rare earth metals such as lanthanum and neodymium. Among the anionically polymerizable active metals, alkali metals and alkaline earth metals are preferred, and alkali metals are more preferred.

[0035] The anionically polymerizable active metal compound is preferably an organic alkali metal compound. Examples of the organic alkali metal compound include organic monolithium compounds such as methyllithium, ethyllithium, n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium, and stilbenelithium; polyfunctional organic lithium compounds such as dilithiomethane, dilithionaphthalene, 1,4-dilithiobutane, 1,4-dilithio-2-ethylcyclohexane, and 1,3,5-trilithiobenzene; sodium naphthalene, potassium naphthalene, and the like. Among these organic alkali metal compounds, organic lithium compounds are preferred, and organic monolithium compounds are more preferred.

[0036] The amount of the organic alkali metal compound used can be appropriately determined depending on the target molecular weight of the conjugated diene polymer, but is usually 0.01 to 3 parts by mass per 100 parts by mass of all monomers.

[0037] The above organic alkali metal compounds can also be reacted with a secondary amine such as dibutylamine, dihexylamine, or dibenzylamine to form organic alkali metal amides.

[0038] In anionic polymerization, polar compounds are usually used to adjust the microstructure (e.g., vinyl content) of the unmodified liquid diene polymer without deactivating the reaction. Examples of polar compounds include ether compounds such as dibutyl ether, tetrahydrofuran, and ethylene glycol diethyl ether; tertiary amines such as tetramethylethylenediamine and trimethylamine; alkali metal alkoxides; and phosphine compounds. The polar compound is usually used in an amount of 0.01 to 1,000 moles per mole of the organic alkali metal compound.

[0039] The temperature for solution polymerization is usually in the range of −80 to 150° C., preferably in the range of 0 to 100° C., and more preferably in the range of 10 to 90° C. The polymerization may be carried out in either a batch or continuous manner.

[0040] The polymerization reaction can be terminated by adding a polymerization terminator. Examples of the polymerization terminator include alcohols such as methanol and isopropanol. The resulting polymerization reaction solution is poured into a poor solvent such as methanol to precipitate the conjugated diene polymer, or the polymerization reaction solution is washed with water, separated, and then dried to isolate the conjugated diene polymer.

[0041] (Base Oil) The base oil contained in the oil composition is not particularly limited, and known base oils may be appropriately selected and used depending on the application of the oil composition. Examples of base oils include fuel oils such as middle distillate fuels, synthetic and natural lubricating oils, unrefined oils, and industrial oils. The base oil may be at least one of paraffinic base oils, naphthenic base oils, and aromatic base oils, or at least one of natural oils and synthetically prepared oils. The base oil may also be any of Groups I to V of the API (American Petroleum Institute) classification. From an economic standpoint, the base oil is preferably at least one selected from the group consisting of base oils belonging to Groups I, II, III, and IV of the API (American Petroleum Institute) classification, and more preferably at least one selected from the group consisting of base oils belonging to Groups I, II, and III. Examples of base oils that can be used in the oil composition of the present invention include the base oils described in Japanese Patent No. 5,933,263 and Japanese Patent Application Laid-Open No. 2005-23320. The oil composition may contain one type of base oil as the base oil, or may contain a combination of two or more types of base oil.

[0042] The content of the base oil in the oil composition may be determined depending on the properties such as viscosity required of the oil composition, and is not particularly limited, but may be preferably 50 to 99.9 mass%, more preferably 60 to 99 mass%, even more preferably 70 to 99 mass%, and even more preferably 80 to 98 mass%, based on the total amount of the oil composition. A base oil content of not less than the above lower limit is preferred from the viewpoint of the production cost of the oil composition, and a base oil content of not more than the above upper limit is preferred from the viewpoint of the viscosity index and low-temperature viscosity of the oil composition.

[0043] (Other Components) The oil composition may contain other components (additives) in addition to the conjugated diene polymer and base oil, depending on the properties required of the oil composition. Examples of other components include at least one additive selected from the group consisting of rust inhibitors, antioxidants, surfactants, pour point depressants, detergent-dispersants, metal deactivators, antifoaming agents, friction modifiers, extreme pressure agents, and antiwear agents. The amount of additives that can be contained in the oil composition is not particularly limited, but from the viewpoint of balancing the various required properties and production costs, it is preferably 0 to 20 mass %, more preferably 0 to 15 mass %, even more preferably 0 to 10 mass %, and even more preferably 0 to 6 mass %, based on the total amount of the oil composition.

[0044] (Oil composition) The kinematic viscosity of the oil composition at 100°C is 24.0 mm ２ The kinematic viscosity of the oil composition at 100°C is 6.8 mm / s or less. ２ / s or more. ２ A kinematic viscosity of 6.8 mm / s or less is preferable from the viewpoint of fuel economy. ２ In the present disclosure, the kinematic viscosity is a value measured at 100°C in accordance with JIS K2283:2000. The kinematic viscosity of the oil composition at 100°C is preferably 6.8 to 24.0 mm / s or more. ２ / s, more preferably 7.5 to 18.5 mm ２ / s, more preferably 13.5 to 18.5 mm ２ / s.

[0045] The total amount of the base oil and the conjugated diene polymer contained in the oil composition is preferably 80 to 100 mass%, more preferably 85 to 100 mass%, even more preferably 90 to 100 mass%, and still more preferably 94 to 100 mass%, based on the total amount of the oil composition, from the viewpoints of thickening property, viscosity index, shear stability, oxidation stability, low-temperature viscosity, and handleability.

[0046] The oil composition of the present disclosure has high shear stability. In a preferred embodiment, when a shear test is performed using the oil composition in accordance with CEC-L45-99, the rate of decrease in kinematic viscosity at 100°C from before to after the shear test is preferably 15% or less, more preferably 10% or less, even more preferably 7% or less, still more preferably 5% or less, particularly preferably 3% or less, and extremely preferably 2% or less.

[0047] The oil composition of the present disclosure has high oxidation stability. In a preferred embodiment, when an oxidation stability test is conducted using the oil composition in accordance with JIS K2514-1:2013 at a test temperature of 120°C for a test time of 24 hours, the rate of decrease in kinematic viscosity at 100°C from before to after the oxidation stability test is preferably 10% or less, more preferably 5% or less, even more preferably 3% or less, still more preferably 1% or less, particularly preferably 0.5% or less, and extremely preferably 0.3% or less.

[0048] The oil composition of the present disclosure has high oxidation stability. In a preferred embodiment, when an oxidation stability test is conducted using the oil composition in accordance with JIS K2514-1:2013 at a test temperature of 120°C for 96 hours, the rate of decrease in kinematic viscosity at 100°C from before to after the oxidation stability test is preferably 10% or less, more preferably 5% or less, even more preferably 3% or less, still more preferably 1% or less, particularly preferably 0.5% or less, and extremely preferably 0.3% or less.

[0049] The oil composition of the present disclosure preferably has a high viscosity index, from the viewpoint of using the oil composition over a wide temperature range. In a preferred embodiment, the viscosity index of the oil composition is such that the kinematic viscosity of the oil composition at 100°C is 13.5 to 24.0 mmHg. ２ When the kinematic viscosity at 100°C of the oil composition is in the range of 13.5 mm / s, it is preferably 180 or more, more preferably 190 or more, and even more preferably 200 or more. ２When the viscosity index is less than 1 / s, it is preferably at least 160, more preferably at least 165, and even more preferably at least 170. The viscosity index can be measured in accordance with JIS K2283:2000.

[0050] From the viewpoint of using the oil composition over a wide temperature range, it is preferable that the low-temperature viscosity of the oil composition of the present disclosure is not too high. Specifically, it is preferable that the Brookfield viscosity at -40°C is not too high. In a preferred embodiment, the Brookfield viscosity of the oil composition at -40°C is 13.5 to 24.0 mmHg, and the kinematic viscosity of the oil composition at 100°C is 13.5 to 24.0 mmHg. ２ When the kinematic viscosity of the oil composition at 100°C is in the range of 1,000 to 85,000 mPa·s, 1,000 to 70,000 mPa·s, more preferably 1,500 to 65,000 mPa·s, and even more preferably 2,000 to 60,000 mPa·s. ２ When the Brookfield viscosity is less than 100 to 2,500 mPa·s, it is preferably 100 to 2,500 mPa·s, more preferably 500 to 2,400 mPa·s, and even more preferably 1,000 to 2,300 mPa·s. The Brookfield viscosity at −40° C. can be measured in accordance with JPI-5S-26.

[0051] The method for producing the oil composition of the present disclosure is not particularly limited, and the oil composition can be produced, for example, by mixing the base oil and the conjugated diene polymer together with other additives, etc., as necessary. Mixing can be carried out using, for example, a known mixing device. Mixing is preferably carried out while heating, and the heating temperature is preferably 40 to 180°C.

[0052] The oil composition of the present disclosure is advantageously used, for example, as a lubricating oil. Therefore, the oil composition of the present disclosure may preferably be a lubricating oil composition. Lubricating oils include drive system oils, industrial lubricating oils, engine oils, etc. Drive system oils include, for example, transmission oils, differential gear oils, and transfer oils. Industrial lubricating oils include, for example, hydraulic oils, industrial gear oils, and bearing oils. Engine oils include, for example, engine oils for gasoline engines and engine oils for diesel engines.

[0053] Examples of transmission oils include manual transmission oils, automatic transmission oils, belt-type continuously variable transmission oils, dual clutch transmission oils, etc. Examples of hydraulic oils include hydraulic oils for machinery, hydraulic oils for construction machinery, hydraulic oils for agricultural machinery, power steering oils, etc. Examples of bearing oils include turbine oils, etc.

[0054] The oil composition of the present disclosure may be preferably a transmission fluid, hydraulic fluid, gear oil, bearing oil, or engine oil, more preferably a transmission fluid or hydraulic fluid, and even more preferably a manual transmission fluid or hydraulic fluid for construction machinery.

[0055] Other preferred aspects of the present disclosure include the following:

[14] An oil composition comprising a base oil and a conjugated diene polymer, wherein the conjugated diene polymer contains structural units derived from butadiene in an amount of 50 mass% or more relative to the total amount of the conjugated diene polymer, the iodine value of the conjugated diene polymer is 200 g / 100 g to 500 g / 100 g, the proportion of cis-1,4-bond units relative to the total amount of 1,4-bond units in the structural units derived from butadiene is 70 mol% or less, and the kinematic viscosity of the oil composition at 100°C is 24.0 mm ２ / s or less.

[15] The oil composition according to

[14] , wherein the vinyl content of the conjugated diene polymer is 0 to 30 mol %.

[16] The oil composition according to

[14] or

[15] , wherein the iodine value of the conjugated diene polymer is 200 g / 100 g to 500 g / 100 g.

[17] The oil composition according to any one of

[14] to

[16] , wherein the conjugated diene polymer is an unmodified polymer.

[18] The oil composition according to any one of

[14] to

[17] , wherein the conjugated diene polymer has a molecular weight distribution of 1.0 to 1.5.

[19] The oil composition according to any one of

[14] to

[18] , wherein the content of the conjugated diene polymer is 0.1 to 20 mass % based on the total amount of the oil composition.

[20] The kinematic viscosity of the oil composition at 100°C is 6.8 mm ２ / s or more.

[21] The oil composition according to any of

[14] to

[20] , wherein the ratio of cis-1,4-bond units to the total amount of 1,4-bond units in the structural units derived from butadiene is 70 mol % or less.

[22] The oil composition according to any of

[14] to

[21] , wherein the base oil is at least one selected from the group consisting of base oils belonging to Groups I, II, III, and IV of the API (American Petroleum Institute) classification.

[23] The oil composition according to any of

[14] to

[22] , further comprising at least one additive selected from the group consisting of rust inhibitors, antioxidants, surfactants, pour point depressants, detergents / dispersants, metal deactivators, antifoam agents, friction modifiers, extreme pressure agents, and antiwear agents.

[24] The oil composition according to any of

[14] to

[23] , wherein the oil composition is a lubricating oil.

[25] The oil composition according to

[24] , wherein the lubricating oil is a transmission oil or a hydraulic oil.

[26] Use of the oil composition according to any one of

[14] to

[25] as a lubricating oil.

[0056] The specific examples and preferred descriptions of the base oil and conjugated diene polymer described above also apply to the base oil and conjugated diene polymer contained in the oil composition of the other preferred embodiment. The oil composition of the other preferred embodiment may further contain other components described above, and preferably has the same oxidation stability, viscosity index, and Brookfield viscosity at -40°C as the oil composition described above. The oil composition of the other preferred embodiment may be produced by the same production method as the oil composition described above, and may be used for the same applications.

[0057] The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In the examples, percentages refer to mass unless otherwise specified. First, the measurement and evaluation methods are described below.

[0058] <Weight-average molecular weight, number-average molecular weight, and molecular weight distribution> The weight-average molecular weight (Mw), number-average molecular weight (Mn), and molecular weight distribution (Mw / Mn) of the conjugated diene polymer (P) were determined by gel permeation chromatography (GPC) in terms of standard polystyrene equivalent molecular weight. The measurement device and conditions were as follows: Device: GPC device "HLC-8320GPC" manufactured by Tosoh Corporation Separation column: "TSKgel Super HZ4000 x 2" manufactured by Tosoh Corporation Eluent: tetrahydrofuran Eluent flow rate: 0.35 mL / min Sample concentration: 5 mg / 10 mL Column temperature: 40°C

[0059] <Iodine Value> According to JIS K 0070:1992, 0.1 g of each conjugated diene polymer (P) was weighed out and diluted with 100 mL of chloroform. Next, 20.0 mL of Wiess's reagent (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 0.1 mol / L iodine chloride / acetic acid solution) was added, the mixture was shaken well, and the mixture was left for 30 minutes to allow the reaction to proceed. 20 mL of a 10% by mass potassium iodide aqueous solution was added thereto, followed by 100 mL of water and stirring. Then, 0.1 N sodium thiosulfate aqueous solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was gradually added dropwise until the solution became transparent (drop amount <X> mL). Next, the blank drop amount (drop amount <Y> mL) was determined in the same manner except that no sample was added. The iodine value of the conjugated diene polymer (P) was calculated using the above <X> and <Y> according to the following formula: Iodine value (g / 100g)=(<Y>-<X>)×1.269 / <weight (g) of conjugated diene polymer (P)>

[0060] <Hydrogenation Rate> Each conjugated diene polymer (P) was subjected to hydrogenation with CDCl ３ Dissolve in １ H-NMR measurement was carried out [apparatus: "AVANCE 400 Nanobay" (manufactured by Bruker), sample concentration: 50 mg / 1 mL, measurement temperature: 30°C, number of accumulations: 1,024]. The hydrogenation rate was calculated from the ratio of the peak area derived from one or more residual olefins selected from butadiene and isoprene to the peak area derived from one or more olefins selected from ethylene, propylene, and butylene.

[0061] <Proportion of cis-1,4-bond units and proportion of trans-1,4-bond units relative to the total amount of structural units derived from conjugated diene monomers, as well as vinyl content and proportion of cis-1,4-bond units in 1,4-bond units> [Production Examples 1 to 3] Each proportion relative to the total amount of structural units derived from butadiene as a conjugated diene monomer was determined by the following method. 30 mg of each conjugated diene polymer (P1 to 3) was dissolved in 10 mL of carbon disulfide and measured with a Fourier transform infrared spectrophotometer (FT-IR). The detected absorption peak absorbance (A ＢＶ ), the absorption peak absorbance (A ＢＣ), the absorption peak absorbance (A ＢＴ The composition ratio was calculated using formula (i) from the absorption coefficient of Morero and the cis-1,4-bond units in the total amount of structural units derived from butadiene. In the present examples and comparative examples, the ratio of cis-1,4-bond units to the total amount of structural units derived from butadiene is equal to the ratio of cis-1,4-bond units in the polymer. Formula (i) cis-1,4-bond (C) ... 1.7455 * A ＢＣ -0.0151*A ＢＶ Trans-1,4-bond (T)...0.4292*A ＢＴ -0.0129*A ＢＶ -0.0454*A ＢＣ 1.2-Bond (V)...0.3746*A ＢＶ -0.007*A ＢＣ Proportion of cis-1,4-bond units in polymer (mol %)=C / (C+V+T)*100 Proportion of trans-1,4-bond units in polymer (mol %)=T / (C+V+T)*100 Proportion of 1,2-bond units in polymer (vinyl content) (mol %)=V / (C+V+T)*100 Proportion of cis-1,4-bond units in 1,4-bond units (mol %)=C / (C+T)*100 [Production Example 4] The proportion of each structural unit relative to the total amount of structural units derived from isoprene as a conjugated diene monomer was determined by the following method. 30 mg of conjugated diene polymer (P-4) was dissolved in 10 mL of carbon disulfide and measured with a Fourier transform infrared spectrophotometer (FT-IR). The wavelength of isoprene detected was 836 cm －１ The absorption peak absorbance (A ８３６ ), wavelength 889cm －１ The absorption peak absorbance (A ８８９ ), wavelength 906cm －１ The absorption peak absorbance (A ９０６ ), wavelength 1128cm －１ The absorption peak absorbance (A １１２８ ), wavelength 1151cm －１ The absorption peak absorbance (A １１５１ ), and cell thickness b (cm), the concentration C of each component in the sample solution can be calculated by solving the following simultaneous equations: Ｃ (concentration of cis-1,4-bonding units), C Ｔ(concentration of trans-1,4-bond units), C １，２ (concentration of 1,2-bond units), C ３，４ The concentration of 3,4-bond units (mol / L) was calculated. ８３６ / b=19.9C Ｃ +9.84C Ｔ +0.633C １，２ +1.95C ３，４ A ８８９ / b=1.79C Ｃ +1.92C Ｔ +10.2C １，２ +145C ３，４ A ９０６ / b=1.75C Ｃ +2.52C Ｔ +149C １，２ +7.36C ３，４ A １１２８ / b=6.18C Ｃ +2.01C Ｔ +3.53C １，２ +1.82C ３，４ A １１５１ / b=3.4C Ｃ +6.06C Ｔ +3.53C １，２ +1.54C ３，４ The composition ratio was calculated from the calculated concentration using calculation formula (ii). In this example and comparative example, the ratio of cis-1,4-bond units and the like to the total amount of structural units derived from isoprene is equal to the ratio of cis-1,4-bond units and the like in the polymer. Calculation formula (ii) Ratio of cis-1,4-bond units in the polymer (mol %) = C Ｃ / (C Ｃ +C Ｔ +C １，２ +C ３，４ ) * 100 Proportion of trans-1,4-bond units in the polymer (mol%) = C Ｔ / (C Ｃ +C Ｔ +C １，２ +C ３，４ ) * 100 Total proportion of 1,2-bond units and 3,4-bond units in the polymer (vinyl content) (mol%) = (C １，２ +C ３，４ ) / (C Ｃ +C Ｔ +C １，２+C ３，４ ) * 100 Ratio of cis-1,4-bonded units in 1,4-bonded units (mol %) = C Ｃ / (C Ｃ +C Ｔ ) * 100

[0062] <Kinematic Viscosity> The kinematic viscosity at 100°C of each oil composition was measured in accordance with JIS K2283:2000.

[0063] <Thickening property> [Examples 1 and 2, Comparative Examples 1 to 3] 13.5 to 24.0 mm ２ In oil compositions having a kinematic viscosity (100°C) of 6.8 mm / sec, the thickening ability was evaluated using the following index depending on the blend amount of the conjugated diene polymer (P). Since comparison was made between oil compositions of similar kinematic viscosity, the lower the blend amount of the conjugated diene polymer (P), the higher the thickening ability. A: Blend amount of conjugated diene polymer (P) is less than 15% by mass B: Blend amount of conjugated diene polymer (P) is 15% by mass or more [Example 3, Comparative Example 4] 6.8 mm ２ / s or more 13.5mm ２ In oil compositions having a kinematic viscosity (100°C) of less than 1 / sec, the thickening property was evaluated using the following index depending on the blend amount of the conjugated diene polymer. Since comparison was made between oil compositions of similar kinematic viscosity, the smaller the blend amount of the conjugated diene polymer (P), the higher the thickening property. A: Blend amount of the conjugated diene polymer (P) is less than 10 mass% B: Blend amount of the conjugated diene polymer (P) is 10 mass% or more

[0064] <Viscosity Index> The viscosity index of each oil composition was measured in accordance with JIS K2283:2000.

[0065] <Brookfield Viscosity at −40° C.> Using each oil composition, the Brookfield viscosity at −40° C. was measured in accordance with JPI-5S-26.

[0066] <Shear Stability> A shear test was carried out using each oil composition in accordance with CEC-L45-99, and the rate of decrease in kinematic viscosity at 100°C before and after the shear test was measured and taken as the shear stability.

[0067] <Oxidation Stability (24 Hours)> Using each oil composition, an oxidation stability test was carried out in accordance with JIS K2514-1:2013 under the following conditions, and the rate of decrease in kinematic viscosity at 100°C before and after the oxidation stability test was measured and defined as the oxidation stability. Test temperature: 120°C Test time: 24 hours

[0068] <Oxidation Stability (96 Hours)> Using each oil composition, an oxidation stability test was carried out in accordance with JIS K2514-1:2013 under the following conditions, and the rate of decrease in kinematic viscosity at 100°C before and after the oxidation stability test was measured and defined as the oxidation stability. Test temperature: 120°C Test time: 96 hours

[0069] [Production Example 1: Synthesis of Conjugated Diene Polymer (P-1)] A thoroughly dried 3 L autoclave was purged with nitrogen, and 955 g of hexane and 21 g of n-butyllithium (17 mass % hexane solution) were charged. The temperature was raised to 60°C, and 770 g of butadiene was successively added under stirring conditions to polymerize. Methanol was then added to terminate the polymerization reaction, yielding a polymer solution. Water was added to the obtained polymer solution, followed by stirring, and the polymer solution was washed with water. After stirring was stopped, it was confirmed that the polymer solution phase and the aqueous phase had separated, and then the water was separated. The polymer solution after washing was vacuum dried at 140°C for 3 hours to yield a conjugated diene polymer (P-1).

[0070] [Production Example 2: Synthesis of Conjugated Diene Polymer (P-2)] A thoroughly dried 3 L autoclave was purged with nitrogen, and 955 g of hexane and 69 g of n-butyllithium (17 mass % hexane solution) were charged. The temperature was raised to 60°C, and 770 g of butadiene was successively added under stirring conditions to polymerize. Methanol was then added to terminate the polymerization reaction, yielding a polymer solution. Water was added to the obtained polymer solution, followed by stirring, and the polymer solution was washed with water. After stirring was stopped, it was confirmed that the polymer solution phase and the aqueous phase had separated, and then the water was separated. The polymer solution after washing was vacuum dried at 140°C for 3 hours to yield a conjugated diene polymer (P-2).

[0071] [Production Example 3: Synthesis of Conjugated Diene Polymer (P-3)] A thoroughly dried 3 L autoclave was purged with nitrogen, and 955 g of hexane and 7.2 g of n-butyllithium (17% by mass hexane solution) were charged. The temperature was raised to 60°C, and 770 g of butadiene was successively added under stirring conditions to polymerize. Methanol was then added to terminate the polymerization reaction, yielding a polymer solution. Water was added to the obtained polymer solution, followed by stirring, and the polymer solution was washed with water. After stirring was stopped, it was confirmed that the polymer solution phase and the aqueous phase had separated, and then the water was separated. The polymer solution after washing was vacuum dried at 140°C for 3 hours to yield a conjugated diene polymer (P-3).

[0072] [Production Example 4: Synthesis of Conjugated Diene Polymer (P-4)] A thoroughly dried 3 L autoclave was purged with nitrogen, and 955 g of hexane and 15 g of n-butyllithium (17% by mass hexane solution) were charged. The temperature was raised to 60°C, and 730 g of isoprene was successively added under stirring conditions to polymerize. Methanol was then added to terminate the polymerization reaction, yielding a polymer solution. Water was added to the obtained polymer solution, followed by stirring, and the polymer solution was washed with water. After stirring was stopped, it was confirmed that the polymer solution phase and the aqueous phase had separated, and then the water was separated. The polymer solution after washing was vacuum dried at 140°C for 3 hours to yield a conjugated diene polymer (P-4).

[0073] [Production Example 5: Synthesis of Conjugated Diene Polymer (P-5)] A thoroughly dried 3 L autoclave was purged with nitrogen, and 955 g of hexane and 12.9 g of n-butyllithium (17 mass % hexane solution) were charged. The temperature was raised to 60°C, and 770 g of butadiene was successively added under stirring conditions to polymerize. Methanol was then added to terminate the polymerization reaction, yielding a polymer solution. Water was added to the obtained polymer solution, followed by stirring, and the polymer solution was washed with water. After stirring was stopped, it was confirmed that the polymer solution phase and the aqueous phase had separated, and then the water was separated. The polymer solution after washing was vacuum dried at 140°C for 3 hours to yield a conjugated diene polymer (P-5).

[0074] [Production Example 6: Synthesis of Conjugated Diene Polymer (P-6)] A thoroughly dried 3 L autoclave was purged with nitrogen, and 955 g of hexane, 30 g of n-butyllithium (17% by mass hexane solution), and 6.4 g of tetrahydrofuran were charged. The temperature was raised to 60°C, and 290 g of butadiene was added sequentially under stirring conditions to polymerize. Methanol was then added to terminate the polymerization reaction, yielding a polymer solution. 450 mL of a Ziegler hydrogenation catalyst (0.095 mmol / L cyclohexane solution) formed from nickel octylate and trimethylaluminum was added to the resulting polymer solution, and the reaction was carried out for 10 hours under conditions of a hydrogen pressure of 1 MPa and 80°C, yielding a solution containing a conjugated diene polymer (P-6). Water was added to the resulting polymer solution, and the mixture was stirred. The polymer solution was then washed with water. After stirring was terminated and it was confirmed that the polymer solution phase and the aqueous phase had separated, the water was separated. After washing, the polymer solution was vacuum dried at 140° C. for 3 hours to obtain a conjugated diene polymer (P-6).

[0075] [Production Example 7: Synthesis of conjugated diene polymer (P-7)] A conjugated diene polymer (P-7) was synthesized with reference to the methods described in US Pat. Nos. 3,329,613, 3,149,173, and 3,312,621.

[0076] The number average molecular weight (Mn), weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), ratio of cis-1,4-bonds to the total amount of structural units derived from conjugated diene monomers, ratio of trans-1,4-bonds to the total amount of structural units derived from conjugated diene monomers, vinyl content, ratio of cis-1,4-bonds in 1,4-bonds, and hydrogenation rate of the resulting conjugated diene polymers (P-1) to (P-7) were measured according to the methods described above. The measurement results are shown in Table 1.

[0077] [Example 1] An oil composition having a kinematic viscosity at 100°C of 15.5 to 17.0 mm ２ / sec, 0.5% by mass of a pour point depressant ("VISCOPLEX (registered trademark) 1-330" manufactured by Evonik Industries), 9.0% by mass of the conjugated diene polymer (P-1) obtained in Production Example 1, and a base oil ("SAMIC (registered trademark) G-150" manufactured by Sanwa Chemical Industry Co., Ltd., Group II mineral oil, kinematic viscosity at 40°C: 29 mm ２ The mixture was stirred for 6 hours in a nitrogen-purged pressure vessel at a heating temperature of 80°C and a rotation speed of 350 rpm. This gave the oil composition of Example 1.

[0078] [Example 2] The kinematic viscosity of the oil composition at 100°C is 15.5 to 17.0 mm ２ / sec, 0.5% by mass of a pour point depressant ("VISCOPLEX (registered trademark) 1-330" manufactured by Evonik Industries), 0.8% by mass of an antioxidant ("ADEKA KICLUB (registered trademark) Z-112" manufactured by ADEKA Corporation), 9.0% by mass of the conjugated diene polymer (P-1) obtained in Production Example 1, and 9.0% by mass of a base oil ("SAMIC (registered trademark) G-150" manufactured by Sanwa Chemical Industry Co., Ltd., Group II mineral oil, kinematic viscosity at 40°C: 29 mm ２ The mixture was stirred for 6 hours in a nitrogen-purged pressure vessel at a heating temperature of 80°C and a rotation speed of 350 rpm. This gave an oil composition of Example 2.

[0079] [Example 3] The kinematic viscosity of the oil composition at 100°C is 8.0 to 9.0 mm ２ / sec, 0.5% by mass of a pour point depressant ("VISCOPLEX (registered trademark) 1-330" manufactured by Evonik Industries), 4.0% by mass of the conjugated diene polymer (P-1) obtained in Production Example 1, and a base oil ("SAMIC (registered trademark) G-150" manufactured by Sanwa Chemical Industry Co., Ltd., Group II mineral oil, kinematic viscosity at 40°C: 29 mm ２ The mixture was stirred for 6 hours in a nitrogen-purged pressure vessel at a heating temperature of 80°C and a rotation speed of 350 rpm, thereby obtaining the oil composition of Example 3.

[0080] [Example 4] Oil composition having a kinematic viscosity at 100°C of 15.5 to 17.0 mm ２ / sec, 0.5% by mass of a pour point depressant ("VISCOPLEX (registered trademark) 1-330" manufactured by Evonik Industries), 7.8% by mass of the conjugated diene polymer (P-5) obtained in Production Example 5, and a base oil ("SAMIC (registered trademark) G-150" manufactured by Sanwa Chemical Industry Co., Ltd., Group II mineral oil, kinematic viscosity at 40°C: 29 mm ２ The mixture was stirred for 6 hours in a nitrogen-purged pressure vessel at a heating temperature of 80°C and a rotation speed of 350 rpm. This gave an oil composition of Example 4.

[0081] [Comparative Examples 1 to 3] Oil compositions of Comparative Examples 1 to 3 were obtained in the same manner as in Example 1, except that the conjugated diene polymer (P) shown in Table 1 was used and the raw materials were mixed in the ratio shown in Table 1.

[0082] Comparative Example 4 An oil composition of Comparative Example 4 was prepared in the same manner as in Example 3, except that the conjugated diene polymer (P-4) was used and the raw materials were mixed in the ratio shown in Table 1.

[0083] Comparative Example 5: The kinematic viscosity of the oil composition at 100°C is 15.5 to 17.0 mm ２ / sec, 0.5% by mass of a pour point depressant ("VISCOPLEX (registered trademark) 1-330" manufactured by Evonik Industries), 20.2% by mass of the conjugated diene polymer (P-6) obtained in Production Example 6, and a base oil ("SAMIC (registered trademark) G-150" manufactured by Sanwa Chemical Industry Co., Ltd., Group II mineral oil, kinematic viscosity at 40°C: 29 mm ２ The mixture was stirred for 6 hours in a nitrogen-purged pressure vessel at a heating temperature of 80°C and a rotation speed of 350 rpm. This gave an oil composition of Comparative Example 5.

[0084] [Comparative Example 6] The kinematic viscosity of the oil composition at 100°C is 15.5 to 17.0 mm ２ / sec, 0.5% by mass of a pour point depressant ("VISCOPLEX (registered trademark) 1-330" manufactured by Evonik Industries), 32.2% by mass of the conjugated diene polymer (P-7) obtained in Production Example 7, and a base oil ("SAMIC (registered trademark) G-150" manufactured by Sanwa Chemical Industry Co., Ltd., Group II mineral oil, kinematic viscosity at 40°C: 29 mm ２ The mixture was stirred for 6 hours in a nitrogen-substituted pressure vessel at a heating temperature of 80°C and a rotation speed of 350 rpm. This gave an oil composition of Comparative Example 6.

[0085] The oil compositions obtained in the above Examples and Comparative Examples were measured and evaluated for kinematic viscosity (100°C), thickening ability, viscosity index, Brookfield viscosity at -40°C, shear stability, and oxidation stability according to the methods described above. The results are shown in Table 1.

[0086] An oil composition comprising a base oil and a conjugated diene polymer having a number average molecular weight of 11,000 to 74,000, wherein the conjugated diene polymer contains structural units derived from butadiene in an amount of 50% by mass or more relative to the total amount of the conjugated diene polymer, and has a kinematic viscosity of 24.0 mm at 100°C. ２The oil compositions of Examples 1 to 4, which correspond to the oil compositions of the present invention, having a number average molecular weight of 0.01 / s or less, were confirmed to have good thickening properties as well as high viscosity indexes, shear stability, and oxidation stability. Furthermore, they were found to have relatively low viscosities even at temperatures as low as -40°C. In contrast, the oil composition of Comparative Example 1, which had a number average molecular weight outside the above range, required approximately four times the amount of conjugated diene polymer to achieve the same viscosity, and therefore could not be said to have high thickening properties. Furthermore, the oil composition of Comparative Example 2 could not be said to have sufficiently high shear stability or oxidation stability. Furthermore, the oil compositions of Comparative Examples 3 and 4, which were not polymers containing structural units derived from butadiene at 50% by mass or more, also could not be said to have sufficiently high shear stability or oxidation stability. Furthermore, the compositions of Comparative Examples 1 to 4 also had high viscosities at temperatures as low as -40°C. Furthermore, the oil composition of Comparative Example 5, which had a number average molecular weight outside the above range and a high degree of hydrogenation, had low thickening properties and was significantly inferior in viscosity index and viscosity at temperatures as low as -40°C. Furthermore, the oil composition of Comparative Example 6, which had a number-average molecular weight outside the above range and a high ratio of cis-1,4-bond units to the total amount of 1,4-bond units, had low thickening properties and was significantly inferior in shear stability and oxidation stability. With regard to shear stability, the kinematic viscosity increased after the shear test, which was an unfavorable result, and with regard to oxidation stability, the oil composition solidified after the oxidation stability test, making it impossible to measure the kinematic viscosity.

Claims

1. An oil composition comprising a base oil and a conjugated diene polymer, the conjugated diene polymer having a number average molecular weight of 11,000 to 74,000 and containing structural units derived from butadiene in an amount of 50 mass% or more relative to the total amount of the conjugated diene polymer, and the kinetic viscosity of the oil composition at 100°C is 24.0 mm ２ / s or less.

2. The oil composition according to claim 1, wherein the vinyl content of the conjugated diene polymer is 0 to 30 mol %.

3. The oil composition according to claim 1 or 2, wherein the iodine value of the conjugated diene polymer is 200 g / 100 g to 500 g / 100 g.

4. The oil composition according to claim 1 or 2, wherein the conjugated diene polymer is an unmodified polymer.

5. The oil composition according to claim 1 or 2, wherein the conjugated diene polymer has a molecular weight distribution of 1.0 to 1.

5.

6. The oil composition according to claim 1 or 2, wherein the content of the conjugated diene polymer is 0.1 to 20 mass % based on the total amount of the oil composition.

7. The kinetic viscosity of the oil composition at 100°C is 6.8 mm ２ The oil composition according to claim 1 or 2, wherein the molar ratio of the oil composition to the oil content is 1:1 or more.

8. The oil composition according to claim 1 or 2, wherein the proportion of cis-1,4-bond units to the total amount of 1,4-bond units in the structural units derived from butadiene is 70 mol % or less.

9. The oil composition according to claim 1 or 2, wherein the base oil is at least one selected from the group consisting of base oils belonging to groups I, II, III, and IV in the API (American Petroleum Institute) classification.

10. The oil composition according to claim 1 or 2, further comprising at least one additive selected from the group consisting of rust inhibitors, antioxidants, surfactants, pour point depressants, detergent-dispersants, metal deactivators, antifoam agents, friction modifiers, extreme pressure agents, and antiwear agents.

11. The oil composition of claim 1 or 2, wherein the oil composition is a lubricating oil.

12. The oil composition of claim 11, wherein the lubricating oil is a transmission fluid or a hydraulic fluid.

13. Use of the oil composition according to claim 1 or 2 as a lubricating oil.

Images