Sulfide compound, extreme pressure additive, and lubricant oil composition containing said extreme pressure additive

Abstract

Provided is a sulfide compound capable of functioning as an extreme pressure additive excellent in oxidation stability and stability of frictional abrasion reduction efficacy. Specifically, the sulfide compound comprises at least a fatty acid triglyceride and sulfur as reaction components, and the content percentage of oleic acid in the fatty acid constituting the fatty acid triglyceride is 80 mass% or more.

Description

Sulfide compound, extreme pressure agent, and lubricating oil composition containing said extreme pressure agent

[0001] The present invention relates to a sulfide compound, an extreme pressure agent, and a lubricating oil composition containing the extreme pressure agent.

[0002] Lubricating oils such as gear oils, engine oils, hydraulic oils, cutting oils, plastic processing oils, and foundry oils are used by blending various additives such as extreme pressure agents, oiliness agents, antioxidants, rust inhibitors, corrosion inhibitors, antifoaming agents, and non-ferrous metal corrosion inhibitors with base oils such as mineral oils, greases, and synthetic oils.

[0003] Of the above additives, extreme pressure agents are additives that reduce friction and wear between metals, and various extreme pressure agents have been proposed, such as chlorine-based extreme pressure agents, sulfur-based extreme pressure agents, phosphorus-based extreme pressure agents, and organometallic compound-based extreme pressure agents (for example, Patent Documents 1 to 3).

[0004] JP 2021-500244 A, WO 2020 / 030189, WO 2014 / 188948

[0005] Lubricating oils are generally exposed to high temperatures and high pressures, which causes extreme pressure agents to oxidize and deteriorate, preventing the intended effect from being achieved. Because of these problems, extreme pressure agents, which are additives, are also required to have oxidation stability, but the extreme pressure agents of Patent Documents 1 to 3 do not meet this required performance. Furthermore, extreme pressure agents are required to stably exert their friction and wear reducing effect under various loads, but the stability of the friction and wear reducing effect of the extreme pressure agents of Patent Documents 1 to 3 was also insufficient.

[0006] The problem to be solved by the present invention is to provide a sulfide compound that has excellent oxidation stability and excellent stability in the effect of reducing friction and wear between metals, and that can function as, for example, an extreme pressure agent. Another problem to be solved by the present invention is to provide an extreme pressure agent that has excellent oxidation stability and stability in the effect of reducing friction and wear, and a lubricating oil composition containing the extreme pressure agent.

[0007] As a result of intensive research to solve the above problems, the present inventors have found that a sulfide compound having at least an oleic acid-rich unsaturated fatty acid and sulfur as reactive components has excellent oxidation stability and friction and wear reducing effect stability, and have completed the present invention.

[0008] That is, the present invention relates to the following sulfide compounds, etc.: 1. A sulfide compound having a fatty acid triglyceride and sulfur as at least reaction components, wherein the fatty acids constituting the fatty acid triglyceride contain 80% by mass or more of oleic acid. 2. The sulfide compound according to 1, wherein the fatty acids constituting the fatty acid triglyceride contain 5% by mass or less of linoleic acid. 3. The sulfide compound according to 1 or 2, wherein the fatty acid triglyceride is algae oil. 4. The sulfide compound according to any one of 1 to 3, wherein the proportion of sulfur in the reaction components is in the range of 5 to 35% by mass based on the total amount of reaction components. 5. The sulfide compound according to any one of 1 to 4, further comprising an unsaturated fatty acid alkyl ester as the reaction component. 6. The sulfide compound according to 5, wherein the unsaturated fatty acid alkyl ester is in the range of 10 to 300 parts by mass based on 100 parts by mass of the fatty acid triglyceride. 7. A kinematic viscosity at 40°C of 100 to 1,500 mm ２ / s. 8. The sulfide compound according to any one of 1 to 7, which is an extreme pressure agent. 9. A lubricating oil composition comprising a base oil and the extreme pressure agent according to claim 8.

[0009] The present invention provides a sulfide compound that is excellent in oxidation stability and stability of the effect of reducing friction and wear between metals, and can function as, for example, an extreme pressure agent.The present invention also provides an extreme pressure agent that is excellent in oxidation stability and stability of the effect of reducing friction and wear between metals, and a lubricating oil composition containing the extreme pressure agent.

[0010] An embodiment of the present invention will be described below. The present invention is not limited to the following embodiment, and can be carried out by making appropriate modifications within the scope that does not impair the effects of the present invention. The compounds in this specification may be derived from fossil resources or biological resources.

[0011] [Sulfide Compound] The sulfide compound of the present invention is a sulfide compound having a fatty acid triglyceride and sulfur as at least reaction components, and the content of oleic acid in the fatty acids constituting the fatty acid triglyceride is 80 mass % or more.

[0012] The sulfide compound of the present invention includes a compound in which fatty acid triglycerides are crosslinked with sulfur, forming a crosslinked structure at carbon-carbon double bonds derived from unsaturated fatty acids constituting the fatty acid triglycerides. In the present invention, by using oleic acid, a monovalent unsaturated fatty acid, as 80% by mass or more of the fatty acids constituting the fatty acid triglycerides, sulfur is easily crosslinked intermolecularly, and a sulfide compound having a long fatty chain and few carbon-carbon unsaturated bonds can be obtained, resulting in excellent oxidation stability. Furthermore, by using oleic acid, an unsaturated fatty acid, as 80% by mass or more of the fatty acids, the proportion of saturated fatty acids is relatively small, and the sulfide compound of the present invention has good fluidity and can exhibit stable friction and wear reduction effects. The reactive components of the sulfide compound are described below.

[0013] Fatty acid triglycerides are triesters in which three hydroxy groups of glycerin are esterified with fatty acids, and are preferably esters of glycerin with a fatty acid having 4 to 30 carbon atoms. The fatty acid is preferably a fatty acid having 8 to 30 carbon atoms, more preferably a fatty acid having 8 to 22 carbon atoms. The fatty acid may be either a saturated fatty acid or an unsaturated fatty acid, but 80% by mass or more of the fatty acid is oleic acid.

[0014] In the present invention, the content of oleic acid in the fatty acids constituting the fatty acid triglyceride is 80% by mass or more, preferably 85% by mass or more, more preferably 87% by mass or more, and even more preferably 90% by mass or more. The upper limit of the oleic acid content is not particularly limited, but is, for example, 95% by mass or less, 99% by mass or less, or 100% by mass or less.

[0015] The content of linoleic acid in the fatty acids constituting the fatty acid triglyceride is preferably 8% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less. By setting the content of linoleic acid, a divalent unsaturated fatty acid, within the above range, the amount of carbon-carbon unsaturated bonds in the sulfide compound can be suppressed, thereby improving oxidation stability. The lower limit of the content of linoleic acid in the unsaturated fatty acid is not particularly limited, but is, for example, 0% by mass or more, 0.1% by mass or more, or 1% by mass or more.

[0016] The contents of various fatty acids constituting the fatty acid triglycerides, such as oleic acid, linoleic acid, parethmic acid, stearic acid, linolenic acid, lauric acid, behenic acid, montanic acid, butanoic acid, pentanoic acid, hexanoic acid, decanoic acid, myristic acid, eicosenoic acid, erucic acid, stearidonic acid, punicic acid, palmitoleic acid, ricinoleic acid, eicosadienoic acid, docosadienoic acid, eleostearic acid, pinolenic acid, 9,11-octadecadienoic acid, and 9,12-octadecadienoic acid, are confirmed by the method described in the Examples.

[0017] The fatty acid triglyceride is preferably algal oil. Algal oil-derived fatty acid triglycerides are generally fatty acid triglycerides rich in oleic acid, and the algal oil-derived fatty acid triglycerides can easily have an oleic acid content of 80% by mass or more and a linoleic acid content of 8% by mass or less.

[0018] Algae (organisms that perform oxygenic photosynthesis) store lipids within their cells, and as used herein, "algal oil" refers to oil extracted from algae, including eubacteria, unicellular eukaryotic organisms, and multicellular eukaryotic organisms.

[0019] Examples of algae that are true bacteria include species of the genus Spirulina and species of the genus Arthrospira.

[0020] Examples of algae that are eukaryotic unicellular organisms and eukaryotic multicellular organisms include, for example, species of the genus Chlorella, species of the genus Pseudochlorella, species of the genus Heterochlorella, species of the genus Prototheca, species of the genus Arthrospira, species of the genus Euglena, and the like. uglena species, Nannochloropsis species, Phaeodactylum species, Chlamydomonas species, Scenedesmus species, Ostreococcus species, Selenastrum species, rum species, Haematococcus species, Nitzschia species, Dunaliella species, Navicula species, Trebouxia species, Pseudotrebouxia species, Vavicula species Examples of the fungus include Bacteroides species, Bacteococcus species, Gomphonema species, Watanabea species, Botryococcus species, Tetraselmis species, and Isochrysis species.

[0021] Algae can be made to produce fatty acid triglycerides with a desired composition by, for example, modifying fatty acid synthesis genes, and the algae referred to in this specification also include genetically modified versions of the above-mentioned algae.

[0022] The fatty acid triglycerides are not limited to those derived from algae oils, but also include fatty acid triglycerides derived from animal oils and vegetable oils, such as lard, beef tallow, fish oil, rapeseed oil, palm oil, canola oil, coconut oil, corn oil, cottonseed oil, olive oil, palm oil, peanut oil, sunflower oil, soybean oil, safflower oil, rice oil, palm oil, sesame oil, linseed oil, and grapeseed oil.

[0023] However, it is difficult to obtain fatty acid triglycerides derived from animal oils and fatty acid triglycerides derived from vegetable oils with an oleic acid content of 80% by mass or more. For example, fatty acid triglycerides derived from lard as an animal oil-derived fatty acid triglyceride have an oleic acid content of less than 50% by mass, and are fatty acid triglycerides with a relatively high saturated fatty acid content. Furthermore, fatty acid triglycerides derived from vegetable oils, such as palm oil-derived fatty acid triglycerides, have an oleic acid content of less than 50% by mass, and canola oil-derived fatty acid triglycerides also have an oleic acid content of less than 65% by mass.

[0024] The proportion of sulfur in the reaction components is, for example, in the range of 5 to 35 mass%, preferably in the range of 5 to 25 mass%, more preferably in the range of 5 to 20 mass%, and even more preferably in the range of 10 to 17 mass% or in the range of 8 to 15 mass%, based on the total amount of the reaction components.

[0025] The reaction components of the sulfide compound of the present invention may contain sulfur and a fatty acid triglyceride, or may contain components other than sulfur and a fatty acid triglyceride.

[0026] Examples of reaction components other than sulfur and fatty acid triglycerides include alkyl esters of unsaturated fatty acids. By using unsaturated fatty acid alkyl esters as reaction components, the sulfide compound of the present invention contains compounds in which unsaturated fatty acid alkyl esters are crosslinked with sulfur, making it possible to adjust the kinematic viscosity of the resulting sulfide compound.

[0027] The compound in which the unsaturated fatty acid alkyl esters are crosslinked with sulfur is, for example, a compound represented by the following general formula (1).

[0028] (In the general formula (1), R １１ and R １３ are each independently an alkylene group having 3 to 29 carbon atoms or a divalent hydrocarbon group having 3 to 29 carbon atoms and one or more carbon-carbon unsaturated bonds, and R １２ and R １４ are each independently an alkyl group having 1 to 12 carbon atoms.

[0029] The compound represented by the general formula (1) is R １１ COOR １２ and R １３ COOR １４ The unsaturated fatty acid alkyl esters corresponding to the above are linked together at the carbon-carbon unsaturated bond portion via (poly)sulfide bonds (where x is an integer of, for example, 1 to 8).

[0030] In the general formula (1), R １１ and R １３ The alkylene group having 3 to 29 carbon atoms may be linear or branched. １１ and R １３ The alkylene group having 3 to 29 carbon atoms is preferably an alkylene group having 7 to 21 carbon atoms.

[0031] In the general formula (1), R １１ and R １３ The "divalent hydrocarbon group having 3 to 29 carbon atoms and one or more carbon-carbon unsaturated bonds" in R is an alkylene group having one or more carbon-carbon unsaturated bonds, such as an alkenylene group, and may be linear or branched. １１ and R １３ The divalent hydrocarbon group having 3 to 29 carbon atoms and one or more carbon-carbon unsaturated bonds is preferably a divalent hydrocarbon group having 7 to 21 carbon atoms and one or more carbon-carbon unsaturated bonds.

[0032] In the general formula (1), R １２ and R １４R is an alkyl group having 1 to 12 carbon atoms, and may be a straight chain or branched chain. １２ and R １４ The alkyl group having 1 to 12 carbon atoms is preferably an alkyl group having 1 to 6 carbon atoms.

[0033] The unsaturated fatty acid alkyl ester may be, for example, an ester of an unsaturated fatty acid having 4 to 30 carbon atoms and an alcohol having 1 to 12 carbon atoms. Here, the unsaturated fatty acid having 4 to 30 carbon atoms is preferably an unsaturated fatty acid having 8 to 22 carbon atoms, and the alcohol having 1 to 12 carbon atoms is preferably an alcohol having 1 to 6 carbon atoms.

[0034] Specific examples of the unsaturated fatty acids having 4 to 30 carbon atoms include oleic acid, linoleic acid, linolenic acid, eicosenoic acid, erucic acid, stearidonic acid, punicic acid, palmitoleic acid, ricinoleic acid, eicosadienoic acid, docosadienoic acid, eleostearic acid, pinolenic acid, 9,11-octadecadienoic acid, and 9,12-octadecadienoic acid.

[0035] Alkyl esters of unsaturated fatty acids can be prepared by decomposing fatty acid triglycerides into glycerin and fatty acids using, for example, sodium hydroxide, and then esterifying the resulting fatty acids with alcohol. Unsaturated fatty acid alkyl esters, which are obtained by decomposing fatty acid triglycerides and esterifying the resulting fatty acids with alcohol, are preferred because they allow for the use of common raw materials. The fatty acids preferably have an oleic acid content of 80% by mass or more. Furthermore, the fatty acids preferably have a linoleic acid content of 8% by mass or less.

[0036] The amount of alkyl ester of unsaturated fatty acid used is, for example, 10 to 300 parts by mass, preferably 50 to 200 parts by mass, and more preferably 70 to 150 parts by mass, per 100 parts by mass of fatty acid triglyceride.

[0037] As a reaction component other than sulfur and fatty acid triglyceride, an unsaturated hydrocarbon can also be used. By using an unsaturated hydrocarbon as a reaction component, the sulfide compound of the present invention contains a compound in which unsaturated hydrocarbons are crosslinked with sulfur, and it becomes possible to adjust the kinematic viscosity of the obtained sulfide compound.

[0038] The compound in which unsaturated hydrocarbons are crosslinked with sulfur is, for example, a compound represented by the following general formula (2).

[0039] (In the general formula (2), R ２１ and R ２２ are each independently an alkyl group having 4 to 30 carbon atoms or a hydrocarbon group having 4 to 30 carbon atoms and one or more carbon-carbon unsaturated bonds.

[0040] The compound represented by the general formula (2) is R ２１ and R ２２ The unsaturated hydrocarbons corresponding to the above are linked together at the carbon-carbon unsaturated bond portion via (poly)sulfide bonds (where y is an integer of, for example, 1 to 8).

[0041] In the general formula (2), R ２１ and R ２２ The alkyl group having 4 to 30 carbon atoms in R may be a straight chain or a branched chain. ２１ and R ２２ The alkyl group having 4 to 30 carbon atoms is preferably an alkyl group having 4 to 22 carbon atoms.

[0042] In the general formula (1), R ２１ and R ２２ The "hydrocarbon group having 4 to 30 carbon atoms and one or more carbon-carbon unsaturated bonds" in R is a hydrocarbon group having one or more carbon-carbon unsaturated bonds, such as an alkenyl group, and may be linear or branched. ２１ and R ２２ The hydrocarbon group having 4 to 30 carbon atoms and one or more carbon-carbon unsaturated bonds is preferably a hydrocarbon group having 4 to 22 carbon atoms and one or more carbon-carbon unsaturated bonds.

[0043] The unsaturated hydrocarbon may be any unsaturated hydrocarbon having at least one carbon-carbon unsaturated bond, and is preferably an unsaturated hydrocarbon having 4 to 30 carbon atoms, and more preferably an unsaturated hydrocarbon having 4 to 22 carbon atoms. Specific examples of unsaturated hydrocarbons include 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, 3-methylpentene, 4-methylheptene, 5-methylundecene, 3,6-dimethylhexanedecene, and diisobutylene.

[0044] Unsaturated hydrocarbons can be used that are derived from, for example, mineral oil.

[0045] The amount of unsaturated hydrocarbon used is, for example, 10 to 300 parts by mass, preferably 50 to 200 parts by mass, and more preferably 70 to 150 parts by mass, per 100 parts by mass of fatty acid triglyceride.

[0046] Fatty acid glycerides from animal oils, vegetable oils, algae oils, etc. are usually present as triglycerides in which three fatty acids are bonded to glycerin, but may also contain fatty acid monoglycerides and fatty acid diglycerides as reactants within a range that does not impair the effects of the present invention. When fatty acid monoglycerides and / or fatty acid diglycerides are contained as reactants, the total amount of fatty acid monoglycerides and fatty acid diglycerides may be, for example, 10% by mass or less, 5% by mass or less, or 3% by mass or less of the total amount of reactants.

[0047] The reaction components of the sulfide compound of the present invention may essentially consist of, for example, sulfur, fatty acid triglycerides, any unsaturated fatty acid alkyl esters, and any unsaturated hydrocarbons. Here, "essentially consist" means that the total content of sulfur, fatty acid triglycerides, any unsaturated fatty acid alkyl esters, and any unsaturated hydrocarbons is 90% by mass or more, 95% by mass or more, 98% by mass or more, or 100% by mass of the total amount of the reaction components of the sulfide compound of the present invention.

[0048] The kinematic viscosity of the sulfide compound of the present invention at 40°C is, for example, 100 to 1,500 mm ２s, preferably 100 to 500 mm ２ The kinematic viscosity at 40°C of the sulfide compound is confirmed by the method described in the examples.

[0049] [Method for Producing Sulfide Compound] The sulfide compound of the present invention can be produced by a known method, for example, by reacting sulfur, a fatty acid triglyceride, any unsaturated fatty acid alkyl ester, and any unsaturated hydrocarbon in the presence of hydrogen sulfide and a basic catalyst.

[0050] The state of sulfur used in the production of the sulfide compound of the present invention is not particularly limited, and may be in a solid state such as small lumps, flakes, or powder, or in a molten state (liquid). Sulfur is preferably in a molten state in order to facilitate the scale-up of production.

[0051] Examples of the basic catalyst include alkali metal hydroxides (e.g., sodium hydroxide, potassium hydroxide, etc.), aliphatic amine compounds, aromatic amine compounds, etc. The amount of the basic catalyst used is, for example, 0.05 to 1.0 part by mass per 100 parts by mass of the reaction components.

[0052] The reaction temperature may be set within the range of, for example, 50 to 200° C., and the reaction time may be set within the range of, for example, 1 to 72 hours.

[0053] [Lubricating Oil Composition] The sulfide compound of the present invention can be suitably used as an extreme pressure agent. Here, an "extreme pressure agent" is an additive that suppresses wear due to friction between metals, and it is believed that the sulfide compound suppresses wear by adsorbing to the metal surface and forming a lubricating film (tribofilm). The extreme pressure agent that is the sulfide compound of the present invention (hereinafter sometimes referred to as the "extreme pressure agent of the present invention") has excellent oxidation stability, so deterioration due to heat generated by friction between metals is reduced and sludge generation can be suppressed.

[0054] The lubricating oil composition of the present invention contains a lubricating base oil and the extreme pressure agent of the present invention. Known lubricating base oils can be used, including mineral oils such as distillates or refined oils of paraffinic crude oil, intermediate crude oil, and naphthenic crude oil; and synthetic oils such as low-molecular-weight polybutene, low-molecular-weight polypropylene, C α-olefin oligomers, hydrogenated C α-olefin oligomers, polyol esters (e.g., fatty acid esters of trimethylolpropane, fatty acid esters of pentaerythritol), ester compounds (e.g., dibasic acid esters, aromatic polycarboxylic acid esters, phosphate esters), alkyl aromatic compounds (e.g., alkylbenzenes, alkylnaphthalenes), polyglycol oils (e.g., polyalkylene glycols), and silicone oils.

[0055] The lubricating base oil may be selected appropriately depending on the intended use and conditions of use, and the lubricating base oils used may be one type alone or two or more types in combination.

[0056] The content of the extreme pressure agent of the present invention in the lubricating oil composition of the present invention is, for example, 0.01 to 50 parts by mass, preferably 1 to 50 parts by mass, and more preferably 1 to 30 parts by mass, per 100 parts by mass of the lubricating base oil.

[0057] The extreme pressure agents of the present invention may be used singly or in combination of two or more.

[0058] The lubricating oil composition of the present invention may contain a lubricating base oil and the extreme pressure agent of the present invention, and may further contain additives such as oiliness agents, antiwear agents, extreme pressure agents other than the extreme pressure agent of the present invention, rust inhibitors, corrosion inhibitors, antifoaming agents, detergent dispersants, pour point depressants, viscosity index improvers, antioxidants, emulsifiers, demulsifiers, fungicides, friction modifiers, surfactants, etc. Any of these additives may be used that are known in the art.

[0059] The lubricating oil composition of the present invention can also be used as a grease by further adding a thickener such as a metal soap.

[0060] The uses of the lubricating oil composition of the present invention are not particularly limited, and it can be used, for example, as an automotive lubricating oil used in drive system devices such as internal combustion engines, automatic transmissions, shock absorbers, and power steering, as well as gears; a metal working oil used in metal working such as cutting, grinding, and plastic working; and a hydraulic oil, which is a power transmission fluid used for power transmission, force control, buffering, and other operations in hydraulic systems such as hydraulic equipment and devices.

[0061] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0062] Example 1 Preparation of Sulfide Compound (1) A 1-liter autoclave equipped with a heating device, a hydrogen sulfide inlet tube, and a hydrogen sulfide absorption device was charged with 300 g of fatty acid triglyceride (fatty acids constituting the fatty acid triglyceride were 94% by mass of oleic acid and less than 2% by mass of linoleic acid), 300 g of methyl ester of the fatty acid triglyceride (obtained by decomposing the fatty acid triglyceride with sodium hydroxide into glycerin and fatty acid, and esterifying the resulting fatty acid with methanol), 52 g of sulfur, and 3.8 g of a mixture of alkylamines having 16 to 22 carbon atoms as a catalyst. After sealing the autoclave, the pressure inside the reaction vessel was reduced to -0.1 MPa or less using a vacuum pump, and the vessel was degassed under vacuum. Thereafter, the vessel was heated until the internal temperature reached 100°C. 12 g of hydrogen sulfide gas (purity 99.9 mol%) was added to the autoclave at a pressure of 6 kg / cm. ２ After heating to 120°C, 18 g of hydrogen sulfide gas was blown in over 3.5 hours, and the temperature was maintained at 120°C for 5 hours. The temperature was then raised to 150°C and maintained for 4 hours. Thereafter, the mixture was cooled to 80°C, and the valve connected to the hydrogen sulfide absorption apparatus was opened to return the pressure to atmospheric pressure. Air was blown in through the blowing tube to distill off the remaining hydrogen sulfide. 3.5 g of thiadiazole and 0.5 g of benzotriazole were added to obtain 669 g of sulfide compound (1) (yield 97%, kinematic viscosity at 40°C: 490 mm ２ / s, sulfur content: 11.0 mass%) was obtained.

[0063] The fatty acid triglyceride used in the preparation of sulfide compound (1) was algal oil derived from Chlorella (manufactured by Checkerspot), and the proportions of the fatty acid components constituting the fatty acid triglyceride were identified using gas chromatography. Specifically, the algal oil was decomposed into glycerin and fatty acids with sodium hydroxide, the fatty acids were extracted, the extracted fatty acids were methyl-esterified with methanol, and the resulting fatty acid methyl esters were analyzed by gas chromatography to identify the various fatty acids.

[0064] The algal oil is simply "fatty acid triglycerides extracted from algae" and does not substantially contain any other components. Therefore, it is possible to artificially reproduce the fatty acid triglycerides by reacting glycerin with fatty acids in the above-mentioned ratio.

[0065] Comparative Example 1: Preparation of sulfide compound (1') 669 g of sulfide compound (1') (yield 97%, kinematic viscosity at 40°C: 330 mm) was obtained in the same manner as in Example 1, except that canola oil (triglyceride of oleic acid: 63% by mass, linoleic acid: 19% by mass) was used instead of algal oil, and the methyl ester of unsaturated fatty acid (oleic acid: 82% by mass, linoleic acid: 9% by mass) was used instead of the methyl ester of algal oil. ２ / s, sulfur content: 11.5% by mass

[0066] Comparative Example 2: Preparation of sulfide compound (2') A 1-liter autoclave equipped with a heating device, a hydrogen sulfide inlet tube, and a hydrogen sulfide absorption device was charged with 300 g of lard (triglyceride of oleic acid: 49% by mass, linoleic acid: 10% by mass), 184 g of commercially available unsaturated fatty acid methyl esters (oleic acid 40-50%, linoleic acid 25-35%) from recovered oil, 48 g of sulfur, and 1 g of a mixture of alkylamines having 16 to 22 carbon atoms as a catalyst. After sealing the autoclave, the pressure inside the reaction vessel was reduced to -0.1 MPa or less using a vacuum pump, and the vessel was degassed under vacuum. Thereafter, the vessel was heated until the internal temperature reached 100°C. 7.5 g of hydrogen sulfide gas (purity 99.9 mol%) was added to the mixture at a pressure of 6 kg / cm. ２After heating to 120°C, 11.2 g of hydrogen sulfide gas was blown in over 3.5 hours and the temperature was maintained at 120°C for 5 hours, and then the temperature was raised to 165°C and maintained for 6 hours. Thereafter, the mixture was cooled to 80°C, and the valve connected to the hydrogen sulfide absorption device was opened to return the pressure to atmospheric pressure. Air was blown in through the blowing tube to distill off the remaining hydrogen sulfide. 3.5 g of thiadiazole and 0.4 g of benzotriazole were added to obtain 539 g of sulfide compound (2') (yield 97%, kinematic viscosity at 40°C: 320 mm ２ / s, sulfur content: 11.5% by mass).

[0067] The sulfide compounds produced in the examples and comparative examples were evaluated as follows. The results are shown in Table 1.

[0068] (Sulfur Content) The sulfur content of the sulfide compound was measured in accordance with JIS K2541-7:2023.

[0069] (Kinematic Viscosity) The kinematic viscosity of the sulfide compound at 40° C. was measured in accordance with JIS K2283: 2000. The higher the kinematic viscosity, the better the handleability of the sulfide compound.

[0070] (Pour Point) The pour point of the sulfide compound was measured in accordance with JIS K2269: 1987. A lower pour point means that the sulfide compound retains fluidity even at low temperatures, and therefore has excellent handleability.

[0071] (Oxidation stability) Group II oil (kinematic viscosity at 40°C is 90 mm ２ The sulfide compounds produced in the Examples and Comparative Examples were added to a lubricating oil composition (aqueous suspension / s) so that the content of each compound was 5 mass %. The prepared lubricating oil compositions were evaluated for acid value stability as described below, and the results are shown in Table 1.

[0072] The oxidation stability of sulfide compounds was evaluated in accordance with JIS K-2514:2013. Specifically, the lubricating oil compositions were degraded at 135°C for 96 hours using an ISOT tester equipped with a glass varnish rod. After the test, the presence or absence of sludge adhering to the varnish rod was visually evaluated according to the following criteria: ○: Almost no sludge adhering to the varnish rod was observed ×: Sludge adhering to the varnish rod was clearly observed

[0073] (Extreme pressure performance) Paraffin oil (kinematic viscosity at 40°C is 9mm ２ The sulfide compounds produced in the Examples and Comparative Examples were added to a lubricating oil composition (aqueous suspension / s) so that the content of each compound was 5 mass %. The lubricating oil compositions were evaluated for extreme pressure performance as described below, and the results are shown in Table 1.

[0074] The extreme pressure performance of the sulfide compounds was evaluated in terms of welding load and maximum non-seizure load in accordance with ASTM D-2783. Specifically, the extreme pressure performance of the lubricating oil compositions was evaluated under the following conditions: Vertical shaft rotation speed: 1770 rpm Test steel ball: 1 / 2 inch for ball bearings (SUJ2) Measurement time for welding load and maximum non-seizure load: 10 seconds

[0075] (Frictional Properties) The change in the coefficient of friction of the sulfide compounds produced in the Examples and Comparative Examples was evaluated in accordance with ASTM D2596. Specifically, a four-ball tester (TE92 manufactured by Plint Corporation) was used as the test machine, and a 1 / 2-inch diameter SUJ2 carbon steel ball was used as the test ball. While rotating the test ball at 200 rpm, a load ranging from 500 to 3000 N was applied in steps every 120 seconds, and the maximum torque value during rotation was observed. From the obtained torque value, the coefficient of friction was calculated using the formula: coefficient of friction = maximum torque value (N cm) / (1.65 x normal load per single ball) (N), and the change in the coefficient of friction was evaluated according to the following criteria. Note that the higher the change in the coefficient of friction, the more corrosive wear due to frictional heat can be reduced. ×: A change in μ of 0.07 or more occurs at a load of less than 1,000 N. △: A change in μ of 0.07 or more occurs at a load of 1,000 N or more but less than 2,000 N. ○: A change in μ of 0.07 or more occurs at a load of 2,000 N or more but less than 3,000 N.

[0076]

[0077] It can be seen that the sulfide compound of Example 1, which uses a fatty acid triglyceride containing 80% or more by mass of oleic acid, is excellent in both oxidation stability and friction characteristics. On the other hand, the sulfide compound of Comparative Example 1, which uses a fatty acid triglyceride containing less than 80% by mass of oleic acid, is significantly inferior in oxidation stability. Furthermore, the sulfide compound of Comparative Example 2 has poor friction characteristics due to the relatively high amount of saturated fatty acids in the fatty acid triglyceride.

Claims

1. A sulfide compound having at least a fatty acid triglyceride and sulfur as reactive components, wherein the content of oleic acid in the fatty acids constituting the fatty acid triglyceride is 80 mass% or more.

2. The sulfide compound according to claim 1, wherein the content of linoleic acid in the fatty acids constituting the fatty acid triglyceride is 5 mass% or less.

3. The sulfide compound according to claim 1 or 2, wherein the fatty acid triglyceride is algae oil.

4. The sulfide compound according to claim 1 or 2, wherein the proportion of sulfur in the reaction components is in the range of 5 to 35 mass % based on the total amount of the reaction components.

5. The sulfide compound according to claim 1 or 2, further comprising an unsaturated fatty acid alkyl ester as the reaction component.

6. The sulfide compound according to claim 5, wherein the unsaturated fatty acid alkyl ester is contained in an amount ranging from 10 to 300 parts by mass per 100 parts by mass of the fatty acid triglyceride.

7. Dynamic viscosity at 40°C is 100 to 1,500 mm ２ The sulfide compound according to claim 1 or 2, wherein the sulfide compound has a molecular weight of 1:1 or more and a molecular weight of 1:1 or more.

8. The sulfide compound according to claim 1 or 2, which is an extreme pressure agent.

9. A lubricating oil composition comprising a base oil and the extreme pressure agent according to claim 8.

Images