Grease composition and method for lubricating sliding parts using this grease composition

Abstract

To provide a grease composition that does not deteriorate a contacting resin, particularly a contacting acetal resin, even under a high temperature condition.SOLUTION: The grease composition for a resin that can solve the above problem comprises: (A) a lubricant base oil; (B) a thickener; and (C) at least one selected from the group consisting of an organic molybdenum compound and a sulfur-based extreme pressure agent, wherein when the composition contains the sulfur-based extreme pressure agent, the content of the sulfur-based extreme pressure agent is 0.05 mass% or more to 2.5 mass% or less based on a total amount of the composition and zinc dialkyldithiophosphate is substantially free.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a grease composition. This invention also relates to a method for lubricating sliding parts using this grease composition. [Background technology]

[0002] Plastic molded products are used as parts for various machines. Among them, molded products made from polyacetal resin (acetal resin) possess excellent properties in terms of mechanical properties and moldability. Due to these properties, molded products made from acetal resin are widely used in home appliances and electrical and electronic products.

[0003] Grease is primarily used in sliding bearings, rolling bearings, or sliding parts. The type of grease used is selected according to the operating conditions. Various selections of base oil, thickeners, and additives have been proposed to improve the lubricity and material compatibility of greases. However, friction characteristics vary depending on the material and other conditions of the sliding parts. Furthermore, the grease used may degrade certain materials. Therefore, it is necessary to select a grease with the optimal composition, taking into account the material and other factors. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2011-157477 [Patent Document 2] International Publication No. WO2015 / 083695 [Overview of the project] [Problems that the invention aims to solve]

[0005] Patent Document 1 discloses a grease composition that prevents lubrication failure and, even if grease is scattered, prevents contamination by preventing it from remaining on surrounding equipment. Patent Document 2 discloses a grease composition that has low sliding resistance and can significantly reduce the power consumption of mechanical elements, especially the power consumption during bearing rotation. However, the suitability of these documents for resins has not been tested. Therefore, it was unclear whether they were suitable for resins. In particular, sliding parts often become hot. Therefore, there was a need for a grease composition that would not degrade the resin it was in contact with, even under high-temperature conditions. [Means for solving the problem]

[0006] The inventors diligently studied grease compositions that do not degrade contacting resins, particularly acetal resins, even under high-temperature conditions. They found that the aforementioned problems could be solved by using a grease composition containing components (A) to (C), and when a sulfur-based extreme pressure agent is included, the content of the sulfur-based extreme pressure agent being 0.05% to 2.5% by mass on a basis of the total composition, and substantially free of zinc dialkyldithiophosphate. This led to the completion of the invention.

[0007] This invention is based on the aforementioned findings and is as follows: <1> (A) Lubricating oil base oil, (B) Thickener, and (C) At least one selected from the group consisting of organic molybdenum compounds and sulfur-based extreme pressure agents, A resin grease composition in which, if it contains a sulfur-based extreme pressure agent, the content of the sulfur-based extreme pressure agent is 0.05% by mass or more and 2.5% by mass or less on a basis of the total amount of the composition, and which substantially does not contain zinc dialkyldithiophosphate. <2> The resin is acetal resin. <1> The resin grease composition described in [reference]. <3> It contains an organic molybdenum compound, and the content of the organic molybdenum compound is 0.05% by mass or more and 5% by mass or less based on the total amount of the composition. <1> or <2> The resin grease composition described in [reference]. <4> Containing both organic molybdenum compounds and sulfur-based extreme pressure agents, <1> ~ <3> A resin grease composition as described in any of the above. <5> The thickener is a metal soap-based thickener. <1> ~ <4> A resin grease composition as described in any of the above. <6> The consistency is between 265 and 475. <1> ~ <5> A resin grease composition as described in any of the above. <7> (A) The lubricating oil base oil content is 50% by mass or more and 95% by mass or less on a basis of the total composition, and (B) The amount of thickener is 2% by mass or more and 30% by mass or less based on the total amount of the composition. <1> ~ <6> A resin grease composition as described in any of the above. <8> sliding part <1> ~ <7> A method for lubricating sliding parts by interposing a grease composition as described in any of the above. The present invention also relates to the following: <1a> (A) Mineral oil and, (B) Lithium complex and, (C) Contains both molybdenum dithiocarbamate and dioctyl polysulfide, A resin grease composition that does not contain zinc dialkyldithiophosphate, The kinematic viscosity of the aforementioned mineral oil at 40°C is 25 mm². 2 / s or more 70mm 2 It is less than or equal to / s, The lithium complex content is 11% by mass or more and 20% by mass or less based on the total amount of the composition. The content of the aforementioned dioctyl polysulfide is 0.1% by mass or more and 2.0% by mass or less based on the total amount of the composition. A resin grease composition wherein the content of the molybdenum dithiocarbamate is 0.05% by mass or more and 5% by mass or less based on the total amount of the composition. <2a> The resin grease composition according to <1a>, wherein the resin is an acetal resin. <3a> The grease composition for resin according to <1a> or <2a>, wherein the dropping point is 265 or higher and 475 or lower. <4a> The grease composition for resin according to <1a> or <2a>, wherein the content of the mineral oil is 50% by mass or more and 95% by mass or less based on the total amount of the composition. <5a> The grease composition for resin according to <1a> or <2a>, wherein the content of zinc dialkyldithiophosphate is 1% by mass or less based on the total amount of the composition. <6a> The grease composition for resin according to <2a>, which is used for a member containing an acetal resin and a metal. <7a> The grease composition for resin according to <6a>, wherein the metal is copper. <8a> The grease composition for resin according to <1a> or <2a>, wherein when the resin is immersed in the grease composition for resin at 90 °C or higher for 100 hours or longer under high temperature conditions, the mass increase of the resin is 0% or more and 0.20% or less. <9a> The grease composition for resin according to <8a>, wherein the high temperature conditions refer to the conditions under which the resin is immersed in the grease composition for resin at 105 °C for 168 hours.

Advantages of the Invention

[0008] According to the grease composition of the present invention, it is possible to provide a grease composition that does not deteriorate the contacting resin, particularly an acetal resin, even under high temperature conditions.

Embodiments for Carrying Out the Invention

[0009] 〔Component (A): Lubricating base oil〕 As the lubricating base oil used in the present invention, either mineral oil or synthetic base oil can be used. The kinematic viscosity of the lubricating base oil at 40 °C is not particularly limited, but from the viewpoint of safely preparing grease having excellent lubricity, it is preferably 10 mm 2 / s or more, more preferably 20 mm 2 / s or more, more preferably 25 mm 2 / s or more, preferably 700 mm 2 / s or less, more preferably 500 mm 2 / s or less, more preferably 70 mm 2 / s or less. Further, in one embodiment, the kinematic viscosity at 40°C of the lubricating oil base oil is preferably 10 mm 2 / s or more and 700 mm 2 / s or less, more preferably 20 mm 2 / s or more and 500 mm 2 / s or less, more preferably 25 mm 2 / s or more and 70 mm 2 / s or less. The viscosity index at 40°C of the lubricating oil base oil is not particularly limited, but from the viewpoint of preparing a grease having excellent lubricity, it is preferably 95 or more and 250 or less, more preferably 95 or more and 150 or less. The viscosity index and kinematic viscosity at 40°C in this specification respectively mean the viscosity index and kinematic viscosity at 40°C measured in accordance with JIS K2283. The flash point of the lubricating oil base oil is not particularly limited, but from the viewpoint of safety, preferably the flash point is 150°C or higher.

[0010] In the present invention, it is preferable to use a hydrocarbon oil (such as a mineral oil or a synthetic base oil), and more preferably to use a mineral oil. Examples of the mineral oil include a distillate oil obtained by atmospheric distillation of crude oil, or a distillate oil obtained by further vacuum distillation of this distillate oil, which is a lubricating oil fraction refined by various refining processes. As the refining processes, hydrorefining, solvent extraction, solvent dewaxing, hydrodewaxing, sulfuric acid washing, clay treatment, etc. can be appropriately combined. By treating these refining processes in an appropriate order in combination, a lubricating oil base oil that can be used in the present invention can be obtained. A mixture of a plurality of refined oils having different properties obtained by subjecting different crude oils or distillate oils to different combinations of refining processes can also be used.

[0011] As the synthetic base oil, a base material with excellent hydrolysis stability can be used. Examples of such base materials with excellent hydrolysis stability include polyolefins such as poly-α-olefin, polyesters, polyalkylene glycols, alkylbenzenes, alkylnaphthalenes, and GTL base oils. Among the synthetic base oils, poly-α-olefin is preferred in terms of availability, cost, viscosity characteristics, and compatibility with oxidation stability.

[0012] The lubricating oil base oil can be mineral oil or synthetic base oil alone, or a mixture of two or more. In the present invention, the lubricating oil base oil may contain only mineral oil, or it may contain other lubricating oil base oils. Specifically, in the grease composition of the present invention, the mineral oil content may be, for example, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more, based on the lubricating oil base oil. In the present invention, the content of lubricating oil base oil is preferably 50% by mass or more, more preferably 60% by mass or more, preferably 95% by mass or less, and more preferably 90% by mass or less, based on the total amount of the grease composition. In one embodiment, it is preferably 50% by mass or more and 95% by mass or less, and more preferably 60% by mass or more and 90% by mass or less. By setting the content of lubricating oil base oil within the above range, a grease composition having the desired consistency can be easily prepared.

[0013] [Ingredient (B): Thickener] The grease composition of the present invention comprises at least one selected from the group consisting of metal soap-based thickeners and urea-based thickeners.

[0014] [Metal soap-based thickeners] Examples of metal soap-based thickeners include single soaps and complex soaps. A single soap is a metal soap obtained by saponifying a fatty acid or oil with an alkali metal hydroxide or alkaline earth metal hydroxide. A complex soap is a compound formed by combining the fatty acid used in a single soap with an organic acid having a different molecular structure. The fatty acid may be a fatty acid derivative having a hydroxyl group, etc. The fatty acid may be an aliphatic carboxylic acid such as stearic acid, or an aromatic carboxylic acid such as terephthalic acid. As the fatty acid, a monovalent or divalent aliphatic carboxylic acid, for example, an aliphatic carboxylic acid having 6 to 20 carbon atoms is used, and in particular, a monovalent aliphatic carboxylic acid having 12 to 20 carbon atoms or a divalent aliphatic carboxylic acid having 6 to 14 carbon atoms is preferred. As the fatty acid, a monovalent aliphatic carboxylic acid containing one hydroxyl group is preferred. Suitable organic acids to be combined with the fatty acid in a complex soap include acetic acid, azelaic acid or sebacic acid, or benzoic acid. As metals used in metal soap-based thickeners, alkali metals such as lithium and sodium, alkaline earth metals such as calcium, and amphoteric metals such as aluminum are used. Among these, alkali metals, and especially lithium, are preferred. In this invention, "6 to 20 carbon atoms" means having 6 to 20 carbon atoms.

[0015] The metal soap-based thickener may be used alone or in combination of two or more types. The content of the metal soap-based thickener is preferably 2% by mass or more, more preferably 3% by mass or more, even more preferably 10% by mass or more, preferably 30% by mass or less, and even more preferably 20% by mass or less, based on the total amount of the grease composition. In one embodiment, the content of the metal soap-based thickener is preferably 2% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 20% by mass or less, and even more preferably 10% by mass or more and 20% by mass or less.

[0016] [Urea-based thickeners] As urea-based thickeners, for example, diurea compounds obtained by the reaction of diisocyanate with a monoamine, or polyurea compounds obtained by the reaction of diisocyanate with a monoamine or diamine can be used.

[0017] Diisocyanates are compounds in which two hydrogen atoms of a hydrocarbon are replaced by isocyanate groups. Preferred diisocyanates include phenylenediisocyanate, tolylenediisocyanate, diphenyldiisocyanate, diphenylmethanediisocyanate, octadecanediisocyanate, decanediisocyanate, or hexanediisocyanate. The hydrocarbon in the diisocyanate may be an acyclic hydrocarbon group, a cyclic hydrocarbon group, an aromatic hydrocarbon group, an alicyclic hydrocarbon group, or an aliphatic hydrocarbon group. The number of carbon atoms is preferably 2 to 20, and particularly preferably 4 to 18.

[0018] Furthermore, a monoamine is a compound having one amino group in one molecule. Preferred monoamines include octylamine, dodecylamine, hexadecylamine, stearylamine, oleylamine, aniline, p-toluidine, and cyclohexylamine. A diamine is a compound having two amino groups in one molecule. Preferred diamines include ethylenediamine, propanediamine, butanediamine, hexanediamine, octanediamine, phenylenediamine, tolylenediamine, xylenediamine, and diaminodiphenylmethane. The hydrocarbon group of a monoamine or diamine may be an acyclic hydrocarbon group or a cyclic hydrocarbon group, and may be an aromatic hydrocarbon group, an alicyclic hydrocarbon group, or an aliphatic hydrocarbon group. The number of carbon atoms is preferably 2 to 20, particularly 4 to 18.

[0019] As urea-based thickeners, diurea compounds are preferred, particularly those having an aromatic hydrocarbon group as a diisocyanate, and even more so alkylenediaryl diisocyanates such as methylenediphenyl diisocyanate. The number of carbon atoms is preferably 12 to 24. In addition, as monoamines, aromatic amines, alicyclic amines, or aliphatic amines can be used, or mixed amines obtained by mixing these can be used.

[0020] The urea-based thickener may be used alone or in combination of two or more types. The content of the urea-based thickener is preferably 2% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, preferably 30% by mass or less, and even more preferably 20% by mass or less, based on the total amount of the grease composition. In one embodiment, the content of the urea-based thickener is preferably 2% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 20% by mass or less, and even more preferably 5% by mass or more and 20% by mass or less.

[0021] The grease composition of the present invention preferably contains a metal soap-based thickener, and more preferably contains a lithium complex soap-based thickener. The grease composition of the present invention may contain both a metal soap-based thickener and a urea-based thickener, but it is preferable to contain only one of them.

[0022] [Component (C): At least one selected from the group consisting of organic molybdenum compounds and sulfur-based extreme pressure agents] The grease composition of the present invention comprises at least one selected from the group consisting of organic molybdenum compounds and sulfur-based extreme pressure agents.

[0023] [Organomolybdenum compounds] Examples of organic molybdenum compounds include molybdenum dithiocarbamates (MoDTC), molybdenum dithiophosphates (MoDTP), and Moamine complexes. It is preferable to use molybdenum dithiocarbamates as the organic molybdenum compound, and more preferably a molybdenum dithiocarbamate represented by the following formula (1).

[0024] Formula (1): JPEG0007867589000001.jpg44160 (In the formula, R1 to 4 may be the same or different, and each is a hydrocarbon group having 1 to 30 carbon atoms, and X1 to X4 may be the same or different, and each is S or O). R1 ​​to 4 are preferably cycloalkyl groups or linear alkyl groups, and linear alkyl groups are more preferably. Furthermore, R1 to 4 are preferably linear alkyl groups having 1 to 5 carbon atoms, and linear alkyl groups having 4 carbon atoms are more preferably.

[0025] The content of the organic molybdenum compound is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, preferably 15% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and most preferably 3% by mass or less, based on the total amount of the grease composition. In one embodiment, the content of the organic molybdenum compound is preferably 0.01% by mass or more and 15% by mass or less, more preferably 0.05% by mass or more and 10% by mass or less, even more preferably 0.05% by mass or more and 5% by mass or less, and most preferably 0.1% by mass or more and 3% by mass or less. By setting the content of the organic molybdenum compound to above the lower limit, the coefficient of friction can be kept low. By setting the content of the organic molybdenum compound to below the upper limit, it is possible to reduce manufacturing costs while obtaining a sufficient effect of reducing the coefficient of friction. The molybdenum content in the organic molybdenum compound is preferably 5% by mass or more and 40% by mass or less, and more preferably 5% by mass or more and 30% by mass or less, based on the organic molybdenum compound.

[0026] [Sulfur-based extreme pressure agent] Known sulfur-based extreme pressure agents can be used, such as sulfurized oils and fats, sulfurized fatty acids, sulfurized esters, sulfurized olefins, dihydrocarbyl (poly)sulfides, alkylthiocarbamoyl compounds, thioterpene compounds, dialkylthiodipropionate compounds, sulfurized mineral oils, and zinc dithiocarbamate compounds. These sulfur-based extreme pressure agents may be used individually or in combination of two or more.

[0027] Sulfurized fats and oils are products obtained by reacting sulfur or sulfur-containing compounds with fats and oils (such as lard, whale oil, vegetable oil, and fish oil). There are no particular restrictions on the sulfur content in sulfurized fats and oils, but it is usually between 5% and 30% by mass.

[0028] As sulfurized fatty acids, products obtained by sulfurizing unsaturated fatty acids by any method can be used, and specific examples include sulfurized oleic acid. As the sulfurized ester, products obtained by sulfurizing unsaturated fatty acid esters (for example, products obtained by reacting unsaturated fatty acids (oleic acid, linoleic acid, or fatty acids extracted from the above-mentioned animal and vegetable oils) with various alcohols) by any method can be used. Specifically, examples include methyl oleate sulfide and octyl rice bran fatty acid sulfide.

[0029] Examples of sulfurized olefins include compounds represented by the following general formula (2). These compounds can be obtained by reacting an olefin having 2 to 15 carbon atoms or a di to tetramer thereof with a sulfurizing agent such as sulfur or sulfur chloride. Examples of olefins that can be used include propylene, isobutene, and diisobutene.

[0030] Formula (2): R11-Sa-R12 (In formula (2), R11 represents an alkenyl group having 2 to 15 carbon atoms, R12 represents an alkyl group or alkenyl group having 2 to 15 carbon atoms, and a represents an integer from 1 to 8.)

[0031] Dihydrocarbyl (poly)sulfide is a compound represented by the following general formula (3). Here, when R13 and R14 are alkyl groups, it is sometimes called an alkyl sulfide.

[0032] Formula (3): R13-Sb-R14 (In formula (3), R13 and R14 may be the same or different, and each independently represents an alkyl group having 1 to 20 carbon atoms (which may be linear or branched, and may have a cyclic structure), an aryl group having 6 to 20 carbon atoms, an alkylaryl group having 7 to 20 carbon atoms, or an arylalkyl group having 7 to 20 carbon atoms, and b represents an integer from 1 to 8.)

[0033] Examples of alkylthiocarbamoyl compounds include those represented by the following general formula (4).

[0034] Formula (4): JPEG0007867589000002.jpg74144 (In formula (4), R15 to R18 may be the same or different, each independently representing an alkyl group with 1 to 20 carbon atoms, and c represents an integer from 1 to 8.)

[0035] Examples of thioterpene compounds include the reaction product of phosphorus pentasulfide and pinene. Examples of dialkylthiodipropionate compounds include dilaurylthiodipropionate and distearylthiodipropionate.

[0036] Sulfurized mineral oil is a substance obtained by dissolving elemental sulfur in mineral oil. While there are no particular restrictions on the type of mineral oil used for sulfurized mineral oil, specific examples include paraffinic mineral oil and naphthenic mineral oil, which are refined by subjecting a lubricating oil fraction obtained by atmospheric and vacuum distillation of crude oil to a combination of known refining processes. Furthermore, elemental sulfur may be used in any form, such as lumps, powder, or molten liquid. While there are no particular restrictions on the sulfur content in sulfurized mineral oil, it is usually between 0.05% by mass and 1.0% by mass, based on the total amount of sulfurized mineral oil.

[0037] As the zinc dithiocarbamate compound, the compound represented by the following general formula (5) can be used.

[0038] Formula (5): JPEG0007867589000003.jpg54140 (In general formula (5), R19 to R22 may be the same or different, and each independently represents a hydrocarbyl group with 1 or more carbon atoms.)

[0039] As the sulfur-based extreme pressure agent, it is preferable to use a dihydrocarbyl (poly)sulfide represented by general formula (3), more preferably a dialkyl polysulfide in which both R13 and R14 in general formula (3) are alkyl groups, and even more preferably a dioctyl polysulfide.

[0040] When a sulfur-based extreme pressure agent is included, its content is 0.05% by mass or more and 2.5% by mass or less based on the total amount of the grease composition, from the viewpoint of imparting extreme pressure properties and not degrading the resin. Furthermore, the content of the sulfur-based extreme pressure agent is preferably 0.1% by mass or more, preferably 2.0% by mass or less, and more preferably 1.5% by mass or less. In one embodiment, it is preferably 0.05% by mass or more and 2.0% by mass or less, and more preferably 0.1% by mass or more and 1.5% by mass or less.

[0041] The grease composition of the present invention preferably contains both an organic molybdenum compound and a sulfur-based extreme pressure agent. Organic molybdenum compounds such as molybdenum dithiocarbamate and molybdenum dithiophosphate contain sulfur molecules. Therefore, these organic molybdenum compounds also fall under the category of sulfur-based extreme pressure agents. However, even if an organic molybdenum compound also falls under the category of a sulfur-based extreme pressure agent, in the present invention, the organic molybdenum compound is not treated as a sulfur-based extreme pressure agent, and the content of the organic molybdenum compound is not added to the content of the sulfur-based extreme pressure agent. Furthermore, "containing both" an organic molybdenum compound and a sulfur-based extreme pressure agent means that, in addition to the organic molybdenum compound, a sulfur-based extreme pressure agent that does not contain molybdenum is also included.

[0042] [Zinc dialkyldithiophosphate] The grease composition of the present invention substantially does not contain zinc dialkyldithiophosphate (hereinafter sometimes referred to as ZnDTP), taking into consideration its effects on resins and metals (particularly copper). Zinc dialkyldithiophosphate is usually added to greases for purposes such as improving corrosion resistance, load-bearing capacity, and wear resistance. The inventors have discovered that adding zinc dialkyldithiophosphate in addition to sulfur-based extreme pressure agents and / or organic molybdenum compounds adversely affects the resins and metals in contact with the grease. In this specification, "substantially absent" means that zinc dialkyldithiophosphate is not present in an amount that would normally be expected to improve corrosion resistance, load-bearing capacity, and wear resistance. In this specification, "substantially absent" means that zinc dialkyldithiophosphate is present in an amount of, for example, 1% by mass or less, preferably 0.1% by mass or less, and more preferably 0.01% by mass or less, based on the grease composition. The grease composition of the present invention most preferably does not contain zinc dialkyldithiophosphate.

[0043] [Other additives] In addition to the above components, the grease composition of the present invention may optionally contain solid lubricants, antioxidants, rust inhibitors, and corrosion inhibitors, which are commonly used in greases.

[0044] Examples of solid lubricants include graphite, graphite fluoride, melamine cyanurate, polytetrafluoroethylene, antimony sulfide, and alkali (earth) metal borates. When a grease composition contains a solid lubricant, its content may be 0.1% by mass or more and 20% by mass or less based on the total amount of the grease composition.

[0045] Examples of antioxidants include phenolic compounds such as 2,6-di-t-butylphenol and 2,6-di-t-butyl-p-cresol, and amine compounds such as monobutylphenylmonoctylphenylamine, dialkyldiphenylamine, phenyl-α-naphthylamine, and p-alkylphenyl-α-naphthylamine. When the grease composition contains an antioxidant, its content may be 0.1% by mass or more and 10% by mass or less based on the total amount of the grease composition.

[0046] Examples of rust inhibitors include amines, neutral or overbasic petroleum-based or synthetic oil-based metal sulfonates, carboxylate metal salts, esters, phosphoric acid, phosphates, and the like. When a grease composition contains a rust inhibitor, its content may be 0.005% by mass or more and 5% by mass or less based on the total amount of the grease composition.

[0047] As corrosion inhibitors, known corrosion inhibitors such as benzotriazole compounds, toltriazole compounds, thiadiazole compounds, and imidazole compounds can be used. If the grease composition contains a corrosion inhibitor, its content may be 0.01% by mass or more and 10% by mass or less based on the total amount of the grease composition.

[0048] The grease composition of the present invention can be obtained by mixing essential components (A) to (C), along with other additives as needed, stirring, and then passing the mixture through a roll mill or the like.

[0049] 〔resin〕 In this specification, "resin" includes both natural resins and synthetic resins. Synthetic resins include general-purpose plastics (such as polyethylene, polystyrene, polypropylene, and polyvinyl chloride) and engineering plastics. From the viewpoint of heat resistance and mechanical strength, preferred synthetic resins include polyamide resins, acetal resins, polycarbonate resins, polysulfone resins, polyphenylene sulfide resins, polyamide-imide resins, polyetheretherketone resins, phenolic resins, polyester resins, and epoxy resins, with acetal resins being more preferred. Applications for the grease composition of the present invention include the sliding parts of transportation machinery such as automobiles, railways, or aircraft; industrial machinery such as machine tools; household electrical appliances such as washing machines, refrigerators, or vacuum cleaners; and precision machinery such as watches or cameras. The grease composition of the present invention is preferably used in bearings, gears, sliding surfaces, belts, joints, and cams containing resin materials within these devices.

[0050] [Grease composition] The consistency of the grease composition of the present invention is preferably 265 to 475, more preferably 265 to 385, and even more preferably 310 to 340. In this specification, consistency refers to mixed consistency measured in accordance with JIS K2220. The specific measurement conditions are as follows: The sample is packed into a consistency measuring vessel and kept at 25°C, then mixed 60 times back and forth for 1 minute using a specified mixer. Next, excess sample is removed with a spatula, the surface of the sample is flattened, and a specified cone is dropped into the sample for 5 seconds. The mixed consistency is defined as 10 times the depth (mm) to which the cone penetrated.

[0051] The grease composition of the present invention exhibits the exceptional effect of not degrading the resin it comes into contact with, particularly acetal resin, even under high-temperature conditions. High-temperature conditions refer to conditions in which the resin is immersed in the grease composition at 90°C or higher for 100 hours or more, and more specifically, at 105°C for 168 hours. "Not degrading the resin" means that the change in the mass of the resin is extremely small, and specifically, when the resin is immersed in the grease composition under the above high-temperature conditions, the increase in the mass of the resin is 0% or more and 0.20% or less. The grease composition of the present invention also exhibits low reactivity with materials other than resin, such as metals (e.g., copper), and has the effect of not degrading metals. Therefore, the grease composition of the present invention may be encapsulated in a single component containing both resin and metal (e.g., copper). Furthermore, embodiments in which the grease composition comes into contact with materials other than metal (e.g., copper) and resin are not excluded. [Examples]

[0052] Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited to the following examples. Unless otherwise specified, % refers to mass %.

[0053] Examples 1, 4, 6-8, 10, Reference Examples 1-4, Examples 4-10, and Comparative Examples 1-3 <Grease composition> Test grease compositions were prepared for each example and comparative example by blending thickeners, base oils, and additives in the proportions shown in Tables 1 and 2. The obtained test grease compositions were evaluated as follows. The evaluation results are shown in Tables 1 and 2.

[0054] (1) Base oil ·Mineral oil 1: Kinematic viscosity 36.8mm 2 / s (40℃) ·Mineral oil 2: Kinematic viscosity 86.6mm 2 / s (40℃) ·Mineral oil 3: Kinematic viscosity 22.7mm 2 / s (40℃) Lubricating oil base oils were prepared by mixing base oils in the mass ratios shown in Tables 1 and 2. (2) Thickener • Urea thickeners: Reaction products of diphenylmethane diisocyanate and cyclohexylamine • Lithium complex thickener: Reaction product of lithium 12-hydroxystearate and azelaic acid (3) Additives As shown in Tables 1 and 2, additives were added. Details of the additives are as follows. Note that the base oil amount (total), thickener, and additive amounts are based on the total amount of the grease composition. • MoDTC ADEKA Corporation (Product name: Sakura Lube 515) • Dioctyl polysulfide, manufactured by DIC Corporation (Product name: DAILUBE GS440L) • ZnDTP1, manufactured by Chevron Oronite Japan (Product name: OLOA5283) • ZnDTP2, manufactured by Lubrizol Japan Co., Ltd. (Product name: LUBRIZOL1095) Other additives: 2,6-di-t-butylphenol, dialkyldiphenylamine, benzotriazole compounds, thiadiazole compounds, tricresyl phosphate

[0055] <Rating> (1) Mass change of acetal resin Test specimens of acetal resin measuring 2 mm thick, 40 mm long, and 20 mm wide were prepared, and each grease composition was applied to these specimens. Each specimen coated with these grease compositions was heated at 105°C for 168 hours. After heating, the grease composition was removed, and the change in mass of the specimen before and after heating was measured. A mass increase of 0% to 0.2% was considered not to degrade the acetal resin.

[0056] (2) Extreme pressure properties In accordance with ASTM D2596, the fusion load (WL) was measured using a four-ball tester under the following conditions, and it was determined that the material possessed extreme pressure properties if the fusion load was 2452N or higher. • Rotation speed: 1800 rpm ·Temperature: Room temperature • Test time: 10 seconds

[0057] (3) Change in the copper plate to black In accordance with JIS K 2220, the corrosion of copper plates was measured after being kept in a constant temperature air bath at 100°C for 24 hours. [Table 1] [Table 2]

[0058] In each of the grease compositions of Examples 1, 4, 6-8, 10, Reference Examples 1-4, and Examples 4-10, the mass increase of the acetal resin was always between 0% and 0.2%, the extreme pressure value was greater than 2452N, and no corrosion of the copper plate was observed. In Comparative Example 1, where ZnDTP1 was added, and Comparative Example 2, where ZnDTP2 was added, the mass of the acetal resin decreased, and corrosion of the copper plate occurred. In Comparative Example 3, where 3% by mass of dioctyl polysulfide was added, the mass of the acetal resin increased by more than 2.0%. [Industrial applicability]

[0059] The grease composition of the present invention provides a grease composition that does not degrade the resin it is in contact with, particularly acetal resin, even under high-temperature conditions.

Claims

1. (A) Mineral oil and, (B) Lithium complex and (C) Contains both molybdenum dithiocarbamate and dioctyl polysulfide, A resin grease composition that does not contain zinc dialkyldithiophosphate, The kinematic viscosity of the aforementioned mineral oil at 40°C is 25 mm². 2 / s or more 70mm 2 It is less than or equal to / s, The lithium complex content is 11% by mass or more and 20% by mass or less based on the total amount of the composition. The content of the aforementioned dioctyl polysulfide is 0.1% by mass or more and 2.0% by mass or less based on the total amount of the composition. A resin grease composition wherein the content of the molybdenum dithiocarbamate is 0.05% by mass or more and 5% by mass or less based on the total amount of the composition.

2. The resin grease composition according to claim 1, wherein the resin is an acetal resin.

3. A resin grease composition according to claim 1 or claim 2, wherein the consistency is 265 or more and 475 or less.

4. The resin grease composition according to claim 1 or claim 2, wherein the mineral oil content is 50% by mass or more and 95% by mass or less based on the total amount of the composition.

5. The resin grease composition according to claim 2, which is used in a component containing acetal resin and metal.

6. The resin grease composition according to claim 5, wherein the metal is copper.

7. The resin grease composition according to claim 1 or claim 2, wherein when a resin is immersed in the resin grease composition at 90°C or higher for 100 hours or more under high temperature conditions, the mass increase of the resin is 0% or more and 0.20% or less.

8. The resin grease composition according to claim 7, wherein the high-temperature conditions refer to the condition of immersing the resin in the resin grease composition at 105°C for 168 hours.

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