Grease composition and method of lubricating sliding parts using the same

Abstract

The problem to be solved by the present invention is to provide a grease composition in which a resin, particularly an acetal resin, in contact with the grease composition is not deteriorated even under high temperature conditions. The problem can be solved by a resin-use grease composition comprising (A) a lubricating oil base oil, (B) a thickening agent, and (C) at least one substance selected from the group consisting of an organic molybdenum compound and a sulfur-based extreme pressure agent. If the sulfur-based extreme pressure agent is contained, the content of the sulfur-based extreme pressure agent is 0.05 to 2.5 mass% with respect to the total amount of the composition, and the composition substantially does not contain zinc dialkyldithiophosphate.

Description

Technical Field

[0001] This invention relates to a grease composition. It also relates to a method of lubricating sliding parts using the grease composition. Background Technology

[0002] Resin molded parts are used as various mechanical parts. Among them, molded parts made from polyacetal resin (acetal resin) have excellent properties in terms of mechanical properties and formability. Due to these properties, molded parts made from acetal resin are widely used in household appliances and electrical or electronic products.

[0003] Lubricating grease is mainly used in thrust bearings, rolling bearings, or sliding parts. The type of grease used is selected based on the operating conditions.

[0004] To improve the lubricity of greases and their compatibility with sliding part materials, various selections of base oils, thickeners, and additives have been proposed. On the other hand, frictional characteristics vary depending on conditions, such as the materials used in the sliding parts. The grease used can degrade certain materials. Therefore, it is necessary to select a grease with the most suitable composition, taking into account the materials of the sliding parts.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2011-157477

[0008] Patent Document 2: International Publication No. WO2015 / 083695 Summary of the Invention

[0009] The problem the invention aims to solve

[0010] Patent Document 1 discloses a grease composition that prevents poor lubrication and prevents grease from splattering and remaining on nearby equipment, thus preventing contamination. Patent Document 2 discloses a grease composition with low sliding resistance and the ability to significantly reduce power consumption of mechanical parts, particularly bearings during rotation. However, neither of these documents tested the aptitude of the resin. Therefore, its suitability for the resin is unknown. In particular, sliding parts typically become hot. Therefore, there is a need for a grease composition that does not degrade the resin it contacts, even under high-temperature conditions.

[0011] Solution for solving the problem

[0012] The inventors have conducted extensive research on grease compositions that do not degrade resins, particularly acetal resins, that come into contact with the material even under high-temperature conditions. The inventors have discovered that the aforementioned problem can be achieved through grease compositions containing components (A) to (C), wherein, when the grease composition contains a sulfur-based extreme pressure agent, the content of the sulfur-based extreme pressure agent is 0.05% by mass or less and 2.5% by mass or less based on the total amount of the composition, and the grease composition is substantially free of zinc dialkyl dithiophosphate. This invention is thus completed.

[0013] The present invention is based on the following discovery and is provided as follows.

[0014] <1>

[0015] A resin-based grease composition comprising

[0016] (A) Lubricating oil base oil,

[0017] (B) Thickener, and

[0018] (C) Selected from at least one of the group consisting of organic molybdenum compounds and sulfur-based extreme pressure agents, wherein

[0019] When the grease composition 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, based on the total amount of the composition.

[0020] The grease composition is substantially free of dialkyl dithiophosphate zinc.

[0021] <2>

[0022] according to <1> The resin-based grease composition, wherein the resin is an acetal resin.

[0023] <3>

[0024] according to <1> or <2> The resin-based grease composition, wherein the grease composition comprises 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.

[0025] <4>

[0026] according to <1> to <3> The resin-based grease composition according to any one of the following statements, wherein the grease compound comprises both an organomolybdenum compound and a sulfur-based extreme pressure agent.

[0027] <5>

[0028] according to <1> to <4> The resin-based grease composition described in any one of the following statements, wherein the thickener is a metal soap-based thickener.

[0029] <6>

[0030] according to <1> to <5> The resin-based grease composition described in any one of the following examples, wherein the penetration of the grease composition is 265 to 475.

[0031] <7>

[0032] according to <1> to <6> The resin grease composition described in any one of the following statements, wherein

[0033] (A) Based on the total amount of the composition, the content of the lubricating oil base oil is 50% by mass or more and 95% by mass or less; and

[0034] (B) Based on the total amount of the composition, the content of the thickener is more than 2% by mass and less than 30% by mass.

[0035] <8>

[0036] according to <1> to <7> The resin grease composition according to any one of the following, wherein the content of zinc dialkyl dithiophosphate is less than 1% by mass based on the total amount of the composition.

[0037] <9>

[0038] according to <2> to <8> The resin grease composition described in any one of the following is used in components comprising acetal resin and metal.

[0039] <10>

[0040] according to <9> The resin-based grease composition wherein the metal is copper.

[0041] <11>

[0042] A method for lubricating sliding parts, the method comprising: according to <1> to <10> The grease composition described in any one of the above statements is placed in the sliding portion.

[0043] The effects of the invention

[0044] The grease composition of the present invention can provide a grease composition that does not degrade the resin, especially acetal resin, in contact with it even under high temperature conditions. Detailed Implementation

[0045] [Component (A): Lubricating oil base oil]

[0046] Any mineral oil or synthetic oil can be used as the base oil for the lubricating oil used in this invention. There are no particular limitations on the kinematic viscosity of the base oil at 40°C, but from the viewpoint of safely preparing a grease with excellent lubricity, a viscosity of 10 mm is preferred. 2 / s or higher, preferably 20mm2 / s or higher, but 25mm is still preferred. 2 / s or higher, and preferably 700mm 2 / s or less, preferably 500mm 2 / s or less, but 70mm is still preferred 2 / s or less. In one embodiment, the kinematic viscosity of the lubricating oil base oil at 40°C is preferably 10 mm. 2 / s or higher and 700mm 2 / s or less, preferably 20mm 2 / s or higher and 500mm 2 For speeds below / s, 25mm is still preferred. 2 / s or higher and 70mm 2 / s or less. There are no particular limitations on the viscosity index of the lubricating oil base oil at 40°C, but from the viewpoint of preparing a grease with excellent lubricity, it is preferred to be 95 or higher and 250 or lower, more preferably 95 or higher and 150 or lower.

[0047] The viscosity index and kinematic viscosity at 40°C mentioned in this article refer to the viscosity index and kinematic viscosity at 40°C measured according to JIS K 2283, respectively.

[0048] There are no particular restrictions on the flash point of the lubricating oil base oil, but from a safety point of view, a flash point above 150°C is preferred.

[0049] In this invention, hydrocarbon oils (mineral oils or synthetic oils, etc.) are preferably used as lubricating oil base oils, and mineral oils are more preferred. Examples of mineral oils include distillates obtained by atmospheric distillation of crude oil, or lubricating oil fractions obtained by further vacuum distillation of said distillates and purification of the resulting distillates through various refining processes. Depending on the requirements, the refining processes may be, for example, combinations of hydrorefining, solvent extraction, solvent dewaxing, hydrodewaxing, sulfuric acid washing, and / or white clay treatment. These refining processes can be combined in a suitable sequence to produce lubricating oil compositions usable in this invention. Mixtures of various refined oils with different properties, obtained through different combinations of refining processes on different crude oils or distillates, can also be used.

[0050] Substrates with excellent hydrolytic stability can be used as synthetic oils. Examples of such substrates include polyolefins such as poly-α-olefins, polyesters, polyalkylene glycols, alkylbenzenes, alkylnaphthalenes, and GTL base oils. Among synthetic oils, poly-α-olefins are preferred in terms of availability, cost, viscosity characteristics, and compatibility with oxidative stability.

[0051] Mineral oil or synthetic oil can be used alone, or a mixture of two or more, as a base oil for lubricating oil. In this invention, only mineral oil may be included as the base oil, or other base oils may be included. Specifically, based on the base oil, the content of the base oil in the grease composition of this invention can 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.

[0052] In this invention, based on the total amount of the grease composition, the content of the lubricating oil base oil is preferably 50% by mass or more, more preferably 60% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less. In one embodiment, the content is preferably 50% by mass or more and 95% by mass or less, more preferably 60% by mass or more and 90% by mass or less. When the content of the lubricating oil base oil falls within the above range, a grease composition having the desired penetration can be conveniently prepared.

[0053] [Component (B): Thickener]

[0054] 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.

[0055] [Metallic soap-based thickener]

[0056] Examples of metallic soap-based thickeners include single soaps and complex soaps. Single soaps are metallic soaps obtained by saponifying fatty acids or fats / oils with alkali metal hydroxides or alkaline earth metal hydroxides. Complex soaps are obtained by further combining the fatty acids used in the single soap with organic acids having different molecular structures. The fatty acids can be fatty acid derivatives having hydroxyl groups, etc. The fatty acids can be aliphatic carboxylic acids such as stearic acid, or aromatic carboxylic acids such as terephthalic acid. Monovalent or divalent aliphatic carboxylic acids, such as C64, are used as fatty acids. 6-20 Aliphatic carboxylic acids, especially, preferably using C 12-20 Monovalent aliphatic carboxylic acids or C 6-14 The fatty acid is a divalent aliphatic carboxylic acid. The fatty acid is preferably a monovalent aliphatic carboxylic acid containing one hydroxyl group. The organic acid combined with the fatty acid in the complex soap is preferably acetic acid, adicarboxylic acid such as azelaic acid or sebacic acid, or benzoic acid, etc.

[0057] For example, alkali metals such as lithium or sodium, alkaline earth metals such as calcium, or amphoteric metals such as aluminum are used as thickeners in metal soaps. Alkali metals, particularly lithium, are preferred. Note that "C" in this invention... 6-20"" refers to having 6 to 20 carbon atoms.

[0058] A single metal soap-based thickener can be used, or two or more can be used in combination. Based on the total amount of the grease composition, the content of the metal soap-based thickener is, for example, preferably 2% by mass or more, more preferably 3% by mass or more, still more preferably 10% by mass or more, and preferably 30% by mass or less, more preferably 20% by mass or less. 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, still more preferably 10% by mass or more and 20% by mass or less.

[0059] [Urea-based thickener]

[0060] For example, diurea compounds obtained by the reaction between diisocyanate and monoamine, or polyurea compounds obtained by the reaction between diisocyanate and monoamine or diamine, can be used as urea-based thickeners.

[0061] Diisocyanates are compounds obtained by replacing two hydrogen atoms of a hydrocarbon with an isocyanate group. Preferred diisocyanates include phenylene diisocyanate, toluene diisocyanate, diphenyl diisocyanate, diphenylmethane diisocyanate, octadecane diisocyanate, decane diisocyanate, or hexane diisocyanate. The hydrocarbon in the diisocyanate can be an acyclic or cyclic hydrocarbon group, and can be an aromatic, alicyclic, or aliphatic hydrocarbon group. The number of carbon atoms is preferably 2 to 20, particularly 4 to 18.

[0062] A monoamine is a compound having one amino group in a molecule. Preferred monoamines include octylamine, dodecylamine, hexadecylamine, octadecylamine, oleylamine, aniline, p-toluidine, or cyclohexylamine. A diamine is a compound having two amino groups in a molecule. Preferred diamines include ethylenediamine, propylenediamine, butanediamine, hexanediamine, octyldiamine, phenylenediamine, toluenediamine, xylenediamine, or diaminodiphenylmethane. The hydrocarbon group of a monoamine or diamine can be acyclic or cyclic, and can be aromatic, alicyclic, or aliphatic. The number of carbon atoms is preferably 2 to 20, particularly 4 to 18.

[0063] Urea-based thickeners are preferably diurea compounds, particularly diisocyanates having aromatic hydrocarbon groups, and more preferably alkylene diaryl diisocyanates such as methylene diphenyl diisocyanate. The number of carbon atoms is preferably 12 to 24. As a monoamine, aromatic amines, alicyclic amines, or aliphatic amines can be used, and mixed amines obtained by mixing these can also be used.

[0064] A single urea-based thickener can be used, or two or more can be used in combination. Based on the total amount of the grease composition, the content of the urea-based thickener is, for example, preferably 2% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more, and preferably 30% by mass or less, more preferably 20% by mass or less. 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, still more preferably 5% by mass or more and 20% by mass or less.

[0065] The grease composition of the present invention preferably contains a metal soap-based thickener, more preferably 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, preferably one of them.

[0066] In the grease composition of the present invention, one of the thickeners listed above may be used alone, or two or more of them may be used in combination. Based on the total amount of the grease composition, the content of the thickener is, for example, preferably 2% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more, and preferably 30% by mass or less, more preferably 20% by mass or less. In one embodiment, the content of the 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, still more preferably 5% by mass or more and 20% by mass or less.

[0067] [Component (C): at least one selected from the group consisting of organomolybdenum compounds and sulfur-based extreme pressure agents]

[0068] The grease composition of the present invention comprises at least one selected from the group consisting of an organic molybdenum compound and a sulfur-based extreme pressure agent.

[0069] [Organomolybdenum compounds]

[0070] Examples of organomolybdenum compounds include molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDTP), and Mo-amine complexes. As an organomolybdenum compound, molybdenum dithiocarbamate is preferred, and more preferably, molybdenum dithiocarbamate represented by the following formula (1) is preferred.

[0071] Equation (1):

[0072]

[0073] Among them, R1 to R4 can be the same or different, and each has a value of C. 1-30 The hydrocarbon groups, X1 to X4, can be the same or different, and each can be S or O.

[0074] R1 to R4 are each preferably cycloalkyl or chain alkyl, and more preferably chain alkyl. R1 to R4 are each preferably C1-5 Chain alkyl, particularly, more preferably C4 chain alkyl.

[0075] Based on the total amount of the grease composition, the content of the organomolybdenum compound is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.1% by mass or more, and preferably 15% by mass or less, more preferably 10% by mass or less, still more preferably 5% by mass or less, and most preferably 3% by mass or less. In one embodiment, the content of the organomolybdenum 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, still 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. The content of the organomolybdenum compound can be set to the lower limit value or above. This maintains low friction. The content of the organomolybdenum compound can be set to the upper limit value or below. This can reduce production costs while achieving sufficient friction reduction.

[0076] Based on organomolybdenum compounds, the molybdenum content of the organomolybdenum compounds is preferably 5% by mass or more and 40% by mass or less, more preferably 5% by mass or more and 30% by mass or less.

[0077] [Sulfur-based extreme pressure additives]

[0078] Known sulfur-based extreme pressure agents include sulfurized oils, sulfurized fatty acids, sulfurized esters, sulfurized olefins, dialkyl (poly)sulfides, alkyl thiocarbamoyl compounds, thioterpene compounds, dialkyl thiodipropionate compounds, sulfurized mineral oils, or zinc dithiocarbamate compounds, which can be used as sulfur-based extreme pressure agents. A single sulfur-based extreme pressure agent can be used, or two or more can be used in combination.

[0079] Sulfurized oils are products obtained by reacting sulfur or sulfur-containing compounds with oils (lard, whale oil, vegetable oil, fish oil, etc.). There are no particular restrictions on the sulfur content of sulfurized oils, and it is usually between 5% and 30% by mass.

[0080] Products obtained by sulfiding unsaturated fatty acids using any method can be used as sulfides of fatty acids. Specific examples include sulfides of oleic acid.

[0081] Products obtained by sulfiding unsaturated fatty acids using any method (e.g., products obtained by reacting unsaturated fatty acids (oleic acid, linoleic acid, or fatty acids extracted from the aforementioned animal or vegetable oils) with various alcohols) can be used as sulfided esters. Specific examples include sulfided methyl oleate and sulfided rice bran fatty acid octyl ester.

[0082] Examples of sulfurized olefins may include compounds represented by the general formula (2) given below. This compound can be produced by making C...2-15 Olefins or their dimers to tetramers are obtained by reacting them with a sulfurizing agent such as sulfur or sulfur chloride. Propylene, isobutylene, or diisobutylene can be used as olefins.

[0083] Equation (2):

[0084] R11-Sa-R12

[0085] Where R11 represents C 2-15 Alkenyl, R12 represents C 2-15 Alkyl or alkenyl, where a represents an integer from 1 to 8.

[0086] Dialkyl(poly)sulfides are compounds represented by the general formula (3) given below. In this context, the compound is also referred to as an alkyl sulfide when each of R13 and R14 is an alkyl group.

[0087] Equation (3):

[0088] R13-Sb-R14

[0089] R13 and R14 can be the same or different, and each independently represents C. 1-20 Alkyl groups (which can be straight-chain or branched, and can have a cyclic structure), C 6-20 Aryl, C 7-20 alkylaryl, or C 7-20 Aryl group, b represents an integer from 1 to 8.

[0090] Examples of alkylthiocarbamoyl compounds may include compounds represented by the following general formula (4).

[0091] Equation (4):

[0092]

[0093] R15 to R18 can be the same or different, and each independently represents C. 1-20 Alkyl group, where c represents an integer from 1 to 8.

[0094] Examples of thioterpenoid compounds may include the reaction products of phosphorus pentasulfide and pinene.

[0095] Examples of dialkyl thiodipropionate compounds may include dilauryl thiodipropionate and distearate thiodipropionate.

[0096] Sulfurized mineral oils are substances obtained by dissolving elemental sulfur in mineral oil. Specific examples of mineral oils used for sulfurized mineral oils include, but are not particularly limited to, paraffinic and naphthalene-based mineral oils obtained by atmospheric or vacuum distillation of crude oil and purification of the resulting lubricating oil fraction by means of a suitable combination of known refining processes. Elemental sulfur can be used in any form, such as bulk, powder, or molten liquid. There are no particular restrictions on the sulfur content of sulfurized mineral oils, which is generally between 0.05% by mass and 1.0% by mass, based on the total amount of sulfurized mineral oil.

[0097] Compounds represented by the following general formula (5) can be used as zinc dithiocarbamate compounds.

[0098] Equation (5):

[0099]

[0100] R19 to R22 can be the same or different, and each independently represents a hydrocarbon group having more than one carbon atom.

[0101] As a sulfur-based extreme pressure agent, a dialkyl (poly) sulfide represented by general formula (3) is preferred, a dialkyl polysulfide of general formula (3) in which both R13 and R14 are alkyl groups is more preferred, and a dioctyl polysulfide is even more preferred.

[0102] When the grease composition contains a sulfur-based extreme pressure agent, from the viewpoint of imparting extreme pressure properties to the grease composition and from the viewpoint of not degrading the resin, the content of the sulfur-based extreme pressure agent is 0.05% by mass or more and 2.5% by mass or less, based on the total amount of the grease composition. The content of the sulfur-based extreme pressure agent is preferably 0.1% by mass or more, and more preferably 2.0% by mass or less, more preferably 1.5% by mass or less. In one embodiment, the content is preferably 0.05% by mass or more and 2.0% by mass or less, more preferably 0.1% by mass or more and 1.5% by mass or less.

[0103] The grease composition of the present invention preferably comprises both an organomolybdenum compound and a sulfur-based extreme pressure agent. Note that organomolybdenum compounds, such as molybdenum dithiocarbamate and molybdenum dithiophosphate, contain sulfur molecules. Therefore, these organomolybdenum compounds also correspond to sulfur-based extreme pressure agents. In this context, even when an organomolybdenum compound also corresponds to a sulfur-based extreme pressure agent, in the present invention, the organomolybdenum compound is not considered a sulfur-based extreme pressure agent, and the content of the organomolybdenum compound is not added to the content of the sulfur-based extreme pressure agent. "Comprising both an organomolybdenum compound and a sulfur-based extreme pressure agent" means comprising both an organomolybdenum compound and a sulfur-based extreme pressure agent that does not contain molybdenum.

[0104] [Dialkyl dithiophosphate zinc]

[0105] Considering the effects of zinc dialkyl dithiophosphate on resins and metals (specifically, copper), the grease composition of the present invention is substantially free of zinc dialkyl dithiophosphate (hereinafter also referred to as ZnDTP). Zinc dialkyl dithiophosphate is typically added to greases for purposes such as improving corrosion inhibition, load-bearing capacity, and wear resistance. The inventors have found that, in addition to sulfur-based extreme pressure agents and / or organomolybdenum compounds, the addition of zinc dialkyl dithiophosphate adversely affects the resins and metals in contact with the grease.

[0106] As used herein, the phrase "substantially free" means that zinc dialkyl dithiophosphate is not contained in an amount intended to improve corrosion inhibition, load-bearing capacity, and wear resistance, for example. As used herein, the phrase "substantially free" means that the grease composition contains, for example, less than 1% by mass, preferably less than 0.1% by mass, more preferably less than 0.01% by mass. More preferably, the grease composition of the present invention is free of zinc dialkyl dithiophosphate.

[0107] [Other Additives]

[0108] In addition to the components described above, the grease composition of the present invention may be appropriately supplemented with solid lubricants, antioxidants, rust inhibitors, and corrosion inhibitors commonly used in greases, as needed.

[0109] Examples of solid lubricants include graphite, fluorinated graphite, melamine cyanurate, polytetrafluoroethylene, antimony sulfide, and alkali (earth) metal borates. When a grease composition contains a solid lubricant, the content of the solid lubricant may be more than 0.1% by mass and less than 20% by mass, based on the total amount of the grease composition.

[0110] Examples of antioxidants include phenolic compounds such as 2,6-di-tert-butylphenol and 2,6-di-tert-butyl-p-cresol, and amine compounds such as monobutylphenyl monooctylaniline, dialkyldiphenylamine, phenyl-α-naphthylamine, and p-alkylphenyl-α-naphthylamine. When the grease composition contains an antioxidant, the antioxidant content may be 0.1% by mass or more and 10% by mass or less, based on the total amount of the grease composition.

[0111] Examples of rust inhibitors include amines, neutral or highly alkaline petroleum-based or synthetic oil-based metal sulfonates, metal carboxylate salts, esters, phosphoric acid, and phosphates. When a grease composition contains a rust inhibitor, the rust inhibitor content may be 0.005% by mass or more and 5% by mass or less, based on the total amount of the grease composition.

[0112] Known corrosion inhibitors, such as benzotriazole compounds, tolyltriazole compounds, thiadiazole compounds, and imidazole compounds, can be used as corrosion inhibitors. When the grease composition contains a corrosion inhibitor, the content of the corrosion inhibitor may be more than 0.01% by mass and less than 10% by mass, based on the total amount of the grease composition.

[0113] The grease composition of the present invention can be obtained by mixing components (A) to (C) as essential components and further other additives as needed, stirring the mixture, and then passing it through a roller mill or the like.

[0114] [Resin]

[0115] As used herein, "resin" includes both natural and synthetic resins. Synthetic resins include general-purpose plastics (polyethylene, polystyrene, polypropylene, polyvinyl chloride, etc.) and engineering plastics. From the viewpoint of heat resistance and mechanical strength, synthetic resins are preferably polyamide resins, acetal resins, polycarbonate resins, polysulfone resins, polyphenylene sulfide resins, polyamide-imide resins, polyetheretherketone resins, phenolic resins, polyester resins, or epoxy resins, with acetal resins being more preferred.

[0116] Examples of objects in which the grease compositions of the present invention are used include, for example, transportation machinery such as automobiles, trains, and aircraft; industrial machinery such as machine tools; household appliances such as washing machines, refrigerators, and vacuum cleaners; and sliding parts of precision measuring equipment such as watches or cameras. The grease compositions of the present invention are preferably used in bearings, gears, surfaces, belts, joints, and cams, etc., included in such equipment and comprising resin materials.

[0117] [Lubricating Grease Composition]

[0118] The penetration of the grease composition of the present invention is preferably 265 to 475, more preferably 265 to 385, and still more preferably 310 to 340.

[0119] The penetration measured in this article refers to the working penetration as determined according to JIS K 2220. The specific measurement conditions are as follows: The penetration measuring container is filled with the sample and maintained at 25°C. Then, the specified plunger is stroked 60 times per minute. Afterward, excess sample is removed with a scraper to smooth the sample surface. Then, a specified cone is placed on the sample, penetrating it for 5 seconds. A value ten times the penetration depth (mm) is considered the working penetration.

[0120] The grease composition of the present invention exhibits the excellent effect of not degrading the resin, particularly acetal resin, in contact with it, even under high-temperature conditions. High-temperature conditions are, for example, immersing the resin in the grease composition at a temperature above 90°C for 100 hours or more, and more specifically, at 105°C for 168 hours. The phrase "not degrading the resin" means that the change in the mass of the resin is very small. Specifically, this means that when the resin is immersed in the grease composition under high-temperature conditions, the mass of the resin increases by more than 0% and less than 0.20%.

[0121] The grease composition of the present invention also has the effect of not degrading metals because it has weak reactivity with metals (e.g., copper) that are materials other than resins. Therefore, the grease composition of the present invention can be encapsulated in a single component comprising both resin and metal (e.g., copper). Embodiments in which the grease composition comes into contact with materials other than metals (e.g., copper) and resins are not excluded.

[0122] Example

[0123] The present invention will now be described with reference to embodiments and comparative examples. However, the present invention is not limited to the embodiments given below. Note that unless otherwise indicated, % refers to mass%.

[0124] Examples 1 to 10 and Comparative Examples 1 to 3

[0125] <Lubricating Grease Compatibility>

[0126] In the various embodiments or comparative examples, thickeners, base oils, and additives were blended in the proportions shown in Tables 1 and 2 to prepare various test grease compositions. The obtained test grease compositions were evaluated as shown below. Tables 1 and 2 show the evaluation results.

[0127] (1) Base oil

[0128] Mineral oil 1: Kinematic viscosity: 36.8 mm 2 / s(40℃)

[0129] Mineral oil 2: Kinematic viscosity: 86.6 mm 2 / s(40℃)

[0130] Mineral oil 3: Kinematic viscosity: 22.7 mm 2 / s(40℃)

[0131] Each lubricating oil base oil was prepared by mixing the base oils at the mass ratios shown in Tables 1 and 2.

[0132] (2) Thickener

[0133] Urea-based thickeners: the reaction product of diphenylmethane diisocyanate and cyclohexylamine

[0134] Lithium complex thickener: the reaction product of lithium 12-hydroxystearate and azelaic acid

[0135] (3) Additives

[0136] Additives are listed in Tables 1 and 2. Details of the additives are as follows. Note that the total amount of base oil and the blending amounts of thickener and additives are based on the total amount of the grease composition.

[0137] MoDTC is manufactured by ADEKA Corp. (Product name: SAKURA-LUBE 515)

[0138] Dioctyl polysulfide is manufactured by DIC Corp. (Product name: DAILUBE GS440L)

[0139] ZnDTP1 is manufactured by Chevron Oronite Co., LLC (product name: OLOA5283).

[0140] ZnDTP2 is manufactured by Lubrizol Corp. (Product name: LUBRIZOL1095)

[0141] Other additives: 2,6-di-tert-butylphenol, dialkyldiphenylamine, benzotriazole compounds, thiadiazole compounds, tricresyl phosphate

[0142] <Evaluation>

[0143] (1) Mass changes of acetal resin

[0144] Acetal resin test pieces, 2 mm thick, 40 mm long, and 20 mm wide, were produced and coated with various grease compositions. Each test piece coated with the grease composition was heated at 105°C for 168 hours. After heating, the grease composition was removed, and the mass change of the test pieces before and after heating was measured. Samples with an increase in mass of 0% to 0.2% were determined to be non-degrading acetal resin.

[0145] (2) Extreme pressure

[0146] According to ASTM D 2596, the sintering load (WL) was measured using a four-ball testing machine under the conditions given below. Samples that obtained a sintering load of 2452 N or higher were identified as having extreme pressure properties.

[0147] Rotation speed: 1800 rpm

[0148] Temperature: Room temperature

[0149] Test time: 10 seconds

[0150] (3) The blackening of copper plates

[0151] According to JIS K 2220, the corrosion of the copper plate was measured after being kept in a constant temperature air bath at 100°C for 24 hours.

[0152] [Table 1]

[0153]

[0154] [Table 2]

[0155]

[0156] For each grease composition of Examples 1 to 10, the mass of acetal resin increased by 0% to 0.2%, the extreme pressure value was greater than 2452 N, and no corrosion of the copper plate was confirmed.

[0157] For the grease compositions of Comparative Example 1 supplemented with ZnDTP1 and Comparative Example 2 supplemented with ZnDTP2, the mass of acetal resin decreased, and copper plate corrosion occurred.

[0158] For the grease composition of Comparative Example 3 supplemented with 3% by mass of dioctyl polysulfide, the mass of acetal resin increased by more than 2.0%.

[0159] Industrial availability

[0160] The grease composition of the present invention can provide a grease composition that does not degrade the resin, especially acetal resin, in contact with it even under high temperature conditions.

Claims

1. A grease composition for resin comprising (A) a lubricating oil base oil, (B) a thickening agent, the thickening agent comprising a lithium complex soap-based thickening agent, and (C) both an organic molybdenum compound and a sulfur-based extreme pressure agent not containing molybdenum, the content of the sulfur-based extreme pressure agent is 0.05 mass% or more and 2.5 mass% or less based on the total amount of the composition, and the grease composition is substantially free of zinc dialkyldithiophosphate.

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

3. The grease composition for resin according to claim 1 or 2, wherein the content of the organic molybdenum compound is 0.05 mass% or more and 5 mass% or less.

4. The grease composition for resin according to claim 1 or 2, wherein the thickening agent is a metal soap-based thickening agent.

5. The grease composition for resin according to claim 1 or 2, wherein the penetration of the grease composition is 265 to 475.

6. The grease composition for resin according to claim 1 or 2, wherein (A) the content of the lubricating oil base oil is 50 mass% or more and 95 mass% or less based on the total amount of the composition; and (B) the content of the thickening agent is 2 mass% or more and 30 mass% or less based on the total amount of the composition.

7. The grease composition for resin according to claim 1 or 2, wherein the content of the zinc dialkyldithiophosphate is 1 mass% or less based on the total amount of the composition.

8. The grease composition for resin according to claim 1 or 2, which is used for a member comprising an acetal resin and a metal.

9. The grease composition for resin according to claim 8, wherein the metal is copper.

10. The grease composition for resin according to claim 1 or 2, wherein the lubricating oil base oil is a mineral oil.

11. The grease composition for a resin according to claim 1 or 2, wherein the kinematic viscosity at 40°C of the lubricating oil base oil is 10 mm2 / s or more and 700 mm2 / s or less. 2 / s or more and 700 mm2 / s or less. 2 / s or more and 700 mm2 / s or less.

12. The grease composition for resin according to claim 1 or 2, wherein the viscosity index of the lubricating oil base oil at 40°C is 95 or more and 250 or less.

13. The grease composition for resin according to claim 1 or 2, wherein the organic molybdenum compound is a molybdenum dithiocarbamate.

14. The grease composition for resin according to claim 1 or 2, wherein the sulfur-based extreme pressure agent is a dihydrocarbyl(poly)sulfide represented by general formula (3): R13-Sb-R14 15. A method for lubricating a sliding portion, the method comprising placing the grease composition for resin according to any one of claims 1 to 14 to a sliding portion. R13 and R14 can be the same or different, and each independently represents C. 1-20 Alkyl, C 6-20 Aryl, C 7-20 alkylaryl, or C 7-20 Aryl alkyl group, wherein the C 1-20 Alkyl groups can be straight-chain or branched and can have a cyclic structure, and b represents an integer from 1 to 8. ​

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