Grease composition

Abstract

This grease composition comprising: (A) a base oil; (B) a thickener; (C) an amino acid derivative; and (D) a polyhydric alcohol fatty acid ester.

Description

Grease composition

[0001] The present invention relates to a grease composition. This application claims priority to Japanese Patent Application No. 2023-207533, filed on December 8, 2023, the contents of which are incorporated herein by reference.

[0002] Grease is a semi-solid lubricant made by dispersing a solid, lipophilic thickener in a base oil. Grease adheres more easily to lubricated parts and is less likely to leak than lubricating oil. Therefore, using grease can simplify the mechanical structure of the lubrication system. Grease also has less leakage than lubricating oil, creating a cleaner environment and allowing for shorter replenishment intervals. Grease is primarily used to lubricate mechanical elements such as rolling bearings, plain bearings, ball screws, linear guides, and gears. Rolling bearings are widely used in machine tool spindles, railroad vehicle rolling stock, engine accessories such as automobile alternators, constant velocity joints, and wheels. In recent years, parts made of synthetic resins have become more common due to their lighter weight and ease of processing.

[0003] The lubrication of such resin sliding parts is significantly different from that of metals, and greases for metals may not exhibit satisfactory properties, so base oils and additives are being considered. For example, Patent Document 1 discloses a grease that uses an amine salt of an unsaturated fatty acid as an additive to a grease base material containing a base oil and a thickener.

[0004] JP 2010-106256 A

[0005] Conventional grease compositions such as those described in Patent Document 1 have room for improvement in terms of lubrication, particularly wear resistance. In order to improve wear resistance, it is necessary to reduce the heat generated by sliding friction, and to achieve this, it is desired to further improve the coefficient of friction of grease compositions.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a grease composition that exhibits low friction between steel and resin.

[0007] In order to solve the above problems, the present invention employs the following configurations. [1] A grease composition containing a base oil (A), a thickener (B), an amino acid derivative (C), and a polyhydric alcohol fatty acid ester (D). [2] The grease composition according to [1], wherein the thickener (B) contains a urea compound. [3] The grease composition according to [2], wherein the urea compound is a diurea compound represented by the following formula (1): R １ -NHCONH-R ２ -NHCONH-R ３ ...(U-1) [In formula (1), R １ and R ３ represents an aliphatic hydrocarbon group having 4 to 24 carbon atoms which may have a substituent, an alicyclic hydrocarbon group having 6 to 15 carbon atoms which may have a substituent, or an aromatic hydrocarbon group having 6 to 15 carbon atoms which may have a substituent, R ２ represents a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms which may have a substituent.] [4] The grease composition according to any one of [1] to [3], wherein the amino acid derivative (C) contains a compound represented by the following general formula (C-1): Rc １ -(C=O)-(N-Rc ２ )-A-(C=O)-OH...(C-1) [In formula (C-1), Rc １ is a monovalent hydrocarbon group, and Rc ２is a hydrogen atom or a monovalent hydrocarbon group, and A is a divalent hydrocarbon group, and these hydrocarbon groups may contain a group having an oxygen atom.] [5] The grease composition according to any one of [1] to [4], wherein the base oil (A) comprises one or more selected from the group consisting of ester-based synthetic oils and poly-α-olefins. [6] The grease composition according to any one of [1] to [5], wherein the polyhydric alcohol fatty acid ester (D) comprises one or more selected from the group consisting of sorbitan fatty acid esters and glycerin fatty acid esters. [7] The grease composition according to any one of [1] to [6], wherein the content of the thickener (B) is 5% by mass or less and 30% by mass or less, based on the total amount of the grease composition. [8] The grease composition according to any one of [1] to [7], wherein the content of the amino acid derivative (C) is 0.15% by mass or more and 14% by mass or less, based on the total amount of the grease composition. [9] The grease composition according to any one of [1] to [8], wherein the content of the polyhydric alcohol fatty acid ester (D) is 0.15 mass % or more and 14 mass % or less relative to the total amount of the grease composition.

[10] The grease composition according to any one of [1] to [9], which is used for sliding contact between resin and steel.

[0008] According to the present invention, it is possible to provide a grease composition that exhibits low friction between steel and resin.

[0009] (Grease Composition) The grease composition of the present embodiment contains a base oil (A), a thickener (B), an amino acid derivative (C), and a polyhydric alcohol fatty acid ester (D). In this specification, the contents are expressed in mass%.

[0010] <Base oil (A)> The grease composition of this embodiment contains base oil (A). The kinematic viscosity of the base oil (A) at 40°C is 15 mm ２ / s or more, and ２ / s or more is more preferable, and 30 mm ２ On the other hand, the kinematic viscosity of the base oil (A) at 40°C is preferably 200 mm / s or more. ２ / s or less, and 150 mm ２ / s or less is more preferable, and 100 mm ２ For example, the kinematic viscosity of the base oil (A) at 40°C is 15 mm / s or less. ２ / s or more 200mm ２ / s or less, and ２ / s or more 150mm ２ / s or less is more preferable, and 30 mm ２ / s or more 100mm ２ It is more preferable that the ratio is 1 / s or less.

[0011] When the kinematic viscosity at 40°C of the base oil (A) of the grease composition of this embodiment is equal to or greater than the above lower limit, the coefficient of friction between steel and resin can be reduced, and when it is equal to or less than the above upper limit, the low-temperature fluidity of the grease composition is improved.

[0012] In this specification, the kinematic viscosity at 40°C means the kinematic viscosity at 40°C measured in accordance with JIS K2283:2000.

[0013] The viscosity index of the base oil (A) is preferably 90 or higher, more preferably 120 to 150. The pour point of the base oil (A) is preferably −10° C. or lower, more preferably −15° C. or lower. The flash point of the base oil (A) is preferably 200° C. or higher. In this specification, the viscosity index means a value measured in accordance with JIS K2283:2000, the pour point means a value measured in accordance with JIS K2269:1987, and the flash point means a value measured in accordance with JIS K2265-4:2007.

[0014] Specific examples of the base oil (A) include synthetic oils and mineral oils.

[0015] Synthetic Oils Examples of synthetic oils include polyolefins such as poly-α-olefins, polybutenes, and copolymers of two or more olefins; ester-based synthetic oils such as diesters and polyol esters; ether-based synthetic oils such as alkyldiphenyls and polypropylene glycols; polyalkylene glycols; alkylbenzenes; and alkylnaphthalenes. Among these, poly-α-olefins or ester-based synthetic oils are preferred in terms of oxidation stability and low-temperature fluidity. Here, the term "ester-based synthetic oil" refers to a full ester. Therefore, the term "ester-based synthetic oil" as used herein does not include partial esters.

[0016] Mineral Oils Mineral oils can be distillates obtained by atmospheric distillation of crude oil. Furthermore, lubricating oil fractions obtained by further vacuum distillation of the distillate and then refining the distillate through various refining processes can also be used. Refining processes can include hydrorefining, solvent extraction, solvent dewaxing, hydrodewaxing, sulfuric acid washing, and clay treatment, and can be combined as appropriate. Mineral oils can be obtained by combining these refining processes in an appropriate order. Alternatively, a mixture of refined oils with different properties obtained by subjecting different crude oils or distillate oils to a combination of different refining processes can also be used.

[0017] As the base oil (A), one of the synthetic oils or mineral oils may be used alone, or a mixture of two or more synthetic oils or mineral oils may be used. When a mixture of two or more base oils is used, as long as the base oil mixture satisfies the above physical properties, the individual base oils before mixing can be used even if they are outside the range of the physical properties. Therefore, the individual base oils do not necessarily have to satisfy the above physical properties, but it is preferable that the physical properties are within the range of the above physical properties.

[0018] The content of the base oil (A) in the grease composition of this embodiment is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 65% ​​by mass or more, and particularly preferably 70% by mass or more, relative to the total amount of the grease composition. On the other hand, the content of the base oil (A) in the grease composition of this embodiment is preferably 95% by mass or less, more preferably 90% by mass or less, relative to the total amount of the grease composition. For example, the content of the base oil (A) in the grease composition of this embodiment is preferably 50% by mass or more and 95% by mass or less, more preferably 60% by mass or more and 95% by mass or less, even more preferably 65% ​​by mass or more and 95% by mass or less, and particularly preferably 70% by mass or more and 90% by mass or less, relative to the total amount of the grease composition.

[0019] When the content of base oil (A) in the grease composition of the present embodiment is within the above-mentioned preferred range, appropriate lubricity can be ensured, and when it is equal to or less than the above-mentioned upper limit, the base oil can be more easily retained in the grease composition.

[0020] <Thickener (B)> The grease composition of this embodiment contains a thickener (B) (hereinafter also referred to as "component (B)"). Either a urea compound or a metal soap can be used as component (B).

[0021] <Urea Compound> Specific examples of the urea compound include a diurea compound and a polyurea compound. A diurea compound is a compound obtained by a reaction between a diisocyanate and a monoamine, and has two urea groups (-NH-CO-NH-). In this specification, a polyurea compound refers to a compound obtained by a reaction between a diisocyanate and a monoamine or a diamine, and has three or more urea groups (-NH-CO-NH-).

[0022] Diisocyanate Diisocyanate is a compound in which two hydrogen atoms of a hydrocarbon are substituted with an isocyanate group (-N=C=O). The hydrocarbon may be a cyclic hydrocarbon or a chain hydrocarbon. The hydrocarbon may also be an aromatic hydrocarbon or an aliphatic hydrocarbon. The hydrocarbon preferably has 4 to 20 carbon atoms, more preferably 8 to 18 carbon atoms.

[0023] Specific preferred examples of diisocyanates include phenylene diisocyanate, tolylene diisocyanate, biphenyl diisocyanate (diphenyl diisocyanate), diphenylmethane-4,4'-diisocyanate (MDI), octadecane diisocyanate, decane diisocyanate, hexane diisocyanate, etc. One type of diisocyanate may be used alone, or two or more types may be used in combination.

[0024] Monoamines Monoamines are compounds in which one hydrogen atom of ammonia is substituted with a hydrocarbon group. Examples of monoamines include aliphatic amines in which one hydrogen atom of ammonia is substituted with an aliphatic hydrocarbon group having 4 to 24 carbon atoms, alicyclic amines in which one hydrogen atom of ammonia is substituted with an alicyclic hydrocarbon group having 6 to 15 carbon atoms, and aromatic amines in which one hydrogen atom of ammonia is substituted with an aromatic hydrocarbon group having 6 to 15 carbon atoms. The substituents of the aliphatic amines, alicyclic amines, and aromatic amines may each further have a substituent. Among these, preferred monoamines are octylamine, dodecylamine, hexadecylamine, octadecylamine, oleylamine, aniline, p-toluidine, cyclohexylamine, and dicyclohexylamine, with octylamine, octadecylamine, and cyclohexylamine being more preferred.

[0025] Diamines Diamines are compounds in which two hydrogen atoms of ammonia are substituted with hydrocarbon groups. Preferred diamines include ethylenediamine, propanediamine, butanediamine, hexanediamine, octanediamine, phenylenediamine, tolylenediamine, xylenediamine, and diaminodiphenylmethane. Diamines may be cyclic or chain amines. Diamines may also be alicyclic, aromatic, or aliphatic amines. The diamine preferably has 4 to 20 carbon atoms, more preferably 8 to 18.

[0026] Of the above, diurea compounds are preferred as urea compounds. The diurea compounds are preferably compounds obtained by reacting a diisocyanate having an aromatic hydrocarbon group with a monoamine. Diphenylmethane-4,4'-diisocyanate (MDI) is preferred as the diisocyanate having an aromatic hydrocarbon group. Stearylamine and cyclohexylamine are preferred as the monoamine.

[0027] As the urea compound for the grease composition of this embodiment, one type of urea compound may be used alone, or a mixture of multiple urea compounds may be used.

[0028] The content of the urea compound is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 9% by mass or more, based on the total amount of the grease composition. The content of the urea compound is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less, based on the total amount of the grease composition. For example, the content of the urea compound is preferably 5% by mass or less to 30% by mass or less, more preferably 7% by mass or less to 25% by mass or less, and even more preferably 9% by mass or more to 20% by mass or less, based on the total amount of the grease composition.

[0029] <Metallic Soaps> Metallic soaps include simple soaps and complex soaps. Simple soaps are metallic soaps made by saponifying fatty acids or fats with alkali metal hydroxides or alkaline earth metal hydroxides. Complex soaps are made by combining the fatty acids used in simple soaps with organic acids of different molecular structures.

[0030] The metal soap used as a thickener may be blended in the form of a metal soap, or the carboxylic acid and a metal source (metal salt, metal salt hydroxide, etc.) may be blended separately and reacted during preparation of the grease composition to form the metal soap.

[0031] The fatty acid may be a fatty acid derivative having a substituent such as a hydroxy group. The fatty acid is preferably a fatty acid having 6 to 20 carbon atoms, and more preferably a monovalent fatty acid having 12 to 20 carbon atoms. The fatty acid is preferably a monovalent aliphatic carboxylic acid containing one hydroxy group, and more preferably 12-hydroxystearic acid. The organic acid to be combined with the fatty acid in the complex soap is preferably a dibasic acid such as acetic acid, azelaic acid, or sebacic acid, or benzoic acid.

[0032] Examples of metals in metal soaps include alkali metals such as lithium and sodium, alkaline earth metals such as calcium, and amphoteric metals such as aluminum.

[0033] The metal soap in the grease composition of this embodiment may be a single type of metal soap, or a mixture of multiple metal soaps.

[0034] The content of the metal soap is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, based on the total amount of the grease composition. The content of the single metal soap is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less, based on the total amount of the grease composition.

[0035] As component (B) of the grease composition of this embodiment, it is preferable to use a urea compound from the viewpoint of heat resistance at high temperatures and the lubricity of the thickener itself.

[0036] The (B) component may be used alone or in combination of two or more. The content of the (B) component is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 9% by mass or more, relative to the total amount of the grease composition. The content of the (B) component is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less, relative to the total amount of the grease composition. For example, the content of the (B) component is preferably 5% by mass or more and 30% by mass or less, more preferably 7% by mass or more and 25% by mass or less, and even more preferably 9% by mass or more and 20% by mass or less, relative to the total amount of the grease composition.

[0037] <Amino Acid Derivative (C)> The grease composition of this embodiment contains an amino acid derivative (C) (hereinafter also referred to as "component (C)").

[0038] Component (C) is a compound containing an amide bond and a carboxyl group within the same compound. Based on the examples and comparative examples in this specification and the inventors' long experience and knowledge, it can be assumed that this type of compound has two polar sites, the amide bond and the carboxyl group, which are strongly chemically adsorbed to the resin surface through hydrogen bonds, improving the oiliness effect and reducing the friction coefficient. As long as the compound contains an amide bond and a carboxyl group within the same compound, the effects of the present invention can be exhibited without any problems. As component (C), a compound represented by the following general formula (C-1) is preferred. Rc １ -(C=O)-(N-Rc ２ )-A-(C=O)-OH...(C-1) [In formula (C-1), Rc １ is a monovalent hydrocarbon group, and Rc ２ is a hydrogen atom or a monovalent hydrocarbon group, and A is a divalent hydrocarbon group, and these hydrocarbon groups may contain a group having an oxygen atom.

[0039] Rc １ Examples of the monovalent hydrocarbon group in Rc include alkyl groups, alkenyl groups, and acyl groups having 4 to 24 carbon atoms. Specific examples include alkyl groups such as pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, icosyl, heneicosyl, docosyl, tricosyl, and tetracosyl groups (these alkyl groups may be linear or branched); alkenyl groups such as pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl, nonadecenyl, icosenyl, heneicosenyl, docosenyl, tricosenyl, and tetracosenyl groups (these alkenyl groups may be linear or branched, and the position of the double bond may be optional); and acyl groups having a ketone group at the terminal of these alkyl or alkenyl groups. １Among the above, the alkyl group is preferably an alkyl group having 7 to 24 carbon atoms or an alkenyl group having 7 to 24 carbon atoms, more preferably an alkyl group having 8 to 20 carbon atoms or an alkenyl group having 8 to 20 carbon atoms, and even more preferably an alkenyl group having 8 to 20 carbon atoms.

[0040] Rc ２ As the monovalent hydrocarbon group in １ Examples of the monovalent hydrocarbon groups include those shown in the above. ２ Among the above, a hydrogen atom or an alkyl group having 1 to 8 carbon atoms is preferable, a hydrogen atom or an alkyl group having 1 to 3 carbon atoms is more preferable, and an alkyl group having 1 to 3 carbon atoms is even more preferable.

[0041] The divalent hydrocarbon group in A is Rc １ Among the above, A is preferably an alkylene group having 1 to 8 carbon atoms, and more preferably an alkylene group having 1 to 4 carbon atoms.

[0042] Of the above, the compound represented by formula (C-1) is preferred as component (C), with oleoyl sarcosine being more preferred.

[0043] The component (C) of the grease composition of this embodiment may be a single amino acid derivative or a mixture of multiple amino acid derivatives.

[0044] The content of component (C) is preferably 0.1 mass% or more, more preferably 0.2 mass% or more, and even more preferably 0.25 mass% or more, relative to the total amount of the grease composition. The content of component (C) is preferably 14 mass% or less, more preferably 10 mass% or less, and even more preferably 7 mass% or less, relative to the total amount of the grease composition. For example, the content of component (C) is preferably 0.1 mass% or more and 14 mass% or less, more preferably 0.2 mass% or more and 10 mass% or less, and even more preferably 0.25 mass% or more and 7 mass% or less, relative to the total amount of the grease composition.

[0045] When the content of component (C) is at least the above-mentioned preferable lower limit, the coefficient of friction between steel and resin is further reduced, and when it is at most the above-mentioned upper limit, the low-temperature fluidity of the grease composition is improved.

[0046] <Polyhydric Alcohol Fatty Acid Ester (D)> The grease composition of this embodiment contains a polyhydric alcohol fatty acid ester (D) (hereinafter also referred to as "component (D)"). Component (D) is different from the above-mentioned ester-based synthetic oils and refers to a partial ester.

[0047] The fatty acid constituting component (D) is an aliphatic monobasic acid. From the viewpoint of further reducing the coefficient of friction between steel and resin, the fatty acid constituting component (D) is preferably a linear or branched fatty acid having 6 to 30 carbon atoms, more preferably a linear or branched fatty acid having 8 to 24 carbon atoms, and even more preferably a linear or branched fatty acid having 10 to 20 carbon atoms. Specific examples of such fatty acids include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid.

[0048] The polyhydric alcohol constituting component (D) is preferably an aliphatic polyhydric alcohol having 2 to 6 carbon atoms, more preferably an aliphatic polyhydric alcohol having 3 to 6 carbon atoms. Furthermore, a dihydric to tetrahydric aliphatic polyhydric alcohol is preferred, more preferably a trihydric or tetrahydric aliphatic polyhydric alcohol. Specific examples of such polyhydric alcohols include ethylene glycol, propylene glycol, glycerin, and sorbitan.

[0049] As component (D), partial esters of linear or branched fatty acids having 10 to 20 carbon atoms and polyhydric alcohols such as glycerin and sorbitan are preferred, with glycerin fatty acid esters such as glycerin monostearate, glycerin distearate, glycerin monooleate, and glycerin dioleate being more preferred, and sorbitan fatty acid esters such as sorbitan monooleate and sorbitan dioleate being even more preferred, with glycerin monostearate, glycerin distearate, and sorbitan monooleate being particularly preferred.

[0050] The component (D) of the grease composition of this embodiment may be a single polyhydric alcohol fatty acid ester, or a mixture of multiple polyhydric alcohol fatty acid esters.

[0051] The content of component (D) is preferably 0.1 mass% or more, more preferably 0.2 mass% or more, and even more preferably 0.25 mass% or more, relative to the total amount of the grease composition. The content of component (D) is preferably 14 mass% or less, more preferably 10 mass% or less, and even more preferably 7 mass% or less, relative to the total amount of the grease composition. For example, the content of component (D) is preferably 0.1 mass% or more and 14 mass% or less, more preferably 0.2 mass% or more and 10 mass% or less, and even more preferably 0.25 mass% or more and 7 mass% or less, relative to the total amount of the grease composition.

[0052] When the content of component (D) is at least the above-mentioned preferable lower limit, the coefficient of friction between steel and resin is further reduced, and when it is at most the above-mentioned upper limit, the low-temperature fluidity of the grease composition is improved.

[0053] The mass ratio of the content of the component (C) to the content of the component (D) in the grease composition of this embodiment is preferably 1:9 to 9:1. The mass ratio of the content of the component (C) to the content of the component (D) in the grease composition of this embodiment ((C) / (D)) is preferably 0.1 to 10.

[0054] <Optional Components> The grease composition of the present embodiment may contain optional components other than the base oil (A), component (B), component (C), and component (D) described above. Examples of the optional components include solid lubricants, antiwear or extreme pressure agents, antioxidants, rust inhibitors, and corrosion inhibitors.

[0055] Examples of solid lubricants include graphite, graphite fluoride, melamine cyanurate, polytetrafluoroethylene, molybdenum disulfide, antimony sulfide, boron nitride, and alkaline (earth) metal borates. When the grease composition contains a solid lubricant, the content thereof is, for example, 0.1 to 20 mass% relative to the total amount of the grease composition. One type of solid lubricant may be used alone, or multiple solid lubricants may be used in combination.

[0056] Examples of anti-wear agents or extreme pressure agents include organic zinc compounds such as zinc dialkyldithiophosphate and zinc dialkyldithiocarbamate; sulfur-containing compounds such as molybdenum dialkyldithiocarbamate, dihydrocarbyl polysulfides, sulfurized esters, thiazole compounds, and thiadiazole compounds; and phosphorus-based extreme pressure agents such as phosphate esters, acidic phosphate esters, amine salts of acidic phosphate esters, and phosphites. When the grease composition contains an anti-wear agent or extreme pressure agent, the content thereof is, for example, 0.1 to 10 mass% based on the total amount of the grease composition. One type of anti-wear agent or extreme pressure agent may be used alone, or multiple anti-wear agents or extreme pressure agents may be used in combination.

[0057] 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 diphenylamine, dialkyldiphenylamine, phenyl-α-naphthylamine, and p-alkylphenyl-α-naphthylamine. When the grease composition contains an antioxidant, the content thereof is, for example, 0.5 to 10 mass% relative to the total amount of the grease composition. One type of antioxidant may be used alone, or multiple antioxidants may be used in combination.

[0058] Examples of the rust inhibitor that can be used include amines, neutral or overbased petroleum-based or synthetic oil-based metal sulfonates, metal carboxylates, esters, phosphoric acid, and phosphates.

[0059] As the corrosion inhibitor, for example, known corrosion inhibitors such as benzotriazole-based compounds, tolyltriazole-based compounds, thiadiazole-based compounds, and imidazole-based compounds can be used. When the grease composition contains a corrosion inhibitor, the content thereof is, for example, 0.01 to 10 mass% based on the total amount of the grease composition. The corrosion inhibitor may be used alone, or multiple corrosion inhibitors may be used in combination.

[0060] <Objects to be Lubricated> The grease composition of this embodiment is suitable for use in lubricating various resin sliding members and steel sliding members. Examples of resins include polyamide resin, polycarbonate, polyamideimide resin, polyacetal resin, polybutylene terephthalate resin, and polyether ether ketone resin, and is particularly suitable for members using polyamide resin. Examples of steel sliding members include bearing steel, carbon steel, and stainless steel (SUS).

[0061] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0062] <Formulation of Grease Compositions> The grease compositions of Examples 1 to 5 and Comparative Examples 1 to 4 were prepared by blending the base oil (A), component (B), component (C), etc. in the blending ratios shown in Tables 1 to 3. The numerical values ​​in Tables 1 to 3 indicate the blending ratio (% by mass) of each component relative to 100% by mass of the grease composition of each example.

[0063] (1) Base oil (A) A-1: ​​Poly-α-olefin (kinematic viscosity at 40°C = 46 mm ２ / s, viscosity index: 136, pour point: <-45°C, flash point: 265°C) A-2: Ester-based synthetic oil (40°C kinematic viscosity = 46 mm ２ / s, viscosity index: 104, pour point: <-45℃, flash point: 270℃) A-3: Mineral oil (40℃ kinematic viscosity = 47mm ２ / s, viscosity index: 114, pour point: <-12.5°C, flash point: 250°C)

[0064] (2) Thickener (B) B-1: Diurea compound (a diurea compound obtained by reacting diphenylmethane-4,4'-diisocyanate with cyclohexylamine) B-2: Diurea compound (a diurea compound obtained by reacting diphenylmethane-4,4'-diisocyanate with octadecylamine) B-3: 12-hydroxystearate lithium soap (single lithium soap)

[0065] (3) Amino acid derivatives (C) C-1: oleoyl sarcosine

[0066] (4) Polyhydric alcohol fatty acid ester (D) D-1: Sorbitan monooleate: 715.5 mm ２ / s (40 ° C) D-2: Glycerin stearate (mixture of partial esters): 252.5 mm ２ / s (40 ° C)

[0067] (5) Other additives X-1: Dialkyldiphenylamine X-2: Neutral Ca sulfonate X-3: Alkenyl succinic acid polyhydric alcohol ester

[0068] [Evaluation of Friction Coefficient] Evaluation tests were carried out using a ball and disk reciprocating friction tester. SUJ-2 balls with a diameter of 1 / 4 inch were used as the balls (steel sliding members), and nylon 66 plates (TPS (registered trademark) N66 (NC) manufactured by Toray Plastics Seiko Co., Ltd.) were used as the disks (resin sliding members). Each grease composition was applied to the disk, and the friction coefficient was measured when sliding was carried out at room temperature (25°C) under the conditions of a test load of 2000 gf, a sliding speed of 10 mm / s, and an amplitude of 20 mm. The results are shown in Tables 1 to 3.

[0069]

[0070]

[0071]

[0072]

[0073] As shown in Tables 1 to 4, the grease compositions of the Examples had lower friction coefficients than the grease compositions of the Comparative Examples. Therefore, it was confirmed that the grease compositions of the Examples exhibit low friction between steel and resin.

[0074] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Addition, omission, substitution, and other modifications of the configuration are possible within the scope of the spirit of the present invention. The present invention is not limited by the above description, but is limited only by the scope of the appended claims.

Claims

1. A grease composition comprising a base oil (A), a thickener (B), an amino acid derivative (C), and a polyhydric alcohol fatty acid ester (D).

2. The grease composition according to claim 1, wherein the thickener (B) contains a urea compound.

3. The grease composition according to claim 2, wherein the urea compound is a diurea compound represented by the following formula (1): １ -NHCONH-R ２ -NHCONH-R ３ ...(U-1) [In formula (1), R １ and R ３ represents an aliphatic hydrocarbon group having 4 to 24 carbon atoms which may have a substituent, an alicyclic hydrocarbon group having 6 to 15 carbon atoms which may have a substituent, or an aromatic hydrocarbon group having 6 to 15 carbon atoms which may have a substituent, R ２ represents a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms which may have a substituent.

4. The grease composition according to claim 1 or 2, wherein the amino acid derivative (C) includes a compound represented by the following general formula (C-1): Rc １ -(C=O)-(N-Rc ２ )-A-(C=O)-OH...(C-1) [In formula (C-1), Rc １ is a monovalent hydrocarbon group, R ２ is a hydrogen atom or a monovalent hydrocarbon group, and A is a divalent hydrocarbon group, and these hydrocarbon groups may contain a group having an oxygen atom.

5. The grease composition according to claim 1 or 2, wherein the base oil (A) comprises at least one oil selected from the group consisting of ester-based synthetic oils and poly-α-olefins.

6. The grease composition according to claim 1 or 2, wherein the polyhydric alcohol fatty acid ester (D) comprises one or more selected from the group consisting of sorbitan fatty acid esters and glycerin fatty acid esters.

7. A grease composition according to claim 1 or 2, wherein the content of the thickener (B) is 5% by mass or less and 30% by mass or less based on the total amount of the grease composition.

8. A grease composition according to claim 1 or 2, wherein the content of the amino acid derivative (C) is 0.15 mass % or more and 14 mass % or less based on the total amount of the grease composition.

9. A grease composition according to claim 1 or 2, wherein the content of the polyhydric alcohol fatty acid ester (D) is 0.15 mass % or more and 14 mass % or less based on the total amount of the grease composition.

10. The grease composition according to claim 1 or 2, which is used for sliding contact between resin and steel.

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