Grease composition

Abstract

The present invention provides a grease composition having excellent load resistance and abrasion resistance. The grease composition contains a base oil, a thickener which is a barium complex soap, and an organomolybdenum compound, and the content of the organomolybdenum compound is 0.25 to 10% by mass in terms of molybdenum. In the above grease composition, the content of the organomolybdenum compound can be 0.6 to 5% by mass in terms of molybdenum, the content of the barium complex soap can be 15 to 45% by mass, the content of the barium complex soap can be 25 to 40% by mass, the kinematic viscosity of the base oil can be 15 to 100 mm2 / s at 40 °C, the weld load measured according to ASTM D2596 is 3900 N or more, and the wear scar diameter measured according to ASTM D2266 can be 0.45 mm or less.

Description

Technical Field

[0001] The present invention relates to a grease composition. Background Art

[0002] Grease compositions are used as lubricants in various fields such as industrial machinery, transportation machinery, and general machinery. In particular, in application parts with large loads such as reduction gearbox gears, ball screws, and bearings, a grease composition with excellent load resistance is required.

[0003] In Patent Document 1, a grease composition for constant velocity joints containing a base oil, a thickener, a detergent-dispersant, a sulfur-phosphorus extreme pressure agent, an organomolybdenum compound, and a lignin compound is disclosed, which has excellent load resistance and friction coefficient reduction effect. On the other hand, it is desired that the grease composition used in lubrication parts with large loads has not only high load resistance but also high wear resistance. However, it is generally difficult to balance load resistance and wear resistance, and a grease composition with both sufficiently excellent properties is still required.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2014-189765 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] The present invention provides a grease composition having excellent load resistance and wear resistance.

[0009] Means for Solving the Problems

[0010] The main configuration of the present invention is as follows.

[0011] [1] A grease composition comprising a base oil, a thickener which is a barium complex soap, and an organomolybdenum compound, wherein the content of the organomolybdenum compound is 0.25 to 10% by mass in terms of molybdenum.

[0012] [2] The grease composition according to [1], wherein the content of the organomolybdenum compound is 0.6 to 5% by mass in terms of molybdenum.

[0013] [3] The grease composition according to [1] or [2], wherein the content of the barium complex soap is 15 to 45% by mass.

[0014] [4] The grease composition according to any one of [1] to [3], wherein the kinematic viscosity of the base oil is 15 to 100 mm 2 / s at 40°C.

[0015] [5] The grease composition according to any one of [1] to [4], wherein the grease composition has a weld load of 3900 N or more as measured by ASTM D2596 and a wear scar diameter of 0.45 mm or less as measured by ASTM D2266.

[0016] Advantages of the Invention

[0017] According to the present invention, a grease composition excellent in load resistance and wear resistance can be provided. Description of the Drawings

[0018] Figure 1 It is a semi-logarithmic graph showing the relationship between the molybdenum equivalent content of the organomolybdenum compound and the weld load of the grease composition in Examples and Comparative Examples. Detailed Description of the Invention

[0019] The grease composition of the present invention contains a base oil, a thickener which is a barium complex soap, and an organomolybdenum compound. The content of the organomolybdenum compound is 0.25 to 10% by mass in terms of molybdenum. Hereinafter, the grease composition of the present invention will be described in detail by components.

[0020] [Base Oil]

[0021] The type of the base oil contained in the grease composition of the present invention is not particularly limited, and examples thereof include synthetic oils and mineral oils. The synthetic oils and mineral oils may be used alone or in combination.

[0022] Examples of the synthetic oil include hydrocarbon oils such as polyalpha-olefins, ethylene-alpha-olefin copolymers, polybutenes (polyisobutenes), alkylbenzenes, and alkylnaphthalenes; ester oils such as diesters (esters of dicarboxylic acids and monohydric alcohols), polyol esters, and aromatic esters; and ether oils such as alkyl diphenyl ethers, but are not limited thereto. These synthetic oils may be used alone or in combination of two or more.

[0023] Among them, hydrocarbon oils are preferred, and polyalpha-olefins are more preferred. Here, polyalpha-olefins are substances obtained by polymerizing at least one alpha-olefin (typically trimerized to octamerized). In addition, alpha-olefins are straight-chain olefins having 3 or more carbon atoms and a carbon-carbon double bond at the alpha position. As the alpha-olefin, for example, alpha-olefins having 3 to 30 carbon atoms, preferably 4 to 20 carbon atoms, and more preferably 6 to 16 carbon atoms can be used, but are not limited thereto. Examples of the alpha-olefin include 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, etc., but are not limited thereto.

[0024] The kinematic viscosity of the base oil contained in the grease composition of the present invention is not particularly limited, and is preferably 5 to 200 mm at 40 °C 2 / s, preferably 15 to 100 mm at 40°C 2 / s, more preferably 20 to 50 mm at 40°C 2 / s. By making the kinematic viscosity of the base oil within an appropriate range, it is possible to better balance load resistance and wear resistance.

[0025] [Thickener]

[0026] The grease composition of the present invention contains a thickener which is a barium complex soap. The grease composition of the present invention contains a barium complex soap as a thickener while containing a specific amount of an organomolybdenum compound, thereby being able to balance load resistance and wear resistance. This effect is more significant compared to the case of selecting other thickeners to be used together with the organomolybdenum compound.

[0027] Examples of the barium complex soap include, but are not limited to, barium complex soaps obtained by reacting at least two compounds selected from the following substances with barium hydroxide: fatty acids such as stearic acid, oleic acid, and palmitic acid; hydroxy fatty acids having 12 to 24 carbon atoms and having one or more hydroxyl groups in the molecule; aromatic carboxylic acids; aliphatic dicarboxylic acids having 2 to 20 carbon atoms; and their esters or amides (especially carboxylic acid monoamides). It should be noted that this reaction can be carried out in the base oil. At this time, the above at least two compounds can be reacted with barium hydroxide simultaneously, or one by one with barium hydroxide. In addition, multiple barium soaps can be separately added to the base oil and made into barium complex soaps in the base oil.

[0028] Examples of the hydroxy fatty acids having 12 to 24 carbon atoms include, but are not limited to, 12-hydroxy stearic acid, 12-hydroxy lauric acid, 16-hydroxy palmitic acid, etc. Among them, 12-hydroxy stearic acid is preferred. Examples of the aromatic carboxylic acids include, but are not limited to, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, salicylic acid, p-hydroxybenzoic acid, etc.

[0029] Examples of the aliphatic dicarboxylic acids having 2 to 20 carbon atoms include, but are not limited to, oxalic acid, malonic acid, succinic acid, methyl succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, nonane dicarboxylic acid, decane dicarboxylic acid, undecane dicarboxylic acid, dodecane dicarboxylic acid, tridecane dicarboxylic acid, tetradecane dicarboxylic acid, pentadecane dicarboxylic acid, hexadecane dicarboxylic acid, heptadecane dicarboxylic acid, octadecane dicarboxylic acid, etc. Among them, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, nonane dicarboxylic acid, decane dicarboxylic acid, undecane dicarboxylic acid, dodecane dicarboxylic acid, tridecane dicarboxylic acid, tetradecane dicarboxylic acid, pentadecane dicarboxylic acid, hexadecane dicarboxylic acid, heptadecane dicarboxylic acid, octadecane dicarboxylic acid are preferred, and azelaic acid and sebacic acid are more preferred.

[0030] As the above-mentioned carboxylic acid monoamide, for example, a carboxylic acid monoamide obtained by amidating one carboxyl group of the above-mentioned aliphatic dicarboxylic acid can be mentioned, but it is not limited thereto. Among them, a carboxylic acid monoamide obtained by amidating one carboxyl group of azelaic acid or sebacic acid is preferred. As the amine used in the amidation, for example: aliphatic primary amines such as butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, laurylamine, myristylamine, palmitylamine, stearylamine, behenylamine; aliphatic secondary amines such as dipropylamine, diisopropylamine, dibutylamine, dipentylamine, dilaurylamine, monomethyllaurylamine, distearylamine, monomethylstearylamine, dimyristylamine, dipalmitylamine; aliphatic unsaturated amines such as allylamine, diallylamine, oleylamine, dioleylamine; cycloaliphatic amines such as cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine; aromatic amines such as aniline, methylaniline, ethylaniline, benzylamine, dibenzylamine, diphenylamine, α-naphthylamine, etc., but it is not limited thereto. Among them, hexylamine, heptylamine, octylamine, nonylamine, decylamine, laurylamine, myristylamine, palmitylamine, stearylamine, behenylamine, dibutylamine, dipentylamine, monomethyllaurylamine, monomethylstearylamine, oleylamine are preferred.

[0031] The content of the barium complex soap in the grease composition of the present invention is not particularly limited, but it is preferably 3 to 50% by mass, more preferably 15 to 45% by mass, further preferably 20 to 43% by mass, particularly preferably 25 to 40% by mass, and most preferably 30 to 35% by mass. By making the content of the barium complex soap within an appropriate range, the load-carrying capacity and wear resistance can be more highly balanced.

[0032] As long as the grease composition of the present invention exhibits the effects of the present invention, it may further contain other thickeners in addition to the barium complex soap. As other thickeners, for example: soap-based thickeners such as lithium soap, lithium complex soap, calcium soap, calcium complex soap, aluminum soap, aluminum complex soap; urea-based thickeners such as biurea compounds, triurea compounds, tetraurea compounds; bentonite; silica gel; fluororesins, etc., but it is not limited thereto.

[0033] [Organic molybdenum compound]

[0034] The grease composition of the present invention contains an organic molybdenum compound. As the organic molybdenum compound, for example, molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDTP), etc. can be mentioned, but it is not limited thereto. The organic molybdenum compound can be used alone in one kind, or two or more kinds can be used in combination.

[0035] The content of the organomolybdenum compound in the grease composition of the present invention is 0.25 to 10% by mass in terms of molybdenum. The grease composition of the present invention can achieve both high load-carrying capacity and wear resistance by using barium complex soap as a thickener and containing the organomolybdenum compound in the above content.

[0036] It should be noted that the content of the organomolybdenum compound in terms of molybdenum can be calculated by multiplying the content of the organomolybdenum compound used by the mass ratio of molybdenum in the organomolybdenum compound. For example, when the grease composition contains 5% by mass of the organomolybdenum compound and the mass ratio of molybdenum in the organomolybdenum compound is 10%, the content of the organomolybdenum compound in the grease composition is 5×(10 / 100) = 0.5% by mass in terms of molybdenum.

[0037] The content of the organomolybdenum compound in the grease composition of the present invention is preferably 0.6 to 5% by mass, more preferably 0.7 to 4% by mass, still more preferably 0.8 to 3.5% by mass, particularly preferably 1 to 3% by mass, and most preferably 1.5 to 2.5% by mass in terms of molybdenum. By making the content of the organomolybdenum compound within an appropriate range, both high load-carrying capacity and wear resistance can be achieved to a higher degree. In addition, by making the content of the organomolybdenum compound within an appropriate range, metal corrosion caused by molybdenum can be prevented.

[0038] In the grease composition of the present invention, the content (in terms of molybdenum) of the organomolybdenum compound is preferably 0.75 to 30 parts by mass, more preferably 1.5 to 15 parts by mass, still more preferably 2 to 12 parts by mass, still more preferably 2.5 to 10 parts by mass, particularly preferably 3 to 8 parts by mass, and most preferably 5 to 7 parts by mass relative to 100 parts by mass of the barium complex soap.

[0039] [Other Components]

[0040] The grease composition of the present invention may contain other components as long as the effects of the present invention are exhibited. Examples of other components include, but are not limited to, extreme pressure agents, antioxidants, rust inhibitors, oiliness agents, viscosity index improvers, etc. other than the organomolybdenum compound.

[0041] Examples of extreme pressure agents other than the organomolybdenum compound include, but are not limited to, phosphorus-based compounds such as phosphates, phosphites, and phosphoester amines; sulfur-based compounds such as thioethers and disulfides; and organometallic compounds (excluding organomolybdenum compounds) such as metal dithiophosphates and metal dithiocarbamates.

[0042] Examples of antioxidants include, but are not limited to, amine-based antioxidants, phenol-based antioxidants, and phosphorus-based antioxidants.

[0043] Examples of amine antioxidants include, but are not limited to, alkylated diphenylamines, triphenylamines, phenyl-α-naphthylamines, phenothiazines, alkylated α-naphthylamines, alkylated phenothiazines, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, N,N'-di-2-naphthyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, etc.

[0044] Examples of phenolic antioxidants include, but are not limited to, 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxyphenylmethyl)-2,4,6-trimethylbenzene, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, etc.

[0045] Examples of phosphorus antioxidants include alkyl phosphites, alkyl aryl phosphites, and aryl phosphites. Examples of aryl phosphites include, but are not limited to, triphenyl phosphite, tricresyl phosphite, tris(ethylphenyl) phosphite, tris(nonylphenyl) phosphite, tris(2,4-di-tert-butylphenyl) phosphite, etc.

[0046] Examples of rust inhibitors include, but are not limited to, calcium or sodium salts of aromatic sulfonic acids or saturated aliphatic dicarboxylic acids, fatty acids, fatty acid amines, metal salts of alkyl sulfonic acids, amine salts of alkyl sulfonic acids, oxidized paraffin waxes, polyoxyalkylene ethers, etc.

[0047] Examples of oiliness agents include, but are not limited to, fatty acids or their esters, higher alcohols, polyhydric alcohols or their esters, aliphatic esters, aliphatic amines, monoglycerides of fatty acids, montan waxes, amide waxes, etc.

[0048] Examples of viscosity index improvers include, but are not limited to, polymethacrylates, ethylene-propylene copolymers, polyisobutylene, polyalkylstyrenes, hydrogenated styrene-isoprene copolymers, etc.

[0049] The grease composition of the present invention can be produced by a method such as mixing the above components by a known method. At this time, the mixing order of the components is not particularly limited.

[0050] Preferably, the grease composition of the present invention has a weld load of 3900 N or more as measured according to ASTM D2596, and a wear scar diameter of 0.45 mm or less as measured according to ASTM D2266. The weld load and the wear scar diameter are evaluated by a four-ball test. It should be noted that the weld load and the wear scar diameter can be measured according to the conditions described in the examples.

[0051] The weld load of the grease composition of the present invention as measured according to ASTM D2596 is more preferably 4000 N or more, further preferably 5000 N or more, particularly preferably 6000 N or more, and most preferably 7000 N or more. In addition, the wear scar diameter of the grease composition of the present invention as measured according to ASTM D2266 is more preferably 0.42 mm or less, further preferably 0.40 mm or less, particularly preferably 0.38 mm or less, and most preferably 0.36 mm or less.

[0052] The grease composition of the present invention is suitable for lubricating applications with large loads such as reducer gears, ball screws, and bearings, and can also be widely used for other applications as needed, such as: components for office equipment such as copiers and printers; power transmission devices such as reducers / gearboxes, gears, chains, and motors, driving system components, braking components such as an anti-lock braking system (ABS), steering components, driving components such as transmissions, steering devices, automotive components such as electric window motors, electric seat motors, and sunroof motors; hinge components of electronic information equipment, mobile phones, etc.; various components in the food / drug industry, steel, construction, glass industry, cement industry, chemical / rubber / resin industry such as film stenter frames, environmental / power equipment, paper / printing industry, wood industry, fiber / apparel industry; other relatively moving mechanical components, etc.

[0053] Examples

[0054] Hereinafter, the present invention will be described in more detail by way of examples, etc., but the present invention is not limited by any of these examples, etc.

[0055] [Preparation of Grease Composition]

[0056] (1) Base Oil

[0057] (1a) Polyalphaolefin 1 (PAO1): Synfluid PAO 6cSt (manufactured by Chevron Phillips Chemical Company), kinematic viscosity at 40 °C is 30 mm 2 / s

[0058] (1b) Polyalphaolefin 2 (PAO2): A mixture of two commercially available polyalphaolefin base oils, kinematic viscosity at 40 °C is 100 mm 2 / s

[0059] (2) Thickening agent

[0060] (2a) Barium complex soap (Ba-comp): A barium complex soap obtained by reacting 27.5% by mass of sebacic acid, 41.5% by mass of carboxylic acid monostearylamide, and 31% by mass of barium hydroxide in a base oil

[0061] (2b) Lithium soap (Li soap): A lithium soap obtained by reacting 88% by mass of 12-hydroxy stearic acid and 12% by mass of lithium hydroxide in a base oil

[0062] (2c) Lithium complex soap (Li-comp): A lithium complex soap obtained by reacting 63.5% by mass of 12-hydroxy stearic acid, 19% by mass of azelaic acid, and 17.5% by mass of lithium hydroxide in a base oil

[0063] (2d) Biurea compound: A biurea compound obtained by reacting 50% by mass of diphenylmethane diisocyanate and 50% by mass of octylamine in a base oil

[0064] (3) Additive (additive containing an organomolybdenum compound)

[0065] (3a) Molybdenum dithiocarbamate 1 (MoDTC1): ADEKASAKURA-LUBE (registered trademark) 600 (manufactured by ADEKA CORPORATION), molybdenum content is about 28% by mass

[0066] (3b) Molybdenum dithiocarbamate 2 (MoDTC2): ADEKA SAKURA-LUBE (registered trademark) 525 (manufactured by ADEKA CORPORATION), molybdenum content is about 10% by mass

[0067] (3c) Molybdenum dithiocarbamate 3 (MoDTC3): ADEKASAKURA-LUBE (registered trademark) 165 (manufactured by ADEKA CORPORATION), molybdenum content is about 4.5% by mass

[0068] (3d) Molybdenum dithiophosphate (MoDTP): ADEKA SAKURA-LUBE (registered trademark) 300 (manufactured by ADEKA CORPORATION), molybdenum content is about 9% by mass

[0069] According to the mixing ratios in Tables 1 to 3, additives are added to the mixture of the above-mentioned base oil and thickening agent and mixed to obtain a uniform grease composition (Examples 1 to 10, Comparative Examples 1 to 16). It should be noted that the numerical values of the mixing amounts in each table are in mass%. It should be noted that “(Mo amount)” in each table represents the amount expressed by converting the content of the organomolybdenum compound into molybdenum.

[0070] [Evaluation of grease composition]

[0071] For the obtained grease composition, the following welding load test and wear scar diameter test were carried out. The results are shown in Tables 1 to 3.

[0072] · Welding load test

[0073] It was measured by a four-ball test under the following conditions in accordance with ASTM D2596.

[0074] Rotational speed: 1770 rpm

[0075] Time: 10 seconds

[0076] Temperature: room temperature

[0077] · Wear scar diameter test

[0078] It was measured by a four-ball test under the following conditions in accordance with ASTM D2266.

[0079] Rotational speed: 1200 rpm

[0080] Time: 60 minutes

[0081] Temperature: 75 °C

[0082] [Table 1]

[0083]

[0084] [Table 2]

[0085]

[0086] [Table 3]

[0087]

[0088] From the results of Examples 1 to 10, it can be seen that for a grease composition containing a base oil, a thickener which is a barium complex soap, and an organomolybdenum compound, and the content of the above organomolybdenum compound is 0.25 to 10% by mass in terms of molybdenum, the load resistance and wear resistance are excellent.

[0089] From the results of Examples 2 to 6, it can be seen that by making the content of the organomolybdenum compound 0.6 to 5% by mass in terms of molybdenum on the above basis, the grease composition can more highly balance the load resistance and wear resistance.

[0090] From the results of Examples 4 and 6, it can be seen that by making the kinematic viscosity of the base oil 15 to 50 mm 2 / s at 40 °C on the above basis, the grease composition can more highly balance the load resistance and wear resistance.

[0091] From the results of Comparative Examples 1 to 5 and 12 to 16, it can be seen that when the content of the organomolybdenum compound is less than 0.25% by mass in terms of molybdenum, the load resistance and wear resistance cannot be sufficiently balanced.

[0092] Comparing the results of Comparative Examples 6 and 7, it can be seen that when lithium soap is used as the thickener and the content of the organomolybdenum compound is 0.25 to 10% by mass in terms of molybdenum, although the load resistance is improved, the wear resistance is not improved but rather decreased.

[0093] Comparing the results of Comparative Examples 8 and 9, it can be seen that when lithium complex soap is used as the thickener and the content of the organomolybdenum compound is 0.25 to 10% by mass in terms of molybdenum, although the load resistance is improved, the wear resistance is not improved but rather decreased.

[0094] Comparing the results of Comparative Examples 10 and 11, it can be seen that when a biurea compound is used as the thickener and the content of the organomolybdenum compound is 0.25 to 10% by mass in terms of molybdenum, although the wear resistance is improved, the improvement effect of the load resistance is limited.

[0095] That is, from the results of Examples 1 to 10 and Comparative Examples 6 to 11, it can be seen that only when barium complex soap is used as the thickener and the content of the organomolybdenum compound is 0.25 to 10% by mass in terms of molybdenum, can the grease composition balance the load resistance and wear resistance.

[0096] Figure 1 is a semi-logarithmic graph showing the relationship between the molybdenum-equivalent content of the organomolybdenum compound and the weld load of the grease composition in Examples and Comparative Examples. From Figure 1 it can be seen that when barium complex soap is used as the thickener and the content of the organomolybdenum compound is 0.25% by mass or more in terms of molybdenum, the weld load is significantly increased.

[0097] Industrial Applicability

[0098] The grease composition of the present invention is particularly suitable for lubrication applications in load-bearing parts such as reduction gearbox gears, ball screws, and bearings.

Claims

1. A grease composition, characterized in that, It contains a base oil, a thickener which is a barium complex soap, and an organomolybdenum compound, the content of the organomolybdenum compound is 0.25 to 10% by mass in terms of molybdenum, the welding load of the grease composition measured according to ASTM D2596 is 3900 N or more, and the wear scar diameter measured according to ASTM D2266 is 0.38 mm or less.

2. The grease composition according to claim 1, wherein, the content of the organomolybdenum compound is 0.6 to 5% by mass in terms of molybdenum.

3. The grease composition according to claim 1 or 2, wherein the content of the barium complex soap is 15 to 45% by mass.

4. The grease composition according to claim 1 or 2, wherein The kinematic viscosity of the base oil is 15 to 100 mm 2 / s at 40 °C.

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