Grease composition

Abstract

To provide a grease composition excellent in load resistance and abrasion resistance.SOLUTION: The grease composition comprises base oil, a thickener, i.e., barium complex soap, and an organomolybdenum compound, with the content of the organomolybdenum compound being 0.25 to 10 mass% in terms of molybdenum. In the grease composition, the content of the organomolybdenum compound is preferably 0.6 to 5 mass% in terms of molybdenum, the content of the barium complex soap is preferably 15 to 45 mass%, the content of the barium complex soap is preferably 25 to 40 mass%, the kinetic viscosity of the base oil is preferably 15 to 100 mm2 / s at 40°C, the fusion load measured according to ASTM D2596 is preferably 3900 N or greater, and the wear mark diameter measured according to ASTM D2266 is preferably 0.45 mm or smaller.SELECTED DRAWING: Figure 1

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 machines, transportation machines, and general machines. In particular, in applications with high loads such as reduction gear gears, ball screws, and bearings, a grease composition with excellent load-carrying capacity is required.

[0003] Patent Document 1 discloses that a grease composition for constant velocity joints containing a base oil, a thickener, a detergent-dispersant, a sulfur-phosphorus extreme pressure agent, an organic molybdenum compound, and a lignin compound is excellent in load-carrying capacity and friction coefficient reduction effect. On the other hand, a grease composition used in lubrication locations with high loads is desired to have not only high load-carrying capacity but also high wear resistance. However, in general, it is difficult to achieve both high load-carrying capacity and high wear resistance, and a grease composition that is sufficiently excellent in both is still required.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention provides a grease composition excellent in load-carrying capacity and wear resistance.

Means for Solving the Problems

[0006] The gist of the present invention is as follows. [1] A grease composition comprising a base oil, a thickener which is a barium complex soap, and an organic molybdenum compound, wherein the content of the organic molybdenum compound is 0.25 to 10% by mass in terms of molybdenum. [2] The grease composition of [1], wherein the content of the organic molybdenum compound is 0.6 to 5% by mass in terms of molybdenum. [3] The grease composition of [1] or [2], wherein the barium complex soap content is 15 to 45% by mass. [4] The kinematic viscosity of the base oil is 15 to 100 mm at 40°C. 2 A grease composition of any of [1] to [3], which is / s. [5] A grease composition according to any of [1] to [4], wherein the fusion load measured according to ASTM D2596 is 3900 N or more, and the abrasion mark diameter measured according to ASTM D2266 is 0.45 mm or less. [Effects of the Invention]

[0007] According to the present invention, a grease composition with excellent load-bearing capacity and wear resistance can be provided. [Brief explanation of the drawing]

[0008] [Figure 1] The examples and comparative examples show a semi-logarithmic plot illustrating the relationship between the molybdenum equivalent content of the organic molybdenum compound and the fusion load of the grease composition. [Modes for carrying out the invention]

[0009] The grease composition of the present invention comprises a base oil, a thickener which is a barium complex soap, and an organic molybdenum compound. The content of the organic molybdenum compound is 0.25 to 10% by mass in terms of molybdenum. The grease composition of the present invention will be described in detail below for each component.

[0010] [Base oil] The type of base oil contained in the grease composition of the present invention is not particularly limited, but examples include synthetic oils and mineral oils. Synthetic oils and mineral oils may be used individually or in combination.

[0011] Examples of the synthetic oils include, but are not limited to, hydrocarbon oils such as poly-α-olefins, ethylene-α-olefin copolymers, polybutene (polyisobutylene), alkylbenzenes, and alkylnaphthalenes; ester oils such as diesters (esters of dicarboxylic acids and monoalcohols), polyol esters, and aromatic esters; and ether oils such as alkyldiphenyl ethers. These synthetic oils may be used individually or in combination of two or more.

[0012] Among these, hydrocarbon oils are preferred, and poly-α-olefins are more preferred. Here, poly-α-olefin refers to a polymer (typically 3 to 8-mers) of at least one type of α-olefin. Furthermore, α-olefin refers to a straight-chain alkene having three or more carbon atoms and a carbon-carbon double bond at the α-position. As α-olefins, for example, those having 3 to 30 carbon atoms, preferably 4 to 20 carbon atoms, and more preferably 6 to 16 carbon atoms are used, but are not limited to these. Examples of α-olefins include, but are not limited to, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, etc.

[0013] The kinematic viscosity of the base oil contained in the grease composition of the present invention is not particularly limited, but is 5 to 200 mm at 40°C. 2 It is preferable that the temperature is / s, and the temperature is 15-100 mm at 40°C. 2 It is preferable that the temperature is / s, and the temperature is 20-50 mm at 40°C. 2 A viscosity of / s is more preferable. By having the kinematic viscosity of the base oil within an appropriate range, a higher level of both load-bearing capacity and wear resistance can be achieved.

[0014] [Thickener] The grease composition of the present invention contains a barium complex soap as a thickener. By including a specific amount of an organic molybdenum compound together with a barium complex soap as a thickener, the grease composition of the present invention can achieve both load-bearing capacity and wear resistance. This effect is more pronounced than when other thickeners are selected to be used together with the organic molybdenum compound.

[0015] Examples of barium complex soaps include, but are not limited to, those obtained by reacting barium hydroxide with at least two compounds selected from the group consisting of fatty acids such as stearic acid, oleic acid, and palmitic acid; hydroxy fatty acids having 12 to 24 carbon atoms and 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). The reaction may be carried out in a base oil. In this case, the at least two compounds may be reacted with barium hydroxide simultaneously, or they may be reacted with barium hydroxide one at a time. Alternatively, multiple barium soaps may be added separately to a base oil to form a barium complex soap in the base oil.

[0016] Examples of the hydroxy fatty acids having 12 to 24 carbon atoms include, but are not limited to, 12-hydroxystearic acid, 12-hydroxylauric acid, and 16-hydroxypalmitic acid. Among these, 12-hydroxystearic 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, and p-hydroxybenzoic acid.

[0017] Examples of the aliphatic dicarboxylic acid having 2 to 20 carbon atoms include, but are not limited to, oxalic acid, malonic acid, succinic acid, methylsuccinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, nonanedicarboxylic acid, decanedicarboxylic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, tridecanedicarboxylic acid, tetradecanedicarboxylic acid, pentadecanedicarboxylic acid, hexadecanedicarboxylic acid, heptadecanedicarboxylic acid, octadecanedicarboxylic acid, etc. Among them, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, nonanedicarboxylic acid, decanedicarboxylic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, tridecanedicarboxylic acid, tetradecanedicarboxylic acid, pentadecanedicarboxylic acid, hexadecanedicarboxylic acid, heptadecanedicarboxylic acid, octadecanedicarboxylic acid are preferred, and azelaic acid and sebacic acid are more preferred.

[0018] Examples of the carboxylic acid monoamide include, but are not limited to, those in which one carboxy group of the aliphatic dicarboxylic acid is amidated. Among them, those in which one carboxy group of azelaic acid or sebacic acid is amidated are preferred. Examples of the amine used for amidation include aliphatic primary amines such as butylamine, amylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, laurylamine, myristylamine, palmitylamine, stearylamine, behenylamine, etc.; aliphatic secondary amines such as dipropylamine, diisopropylamine, dibutylamine, diamylamine, dilaurylamine, monomethyllaurylamine, distearylamine, monomethylstearylamine, dimyristylamine, dipalmitylamine, etc.; aliphatic unsaturated amines such as allylamine, diallylamine, oleylamine, dioleylamine, etc.; alicyclic amines such as cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine, etc.; aromatic amines such as aniline, methylaniline, ethylaniline, benzylamine, dibenzylamine, diphenylamine, α-naphthylamine, etc., but are not limited thereto. Among them, hexylamine, heptylamine, octylamine, nonylamine, decylamine, laurylamine, myristylamine, palmitylamine, stearylamine, behenylamine, dibutylamine, diamylamine, monomethyllaurylamine, monomethylstearylamine, oleylamine are preferred.

[0019] The content of the barium complex soap in the grease composition of the present invention is not particularly limited, but is preferably 3 to 50% by mass, more preferably 15 to 45% by mass, still more preferably 20 to 43% by mass, particularly preferably 25 to 40% by mass, and most preferably 30 to 35% by mass. When the content of the barium complex soap is within an appropriate range, the load resistance and wear resistance can be more highly balanced.

[0020] The grease composition of the present invention may further contain other thickeners other than barium complex soap, as long as the effects of the present invention are achieved. Examples of other thickeners include, but are not limited to, soap-based thickeners such as lithium soap, lithium complex soap, calcium soap, calcium complex soap, aluminum soap, and aluminum complex soap; urea-based thickeners such as diurea compounds, triurea compounds, and tetraurea compounds; bentonite; silica gel; and fluororesins.

[0021] [Organomolybdenum compounds] The grease composition of the present invention contains an organic molybdenum compound. Examples of organic molybdenum compounds include, but are not limited to, molybdenum dithiocarbamate (MoDTC) and molybdenum dithiophosphate (MoDTP). The organic molybdenum compound may be used alone or in a mixture of two or more types.

[0022] The content of the organic molybdenum 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 load-bearing capacity and wear resistance by using barium complex soap as a thickener and including the organic molybdenum compound in the above-mentioned content.

[0023] The molybdenum content of an organic molybdenum compound can be calculated by multiplying the content of the organic molybdenum compound used by the mass percentage of molybdenum in that organic molybdenum compound. For example, if a grease composition contains 5% by mass of an organic molybdenum compound and the mass percentage of molybdenum in that organic molybdenum compound is 10% by mass, then the content of the organic molybdenum compound in the grease composition is 5 × (10 / 100) = 0.5% by mass in terms of molybdenum.

[0024] The content of the organic molybdenum 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, even 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 equivalent. By having an appropriate content of the organic molybdenum compound, a higher level of both load-bearing capacity and wear resistance can be achieved. Furthermore, by having an appropriate content of the organic molybdenum compound, corrosion of metals by molybdenum can be prevented.

[0025] In the grease composition of the present invention, the content of the organic molybdenum compound (in terms of molybdenum) is preferably 0.75 to 30 parts by mass, more preferably 1.5 to 15 parts by mass, even more preferably 2 to 12 parts by mass, even 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, per 100 parts by mass of barium complex soap.

[0026] [Other ingredients] The grease composition of the present invention may contain other components as long as the effects of the present invention are achieved. Examples of other components include, but are not limited to, extreme pressure agents other than organic molybdenum compounds, antioxidants, rust inhibitors, lubricity agents, viscosity index improvers, etc.

[0027] Examples of extreme pressure agents other than organomolybdenum compounds include, but are not limited to, phosphorus compounds such as phosphate esters, phosphite esters, and phosphate esteramines; sulfur compounds such as sulfides and disulfides; and organometallic compounds such as metal dithiophosphates and metal dithiocarbamates (excluding organomolybdenum compounds).

[0028] Examples of antioxidants include, but are not limited to, amine-based antioxidants, phenol-based antioxidants, and phosphorus-based antioxidants. Examples of amine-based antioxidants include, but are not limited to, alkylated diphenylamine, triphenylamine, phenyl-α-naphthylamine, phenothiazine, alkylated α-naphthylamine, alkylated phenothiazine, 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, and N-phenyl-N'-isopropyl-p-phenylenediamine.

[0029] Examples of phenolic antioxidants include, but are not limited to, 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 1,3,5-tris(3,5-di-t-butyl-4-hydroxyphenylmethyl)-2,4,6-trimethylbenzene, and 1,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione.

[0030] Examples of phosphorus-based antioxidants include alkyl phosphites, alkylaryl phosphites, and aryl phosphites. Examples of aryl phosphites include, but are not limited to, triphenyl phosphite, tricresyl phosphite, tris(ethylphenyl) phosphite, tris(nonylphenyl) phosphite, and tris(2,4-di-t-butylphenyl) phosphite.

[0031] 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, alkyl sulfonic acid metal salts, alkyl sulfonic acid amine salts, paraffin oxides, and polyoxyalkyl ethers.

[0032] Examples of oily agents include, but are not limited to, fatty acids or their esters, higher alcohols, polyhydric alcohols or their esters, aliphatic esters, aliphatic amines, fatty acid monoglycerides, montan wax, and amide waxes.

[0033] Examples of viscosity index improvers include, but are not limited to, polymethacrylate, ethylene-propylene copolymer, polyisobutylene, polyalkylstyrene, and hydrogenated styrene-isoprene copolymer.

[0034] The grease composition of the present invention can be manufactured by mixing the above components using known methods, etc. In this case, the mixing order of the components is not particularly limited.

[0035] The grease composition of the present invention preferably has a fusion load of 3900 N or more, as measured according to ASTM D2596, and an abrasion mark diameter of 0.45 mm or less, as measured according to ASTM D2266. The fusion load and abrasion mark diameter are evaluated by a four-ball test. The fusion load and abrasion mark diameter can be measured according to the conditions described in the examples.

[0036] The grease composition of the present invention more preferably has a fusion load of 4000 N or more, even more preferably 5000 N or more, particularly preferably 6000 N or more, and most preferably 7000 N or more, as measured according to ASTM D2596. Furthermore, the grease composition of the present invention more preferably has an abrasion mark diameter of 0.42 mm or less, even more preferably 0.40 mm or less, particularly preferably 0.38 mm or less, and most preferably 0.36 mm or less, as measured according to ASTM D2266.

[0037] The grease composition of the present invention is suitable for lubrication applications in areas subject to heavy loads, such as reduction gears, ball screws, and bearings. However, it can also be widely applied to other applications as needed, such as parts for office equipment like photocopiers and printers; power transmission devices such as reduction gears and speed increasers, gears, chains, and motors; running gear components; braking system components such as ABS; steering system components; drive system components such as transmissions; steering devices; automotive parts such as power window motors, power seat motors, and sunroof motors; hinge components for electronic information equipment and mobile phones; various parts in the food and pharmaceutical industry, steel industry, construction industry, glass industry, cement industry, chemical, rubber and resin industry such as film tenters, environmental and power equipment, paper and printing industry, wood industry, and textile and apparel industry; and other mechanical parts in relative motion. [Examples]

[0038] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these examples.

[0039] [Preparation of grease composition] (1) Base oil (1a) Poly-α-olefin 1 (PAO1): Synfluid PAO 6cSt (manufactured by Chevron Phillips Chemical), kinematic viscosity at 40°C 30 mmHg 2 / s (1b) Poly-α-olefin 2 (PAO2): A mixture of two commercially available poly-α-olefin base oils, kinematic viscosity at 40°C: 100 mm² 2 / s

[0040] (2) Thickener (2a) Barium complex soap (Ba-comp): Obtained by reacting 27.5% by mass of sebaciic acid, 41.5% by mass of monostearyl carboxylic acid, and 31% by mass of barium hydroxide in a base oil. (2b) Lithium soap (Li soap): Obtained by reacting 88% by mass of 12-hydroxystearic acid and 12% by mass of lithium hydroxide in a base oil. (2c) Lithium complex soap (Li-comp): Obtained by reacting 63.5% by mass of 12-hydroxystearic acid, 19% by mass of azelaic acid, and 17.5% by mass of lithium hydroxide in a base oil. (2d) Diurea compound: obtained by reacting 50% by mass of diphenylmethane diisocyanate and 50% by mass of octylamine in a base oil.

[0041] (3) Additives (additives containing organomolybdenum compounds) (3a) Molybdenum dithiocarbamate 1 (MoDTC1): ADEKA Sakura Lube (registered trademark) 600 (manufactured by ADEKA Corporation), molybdenum content approximately 28% by mass (3b) Molybdenum dithiocarbamate 2 (MoDTC2): ADEKA Sakura Lube (registered trademark) 525 (manufactured by ADEKA Corporation), molybdenum content approximately 10% by mass (3c) Molybdenum dithiocarbamate 3 (MoDTC3): ADEKA Sakura Lube (registered trademark) 165 (manufactured by ADEKA Corporation), molybdenum content approximately 4.5% by mass (3d) Molybdenum dithiophosphate (MoDTP): ADEKA Sakura Lube (registered trademark) 300 (manufactured by ADEKA Corporation), molybdenum content approximately 9% by mass

[0042] Additives were added to the mixture of the base oil and thickener described above to obtain the blending ratios shown in Tables 1 to 3, and the mixture was then mixed to obtain a uniform grease composition (Examples 1 to 10, Comparative Examples 1 to 16). The numerical values ​​for the blending amounts in each table are in mass percent. In each table, "(Mo amount)" represents the amount of organic molybdenum compound content expressed in molybdenum equivalent.

[0043] [Evaluation of grease composition] The obtained grease compositions were subjected to the following fusion load tests and abrasion mark diameter tests. The results are shown in Tables 1 to 3.

[0044] • Fusion load test The measurements were taken by a walk test under the following conditions, in accordance with ASTM D2596. Rotation speed: 1770 rpm Time: 10 seconds Temperature: room temperature

[0045] • Abrasion mark diameter test The measurements were taken by a walk test under the following conditions, in accordance with ASTM D2266. Rotation speed: 1200 rpm Duration: 60 minutes Temperature: 75℃

[0046] [Table 1]

[0047] [Table 2]

[0048] [Table 3]

[0049] The results from Examples 1 to 10 show that a grease composition comprising a base oil, a barium complex soap thickener, and an organic molybdenum compound, wherein the content of the organic molybdenum compound is 0.25 to 10% by mass in terms of molybdenum, exhibits excellent load-bearing capacity and wear resistance.

[0050] The results from Examples 2 to 6 show that, in addition to the above, a grease composition can achieve a higher level of both load-bearing capacity and wear resistance when the content of the organic molybdenum compound is 0.6 to 5% by mass in terms of molybdenum.

[0051] From the results of Examples 4 and 6, in addition to the above, the kinematic viscosity of the base oil was 15-50 mm at 40°C. 2 The fact that it is / s indicates that the grease composition can achieve a higher level of both load-bearing capacity and wear resistance.

[0052] The results from Comparative Examples 1-5 and 12-16 show that when the content of the organic molybdenum compound falls below 0.25% by mass in terms of molybdenum equivalent, it is not possible to achieve a sufficient balance between load-bearing capacity and abrasion resistance.

[0053] Comparing the results of Comparative Examples 6 and 7, it can be seen that when lithium soap is used as a thickener, if the content of the organic molybdenum compound is 0.25 to 10% by mass in terms of molybdenum, the load-bearing capacity improves, but the abrasion resistance does not improve, and in fact decreases.

[0054] Comparing the results of Comparative Examples 8 and 9, it can be seen that when lithium complex soap is used as a thickener, if the content of the organic molybdenum compound is 0.25 to 10% by mass in terms of molybdenum, the load-bearing capacity improves, but the abrasion resistance does not improve, and in fact decreases.

[0055] Comparing the results of Comparative Examples 10 and 11, it can be seen that when a diurea compound is used as a thickener, if the content of the organic molybdenum compound is 0.25 to 10% by mass in terms of molybdenum, the abrasion resistance improves, but the effect on load-bearing capacity is limited.

[0056] In other words, the results from Examples 1 to 10 and Comparative Examples 6 to 11 show that a grease composition can achieve both load-bearing capacity and wear resistance only when a barium complex soap is used as a thickener and the content of the organic molybdenum compound is 0.25 to 10% by mass in terms of molybdenum.

[0057] Figure 1 is a semi-logarithmic plot showing the relationship between the molybdenum equivalent content of the organic molybdenum compound and the fusion load of the grease composition in the examples and comparative examples. As can be seen from Figure 1, when barium complex soap is used as a thickener and the content of the organic molybdenum compound is set to 0.25% by mass or more in terms of molybdenum, the fusion load is significantly improved. [Industrial applicability]

[0058] The grease composition of the present invention is particularly suitable for lubrication applications in areas subject to heavy loads, such as reduction gears, ball screws, and bearings.

Claims

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

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

5. The grease composition according to claim 1 or 2, wherein the fusion load measured according to ASTM D2596 is 3900 N or more, and the wear mark diameter measured according to ASTM D2266 is 0.45 mm or less.

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