Grease composition

Abstract

A grease composition containing a base oil and a calcium complex soap as a thickening agent, wherein C18-22 straight-chain substituted or unsubstituted higher fatty acid; substituted or unsubstituted aromatic monocarboxylic acid having a benzene ring; C2-4 straight-chain saturated lower fatty acid; and substituted or unsubstituted saturated dicarboxylic acid are used as carboxylic acids constituting the calcium complex soap.

Description

[0001] This application is a divisional application of patent application No. 201880061911.1, filed on September 28, 2018, entitled "Lubricating Grease Composition". Technical Field

[0002] This invention relates to a grease composition. More specifically, this invention relates to a calcium-based complex grease composition. Background Technology

[0003] In recent years, with the advancement of mechanical technology, the lubrication environment has become increasingly harsh, thus creating a growing demand for greases with improved performance at high temperatures that meet this requirement.

[0004] Among these greases, for example, lithium soap-based greases, lithium-composite greases with a wider operating temperature range than lithium-based greases have been proposed. However, since lithium is a raw material for lithium-based greases, there are concerns that increased demand in the near term could lead to future supply instability or a significant rise in costs.

[0005] On the other hand, urea-based greases are widely used as high-temperature greases, but some of the substances used as raw materials are highly toxic. Therefore, sufficient attention needs to be paid to the treatment of these substances during grease preparation. Consequently, there is a need for materials that constitute grease compositions with high supply stability, high environmental compatibility, and heat resistance.

[0006] Based on the above background, the applicant has invented a calcium composite grease according to JP5943479, which is a grease that can maintain appropriate consistency even when using a small amount of thickener.

[0007] However, due to further increases in market demand, there is a strong need to improve the shear stability of greases.

[0008] The inventors have discovered that the above-mentioned shear stability (softening) problem can be solved by further introducing specific carboxylic acids into the components of a calcium composite thickener composed of higher fatty acids, lower fatty acids and aromatic carboxylic acids. Summary of the Invention

[0009] The purpose of this invention is to provide A grease composition comprising a base oil and a calcium complex soap as a thickener, wherein C18-22 straight-chain substituted or unsubstituted higher monofatty acids; substituted or unsubstituted aromatic monocarboxylic acids having a benzene ring; C2-4 straight-chain saturated lower monofatty acids; and substituted or unsubstituted saturated dicarboxylic acids as carboxylic acids constituting said calcium complex soap.

[0010] The present invention also aims to provide The grease composition wherein the weight ratio of the calcium dicarboxylate compound to the total thickener is 5% to 70%.

[0011] The present invention also aims to provide The grease composition wherein the substituted or unsubstituted saturated dicarboxylic acid has 4 to 20 carbon atoms. Detailed Implementation

[0012] The calcium-based composite grease composition according to the present invention provides a grease composition with excellent shear stability compared to conventional calcium-based composite greases.

[0013] Embodiments of the invention will be described below, but the scope of the invention is not limited by the embodiments described.

[0014] The grease composition of this embodiment includes a "base oil" and a "thickener" as basic structural components. Hereinafter, the components included in the grease composition, the amounts (mixing amounts) of each component in the grease composition, the method of preparing the grease composition, the properties of the grease composition, and the uses of the grease composition will be described in the order stated.

[0015] The base oil used in the grease composition of this embodiment is not particularly limited. For example, oils commonly used in general grease compositions, such as mineral oils, synthetic oils, animal and vegetable oils, or blends thereof, can be used appropriately. For example, base oils belonging to Group 1, Group 2, Group 3, Group 4, etc. of the API (American Petroleum Organization) base oil categories can be used alone or as a mixture.

[0016] Examples of Group 1 base oils include paraffinic mineral oils, which are obtained by refining lubricating oil fractions (obtained by atmospheric distillation of crude oil) through a suitable combination of solvent refining, hydrorefining, dewaxing, and other methods. Examples of Group 2 base oils include paraffinic mineral oils, which are obtained by refining lubricating oil fractions (obtained by atmospheric distillation of crude oil) through a suitable combination of hydrolysis, dewaxing, and other methods. Group 2 base oils refined by methods such as Gulf hydrorefining have a sulfur content of less than 10 ppm and an aroma content of 5% or less, and are preferred for use in this invention.

[0017] Examples of Group 3 base oils and Group 2 supplementary base oils include paraffinic mineral oils obtained by highly hydrorefining lubricating oil fractions (obtained by atmospheric distillation of crude oil); base oils produced by the ISODEWAX process (where the wax produced by the dewaxing process is converted / dewaxed to isoparaffin); and base oils refined by the Mobil wax isomerization process, which may be preferred in this embodiment.

[0018] Examples of synthetic oils include polyolefins, diesters of dicarboxylic acids, trimellitic acid esters, polyol esters, alkylbenzenes, alkylnaphthalenes, esters, polyoxyalkylene glycols, polyoxyalkylene glycol esters, polyoxyalkylene glycol ethers, polyphenylene ethers, dialkyl diphenyl ethers, fluorinated compounds (perfluoropolyethers, fluorinated polyolefins, etc.), silicones, etc. The aforementioned polyolefins include various olefin polymers and their hydrides. Any olefin can be used, and examples include ethylene, propylene, butene, α-olefins containing five or more carbon atoms, etc. Polyolefins can be prepared using the aforementioned olefins or combinations of two or more olefins. In particular, so-called polyα-olefins (PAOs) are preferably used as polyolefins, which are Group 4 base oils.

[0019] Oils synthesized via GTL (natural gas synthetic oil) through the Fischer-Tropsch synthesis process (a technique for obtaining liquid fuels from natural gas) exhibit significantly lower sulfur and aromatic content and a significantly higher paraffin content compared to mineral oil base oils obtained from crude oil refining, thus demonstrating excellent oxidative stability and very low evaporation loss. Therefore, this oil is preferably used as the base oil in this embodiment.

[0020] The thickener used in this embodiment is a calcium complex soap obtained by reacting multiple carboxylic acids with a specific base (typical examples include calcium hydroxide). Here, the term "complex" in the calcium complex soap according to this embodiment means that multiple carboxylic acids are used. Four sources of carboxylic acids can be used in the calcium complex soap according to this embodiment, namely (1) higher fatty acids, (2) aromatic monocarboxylic acids, (3) lower fatty acids, and (4) dicarboxylic acids. It is worth noting that carboxylic acids other than these can be used without affecting the effects of the present invention. The carboxylic acid portion (anionic portion) of the calcium complex soap will be described in detail below.

[0021] The higher fatty acids used in this embodiment are C18-22 straight-chain higher fatty acids. Here, the straight-chain higher fatty acid can be unsubstituted or substituted with one or more substituents (e.g., hydroxyl groups or similar). The straight-chain higher fatty acid can be a saturated or unsaturated fatty acid, but is preferably a saturated fatty acid. Specific examples of saturated fatty acids include stearic acid (octadecanoic acid, C18), nodular stearic acid (nonadecanoic acid, C19), arachidic acid (eicosanoic acid, C20), icosanoic acid (C21), behenic acid (docosahexaenoic acid, C22), and hydroxystearic acid (C18, hydrogenated castor oil fatty acid), while examples of unsaturated fatty acids include oleic acid, linoleic acid, linolenic acid (C18), enoic acid, eicosapentaenoic acid, eicosatrienoic acid (C20), erucic acid, docosahexaenoic acid (C22), etc. Hydrogenated oils obtained by hydrogenating unsaturated fatty acid-rich oils, such as castor oil, using a catalyst such as nickel, can replace the higher fatty acids. These acids can be used alone or in combination. For example, when unsaturated fatty acids are included, it is preferable to use them in combination with saturated fatty acids.

[0022] The aromatic monocarboxylic acids used in this embodiment are substituted or unsubstituted aromatic monocarboxylic acids having a benzene ring. In this document, aromatic monocarboxylic acids may be unsubstituted or substituted by one or more substituents (e.g., ortho-, meta-, or para-alkyl, hydroxyl, alkoxy, etc.). Specific examples include benzoic acid, methylbenzoic acid {toluic acid (p-, meta-, ortho-)}, dimethylbenzoic acid (xylenecarboxylic acid, 2,3-dimethylbenzoic acid, 3,5-xylenecarboxylic acid), trimethylbenzoic acid {2,3,4-trimethylbenzoic acid, 2,3,5-trimethylbenzenecarboxylic acid, iso-2,3,5-trimethylbenzenecarboxylic acid (α-, β-, γ-)}, 4-isopropylbenzoic acid (cumulonic acid), hydroxybenzoic acid (salicylic acid), and dihydroxybenzoic acid {pyrocatechinic acid} Resoric acid (α-, β-, γ-), gentianic acid, protocatechuic acid, trihydroxybenzoic acid (gallic acid), hydroxymethylbenzoic acid (cresolic acid (p-, meta-, o-)), dihydroxymethylbenzoic acid (crosinic acid), methoxybenzoic acid (anisinic acid (p-, meta-, o-)), dimethoxybenzoic acid (vermiculic acid), trimethoxybenzoic acid (asaric acid), hydroxymethoxybenzoic acid (vanillic acid, isovaleric acid), hydroxydimethoxybenzoic acid (syringic acid), etc. These can be used alone or in combination. In this specification, the alkyl and alkoxy groups in "substituent" are, for example, 1 to 4 straight-chain or branched alkyl groups.

[0023] The lower fatty acids used in this embodiment are C2-4 straight-chain saturated lower fatty acids. Specific examples include acetic acid (C2), propionic acid (C3), and butyric acid (C4). Acetic acid (C2) is particularly preferred. These can be used alone or in combination.

[0024] The dicarboxylic acid used in this embodiment is a substituted or unsubstituted saturated dicarboxylic acid. In this document, the saturated dicarboxylic acid may be unsubstituted or substituted with one or more substituents (e.g., hydroxyl groups). The saturated dicarboxylic acid may be straight-chain or branched, but is preferably straight-chain. The number of carbon atoms in the saturated dicarboxylic acid (in the case of a branched chain, the total number of carbon atoms in the main chain and side chains) is not particularly limited, but is preferably 4 to 20, more preferably 4 to 16, and particularly preferably 4 to 10. Specific examples include oxalic acid (C2), malonic acid (C3), succinic acid (C4), glutaric acid (C5, such as 2-methylsuccinic acid and glutaric acid), adipic acid (C6, such as adipic acid), pimelic acid (C7, such as phytic acid), octanoic acid (C8, such as cork acid), azelaic acid (C9, such as azelaic acid), sebacic acid (C10, such as sebacic acid), undecanoic acid (C11), dodecanoic acid (C11), tridecanoic acid (C13, such as salicylic acid), tetradecanoic acid (C14), pentadecanoic acid (C15), hexadecanoic acid (C16), heptadecanoic acid (C17), octadecanoic acid (C18), nonadecanoic acid (C19), and eicosanoic acid (C20). These can be used alone or in combination.

[0025] Therefore, the grease composition in this embodiment contains not only straight-chain higher fatty acids, aromatic monocarboxylic acids, and lower fatty acids, but also dicarboxylic acids. By further specifying dicarboxylic acids as structural components, the fibers of these multiple soaps—higher monocarboxylic acids, aromatic monocarboxylic acids, and lower monocarboxylic acids—are highly complex and tightly intertwined. Therefore, the grease composition according to this embodiment is estimated to exhibit superior shear stability (and also excellent heat resistance). The reason why specifying dicarboxylic acids can effectively enwrap and strengthen fibers is currently unclear. However, it is believed that random bonding of divalent calcium and dicarboxylic acids leads to polymers including calcium dicarboxylate, which readily transform fibers into longer fibers and readily enwrap within individual fibers to become stronger.

[0026] It is worth noting that the combination of stearic acid or behenic acid as straight-chain higher fatty acids, benzoic acid as an aromatic monocarboxylic acid, and acetic acid as a lower fatty acid is the most preferred combination.

[0027] For the grease composition of this embodiment, other thickeners can also be used in combination with the calcium complex soap described above. Examples of thickeners include tricalcium phosphate, alkali metal soaps, alkali metal complex soaps, alkaline earth metal soaps, alkaline earth metal complex soaps (except calcium complex soaps), alkali metal sulfonates, alkaline earth metal sulfonates, other metal soaps, terephthalic acid metal salts, clay, silica (silica, such as silica aerogel), fluoropolymers (such as polytetrafluoroethylene), etc. These can be used alone or in combination of two or more. In addition to the examples listed, any substance capable of thickening liquid substances can be used.

[0028] The grease composition of this embodiment may further include optional additives such as antioxidants, rust inhibitors, oiliness modifiers, extreme pressure agents, anti-wear agents, solid lubricants, metal deactivators, polymers, metal detergents, non-metal detergents, defoamers, colorants, and water-repellent agents, wherein the total amount of optional components is about 0.1 to 20 parts by weight per 100 parts by weight of the total grease composition. Examples of antioxidants include 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-p-cresol, p,p'-dioctyldiphenylamine, N-phenyl-α-naphthylamine, phenothiazine, etc. Examples of rust inhibitors include paraffin oxides, metal salts of carboxylic acids, metal salts of sulfonates, carboxylic esters, sulfonates, salicylates, succinates, sorbitan esters, and various other amine salts. Examples of oiliness modifiers, extreme pressure agents, and anti-wear agents include zinc dialkyl dithiophosphate sulfide, zinc diallyl dithiophosphate sulfide, zinc dialkyl dithiocarbamate sulfide, zinc diallyl dithiocarbamate sulfide, molybdenum dialkyl dithiophosphate sulfide, molybdenum dialkyl dithiocarbamate sulfide, molybdenum dithiocarbamate sulfide, organomolybdenum complexes, sulfurized olefins, triphenyl phosphate, triphenyl thiophosphate, tricresyl phosphate, other phosphate esters, sulfurized grease oils, etc. Examples of solid lubricants include molybdenum disulfide, graphite, boron nitride, melamine cyanurate, PTFE (polytetrafluoroethylene), tungsten disulfide, fluorinated graphite, etc. Examples of metal deactivators include N,N'-disalicylic acid-1,2-diaminopropane, benzotriazole, benzimidazole, benzothiazole, thiadiazole, etc. Examples of this polymer include polybutene, polyisobutylene, polyisobutylene, polyisoprene, polymethacrylate, etc. Examples of this metallic detergent include metal sulfonates, metal salicylates, metal benzoates, etc. Examples of this non-metallic detergent include succinic imide, etc. Examples of this defoamer include methyl silicone, dimethyl silicone, fluorosilicone, polyacrylate, etc.

[0029] Next, the mixing amount of the grease composition according to this embodiment will be described.

[0030] The amount of base oil mixed relative to 100 parts by weight of the total amount of the grease composition is preferably 60 to 99 parts by weight, more preferably 70 to 97 parts by weight, and even more preferably 80 to 95 parts by weight.

[0031] The amount of the calcium complex soap mixed is preferably 1 to 40 parts by weight relative to the total amount of 100 parts by weight of the grease composition, and more preferably 3 to 25 parts by weight.

[0032] The higher fatty acid is preferably 20 to 70 parts by mass relative to 100 parts by mass of total carboxylic acid, and more preferably 30 to 65 parts by mass.

[0033] The amount of the aromatic monocarboxylic acid mixed is preferably 1 to 10 parts by mass relative to 100 parts by mass of total carboxylic acid. More preferably, it is 3 to 10 parts by mass.

[0034] The amount of the lower fatty acids mixed is preferably 5 to 30 parts by mass relative to the total amount of carboxylic acids, and more preferably 10 to 25 parts by mass.

[0035] The amount of the dicarboxylic acid mixed relative to 100 parts by mass is preferably 1 to 70 parts by mass, and more preferably 5 to 55 parts by mass.

[0036] Here, based on the total amount of thickener (the content of dehydrated calcium complex soap) in the grease composition, the amount of calcium dicarboxylate compound (dehydrated calcium dicarboxylate soap) resulting from the saponification of dicarboxylic acid and basic calcium (usually calcium hydroxide) is preferably 5 to 70 parts by mass, more preferably 5 to 60 parts by mass. It is worth noting that the calcium dicarboxylate compound shown here can be a reaction product of dicarboxylic acid and basic calcium, and includes cyclic compounds and polymeric compounds, as well as compounds terminated in monocarboxylate calcium.

[0037] The mass ratio of the higher fatty acid to the dicarboxylic acid is preferably 20:80 to 95:5, and more preferably 30:70 to 85:15.

[0038] The mass ratio of the aromatic monocarboxylic acid to the dicarboxylic acid is preferably 5:95 to 70:30, and more preferably 15:85 to 65:35.

[0039] The mass ratio of the lower fatty acid to the dicarboxylic acid is preferably 5:95 to 85:15, and more preferably 15:85 to 80:20.

[0040] The grease composition in this embodiment can be prepared according to methods commonly used to prepare greases. The preparation method is not particularly limited, and examples include the method used in Example 1, which involves mixing a base oil, higher fatty acids, lower fatty acids, and aromatic monocarboxylic acids in a grease production container and dissolving the contents at a temperature of 60 to 90°C. Subsequently, calcium hydroxide, pre-dissolved and dispersed in an appropriate amount of distilled water, is added to the container. The various carboxylic acids undergo a saponification reaction with basic calcium (typically calcium hydroxide), slowly forming soaps in the base oil, and the resulting product is further heated and dehydrated. Subsequently, dicarboxylic acids are mixed in the container while calcium hydroxide, dissolved and dispersed in distilled water, is added to the container. The mixture is then saponified and dehydrated to form a grease thickener. After dehydration, the grease is heated to 180 to 220°C, thoroughly stirred and mixed, and cooled to room temperature. Thereafter, a mill (e.g., a three-roll mill, etc.) is used to obtain a homogeneous grease composition. Alternatively, the method used in Preparation Example 2 involves mixing base oil, higher fatty acids, lower fatty acids, aromatic monocarboxylic acids and organic acids, and dicarboxylic acids in a grease production container, and dissolving the contents at a temperature of 60 to 90°C. Subsequently, alkaline calcium (typically calcium hydroxide) pre-dissolved and dispersed in an appropriate amount of distilled water is added to the container, followed by saponification, with soaps slowly forming in the base oil. The resulting product is further heated and dehydrated to form a grease thickener. After dehydration, the grease is heated to 180 to 220°C, thoroughly stirred, and cooled to room temperature. Thereafter, a milling machine (e.g., a three-roll mill) is used to obtain a homogeneous grease composition. Here, since the amount of calcium dicarboxylate compound in the grease composition depends on the amount of dicarboxylic acid in the thickener raw material, it can be considered that even if the preparation methods of Preparation Example 1 and Preparation Example 2 are different, the amount of calcium dicarboxylate compound prepared will not show a significant difference. Therefore, the amount of calcium dicarboxylate compound in this grease composition can be controlled by the amount of dicarboxylic acid to be mixed. It is worth noting that, based on the amount of carboxylic acid to be mixed, the amount of alkaline calcium (usually calcium hydroxide) can be appropriately set according to the amount of carboxylic acid to be mixed.

[0041] For the grease composition of this embodiment, it is preferred to use a composition with a dropping point equal to or higher than 180°C, more preferably equal to or higher than 210°C, further preferably equal to or higher than 250°C, and particularly preferably equal to or higher than 260°C. It is believed that when the dropping point of the grease composition is 180°C or higher (typically at least 50°C higher than calcium grease), lubrication problems, such as viscosity loss at high temperatures and the resulting possibility of leakage, burning, etc., are suppressed. The dropping point referred to herein is the temperature at which a viscous grease loses its thickener configuration as temperature increases. Here, the dropping point is measured according to JIS K 2220 8.

[0042] Based on consistency testing, the grease consistency in this embodiment is preferably No. 000 to 6 (85 to 475), more preferably No. 0 to 4 (175 to 385), and even more preferably No. 1 to 3 (220 to 340). Consistency indicates the apparent hardness of the grease. Consistency is measured by performing a post-work penetration measurement according to JIS K 2220 7.

[0043] Before and after the rolling stability test (25°C, 24 hours), the difference (absolute value) in the working penetration of the grease in this embodiment is preferably 80 or less, more preferably 70 or less, and even more preferably 60 or less. Furthermore, before and after the rolling stability test (100°C, 24 hours), the difference (absolute value) in the working penetration of the grease is preferably 100 or less, more preferably 90 or less, and even more preferably 80 or less. The rolling stability test is used to evaluate the shear stability of the grease by measuring its consistency (hardness) after kneading 50 g of test grease using equipment for a predetermined period of time. The shear stability of the grease composition is an important factor in maintaining the lubricating ability and physical behavior of the grease. Poor shear stability causes the grease to easily escape from the lubricated parts of the machine and fails to provide the required lubrication, which leads to shortened life and may also cause grease dispersion, contaminating the area around the machine and damaging the working environment. Here, the rolling stability test is performed according to ASTM D 1831 to evaluate shear stability.

[0044] The grease composition in this embodiment exhibits excellent shear stability; therefore, it can certainly be used in general-purpose machines, bearings, gears, etc., and demonstrates excellent performance under harsh conditions (e.g., high temperatures). For example, this grease composition is preferably used for the lubrication of various components in automobiles, such as engine peripherals including starters, alternators, and various actuators; power systems including propeller shafts, constant speed joints (CVJs), wheel bearings and clutches; electric power steering (EPS); braking units; ball joints; door hinges; steering wheels; cooling fan motors; brake expanders, etc. Furthermore, this grease composition is also preferably used for various high-temperature / heavy-duty components in construction machinery, such as electric shovels, bulldozers and cranes; in the steel industry; paper industry; forestry machinery; agricultural machinery; chemical plants; power generation facilities; drying ovens; photocopiers; railway vehicles; threaded joints of seamless pipes, etc. For other purposes, this composition is also preferably used for hard disk bearings, plastic lubrication, ink cartridge grease, etc.

[0045] Example The invention will now be described in more detail with reference to examples and comparative examples, but the invention is not limited by these examples.

[0046] The raw materials used in this example and comparative examples are as follows. Unless otherwise stated, the amounts given in Table 1 are for Examples 1 to 8 and Comparative Examples 1 to 3. The amounts of raw materials shown in Table 1 {particularly calcium hydroxide and various carboxylic acids (higher fatty acids, aromatic monocarboxylic acids, lower fatty acids and dicarboxylic acids)} are amounts of reagents. Therefore, the actual component content in the composition can be calculated based on the values ​​in Table 1 and the purity levels described below.

[0047] Calcium hydroxide: a premium grade reagent with a purity of 96.0%.

[0048] Stearic acid: a C18 straight-chain alkyl saturated fatty acid, supplied as a premium reagent with a purity of 95.0%.

[0049] Acetic acid: an alkyl fatty acid containing two carbon atoms, supplied as a premium reagent with a purity of 99.7%.

[0050] Tartaric acid: a straight-chain dicarboxylic acid containing four carbon atoms, supplied as a premium reagent with a purity of 99.0% or higher.

[0051] Adipic acid: a straight-chain dicarboxylic acid containing 6 carbon atoms, supplied as a premium reagent with a purity of 99.5% or higher.

[0052] Azadirachtic acid: a straight-chain dicarboxylic acid containing 9 carbon atoms, supplied as a premium reagent with a purity of 80.0% or higher.

[0053] Sebaceous acid: a straight-chain dicarboxylic acid containing 10 carbon atoms, supplied as a premium reagent with a purity of 98.0% or higher.

[0054] Eicosanoidic acid: a straight-chain dicarboxylic acid containing 20 carbon atoms, supplied as SL-20 manufactured by Okamura Seiyu Co., Ltd., with a purity of 75.0% or higher.

[0055] Base oil A: Paraffinic mineral oil refined by dewaxing solvent, belonging to Group 1, with a kinetic viscosity of 11.25 mm at 100°C. 2 / s, and the viscosity index is 97.

[0056] Base oil B: A cycloalkanes mineral oil obtained by dewaxing solvent refining, belonging to Group 1, with a kinetic viscosity of 10.71 mm at 100°C. 2 / s, and the viscosity index is 30.34.

[0057] Base oil C: GTL (natural gas synthetic oil) oil synthesized by the Fischer-Tropsch synthesis process, belonging to Group 3, with a kinetic viscosity of 7.77 mm at 100°C. 2 / s, and the viscosity index is 148.

[0058] Example 1 The base oil and carboxylic acids (except dicarboxylic acids) are heated in a container to dissolve the contents. Next, calcium hydroxide, pre-dissolved and dispersed in an appropriate amount of distilled water, is added to the container. At this point, the various carboxylic acids undergo saponification with calcium hydroxide and lithium hydroxide, slowly forming soaps in the base oil. The resulting product is further heated and dehydrated. Subsequently, tartaric acid, as a dicarboxylic acid, is mixed in the container, while calcium hydroxide dissolved and dispersed in distilled water is added simultaneously. The mixture is then saponified and dehydrated to form a grease thickener. After dehydration, the grease is heated to 200°C, thoroughly stirred, and cooled to room temperature. Thereafter, a three-roll mill is used to obtain a uniform grease with a consistency of 2.5.

[0059] Examples 2 to 8, in contrast to Examples 1 to 3 Except for the raw materials to be mixed as shown in Table 1, the grease composition was prepared in the same manner as in Example 1.

[0060] For the grease compositions prepared using the above-described raw material composition and production method, consistency, dropping point, and rolling stability (24 hours) were measured according to the above method. The results are shown in Table 1. Rolling stability represents the difference (absolute value) in penetration of the grease before and after the test.

[0061] Table 1

Claims

1. A grease composition comprising a base oil and a calcium complex soap as a thickener, wherein a C18-22 straight-chain substituted or unsubstituted higher monofatty acid; a substituted or unsubstituted aromatic monocarboxylic acid having a benzene ring; a C2-4 straight-chain saturated lower monofatty acid; and a substituted or unsubstituted saturated dicarboxylic acid as the carboxylic acid constituting said calcium complex soap.

2. The grease composition according to claim 1, wherein, The weight ratio of the calcium dicarboxylate compound to the total thickener of the grease composition is 5% to 70%.

3. The grease composition according to claim 1 or 2, wherein the substituted or unsubstituted saturated dicarboxylic acid has 4 to 20 carbon atoms.

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