JP7730653B2 - Grease composition - Google Patents

Description

The present invention relates to a grease composition containing a specific clay mineral, which is highly environmentally friendly and possesses the main properties of a grease.

With advances in mechanical technology, the environments in which grease is used are changing dramatically year by year. For example, in automobiles and electrical equipment, the trend toward smaller, lighter, and more powerful devices is resulting in higher temperatures and more severe lubrication conditions. Greases used in continuous steel casting equipment and hot rolling mills are required to have excellent heat resistance and oxidation stability. Recently, there has been a growing demand not only for improved grease performance at high temperatures, but also for materials that are environmentally compatible (high safety for humans during use and low environmental impact during manufacturing, etc.).

Lithium grease currently accounts for over 50% of the grease market. Lithium grease can be used at temperatures up to approximately 120°C, has relatively good shear stability and water resistance, and its raw materials, oils and fatty acids, are easily available and easy to handle. It can also be produced at relatively low cost, making it a versatile grease. Lithium complex greases have also been proposed as greases that can be used over a wider temperature range than standard lithium greases (Patent Document 1). However, lithium hydroxide, which is used to saponify the oils and fatty acids used as raw materials in these lithium greases, is subject to restrictions on its handling due to its designation as a toxic and hazardous substance. Furthermore, as lithium demand diversifies and its price gradually rises, there are concerns that the positioning of lithium grease as a versatile product may change in the future.

Other greases besides lithium grease include sodium grease and aluminum grease, but sodium grease has the problem that when mixed with water, the grease turns into a fluid and flows out of bearings, etc., so it is gradually being eliminated from the grease market. Furthermore, the operating temperature range of aluminum grease is the same or lower than that of calcium grease, so it is limited to specific applications.

One way to make grease more environmentally friendly is to use naturally occurring minerals or artificially synthesized inorganic compounds as raw materials for the grease. For example, Patent Document 2 discloses a grease composition that uses naturally occurring minerals or artificially synthesized inorganic substances as a grease thickener. However, while this grease can meet the demand for reduced environmental impact, it cannot maintain its structure unless a large amount of thickener is blended, and it also has issues such as excessive softening when it absorbs water and reduced rust prevention properties.

An example of a grease that can be used as a heat-resistant grease is urea grease. Urea grease is a high-performance grease composition that can be used at even higher temperatures than lithium complex grease and is therefore widely used in heat-resistant applications. For example, Patent Document 3 discloses a grease composition in which a polyurea compound is mixed with an inorganic solid lubricant such as calcium carbonate, polytetrafluoroethylene, or graphite. This grease composition has excellent heat resistance and extreme pressure properties even at high temperatures and under high loads, and can suppress hardening even when the grease is locally exposed to high temperatures.

However, such urea greases have the problem of being poorly environmentally friendly due to safety and handling issues with the raw materials, isocyanates and amines. Furthermore, they require advanced manufacturing techniques and equipment, which increases costs and limits their applications.

Japanese Unexamined Patent Publication No. 1-170691 JP 2011-57761 A JP 2008-94991 A

The present invention was made in light of these circumstances, and its purpose is to provide a grease composition that has excellent key grease properties (worked penetration, dropping point, heat resistance) and environmental compatibility.

As a result of extensive research to achieve the above objective, we discovered that a specific naturally occurring inorganic compound is environmentally friendly and improves the main properties of grease compositions, including worked penetration, leading to the completion of this invention.

More specifically, the present invention provides the following [1] to [4].
[1] A grease composition containing a base oil (a) and a thickener (b),
The thickener (b) is composed of particles represented by structural formula (1) (for example, having an average primary particle diameter of 0.1 to 200 μm): [A _0-0.2 ][B _1-8 ][C _0-5 |D _2n O _5n ]·mH ₂ O (Formula 1)
A: [Ca, Ba, K, Na, Rb, Cs, _NH4 ]
B: [Ti, Al, Cr, V, Fe, Mn, Mg, Li]
C: [S, OH, F, Cl]
D: [Si, Al, Fe, B, Be]
n = 1 to 10
m = 5 to 15
1. A grease composition comprising:
[2] The elements A, B, C, and D of the thickener (b) are: A: None; B: [Mg, Mn, Fe]
C: [OH]
D: [Si]
The grease composition according to [1] above.
[3] The grease composition according to [1] or [2], wherein the thickener (b) is 0.1 to 10 mass % relative to 100 mass % of the entire grease composition.
[4] The grease composition according to any one of [1] to [3], wherein the grease composition contains a stabilizer (c), the stabilizer (c) being a dihydric alcohol or trihydric alcohol having 2 to 5 carbon atoms, and the stabilizer (c) is contained in an amount of 0.1 to 5 mass% relative to 100 mass% of the grease composition.

The present invention makes it possible to provide a grease composition that has excellent key grease properties (worked penetration, dropping point, heat resistance) and environmental compatibility.

The grease composition of this embodiment contains a powder represented by structural formula (1) added as a thickener. The specific components, amounts of each component, manufacturing method, physical properties, and uses of the grease composition of this embodiment are described in detail below, but the present invention is in no way limited to these. For example, the grease composition of this embodiment contains a powder represented by structural formula (1) blended specifically as a thickener. However, as long as the effects of the present invention are achieved, even if a powder represented by structural formula (1) is blended into a grease composition for uses other than as a thickener, it should be understood to fall within the technical scope of the present invention. Furthermore, in this specification and claims, a to b mean a to b, unless otherwise specified.

<Grease composition (components)>
[Base oil]
The base oil used in the grease composition of this embodiment is not particularly limited. For example, mineral oil, synthetic oil, animal or vegetable oil, or a mixture thereof, which are used in ordinary grease compositions, can be used as appropriate. Specific examples include base oils in Groups 1 to 5 of the API (American Petroleum Institute) base oil categories. Here, the API base oil categories are broad classifications of base oil materials defined by the American Petroleum Institute to create guidelines for lubricating base oils.

In the present invention, the type of mineral oil is not particularly specified, but preferred examples include paraffinic or naphthenic mineral oils obtained by subjecting lubricating oil fractions obtained by atmospheric and vacuum distillation of crude oil to one or more appropriate combinations of refining methods, such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, and clay treatment.

While the type of synthetic oil is not particularly specified in the present invention, preferred examples include poly-α-olefins (PAOs) and hydrocarbon-based synthetic oils (oligomers). PAOs are homopolymers or copolymers of α-olefins. For example, α-olefins are compounds with a terminal C-C double bond, such as butene, butadiene, hexene, cyclohexene, methylcyclohexene, octene, nonene, decene, dodecene, tetradecene, hexadecene, octadecene, and eicosene. Hydrocarbon-based synthetic oils (oligomers) include homopolymers or copolymers of ethylene, propylene, or isobutene. These compounds can be used alone or as a mixture of two or more. Furthermore, as long as the C-C double bond is terminal, these compounds may have any isomeric structure, whether branched or linear. Two or more of these structural isomers or double bond positional isomers can also be used in combination. Of these olefins, those with 5 or fewer carbon atoms have a low flash point, and those with 31 or more carbon atoms have a high viscosity and are not very practical, so it is more preferable to use linear olefins with 6 to 30 carbon atoms.

In addition, in the present invention, GTL (gas-to-liquid) synthesized by the Fischer-Tropsch process, a technology for converting natural gas into liquid fuel, may be used as the base oil. Compared to mineral oil base oils refined from crude oil, GTL has extremely low sulfur and aromatic content and an extremely high paraffin composition ratio, resulting in excellent oxidation stability and very small evaporation losses, making it suitable for use as the base oil in the present invention.

[Thickener]
(Powder represented by structural formula (1))
The thickener used in this embodiment is a powder represented by structural formula (1). Examples include lisardite, antigorite, caryopilite, berthierine, kaolinite, dickite, nactite, metahalloysite, pyrophyllite, talc, bementite, iron pyrosmalite, and manganese pyrosmalite. Powders represented by structural formula (1) are widely used in industry as adsorbents and nonmetallic conductive fillers, and are preferably naturally occurring minerals and inorganic compounds with high environmental compatibility (e.g., high safety for humans during use and low environmental impact during production). Furthermore, the addition of a surface-modifying additive can enhance affinity with the solvent. Examples of modifying additives include quaternary ammonium salt treatments.

Soap-based greases are the most commonly used greases. Among these, lithium soap greases excel in consistency yield (the degree to which the grease hardens) and shear stability, making them the most widely used general-purpose grease. The aforementioned advantages are a major factor behind this. The structure of lithium soap grease is such that lithium stearate, which functions as a thickener, is dispersed in the base oil in string-like forms, entangled, and forming a three-dimensional fibrous structure. The basic form of grease is that the base oil is held within this fibrous structure, maintaining the grease's semi-solid physical properties. Thus, the composition of most soap-based greases is composed of stearates with relatively long chain lengths. This is due to the optimal balance between the base oil retention ability of hydrocarbons and the intermolecular forces between the micelles that make up the fibers. This results in good consistency yield and effective shear stability.

On the other hand, inorganic substances do not form a three-dimensional fibrous structure, and instead, particles dispersed in a base oil gel due to interactions such as intermolecular forces, maintaining the grease structure. For example, in aqueous solvents, bentonite crystals electrostatically bond with each other, swelling and forming a house-of-cards structure, gelling and transforming into a semi-solid state. However, electrostatic bonding does not occur easily in the base oil used to make grease, making it impossible for the substance to swell/gel and form a strong grease structure. Therefore, water-soluble polar solvents are often added as binders to promote swelling. However, most inorganic substances swell in base oil, and have little effect worthy of demonstrating the basic properties of grease (becoming semi-solid and allowing the consistency to be measured). As a result, the only greases currently available on the market that use inorganic thickeners are silica grease, in addition to the bentonite mentioned above.

Under these circumstances, the powder represented by structural formula (1) used as the thickener of the present invention is highly effective as a grease thickener. Considering this effect, it is believed that this compound forms secondary particles in which the voids and primary particles within the structure of the powder represented by structural formula (1) are tightly agglomerated, resulting in a structure in which lubricating oil is easily absorbed into the voids that form between these secondary particles. Additionally, due to factors such as a high bulk density (large specific surface area), the compound also has high dispersibility in lubricating oil. Therefore, it is believed that these combined effects result in an excellent thickening effect.

The powder represented by structural formula (1) of the component according to this embodiment preferably has an average primary particle diameter of 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less. The lower limit of the average primary particle diameter is not particularly limited, but is preferably 0.1 μm or more. Fine powders such as the powder represented by structural formula (1) are known to form secondary particles, which are aggregates of primary particles. To suppress this aggregation, treatments using crystallization inhibitors or dispersants are performed. However, the powder represented by structural formula (1) used in this invention is not limited by these surface treatment methods. It is believed that the smaller the primary particle diameter of the powder represented by structural formula (1), the larger the surface area of the voids between the aggregated secondary particles and the greater the amount of oil absorption, resulting in a stronger thickening effect and a harder grease. The average primary particle diameter can be measured by laser diffraction, dynamic light scattering, centrifugal sedimentation, field-flow fractionation (FFF), or electrical detector method, etc. The average primary particle size in the present invention is the volume average particle size, but may also be calculated as the number average particle size.

In the structural formula (1) of the component according to this embodiment, element A is preferably Ca, Ba, K, Na, Rb, Cs, or _NH4 , more preferably Ca, Ba, K, or Na, and even more preferably Ca, K, or Na. Element B is preferably Ti, Al, Cr, V, Fe, Mn, Mg, or Li, more preferably Fe, Mn, or Mg, and even more preferably Mg. Element C is preferably S, OH, F, or Cl, more preferably S or OH, and even more preferably OH. Element D is preferably Si, Al, Fe, B, or Be, more preferably Si, Al, or Fe, and even more preferably Si. The reason for this is that a porous structure is formed by the structure formed by Si and OH, and the insertion of Fe, Mn, or Mg into this structure makes it easier to form a porous structure, strengthens the mineral structure, and increases the number of sites that hold the base oil, thereby enhancing the thickening effect.

(Other thickeners)
The grease composition of this embodiment may contain a thickener other than the powder represented by structural formula (1) in addition to the thickener described above. Examples of such thickeners include calcium triphosphate, alkali metal soap, alkali metal complex soap, alkaline earth metal soap, alkaline earth metal complex soap, alkali metal sulfonate, alkaline earth metal sulfonate, other metal soaps, terephthalamate metal salts, triurea monourethane, diurea, tetraurea, other polyureas, inorganic substances such as barium sulfate, clay, and silica (silicon oxide) such as silica aerogel, and fluororesins such as polytetrafluoroethylene. One or more of these may be used in combination. Furthermore, any other thickener that can impart a thickening effect to a liquid substance may also be used.

[Additives]
(Alcoholic beverages)
The grease composition of this embodiment can exhibit heat resistance by adding specific additives to the grease made from the thickener. The alcohols used in this embodiment are polyhydric alcohols, and suitable examples of such polyhydric alcohols include 1,1-ethanediol, 1,2-ethanediol (ethylene glycol), 1,1-butanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-heptanediol, and 1,2,3-propanetriol (glycerin), and at least one polyhydric alcohol can be used.

(Quaternary ammonium salts)
The quaternary ammonium salts used as additives in this embodiment are preferably quaternary ammonium chloride salts, and examples of such salts include one or more quaternary ammonium salts selected from the group consisting of hardened tallow alkyl dimethyl benzyl ammonium chloride, di-hardened tallow alkyl methyl benzyl ammonium chloride, tallow alkyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride, and di-coconut alkyl dimethyl ammonium chloride. Furthermore, the quaternary ammonium salts may be added in a proportion of 5 to 15% by mass relative to 100% by mass of the powder represented by structural formula (1) as a thickener, i.e., any amount between 0.005 and 7.5% by mass when the grease composition is taken as 100% by mass. Adding a quaternary ammonium salt can improve the consistency yield of the powder represented by structural formula (1) and enhance its function as a thickener.

Polyhydric alcohols and quaternary ammonium salts are used as oiliness improvers and dispersants for hydraulic oils, and are known to exhibit lubrication effects by adsorbing to the metal surfaces of the lubricated object and forming an adsorbed film. However, the function of these additives blended into greases that use the powder represented by structural formula (1) of the present invention as a thickener is not the same as the function expected of them as additives to hydraulic oils described above. In the present invention, the polyhydric alcohols and quaternary ammonium salts maintain a homogeneous dispersion of the inorganic powder represented by structural formula (1) in the base oil, improving the basic functions of grease, such as weakening of the structure due to heat, weakening and softening of the grease structure due to the effects of moisture in the air or moisture introduced from outside, and rust formation and reduced lubricity due to insufficient water dispersibility.

The powder represented by structural formula (1) used as the thickener of the present invention basically has voids within its structure and primary particles that tightly aggregate to form secondary particles, with the voids that form between these secondary particles easily absorbing lubricating oil, forming a network with the grease thickener. This structure is thought to be further strengthened by the effects of the additives mentioned above, allowing the powder to demonstrate its basic grease performance. Therefore, adding these additives can improve the heat resistance and consistency yield of the grease. These performances are among the essential properties required in practical environments, and adding these properties enables the grease to be used in a wider range of applications.

[Optional ingredients]
The grease composition of this embodiment may further contain optional additives such as antioxidants, rust inhibitors, oiliness agents, extreme pressure agents, antiwear agents, solid lubricants, metal deactivators, polymers, non-metallic detergents, and colorants, with the total amount of optional components being approximately 0.1 to 20 mass% based on 100 mass% of the total grease composition. Examples of antioxidants include 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-paracresol, p,p'-dioctyldiphenylamine, N-phenyl-α-naphthylamine, and phenothiazine. Examples of rust inhibitors include oxidized paraffin, metal carboxylates, metal sulfonates, carboxylate esters, sulfonate esters, salicylate esters, succinate esters, sorbitan esters, and various amine salts. For example, oiliness agents, extreme pressure agents, and anti-wear agents include zinc sulfide dialkyldithiophosphate, zinc sulfide diallyldithiophosphate, zinc sulfide dialkyldithiocarbamate, zinc sulfide diallyldithiocarbamate, molybdenum sulfide dialkyldithiophosphate, molybdenum sulfide diallyldithiophosphate, molybdenum sulfide dialkyldithiocarbamate, molybdenum sulfide diallyldithiocarbamate, organic molybdenum complexes, sulfurized olefins, triphenyl phosphate, triphenyl phosphorothionate, tricresin phosphate, other phosphate esters, sulfurized oils and fats, etc. For example, solid lubricants include molybdenum disulfide, graphite, boron nitride, melamine cyanurate, PTFE (polytetrafluoroethylene), tungsten disulfide, graphite fluoride, etc. For example, metal deactivators include N,N'-disalicylidene-1,2-diaminopropane, benzotriazole, benzimidazole, benzothiazole, thiadiazole, etc. For example, polymers include polybutene, polyisobutene, polyisobutylene, polyisoprene, polymethacrylate, etc. For example, non-metallic detergents include succinimide, etc.

<Grease composition (amount of each component)>
Next, the blending amounts of the base oil and thickener or additives in the grease composition according to the present embodiment will be described. Note that, with regard to the blending amounts of optional components, they may be blended appropriately in the blending amounts described above, if necessary.

[Base oil]
The amount of the base oil blended is preferably 50 to 98 mass %, and more preferably 70 to 97 mass %, with the total amount of the grease composition being 100 mass %.

[Thickener]
The total amount of thickener blended is preferably 0.1 to 50 mass%, more preferably 0.5 to 30 mass%, and even more preferably 3 to 10 mass%, based on 100 mass% of the total grease composition.

As mentioned above, the grease composition according to this embodiment contains at least the powder represented by structural formula (1) as a thickener, and appropriately combines other thickeners. However, even when the powder represented by structural formula (1) is the only thickener, i.e., when no thickeners other than the powder represented by structural formula (1) are substantially contained, it is possible to achieve a high thickening effect (i.e., to produce a grease composition with a high thickening effect). Furthermore, because the powder represented by structural formula (1) is highly environmentally friendly, reducing the blending ratio of other thickeners in the overall thickener composition is also advantageous from the perspective of environmental compatibility.

Therefore, when combined with the total amount of thickeners in the grease composition, the powder represented by structural formula (1) preferably accounts for 0.5 to 50 mass%, more preferably 2 to 30 mass%, and even more preferably 3 to 28 mass%, of the total grease composition being 100 mass%. Furthermore, the amount of thickeners other than the powder represented by structural formula (1) (other thickeners) is preferably 20 mass% or less, and more preferably 10 mass% or less.

[Additives]
The amount of polyhydric alcohols used as additives, for example at least one polyhydric alcohol selected from the group consisting of 1,1-ethanediol, 1,2-ethanediol (ethylene glycol), 1,1-butanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-propanediol, and 1,2,3-propanetriol (glycerin), is preferably 0.1 to 5 mass%, more preferably 0.2 to 4 mass%, and even more preferably 0.5 to 3 mass%, based on 100 mass% of the entire grease composition.

The amount of quaternary ammonium salt used as an additive, for example, at least one quaternary ammonium salt selected from the group consisting of hardened tallow alkyl dimethyl benzyl ammonium chloride, di-hardened tallow alkyl methyl benzyl ammonium chloride, tallow alkyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride, and di-coconut alkyl dimethyl ammonium chloride, is preferably 0.005 to 7.5% by mass, more preferably 0.01 to 5% by mass, and even more preferably 0.15 to 1.5% by mass, based on 100% by mass of the entire grease composition.

<Method for producing grease composition>
[When substantially no thickener other than the powder represented by structural formula (1) is contained]
The grease composition according to the present embodiment can be produced by any suitable existing method, but can be produced, for example, by the following steps: A base oil, a thickener, and additives are blended and placed in a dedicated grease production device (a programmable grease prototype device). Next, the mixture is stirred at room temperature (e.g., about 25°C) (stirring conditions include, for example, a stirring rotation speed of 20 to 300 rpm and a stirring time of 10 to 15 minutes), and then processed in a homogenizer (e.g., a triple-roll mill) and degassed under vacuum to obtain a homogenous grease composition. When using other optional components (e.g., additives), the base oil and additives may be mixed in advance at an appropriate temperature (e.g., 80 to 100°C), the mixture may be returned to room temperature, and the powder represented by structural formula (1) may be added (alternatively, the powder represented by structural formula (1) may be mixed with the base oil at room temperature, and the temperature may be raised before mixing the additives).

Here, if the grease contains substantially no thickeners other than the powder represented by structural formula (1), no special chemical reaction occurs when the thickener is added and stirred, so the grease can be produced without including a process of raising the temperature (or, if high-temperature heating is required to mix the additives, the process of maintaining high temperatures can be shortened), making it possible to reduce energy consumption and costs. Furthermore, in the process of mixing and stirring the powder represented by structural formula (1), base oil, and additives, it is acceptable to perform a heat treatment (for example, below approximately 140°C) rather than a process at room temperature.

[When a thickener other than the powder represented by structural formula (1) is used in combination]
Next, a method for producing a grease composition according to the present embodiment, in which a powder represented by structural formula (1) and a thickener other than the powder represented by structural formula (1) (another thickener) are used in combination as thickeners for the grease composition, will be described using an example in which a urea thickener is used as the other thickener. First, raw materials for the urea thickener (diisocyanate, primary monoamine, primary diamine, etc.) are appropriately blended and subjected to a synthesis reaction in a base oil, followed by heating to approximately 180°C and cooling. Additives and other additives are then mixed at a temperature of 80 to 100°C, thoroughly stirred and mixed, and then cooled to room temperature. The powder represented by structural formula (1) is then blended, and the resulting dispersion is homogenized using a kneader (e.g., a three-roll mill, etc.) to obtain a grease composition.

In this way, when a conventional thickener is used in combination with a powder represented by structural formula (1), a grease composition can be formed using the conventional thickener according to a commonly used grease manufacturing method, and then the powder represented by structural formula (1) can be added to improve thickening properties and complete the grease composition. Furthermore, the powder represented by structural formula (1) and another thickener can be blended in the same process (timing) to produce a grease composition according to a commonly used grease manufacturing method. Alternatively, a grease composition produced using the above-mentioned powder represented by structural formula (1) as a thickener and a conventional grease composition using a thickener other than the powder represented by structural formula (1) can be separately produced and mixed.

<Physical properties of grease composition>
[Dripping point]
The grease composition of this embodiment preferably has a dropping point of 200°C or higher, more preferably 220°C or higher, and particularly preferably 250°C or higher. If the grease composition has a dropping point of 200°C or higher, it is believed that the possibility of lubrication problems, such as loss of viscosity at high temperatures and the associated leakage and seizure, can be reduced. The dropping point refers to the temperature at which a viscous grease loses its thickener structure as the temperature is increased. Here, the dropping point can be measured in accordance with JIS K 2220 8.

[Worked penetration]
The grease composition of this embodiment preferably has a consistency of No. 00 to No. 4 (175 to 430) in a worked penetration test, and more preferably a consistency of No. 1 to No. 3 (220 to 340). The consistency indicates the physical hardness of the grease. The consistency used here is the value of worked penetration measured in accordance with JIS K 2220 7.

[Heat resistance test]
The grease composition of this embodiment is preferably heated to 100°C, and more preferably 150°C, in a heat resistance test. The heat resistance test is carried out as follows: The grease composition is filled into a consistency measuring device, heated, and allowed to stand for 2 hours, after which the unworked consistency is measured. If the change in the unworked consistency from 25°C is within 100, the composition is evaluated as having heat resistance at the specified temperature in the heat resistance test. The test temperature range is from 80°C, and the test is carried out in 10°C increments until the change in consistency exceeds 100. Note that if the heat resistance is insufficient and the consistency softens significantly, the grease composition will leak, preventing sufficient oil from being supplied to the lubrication interface, resulting in a loss of lubrication properties.

<Applications of grease composition>
The grease composition of the present invention can be used not only in commonly used machines, bearings, gears, etc., but also exhibits excellent performance under more severe conditions, such as high-temperature conditions. For example, in automobiles, it can be suitably used for lubricating various parts such as engine peripherals such as starters, alternators, and various actuators, powertrains such as propeller shafts, constant velocity joints (CVJs), wheel bearings, and clutches, electric power steering (EPS), braking systems, ball joints, door hinges, handlebars, cooling fan motors, and brake expanders. It is also suitable for use in various high-temperature, high-load locations, such as construction machinery such as power shovels, bulldozers, and crane trucks, the steel industry, the paper industry, forestry machinery, agricultural machinery, chemical plants, power generation facilities, drying furnaces, copiers, railway vehicles, and threaded joints in seamless pipes. Other applications include hard disk bearings, plastic lubrication, and cartridge grease, and the grease is also suitable for these applications.

Next, the present invention will be explained in more detail using examples and comparative examples, but the present invention is not limited to these examples in any way.

≪Raw materials≫
The raw materials used in Examples 1 to 14 and Comparative Examples 1 to 4 are as follows.

(Base oil)
Base oil A: A paraffinic mineral oil having a kinematic viscosity at 40°C of 100.0 mm ² /s and a kinematic viscosity at 100°C of 11.55 mm ² /s, obtained by mixing a paraffinic mineral oil having a kinematic viscosity at ⁴⁰ °C of 24.22 ^{mm 2} /s and a kinematic viscosity at 100°C of 4.640 mm ² /s with a paraffinic mineral oil having a kinematic viscosity at 40°C of 480.2 mm 2 /s and a kinematic viscosity at 100°C of 31.56 mm ² /s.
Base oil B: naphthenic mineral oil having a kinematic viscosity at 40°C of 143.6 mm ² /s and a kinematic viscosity at 100°C of 10.71 mm ² /s.
Base oil C: an unsaturated polyol ester oil having a kinematic viscosity at 40°C of 20.50 mm ² /s and a kinematic viscosity at 100°C of 4.550 mm ² /s.
Base oil D: an alkyldiphenyl ether oil having a kinematic viscosity at 40°C of 102.2 mm ² /s and a kinematic viscosity at 100°C of 12.64 mm ² /s.
Base oil E: A poly-α-olefin oil having a kinematic viscosity of 100.0 mm ² /s at 40°C and a kinematic viscosity of 15.14 mm ² /s at 100°C, obtained by mixing a poly-α-olefin oil having a kinematic viscosity of 30.50 mm ² /s at 40°C and a kinematic viscosity of 6.340 mm ² /s at 100°C with a poly-α-olefin oil having a kinematic viscosity of 396.5 mm ² /s at 40°C and a kinematic viscosity of 39.99 mm ² /s at 100°C.
Base oil F: A GTL (gas-to-liquid) oil synthesized by the Fischer-Tropsch process, having a kinematic viscosity of 44.61 mm ² /s at 40°C and a kinematic viscosity of 7.640 mm ² /s at 100°C.
(Thickener)
Powder A: Powder having an average primary particle diameter of 65 μm as shown in formula (2):
Si ₁₂ Mg ₈ O ₃₀ (OH) ₄ (OH ₂ ) _{4.8H 2} O...Formula 2
Powder B: Powder represented by formula (3) (common name: bentonite):
_Na2Si24 ( _Al10Mg2 ) _{O60 .} (OH) _{12 ...} Formula 3
Powder C: Powder represented by formula (4) (general name: vermiculite):
(Mg, Fe ²⁺ , Al) ₃ (Al, Si) ₄ O ₁₀ (OH) _{2.4H 2} O...Formula 4
(Additives)
Additive A: Glycerin (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)
Additive B: Ethylene glycol (Fujifilm Wako Pure Chemical Industries, Ltd.)
Additive C: hydrogenated tallow alkyldimethylbenzyl ammonium chloride (Kao)

≪Manufacturing method≫
Example 1
Base oil A and powder A were weighed out at the blending ratios shown in Table 1 so that the total amount was 500 g, and then charged into a 1.0 kg capacity grease manufacturing device. The dispersion was stirred at room temperature at 200 rpm for 15 minutes, processed using a triple roll mill, and then vacuum degassed to obtain a homogeneous grease with No. 2 consistency.

Example 2
Base oil A and powder A were mixed as raw materials in the amounts shown in Table 1 into a grease production kettle, and production was carried out in the same manner as in Example 1, to obtain a homogeneous grease with No. 1 consistency.

Example 3
Base oil A and powder A were mixed as raw materials in the amounts shown in Table 1 into a grease production vessel, and production was carried out in the same manner as in Example 1, to obtain a homogeneous grease with No. 3 consistency.

Example 4
Base oil B and powder A were mixed as raw materials in the amounts shown in Table 1 into a grease production vessel, and production was carried out in the same manner as in Example 1, to obtain a homogeneous grease with No. 2 consistency.

Example 5
Base oil C and powder A were mixed as raw materials in the amounts shown in Table 1 into a grease production vessel, and production was carried out in the same manner as in Example 1, to obtain a homogeneous grease with No. 2 consistency.

Example 6
Base oil D and powder A were mixed as raw materials in the amounts shown in Table 1 into a grease production vessel, and production was carried out in the same manner as in Example 1, to obtain a homogeneous grease with No. 2 consistency.

Example 7
Base oil E and powder A were mixed as raw materials in the amounts shown in Table 1 into a grease production vessel, and production was carried out in the same manner as in Example 1 to obtain a homogeneous grease with No. 2 consistency.

(Example 8)
Base oil F and powder A were mixed as raw materials in the amounts shown in Table 1 into a grease production vessel, and production was carried out in the same manner as in Example 1, to obtain a homogeneous grease with No. 2 consistency.

Example 9
Base oil A, powder A, and additive A were mixed as raw materials in the amounts shown in Table 1 into a grease production kettle, and production was carried out in the same manner as in Example 1, to obtain a homogeneous grease with No. 1 consistency.

Example 10
Base oil A, powder A, and additive A were mixed as raw materials in the amounts shown in Table 1 into a grease production kettle, and production was carried out in the same manner as in Example 1, to obtain a homogeneous grease with No. 2 consistency.

Example 11
Base oil A, powder A, and additive A were mixed as raw materials in the amounts shown in Table 1 into a grease production kettle, and production was carried out in the same manner as in Example 1, to obtain a homogeneous grease with No. 3 consistency.

Example 12
Base oil A, powder A, and additive B were mixed as raw materials in the amounts shown in Table 1 into a grease production kettle, and production was carried out in the same manner as in Example 1, to obtain a homogeneous grease with No. 2 consistency.

Example 13
Base oil A, powder A, additive A, and additive C were mixed as raw materials in the amounts shown in Table 1 into a grease production kettle, and production was carried out in the same manner as in Example 1, to obtain a homogeneous grease with a No. 3 consistency.

Example 14
Base oil A, powder A, additive A, and additive C were mixed as raw materials in the amounts shown in Table 1 into a grease production kettle, and production was carried out in the same manner as in Example 1, to obtain a homogeneous grease with a No. 3 consistency.

(Comparative Example 1)
Base oil A and powder B were mixed as raw materials in the amounts shown in Table 2 into a grease production vessel, and production was carried out in the same manner as in Example 1 to obtain a homogeneous grease with No. 1 consistency.

(Comparative Example 2)
Base oil A and powder C were mixed as raw materials in the amounts shown in Table 2 into a grease production vessel, and a grease was produced in the same manner as in Example 1, but a fluid (non-grease-like) substance was obtained.

(Comparative Example 3)
The thickener is lithium 12-hydroxystearate soap, and a commercially available general-purpose lithium-based grease (manufactured by Shell Lubricants Japan Co., Ltd.) using mineral oil-based lubricating oil as the base oil, the viscosity of which is 12.2 mm ² /s at 100°C.

(Comparative Example 4)
The grease used was a commercially available general-purpose urea-based grease (manufactured by Shell Lubricants Japan Co., Ltd.) that used a mineral oil-based lubricating oil as the base oil, and the viscosity of the base oil was 11.3 mm ² /s at 100°C.

<Exam>
The dropping point, worked penetration, and heat resistance tests were performed for the Examples and Comparative Examples using the test methods described above. The properties of the resulting greases from the Examples and Comparative Examples are also listed in Tables 1 and 2. The "grain quality" was evaluated as follows: fine, smooth, and glossy greases were marked with "◎"; fine, smooth, but lacking in gloss; slightly coarse, lacking in gloss; and coarse, lacking in gloss. The grain quality was determined based on the feel and appearance of the test sample when directly touched with the fingers of a hand. Viscoelasticity (firmness) was evaluated as follows: firm and elastic greases were marked with "◎"; firm and elastic greases were marked with "○"; weak and inelastic greases were marked with "△"; and no firmness was detected (e.g., liquid state). Viscoelasticity was evaluated based on the feel of the test sample when directly touched with the fingers of a hand.

≪Results≫
As shown in Table 1, all of Examples 1 to 14 are excellent in worked penetration, dropping point, and heat resistance.

Claims (3)

A grease composition comprising a base oil (a) and a thickener (b),
The thickener (b) is a particle represented by structural formula (1): [A _0-0.2 ][B _1-8 ][C _0-5 ][D _2n ][O _5n ]·mH ₂ O (Formula 1)
A: None B: One or more selected from Mg, Mn and Fe C: OH
D: Si
n = 1 to 10
m = 5 to 15
and
The particles have an average primary particle diameter of 0.1 to 200 μm,
Substantially does not contain any thickener other than the particles represented by the structural formula (1) ,
A grease composition , wherein the particles represented by the structural formula (1) are _a porous clay mineral represented by _{Si12Mg8O30 (} OH) ₄ ( _OH2 ) _{4.8H2O .} The grease composition according to claim 1, wherein the thickener (b) accounts for 0.1 to 10 mass % of the total grease composition, taken as 100 mass %. The grease composition according to claim 1 or 2, wherein the grease composition contains a stabilizer (c), which is a dihydric or trihydric alcohol having 2 to 5 carbon atoms, and the stabilizer (c) is present in an amount of 0.1 to 5 mass % relative to 100 mass % of the grease composition.