Grease composition and method for producing grease composition

Abstract

To provide a grease composition having excellent lubricity and thermal stability.SOLUTION: A grease composition comprises a base oil (A) and a thickener (B), wherein the base oil (A) includes one or more components selected from the group consisting of a component (A1) and a component (A2), the component (A1) is an ester of a polyol (A11) having 3 to 6 hydroxyl groups and a branched fatty acid (A12) having 14 to 20 carbon atoms, the component (A2) is an alkylnaphthalene having a temperature at which 3 mass% is distilled off at 450°C or higher in gas chromatography distillation in accordance with ASTM-D7500, and the thickener (B) includes one or more selected from the group consisting of the following component (B1) and component (B2) (the component (B1) is melamine cyanurate and the component (B2) is preformed urea).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a grease composition and a method for producing the grease composition. [Background technology]

[0002] As a grease composition used in semiconductor manufacturing equipment, for example, a fluorine grease composition using perfluoropolyether (PFPE) as a base oil and polytetrafluoroethylene (PTFE) as a thickener is known. Patent Document 1 proposes a grease composition containing a base oil including an ester oil or a fluorine-free ether oil, and a thickener including at least a urea compound and a thickener having self-lubricating properties. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-202061 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, fluorine grease compositions that use a fluorine oil such as perfluoropolyether (PFPE) as a base oil sometimes have insufficient lubrication properties, and improvements in this area are required. Furthermore, in semiconductor manufacturing equipment, processes such as film formation and etching may be performed at high temperatures of 200° C. or higher. Under such high temperatures, the grease composition is also required to have thermal stability.

[0005] The present invention has been made in consideration of such demands, and an object of the present invention is to provide a grease composition that is excellent in lubricity and thermal stability. [Means for solving the problem]

[0006] According to the present invention, the following [1] and [2] are provided. [1] A grease composition comprising a base oil (A) and a thickener (B), The base oil (A) contains one or more components selected from the group consisting of the following component (A1) and the following component (A2), Component (A1): Ester of polyol (A11) having 3 to 6 hydroxyl groups and branched fatty acid (A12) having 14 to 20 carbon atoms Component (A2): Alkylnaphthalene that exhibits a 3% mass loss temperature of 450°C or higher in gas chromatography distillation according to ASTM-D7500 The thickener (B) comprises one or more components selected from the group consisting of the following component (B1) and the following component (B2): Ingredient (B1): Melamine cyanurate Ingredient (B2): Premade urea [2] The method includes a step (S) of mixing a base oil (A) and a thickener (B), In the step (S), one or more components selected from the group consisting of the following component (A1) and the following component (A2) are blended as the base oil (A), Component (A1): Ester of polyol (A11) having 3 to 6 hydroxyl groups and branched fatty acid (A12) having 14 to 20 carbon atoms Component (A2): Alkylnaphthalene that exhibits a 3% mass loss temperature of 450°C or higher in gas chromatography distillation according to ASTM-D7500 A method for producing a grease composition, comprising blending, as the thickener (B), one or more components selected from the group consisting of the following component (B1) and the following component (B2): Ingredient (B1): Melamine cyanurate Ingredient (B2): Premade urea Effect of the Invention

[0007] According to the present invention, it is possible to provide a grease composition having excellent lubricity and thermal stability. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The upper and lower limit values ​​of the numerical ranges described in this specification can be combined in any way. For example, when "A to B" and "C to D" are described as numerical ranges, the numerical ranges "A to D" and "C to B" are also included in the scope of the present invention. In addition, unless otherwise specified, a numerical range of "lower limit value to upper limit value" described in this specification means not less than the lower limit value and not more than the upper limit value. In this specification, the numerical values ​​in the examples are numerical values ​​that can be used as upper or lower limits.

[0009] [Embodiments of the grease composition] The grease composition of the present embodiment contains a base oil (A) and a thickener (B). The base oil (A) contains one or more components selected from the group consisting of the following component (A1) and the following component (A2). Component (A1): Ester of polyol (A11) having 3 to 6 hydroxyl groups and branched fatty acid (A12) having 14 to 20 carbon atoms Component (A2): Alkylnaphthalene that exhibits a 3% mass loss temperature of 450°C or higher in gas chromatography distillation according to ASTM-D7500 The thickener (B) contains one or more components selected from the group consisting of the following component (B1) and the following component (B2). Ingredient (B1): Melamine cyanurate Ingredient (B2): Premade urea

[0010] The present inventors have conducted extensive research in order to solve the above problems. As a result, the inventors have discovered that a grease composition containing the above-mentioned base oil (A) and the above-mentioned thickener (B) has excellent lubricity and thermal stability. Based on the above findings, the present inventors further conducted various studies and completed the present invention.

[0011] The grease composition of the present embodiment may be composed only of the base oil (A) and the thickener (B), or may further contain other components in addition to the base oil (A) and the thickener (B). In the grease composition of this embodiment, the total content of the base oil (A) and the thickener (B) is preferably 90 mass % to 100 mass %, more preferably 95 mass % to 100 mass %, based on the total amount of the grease composition.

[0012] Each component contained in the grease composition of the present embodiment will be described in detail below.

[0013] <Base oil (A)> The grease composition of the present embodiment contains a base oil (A). The base oil (A) contains one or more components selected from the group consisting of the following component (A1) and the following component (A2). Component (A1): Ester of polyol (A11) having 3 to 6 hydroxyl groups and branched fatty acid (A12) having 14 to 20 carbon atoms Component (A2): Alkylnaphthalene that exhibits a 3% mass loss temperature of 450°C or higher in gas chromatography distillation according to ASTM-D7500

[0014] By using a base oil (A) containing one or more selected from the group consisting of components (A1) and (A2) together with a thickener (B), a grease composition having excellent lubricity and thermal stability can be obtained. Here, "one or more types selected from the group consisting of component (A1) and component (A2)" means "one or more types selected from component (A1)", "one or more types selected from component (A2)", or "a combination of one or more types selected from component (A1) and one or more types selected from component (A2)". In the grease composition of the present embodiment, from the viewpoint of improving the effects of the present invention, it is preferable that "one or more types selected from the group consisting of component (A1) and component (A2)" is "one or more types selected from component (A1)" or "one or more types selected from component (A2)". Furthermore, from the viewpoint of improving the effects of the present invention while providing a grease composition with excellent low dust generation, it is preferable that "one or more types selected from the group consisting of component (A1) and component (A2)" is "one or more types selected from component (A2)".

[0015] Here, from the viewpoint of improving the effects of the present invention, the content of "one or more selected from the group consisting of component (A1) and component (A2)" is preferably 50 mass% to 100 mass%, more preferably 60 mass% to 100 mass%, even more preferably 70 mass% to 100 mass%, still more preferably 80 mass% to 100 mass%, even more preferably 90 mass% to 100 mass%, still more preferably 95 mass% to 100 mass%, even more preferably 99 mass% to 100 mass%, and even more preferably 100 mass%, based on the total amount of base oil (A). Furthermore, from the viewpoint of obtaining a grease composition having excellent low dust generation while improving the effects of the present invention, the content of "one or more selected from component (A2)" is preferably 50 mass% to 100 mass%, more preferably 60 mass% to 100 mass%, even more preferably 70 mass% to 100 mass%, still more preferably 80 mass% to 100 mass%, even more preferably 90 mass% to 100 mass%, still more preferably 95 mass% to 100 mass%, even more preferably 99 mass% to 100 mass%, and even more preferably 100 mass%, based on the total amount of base oil (A).

[0016] The content of the base oil (A) is preferably 40% by mass to 90% by mass, and more preferably 45% by mass to 85% by mass, based on the total amount of the grease composition.

[0017] The components (A1) and (A2) will be described in detail below.

[0018] <<Component (A1)>> The component (A1) is an ester of a polyol (A11) having 3 to 6 hydroxyl groups and a branched fatty acid (A12) having 14 to 20 carbon atoms. By including the component (A1) in the base oil (A), it is possible to obtain a grease composition having excellent thermal stability and being less likely to volatilize even under high vacuum (hereinafter also referred to as "low volatility"). Although component (A1) may be a partial ester or a full ester, it is preferable that the full ester is contained from the viewpoint of obtaining a grease composition having superior thermal stability and low volatility. The content of the full ester in component (A1) is preferably 90 mass% or more, more preferably 95 mass% or more, and even more preferably 97 mass% or more, based on the total amount of component (A1). The polyol (A11) and the branched fatty acid (A12) will be described in detail below.

[0019] (Polyol (A11)) The polyol (A11) is a polyol having 3 to 6 hydroxyl groups. By using a polyol having 3 to 6 hydroxyl groups as the alcohol component constituting the ester, the component (A1) can be made to have excellent thermal stability and low volatility. Specific examples of polyols having 3 to 6 hydroxyl groups include trihydric alcohols (polyols having 3 hydroxyl groups) such as glycerin, trimethylolethane, trimethylolpropane, and trimethylolnonane; and tetrahydric to hexahydric alcohols (polyols having 4 to 6 hydroxyl groups) such as pentaerythritol, ditrimethylolpropane, dipentaerythritol, sorbitol, and mannitol. Among these, tetrahydric to hexahydric alcohols are preferred from the viewpoint of increasing the molecular weight of component (A1) and making it easier to improve low volatility. Among tetrahydric to hexahydric alcohols, pentaerythritol is preferred from the viewpoint of improving thermal stability and low volatility. That is, polyol (A11) preferably contains pentaerythritol. It is presumed that the inclusion of pentaerythritol in polyol (A11) makes it easier to improve the thermal stability of component (A1) due to the suppression of molecular cleavage caused by an intramolecular condensation reaction of an ester composed of pentaerythritol and a branched fatty acid (A12) and the effective protection of the ester group by the alkyl group of the branched fatty acid (A12). The content of pentaerythritol, based on the total amount of polyol (A11), is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, even more preferably 70% by mass to 100% by mass, still more preferably 80% by mass to 100% by mass, even more preferably 90% by mass to 100% by mass, still more preferably 95% by mass to 100% by mass, even more preferably 99% by mass to 100% by mass, and even more preferably 100% by mass.

[0020] (Branched fatty acid (A12)) The branched fatty acid (A12) is a branched fatty acid having 14 to 20 carbon atoms. By using a branched fatty acid having 14 to 20 carbon atoms as the fatty acid component constituting the ester, the thermal stability and low volatility of the component (A1) can be improved, and the fluidity and viscosity index of the component (A1) can also be improved. From the viewpoint of improving the thermal stability and the viscosity index, the branched fatty acid having 14 to 20 carbon atoms preferably has one branch. Preferred specific examples of the branched fatty acid having 14 to 20 carbon atoms and one branch include branched saturated fatty acids such as butyloctanoic acid, hexyldecanoic acid, and octyldodecanoic acid. Among these, hexyldecanoic acid is preferred from the viewpoint of improving the thermal stability, fluidity, etc. of the ester. Moreover, among hexyldecanoic acids, it is preferred to have a branch at the α-position (carbon atom adjacent to the carboxy group) from the viewpoint of further improving the thermal stability, fluidity, etc. In other words, the branched fatty acid (A12) preferably contains a branched fatty acid having 14 to 20 carbon atoms, one branch, and a branch at the α-position. The content of the branched fatty acid having 14 to 20 carbon atoms, one branch and having a branch at the α-position is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, even more preferably 70% by mass to 100% by mass, still more preferably 80% by mass to 100% by mass, even more preferably 90% by mass to 100% by mass, still more preferably 95% by mass to 100% by mass, even more preferably 99% by mass to 100% by mass, and even more preferably 100% by mass, based on the total amount of the branched fatty acid (A12).

[0021] <<Component (A2)>> Component (A2) is an alkylnaphthalene that exhibits a 3% mass loss temperature of 450° C. or higher in gas chromatography distillation according to ASTM-D7500. By including the component (A2) in the base oil (A), the grease composition can have excellent thermal stability and low volatility.

[0022] Alkylnaphthalene is a compound in which at least one hydrogen atom on the naphthalene ring is substituted with an alkyl group. By using alkylnaphthalene that has a temperature of 450°C or higher at which it loses 3% by mass in gas chromatography distillation according to ASTM-D7500, it is possible to obtain a grease composition with excellent thermal stability (and low volatility). From the viewpoint of further improving the thermal stability (and furthermore, low volatility), the temperature at which the alkylnaphthalene is reduced by 3% by mass is preferably 455° C. or higher, more preferably 460° C. or higher, and even more preferably 470° C. or higher.

[0023] The 40°C kinematic viscosity of the alkylnaphthalene is preferably 75mm from the viewpoint of further improving the thermal stability (and further reducing the volatility). 2 / s~400mm 2 / s, more preferably 100 mm 2 / s~350m 2 / s, more preferably 150 mm 2 / s~300mm 2 / s. In this specification, the 40° C. kinematic viscosity refers to a value measured in accordance with JIS K2283:2000.

[0024] <Thickener (B)> The grease composition of the present embodiment contains a thickener (B). The thickener (B) contains one or more components selected from the group consisting of the following component (B1) and the following component (B2). Ingredient (B1): Melamine cyanurate Ingredient (B2): Premade urea

[0025] By using a thickener (B) containing one or more selected from the group consisting of components (B1) and (B2) together with a base oil (A), it is possible to obtain a grease composition that has excellent thermal stability, low volatility, and excellent lubricity. In addition, "one or more types selected from the group consisting of component (B1) and component (B2)" means "one or more types selected from component (B1)", "one or more types selected from component (B2)", or "a combination of one or more types selected from component (B1) and one or more types selected from component (B2)". In the grease composition of the present embodiment, from the viewpoint of improving the effects of the present invention, it is preferable that "one or more types selected from the group consisting of component (B1) and component (B2)" is "one or more types selected from component (B1)" or "one or more types selected from component (B2)". Furthermore, from the viewpoint of improving the effects of the present invention while providing a grease composition that has excellent low dust generation properties, it is preferable that "one or more types selected from the group consisting of component (B1) and component (B2)" is "one or more types selected from component (B1)".

[0026] Here, from the viewpoint of improving the effects of the present invention, the content of "one or more selected from the group consisting of component (B1) and component (B2)" is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, even more preferably 70% by mass to 100% by mass, still more preferably 80% by mass to 100% by mass, even more preferably 90% by mass to 100% by mass, still more preferably 95% by mass to 100% by mass, even more preferably 99% by mass to 100% by mass, and even more preferably 100% by mass, based on the total amount of thickener (B). Furthermore, from the viewpoint of obtaining a grease composition having excellent low dust generation while improving the effects of the present invention, the content of "one or more types selected from component (B1)" is preferably 50 mass% to 100 mass%, more preferably 60 mass% to 100 mass%, even more preferably 70 mass% to 100 mass%, still more preferably 80 mass% to 100 mass%, even more preferably 90 mass% to 100 mass%, still more preferably 95 mass% to 100 mass%, even more preferably 99 mass% to 100 mass%, and even more preferably 100 mass% based on the total amount of thickener (B).

[0027] The content of the thickener (B) is preferably 5% by mass to 60% by mass, and more preferably 10% by mass to 55% by mass, based on the total amount of the grease composition.

[0028] The components (B1) and (B2) will be described in detail below.

[0029] <<Component (B1)>> Component (B1) is melamine cyanurate. By mixing melamine cyanurate with base oil (A), the melamine cyanurate functions as a thickener to prepare a grease composition. In addition, since melamine cyanurate does not contain metal, it is extremely suitable as a thickener for preparing a grease composition used in semiconductor device manufacturing. In addition, melamine cyanurate has excellent thermal stability and can improve the lubricity of the grease composition. Melamine cyanurate is an organic salt of melamine and cyanuric acid, and has a graphite structure. The particle size of the melamine cyanurate is preferably 5.0 μm or less, more preferably 4.0 μm or less, even more preferably 3.0 μm or less, still more preferably 2.5 μm or less, and even more preferably 2.0 μm or less, as an average particle size. There is no particular lower limit for the particle size of the melamine cyanurate, but it is usually 0.005 μm or more. In this specification, the particle size of melamine cyanurate is the 50% particle size (volume median particle size, D) based on scattering intensity, calculated from the dispersed particle size distribution measured at 25°C by dynamic light scattering (photon correlation method) and analyzed by the CONTIN method. 50 ) When component (B1) is used alone as the thickener (B), the content of component (B1) is preferably 20 mass % to 60 mass %, and more preferably 25 mass % to 55 mass %, based on the total amount of the grease composition.

[0030] <<Component (B2)>> Component (B2) is premade urea. In general, when producing a grease composition, amines and isocyanates are added to a base oil and reacted with each other to synthesize a urea compound that functions as a thickener in the base oil. In other words, the urea compound as a thickener is synthesized in the base oil that constitutes the grease composition during the production process of the grease composition. However, in such a method, unreacted amines and / or isocyanates may remain in the grease composition, and the inventors' investigations have revealed that such low molecular weight compounds are a factor that reduces the thermal stability of the grease composition. Therefore, in this embodiment, the urea compound is not synthesized during the production process of the grease composition, but is prepared by mixing a pre-synthesized urea compound with a base oil. Such a urea compound is called "premade urea."

[0031] The urea compound constituting the primed urea may be any compound having a urea bond, but is preferably a diurea compound having two urea bonds, and more preferably a diurea compound represented by the following general formula (b2-1). R 1 -NHCONH-R 3 -NHCONH-R 2 (b2-1)

[0032] In the above general formula (b2-1), R 1 and R 2 R each independently represents a monovalent hydrocarbon group having 6 to 24 carbon atoms. 1 and R 2 may be the same or different from each other. 3 represents a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R in the above general formula (b2-1) 1 and R 2 The monovalent hydrocarbon group that can be selected for has 6 to 24 carbon atoms, preferably 6 to 20 carbon atoms, and more preferably 6 to 18 carbon atoms. Also, R 1 and R 2 Examples of the monovalent hydrocarbon group that can be selected as include a saturated or unsaturated monovalent chain hydrocarbon group, a saturated or unsaturated monovalent alicyclic hydrocarbon group, and a monovalent aromatic hydrocarbon group.

[0033] Examples of the monovalent saturated chain hydrocarbon group include linear or branched alkyl groups having 6 to 24 carbon atoms, and specific examples thereof include a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, an octadecenyl group, a nonadecyl group, and an icosyl group. Examples of the monovalent unsaturated chain hydrocarbon group include linear or branched alkenyl groups having 6 to 24 carbon atoms, and specific examples thereof include a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, an undecenyl group, a dodecenyl group, a tridecenyl group, a tetradecenyl group, a pentadecenyl group, a hexadecenyl group, a heptadecenyl group, an octadecenyl group, a nonadecenyl group, an icosenyl group, an oleyl group, a geranyl group, a farnesyl group, and a linoleyl group. The monovalent saturated chain hydrocarbon group and the monovalent unsaturated chain hydrocarbon group may be linear or branched.

[0034] Examples of the monovalent saturated alicyclic hydrocarbon group include cycloalkyl groups such as a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, and a cyclononyl group; and cycloalkyl groups substituted with an alkyl group having 1 to 6 carbon atoms, such as a methylcyclohexyl group, a dimethylcyclohexyl group, an ethylcyclohexyl group, a diethylcyclohexyl group, a propylcyclohexyl group, an isopropylcyclohexyl group, a 1-methyl-propylcyclohexyl group, a butylcyclohexyl group, a pentylcyclohexyl group, a pentyl-methylcyclohexyl group, and a hexylcyclohexyl group (preferably a cyclohexyl group substituted with an alkyl group having 1 to 6 carbon atoms).

[0035] Examples of the monovalent unsaturated alicyclic hydrocarbon group include cycloalkenyl groups such as a cyclohexenyl group, a cycloheptenyl group, and a cyclooctenyl group; cycloalkenyl groups substituted with an alkyl group having 1 to 6 carbon atoms such as a methylcyclohexenyl group, a dimethylcyclohexenyl group, an ethylcyclohexenyl group, a diethylcyclohexenyl group, and a propylcyclohexenyl group (preferably a cyclohexenyl group substituted with an alkyl group having 1 to 6 carbon atoms); and the like.

[0036] Examples of the monovalent aromatic hydrocarbon group include a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a diphenylmethyl group, a diphenylethyl group, a diphenylpropyl group, a methylphenyl group, a dimethylphenyl group, an ethylphenyl group, and a propylphenyl group.

[0037] R in the above general formula (b2-1) 3 The divalent aromatic hydrocarbon group that can be selected as has 6 to 18 carbon atoms, preferably 6 to 15 carbon atoms, and more preferably 6 to 13 carbon atoms. R 3 Examples of the divalent aromatic hydrocarbon group that can be selected for include a phenylene group, a diphenylmethylene group, a diphenylethylene group, a diphenylpropylene group, a methylphenylene group, a dimethylphenylene group, and an ethylphenylene group. Among these, a phenylene group, a diphenylmethylene group, a diphenylethylene group, or a diphenylpropylene group is preferable, and a diphenylmethylene group is more preferable.

[0038] The particle size of the premade urea is preferably 5.0 μm or less, more preferably 4.0 μm or less, even more preferably 3.0 μm or less, still more preferably 2.5 μm or less, and even more preferably 2.0 μm or less, as an average particle size. There is no particular lower limit for the particle size of the premade urea, but it is usually 0.005 μm or more. In this specification, the particle size of the preformed urea is the 50% particle size (volume median particle size, D) based on scattering intensity, which is measured at 25°C by dynamic light scattering (photon correlation method) and calculated from the dispersed particle size distribution analyzed by the CONTIN method. 50 ) When component (B2) is used alone as the thickener (B), the content of component (B2) is preferably 5 mass% to 45 mass%, more preferably 10 mass% to 40 mass%, and even more preferably 15 mass% to 35 mass%, based on the total amount of the grease composition.

[0039] The urea compound constituting the premade urea can usually be obtained by reacting a diisocyanate with a monoamine in a suitable solvent. Examples of diisocyanates include diphenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and tolylene diisocyanate. As the monoamine, R 1 and R 2 Examples of amines include amines corresponding to a saturated or unsaturated monovalent chain hydrocarbon group, a saturated or unsaturated monovalent alicyclic hydrocarbon group, a monovalent aromatic hydrocarbon group, and the like, represented by the following formula: and examples thereof include chain hydrocarbon amines such as octylamine, dodecylamine, octadecylamine, and octadecenylamine; alicyclic hydrocarbon amines such as cyclohexylamine; aromatic hydrocarbon amines such as aniline and toluidine; and mixed amines obtained by mixing these. Examples of the solvent for synthesizing the urea compound include various organic solvents such as dichloromethane and toluene. The urea compound obtained by the above synthesis process can be washed with a solvent at least once to remove unreacted raw materials, and then the solvent is removed, followed by suitable fine pulverization treatment by a conventional method to provide the component (B2).

[0040] <Other ingredients> The grease composition of the present embodiment may further contain other components in addition to the base oil (A) and the thickener (B) without departing from the spirit of the present invention. Examples of other components include base oils other than the base oil (A), antioxidants, and viscosity index improvers. The other components may be used alone or in combination of two or more. The total content of other components in the grease composition of this embodiment is preferably 0 mass% to 10 mass%, more preferably 0 mass% to 5.0 mass%, and even more preferably 0 mass% to 2.0 mass%, based on the total amount of the grease composition.

[0041] From the viewpoint of improving the effects of the present invention, it is preferable that the content of the base oil other than the base oil (A) is small. Specifically, the content of the base oil other than the base oil (A) is preferably less than 10 parts by mass, more preferably less than 1 part by mass, and even more preferably less than 0.1 parts by mass, per 100 parts by mass of the base oil (A). Examples of base oils that do not fall under the category of base oil (A) include mineral oils and diesters. That is, the content of one or more base oils selected from the group consisting of mineral oils and diesters is preferably small, and the specific content thereof is preferably within the above range.

[0042] (metal atom-containing compound) In the grease composition of this embodiment, the content of the metal atom-containing compound is preferably adjusted to a low content. This is because, if a grease composition containing a metal atom-containing compound is dispersed within semiconductor manufacturing equipment and adheres to semiconductor products within the equipment, malfunctions will occur due to the metal atoms contained in the metal atom-containing compound, significantly affecting the yield of the semiconductor products. From this viewpoint, the content of metal atoms derived from the metal atom-containing compound in the grease composition of this embodiment is preferably less than 1.0 mass%, more preferably less than 0.1 mass%, even more preferably less than 0.01 mass%, and even more preferably less than 0.001 mass%, based on the total amount of the grease composition. In addition, since the base oil (A) and the thickener (B) do not substantially contain metal atoms, the content of metal atoms derived from the above-mentioned metal atom-containing compound can also be said to be the content of metal atoms in the grease composition.

[0043] Examples of metal atoms include alkali metal atoms such as lithium atom and sodium atom, alkaline earth metal atoms such as calcium atom and magnesium atom, and transition metal atoms such as zinc and molybdenum. Examples of the metal atom-containing compound include metal soaps and metal complex soaps such as lithium complex soaps, which are prepared by saponifying carboxylic acids or their esters with hydroxides of alkali metals, alkaline earth metals, aluminum, or the like, and which are used as thickeners; and metal salts and metal oxides which are used as metal dispersants, metal detergents, metal extreme pressure agents, metal rust inhibitors, and the like. That is, the content of metal atoms derived from one or more metal atom-containing compounds selected from the group consisting of the above components is preferably small, and the specific content is preferably within the above range.

[0044] (Fluorine atom-containing compounds) In the grease composition of the present embodiment, from the viewpoint of improving lubricity and from the viewpoint of PFAS regulations, it is preferable to adjust the content of fluorine atom-containing compounds to be low. From this viewpoint, the content of fluorine atoms derived from the fluorine atom-containing compound in the grease composition of the present embodiment is preferably less than 1.0 mass%, more preferably less than 0.1 mass%, even more preferably less than 0.01 mass%, and still more preferably less than 0.001 mass%, based on the total amount of the grease composition. In addition, since the base oil (A) and the thickener (B) do not substantially contain fluorine atoms, the content of fluorine atoms derived from the above-mentioned fluorine atom-containing compound can also be said to be the content of fluorine atoms in the grease composition.

[0045] Specific examples of fluorine atom-containing compounds include perfluoropolyether (PEPE) used as a base oil, polytetrafluoroethylene (PTFE) used as a thickening agent, and fluorinated silicone compounds used as antifoaming agents. That is, the content of fluorine atoms derived from one or more fluorine-containing compounds selected from the group consisting of the above components is preferably small, and the specific content thereof is preferably within the above range.

[0046] [Properties of grease composition] The grease composition of the present embodiment preferably satisfies the following physical properties.

[0047] <Thermal stability> The grease composition of this embodiment preferably has a thermal stability (temperature at which 1% by mass is lost) of 250° C. or higher as measured by the method described in the Examples section below.

[0048] <Lubricity> The grease composition of this embodiment has a wear scar diameter, measured by the method described in the examples below, of preferably 600 μm or less, more preferably 500 μm or less, and even more preferably 450 μm or less.

[0049] <Low dust generation> The grease composition of the present embodiment has a dust number, measured by the method described in the examples described below, of preferably 1,200 or less, more preferably 1,000 or less, even more preferably 800 or less, still more preferably 500 or less, and even more preferably 300 or less.

[0050] [Method of producing grease composition] The method for producing the grease composition of the present embodiment is not particularly limited. For example, the method for producing the grease composition of the present embodiment includes a step (S) of mixing a base oil (A) and a thickener (B). In the step (S), one or more components selected from the group consisting of the following component (A1) and the following component (A2) are blended as the base oil (A), Component (A1): Ester of polyol (A11) having 3 to 6 hydroxyl groups and branched fatty acid (A12) having 14 to 20 carbon atoms Component (A2): Alkylnaphthalene that exhibits a 3% mass loss temperature of 450°C or higher in gas chromatography distillation according to ASTM-D7500 As the thickener (B), at least one selected from the group consisting of the following component (B1) and the following component (B2) is blended. Ingredient (B1): Melamine cyanurate Ingredient (B2): Premade urea An example of a method for mixing (kneading) the base oil (A) and the thickener (B) is a method using a roll mill.

[0051] [Uses of grease composition] The grease composition of the present embodiment is excellent in lubricity and thermal stability. Therefore, the lubricating oil composition of this embodiment can be used in all applications that require lubricity and thermal stability, and is particularly suitable for use in semiconductor manufacturing equipment. In particular, the grease composition of this embodiment can be used to lubricate moving parts in high vacuum and high temperature environments such as vacuum chambers in semiconductor manufacturing equipment. Examples of such moving parts include, but are not limited to, linear motion mechanisms, reducers, and speed increasers. Examples of semiconductor manufacturing equipment include equipment that performs physical vapor deposition (PVD) and equipment that performs chemical vapor deposition (CVD). Examples of physical vapor deposition include vacuum vapor deposition, sputtering, ion plating, and ion bombardment using various ion guns. Examples of vacuum vapor deposition include general resistance heating vapor deposition, electron beam vapor deposition, ion-assisted electron beam vapor deposition, and arc vapor deposition. These physical vapor depositions may be used in appropriate combination. Examples of chemical vapor deposition include thermal CVD, plasma CVD, photo CVD, epitaxial CVD, and atomic layer CVD. These chemical vapor deposition methods may be used in appropriate combination, and may be used in appropriate combination with physical vapor deposition.

[0052] The grease composition of the present embodiment can also be suitably used in devices mounted on devices used in outer space, which is a high vacuum environment, such as artificial satellites, probes, and lunar vehicles.

[0053] [One aspect of the present invention provided] In one embodiment of the present invention, the following [1] to [8] are provided. [1] A grease composition comprising a base oil (A) and a thickener (B), The base oil (A) contains one or more components selected from the group consisting of the following component (A1) and the following component (A2), Component (A1): Ester of polyol (A11) having 3 to 6 hydroxyl groups and branched fatty acid (A12) having 14 to 20 carbon atoms Component (A2): Alkylnaphthalene that exhibits a 3% mass loss temperature of 450°C or higher in gas chromatography distillation according to ASTM-D7500 The thickener (B) comprises one or more components selected from the group consisting of the following component (B1) and the following component (B2): Ingredient (B1): Melamine cyanurate Ingredient (B2): Premade urea [2] The grease composition according to the above [1], wherein the polyol (A11) contains pentaerythritol. [3] The grease composition according to the above [1] or [2], wherein the branched fatty acid (A12) contains a branched fatty acid having one branch and a branch at the α-position. [4] The grease composition according to any one of the above [1] to [3], wherein a total content of the base oil (A) and the thickener (B) is 90 mass% to 100 mass% based on the total amount of the grease composition. [5] The base oil (A) contains one or more components selected from the component (A2), The grease composition according to any one of the above [1] to [4], wherein the thickener (B) includes one or more types selected from the component (B1). [6] The grease composition according to any one of the above [1] to [5], wherein the content of the thickener (B) is 5.0 mass % to 60 mass % based on the total amount of the grease composition. [7] The grease composition according to any one of the above [1] to [6], for use in semiconductor manufacturing equipment. [8] A process (S) for mixing a base oil (A) and a thickener (B), In the step (S), one or more components selected from the group consisting of the following component (A1) and the following component (A2) are blended as the base oil (A), Component (A1): Ester of polyol (A11) having 3 to 6 hydroxyl groups and branched fatty acid (A12) having 14 to 20 carbon atoms Component (A2): Alkylnaphthalene that exhibits a 3% mass loss temperature of 450°C or higher in gas chromatography distillation according to ASTM-D7500 A method for producing a grease composition, comprising blending, as the thickener (B), one or more components selected from the group consisting of the following component (B1) and the following component (B2): Ingredient (B1): Melamine cyanurate Ingredient (B2): Premade urea EXAMPLES

[0054] The present invention will be described in more detail with reference to the following examples, although the present invention is not limited to the following examples.

[0055] [Methods for measuring various physical properties] The properties of the raw materials used in each of the Examples and Comparative Examples were measured according to the procedures described below. (1) Physical properties of alkylnaphthalenes The temperature at which a 3% mass loss occurred was measured using gas chromatography distillation according to ASTM-D7500. (2) Average particle size of melamine cyanurate The 50% particle size (volume median particle size, D) based on scattering intensity was calculated from the dispersed particle size distribution measured at 25°C by dynamic light scattering (photon correlation method) and analyzed by the CONTIN method. 50 ) was used. (3) Average particle size of premade urea The 50% particle size (volume median particle size, D) based on scattering intensity was calculated from the dispersed particle size distribution measured at 25°C by dynamic light scattering (photon correlation method) and analyzed by the CONTIN method. 50 ) was used. (4)Kinematic viscosity at 40℃ Measurements were performed in accordance with JIS K2283:2000.

[0056] [Raw materials, etc.] In the present examples, the raw materials used to prepare the grease compositions are shown below.

[0057] <Base oil (A)> "Component (A1)": full ester of pentaerythritol and 2-hexyldecanoic acid (number of carbon atoms: 16, branch position: α-position, number of branches: 1) represented by the following structural formula (pentaerythritol tetrastearate, ISOCARBESTER 1605, manufactured by SASOL) [ka] "Component (A2)": alkylnaphthalene (KR-023, King Industries, kinematic viscosity at 40°C: 206 mm 2 / s) This alkylnaphthalene had a temperature of 486° C. when it was reduced by 3% by mass in gas chromatography distillation according to ASTM-D7500.

[0058] "Base oil (A')-1": A full ester (tris-(2-octyldodecyl) trimellitic acid ester) of trimellitic acid (manufactured by Wako Pure Chemical Industries, Ltd.) represented by the following structural formula and 2-octyl-1-dodecanol (manufactured by Wako Pure Chemical Industries, carbon number: 20, branch position: α position, number of branches: 1) represented by the following structural formula. [ka] "Base oil (A')-2": Fluorine oil (perfluoropolyether (PFPE), manufactured by Solvay, product name: Fomblin M30)

[0059] <Thickener (B)> "Component (B1)": Melamine cyanurate (manufactured by Nissan Chemical Industries, Ltd., product name: MC-6000, average particle size: 2 μm) "Component (B2)": Premade urea (urea structure: aromatic diurea, average particle size: 2 μm) In a 500mL separable four-neck flask equipped with a thermometer, stirring blade, and cooling reflux tube, 100mL of dichloromethane and 10.8g of 4,4'-diphenylmethane diisocyanate (MDI) were added and dissolved by stirring at room temperature (25℃) to prepare an MDI / dichloromethane solution. In another 200mL beaker, 25mL of dichloromethane and 9.2g of toluidine were taken and dissolved by stirring at room temperature to prepare a toluidine / dichloromethane solution. The toluidine / dichloromethane solution was added dropwise to the MDI / dichloromethane solution over 10 minutes to synthesize a diurea compound. After the heat generated during the dropwise addition subsided, the whole was heated to 45℃ using an oil bath to complete the reaction. The resulting paste-like diurea compound / dichloromethane was taken out and washed three times with 50 mL of dichloromethane while performing suction filtration to remove unreacted raw materials. The resulting solid was thoroughly dried under reduced pressure and confirmed to be the desired diurea compound by NMR. The diurea compound thus obtained is represented by the general formula (b2-1), 1 and R 2 is a methylphenyl group, and R 3 is a diphenylmethylene group. The resulting white solid was then pulverized in a mortar to obtain 8.4 g of premade urea in the form of a fine powder.

[0060] <Thickener (B')> "Non-prepared urea": ​​This is a diurea compound produced (synthesized) during the preparation of the grease composition in Comparative Example 1 described below, which is produced using 4,4'-diphenylmethane diisocyanate and toluidine as raw materials. In Table 1, this is listed as "Urea (conventional method)." "Polytetrafluoroethylene (PTFE)": 3M, TF9207Z

[0061] [Example 1] The grease composition of Example 1 was obtained by kneading 32 g of alkylnaphthalene (the above component (A2)) and 18 g of melamine cyanurate using a three-roll mill.

[0062] [Example 2] The grease composition of Example 2 was obtained by kneading 32 g of pentaerythritol tetrastearate (the above component (A1)) and 18 g of melamine cyanurate using a three-roll mill.

[0063] [Example 3] The grease composition of Example 3 was obtained by kneading 35 g of alkylnaphthalene (component (A2) above) and 15 g of premade urea using a three-roll mill.

[0064] [Comparative Example 1] In a separable flask, 46 g of alkylnaphthalene (component (A2) above) and 11 g of MDI (4,4'-diphenylmethane diisocyanate) were placed, and the mixture was heated to 80°C and dissolved to prepare an MDI / alkylnaphthalene solution. In a separate beaker, 13 g of toluidine and 50 g of alkylnaphthalene (component (A2) above) were placed, and the mixture was similarly heated and dissolved to prepare a toluidine / alkylnaphthalene solution. The toluidine / alkylnaphthalene solution was added dropwise to the stirred MDI / alkylnaphthalene solution to carry out a urea reaction. The reaction was completed by increasing the temperature to 160°C while stirring. The diurea compound thus obtained is represented by the general formula (b2-1), 1 and R 2 is a methylphenyl group, and R 3 is a diphenylmethylene group. After completing the reaction, the mixture was cooled to room temperature and then subjected to a roll mill to obtain the grease composition of Comparative Example 1.

[0065] [Comparative Example 2] Tris-(2-octyldodecyl) trimellitic ester (the above base oil (A′)-1) and melamine cyanurate were blended in the blending ratio shown in Table 1, and the grease composition of Comparative Example 2 was obtained in the same manner as in Example 1.

[0066] [Comparative Example 3] The grease composition of Comparative Example 3 was obtained by blending the fluorinated oil (the above base oil (A′)-2) and PTFE in the blending ratio shown in Table 1 and using the same method as in Example 1.

[0067] [evaluation] The grease compositions of Examples 1 to 3 and Comparative Examples 1 to 3 were subjected to the following Evaluations 1 and 2.

[0068] <Evaluation 1: Evaluation of thermal stability> The grease composition was subjected to a thermogravimetric differential thermal analysis using a thermogravimetric differential thermal analyzer (TG-DTA apparatus, manufactured by Seiko Instruments, product name: TG / DTA6200). Specifically, 0.5 g of the grease composition was filled into an aluminum pan, and the weight change was measured when the temperature was increased from 50° C. to 500° C. at a rate of 10° C. / min in a nitrogen atmosphere. Then, the temperature at which the grease composition was reduced by 1% by mass was confirmed. In this example, a temperature at which the grease composition lost 1% by mass of 250° C. or higher was determined as pass (A), and a temperature below 250° C. was determined as fail (B).

[0069] <Evaluation 2: Evaluation of lubricity> Using a high-speed reciprocating friction tester TE77 (manufactured by Phoenix Tribology), the grease composition was introduced between the test plate and the test ball, and the test was performed by moving the test ball under the conditions described below. After the test, the wear scar diameters in the vertical direction and the horizontal direction of the test ball were measured, and the average wear scar diameter was calculated using the following formula. Test plate Material: SUJ2, Shape: Length 58mm x Width 38mm x Thickness 3.9mm Test ball Material: SUJ2, diameter 10mm Grease conditions: Grease bath, grease amount 3mL Load: 200N (300 seconds) ·Temperature: 100℃ ·Amplitude: 10mm Frequency: 10Hz Average wear scar diameter = {(longitudinal wear scar diameter) + (lateral wear scar diameter)} / 2 The smaller the wear scar diameter, the more excellent the lubricity of the grease composition. In this example, grease compositions with a wear scar diameter of 600 μm or less were rated as pass (A), and grease compositions with a wear scar diameter of more than 600 μm were rated as fail (B).

[0070] The results of Evaluation 1 and Evaluation 2 are shown in Table 1. [Table 1]

[0071] From Table 1, we can see the following: It is clear that the grease compositions of Examples 1 to 3 are excellent in thermal stability and lubricity. In contrast, it is clear that the grease compositions of Comparative Examples 1 to 3 are inferior in thermal stability or lubricity.

[0072] Next, the grease compositions of Examples 1 to 3 and Comparative Examples 1 to 3 were subjected to the following Evaluation 3.

[0073] <Evaluation 3: Evaluation of low dust generation> The number of particles generated by the grease compositions was evaluated using a linear guide installed in a clean room (class 2 as defined by ISO14644-1). Specifically, 3 g of the grease composition was filled onto the entire rail surface of the linear guide, and the acceleration was 1.0 mm / s 2 The device was operated for 50 hours under the conditions of a stroke of 200 mm. Air was sampled (suction speed: 3 L / min) from an intake port installed close to the screw at the center of the reciprocating motion, and a particle counter (device name: Airborne Particle Counter KC-03B, manufactured by Rion Co., Ltd.) was started for 10 minutes every 30 minutes to measure the number of particles generated. The average number of particles generated over 10 minutes was calculated over the 40 to 50 hours when the friction state reached a steady state.

[0074] The results of Evaluation 3 are shown in Table 2. [Table 2]

[0075] It can be seen from Table 2 that the grease composition of Example 1 is particularly excellent in terms of low dust generation.

Claims

1. A grease composition containing a base oil (A) and a thickener (B), The base oil (A) comprises one or more components selected from the group consisting of the following components (A1) and (A2), • Component (A1): Ester of a polyol (A11) with 3 to 6 hydroxyl groups and a branched fatty acid (A12) with 14 to 20 carbon atoms. • Component (A2): Alkylnaphthalene whose temperature at which a 3% reduction by mass occurs in gas chromatography distillation compliant with ASTM-D7500 is 450°C or higher. A grease composition wherein the thickener (B) comprises one or more selected from the group consisting of the following components (B1) and (B2). • Ingredient (B1): Melamine cyanurate • Ingredient (B2): Pre-made urea

2. The grease composition according to claim 1, wherein the polyol (A11) comprises pentaerythritol.

3. The grease composition according to claim 1 or 2, wherein the branched fatty acid (A12) comprises a branched fatty acid having one branch and having a branch at the α-position.

4. The grease composition according to claim 1 or 2, wherein the total content of the base oil (A) and the thickener (B) is 90% by mass to 100% by mass on a basis of the total amount of the grease composition.

5. The base oil (A) comprises one or more selected from the components (A2), The grease composition according to claim 1 or 2, wherein the thickener (B) comprises one or more selected from the components (B1).

6. The grease composition according to claim 1 or 2, wherein the content of the thickener (B) is 5.0% by mass to 60% by mass on a basis of the total amount of the grease composition.

7. A grease composition according to claim 1 or 2, used in semiconductor manufacturing equipment.

8. The process includes a step (S) of mixing a base oil (A) and a thickener (B), In the above step (S), the base oil (A) is blended with one or more components selected from the group consisting of the following components (A1) and (A2), • Component (A1): Ester of a polyol (A11) with 3 to 6 hydroxyl groups and a branched fatty acid (A12) with 14 to 20 carbon atoms. • Component (A2): Alkylnaphthalene whose temperature at which a 3% reduction by mass occurs in gas chromatography distillation compliant with ASTM-D7500 is 450°C or higher. A method for producing a grease composition, comprising: a thickener (B) comprising one or more selected from the group consisting of the following components (B1) and (B2). • Ingredient (B1): Melamine cyanurate • Ingredient (B2): Pre-made urea