Grease composition and method for producing grease composition

Abstract

A grease composition containing a base oil (A) and a thickener (B), the base oil (A) containing one or more components selected from the group consisting of the following component (A1) and the following component (A2): component (A1): an ester of a polyol (A11) having 3-6 hydroxyl groups and a branched fatty acid (A12) having 14-20 carbon atoms; component (A2): an alkylnaphthalene whose temperature reduced by 3 mass% in gas chromatographic distillation according to ASTM-D7500 is 450 DEG C or more, and the thickener (B) contains one or more components selected from the group consisting of the following component (B1) and the following component (B2). Component (B1): melamine cyanurate; and component (B2): prefabricated urea.

Description

TECHNICAL FIELD

[0001] The present application relates to a grease composition and a method for producing a grease composition. BACKGROUND

[0002] As a grease composition used in a semiconductor manufacturing apparatus or the like, for example, a fluorine grease composition using a perfluoropolyether (PFPE) as a base oil and using polytetrafluoroethylene (PTFE) as a thickening agent is known. In addition, in Patent Literature 1, a grease composition containing a base oil including an ester oil or an ether oil not containing fluorine and a thickening agent including at least a urea compound and a thickening agent having self-lubricating properties is proposed.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Laid-Open No. 2011-202061 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] However, the fluorine grease composition using a fluorine oil such as a perfluoropolyether (PFPE) as a base oil sometimes has insufficient lubricity, and improvement thereof is required.

[0008] In addition, in a semiconductor manufacturing apparatus, for example, processes such as film formation and etching are sometimes performed at a high temperature of 200°C or higher. At such a high temperature, the grease composition is also required to have heat stability.

[0009] The present application has been achieved in view of the above-described requirements, and an object thereof is to provide a grease composition excellent in lubricity and heat stability.

[0010] MEANS FOR SOLVING THE PROBLEMS

[0011] According to the present application, the following [1] to [2] are provided.

[0012] [1] A grease composition containing a base oil (A) and a thickening agent (B),

[0013] The above-described base oil (A) contains one or more selected from the following component (Al) and the following component (A2),

[0014] • Component (Al): an ester of a polyol (Al l) having a hydroxyl group number of 3 to 6 and a branched fatty acid (Al2) having a carbon atom number of 14 to 20;

[0015] • Component (A2): an alkyl naphthalene having a temperature of 450°C or higher at which 3% by mass is reduced in gas chromatography distillation according to ASTM-D7500,

[0016] The above thickening agent (B) contains one or more selected from the following component (B1) and the following component (B2).

[0017] • Component (B1): melamine cyanurate;

[0018] • Component (B2): preformed urea.

[0019] [2] A method for producing a grease composition, comprising a step (S) of mixing a base oil (A) and a thickening agent (B),

[0020] In the above step (S), as the above base oil (A), one or more selected from the following component (A1) and the following component (A2) is blended,

[0021] • Component (A1): an ester of a polyol (A11) having a hydroxyl group number of 3 to 6 and a branched fatty acid (A12) having a carbon number of 14 to 20;

[0022] • Component (A2): an alkyl naphthalene having a temperature of 450°C or higher at which 3% by mass is reduced in gas chromatography distillation according to ASTM-D7500,

[0023] As the above thickening agent (B), one or more selected from the following component (B1) and the following component (B2) is blended.

[0024] • Component (B1): melamine cyanurate;

[0025] • Component (B2): preformed urea.

[0026] Effects of the Invention

[0027] According to the present application, it is possible to provide a grease composition which is excellent in lubricity and thermal stability. DETAILED DESCRIPTION

[0028] The upper limit value and the lower limit value of the numerical range described in the present specification can be combined arbitrarily. For example, in the case where "A to B" and "C to D" are described as numerical ranges, the numerical ranges of "A to D" and "C to B" are also included in the range of the present application.

[0029] In addition, unless otherwise specified, the numerical range "lower limit value to upper limit value" described in the present specification means above the lower limit value and below the upper limit value.

[0030] In addition, in the present specification, the numerical value of the examples is a numerical value that can be used as the upper limit value or the lower limit value.

[0031] [Mode of the Grease Composition]

[0032] The grease composition of the present embodiment contains a base oil (A) and a thickening agent (B).

[0033] The base oil (A) contains one or more selected from the following component (Al) and the following component (A2).

[0034] • Component (Al): ester of a polyol (Al l) having a hydroxyl group number of 3 to 6 and a branched fatty acid (A12) having a carbon number of 14 to 20;

[0035] • Component (A2): alkyl naphthalene having a temperature of 450°C or higher at which 3% by mass is reduced in gas chromatography distillation according to ASTM-D7500,

[0036] Further, the thickening agent (B) contains one or more selected from the following component (Bl) and the following component (B2).

[0037] • Component (Bl): melamine cyanurate;

[0038] • Component (B2): preformed urea.

[0039] The present inventors and others have repeatedly conducted intensive research in order to solve the above problem.

[0040] As a result, it was found that the grease composition containing the above base oil (A) and the above thickening agent (B) is excellent in lubricity and thermal stability.

[0041] The present inventors and others have further repeatedly conducted various researches based on the above insight, thereby completing the present application.

[0042] The grease composition of the present embodiment can be composed of only the base oil (A) and the thickening agent (B), or can further contain other components other than the base oil (A) and the thickening agent (B).

[0043] In the grease composition of the present embodiment, the total content of the base oil (A) and the thickening agent (B) is preferably 90 to 100% by mass, more preferably 95 to 100% by mass, based on the total amount of the grease composition.

[0044] Hereinafter, each component contained in the grease composition of the present embodiment will be described in detail.

[0045] < Base oil (A) >

[0046] The grease composition of the present embodiment contains a base oil (A).

[0047] Further, the base oil (A) contains one or more selected from the following component (Al) and the following component (A2).

[0048] • Component (A1): an ester of a polyol (A11) having a hydroxyl group number of 3 to 6 and a branched aliphatic acid (A12) having a carbon number of 14 to 20;

[0049] • Component (A2): an alkyl naphthalene having a temperature of 450°C or higher at which 3% by mass is reduced in gas chromatography distillation according to ASTM-D7500.

[0050] By using a base oil (A) containing one or more selected from the group consisting of component (A1) and component (A2) together with a thickener (B), a lubricating grease composition having excellent lubricity and thermal stability can be produced.

[0051] Note that "one or more selected from the group consisting of component (A1) and component (A2)" means "one or more selected from component (A1)", "one or more selected from component (A2)", or "a combination of one or more selected from component (A1) and one or more selected from component (A2)".

[0052] In the lubricating grease composition of the present embodiment, from the viewpoint of improving the effects of the present application, "one or more selected from the group consisting of component (A1) and component (A2)" is preferably "one or more selected from component (A1)" or "one or more selected from component (A2)".

[0053] In addition, from the viewpoint of improving the effects of the present application and producing a lubricating grease composition having excellent low dusting properties, "one or more selected from the group consisting of component (A1) and component (A2)" is preferably "one or more selected from component (A2)".

[0054] Here, from the viewpoint of improving the effects of the present application, the content of "one or more selected from the group consisting of component (A1) and component (A2)" is preferably 50% by mass or more, more preferably 60% by mass or more, further preferably 70% by mass or more, still further preferably 80% by mass or more, yet further preferably 90% by mass or more, yet more preferably 95% by mass or more, yet again preferably 99% by mass or more, and yet further preferably 100% by mass, based on the total amount of the base oil (A).

[0055] Furthermore, from the viewpoint of improving the effect of the present invention and producing a lubricating grease composition with excellent low dust generation, the content of "one or more selected from component (A2)" is preferably 50% to 100% by mass, more preferably 60% to 100% by mass, further preferably 70% to 100% by mass, even more preferably 80% to 100% by mass, even more preferably 90% to 100% by mass, even more preferably 95% to 100% by mass, even more preferably 99% to 100% by mass, and even more preferably 100% by mass, based on the total amount of base oil (A).

[0056] In addition, based on the total amount of the grease composition, the content of base oil (A) is preferably 40% to 90% by mass, more preferably 45% to 85% by mass.

[0057] The following is a detailed description of ingredients (A1) and (A2).

[0058] <<Ingredients (A1)>>

[0059] The component (A1) is an ester of a polyol (A11) with 3 to 6 hydroxyl groups and a branched fatty acid (A12) with 14 to 20 carbon atoms.

[0060] By including component (A1) in the base oil (A), a grease composition with excellent thermal stability can be produced. Furthermore, a grease composition that is difficult to volatilize even under high vacuum (hereinafter also referred to as "low volatility") can be produced.

[0061] It should be noted that component (A1) can be either a partial ester or a full ester. From the viewpoint of producing a grease composition with superior thermal stability and low volatility, it is preferable to include a full ester. Based on the total amount of component (A1), the content of full ester in component (A1) is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 97% by mass or more.

[0062] The following provides a detailed explanation of polyols (A11) and branched-chain fatty acids (A12).

[0063] (Polyol (A11))

[0064] Polyols (A11) are polyols with 3 to 6 hydroxyl groups.

[0065] By using polyols with 3 to 6 hydroxyl groups as the alcohol component of the ester, the thermal stability and low volatility of component (A1) can be improved.

[0066] Specific examples of polyols with 3 to 6 hydroxyl groups include trihydric alcohols such as glycerol, trimethylolethane, trimethylolpropane, and trimethylolnonane (polyols with 3 hydroxyl groups); and quaternary to 6-membered alcohols such as pentaerythritol, bis(trimethylolpropane), dipentaerythritol, sorbitol, and mannitol (polyols with 4 to 6 hydroxyl groups).

[0067] From the viewpoint of easily improving low volatility by increasing the molecular weight of component (A1), alcohols with 4 to 6 members are preferred. Furthermore, among alcohols with 4 to 6 members, pentaerythritol is preferred from the viewpoint of improving thermal stability and low volatility. That is, the polyol (A11) preferably contains pentaerythritol. It is presumed that by including pentaerythritol in the polyol (A11), molecular cleavage caused by intramolecular condensation reactions of the ester composed of pentaerythritol and branched fatty acids (A12) is suppressed, and the thermal stability of component (A1) is easily improved through the effective protection of the ester group by the alkyl group possessed by the branched fatty acids (A12).

[0068] Based on the total amount of polyol (A11), the content of pentaerythritol is preferably 50% to 100% by mass, more preferably 60% to 100% by mass, even more preferably 70% to 100% by mass, even more preferably 80% to 100% by mass, even more preferably 90% to 100% by mass, even more preferably 95% to 100% by mass, even more preferably 99% to 100% by mass, and even more preferably 100% by mass.

[0069] (Branched-chain fatty acids (A12))

[0070] Branched-chain fatty acids (A12) are branched-chain fatty acids with 14 to 20 carbon atoms.

[0071] By using branched-chain fatty acids with 14 to 20 carbon atoms as the fatty acid components of the ester, the component (A1) exhibits excellent thermal stability and low volatility. Furthermore, the flowability of component (A1) can be improved, and the viscosity index can also be increased.

[0072] Furthermore, from the perspectives of improving thermal stability and increasing viscosity index, the branched fatty acids with 14 to 20 carbon atoms preferably have 1 branch.

[0073] Specific examples of branched fatty acids with 14 to 20 carbon atoms and one branch are preferably branched saturated fatty acids such as butyloctanoic acid, hexyldecanoic acid, and octyldodecanoic acid.

[0074] From the viewpoint of improving the thermal stability and fluidity of the ester, hexyldecanoic acid is preferred. Furthermore, from the viewpoint of further improving thermal stability and fluidity, hexyldecanoic acid is preferred to have a branched chain at the α-position (the carbon atom adjacent to the carboxyl group). That is, the branched fatty acid (A12) is preferably a branched fatty acid containing 14 to 20 carbon atoms, having one branch, and having a branch at the α-position.

[0075] Based on the total amount of branched-chain fatty acids (A12), the content of branched-chain fatty acids with 14 to 20 carbon atoms, 1 branch and a branch at the α position is preferably 50% to 100% by mass, more preferably 60% to 100% by mass, further preferably 70% to 100% by mass, even more preferably 80% to 100% by mass, even more preferably 90% to 100% by mass, even more preferably 95% to 100% by mass, even more preferably 99% to 100% by mass, and even more preferably 100% by mass.

[0076] <<Ingredients (A2)>>

[0077] Component (A2) is an alkyl naphthalene that is reduced by 3% by mass at a temperature of 450°C or higher during gas chromatographic distillation according to ASTM-D7500.

[0078] By including component (A2) in the base oil (A), a grease composition with excellent thermal stability can be produced. Furthermore, a grease composition with low volatility can be produced.

[0079] Alkylnaphthalene is a compound in which at least one hydrogen atom of the naphthalene ring is replaced by an alkyl group. Furthermore, by reducing alkylnaphthalene by 3% by mass at a temperature of 450°C or higher in gas chromatographic distillation according to ASTM-D7500, it is possible to produce a grease composition with excellent thermal stability (and thus low volatility).

[0080] From the viewpoint of further improving thermal stability (and thus lower volatility), the temperature at which 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.

[0081] From the perspective of further improving thermal stability (and reducing volatility), the kinematic viscosity of alkylnaphthalene at 40°C is preferably 75 mm. 2 / s~400mm 2 / s, more preferably 100mm 2 / s~350m 2 / s, further preferably 150mm 2 / s~300mm 2 / s.

[0082] In this specification, the kinematic viscosity at 40°C refers to the value measured according to JIS K2283:2000.

[0083] <Thickener (B)>

[0084] The grease composition of this embodiment contains a thickener (B).

[0085] Furthermore, the thickener (B) contains one or more ingredients selected from the following components (B1) and the following components (B2).

[0086] • Ingredient (B1): Melamine cyanurate;

[0087] • Ingredient (B2): Pre-formed urea.

[0088] By using a thickener (B) selected from components (B1) and (B2) with a base oil (A), a grease composition with excellent thermal stability, low volatility, and excellent lubricity can be prepared.

[0089] It should be noted that "selected from one or more of ingredients (B1) and ingredients (B2)" means "selected from one or more of ingredients (B1)," "selected from one or more of ingredients (B2)," or "a combination of one or more of ingredients (B1) and one or more of ingredients (B2)."

[0090] In the grease composition of this embodiment, from the viewpoint of improving the effect of the present invention, "selected from one or more of component (B1) and component (B2)" is preferably "selected from one or more of component (B1)" or "selected from one or more of component (B2)".

[0091] Furthermore, from the viewpoint of improving the effect of the present invention and producing a lubricating grease composition with excellent low dust generation, "selected from one or more of component (B1) and component (B2)" is preferably "selected from one or more of component (B1)".

[0092] From the viewpoint of improving the effect of the present invention, based on the total amount of thickener (B), the content of "one or more selected from components (B1) and components (B2)" is preferably 50% to 100% by mass, more preferably 60% to 100% by mass, further preferably 70% to 100% by mass, even more preferably 80% to 100% by mass, even more preferably 90% to 100% by mass, even more preferably 95% to 100% by mass, even more preferably 99% to 100% by mass, and even more preferably 100% by mass.

[0093] Furthermore, from the viewpoint of improving the effect of the present invention and producing a lubricating grease composition with excellent low dust generation, the content of "one or more selected from component (B1)" is preferably 50% to 100% by mass, more preferably 60% to 100% by mass, further preferably 70% to 100% by mass, even more preferably 80% to 100% by mass, even more preferably 90% to 100% by mass, even more preferably 95% to 100% by mass, even more preferably 99% to 100% by mass, and even more preferably 100% by mass, based on the total amount of thickener (B).

[0094] In addition, based on the total amount of the grease composition, the content of thickener (B) is preferably 5% to 60% by mass, more preferably 10% to 55% by mass.

[0095] The following is a detailed description of ingredients (B1) and (B2).

[0096] <<Ingredient (B1)>>

[0097] Component (B1) is melamine cyanurate.

[0098] A grease composition was prepared by mixing melamine cyanurate with a base oil (A), thereby allowing melamine cyanurate to function as a thickener. Furthermore, melamine cyanurate is free of metal components, making it highly suitable as a thickener for preparing grease compositions used in semiconductor device manufacturing. Additionally, melamine cyanurate exhibits excellent thermal stability and can also improve the lubricity of the grease composition.

[0099] It should be noted that melamine cyanurate refers to an organic salt composed of melamine and cyanuric acid, which has a graphite structure.

[0100] Based on average particle size, the particle size of melamine cyanurate is preferably 5.0 μm or less, more preferably 4.0 μm or less, even more preferably 3.0 μm or less, even more preferably 2.5 μm or less, and still even more preferably 2.0 μm or less. Furthermore, there is no particular limitation on the lower limit of the particle size of melamine cyanurate, and it is typically 0.005 μm or more.

[0101] It should be noted that, in this specification, the particle size of melamine cyanurate refers to the 50% particle size (volume median particle size, D) calculated based on the scattering intensity, using dynamic light scattering (photon correlation) at 25°C, and determined according to the dispersed particle size distribution analyzed by the CONTIN method. 50 ).

[0102] It should be noted that when component (B1) is used alone as thickener (B), the content of component (B1) is preferably 20% to 60% by mass, more preferably 25% to 55% by mass, based on the total amount of the grease composition.

[0103] <<Ingredient (B2)>>

[0104] Component (B2) is pre-formulated urea.

[0105] Generally, in the manufacture of grease compositions, urea compounds that function as thickeners in a base oil are synthesized by adding amines and isocyanates to the base oil and reacting them. That is, the urea compounds, which function as thickeners, are synthesized in the base oil constituting the grease composition during the manufacturing process.

[0106] However, under such methods, unreacted amines and / or isocyanates sometimes remain in the grease composition. According to the researchers of the present invention, such low-molecular-weight compounds are a major cause of reduced thermal stability of the grease composition.

[0107] Therefore, in this embodiment, instead of synthesizing urea compounds during the manufacturing process of the grease composition, a pre-synthesized urea compound is used and mixed into the base oil to prepare the grease composition. Such a urea compound is referred to as a "pre-synthesized urea".

[0108] The urea compound constituting the preformed urea can be a compound having urea bonds, preferably a diurea compound having two urea bonds, and more preferably a diurea compound represented by the following general formula (b2-1).

[0109] R 1 -NHCONH-R 3 -NHCONH-R 2 (b2-1)

[0110] In the above general formula (b2-1), R 1 and R 2 Each group independently represents a monovalent hydrocarbon group with 6 to 24 carbon atoms. R 1 and R 2 They can be the same, or they can be different from each other. R 3 It represents a divalent aromatic hydrocarbon group with 6 to 18 carbon atoms.

[0111] As R can be selected as the above general formula (b2-1) 1 and R 2 The number of carbon atoms in the monovalent hydrocarbon group is 6 to 24, preferably 6 to 20, and more preferably 6 to 18.

[0112] Additionally, as an option that can be selected as R 1 and R 2 The monovalent hydrocarbon group can be categorized as saturated or unsaturated monovalent chain hydrocarbon group, saturated or unsaturated monovalent alicyclic hydrocarbon group, and monovalent aromatic hydrocarbon group.

[0113] Examples of monovalent saturated chain hydrocarbon groups include straight-chain or branched alkyl groups with 6 to 24 carbon atoms, specifically hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecanyl, octadecyl, octadecenyl, nonadecanyl, and eicosyl.

[0114] Examples of monovalent unsaturated chain hydrocarbon groups include straight-chain or branched alkenyl groups with 6 to 24 carbon atoms. Specifically, examples include hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl, nonadecenyl, eicoseneyl, oleyl, geranyl, farnesyl, and linoleyl.

[0115] It should be noted that monovalent saturated chain hydrocarbon groups and monovalent unsaturated chain hydrocarbon groups can be straight-chain or branched.

[0116] Examples of monovalent saturated alicyclic hydrocarbon groups include cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, and other cycloalkyl groups; cycloalkyl groups substituted with alkyl groups having 1 to 6 carbon atoms, such as methylcyclohexyl, dimethylcyclohexyl, ethylcyclohexyl, diethylcyclohexyl, propylcyclohexyl, isopropylcyclohexyl, 1-methyl-propylcyclohexyl, butylcyclohexyl, pentylcyclohexyl, pentyl-methylcyclohexyl, and hexylcyclohexyl (preferably cyclohexyl substituted with alkyl groups having 1 to 6 carbon atoms).

[0117] Examples of monovalent unsaturated alicyclic hydrocarbon groups include cyclohexenyl, cycloheptenyl, cyclooctenyl, and other cycloalkenyl groups; cycloalkenyl groups substituted with alkyl groups having 1 to 6 carbon atoms, such as methylcyclohexenyl, dimethylcyclohexenyl, ethylcyclohexenyl, diethylcyclohexenyl, and propylcyclohexenyl (preferably cyclohexenyl groups substituted with alkyl groups having 1 to 6 carbon atoms).

[0118] Examples of monovalent aromatic hydrocarbon groups include phenyl, biphenyl, terphenyl, naphthyl, diphenylmethyl, diphenylethyl, diphenylpropyl, methylphenyl, dimethylphenyl, ethylphenyl, propylphenyl, etc.

[0119] As R can be selected as the above general formula (b2-1) 3 The number of carbon atoms in the divalent aromatic hydrocarbon group is 6 to 18, preferably 6 to 15, and more preferably 6 to 13.

[0120] As can be selected as R3 Divalent aromatic hydrocarbon groups, for example, include phenylene, diphenylmethylene, diphenylethylene, diphenylpropylene, methylphenylene, dimethylphenylene, ethylphenylene, etc.

[0121] Preferably, it is phenylene, diphenylmethylene, diphenylethylene, or diphenylpropylene, with diphenylmethylene being more preferred.

[0122] Based on average particle size, the particle size of the pre-formed urea is preferably 5.0 μm or less, more preferably 4.0 μm or less, even more preferably 3.0 μm or less, even more preferably 2.5 μm or less, and still even more preferably 2.0 μm or less. Furthermore, there is no particular limitation on the lower limit value of the particle size of the pre-formed urea, and it is typically 0.005 μm or more.

[0123] It should be noted that, in this specification, the particle size of pre-prepared urea refers to the 50% particle size (volume median particle size, D) calculated based on the scattering intensity, using dynamic light scattering (photon correlation) at 25°C and determined according to the dispersed particle size distribution analyzed by the CONTIN method. 50 ).

[0124] It should be noted that when component (B2) is used alone as thickener (B), the content of component (B2) is preferably 5% to 45% by mass, more preferably 10% to 40% by mass, and even more preferably 15% to 35% by mass, based on the total amount of the grease composition.

[0125] Urea compounds that constitute pre-urea can usually be obtained by reacting diisocyanates with monoamines in a suitable solvent.

[0126] Examples of diisocyanates include diphenyl diisocyanate, 4,4'-diphenylmethane diisocyanate, and toluene diisocyanate.

[0127] As a monoamine, examples include R in the above general formula (b2-1). 1 and R 2 The amines corresponding to saturated or unsaturated monovalent chain hydrocarbon groups, saturated or unsaturated monovalent alicyclic hydrocarbon groups, and monovalent aromatic hydrocarbon groups shown include, for example, 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 formed by mixing them.

[0128] Examples of organic solvents used in the synthesis of urea compounds include dichloromethane and toluene.

[0129] The urea compound obtained through the above synthesis process can be removed by washing with solvent more than once to remove unreacted raw materials, and then subjected to appropriate micro-pulverization by conventional methods to be supplied as component (B2).

[0130] <Other Ingredients>

[0131] The grease composition of this embodiment may further contain other components besides the base oil (A) and thickener (B) without departing from the spirit of the invention.

[0132] Other components include, for example, base oils that are not equivalent to base oil (A), antioxidants, and viscosity index improvers.

[0133] Other ingredients can be used alone or in combination of two or more.

[0134] Based on the total amount of the grease composition, the total content of other components in the grease composition of this embodiment is preferably 0% to 10% by mass, more preferably 0% to 5.0% by mass, and even more preferably 0% to 2.0% by mass.

[0135] It should be noted that, from the viewpoint of improving the effectiveness of the present invention, the content of base oil that is not equivalent to base oil (A) is preferably low. Specifically, relative to 100 parts by weight of base oil (A), the content of base oil that is not equivalent to base oil (A) is preferably less than 10 parts by weight, more preferably less than 1 part by weight, and even more preferably less than 0.1 parts by weight.

[0136] Examples of base oils that are not equivalent to base oil (A) include mineral oils and diesters.

[0137] That is, the content of one or more base oils selected from mineral oil and diester is preferably low, and the specific content is preferably within the above range.

[0138] (Compounds containing metal atoms)

[0139] In the grease composition of this embodiment, the content of compounds containing metal atoms is preferably prepared to be low.

[0140] This is because, in semiconductor manufacturing equipment, when a grease composition containing a compound with metal atoms is dispersed and adheres to the semiconductor products inside the equipment, malfunctions caused by the metal atoms contained in the compound with metal atoms occur, which has a significant impact on the yield of the semiconductor products.

[0141] From this perspective, the metal atom content of the compound containing metal atoms in the grease composition of this embodiment, based on the total amount of the grease composition, is preferably less than 1.0% by mass, more preferably less than 0.1% by mass, even more preferably less than 0.01% by mass, and even more preferably less than 0.001% by mass.

[0142] It should be noted that the base oil (A) and thickener (B) do not actually contain metal atoms, so the metal atom content of the above-mentioned compounds containing metal atoms can also be said to be the metal atom content in the grease composition.

[0143] It should be noted that, for example, metal atoms include alkali metal atoms such as lithium atoms and sodium atoms, alkaline earth metal atoms such as calcium atoms and magnesium atoms, and transition metal atoms such as zinc and molybdenum.

[0144] Examples of metal-containing compounds include metal-based soaps such as lithium-based complex soaps, which are obtained by saponifying carboxylic acids or their esters with hydroxides of alkali metals, alkaline earth metals, aluminum, etc., as thickeners; and metal salts and metal oxides, which are used as metal-based dispersants, metal-based detergents, metal-based extreme pressure agents, and metal-based rust inhibitors.

[0145] That is, preferably, the metal atom content of compounds containing metal atoms selected from the above-mentioned components is low, and the specific content is preferably within the above-mentioned range.

[0146] (Compounds containing fluorine atoms)

[0147] In the grease composition of this embodiment, from the viewpoint of improving lubricity and controlling PFAS, it is preferable to reduce the content of fluorine-containing compounds.

[0148] From this perspective, the fluorine atom content of the fluorine-containing compound in the grease composition of this embodiment, based on the total amount of the grease composition, is preferably less than 1.0% by mass, more preferably less than 0.1% by mass, even more preferably less than 0.01% by mass, and even more preferably less than 0.001% by mass.

[0149] It should be noted that the base oil (A) and thickener (B) do not actually contain fluorine atoms, so the fluorine atom content of the above-mentioned compounds derived from fluorine atoms can also be said to be the fluorine atom content in the grease composition.

[0150] Specific examples of fluorine-containing compounds include perfluoropolyethers (PEPE) used as base oils, polytetrafluoroethylene (PTFE) used as thickeners, and fluorinated organosilicon compounds used as defoamers.

[0151] That is, the fluorine atom content is preferably low in compounds derived from one or more fluorine-containing atoms selected from the above-mentioned components, and the specific content is preferably within the above-mentioned range.

[0152] [Physical properties of the grease composition]

[0153] The grease composition of this embodiment preferably satisfies the following physical properties.

[0154] <Thermal Stability>

[0155] The thermal stability (temperature at which mass decreases by 1%) of the grease composition of this embodiment, as determined by the method described in the examples below, is preferably 250°C or higher.

[0156] <Lubricity>

[0157] The wear mark diameter of the grease composition of this embodiment, as measured by the method described in the examples below, is preferably 600 μm or less, more preferably 500 μm or less, and even more preferably 450 μm or less.

[0158] Low dust emission

[0159] The dust emission count of the grease composition of this embodiment, as measured by the method described in the examples below, is preferably 1200 or less, more preferably 1000 or less, even more preferably 800 or less, even more preferably 500 or less, and still more preferably 300 or less.

[0160] [Method for manufacturing grease composition]

[0161] The method for manufacturing the grease composition in this embodiment is not particularly limited.

[0162] For example, the method for manufacturing the grease composition of this embodiment includes a step (S) of mixing a base oil (A) with a thickener (B).

[0163] Furthermore, in the aforementioned process (S), as the aforementioned base oil (A), one or more components selected from the following ingredients (A1) and the following ingredients (A2) are incorporated.

[0164] • Component (A1): An ester of a polyol (A11) with 3 to 6 hydroxyl groups and a branched fatty acid (A12) with 14 to 20 carbon atoms;

[0165] • Composition (A2): 3% by mass of alkyl naphthalene at a temperature of 450°C or higher, obtained by gas chromatographic distillation according to ASTM-D7500.

[0166] As the thickener (B) mentioned above, it is combined with one or more of the following components (B1) and (B2).

[0167] • Ingredient (B1): Melamine cyanurate;

[0168] • Ingredient (B2): Pre-formed urea.

[0169] As a method for mixing (blending) base oil (A) with thickener (B), for example, the method of using a roller mill can be cited.

[0170] [Uses of the grease composition]

[0171] The grease composition of this embodiment exhibits excellent lubricity and thermal stability.

[0172] Therefore, the lubricating oil composition of this embodiment can be used in all applications requiring lubricity and thermal stability, and is suitable for use in semiconductor manufacturing apparatuses. More specifically, the lubricating grease composition of this embodiment is suitable for lubricating drive components in high-vacuum and high-temperature environments such as vacuum chambers within semiconductor manufacturing apparatuses. Examples of such drive components include linear motion mechanisms, speed reducers, and speed increasers, but these are not limited to these.

[0173] Examples of semiconductor manufacturing apparatus include apparatuses for physical vapor deposition (PVD) and apparatuses for chemical vapor deposition (CVD).

[0174] Examples of physical vapor deposition methods include vacuum evaporation, sputtering, ion plating, and ion implantation using various ion guns. Vacuum evaporation methods, besides the common resistance heating evaporation, include electron beam evaporation, ion-assisted electron beam evaporation, and arc evaporation. These physical vapor deposition methods can be used in appropriate combinations.

[0175] Examples of chemical vapor deposition methods include thermal CVD, plasma CVD, photochemical CVD, epitaxial CVD, and atomic layer CVD. These chemical vapor deposition methods can be used in appropriate combinations, or in combination with physical vapor deposition methods.

[0176] Furthermore, the grease composition of this embodiment can also be used in devices mounted in space, such as satellites, probes, and lunar rovers, which are used in the high vacuum environment of outer space.

[0177] [One aspect of the present invention provided]

[0178] In one embodiment of the present invention, the following [1] to [8] are provided.

[0179] [1] A grease composition comprising a base oil (A) and a thickener (B).

[0180] The base oil (A) described above contains one or more components selected from the following ingredients (A1) and the following ingredients (A2).

[0181] • Component (A1): An ester of a polyol (A11) with 3 to 6 hydroxyl groups and a branched fatty acid (A12) with 14 to 20 carbon atoms;

[0182] • Composition (A2): 3% by mass of alkyl naphthalene at a temperature of 450°C or higher, obtained by gas chromatographic distillation according to ASTM-D7500.

[0183] The thickener (B) described above contains one or more ingredients selected from the following components (B1) and (B2).

[0184] • Ingredient (B1): Melamine cyanurate;

[0185] • Ingredient (B2): Pre-formed urea.

[0186] [2] According to the grease composition described in [1] above, wherein the polyol (A11) comprises pentaerythritol.

[0187] [3] According to the grease composition described in [1] or [2] above, wherein the branched fatty acid (A12) comprises a branched fatty acid having one branch and having a branch at the α position.

[0188] [4] The grease composition described in any one of [1] to [3] above, wherein the total content of the base oil (A) and the thickener (B) is 90% to 100% by mass based on the total amount of the grease composition.

[0189] [5] The lubricating grease composition according to any one of [1] to [4] above, wherein the base oil (A) contains one or more components selected from the above-mentioned components (A2),

[0190] The thickener (B) mentioned above contains one or more ingredients selected from the above components (B1).

[0191] [6] The grease composition according to any one of [1] to [5] above, wherein the content of the thickener (B) is 5.0% to 60% by mass based on the total amount of the grease composition above.

[0192] [7] The grease composition described in any one of [1] to [6] above is used in a semiconductor manufacturing apparatus.

[0193] [8] A method for manufacturing a grease composition, comprising a step (S) of mixing a base oil (A) with a thickener (B).

[0194] In the above process (S), as the base oil (A), one or more components selected from the following components (A1) and (A2) are incorporated.

[0195] • Component (A1): An ester of a polyol (A11) with 3 to 6 hydroxyl groups and a branched fatty acid (A12) with 14 to 20 carbon atoms;

[0196] • Composition (A2): 3% by mass of alkyl naphthalene at a temperature of 450°C or higher, obtained by gas chromatographic distillation according to ASTM-D7500.

[0197] As the thickener (B) mentioned above, it is combined with one or more of the following components (B1) and (B2).

[0198] • Ingredient (B1): Melamine cyanurate;

[0199] • Ingredient (B2): Pre-formed urea.

[0200] Example

[0201] The present invention will be specifically described through the following embodiments. However, the present invention is not limited to the following embodiments.

[0202] [Methods for determining various physical properties]

[0203] The properties of each raw material used in each embodiment and each comparative example were determined according to the following procedures.

[0204] (1) Properties of alkylnaphthalenes

[0205] The temperature at which a 3% mass reduction occurs during gas chromatographic distillation according to ASTM-D7500 is determined.

[0206] (2) Average particle size of melamine cyanurate

[0207] Measurements were performed at 25°C using dynamic light scattering (photon correlation) and the 50% particle size (volume median particle size, D) calculated based on the scattering intensity, using the dispersed particle size distribution resolved by the CONTIN method. 50 ).

[0208] (3) Average particle size of pre-formed urea

[0209] Measurements were performed at 25°C using dynamic light scattering (photon correlation) and the 50% particle size (volume median particle size, D) calculated based on the scattering intensity, using the dispersed particle size distribution resolved by the CONTIN method. 50 ).

[0210] (4) Kinematic viscosity at 40℃

[0211] The determination was performed according to JIS K2283:2000.

[0212] [Raw materials, etc.]

[0213] In this embodiment, the raw materials used to prepare the grease composition are shown below.

[0214] <Base Oil (A)>

[0215] • "Ingredient (A1)": The full ester of pentaerythritol and 2-hexyldecanoic acid (carbon number: 16, branch position: α, branch number: 1) as shown in the following structural formula (pentaerythritol tetra(2-hexyldecanoate), ISOCARBESTER 1605, manufactured by SASOL).

[0216] [Chemical Formula 1]

[0217]

[0218] • "Ingredients (A2)": Alkyl naphthalene (KR-023, manufactured by King Industries, kinematic viscosity at 40°C: 206 mm) 2 / s)

[0219] The temperature at which the alkylnaphthalene is reduced by 3% by mass during gas chromatographic distillation according to ASTM-D7500 is 486°C.

[0220] • "Base Oil (A')-1": Tris-(2-octyldodecyl)trimethicone ester (tri-(2-octyldodecyl)trimethicone ester) of trimellitic acid (Wako Pure Chemical Industries Co., Ltd.) shown in the following structural formula and 2-octyl-1-dodecanool (Wako Pure Chemical Industries Co., Ltd., carbon number: 20, branch position: α, branch number: 1) shown in the following structural formula.

[0221] [Chemical Formula 2]

[0222]

[0223] • "Base Oil (A')-2": Fluorinated oil (perfluoropolyether (PFPE), manufactured by Solvay, product name: Fomblin M30)

[0224] <Thickener (B)>

[0225] • "Ingredient (B1)": Melamine cyanurate (manufactured by Nissan Chemical Co., Ltd., product name: MC-6000, average particle size: 2μm)

[0226] • "Component (B2)": Pre-formed urea (Urea structure: aromatic diurea, average particle size: 2μm)

[0227] In a 500 mL detachable four-necked flask equipped with a thermometer, stirring blade, and cooling reflux tube, 100 mL of dichloromethane and 10.8 g of 4,4'-diphenylmethane diisocyanate (MDI) were added and stirred at room temperature (25 °C) to dissolve them, preparing an MDI / dichloromethane solution. In a separate 200 mL beaker, 25 mL of dichloromethane and 9.2 g of toluidine were added and stirred at room temperature to dissolve them, preparing a toluidine / dichloromethane solution. The toluidine / dichloromethane solution was then added dropwise to the MDI / dichloromethane solution over 10 minutes to synthesize a diurea compound. After the heating during the addition was complete, the entire reaction was heated to 45 °C using an oil bath to finish the reaction.

[0228] The resulting paste-like diurea compound / dichloromethane was collected and washed three times with 50 mL of dichloromethane while being filtered to remove unreacted raw materials. The resulting solid was dried thoroughly under reduced pressure and confirmed as the target diurea compound by NMR.

[0229] It should be noted that the diurea compound obtained is the one in the above general formula (b2-1), where R... 1 and R 2 Methylphenyl, R 3 It is an aromatic diurea compound with diphenylmethylene.

[0230] The obtained white solid was then pulverized using a mortar and pestle to obtain 8.4 g of pre-prepared urea in fine powder form.

[0231] <Thickener (B')>

[0232] • “Non-prepared urea”: In Comparative Example 1 described later, it is a diurea compound manufactured (synthesized) in the process of preparing a grease composition, using 4,4'-diphenylmethane diisocyanate and toluidine as raw materials.

[0233] In Table 1, it is recorded as "urea (normal method)".

[0234] • "Polytetrafluoroethylene (PTFE)": Manufactured by 3M, TF9207Z

[0235] [Example 1]

[0236] The grease composition of Example 1 was obtained by mixing 32g of alkylnaphthalene (the above component (A2)) and 18g of melamine cyanurate using a three-roll mill.

[0237] [Example 2]

[0238] The grease composition of Example 2 was obtained by mixing 32g of pentaerythritol tetra(2-hexyldecanoate) (the above component (A1)) and 18g of melamine cyanurate using a three-roll mill.

[0239] [Example 3]

[0240] The grease composition of Example 3 was obtained by mixing 35g of alkylnaphthalene (the above component (A2)) and 15g of preformed urea using a three-roll mill.

[0241] [Comparative Example 1]

[0242] In a separable flask, 46 g of alkylnaphthalene (component (A2) above) and 11 g of MDI (4,4'-diphenylmethane diisocyanate) were added and heated to 80 °C to dissolve, thus preparing an MDI / alkylnaphthalene solution. In a separate beaker, 13 g of toluidine and 50 g of alkylnaphthalene (component (A2) above) were added and similarly heated to dissolve, thus preparing a toluidine / alkylnaphthalene solution. The toluidine / alkylnaphthalene solution was then added dropwise to the stirred MDI / alkylnaphthalene solution to initiate a urea reaction. The reaction was brought to a complete temperature of 160 °C while stirring.

[0243] It should be noted that the diurea compound obtained is R in the above general formula (b2-1). 1 and R 2 Methylphenyl, R 3 It is an aromatic diurea compound with diphenylmethylene.

[0244] After the reaction was completed, the mixture was cooled to room temperature and then milled to obtain the grease composition of Comparative Example 1.

[0245] [Comparative Example 2]

[0246] Tri-(2-octyldodecyl)trimethoxytriester (the base oil (A')-1) and melamine cyanurate were blended at the blending ratios in Table 1, and the grease composition of Comparative Example 2 was obtained by the same method as in Example 1.

[0247] [Comparative Example 3]

[0248] Fluorinated oil (the base oil (A')-2) and PTFE were blended in the proportions shown in Table 1, and the grease composition of Comparative Example 3 was obtained by the same method as in Example 1.

[0249] [evaluate]

[0250] The following evaluations were performed on the grease compositions of Examples 1-3 and Comparative Examples 1-3.

[0251] <Evaluation 1: Evaluation of Thermal Stability>

[0252] Thermogravimetric analysis of the grease composition was performed using a thermogravimetric-differential thermal analysis apparatus (TG-DTA apparatus, manufactured by Seiko Instruments, product name: TG / DTA6200).

[0253] Specifically, 0.5 g of a grease composition was filled into an aluminum pan, and the weight change was measured under a nitrogen atmosphere as the temperature was increased from 50 °C to 500 °C at a heating rate of 10 °C / min.

[0254] Then, confirm that the temperature at which the grease composition decreases by 1% by mass is measured.

[0255] In this embodiment, a temperature above 250°C is considered acceptable (A) when the grease composition is reduced by 1% by mass, and a temperature below 250°C is considered unacceptable (B).

[0256] <Evaluation 2: Evaluation of Lubricity>

[0257] Using a high-speed reciprocating dynamic friction testing machine TE77 (manufactured by Phoenix Tribology), a grease composition is introduced between the test plate and the test ball. Under the following conditions, the test ball is moved to conduct the test, and the longitudinal and transverse wear marks of the test ball after the test are measured. The average value of the wear mark diameter is calculated according to the following formula.

[0258] • Test plate material: SUJ2, shape: 58mm (length) × 38mm (width) × 3.9mm (thickness)

[0259] • Test ball material: SUJ2, diameter 10mm

[0260] • Grease supply conditions: Grease bath, grease volume 3mL

[0261] • Load: 200N (300 seconds)

[0262] • Temperature: 100℃

[0263] • Amplitude: 10mm

[0264] • Vibration frequency: 10Hz

[0265] Average wear mark diameter = {(longitudinal wear mark diameter) + (transverse wear mark diameter)} / 2

[0266] The smaller the wear mark diameter, the better the lubricating properties of the grease composition.

[0267] In this embodiment, grease compositions with a wear mark diameter of less than 600 μm are designated as qualified (A), and grease compositions with a wear mark diameter exceeding 600 μm are designated as unqualified (B).

[0268] The results of evaluations 1 to 2 are shown in Table 1.

[0269] [Table 1]

[0270]

[0271] The following information can be obtained from Table 1.

[0272] It can be seen that the grease compositions of Examples 1 to 3 are grease compositions with excellent thermal stability and lubricity.

[0273] In contrast, it can be seen that the grease compositions of Comparative Examples 1 to 3 have poor thermal stability or lubricity.

[0274] Next, the following evaluation was performed on the grease compositions of Examples 1-3 and Comparative Examples 1-3.

[0275] <Evaluation 3: Evaluation of low dust emission>

[0276] The dust generation number of the grease composition was evaluated using a linear guide rail installed in a cleanroom (Class 2 as specified in ISO 14644-1).

[0277] Specifically, 3g of a lubricating grease composition is filled onto the entire guide surface of the linear guide at an acceleration of 1.0mm / s². 2 Stroke: 50 hours of operation under a 200mm stroke condition. Air was collected from the intake port located near the screw at the center of the reciprocating mechanism (suction speed: 3L / min). Every 30 minutes, a particle counter (device name: Gas Particle Counter KC-03B, manufactured by RION Co., Ltd.) was activated for 10 minutes to measure the dust generation. Over a period of 40-50 hours after the frictional state stabilized, the average dust generation rate over 10 minutes was calculated.

[0278] The results of evaluation 3 are shown in Table 2.

[0279] [Table 2]

[0280]

[0281] As shown in Table 2, the grease composition of Example 1 exhibits particularly excellent low dust generation properties.

Claims

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 following components (A1) and the following components (A2). • Component (A1): An ester of a polyol (A11) with 3 to 6 hydroxyl groups and a branched fatty acid (A12) with 14 to 20 carbon atoms; • Composition (A2): 3% by mass of alkyl naphthalene at a temperature of 450°C or higher, obtained by gas chromatographic distillation according to ASTM-D7500. The thickener (B) comprises one or more components selected from the following ingredients (B1) and the following ingredients (B2). • Ingredient (B1): Melamine cyanurate; • Ingredient (B2): Pre-formed urea.

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

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

4. The grease composition according to any one of claims 1 to 3, wherein, Based on the total amount of the grease composition, the total content of the base oil (A) and the thickener (B) is 90% to 100% by mass.

5. The grease composition according to any one of claims 1 to 4, wherein, The base oil (A) contains one or more components selected from the ingredients (A2). The thickener (B) comprises one or more ingredients (B1).

6. The grease composition according to any one of claims 1 to 5, wherein, Based on the total amount of the grease composition, the content of the thickener (B) is 5.0% to 60% by mass.

7. The grease composition according to any one of claims 1 to 6, used in a semiconductor manufacturing apparatus.

8. A method for manufacturing a grease composition, comprising a step (S) of mixing a base oil (A) with a thickener (B). In the process (S), the base oil (A) is formulated with one or more components selected from the following ingredients (A1) and the following ingredients (A2). • Component (A1): An ester of a polyol (A11) with 3 to 6 hydroxyl groups and a branched fatty acid (A12) with 14 to 20 carbon atoms; • Composition (A2): 3% by mass of alkyl naphthalene at a temperature of 450°C or higher, obtained by gas chromatographic distillation according to ASTM-D7500. As the thickener (B), it is combined with one or more components selected from the following ingredients (B1) and the following ingredients (B2). • Ingredient (B1): Melamine cyanurate; • Ingredient (B2): Pre-formed urea.

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