Uncrosslinked fluororubber composition, seal material produced using the same, and method for producing the same

Abstract

To provide an uncrosslinked fluororubber composition, a seal material produced using the same, and a method for producing the same.SOLUTION: An uncrosslinked fluororubber composition contains a rubber component containing fluororubber as a main component, an ionic liquid, an organic resin filler other than perfluoro resin, and dry silica whose surface has been subjected to hydrophobization treatment. The organic resin filler comprises a phenolic resin filler.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an uncrosslinked fluororubber composition, a sealing material produced using the same, and a method for producing the same. [Background technology]

[0002] For example, it is known to use a rubber composition containing a fluororubber and an ionic liquid as a rubber material for a seal. Patent Document 1 discloses a rubber material for a seal containing an uncrosslinked crosslinkable fluororubber, an ionic liquid, and a crosslinking agent. Patent Document 2 discloses the use of a rubber composition containing a partially fluorinated elastomer rubber and an ionic liquid for forming a seal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-85475 [Patent Document 2] Japanese Patent Application Publication No. 2019-116629 Summary of the Invention

[0004] The present invention provides an uncrosslinked fluororubber composition comprising a rubber component mainly composed of a fluororubber, an ionic liquid, an organic resin filler other than a perfluororesin, and dry-process silica having a hydrophobized surface, wherein the organic resin filler contains a phenolic resin filler.

[0005] The present invention is a sealing material formed from a crosslinked fluororubber composition obtained by crosslinking the rubber component of the uncrosslinked fluororubber composition of the present invention.

[0006] The present invention is a method for producing a seal material, which comprises forming the uncrosslinked fluororubber composition of the present invention into a seal material shape and crosslinking the rubber component. DETAILED DESCRIPTION OF THE INVENTION

[0007] The embodiments will be described in detail below.

[0008] The uncrosslinked fluororubber composition according to the embodiment contains a rubber component mainly composed of fluororubber, an ionic liquid, and an organic resin filler other than perfluororesin (hereinafter referred to as "organic resin filler A"). This uncrosslinked fluororubber composition can be used as a rubber material for various rubber products, and is suitable for use as a rubber material for sealing materials such as O-rings, particularly for sealing materials used in semiconductor manufacturing equipment. Here, the term "perfluororesin" as used herein refers to a polymer in which all monovalent atoms bonded to carbon atoms constituting the main chain are fluorine atoms. Examples of such perfluororesins include polytetrafluoroethylene (PTFE) and copolymers of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) (FEP).

[0009] However, in an uncrosslinked fluororubber composition in which an ionic liquid is blended with a fluororubber, the ionic liquid is in a liquid state, and therefore, a crosslinked fluororubber composition obtained by crosslinking the ionic liquid has a problem in that sufficient mechanical properties cannot be obtained.

[0010] In contrast, the uncrosslinked fluororubber composition according to the above embodiment has a fluororubber as the main component of the rubber component, and contains an ionic liquid, but also contains organic resin filler A, which exerts a reinforcing effect, thereby enabling the crosslinked fluororubber composition to obtain sufficient mechanical properties. Furthermore, since the composition contains organic resin filler A, when used as a rubber material for a sealant used in semiconductor manufacturing equipment, dust generation can be suppressed even if the sealant is exposed to a plasma atmosphere.

[0011] The content of the fluororubber in the rubber component is 50% by mass or more, and from the viewpoint of obtaining sufficient mechanical properties of the crosslinked fluororubber composition, it is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass. In addition to the fluororubber, the rubber component may contain nitrile rubber, silicone rubber, ethylene propylene rubber, etc.

[0012] Examples of fluororubbers include copolymers of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) (binary FKM), copolymers of vinylidene fluoride (VDF), hexafluoropropylene (HFP), and tetrafluoroethylene (TFE) (ternary FKM), copolymers of tetrafluoroethylene (TFE) and propylene (Pr) (FEP), copolymers of vinylidene fluoride (VDF), propylene (Pr), and tetrafluoroethylene (TFE), copolymers of ethylene (E) and tetrafluoroethylene (T Examples of suitable fluororubbers include a copolymer of ethylene (E), tetrafluoroethylene (TFE), and perfluoromethyl vinyl ether (PMVE), a copolymer of vinylidene fluoride (VDF), tetrafluoroethylene (TFE), and perfluoromethyl vinyl ether (PMVE), a copolymer of tetrafluoroethylene (TFE), and perfluoromethyl vinyl ether (PMVE) (FFKM), and a copolymer of vinylidene fluoride (VDF) and perfluoromethyl vinyl ether (PMVE). The fluororubber preferably contains one or more of these. From the viewpoint of obtaining sufficient mechanical properties of the crosslinked fluororubber composition, it is more preferable to contain a vinylidene fluoride-based fluororubber such as a binary FKM or ternary FKM. Furthermore, from the viewpoint of obtaining excellent plasma resistance when the uncrosslinked fluororubber composition is used as a rubber material for a sealant used in semiconductor manufacturing equipment, even if the sealant is exposed to a plasma atmosphere, it is even more preferable to contain a ternary FKM.

[0013] In this application, the term "ionic liquid" refers to a salt composed of cations and anions, and is a liquid with a melting point of 100°C or lower.

[0014] Examples of cations of the ionic liquid include imidazolium-based cations, pyridinium-based cations, pyrrolidinium-based cations, ammonium-based cations, etc. Examples of imidazolium-based cations include 1-ethyl-3-methylimidazolium cation, 1-methyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-hexyl-3-methylimidazolium cation, 1-octyl-3-methylimidazolium cation, 1-methyl-2,3-dimethylimidazolium cation, 1-butyl-2,3-dimethylimidazolium cation, 1-hexyl-2,3-dimethylimidazolium cation, 1-octyl-2,3-dimethylimidazolium cation, etc. Examples of pyridinium cations include 1-octyl-4-methyl-pyridinium cation, 1-methyl-pyridinium cation, 1-butyl-pyridinium cation, and 1-hexyl-pyridinium cation. Examples of pyrrolidinium cations include 1-ethyl-1-methylpyrrolidinium cation. Examples of ammonium cations include tributylmethylammonium cation. The cations of the ionic liquid preferably include one or more of these.

[0015] Examples of anions of the ionic liquid include bisfluorosulfonylimide anions, fluorinated sulfonic acid anions, fluorinated carboxylic acid anions, thiocyanate anions, dicyanamide anions, and tetracyanoborate anions. Examples of bisfluorosulfonylimide anions include bisfluorosulfonylimide anions, bistrifluoromethanesulfonylimide anions, and bistrifluorobutanesulfonylimide anions. Examples of fluorinated sulfonic acid anions include tetrafluoroborate anions, hexafluoroborate anions, and trifluoromethanesulfonate anions. Examples of fluorinated carboxylic acid anions include trifluoroacetic acid anions. The anions of the ionic liquid preferably include one or more of these anions. From the viewpoint of obtaining sufficient mechanical properties of the crosslinked fluororubber composition, it is more preferable to include an anion having a fluorine atom, such as a bisfluorosulfonylimide anion, a fluorinated sulfonic acid anion, or a fluorinated carboxylic acid anion.

[0016] The ionic liquid preferably contains a combination of one or more of these cations and one or more of these anions, and from the viewpoint of obtaining sufficient mechanical properties of the crosslinked fluororubber composition, it more preferably contains 1-butyl-3-methylimidazolium bistrifluoromethanesulfonylimide, 1-ethyl-1-methylpyrrolidinium bistrifluoromethanesulfonylimide, or tributylmethylammonium bistrifluoromethanesulfonylimide.

[0017] The content P of the ionic liquid in the uncrosslinked fluororubber composition according to the embodiment is preferably 0.1 parts by mass or more and 10 parts by mass or less, more preferably 0.2 parts by mass or more and 5 parts by mass or less, and even more preferably 0.5 parts by mass or more and 1.5 parts by mass or less, per 100 parts by mass of the rubber component, from the viewpoint of obtaining sufficient mechanical properties of the crosslinked fluororubber composition.

[0018] Examples of the organic resin filler A include phenolic resin fillers, polyether ether ketone (PEEK) resin fillers, and fluororesin fillers other than perfluororesins such as polyvinylidene fluoride (PVDF) resin fillers. The organic resin filler A preferably contains one or more of these.

[0019] The organic resin filler A preferably contains a phenolic resin filler from the viewpoints of obtaining sufficient mechanical properties of the crosslinked fluororubber composition and promoting crosslinking of the uncrosslinked fluororubber composition. From the same viewpoint, the phenolic resin is preferably neither a resol type nor a novolac type. From the same viewpoint, the phenolic resin preferably has a methylol group in the molecule.

[0020] From the viewpoint of being able to suppress dust generation even when the sealing material is exposed to a plasma atmosphere when the uncrosslinked fluororubber composition is used as a rubber material for a sealing material used in semiconductor manufacturing equipment, the organic resin filler A preferably contains a fluororesin filler other than perfluororesin, and more preferably contains a PVDF resin filler.

[0021] From the viewpoint of obtaining sufficient mechanical properties of the crosslinked fluororubber composition, the average particle size of the organic resin filler A is preferably 0.5 μm or more and 20 μm or less, more preferably 1 μm or more and 10 μm or less, and even more preferably 1.2 μm or more and 2 μm or less.

[0022] In order to obtain sufficient mechanical properties of the crosslinked fluororubber composition when a filler other than the organic resin filler A is contained, the content Q of the organic resin filler A in the uncrosslinked fluororubber composition according to the embodiment is preferably 0.5 to 30 parts by mass, more preferably 1 to 20 parts by mass, and even more preferably 1 to 10 parts by mass, per 100 parts by mass of the rubber component. When no filler other than the organic resin filler A is contained, the content Q is preferably 1 to 50 parts by mass, more preferably 2 to 40 parts by mass, and even more preferably 3 to 30 parts by mass, per 100 parts by mass of the rubber component.

[0023] When the organic resin filler A contains a fluororesin filler other than perfluororesin, the content of the fluororesin filler other than perfluororesin in the uncrosslinked fluororubber composition according to the embodiment is preferably 1 part by mass or more and 25 parts by mass or less, more preferably 2 parts by mass or more and 10 parts by mass or less, and even more preferably 3 parts by mass or more and 7 parts by mass or less, per 100 parts by mass of the rubber component, from the viewpoint that when the uncrosslinked fluororubber composition is used as a rubber material for a seal material used in semiconductor manufacturing equipment, dust generation can be suppressed even when the seal material is exposed to a plasma atmosphere.

[0024] When a filler other than the organic resin filler A is contained in the uncrosslinked fluororubber composition according to the embodiment, the content Q of the organic resin filler A is preferably equal to or greater than the content P of the ionic liquid, from the viewpoint of obtaining sufficient mechanical properties of the crosslinked fluororubber composition. In this case, the ratio (Q / P) of the content Q of the organic resin filler A to the content P of the ionic liquid in the uncrosslinked fluororubber composition is preferably 1 or more and 15 or less, more preferably 1.5 or more and 10 or less, from the same viewpoint. When no filler other than the organic resin filler A is contained, the content Q of the organic resin filler A is preferably greater than the content P of the ionic liquid, from the same viewpoint. In this case, the ratio (Q / P) of the content Q of the organic resin filler A to the content P of the ionic liquid in the uncrosslinked fluororubber composition is preferably 5 or more and 40 or less, more preferably 10 or more and 30 or less, from the same viewpoint.

[0025] The uncrosslinked fluororubber composition according to the embodiment preferably further contains silica as a filler, from the viewpoint of obtaining sufficient mechanical properties of the crosslinked fluororubber composition. Examples of silica include dry-process silica such as fumed silica and wet-process silica such as precipitated silica. The silica may also be surface-hydrophobized with organochlorosilane, organoalkoxysilane, hexaorganodisilazane, organosiloxane oligomer, or the like. The silica preferably contains one or more of these. From the same viewpoint, it is more preferable to contain dry-process silica whose surface has been hydrophobized with organochlorosilane, and even more preferable to contain fumed silica whose surface has been hydrophobized with dimethyldichlorosilane.

[0026] When silica is contained as a filler in the uncrosslinked fluororubber composition according to the embodiment, the mechanical properties of the crosslinked fluororubber composition can be effectively improved even with a small silica content. Furthermore, when the uncrosslinked fluororubber composition is used as a rubber material for a sealant used in semiconductor manufacturing equipment, the silica does not generate dust even when the sealant is exposed to a plasma atmosphere. On the other hand, when silica is used in combination with an ionic liquid, there is a risk that crosslinking of the uncrosslinked fluororubber composition may be inhibited. However, if a phenolic resin filler is used as the organic resin filler A, crosslinking of the uncrosslinked fluororubber composition can be promoted as described above, thereby suppressing the inhibition of crosslinking. For this reason, when the uncrosslinked fluororubber composition contains silica as a filler, it is preferable that the organic resin filler A also contains a phenolic resin filler.

[0027] In the uncrosslinked fluororubber composition according to the embodiment, when the organic resin filler A contains a fluororesin filler other than perfluororesin, it is preferable that the uncrosslinked fluororubber composition does not contain silica, since sufficiently high mechanical properties of the crosslinked fluororubber composition can be obtained. However, even in this case, the uncrosslinked fluororubber composition may contain silica.

[0028] The content R of silica in the uncrosslinked fluororubber composition according to the embodiment is preferably 1 part by mass or more and 20 parts by mass or less, more preferably 5 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of the rubber component, from the viewpoint of obtaining sufficient mechanical properties of the crosslinked fluororubber composition.

[0029] From the viewpoint of obtaining sufficient mechanical properties of the crosslinked fluororubber composition, the silica content R in the uncrosslinked fluororubber composition according to the embodiment is preferably greater than the ionic liquid content P. From the same viewpoint, the ratio (R / P) of the silica content R to the ionic liquid content P in the uncrosslinked fluororubber composition is preferably 3 or more and 20 or less, more preferably 5 or more and 15 or less.

[0030] From the viewpoint of obtaining sufficient mechanical properties of the crosslinked fluororubber composition, the silica content R in the uncrosslinked fluororubber composition according to the embodiment is preferably equal to or greater than the content Q of the organic resin filler A. From the same viewpoint, the ratio (R / Q) of the silica content R to the organic resin filler A content Q in the uncrosslinked fluororubber composition is preferably 1 or more and 15 or less, more preferably 1 or more and 3 or less.

[0031] The uncrosslinked fluororubber composition according to the embodiment may further contain a crosslinking agent. Examples of the crosslinking agent include organic peroxides, polyols, polyamines, triazines, etc. Among these, the crosslinking agent preferably contains an organic peroxide, from the viewpoint of obtaining sufficient mechanical properties of the crosslinked fluororubber composition.

[0032] Examples of organic peroxides include dialkyl peroxides such as dicumyl peroxide, 1,3-di(t-butylperoxy)diisopropylbenzene, 1,4-di(t-butylperoxy)diisopropylbenzene, t-butylcumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane-3; peroxyketals such as 1,1-di(t-hexylperoxy)cyclohexane, 1,1-di(t-butylperoxy)cyclohexane, and n-butyl-4,4-di(t-butylperoxy)valerate; and peroxyesters such as 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-hexylperoxybenzoate, and t-butylperoxybenzoate. The organic peroxide preferably contains one or more of these, and from the viewpoint of obtaining sufficient mechanical properties of the crosslinked fluororubber composition, it is even more preferable that it contains 2,5-dimethyl-2,5-di(t-butylperoxy)hexane.

[0033] The content X of the organic peroxide in the crosslinking agent in the uncrosslinked fluororubber composition according to the embodiment is preferably 0.5 parts by mass or more and 5 parts by mass or less, more preferably 0.5 parts by mass or more and 4 parts by mass or less, and even more preferably 1 part by mass or more and 2 parts by mass or less, per 100 parts by mass of the rubber component, from the viewpoint of obtaining sufficient mechanical properties of the crosslinked fluororubber composition.

[0034] When the uncrosslinked fluororubber composition according to the present invention contains an organic peroxide crosslinking agent, it may further contain a crosslinking aid. Examples of crosslinking aids include allyl crosslinking aids such as triallyl isocyanurate, diallyl fumarate, diallyl phthalate, tetraallyloxyethane, and trimethallyl isocyanurate; maleimide crosslinking aids such as N,N'-m-phenylene bismaleimide, maleimide, and phenylmaleimide; methacrylate crosslinking aids such as trimethylolpropane trimethacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and polyethylene glycol dimethacrylate; and 1,2-polybutadiene. The crosslinking aid preferably contains one or more of these. From the viewpoint of obtaining sufficient mechanical properties of the crosslinked fluororubber composition, it is more preferable to contain an allyl crosslinking aid, and even more preferable to contain triallyl isocyanurate.

[0035] The content Y of the cross-linking aid in the uncross-linked fluororubber composition according to the embodiment is preferably 1 part by mass or more and 10 parts by mass or less, more preferably 2 parts by mass or more and 8 parts by mass or less, and even more preferably 2 parts by mass or more and 6 parts by mass or less, per 100 parts by mass of the rubber component, from the viewpoint of obtaining sufficient mechanical properties of the cross-linked fluororubber composition.

[0036] From the viewpoint of obtaining sufficient mechanical properties of the crosslinked fluororubber composition, the content Y of the crosslinking aid in the uncrosslinked fluororubber composition according to the embodiment is preferably larger than the content X of the organic peroxide. From the same viewpoint, the ratio (Y / X) of the content Y of the crosslinking aid to the content X of the organic peroxide in the uncrosslinked fluororubber composition is preferably 1 or more and 10 or less, more preferably 1.5 or more and 4 or less.

[0037] The uncrosslinked fluororubber composition according to the embodiment may contain other rubber compounding ingredients as necessary. However, when used as a rubber material for a sealant used in a semiconductor manufacturing device, from the viewpoint of preventing dust generation when the sealant is exposed to a plasma atmosphere, the uncrosslinked fluororubber composition preferably does not contain a conductive filler such as carbon black, conductive carbon, or metal oxide.

[0038] The uncrosslinked fluororubber composition according to the embodiment can be obtained by feeding a rubber component containing fluororubber as a main component into a rubber kneader such as an open roll or a Banbury mixer, masticating the mixture, and then adding various rubber compounding agents including the ionic liquid and the organic resin filler A and kneading the mixture.

[0039] By using the uncrosslinked fluororubber composition according to the embodiment having the above-described configuration and crosslinking the rubber component, it is possible to produce a sealing material used in, for example, semiconductor manufacturing equipment.

[0040] In a sealing material produced using the uncrosslinked fluororubber composition according to the embodiment, the hardness Hs of the crosslinked fluororubber composition forming the sealing material is preferably A50 or more and A95 or less. This hardness Hs is measured based on JIS K6253-3:2012 using a type A durometer as the instantaneous value when a pressure plate is brought into contact with a test piece.

[0041] The cross-linked fluororubber composition forming the sealing material preferably has a tensile strength Tb of 10 MPa or more. The elongation Eb is preferably 100% or more. The tensile stress S100 at 100% elongation is preferably 1 MPa or more and 10 MPa or less. The tensile strength Tb, elongation Eb, and tensile stress S100 at 100% elongation are measured using a dumbbell-shaped No. 3 test piece in accordance with JIS K6251:2017.

[0042] The compression set of the crosslinked fluororubber composition forming the sealing material is preferably 40% or less, more preferably 35% or less, and even more preferably 30% or less. This compression set is measured based on JIS K6262:2013 at a test temperature of 200°C for a test time of 72 hours using a sample cut in half of an AS-214 O-ring.

[0043] The volume resistivity of the crosslinked fluororubber composition forming the sealing material is preferably 1.0×10 13 Ω·cm or less, preferably 1.0×10 12 The volume resistivity is Ω·cm or less. This volume resistivity is measured using the double ring electrode method at an applied voltage of 500V based on JIS K6271-1:2015.

[0044] The mass loss rate (plasma resistance) of the crosslinked fluororubber composition forming the sealing material due to plasma irradiation is preferably 3% or less, more preferably 2.5% or less. This mass loss rate is calculated based on the following formula from the masses before and after exposing the crosslinked fluororubber composition to plasma generated for 30 minutes using a mixed gas of O2 gas and CF4 gas in a volume ratio of 50:1 under conditions of a frequency of 2.45 GHz, a pressure of 100 Pa, and an output of 1500 W. Mass reduction rate (%) = {(mass before exposure - mass after exposure) / mass before exposure} × 100

[0045] Next, an example of a method for producing a sealing material in which the uncrosslinked fluororubber composition according to the embodiment is formed into a sealing material shape and the rubber component is crosslinked will be described.

[0046] First, a predetermined amount of the uncrosslinked fluororubber composition according to the embodiment is taken and filled into a cavity in the shape of a sealing material formed in a mold, and then the mold is clamped to form the uncrosslinked fluororubber composition into the shape of the sealing material.

[0047] Next, the mold is sandwiched between hot plates, and the uncrosslinked fluororubber composition formed into the shape of a sealing material is press-molded by heating and pressurizing it at a predetermined temperature (e.g., 160°C to 170°C) and a predetermined pressure (e.g., 10 MPa to 20 MPa) for a predetermined time (e.g., 5 minutes to 30 minutes), thereby primary crosslinking the rubber component and obtaining a primary crosslinked product (primary crosslinking step).

[0048] Then, after the primary crosslinked product is removed from the mold, it is placed in an oven and annealed by heating it at a higher temperature (e.g., 190°C to 210°C) than in the primary crosslinking step for a longer period of time (e.g., 3 to 5 hours) to secondarily crosslink the rubber component, thereby obtaining a secondary crosslinked product (secondary crosslinking step).

[0049] The method for producing a sealing material may comprise a primary crosslinking step and a secondary crosslinking step, and the secondary crosslinked product may be used as the sealing material as is. However, from the viewpoint of obtaining sufficient mechanical properties of the crosslinked fluororubber composition, the method for producing a sealing material may further comprise, in addition to the primary crosslinking step and the secondary crosslinking step, a radiation crosslinking step in which radiation is irradiated to crosslink the rubber component. In this case, from the same viewpoint, it is preferable that the radiation crosslinking step involves irradiating the secondary crosslinked product with radiation, that is, that the radiation crosslinking step is performed after the secondary crosslinking step. Here, examples of radiation include α-rays, β-rays, γ-rays, electron beams, and ions. Of these, electron beams or γ-rays are preferred as the radiation. The radiation exposure dose is, for example, 10 kGy or more and 100 kGy or less. [Example]

[0050] (Uncrosslinked fluororubber composition) The following uncrosslinked fluororubber compositions were prepared in Examples 1 to 4, Reference Examples 1 to 7, and Comparative Examples 1 to 5. The constitutions of each are also shown in Table 1.

[0051] Example 1 Example 1 was an uncrosslinked fluororubber composition prepared by blending 100 parts by mass of a ternary FKM (Technoflon P959, manufactured by Solvay Specialty Polymers Japan) as the rubber component with 1 part by mass of the ionic liquid 1-butyl-3-methylimidazolium bistrifluoromethanesulfonylimide (BMIN111, manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.), 1 part by mass of a phenolic resin filler (Bellpearl R100, manufactured by Air Water Bellpearl, average particle size 1.5 μm), 10 parts by mass of fumed silica hydrophobized with dimethyldichlorosilane (Aerosil R976S, manufactured by Nippon Aerosil Co., Ltd.), 1.5 parts by mass of an organic peroxide 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (Perhexa 25B, manufactured by NOF Corporation), and 4 parts by mass of a crosslinking coagent triallyl isocyanurate (TAIC, manufactured by Mitsubishi Chemical Corporation).

[0052] <Example 2> An uncrosslinked fluororubber composition was prepared as Example 2 in the same manner as in Example 1, except that the compounding amount of the phenol resin filler was 5 parts by mass per 100 parts by mass of the rubber component.

[0053] Example 3 An uncrosslinked fluororubber composition was prepared in the same manner as in Example 2, except that 1-ethyl-1-methylpyrrolidinium bistrifluoromethanesulfonylimide (P12N111, manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.) was used as the ionic liquid.

[0054] Example 4 Example 4 was an uncrosslinked fluororubber composition prepared in the same manner as in Example 2, except that tributylmethylammonium bistrifluoromethanesulfonylimide (FC-4400, manufactured by 3M) was used as the ionic liquid.

[0055] <Reference example 1> An uncrosslinked fluororubber composition was prepared in the same manner as in Example 2, except that non-hydrophobically treated hydrophilic fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) was used as Reference Example 1.

[0056] <Reference example 2> An uncrosslinked fluororubber composition was prepared in the same manner as in Example 1, except that no fumed silica was added and the amount of phenolic resin filler added was 25 parts by mass per 100 parts by mass of the rubber component, and this was designated Reference Example 2.

[0057] <Reference example 3> An uncrosslinked fluororubber composition was prepared in the same manner as in Example 1, except that the phenolic resin filler and fumed silica were not blended, and 25 parts by mass of a PVDF resin filler (Kynar MG15 manufactured by Arkema, average particle size 10 μm) was blended per 100 parts by mass of the rubber component. This was designated Reference Example 3.

[0058] <Reference example 4> Reference Example 4 was an uncrosslinked fluororubber composition prepared in the same manner as in Example 1, except that the phenolic resin filler and fumed silica were not blended, and 25 parts by mass of a PEEK resin filler (Vestakeep 2000UFP10 manufactured by Daicel-Evonik Co., Ltd., average particle size 10 μm) was blended per 100 parts by mass of the rubber component.

[0059] <Reference example 5> An uncrosslinked fluororubber composition was prepared in the same manner as in Example 1, except that no fumed silica was added and the amount of phenolic resin filler added was 5 parts by mass per 100 parts by mass of the rubber component, and this was designated Reference Example 5.

[0060] <Reference example 6> Reference Example 6 was an uncrosslinked fluororubber composition prepared in the same manner as Reference Example 5, except that no phenolic resin filler was added and 5 parts by mass of PVDF resin filler was added per 100 parts by mass of the rubber component.

[0061] <Reference example 7> Reference Example 7 was an uncrosslinked fluororubber composition prepared in the same manner as Reference Example 5, except that no phenolic resin filler was added and 5 parts by mass of PEEK resin filler was added per 100 parts by mass of the rubber component.

[0062] <Comparative Example 1> Comparative Example 1 was an uncrosslinked fluororubber composition prepared in the same manner as in Example 1 except that the phenolic resin filler and fumed silica were not compounded.

[0063] <Comparative Example 2> An uncrosslinked fluororubber composition was prepared as Comparative Example 2 in the same manner as in Example 1, except that the ionic liquid and phenolic resin filler were not blended.

[0064] <Comparative Example 3> Comparative Example 3 was an uncrosslinked fluororubber composition prepared in the same manner as in Example 1, except that the phenolic resin filler and fumed silica were not blended, and 25 parts by mass of a PTFE resin filler (Lubron L-5, manufactured by Daikin Industries, Ltd., average particle size 5 to 7 μm) was blended per 100 parts by mass of the rubber component.

[0065] <Comparative Example 4> Comparative Example 4 was an uncrosslinked fluororubber composition prepared in the same manner as in Example 1, except that no phenolic resin filler or fumed silica was blended, and 25 parts by mass of carbon black (Thermax N990, manufactured by Cancarb) was blended per 100 parts by mass of the rubber component.

[0066] <Comparative Example 5> Comparative Example 5 was an uncrosslinked fluororubber composition prepared in the same manner as in Reference Example 5, except that no phenolic resin filler was added and 5 parts by mass of PTFE resin filler was added per 100 parts by mass of the rubber component.

[0067] [Table 1]

[0068] An uncrosslinked fluororubber composition similar to that of Example 1 except that no phenolic resin filler was blended, and an uncrosslinked fluororubber composition similar to that of Example 1 except that no phenolic resin filler was blended and the blending amount of the ionic liquid was 0.1 parts by mass per 100 parts by mass of the rubber component were also prepared, but no crosslinked products were obtained from these compositions.

[0069] (Test method and results) The uncrosslinked fluororubber composition was crosslinked to prepare a test piece of the crosslinked fluororubber composition, and the following tests were carried out using the test piece. The results are shown in Table 1.

[0070] <Hardness> A 6 mm thick sheet-shaped test piece of a crosslinked fluororubber composition was prepared from each of the uncrosslinked fluororubber compositions of Examples 1 to 4, Reference Examples 1 to 7, and Comparative Examples 1 to 5, and the hardness Hs was measured as the instantaneous value when a pressure plate was brought into contact with the test piece using a Type A durometer in accordance with JIS K6253-3:2012.

[0071] <Tensile properties> Dumbbell-shaped No. 3 test pieces of cross-linked fluororubber compositions were prepared from the uncross-linked fluororubber compositions of each of Examples 1 to 4, Reference Examples 1 to 7, and Comparative Examples 1 to 5, and the tensile strength Tb, elongation Eb, and tensile stress S100 at 100% elongation were measured in accordance with JIS K6251:2017.

[0072] <Compression set> An AS-214 O-ring formed of a crosslinked fluororubber composition was prepared from the uncrosslinked fluororubber composition of each of Examples 1 to 4, Reference Examples 1 to 7, and Comparative Examples 1 to 5, and each was cut in half to serve as a sample. The compression set CS was measured in accordance with JIS K6262:2013 at a test temperature of 200°C for a test time of 72 hours.

[0073] <Volume resistivity> Test pieces (100 × 100 × t2 mm sheets) of crosslinked fluororubber compositions were prepared from the uncrosslinked fluororubber compositions of Examples 1 to 4, Reference Examples 1 to 7, and Comparative Examples 1 to 5, and the volume resistivity was measured by the double ring electrode method at an applied voltage of 500 V in accordance with JIS K6271-1:2015.

[0074] <Plasma resistance> AS-214 O-rings formed from the crosslinked fluororubber compositions of Examples 1 to 4, Reference Examples 1 to 7, and Comparative Examples 1 to 5 were prepared as samples. These samples were placed in a plasma exposure device (manufactured by Shinko Seiki Co., Ltd.) and exposed for 30 minutes to plasma generated using a 50:1 volumetric mixture of O2 gas and CF4 gas at a frequency of 2.45 GHz, a pressure of 100 Pa, and an output of 1500 W. The presence or absence of dust generation was visually confirmed. The mass loss rate was calculated from the masses before and after exposure using the following formula: Mass reduction rate (%) = {(mass before exposure - mass after exposure) / mass before exposure} × 100

[0075] Among Examples 1 to 4, Reference Examples 1 to 7, and Comparative Examples 1 to 5, Reference Example 6, which blended 5 parts by mass of PVDF resin filler with 100 parts by mass of three-dimensional FKM as the rubber component, showed the smallest mass loss rate and excellent plasma resistance. [Industrial Applicability]

[0076] INDUSTRIAL APPLICABILITY The present invention is useful in the technical fields of an uncrosslinked fluororubber composition, a sealing material produced using the same, and a method for producing the same.

Claims

1. The rubber composition contains a rubber component mainly composed of fluororubber, an ionic liquid, an organic resin filler other than perfluororesin, and dry-process silica whose surface has been hydrophobized, The uncrosslinked fluororubber composition, wherein the organic resin filler contains a phenolic resin filler.

2. The uncrosslinked fluororubber composition according to claim 1, The uncrosslinked fluororubber composition, wherein the fluororubber contains a vinylidene fluoride fluororubber.

3. The uncrosslinked fluororubber composition according to claim 2, The fluororubber composition contains a copolymer of vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene.

4. The uncrosslinked fluororubber composition according to claim 1, An uncrosslinked fluororubber composition, wherein the anion of the ionic liquid has a fluorine atom.

5. The uncrosslinked fluororubber composition according to claim 1, The uncrosslinked fluororubber composition, wherein the cation of the ionic liquid contains one or more of imidazolium-based cations, pyridinium-based cations, pyrrolidinium-based cations, and ammonium-based cations.

6. The uncrosslinked fluororubber composition according to claim 1, The uncrosslinked fluororubber composition, wherein the organic resin filler has an average particle size of 0.5 μm or more and 20 μm or less.

7. The uncrosslinked fluororubber composition according to claim 1, The uncrosslinked fluororubber composition is one in which the phenolic resin of the phenolic resin filler is neither a resol type nor a novolac type.

8. The uncrosslinked fluororubber composition according to claim 1, The uncrosslinked fluororubber composition comprises a phenolic resin of the phenolic resin filler having a methylol group in the molecule.

9. The uncrosslinked fluororubber composition according to claim 1, The uncrosslinked fluororubber composition has an organic resin filler content of 0.5 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the rubber component.

10. The uncrosslinked fluororubber composition according to claim 1, The surface of the dry-process silica is subjected to hydrophobic treatment with an organochlorosilane.

11. The uncrosslinked fluororubber composition according to claim 1, The uncrosslinked fluororubber composition has a dry process silica content of 1 part by mass or more and 20 parts by mass or less per 100 parts by mass of the rubber component.

12. The uncrosslinked fluororubber composition according to claim 1, The uncrosslinked fluororubber composition has a content of the dry-process silica greater than a content of the ionic liquid.

13. The uncrosslinked fluororubber composition according to claim 12, The uncrosslinked fluororubber composition has a mass ratio of the content of the dry process silica to the content of the ionic liquid of 3 or more and 20 or less.

14. The uncrosslinked fluororubber composition according to claim 1, The uncrosslinked fluororubber composition has a content of the dry process silica equal to or greater than a content of the organic resin filler.

15. The uncrosslinked fluororubber composition according to claim 14, The uncrosslinked fluororubber composition has a mass ratio of the content of the dry process silica to the content of the organic resin filler of 1 or more and 15 or less.

16. The uncrosslinked fluororubber composition according to claim 1, The uncrosslinked fluororubber composition further contains an organic peroxide as a crosslinking agent.

17. The uncrosslinked fluororubber composition according to claim 16, The uncrosslinked fluororubber composition further contains a crosslinking aid.

18. A sealing material formed from a crosslinked fluororubber composition obtained by crosslinking the rubber component of the uncrosslinked fluororubber composition according to any one of claims 1 to 17.

19. The sealing material according to claim 18, The crosslinked fluororubber composition has a compression set of 40% or less.

20. The sealing material according to claim 18, The crosslinked fluororubber composition is prepared by mixing the crosslinked fluororubber composition with O ２ Gas and CF ４ A sealing material that exhibits a mass loss rate of 3% or less when exposed for 30 minutes to plasma generated using a mixed gas in a volume ratio of 50:1 at a frequency of 2.45 GHz, a pressure of 100 Pa, and an output of 1500 W, as calculated from the mass before and after exposure.

21. The sealing material according to claim 18, A sealing material used in semiconductor manufacturing equipment.

22. A method for producing a seal material, comprising forming the uncrosslinked fluororubber composition according to any one of claims 1 to 17 into a seal material shape and crosslinking the rubber component.

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