sealing material

Abstract

To provide a sealant with excellent plasma resistance and excellent sealability at low temperatures.SOLUTION: A sealant is formed through crosslinking of an uncrosslinked rubber composition containing an ethylene-α-olefin-diene rubber and a compound having a perfluoropolyether skeleton. The ethylene-α-olefin-diene rubber includes an ethylene-butene-diene terpolymer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a sealing material. [Background technology]

[0002] Seals made of fluororubber are widely known. For example, Patent Document 1 discloses a seal formed by crosslinking an uncrosslinked rubber composition containing a crosslinkable fluororubber and a reactive fluorine-based compound. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5189728 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a sealing material that has excellent plasma resistance and sealing properties at low temperatures. [Means for solving the problem]

[0005] The present invention provides a sealing material formed by crosslinking an uncrosslinked rubber composition containing an ethylene-α-olefin-diene rubber and a compound having a perfluoropolyether skeleton, wherein the ethylene-α-olefin-diene rubber contains an ethylene-butene-diene terpolymer. [Effects of the Invention]

[0006] According to the present invention, an uncrosslinked rubber composition containing an ethylene-alpha-olefin-diene rubber and a compound having a perfluoropolyether skeleton is crosslinked, thereby providing excellent plasma resistance and sealing properties at low temperatures. DETAILED DESCRIPTION OF THE INVENTION

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

[0008] The sealing material according to the embodiment is an O-ring used in an apparatus that uses plasma, such as a semiconductor etching apparatus or a plasma CVD apparatus.

[0009] The sealing material according to the embodiment is a crosslinked uncrosslinked rubber composition containing an ethylene-alpha-olefin-diene rubber (hereinafter referred to as "Component A") and a compound having a perfluoropolyether skeleton (hereinafter referred to as "Component B").

[0010] According to the sealing material of the embodiment, since the uncrosslinked rubber composition containing the A component and the B component is crosslinked, it is possible to obtain excellent plasma resistance and sealing properties at low temperatures.

[0011] Examples of component A include ethylene-propylene-diene terpolymer (hereinafter referred to as "EPDM"), ethylene-butene-diene terpolymer (hereinafter referred to as "EBT"), etc. Component A preferably contains one or both of these, and more preferably contains at least EBT from the viewpoint of obtaining excellent plasma resistance and low-temperature sealing properties.

[0012] Examples of the α-olefin component in Component A include propylene and butene. From the viewpoint of obtaining excellent plasma resistance and sealing properties at low temperatures, the α-olefin component is preferably butene. Examples of the diene component in Component A include ethylidene norbornene, vinyl norbornene, dicyclopentadiene, 1,4-hexadiene, etc. From the same viewpoint as above, the diene component is preferably ethylidene norbornene.

[0013] From the viewpoint of obtaining excellent plasma resistance and low-temperature sealing properties, the ethylene content of Component A is preferably 40% by mass or more and 70% by mass or less, more preferably 55% by mass or more and 60% by mass or less when the α-olefin component is propylene, and more preferably 48% by mass or more and 53% by mass or less when the α-olefin component is butene. This ethylene content is measured in accordance with ASTM D 3900.

[0014] When the diene component is ethylidene norbornene, the ENB content (diene content) in Component A is preferably 3% by mass or more and 10% by mass or less, from the viewpoint of obtaining excellent plasma resistance and low-temperature sealing properties, more preferably 3.5% by mass or more and 5.5% by mass or less, when the α-olefin component is propylene, and more preferably 6.5% by mass or more and 7.5% by mass or less, when the α-olefin component is butene. This ENB content is measured according to ASTM D 6047.

[0015] The uncrosslinked rubber composition may contain rubber components other than component A, so long as component A is the main rubber component. Examples of rubber components other than component A include ethylene propylene copolymer rubber (EPR), fluororubber, silicone rubber, chloroprene rubber, and hydrogenated nitrile rubber.

[0016] From the viewpoint of obtaining excellent plasma resistance and sealing properties at low temperatures, component B is preferably a liquid material of a compound having a perfluoropolyether skeleton uniformly mixed in component A, and more preferably a one-component material.

[0017] Component B also functions as a co-crosslinking agent that crosslinks component A through addition polymerization, and from the viewpoint of obtaining excellent plasma resistance and low-temperature sealing properties, it is preferable that component B has multiple alkenyl groups in the molecule. Examples of alkenyl groups include vinyl groups, allyl groups, butenyl groups, pentenyl groups, hexenyl groups, and heptenyl groups. Of these, vinyl groups are preferred as the alkenyl group from the same viewpoint as above. The multiple alkenyl groups in the molecule may be the same or different.

[0018] From the viewpoint of obtaining excellent plasma resistance and sealing properties at low temperatures, the content of component B in the uncrosslinked rubber composition is preferably 5 parts by mass or more and 40 parts by mass or less, more preferably 15 parts by mass or more and 35 parts by mass or less, and even more preferably 20 parts by mass or more and 30 parts by mass or less, per 100 parts by mass of component A.

[0019] Commercially available materials for component B include, for example, SIFEL manufactured by Shin-Etsu Chemical Co., Ltd., and the SIFEL 3000 series is particularly preferred.

[0020] The uncrosslinked rubber composition may contain a powder filler dispersed in Component A. Examples of powder fillers include PVdF resin filler, carbon black, silica, silicon carbide, boron carbide, silicon nitride, and boron nitride. The powder filler preferably contains one or more of these, more preferably one or more of PVdF resin filler, carbon black, and silica, and even more preferably contains a PVdF resin filler from the viewpoint of suppressing particle generation even when used in a plasma atmosphere. Commercially available PVdF resin fillers include, for example, the Kynar series manufactured by Arkema.

[0021] Examples of carbon black include MT (N990), FEF (N550), GPF (N600), FT (N880), etc. Of these, the carbon black preferably includes MT.

[0022] Examples of silica include dry-process silica such as fumed silica and wet-process silica such as precipitated silica. The silica may have its surface hydrophobized with organochlorosilane, organoalkoxysilane, hexaorganodisilazane, organosiloxane oligomer, or the like. Of these, the silica preferably contains dry-process silica, more preferably dry-process silica whose surface has been hydrophobized with organochlorosilane, and even more preferably fumed silica whose surface has been hydrophobized with dimethyldichlorosilane.

[0023] From the viewpoint of obtaining excellent mechanical properties after crosslinking, the average particle size of the powder filler is preferably 0.01 μm or more and 20 μm or less, more preferably 0.1 μm or more and 18 μm or less, even more preferably 5 μm or more and 15 μm or less, and still more preferably 8 μm or more and 12 μm or less.

[0024] From the viewpoint of obtaining excellent mechanical properties after crosslinking, the content of the powder filler in the uncrosslinked rubber composition is preferably 1 part by mass or more and 30 parts by mass or less, preferably 5 parts by mass or more and 15 parts by mass or less, and more preferably 8 parts by mass or more and 12 parts by mass or less, per 100 parts by mass of Component A.

[0025] The uncrosslinked rubber composition may contain a crosslinking agent for crosslinking component A. Examples of the crosslinking agent include organic peroxides, polyols, polyamines, triazines, etc. Of these, organic peroxides are preferred as the crosslinking agent.

[0026] Examples of organic peroxides include dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, etc. The crosslinking agent preferably contains one or more of these, and more preferably contains dicumyl peroxide.

[0027] The content of the organic peroxide crosslinking agent in the uncrosslinked rubber composition is preferably 1 part by mass to 6 parts by mass, more preferably 1.5 parts by mass to 5 parts by mass, per 100 parts by mass of Component A.

[0028] The uncrosslinked rubber composition may contain a co-crosslinking agent for crosslinking Component A together with the crosslinking agent. Examples of the co-crosslinking agent include liquid polybutadiene, amylphenol disulfide polymer, m-phenylenedimaleimide, triallyl isocyanurate, etc. The co-crosslinking agent preferably contains one or more of these, and more preferably contains low-viscosity liquid polybutadiene having double bonds that serve as crosslinking points in both the main chain and side chains, from the viewpoints of excellent kneading processability with Component A and obtaining excellent mechanical properties after crosslinking.

[0029] The liquid polybutadiene contains a 1,2 addition polymerization moiety and a 1,4 addition polymerization moiety. The content of the 1,2 addition polymerization moiety (vinyl content) in the liquid polybutadiene is preferably 1% by mass or more and 95% by mass or less, more preferably 5% by mass or more and 70% by mass or less. The number average molecular weight of the liquid polybutadiene is preferably 2,000 to 15,000, more preferably 8,000 to 10,000.

[0030] The content of the co-crosslinking agent in the uncrosslinked rubber composition is preferably 0.3 parts by mass or more and 30 parts by mass or less relative to 100 parts by mass of Component A, and in the case of liquid polybutadiene and m-phenylenedimaleimide, it is more preferably 5 parts by mass or more and 25 parts by mass or less, in the case of amylphenol disulfide polymer, it is more preferably 0.5 parts by mass or more and 1.5 parts by mass or less, and in the case of triallyl isocyanurate, it is more preferably 2 parts by mass or more and 6 parts by mass or less.

[0031] The uncrosslinked rubber composition may contain other rubber compounding agents such as a processing aid, an antioxidant, a plasticizer, a vulcanization accelerator, and a vulcanization accelerator assistant, as required.

[0032] The sealing material according to the embodiment can be produced by preparing an uncrosslinked rubber composition containing the above-described components A and B and crosslinking the uncrosslinked rubber composition, i.e., crosslinking the component A of the rubber component. Therefore, the sealing material is formed from a rubber composition obtained by crosslinking the uncrosslinked rubber composition. A typical example of the crosslinking method is a method in which the uncrosslinked rubber composition is crosslinked by a crosslinking agent under heating and pressure. In this case, after a primary crosslinking treatment by heating and pressure, a secondary crosslinking treatment may be performed in which the composition is held in a heating furnace for a predetermined time, or a secondary crosslinking treatment by irradiation with radiation.

[0033] The hardness Hs of the rubber composition forming the sealing material is preferably A40 or more and A70 or less, more preferably A50 or more and A60 or less, as measured with a type A durometer in accordance with JIS K6253-3:2012.

[0034] The tensile strength Tb of the rubber composition X is preferably 2 MPa or more, more preferably 5 MPa or more, and even more preferably 8 MPa or more. The elongation Eb of the rubber composition is preferably 100% or more and 500% or less, more preferably 130% or more and 250% or less, and even more preferably 150% or more and 200% or less. The tensile stress S100 at 100% elongation of the rubber composition is preferably 1 MPa or more and 6 MPa or less, more preferably 2 MPa or more and 5 MPa or less, and even more preferably 3 MPa or more and 4 MPa or less. The tensile strength Tb, elongation Eb, and tensile stress S100 at 100% elongation are measured in accordance with JIS K6251:2017. [Example]

[0035] (Uncrosslinked rubber composition) The following uncrosslinked rubber compositions were prepared in Examples 1 to 14 and Comparative Examples 1 and 2. The constitutions of each are also shown in Table 1.

[0036] <Example 1 (Reference Example)> EPDM (Mitsui EPT3070, manufactured by Mitsui Chemicals, Inc., ethylene content: 58% by mass, ENB content: 4.7% by mass) was used as component A. 100 parts by mass of component A was blended with 24 parts by mass of component B (SIFEL3000 Series X-71-359, manufactured by Shin-Etsu Chemical Co., Ltd.), 10 parts by mass of PVdF resin filler (Kynar MG 15, manufactured by Arkema, average particle size: 10 μm), 4 parts by mass of organic peroxide (dicumyl peroxide) as a crosslinking agent, and 10 parts by mass of liquid polybutadiene 1 (NISSO-PB B-3000, manufactured by Nippon Soda Co., Ltd., vinyl content: 90% or more, number average molecular weight: 3200) as a co-crosslinking agent to prepare an uncrosslinked fluororubber composition, which was designated Example 1 (Reference Example).

[0037] <Example 2> EBT (Metallocene EBT K-9330M manufactured by Mitsui Chemicals, Inc., ethylene content: 50% by mass, ENB content: 7.1% by mass) was used as component A. 24 parts by mass of component B, 10 parts by mass of PVdF resin filler, 2 parts by mass of an organic peroxide crosslinking agent, and 15 parts by mass of liquid polybutadiene 2 (Kuraplane LBR-352 manufactured by Kuraray Co., Ltd., vinyl content: 5 to 70%, number average molecular weight: 9000) as a co-crosslinking agent were blended and kneaded to prepare an uncrosslinked fluororubber composition, which was designated Example 2.

[0038] Example 3 An uncrosslinked fluororubber composition was prepared using the same formulation as in Example 2, except that the amount of liquid polybutadiene 2 was 10 parts by mass per 100 parts by mass of component A. This was designated Example 3.

[0039] Example 4 An uncrosslinked fluororubber composition was prepared using the same formulation as in Example 2, except that the amount of liquid polybutadiene 2 was 20 parts by mass per 100 parts by mass of component A. This was designated Example 4.

[0040] <Example 5> An uncrosslinked fluororubber composition was prepared using the same formulation as in Example 3, except that the amount of organic peroxide used as the crosslinking agent was 3 parts by mass per 100 parts by mass of Component A. This was designated Example 5.

[0041] Example 6 An uncrosslinked fluororubber composition was prepared using the same formulation as in Example 2, except that the amount of organic peroxide used as the crosslinking agent was 3 parts by mass per 100 parts by mass of Component A. This was designated Example 6.

[0042] Example 7 An uncrosslinked fluororubber composition was prepared using the same formulation as in Example 3, except that the amount of organic peroxide used as the crosslinking agent was 4 parts by mass per 100 parts by mass of Component A. This was designated Example 7.

[0043] Example 8 An uncrosslinked fluororubber composition was prepared with the same formulation as in Example 7, except that 10 parts by mass of carbon black MT (THERMAX N990, manufactured by Cancarb, average particle size: 0.3 μm) was blended with 10 parts by mass of component A per 100 parts by mass of component A instead of the PVdF resin filler, and 1 part by mass of amylphenol disulfide polymer (Suncerer AP, manufactured by Sanshin Chemical Industry Co., Ltd.) was blended with 1 part by mass of co-crosslinking agent per 100 parts by mass of component A instead of the co-crosslinking agent liquid polybutadiene 2, and this was designated Example 8.

[0044] Example 9 An uncrosslinked fluororubber composition was prepared with the same formulation as in Example 8, except that 10 parts by mass of hydrophobic dry silica (Aerosil R972, manufactured by Evonik, average particle size: 0.02 μm) surface-treated with dimethyldichlorosilane was blended instead of carbon black MT, per 100 parts by mass of component A. This was designated Example 9.

[0045] Example 10 An uncrosslinked fluororubber composition was prepared with the same formulation as in Example 7, except that 1 part by mass of amylphenol disulfide polymer as a co-crosslinking agent was blended per 100 parts by mass of Component A instead of liquid polybutadiene 2 as a co-crosslinking agent, and this was designated Example 10.

[0046] Example 11 An uncrosslinked fluororubber composition was prepared with the same formulation as in Example 2, except that 10 parts by mass of a co-crosslinking agent m-phenylenedimaleimide (Balnoc PM, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) was blended per 100 parts by mass of Component A instead of the co-crosslinking agent liquid polybutadiene 2, and this was designated Example 11.

[0047] Example 12 An uncrosslinked fluororubber composition was prepared with the same formulation as in Example 2, except that 4 parts by mass of a co-crosslinking agent, triallyl isocyanurate (TAIC, manufactured by Mitsubishi Chemical Corporation), was blended per 100 parts by mass of component A instead of liquid polybutadiene 2 as a co-crosslinking agent, and this was designated Example 12.

[0048] Example 13 An uncrosslinked fluororubber composition was prepared using the same formulation as in Example 2, except that the amount of PVdF resin filler was 12 parts by mass per 100 parts by mass of component A. This was designated Example 13.

[0049] Example 14 An uncrosslinked fluororubber composition was prepared with the same formulation as in Example 2, except that the amount of PVdF resin filler was 18 parts by mass per 100 parts by mass of component A. This was designated Example 14.

[0050] <Comparative Example 1> An uncrosslinked fluororubber composition was prepared using the same formulation as in Example 2, except that Component B was not blended, and this was designated Comparative Example 1.

[0051] <Comparative Example 2> An uncrosslinked fluororubber composition was prepared using the same formulation as in Example 9 except that Component B was not blended, and this was designated Comparative Example 2.

[0052] [Table 1]

[0053] (Test method and results) Test pieces of the rubber composition obtained by crosslinking the above uncrosslinked rubber composition were prepared, and the following tests were carried out using them. The results are shown in Tables 2 and 3.

[0054] <Hardness> Three sheet-shaped rubber compositions with a thickness of 2 mm prepared by crosslinking each of the uncrosslinked rubber compositions of Examples 1 to 14 and Comparative Examples 1 and 2 were stacked to form a test piece. Based on JIS K6253-3:2012, using a Type A durometer, the hardness Hs was measured as the instantaneous value when the pressure plate contacted the test piece.

[0055] <Tensile properties> Dumbbell-shaped No. 3 test pieces were cut out from the sheet-shaped rubber compositions prepared by crosslinking each of the uncrosslinked rubber compositions of Examples 1 to 14 and Comparative Examples 1 and 2. Based on JIS K6251:2017, the tensile strength Tb, elongation Eb, and tensile stress S100 at 100% elongation were measured.

[0056] <Plasma resistance> AS-214 O-rings prepared by crosslinking each of the uncrosslinked rubber compositions of Examples 1 to 13 and Comparative Examples 1 and 2 were used as test pieces, which were set in a plasma exposure apparatus (manufactured by Shinko Seiki Co., Ltd.). Using a mixed gas of O2 gas and CF4 gas mixed at a volume ratio of 50:1, it was exposed to the plasma generated under the conditions of a frequency of 2.45 GHz, a pressure of 100 Pa, and an output of 1500 W for 30 minutes. Then, the presence or absence of dust generation at that time was visually confirmed. Also, the mass reduction rate was calculated based on the following formula from the mass before and after that. Mass reduction rate (%) = {(mass before exposure - mass after exposure) / mass before exposure} × 100

[0057] <He leak test> The AS-214 O-rings prepared by crosslinking the uncrosslinked rubber compositions of Examples 2, 7, and 10, and the fluororubber and silicone rubber were used as test specimens, which were set in a He leak detector (manufactured by INFICON) and used to measure the amount of He leak at test temperatures of 23°C and -50°C, with a He flow rate of 80 ml / min and an O-ring crushing rate of 25%.

[0058] [Table 2]

[0059] [Table 3] [Industrial Applicability]

[0060] The present invention is useful in the technical field of sealing materials.

Claims

1. A sealing material formed by crosslinking an uncrosslinked rubber composition containing an ethylene-α-olefin-diene rubber and a compound having a perfluoropolyether skeleton, The sealing material, wherein the ethylene-α-olefin-diene rubber contains an ethylene-butene-diene terpolymer.

2. The sealing material according to claim 1, The sealing material, wherein the uncrosslinked rubber composition further contains a co-crosslinking agent.

3. The sealing material according to claim 2, The sealing material, wherein the co-crosslinking agent contains liquid polybutadiene.

4. The sealing material according to claim 3, A sealing material, wherein the vinyl content of the liquid polybutadiene of the co-crosslinking agent is 5% by mass or more and 70% by mass or less.

5. The sealing material according to claim 1, The ethylene-α-olefin-diene rubber has an ethylene content of 40% by mass or more and 70% by mass or less.

6. The sealing material according to claim 1, The ethylene-α-olefin-diene rubber has a diene component of ethylidene norbornene, and the diene content of the sealant is 3% by mass or more and 10% by mass or less.

7. The sealing material according to claim 1, The sealing material is a one-component material, wherein the compound having a perfluoropolyether skeleton is a one-component material.

8. The sealing material according to claim 1, The sealing material has a content of the compound having a perfluoropolyether skeleton in the uncrosslinked rubber composition of 5 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the ethylene-α-olefin-diene rubber.

9. The sealing material according to claim 1, The sealing material, wherein the uncrosslinked rubber composition further contains a powder filler dispersed in the ethylene-alpha-olefin-diene rubber.

10. The sealing material according to claim 9, The sealing material, wherein the powder filler contains one or more of a PVdF resin filler, carbon black, and silica.

11. The sealing material according to claim 9, The sealing material, wherein the powder filler has an average particle size of 0.01 μm or more and 20 μm or less.

12. The sealing material according to claim 9, The sealing material, wherein the content of the powder filler in the uncrosslinked rubber composition is 1 part by mass or more and 30 parts by mass or less per 100 parts by mass of the ethylene-α-olefin-diene rubber.

13. The sealing material according to claim 3, The sealing material, wherein the liquid polybutadiene of the co-crosslinking agent has a number average molecular weight of 2,000 or more and 15,000 or less.

14. The sealing material according to claim 2, The sealing material, wherein the content of the co-crosslinking agent in the uncrosslinked rubber composition is 0.3 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the ethylene-α-olefin-diene rubber.

15. The sealing material according to claim 1, The rubber composition obtained by crosslinking the uncrosslinked rubber composition has a hardness of A40 or more and A70 or less as measured with a type A durometer in accordance with JIS K6253-3:2012, and a tensile strength of 2 MPa or more, an elongation Eb of 100% or more and 500% or less, and a tensile stress at 100% elongation of 1 MPa or more and 6 MPa or less as measured in accordance with JIS K6251:2017.

16. The sealing material according to claim 1, The sealing material is used in a device that uses plasma.

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