Seal

Abstract

The seal is formed by crosslinking an uncrosslinked rubber composition containing an ethylene-alpha olefin-diene rubber and a compound having a perfluoropolyether skeleton.

Description

Technical Field

[0001] The present invention relates to a sealing element. Background Art

[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.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Publication No. 5189728 Summary of the Invention

[0006] The present invention is a seal member formed by cross-linking an uncross-linked rubber composition containing an ethylene-α-olefin-diene rubber and a compound having a perfluoropolyether skeleton. DETAILED DESCRIPTION

[0007] Hereinafter, the embodiments will be described in detail.

[0008] The sealing material according to the embodiment is an O-ring used in an apparatus using plasma, such as a semiconductor etching apparatus or a plasma chemical vapor deposition (CVD) apparatus.

[0009] The seal according to the embodiment is formed by crosslinking an uncrosslinked rubber composition containing an ethylene-α-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 seal member of the embodiment, since the seal member is formed by cross-linking the uncrosslinked rubber composition containing the components A and B, excellent plasma resistance and sealing performance at low temperatures can be obtained.

[0011] Here, examples of component A include ethylene-propylene-diene terpolymer (hereinafter referred to as "EPDM") and ethylene-butene-diene terpolymer (hereinafter referred to as "EBT"). Component A preferably contains one or both of the above copolymers. From the perspective of achieving excellent plasma resistance and sealing properties at low temperatures, component A more preferably contains at least EBT.

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

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

[0014] When the diene component is vinyl norbornene, the ENB content (diene content) in component A is preferably 3% by mass to 10% by mass from the viewpoint of achieving excellent plasma resistance and sealing properties at low temperatures. When the α-olefin component is propylene, the ENB content is more preferably 3.5% by mass to 5.5% by mass. When the α-olefin component is butene, the ENB content is more preferably 6.5% by mass to 7.5% by mass. This ENB content is measured in accordance with ASTM D 6047.

[0015] The uncrosslinked rubber composition may contain a rubber component other than component A as long as component A constitutes the main component of the rubber component. Examples of the rubber component 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, the component B is preferably a liquid material of the compound having a perfluoropolyether skeleton uniformly mixed with the component A, and more preferably a one-liquid material.

[0017] From the perspective of functioning as a co-crosslinking agent for crosslinking component A by polyaddition and obtaining excellent plasma resistance and sealing properties at low temperatures, component B preferably has multiple alkenyl groups in the molecule. Examples of alkenyl groups include vinyl, propenyl, butenyl, pentenyl, hexenyl, and heptenyl. From the same perspective as above, the alkenyl group is preferably vinyl among the above alkenyl groups. 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, relative to 100 parts by mass of component A.

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

[0020] The uncrosslinked rubber composition may also contain a powder filler dispersed in component A. Examples of powder fillers include polyvinylidene fluoride (PVdF) resin fillers, carbon black, silica, silicon carbide, boron carbide, silicon nitride, and boron nitride. The powder filler preferably comprises one or more of the above substances, more preferably one or more of PVdF resin fillers, carbon black, and silica. From the perspective of suppressing particle generation even when used in a plasma atmosphere, the powder filler further preferably comprises a PVdF resin filler. Commercially available materials for PVdF resin fillers include, for example, the Kynar series manufactured by Arkema.

[0021] Examples of carbon black include MT (N990), FEF (N550), GPF (N600), and FT (N880). The carbon black preferably includes MT among the above.

[0022] As silicon dioxide, for example, dry-process silicon dioxide such as fumed silica and wet-process silicon dioxide such as precipitated silica can be cited. In addition, the surface of the silicon dioxide can also be hydrophobized using organochlorosilanes, organoalkoxysilanes, hexaorganodisilazane, organosiloxane oligomers, etc. The silicon dioxide preferably comprises the dry-process silicon dioxide among the above-mentioned silicon dioxides, more preferably comprises dry-process silicon dioxide whose surface has been hydrophobized using organochlorosilanes, and further preferably comprises fumed silicon dioxide whose surface has been hydrophobized using dimethyldichlorosilane.

[0023] From the viewpoint of obtaining excellent mechanical properties after cross-linking, the average particle size of the powder filler is preferably 0.01 μm to 20 μm, more preferably 0.1 μm to 18 μm, further preferably 5 μm to 15 μm, and even more preferably 8 μm to 12 μm.

[0024] From the viewpoint of obtaining excellent mechanical properties after crosslinking, the content of the powder filler in the uncrosslinked rubber composition is preferably from 1 part by mass to 30 parts by mass, more preferably from 5 parts by mass to 15 parts by mass, and even more preferably from 8 parts by mass to 12 parts by mass, relative to 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, and triazines. Of the above, the crosslinking agent is preferably an organic peroxide.

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

[0027] The content of the organic peroxide as a 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 also contain a co-crosslinking agent for crosslinking component A together with the crosslinking agent. Examples of the co-crosslinking agent include liquid polybutadiene, poly-tert-amylphenol disulfide, N,N'-m-phenylene bismaleimide, and triallyl isocyanurate. The co-crosslinking agent preferably comprises one or more of the above-mentioned substances. From the perspective of excellent kneading processability with component A and excellent mechanical properties after crosslinking, the co-crosslinking agent more preferably comprises a low-viscosity liquid polybutadiene having double bonds serving as crosslinking points in both the main chain and the side chains.

[0029] Liquid polybutadiene contains 1,2-addition polymerized moieties and 1,4-addition polymerized moieties. The content of 1,2-addition polymerized moieties (vinyl content) in the liquid polybutadiene is preferably from 1% to 95% by mass, more preferably from 5% to 70% by mass. The number average molecular weight of the liquid polybutadiene is preferably from 2,000 to 15,000, more preferably from 8,000 to 10,000.

[0030] The content of the co-crosslinking agent in the uncrosslinked rubber composition is preferably from 0.3 parts by mass to 30 parts by mass per 100 parts by mass of component A. In the case of liquid polybutadiene or N,N'-m-phenylene bismaleimide, the content of the co-crosslinking agent is more preferably from 5 parts by mass to 25 parts by mass. In the case of poly-tert-amylphenol disulfide, the content of the co-crosslinking agent is more preferably from 0.5 parts by mass to 1.5 parts by mass. In the case of triallyl isocyanurate, the content of the co-crosslinking agent is more preferably from 2 parts by mass to 6 parts by mass.

[0031] The uncrosslinked rubber composition may contain other rubber additives such as a processing aid, an antioxidant, a plasticizer, a vulcanization accelerator, and a vulcanization accelerating aid, as needed.

[0032] The seal according to the embodiment can be manufactured by preparing an uncrosslinked rubber composition containing the above-mentioned components A and B and crosslinking the uncrosslinked rubber composition, that is, crosslinking component A as a rubber component. Therefore, the seal is formed from a rubber composition obtained by crosslinking the uncrosslinked rubber composition. As a typical crosslinking method in this case, a method of crosslinking the uncrosslinked rubber composition by heating and pressurizing and using a crosslinking agent can be listed. In addition, in this case, after the primary crosslinking treatment by heating and pressurizing, a secondary crosslinking treatment by holding the rubber composition in a heating furnace for a predetermined time or a secondary crosslinking treatment by irradiation can be performed. Alternatively, after the secondary crosslinking treatment by holding the rubber composition in a heating furnace for a predetermined time, a tertiary crosslinking treatment by irradiation can be further performed.

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

[0034] The rubber composition forming the seal preferably has a tensile strength Tb of 2 MPa or greater, more preferably 5 MPa or greater, and even more preferably 8 MPa or greater. The elongation Eb is preferably 100% or greater and 500% or less, more preferably 130% or greater and 250% or less, and even more preferably 150% or greater and 200% or less. The tensile stress S100 at 100% elongation is preferably 1 MPa or greater and 6 MPa or less, more preferably 2 MPa or greater and 5 MPa or less, and even more preferably 3 MPa or greater 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.

[0035] [Example]

[0036] (Uncrosslinked rubber composition)

[0037] The following uncrosslinked rubber compositions were prepared in Examples 1 to 14 and Comparative Examples 1 and 2. The composition of each example is also shown in Table 1.

[0038] <Example 1>

[0039] EPDM (Mitsui EPT3070, manufactured by Mitsui Chemicals, ethylene content: 58% by mass, ENB content: 4.7% by mass) was used as component A. To 100 parts by mass of component A, 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 MG15, manufactured by Arkema, average particle size: 10 μm), 4 parts by mass of an 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 were added and kneaded to produce an uncrosslinked fluororubber composition, which was used as Example 1.

[0040] <Example 2>

[0041] EBT (metallocene EBT K-9330M, manufactured by Mitsui Chemicals, ethylene content: 50% by mass, ENB content: 7.1% by mass) was used as component A. To 100 parts by mass of 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 as a crosslinking agent, and 15 parts by mass of liquid polybutadiene 2 (KURAPRENELBR-352, manufactured by Kuraray, vinyl content: 5 to 70%, number average molecular weight: 9000) as a co-crosslinking agent were added and kneaded to produce an uncrosslinked fluororubber composition, which was used as Example 2.

[0042] <Example 3>

[0043] An uncrosslinked fluororubber composition was prepared as Example 3 in the same manner as in Example 2 except that the amount of liquid polybutadiene 2 added was 10 parts by mass relative to 100 parts by mass of component A.

[0044] <Example 4>

[0045] An uncrosslinked fluororubber composition was prepared as Example 4 in the same amounts as in Example 2 except that the amount of liquid polybutadiene 2 added was 20 parts by mass relative to 100 parts by mass of component A.

[0046] <Example 5>

[0047] An uncrosslinked fluororubber composition was prepared as Example 5 in the same amounts as in Example 3 except that the amount of the organic peroxide added as a crosslinking agent was 3 parts by mass per 100 parts by mass of component A.

[0048] <Example 6>

[0049] An uncrosslinked fluororubber composition was prepared as Example 6 in the same manner as in Example 2 except that the amount of the organic peroxide added as a crosslinking agent was 3 parts by mass per 100 parts by mass of component A.

[0050] <Example 7>

[0051] An uncrosslinked fluororubber composition was prepared as Example 7 in the same manner as in Example 3 except that the amount of the organic peroxide added as a crosslinking agent was 4 parts by mass per 100 parts by mass of component A.

[0052] <Example 8>

[0053] An uncrosslinked fluororubber composition was prepared as Example 8, except that 10 parts by mass of MT (THERMAX N990, manufactured by Cancarb, average particle size: 0.3 μm) as carbon black was added to 100 parts by mass of component A instead of the PVdF resin filler, and 1 part by mass of poly-tert-amylphenol disulfide (Sanceler AP, manufactured by Sanshin Chemical Co., Ltd.) as a co-crosslinking agent was added to 100 parts by mass of component A instead of the liquid polybutadiene 2 as a co-crosslinking agent. The other addition amounts were the same as in Example 7.

[0054] <Example 9>

[0055] An uncrosslinked fluororubber composition was prepared as Example 9, 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 added to 100 parts by mass of component A instead of carbon black MT. The other addition amounts were the same as in Example 8.

[0056] <Example 10>

[0057] An uncrosslinked fluororubber composition was prepared as Example 10, except that 1 part by mass of poly-tert-amylphenol disulfide was added as a co-crosslinking agent to 100 parts by mass of component A instead of liquid polybutadiene 2 as a co-crosslinking agent. Other addition amounts were the same as in Example 7.

[0058] <Example 11>

[0059] An uncrosslinked fluororubber composition was prepared as Example 11 in the same manner as in Example 2, except that 10 parts by mass of N,N'-m-phenylene bismaleimide (VULNOC PM, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) was added as a co-crosslinking agent instead of liquid polybutadiene 2 per 100 parts by mass of component A.

[0060] <Example 12>

[0061] An uncrosslinked fluororubber composition was prepared as Example 12, except that 4 parts by mass of triallyl isocyanurate (TAIC, manufactured by Mitsubishi Chemical Corporation) was added as a co-crosslinking agent instead of liquid polybutadiene 2 as a co-crosslinking agent relative to 100 parts by mass of component A. The other added amounts were the same as in Example 2.

[0062] <Example 13>

[0063] An uncrosslinked fluororubber composition was prepared as Example 13 by using the same addition amounts as in Example 2 except that the addition amount of the PVdF resin filler was 12 parts by mass relative to 100 parts by mass of component A.

[0064] <Example 14>

[0065] An uncrosslinked fluororubber composition was prepared as Example 14 by using the same addition amounts as in Example 2 except that the addition amount of the PVdF resin filler was 18 parts by mass relative to 100 parts by mass of component A.

[0066] <Comparative Example 1>

[0067] A non-crosslinked fluororubber composition was prepared as Comparative Example 1, with the addition amounts being the same as in Example 2 except that component B was not added.

[0068] Comparative Example 2

[0069] A non-crosslinked fluororubber composition was prepared as Comparative Example 2 using the same addition amounts as in Example 9 except that component B was not added.

[0070]

Table 1

[0071]

[0072] (Test methods and results)

[0073] Test pieces of the rubber composition obtained by crosslinking the above-mentioned uncrosslinked rubber composition were prepared, and the following tests were carried out using the test pieces. The results are shown in Tables 2 and 3.

[0074] Hardness

[0075] Three 2-mm-thick sheets of rubber composition prepared by crosslinking the uncrosslinked rubber compositions of Examples 1 to 14 and Comparative Examples 1 and 2 were stacked together to form test pieces. The hardness Hs was measured using a type A durometer in accordance with JIS K6253-3:2012 at the moment a pressure plate came into contact with the test piece.

[0076] Tensile properties

[0077] Dumbbell-shaped No. 3 test pieces were cut from the rubber composition sheets produced by crosslinking the uncrosslinked rubber compositions of Examples 1 to 14 and Comparative Examples 1 and 2. The tensile strength Tb, elongation Eb, and tensile stress S100 at 100% elongation were measured in accordance with JIS K6251:2017.

[0078] <Plasma resistance>

[0079] AS-214 O-rings, produced by crosslinking the uncrosslinked rubber compositions of Examples 1 to 13 and Comparative Examples 1 and 2, were used as test specimens. These specimens were placed in a plasma exposure apparatus (manufactured by Shinko Seiki Co., Ltd.) and exposed to plasma for 30 minutes. The plasma was generated using a mixture of O₂ and CF₄ gases at a volume ratio of 50:1 at a frequency of 2.45 GHz, a pressure of 100 Pa, and an output of 1500 W. The presence of dust during this period was visually inspected. The mass loss rate was calculated from the masses before and after exposure using the following formula.

[0080] Mass reduction rate (%) = {(mass before exposure - mass after exposure) / mass before exposure} × 100

[0081] <Helium leak test>

[0082] AS-214 O-rings produced by crosslinking the uncrosslinked rubber compositions of Examples 2, 7, and 10, as well as the respective fluororubber and silicone rubber compositions, were used as test pieces and placed on a helium leak detector (manufactured by INFICON). Helium leakage was measured at test temperatures of 23°C and -50°C, with a helium flow rate of 80 ml / min and an O-ring crush rate of 25%.

[0083]

Table 2

[0084]

[0085]

Table 3

[0086]

[0087] Industrial Applicability

[0088] The present invention is very useful in the technical field of seals.

Claims

1. A seal, characterized in that: The sealing member is formed by cross-linking an uncross-linked rubber composition containing an ethylene-α-olefin-diene rubber and a compound having a perfluoropolyether skeleton.

2. The seal according to claim 1, characterized in that: The ethylene-α-olefin-diene rubber comprises an ethylene-butene-diene terpolymer.

3. The seal according to claim 2, characterized in that: The ethylene content of the ethylene-butene-diene terpolymer is 48% by mass or more and 53% by mass or less.

4. The seal according to claim 2 or 3, characterized in that: The diene component of the ethylene-butene-diene terpolymer is ethylidene norbornene, and the diene content is 6.5% by mass or more and 7.5% by mass or less.

5. The seal according to any one of claims 1 to 4, characterized in that: The compound having a perfluoropolyether skeleton is a one-liquid material.

6. The seal according to any one of claims 1 to 5, characterized in that: The compound having a perfluoropolyether skeleton has a plurality of alkenyl groups in the molecule.

7. The seal according to any one of claims 1 to 6, characterized in that: The content of the compound having a perfluoropolyether skeleton in the uncrosslinked rubber composition is 5 parts by mass or more and 40 parts by mass or less relative to 100 parts by mass of the ethylene-α-olefin-diene rubber.

8. The seal according to any one of claims 1 to 7, characterized in that: The uncrosslinked rubber composition further contains a powder filler.

9. The seal according to claim 8, characterized in that: The powder filler comprises one or more of polyvinylidene fluoride resin filler, carbon black and silicon dioxide.

10. The seal according to claim 8 or 9, characterized in that: The powder filler has an average particle size of 0.01 μm or more and 20 μm or less.

11. The seal according to any one of claims 8 to 10, characterized in that: 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 relative to 100 parts by mass of the ethylene-α-olefin-diene rubber.

12. The seal according to any one of claims 1 to 11, characterized in that: The uncrosslinked rubber composition further contains a co-crosslinking agent.

13. The seal according to claim 12, characterized in that: The co-crosslinking agent comprises liquid polybutadiene.

14. The seal according to claim 13, wherein: The liquid polybutadiene has a vinyl content of 5% by mass or more and 70% by mass or less.

15. The seal according to claim 13 or 14, characterized in that: The content of the liquid polybutadiene in the uncrosslinked rubber composition is 5 parts by mass or more and 25 parts by mass or less relative to 100 parts by mass of the ethylene-α-olefin-diene rubber.

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