Rubber composition, fluorine-containing elastomer and sealing material

Abstract

To provide a new rubber composition for producing a sealing material which has predetermined plasma resistance and predetermined hardness, a fluorine-containing elastomer obtained by crosslinking the rubber composition, and a sealing material including a fluorine-containing elastomer.SOLUTION: A rubber composition is provided which includes (a) crosslinking reactive fluorine rubber, (b) crosslinking reactive perfluoro rubber, (c) a fluorine oligomer having a perfluoro skeleton, and (d) a fluororesin.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The disclosure in the present application relates to a sealing material used for a site where plasma resistance is required, as well as a rubber composition and a fluorine-containing elastomer for forming the sealing material.

Background Art

[0002] For sealing materials that require plasma resistance, mainly fluorine-containing elastomers are used. While the sealing material is required to have plasma resistance, it is also required to have a predetermined hardness. Patent Document 1 discloses that by using (a) a crosslinkable fluororubber or (b) a crosslinkable perfluororubber as a rubber component, adding (c) a fluorine oligomer having a perfluoro skeleton, and further combining a newly developed crosslinking agent, a sealing material having a predetermined hardness can be provided while maintaining plasma resistance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, for the invention described in Patent Document 1, an expensive crosslinking agent needs to be used in order for the sealing material to have a predetermined hardness. In an actual manufacturing site, it is necessary to manufacture products while considering various factors such as the cost of materials and the availability of materials. Therefore, the development of a new rubber composition for manufacturing a sealing material having a predetermined plasma resistance and a predetermined hardness is required.

[0005] The disclosure in the present application is made to solve the above problems. As a result of intensive research, the inventors have newly found that the above problems can be solved by using in combination (a) a crosslink-reactive fluororubber, (b) a crosslink-reactive perfluororubber, (c) a fluorine oligomer having a perfluoroskeleton, and (d) a fluororesin.

[0006] That is, the object of the disclosure of the present application is to provide a new rubber composition for producing a sealing material having a predetermined plasma resistance and a predetermined hardness, a fluorine-containing elastomer obtained by crosslinking the rubber composition, and a sealing material containing the fluorine-containing elastomer.

Means for Solving the Problems

[0007] The disclosure in the present application relates to the following rubber composition, fluorine-containing elastomer, and sealing material.

[0008] (1) A rubber composition containing (a) a crosslink-reactive fluororubber, (b) a crosslink-reactive perfluororubber, (c) a fluorine oligomer having a perfluoroskeleton, (d) a fluororesin. (2) The rubber composition according to (1) above, wherein the component (c) is contained in an amount of 0.1 phr or more and 40 phr or less with respect to 100 phr of the components (a) and (b) which are rubber components. (3) The rubber composition according to (1) above, wherein the weight ratio of the component (d) / the component (c) is 0.1 or more. (4) The rubber composition according to (2) above, wherein the weight ratio of the component (d) / the component (c) is 0.1 or more. (5) The rubber composition according to (1) above, wherein the weight ratio of the component (d) / the component (b) is 0.1 or more and 2 or less. (6) The rubber composition according to (2) above, wherein the weight ratio of the component (d) / the component (b) is 0.1 or more and 2 or less. (7) The rubber composition according to (3) above, wherein the weight ratio of the component (d) / the component (b) is 0.1 or more and 2 or less. (8) The rubber composition according to (4) above, wherein the weight ratio of component (d) / component (b) is 0.1 or more and 2 or less. (9) A fluorine-containing elastomer obtained by crosslinking the rubber composition according to any one of (1) to (8) above. (10) In the fluorine-containing elastomer, components (a) and (b) are incompatible with each other and have a phase-separated structure, component (d) is dispersed in component (b), when comparing the (d) component dispersed in component (b) with the (d) component not dispersed in component (b), the amount of the (d) component dispersed in component (b) is larger, The fluorine-containing elastomer according to (9) above. (11) A sealing material containing the fluorine-containing elastomer according to (9) above. (12) Using a surface wave plasma etching apparatus, gas flow rate O 2 (2000 sccm) + CF 4 (40 sccm), the fluorine-containing elastomer according to (10) above, wherein the weight loss rate after plasma exposure under the conditions of a processing pressure of 133 Pa, an output of 3 kW, and an exposure time of 2 hours is 2% or less.

Advantages of the Invention

[0009] By using the rubber composition disclosed in the present application, a fluorine-containing elastomer having a predetermined plasma resistance and a predetermined hardness, and a sealing material containing the fluorine-containing elastomer can be obtained.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0011] Hereinafter, the rubber composition, fluorine-containing elastomer, and sealing material disclosed in the present application will be described in detail.

[0012] In the present specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. Further, in the present specification, numerical values, numerical ranges, and qualitative expressions (for example, expressions such as "identical" and "the same") are interpreted as indicating numerical values, numerical ranges, and properties including generally acceptable errors in the relevant technical field.

[0013] (Embodiment of Rubber Composition) The rubber composition according to the embodiment contains (a) a crosslinkable fluororubber, (b) a crosslinkable perfluororubber, (c) a fluorine oligomer having a perfluoroskeleton, and (d) a fluororesin.

[0014] <Regarding Component (a) and Component (b)> First, the crosslinkable fluororubber as component (a) (hereinafter, may be referred to as "FKM") and the crosslinkable perfluororubber as component (b) (hereinafter, may be referred to as "FFKM") will be described. When FKM and FFKM are grouped together, they may simply be referred to as "fluorine-containing crosslinkable rubber".

[0015] "Crosslinkable" means a fluorine-containing rubber that can be crosslinked by a crosslinking reaction. The fluorine-containing crosslinkable rubber can contain, for example, repeating units derived from fluorine-containing monomers. The fluorine-containing crosslinkable rubber can contain repeating units derived from one or more fluorine-containing monomers.

[0016] Examples of the fluorine-containing monomer include tetrafluoroethylene (TFE) represented by the following formula (a-1), hexafluoropropylene (HFP) represented by the following formula (a-2), and the like. CF 2 =CF 2 (a-1) CF 2 =CFCF 3 (a-2)

[0017] Examples of the fluorine-containing monomer also include, for example, preferably perfluoroolefins having one ethylenic unsaturated bond at the terminal position. Specific examples include perfluoroalkyl vinyl ether (PAVE) represented by the following formula (a-3), perfluorooxyalkyl vinyl ether represented by the following formula (a-4), perfluorovinyl ether represented by the following formula (a-5), and the like.

[0018] CF 2 =CFOR f1 (a-3) (In formula (a-3), R f1 is a perfluoroalkyl having 1 to 6 carbon atoms, such as trifluoromethyl or pentafluoropropyl.)

[0019] CF 2 =CFOR f2 (a-4) (In formula (a-4), R f2 is a perfluorooxyalkyl having 1 to 12 carbon atoms containing one or more ether groups, such as perfluoro-2-propoxypropyl.)

[0020] CF 2 =CFOCF 2 OR f3 (a-5) (In formula (a-5), R f3 is a linear or branched perfluoroalkyl having 2 to 6 carbon atoms, a cyclic perfluoroalkyl having 5 or 6 carbon atoms, or a linear or branched perfluorooxyalkyl having 2 to 6 carbon atoms containing 1 to 3 oxygen atoms.)

[0021] In one embodiment, the perfluorovinyl ether represented by formula (a-5) is represented by the following formula (a-6) or formula (a-7). The perfluorovinyl ether represented by formula (a-6) may be referred to as "MOVE1", and the perfluorovinyl ether represented by formula (a-7) may be referred to as "MOVE2".

[0022] CF 2 =CFOCF 2 OCF 2 CF 3 (a-6) CF 2 =CFOCF 2 OCF 2 CF 2 OCF 3 (a-7) In one embodiment, the fluorine-containing crosslinkable rubber can be a copolymer containing repeating units derived from one or more fluorine-containing monomers selected from the group consisting of formula (a-1) and formula (a-2), and repeating units derived from one or more fluorine-containing monomers (comonomers) selected from the group consisting of formula (a-3) to formula (a-5).

[0023] The composition (molar ratio) of the fluorine-containing monomers used for producing the fluorine-containing crosslinkable rubber is not particularly limited.

[0024] In one embodiment, the fluorine-containing crosslinkable rubber is produced using 50 to 85 mol% of one or more fluorine-containing monomers selected from the group consisting of formula (a-1) and formula (a-2), and 15 to 50 mol% of one or more fluorine-containing monomers selected from the group consisting of formula (a-3) to formula (a-5).

[0025] In one embodiment, the fluorine-containing crosslinkable rubber is produced using 50 to 85 mol% of TFE and 15 to 50 mol% of PAVE.

[0026] In one embodiment, the fluorine-containing crosslinkable rubber is produced using 50 to 85 mol% of TFE and 15 to 50 mol% of MOVE. Here, "MOVE" is one or more selected from the group consisting of MOVE1 and MOVE2.

[0027] In one embodiment, the fluorine-containing crosslinkable rubber may or may not contain units derived from vinylidene fluoride.

[0028] As used herein, FKM means a rubber containing hydrogen in its chemical structure among the above-mentioned fluorine-containing crosslinkable rubbers. FKM includes, for example, but is not limited to, vinylidene fluoride / hexafluoropropylene copolymer (binary FKM), vinylidene fluoride / hexafluoropropylene / tetrafluoroethylene copolymer (ternary FKM), vinylidene fluoride / hexafluoropropylene / perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene / propylene copolymer, hexafluoropropylene / ethylene copolymer, tetrafluoroethylene / ethylene / perfluoroalkyl vinyl ether copolymer, fluorine rubber (FKM) such as vinylidene fluoride / 2,3,3,3-tetrafluoropropylene, etc.

[0029] As used herein, FFKM means a rubber containing no hydrogen in its chemical structure among the above-mentioned fluorine-containing crosslinkable rubbers. FFKM includes, for example, but is not limited to, perfluororubbers such as tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (FFKM).

[0030] FKM is inexpensive and has a certain degree of plasma resistance and heat resistance. When higher plasma resistance is required, it is used in mixture with FFKM. In the rubber composition according to the embodiment, FKM and FFKM are included as essential components. Note that FKM and FFKM are incompatible. Therefore, FKM and FFKM form a phase-separated structure such as a sea-island structure or a co-continuous structure depending on the blending ratio.

[0031] As described above, FKM contains hydrogen in its chemical structure. On the other hand, FFKM does not contain hydrogen in its chemical structure and contains more fluorine compared to FKM. Therefore, FFKM is superior to FKM in plasma resistance. Also, FKM and FFKM are not compatible due to the difference in properties based on the difference in chemical structure and form a phase-separated structure as described above. The higher the proportion of FFKM among the rubber components (FKM and FFKM) contained in the fluorine-containing elastomer, the more the plasma resistance and heat resistance are improved. However, since FFKM is more expensive than FKM, the cost increases. The proportions of FKM and FFKM in the fluorine-containing crosslinkable rubber may be appropriately set in consideration of the properties and cost required for the fluorine-containing elastomer. Although not limited, for example, the proportion of FKM relative to 100 phr of the fluorine-containing crosslinkable rubber may be 0.1 to 99.9. From the perspective of cost rather than technology, the proportion of FKM relative to 100 phr of the fluorine-containing crosslinkable rubber may be 50.1 to 99.9. Although the description of specific numerical ranges is omitted, any single-digit decimal number within the range of 0.1 to 99.9 may be selected and the range may be specified as a to b.

[0032] In the fluorine-containing elastomer disclosed in the present application, FFKM also functions as a phase for dispersing a fluororesin, which is a filler for increasing hardness.

[0033] In one embodiment, the fluorine-containing crosslinkable rubber may or may not contain a unit derived from a fluoroolefin having 3 to 8 carbon atoms containing iodine and / or bromine. When the fluorine-containing crosslinkable rubber contains the unit, it preferably contains iodine and / or bromine, more preferably iodine, as a radical attack site during crosslinking (curing). The fluorine-containing crosslinkable rubber curable with a peroxide is described, for example, in JP-A-2006-9010. When the fluorine-containing crosslinkable rubber contains the unit, generally, it contains iodine in an amount of 0.001% by mass to 5% by mass, preferably 0.01% by mass to 2.5% by mass, based on the total polymer mass. The iodine atoms may be present along and / or at the terminal positions of the fluorine-containing crosslinkable rubber chain.

[0034] <Regarding component (c)> Next, a fluorine oligomer of a perfluoro skeleton as component (c) (hereinafter sometimes referred to as "PFPE") will be described. While PFPE has a function of improving the plasma resistance of the fluorine-containing elastomer, it also has a function of reducing the hardness. PFPE is an oligomer composed of the elements C, F, and O (where all the hydrogens of hydrocarbons are replaced by fluorine), and examples thereof include fluorine oligomers (c-1) to (c-8) containing the following basic skeletons.

[0035] [Chemical formula]

[0036] [Chemical formula]

[0037] The PFPEs represented by the above formulas (c-1) to (c-8) have different molecular weights depending on the numbers of n and m, and generally, the higher the molecular weight, the higher the viscosity and boiling point. For the PFPE containing the above basic skeleton, synthesized ones may be used, or those commercially available as fluorine-based solvents (oils, greases) may be used. Commercially available PFPEs are known to have various grades with different properties such as viscosity depending on the numbers of n and m. For example, Krytox (registered trademark) series manufactured by DuPont; Fomblin (registered trademark) series, Galden (registered trademark) series of Solvay; Demnum series manufactured by Daikin; etc. It should be noted that the above products and skeletons are merely examples, and other skeletons and products may be used as long as they do not contain hydrogen. Also, as shown in the above formulas (c-1) to (c-8), PFPE contains an ether bond in the basic skeleton, and PFPEs do not bond (crosslink) with each other during the crosslinking (curing) of the rubber composition. PFPE can be used alone or in combination of two or more of the above-described types.

[0038] In the rubber composition according to the embodiment, non-reactive PFPE is used as the component (c). Alternatively, it may be a reactive compound by bonding a group having reactivity to the perfluorinated skeleton.

[0039] The fact that it is a "reactive" compound means that the reactive compounds can react with each other when the rubber composition is crosslinked (cured). By this reaction, the reactive compounds can be bonded to each other. Also, the reactive compound can react with both the components (a) and (b). By this reaction, the reactive compound can be bonded to the components (a) and (b). The reactive compound preferably contains an alkenyl group as a group (reactive group) that imparts such reactivity.

[0040] Examples of the alkenyl group include a vinyl group, an allyl group, a butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, and the like. Among these, the vinyl group is preferable as the alkenyl group.

[0041] The reactive compound preferably has two or more alkenyl groups in the molecule. The two or more alkenyl groups may be the same or different.

[0042] In one embodiment, the reactive compound is a compound having a perfluorinated skeleton with an alkenyl group. The compound having a perfluorinated skeleton with an alkenyl group in the molecule may have, for example, a divalent perfluoropolyether structure or a divalent perfluoroalkylene structure.

[0043] In one embodiment, the reactive compound has a divalent perfluoropolyether structure or a divalent perfluoroalkylene structure and has two or more alkenyl groups at the terminals or side chains. Such reactive compounds can be the same as those described in, for example, the fluorine-based elastomers described in paragraphs

[0016] to

[0022] of JP-A-2003-183402, the perfluorinated compounds described in JP-A-11-116684 or JP-A-11-116685

[0006] to

[0014] , and the like.

[0044] In one embodiment, the reactive compound is represented by the following formula (c-9). CH 2 =CH-(X) p -(R f -Q) a -R f -(X) p -CH=CH 2 (c-9) In formula (c-9), the two Xs are each independently -CH 2 -, -CH 2 O-, CH 2 OCH 2 -, -Y-NR 1 SO 2 - or -Y-NR 1 -CO- (where Y is -CH 2 - or -Si(CH 3 ) 2 -Ph- (Ph: phenylene group)). R 1 is a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group). R f is a divalent perfluoroalkylene group or a divalent perfluoropolyether group. The two p values are each independently 0 or 1. a is an integer of 0 or more. Also, Q is a divalent group represented by any one of the following formulas (c-10) to (c-12).

[0045]

Chemical formula

[0046] In formulas (c-10) to (c-12), X, p, and R 1 are as defined in formula (c-9). R 3 is a substituted or unsubstituted divalent hydrocarbon group. R 4 is a substituted or unsubstituted divalent hydrocarbon group which may have one or more oxygen atoms, nitrogen atoms, silicon atoms, and sulfur atoms intervening in the middle of the bond, or a functional group represented by the following formula (c-13) or (c-14).

[0047]

Chem.

[0048] In formulas (c-13) and (c-14), R 5 is a substituted or unsubstituted monovalent hydrocarbon group, and R 6 is a group containing one or more of a carbon atom, an oxygen atom, a nitrogen atom, a silicon atom, and a sulfur atom in the main chain structure.

[0049] In one embodiment, a = 0 in formula (c-9). In this case, formula (c-9) is represented by the following formula (c-15). CH 2 =CH-(X) p -R f -(X) p -CH=CH 2 (c-15) In formula (c-15), X, p, and R f are as defined in formula (c-9).

[0050] Specific examples of R f include the following groups. -C m F 2n -(m, n: integers of 1 or more) -[CF(CF 3 )OCF 2 p -(CF 2 ) r -[CF 2 OCF(CF 3 )] q - -CF 2 CF 2 -[OCF 2 CF 2 CF 2 w -OCF 2 CF 2 -

[0051] ​​In addition to those exemplified above, the reactive compound may be a compound having a siloxane skeleton with an alkenyl group. Examples of the compound having a siloxane skeleton with an alkenyl group in the molecule include polymers of methylvinylsiloxane, polymers of dimethylsiloxane, copolymers of dimethylsiloxane and methylvinylsiloxane, copolymers of dimethylsiloxane, methylvinylsiloxane and methylphenylsiloxane, and the like. Other examples include organopolysiloxanes containing an alkenyl group in the molecule, which are addition-curable liquid silicone rubbers.

[0052] The reactive compound is also available as a commercial product. Examples thereof include "SIFEL" (registered trademark) manufactured by Shin-Etsu Chemical Co., Ltd.

[0053] As described above, by adding a fluorine oligomer having a perfluoro skeleton and a reactive compound that can be alternatively used (hereinafter, the fluorine oligomer having a perfluoro skeleton and the reactive compound may be collectively referred to as "Compound C"), the plasma resistance of the fluorine-containing elastomer obtained by crosslinking FKM and FFKM can be significantly improved. On the other hand, when a large amount of Compound C is added, the hardness of the fluorine-containing elastomer decreases. Further, since Compound C is a liquid lubricating oil having fluidity, it is difficult to knead and mix a large amount of Compound C with the rubber components FKM and FFKM. Therefore, the lower limit of the Compound C component with respect to 100 phr of the FKM component and the FFKM component, which are rubber components, is, for example, 0.1 phr or more, 0.2 phr or more, 0.3 phr or more, 0.4 phr or more, 0.5 phr or more, 0.6 phr or more, 0.7 phr or more, 0.8 phr or more, 0.9 phr or more, 1.0 phr or more, 1.1 phr or more, 1.2 phr or more, 1.3 phr or more, 1.4 phr or more, 1.5 phr or more, 1.6 phr or more, 1.7 phr or more, 1.8 phr or more, 1.9 phr or more, 2.0 phr or more. On the other hand, the upper limit of the Compound C component is, for example, 40 phr or less, 39 phr or less, 38 phr or less, 37 phr or less, 36 phr or less, 35 phr or less, 34 phr or less, 33 phr or less, 32 phr or less, 31 phr or less, 30 phr or less, 29 phr or less, 28 phr or less, 27 phr or less, 26 phr or less, 25 phr or less, 24 phr or less, 23 phr or less, 22 phr or less, 21 phr or less, 20 phr or less.

[0054] <Regarding component (d)> Next, the fluororesin, which is the component (d), will be described. The fluororesin is added for the purpose of improving the plasma resistance and hardness of the fluorine-containing elastomer. The fluororesin is not particularly limited as long as it can improve the plasma resistance and hardness. Although not limited, for example, polytetrafluoroethylene (PTFE), perfluoroalkoxy fluororesin (PFA), ethylene tetrafluoride - hexafluoropropylene copolymer (FEP), ethylene - tetrafluoroethylene copolymer (ETFE), ethylene - chlorotrifluoroethylene copolymer (ECTFE), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene (CTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), etc. can be mentioned. The molecular weight of the fluororesin is not particularly limited as long as the effects disclosed in the present application can be obtained. Although not limited, for example, the lower limit value can be 10,000 or more, 50,000 or more, 100,000 or more, 200,000 or more, 300,000 or more, 400,000 or more, 500,000 or more, 600,000 or more, 700,000 or more, 800,000 or more, 1,000,000 or more, etc. On the other hand, the upper limit value can be 12,000,000 or less, 11,000,000 or less, 10,000,000 or less, 9,000,000 or less, 8,000,000 or less, 7,000,000 or less, 6,000,000 or less, 5,000,000 or less, etc.

[0055] In addition, as shown in the examples and comparative examples described later, when the fluororesin is dispersed in FKM, which has lower plasma resistance than FFKM, when the FKM is eroded and gasified by plasma irradiation, the fluororesin is likely to fall off from the fluorine-containing elastomer (sealing material) as particles. The fluororesin preferably exists (is dispersed) more in the FFKM with higher plasma resistance among the two phases of incompatible FKM and FFKM. Examples of such fluororesins include, for example, PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxy alkane), FEP (ethylene tetrafluoride - hexafluoropropylene copolymer), PCTFE (polychlorotrifluoroethylene), ETFE (ethylene - tetrafluoroethylene), PVDF (polyvinylidene fluoride), etc. Among the exemplified fluororesins, PTFE, PFA, and FEP, which have high affinity with FFKM, are preferred.

[0056] Regarding products such as sealing materials using fluorine-containing elastomers, it is preferable that there are fewer particles generated when the product is used in a plasma environment. However, depending on the required usage environment, the amount of generated particles may be acceptable if it is below the specified value. Therefore, it is preferable that more fluororesin is dispersed in FFKM, but it is also acceptable that the fluororesin is dispersed in FKM. In other words, when comparing the fluororesin dispersed in FFKM with the fluororesin not dispersed in FFKM (for example, dispersed in FKM), it can be said that there is more fluororesin dispersed in FFKM.

[0057] The shape of the fluororesin is not particularly limited as long as more of it is dispersed in FFKM, but it is preferably in particle form and may also be fibrous.

[0058] The average particle diameter of the primary particles of the particulate fluororesin is not particularly limited as long as it is within the range where the hardness of the fluorine-containing elastomer can be improved. Although not limited, examples of the lower limit value of the average particle diameter include 0.05 μm or more, 0.06 μm or more, 0.07 μm or more, 0.08 μm or more, 0.09 μm or more, 0.1 μm or more, 0.125 μm or more, 0.15 μm or more, 0.175 μm or more, 0.2 μm or more, 0.25 μm or more, 0.3 μm or more, 0.4 μm or more, 0.5 μm or more. On the other hand, examples of the upper limit value of the average particle diameter include 50 μm or less, 47.5 μm or less, 45 μm or less, 42.5 μm or less, 40 μm or less, 37.5 μm or less, 35 μm or less, 32.5 μm or less, 30 μm or less, 27.5 μm or less, 25 μm or less, etc.

[0059] The average particle diameter may be measured by a known method such as the laser diffraction / scattering method. In addition, commercially available products may be used as the fluororesin. In the case of commercially available products, the particle diameter described in the catalog or the like may be used as the average particle diameter.

[0060] Examples of commercially available fluororesins that do not contain hydrogen include PTFE such as TLP 10F-1, MP-1300-J, and Teflon (registered trademark) PTFE series manufactured by Mitsui Chemicals Fluoro Products Co., Ltd., and Polyflon PTFE series manufactured by Daikin Industries, Ltd.; PFA such as Neoflon PFA powder coating series manufactured by Daikin Industries, Ltd.; FEP such as FEP powder coating series manufactured by Daikin Industries, Ltd.

[0061] Examples of commercially available fluororesins that contain hydrogen include ETFE such as Fluon (registered trademark) LM-2150 manufactured by AGC Inc. and Neoflon ETFE EC-6520 manufactured by Daikin Industries, Ltd.; PVDF such as KYNAR (registered trademark) series PVDF manufactured by Arkema Inc. and KF polymer series manufactured by Kuraray Co., Ltd.

[0062] The fluororesin is added to increase the hardness of the fluorine-containing elastomer that decreases due to the addition of Compound C. Therefore, the addition amount of the fluororesin may be appropriately adjusted according to the addition amount of Compound C and the required hardness value. The lower limit of the weight ratio of the fluororesin to Compound C (fluororesin / Compound C) is not limited, but examples include 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1.0 or more. On the other hand, if the weight ratio of fluororesin / Compound C becomes too large, there is a risk that the hardness will become too high. The upper limit of the weight ratio may also be appropriately adjusted while considering the required hardness, etc., and is not limited, but examples include 6 or less, 5.5 or less, 5.0 or less, 4.5 or less, 4.0 or less, 3.5 or less, 3.0 or less, etc.

[0063] As described above, it is preferable that most of the added fluororesin is dispersed in the FFKM. If the addition amount of the fluororesin to the FFKM is too large, the FFKM may not be able to disperse (include) the added fluororesin completely, and there is a risk that the fluororesin will disperse (migrate) into the FKM. Therefore, the ratio of the fluororesin in the rubber composition may be appropriately adjusted according to the ratio of the FFKM which is the rubber component. The upper limit of the weight ratio of the fluororesin (fluororesin / FFKM) to the FFKM is not limited, but examples include 2 or less, 1.9 or less, 1.8 or less, 1.7 or less, 1.6 or less, 1.5 or less, 1.4 or less, 1.3 or less, 1.2 or less, 1.1 or less, 1.0 or less, etc. On the other hand, the lower limit of the weight ratio of the fluororesin / FFKM is not limited, but for example, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, etc. can be mentioned, because the hardness will not increase if the addition amount of the fluororesin is small.

[0064] In addition, as a reinforcing filler for increasing the hardness of the fluorine-containing elastomer, carbon black, silica, etc. are known. However, the rubber composition according to the embodiment uses a combination of FFKM and a fluororesin having high affinity for FFKM as a filler, so that the generation of particles during plasma irradiation can be suppressed. That is, the rubber composition according to the embodiment uses a fluororesin having high affinity for FFKM as a filler, and exhibits a remarkable synergistic effect that is not found in conventional fillers, that is, while suppressing the generation of particles, the plasma resistance and the hardness are improved.

[0065] The hardness of the fluorine-containing elastomer obtained by crosslinking the rubber composition according to the embodiment may be appropriately adjusted according to the intended use of the fluorine-containing elastomer. For example, when a sealing material made of a fluorine-containing elastomer is used as a sealing material for a semiconductor device, the required hardness is approximately 50 to 80. Also, when the sealing material is used as a sealing material for an oil drilling device, the required hardness is approximately 70 to 90. The lower limit value of the hardness of the fluorine-containing elastomer is not limited, but examples include 50 or more, 51 or more, 52 or more, 53 or more, 54 or more, 55 or more, 56 or more, 57 or more, 58 or more, 59 or more, 60 or more. On the other hand, the upper limit value of the hardness of the fluorine-containing elastomer is not limited, but examples include 90 or less, 89 or less, 88 or less, 87 or less, 86 or less, 85 or less, 84 or less, 83 or less, 82 or less, 81 or less, 80 or less, etc. The proportions of FKM, FFKM, Compound C, and fluororesin contained in the rubber composition may be appropriately adjusted so as to obtain the above hardness.

[0066] <Regarding optional additional components that may be included in the rubber composition> Subsequently, optional additional components that may be included in the rubber composition will be described. (e) Crosslinking agent, co-crosslinking agent The rubber composition may be crosslinked with an organic peroxide. As the organic peroxide crosslinking agent, known ones for crosslinking fluorine-based elastomers can be used. For example, dicumyl peroxide, di-t-butylperoxydiisopropylbenzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, etc. can be mentioned.

[0067] As the co-crosslinking agent, known ones for crosslinking fluorine-based elastomers can be used. For example, triallyl isocyanurate, triallyl cyanurate, triallyl trimellitate, N,N'-m-phenylenedimaleimide, trimethylolpropane trimethacrylate, etc. can be mentioned. In addition, acrylate-based, methacrylate-based monomers, etc. can also be used.

[0068] Also, as the crosslinking agent, a compound represented by the following formula (e-1), which is a compound described in Patent Document 1, and / or a compound represented by the following formula (e-2) may be used. [Chemical formula] (In formula (e-1), A is a single bond, -O-, -S-, a heteroatom-containing group, a linear or branched alkylene group, a cycloalkylene group or an arylene group. In these groups, the hydrogen atom is not substituted with a fluorine atom, or some or all of the hydrogen atoms are substituted with fluorine atoms. R 1 , R 2 , R 3 and R 4 are each independently a hydrogen atom, a fluorine atom, an alkyl group, a fluorinated alkyl group or a substituted or unsubstituted aryl group. A plurality of R 1 are the same or different. A plurality of R 2 are the same or different. A plurality of R 3 are the same or different. A plurality of R 4 are the same or different. A plurality of R 1 , R 2 and R 3 at least one of is a fluorine atom or a group containing a fluorine atom. m is an integer from 1 to 5. n is an integer from 1 to 5.)

[0069] [Chemical formula] (In formula (e-2), n and m are each 0 or 1. t is an integer of 2 or more. Z is a t-valent linking group.)

[0070] Note that the detailed description of the compounds described in the above formula (e-1) and formula (e-2) is described in Patent Document 1. Therefore, in this specification, the description of the above formula (e-1) and formula (e-2) is omitted. The matters described in Patent Document 1 (International Publication No. 2021 / 230231) are incorporated herein by reference.

[0071] The crosslinking agent and the co-crosslinking agent only need to be included when crosslinking the rubber composition. Therefore, when the rubber composition is provided, the crosslinking agent and the co-crosslinking agent do not necessarily need to be included as essential components, and the crosslinking agent and the co-crosslinking agent may be separately added when crosslinking the rubber composition. Of course, the rubber composition according to the embodiment itself may contain a crosslinking agent and a co-crosslinking agent. Further, the above-described crosslinking agent may be used alone or in combination of two or more. Similarly, the above-described co-crosslinking agent may be used alone or in combination of two or more.

[0072] (f) Other components Examples of optional additional components other than those described in the above (e) include fillers, thickeners, pigments, coupling agents, antioxidants, stabilizers, and the like. Examples of the filler include carbon black, silica, and the like.

[0073] (Embodiment of fluorine-containing elastomer) The fluorine-containing elastomer according to the embodiment can be produced by crosslinking the rubber composition of any embodiment disclosed in the present application. The conditions (crosslinking conditions) when crosslinking the rubber composition are not particularly limited. For example, the rubber composition may be heated at 100 to 250 ° C for 10 minutes to 5 hours. Usually, as the primary crosslinking, the raw material (rubber composition) is put into a mold and crosslinked while performing press working. The primary crosslinking is, for example, heating at 150 to 200 ° C for 5 to 60 minutes. Thereafter, it is taken out of the mold and subjected to secondary crosslinking in air or an inert gas atmosphere. The secondary crosslinking is, for example, heating at 150 to 300 ° C for 1 to 100 hours. Crosslinking can be performed using an electric furnace or the like. By giving a heat history in the secondary crosslinking, deformation during use and the like can be prevented. Radiation treatment is not necessarily required during crosslinking, and it is preferable to omit the radiation treatment.

[0074] (Embodiment of sealing material) The sealing material according to the embodiment includes a fluorine-containing elastomer according to any of the embodiments disclosed in the present application. The form of the sealing material is not particularly limited, and examples thereof include molded articles such as gaskets or sealing rings. The use of the sealing material is not particularly limited and can be widely applied to various devices. However, since the sealing material disclosed in the present application is excellent in plasma resistance and can have a relatively high hardness, it is suitable as a sealing material for semiconductor manufacturing devices, for example. Examples of semiconductor manufacturing devices include plasma devices, etching devices, plasma CVD devices, and the like.

[0075] Examples are given below to specifically describe the embodiments disclosed in the present application. However, these examples are merely for the purpose of explaining the embodiments and do not represent any limitation or restriction on the scope of the invention disclosed in the present application.

Examples

[0076] [Materials] The components used in the examples and comparative examples are as follows. (a) FKM: Di-Ell G912, manufactured by Daikin Industries, Ltd. (b) FFKM: AFLAS (registered trademark) FFKM PM3000, manufactured by AGC Inc. (c) Compound C (PFPE): Krytox VPF16256, manufactured by DuPont (d) Fluororesin: PFA: Neoflon ACX-34, manufactured by Daikin Industries, Ltd. PTFE: TLP-10-1 (average particle size 0.2 μm), manufactured by Mitsui Chemicals Fluoro Products Co., Ltd. MP-1300-J (average particle size 11 μm), manufactured by Mitsui Chemicals Fluoro Products Co., Ltd. · Crosslinking agent: 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, Perhexa 25B, manufactured by NOF Corporation · Co-crosslinking agent: TAIC (triallyl isocyanurate), manufactured by Mitsubishi Chemical Corporation

[0077] [Examples 1 to 6, Comparative Examples 1 to 4] After kneading the rubber composition having the composition (weight ratio) shown in Table 1 with an open roll, it was put into a mold and heat-treated in the air at a temperature of 160 °C for 10 minutes (15 minutes for Comparative Examples 1 and 3), and primary cross-linking was carried out while press-molding. Then, it was taken out of the mold and secondary cross-linking was carried out at 200 °C for 4 hours in the air. In this way, a molded body of the fluorine-containing elastomer was obtained. The shape of the molded body was an O-ring (AS568-214; inner diameter 24.99 mm, thickness 3.53 mm).

[0078] The following evaluations were made on the obtained fluorine-containing elastomer. (1) Hardness The molded body (O-ring) was placed on a BAREISS micro rubber hardness tester (model: HPEII shore AM / M), and the hardness was measured.

[0079] (2) Heat resistance An assembly was prepared by sandwiching the obtained O-ring between two flat plates and tightening it with bolts using a spacer so as to compress it by 25%. The assembly was heat-exposed in a gear oven under predetermined conditions (in an air environment, 150 °C × 72 hours). Then, it was taken out of the gear oven, and the O-ring was released while the assembly was hot and allowed to cool to room temperature for 30 minutes. The thicknesses before and after the test were measured in accordance with JIS K 6262, and the compression set was calculated by the following formula (unit: %). This compression set (CS) was taken as the heat resistance. Compression set = (thickness before test - thickness after test) / (thickness before test - spacer thickness) × 100

[0080] (3) Tensile properties Using a tabletop precision universal testing machine (manufactured by Shimadzu Corporation, model: Autograph AGS-500NX), the breaking strength [MPa], elongation at break [%], and M100 [MPa] of the molded body (O-ring) were measured at room temperature of 25 ± 2 °C and a tensile speed of 300 mm / min.

[0081] (4) Plasma resistance (4-1) Weight loss rate [%] The molded body (O-ring) was exposed to plasma under the following conditions, and the weight loss rate of the molded body before and after the exposure was calculated. · Equipment: Surface Acoustic Wave Plasma Etching Equipment manufactured by Shinko Seiki Co., Ltd. · Gas: O 2 (2000 sccm) + CF 4 (40 sccm) · Processing Pressure: 133 Pa · Output: 3 kW · Exposure Time: 2 hours (Examples 1 - 6, Comparative Examples 1 - 4), 5 hours (Comparative Example 4 and Example 1) · Weight Loss Rate [%] = [(Weight before Plasma Exposure - Weight Immediately after Plasma Exposure) / (Weight before Plasma Exposure)] × 100 (4 - 2) Particles The presence or absence of particle generation associated with the above plasma exposure was visually observed. Also, for some examples and comparative examples, photographs of the molded body before and after plasma irradiation were taken, and photographs of the sample after plasma irradiation were taken after pressing it onto black tape.

[0082] The results are shown in Table 1. Figure 1 shows the molded bodies (O - rings) of Comparative Examples 1 - 3, where Lane A is a photograph before plasma irradiation, Lane B is a photograph after 2 - hour plasma irradiation, and Lane C is a photograph of the molded body after 2 - hour plasma irradiation transferred onto black tape. Figure 2 shows the molded bodies (O - rings) of Comparative Example 4 and Example 1, where Lane A is a photograph before plasma irradiation and Lane B is a photograph after 5 - hour plasma irradiation.

[0083] Also, Figure 3 shows an image of the cross - section of the molded body of Example 4 subjected to elastic modulus mapping using a scanning probe microscope SPM (manufactured by Bruker, Demention Icon).

Table 1

[0084] From the results shown in Table 1 and Figures 1 and 2, it was confirmed that the rubber composition, fluorine - containing elastomer, and sealing material disclosed in this application have the following effects (or technical matters).

[0085] (1) With respect to the plasma resistance of the molded body of Comparative Example 4 containing the three components of FKM, FFKM, and Compound C, the plasma resistance of the molded bodies of Comparative Examples 1 to 3 that did not contain any of the three components was significantly inferior. Therefore, it was confirmed that it is important to contain the three components of FKM, FFKM, and Compound C in order to improve the plasma resistance. On the other hand, as shown in Comparative Examples 3 and 4, it was confirmed that the hardness of the molded body decreased by adding Compound C. However, from the comparison between Comparative Example 4 and Examples 1 to 6, it was confirmed that when a fluororesin was further added to FKM, FFKM, and Compound C, the hardness of the molded body increased and the plasma resistance improved. From the above results, it was confirmed that it is important to mix the four components of FKM, FFKM, Compound C, and fluororesin to form a molded body having excellent plasma resistance and high hardness.

[0086] (2) Since the sealing material of Comparative Example 1 does not contain FFKM and Compound C, the fluororesin will be dispersed in FKM. Since FKM is inferior in plasma resistance compared to FFKM and Compound C, as shown in Table 1 and Figure 1, when FKM was eroded by plasma irradiation, fluororesin particles were exposed on the surface of the molded body to such an extent that they were clearly visible. On the other hand, in the examples, no fluororesin particles were generated. Therefore, an SPM image of Example 4 was taken. In the SPM image, the brighter the color, the higher the elastic modulus. Therefore, in the SPM image shown in Figure 3, the fluororesin appears white, FKM appears gray, and FFKM appears black. As shown in Figure 3, it was confirmed that most of the fluororesin (white lumps) was dispersed in the black FFKM. Therefore, it was confirmed that when the fluororesin is dispersed in FFKM, even if FKM is eroded by plasma irradiation, it is difficult for the fluororesin to be generated as particles.

[0087] (3) From the results of Comparative Example 4 and Examples 1 to 3, it was confirmed that the higher the addition ratio of the fluororesin to the rubber composition, the higher the hardness of the molded body and the better the plasma resistance.

[0088] (4) From the results of Examples 3 to 5, it was confirmed that the particle size of the fluororesin does not significantly affect the hardness and plasma resistance of the sealing material.

[0089] (5) From the results of Comparative Example 4 and Examples 1 to 7, it was confirmed that by mixing the four components of FKM, FFKM, Compound C, and the fluororesin, it is easy to adjust the balance of hardness, heat resistance, tensile properties, and plasma resistance.

Industrial Applicability

[0090] The rubber composition, fluorine-containing elastomer, and sealing material disclosed in the present application can increase the hardness while improving the plasma resistance. Therefore, it is useful for the sealing material industry that requires plasma resistance and a predetermined hardness, and for the semiconductor industry such as plasma processing apparatuses and semiconductor manufacturing apparatuses that use such sealing materials.

Claims

1. (a) A crosslinkable fluororubber, (b) A crosslinkable perfluoropolymer, (c) A fluorine oligomer having a perfluoroskeleton, (d) A fluororesin, A rubber composition containing the same.

2. The rubber composition according to Claim 1, wherein the component (c) is contained in an amount of 0.1 phr or more and 40 phr or less with respect to 100 phr of the components (a) and (b) which are rubber components.

3. The rubber composition according to Claim 1, wherein the weight ratio of the component (d) / the component (c) is 0.1 or more.

4. The rubber composition according to Claim 2, wherein the weight ratio of the component (d) / the component (c) is 0.1 or more.

5. The rubber composition according to Claim 1, wherein the weight ratio of the component (d) / the component (b) is 0.1 or more and 2 or less.

6. The rubber composition according to Claim 2, wherein the weight ratio of the component (d) / the component (b) is 0.1 or more and 2 or less.

7. The rubber composition according to Claim 3, wherein the weight ratio of the component (d) / the component (b) is 0.1 or more and 2 or less.

8. The rubber composition according to Claim 4, wherein the weight ratio of the component (d) / the component (b) is 0.1 or more and 2 or less.

9. A fluorine-containing elastomer obtained by crosslinking the rubber composition according to any one of Claims 1 to 8.

10. In the fluorine-containing elastomer, The components (a) and (b) are incompatible with each other and have a phase-separated structure, The component (d) is dispersed in the component (b), When comparing the component (d) dispersed in the component (b) with the component (d) not dispersed in the component (b), the component (d) dispersed in the component (b) is more, The fluorine-containing elastomer according to Claim 9.

11. A sealing material containing the fluorine-containing elastomer according to Claim 9.

12. Using a surface wave plasma etching apparatus, with a gas flow rate of O ２ (2000 sccm) + CF ４ (40 sccm), a processing pressure of 133 Pa, an output of 3 kW, and an exposure time of 2 hours, the fluorine-containing elastomer according to claim 10, wherein the weight loss rate after plasma exposure is 2% or less.

Images