JP7630472B2 - Sealing material and its manufacturing method - Google Patents

Description

The present invention relates to a sealing material and a method for manufacturing the same.

Sealing materials formed from crosslinked rubber compositions of hydrogen-containing fluororubber are known. For example, Patent Document 1 discloses a sealing material formed from a crosslinked rubber composition obtained by crosslinking an uncrosslinked rubber composition containing a hydrogen-containing fluororubber, an organic peroxide, and a one-component material containing a perfluoro skeleton compound having two or more alkenyl groups in the molecule.

JP 2019-52226 A

The objective of the present invention is to provide a sealing material with excellent radical resistance.

The present invention provides a sealing material formed of a crosslinked rubber composition obtained by crosslinking an uncrosslinked rubber composition containing a hydrogen-containing fluororubber, a thermal crosslinking agent, and a radical resistance improver, wherein the radical resistance improver is composed of only the A liquid of a two-component material having an A liquid containing a perfluoro skeleton compound having two or more alkenyl groups in its molecule and not containing a crosslinking agent , and a B liquid containing a perfluoro skeleton compound having two or more alkenyl groups in its molecule and a crosslinking agent, and only the A liquid of the two-component material is added to the uncrosslinked rubber composition, and the B liquid is not added .

The present invention relates to a method for producing a sealing material of the present invention, and includes preparing the uncrosslinked rubber composition containing the hydrogen-containing fluororubber, the thermal crosslinking agent, and the radical resistance improver, and then molding an uncrosslinked molded article having a shape of a sealing material from the uncrosslinked rubber composition. The uncrosslinked molded article is heated to crosslink the hydrogen-containing fluororubber with the thermal crosslinking agent, thereby obtaining a molded article.

According to the present invention, by using only liquid A of a two-liquid material having liquid A containing a perfluoro skeleton compound having two or more alkenyl groups in the molecule and liquid B containing a perfluoro skeleton compound having two or more alkenyl groups in the molecule and a crosslinking agent as a radical resistance improver to be contained in an uncrosslinked rubber composition used for manufacturing a sealing material, it is possible to obtain excellent radical resistance.

The following describes the embodiments in detail.

The sealing material according to the embodiment is manufactured using an uncrosslinked rubber composition containing hydrogen-containing fluororubber, a thermal crosslinking agent, and a radical resistance improver. In other words, this sealing material is formed of a crosslinked rubber composition in which an uncrosslinked molded body of the uncrosslinked rubber composition in the shape of a sealing material is heated to crosslink the hydrogen-containing fluororubber with the thermal crosslinking agent. The radical resistance improver is composed of only the former liquid A, which does not contain a crosslinking agent, of a two-liquid material having liquid A containing a perfluoro skeleton compound having two or more alkenyl groups in the molecule (hereinafter referred to as "compound X") and liquid B containing compound X and a crosslinking agent.

According to the sealing material of this embodiment, excellent radical resistance can be obtained by using only liquid A of a two-liquid material having liquid A containing compound X and liquid B containing compound X and a crosslinking agent as a radical resistance improver contained in the uncrosslinked rubber composition used to manufacture the sealing material. Therefore, this sealing material can be suitably used in semiconductor processing equipment that uses plasma, such as semiconductor etching equipment and plasma CVD equipment.

The hydrogen-containing fluororubber constitutes the rubber component of the matrix in the uncrosslinked rubber composition and the crosslinked rubber composition. Here, the "hydrogen-containing fluororubber" in this application is a fluororubber that contains carbon with hydrogen bonded to the main chain of the polymer.

Examples of hydrogen-containing fluororubbers include polymers of vinylidene fluoride (VDF) (PVDF), copolymers of vinylidene fluoride (VDF) and hexafluoropropylene (HFP), copolymers of vinylidene fluoride (VDF), hexafluoropropylene (HFP), and tetrafluoroethylene (TFE), copolymers of tetrafluoroethylene (TFE) and propylene (Pr) (FEP), and copolymers of vinylidene fluoride (VDF), propylene (Pr), and tetrafluoroethylene (TFE). Examples of such copolymers include copolymers of vinylidene fluoride (VDF), tetrafluoroethylene (TFE), ethylene (E) and perfluoromethylvinylether (PMVE), copolymers of vinylidene fluoride (VDF), tetrafluoroethylene (TFE), and perfluoromethylvinylether (PMVE), and copolymers of vinylidene fluoride (VDF) and perfluoromethylvinylether (PMVE). The hydrogen-containing fluororubber preferably contains one or more of these, and more preferably contains vinylidene fluoride rubber (FKM) having vinylidene fluoride (VDF) as a monomer.

The thermal crosslinking agent crosslinks the hydrogen-containing fluororubber when heated to a specified temperature. Examples of the thermal crosslinking agent include peroxides, polyols, polyamines, triazines, etc. Of these, peroxides are preferred as the thermal crosslinking agent, since they do not require the use of an acid acceptor that can cause particle generation in a plasma atmosphere.

Examples of peroxides in the thermal crosslinking agent include 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, α,α-bis(t-butylperoxy)-p-diisopropylbenzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)-hexyne-3, benzoyl peroxide, t-butylperoxybenzene, t-butylperoxymaleic acid, t-butylperoxyisopropylcarbonate, and t-butylperoxybenzoate. The peroxide in the thermal crosslinking agent preferably contains one or more of these, and more preferably contains 2,5-dimethyl-2,5-di(t-butylperoxy)hexane.

The content of the peroxide in the thermal crosslinking agent in the uncrosslinked rubber composition is preferably 0.5 parts by mass or more and 2.5 parts by mass or less, more preferably 0.5 parts by mass or more and 2.0 parts by mass or less, per 100 parts by mass of the hydrogen-containing fluororubber, from the viewpoint of sufficiently promoting crosslinking and obtaining good physical properties as a sealing material.

The radical resistance improver improves the radical resistance of the sealing material according to the embodiment. As described above, the radical resistance improver is composed of only the A liquid, which does not contain a crosslinking agent, of the two-component material having the A liquid containing compound X and the B liquid containing compound X and a crosslinking agent. Examples of commercially available two-component materials include SIFEL3405A/B, SIFEL3505A/B, and SIFEL3705A/B of the SIFEL series manufactured by Shin-Etsu Chemical Co., Ltd.

Examples of compound X contained in solution A constituting the radical resistance improver include compounds with a perfluoropolyether structure and compounds with a perfluoroalkylene structure. 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. The two or more alkenyl groups may be the same or different.

Examples of crosslinking agents not contained in the A liquid constituting the radical resistance improver include organohydrogenpolysiloxanes that react with the alkenyl groups in compound X.

Liquid A, which constitutes the radical resistance improver, may contain silica in addition to compound X. From the viewpoint of obtaining excellent radical resistance, the content of silica in liquid A is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less. Liquid A may also contain a metal catalyst, etc.

From the viewpoint of obtaining excellent radical resistance, the viscosity of the A liquid constituting the radical resistance improver at 23°C is preferably 40 Pa·s or more and 1200 Pa·s or less, more preferably 50 Pa·s or more and 500 Pa·s or less, and even more preferably 60 Pa·s or more and 200 Pa·s or less.

The content of the A liquid, which constitutes the radical resistance improver in the uncrosslinked rubber composition, is preferably 7 parts by mass or more and 20 parts by mass or less, more preferably 10 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of the hydrogen-containing fluororubber, from the viewpoint of obtaining excellent plasma resistance.

The uncrosslinked rubber composition may further contain a crosslinking aid. The crosslinking aid bonds with the hydrogen-containing fluororubber so as to be interposed between the molecules of the hydrogen-containing fluororubber when the hydrogen-containing fluororubber is crosslinked by the thermal crosslinking agent.

Examples of crosslinking aids include triallyl cyanurate, trimethallyl isocyanurate, triallyl isocyanurate, triacrylformal, triallyl trimellitate, N,N'-m-phenylene bismaleimide, dipropargyl terephthalate, diallyl phthalate, tetraallyl terephthalate amide, triallyl phosphate, bismaleimide, fluorinated triallyl isocyanurate (1,3,5-tris(2,3,3-trifluoro-2-propenyl)-1,3,5-triazine -2,4,6-trione), tris(diallylamine)-S-triazine, triallyl phosphite, N,N-diallylacrylamide, 1,6-divinyldodecafluorohexane, hexaallyl phosphoramide, N,N,N',N'-tetraallylphthalamide, N,N,N',N'-tetraallylmalonamide, trivinyl isocyanurate, 2,4,6-trivinylmethyltrisiloxane, tri(5-norbornene-2-methylene) cyanurate, triallyl phosphite, etc. The crosslinking aid preferably contains one or more of these, and more preferably contains triallyl isocyanurate from the viewpoint of obtaining excellent plasma resistance.

The content of the crosslinking aid in the uncrosslinked rubber composition is preferably 1 part by mass or more and 10 parts by mass or less, more preferably 3 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of the hydrogen-containing fluororubber, from the viewpoint of obtaining excellent plasma resistance.

The uncrosslinked rubber composition may contain polyvinylidene fluoride powder (PVDF powder) dispersed as a filler, since the problem of contamination inside the device due to the release of particles is unlikely to occur. The PVDF powder may be formed of either a homopolymer of vinylidene fluoride (VDF) or a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP), but the former is preferred from the viewpoint of obtaining excellent radical resistance.

From the viewpoint of obtaining excellent radical resistance, the volume average particle size of the PVDF powder is preferably 15 μm or less, more preferably 10 μm or less. From the similar viewpoint, the melting point of the PVDF powder is preferably 165° C. or more and 172° C. or less. From the similar viewpoint, the melt viscosity of the PVDF powder is preferably 35 kpoise or more and 39 kpoise or less. This melt viscosity is measured according to ASTM D3835 at 232° C. for 100 seconds.

The content of the PVDF powder in the uncrosslinked rubber composition is preferably 1 part by mass or more and 12 parts by mass or less, more preferably 3 parts by mass or more and 7 parts by mass or less, per 100 parts by mass of the hydrogen-containing fluororubber, from the viewpoint of obtaining excellent plasma resistance.

If the application of the sealing material according to the embodiment allows, the uncrosslinked rubber composition may also contain rubber components other than the hydrogen-containing fluororubber, reinforcing materials such as carbon black, plasticizers, processing aids, vulcanization accelerators, antioxidants, surfactants, etc.

The hardness of the crosslinked rubber composition forming the sealing material according to the embodiment is preferably 50A or more and 70A or less, more preferably 55A or more and 65A or less. This hardness is measured with a type A durometer according to JIS K6253-3:2012.

The tensile strength (TB) of the crosslinked rubber composition forming the sealing material according to the embodiment is preferably 13 MPa or more and 20 MPa or less, more preferably 14 MPa or more and 16 MPa or less. The elongation at break (EB) is preferably 150% or more and 400% or less, more preferably 250% or more and 350% or less. The 100% modulus (M ₁₀₀ : tensile stress at 100% elongation) is preferably 1.5 MPa or more and 3.5 MPa or less, more preferably 2 MPa or more and 3.0 MPa or less. The tensile strength (TB), elongation at break (EB), and 100% modulus (M ₁₀₀ ) are measured by a tensile test based on JIS K6251.

The compression set of the crosslinked rubber composition forming the sealing material according to the embodiment is preferably 15% to 50%, more preferably 25% to 35%, when the test time is 72 hours and the test temperature is 200°C, and is preferably 5% to 25%, more preferably 10% to 20%, when the test time is 72 hours and the test temperature is 150°C. These compression sets are measured based on JIS K6262:2013.

Next, we will explain the manufacturing method of the sealing material according to the embodiment.

In the manufacture of the sealing material according to the embodiment, first, an uncrosslinked rubber composition is prepared by kneading using an open-type rubber kneader such as an open roll or a closed-type rubber kneader such as a kneader.

Then, a predetermined amount of the uncrosslinked rubber composition is filled into the cavity of a preheated mold, the mold is closed, and in this state, it is maintained at a predetermined molding temperature and a predetermined molding pressure for a predetermined molding time. In this way, the uncrosslinked rubber composition is molded into an uncrosslinked molded body in the shape of a sealant for the cavity, and the uncrosslinked molded body in the shape of a sealant is heated to crosslink the hydrogen-containing fluororubber with the thermal crosslinking agent. This molding may be press molding or injection molding. The molding temperature is, for example, 150°C or higher and 180°C or lower. The molding pressure is, for example, 0.1 MPa or higher and 25 MPa or lower. The molding time is, for example, 3 minutes or higher and 20 minutes or lower.

Then, the mold is opened and the sealing material according to the embodiment is removed from the inside.

The sealing material according to the embodiment of the molded article released from the mold may be irradiated with radiation to perform post-crosslinking. In this case, examples of radiation include α-rays, β-rays, γ-rays, electron beams, ions, etc. Of these, the radiation is preferably electron beams or γ-rays. The radiation exposure dose is preferably 20 kGy or more and 100 kGy or less. However, from the viewpoint of obtaining excellent heat aging resistance, it is preferable not to perform this radiation irradiation treatment on the molded article obtained by heating the uncrosslinked molded body to crosslink the hydrogen-containing fluororubber with a thermal crosslinking agent.

(Crosslinked Rubber Composition)
The crosslinked rubber compositions of the following Examples and Comparative Examples were prepared. The configurations of each are also shown in Table 1.

<Example 1-1>
The mixture was 100 parts by mass of hydrogen-containing fluororubber FKM (Tecnoflon P959, Solvay), 1.5 parts by mass of thermal crosslinking agent peroxide (Perhexa 25B, NOF Corporation, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane), 12 parts by mass of crosslinking agent-free liquid A (silica content: 8.3% by mass, viscosity (23°C): 70 Pa·s) of two-liquid material 1 (SIFEL3405A/B, Shin-Etsu Chemical Co., Ltd.) having liquid A containing compound X and liquid B containing compound X and a crosslinking agent, 4 parts by mass of crosslinking assistant triallyl isocyanurate (TAIC, Mitsubishi Chemical Corporation), and PVDF powder (Kynar MG15) as a filler. An uncrosslinked rubber composition was prepared by adding 5 parts by mass of Arkema (volume average particle size: 7.9 μm, melting point: 165 to 172° C., melt viscosity: 35 to 39 kpoise) and 0.5 parts by mass of a surfactant and kneading them. The uncrosslinked rubber composition was heated to crosslink the hydrogen-containing fluororubber FKM with the thermal crosslinking agent peroxide, to obtain a crosslinked rubber composition designated as Example 1-1.

<Example 1-2>
The crosslinked rubber composition of Example 1-1 was irradiated with 30 kGy of gamma rays to obtain Example 1-2.

<Comparative Examples 1-1 and 1-2>
The crosslinked rubber compositions obtained in the same manner as in Examples 1-1 and 1-2, except that the A component of the two-component material 1 was replaced with the B component containing a crosslinking agent (silica content: 10.6 mass%, viscosity (23°C): 80 Pa·s), were designated as Comparative Examples 1-1 and 1-2, respectively.

<Comparative Examples 1-3 and 1-4>
The crosslinked rubber compositions obtained in the same manner as in Examples 1-1 and 1-2, except that half of the A component of the two-component material 1 was replaced with B component, and both A component and B component were used, were designated as Comparative Examples 1-3 and 1-4, respectively.

<Examples 2-1 and 2-2>
The crosslinked rubber compositions obtained in the same manner as in Examples 1-1 and 1-2, except that the A component of the two-component material 1 was replaced with the A component (silica content: 21.8 mass%, viscosity (23°C): 1100 Pa·s) of the two-component material 2 (SIFEL3705A/B manufactured by Shin-Etsu Chemical Co., Ltd.) that did not contain a crosslinking agent, were designated as Examples 2-1 and 2-2, respectively.

<Reference Examples 1 and 2>
The crosslinked rubber compositions obtained in the same manner as in Examples 1-1 and 1-2, except that a one-component material (X-71-369 manufactured by Shin-Etsu Chemical Co., Ltd., silica content: 10 mass%, viscosity (23°C): 9 Pa·s) was used instead of the A component of the two-component material 1, were designated as Reference Examples 1 and 2, respectively.

(Test Method)
<Hardness>
For each of the Examples, Comparative Examples, and Reference Examples, the hardness was measured using a type A durometer based on JIS K6253-3:2012.

<Tensile properties>
For each of the Examples, Comparative Examples and Reference Examples, a tensile test was carried out based on JIS K6251 to measure the tensile strength (TB), elongation at break (EB) and 100% modulus (M ₁₀₀ ).

<Compression set>
For each of the Examples, Comparative Examples, and Reference Examples, compression set (CS) was measured based on JIS K6262:2013 for a test time of 72 hours at a test temperature of 200°C, and for a test time of 72 hours at a test temperature of 150°C.

<Plasma resistance>
For each of the examples, comparative examples, and reference examples, _O2 plasma was irradiated using a microwave plasma generator. _O2 and _CF4 were used as reaction gases, and the flow rate ratio between them was 50:1. The reaction pressure was 100 Pa and the plasma irradiation time was 60 minutes. The time from the start of plasma irradiation to the start of crack generation was measured. The mass loss rate after irradiating _O2 plasma for 60 minutes was also calculated.

(Test Results)
The test results are shown in Table 2.

According to Table 2, Examples 1-1 and 1-2, which used only the A liquid of the two-component material 1, had a longer time from the start of plasma irradiation to when cracks began to occur than the corresponding Comparative Examples 1-1 and 1-2, which used only the B liquid, and Comparative Examples 1-3 and 1-4, which used both the A liquid and the B liquid, and therefore had superior plasma resistance.

It can be seen that Examples 1-1 and 1-2, which use only the A liquid of two-component material 1, have superior plasma resistance compared to Examples 2-1 and 2-2, which use only the A liquid of two-component material 2.

Example 1-1, which was not irradiated with gamma rays, has a smaller compression set than Example 1-2, which was irradiated with gamma rays, and therefore has superior heat aging resistance.

The present invention is useful in the technical field of sealing materials and their manufacturing methods.

Claims (10)

A sealing material formed of a crosslinked rubber composition obtained by crosslinking an uncrosslinked rubber composition containing a hydrogen-containing fluororubber, a thermal crosslinking agent, and a radical resistance improver,
The radical resistance improver is composed of only the A liquid of a two-component material having an A liquid containing a perfluoro skeleton compound having two or more alkenyl groups in its molecule and no crosslinking agent , and a B liquid containing a perfluoro skeleton compound having two or more alkenyl groups in its molecule and a crosslinking agent , and the uncrosslinked rubber composition is a sealing material to which only the A liquid of the two-component material is added, and no B liquid is added . The sealing material according to claim 1,
The sealing material, wherein the content of silica in the liquid A is 25 mass % or less. The sealing material according to claim 1,
The sealing material, wherein the viscosity of the liquid A at 23° C. is 40 Pa·s or more and 1200 Pa·s or less. The sealing material according to claim 1,
The sealing material, wherein the content of the solution A in the uncrosslinked rubber composition is 7 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the hydrogen-containing fluororubber. The sealing material according to claim 1,
The sealing material comprises the uncrosslinked rubber composition containing polyvinylidene fluoride powder dispersed therein. The sealing material according to claim 5,
The sealing material, wherein the content of the polyvinylidene fluoride powder in the uncrosslinked rubber composition is 1 part by mass or more and 12 parts by mass or less per 100 parts by mass of the hydrogen-containing fluororubber. The sealing material according to claim 1,
The crosslinked rubber composition has a tensile strength of 13 MPa or more as measured in accordance with JIS K6251. The sealing material according to claim 1,
The crosslinked rubber composition has a compression set of 35% or less, as measured based on JIS K6262:2013 at a test time of 72 hours and a test temperature of 200°C. A method for producing the sealing material according to any one of claims 1 to 8, comprising the steps of:
A method for producing a sealing material, comprising the steps of: preparing an uncrosslinked rubber composition containing the hydrogen-containing fluororubber, the thermal crosslinking agent, and the radical resistance improver ; molding the uncrosslinked rubber composition into an uncrosslinked molded article having a shape of a sealing material; and heating the uncrosslinked molded article to crosslink the hydrogen-containing fluororubber with the thermal crosslinking agent , thereby obtaining a molded article. The method for producing a sealing material according to claim 9 ,
The method for producing a sealing material does not involve irradiating the molded product obtained by heating the uncrosslinked molded body to crosslink the hydrogen-containing fluororubber with the thermal crosslinking agent.