Sealing material-forming material, sealing material, and production method for sealing material

Abstract

To provide a sealing material-forming material that facilitates easy reuse of a crosslinked perfluoro (co)polymer and that can form a sealing material having a low compression set and having excellent heat resistance and plasma resistance.SOLUTION: Provided is a sealing material-forming material containing a regenerated perfluoro (co)polymer, wherein the regenerated perfluoro (co)polymer is a (co)polymer in which at least a part of a crosslinking site has been regenerated by heat-treating a crosslinked perfluoro (co)polymer obtained by crosslinking a perfluoro (co)polymer having a nitrile group as the crosslinking site, and the perfluoro (co)polymer having a nitrile group contains a structural unit derived from at least one selected from perfluoroolefins and perfluoro vinyl ethers and a structural unit having a nitrile group.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a sealing material, a sealing material, and a method for manufacturing a sealing material. [Background technology]

[0002] Conventionally, sealing materials have been widely used in various applications. Among these applications, an example of an application of a sealing material that places the greatest load on the sealing material is a sealing material used in semiconductor manufacturing equipment, etc.

[0003] Cross-linkable fluoroelastomers such as fluoroelastomers (FKM) and perfluoroelastomers (FFKM) are used as such sealing materials because they have excellent plasma resistance and radical resistance, and FFKM is used particularly when high temperatures or harsh chemicals are used.

[0004] The sealing material made of the crosslinkable fluoroelastomer as described above is usually prepared by blending the crosslinkable fluoroelastomer with additives such as a crosslinking agent and a crosslinking aid to prepare an elastomer composition, which is then molded and crosslinked to form a sealing material.

[0005] As with general molded products, the sealing materials may require disposal of molding scraps (burrs), defective products, used molded products, etc. However, the excellent properties of crosslinked fluoroelastomers make them difficult to chemically treat, and they produce corrosive decomposition products when burned, making thermal recycling difficult. Therefore, they have been disposed of by landfilling or the like until now.

[0006] However, in recent years, with increasing awareness of environmental protection through reduction of landfill volume and effective utilization of resources, there has been a demand for the development of a method for reusing crosslinked fluoroelastomers that have conventionally been discarded.

[0007] As an example of a molded article obtained by reusing such a crosslinked fluoroelastomer, Patent Document 1 discloses a molded article obtained by decrosslinking a crosslinked fluoropolymer in a supercritical fluid or subcritical fluid of a compound having active hydrogen, and then crosslinking the resulting decrosslinked fluoropolymer. Furthermore, Patent Document 2 discloses a sealant containing a treated perfluoropolymer obtained by decomposing the crosslinking points of a crosslinked iodine- or bromine-containing perfluoropolymer. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-63334 [Patent Document 2] Patent No. 6134293 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the method described in Patent Document 1, which uses a supercritical fluid or a subcritical fluid, is not easy to process and the crosslinked fluoroelastomer cannot be easily reused, so there is room for improvement. Furthermore, as a result of intensive research by the present inventors, it was found that when the treated perfluoropolymer used in the sealing material described in Patent Document 2 is obtained, the perfluoropolymer decomposes, resulting in a significant decrease in mass of the perfluoropolymer, and further that the resulting sealing material has a large compression set and is poor in heat resistance and plasma resistance.

[0010] The present invention has been made in view of the above, and an object of the present invention is to provide a sealant-forming material that can easily reuse crosslinked perfluoro(co)polymers and can form sealants that have small compression set and excellent heat resistance and plasma resistance. [Means for solving the problem]

[0011] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by the following configuration examples, and have completed the present invention. An example of the configuration of the present invention is as follows.

[0012] [1] A sealant-forming material containing recycled perfluoro(co)polymer, The recycled perfluoro(co)polymer is a (co)polymer in which at least a part of the crosslinking sites is regenerated by heat-treating a crosslinked perfluoro(co)polymer obtained by crosslinking a perfluoro(co)polymer having a nitrile group as a crosslinking site, The perfluoro(co)polymer having a nitrile group contains a structural unit derived from at least one selected from a perfluoroolefin and a perfluorovinyl ether, and a structural unit having a nitrile group. Seal forming material.

[0013] [2] The sealing material according to [1], wherein the recycled perfluoro(co)polymer is a (co)polymer having at least one crosslinked structure selected from a triazine structure, an oxazole structure, an amidine structure, and an imidazole structure.

[0014] [3] The sealant-forming material according to [1] or [2], further comprising a crosslinking agent having a functional group capable of reacting with a nitrile group.

[0015] [4] The sealant-forming material according to any one of [1] to [3], further comprising an uncrosslinked perfluoro(co)polymer. [5] The sealant-forming material according to [4], wherein the content of the recycled perfluoro(co)polymer is 0.5 parts by mass or more per 100 parts by mass of the uncrosslinked perfluoro(co)polymer.

[0016] [6] A sealant obtained by crosslinking and molding the sealant-forming material according to any one of [1] to [5].

[0017] [7] A method for producing a sealant, comprising a step of crosslinking the sealant-forming material according to any one of [1] to [5].

[0018] [8] A method for producing the sealing material according to [7], comprising a step of heat-treating a crosslinked perfluoro(co)polymer obtained by crosslinking a perfluoro(co)polymer having nitrile groups as crosslinking sites to regenerate at least a portion of the crosslinking sites, thereby obtaining a regenerated perfluoro(co)polymer. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a sealing material-forming material that can easily reuse a crosslinked perfluoro(co)polymer and can form a sealing material that has small compression set and excellent heat resistance and plasma resistance. Furthermore, the present invention can provide a sealing material that has excellent moldability into a sealing material having desired physical properties. DETAILED DESCRIPTION OF THE INVENTION

[0020] <Sealing material> The sealing material according to the present invention (hereinafter also referred to as "the material") contains a recycled perfluoro(co)polymer (hereinafter also referred to as "recycled product") in which at least a portion of the crosslinking sites are regenerated by heat-treating a crosslinked perfluoro(co)polymer formed by crosslinking a perfluoro(co)polymer having nitrile groups as crosslinking sites. Because the material contains such recycled products, it can form a sealing material with smaller compression set and excellent heat resistance and plasma resistance than a sealing material obtained using a heat-treated product obtained by heat-treating a crosslinked perfluoro(co)polymer in which a perfluoro(co)polymer having halogen atoms (e.g., iodine atoms or bromine atoms) as crosslinking sites is crosslinked, which is usually crosslinked using a peroxide-based crosslinking agent.Furthermore, compared to a sealing material-forming material containing the heat-treated product, the material has excellent kneadability of the components used to form the sealing material and excellent moldability into a sealing material with desired physical properties.

[0021] <Recycled product> The recycled product is a crosslinked perfluoro(co)polymer (hereinafter also referred to as the "recycled product") in which a perfluoro(co)polymer having nitrile groups as crosslinking sites (hereinafter also referred to as the "uncrosslinked perfluoro(co)polymer") is crosslinked, and at least a portion of the nitrile groups that serve as crosslinking sites are regenerated by heat treating the crosslinked perfluoro(co)polymer (hereinafter also referred to as the "uncrosslinked perfluoro(co)polymer"). The recycled product used in the present material may be one type or two or more types.

[0022] Examples of the regenerated product include a crosslinked perfluoro(co)polymer having at least one crosslinked structure selected from a triazine structure, an oxazole structure, an amidine structure, and an imidazole structure. The regenerated product may have one type of crosslinked structure or two or more types of crosslinked structures. Examples of the crosslinked perfluoro(co)polymer having a triazine structure include a (co)polymer having a structure represented by the left side of the following formula (1), and examples of the crosslinked perfluoro(co)polymer having an oxazole structure include a (co)polymer having a structure represented by the left side of the following formula (2). In this specification, -RC≡N represents a perfluoro(co)polymer having a nitrile group as a crosslinking site.

[0023] The reaction formula when the crosslinked perfluoro(co)polymer having a triazine structure is heat-treated can be represented, for example, by the following formula (1): The reaction formula when the crosslinked perfluoro(co)polymer having an oxazole structure is heat-treated can be represented, for example, by the following formula (2):

[0024] [ka]

[0025] [ka] [In formula (2), X is a structure derived from an oxazole-based crosslinking agent, and examples thereof include a hexafluoropropane-2,2-diyl group, a sulfonyl group, and a 9,9-fluorenyl group.]

[0026] The recycled product is a perfluoro(co)polymer having nitrile groups as crosslinking sites, which is obtained by heat treating the recycled product to regenerate the nitrile groups as crosslinking sites. In this way, the process goes from perfluoro(co)polymer having nitrile groups → crosslinking → perfluoro(co)polymer having nitrile groups, and this cycle can be repeated multiple times (recycled multiple times) for perfluoro(co)polymer having nitrile groups.

[0027] On the other hand, perfluoro(co)polymers having halogen atoms (e.g., iodine atoms or bromine atoms) as crosslinking sites are usually crosslinked using peroxide-based crosslinking agents. When a crosslinked perfluoro(co)polymer in which such perfluoro(co)polymers having halogen atoms as crosslinking sites are crosslinked is heat-treated, the crosslinked structure is "decomposed," resulting in the generation of C=C bonds and carboxyl groups, which then become crosslinking sites for re-crosslinking.

[0028] In other words, in perfluoro(co)polymers having nitrile groups as crosslinking sites, the nitrile groups as crosslinking sites react to form crosslinked perfluoro(co)polymers, as shown in the following formulas (3) and (4), and the nitrile groups as crosslinking sites are "regenerated" by heat treatment, whereas in perfluoro(co)polymers having halogen atoms as crosslinking sites, the halogen atoms as crosslinking sites react to form crosslinked perfluoro(co)polymers, and the crosslinked structure is "decomposed" by heat treatment, resulting in C=C bonds and carboxyl groups, but the halogen atoms as crosslinking sites are not regenerated. Therefore, the mechanisms by which crosslinking sites are regenerated are completely different between "perfluoro(co)polymers having nitrile groups as crosslinking sites" and "perfluoro(co)polymers having halogen atoms as crosslinking sites," and further, the effects of heat resistance and compression set on sealing materials obtained using the regenerated products are different.

[0029] The recycled product is preferably not a (co)polymer in which all of the crosslinking sites of the recycled product are recycled. In other words, the recycled product preferably has a crosslinked structure at least in part, and more preferably has at least one crosslinked structure selected from the triazine structure, oxazole structure, amidine structure, and imidazole structure.

[0030] The content of nitrile groups in the recycled product is preferably 101% or more, more preferably 200% or more, assuming that the content of nitrile groups in the recycled product is 100%. There is no particular upper limit, but the content is equal to or less than the content of nitrile groups in the uncrosslinked perfluoro(co)polymer before the recycled product is crosslinked, specifically 15,000% or less, more preferably 7,000% or less. By using a recycled product having a nitrile group content within the above range, a sealing material with a smaller compression set can be easily formed. The content of the nitrile group can be measured using FT-IR, specifically by the method described in the examples below.

[0031] Furthermore, since the obtained recycled product can be used to easily form a sealing material having desired physical properties, the mass reduction rate due to the heat treatment, specifically, the mass reduction rate represented by the following formula (A), is preferably 10% or less, more preferably 3% or less. Mass reduction rate (%) = [(mass of recycled product - mass of recycled product) / mass of recycled product] × 100 (A)

[0032] Considering the balance between environmental protection, effective utilization of resources, and the ability to easily form a sealing material having the desired physical properties, the amount of recycled material used is preferably 0.5 to 100% by mass, more preferably 1 to 90% by mass, and even more preferably 10 to 80% by mass, relative to 100% by mass of the material. Furthermore, when an uncrosslinked perfluoro(co)polymer is used in the material, the amount of the recycled product used is preferably 0.5 parts by mass or more, more preferably 0.5 to 100 parts by mass, even more preferably 1 to 90 parts by mass, and particularly preferably 10 to 80 parts by mass, per 100 parts by mass of the uncrosslinked perfluoro(co)polymer, from the viewpoint that a sealing material having the desired physical properties can be easily formed.

[0033] <Recycled products> The recycled product is a crosslinked perfluoro(co)polymer formed by crosslinking a perfluoro(co)polymer having a nitrile group as a crosslinking site, and examples thereof include crosslinked perfluoro(co)polymers contained in (unused) molded products such as sealing materials formed using conventional uncrosslinked perfluoro(co)polymers (virgin products), scraps (burrs) generated during the production of such molded products, defective products, used molded products, etc. Examples of the used compacts include not only those used in semiconductor manufacturing equipment but also those used in chemical plants, various industrial equipment, and the like. The raw material to be subjected to the heat treatment may be the crosslinked perfluoro(co)polymer itself, the (unused) molded body, the scraps (burrs) or defective products, or the used molded body.

[0034] The crosslinked perfluoro(co)polymer in the recycled product is a crosslinked product obtained by crosslinking the following uncrosslinked perfluoro(co)polymer (virgin product) by a conventionally known method. The conventionally known method includes crosslinking using a crosslinking agent, such as a triazine-based crosslinking agent, an oxazole-based crosslinking agent, or an imidazole-based crosslinking agent. In other words, the recycled product includes a crosslinked perfluoro(co)polymer having a crosslinked structure derived from these crosslinking agents, specifically, at least one crosslinked structure selected from a triazine structure, an oxazole structure, an imidazole structure, and an intermediate structure when these crosslinked structures are formed (e.g., an amidine structure when an oxazole structure is formed). The degree of crosslinking in the recycled product is not particularly limited, and it is sufficient if the degree of crosslinking is the same as that when forming a molded product such as a sealing material.

[0035] The crosslinking using the triazine-based crosslinking agent (triazine structure) can be represented, for example, by the following formula (3), and the crosslinking using the oxazole-based crosslinking agent (oxazole structure) can be represented, for example, by the following formula (4). Furthermore, the crosslinked structure obtained using the oxazole-based crosslinking agent may be an oxazole structure that is ultimately obtained in the following formula (4), or an amidine structure that is an intermediate structure thereof.

[0036] [ka]

[0037] [ka] [In formula (4), X is a structure derived from an oxazole-based crosslinking agent, and examples thereof include a hexafluoropropane-2,2-diyl group, a sulfonyl group, and a 9,9-fluorenyl group.]

[0038] [Uncrosslinked perfluoro(co)polymer] The uncrosslinked perfluoro(co)polymer contains a structural unit derived from at least one selected from perfluoroolefins and perfluorovinyl ethers, and a structural unit having a nitrile group. The uncrosslinked perfluoro(co)polymer is a perfluoro(co)polymer having nitrile groups as crosslinking sites before crosslinking, and can also be called a "virgin product."

[0039] The uncrosslinked perfluoro(co)polymer is preferably a perfluoroelastomer (FFKM). The non-crosslinked perfluoro(co)polymer is preferably a (co)polymer that does not contain a carbon-hydrogen bond in the main chain of the (co)polymer. The perfluoroolefin is preferably tetrafluoroethylene.

[0040] The FFKM is not particularly limited, but examples thereof include tetrafluoroethylene (TFE)-perfluorovinyl ether copolymers having nitrile groups as crosslinking sites, and copolymers containing TFE-derived structural units and perfluorovinyl ether-derived structural units, and further containing, if necessary, structural units derived from nitrile group-containing monomers, are preferred.

[0041] Suitable examples of the perfluorovinyl ether include perfluoro(alkyl vinyl ether) and perfluoro(alkoxyalkyl vinyl ether).

[0042] The perfluoro(alkyl vinyl ether) may be a compound in which the alkyl group has, for example, 1 to 10 carbon atoms. Specific examples include perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), and perfluoro(propyl vinyl ether), and preferably perfluoro(methyl vinyl ether).

[0043] Examples of the perfluoro(alkoxyalkyl vinyl ether) include compounds in which the group bonding to the vinyl ether group (CF2=CFO-) has 3 to 15 carbon atoms, and specific examples include the following compounds. CF2=CFOCF2CF(CF3)OC n F 2n+1 CF2=CFO(CF2)3OC n F 2n+1 CF2=CFOCF2CF(CF3)O(CF2O) m C n F 2n+1 CF2=CFO(CF2)2OC n F 2n+1 In these formulas, n is independently 1 to 5, for example, and m is 1 to 3, for example.

[0044] Examples of the nitrile group-containing monomer include nitrile group-containing perfluorovinyl ethers, and specific examples thereof include the following compounds. CF2=CFO(CF2) n OCF(CF3)CN (n is, for example, 2 to 4) CF2=CFO(CF2) n CN (n is, for example, 2 to 12) CF2=CFO[CF2CF(CF3)O] m (CF2) n CN (n is, for example, 1 to 4, m is, for example, 1 to 5) CF2=CFO[CF2CF(CF3)O] n CF2CF(CF3)CN (n is, for example, 0 to 4) CF2=CF(CF2) n CN (n is an integer of, for example, 1 to 8) CF2=CFCF2(OCF2) n CN (n is an integer of, for example, 0 to 5) CF2=CFCF2(OCF(CF3)CF2) m -CN (m is, for example, an integer of 0 to 5, and n is, for example, an integer of 0 to 5) CF2=CF(OCF2CF(CF3)) m O(CF2) n -CN (m is, for example, an integer of 0 to 5, and n is, for example, an integer of 1 to 8) CF2=CF(OCF2CF(CF3)) m -CN (m is, for example, an integer of 1 to 5) CF2=CFOCF2(CF(CF3)OCF2) n CF(-CN)CF3 (n is, for example, an integer of 1 to 4) CF2=CFO(CF2) n OCF(CF3)-CN (n is, for example, an integer of 2 to 5) CF2=CF(OCF2CF(CF3)) n OCF2CF(CF3)-CN (n is, for example, an integer of 1 to 2) CF2=CFO(CF2CF(CF3)O) m (CF2) n-CN (m is, for example, an integer of 0 to 5, and n is, for example, an integer of 1 to 3) CF2=CFO(CF2CF(CF3)O) m CF2CF(CF3)-CN (m is an integer greater than or equal to 0) CF2=CFOCF(CF3)CF2O(CF2) n -CN (n is an integer greater than or equal to 1) CF2=CFOCF2OCF2CF(CF3)OCF2-CN

[0045] In FFKM, the content of structural units derived from TFE is preferably 50.0 to 79.9 mol %, the content of structural units derived from perfluorovinyl ether is preferably 20.0 to 46.9 mol %, and the content of structural units derived from nitrile group-containing monomers is preferably 0.1 to 2.0 mol %.

[0046] <Heat treatment conditions, etc.> The heat treatment is not particularly limited as long as it is a heat treatment that regenerates nitrile groups, which are crosslinking sites, in the regenerated product. The heat treatment may be carried out in an oxygen-containing gas atmosphere or an inert gas atmosphere, but it is preferable to carry out the heat treatment in an inert gas atmosphere, because this can suppress decomposition of the recycled product when obtaining a recycled product from the recycled product, suppress mass loss of the perfluoro(co)polymer, and furthermore, it is possible to easily obtain a recycled product in which a large amount of nitrile groups, which are crosslinking sites, are recovered.

[0047] The oxygen-containing gas is, for example, a gas in which the oxygen content is preferably 5% by volume or more relative to the total volume, and a specific example is air. Specific examples of the inert gas include nitrogen gas, argon gas, and helium gas, and among these, nitrogen gas is preferred. The inert gas may be used alone or in combination of two or more kinds. The inert gas is preferably a gas that does not contain oxygen or a gas that contains a small amount of oxygen, in order to more effectively exhibit the effects of the present invention. As for the gas containing a small amount of oxygen, since a high oxygen content makes it easier for the thermal decomposition of the product to be recycled to proceed, it is desirable that the oxygen content be less than 5% by volume, more preferably 3% by volume or less, and even more preferably 1% by volume or less, of the total.

[0048] The temperature and time for the heat treatment are not particularly limited as long as they allow the nitrile groups, which are crosslinking sites, to be regenerated on the regenerated product. The temperature during the heat treatment is usually higher than the temperature at which the uncrosslinked perfluoro(co)polymer (virgin product) is crosslinked by a conventionally known method, and is preferably 300 to 400°C, more preferably 320 to 390°C, and even more preferably 350 to 380°C. The time for the heat treatment varies depending on the heat treatment temperature, but is preferably 30 minutes to 5 hours, more preferably 1 to 3 hours. The pressure during the heat treatment is not particularly limited, but it is preferable to carry out the heat treatment under normal pressure.

[0049] <Other ingredients> The material is not particularly limited as long as it contains the recycled product, and may be a material consisting essentially of the recycled product, but may also contain other conventionally known components that have been blended into molded articles such as sealing materials, as necessary. Examples of such other components include uncrosslinked perfluoro(co)polymers (virgin products); crosslinking agents; crosslinking aids; compounds containing ethylenically unsaturated bonds; reactive organosilicon compounds having two or more hydrosilyl groups in the molecule; perfluoropolyethers; non-adhesive agents such as fluorine oils; catalysts; polyol-based compounds; (co)polymers other than the above-mentioned perfluoro(co)polymers (e.g., fluororesins); acid acceptors such as magnesium oxide and calcium hydroxide; organic pigments such as anthraquinone-based pigments, perylene-based pigments, and dioxazine-based pigments; processing aids; vulcanization accelerators; antioxidants; antioxidants; inorganic fillers; and organic fillers. The other components may each be used alone or in combination of two or more.

[0050] <Uncrosslinked perfluoro (co)polymer> It is preferable to use an uncrosslinked perfluoro(co)polymer (virgin product) for this material, since this material has excellent moldability and can be easily obtained, and a sealing material having the desired physical properties (hardness, tensile strength, elongation at break, compression set, and plasma resistance) can be easily formed. Examples of the uncrosslinked perfluoro(co)polymer include (co)polymers similar to the uncrosslinked perfluoro(co)polymers described in the section on the recycled product. As the uncrosslinked perfluoro(co)polymer, a perfluoro(co)polymer having a crosslinking site other than a nitrile group may be used, but it is preferable to use a perfluoro(co)polymer having a nitrile group.

[0051] When an uncrosslinked perfluoro(co)polymer is used in the present material, the amount of the uncrosslinked perfluoro(co)polymer used is preferably 0.5 to 99.5 mass%, more preferably 1 to 90 mass%, and even more preferably 10 to 80 mass%, relative to 100 mass% of the present material, from the viewpoint of easily forming a sealing material having the desired physical properties.

[0052] <Crosslinking agent> Although this material can be crosslinked without using a crosslinking agent, it is preferable to use a crosslinking agent appropriate for the type of recycled product or uncrosslinked perfluoro(co)polymer used for this material, because it is possible to easily form a sealing material that is sufficiently crosslinked and has a good balance of hardness, tensile strength, elongation at break, and tensile stress at 100% elongation (100% Mo). It is more preferable to use a crosslinking agent that has a functional group that can react with a nitrile group.

[0053] The crosslinking agent having a functional group capable of reacting with a nitrile group can be any conventionally known crosslinking agent, such as the crosslinking agent described in Japanese Patent No. 5278312, without any particular limitation. Specific examples include triazine-based crosslinking agents, oxazole-based crosslinking agents, imidazole-based crosslinking agents, thiazole-based crosslinking agents, amidoxime-based crosslinking agents, and amidrazone-based crosslinking agents. Among these, triazine-based crosslinking agents, oxazole-based crosslinking agents, and imidazole-based crosslinking agents are preferred.

[0054] Examples of triazine crosslinking agents include 2,4,6-trimercapto-1,3,5-triazine, 2-hexylamino-4,6-dimercaptotriazine, 2-diethylamino-4,6-dimercaptotriazine, 2-cyclohexylamino-4,6-dimercaptotriazine, 2-dibutylamino-4,6-dimercaptotriazine, 2-anilino-4,6-dimercaptotriazine, and 2-phenylamino-4,6-dimercaptotriazine. The triazine crosslinking agent may also be a compound that can act as a catalyst to form a triazine ring using only the nitrile groups contained in the recycled product or the uncrosslinked perfluoro(co)polymer, such as an organic tin compound such as tetraphenyltin or triphenyltin.

[0055] Examples of oxazole-based crosslinking agents include those that react with nitrile groups to form an oxazole ring or an amidine structure to give a crosslinked product, and specific examples include 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (BOAP), 4,4'-sulfonylbis(2-aminophenol), and 9,9-bis(3-amino-4-hydroxyphenyl)fluorene.

[0056] Examples of imidazole crosslinking agents include those that react with a nitrile group to form an imidazole ring and give a crosslinked product, and specific examples include 2,2-bis(3,4-diaminophenyl)hexafluoropropane, 2,2-bis[3-amino-4-(N-methylamino)phenyl]hexafluoropropane, 2,2-bis[3-amino-4-(N-ethylamino)phenyl]hexafluoropropane, 2,2-bis[3-amino-4-(N-propylamino)phenyl]hexafluoropropane, 2,2-bis[3-amino-4-(N-phenylamino)phenyl]hexafluoropropane, 2,2-bis[3-amino-4-(N-perfluorophenylamino)phenyl]hexafluoropropane, and 2,2-bis[3-amino-4-(N-benzylamino)phenyl]hexafluoropropane.

[0057] When a crosslinking agent is used in this material, the amount of the crosslinking agent used is preferably 0.2 to 4 parts by mass, more preferably 0.2 to 2.5 parts by mass, per 100 parts by mass of the recycled product and uncrosslinked perfluoro(co)polymer in total, from the viewpoint that the crosslinking reaction proceeds sufficiently and a sealing material having excellent balance of hardness, tensile strength, elongation at break, and 100% Mo can be easily formed.

[0058] <Ethylenically unsaturated bond-containing compound> Examples of the ethylenically unsaturated bond-containing compound include compounds described in WO 2022 / 065054, JP 2003-183402 A, and JP 11-116684 A.

[0059] <Reactive organosilicon compounds> Examples of the reactive organosilicon compound include compounds similar to the organosilicon compounds described in JP-A Nos. 2003-183402 and 11-116684.

[0060] <catalyst> Examples of the catalyst include the same catalysts as those described in JP-A Nos. 2003-183402 and 11-116684.

[0061] <Organic pigments> Examples of the organic pigment include organic pigments similar to those described in International Publication No. 2016 / 043100, Japanese Patent No. 4720501, International Publication No. 2004 / 094527, Japanese Patent No. 5278312, and the like.

[0062] <Filling material> Examples of the inorganic filler include particulate (powdered) inorganic materials such as carbon black, silica, barium sulfate, titanium oxide, and aluminum oxide. Examples of the organic filler include particulate (powdered) organic materials such as fluororesins such as PTFE, PFA, FEP, ETFE, and PVDF, polyethylene, polyimide, polyamideimide, polyetherimide, polyetheretherketone, polyetherketone, silicone resin, and melamine resin.

[0063] <How to prepare this material> This material can be prepared by mixing (kneading) the recycled product and, if necessary, the other components. When mixing the recycled product with the other components, the order of mixing is not particularly limited, and they may be mixed (kneaded) sequentially in any order, or they may be mixed (kneaded) all at once, but it is preferable to mix (knead) them sequentially so that each component is uniform.

[0064] For the mixing (kneading), a conventionally known mixer (kneader) can be used, and examples thereof include an open roll, a Banbury mixer, a twin-screw roll, and a kneader. Furthermore, during the mixing (kneading) process, the components may be mixed (kneaded) under heating or cooling, as necessary, depending on the mixer (kneader) used.

[0065] <Sealing material> The sealing material according to the present invention (hereinafter also referred to as "the sealing material") is a crosslinked product of the present material obtained by crosslinking and molding the present material. Although this sealing material uses recycled perfluoro(co)polymer, it has physical properties (hardness, tensile strength, elongation at break, compression set, and plasma resistance) comparable to those of virgin products (uncrosslinked perfluoro(co)polymers), and is particularly characterized by its small compression set and excellent heat resistance and plasma resistance.

[0066] The tensile strength of the present sealing material, measured by the method described in the examples below, is preferably 7 MPa or more, more preferably 8 MPa or more. The elongation at break of the sealing material, measured by the method described in the examples below, is preferably 120% or more, and more preferably 130% or more. The compression set of this sealing material measured according to JIS K 6262:2013 (200°C x 72 hours, compression rate 25%) is preferably 10% or less, more preferably 5% or less, and the lower limit is not particularly limited, but is, for example, 0%. The compression set of this sealing material measured in accordance with JIS K 6262:2013 (260°C x 72 hours, compression rate 20%) is preferably 15% or less, more preferably 10% or less, and the lower limit is not particularly limited, but is, for example, 0%. The mass loss rate of the present sealing material measured by the method described in the examples below is preferably 5% or less, more preferably 3% or less, and the lower limit is not particularly limited, but is, for example, 0%.

[0067] The sealing material of the present invention is not particularly limited, but can be used, for example, as a gasket or packing for various components, and is particularly suitable for use as a sealing material for semiconductor manufacturing equipment and plasma processing equipment, particularly as a sealing material for drive parts such as gate valves used in the openings of plasma processing chamber units. Examples of the sealing material include O-rings, square rings, gaskets, packings, oil seals, bearing seals, and lip seals. The shape and other properties of the sealing material may be appropriately selected depending on the intended use.

[0068] The semiconductor manufacturing equipment is not limited to equipment specifically for manufacturing semiconductors, but broadly includes all manufacturing equipment used in the semiconductor field that requires a high degree of cleanliness, such as equipment for manufacturing liquid crystal panels, plasma panels, etc., and specific examples include the equipment described in Japanese Patent No. 5278312, etc.

[0069] <Method for manufacturing sealing material> The method for producing a sealing material according to the present invention (hereinafter also referred to as the "method for producing the present sealing material") includes step I of crosslinking the present material.

[0070] When forming a sealing material from this material, it is preferable to carry out a separating step in order to improve the efficiency of the molding work, reduce the defective rate, etc. This separating step is usually carried out using a roll or the like, and is usually also a step of preliminarily forming this material into a sheet.

[0071] The sheet obtained in the separating step is preferably preformed into a desired shape of the sealing material before the crosslinking step. This preforming may involve directly forming the desired sealing material shape from the sheet obtained in the extrusion process, or the sheet obtained in the extrusion process may be cut or extrusion molded into a rope-like shape (which also has the same meaning as a ribbon-like or noodle-like shape), and the resulting rope-like material may be formed into the desired sealing material shape.

[0072] <Process I> More preferably, the step I includes a primary crosslinking step and a secondary crosslinking step. The step I is preferably carried out using a preform having a desired sealing material shape obtained by the preforming.

[0073] The primary crosslinking step is preferably a step of heating and pressurizing a preformed body having a desired sealing material shape obtained by the preforming step. A specific example of this step is a step of placing the preformed body in a mold and crosslinking it using a heating press or the like under a pressure of about 2 to 15 MPa at a temperature of, for example, 150 to 200°C for, for example, about 5 minutes to 1 hour.

[0074] The secondary crosslinking step is preferably a step of heating the molded body obtained in the primary crosslinking step, and specifically includes a step of heating the molded body at normal pressure to reduced pressure using various ovens, preferably a vacuum oven, at a temperature of, for example, 150 to 300°C for 1 to 48 hours, more preferably for 3 to 24 hours. This secondary crosslinking step accelerates crosslinking, and even if unreacted components remain after the primary crosslinking step, the unreacted components can be decomposed and evaporated, thereby forming a sealing material that emits less gas.

[0075] In the method for producing the sealing material of the present invention, a step of irradiating with radiation (radiation irradiation step) may be carried out after the crosslinking step, in order to more easily suppress cracks that may occur in the sealing material in a plasma atmosphere, etc. The sealing material obtained through this radiation irradiation step can be said to be a radiation-treated product.

[0076] The radiation to be irradiated in the radiation irradiation step is not particularly limited, but examples thereof include X-rays, gamma rays, electron beams, proton beams, neutron beams, heavy particle beams, alpha rays, and beta rays, and among these, gamma rays and electron beams are preferred. The radiation to be irradiated may be of one type alone or of two or more types.

[0077] When irradiating with radiation, it is desirable to irradiate so that the absorbed dose is preferably 1 to 120 kGy, more preferably 20 to 100 kGy. Irradiation with such an amount of radiation can reduce unreacted components that can become particles or released gases, and can easily form a sealing material that is excellent in plasma resistance, crack resistance, etc., without excessively lowering the molecular weight of the recycled product and uncrosslinked perfluoro(co)polymer. The radiation irradiation step may be carried out in two or more stages by changing the conditions.

[0078] Although irradiation with radiation may be performed in air, the presence of oxygen during irradiation may inhibit the crosslinking reaction, resulting in a decrease in the mechanical strength of the resulting sealant and a possibility of the resulting sealant becoming sticky on its surface. For this reason, the radiation irradiation step is preferably performed in an atmosphere of an inert gas such as nitrogen or argon.

[0079] <Process II> The method for producing the sealing material preferably includes, before step I and the separation step, step II in which a crosslinked perfluoro(co)polymer (processed product) in which a perfluoro(co)polymer having nitrile groups as crosslinking sites is crosslinked is heat-treated to regenerate at least a portion of the crosslinking sites to obtain a regenerated perfluoro(co)polymer (regenerated product). The treated article used in step II, the recycled article obtained in step II, and the heat treatment conditions in step II are as described in the section on the sealing material. [Example]

[0080] Next, the present invention will be described in more detail by showing examples, but the present invention is not limited to these examples.

[0081] <Uncrosslinked perfluoro (co)polymer (virgin product)> The uncrosslinked perfluoro(co)polymers (virgin products) used in the following examples and comparative examples are as follows: "Uncrosslinked perfluoro(co)polymer-1": PFE131T (3M, perfluoro(co)polymer with nitrile groups as crosslinking sites) "Uncrosslinked perfluoro(co)polymer-c1": Tecnoflon PFR94 (manufactured by Solvay, a perfluoro(co)polymer in which the crosslinking site is a halogen atom)

[0082] <Crosslinked perfluoro(co)polymer (recycled product)> The crosslinked perfluoro(co)polymers (products to be recycled) used in the following preparation examples are as follows: "Crosslinked perfluoro(co)polymer-1": 100 parts by mass of perfluoroelastomer (PFE131T [manufactured by 3M]) and 0.5 parts by mass of an oxazole-based crosslinking agent (BOAP, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, manufactured by Tokyo Chemical Industry Co., Ltd.) were mixed using an open roll, and the resulting bulk elastomer composition was filled into an O-ring-shaped mold and press-molded at 180°C for 30 minutes (primary crosslinking) using a compression vacuum press under a pressure of 5 MPa. The press-molded sheet was then heated in an oven at 250°C for 24 hours (secondary crosslinking), producing a molded product (O-ring) (corresponding to an unused or used molded product). "Crosslinked perfluoro(co)polymer-2": A primary crosslinked molded product (burr) that protrudes from the joints of a mold when primary crosslinking is performed in a mold during the manufacturing process of "Crosslinked perfluoro(co)polymer-1." "Crosslinked perfluoro(co)polymer-c1": a molded product (O-ring) (corresponding to an unused or used molded product) produced by kneading 100 parts by mass of a perfluoroelastomer (Tecnoflon PFR94 [manufactured by Solvay]), 1 part by mass of TAIC (manufactured by Mitsubishi Chemical Corporation, triallyl isocyanurate), and 0.5 parts by mass of Perhexa 25B (manufactured by NOF Corporation) using an open roll, filling the resulting block of elastomer composition into an O-ring-shaped mold, and press-molding it at 170°C for 10 minutes using a compression vacuum press under a pressure of 5 MPa (primary crosslinking), and then heating the press-molded sheet in an oven at 200°C for 4 hours (secondary crosslinking).

[0083] [Production Example 1] The crosslinked perfluoro(co)polymer-1 (the product to be recycled) was placed in a KDF-75Plus manufactured by Yamato Scientific Co., Ltd. and heat-treated at 380°C and 1 atmosphere for 1 hour in a nitrogen atmosphere to obtain a recycled perfluoro(co)polymer-1 (the recycled product).

[0084] <Crosslinking site content> FT-IR (Bruker, HYPERION3000) was used, resolution: 4 cm -1 , Number of scans: 32, Transmission method, Measurement range: 400~4000cm-1 Under the conditions above, the contents of crosslinking sites in the crosslinked perfluoro(co)polymer-1 (product to be recycled) and the recycled perfluoro(co)polymer-1 (product recycled) were measured. Specifically, 2230-2290cm -1 The maximum intensity when the intensity of the -1 The intensity of the 2500cm -1 The value obtained by dividing the strength by the strength at 1000 kJ / g was taken as the content of crosslinking sites (nitrile groups). However, if the calculation result (content of crosslinking sites (nitrile groups)) was less than 0.01, the content of crosslinking sites (nitrile groups) was taken as 0.01.

[0085] The content of crosslinking sites (nitrile groups) in the crosslinked perfluoro(co)polymer-1 (recycled product) was 0.1, and the content of crosslinking sites (nitrile groups) in the recycled perfluoro(co)polymer-1 (recycled product) was 0.35.

[0086] <Mass reduction rate> The mass of the crosslinked perfluoro(co)polymer-1 (recycled product) was measured, and the mass of the resulting recycled perfluoro(co)polymer-1 (recycled product) was also measured, and the mass loss rate (%) was calculated using the following formula (A). The mass loss rate was 0.6%. Mass reduction rate (%) = [(mass of recycled product - mass of recycled product) / mass of recycled product] × 100 (A)

[0087] [Production Example 2] A recycled perfluoro(co)polymer-2 (recycled product) was obtained in the same manner as in Preparation Example 1, except that the heat treatment was carried out in air instead of in a nitrogen atmosphere. The content of crosslinking sites (nitrile groups) in the recycled perfluoro(co)polymer-2 (recycled product) was measured in the same manner as in Preparation Example 1, and was found to be 0.22. Furthermore, the mass loss rate was measured in the same manner as in Preparation Example 1 and was found to be 2.3%.

[0088] [Preparation Example 3] Recycled perfluoro(co)polymer-3 (recycled product) was obtained in the same manner as in Preparation Example 1, except that crosslinked perfluoro(co)polymer-2 (recycled product) was used instead of crosslinked perfluoro(co)polymer-1. In the same manner as in Preparation Example 1, the content of crosslinking sites (nitrile groups) in the crosslinked perfluoro(co)polymer-2 (recycled product) was measured to be 0.01, and the content of crosslinking sites (nitrile groups) in the recycled perfluoro(co)polymer-3 (recycled product) was measured to be 0.6. Furthermore, the mass loss rate was measured in the same manner as in Preparation Example 1 and was found to be 2.3%.

[0089] [Preparation Example 4] A recycled perfluoro(co)polymer-4 (recycled product) was obtained in the same manner as in Preparation Example 3, except that the heat treatment was carried out in air instead of in a nitrogen atmosphere. The content of crosslinking sites (nitrile groups) in the recycled perfluoro(co)polymer-4 (recycled product) was measured in the same manner as in Preparation Example 1, and was found to be 0.61. Furthermore, the mass loss rate was measured in the same manner as in Preparation Example 1 and was found to be 4.1%.

[0090] [Preparation Example 5] A recycled perfluoro(co)polymer-c1 (recycled product) was obtained in the same manner as in Preparation Example 1, except that in Preparation Example 1, crosslinked perfluoro(co)polymer-c1 (recycled product) was used instead of crosslinked perfluoro(co)polymer-1. The mass loss rate was measured in the same manner as in Preparation Example 1 and was found to be 0.9%.

[0091] [Preparation Example 6] A recycled perfluoro(co)polymer-c2 (recycled product) was obtained in the same manner as in Preparation Example 5, except that the heat treatment was carried out in air instead of in a nitrogen atmosphere. The mass loss rate was measured in the same manner as in Preparation Example 1 and was found to be 2.4%.

[0092] [Example 1] A bulk elastomer composition was obtained by kneading 60 parts by mass of uncrosslinked perfluoro(co)polymer-1 (virgin product), 40 parts by mass of recycled perfluoro(co)polymer-1 (recycled product), and 0.5 parts by mass of an oxazole-based crosslinking agent (BOAP, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, manufactured by Tokyo Chemical Industry Co., Ltd.) using an open roll. The obtained bulk elastomer composition was subjected to a separating step (sheet forming step) using rolls (roll gap: 8 mm, temperature: 50°C). The sheet obtained in the above-mentioned separation process was press-molded using a compression vacuum press at 180°C for 30 minutes under a pressure of 5 MPa (primary crosslinking), and then the press-molded sheet was heated in an oven at 250°C for 24 hours (secondary crosslinking) to obtain a molded body (O-ring).

[0093] [Examples 2 to 4 and Comparative Example 1] In Example 1, a molded body was obtained in the same manner as in Example 1, except that (co)polymers of the types and amounts (numbers, parts by mass) shown in Table 1 were used as the uncrosslinked perfluoro(co)polymer and recycled perfluoro(co)polymer.

[0094] Comparative Example 2 A bulk elastomer composition was obtained by kneading 60 parts by mass of uncrosslinked perfluoro(co)polymer-c1 (virgin product), 40 parts by mass of recycled perfluoro(co)polymer-c1 (recycled product), 10 parts by mass of PTFE particles (Lubron L5 (manufactured by Daikin Industries, Ltd.)), 0.5 parts by mass of Perhexa 25B (manufactured by NOF Corporation), and 1 part by mass of TAIC (triallyl isocyanurate, manufactured by Mitsubishi Chemical Corporation) using an open roll. The obtained bulk elastomer composition was filled into an O-ring-shaped mold and press-molded using a compression vacuum press at 170°C for 10 minutes under a pressure of 5 MPa (primary crosslinking). The press-molded sheet was then heated in an oven at 200°C for 4 hours (secondary crosslinking) to obtain a molded product (O-ring).

[0095] [Comparative Examples 3 to 4] In Comparative Example 2, a molded body was obtained in the same manner as in Comparative Example 2, except that (co)polymers of the types and amounts (numbers, parts by mass) shown in Table 1 were used as the uncrosslinked perfluoro(co)polymer and recycled perfluoro(co)polymer.

[0096] <Tensile strength and elongation at break> The obtained molded article (O-ring) was stretched at 500 mm / min, and the tensile strength and elongation at break were measured using a Schopper tensile tester at 23° C. The results are shown in Table 1.

[0097] <Compression set> The compression set of the sealing material was determined in accordance with JIS K 6262:2013. The obtained molded body was kept at 200°C for 72 hours at a compression ratio of 25%, and then the pressure was released and the body was allowed to cool at the standard temperature of the test room for 30 minutes, after which the thickness of the molded body was measured. The obtained molded body was kept at 260°C for 72 hours at a compression ratio of 20%, and then the pressure was released and the body was allowed to cool at the standard temperature of the test room for 30 minutes, after which the thickness of the molded body was measured. The compression set (CS) was calculated based on the following formula: The results are shown in Table 1. Compression set rate (%) = {(h0-h1) / (h0-h2)} x 100 [h0: thickness of the compact before compression (mm), h1: thickness of the compact after cooling for 30 minutes (mm), h2: thickness (height) of the spacer (mm)]

[0098] <Mass reduction rate (plasma resistance)> The plasma resistance (mass reduction rate) of the obtained molded body was measured. Specifically, the measurement was performed as follows. The results are shown in Table 1. A fluorine radical exposure test was conducted under the following conditions, in which the obtained molded body (O-ring) was exposed to fluorine radicals generated from NF3 by remote plasma. The mass of the molded body (O-ring) was measured before and after the test, and the mass loss rate was calculated using the following formula to evaluate plasma resistance. The smaller the mass loss rate, the better the plasma resistance. Mass reduction rate (%) = {(mass before test - mass after test) / (mass before test)} x 100

[0099] (conditions) Plasma source: Remote plasma source Plasma power: 5000W Gas flow rate: NF3 1.5SLM, Argon 1.5SLM ·Vacuum level: 7torr Test temperature: 250℃ Exam duration: 5 hours

[0100] [Table 1]

[0101] In Examples 1 to 4, molded bodies having the same physical properties as Comparative Example 1, which used only virgin products, were obtained, and molded bodies having smaller compression set and excellent heat resistance and plasma resistance (smaller mass loss rate) were obtained compared to Comparative Examples 2 to 4.

Claims

1. A sealant-forming material containing recycled perfluoro(co)polymer, The recycled perfluoro(co)polymer is a (co)polymer in which at least a part of the crosslinking sites is regenerated by heat-treating a crosslinked perfluoro(co)polymer obtained by crosslinking a perfluoro(co)polymer having nitrile groups as crosslinking sites, The perfluoro (co)polymer having a nitrile group contains a structural unit derived from at least one selected from a perfluoroolefin and a perfluorovinyl ether, and a structural unit having a nitrile group. Seal forming material.

2. 2. The sealant-forming material according to claim 1, wherein the recycled perfluoro (co)polymer is a (co)polymer having at least one crosslinked structure selected from a triazine structure, an oxazole structure, an amidine structure, and an imidazole structure.

3. The sealant-forming material according to claim 1 , further comprising a crosslinking agent having a functional group capable of reacting with a nitrile group.

4. The sealant-forming material according to claim 1 , further comprising an uncrosslinked perfluoro (co)polymer.

5. The sealant-forming material according to claim 4, wherein the content of the recycled perfluoro(co)polymer is 0.5 parts by mass or more per 100 parts by mass of the uncrosslinked perfluoro(co)polymer.

6. A sealing material obtained by crosslinking and molding the sealing material according to any one of claims 1 to 5.

7. A method for producing a sealant, comprising a step of crosslinking the sealant-forming material according to any one of claims 1 to 5.

8. 8. The method for producing a sealing material according to claim 7, comprising a step of heat-treating a crosslinked perfluoro(co)polymer obtained by crosslinking a perfluoro(co)polymer having nitrile groups as crosslinking sites to regenerate at least a portion of the crosslinking sites, thereby obtaining a regenerated perfluoro(co)polymer.

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