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

Abstract

[Problem] To provide a sealing material–forming material that can easily reuse 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] 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 a 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.

Description

Sealant-forming material, sealant, and method for manufacturing sealant

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

[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 a molded article made by reusing such a crosslinked fluoroelastomer, for example, 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. Also, Patent Document 2 discloses a sealing material containing a treated perfluoropolymer obtained by decomposing the crosslinking points of a crosslinked iodine- or bromine-containing perfluoropolymer.

[0008] JP 2007-63334 A Japanese Patent No. 6134293 A

[0009] However, the method described in Patent Document 1, which uses a supercritical fluid or 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 has been found that the sealing material described in Patent Document 2 undergoes decomposition when the treated perfluoropolymer used is obtained, resulting in a significant decrease in the mass of the perfluoropolymer, and further, the obtained 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.

[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.

[0012] [1] A sealant-forming material containing a recycled perfluoro(co)polymer, wherein the recycled perfluoro(co)polymer is a (co)polymer in which at least a portion of the crosslinking sites is regenerated by heat-treating a crosslinked perfluoro(co)polymer formed by crosslinking a perfluoro(co)polymer having a nitrile group as a crosslinking site, and the perfluoro(co)polymer having a nitrile group contains a constituent unit derived from at least one selected from perfluoroolefins and perfluorovinyl ethers, and a constituent unit having a nitrile group.

[0013] [2] The sealant-forming 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 sealing material obtained by crosslinking the sealing material-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 a nitrile group as a crosslinking site to regenerate at least a part of the crosslinking sites, thereby obtaining a regenerated perfluoro(co)polymer.

[0019] According to the present invention, a sealant-forming material can be provided that can easily reuse a crosslinked perfluoro(co)polymer and form a sealant having small compression set and excellent heat resistance and plasma resistance. Furthermore, according to the present invention, a sealant-forming material that has excellent moldability into a sealant having desired physical properties can also be provided.

[0020] <Sealing Material> The sealing material according to the present invention (hereinafter also referred to as "the material") comprises a recycled perfluoro(co)polymer (hereinafter also referred to as "recycled product") obtained by heat-treating a crosslinked perfluoro(co)polymer obtained by crosslinking a perfluoro(co)polymer having nitrile groups as crosslinking sites, thereby regenerating at least a portion of the crosslinking sites. Because the material contains such a recycled product, it is possible to form a sealing material that has a smaller compression set and excellent heat resistance and plasma resistance than a sealing material obtained by heat-treating a crosslinked perfluoro(co)polymer obtained by crosslinking a perfluoro(co)polymer having halogen atoms (e.g., iodine atoms or bromine atoms) as crosslinking sites, which is typically crosslinked using a peroxide-based crosslinking agent. Furthermore, compared to a sealing material-forming material containing the heat-treated product, the material exhibits excellent kneadability of the components used in forming 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 "recycled product") obtained by crosslinking a perfluoro(co)polymer having nitrile groups as crosslinking sites (hereinafter also referred to as "uncrosslinked perfluoro(co)polymer"), and then heat-treating the crosslinked perfluoro(co)polymer (hereinafter also referred to as "recycled product") to recycle at least a portion of the nitrile groups as crosslinking sites. The recycled product used for this 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, ~-R-C≡N represents a perfluoro(co)polymer having a nitrile group as a crosslinked 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]

[0025] [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 perfluoro(co)polymer having nitrile groups is crosslinked, and then the perfluoro(co)polymer having nitrile groups is obtained. Therefore, this cycle can be repeated multiple times (recycled multiple times) for the 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 a peroxide-based crosslinking agent. 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 a perfluoro(co)polymer having nitrile groups as crosslinking sites, as shown in the following formulas (3) and (4), the nitrile groups as crosslinking sites react to form a crosslinked perfluoro(co)polymer, and the nitrile groups as crosslinking sites are "regenerated" by heat treatment, whereas in a perfluoro(co)polymer having halogen atoms as crosslinking sites, the halogen atoms as crosslinking sites react to form a crosslinked perfluoro(co)polymer, and the crosslinked structure is "decomposed" by heat treatment to produce C=C bonds and carboxyl groups, and the halogen atoms as crosslinking sites are not regenerated. Therefore, the mechanisms by which crosslinking sites are regenerated are completely different between a "perfluoro(co)polymer having nitrile groups as crosslinking sites" and a "perfluoro(co)polymer having halogen atoms as crosslinking sites," and further, the effects on heat resistance and compression set of sealing materials obtained using the regenerated products are different.

[0029] It is preferable that the recycled product is not a (co)polymer in which all of the crosslinking sites of the recycled product are recycled. In other words, it is preferable that the recycled product 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%. While there is no particular upper limit, it is an amount equal to or less than the content of nitrile groups in the uncrosslinked perfluoro(co)polymer before the recycled product was crosslinked, specifically 15,000% or less, more preferably 7,000% or less. By using recycled products with a nitrile group content within this range, sealing materials with smaller compression set can be easily formed. The content of nitrile groups can be measured using FT-IR, specifically by the method described in the Examples below.

[0031] Furthermore, in order to facilitate the formation of a sealing material having desired physical properties using the obtained recycled product, 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] x 100 (A)

[0032] Considering the balance between environmental protection, effective utilization of resources, and the ease of forming a sealing material having the desired physical properties, the amount of the recycled product 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 parts by mass of the present material. Furthermore, when an uncrosslinked perfluoro(co)polymer is used in the present 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, relative to 100 parts by mass of the uncrosslinked perfluoro(co)polymer, from the standpoint of the ease of forming a sealing material having the desired physical properties.

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

[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) using a conventionally known method. Examples of the conventionally known method include 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 may be 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 forming these crosslinked structures (e.g., an amidine structure when forming an oxazole structure). The degree of crosslinking in the recycled product is not particularly limited, and may be 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 crosslinking structure using the oxazole-based crosslinking agent may be an oxazole structure finally obtained in the following formula (4), or an amidine structure which is an intermediate structure thereof.

[0036]

[0037] [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 a nitrile group as a crosslinking site before crosslinking, and can also be called a "virgin product."

[0039] The uncrosslinked perfluoro(co)polymer is preferably a perfluoroelastomer (FFKM). The uncrosslinked 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, as necessary, structural units derived from a nitrile group-containing monomer, are preferred.

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

[0042] Examples of the perfluoro(alkyl vinyl ether) include compounds in which the alkyl group has 1 to 10 carbon atoms, and specific examples include perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), and perfluoro(propyl vinyl ether), with perfluoro(methyl vinyl ether) being preferred.

[0043] The perfluoro(alkoxyalkyl vinyl ether) may be a compound in which the carbon number of the group bonded to the vinyl ether group (CF2=CFO-) is, for example, 3 to 15, and specific examples include the following compound: 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] The nitrile group-containing monomer may be, for example, a nitrile group-containing perfluorovinyl ether, and specific examples thereof include the following compound: CF═CFO(CF) 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, for example, an integer from 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) nCF(-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 or 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 of 0 or more) CF2=CFOCF(CF3)CF2O(CF2) n -CN (n is an integer of 1 or more) CF2=CFOCF2OCF2CF(CF3)OCF2-CN

[0045] In FFKM, the content of constituent units derived from TFE is preferably 50.0 to 79.9 mol%, the content of constituent units derived from perfluorovinyl ether is preferably 20.0 to 46.9 mol%, and the content of constituent 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 the nitrile groups that are crosslinking sites in the recycled product. The heat treatment may be carried out in an oxygen-containing gas atmosphere or an inert gas atmosphere, but is preferably carried out in an inert gas atmosphere because, when obtaining a recycled product from the recycled product, decomposition of the recycled product can be suppressed, mass loss of the perfluoro(co)polymer can be suppressed, and further, a recycled product with a large amount of regenerated nitrile groups that are crosslinking sites can be easily obtained.

[0047] Examples of the oxygen-containing gas include a gas having an oxygen content of preferably 5% by volume or more relative to the total, and a specific example is air. Specific examples of the inert gas include nitrogen gas, argon gas, and helium gas, with nitrogen gas being preferred. One or more of the inert gases may be used. In order to further demonstrate the effects of the present invention, it is preferable that the inert gas be a gas that does not contain oxygen or a gas that contains a small amount of oxygen. Since a high oxygen content tends to promote thermal decomposition of the product to be recycled, the gas that contains a small amount of oxygen is preferably a gas that contains less than 5% by volume, more preferably 3% by volume or less, and even more preferably 1% by volume or less relative to the total.

[0048] The temperature and time during the heat treatment are not particularly limited as long as they are such that the nitrile groups, which are the crosslinking sites, are regenerated in the regenerated product. The temperature during the heat treatment is usually a temperature exceeding the temperature used when 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 during 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 preferably performed under normal pressure.

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

[0050] <Uncrosslinked perfluoro(co)polymer> For this material, it is preferable to use an uncrosslinked perfluoro(co)polymer (virgin product) because it is possible to easily obtain a material with excellent moldability and to easily form a sealing material with desired physical properties (hardness, tensile strength, elongation at break, compression set, and plasma resistance). Examples of the uncrosslinked perfluoro(co)polymer include (co)polymers similar to the uncrosslinked perfluoro(co)polymers listed in the section on recycled products. Note that, 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% 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 present material, from the viewpoint of being able to easily form a sealing material having desired physical properties, etc.

[0052] <Crosslinking Agent> The present material can be crosslinked without using a crosslinking agent. However, in order to easily form a sealing material that is sufficiently crosslinked and has a good balance of excellent hardness, tensile strength, elongation at break, and tensile stress at 100% elongation (100% Mo), it is preferable to use a crosslinking agent appropriate for the type of recycled product or uncrosslinked perfluoro(co)polymer used for the present material, and it is more preferable to use a crosslinking agent having 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. Furthermore, the triazine crosslinking agent may be a compound that can act as a catalyst for forming 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 a nitrile group 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] The imidazole crosslinking agent may be a crosslinking agent that reacts with a nitrile group to form an imidazole ring and give a crosslinked product, and specific examples thereof 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 the present 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 that is excellent in hardness, tensile strength, elongation at break, and 100% Mo can be easily formed in a well-balanced manner.

[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 Compound> 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 Pigment> Examples of the organic pigment include organic pigments similar to those described in WO 2016 / 043100, Japanese Patent No. 4720501, WO 2004 / 094527, and Japanese Patent No. 5278312.

[0062] <Filler> Examples of the inorganic filler include particulate (powdered) inorganic materials such as carbon black, silica, barium sulfate, titanium oxide, aluminum oxide, etc. 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] <Method for preparing the present material> The present material can be prepared by mixing (kneading) the recycled product and, if necessary, the other components. When mixing the recycled product and 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] The mixing (kneading) can be carried out using a conventionally known mixer (kneader), for example, an open roll, a Banbury mixer, a twin-screw roll, or a kneader. Depending on the mixer (kneader), the mixing (kneading) may be carried out under heating or cooling, as necessary.

[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 the present material. Despite using recycled perfluoro(co)polymer, the sealing material has physical properties (hardness, tensile strength, elongation at break, compression set, and plasma resistance) comparable to those of a virgin product (uncrosslinked perfluoro(co)polymer), and is particularly small in compression set and has excellent heat resistance and plasma resistance.

[0066] The tensile strength of this 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 this sealing material, measured by the method described in the Examples below, is preferably 120% or more, 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, with no particular lower limit, for example, 0%. The compression set of this sealing material, measured according to JIS K 6262:2013 (260°C x 72 hours, compression rate 20%), is preferably 15% or less, more preferably 10% or less, with no particular lower limit, for example, 0%. The mass loss rate of this sealing material, measured by the method described in the Examples below, is preferably 5% or less, more preferably 3% or less, with no particular lower limit, for example, 0%.

[0067] The present sealant 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 sealant for semiconductor manufacturing equipment or plasma processing equipment, particularly as a sealant for drive parts such as gate valves used at the openings of plasma processing chamber units. Examples of the present sealant include O-rings, square rings, gaskets, packing, oil seals, bearing seals, and lip seals. The shape and other properties of the present sealant may be selected appropriately 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 Producing Sealing Material>> The method for producing a sealing material according to the present invention (hereinafter also referred to as the "method for producing the 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 forming 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 dividing step is preferably preformed into a desired sealing material shape before the crosslinking step. This preforming may involve directly forming the desired sealing material shape from the sheet obtained in the dividing step, or may involve cutting or extrusion molding the sheet obtained in the dividing step into a rope-like shape (which also has the same meaning as a ribbon-like shape or noodle-like shape), and then forming the resulting rope-like product into the desired sealing material shape.

[0072] <Step I> More preferably, Step I includes a primary crosslinking step and a secondary crosslinking step. Step I is preferably performed using a preformed body having a desired sealing material shape obtained by the preforming step.

[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 the primary crosslinking step is a step of placing the preformed body in a mold and crosslinking the preformed body 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 obtained in the primary crosslinking step 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 3 to 24 hours. This secondary crosslinking step promotes crosslinking, and even if unreacted components remain after the primary crosslinking step, the unreacted components can be decomposed and volatilized, 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, and 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 one type alone or 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. Irradiating with radiation at such an amount 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] <Step II> The method for producing the present sealant preferably includes, before Step I and the separating step, Step II, in which a crosslinked perfluoro(co)polymer (processed article) formed by crosslinking a perfluoro(co)polymer having nitrile groups as crosslinking sites is heat-treated to regenerate at least a portion of the crosslinking sites to obtain a regenerated perfluoro(co)polymer (regenerated product). The process used in Step II, the regenerated product obtained in Step II, and the heat treatment conditions in Step II are as described in the section for the sealant-forming material.

[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 (manufactured by 3M, a perfluoro(co)polymer in which the crosslinked site is a nitrile group) "Uncrosslinked perfluoro(co)polymer-c1": Tecnoflon PFR94 (manufactured by Solvay, a perfluoro(co)polymer in which the crosslinked site is a halogen atom)

[0082] <Crosslinked perfluoro(co)polymer (product to be recycled)> The crosslinked perfluoro(co)polymer (product to be recycled) used in the following Preparation Examples is as follows: - "Crosslinked perfluoro(co)polymer-1": a molded article (O-ring) (corresponding to an unused or used molded article) produced by kneading 100 parts by mass of a 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.) using an open roll, filling the resulting bulk elastomer composition into an O-ring-shaped mold, and press-molding the mixture at 180°C for 30 minutes under a pressure of 5 MPa using a compression vacuum press (primary crosslinking), and then heating the press-molded sheet in an oven at 250°C for 24 hours (secondary crosslinking). "Crosslinked perfluoro(co)polymer-2": A primary crosslinked molded product (burr) that protruded from the mold seam during primary crosslinking in a mold during the production 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 the mixture using a compression vacuum press at 170°C for 10 minutes under a pressure of 5 MPa (primary crosslinking), followed by heating the press-molded sheet in an oven at 200°C for 4 hours (secondary crosslinking).

[0083] [Preparation Example 1] Crosslinked perfluoro(co)polymer-1 (the product to be recycled) was placed in 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 recycled perfluoro(co)polymer-1 (the recycled product).

[0084] <Content of crosslinked sites> FT-IR (HYPERION 3000, manufactured by Bruker) was used, resolution: 4 cm -1 , Number of scans: 32, Transmission method, Measurement range: 400 to 4000 cm-1 The content of crosslinking sites in the crosslinked perfluoro(co)polymer-1 (recycled product) and the recycled perfluoro(co)polymer-1 (recycled product) was measured under the conditions of -1 The maximum intensity when the intensity of the -1 The intensity of 2500 cm is connected to the baseline. -1 The value obtained by dividing the strength at 1000 kJ / g 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 reduction rate (%) was calculated using the following formula (A). The mass reduction rate was 0.6%. Mass reduction rate (%) = [(mass of recycled product - mass of recycled product) / mass of recycled product] x 100 (A)

[0087] [Preparation 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 under 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 found to be 0.22. The mass loss rate was also measured in the same manner as in Preparation Example 1 and 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 Preparation Example 1. The content of crosslinking sites (nitrile groups) in the crosslinked perfluoro(co)polymer-2 (recycled product) was measured in the same manner as in Preparation Example 1 and found to be 0.01, and the content of crosslinking sites (nitrile groups) in the recycled perfluoro(co)polymer-3 (recycled product) was measured and found to be 0.6. Furthermore, the mass loss rate was measured in the same manner as in Preparation Example 1 and 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 under 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 found to be 0.61. The mass loss rate was also measured in the same manner as in Preparation Example 1 and 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 crosslinked perfluoro(co)polymer-c1 (recycled product) was used instead of crosslinked perfluoro(co)polymer-1 in Preparation Example 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 under 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 resulting bulk elastomer composition was subjected to a separation step (sheet formation step) using a roll (roll spacing: 8 mm, temperature: 50°C). The sheet obtained in the separation step 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 product (O-ring).

[0093] [Examples 2 to 4 and Comparative Example 1] Molded articles were 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 the recycled perfluoro(co)polymer in Example 1.

[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 Molded articles were 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 the recycled perfluoro(co)polymer in Comparative Example 2.

[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 held at 200°C for 72 hours at a compression rate of 25%, after which the pressure was released and the body was allowed to cool at the standard temperature of the test room for 30 minutes, and the thickness of the molded body was measured. The obtained molded body was also held at 260°C for 72 hours at a compression rate of 20%, after which the pressure was released and the body was allowed to cool at the standard temperature of the test room for 30 minutes, and the thickness of the molded body was measured. The compression set rate (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 molded body before compression (mm), h1: thickness of molded body after cooling for 30 minutes (mm), h2: thickness (height) of 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 performed in which the obtained molded body (O-ring) was exposed to fluorine radicals generated from NF3 by remote plasma under the following conditions. The mass of the molded body (O-ring) was measured before and after the test, and the mass reduction rate was calculated according to the following formula to evaluate the plasma resistance. The smaller the mass reduction 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 output: 5000 W Gas flow rate: NF3; 1.5 SLM, argon; 1.5 SLM Degree of vacuum: 7 torr Test temperature: 250°C Test time: 5 hours

[0100]

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

Claims

1. A sealant-forming material comprising a recycled perfluoro(co)polymer, wherein the recycled perfluoro(co)polymer is a (co)polymer in which at least a portion of the crosslinking sites has been regenerated by heat-treating a crosslinked perfluoro(co)polymer formed by crosslinking a perfluoro(co)polymer having nitrile groups as crosslinking sites, and the perfluoro(co)polymer having nitrile groups contains a constituent unit derived from at least one selected from perfluoroolefins and perfluorovinyl ethers, and a constituent unit having a nitrile group.

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 sealing 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. A 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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