Method for producing regenerated perfluoro (CO)polymer and method for producing regenerated material

Abstract

To provide a method for producing a regenerated perfluoro (co)polymer by regenerating a crosslinking site of a crosslinked perfluoro (co)polymer, wherein the crosslinking site can be sufficiently regenerated by a simple method while suppressing a decrease in the mass of the perfluoro (co)polymer when regenerating the crosslinking site.SOLUTION: Provided is a method for producing a regenerated perfluoro (co)polymer, including a step of regenerating a crosslinking site by heat-treating a crosslinked perfluoro (co)polymer in which a perfluoro (co)polymer having the crosslinking site is crosslinked, under an inert gas atmosphere.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a recycled perfluoro(co)polymer and a method for producing a recycled 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 a method for reusing such crosslinked fluoroelastomers, for example, Patent Document 1 discloses a method for decrosslinking a crosslinked fluoropolymer in a supercritical fluid or subcritical fluid of a compound having active hydrogen. Furthermore, Patent Document 2 discloses a method of heat treating vulcanized fluororubber in air. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-63334 [Patent Document 2] Japanese Patent Application Publication No. 61-69805 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 cannot be carried out simply, so there is room for improvement. Furthermore, as a result of intensive research by the present inventors, it has been found that the method described in Patent Document 2 does not sufficiently devulcanize the vulcanized fluororubber (regenerate crosslinking sites), and that the heat treatment causes decomposition of the vulcanized fluororubber, resulting in a large mass loss rate of the fluororubber before and after the heat treatment.

[0010] The present invention has been made in view of the above, and aims to provide a method for producing a regenerated perfluoro(co)polymer that regenerates the crosslinking sites of a crosslinked crosslinked perfluoro(co)polymer, and an object of the present invention is to provide a method for producing a regenerated perfluoro(co)polymer that can sufficiently regenerate the crosslinking sites in a simple manner while suppressing the mass loss of the perfluoro(co)polymer when the crosslinking sites are regenerated. [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 method for producing a regenerated perfluoro(co)polymer, comprising a step of heat-treating a crosslinked perfluoro(co)polymer, in which a perfluoro(co)polymer having a crosslinking site is crosslinked, under an inert gas atmosphere to regenerate the crosslinking site.

[0013] [2] The method for producing a recycled perfluoro(co)polymer according to [1], wherein the crosslinking site is a nitrile group.

[0014] [3] The method for producing a recycled perfluoro(co)polymer according to [1] or [2], wherein the inert gas is at least one selected from nitrogen gas, argon gas, and helium gas.

[0015] [4] The method for producing a recycled perfluoro(co)polymer according to any one of [1] to [3], wherein the perfluoro(co)polymer having a crosslinking site is a (co)polymer that does not contain a carbon-hydrogen bond in the main chain of the (co)polymer.

[0016] [5] A method for producing a recycled material, comprising a step of crosslinking a recycled material-forming material containing a recycled perfluoro(co)polymer obtained by the method for producing a recycled perfluoro(co)polymer according to any one of [1] to [4].

[0017] [6] The method for producing a recycled material according to [5], wherein the recycled material-forming material further contains a crosslinking agent.

[0018] [7] The method for producing a recycled material according to [5] or [6], wherein the recycled material-forming material further contains an uncrosslinked perfluoro(co)polymer.

[0019] [8] The method for producing a recycled material according to [7], wherein the content of the recycled perfluoro(co)polymer in the recycled material-forming material is 0.5 parts by mass or more per 100 parts by mass of uncrosslinked perfluoro(co)polymer.

[0020] [9] The method for producing a recycled material according to any one of [5] to [8], wherein the recycled material is a sealing material. [Effects of the Invention]

[0021] According to the present invention, when regenerating the crosslinking sites of a crosslinked crosslinked perfluoro(co)polymer, the crosslinking sites of the crosslinked perfluoro(co)polymer can be sufficiently regenerated by a simple method while suppressing the mass loss of the perfluoro(co)polymer when regenerating the crosslinking sites. In this way, the crosslinking sites of the crosslinked perfluoro(co)polymer can be sufficiently regenerated while suppressing mass loss, and therefore, even when the resulting recycled perfluoro(co)polymer is used, a molded product (regenerated material) can be formed that has physical properties (hardness, tensile strength, elongation at break, compression set, and plasma resistance) comparable to those when a virgin product (uncrosslinked perfluoro(co)polymer) is used. Therefore, the recycled material can be suitably used as a sealing material for semiconductor manufacturing equipment, a sealing material for plasma processing equipment, etc. DETAILED DESCRIPTION OF THE INVENTION

[0022] <Production method for recycled perfluoro (co)polymer> The method for producing a recycled perfluoro(co)polymer (hereinafter also referred to as "the recycled product") according to the present invention (hereinafter also referred to as "the method for producing the recycled product") includes a step of heat-treating a crosslinked perfluoro(co)polymer (hereinafter also referred to as "the recycled product") in an inert gas atmosphere, in which a perfluoro(co)polymer having crosslinking sites is crosslinked, thereby regenerating the crosslinking sites.

[0023] Whether or not crosslinking sites have been regenerated in the regenerated product can be determined, for example, by using FT-IR to measure the amount of crosslinking sites in the regenerated product and the amount of crosslinking sites in the obtained regenerated product. The method for producing the recycled product is preferably a method in which the content of crosslinking sites in the resulting recycled product is preferably 150% or more, more preferably 200% or more, when the content of crosslinking sites in the recycled product is taken as 100%, because the obtained recycled product can be used to easily form a recycled material with desired physical properties. The content of the crosslinking sites can be measured using FT-IR, specifically by the method described in the examples below.

[0024] Furthermore, since the method for producing the recycled product can easily form recycled materials having desired physical properties using the obtained recycled product, it is desirable that the mass loss rate due to the heat treatment, specifically the mass loss rate represented by the following formula (1), is preferably 2% or less, more preferably 1% or less. Mass reduction rate (%) = [(mass of recycled product - mass of main recycled product) / mass of recycled product] × 100 ···(1)

[0025] <Recycled products> The recycled product is a crosslinked perfluoro(co)polymer obtained by crosslinking a perfluoro(co)polymer having crosslinking sites (hereinafter also referred to as "uncrosslinked perfluoro(co)polymer"). Examples 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. In the method for producing the recycled product, 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.

[0026] 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. Examples of the conventionally known method include crosslinking using a crosslinking agent, which may be appropriately selected depending on the uncrosslinked perfluoro(co)polymer to be used, and include, for example, peroxide-based crosslinking agents, bisphenol-based crosslinking agents, 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. In other words, the recycled product may be a crosslinked perfluoro(co)polymer having at least one crosslinked structure selected from crosslinked structures derived from these crosslinking agents and intermediate structures when these crosslinked structures are formed (e.g., amidine structure when forming an oxazole structure). 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.

[0027] [Uncrosslinked perfluoro(co)polymer] The uncrosslinked perfluoro(co)polymer is a perfluoro(co)polymer having crosslinking sites before crosslinking, and can also be called a "virgin product." The uncrosslinked perfluoro(co)polymer is preferably a perfluoroelastomer (FFKM). The FFKM is not particularly limited, but is preferably a polymer that does not contain hydrogen atoms (carbon-hydrogen bonds) in the polymer main chain (excluding the terminals), and specifically includes a tetrafluoroethylene (TFE)-perfluorovinyl ether copolymer having a crosslinking site, and is preferably a copolymer that contains a TFE-derived structural unit and a perfluorovinyl ether-derived structural unit, and further contains, if necessary, a structural unit derived from a crosslinking site-containing monomer.

[0028] Suitable examples of the perfluorovinyl ether include perfluoro(alkyl vinyl ether) and perfluoro(alkoxyalkyl vinyl ether).

[0029] 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).

[0030] 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.

[0031] The crosslinking site means a site capable of crosslinking, and examples thereof include a nitrile group, a halogen atom (e.g., I, Br), and a perfluorophenyl group. Among these, a nitrile group is preferred in that the effects of the present invention are more effectively exhibited.

[0032] Examples of crosslinking site monomers having a nitrile group as a crosslinking site include nitrile group-containing perfluorovinyl ethers, and specific examples 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

[0033] Examples of crosslinking site-containing monomers having halogen atoms as crosslinking sites include halogen-containing perfluorovinyl ethers, and specific examples thereof include compounds in which the nitrile groups in the specific examples of the nitrile-containing perfluorovinyl ethers described above are substituted with halogen atoms. Examples of crosslinking site-containing monomers having halogen atoms include compounds described in WO 2009 / 119409, JP 2002-97329 A, and JP 2008-56739 A.

[0034] 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 crosslinking site-containing monomers is preferably 0.1 to 2.0 mol %.

[0035] <Heat treatment conditions, etc.> The heat treatment in this method for producing recycled products is characterized by being carried out in an inert gas atmosphere. By carrying out the heat treatment under an inert gas atmosphere, it is possible to suppress decomposition of the recycled product when obtaining a recycled product from the recycled product, thereby suppressing mass loss, and furthermore, it is possible to easily obtain a recycled product with a large amount of regenerated crosslinking sites.

[0036] 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.

[0037] The temperature and time for the heat treatment are not particularly limited as long as they are such that crosslinking sites are regenerated in 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.

[0038] <Recycled material manufacturing method> The method for producing a recycled material according to the present invention (hereinafter also referred to as the "method for producing the recycled material") includes a step of crosslinking a recycled material-forming material including the recycled product obtained by the method for producing the recycled product. In this method for producing recycled materials, recycled products obtained by heat treatment in an inert gas atmosphere are used, making it possible to form recycled materials that are particularly superior in plasma resistance compared to, for example, recycled products obtained by heat treatment in air.

[0039] <Recycled material forming material> The recycled material-forming material is not particularly limited as long as it contains the recycled product, and may be a material consisting essentially of the recycled product alone, but may also contain other components that have been conventionally known and have been incorporated into molded products such as sealing materials, if 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.

[0040] [Recycled product] The recycled product used for the recycled material-forming material may be one type or two or more types. Considering the balance between environmental protection and effective utilization of resources, and the ease of forming a recycled material having the desired physical properties, the amount of the recycled product used is preferably 0.5 to 60 mass%, more preferably 1 to 50 mass%, and even more preferably 10 to 40 mass%, relative to 100 mass% of the recycled material-forming material. Furthermore, when an uncrosslinked perfluoro(co)polymer is used as the recycled material-forming material, the amount of this recycled product used is preferably 0.5 parts by mass or more, more preferably 0.5 to 90 parts by mass, even more preferably 1 to 80 parts by mass, and particularly preferably 10 to 70 parts by mass per 100 parts by mass of the uncrosslinked perfluoro(co)polymer, in order to easily form a recycled material having the desired physical properties.

[0041] [Uncrosslinked perfluoro(co)polymer] It is preferable to use an uncrosslinked perfluoro(co)polymer (virgin product) as the recycled material-forming material, since it is possible to easily obtain a recycled material-forming material with excellent moldability and to easily form a recycled material having the 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 described in the section on the recycled product. As the uncrosslinked perfluoro(co)polymer, a perfluoro(co)polymer having a crosslinking site different from the crosslinking site contained in the recycled product used in the recycled material-forming material may be used, but it is preferable to use a perfluoro(co)polymer having a crosslinking site similar to the crosslinking site contained in the recycled product used in the recycled material-forming material.

[0042] When an uncrosslinked perfluoro(co)polymer is used as the recycled material-forming material, the amount of the uncrosslinked perfluoro(co)polymer used is preferably 40 to 99.5% by mass, more preferably 50 to 99% by mass, and even more preferably 50 to 90% by mass relative to 100% by mass of the recycled material-forming material, in order to easily form a recycled material having the desired physical properties.

[0043] [Crosslinking agent] The recycled material-forming material can be crosslinked without using a crosslinking agent, but it is preferable to use a crosslinking agent appropriate for the type of recycled product or uncrosslinked perfluoro(co)polymer used in the recycled material-forming material, since this allows for sufficient crosslinking and makes it easy to form a recycled material that is well-balanced in terms of hardness, tensile strength, elongation at break, and tensile stress at 100% elongation (100% Mo).

[0044] As the crosslinking agent, for example, a conventionally known crosslinking agent such as the crosslinking agent described in Japanese Patent No. 5278312 can be used without any particular limitation, and specific examples include peroxide-based crosslinking agents, bisphenol-based crosslinking agents, 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.

[0045] Examples of peroxide-based crosslinking agents include 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, di-t-butyl peroxide, t-butyldicumyl peroxide, benzoyl peroxide, 2,5-dimethyl-2,5-(t-butylperoxy)hexyne-3, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, and t-butylperoxyisopropyl. Examples of peroxybenzoates include propyl carbonate, di-(4-t-butylcyclohexyl) peroxydicarbonate, p-chlorobenzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butyl peroxybenzoate, 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroperoxide, α,α-bis(t-butylperoxy)-p-diisopropylbenzene, t-butylperoxybenzene, and t-butylperoxymaleic acid.

[0046] Examples of bisphenol-based crosslinking agents include bisphenol AF and bisphenol S.

[0047] 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.

[0048] Examples of oxazole-based crosslinking agents include 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (BOAP), 4,4'-sulfonylbis(2-aminophenol), and 9,9-bis(3-amino-4-hydroxyphenyl)fluorene.

[0049] Examples of imidazole crosslinking agents 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.

[0050] Examples of thiazole-based crosslinking agents include 2-mercaptobenzothiazole and dibenzothiazyl disulfide.

[0051] When a crosslinking agent is used in the recycled material-forming 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, in order to ensure that the crosslinking reaction proceeds sufficiently and to easily form a recycled material that is well-balanced and excellent in hardness, tensile strength, elongation at break, and 100% Mo.

[0052] [Crosslinking aid] In the recycled material-forming material, the crosslinking agent may be used alone, but when a crosslinking agent such as the peroxide-based crosslinking agent is used, it is preferable to use a crosslinking aid, which may be selected from known crosslinking aids depending on the type of crosslinking agent.

[0053] For example, examples of crosslinking aids that can be used when using peroxide-based crosslinking agents include triallyl isocyanurate, triallyl cyanurate, trimethallyl isocyanurate, triallyl formal, triallyl trimellitate, N,N'-m-phenylene bismaleimide, dipropargyl terephthalate, diallyl phthalate, tetraallyl terephthalamide, polyfunctional (meth)acrylates such as ethylene glycol di(meth)acrylate and trimethylolpropane tri(meth)acrylate, and other compounds capable of co-crosslinking by radicals (polyfunctional monomers), metal salts of higher carboxylic acids, polyhydric alcohol (meth)acrylates, and metal (meth)acrylic acid salts. Among these, triallyl isocyanurate is preferred because it has excellent reactivity, excellent heat resistance, and can easily produce a sealing material with high hardness and high modulus.

[0054] When a crosslinking aid is used in the recycled material-forming material, the amount of the crosslinking aid used is preferably 0.5 parts by mass or more, and preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 6 parts by mass or less, per 100 parts by mass of the recycled product and uncrosslinked perfluoro(co)polymer in total, in order to ensure that the crosslinking reaction proceeds sufficiently and to easily form a sealing material that is well-balanced and excellent in hardness, tensile strength, elongation at break, and 100% Mo.

[0055] When a crosslinking agent and a crosslinking aid are used in the recycled material-forming material, the mass ratio of the content of the crosslinking aid to the content of the crosslinking agent in the recycled material-forming material (content of crosslinking aid / content of crosslinking agent) is preferably 1 or more, more preferably 2 or more, and preferably 30 or less, more preferably 20 or less, in order to allow the crosslinking agent to react in the right amount and to easily form a recycled material that exhibits the desired physical properties.

[0056] [Ethylenically unsaturated bond-containing compounds] Examples of the ethylenically unsaturated bond-containing compound include compounds described in WO 2022 / 065054, JP 2003-183402 A, and JP 11-116684 A.

[0057] [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.

[0058] [catalyst] Examples of the catalyst include the same catalysts as those described in JP-A Nos. 2003-183402 and 11-116684.

[0059] [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.

[0060] [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.

[0061] [Method for preparing recycled material] The recycled material-forming material can be prepared by mixing (kneading) the recycled product with the other components as required. 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.

[0062] 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.

[0063] <Process for cross-linking recycled material-forming materials> The method for producing the present recycled material is not particularly limited as long as it includes a step of crosslinking the recycled material-forming material.

[0064] When forming a recycled material from the recycled material-forming 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 the recycled material-forming material into a sheet shape.

[0065] The sheet obtained in the separating step is preferably preformed into the shape of the desired recycled material before the crosslinking step. This pre-forming may involve directly forming the desired recycled material shape from the sheet obtained in the separating process, or the sheet obtained in the separating process may be cut or extruded to form 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 then be formed into the desired recycled material shape.

[0066] The crosslinking step more preferably includes a primary crosslinking step and a secondary crosslinking step. The crosslinking step is preferably carried out using a preformed body having the desired recycled material shape obtained by the preforming step.

[0067] The primary crosslinking step is preferably a step of heating and pressurizing a preformed body having the desired recycled material shape obtained by the preforming step. A specific example 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.

[0068] 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 process accelerates crosslinking, and even if unreacted components remain after the primary crosslinking process, the unreacted components can be decomposed and evaporated, resulting in the formation of a recycled material that emits less gas.

[0069] In the method for producing the recycled material, 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 recycled material in a plasma atmosphere, etc. The recycled material obtained through this radiation irradiation step can be said to be a radiation-treated product.

[0070] 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.

[0071] When irradiating with radiation, it is desirable to irradiate with radiation 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 recycled materials that are 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.

[0072] Although irradiation may be carried out in air, the presence of oxygen during irradiation may inhibit the crosslinking reaction, resulting in a decrease in the mechanical strength of the resulting recycled material and a sticky surface. For this reason, the irradiation step is preferably carried out in an atmosphere of an inert gas such as nitrogen or argon.

[0073] <Recycled material> The recycled material obtained by this recycled material manufacturing method is not particularly limited, but can be used, for example, as gaskets or packings for various components, and can be particularly suitably used as a sealing material for semiconductor manufacturing equipment or a sealing material for plasma processing equipment, and particularly as a sealing material for driving parts such as gate valves used in the openings of plasma processing chamber units. The recycled material is preferably a sealing material, and examples of the sealing material include O-rings, square rings, gaskets, packing, oil seals, bearing seals, and lip seals. The shape of the recycled material may be appropriately selected depending on the intended use.

[0074] 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.

[0075] The IRHD of the recycled material measured in accordance with JIS K 6253-2:2012 is preferably 45 or more, more preferably 50 or more. The tensile strength of the recycled material, measured by the method described in the examples below, is preferably 7 MPa or more, and more preferably 8 MPa or more. The elongation at break of the recycled material, measured by the method described in the examples below, is preferably 120% or more, and more preferably 130% or more. The mass loss rate of the recycled 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%. [Example]

[0076] Next, the present invention will be described in more detail by showing examples, but the present invention is not limited to these examples.

[0077] <Crosslinked perfluoro(co)polymer (recycled product)> The crosslinked perfluoro(co)polymers (products to be recycled) used in the following examples and comparative examples are as follows: "Crosslinked perfluoro(co)polymer-1": 100 parts by mass of a perfluoroelastomer (PFE131T [3M], a perfluoro(co)polymer in which the crosslinking site is a nitrile group) and 0.5 parts by mass of an oxazole-based crosslinking agent (BOAP, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 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 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], a perfluoro(co)polymer in which the crosslinking site is a halogen atom), 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).

[0078] [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).

[0079] [Example 2] A recycled perfluoro(co)polymer-2 (recycled product) was obtained in the same manner as in Example 1, except that the crosslinked perfluoro(co)polymer-2 (recycled product) was used instead of the crosslinked perfluoro(co)polymer-1.

[0080] [Example 3] 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 370°C and 1 atmosphere for 1 hour under a helium gas atmosphere to obtain a recycled perfluoro(co)polymer-3 (the recycled product).

[0081] [Example 4] 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 370°C and 1 atmosphere for 1 hour under an argon gas atmosphere to obtain a recycled perfluoro(co)polymer-4 (the recycled product).

[0082] [Comparative 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 in air at 380°C and 1 atmosphere for 1 hour to obtain a recycled perfluoro(co)polymer-c1 (the recycled product).

[0083] Comparative Example 2 Recycled perfluoro(co)polymer-c2 (recycled product) was obtained in the same manner as in Comparative Example 1, except that crosslinked perfluoro(co)polymer-2 (recycled product) was used instead of crosslinked perfluoro(co)polymer-1.

[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 The contents of crosslinking sites in the crosslinked perfluoro(co)polymer (recycled product) and the recycled perfluoro(co)polymer (recycled product) were measured under the conditions above. The results are shown in Table 1. 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] In the column for Example 2 in Table 1 below, the content of crosslinked sites is marked with "-", but in Example 2, it is believed that the regeneration of the crosslinked sites (C=C bonds) on the right side of the formula below has occurred sufficiently.

[0086] [ka]

[0087] <Mass reduction rate> The mass of the crosslinked perfluoro(co)polymer (recycled product) used in the above Examples or Comparative Examples before heat treatment was measured, and the mass of the resulting recycled perfluoro(co)polymer (recycled product) was also measured. The mass loss rate (%) was calculated using the following formula: The results are shown in Table 1. Mass reduction rate (%) = [(mass of recycled product - mass of recycled product) / mass of recycled product] x 100

[0088] [Table 1]

[0089] <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) "Uncrosslinked perfluoro (co)polymer-2": Tecnoflon PFR94 (manufactured by Solvay)

[0090] [Example 5] 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 filled into an O-ring-shaped mold and press-molded using a compression vacuum press at 180°C for 30 minutes under a pressure of 5 MPa (primary crosslinking). The press-molded sheet was then heated in an oven at 250°C for 24 hours (secondary crosslinking) to obtain a molded product (O-ring).

[0091] [Comparative Examples 3 to 4] In Example 5, a molded body was obtained in the same manner as in Example 5, except that (co)polymers of the types and amounts (numbers, parts by mass) shown in Table 2 were used as the uncrosslinked perfluoro(co)polymer and recycled perfluoro(co)polymer.

[0092] [Example 6] A bulk elastomer composition was obtained by kneading 60 parts by mass of uncrosslinked perfluoro(co)polymer-2 (virgin product), 40 parts by mass of recycled perfluoro(co)polymer-2 (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).

[0093] [Comparative Examples 5 to 6] In Example 6, a molded body was obtained in the same manner as in Example 6, except that the uncrosslinked perfluoro(co)polymer and recycled perfluoro(co)polymer were (co)polymers of the types and amounts (numbers, parts by mass) shown in Table 2.

[0094] <irhd> The hardness of the resulting molded body was measured at 23° C. using an IRHD hardness measuring device in accordance with JIS K 6253-2:2012. The results are shown in Table 2.

[0095] <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 2.

[0096] <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 2. 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)]

[0097] <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 2. 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

[0098] (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

[0099] [Table 2]

[0100] In Example 5, a molded product was obtained that had the same IRHD and elongation at break as Comparative Example 4, which used only virgin products, and a molded product that had a smaller compression set and excellent plasma resistance (low mass loss rate) compared to Comparative Example 3. Furthermore, in Example 6, a molded body having the same IRHD and tensile strength as Comparative Example 6, which used only virgin material, was obtained. Compared to Comparative Example 5, the molded body had a smaller compression set when maintained at 200°C for 72 hours at a compression ratio of 25%, and had excellent plasma resistance (low mass loss rate).< / irhd>

Claims

1. A method for producing a regenerated perfluoro(co)polymer, comprising a step of heat-treating a crosslinked perfluoro(co)polymer obtained by crosslinking a perfluoro(co)polymer having crosslinking sites under an inert gas atmosphere to regenerate the crosslinking sites.

2. The method for producing recycled perfluoro(co)polymers according to claim 1, wherein the crosslinking sites are nitrile groups.

3. 2. The method for producing a recycled perfluoro(co)polymer according to claim 1, wherein the inert gas is at least one selected from nitrogen gas, argon gas, and helium gas.

4. The method for producing a recycled perfluoro(co)polymer according to claim 1, wherein the perfluoro(co)polymer having the crosslinking site is a (co)polymer that does not contain a carbon-hydrogen bond in the main chain of the (co)polymer.

5. A method for producing a recycled material, comprising a step of crosslinking a recycled material-forming material containing a recycled perfluoro(co)polymer obtained by the method for producing a recycled perfluoro(co)polymer according to any one of claims 1 to 4.

6. The method for producing a recycled material according to claim 5 , wherein the recycled material-forming material further comprises a cross-linking agent.

7. The method for producing recycled materials according to claim 5 , wherein the recycled material-forming material further contains an uncrosslinked perfluoro (co)polymer.

8. The method for producing a recycled material according to claim 7, wherein the content of the recycled perfluoro(co)polymer in the recycled material-forming material is 0.5 parts by mass or more per 100 parts by mass of the uncrosslinked perfluoro(co)polymer.

9. The method for producing a recycled material according to claim 5, wherein the recycled material is a sealing material.

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