JP2007063334A - Method for producing fluorine-containing polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a fluorine-containing polymer, including a process for removing the cross links of a cross-linked fluorine-containing polymer, to provide the cross link-removed fluorine-containing polymer obtained by the method, and to provide a molded article obtained by cross-linking the fluorine-containing polymer. <P>SOLUTION: This method for producing the fluorine-containing polymer includes a process for removing the cross links of the cross-linked fluorine-containing polymer in a supercritical fluid or semi-supercritical fluid of an active hydrogen-having compound. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a fluorine-containing polymer including a step of decrosslinking a crosslinked fluorine-containing polymer, a decrosslinked fluorine-containing polymer obtained by the method, and a molding obtained by crosslinking the fluorine-containing polymer. Related to goods.

  Crosslinked fluorine-containing polymers exhibit excellent chemical resistance, solvent resistance, and heat resistance. Therefore, in a wide range of fields such as aerospace, semiconductor manufacturing equipment, and chemical plant, sealing materials are used in harsh environments. It is used as a molded product.

  Molded products made of such cross-linked fluoropolymers have excellent properties, but are difficult to recycle because they are cross-linked. So far, scraps and defective products during molding, used molding The goods were disposed of by landfill. However, with the recent increase in awareness of environmental problems, it is required to recycle fluorine-containing polymers.

There are three known methods for recycling fluorine-containing polymers: 1) re-molding the polymer, 2) returning to the monomer, and 3) recovering hydrofluoric acid generated by treatment at high temperature in the form of CaF _2. It has been. The method 1) is the best recycling method for molten resins, but cannot be applied to crosslinked elastomers. The method 2) can be applied to fluoropolymers that are close to homopolymers such as PTFE. Monomers can be obtained with high efficiency, but in the case of a copolymer such as a fluorine-containing elastomer, the monomer yield is extremely reduced and the monomer cannot be obtained. The method 3) can be applied to any fluorine-containing polymer. Although it is a method, it requires a large amount of energy and is not an excellent recycling method. Therefore, in order to recycle the cross-linked fluorine-containing polymer, the most preferable method is to de-crosslink the once-crosslinked molded body and re-crosslink the obtained de-crosslinked product to obtain a molded body.

  As a method of decrosslinking the cross-linked fluoropolymer, 1) a method of treating with a chemical that chemically degrades the fluoropolymer such as amines (for example, see Patent Documents 1 to 4), 2) in a supercritical fluid A method of dispersing the alkali in the fluorinated polymer so as to reach the inside of the fluorine-containing polymer and decrosslinking (for example, see Patent Documents 5 and 6), 3) a method of decrosslinking by heating (for example, see Patent Documents 7 and 8) 4) A method of decrosslinking by mechanical force (for example, see Patent Document 9) is known. In the methods 1) and 2), it is difficult to remove the chemical used for decrosslinking from the regenerated polymer, and in the methods 3) and 4), it is difficult to sufficiently decrosslink. .

  Therefore, there is still no decrosslinking method for a cross-linked fluoropolymer capable of selectively decomposing the cross-linking points, without using special chemicals, cleanly and efficiently, further minimizing main chain degradation. There is no current situation.

JP 59-217734 A JP 59-217735 A Japanese Patent Laid-Open No. 9-031237 JP-T-2001-516378 Japanese Patent Application Laid-Open No. H8-169979 JP-A-8-291228 Japanese Patent Laid-Open No. 61-069805 Japanese Patent Laid-Open No. 2003-21460 JP 2004-148570 A

  The present invention relates to a method for producing a fluorine-containing polymer including a step of decrosslinking a crosslinked fluorine-containing polymer, a decrosslinked fluorine-containing polymer obtained by the method, and a molding obtained by crosslinking the fluorine-containing polymer. Provide goods.

  That is, the present invention relates to a method for producing a fluorinated polymer comprising a step of decrosslinking a crosslinked fluorinated polymer in a supercritical fluid or subcritical fluid of a compound having active hydrogen.

  The fluorine-containing polymer is preferably a fluorine-containing elastomer.

  The crosslinked fluorine-containing elastomer is preferably a fluorine-containing elastomer that is polyamine-crosslinked, polyol-crosslinked, peroxide-crosslinked and / or heterocyclic-crosslinked.

  The compound having active hydrogen is preferably water, alcohol or hydrocarbon.

  The present invention also relates to a decrosslinked fluoropolymer obtained by the above method.

  Furthermore, this invention relates to the molded article obtained by bridge | crosslinking the said fluorine-containing polymer.

  According to the present invention, since a compound having active hydrogen is processed in a supercritical fluid or subcritical fluid, crosslinking is performed without using special chemicals, and efficiently with cleanliness and with minimal deterioration of the main chain. Points can be selectively decomposed.

  The present invention relates to a method for producing a fluorine-containing polymer, which comprises a step of decrosslinking a crosslinked fluorine-containing polymer in a supercritical fluid or subcritical fluid of a compound having active hydrogen.

  The cross-linked fluorine-containing polymer is not particularly limited, but is preferably a cross-linked fluorine-containing elastomer, and is a polyamine cross-linked, polyol cross-linked, peroxide cross-linked and / or heterocyclic cross-linked fluorine-containing elastomer. It is more preferable that

  Examples of the fluorine-containing elastomer include non-perfluoro fluorine rubber (a) and perfluoro fluorine rubber (b). In addition, perfluoro fluororubber means the thing which 90 mol% or more consists of a perfluoro monomer among the structural units.

  Non-perfluoro fluorine rubber (a) includes vinylidene fluoride (VdF) fluorine rubber, tetrafluoroethylene (TFE) / propylene fluorine rubber, tetrafluoroethylene (TFE) / propylene / vinylidene fluoride (VdF) fluorine. Rubber, ethylene / hexafluoropropylene (HFP) fluorine rubber, ethylene / hexafluoropropylene (HFP) / vinylidene fluoride (VdF) fluorine rubber, ethylene / hexafluoropropylene (HFP) / tetrafluoroethylene (TFE) fluorine Examples thereof include rubber, fluorosilicone-based fluororubber, or fluorophosphazene-based fluororubber, and these can be used alone or in any combination as long as the effects of the present invention are not impaired.

  As the vinylidene fluoride (VdF) -based fluororubber, those represented by the following general formula (1) are preferable.

-(M ¹ )-(M ² )-(N ¹ )-(1)
(In the formula, the structural unit M ¹ is a structural unit derived from vinylidene fluoride (m ¹ ), the structural unit M ² is a structural unit derived from a fluorine-containing ethylenic monomer (m ² ), and the structural unit N ¹ Is a repeating unit derived from the monomer (m ¹ ) and the monomer (n ¹ ) copolymerizable with the monomer (m ² )

Formula Among vinylidene fluoride (VdF) fluorine rubber represented by (1), the structural unit M ¹ 45 to 85 mol%, preferably not containing a structural unit M ² fifty-five to fifteen mole%, more preferably structure The unit M ¹ is 50 to 80 mol%, and the structural unit M ² is 50 to 20 mol%. The structural unit N ¹ is preferably 0 to 10 mol% with respect to the total amount of the structural unit M ¹ and the structural unit M ² .

As the fluorine-containing ethylenic monomer (m ² ), one or more monomers can be used. For example, tetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE), trifluoroethylene, hexafluoro Fluorine-containing monomers such as propylene (HFP), trifluoropropylene, tetrafluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutene, perfluoro (alkyl vinyl ether) (PAVE), and vinyl fluoride can be mentioned. Of these, tetrafluoroethylene, hexafluoropropylene, and perfluoro (alkyl vinyl ether) are preferable.

The monomer (n ¹ ) may be any monomer as long as it is copolymerizable with the monomer (m ¹ ) and the monomer (m ² ). For example, ethylene, propylene, alkyl vinyl ether, etc. can give.

The monomer (n ¹ ) is preferably a monomer that gives a cross-linked site.

As a monomer that gives such a crosslinking site, the general formula (2):
CY ¹ ₂ = CY ¹ −R _f ¹ CHR ¹ X ¹ (2)
Wherein Y ¹ is a hydrogen atom, a fluorine atom or —CH ₃ , R _f ¹ is a fluoroalkylene group, a perfluoroalkylene group, a fluoropolyoxyalkylene group or a perfluoropolyoxyalkylene group, and R ¹ is a hydrogen atom Atom or —CH ₃ , X ¹ is an iodine atom or a bromine atom), or an iodine or bromine-containing monomer represented by the general formula (3):
_{CF 2 = CFO (CF 2 CF} (CF 3) O) m (CF 2) n -X 2 (3)
(Wherein, m is an integer of 0 to 5, n is an integer of 1 to 3, X ² is a cyano group, a carboxyl group, an alkoxycarbonyl group, a bromine atom, an iodine atom), General formula (4):
CH ₂ = CH (CF ₂ ) _p I (4)
(Wherein p is an integer of 1 to 10) and the like, and examples thereof include perfluoro (described in JP-B-5-63482 and JP-A-7-316234). Iodine-containing monomers such as 6,6-dihydro-6-iodo-3-oxa-1-hexene) and perfluoro (5-iodo-3-oxa-1-pentene), described in JP-A-4-217936 Iodine-containing monomers such as CF ₂ = CFOCF ₂ CF ₂ CH ₂ I, bromine-containing monomers described in JP-A-4-505341, JP-A-4-505345, JP-A-5-500070 And cyano group-containing monomers, carboxyl group-containing monomers, alkoxycarbonyl group-containing monomers, and the like as described in Japanese Patent Publication. These can be used alone or in any combination.

  Specific examples of such vinylidene fluoride (VdF) fluororubbers include VdF / HFP rubber, VdF / HFP / TFE rubber, VdF / CTFE rubber, VdF / CTFE / TFE rubber, and the like. It is done.

  The tetrafluoroethylene (TFE) / propylene-based fluororubber is preferably represented by the following general formula (5).

^{- (M 3) - (M} 4) - (N 2) - (5)
(In the formula, the structural unit M ³ is a structural unit derived from tetrafluoroethylene (m ³ ), the structural unit M ⁴ is a structural unit derived from propylene (m ⁴ ), and the structural unit N ² is a monomer (m ³ ) and repeating unit derived from monomer (n ² ) copolymerizable with monomer (m ⁴ ))

Formula (5) tetrafluoroethylene represented by (TFE) / Among the propylene fluorine rubber, a structural unit M ³ 40 to 70 mol%, preferably not containing a structural unit M ⁴ 60 to 30 mol%, more preferably it is a structural unit M ³ 50-60 mol%, in which the structural unit M ⁴ 50-40 mol%. The structural unit N ² is preferably 0 to 40 mol% with respect to the total amount of the structural unit M ³ and the structural unit M ⁴ .

The monomer (n ² ) may be any monomer that can be copolymerized with the monomer (m ³ ) and the monomer (m ⁴ ). Is preferred. Examples thereof include vinylidene fluoride and ethylene.

  As the perfluoro fluorine rubber (b), those represented by the following general formula (6) are preferable.

^{- (M 5) - (M} 6) - (N 3) - (6)
(In the formula, structural unit M ⁵ is a structural unit derived from tetrafluoroethylene (m ⁵ ), structural unit M ⁶ is a structural unit derived from perfluoro (alkyl vinyl ether) (m ⁶ ), and structural unit N ³ is (It is a repeating unit derived from the monomer (m ³ ) and the monomer (n ³ ) copolymerizable with the monomer (m ⁶ ))

Among the perfluoro fluorine-containing rubbers represented by the general formula (6) (b), the structural unit M ⁵ 50 to 90 mol%, preferably not containing a structural unit M ⁶ 10 to 50 mol%, more preferably the structural unit M ⁵ 50 to 80 mol%, which comprises a structural unit M ⁶ 20 to 50 mol%, more preferably a structural unit M ⁵ 55 to 70 mol%, in which the structural unit M ⁶ 30-45 mol%. The structural unit N ³ is preferably 0 to 5 mol%, more preferably 0 to 2 mol%, based on the total amount of the structural unit M ⁵ and the structural unit M ⁶ . When the composition is out of the range, the properties as a rubber elastic body are lost, and the properties tend to be similar to those of a resin.

Examples of perfluoro (alkyl vinyl ether) (m ⁶ ) include perfluoro (methyl vinyl ether) and perfluoro (propyl vinyl ether), and these can be used alone or in any combination.

The monomer (n ³ ) may be any monomer as long as it is copolymerizable with the monomer (m ⁵ ) and the monomer (m ⁶ ). preferable.

Examples of the monomer that gives such a crosslinking site include vinylidene fluoride, an iodine or bromine-containing monomer represented by the general formula (2), a monomer represented by the general formula (3), and a general formula (4) monomers such as perfluoro (6,6-dihydro-6-iodo as described in JP-B-5-63482 and JP-A-7-316234. Iodine-containing monomers such as -3-oxa-1-hexene) and perfluoro (5-iodo-3-oxa-1-pentene), CF ₂ = CFOCF ₂ CF ₂ CH described in JP-A-4-217936 ₂ I and other iodine-containing monomers, bromine-containing monomers described in JP-A-4-505341, JP-A-4-505345, and JP-A-5-500070 Shi Amino group-containing monomer, carboxyl group-containing monomers, and alkoxycarbonyl group-containing monomers and the like. These can be used alone or in any combination.

  The iodine atom, bromine atom, vinyl group, cyano group, carboxyl group, and alkoxycarbonyl group can function as a crosslinking point.

  Specific examples of such perfluorofluororubber (b) are described in International Publication No. 97/24381 pamphlet, Japanese Examined Patent Publication No. 61-57324, Japanese Examined Patent Publication No. 4-81608, Japanese Patent Publication No. 5-13961. Fluoro rubber etc.

  Among these, as the fluorine-containing elastomer, VdF-based fluororubber is preferable from the viewpoint of easy decrosslinking and easy crosslinking at the time of re-crosslinking, and in particular, VdF / HFP-based rubber, VdF / HFP / TFE rubber or VdF / TFE rubber is preferable.

  The non-perfluorofluororubber (a) and the perfluorofluororubber (b) described above can be produced by a conventional method, but the obtained polymer has a narrow molecular weight distribution and is easy to control the molecular weight. A known iodine transfer polymerization method is preferred as a method for producing fluororubber because an iodine atom can be introduced into the terminal.

  The cross-linking system for cross-linking the fluoropolymer may be appropriately selected depending on the type of cure site or the use of the obtained molded product when the fluoropolymer contains a crosslinkable group (cure site). As the crosslinking system, any of a polyol crosslinking system, a peroxide crosslinking system, a polyamine crosslinking system, and a heterocyclic crosslinking system can be adopted. Among these, from the viewpoint of ease of decrosslinking, a polyamine crosslinking system, a polyol crosslinking system, Heterocyclic crosslinking systems are preferred.

  Examples of the polyamine cross-linking agent include polyamine compounds such as hexamethylenediamine carbamate, N, N′-dicinnamylidene-1,6-hexamethylenediamine, and 4,4′-bis (aminocyclohexyl) methanecarbamate. . Among these, N, N′-dicinnamylidene-1,6-hexamethylenediamine is preferable.

  As the polyol crosslinking-type crosslinking agent, a compound conventionally known as a fluororubber crosslinking agent can be used. For example, a polyhydroxy compound, particularly a polyhydroxy aromatic compound is preferred because of its excellent heat resistance. Used.

  The polyhydroxy aromatic compound is not particularly limited. For example, 2,2-bis (4-hydroxyphenyl) propane (hereinafter referred to as bisphenol A), 2,2-bis (4-hydroxyphenyl) perfluoropropane. (Hereinafter referred to as bisphenol AF), resorcin, 1,3-dihydroxybenzene, 1,7-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 4,4′-dihydroxydiphenyl, 4,4 ′ -Dihydroxystilbene, 2,6-dihydroxyanthracene, hydroquinone, catechol, 2,2-bis (4-hydroxyphenyl) butane (hereinafter referred to as bisphenol B), 4,4-bis (4-hydroxyphenyl) valeric acid, 2 , 2-Bis (4-hydroxyphenyl) Tetrafluorodichloropropane, 4,4′-dihydroxydiphenyl sulfone, 4,4′-dihydroxydiphenyl ketone, tri (4-hydroxyphenyl) methane, 3,3 ′, 5,5′-tetrachlorobisphenol A, 3,3 Examples include ', 5,5'-tetrabromobisphenol A. These polyhydroxy aromatic compounds may be an alkali metal salt, an alkaline earth metal salt or the like, but when the copolymer is coagulated using an acid, it is preferable not to use the metal salt.

  The peroxide cross-linking agent may be an organic peroxide that can easily generate a peroxy radical in the presence of heat or a redox system. Specifically, for example, 1,1-bis (t -Butylperoxy) -3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, α, α-bis (t-butylperoxy) -p-diisopropylbenzene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di ( t-butylperoxy) -hexyne-3, benzoyl peroxide, t-butylperoxybenzene, t-butylperoxymaleic acid, t-butylperoxy Examples thereof include isopropyl carbonate. Among these, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane is preferable.

  Examples of the heterocyclic crosslinking agent include an oxazole crosslinking agent, an imidazole crosslinking agent, a thiazole crosslinking agent, and a triazine crosslinking agent.

  As the oxazole crosslinking agent, imidazole crosslinking agent, thiazole crosslinking agent, and triazine crosslinking agent, the general formula (7):

（式中、Ｒ²は、同じかまたは異なり、−ＮＨ₂、−ＮＨＲ³、−ＯＨまたは−ＳＨであり、Ｒ³は、フッ素原子または１価の有機基である）で示される架橋性反応基を少なくとも２個含む化合物、一般式（８）：

Wherein R ² is the same or different and is —NH ₂ , —NHR ³ , —OH or —SH, and R ³ is a fluorine atom or a monovalent organic group. Compounds containing at least two groups, general formula (8):

で示される化合物、一般式（９）：

A compound represented by the general formula (9):

（式中、Ｒ_f ²は炭素数１〜１０のパーフルオロアルキレン基）で示される化合物、および一般式（１０）：

(Wherein R _f ² is a C 1-10 perfluoroalkylene group), and the general formula (10):

（式中、ｎは１〜１０の整数）で示される化合物からなる群から選択される少なくとも１つの化合物であることが、耐熱性の点から好ましい。

It is preferable from a heat resistant point that it is at least 1 compound selected from the group which consists of a compound shown by (In formula, n is an integer of 1-10).

  Among these, a compound having at least two crosslinkable reactive groups represented by the general formula (7) is preferable from the viewpoint of improving heat resistance because the form after crosslinking is stabilized by an aromatic ring.

The substituent R ³ in the crosslinkable reactive group represented by the general formula (7) is a monovalent organic group other than a hydrogen atom or a fluorine atom. The N—R ³ bond is preferable because it has higher oxidation resistance than the N—H bond.

Examples of the monovalent organic group include, but are not limited to, an aliphatic hydrocarbon group, a phenyl group, and a benzyl group. More specifically, for example, at least one -CH ₃ of ^{_{R 3, -C 2 H 5,}} -C 3 carbon atoms, such as H ₇ 1 to 10, especially 1 to 6 lower alkyl group; -CF _3, - Fluorine atom-containing lower alkyl group having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms such as C ₂ F ₅ , —CH ₂ F, —CH ₂ CF ₃ , —CH ₂ C ₂ F ₅ ; phenyl group; benzyl group; _{C 6 F 5, -CH 2 C} 6 F 5 phenyl or benzyl 1-5 hydrogen atoms with fluorine atoms is substituted, such _{as; -C 6 H 5-n (} CF 3) n, -CH 2 Examples thereof include a phenyl group or a benzyl group in which 1 to 5 hydrogen atoms are substituted with —CF ₃ such as C ₆ H _5-n (CF ₃ ) _n (n is an integer of 1 to 5).

  Specific examples include, but are not limited to, 2,2-bis (3,4-diaminophenyl) hexafluoropropane, 2,2-bis [3-amino-4- (N-methylamino) phenyl], for example. Hexafluoropropane, 2,2-bis [3-amino-4- (N-ethylamino) phenyl] hexafluoropropane, 2,2-bis [3-amino-4- (N-propylamino) phenyl] hexafluoro Propane, 2,2-bis [3-amino-4- (N-phenylamino) phenyl] hexafluoropropane, 2,2-bis [3-amino-4- (N-perfluorophenylamino) phenyl] hexafluoro Examples thereof include propane and 2,2-bis [3-amino-4- (N-benzylamino) phenyl] hexafluoropropane.

  These bisamidoxime crosslinkers, bisamidrazone crosslinkers, bisaminophenol crosslinkers, bisaminothiophenol crosslinkers, bisdiaminophenyl crosslinkers, etc. are the cyano group, carboxyl group and fluorinated elastomer. Reacts with an alkoxycarbonyl group to form an oxazole ring, a thiazole ring, an imidazole ring, or a triazine ring to give a crosslinked product.

  Moreover, a crosslinking accelerator can be used together with the said crosslinking agent as needed.

  An onium compound is generally used as a crosslinking accelerator for a polyol crosslinking system. The onium compound is not particularly limited, and examples thereof include ammonium compounds such as quaternary ammonium salts, phosphonium compounds such as quaternary phosphonium salts, oxonium compounds, sulfonium compounds, cyclic amines, and monofunctional amine compounds. Of these, quaternary ammonium salts and quaternary phosphonium salts are preferred.

  The quaternary ammonium salt is not particularly limited. For example, 8-methyl-1,8-diazabicyclo [5,4,0] -7-undecenium chloride, 8-methyl-1,8-diazabicyclo [5, 4,0] -7-undecenium iodide, 8-methyl-1,8-diazabicyclo [5,4,0] -7-undecenium hydroxide, 8-methyl-1,8-diazabicyclo [5 , 4,0] -7-Undecenium methyl sulfate, 8-ethyl-1,8-diazabicyclo [5,4,0] -7-undecenium bromide, 8-propyl-1,8-diazabicyclo [5 , 4,0] -7-undecenium bromide, 8-dodecyl-1,8-diazabicyclo [5,4,0] -7-undecenium chloride, 8-dodecyl-1,8-diazabicyclo [5 4,0] -7-undecenium hydroxide, 8-eicosyl-1,8-diazabicyclo [5,4,0] -7-undecenium chloride, 8-tetracosyl-1,8-diazabicyclo [5, 4,0] -7-undecenium chloride, 8-benzyl-1,8-diazabicyclo [5,4,0] -7-undecenium chloride (hereinafter referred to as DBU-B), 8-benzyl-1 , 8-diazabicyclo [5,4,0] -7-undecenium hydroxide, 8-phenethyl-1,8-diazabicyclo [5,4,0] -7-undecenium chloride, 8- (3- Phenylpropyl) -1,8-diazabicyclo [5,4,0] -7-undecenium chloride and the like. Among these, DBU-B is preferable from the viewpoint of crosslinkability and physical properties of the cross-linked product.

  The quaternary phosphonium salt is not particularly limited. For example, tetrabutylphosphonium chloride, benzyltriphenylphosphonium chloride (hereinafter referred to as BTPPC), benzyltrimethylphosphonium chloride, benzyltributylphosphonium chloride, tributylallylphosphonium chloride, tributyl. Examples thereof include -2-methoxypropylphosphonium chloride, benzylphenyl (dimethylamino) phosphonium chloride, and among these, benzyltriphenylphosphonium chloride (BTPPC) is preferable from the viewpoint of crosslinkability and physical properties of the crosslinked product.

  Further, as a crosslinking accelerator, a quaternary ammonium salt, a solid solution of a quaternary phosphonium salt and bisphenol AF, or a chlorine-free crosslinking accelerator disclosed in JP-A-11-147891 can also be used.

  Examples of peroxide-crosslinking accelerators include triallyl cyanurate, triallyl isocyanurate (TAIC), triacryl formal, triallyl trimellitate, N, N′-m-phenylenebismaleimide, dipropargyl. Terephthalate, diallyl phthalate, tetraallyl terephthalate amide, triallyl phosphate, bismaleimide, fluorinated triallyl isocyanurate (1,3,5-tris (2,3,3-trifluoro-2-propenyl) -1,3, 5-triazine-2,4,6-trione), tris (diallylamine) -S-triazine, triallyl phosphite, N, N-diallylacrylamide, 1,6-divinyldodecafluorohexane, hexaallylphosphoramide, N , N, N ′, N′-tetraa Ruphthalamide, N, N, N ′, N′-tetraallylmalonamide, trivinylisocyanurate, 2,4,6-trivinylmethyltrisiloxane, tri (5-norbornene-2-methylene) cyanurate, triallyl phosphite Etc. Among these, triallyl isocyanurate (TAIC) is preferable from the viewpoint of crosslinkability and physical properties of the cross-linked product.

  The addition amount of the crosslinking agent and the crosslinking accelerator and the crosslinking treatment conditions are not particularly limited and can be appropriately selected depending on the type of the fluorine-containing polymer. preferable.

  As a compounding quantity of a crosslinking agent, it is preferable that it is 0.01-10 weight part with respect to 100 weight part of fluoropolymers, and it is more preferable that it is 0.1-5 weight part. If it is less than 0.01 part by weight, there is a tendency that the crosslinking cannot be performed sufficiently. If it exceeds 10 parts by weight, the crosslinking density becomes too high, so that the crosslinking time becomes long and economically preferable. There is no tendency.

  As a compounding quantity of a crosslinking adjuvant, it is preferable that it is 0.01-10 weight part with respect to 100 weight part of fluorine-containing polymers, and it is more preferable that it is 0.1-5.0 weight part. If the crosslinking aid is less than 0.01 parts by weight, there is a tendency that sufficient crosslinking cannot be performed, and if it exceeds 10 parts by weight, the crosslinking density becomes too high and the crosslinking time becomes long. There is a tendency to be unfavorable economically.

  When crosslinking the fluorine-containing polymer, usual additives such as fillers, processing aids, plasticizers, colorants, antioxidants, anti-aging agents, ozone degrading agents, ultraviolet absorbers and the like are added as necessary. Can be blended. Moreover, each component can be prepared by mixing using an ordinary elastomer processing machine, for example, an open roll, a Banbury mixer, a kneader or the like. In addition, it can be prepared by a method using a closed mixer or a method of co-coagulation from emulsion mixing. The composition thus prepared is crosslinked and molded according to a conventional method. That is, it is molded by compression molding, injection molding, extrusion molding, calendar molding, dip molding, coating, etc. by dissolving in a solvent.

  The crosslinking conditions vary depending on the molding method and the shape of the molded product, but are generally in the range of several seconds to 5 hours at 100 ° C to 300 ° C. Further, secondary crosslinking may be performed in order to stabilize the physical properties of the crosslinked product. The secondary crosslinking conditions are 150 ° C. to 300 ° C. and about 30 minutes to 48 hours.

  In the present invention, a crosslinked fluorine-containing polymer comprising the above components is decrosslinked in a supercritical fluid or subcritical fluid of a compound having active hydrogen.

  The active hydrogen-containing compound is not particularly limited, and examples thereof include supercritical fluids such as water, ammonia and organic solvents, and subcritical fluids. From the viewpoint of the feasibility, practicality, and operability of the supercritical state as seen from the pressure, and the solvent ability for promoting thermal decomposition, oxidative decomposition, and hydrolysis, water, alcohol, or hydrocarbon is preferable. .

Examples of the hydrocarbon include saturated hydrocarbons and unsaturated hydrocarbons represented by the chemical formulas C _n H _{2n + 2} and C _n H _2n such as methane, ethane, propane, pentane, ethylene, and butylene. The hydrocarbon is preferably 8 and may be linear or branched. Furthermore, a saturated hydrocarbon is preferable from the viewpoint of explosibility.

The alcohols include methanol, ethanol, formula C _n H _{2n + 1} OH such as propanol, be those represented by C _n H _2n-1 OH, it is preferable that an alcohol having 1 to 8 carbon atoms.

  Here, the supercritical fluid refers to a state in which the pressure and temperature are made higher than the critical point of the compound having active hydrogen to be used. For example, the critical point of water is 374.1 ° C. and 22.12 MPa, and the critical point of methanol is 239.4 ° C. and 8.09 MPa. By making the critical point or higher, a supercritical fluid is obtained. In general, the subcritical fluid is not necessarily clearly defined, but in the present invention, the temperature T and the pressure P are T / Tc ≧ 0.7 and P / Pc ≧ 0.7. And satisfying at least one of T / Tc ≦ 1 and P / Pc ≦ 1 (in the PT diagram, from the region where T ≧ 0.7Tc and P ≧ 0.7Pc, T> Tc and A fluid in an L-shaped region excluding a supercritical region where P> Pc. Here, Pc and Tc indicate a critical pressure and a critical temperature, respectively.

  Among these, water is preferably a supercritical fluid or subcritical fluid from the viewpoint of promoting the decomposition reaction, and particularly at high pressure, since it has a large ion product even in the supercritical region, the ionic reaction is dominant. Thus, it is known that only water exhibits an acid catalyst / alkali catalyst action, and hydrolysis is promoted. On the other hand, as the temperature rises, radical reactions become dominant and thermal decomposition reactions are promoted. From these facts, it is considered that the reaction field as a resource recycling technology is superior in the subcritical region, but the reaction rate increases with temperature, so the conditions vary from subcritical to supercritical depending on the target reaction. It is necessary to select with. In any case, it is preferable to use water to bring the temperature to a subcritical state or higher, that is, 180.0 ° C. or higher and 15.47 MPa or higher, preferably 244.6 ° C. or higher and 17.68 MPa or higher. It is more preferable.

  On the other hand, supercritical and subcritical methanol, known as supercritical and subcritical alcohols, are recognized as supercritical water as decomposition solvents. The critical temperature and critical pressure are lower than water and have the advantage of good operability. Further, it can be said that the gradual progress of the decomposition reaction is excellent in operability.

In order to further accelerate the decomposition reaction, it is effective to add a small amount of an oxidizing agent and a reducing agent in addition to controlling the temperature and pressure. In particular, it has been known so far that decomposition is promoted by adding hydrogen peroxide H ₂ O ₂ .

  The time for decrosslinking the cross-linked fluorine-containing polymer in the supercritical fluid or subcritical fluid is not particularly limited, but for a supercritical fluid, it is preferably 0.1 second to 10 hours. In the subcritical fluid, it is preferably 1 second to 20 hours.

  As a specific method, a crosslinked fluorine-containing polymer and a compound having active hydrogen such as water are sealed in a sealed container, and heated / applied to a temperature / pressure at which the active hydrogen-containing compound becomes critical or subcritical. The defluorinated fluorine-containing polymer is obtained by cooling, after completion of the decrosslinking reaction, cooling, taking out the contents, and separating the solid content.

  The method for separating the solid content is not particularly limited, and examples thereof include a method of immersing in a solvent in which a non-crosslinked fluoropolymer dissolves and dissolving the obtained decrosslinked fluoropolymer. .

  Examples of the solvent include acetone, methanol, ethanol, HCFC-141b, and the like.

  The amount of the compound having active hydrogen such as water to be initially sealed together with the crosslinked fluorine-containing polymer in the sealed container is not particularly limited, but with respect to 100 parts by weight of the crosslinked fluorine-containing polymer, It is preferable that it is 10-10000 weight part, and it is preferable that it is 50-5000 weight part. When the amount is less than 10 parts by weight, water tends to be adsorbed or sorbed onto the fluoropolymer, losing its function as free water and not functioning as a solvent. There is a tendency that the decomposition treatment speed of the fluoropolymer decreases.

  In the method of the present invention, the decrosslinking reaction is performed by reacting with active hydrogen of a supercritical fluid or subcritical fluid, for example, when the crosslinking is polyol crosslinking,

のように脱架橋反応が進むものであり、架橋が、イミダゾール架橋である場合、

In the case where the decrosslinking reaction proceeds and the crosslink is an imidazole crosslink,

のように脱架橋反応が進み、特殊な薬品を用いることなく、クリーンに効率よく、さらに主鎖劣化を最小限に抑え、架橋点を選択的に分解することができるものである。

As described above, the decrosslinking reaction proceeds, and without using special chemicals, it is possible to cleanly and efficiently, further minimize degradation of the main chain, and selectively decompose the crosslinking points.

  The obtained decrosslinked fluorine-containing polymer can be crosslinked again to form a molded product.

  As the crosslinking agent and crosslinking aid used for re-crosslinking, those described above can be suitably used. Moreover, the above-mentioned conditions etc. can be used suitably also for bridge | crosslinking conditions.

  When the fluorine-containing polymer is a VdF rubber, the polymer obtained by the decrosslinking reaction can be subjected to polyol crosslinking, regardless of which crosslinking method is used.

  Further, when the fluorine-containing polymer crosslinked by polyol crosslinking is decrosslinked, a double bond remains in the main chain, which is preferable because it can be recrosslinked without adding a crosslinking accelerator such as an onium salt.

  In the case of a perfluoro-based or TFE / propylene-based rubber, it is often peroxide-crosslinked or heterocyclic-crosslinked, and when the decrosslinking reaction is carried out, many terminals are carboxylic acids. In addition, when a decrosslinking treatment is performed, a part of the main chain is also cleaved, but the cut end is often a carboxylic acid. In that case, re-crosslinking can be performed by using, for example, tetraamine or the like using a terminal carboxylic acid.

  The molded products of the present invention are semiconductor related fields, automobile fields, aircraft fields, rocket fields, ship fields, chemical fields such as plants, pharmaceutical fields such as pharmaceuticals, photographic fields such as developing machines, printing fields such as printing machines, Painting field such as painting equipment, tube analysis / physical and chemical machine field, food plant equipment field, nuclear power plant equipment field, steel field such as iron plate processing equipment, general industrial field, electrical field, fuel cell field, electronic parts field, field construction It can be widely used in fields such as mold forming.

  Next, the present invention will be described with reference to examples, but the present invention is not limited to such examples.

Example 1 (Decrosslinking of polyol crosslinking with supercritical water)
Fluororubber (polyol-based crosslinker-containing VdF / TFE copolymer, trade name: Daiel G-701, manufactured by Daikin Industries, Ltd.) 100 parts, thermal black (N-990 Cancarb) 20 parts, high activity oxidation Usually, 3 parts of magnesium (MA-150 manufactured by Kyowa Chemical Industry Co., Ltd.) and 6 parts of calcium hydroxide (CALDIC 2000 manufactured by Omi Chemical Industry Co., Ltd.) are added and a kneading roll machine equipped with two 8-inch rolls is usually used. Kneading at 25 to 70 ° C. This was left at room temperature for about 20 hours, kneaded again in the same roll machine, and finally sheeted to a thickness of about 2 mm to take out an uncrosslinked rubber sheet.

The obtained uncrosslinked rubber sheet was subjected to primary crosslinking with a 100-ton compression press at a gauge pressure of 60 kgf / cm ² at 170 ° C. for 10 minutes to obtain a crosslinked sheet (width: about 140 mm, length: about 110 mm, thickness: about 2 mm). Furthermore, the obtained crosslinked sheet was subjected to secondary crosslinking at 230 ° C. for 24 hours.

  0.5 g of the obtained cross-linked sheet and 0.65 g of water were sealed in a stainless steel sealed container having an internal volume of 2.1 mL and heated in an electric furnace at 390 ° C. for 3 hours. At this time, the internal pressure was 27 MPa, and water was in a supercritical state. After cooling, the contents were taken out and the solid content was separated. When solid content was immersed in acetone and solid content was further separated, 6.8% acetone-soluble content was obtained with respect to the total weight of the fluororubber before crosslinking.

Comparative Example 1 (Analysis of non-decrosslinked rubber)
When the crosslinked sheet obtained in Example 1 was immersed in acetone and the solid content was further separated, only 1.6% acetone-soluble component was obtained with respect to the total weight of the fluororubber before crosslinking.

Comparative Example 2 (analysis of uncrosslinked rubber)
When the fluororubber (polyol-based crosslinking agent-containing VdF / TFE copolymer, trade name: Daiel G-701, manufactured by Daikin Industries, Ltd.) used in Example 1 was immersed in acetone, it was completely dissolved.

Claims (6)

A method for producing a fluorine-containing polymer, comprising a step of decrosslinking a crosslinked fluorine-containing polymer in a supercritical fluid or subcritical fluid of a compound having active hydrogen. The method for producing a fluorine-containing polymer according to claim 1, wherein the fluorine-containing polymer is a fluorine-containing elastomer. The method for producing a fluorine-containing polymer according to claim 2, wherein the crosslinked fluorine-containing elastomer is a fluorine-containing elastomer which is polyamine-crosslinked, polyol-crosslinked, peroxide-crosslinked and / or heterocyclic-crosslinked. The method for producing a fluoropolymer according to any one of claims 1 to 3, wherein the compound having active hydrogen is water, alcohol or hydrocarbon. A decrosslinked fluoropolymer obtained by the production method according to claim 1. A molded product obtained by crosslinking the fluorine-containing polymer according to claim 5.