JP2008074967A - Manufacturing method for re-crosslinking fluorine-containing elastomer, re-crosslinking fluorine-containing elastmer obtained by the method and molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a re-crosslinking fluorine-containing elastomer including a step for reacting the de-crosslinked fluorine-containing elastomer with a crosslinking agent containing two or more of functional groups reactable with a carboxyl group, a crosslinking fluorine-containing elastomer obtained by the method, and a molded product formed from the re-crosslinking fluorine-containing elastomer. <P>SOLUTION: The manufacturing method for the re-crosslinking fluorine-containing elastomer includes a step for reacting the de-crosslinked fluorine-containing elastomer with the crosslinking agent containing two or more of functional groups reactable with the carboxyl group. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a recrosslinked fluoroelastomer obtained by crosslinking a decrosslinked fluoroelastomer, a recrosslinked fluoroelastomer obtained by the method, and a molding formed from the recrosslinked fluoroelastomer. Related to goods.

In recent years, with increasing environmental problems, it is required to recycle fluorine-containing polymers. In order to recycle the fluorine-containing polymer, there are three methods: (1) reforming the polymer, (2) returning to the monomer, and (3) recovering hydrofluoric acid generated by treatment at a high temperature in the form of CaF _2. It has been known.

  The method (1) is the best recycling method for molten resins, but cannot be applied to crosslinked elastomers. The method (2) is a homopolymer such as polytetrafluoroethylene (PTFE). Monomers can be obtained with good yields if they are close to fluoropolymers, but monomers such as fluorine-containing elastomers are extremely low in monomer yield and cannot be obtained. In addition, the method (3) is a method that can be applied to any fluorine-containing polymer. However, since a large amount of energy is required, it cannot be said to be an excellent recycling method. Therefore, in order to recycle the fluorine-containing elastomer, the most preferable method is to decrosslink a once-crosslinked molded body and recrosslink the obtained decrosslinked product to obtain a molded body.

  In order to reuse after decrosslinking, it is necessary to perform recrosslinking. There are many techniques for performing decrosslinking, but there are few methods for performing recrosslinking, and methods of performing polyol crosslinking, polyamine crosslinking, and peroxide crosslinking by plasticizing with a roll and then mixing with virgin rubber (for example, Patent Document 1) And 2), a method of subjecting peroxide-crosslinked waste fluororubber to heat treatment, followed by polyol crosslinking or polyamine crosslinking (for example, see Patent Document 3), decrosslinking with a super strong acid, and then polyol crosslinking / polyamine crosslinking / peroxide crosslinking. There are known methods (for example, see Patent Document 4), methods for performing polyol crosslinking after decrosslinking with a gas and an alkali in a supercritical state (for example, see Patent Documents 5 and 6), and the like. In any of the methods, it is difficult to selectively cut only the crosslinking points when decrosslinking, and the main chain is also cut in parallel, which reduces the molecular weight of the main chain. For this reason, the recrosslinked product composed only of the regenerated elastomer does not proceed sufficiently to be inferior in properties and has to be mixed with a virgin polymer in order to perform sufficient crosslinking.

JP 2004-148570 A JP-A-2005-212174 Japanese Patent Laid-Open No. 2003-21460 Japanese Patent Laid-Open No. 9-031237 JP-A-8-291228 Japanese Patent Application Laid-Open No. H8-169979

  The present invention provides a method for producing a recrosslinked fluorine-containing elastomer that can be sufficiently crosslinked only by a decrosslinked fluorine-containing elastomer, in particular, only a decrosslinked fluorine-containing elastomer, and can obtain a good molded product. Another object is to provide a recrosslinked fluorine-containing elastomer and a molded product formed from the recrosslinked fluorine-containing elastomer.

  That is, the present invention relates to a method for producing a recrosslinked fluorine-containing elastomer, comprising a step of reacting a decrosslinked fluorine-containing elastomer with a crosslinking agent containing two or more functional groups capable of reacting with a carboxyl group.

  The decrosslinked fluorine-containing elastomer is preferably a fluorine-containing elastomer obtained by heating the crosslinked fluorine-containing elastomer at 240 to 450 ° C. in the presence of oxygen.

  The decrosslinked fluorine-containing elastomer is preferably a fluorine-containing elastomer obtained by decrosslinking the crosslinked fluorine-containing elastomer in a supercritical fluid or subcritical fluid of a compound having active hydrogen.

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

  The cross-linked fluorine-containing elastomer is preferably a fluorine-containing elastomer cross-linked by peroxide cross-linking or polyol cross-linking.

  The crosslinking agent is preferably a crosslinking agent containing two or more functional groups that generate a heterocyclic ring.

  The crosslinking agent is preferably an oxazole crosslinking agent, an imidazole crosslinking agent or a thiazole crosslinking agent.

  The crosslinking agent is preferably an imidazole crosslinking agent.

  The present invention also relates to a recrosslinked fluorine-containing elastomer obtained by the production method. Furthermore, the present invention relates to a molded article formed from the recrosslinked fluorine-containing elastomer.

  According to the present invention, a sufficiently cross-linked re-crosslinked fluorine-containing elastomer is obtained by reacting the decrosslinked fluorine-containing elastomer with a crosslinking agent containing two or more functional groups capable of reacting with a carboxyl group. The fluorine-containing elastomer can be recycled.

  The present invention relates to a method for producing a re-crosslinked fluorine-containing elastomer, comprising a step of reacting a decrosslinked fluorine-containing elastomer with a crosslinking agent containing two or more functional groups capable of reacting with a carboxyl group.

  The fluorine-containing elastomer is not particularly limited, and examples thereof 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 described in the above publication. These can be used alone or in any combination.

  Specific examples of such vinylidene fluoride (VdF) -based fluororubber 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 cross-linking system for cross-linking the fluorine-containing elastomer may be appropriately selected depending on the type of the cure site or the use of the obtained molded product when the fluorine-containing elastomer contains a crosslinkable group (cured site). As the crosslinking system, any of a polyamine crosslinking system, a polyol crosslinking system, a peroxide crosslinking system, and a heterocyclic crosslinking system can be employed.

  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, and a thiazole crosslinking agent.

  In addition, when the fluorine-containing elastomer has a cyano group, it can be triazine-crosslinked by forming a triazine ring by the inclusion of an organic tin compound such as tetraphenyltin or triphenyltin. The organotin compound may be contained.

  As the oxazole crosslinking agent, imidazole crosslinking agent, and thiazole crosslinking agent, 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. 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).

Of these, a phenyl group and —CH ₃ are preferred because they are particularly excellent in heat resistance, have good crosslinking reactivity, and are relatively easy to synthesize.

  As a compound having two crosslinkable reactive groups represented by the general formula (7), the general formula (11):

（式中、Ｒ²は前記と同じ、Ｒ⁶は、−ＳＯ₂−、−Ｏ−、−ＣＯ−、炭素数１〜６のアルキレン基、炭素数１〜１０のパーフルオロアルキレン基、単結合手、または

(Wherein R ² is the same as above, R ⁶ is —SO ₂ —, —O—, —CO—, an alkylene group having 1 to 6 carbon atoms, a perfluoroalkylene group having 1 to 10 carbon atoms, and a single bond. Hand, or

で示される基である）で示される化合物が合成が容易な点から好ましい。

From the viewpoint of easy synthesis.

  Preferable specific examples of the alkylene group having 1 to 6 carbon atoms include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, and the like. As the perfluoroalkylene group having 1 to 10 carbon atoms, Is

などがあげられる。なお、これらの化合物は、特公平２−５９１７７号公報、特開平８−１２０１４６号公報などで、ビスジアミノフェニル化合物の例示として知られているものである。

Etc. These compounds are known as examples of bisdiaminophenyl compounds in JP-B-2-59177 and JP-A-8-120146.

  Among these, more preferred compounds are those represented by the general formula (12):

（式中、Ｒ⁷は、同じかまたは異なり、いずれも水素原子、炭素数１〜１０のアルキル基；フッ素原子を含有する炭素数１〜１０のアルキル基；フェニル基；ベンジル基；フッ素原子および／または−ＣＦ₃で１〜５個の水素原子が置換されたフェニル基またはベンジル基である）で示される化合物である。

(Wherein R ⁷ are the same or different and both are hydrogen atoms, alkyl groups having 1 to 10 carbon atoms; alkyl groups having 1 to 10 carbon atoms containing fluorine atoms; phenyl groups; benzyl groups; fluorine atoms and And / or a phenyl group or a benzyl group in which 1 to 5 hydrogen atoms are substituted with —CF ₃ ).

  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. Among these, 2,2-bis (3,4-diaminophenyl) hexafluoropropane is more preferable from the viewpoint of excellent heat resistance and particularly good crosslinking reactivity.

  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 fluorine-containing elastomers, 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 elastomers, 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 elastomer, conventional additives such as a filler, a processing aid, a plasticizer, a colorant, an antioxidant, an anti-aging agent, an ozone degrading agent, an ultraviolet absorber, etc. 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.

  The decrosslinked fluorine-containing elastomer used in the present invention is obtained by decrosslinking a crosslinked fluorine-containing elastomer composed of the above components.

  The method for decrosslinking is not particularly limited, but for example, a method of heating in the presence of oxygen, a method of decrosslinking in a supercritical fluid or subcritical fluid of a compound having active hydrogen, a method of mechanically decrosslinking And a decrosslinking method using chemicals. Among these, the method of heating in the presence of oxygen is preferable for the peroxide-crosslinked fluorine-containing elastomer because the decrease in molecular weight is small and the yield of the decrosslinked polymer is high, and the active hydrogen is used in the polyol-crosslinked fluorine-containing elastomer. A method of treating with a supercritical fluid or subcritical fluid is preferred. Moreover, you may use combining these methods.

  Further, the weight average molecular weight (Mw) of the decrosslinked fluorine-containing elastomer is preferably 10,000 to 500,000, and more preferably 20,000 to 300,000. If it is less than 10,000, the re-crosslinked fluorine-containing elastomer has a low rubber elasticity and tends to be hard and resinous, and if it exceeds 500,000, the plasticity is lost, and the compounding agent is added with a roll or a mixer at the time of re-crosslinking. There is a tendency to be unable to knead.

  When the crosslinked fluorine-containing elastomer is heated in the presence of oxygen, the heating temperature is preferably 240 to 450 ° C, more preferably 240 to 400 ° C. When the temperature is lower than 240 ° C., the de-crosslinking of the cross-linked fluorine-containing elastomer tends not to proceed sufficiently, and when the temperature exceeds 450 ° C., the volatile components increase and the molecular weight tends to decrease.

  Although the heating conditions depend on the type of crosslinked fluorine-containing elastomer and the degree of crosslinking, the heating time is preferably 0.01 to 200 hours from the viewpoint that sufficient crosslinking sites can be cut. More preferably, it is 1 to 100 hours. If the heating time is less than 0.01 hours, heat and oxygen do not conduct to the inside of the crosslinked fluorine-containing elastomer, and decrosslinking does not proceed. Tend to be disadvantageous.

  In the case of decrosslinking in a supercritical fluid or subcritical fluid of a compound having active hydrogen, the compound having active hydrogen is not particularly limited, but may be supercritical fluid such as water, ammonia, organic solvent, Among them, critical fluids can be mentioned. Among these, supercritical state feasibility, practicality and operability from the viewpoint of environmental load, critical temperature and critical pressure, thermal decomposition, oxidative decomposition, and hydrolysis are promoted. From the viewpoint of the solvent ability for the water, it is preferably water, alcohol or hydrocarbon.

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, have been recognized as supercritical water as a decomposition solvent. 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 elastomer 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 cross-linked fluorine-containing elastomer 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 elastomer can be obtained by cooling and cooling after completion of the decrosslinking reaction, taking out the contents, and separating the solid content.

  A 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 fluorine-containing elastomer is dissolved and dissolving the obtained decrosslinked fluorine-containing elastomer. .

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

  The amount of the compound having active hydrogen such as water that is initially sealed together with the crosslinked fluorine-containing elastomer in the sealed container is not particularly limited, but with respect to 100 parts by weight of the crosslinked fluorine-containing elastomer, 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 to the fluorine-containing elastomer, losing the function as free water and not functioning as a solvent. The decomposition rate of the fluorine-containing elastomer tends to decrease.

  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.

  Mechanical decrosslinking methods include applying a mechanical shearing force with a roll, kneader, mixer, etc. to perform decrosslinking, applying heat in addition to mechanical force, and applying pressure and heat with ultrasonic waves. There are methods.

Examples of chemical decrosslinking methods include amines such as alkylamines, alkalis such as NaOH and ammonia, strong acids such as CH ₃ SO ₃ H and CF ₃ SO ₂ H, and NaBH ₄ and B ₂ H ₆ . And a method of decrosslinking using a chemical such as a reducing agent.

  The above methods such as heating in the presence of oxygen, debridging in a supercritical fluid or subcritical fluid of a compound having active hydrogen, mechanical debridging, and chemical debridging A crosslinked fluorine-containing elastomer is obtained, and the terminal portion of the uncrosslinked fluorine-containing elastomer becomes a carboxyl group.

The mechanism of de-crosslinking is that with peroxide-crosslinked fluorine-containing elastomers, hydrogen is released from CH ₂ -CH ₂ bonds such as TAIC as a cross-linking agent and the bond is cleaved by oxygen attack and reacts with moisture. In the end, it is considered to be —CH ₂ COOH. In addition, in the polyol-crosslinked fluorine-containing elastomer, it is considered that the CF = CH olefin structure of the main chain by-produced at the time of crosslinking is decomposed and finally becomes —CH ₂ COOH or —CF ₂ COOH.

  Since the obtained decrosslinked fluorine-containing elastomer becomes a relatively low molecular weight elastomer having a carboxyl group at the terminal, crosslinking can be performed again using the carboxyl group as a crosslinking point.

  The crosslinking agent may be any crosslinking agent containing two or more functional groups capable of reacting with a carboxyl group, and is not particularly limited. For example, an oxazole crosslinking agent, an imidazole crosslinking agent, a thiazole crosslinking agent, an isocyanate crosslinking agent, Examples thereof include an epoxy crosslinking agent, an amine crosslinking agent, a methylol crosslinking agent, an aziridine crosslinking agent, and an oxazoline crosslinking agent. Among these, an oxazole crosslinking agent, an imidazole crosslinking agent, and a thiazole crosslinking agent are preferable from the viewpoint of heat resistance. Examples of these cross-linking agents include the same ones as described above, and among them, an imidazole cross-linking agent is preferable from the viewpoint of easy progress of the cross-linking reaction and easy synthesis of the cross-linking agent.

  Specific examples of the crosslinking agent and crosslinking aid used for re-crosslinking include those described above.

  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 fluorine-containing elastomers, 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 elastomers, and it is more preferable that it is 0.1-5 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.

  Moreover, the above-mentioned conditions etc. can be used suitably also for bridge | crosslinking conditions.

  Moreover, as other crosslinking conditions, the conditions normally used for crosslinking of the fluorine-containing elastomer can be appropriately employed. For example, the above-described conditions can be employed.

  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 and recrosslinking of polyol crosslinking by heating in air)
Fluororubber (polyol-based crosslinking agent-containing VdF / HFP 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.

  3 g of the obtained crosslinked rubber was cut to about 5 mm square, put in a magnetic dish, and heated in an electric furnace at 350 ° C. for 1 hour in an air atmosphere. The obtained heat-treated rubber was put into 30 mL of acetone, allowed to stand overnight and filtered, and the filtrate was evaporated to dryness to obtain a decrosslinked rubber. 0.345 g of decrosslinked rubber was obtained, and 15% of the polymer component in the crosslinked rubber could be obtained as decrosslinked rubber.

When the molecular weight of the decrosslinked rubber was measured by GPC, it was Mw = 29,000 (uncrosslinked raw rubber was Mw = 210,000). The measured infrared spectra of delinking rubber, the 1720 cm ^-1 and 1750 cm ^-1, a peak presumed each -CH ₂ COOH, a carboxyl group, such as -CF ₂ COOH were observed.

  To 0.50 g of the obtained decrosslinked rubber, 0.025 g of a crosslinking agent 2,2-bis (3,4-diaminophenyl) hexafluoropropane (crosslinking agent / rubber = 5/100) was added and then dissolved in 20 mL of acetone. After putting in a petri dish, acetone was evaporated to form a cast film, which was heated at 180 ° C. for 5 hours. The obtained sample was immersed in acetone overnight and then filtered to dry the solid content. The gel fraction defined by acetone insoluble component / input solid content × 100 was 89%.

Comparative Example 1 (Virgin rubber cross-linking)
When the raw rubber before crosslinking used in Example 1 was charged with a crosslinking agent in the same manner as in Example 1 and measured for the gel fraction, it was less than 1%.

Comparative example 2 (polyol crosslinking of recycled rubber)
To 0.50 g of the decrosslinked rubber obtained in Example 1, 0.01 g of 2,2-bis (4-hydroxyphenyl) hexafluoropropane (bisphenol AF) (2 parts with respect to 100 parts of the fluorine-containing elastomer), benzyl 0.002 g of triphenylphosphonium chloride (BTPPC) (0.4 parts with respect to 100 parts of fluorine-containing elastomer), 0.03 g of calcium hydroxide (Caldic # 2000, manufactured by Omi Chemical Co., Ltd.) (fluorine-containing elastomer 100) 6 parts), magnesium oxide (Kyowa Mag 150, manufactured by Kyowa Chemical Industry Co., Ltd.) 0.015 g (3 parts for 100 parts of fluorine-containing elastomer), dissolved in 20 mL of acetone, and placed in a petri dish Thereafter, acetone was evaporated to form a cast film, which was heated at 170 ° C. for 5 hours. The obtained sample was immersed in acetone overnight and then filtered to dry the solid content. The gel fraction was 68%.

Comparative Example 3 (Virgin rubber polyol cross-linking)
When the gel fraction was measured by adding a crosslinking agent to the raw rubber before crosslinking used in Example 1 and heating it in the same manner as in Comparative Example 2, it was 97%.

Example 2 (Decrosslinking and recrosslinking of peroxide crosslinking by heating in air)
Fluoro rubber (iodine-containing VdF / HFP / TFE copolymer, trade name: Daiel G-902, manufactured by Daikin Industries, Ltd.) 100 parts, thermal black (N-990 Cancarb) 20 parts, triallyl isocyan 4 parts by weight of nurate (TAIC, manufactured by Nippon Kasei Co., Ltd.) and 1.5 parts by weight of peroxide (trade name: Perhexa 2.5B, manufactured by Nippon Oil & Fats Co., Ltd.) were added, and two 8-inch rolls were provided. It knead | mixed at 25-70 degreeC by the normal method using the kneading roll machine. 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 160 ° 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 180 ° C. for 4 hours.

  The crosslinked sheet was again crushed by passing it through an 8-inch double roll. 128 g of the obtained crosslinked rubber powder was put in a magnetic dish and heated in an electric furnace at 350 ° C. for 1 hour in an air atmosphere. The obtained heat-treated rubber powder was put into 1.5 L of acetone, allowed to stand overnight and filtered, and the filtrate was evaporated to dryness to obtain a decrosslinked rubber. 45.66 g of decrosslinked rubber was obtained, and 43% of the polymer component in the crosslinked rubber could be obtained as decrosslinked rubber.

When the molecular weight of the decrosslinked rubber was measured by GPC, it was Mw = 57,000 (uncrosslinked raw rubber was Mw = 90,000). The measured infrared spectra of delinking rubber, in the same manner as in Example 1, to 1720 cm ^-1 and 1750 cm ^-1, a peak is estimated each -CH ₂ COOH, and groups such as -CF ₂ COOH appearance Was.

  To 0.50 g of the obtained decrosslinked rubber, 0.025 g of a crosslinking agent 2,2-bis (3,4-diaminophenyl) hexafluoropropane (crosslinking agent / rubber = 5/100) was added and then dissolved in 20 mL of acetone. After putting in a petri dish, acetone was evaporated to form a cast film, which was heated at 180 ° C. for 5 hours. The obtained sample was immersed in acetone overnight and then filtered to dry the solid content. The gel fraction was 33%.

Comparative Example 4 (Virgin rubber cross-linking)
The raw rubber before crosslinking used in Example 2 was charged with a crosslinking agent in the same manner as in Example 1, and the gel fraction was measured by heating and found to be less than 1%.

Claims (10)

A method for producing a recrosslinked fluorine-containing elastomer, comprising a step of reacting a decrosslinked fluorine-containing elastomer with a crosslinking agent containing two or more functional groups capable of reacting with a carboxyl group. The production method according to claim 1, wherein the decrosslinked fluorine-containing elastomer is a fluorine-containing elastomer obtained by heating the crosslinked fluorine-containing elastomer at 240 to 450 ° C in the presence of oxygen. 2. The production according to claim 1, wherein the defluorinated fluorine-containing elastomer is a fluorine-containing elastomer obtained by decrosslinking the crosslinked fluorine-containing elastomer in a supercritical fluid or subcritical fluid of a compound having active hydrogen. Method. The method according to claim 3, wherein the compound having active hydrogen is water, alcohol or hydrocarbon. The production method according to any one of claims 2 to 4, wherein the crosslinked fluorine-containing elastomer is a fluorine-containing elastomer crosslinked by peroxide crosslinking or polyol crosslinking. The production method according to claim 1, wherein the crosslinking agent is a crosslinking agent containing two or more functional groups that generate a heterocyclic ring. The production method according to claim 1, wherein the crosslinking agent is an oxazole crosslinking agent, an imidazole crosslinking agent, or a thiazole crosslinking agent. The production method according to claim 1, wherein the crosslinking agent is an imidazole crosslinking agent. A recrosslinked fluorine-containing elastomer obtained by the production method according to claim 1. A molded article formed from the recrosslinked fluorine-containing elastomer according to claim 9.