Method for producing aqueous fluorine-containing elastomer dispersion

Abstract

Provided is a method for producing an aqueous dispersion, which contains a fluorine-containing elastomer, by polymerizing a fluorine-containing monomer in the presence of an aqueous medium and a fluorine-containing compound (A). The fluorine-containing elastomer contains a methylene group in the main chain. The fluorine-containing compound (A) is represented by general formula (A): CXiXk=CXjRa-(CZ1Z2)k-Y3 (In the formula, Xi, Xj and Xk may be the same as, or different from, each other and are F, Cl, H or CF3; Y3 is a hydrophilic group; Ra is a linking group; Z1 and Z2 may be the same as, or different from, each other and are H, F or CF3; and k is 0 or 1. However, at least one of Xi, Xk, Xj, Ra, Z1 and Z2 contains F. The number of carbon atoms in a portion excluding the hydrophilic group is 6 or fewer). The fluorine-containing compound (A) is supplied after polymerization of the fluorine-containing monomer is initiated.

Description

[Technical field]

[0001] The present disclosure relates to a method for producing an aqueous fluorine-containing elastomer dispersion. [Background technology]

[0002] As a method for producing an aqueous fluorine-containing elastomer dispersion, Patent Document 1 describes emulsion polymerization using a reactive surfactant consisting of a compound having a radically polymerizable unsaturated bond and a hydrophilic group in the molecule. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-045970 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present disclosure is to provide a production method which can smoothly proceed with the polymerization of a fluorinated monomer while suppressing adhesion of the fluorinated elastomer to a polymerization tank, without using a relatively large amount of a reactive surfactant as in conventional production methods. [Means for solving the problem]

[0005] According to the present disclosure, there is provided a method for producing an aqueous fluorine-containing elastomer dispersion, which comprises polymerizing a fluorine-containing monomer in the presence of an aqueous medium and a fluorine-containing compound (A) to produce an aqueous dispersion containing a fluorine-containing elastomer, the aqueous dispersion comprising the fluorine-containing elastomer having a methylene group in its main chain, and the fluorine-containing compound (A) having a structure represented by the general formula (A): CX i X k =CX j R a -(CZ 1 Z 2 ) k -Y 3 (A) (In the formula, X i , X j and X k are the same or different and are F, Cl, H or CF3; Y 3 is a hydrophilic group; R a is a linking group; Z 1 and Z 2 are the same or different and are H, F or CF3; k is 0 or 1. i , X k , X j , R a , Z 1 and Z 2 at least one of which contains F. The number of carbon atoms in the portion excluding the hydrophilic group is 6 or less. The present invention provides a production method for a compound represented by the formula (I), which comprises initiating polymerization of the fluorine-containing monomer and then supplying a fluorine-containing compound (A).

[0006] The hydrophilic group is -NH2, -P(O)(OM)2, -OP(O)(OM)2, -SO3M, -OSO3M or -COOM (in each formula, M is H, a metal atom, NR 7 4. An imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent, R 7 are H or an organic group and may be the same or different. Any two of them may be bonded to each other to form a ring. The fluorine-containing elastomer preferably contains a vinylidene fluoride unit. The fluorine-containing elastomer preferably contains vinylidene fluoride units in an amount of 50 mol % or more based on the total monomer units. It is preferable to supply the fluorine-containing compound (A) also before the initiation of polymerization of the fluorine-containing monomer. The amount of the fluorine-containing compound (A) supplied after the initiation of polymerization of the fluorine-containing monomer is preferably 30 to 300 ppm by mass relative to the aqueous medium. It is preferable to polymerize the fluorine-containing monomer in the absence of a fluorine-containing surfactant having substantially no radically polymerizable unsaturated bond. The fluorine-containing elastomer preferably has a Mooney viscosity (ML1+10 (100° C.)) of 10-130. The fluorine-containing compound (A) is represented by the general formula (A1): CX i X k =CX j -OR-(CZ 1 Z 2 ) k -Y 3 (In the formula, X i , X j , X k , Z 1 , Z 2 , k and Y 3 is as described above, and R is a fluorinated alkylene group or a fluorinated oxyalkylene group having 1 to 3 carbon atoms.) and a compound represented by general formula (A2): CX i X k =CX j -CZ 1 Z 2 -OR-(CZ 1 Z 2 ) k -Y 3 (In the formula, X i , X j , X k , Z 1 , Z 2 , k and Y 3 is as described above, and R is a fluorinated alkylene group or a fluorinated oxyalkylene group having 1 or 2 carbon atoms. Effect of the Invention

[0007] According to the present disclosure, it is possible to provide a production method which can smoothly proceed with the polymerization of a fluorine-containing monomer while suppressing adhesion of the fluorine-containing elastomer to a polymerization tank, without using a relatively large amount of a reactive surfactant as in conventional production methods. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Before describing specific embodiments of the present disclosure, some terms used in the present disclosure will be defined or explained.

[0009] In this disclosure, a fluoroelastomer is an amorphous fluoropolymer. "Amorphous" refers to a fluoropolymer having a melting peak (ΔH) of 4.5 J / g or less in differential scanning calorimetry (DSC) (heating rate 10°C / min) or differential thermal analysis (DTA) (heating rate 10°C / min). A fluoroelastomer exhibits elastomeric properties by crosslinking. Elastomeric properties refer to the property that a polymer can be stretched and retains its original length when the force required to stretch the polymer is no longer applied.

[0010] In the present disclosure, a perfluoromonomer is a monomer that does not contain a carbon atom-hydrogen atom bond in the molecule. The perfluoromonomer may be a monomer in which some of the fluorine atoms bonded to the carbon atom are replaced with chlorine atoms, in addition to carbon atoms and fluorine atoms, and may also have nitrogen atoms, oxygen atoms, sulfur atoms, phosphorus atoms, boron atoms, or silicon atoms in addition to carbon atoms. The perfluoromonomer is preferably a monomer in which all hydrogen atoms are replaced with fluorine atoms. The perfluoromonomer does not include a monomer that gives a crosslinkable group.

[0011] The monomer that provides a crosslinking site is a monomer (cure site monomer) that provides a crosslinking site to the fluoropolymer for forming a crosslink with a curing agent. The monomer that provides a crosslinking site includes a monomer that provides a crosslinkable group.

[0012] In the present disclosure, the content of each monomer unit constituting the fluorine-containing elastomer can be calculated by an appropriate combination of NMR, FT-IR, elemental analysis and X-ray fluorescence analysis depending on the type of monomer.

[0013] In this disclosure, "organic group" means a group containing one or more carbon atoms or a group formed by removing a hydrogen atom from an organic compound. Examples of the "organic group" are: an alkyl group which may have one or more substituents; an alkenyl group optionally having one or more substituents; an alkynyl group optionally having one or more substituents; a cycloalkyl group optionally having one or more substituents, a cycloalkenyl group optionally having one or more substituents, a cycloalkadienyl group optionally having one or more substituents, an aryl group which may have one or more substituents; an aralkyl group optionally having one or more substituents; a non-aromatic heterocyclic group optionally having one or more substituents, a heteroaryl group optionally having one or more substituents, Cyano group, Formyl group, RaO-, RaCO-, RaSO2-, RaCOO-, RaNRaCO-, RaCONRa-, RaOCO-, RaOSO2-, and RaNRbSO2- (In these formulas, Ra is independently an alkyl group which may have one or more substituents; an alkenyl group optionally having one or more substituents; an alkynyl group optionally having one or more substituents; a cycloalkyl group optionally having one or more substituents, a cycloalkenyl group optionally having one or more substituents, a cycloalkadienyl group optionally having one or more substituents, an aryl group which may have one or more substituents; an aralkyl group optionally having one or more substituents; a non-aromatic heterocyclic group optionally having one or more substituents, or a heteroaryl group optionally having one or more substituents, Rb is independently H or an alkyl group which may have one or more substituents. Includes: The organic group is preferably an alkyl group which may have one or more substituents.

[0014] In the present disclosure, a "substituent" means a substitutable group. Examples of the "substituent" include an aliphatic group, an aromatic group, a heterocyclic group, an acyl group, an acyloxy group, an acylamino group, an aliphatic oxy group, an aromatic oxy group, a heterocyclic oxy group, an aliphatic oxycarbonyl group, an aromatic oxycarbonyl group, a heterocyclic oxycarbonyl group, a carbamoyl group, an aliphatic sulfonyl group, an aromatic sulfonyl group, a heterocyclic sulfonyl group, an aliphatic sulfonyloxy group, an aromatic sulfonyloxy group, a heterocyclic sulfonyloxy group, a sulfamoyl group, an aliphatic sulfonamide group, an aromatic sulfonamide group, a heterocyclic sulfonamide group, an amino group, an aliphatic amino These include an aromatic amino group, an aromatic amino group, a heterocyclic amino group, an aliphatic oxycarbonylamino group, an aromatic oxycarbonylamino group, a heterocyclic oxycarbonylamino group, an aliphatic sulfinyl group, an aromatic sulfinyl group, an aliphatic thio group, an aromatic thio group, a hydroxy group, a cyano group, a sulfo group, a carboxy group, an aliphatic oxyamino group, an aromatic oxyamino group, a carbamoylamino group, a sulfamoylamino group, a halogen atom, a sulfamoylcarbamoyl group, a carbamoylsulfamoyl group, a dialiphatic oxyphosphinyl group, and a diaromatic oxyphosphinyl group.

[0015] The aliphatic group may be saturated or unsaturated, and may have a hydroxy group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the aliphatic group include alkyl groups having a total of 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms, such as a methyl group, an ethyl group, a vinyl group, a cyclohexyl group, and a carbamoylmethyl group.

[0016] The aromatic group may have, for example, a nitro group, a halogen atom, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the aromatic group include aryl groups having 6 to 12 carbon atoms, preferably 6 to 10 carbon atoms in total, such as a phenyl group, a 4-nitrophenyl group, a 4-acetylaminophenyl group, and a 4-methanesulfonylphenyl group.

[0017] The heterocyclic group may have a halogen atom, a hydroxy group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the heterocyclic group include a 5- or 6-membered heterocycle having a total of 2 to 12, preferably 2 to 10, carbon atoms, such as a 2-tetrahydrofuryl group and a 2-pyrimidyl group.

[0018] The acyl group may have an aliphatic carbonyl group, an arylcarbonyl group, a heterocyclic carbonyl group, a hydroxy group, a halogen atom, an aromatic group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the acyl group include acyl groups having a total of 2 to 8 carbon atoms, preferably 2 to 4 carbon atoms, such as an acetyl group, a propanoyl group, a benzoyl group, and a 3-pyridinecarbonyl group.

[0019] The acylamino group may have an aliphatic group, an aromatic group, a heterocyclic group, etc., such as an acetylamino group, a benzoylamino group, a 2-pyridinecarbonylamino group, a propanoylamino group, etc. Examples of the acylamino group include an acylamino group having a total of 2 to 12 carbon atoms, preferably 2 to 8 carbon atoms, and an alkylcarbonylamino group having a total of 2 to 8 carbon atoms, such as an acetylamino group, a benzoylamino group, a 2-pyridinecarbonylamino group, a propanoylamino group, etc.

[0020] The aliphatic oxycarbonyl group may be saturated or unsaturated, and may have a hydroxy group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the aliphatic oxycarbonyl group include alkoxycarbonyl groups having a total of 2 to 8 carbon atoms, preferably 2 to 4 carbon atoms, such as a methoxycarbonyl group, an ethoxycarbonyl group, and a (t)-butoxycarbonyl group.

[0021] The carbamoyl group may have an aliphatic group, an aromatic group, a heterocyclic group, etc. Examples of the carbamoyl group include an unsubstituted carbamoyl group, an alkylcarbamoyl group having a total of 2 to 9 carbon atoms, preferably an unsubstituted carbamoyl group, an alkylcarbamoyl group having a total of 2 to 5 carbon atoms, such as an N-methylcarbamoyl group, an N,N-dimethylcarbamoyl group, and an N-phenylcarbamoyl group.

[0022] The aliphatic sulfonyl group may be saturated or unsaturated, and may have a hydroxy group, an aromatic group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the aliphatic sulfonyl group include alkylsulfonyl groups having a total of 1 to 6 carbon atoms, preferably a total of 1 to 4 carbon atoms, such as a methanesulfonyl group.

[0023] The aromatic sulfonyl group may have a hydroxy group, an aliphatic group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the aromatic sulfonyl group include arylsulfonyl groups having a total of 6 to 10 carbon atoms, such as a benzenesulfonyl group.

[0024] The amino group may have an aliphatic group, an aromatic group, a heterocyclic group, or the like.

[0025] The acylamino group may have, for example, an acetylamino group, a benzoylamino group, a 2-pyridinecarbonylamino group, a propanoylamino group, etc. Examples of the acylamino group include an acylamino group having a total of 2 to 12 carbon atoms, preferably a total of 2 to 8 carbon atoms, and more preferably an alkylcarbonylamino group having a total of 2 to 8 carbon atoms, such as an acetylamino group, a benzoylamino group, a 2-pyridinecarbonylamino group, a propanoylamino group, etc.

[0026] The aliphatic sulfonamide group, aromatic sulfonamide group, and heterocyclic sulfonamide group may be, for example, a methanesulfonamide group, a benzenesulfonamide group, or a 2-pyridinesulfonamide group.

[0027] The sulfamoyl group may have an aliphatic group, an aromatic group, a heterocyclic group, etc. Examples of the sulfamoyl group include a sulfamoyl group, an alkylsulfamoyl group having a total of 1 to 9 carbon atoms, a dialkylsulfamoyl group having a total of 2 to 10 carbon atoms, an arylsulfamoyl group having a total of 7 to 13 carbon atoms, and a heterocyclic sulfamoyl group having a total of 2 to 12 carbon atoms, more preferably a sulfamoyl group, an alkylsulfamoyl group having a total of 1 to 7 carbon atoms, a dialkylsulfamoyl group having a total of 3 to 6 carbon atoms, an arylsulfamoyl group having a total of 6 to 11 carbon atoms, and a heterocyclic sulfamoyl group having a total of 2 to 10 carbon atoms, such as a sulfamoyl group, a methylsulfamoyl group, an N,N-dimethylsulfamoyl group, a phenylsulfamoyl group, and a 4-pyridine sulfamoyl group.

[0028] The aliphatic oxy group may be saturated or unsaturated and may have a methoxy group, an ethoxy group, an i-propyloxy group, a cyclohexyloxy group, a methoxyethoxy group, etc. Examples of the aliphatic oxy group include alkoxy groups having a total of 1 to 8 carbon atoms, preferably 1 to 6 carbon atoms, such as a methoxy group, an ethoxy group, an i-propyloxy group, a cyclohexyloxy group, a methoxyethoxy group, etc.

[0029] The aromatic amino group and heterocyclic amino group may have an aliphatic group, an aliphatic oxy group, a halogen atom, a carbamoyl group, a heterocyclic group condensed with the aryl group, or an aliphatic oxycarbonyl group, preferably an aliphatic group having 1 to 4 carbon atoms in total, an aliphatic oxy group having 1 to 4 carbon atoms in total, a halogen atom, a carbamoyl group having 1 to 4 carbon atoms in total, a nitro group, or an aliphatic oxycarbonyl group having 2 to 4 carbon atoms in total.

[0030] The aliphatic thio group may be saturated or unsaturated and is an alkylthio group having a total of 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, such as a methylthio group, an ethylthio group, a carbamoylmethylthio group, or a t-butylthio group.

[0031] The carbamoylamino group may have an aliphatic group, an aryl group, a heterocyclic group, etc. Examples of the carbamoylamino group include a carbamoylamino group, an alkylcarbamoylamino group having a total of 2 to 9 carbon atoms, a dialkylcarbamoylamino group having a total of 3 to 10 carbon atoms, an arylcarbamoylamino group having a total of 7 to 13 carbon atoms, and a heterocyclic carbamoylamino group having a total of 3 to 12 carbon atoms, preferably a carbamoylamino group, an alkylcarbamoylamino group having a total of 2 to 7 carbon atoms, a dialkylcarbamoylamino group having a total of 3 to 6 carbon atoms, an arylcarbamoylamino group having a total of 7 to 11 carbon atoms, and a heterocyclic carbamoylamino group having a total of 3 to 10 carbon atoms, such as a carbamoylamino group, a methylcarbamoylamino group, an N,N-dimethylcarbamoylamino group, a phenylcarbamoylamino group, and a 4-pyridinecarbamoylamino group.

[0032] In this disclosure, ranges expressed by endpoints include all numbers subsumed within that range (eg, 1 to 10 includes 1.4, 1.9, 2.33, 5.75, 9.98, etc.).

[0033] In this disclosure, the term "at least 1" includes all numbers greater than or equal to 1 (e.g., at least 2, at least 4, at least 6, at least 8, at least 10, at least 25, at least 50, at least 100, etc.).

[0034] Specific embodiments of the present disclosure will be described in detail below, but the present disclosure is not limited to the following embodiments.

[0035] In the production method of the present disclosure, when a fluorine-containing elastomer-containing aqueous dispersion is produced by polymerizing a fluorine-containing monomer in the presence of an aqueous medium, the fluorine-containing compound (A) represented by general formula (A) is supplied to the polymerization system after initiating the polymerization of the fluorine-containing monomer.

[0036] General formula (A):CX i X k =CX j Ra -(CZ 1 Z 2 ) k -Y 3 (A) (In the formula, X i , X j and X k are the same or different and are F, Cl, H or CF3; Y 3 is a hydrophilic group; R a is a linking group; Z 1 and Z 2 are the same or different and are H, F or CF3; k is 0 or 1. i , X k , X j , R a , Z 1 and Z 2 At least one of the groups contains F. The number of carbon atoms in the portion excluding the hydrophilic group is 6 or less.)

[0037] By supplying the fluorine-containing compound (A) to the polymerization system after the initiation of polymerization, even if the amount of the fluorine-containing compound (A) supplied is relatively small, adhesion of the fluorine-containing elastomer produced by the polymerization reaction to the polymerization vessel can be suppressed, and the polymerization reaction of the fluorine-containing monomer also proceeds smoothly, enabling the generation of a sufficient number of fluorine-containing elastomer particles.

[0038] The fluorine-containing compound (A) used in the production method of the present disclosure has a hydrophilic group (Y 3 The number of carbon atoms in the portion excluding the hydrophilic group (Y) is 6 or less, and the portion corresponding to the hydrophobic group in the molecule is a short chain. 3 ) exceeds 6, it becomes necessary to use a relatively large amount of the compound in order to suppress adhesion of the fluoroelastomer to the polymerization vessel, which is economically disadvantageous and also disadvantageous in that the after-treatment becomes complicated.

[0039] The hydrophilic group (Y 3The number of carbon atoms in the portion excluding the fluorine-containing monomer is preferably 3 or more, more preferably 4 or more, and further preferably 5 or more, since this can further suppress adhesion of the fluorine-containing elastomer to the polymerization tank while more smoothly proceeding the polymerization of the fluorine-containing monomer.

[0040] The hydrophilic group (Y 3 ) may be any group exhibiting hydrophilicity, and may be an anionic hydrophilic group, a cationic hydrophilic group, or a nonionic hydrophilic group, but is preferably an anionic hydrophilic group.

[0041] The hydrophilic group (Y 3 ) are, for example, -NH2, -P(O)(OM)2, -OP(O)(OM)2, -SO3M, -OSO3M, -COOM (in each formula, M is H, a metal atom, NR 7 4. An imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent, R 7 are H or organic groups and may be the same or different. Any two of them may be bonded to each other to form a ring. ) is mentioned. As the hydrophilic group, -SO3M or -COOM is preferable, and -COOM is more preferable. R 7 The organic group of R is preferably an alkyl group. 7 As the 1-10 is preferably an organic group represented by the formula: 1-4 More preferred is an organic group represented by the formula: 1-4 More preferred is an alkyl group such as the above, and most preferred is H. The metal atom includes monovalent or divalent metal atoms, and is preferably an alkali metal (Group 1) or alkaline earth metal (Group 2), and more preferably Na, K or Li.

[0042] R in general formula (A) a is a linking group. In the present disclosure, the term "linking group" refers to a divalent linking group. The linking group is preferably a single bond or a group containing at least one carbon atom. The number of carbon atoms in the linking group is selected so that the number of carbon atoms in the portion of the fluorine-containing compound (A) excluding the hydrophilic group is 6 or less.

[0043] The linking group may be linear or branched, cyclic or acyclic in structure, saturated or unsaturated, substituted or unsubstituted, and may optionally contain one or more heteroatoms selected from the group consisting of sulfur, oxygen, and nitrogen, and may optionally contain one or more functional groups selected from the group consisting of esters, amides, sulfonamides, carbonyls, carbonates, urethanes, ureas, and carbamates. The linking group may not contain carbon atoms, but may be a catenary heteroatom such as oxygen, sulfur, or nitrogen.

[0044] R a is preferably, for example, a catenary heteroatom such as oxygen, sulfur, or nitrogen, or a divalent organic group.

[0045] R a When R is a divalent organic group, the hydrogen atom bonded to the carbon atom may be replaced with a halogen atom other than fluorine, such as chlorine, and may or may not contain a double bond. a may be either linear or branched, and may be either cyclic or noncyclic. a may contain functional groups (eg, esters, ethers, ketones, amines, halides, etc.).

[0046] R a may also be a non-fluorinated divalent organic group, or a partially fluorinated or perfluorinated divalent organic group.

[0047] R a Examples of the hydrocarbon group include a hydrocarbon group having no fluorine atoms bonded to a carbon atom, a hydrocarbon group in which some of the hydrogen atoms bonded to a carbon atom are substituted with fluorine atoms, a hydrocarbon group in which all of the hydrogen atoms bonded to a carbon atom are substituted with fluorine atoms, -(C=O)-, -(C=O)-O-, or a hydrocarbon group containing an ether bond, which may contain an oxygen atom, a double bond, or a functional group.

[0048] R ais preferably -(C=O)-, -(C=O)-O-, or a hydrocarbon group having 1 to 4 carbon atoms which may contain an ether bond and may contain a carbonyl group, and in the hydrocarbon group, some or all of the hydrogen atoms bonded to the carbon atoms may be substituted with fluorine.

[0049] R a is preferably a fluorinated alkylene group or a fluorinated oxyalkylene group. These are preferably linear. The number of carbon atoms is selected so that the carbon number of the portion excluding the hydrophilic group of the fluorine-containing compound (A) is 6 or less.

[0050] As the fluorine-containing compound (A), a fluorine-containing compound represented by the general formula (A1): is preferred, since it can further suppress adhesion of the fluorine-containing elastomer to the polymerization vessel while more smoothly promoting the polymerization of the fluorine-containing monomer: CX i X k =CX j -OR-(CZ 1 Z 2 ) k -Y 3 (In the formula, X i , X j , X k , Z 1 , Z 2 , k and Y 3 is as described above, and R is a fluorinated alkylene group or a fluorinated oxyalkylene group having 1 to 3 carbon atoms.) and a compound represented by general formula (A2): CX i X k =CX j -CZ 1 Z 2 -OR-(CZ 1 Z 2 ) k -Y 3 (In the formula, X i , X j , X k , Z 1 , Z 2 , k and Y 3is as described above, and R is a fluorinated alkylene group or a fluorinated oxyalkylene group having 1 or 2 carbon atoms.

[0051] As the fluorine-containing compound (A), among others, CF2=CFOCF2-Y 3 , CF2=CFOCF2CF2-Y 3 , CF2=CF0CF2CF2CF2-Y 3 , CF2=CFOCF2CF2CH2-Y 3 , CF2=CF0CF2CF2CF2CF2-Y 3 , CF2 = CFOCF2CF(CF3)OCF2-Y 3 , CF2=CFOCF2CF2OCF(CF3)-Y 3 , CF2=CFOCF2CF2OCF2-Y 3 , CH2=CFCF2OCF2-Y 3 , CH2=CFCF2OCF(CF3)-Y 3 , CH2=CFCF2OCH2CF2-Y 3 , CH2=CFCF2OCF2CF2-Y 3 , CH2=CFCF2OCF2CH2-Y 3 , CH2=CFCF2OCH2CF2CH2-Y 3 , CH2=CFCF2OCF2CF2CH2-Y 3 , CH2=CFCF2OCF2CF2CF2-Y 3 , CH2=CFCF2OCF(CF3)CH2-Y 3 , CH2=CFCF2OCF(CF3)CF2-Y 3 , CH2=CFCF2OCF2CF2OCF2-Y 3 , CF2=CFCF2OCF2CF2CF2-Y 3 , CF2=CFCF2OCF2CF(CF3)-Y 3 , CF2=CFCF2OCF(CF3)-Y 3 , CF2 = CFCF2OCF(CF3)CH2-Y 3 , CF2=CFCF2OCF(CF3)CF2-Y 3 , is preferred.

[0052] The method of supplying the fluorine-containing compound (A) is not particularly limited, and may be supplied all at once at one time after the start of polymerization, may be supplied continuously after the start of polymerization, or may be supplied intermittently.For example, when the fluorine-containing monomer is supplied continuously or intermittently to the polymerization system, the fluorine-containing compound (A) may be supplied intermittently from the time when the supply amount of the fluorine-containing monomer reaches a given amount until the supply amount of the fluorine-containing monomer reaches a given time.

[0053] The time of supplying the fluorine-containing compound (A) is not particularly limited as long as it is after the start of polymerization. In the case of continuously or intermittently supplying the fluorine-containing monomer to the polymerization system, the suitable time of supplying the fluorine-containing compound (A) in a lump, or the suitable time of supplying the fluorine-containing compound (A) in a continuous or intermittent manner are exemplified below.

[0054] When the fluorine-containing compound (A) is fed all at once at one time after the initiation of polymerization, it is preferable to feed the fluorine-containing compound (A) after the amount (g) of the fluorine-containing monomer fed after the initiation of polymerization reaches 5% relative to the total amount (g) of the fluorine-containing monomer fed after the initiation of polymerization. It is also preferable to feed the fluorine-containing compound (A) after the amount of the fluorine-containing monomer fed after the initiation of polymerization reaches 10%, 20%, 30% or 40%.

[0055] In addition, when the fluorine-containing compound (A) is supplied all at once at one time point after the initiation of polymerization, it is preferable to supply the fluorine-containing compound (A) before the amount (g) of the fluorine-containing monomer supplied after the initiation of polymerization reaches 90% relative to the total amount (g) of the fluorine-containing monomer supplied after the initiation of polymerization. It is also preferable to supply the fluorine-containing compound (A) before the amount of the fluorine-containing monomer supplied after the initiation of polymerization reaches 85%, 80%, 75% or 70%.

[0056] When the fluorine-containing compound (A) is continuously or intermittently fed, it is preferable to start feeding the fluorine-containing compound (A) after the amount (g) of the fluorine-containing monomer fed after the initiation of polymerization reaches 5% relative to the total amount (g) of the fluorine-containing monomer fed after the initiation of polymerization, since this can further suppress adhesion of the fluorine-containing elastomer to the polymerization tank. It is also preferable to start feeding the fluorine-containing compound (A) after the amount of the fluorine-containing monomer fed after the initiation of polymerization reaches 10%, 20%, 30% or 40%.

[0057] In addition, when the fluorine-containing compound (A) is continuously or intermittently fed, it is preferable to stop feeding the fluorine-containing compound (A) before the amount (g) of the fluorine-containing monomer fed after the initiation of polymerization reaches 90% of the total amount (g) of the fluorine-containing monomer fed after the initiation of polymerization, since this can further suppress adhesion of the fluorine-containing elastomer to the polymerization tank. It is also preferable to stop feeding the fluorine-containing compound (A) before the amount of the fluorine-containing monomer fed after the initiation of polymerization reaches 85%, 80%, 75% or 70%.

[0058] The fluorine-containing compound (A) may be supplied immediately after the start of polymerization, and may be further supplied after the polymerization reaction has proceeded for a certain period of time. For example, when the fluorine-containing monomer is continuously or intermittently supplied to the polymerization system, the fluorine-containing compound (A) may be supplied immediately after the start of polymerization, and may be further supplied after a certain amount of the fluorine-containing monomer is supplied. This supply method not only suppresses the adhesion of the fluorine-containing elastomer to the polymerization tank, but also increases the number of particles of the fluorine-containing elastomer generated by polymerization, and allows the polymerization of the fluorine-containing monomer to proceed more smoothly. In the present disclosure, "immediately after the start of polymerization" refers to, for example, the period before the amount (g) of the fluorine-containing monomer supplied after the start of polymerization reaches 1% relative to the total amount (g) of the fluorine-containing monomer supplied after the start of polymerization, when the fluorine-containing monomer is continuously or intermittently supplied to the polymerization system. When the fluorine-containing compound (A) is further supplied after the polymerization reaction has proceeded for a certain period of time (after a certain amount of the fluorine-containing monomer has been supplied), the supply time or timing of the fluorine-containing compound (A) may be the preferred supply time when the fluorine-containing compound (A) is supplied all at once as exemplified above, or the preferred supply timing when the fluorine-containing compound (A) is supplied continuously or intermittently.

[0059] Since the polymerization of a fluorine-containing monomer is usually initiated by the addition of a polymerization initiator to a polymerization system, the time when the polymerization reaction of the fluorine-containing monomer is initiated is usually the time when the polymerization initiator is added to the polymerization system, and when the polymerization initiator is added to the polymerization system continuously or intermittently, it is the time when the polymerization initiator is first added to the polymerization system. In the present disclosure, "after the start of polymerization" means the polymerization period from the time when the polymerization initiator is first added to the polymerization system to the time when the polymerization reaction of the fluorine-containing monomer is completed. In addition, in the present disclosure, "before the start of polymerization" means the time when the polymerization initiator is first added to the polymerization system and the period before that time.

[0060] The amount of the fluorine-containing compound (A) to be supplied after the initiation of polymerization of the fluorine-containing monomer is preferably 30 to 5000 ppm by mass, more preferably 80 ppm by mass or more, still more preferably 130 ppm by mass or more, particularly preferably 150 ppm by mass or more, most preferably 180 ppm by mass or more, and more preferably 1000 ppm by mass or less, still more preferably 500 ppm by mass or less, particularly preferably 450 ppm by mass or less, based on the aqueous medium. By setting the amount of the fluorine-containing compound (A) to be supplied after the initiation of polymerization of the fluorine-containing monomer within the above range, the polymerization of the fluorine-containing monomer can be more smoothly promoted while the adhesion of the fluorine-containing elastomer to the polymerization tank can be further suppressed.

[0061] Furthermore, in the production method of the present disclosure, the amount of fluorine-containing compound (A) supplied after the initiation of polymerization of the fluorine-containing monomer may be 300 ppm by mass or less, 250 ppm by mass or less, or 200 ppm by mass or less. Since the production method of the present disclosure uses the fluorine-containing compound (A) having a specific structure, even when the amount of fluorine-containing compound (A) supplied is extremely small, the polymerization of the fluorine-containing monomer can be smoothly promoted while suppressing adhesion of the fluorine-containing elastomer to the polymerization tank.

[0062] In the present disclosure, the supply amount of the fluorine-containing compound (A) supplied after the initiation of polymerization means the supply amount of the fluorine-containing compound (A) supplied to the polymerization system after the initiation of polymerization of the fluorine-containing monomer until the completion of the polymerization reaction of the fluorine-containing monomer, and does not include the supply amount of the fluorine-containing compound (A) supplied to the polymerization system at the start of the polymerization reaction of the fluorine-containing monomer and before that time.

[0063] In the production method of the present disclosure, the fluorine-containing compound (A) is supplied after the initiation of polymerization of the fluorine-containing monomer, but it is preferable to also supply the fluorine-containing compound (A) before the initiation of polymerization of the fluorine-containing monomer. By supplying the fluorine-containing compound (A) before the initiation of polymerization of the fluorine-containing monomer, the number of fluorine-containing elastomer particles generated by polymerization can be increased, and the polymerization of the fluorine-containing monomer can be made to proceed more smoothly.

[0064] The amount of the fluorine-containing compound (A) supplied before the initiation of polymerization of the fluorine-containing monomer is preferably 5 to 5000 ppm by mass, more preferably 10 ppm by mass or more, further preferably 15 ppm by mass or more, more preferably 1000 ppm by mass or less, further preferably 500 ppm by mass or less, particularly preferably 300 ppm by mass or less, and most preferably 200 ppm by mass or less, based on the aqueous medium. By setting the amount of the fluorine-containing compound (A) supplied before the initiation of polymerization of the fluorine-containing monomer within the above range, many fluorine-containing elastomer particles can be generated, and the polymerization of the fluorine-containing monomer can proceed more smoothly.

[0065] Furthermore, in the production method of the present disclosure, the amount of fluorine-containing compound (A) supplied before the initiation of polymerization of the fluorine-containing monomer may be 150 ppm by mass or less, 100 ppm by mass or less, or 70 ppm by mass or less. Since the production method of the present disclosure uses the fluorine-containing compound (A) having a specific structure, even if the amount of fluorine-containing compound (A) supplied before the initiation of polymerization is extremely small, a sufficient number of fluorine-containing elastomer particles can be generated, and the polymerization of the fluorine-containing monomer can be smoothly progressed.

[0066] When the fluorine-containing compound (A) is supplied before and after the initiation of polymerization, the total amount of the fluorine-containing compound (A) supplied before the initiation of polymerization of the fluorine-containing monomer and the total amount of the fluorine-containing compound (A) supplied after the initiation of polymerization of the fluorine-containing monomer is preferably 30 to 5000 mass ppm, more preferably 100 mass ppm or more, even more preferably 150 mass ppm or more, particularly preferably 200 mass ppm or more, most preferably 250 mass ppm or more, and more preferably 1000 mass ppm or less, even more preferably 500 mass ppm or less, based on the aqueous medium. By making the total amount of the fluorine-containing compound (A) supplied within the above range, more fluorine-containing elastomer particles can be generated at a higher polymerization rate while further suppressing the adhesion of the fluorine-containing elastomer to the polymerization tank, and furthermore, the polymerization of the fluorine-containing monomer can be more smoothly progressed.

[0067] Furthermore, in the production method of the present disclosure, when the fluorine-containing compound (A) is supplied before and after the initiation of polymerization, the total amount of the fluorine-containing compound (A) supplied before the initiation of polymerization of the fluorine-containing monomer and the amount of the fluorine-containing compound (A) supplied after the initiation of polymerization of the fluorine-containing monomer may be 450 mass ppm or less, 400 mass ppm or less, 350 mass ppm or less, 300 mass ppm or less, or 250 mass ppm or less. Since the production method of the present disclosure uses the fluorine-containing compound (A) having a specific structure, even if the total amount of the fluorine-containing compound (A) supplied is extremely small, a sufficient number of fluorine-containing elastomer particles can be generated at a sufficient polymerization rate while suppressing adhesion of the fluorine-containing elastomer to the polymerization tank, and further, the polymerization of the fluorine-containing monomer can be smoothly advanced.

[0068] When the fluorine-containing compound (A) is supplied before or after the initiation of polymerization, the mass ratio ((a) / (b)) of the amount (a) of the fluorine-containing compound (A) supplied before the initiation of polymerization to the amount (b) of the fluorine-containing compound (A) supplied after the initiation of polymerization is preferably 1 / 20 to 2 / 1, more preferably 1 / 10 to 1 / 1, and further preferably 1 / 10 to 7 / 10. By setting the mass ratio ((a) / (b)) within the above range, more fluorine-containing elastomer particles can be generated at a higher polymerization rate while further suppressing adhesion of the fluorine-containing elastomer to the polymerization tank, and furthermore, the polymerization of the fluorine-containing monomer can proceed more smoothly.

[0069] As a method for supplying the fluorine-containing compound (A), for example, a method of supplying the fluorine-containing compound (A) from a pipe connected to a polymerization tank using a pump can be mentioned. The supply rate of the fluorine-containing compound (A) may be constant or may be changed. The fluorine-containing compound (A) may be continuously added dropwise. The fluorine-containing compound (A) may be dissolved or dispersed in water to prepare an aqueous solution of the fluorine-containing compound (A), and then the aqueous solution of the fluorine-containing compound (A) may be supplied.

[0070] In the production method of the present disclosure, the polymerization of the fluorine-containing monomer can be carried out, for example, by charging an aqueous medium into a pressure-resistant polymerization tank equipped with a stirrer, deoxidizing, charging the monomer, bringing the temperature to a predetermined level, adding a polymerization initiator to start polymerization, and supplying the fluorine-containing compound (A) to the polymerization tank after the start of polymerization. In addition to supplying the fluorine-containing compound (A) to the polymerization tank after the start of polymerization, the fluorine-containing compound (A) may also be supplied to the polymerization tank before the start of polymerization. Since the pressure decreases as the reaction proceeds, additional monomer is continuously or intermittently supplied to maintain the initial pressure, and when a predetermined amount of monomer is supplied, the supply is stopped, the monomer in the reaction vessel is purged, and the temperature is returned to room temperature to terminate the reaction.

[0071] In the production method of the present disclosure, the polymerization may be carried out in the presence of a polymerization initiator.

[0072] The polymerization initiator may be a radical polymerization initiator. The polymerization initiator is not particularly limited as long as it can generate radicals at the temperature at which the fluorine-containing monomer is polymerized, and an oil-soluble polymerization initiator, a water-soluble polymerization initiator, etc. may be used, but a water-soluble polymerization initiator is preferred. The polymerization initiator may also be used as a redox initiator in combination with a reducing agent, etc.

[0073] The amount of the polymerization initiator used in polymerizing the fluorine-containing monomer is appropriately determined depending on the type of monomer, the molecular weight of the desired fluorine-containing elastomer, and the reaction rate. The amount of the polymerization initiator is appropriately determined depending on the molecular weight of the desired fluorine-containing elastomer and the polymerization reaction rate, and is preferably 0.00001 to 10% by mass, more preferably 0.0001 to 1% by mass, based on 100% by mass of the total amount of monomers.

[0074] As the polymerization initiator, an oil-soluble radical polymerization initiator, a water-soluble radical polymerization initiator, or an azo compound can be used.

[0075] The oil-soluble radical polymerization initiator may be a known oil-soluble peroxide, for example, dialkyl peroxycarbonates such as diisopropyl peroxydicarbonate and disec-butyl peroxydicarbonate, peroxyesters such as t-butyl peroxyisobutyrate and t-butyl peroxypivalate, dialkyl peroxides such as di-t-butyl peroxide, and the like. In addition, di(ω-hydro-dodecafluoroheptanoyl) peroxide, di(ω-hydro-tetradecafluorooctanoyl) peroxide, di(ω-hydro-hexadecafluorononanoyl) peroxide, di(perfluorobutyryl) peroxide, di(perfluorovaleryl) peroxide, di(perfluorohexanoyl) peroxide, di(perfluoroheptanoyl) peroxide, di(perfluorooctanoyl) peroxide, di(perfluorononanoyl) peroxide, di(ω-chloro Representative examples of perfluoro(or fluorochloro)acyl]peroxides include di(ω-hexafluorobutyryl) peroxide, di(ω-chloro-decafluorohexanoyl) peroxide, di(ω-chloro-tetradecafluorooctanoyl) peroxide, ω-hydro-dodecafluoroheptanoyl-ω-hydrohexadecafluorononanoyl-peroxide, ω-chloro-hexafluorobutyryl-ω-chloro-decafluorohexanoyl-peroxide, ω-hydrododecafluoroheptanoyl-perfluorobutyryl-peroxide, di(dichloropentafluorobutanoyl) peroxide, di(trichlorooctafluorohexanoyl) peroxide, di(tetrachloroundecafluorooctanoyl) peroxide, di(pentachlorotetradecafluorodecanoyl) peroxide, and di(undecachlorodotriacontafluorodocosanoyl) peroxide.

[0076] Examples of the azo compound include azodicarboxylate, azodicarboxyldiamide, 2,2'-azobisisobutyronitrile, 2,2'-azobis2,4-dimethylvaleronitrile, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and 4,4'-azobis(4-cyanovaleric acid).

[0077] The water-soluble radical polymerization initiator may be a known water-soluble peroxide, such as ammonium salts, potassium salts, and sodium salts of persulfuric acid, perboric acid, perchloric acid, perphosphoric acid, and percarbonic acid, organic peroxides such as disuccinic acid peroxide and diglutaric acid peroxide, t-butyl permaleate, t-butyl hydroperoxide, etc. A reducing agent such as a sulfite may also be contained, and the amount used may be 0.1 to 20 times that of the peroxide.

[0078] As the water-soluble peroxide, a salt of persulfuric acid is preferable because the amount of radicals generated can be easily adjusted. Potassium persulfate (K2S2O8), ammonium persulfate ((NH4)2S2O8), and sodium persulfate (Na2S2O8) are preferable, and ammonium persulfate is most preferable.

[0079] When the polymerization is carried out using a water-soluble peroxide at a polymerization temperature of 45° C. or higher, it is preferable to carry out the polymerization without using a reducing agent.

[0080] For example, when polymerization is carried out at a low temperature of 60° C. or less, it is preferable to use a redox initiator that combines an oxidizing agent and a reducing agent as the polymerization initiator. That is, it is preferable to carry out the polymerization in the presence of a redox initiator.

[0081] Examples of the oxidizing agent include persulfates, organic peroxides, potassium permanganate, manganese triacetate, cerium ammonium nitrate, and bromates. Examples of the reducing agent include sulfites, bisulfites, bromates, diimines, oxalic acid, and metal sulfinates. Examples of the persulfates include ammonium persulfate, potassium persulfate, and sodium persulfate. Examples of the sulfites include sodium sulfite and ammonium sulfite. In order to increase the decomposition rate of the initiator, it is also preferable to add a copper salt or an iron salt to the combination of the redox initiator. Examples of the copper salt include copper(II) sulfate, and examples of the iron salt include iron(II) sulfate. In addition, when using copper salts and iron salts, it is particularly preferable to add a chelating agent. As a chelating agent, disodium salt dihydrate of ethylenediaminetetraacetic acid is preferable.

[0082] Examples of the redox initiator include potassium permanganate / oxalic acid, ammonium persulfate / bisulfite / iron(II) sulfate, ammonium persulfate / sulfite / iron(II) sulfate, ammonium persulfate / sulfite, ammonium persulfate / iron(II) sulfate, manganese triacetate / oxalic acid, cerium ammonium nitrate / oxalic acid, bromate / sulfite, bromate / bisulfite, ammonium persulfate / sodium hydroxymethanesulfinate dihydrate, and the like, with ammonium persulfate / sodium hydroxymethanesulfinate dihydrate being preferred.

[0083] When a redox initiator is used, either the oxidizing agent or the reducing agent may be charged in advance into a polymerization tank, and then the other may be added continuously or intermittently to initiate polymerization. For example, when ammonium persulfate / sodium hydroxymethanesulfinate dihydrate is used, it is preferable to charge ammonium persulfate into a polymerization tank and continuously add sodium hydroxymethanesulfinate dihydrate thereto.

[0084] The amount of the persulfate used in the redox initiator is preferably from 0.001 to 2.0% by mass, more preferably from 0.01 to 1.5% by mass, and particularly preferably from 0.05 to 1.0% by mass, based on the aqueous medium used in the polymerization.

[0085] The amount of the reducing agent used is preferably from 1 to 30% by mass, more preferably from 3 to 25% by mass, and particularly preferably from 5 to 20% by mass, based on the amount of the aqueous medium used in the polymerization.

[0086] The amount of the third component (the above copper salt, iron salt, etc.) used is preferably 0.001 to 0.5 mass %, more preferably 0.005 to 0.4 mass %, particularly preferably 0.01 to 0.3 mass %, based on the above aqueous medium used in the polymerization.

[0087] In the production method of the present disclosure, the fluorine-containing monomer may be polymerized in the presence of a chain transfer agent. As the chain transfer agent, a known agent may be used, for example, a hydrocarbon, an ester, an ether, an alcohol, a ketone, a halogen-containing compound, a carbonate, etc. Among them, isopentane, diethyl malonate, and ethyl acetate are preferred from the viewpoint of being unlikely to decrease the reaction rate, and diiodine compounds such as I(CF2)4I, I(CF2)6I, and ICH2I are preferred from the viewpoint of being capable of iodinating the polymer terminal and being usable as a reactive polymer.

[0088] As the chain transfer agent, it is particularly preferable to use a bromine compound or an iodine compound. Examples of the polymerization method using a bromine compound or an iodine compound include iodine transfer polymerization and bromine transfer polymerization.

[0089] Iodine compounds and bromine compounds are water-insoluble and difficult to emulsify. Therefore, emulsion polymerization is inherently limited, and there is a tendency to require the use of a large amount of surfactant. The production method of the present disclosure makes it possible to obtain a fluorine-containing elastomer by polymerization using an iodine compound or a bromine compound, for example, iodine transfer polymerization or bromine transfer polymerization, even in the absence of a surfactant that has been used conventionally.

[0090] Iodine transfer polymerization is a method that utilizes living radical polymerization by a radical chain reactivation mechanism, which occurs due to the low dissociation energy of carbon-iodine bonds, which are radically active and involve chain transfer reactions during the radical polymerization reaction. The reaction conditions can be appropriately selected from known conditions and are not particularly limited. For example, the conditions described in "Polymer Research Papers, Vol. 49, No. 10, pp. 765-783, October 1992" and JP-A-53-3495 can be appropriately adopted. A similar polymerization can be performed using a bromine compound instead of an iodine compound, and in the present disclosure, such polymerization is referred to as bromine transfer polymerization.

[0091] Among these, iodine transfer polymerization is preferred from the standpoint of polymerization reactivity, crosslinking reactivity, and the like.

[0092] Representative examples of bromine or iodine compounds include those represented by the general formula: R 8 I x Br y (In the formula, x and y are each an integer of 0 to 2, and 1≦x+y≦2 is satisfied; R 8 is a saturated or unsaturated fluorohydrocarbon group or chlorofluorohydrocarbon group having 1 to 16 carbon atoms, or a hydrocarbon group having 1 to 3 carbon atoms, which may contain an oxygen atom). By using a bromine compound or an iodine compound, iodine or bromine is introduced into the polymer and functions as a crosslinking point.

[0093] Examples of bromine compounds and iodine compounds include 1,3-diiodoperfluoropropane, 2-iodoperfluoropropane, 1,3-diiodo-2-chloroperfluoropropane, 1,4-diiodoperfluorobutane, 1,5-diiodo-2,4-dichloroperfluoropentane, 1,6-diiodoperfluorohexane, 1,8-diiodoperfluorooctane, 1,12-diiodoperfluorododecane, 1,16-diiodoperfluorohexadecane, diiodomethane, 1,2-diiodoethane, 1,3-diiodo-n-propane, CF2Br2, BrCF2CF2Br, CF3CFBrCF2Br, CFClBr2, BrCF2 Examples of the iodoperfluoroalkyl group include CFClBr, CFBrClCFClBr, BrCF2CF2CF2Br, BrCF2CFBrOCF3, 1-bromo-2-iodoperfluoroethane, 1-bromo-3-iodoperfluoropropane, 1-bromo-4-iodoperfluorobutane, 2-bromo-3-iodoperfluorobutane, 3-bromo-4-iodoperfluorobutene-1, 2-bromo-4-iodoperfluorobutene-1, monoiodomonobromo-substituted benzene, diiodomonobromo-substituted benzene, and (2-iodoethyl) and (2-bromoethyl)-substituted benzene. These compounds may be used alone or in combination with each other. Among these, compounds that do not contain bromine and contain only iodine are preferred from the standpoints of polymerization reactivity, crosslinking reactivity, availability, and the like, and it is preferable to use 1,4-diiodoperfluorobutane, 1,6-diiodoperfluorohexane, or 2-iodoperfluoropropane.

[0094] The amount of the chain transfer agent is preferably 0.2×10 based on the total amount of monomers used in the polymerization. -3 %. More preferably, it is 1.0×10 -3 %.

[0095] The aqueous medium means a liquid containing water. The aqueous medium is not particularly limited as long as it contains water, and may contain water and, for example, a fluorine-free organic solvent such as an alcohol, an ether, or a ketone, and / or a fluorine-containing organic solvent having a boiling point of 40° C. or lower.

[0096] In the polymerization of the fluorine-containing monomer, a pH adjuster such as a phosphate, sodium hydroxide, potassium hydroxide, or aqueous ammonia may be used.

[0097] The aqueous medium is preferably acidic. By polymerizing the fluorine-containing monomer in the presence of the fluorine-containing compound (A) using an acidic aqueous medium, the adhesion of the fluorine-containing polymer to the polymerization tank can be further suppressed. The pH of the aqueous medium is preferably 7 or less, more preferably 6 or less, and preferably 3 or more.

[0098] In the production method of the present disclosure, the fluorine-containing monomer may be polymerized in the presence or absence of fluorine-containing monomer polymerization seed particles.

[0099] The above-mentioned "fluorine-containing monomer polymerization seed particles" are obtained by polymerizing a fluorine-containing monomer in an aqueous medium, and are present during the second polymerization in which the types and abundance ratios of components such as monomers and additives (e.g., polymerization initiators) constituting the polymerization reaction system, and reaction conditions, etc. are different. The fluorine-containing monomer polymerization seed particles act as so-called seed particles during the polymerization of a fluorine-containing monomer, and constitute the polymerization of the fluorine-containing monomer in the presence of the seed particles, that is, the so-called seed polymerization. In the production method of the present disclosure, such seed polymerization may not be performed when polymerizing a fluorine-containing monomer.

[0100] In the production method of the present disclosure, the polymerization temperature for polymerizing the fluorine-containing monomer is preferably 10 to 120° C., more preferably 20 to 100° C. From the viewpoints of the stability of the aqueous dispersion and the reduction of the adhesion rate, the polymerization temperature is preferably 15 to 60° C., more preferably 18 to 55° C., and still more preferably 20 to 50° C. The polymerization temperature is preferably 60 to 120° C., more preferably 60 to 100° C., and still more preferably 70 to 90° C., since a fluorine-containing elastomer that has a high polymerization rate and can give a molded product having excellent physical properties can be obtained.

[0101] In the production method of the present disclosure, the polymerization pressure for polymerizing the fluorine-containing monomer is preferably from 0.5 to 10 MPaG, more preferably from 1 to 7 MPaG.

[0102] In the production method of the present disclosure, a fluorine-containing monomer is polymerized in the presence of a fluorine-containing compound (A) and an aqueous medium, and therefore adhesion of a polymer (fluorine-containing elastomer) to a polymerization tank can be suppressed. The rate of polymer adhesion to a polymerization tank is preferably 8% by mass or less, more preferably 4% by mass or less, further preferably 3% by mass or less, and most preferably 2% by mass or less.

[0103] The polymer adhesion rate is the ratio of the mass of the polymer adhesion that adheres to the polymerization tank after the polymerization is completed to the total amount of the polymer (fluoroelastomer) after the polymerization is completed (the adhesion rate to the polymerization tank). The polymer adhesion includes the polymer that adheres to the inside of the polymerization tank, such as the inner wall of the polymerization tank and the stirring blades, after the aqueous dispersion is removed from the polymerization tank after the polymerization is completed, and the polymer that has been released from the aqueous dispersion due to aggregation and is floating or settling without being dispersed in the aqueous dispersion. The mass of the polymer adhesion is the mass after the moisture contained in the polymer adhesion is removed by drying at 120°C. Polymer adhesion rate (mass%) = mass of polymer adhesion / mass of obtained polymer (including adhesion) × 100 Mass of obtained polymer = mass of aqueous dispersion x solids concentration of aqueous dispersion (mass%) / 100 + mass of polymer deposit

[0104] In the production method of the present disclosure, an aqueous dispersion of a fluorine-containing elastomer is obtained by polymerizing a fluorine-containing monomer. The fluorine-containing monomer is preferably a fluorine-containing monomer (excluding the fluorine-containing compound (A)), and more preferably does not contain a hydrophilic group.

[0105] Examples of fluorine-containing monomers include vinylidene fluoride (VdF), tetrafluoroethylene (TFE), hexafluoropropylene (HFP), perfluoro(alkyl vinyl ether) (PAVE), chlorotrifluoroethylene (CTFE), trifluoroethylene, trifluoropropylene, tetrafluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutene, hexafluoroisobutene, vinyl fluoride, iodine-containing fluorinated vinyl ether, and fluorinated vinyl ethers represented by the general formula (2): CHX 1 =CX 2 Rf (2) (In the formula, X 1 and X 2 One of Rf is H and the other is F, and Rf is a linear or branched fluoroalkyl group having 1 to 12 carbon atoms.

[0106] As the PAVE, perfluoro(methyl vinyl ether) (PMVE), perfluoro(ethyl vinyl ether) (PEVE) and perfluoro(propyl vinyl ether) (PPVE) are more preferred, and PMVE is particularly preferred.

[0107] In addition, PAVE has the formula: CF2 = CFOCF2ORf c (In the formula, Rf cis a straight or branched perfluoroalkyl group having 1 to 6 carbon atoms, a cyclic perfluoroalkyl group having 5 to 6 carbon atoms, or a straight or branched perfluorooxyalkyl group having 2 to 6 carbon atoms and containing 1 to 3 oxygen atoms). As the PAVE, for example, CF2=CFOCF2OCF3, CF2=CFOCF2OCF2CF3, or CF2=CFOCF2OCF2CF2OCF3 is preferable.

[0108] As the fluorine-containing monomer (2), a monomer in which Rf is a linear fluoroalkyl group is preferable, and a monomer in which Rf is a linear perfluoroalkyl group is more preferable. Rf preferably has 1 to 6 carbon atoms.

[0109] Examples of the fluorine-containing monomer (2) include CH2=CFCF3, CH2=CFCF2CF3, CH2=CFCF2CF2CF3, CH2=CFCF2CF2CF2CF3, CHF=CHCF3 (1,3,3,3-tetrafluoropropene), CHF=CHCF3 (E form), CHF=CHCF3 (Z form), and the like. Of these, 2,3,3,3-tetrafluoropropylene represented by CH2=CFCF3 is preferred.

[0110] In the production method of the present disclosure, it is preferable to polymerize at least vinylidene fluoride or tetrafluoroethylene as the fluorine-containing monomer, and it is more preferable to polymerize vinylidene fluoride, since this can further suppress adhesion of the fluorine-containing elastomer to the polymerization tank.

[0111] In the production method of the present disclosure, a fluorine-free monomer may be polymerized together with the fluorine-containing monomer. Examples of the fluorine-free monomer include α-olefin monomers having 2 to 10 carbon atoms, such as ethylene, propylene, butene, and pentene; and alkyl vinyl ethers having an alkyl group having 1 to 20 carbon atoms, such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, and butyl vinyl ether. These monomers and compounds may be used alone or in combination of two or more.

[0112] According to the production method of the present disclosure, an aqueous dispersion containing a fluorine-containing elastomer can be produced. The fluorine-containing elastomer obtained by the production method of the present disclosure contains a methylene group (-CH2-) in the main chain. The fluorine-containing elastomer containing -CH2- in the main chain is not particularly limited as long as it contains a chemical structure represented by -CH2-, and examples thereof include fluorine-containing elastomers containing structures such as -CH2-CF2-, -CH2-CH(CH3)-, -CH2-CH2-, and -CH2-CF2-(CF3)-, which can be introduced into the main chain of the fluorine-containing elastomer by polymerizing, for example, vinylidene fluoride, propylene, ethylene, 2,3,3,3-tetrafluoropropylene, etc. The content of tetrafluoroethylene units in the fluorine-containing elastomer (the content of monomer units based on tetrafluoroethylene relative to the total monomer units of the fluorine-containing elastomer) may be less than 40 mol%.

[0113] As the fluorine-containing elastomer, a partially fluorinated elastomer is preferred because it can further suppress adhesion of the fluorine-containing elastomer to the polymerization tank while allowing the polymerization of the fluorine-containing monomer to proceed more smoothly. The partially fluorinated elastomer is a fluoropolymer that contains fluorine-containing monomer units, has a perfluoromonomer unit content of less than 90 mol% relative to the total monomer units, has a glass transition temperature of 20°C or less, and has a melting peak (ΔH) of 4.5 J / g or less.

[0114] Examples of fluorine-containing elastomers include tetrafluoroethylene (TFE), vinylidene fluoride (VdF) and fluoroelastomers represented by the general formula: CF2=CF-Rf a (In the formula, Rf a -CF3 or -ORf b (Rf b It is preferable that the fluorine-containing elastomer contains a monomer unit based on at least one monomer selected from the group consisting of perfluoroethylenically unsaturated compounds represented by the formula (I) (wherein R is a perfluoroalkyl group having 1 to 5 carbon atoms) (for example, hexafluoropropylene (HFP), perfluoro(alkyl vinyl ether) (PAVE), etc.). Among them, the fluorine-containing elastomer preferably contains a VdF unit or a TFE unit, and more preferably contains a VDF unit.

[0115] More specific examples of the fluorine-containing elastomer include VdF-based fluorine-containing elastomers, TFE / propylene (Pr)-based fluorine-containing elastomers, TFE / Pr / VdF-based fluorine-containing elastomers, ethylene (Et) / HFP-based fluorine-containing elastomers, Et / HFP / VdF-based fluorine-containing elastomers, Et / HFP / TFE-based fluorine-containing elastomers, Et / TFE / PAVE-based fluorine-containing elastomers, etc. Among these, VdF-based fluorine-containing elastomers, TFE / Pr-based fluorine-containing elastomers, TFE / Pr / VdF-based fluorine-containing elastomers and Et / TFE / PAVE-based fluorine-containing elastomers are more preferred in terms of good heat aging resistance and oil resistance.

[0116] The VdF-based fluorine-containing elastomer is a fluorine-containing elastomer having a VdF unit. The content of the VdF unit in the fluorine-containing elastomer is preferably 20 mol% or more, more preferably 40 mol% or more, even more preferably 50 mol% or more, and particularly preferably 60 mol% or more, based on the total monomer units. In the VdF-based fluorine-containing elastomer, the VdF unit is preferably 20 mol% or more and 90 mol% or less, more preferably 40 mol% or more and 85 mol% or less, even more preferably 45 mol% or more and 80 mol% or less, and particularly preferably 50 mol% or more and 80 mol% or less, based on the total number of moles of the VdF unit and the monomer units based on other monomers.

[0117] The other monomer in the VdF-based fluorine-containing elastomer is not particularly limited as long as it is a monomer copolymerizable with VdF, and for example, the above-mentioned fluorine-containing monomers can be used.

[0118] The VdF-based fluorine-containing elastomer is preferably at least one copolymer selected from the group consisting of VdF / HFP copolymer, VdF / TFE / HFP copolymer, VdF / CTFE copolymer, VdF / CTFE / TFE copolymer, VdF / PAVE copolymer, VdF / TFE / PAVE copolymer, VdF / HFP / PAVE copolymer, VdF / HFP / TFE / PAVE copolymer, VdF / TFE / Pr copolymer, VdF / Et / HFP copolymer and VdF / fluorine-containing monomer (2) copolymer. Also, it is more preferable that the VdF-based fluorine-containing elastomer has at least one monomer selected from the group consisting of TFE, HFP and PAVE as a monomer other than VdF.

[0119] Of these, the VdF-based fluorine-containing elastomer is preferably at least one copolymer selected from the group consisting of VdF / HFP copolymer, VdF / TFE / HFP copolymer, VdF / fluorine-containing monomer (2) copolymer, VdF / PAVE copolymer, VdF / TFE / PAVE copolymer, VdF / HFP / PAVE copolymer and VdF / HFP / TFE / PAVE copolymer, and more preferably at least one copolymer selected from the group consisting of VdF / HFP copolymer, VdF / HFP / TFE copolymer, VdF / fluorine-containing monomer (2) copolymer and VdF / PAVE copolymer.

[0120] The VdF / PAVE copolymer preferably has a VdF / PAVE composition of (65 to 90) / (35 to 10) (mol %). In addition, one of the preferred embodiments has a VdF / PAVE composition of (50 to 78) / (50 to 22) (mol %).

[0121] The VdF / TFE / PAVE copolymer preferably has a VdF / TFE / PAVE composition of (40 to 80) / (3 to 40) / (15 to 35) (mol %).

[0122] As the VdF / HFP / PAVE copolymer, one having a VdF / HFP / PAVE composition of (65 to 90) / (3 to 25) / (3 to 25) (mol %) is preferred.

[0123] The VdF / HFP / TFE / PAVE copolymer preferably has a VdF / HFP / TFE / PAVE composition of (40-90) / (0-25) / (0-40) / (3-35) (mol %), and more preferably has a composition of (40-80) / (3-25) / (3-40) / (3-25) (mol %).

[0124] The copolymer of VdF / fluorine-containing monomer (2) preferably has a VdF / fluorine-containing monomer (2) unit ratio of (85-20) / (15-80) (mol%) and monomer units other than VdF and fluorine-containing monomer (2) of 0-50 mol% of the total monomer units, and more preferably has a VdF / fluorine-containing monomer (2) unit molar ratio of (80-20) / (20-80). In addition, one preferred embodiment has a VdF / fluorine-containing monomer (2) unit composition of (78-50) / (22-50) (mol%).

[0125] Also preferred is a copolymer of VdF / fluorine-containing monomer (2) in which the ratio of VdF / fluorine-containing monomer (2) units is (85-50) / (15-50) (mol%) and monomer units other than VdF and fluorine-containing monomer (2) account for 1-50 mol% of the total monomer units. Preferred monomers other than VdF and fluorine-containing monomer (2) are those exemplified as other monomers in VdF-based fluorine-containing elastomers, such as TFE, HFP, PMVE, perfluoroethyl vinyl ether (PEVE), PPVE, CTFE, trifluoroethylene, hexafluoroisobutene, vinyl fluoride, Et, Pr, alkyl vinyl ether, and monomers that give crosslinkable groups, and among these, PMVE, CTFE, HFP, and TFE are more preferred.

[0126] The TFE / Pr-based fluorine-containing elastomer refers to a fluorine-containing copolymer consisting of 45-70 mol % of TFE and 55-30 mol % of Pr. In addition to these two components, a specific third component may be contained.

[0127] The specific third component may include, for example, fluorine-containing monomers such as fluorine-containing olefins other than TFE (e.g., VdF, HFP, CTFE, perfluoro(butyl ethylene), etc.), fluorine-containing vinyl ethers (perfluoro(propyl vinyl ether), perfluoro(methyl vinyl ether), etc.), and hydrocarbon monomers such as α-olefins (ethylene, 1-butene, etc.), vinyl ethers (ethyl vinyl ether, butyl vinyl ether, hydroxybutyl vinyl ether, etc.), and vinyl esters (vinyl acetate, vinyl benzoate, vinyl crotonate, vinyl methacrylate, etc.). The specific third component may be one type, or two or more types may be used in combination.

[0128] The TFE / Pr-based fluorine-containing elastomer preferably contains VdF, and among the TFE / Pr-based fluorine-containing elastomers, an elastomer consisting of TFE, Pr and VdF is called a TFE / Pr / VdF-based fluorine-containing elastomer.

[0129] The TFE / Pr / VdF fluorine-containing elastomer may further contain the specific third component other than VdF. The specific third component may be one type or a combination of two or more types. The total content of the third components in the TFE / Pr fluorine-containing elastomer is preferably 35 mol% or less, more preferably 33 mol% or less, and even more preferably 31 mol% or less.

[0130] The Et / HFP copolymer preferably has an Et / HFP composition of (35 to 80) / (65 to 20) (mol %), and more preferably has an Et / HFP composition of (40 to 75) / (60 to 25) (mol %).

[0131] The Et / HFP / TFE copolymer preferably has an Et / HFP / TFE composition of (35-75) / (25-50) / (0-15) (mol %), and more preferably has an Et / HFP / TFE composition of (45-75) / (25-45) / (0-10) (mol %).

[0132] The Et / TFE / PAVE copolymer preferably has a composition of Et / TFE / PAVE of (10-40) / (32-60) / (20-40) (mol%), more preferably (20-40) / (40-50) / (20-30) (mol%). As the PAVE, PMVE is preferred.

[0133] The fluorine-containing elastomer is preferably a fluorine-containing elastomer containing a VdF unit, more preferably a VdF / HFP copolymer or a VdF / HFP / TFE copolymer, and particularly preferably a VdF / HFP / TFE composition of (32-85) / (10-34) / (0-40) (mol%). The VdF / HFP / TFE composition is more preferably (32-85) / (15-34) / (0-34) (mol%), and further preferably (47-81) / (17-32) / (0-26) (mol%).

[0134] For example, in the above VdF / HFP copolymer, the VdF / HFP composition is preferably (45 to 85) / (15 to 55) (mol%), more preferably (50 to 83) / (17 to 50) (mol%), still more preferably (55 to 81) / (19 to 45) (mol%), and particularly preferably (60 to 80) / (20 to 40) (mol%).

[0135] The above-mentioned constitution is the constitution of the main monomer of the fluorine-containing elastomer, and in addition to the main monomer, a monomer that gives a crosslinkable group may be copolymerized. The monomer that gives a crosslinkable group may be any monomer that can introduce an appropriate crosslinkable group into the fluorine-containing elastomer depending on the production method and crosslinking system, and examples of such monomers include known polymerizable compounds that contain a crosslinkable group such as an iodine atom, a bromine atom, a carbon-carbon double bond, a cyano group, a carboxyl group, a hydroxyl group, an amino group, or an ester group.

[0136] Preferred examples of the monomer that provides a crosslinkable group include those represented by the general formula (3): C.Y. 1 2=CY 2 R f 2 X 1 (3) (In the formula, Y1 , Y 2 is a fluorine atom, a hydrogen atom or -CH3; R f 2 a linear or branched fluorine-containing alkylene group in which some or all of the hydrogen atoms have been substituted with fluorine atoms, which may have one or more ether-bonded oxygen atoms and which may have an aromatic ring; X 1 is an iodine or bromine atom) Examples of the compound include those represented by the following formula:

[0137] Specific examples of the monomer that provides a crosslinkable group include those represented by the general formula (4): C.Y. 1 2=CY 2 R f 3 CHR 1 -X 1 (4) (In the formula, Y 1 , Y 2 , X 1 is the same as above, and R f 3 is a linear or branched fluorine-containing alkylene group which may have one or more ether-bonded oxygen atoms and in which some or all of the hydrogen atoms have been substituted with fluorine atoms, i.e., a linear or branched fluorine-containing alkylene group in which some or all of the hydrogen atoms have been substituted with fluorine atoms, a linear or branched fluorine-containing oxyalkylene group in which some or all of the hydrogen atoms have been substituted with fluorine atoms, or a linear or branched fluorine-containing polyoxyalkylene group in which some or all of the hydrogen atoms have been substituted with fluorine atoms; R 1 is a hydrogen atom or a methyl group) Iodine- or bromine-containing monomers represented by the general formulas (5) to (22): C.Y. 4 2=CY 4 (CF2) n -X 1 (5) (In the formula, Y 4 are the same or different and are a hydrogen atom or a fluorine atom, and n is an integer of 1 to 8. CF2=CFCF2R f 4 -X 1 (6) (In the formula, R 4 is -(OCF2) n -or-(OCF(CF3)) n -, where n is an integer from 0 to 5. CF2=CFCF2(OCF(CF3)CF2) m (OCH2CF2CF2) n OCH2CF2-X 1 (7) (In the formula, m is an integer of 0 to 5, and n is an integer of 0 to 5). CF2=CFCF2(OCH2CF2CF2) m (OCF(CF3)CF2) n OCF(CF3)-X 1 (8) (In the formula, m is an integer of 0 to 5, and n is an integer of 0 to 5). CF2=CF(OCF2CF(CF3)) m O(CF2) n -X 1 (9) (In the formula, m is an integer of 0 to 5, and n is an integer of 1 to 8). CF2=CF(OCF2CF(CF3)) m -X 1 (10) (In the formula, m is an integer of 1 to 5). CF2 = CFOCF2 (CF(CF3)OCF2) n CF(-X 1 )CF3(11) (wherein n is an integer of 1 to 4). CF2 = CFO(CF2) n OCF(CF3)-X 1 (12) (wherein n is an integer of 2 to 5). CF2 = CFO(CF2) n -(C6H4)-X 1 (13) (wherein n is an integer of 1 to 6). CF2=CF(OCF2CF(CF3)) n OCF2CF(CF3)-X 1 (14) (wherein n is an integer of 1 to 2). CH2=CFCF2O(CF(CF3)CF2O) nCF(CF3)-X 1 (15) (wherein n is an integer of 0 to 5), CF2 = CFO(CF2CF(CF3)O) m (CF2) n -X 1 (16) (In the formula, m is an integer of 0 to 5, and n is an integer of 1 to 3). CH2=CFCF2OCF(CF3)OCF(CF3)-X 1 (17) CH2=CFCF2OCH2CF2-X 1 (18) CF2 = CFO(CF2CF(CF3)O) m CF2CF(CF3)-X 1 (19) (wherein m is an integer of 0 or more) CF2 = CFOCF(CF3)CF2O(CF2) n -X 1 (20) (wherein n is an integer of 1 or more) CF2 = CFOCF2OCF2CF(CF3)OCF2-X 1 (twenty one) CH2=CH-(CF2) n X 1 (twenty two) (wherein n is an integer of 2 to 8). (In general formulas (5) to (22), X 1 is the same as above) These can be used alone or in any combination.

[0138] The iodine- or bromine-containing monomer represented by the general formula (4) may be a monomer represented by the general formula (23): [ka] (In the formula, m is an integer of 1 to 5, and n is an integer of 0 to 3). Preferred examples of the iodine-containing fluorinated vinyl ethers include those represented by the following formula: [ka] Among these, ICH2CF2CF2OCF=CF2 is preferred.

[0139] More specifically, preferred examples of the iodine- or bromine-containing monomer represented by the general formula (5) include ICF2CF2CF=CH2 and I(CF2CF2)2CF=CH2.

[0140] A more specific example of the iodine- or bromine-containing monomer represented by the general formula (9) is I(CF2CF2)2OCF=CF2.

[0141] More specifically, preferred examples of the iodine- or bromine-containing monomer represented by the general formula (22) include CH2=CHCF2CF2I and I(CF2CF2)2CH=CH2.

[0142] Also, the formula: R 2 R 3 C=CR 4 -Z-CR 5 =CR 6 R 7 (In the formula, R 2 , R 3 , R 4 , R 5 , R 6 and R 7 are the same or different and both are H or an alkyl group having 1 to 5 carbon atoms; Z is a linear or branched alkylene or cycloalkylene group having 1 to 18 carbon atoms, which may contain an oxygen atom and is preferably at least partially fluorinated, or a (per)fluoropolyoxyalkylene group), and a bisolefin compound represented by the above is also preferred as a monomer that provides a crosslinkable group. In the present disclosure, the term "(per)fluoropolyoxyalkylene group" means "fluoropolyoxyalkylene group or perfluoropolyoxyalkylene group".

[0143] Z is preferably a (per)fluoroalkylene group having 4 to 12 carbon atoms, and R 2 , R 3 , R4 , R 5 , R 6 and R 7 is preferably a hydrogen atom.

[0144] When Z is a (per)fluoropolyoxyalkylene group, the formula: -(Q) p -CF2O-(CF2CF2O) m -(CF2O) n -CF2-(Q) p - (wherein Q is an alkylene group having 1 to 10 carbon atoms or an oxyalkylene group having 2 to 10 carbon atoms, p is 0 or 1, and m and n are integers such that the m / n ratio is 0.2 to 5 and the molecular weight of the (per)fluoropolyoxyalkylene group is in the range of 500 to 10,000, preferably 1,000 to 4,000.) In this formula, Q is preferably -CH2OCH2- or -CH2O(CH2CH2O) s Selected from CH2-(s=1~3).

[0145] Preferred bis-olefins are CH2=CH-(CF2)2-CH=CH2, CH2=CH-(CF2)4-CH=CH2, CH2=CH-(CF2)6-CH=CH2, Formula: CH2=CH-Z 1 -CH=CH2 (In the formula, Z 1 is -CH2OCH2-CF2O-(CF2CF2O) m -(CF2O) n -CF2-CH2OCH2- (m / n is 0.5, molecular weight is preferably 2000) etc.

[0146] Among these, 3,3,4,4,5,5,6,6,7,7,8,8-dodecafluoro-1,9-decadiene, represented by CH2=CH-(CF2)6-CH=CH2, is preferred.

[0147] The number average molecular weight Mn of the fluorine-containing elastomer is preferably from 1,000 to 1,000,000, more preferably from 10,000 to 500,000, and particularly preferably from 20,000 to 300,000.

[0148] The fluorine-containing elastomer preferably has a fluorine content of 50% by mass or more, more preferably 55% by mass or more, and even more preferably 60% by mass or more. The upper limit of the fluorine content is preferably 75% by mass or less, and more preferably 73% by mass or less. The fluorine content is 19 F-NMR and 1 It is calculated based on measurements such as H-NMR and elemental analysis.

[0149] The fluorine-containing elastomer preferably has a Mooney viscosity at 100°C (ML1+10(100°C)) of 130 or less. The Mooney viscosity is more preferably 110 or less, and even more preferably 90 or less. The Mooney viscosity is more preferably 10 or more, and even more preferably 20 or more. The Mooney viscosity here is a value measured in accordance with JIS K 6300-1.2013.

[0150] The fluorine-containing elastomer preferably has a glass transition temperature of -50 to 0°C. The glass transition temperature is more preferably -2°C or lower, and even more preferably -3°C or lower. The glass transition temperature is more preferably -45°C or higher, and even more preferably -40°C or higher. The glass transition temperature may be -10°C or higher, or may be -9°C or higher. Here, the glass transition temperature can be determined from the DSC differential curve by raising the temperature of 10 mg of a sample at 20°C / min using a differential scanning calorimeter (e.g., X-DSC7000 manufactured by Hitachi High-Tech Science Corporation) and calculating the glass transition temperature in accordance with JIS K6240:2011.

[0151] The fluorine-containing elastomer preferably has an iodine content of 0.05 to 1.0% by mass, more preferably 0.08% by mass or more, even more preferably 0.10% by mass or more, and more preferably 0.80% by mass or less, even more preferably 0.60% by mass or less.

[0152] The iodine content can be determined by elemental analysis. Specifically, 5 mg of Na2SO3 is mixed with 12 mg of fluorine-containing elastomer, and 30 mg of a 1:1 mixture of Na2CO3 and K2CO3 (by mass) is dissolved in 20 ml of pure water to obtain an absorption liquid. The mixture is burned in oxygen in a quartz flask, and after leaving it for 30 minutes, the iodine content can be measured using a Shimadzu 20A ion chromatograph. For the calibration curve, a KI standard solution, one containing 0.5 ppm by mass of iodine ion, and one containing 1.0 ppm by mass of iodine ion can be used.

[0153] The fluorine-containing elastomer preferably contains a -CHI structure. The inclusion of a -CHI structure means that 1 This can be confirmed by H-NMR spectrum. Fluorine-containing elastomers containing the -CH2I structure can be obtained by iodine transfer polymerization.

[0154] In the fluorine-containing elastomer, the amount of -CH2I structures relative to 100 mol % of -CH2- structures is preferably 0.05 to 1.50 mol %. The amount of -CH2I structures is more preferably 0.08 mol % or more, even more preferably 0.12 mol % or more, more preferably 1.20 mol % or less, even more preferably 1.00 mol % or less, and particularly preferably 0.80 mol % or less. The amount of -CH2I structures is 1 It can be determined by H-NMR spectroscopy.

[0155] The fluorine-containing elastomer more preferably contains a -CF2CH2I structure. The fluorine-containing elastomer containing a -CF2CH2I structure can be obtained by producing a VdF-based fluorine-containing elastomer by iodine transfer polymerization.

[0156] In the fluorine-containing elastomer, the amount of -CF2CH2I structure relative to 100 mol% of -CH2- structure is preferably 0.05 to 1.50 mol%. The amount of -CF2CH2I structure is more preferably 0.08 mol% or more, even more preferably 0.12 mol% or more, more preferably 1.20 mol% or less, even more preferably 1.00 mol% or less, and particularly preferably 0.80 mol% or less. The amount of -CF2CH2I structure is 1 In the H-NMR spectrum, the integral value A of the total peak intensity observed in the region of the chemical shift from 3.75 to 4.05 ppm originating from -CH2I is calculated from the integral value B of the total peak intensity observed in the region of the chemical shift from 2.3 to 2.7 ppm and 2.9 to 3.75 ppm originating from -CH2-, using A / B*100.

[0157] As the fluorine-containing monomer used in the production method of the present disclosure, the fluorine-containing monomers described for the fluorine-containing elastomer can be appropriately used.

[0158] The production method of the present disclosure can efficiently produce a fluorine-containing elastomer by using at least one fluorine-containing compound (A). In the production method of the present disclosure, two or more fluorine-containing compounds (A) may be used simultaneously, and other compounds having surface activity may be used simultaneously as long as they are volatile or may remain in a molded article containing the fluorine-containing elastomer.

[0159] The production method of the present disclosure is preferably one in which a fluorine-containing monomer is polymerized in the absence of a fluorine-containing surfactant having substantially no radically polymerizable unsaturated bond (hereinafter, sometimes simply referred to as a "fluorine-containing surfactant").

[0160] Conventionally, a fluorine-containing surfactant has been used for the polymerization of a fluorine-containing monomer, but the production method of the present disclosure uses the fluorine-containing compound (A) so that a fluorine-containing monomer can be polymerized to give a fluorine-containing elastomer without using a fluorine-containing surfactant.

[0161] In the present disclosure, "substantially in the absence of a fluorinated surfactant" means that the content ratio of the fluorinated surfactant relative to the aqueous medium is 10 ppm by mass or less, and the content ratio of the fluorinated surfactant is preferably 1 ppm by mass or less, more preferably 100 ppb by mass or less, even more preferably 10 ppb by mass or less, and particularly preferably 1 ppb by mass or less.

[0162] The above-mentioned fluorine-containing surfactant includes anionic fluorine-containing surfactants.

[0163] The anionic fluorine-containing surfactant may be, for example, a surfactant containing fluorine atoms and having a total carbon number of 20 or less excluding the anionic group.

[0164] The above-mentioned fluorine-containing surfactant may also be a surfactant containing fluorine in the anionic moiety having a molecular weight of 1000 or less, preferably 800 or less.

[0165] The above-mentioned "anionic portion" means the portion of the above-mentioned fluorine-containing surfactant excluding the cation. For example, F(CF2) represented by the formula (I) described below n1 In the case of COOM, "F(CF2) n1 The "COO" part.

[0166] The above-mentioned fluorosurfactant also includes a fluorosurfactant having a LogPOW of 3.5 or less. The LogPOW is a partition coefficient between 1-octanol and water, and is expressed as LogP [wherein P represents the ratio of the fluorosurfactant concentration in octanol to the fluorosurfactant concentration in water when a 1:1 octanol / water mixture containing the fluorosurfactant undergoes phase separation].

[0167] The LogPOW is calculated from the HPLC elution time of the sample solution using a calibration curve of each elution time and the known octanol / water partition coefficient, which is prepared by performing HPLC on standard substances (heptanoic acid, octanoic acid, nonanoic acid, and decanoic acid) having known octanol / water partition coefficients under the following conditions: column: TOSOH ODS-120T column (φ4.6 mm×250 mm, manufactured by Tosoh Corporation), eluent: acetonitrile / 0.6% by mass HClO4 water=1 / 1 (vol / vol%), flow rate: 1.0 ml / min, sample amount: 300 μL, column temperature: 40° C., detection light: UV 210 nm.

[0168] Specific examples of the fluorine-containing surfactant include those described in U.S. Patent Application Publication No. 2007 / 0015864, U.S. Patent Application Publication No. 2007 / 0015865, U.S. Patent Application Publication No. 2007 / 0015866, U.S. Patent Application Publication No. 2007 / 0276103, U.S. Patent Application Publication No. 2007 / 0117914, U.S. Patent Application Publication No. 2007 / 0142541, U.S. Patent Application Publication No. 2008 / 0015319, U.S. Patent No. 3,250,808, and the like. No. 3,271,341, JP 2003-119204 A, WO 2005 / 042593 A, WO 2008 / 060461 A, WO 2007 / 046377 A, JP 2007-119526 A, WO 2007 / 046482 A, WO 2007 / 046345 A, U.S. Patent Application Publication No. 2014 / 0228531 A, WO 2013 / 189824 A, and WO 2013 / 189826 A.

[0169] The anionic fluorine-containing surfactant may be a surfactant represented by the following general formula (N 0 ): X n0 -Rf n0 -Y 0 (N 0 ) (In the formula, X n0 is H, Cl or F. n0Y is a linear, branched or cyclic alkylene group having 3 to 20 carbon atoms, in which some or all of the H's are substituted with F, and the alkylene group may contain one or more ether bonds, and some of the H's may be substituted with Cl. 0 is an anionic group.

[0170] Y 0 The anionic group may be -COOM, -SO2M, or -SO3M, and may be -COOM or -SO3M.

[0171] M is H, a metal atom, or NR 7 4. An optionally substituted imidazolium, an optionally substituted pyridinium, or an optionally substituted phosphonium, wherein R 7 is -H or an organic group.

[0172] The metal atom includes alkali metals (group 1) and alkaline earth metals (group 2), such as Na, K, or Li.

[0173] R 7 As the aryl group, -H or C 1-10 may be an organic group of -H or C 1-4 may be an organic group of -H or C 1-4 The alkyl group may be:

[0174] M is H, a metal atom or NR 7 4, H, an alkali metal (group 1), an alkaline earth metal (group 2) or NR 7 4, which may be H, Na, K, Li or NH4.

[0175] Above Rf n0 may be one in which 50% or more of H is substituted with fluorine.

[0176] The above general formula (N 0 ) is represented by the following: The following general formula (N 1): X n0 -(CF2) m1 -Y 0 (N 1 ) (In the formula, X n0 is H, Cl, or F; m1 is an integer from 3 to 15; Y 0 is as defined above, a compound represented by the following general formula (N 2 ): Rf n1 -O-(CF(CF3)CF2O) m2 CFX n1 -Y 0 (N 2 ) (In the formula, Rf n1 is a perfluoroalkyl group having 1 to 5 carbon atoms, m2 is an integer of 0 to 3, and X n1 is F or CF3, and Y 0 is as defined above, a compound represented by the following general formula (N 3 ): Rf n2 (CH2) m3 -(Rf n3 ) q -Y 0 (N 3 ) (In the formula, Rf n2 is a partially or fully fluorinated alkyl group having 1 to 13 carbon atoms, which may contain an ether bond and / or a chlorine atom, m3 is an integer of 1 to 3, Rf n3 is a linear or branched perfluoroalkylene group having 1 to 3 carbon atoms, q is 0 or 1, and Y 0 is as defined above, a compound represented by the following general formula (N 4 ): Rf n4 -O-(CY n1 Y n2 ) p CF2-Y 0 (N 4 ) (In the formula, Rf n4 is a linear or branched partially or fully fluorinated alkyl group having 1 to 12 carbon atoms, which may contain an ether bond; Y n1and Y n2 are the same or different and are H or F, p is 0 or 1, and Y 0 is as defined above.) and a compound represented by the following general formula (N 5 ): [ka] (In the formula, X n2 , X n3 and X n4 Rf may be the same or different and are H, F, or a linear or branched partially or completely fluorinated alkyl group having 1 to 6 carbon atoms, which may contain an ether bond. n5 is a linear or branched, partially or completely fluorinated alkylene group having 1 to 3 carbon atoms, which may contain an ether bond; L is a linking group; Y 0 is as defined above, where X n2 , X n3 , X n4 and Rf n5 The total number of carbon atoms is 18 or less.

[0177] The above general formula (N 0More specifically, the compound represented by the formula (I) is a perfluorocarboxylic acid (I), a ω-H perfluorocarboxylic acid (II), a perfluoroether carboxylic acid (III), a perfluoroalkyl alkylene carboxylic acid (IV), a perfluoroalkoxy fluorocarboxylic acid (V), a perfluoroalkyl sulfonic acid (VI), a ω-H perfluoro sulfonic acid (VII), a perfluoroalkyl alkylene sulfonic acid (VIII), a perfluoroalkyl alkylene sulfonic acid (IX), a fluorocarboxylic acid (X), a fluorocarboxylic acid (X), a alkoxy fluoro sulfonic acid (XI), a compound (XII), a compound (XIII), and the like.

[0178] The perfluorocarboxylic acid (I) is represented by the following general formula (I): F(CF2) n1 COOM (I) (In the formula, n1 is an integer of 3 to 14, and M is H, a metal atom, or NR 7 4. An optionally substituted imidazolium, an optionally substituted pyridinium, or an optionally substituted phosphonium, wherein R 7 is -H or an organic group.

[0179] The ω-H perfluorocarboxylic acid (II) is represented by the following general formula (II): H(CF2) n2 COOM (II) (wherein n2 is an integer of 4 to 15, and M is as defined above).

[0180] The perfluoroether carboxylic acid (III) is represented by the following general formula (III): Rf 1-O-(CF(CF3)CF2O) n3 CF(CF3)COOM (III) (In the formula, Rf 1 is a perfluoroalkyl group having 1 to 5 carbon atoms, n3 is an integer of 0 to 3, and M is as defined above.

[0181] The perfluoroalkyl alkylene carboxylic acid (IV) is represented by the following general formula (IV): Rf 2 (CH2) n4 Rf 3 COOM (IV) (In the formula, Rf 2 is a perfluoroalkyl group having 1 to 5 carbon atoms, and Rf 3 is a linear or branched perfluoroalkylene group having 1 to 3 carbon atoms, n4 is an integer of 1 to 3, and M is as defined above.

[0182] The alkoxyfluorocarboxylic acid (V) is represented by the following general formula (V): Rf 4 -O-CY 1 Y 2 CF2-COOM (V) (In the formula, Rf 4 is a linear or branched partially or fully fluorinated alkyl group having 1 to 12 carbon atoms, which may contain an ether bond and / or a chlorine atom; Y 1 and Y 2 are the same or different and are H or F, and M is as defined above.

[0183] The perfluoroalkylsulfonic acid (VI) is represented by the following general formula (VI): F(CF2) n5 SO3M (VI) (wherein n5 is an integer of 3 to 14, and M is as defined above).

[0184] The above ω-H perfluorosulfonic acid (VII) is represented by the following general formula (VII): H(CF2) n6 SO3M (VII) (wherein n6 is an integer of 4 to 14, and M is as defined above).

[0185] The perfluoroalkyl alkylene sulfonic acid (VIII) is represented by the following general formula (VIII): Rf 5 (CH2) n7 SO3M (VIII) (In the formula, Rf 5 is a perfluoroalkyl group having 1 to 13 carbon atoms, n7 is an integer of 1 to 3, and M is as defined above.

[0186] The alkyl alkylene carboxylic acid (IX) is represented by the following general formula (IX): Rf 6 (CH2) n8 COOM (IX) (In the formula, Rf 6 is a linear or branched partially or completely fluorinated alkyl group having 1 to 13 carbon atoms which may contain an ether bond, n8 is an integer from 1 to 3, and M is as defined above.

[0187] The fluorocarboxylic acid (X) is represented by the following general formula (X): Rf 7 -O-Rf 8 -O-CF2-COOM (X) (In the formula, Rf 7 is a linear or branched partially or fully fluorinated alkyl group having 1 to 6 carbon atoms, which may contain an ether bond and / or a chlorine atom, and Rf 8 is a linear or branched, partially or completely fluorinated alkyl group having 1 to 6 carbon atoms, and M is as defined above.

[0188] The alkoxyfluorosulfonic acid (XI) is represented by the following general formula (XI): Rf 9 -O-CY1 Y 2 CF2-SO3M (XI) (In the formula, Rf 9 is a linear or branched alkyl group having 1 to 12 carbon atoms, which may contain an ether bond, and which may contain chlorine, and which is partially or completely fluorinated; Y 1 and Y 2 are the same or different and are H or F, and M is as defined above.

[0189] The compound (XII) is represented by the following general formula (XII): [ka] (In the formula, X 1 , X 2 and X 3 Rf may be the same or different and are H, F and linear or branched partially or completely fluorinated alkyl groups having 1 to 6 carbon atoms, which may contain ether bonds; 10 is a perfluoroalkylene group having 1 to 3 carbon atoms, L is a linking group, and Y 0 is an anionic group.

[0190] Y 0 may be -COOM, -SO2M, or -SO3M, or may be -SO3M, or -COOM (wherein M is defined above).

[0191] Examples of L include a single bond, and a partially or completely fluorinated alkylene group having 1 to 10 carbon atoms which may contain an ether bond.

[0192] The compound (XIII) is represented by the following general formula (XIII): Rf 11 -O-(CF2CF(CF3)O) n9 (CF2O) n10 CF2COOM (XIII) (In the formula, Rf 11is a fluoroalkyl group containing chlorine and having 1 to 5 carbon atoms, n9 is an integer of 0 to 3, n10 is an integer of 0 to 3, and M is as defined above.) Compound (XIII) is represented by CF2ClO(CF2CF(CF3)O) n9 (CF2O) n10 CF2COONH4 (a mixture having an average molecular weight of 750, where n9 and n10 are defined above).

[0193] The fluorine-containing surfactant may be one type of fluorine-containing surfactant or a mixture containing two or more types of fluorine-containing surfactants.

[0194] The fluorine-containing surfactant may be a compound represented by the following formula: The fluorine-containing surfactant may be a mixture of these compounds. In one embodiment of the above polymerization, the fluoromonomer is polymerized substantially in the absence of the compound represented by the following formula: F(CF2)7COOM, F(CF2)5COOM, H(CF2)6COOM, H(CF2)7COOM, CF3O(CF2)3OCHFCF2COOM, C3F7OCF(CF3)CF2OCF(CF3)COOM, CF3CF2CF2OCF(CF3)COOM, CF3CF2OCF2CF2OCF2COOM, C2F5OCF(CF3)CF2OCF(CF3)COOM, CF3OCF(CF3)CF2OCF(CF3)COOM, CF2ClCF2CF2OCF(CF3)CF2OCF2COOM, CF2ClCF2CF2OCF2CF(CF3)OCF2COOM, CF2ClCF(CF3)OCF(CF3)CF2OCF2COOM, CF2ClCF(CF3)OCF2CF(CF3)OCF2COOM, [ka] (In each formula, M is H, metal atom, NR 7 4. An imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent. 7 is H or an organic group.

[0195] According to the production method of the present disclosure, an aqueous dispersion of a fluorine-containing elastomer can be obtained. The solids concentration (content of the fluorine-containing elastomer) of the obtained aqueous dispersion of the fluorine-containing elastomer is preferably 10 to 50 mass%, more preferably 15 to 40 mass%, and further preferably 20 to 30 mass% at the time when the polymerization is completed.

[0196] The solids concentration of the fluorine-containing elastomer aqueous dispersion (the fluorine-containing elastomer content) can be determined by drying 1 g of the aqueous dispersion at 150°C for 180 minutes, measuring the mass of the heating residue, and calculating the ratio of the mass of the heating residue to the mass of the aqueous dispersion.

[0197] The aqueous dispersion of the fluorine-containing elastomer may contain fluorine-containing elastomer particles. The average particle size of the fluorine-containing elastomer particles is preferably 10 to 800 nm, more preferably 50 to 500 nm, and further preferably 70 to 300 nm. The average particle size of the fluorine-containing elastomer particles is a cumulant average size, and can be measured by a dynamic light scattering method.

[0198] The number of fluorine-containing elastomer particles contained in the aqueous dispersion of the fluorine-containing elastomer is preferably 1.0×10 12 pcs / cc or more, more preferably 5.0×10 12 pcs / cc or more, and more preferably 1.0×10 13 pcs / cc or more, and particularly preferably 1.2×10 14 particles / cc or more, most preferably 1.3×10 14The number of particles (the number of polymer particles) can be calculated according to the following formula.

[0199]

number

[0200] The aqueous dispersion of the fluorine-containing elastomer may be subjected to treatment such as coagulation or heating.

[0201] The coagulation can be carried out by adding alkaline earth and earth metal salts to the aqueous dispersion, such as sulfates, nitrates, hydrochlorides, and acetates of calcium, magnesium, aluminum, and the like.

[0202] The coagulated fluorine-containing elastomer may be washed with water to remove impurities such as a small amount of buffer solution and salt present in the fluorine-containing elastomer, and then the washed fluorine-containing elastomer may be dried at a drying temperature of preferably 40 to 200°C, more preferably 60 to 180°C, and further preferably 80 to 150°C.

[0203] The form of the fluorine-containing elastomer obtained after coagulation is not particularly limited, and may be gum, crumb, powder, pellet, etc., and is preferably gum or crumb. A gum is a small granular mass of a fluorine-containing elastomer, and a crumb is an amorphous mass of a fluorine-containing elastomer that cannot maintain its small granular shape as a gum at room temperature and is fused to each other. The gum or crumb is preferably obtained by coagulating, drying, etc., the aqueous dispersion obtained by the production method of the present disclosure by a conventionally known method.

[0204] A fluorine-containing elastomer composition can be produced by adding a crosslinking agent, etc. to the aqueous dispersion of the fluorine-containing elastomer or the fluorine-containing elastomer obtained by the production method of the present disclosure. The type and amount of the crosslinking agent are not particularly limited, and any crosslinking agent may be used within the known range.

[0205] When the fluorine-containing elastomer is an uncrosslinked elastomer, the crosslinking system thereof may be, for example, a peroxide crosslinking system, a polyol crosslinking system, a polyamine crosslinking system, etc., and is preferably at least one selected from the group consisting of a peroxide crosslinking system and a polyol crosslinking system. From the viewpoint of chemical resistance, a peroxide crosslinking system is preferred, and from the viewpoint of heat resistance, a polyol crosslinking system is preferred.

[0206] Therefore, the crosslinking agent is preferably at least one crosslinking agent selected from the group consisting of polyol crosslinking agents and peroxide crosslinking agents, and more preferably a peroxide crosslinking agent.

[0207] The amount of the crosslinking agent to be added may be appropriately selected depending on the type of crosslinking agent, etc., but is preferably 0.2 to 6.0 parts by mass, more preferably 0.3 to 5.0 parts by mass, per 100 parts by mass of the fluorine-containing elastomer.

[0208] The peroxide crosslinking can be carried out by using a peroxide crosslinkable uncrosslinked elastomer as the fluorine-containing elastomer and an organic peroxide as the crosslinking agent.

[0209] The peroxide-crosslinkable uncrosslinked elastomer is not particularly limited as long as it has a peroxide-crosslinkable moiety. The peroxide-crosslinkable moiety is not particularly limited as long as it has an iodine atom or a bromine atom.

[0210] The organic peroxide may be any organic peroxide that can easily generate peroxy radicals in the presence of heat or an oxidation-reduction system, and examples thereof include 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-butylperoxyisopropyl carbonate, and t-butylperoxybenzoate. Among these, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane and 2,5-dimethyl-2,5-di(t-butylperoxy)-hexyne-3 are preferred.

[0211] The amount of the organic peroxide to be added is preferably from 0.1 to 15 parts by mass, more preferably from 0.3 to 5 parts by mass, based on 100 parts by mass of the fluorine-containing elastomer.

[0212] When the crosslinking agent is an organic peroxide, the fluorine-containing elastomer composition preferably further contains a crosslinking aid. Examples of the crosslinking aid include triallyl cyanurate, triallyl isocyanurate (TAIC), triacrylformal, triallyl trimellitate, N,N'-m-phenylene bismaleimide, 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-trimethylsilyl) and tetramethylsilyl. Examples of suitable amines include tris(diallylamine)-S-triazine, N,N-diallylacrylamide, 1,6-divinyldodecafluorohexane, hexaallyl phosphoramide, N,N,N',N'-tetraallylphthalamide, N,N,N',N'-tetraallylmalonamide, trivinyl isocyanurate, 2,4,6-trivinylmethyltrisiloxane, tri(5-norbornene-2-methylene) cyanurate, triallyl phosphite, and trimethallyl isocyanurate. Among these, triallyl isocyanurate (TAIC) is preferred because of its excellent crosslinkability, mechanical properties, and flexibility.

[0213] The amount of the crosslinking aid is preferably 0.01 to 10 parts by mass, more preferably 0.01 to 7.0 parts by mass, and even more preferably 0.1 to 5.0 parts by mass, based on 100 parts by mass of the fluorine-containing elastomer. If the amount of the crosslinking aid is less than 0.01 parts by mass, the mechanical properties and flexibility are reduced. If the amount exceeds 10 parts by mass, the heat resistance is poor and the durability of the molded product also tends to decrease.

[0214] Polyol crosslinking can be carried out by using a polyol-crosslinkable uncrosslinked elastomer as the fluorine-containing elastomer and a polyhydroxy compound as the crosslinking agent. The amount of the polyhydroxy compound in the polyol crosslinking system is preferably 0.01 to 10 parts by mass per 100 parts by mass of the polyol-crosslinkable uncrosslinked elastomer. By setting the amount of the polyhydroxy compound in this range, polyol crosslinking can be sufficiently promoted. It is more preferably 0.02 to 8 parts by mass. It is further preferably 0.03 to 4 parts by mass.

[0215] The polyol-crosslinkable uncrosslinked elastomer is not particularly limited, and may be an uncrosslinked elastomer having a polyol-crosslinkable site. The polyol-crosslinkable site is not particularly limited, and may be, for example, a site having a vinylidene fluoride (VdF) unit. The method of introducing the crosslinkable site may be a method of copolymerizing a monomer that provides a crosslinkable site during polymerization of the uncrosslinked elastomer.

[0216] As the polyhydroxy compound, a polyhydroxy aromatic compound is preferably used because of its excellent heat resistance.

[0217] The polyhydroxy aromatic compound is not particularly limited, and examples thereof include 2,2-bis(4-hydroxyphenyl)propane (hereinafter referred to as bisphenol A), 2,2-bis(4-hydroxyphenyl)perfluoropropane (hereinafter referred to as bisphenol AF. Bisphenol AF is available from, for example, Fujifilm Wako Pure Chemical Industries, Ltd., Central Glass Co., Ltd., etc.), 1,3-dihydroxybenzene, 1,7-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 4,4'-dihydroxydiphenyl, 4,4'-dihydro Examples of the polyhydroxy aromatic compounds include hydroxystilbene, 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'-dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylketone, tri(4-hydroxyphenyl)methane, 3,3',5,5'-tetrachlorobisphenol A, and 3,3',5,5'-tetrabromobisphenol A. These polyhydroxy aromatic compounds may be alkali metal salts, alkaline earth metal salts, etc., but when the copolymer is coagulated using an acid, it is preferable not to use the above metal salts. The amount of the polyhydroxy aromatic compound is 0.1 to 15 parts by mass, preferably 0.5 to 5 parts by mass, based on 100 parts by mass of the uncrosslinked elastomer.

[0218] When the crosslinking agent is a polyhydroxy compound, the fluorine-containing elastomer composition preferably further contains a crosslinking accelerator, which accelerates the formation of intramolecular double bonds in the dehydrofluorination reaction of the polymer main chain and the addition of the polyhydroxy compound to the double bonds thus formed.

[0219] The crosslinking accelerator may be used in combination with an acid acceptor such as magnesium oxide or a crosslinking assistant.

[0220] The crosslinking accelerator may be an onium compound. Among the onium compounds, at least one selected from the group consisting of ammonium compounds such as quaternary ammonium salts, phosphonium compounds such as quaternary phosphonium salts, oxonium compounds, sulfonium compounds, cyclic amines, and monofunctional amine compounds is preferred, and at least one selected from the group consisting of quaternary ammonium salts and quaternary phosphonium salts is more preferred.

[0221] The quaternary ammonium salt is not particularly limited, and examples thereof include 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 ester, and 8-methyl-1,8-diazabicyclo[5,4,0]-7-undecenium methyl ester. ethyl 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-di Examples of the compound include azabicyclo[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. DBU-B can be obtained, for example, from Fujifilm Wako Pure Chemical Industries, Ltd.), 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, tetrabutylammonium hydrogen sulfate, tetrabutylammonium hydroxide, tetrabutylammonium chloride, and tetrabutylammonium bromide. Among these, DBU-B is preferred from the viewpoints of crosslinkability, mechanical properties, and flexibility.

[0222] Furthermore, the quaternary phosphonium salt is not particularly limited, and examples thereof include tetrabutyl phosphonium chloride, benzyl triphenyl phosphonium chloride (hereinafter referred to as BTPPC), benzyl trimethyl phosphonium chloride, benzyl tributyl phosphonium chloride, tributyl allyl phosphonium chloride, tributyl-2-methoxypropyl phosphonium chloride, and benzyl phenyl (dimethylamino) phosphonium chloride. Among these, benzyl triphenyl phosphonium chloride (BTPPC) is preferred from the viewpoints of crosslinkability, mechanical properties, and flexibility.

[0223] In addition, as the crosslinking accelerator, a solid solution of a quaternary ammonium salt and bisphenol AF, 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.

[0224] The amount of the crosslinking accelerator is preferably 0.01 to 8.00 parts by mass, more preferably 0.02 to 5.00 parts by mass, and even more preferably 0.03 to 3.00 parts by mass, based on 100 parts by mass of the uncrosslinked elastomer. If the amount of the crosslinking accelerator is less than 0.01 part by mass, the crosslinking of the uncrosslinked elastomer may not proceed sufficiently, and the heat resistance of the obtained molded product may decrease. If the amount exceeds 8.00 parts by mass, the moldability of the fluorine-containing elastomer composition may decrease, and the elongation and flexibility in mechanical properties tend to decrease.

[0225] The acid acceptor is used to neutralize acidic substances generated during polyol crosslinking, and specific examples thereof include magnesium oxide, calcium hydroxide (e.g., NICC5000 (manufactured by Inoue Lime Industry Co., Ltd.), CALDIC#2000, CALDIC#1000 (manufactured by Ohmi Chemical Industry Co., Ltd.)), calcium oxide, litharge (lead oxide), zinc oxide, dibasic lead phosphite, hydrotalcite, and the like. It is preferable that the acid acceptor be at least one selected from the group consisting of high activity magnesium oxide and low activity magnesium oxide.

[0226] The polyamine crosslinking can be carried out by using a polyamine-crosslinkable fluorine-containing elastomer as the fluorine-containing elastomer and a polyamine compound as the crosslinking agent.

[0227] The polyamine crosslinkable fluorine-containing elastomer is not particularly limited, and may be any fluorine-containing elastomer having a polyamine crosslinkable site. The polyamine crosslinkable site is not particularly limited, and may be, for example, a site having a vinylidene fluoride (VdF) unit. The method for introducing the crosslinkable site may be a method of copolymerizing a monomer that provides a crosslinkable site during polymerization of the fluorine-containing elastomer.

[0228] Examples of polyamine compounds include hexamethylenediamine carbamate, N,N'-dicinnamylidene-1,6-hexamethylenediamine, 4,4'-bis(aminocyclohexyl)methane carbamate, etc. Among these, N,N'-dicinnamylidene-1,6-hexamethylenediamine is preferred.

[0229] The method for obtaining the fluorine-containing elastomer composition is not particularly limited as long as it can uniformly mix the fluorine-containing elastomer obtained by the production method of the present disclosure with the crosslinking agent. For example, there is a method in which a powder obtained by coagulating the fluorine-containing elastomer alone is kneaded with other additives and compounding agents as necessary using a kneader such as an open roll.

[0230] The fluorine-containing elastomer composition may contain at least one polyfunctional compound. A polyfunctional compound is a compound having two or more functional groups of the same or different structures in one molecule. As the functional group of the polyfunctional compound, any functional group that is generally known to have reactivity, such as a carbonyl group, a carboxyl group, a haloformyl group, an amide group, an olefin group, an amino group, an isocyanate group, a hydroxyl group, an epoxy group, etc., can be used.

[0231] The fluorine-containing elastomer composition may, if necessary, be blended with various additives which are commonly used in elastomers, such as fillers (carbon black, barium sulfate, etc.), processing aids (wax, etc.), plasticizers, colorants, stabilizers, tackifiers (coumarone resins, coumarone-indene resins, etc.), release agents, electrical conductivity imparting agents, thermal conductivity imparting agents, surface non-tackifying agents, flexibility imparting agents, heat resistance improving agents, flame retardants, and the like, and may also be blended with one or more commonly used crosslinking agents and crosslinking accelerators different from the above-mentioned ones.

[0232] The content of the filler such as carbon black is not particularly limited, but is preferably 0 to 300 parts by mass, more preferably 1 to 150 parts by mass, further preferably 2 to 100 parts by mass, and particularly preferably 2 to 75 parts by mass, relative to 100 parts by mass of the fluorine-containing elastomer.

[0233] The content of processing aids such as wax is preferably 0 to 10 parts by mass, more preferably 0 to 5 parts by mass, per 100 parts by mass of the fluorine-containing elastomer. When processing aids, plasticizers and release agents are used, the mechanical properties and sealing properties of the resulting molded article tend to decrease, so it is necessary to adjust the contents of these agents within the range in which the properties of the intended molded article obtained are acceptable.

[0234] A molded article can be obtained by crosslinking the fluorine-containing elastomer composition. A molded article can also be obtained by molding and crosslinking the fluorine-containing elastomer composition. The fluorine-containing elastomer composition can be molded by a conventionally known method. The molding and crosslinking methods and conditions may be within the range of known methods and conditions for the molding and crosslinking employed. The order of molding and crosslinking is not limited, and molding may be followed by crosslinking, crosslinking may be followed by molding, or molding and crosslinking may be performed simultaneously.

[0235] Examples of the molding method include, but are not limited to, compression molding, casting, injection molding, extrusion molding, and roto-cure molding. Examples of the crosslinking method include steam crosslinking, heat crosslinking, and radiation crosslinking, among which steam crosslinking and heat crosslinking are preferred. Specific crosslinking conditions that are not limited to these are usually within a temperature range of 140 to 250°C and a crosslinking time of 1 minute to 24 hours, and may be appropriately determined depending on the types of crosslinking accelerator, crosslinking agent, and acid acceptor.

[0236] Furthermore, by heating the obtained molded article in an oven, etc., it is possible to improve the mechanical properties and the compression set properties at high temperatures, etc. Specific crosslinking conditions, which are not limited, are usually within a temperature range of 140 to 300°C and a time range of 30 minutes to 72 hours, and may be appropriately determined depending on the types of crosslinking accelerator, crosslinking agent, acid acceptor, etc.

[0237] The obtained molded article can be used as various parts in various fields such as the automobile industry, the aircraft industry, the semiconductor industry, etc. The molded article can be used for applications similar to those of the crosslinked rubber molded article described in JP-A-2013-216915 and the fluororubber molded article described in JP-A-2019-94430, such as sealing materials, sliding members, and non-adhesive members.

[0238] Examples of the use forms of the molded products include various sealing materials and packings such as rings, packings, gaskets, diaphragms, oil seals, and bearing seals. As a sealing material, it can be used in applications requiring excellent non-adhesiveness and low friction. In particular, it can be suitably used as various sealing materials in the automobile industry, etc.

[0239] They can also be used as tubes, hoses, rolls, various rubber rolls, flexible joints, rubber sheets, coatings, belts, dampers, valves, valve seats, valve bodies, chemical-resistant coating materials, laminating materials, lining materials, etc.

[0240] Although the embodiments have been described above, it will be understood that various changes in form and details are possible without departing from the spirit and scope of the claims. EXAMPLES

[0241] Next, embodiments of the present disclosure will be described with reference to examples, but the present disclosure is not limited to these examples.

[0242] The values ​​in the examples were measured by the following methods.

[0243] Solids concentration of aqueous dispersion 1 g of the aqueous dispersion was dried in a blower dryer at 150° C. for 180 minutes, the mass of the heating residue was measured, and the ratio (mass %) of the mass of the heating residue to the mass (1 g) of the aqueous dispersion was calculated.

[0244] Copolymer composition This was determined by NMR analysis.

[0245] Polymer adhesion rate The ratio of the mass of the polymer adhering to the polymerization vessel after the completion of the polymerization to the total amount of the polymer (fluoroelastomer) after the completion of the polymerization (adhesion rate to the polymerization vessel) was calculated according to the following formula. Polymer adhesion rate (mass%) = mass of polymer adhesion / mass of obtained polymer (including polymer adhesion) × 100 Mass of obtained polymer = mass of aqueous dispersion x solids concentration of aqueous dispersion (mass%) / 100 + mass of polymer deposit The polymer deposits include the polymer that is attached to the inside of the polymerization tank, such as the inner wall of the polymerization tank or the stirring blades, after the aqueous dispersion is removed from the polymerization tank after the polymerization is completed, and the polymer that is liberated from the aqueous dispersion by aggregation and floats or precipitates without being dispersed in the aqueous dispersion. The mass of the polymer deposits is the mass after the moisture contained in the polymer deposits is removed by drying at 120°C.

[0246] Particle number (number of fluorine-containing elastomer particles in aqueous dispersion) Calculated using the following formula.

[0247]

number

[0248] In the formula, the average particle size is the average particle size (cumulant average size) of the fluorine-containing elastomer particles in the aqueous dispersion, and is measured by dynamic light scattering using an ELSZ-1000S (manufactured by Otsuka Electronics Co., Ltd.) and calculated by the cumulant method. In the formula, the number of polymer particles (number of fluorine-containing elastomer particles) is the number per cc of water, and the specific gravity of all the fluorine-containing elastomers in the examples and comparative examples was set to 1.8.

[0249] Mooney Viscosity (ML1+10(100℃)) The Mooney viscosity was measured at 100° C. using a Mooney viscometer MV2000E manufactured by ALPHA TECHNOLOGIES in accordance with JIS K 6300-1.2013.

[0250] Maximum torque level (MH) For the fluorine-containing elastomer compositions prepared in the Examples and Comparative Examples, crosslinking curves were obtained during crosslinking at 160°C using a rubber vulcanization tester MDRH2030 (manufactured by M&K Co., Ltd.), and maximum torque levels (MH) were determined.

[0251] Compression set (CS) In accordance with JIS K6262, the compression set of the O-rings produced in the examples and comparative examples was measured under conditions of 200° C., 72 hours, and a compression ratio of 25%.

[0252] Example 1 (Production of Fluorine-Containing Elastomer Aqueous Dispersion) 1500g of deionized water and 1.50g of a 10% by mass aqueous solution of CH2=CFCF2OCF(CF3)COONH4 (compound (a1)) were added to a 3L stainless steel polymerization tank, the polymerization tank was sealed, and the system was replaced with nitrogen to remove oxygen. The polymerization tank was heated to 80°C, and VdF, TFE, and HFP (initial monomer) were injected with stirring in a molar ratio of vinylidene fluoride [VdF] / tetrafluoroethylene [TFE] / hexafluoropropylene [HFP] (=19 / 11 / 70 mol%) so that the internal pressure of the polymerization tank was 1.47 MPaG.

[0253] Next, a polymerization initiator solution containing 0.026 g of ammonium persulfate (APS) dissolved in deionized water was injected with nitrogen gas to initiate polymerization. As the polymerization progressed, when the internal pressure dropped to 1.45 MPaG, a mixed monomer of VDF / TFE / HFP (=50 / 20 / 30 mol%) was charged so that the internal pressure remained constant at 1.47 MPaG.

[0254] When 14 g of the mixed monomer was added, 2.19 g of the diiodine compound I(CF2)4I was injected with nitrogen gas.

[0255] After 3.0 hours from the start of polymerization, an aqueous solution of polymerization initiator containing 0.026 g of APS was injected with nitrogen gas.

[0256] Immediately after the diiodine compound I(CF2)4I was injected until 70% of the total amount of the mixed monomer was supplied, a total of 3.00 g of a 10 mass% aqueous solution of CH2=CFCF2OCF(CF3)COONH4 (compound (a1)) was intermittently supplied to the polymerization tank.

[0257] 5.30 hours after the start of polymerization, stirring was stopped, and the pressure in the polymerization tank was reduced to atmospheric pressure, thereby terminating the polymerization.

[0258] The polymerization tank was cooled to obtain an aqueous fluorine-containing elastomer dispersion. The solids concentration, polymer adhesion rate and particle number of the aqueous dispersion are shown in Table 1.

[0259] To the obtained aqueous dispersion of fluorine-containing elastomer, an aqueous aluminum sulfate solution was added to perform coagulation. The obtained coagulation was washed with water and dried to obtain a fluorine-containing elastomer. The copolymer composition was examined by NMR analysis and found to be VdF / TFE / HFP=50 / 20 / 30 (mol%). The Mooney viscosity of the fluorine-containing elastomer is shown in Table 1.

[0260] Example 2 (Production of Fluorine-Containing Elastomer Aqueous Dispersion) 1500g of deionized water and 0.93g of a 10% by mass aqueous solution of CH2=CFCF2OCF(CF3)COONH4 (compound (a1)) were added to a 3L stainless steel polymerization tank, the tank was sealed, and the system was replaced with nitrogen to remove oxygen. The tank was heated to 80°C, and VdF, TFE, and HFP (initial monomer) were injected with stirring in a molar ratio of vinylidene fluoride [VdF] / tetrafluoroethylene [TFE] / hexafluoropropylene [HFP] (=19 / 11 / 70 mol%) so that the internal pressure of the tank was 1.47 MPaG.

[0261] Next, a polymerization initiator solution containing 0.026 g of ammonium persulfate (APS) dissolved in deionized water was injected with nitrogen gas to initiate polymerization. As the polymerization progressed, when the internal pressure dropped to 1.45 MPaG, a mixed monomer of VDF / TFE / HFP (=50 / 20 / 30 mol%) was charged so that the internal pressure remained constant at 1.47 MPaG.

[0262] When 14 g of the mixed monomer was added, 2.19 g of the diiodine compound I(CF2)4I was injected with nitrogen gas.

[0263] 3.0 hours and 6.0 hours after the start of polymerization, an aqueous solution of polymerization initiator (APS, 0.026 g) was injected with nitrogen gas.

[0264] Immediately after the diiodine compound I(CF2)4I was injected until 70% of the total amount of the mixed monomer was supplied, a total of 2.81 g of a 10 mass% aqueous solution of CH2=CFCF2OCF(CF3)COONH4 (compound (a1)) was intermittently supplied to the polymerization tank.

[0265] 6.32 hours after the start of polymerization, stirring was stopped, and the pressure in the polymerization tank was reduced to atmospheric pressure, thereby terminating the polymerization.

[0266] The polymerization tank was cooled to obtain an aqueous fluorine-containing elastomer dispersion. The solids concentration, polymer adhesion rate and particle number of the aqueous dispersion are shown in Table 1.

[0267] To the obtained aqueous dispersion of fluorine-containing elastomer, an aqueous aluminum sulfate solution was added to perform coagulation. The obtained coagulation was washed with water and dried to obtain a fluorine-containing elastomer. The copolymer composition was examined by NMR analysis and found to be VdF / TFE / HFP=50 / 20 / 30 (mol%). The Mooney viscosity of the fluorine-containing elastomer is shown in Table 1.

[0268] Example 3 (Production of Fluorine-Containing Elastomer Aqueous Dispersion) 1500g of deionized water and 0.93g of a 10% by mass aqueous solution of CH2=CFCF2OCF(CF3)COONH4 (compound (a1)) were added to a 3L stainless steel polymerization tank, the tank was sealed, and the system was replaced with nitrogen to remove oxygen. The tank was heated to 80°C, and VdF, TFE, and HFP (initial monomer) were injected with stirring in a molar ratio of vinylidene fluoride [VdF] / tetrafluoroethylene [TFE] / hexafluoropropylene [HFP] (=19 / 11 / 70 mol%) so that the internal pressure of the tank was 1.47 MPaG.

[0269] Next, a polymerization initiator solution containing 0.026 g of ammonium persulfate (APS) dissolved in deionized water was injected with nitrogen gas to initiate polymerization. As the polymerization progressed, when the internal pressure dropped to 1.45 MPaG, a mixed monomer of VDF / TFE / HFP (=50 / 20 / 30 mol%) was charged so that the internal pressure remained constant at 1.47 MPaG.

[0270] When 14 g of the mixed monomer was added, 2.19 g of the diiodine compound I(CF2)4I was injected with nitrogen gas.

[0271] After 3.0 hours from the start of polymerization, an aqueous solution of polymerization initiator containing 0.026 g of APS was injected with nitrogen gas.

[0272] Immediately after the diiodine compound I (CF2)4I was injected until 70% of the total amount of the mixed monomer was supplied, a total of 3.00 g of a 10 mass% aqueous solution of CF2=CFOCF2CF2COONH4 (compound (a2)) was intermittently supplied to the polymerization tank.

[0273] 5.72 hours after the start of polymerization, stirring was stopped, and the pressure in the polymerization tank was reduced to atmospheric pressure, thereby terminating the polymerization.

[0274] The polymerization tank was cooled to obtain an aqueous fluorine-containing elastomer dispersion. The solids concentration, polymer adhesion rate and particle number of the aqueous dispersion are shown in Table 1.

[0275] To the obtained aqueous dispersion of fluorine-containing elastomer, an aqueous aluminum sulfate solution was added to perform coagulation. The obtained coagulation was washed with water and dried to obtain a fluorine-containing elastomer. The copolymer composition was examined by NMR analysis and found to be VdF / TFE / HFP=50 / 20 / 30 (mol%). The Mooney viscosity of the fluorine-containing elastomer is shown in Table 1.

[0276] Example 4 (Production of Fluorine-Containing Elastomer Aqueous Dispersion) 1500g of deionized water and 0.93g of a 10% by mass aqueous solution of CH2=CFCF2OCF(CF3)COONH4 (compound (a1)) were added to a 3L stainless steel polymerization tank, the tank was sealed, and the system was replaced with nitrogen to remove oxygen. The tank was heated to 80°C, and VdF, TFE, and HFP (initial monomer) were injected with stirring in a molar ratio of vinylidene fluoride [VdF] / tetrafluoroethylene [TFE] / hexafluoropropylene [HFP] (=19 / 11 / 70 mol%) so that the internal pressure of the tank was 1.47 MPaG.

[0277] Next, a polymerization initiator solution containing 0.026 g of ammonium persulfate (APS) dissolved in deionized water was injected with nitrogen gas to initiate polymerization. As the polymerization progressed, when the internal pressure dropped to 1.45 MPaG, a mixed monomer of VDF / TFE / HFP (=50 / 20 / 30 mol%) was charged so that the internal pressure remained constant at 1.47 MPaG.

[0278] When 14 g of the mixed monomer was added, 2.19 g of the diiodine compound I(CF2)4I was injected with nitrogen gas.

[0279] After 3.0 hours from the start of polymerization, an aqueous solution of polymerization initiator containing 0.026 g of APS was injected with nitrogen gas.

[0280] Immediately after the diiodine compound I (CF2)4I was injected until 70% of the total amount of the mixed monomer was supplied, a total of 3.00 g of a 10 mass% aqueous solution of CF2=CFOCF2CF2SO3Na (compound (a3)) was intermittently supplied to the polymerization tank.

[0281] 5.82 hours after the initiation of polymerization, stirring was stopped, and the pressure in the polymerization tank was reduced to atmospheric pressure, thereby terminating the polymerization.

[0282] The polymerization tank was cooled to obtain an aqueous fluorine-containing elastomer dispersion. The solids concentration, polymer adhesion rate and particle number of the aqueous dispersion are shown in Table 1.

[0283] To the obtained aqueous dispersion of fluorine-containing elastomer, an aqueous aluminum sulfate solution was added to perform coagulation. The obtained coagulation was washed with water and dried to obtain a fluorine-containing elastomer. The copolymer composition was examined by NMR analysis and found to be VdF / TFE / HFP=50 / 20 / 30 (mol%). The Mooney viscosity of the fluorine-containing elastomer is shown in Table 1.

[0284] Comparative Example 1 (Production of Fluorine-Containing Elastomer Aqueous Dispersion) In a 3L stainless steel polymerization tank, 1500g of deionized water and 3.00g of a 5% by mass aqueous solution of CH2=CFCF2OCF(CF3)CF2OCF(CF3)COONH4 (compound (b)) were added, the polymerization tank was sealed, and the system was replaced with nitrogen to remove oxygen. The polymerization tank was heated to 80°C, and VdF, TFE, and HFP (initial monomer) were injected with stirring in a molar ratio of vinylidene fluoride [VdF] / tetrafluoroethylene [TFE] / hexafluoropropylene [HFP] (=19 / 11 / 70 mol%) so that the internal pressure of the polymerization tank was 1.47 MPaG.

[0285] Next, a polymerization initiator solution containing 0.026 g of ammonium persulfate (APS) dissolved in deionized water was injected with nitrogen gas to initiate polymerization. As the polymerization progressed, when the internal pressure dropped to 1.45 MPaG, a mixed monomer of VDF / TFE / HFP (=50 / 20 / 30 mol%) was charged so that the internal pressure remained constant at 1.47 MPaG.

[0286] When 14 g of the mixed monomer was added, 2.19 g of the diiodine compound I(CF2)4I was injected with nitrogen gas.

[0287] 3.0 hours and 6.0 hours after the start of polymerization, an aqueous solution of polymerization initiator (APS, 0.026 g) was injected with nitrogen gas.

[0288] Immediately after the diiodine compound I(CF2)4I was injected until 70% of the total amount of the mixed monomers was supplied, a total of 6.00 g of a 5 mass% aqueous solution of CH2=CFCF2OCF(CF3)CF2OCF(CF3)COONH4 (compound (b)) was intermittently supplied to the polymerization tank.

[0289] 6.93 hours after the initiation of polymerization, stirring was stopped, and the pressure in the polymerization tank was reduced to atmospheric pressure, thereby terminating the polymerization.

[0290] The polymerization tank was cooled to obtain an aqueous fluorine-containing elastomer dispersion. The solids concentration, polymer adhesion rate and particle number of the aqueous dispersion are shown in Table 1.

[0291] To the obtained aqueous dispersion of fluorine-containing elastomer, an aqueous aluminum sulfate solution was added to perform coagulation. The obtained coagulation was washed with water and dried to obtain a fluorine-containing elastomer. The copolymer composition was examined by NMR analysis and found to be VdF / TFE / HFP=50 / 20 / 30 (mol%). The Mooney viscosity of the fluorine-containing elastomer is shown in Table 1.

[0292] Comparative Example 2 (Production of Fluorine-Containing Elastomer Aqueous Dispersion) 1500g of deionized water and 0.93g of a 10% by mass aqueous solution of CH2=CFCF2OCF(CF3)COONH4 (compound (a1)) were added to a 3L stainless steel polymerization tank, the tank was sealed, and the system was replaced with nitrogen to remove oxygen. The tank was heated to 80°C, and VdF, TFE, and HFP (initial monomer) were injected with stirring in a molar ratio of vinylidene fluoride [VdF] / tetrafluoroethylene [TFE] / hexafluoropropylene [HFP] (=19 / 11 / 70 mol%) so that the internal pressure of the tank was 1.47 MPaG.

[0293] Next, a polymerization initiator solution containing 0.026 g of ammonium persulfate (APS) dissolved in deionized water was injected with nitrogen gas to initiate polymerization. As the polymerization progressed, when the internal pressure dropped to 1.45 MPaG, a mixed monomer of VDF / TFE / HFP (=50 / 20 / 30 mol%) was charged so that the internal pressure remained constant at 1.47 MPaG.

[0294] When 14 g of the mixed monomer was added, 2.19 g of the diiodine compound I(CF2)4I was injected with nitrogen gas.

[0295] After 3.0 hours from the start of polymerization, an aqueous solution of polymerization initiator containing 0.026 g of APS was injected with nitrogen gas.

[0296] 5.52 hours after the start of polymerization, stirring was stopped, and the pressure in the polymerization tank was reduced to atmospheric pressure, thereby terminating the polymerization.

[0297] The polymerization tank was cooled to obtain an aqueous fluorine-containing elastomer dispersion. The solids concentration, polymer adhesion rate and particle number of the aqueous dispersion are shown in Table 1.

[0298] To the obtained aqueous dispersion of fluorine-containing elastomer, an aqueous aluminum sulfate solution was added to perform coagulation. The obtained coagulation was washed with water and dried to obtain a fluorine-containing elastomer. The copolymer composition was examined by NMR analysis and found to be VdF / TFE / HFP=50 / 20 / 30 (mol%). The Mooney viscosity of the fluorine-containing elastomer is shown in Table 1.

[0299] (Making O-rings) 100 parts by mass of the fluorine-containing elastomer obtained in the above Examples and Comparative Examples, 20 parts by mass of carbon black (MT carbon, Thermax N-990, manufactured by Cancarb), 4 parts by mass of triallyl isocyanurate (TAIC, manufactured by Nippon Kasei), and 1.5 parts by mass of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (Perhexa 25B, manufactured by NOF Corp.) were kneaded using an open roll to prepare a fluorine-containing elastomer composition. The maximum torque level (MH) of the fluorine-containing elastomer composition is shown in Table 1.

[0300] The obtained fluorine-containing elastomer composition was press-crosslinked at 160° C. for 10 minutes and oven-crosslinked at 180° C. for 4 hours to prepare an O-ring (P24 size). The compression set (CS) of the O-ring is shown in Table 1.

[0301] [Table 1]

Claims

1. A method for producing an aqueous fluorine-containing elastomer dispersion, comprising polymerizing a fluorine-containing monomer in the presence of an aqueous medium and a fluorine-containing compound (A) to produce an aqueous dispersion containing a fluorine-containing elastomer, comprising the steps of: the fluorine-containing elastomer contains a methylene group in its main chain, The fluorine-containing compound (A) is represented by the general formula (A): CX ｉ X ｋ =CX ｊ R ａ -(CZ １ Z ２ ) ｋ -Y ３ (A) (In the formula, X ｉ , X ｊ and X ｋ are the same or different and are F, Cl, H or CF ３ and Y ３ is a hydrophilic group, which is -NH 2 , -P(O)(OM) 2 , -OP(O)(OM) 2 , -SO 3 M, -OSO 3 M or -COOM (in each formula, M is H, a metal atom, NR 7 4 , an imidazolium which may have a substituent, a pyridinium which may have a substituent or a phosphonium which may have a substituent, R 7 is H or an organic group and may be the same or different. Any two of the four R 7 in NR 7 4 may be bonded to each other to form a ring); R ａ represents -(C=O)-, -(C=O)-O-, or a hydrocarbon group which may contain an ether bond and in which some or all of the hydrogen atoms bonded to carbon atoms may be substituted with fluorine; Z １ and Z ２ are the same or different and are H, F or CF ３ and k is 0 or 1. ｉ , X ｋ , X ｊ , R ａ , Z １ and Z ２ At least one of the groups contains F. The number of carbon atoms in the portion excluding the hydrophilic group is 6 or less. After the polymerization of the fluorine-containing monomer is started, the fluorine-containing compound (A) is supplied. Manufacturing method.

2. The process according to claim 1, wherein the fluorine-containing elastomer contains vinylidene fluoride units.

3. 3. The process according to claim 1, wherein the fluorine-containing elastomer contains vinylidene fluoride units in an amount of 50 mol % or more based on the total monomer units.

4. The process according to claim 1 or 2, wherein the fluorine-containing compound (A) is supplied even before the initiation of polymerization of the fluorine-containing monomer.

5. 3. The production method according to claim 1, wherein the amount of the fluorine-containing compound (A) supplied after initiation of polymerization of the fluorine-containing monomer is 30 to 300 ppm by mass based on the aqueous medium.

6. A method for producing a polymer according to claim 1 or 2, wherein the content of a fluorine-containing surfactant having no radically polymerizable unsaturated bond in the aqueous medium is 10 ppm by mass or less, and the fluorine-containing monomer is polymerized.

7. 3. The process according to claim 1, wherein the fluorine-containing elastomer has a Mooney viscosity (ML1+10 (100° C.)) of 10 to 130.

8. The fluorine-containing compound (A) is represented by the general formula (A1): CX ｉ X ｋ =CX ｊ -O-R-(CZ １ Z ２ ) ｋ -Y ３ (In the formula, X ｉ , X ｊ , X ｋ , Z １ , Z ２ , k and Y ３ is as described above, and R is a fluorinated alkylene group or a fluorinated oxyalkylene group having 1 to 3 carbon atoms. CX ｉ X ｋ =CX ｊ -CZ １ Z ２ -O-R-(CZ １ Z ２ ) ｋ -Y ３ (In the formula, X ｉ , X ｊ , X ｋ , Z １ , Z ２ , k and Y ３ wherein R is a fluorinated alkylene group or a fluorinated oxyalkylene group having 1 or 2 carbon atoms.

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