Process for producing an aqueous dispersion of a fluorine-containing elastomer, fluorine-containing elastomer and composition

Abstract

The present invention provides a production method for an aqueous fluorine-containing elastomer dispersion in which an aqueous dispersion of a fluorine-containing elastomer that has a methylene group in the main chain is produced by polymerizing fluorine-containing monomers in the presence of: a fluorine-containing allyl ether (1) represented by general formula (1) CX11 2=CY11(-CZ11 2-O-Rf11-Y12); a fluorine-containing vinyl ether (2) represented by general formula (2) CX21 2=CY21(-O-Rf21-Y22); and an aqueous medium.

Description

Technical Field

[0001] The present disclosure relates to a method for producing an aqueous dispersion of a fluorine-containing elastomer, a fluorine-containing elastomer, and a composition.

Background Art

[0002] Patent Document 1 discloses that when producing a fluorine-containing elastomer by copolymerizing at least one kind of each of a fluoromonomer and a comonomer containing or not containing fluorine by the action of a polymerization initiation source, a compound represented by the general formula CF2 = CFO(CF2) n OOM (wherein n is an integer of 1 to 7, and M represents NH4 or an alkali metal) is present in the total monomer mixture in an amount of 0.5 to 10 mol%, and the polymerization reaction is carried out in an aqueous medium in which the liquid pH is maintained at 5 to 10 substantially in the absence of a surfactant. A method for producing a fluorine-containing elastomer is described.

[0003] Patent Document 2 discloses that a fluorine-containing monomer is represented by the general formula CF2 = CF〔OCF2CF(CF3)〕 b O(CF2) a O〔CF(CF3)CF2O〕 c CF(CF3)COOM 〔I〕 (wherein M is sodium or potassium, a is an integer of 1 to 6, and b + c is an integer of 0 to 6), and a copolymerization reaction is carried out in the presence of a perfluorovinyloxy polyether carboxylic acid alkali metal salt as a fluorine-based reactive emulsifier. A method for producing a fluorine-containing elastomer according to claim 1 is described.

[0004] Patent Document 3 discloses a method for producing a partially fluorinated polymer dispersion, which includes polymerizing one or more fluorinated monomers by aqueous emulsion polymerization in the presence of a polymerizable fluorinated emulsifier, and the polymerizable fluorinated emulsifier has the formula: X2C = CX(CF2) m (CH2) n [O-(CX2) pq -[O-(CX2) r s -[O-(CX2-CX2)] t -[(O) w -(CX2) u v -[CH2] z -Y (wherein X is independently selected from H, F, or CF3; Y is COOM or SO3M, M is H, an alkali metal, or NH4, m is from 0 to 5, n is from 0 to 5, p is at least 1, q is from 0 to 5, r is from 0 to 5, s is from 0 to 5, t is from 0 to 5, u is from 0 to 5, v is from 0 to 5, w is 0 or 1, z is from 0 to 5; at least one of m, n, q, s, t, u, v, and z is at least 1), and the polymerizable fluorinated emulsifier contains (a) at least one fluorine atom and (b) less than 1% by weight based on the total weight of the monomers used, and the partially fluorinated polymer contains less than 50 mol% of vinylidene fluoride, and a method is described.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present disclosure is to provide a method for producing an aqueous dispersion of a fluorine-containing elastomer that can generate a sufficient number of fluorine-containing elastomer particles and can greatly suppress the adhesion of the fluorine-containing elastomer to the polymerization tank.

Means for Solving the Problems

[0007] According to the present disclosure, there is provided a method for producing an aqueous dispersion of a fluorine-containing elastomer containing a methylene group in the main chain by polymerizing a fluorine-containing monomer in the presence of a fluorine-containing allyl ether (1) represented by the general formula (1), a fluorine-containing vinyl ether (2) represented by the general formula (2), and an aqueous medium. CX 11 2=CY 11 (-CZ 11 2-O-Rf 11 -Y 12 ) (1) (In the formula, X 11 is the same or different and is -H or -F, Y 11 is -H, -F, an alkyl group or a fluorine-containing alkyl group, and Z 11 is the same or different and is -H, -F, an alkyl group or a fluorine-containing alkyl group. Rf 11 is a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having an ether bond and having 2 to 100 carbon atoms. Y 12 has a hydrophilic group.) CX 21 2=CY 21 (-O-Rf 21 -Y 22 ) (2) (In the formula, X 21 is the same or different and is -H or -F, Y 21 is -H, -F, an alkyl group or a fluorine-containing alkyl group, and Rf 21 is a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having an ether bond and having 2 to 100 carbon atoms. Y 22 is a hydrophilic group.)

[0008] In the production method of the present disclosure, Y 12 is -NH2, -P(O)(OM)2, -OP(O)(OM)2, -SO3M, -OSO3M, -COOM, -B(OM)2 or -OB(OM)2 (in each formula, M is H, a metal atom, NR 74. An optionally substituted imidazolium, an optionally substituted pyridinium or an optionally substituted phosphonium, R 7 is H or an organic group, and they may be the same or different. Any two of them may be bonded to each other to form a ring. It is preferably (). In the production method of the present disclosure, X 11 is preferably the production method according to claim 1 or 2, wherein all are -H. In the production method of the present disclosure, the amount of the fluorine-containing allyl ether (1) is preferably 3 to 5000 mass ppm with respect to the aqueous medium. In the production method of the present disclosure, Y 22 is -NH2, -P(O)(OM)2, -OP(O)(OM)2, -SO3M, -OSO3M, -COOM, -B(OM)2 or -OB(OM)2 (in each formula, M is H, a metal atom, NR 7 4. An optionally substituted imidazolium, an optionally substituted pyridinium or an optionally substituted phosphonium, R 7 is H or an organic group, and they may be the same or different. Any two of them may be bonded to each other to form a ring. It is preferably (). In the production method of the present disclosure, the amount of the fluorine-containing vinyl ether (2) is preferably 3 to 5000 mass ppm with respect to the aqueous medium. In the production method of the present disclosure, it is preferable to polymerize the fluorine-containing monomer in the presence of a chain transfer agent. In the production method of the present disclosure, it is preferable to polymerize the fluorine-containing monomer at 10 to 120 °C. In the production method of the present disclosure, it is preferable to polymerize the fluorine-containing monomer at 0.5 to 10 MPaG. In the production method of the present disclosure, the fluorine-containing elastomer preferably contains vinylidene fluoride units. In the production method of the present disclosure, the fluorine-containing elastomer preferably contains 50 mol% or more of vinylidene fluoride units based on all monomer units. In the production method of the present disclosure, it is preferable that the Mooney viscosity (ML1+10(100°C)) of the fluorine-containing elastomer is 10 to 130.

[0009] Further, according to the present disclosure, there is provided a fluorine-containing elastomer containing a methylene group in the main chain, and further containing a monomer unit (1) based on a fluorine-containing allyl ether (1) represented by the general formula (1) and a monomer unit (2) based on a fluorine-containing vinyl ether (2) represented by the general formula (2). CX 11 2=CY 11 (-CZ 11 2-O-Rf 11 -Y 12 ) (1) (In the formula, X 11 is the same or different and is -H or -F, Y 11 is -H, -F, an alkyl group or a fluorine-containing alkyl group, and Z 11 is the same or different and is -H, -F, an alkyl group or a fluorine-containing alkyl group. Rf 11 is a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having an ether bond and having 2 to 100 carbon atoms. Y 12 is a hydrophilic group.) CX 21 2=CY 21 (-O-Rf 21 -Y 22 ) (2) (In the formula, X 21 is the same or different and is -H or -F, Y 21 is -H, -F, an alkyl group or a fluorine-containing alkyl group, and Rf 21 is a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having an ether bond and having 2 to 100 carbon atoms. Y 22 is a hydrophilic group.)

[0010] The fluorine-containing elastomer of the present disclosure preferably contains a vinylidene fluoride unit.

[0011] Also, according to the present disclosure, there is provided an aqueous dispersion of a fluorine-containing elastomer containing the above fluorine-containing elastomer and an aqueous medium.

Advantages of the Invention

[0012] According to the present disclosure, it is possible to provide a method for producing an aqueous dispersion of a fluorine-containing elastomer that can generate a sufficient number of fluorine-containing elastomer particles and can greatly suppress the adhesion of the fluorine-containing elastomer to the polymerization tank.

Embodiments for Carrying Out the Invention

[0013] Before describing specific embodiments of the present disclosure, some terms used in the present disclosure will be defined or explained.

[0014] In the present disclosure, the fluorine-containing elastomer is an amorphous fluoropolymer. "Amorphous" means that the size of the melting peak (ΔH) appearing in the differential scanning calorimetry [DSC] (heating rate 10 ° C / min) or differential thermal analysis [DTA] (heating rate 10 ° C / min) of the fluoropolymer is 4.5 J / g or less. The fluorine-containing elastomer exhibits elastomeric properties by crosslinking. The elastomeric property means a property that the polymer can be stretched and can retain its original length when the force required to stretch the polymer is no longer applied.

[0015] In the present disclosure, the perfluoro monomer is a monomer that does not contain a carbon atom-hydrogen atom bond in the molecule. The perfluoro monomer may be a monomer in which some of the fluorine atoms bonded to the carbon atom are substituted with chlorine atoms in addition to the carbon atom and fluorine atoms, or may have a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, a boron atom, or a silicon atom in addition to the carbon atom. The perfluoro monomer is preferably a monomer in which all hydrogen atoms are substituted with fluorine atoms. The perfluoro monomer does not include a monomer that provides a crosslinkable group.

[0016] The monomer that provides a crosslinking site is a monomer (cure site monomer) that provides a crosslinking site for forming a crosslink with a curing agent to a fluoropolymer. The monomer that provides a crosslinking site includes a monomer that provides a crosslinkable group.

[0017] In the present disclosure, the content of each monomer unit constituting the fluorine-containing elastomer can be calculated by appropriately combining NMR, FT-IR, elemental analysis, and X-ray fluorescence analysis according to the type of monomer.

[0018] In the present disclosure, the "organic group" means a group containing one or more carbon atoms, or a group formed by removing one 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 which may have one or more substituents, an alkynyl group which may have one or more substituents, a cycloalkyl group which may have one or more substituents, a cycloalkenyl group which may have one or more substituents, a cycloalkadienyl group which may have one or more substituents, an aryl group which may have one or more substituents, an aralkyl group which may have one or more substituents, a non-aromatic heterocyclic group which may have one or more substituents, a heteroaryl group which may have one or more substituents, a cyano group, a 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 which may have one or more substituents, An alkynyl group which may have one or more substituents, A cycloalkyl group which may have one or more substituents, A cycloalkenyl group which may have one or more substituents, A cycloalkadienyl group which may have one or more substituents, An aryl group which may have one or more substituents, An aralkyl group which may have one or more substituents, A non-aromatic heterocyclic group which may have one or more substituents, or A heteroaryl group which may have one or more substituents, Rb is independently H or an alkyl group which may have one or more substituents.) is included. As the above organic group, an alkyl group which may have one or more substituents is preferable.

[0019] In the present disclosure, a "substituent" means a group that can be substituted. 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 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 di-aliphatic oxyphosphinyl group, and a di-aromatic oxyphosphinyl group.

[0020] The above aliphatic group may be saturated or unsaturated, and may also 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 above aliphatic group include an alkyl group having 1 to 8, preferably 1 to 4 carbon atoms in total, such as a methyl group, an ethyl group, a vinyl group, a cyclohexyl group, a carbamoylmethyl group, etc.

[0021] The above 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 above aromatic group include an aryl group having 6 to 12 carbon atoms, preferably 6 to 10 total carbon atoms, such as a phenyl group, a 4-nitrophenyl group, a 4-acetylaminophenyl group, a 4-methanesulfonylphenyl group, etc.

[0022] The above heterocyclic group may have, for example, 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 above heterocyclic group include a 5- to 6-membered heterocyclic ring having 2 to 12 total carbon atoms, preferably 2 to 10, such as a 2-tetrahydrofuryl group, a 2-pyrimidyl group, etc.

[0023] The above acyl group may have, for example, 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 above acyl group include an acyl group having 2 to 8 total carbon atoms, preferably 2 to 4, such as an acetyl group, a propanoyl group, a benzoyl group, a 3-pyridinecarbonyl group, etc.

[0024] The above acylamino group may have, for example, an aliphatic group, an aromatic group, a heterocyclic group, etc., and may have, for example, an acetylamino group, a benzoylamino group, a 2-pyridinecarbonylamino group, a propanoylamino group, etc. Examples of the above acylamino group include an acylamino group having 2 to 12 total carbon atoms, preferably 2 to 8, and an alkylcarbonylamino group having 2 to 8 total carbon atoms, such as an acetylamino group, a benzoylamino group, a 2-pyridinecarbonylamino group, a propanoylamino group, etc.

[0025] The above aliphatic oxycarbonyl group may be saturated or unsaturated, and may also 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 above aliphatic oxycarbonyl group include an alkoxycarbonyl group having 2 to 8, preferably 2 to 4 carbon atoms in total, such as a methoxycarbonyl group, an ethoxycarbonyl group, a (t)-butoxycarbonyl group, etc.

[0026] The above carbamoyl group may have an aliphatic group, an aromatic group, a heterocyclic group, etc. Examples of the above carbamoyl group include an unsubstituted carbamoyl group, an alkylcarbamoyl group having 2 to 9 carbon atoms in total, preferably an unsubstituted carbamoyl group, an alkylcarbamoyl group having 2 to 5 carbon atoms in total, such as an N-methylcarbamoyl group, an N,N-dimethylcarbamoyl group, an N-phenylcarbamoyl group, etc.

[0027] The above aliphatic sulfonyl group may be saturated or unsaturated, and may also 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 above aliphatic sulfonyl group include an alkylsulfonyl group having 1 to 6, preferably 1 to 4 carbon atoms in total, such as a methanesulfonyl group, etc.

[0028] The above 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 above aromatic sulfonyl group include an arylsulfonyl group having 6 to 10 carbon atoms in total, such as a benzenesulfonyl group, etc.

[0029] The above amino group may have an aliphatic group, an aromatic group, a heterocyclic group, etc.

[0030] The acylamino group may have, for example, an acetylamino group, a benzoylamino group, a 2-pyridinecarbonylamino group, a propanoylamino group, etc. The acylamino group is preferably an acylamino group having 2 to 12 carbon atoms in total, more preferably an acylamino group having 2 to 8 carbon atoms in total, still more preferably an alkylcarbonylamino group having 2 to 8 carbon atoms in total, such as an acetylamino group, a benzoylamino group, a 2-pyridinecarbonylamino group, a propanoylamino group, etc.

[0031] The aliphatic sulfonamide group, aromatic sulfonamide group, and heterocyclic sulfonamide group may be, for example, a methanesulfonamide group, a benzenesulfonamide group, a 2-pyridinesulfonamide group, etc.

[0032] The sulfamoyl group may have an aliphatic group, an aromatic group, a heterocyclic group, etc. The sulfamoyl group is preferably a sulfamoyl group, an alkylsulfamoyl group having 1 to 9 carbon atoms in total, a dialkylsulfamoyl group having 2 to 10 carbon atoms in total, an arylsulfamoyl group having 7 to 13 carbon atoms in total, a heterocyclic sulfamoyl group having 2 to 12 carbon atoms in total, more preferably a sulfamoyl group, an alkylsulfamoyl group having 1 to 7 carbon atoms in total, a dialkylsulfamoyl group having 3 to 6 carbon atoms in total, an arylsulfamoyl group having 6 to 11 carbon atoms in total, a heterocyclic sulfamoyl group having 2 to 10 carbon atoms in total, such as a sulfamoyl group, a methylsulfamoyl group, an N,N-dimethylsulfamoyl group, a phenylsulfamoyl group, a 4-pyridinesulfamoyl group, etc.

[0033] The aliphatic oxy group may be saturated or unsaturated and may have, for example, a methoxy group, an ethoxy group, an i-propyloxy group, a cyclohexyloxy group, a methoxyethoxy group, etc. The aliphatic oxy group is preferably an alkoxy group having 1 to 8 carbon atoms in total, more preferably 1 to 6 carbon atoms in total, such as a methoxy group, an ethoxy group, an i-propyloxy group, a cyclohexyloxy group, a methoxyethoxy group, etc.

[0034] The above 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, 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, and an aliphatic oxycarbonyl group having 2 to 4 carbon atoms in total.

[0035] The above aliphatic thio group may be saturated or unsaturated, and examples thereof include an alkylthio group having 1 to 8 carbon atoms in total, more preferably an alkylthio group having 1 to 6 carbon atoms in total, such as a methylthio group, an ethylthio group, a carbamoylmethylthio group, and a t-butylthio group.

[0036] The above carbamoylamino group may have an aliphatic group, an aryl group, a heterocyclic group, etc. Examples of the above carbamoylamino group include a carbamoylamino group, an alkylcarbamoylamino group having 2 to 9 carbon atoms in total, a dialkylcarbamoylamino group having 3 to 10 carbon atoms in total, an arylcarbamoylamino group having 7 to 13 carbon atoms in total, a heterocyclic carbamoylamino group having 3 to 12 carbon atoms in total, preferably a carbamoylamino group, an alkylcarbamoylamino group having 2 to 7 carbon atoms in total, a dialkylcarbamoylamino group having 3 to 6 carbon atoms in total, an arylcarbamoylamino group having 7 to 11 carbon atoms in total, a heterocyclic carbamoylamino group having 3 to 10 carbon atoms in total, for example, a carbamoylamino group, a methylcarbamoylamino group, an N,N-dimethylcarbamoylamino group, a phenylcarbamoylamino group, a 4-pyridinecarbamoylamino group, etc.

[0037] In the present disclosure, a range represented by endpoints includes all numerical values included in that range (for example, 1 to 10 includes 1.4, 1.9, 2.33, 5.75, 9.98, etc.).

[0038] In the present disclosure, the description of "at least 1" includes all numerical values of 1 or more (for example, 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.).

[0039] Hereinafter, specific embodiments of the present disclosure will be described in detail, but the present disclosure is not limited to the following embodiments.

[0040] The production method of the present disclosure is a method for producing an aqueous dispersion of a fluorine-containing elastomer that produces an aqueous dispersion of a fluorine-containing elastomer containing a methylene group in the main chain, and has the general formula (1): CX 11 2=CY 11 (-CZ 11 2-O-Rf 11 -Y 11 ) represented by the fluorine-containing allyl ether (1), the general formula (2): CX 21 2=CY 21 (-O-Rf 21 -Y 21 ) represented by the fluorine-containing vinyl ether (2) and in the presence of an aqueous medium, polymerizes a fluorine-containing monomer.

[0041] By using two types of compounds having different structures, namely, the fluorine-containing allyl ether (1) and the fluorine-containing vinyl ether (2), it is possible to generate a sufficient number of fluorine-containing elastomer particles for the polymerization reaction to proceed smoothly, and to greatly suppress the adhesion of the fluorine-containing elastomer to the polymerization tank. The reason for this is not clear, but the two types of compounds with different structures have different reactivities with the fluorine-containing monomer. In the initial stage of the polymerization reaction, mainly the fluorine-containing allyl ether (1) reacts with the fluorine-containing monomer to generate a sufficient number of fluorine-containing elastomer particles. In the subsequent polymerization reaction, mainly the fluorine-containing vinyl ether (2) reacts with the fluorine-containing monomer to form fluorine-containing elastomer particles having a hydrophilic group and high stability. This is presumably the reason.

[0042] The fluorine-containing allyl ether (1) is represented by the general formula (1). CX 112 = CY 11 (-CZ 11 2 - O - Rf 11 -Y 12 ) (1) (In the formula, X 11 is, the same or different, -H or -F, and Y 11 is -H, -F, an alkyl group or a fluorine-containing alkyl group, and Z 11 is, the same or different, -H, -F, an alkyl group or a fluorine-containing alkyl group. Rf 11 is a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having an ether bond with 2 to 100 carbon atoms. Y 12 has a hydrophilic group.)

[0043] In the general formula (1), X 11 is -H or -F. X 11 Both may be -F, or at least one may be -H. For example, one may be -F and the other may be -H, or both may be -H. Since more fluorine-containing elastomer particles can be generated and the adhesion of the fluorine-containing elastomer to the polymerization tank can be further suppressed, X 11 is preferably -H in both cases.

[0044] In the general formula (1), Y 11 is -H, -F, an alkyl group or a fluorine-containing alkyl group. The alkyl group is an alkyl group that does not contain a fluorine atom, and the carbon number may be 1 or more. The carbon number of the above alkyl group is preferably 6 or less, more preferably 4 or less, and still more preferably 3 or less. The fluorine-containing alkyl group is an alkyl group that contains at least one fluorine atom, and the carbon number may be 1 or more. The carbon number of the above fluorine-containing alkyl group is preferably 6 or less, more preferably 4 or less, and still more preferably 3 or less. Y 11 is preferably -H, -F or -CF3, and more preferably -F.

[0045] In the general formula (1), Z 11is, the same or different, -H, -F, an alkyl group or a fluoroalkyl group. The alkyl group is an alkyl group that does not contain a fluorine atom, and the number of carbon atoms may be 1 or more. The number of carbon atoms of the above alkyl group is preferably 6 or less, more preferably 4 or less, and still more preferably 3 or less. The fluorine-containing alkyl group is an alkyl group that contains at least one fluorine atom, and the number of carbon atoms may be 1 or more. The number of carbon atoms of the above fluorine-containing alkyl group is preferably 6 or less, more preferably 4 or less, and still more preferably 3 or less. Z 11 is preferably -H, -F or -CF3, and more preferably -F.

[0046] In the general formula (1), the above X 11 , Y 11 and Z 11 are preferably at least one containing a fluorine atom. For example, X 11 is -H, and Y 11 and Z 11 may be -F.

[0047] In the general formula (1), the above Rf 11 is a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having an ether bond and having 2 to 100 carbon atoms. The fluorine-containing alkylene group having an ether bond and having 2 to 100 carbon atoms does not include a structure in which an oxygen atom is at the end, and is an alkylene group containing an ether bond between carbon atoms. The number of carbon atoms of the fluorine-containing alkylene group is preferably 2 or more. Further, the number of carbon atoms of the above fluorine-containing alkylene group is preferably 30 or less, more preferably 20 or less, and still more preferably 10 or less. Examples of the above fluorine-containing alkylene group include -CF2-, -CH2CF2-, -CF2CF2-, -CF2CH2-, -CF2CF2CH2-, -CF(CF3)-, -CF(CF3)CF2-, -CF(CF3)CH2- and the like. The above fluorine-containing alkylene group is preferably a perfluoroalkylene group.

[0048] The number of carbon atoms in the fluorine-containing alkylene group having an ether bond is preferably 3 or more. Further, the number of carbon atoms in the fluorine-containing alkylene group having an ether bond is preferably 60 or less, more preferably 30 or less, and still more preferably 12 or less.

[0049] Examples of the fluorine-containing alkylene group having an ether bond include the following formula: -(CFZ 12 CF2O) p1 -(CF2O) q1 -(CZ 13 2CF2CF2O) r1 -CZ 14 Z 15 -(CF2) s1 -(CH2) t1 - (In the formula, Z 12 is F or CF3; Z 13 and Z 14 are each H or F; Z 15 is H, F or CF3; p1 + q1 + r1 is an integer from 1 to 10; s1 is 0 or 1; t1 is an integer from 0 to 5), and it is also preferably a divalent group represented by

[0050] Specific examples of the fluorine-containing alkylene group having an ether bond include -CF(CF3)CF2-O-CF(CF3)-, -(CF(CF3)CF2-O) n -CF(CF3)-(where n is an integer from 1 to 10), -CF(CF3)CF2-O-CF(CF3)CH2-, -(CF(CF3)CF2-O) n -CF(CF3)CH2-(where n is an integer from 1 to 10), -CH2CF2CF2O-CH2CF2CH2-, -CF2CF2CF2O-CF2CF2-, -CF2CF2CF2O-CF2CF2CH2-, -CF2CF2O-CF2-, -CF2CF2O-CF2CH2-, and the like. The fluorine-containing alkylene group having an ether bond is preferably a perfluoroalkylene group.

[0051] Y in the general formula (1) 12is a hydrophilic group. Examples of the hydrophilic group include -NH2, -P(O)(OM)2, -OP(O)(OM)2, -SO3M, -OSO3M, -COOM, -B(OM)2, -OB(OM)2 (in each formula, M is H, a metal atom, NR 7 4, imidazolium which may have a substituent, pyridinium which may have a substituent, or phosphonium which may have a substituent, R 7 is H or an organic group, and they may be the same or different. Any two of them may be bonded to each other to form a ring.). Preferred. As the above hydrophilic group, an anionic group is preferred, and -P(O)(OM)2, -OP(O)(OM)2, -SO3M, -OSO3M, -COOM, -B(OM)2, -OB(OM)2 are more preferred. As the organic group of R 7 an alkyl group is preferred. As R 7 H or a C 1-10 organic group is preferred, H or a C 1-4 organic group is more preferred, H or a C 1-4 alkyl group is even more preferred, and H is most preferred. Examples of the metal atom include monovalent or divalent metal atoms, and alkali metals (Group 1) or alkaline earth metals (Group 2) are preferred, and Na, K or Li are more preferred.

[0052] In the general formula (1), Y 12 can generate more fluorine-containing elastomer particles and can further suppress the adhesion of the fluorine-containing elastomer to the polymerization tank. Therefore, -COOM, -SO3M or -OSO3M (M is H, a metal atom, NR 7 4, imidazolium which may have a substituent, pyridinium which may have a substituent, or phosphonium which may have a substituent, R 7 is H or an organic group, and they may be the same or different. Any two of them may be bonded to each other to form a ring.). Preferred.

[0053] As the organic group of R 7 an alkyl group is preferred. As R 7 H or a C 1-10 organic group is preferred, H or a C1-4 The organic group of 1-4 is more preferable, and H or C 7 is further preferable. Examples of the metal atom include alkali metals (Group 1), alkaline earth metals (Group 2), etc., and Na, K, or Li is preferable. As M, -H, a metal atom, or -NR 7 4 is preferable, -H, an alkali metal (Group 1), an alkaline earth metal (Group 2), or -NR 12 4 is more preferable, -H, -Na, -K, -Li, or -NH4 is further preferable, -Na, -K, or -NH4 is even more preferable, -Na or -NH4 is particularly preferable, and -NH4 is most preferable. Y

[0054] The fluorine-containing allyl ether (1) is preferably a compound (1a) represented by the general formula (1a). CH2=CF(-CF2-O-Rf 11 -Y 12 ) (1a) (In the formula, Rf 11 and Y 12 are the same as described above.)

[0055] Specific examples of the compound (1a) include the following formula CH2=CFCF2O-(CFZ 12 CF2O) p1 -(CF2O) q1 -(CZ 13 2CF2CF2O) r1 -CZ 14 Z 15 -(CF2) s1 -(CH2) t1 -Y 12 (In the formula, Z 12 is F or CF3; Z 13 and Z 14 are each H or F; Z 15 is H, F, or CF3; p1 + q1 + r1 is an integer from 0 to 10; s1 is 0 or 1; t1 is an integer from 0 to 5, and Y 12 is the same as described above. However, Z 14 and Z 15Examples of the compound represented by (when both are H, p1 + q1 + r1 + s1 is not 0) include compounds represented by the following formulae.

[0056] More specifically, as the compound (1a), CH2=CFCF2OCF(CF3)-Y 12 CH2=CFCF2OCF(CF3)CF2OCF(CF3)-Y 12 CH2=CFCF2O-[CF(CF3)CF2O]2-CF(CF3)-Y 12 CH2=CFCF2OCF(CF3)CH2-Y 12 CH2=CFCF2OCF(CF3)CF2OCF(CF3)CH2-Y 12 CH2=CFCF2O-[CF(CF3)CF2O]2-CF(CF3)CH2-Y 12 CH2=CFCF2OCH2CF2-Y 12 CH2=CFCF2O-[CH2CF2CF2O]2-CH2CF2-Y 12 CH2=CFCF2OCF2CH2CF2-Y 12 CH2=CFCF2O(CH2CF2CF2O)CH2CF2CH2-Y 12 CH2=CFCF2OCF2CF2-Y 12 CH2=CFCF2O(CF2CF2CF2O)CF2CH2-Y 12 CH2=CFCF2OCF2CF2CH2-Y 12 CH2=CFCF2O(CF2CF2CF2O)CF2CF2CH2-Y 12 CH2=CFCF2OCF2-Y 12 CH2=CFCF2O(CF2CF2O)CF2-Y 12 CH2=CFCF2OCF2CH2-Y 12 CH2=CFCF2O(CF2CF2O)CF2CH2-Y 12 such as etc. can be mentioned.

[0057] Among others, as the compound (1a), CH2=CFCF2OCF(CF3)-Y 12 CH2=CFCF2OCF(CF3)CF2OCF(CF3)-Y 12 CH2=CFCF2O-[CF(CF3)CF2O]2-CF(CF3)-Y 12 CH2=CFCF2OCF(CF3)CH2-Y 12 CH2=CFCF2OCF(CF3)CF2OCF(CF3)CH2-Y 12 CH2=CFCF2O-[CF(CF3)CF2O]2-CF(CF3)CH2-Y 12 are preferred.

[0058] As the compound (1a), compounds having -COOM as Y in the formula (1a) are preferred, and in particular, at least one selected from the group consisting of CH2=CFCF2OCF(CF3)COOM and CH2=CFCF2OCF(CF3)CF2OCF(CF3)COOM (wherein M is the same as defined above) is preferred. 12

[0059] The fluorine-containing allyl ether (1) is preferably a compound (1b) represented by the general formula (1b). CX 12 2=CFCF2-O-(CF(CF3)CF2O) n5 -CF(CF3)-Y 12 (1b) (wherein each X 12 is the same and represents F or H. n5 represents 0 or an integer from 1 to 10, and Y 12 is the same as defined above.)

[0060] In the general formula (1b), n5 is preferably 0 or an integer of 1 to 5, more preferably 0, 1 or 2, and still more preferably 0 or 1, in terms of the stability of the resulting aqueous dispersion. Y 12 is preferably -COOM in terms of obtaining appropriate water solubility and the stability of the aqueous dispersion, and M is preferably H or NH4 in terms of being difficult to remain as an impurity and improving the heat resistance of the obtained molded product.

[0061] Examples of the compound (1b) include CH2 = CFCF2OCF(CF3)COOM and CH2 = CFCF2OCF(CF3)CF2OCF(CF3)COOM (wherein M is the same as defined above).

[0062] Examples of the fluorine-containing allyl ether (1) also include a compound (1c) represented by the general formula (1c). CF2 = CFCF2 - O - Rf 11 -Y 12 (1c) (wherein Rf 11 and Y 12 are the same as above)

[0063] More specifically, examples of the compound (1c) include CF2 = CFCF2OCF2CF2CF2 - Y 12 CF2 = CFCF2OCFCF(CF3) - Y 12 CF2 = CFCF2OCF2CF2CF2CH2 - Y 12 CF2 = CFCF2OCF2CF(CF3)CH2 - Y 12 and the like.

[0064] The fluorine-containing allyl ether (1) is preferably a compound (1a) represented by the general formula (1a), and more preferably at least one selected from the group consisting of CH2 = CFCF2OCF(CF3)COOM and CH2 = CFCF2OCF(CF3)CF2OCF(CF3)COOM (wherein M is the same as defined above).

[0065] In the polymerization of the fluorine-containing monomer, the amount of the fluorine-containing allyl ether (1) is preferably 3 to 5000 ppm by mass, more preferably 5 ppm by mass or more, still more preferably 10 ppm by mass or more, particularly preferably 20 ppm by mass or more, most preferably 30 ppm by mass or more, and also more preferably 1000 ppm by mass or less, still more preferably 500 ppm by mass or less, particularly preferably 200 ppm by mass or less, and most preferably 100 ppm by mass or less, based on the aqueous medium.

[0066] It is also preferable to adjust the amount of the fluorine-containing allyl ether (1) according to the type of the polymerization initiator used in the polymerization and the polymerization temperature. When a non-redox polymerization initiator is used as the polymerization initiator and the polymerization is carried out at 40 to 70°C, the amount of the fluorine-containing allyl ether (1) is preferably 3 to 300 ppm by mass, more preferably 3 to 150 ppm by mass, still more preferably 5 to 100 ppm by mass, and most preferably 8 to 80 ppm by mass, based on the aqueous medium. When a non-redox polymerization initiator is used as the polymerization initiator and the polymerization is carried out at above 70°C and 98°C or lower, the amount of the fluorine-containing allyl ether (1) is preferably 3 to 500 ppm by mass, more preferably 3 to 200 ppm by mass, still more preferably 5 to 120 ppm by mass, and most preferably 20 to 110 ppm by mass, based on the aqueous medium. When a redox polymerization initiator is used as the polymerization initiator and the polymerization is carried out at 10°C or higher and lower than 40°C, the amount of the fluorine-containing allyl ether (1) is preferably 3 to 300 ppm by mass, more preferably 3 to 100 ppm by mass, still more preferably 5 to 80 ppm by mass, and most preferably 10 to 70 ppm by mass, based on the aqueous medium. When a redox polymerization initiator is used as the polymerization initiator and the polymerization is carried out at 40 to 70°C, the amount of the fluorine-containing allyl ether (1) is preferably 3 to 500 ppm by mass, more preferably 5 to 300 ppm by mass, still more preferably 10 to 200 ppm by mass, and most preferably 15 to 150 ppm by mass, based on the aqueous medium. When a redox polymerization initiator is used as the polymerization initiator and polymerization is carried out at a temperature exceeding 70 °C and not exceeding 98 °C, the amount of the fluorine-containing allyl ether (1) is preferably 5 to 500 ppm by mass, more preferably 8 to 300 ppm by mass, still more preferably 15 to 200 ppm by mass, and most preferably 20 to 150 ppm by mass with respect to the aqueous medium. When the amount of the fluorine-containing allyl ether (1) is within the above range, the adhesion rate can be further reduced and the polymerization time can be shortened.

[0067] The fluorine-containing allyl ether (1) is preferably added before adding the polymerization initiator to initiate the polymerization reaction. Further, it is preferably added only before the polymerization reaction is initiated and not added after the polymerization is initiated.

[0068] The fluorine-containing vinyl ether (2) is represented by the general formula (2). CX 21 2=CY 21 (-O-Rf 21 -Y 22 ) (2) (In the formula, X 21 is the same or different and is -H or -F, Y 21 is -H, -F, an alkyl group or a fluorine-containing alkyl group, and Rf 21 is a fluorine-containing alkylene group having 1 to 40 carbon atoms or a fluorine-containing alkylene group having an ether bond and having 2 to 100 carbon atoms. Y 22 is a hydrophilic group.)

[0069] In the general formula (2), X 21 is -H or -F. X 21 Both may be -F, or at least one may be -H. For example, one may be -F and the other may be -H, or both may be -H. Since more fluorine-containing elastomer particles can be generated and the adhesion of the fluorine-containing elastomer to the polymerization tank can be further suppressed, X 21 is preferably -F in both cases.

[0070] In the general formula (2), Y21 is -H, -F, an alkyl group or a fluorine-containing alkyl group. The alkyl group is an alkyl group that does not contain a fluorine atom, and the number of carbon atoms may be 1 or more. The number of carbon atoms of the above alkyl group is preferably 6 or less, more preferably 4 or less, and still more preferably 3 or less. The fluorine-containing alkyl group is an alkyl group that contains at least one fluorine atom, and the number of carbon atoms may be 1 or more. The number of carbon atoms of the above fluorine-containing alkyl group is preferably 6 or less, more preferably 4 or less, and still more preferably 3 or less. Y 21 is preferably -H, -F or -CF3, and more preferably -F.

[0071] In general formula (2), X 21 and Y 21 at least one of which preferably contains a fluorine atom. For example, X 21 is -H, and Y 21 and Z may be -F.

[0072] In general formula (2), Rf 21 is a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having an ether bond and having 2 to 100 carbon atoms. The fluorine-containing alkylene group having an ether bond and having 2 to 100 carbon atoms does not include a structure in which an oxygen atom is at the terminal, and is an alkylene group containing an ether bond between carbon atoms. The number of carbon atoms of the fluorine-containing alkylene group is preferably 2 or more. Also, the number of carbon atoms of the fluorine-containing alkylene group is preferably 30 or less, more preferably 20 or less, and still more preferably 10 or less. Examples of the fluorine-containing alkylene group include -CF2-, -CH2CF2-, -CF2CF2-, -CF2CH2-, -CF2CF2CH2-, -CF(CF3)-, -CF(CF3)CF2-, -CF2CF(CF3)-, -CF(CF3)CH2- and the like. The fluorine-containing alkylene group is preferably a perfluoroalkylene group.

[0073] Y in general formula (2) 22is a hydrophilic group. Examples of the hydrophilic group include -NH2, -P(O)(OM)2, -OP(O)(OM)2, -SO3M, -OSO3M, -COOM, -B(OM)2, -OB(OM)2 (in each formula, M is H, a metal atom, NR 7 4, imidazolium which may have a substituent, pyridinium which may have a substituent or phosphonium which may have a substituent, R 7 is H or an organic group, and they may be the same or different. Any two of them may be bonded to each other to form a ring.). The above hydrophilic group is preferably an anionic group, and -P(O)(OM)2, -OP(O)(OM)2, -SO3M, -OSO3M, -COOM, -B(OM)2, -OB(OM)2 are more preferred. As the organic group of R 7 an alkyl group is preferred. As R 7 H or a C 1-10 organic group is preferred, H or a C 1-4 organic group is more preferred, H or a C 1-4 alkyl group is even more preferred, and H is most preferred. When two Ms are included in each formula, the two Ms may be the same or different. Examples of the metal atom include monovalent or divalent metal atoms, and alkali metals (Group 1) or alkaline earth metals (Group 2) are preferred, and Na, K or Li are more preferred.

[0074] In the above general formula (2), Y 22 can generate more fluorine-containing elastomer particles and can further suppress the adhesion of the fluorine-containing elastomer to the polymerization tank. Therefore, -COOM, -SO3M or -OSO3M (M is H, a metal atom, NR 7 4, imidazolium which may have a substituent, pyridinium which may have a substituent or phosphonium which may have a substituent, R 7 is H or an organic group, and they may be the same or different. Any two of them may be bonded to each other to form a ring.) is preferred.

[0075] As the organic group of R 7 an alkyl group is preferred. R 7is preferably H or C 1-10 and more preferably an organic group of H or C 1-4 and still more preferably an alkyl group of H or C 1-4 Examples of the metal atom include alkali metals (Group 1) and alkaline earth metals (Group 2), and Na, K, or Li is preferable. As the above M, -H, a metal atom, or -NR 7 4 is preferable, -H, an alkali metal (Group 1), an alkaline earth metal (Group 2), or -NR 7 4 is more preferable, -H, -Na, -K, -Li, or -NH4 is still more preferable, -Na, -K, or -NH4 is even more preferable, -Na or -NH4 is particularly preferable, and -NH4 is most preferable. As the above Y 22 is preferably -COOM or -SO3M.

[0076] The compound represented by the general formula (2) is preferably at least one selected from the group consisting of the compounds represented by the general formulas (2a) to (2f). CF2=CF-O-(CF2) n1 -Y 22 (2a) (In the formula, n1 represents an integer of 1 to 10, and Y 22 is as defined above) CF2=CF-O-(CF2C(CF3)F) n2 -Y 22 (2b) (In the formula, n2 represents an integer of 1 to 5, and Y 22 is as defined above.) CF2=CF-O-(CFX 22 ) n3 -Y 22 (2c) (In the formula, X 22 represents F or CF3, n3 represents an integer of 1 to 10, and Y 22 is as defined above.) CF2=CF-O-(CF2CFX 22 O) n4 -(CF2) n6 -Y 22 (2d) (In the formula, n4 represents an integer of 1 to 10, n6 represents an integer of 1 to 3, and Y22 and X 22 is the same as the above definition.) CF2=CF-O-(CF2CF2CFX 22 O) n5 -CF2CF2CF2-Y 22 (2e) (wherein n5 represents an integer of 0 to 10, and Y 22 and X 22 is the same as the above definition.) CF2=CF-O(-CF2) n6 -O-CF2-Y 22 (2f) (wherein n6 represents an integer of 1 to 6, and Y 22 is the same as the above definition.)

[0077] In the general formula (2a), n1 is preferably an integer of 5 or less, and more preferably an integer of 2 or less. Y 22 is preferably -COOM or -SO3M in terms of obtaining appropriate water solubility and stability of the aqueous dispersion. M is preferably Na or H or NH4 because the synthesis of the fluorine-containing vinyl ether (2) is easy. M is preferably H or NH4 in terms of being difficult to remain as an impurity and improving the heat resistance of the resulting molded product.)

[0078] Examples of the compound represented by the general formula (2a) include CF2=CF-O-CF2COOM, CF2=CF(OCF2CF2COOM), CF2=CF(OCF2CF2CF2COOM), CF2=CF(OCF2CF2SO3M), CF2=CF(OCF2SO3M), CF2=CF(OCF2CF2CF2SO3M) (wherein M is the same as the above definition).

[0079] In the general formula (2b), n2 is preferably an integer of 3 or less in terms of the stability of the resulting aqueous dispersion, and Y 22In terms of obtaining appropriate water solubility and stability of the aqueous dispersion, it is preferably -COOM or -SO3M. Since M facilitates the synthesis of the fluorine-containing vinyl ether (2), M is preferably Na or H or NH4. M is preferably H or NH4 in terms of being less likely to remain as an impurity and improving the heat resistance of the resulting molded article.

[0080] In general formula (2c), n3 is preferably an integer of 5 or less in terms of water solubility, and Y 22 In terms of obtaining appropriate water solubility and stability of the aqueous dispersion, it is preferably -COOM or -SO3M. M is preferably Na or H or NH4 in terms of improving dispersion stability.

[0081] In general formula (2d), X 22 is preferably -CF3 in terms of the stability of the aqueous dispersion. n4 is preferably an integer of 5 or less in terms of water solubility, and Y 22 is preferably -COOM or -SO3M in terms of obtaining appropriate water solubility and stability of the aqueous dispersion. M is preferably Na or H or NH4.

[0082] Examples of the compound represented by general formula (2d) include CF2=CFOCF2CF(CF3)OCF2CF2COOM, CF2=CFOCF2CF(CF3)OCF2COOM, CF2=CFOCF2CF(CF3)OCF2CF2CF2COOM, CF2=CFOCF2CF(CF3)OCF2SO3M, CF2=CFOCF2CF(CF3)OCF2CF2SO3M, CF2=CFOCF2CF(CF3)OCF2CF2CF2SO3M (wherein M represents H, NH4 or an alkali metal).

[0083] In general formula (2e), n5 is preferably an integer of 5 or less in terms of water solubility, and Y 22 is preferably -COOM or -SO3M in terms of obtaining appropriate water solubility and stability of the aqueous dispersion. M is preferably Na or H or NH4.

[0084] Examples of the compound represented by the general formula (2e) include CF2=CFOCF2CF2CF2COOM (wherein M represents H, NH4 or an alkali metal).

[0085] Examples of the compound represented by the general formula (2f) include CF2=CFOCF2CF2CF2OCF2COOM (wherein M represents H, NH4 or an alkali metal).

[0086] As the fluorine-containing vinyl ether (2), at least one selected from the group consisting of the compound represented by the general formula (2a) and the compound represented by the general formula (2d) is preferable, and at least one selected from the group consisting of CF2=CF(OCF2CF2COOM), CF2=CF(OCF2CF2SO3M), CF2=CFOCF2CF(CF3)OCF2CF2COOM and CF2=CFOCF2CF(CF3)OCF2CF2SO3M (wherein M is the same as defined above) is preferable.

[0087] In the polymerization of the fluorine-containing monomer, the amount of the fluorine-containing vinyl ether (2) is preferably 3 to 5000 ppm by mass, more preferably 5 ppm by mass or more, still more preferably 10 ppm by mass or more, particularly preferably 20 ppm by mass or more, most preferably 30 ppm by mass or more, also more preferably 1000 ppm by mass or less, still more preferably 500 ppm by mass or less, particularly preferably 200 ppm by mass or less, and most preferably 100 ppm by mass or less, based on the aqueous medium.

[0088] It is also preferable to adjust the amount of the fluorine-containing vinyl ether (2) according to the type of the polymerization initiator used in the polymerization and the polymerization temperature. When a non-redox polymerization initiator is used as the polymerization initiator and the polymerization is carried out at 40 to 70°C, the amount of the fluorine-containing vinyl ether (2) is preferably 3 to 300 ppm by mass, more preferably 3 to 150 ppm by mass, still more preferably 5 to 100 ppm by mass, and most preferably 8 to 80 ppm by mass, based on the aqueous medium. When a non-redox polymerization initiator is used as the polymerization initiator and polymerization is carried out at a temperature above 70°C and below 98°C, the amount of the fluorine-containing vinyl ether (2) is preferably 3 to 500 ppm by mass, more preferably 3 to 200 ppm by mass, still more preferably 5 to 120 ppm by mass, and most preferably 20 to 110 ppm by mass based on the aqueous medium. When a redox polymerization initiator is used as the polymerization initiator and polymerization is carried out at a temperature of 10°C or higher and lower than 40°C, the amount of the fluorine-containing vinyl ether (2) is preferably 3 to 300 ppm by mass, more preferably 3 to 100 ppm by mass, still more preferably 5 to 80 ppm by mass, and most preferably 10 to 70 ppm by mass based on the aqueous medium. When a redox polymerization initiator is used as the polymerization initiator and polymerization is carried out at a temperature of 40 to 70°C, the amount of the fluorine-containing vinyl ether (2) is preferably 3 to 500 ppm by mass, more preferably 5 to 300 ppm by mass, still more preferably 10 to 200 ppm by mass, and most preferably 15 to 150 ppm by mass based on the aqueous medium. When a redox polymerization initiator is used as the polymerization initiator and polymerization is carried out at a temperature above 70°C and below 98°C, the amount of the fluorine-containing vinyl ether (2) is preferably 5 to 500 ppm by mass, more preferably 8 to 300 ppm by mass, still more preferably 15 to 200 ppm by mass, and most preferably 20 to 150 ppm by mass based on the aqueous medium. When the amount of the fluorine-containing vinyl ether (2) is within the above range, the adhesion rate can be further reduced and the polymerization time can be shortened.

[0089] The fluorine-containing vinyl ether (2) is preferably added before adding the polymerization initiator to start the polymerization reaction. Further, it is preferably added only before starting the polymerization reaction and not added after the start of the polymerization reaction.

[0090] The mass ratio ((1) / (2)) of the amount of the fluorine-containing allyl ether (1) used in the polymerization of the fluorine-containing monomer to the amount of the fluorine-containing vinyl ether (2) is preferably from 1 / 99 to 99 / 1, more preferably from 20 / 80 to 80 / 20, and still more preferably from 20 / 80 to 60 / 40. By setting the mass ratio ((1) / (2)) within the above range, more fluorine-containing elastomer particles can be generated, and the adhesion of the fluorine-containing elastomer to the polymerization tank can be further suppressed.

[0091] In the production method of the present disclosure, if at least the fluorine-containing allyl ether (1) and the fluorine-containing vinyl ether (2) are used in combination, it is possible to efficiently produce a fluorine-containing elastomer. Further, in the production method of the present disclosure, two or more kinds of the fluorine-containing allyl ether (1) may be used simultaneously, two or more kinds of the fluorine-containing vinyl ether (2) 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 a fluorine-containing elastomer.

[0092] In one embodiment of the production method of the present disclosure, the fluorine-containing monomer is polymerized in the presence of a fluorine-free surfactant (hydrocarbon-based surfactant). Further, in one embodiment of the production method of the present disclosure, the fluorine-containing monomer is polymerized in the absence of a fluorine-free surfactant (hydrocarbon-based surfactant). According to the production method of the present disclosure, even when the fluorine-containing monomer is polymerized in the absence of a fluorine-free surfactant, a sufficient number of fluorine-containing elastomer particles can be generated, and the adhesion of the fluorine-containing elastomer to the polymerization tank can be greatly suppressed.

[0093] In one embodiment of the production method of the present disclosure, a fluorine-containing monomer is polymerized in the absence of a fluorine-containing surfactant (excluding the fluorine-containing allyl ether (1) and the fluorine-containing vinyl ether (2)). According to the production method of the present disclosure, even when a fluorine-containing monomer is polymerized in the absence of a fluorine-containing surfactant, a sufficient number of fluorine-containing elastomer particles can be generated, and the adhesion of the fluorine-containing elastomer to the polymerization tank can be greatly suppressed.

[0094] Examples of the fluorine-containing surfactant include anionic fluorine-containing surfactants. The anionic fluorine-containing surfactant may be, for example, a surfactant containing a fluorine atom and having a total carbon number of 20 or less in the portion excluding the anionic group.

[0095] The fluorine-containing surfactant may also be a surfactant containing fluorine and having a molecular weight of the anionic portion of 1000 or less, preferably 800 or less. The "anionic portion" means the portion excluding the cation of the fluorine-containing surfactant. For example, in the case of F(CF2) n1 COOM represented by the formula (I) described later, it is the portion of "F(CF2) n1 COO".

[0096] Examples of the fluorine-containing surfactant also include a fluorine-containing surfactant having a LogPOW of 3.5 or less. The LogPOW is the partition coefficient between 1-octanol and water, and is represented by LogP [where P represents the ratio of the concentration of the fluorine-containing surfactant in octanol to the concentration of the fluorine-containing surfactant in water when an octanol / water (1:1) mixture containing the fluorine-containing surfactant is phase-separated].

[0097] The above LogPOW is determined by performing HPLC on standard substances (heptanoic acid, octanoic acid, nonanoic acid, and decanoic acid) having a known octanol / water partition coefficient under the conditions of a column; TOSOH ODS-120T column (φ4.6 mm × 250 mm, manufactured by Tosoh Corporation), eluent; acetonitrile / 0.6 mass% HClO4 aqueous solution = 1 / 1 (vol / vol%), flow rate; 1.0 ml / min, sample amount; 300 μL, column temperature; 40 °C, detection light; UV210 nm, creating a calibration curve between each elution time and the known octanol / water partition coefficient, and calculating from the elution time of HPLC in the sample solution based on this calibration curve.

[0098] Specific examples of the above 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 / 142541, U.S. Patent Application Publication No. 2008 / 0015319, U.S. Patent No. 3250808, U.S. Patent No. 3271341, Japanese Unexamined Patent Application Publication No. 2003-119204, International Publication No. 2005 / 042593, International Publication No. 2008 / 060461, International Publication No. 2007 / 046377, Japanese Unexamined Patent Application Publication No. 2007-119526, International Publication No. 2007 / 046482, International Publication No. 2007 / 046345, U.S. Patent Application Publication No. 2014 / 0228531, International Publication No. 2013 / 189824, International Publication No. 2013 / 189826, etc.

[0099] As the above anionic fluorine-containing surfactant, the following general formula (N 0 ): X n0 -Rf n0 -Y 0 (N 0 ) (In the formula, X n0 is H, Cl, or F. Rf n0is an alkylene group having 3 to 20 carbon atoms, which is linear, branched or cyclic, and in which some or all of the H are substituted by F. The alkylene group may contain one or more ether bonds, and some of the H may be substituted by Cl. Y 0 is an anionic group. Examples of the compound represented by ) include those.)

[0100] Y 0 The anionic group of Y may be -COOM, -SO2M, or -SO3M, and may be -COOM or -SO3M. 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, and R 7 is H or an organic group. Examples of the above metal atom include alkali metals (Group 1), alkaline earth metals (Group 2), etc., and for example, Na, K or Li. R 7 may be H or an organic group of C 1-10 may be H or an organic group of C 1-4 may be H or an organic group of C 1-4 and may be an alkyl group. M may be H, a metal atom or NR 7 4, may be H, an alkali metal (Group 1), an alkaline earth metal (Group 2) or NR 7 4, and may be H, Na, K, Li or NH4. The above Rf n0 may be one in which 50% or more of H is substituted by fluorine.

[0101] Examples of the compound represented by the above general formula (N 0 ) include the following general formula (N 1 ): X n0 -(CF2) m1 -Y 0 (N 1 ) (In the formula, X n0 is H, Cl and F, m1 is an integer of 3 to 15, and Y 0is as defined above.) The 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, X n1 is F or CF3, and Y 0 is as defined above.) The 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, 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.) The 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 n1 and Y n2 are the same or different and are H or F, p is 0 or 1, and Y 0 is as defined above.) The compound represented by the following general formula (N 5 ):

Chemical formula

[0102] More specifically, as the compound represented by the general formula (N 0 ), a perfluorocarboxylic acid (I) represented by the following general formula (I), an ω-H perfluorocarboxylic acid (II) represented by the following general formula (II), a perfluoroether carboxylic acid (III) represented by the following general formula (III), a perfluoroalkyl alkylene carboxylic acid (IV) represented by the following general formula (IV), a perfluoroalkoxyfluorocarboxylic acid (V) represented by the following general formula (V), a perfluoroalkylsulfonic acid (VI) represented by the following general formula (VI), an ω-H perfluorosulfonic acid (VII) represented by the following general formula (VII), a perfluoroalkyl alkylene sulfonic acid (VIII) represented by the following general formula (VIII), an alkyl alkylene carboxylic acid (IX) represented by the following general formula (IX), a fluorocarboxylic acid (X) represented by the following general formula (X), an alkoxyfluorosulfonic acid (XI) represented by the following general formula (XI), a compound (XII) represented by the following general formula (XII), and a compound (XIII) represented by the following general formula (XIII) are exemplified.

[0103] The above perfluorocarboxylic acid (I) is represented by the following general formula (I) F(CF2) n1 COOM (I) (wherein, n1 is an integer of 3 to 14, and M is H, a metal atom, NR7 4. An optionally substituted imidazolium, an optionally substituted pyridinium or an optionally substituted phosphonium, where R 7 is H or an organic group.) represented thereby.

[0104] The above ω-H perfluorocarboxylic acid (II) is represented by the following general formula (II) H(CF2) n2 COOM (II) (In the formula, n2 is an integer from 4 to 15, and M is as defined above.) represented thereby.

[0105] The above 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 from 0 to 3, and M is as defined above.) represented thereby.

[0106] The above 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, Rf 3 is a linear or branched perfluoroalkylene group having 1 to 3 carbon atoms, n4 is an integer from 1 to 3, and M is as defined above.) represented thereby.

[0107] The above 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 4is a linear or branched or fully fluorinated alkyl group that may contain an ether bond having 1 to 12 carbon atoms, and Y 1 and Y 2 are the same or different and are H or F, and M is as defined above.) is represented by

[0108] The above 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.) is represented by

[0109] 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.) is represented by

[0110] The above perfluoroalkylalkylene sulfonic acid (VIII) is represented by the following general formula (VIII) Rf 5 (CH2) n7 SO3M (VIII) (wherein 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.) is represented by

[0111] The above alkylalkylene carboxylic acid (IX) is represented by the following general formula (IX) Rf 6 (CH2) n8 COOM (IX) (wherein Rf 6 is a linear or branched or fully fluorinated alkyl group that may contain an ether bond having 1 to 13 carbon atoms, n8 is an integer of 1 to 3, and M is as defined above.) is represented by

[0112] The above 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 or completely fluorinated alkyl group which may contain an ether bond having 1 to 6 carbon atoms, and Rf 8 is a linear or branched or completely fluorinated alkyl group having 1 to 6 carbon atoms, and M is as defined above.)

[0113] The above alkoxyfluorosulfonic acid (XI) is represented by the following general formula (XI): Rf 9 -O-CY 1 Y 2 CF2-SO3M (XI) (In the formula, Rf 9 is a linear or branched group which may contain an ether bond having 1 to 12 carbon atoms and may contain chlorine, and is a partially or completely fluorinated alkyl group, and Y 1 and Y 2 are the same or different and are H or F, and M is as defined above.)

[0114] The above compound (XII) is represented by the following general formula (XII):

Chemical formula

[0115] Y 0It may be -COOM, -SO2M, or -SO3M, and may be -SO3M or COOM (wherein M is as defined above). Examples of L include a single bond, a moiety that may contain an ether bond having 1 to 10 carbon atoms, or a fully fluorinated alkylene group.

[0116] The above compound (XIII) has the following general formula (XIII) Rf 11 -O-(CF2CF(CF3)O) n9 (CF2O) n10 CF2COOM (XIII) (wherein Rf 11 is a fluoroalkyl group having 1 to 5 carbon atoms containing chlorine, n9 is an integer from 0 to 3, n10 is an integer from 0 to 3, and M is as defined above). The compound (XIII) includes CF2ClO(CF2CF(CF3)O) n9 (CF2O) n10 CF2COONH4 (a mixture with an average molecular weight of 750, wherein n9 and n10 are as defined above).

[0117] In one embodiment of the production method of the present disclosure, a fluorine-containing monomer is polymerized in the presence of a fluorine-containing surfactant (excluding the fluorine-containing allyl ether (1) and the fluorine-containing vinyl ether (2)). In one embodiment of the production method of the present disclosure, a fluorine-containing monomer can be polymerized in the absence of a fluorine-containing compound represented by the general formula: X-(CF2) m2 -Y. In one embodiment of the production method of the present disclosure, a fluorine-containing monomer can be polymerized in the presence of a fluorine-containing surfactant (excluding the fluorine-containing allyl ether (1) and the fluorine-containing vinyl ether (2)) and in the absence of a fluorine-containing compound represented by the general formula: X-(CF2) m2 -Y.

[0118] As the fluorine-containing surfactant that can be present during polymerization (excluding fluorine-containing allyl ether (1) and fluorine-containing vinyl ether (2)), among the fluorine-containing surfactants, the general formula: X-(CF2) m2 -Y (wherein X represents H or F, m2 represents an integer of 6 or more, and Y represents -SO3M, -SO4M, -SO3R, -SO4R, -COOM, -PO3M2, -PO4M2 (M represents H, NH4 or an alkali metal, and R represents an alkyl group having 1 to 12 carbon atoms).) Fluorine-containing surfactants other than the fluorine-containing compounds represented by the formula can be mentioned. That is, in one embodiment of the production method of the present disclosure, in the presence of a fluorine-containing surfactant (excluding fluorine-containing allyl ether (1), fluorine-containing vinyl ether (2) and the general formula: X-(CF2) m2 -Y represented fluorine-containing compounds), it is preferable to polymerize the fluorine-containing monomer.

[0119] As the fluorine-containing surfactant that can be present during polymerization, among the fluorine-containing surfactants exemplified above as the fluorine-containing surfactant that is not present during polymerization, the general formula: X-(CF2) m2 -Y (wherein X represents H or F, m2 represents an integer of 6 or more, and Y represents -SO3M, -SO4M, -SO3R, -SO4R, -COOM, -PO3M2, -PO4M2 (M represents H, NH4 or an alkali metal, and R represents an alkyl group having 1 to 12 carbon atoms).) Fluorine-containing surfactants other than the fluorine-containing compounds represented by the formula can be mentioned. Further, as the fluorine-containing surfactant that can be present during polymerization, those described in International Publication No. 2019 / 009248, International Publication No. 2007 / 120346, International Publication No. 2007 / 011633, International Publication No. 2007 / 011631, International Publication No. 2007 / 062059, etc. can be mentioned.

[0120] In the production method of the present disclosure, the polymerization may be carried out in the presence of a polymerization initiator.

[0121] In the manufacturing method of the present disclosure, the polymerization of the fluorine-containing monomer can be carried out, for example, by charging a fluorine-containing allyl ether (1), a fluorine-containing vinyl ether (2) and an aqueous medium into a pressure-resistant polymerization tank equipped with a stirrer, deoxygenating, charging the monomer, bringing it to a predetermined temperature, adding a polymerization initiator, and starting the reaction. Since the pressure decreases as the reaction proceeds, additional monomer is continuously or intermittently added to maintain the initial pressure. When a predetermined amount of monomer has been supplied, the supply is stopped, the monomer in the reaction vessel is purged, the temperature is returned to room temperature, and the reaction is terminated.

[0122] Examples of the polymerization initiator include radical polymerization initiators. 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 oil-soluble polymerization initiators, water-soluble polymerization initiators, etc. can be used, but water-soluble polymerization initiators are preferred. Further, the polymerization initiator may be used as a redox initiator in combination with a reducing agent or the like.

[0123] The amount of the polymerization initiator when polymerizing the fluorine-containing monomer is appropriately determined according to the type of the monomer, the molecular weight of the target fluorine-containing elastomer, and the reaction rate. The amount of the polymerization initiator is appropriately determined according to the molecular weight of the target fluorine-containing elastomer and the polymerization reaction rate, but 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 the monomer.

[0124] As the polymerization initiator, an oil-soluble radical polymerization initiator, a water-soluble radical polymerization initiator, or an azo compound can be used.

[0125] The oil-soluble radical polymerization initiator may be a known oil-soluble peroxide. For example, dialkyl peroxydicarbonates such as diisopropyl peroxydicarbonate and di-sec-butyl peroxydicarbonate, peroxy esters such as t-butyl peroxyisobutyrate and t-butyl peroxypivalate, dialkyl peroxides such as di-t-butyl peroxide, etc. Also, di(ω-hydroxy-dodecafluorooctanoyl) peroxide, di(ω-hydroxy-tetradecafluorononanoyl) peroxide, di(ω-hydroxy-hexadecafluorodecanoyl) peroxide, di(perfluorobutyryl) peroxide, di(perfluorovaleryl) peroxide, di(perfluorohexanoyl) peroxide, di(perfluoroheptanoyl) peroxide, di(perfluorooctanoyl) peroxide, di(perfluorononanoyl) peroxide, di(ω-chloro-hexafluorobutyryl) peroxide, di(ω-chloro-decafluorohexanoyl) peroxide, di(ω-chloro-tetradecafluorononanoyl) peroxide, ω-hydroxy-dodecafluorooctanoyl-ω-hydroxy-hexadecafluorodecanoyl-peroxide, ω-chloro-hexafluorobutyryl-ω-chloro-decafluorohexanoyl-peroxide, ω-hydroxy-dodecafluorooctanoyl-perfluorobutyryl-peroxide, di(dichloropentafluorobutanoyl) peroxide, di(trichlorooctafluorononanoyl) peroxide, di(tetrachloroundecafluorodecanoyl) peroxide, di(pentachlorotetradecafluorododecanoyl) peroxide, di(undecachlorodotriacontapentafluorotricosanyl) peroxide, etc. are typical examples of di[perfluoro(or fluorochloro)acyl] peroxides.

[0126] Examples of the azo compound include azodicarboxylate, azodicarboxyldiamide, 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and 4,4'-azobis(4-cyanovaleric acid).

[0127] The water-soluble radical polymerization initiator may be a known water-soluble peroxide. For example, ammonium salts, potassium salts, sodium salts of persulfuric acid, perboric acid, perchloric acid, phosphoric acid, percarbonic acid, etc., organic peroxides such as disuccinic peroxide, diglutaric peroxide, t-butyl permaleate, t-butyl hydroperoxide, etc. may be mentioned. Reducing agents such as sulfites may also be included, and the amount used may be 0.1 to 20 times that of the peroxide.

[0128] As the water-soluble peroxide, since it is easy to adjust the amount of generated radicals, salts of persulfuric acid are preferred, potassium persulfate (K2S2O8), ammonium persulfate ((NH4)2S2O8), sodium persulfate (Na2S2O8) are preferred, and ammonium persulfate is most preferred.

[0129] When the polymerization temperature is 45 °C or higher and the polymerization is carried out using a water-soluble peroxide, it is preferable to carry out the polymerization without using a reducing agent.

[0130] For example, when carrying out the polymerization at a low temperature of 60 °C or lower, etc., it is preferable to use a redox initiator that combines an oxidizing agent and a reducing agent as the polymerization initiator. That is, the above polymerization is preferably carried out in the presence of a redox initiator.

[0131] Examples of the oxidizing agent include persulfates, organic peroxides, potassium permanganate, manganese triacetate, ammonium cerium nitrate, bromates, etc. Examples of the reducing agent include sulfites, bisulfites, bromates, diimines, oxalic acid, metal sulfinates, etc. Examples of the persulfate include ammonium persulfate, potassium persulfate, and sodium persulfate. Examples of the sulfite 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 and 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. When using a copper salt and an iron salt, it is particularly preferable to add a chelating agent. As the chelating agent, disodium ethylenediaminetetraacetate dihydrate is preferable.

[0132] Examples of the redox initiator include, for example, 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, ammonium cerium nitrate / oxalic acid, bromate / sulfite, bromate / bisulfite, ammonium persulfate / sodium hydroxymethanesulfinate dihydrate, etc., and ammonium persulfate / sodium hydroxymethanesulfinate dihydrate is preferable.

[0133] When using a redox initiator, either the oxidizing agent or the reducing agent may be charged into the polymerization tank in advance, and then the other may be added continuously or intermittently to initiate the polymerization. For example, when using ammonium persulfate / sodium hydroxymethanesulfinate dihydrate, it is preferable to charge ammonium persulfate into the polymerization tank and continuously add sodium hydroxymethanesulfinate dihydrate thereto.

[0134] The amount of the persulfate used in the redox initiator is preferably 0.001 to 2.0% by mass, more preferably 0.01 to 1.5% by mass, and particularly preferably 0.05 to 1.0% by mass based on the aqueous medium used for the polymerization.

[0135] The amount of the reducing agent used is preferably 1 to 30% by mass, more preferably 3 to 25% by mass, and particularly preferably 5 to 20% by mass based on the aqueous medium used for the polymerization.

[0136] Also, the amount of the third component (such as the copper salt and iron salt) used is preferably 0.001 to 0.5% by mass, more preferably 0.005 to 0.4% by mass, and particularly preferably 0.01 to 0.3% by mass based on the aqueous medium used for the polymerization.

[0137] 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, known ones can be used. For example, hydrocarbons, esters, ethers, alcohols, ketones, halogen-containing compounds, carbonates, etc. can be used. Among them, isopentane, diethyl malonate, and ethyl acetate are preferable from the viewpoint that the reaction rate is less likely to decrease, and diiodine compounds such as I(CF2)4I, I(CF2)6I, and ICH2I are preferable from the viewpoint that iodination of the polymer terminal is possible and it can be used as a reactive polymer.

[0138] Particularly, it is preferable to use a bromine compound or an iodine compound as the chain transfer agent. Examples of the polymerization method using a bromine compound or an iodine compound include iodine transfer polymerization or bromine transfer polymerization.

[0139] Iodine compounds and bromine compounds are water-insoluble and difficult to emulsify. Therefore, there has been a tendency to have limitations in emulsion polymerization originally and to use a large amount of surfactant. According to the production method of the present disclosure, it has become 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 the surfactant conventionally used.

[0140] Iodine transfer polymerization is a method that utilizes living radical polymerization by a radical chain reactivation mechanism, which occurs due to the involvement of a chain transfer reaction during a radical polymerization reaction because the dissociation energy of the carbon-iodine bond is low and it is radically active. Regarding the reaction conditions, known conditions can be appropriately used and are not particularly limited. For example, the conditions described in "Polymer Journal, Vol. 49, No. 10, pp. 765-783, October 1992" and Japanese Patent Laid-Open No. 53-3495 can be appropriately adopted. Similar polymerization can be carried out using a bromine compound instead of an iodine compound. In the present disclosure, such polymerization is referred to as bromine transfer polymerization.

[0141] Among these, iodine transfer polymerization is preferred from the viewpoints of polymerization reactivity, crosslinking reactivity, and the like.

[0142] Typical examples of the bromine compound or iodine compound include, for example, the general formula: R 8 I x Br y (In the formula, x and y are each an integer from 0 to 2, and satisfy 1 ≦ x + y ≦ 2, and 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, and may contain an oxygen atom). By using a bromine compound or iodine compound, iodine or bromine is introduced into the polymer and functions as a crosslinking point.

[0143] 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-diiodoperfluorhexane, 1,8-diiodoperfluorooctane, 1,12-diiodoperfluorododecane, 1,16-diiodoperfluorohexadecane, diiodomethane, 1,2-diiodoethane, 1,3-diiodo-n-propane, CF2Br2, BrCF2CF2Br, CF3CFBrCF2Br, CFClBr2, BrCF2CFClBr, CFBrClCFClBr, BrCF2CF2CF2Br, BrCF2CFBrOCF3, 1-bromo-2-iodoperfluoroethane, 1-bromo-3-iodoperfluoropropane, 1-bromo-4-iodoperfluorobutane, 2-bromo-3-iodoperfluorobutane, 3-bromo-4-iodoperfluorobuten-1, 2-bromo-4-iodoperfluorobuten-1, monoiodomonobromo-substituted benzene, diiodomonobromo-substituted benzene, and (2-iodoethyl) and (2-bromoethyl) substituents. These compounds may be used alone or in combination with each other. Among these, from the viewpoints of polymerization reactivity, crosslinking reactivity, availability, etc., compounds containing only iodine and no bromine are preferable, and it is preferable to use 1,4-diiodoperfluorobutane, 1,6-diiodoperfluorohexane, or 2-iodoperfluoropropane.

[0144] The amount of the chain transfer agent is preferably 0.2×10 -3 ~2 mol%, more preferably 1.0×10 -3 ~1 mol% based on the total amount of the monomers used in the polymerization.

[0145] An 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 alcohol, ether, ketone, etc., and / or a fluorine-containing organic solvent having a boiling point of 40 °C or lower.

[0146] In the polymerization of the fluorine-containing monomer, phosphates, sodium hydroxide, potassium hydroxide, aqueous ammonia, etc. may be used as the pH adjuster.

[0147] The aqueous medium is preferably acidic. By using an acidic aqueous medium and polymerizing the fluorine-containing monomer in the presence of the fluorine-containing allyl ether (1) and the fluorine-containing vinyl ether (2), 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.

[0148] In the production method of the present disclosure, the fluorine-containing monomer may be polymerized in the presence or absence of the fluorine-containing monomer polymerization seed particles.

[0149] The above-mentioned "fluorine-containing monomer polymerization seed particles" are obtained by polymerizing the fluorine-containing monomer in an aqueous medium, and are present during the second polymerization in which the types and proportions of components such as monomers and additives (for example, polymerization initiators, etc.) constituting the polymerization reaction system and the reaction conditions are different. The fluorine-containing monomer polymerization seed particles act as so-called seed particles during the polymerization of the fluorine-containing monomer and constitute the polymerization of the fluorine-containing monomer in the presence of the seed particles, so-called seed polymerization. In the production method of the present disclosure, such seed polymerization may not be performed when polymerizing the fluorine-containing monomer.

[0150] 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. Further, 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 even more preferably 20 to 50°C. Further, as the polymerization temperature, since a high polymerization rate can be achieved and a fluorine-containing elastomer that gives a molded article having excellent physical properties can be obtained, 60 to 120°C is preferable, 60 to 100°C is more preferable, and 70 to 90°C is even more preferable.

[0151] In the production method of the present disclosure, the polymerization pressure for polymerizing the fluorine-containing monomer is preferably 0.5 to 10 MPaG, more preferably 1 to 7 MPaG.

[0152] Since the production method of the present disclosure polymerizes the fluorine-containing monomer in the presence of the fluorine-containing allyl ether (1), the fluorine-containing vinyl ether (2) and the aqueous medium, it is possible to suppress the adhesion of the polymer (fluorine-containing elastomer) to the polymerization tank. The polymer adhesion rate to the polymerization tank is preferably 8% by mass or less, more preferably 4% by mass or less, even more preferably 3% by mass or less, and most preferably 2% by mass or less.

[0153] The polymer adhesion rate is the ratio (adhesion rate to the polymerization tank) of the mass of the polymer deposit adhering to the polymerization tank after the completion of polymerization to the total amount of the polymer (fluorine-containing elastomer) after the completion of polymerization. The polymer deposit includes the polymer adhering to the inside of the polymerization tank such as the inner wall of the polymerization tank and the stirring blade after the aqueous dispersion is withdrawn from the polymerization tank after the completion of polymerization, and the polymer that is released from the aqueous dispersion by aggregation and floats or precipitates without being dispersed in the aqueous dispersion. The mass of the polymer deposit is the mass after drying and removing the moisture contained in the polymer deposit at 120°C. Polymer adhesion rate (% by mass) = mass of polymer deposit / mass of obtained polymer (including deposit) × 100 Mass of obtained polymer = mass of aqueous dispersion × solid content concentration of aqueous dispersion (% by mass) / 100 + mass of polymer deposit

[0154] 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 fluorine-containing allyl ether (1) and fluorine-containing vinyl ether (2)), and more preferably does not contain a hydrophilic group.

[0155] Examples of the fluorine-containing monomer 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, general formula (2): CHX 1 =CX 2 Rf (2) (wherein X 1 and X 2 are such that one is H and the other is F, and Rf is a linear or branched fluoroalkyl group having 1 to 12 carbon atoms), and fluorine-containing monomers such as the fluorine-containing monomer (2) represented thereby are exemplified.

[0156] As PAVE, perfluoro(methyl vinyl ether) (PMVE), perfluoro(ethyl vinyl ether) (PEVE), and perfluoro(propyl vinyl ether) (PPVE) are more preferable, and particularly PMVE is preferable.

[0157] Also, as PAVE, the formula: CF2=CFOCF2ORf c (wherein Rf cIt is also possible to use a perfluorovinyl ether represented by (a linear or branched perfluoroalkyl group having 1 to 6 carbon atoms, a cyclic perfluoroalkyl group having 5 to 6 carbon atoms, or a linear or branched perfluorooxyalkyl group having 2 to 6 carbon atoms containing 1 to 3 oxygen atoms). As the PAVE, for example, CF2=CFOCF2OCF3, CF2=CFOCF2OCF2CF3 or CF2=CFOCF2OCF2CF2OCF3 is preferable.

[0158] 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. The number of carbon atoms of Rf is preferably 1 to 6.

[0159] 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 isomer), CHF=CHCF3 (Z isomer), etc. Among them, 2,3,3,3-tetrafluoropropylene represented by CH2=CFCF3 is preferable.

[0160] In the production method of the present disclosure, since the adhesion of the fluorine-containing elastomer to the polymerization tank can be further suppressed, 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.

[0161] In the production method of the present disclosure, a fluorine-free monomer may be polymerized together with a 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; alkyl vinyl ethers having 1 to 20 carbon atoms in the alkyl group such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, and butyl vinyl ether. One or more of these monomers or compounds can be used in combination.

[0162] 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-. For example, fluorine-containing elastomers containing structures such as -CH2-CF2-, -CH2-CH(CH3)-, -CH2-CH2-, and -CH2-CF2-(CF3)- can be mentioned. These 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 with respect to all monomer units of the fluorine-containing elastomer) may be less than 40 mol%.

[0163] As the fluorine-containing elastomer, a partially fluorinated elastomer is preferred because it can generate more fluorine-containing elastomer particles and can further suppress the adhesion of the fluorine-containing elastomer to the polymerization tank. A partially fluorinated elastomer is a fluoropolymer containing fluorine-containing monomer units and having a content of perfluoromonomer units of less than 90 mol% with respect to all monomer units, having a glass transition temperature of 20°C or lower, and having a melting peak (ΔH) size of 4.5 J / g or less.

[0164] Examples of the fluorine-containing elastomer include tetrafluoroethylene (TFE), vinylidene fluoride (VdF), and the general formula: CF2=CF-Rf a (wherein, Rf a is -CF3 or -ORf b (Rf b is a perfluoroethylene unsaturated compound represented by a perfluoroalkyl group having 1 to 5 carbon atoms (e.g., hexafluoropropylene (HFP), perfluoro(alkyl vinyl ether) (PAVE), etc.)) and preferably contains monomer units based on at least one monomer selected from the group consisting of. The fluorine-containing elastomer preferably contains a VdF unit or a TFE unit, and more preferably contains a VDF unit.

[0165] More specifically, 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, and the like. Among these, VdF-based fluorine-containing elastomers, TFE / Pr-based fluorine-containing elastomers, TFE / Pr / VdF-based fluorine-containing elastomers, or Et / TFE / PAVE-based fluorine-containing elastomers are more suitable in terms of good heat aging resistance and oil resistance.

[0166] VdF-based fluorine-containing elastomers are fluorine-containing elastomers having VdF units. The content of VdF units in the fluorine-containing elastomer is preferably 20 mol% or more, more preferably 40 mol% or more, still more preferably 50 mol% or more, and particularly preferably 60 mol% or more based on all monomer units. In the VdF-based fluorine-containing elastomer, the VdF units are preferably 20 mol% or more and 90 mol% or less, more preferably 40 mol% or more and 85 mol% or less, still more preferably 45 mol% or more and 80 mol% or less, and particularly preferably 50 mol% or more and 80 mol% or less of the total number of moles of the VdF units and the monomer units based on the VdF units and other monomers.

[0167] As other monomers in the VdF-based fluorine-containing elastomer, there is no particular limitation as long as they are monomers copolymerizable with VdF. For example, the above-mentioned fluorine-containing monomers can be used.

[0168] As the VdF-based fluorine-containing elastomer, 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 copolymer of VdF / fluorine-containing monomer (2) is preferred. Further, it is more preferred that it has at least one monomer selected from the group consisting of TFE, HFP, and PAVE as monomers other than VdF.

[0169] Among these, as the VdF-based fluorine-containing elastomers, at least one copolymer selected from the group consisting of VdF / HFP copolymers, VdF / TFE / HFP copolymers, copolymers of VdF and a fluorine-containing monomer (2), VdF / PAVE copolymers, VdF / TFE / PAVE copolymers, VdF / HFP / PAVE copolymers, and VdF / HFP / TFE / PAVE copolymers is preferred, and at least one copolymer selected from the group consisting of VdF / HFP copolymers, VdF / HFP / TFE copolymers, copolymers of VdF and a fluorine-containing monomer (2), and VdF / PAVE copolymers is more preferred.

[0170] As the VdF / PAVE copolymer, those having a VdF / PAVE composition of (65 to 90) / (35 to 10) (mol%) are preferred. Also, a form in which the VdF / PAVE composition is (50 to 78) / (50 to 22) (mol%) is also a preferred form.

[0171] As the VdF / TFE / PAVE copolymer, those having a VdF / TFE / PAVE composition of (40 to 80) / (3 to 40) / (15 to 35) (mol%) are preferred.

[0172] As the VdF / HFP / PAVE copolymer, those having a VdF / HFP / PAVE composition of (65 to 90) / (3 to 25) / (3 to 25) (mol%) are preferred.

[0173] As the VdF / HFP / TFE / PAVE copolymer, those having a VdF / HFP / TFE / PAVE composition of (40 to 90) / (0 to 25) / (0 to 40) / (3 to 35) (mol%) are preferred, and those having a composition of (40 to 80) / (3 to 25) / (3 to 40) / (3 to 25) (mol%) are more preferred.

[0174] As the copolymer of VdF / fluorine-containing monomer (2), the VdF / fluorine-containing monomer (2) units are (85 to 20) / (15 to 80) (mol%), and the other monomer units other than VdF and the fluorine-containing monomer (2) are preferably 0 to 50 mol% of the total monomer units, and the molar% ratio of the VdF / fluorine-containing monomer (2) units is more preferably (80 to 20) / (20 to 80). Further, the composition of the VdF / fluorine-containing monomer (2) units being (78 to 50) / (22 to 50) (mol%) is also one of the preferred forms.

[0175] Also, as the copolymer of VdF / fluorine-containing monomer (2), those in which the VdF / fluorine-containing monomer (2) units are (85 to 50) / (15 to 50) (mol%) and the other monomer units other than VdF and the fluorine-containing monomer (2) are 1 to 50 mol% of the total monomer units are also preferred. As the other monomers other than VdF and the fluorine-containing monomer (2), the monomers exemplified as the 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 giving crosslinkable groups are preferred, and among them, PMVE, CTFE, HFP, and TFE are more preferred.

[0176] The TFE / Pr-based fluorine-containing elastomer refers to a fluorine-containing copolymer composed of 45 to 70 mol% of TFE and 55 to 30 mol% of Pr. In addition to these two components, a specific third component may be included.

[0177] Examples of the specific third component include fluorine-containing olefins other than TFE (e.g., VdF, HFP, CTFE, perfluoro(butylethylene), etc.), fluorine-containing vinyl ethers (perfluoro(propyl vinyl ether), perfluoro(methyl vinyl ether), etc.) and other fluorine-containing monomers; hydrocarbon monomers such as α-olefins (ethylene, 1-butene, etc.), vinyl ethers (ethyl vinyl ether, butyl vinyl ether, hydroxybutyl vinyl ether, etc.), vinyl esters (vinyl acetate, vinyl benzoate, vinyl crotonate, vinyl methacrylate, etc.); etc. The above specific third component may be one kind or a combination of two or more kinds.

[0178] The TFE / Pr-based fluorine-containing elastomer preferably contains VdF. Among the TFE / Pr-based fluorine-containing elastomers, an elastomer composed of TFE, Pr, and VdF is referred to as a TFE / Pr / VdF-based fluorine-containing elastomer.

[0179] The TFE / Pr / VdF-based fluorine-containing elastomer may further contain the above specific third component other than VdF. The above specific third component may be one kind or a combination of two or more kinds. In the TFE / Pr-based fluorine-containing elastomer, the total content of the third component is preferably 35 mol% or less, more preferably 33 mol% or less, and still more preferably 31 mol% or less.

[0180] As for the Et / HFP copolymer, those having a composition of Et / HFP of (35 - 80) / (65 - 20) (mol%) are preferred, and those having a composition of (40 - 75) / (60 - 25) (mol%) are more preferred.

[0181] As for the Et / HFP / TFE copolymer, those having a composition of Et / HFP / TFE of (35 - 75) / (25 - 50) / (0 - 15) (mol%) are preferred, and those having a composition of (45 - 75) / (25 - 45) / (0 - 10) (mol%) are more preferred.

[0182] The Et / TFE / PAVE copolymer preferably has a composition of Et / TFE / PAVE of (10 to 40) / (32 to 60) / (20 to 40) (mol %), more preferably (20 to 40) / (40 to 50) / (20 to 30) (mol %). PMVE is preferred as PAVE.

[0183] As the fluorine-containing elastomer, a fluorine-containing elastomer containing VdF units is preferred, a VdF / HFP copolymer or a VdF / HFP / TFE copolymer is more preferred, and those having a composition of VdF / HFP / TFE of (32 to 85) / (10 to 34) / (0 to 40) (mol %) are particularly preferred. As the composition of VdF / HFP / TFE, (32 to 85) / (15 to 34) / (0 to 34) (mol %) is more preferred, and (47 to 81) / (17 to 32) / (0 to 26) (mol %) is even more preferred.

[0184] For example, in the above VdF / HFP copolymer, the composition of VdF / HFP 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 %).

[0185] The above-described configuration is the configuration of the main monomer of the fluorine-containing elastomer. In addition to the main monomer, a monomer that provides a crosslinkable group may be copolymerized. As the monomer that provides a crosslinkable group, any monomer that can introduce an appropriate crosslinkable group into the fluorine-containing elastomer according to the production method and the crosslinking system may be used. For example, known polymerizable compounds containing crosslinkable groups such as iodine atoms, bromine atoms, carbon-carbon double bonds, cyano groups, carboxyl groups, hydroxyl groups, amino groups, and ester groups can be mentioned.

[0186] Preferred monomers that provide a crosslinkable group are represented by the general formula (3): CY 1 2=CY 2 R f 2 X 1 (3) (In the formula, Y1 and Y 2 is a fluorine atom, a hydrogen atom or -CH3; R f 2 may have one or more ether-bonding oxygen atoms, may have an aromatic ring, and is a linear or branched fluorine-containing alkylene group in which part or all of the hydrogen atoms are substituted with fluorine atoms; X 1 is an iodine atom or a bromine atom) Examples thereof include compounds represented by

[0187] Specific examples of the monomer that provides a crosslinkable group include, for example, general formula (4): CY 1 2=CY 2 R f 3 CHR 1 -X 1 (4) (In the formula, Y 1 and Y 2 and X 1 are the same as described above, and R f 3 may have one or more ether-bonding oxygen atoms and is a linear or branched fluorine-containing alkylene group in which part or all of the hydrogen atoms are substituted with fluorine atoms, that is, a linear or branched fluorine-containing alkylene group in which part or all of the hydrogen atoms are substituted with fluorine atoms, a linear or branched fluorine-containing oxyalkylene group in which part or all of the hydrogen atoms are substituted with fluorine atoms, or a linear or branched fluorine-containing polyoxyalkylene group in which part or all of the hydrogen atoms are substituted with fluorine atoms; R 1 is a hydrogen atom or a methyl group) iodine- or bromine-containing monomers represented by CY 4 2=CY 4 (CF2) n -X 1 (5) (In the formula, Y 4 is the same or different and is a hydrogen atom or a fluorine atom, and n is an integer of 1 to 8) CF2=CFCF2R f 4 -X 1 (6) (wherein, R 4 is -(OCF2) n - or -(OCF(CF3)) n - and n is an integer from 0 to 5) CF2=CFCF2(OCF(CF3)CF2) m (OCH2CF2CF2) n OCH2CF2-X 1 (7) (wherein, m is an integer from 0 to 5 and n is an integer from 0 to 5) CF2=CFCF2(OCH2CF2CF2) m (OCF(CF3)CF2) n OCF(CF3)-X 1 (8) (wherein, m is an integer from 0 to 5 and n is an integer from 0 to 5) CF2=CF(OCF2CF(CF3)) m O(CF2) n -X 1 (9) (wherein, m is an integer from 0 to 5 and n is an integer from 1 to 8) CF2=CF(OCF2CF(CF3)) m -X 1 (10) (wherein, m is an integer from 1 to 5) CF2=CFOCF2(CF(CF3)OCF2) n CF(-X 1 )CF3(11) (wherein, n is an integer from 1 to 4) CF2=CFO(CF2) n OCF(CF3)-X 1 (12) (wherein, n is an integer from 2 to 5) CF2=CFO(CF2) n -(C6H4)-X 1 (13) (wherein, n is an integer from 1 to 6) CF2=CF(OCF2CF(CF3)) n OCF2CF(CF3)-X 1 (14) (wherein, n is an integer from 1 to 2) CH2=CFCF2O(CF(CF3)CF2O) nCF(CF3)-X 1 (15) (wherein n is an integer from 0 to 5), CF2=CFO(CF2CF(CF3)O) m (CF2) n -X 1 (16) (wherein m is an integer from 0 to 5 and n is an integer from 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 (21) CH2=CH-(CF2) n X 1 (22) (wherein n is an integer from 2 to 8) (In general formulas (5) to (22), X 1 is the same as described above) Examples include iodine- or bromine-containing monomers represented by these, and these can be used alone or in any combination.

[0188] As the iodine- or bromine-containing monomer represented by general formula (4), general formula (23):

Chemical formula

Chemical formula

[0189] More specifically, as the iodine- or bromine-containing monomer represented by the general formula (5), ICF2CF2CF=CH2 and I(CF2CF2)2CF=CH2 are preferably mentioned.

[0190] More specifically, as the iodine- or bromine-containing monomer represented by the general formula (9), I(CF2CF2)2OCF=CF2 is preferably mentioned.

[0191] More specifically, as the iodine- or bromine-containing monomer represented by the general formula (22), CH2=CHCF2CF2I and I(CF2CF2)2CH=CH2 are preferably mentioned.

[0192] 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 are each 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 the bisolefin compound represented by this formula is also preferred as a monomer giving a crosslinkable group. In the present disclosure, the "(per)fluoropolyoxyalkylene group" means a "fluoropolyoxyalkylene group or a perfluoropolyoxyalkylene group".

[0193] 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 are preferably hydrogen atoms.

[0194] 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 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 1000 to 4000. ) is preferably a (per)fluoropolyoxyalkylene group represented by. In this formula, Q is preferably selected from -CH2OCH2- and -CH2O(CH2CH2O) s CH2-(s = 1 to 3).

[0195] Preferred bisolefins 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 (wherein Z 1 is -CH2OCH2-CF2O-(CF2CF2O) m -(CF2O) n -CF2-CH2OCH2-(m / n is 0.5, and the molecular weight is preferably 2000) and the like.

[0196] Among them, 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.

[0197] 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.

[0198] The fluorine-containing elastomer preferably has a fluorine content of 50% by mass or more, more preferably 55% by mass or more, and still 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 calculated based on the measured values by F-NMR and 1 H-NMR, elemental analysis, etc.

[0199] The fluorine-containing elastomer preferably has a Mooney viscosity (ML1+10(100°C)) at 100°C of 130 or less. The above Mooney viscosity is more preferably 110 or less, and still more preferably 90 or less. Also, the above Mooney viscosity is more preferably 10 or more, and still more preferably 20 or more. Here, the Mooney viscosity is a value measured in accordance with JIS K 6300-1.2013.

[0200] The fluorine-containing elastomer preferably has a glass transition temperature of -50 to 0°C. The above glass transition temperature is more preferably -2°C or lower, and still more preferably -3°C or lower. Also, the above glass transition temperature is more preferably -45°C or higher, and still more preferably -40°C or higher. The above glass transition temperature may be -10°C or higher, or may be -9°C or higher. Here, the glass transition temperature can be obtained by using a differential scanning calorimeter (for example, X-DSC7000 manufactured by Hitachi High-Tech Science Corporation), obtaining a DSC curve by heating 10 mg of the sample at 20°C / min, and determining the glass transition temperature from the DSC differential curve in accordance with JISK6240:2011.

[0201] The fluorine-containing elastomer preferably has an iodine content of 0.05 to 1.0% by mass. The iodine content is more preferably 0.08% by mass or more, still more preferably 0.10% by mass or more, and more preferably 0.80% by mass or less, still more preferably 0.60% by mass or less.

[0202] The iodine content can be determined by elemental analysis. Specifically, 5 mg of Na2SO3 is mixed with 12 mg of the fluorine-containing elastomer, and an absorbent solution prepared by dissolving 30 mg of a mixture of Na2CO3 and K2CO3 in a 1:1 (mass ratio) in 20 ml of pure water is used. It is burned in oxygen in a quartz flask, left standing for 30 minutes, and then can be measured using a Shimadzu 20A ion chromatograph. As the calibration curve, a KI standard solution, one containing 0.5 ppm by mass of iodine ions, and one containing 1.0 ppm by mass of iodine ions can be used.

[0203] The fluorine-containing elastomer preferably contains a -CH2I structure. The inclusion of a -CH2I structure can be 1 confirmed by an H-NMR spectrum. The fluorine-containing elastomer containing a -CH2I structure can be obtained by iodine transfer polymerization.

[0204] In the fluorine-containing elastomer, the amount of the -CH2I structure relative to 100 mol% of the -CH2- structure is preferably 0.05 to 1.50 mol%. The amount of the -CH2I structure is more preferably 0.08 mol% or more, still more preferably 0.12 mol% or more, more preferably 1.20 mol% or less, still more preferably 1.00 mol% or less, and particularly preferably 0.80 mol% or less. The amount of the -CH2I structure can be 1 determined by an H-NMR spectrum.

[0205] 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.

[0206] The fluorine-containing elastomer preferably has an amount of -CF2CH2I structure of 0.05 to 1.50 mol% based on 100 mol% of the -CH2- structure. The amount of the -CF2CH2I structure is more preferably 0.08 mol% or more, still more preferably 0.12 mol% or more, more preferably 1.20 mol% or less, still more preferably 1.00 mol% or less, and particularly preferably 0.80 mol% or less. The amount of the -CF2CH2I structure is 1 calculated by A / B * 100, where A is the integrated value of the total peak intensities observed in the region of the chemical shift of 3.75 to 4.05 ppm derived from -CH2I and B is the integrated value of the total peak intensities observed in the regions of the chemical shifts of 2.3 to 2.7 ppm and 2.9 to 3.75 ppm derived from -CH2- in the 1H-NMR spectrum.

[0207] 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.

[0208] According to the production method of the present disclosure, an aqueous dispersion of a fluorine-containing elastomer can be obtained. The solid content concentration (content of the fluorine-containing elastomer) of the obtained aqueous dispersion of the fluorine-containing elastomer is preferably 10 to 50% by mass, more preferably 15 to 40% by mass, and still more preferably 20 to 30% by mass at the end of the polymerization.

[0209] The aqueous dispersion of the fluorine-containing elastomer may contain fluorine-containing elastomer particles. The average particle diameter of the fluorine-containing elastomer particles is preferably 10 to 800 nm, more preferably 50 to 500 nm, and still more preferably 70 to 300 nm. The average particle diameter of the fluorine-containing elastomer particles is the cumulative average diameter and can be measured by the dynamic light scattering method.

[0210] The number of fluorine-containing elastomer particles contained in the aqueous dispersion of the fluorine-containing elastomer is preferably 1.0×10 12 pieces / cc or more, more preferably 5.0×10 12 pieces / cc or more, still more preferably 1.0×1013 more than [X] particles / cc, particularly preferably 1.2×10 14 more than [X] particles / cc, most preferably 1.3×10 14 more than [X] particles / cc. The above particle number (number of polymer particles) can be calculated according to the following formula.

[0211]

Number

[0212] Treatment such as coagulation and heating may be performed on the aqueous dispersion of the fluorine-containing elastomer.

[0213] The above coagulation can be carried out by adding alkaline earth and earth metal salts to the aqueous dispersion. Examples of the alkaline earth and earth metal salts include sulfates, nitrates, hydrochlorides, acetates, etc. of calcium, magnesium, aluminum, etc.

[0214] 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. The drying temperature is preferably 40 to 200 °C, more preferably 60 to 180 °C, and still more preferably 80 to 150 °C.

[0215] The form of the fluorine-containing elastomer obtained after coagulation is not particularly limited and may be, for example, gum, crumb, powder, pellet, etc., and is preferably gum or crumb. Gum is a small granular lump composed of a fluorine-containing elastomer, and crumb is an amorphous lump formed as a result of the fluorine-containing elastomer not being able to maintain a small granular form as gum at room temperature and fusing with each other. Gum or crumb is preferably obtained by coagulating, drying, etc. from the aqueous dispersion obtained by the production method of the present disclosure by a conventionally known method.

[0216] A composition (crosslinkable composition) can be produced by adding a crosslinking agent or the like 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 can be used within a known range.

[0217] When the above fluorine-containing elastomer is an uncrosslinked elastomer, the crosslinking system includes, 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, the peroxide crosslinking system is preferable, and from the viewpoint of heat resistance, the polyol crosslinking system is preferable.

[0218] Therefore, as the above crosslinking agent, at least one crosslinking agent selected from the group consisting of a polyol crosslinking agent and a peroxide crosslinking agent is preferable, and a peroxide crosslinking agent is more preferable.

[0219] The compounding amount of the crosslinking agent may be appropriately selected depending on the type of the crosslinking agent, etc., but is preferably 0.2 to 6.0 parts by mass, more preferably 0.3 to 5.0 parts by mass, based on 100 parts by mass of the fluorine-containing elastomer.

[0220] Peroxide crosslinking can be carried out by using an uncrosslinked elastomer capable of peroxide crosslinking as the fluorine-containing elastomer and an organic peroxide as the crosslinking agent.

[0221] The peroxide-crosslinkable uncrosslinked elastomer is not particularly limited as long as it is an uncrosslinked elastomer having a peroxide-crosslinkable site. The peroxide-crosslinkable site is not particularly limited, and examples thereof include a site having an iodine atom and a site having a bromine atom.

[0222] The organic peroxide may be any organic peroxide that can easily generate peroxy radicals in the presence of heat or an oxidation-reduction system. Examples thereof include 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butyl peroxide, t-butyl cumyl 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-butyl peroxybenzene, t-butyl peroxymaleic acid, t-butyl peroxyisopropyl carbonate, t-butyl peroxybenzoate, and the like. Among these, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane and 2,5-dimethyl-2,5-di(t-butylperoxy)-hexyne-3 are preferred.

[0223] The compounding amount of the organic peroxide is preferably 0.1 to 15 parts by mass, more preferably 0.3 to 5 parts by mass, based on 100 parts by mass of the fluorine-containing elastomer.

[0224] When the crosslinking agent is an organic peroxide, it is preferable that the fluorine-containing elastomer composition further contains a crosslinking aid. Examples of the crosslinking aid include triallyl cyanurate, triallyl isocyanurate (TAIC), triacryl formal, triallyl trimellitate, N,N′-m-phenylene bismaleimide, dipropargyl terephthalate, diallyl phthalate, tetraallyl terephthalamide, triallyl phosphate, bismaleimide, fluorinated triallyl isocyanurate (1,3,5-tris(2,3,3-trifluoro-2-propenyl)-1,3,5-triazine-2,4,6-trione), tris(diallylamine)-S-triazine, N,N-diallyl acrylamide, 1,6-divinyldodecafluorohexane, hexaallyl phosphoramide, N,N,N′,N′-tetraallyl phthalamide, N,N,N′,N′-tetraallyl malonamide, trivinyl isocyanurate, 2,4,6-trivinylmethyltrisiloxane, tri(5-norbornene-2-methylene) cyanurate, triallyl phosphite, trimetaallyl isocyanurate, and the like. Among these, triallyl isocyanurate (TAIC) is preferable in terms of excellent crosslinkability, mechanical properties, and flexibility.

[0225] The compounding 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 still more preferably 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the fluorine-containing elastomer. When the crosslinking aid is less than 0.01 part by mass, the mechanical properties or flexibility may decrease. When it exceeds 10 parts by mass, the heat resistance is inferior, and the durability of the molded product also tends to decrease.

[0226] Polyol crosslinking can be carried out by using a polyol-crosslinkable uncrosslinked elastomer as a fluorine-containing elastomer and a polyhydroxy compound as a crosslinking agent. In the polyol crosslinking system, the compounding amount of the polyhydroxy compound is preferably 0.01 to 10 parts by mass with respect to 100 parts by mass of the polyol-crosslinkable uncrosslinked elastomer. When the compounding amount of the polyhydroxy compound is within such a range, polyol crosslinking can proceed sufficiently. More preferably, it is 0.02 to 8 parts by mass. Even more preferably, it is 0.03 to 4 parts by mass.

[0227] The above polyol-crosslinkable uncrosslinked elastomer is not particularly limited as long as it is an uncrosslinked elastomer having a polyol-crosslinkable site. The polyol-crosslinkable site is not particularly limited, and examples thereof include a site having a vinylidene fluoride (VdF) unit. Examples of the method for introducing the crosslinking site include a method of copolymerizing a monomer that gives a crosslinking site during the polymerization of the uncrosslinked elastomer.

[0228] As the polyhydroxy compound, a polyhydroxy aromatic compound is preferably used from the viewpoint of excellent heat resistance.

[0229] The polyhydroxy aromatic compound is not particularly limited. For example, 2,2-bis(4-hydroxyphenyl)propane (hereinafter referred to as bisphenol A), 2,2-bis(4-hydroxyphenyl)perfluoropropane (hereinafter referred to as bisphenol AF. Bisphenol AF can be obtained from, for example, Fujifilm Wako Pure Chemical Corporation, Central Glass Co., Ltd., etc.), 1,3-dihydroxybenzene, 1,7-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxystilbene, 2,6-dihydroxyanthracene, hydroquinone, catechol, 2,2-bis(4-hydroxyphenyl)butane (hereinafter referred to as bisphenol B), 4,4-bis(4-hydroxyphenyl)valeric acid, 2,2-bis(4-hydroxyphenyl)tetrafluorodichloropropane, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl ketone, tri(4-hydroxyphenyl)methane, 3,3',5,5'-tetrachlorobisphenol A, 3,3',5,5'-tetrabromobisphenol A, and the like can be mentioned. 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 compounding 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.

[0230] When the crosslinking agent is a polyhydroxy compound, the fluorine-containing elastomer composition preferably further contains a crosslinking accelerator. The crosslinking accelerator promotes the formation of intramolecular double bonds in the dehydrofluorination reaction of the polymer main chain and the addition of the polyhydroxy compound to the generated double bonds.

[0231] In addition, the crosslinking accelerator may be further used in combination with an acid acceptor such as magnesium oxide or a crosslinking aid.

[0232] Examples of the crosslinking accelerator include onium compounds. Among the onium compounds, it is preferably 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, and more preferably at least one selected from the group consisting of quaternary ammonium salts and quaternary phosphonium salts.

[0233] The quaternary ammonium salts are not particularly limited. For example, 8-methyl-1,8-diazabicyclo[5,4,0]-7-undecenium chloride, 8-methyl-1,8-diazabicyclo[5,4,0]-7-undecenium iodide, 8-methyl-1,8-diazabicyclo[5,4,0]-7-undecenium hydroxide, 8-methyl-1,8-diazabicyclo[5,4,0]-7-undecenium methyl sulfate, 8-ethyl-1,8-diazabicyclo[5,4,0]-7-undecenium bromide, 8-propyl-1,8-diazabicyclo[5,4,0]-7-undecenium bromide, 8-dodecyl-1,8-diazabicyclo[5,4,0]-7-undecenium chloride, 8-dodecyl-1,8-diazabicyclo[5,4,0]-7-undecenium hydroxide, 8-eicosyl-1,8-diazabicyclo[5,4,0]-7-undecenium chloride, 8-tetracosyl-1,8-diazabicyclo[5,4,0]-7-undecenium chloride, 8-benzyl-1,8-diazabicyclo[5,4,0]-7-undecenium chloride (hereinafter referred to as DBU-B. DBU-B can be obtained from, for example, Fujifilm Wako Pure Chemical Corporation, etc.), 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, tetrabutylammonium bromide, etc. Among these, DBU-B is preferable from the viewpoints of crosslinkability, mechanical properties, and flexibility.

[0234] The quaternary phosphonium salt is not particularly limited. For example, tetrabutylphosphonium chloride, benzyltriphenylphosphonium chloride (hereinafter referred to as BTPPC), benzyltrimethylphosphonium chloride, benzyltributylphosphonium chloride, tributylallylphosphonium chloride, tributyl-2-methoxypropylphosphonium chloride, benzylphenyl(dimethylamino)phosphonium chloride, etc. can be mentioned. Among these, benzyltriphenylphosphonium chloride (BTPPC) is preferable from the viewpoints of crosslinkability, mechanical properties, and flexibility.

[0235] 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.

[0236] The blending 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 still more preferably 0.03 to 3.00 parts by mass, based on 100 parts by mass of the uncrosslinked elastomer. If 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 resulting molded product may decrease. If it exceeds 8.00 parts by mass, the moldability of the fluorine-containing elastomer composition may decrease, the elongation in mechanical properties may decrease, and the flexibility may also tend to decrease.

[0237] The acid acceptor is used to neutralize the acidic substances generated during polyol crosslinking. Specific examples include magnesium oxide, calcium hydroxide (e.g., NICC5000 (manufactured by Inoue Lime Industry Co., Ltd.), CALDIC#2000, CALDIC#1000 (manufactured by Omi Chemical Industry Co., Ltd.)), calcium oxide, litharge, zinc white, dibasic lead phosphite, hydrotalcite, etc. It is preferably at least one selected from the group consisting of highly active magnesium oxide and low-activity magnesium.

[0238] 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.

[0239] The polyamine-crosslinkable fluorine-containing elastomer is not particularly limited as long as it is a fluorine-containing elastomer having a polyamine-crosslinkable site. The polyamine-crosslinkable site is not particularly limited, and examples thereof include a site having a vinylidene fluoride (VdF) unit. Examples of the method for introducing the crosslinking site include a method of copolymerizing a monomer that provides a crosslinking site during the polymerization of the fluorine-containing elastomer.

[0240] Examples of the polyamine compound include hexamethylenediamine carbamate, N,N'-dicinamylidene-1,6-hexamethylenediamine, 4,4'-bis(aminocyclohexyl)methane carbamate, etc. Among these, N,N'-dicinamylidene-1,6-hexamethylenediamine is preferred.

[0241] The method for obtaining a composition containing a crosslinking agent is not particularly limited as long as it can uniformly mix the fluorine-containing elastomer obtained by the production method of the present disclosure and the crosslinking agent. For example, a method of kneading a powder obtained by coagulating the fluorine-containing elastomer alone with other additives and compounding agents as needed using a kneader such as an open roll can be mentioned.

[0242] The present disclosure also relates to a fluorine-containing elastomer containing a methylene group in the main chain and further containing a monomer unit (1) based on a fluorine-containing allyl ether (1) and a monomer unit (2) based on a fluorine-containing vinyl ether (2). The fluorine-containing elastomer of the present disclosure can preferably be produced by the production method of the present disclosure.

[0243] The form of the composition of the present disclosure is not particularly limited and may be, for example, an aqueous dispersion, gum, clam, powder, pellet, etc. An aqueous dispersion is a dispersion system in which an aqueous medium is a dispersion medium and a fluorine-containing elastomer is a dispersed substance. The above aqueous medium is not particularly limited as long as it is a liquid containing water, and in addition to water, it may contain, for example, an organic solvent such as alcohol, ether, ketone, paraffin wax, etc.

[0244] A preferred configuration of the fluorine-containing elastomer is the same as the configuration of the fluorine-containing elastomer obtained by the production method of the present disclosure.

[0245] Preferred configurations of the fluorine-containing allyl ether (1) and the fluorine-containing vinyl ether (2) are the same as the configurations of the fluorine-containing allyl ether (1) and the fluorine-containing vinyl ether (2) used in the production method of the present disclosure.

[0246] The content of the monomer unit (1) based on the fluorine-containing allyl ether (1) in the fluorine-containing elastomer is preferably 0.0009 to 1.5% by mass, more preferably 0.0015% by mass or more, still more preferably 0.0030% by mass or more, particularly preferably 0.0060% by mass or more, most preferably 0.0090% by mass or more, more preferably 0.30% by mass or less, still more preferably 0.15% by mass or less, particularly preferably 0.09% by mass or less, and most preferably 0.06% by mass or less with respect to all monomer units. If the content of the monomer unit (1) based on the fluorine-containing allyl ether (1) is too large, there is a risk of impairing the properties required for the fluorine-containing elastomer.

[0247] The content of the monomer unit (2) based on the fluorine-containing vinyl ether (2) in the fluorine-containing elastomer is preferably 0.0009 to 1.5% by mass, more preferably 0.0015% by mass or more, still more preferably 0.0030% by mass or more, particularly preferably 0.0060% by mass or more, most preferably 0.0090% by mass or more, more preferably 0.30% by mass or less, still more preferably 0.15% by mass or less, particularly preferably 0.09% by mass or less, and most preferably 0.06% by mass or less, based on all the monomer units. If the content of the monomer unit (2) based on the fluorine-containing vinyl ether (2) is too large, there is a risk of impairing the properties required for the fluorine-containing elastomer.

[0248] The contents of the monomer unit (1) and the monomer unit (2) in the fluorine-containing elastomer can be calculated by appropriately combining NMR, FT-IR, elemental analysis, and X-ray fluorescence analysis according to the types of monomers.

[0249] In one embodiment of the fluorine-containing elastomer, the composition, and the aqueous dispersion described later of the present disclosure, a fluorine-containing surfactant (excluding the fluorine-containing allyl ether (1) and the fluorine-containing vinyl ether (2)) is contained. The fluorine-containing elastomer, composition, and aqueous dispersion containing the fluorine-containing surfactant have the advantage that they can be stably produced with high productivity using a fluorine-containing surfactant (excluding the fluorine-containing allyl ether (1) and the fluorine-containing vinyl ether (2)). As the fluorine-containing surfactant, a fluorine-containing surfactant (excluding the fluorine-containing allyl ether (1), the fluorine-containing vinyl ether (2), and the fluorine-containing compound represented by the general formula: X-(CF2) m2 -Y) is preferred, and examples thereof include those exemplified as the fluorine-containing surfactant that can be present during polymerization. As the fluorine-containing surfactant, a fluorine-containing surfactant (excluding the fluorine-containing allyl ether (1) and the fluorine-containing vinyl ether (2)) is more preferred. The aqueous dispersion does not necessarily contain a fluorine-containing compound represented by the general formula: X-(CF2) m2 -Y.

[0250] In one embodiment of the fluorine-containing elastomer, composition, and aqueous dispersion, it substantially does not contain a fluorine-containing surfactant (excluding the fluorine-containing allyl ether (1) and the fluorine-containing vinyl ether (2)). The fluorine-containing elastomer, composition, and aqueous dispersion substantially free of a fluorine-containing surfactant need to be produced by polymerizing a fluorine-containing monomer without using a fluorine-containing surfactant (excluding the fluorine-containing allyl ether (1) and the fluorine-containing vinyl ether (2)), but the production method of the fluorine-containing elastomer aqueous dispersion of the present disclosure using the fluorine-containing allyl ether (1) and the fluorine-containing vinyl ether (2) enables the production.

[0251] In the present disclosure, "substantially free of a fluorine-containing surfactant" means that the content of the fluorine-containing surfactant (excluding the fluorine-containing allyl ether (1) and the fluorine-containing vinyl ether (2)) in the fluorine-containing elastomer, composition, and aqueous dispersion is 10 mass ppm or less, preferably 1 mass ppm or less, more preferably 100 mass ppb or less, still more preferably 10 mass ppb or less, still more preferably 1 mass ppb or less, and particularly preferably, the fluorine-containing surfactant is below the detection limit by measurement using liquid chromatography-mass spectrometry (LC / MS).

[0252] The content of the fluorine-containing surfactant (excluding the fluorine-containing allyl ether (1) and the fluorine-containing vinyl ether (2)) can be quantified by a known method, for example, it can be quantified by LC / MS analysis. First, methanol is added to the fluorine-containing elastomer, composition, or aqueous dispersion for extraction, and the obtained extract is subjected to LC / MS analysis. In order to further improve the extraction efficiency, treatments such as Soxhlet extraction and ultrasonic treatment may be performed. Molecular weight information is extracted from the obtained LC / MS spectrum, and the match with the structural formula of the candidate fluorine-containing surfactant is confirmed. Thereafter, an aqueous solution with a content of the confirmed fluorosurfactant of 5 levels or more is prepared, LC / MS analysis of the aqueous solution of each content is performed, the relationship between the content and the area of the area corresponding to the content is plotted, and a calibration curve is drawn. Then, using the calibration curve, the area of the LC / MS chromatogram of the fluorosurfactant in the extract can be converted into the content of the fluorosurfactant.

[0253] The present disclosure also relates to a composition containing a fluorine-containing elastomer. The composition of the present disclosure may be an aqueous dispersion containing a fluorine-containing elastomer and an aqueous medium. The upper limit value of the solid content concentration of the aqueous dispersion is preferably 50% by mass, more preferably 40% by mass, still more preferably 35% by mass, and particularly preferably 30% by mass with respect to the aqueous dispersion. The lower limit value of the solid content concentration of the aqueous dispersion is preferably 5% by mass, more preferably 10% by mass, still more preferably 15% by mass, and particularly preferably 20% by mass. The solid content concentration of the aqueous dispersion can be adjusted by diluting or concentrating the aqueous dispersion obtained by polymerization.

[0254] The solid content concentration of the aqueous dispersion is the concentration of the solid content contained in the aqueous dispersion. Examples of the solid content include a fluorine-containing elastomer. Further, the solid content concentration of the aqueous dispersion may be the content of the fluorine-containing elastomer in the aqueous dispersion. The solid content concentration of the aqueous dispersion can be specified by drying 1 g of the aqueous dispersion under the conditions of 150 °C for 180 minutes, measuring the mass of the heat residue, and calculating the ratio of the mass of the heat residue to the mass of the aqueous dispersion.

[0255] The aqueous dispersion may further contain a crosslinking agent, a filler, etc. The preferred configuration of the crosslinking agent is the same as the configuration of the composition (crosslinkable composition) obtained by the production method of the present disclosure.

[0256] The aqueous dispersion can be made into a dispersion suitable for rubber molding processing by adding, concentrating, etc., a dispersion stabilizer such as a hydrocarbon surfactant as necessary. The dispersion is subjected to treatment such as pH adjustment, coagulation, heating, etc.

[0257] The compositions of the present disclosure may be condensates, gums, crumbs, powders, pellets, etc. obtained by condensing a fluorine-containing elastomer contained in an aqueous dispersion, and are preferably gums or crumbs. A gum is a small granular lump composed of a fluorine-containing elastomer, and a crumb is an amorphous lump formed as a result of the fluorine-containing elastomer not being able to maintain a small granular form as a gum at room temperature and fusing with each other. The gum or crumb is preferably obtained by condensing, drying, etc. from the aqueous dispersion obtained by the production method of the present disclosure by a conventionally known method.

[0258] The water content of the composition is not particularly limited, but is preferably 1% by mass or less, more preferably 0.1% by mass or less, and still more preferably 0.01% by mass or less with respect to the mass of the composition. The water content of the composition can be calculated, for example, by sufficiently drying the composition by heating it to 120°C or higher, measuring the weights of the composition before and after heating, and dividing the weight reduction amount by the weight before heating.

[0259] The composition can contain a crosslinking agent. A preferred configuration of the crosslinking agent is the same as that of the composition (crosslinkable composition) obtained by the production method of the present disclosure.

[0260] The 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 groups possessed by the polyfunctional compound, any functional group known to generally have reactivity, such as a carbonyl group, a carboxyl group, a halocarbonyl group, an amide group, an olefin group, an amino group, an isocyanate group, a hydroxy group, an epoxy group, etc. can be arbitrarily used.

[0261] The composition can be blended with ordinary additives that are optionally blended into the elastomer, such as fillers (carbon black, barium sulfate, etc.), processing aids (waxes, etc.), plasticizers, colorants, stabilizers, tackifiers (coumarone resins, coumarone-indene resins, etc.), mold release agents, conductivity imparting agents, heat conductivity imparting agents, surface non-sticking agents, flexibility imparting agents, heat resistance improvers, flame retardants, and other various additives, and one or more common crosslinking agents and crosslinking accelerators different from the above may be blended.

[0262] The content of fillers 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, still more preferably 2 to 100 parts by mass, and particularly preferably 2 to 75 parts by mass with respect to 100 parts by mass of the fluorine-containing elastomer.

[0263] The content of processing aids such as waxes is preferably 0 to 10 parts by mass, and more preferably 0 to 5 parts by mass with respect to 100 parts by mass of the fluorine-containing elastomer. When using processing aids, plasticizers, or mold release agents, the mechanical properties and sealing properties of the resulting molded product tend to decrease, so it is necessary to adjust the content of these within the range where the properties of the desired molded product are acceptable.

[0264] A molded product can be obtained by molding the composition. Also, a molded product can be obtained by molding and crosslinking the composition. The composition can be molded by a conventionally known method. The methods and conditions for molding and crosslinking 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 it may be crosslinked after molding, molded after crosslinking, or molding and crosslinking may be performed simultaneously.

[0265] Examples of the molding method include, but are not limited to, compression molding method, injection molding method, injection molding method, extrusion molding method, molding method by rotor cure, etc. Examples of the cross-linking method include steam cross-linking method, cross-linking method by heating, radiation cross-linking method, etc. Among them, steam cross-linking method and cross-linking method by heating are preferable. Specific cross-linking conditions that are not limited may be appropriately determined according to the types of cross-linking accelerator, cross-linking agent, acid acceptor, etc. usually within the temperature range of 140 to 250 °C and the cross-linking time of 1 minute to 24 hours.

[0266] In addition, by heating the obtained molded product with an oven or the like, mechanical properties and compression set characteristics at high temperature can be improved. Specific cross-linking conditions that are not limited may be appropriately determined according to the types of cross-linking accelerator, cross-linking agent, acid acceptor, etc. usually within the temperature range of 140 to 300 °C and the range of 30 minutes to 72 hours.

[0267] The obtained molded product can be used as various parts in fields such as the automotive industry, aircraft industry, semiconductor industry, etc. The molded product can be used for the same applications as, for example, cross-linked rubber molded products described in JP-A-2013-216915 and fluororubber molded bodies described in JP-A-2019-94430, such as sealing materials, sliding members, non-sticking members, etc.

[0268] Examples of the usage form of the molded product include various sealing materials and packings such as rings, packings, gaskets, diaphragms, oil seals, bearing seals, etc. As the sealing material, it can be used for applications that require excellent non-sticking properties and low friction properties. In particular, it can be suitably used for various sealing materials in the automotive industry, etc.

[0269] In addition, it can also be used as tubes, hoses, rolls, various rubber rolls, flexible joints, rubber sheets, coatings, belts, dampers, valves, valve sheets, valve bodies of valves, chemical-resistant coating materials, laminating materials, lining materials, etc.

[0270] Although the embodiments have been described above, it will be understood that various changes in form and detail can be made without departing from the spirit and scope of the claims.

Example

[0271] Next, embodiments of the present disclosure will be described with examples, but the present disclosure is not limited to such examples.

[0272] Each numerical value in the examples was measured by the following method.

[0273] <Mooney viscosity> The Mooney viscosity was measured at 100 °C in accordance with JIS K 6300-1.2013 using a Mooney viscometer model MV2000E manufactured by ALPHA TECHNOLOGIES.

[0274] <Composition of fluorine-containing elastomer> Determined by NMR analysis.

[0275] <Polymer adhesion rate> After polymerization, the ratio (adhesion rate to the polymerization tank) of the mass of the polymer deposit adhering to the polymerization tank to the total amount of the polymer (fluorine-containing elastomer) after polymerization was determined by the following formula. Polymer adhesion rate (mass%) = mass of polymer deposit / mass of obtained polymer (including polymer deposit) × 100 Mass of obtained polymer = mass of aqueous dispersion × solid content concentration of aqueous dispersion (mass%) / 100 + mass of polymer deposit The polymer deposit includes the polymer adhering to the inside of the polymerization tank such as the inner wall of the polymerization tank and the stirring blade, and the polymer that has been released from the aqueous dispersion by aggregation and is floating or precipitating without being dispersed in the aqueous dispersion. The mass of the polymer deposit is the mass after drying and removing the moisture contained in the polymer deposit at 120 °C.

[0276] <Solid content concentration of aqueous dispersion> 1 g of the aqueous dispersion was dried in a forced-air dryer at 150 °C for 180 minutes, the mass of the heat residue was measured, and the ratio (mass %) of the mass of the heat residue to the mass of the aqueous dispersion (1 g) was determined.

[0277] <Average particle size> The average particle size (cumulant average diameter) of the fluorine-containing elastomer particles in the aqueous dispersion was measured by the dynamic light scattering method using an ELSZ-1000S (manufactured by Otsuka Electronics Co., Ltd.) and calculated by the cumulant method.

[0278] <Number of fluorine-containing elastomer particles in the aqueous dispersion> It was calculated by the following formula.

[0279]

Equation

[0280] In the formula, the average particle size is the cumulant average diameter calculated by the method described above, the number of polymer particles (number of fluorine-containing elastomer particles) is the number per 1 cc of water, and the specific gravity of all the fluorine-containing elastomers in the examples and comparative examples was assumed to be 1.8.

[0281] Example 1 1500 g of deionized water, a 10 mass% aqueous solution of 0.75 g of CH2=CF-CF2OCF(CF3)COONH4, and a 7.22 mass% aqueous solution of 1.0394 g of CF2=CF-O-CF2CF2SO3Na were added to a 3 L SUS polymerization tank, the polymerization tank was sealed, and the inside of the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 80 °C, and while stirring, the monomer (initial monomer) was press-fitted 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 became 2.03 MPaG.

[0282] Subsequently, an aqueous solution of a polymerization initiator in which 0.030 g of ammonium persulfate (APS) was dissolved in deionized water was injected with nitrogen gas to initiate polymerization. As the polymerization proceeded, when the internal pressure dropped to 2.00 MPaG, a mixed monomer of VDF / TFE / HFP (= 50 / 20 / 30 mol%) was charged so that the internal pressure became constant at 2.03 MPaG.

[0283] When 10 g of the mixed monomer was added, 2.45 g of iodine compound I (CF2)4I2 was injected with nitrogen gas.

[0284] Three hours after the start of polymerization, an aqueous solution of a polymerization initiator of 0.030 g of APS was injected with nitrogen gas.

[0285] When 500 g of the mixed monomer was added, stirring was stopped and the polymerization tank was depressurized until the pressure reached atmospheric pressure. The polymerization tank was cooled to obtain an aqueous dispersion. The polymer adhesion rate, the solid content concentration of the aqueous dispersion, the mass of the aqueous dispersion, the average particle diameter, and the number of particles are shown in Table 1.

[0286] An aqueous solution of aluminum sulfate was added to the above aqueous dispersion for coagulation. The obtained coagulum was washed with water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1+10(100℃) = 52.7. When the copolymer composition was examined by NMR analysis, it was VDF / TFE / HFP = 50 / 20 / 30 (mol%).

[0287] Example 2 Polymerization was carried out in the same manner as in Example 1 except that the amount of deionized water was changed from 1500 g to 1496 g and the amount of an aqueous solution of CF2=CF-O-CF2CF2SO3Na was changed from 1.0394 g to 4.157 g.

[0288] When 500 g of the mixed monomer was added, stirring was stopped and the polymerization tank was depressurized until the pressure reached atmospheric pressure. The polymerization tank was cooled to obtain an aqueous dispersion. The polymer adhesion rate, the solid content concentration of the aqueous dispersion, the mass of the aqueous dispersion, the average particle diameter, and the number of particles are shown in Table 1.

[0289] An aqueous solution of aluminum sulfate was added to the above aqueous dispersion to cause coagulation. The obtained coagulum was washed with water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1+10(100°C)=59.3. When the copolymer composition was examined by NMR analysis, it was VDF / TFE / HFP = 50 / 20 / 30 (mol%).

[0290] Example 3 Polymerization was carried out in the same manner as in Example 1, except that a 10% by mass aqueous solution of 0.750 g of CF2=CFOCF2CF2COONH4 was added instead of the aqueous solution of CF2=CF-O-CF2CF2SO3Na.

[0291] When 500 g of the mixed monomer was further added, stirring was stopped and the pressure in the polymerization tank was reduced until it reached atmospheric pressure. The polymerization tank was cooled to obtain an aqueous dispersion. The polymer adhesion rate, the solid content concentration of the aqueous dispersion, the mass of the aqueous dispersion, the average particle diameter, and the number of particles are shown in Table 1.

[0292] An aqueous solution of aluminum sulfate was added to the above aqueous dispersion to cause coagulation. The obtained coagulum was washed with water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1+10(100°C)=58.8. When the copolymer composition was examined by NMR analysis, it was VDF / TFE / HFP = 50 / 20 / 30 (mol%).

[0293] Example 4 Polymerization was carried out in the same manner as in Example 1, except that a 10% by mass aqueous solution of 0.750 g of CF2=CFOCF2CF(CF3)OCF2CF2COONH4 was added instead of the aqueous solution of CF2=CF-O-CF2CF2SO3Na.

[0294] When 500 g of the mixed monomer was further added, stirring was stopped and the pressure in the polymerization tank was reduced until it reached atmospheric pressure. The polymerization tank was cooled to obtain an aqueous dispersion. The polymer adhesion rate, the solid content concentration of the aqueous dispersion, the mass of the aqueous dispersion, the average particle diameter, and the number of particles are shown in Table 1.

[0295] An aqueous solution of aluminum sulfate was added to the above aqueous dispersion for coagulation. The obtained coagulum was washed with water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1+10(100°C)=55.6. When the copolymer composition was examined by NMR analysis, it was VDF / TFE / HFP = 50 / 20 / 30 (mol%).

[0296] Comparative Example 1 Polymerization was carried out in the same manner as in Example 1, except that an aqueous solution of CH2=CF-CF2OCF(CF3)COONH4 was not added, and an aqueous solution of 0.030 g of APS as a polymerization initiator was injected with nitrogen gas at 6.0 hours after the start of polymerization.

[0297] When 500 g of the mixed monomer was added, stirring was stopped, and the pressure was released until the polymerization tank reached atmospheric pressure. The polymerization tank was cooled to obtain an aqueous dispersion. The polymer adhesion rate, the solid content concentration of the aqueous dispersion, the mass of the aqueous dispersion, the average particle diameter, and the number of particles are shown in Table 1.

[0298] An aqueous solution of aluminum sulfate was added to the above aqueous dispersion for coagulation. The obtained coagulum was washed with water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1+10(100°C)=43.9. When the copolymer composition was examined by NMR analysis, it was VDF / TFE / HFP = 50 / 20 / 30 (mol%).

[0299] Comparative Example 2 Polymerization was carried out in the same manner as in Example 1, except that an aqueous solution of CF2=CF-O-CF2CF2SO3Na was not added.

[0300] When 500 g of the mixed monomer was added, stirring was stopped, and the pressure was released until the polymerization tank reached atmospheric pressure. The polymerization tank was cooled to obtain an aqueous dispersion. The polymer adhesion rate, the solid content concentration of the aqueous dispersion, the mass of the aqueous dispersion, the average particle diameter, and the number of particles are shown in Table 1.

[0301] An aqueous aluminum sulfate solution was added to the above aqueous dispersion for coagulation. The obtained coagulum was washed with water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1+10(100℃)=53.1. When the copolymer composition was examined by NMR analysis, it was found to be VDF / TFE / HFP = 50 / 20 / 30 (mol%).

[0302]

Table 1

[0303] <Crosslinking characteristics> The fluorine-containing elastomer obtained above was kneaded with the formulation shown in Table 2 to obtain a fluorine-containing elastomer composition. For the obtained fluorine-containing elastomer composition, a crosslinking curve was determined using a rubber vulcanization tester MDRH2030 (manufactured by M & C Co., Ltd.) during press crosslinking, and the minimum viscosity (ML), maximum torque level (MH), induction time (T10), and optimum vulcanization time (T90) were determined. Also, a crosslinked molded product sheet was obtained by crosslinking the fluorine-containing elastomer composition by press crosslinking and oven crosslinking following the press crosslinking. Kneading method: Roll kneading Press crosslinking: 10 minutes at 160°C Oven crosslinking: 4 hours at 180°C

[0304] The materials shown in Table 2 are as follows. MT Carbon: Thermax N-990, manufactured by Cancarb TAIC: Triallyl isocyanurate, manufactured by Tic Japan Chemical Co., Ltd. Perhexa 25B: 2,5-Dimethyl-2,5-di(t-butylperoxy)hexane, manufactured by NOF Corporation

[0305] <Normal physical properties> Using the crosslinked molded product sheet, a test piece in the shape of dumbbell No. 6 was prepared according to JIS K6251, and the 100% modulus (M100), tensile strength at break (TB), and elongation at break (EB) of the prepared test piece in the normal state were measured.

[0306] <Hardness> In the same manner as above, a dumbbell No. 6-shaped test piece was prepared, and in accordance with JIS K6253, the hardness (Shore A) of the prepared test piece was measured (peak value, 1 sec, 3 sec).

[0307] <Compression set> Using the fluorine-containing elastomer composition, press crosslinking and oven crosslinking were carried out under the above conditions to produce an O-ring (P24 size), and in accordance with JIS K6262, the compression set of the produced O-ring was measured under the conditions of 200 °C, 72 hours, and a compression ratio of 25%.

[0308] The above results are shown in Table 2.

[0309]

Table 2

[0310] Example 5 1500 g of deionized water, 0.93 g of a 10% by mass aqueous solution of CH2=CF-CF2OCF(CF3)COONH4, and 3.00 g of a 10% by mass aqueous solution of CF2=CFOCF2CF2COONH4 were added to a SUS polymerization tank with an internal volume of 3 L. The polymerization tank was sealed, and the inside of the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 80 °C, and while stirring, a monomer (initial monomer) was press-fitted 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 became 1.47 MPaG.

[0311] Next, an aqueous polymerization initiator solution prepared by dissolving 0.0255 g of ammonium persulfate (APS) in deionized water was press-fitted with nitrogen gas to initiate polymerization. When the internal pressure dropped to 1.44 MPaG as the polymerization progressed, a mixed monomer of VDF / TFE / HFP (=50 / 20 / 30 mol%) was charged so that the internal pressure became constant at 1.47 MPaG.

[0312] When 15 g of the mixed monomer was added, 19 g of iodine compound I (CF2)4I2 was pressured in with nitrogen gas.

[0313] 3.0 hours after the start of polymerization, an aqueous solution of 0.0255 g of APS as a polymerization initiator was pressured in with nitrogen gas.

[0314] When 477 g of the mixed monomer was added, stirring was stopped and the pressure in the polymerization tank was released until it reached atmospheric pressure. The polymerization tank was cooled to obtain an aqueous dispersion. The polymer adhesion rate, the solid content concentration of the aqueous dispersion, the mass of the aqueous dispersion, the average particle diameter, and the number of particles are shown in Table 3.

[0315] An aqueous solution of aluminum sulfate was added to the above aqueous dispersion for coagulation. The obtained coagulum was washed with water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1+10(100°C)=64.8. When the copolymer composition was examined by NMR analysis, it was VDF / TFE / HFP = 50 / 20 / 30 (mol%).

[0316] Comparative Example 3 Polymerization was carried out in the same manner as in Example 5 except that an aqueous solution of CF2=CFOCF2CF2COONH4 was not added.

[0317] When 477 g of the mixed monomer was added, stirring was stopped and the pressure in the polymerization tank was released until it reached atmospheric pressure. The polymerization tank was cooled to obtain an aqueous dispersion. The polymer adhesion rate, the solid content concentration of the aqueous dispersion, the mass of the aqueous dispersion, the average particle diameter, and the number of particles are shown in Table 3.

[0318] An aqueous solution of aluminum sulfate was added to the above aqueous dispersion for coagulation. The obtained coagulum was washed with water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1+10(100°C)=66.7. When the copolymer composition was examined by NMR analysis, it was VDF / TFE / HFP = 50 / 20 / 30 (mol%).

[0319]

Table 3

[0320] Using the fluorine-containing elastomers obtained in Example 5 and Comparative Example 3, in the same manner as in Example 1, the minimum viscosity (ML), maximum torque level (MH), induction time (T10), and optimum vulcanization time (T90) were determined. Also, using the fluorine-containing elastomers obtained in Example 5 and Comparative Example 3, in the same manner as in Example 1, a fluorine-containing elastomer composition and a crosslinked molded product sheet were prepared, and the physical properties at normal temperature, hardness, and compression set were measured.

[0321] The above results are shown in Table 4.

Table 4

Claims

1. A method for producing an aqueous dispersion of a fluorine-containing elastomer containing a methylene group in the main chain by polymerizing a fluorine-containing monomer in the presence of a fluorine-containing allyl ether (1) represented by the general formula (1), a fluorine-containing vinyl ether (2) represented by the general formula (2), and an aqueous medium, in the absence of a fluorine-containing surfactant (excluding the fluorine-containing allyl ether (1) and the fluorine-containing vinyl ether (2)). CX １１ ２ = CY １１ (- CZ １１ ２ - O - Rf １１ - Y １２ ) (1) (wherein X １１ is the same as or different from, -H or -F, Y １１ is -H, -F, an alkyl group or a fluorine-containing alkyl group, Z １１ is the same as or different from, -H, -F, an alkyl group or a fluorine-containing alkyl group. Rf １１ is a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having an ether bond and having 2 to 100 carbon atoms. Y １２ has a hydrophilic group.) CX ２１ ２ = CY ２１ (–O–Rf ２１ –Y ２２ ) (2) (wherein X ２１ is the same or different and is -H or -F, and Y ２１ is -H, -F, an alkyl group or a fluorinated alkyl group, and Rf ２１ is a fluorinated alkylene group having 1 to 40 carbon atoms, or a fluorinated alkylene group having an ether bond and having 2 to 100 carbon atoms. Y ２２ is a hydrophilic group.)

2. Y １２ is -NH ２ , -P(O)(OM) ２ , -OP(O)(OM) ２ , -SO ３ M, -OSO ３ M, -COOM, -B(OM) ２ or -OB(OM) ２ (in each formula, M is H, a metal atom, NR ７ ４ , imidazolium which may have a substituent, pyridinium which may have a substituent or phosphonium which may have a substituent, R ７ is H or an organic group, may be the same or different, and R7 may be such that any two of them are bonded to each other to form a ring.). The production method according to claim 1.

3. X １１ The manufacturing method according to claim 1 or 2, wherein each of them is -H.

4. The production method according to claim 1 or 2, wherein the amount of the fluorine-containing allyl ether (1) is 3 to 5000 ppm by mass based on the aqueous medium.

5. Y ２２ is -NH ２ , -P(O)(OM) ２ , -OP(O)(OM) ２ , -SO ３ M, -OSO ３ M, -COOM, -B(OM) ２ or -OB(OM) ２ (in each formula, M is H, a metal atom, NR ７ ４ , imidazolium which may have a substituent, pyridinium which may have a substituent or phosphonium which may have a substituent, R ７ is H or an organic group, may be the same or different, and R7 may be such that any two of them are bonded to each other to form a ring.). The production method according to claim 1 or 2.

6. The production method according to claim 1 or 2, wherein the amount of the fluorine-containing vinyl ether (2) is 3 to 5000 ppm by mass based on the aqueous medium.

7. The production method according to claim 1 or 2, further comprising polymerizing the fluorine-containing monomer in the presence of a chain transfer agent.

8. The production method according to claim 1 or 2, wherein the fluorine-containing monomer is polymerized at 10 to 120 °C.

9. The production method according to claim 1 or 2, wherein the fluorine-containing monomer is polymerized at 0.5 to 10 MPaG.

10. The production method according to claim 1 or 2, wherein the fluorine-containing elastomer contains a vinylidene fluoride unit.

11. The production method according to claim 1 or 2, wherein the fluorine-containing elastomer contains 50 mol% or more of vinylidene fluoride units based on all monomer units.

12. The production method according to claim 1 or 2, wherein the Mooney viscosity (ML1+10(100 °C)) of the fluorine-containing elastomer is 10 to 130.

13. An aqueous dispersion of a fluorine-containing elastomer containing a methylene group in the main chain, further containing a monomer unit (1) based on the fluorine-containing allyl ether (1) represented by the general formula (1) and a monomer unit (2) based on the fluorine-containing vinyl ether (2) represented by the general formula (2), and substantially free of a fluorine-containing surfactant (excluding the fluorine-containing allyl ether (1) and the fluorine-containing vinyl ether (2)). CX １１ ２ = CY １１ (- CZ １１ ２ - O - Rf １１ - Y １２ ) (1) (In the formula, X １１ is the same or different and is -H or -F, and Y １１ is -H, -F, an alkyl group or a fluorine-containing alkyl group, and Z １１ is the same or different and is -H, -F, an alkyl group or a fluorine-containing alkyl group. Rf １１ is a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having an ether bond and having 2 to 100 carbon atoms. Y １２ has a hydrophilic group.) CX ２１ ２ = CY ２１ (-O-Rf ２１ -Y ２２ )(2) (wherein X ２１ is the same or different and is -H or -F, and Y ２１ is -H, -F, an alkyl group or a fluorine-containing alkyl group, and Rf ２１ is a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having an ether bond and having 2 to 100 carbon atoms. Y ２２ is a hydrophilic group.)

14. The aqueous dispersion of a fluorine-containing elastomer according to claim 13, wherein the fluorine-containing elastomer contains a vinylidene fluoride unit.

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