Method for producing aqueous fluoroelastomer dispersion

Abstract

Provided is a method for producing an aqueous fluoroelastomer dispersion, the production method comprising: (1) preparing a fluoropolymer-containing first aqueous dispersion by carrying out a first polymerization of fluorine-containing monomer in a container in the presence of an aqueous medium and a polymerization initiator and substantially in the absence of fluorine-containing surfactant that lacks a functional group capable of reacting by radical polymerization; (2) removing the first aqueous dispersion from the container and diluting the removed first aqueous dispersion 3- to 40-fold to prepare a second aqueous dispersion, or diluting the first aqueous dispersion in the container 3- to 40-fold to prepare a second aqueous dispersion and removing the second aqueous dispersion from the container; and (3) preparing a fluoroelastomer-containing third aqueous dispersion by carrying out, in the same container as the container in which the first polymerization was performed or in a container different from the container in which the first polymerization was performed, a second polymerization of fluorine-containing monomer substantially in the absence of fluorine-containing surfactant that lacks a functional group capable of reacting by radical polymerization and in the presence of the second aqueous dispersion, a chain transfer agent having an iodine atom or a bromine atom, and at least one selection from the group consisting of monomers that provide a crosslinkable group containing an iodine atom, a bromine atom, or a cyano group.

Description

Method for producing an aqueous dispersion of fluorine-containing elastomer

[0001] This disclosure relates to a method for producing an aqueous dispersion of a fluorine-containing elastomer.

[0002] Patent Document 1 describes a method for producing a curable fluoropolymer, comprising: i) preparing a seed composition obtained by aqueous emulsion polymerization of one fluorinated monomer and at least one other fluorinated comonomer in the presence of one or more non-fluorinated saturated emulsifiers, although the fluorinated emulsifier is essentially absent; and ii) polymerizing VDF, TFE, and at least one other comonomer by aqueous emulsion polymerization in the presence of the seed composition, in the presence of an iodine-containing chain transfer agent (CTA), one or more perfluorinated bisolefin ether modifiers, and optionally one or more iodine-containing curable site monomers, wherein the iodine-containing CTA is selected from fluorinated iodoolefins in which ether oxygen may be interposed once or twice or more in the olefin chain, and the modifier has the general formula: CF ２ = CF - (CF ２ ) ｎ -O-(R ｆ )-O-(CF ２ ) ｍ -CF = CF ２ (In the formula, n and m are independently either 1 or 0, R ｆ The description includes a method for selecting from perfluorinated bisolefin ether modifiers corresponding to perfluorinated linear or branched, cyclic or acyclic, aliphatic or aromatic hydrocarbon residues containing up to 30 carbon atoms, which may have one or more oxygen atoms interposed therein.

[0003] International Publication No. 2016 / 137851

[0004] The object of this disclosure is to provide a method for producing an aqueous dispersion of a fluorine-containing elastomer that can suppress the adhesion of the resulting polymer to the container used in the polymerization reaction.

[0005] According to this disclosure, a method for producing an aqueous dispersion of a fluorine-containing elastomer is provided, (1) in a container, substantially in the absence of a fluorine-containing surfactant that does not have functional groups that can react by radical polymerization, and in the presence of an aqueous medium and a polymerization initiator, a first polymerization of a fluorine-containing monomer is carried out to prepare a first aqueous dispersion containing a fluorine-containing polymer; (2) the first aqueous dispersion is removed from the container, and the removed first aqueous dispersion is diluted 3 to 40 times to prepare a second aqueous dispersion, or the first aqueous dispersion is diluted 3 to 40 times in the container to prepare a second aqueous dispersion, and then removed from the container. (3) A method is provided for preparing a third aqueous dispersion containing a fluorine-containing elastomer by performing a second polymerization of a fluorine-containing monomer in the same container in which the first polymerization was performed, or in a container different from the container in which the first polymerization was performed, in the absence of a fluorine-containing surfactant that substantially does not have a functional group that can react by radical polymerization, and in the presence of a chain transfer agent having an iodine atom or a bromine atom, and at least one selected from the group consisting of monomers that give a crosslinkable group containing an iodine atom, a bromine atom or a cyano group, and a second aqueous dispersion.

[0006] According to this disclosure, it is possible to provide a method for producing an aqueous dispersion of a fluorine-containing elastomer that can suppress the adhesion of the resulting polymer to the container used in the polymerization reaction.

[0007] Before describing specific embodiments of this disclosure, we define or explain some terms used in this disclosure.

[0008] In this disclosure, fluorine-containing elastomers are amorphous fluoropolymers. "Amorphous" means that the magnitude of the melting peak (ΔH) observed in 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. Fluorine-containing elastomers exhibit elastomer properties by crosslinking. Elastomer properties refer to the ability of a polymer to be stretched and to retain its original length when the force required to stretch the polymer is no longer applied.

[0009] In this disclosure, a perfluoro monomer is a monomer that does not contain carbon-hydrogen atom bonds in its molecule. The perfluoro monomer may be a monomer in which some of the fluorine atoms bonded to the carbon atoms are replaced with chlorine atoms, or it may have nitrogen atoms, oxygen atoms, sulfur atoms, phosphorus atoms, boron atoms, or silicon atoms in addition to carbon atoms. Preferably, the perfluoro monomer is a monomer in which all hydrogen atoms are replaced with fluorine atoms. The perfluoro monomer does not contain monomers that provide a crosslinking group.

[0010] A monomer that provides crosslinking sites is a monomer (curation monomer) that provides crosslinking sites for crosslinking to a fluoropolymer using a crosslinking agent. This includes monomers that provide crosslinkable groups.

[0011] In this 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 depending on the type of monomer.

[0012] In this disclosure, "organic group" means a group containing one or more carbon atoms, or a group formed by removing one hydrogen atom from an organic compound. The organic group is preferably an alkyl group, which may have one or more substituents.

[0013] In this disclosure, the range represented by an endpoint includes all numerical values ​​that fall within that range (for example, 1 to 10 includes 1.4, 1.9, 2.33, 5.75, 9.98, etc.).

[0014] In this disclosure, the phrase "at least one" includes all numbers one or more (for example, at least two, at least four, at least six, at least eight, at least ten, at least 25, at least 50, at least 100, etc.).

[0015] The following describes specific embodiments of this disclosure in detail, but this disclosure is not limited to the embodiments described below.

[0016] This disclosure relates to a method for producing an aqueous dispersion of a fluorine-containing elastomer by polymerizing a fluorine-containing monomer in the presence of an aqueous medium and a polymerization initiator.

[0017] Conventionally, a method for producing an aqueous dispersion of fluorine-containing elastomers is known, as described in Patent Document 1, in which a seed composition is prepared, and then fluorinated monomers are further polymerized in the presence of the seed composition. However, the method described in Patent Document 1 has the problem of a large amount of the resulting polymer adhering to the container used for the polymerization reaction.

[0018] Therefore, after diligently investigating means to solve the above problem, it has now become clear that, for example, the method described in Patent Document 1 has the problem that the seed composition is diluted too much, resulting in a large amount of the resulting polymer adhering to the container used for the polymerization reaction.

[0019] In the manufacturing method of the present disclosure, a first aqueous dispersion is prepared, then the first aqueous dispersion is diluted to a predetermined ratio to prepare a second aqueous dispersion, and the aqueous dispersions are removed from the container used for the polymerization reaction before and after dilution. Then, polymerization is carried out in the presence of the second aqueous dispersion to prepare a third aqueous dispersion. As a result, even though polymerization is carried out without using a fluorine-containing surfactant that does not have functional groups that can react in radical polymerization, adhesion of the resulting polymer (fluorine-containing polymer and fluorine-containing elastomer) to the container used for the polymerization reaction can be suppressed in the second polymerization, and the crosslinking properties of the obtained fluorine-containing elastomer can be improved.

[0020] The manufacturing method of this disclosure is described in detail below.

[0021] The manufacturing method disclosed herein is a method for producing an aqueous dispersion of a fluorine-containing elastomer. In the manufacturing method of the present disclosure, (1) a first polymerization of a fluorine monomer is carried out in a container in the absence of a fluorine-containing surfactant that substantially does not have functional groups that can react by radical polymerization, and in the presence of an aqueous medium and a polymerization initiator to prepare a first aqueous dispersion containing a fluorine-containing polymer; (2) the first aqueous dispersion is removed from the container, and the removed first aqueous dispersion is diluted 3 to 40 times to prepare a second aqueous dispersion, or the first aqueous dispersion is diluted 3 to 40 times in the container to prepare a second aqueous dispersion, and removed from the container; (3) a third aqueous dispersion containing a fluorine-containing elastomer is prepared by carrying out a second polymerization of a fluorine monomer in the same container in which the first polymerization was carried out, or in a different container from the container in which the first polymerization was carried out, in the absence of a fluorine-containing surfactant that substantially does not have functional groups that can react by radical polymerization, and in the presence of the second aqueous dispersion and a chain transfer agent having an iodine atom or a bromine atom.

[0022] (1) Preparation of the first aqueous dispersion In the manufacturing method of the present disclosure, in order to prepare a first aqueous dispersion containing a fluorine-containing polymer, the first polymerization of a fluorine-containing monomer is carried out in a container, substantially in the absence of a fluorine-containing surfactant that does not have functional groups that can react by radical polymerization, and in the presence of an aqueous medium and a polymerization initiator.

[0023] The fluorine-containing monomer used in the first polymerization will be described later.

[0024] (Fluorine-free compound having a hydrophilic group) In the production method of the present disclosure, it is preferable to carry out the first polymerization in the presence of a fluorine-free compound having a hydrophilic group. It is preferable that the fluorine-free compound having a hydrophilic group does not have a functional group that can react by radical polymerization.

[0025] In the present disclosure, a hydrophilic group is a group that exhibits an affinity for an aqueous medium. A fluorine-free compound having a hydrophilic group preferably contains an anionic or nonionic hydrophilic group, and more preferably contains an anionic hydrophilic group. A fluorine-free compound having a hydrophilic group may contain, for example, only an anionic hydrophilic group or only a nonionic hydrophilic group. Further, as the fluorine-free compound having a hydrophilic group, only a compound containing an anionic hydrophilic group may be used, only a compound containing a nonionic hydrophilic group may be used, or a compound containing an anionic hydrophilic group and a compound containing a nonionic hydrophilic group may be used in combination.

[0026] Examples of the hydrophilic group possessed by the fluorine-free compound include, for example, -NH ２ , -P(O)(OM) ２ , -OP(O)(OM) ２ , -SO ３ M, -OSO ３ M, -COOM, -B(OM) ２ , -OB(OM) ２ (in each formula, M is H, a metal atom, NR ７ ４ , imidazolium optionally having a substituent, pyridinium optionally having a substituent or phosphonium optionally having a substituent, R ７ is H or an organic group, and may be the same or different. Any two of them may be bonded to each other to form a ring.). Among these hydrophilic groups, -SO ３ M or -COOM is preferable, and -COOM is more preferable. The organic group of R ７ is preferably an alkyl group. R ７ is preferably H or an organic group of C １－１０ , more preferably H or an organic group of C １－４ , still more preferably H or an alkyl group of C １－４ , and most preferably H. 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, preferably alkali metals (Group 1) or alkaline earth metals (Group 2), and more preferably Na, K or Li.

[0027] In the first polymerization, a fluorine-free anionic surfactant can be suitably used as the fluorine-free compound having a hydrophilic group. A fluorine-free anionic surfactant is an anionic surfactant that does not contain a fluorine atom. Preferably, the fluorine-free anionic surfactant does not have a functional group that can react in radical polymerization.

[0028] Examples of fluorine-free anionic surfactants include those with the general formula (X): R Ｚ - (L-M) ｘ (In the formula, R Ｚ An example of anionic surfactants is represented by , where represents a hydrophobic hydrocarbon moiety containing one or more carbon atoms, L may be the same or different in each occurrence and represents an ionic hydrophilic moiety, M may be the same or different in each occurrence and represents one or more counterions of the ionic hydrophilic moiety, x represents the number of groups represented by -L-M bonded to Rz and is an integer from 1 to 3.

[0029] R Ｚ As for L, a hydrocarbon group having 1 to 100 carbon atoms, which may contain heteroatoms, is preferred. The heteroatoms may be inserted between carbon atoms or may be included in substituents bonded to carbon atoms. As for L, -ArSO ３ － , -SO ３ － , -SO ４ -, -PO ３ － or -COO － This is preferable. -ArSO ３ － It is an aryl sulfonate. M is H, a metal atom, NR ５Ｚ ４ Preferably, imidazolium which may have substituents, pyridinium which may have substituents, or phosphonium which may have substituents. ５Ｚ The element is preferably H or an organic group (preferably an alkyl group having 1 to 3 carbon atoms). More specifically, the anionic surfactants described below are examples.

[0030] As for fluorine-free anionic surfactants, R Ｚ -LM (wherein, R Ｚ However, it is a monovalent organic group containing one or more carbon atoms. L is -ArSO ３ － , -SO ３ － , -SO ４ -, -PO ３ － or -COO － And M is H, a metal atom, NR ５Ｚ ４ , optionally substituted imidazolium, optionally substituted pyridinium, or optionally substituted phosphonium, R ５Ｚ is H or an organic group, -ArSO ３ － Anionic surfactants, represented by aryl sulfonates, are also mentioned. Specifically, these include CH4 compounds such as lauric acid and lauryl sulfate (dodecyl sulfate). ３ - (CH ２ ) ｎ Examples include those expressed by -L-M (wherein n is an integer between 6 and 17, and L and M are the same as above). Ｚ However, it may be a linear or branched alkyl group having 1 or more carbon atoms, which may have substituents, or a cyclic alkyl group having 3 or more carbon atoms, which may have substituents. Ｚ If the alkyl group has three or more carbon atoms, it may contain a monovalent or divalent heterocycle, or it may form a ring. Ｚ However, it is preferable that it be an alkyl group having 3 to 18 carbon atoms. Ｚ However, a mixture of alkyl groups having 12 to 16 carbon atoms, where L-M is a sulfate, can also be used. Ｚ However, R ｚ１ R ｚ２ R ｚ３ C-(wherein, R ｚ１ and R ｚ２ However, independently, alkyl or alkenyl group, R ｚ３ However, H is an alkyl group or an alkenyl group, and R ｚ１ ~Rｚ３ It is also preferable that it is a group represented by (the total carbon number is 2 to 25). In one embodiment, R ｚ３ is H, and R ｚ１ and R ｚ２ are, independently, an alkyl group or an alkenyl group having a total carbon number of 10 to 20, preferably an alkyl group having a total carbon number of 10 to 20, and L-M is a sulfate.

[0031] As other compounds having surface activity, R ６Ｚ (-L-M) ２ (wherein, R ６Ｚ is a monovalent organic group containing one or more carbon atoms. L is -ArSO ３ － , -SO ３ － , -SO ４ -, -PO ３ － or -COO － and M is H, a metal atom, NR ５Ｚ ４ , an optionally substituted imidazolium, an optionally substituted pyridinium or an optionally substituted phosphonium, R ５Ｚ is H or an organic group, -ArSO ３ － is an arylsulfonate. ) The anionic surfactant represented by is also mentioned. R ６Ｚ may be a linear or branched alkylene group having 1 or more carbon atoms which may have a substituent, or a cyclic alkylene group having 3 or more carbon atoms which may have a substituent. When the alkylene group of R ６Ｚ has 3 or more carbon atoms, it may contain a monovalent or divalent heterocyclic ring or may form a ring.

[0032] As the fluorine-free anionic surfactant, R ７Ｚ (-L-M) ３ (wherein, R ７Ｚ is a monovalent organic group containing one or more carbon atoms. L is -ArSO ３ － , -SO ３ － , -SO ４ -, -PO３ － or -COO － And M is H, a metal atom, NR ５Ｚ ４ , optionally substituted imidazolium, optionally substituted pyridinium, or optionally substituted phosphonium, R ５Ｚ is H or an organic group. -ArSO ３ － Anionic surfactants represented by aryl sulfonates are also mentioned. ７Ｚ However, it may be a linear or branched alkylidine group having 1 or more carbon atoms, which may have substituents, or a cyclic alkylidine group having 3 or more carbon atoms, which may have substituents. ７Ｚ If the alkylidine group has three or more carbon atoms, it may contain a monovalent or divalent heterocycle, or it may form a ring. ５ｚ H or an alkyl group is preferred, H or an alkyl group having 1 to 10 carbon atoms is more preferred, and H or an alkyl group having 1 to 4 carbon atoms is even more preferred.

[0033] Throughout this disclosure, unless otherwise specified, "substituent" means a substituted group. Examples of substituents include alkyl groups having 1 to 10 carbon atoms, halogen atoms, amino groups, hydroxyl groups, and cyano groups.

[0034] As a fluorine-free anionic surfactant, carboxylic acid-type fluorine-free anionic surfactants are also preferred.

[0035] As carboxylic acid-type fluorine-free anionic surfactants, at least one selected from the group consisting of lauric acid, capric acid, myristic acid, pentadecyl acid, palmitic acid, and salts thereof, and compounds obtained by radical treatment or oxidation treatment of these compounds is particularly preferred; at least one selected from the group consisting of lauric acid and its salts, and compounds obtained by radical treatment or oxidation treatment of these compounds is more preferred; at least one selected from the group consisting of salts of lauric acid and compounds obtained by radical treatment or oxidation treatment thereof is even more preferred; and at least one selected from the group consisting of sodium laurate and compounds obtained by radical treatment or oxidation treatment thereof is even more preferred. In the above salts, the hydrogen atom of the carboxyl group (-COOH) is a metal atom, NR ７ ４ (R ７ As mentioned above, examples include, but are not limited to, imidazolium which may have substituents, pyridinium which may have substituents, or phosphonium which may have substituents.

[0036] Radical treatment refers to any treatment in which a radical is applied to a fluorine-free anionic surfactant. For example, this treatment involves adding deionized water and a fluorine-free anionic surfactant to a reactor, sealing the reactor, purging the system with nitrogen, raising the temperature and pressure of the reactor, adding a polymerization initiator, stirring for a certain period of time, then depressurizing the reactor to atmospheric pressure and cooling it. The oxidation treatment refers to a treatment in which an oxidizing agent is applied to a fluorine-free anionic surfactant. Examples of oxidizing agents include oxygen, ozone, hydrogen peroxide, manganese(IV) oxide, potassium permanganate, potassium dichromate, nitric acid, and sulfur dioxide.

[0037] The amount of hydrophilic, fluorine-free compound used in the first polymerization is preferably 0.0001 to 10% by mass, more preferably 0.001% or more by mass, and more preferably 1% or less by mass, based on 100% by mass of the aqueous medium. The amount of hydrophilic, fluorine-free compound is appropriately determined depending on the type of monomer used, the molecular weight of the target fluorine-containing polymer, etc.

[0038] In the first polymerization, it is preferable that the mass ratio (fluorine-free compound having hydrophilic groups / polymerization initiator) of the fluorine-free compound having hydrophilic groups to the polymerization initiator (total amount of polymerization initiator added during the first polymerization) be 0.600 or less. More preferably, the mass ratio (fluorine-free compound having hydrophilic groups / polymerization initiator) is 0.500 or less, even more preferably 0.300 or less, preferably 0.010 or more, and even more preferably 0.015 or more. By balancing the amount of fluorine-free compound having hydrophilic groups added and the amount of polymerization initiator added to achieve the above mass ratio and performing the first polymerization, it is possible to produce an aqueous dispersion containing a fluorine-containing elastomer with even better crosslinking properties while further suppressing the adhesion of the generated polymer to the container used for the polymerization reaction in the second polymerization.

[0039] (Polymerization initiator) In the manufacturing method of the present disclosure, the first polymerization is carried out in the presence of a polymerization initiator.

[0040] Persulfates are preferred as polymerization initiators used in the first polymerization. By using persulfates as polymerization initiators, it is possible to produce an aqueous dispersion containing a fluorine-containing elastomer with even better crosslinking properties while further suppressing the adhesion of the resulting polymer to the container used in the polymerization reaction.

[0041] Examples of persulfates include potassium persulfate (K ２ S ２ O ８ ), ammonium persulfate ((NH ４ ) ２ S ２ O ８ ), sodium persulfate (Na ２ S ２ O ８ ) is preferred, and ammonium persulfate is even more preferred.

[0042] The total amount of polymerization initiator used in the first polymerization is preferably 500 ppm by mass or more, more preferably 700 ppm by mass or more, even more preferably 900 ppm by mass or more, preferably 5000 ppm by mass or less, and even more preferably 4500 ppm by mass or less, relative to the aqueous medium. By adding a relatively large amount of polymerization initiator and performing the first polymerization, it is possible to produce an aqueous dispersion containing a fluorine-containing elastomer with even better crosslinking properties while further suppressing the adhesion of the produced polymer to the container used for the polymerization reaction in the second polymerization. The polymerization initiator may be added all at once when starting the first polymerization, or a portion may be added when starting the first polymerization, and the remainder may be added all at once or in installments during the first polymerization.

[0043] In one embodiment of the manufacturing method of the present disclosure, polymerization of a fluorine-containing monomer is carried out substantially in the absence of a redox initiator. A redox initiator is a polymerization initiator that combines an oxidizing agent and a reducing agent. Examples of oxidizing agents include persulfates, organic peroxides, potassium permanganate, manganese triacetate, ammonium cerium nitrate, and bromates. Examples of reducing agents include sulfites, bisulfites, bromates, diimines, oxalic acid, and metal sulfinates. Examples of persulfates include ammonium persulfate, potassium persulfate, and sodium persulfate.

[0044] In this disclosure, "substantially in the absence of a redox initiator" means that the content ratio of the reducing agent constituting the redox initiator to the aqueous medium is 10 ppm by mass or less. The content ratio of the reducing agent constituting the redox initiator is preferably 1 ppm by mass or less, more preferably 100 ppb by mass or less, even more preferably 10 ppb by mass or less, and particularly preferably 1 ppb by mass or less.

[0045] In one embodiment of the manufacturing method of the present disclosure, polymerization of fluorine-containing monomers is carried out substantially in the absence of transition metal salts of groups 3 to 11. Transition metal salts of groups 3 to 11 are sometimes used to increase the decomposition rate of the initiator when a redox initiator is used. Examples of transition metal salts of groups 3 to 11 include copper salts, iron salts, and cobalt salts, with copper(II) sulfate being an example of a copper salt, iron(II) sulfate being an example of an iron salt, and cobalt(II) chloride being an example of a cobalt salt.

[0046] In this disclosure, "substantially in the absence of transition metal salts from groups 3 to 11" means that the content of transition metal salts from groups 3 to 11 in the aqueous medium is 10 ppm by mass or less. The content of transition metal salts from groups 3 to 11 in the aqueous medium is preferably 1 ppm by mass or less, more preferably 100 ppb by mass or less, even more preferably 10 ppb by mass or less, and particularly preferably 1 ppb by mass or less.

[0047] (Chain Transfer Agent) In the manufacturing method of the present disclosure, the first polymerization may be carried out in the presence of a chain transfer agent. Known chain transfer agents can be used, for example, hydrocarbons, esters, ethers, alcohols, ketones, halogen-containing compounds, carbonates, etc. Among these, isopentane, diethyl malonate and ethyl acetate are preferred from the viewpoint of not reducing the reaction rate, and I(CF ２ ) ４ I, I (CF ２ ) ６ I, ICH ２ Iodine compounds such as I are preferred from the viewpoint that they can be used as reactive polymers because they allow for iodination of the polymer ends.

[0048] As the chain transfer agent, it is particularly preferable to use a bromine compound or an iodine compound. Examples of polymerization methods using a bromine compound or an iodine compound include iodine transfer polymerization or bromine transfer polymerization.

[0049] Iodine and bromine compounds are water-insoluble and difficult to emulsify. Therefore, emulsion polymerization has traditionally been limited, and there has been a tendency to use large amounts of surfactants. The manufacturing method of this disclosure makes it possible to obtain fluorine-containing elastomers by polymerization using iodine or bromine compounds, for example, by iodine transfer polymerization or bromine transfer polymerization, even in the absence of conventionally used surfactants. In one embodiment, the first polymerization is carried out in the absence of a chain transfer agent having iodine or bromine atoms, and the second polymerization is carried out in the presence of a chain transfer agent having iodine or bromine atoms, and at least one selected from the group consisting of monomers that give a crosslinkable group containing iodine, bromine, or cyano groups.

[0050] Iodine transfer polymerization is a method that utilizes living radical polymerization via a radical chain reactivation mechanism, where the carbon-iodine bond is radically active due to its low dissociation energy, and a chain transfer reaction is involved in the radical polymerization reaction. The reaction conditions are not particularly limited and any known conditions can be used as appropriate, but for example, the conditions described in "Proceedings of the Polymer Science, Vol. 49, No. 10, pp. 765-783, October 1992" and Japanese Patent Publication No. 53-3495 can be appropriately adopted. Similar polymerization can be carried out using a bromine compound instead of an iodine compound, and in this disclosure, such polymerization is referred to as bromine transfer polymerization.

[0051] Among these, iodine transfer polymerization is preferred in terms of polymerization reactivity and crosslinking reactivity.

[0052] Typical examples of bromine or iodine compounds include, for example, those with the general formula: R ８ I ｘ Br ｙ (In the formula, x and y are integers from 0 to 2, and satisfy 1 ≤ x + y ≤ 2, R ８Examples of compounds represented by a saturated or unsaturated fluorohydrocarbon group or chlorofluorohydrocarbon group having 1 to 16 carbon atoms, or a hydrocarbon group having 1 to 3 carbon atoms (which may contain an oxygen atom). By using a bromine compound or an iodine compound, iodine or bromine is introduced into the polymer and functions as a crosslinking point.

[0053] Examples of bromine and iodine compounds include 1,3-diiodoperfluoropropane, 2-iodoperfluoropropane, 1,3-diiodo-2-chloroperfluoropropane, 1,4-diiodoperfluorobutane, 1,5-diiodo-2,4-dichloroperfluoropentane, 1,6-diiodoperfluorohexane, 1,8-diiodoperfluorooctane, 1,12-diiodoperfluorododecane, 1,16-diiodoperfluorohexadecane, diiodomethane, 1,2-diiodoethane, 1,3-diiodo-n-propane, CF ２ Br ２ , BrCF ２ CF ２ Br, CF ３ CFBrCF ２ Br, CFClBr ２ , BrCF ２ CFClBr, CFBrClCFClBr, BrCF ２ CF ２ CF ２ Br, BrCF ２ CFBrOCF ３Examples include 1-bromo-2-iodoperfluoroethane, 1-bromo-3-iodoperfluoropropane, 1-bromo-4-iodoperfluorobutane, 2-bromo-3-iodoperfluorobutane, 3-bromo-4-iodoperfluorobutene-1, 2-bromo-4-iodoperfluorobutene-1, monoiodomonobromo substituted derivatives of benzene, diiodomonobromo substituted derivatives, and (2-iodoethyl) and (2-bromoethyl) substituted derivatives. These compounds may be used individually or in combination. Among these, compounds containing only iodine and no bromine are preferred in terms of polymerization reactivity, crosslinking reactivity, and availability, and it is preferable to use 1,4-diiodoperfluorobutane, 1,6-diiodoperfluorohexane, or 2-iodoperfluoropropane.

[0054] The amount of chain transfer agent used in the first polymerization is preferably 0.2 × 10⁻¹⁰ of the total amount of monomers used in polymerization. －３ ~2 mol%, more preferably 1.0 × 10 －３ It is approximately 1 mole%.

[0055] (Compound (A)) In the manufacturing method of the present disclosure, it is preferable to carry out the first polymerization in the presence of compound (A), which contains a functional group and a hydrophilic group that can react by radical polymerization. Compound (A) may be either a fluorine-containing compound or a fluorine-free compound, but it is preferable that it is a fluorine-containing compound.

[0056] In this disclosure, a hydrophilic group is a group that exhibits affinity for an aqueous medium. Compound (A) is preferably a compound containing an anionic or nonionic hydrophilic group, and more preferably a compound containing an anionic hydrophilic group. Compound (A) may, for example, contain only anionic hydrophilic groups or only nonionic hydrophilic groups. Furthermore, as compound (A), only compounds containing anionic hydrophilic groups may be used, only compounds containing nonionic hydrophilic groups may be used, or a combination of compounds containing anionic hydrophilic groups and compounds containing nonionic hydrophilic groups may be used.

[0057] Examples of hydrophilic groups in compound (A) include -NH ２ , -P(O)(OM) ２ , -OP(O)(OM) ２ , -SO ３ M, -OSO ３ M, -COOM, -B (OM) ２ , -OB (OM) ２ (In each formula, M is H, a metal atom, NR) ７ ４ , optionally substituted imidazolium, optionally substituted pyridinium, or optionally substituted phosphonium, R ７ is H or an organic group, which may be the same or different. Any two may bond to each other to form a ring. ) are examples of the above hydrophilic groups, among others, -SO ３ M or -COOM is preferred, and -COOM is more preferred. ７ An alkyl group is preferred as the organic group. ７ For example, H or C １－１０ The organic group is preferably H or C １－４ The organic group is more preferably H or C １－４ Alkyl alkyl groups are more preferred, and H is most preferred. If two M atoms are included in each formula, the two M atoms may be the same or different. Examples of metal atoms include monovalent or divalent metal atoms, alkali metals (Group 1) or alkaline earth metals (Group 2) are preferred, and Na, K, or Li are more preferred.

[0058] Examples of "functional groups that can react by radical polymerization" in compound (A) include groups containing radically polymerizable unsaturated bonds.

[0059] Examples of groups having radically polymerizable unsaturated bonds include vinyl groups, allyl groups, and other groups having ethylenically unsaturated bonds.

[0060] Since compound (A) has a functional group that can react in radical polymerization, when used in the above polymerization, it is presumed to react with the fluorine-containing monomer in the initial stages of the polymerization reaction, forming highly stable particles that have hydrophilic groups derived from compound (A). For this reason, it is thought that the number of fluorine-containing polymer particles generated during polymerization will increase when polymerization is carried out in the presence of compound (A).

[0061] As compound (A), a fluorine-containing compound (A0) represented by general formula (A0) is preferred. General formula (A0): CX ｉ X ｋ = CX ｊ R ａ - (CZ １ Z ２ ) ｋ -Y ３ (In the formula, X ｉ , X ｊ and X ｋ These are, independently, F, Cl, H, or CF ３ Y ３ R is a hydrophilic group; ａ is a linking group; Z １ and Z ２ These are H, F, or CF, each independently. ３ And; k is 0 or 1. However, X ｉ , X ｋ , X ｊ , R ａ Z １ and Z ２ At least one of them contains F, except when k is 0, R ａ (This is a linking group other than a single bond.)

[0062] Y in general formula (A0) ３ This is a hydrophilic group. The hydrophilic group is as described above.

[0063] R in general formula (A0) ａ is a linking group. In this disclosure, “linking group” refers to a divalent linking group. Preferably, the linking group is a single bond or a group containing at least one carbon atom. However, when k is 0, R ａ It is preferable that the linking group is a group other than a single bond and contains at least one carbon atom.

[0064] R ａ It is more preferably a hydrocarbon group having 1 to 100 carbon atoms, which may contain a -(C=O)-, -(C=O)-O-, or ether bond, and may also contain a carbonyl group, and in the hydrocarbon group, some or all of the hydrogen atoms bonded to the carbon atom may be substituted with fluorine.

[0065] As the fluorine-containing compound (A0), at least one selected from the group consisting of the compound represented by general formula (A0-1) (A0-1), the compound represented by general formula (A0-2) (A0-2), and the compound represented by general formula (A0-3) (A0-3) is preferred. ２ =CY(-CZ) ２ -O-Rf-Y ３ ) (A0-1) (wherein X is the same or different -H or -F, Y is -H, -F, alkyl group or fluorine-containing alkyl group, and Z is the same or different -H, -F, alkyl group or fluorine-containing alkyl group. Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having an ether bond having 2 to 100 carbon atoms. Y ３ (This is the same as above.) CX ２ =CY(-O-Rf-Y ３ ) (A0-2) (wherein X is the same or different -H or -F, Y is -H, -F, an alkyl group or a fluorine-containing alkyl group, and Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having an ether bond having 2 to 100 carbon atoms. Y ３ (This is the same as above.) CX ２ =CY(-Rf-Y ３ ) (A0-3) (wherein X is the same or different -H or -F, Y is -H, -F, an alkyl group or a fluorine-containing alkyl group, and Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having an ether bond having 2 to 100 carbon atoms. Y ３ (This is the same as above.)

[0066] As the fluorine-containing compound (A0-1), compound (A0-1) is more preferred.

[0067]

[0068] That is even more preferable.

[0069] As for compound (A0-1), Y in the formula ３ It is preferable that it be -COOM, and in particular CH ２ = CFCF ２ OCF (CF ３ ) COOM, and CH ２ = CFCF ２ OCF (CF ３ ) CF ２ OCF (CF ３ Preferably, at least one selected from the group consisting of COOM (wherein M is the same as defined above).

[0070] Compound (A) is preferably added before the polymerization initiator is added to initiate the first polymerization. Furthermore, it is preferable to add it only before the first polymerization begins and not after polymerization has started.

[0071] The amount of compound (A) used in the first polymerization is preferably 3 to 5000 ppm by mass, more preferably 5 ppm by mass or more, even 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 more preferably 1000 ppm by mass or less, even more preferably 750 ppm by mass or less, particularly preferably 500 ppm by mass or less, and most preferably 250 ppm by mass or less, relative to the aqueous medium.

[0072] (Aqueous medium) In the manufacturing method of the present disclosure, the first polymerization is carried out in the presence of an aqueous medium. The aqueous medium is a reaction medium for carrying out polymerization and 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 ether or ketone, and / or a fluorine-containing organic solvent having a boiling point of 40°C or less.

[0073] As an aqueous medium, an aqueous medium containing only water, or an aqueous medium containing only water and a fluorine-free organic solvent, is preferred because it allows polymerization to proceed smoothly, and an aqueous medium containing only water is more preferred.

[0074] The water content in the aqueous medium is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 99.0% by mass or more, even more preferably 99.5% by mass or more, particularly preferably 99.9% by mass or more, and may be 100% by mass, in order to facilitate polymerization.

[0075] (First polymerization) The first polymerization can be carried out, for example, by charging an aqueous medium into a pressure-resistant container (polymerization tank) equipped with a stirrer, deoxygenating it, charging monomers, raising it to a predetermined temperature, adding a polymerization initiator, and starting the reaction. As the reaction progresses, the pressure decreases, so additional monomers are continuously or intermittently supplied to maintain the initial pressure, and when a predetermined amount of monomers has been supplied, the supply is stopped, the monomers in the container are purged, and the temperature is returned to room temperature to terminate the reaction. In order to ensure control of the second polymerization, it is preferable to perform heat treatment after purging the monomers in order to decompose all undecomposed polymerization initiators.

[0076] The first polymerization preferably involves polymerization of a fluorine-containing monomer in the absence of a fluorine-containing surfactant (hereinafter sometimes simply referred to as "fluorine-containing surfactant") that substantially does not have functional groups that can react by radical polymerization.

[0077] In this disclosure, "in the absence of a fluorine-containing surfactant that substantially does not have a functional group that can react by radical polymerization" means that the content of the fluorine-containing surfactant in the aqueous medium is 10 ppm by mass or less. The content of the fluorine-containing surfactant in the aqueous medium is preferably 1 ppm by mass or less, more preferably 100 ppb by mass or less, even more preferably 10 ppb by mass or less, and particularly preferably 1 ppb by mass or less.

[0078] Examples of the fluorine-containing surfactants mentioned above include anionic fluorine-containing surfactants.

[0079] The above-mentioned anionic fluorine-containing surfactant may be, for example, a surfactant containing fluorine atoms with a total number of carbon atoms of 20 or less in the portion excluding the anionic group.

[0080] The above-mentioned fluorine-containing surfactant may also be a surfactant containing fluorine, wherein the molecular weight of the anionic portion is 1000 or less, preferably 800 or less.

[0081] The above-mentioned "anionic portion" refers to the portion of the fluorine-containing surfactant excluding the cation. For example, F(CF) represented by formula (I) described later. ２ ) ｎ１ In the case of COOM, "F(CF) ２ ) ｎ１ This is the "COO" part.

[0082] The above-mentioned fluorine-containing surfactants also include fluorine-containing surfactants with a LogPOW of 3.5 or less. The above LogPOW is the partition coefficient between 1-octanol and water, and is expressed as LogP [wherein 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 a 1:1 octanol / water mixture containing the fluorine-containing surfactant undergoes phase separation].

[0083] The above LogPOW was performed using a column; TOSOH ODS-120T column (φ4.6 mm × 250 mm, manufactured by Tosoh Corporation), and an eluent; acetonitrile / 0.6% by mass HClO ４ Under the conditions of water = 1 / 1 (vol / vol%), flow rate; 1.0 ml / min, sample volume; 300 μL, column temperature; 40°C, and detection light; UV 210 nm, HPLC was performed on standard substances with known octanol / water partition coefficients (heptanoic acid, octanoic acid, nonanoic acid, and decanoic acid). A calibration curve was created between the elution time and the known octanol / water partition coefficient, and the result was calculated from the HPLC elution time in the sample solution based on this calibration curve.

[0084] Examples of fluorine-containing surfactants include compounds represented by the following formula. The fluorine-containing surfactant may be a mixture of these compounds. In one embodiment of the polymerization described above, the fluorine-containing monomer is polymerized in substantially the absence of a compound represented by the following formula: F(CF) ２ ) ７ COOM, F (CF ２ ) ５ COOM, H(CF) ２ ) ６ COOM, H(CF) ２ ) ７ COOM, CF ３ O(CF) ２ ) ３ OCHFCF ２ COOM, C ３ F ７ OCF (CF ３ ) CF ２ OCF (CF ３ ) COOM, CF ３ CF ２ CF ２ OCF (CF ３ ) COOM, CF ３ CF ２ OCF ２ CF ２ OCF ２ COOM, C ２ F ５ OCF (CF ３ ) CF ２ OCF (CF ３ ) COOM, CF ３ OCF (CF ３ ) CF ２ OCF (CF ３ ) COOM, CF ２ ClCF ２ CF ２ OCF (CF ３ ) CF ２ OCF ２ COOM, CF ２ ClCF ２ CF ２ OCF ２ CF (CF ３ ) OCF ２ COOM, CF ２ ClCF(CF ３ )OCF(CF３ ) CF ２ OCF ２ COOM, CF ２ ClCF(CF ３ ) OCF ２ CF (CF ３ ) OCF ２ COOM, (In each formula, M is H, metal atom, NR ７ ４ , optionally substituted imidazolium, optionally substituted pyridinium, or optionally substituted phosphonium. ７ (This is either H or an organic group.)

[0085] In the first polymerization, phosphates, sodium hydroxide, potassium hydroxide, aqueous ammonia, etc., may be used as pH adjusters. Disodium hydrogen phosphate or sodium hydroxide are preferred as pH adjusters because they can prevent corrosion of the reaction vessel.

[0086] The aqueous medium is preferably acidic. By performing the first polymerization using an acidic aqueous medium, the adhesion of the resulting polymer to the container used for the polymerization reaction in the second polymerization 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.

[0087] The polymerization temperature for the first polymerization is preferably 10 to 120°C, and more preferably 20 to 100°C. Furthermore, the polymerization temperature is preferably 60 to 120°C, more preferably 60 to 100°C, and even more preferably 70 to 90°C, as this yields a fluorine-containing polymer with a high polymerization rate and excellent physical properties.

[0088] The polymerization pressure for the first polymerization is preferably 0.1 to 10 MPaG, and more preferably 0.4 to 7 MPaG.

[0089] (First aqueous dispersion) As described above, a first aqueous dispersion containing a fluorine-containing polymer can be prepared.

[0090] The solid content concentration of the first aqueous dispersion is preferably less than 12% by mass, preferably 10% by mass or less, more preferably 9% by mass or less, preferably 2% by mass or more, and more preferably 3% by mass or more. The solid content concentration of the first aqueous dispersion can be adjusted by adjusting the polymerization time, the degree of stirring during polymerization, and the like.

[0091] The first aqueous dispersion may be heat-treated at 70 °C or higher for 3 hours or longer. As a result, the first polymerization can be sufficiently stopped, so that in the second polymerization, an aqueous dispersion containing a fluorine-containing elastomer having more excellent crosslinking properties can be produced while further suppressing the adhesion of the produced polymer to the container used for the polymerization reaction.

[0092] (2) Dilution of the second aqueous dispersion In the production method of the present disclosure, the first aqueous dispersion is taken out from the container, and the taken-out first aqueous dispersion is diluted 3 to 40 times to prepare a second aqueous dispersion, or the first aqueous dispersion is diluted 3 to 40 times in the container to prepare a second aqueous dispersion, and then taken out from the container.

[0093] The dilution ratio is 3 to 40 times, preferably 5 times or more, more preferably 8 times or more, preferably 38 times or less, and more preferably 35 times or less. If the dilution ratio is too high, there is a possibility that the adhesion of the produced polymer to the container used for the polymerization reaction cannot be suppressed. If the dilution ratio is too low, there is a possibility that a fluorine-containing elastomer having excellent crosslinking properties cannot be obtained.

[0094] Dilution can be performed in the container in which the first polymerization was carried out or in a container different from the container in which the first polymerization was carried out. In the latter case, the first aqueous dispersion is taken out from the container in which the first polymerization was carried out and accommodated in an arbitrary container, and the first aqueous dispersion is diluted in the container. In the production method of the present disclosure, regardless of the type of the container for dilution, the first aqueous dispersion is taken out from the container in which the first polymerization was carried out before dilution, or the second aqueous dispersion is taken out from the container in which the first polymerization was carried out after dilution.

[0095] The solid content concentration of the second aqueous dispersion is preferably 0.01 to 5% by mass, more preferably 0.10% by mass or more, still more preferably 0.50% by mass or more, more preferably 2.0% by mass or less, and still more preferably 1.0% by mass or less. If the solid content concentration is too low, there is a risk that the adhesion of the produced polymer to the container used for the polymerization reaction cannot be suppressed. If the solid content concentration is too high, there is a risk that a fluorine-containing elastomer having excellent cross-linking properties cannot be obtained.

[0096] (3) Preparation of the third aqueous dispersion In the production method of the present disclosure, in the same container as the container in which the first polymerization is carried out or in a container different from the container in which the first polymerization is carried out, substantially in the absence of a fluorine-containing surfactant having no functional group capable of reacting by radical polymerization, and at least one selected from the group consisting of a chain transfer agent and a monomer that gives a cross-linkable group, and in the presence of the second aqueous dispersion, a second polymerization of a fluorine-containing monomer is carried out to prepare a third aqueous dispersion containing a fluorine-containing elastomer.

[0097] In one embodiment, the second polymerization is carried out in the presence of a chain transfer agent having an iodine atom or a bromine atom and the second aqueous dispersion. In one embodiment, the second polymerization is carried out in the presence of a monomer that gives a cross-linkable group containing an iodine atom, a bromine atom or a cyano group and the second aqueous dispersion. In one embodiment, the second polymerization is carried out in the presence of a chain transfer agent having an iodine atom or a bromine atom, a monomer that gives a cross-linkable group containing an iodine atom, a bromine atom or a cyano group, and the second aqueous dispersion.

[0098] The second polymerization can be carried out in the same container as the container in which the first polymerization is carried out, in the container in which dilution is carried out, or in a container different from both the container in which the first polymerization is carried out and the container in which dilution is carried out. In any case, the second polymerization is carried out in an arbitrary container containing the second aqueous dispersion.

[0099] In the production method of the present disclosure, the second polymerization is carried out in the presence of the second aqueous dispersion. The amount of the second aqueous dispersion can be appropriately selected depending on the polymerization scale and the like.

[0100] In one embodiment, the second polymerization is carried out in a second aqueous dispersion. An aqueous medium may be added to the second aqueous dispersion either before or after the start of the second polymerization, but it is necessary to add the aqueous medium in such a way that the dilution ratio does not fall outside the range described above.

[0101] (Fluorine-free compound having a hydrophilic group) In the manufacturing method of the present disclosure, the second polymerization can be carried out in or out of the presence of a fluorine-free compound having a hydrophilic group. Examples of fluorine-free compounds having a hydrophilic group that can be used in the second polymerization are the same as those of the fluorine-free compound having a hydrophilic group that can be used in the first polymerization.

[0102] In one embodiment, the second polymerization is carried out in the absence of a fluorine-free compound having substantially hydrophilic groups.

[0103] In this disclosure, "in the absence of a substantially hydrophilic fluorine-free compound" means that the content of the hydrophilic fluorine-free compound in the aqueous medium is 10 ppm by mass or less. The content of the hydrophilic fluorine-free compound in the aqueous medium is preferably 1 ppm by mass or less, more preferably 100 ppb by mass or less, even more preferably 10 ppb by mass or less, and particularly preferably 1 ppb by mass or less.

[0104] (Polymerization initiator) In the manufacturing method of the present disclosure, a second polymerization is carried out in the presence of a polymerization initiator.

[0105] Radical polymerization initiators can be used as polymerization initiators in the second polymerization. The polymerization initiator is not particularly limited as long as it can generate radicals at the polymerization temperature of the fluorine-containing monomer, and oil-soluble polymerization initiators and water-soluble polymerization initiators can be used, but water-soluble polymerization initiators are preferred. In addition, the polymerization initiator may be used as a redox initiator in combination with a reducing agent or the like.

[0106] The amount of polymerization initiator used in the second polymerization is appropriately determined depending on the type of monomer, the molecular weight of the target fluorine-containing elastomer, and the reaction rate. The amount of polymerization initiator is appropriately determined depending on the molecular weight of the target fluorine-containing elastomer and the polymerization reaction rate, but is preferably 0.00001 to 10% by mass, and more preferably 0.0001 to 1% by mass, based on 100% by mass of the total amount of monomer.

[0107] As polymerization initiators, oil-soluble radical polymerization initiators, water-soluble radical polymerization initiators, or azo compounds can be used.

[0108] The oil-soluble radical polymerization initiator may be a known oil-soluble peroxide, such as dialkyl peroxycarbonates such as diisopropyl peroxydicarbonate and disec-butyl peroxydicarbonate, peroxyesters such as t-butyl peroxyisobutyrate and t-butyl peroxypivalate, and dialkyl peroxides such as di-t-butyl peroxide. Also, di(ω-hydro-dodecafluoroheptanoyl) peroxide, di(ω-hydro-tetradecafluorooctanoyl) peroxide, di(ω-hydro-hexadecafluorononanoyl) peroxide, di(perfluorobutyryl) peroxide, di(perfluorovaleryl) peroxide, di(perfluorohexanoyl) peroxide, di(perfluoroheptanoyl) peroxide, di(perfluorooctanoyl) peroxide, di(perfluorononanoyl) peroxide, di(ω-chloro Di[perfluoro(or fluorochloro)acyl]peroxides such as -hexafluorobutyryl) peroxide, di(ω-chloro-decafluorohexanoyl) peroxide, di(ω-chloro-tetradecafluorooctanoyl) peroxide, ω-hydro-dodecafluoroheptanoyl-ω-hydrohexadecafluorononanoyl-peroxide, ω-chloro-hexafluorobutyryl-ω-chloro-decafluorohexanoyl-peroxide, ω-hydrododecafluoroheptanoyl-perfluorobutyryl-peroxide, di(dichloropentafluorobutanoyl) peroxide, di(trichlorooctafluorohexanoyl) peroxide, di(tetrachloroundafluorooctanoyl) peroxide, di(pentachlorotetradecafluorodecanoyl) peroxide, and di(undachlorodotriacontafluorodocosanoyl) peroxide are typical examples.

[0109] Examples of azo compounds include azodicarboxylates, azodicarboxyldiamides, 2,2'-azobisisobutyronitrile, 2,2'-azobis2,4-dimethylvaleronitrile, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and 4,4'-azobis(4-cyanovaleric acid).

[0110] The water-soluble radical polymerization initiator may be a known water-soluble peroxide, such as ammonium salts, potassium salts, and sodium salts of persulfuric acid, perboric acid, perchloric acid, superphosphate, and percarbonate; organic peroxides such as disuccinate peroxide and diglutaric acid peroxide; t-butyl permalate; and t-butyl hydroperoxide. A reducing agent such as sulfites may also be included, and the amount used may be 0.1 to 20 times the amount of the peroxide.

[0111] As a water-soluble peroxide, persulfate salts are preferred because the amount of radicals generated can be easily adjusted, and potassium persulfate (K) is preferred. ２ S ２ O ８ ), ammonium persulfate ((NH ４ ) ２ S ２ O ８ ), sodium persulfate (Na ２ S ２ O ８ ) is preferred, and ammonium persulfate is most preferred.

[0112] When polymerization is carried out at a polymerization temperature of 45°C or higher using a water-soluble peroxide, it is preferable to perform polymerization without using a reducing agent.

[0113] For example, when polymerization is carried out at low temperatures of 60°C or below, it is preferable to use a redox initiator, which is a combination of an oxidizing agent and a reducing agent, as the polymerization initiator. In other words, it is preferable to carry out the polymerization in the presence of a redox initiator.

[0114] Examples of oxidizing agents include persulfates, organic peroxides, potassium permanganate, manganese triacetate, ammonium cerium nitrate, and bromates. Examples of reducing agents include sulfites, bisulfites, bromates, diimines, oxalic acid, and metal sulfinates. Examples of persulfates include ammonium persulfate, potassium persulfate, and sodium persulfate. Examples of sulfites include sodium sulfite and ammonium sulfite. To increase the decomposition rate of the initiator, it is also preferable to add transition metal salts from groups 3 to 11 to the redox initiator combination. Examples of transition metal salts from groups 3 to 11 include copper salts, iron salts, and cobalt salts, with copper(II) sulfate being an example of a copper salt, iron(II) sulfate being an example of an iron salt, and cobalt(II) chloride being an example of a cobalt salt. Furthermore, when using copper salts or iron salts, it is particularly preferable to add a chelating agent. Ethylenediaminetetraacetate disodium salt dihydrate is preferred as a chelating agent.

[0115] Examples of redox initiators include potassium permanganate / oxalic acid, ammonium persulfate / bisulfite / ferrous sulfate, ammonium persulfate / sulfite / ferrous sulfate, ammonium persulfate / sulfite, ammonium persulfate / ferrous sulfate, manganese triacetate / oxalic acid, cerium ammonium nitrate / oxalic acid, bromate / sulfite, bromate / bisulfite, and ammonium persulfate / sodium hydroxymethanesulfinate dihydrate, with ammonium persulfate / sodium hydroxymethanesulfinate dihydrate being preferred.

[0116] When using a redox initiator, either the oxidizing agent or the reducing agent may be placed in the polymerization tank beforehand, and then the other may be added continuously or intermittently to initiate polymerization. For example, when using ammonium persulfate / sodium hydroxymethanesulfinate dihydrate, it is preferable to place ammonium persulfate in the polymerization tank and then continuously add sodium hydroxymethanesulfinate dihydrate thereto.

[0117] The amount of 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, relative to the aqueous medium used for polymerization.

[0118] The amount of reducing agent used is preferably 0.01 to 30% by mass, more preferably 0.05 to 10% by mass, and particularly preferably 0.1 to 5% by mass, relative to the aqueous medium used for polymerization.

[0119] Furthermore, the amount of the third component (the copper salt, iron salt, etc. mentioned above) 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, relative to the aqueous medium used for polymerization.

[0120] (Chain Transfer Agent) In the manufacturing method of the present disclosure, a second polymerization can be carried out in the presence of a chain transfer agent having an iodine atom or a bromine atom. Examples of chain transfer agents having an iodine atom or a bromine atom used in the second polymerization are the same as those that can be used in the first polymerization. By carrying out the second polymerization in the presence of a chain transfer agent having an iodine atom or a bromine atom, it is possible to produce an aqueous dispersion containing a fluorine-containing elastomer with excellent crosslinking properties while suppressing the adhesion of the resulting polymer to the container used for the polymerization reaction.

[0121] The amount of chain transfer agent having an iodine atom or a bromine atom used in the second polymerization is preferably 0.2 × 10¹⁶ of the total amount of monomers used in polymerization. －３ ~2 mol%, more preferably 1.0 × 10 －３ It is approximately 1 mole%.

[0122] (Compound (A)) In the manufacturing method of the present disclosure, a second polymerization can be carried out in the presence of compound (A) containing a functional group and a hydrophilic group that can react by radical polymerization. Examples of compound (A) used in the second polymerization are the same as those used in compound (A) used in the first polymerization.

[0123] When carrying out the second polymerization, compound (A) may be added, and the second polymerization may be carried out in the presence of compound (A). Also, if compound (A) is contained in the second aqueous dispersion, the second polymerization may be carried out in the presence of compound (A) contained in the second aqueous dispersion, or compound (A) may be further added in the second polymerization in addition to compound (A) contained in the second aqueous dispersion, and the second polymerization may be carried out. It is also not necessary to add compound (A) in the second polymerization.

[0124] The amount of compound (A) used in the second polymerization is preferably 3 to 5000 ppm by mass, more preferably 5 ppm by mass or more, even 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 more preferably 1000 ppm by mass or less, even 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.

[0125] (Aqueous medium) In the manufacturing method of the present disclosure, a second polymerization is carried out in the presence of an aqueous medium. Examples of aqueous medium include those that can be used in the first polymerization. The aqueous medium used in the second polymerization is mostly derived from the aqueous medium contained in the second aqueous dispersion. For example, an aqueous solution in which a polymerization initiator is dissolved in an aqueous medium may be added to the container in which the second polymerization is carried out, but it is necessary to add the aqueous solution so that the dilution ratio does not fall outside the range described above.

[0126] (Second polymerization) The second polymerization can be carried out, for example, by charging the second aqueous dispersion into a pressure-resistant container (polymerization tank) equipped with a stirrer, deoxygenating it, charging the monomer, raising it to a predetermined temperature, adding a polymerization initiator, and starting the reaction. As the reaction progresses, the pressure decreases, so additional monomers are continuously or intermittently supplied to maintain the initial pressure, and when a predetermined amount of monomers has been supplied, the supply is stopped, the monomers in the container are purged, and the temperature is returned to room temperature to terminate the reaction.

[0127] The second polymerization is preferably carried out in the absence of a fluorine-containing surfactant having no functional group capable of reacting by radical polymerization (hereinafter sometimes simply referred to as "fluorine-containing surfactant"). The fluorine-containing surfactant having no functional group capable of reacting by radical polymerization is as described in the first polymerization.

[0128] In the second polymerization, phosphates, sodium hydroxide, potassium hydroxide, aqueous ammonia, etc. may be used as the pH adjuster.

[0129] The aqueous medium is preferably acidic. By carrying out the second polymerization using an acidic aqueous medium, adhesion of the produced polymer to the container used for the polymerization reaction can be further suppressed. The pH of the aqueous medium is preferably 7 or less, more preferably 6.5 or less, and preferably 3 or more.

[0130] The polymerization temperature of the second polymerization is preferably 10 to 120°C, more preferably 20 to 100°C. Also, as the polymerization temperature, since a fluorine-containing elastomer with a high polymerization rate and further capable of giving a molded product 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.

[0131] The polymerization pressure of the second polymerization is preferably 0.5 to 10 MPaG, more preferably 1 to 7 MPaG.

[0132] (Third aqueous dispersion) As described above, a third aqueous dispersion containing a fluorine-containing elastomer can be prepared. The fluorine-containing elastomer will be described later.

[0133] In the production method of the present disclosure, the second polymerization can be carried out until the solid content concentration of the third aqueous dispersion reaches 15% by mass or more. The solid content concentration of the third aqueous dispersion is preferably 18% by mass or more, more preferably 21% by mass or more, and the upper limit is not particularly limited, but may be 50% by mass or less, 40% by mass or less, or 30% by mass or less.

[0134] The solid content concentration of an aqueous dispersion refers to the concentration of solids contained in the aqueous dispersion. Examples of solids include fluorine-containing elastomers. Alternatively, the solid content concentration of an aqueous dispersion may be the amount of fluorine-containing elastomer contained in the aqueous dispersion. The solid content concentration of an aqueous dispersion can be determined by drying 1 g of the aqueous dispersion at 150°C for 180 minutes, measuring the mass of the residue after heating, and calculating the ratio of the mass of the residue to the mass of the aqueous dispersion.

[0135] The third aqueous dispersion may contain fluorine-containing elastomer particles. The average particle size of the fluorine-containing elastomer particles is preferably 10 to 800 nm, more preferably 50 to 500 nm, and even more preferably 70 to 300 nm. The average particle size of the fluorine-containing elastomer particles is the cumulant average diameter and can be measured by dynamic light scattering.

[0136] The number of fluorine-containing elastomer particles contained in the third aqueous dispersion is preferably 1.0 × 10⁶ １２ The amount is 5.0 × 10¹⁶ or more per cc, and more preferably 5.0 × 10¹⁶. １２ The amount is 1.0 × 10¹ / cc or more, and more preferably 1.0 × 10¹⁶ １３ The amount is 1 / cc or more, and is particularly preferably 2.5 × 10 １３ The amount is 5.0 × 10¹ / cc or more, and most preferably 5.0 × 10¹ １３ The number of particles / cc is greater than or equal to the number of particles. The above number of particles (number of polymer particles) can be calculated according to the following formula.

[0137] The number of fluorine-containing elastomer particles obtained by the above formula is the number of particles per 1 cc of water. The specific gravity is the specific gravity of the fluorine-containing elastomer. The specific gravity of the fluorine-containing elastomer can be determined according to JIS Z 8807:2012.

[0138] (Fluorine-containing monomers) In the first polymerization and the second polymerization in the manufacturing method of this disclosure, fluorine-containing monomers are polymerized. The fluorine-containing monomers used in the first polymerization and the second polymerization may be the same or different. The fluorine-containing monomers used in the first polymerization and the second polymerization are appropriately selected according to the composition of the desired fluorine-containing elastomer.

[0139] Examples of fluorine-containing monomers include vinylidene fluoride (vinylidene fluoride) (VdF), tetrafluoroethylene (TFE), hexafluoropropylene (HFP), perfluoro(alkyl vinyl ether) (PAVE), chlorotrifluoroethylene (CTFE), trifluoroethylene, trifluoropropylene, tetrafluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutene, hexafluoroisobutene, vinyl fluoride, iodine-containing fluorinated vinyl ether, and general formula (2): CHX １ = CX ２ Rf (2) (wherein, X １ and X ２ Examples of fluorine-containing monomers include fluorine-containing monomers (2) represented by a fluorine monomer (where one atom is H and the other is F, and Rf is a linear or branched fluoroalkyl group having 1 to 12 carbon atoms).

[0140] As PAVE, perfluoro(methyl vinyl ether) (PMVE), perfluoro(ethyl vinyl ether) (PEVE), and perfluoro(propyl vinyl ether) (PPVE) are more preferred, with PMVE being particularly preferred.

[0141] Furthermore, PAVE is given by formula: CF ２ = CFOCF ２ ORf ｃ (wherein, Rf ｃ Perfluorovinyl ethers 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) can also be used. For example, PAVE is CF ２ = CFOCF２ OCF ３ CF ２ = CFOCF ２ OCF ２ CF ３ or CF ２ = CFOCF ２ OCF ２ CF ２ OCF ３ It is preferable.

[0142] As the fluorine-containing monomer (2), a monomer in which Rf is a linear fluoroalkyl group is preferred, and a monomer in which Rf is a linear perfluoroalkyl group is more preferred. The number of carbon atoms in Rf is preferably 1 to 6.

[0143] As for fluorine-containing monomer (2), CH ２ = CFCF ３ ,CH ２ = CFCF ２ CF ３ ,CH ２ = CFCF ２ CF ２ CF ３ ,CH ２ = CFCF ２ CF ２ CF ２ CF ３ CHF = CHCF ３ (1,3,3,3-tetrafluoropropene), CHF = CHCF ３ (E form), CHF=CHCF ３ Examples include (Z-form), and among them, CH ２ = CFCF ３ 2,3,3,3-tetrafluoropropylene, represented by [formula], is preferred.

[0144] In the manufacturing method of this disclosure, adhesion of the resulting polymer to the container used in the polymerization reaction can be further suppressed. Therefore, it is preferable to polymerize at least vinylidene fluoride or tetrafluoroethylene as the fluorine-containing monomer, and more preferably vinylidene fluoride.

[0145] In the manufacturing method of this disclosure, a fluorine-free monomer may be polymerized together with a fluorine-containing monomer. Examples of fluorine-free monomers include α-olefin monomers having 2 to 10 carbon atoms, such as ethylene, propylene, butene, and pentene; and alkyl vinyl ethers having alkyl groups with 1 to 20 carbon atoms, such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, and butyl vinyl ether. One or more of these monomers and compounds can be used in combination.

[0146] Among fluorine-containing elastomers, perfluoroelastomers are obtained by polymerizing perfluoro monomers.

[0147] Examples of perfluoro monomers include tetrafluoroethylene (TFE), hexafluoropropylene (HFP), and general formula (160): CF ２ =CF - ORf １３ (wherein, Rf １３ ) represents a perfluoroalkyl group having 1 to 8 carbon atoms. Fluoromers represented by the general formula (130): CF ２ = CFOCF ２ ORf １４ (wherein, Rf １４ Fluoromers represented by (where C1-C6 is a linear or branched perfluoroalkyl group, C5-C6 is a cyclic perfluoroalkyl group, or C2-C6 is a linear or branched perfluorooxyalkyl group containing 1-3 oxygen atoms), and General formula (140): CF ２ = CFO (CF ２ CF(Y １５ )O) ｍ (CF ２ ) ｎ F (wherein, Y １５ represents a fluorine atom or a trifluoromethyl group. m is an integer from 1 to 4. n is an integer from 1 to 4. At least one selected from the group consisting of fluoromonomers represented by ) is preferred.

[0148] Furthermore, in the polymerization of perfluoro monomers, a monomer that provides a crosslinking site, such as a monomer that provides a crosslinkable group as described later, may be polymerized together with the perfluoro monomer.

[0149] (Fluorine-containing elastomer) The fluorine-containing elastomer may be a partially fluorinated rubber or a perfluoroelastomer.

[0150] According to the manufacturing method of the present disclosure, an aqueous dispersion containing a fluorine-containing elastomer can be produced. The fluorine-containing elastomer obtained by the manufacturing method of the present disclosure has a methylene group (-CH) in its main chain. ２ It is preferable to include -). The main chain contains -CH ２ Examples of fluorine-containing elastomers include -CH ２ It is not particularly limited as long as it contains a chemical structure represented by -, for example, -CH ２ -CF ２ -ien-CH ２ -CH(CH ３ ) -, -CH ２ -CH ２ -ien-CH ２ -CF ２ - (CF ３ Examples include fluorine-containing elastomers containing structures such as ), which can be introduced into the main chain of a fluorine-containing elastomer by polymerizing vinylidene fluoride, propylene, ethylene, 2,3,3,3-tetrafluoropropylene, etc. The content of tetrafluoroethylene units in the fluorine-containing elastomer (content of monomer units based on tetrafluoroethylene relative to the total monomer units of the fluorine-containing elastomer) may be less than 40 mol%.

[0151] As the fluorine-containing elastomer, a partially fluorinated elastomer is preferred. A partially fluorinated elastomer is a fluoropolymer that contains fluorine-containing monomer units, has a perfluoro monomer unit content of less than 90 mol% relative to the total monomer units, has a glass transition temperature of 20°C or lower, and has a melting peak (ΔH) magnitude of 4.5 J / g or lower.

[0152] Examples of fluorine-containing elastomers include tetrafluoroethylene (TFE), vinylidene fluoride (VdF), and general formula: CF ２ = CF - Rf ａ (wherein, Rf ａ Ha-CF ３ or -ORf ｂ (Rf ｂ It is preferable to contain monomer units based on at least one monomer selected from the group consisting of perfluoroethylenically unsaturated compounds represented by perfluoroalkyl groups having 1 to 5 carbon atoms (for example, hexafluoropropylene (HFP), perfluoro(alkyl vinyl ether) (PAVE), etc.). The fluorine-containing elastomer is more preferably one that contains VdF units or TFE units, and more preferably one that contains VDF units.

[0153] More specifically, examples of fluorinated elastomers include VdF-based fluorinated elastomers, TFE / propylene (Pr)-based fluorinated elastomers, TFE / Pr / VdF-based fluorinated elastomers, ethylene (Et) / HFP-based fluorinated elastomers, Et / HFP / VdF-based fluorinated elastomers, Et / HFP / TFE-based fluorinated elastomers, and Et / TFE / PAVE-based fluorinated elastomers. Among these, VdF-based fluorinated elastomers, TFE / Pr-based fluorinated elastomers, TFE / Pr / VdF-based fluorinated elastomers, or Et / TFE / PAVE-based fluorinated elastomers are more preferred due to their good heat aging resistance and oil resistance.

[0154] 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, even more preferably 50 mol% or more, and particularly preferably 60 mol% or more, relative to the total number of monomer units. In VdF-based fluorine-containing elastomers, the amount of VdF units is preferably 20 mol% or more and 90 mol% or less, more preferably 40 mol% or more and 85 mol% or less, even more preferably 45 mol% or more and 80 mol% or less, and particularly preferably 50 mol% or more and 80 mol% or less, relative to the total number of moles of VdF units and monomer units based on other monomers.

[0155] Other monomers in the VdF-based fluorine-containing elastomer are not particularly limited as long as they are monomers copolymerizable with VdF; for example, the fluorine-containing monomers mentioned above can be used.

[0156] 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 VdF / fluorine-containing monomer (2) copolymer is preferred. Furthermore, it is more preferable that the monomer other than VdF is at least one monomer selected from the group consisting of TFE, HFP, and PAVE.

[0157] Among these, the VdF-based fluorine-containing elastomer is preferably at least one copolymer selected from the group consisting of VdF / HFP copolymer, VdF / TFE / HFP copolymer, VdF / fluorine-containing monomer (2) copolymer, VdF / PAVE copolymer, VdF / TFE / PAVE copolymer, VdF / HFP / PAVE copolymer and VdF / HFP / TFE / PAVE copolymer, and more preferably at least one copolymer selected from the group consisting of VdF / HFP copolymer, VdF / HFP / TFE copolymer, VdF / fluorine-containing monomer (2) copolymer and VdF / PAVE copolymer.

[0158] As for the VdF / PAVE copolymer, a VdF / PAVE composition of (65-90) / (35-10) (mol%) is preferred. Another preferred form is a VdF / PAVE composition of (50-78) / (50-22) (mol%).

[0159] As a VdF / TFE / PAVE copolymer, a VdF / TFE / PAVE composition of (40-80) / (3-40) / (15-35) (mol%) is preferred.

[0160] As a VdF / HFP / PAVE copolymer, a VdF / HFP / PAVE composition of (65-90) / (3-25) / (3-25) (mol%) is preferred.

[0161] As for the VdF / HFP / TFE / PAVE copolymer, a VdF / HFP / TFE / PAVE composition of (40-90) / (0-25) / (0-40) / (3-35) (mol%) is preferred, and a composition of (40-80) / (3-25) / (3-40) / (3-25) (mol%) is more preferred.

[0162] The VdF / fluorine-containing monomer (2) copolymer preferably has a VdF / fluorine-containing monomer (2) unit ratio of (85-20) / (15-80) (mol%), with other monomer units other than VdF and fluorine-containing monomer (2) making up 0-50 mol% of the total monomer units, and more preferably a mol% ratio of VdF / fluorine-containing monomer (2) units of (80-20) / (20-80). Another preferred form is when the composition of the VdF / fluorine-containing monomer (2) units is (78-50) / (22-50) (mol%).

[0163] Furthermore, as a copolymer of VdF / fluorine-containing monomer (2), it is also preferable that the VdF / fluorine-containing monomer (2) units are (85-50) / (15-50) (mol%), and that other monomer units other than VdF and fluorine-containing monomer (2) make up 1-50 mol% of the total monomer units. As other monomers other than VdF and fluorine-containing monomer (2), the monomers exemplified as other monomers in VdF-based fluorine-containing elastomers are preferred, and among these, PMVE, CTFE, HFP, PMVE, perfluoroethyl vinyl ether (PEVE), PPVE, CTFE, trifluoroethylene, hexafluoroisobutene, vinyl fluoride, Et, Pr, alkyl vinyl ether, and monomers that provide crosslinking groups are preferred, and among these, PMVE, CTFE, HFP, and TFE are more preferred.

[0164] TFE / Pr-based fluorine-containing elastomers refer to fluorine-containing copolymers consisting of 45-70 mol% TFE and 55-30 mol% Pr. In addition to these two components, a specific third component may also be included.

[0165] The specific third component may include, for example, fluorine-containing monomers such as fluorine-containing olefins other than TFE (e.g., VdF, HFP, CTFE, perfluoro(butylethylene), etc.), fluorine-containing vinyl ethers (perfluoro(propyl vinyl ether), perfluoro(methyl vinyl ether), etc.); hydrocarbon monomers such as α-olefins (ethylene, 1-butene, etc.), vinyl ethers (ethyl vinyl ether, butyl vinyl ether, hydroxybutyl vinyl ether, etc.), and vinyl esters (vinyl acetate, vinyl benzoate, vinyl crotate, vinyl methacrylate, etc.). The specific third component may be used individually or in combination of two or more.

[0166] TFE / Pr-based fluorine-containing elastomers preferably contain VdF, and among TFE / Pr-based fluorine-containing elastomers, those consisting of TFE, Pr, and VdF are called TFE / Pr / VdF-based fluorine-containing elastomers.

[0167] The TFE / Pr / VdF-based fluorine-containing elastomer may further contain the above-mentioned specific third component other than VdF. The above-mentioned specific third component may be one type or two or more types in combination. The total content of the third component in the TFE / Pr-based fluorine-containing elastomer is preferably 35 mol% or less, more preferably 33 mol% or less, and even more preferably 31 mol% or less.

[0168] The Et / HFP copolymer is preferably one in which the Et / HFP composition is (35-80) / (65-20) (mol%), and more preferably one in which the composition is (40-75) / (60-25) (mol%).

[0169] The Et / HFP / TFE copolymer is preferably composed of Et / HFP / TFE in a ratio of (35-75) / (25-50) / (0-15) (mol%), and more preferably in a ratio of (45-75) / (25-45) / (0-10) (mol%).

[0170] The Et / TFE / PAVE copolymer preferably has an Et / TFE / PAVE composition of (10-40) / (32-60) / (20-40) (mol%), and more preferably (20-40) / (40-50) / (20-30) (mol%). PMVE is preferred as the PAVE.

[0171] 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 a VdF / HFP / TFE composition of (32-85) / (10-34) / (0-40) (mol%) is particularly preferred. As the VdF / HFP / TFE composition, (32-85) / (15-34) / (0-34) (mol%) is more preferred, and (47-81) / (17-32) / (0-26) (mol%) is even more preferred.

[0172] For example, in the above VdF / HFP copolymer, the VdF / HFP composition is preferably (45-85) / (15-55) (mol%), more preferably (50-83) / (17-50) (mol%), even more preferably (55-81) / (19-45) (mol%), and particularly preferably (60-80) / (20-40) (mol%).

[0173] The above-described configuration is the main monomer of the fluorine-containing elastomer, and in addition to the main monomer, monomers that provide crosslinking groups may be copolymerized. Any monomer that can introduce appropriate crosslinking groups into the fluorine-containing elastomer depending on the manufacturing method and crosslinking system can be used, and examples include known polymerizable compounds containing crosslinking groups such as iodine atoms, bromine atoms, carbon-carbon double bonds, cyano groups, carboxyl groups, hydroxyl groups, amino groups, and ester groups.

[0174] In the manufacturing method of this disclosure, a second polymerization can be carried out in the presence of a monomer that provides a crosslinkable group containing an iodine atom, a bromine atom, or a cyano group. Examples of monomers that provide a crosslinkable group used in the second polymerization include monomers that contain an iodine atom, a bromine atom, or a cyano group as the crosslinkable group. By carrying out the second polymerization in the presence of a monomer that provides a crosslinkable group, it is possible to produce an aqueous dispersion containing a fluorine-containing elastomer with excellent crosslinking properties while suppressing the adhesion of the resulting polymer to the container used for the polymerization reaction.

[0175] A monomer that gives a desirable crosslinking group is the one with general formula (3): CY １ ２ =CY ２ R ｆ ２ X １ (3) (wherein, Y １ , Y ２ is a fluorine atom, a hydrogen atom, or -CH ３ ;R ｆ ２ X is a linear or branched fluorine-containing alkylene group having one or more ether-bonded oxygen atoms and an aromatic ring, in which some or all of the hydrogen atoms are substituted with fluorine atoms; １ Examples include compounds represented by an iodine atom, a bromine atom, or a cyano group.

[0176] Specifically, examples of monomers that provide crosslinking groups include, for example, the general formula (4): CY １ ２ =CY ２ R ｆ ３ CHR １ -X １ (4) (wherein, Y １ , Y ２ , X １ The same applies as above, R ｆ ３R may have one or more ether-bonded oxygen atoms, and is a linear or branched fluorinated alkylene group in which some or all of the hydrogen atoms are substituted with fluorine atoms, i.e., a linear or branched fluorinated alkylene group in which some or all of the hydrogen atoms are substituted with fluorine atoms, a linear or branched fluorinated oxyalkylene group in which some or all of the hydrogen atoms are substituted with fluorine atoms, or a linear or branched fluorinated polyoxyalkylene group in which some or all of the hydrogen atoms are substituted with fluorine atoms; １ Monomers represented by a hydrogen atom or a methyl group, general formulas (5) to (22): CY ４ ２ =CY ４ (CF ２ ) ｎ -X １ (5) (wherein, Y ４ (These are the same or different hydrogen atoms or fluorine atoms, and n is an integer from 1 to 8) CF ２ = CFCF ２ R ｆ ４ -X １ (6) (wherein, R ４ is, -(OCF ２ ) ｎ - or - (OCF (CF ３ )) ｎ - and n is an integer from 0 to 5) CF ２ = CFCF ２ (OCF(CF ３ ) CF ２ ) ｍ (OCH ２ CF ２ CF ２ ) ｎ OCH ２ CF ２ -X １ (7) (wherein m is an integer from 0 to 5, and n is an integer from 0 to 5) CF ２ = CFCF ２ (OCH ２ CF ２ CF ２ ) ｍ (OCF(CF ３ ) CF ２ ) ｎ OCF (CF ３ )-X１ (8) (wherein m is an integer from 0 to 5, and n is an integer from 0 to 5) CF ２ =CF(OCF) ２ CF (CF ３ )) ｍ O(CF) ２ ) ｎ -X １ (9) (wherein m is an integer from 0 to 5, and n is an integer from 1 to 8) CF ２ =CF(OCF) ２ CF (CF ３ )) ｍ -X １ (10) (wherein m is an integer from 1 to 5) CF ２ = CFOCF ２ (CF(CF ３ ) OCF ２ ) ｎ CF(-X １ ) CF ３ (11) (wherein n is an integer from 1 to 4) CF ２ = CFO (CF ２ ) ｎ OCF (CF ３ )-X １ (12) (wherein n is an integer from 2 to 5) CF ２ = CFO (CF ２ ) ｎ - (C ６ H ４ )-X １ (13) (wherein n is an integer from 1 to 6) CF ２ =CF(OCF) ２ CF (CF ３ )) ｎ OCF ２ CF (CF ３ )-X １ (14) (wherein n is an integer between 1 and 2) CH ２ = CFCF ２ O(CF(CF ３ ) CF ２ O) ｎ CF (CF ３ )-X １ (15) (wherein n is an integer from 0 to 5), CF ２ = CFO (CF ２ CF (CF ３ )O) ｍ(CF ２ ) ｎ -X １ (16) (wherein m is an integer from 0 to 5, and n is an integer from 1 to 3) CH ２ = CFCF ２ OCF (CF ３ )OCF(CF ３ )-X １ (17) CH ２ = CFCF ２ OCH ２ CF ２ -X １ (18) CF ２ = CFO (CF ２ CF (CF ３ )O) ｍ CF ２ CF (CF ３ )-X １ (19) (wherein m is a non-negative integer) CF ２ = CFOCF(CF ３ ) CF ２ O(CF) ２ ) ｎ -X １ (20) (wherein n is an integer greater than or equal to 1) CF ２ = CFOCF ２ OCF ２ CF (CF ３ ) OCF ２ -X １ (21) CH ２ = CH - (CF ２ ) ｎ X １ (22) (wherein n is an integer from 2 to 8) (In general formulas (5) to (22), X １ Examples include monomers represented by (as described above), and these can be used individually or in any combination.

[0177] The monomer represented by general formula (4) is general formula (23): Iodine-containing fluorinated vinyl ethers represented by the formula (wherein m is an integer from 1 to 5 and n is an integer from 0 to 3) are preferred, and more specifically, These are some examples, but among them, ICH ２ CF ２ CF２ OCF = CF ２ It is preferable.

[0178] More specifically, the monomer represented by general formula (5) is ICF. ２ CF ２ CF=CH ２ , I (CF ２ CF ２ ) ２ CF=CH ２ These are preferred.

[0179] More specifically, the monomer represented by general formula (9) is I(CF ２ CF ２ ) ２ OCF = CF ２ CF ２ =CF(OCF) ２ CF (CF ３ )) ｍ O(CF) ２ ) ｎ -CN is preferred.

[0180] More specifically, the monomer represented by general formula (22) is CH ２ =CHCF ２ CF ２ I, I (CF ２ CF ２ ) ２ CH=CH ２ These are preferred.

[0181] Also, 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 ７The groups are the same or different, and both consist of H or an alkyl group having 1 to 5 carbon atoms; Z is a linear or branched, preferably partially fluorinated alkylene or cycloalkylene group having 1 to 18 carbon atoms, which may contain an oxygen atom. Bisolefin compounds represented by these groups are also preferred as monomers that provide a crosslinking group. In this disclosure, "(per)fluoropolyoxyalkylene group" means "fluoropolyoxyalkylene group or perfluoropolyoxyalkylene group".

[0182] Z is preferably a (per)fluoroalkylene group having 4 to 12 carbon atoms, and R ２ , R ３ , R ４ , R ５ , R ６ and R ７ Preferably, it is a hydrogen atom.

[0183] If Z is a (per)fluoropolyoxyalkylene group, the formula is: -(Q) ｐ -CF ２ O-(CF ２ CF ２ O) ｍ - (CF ２ O) ｎ -CF ２ - (Q) ｐ It is preferable that the (per)fluoropolyoxyalkylene group is represented by - (wherein Q is an alkylene group having 1 to 10 carbon atoms or an oxyalkylene group having 2 to 10 carbon atoms, p is 0 or 1, and m and n are integers such that the m / n ratio is 0.2 to 5 and the molecular weight of the (per)fluoropolyoxyalkylene group is in the range of 500 to 10000, preferably 1000 to 4000). In this formula, Q is preferably -CH ２ OCH ２ - and -CH ２ O(CH ２ CH ２ O) ｓ CH ２ - Selected from (s = 1 to 3).

[0184] Preferred bisolefins are CH ２ = CH - (CF２ ) ２ -CH=CH ２ IEEE CH ２ = CH - (CF ２ ) ４ -CH=CH ２ IEEE CH ２ = CH - (CF ２ ) ６ -CH=CH ２ , Formula: CH ２ =CH-Z １ -CH=CH ２ (In the formula, Z １ ha-CH ２ OCH ２ -CF ２ O-(CF ２ CF ２ O) ｍ - (CF ２ O) ｎ -CF ２ -CH ２ OCH ２ Examples include - (m / n is 0.5, and the molecular weight is preferably 2000).

[0185] Among them, CH ２ = CH - (CF ２ ) ６ -CH=CH ２ 3,3,4,4,5,5,6,6,7,7,8,8-dodecafluoro-1,9-decadien, represented by [formula], is preferred.

[0186] The number-average molecular weight Mn of the fluorine-containing elastomer is preferably 1,000 to 1,000,000, more preferably 10,000 to 500,000, and particularly preferably 20,000 to 300,000.

[0187] The fluorine-containing elastomer preferably has a fluorine content of 50% by mass or more, more preferably 55% by mass or more, and even more preferably 60% by mass or more. The upper limit of the fluorine content is preferably 75% by mass or less, and more preferably 73% by mass or less. １９ F-NMR and １ It is calculated based on measurements obtained from methods such as H-NMR and elemental analysis.

[0188] The fluorine-containing elastomer preferably has a Mooney viscosity (ML1 + 10 (100°C)) of 10 to 130 at 100°C, more preferably 20 or higher, more preferably 110 or lower, and even more preferably 90 or lower. The Mooney viscosity is measured in accordance with JIS K 6300-1.2013.

[0189] The fluorine-containing elastomer preferably has a glass transition temperature of -50 to 0°C. More preferably, the glass transition temperature is -2°C or lower, and even more preferably -3°C or lower. Furthermore, the glass transition temperature is more preferably -45°C or higher, and even more preferably -40°C or higher. The glass transition temperature may be -10°C or higher, or -9°C or higher. Here, the glass transition temperature can be determined by obtaining a DSC curve by heating 10 mg of the sample at 20°C / min using a differential scanning calorimeter (for example, Hitachi High-Tech Science X-DSC7000), and then determining the glass transition temperature from the DSC differential curve according to JIS K6240:2011.

[0190] The fluorine-containing elastomer preferably has an iodine content of 0.05 to 1.0% by mass. More preferably, the iodine content is 0.08% by mass or more, even more preferably 0.10% by mass or more, even more preferably 0.80% by mass or less, and even more preferably 0.60% by mass or less.

[0191] The iodine content can be determined by elemental analysis. Specifically, 12 mg of fluorine-containing elastomer contains Na ２ SO ３ Mix 5 mg of [ingredient] with 20 ml of pure water and add Na [ingredient]. ２ CO ３ and K ２ CO ３ An absorption solution prepared by dissolving 30 mg of a 1:1 (mass ratio) mixture of the two substances is burned in oxygen in a quartz flask, left for 30 minutes, and then measured using a Shimadzu 20A ion chromatograph. Calibration curves can be used that contain KI standard solution, 0.5 ppm by mass iodide ions, and 1.0 ppm by mass iodide ions.

[0192] The fluorine-containing elastomer is preferably -CH ２It is preferable to include an I structure. -CH ２ Including structure I means １ This can be confirmed by 1H-NMR spectroscopy. -CH ２ Fluorine-containing elastomers containing structure I can be obtained by iodine transfer polymerization.

[0193] Fluorine-containing elastomers are -CH ２ - CH4 relative to 100 mol% of the structure ２ The amount of structure I is preferably 0.05 to 1.50 mol%. -CH ２ The amount of structure I is more preferably 0.08 mol% or more, even more preferably 0.12 mol% or more, more preferably 1.20 mol% or less, even more preferably 1.00 mol% or less, and particularly preferably 0.80 mol% or less. -CH ２ The amount of structure I is １ It can be determined by 1H-NMR spectroscopy.

[0194] Fluorine-containing elastomers are more preferably -CF ２ CH ２ Includes structure I. -CF ２ CH ２ Fluorine-containing elastomers containing structure I can be obtained by producing VdF-based fluorine-containing elastomers by iodine transfer polymerization.

[0195] Fluorine-containing elastomers are -CH ２ -CF relative to 100 mol% of structure ２ CH ２ The amount of structure I is preferably 0.05 to 1.50 mol%. -CF ２ CH ２ The amount of structure I is more preferably 0.08 mol% or more, even more preferably 0.12 mol% or more, more preferably 1.20 mol% or less, even more preferably 1.00 mol% or less, and particularly preferably 0.80 mol% or less. -CF ２ CH ２ The amount of structure I is １ In the 1H-NMR spectrum, -CH ２ The integral value A of the total peak intensity observed in the chemical shift region of 3.75–4.05 ppm originating from I, and -CH ２- The integral value B is calculated by subtracting the integral value of the water peak intensity observed in the 2.7–2.9 region from the integral value of the chemical shift of origin observed in the 2.30–3.75 ppm region, and then A / B*100.

[0196] The fluorine-containing elastomer may also be a perfluoroelastomer. In this disclosure, a perfluoroelastomer is a fluoropolymer having a perfluoro monomer unit content of 90 mol% or more, preferably 91 mol% or more, relative to the total polymerization units, having a glass transition temperature of 20°C or less, and having a melting peak (ΔH) of 4.5 J / g or less, and further having a fluorine atom concentration of 71% by mass or more, preferably 71.5% by mass or more. In this disclosure, the fluorine atom concentration of the fluoropolymer is calculated from the type and content of each monomer constituting the fluoropolymer.

[0197] As the perfluoroelastomer, at least one selected from the group consisting of perfluoroelastomers containing TFE, such as TFE / fluoromonomer copolymers represented by general formula (160), (130), or (140) and TFE / fluoromonomers represented by general formula (160), (130), or (140) / monomer copolymers that provide crosslinking sites is preferred. As the monomer that provides the crosslinking sites, the monomer that provides the crosslinkable group as described above is preferred.

[0198] The composition, in the case of the TFE / PMVE copolymer, is preferably 45-90 / 10-55 (mol%), more preferably 55-80 / 20-45, and even more preferably 55-70 / 30-45.

[0199] In the case of monomer copolymers that provide TFE / PMVE / crosslinking sites, the preferred values ​​are 45-89.9 / 10-54.9 / 0.01-4 (mol%), more preferably 55-77.9 / 20-49.9 / 0.1-3.5, and even more preferably 55-69.8 / 30-44.8 / 0.2-3.

[0200] In the case of a fluoromonomer copolymer represented by general formula (160), (130), or (140) with 4 to 12 carbon atoms, the ratio is preferably 50 to 90 / 10 to 50 (mol%), more preferably 60 to 88 / 12 to 40, and even more preferably 65 to 85 / 15 to 35.

[0201] In the case of a TFE / fluoromonomer represented by general formula (160), (130), or (140) having 4 to 12 carbon atoms / monomer copolymer that gives a crosslinking site, the preferred values ​​are 50 to 89.9 / 10 to 49.9 / 0.01 to 4 (mol%), more preferably 60 to 87.9 / 12 to 39.9 / 0.1 to 3.5, and even more preferably 65 to 84.8 / 15 to 34.8 / 0.2 to 3.

[0202] The perfluoroelastomer is preferably at least one selected from the group consisting of TFE / fluoromonomer represented by general formula (140) / monomer copolymer giving a crosslinking site, TFE / fluoromonomer copolymer represented by general formula (140), TFE / fluoromonomer copolymer represented by general formula (160), and TFE / fluoromonomer / monomer copolymer giving a crosslinking site.

[0203] Examples of the above-mentioned perfluoroelastomers include those described in International Publication No. 97 / 24381, Japanese Patent Publication No. 61-57324, Japanese Patent Publication No. 4-81608, Japanese Patent Publication No. 5-13961, etc.

[0204] As the fluorine-containing monomer used in the manufacturing method of this disclosure, the fluorine-containing monomers described for fluorine-containing elastomers can be used as appropriate.

[0205] (Post-treatment of the third aqueous dispersion) The third aqueous dispersion (fluorine-containing elastomer aqueous dispersion) may be subjected to treatments such as coagulation or heating.

[0206] The above coagulation can be carried out by adding alkaline earth metals and earth metal salts to an aqueous dispersion. Examples of alkaline earth metals and earth metal salts include sulfates, nitrates, hydrochlorides, and acetates of calcium, magnesium, and aluminum.

[0207] The coagulated fluorine-containing elastomer may be washed with water to remove small amounts of buffer solutions, salts, and other impurities 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 even more preferably 80 to 150°C.

[0208] The form of the fluorine-containing elastomer obtained after coagulation is not particularly limited, but may be gum, crumb, powder, pellets, etc., and gum or crumb is preferred. Gum is a small granular mass made of fluorine-containing elastomer, and crumb is an amorphous mass formed when the fluorine-containing elastomer cannot maintain its small granular shape as gum at room temperature and fuses with each other. Gum or crumb is preferably obtained by coagulation, drying, etc., from an aqueous dispersion obtained by the manufacturing method of this disclosure using a conventionally known method.

[0209] (Crosslinkable composition) A crosslinkable composition can be produced by mixing a fluorine-containing elastomer aqueous dispersion obtained by the manufacturing method of the present disclosure with a crosslinking agent.

[0210] The crosslinkable composition of this disclosure contains a fluorine-containing elastomer and a crosslinking agent. The type and amount of the crosslinking agent are not particularly limited and can be used within known limits.

[0211] Examples of crosslinking systems for fluorine-containing elastomers include peroxide crosslinking systems, polyol crosslinking systems, and polyamine crosslinking systems, and it is preferable that at least one is selected from the group consisting of peroxide crosslinking systems and polyol crosslinking systems. From the viewpoint of chemical resistance, peroxide crosslinking systems are preferred, and from the viewpoint of heat resistance, polyol crosslinking systems are preferred.

[0212] The crosslinking agent is preferably at least one selected from the group consisting of polyol crosslinking agents and peroxide crosslinking agents, and more preferably a peroxide crosslinking agent.

[0213] The amount of crosslinking agent can be appropriately selected depending on the type of crosslinking agent, but it is preferably 0.2 to 6.0 parts by mass, and more preferably 0.3 to 5.0 parts by mass, per 100 parts by mass of fluorine-containing elastomer.

[0214] Peroxide crosslinking can be performed by using a peroxide-crosslinkable fluorine-containing elastomer as the fluorine-containing elastomer and an organic peroxide as the crosslinking agent.

[0215] Any organic peroxide that can readily generate peroxy radicals in the presence of heat or a redox system can be used, and examples include 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butylperoxide, t-butylcumylperoxide, dicumylperoxide, 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, benzoylperoxide, t-butylperoxybenzene, t-butylperoxymaleic acid, t-butylperoxyisopropyl carbonate, and t-butylperoxybenzoate. Among these, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane and 2,5-dimethyl-2,5-di(t-butylperoxy)-hexyne-3 are preferred.

[0216] The amount of organic peroxide added is preferably 0.1 to 15 parts by mass, and more preferably 0.3 to 5 parts by mass, per 100 parts by mass of fluorine-containing elastomer.

[0217] When the crosslinking agent is an organic peroxide, the crosslinkable composition preferably further contains a crosslinking aid. Examples of crosslinking aids include triallyl cyanurate, triallyl isocyanurate (TAIC), triacrylic formal, triallyl trimellitate, N,N'-m-phenylene bismaleimide, dipropagyl terephthalate, diallyl phthalate, tetraallyl terephthalate amide, triallyl phosphate, bismaleimide, and fluorinated triallyl isocyanurate (1,3,5-tris(2,3,3-trifluoro-2-propenyl)-1,3,5-triazine-2,4,6- Examples include ion), tris(diallylamine)-S-triazine, N,N-diallylcrylamide, 1,6-divindodecafluorohexane, hexaarylphosphoramide, N,N,N',N'-tetraallylphthalamide, N,N,N',N'-tetraallylmalonamide, trivinyl isocyanurate, 2,4,6-trivinylmethyltrisiloxane, tri(5-norbornene-2-methylene)cyanurate, triallyl phosphite, and trimethallyl isocyanurate. Among these, triallyl isocyanurate (TAIC) is preferred due to its excellent crosslinkability, mechanical properties, and flexibility.

[0218] The amount of crosslinking aid added is preferably 0.01 to 10 parts by mass, more preferably 0.01 to 7.0 parts by mass, and even more preferably 0.1 to 5.0 parts by mass, per 100 parts by mass of fluorine-containing elastomer. If the amount of crosslinking aid is less than 0.01 parts by mass, the mechanical properties and flexibility will decrease. If it exceeds 10 parts by mass, the heat resistance will be poor and the durability of the molded product will tend to decrease.

[0219] The method for obtaining the crosslinkable composition is not particularly limited as long as it uses an aqueous dispersion of the fluorine-containing elastomer obtained by the manufacturing method of the present disclosure, or a method that allows for the uniform mixing of the fluorine-containing elastomer obtained by the manufacturing method of the present disclosure and a crosslinking agent. For example, one method is to knead a powder obtained by coagulating the fluorine-containing elastomer alone with other additives or compounding agents as needed in a kneader such as an open roll.

[0220] The form of the crosslinkable composition is not particularly limited, but may be, for example, an aqueous dispersion, gum, crumb, powder, pellet, etc. An aqueous dispersion is a dispersion system in which an aqueous medium is used as the dispersion medium and a fluorine-containing elastomer is used as the dispersed phase. The aqueous medium is not particularly limited as long as it is a liquid containing water, and may contain, in addition to water, organic solvents such as alcohol, ether, ketone, or paraffin wax.

[0221] The crosslinkable composition may be an aqueous dispersion containing a fluorine-containing elastomer, a crosslinking agent, and an aqueous medium. The upper limit of the solid content concentration of the aqueous dispersion is preferably 50% by mass, more preferably 40% by mass, even more preferably 35% by mass, and particularly preferably 30% by mass, relative to the aqueous dispersion. The lower limit of the solid content concentration of the aqueous dispersion is preferably 5% by mass, more preferably 10% by mass, even 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.

[0222] The solid content concentration of an aqueous dispersion refers to the concentration of solids contained in the aqueous dispersion. Examples of solids include fluorine-containing elastomers. Alternatively, the solid content concentration of an aqueous dispersion may be the amount of fluorine-containing elastomer contained in the aqueous dispersion. The solid content concentration of an aqueous dispersion can be determined by drying 1 g of the aqueous dispersion at 150°C for 180 minutes, measuring the mass of the residue after heating, and calculating the ratio of the mass of the residue to the mass of the aqueous dispersion.

[0223] The crosslinkable 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 a single molecule. The functional groups of the polyfunctional compound can be any functional group that is generally known to be reactive, such as carbonyl groups, carboxyl groups, haloformyl groups, amide groups, olefin groups, amino groups, isocyanate groups, hydroxyl groups, epoxy groups, etc.

[0224] The crosslinkable composition may contain various additives that are commonly used in elastomers as needed, such as fillers (carbon black, barium sulfate, etc.), processing aids (wax, etc.), plasticizers, colorants, stabilizers, tackifiers (coumarone resin, coumarone-indene resin, etc.), release agents, conductivity modifiers, thermal conductivity modifiers, surface non-tackeners, flexibility modifiers, heat resistance improvers, flame retardants, etc., and may also contain one or more commonly used crosslinking agents and crosslinking accelerators different from those mentioned above.

[0225] The content of fillers such as carbon black is not particularly limited, but it is preferably 0 to 300 parts by mass, more preferably 1 to 150 parts by mass, even more preferably 2 to 100 parts by mass, and particularly preferably 2 to 75 parts by mass per 100 parts by mass of fluorine-containing elastomer.

[0226] The content of processing aids such as wax is preferably 0 to 10 parts by mass, and more preferably 0 to 5 parts by mass, per 100 parts by mass of fluorine-containing elastomer. Since the use of processing aids, plasticizers, and mold release agents tends to reduce the mechanical properties and sealing properties of the resulting molded product, it is necessary to adjust their content within an acceptable range for the desired properties of the resulting molded product.

[0227] (Molded articles) Molded articles can be obtained by molding a crosslinkable composition. Alternatively, molded articles can be obtained by molding and crosslinking the composition. The composition can be molded by conventionally known methods. The molding and crosslinking methods and conditions may be within the range of known methods and conditions for the molding and crosslinking adopted. The order of molding and crosslinking is not limited; the crosslinking may be performed after molding, or the molding may be performed after crosslinking, or the molding and crosslinking may be performed simultaneously.

[0228] Examples of molding methods include compression molding, injection molding, injection molding, extrusion molding, and molding by funnel curing, but are not limited to these. Crosslinking methods include steam crosslinking, heating crosslinking, and radiation crosslinking, with steam crosslinking and heating crosslinking being preferred. Specific crosslinking conditions, which are not limited to these, can generally be determined appropriately based on the type of crosslinking accelerator, crosslinking agent, and acid acceptor, within a temperature range of 140 to 250°C and a crosslinking time of 1 minute to 24 hours.

[0229] Furthermore, heating the resulting molded product in an oven or the like can improve its mechanical properties and compression set characteristics at high temperatures. Specific crosslinking conditions, though not limited to these, are typically within a temperature range of 140 to 300°C and a duration of 30 minutes to 72 hours, depending on the type of crosslinking accelerator, crosslinking agent, and acid acceptor.

[0230] The resulting molded articles can be used as various components in fields such as the automotive, aerospace, and semiconductor industries. The molded articles can be used for applications similar to those of the crosslinked rubber molded articles described in Japanese Patent Application Publication No. 2013-216915 and the fluororubber molded articles described in Japanese Patent Application Publication No. 2019-94430, such as sealing materials, sliding members, and non-stick members.

[0231] Examples of applications for the molded products include various sealing materials and packings such as rings, packings, gaskets, diaphragms, oil seals, and bearing seals. As a sealing material, it can be used in applications requiring excellent non-stick properties and low friction. In particular, it can be suitably used as a sealing material in various applications in the automotive industry and other sectors.

[0232] It can also be used as a tube, hose, roll, various rubber rolls, flexible joint, rubber sheet, coating, belt, damper, valve, valve seat, valve body, chemical-resistant coating material, laminating material, lining material, and more.

[0233] Although embodiments have been described above, it should be understood that various modifications to the form and details are possible without departing from the spirit and scope of the claims.

[0234] <1> According to the first aspect of this disclosure, a method for producing an aqueous dispersion of a fluorine-containing elastomer, comprising: (1) carrying out a first polymerization of a fluorine-containing monomer in a container, substantially in the absence of a fluorine-containing surfactant that does not have functional groups that can react by radical polymerization, and in the presence of an aqueous medium and a polymerization initiator, to prepare a first aqueous dispersion containing a fluorine-containing polymer; (2) removing the first aqueous dispersion from the container, diluting the removed first aqueous dispersion 3 to 40 times to prepare a second aqueous dispersion, or diluting the first aqueous dispersion 3 to 40 times in the container to prepare a second aqueous dispersion, and removing it from the container. (3) A method is provided for preparing a third aqueous dispersion containing a fluorine-containing elastomer by performing a second polymerization of a fluorine-containing monomer in the same container in which the first polymerization was performed, or in a container different from the container in which the first polymerization was performed, substantially in the absence of a fluorine-containing surfactant that does not have a functional group that can react by radical polymerization, and in the presence of a chain transfer agent having an iodine atom or a bromine atom, and at least one selected from the group consisting of monomers that give a crosslinking group containing an iodine atom, a bromine atom or a cyano group, and a second aqueous dispersion. <2> According to a second aspect of this disclosure, a method is provided according to a first aspect, in which the first polymerization is performed in the presence of a fluorine-free compound having a hydrophilic group. <3> According to a third aspect of this disclosure, a method is provided according to a second aspect, in which the fluorine-free compound having a hydrophilic group is a fluorine-free anionic surfactant. <4> According to a fourth aspect of this disclosure, the fluorine-free compound having a hydrophilic group is a compound with general formula (X): R Ｚ - (L-M) ｘ (In the formula, R ＺA method for producing an anionic surfactant represented by ) is provided. <5> According to a fifth aspect of this disclosure, a method for producing an anionic surfactant represented by any of the second to fourth aspects is provided, wherein in the first polymerization, the mass ratio of the fluorine-free compound having a hydrophilic group to the polymerization initiator (fluorine-free compound having a hydrophilic group / polymerization initiator) is 0.600 or less. <6> According to a sixth aspect of this disclosure, a method for producing an anionic surfactant represented by any of the first to fifth aspects is provided, wherein in the first polymerization, the amount of the polymerization initiator is 500 ppm by mass or more with respect to the aqueous medium. <7> According to the seventh aspect of this disclosure, a manufacturing method according to any of the first to sixth aspects is provided, wherein the polymerization initiator used in the first polymerization is a persulfate. <8> According to the eighth aspect of this disclosure, a manufacturing method according to any of the first to seventh aspects is provided, wherein the first polymerization is carried out in the presence of a compound (A) containing a functional group and a hydrophilic group that can react by radical polymerization. <9> According to the ninth aspect of this disclosure, a manufacturing method according to any of the first to eighth aspects is provided, wherein the first polymerization is carried out substantially in the absence of a redox initiator. <10> According to the tenth aspect of this disclosure, a manufacturing method according to any of the first to ninth aspects is provided, wherein the first polymerization is carried out in the presence of a pH adjuster. <11> According to the eleventh aspect of this disclosure, a manufacturing method according to any of the first to tenth aspects is provided, wherein the solid content concentration of the first aqueous dispersion is less than 12% by mass. <12> According to the twelfth aspect of this disclosure, a manufacturing method according to any of the first to eleventh aspects is provided, further comprising heat-treating the first aqueous dispersion at 70°C or higher for 3 hours or more. <13> According to the thirteenth aspect of this disclosure, a manufacturing method according to any of the first to twelfth aspects is provided, wherein the solid content concentration of the third aqueous dispersion is 15% by mass or more.<14> According to the 14th aspect of this disclosure, a manufacturing method according to any of the first to 13 aspects is provided, wherein the polymerization temperatures of the first and second polymerizations are 10 to 120°C. <15> According to the 15th aspect of this disclosure, a manufacturing method according to any of the first to 14 aspects is provided, wherein the polymerization pressures of the first and second polymerizations are 0.5 to 10 MPaG. <16> According to the 16th aspect of this disclosure, a manufacturing method according to any of the first to 15 aspects is provided, wherein the fluorine-containing elastomer has a methylene group in its main chain. <17> According to the 17th aspect of this disclosure, the fluorine-containing elastomer is -CH. ２ Includes an I structure, -CH ２ - CH4 relative to 100 mol% of the structure ２ A method for producing a fluorine-containing elastomer is provided according to any of the first to sixteen aspects, wherein the amount of structure I is 0.05 to 1.50 mol%. <18> According to the eighteenth aspect of the present disclosure, a method for producing a fluorine-containing elastomer is provided according to any of the first to fifteen aspects, wherein the fluorine-containing elastomer is a perfluoroelastomer. <19> According to the ninth aspect of the present disclosure, a method for producing a fluorine-containing elastomer is provided according to any of the first to eighteen aspects, wherein the Mooney viscosity (ML1 + 10 (100°C)) of the fluorine-containing elastomer is 10 to 130.

[0235] Next, embodiments of the present disclosure will be described with reference to examples, but the present disclosure is not limited to such embodiments.

[0236] Each value in the examples was measured by the following method.

[0237] Solid content of aqueous dispersion: 1 g of aqueous dispersion was dried in a forced-air dryer at 150°C for 180 minutes, and the mass of the residue after heating was measured. The ratio (mass%) of the mass of the residue to the mass of the aqueous dispersion (1 g) was then determined.

[0238] Polymer Adhesion Rate The ratio of the mass of polymer deposits adhering to the polymerization tank (container used for the polymerization reaction) after polymerization to the total amount of polymer (fluorine-containing elastomer) after polymerization (adhesion rate to the polymerization tank) was calculated using the following formula: Polymer Adhesion Rate (mass%) = Mass of Polymer Deposits / Mass of Obtained Polymer (including Polymer Deposits) × 100 Mass of Obtained Polymer = Mass of Aqueous Dispersion × Solid Content Concentration of Aqueous Dispersion (mass%) / 100 + Mass of Polymer Deposits Polymer deposits include polymers adhering to the inside of the polymerization tank, such as the inner wall and stirring blades, after the aqueous dispersion is removed from the polymerization tank after polymerization is complete, and polymers that have been released from the aqueous dispersion by aggregation and are suspended or settled without being dispersed in the aqueous dispersion. The mass of polymer deposits is the mass after the water contained in the polymer deposits has been dried and removed at 120°C.

[0239] The average particle size (cumulant average diameter) of fluorine-containing elastomer particles in an aqueous dispersion was measured using dynamic light scattering with an ELSZ-1000S (manufactured by Otsuka Electronics Co., Ltd.) and calculated using the cumulant method.

[0240] The number of particles (number of fluorine-containing elastomer particles in the aqueous dispersion) was calculated using the following formula.

[0241]

[0242] In the formula, the average particle diameter is the average cumulant 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 fluorine-containing elastomers in the examples and comparative examples was set to 1.8.

[0243] Mooney viscosity was measured using an ALPHA TECHNOLOGIES Premier MV Mooney viscometer at 100°C or 121°C, in accordance with JIS K 6300-1.2013.

[0244] The copolymer composition was determined by NMR analysis.

[0245] Fluorine-containing elastomer -CH ２ - CH4 relative to 100 mol% of the structure ２I-structure fluorine-containing elastomer １ This was determined by 1H-NMR spectroscopy.

[0246] pH value: The pH value was measured using pH test paper.

[0247] Preparation Example 1: Add 1500g of deionized water and CH to a SUS polymerization tank with an internal volume of 3L. ２ = CFCF ２ OCF (CF ３ ) CF ２ OCF (CF ３ ) COONH ４ 1.5 g of a 10% by mass aqueous solution and 0.3 g of sodium laurate were added, the polymerization vessel was sealed, and the system was purged with nitrogen to remove oxygen. The polymerization vessel was heated to 80°C, and while stirring, the monomer (initial monomer) vinylidene fluoride [VDF] / hexafluoropropylene [HFP] (= 50 / 50 mol%) was injected under pressure to a pressure of 1.80 MPaG. Next, an aqueous polymerization initiator solution, in which 0.60 g of ammonium persulfate (APS) was dissolved in deionized water, was injected under pressure with nitrogen gas. The reaction was then started. As polymerization progressed, when the internal pressure dropped to 1.795 MPaG, a mixed monomer of VDF / HFP (= 78 / 22 mol%) was added to maintain a constant internal pressure of 1.80 MPaG. APS was added in 3.9 g and 1.5 g portions 2 and 3 hours after the start of the reaction, and 20% by mass sodium hydroxide aqueous solution was added in 2.629 g, 2.629 g, and 5.258 g portions 3, 4.5, and 6 hours after the start of the reaction. The addition of the mixed monomer was repeated, and stirring was stopped 6 hours after the start of the reaction. The polymerization tank was depressurized until it reached atmospheric pressure. The total amount of mixed monomer added at the end of the reaction was 132 g. During the reaction, the stirring speed was adjusted to control the reaction rate. After depressurization, the polymerization tank was heated to 90°C and heat-treated for 2 hours. The polymerization tank was cooled to obtain an aqueous dispersion with a solid content of 8.3% by mass. The polymerization time, mass of the aqueous dispersion, pH, average particle size, and number of particles are shown in Table 1.

[0248] Preparation Example 2 was carried out in the same manner as Preparation Example 1, except that sodium persulfate (NaPS) was added as the initiator instead of ammonium persulfate (APS) at the beginning (1.565 g) and 3 hours after the start of the reaction (1.565 g), 0.15 g of sodium laurate was added, 2.629 g and 2.629 g of 20% by mass aqueous sodium hydroxide solution were added at 3 and 6 hours after the start of the reaction, the internal pressure during polymerization was set to 0.50 MPaG, and 71 g of mixed monomer was added. An aqueous dispersion with a solid content of 4.8% by mass was obtained. The polymerization time, mass of the aqueous dispersion, average particle size, and number of particles are shown in Table 1.

[0249] Preparation example 3 CH ２ = CFCF ２ OCF (CF ３ ) CF ２ OCF (CF ３ ) COONH ４ Except for adding 0.750 g of a 50% by mass aqueous solution, adding 3.00 g of APS as an initiator at the start of the reaction, adding 9.100 g of disodium hydrogen phosphate heptahydrate (dissolved in 35 g of deionized water) one hour after the start of the reaction instead of a 20% by mass aqueous solution of sodium hydroxide, and adding 108 g of mixed monomer, the procedure was carried out in the same manner as in Preparation Example 1 to obtain an aqueous dispersion with a solid content of 7.1% by mass. The polymerization time, mass of the aqueous dispersion, average particle size, and number of particles are shown in Table 1.

[0250] Preparation Example 4 was carried out in the same manner as Preparation Example 3, except that 0.075 g of sodium laurate was added and 96 g of the mixed monomer was added to obtain an aqueous dispersion with a solid content of 6.6% by mass. The polymerization time, mass of the aqueous dispersion, average particle size, and number of particles are shown in Table 1.

[0251] Preparation example 5 CH ２ = CFCF ２ OCF (CF ３ ) CF ２ OCF (CF ３ ) COONH ４Except for adding 1,500 g of a 50% by mass aqueous solution of [the substance], adding 1,500 g of APS as an initiator at the start of the reaction, adding 4.5502 g of disodium hydrogen phosphate heptahydrate (dissolved in 22 g of deionized water) 1 hour after the start of the reaction, and adding 107 g of mixed monomer, the procedure was carried out in the same manner as in Preparation Example 1 to obtain an aqueous dispersion with a solid content of 7.0% by mass. The polymerization time, mass of the aqueous dispersion, average particle size, and number of particles are shown in Table 1.

[0252]

[0253] Example 1 In a SUS polymerization tank with an internal volume of 3 L, 1350 g of deionized water and 150 g of the aqueous dispersion prepared in Preparation Example 1 were added. The polymerization tank was sealed, and the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 80°C, and while stirring, monomers (initial monomers) vinylidene fluoride [VDF] / tetrafluoroethylene [TFE] / hexafluoropropylene [HFP] (= 19 / 11 / 70 mol%) were injected under pressure to a pressure of 2.00 MPaG. Next, an aqueous polymerization initiator solution, in which 0.03 g of ammonium persulfate (APS) was dissolved in deionized water, was injected under pressure with nitrogen gas. Polymerization was then started. As polymerization progressed, when the internal pressure dropped to 1.995 MPaG, a mixed monomer of VDF / TFE / HFP (= 50 / 20 / 30 mol%) was added so that the internal pressure remained constant at 2.00 MPaG. The addition of the mixed monomer was repeated until 4 g of the mixed monomer had been added, at which point iodine compound I (CF) was added. ２ ) ４ 2.45 g of I was injected under pressure with nitrogen gas. 0.03 g of APS was added 3 hours after the start of the reaction. The mixing monomer was added repeatedly until 467 g of the mixed monomer had been added, at which point stirring was stopped and the polymerization tank was depressurized until it reached atmospheric pressure. The polymerization tank was cooled to obtain an aqueous dispersion with a solid content of 23.2% by mass. Table 2 shows the polymerization time, adhesion rate, mass of the aqueous dispersion, average particle size, and number of particles.

[0254] An aqueous solution of aluminum sulfate was added to the above aqueous dispersion to induce coagulation. The resulting coagulation was washed with water and dried to obtain a rubbery fluorine-containing copolymer. The Mooney viscosity of the above rubbery fluorine-containing copolymer was ML1 + 10 (100°C) = 40. The copolymer composition was determined by NMR analysis to be VDF / TFE / HFP = 54 / 20 / 26 (mol%). Also, -CH ２ - CH4 relative to 100 mol% of the structure ２ Table 2 shows the amount of structure I.

[0255] Example 2 The procedure was the same as in Example 1, except that 300 g of the aqueous dispersion prepared in Preparation Example 2 was added instead of the aqueous dispersion prepared in Preparation Example 1, and 1250 g of deionized water was added. When 464 g of the mixed monomer had been 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 with a solid content of 23.3% by mass. The polymerization time, adhesion rate, mass of the aqueous dispersion, average particle size, and number of particles are shown in Table 2.

[0256] An aqueous solution of aluminum sulfate was added to the above aqueous dispersion to induce coagulation. The resulting coagulation was washed with water and dried to obtain a rubbery fluorine-containing copolymer. The Mooney viscosity of the above rubbery fluorine-containing copolymer was ML1 + 10 (100°C) = 43. The copolymer composition was determined by NMR analysis to be VDF / TFE / HFP = 54 / 21 / 25 (mol%). Also, -CH ２ - CH4 relative to 100 mol% of the structure ２ Table 2 shows the amount of structure I.

[0257] Example 3: When 8 g of mixed monomer was added, without adding the aqueous dispersion prepared in Preparation Example 1, 50 g of the aqueous dispersion prepared in Preparation Example 2 was added, and 1450 g of deionized water was added, iodine compound I (CF) ２ ) ４ The procedure was the same as in Example 1, except that 2.45 g of I was injected under pressure with nitrogen gas. When 475 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 with a solid content of 22.7% by mass. The polymerization time, adhesion rate, mass of the aqueous dispersion, average particle size, and number of particles are shown in Table 2.

[0258] An aqueous aluminum sulfate solution was added to the above aqueous dispersion to induce coagulation. The resulting coagulation was washed with water and dried to obtain a rubbery fluorine-containing copolymer. The Mooney viscosity of the above rubbery fluorine-containing copolymer was ML1 + 10 (100°C) = 51. The copolymer composition was determined by NMR analysis to be VDF / TFE / HFP = 54 / 21 / 25 (mol%). Also, -CH ２ - CH4 relative to 100 mol% of the structure ２ Table 2 shows the amount of structure I.

[0259] Example 4 1425 g of deionized water and 75 g of the aqueous dispersion prepared in Preparation Example 1 were added to a 3 L SUS polymerization tank. The polymerization tank was sealed, and the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 80°C, and while stirring, the monomer (initial monomer) vinylidene fluoride [VDF] / hexafluoropropylene [HFP] (= 50 / 50 mol%) was injected under pressure to a pressure of 2.00 MPaG. Next, an aqueous polymerization initiator solution, in which 0.03 g of ammonium persulfate (APS) was dissolved in deionized water, was injected under pressure with nitrogen gas. The reaction was then started. As polymerization progressed, when the internal pressure dropped to 1.995 MPaG, the VDF / HFP (= 50 / 50 mol%) mixed monomer was added to maintain a constant internal pressure of 2.00 MPaG. The preparation of the mixed monomer was repeated, and when 4g of the mixed monomer was added, iodine compound I (CF) ２ ) ４ 2.16 g of I was injected under pressure with nitrogen gas. 0.03 g of APS was added 3 hours after the start of the reaction. The mixing monomer was added repeatedly until 495 g of the mixed monomer had been added, at which point stirring was stopped and the polymerization tank was depressurized until it reached atmospheric pressure. The polymerization tank was cooled to obtain an aqueous dispersion with a solid content of 24.9% by mass. The polymerization time, adhesion rate, mass of the aqueous dispersion, average particle size, and number of particles are shown in Table 2.

[0260] An aqueous aluminum sulfate solution was added to the above aqueous dispersion to induce coagulation. The resulting coagulation was washed with water and dried to obtain a rubbery fluorine-containing copolymer. The Mooney viscosity of the above rubbery fluorine-containing copolymer was ML1 + 10 (100°C) = 46. The copolymer composition was determined by NMR analysis to be VDF / HFP = 78 / 22 (mol%). Also, -CH２ - CH4 relative to 100 mol% of the structure ２ Table 2 shows the amount of structure I.

[0261] Example 5: When the aqueous dispersion prepared in Preparation Example 1 was not added, 150 g of the aqueous dispersion prepared in Preparation Example 3 was added, 1350 g of deionized water was added, and 1 g of mixed monomer was added, iodine compound I (CF) ２ ) ４ The procedure was the same as in Example 4, except that 2.16 g of I was injected under pressure with nitrogen gas. When 488 g of the mixed monomer was added, stirring was stopped and the polymerization tank was depressurized until it reached atmospheric pressure. The polymerization tank was cooled to obtain an aqueous dispersion with a solid content of 25.1% by mass. The polymerization time, adhesion rate, mass of the aqueous dispersion, average particle size, and number of particles are shown in Table 2.

[0262] An aqueous aluminum sulfate solution was added to the above aqueous dispersion to induce coagulation. The resulting coagulation was washed with water and dried to obtain a rubbery fluorine-containing copolymer. The Mooney viscosity of the above rubbery fluorine-containing copolymer was ML1 + 10 (100°C) = 46. The copolymer composition was determined by NMR analysis to be VDF / HFP = 78 / 22 (mol%). Also, -CH ２ - CH4 relative to 100 mol% of the structure ２ Table 2 shows the amount of structure I.

[0263] Example 6 When 2 g of mixed monomer was added, iodine compound I (CF ２ ) ４ When 1.67 g of I and 9 g of mixed monomers were added, the iodine compound CF ２ = CFOCF ２ CF ２ CH ２ The procedure was the same as in Example 5, except that 1.24 g of I was injected under pressure with nitrogen gas. When 488 g of the mixed monomer was added, stirring was stopped and the polymerization tank was depressurized until it reached atmospheric pressure. The polymerization tank was cooled to obtain an aqueous dispersion with a solid content of 25.1% by mass. The polymerization time, adhesion rate, mass of the aqueous dispersion, average particle size, and number of particles are shown in Table 2.

[0264] An aqueous aluminum sulfate solution was added to the above aqueous dispersion to induce coagulation. The resulting coagulation was washed with water and dried to obtain a rubbery fluorine-containing copolymer. The Mooney viscosity of the above rubbery fluorine-containing copolymer was ML1 + 10 (100°C) = 49. The copolymer composition was determined by NMR analysis to be VDF / HFP = 78 / 22 (mol%). Also, -CH ２ - CH4 relative to 100 mol% of the structure ２ Table 2 shows the amount of structure I.

[0265] Example 7: The aqueous dispersion prepared in Preparation Example 3 was not added, and 150 g of the aqueous dispersion prepared in Preparation Example 4 was added. When 1 g of the mixed monomer was added, the iodine compound I (CF) ２ ) ４ The procedure was the same as in Example 5, except that 2.16 g of I was injected under pressure with nitrogen gas. When 492 g of the mixed monomer was added, stirring was stopped and the polymerization tank was depressurized until it reached atmospheric pressure. The polymerization tank was cooled to obtain an aqueous dispersion with a solid content of 25.1% by mass. The polymerization time, adhesion rate, mass of the aqueous dispersion, average particle size, and number of particles are shown in Table 2.

[0266] An aqueous solution of aluminum sulfate was added to the above aqueous dispersion to induce coagulation. The resulting coagulation was washed with water and dried to obtain a rubbery fluorine-containing copolymer. The Mooney viscosity of the above rubbery fluorine-containing copolymer was ML1 + 10 (100°C) = 43.5. The copolymer composition was determined by NMR analysis to be VDF / HFP = 78 / 22 (mol%). Also, -CH ２ - CH4 relative to 100 mol% of the structure ２ Table 2 shows the amount of structure I.

[0267] Example 8 In a 3 L SUS polymerization tank, 1625 g of deionized water and 179 g of the aqueous dispersion prepared in Preparation Example 4 were added. The polymerization tank was sealed, and the system was purged with nitrogen to remove oxygen. The temperature was raised to 80°C while stirring at 560 rpm, and then monomer (initial monomer) VDF / HFP (= 39 / 61 mol%) was injected under pressure while stirring to a pressure of 6.0 MPaG. Next, an aqueous polymerization initiator solution, in which 0.111 g of APS was dissolved in 5 ml of deionized water, was injected under pressure with nitrogen gas to start polymerization.

[0268] As polymerization progresses, the internal pressure begins to decrease, so VDF monomers were added so that the internal pressure remained constant at 6.0 MPaG. Seven minutes after the start of polymerization, iodine compound I (CF) ２ ) ４ 3.6 g of I was injected under pressure with nitrogen gas. After adding 353 g of polymerized VDF monomer, unreacted monomers were released, and the autoclave was cooled to obtain an aqueous dispersion with a solid content of 26.5% by mass. The polymerization time, adhesion rate, mass of the aqueous dispersion, average particle size, and number of particles are shown in Table 2.

[0269] An aqueous solution of aluminum sulfate was added to the above aqueous dispersion to induce coagulation. The obtained coagulation was washed with water and dried to obtain a rubbery fluorine-containing copolymer. The Mooney viscosity of the above rubbery fluorine-containing copolymer was ML1 + 10 (100°C) = 38 and ML1 + 10 (121°C) = 17. The copolymer composition was determined by NMR analysis to be VDF / HFP = 78 / 22 (mol%). Also, -CH ２ - CH4 relative to 100 mol% of the structure ２ Table 2 shows the amount of structure I.

[0270] Example 9 was carried out in the same manner as in Example 8, except that 1680 g of deionized water and 120 g of the aqueous dispersion prepared in Preparation Example 4 were added to obtain an aqueous dispersion with a solid content of 26.9% by mass. The polymerization time, adhesion rate, mass of the aqueous dispersion, average particle size, and number of particles are shown in Table 2.

[0271] The above aqueous dispersion was subjected to the same procedure as in Example 8 to obtain a rubbery fluorine-containing copolymer. The Mooney viscosity of the above rubbery fluorine-containing copolymer was ML1 + 10 (100°C) = 39 and ML1 + 10 (121°C) = 17. The copolymer composition was determined by NMR analysis to be VDF / HFP = 78 / 22 (mol%). Also, -CH ２ - CH4 relative to 100 mol% of the structure ２ Table 2 shows the amount of structure I.

[0272] Example 10 Without adding the aqueous dispersion prepared in Preparation Example 4, 120 g of the aqueous dispersion prepared in Preparation Example 5 was added, and iodine compound I (CF) ２ ) ４Except for using 3.40 g of I, the procedure was carried out in the same manner as in Example 9 to obtain an aqueous dispersion with a solid content of 27.2% by mass. The polymerization time, adhesion rate, mass of the aqueous dispersion, average particle size, and number of particles are shown in Table 2.

[0273] The above aqueous dispersion was subjected to the same procedure as in Example 8 to obtain a rubbery fluorine-containing copolymer. The Mooney viscosity of the above rubbery fluorine-containing copolymer was ML1 + 10 (100°C) = 48 and ML1 + 10 (121°C) = 23. The copolymer composition was determined by NMR analysis to be VDF / HFP = 78 / 22 (mol%). Also, -CH ２ - CH4 relative to 100 mol% of the structure ２ Table 2 shows the amount of structure I.

[0274]

[0275] Experimental Example 1 The rubbery fluorine-containing copolymer (fluorine-containing elastomer) obtained in Example 1 was kneaded according to the formulation shown in Table 3 to obtain a crosslinkable composition. For the obtained crosslinkable composition, the crosslinking curve was determined using a rubber vulcanization tester MDRH2030 (manufactured by M&K Co., Ltd.) during primary press crosslinking, and the minimum viscosity (ML), maximum torque level (MH), induction time (T10), and optimal crosslinking time (T90) were determined. The results are shown in Table 3. Kneading method: Roll kneading Press crosslinking: 10 minutes at 160°C Oven crosslinking: 4 hours at 180°C

[0276] The materials shown in Table 3 are as follows: MT Carbon: Thermax N-990, manufactured by Cancarb. Ltd. TAIC: Triallyl isocyanurate, manufactured by Taik Shinryo Co., Ltd. Perhexa 25B: 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, manufactured by NOF Corporation

[0277] Normal Physical Properties: The 100% modulus (M100), tensile strength at break (TB), and elongation at break (EB) of a cross-linked molded sheet (dumbbell-shaped test specimen) prepared in accordance with JIS K6251 were measured under normal conditions.

[0278] The hardness (Shore A) of the cross-linked molded product (dumbbell-shaped test piece, No. 6) was measured in accordance with JIS K6253 (peak value, 1 sec, 3 sec).

[0279] For P-24 O-rings manufactured in accordance with JIS K6262, the compression set was measured at 200°C for 72 hours under 25% compression.

[0280] Experimental Examples 2-10 were evaluated in the same manner as in Experimental Example 1, except that the rubbery fluorine-containing copolymer obtained in Examples 2-10 was used instead of the rubbery fluorine-containing copolymer obtained in Example 1. The results are shown in Table 3.

[0281]

[0282] Example 11 A SUS polymerization tank with an internal volume of 6 L and no ignition source was used to add 2088 g of deionized water and 500 g of the aqueous dispersion prepared in Preparation Example 5. The system was then purged with nitrogen to remove oxygen. The temperature was raised to 50°C while stirring at 400 rpm. A mixed gas of tetrafluoroethylene (TFE) and perfluoromethyl vinyl ether (PMVE) (TFE / PMVE = 25.6 / 74.4 mol%) was added to bring the internal pressure to 0.83 MPa·G. Then, 4.257 g of ammonium persulfate (APS) was dissolved in 5.0 g of deionized water, and the reaction was started by injecting it under pressure with nitrogen.

[0283] As polymerization progresses, when the pressure reaches 0.735 MPa·G, 14 g of TFE and 12 g of PMVE are introduced into the autoclave to increase the pressure, and iodine compound I (CF2) is used as a chain transfer agent. ４ 5.11 g of 1 was injected under pressure along with 5.0 g of deionized water. As the reaction progressed, TFE and PMVE were similarly injected at a ratio of 65.9 / 34.1 mol%, and the pressure was repeatedly increased and decreased between 0.735 MPa·G and approximately 0.87 MPa·G. After the start of the reaction, 0.798 g of APS was injected under pressure with nitrogen along with 3.0 g of deionized water every 12 hours to continue the reaction. By the time polymerization was complete, 616 g of TFE and 528 g of PMVE had been injected under pressure. During polymerization, 1,1,2,2-tetrafluoro-3-iodo-1-((1,2,2-trifluorovinyl)oxy)propane was added four times, and when the total amount of TFE charged reached 308, 364, 434, and 490 g, 2.08 g portions were injected under pressure with nitrogen along with 1.5 g of deionized water.

[0284] Subsequently, the autoclave was cooled to release unreacted monomers, yielding 3770 g of an aqueous dispersion with a solid content of 29.4% by mass. The adhesion rate was 0.02% by mass. 200 g of the obtained aqueous dispersion was mixed and diluted with 150 g of deionized water. This diluted mixture was added dropwise to 1300 g of a 10% hydrochloric acid aqueous solution. The dropwise addition was carried out while stirring the hydrochloric acid aqueous solution.

[0285] The perfluoroelastomer coagulated in the hydrochloric acid solution. The coagulated perfluoroelastomer was filtered off and transferred to 200 g of deionized water, and washed with stirring for 5 minutes. After 5 minutes, the perfluoroelastomer was filtered off again and transferred to 100 g of deionized water, and washed with stirring for 5 minutes. After this, the washing operation with 100 g of deionized water was repeated, and when the pH of the washing water after washing reached 6 or higher, the perfluoroelastomer was filtered off. The filtered perfluoroelastomer was vacuum-dried at 70°C for 48 hours. The amount of perfluoroelastomer obtained was 55 g.

[0286] Analysis of the obtained perfluoroelastomer yielded the following results: Perfluoroelastomer composition: TFE / PMVE = 64 / 36 mol% Iodine content: 0.43 mass% Mooney viscosity: ML1 + 10 (100°C) = 58

[0287] Example 12 A SUS polymerization tank with an internal volume of 6 L and no ignition source was used to add 1886 g of deionized water and 452 g of the aqueous dispersion prepared in Preparation Example 5. The system was then purged with nitrogen to remove oxygen. While stirring at 400 rpm, the temperature was raised to 54.5°C, and a mixed gas of tetrafluoroethylene (TFE) and perfluoromethyl vinyl ether (PMVE) (TFE / PMVE = 24 / 76 mol%) was added to bring the internal pressure to 0.83 MPa·G. Next, CF ２ = CFOCF ２ CF (CF ３ ) OCF ２ CF ２ 1.21 g of CN (CNVE) was injected under nitrogen pressure along with 1.5 g of deionized water. Then, 14.7 g of ammonium persulfate (APS) was dissolved in 30 g of deionized water and injected under nitrogen pressure to initiate the reaction.

[0288] As polymerization progressed, when the pressure reached 0.735 MPa·G, 12 g of TFE and 13.3 g of PMVE were introduced into the autoclave and the pressure was increased. As the reaction progressed, TFE and PMVE were similarly injected at a ratio of 60 / 40 mol%, and the pressure was repeatedly increased and decreased between 0.735 MPa·G and approximately 0.85 MPa·G. When 202.4 g of mixed monomer had been added, 16.44 g of 10% aqueous ammonia solution was injected under nitrogen, and by the time polymerization was complete, a total of 328 g of TFE and 363.1 g of PMVE had been injected, including the aforementioned 12 g of TFE and 13.3 g of PMVE. During polymerization, CNVE was added 17 times in increments of 1.21 g each, along with 1.5 g of deionized water, and injected into the polymerization vessel. The xth addition of CNVE (1 ≤ x ≤ 17) was performed when the amount of TFE added exceeded {(328 / 18) × x} g.

[0289] Subsequently, the autoclave was cooled to release unreacted monomers, yielding 3130 g of an aqueous dispersion with a solid content of 23.2% by mass. The adhesion rate was 1.3% by mass.

[0290] The obtained aqueous dispersion was subjected to the same post-treatment as in Example 11 to obtain a perfluoroelastomer.

[0291] Analysis of the obtained perfluoroelastomer yielded the following results: Perfluoroelastomer composition: TFE / PMVE / CNVE = 58.5 / 40.9 / 0.55 mol% Mooney viscosity: ML1 + 20 (170°C) = 70

Claims

1. A method for producing an aqueous dispersion of a fluorine-containing elastomer, comprising: (1) carrying out a first polymerization of a fluorine-containing monomer in a container, substantially in the absence of a fluorine-containing surfactant that does not have functional groups that can react by radical polymerization, and in the presence of an aqueous medium and a polymerization initiator, to prepare a first aqueous dispersion containing a fluorine-containing polymer; (2) removing the first aqueous dispersion from the container, diluting the removed first aqueous dispersion 3 to 40 times to prepare a second aqueous dispersion, or diluting the first aqueous dispersion 3 to 40 times in the container to prepare a second aqueous dispersion, and removing it from the container. (3) A method for preparing a third aqueous dispersion containing a fluorine-containing elastomer by performing a second polymerization of a fluorine-containing monomer in the same container in which the first polymerization was performed or in a different container from the container in which the first polymerization was performed, in the absence of a fluorine-containing surfactant that substantially does not have a functional group that can react by radical polymerization, and in the presence of a chain transfer agent having an iodine atom or a bromine atom, and at least one selected from the group consisting of monomers that give a crosslinkable group containing an iodine atom, a bromine atom or a cyano group, and a second aqueous dispersion.

2. The manufacturing method according to claim 1, wherein the first polymerization is carried out in the presence of a fluorine-free compound having a hydrophilic group.

3. The method for producing a product according to claim 2, wherein the fluorine-free compound having a hydrophilic group is a fluorine-free anionic surfactant.

4. A fluorine-free compound having a hydrophilic group, with general formula (X): R Ｚ - (L-M) ｘ (In the formula, R Ｚ The method for producing an anionic surfactant represented by ) is as described in claim 2 or 3.

5. The manufacturing method according to any one of claims 2 to 4, wherein in the first polymerization, the mass ratio of the fluorine-free compound having a hydrophilic group to the polymerization initiator (fluorine-free compound having a hydrophilic group / polymerization initiator) is 0.600 or less.

6. The manufacturing method according to any one of claims 1 to 5, wherein in the first polymerization, the amount of polymerization initiator is 500 ppm by mass or more relative to the aqueous medium.

7. The manufacturing method according to any one of claims 1 to 6, wherein the polymerization initiator used in the first polymerization is a persulfate.

8. The manufacturing method according to any one of claims 1 to 7, wherein the first polymerization is carried out in the presence of a compound (A) containing a functional group and a hydrophilic group that can react by radical polymerization.

9. The manufacturing method according to any one of claims 1 to 8, wherein the first polymerization is carried out substantially in the absence of a redox initiator.

10. A manufacturing method according to any one of claims 1 to 9, wherein the first polymerization is carried out in the presence of a pH adjusting agent.

11. The manufacturing method according to any one of claims 1 to 10, wherein the solid content concentration of the first aqueous dispersion is less than 12% by mass.

12. The manufacturing method according to any one of claims 1 to 11, further comprising heat-treating the first aqueous dispersion at 70°C or higher for 3 hours or more.

13. The manufacturing method according to any one of claims 1 to 12, wherein the solid content concentration of the third aqueous dispersion is 15% by mass or more.

14. The manufacturing method according to any one of claims 1 to 13, wherein the polymerization temperature of the first polymerization and the second polymerization is 10 to 120°C.

15. The manufacturing method according to any one of claims 1 to 14, wherein the polymerization pressure of the first polymerization and the second polymerization is 0.5 to 10 MPaG.

16. The manufacturing method according to any one of claims 1 to 15, wherein the fluorine-containing elastomer contains a methylene group in its main chain.

17. Fluorine-containing elastomers, -CH ２ Includes an I structure, -CH ２ - CH4 relative to 100 mol% of the structure ２ The manufacturing method according to any one of claims 1 to 16, wherein the amount of structure I is 0.05 to 1.50 mol%.

18. The manufacturing method according to any one of claims 1 to 15, wherein the fluorine-containing elastomer is a perfluoroelastomer.

19. The manufacturing method according to any one of claims 1 to 18, wherein the Mooney viscosity (ML1 + 10 (100°C)) of the fluorine-containing elastomer is 10 to 130.

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