Method for producing an aqueous dispersion of fluorine-containing elastomer and fluorine-containing elastomer

Abstract

To provide a manufacturing method that enables the production of an aqueous dispersion containing a fluorine-containing elastomer with excellent crosslinking properties, even when surfactants are not used during polymerization, with high productivity. [Solution] In a method for producing an aqueous dispersion of a fluorine-containing elastomer, which is produced by polymerizing a fluorine-containing monomer in the presence of an aqueous medium and a polymerization initiator, the present invention provides a method for adjusting the amount of radicals generated.

Description

[Technical Field]

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

[0002] Patent Document 1 contains: A method for producing a fluorine-containing polymer, comprising: a first step of polymerizing a fluorine-containing monomer mixture (i) using a water-soluble radical polymerization initiator (a) with or without an emulsifier to produce a dispersion containing ionic functional group-containing fluorine-containing emulsion particles (A); and a second step of emulsion polymerization of a fluorine-containing monomer (ii) using a radical polymerization initiator (b) in the presence of the ionic functional group-containing fluorine-containing emulsion particles (A) with or without an emulsifier to produce a fluorine-containing polymer (B) with a low amount of ionic functional groups, wherein (1) The fluorine-containing monomer mixture (i) used in the first stage is a monomer mixture containing a perhalo-type ethylenic monomer and a non-perhalo-type ethylenic monomer, (2) The ionic functional group-containing fluorine-containing emulsion particles (A) produced in the first stage are used in an amount of 0.01 to 5.0% by mass of the fluorine-containing polymer (B) obtained in the second stage. (3) A method for producing a fluorine-containing polymer, characterized in that the amount of water-soluble radical polymerization initiator (a) used in the first step is 0.01 to 1000% by mass of the ionic functional group-containing fluorine-containing emulsion particles (A) obtained in the first step. It is stated. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2007 / 129735 [Overview of the project] [Problems that the invention aims to solve]

[0004] The present disclosure aims to provide a manufacturing method that enables the production of an aqueous dispersion containing a fluorine-containing elastomer having excellent crosslinking properties with high productivity, even when surfactants are not used during polymerization. [Means for solving the problem]

[0005] The present disclosure provides 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, wherein the solid content concentration of the final obtained aqueous dispersion of the fluorine-containing elastomer is 15% by mass or more, and the polymerization is carried out continuously from the initial addition of the polymerization initiator until the solid content concentration of the aqueous dispersion of the fluorine-containing elastomer reaches 15% by mass or more, without removing the product from the reaction vessel, and the ratio of radical generation (B / A) calculated by the following formula is 0.70 or less. The ratio of radical generation (B / A) = B / A A: Radical generation rate per gram of aqueous medium per minute from the initial addition of polymerization initiator (A) (mol / (g·min)) B: Radical generation rate per gram of aqueous medium (mol / (g·min)) from the point when the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer. [Effects of the Invention]

[0006] According to this disclosure, a manufacturing method is provided that allows for the production of an aqueous dispersion containing a fluorine-containing elastomer having excellent crosslinking properties with high productivity, even when no surfactant is used during polymerization. [Modes for carrying out the invention]

[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 ranges represented by endpoints include 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 1" includes all numbers greater than or equal to 1 (for example, at least 2, at least 4, at least 6, at least 8, at least 10, at least 25, at least 50, at least 100, etc.).

[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 elastomer is known, as described in Patent Document 1, comprising a first step of producing fluorine-containing emulsion particles (A) containing a large number of ionic functional groups, and a second step of emulsion polymerization of a fluorine-containing monomer in the presence of the ionic functional group-containing fluorine-containing emulsion particles (A). Patent Document 1 states that by using this production method, polymerization proceeds stably without the use of emulsifiers, without the resulting polymer adhering to the walls of the polymerization tank, and moreover, it is possible to produce a fluorine-containing polymer with few ionic functional groups. Furthermore, Patent Document 1 states that this production method can also be suitably applied to the production of polyol vulcanization-based fluororubbers, in which ionic ends are thought to hinder processability and vulcanization properties.

[0018] However, when using the manufacturing method described in Patent Document 1, it is necessary to remove the emulsion containing the emulsion particles (A) produced in the first stage from the reaction vessel and then refill it into the reaction vessel to start the second stage, which results in poor productivity.

[0019] The manufacturing method disclosed herein solves this problem and enables the production of an aqueous dispersion containing a fluorine-containing elastomer with excellent crosslinking properties with high productivity, even when a surfactant is not used during polymerization.

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

[0021] (First manufacturing method) In the first manufacturing method of this disclosure, when producing an aqueous dispersion containing a fluorine-containing elastomer by polymerization of a fluorine-containing monomer in the presence of an aqueous medium and a polymerization initiator, the solid content concentration of the final obtained aqueous dispersion of the fluorine-containing elastomer is set to 15% by mass or more, and polymerization is continued from the initial addition of the polymerization initiator until the solid content concentration of the aqueous dispersion of the fluorine-containing elastomer reaches 15% by mass or more, without removing the product from the reaction vessel, and the amount of radical generation is adjusted so that the ratio of radical generation amount (B / A) calculated by the formula described later is 0.70 or less.

[0022] In the first manufacturing method of this disclosure, polymerization is carried out in a reaction vessel until the solid content concentration of the final obtained fluorine-containing elastomer aqueous dispersion reaches 15% by mass or more. The final obtained fluorine-containing elastomer aqueous dispersion is the fluorine-containing elastomer aqueous dispersion obtained after the polymerization reaction has been stopped. The solid content concentration of the final obtained fluorine-containing elastomer aqueous dispersion is preferably 18% by mass or more, more preferably 21% by mass or more, and there is no particular upper limit, but it may be 50% by mass or less, 40% by mass or less, or 30% by mass or less.

[0023] 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.

[0024] In the first manufacturing method of this disclosure, polymerization is carried out continuously from the initial addition of the polymerization initiator until the solid content concentration of the fluorine-containing elastomer aqueous dispersion reaches 15% by mass or more, without removing the product from the reaction vessel. That is, the polymerization in the first manufacturing method of this disclosure is carried out in the same reaction vessel until the solid content concentration of the aqueous dispersion reaches at least 15% by mass. Therefore, the first manufacturing method of this disclosure can produce the aqueous dispersion with high productivity. In one embodiment, all polymerization reactions in the first manufacturing method of this disclosure are carried out in the same reaction vessel.

[0025] In this disclosure, "initial addition of polymerization initiator" refers to the point in time when the polymerization initiator is added to start polymerization, and is different from the time when the polymerization initiator is added additionally during the polymerization reaction. Furthermore, if polymerization is carried out in multiple stages, it refers to the point in time when the polymerization initiator is added to start the first of the multiple polymerization stages, and is different from the point in time when the polymerization initiator is added to start the second or subsequent polymerization stages. In addition, "continuing polymerization without removing the product from the reaction vessel" means not removing the product produced by the polymerization reaction from the reaction vessel, nor stopping the polymerization. For example, operations to remove compounds other than the product, such as discharging unreacted substances such as monomers present in the gas phase of the reaction vessel, are not prohibited as long as the polymerization is not stopped. Furthermore, removing an amount of product less than 10% by mass of the total amount produced for reasons such as checking the polymerization progress is also not prohibited as long as the polymerization is not stopped.

[0026] In the first manufacturing method of this disclosure, the amount of radicals generated is adjusted so that the ratio of radical generation amounts (B / A) calculated by the following formula is 0.70 or less. The ratio of radical generation (B / A) = B / A A: Radical generation rate per gram of aqueous medium per minute from the initial addition of polymerization initiator (A) (mol / (g·min)) B: Radical generation rate per gram of aqueous medium (mol / (g·min)) from the point when the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer.

[0027] When a persulfate is used as a polymerization initiator, the amount of radicals generated (C(t)) can be calculated using the following formula.

number

[0028] kd: Decomposition rate constant of persulfate (min) -1 ) T: Polymerization temperature (Kelvin) A: Amount of persulfate added per gram of aqueous medium (g / g) t: Time elapsed since persulfate was added (minutes) B(t): Amount of persulfate that decomposes per 1 g of aqueous medium between t (min) and t+1 (min) (g / (g·min)) M: Molecular weight of persulfate C(t): Amount of radicals generated per gram of aqueous medium between t(min) and t+1(min) (mol / (g·min))

[0029] The ratio of radical generation (B / A) is 0.70 or less, preferably 0.67 or less, more preferably 0.64 or less, and even more preferably 0.61 or less. The lower limit is not particularly limited, but may be 0.05 or more or 0.10 or more. The first manufacturing method of this disclosure involves polymerization while appropriately adjusting the amount of radical generation. Therefore, even though polymerization is carried out continuously without removing the product from the reaction vessel, an aqueous dispersion containing a fluorine-containing elastomer with excellent crosslinking properties can be produced with high productivity, even when no surfactant is used during polymerization. The reason why a fluorine-containing elastomer with excellent crosslinking properties can be obtained is presumed to be that by appropriately adjusting the amount of radical generation, terminal groups derived from the polymerization initiator are less likely to be introduced into the polymer chain, while terminal groups derived from chain transfer agents and the like are more likely to be introduced into the polymer chain.

[0030] The ratio of radical generation (B / A) can be adjusted by controlling the amount of polymerization initiator added, the polymerization temperature, and the number of stirs during polymerization. In particular, by adding a relatively large amount of polymerization initiator initially to start polymerization, setting a relatively high polymerization temperature, and slowly stirring the contents of the reaction vessel during the period until the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer (initial polymerization period), it becomes easier to adjust the ratio of radical generation (B / A) within the above range. That is, a relatively large amount of polymerization initiator and a relatively high polymerization temperature increase the amount of radical generation during the initial polymerization period. Also, gentle stirring makes the polymerization reaction less likely to proceed, and the time required for the initial polymerization period is extended. Therefore, since a large amount of polymerization initiator can be decomposed during the initial polymerization period, the "radical generation amount (A)" can be increased. On the other hand, after the initial polymerization period has elapsed, the amount of polymerization initiator that can be decomposed decreases, so the "radical generation amount (B)" can be decreased.

[0031] During the period after the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer, it is preferable to thoroughly stir the contents of the reaction vessel. Thorough stirring of the contents of the reaction vessel allows the polymerization reaction to proceed smoothly, and the solid content concentration of the aqueous dispersion of the fluorine-containing elastomer can be rapidly increased while suppressing the introduction of terminal groups derived from the polymerization initiator into the polymer chain.

[0032] In the first manufacturing method of this disclosure, the polymerization rate (C) from the time the polymerization initiator is first added until the time when the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer is preferably 10 g / (hr·L) or less. The polymerization rate is the amount of fluorine-containing elastomer produced per hour per liter of aqueous medium. The polymerization rate (C) during the above period is preferably 9.0 g / (hr·L) or less, more preferably 8.0 g / (hr·L) or less, and the lower limit is not particularly limited, but may be 1.0 g / (hr·L) or more or 2.0 g / (hr·L) or more. By adjusting the polymerization rate (C) within the above range, an aqueous dispersion containing a fluorine-containing elastomer with even better crosslinking properties can be produced with even higher productivity, even when a surfactant is not used during polymerization.

[0033] In the first manufacturing method of this disclosure, it is preferable that the polymerization rate (D) from the point when the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer to the point when polymerization is stopped is greater than 10 g / (hr·L). The polymerization rate during the above period is more preferably 15 g / (hr·L) or more, even more preferably 20 g / (hr·L) or more, even more preferably 25 g / (hr·L) or more, and particularly preferably 30 g / (hr·L) or more. The upper limit is not particularly limited, but may be 200 g / (hr·L) or less or 150 g / (hr·L) or less. By adjusting the polymerization rate (D) within the above range, an aqueous dispersion containing a fluorine-containing elastomer with even better crosslinking properties can be produced with even higher productivity, even when a surfactant is not used during polymerization.

[0034] In one embodiment of the first manufacturing method of this disclosure, the polymerization rate is adjusted so that the polymerization rate ratio (D / C) calculated by the following formula is 5.0 or higher. Polymerization rate ratio (D / C)=D / C C: Polymerization rate (C) (g / (hr·L)) from the time the polymerization initiator is first added until the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer. D: Polymerization rate (D) (g / (hr·L)) from the point when the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer to the point when polymerization is stopped.

[0035] In the first manufacturing method of this disclosure, the polymerization rate ratio (D / C) may be 5.0 or higher, preferably 6.0 or higher, more preferably 7.0 or higher, and even more preferably 8.0 or higher, and there is no particular upper limit, but it may be 100 or less or 50 or less. In the first manufacturing method of this disclosure, by performing polymerization while appropriately adjusting both the amount of radicals generated and the polymerization rate, an aqueous dispersion containing a fluorine-containing elastomer having even better crosslinking properties can be produced with even higher productivity, even when a surfactant is not used during polymerization.

[0036] (Second manufacturing method) In the second manufacturing method of this disclosure, when producing an aqueous dispersion containing a fluorine-containing elastomer by polymerization of a fluorine-containing monomer in the presence of an aqueous medium and a polymerization initiator, the solid content concentration of the final obtained aqueous dispersion of the fluorine-containing elastomer is 15% by mass or more, and polymerization is continued from the initial addition of the polymerization initiator until the solid content concentration of the aqueous dispersion of the fluorine-containing elastomer reaches 15% by mass or more, without removing the product from the reaction vessel, and the polymerization rate is adjusted so that the polymerization rate ratio (D / C) calculated by the formula described later is 5.0 or more.

[0037] In the second manufacturing method of this disclosure, polymerization is carried out until the solid content concentration of the final obtained fluorine-containing elastomer aqueous dispersion reaches 15% by mass or more. The final obtained fluorine-containing elastomer aqueous dispersion is the fluorine-containing elastomer aqueous dispersion obtained after the polymerization reaction has been stopped. The solid content concentration of the final obtained fluorine-containing elastomer aqueous dispersion is preferably 18% by mass or more, more preferably 21% by mass or more, and there is no particular upper limit, but it may be 50% by mass or less, 40% by mass or less, or 30% by mass or less.

[0038] In the second manufacturing method of this disclosure, polymerization is carried out continuously from the initial addition of the polymerization initiator until the solid content concentration of the fluorine-containing elastomer aqueous dispersion reaches 15% by mass or more, without removing the product from the reaction vessel. That is, the polymerization in the second manufacturing method of this disclosure is carried out in the same reaction vessel until the solid content concentration of the aqueous dispersion reaches at least 15% by mass. Therefore, the second manufacturing method of this disclosure can produce aqueous dispersions with high productivity. In one embodiment, all polymerization reactions in the second manufacturing method of this disclosure are carried out in the same reaction vessel.

[0039] In the second manufacturing method of this disclosure, the polymerization rate is adjusted so that the polymerization rate ratio (D / C) calculated by the following formula is 5.0 or higher. Polymerization rate ratio (D / C)=D / C C: Polymerization rate (C) (g / (hr·L)) from the time the polymerization initiator is first added until the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer. D: Polymerization rate (D) (g / (hr·L)) from the point when the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer to the point when polymerization is stopped.

[0040] The polymerization rate ratio (D / C) is 5.0 or higher, preferably 6.0 or higher, more preferably 7.0 or higher, and even more preferably 8.0 or higher. The upper limit is not particularly limited, but may be 100 or less or 50 or less. The second manufacturing method of this disclosure involves polymerization while appropriately adjusting the polymerization rate. Therefore, even though polymerization is carried out continuously without removing the product from the reaction vessel, an aqueous dispersion containing a fluorine-containing elastomer with excellent crosslinking properties can be produced with high productivity, even when no surfactant is used during polymerization. The reason why a fluorine-containing elastomer with excellent crosslinking properties can be obtained is presumed to be that by appropriately adjusting the polymerization rate ratio, end groups derived from the polymerization initiator are less likely to be introduced into the polymer chain, while end groups derived from chain transfer agents and the like are more likely to be introduced into the polymer chain.

[0041] The polymerization rate ratio (D / C) can be adjusted by controlling the amount of polymerization initiator added, the polymerization temperature, and the number of stirs during polymerization. In particular, by adding a relatively large amount of polymerization initiator initially to start polymerization, setting a relatively high polymerization temperature, and slowly stirring the contents of the reaction vessel during the period until the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer (initial polymerization period), and then thoroughly stirring the contents of the reaction vessel after the initial polymerization period, it becomes easier to adjust the polymerization rate ratio (D / C) within the above range. That is, gentle stirring makes the polymerization reaction less likely to proceed, resulting in a lower polymerization rate (C). Consequently, the time required for the initial polymerization period becomes longer. At the same time, by adding a relatively large amount of polymerization initiator initially to start polymerization and setting a relatively high polymerization temperature, a large amount of radicals can be generated during the initial polymerization period. After the initial polymerization period, thoroughly stirring the contents of the reaction vessel increases the polymerization rate (D). Therefore, the solid content concentration of the fluorine-containing elastomer aqueous dispersion can be rapidly increased while suppressing the introduction of terminal groups derived from the polymerization initiator into the polymer chain.

[0042] In the second manufacturing method of this disclosure, it is preferable that the polymerization rate (C) from the time the polymerization initiator is first added until the time the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer is 10 g / (hr·L) or less. The polymerization rate (C) is preferably 9.0 g / (hr·L) or less, and the lower limit is not particularly limited, but may be 1.0 g / (hr·L) or more or 2.0 g / (hr·L) or more. By adjusting the polymerization rate (C) to the above range, an aqueous dispersion containing a fluorine-containing elastomer with even better crosslinking properties can be produced with even higher productivity, even when a surfactant is not used during polymerization.

[0043] In the second manufacturing method of this disclosure, it is preferable that the polymerization rate (D) from the point when the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final obtained fluorine-containing elastomer until the point when polymerization is stopped is greater than 10 g / (hr·L). The polymerization rate (D) is more preferably 15 g / (hr·L) or more, even more preferably 20 g / (hr·L) or more, even more preferably 25 g / (hr·L) or more, and particularly preferably 30 g / (hr·L) or more. The upper limit is not particularly limited, but may be 200 g / (hr·L) or less or 150 g / (hr·L) or less. By adjusting the polymerization rate (D) within the above range, an aqueous dispersion containing a fluorine-containing elastomer with even better crosslinking properties can be produced with even higher productivity, even when a surfactant is not used during polymerization.

[0044] Next, the common features of the first manufacturing method and the second manufacturing method (which may be collectively referred to as the "manufacturing method of this disclosure" or "manufacturing method" in this disclosure) will be described in detail.

[0045] (aqueous medium) In the manufacturing method of this disclosure, polymerization of a fluorine-containing monomer is carried out in the presence of an aqueous medium. The aqueous medium is a reaction medium for 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 with a boiling point of 40°C or less.

[0046] 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.

[0047] 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.

[0048] (Polymerization initiator) In the manufacturing method of this disclosure, polymerization of a fluorine-containing monomer is carried out in the presence of a polymerization initiator. Polymerization of the fluorine-containing monomer begins from the time of the first addition of the polymerization initiator.

[0049] Examples of polymerization initiators include radical polymerization initiators. The polymerization initiator is not particularly limited as long as it can generate radicals at the polymerization temperature of the fluorine-containing monomer; oil-soluble polymerization initiators and water-soluble polymerization initiators can be used, but water-soluble polymerization initiators are preferred. Furthermore, polymerization initiators may be used in combination with reducing agents or the like as redox initiators.

[0050] The amount of polymerization initiator used when polymerizing fluorine-containing monomers is appropriately determined depending on the type of monomer, the molecular weight of the target fluorine-containing elastomer, and the reaction rate.

[0051] In the manufacturing method of this disclosure, the amount of polymerization initiator initially added is preferably 30 to 1200 ppm by mass, more preferably 35 ppm by mass or more, even more preferably 40 ppm by mass or more, more preferably 1000 ppm by mass or less, even more preferably 800 ppm by mass or less, and still more preferably 600 ppm by mass or less, relative to the aqueous medium. By adjusting the amount of polymerization initiator initially added within the above range, it becomes even easier to adjust the amount of radicals generated and the polymerization rate.

[0052] When producing an aqueous dispersion containing a peroxide-crosslinkable fluorine-containing elastomer using the manufacturing method of the present disclosure, the amount of polymerization initiator added initially is preferably 30 to 400 ppm by mass, more preferably 35 ppm by mass or more, even more preferably 40 ppm by mass or more, even more preferably 150 ppm by mass or less, and even more preferably 80 ppm by mass or less, relative to the aqueous medium.

[0053] When producing an aqueous dispersion containing a polyol-crosslinkable fluorine-containing elastomer using the manufacturing method of the present disclosure, the amount of polymerization initiator added initially is preferably 150 to 800 ppm by mass, more preferably 200 ppm or more by mass, even more preferably 300 ppm or more by mass, more preferably 600 ppm or less by mass, and even more preferably 500 ppm or less by mass, relative to the aqueous medium.

[0054] When producing an aqueous dispersion containing a fluorine-containing elastomer containing cyano groups using the manufacturing method of the present disclosure, the amount of polymerization initiator added initially is preferably 150 to 1500 ppm by mass, more preferably 200 ppm or more by mass, even more preferably 300 ppm or more by mass, more preferably 1200 ppm or less by mass, and even more preferably 1100 ppm or less by mass, relative to the aqueous medium.

[0055] In the manufacturing method of the present disclosure, a polymerization initiator may be added only once to start polymerization, or a polymerization initiator may be added to start polymerization and then additional polymerization initiators may be added during polymerization. In the manufacturing method of the present disclosure, the total amount of polymerization initiator added from the start of polymerization to the cessation of polymerization is preferably 30 to 1500 ppm by mass, more preferably 35 ppm by mass or more, even more preferably 40 ppm by mass or more, more preferably 1300 ppm by mass or less, and even more preferably 500 ppm by mass or less, relative to the aqueous medium.

[0056] When producing an aqueous dispersion containing a peroxide-crosslinkable fluorine-containing elastomer using the manufacturing method of the present disclosure, the total amount of polymerization initiator added from the start of polymerization to the cessation of polymerization is preferably 30 to 500 ppm by mass, more preferably 35 ppm by mass or more, even more preferably 40 ppm by mass or more, more preferably 200 ppm by mass or less, and even more preferably 100 ppm by mass or less, relative to the aqueous medium.

[0057] When producing an aqueous dispersion containing a polyol-crosslinkable fluorine-containing elastomer using the manufacturing method of the present disclosure, the total amount of polymerization initiator added from the start of polymerization to the cessation of polymerization is preferably 200 to 1500 ppm by mass, more preferably 300 ppm by mass or more, even more preferably 350 ppm by mass or more, more preferably 800 ppm by mass or less, and even more preferably 550 ppm by mass or less.

[0058] When producing an aqueous dispersion containing a fluorine-containing elastomer containing cyano groups using the manufacturing method of the present disclosure, the total amount of polymerization initiator added from the start of polymerization to the cessation of polymerization is preferably 200 to 4000 ppm by mass, more preferably 300 ppm by mass or more, even more preferably 350 ppm by mass or more, even more preferably 3800 ppm by mass or less, and even more preferably 3500 ppm by mass or less.

[0059] As polymerization initiators, oil-soluble radical polymerization initiators, water-soluble radical polymerization initiators, or azo compounds can be used.

[0060] 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 dit-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.

[0061] Examples of azo compounds include azodicarboxylates, azodicarboxyldiamides, 2,2'-azobisisobutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and 4,4'-azobis(4-cyanovaleric acid).

[0062] 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.

[0063] As for water-soluble peroxides, persulfate salts are preferred because they allow for easy adjustment of the amount of radical generation. Potassium persulfate (K2S2O8), ammonium persulfate ((NH4)2S2O8), and sodium persulfate (Na2S2O8) are preferred, with ammonium persulfate being the most preferred.

[0064] In one embodiment of the manufacturing method of this disclosure, a persulfate is used as a polymerization initiator to polymerize a fluorine-containing monomer. By using a persulfate as a polymerization initiator, the amount of radicals generated and the polymerization rate can be more easily adjusted. Potassium persulfate (K2S2O8), ammonium persulfate ((NH4)2S2O8), and sodium persulfate (Na2S2O8) are preferred as persulfates, with ammonium persulfate being more preferred.

[0065] In one embodiment of the manufacturing method of this 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. By carrying out polymerization without using a redox initiator, it becomes easier to adjust the amount of radicals generated and the polymerization rate. 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.

[0066] In this disclosure, "substantially in the absence of a redox initiator" means that the proportion of the reducing agent constituting the redox initiator in the aqueous medium is 10 ppm by mass or less. The proportion 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.

[0067] 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. By carrying out polymerization without using transition metal salts of groups 3 to 11, it becomes easier to adjust the amount of radicals generated and the polymerization rate. Transition metal salts 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.

[0068] 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.

[0069] (Chain transfer agent) In the manufacturing method of this disclosure, the fluorine-containing monomer may be further polymerized in the presence of a chain transfer agent. Known chain transfer agents can be used, such as 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 iodine compounds such as I(CF2)4I, I(CF2)6I, and ICH2I are preferred from the viewpoint of enabling iodination of the polymer ends and being usable as reactive polymers.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] Among these, iodine transfer polymerization is preferred in terms of polymerization reactivity and crosslinking reactivity.

[0074] Typical examples of bromine or iodine compounds include, for example, 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 8 Examples 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.

[0075] 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, CF2Br2, BrCF2CF2Br, CF3CFBrCF2Br, CFClBr2, and BrCF2. Examples include CFClBr, CFBrClCFClBr, BrCF2CF2CF2Br, BrCF2CFBrOCF3, 1-bromo-2-iodoperfluoroethane, 1-bromo-3-iodoperfluoropropane, 1-bromo-4-iodoperfluorobutane, 2-bromo-3-iodoperfluorobutane, 3-bromo-4-iodoperfluorobutene-1, 2-bromo-4-iodoperfluorobutene-1, monoiodomonobromo substituted derivatives of benzene, diiodomonobromo substituted derivatives, and (2-iodoethyl) and (2-bromoethyl) substituted derivatives. These compounds may be used individually or in combination with each other. 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.

[0076] The amount of chain transfer agent is preferably 0.2 × 10⁻¹⁶ relative to the total amount of monomers used in polymerization. -3 It is approximately 2 mol%, and more preferably 1.0 × 10 -3 It is approximately 1 mole%.

[0077] (Compound (A)) In the production method of the present disclosure, further, a fluorine-containing monomer may be polymerized in the presence of a compound (A) containing a functional group capable of reacting by radical polymerization and a hydrophilic group. The compound (A) may be either a fluorine-containing compound or a fluorine-free compound, but is preferably a fluorine-containing compound.

[0078] In the present disclosure, the hydrophilic group is a group showing affinity for an aqueous medium. The compound (A) is preferably a compound containing an anionic or nonionic hydrophilic group, and more preferably a compound containing an anionic hydrophilic group. The compound (A) may contain, for example, only an anionic hydrophilic group or only a nonionic hydrophilic group. Further, as the compound (A), 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.

[0079] Examples of the hydrophilic group in the compound (A) include, for example, -NH2, -P(O)(OM)2, -OP(O)(OM)2, -SO3M, -OSO3M, -COOM, -B(OM)2, -OB(OM)2 (in each formula, M is H, a metal atom, NR 7 4, an imidazolium which may have a substituent, a pyridinium which may have a substituent or a phosphonium which may have a substituent, R 7 is H or an organic group, and may be the same or different. Any two of them may be bonded to each other to form a ring.). Among the above hydrophilic groups, -SO3M or -COOM is preferable, and -COOM is more preferable. R 7 The organic group of is preferably an alkyl group. R 7 is preferably H or an organic group of C 1-10 and more preferably H or an organic group of C 1-4 and still more preferably H or an organic group of C 1-4Alkyl alkyl groups are more preferred, and H is most preferred. If two Ms are included in each formula, the two Ms 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.

[0080] Examples of "functional groups that can react by radical polymerization" in compound (A) include groups containing radically polymerizable unsaturated bonds.

[0081] Examples of groups having radically polymerizable unsaturated bonds include vinyl groups, allyl groups, and other groups having ethylenically unsaturated bonds.

[0082] 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 elastomer particles generated during polymerization will increase when polymerization is carried out in the presence of compound (A).

[0083] 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 CF3; Y 3 R is a hydrophilic group; a is a linking group; Z 1 and Z 2 These are H, F, or CF3 independently; k is 0 or 1. However, X i , X k , Xj , 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.)

[0084] Y in general formula (A0) 3 This is a hydrophilic group. The hydrophilic group is as described above.

[0085] 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.

[0086] R a It is more preferably a hydrocarbon group having 1 to 100 carbon atoms, which may contain -(C=O)-, -(C=O)-O-, or ether bonds, and may also contain a carbonyl group, and in this hydrocarbon group, some or all of the hydrogen atoms bonded to the carbon atom may be substituted with fluorine.

[0087] 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. CX2=CY(-CZ2-O-Rf-Y 3 ) (A0-1) (In the formula, X is the same or different -H or -F, Y is -H, -F, an alkyl group or a fluorine-containing alkyl group, and Z is the same or different -H, -F, an alkyl group or a 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.) CX2=CY(-O-Rf-Y 3 ) (A0-2) (In the formula, 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 2 to 100 carbon atoms and having an ether bond. 3 (This is the same as above.) CX2=CY(-Rf-Y 3 ) (A0-3) (In the formula, 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 2 to 100 carbon atoms and having an ether bond. 3 (This is the same as above.)

[0088] As the fluorine-containing compound (A), compound (A0-1) is more preferred.

[0089] [ka]

[0090] That is even more preferable.

[0091] As for compound (A0-1), Y in the formula 3 It is preferable that -COOM is present, and in particular, at least one selected from the group consisting of CH2=CFCF2OCF(CF3)COOM and CH2=CFCF2OCF(CF3)CF2OCF(CF3)COOM (wherein M is the same as defined above).

[0092] Compound (A) is preferably added before the polymerization initiator is added to initiate the polymerization reaction. Furthermore, it is preferable to add it only before the polymerization reaction begins and not after it has started.

[0093] The amount of compound (A) used when polymerizing the fluorine-containing monomer is preferably 3 to 5000 ppm by mass, more preferably 5 ppm or more by mass, even more preferably 10 ppm or more by mass, particularly preferably 20 ppm or more by mass, most preferably 30 ppm or more by mass, and more preferably 1000 ppm or less by mass, even more preferably 500 ppm or less by mass, particularly preferably 200 ppm or less by mass, and most preferably 100 ppm or less by mass.

[0094] (Polymers containing ionic groups (I)) In the manufacturing method of the present disclosure, a fluorine-containing monomer may be further polymerized in the presence of a polymer (I) having an ionic group.

[0095] Polymer (I) having an ionic group is a polymer having one or more ionic groups in its molecule. Anionic groups are preferred as the ionic groups.

[0096] The anionic groups of polymer (I) include not only anionic groups such as sulfate groups and carboxylate groups, but also functional groups that give anionic groups such as acidic groups like -COOH and acid-base groups like -COONH4. Anionic groups include sulfate groups, carboxylate groups, phosphate groups, phosphonate groups, sulfonate groups, or -C(CF3)2OM (wherein M is -H, a metal atom, -NR). 7 4. Imidazolium which may have substituents, pyridinium which may have substituents, or phosphonium which may have substituents, 7 (where is H or an organic group.) is preferred.

[0097] The preferred ion exchange capacity of polymer (I) is, in descending order, 0.80 meq / g or more, 1.50 meq / g or more, 1.75 meq / g or more, 2.00 meq / g or more, 2.20 meq / g or more, greater than 2.20 meq / g, 2.50 meq / g or more, 2.60 meq / g or more, 3.00 meq / g or more, and 3.50 meq / g or more. The ion exchange capacity is the content of ionic groups (anionic groups) in polymer (I), and can be calculated from the composition and molecular weight of polymer (I). Polymer (I) only needs to have a sufficient content of ionic groups to give polymer (I) an ion exchange capacity within the above numerical range, and it is not necessary for some molecular chains constituting polymer (I) to contain ionic groups.

[0098] The position of the ionic groups in polymer (I) is not limited. Polymer (I) may have ionic groups at the ends of the main chain, or on the side chains, or on both the ends of the main chain and the side chains. In one embodiment, in polymer (I), the ionic groups (anionic groups) are distributed at the ends of the main chain or along the polymer main chain. When the ionic groups (anionic groups) are distributed along the polymer main chain, it is preferable that they are included together with repeating side chains bonded to this main chain, and that these side chains have ionic groups.

[0099] Polymer (I) preferably contains ionic groups having a pKa of less than 10, more preferably less than 7. The ionic groups of polymer (I) are preferably selected from the group consisting of sulfonates, carboxylates, phosphonates, and phosphates.

[0100] The terms "sulfonate, carboxylate, phosphonate, and phosphate" are intended to refer to their respective salts, or the respective acids that can form salts. When salts are used, they are preferably alkali metal salts or ammonium salts. Preferred ionic groups are carboxylate groups and sulfonate groups.

[0101] Preferred ionic groups are -SO3M, -COOM, or -P(O)(OM)2. The "M" in the ionic group (anionic group) is referred to as "anionic group (A)" as described later. 0 This is the same as the "M" in ")".

[0102] Polymer (I) preferably has an ion exchange rate (IXR) of 53 or less. The IXR is defined as the number of carbon atoms in the polymer backbone relative to the ionic group. Precursor groups that become ionic by hydrolysis (e.g., -SO2F) are not considered ionic groups for the purpose of determining the IXR.

[0103] IXR is preferably 0.5 or higher, more preferably 1 or higher, even more preferably 3 or higher, even more preferably 4 or higher, especially preferably 5 or higher, and particularly preferably 8 or higher. Furthermore, IXR is more preferably 43 or lower, even more preferably 33 or lower, and particularly preferably 23 or lower.

[0104] Polymer (I) is preferably water-soluble. Water solubility means the property of readily dissolving or dispersing in an aqueous medium. For example, water-soluble polymer (I) may not have a particle size that can be measured by dynamic light scattering (DLS), or may exhibit a particle size of 30 nm or less.

[0105] The number-average molecular weight of polymer (I) is 0.1 × 10⁻⁶. 4 The above is preferable, 0.2 × 10 4 The above is more preferable, 0.3 × 10 4 The above is even more preferable, 0.4 × 10 4 The above is even more preferable, 0.5 × 10 4 The above is particularly preferable, 1.0 × 10 4 The above is particularly preferred, 3.0 × 10 4 The above is particularly preferred, 3.1 × 10 4 The above is the most preferable. Also, 75.0 × 10 4 The following is preferable: 50.0 × 10 4 The following is more preferable: 40.0 × 10 4 The following is even more preferable: 30.0 × 10 4The following is particularly preferable: 20.0 × 10 4 The following are particularly preferred. The number-average molecular weight and weight-average molecular weight are values ​​calculated by gel permeation chromatography (GPC) using monodisperse polymethyl methacrylate or polyethylene glycol / oxide as standards. If GPC measurement is not possible, the number-average molecular weight of polymer (I) can be determined by the correlation between the number-average molecular weight calculated from the number of terminal groups obtained by NMR, FT-IR, etc., and the melt flow rate. The melt flow rate can be measured in accordance with JIS K 7210.

[0106] The lower limit of the weight-average molecular weight of polymer (I) is, in order of preference, 0.2 × 10⁻⁶. 4 The above is 0.4 × 10 4 The above is 0.6 × 10 4 The above is 0.8 × 10 4 The above is 1.0 × 10 4 The above is 2.0 × 10 4 The above is 5.0 x 10 4 The above is 10.0 × 10 4 The above is 15.0 x 10 4 The above is 20.0 × 10 4 The above is 25.0 × 10 4 That concludes the explanation. Furthermore, the upper limit of the weight-average molecular weight of polymer (I) is, in order of preference, 150.0 × 10⁻⁶. 4 Below, 100.0 × 10 4 Below, 60.0 × 10 4 Below, 50.0 × 10 4 Below, 40.0 × 10 4 The following applies:

[0107] The viscosity of the mixed solution containing polymer (I) and water is preferably 1.0 mPa.s or more, more preferably 2.0 mPa.s or more, even more preferably 5.0 mPa.s or more, particularly preferably 110.0 mPa.s or more, most preferably 14.0 mPa.s or more, preferably 100.0 mPa.s or less, more preferably 50.0 mPa.s or less, even more preferably 25.0 mPa.s or less, and especially preferably 20.0 mPa.s or less.

[0108] The viscosity of a mixture containing polymer (I) and water can be determined by adjusting the polymer (I) content in the mixture to 33% by mass relative to the mixture, and then measuring the viscosity of the resulting mixture at 20°C using an A&D tuning fork vibratory viscometer (model: SV-10).

[0109] The critical micelle concentration (CMC) of polymer (I) is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0110] The critical micelle concentration of polymer (I) can be determined by measuring its surface tension. Surface tension can be measured, for example, with a surface tension meter, model DY-300, manufactured by Kyowa Interfacial Chemical Co., Ltd.

[0111] The acid value of polymer (I) is preferably 60 or higher, more preferably 90 or higher, even more preferably 120 or higher, particularly preferably 150 or higher, most preferably 180 or higher, and there is no particular upper limit, but it is preferably 300 or lower.

[0112] The acid value of polymer (I) is determined by whether polymer compound (I) has anionic groups other than acidic functional groups, such as -COOM, -SO3M, -OSO3M, or -C(CF3)2OM(M is a metal atom, NR). 7 4. Imidazolium which may have substituents, pyridinium which may have substituents, or phosphonium which may have substituents, 7 If the substance has H or an organic group, these groups can be converted to acidic groups and then measured by acid-base titration.

[0113] As the polymer (I), a polymer containing a polymerization unit (I) based on at least one selected from tetrafluoroethylene (TFE), hexafluoropropylene (HFP), perfluoro(alkyl vinyl ether) (PAVE), vinylidene fluoride (VdF), chlorotrifluoroethylene (CTFE), 1,2-difluoroethylene, trifluoroethylene, trifluoropropylene, tetrafluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutene, hexafluoroisobutene, vinyl fluoride, and the monomer (I) represented by the general formula (I) is preferred. CX 1 X 3 =CX 2 R(-CZ 1 Z 2 -A 0 ) m (I) (In the formula, X 1 and X 3 are each independently F, Cl, H or CF3; X 2 is H, F, an alkyl group or a fluorinated alkyl group; A 0 is an anionic group; R is a linking group; Z 1 and Z 2 are each independently H, F, an alkyl group or a fluorinated alkyl group; and m is an integer of 1 or more.)

[0114] R is a linking group. In the present disclosure, the "linking group" is a (m + 1)-valent linking group, and when m is 1, it is a divalent linking group. The linking group may be a single bond, and preferably contains at least one carbon atom. The number of carbon atoms may be 2 or more, 4 or more, 8 or more, 10 or more, or 20 or more. The upper limit is not limited, but for example, it may be 100 or less, or 50 or less.

[0115] The linking group may be linear or branched, cyclic or acyclic, saturated or unsaturated, substituted or unsubstituted, and may contain one or more heteroatoms selected from the group consisting of sulfur, oxygen, and nitrogen, and may optionally contain one or more functional groups selected from the group consisting of ester, amide, sulfonamide, carbonyl, carbonate, urethane, urea, and carbamate. The linking group may not contain a carbon atom and may be a chain heteroatom such as oxygen, sulfur, or nitrogen.

[0116] m is an integer of 1 or more, preferably 1 or 2, more preferably 1. When m is an integer of 2 or more, Z 1 , Z 2 and A 0 may be the same or different. Next, a preferred configuration when m is 1 in the general formula (I) will be described.

[0117] R is preferably a chain heteroatom such as oxygen, sulfur, or nitrogen, or a divalent organic group.

[0118] When R is a divalent organic group, the hydrogen atom bonded to the carbon atom may be replaced by a halogen other than fluorine, such as chlorine, and may or may not contain a double bond. Also, R may be either linear or branched, and may be either cyclic or acyclic. Further, R may contain a functional group (for example, ester, ether, ketone (keto group), amine, halide, etc.).

[0119] R may also be a non-fluorinated divalent organic group or a partially fluorinated or perfluorinated divalent organic group.

[0120] R may be, for example, a hydrocarbon group in which no fluorine atoms are bonded to a carbon atom, a hydrocarbon group in which some of the hydrogen atoms bonded to a carbon atom are replaced by fluorine atoms, or a hydrocarbon group in which all of the hydrogen atoms bonded to a carbon atom are replaced by fluorine atoms. These may contain oxygen atoms, double bonds, or functional groups.

[0121] R is preferably a hydrocarbon group having 1 to 100 carbon atoms, which may contain an ether bond or a keto group, and the hydrocarbon group may have some or all of the hydrogen atoms bonded to the carbon atoms substituted with fluorine.

[0122] R is preferably -(CH2) a -,-(CF2) a -,-(CF2) a -O-, -O-(CF2) a -,-(CF2) a -O-(CF2) b -, -O(CF2) a -O-(CF2) b -,-(CF2) a -[O-(CF2) b ] c -, -O(CF2) a -[O-(CF2) b ] c -,-[(CF2) a -O] b -[(CF2) c -O] d -, -O[(CF2) a -O] b -, -O[(CF2) a -O] b -[(CF2) c -O] d -,-O-[CF2CF(CF3)O] a -(CF2) b -, -O-(CF2) a -O-[CF(CF3)CF2O] b -,-O-[CF2CF(CF3)O] a -(CF2) b -O-, -O-[CF2CF(CF3)O] a-(CF2) b -O-[CF(CF3)CF2O] c -,-[CF2CF(CF3)O] a -,-[CF(CF3)CF2O] a -,-(CF2) a -O-[CF(CF3)CF2O] a -,-(CF2) a -O-[CF(CF3)CF2O] a -(CF2) b -,-[CF2CF(CF3)] a -CO-(CF2) b -, and at least one of these combinations. In the formula, a, b, c, and d are independently at least 1. A, b, c, and d may independently be 2 or more, 3 or more, 4 or more, 10 or more, or 20 or more. The upper limit for a, b, c, and d is, for example, 100.

[0123] More specifically, R is at least one selected from -O-CF2-, -O-CF2CF2-, -O-CF2CF2-O-, -O-CF2CF2CF2-, -O-CF2CF2CF2-O-, -O-CF2CF(CF3)-O-, -O-CF2CF2-O-CF(CF3)CF2-O-, -O-CF2CF(CF3)-O-CF2CF2-O-, and -O-CF2CF(CF3)-O-CF2-.

[0124] For R, the general formula is (r1): -CF2-O-(CX 6 2) e -{O-CF(CF3)} f -(O) g - (r1) (In the formula, X 6 A divalent group represented by the general formula (r2) is preferred, where each is independently H, F, or CF3, e is an integer from 0 to 3, f is an integer from 0 to 3, and g is 0 or 1. -CF2-O-(CX 7 2) e -(O) g- (r2) (In the formula, X 7 A divalent group is more preferable, represented by (where each is independently H, F, or CF3, e is an integer from 0 to 3, and g is 0 or 1).

[0125] Specific examples suitable for R include -CF2-O-, -CF2-O-CF2-, -CF2-O-CH2-, -CF2-O-CH2CF2-, -O-CF2-, -O-CF2CF 2-, -O-CF2CF2CF2-, -O-CF2CF2CF2CF2-, -O-CF2CF(CF3)-O-CF2-, -O-CF2CF(CF3)-O-CF2CF2- , -CF2-O-CF2CF2-, -CF2-O-CF2CH2-, -CF2-O-CF2CF2CH2-, -CF2-O-CF(CF3)-, -CF2-O-CF(CF3 )CF2-, -CF2-O-CF(CF3)CF2-O-, -CF2-O-CF(CF3)CF2-O-CF2-, -CF2-O-CF(CF3)CH2-, and the like. In particular, R is preferably a perfluoroalkylene group which may contain an oxygen atom, specifically -CF2-O-, -CF2-O-CF2-, -O-CF2-, -O-CF2CF2-, -O-CF2CF(CF3)-O-CF2-, -O-CF2CF(CF3)-O-CF2CF2-, -CF2-O-CF2CF2-, -CF2-O-CF(CF3)-, -CF2-O-CF(CF3)CF2-, or -CF2-O-CF(CF3)CF2-O-.

[0126] General formula (I) -R-CZ 1 Z 2 -For example, the general formula (s1): -CF2-O-(CX 6 2) e -{O-CF(CF3)} f -(O) g -CZ 1 Z 2 - (s1) (In the formula, X 6 Each of these is independently H, F, or CF3, e is an integer from 0 to 3, f is an integer from 0 to 3, g is 0 or 1, Z 1 and Z 2Preferably, each of these is independently represented as H, F, an alkyl group, or a fluorine-containing alkyl group, and in formula (s1), Z 1 and Z 2 F or CF3 is more preferable, and it is even more preferable that one is F and the other is CF3.

[0127] Furthermore, in general formula (I), -R-CZ 1 Z 2 -For example, the general formula (s2): -CF2-O-(CX 7 2) e -(O) g -CZ 1 Z 2 - (s2) (In the formula, X 7 Each of them is independently H, F, or CF3, e is an integer from 0 to 3, g is 0 or 1, and Z 1 and Z 2 Preferably, each of these is independently represented as H, F, an alkyl group, or a fluorine-containing alkyl group, and in formula (s2), Z 1 and Z 2 F or CF3 is more preferable, and it is even more preferable that one is F and the other is CF3.

[0128] General formula (I) -R-CZ 1 Z 2- as -CF2-O-CF2-, -O-CF2CF2-, -O-CF2CF2CF2-, -O-CF2CF2CF2CF2-, -O-CF2CF(CF3)-O-CF2-, -O-CF2CF(CF3)-O-CF 2CF2-, -O-CF2CF(CF3)-O-CF2CF2CF2-, -CF2-O-CF(CF3)-, -CF2-OC(CF3)2-, -CF2-O-CF2-CF2-, -CF2-O-CF2-CF(CF3)-, -CF2-O-CF2-C(CF3)2-, -CF2-O-CF2CF2-CF2-, -CF2-O-CF2CF2-CF(CF3)-, -CF2-O-CF2CF2-C(CF3)2-, -CF2-O-CF(CF3)- CF2-, -CF2-O-CF(CF3)-CF(CF3)-, -CF2-O-CF(CF3)-C(CF3)2-, -CF2-O-CF(CF3)CF2-CF2-, -CF2-O-CF(CF3)CF2-CF(CF3 )-, -CF2-O-CF(CF3)CF2-C(CF3)2-, -CF2-O-CF(CF3)CF2-O-CF2-, -CF2-O-CF(CF3)CF2-O-CF(CF3)-, or -CF2-O-CF(CF 3) CF2-OC(CF3)2- is preferred, -O-CF2CF2-, -O-CF2CF2CF2-, -O-CF2CF2CF2CF2-, -O-CF2CF(CF3)-O-CF2-, -O-CF2CF(CF3)-O- CF2CF2-, -CF2-O-CF(CF3)-, -CF2-O-CF2-CF(CF3)-, -CF2-O-CF2CF2-CF(CF3)-, -CF2-O-CF(CF3)-CF(CF3)-, -CF2-O-CF(CF3)CF2-CF(CF3)-, or -CF2-O-CF(CF3)CF2-O-CF(CF3)- are more preferred, and -O-CF2CF2-, -O-CF2CF(CF3)-O-CF2CF2- are even more preferred.

[0129] Polymer (I) is also preferably highly fluorinated. For example, anionic groups such as a phosphate group moiety (e.g., CH2OP(O)(OM)2) and a sulfate group moiety (e.g., CH2OS(O)2OM) (A 0Except for the above, it is preferable that 80% or more, 90% or more, 95% or more, or 100% of the CH bonds in polymer compound (I) are replaced by CF bonds.

[0130] Monomer (I) and polymer (I) have an anionic group (A 0 Except for ), it is also preferable that it has CF bonds and does not have CH bonds. That is, in general formula (I), X 1 , X 2 , and X 3 Preferably, all of the elements are F, and R is a perfluoroalkylene group having 1 or more carbon atoms. The perfluoroalkylene group may be linear or branched, cyclic or acyclic, and may contain at least one catenary heteroatom. The number of carbon atoms in the perfluoroalkylene group may be 2 to 20 or 4 to 18.

[0131] The monomer (I) and polymer (I) may be partially fluorinated. That is, the monomer (I) and polymer compound (I) may have an anionic group (A 0 Except for the above, it is preferable to have at least one hydrogen atom bonded to a carbon atom, and also to have at least one fluorine atom bonded to a carbon atom.

[0132] Anionic group (A 0) may be -SO2M, -SO3M, -OSO3M, -COOM, -SO2NR'CH2COOM, -CH2OP(O)(OM)2, [-CH2O]2P(O)(OM), -CH2CH2OP(O)(OM)2, [-CH2CH2O]2P(O)(OM), -CH2CH2OSO3M, -P(O)(OM)2, -SO2NR'CH2CH2OP(O)(OM)2, [-SO2NR'CH2CH2O]2P(O)(OM), -CH2OSO3M, -SO2NR'CH2CH2OSO3M, or -C(CF3)2OM. Among these, -SO3M, -OSO3M, -COOM, -P(O)(OM)2 or -C(CF3)2OM are preferred, -COOM, -SO3M, -OSO3M, -P(O)(OM)2 or -C(CF3)2OM are more preferred, -SO3M, -COOM or -P(O)(OM)2 are even more preferred, and -SO3M or -COOM are particularly preferred.

[0133] M is H, a metal atom, NR 7 4. Imidazolium which may have substituents, pyridinium which may have substituents, or phosphonium which may have substituents, 7 is either H or an organic group.

[0134] Examples of metal atoms include alkali metals (Group 1) and alkaline earth metals (Group 2), with Na, K, or Li being preferred.

[0135] For M, this could be -H, a metal atom, or NR. 7 4 is preferred, and -H, alkali metals (Group 1), alkaline earth metals (Group 2), or NR 7 4 is more preferred, -H, -Na, -K, -Li or NH4 is even more preferred, -H, -Na, -K or NH4 is even more preferred, -H, -Na or NH4 is particularly preferred, and -H or NH4 is most preferred.

[0136] In polymer (I), each polymerization unit (I) may have different anionic groups, or it may have the same anionic group.

[0137] The monomer (I) is preferably monomer (1) represented by general formula (1). The polymer (I) is preferably a polymer (1) that includes polymerization units (1) based on monomers represented by general formula (1). CX2 = CY(-CZ2-O-Rf-A) (1) (In the formula, 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 fluoroalkyl group. Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having 2 to 100 carbon atoms and having an ether bond. A is -COOM, -SO3M, -OSO3M or -C(CF3)2OM (M is -H, a metal atom, -NR) 7 4. Imidazolium which may have substituents, pyridinium which may have substituents, or phosphonium which may have substituents, 7 (wherein X, Y, and Z are H or organic groups, at least one of them contains a fluorine atom.)

[0138] The monomer (1) is preferably a monomer represented by the general formula (1A). The polymerization unit (1) is preferably a polymerization unit (1A) based on a monomer represented by general formula (1A). CH2=CF(-CF2-O-Rf-A) (1A) (In the formula, Rf and A are the same as above.)

[0139] The monomer represented by the general formula (1A) is preferably -COOM, and in particular, at least one selected from the group consisting of CH2=CFCF2OCF(CF3)COOM and CH2=CFCF2OCF(CF3)CF2OCF(CF3)COOM (wherein M is the same as defined above), with CH2=CFCF2OCF(CF3)COOM being more preferred.

[0140] It is also preferable that monomer (I) is monomer (2) represented by general formula (2). Polymer (I) is also preferably polymer (2) which contains polymerization units (2) based on monomers represented by general formula (2). CX2 = CY(-O-Rf-A) (2) (In the formula, X is -H or F, either the same or different; Y is -H, -F, an alkyl group, or a 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 or a keto group having 2 to 100 carbon atoms. A is the same as described above.)

[0141] Examples of monomers (2) include CF2 = CF-O-CF2-CF(CF3)-O-CF2-CF2-COOM, CF2 = CF-O-CF2-CF2-COOM, and CF2 = CF-O-CF2-CF2-SO3M (wherein M is the same as defined above).

[0142] It is also preferable that monomer (I) is monomer (3) represented by general formula (3). The polymer (I) is also preferably a polymer (3) that includes polymerization units (3) based on monomers represented by general formula (3). CX2 = CY(-Rf-A) (3) (In the formula, X is either -H or F, either the same or different; Y is -H, -F, an alkyl group, or a fluorine-containing alkyl group; Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having 2 to 100 carbon atoms and possessing an ether bond. A is the same as described above.)

[0143] Polymer (I) may be a homopolymer consisting only of polymerization units (I), or it may be a copolymer containing polymerization units (I) and polymerization units based on other monomers copolymerizable with the monomer represented by general formula (I). From the viewpoint of solubility in aqueous media, a homopolymer consisting only of polymerization units (I) is preferred. Polymerization units (I) may be the same or different in each appearance, and polymer (I) may contain polymerization units (I) based on two or more different monomers represented by general formula (I).

[0144] Polymer (I) typically has end groups. These end groups are generated during polymerization, and typical end groups are independently selected from hydrogen, iodine, bromine, linear or branched alkyl groups, and linear or branched fluoroalkyl groups, and may optionally contain at least one additional catenary heteroatom. The alkyl or fluoroalkyl group preferably has 1 to 20 carbon atoms. These end groups are generally generated from initiators or chain transfer agents used to form polymer (I), or during the chain transfer reaction.

[0145] In one embodiment, polymer (I) includes molecular chains having an ionic group at at least one main chain end. In another embodiment, polymer (I) includes molecular chains having ionic groups at at least both main chain ends. Ionic groups at the main chain ends can be introduced into the molecular chains constituting polymer (I) by appropriately selecting the type of polymerization initiator, the type of monomer, etc. Furthermore, if a chain transfer agent is not used during polymerization, ionic groups can be introduced to both ends of the molecular chains constituting polymer (I). For example, by polymerizing perfluoro monomers using a persulfate as a polymerization initiator, carboxylic acid groups can be introduced to the main chain ends of the molecular chains constituting polymer (I). In this case, if perfluoro monomers are polymerized without using a chain transfer agent, carboxylic acid groups can be introduced to both ends of the main chains of the molecular chains constituting polymer (I). It is preferable that polymer (I) does not have crystalline components, as this allows for greater polymerization stability.

[0146] In polymer (I), the content of polymerization units (I) is, in order of preference, 1.0 mol% or more, 3.0 mol% or more, 5.0 mol% or more, 10 mol% or more, 20 mol% or more, 30 mol% or more, 40 mol% or more, 50 mol% or more, 60 mol% or more, 70 mol% or more, 80 mol% or more, and 90 mol% or more, relative to the total polymerization units. The content of polymerization units (I) is particularly preferably substantially 100 mol%, and it is most preferable that the polymer compound (I) consists only of polymerization units (I).

[0147] In polymer (I), the content of polymerization units based on other monomers copolymerizable with the monomer represented by general formula (I) is, in order of preference, 99.0 mol% or less, 97.0 mol% or less, 95.0 mol% or less, 90 mol% or less, 80 mol% or less, 70 mol% or less, 60 mol% or less, 50 mol% or less, 40 mol% or less, 30 mol% or less, 20 mol% or less, and 10 mol% or less, relative to the total polymerization units. It is particularly preferable that the content of polymerization units based on other monomers copolymerizable with the monomer represented by general formula (I) be substantially 0 mol%, and it is most preferable that polymer (I) does not contain polymerization units based on other monomers.

[0148] The amount of polymer (I) added is preferably 0.01 to 20% by mass per 100% by mass of the aqueous medium. More preferably, the amount of polymer (I) added is 0.0001% by mass or more, even more preferably 0.0005% by mass or more, still more preferably 0.001% by mass or more, particularly preferably 0.005% by mass or more, and most preferably 0.01% by mass or more, per 100% by mass of the aqueous medium.

[0149] Polymer (I) can be produced, for example, by polymerizing monomers that provide polymerization units (I) in an aqueous medium. The mixture containing polymer (I) obtained by polymerization and the aqueous medium may be purified using methods such as ion exchange treatment or ultrafiltration before polymer (I) is used for polymerization.

[0150] (polymerization) In the manufacturing method of the present disclosure, polymerization of fluorine-containing monomers can be carried out, for example, by charging an aqueous medium into a pressure-resistant reaction vessel (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 reaction vessel are purged, and the temperature is returned to room temperature to stop the reaction.

[0151] In the manufacturing method of this disclosure, the time from the time when the polymerization initiator is first added to the time when polymerization is stopped is preferably 20 hours or less, more preferably 15 hours or less, and 10 hours or less. The lower limit is not particularly limited, but may be 2 hours or more. By adjusting the time until polymerization is stopped within the above range, it becomes easier to adjust the amount of radicals generated and the polymerization rate, and even when a surfactant is not used during polymerization, an aqueous dispersion containing a fluorine-containing elastomer with even better crosslinking properties can be produced with even higher productivity.

[0152] The manufacturing method of the present disclosure 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 a functional group that can react by radical polymerization.

[0153] Conventionally, fluorine-containing surfactants have been used for the polymerization of fluorine-containing monomers. However, the manufacturing method disclosed herein allows polymerization to be carried out while appropriately adjusting the amount of radicals generated or the polymerization rate. Therefore, fluorine-containing monomers can be polymerized and fluorine-containing elastomers can be obtained without using fluorine-containing surfactants.

[0154] 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.

[0155] Examples of the fluorine-containing surfactants mentioned above include anionic fluorine-containing surfactants.

[0156] 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.

[0157] The fluorine-containing surfactant may also be a surfactant containing fluorine with the molecular weight of the anionic moiety being 1000 or less, preferably 800 or less.

[0158] Note that the above-mentioned "anionic moiety" means the part excluding the cation of the fluorine-containing surfactant. For example, in the case of F(CF2) n1 COOM represented by the formula (I) described later, it is the part of "F(CF2) n1 COO".

[0159] Examples of the fluorine-containing surfactant 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 represented by LogP [where P represents the ratio of the concentration of the fluorine-containing surfactant in octanol to the concentration of the fluorine-containing surfactant in water when an octanol / water (1:1) mixed solution containing the fluorine-containing surfactant is phase-separated].

[0160] The above LogPOW is determined by performing HPLC on standard substances (heptanoic acid, octanoic acid, nonanoic acid, and decanoic acid) having a known octanol / water partition coefficient under the conditions of column; TOSOH ODS-120T column (φ4.6 mm × 250 mm, manufactured by Tosoh Corporation), eluent; acetonitrile / 0.6 mass% HClO4 water = 1 / 1 (vol / vol%), flow rate; 1.0 ml / min, sample volume; 300 μL, column temperature; 40 °C, detection light; UV210 nm, creating a calibration curve between each elution time and the known octanol / water partition coefficient, and calculating from the elution time of HPLC in the sample solution based on this calibration curve.

[0161] Examples of the fluorine-containing surfactant include compounds represented by the following formula. The fluorine-containing surfactant may be a mixture of these compounds. In one embodiment of the above polymerization, the fluoromonomer is polymerized substantially in the absence of a compound represented by the following formula. F(CF2)7COOM, F(CF2)5COOM, H(CF2)6COOM, H(CF2)7COOM, CF3O(CF2)3OCHFCF2COOM, C3F7OCF(CF3)CF2OCF(CF3)COOM, CF3CF2CF2OCF(CF3)COOM, CF3CF2OCF2CF2OCF2COOM, C2F5OCF(CF3)CF2OCF(CF3)COOM, CF3OCF(CF3)CF2OCF(CF3)COOM, CF2ClCF2CF2OCF(CF3)CF2OCF2COOM, CF2ClCF2CF2OCF2CF(CF3)OCF2COOM, CF2ClCF(CF3)OCF(CF3)CF2OCF2COOM, CF2ClCF(CF3)OCF2CF(CF3)OCF2COOM,

Chem.

[0162] The production method of the present disclosure preferably performs polymerization of a fluorine-containing monomer substantially in the absence of a fluorine-free surfactant. Since the production method of the present disclosure performs polymerization while appropriately adjusting the radical generation amount or the polymerization rate, a fluorine-containing elastomer can be obtained by polymerizing a fluorine-containing monomer without using a fluorine-free surfactant.

[0163] In this disclosure, "substantially in the absence of fluorine-free surfactants" means that the proportion of fluorine-free surfactants in the aqueous medium is 10 ppm by mass or less. The proportion of fluorine-free surfactants 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.

[0164] Examples of fluorine-free surfactants include fluorine-free anionic surfactants, fluorine-free nonionic surfactants, and fluorine-free cationic surfactants.

[0165] The manufacturing method of the present disclosure preferably involves polymerization of a fluorine-containing monomer in the substantially absence of a fluorine-containing solvent. Since the manufacturing method of the present disclosure involves polymerization while appropriately adjusting the amount of radical generation or polymerization rate, a fluorine-containing elastomer can be obtained by polymerization of a fluorine-containing monomer without using a fluorine-containing solvent.

[0166] In this disclosure, "substantially in the absence of a fluorine-containing solvent" means that the proportion of the fluorine-containing solvent in the aqueous medium is 10 ppm by mass or less. The proportion of the fluorine-containing solvent 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.

[0167] Examples of fluorine-containing solvents include fluorine-containing ether solvents, fluorine-containing ketone solvents, and fluorocarbon solvents. Examples of fluorine-containing ether solvents include the Galden HT series (manufactured by Solvay) and Novec HFE-7500 (manufactured by 3M), while examples of fluorocarbon solvents include Freon 113 and Freon 141b.

[0168] In the polymerization of fluorine-containing monomers, phosphates, sodium hydroxide, potassium hydroxide, aqueous ammonia, etc., may be used as pH adjusters.

[0169] The aqueous medium is preferably acidic. By polymerizing the fluorine-containing monomer using an acidic aqueous medium, the adhesion of the fluorine-containing polymer to the reaction vessel can be further suppressed. The pH of the aqueous medium is preferably 7 or less, more preferably 6 or less, and preferably 3 or higher.

[0170] In the manufacturing method of this disclosure, the polymerization temperature for polymerizing the fluorine-containing monomer is preferably 10 to 120°C, and more preferably 20 to 100°C. Furthermore, a polymerization temperature of 40 to 120°C is preferred, more preferably 50 to 100°C, and even more preferably 50 to 90°C, as this yields a fluorine-containing elastomer with a high polymerization rate and excellent physical properties. The polymerization temperature may be 60 to 120°C, 60 to 100°C, or 70 to 90°C.

[0171] In one embodiment of the manufacturing method of this disclosure, the polymerization temperature is adjusted to 50-85°C or 65-85°C from the point when the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer mass, until the point when polymerization is stopped. By adjusting the temperature to a relatively low level after the initial polymerization period has elapsed, it becomes easier to adjust the amount of radicals generated and the polymerization rate.

[0172] In one embodiment of the manufacturing method of this disclosure, the polymerization temperature is adjusted to 75-100°C from the time the polymerization initiator is first added until the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer. By adjusting the temperature during the initial polymerization period to a relatively high level, it becomes easier to adjust the amount of radicals generated and the polymerization rate.

[0173] In the production method of the present disclosure, the polymerization pressure for polymerizing the fluorine-containing monomer is preferably 0.5 to 10 MPaG, more preferably 0.6 to 7 MPaG. The polymerization pressure may be 1 to 7 MPaG. In one embodiment, the polymerization pressure from the time when the polymerization initiator is first added to the time when the polymerization is stopped is maintained within the above-mentioned range. In another embodiment, the polymerization pressure from the time when the polymerization initiator is first added to the time when the polymerization is stopped is maintained within the above-mentioned range.

[0174] (fluorine-containing monomer) In the production method of the present disclosure, an aqueous dispersion of a fluorine-containing elastomer is obtained by polymerizing a fluorine-containing monomer.

[0175] Examples of the fluorine-containing monomer include vinylidene fluoride (VdF), tetrafluoroethylene (TFE), hexafluoropropylene (HFP), perfluoro(alkyl vinyl ether) (PAVE), chlorotrifluoroethylene (CTFE), 1,2-difluoroethylene, trifluoroethylene, trifluoropropylene, tetrafluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutene, hexafluoroisobutene, vinyl fluoride, iodine-containing fluorinated vinyl ether, general formula (2): CHX 1 =CX 2 Rf (2) (wherein X 1 and X 2 are such that one is H and the other is F, and Rf is a linear or branched fluoroalkyl group having 1 to 12 carbon atoms), and fluorine-containing monomers such as the fluorine-containing monomer (2) represented by the formula are exemplified.

[0176] In one embodiment of the manufacturing method of the present disclosure, at least one of the fluorine-containing monomers subjected to polymerization is a fluorine-containing monomer having a boiling point of 0°C or lower. In particular, by using at least one fluorine-containing monomer that can exist in a gaseous state at the polymerization temperature, it becomes even easier to adjust the amount of radicals generated and the polymerization rate. In this embodiment, it is sufficient to use at least one fluorine-containing monomer having a boiling point of 0°C or lower, and it is also possible to use only fluorine-containing monomers having a boiling point of 0°C or lower, or to use a combination of fluorine-containing monomers having a boiling point of 0°C or lower and fluorine-containing monomers having a boiling point above 0°C.

[0177] As a fluorine-containing monomer having a boiling point below 0°C, at least one selected from the group consisting of vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene is preferred.

[0178] 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.

[0179] Furthermore, PAVE is given by the formula: CF2 = CFOCF2ORf c (In the formula, 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. As PAVE, for example, CF2=CFOCF2OCF3, CF2=CFOCF2OCF2CF3, or CF2=CFOCF2OCF2CF2OCF3 are preferred.

[0180] Furthermore, PAVE is given by the formula: CF2 = CFORf d ORf e (In the formula, Rf dThis refers to a linear or branched perfluoroalkylene group having 2 to 4 carbon atoms, a cyclic perfluoroalkylene group having 5 to 6 carbon atoms, or a linear or branched perfluorooxyalkylene group having 2 to 8 carbon atoms containing 1 to 5 oxygen atoms, where Rf e 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. As PAVE, for example, CF2=CF-(OCF2CF2)2-OCF2CF3, CF2=CF-(OCF2CF2)3-OCF2CF3, or CF2=CF-OCF2CF2CF2-OCF3 are preferred.

[0181] 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.

[0182] Examples of fluorine-containing monomers (2) include CH2=CFCF3, CH2=CFCF2CF3, CH2=CFCF2CF2CF3, CH2=CFCF2CF2CF2CF3, CHF=CHCF3 (1,3,3,3-tetrafluoropropene), CHF=CHCF3 (E-isomer), and CHF=CHCF3 (Z-isomer), among which 2,3,3,3-tetrafluoropropylene represented by CH2=CFCF3 is preferred.

[0183] In the manufacturing method of this disclosure, adhesion of the fluorine-containing elastomer to the reaction vessel can be further suppressed, so it is preferable to polymerize at least vinylidene fluoride or tetrafluoroethylene as the fluorine-containing monomer, and more preferably vinylidene fluoride.

[0184] 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 in which the alkyl group has 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 or compounds can be used in combination.

[0185] Among fluorine-containing elastomers, perfluoroelastomers are obtained by polymerizing perfluoro monomers.

[0186] As perfluoro monomers, Tetrafluoroethylene (TFE), Hexafluoropropylene [HFP] General formula (160): CF2=CF-ORf 13 (In the formula, Rf 13 ) represents a perfluoroalkyl group having 1 to 8 carbon atoms. General formula (130): CF2=CFOCF2ORf 14 (In the formula, Rf 14 (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): CF2=CFO(CF2CF(Y 15 )O) m (CF2) n F (In the formula, 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. ) Fluoromer represented by At least one selected from the group consisting of is preferred.

[0187] 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.

[0188] (Fluorine-containing elastomer) According to the manufacturing method of this disclosure, an aqueous dispersion containing a fluorine-containing elastomer can be produced. The fluorine-containing elastomer in the resulting aqueous dispersion may be a polyol-crosslinkable fluorine-containing elastomer, a peroxide-crosslinkable fluorine-containing elastomer, and the like.

[0189] Fluorine-containing elastomers are preferably those having an ion exchange rate (IXR) higher than 53. Preferred fluorine-containing elastomers either have no ionic groups at all or have a limited number of ionic groups that result in an ion exchange rate higher than about 100. The ion exchange rate of preferred fluorine-containing elastomers is preferably 1000 or higher, more preferably 2000 or higher, and even more preferably 5000 or higher.

[0190] The fluorine-containing elastomer may be a partially fluorinated rubber or a perfluoroelastomer.

[0191] The fluorine-containing elastomer obtained by the manufacturing method of this disclosure preferably contains a methylene group (-CH2-) in its main chain. The fluorine-containing elastomer containing -CH2- in its main chain is not particularly limited as long as it contains a chemical structure represented by -CH2-, and examples include fluorine-containing elastomers containing structures such as -CH2-CF2-, -CH2-CH(CH3)-, -CH2-CH2-, and -CH2-CF2-(CF3)-, which can be introduced into the main chain of the fluorine-containing elastomer by polymerizing 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%.

[0192] 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 25°C or lower, preferably 20°C or lower, and has a melting peak (ΔH) of 4.5 J / g or lower.

[0193] Examples of fluorine-containing elastomers include tetrafluoroethylene (TFE), vinylidene fluoride (VdF), and those with the general formula: CF2=CF-Rf a (In the formula, Rf a -CF3 or -ORf b (Rf b It is preferable that the fluorine-containing elastomer contains 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.). In particular, it is preferable that the fluorine-containing elastomer contains VdF units or TFE units, and more preferably VDF units.

[0194] 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.

[0195] 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, based on the total number of moles of VdF units and monomer units based on other monomers.

[0196] 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.

[0197] 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 copolymer has at least one monomer selected from the group consisting of TFE, HFP, and PAVE as the monomer other than VdF.

[0198] Among the VdF-based fluorine-containing elastomers, 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 is preferred, and 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 is more preferred.

[0199] As the VdF / PAVE copolymer, a VdF / PAVE composition of (65-90) / (35-10) (mol%) is preferred. Furthermore, a VdF / PAVE composition of (50-78) / (50-22) (mol%) is also a preferred form.

[0200] As a VdF / TFE / PAVE copolymer, one with a VdF / TFE / PAVE composition of (40-80) / (3-40) / (15-35) (mol%) is preferred.

[0201] As a VdF / HFP / PAVE copolymer, one with a VdF / HFP / PAVE composition of (65-90) / (3-25) / (3-25) (mol%) is preferred.

[0202] 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.

[0203] 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). Furthermore, a composition of VdF / fluorine-containing monomer (2) units of (78-50) / (22-50) (mol%) is also a preferred form.

[0204] 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, such as TFE, HFP, PMVE, perfluoroethyl vinyl ether (PEVE), PPVE, CTFE, trifluoroethylene, hexafluoroisobutene, vinyl fluoride, Et, Pr, alkyl vinyl ether, and monomers that provide crosslinking groups, and among these, PMVE, CTFE, HFP, and TFE are more preferred.

[0205] 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.

[0206] 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.

[0207] TFE / Pr-based fluorine-containing elastomers preferably contain VdF, and among TFE / Pr-based fluorine-containing elastomers, those composed of TFE, Pr, and VdF are called TFE / Pr / VdF-based fluorine-containing elastomers.

[0208] 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 a combination of two or more types. 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.

[0209] 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%).

[0210] 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%).

[0211] 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.

[0212] 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.

[0213] 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%).

[0214] 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.

[0215] A monomer that gives a preferred crosslinking group is the general formula (3): CY 1 2 = CY 2 R f 2 X 1 (3) (In the formula, Y1 , Y 2 is a fluorine atom, a hydrogen atom or -CH3;R f 2 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 (This refers to an iodine atom or a bromine atom.) Examples of compounds shown are:

[0216] Examples of monomers that provide crosslinking groups include, for example, general formula (4): CY 1 2 = CY 2 R f 3 CHR 1 -X 1 (4) (In the formula, Y 1 , Y 2 , X 1 The same applies as above, R f 3 R 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 (This refers to a hydrogen atom or a methyl group.) Iodine or bromine-containing monomers represented by the following, general formulas (5) to (22): CY 4 2 = CY 4 (CF2) n -X 1 (5) (In the formula, Y 4 (These are either the same or different hydrogen atoms or fluorine atoms, and n is an integer from 1 to 8.) CF2 = CFCF2R f 4 -X 1 (6) (In the formula, R 4 is, -(OCF2) n -or-(OCF(CF3)) n - where n is an integer between 0 and 5) CF2 = CFCF2(OCF(CF3)CF2) m (OCH2CF2CF2) n OCH2CF2-X 1 (7) (In the formula, m is an integer between 0 and 5, and n is an integer between 0 and 5) CF2 = CFCF2(OCH2CF2CF2) m (OCF(CF3)CF2) n OCF(CF3)-X 1 (8) (In the formula, m is an integer between 0 and 5, and n is an integer between 0 and 5) CF2 = CF(OCF2CF(CF3)) m O(CF2) n -X 1 (9) (In the formula, m is an integer from 0 to 5, and n is an integer from 1 to 8) CF2 = CF(OCF2CF(CF3)) m -X 1 (10) (In the formula, m is an integer from 1 to 5) CF2 = CFOCF2(CF(CF3)OCF2) n CF(-X 1 )CF3(11) (In the formula, n is an integer from 1 to 4) CF2 = CFO(CF2) n OCF(CF3)-X 1 (12) (In the formula, n is an integer between 2 and 5) CF2 = CFO(CF2) n -(C6H4)-X 1 (13) (In the formula, n is an integer from 1 to 6) CF2 = CF(OCF2CF(CF3)) n OCF2CF(CF3)-X 1 (14) (In the formula, n is an integer between 1 and 2) CH2=CFCF2O(CF(CF3)CF2O) nCF(CF3)-X 1 (15) (In the formula, n is an integer from 0 to 5) CF2 = CFO(CF2CF(CF3)O) m (CF2) n -X 1 (16) (In the formula, m is an integer from 0 to 5, and n is an integer from 1 to 3) CH2 = CFCF2OCF(CF3)OCF(CF3) - X 1 (17) CH2=CFCF2OCH2CF2-X 1 (18) CF2 = CFO(CF2CF(CF3)O) m CF2CF(CF3)-X 1 (19) (In the formula, m is a non-negative integer) CF2 = CFOCF(CF3)CF2O(CF2) n -X 1 (20) (In the formula, n is an integer greater than or equal to 1) CF2 = CFOCF2OCF2CF(CF3)OCF2 - X 1 (twenty one) CH2=CH-(CF2) n X 1 (twenty two) (In the formula, n is an integer between 2 and 8) (In general formulas (5) to (22), X 1 (As mentioned above) Examples include iodine or bromine-containing monomers represented by [formula], which can be used individually or in any combination.

[0217] As an iodine or bromine-containing monomer represented by general formula (4), general formula (23): [ka] (In the formula, m is an integer between 1 and 5, and n is an integer between 0 and 3.) Iodine-containing fluorinated vinyl ethers represented by are preferred, and more specifically, [ka] These are some examples, but among them, ICH2CF2CF2OCF=CF2 is preferred.

[0218] More specifically, the iodine or bromine-containing monomer represented by general formula (5) is preferably ICF2CF2CF=CH2 or I(CF2CF2)2CF=CH2.

[0219] More specifically, I(CF2CF2)2OCF=CF2 is a preferred example of the iodine or bromine-containing monomer represented by general formula (9).

[0220] More specifically, preferred iodine or bromine-containing monomers represented by general formula (22) include CH2=CHCF2CF2I and I(CF2CF2)2CH=CH2.

[0221] 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 7 The group (H) is the same or different, and both are C1-C5 alkyl groups; Z is a linear or branched, possibly oxygen-containing, preferably at least partially fluorinated C1-C18 alkylene or cycloalkylene group, or (per)fluoropolyoxyalkylene group. 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".

[0222] Z is preferably a (per)fluoroalkylene group having 4 to 12 carbon atoms, and R 2 , R 3 , R4 , R 5 , R 6 and R 7 Preferably, it is a hydrogen atom.

[0223] If Z is a (per)fluoropolyoxyalkylene group, the formula is: -(Q) p -CF2O-(CF2CF2O) m -(CF2O) n -CF2-(Q) p - It is preferable that the (per)fluoropolyoxyalkylene group is represented by the formula (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 -CH2OCH2- and -CH2O(CH2CH2O) s It is selected from CH2-(s=1~3).

[0224] Preferred bisolefins are CH2=CH-(CF2)2-CH=CH2, CH2=CH-(CF2)4-CH=CH2, CH2=CH-(CF2)6-CH=CH2, Formula: CH2=CH-Z 1 -CH=CH2 (In the formula, Z 1 is -CH2OCH2-CF2O-(CF2CF2O) m -(CF2O) n -CF2-CH2OCH2- (m / n is 0.5, molecular weight preferably 2000) These are some examples.

[0225] Among these, 3,3,4,4,5,5,6,6,7,7,8,8-dodecafluoro-1,9-decadien, represented as CH2=CH-(CF2)6-CH=CH2, is preferred.

[0226] Monomers that provide crosslinking groups include monomers having a cyano group (-CN group). Monomers having a cyano group (-CN group) include: Formula: CF2 = CF(OCF2CF(CF3)) m O(CF2) n -CN (In the formula, m is an integer from 0 to 5, and n is an integer from 1 to 8), or, Formula: CF2 = CFO(CF2) n CN A monomer represented by the formula (where n is an integer of 1 or more) is preferred, and CF2 = CFOCF2CF(CF3)OCF2CF2CN is more preferred.

[0227] 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.

[0228] 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 from methods such as H-NMR and elemental analysis.

[0229] The fluorine-containing elastomer preferably has a Mooney viscosity (ML1 + 10 (100°C)) of 130 or less at 100°C. More preferably, the Mooney viscosity is 110 or less, and even more preferably 90 or less. Furthermore, the Mooney viscosity is more preferably 10 or more, and even more preferably 20 or more. The Mooney viscosity is measured in accordance with JIS K 6300-1.2013.

[0230] The fluorine-containing elastomer preferably has a Mooney viscosity (ML1+10(121°C)) of 130 or less at 121°C. More preferably, the Mooney viscosity is 110 or less, and even more preferably 90 or less. Furthermore, the Mooney viscosity is more preferably 2 or more, and even more preferably 5 or more. The Mooney viscosity is measured in accordance with JIS K 6300-1.2013.

[0231] The fluorine-containing elastomer preferably has a Mooney viscosity (ML1+20(170°C)) of 130 or less at 170°C. More preferably, the Mooney viscosity is 110 or less, and even more preferably 90 or less. Furthermore, the Mooney viscosity is more preferably 2 or more, and even more preferably 5 or more. The Mooney viscosity is measured in accordance with JIS K 6300-1.2013.

[0232] The fluorine-containing elastomer preferably has a glass transition temperature of -50 to 5°C. More preferably, the glass transition temperature is 3°C or lower, and even more preferably 0°C or lower. The glass transition temperature may also be 0°C or lower, -2°C or lower, or -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, and even more preferably -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 in accordance with JIS K6240:2011.

[0233] 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.

[0234] The iodine content can be determined by elemental analysis. Specifically, 12 mg of fluorine-containing elastomer is mixed with 5 mg of Na2SO3, and an absorption solution is prepared by dissolving 30 mg of a 1:1 (mass ratio) mixture of Na2CO3 and K2CO3 in 20 ml of pure water. This solution is then burned in a quartz flask under oxygen, left for 30 minutes, and measured using a Shimadzu 20A ion chromatograph. Calibration curves can be used, including KI standard solutions, solutions containing 0.5 ppm by mass of iodide ions, and solutions containing 1.0 ppm by mass.

[0235] Fluorine-containing elastomers preferably contain a -CH2I structure. Containing a -CH2I structure means that 1 This can be confirmed by 1H-NMR spectroscopy. Fluorine-containing elastomers containing the -CH2I structure can be obtained by iodine transfer polymerization.

[0236] The fluorine-containing elastomer preferably has an amount of -CH2I structure of 0.05 to 1.50 mol% relative to 100 mol% of -CH2- structure. The amount of -CH2I structure is more preferably 0.08 mol% or more, even more preferably 0.12 mol% or more, more preferably 1.20 mol% or less, even more preferably 1.00 mol% or less, and particularly preferably 0.80 mol% or less. 1 This can be determined by 1H-NMR spectroscopy.

[0237] The fluorine-containing elastomer more preferably contains a -CF2CH2I structure. A fluorine-containing elastomer containing a -CF2CH2I structure can be obtained by producing a VdF-based fluorine-containing elastomer by iodine transfer polymerization.

[0238] The fluorine-containing elastomer preferably has an amount of -CF2CH2I structure of 0.05 to 1.50 mol% relative to 100 mol% of -CH2- structure. The amount of -CF2CH2I structure is more preferably 0.08 mol% or more, even more preferably 0.12 mol% or more, more preferably 1.20 mol% or less, even more preferably 1.00 mol% or less, and particularly preferably 0.80 mol% or less. 1In the 1H-NMR spectrum, the integral value A is calculated by subtracting the integral value B, obtained by subtracting the integral value of the water peak intensity observed in the 2.7-2.9 region from the integral value of the peak intensity observed in the 2.30-3.75 ppm region of the chemical shift originating from -CH2-, from the integral value A of all peak intensities observed in the chemical shift region of -CH2-, and the integral value B of water observed in the 2.7-2.9 region. The integral value B is calculated by A / B*100.

[0239] 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 25°C or less, preferably 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 contained in the fluoropolymer is calculated from the type and content of each monomer constituting the fluoropolymer.

[0240] 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 / fluoromonomer / monomer copolymers that provide crosslinking sites represented by general formula (160), (130), or (140). As the monomer that provides the crosslinking sites, the monomer that provides the crosslinkable group as described above is preferred.

[0241] In the case of the TFE / PMVE copolymer, the composition is preferably 45-90 / 10-55 (mol%), more preferably 55-80 / 20-45, and even more preferably 55-70 / 30-45.

[0242] 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.

[0243] 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.

[0244] In the case of TFE / fluoromonomers represented by general formulas (160), (130), or (140) having 4 to 12 carbon atoms / monomer copolymers that provide crosslinking sites, 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.

[0245] 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.

[0246] 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.

[0247] 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.

[0248] (aqueous dispersion) According to the manufacturing method of the present disclosure, an aqueous dispersion of a fluorine-containing elastomer is obtained. The solid content concentration (fluorine-containing elastomer content) of the obtained aqueous dispersion of fluorine-containing elastomer is preferably 15 to 50% by mass, more preferably 15 to 40% by mass, and even more preferably 20 to 30% by mass, at the time polymerization is stopped.

[0249] The aqueous dispersion of the fluorine-containing elastomer may contain fluorine-containing elastomer particles. The average particle diameter of the fluorine-containing elastomer particles is preferably 10 to 800 nm, more preferably 50 to 500 nm, and even more preferably 70 to 300 nm. The average particle diameter of the fluorine-containing elastomer particles is the cumulant average diameter and can be measured by dynamic light scattering.

[0250] The number of fluorine-containing elastomer particles in the aqueous dispersion of fluorine-containing elastomer is preferably 1.0 × 10⁶ 12 The amount is 5.0 × 10⁻¹ or more per cc, more preferably 5.0 × 10⁻¹⁰ 12 The amount is 1.0 × 10¹ / cc or more, and more preferably 1.0 × 10¹⁶ 13 The amount is 1.2 × 10¹ / cc or more, and is particularly preferably 1.2 × 10¹⁶. 14 The amount is 1.3 × 10¹ / cc or more, most preferably 1.3 × 10¹⁶. 14 The number of particles / cc is greater than or equal to 1 or more. The above number of particles (number of polymer particles) can be calculated according to the following formula.

[0251]

number

[0252] The aqueous dispersion of the fluorine-containing elastomer may be subjected to treatments such as coagulation and heating.

[0253] The above coagulation can be carried out by adding alkaline earth elements, earth metal salts, acidic aqueous solutions, and alcohols to an aqueous dispersion. Examples of alkaline earth elements and earth metal salts include sulfates, nitrates, hydrochlorides, and acetates of calcium, magnesium, and aluminum. Examples of acids include sulfuric acid, nitric acid, and hydrochloric acid. An example of an alcohol is 2-butanol.

[0254] The coagulated fluorine-containing elastomer may be washed with pure water to remove small amounts of buffer, salts, acids, alcohols, 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.

[0255] 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 lump form obtained 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.

[0256] This disclosure also relates to fluorine-containing elastomers. The fluorine-containing elastomers of this disclosure will be described in detail below. The fluorine-containing elastomers of this disclosure can be suitably manufactured by the manufacturing methods of this disclosure described above.

[0257] (First fluorine-containing elastomer) The first fluorine-containing elastomer of this disclosure is a polyol-crosslinkable fluorine-containing elastomer. The polyol-crosslinkable fluorine-containing elastomer is not particularly limited and may be any fluorine-containing elastomer having polyol-crosslinkable moieties. The polyol-crosslinkable moieties are not particularly limited and may include, for example, moieties having vinylidene fluoride (VdF) units. A method for introducing the crosslinking moieties may be a copolymerization method in which monomers that provide crosslinking moieties are polymerized during polymerization of the fluorine-containing elastomer. The first fluorine-containing elastomer of this disclosure may have a structure similar to that of the fluorine-containing elastomer obtained by the manufacturing method of this disclosure, and preferably contains a methylene group (-CH2-) in the main chain.

[0258] The first fluorine-containing elastomer of this disclosure has a ratio of component (A) with a molecular weight of less than 50,000, calculated from an integrated molecular weight distribution curve obtained by gel permeation chromatography using monodisperse polystyrene as a standard, which is 20-60%, preferably 30-60%.

[0259] A first fluorine-containing elastomer having such a characteristic molecular weight distribution can be produced by using the production method of the present disclosure.

[0260] The first fluorine-containing elastomer of this disclosure preferably has a ratio of 5 to 25% of component (B) having a molecular weight of 50,000 or more and less than 100,000, calculated from an integrated molecular weight distribution curve obtained by gel permeation chromatography using monodisperse polystyrene as a standard.

[0261] The first fluorine-containing elastomer of this disclosure preferably has a ratio of 30-60% of component (C) with a molecular weight of 100,000 or more, calculated from an integrated molecular weight distribution curve obtained by gel permeation chromatography using monodisperse polystyrene as a standard.

[0262] In one embodiment, the first fluorine-containing elastomer of the present disclosure has a ratio of 20-60% of component (A) with a molecular weight of less than 50,000, a ratio of 5-25% of component (B) with a molecular weight of 50,000 or more and less than 100,000, and a ratio of 30-60% of component (C) with a molecular weight of 100,000 or more.

[0263] In one embodiment, the first fluorine-containing elastomer of the present disclosure has a ratio of 30-60% of component (A) with a molecular weight of less than 50,000, a ratio of 5-25% of component (B) with a molecular weight of 50,000 or more and less than 100,000, and a ratio of 30-60% of component (C) with a molecular weight of 100,000 or more.

[0264] The first fluorine-containing elastomer of the present disclosure preferably has a bimodal molecular weight distribution. In one embodiment, the first fluorine-containing elastomer of the present disclosure satisfies the following relationship in the ratios of component (A), component (B), and component (C). Ratio of component (A) > Ratio of component (B) Ratio of component (C) > Ratio of component (B)

[0265] The ratios of components (A), (B), and (C) can be calculated from the integrated molecular weight distribution curve obtained by gel permeation chromatography.

[0266] Having a bimodal molecular weight distribution allows for excellent extrusion processability during extrusion molding, and sufficient green strength during hose molding enables the maintenance of the molded shape.

[0267] The first fluorine-containing elastomer of this disclosure substantially does not contain a fluorine-containing surfactant that does not have a functional group that can react by radical polymerization. Examples of fluorine-containing surfactants include the fluorine-containing surfactants described above.

[0268] In this disclosure, "substantially free of fluorine-containing surfactants that do not have functional groups that can react by radical polymerization" means that the content of fluorine-containing surfactants in the fluorine-containing elastomer is 10 ppm by mass or less, preferably 1 ppm by mass or less, more preferably 100 ppb by mass or less, even more preferably 1 ppb by mass or less, and particularly preferably the amount of fluorine-containing surfactants is below the detection limit as measured by liquid chromatography-mass spectrometry (LC / MS).

[0269] The proportion of fluorine-containing surfactants can be quantified by known methods, such as LC / MS analysis. First, a methanol / pure water solution in a weight ratio of 10 / 0 to 8 / 2 is added to the fluorine-containing elastomer, and extraction is performed. The resulting extract is then analyzed by LC / MS. To further improve extraction efficiency, treatments such as Soxhlet extraction or sonication may be performed. From the obtained LC / MS spectrum, molecular weight information is extracted and its agreement with the structural formula of the candidate fluorine-containing surfactant is confirmed. Subsequently, aqueous solutions containing five or more levels of the identified fluorine-containing surfactant were prepared, and LC / MS analysis was performed on each aqueous solution with its respective content. The relationship between the content and the area area corresponding to that content was plotted, and a calibration curve was drawn. Furthermore, using a calibration curve, the area of ​​the LC / MS chromatogram for fluorine-containing surfactants in the extract can be converted to the content of fluorine-containing surfactants.

[0270] Furthermore, the first fluorine-containing elastomer of this disclosure substantially does not contain a fluorine-containing solvent. Examples of fluorine-containing solvents include the fluorine-containing solvents described above.

[0271] In this disclosure, "substantially free of fluorine-containing solvents" means that the content of fluorine-containing solvents in the fluorine-containing elastomer is 10 ppm by mass or less, preferably 1 ppm by mass or less, more preferably 100 ppb by mass or less, even more preferably 1 ppb by mass or less, and particularly preferably the fluorine-containing solvent is below the detection limit.

[0272] The content of fluorine-containing solvents in fluorine-containing elastomers can be measured by gas chromatography-mass spectrometry (GC / MS).

[0273] The first fluorine-containing elastomer of this disclosure preferably has a Mooney viscosity (ML1 + 10 (100°C)) of 130 or less at 100°C. More preferably, the Mooney viscosity is 110 or less, and even more preferably 90 or less. Furthermore, the Mooney viscosity is 10 or more, and even more preferably 20 or more. Here, the Mooney viscosity is a value measured in accordance with JIS K 6300-1.2013.

[0274] The first fluorine-containing elastomer of this disclosure has a glass transition temperature of 25°C or less, preferably 20°C or less, more preferably 10°C or less, even more preferably 0°C or less, preferably -50°C or higher, and more preferably -45°C or higher. The glass transition temperature can be measured by the method described above.

[0275] The first fluorine-containing elastomer of this disclosure preferably contains an iodine atom.

[0276] The first fluorine-containing elastomer of this disclosure preferably has an iodine content of 0.20% by mass or more, more preferably 0.25% by mass or more, even more preferably 0.30% by mass or more, preferably 2.00% by mass or less, more preferably 1.00% by mass or less, and even more preferably 0.50% by mass or less. The iodine content can be measured by the method described above.

[0277] The first fluorine-containing elastomer of this disclosure has an amount of -CH2OH structure relative to 100 mol% of -CH2- structure, preferably 0.03 mol% or less, more preferably 0.02 mol% or less. The amount of -CH2OH structure is 1 It can be determined by 1H-NMR spectroscopy. The amount of the -CH2OH structure can be adjusted by selecting the type and amount of polymerization initiator and chain transfer agent, among other methods.

[0278] The first fluorine-containing elastomer of this disclosure has an amount of -CH2I structure relative to 100 mol% of -CH2- structure that is preferably 0.30 to 1.50 mol%, more preferably 0.35 mol% or more, even more preferably 0.40 mol% or more, more preferably 1.00 mol% or less, and even more preferably 0.70 mol% or less. The amount of -CH2I structure is 1 This can be determined by 1H-NMR spectroscopy.

[0279] (Second fluorine-containing elastomer) The second fluorine-containing elastomer of this disclosure is a peroxide-crosslinkable fluorine-containing elastomer. The peroxide-crosslinkable fluorine-containing elastomer is not particularly limited and may be any fluorine-containing elastomer having peroxide-crosslinkable moieties. The peroxide-crosslinkable moieties are not particularly limited and may include, for example, moieties having iodine atoms or moieties having bromine atoms. The second fluorine-containing elastomer of this disclosure may have a structure similar to that of the fluorine-containing elastomer obtained by the manufacturing method of this disclosure, and preferably contains a methylene group (-CH2-) or a perfluoromethylene group (-CF2-) in the main chain.

[0280] The second fluorine-containing elastomer of this disclosure substantially does not contain a fluorine-containing surfactant that does not have a functional group that can react by radical polymerization.

[0281] In one embodiment, the second fluorine-containing elastomer of the present disclosure is substantially free of polymer (I), which is as described above.

[0282] In this disclosure, "substantially free of polymer (I)" means that the polymer (I) content in the fluorine-containing elastomer is 10 ppm by mass or less, 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 even more preferably 1 ppb by mass or less. The content of polymer (I) in the fluorine-containing elastomer can be determined by solid-state NMR or fusion NMR. If polymer (I) contains carbonyl groups, it can also be determined by Fourier transform infrared spectroscopy. Also, International Publication Nos. 2014 / 099453, 2010 / 075497, 2010 / 075496, 2011 / 008381, 2009 / 055521, 1987 / 007619, Japanese Patent Publication No. 61-293476, 2010 / 075494, 2010 / 075359, 2012 / 082454, 2006 / 119224, 2013 / 085864, International Publication Nos. 2012 / 082707, 2012 / 082703, 2012 / 082451, 2006 / 135825, 2004 / 067588, 2009 / 068528, JP A 2004-075978, JP A 2001-226436, JP A 1992 / 017635, 2014 / 069165, and JP A H11-181009 describe the measurement methods for each polymer. The measurement methods for each polymer described in these publications can be used as methods for measuring the content of polymer (I).

[0283] The second fluorine-containing elastomer of this disclosure has a long-chain branching index (LCBindex) of 4.0 or higher, preferably 4.1 or higher, more preferably 4.2 or higher, with no particular upper limit, but may be 20 or lower.

[0284] The long-chain branching index (LCBindex) can be calculated by measuring the Large Amplitude Oscillatory Shear (LAOS) using a rubber process analyzer RPA-2000 (Alpha Technologies) at a strain of 1000%, a frequency of 1 rad / s, and a temperature of 100°C. The LCBindex indicates the proportion of long-chain branches present in the polymer chain of a fluorine-containing elastomer. A large LCBindex means that there are many long-chain branches in the polymer chain.

[0285] To explain in more detail, the shear storage modulus obtained by changing the strain up to 1000% can be transformed using FT to derive the first and fifth harmonics, and the ratio of the first harmonic of the storage modulus to the fifth harmonic can be calculated as the LCB Index. If we define the first and fifth harmonics of the measured storage modulus as G'1 and G'5, respectively, the LCB Index can be expressed by the following general formula. LCB Index = G'1 / G'5 When the LCB Index falls within the range described above, it is possible to simultaneously satisfy excellent mechanical properties along with superior machinability and improved elasticity.

[0286] The second fluorine-containing elastomer of this disclosure has a glass transition temperature preferably 25°C or lower, more preferably 20°C or lower, even more preferably 10°C or lower, even more preferably 0°C or lower, preferably -50°C or higher, and more preferably -45°C or higher. The glass transition temperature can be measured by the method described above.

[0287] The second fluorine-containing elastomer of this disclosure preferably contains an iodine atom.

[0288] The second fluorine-containing elastomer of this disclosure preferably has an iodine content of 0.20% by mass or more, more preferably 0.30% by mass or more, even more preferably 0.40% by mass or more, preferably 2.00% by mass or less, more preferably 1.00% by mass or less, and even more preferably 0.80% by mass or less. The iodine content can be measured by the method described above.

[0289] The second fluorine-containing elastomer of this disclosure preferably has a Mooney viscosity (ML1 + 10 (121°C)) of 130 or less at 121°C. More preferably, the Mooney viscosity is 110 or less, and even more preferably 90 or less. Furthermore, the Mooney viscosity is more preferably 2 or more, and even more preferably 5 or more. Here, the Mooney viscosity is a value measured in accordance with JIS K 6300-1.2013.

[0290] The second fluorine-containing elastomer of this disclosure preferably contains substantially no fluorine-containing solvent.

[0291] The second fluorine-containing elastomer of this disclosure has an amount of -CH2I structure relative to 100 mol% of -CH2- structure that is preferably 0.30 to 1.50 mol%, more preferably 0.45 mol% or more, even more preferably 0.50 mol% or more, more preferably 1.00 mol% or less, and even more preferably 0.80 mol% or less. The amount of -CH2I structure is 1 This can be determined by 1H-NMR spectroscopy.

[0292] The second fluorine-containing elastomer of this disclosure has an amount of -CH2OH structure relative to 100 mol% of -CH2- structure, preferably 0.03 mol% or less, more preferably 0.02 mol% or less. The amount of -CF2OH structure is 1 It can be determined by 1H-NMR spectroscopy. The amount of the -CH2OH structure can be adjusted by selecting the type and amount of polymerization initiator and chain transfer agent, among other methods.

[0293] The second fluorine-containing elastomer of this disclosure may be a perfluoroelastomer, as described above.

[0294] The second fluorine-containing elastomer of this disclosure preferably contains monomer units based on an iodine or bromine-containing monomer. The content of monomer units based on an iodine or bromine-containing monomer is preferably 0.0010 to 0.100 mol%, more preferably 0.0015 mol% or more, even more preferably 0.0020 mol% or more, even more preferably 0.05 mol% or less, and even more preferably 0.01 mol% or less, based on the total monomer units.

[0295] The second fluorine-containing elastomer of this disclosure is preferably low in metal content. In particular, if the fluorine-containing elastomer is a perfluoroelastomer, it is preferable that the metal content in the perfluoroelastomer is low. The metal content is preferably 10 ppm by mass or less, more preferably 7 ppm by mass or less, even more preferably 5 ppm by mass or less, even more preferably 3 ppm by mass or less, particularly preferably 2 ppm by mass or less, and most preferably 1 ppm by mass or less, relative to the mass of the fluorine-containing elastomer. The metal content in the fluorine-containing elastomer can be measured by the method described in the examples.

[0296] (Third fluorine-containing elastomer) The third fluorine-containing elastomer of this disclosure is a fluorine-containing elastomer containing cyano groups. The fluorine-containing elastomer containing cyano groups is not particularly limited and may be any fluorine-containing elastomer containing cyano groups. In one embodiment, the third fluorine-containing elastomer of this disclosure is a perfluoroelastomer.

[0297] In one embodiment, the third fluorine-containing elastomer of the present disclosure substantially does not contain a fluorine-containing surfactant that does not have a functional group that can react by radical polymerization.

[0298] In one embodiment, the third fluorine-containing elastomer of the present disclosure is substantially free of a fluorine-containing solvent.

[0299] In one embodiment, the third fluorine-containing elastomer of the present disclosure has a Mooney viscosity (ML1+20(170°C)) of 130 or less at 170°C. More preferably, the Mooney viscosity is 110 or less, and even more preferably 90 or less. Furthermore, the Mooney viscosity is more preferably 2 or more, and even more preferably 5 or more. The Mooney viscosity is a value measured in accordance with JIS K 6300-1.2013.

[0300] The third fluorine-containing elastomer of this disclosure has a glass transition temperature of 25°C or less, preferably 20°C or less, more preferably 10°C or less, even more preferably 0°C or less, preferably -50°C or higher, and more preferably -45°C or higher. The glass transition temperature can be measured by the method described above.

[0301] The third fluorine-containing elastomer of this disclosure contains cyano groups. The third fluorine-containing elastomer of this disclosure preferably has a cyano group content of 0.30 mol% or more, more preferably 0.400 mol% or more, even more preferably 0.45 mol% or more, preferably 2.00 mol% or less, more preferably 1.50 mol% or less, and even more preferably 1.00 mol% or less. The cyano group content can be measured by NMR or IR.

[0302] The third fluorine-containing elastomer of this disclosure is preferably low in metal content. The metal content is preferably 10 ppm by mass or less, more preferably 7 ppm by mass or less, even more preferably 5 ppm by mass or less, even more preferably 3 ppm by mass or less, particularly preferably 2 ppm by mass or less, and most preferably 1 ppm by mass or less, relative to the mass of the fluorine-containing elastomer.

[0303] The first, second, and third fluorine-containing elastomers of this disclosure may be coagulated products, gums, crumbs, powders, pellets, etc., obtained by coagulating a fluorine-containing elastomer contained in an aqueous dispersion, and gums or crumbs are preferred. Gums are small granular lumps made of fluorine-containing elastomers, and crumbs are amorphous lumps resulting from the fluorine-containing elastomers fusing together because they cannot maintain a small granular shape as gum at room temperature. Gums or crumbs are preferably obtained by coagulation, drying, etc., from an aqueous dispersion obtained by the manufacturing method of this disclosure using a conventionally known method.

[0304] The water content of the fluorine-containing elastomer is not particularly limited, but is preferably 1% by mass or less, more preferably 0.1% by mass or less, and even more preferably 0.01% by mass or less, relative to the mass of the fluorine-containing elastomer. The water content of the fluorine-containing elastomer can be calculated, for example, by thoroughly drying the fluorine-containing elastomer by heating it at 120°C for 12 hours or more, or at 70°C for 24 hours or more, measuring the weight of the fluorine-containing elastomer before and after heating, and dividing the weight loss by the weight before heating.

[0305] (Crosslinkable composition) A crosslinkable composition can be produced by mixing an aqueous dispersion of a fluorine-containing elastomer obtained by the manufacturing method of the present disclosure, a fluorine-containing elastomer obtained by the manufacturing method of the present disclosure, the first fluorine-containing elastomer of the present disclosure, or the second fluorine-containing elastomer of the present disclosure, or the third fluorine-containing elastomer of the present disclosure (in the present disclosure, these fluorine-containing elastomers may be simply referred to as "fluorine-containing elastomer of the present disclosure" or "fluorine-containing elastomer") with a crosslinking agent.

[0306] 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.

[0307] Examples of crosslinking systems for fluorine-containing elastomers include peroxide crosslinking systems, polyol crosslinking systems, polyamine crosslinking systems, oxazole crosslinking systems, imidazole crosslinking systems, and triazine crosslinking systems, and it is preferable that at least one is selected from the group consisting of peroxide crosslinking systems, polyol crosslinking systems, imidazole crosslinking systems, and triazine crosslinking systems.

[0308] Therefore, as the crosslinking agent, at least one crosslinking agent selected from the group consisting of polyol crosslinking agents, peroxide crosslinking agents, imidazole crosslinking agents, and triazine crosslinking agents is preferred.

[0309] 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.

[0310] Polyol crosslinking can be achieved by using a fluorine-containing elastomer that can be crosslinked with a polyol as the fluorine-containing elastomer and a polyhydroxy compound as the crosslinking agent. In the polyol crosslinking system, the amount of polyhydroxy compound is preferably 0.01 to 10 parts by mass per 100 parts by mass of the fluorine-containing elastomer that can be crosslinked with a polyol. By having the amount of polyhydroxy compound in this range, polyol crosslinking can be sufficiently carried out. More preferably, it is 0.02 to 8 parts by mass. Even more preferably, it is 0.03 to 4 parts by mass.

[0311] As for polyhydroxy compounds, polyhydroxy aromatic compounds are preferably used due to their excellent heat resistance.

[0312] The above polyhydroxyaromatic compounds are not particularly limited and include, for example, 2,2-bis(4-hydroxyphenyl)propane (hereinafter referred to as bisphenol A), 2,2-bis(4-hydroxyphenyl)perfluoropropane (hereinafter referred to as bisphenol AF; bisphenol AF can be obtained, for example, from Fujifilm Wako Pure Chemical Industries, Central Glass Co., Ltd.), 1,3-dihydroxybenzene, 1,7-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 4,4'-dihydroxydiphenyl, and 4,4'-dihydro Examples include xistilbene, 2,6-dihydroxyanthracene, hydroquinone, catechol, 2,2-bis(4-hydroxyphenyl)butane (hereinafter referred to as bisphenol B), 4,4-bis(4-hydroxyphenyl)valeric acid, 2,2-bis(4-hydroxyphenyl)tetrafluorodichloropropane, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl ketone, tri(4-hydroxyphenyl)methane, 3,3',5,5'-tetrachlorobisphenol A, and 3,3',5,5'-tetrabromobisphenol A. These polyhydroxy aromatic compounds may also be alkali metal salts or alkaline earth metal salts, but it is preferable not to use the above metal salts when the copolymer is coagulated using acid. The amount of polyhydroxy aromatic compound blended is 0.1 to 15 parts by mass, preferably 0.5 to 5 parts by mass, per 100 parts by mass of fluorine-containing elastomer.

[0313] When the crosslinking agent is a polyhydroxy compound, the crosslinkable composition preferably further contains a crosslinking accelerator. The crosslinking accelerator promotes the formation of intramolecular double bonds in the dehydrofluoric acid reaction of the polymer backbone and the addition of the polyhydroxy compound to the formed double bonds.

[0314] Furthermore, the crosslinking accelerator may be used in combination with an acid acceptor such as magnesium oxide or a crosslinking aid.

[0315] Examples of crosslinking promoters include onium compounds, and among onium compounds, it is preferable that at least one is selected from the group consisting of ammonium compounds such as quaternary ammonium salts, phosphonium compounds such as quaternary phosphonium salts, oxonium compounds, sulfonium compounds, cyclic amines, and monofunctional amine compounds, and more preferably at least one is selected from the group consisting of quaternary ammonium salts and quaternary phosphonium salts.

[0316] The quaternary ammonium salt is not particularly limited, and examples include 8-methyl-1,8-diazabicyclo[5,4,0]-7-undecenium chloride, 8-methyl-1,8-diazabicyclo[5,4,0]-7-undecenium iodide, 8-methyl-1,8-diazabicyclo[5,4,0]-7-undecenium hydrooxide, and 8-methyl-1,8-diazabicyclo[5,4,0]-7-undecenium Chil sulfate, 8-ethyl-1,8-diazabicyclo[5,4,0]-7-undecenium bromide, 8-propyl-1,8-diazabicyclo[5,4,0]-7-undecenium bromide, 8-dodecyl-1,8-diazabicyclo[5,4,0]-7-undecenium chloride, 8-dodecyl-1,8-diazabicyclo[5,4,0]-7-undecenium hydrooxide, 8-eicosyl-1,8-di Examples include azabicyclo[5,4,0]-7-undecenium chloride, 8-tetracosyl-1,8-diazabicyclo[5,4,0]-7-undecenium chloride, 8-benzyl-1,8-diazabicyclo[5,4,0]-7-undecenium chloride (hereinafter referred to as DBU-B; DBU-B can be obtained from, for example, Fujifilm Wako Pure Chemical Industries, Ltd.), 8-benzyl-1,8-diazabicyclo[5,4,0]-7-undecenium hydrooxide, 8-phenethyl-1,8-diazabicyclo[5,4,0]-7-undecenium chloride, 8-(3-phenylpropyl)-1,8-diazabicyclo[5,4,0]-7-undecenium chloride, tetrabutylammonium bisulfate, tetrabutylammonium hydroxide, tetrabutylammonium chloride, and tetrabutylammonium bromide. Among these, DBU-B is preferred in terms of crosslinking properties, mechanical properties, and flexibility.

[0317] Furthermore, the quaternary phosphonium salt is not particularly limited, and examples include tetrabutylphosphonium chloride, benzyltriphenylphosphonium chloride (hereinafter referred to as BTPPC), benzyltrimethylphosphonium chloride, benzyltributylphosphonium chloride, tributylallylphosphonium chloride, tributyl-2-methoxypropylphosphonium chloride, and benzylphenyl(dimethylamino)phosphonium chloride. Among these, benzyltriphenylphosphonium chloride (BTPPC) is preferred in terms of crosslinkability, mechanical properties, and flexibility.

[0318] Furthermore, as a crosslinking accelerator, a solid solution of a quaternary ammonium salt and bisphenol AF, a solid solution of a quaternary phosphonium salt and bisphenol AF, or a chlorine-free crosslinking accelerator disclosed in Japanese Patent Publication No. 11-147891 can also be used.

[0319] The amount of crosslinking accelerator is preferably 0.01 to 8.00 parts by mass, more preferably 0.02 to 5.00 parts by mass, per 100 parts by mass of fluorine-containing elastomer. Even more preferably, it is 0.03 to 3.00 parts by mass. If the amount of crosslinking accelerator is less than 0.01 parts by mass, the crosslinking of the fluorine-containing elastomer may not proceed sufficiently, and the heat resistance and other properties of the resulting molded product may decrease. If it exceeds 8.00 parts by mass, the moldability of the crosslinkable composition may decrease, and the elongation in mechanical properties and flexibility tend to decrease.

[0320] The acid acceptor is used to neutralize the acidic substances generated during polyol crosslinking. Specific examples include magnesium oxide, calcium hydroxide (e.g., NICC5000 (manufactured by Inoue Lime Industry Co., Ltd.), CALDIC#2000, CALDIC#1000 (manufactured by Omi Chemical Industry Co., Ltd.)), calcium oxide, Lissage (lead oxide), zinc oxide, dibasic lead phosphite, hydrotalcite, etc. It is preferable that the acid acceptor be at least one selected from the group consisting of highly active magnesium oxide and low-activity magnesium.

[0321] 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.

[0322] Any organic peroxide that can readily generate peroxy radicals in the presence of heat or a redox system can be used as an organic peroxide. 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.

[0323] 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.

[0324] 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-triazine). Examples include tri(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.

[0325] 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.

[0326] Polyamine crosslinking can be achieved by using a fluorine-containing elastomer that can be crosslinked with polyamines as the fluorine-containing elastomer and a polyamine compound as the crosslinking agent.

[0327] The polyamine-crosslinkable fluorine-containing elastomer is not particularly limited, and any fluorine-containing elastomer having polyamine-crosslinkable sites is acceptable. The polyamine-crosslinkable sites are not particularly limited, and examples include sites having vinylidene fluoride (VdF) units. A method for introducing the crosslinking sites is to copolymerize monomers that provide crosslinking sites during polymerization of the fluorine-containing elastomer.

[0328] Examples of polyamine compounds include hexamethylenediamine carbamate, N,N'-disinnamyridene-1,6-hexamethylenediamine, and 4,4'-bis(aminocyclohexyl)methanecarbamate. Among these, N,N'-disinnamyridene-1,6-hexamethylenediamine is preferred.

[0329] Furthermore, crosslinking agents used in triazine crosslinking, oxazole crosslinking, imidazole crosslinking, and thiazole crosslinking may be used as crosslinking agents. Examples of such crosslinking agents include 2,2-bis[3-amino-4-(N-phenylamino)phenyl]hexafluoropropane.

[0330] Furthermore, the crosslinkable composition of this disclosure may also contain a fluorine-containing elastomer and at least one selected from the group consisting of inorganic nitrides, organotin compounds, and ammonia-generating compounds. Examples of inorganic nitrides include silicon nitride (Si3N4). Examples of organotin compounds include tetraphenyltin and triphenyltin. As for ammonia-generating compounds, compounds that generate ammonia at 40 to 330°C are preferred, and examples include urea, biurea, thiourea, urea hydrochloride, biuret, acetaldehyde ammonia, hexamethylenetetramine, formamidine, formamidine hydrochloride, formamidine acetate, t-butylcarbamate, benzylcarbamate, and phthalamide.

[0331] The method for obtaining a crosslinkable composition is not particularly limited as long as it can uniformly mix an aqueous dispersion of a fluorine-containing elastomer obtained by the manufacturing method of the present disclosure, a fluorine-containing elastomer obtained by the manufacturing method of the present disclosure, the first fluorine-containing elastomer or the second or third fluorine-containing elastomer of the present disclosure, and a crosslinking agent. For example, one method is to knead a coagulated product obtained by coagulating a fluorine-containing elastomer alone with other additives or compounding agents as needed using a kneader such as an open roll.

[0332] The form of the crosslinkable composition is not particularly limited, but may be, for example, gum, crumb, powder, pellets, etc.

[0333] 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.

[0334] The crosslinkable composition may contain, as needed, various additives commonly used in elastomers, 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 enhancers, thermal conductivity enhancers, surface non-tackeners, flexibility enhancers, 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.

[0335] 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.

[0336] 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 the content of these within an acceptable range for the desired properties of the resulting molded product.

[0337] (molded product) A molded article can be obtained by molding a crosslinkable composition. Alternatively, a molded article can be obtained by molding and crosslinking the composition. The composition can be molded using 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 process may be performed after molding, after crosslinking, or simultaneously.

[0338] 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 140-250°C and a crosslinking time of 1 minute to 24 hours.

[0339] 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 140-300°C and a duration of 30 minutes to 72 hours, and can be appropriately determined depending on the type of crosslinking accelerator, crosslinking agent, and acid acceptor.

[0340] 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 Publication No. 2013-216915 and the fluororubber molded articles described in Japanese Patent Publication No. 2019-94430, such as sealing materials, sliding members, and non-stick members.

[0341] 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.

[0342] 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.

[0343] 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.

[0344] <1> According to the first aspect of this disclosure, A method for producing an aqueous dispersion of a fluorine-containing elastomer, comprising polymerizing a fluorine-containing monomer in the presence of an aqueous medium and a polymerization initiator, wherein the aqueous dispersion contains a fluorine-containing elastomer, The final obtained aqueous dispersion of fluorine-containing elastomer has a solid content concentration of 15% by mass or more. Without removing the product from the reaction vessel, polymerization is carried out continuously from the initial addition of the polymerization initiator until the solid content concentration of the fluorine-containing elastomer aqueous dispersion reaches 15% by mass or more. The ratio of radical generation (B / A) calculated by the following formula is 0.70 or less. A manufacturing method is provided. The ratio of radical generation (B / A) = B / A A: Radical generation rate per gram of aqueous medium per minute from the initial addition of polymerization initiator (A) (mol / (g·min)) B: Radical generation rate per gram of aqueous medium (mol / (g·min)) from the point when the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer. <2> According to the second aspect of this disclosure, A manufacturing method is provided in which, from the time the polymerization initiator is first added until the time the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer, the polymerization rate is 10 g / (hr·L) or less. <3> According to the third aspect of this disclosure, A manufacturing method is provided in which the polymerization rate ratio (D / C) calculated by the following formula is 5.0 or greater, according to a first or second viewpoint. Polymerization rate ratio (D / C)=D / C C: Polymerization rate (C) (g / (hr·L)) from the time the polymerization initiator is first added until the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer. D: Polymerization rate (D) (g / (hr·L)) from the point when the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer to the point when polymerization is stopped. <4> According to the fourth aspect of this disclosure, A manufacturing method is provided in which the amount of polymerization initiator initially added is 30 to 1000 ppm by mass relative to the aqueous medium, according to any of the first to third aspects. <5> According to the fifth aspect of this disclosure, A method for producing a polymer according to any of the first to fourth aspects is provided, wherein the polymerization initiator is a persulfate. <6> According to the sixth aspect of this disclosure, A manufacturing method is provided that allows for the polymerization of fluorine-containing monomers in the substantially absence of a redox initiator, according to any of the first to fifth viewpoints. <7> According to the seventh aspect of this disclosure, A manufacturing method is provided that involves polymerizing at least a fluorine-containing monomer having a boiling point below 0°C, according to any one of the first to sixth aspects. <8> According to the eighth aspect of this disclosure, A manufacturing method is provided according to any of the first to seventh aspects, wherein the time from the time when the polymerization initiator is first added to the time when polymerization is stopped is 20 hours or less. <9> According to the ninth aspect of this disclosure, A manufacturing method is provided that carries out polymerization of a fluorine-containing monomer in the absence of a fluorine-containing surfactant that does not substantially have a functional group that can react by radical polymerization, and in the absence of a fluorine-free surfactant. <10> According to the tenth aspect of this disclosure, A manufacturing method is provided in which the polymerization temperature is 10 to 120°C, according to any of the first to ninth aspects. <11> According to the eleventh aspect of this disclosure, A manufacturing method is provided in which, from the point in time when the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer, the polymerization temperature from the point in time when polymerization is stopped is 65 to 85°C. <12> According to the 12th aspect of this disclosure, A manufacturing method is provided in which the polymerization pressure is 0.5 to 10 MPaG, according to any of the first to eleventh aspects. <13> According to the 13th aspect of this disclosure, A method for producing a fluorine-containing elastomer, comprising a methylene group in the main chain, is provided, according to any of the first to twelfth aspects. <14> According to the fourteenth aspect of this disclosure, A method for producing a fluorine-containing elastomer is provided, according to any of the first to twelfth aspects, wherein the elastomer is a perfluoroelastomer. <15> According to the 15th aspect of this disclosure, A method for producing a fluorine-containing elastomer is provided, according to any of the first to fourteen aspects, wherein the Mooney viscosity (ML1 + 10 (100°C)) of the elastomer is 10 to 130. <16> According to the sixteenth aspect of this disclosure, A method for producing a fluorine-containing elastomer is provided, according to any of the first to fifteen aspects, wherein the Mooney viscosity (ML(1+10)121℃) of the elastomer is 2 to 130. <17> According to the seventeenth aspect of this disclosure, A method for producing a fluorine-containing elastomer is provided, according to any of the first to sixteen aspects, wherein the Mooney viscosity (ML1 + 20 (170°C)) of the elastomer is 2 to 130. <18> According to the 18th aspect of this disclosure, A polyol crosslinkable fluorine-containing elastomer, It substantially does not contain fluorine-containing surfactants that do not have functional groups that can react by radical polymerization, and it also substantially does not contain fluorine-containing solvents. Using monodisperse polystyrene as the standard, the proportion of component (A) with a molecular weight of less than 50,000, calculated from the integrated molecular weight distribution curve obtained by gel permeation chromatography, is 20-60%. The Mooney viscosity (ML(1+10)100℃) is 20 or higher. The glass transition temperature is 25°C or lower. A fluorine-containing elastomer is provided. <19> According to the 19th aspect of this disclosure, A fluorine-containing elastomer is provided according to the 18th perspective, in which the proportion of component (B) with a molecular weight of 50,000 or more and less than 100,000, calculated from the integrated molecular weight distribution curve obtained by gel permeation chromatography using monodisperse polystyrene as the standard, is 5-25%. <20> According to the 20th aspect of this disclosure, A fluorine-containing elastomer is provided according to the 18th or 19th viewpoint, in which the proportion of component (C) with a molecular weight of 100,000 or more, calculated from the integrated molecular weight distribution curve obtained by gel permeation chromatography using monodisperse polystyrene as the standard, is 30-60%. <21> According to the 21st aspect of this disclosure, A fluorine-containing elastomer containing an iodine atom is provided according to any of the 18th to 20th aspects. <22> According to the 22nd aspect of this disclosure, A fluorine-containing elastomer is provided that has an iodine content of 0.20% by mass or more, according to any of the 18th to 21st views. <23> According to the 23rd aspect of this disclosure, A fluorine-containing elastomer is provided from any of the 18th to 22nd viewpoints, wherein the ratios of component (A), component (B), and component (C) satisfy the following relationship. Ratio of component (A) > Ratio of component (B) Ratio of component (C) > Ratio of component (B) <24> According to the 24th aspect of this disclosure, A fluorine-containing elastomer is provided that contains a methylene group (-CH2-) in the main chain, and the amount of -CH2OH structure relative to 100 mol% of -CH2- structure is 0.03 mol% or less, according to any of the 18th to 23rd views. <25> According to Perspective 25 of this Disclosure, A fluorine-containing elastomer according to any of the 18th to 24th aspects is provided, and a crosslinkable composition containing a polyhydroxy compound as a crosslinking agent is also provided. <26> According to Perspective 26 of this Disclosure, A peroxide crosslinkable fluorine-containing elastomer, It substantially does not contain fluorine-containing surfactants that do not have functional groups that can react by radical polymerization, The long-chain branch index (LCBindex) is 4.0 or higher. A fluorine-containing elastomer is provided. <27> According to Perspective 27 of this Disclosure, A fluorine-containing elastomer is provided that has a glass transition temperature of 25°C or lower, according to a 26th aspect. <28> According to Perspective 28 of this Disclosure, A fluorine-containing elastomer according to the 26th or 27th aspect is provided, having an iodine content of 0.30% by mass or more. <29> According to Perspective 29 of this Disclosure, A fluorine-containing elastomer is provided that has a Mooney viscosity (ML(1+10)121℃) of 2 or more, according to any of the 26th to 28th views. <30> According to the 30th aspect of this disclosure, A fluorine-containing elastomer is provided that is substantially free of fluorine-containing solvents according to any of the 26th to 29th aspects. <31> According to the third aspect of this disclosure, A fluorine-containing elastomer is provided, comprising a methylene group (-CH2-) in the main chain, wherein the amount of -CH2I structures relative to 100 mol% of -CH2- structures is 0.30 to 1.50 mol%, according to any of the 26th to 30th views. <32> According to the third aspect of this disclosure, A fluorine-containing elastomer is provided that is a perfluoroelastomer according to any of the 26th to 30th aspects. <33> According to the third aspect of this disclosure, A fluorine-containing elastomer is provided that contains monomer units based on iodine or bromine-containing monomers, according to any of the 26th to 32nd viewpoints. <34> According to the third aspect of this disclosure, A fluorine-containing elastomer according to any of the 26th to 33rd aspects is provided, as well as a crosslinkable composition containing an organic peroxide as a crosslinking agent. <35> According to Perspective 35 of this Disclosure, A molded article obtained from a crosslinkable composition according to the 25th or 34th aspect is provided. [Examples]

[0345] Next, embodiments of the present disclosure will be described with reference to examples, but the present disclosure is not limited to such embodiments.

[0346] Each value in the examples was measured by the following method.

[0347] Solid content concentration of aqueous dispersion One g of aqueous dispersion was dried in a forced-air dryer at 150°C for 180 minutes. The mass of the residue after heating was measured, and the ratio (mass%) of the mass of the residue to the mass of the aqueous dispersion (1 g) was determined.

[0348] Polymer adhesion rate The ratio of the mass of polymer deposits adhering to the polymerization tank (reaction vessel) after polymerization cessation to the total amount of polymer (fluorine-containing elastomer) after polymerization cessation (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 interior of the polymerization tank, such as the inner walls and stirring blades, after the aqueous dispersion has been removed from the polymerization tank following the cessation of polymerization, and polymers that have been released from the aqueous dispersion due to aggregation and are suspended or settled without being dispersed in the aqueous dispersion. The mass of the polymer deposits is the mass after the water contained in the polymer deposits has been dried and removed at 120°C.

[0349] Average particle size 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.

[0350] Particle count (number of fluorine-containing elastomer particles in aqueous dispersion) It was calculated using the following formula.

number

[0351] Mooney viscosity The viscosity was measured using a Mooney viscometer (Premier MV, manufactured by ALPHA TECHNOLOGIES) at 100°C or 121°C, in accordance with JIS K 6300-1.2013.

[0352] glass transition temperature Using a differential scanning calorimeter (Hitachi High-Tech Science Corporation, X-DSC7000), a 10 mg sample was cooled to -75°C, and then heated at 20°C / min to obtain a DSC curve. The glass transition temperature was determined by finding the temperature at which the extension of the baseline before and after the second-order transition of the DSC curve intersects with the tangent line at the inflection point of the DSC curve.

[0353] Iodine content 12 mg of the sample (fluorine-containing elastomer) was mixed with 5 mg of Na2SO3, and an absorption solution was prepared by dissolving 30 mg of a 1:1 (by weight) mixture of Na2CO3 and K2CO3 in 20 ml of pure water. This solution was burned in a quartz flask under oxygen, and after standing for 30 minutes, it was measured using a Shimadzu 20A ion chromatograph. Calibration curves were calculated using KI standard solutions, solutions containing 0.5 ppm and 1.0 ppm of iodide ions.

[0354] Polymer composition, end group content The polymer composition was determined by fluorine and proton measurements using solution NMR. "End groups" include groups located at the ends of the polymer main chain and groups located at the ends of the polymer side chains. Measuring device: JEOL JMN-ECZ500R • Proton measurement Resonance frequency: 500.16(Sfrq) Pulse width: 45° Fluorine measurement Resonance frequency: 470.62 (Sfrq) Pulse width: 30°

[0355] The amounts of -CF2CH3, -CH2OH, -CF2CH2I, and -CF2H structures relative to 100 mol% of -CH2- structures were calculated using the following method.

[0356] In the NMR spectrum, the integral value A of all peak intensities observed in the chemical shift region of 1.72~1.86 ppm originating from -CF2CH3, the integral value B of all peak intensities observed in the chemical shift region of 3.73~3.81 ppm originating from -CH2OH, the integral value C of all peak intensities observed in the chemical shift region of 3.75~4.05 ppm originating from -CH2I, and the chemical shift region of 6.00~6.80 ppm originating from -CF2H. The integral value D of all peak intensities observed in the m region, and the integral value E obtained by subtracting the integral value of the water peak intensity observed in the 2.7-2.9 region from the integral value of the peak intensities observed in the 2.30-3.75 ppm chemical shift region originating from -CH2-, were used to calculate the following: -CF2CH3 structure: A / E*100, -CH2OH structure: B / E*100, -CF2CH2I structure: C / E*100, and -CF2H structure: D / E*100.

[0357] Molecular weight [number average molecular weight (Mn), weight average molecular weight (Mw), molecular weight distribution] Based on the results measured by gel permeation chromatography (GPC), the molecular weight was calculated using standard polystyrene as a reference. GPC device: TOSOH HLC-8420GPC Columns: 2 x Shodex GPC806M, 1 x GPC801, 1 x GPC802 Developing solvent: Tetrahydrofuran [THF] Sample concentration: 0.1% by mass Measurement temperature: 40℃

[0358] Long-chain branching index The long-chain branching index (LCBindex) was measured using a rubber process analyzer RPA-2000 (Alpha Technologies). The obtained sample was sandwiched between polyester films and placed on the die of the measuring device. The LCBindex was calculated by measuring the Large Amplitude Oscillatory Shear (LAOS) at a strain of 1000%, a frequency of 1 rad / s, and a temperature of 100°C.

[0359] Storage modulus The storage modulus (G') was measured using a rubber process analyzer RPA-2000 (Alpha Technologies). The obtained sample was sandwiched between polyester films and placed on the die of the measuring device. The die temperature was pre-set to 40°C. Next, the sample was held at 40°C, with a strain of 0.1% and a frequency of 1 Hz for 5 minutes. Then, with a strain of 1% and a frequency of 1 Hz, the temperature was increased from 40°C at a rate of 2°C / min and the storage modulus was measured. At this time, the storage modulus at 100°C and 160°C was also taken as the sample's storage modulus G'(100°C) and G'(160°C).

[0360] metal content The metal content was determined by washing the fluoropolymer in a platinum crucible with dilute nitric acid and ultrapure water, ashing it with a burner and electric furnace, thermal decomposition with sulfuric acid and hydrofluoric acid, and dissolving it in dilute nitric acid to prepare a measurement solution. The content of 30 different metal elements (Fe, Na, K, Li, Be, Mg, Al, Ca, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Rb, Sr, Zr, Mo, Ag, Cd, In, Sn, Cs, Ba, Pb, Bi, Th) was measured using an ICP mass spectrometer (Agilent Technologies, Agilent 8800), and the individual measured values ​​were summed up to determine the final metal content.

[0361] Experimental Example 1 3503g of deionized water was added to a 6L SUS polymerization tank, the tank was sealed, and the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 80°C, and monomers (initial monomers) were injected under pressure at a molar ratio of vinylidene fluoride [VDF] / tetrafluoroethylene [TFE] / hexafluoropropylene [HFP] (=44 / 16 / 40 mol%) so that the internal pressure of the polymerization tank was 1.48 MPaG.

[0362] Next, an aqueous polymerization initiator solution, prepared by dissolving 0.075 cc of isopentane and 1.401 g of ammonium persulfate (APS) in deionized water, was injected under pressure with nitrogen gas to start the reaction. As polymerization progressed, when the internal pressure dropped to 1.46 MPaG, a mixed monomer of VDF / TFE / HFP (=58 / 20 / 22 mol%) was added so that the internal pressure remained constant at 1.48 MPaG.

[0363] Two hours after the start of the reaction, the stirring speed was changed to 300 rpm. When 666 g of the mixed monomer was added, an aqueous solution of polymerization initiators, 15.04 g of iodine compound CF3CFICF3 and 0.141 g of APS, was injected under pressure with nitrogen gas, and the stirring speed was changed to 350 rpm.

[0364] After adding 1299g of the mixed monomer, stirring was stopped, and the polymerization vessel was depressurized until the internal pressure reached atmospheric pressure. The polymerization vessel was cooled to obtain an aqueous dispersion with a solid content of 26.5% by mass. The polymer adhesion rate, average particle size, number of particles, polymerization rate, and radical generation ratio (B / A) are shown in Table 1.

[0365] Aluminum sulfate aqueous solution was added to the above aqueous dispersion to induce coagulation. The obtained coagulation was washed with pure water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1 + 10 (100°C) = 49. The polymer composition, end group weight, iodine content, and glass transition temperature are shown in Table 2. The number-average molecular weight (Mn) determined by GPC analysis was 40,000 and the weight-average molecular weight (Mw) was 430,000. Furthermore, the proportion of components with a molecular weight of less than 50,000 (A) determined by integral molecular weight distribution was 41.0%, the proportion of components between 50,000 and 100,000 (B) was 10.1%, and the proportion of components with a molecular weight of 100,000 or more (C) was 48.9%.

[0366] Experimental Example 2 1639 g of deionized water and 0.082 g of CH2=CFCF2OCF(CF3)CF2OCF(CF3)COONH4 were added to a 3 L SUS polymerization tank. The polymerization tank was then sealed, and the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 90°C, and monomers (initial monomers) were injected under pressure at a molar ratio of VDF / TFE / HFP (=22 / 13 / 65 mol%) so that the internal pressure of the polymerization tank was 1.47 MPaG, while stirring at 150 rpm.

[0367] Next, an aqueous polymerization initiator solution, prepared by dissolving 0.6555g of APS in deionized water, was injected under pressure with nitrogen gas to start the reaction. As polymerization progressed, when the internal pressure dropped to 1.44 MPaG, a mixed monomer of VDF / TFE / HFP (=53 / 22 / 25 mol%) was added so that the internal pressure remained constant at 1.50 MPaG.

[0368] 1.9 hours after the start of the reaction, 12 g of the mixed monomer was reached, and the stirring speed was changed to 55 rpm. After 3.5 hours, the polymerization vessel temperature was changed to 80°C over 30 minutes, and then the stirring speed was changed to 580 rpm. 4.0 hours after the start of the reaction, when 14 g of the mixed monomer had been added, 2.05 g of the iodine compound CF3CFICF3 was injected under pressure with nitrogen gas, and an aqueous solution of 0.048 g of polymerization initiator APS was injected under pressure with nitrogen gas. 7.1 hours and 9.6 hours after the start of the reaction, an aqueous solution of 0.025 g of polymerization initiator APS was injected under pressure with nitrogen gas.

[0369] After adding 616 g of the mixed monomer, stirring was stopped, and the polymerization vessel was depressurized until the internal pressure reached atmospheric pressure. The polymerization vessel was cooled to obtain an aqueous dispersion with a solid content of 26.7% by mass. Table 1 shows the polymer adhesion rate, average particle size, number of particles, polymerization rate, and radical generation ratio (B / A).

[0370] An aqueous aluminum sulfate solution was added to the above aqueous dispersion to induce coagulation. The resulting coagulation was washed with pure water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1 + 10 (121°C) = 38. The polymer composition, end group weight, iodine content, and glass transition temperature are shown in Table 2. The number-average molecular weight (Mn) was 80,000 and the weight-average molecular weight (Mw) was 151,000, as determined by GPC analysis.

[0371] Experimental Example 3 3327g of deionized water was added to a 6L SUS polymerization tank, the tank was sealed, and the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 80°C, and monomers (initial monomers) were injected under pressure at a molar ratio of VDF / TFE / HFP (=63 / 5 / 32 mol%) so that the internal pressure of the polymerization tank was 1.27 MPaG, while stirring at 170 rpm.

[0372] Next, an aqueous polymerization initiator solution, prepared by dissolving 0.052 cc of isopentane and 1.3308 g of APS in deionized water, was injected under pressure with nitrogen gas to start the reaction. As polymerization progressed, when the internal pressure dropped to 1.26 MPaG, a mixed monomer of VDF / TFE / HFP (=77 / 6 / 17 mol%) was added so that the internal pressure remained constant at 1.28 MPaG.

[0373] Two hours after the start of the reaction, the stirring speed was changed to 475 rpm, and when 482 g, 603 g, 724 g, 844 g, and 1025 g of the mixed monomer were added, an aqueous solution of polymerization initiators, 0.300 cc of isopentane and 0.599 g of APS, was injected under pressure with nitrogen gas.

[0374] After adding 1206 g of the mixed monomer, stirring was stopped, and the polymerization vessel was depressurized until the internal pressure reached atmospheric pressure. The polymerization vessel was cooled to obtain an aqueous dispersion with a solid content of 26.6% by mass. The polymer adhesion rate, average particle size, number of particles, polymerization rate, and radical generation ratio (B / A) are shown in Table 1.

[0375] An aqueous aluminum sulfate solution was added to the above aqueous dispersion to induce coagulation. The resulting coagulation was washed with pure water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1 + 10 (100°C) = 67. The polymer composition, end group weight, and glass transition temperature are shown in Table 2. The number-average molecular weight (Mn) was 78,000 and the weight-average molecular weight (Mw) was 440,000, as determined by GPC analysis.

[0376] Experimental Example 4 1619 g of deionized water was added to a 3 L capacity SUS polymerization tank, the tank was sealed, and the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 80°C, and monomers (initial monomers) were injected under pressure at a molar ratio of VDF / HFP (=60 / 40 mol%) so that the internal pressure of the polymerization tank was 1.48 MPaG while stirring at 150 rpm.

[0377] Next, an aqueous polymerization initiator solution, prepared by dissolving 0.052 cc of isopentane and 0.809 g of APS in deionized water, was injected under pressure with nitrogen gas to start the reaction. As polymerization progressed, when the internal pressure dropped to 1.46 MPaG, a mixed monomer of VDF / HFP (=78 / 22 mol%) was added so that the internal pressure remained constant at 1.48 MPaG.

[0378] 1.5 hours after the start of the reaction, the stirring speed was changed to 580 rpm, and when 257 g, 321 g, 385 g, 449 g, and 546 g of the mixed monomer were added, an aqueous solution of polymerization initiators, 0.300 cc of isopentane and 0.212 g of APS, was injected under pressure with nitrogen gas.

[0379] After adding 642 g of the mixed monomer, stirring was stopped, and the polymerization vessel was depressurized until the internal pressure reached atmospheric pressure. The polymerization vessel was cooled to obtain an aqueous dispersion with a solid content of 27.7% by mass. The polymer adhesion rate, average particle size, number of particles, polymerization rate, and radical generation ratio (B / A) are shown in Table 1.

[0380] An aqueous aluminum sulfate solution was added to the above aqueous dispersion to induce coagulation. The resulting coagulation was washed with pure water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1 + 10 (100°C) = 32. The polymer composition, end group weight, and glass transition temperature are shown in Table 2. The number-average molecular weight (Mn) was 53,000 and the weight-average molecular weight (Mw) was 221,000, as determined by GPC analysis.

[0381] Experimental Example 5 3816g of deionized water was added to a 6L SUS polymerization tank, the tank was sealed, and the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 80°C, and monomers (initial monomers) were injected under pressure at a molar ratio of VDF / TFE / HFP (=19 / 11 / 70 mol%) so that the internal pressure of the polymerization tank was 2.00 MPaG, while stirring at 200 rpm.

[0382] Next, an aqueous polymerization initiator solution, prepared by dissolving 0.229g of APS in deionized water, was injected under pressure with nitrogen gas to start the reaction. As polymerization progressed, when the internal pressure dropped to 1.98 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.

[0383] 90 minutes after the start of the reaction, the stirring speed was changed to 498 rpm. When 44 g of the mixed monomer was added, 2.594 g of iodine compound I(CF2)4I was added under nitrogen gas pressure. When 81 g of the mixed monomer was added, 7.4 g of CF2=CFOCF2CF2CH2I was added. When 975 g of the mixed monomer was added, 4.537 g of iodine compound I(CF2)4I was added. Furthermore, when 623 g of the mixed monomer was added, the stirring speed was changed to 427 rpm.

[0384] After adding 1246 g of the mixed monomer, stirring was stopped, and the polymerization vessel was depressurized until the internal pressure reached atmospheric pressure. The polymerization vessel was cooled to obtain an aqueous dispersion with a solid content of 23.8% by mass. The polymer adhesion rate, average particle size, number of particles, polymerization rate, and radical generation ratio (B / A) are shown in Table 1.

[0385] 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 fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1 + 10 (121°C) = 20. The polymer composition, end group content, iodine content, and glass transition temperature are shown in Table 2. The number-average molecular weight (Mn) was 52,000 and the weight-average molecular weight (Mw) was 107,000, as determined by GPC analysis. The LCB Index was 4.55, as determined by RPA analysis.

[0386] Experimental Example 6 1870g of deionized water and 0.096g of CH2=CFCF2OCF(CF3)CF2OCF(CF3)COONH4 were added to a 3L SUS polymerization tank. The polymerization tank was then sealed, and the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 95°C, and monomers (initial monomers) were injected under pressure at a molar ratio of VDF / TFE / HFP (=19 / 11 / 70 mol%) so that the internal pressure of the polymerization tank was 2.01 MPaG, while stirring at 150 rpm.

[0387] Next, an aqueous polymerization initiator solution, prepared by dissolving 0.747g of APS in deionized water, was injected under pressure with nitrogen gas to start the reaction. As polymerization progressed, when the internal pressure dropped to 1.98 MPaG, a mixed monomer of VDF / TFE / HFP (=50 / 20 / 30 mol%) was added so that the internal pressure remained constant at 2.02 MPaG.

[0388] 1.5 hours after the start of the reaction, 12 g of the mixed monomer was reached, and the stirring speed was changed to 10 rpm. After 2.0 hours, the polymerization vessel temperature was changed to 80°C over 30 minutes, and then the stirring speed was changed to 580 rpm. When 23 g of the mixed monomer was added, 2.91 g of iodine compound I(CF2)4I was injected under pressure with nitrogen gas. At 2.5 hours, 2.8 hours, and 6.5 hours after the start of the reaction, 0.018 g, 0.019 g, and 0.047 g of aqueous polymerization initiator solution of APS were injected under pressure with nitrogen gas.

[0389] After adding 622 g of the mixed monomer, stirring was stopped, and the polymerization vessel was depressurized until the internal pressure reached atmospheric pressure. The polymerization vessel was cooled to obtain an aqueous dispersion with a solid content of 24.8% by mass. The polymer adhesion rate, average particle size, number of particles, polymerization rate, and radical generation ratio (B / A) are shown in Table 1.

[0390] An aqueous aluminum sulfate solution was added to the above aqueous dispersion to induce coagulation. The resulting coagulation was washed with pure water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1 + 10 (100°C) = 50. The polymer composition, end group content, iodine content, and glass transition temperature are shown in Table 2. The number-average molecular weight (Mn) was 65,000 and the weight-average molecular weight (Mw) was 94,000, as determined by GPC analysis. The LCB Index was 3.51, as determined by RPA analysis.

[0391] Experimental Example 7 1937 g of deionized water and 0.111 g of CH2=CFCF2OCF(CF3)CF2OCF(CF3)COONH4 were added to a 3 L SUS polymerization tank. The polymerization tank was then sealed, and the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 89°C, and monomers (initial monomers) were injected under pressure at a molar ratio of VDF / HFP (=50 / 50 mol%) so that the internal pressure of the polymerization tank reached 2.00 MPaG while stirring at 150 rpm.

[0392] Next, an aqueous polymerization initiator solution, prepared by dissolving 0.145g of APS in deionized water, was injected under pressure with nitrogen gas to start the reaction. As polymerization progressed, when the internal pressure dropped to 1.98 MPaG, a mixed monomer of VDF / HFP (=78 / 22 mol%) was added so that the internal pressure remained constant at 2.02 MPaG.

[0393] Two hours after the start of the reaction, when the mixed monomer reached 8 g, the polymerization vessel temperature was changed to 80°C over 22 minutes, and then the stirring speed was changed to 685 rpm. An aqueous polymerization initiator solution, in which 0.014 g of APS was dissolved in deionized water, was injected under pressure with nitrogen gas. When 20 g of the mixed monomer was added, 2.32 g of iodine compound I(CF2)4I was injected under pressure with nitrogen gas. At 5 hours and 8 hours after the start of the reaction, an aqueous polymerization initiator solution, in which 0.014 g of APS was dissolved in deionized water, was injected under pressure with nitrogen gas.

[0394] After adding 628 g of the mixed monomer, stirring was stopped, and the polymerization vessel was depressurized until the internal pressure reached atmospheric pressure. The polymerization vessel was cooled to obtain an aqueous dispersion with a solid content of 23.9% by mass. The polymer adhesion rate, average particle size, number of particles, polymerization rate, and radical generation ratio (B / A) are shown in Table 1.

[0395] An aqueous aluminum sulfate solution was added to the above aqueous dispersion to induce coagulation. The resulting coagulation was washed with pure water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1 + 10 (100°C) = 67. The polymer composition, end group content, iodine content, and glass transition temperature are shown in Table 2. The number-average molecular weight (Mn) was 103,000 and the weight-average molecular weight (Mw) was 183,000, as determined by GPC analysis.

[0396] Experimental Example 8 1913 g of deionized water and 0.161 g of CH2=CFCF2OCF(CF3)CF2OCF(CF3)COONH4 were added to a 3 L SUS polymerization tank. The polymerization tank was then sealed, and the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 95°C, and monomers (initial monomers) were injected under pressure at a molar ratio of VDF / TFE / perfluoromethyl vinyl ether [PMVE] (=72 / 6 / 22 mol%) so that the internal pressure of the polymerization tank was 1.48 MPaG, while stirring at 150 rpm.

[0397] Next, an aqueous polymerization initiator solution, prepared by dissolving 0.144g of APS in deionized water, was injected under pressure with nitrogen gas to start the reaction. As polymerization progressed, when the internal pressure dropped to 1.46 MPaG, a mixed monomer of VDF / TFE / PMVE (=72.5 / 7.5 / 20 mol%) was added so that the internal pressure remained constant at 1.48 MPaG.

[0398] 1.4 hours after the start of the reaction, 6 g of the mixed monomer was reached, and the stirring speed was changed to 50 rpm. Subsequently, the polymerization vessel temperature was changed to 80°C over 15 minutes, and 1.9 hours after the start of the reaction, the stirring speed was changed to 700 rpm. When 12 g of the mixed monomer was added, 1.47 g of iodine compound I(CF2)4I was injected under pressure with nitrogen gas. Also, when 330 g of the mixed monomer was added, 4.38 g of CF2=CFOCF2CF2CH2I was injected under pressure with nitrogen gas. At 1.9 hours, 4.9 hours, and 7.9 hours after the start of the reaction, 0.011 g, 0.011 g, and 0.012 g of aqueous polymerization initiator solution of APS were injected under pressure with nitrogen gas.

[0399] After adding 600 g of the mixed monomer, stirring was stopped, and the polymerization vessel was depressurized until the internal pressure reached atmospheric pressure. The polymerization vessel was cooled to obtain an aqueous dispersion with a solid content of 22.5% by mass. Table 1 shows the polymer adhesion rate, average particle size, number of particles, polymerization rate, and radical generation ratio (B / A).

[0400] An aqueous aluminum sulfate solution was added to the above aqueous dispersion to induce coagulation. The resulting coagulation was washed with pure water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1 + 10 (100°C) = 66. The polymer composition, end group content, iodine content, and glass transition temperature are shown in Table 2. The number-average molecular weight (Mn) was 129,000 and the weight-average molecular weight (Mw) was 197,000, as determined by GPC analysis. The LCB Index was 7.83, as determined by RPA analysis.

[0401] Experimental Example 9 1871 g of deionized water and 0.187 g of CH2=CFCF2OCF(CF3)CF2OCF(CF3)COONH4 were added to a 3 L SUS polymerization tank. The polymerization tank was then sealed, and the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 80°C, and monomers (initial monomers) were injected under pressure at a molar ratio of VDF / TFE / HFP (=35 / 12 / 53 mol%) so that the internal pressure of the polymerization tank was 2.01 MPaG, while stirring at 150 rpm.

[0402] Next, an aqueous polymerization initiator solution, prepared by dissolving 0.094g of APS in deionized water, was injected under pressure with nitrogen gas to start the reaction. As polymerization progressed, when the internal pressure dropped to 1.995 MPaG, a mixed monomer of VDF / TFE / HFP (=61 / 21 / 18 mol%) was added so that the internal pressure remained constant at 2.02 MPaG.

[0403] Three hours after the reaction started, the stirring speed was changed to 580 rpm. When 12 g of the mixed monomer was added, 2.24 g of iodine compound I(CF2)4I was injected under pressure with nitrogen gas. When 290 g of the mixed monomer was added, the stirring speed was changed to 500 rpm.

[0404] After adding 580g of the mixed monomer, stirring was stopped, and the polymerization vessel was depressurized until the internal pressure reached atmospheric pressure. The polymerization vessel was cooled to obtain an aqueous dispersion with a solid content of 23.9% by mass. The polymer adhesion rate, average particle size, number of particles, polymerization rate, and radical generation ratio (B / A) are shown in Table 1.

[0405] An aqueous aluminum sulfate solution was added to the above aqueous dispersion to induce coagulation. The resulting coagulation was washed with pure water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1 + 10 (100°C) = 116. The polymer composition, end group content, iodine content, and glass transition temperature are shown in Table 2. The number-average molecular weight (Mn) was 133,000 and the weight-average molecular weight (Mw) was 234,000, as determined by GPC analysis.

[0406] Experimental Example 10 3816g of deionized water was added to a 6L SUS polymerization tank, the tank was sealed, and the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 80°C, and monomers (initial monomers) were injected under pressure at a molar ratio of VDF / TFE / HFP (=51 / 7 / 42 mol%) so that the internal pressure of the polymerization tank was 2.00 MPaG, while stirring at 150 rpm.

[0407] Next, an aqueous polymerization initiator solution, prepared by dissolving 0.229g of APS in deionized water, was injected under pressure with nitrogen gas to start the reaction. As polymerization progressed, when the internal pressure dropped to 1.98 MPaG, a mixed monomer of VDF / TFE / HFP (=70 / 12 / 18 mol%) was added so that the internal pressure remained constant at 2.00 MPaG.

[0408] 90 minutes after the start of the reaction, the stirring speed was changed to 498 rpm. When 44 g of the mixed monomer was added, 2.594 g of iodine compound I(CF2)4I was added. When 81 g of the mixed monomer was added, 3.223 g of CF2=CFOCF2CF2CH2I was added. When 975 g of the mixed monomer was added, 4.794 g of iodine compound I(CF2)4I was added under nitrogen gas pressure. Furthermore, when 623 g of the mixed monomer was added, the stirring speed was changed to 427 rpm. Also, 4.5 hours after the start of the reaction, 0.076 g of an aqueous polymerization initiator solution of APS was added under nitrogen gas pressure.

[0409] After adding 1246 g of the mixed monomer, stirring was stopped, and the polymerization vessel was depressurized until the internal pressure reached atmospheric pressure. The polymerization vessel was cooled to obtain an aqueous dispersion with a solid content of 23.6% by mass. The polymer adhesion rate, average particle size, number of particles, polymerization rate, and radical generation ratio (B / A) are shown in Table 1.

[0410] An aqueous aluminum sulfate solution was added to the above aqueous dispersion to induce coagulation. The resulting coagulation was washed with pure water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1 + 10 (121°C) = 20. The polymer composition, end group content, iodine content, and glass transition temperature are shown in Table 2. The number-average molecular weight (Mn) was 80,000 and the weight-average molecular weight (Mw) was 183,000, as determined by GPC analysis. The LCB Index was 5.80, as determined by RPA analysis.

[0411] Comparative Example 1 3503g of deionized water was added to a 6L SUS polymerization tank, the tank was sealed, and the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 80°C, and monomers (initial monomers) were injected under pressure at a molar ratio of VDF / TFE / HFP (=44 / 16 / 40 mol%) so that the internal pressure of the polymerization tank was 1.48 MPaG, while stirring at 300 rpm.

[0412] Next, an aqueous polymerization initiator solution, prepared by dissolving 6.6557 g of ammonium persulfate (APS) in deionized water, was injected under pressure with nitrogen gas to start the reaction. As polymerization progressed, when the internal pressure dropped to 1.46 MPaG, a mixed monomer of VDF / TFE / HFP (=58 / 20 / 22 mol%) was added so that the internal pressure remained constant at 1.48 MPaG.

[0413] When 69g, 210g, 324g, 455g, 649g, 779g, 974g, and 1169g of the mixed monomer were added, 0.11cc of isopentane was injected under pressure with nitrogen gas.

[0414] After adding 1298 g of the mixed monomer, stirring was stopped, and the polymerization vessel was depressurized until the internal pressure reached atmospheric pressure. The polymerization vessel was cooled to obtain an aqueous dispersion with a solid content of 26.0% by mass. Table 1 shows the polymer adhesion rate, average particle size, number of particles, polymerization rate, and radical generation ratio (B / A).

[0415] Aluminum sulfate aqueous solution was added to the above aqueous dispersion to induce coagulation. The obtained coagulation was washed with pure water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1 + 10 (100°C) = 43. The polymer composition, end group weight, iodine content, and glass transition temperature are shown in Table 2. The number-average molecular weight (Mn) determined by GPC analysis was 86,000 and the weight-average molecular weight (Mw) was 247,000. Furthermore, the proportion of components with molecular weights less than 50,000 (A) determined by integral molecular weight distribution was 15.1%, the proportion of components between 50,000 and 100,000 (B) was 26.3%, and the proportion of components with molecular weights of 100,000 or more (C) was 58.6%.

[0416] Comparative Example 2 3503g of deionized water was added to a 6L SUS polymerization tank, the tank was sealed, and the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 80°C, and monomers (initial monomers) were injected under pressure at a molar ratio of VDF / TFE / HFP (=44 / 16 / 40 mol%) so that the internal pressure of the polymerization tank was 1.48 MPaG, while stirring at 300 rpm.

[0417] Next, an aqueous polymerization initiator solution, prepared by dissolving 0.075 cc of isopentane and 6.6555 g of ammonium persulfate (APS) in deionized water, was injected under pressure with nitrogen gas to start the reaction. As polymerization progressed, when the internal pressure dropped to 1.46 MPaG, a mixed monomer of VDF / TFE / HFP (=58 / 20 / 22 mol%) was added so that the internal pressure remained constant at 1.48 MPaG.

[0418] After adding 1299g of the mixed monomer, stirring was stopped, and the polymerization vessel was depressurized until the internal pressure reached atmospheric pressure. The polymerization vessel was cooled to obtain an aqueous dispersion with a solid content of 26.0% by mass. The polymer adhesion rate, average particle size, number of particles, polymerization rate, and radical generation ratio (B / A) are shown in Table 1.

[0419] An aqueous aluminum sulfate solution was added to the above aqueous dispersion to induce coagulation. The obtained coagulation was washed with pure water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1 + 10 (100°C) = 140. The polymer composition, end group weight, iodine content, and glass transition temperature are shown in Table 2. The number-average molecular weight (Mn) determined by GPC analysis was 222,000 and the weight-average molecular weight (Mw) was 1,429,000. Furthermore, the proportion of components with a molecular weight of less than 50,000 (A) determined by the integrated molecular weight distribution was 3.5%, the proportion of components with a molecular weight of 50,000 to less than 100,000 (B) was 8.1%, and the proportion of components with a molecular weight of 100,000 or more (C) was 87.4%.

[0420] [Table 1]

[0421] In Table 1, "Time to reach 3% by mass" refers to the time from the initial addition of the polymerization initiator to the point in time when the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer.

[0422] [Table 2]

[0423] In Table 2, "ND" means that the amount of terminal groups was below the detection limit.

[0424] Evaluation of crosslinking properties The fluorine-containing elastomers obtained in Experimental Examples 1-10 were kneaded with rolls according to the formulations shown in Tables 3 and 4 to obtain crosslinkable compositions. For the obtained crosslinkable compositions, the crosslinking curve was determined using a rubber vulcanization tester MDRH2030 (M&K Co., Ltd.), and the minimum viscosity (ML), maximum torque level (MH), induction time (T10), and optimal crosslinking time (T90) were determined. Furthermore, crosslinked molded sheets were obtained by crosslinking the crosslinkable compositions using press crosslinking and subsequent oven crosslinking.

[0425] The materials shown in Tables 3 and 4 are as follows: Polyhydroxy compound: 2,2-bis(4-hydroxyphenyl)perfluoropropane, manufactured by Central Glass Company. Crosslinking accelerator: 8-benzyl-1,8-diazabicyclo-7-undecenium chloride, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Carbon Black A: Seast S, N-744, manufactured by Tokai Carbon Co., Ltd. Carbon Black B: Thermax MT, N-990, manufactured by Cancarb. Calcium hydroxide: CALDIC2000, manufactured by Omi Chemical Industry Co., Ltd. Magnesium oxide: Kyowa Mag 150, manufactured by Kyowa Chemical Co., Ltd. Crosslinking agent: Triaryl isocyanurate, manufactured by Shinryo Co., Ltd. Organic peroxide: 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, Perhexa 25B, manufactured by NOF Corporation.

[0426] Normal physical properties Using a cross-linked molded sheet, a dumbbell-shaped test specimen (No. 6) was prepared in accordance with JIS K6251, and the 100% modulus (M100), tensile strength at break (TB), and elongation at break (EB) of the prepared test specimen were measured under normal conditions.

[0427] hardness A dumbbell-shaped test specimen (No. 6) was prepared in the same manner as described above, and the hardness (Shore A) of the prepared test specimen was measured in accordance with JIS K6253 (peak value, 1 sec, 3 sec).

[0428] Compression set Using a crosslinkable composition, press crosslinking and oven crosslinking were performed under the above conditions to produce O-rings (P24 size). The compression set of the produced O-rings was measured in accordance with JIS K6262 at 150°C or 200°C for 72 hours with a compressibility of 25%.

[0429] The results are shown in Tables 3 and 4.

[0430] [Table 3]

[0431] [Table 4]

[0432] Extrusion molding evaluation The fluorine-containing elastomers obtained in Experimental Example 1 and Comparative Examples 1-2 were kneaded with rolls according to the formulations shown in Table 5 to obtain crosslinkable compositions. Extrusion molding was performed using the obtained crosslinkable compositions by the following method, and the molding results were evaluated according to the following criteria. Equipment: Φ20 extruder (model number EMR-20D12) manufactured by E.M. Giken Co., Ltd. Extrusion conditions: Cylinder temperature 80°C, head temperature 90°C, die temperature 100°C, die size inner diameter 3mm x outer diameter 5mmφ x 5t, rotation speed 20rpm For the extruded surface, the fineness of the surface texture was judged visually, and a three-level evaluation was used, with A for excellent and C for inferior. The shape retention after hose molding was judged visually, and a three-level evaluation system was used, with A for excellent performance and C for poor performance.

[0433] The results are shown in Table 5.

[0434] [Table 5]

[0435] The results in Table 5 show that the fluorine-containing elastomer has a bimodal molecular weight distribution, which allows it to maintain excellent extrusion properties and the shape after hose molding.

[0436] Processability evaluation <Mold releasability> The fluorine-containing elastomers obtained in Experimental Examples 5-6 were kneaded with rolls according to the formulations shown in Table 6 to obtain crosslinkable compositions. Compression molding was performed using the obtained crosslinkable compositions by the following method. A mold with a cavity capable of producing 65 O-rings at once was placed in a vacuum press. After degassing the chamber, the mold was filled with a crosslinkable composition. The filled crosslinkable composition was pressed at a pressure of 10 MPa and primary crosslinked at 160°C for 7 minutes to obtain an O-ring sheet. The obtained O-ring sheet was then removed from the mold. These operations were repeated a total of three times without the application of a release agent. The molds used in the three molding cycles and the O-ring sheet obtained in the third molding cycle were observed, and the release properties were evaluated according to the following criteria. ○: The upper and lower surfaces of the mold have less burr and contamination, resulting in fewer O-ring defects. ×: The O-ring sheet is torn, there are many burrs and stains, and the O-ring has noticeable molding defects such as cracks and dents.

[0437] The results are shown in Table 6.

[0438] [Table 6]

[0439] Experimental Example 11 In a 6L SUS polymerization tank, 856.2g of deionized water and 1390g of polymer K aqueous solution K-2 (solid content concentration 1.6 mass%) described in International Publication No. 2022 / 244784 were added, and then ammonia water was added to adjust the pH to 7. The polymerization tank was sealed, and the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 70°C, and monomers (initial monomers) were injected under pressure at a molar ratio of TFE / PMVE (=24 / 76) so that the internal pressure of the polymerization tank was 0.77 MPaG while stirring at 250 rpm.

[0440] Next, an aqueous polymerization initiator solution, prepared by dissolving 1.2 g of ammonium persulfate (APS) in deionized water, was injected under pressure with nitrogen gas to start the reaction. As polymerization progressed, when the internal pressure dropped to 0.72 MPaG, the mixture was injected under pressure with a molar ratio of TFE / PMVE (=65 / 35) (hereinafter referred to as the mixed monomer) to bring the internal pressure of the polymerization vessel to 0.77 MPaG.

[0441] Three hours after the reaction began, the mixed monomer reached 22 g, and the stirring speed was changed to 10 rpm. After changing the polymerization vessel temperature to 50°C over 30 minutes, the stirring speed was changed to 400 rpm, and 4.25 g of iodine compound I(CF2)4I was injected under pressure with nitrogen gas. When the mixed monomer reached 31 g, 0.36 g of an aqueous polymerization initiator solution of APS was injected under pressure with nitrogen gas.

[0442] IM 1.88g was injected with nitrogen gas at each point in time when 514g, 616g, 719g, and 822g of the mixed monomer were added.

[0443] After adding 1027 g of the mixed monomer, stirring was stopped, and the polymerization vessel was depressurized until the internal pressure reached atmospheric pressure. The polymerization vessel was cooled to obtain an aqueous dispersion with a solid content of 31.0% by mass. The polymer adhesion rate, average particle size, number of particles, polymerization rate, and radical generation ratio (B / A) are shown in Table 7.

[0444] The above aqueous dispersion was mixed with pure water to achieve a solid content concentration of 10% by mass, and the diluted aqueous dispersion was added to a mixed solution with a mass ratio of 2-butanol / pure water = 70 / 30 to induce coagulation. The obtained coagulation was washed with pure water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1 + 10 (100°C) = 60. The polymer composition, iodine content, and glass transition temperature are shown in Table 8. The LCB Index from RPA analysis was 4.83.

[0445] Experimental Example 12 2224 g of deionized water was added to a 6 L capacity SUS polymerization tank, the tank was sealed, and the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 70°C, and monomers (initial monomers) were injected under pressure at a molar ratio of TFE / PMVE (=24 / 76) so that the internal pressure of the polymerization tank was 0.77 MPaG while stirring at 250 rpm.

[0446] Next, an aqueous polymerization initiator solution, prepared by dissolving 1.2 g of ammonium persulfate (APS) in deionized water, was injected under pressure with nitrogen gas to start the reaction. As polymerization progressed, when the internal pressure dropped to 0.72 MPaG, the mixture was injected under pressure with a molar ratio of TFE / PMVE (=65 / 35) (hereinafter referred to as the mixed monomer) to bring the internal pressure of the polymerization vessel to 0.77 MPaG.

[0447] Three hours after the reaction began, the mixed monomer reached 16 g, and the stirring speed was changed to 10 rpm. After changing the polymerization vessel temperature to 50°C over 30 minutes, the stirring speed was changed to 400 rpm, and when the mixed monomer reached 22 g, 4.25 g of iodine compound I(CF2)4I was injected under pressure with nitrogen gas. When the mixed monomer reached 31 g, 0.36 g of an aqueous polymerization initiator solution of APS was injected under pressure with nitrogen gas.

[0448] IM 1.88g was injected with nitrogen gas at each point in time when 514g, 616g, 719g, and 822g of the mixed monomer were added.

[0449] After adding 1027 g of the mixed monomer, stirring was stopped, and the polymerization vessel was depressurized until the internal pressure reached atmospheric pressure. The polymerization vessel was cooled to obtain an aqueous dispersion with a solid content of 30.9% by mass. The polymer adhesion rate, average particle size, number of particles, polymerization rate, and radical generation ratio (B / A) are shown in Table 7.

[0450] The above aqueous dispersion was diluted with pure water to a solid content of 15% by mass, and then the aqueous dispersion diluted with 5% by mass nitric acid aqueous solution was added to induce coagulation. The obtained coagulation was washed with pure water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1 + 10 (100°C) = 59. The polymer composition, iodine content, and glass transition temperature are shown in Table 8. The LCB Index from RPA analysis was 4.81.

[0451] Experimental Example 13 In a 6L SUS polymerization tank, 2030.8g of deionized water and 674g of polymer K aqueous solution K-2 (solid content concentration 1.6% by mass) described in International Publication No. 2022 / 244784 were added, and then ammonia water was added to adjust the pH to 7. The polymerization tank was sealed, and the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 70°C, and monomers (initial monomers) were injected under pressure at a molar ratio of TFE / PMVE (=24 / 76) so that the internal pressure of the polymerization tank was 0.77 MPaG while stirring at 250 rpm.

[0452] Next, 0.993g of CF2=CFOCF2CF(CF3)OCF2CF2CN(CNVE) was injected under pressure with nitrogen along with deionized water. Then, an aqueous polymerization initiator solution, in which 1.4g of ammonium persulfate (APS) was dissolved in deionized water, was injected under pressure with nitrogen gas to start the reaction. As polymerization progressed, when the internal pressure dropped to 0.72 MPaG, the mixture was injected under pressure with a molar ratio of TFE / PMVE (=58 / 42) (hereinafter referred to as the mixed monomer) to bring the internal pressure of the polymerization vessel to 0.77 MPaG. In addition, 0.26g of CNVE was injected under pressure with nitrogen along with deionized water for every 11g of the mixed monomer.

[0453] Two hours after the reaction started, the mixed monomer reached 11 g, and the stirring speed was changed to 10 rpm. After changing the polymerization vessel temperature to 54.5°C over 30 minutes, the stirring speed was changed to 450 rpm, and 6.47 g of polymerization initiator aqueous solution of APS was injected under pressure with nitrogen gas.

[0454] After adding 968 g of the mixed monomer, stirring was stopped, and the polymerization vessel was depressurized until the internal pressure reached atmospheric pressure. The polymerization vessel was cooled to obtain an aqueous dispersion with a solid content of 26.0% by mass. The polymer adhesion rate, average particle size, number of particles, polymerization rate, and radical generation ratio (B / A) are shown in Table 7.

[0455] The above aqueous dispersion was mixed with pure water to achieve a solid content concentration of 10% by mass, and the diluted aqueous dispersion was added to the resulting mixed solution with a mass ratio of 2-butanol / pure water = 70 / 30 to induce coagulation. The obtained coagulation was washed with pure water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1 + 20 (170°C) = 65. The polymer composition and glass transition temperature are shown in Table 8.

[0456] Experimental Example 14 2694g of deionized water was placed in a 6L SUS polymerization tank, the tank was sealed, and the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 90°C, and monomers (initial monomers) were injected under pressure at a molar ratio of TFE / PMVE (=24 / 76) so that the internal pressure of the polymerization tank was 1.20 MPaG while stirring at 250 rpm.

[0457] Next, 0.993g of CF2=CFOCF2CF(CF3)OCF2CF2CN(CNVE) was injected under pressure with deionized water and nitrogen. Then, an aqueous polymerization initiator solution, in which 3.0g of ammonium persulfate (APS) was dissolved in deionized water, was injected under pressure with nitrogen gas to start the reaction. As polymerization progressed, when the internal pressure dropped to 0.72 MPaG, the mixture was injected under pressure with a molar ratio of TFE / PMVE (=58 / 42) (hereinafter referred to as the mixed monomer) to bring the internal pressure of the polymerization vessel to 0.77 MPaG. In addition, 0.26g of CNVE was injected under pressure with deionized water and nitrogen for every 11g of the mixed monomer.

[0458] Two hours after the reaction began, the mixed monomer reached 11 g, and the stirring speed was changed to 10 rpm. After changing the polymerization vessel temperature to 80°C over 30 minutes, the stirring speed was changed to 400 rpm.

[0459] After adding 968 g of the mixed monomer, stirring was stopped, and the polymerization vessel was depressurized until the internal pressure reached atmospheric pressure. The polymerization vessel was cooled to obtain an aqueous dispersion with a solid content of 26.0% by mass. The polymer adhesion rate, average particle size, number of particles, polymerization rate, and radical generation ratio (B / A) are shown in Table 7.

[0460] The above aqueous dispersion was diluted with pure water to a solid content concentration of 15% by mass, and then the aqueous dispersion diluted with 5% by mass nitric acid aqueous solution was added to induce coagulation. The obtained coagulation was washed with pure water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1 + 20 (170°C) = 70. The polymer composition and glass transition temperature are shown in Table 8.

[0461] [Table 7]

[0462] In Table 7, "Time to reach 3% by mass" refers to the time from the initial addition of the polymerization initiator until the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer.

[0463] [Table 8]

[0464] Evaluation of crosslinking properties The fluorine-containing elastomers obtained in Experimental Examples 11-14 were kneaded with rolls according to the formulations shown in Table 9 to obtain crosslinkable compositions. For the obtained crosslinkable compositions, the crosslinking curve was determined using a rubber vulcanization tester MDRH2030 (M&K Co., Ltd.), and the minimum viscosity (ML), maximum torque level (MH), induction time (T10), and optimal crosslinking time (T90) were determined. Furthermore, crosslinked molded sheets were obtained by crosslinking the crosslinkable compositions using press crosslinking and subsequent oven crosslinking.

[0465] The materials shown in Table 9 are as follows: Carbon Black B: Thermax MT, N-990, manufactured by Cancarb. Crosslinking agent: Triaryl isocyanurate, manufactured by Shinryo Co., Ltd. Organic peroxide: 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, Perhexa 25B, manufactured by NOF Corporation. AFTA-PH:2,2-bis[3-amino-4-(N-phenylamino)phenyl]hexafluoropropane

[0466] [Table 9]

Claims

1. A method for producing an aqueous dispersion of a fluorine-containing elastomer, comprising polymerizing a fluorine-containing monomer in the presence of an aqueous medium and a polymerization initiator, wherein the aqueous dispersion contains a fluorine-containing elastomer, The final obtained aqueous dispersion of fluorine-containing elastomer has a solid content concentration of 15% by mass or more. Without removing the product from the reaction vessel, polymerization is carried out continuously from the initial addition of the polymerization initiator until the solid content concentration of the fluorine-containing elastomer aqueous dispersion reaches 15% by mass or more. The ratio of radical generation (B / A) calculated by the following formula is 0.70 or less. Manufacturing method. The ratio of radical generation (B / A) = B / A A: Radical generation per gram of aqueous medium per minute from the initial addition of the polymerization initiator (A) (mol / (g・min)) B: Radical generation rate per gram of aqueous medium (mol / (g・min)) from the point when the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer.

2. The manufacturing method according to claim 1, wherein the polymerization rate from the time the polymerization initiator is first added until the time when the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer is 10 g / (hr·L) or less.

3. The polymerization rate ratio (D / C) calculated by the following formula is 5.0 or higher. The manufacturing method according to claim 1 or 2. Polymerization rate ratio (D / C) = D / C C: Polymerization rate (C) (g / (hr·L)) from the time the polymerization initiator is first added until the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer. D: Polymerization rate (D) (g / (hr·L)) from the point when the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer mass to the point when polymerization is stopped.

4. The manufacturing method according to claim 1 or 2, wherein the amount of polymerization initiator added initially is 30 to 1200 ppm by mass relative to the aqueous medium.

5. The manufacturing method according to claim 1 or 2, wherein the polymerization initiator is a persulfate.

6. The method for producing a fluorine-containing monomer in substantially the absence of a redox initiator, according to claim 1 or 2.

7. The manufacturing method according to claim 1 or 2, comprising polymerizing at least a fluorine-containing monomer having a boiling point of 0°C or lower.

8. The manufacturing method according to claim 1 or 2, wherein the time from the time when the polymerization initiator is first added to the time when polymerization is stopped is 20 hours or less.

9. The manufacturing method according to claim 1 or 2, wherein polymerization of a fluorine-containing monomer is carried out in the absence of a fluorine-containing surfactant that does not substantially have a functional group that can react by radical polymerization, and in the absence of a substantially fluorine-free surfactant.

10. The manufacturing method according to claim 1 or 2, wherein the polymerization temperature is 10 to 120°C.

11. The manufacturing method according to claim 1 or 2, wherein the polymerization temperature from the point when the mass of the fluorine-containing elastomer produced by polymerization reaches 3% by mass of the final fluorine-containing elastomer to the point when polymerization is stopped is 65 to 85°C.

12. The manufacturing method according to claim 1 or 2, wherein the polymerization pressure is 0.5 to 10 MPaG.

13. The method for producing the fluorine-containing elastomer according to claim 1 or 2, wherein the main chain contains a methylene group.

14. The manufacturing method according to claim 1 or 2, wherein the fluorine-containing elastomer is a perfluoroelastomer.

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

16. The manufacturing method according to claim 1 or 2, wherein the Mooney viscosity (ML(1+10)121°C) of the fluorine-containing elastomer is 2 to 130.

17. The manufacturing method according to claim 1 or 2, wherein the Mooney viscosity (ML1 + 20 (170°C)) of the fluorine-containing elastomer is 2 to 130.

18. A polyol crosslinkable fluorine-containing elastomer, It substantially does not contain fluorine-containing surfactants that do not have functional groups that can react by radical polymerization, and it also substantially does not contain fluorine-containing solvents. Using monodisperse polystyrene as the standard, the proportion of component (A) with a molecular weight of less than 50,000, calculated from the integrated molecular weight distribution curve obtained by gel permeation chromatography, is 20-60%. The Mooney viscosity (ML(1+10) at 100°C) is 20 or higher. The glass transition temperature is 25°C or lower. Fluorine-containing elastomer.

19. The fluorine-containing elastomer according to claim 18, wherein the proportion of component (B) having a molecular weight of 50,000 or more and less than 100,000, calculated from an integrated molecular weight distribution curve obtained by gel permeation chromatography using monodisperse polystyrene as the standard, is 5 to 25%.

20. The fluorine-containing elastomer according to claim 18, wherein the proportion of component (C) with a molecular weight of 100,000 or more, calculated from the integrated molecular weight distribution curve obtained by gel permeation chromatography using monodisperse polystyrene as the standard, is 30 to 60%.

21. The fluorine-containing elastomer according to claim 18, which contains an iodine atom.

22. The fluorine-containing elastomer according to claim 18, wherein the iodine content is 0.20% by mass or more.

23. The fluorine-containing elastomer according to claim 18, wherein the ratios of component (A), component (B), and component (C) satisfy the following relationship. Ratio of component (A) > Ratio of component (B) Ratio of component (C) > Ratio of component (B)

24. The main chain contains methylene groups (-CH ２ -) includes -CH ２ - CH4 relative to 100 mol% of the structure ２ The fluorine-containing elastomer according to claim 18, wherein the amount of OH structure is 0.03 mol% or less.

25. A crosslinkable composition containing a fluorine-containing elastomer according to claim 18, and a polyhydroxy compound as a crosslinking agent.

26. A peroxide crosslinkable fluorine-containing elastomer, It substantially does not contain fluorine-containing surfactants that do not have functional groups that can react by radical polymerization, The long-chain branching index LCBindex is 4.0 or higher. Fluorine-containing elastomer.

27. The fluorine-containing elastomer according to claim 26, wherein the glass transition temperature is 25°C or lower.

28. The fluorine-containing elastomer according to claim 26, wherein the iodine content is 0.30% by mass or more.

29. The fluorine-containing elastomer according to claim 26, wherein the Mooney viscosity (ML(1+10)121℃) is 2 or more.

30. The fluorine-containing elastomer according to claim 26, which substantially does not contain a fluorine-containing solvent.

31. The main chain contains methylene groups (-CH ２ -) includes -CH ２ - CH4 relative to 100 mol% of the structure ２ The fluorine-containing elastomer according to claim 26, wherein the amount of structure I is 0.30 to 1.50 mol%.

32. The fluorine-containing elastomer according to claim 26, which is a perfluoroelastomer.

33. The fluorine-containing elastomer according to claim 26, which contains monomer units based on iodine or bromine-containing monomers.

34. A crosslinkable composition containing a fluorine-containing elastomer according to claim 26, and an organic peroxide as a crosslinking agent.

35. A molded article obtained from the crosslinkable composition according to claim 25 or 34.

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