Method for producing a fluorine-containing polymer, aqueous dispersion of a fluorine-containing polymer, and polymer composition

Abstract

Provided is a method for producing a fluorine-containing polymer in which an aqueous medium having a low environmental impact is used and in which no emulsifier is required.　In the method for producing a fluorine-containing polymer, the fluorine-containing polymer is produced by polymerizing, in an aqueous medium, at least one type of fluorine-containing monomer selected from among tetrafluoroethylene, chlorotrifluoroethylene, and vinylidene fluoride, in the presence of a specific polymer containing at least one type of unit selected from among units based on a compound represented by formula (1) and units based on a compound represented by formula (2) (where, if the tetrafluoroethylene is polymerized, the tetrafluoroethylene is polymerized such that the amount of a unit based on the tetrafluoroethylene in the fluorine-containing polymer is less than 99 mass% with respect to all units in the fluorine-containing polymer).　Formula (1): CXY=CR1-COO-(L-O)n-R2 Formula (2): CXY=CR3-(O)m-CH2-Z-R4

Description

[Technical Field]

[0001] This invention relates to a method for producing a fluorine-containing polymer, an aqueous dispersion of a fluorine-containing polymer, and a polymer composition. [Background technology]

[0002] Fluorine-containing polymers such as ethylene / tetrafluoroethylene copolymers and tetrafluoroethylene / perfluoroalkyl vinyl ether copolymers are used in various industrial fields because they have excellent heat resistance, chemical resistance, flame retardancy, and weather resistance. One method for producing fluorine-containing polymers is to use a fluorine-containing emulsifier and emulsion polymerize fluorine-containing monomers in an aqueous medium (see Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2007 / 046377 [Overview of the project] [Problems that the invention aims to solve]

[0004] Although Patent Document 1 uses an aqueous medium and therefore has a low environmental impact, if a large amount of the essential emulsifier remains in the aqueous dispersion obtained by polymerization, removal of the emulsifier may be necessary depending on the application.

[0005] The object of this invention is to provide a method for producing a fluorine-containing polymer that does not require an emulsifier, while using an aqueous medium that has a low environmental impact. Furthermore, the present invention also aims to provide aqueous dispersions and polymer compositions of fluorine-containing polymers. [Means for solving the problem]

[0006] As a result of diligent research, the inventors have found that the above problem can be solved by the following configuration.

[0007] [1] In an aqueous medium, at least one unit selected from the unit based on the compound represented by the following formula (1) and the unit based on the compound represented by the following formula (2) is included. At least one fluorine-containing monomer selected from tetrafluoroethylene, chlorotrifluoroethylene, and vinylidene fluoride is polymerized to produce a fluorine-containing polymer. (However, when tetrafluoroethylene is polymerized, tetrafluoroethylene is copolymerized so that the content of the unit based on tetrafluoroethylene in the fluorine-containing polymer is less than 99% by mass with respect to all the units of the fluorine-containing polymer.) A method for producing a fluorine-containing polymer. Formula (1): CXY=CR 1 -COO-(L-O) n -R 2 Formula (2): CXY=CR 3 -(O) m -CH2-Z-R 4 Each symbol in Formula (1) and Formula (2) represents the following. X and Y each independently represent a hydrogen atom, a halogen atom, or a methyl group. R 1 represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 3 carbon atoms. R 2 represents an alkyl group, an alkyl group in which at least one -CH2- in the alkyl group is replaced by -CO-, or a group represented by the following formula (3). R 3 represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 3 carbon atoms, or -CO-OCH3. R 4 represents an alkyl group. L represents an alkylene group. Z represents -CO-O-* or -O-CO-*. However, * represents the bonding position with R 4 and represents the bonding position with R m represents 0 or 1, and n represents an integer of 1 or more. Formula (3): -CO-CR 1 =CXY In equation (3), X, Y and R 1 These are X, Y, and R in equation (1), respectively. 1 This is the same as the definition of [the same thing]. [2] The manufacturing method according to [1], wherein the amount of the specific polymer is 0.0001 to 1.0 part by mass per 100 parts by mass of the aqueous medium.

[0008] [3] A method for producing a fluorine-containing polymer, comprising polymerizing at least one specific compound selected from the compounds represented by formula (1) and the compounds represented by formula (2) below in an aqueous medium to obtain an aqueous medium containing the specific polymer, and then polymerizing at least one fluorine-containing monomer selected from tetrafluoroethylene, chlorotrifluoroethylene, and vinylidene fluoride in the aqueous medium containing the specific polymer to produce a fluorine-containing polymer (however, when polymerizing tetrafluoroethylene, the tetrafluoroethylene is copolymerized such that the content of units based on tetrafluoroethylene in the fluorine-containing polymer is less than 99% by mass of the total units of the fluorine-containing polymer). Formula (1): CXY=CR 1 -COO-(LO) n -R 2 Formula (2): CXY=CR 3 -(O) m -CH2-ZR 4 The symbols in equations (1) and (2) represent the following: X and Y independently represent a hydrogen atom, a halogen atom, or a methyl group. R 1 This represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 3 carbon atoms. R 2 This represents an alkyl group, an alkyl group in which at least one -CH2- is replaced with -CO-, or a group represented by the following formula (3). R 3 This represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 3 carbon atoms, or -CO-OCH3. R 4 This represents an alkyl group. L represents an alkylene group. Z represents -CO-O-* or -O-CO-*, where * is R 4 This indicates the connection point with [the other element]. m represents 0 or 1, and n represents an integer greater than or equal to 1. Formula (3): -CO-CR 1 =CXY In equation (3), X, Y and R 1 These are X, Y, and R in equation (1), respectively. 1 This is the same as the definition of [the same thing]. [4] The manufacturing method according to [3], wherein the aqueous medium containing the specific polymer is an aqueous medium that was used in the production of the specific polymer and came to contain the specific polymer. [5] The manufacturing method according to [3] or [4], wherein the amount of the specific polymer present in the polymerization of the fluorine-containing monomer is 0.0001 to 1.0 parts by mass per 100 parts by mass of the aqueous medium.

[0009] [6] A method for producing a fluorine-containing polymer, comprising polymerizing at least one fluorine-containing monomer selected from tetrafluoroethylene, chlorotrifluoroethylene, and vinylidene fluoride in an aqueous medium in the presence of a polyalkylene oxide compound and substantially without an emulsifier (provided that when polymerizing tetrafluoroethylene, the tetrafluoroethylene is copolymerized such that the content of units based on tetrafluoroethylene in the fluorine-containing polymer is less than 99% by mass of the total units of the fluorine-containing polymer).

[0010] [7] A fluorine polymer aqueous dispersion comprising an aqueous medium, a fluorine polymer having units based on at least one fluorine monomer selected from tetrafluoroethylene, chlorotrifluoroethylene, and vinylidene fluoride (provided that if the fluorine polymer contains units based on tetrafluoroethylene, the content of units based on tetrafluoroethylene in the fluorine polymer is less than 99% by mass of the total units of the fluorine polymer), particles having a volume-based cumulative 50% diameter of 20 to 3000 nm, and a specific polymer having at least one unit selected from units based on a compound represented by the following formula (1) and units based on a compound represented by the following formula (2), the specific polymer being contained as particles in the aqueous medium or contained in particles containing the fluorine polymer, and substantially free of emulsifiers. Formula (1): CXY=CR 1 -COO-(LO) n -R 2 Formula (2): CXY=CR 3 -(O) m -CH2-ZR 4 The symbols in equations (1) and (2) represent the following: X and Y independently represent a hydrogen atom, a halogen atom, or a methyl group. R 1 This represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 3 carbon atoms. R 2 This represents an alkyl group, an alkyl group in which at least one -CH2- is replaced with -CO-, or a group represented by the following formula (3). R 3 This represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 3 carbon atoms, or -CO-OCH3. R 4 This represents an alkyl group. L represents an alkylene group. Z represents -CO-O-* or -O-CO-*, where * is R 4 This indicates the connection point with [the other element]. m represents 0 or 1, and n represents an integer greater than or equal to 1. Formula (3): -CO-CR 1 =CXY In equation (3), X, Y and R 1 These are X, Y, and R in equation (1), respectively. 1 This is the same as the definition of [the same thing]. [8] The aqueous dispersion of the fluorine-containing polymer according to [7], comprising 1.0 to 50.0 parts by mass of particles containing the fluorine-containing polymer per 100 parts by mass of an aqueous medium. [9] An aqueous dispersion of a fluorine-containing polymer according to [7] or [8], comprising 0.0001 to 1.0 parts by mass of particles of the specified polymer per 100 parts by mass of an aqueous medium.

[10] An aqueous dispersion of a fluorine-containing polymer according to any one of [7] to [9], comprising 0.001 to 5.00 parts by mass of particles of the specified polymer per 100 parts by mass of particles containing the fluorine-containing polymer.

[0011]

[11] A fluorine-containing polymer aqueous dispersion comprising an aqueous medium, a fluorine-containing polymer having units based on at least one fluorine-containing monomer selected from tetrafluoroethylene, chlorotrifluoroethylene, and vinylidene fluoride (provided that if the fluorine-containing polymer contains units based on tetrafluoroethylene, the content of units based on tetrafluoroethylene in the fluorine-containing polymer is less than 99% by mass of the total units of the fluorine-containing polymer), particles having a volume-based cumulative 50% diameter of 20 to 3000 nm, and a polyalkylene oxide compound, and substantially free of emulsifiers.

[0012]

[12] A polymer composition comprising a fluorine-containing polymer having units based on at least one fluorine-containing monomer selected from tetrafluoroethylene, chlorotrifluoroethylene, and vinylidene fluoride (provided that if the fluorine-containing polymer contains units based on tetrafluoroethylene, the content of units based on tetrafluoroethylene in the fluorine-containing polymer is less than 99% by mass of the total units of the fluorine-containing polymer), and a specific polymer containing at least one unit selected from units based on a compound represented by the following formula (1) and units based on a compound represented by the following formula (2), and substantially free of emulsifiers. Formula (1): CXY=CR 1 -COO-(LO) n -R 2 Formula (2): CXY=CR 3 -(O) m -CH2-ZR 4 The symbols in equations (1) and (2) represent the following: X and Y independently represent a hydrogen atom, a halogen atom, or a methyl group. R 1 This represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 3 carbon atoms. R 2 This represents an alkyl group, an alkyl group in which at least one -CH2- is replaced with -CO-, or a group represented by the following formula (3). R 3 This represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 3 carbon atoms, or -CO-OCH3. R 4 This represents an alkyl group. L represents an alkylene group. Z represents -CO-O-* or -O-CO-*, where * is R 4 This indicates the connection point with [the other element]. m represents 0 or 1, and n represents an integer greater than or equal to 1. Formula (3): -CO-CR 1 =CXY In equation (3), X, Y and R 1These are X, Y, and R in equation (1), respectively. 1 This is the same as the definition of [the same thing].

[13] The polymer composition according to

[12] , wherein the content of the specific polymer relative to 100 parts by mass of the fluorine-containing polymer is 0.001 to 5.00 parts by mass.

[0013]

[14] A polymer composition comprising a fluorine-containing polymer having units based on at least one fluorine-containing monomer selected from tetrafluoroethylene, chlorotrifluoroethylene, and vinylidene fluoride (provided that if the fluorine-containing polymer contains units based on tetrafluoroethylene, the content of units based on tetrafluoroethylene in the fluorine-containing polymer is less than 99% by mass of the total units of the fluorine-containing polymer), and a polyalkylene oxide compound, and substantially free of emulsifiers. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a method for producing a fluorine-containing polymer using an aqueous medium with low environmental impact, without requiring an emulsifier. Furthermore, according to the present invention, aqueous dispersions of fluorine-containing polymers and polymer compositions can also be provided. [Modes for carrying out the invention]

[0015] The meanings of the terms used in this invention are as follows: The mass percentage (%) of each unit relative to the total units contained in a polymer can be determined by analyzing the polymer using solid-state nuclear magnetic resonance (NMR) spectroscopy, but it can also be estimated from the amount of each monomer used. Typically, the amount of each unit calculated from the amount of each monomer used closely matches the actual amount of each unit. "Volume-based cumulative 50% diameter" is the particle diameter at the point on the cumulative curve where the cumulative volume reaches 50%, determined by measuring the particle size distribution using laser diffraction and scattering methods and setting the total volume of the particle collection to 100%. Hereafter, this will also be referred to as "D50".

[0016] <<First Embodiment>> The first embodiment of the method for producing a fluorine-containing polymer of the present invention is a method of polymerizing at least one fluorine-containing monomer selected from tetrafluoroethylene, chlorotrifluoroethylene, and vinylidene fluoride (hereinafter also referred to as "specific fluorine-containing monomer") in an aqueous medium in the presence of a specific polymer containing at least one unit selected from a unit based on a compound represented by the following formula (1) (hereinafter also referred to as "compound (1)") and a unit based on a compound represented by the following formula (2) (hereinafter also referred to as "compound (2)"). However, when polymerizing tetrafluoroethylene, the tetrafluoroethylene is copolymerized such that the content of units based on tetrafluoroethylene in the fluorine-containing polymer is less than 99% by mass of the total units of the fluorine-containing polymer. In the first embodiment of the method for producing a fluorine-containing polymer of the present invention, a specific polymer obtained by polymerization separately may be used, or the specific polymer may be polymerized in an aqueous medium, and then the specific fluorine-containing monomer may be polymerized in the same polymerization system. "Continuing to polymerize in the same polymerization system" means using the aqueous medium that was used to produce the specific polymer and into which the specific polymer is present, and polymerizing the specific fluorine-containing monomer in the aqueous medium containing the specific polymer. A commercially available product may be used as the specific polymer obtained by polymerization separately. In the first embodiment of the method for producing a fluorine-containing polymer of the present invention, it is preferable to polymerize at least one specific compound selected from compound (1) and compound (2) in an aqueous medium to obtain an aqueous medium containing the specific polymer, and then polymerize a specific fluorine-containing monomer in the aqueous medium containing the specific polymer to produce a fluorine-containing polymer. In this two-step production method, the step of obtaining the aqueous medium containing the specific polymer in the first step is hereinafter referred to as "Step 1," and the step of producing the fluorine-containing polymer in the second step is hereinafter referred to as "Step 2." The polymerization of compound (1) in step 1 and the polymerization of the specific fluorine-containing monomer in step 2 are preferably carried out in the presence of a polymerization initiator. A water-soluble polymerization initiator is preferred as the polymerization initiator.

[0017] <Process 1> (Specific compound) In step 1, at least one specific compound selected from compound (1) and compound (2) is used. Two or more specific compounds may be used in combination. Formula (1): CXY=CR 1 -COO-(LO) n -R 2 Formula (2): CXY=CR 3 -(O) m -CH2-ZR 4 The symbols in equations (1) and (2) represent the following: X and Y independently represent a hydrogen atom, a halogen atom, or a methyl group. R 1 R represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 3 carbon atoms. 2 R represents an alkyl group, an alkyl group in which at least one -CH2- is replaced with -CO- (hereinafter also referred to as "substituted alkyl group"), or a group represented by the following formula (3). 3 R represents a hydrogen atom, a halogen atom, an alkyl group with 1 to 3 carbon atoms, or a -CO-OCH3 group. 4 This represents an alkyl group. L represents an alkylene group. Z represents -CO-O-* or -O-CO-* (where * is R). 4 This represents the connection position with ). m represents 0 or 1, and n represents an integer greater than or equal to 1. Formula (3): -CO-CR 1 =CXY In equation (3), X, Y and R 1 These are X, Y, and R in equation (1), respectively. 1 This is the same as the definition of [the same thing].

[0018] Since it is easy to obtain specific polymers, the following groups are preferred for each group in formula (1). X and Y are preferably, independently of each other, a hydrogen atom, a fluorine atom, or a chlorine atom, and more preferably both are hydrogen atoms. R 1 Preferably, the alkyl group has 1 to 3 carbon atoms, and a methyl group is more preferable. L is preferably an alkylene group having 2 to 6 carbon atoms, more preferably an alkylene group having 2 or 3 carbon atoms, and even more preferably an ethylene group. The alkylene group of L may be linear or branched. R 2 The alkyl group is preferably an alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group. R 2 The number of -CO- groups in the substituted alkyl group is preferably 1 to 3, and more preferably 2. The position of the -CO- in the substituted alkyl group may be at the end of the substituted alkyl group, or it may be between -CH2- and -CH2-. 2 A preferred substituted alkyl group is -CO-CH2-CO-CH3. R 2 X, Y and R in the base represented by formula (3) 1 These are X, Y, and R in equation (1), respectively. 1 The definition is the same as that of [the specified entity], and the preferred embodiment is also the same. n is preferably between 1 and 100, and more preferably between 1 and 50.

[0019] As compound (1), compounds represented by formula (1A), compounds represented by formula (1B), and compounds represented by formula (1C) are preferred. Formula (1A): CXY=CR 1 -COO-(LO) n -R 2a Formula (1B): CXY=CR 1 -COO-(LO) n -CO-CR 1 =CXY Formula (1C): CXY=CR 1 -COO-LOR 2b In formula (1A), formula (1B), formula (1C), X, Y, R 1 , L and n are X, Y and R in equation (1), respectively. 1 This is the same as the definitions of L and n. In formula (1A), R 2a This represents an alkyl group. In formula (1C), R2b represents a substituted alkyl group.

[0020] Since it is easy to obtain a specific polymer, each group in formula (2) is preferably the following. In formula (2), the preferred ranges of X and Y are the same as the preferred ranges of X and Y in formula (1), respectively. R 3 is preferably an alkyl group having 1 to 3 carbon atoms or -CO-OCH3. Z is preferably -O-CO-*. R 4 is preferably an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group. m is preferably 0.

[0021] As the compound (2), a compound represented by formula (2A) is preferred. Formula (2A) CXY=CR 3a -CH2-O-CO-R 4 In formula (2A), X, Y and R 4 are the same as the definitions of X, Y and R in formula (2), respectively. 4 respectively. R 3a represents an alkyl group having 1 to 3 carbon atoms.

[0022] (aqueous medium) Examples of the aqueous medium include water and a mixture of water and a water-soluble organic solvent. Examples of the water-soluble organic solvent include tert-butanol, propylene glycol, and dipropylene glycol. In the case of a mixture of water and a water-soluble organic solvent, the concentration of the water-soluble organic solvent is preferably 10% by mass or less. The aqueous medium is preferably only water.

[0023] (water-soluble polymerization initiator) As the water-soluble polymerization initiator, a water-soluble radical initiator and a water-soluble redox catalyst are preferred. Preferred water-soluble radical initiators include persulfates such as ammonium persulfate and potassium persulfate, and water-soluble organic peroxides such as disuccinic acid peroxide, bisglutaric acid peroxide, and tert-butyl hydroperoxide. As a water-soluble redox catalyst, a combination of an oxidizing agent such as bromate or its salt, chloric acid or its salt, persulfate or its salt, permanganate or its salt, or hydrogen peroxide, and a reducing agent such as sulfurous acid or its salt, bisulfite or its salt, thiosulfate or its salt, organic acid, or inorganic salt is preferred. As persulfates, potassium persulfate and ammonium persulfate are preferred. As sulfites, sodium sulfite is preferred. As inorganic salts, combinations of sulfate anions, sulfite anions, or chloride anions with metal ions are examples. As metal ions, transition metal ions are preferred, including manganese, iron, cobalt, nickel, copper, zinc, cerium, and silver ions, with iron ions being preferred. As an inorganic salt, iron(II) sulfate is preferred. As a water-soluble polymerization initiator, a water-soluble redox catalyst is preferred, with combinations of potassium persulfate and sodium sulfite, combinations of potassium persulfate, sodium sulfite and an inorganic salt being preferred, and combinations of potassium persulfate and sodium sulfite, and combinations of potassium persulfate, sodium sulfite and iron(II) sulfate being more preferred. Furthermore, since polymerization of specific compounds proceeds easily, the pH of the reaction system is preferably set to 3-10, and more preferably to 6-8. Sulfites such as sodium sulfite, ammonia, sodium hydroxide, hydrochloric acid, etc., may be added as needed to adjust the pH. Water-soluble polymerization initiators may be used in combination of two or more types. Regarding the method of preparing the water-soluble polymerization initiator, the entire amount may be added to the reaction system before the polymerization reaction begins, or it may be added to the reaction system continuously or intermittently.

[0024] The amount of the specific compound used is preferably 0.0001 to 1.0 parts by mass, and more preferably 0.001 to 0.5 parts by mass, per 100 parts by mass of aqueous medium. Within this range, a decrease in the polymerization rate can be prevented, and the amount of the specific compound mixed in with the fluorine-containing polymer when the fluorine-containing polymer is produced in step 2 can be reduced. As for the method of adding the specific compound, it is preferable to add the entire amount to the reaction system at the beginning of the polymerization reaction.

[0025] The amount of water-soluble polymerization initiator used is preferably 0.1 to 50.0 moles, more preferably 0.1 to 40.0 moles, and even more preferably 0.5 to 10.0 moles, per mole of the specific compound.

[0026] The polymerization temperature of the specific compound is preferably 10 to 95°C, and more preferably 50 to 90°C. The polymerization time is preferably 5 to 400 minutes, and more preferably 5 to 300 minutes, in the case of batch processing. The pressure conditions during polymerization are preferably reduced pressure or atmospheric pressure.

[0027] The above polymerization yields an aqueous dispersion containing a specific polymer. The specific polymer is in particulate form and uniformly dispersed in the aqueous medium. The aqueous dispersion is colloidal. It is presumed that, during the polymerization of the specific fluorine-containing monomer described later, the particles of the specific polymer (hereinafter also referred to as "specific particles") adsorb and incorporate the specific fluorine-containing monomer in their hydrophobic regions, thereby solubilizing the specific fluorine-containing monomer. Adding an initiator then causes the specific fluorine-containing monomer to polymerize within the particles. Furthermore, it is presumed that the specific particles contribute to dispersion stabilization in aqueous and organic solvents. The D50 of the specific particles is preferably 10 to 1000 nm, more preferably 10 to 300 nm, even more preferably 10 to 200 nm, and particularly preferably 10 to 150 nm.

[0028] The specific particles are composed of a specific polymer containing units based on a specific compound (units based on compound (1) and units based on compound (2)). The content of units based on a specific compound in a specific polymer is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more, relative to the total units of the specific polymer. The upper limit is 100% by mass.

[0029] The above polymerization makes it easy to obtain an aqueous dispersion of a fluorine-containing polymer containing specific particles with a D50 of 10 to 1000 nm in an amount of 0.0001 to 1.0 parts by mass per 100 parts by mass of aqueous medium. Preferably, the specific particles are present in an amount of 0.0001 to 0.5 parts by mass, and more preferably 0.0005 to 0.1 parts by mass per 100 parts by mass of aqueous medium.

[0030] <Process 2> Step 2 is a process for producing a fluorine-containing polymer, in which at least one fluorine-containing monomer selected from tetrafluoroethylene, chlorotrifluoroethylene, and vinylidene fluoride (i.e., a specific fluorine-containing monomer) is polymerized in an aqueous medium containing the specific polymer obtained in Step 1. Polymerization of specific fluorine-containing monomers is preferably carried out using a water-soluble polymerization initiator, and examples of water-soluble polymerization initiators include the water-soluble polymerization initiators described in step 1. Furthermore, polymerization of specific fluorine-containing monomers is also preferably carried out using a chain transfer agent. Examples of fluorine-containing polymers include tetrafluoroethylene-based polymers having units based on tetrafluoroethylene (TFE) (hereinafter also referred to as "TFE units"), polyvinylidene fluoride (hereinafter also referred to as "PVdF"), polychlorotrifluoroethylene, and copolymers of ethylene and chlorotrifluoroethylene. Among these, tetrafluoroethylene-based polymers are preferred.

[0031] Fluorine-containing polymers may have units based on monomers other than specific fluorine-containing monomers. Other monomers include fluorine-containing monomers such as hexafluoropropylene (hereinafter also referred to as "HFP"), perfluoro(alkyl vinyl ether) (hereinafter also referred to as "PAVE"), and fluoroalkylethylene (hereinafter also referred to as "FAE"). Examples of PAVE include CF2=CFOCF3 (hereinafter also referred to as "PMVE"), CF2=CFOCF2CF3, CF2=CFOCF2CF2CF3 (hereinafter also referred to as "PPVE"), CF2=CFOCF2CF2CF2CF3, and CF2=CFO(CF2)8F, with PMVE and PPVE being preferred. Examples of FAEs include CH2=CH(CF2)2F (hereinafter also referred to as "PFEE"), CH2=CH(CF2)3F, CH2=CH(CF2)4F (hereinafter also referred to as "PFBE"), CH2=CF(CF2)3H, and CH2=CF(CF2)4H, with PFEE and PFBE being preferred. Other monomers include ethylene, propylene, vinyl chloride, vinylidene chloride, and vinyl fluoride. Other monomers include monomers having oxygen-containing polar groups. Preferred oxygen-containing polar groups are acid anhydride residues, hydroxyl groups, carbonyl group-containing groups, acetal groups, and oxycycloalkane groups, with acid anhydride residues being more preferred. Among monomers having acid anhydride residues, monomers having cyclic acid anhydride residues are preferred, with itaconic anhydride (hereinafter also referred to as "IAH"), citraconic anhydride, 5-norbornene-2,3-dicarboxylic acid anhydride (also known as himic anhydride; hereinafter also referred to as "NAH"), and maleic anhydride being more preferred.

[0032] Examples of tetrafluoroethylene polymers include copolymers of TFE and PAVE, copolymers of TFE and HFP (hereinafter also referred to as "FEP"), copolymers of TFE and ethylene (hereinafter also referred to as "ETFE"), copolymers of TFE and propylene, and copolymers of TFE and vinylidene fluoride. However, when polymerizing TFE, the TFE copolymerizes such that the content of TFE units in the fluorine-containing polymer is less than 99% by mass of the total units of the fluorine-containing polymer. Furthermore, if the polymer does not contain units based on at least one fluorine-containing monomer selected from chlorotrifluoroethylene and vinylidene fluoride, and contains TFE units, it is preferable that the content of TFE units is 10% by mass or more and less than 99% by mass of the total units of the fluorine-containing polymer. Furthermore, the tetrafluoroethylene polymers do not contain the following specific high-heat-resistant polymers. Specific high heat-resistant polymer: A polymer in which, as measured by differential scanning calorimeter, the first endothermic peak upon a 10°C / min heating increase is at least 330°C, and the endothermic peak after the first endothermic peak is at least 320°C.

[0033] In the present invention, ETFE, copolymers of TFE and PAVE, and FEP are preferred as tetrafluoroethylene polymers, and ETFE and PFA (described later) are more preferred. As for FEP, FEP in which the ratio of HFP units to the total of TFE units is 1 to 15 mol% is preferred, and FEP in which the ratio is 5 to 13 mol% is more preferred.

[0034] ETFE has TFE units and ethylene-based units (hereinafter also referred to as "E units"). In a copolymer having TFE units and E units, the ratio of E units to the total of E units and TFE units is preferably 20 to 70 mol%, more preferably 25 to 60 mol%, and even more preferably 35 to 55 mol%. The total ratio of E units to TFE units relative to the total number of units constituting ETFE is preferably 80 mol% or more, more preferably 85 mol% or more, and even more preferably 90 mol% or more. Furthermore, it is preferable to have FAE units in addition to E units and TFE units. The ratio of FAE units to the total of E units and TFE units is preferably 0.1 to 10 mol%, more preferably 0.1 to 5 mol%, and even more preferably 0.2 to 4 mol%. Furthermore, it is preferable to have monomer units having oxygen-containing polar groups in addition to E units and TFE units. The ratio of monomer units having oxygen-containing polar groups to the total of E units and TFE units is preferably 0.01 to 5 mol%, and more preferably 0.05 to 3 mol%. The method for producing the fluorine-containing polymer of the present invention is emulsion polymerization using an aqueous medium, but even when monomers having oxygen-containing polar groups, such as monomers having highly hydrophilic cyclic acid anhydride residues, are used, excessive dissolution does not occur, copolymerization with tetrafluoroethylene and the like is easy, and oxygen-containing polar groups can be easily introduced into the fluorine-containing polymer.

[0035] A copolymer of TFE and PAVE has TFE units and PAVE units. Preferred copolymers of TFE and PAVE are those in which the proportion of PAVE units to the total of TFE units is 0.1 mol% or more and less than 20 mol% (hereinafter also referred to as "PF1"), and copolymers in which the proportion of PAVE units is 20 to 70 mol% (hereinafter also referred to as "PF2").

[0036] In PF1, the ratio of PAVE units to the total of TFE units is preferably 0.5 to 10 mol%, and more preferably 0.5 to 5.0 mol%. PF1 may be a copolymer consisting only of TFE units and PAVE units, or it may contain one or more units based on other monomers. Other preferred monomers include other fluorine monomers and monomers having oxygen-containing polar groups. Hexafluoropropylene is a preferred other fluorine monomer. NAH is a preferred monomer having oxygen-containing polar groups. When units based on other monomers are included, the content of other fluorine monomers is preferably 0.1 to 10 mol%, more preferably 0.1 to 6 mol%, relative to the total of TFE units and PAVE units. Monomers having oxygen-containing polar groups are preferably 0.01 to 5 mol%, more preferably 0.05 to 3 mol%. The total ratio of TFE units and PAVE units to all units constituting PF1 is preferably 80 mol% or more, more preferably 85 mol% or more, and even more preferably 90 mol% or more. PF1 will also be referred to as "PFA" below.

[0037] In PF2, the ratio of PAVE units to the total of TFE units is preferably 20 to 50 mol%, and more preferably 25 to 45 mol%. Furthermore, in addition to TFE units and PAVE units, it is also preferable to have units based on monomers having a fluorine atom and a nitrile group (hereinafter also referred to as "CN units") and units based on monomers having a fluorine atom and multiple vinyl groups (hereinafter also referred to as "DV units"). Examples of monomers having a fluorine atom and a nitrile group include CF2=CFO(CF2)5CN and CF2=CFOCF2CF(CF3)CF2CF2CN. Examples of monomers having a fluorine atom and multiple vinyl groups include CF2=CFO(CF2)3OCF=CF2, CF2=CFO(CF2)4OCF=CF2, and CH2=CH(CF2)6CH=CH2. The ratio of CN units to the total of TFE units and PAVE units is preferably 0.1 to 10.0 mol%, and more preferably 0.5 to 5.0 mol%. The ratio of DV units to the total of TFE units and PAVE units is preferably 0.01 to 1.0 mol%, and more preferably 0.01 to 0.5 mol%. The total ratio of TFE units and PAVE units to all units constituting PF2 is preferably 80 mol% or more, more preferably 85 mol% or more, and even more preferably 90 mol% or more.

[0038] Specific fluorine-containing monomers and other monomers are introduced into the reaction system (i.e., polymerization reaction vessel) by conventional methods. For example, TFE is introduced into the reaction system continuously or intermittently so that the polymerization pressure reaches a predetermined pressure. Alternatively, for example, other monomers are dissolved in an aqueous medium, and the resulting solution is introduced into the reaction system continuously or intermittently. When using a water-soluble polymerization initiator, the water-soluble polymerization initiator may be added to the reaction system all at once or in separate portions. When using a chain transfer agent, alcohols, hydrocarbons, and hydrofluorocarbons are preferred, with alcohols and hydrocarbons being more preferred, because they have the effect of stabilizing the end structure of the resin. As for alcohols, methanol and ethanol are preferred because they are readily soluble in water and easily separated from the copolymer after production. As for hydrocarbons, n-pentane, cyclohexane, methane, and propane are preferred because they have good thermal stability and high chain transfer properties when introduced into the end structure of the resin.

[0039] The polymerization temperature is preferably 10 to 95°C, and more preferably 15 to 90°C. The polymerization pressure is preferably 0.5 to 4.0 MPaG, and more preferably 0.6 to 3.5 MPaG. The polymerization time, in the case of batch processing, is preferably 90 to 1000 minutes, and more preferably 90 to 700 minutes.

[0040] Polymerization of specific fluorine-containing monomers may be carried out in the substantially absence of emulsifiers. Examples of emulsifiers include well-known emulsifiers and common surfactants. The emulsifier mentioned above does not refer to the specific polymer in the present invention, the polyalkylene oxide compound described later, or the decomposition product obtained by mixing the polyalkylene oxide compound with an oxidizing agent. "Substantially free of emulsifiers" means an environment in which the emulsifier content is 0.03 ppm by mass or less relative to the total mass of the aqueous medium, preferably 0.02 ppm by mass or less, and more preferably 0 ppm by mass.

[0041] Furthermore, the production of specific polymers and fluorine-containing polymers may be carried out continuously in the same polymerization reaction vessel. Furthermore, in the manufacturing method of the present invention, it is sufficient that specific particles are formed in the production of the specific polymer, and the production of the fluorine-containing polymer may be carried out before the specific compound is completely consumed in the production of the specific polymer. In this case, it is thought that a fluorine-containing polymer containing units based on the specific compound may be produced.

[0042] When the production of a specific polymer and the production of a fluorine-containing polymer are carried out in succession, the content of the specific polymer obtained in step 1 and present in step 2 in the aqueous medium is preferably 0.0001 to 1.0 parts by mass, and more preferably 0.0005 to 0.5 parts by mass, per 100 parts by mass of the aqueous medium.

[0043] If the production of the specific polymer and the production of the fluorine-containing polymer are not carried out consecutively, step 1 can be omitted. In place of step 1, a commercially available specific polymer is prepared, and the content of the specific polymer present in the aqueous medium in step 2 is preferably 0.0001 to 1.0 parts by mass, and more preferably 0.001 to 0.5 parts by mass, per 100 parts by mass of the aqueous medium. For commercially available specific polymers, the D50 of the particles is preferably 10 to 1000 nm, more preferably 10 to 300 nm, even more preferably 10 to 200 nm, and particularly preferably 10 to 150 nm. Furthermore, the content of units based on specific compounds in commercially available specific polymers is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more, relative to the total units of the polymer. The upper limit is 100% by mass.

[0044] By the above procedure, an aqueous dispersion of a fluorine-containing polymer can be easily obtained, which contains particles with a D50 of 20 to 3000 nm, including a fluorine-containing polymer having units based on a specific fluorine-containing monomer, and specific particles. Furthermore, as mentioned above, since it is presumed that monomer polymerization occurs within specific particles during the polymerization of specific fluorine-containing monomers, the resulting fluorine-containing polymer particles may incorporate specific particles, potentially producing particles containing both the fluorine-containing polymer and the specific polymer. In particular, if the specific particles have a high affinity for the specific fluorine-containing monomer (for example, if the specific particles are particles of a specific polymer containing fluorine atoms), it is likely that particles containing both the fluorine-containing polymer and the specific polymer, with a D50 of 20-3000 nm, will be easily produced. The aqueous dispersion of the fluorine-containing polymer of the present invention is preferably an aqueous dispersion comprising an aqueous medium as described above, particles containing a fluorine-containing polymer with a D50 of 20 to 3000 nm, and a specific polymer contained as particles in the aqueous medium or contained in the particles containing the fluorine-containing polymer. Hereinafter, "particles containing fluorine-containing polymers" refers to particles that may contain specific polymers unless otherwise specified. The aqueous dispersion of the fluorine-containing polymer preferably contains 1.0 to 50.0 parts by mass of particles containing the fluorine-containing polymer per 100 parts by mass of the aqueous medium, and more preferably 2.0 to 40.0 parts by mass. The aqueous dispersion of the fluorine-containing polymer preferably contains 0.0001 to 1.0 part by mass of the specific polymer per 100 parts by mass of the aqueous medium. Furthermore, in the aqueous dispersion of the fluorine-containing polymer, the content of the specific polymer per 100 parts by mass of particles containing the fluorine-containing polymer is preferably 0.001 to 5.00 parts by mass, and more preferably 0.005 to 3.00 parts by mass. The D50 of particles containing a fluorine-containing polymer is preferably 20 to 1000 nm.

[0045] The above-mentioned aqueous dispersion of fluorine-containing polymer is substantially free of emulsifiers. As mentioned above, emulsifiers are... In an aqueous dispersion of a fluorinated polymer, the emulsifier is substantially absent, meaning that the emulsifier content is 0.03 ppm by mass or less relative to the total mass of the aqueous medium, preferably 0.02 ppm by mass or less, and more preferably 0% by mass.

[0046] Furthermore, if TFE units are present in the fluorine-containing polymer contained in the aqueous dispersion of the fluorine-containing polymer, the content of TFE units in the fluorine-containing polymer is less than 99% by mass of the total units of the fluorine-containing polymer.

[0047] As mentioned above, the above-mentioned aqueous dispersion of fluorinated polymer does not require an emulsifier, and therefore can be easily converted into a dispersion of organic solvents such as N-methylpyrrolidone or acetone by solvent substitution. A dispersion of a fluorinated polymer containing particles can be mixed with an organic solvent and dehydrated by evaporation or using anhydrous sodium sulfate or the like to obtain a dispersion of the organic solvent.

[0048] The above-mentioned aqueous dispersion of fluorinated polymers provides stable dispersion of the fluorinated polymer even without the presence of emulsifiers. Therefore, it can be suitably used in coating applications, binders, and the like.

[0049] The polymer composition of the present invention is preferably a composition comprising a specific polymer and a fluorine-containing polymer containing units based on a specific fluorine-containing monomer. The above polymer composition can be easily obtained from the aqueous dispersion of the fluorine-containing polymer obtained in step 2. That is, a powder of the polymer composition can be obtained by agglomerating the polymer from the aqueous dispersion of the fluorine-containing polymer. Furthermore, the powdered polymer composition obtained by agglomeration can be homogenized by melt kneading or the like to form a molding material in the shape of pellets, granules, etc., containing the fluorine-containing polymer and the specific polymer. Alternatively, a molded product can be made from the powdered polymer composition obtained by agglomeration by melt molding or the like.

[0050] Methods of coagulation include, but are not limited to, freeze coagulation, acid coagulation, base coagulation, and coagulation using coagulants. In the case of freeze-coagulation, the coagulation temperature is preferably 0 to 5°C. The coagulation time is preferably 1 hour or more, and more preferably 2 hours or more. In the case of acid agglutination, it is preferable to add an acid-containing solution to an aqueous dispersion of a fluoropolymer. Examples of acids to be added include hydrochloric acid, nitric acid, sulfuric acid, oxalic acid, hydrofluoric acid, etc., with hydrochloric acid being preferred. The concentration of the acid in the acid-containing solution is preferably 0.1 to 50% by mass, more preferably 1 to 30% by mass, and even more preferably 1 to 10% by mass. As for base aggregation, a method of adding a solution containing a base to an aqueous dispersion of a fluoropolymer is preferable. Examples of the base to be added include sodium hydroxide, potassium hydroxide, ammonium carbonate, etc., and sodium hydroxide is preferable. The concentration of the base in the solution containing the base is preferably 0.1 to 50% by mass, more preferably 1 to 30% by mass, and even more preferably 1 to 10% by mass. As for aggregation by a flocculant, known flocculants can be used. Examples of known flocculants include aluminum salts, calcium salts, and magnesium salts. Specifically, aluminum sulfate, alum represented by the general formula M’Al(SO4)2· 12 H2O [where M’ is a monovalent cation other than lithium], calcium nitrate, and magnesium sulfate can be mentioned. Among them, alum is preferable, and potassium alum where M is potassium is more preferable. As for the aggregation method, base aggregation is preferable because aggregation particularly easily proceeds.

[0051] The melting point of the fluoropolymer in the polymer composition is preferably 150°C or higher, more preferably 150 to 330°C, even more preferably 180 to 320°C, particularly preferably 220 to 310°C, and most preferably 260 to 300°C. When the melting point is within this range, it is preferable because the heat resistance of the fluoropolymer is high.

[0052] The above polymer composition preferably substantially does not contain an emulsifier. The emulsifier is as described above. That the polymer composition substantially does not contain an emulsifier means that the content of the emulsifier is 0.03 mass ppm or less with respect to the total mass of the fluoropolymer containing units based on the specific polymer and the specific fluoromonomer in the polymer composition, preferably 0.02 mass ppm or less, and more preferably 0% by mass.

[0053] <<Second Embodiment>> A second embodiment of the method for producing a fluorine-containing polymer of the present invention is a method for polymerizing a specific fluorine-containing monomer in an aqueous medium in the presence of a polyalkylene oxide compound and substantially the absence of an emulsifier. However, when polymerizing TFE, the TFE is copolymerized such that the content of TFE units in the fluorine-containing polymer is less than 99% by mass of the total units of the fluorine-containing polymer. In the first embodiment of the method for producing a fluorine-containing polymer described above, polymerization of a specific fluorine-containing monomer was carried out in the presence of a specific polymer, whereas in the second embodiment of the method for producing a fluorine-containing polymer, polymerization of a specific fluorine-containing monomer was carried out in the presence of a polyalkylene oxide compound and substantially without an emulsifier. In other words, the first embodiment of the method for producing a fluorine-containing polymer uses a specific polymer, while the second embodiment uses a polyalkylene oxide compound. The procedure for polymerization of the specific fluorine-containing monomer in the second embodiment of the method for producing a fluorine-containing polymer is the same as the procedure for polymerization of the specific fluorine-containing monomer in the first embodiment (specifically, the procedure in step 2). Therefore, The following will primarily describe the differences between the second embodiment and the first embodiment.

[0054] (Polyalkylene oxide compounds) Polyalkylene oxide compounds are compounds that form nuclei (seeds) during the polymerization of specific fluorine-containing monomers. In other words, they are nucleation additives. Polyalkylene oxide compounds are compounds containing polyoxyalkylene chains, and examples of polyoxyalkylene chains include polyoxyethylene chains, polyoxypropylene chains, and polyoxytetramethylene chains.

[0055] The polyalkylene oxide compound preferably has a surface tension in water of more than approximately 40 dynes / cm at a concentration of 1000 ppm. More preferably, the surface tension is greater than approximately 42 dynes / cm, and even more preferably greater than approximately 45 dynes / cm. Preferably, the surface tension is 73 dynes / cm or less.

[0056] The number-average molecular weight of the polyalkylene oxide compound is preferably 50 to 2000, more preferably 100 to 1500, and even more preferably 150 to 1300.

[0057] As the polyalkylene oxide compound, the compound represented by formula (4) is preferred. Formula (4): R a -(OR c ) p -OR b In formula (4), R a and R b Each of these independently represents a hydrogen atom, an alkyl group, an acryloyl group, or a methacryloyl group. R c This represents an alkylene group having 2 to 4 carbon atoms, which may be linear or branched. p represents an integer between 1 and 50.

[0058] Examples of polyalkylene oxide compounds include polyethylene glycol, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, polyethylene glycol monomethyl ether, polyethylene glycol dimethyl ether, polyethylene glycol monobutyl ether, polypropylene glycol, polypropylene glycol monoacrylate, polypropylene glycol monomethacrylate, polypropylene glycol dimethacrylate, polypropylene glycol monomethyl ether, polypropylene glycol dimethyl ether, polypropylene glycol monobutyl ether, and polytetramethylene glycol.

[0059] Polyalkylene oxide compounds may be used individually or in combination of two or more. The amount of polyalkylene oxide compound used is preferably 0.1 to 10 ppm by mass, and more preferably 1 to 10 ppm by mass, relative to the total mass of the aqueous medium.

[0060] (emulsifier) In the second embodiment, polymerization of a specific fluorine-containing monomer is carried out in the substantially absence of an emulsifier. As mentioned above, emulsifiers are... "Substantially free of emulsifiers" means an environment in which the amount of emulsifier used is 0.03 ppm by mass or less relative to the total mass of the aqueous medium, preferably 0.02 ppm by mass or less, and more preferably 0% by mass.

[0061] In the second embodiment, it is preferable to obtain a dispersion by mixing a polyalkylene oxide compound and an oxidizing agent in an aqueous medium, and then to produce a fluorine-containing polymer by polymerizing a specific fluorine-containing monomer in the obtained dispersion.

[0062] (Oxidizing agent) Examples of oxidizing agents include hydrogen peroxide and polymerization initiators. Examples of polymerization initiators include the compounds exemplified in the water-soluble polymerization initiators described in Step 1 above. Persulfates are preferred as polymerization initiators, and ammonium persulfate and potassium persulfate are more preferred.

[0063] When a polyalkylene oxide compound and an oxidizing agent are mixed in an aqueous medium, a dispersion is obtained in which lipophilic nucleation sites are dispersed in the aqueous medium. More specifically, when a polyalkylene oxide compound and an oxidizing agent are mixed, the hydrophilic portion of the polyalkylene oxide compound is decomposed, and the hydrophobic portion of the polyalkylene oxide compound becomes the lipophilic nucleation sites. These lipophilic nucleation sites are dispersed in the aqueous medium, and it becomes possible to finely disperse fluorine-containing polymers at these sites. Because lipophilic nucleation sites exhibit excellent affinity for specific fluorine-containing monomers, polymerization of these monomers proceeds easily in dispersions containing these lipophilic nucleation sites. In other words, lipophilic nucleation sites can serve as a hydrophobic environment for the polymerization of specific fluorine-containing monomers.

[0064] The amount of oxidizing agent used is preferably 0.01 to 1.00% by mass, and more preferably 0.05 to 0.5% by mass, relative to the total mass of the aqueous medium. The temperature at which the polyalkylene oxide compound and the oxidizing agent are mixed is preferably 20 to 120°C, and more preferably 40 to 120°C. The mixing time when mixing the polyalkylene oxide compound with the oxidizing agent is preferably 0.05 to 1.00 hours.

[0065] It is preferable to add the water-soluble inorganic salt to the aqueous medium before or during the mixing of the polyalkylene oxide compound and the oxidizing agent. The amount of water-soluble inorganic salt used is preferably 1 to 1000 ppm by mass, and more preferably 10 to 1000 ppm by mass, relative to the total mass of the aqueous medium. Examples of water-soluble inorganic salts include sodium sulfite, sodium bisulfite, sodium chloride, potassium sulfite, potassium bisulfite, potassium carbonate, ammonium oxalate, sodium tetraborate, sodium acetate, ammonium carbonate, ammonium dihydrogen phosphate, and diammonium phosphate. Sulfites are preferred, with sodium sulfite and ammonium sulfite being more preferred.

[0066] By the above procedure, an aqueous dispersion of a fluorine-containing polymer can be easily obtained, which contains particles with a D50 of 20 to 3000 nm, having a fluorine-containing polymer with units based on a specific fluorine-containing monomer, and a polyalkylene oxide compound. The aqueous dispersion of the fluorine-containing polymer preferably contains 1.0 to 50.0 parts by mass of particles containing the fluorine-containing polymer per 100 parts by mass of the aqueous medium, and more preferably 3 to 40 parts by mass. The aqueous dispersion of the fluorine-containing polymer preferably contains 0.1 to 10 ppm by mass of the polyalkylene oxide compound, and more preferably 1 to 10 ppm by mass, based on the total mass of the aqueous dispersion of the fluorine-containing polymer. Furthermore, in the aqueous dispersion of the fluorine-containing polymer, the content of the polyalkylene oxide compound per 100 parts by mass of particles containing the fluorine-containing polymer is preferably 0.001 to 5.00 parts by mass, and more preferably 0.005 to 3.00 parts by mass. The D50 of particles containing a fluorine-containing polymer is preferably 20 to 1000 nm.

[0067] The above-mentioned aqueous dispersion of fluorine-containing polymer is substantially free of emulsifiers. As mentioned above, emulsifiers are... In an aqueous dispersion of a fluorinated polymer, the emulsifier is substantially absent, meaning that the emulsifier content is 0.03 ppm by mass or less relative to the total mass of the aqueous medium, preferably 0.02 ppm by mass or less, and more preferably 0% by mass.

[0068] Furthermore, if TFE units are present in the fluorine-containing polymer contained in the aqueous dispersion of the fluorine-containing polymer, the content of TFE units in the fluorine-containing polymer is less than 99% by mass of the total units of the fluorine-containing polymer.

[0069] As mentioned above, the above-mentioned aqueous dispersion of fluorinated polymer does not require an emulsifier, and therefore can be easily converted into a dispersion of organic solvents such as N-methylpyrrolidone or acetone by solvent substitution. A dispersion of a fluorinated polymer containing particles can be mixed with an organic solvent and dehydrated by evaporation or using anhydrous sodium sulfate or the like to obtain a dispersion of the organic solvent.

[0070] The above-mentioned aqueous dispersion of fluorinated polymers provides stable dispersion of the fluorinated polymer even without the presence of emulsifiers. Therefore, it can be suitably used in coating applications, binders, and the like.

[0071] The polymer composition of the present invention is preferably a composition comprising a polyalkylene oxide compound and a fluorine-containing polymer containing units based on a specific fluorine-containing monomer. The above polymer composition can be easily obtained from the above fluorine-containing polymer aqueous dispersion. That is, a powder of the polymer composition can be obtained by agglomerating the polymer from the above fluorine-containing polymer aqueous dispersion. Furthermore, the powdered polymer composition obtained by agglomeration can be homogenized by melt kneading or the like to form a molding material in the shape of pellets, granules, etc., containing the fluorine-containing polymer and the polyalkylene oxide compound. Alternatively, a molded product can be made from the powdered polymer composition obtained by agglomeration by melt molding or the like. The aggregation method is as described above.

[0072] The above polymer composition preferably contains substantially no emulsifier. As mentioned above, emulsifiers are... A polymer composition being substantially free of emulsifiers means that the emulsifier content is 0.03 ppm by mass or less relative to the total mass of the polyalkylene oxide compound and the fluorine-containing polymer containing units based on specific fluorine-containing monomers in the polymer composition, preferably 0.02 ppm by mass or less, and more preferably 0% by mass. [Examples]

[0073] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited thereto. Examples 1 to 7 are examples.

[0074] The various measurement and evaluation methods are as follows. D50 (nm) of polymer particles in aqueous dispersion: An aqueous dispersion of polymer particles was used as the sample, and the particle size distribution was measured using a laser diffraction / scattering particle size analyzer (Otsuka Electronics Co., Ltd., ELSZ). Identification of specific polymers: The fact that a specific polymer has been obtained 1 Confirmed by 1H-NMR analysis.

[0075] Q(mm 3 Measurement of / s: The Q-value (also known as volumetric flow velocity) of ETFE was measured using a flow tester (manufactured by Shimadzu Corporation) at a temperature of 297°C and a load of 50 kg.

[0076] The proportion of each unit in the polymer: The proportion of each unit in a polymer is, 19 The results were obtained from 1F-NMR analysis, fluorine content analysis, and infrared absorption spectroscopy.

[0077] Melting point (°C): The melting point is the temperature at the endothermic peak due to melting, measured under a nitrogen atmosphere using a differential scanning thermal analyzer (NETZSCH DSC 3500Sirius). The temperature transition program during measurement was -20°C → 310°C → -70°C → 310°C, with a heating rate of 10°C / min and a cooling rate of 5°C / min for each step. The "melting point" is defined as the temperature at the endothermic peak due to the heat of fusion during the second heating step after cooling to -70°C.

[0078] [Production of fluorine-containing polymers] (Example 1) [Process 1] After purging a 2.1 L stainless steel polymerization tank with nitrogen, the pressure was reduced to -0.1 MPaG, and ultrapure water (624 g), sodium sulfite (74 mg), and 2-methoxyethyl methacrylate (hereinafter also referred to as "MEM"; see structural formula below) (34 mg) were charged. Next, the solution in the polymerization tank was heated to 60°C while stirring, and 4.0 ml of a solution (5% by mass) of potassium persulfate (hereinafter also referred to as "KPS") dissolved in deionized water was poured into the polymerization tank to polymerize the MEM. From the amount of MEM charged, the amount of polyMEM in 100 parts by mass of aqueous medium was 0.0054 parts by mass. [ka]

[0079] [Process 2] Next, the polymerization tank was pressurized to 1.9 MPaG with a mixed monomer mixture of TFE / E = 86 / 14 molar ratio, and 10 ml of a solution of KPS (5% by mass) and sodium acetate (1.2% by mass) dissolved in deionized water, along with PFBE (0.7 g), was injected into the polymerization tank. Once the pressure inside the polymerization tank began to drop, a mixed monomer mixture of TFE / E = 54 / 46 molar ratio was added to maintain the internal pressure at 1.9 MPaG, and polymerization proceeded. When the continuous addition of the mixed monomer reached 30 g, the polymerization tank was cooled to room temperature, and the gas inside the polymerization tank was released into the atmosphere. The polymerization time was 329 minutes. The solid content concentration of the obtained fluorine-containing polymer in the aqueous dispersion of the fluorine-containing polymer was approximately 3.7%. Furthermore, the D50 of the fluorine-containing polymer particles in the aqueous dispersion was 92 nm. An aqueous dispersion of a fluorine-containing polymer was cooled to agglomerate the fluorine-containing polymer particles and obtain a powder. Next, this fluorine-containing polymer powder was dried at 150°C. The Q value of the obtained fluorine-containing polymer powder at a 50 kg load was 8.3 mm. 3 At s, the molar ratio of TFE units / E units / PFBE units in the fluorine-containing polymer was 53.0 / 46.0 / 1.0. The melting point of the obtained fluorine-containing polymer was 266°C.

[0080] (Examples 2-7) Fluorine-containing polymers were prepared using the same procedure as in Example 1, except that predetermined amounts of the compounds listed in Table 1 were used instead of MEM. The results are summarized in Table 1. The symbols for the compounds listed in Table 1 represent the following:

[0081] "DiGMEMA": Diethylene glycol monomethyl ether methacrylate (see structural formula below) [ka]

[0082] "TeEDGDMA": Tetraethylene glycol dimethacrylate (see structural formula below) [ka]

[0083] "PMEM": Methoxypolyethylene glycol methacrylate (see structural formula below. Mw: 500. n=11) [ka]

[0084] "EGMMMA": Ethylene glycol monoacetate monomethacrylate (see structural formula below) [ka]

[0085] "PEG1000": Polyethylene glycol (see structural formula below. Mw: 1000. n=23) [ka]

[0086] "MPA": 2-methyl-2-propenyl acetate (see structural formula below) [ka]

[0087] In Table 1, the "parts by mass" column in the "Compound" column represents the amount of the specific polymer per 100 parts by mass of the aqueous medium for Examples 1-5 and 7, and the amount of the polyalkylene oxide compound per 100 parts by mass of the aqueous medium for Example 6. In Table 1, the column "Amount of initiator used when polymerizing a specific compound" shows the amount (g) of water-soluble polymerization initiator used when polymerizing a specific compound in Examples 1-5 and 7. In Table 1, the "Solid Content (%)" column represents the solid content concentration of the fluorine-containing polymer in an aqueous dispersion of the fluorine-containing polymer. In Table 1, the "D50(nm)" column represents the D50(nm) of the fluorine-containing polymer particles. In Table 1, "Q value (mm)" 3 The column " / g)" indicates the Q value (mm²) of the fluorine-containing polymer powder at a 50 kg load. 3 / g) represents In Table 1, the "Melting Point (°C)" column represents the melting point (°C) of the fluorine-containing polymer. In Table 1, "TFE units (mol%)", "E units (mol%)", and "PFBE units (mol%)" represent the content of TFE units, E units, and PFBE units, respectively, in the obtained fluorine-containing polymer. In Examples 1-7, the emulsifier was substantially absent during the polymerization of the fluorine-containing monomers.

[0088] [Table 1]

[0089] As shown in Examples 1-7, it has been confirmed that the desired effect can be obtained according to the manufacturing method of the present invention. Furthermore, the entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2020-165490, filed on September 30, 2020, are incorporated herein by reference as disclosure of the present invention.

Claims

1. A method for producing a fluorine-containing polymer, comprising polymerizing at least one fluorine-containing monomer selected from tetrafluoroethylene, chlorotrifluoroethylene, and vinylidene fluoride in an aqueous medium in the presence of a specific polymer containing at least one unit selected from a unit based on a compound represented by the following formula (1) and a unit based on a compound represented by the following formula (2) (however, when polymerizing tetrafluoroethylene, the tetrafluoroethylene is copolymerized such that the content of units based on tetrafluoroethylene in the fluorine-containing polymer is less than 99% by mass of the total units of the fluorine-containing polymer). A method for producing a fluorine-containing polymer, wherein the total content of units based on the compound represented by formula (1) and units based on the compound represented by formula (2) is 50% by mass or more relative to the total units of the specified polymer. Equation (1): CXY = CR １ -COO-(L-O) ｎ -R ２ Formula (2): CXY = CR ３ -(O) ｍ -CH ２ -Z-R ４ The symbols in equations (1) and (2) represent the following: X and Y independently represent a hydrogen atom, a halogen atom, or a methyl group. R １ This represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 3 carbon atoms. R ２ represents an alkyl group, an alkyl group in which at least one -CH ２ - is replaced by -CO-, or a group represented by the following formula (3). R ３ This includes hydrogen atoms, halogen atoms, C1-C3 alkyl groups, or -CO-OCH ３ It represents. R ４ This represents an alkyl group. L represents an alkylene group. Z represents -CO-O-* or -O-CO-*, where * is R ４ This indicates the connection point with [the other element]. m represents 0 or 1, and n represents an integer greater than or equal to 1. Equation (3): -CO-CR １ =CXY In equation (3), X, Y and R １ These are X, Y, and R in equation (1), respectively. １ This is the same as the definition of [the same thing].

2. The manufacturing method according to claim 1, wherein the amount of the specific polymer present is 0.0001 to 1.0 part by mass per 100 parts by mass of the aqueous medium.

3. A method for producing a fluorine-containing polymer, comprising polymerizing at least one specific compound selected from the compounds represented by the following formula (1) and the compounds represented by the following formula (2) in an aqueous medium to obtain an aqueous medium containing a specific polymer, and then polymerizing at least one fluorine-containing monomer selected from tetrafluoroethylene, chlorotrifluoroethylene, and vinylidene fluoride in the aqueous medium containing the specific polymer to produce a fluorine-containing polymer (however, when polymerizing tetrafluoroethylene, the tetrafluoroethylene is copolymerized such that the content of units based on tetrafluoroethylene in the fluorine-containing polymer is less than 99% by mass of the total units of the fluorine-containing polymer), A method for producing a fluorine-containing polymer, wherein the total content of units based on the compound represented by formula (1) and units based on the compound represented by formula (2) is 50% by mass or more relative to the total units of the specified polymer. Equation (1): CXY = CR １ -COO-(L-O) ｎ -R ２ Formula (2): CXY = CR ３ -(O) ｍ -CH ２ -Z-R ４ The symbols in equations (1) and (2) represent the following: X and Y independently represent a hydrogen atom, a halogen atom, or a methyl group. R １ This represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 3 carbon atoms. R ２ is an alkyl group, at least one -CH group in the alkyl group ２ This represents an alkyl group in which - is replaced by -CO- or a group represented by the following formula (3). R ３ This includes hydrogen atoms, halogen atoms, C1-C3 alkyl groups, or -CO-OCH ３ It represents. R ４ This represents an alkyl group. L represents an alkylene group. Z represents -CO-O-* or -O-CO-*, where * is R ４ This indicates the connection point with [the other element]. m represents 0 or 1, and n represents an integer greater than or equal to 1. Equation (3): -CO-CR １ =CXY In equation (3), X, Y and R １ These are X, Y, and R in equation (1), respectively. １ This is the same as the definition of [the same thing].

4. The manufacturing method according to claim 3, wherein the aqueous medium containing the specified polymer is an aqueous medium used in the production of the specified polymer until the specified polymer is present.

5. The manufacturing method according to claim 3 or 4, wherein the amount of the specific polymer present in the polymerization of the fluorine-containing monomer is 0.0001 to 1.0 part by mass per 100 parts by mass of the aqueous medium.

6. In an aqueous medium, a polyalkylene oxide compound is present, and an emulsifier (excluding the aforementioned polyalkylene oxide compound) is used. A method for producing a fluorine-containing polymer having units based on tetrafluoroethylene and units based on ethylene, in the absence of substantially any other substances, The amount of emulsifier used is 0.03 ppm by mass or less relative to the total mass of the aqueous medium. The polyalkylene oxide compound is a compound represented by formula (4), The amount of the polyalkylene oxide compound used is 0.1 to 10 ppm by mass relative to the total mass of the aqueous medium. The total ratio of the tetrafluoroethylene-based units and the ethylene-based units to the total units constituting the fluorine-containing polymer is 80 mol% or more. A method for producing a fluorine-containing polymer, wherein the ratio of the ethylene-based units to the total of the tetrafluoroethylene-based units and the ethylene-based units is 20 to 70 mol%. Formula (4): R a -(O-R c ) p -O-R b In formula (4), Ra and Rb each independently represent a hydrogen atom or an alkyl group, Rc represents an alkylene group having 2 to 4 carbon atoms, and p represents an integer from 1 to 50.

7. A specific polymer comprising an aqueous medium, particles having a volume-based cumulative 50% diameter of 20 to 3000 nm, comprising a fluorine-containing polymer having units based on at least one fluorine-containing monomer selected from tetrafluoroethylene, chlorotrifluoroethylene, and vinylidene fluoride (provided that if the fluorine-containing polymer contains units based on tetrafluoroethylene, the content of units based on tetrafluoroethylene in the fluorine-containing polymer is less than 99% by mass of the total units of the fluorine-containing polymer), and a specific polymer comprising at least one unit selected from units based on a compound represented by the following formula (1) and units based on a compound represented by the following formula (2), wherein the specific polymer is contained as particles in the aqueous medium or contained in particles containing the fluorine-containing polymer, and substantially free of emulsifiers. The total content of units based on the compound represented by formula (1) and units based on the compound represented by formula (2) is 50% by mass or more relative to the total units of the specified polymer. A fluorine-containing polymer aqueous dispersion in which the emulsifier content is 0.03 ppm by mass or less relative to the total mass of the aqueous medium. Equation (1): CXY = CR １ -COO-(L-O) ｎ -R ２ Formula (2): CXY = CR ３ -(O) ｍ -CH ２ -Z-R ４ The symbols in equations (1) and (2) represent the following: X and Y independently represent a hydrogen atom, a halogen atom, or a methyl group. R １ This represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 3 carbon atoms. R ２ is an alkyl group, at least one -CH group in the alkyl group ２ This represents an alkyl group in which - is replaced by -CO- or a group represented by the following formula (3). R ３ This includes hydrogen atoms, halogen atoms, C1-C3 alkyl groups, or -CO-OCH ３ It represents. R ４ This represents an alkyl group. L represents an alkylene group. Z represents -CO-O-* or -O-CO-*, where * is R ４ This indicates the connection point with [the other element]. m represents 0 or 1, and n represents an integer greater than or equal to 1. Equation (3): -CO-CR １ =CXY In equation (3), X, Y and R １ These are X, Y, and R in equation (1), respectively. １ This is the same as the definition of [the same thing].

8. The aqueous dispersion of the fluorine-containing polymer according to claim 7, comprising 1.0 to 50.0 parts by mass of particles containing the fluorine-containing polymer per 100 parts by mass of an aqueous medium.

9. The aqueous dispersion of a fluorine-containing polymer according to claim 7 or 8, comprising 0.0001 to 1.0 part by mass of particles of the specified polymer per 100 parts by mass of an aqueous medium.

10. An aqueous dispersion of a fluorine-containing polymer according to any one of claims 7 to 9, wherein the particles of the specified polymer are present in an amount of 0.001 to 5.00 parts by mass per 100 parts by mass of particles containing the fluorine-containing polymer.

11. The present invention comprises an aqueous medium, particles having a volume-based cumulative 50% diameter of 20 to 3000 nm, which include a fluorine-containing polymer having tetrafluoroethylene-based units and ethylene-based units, and a polyalkylene oxide compound, and an emulsifier (excluding the polyalkylene oxide compound). A fluorine-containing polymer aqueous dispersion that substantially does not contain ) The content of the emulsifier is 0.03 ppm by mass or less with respect to the total mass of the aqueous medium. The polyalkylene oxide compound is a compound represented by formula (4), The content of the polyalkylene oxide compound per 100 parts by mass of the particles is 0.001 to 5.00 parts by mass. The total ratio of the tetrafluoroethylene-based units and the ethylene-based units to the total units constituting the fluorine-containing polymer is 80 mol% or more. A fluorine-containing polymer aqueous dispersion in which the proportion of the ethylene-based units to the sum of the tetrafluoroethylene-based units and the ethylene-based units is 20 to 70 mol%. Formula (4): R a -(O-R c ) p -O-R b In formula (4), Ra and Rb each independently represent a hydrogen atom or an alkyl group, Rc represents an alkylene group having 2 to 4 carbon atoms, and p represents an integer from 1 to 50.

12. A fluorine-containing polymer having units based on at least one fluorine-containing monomer selected from tetrafluoroethylene, chlorotrifluoroethylene, and vinylidene fluoride (provided that if the fluorine-containing polymer contains units based on tetrafluoroethylene, the content of units based on tetrafluoroethylene in the fluorine-containing polymer is less than 99% by mass of the total units of the fluorine-containing polymer), and a specific polymer containing at least one unit selected from units based on the compound represented by the following formula (1) and units based on the compound represented by the following formula (2), and substantially free of emulsifiers, The amount of the emulsifier is 0.03 ppm by mass or less relative to the total mass of the specified polymer and the fluorine-containing polymer. A polymer composition in which the total content of units based on the compound represented by formula (1) and units based on the compound represented by formula (2) is 50% by mass or more relative to the total units of the specified polymer. Equation (1): CXY = CR １ -COO-(L-O) ｎ -R ２ Formula (2): CXY = CR ３ -(O) ｍ -CH ２ -Z-R ４ The symbols in equations (1) and (2) represent the following: X and Y independently represent a hydrogen atom, a halogen atom, or a methyl group. R １ This represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 3 carbon atoms. R ２ is an alkyl group, at least one -CH group in the alkyl group ２ This represents an alkyl group in which - is replaced by -CO- or a group represented by the following formula (3). R ３ This includes hydrogen atoms, halogen atoms, C1-C3 alkyl groups, or -CO-OCH ３ It represents. R ４ This represents an alkyl group. L represents an alkylene group. Z represents -CO-O-* or -O-CO-*, where * is R ４ This indicates the connection point with [the other element]. m represents 0 or 1, and n represents an integer greater than or equal to 1. Equation (3): -CO-CR １ =CXY In equation (3), X, Y and R １ These are X, Y, and R in equation (1), respectively. １ This is the same as the definition of [the same thing].

13. The polymer composition according to claim 12, wherein the content of the specific polymer relative to 100 parts by mass of the fluorine-containing polymer is 0.001 to 5.00 parts by mass.

14. The product comprises a fluorine-containing polymer having units based on tetrafluoroethylene and units based on ethylene, and a polyalkylene oxide compound, and an emulsifier (excluding the polyalkylene oxide compound). A polymer composition that substantially does not contain ) The content of the emulsifier is 0.03 ppm by mass or less with respect to the total mass of the polyalkylene oxide compound and the fluorine-containing polymer. The polyalkylene oxide compound is a compound represented by formula (4), The content of the polyalkylene oxide compound relative to 100 parts by mass of the fluorine-containing polymer is 0.001 to 5.00 parts by mass. The total ratio of the tetrafluoroethylene-based units and the ethylene-based units to the total units constituting the fluorine-containing polymer is 80 mol% or more. A polymer composition in which the proportion of the ethylene-based units to the total of the tetrafluoroethylene-based units and the ethylene-based units is 20 to 70 mol%. Formula (4): R a -(O-R c ) p -O-R b In formula (4), Ra and Rb each independently represent a hydrogen atom or an alkyl group, Rc represents an alkylene group having 2 to 4 carbon atoms, and p represents an integer from 1 to 50.

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