Method for producing aqueous fluoropolymer dispersion, method for polymerizing fluoromonomer, method for producing fluoropolymer

Abstract

A novel method for producing an aqueous fluoropolymer dispersion is provided. The method comprises the steps of: reacting one or more fluoromonomers with a compound of the formula: TIFF0007792545000020.tif8136 and a non-fluorinated hydrocarbon compound which is a compound represented by the following formula (I) or a salt thereof in water to obtain an aqueous fluoropolymer dispersion; a step of aqueously polymerizing one or more fluoromonomers in the aqueous fluoromonomer dispersion to obtain an aqueous fluoropolymer dispersion; a step of dispersing one or more fluoromonomers in the aqueous fluoropolymer dispersion or a dilution thereof to obtain a second aqueous fluoromonomer dispersion; and a step of aqueously polymerizing one or more fluoromonomers in the second aqueous fluoromonomer dispersion to obtain an aqueous fluoropolymer dispersion.

Description

[Technical Field]

[0001] The present invention relates to a method for producing an aqueous fluoropolymer dispersion, and further to a method for polymerizing a fluoromonomer. [Background technology]

[0002] Fluoropolymers (fluorinated polymers), which have characteristics such as heat resistance, chemical resistance, weather resistance, low friction, and non-stick properties, have long been used in a variety of applications. Common fluoropolymers include fluororesins such as polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropene copolymer (FEP), and tetrafluoroethylene-ethylene copolymer (ETFE), as well as fluoroelastomers (FKM) and perfluoroelastomers (FFKM). Due to their characteristics, these polymers are used in moldings for valves and gaskets, as well as coatings.

[0003] Fluoropolymers can be obtained by polymerizing various fluoromonomers (fluorinated monomers) using various known polymerization techniques. However, from an industrial standpoint, they are generally produced by emulsion polymerization, in which fluoromonomers are reacted in water in the presence of a suitable emulsifier and a radical polymerization initiator.

[0004] Patent Document 1 discloses a method for producing a fluoropolymer by emulsion polymerization of one or more fluorinated monomers in an aqueous phase in the presence of a fluorinated emulsifier. Partially fluorinated or perfluorinated emulsifiers are expensive and have low biodegradability, so if they remain in the fluoropolymer, they can cause problems during waste disposal of the fluoropolymer. Patent Document 2 discloses a method for polymerizing a fluoromonomer without using an emulsifier or a surfactant. However, when a fluoromonomer is polymerized in the absence of an emulsifier, it is difficult to generate fluoromonomer particles in an aqueous medium, and sufficient reaction sites for aqueous polymerization of the fluoromonomer cannot be obtained. As a result, the stability of the resulting aqueous fluoropolymer dispersion is low, and the industrial process after the polymerization reaction is troublesome and inconvenient. Patent Document 3 discloses a method for polymerizing a fluoromonomer using a non-fluorinated emulsifier. In the method of Patent Document 3, side reactions occur due to the presence of the non-fluorinated emulsifier, making it difficult for the polymerization of the fluoromonomer to proceed stably, and therefore making it difficult to polymerize the fluoromonomer at an industrially suitable reaction rate. Furthermore, there is a problem in that the stability of the aqueous fluoropolymer dispersion obtained after polymerization is low. It is desired to propose a method for aqueous polymerization of fluoromonomers at a suitable reaction rate to produce highly stable aqueous fluoropolymer dispersions. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2010-536996 [Patent Document 2] U.S. Patent No. 5,453,477 [Patent Document 3] U.S. Patent No. 6,869,997 Summary of the Invention [Problem to be solved by the invention]

[0006] The present inventors propose a novel method for producing an aqueous fluoropolymer dispersion, which comprises first aqueously polymerizing a trace amount of fluoromonomer using a non-fluorinated emulsifier to obtain an aqueous fluoropolymer dispersion, and then aqueously polymerizing a fluoromonomer using the obtained aqueous fluoropolymer dispersion as an emulsifier. [Means for solving the problem]

[0007] One aspect of the present invention is a method for producing a pharmaceutical composition comprising the steps of: one or more fluoromonomers; The formula below: [ka] (wherein R represents a linear or branched hydrocarbon group having 4 to 20 carbon atoms, which may have a double bond and may contain an oxygen atom; and X1 and X2 may be the same or different and represent a functional group selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic acid group and a phosphonic acid group), or a salt thereof. Non-fluorinated compounds and a step of dispersing the resulting mixture in water to obtain an aqueous fluoromonomer dispersion; Aqueous polymerization of one or more fluoromonomers in an aqueous fluoromonomer dispersion to obtain a first aqueous fluoropolymer dispersion; dispersing one or more fluoromonomers in the first aqueous fluoropolymer dispersion or a dilution thereof to obtain a second aqueous fluoromonomer dispersion; and Aqueous polymerizing one or more fluoromonomers in said second aqueous fluoromonomer dispersion to obtain a second aqueous fluoropolymer dispersion; A method for producing an aqueous fluoropolymer dispersion, comprising:

[0008] An anionic surfactant may be added to the second aqueous fluoropolymer dispersion. The aforementioned Non-fluorinated compounds But the following formula: [ka] (wherein R represents a linear or branched hydrocarbon group having 4 to 20 carbon atoms, which may have a double bond and may contain an oxygen atom; and X1 and X2 represent sulfonic acid groups), or a salt thereof.

[0009] A second aspect of the present invention is a polymerizable composition comprising one or more fluoromonomers and The formula below: [ka] (wherein R represents a linear or branched hydrocarbon group having 4 to 20 carbon atoms, which may have a double bond and may contain an oxygen atom; and X1 and X2 may be the same or different and represent a functional group selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic acid group and a phosphonic acid group), or a salt thereof. Non-fluorinated compounds and, and preparing an aqueous dispersion containing water; aqueously polymerizing the one or more fluoromonomers in the aqueous dispersion to obtain a first aqueous fluoropolymer dispersion; diluting the first aqueous fluoropolymer dispersion as needed; adding one or more fluoromonomers to the first aqueous fluoropolymer dispersion or a dilution thereof to obtain a second aqueous fluoromonomer dispersion; In the method for polymerizing a fluoromonomer, the one or more added fluoromonomers are aqueous-polymerized in the second fluoromonomer aqueous dispersion to obtain a second fluoropolymer aqueous dispersion.

[0010] An anionic surfactant may be added to the second aqueous fluoropolymer dispersion. The aforementioned Non-fluorinated compounds But the following formula: [ka] (wherein R represents a linear or branched hydrocarbon group having 4 to 20 carbon atoms, which may have a double bond and may contain an oxygen atom; and X1 and X2 represent sulfonic acid groups), or a salt thereof.

[0011] A third aspect of the present invention provides a method for producing a pharmaceutical composition comprising the steps of: one or more fluoromonomers; The formula below: [ka] (wherein R represents a linear or branched hydrocarbon group having 4 to 20 carbon atoms, which may have a double bond and may contain an oxygen atom; and X1 and X2 may be the same or different and represent a functional group selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic acid group and a phosphonic acid group), or a salt thereof. Non-fluorinated compounds and dispersing the mixture in water to obtain a first fluoromonomer aqueous dispersion; Aqueous polymerizing one or more fluoromonomers in said first aqueous fluoromonomer dispersion to obtain a first aqueous fluoropolymer dispersion; dispersing one or more fluoromonomers in the first aqueous fluoropolymer dispersion or a dilution thereof to obtain a second aqueous fluoromonomer dispersion; Aqueous polymerizing one or more fluoromonomers in said second aqueous fluoromonomer dispersion to obtain a second aqueous fluoropolymer dispersion; and coagulating the fluoropolymer from the second aqueous fluoropolymer dispersion to obtain a fluoropolymer; A method for producing a fluoropolymer, comprising:

[0012] An anionic surfactant may be added to the second aqueous fluoropolymer dispersion. The aforementioned Non-fluorinated compounds But the following formula: [ka] (wherein R represents a linear or branched hydrocarbon group having 4 to 20 carbon atoms, which may have a double bond and may contain an oxygen atom; and X1 and X2 represent sulfonic acid groups), or a salt thereof. [Effects of the Invention]

[0013] By using the fluoropolymer obtained by the aqueous polymerization of the first-stage fluoromonomer as an emulsifier or dispersant, it has become possible to efficiently carry out the aqueous polymerization of the second-stage fluoromonomer. DETAILED DESCRIPTION OF THE INVENTION

[0014] The embodiments of the present invention will be described in more detail below, but the present invention is not limited to the following embodiments.

[0015] One embodiment comprises the steps of: one or more fluoromonomers; The formula below: [ka] (wherein R represents a linear or branched hydrocarbon group having 4 to 20 carbon atoms, which may have a double bond and may contain an oxygen atom; and X1 and X2 may be the same or different and represent a functional group selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic acid group and a phosphonic acid group), or a salt thereof. Non-fluorinated compounds and dispersing the mixture in water to obtain a first fluoromonomer aqueous dispersion; Aqueous polymerizing one or more fluoromonomers in said first aqueous fluoromonomer dispersion to obtain a first aqueous fluoropolymer dispersion; dispersing one or more fluoromonomers in the first aqueous fluoropolymer dispersion or a dilution thereof to obtain a second aqueous fluoromonomer dispersion; and Aqueous polymerizing one or more fluoromonomers in said second aqueous fluoromonomer dispersion to obtain a second aqueous fluoropolymer dispersion; A method for producing an aqueous fluoropolymer dispersion, comprising:

[0016] In one embodiment, the term "fluoromonomer" refers to a compound having at least one polymerizable substituent in the molecule, and is a partially fluorinated or perfluorinated compound. In this specification, the term "fluoromonomer" may be referred to as a "fluorinated monomer," and these terms may be considered to be synonymous. Examples of the fluoromonomer include tetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE), hexafluoropropene (HFP), perfluoro(2-phenoxypropyl)vinyl ether (PVE), vinylidene fluoride (VDF), trifluoroethylene (TrFE), perfluoroalkyl vinyl ethers such as perfluoromethyl vinyl ether, and perfluoroalkoxyalkyl vinyl ethers (PAAV) such as perfluoromethyl-oligo(isopropoxy)vinyl ether.

[0017] An aqueous fluoromonomer dispersion is an aqueous liquid in which a fluoromonomer is emulsified or dispersed. In this specification, the term "aqueous fluoromonomer dispersion" also includes an aqueous emulsion of a fluoromonomer.

[0018] In one embodiment, first, one or more fluoromonomers and Non-fluorinated compounds and are dispersed in water to obtain a fluoromonomer aqueous dispersion (first fluoromonomer aqueous dispersion). Non-fluorinated compounds is the following formula: [ka] (wherein R represents a linear or branched hydrocarbon group having 4 to 20 carbon atoms, which may have a double bond and may contain an oxygen atom; and X1 and X2 may be the same or different and represent a functional group selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic acid group, and a phosphonic acid group), or a salt thereof. In particular, Non-fluorinated compounds is the following formula: [ka] (wherein R represents a linear or branched hydrocarbon group having 4 to 20 carbon atoms, which may have a double bond and may contain an oxygen atom; and X1 and X2 represent sulfonic acid groups), or a salt thereof.

[0019] Non-fluorinated compounds is thought to emulsify or disperse the fluoromonomer in water, but its role is not necessarily clear. Non-fluorinated compounds does not include fluorine-containing substituents. Non-fluorinated compounds Examples of the sulfonate include alkanedisulfonates such as disodium 1,4-butanedisulfonate, disodium 1,5-pentanedisulfonate, and disodium 1,6-hexanedisulfonate. Non-fluorinated compounds can be used alone or in combination with several different compounds. one or more fluoromonomers; Non-fluorinated compounds and 3 are added to water, and the mixture is preferably stirred vigorously to obtain an aqueous fluoromonomer dispersion in which the fluoromonomer is emulsified or dispersed in water.

[0020] Next, one or more fluoromonomers are aqueously polymerized in the obtained fluoromonomer aqueous dispersion to obtain an aqueous fluoropolymer dispersion (first aqueous fluoropolymer dispersion) (first-stage polymerization of fluoromonomers). Here, aqueous polymerization refers to polymerization of monomers in an aqueous liquid, and may be any of radical polymerization, cationic polymerization, and anionic polymerization. It is preferable to add any of a radical polymerization initiator, an anionic polymerization initiator, and a cationic polymerization initiator to the fluoromonomer aqueous dispersion obtained in the previous step. Examples of the radical polymerization initiator include thermal radical polymerization initiators such as ammonium peroxodisulfate (ammonium persulfate), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), di-tert-butyl peroxide, benzoyl peroxide, and cumene hydroperoxide; and photoradical polymerization initiators such as benzil, benzophenone, benzoin isopropyl ether, benzoin ethyl ether, 4,4'-dimethylbenzyl, acetophenone, 3'-hydroxyacetophenone, and anthraquinone. Examples of the anionic polymerization initiator include photoanionic polymerization initiators such as acetophenone O-benzoyloxime, 1,2-bis(4-methoxyphenyl)-2-oxoethyl cyclohexylcarbamate, nifedipine, 2-(piperidine-1-carbonyl)benzaldehyde, 2-(O-benzoyloxime)-1-[4-(phenylthio)phenyl]-1,2-octanedione, and 2-(9-oxoxanthen-2-yl)propionic acid 1,8-diazabicyclo[5.4.0]undec-7-ene. Examples of cationic polymerization initiators include photocationic polymerization initiators such as bis(4-tert-butylphenyl)iodonium hexafluorophosphate, diphenyliodonium hexafluoroarsenate, 2-(3,4-dimethoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine, and 4-nitrobenzenediazonium tetrafluoroborate. When an oil-soluble polymerization initiator is used, the initiator is added to the fluoromonomer droplets to initiate suspension polymerization. When a water-soluble polymerization initiator is used, the initiator is added to the aqueous phase to initiate emulsion polymerization.In any event, the polymerization of the fluoromonomers herein is a heterogeneous polymerization in water. The aqueous polymerization of one or more fluoromonomers is preferably carried out by radical polymerization. The first-stage aqueous polymerization of one or more fluoromonomers is carried out at a temperature of from room temperature to 100°C, preferably from 30 to 90°C, and more preferably from 40 to 80°C, depending on the type of polymerization initiator used. The aqueous polymerization of one or more fluoromonomers is preferably carried out under deoxygenated conditions or in an inert gas environment. In this way, the first-stage aqueous polymerization of fluoromonomers in an aqueous dispersion containing one or more fluoromonomers can be carried out to obtain an aqueous fluoropolymer dispersion.

[0021] In this specification, an aqueous fluoropolymer dispersion refers to an aqueous liquid in which a fluoropolymer is emulsified or dispersed. The term "aqueous fluoropolymer dispersion" as used herein also includes an aqueous emulsion of a fluoropolymer. In the narrow sense, the term "fluoropolymer" refers to a polymer obtained by polymerizing (or copolymerizing) one or more of the above-mentioned fluoromonomers. In this specification, the term "fluoropolymer" also includes a polymer obtained by copolymerizing one or more of the above-mentioned fluoromonomers with a compound (monomer) having a polymerizable substituent. Examples of monomers that can be copolymerized with the fluoromonomer include olefins such as ethylene, propylene, butene, hexene, and octene; acrylic monomers such as methyl methacrylate, ethyl methacrylate, and methyl acrylate; and aromatic hydrocarbon monomers such as styrene and divinylbenzene.

[0022] Next, the obtained aqueous fluoropolymer dispersion is used as is or after appropriate dilution, and one or more fluoromonomers are dispersed in it to obtain a second aqueous fluoromonomer dispersion. The one or more fluoromonomers added in this stage may be exactly the same as the fluoromonomers aqueously polymerized in the first stage, or they may be different. The aqueous fluoropolymer dispersion obtained in the previous step contains the fluoropolymer described above, and this fluoropolymer plays the role of an emulsifier or dispersant.

[0023] One or more fluoromonomers can be added to the aqueous fluoropolymer dispersion or a dilution thereof, preferably with vigorous stirring, to obtain a second aqueous fluoromonomer dispersion in which the fluoromonomer is emulsified or dispersed in the aqueous fluoropolymer dispersion or a dilution thereof.

[0024] Subsequently, one or more fluoromonomers are aqueously polymerized in the second fluoromonomer aqueous dispersion (second-stage polymerization of the fluoromonomer). Here, the one or more fluoromonomers can be aqueously polymerized by either radical polymerization, cationic polymerization, or anionic polymerization, but radical polymerization is preferred. The above-mentioned polymerization initiator can be added to the second fluoromonomer aqueous dispersion, and if necessary, a chain transfer agent can also be added. In radical polymerization, the process in which a growing radical reacts with a substance other than the monomer in the polymerization system, resulting in radical transfer and reinitiation, is called a chain transfer reaction. A chain transfer agent can be used as the "other substance" in this case. When a chain transfer agent is added to the second fluoromonomer aqueous dispersion and radical polymerization is performed, the chain transfer agent accepts a radical from the growing polymer chain and generates a new radical. As a result, polymer elongation stops and another propagation reaction begins, allowing molecular weight adjustment. Examples of chain transfer agents that can be used include alkanes such as hexane, alcohols such as methanol and isopropyl alcohol, ketones such as acetone, esters such as ethyl acetate and diethyl malonate, ethers such as dimethyl ether, and many other hydrocarbon compounds. Furthermore, fluoroalkyl iodides such as 1,4-diiodooctafluorobutane and 1,6-diiodoperfluoro-n-hexane can also be used as chain transfer agents. When these are used, iodine is introduced into the fluoropolymer terminals, which can be used as reaction points during molding and vulcanization.

[0025] In this way, one or more fluoromonomers are aqueously polymerized in the second fluoromonomer aqueous dispersion to obtain a second fluoropolymer aqueous dispersion. The obtained second fluoropolymer aqueous dispersion is the target of the production method of this embodiment. Here, an anionic surfactant can be added to the second fluoropolymer aqueous dispersion to improve the dispersion stability of the second fluoropolymer aqueous dispersion. The anionic surfactant may be a widely known anionic surfactant such as sodium lauryl sulfate, sodium laureth sulfate, or sodium alkylbenzenesulfonate. The second fluoropolymer aqueous dispersion can be precipitated by salting out using a metal salt such as sodium chloride or calcium chloride, and the resulting crumbs can be washed with water and dried using a known means such as an oven to isolate the fluoropolymer.

[0026] A second embodiment of the present invention is a polymerizable composition comprising one or more fluoromonomers and The formula below: [ka] (wherein R represents a linear or branched hydrocarbon group having 4 to 20 carbon atoms, which may have a double bond and may contain an oxygen atom; and X1 and X2 may be the same or different and represent a functional group selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic acid group and a phosphonic acid group), or a salt thereof. Non-fluorinated compounds and, and preparing an aqueous dispersion containing water; aqueously polymerizing the one or more fluoromonomers in the aqueous dispersion to obtain a first aqueous fluoropolymer dispersion; adding one or more fluoromonomers to the first aqueous fluoropolymer dispersion or a dilution thereof to obtain a second aqueous fluoromonomer dispersion; This is a method for polymerizing a fluoromonomer, in which the one or more added fluoromonomers are aqueous-polymerized in the second aqueous fluoromonomer dispersion.

[0027] In the second embodiment, the fluoromonomer refers to a compound having at least one polymerizable substituent in the molecule, and is a partially fluorinated or perfluorinated compound. Examples of the fluoromonomer include tetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE), hexafluoropropene (HFP), perfluoro(2-phenoxypropyl)vinyl ether (PVE), vinylidene fluoride (VDF), trifluoroethylene (TrFE), and perfluoroalkoxyalkyl vinyl ethers such as perfluoromethyl vinyl ether and perfluoromethyl-oligo(isopropoxy)vinyl ether. Examples include esters (PAAVE).

[0028] In a second embodiment, first, one or more fluoromonomers and Non-fluorinated compounds and are dispersed in water to prepare an aqueous fluoromonomer dispersion. Non-fluorinated compounds is the following formula: [ka] (wherein R represents a linear or branched hydrocarbon group having 4 to 20 carbon atoms, which may have a double bond and may contain an oxygen atom; and X1 and X2 may be the same or different and represent a functional group selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic acid group, and a phosphonic acid group), or a salt thereof. Non-fluorinated compounds is the following formula: [ka] (wherein R represents a linear or branched hydrocarbon group having 4 to 20 carbon atoms, which may have a double bond and may contain an oxygen atom; and X1 and X2 represent sulfonic acid groups), or a salt thereof. Non-fluorinated compounds is thought to emulsify or disperse the fluoromonomer in water, but its role is not necessarily clear. Non-fluorinated compoundsdoes not include fluorine-containing substituents. Non-fluorinated compounds Examples of the sulfonate include alkanedisulfonates such as disodium 1,4-butanedisulfonate, disodium 1,5-pentanedisulfonate, and disodium 1,6-hexanedisulfonate. Non-fluorinated compounds can be used alone or in combination with several different compounds. one or more fluoromonomers; Non-fluorinated compounds and 3 are added to water, and the mixture is preferably stirred vigorously to prepare an aqueous fluoromonomer dispersion in which the fluoromonomer is emulsified or dispersed in water.

[0029] Next, one or more fluoromonomers are aqueously polymerized in the resulting fluoromonomer aqueous dispersion to obtain a fluoropolymer aqueous dispersion. It is preferable to add any one of a radical polymerization initiator, an anionic polymerization initiator, and a cationic polymerization initiator to the fluoromonomer aqueous dispersion. Examples of radical polymerization initiators include thermal radical polymerization initiators such as ammonium peroxodisulfate (ammonium persulfate), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), di-tert-butyl peroxide, benzoyl peroxide, and cumene hydroperoxide; and photoradical polymerization initiators such as benzyl, benzophenone, benzoin isopropyl ether, benzoin ethyl ether, 4,4'-dimethylbenzyl, acetophenone, 3'-hydroxyacetophenone, and anthraquinone. Examples of the anionic polymerization initiator include photoanionic polymerization initiators such as acetophenone O-benzoyloxime, 1,2-bis(4-methoxyphenyl)-2-oxoethyl cyclohexylcarbamate, nifedipine, 2-(piperidine-1-carbonyl)benzaldehyde, 2-(O-benzoyloxime)-1-[4-(phenylthio)phenyl]-1,2-octanedione, and 2-(9-oxoxanthen-2-yl)propionic acid 1,8-diazabicyclo[5.4.0]undec-7-ene. Examples of cationic polymerization initiators include photocationic polymerization initiators such as bis(4-tert-butylphenyl)iodonium hexafluorophosphate, diphenyliodonium hexafluoroarsenate, 2-(3,4-dimethoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine, and 4-nitrobenzenediazonium tetrafluoroborate. When an oil-soluble polymerization initiator is used, the polymerization initiator is added to the fluoromonomer droplets to initiate suspension polymerization. When a water-soluble polymerization initiator is used, the polymerization initiator is added to the aqueous phase to initiate emulsion polymerization. Aqueous polymerization of one or more fluoromonomers is preferably carried out by radical polymerization.

[0030] The aqueous polymerization of one or more fluoromonomers is carried out at a temperature of from room temperature to 100°C, preferably from 30 to 90°C, and more preferably from 40 to 80°C, depending on the type of polymerization initiator used. The aqueous polymerization of one or more fluoromonomers is preferably carried out under deoxygenated conditions or in an inert gas environment. In this way, the first-stage aqueous polymerization of fluoromonomers in an aqueous dispersion containing one or more fluoromonomers can be carried out to obtain an aqueous fluoropolymer dispersion (first aqueous fluoropolymer dispersion).

[0031] In the second embodiment, the fluoropolymer includes not only polymers obtained by polymerizing (or copolymerizing) one or more of the above-mentioned fluoromonomers, but also polymers obtained by copolymerizing one or more of the above-mentioned fluoromonomers with a compound (monomer) having a polymerizable substituent. Examples of the monomer copolymerizable with the fluoromonomer include olefins such as ethylene, propylene, butene, hexene, and octene, acrylic monomers such as methyl methacrylate, ethyl methacrylate, and methyl acrylate, and aromatic hydrocarbon monomers such as styrene and divinylbenzene.

[0032] Next, the obtained aqueous fluoropolymer dispersion is used as is or after appropriate dilution, and one or more fluoromonomers are dispersed in it to obtain a second aqueous fluoromonomer dispersion. The one or more fluoromonomers added in this stage may be exactly the same as the fluoromonomers aqueously polymerized in the first stage, or they may be different. The aqueous fluoropolymer dispersion obtained in the previous step contains the fluoropolymer described above, and this fluoropolymer plays the role of an emulsifier or dispersant.

[0033] One or more fluoromonomers can be added to the aqueous fluoropolymer dispersion or a dilution thereof, preferably with vigorous stirring, to obtain a second aqueous fluoromonomer dispersion in which the fluoromonomer is emulsified or dispersed in the aqueous fluoropolymer dispersion or a dilution thereof.

[0034] Subsequently, one or more fluoromonomers are aqueously polymerized in the second fluoromonomer aqueous dispersion (second-stage polymerization of the fluoromonomer). Here, the one or more fluoromonomers can be aqueously polymerized by either radical polymerization, cationic polymerization, or anionic polymerization, but radical polymerization is preferred. The above-mentioned polymerization initiator can be added to the second fluoromonomer aqueous dispersion, and if necessary, a chain transfer agent can also be added. In radical polymerization, the process in which a growing radical reacts with a substance other than the monomer in the polymerization system, resulting in radical transfer and reinitiation, is called a chain transfer reaction. A chain transfer agent can be used as the "other substance" in this case. When a chain transfer agent is added to the second fluoromonomer aqueous dispersion and radical polymerization is performed, the chain transfer agent accepts a radical from the growing polymer chain and generates a new radical. As a result, polymer elongation stops and another propagation reaction begins, allowing molecular weight adjustment. Examples of chain transfer agents that can be used include alkanes such as hexane, alcohols such as methanol and isopropyl alcohol, ketones such as acetone, esters such as ethyl acetate and diethyl malonate, ethers such as dimethyl ether, and many other hydrocarbon compounds. Furthermore, fluoroalkyl iodides such as 1,4-diiodooctafluorobutane and 1,6-diiodoperfluoro-n-hexane can also be used as chain transfer agents. When these are used, iodine is introduced into the fluoropolymer terminals, which can be used as reaction points during molding and vulcanization.

[0035] In this way, one or more fluoromonomers can be aqueously polymerized in the second fluoromonomer aqueous dispersion. As a result, a second fluoropolymer aqueous dispersion is obtained. An anionic surfactant can be added to the second fluoropolymer aqueous dispersion thus obtained to improve the dispersion stability of the second fluoropolymer aqueous dispersion. The anionic surfactant may be a widely known anionic surfactant such as sodium lauryl sulfate, sodium laureth sulfate, or sodium alkylbenzenesulfonate. The second fluoropolymer aqueous dispersion obtained can be precipitated by salting out using a metal salt such as sodium chloride or calcium chloride, and the resulting crumbs can be washed with water and dried using a known means such as an oven to isolate the fluoropolymer.

[0036] A third embodiment of the present invention is a method for producing a method for manufacturing a semiconductor device comprising the steps of: one or more fluoromonomers; The formula below: [ka] (wherein R represents a linear or branched hydrocarbon group having 4 to 20 carbon atoms, which may have a double bond and may contain an oxygen atom; and X1 and X2 may be the same or different and represent a functional group selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic acid group and a phosphonic acid group), or a salt thereof. Non-fluorinated compounds and dispersing the mixture in water to obtain a first fluoromonomer aqueous dispersion; Aqueous polymerizing one or more fluoromonomers in said first aqueous fluoromonomer dispersion to obtain a first aqueous fluoropolymer dispersion; dispersing one or more fluoromonomers in the first aqueous fluoropolymer dispersion or a dilution thereof to obtain a second aqueous fluoromonomer dispersion; Aqueous polymerizing one or more fluoromonomers in said second aqueous fluoromonomer dispersion to obtain a second aqueous fluoropolymer dispersion; and coagulating the fluoropolymer from the second aqueous fluoropolymer dispersion to obtain a fluoropolymer; A method for producing a fluoropolymer, comprising:

[0037] The third embodiment includes a step of obtaining a fluoropolymer by coagulating the second fluoropolymer aqueous dispersion produced by the first embodiment. Preferably, an anionic surfactant is added to the second fluoropolymer aqueous dispersion to improve the dispersion stability of the second fluoropolymer aqueous dispersion. The anionic surfactant may be one of widely known anionic surfactants such as sodium lauryl sulfate, sodium laureth sulfate, or sodium alkylbenzene sulfonate. The fluoropolymer coagulation is carried out, for example, by adding a metal salt such as sodium chloride or calcium chloride to the second fluoropolymer aqueous dispersion obtained by the first embodiment to precipitate the fluoropolymer by salting out. The crumbs thus obtained are washed with water and dried by known means such as an oven to obtain the fluoropolymer. [Example]

[0038] The following describes in detail the embodiments of the present invention, but the present invention is not limited to the following examples.

[0039] [Example 1] In a 10-liter stainless steel reactor equipped with a stirring blade, 4550 g of water, disodium 1,4-butanedisulfonate ( wealth1.0 g of Fujifilm (Wako Pure Chemical Industries) was charged. After charging was complete, the reactor was deoxygenated under reduced pressure and then heated to 80°C. A mixed gas of tetrafluoroethylene / hexafluoropropene / vinylidene fluoride (58 / 12 / 30 mol%) was charged until the reactor pressure reached 0.60 MPa. 150 g of an aqueous solution of ammonium persulfate (Fujifilm Wako Pure Chemical Industries) (concentration 2.7%) was charged into the reactor to initiate the aqueous polymerization reaction. When the pressure inside the reactor reached 0.37 MPa, the reactor was cooled and unreacted monomer was degassed. The reaction took 54 minutes. 4750 g of aqueous dispersion was obtained, and the solids concentration in the aqueous dispersion was 1.6 wt% (first-stage polymerization of fluoromonomer).

[0040] 1230 g of this obtained aqueous dispersion was charged together with 4170 g of water into a 10-liter stainless steel reactor equipped with a stirring blade. After charging was completed, the reactor was deoxygenated under reduced pressure and then heated to 80°C, and a mixed gas of tetrafluoroethylene / vinylidene fluoride / perfluoromethyl vinyl ether = 8 / 64 / 28 mol % was charged into the reactor until the pressure inside the reactor reached 2.7 MPa. 11 g of diiodooctafluorobutane (Tosoh Finechem) and 200 g of an aqueous solution of ammonium persulfate (concentration 0.4%) were charged into the reactor to initiate the aqueous polymerization reaction. During the reaction, the tetrafluoroethylene / vinylidene fluoride / perfluoromethyl vinyl ether A mixed gas with a molar ratio of 9 / 71 / 20 was continuously added to maintain the reaction pressure at 3.0 MPa. When the continuous addition of the mixed gas reached 1550 g, the addition was stopped, and when the pressure inside the reactor reached 1.5 MPa, the reactor was cooled and unreacted monomer was degassed. The reaction took 232 minutes. The resulting aqueous dispersion was 7738 g, and the solids concentration in the aqueous dispersion was 24.9 wt% (second-stage polymerization of fluoromonomer).

[0041] The resulting aqueous dispersion was coagulated with an aqueous calcium chloride solution (concentration 2%), and the precipitated crumbs were washed with water until the conductivity of the wash water fell below 100 μS / cm. The crumbs were then dried in an oven at 70°C for 16 hours, and the Mooney viscosity (ML(1+10)121°C) of the resulting solid was measured and found to be 49 points.

[0042] [Comparative Example 1] In Example 1, the first stage polymerization of the fluoromonomer was not carried out, and 5,000 g of water was charged into a 10-liter stainless steel reactor equipped with a stirring blade. After deoxygenation under reduced pressure, the temperature was raised to 80°C, and a tetrafluoroethylene / vinylidene fluoride / perfluoromethyl vinylidene copolymer was added. A mixed gas of tetrafluoroethylene / vinylidene fluoride / perfluoromethyl vinyl ether = 8 / 64 / 28 mol % was charged into the reactor until the pressure inside the reactor reached 2.7 MPa. 11 g of diiodooctafluorobutane and 600 ml of an aqueous ammonium sulfate solution (concentration 0.4%) were charged into the reactor to start the aqueous polymerization reaction. During the reaction, the mixture was tetrafluoroethylene / vinylidene fluoride / perfluoromethyl vinyl ether = 9 / 71 / 20 mol %. The mixed gas was continuously added to maintain the reaction pressure at 3.0 MPa. When the continuous addition of the mixed gas reached 430 g, the reaction stopped, so the reactor was cooled and unreacted monomer was degassed. The reaction took 748 minutes. The resulting aqueous dispersion was 5,970 g, and the solids concentration in the aqueous dispersion was 6.0 wt%.

[0043] The resulting aqueous dispersion was coagulated with an aqueous calcium chloride solution (concentration 2%), and the precipitated crumbs were washed with water until the conductivity of the wash water fell below 100 μS / cm. The crumbs were then dried in an oven at 70°C for 16 hours, and the Mooney viscosity (ML(1+10)121°C) of the resulting solid was measured and found to be 5 points.

[0044] have a specific structure Non-fluorinated compounds In the presence of the first stage, polymerization of the fluoromonomer was carried out to obtain an aqueous fluoropolymer dispersion, and then aqueous polymerization of the second stage fluoromonomer was carried out in the obtained aqueous fluoropolymer dispersion (Example 1). polymerizationIn this paper, we have attempted to carry out aqueous polymerization of fluoromonomers without carrying out the first stage, but were unable to achieve proper polymerization. The method of the present invention makes it possible to efficiently carry out aqueous polymerization of fluoromonomers in the second stage by using the fluoropolymer obtained by aqueous polymerization of fluoromonomers in the first stage as an emulsifier or dispersant.

Claims

1. The following steps: one or more fluoromonomers; The following formula: 【Chemistry 1】 (wherein R represents a linear or branched hydrocarbon group having 4 to 20 carbon atoms, which may have a double bond and may contain an oxygen atom; X １ and X ２ and each of the formula (I) and (II) may be the same or different and represent a functional group selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic acid group, and a phosphonic acid group, and a non-fluorinated compound which is a compound represented by the formula (I) or a salt thereof, in water to obtain a first fluoromonomer aqueous dispersion; Aqueous polymerizing one or more fluoromonomers in said first aqueous fluoromonomer dispersion to obtain a first aqueous fluoropolymer dispersion; dispersing one or more fluoromonomers, including at least one fluoromonomer different from the one or more fluoromonomers, in the first aqueous fluoropolymer dispersion or a dilution thereof to obtain a second aqueous fluoromonomer dispersion; Aqueous polymerizing one or more fluoromonomers, including at least one fluoromonomer different from the one or more fluoromonomers, in the second fluoromonomer aqueous dispersion to obtain a second fluoropolymer aqueous dispersion; A method for producing an aqueous fluoropolymer dispersion, comprising:

2. The method for producing an aqueous fluoropolymer dispersion according to claim 1, wherein an anionic surfactant is added to the second aqueous fluoropolymer dispersion.

3. The non-fluorinated compound has the following formula: 【Chemistry 2】 (wherein R represents a linear or branched hydrocarbon group having 4 to 20 carbon atoms, which may have a double bond and may contain an oxygen atom; X １ and X ２ The method for producing an aqueous fluoropolymer dispersion according to claim 1 or 2, wherein the compound is a compound represented by the formula:

4. one or more fluoromonomers; The following formula: 【Transformation 3】 (wherein R represents a linear or branched hydrocarbon group having 4 to 20 carbon atoms, which may have a double bond and may contain an oxygen atom; X １ and X ２ and each may be the same or different and represent a functional group selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic acid group, and a phosphonic acid group. and preparing an aqueous dispersion containing water; aqueously polymerizing the one or more fluoromonomers in the aqueous dispersion to obtain a first aqueous fluoropolymer dispersion; diluting the first aqueous fluoropolymer dispersion as needed; adding one or more fluoromonomers, including at least one fluoromonomer different from the one or more fluoromonomers, to the first fluoropolymer aqueous dispersion or a dilution thereof to obtain a second fluoromonomer aqueous dispersion; In the second fluoromonomer aqueous dispersion, one or more fluoromonomers containing at least one fluoromonomer different from the one or more fluoromonomers added are aqueous-polymerized to obtain a second fluoropolymer aqueous dispersion.

5. The method for polymerizing a fluoromonomer according to claim 4, wherein an anionic surfactant is added to the second aqueous fluoropolymer dispersion.

6. The non-fluorinated compound has the following formula: 【Chemistry 4】 (wherein R represents a linear or branched hydrocarbon group having 4 to 20 carbon atoms, which may have a double bond and may contain an oxygen atom; X １ and X ２ The method for polymerizing a fluoromonomer according to claim 4 or 5, wherein the fluoromonomer is a compound represented by the formula:

7. The following steps: one or more fluoromonomers; The following formula: 【Transformation 5】 (wherein R represents a linear or branched hydrocarbon group having 4 to 20 carbon atoms, which may have a double bond and may contain an oxygen atom; X １ and X ２ and each of the formula (I) and (II) may be the same or different and represent a functional group selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic acid group, and a phosphonic acid group, and a non-fluorinated compound which is a compound represented by the formula (I) or a salt thereof, in water to obtain a first fluoromonomer aqueous dispersion; Aqueous polymerizing one or more fluoromonomers in said first aqueous fluoromonomer dispersion to obtain a first aqueous fluoropolymer dispersion; dispersing one or more fluoromonomers, including at least one fluoromonomer different from the one or more fluoromonomers, in the first aqueous fluoropolymer dispersion or a dilution thereof to obtain a second aqueous fluoromonomer dispersion; Aqueous polymerizing one or more fluoromonomers, including at least one fluoromonomer different from the one or more fluoromonomers, in the second aqueous fluoromonomer dispersion to obtain a second aqueous fluoropolymer dispersion; and coagulating the fluoropolymer from the second aqueous fluoropolymer dispersion to obtain a fluoropolymer; A method for producing a fluoropolymer, comprising:

8. The method for producing a fluoropolymer according to claim 1, wherein an anionic surfactant is added to the second aqueous fluoropolymer dispersion.

9. The non-fluorinated compound has the following formula: 【Transformation 6】 (wherein R represents a linear or branched hydrocarbon group having 4 to 20 carbon atoms, which may have a double bond and may contain an oxygen atom; X １ and X ２ represents a sulfonic acid group.) or a salt thereof.

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