Method for producing perfluoroelastomer

Abstract

Provided is a method for producing a perfluoroelastomer by polymerizing tetrafluoroethylene (1) and a perfluoromonomer (2) other than tetrafluoroethylene (1) in a reaction vessel, in which the volume of water and a fluorine-containing solvent in the interior volume of the reaction vessel is 2.0 vol% or less.

Description

Technical Field

[0001] The present invention relates to a method for producing a perfluoroelastomer. Background Art

[0002] Patent Document 1 describes a method for producing a fluorine-containing polymer, which method comprises the step of polymerizing tetrafluoroethylene or chlorotrifluoroethylene in the presence of a peroxydicarbonate to obtain a fluorine-containing polymer. The peroxydicarbonate is represented by the following general formula.

[0003] ROC(=O)-OOC(=O)-OR

[0004] (In the formula, R is the same or different and represents an alkyl group or an alkoxyalkyl group having 4 carbon atoms.)

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2015-7218 Summary of the invention

[0008] Problems to be solved by the invention

[0009] An object of the present invention is to provide a method for producing a perfluoroelastomer without using water or a fluorinated solvent at all or almost at all.

[0010] Means for solving problems

[0011] According to the present invention, there is provided a method for producing a perfluoroelastomer, which comprises polymerizing tetrafluoroethylene (1) and a perfluoromonomer (2) other than tetrafluoroethylene (1) in a reaction vessel to produce the perfluoroelastomer, wherein the volume of water and fluorine-containing solvent in the internal volume of the reaction vessel is 2.0 volume % or less.

[0012] Effects of the Invention

[0013] According to the present invention, it is possible to provide a method for producing a perfluoroelastomer without using water or a fluorinated solvent at all or almost at all. DETAILED DESCRIPTION

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

[0015] Patent Document 1 describes that polymerization for obtaining a fluorinated polymer is carried out by emulsion polymerization, suspension polymerization, solution polymerization or bulk polymerization. However, a method for producing a perfluoroelastomer by bulk polymerization or the like without using water or a fluorinated solvent at all or almost at all is unknown.

[0016] The manufacture method of the present invention is a manufacture method for manufacturing perfluoroelastomer by polymerizing tetrafluoroethylene (1) and perfluoromonomer (2) other than tetrafluoroethylene (1) in a reaction vessel. During polymerization, the volume shared by water and fluorinated solvent in the internal volume of the reaction vessel is set to below 2.0 volume %. Therefore, according to the manufacture method of the present invention, perfluoroelastomer can certainly be manufactured smoothly, and perfluoroelastomer can be recovered without the necessary precipitation process in the previous manufacture method. In addition, a solvent containing a precipitating agent is produced after precipitation in the previous manufacture method, but owing to not needing the precipitation process, the generation of such a solvent can be avoided. And then, owing to not needing to use precipitating agents such as metal salts, acids, even when using metal pipes and grooves to manufacture perfluoroelastomer, the pollution of perfluoroelastomer caused by the metal component from the precipitating agent or the metal component produced by the corrosion of the metal pipes and grooves can be avoided.

[0017] The volume of water and the fluorinated solvent in the internal volume of the reaction container is 2.0 volume % or less, preferably 1.0 volume % or less, and more preferably 0.1 volume % or less. In the production method of the present invention, for example, a solution prepared by dissolving a polymerization initiator in a fluorinated solvent may be added to the reaction container, but the amount of the fluorinated solvent added to the reaction container needs to be suppressed within the above numerical range.

[0018] The internal volume of the reaction container can be obtained by measuring the volume of water required to fill the reaction container, for example.

[0019] In the production method of the present invention, water and fluorinated solvents are not used at all or are hardly used during polymerization. "Fluorinated solvents" include compounds containing fluorine, i.e., inactive compounds used as solvents, but do not include compounds that react with other compounds during polymerization, such as monomers, polymerization initiators, chain transfer agents, and polymerization terminators.

[0020] In the production method of the present invention, it is also a preferred embodiment that the volume of water, fluorinated solvent and carbon dioxide in the internal volume of the reaction container is 2.0 volume % or less. Carbon dioxide also includes supercritical carbon dioxide (carbon dioxide in a supercritical state).

[0021] In the production method of the present invention, it is also one of the preferred embodiments that the volume of water, fluorinated solvent and non-fluorinated solvent (excluding water) in the internal volume of the reaction container is 2.0 volume % or less. That is, in the production method of the present invention, it is preferred that no inert solvent is used at all or almost not used during the polymerization.

[0022] The volume of water, fluorinated solvent and fluorinated solvent (excluding water) in the internal volume of the reaction container is preferably 2.0 volume % or less, more preferably 1.0 volume % or less, and further preferably 0.1 volume % or less. In the production method of the present invention, for example, a solution prepared by dissolving a polymerization initiator in a fluorinated solvent or a fluorinated solvent may be added to the reaction container, but the amount of the fluorinated solvent or the fluorinated solvent added to the reaction container needs to be suppressed within the above numerical range.

[0023] In the manufacturing method of the present invention, during the polymerization, it is preferred that at least a portion of the perfluoromonomer (2) is present in the reaction vessel in the form of a liquid. By allowing at least a portion of the perfluoromonomer (2) to be present in the form of a liquid, the polymerization reaction of tetrafluoroethylene (1) and the perfluoromonomer (2) can be carried out smoothly. By appropriately adjusting the polymerization temperature and the internal pressure of the reaction vessel, and appropriately selecting the type of perfluoromonomer (2), at least a portion of the perfluoromonomer (2) can be present in the form of a liquid during the polymerization reaction. In the manufacturing method of the present invention, allowing at least a portion of the perfluoromonomer (2) to be present in the form of a liquid in the reaction vessel during the entire period from the start to the stop of the polymerization reaction is also one of the preferred embodiments.

[0024] In the manufacturing method of the present invention, during polymerization, it is preferred that the internal pressure of the reaction container is greater than the saturated vapor pressure of the perfluoromonomer (2) at the temperature of the liquid in the reaction container. By increasing the internal pressure of the reaction container to greater than the saturated vapor pressure, at least a portion of the perfluoromonomer (2) is easily present in the form of liquid in the reaction container during polymerization, so that the polymerization reaction of tetrafluoroethylene (1) and perfluoromonomer (2) can proceed smoothly. The internal pressure of the reaction container can be adjusted by the amount of tetrafluoroethylene (1) pressed into the reaction container. In the manufacturing method of the present invention, it is also one of the preferred embodiments to maintain the internal pressure of the reaction container at greater than the saturated vapor pressure of the perfluoromonomer (2) at the temperature of the liquid in the reaction container during the entire period from the start to the stop of the polymerization reaction.

[0025] In the production method of the present invention, the internal pressure of the reaction container during polymerization is, for example, 0.05 MPaG to 10 MPaG. It is also a preferred embodiment to adjust the internal pressure of the reaction container during polymerization within the range of 0.05 MPaG to 10 MPaG to a value not less than the saturated vapor pressure of the perfluoromonomer (2) at the temperature of the liquid in the reaction container.

[0026] In the production method of the present invention, the polymerization temperature is, for example, 5 to 120° C. It is also a preferred embodiment to adjust the polymerization temperature within the range of 5 to 120° C. so that the internal pressure of the reaction container during polymerization is equal to or higher than the saturated vapor pressure of the perfluoromonomer (2) at the temperature of the liquid in the reaction container.

[0027] In the production method of the present invention, tetrafluoroethylene (1) and a perfluoromonomer (2) other than tetrafluoroethylene (1) are polymerized.

[0028] In the present invention, a perfluoromonomer refers to a monomer that does not contain a carbon atom-hydrogen atom bond in the molecule. However, in the case where the perfluoromonomer is a monomer that provides a crosslinking site, the crosslinking site may contain a carbon atom-hydrogen atom bond. The perfluoromonomer may also be a monomer in which some of the fluorine atoms bonded to carbon atoms other than carbon atoms and fluorine atoms are replaced by chlorine atoms, and may also have nitrogen atoms, oxygen atoms, sulfur atoms, phosphorus atoms, boron atoms or silicon atoms in addition to carbon atoms.

[0029] In the present invention, the monomer providing a crosslinking site refers to a monomer having a crosslinking group that provides a crosslinking site for forming a crosslink to the fluorinated polymer (curing site monomer). Examples of the crosslinking site include -I, -CH2I, -Br, -CH2Br, -CN, carboxyl, alkoxycarbonyl, hydroxyl, vinyl, azido, sulfonylazido, carbonylazido, alkynyl (e.g., ethynyl), etc.

[0030] Examples of the perfluoromonomer (2) other than tetrafluoroethylene (1) include:

[0031] Hexafluoropropylene [HFP],

[0032] General formula (21): CF2=CF-ORf 13

[0033] (Where Rf 13 represents a perfluoroalkyl group having 1 to 8 carbon atoms. ) A fluorinated monomer represented by the general formula (22): CF2=CFOCF2ORf 14

[0034] (Where Rf 14 A fluorinated monomer represented by a perfluoroalkyl group having 1 to 6 carbon atoms, a cyclic perfluoroalkyl group having 5 to 6 carbon atoms, or a perfluorooxyalkyl group having 2 to 6 carbon atoms containing an oxygen atom between carbon atoms, and

[0035] General formula (23): CF2 = CFO-((CF2) l -CF(Y 15 )O) m -(CF2) n F

[0036] (In the formula, Y 15 represents a fluorine atom or a trifluoromethyl group. l is an integer of 1 to 4, m is an integer of 1 to 4, and n is an integer of 1 to 4. ) represents a fluorine-containing monomer,

[0037] General formula (24): CX 4 2=CX 5 Rf 2 X 6

[0038] (Where X 4 , X 5 are independently F or a perfluoroalkyl group, R f 2 is a perfluoroalkylene group which may have an oxygen atom between one or more carbon atoms and may have an aromatic ring, X 6 A monomer providing a crosslinking site represented by -I, -CH2I, -Br, -CH2Br, -CN, carboxyl, alkoxycarbonyl, hydroxyl, vinyl, azido, sulfonylazido, carbonylazido or alkynyl (e.g., ethynyl); etc.

[0039] In the present invention, the perfluoroalkyl group and the perfluorooxyalkylene group may be either linear or branched.

[0040] The fluorinated monomer represented by the general formula (21) is preferably at least one selected from the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether) and perfluoro(propyl vinyl ether), more preferably at least one selected from the group consisting of perfluoro(methyl vinyl ether) and perfluoro(propyl vinyl ether), and further preferably perfluoro(methyl vinyl ether).

[0041] The fluorine-containing monomer represented by the general formula (22) is preferably at least one selected from the group consisting of CF2=CFOCF2OCF3, CF2=CFOCF2OCF2CF3 and CF2=CFOCF2OCF2CF2OCF3.

[0042] The fluorine-containing monomer represented by the general formula (23) is preferably at least one selected from the group consisting of CF2=CFOCF2CF(CF3)O(CF2)3F, CF2=CFO(CF2CF(CF3)O)2(CF2)3F, CF2=CFO(CF2CF(CF3)O)2(CF2)2F and CF2=CFOCF2CF2CF2OCF3.

[0043] Examples of the monomer providing a crosslinking site represented by the general formula (24) include:

[0044] General formula: CF2 = CFO (CF2CF (CF3) O) m (CF2) n -X 201

[0045] (wherein, m is an integer from 0 to 5, n is an integer from 1 to 3, and X 201 is -I, -CH2I, -Br, -CH2Br, -CN, carboxyl or alkoxycarbonyl. ) is a fluorine-containing monomer. X201 Preferred are -I, -CH2I, -Br, -CH2Br or -CN.

[0046] As the monomer providing a cross-linking site represented by the general formula (24), it is preferably at least one selected from the group consisting of CF2=CFOCF2CF(CF3)OCF2CF2CN, CF2=CFOCF2CF(CF3)OCF2CF2COOH, CF2=CFOCF2CF(CF3)OCF2CF2CH2I, CF2=CFOCF2CF2CH2I and CF2=CFO(CF2)5CN, and more preferably at least one selected from the group consisting of CF2=CFOCF2CF(CF3)OCF2CF2CN and CF2=CFOCF2CF2CH2I.

[0047] In the polymerization of the perfluoromonomer, a monomer providing a crosslinking site (excluding the perfluoromonomer) may be polymerized together with the perfluoromonomer.

[0048] As the monomer providing a crosslinking site (excluding perfluoro monomers), it is preferably selected from

[0049] General formula (11): CX 181 2=CX 182 -R f 181 CHR 181 X 183

[0050] (Where X 181 and X 182 are independently a hydrogen atom, a fluorine atom or CH3, R f 181 is a fluoroalkylene group, a perfluoroalkylene group, a fluoro(poly)oxyalkylene group or a perfluoro(poly)oxyalkylene group, R 181 is a hydrogen atom or CH3, X 183 is an iodine atom or a bromine atom),

[0051] General formula (12): CX 191 2=CX 192 -R f 191 X 193

[0052] (Where X 191 and X 192 are independently a hydrogen atom, a fluorine atom or CH3, R f 191 is a fluoroalkylene group, a perfluoroalkylene group, a fluoropolyoxyalkylene group or a perfluoropolyoxyalkylene group, X 193 is an iodine atom or a bromine atom),

[0053] General formula (13): CH2=CFCF2O(CF(CF3)CF2O) m (CF(CF3)) n -X 211

[0054] (wherein, m is an integer from 0 to 5, n is an integer from 1 to 3, and X 211 is a fluorine-containing monomer represented by a cyano group, a carboxyl group, an alkoxycarbonyl group, an iodine atom, a bromine atom or -CH2OH), and

[0055] General formula (14): CR 221 R 222 =CR 223 -Z 221 -CR 224 =CR 225 R 226

[0056] (Where R 221 , R 222 , R 223 , R 224 , R 225 and R 226 Z are the same or different and are hydrogen or an alkyl group having 1 to 5 carbon atoms. 221 A linear or branched alkylene group having 1 to 18 carbon atoms, a cycloalkylene group having 3 to 18 carbon atoms, an alkylene group or an oxyalkylene group having 1 to 10 carbon atoms which is at least partially fluorinated, or

[0057] -(Q) p -CF2O-(CF2CF2O) m (CF2O) n -CF2-(Q) p -

[0058] (wherein Q is an alkylene group or an oxyalkylene group. p is 0 or 1. m / n is 0.2 to 5) and a (per)fluoropolyoxyalkylene group having a molecular weight of 500 to 10000)

[0059] At least one of the group consisting of.

[0060] X 183 and X 193 Preferably it is an iodine atom. f 181 and R f 191 It is preferably a perfluoroalkylene group having 1 to 5 carbon atoms. 181 Preferably, it is a hydrogen atom. 211Preferred is a cyano group, an alkoxycarbonyl group, an iodine atom, a bromine atom or -CH2OH.

[0061] As a monomer providing a cross-linking site (excluding perfluoro monomers), it is preferably at least one selected from the group consisting of CH2=CFCF2OCF(CF3)CF2OCF(CF3)CN, CH2=CFCF2OCF(CF3)CF2OCF(CF3)COOH, CH2=CFCF2OCF(CF3)CF2OCF(CF3)CH2OH, CH2=CHCF2CF2I, CH2=CH(CF2)2CH=CH2 and CH2=CH(CF2)6CH=CH2.

[0062] As the perfluoromonomer (2), among them, preferred

[0063] General formula (2): CF2=CY-Rf-X

[0064] (wherein, Rf is a perfluoroalkylene group, a perfluoroalkylene group containing an oxygen atom between carbon atoms, a perfluoroalkylene oxide group, or a perfluoroalkylene oxide group containing an oxygen atom between carbon atoms, X is -F, -I, -CH2I, -Br, -CH2Br or -CN, and Y is F or a perfluoroalkyl group).

[0065] By using the monomer represented by the general formula (2) as the perfluoromonomer (2), at least a portion of the perfluoromonomer (2) is likely to exist in the form of liquid in the reaction vessel during polymerization, and the polymerization reaction of tetrafluoroethylene (1) and the perfluoromonomer (2) can proceed smoothly.

[0066] In the general formula (2), Rf is preferably a perfluoroalkylene group having 1 to 12 carbon atoms, a perfluoroalkylene group having 2 to 12 carbon atoms and containing an oxygen atom between carbon atoms, a perfluoroalkylene oxide group having 1 to 12 carbon atoms, or a perfluoroalkylene oxide group containing an oxygen atom between carbon atoms.

[0067] In the general formula (2), Y is preferably F or a perfluoroalkyl group having 1 to 12 carbon atoms, and more preferably F or CF3.

[0068] As the perfluoromonomer (2), preferably selected from the group consisting of

[0069] General formula (2a): CF2=CY-O-Rf 11

[0070] (Where Rf 11 is a perfluoroalkyl group, or a perfluoroalkyl group containing an oxygen atom between carbon atoms, and Y is F or a perfluoroalkyl group), and

[0071] General formula (2b): CF2=CY-Rf 12-X

[0072] (Where Rf 12 is a monomer represented by a perfluoroalkylene group, a perfluoroalkylene group containing an oxygen atom between carbon atoms, a perfluoroalkylene oxide group, or a perfluoroalkylene oxide group containing an oxygen atom between carbon atoms, X is -I, -CH2I, -Br, -CH2Br or -CN, and Y is F or a perfluoroalkyl group)

[0073] At least one of the group consisting of.

[0074] As the perfluoromonomer (2), among them, preferred

[0075] General formula (2a): CF2=CY-O-Rf 11

[0076] (Where Rf 11 is a perfluoroalkyl group, or a perfluoroalkyl group containing an oxygen atom between carbon atoms, and Y is F or a perfluoroalkyl group).

[0077] When the monomer represented by the general formula (2a) is used as the perfluoromonomer (2), it is also one of the preferred embodiments to use a monomer represented by the general formula (2b) together with the monomer represented by the general formula (2a).

[0078] In the general formula (2a), Rf 11 , preferably a perfluoroalkyl group having 1 to 12 carbon atoms, or a perfluoroalkyl group having 2 to 12 carbon atoms containing an oxygen atom between carbon atoms.

[0079] In the general formula (2a), Y is preferably F or a perfluoroalkyl group having 1 to 12 carbon atoms, and more preferably F or CF3.

[0080] In the general formula (2b), Rf 12 , preferably a perfluoroalkylene group having 1 to 12 carbon atoms, a perfluoroalkylene group having 2 to 12 carbon atoms and containing an oxygen atom between carbon atoms, a perfluoroalkylene oxide having 1 to 12 carbon atoms, or a perfluoroalkylene oxide containing an oxygen atom between carbon atoms.

[0081] In the general formula (2b), Y is preferably F or a perfluoroalkyl group having 1 to 12 carbon atoms, and more preferably F or CF3.

[0082] The monomer represented by the general formula (2a) is preferably at least one selected from the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether) and perfluoro(propyl vinyl ether), more preferably at least one selected from the group consisting of perfluoro(methyl vinyl ether) and perfluoro(propyl vinyl ether), and further preferably perfluoro(methyl vinyl ether).

[0083] As the monomer represented by the general formula (2b), it is preferably at least one selected from the group consisting of CF2=CFOCF2CF(CF3)OCF2CF2CN, CF2=CFOCF2CF(CF3)OCF2CF2COOH, CF2=CFOCF2CF(CF3)OCF2CF2CH2I, CF2=CFOCF2CF2CH2I and CF2=CFO(CF2)5CN, and it is more preferably at least one selected from the group consisting of CF2=CFOCF2CF(CF3)OCF2CF2CN and CF2=CFOCF2CF2CH2I.

[0084] When a monomer having an iodine atom is used as the perfluoromonomer (2), the iodine content of the obtained perfluoroelastomer is preferably 0.02 to 5.0 mass %, more preferably 0.05 to 3.0 mass %, and even more preferably 0.1 to 2.0 mass %, from the viewpoint that the perfluoroelastomer can be peroxide-crosslinked to obtain an elastomer having excellent mechanical properties.

[0085] In the production method of the present invention, the polymerization of the perfluoromonomer can be carried out in the presence of a polymerization initiator. As the polymerization initiator, for example, the following peroxides can be cited as representative substances:

[0086] Dialkyl peroxycarbonates such as diisopropyl peroxydicarbonate and di-sec-butyl peroxydicarbonate;

[0087] Peroxyesters such as tert-butyl peroxyisobutyrate and tert-butyl peroxypivalate;

[0088] Dialkyl peroxides such as di-tert-butyl peroxide;

[0089] di(ω-hydro-dodecafluoroheptanoyl) peroxide, di(ω-hydro-tetrafluorooctanoyl) peroxide, di(ω-hydro-hexafluorononanoyl) peroxide, di(perfluorobutyryl) peroxide, di(perfluoropentanoyl) peroxide, di(perfluorohexanoyl) peroxide, di(perfluoroheptanoyl) peroxide, di(perfluorooctanoyl) peroxide, di(perfluorononanoyl) peroxide, di(ω-chloro-hexafluorobutyryl) peroxide, di(ω-chloro-decafluorohexanoyl) peroxide, di(ω-chloro-tetrafluorooctanoyl) peroxide, ) peroxide, ω-hydro-dodecafluoroheptanoyl-ω-hydrohexafluorononanoyl-peroxide, ω-chloro-hexafluorobutyryl-ω-chloro-decafluorohexanoyl-peroxide, ω-hydro-dodecafluoroheptanoyl-perfluorobutyryl-peroxide, bis(dichloropentafluorobutyryl) peroxide, bis(trichlorooctafluorohexanoyl) peroxide, bis(tetrachloroundecanoyl) peroxide, bis(pentachlorotetrafluorodecanoyl) peroxide, bis(undecanoyltriafluorobehenoyl) peroxide and the like di[perfluoro(or chlorofluoro)acyl] peroxides;

[0090] Iodine / bromine peroxides such as di(3-iodo-2,2,3,3-tetrafluoropropionyl) peroxide, di(difluoroiodoacetyl) peroxide, di(bromodifluoroacetyl) peroxide, and di(bromofluoroiodoacetyl) peroxide;

[0091] 3,3-Dioxybis(2,2-difluoro-3-oxopropanenitrile) and other nitrile-containing peroxides.

[0092] The amount of the polymerization initiator added is preferably 0.0001 to 10% by mass, more preferably 0.01 to 5% by mass, when the total of tetrafluoroethylene (1) and perfluoromonomer (2) is 100% by mass.

[0093] The timing of adding the polymerization initiator in the polymerization is not particularly limited, and it can be added before the start of the polymerization or after the start of the polymerization. In addition, in the above-mentioned polymerization, the polymerization initiator can be added at any time or continuously. The so-called continuous addition of the polymerization initiator, for example, refers to adding the polymerization initiator not at one time but over time and uninterruptedly or in batches. In the case of continuous addition of the polymerization initiator, it is preferably added in a manner that the total amount of the added polymerization initiator becomes the addition amount within the above range. In the case of adding the polymerization initiator, a solution containing the polymerization initiator and the fluorinated solvent can be prepared and added.

[0094] In the production method of the present invention, the polymerization of the monomer is usually carried out in the absence of a surfactant. As the surfactant, a fluorinated surfactant can be mentioned. As the fluorinated surfactant, an anionic fluorinated surfactant can be mentioned. The anionic fluorinated surfactant can be, for example, a surfactant containing fluorine atoms in which the total carbon number of the part other than the anionic group is 20 or less.

[0095] In the present invention, "in the absence of a surfactant" means that the amount of the surfactant is 10 ppm by mass or less relative to the total mass of tetrafluoroethylene (1) and perfluoromonomer (2). The amount of the surfactant is preferably 1 ppm by mass or less, more preferably 100 ppb by mass or less, further preferably 10 ppb by mass or less, and even more preferably 1 ppb by mass or less.

[0096] The polymerization reaction of tetrafluoroethylene (1) and perfluoromonomer (2) can be initiated, for example, in the following manner: oxygen is removed from a pressure-resistant reaction vessel equipped with a stirrer, perfluoromonomer (2) is added to the reaction vessel to reach a specified temperature, tetrafluoroethylene (1) is added to the reaction vessel to reach a specified pressure, and a polymerization initiator is added to the reaction vessel to initiate the polymerization reaction. At the moment when a specified amount of tetrafluoroethylene (1) is supplied, the supply is stopped, the tetrafluoroethylene (1) in the reaction vessel is purged, and the reaction is stopped. In the case where the pressure decreases as the reaction proceeds, additional tetrafluoroethylene (1) can be continuously or intermittently added to the reaction vessel to maintain the initial pressure. In addition, additional perfluoromonomer (2) can be continuously or intermittently added to the reaction vessel as needed.

[0097] In one embodiment of the production method of the present invention, after the polymerization is completed, the generated perfluoroelastomer is obtained in a state of being dissolved in a liquid perfluoromonomer (2) in a reaction vessel. Therefore, by recovering the perfluoroelastomer solution in the reaction vessel and drying the recovered solution, a block-shaped perfluoroelastomer can be obtained. The drying temperature is preferably 40° C. to 250° C.

[0098] In the production method of the present invention, a perfluoroelastomer is produced.

[0099] In the present invention, an elastomer refers to an amorphous polymer. "Amorphous" means that the size of the melting peak (ΔH) appearing in the differential scanning calorimetry [DSC] (heating temperature 10°C / min) or differential thermal analysis [DTA] (heating rate 10°C / min) of the polymer is 4.5 J / g or less. The perfluoroelastomer exhibits elastomeric properties by crosslinking. Elastomeric properties refer to the following properties: the polymer can be stretched and can maintain its original length when the force required to stretch the polymer is no longer applied.

[0100] In the present invention, the perfluoroelastomer refers to a fluorine-containing polymer having a perfluoro monomer unit content of 90 mol% or more, preferably 91 mol% or more relative to the total polymer units, a fluorine-containing polymer having a glass transition temperature of 25°C or less, a melting peak (ΔH) of 4.5 J / g or less, and a fluorine-containing polymer having a fluorine atom concentration of 71 mass% or more, preferably 71.5 mass% or more. In the present invention, the concentration of fluorine atoms contained in the fluorine-containing polymer is calculated by the type and content of each monomer constituting the fluorine-containing polymer to obtain the concentration (mass%) of fluorine atoms contained in the fluorine-containing polymer.

[0101] In the present invention, the content of each monomer constituting the perfluoroelastomer can be calculated by appropriately combining NMR, FT-IR, elemental analysis, fluorescent X-ray analysis, and other known methods according to the types of monomers.

[0102] The glass transition temperature of the perfluoroelastomer is 25°C or lower, preferably 5°C or lower, more preferably 1°C or lower, preferably -70°C or higher, more preferably -60°C or higher, further preferably -50°C or higher.

[0103] The glass transition temperature can be calculated as follows: using a differential scanning calorimeter (DSC822e, manufactured by Mettler-Toledo), 10 mg of a sample is heated at 10°C / min to obtain a DSC curve, and the temperature is calculated as the midpoint of the two intersections of the extended line of the baseline before and after the secondary transition of the DSC curve and the tangent line at the inflection point of the DSC curve.

[0104] The ratio of tetrafluoroethylene (1) units to perfluoromonomer (2) units ((1) / (2)) in the perfluoroelastomer is preferably 45 to 90 / 55 to 10 (mol %). In order to obtain a perfluoroelastomer having such a molar ratio, the polymerization reaction of tetrafluoroethylene (1) and perfluoromonomer (2) can be smoothly carried out by adjusting the ratio of tetrafluoroethylene (1) and perfluoromonomer (2) charged into a reaction vessel.

[0105] The perfluoroelastomer is preferably at least one selected from the group consisting of a copolymer of tetrafluoroethylene (TFE) / a fluorinated monomer represented by the general formula (21), (22) or (23) and a copolymer of TFE / a fluorinated monomer represented by the general formula (21), (22) or (23) / a monomer providing a crosslinking site.

[0106] The composition thereof is preferably 45 to 90 / 10 to 55 (mol %), more preferably 55 to 80 / 20 to 45, and even more preferably 55 to 70 / 30 to 45 in the case of a TFE / perfluoro(methyl vinyl ether) (PMVE) copolymer.

[0107] In the case of a copolymer of TFE / PMVE / a monomer providing a crosslinking site, the ratio is preferably 45 to 89.9 / 10 to 54.9 / 0.01 to 4 (mol %), more preferably 55 to 77.9 / 20 to 49.9 / 0.1 to 3.5, and further preferably 55 to 69.8 / 30 to 44.8 / 0.2 to 3.

[0108] In the case of a copolymer of TFE / a fluorinated monomer having 4 to 12 carbon atoms and represented by the general formula (21), (22) or (23), the ratio is preferably 50 to 90 / 10 to 50 (mol %), more preferably 60 to 88 / 12 to 40, further preferably 65 to 85 / 15 to 35.

[0109] In the case of a copolymer of TFE / a fluorinated monomer represented by the general formula (21), (22) or (23) having 4 to 12 carbon atoms / a monomer providing a crosslinking site, the ratio is preferably 50 to 89.9 / 10 to 49.9 / 0.01 to 4 (mol %), more preferably 60 to 87.9 / 12 to 39.9 / 0.1 to 3.5, and still more preferably 65 to 84.8 / 15 to 34.8 / 0.2 to 3.

[0110] Outside this composition range, the properties as a rubber elastic body are lost and the properties close to those of a resin tend to be exhibited.

[0111] The perfluoroelastomer is preferably at least one selected from the group consisting of a copolymer of TFE / fluorinated monomer represented by the general formula (23) / fluorinated monomer providing crosslinking sites, a copolymer of TFE / perfluorovinyl ether represented by the general formula (23), a copolymer of TFE / fluorinated monomer represented by the general formula (21) and a copolymer of TFE / fluorinated monomer represented by the general formula (21) / monomer providing crosslinking sites.

[0112] Examples of the perfluoroelastomer include those described in International Publication No. 97 / 24381, Japanese Examined Patent Publication No. 61-57324, Japanese Examined Patent Publication No. 4-81608, and Japanese Examined Patent Publication No. 5-13961.

[0113] In view of good heat resistance, the Mooney viscosity ML (1+20) of the perfluoroelastomer at 170° C. is preferably 30 or more, more preferably 40 or more, and further preferably 50 or more. In view of good processability, it is preferably 150 or less, more preferably 120 or less, and further preferably 110 or less.

[0114] In view of good heat resistance, the Mooney viscosity ML (1+20) of the perfluoroelastomer at 140° C. is preferably 30 or more, more preferably 40 or more, and further preferably 50 or more. In view of good processability, it is preferably 180 or less, more preferably 150 or less, and further preferably 110 or less.

[0115] In view of good heat resistance, the Mooney viscosity ML (1+10) of the perfluoroelastomer at 100° C. is preferably 10 or more, more preferably 20 or more, and further preferably 30 or more. In view of good processability, it is preferably 120 or less, more preferably 100 or less, and further preferably 80 or less.

[0116] The Mooney viscosity can be measured at 170° C., 140° C., or 100° C. in accordance with JIS K6300 using a Mooney viscometer MV2000E manufactured by ALPHA TECHNOLOGIES.

[0117] A curing agent, a filler, etc. may be added to the perfluoroelastomer obtained by the production method of the present invention to prepare a perfluoroelastomer composition.

[0118] Examples of the curing agent include polyols, polyamines, organic peroxides, organic tin, bis(aminophenol)tetraamine, and bis(thioaminophenol).

[0119] By using the above perfluoroelastomer for molding, a perfluoroelastomer molded body can be obtained. The above molding method is not particularly limited, and a known method using the above curing agent can be cited. As molding methods, compression molding, injection molding, injection molding, extrusion molding, and molding using a drum vulcanizer (rotocure) can be exemplified, but are not limited to these.

[0120] When the perfluoroelastomer composition contains a curing agent (crosslinking agent), a crosslinked product can be obtained in the form of a perfluoroelastomer molded body by crosslinking the perfluoroelastomer composition. As the crosslinking method, a steam crosslinking method, a crosslinking method using heating, a radiation crosslinking method, etc. can be used, among which a steam crosslinking method and a crosslinking method using heating are preferred. As non-limiting specific crosslinking conditions, it is usually appropriately determined according to the types of crosslinking accelerators, crosslinking agents, acid acceptors, etc. within a temperature range of 140°C to 250°C and a crosslinking time of 1 minute to 24 hours.

[0121] The perfluoroelastomer molded article is suitable for seals, gaskets, wire coverings, hoses, tubes, laminates, decorative articles, and the like, and is particularly suitable for parts for semiconductor manufacturing equipment, automobile parts, and the like.

[0122] Although the embodiments have been described above, it should be understood that various modifications may be made to the embodiments and details without departing from the spirit and scope of the claims.

[0123] <1> According to a first aspect of the present invention, there is provided a method for producing a perfluoroelastomer, the method comprising polymerizing tetrafluoroethylene (1) and a perfluoromonomer (2) other than tetrafluoroethylene (1) in a reaction vessel to produce the perfluoroelastomer, wherein the volume of water and the fluorine-containing solvent in the internal volume of the reaction vessel is 2.0% by volume or less.

[0124] <2> According to a second aspect of the present invention, there is provided the production method according to the first aspect, wherein at least a portion of the perfluoromonomer (2) is present in the form of a liquid in the reaction container.

[0125] <3> According to a third aspect of the present invention, there is provided the production method according to the second aspect, wherein the internal pressure of the reaction container is equal to or higher than the saturated vapor pressure of the perfluoromonomer (2) at the temperature of the liquid in the reaction container.

[0126] <4> According to a fourth aspect of the present invention, there is provided the production method according to any one of the first to third aspects, wherein the perfluoromonomer (2) is a monomer represented by the following general formula (2).

[0127] General formula (2): CF2=CY-Rf-X

[0128] (wherein, Rf is a perfluoroalkylene group, a perfluoroalkylene group containing an oxygen atom between carbon atoms, a perfluoroalkylene oxide group, or a perfluoroalkylene oxide group containing an oxygen atom between carbon atoms, X is -F, -I, -CH2I, -Br, -CH2Br or -CN, and Y is F or a perfluoroalkyl group)

[0129] <5> According to a fifth aspect of the present invention, there is provided a production method based on any one of the first to fourth aspects, wherein the perfluoromonomer (2) is at least one selected from the group consisting of a monomer represented by the following general formula (2a) and a monomer represented by the following general formula (2b).

[0130] General formula (2a): CF2=CY-O-Rf 11

[0131] (Where Rf 11 is a perfluoroalkyl group, or a perfluoroalkyl group containing an oxygen atom between carbon atoms, and Y is F or a perfluoroalkyl group)

[0132] General formula (2b): CF2=CY-Rf 12 -X

[0133] (Where Rf 12 is a perfluoroalkylene group, a perfluoroalkylene group containing an oxygen atom between carbon atoms, a perfluoroalkylene oxide group, or a perfluoroalkylene oxide group containing an oxygen atom between carbon atoms, X is -I, -CH2I, -Br, -CH2Br or -CN, and Y is F or a perfluoroalkyl group)

[0134] <6> According to a sixth aspect of the present invention, there is provided the production method according to any one of the first to fifth aspects, wherein the perfluoromonomer (2) is a monomer represented by the following general formula (2a).

[0135] General formula (2a): CF2=CY-O-Rf 11

[0136] (Where Rf 11is a perfluoroalkyl group, or a perfluoroalkyl group containing an oxygen atom between carbon atoms, and Y is F or a perfluoroalkyl group)

[0137] <7> According to a seventh aspect of the present invention, there is provided the production method according to any one of the first to sixth aspects, wherein the perfluoroelastomer has a glass transition temperature of 25° C. or less.

[0138] <8> According to an eighth aspect of the present invention, there is provided a production method according to any one of the first to seventh aspects, wherein the ratio ((1) / (2)) of the tetrafluoroethylene (1) unit to the perfluoromonomer (2) unit in the perfluoroelastomer is 45 to 90 / 55 to 10 (mol %).

[0139] <9> According to a ninth aspect of the present invention, there is provided the production method according to any one of the first to eighth aspects, wherein the polymerization is performed in the substantial absence of a surfactant.

[0140] Example

[0141] Next, embodiments of the present invention will be described with reference to examples, but the present invention is not limited to the examples.

[0142] Each numerical value in the examples was measured by the following method.

[0143] (Polymer composition)

[0144] pass 19 The results were measured by F-NMR (melting NMR) and Fourier transform infrared spectrophotometer (FT-IR).

[0145] (Storage modulus (G'))

[0146] The storage modulus G' at a dynamic strain of 1% was measured at 100°C and 1 Hz using a rubber processing analyzer (model: RPA2000) manufactured by Alpha Technologies.

[0147] (iodine content)

[0148] Determined by elemental analysis.

[0149] (Glass transition temperature)

[0150] The glass transition temperature was determined by heating 10 mg of a sample at 10° C. / min using a differential scanning calorimeter (DSC822e, manufactured by Mettler-Toledo Co., Ltd.) to obtain a DSC curve, and the peak top temperature of the differential curve specified in JIS K6240 was defined as the glass transition temperature.

[0151] Example 1

[0152] A 3L stainless steel autoclave was replaced with vacuum nitrogen to remove oxygen, and the inside of the tank was evacuated to vacuum suck 2332g of 2-(2-(heptafluoropropoxy)-1,1,2,3,3,3-hexafluoropropoxy)-1,1,2,3,3,3-hexafluoropropyl (trifluorovinyl) ether (VE-1) and 68g of 1,1,2,2-tetrafluoro-3-iodo-1-(1,2,2-trifluorovinyloxy) propane. The system was stirred and the temperature was adjusted to 25°C, and tetrafluoroethylene (TFE) was injected so that the pressure inside the polymerization tank reached 0.502MPaG. 1.04g of a perfluorohexane solution (DHP) containing 8% by mass of di-(2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptanoyl) peroxide and 5g of VE-1 were injected with nitrogen to start the reaction. When the pressure drops to 0.490 MPaG, TFE is added in such a way as to reach 0.510 MPaG. Five hours after the reaction begins, 1.08 g of DHP and 5 g of VE-1 are pressed in with nitrogen. The above operation is repeated until 90 g of TFE is added, the supply is stopped, the gas in the autoclave is released, and the solution extracted after cooling is vacuum dried at 200°C, thereby obtaining 223.5 g of polymer. The obtained polymer is a TFE / VE-1 copolymer, which contains TFE units and VE-1 units in a molar ratio (TFE / VE-1) of 84.0 / 16.0. The G' of the obtained polymer at 100°C is 350 kPa. The obtained polymer contains 0.69 mass% of iodine. The glass transition temperature is -16.2°C.

[0153] Example 2

[0154] A 3L stainless steel autoclave was replaced with vacuum nitrogen to remove oxygen, and the inside of the tank was evacuated to vacuum suck 2332g of VE-1 and 68g of 1,1,2,2-tetrafluoro-3-iodo-1-(1,2,2-trifluoroethyleneoxy)propane. The system was stirred and the temperature was adjusted to 25°C, and TFE was pressed into the polymerization tank so that the pressure reached 0.714MPaG. 3.60g of DHP and 5g of VE-1 were pressed into the reactor with nitrogen to start the reaction. When the pressure dropped to 0.690MPaG, TFE was added to reach 0.705MPaG, and 5 hours after the reaction started, 1.80g of DHP and 5g of VE-1 were pressed into the reactor with nitrogen. The above operation was repeated until 64g of TFE was added, and the supply was stopped, the gas in the autoclave was released, and the solution extracted after cooling was vacuum dried at 200°C to obtain 165.0g of polymer. The obtained polymer was a TFE / VE-1 copolymer, containing TFE units and VE-1 units at a molar ratio (TFE / VE-1) of 79.8 / 20.2. The G' of the obtained polymer at 100°C was 70 kPa. The obtained polymer contained 0.64% by mass of iodine. The glass transition temperature was -19.7°C.

[0155] Example 3

[0156] A 3L stainless steel autoclave was replaced with vacuum nitrogen to remove oxygen, and the inside of the tank was evacuated to vacuum suck in 2400g of VE-1, 20g of 1,1,2,2-tetrafluoro-3-iodo-1-(1,2,2-trifluoroethyleneoxy)propane, and 2.5g of 1,1,2,2,3,3,4,4-octafluoro-1,4-diiodobutane. The system was stirred and the temperature was adjusted to 25°C, and TFE was pressed into the polymerization tank so that the pressure reached 0.610MPaG. 2.08g of DHP and 5g of VE-1 were pressed into the polymerization tank with nitrogen to start the reaction. When the pressure dropped to 0.590MPaG, TFE was added so that it reached 0.605MPaG. 8 hours and 12 hours after the start of the reaction, 1.80g of DHP and 5g of VE-1 were pressed into the polymerization tank with nitrogen. The above operation was repeated until 126 g of TFE was added, the supply was stopped, the gas in the autoclave was released, and the solution extracted after cooling was vacuum dried at 200°C, thereby obtaining 372.8 g of polymer. The obtained polymer was a TFE / VE-1 copolymer, which contained TFE units and VE-1 units in a molar ratio (TFE / VE-1) of 82.0 / 18.0. The G' of the obtained polymer at 100°C was 24 kPa. The obtained polymer contained 0.56% by mass of iodine. The glass transition temperature was -20.6°C.

[0157] Example 4

[0158] A 0.5L stainless steel autoclave was replaced with vacuum nitrogen to remove oxygen, the tank was evacuated, the temperature was adjusted to 15°C while stirring the system, and 109g of trifluoromethyl trifluorovinyl ether (VE-2) and 6.7g of TFE were introduced. 2.05g of DHP was pressed into the autoclave with nitrogen to start the reaction. The pressure at the start of the reaction was 0.575MPaG. When the pressure dropped to 0.5640MPaG, the liquefied gas in the autoclave was liquid when it was extracted from the bottom valve of the autoclave, so it was confirmed that the gas in the reaction container was in a liquefied state. The extracted liquid was placed in a glass container, and after the liquid in the glass container was volatilized, it was dried at 100°C to obtain 0.2g of polymer. The obtained polymer is a TFE / VE-2 copolymer, which contains TFE units and VE-2 units at a molar ratio of 61.1 / 38.9 (TFE / VE-2). The glass transition temperature is 0.5°C.

Claims

1. A method for producing a perfluoroelastomer, comprising polymerizing tetrafluoroethylene (1) and a perfluoromonomer (2) other than tetrafluoroethylene (1) in a reaction vessel to produce the perfluoroelastomer, wherein: The volume of water and the fluorinated solvent in the internal volume of the reaction container is 2.0 volume % or less.

2. The manufacturing method according to claim 1, wherein: At least a portion of the perfluoromonomer (2) is present in the reaction container in the form of a liquid.

3. The manufacturing method according to claim 2, wherein: The internal pressure of the reaction container is equal to or higher than the saturated vapor pressure of the perfluoromonomer (2) at the temperature of the liquid in the reaction container.

4. The production method according to any one of claims 1 to 3, wherein The perfluoromonomer (2) is a monomer represented by the following general formula (2), General formula (2): CF2=CY-Rf-X In the formula, Rf is a perfluoroalkylene group, a perfluoroalkylene group containing an oxygen atom between carbon atoms, a perfluoroalkylene oxide group, or a perfluoroalkylene oxide group containing an oxygen atom between carbon atoms, X is -F, -I, -CH2I, -Br, -CH2Br or -CN, and Y is F or a perfluoroalkyl group.

5. The production method according to any one of claims 1 to 4, wherein The perfluoromonomer (2) is at least one selected from the group consisting of a monomer represented by the following general formula (2a) and a monomer represented by the following general formula (2b), General formula (2a): CF2=CY-O-Rf 11 In the formula, Rf 11 is a perfluoroalkyl group, or a perfluoroalkyl group containing an oxygen atom between carbon atoms, Y is F or a perfluoroalkyl group, General formula (2b): CF2=CY-Rf 12 -X In the formula, Rf 12 It is a perfluoroalkylene group, a perfluoroalkylene group containing an oxygen atom between carbon atoms, a perfluoroalkylene group, or a perfluoroalkylene group containing an oxygen atom between carbon atoms, X is -I, -CH2I, -Br, -CH2Br or -CN, and Y is F or a perfluoroalkyl group.

6. The production method according to any one of claims 1 to 5, wherein The perfluoromonomer (2) is a monomer represented by the following general formula (2a), General formula (2a): CF2=CY-O-Rf 11 In the formula, Rf 11 is a perfluoroalkyl group or a perfluoroalkyl group containing an oxygen atom between carbon atoms, and Y is F or a perfluoroalkyl group.

7. The production method according to any one of claims 1 to 6, wherein The glass transition temperature of the perfluoroelastomer is 25°C or less.

8. The production method according to any one of claims 1 to 7, wherein The ratio of the tetrafluoroethylene (1) unit to the perfluoromonomer (2) unit in the perfluoroelastomer, i.e., (1) / (2), is 45 to 90 / 55 to 10 (mol %).

9. The production method according to any one of claims 1 to 8, wherein The polymerization is carried out in the substantial absence of surfactant.