JPWO2014112592A1 - Process for producing dried ethylene-tetrafluoroethylene copolymer, pellets and molded product - Google Patents

Abstract

Provided is a method for producing a dry product of ethylene-tetrafluoroethylene copolymer, which can provide excellent stress crack resistance while reducing environmental load. Ethylene and tetrafluoroethylene are solution-polymerized by using a water-soluble chain transfer agent in at least one fluorine-containing organic solvent selected from the group consisting of perfluorocarbon, hydrofluorocarbon, hydrochlorofluorocarbon, and hydrofluoroether. An ethylene-tetrafluoroethylene copolymer having a polymerization step for obtaining a slurry in which fine particles of tetrafluoroethylene copolymer are dispersed, and an evaporation step for evaporating a volatile component from the slurry without bringing water into contact with the slurry. A method for producing a dried polymer.

Description

  The present invention relates to a method for producing a dried ethylene-tetrafluoroethylene copolymer, pellets and molded products.

  BACKGROUND ART Ethylene-tetrafluoroethylene copolymers (hereinafter also referred to as “ETFE”) are used in a wide range of fields such as automobile parts, agricultural greenhouses, building materials, and wire covering materials. ETFE is usually produced by solution polymerization of monomers in a fluorine-containing organic solvent that is a polymerization medium. In this method, a slurry having a relatively high viscosity in which fine particles of ETFE are dispersed in a fluorine-containing organic solvent can be obtained. Thereafter, volatile components such as unreacted monomers and polymerization medium are evaporated from the slurry and granulated, and then dried ethylene-tetrafluoroethylene copolymer (hereinafter referred to as “ethylene-tetrafluoroethylene dried product”), or Also referred to as “ETFE dried product”).

By reducing the residual amount of volatile components in the dried ETFE as much as possible, foaming at the time of molding using the dried ETFE is suppressed, and the workability is improved. Moreover, if the volatile component evaporated from the slurry is recovered and reused, the cost can be reduced.
As a method of evaporating volatile components from the slurry to obtain a dried ETFE product, the slurry is added to water and stirred, and the slurry is heated in a dispersed state in water to evaporate the volatile components, and then water. A method of separating and drying ETFE and liquid is widely used (for example, Patent Document 1).

International Publication No. 2010/074039

  Conventionally, organic chain transfer agents such as hydrochlorofluorocarbons have been used in the polymerization of ETFE for the purpose of controlling the molecular weight and physical properties, but in recent years water-soluble chains such as methanol and ethanol have been used to reduce the environmental burden. A transfer agent is used. However, as a result of investigations by the present inventors, when an ETFE dry product is obtained from the slurry polymerized using a water-soluble chain transfer agent by the above-described method, the stress crack resistance is higher than when an organic chain transfer agent is used. Was found to tend to decline.

  The present invention provides a method for producing a dried ETFE product that provides excellent stress crack resistance while reducing environmental burden. In the present invention, ethylene-tetrafluoroethylene pellets (hereinafter referred to as “ETFE pellets”) and ethylene-tetrafluoroethylene molded products (hereinafter referred to as “ETFE molded products”) using the dried ETFE product. A manufacturing method is provided.

  The method for producing a dried ETFE product of the present invention uses a water-soluble chain transfer agent in at least one fluorine-containing organic solvent selected from the group consisting of perfluorocarbon, hydrofluorocarbon, hydrochlorofluorocarbon and hydrofluoroether. A polymerization step of solution polymerization of ethylene (hereinafter referred to as “E”) and tetrafluoroethylene (hereinafter referred to as “TFE”) to obtain a slurry in which fine particles of ETFE are dispersed; and without bringing the slurry into contact with water And an evaporation step of evaporating volatile components from the slurry.

The water-soluble chain transfer agent is preferably at least one selected from the group consisting of alcohols having 1 to 4 carbon atoms, ketones having 3 to 4 carbon atoms, tetrahydrofuran, dimethyl sulfoxide, and dimethylformamide.
The water-soluble chain transfer agent is preferably methanol.
It is preferable that the usage-amount of the water-soluble chain transfer agent in the said polymerization process is 0.01-20 mass parts with respect to 100 mass parts of fluorine-containing organic solvents.
The evaporation step is a rotation in which a cylindrical heat transfer body and a stirring blade are provided on a rotating shaft, and the tip of the stirring blade rotates in the heat transfer body so as to give up the inner wall surface of the heat transfer body. It is preferable that it is the process of evaporating a volatile component from the said slurry using the centrifugal thin film evaporator which has a stirring part and the heating part which heats the said heat-transfer body part.
In the method for producing a dried ETFE product of the present invention, it is preferable to obtain a dried ETFE product having an average particle size of 10 to 500 μm.
The molar ratio of the repeating unit based on E and the repeating unit based on TFE in the ETFE is preferably 30/70 to 60/40.
The ETFE may have a repeating unit based on another monomer other than E and TFE.
The other monomer is preferably a monomer represented by the following formula (1).
CH ₂ = CR ^1- (CF ₂ ) _a R ² (1)
(However, the equation (1), ^{R 1} and ^{R 2} are each independently a hydrogen atom or a fluorine atom, a is an integer from 1 to 12.)
It is preferable that the concentration of the fine particles of the ethylene-tetrafluoroethylene copolymer in the slurry in which the fine particles of the ethylene-tetrafluoroethylene copolymer are dispersed obtained in the polymerization step is 0.1 to 45% by mass. .

The method for producing ETFE pellets of the present invention is a method characterized in that the ETFE dried product obtained by the production method of the present invention is melted and then pelletized.
The method for producing an ETFE molded product of the present invention is a method characterized by melt-molding an ETFE dried product obtained by the production method of the present invention or an ETFE pellet obtained by the production method of the present invention.

According to the method for producing a dried ETFE product of the present invention, a dried ETFE product capable of forming an ETFE molded product having excellent stress crack resistance while reducing environmental burden is obtained.
Moreover, according to the method for producing ETFE pellets of the present invention, ETFE pellets capable of forming an ETFE molded product having excellent stress crack resistance while reducing environmental burden can be obtained.
According to the method for producing an ETFE molded product of the present invention, an ETFE molded product having excellent stress crack resistance can be obtained while reducing the environmental load.

It is the schematic which showed an example of the evaporation apparatus used for the evaporation process of the manufacturing method of this invention. It is sectional drawing when the raw material supply port part of the centrifugal thin film evaporator in the evaporator of FIG. 1 is cut | disconnected in the direction perpendicular | vertical to an axial direction.

<Method for producing ETFE dry product>
The method for producing a dried ETFE product of the present invention includes the following polymerization step and evaporation step.
Polymerization step: Slurry in which fine particles of ETFE (hereinafter referred to as “ETFE fine particles”) are dispersed by solution polymerization of E and TFE in a fluorine-containing organic solvent using a water-soluble chain transfer agent (hereinafter referred to as “ETFE slurry”). The process of obtaining.
Evaporation step: a step of evaporating volatile components from the ETFE slurry without bringing water into contact with the ETFE slurry.

[Polymerization process]
In a fluorine-containing organic solvent, E and TFE are solution polymerized using a water-soluble chain transfer agent to obtain an ETFE slurry.
As the fluorine-containing organic solvent, at least one selected from the group consisting of perfluorocarbon (PFC), hydrofluorocarbon (HFC), hydrochlorofluorocarbon (HCFC) and hydrofluoroether (HFE) is used.
The structure of the fluorine-containing organic solvent may be linear, branched or cyclic. PFC, HFC and HCFC may contain an etheric oxygen atom in the molecule.

Examples of PFC include perfluorocyclobutane, perfluorohexane, perfluoro (dipropyl ether), perfluorocyclohexane, perfluoro (2-butyltetrahydrofuran) and the like.
The _{HFC, CH 3 OC 2 F 5} , CH 3 OC 3 F 7, CF 3 CFHCFHCF 2 CF 2 CF 3, CF 2 HCF 2 CF 2 CF 2 CF 2 CF 2 H C 6 F 12 H 2 , such as, CF Compounds having a larger number of fluorine atoms in the molecule than the number of hydrogen atoms such as C ₇ F ₁₅ H such as ₃ CF ₂ CF ₂ CF ₂ CF ₂ CF ₂ CF ₂ H are preferred.
As the HCFC, a compound having 3 or less hydrogen atoms such as CHClFCF ₂ CF ₂ Cl is preferable.
The _{HFE, CF 3 CF 2 CH 2} OCHF 2, CF 3 CHFCF 2 OCH 3, CHF 2 CF 2 OCH 2 F, (CF 3) 2 CHCF 2 OCH 3, CF 3 CF 2 CH 2 OCH 2 CHF 2, CF ₃ CHFCF ₂ OCH ₂ CF _{3 and the} like.
1 type may be sufficient as a fluorine-containing organic solvent, and 2 or more types may be sufficient as it.

The fluorine-containing organic solvent is preferably a saturated compound because it hardly affects the polymerization reaction. Moreover, since the fluorine-containing organic solvent is liquid at the polymerization temperature and can be easily separated from ETFE by being evaporated in the evaporation step described later, the PFC having 3 to 10 carbon atoms and the carbon number having 3 to 10 carbon atoms. At least one selected from the group consisting of HFC and HCFC having 3 to 10 carbon atoms is preferred, and CF ₃ (CF ₂ ) _n CF ₂ H (where n is an integer of 4 to 8), CHClFCF ₂ CF more preferably ₂ Cl or mixtures thereof, at least one of the CHClFCF ₂ CF ₂ Cl and _{CF 3 CF 2 CF 2 CF 2} CF 2 CF 2 H are particularly preferred.

  As for the usage-amount of a fluorine-containing organic solvent, 10-90 volume% is preferable with respect to the volume (100 volume%) of a polymerization tank. When the amount of the fluorine-containing organic solvent used is within the above range, the amount of the monomer dissolved or dispersed in the fluorine-containing organic solvent and the resulting ETFE can be increased. Therefore, the yield of ETFE becomes higher and is industrially advantageous.

  A radical polymerization initiator is used for the polymerization. Examples of the radical polymerization initiator include perfluoro radical polymerization initiators such as perfluoroalkyl peroxides and perfluoroalkyl azo compounds, hydrocarbon peroxides, hydrocarbon azo compounds, and the like.

Examples of the perfluoroalkyl peroxide include acyl peroxides obtained from chlorocarbons or fluorocarbons as starting materials. Specific examples include trichloroacetyl peroxide, bis (perfluoro-2-propoxypropionyl) peroxide, [CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) COO] ₂ , perfluoropropionyl peroxide, (CF ₃ CF ₂ CF ₂ COO) ₂ , (CF ₃ CF ₂ COO) ₂ , {CF ₃ CF ₂ CF ₂ [CF (CF ₃ ) CF ₂ O] _c CF (CF ₃ ) COO} ₂ (where c is 0-8) It is an integer.), [ClCF ₂ (CF ₂ ) _d COO] ₂ (where d is an integer of 0 to 8), perfluorocyclohexanecarbonyl peroxide, perfluorobenzenecarbonyl peroxide, and the like.

The perfluoroalkyl azo compounds, perfluoro azo _{isopropane, (CF 3) 2 CFN =} NCF (CF 3) _2, etc. ^R 4 N = NR ⁵ (provided that, ^{R 4} and ^{R 5,} carbon atoms 1-8 Or a linear or branched perfluoroalkyl group.) And the like.
Examples of the hydrocarbon peroxide include 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, dialkyl peroxide such as di-t-butyl peroxide; isobutyl peroxide, 3,5,5 -Diacyl peroxides such as trimethylhexanoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, succinic acid peroxide; dinormalpropyl peroxydicarbonate, bis (4-t-butylcyclohexyl) peroxy Peroxydicarbonates such as dicarbonate, di-2-ethoxyerythoxyperoxydicarbonate, di-2-ethylhexylperoxydicarbonate; 1,1,3,3-tetramethylbutylperoxyneodecanoate, 1 - Rohexyl-1-methylethylperoxyneodecanoate, t-hexylperoxyneodecanoate, t-hexylperoxypivalate, t-butylperoxypivalate, 1,1,3,3-tetramethylbutyl Peroxy-2-ethylhexanoate, 2,5-dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-hexylperoxyisopropylmonocarbonate, t-butylperoxy- 3,5,5-trimethylhexanoate, t-butyl peroxylaurate, t Butyl peroxy isopropyl monocarbonate, peroxy esters such as t- butyl peroxy acetate.

  Examples of the hydrocarbon azo compound include cyano-2-propylazoformamide, 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis (2-aminodinopropane) dihydrochloride, 2,2 '-Azobis (2-methylbutyronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis [N- (2-propenyl) -2-methylpropionamide], Polydimethylsiloxane segment-containing macroazo compound, 2,2′-azobis (2-2,4,4-trimethylpentane), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 4,4 '-Azobis (4-cyanovaleric acid), 2,2'-azobisisobutyric acid dimethyl, 2,2'-azobis [2- (2-imidazolin-2-yl) propyl Pan] dihydrochloride, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate, 2,2'-azobis [2- (2-imidazoline-2- Yl) propane], 2,2′-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide}, 2,2′-azobis {2-methyl-N -[1,1-bis (hydroxymethyl) ethyl] propionamide}, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], 2,2′-azobisisobutyramide Hydrates, 2,2′-azobis [2- (hydroxymethyl) propionitrile] and the like can be mentioned.

The radical polymerization initiator may be one type or two or more types.
As the radical polymerization initiator, a peroxide is preferable, and t-butyl peroxypivalate is particularly preferable.
The amount of the radical polymerization initiator used is preferably 10 ⁻⁶ to 10 parts by mass, more preferably 10 ^{−5 to} 5 parts by mass, and more preferably 0.005 to 1 part by mass, with the total mass of the monomers being 100 parts by mass. Further preferred.

In the polymerization, a water-soluble chain transfer agent is used in order to control the molecular weight and physical or chemical properties. Here, the water-soluble chain transfer agent means a chain transfer agent having a solubility in water at 20 ° C. of 20 g / 100 ml or more.
As the water-soluble chain transfer agent, alcohol having 1 to 4 carbon atoms (methanol, ethanol, propanol, butanol, etc.), carbon number 3 from the viewpoint that the effect as a chain transfer agent can be easily obtained while reducing the environmental load. -4 ketones (acetone, methyl ethyl ketone, etc.), tetrahydrofuran, dimethyl sulfoxide, or dimethylformamide are preferred, those mixed with water in any proportion are preferred, alcohols having 1 to 4 carbon atoms are more preferred, and methanol is particularly preferred. .
A water-soluble chain transfer agent may be used individually by 1 type, and may use 2 or more types together.

  0.01-20 mass parts is preferable with respect to 100 mass parts of polymerization solvents, and, as for the usage-amount of a water-soluble chain transfer agent, 0.1-5 mass parts is more preferable. If the usage-amount of a water-soluble chain transfer agent is more than a lower limit, the effect as a chain transfer agent will be easy to be acquired. If the amount of water-soluble chain transfer agent used is not more than the upper limit, ETFE can be easily controlled to an appropriate molecular weight range, and purification for reusing the recovered solvent is easy, and the burden on the environment is small. .

Although polymerization temperature changes with kinds etc. of radical polymerization initiator, 0-100 degreeC is preferable and 30-90 degreeC is more preferable.
The polymerization pressure varies depending on the polymerization temperature, but is preferably 0.1 MPa to 10 MPa, more preferably 0.5 MPa to 3 MPa, and further preferably 0.8 MPa to 2 MPa.
The polymerization time is preferably from 0.1 to 30 hours, more preferably from 0.5 to 20 hours, and even more preferably from 1 to 15 hours from the viewpoint of economy.

  In addition to E and TFE, other monomers other than E and TFE may be used for the polymerization. That is, in addition to the repeating unit based on E and the repeating unit based on TFE, ETFE having a repeating unit based on another monomer other than E and TFE may be used.

Examples of the other monomer include fluorine-containing ethylene such as vinylidene fluoride and trifluorochloroethylene (excluding TFE); CF ₂ = CFCF ₃ , CF ₂ = CHCF ₃ , CH ₂ = CHCF _{3 and the} like. Fluorine-containing propylene; monomer represented by the following formula (1) (hereinafter referred to as “monomer (1)”); perfluorovinyl ether such as a monomer represented by the following formula (2); CH ₃ OC (═O) CF ₂ CF ₂ CF ₂ OCF═CF ₂ , FSO ₂ CF ₂ CF ₂ OCF (CF ₃ ) CF ₂ OCF═CF _{2 and} other groups that can be easily converted into a carboxylic acid group or a sulfonic acid group A perfluorovinyl ether having 3 to 4 carbon atoms such as propylene and butene; 4-methyl-1-pentene; cyclohexene; vinyl acetate, vinyl lactate, vinyl butyrate, Examples thereof include vinyl esters such as vinyl valinate; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, isobutyl vinyl ether, tert-butyl vinyl ether, cyclohexyl vinyl ether, and hydroxybutyl vinyl ether.
CH ₂ = CR ^1- (CF ₂ ) _a R ² (1)
Rf (OCFR ³ CF ₂ ) _b OCF═CF ₂ (2)
However, the formula (1), ^{R 1} and ^{R 2} are each independently a hydrogen atom or a fluorine atom, a is an integer from 1 to 12. Further, the formula (2), Rf is a perfluoroalkyl group having 1 to 6 carbon atoms, ^{R 3} is fluorine atom or a trifluoromethyl group, b is an integer of 0 to 5.

As the monomer (1), CF ₃ CF ₂ CH═CH ₂ , CF ₃ CF ₂ CF ₂ CF ₂ CH═CH ₂ , CF ₃ CF ₂ CF ₂ CF ₂ CF ₂ CF ₂ CH═CH ₂ , CF _{3 CF 2 CF 2 CF 2 CF =} CH 2, CF 2 HCF 2 CF 2 CF = CH 2 and the like.
As the monomer _{(2), CF 3 CF 2} OCF 2 CF 2 OCF = CF 2, C 3 F 7 OCF (CF 3) CF 2 OCF = CF 2 , and the like.

The other monomer is preferably monomer (1) because it can improve the mechanical strength of ETFE. R ¹ in the formula (1) is a hydrogen atom and R ² is a fluorine atom. A certain monomer is more preferable, and CF ₃ CF ₂ CF ₂ CF ₂ CH═CH ₂ or CF ₃ CF ₂ CF ₂ CF ₂ CF ₂ CF ₂ CH═CH ₂ is particularly preferable.

The molar ratio (E / TFE) of the repeating unit based on E and the repeating unit based on TFE in ETFE obtained by polymerization is preferably 30/70 to 60/40, more preferably 40/60 to 55/45, 43/57 to 50/50 is more preferable. If the molar ratio (E / TFE) is at least the lower limit, the transparency of ETFE will be good. When the molar ratio (E / TFE) is equal to or lower than the upper limit value, the heat resistance is improved.
The molar ratio (E / TFE) is measured by FT-IR.

  When a repeating unit based on another monomer other than E and TFE is introduced into ETFE, the ratio of the repeating unit based on the other monomer is 0 with respect to the total repeating units (100 mol%) in ETFE. 0.1-50 mol% is preferable, 0.1-30 mol% is more preferable, 0.1-20 mol% is further more preferable, 0.1-10 mol% is especially preferable. When the ratio of the repeating unit based on the other monomer is within this range, characteristics such as stress crack resistance and workability become better.

  The concentration of ETFE fine particles in the ETFE slurry obtained by polymerization varies depending on conditions such as polymerization temperature, polymerization pressure, polymerization time, the amount of monomer charged, etc., but is preferably 0.1 to 45% by mass, 30 mass% is more preferable.

  As the ETFE fine particles, particles having an average primary particle diameter of 10 nm to 5 μm are preferable, and 50 nm to 1 μm are more preferable. If the average primary particle diameter of the ETFE fine particles is within this range, the applicability to the evaporation step is excellent. The average primary particle size of the ETFE fine particles is a value measured by a laser diffraction / scattering particle size / particle size distribution measuring device.

[Evaporation process]
Volatile components are evaporated from the slurry without contacting water with the slurry obtained in the polymerization step. Examples of the volatile component include a fluorine-containing organic solvent used for polymerization, an unreacted monomer, a chain transfer agent, an initiator residue, and the like.
As a method for evaporating volatile components without bringing water into contact with the slurry, a cylindrical heat transfer body and a stirring blade are provided on the rotating shaft, and the tip of the stirring blade is placed in the heat transfer body. A method using a centrifugal thin film evaporator having a rotary stirring unit that rotates so as to give up the inner wall surface of the heat drum portion and a heating portion that heats the heat transfer drum portion is preferable. If the centrifugal thin film evaporator is used, it is easy to obtain an ETFE dry product having a preferable average particle size described later.

(Evaporation device)
1 and 2 are examples of an evaporation apparatus having a centrifugal thin film evaporator.
The evaporation apparatus 1 includes a storage tank 10 that stores ETFE slurry, a centrifugal thin film evaporator 12 that evaporates volatile components from the ETFE slurry supplied from the storage tank 10, and a volatile component that is discharged from the centrifugal thin film evaporator 12. A condenser 14 that condenses the volatile component, a recovery tank 16 that collects the volatile component condensed by the condenser 14, and a blower 18 that sucks the evaporated volatile component from the centrifugal thin film evaporator 12.
The storage tank 10 and the centrifugal thin film evaporator 12 are connected from the storage tank 10 side by a pipe 24 provided with a liquid feed pump 20 and a back pressure valve 22. The centrifugal thin film evaporator 12 and the condenser 14 are connected by a pipe 26, and the condenser 14 and the recovery tank 16 are connected by a pipe 28. The condenser 14 and the blower 18 are connected by a pipe 32 provided with a pressure regulating valve 30 in the middle.

  The centrifugal thin film evaporator 12 includes a cylindrical heat transfer drum 34, a dispersion rotor 36 for dispersing the ETFE slurry supplied into the heat transfer drum 34 on the inner wall surface 34a, and a stirring blade 40 on the rotary shaft 38. A rotating stirrer 42 that rotates so that the tip of the stirring blade 40 praises the inner wall surface 34a of the heat transfer drum 34 in the heat transfer drum 34, and a first heating unit 44 that heats the heat transfer drum 34; And a powder receiver 46 that receives the dried ETFE material falling from within the heat transfer barrel 34, and a second heating unit 48 that heats the powder receiver 46.

A raw material supply port 34 b for supplying the ETFE slurry is formed in the upper part of the heat transfer body 34.
A nozzle 50 provided at the tip of the pipe 24 is installed at the raw material supply port 34b of the heat transfer barrel 34, and a dispersion rotor 36 is installed at a position corresponding to the raw material supply port 34b. The tip of the nozzle 50 is located between the inner wall surface 34 a of the heat transfer body portion 34 and the outer surface of the dispersion rotor 36. That is, the ETFE slurry is supplied from the nozzle 50 of the raw material supply port 34 b between the inner wall surface 34 a in the upper part of the heat transfer body portion 34 and the outer surface of the rotary shaft 38.

The nozzle 50 has an angle θ () formed by the direction in which the ETFE slurry is supplied into the heat transfer body 34, and the tangential direction of the inner wall surface 34 a at the intersection of the supply direction and the inner wall surface 34 a of the heat transfer body 34. 2) is preferably installed so as to be 30 ° or less, more preferably 25 ° or less. As a result, the ETFE slurry supplied into the heat transfer body 34 is uniformly supplied to the inner wall surface 34a, and it is easy to suppress the occurrence of a single flow in which the ETFE slurry locally flows through a part of the inner wall surface 34a. Then, a sufficient time for heating the ETFE slurry in the heat transfer barrel 34 is ensured, volatile components are sufficiently removed, and an ETFE dried product excellent in handling and workability can be obtained more easily.
The lower limit value of the angle θ is ideally 0 °, but is slightly larger than 0 ° by the thickness of the discharge port portion of the nozzle 50 (difference between the inner diameter and the outer diameter).

  The dispersion rotor 36 has a disk shape and is installed so as to rotate in conjunction with the rotation of the rotation shaft 38 of the rotary stirring unit 42. The ETFE slurry supplied from the nozzle 50 to the inside of the heat transfer body 34 is uniformly dispersed on the inner wall surface 34a of the heat transfer body 34 by the rotation of the dispersion rotor 36, and naturally falls through the inner wall surface 34a. .

  In addition, a volatile component recovery port 34c for recovering volatile components evaporated inside is formed in the upper portion of the heat transfer barrel 34. The volatile component recovery port 34 c is formed above the raw material supply port 34 b so that the ETFE slurry is not introduced into the condenser 14 through the pipe 26. The volatile component recovery port 34 c is connected to the condenser 14 via the pipe 26, and the volatile component volatilized in the heat transfer body portion 34 is recovered by the suction by the blower 18 connected to the condenser 14. It is recovered from the mouth 34c.

The rotary stirring unit 42 includes a rotary shaft 38 and a plurality of stirring blades 40 attached to the rotary shaft 38, and the rotary shaft 38 is received by a bearing 52 provided at the lower portion of the heat transfer body 34. Rotates inside the heat transfer barrel 34.
An upper portion of the rotation shaft 38 is connected to the rotation drive unit 56 via the belt 54, and is rotated by the rotation drive unit 56.

The stirring blade 40 is located below the dispersion rotor 36. Further, the plurality of stirring blades 40 are provided so that their positions are spirally displaced in order from the top along the axial direction of the rotation shaft 38. Specifically, in this example, when the rotary stirring unit 42 is viewed from above, the respective stirring blades 40 are provided so as to be shifted by 90 ° about the rotation shaft 38 in order from the top.
The stirring blade 40 has a fixed portion 40 a fixed to the rotating shaft 38, and a movable blade portion 40 c connected by the fixed portion 40 a and the connecting portion 40 b, and the movable blade portion 40 c is connected to the rotating shaft 38. The connection portion 40b can be bent as a fulcrum so as to face in the opposite direction to the rotation. Thereby, when the front-end | tip of the stirring blade 40 contacts with the layer of the ETFE dry matter formed in the inner wall surface 34a of the heat-transfer body part 34, it is suppressed that an excessive force is added to the stirring blade 40, and a rotation stirring part 42 is less likely to be damaged.

The first heating unit 44 is a heating jacket that heats the heat transfer body 34 by circulating the heat medium outside the heat transfer body 34, and supplies the heat medium from a heat medium supply port 44 a provided in the lower part. Then, after circulating the inside of the heating jacket, it is discharged from the heat medium outlet 44b provided in the upper part. The heat transfer drum 34 is heated by the heat medium flowing through the first heating unit 44, and the raw material slurry is heated by the inner wall surface 34 a of the heat transfer drum 34, whereby the volatile components in the ETFE slurry are evaporated.
Examples of the heating medium of the first heating unit 44 include pressurized steam and silicone oil.

The rotating stirring unit 42 rotates so that the tip of the stirring blade 40 gives up the inner wall surface 34 a of the heat transfer body 34 by the rotation of the rotating shaft 38. As a result, the ETFE slurry applied to the inner wall surface 34 a of the heat transfer drum portion 34 is formed into a thin film having a thickness corresponding to the clearance between the tip of the stirring blade 40 and the inner wall surface 34 a of the heat transfer drum portion 34. Since the ETFE slurry becomes a thin film on the inner wall surface 34a of the heat transfer barrel 34, the volatile component can be volatilized in a short time.
Since the ETFE slurry can be pulverized, the clearance between the tip of the stirring blade 40 and the inner wall surface 34a of the heat transfer body 34 is preferably 0.1 mm or more, and more preferably 0.3 mm or more. Moreover, since the volatile component can be volatilized in a shorter time, the clearance is preferably 2.0 mm or less, and more preferably 1.5 mm or less.
The clearance is a clearance when the angle of the fixed portion 40a and the movable blade portion 40c in the stirring blade 40 is 180 ° (not bent).
The number of stirring blades 40 is not particularly limited, but is preferably 4 to 100.

  In addition, when the layer of the ETFE dry matter formed on the inner wall surface 34a of the heat transfer drum 34 becomes thicker than the clearance between the tip of the stirring blade 40 and the inner wall 34a of the heat transfer drum 34, the layer of the stirring blade 40 becomes thicker. Drops when scraped in contact with the tip.

  The powder receiving portion 46 is a portion that receives the powdered ETFE dried material that has fallen from the heat transfer barrel portion 34, and is provided with a rotary outlet 46 a at the lower portion and the second heating portion 48 on the outer side. Is provided. In the powder receiver 46, the powdered ETFE dried product that has dropped from the heat transfer barrel 34 is heated as necessary, and the content of the fluorinated organic solvent in the ETFE dried product becomes a desired content. After the adjustment, it is taken out from the outlet 46a.

The second heating unit 48 is a heating jacket that heats the powder receiving unit 46 by circulating a heating medium outside the powder receiving unit 46, and supplies the heating medium from a heating medium supply port 48a provided in the lower part. Then, after circulating in the heating jacket, it is discharged from the heat medium outlet 48b provided in the upper part.
Examples of the heating medium for the second heating unit 48 include the same ones as those for the first heating unit 44.

The condenser 14 is a portion that volatilizes in the heat transfer barrel 34 and condenses by cooling the volatile component recovered from the volatile component recovery port 34c. The condenser 14 is provided with a refrigerant supply port 14a on the downstream side and a refrigerant discharge port 14b on the upstream side, and the refrigerant supplied from the refrigerant supply port 14a circulates from the downstream side toward the upstream side, and the refrigerant discharge port 14b. Discharged from. In the condenser 14, the volatile component is condensed by heat exchange between the refrigerant and the volatile component.
Volatile components condensed by the condenser 14 are collected in the collection tank 16 through the pipe 28.

  In the evaporation process by the evaporation apparatus 1 described above, first, the ETFE slurry in which the ETFE fine particles are dispersed in the fluorine-containing organic solvent is stored in the storage tank 10. Next, the ETFE slurry is fed by the liquid feed pump 20 and the back pressure valve 22 and supplied into the heat transfer body 34 of the centrifugal thin film evaporator 12 from the nozzle 50 provided at the raw material supply port 34b. The ETFE slurry supplied into the heat transfer body 34 is dispersed on the inner wall surface 34a by the dispersion rotor 36, is turned into a thin film on the inner wall surface 34a by the rotation of the rotary stirring unit 42, and is heated while falling naturally. The volatile components are removed by evaporation in ETFE, resulting in a dry ETFE.

The supply linear speed of the ETFE slurry supplied from the nozzle 50 into the heat transfer barrel 34 of the centrifugal thin film evaporator 12 is preferably a speed exceeding 0.10 m / sec. As a result, the ETFE slurry is dispersed throughout the inner wall surface 34a of the heat transfer barrel 34, and it is easy to form a uniform thin film of the ETFE slurry on the inner wall surface 34a. Therefore, it is possible to prevent the ETFE slurry from flowing through a part of the inner wall surface 34a of the heat transfer barrel portion 34, so that the ETFE slurry can be sufficiently heated in the heat transfer barrel portion 34, and a fluorine-containing organic solvent, etc. It is easy to obtain a dried ETFE product from which the volatile components are sufficiently removed. Moreover, since the generation of a single flow of the ETFE slurry can be more easily suppressed and the volatile components can be more efficiently removed, the supply linear velocity of the ETFE slurry is more preferably 0.11 m / second or more, and 0.12 m / second or more. Is more preferable.
In addition, the liquid feed pump 20 having an excessive supply capacity may not be used, and the size of the nozzle 50 and the raw material supply port 34b can be suppressed, so that the supply line speed of the ETFE slurry is 2. 00 m / sec or less is preferable, 0.50 m / sec or less is more preferable, and 0.20 m / sec or less is particularly preferable.

In addition, the supply linear velocity of the ETFE slurry in the production method of the present invention is defined by the following formula (I).
V = Q / A (I)
In the above formula (I), V is the supply linear velocity (unit: m / sec), Q is the flow rate (m ³ / sec) of the raw material slurry supplied to the nozzle 50, and A is the disconnection of the nozzle 50 outlet. Area (m ² ).

The concentration of ETFE fine particles in the ETFE slurry (100% by mass) supplied to the centrifugal thin film evaporator 12 is preferably 1.0 to 15.0% by mass, more preferably 2.0 to 15.0% by mass. 0-15.0 mass% is further more preferable. If the density | concentration of the said ETFE fine particle is more than a lower limit, the heat energy required for distillation of a fluorine-containing organic solvent can be reduced, and operating cost will fall. Further, when the concentration of the ETFE fine particles is not more than the upper limit value, the dispersion stability of the ETFE fine particles in the ETFE slurry is improved, and the handling property of the ETFE slurry becomes better.
When the concentration of the ETFE fine particles in the ETFE slurry after the solution polymerization is not within the above range, it is preferable that the concentration of the ETFE fine particles is within the above range by performing concentration by heating or dilution with a fluorine-containing organic solvent.

The internal temperature of the centrifugal thin film evaporator 12 is preferably 30 to 180 ° C, more preferably 40 to 150 ° C, and still more preferably 90 to 150 ° C. If the said internal temperature is more than a lower limit, it will be easy to suppress that the centrifugal thin film evaporator 12 becomes excessive, and equipment cost can be reduced more. Moreover, if the internal temperature is equal to or lower than the upper limit value, it is easy to suppress ETFE deterioration.
The internal temperature of the heat transfer barrel 34 in the centrifugal thin film evaporator 12 is the highest temperature during operation of the inner wall surface 34a at the intermediate point in the vertical direction of the heat transfer barrel 34.

  The internal pressure of the centrifugal thin film evaporator 12 is preferably 1 to 500 kPa (abs), more preferably 5 to 300 kPa (abs), and still more preferably 5 to 200 kPa (abs). If the internal pressure is equal to or higher than the lower limit, it is easy to suppress the internal decompression and the equipment used for the recovery of the fluorinated organic solvent, which is economically advantageous. Moreover, if the said internal pressure is below an upper limit, in order to improve the pressure | voltage resistance of the centrifugal thin film evaporator 12, it becomes easy to suppress that an installation cost becomes excessive, and it is economically advantageous.

10-500 micrometers is preferable, as for the average particle diameter of the ETFE dried material manufactured by the manufacturing method of this invention, 20-400 micrometers is more preferable, and 20-300 micrometers is more preferable. When the average particle size of the dried ETFE is not less than the lower limit value, handling properties are improved. In addition, when the average particle size of the ETFE dried product is not more than the upper limit value, the fluidity of the ETFE dried product is improved, so that sufficient handling properties are easily obtained.
The average particle diameter of the dried ETFE means a value measured by a laser diffraction / scattering particle diameter / particle size distribution measuring apparatus.

Further, the bulk density of the dried ETFE is preferably 0.4 to 1.8 g / mL, and more preferably 0.6 to 1.8 g / mL. If the bulk density of the ETFE dried product is equal to or higher than the lower limit value, the handling property is improved. Moreover, since the true density of the ETFE dried product is about 1.8 g / mL, the upper limit of the bulk density is 1.8 g / mL.
The bulk density of the dried ETFE material is calculated by placing the dried ETFE material in a container having a predetermined capacity and measuring the mass of the dried ETFE material contained in the container.

Moreover, 0.0001-50.0 mass% is preferable, as for content of the fluorine-containing organic solvent in ETFE dried material, 0.001-30.0 mass% is more preferable, 0.001-10.0 mass% Is more preferable. If content of the said fluorine-containing organic solvent is more than a lower limit, it will be easy to suppress that the average particle diameter of an ETFE dried material becomes small too much, and handling property will improve. When the content of the fluorinated organic solvent is not more than the upper limit, the recovery efficiency of the fluorinated organic solvent is improved, which is economically advantageous.
The content of the fluorine-containing organic solvent in the ETFE dried product is measured by a gas chromatography method.

The molecular weight of the dried ETFE product is not particularly limited, and can be widely used from a low molecular weight product which is liquid at 40 ° C. to a high molecular weight product which can be melt-molded.
For example, the molar ratio (E / TFE) is 30 / 70-60 / 40, with 0.1 to 10 mol% of repeating units based on _{CF 3 CF 2 CF 2 CF 2} CF = CH 2 with respect to the total repeating units for ETFE dry matter, capacitance is a measure of the molecular weight flow rate (mm ³ / sec) is preferably 0.1~500mm ³ / sec, more preferably 0.1~200mm ³ / sec, 1 to 50 mm ³ / sec Is more preferable. If the capacity flow rate is equal to or higher than the lower limit value, molding processing by heat melting of ETFE is possible in terms of equipment. If the volume flow rate is equal to or less than the upper limit value, the molded product tends to have a strength that can be used in actual applications.
The capacity flow rate is an extrusion speed when extruding ETFE from an orifice having a diameter of 2.1 mm and a length of 8 mm under a condition of 297 ° C. and a load of 7 kg using a flow tester.

180-280 degreeC is preferable, as for melting | fusing point of an ETFE dried material, 220-280 degreeC is more preferable, and 240-270 degreeC is further more preferable. If the melting point of the dried ETFE is not less than the lower limit, the heat resistance is excellent. If the melting point of the dried ETFE product is not more than the upper limit value, it is advantageous for molding.
The melting point of the dried ETFE product is determined from an endothermic peak when ETFE is heated up to 300 ° C. at 10 ° C./min in an air atmosphere by scanning differential thermal analysis.

  According to the above-described method for producing a dried ETFE product of the present invention, the reason is unknown, but by evaporating volatile components from the slurry without contacting the slurry and water in the evaporation step, excellent resistance It is possible to produce a dried ETFE product that provides stress cracking properties. Moreover, in the manufacturing method of the ETFE dry substance of this invention, since a water-soluble chain transfer agent is used, an environmental load can also be reduced.

In addition, the manufacturing method of the ETFE dry substance of this invention is not limited to an above described method. For example, the method for producing a dried ETFE product of the present invention may be a method that does not use a centrifugal thin film evaporator.
Specifically, the ETFE slurry obtained in the polymerization step may be filtered through a glass filter, and the separated ETFE may be heated to evaporate volatile components to obtain a dried ETFE product. However, in the method for producing a dried ETFE product of the present invention, it is preferable to perform the evaporation step using a centrifugal thin film evaporator because the average particle diameter of the obtained dried ETFE product can be easily within the above range.

<Method for producing ETFE pellet>
The method for producing ETFE pellets of the present invention is a method of pelletizing the ETFE dried product obtained by the production method of the present invention after melting. The manufacturing method of the ETFE pellet of this invention can employ | adopt a well-known method except using the ETFE dried material obtained by the manufacturing method of this invention.
For example, as a method for producing the ETFE pellets of the present invention, the ETFE dried product obtained by the production method of the present invention is melted and extruded into a strand shape, and then the tip of the strand is continuously cut by a pelletizer. The method of pelletizing is mentioned. Conventionally known methods such as a hot cut method, an underwater cut method, and a sheet cut method can also be employed.
The bulk density of the ETFE pellet used in the treatment method of the present invention is preferably 0.5 to 1.5 g / ml, more preferably 0.8 to 1.2 g / ml, and most preferably 0.9 to 1.1 g / ml. . If the bulk density is in the above range, the handling property in producing a molded body using ETFE pellets is good. In addition, the value of the said bulk density is the value measured based on JISK6981 ethylene tetrafluoride resin molding powder test method.
The average particle diameter of the ETFE pellet is preferably 1 to 5 mm, more preferably 1.5 to 3.5 mm, and most preferably 2 to 3 mm. When the average particle diameter of the ETFE pellet is too small, the handling property in producing an ETFE molded product using the ETFE pellet is likely to be impaired. If the average particle size of the ETFE pellets is too large, the ratio of the surface area to the volume of the ETFE pellets becomes small and the drying time becomes long.
The measurement method of the average particle diameter is a value obtained by extracting several tens of arbitrary ETFE pellets from the ETFE pellet to be measured, measuring the major axis and the minor axis of each ETFE pellet, and calculating the average value.

<Method for producing ETFE molding>
The method for producing an ETFE molded product of the present invention is a method for melt-molding an ETFE dried product obtained by the production method of the present invention or an ETFE pellet obtained by the production method of the present invention. As a method for producing the ETFE molded product of the present invention, a known method can be adopted except that the ETFE dried product obtained by the production method of the present invention or the ETFE pellet obtained by the production method of the present invention is used.
For example, in the case of an electric wire coating material, a method of coating a dried ETFE product or ETFE pellet on the outside of the core wire by melt extrusion molding can be mentioned.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by the following description. Examples 1, 3, 5, and 7 are examples, and examples 2, 4, 6, and 8 are comparative examples.
[Measuring method]
1. Copolymerization composition of dried ETFE The copolymer composition of the dried ETFE was measured by FT-IR.
2. Volumetric flow rate of ETFE dried product From the orifice of 2.1 mm in diameter and 8 mm in length, using a flow tester manufactured by Shimadzu Corporation as the volumetric flow rate (mm ³ / sec) of ETFE dried product under the conditions of 297 ° C and load of 7 kg. The extrusion speed when extruding ETFE was measured.
3. Melting point of dried ETFE Using a scanning differential thermal analyzer (DSC7020, manufactured by SII Nano Technologies), the ETFE dried product was heated to 300 ° C at 10 ° C / min in an air atmosphere, and the endothermic peak when heated. I asked for it.
4). Stress crack resistance test (stress crack temperature)
A plurality of wires coated with a thickness of 0.5 mm were prepared on each core wire having a diameter of 1.8 mm by melt extrusion using each ETFE dried product. Each electric wire was heat treated for 96 hours (hereinafter referred to as “heat treatment A”) at 180 ° C., 185 ° C., 190 ° C., and 195 ° C. in an oven. Thereafter, a part of the electric wire was folded back, the folded portion was wound around the electric wire itself for 8 or more turns, fixed in that state, and further heat treated at 200 ° C. for 1 hour in an oven, and then the state of the electric wire was confirmed. When heat treatment A is performed at each temperature, five wires are tested, the ratio (%) of the number of broken wires to the number of cracked wires is calculated, and the stress crack temperature Tb (unit: ° C) is calculated by the following equation ) Was calculated.
Tb = Th−ΔT (S / 100−1 / 2)
Th: The highest temperature in the temperature of the heat treatment A when all the wires are cracked.
ΔT: Test temperature interval of heat treatment A (° C.). In this example, 5 ° C.
S: Sum of the ratios of crack destruction from the case where the temperature of the heat treatment A is lowest when the crack failure does not occur in all the wires to the case where the temperature of the heat treatment A is Th.

[Example 1]
(Polymerization process)
After degassing the inside of a 430 liter stainless steel autoclave, 417.2 kg of CF ₃ (CF ₂ ) ₅ H, 3.8 kg of methanol, and 1.9 kg of perfluorobutylethylene (hereinafter referred to as “PFBE”). The temperature was raised to 66 ° C. while stirring, and a mixed gas of TFE / E = 83/17 (mol%) was introduced until the pressure reached 1.5 MPaG. Next, 1048 g of a CF ₃ (CF ₂ ) ₅ H solution having a tert-butyl peroxypivalate concentration of 1% by mass was injected into the autoclave to initiate polymerization. During the polymerization, a mixed gas of TFE / E = 54/46 (mol%) and an amount of PFBE corresponding to 1.4 mol% with respect to the mixed gas are adjusted so that the pressure in the autoclave becomes 1.5 MPaG. Added continuously. When the amount of the mixed gas reached 27 kg, the autoclave was cooled, and a part of the residual monomer gas was purged to obtain ETFE slurry 1.

(Evaporation process)
120 kg of the obtained slurry 1 is stored in a storage tank, and the internal temperature of the centrifugal thin film evaporator (manufactured by Hitachi Plant Technologies) is set to 130 ° C. and the internal pressure is set to 53 kPa. The liquid was sent to a centrifugal thin film evaporator at / hour to evaporate volatile components, and the powdered ETFE dried product 1 was recovered.

[Example 2]
(Evaporation process)
Transfer 300 kg of the slurry 1 obtained in Example 1 to an 850 liter granulation tank, add 340 L of water, heat the disk turbine blade at 85 rpm, and heat from 40 ° C. to 104 ° C. while stirring. Then, the fluorine-containing organic solvent and the residual monomer were distilled off over 230 minutes to obtain an ETFE granulated product. Next, water and ETFE granulated material were separated using a mesh-like wire mesh. Next, the ETFE granulated product was transferred to a vacuum dryer and dried by heating at 130 ° C. for 4.5 hours to obtain a particulate ETFE dried product 2.

[Example 3]
(Polymerization process)
_{CF 3 (CF 2) 5 H} 417.5kg usage, except that the concentration of tert- butyl peroxypivalate has a 2991g usage 1 wt% of _CF 3 _{(CF 2) 5} H solution, Example In the same manner as in Example 1, slurry 2 of ETFE was obtained. (Evaporation process)
Next, using 120 kg of the obtained slurry 2, the powdered ETFE dry product 3 was recovered in the same manner as in Example 1.

[Example 4]
(Evaporation process)
Using 300 kg of the slurry 2 obtained in Example 3, a particulate ETFE dried product 4 was obtained in the same manner as in Example 2.

[Example 5]
(Polymerization process)
After degassing the inside of a 430 liter stainless steel autoclave, 417.7 kg of CF ₃ (CF ₂ ) ₅ H, 3.1 kg of methanol, and 1.7 kg of PFBE were charged, and the temperature was raised to 75 ° C. while stirring. Then, a mixed gas of TFE / E = 83/17 (mol%) was introduced until the pressure became 1.5 MPaG. Next, 2096 g of a 1% by mass CF ₃ (CF ₂ ) ₅ H solution of tert-butyl peroxypivalate was injected into the autoclave to initiate polymerization. During the polymerization, a mixed gas of TFE / E = 54/46 (mol%) and PFBE in an amount corresponding to 1.4 mol% with respect to the mixed gas are continuously added so that the pressure in the autoclave becomes 1.5 MPaG. Was added. When the amount of the mixed gas reached 27 kg, the autoclave was cooled, and a part of the residual monomer gas was purged to obtain ETFE slurry 3.
(Evaporation process)
Using 120 kg of the obtained slurry 3, the powdered ETFE dry product 5 was recovered in the same manner as in Example 1.

[Example 6]
(Evaporation process)
Using 300 kg of the slurry 3 obtained in Example 5, a particulate ETFE dried product 6 was obtained in the same manner as in Example 2.

[Example 7]
(Polymerization process)
An ETFE slurry 4 was obtained in the same manner as in Example 5 except that the amount of CF ₃ (CF ₂ ) ₅ H used was 419.8 kg and the amount of methanol used was 2.7 kg. (Evaporation process)
Using 120 kg of the obtained slurry 4, a powdery ETFE dry product 7 was recovered in the same manner as in Example 1.

[Example 8]
(Evaporation process)
Using 300 kg of the slurry 4 obtained in Example 7, particulate ETFE8 was obtained in the same manner as in Example 2.

Table 1 shows the copolymer composition, capacity flow rate, melting point, and stress crack temperature of the dried ETFE obtained in each example.
In the columns of TFE, E, and PFBE of the copolymer composition in Table 1, the ratio (mol%) of the repeating unit based on TFE, the repeating unit based on E, and the repeating unit based on PFBE are shown. In the column of “contact with water in the evaporation step”, presence / absence of contact between the slurry and water in the evaporation step is shown.

As shown in Table 1, comparing Example 1 and Example 2, Example 3 and Example 4, Example 5 and Example 6, Example 7 and Example 8, regardless of the presence or absence of water contact with the slurry in the evaporation step, An ETFE dry product was obtained that exhibited approximately the same sufficient volumetric flow rate and melting point.
On the other hand, in Examples 1, 3, 5, and 7, in which the volatile component was evaporated from the slurry without contacting the slurry and water in the evaporation step to obtain a dried ETFE, Examples in which water was brought into contact with the slurry in the drying step Compared to 2, 4, 6, and 8, the stress crack temperature was high, and excellent stress crack resistance was obtained.

According to the method for producing a dried ETFE product of the present invention, a dried ETFE product capable of forming an ETFE molded product having excellent stress crack resistance while reducing environmental burden is obtained.
It should be noted that the entire content of the specification, claims, drawings and abstract of Japanese Patent Application No. 2013-007438 filed on January 18, 2013 is cited herein as the disclosure of the specification of the present invention. Incorporated.

DESCRIPTION OF SYMBOLS 1 Evaporator 10 Reservoir 12 Centrifugal thin film evaporator 14 Condenser 16 Recovery tank 18 Blower 20 Liquid feed pump 22 Back pressure valve 24, 26, 28, 32 Piping 30 Pressure adjustment valve 34 Heat transfer body 34a Inner wall surface 34b Raw material supply port 34c Volatile component recovery port 36 Dispersing rotor 38 Rotating shaft 40 Stirring blade 42 Rotating stirring unit 44 First heating unit 46 Powder receiving unit 48 Second heating unit 50 Nozzle

Claims (12)

Ethylene and tetrafluoroethylene are solution-polymerized by using a water-soluble chain transfer agent in at least one fluorine-containing organic solvent selected from the group consisting of perfluorocarbon, hydrofluorocarbon, hydrochlorofluorocarbon, and hydrofluoroether. A polymerization step for obtaining a slurry in which fine particles of tetrafluoroethylene copolymer are dispersed;
An evaporation step of evaporating volatile components from the slurry without contacting water with the slurry;
A process for producing a dried ethylene-tetrafluoroethylene copolymer, comprising:   2. The ethylene according to claim 1, wherein the water-soluble chain transfer agent is at least one selected from the group consisting of alcohols having 1 to 4 carbon atoms, ketones having 3 to 4 carbon atoms, tetrahydrofuran, dimethyl sulfoxide, and dimethylformamide. -Method for producing dried tetrafluoroethylene copolymer.   The method for producing a dried ethylene-tetrafluoroethylene copolymer according to claim 1, wherein the water-soluble chain transfer agent is methanol.   The amount of the water-soluble chain transfer agent used in the polymerization step is 0.01 to 20 parts by mass with respect to 100 parts by mass of the fluorine-containing organic solvent. A method for producing a dried fluoroethylene copolymer.   The evaporation step is a rotation in which a cylindrical heat transfer drum portion and a rotating blade are provided with a stirring blade, and the tip of the stirring blade rotates in the heat transfer drum portion so as to give up the inner wall surface of the heat transfer drum portion. It is a process of evaporating a volatile component from the said slurry using the centrifugal thin film evaporator which has a stirring part and the heating part which heats the said heat-transfer trunk | drum, As described in any one of Claims 1-4. A method for producing a dried ethylene-tetrafluoroethylene copolymer.   The method for producing a dried ethylene-tetrafluoroethylene copolymer according to any one of claims 1 to 5, wherein an dried ethylene-tetrafluoroethylene product having an average particle size of 10 to 500 µm is obtained.   The molar ratio of the repeating unit based on ethylene and the repeating unit based on tetrafluoroethylene in the ethylene-tetrafluoroethylene copolymer is 30/70 to 60/40. The manufacturing method of the ethylene-tetrafluoroethylene copolymer dried material of description.   The ethylene-tetrafluoroethylene copolymer according to any one of claims 1 to 7, wherein the ethylene-tetrafluoroethylene copolymer has a repeating unit based on ethylene and another monomer other than tetrafluoroethylene. A method for producing a combined dried product. The method for producing a dried ethylene-tetrafluoroethylene copolymer according to claim 8, wherein the other monomer is a monomer represented by the following formula (1).
CH ₂ = CR ^1- (CF ₂ ) _a R ² (1)
(However, the equation (1), ^{R 1} and ^{R 2} are each independently a hydrogen atom or a fluorine atom, a is an integer from 1 to 12.)   The concentration of the fine particles of the ethylene-tetrafluoroethylene copolymer in the slurry in which the fine particles of the ethylene-tetrafluoroethylene copolymer are dispersed obtained in the polymerization step is 0.1 to 45% by mass. The manufacturing method of the ethylene-tetrafluoroethylene copolymer dried material as described in any one of 1-9.   An ethylene-tetrafluoroethylene copolymer, wherein the ethylene-tetrafluoroethylene copolymer dried product obtained by the production method according to any one of claims 1 to 10 is melted and pelletized. Pellet manufacturing method.   The ethylene-tetrafluoroethylene copolymer dried product obtained by the production method according to any one of claims 1 to 10, or the ethylene-tetrafluoroethylene copolymer obtained by the production method according to claim 11. A method for producing an ethylene-tetrafluoroethylene copolymer molded product, comprising melt-molding a coalescent pellet.

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