JP2011225677A - Manufacturing method for fluorine-containing copolymer powder, and porous fluorine-containing copolymer powder - Google Patents

Abstract

An ethylene / tetrafluoroethylene-based fluorine-containing copolymer powder having excellent moldability with suppressed generation of square-shaped and beard-like particles is obtained from an ethylene / tetrafluoroethylene-based fluorine-containing copolymer. Provided is a method for producing easily regardless of the type, and a porous ethylene / tetrafluoroethylene-based fluorine-containing copolymer powder having good moldability obtained thereby.
A solvent capable of dissolving a fluorine-containing copolymer containing a repeating unit based on ethylene and a repeating unit based on tetrafluoroethylene at a temperature lower than the melting point of the fluorine-containing copolymer. And a step (A) of obtaining a fluorine-containing copolymer solution by dissolving in a solution and a step (B) of spray-drying the fluorine-containing copolymer solution. Method.
[Selection figure] None

Description

  The present invention relates to a method for producing an ethylene / tetrafluoroethylene-based fluorine-containing copolymer powder and a porous ethylene / tetrafluoroethylene-based fluorine-containing copolymer powder obtained by the method.

  The fluorinated copolymer powder is suitably used as a powder coating, and is used for non-adhesive coatings and corrosion-resistant lining applications.

  As a method for producing a fluorinated copolymer powder, a powder obtained by agglomerating fine particles of a tetrafluoroethylene copolymer obtained by polymerization to about 0.18 to 2.6 mm, together with a gas flow, has a melting point of the copolymer. Patent Document 1 describes a method of spraying into a firing chamber having an atmosphere maintained at the above temperature.

  However, the aggregated tetrafluoroethylene copolymer powder is easily crushed into tetrafluoroethylene copolymer fine particles by spraying with a spray nozzle. These fine particles have a small particle diameter, and the particles are easily fused when melted in the baking chamber. When such a powder is used in a powder coating, the coating film surface has poor smoothness and pinholes are formed in the coating film. Therefore, it is necessary to remove the aggregate in which the particles are fused. As a result, there are disadvantages that the product yield is low and the product cost is high.

  On the other hand, Patent Document 2 discloses a powder of a copolymer raw powder, which is a dried product of a tetrafluoroethylene copolymer obtained by suspension polymerization, formed into a sheet by a roll press to increase the apparent density and then pulverized. A manufacturing method is described.

  However, the powder after the polymerization drying of the tetrafluoroethylene copolymer contains a large amount of fine particles, the handling is poor, and it is difficult to form a uniform sheet with a roll press. The portion with insufficient compression is pulverized into fine particles by pulverizing in a subsequent step, and the portion with excessive compression is pulverized to become large particles or whisker-like particles. Further, the particle surface of the powder obtained by pulverizing the sheet is cracked in some places, and voids exist inside the particles. When such a powder is used for a powder coating material, the coating film easily includes bubbles and easily causes pinholes.

  Patent Document 3 discloses that a fluorine-containing copolymer raw powder (no description regarding the production method and obtaining method) is compression-molded with a roll under the condition that a specific gravity of 90% or more of the true specific gravity of the copolymer is obtained. A method is described in which fine particles of 3 to 40% by mass of the entire particle size distribution are removed after densification and pulverization of the molded product, and further coarse particles of 1 to 20% by mass of the entire particle size distribution are removed.

  When a high pressure is applied to make the true specific gravity of the fluorine-containing copolymer 90% or more, excessive energy is converted into heat, the temperature of the polymer rises, and the sheet obtained by molding under such high pressure is partially It tends to be in a semi-molten state and impair brittleness. If such a sheet is pulverized, beard-like particles are likely to be formed, and as a result, the moldability of the fluorinated copolymer is likely to be impaired.

  Furthermore, according to the method described above, after pulverization, 4 to 60% by mass of fine particles and coarse particles of the entire particle size distribution must be removed, resulting in poor production efficiency.

  Patent Document 4 discloses a fluorine-containing copolymer that is solid at room temperature, in particular, a fluorine-containing copolymer containing a fluorine-containing vinyl monomer and vinyl ether and / or carboxylic acid vinyl ester as essential monomer components, and a solvent. A method for producing a powdery fluorine-containing copolymer by spray-drying a fluorine-containing copolymer solution containing benzene is described.

  Patent Document 4 describes that the number average molecular weight of the fluorinated copolymer is suitably from 500 to 50,000, particularly preferably from 1,000 to 10,000. Further, it is described that drying at 70 ° C. or less is preferable for preventing thermal yellowing by heating the solution for a long time, and 70 ° C. or less is also preferable for drying the obtained powder.

  Here, among fluorine-containing copolymers, an ethylene / tetrafluoroethylene-based fluorine-containing copolymer is a fluorine-containing copolymer obtained by copolymerizing monomer components mainly containing ethylene and tetrafluoroethylene. The number average molecular weight of the coalescence (hereinafter referred to as “ETFE” as needed) is generally several hundred thousand, and it becomes brittle in the molecular weight range of 50000 or less, which is preferable in the above-mentioned Patent Document 4, and the original characteristics of ETFE Cannot be obtained. Furthermore, in Patent Document 4, the object is limited to a fluorine-containing copolymer essentially comprising a repeating unit based on a fluorine-containing vinyl monomer and vinyl ether and / or vinyl carboxylic acid ester. There is no description.

  In Patent Document 5, as a method for producing a fluorine-containing copolymer powder having good moldability, for example, ETFE powder, (1) fluorine-containing copolymer fine particles obtained by polymerization are prepared. A step of stirring and granulating in a granular medium to form a granulated product, (2) a step of pulverizing the granulated product, and (3) further heat-treating the pulverized fluorine-containing copolymer fine particles at a melting point or higher. A method for producing a powder characterized by comprising steps is described.

  However, ETFE often contains repeating units based on monomers having various functions in addition to ethylene and tetrafluoroethylene. Therefore, even in the case of a fluorinated copolymer classified as ETFE, characteristics (hardness and the like) other than those common to ETFE may be different. In the method for producing a powder described in Patent Document 5, for example, in order to produce a powder of relatively soft ETFE among ETFEs, if the pulverization step (2) is performed at room temperature, the horn- Since it is easy to produce the particles, a pulverization process at a very low temperature using liquid nitrogen or the like is necessary, and there is a problem that productivity is low.

Japanese Patent Publication No.53-11296 Japanese Patent Publication No. 7-5743 International Publication No. 1997/40089 Pamphlet Japanese Patent No. 4171946 JP 2000-103865 A

  The present invention relates to an ethylene / tetrafluoroethylene-based fluorine-containing copolymer powder having an excellent moldability with suppressed generation of square and beard-like particles. It is an object of the present invention to provide a method for easily producing any kind of the above and a porous ethylene / tetrafluoroethylene-based fluorine-containing copolymer powder having good moldability obtained thereby.

The present invention provides a method for producing an ethylene / tetrafluoroethylene-based fluorine-containing copolymer powder having the following constitution and a porous ethylene / tetrafluoroethylene-based fluorine-containing copolymer powder obtained by the method. .
[1] A fluorine-containing copolymer containing a repeating unit based on ethylene and a repeating unit based on tetrafluoroethylene is dissolved in a solvent capable of dissolving the fluorine-containing copolymer at a temperature lower than the melting point of the fluorine-containing copolymer. A method for producing a fluorinated copolymer powder, comprising: a step (A) for dissolving to obtain a fluorinated copolymer solution; and a step (B) for spray-drying the fluorinated copolymer solution. .
[2] In the above [1], the solvent is at least one selected from the group consisting of a fluorine-containing aromatic compound, an aliphatic compound having at least one carbonyl group, and a hydrofluoroalkyl ether. The manufacturing method of the fluorine-containing copolymer powder of description.

[3] The method for producing a fluorinated copolymer powder according to [1] or [2], wherein the step (A) is performed at a temperature not higher than the melting point of the fluorinated copolymer.
[4] The method for producing a fluorinated copolymer powder according to any one of [1] to [3], wherein the step (B) is performed at 40 to 350 ° C.
[5] The fluorine-containing copolymer according to any one of [1] to [4], wherein the fluorine-containing copolymer contains a repeating unit based on a monomer having an acid anhydride residue and a polymerizable unsaturated bond. A method for producing a copolymer powder.

[6] The content of the fluorine-containing copolymer in the fluorine-containing copolymer solution is 0.1 to 80% by mass with respect to the total amount of the solution, according to any one of [1] to [5]. A method for producing a fluorinated copolymer powder.
[7] A porous fluorine-containing copolymer powder having an average particle diameter of 0.01 to 1000 μm, obtained by the production method according to any one of [1] to [6].

  According to the method of the present invention, an ethylene / tetrafluoroethylene-based fluorine-containing copolymer powder having a good moldability with suppressed generation of square and whisker-like particles is contained in an ethylene / tetrafluoroethylene-based powder. Regardless of the type of fluorine copolymer, for example, even a flexible ethylene / tetrafluoroethylene-based fluorine-containing copolymer can be easily produced. Further, the porous ethylene / tetrafluoroethylene-based fluorine-containing copolymer powder obtained by the production method of the present invention is a powder having good moldability.

Hereinafter, embodiments of the present invention will be described in detail.
The method for producing a fluorinated copolymer powder of the present invention is characterized by having the following steps (A) and (B).
Step (A): A fluorine-containing copolymer containing a repeating unit based on ethylene and a repeating unit based on tetrafluoroethylene can be dissolved at a temperature below the melting point of the fluorine-containing copolymer. Step (B) of obtaining a fluorine-containing copolymer solution by dissolving in a solvent: Step of spray-drying the fluorine-containing copolymer solution

<Fluorine-containing copolymer>
The fluorine-containing copolymer in the present invention includes an ethylene / tetrafluoroethylene-based fluorine-containing copolymer containing a repeating unit based on ethylene and a repeating unit based on tetrafluoroethylene (hereinafter sometimes abbreviated as TFE). There is no particular limitation as long as it is a polymer, that is, ETFE. In this specification, the term “ETFE” may include a repeating unit based on a comonomer other than TFE and ethylene as a constituent unit of the copolymer, and TFE and ethylene are the main repeating units in the copolymer. It is used as a general term for a fluorine-containing copolymer as a unit.

  Here, as ETFE used in the present invention, when the repeating unit based on TFE is (a) and the repeating unit based on ethylene is (b), the molar ratio represented by (a) / (b) is 30 / 70-80 / 20 is preferable, 40 / 60-75 / 25 is more preferable, and 45 / 55-65 / 35 is most preferable. When the molar ratio represented by (a) / (b) is small, the heat resistance, weather resistance, chemical resistance, gas barrier property, fuel barrier, etc. of ETFE tend to be low. When the molar ratio is large, mechanical strength and molding Tend to be low in nature. ETFE in which (a) / (b) is in the above range is excellent in heat resistance, weather resistance, chemical resistance, gas barrier properties, fuel barrier, mechanical strength, moldability and the like.

ETFE in the present invention may contain a repeating unit based on another monomer in addition to the above repeating unit based on TFE and ethylene.
Other monomers include hydrocarbon olefins such as propylene and butene, CH ₂ ═CX (CF ₂ ) _n Y (where X and Y are independently hydrogen or fluorine atoms, n is an integer of 2 to 8) And a hydrogen atom in an unsaturated group such as hexafluoropropylene or chlorotrifluoroethylene having a hydrogen atom in an unsaturated group such as a compound represented by formula (1), vinylidene fluoride, vinyl fluoride or trifluoroethylene. Perfluoro (alkyl vinyl ether) such as perfluoro (propyl vinyl ether), alkyl vinyl ether, (fluoroalkyl) vinyl ether, glycidyl vinyl ether, hydroxybutyl vinyl ether, methyl vinyloxybutyl carbonate, etc. Bini Ether, vinyl acetate, vinyl chloroacetate, vinyl butanoate, vinyl pivalate, vinyl benzoate, vinyl crotonate, and other (meth) acrylic esters such as (polyfluoroalkyl) acrylate and (polyfluoroalkyl) methacrylate Etc. These monomers may be used individually by 1 type, and may use 2 or more types together.

In the ETFE used in the present invention, these monomers include at least one selected from the group consisting of hexafluoropropylene, perfluoro (propyl vinyl ether) and the compound represented by CH ₂ ═CX (CF ₂ ) _n Y. Preferably, a compound represented by CH ₂ ═CX (CF ₂ ) _n Y is more preferable. Here, X and Y are each independently a hydrogen atom or a fluorine atom, and n is an integer of 2 to 8. If n in the formula is less than 2, the properties of ETFE may be insufficient (for example, occurrence of stress cracks in the ETFE formed body). On the other hand, if n in the formula exceeds 8, the point of polymerization reactivity May be disadvantageous. Further, n = 2 to 4 in the compound is more preferable because the obtained ETFE is excellent in fuel barrier properties, stress crack resistance, and the like. Specific examples thereof include CH ₂ = CF (CF ₂ ) ₂ F, CH ₂ = CF (CF ₂ ) ₃ F, CH ₂ = CF (CF ₂ ) ₄ F, CH ₂ = CF (CF ₂ ) ₂ H, _{CH 2 = CF (CF 2)} 3 H, CH 2 = CF (CF 2) 4 H, CH 2 = CH (CF 2) 2 F, CH 2 = CH (CF 2) 3 F, CH 2 = CH (CF ₂ ) ₄ F, CH ₂ ═CH (CF ₂ ) ₂ H, CH ₂ ═CH (CF ₂ ) ₃ H, CH ₂ ═CH (CF ₂ ) ₄ H, and the like. These 1 type (s) or 2 or more types can be used. Among these, a compound represented by CH ₂ ═CH (CF ₂ ) _n Y is more preferable, and in this case, n in the formula is n = 2 to 6, so that the molded article has stress rack resistance. Since it is excellent, it is further preferable, and n = 2 to 4 is most preferable.

  When ETFE contains repeating units based on other monomers, the content is preferably 0.01 to 20 mol%, more preferably 0.1 to 15 mol%, based on all repeating units of ETFE. 1-10 mol% is the most preferable.

In addition to the above-mentioned monomers, other monomers that ETFE in the present invention may contain are monomers for adding various functions to ETFE, for example, added to improve adhesiveness. And a monomer having a crosslinkable functional group. Examples of the monomer having a crosslinkable functional group include a monomer having an acid anhydride residue and a polymerizable unsaturated bond.
Here, as ETFE in the present invention, other monomers are monomers having an acid anhydride residue and a polymerizable unsaturated bond, and relatively flexible ETFE is preferable.

  The content of the repeating unit based on the monomer having an acid anhydride residue and a polymerizable unsaturated bond in ETFE is preferably 0.01 to 5 mol% with respect to all the repeating units of ETFE. 0.1-5 mol% is more preferable, 0.15-3 mol% is further more preferable, and 0.3-3 mol% is the most preferable. If the content is small, the adhesion to the substrate tends to be low, and if it is high, the fuel barrier property tends to be low. Therefore, when the content of the repeating unit based on the monomer having an acid anhydride residue and a polymerizable unsaturated bond is in the above range, the obtained ETFE is excellent in both the fuel barrier property and the adhesion to the substrate. It will be a thing.

  The ETFE containing a repeating unit based on TFE and ethylene, and a repeating unit based on a monomer having an acid anhydride residue and a polymerizable unsaturated bond is a repeating unit based on the above other monomers. May be included. In that case, the content ratio of the repeating unit based on other monomers other than the monomer having TFE, ethylene, an acid anhydride residue and a polymerizable unsaturated bond is 0.000 based on the total repeating units of ETFE. 01-20 mol% is preferable, 0.1-15 mol% is more preferable, and 1-10 mol% is the most preferable.

  Examples of the monomer having an acid anhydride residue and a polymerizable unsaturated bond include maleic anhydride, itaconic anhydride (hereinafter referred to as IAH), citraconic anhydride (hereinafter referred to as CAH), and 5-norbornene. -2,3-dicarboxylic anhydride is preferred, and IAH or CAH is more preferred. When IAH or CAH is used, a special polymerization method required when maleic anhydride is used, that is, an acid anhydride is used without using a perfluorocarboxylic acid or a polymerization method of copolymerizing hexafluoropropylene. Since ETFE having a residue is obtained, it is preferable.

  A part of the acid anhydride residue in the monomer having an acid anhydride residue and a polymerizable unsaturated bond may be hydrolyzed before polymerization. For example, the IAH may be a mixture of IAH and itaconic acid in which a part of the IAH is hydrolyzed. Further, CAH may be a mixture of CAH and citraconic acid in which a part of CAH is hydrolyzed. Moreover, a part of repeating unit based on IAH or CAH in ETFE may be hydrolyzed after polymerization. These repeating units generated by hydrolysis before or after polymerization are regarded as a part of repeating units based on a monomer having an acid anhydride residue and a polymerizable unsaturated bond in the present invention. In that case, the content of the repeating unit based on the monomer having an acid anhydride residue and a polymerizable unsaturated bond is, for example, a monomer having an acid anhydride residue and a polymerizable unsaturated bond. In the case of IAH, it represents the total amount of the repeating unit based on IAH and the repeating unit based on itaconic acid in which a part of IAH is hydrolyzed.

The capacity flow rate (hereinafter referred to as Q value) of ETFE in the present invention is preferably 1 to 1000 mm ³ / sec. The Q value is an index representing the melt fluidity of ETFE and is a measure of molecular weight. A large Q value indicates a low molecular weight, and a small Q value indicates a high molecular weight. In this specification, the ETFE Q value was measured in an orifice having a diameter of 2.1 mm and a length of 8 mm under a temperature of 297 ° C. and a load of 7 kg using a flow tester manufactured by Shimadzu Corporation as described in the examples. It refers to the extrusion rate of ETFE during extrusion. When the Q value is small, the smoothness of the coating film produced using the powder of the present invention tends to be insufficient, and when it is large, the mechanical strength of the coating film tends to be low. Therefore, the Q value of ETFE in the present invention is preferably in the above range, and more preferably in the range of 5 to 500 mm ³ / sec.

  Although it does not specifically limit as melting | fusing point of ETFE in this invention, From points, such as solubility and intensity | strength, Preferably it is 130 to 275 degreeC, More preferably, it is 140 to 265 degreeC, Most preferably, it is 150 to 260 degreeC. .

  As a method for producing ETFE in the present invention, a method of copolymerizing ethylene, TFE, and other monomers which may optionally be contained by an ordinary method can be employed. The method for producing ETFE is not particularly limited, and a polymerization method using a generally used radical polymerization initiator can be applied. Examples of polymerization methods include bulk polymerization methods, solution polymerization methods using organic solvents such as fluorinated hydrocarbons, chlorinated hydrocarbons, fluorinated chlorohydrocarbons, alcohols, hydrocarbons, aqueous media and suitable as needed. A suspension polymerization method using an organic solvent and an emulsion polymerization method using an aqueous medium and an emulsifier can be mentioned, and a solution polymerization method is most preferable.

The radical polymerization initiator preferably has a half-life of 10 hours and preferably has a temperature of 0 ° C to 100 ° C, more preferably 20 to 90 ° C. Specific examples include azo compounds such as azobisisobutyronitrile, non-fluorine diacyl peroxides such as isobutyryl peroxide, octanoyl peroxide, benzoyl peroxide and lauroyl peroxide, peroxydicarbonates such as diisopropylperoxydicarbonate, tert - butyl peroxypivalate, tert- butylperoxy isobutyrate, tert- butyl peroxy ester peroxy acetate, _{etc., 2} (where _{(Z (CF 2) p COO} ), Z represents a hydrogen atom, a fluorine atom or a chlorine atom , P is an integer of 1 to 10.) Fluorine-containing diacyl peroxide such as a compound represented by formula (1), inorganic peroxides such as potassium persulfate, sodium persulfate, and ammonium persulfate.

  In order to control the Q value of ETFE, a chain transfer agent may be appropriately used during the polymerization. Chain transfer agents include alcohols such as methanol and ethanol, chlorofluorohydrocarbons such as 1,3-dichloro-1,1,2,2,3-pentafluoropropane, 1,1-dichloro-1-fluoroethane, Hydrocarbons such as pentane, hexane, and cyclohexane are listed. Further, it is preferable to use a chain transfer agent having a functional group such as an ester group, a carbonate group, a hydroxyl group, a carboxyl group, or a carbonyl fluoride group because a polymer end group having excellent adhesion to a base material such as polyamide is introduced. . Examples of the chain transfer agent include acetic acid, methyl acetate, ethylene glycol, propylene glycol and the like.

  In the present invention, the polymerization conditions are not particularly limited, and the polymerization temperature is preferably 0 ° C to 100 ° C, more preferably 20 to 90 ° C. The polymerization pressure is preferably from 0.1 to 10 MPa, more preferably from 0.5 to 3 MPa. The polymerization time is preferably 1 to 30 hours.

  Further, during the polymerization, the concentration of each monomer is charged into the polymerization tank within the above preferred range, but the concentration of each monomer in the polymerization medium may not be increased in consideration of the polymerization rate and the like. In that case, it is preferable to supply the consumed amount of the monomer into the polymerization tank continuously or intermittently as each monomer is consumed in the polymerization.

  In addition, what is obtained as a commercial item can also be used as ETFE in this invention. As commercial products, for example, as for ETFE, Asahi Glass Co., Ltd .: Fluon (Registered Trademark) ETFE Series, Fluon (Registered Trademark) LM Series, Daikin Industries, Ltd .: Neofron (Registered Trademark), Dyneon Co., Ltd .: Dyneon (Registered Trademark) Commercial products such as ETFE, manufactured by DuPont: Tefzel (registered trademark) are listed.

  In the production method of the present invention, the shape of ETFE when ETFE is dissolved in a solvent is preferable because a powder can be dissolved in a short time, but other shapes such as pellets can also be used.

  In the production method of the present invention, one of these ETFEs can be used alone, or two or more of them can be used in combination.

<Process (A)>
Step (A) in the production method of the present invention is a step of obtaining the fluorine-containing copolymer solution by dissolving the ETFE in a solvent capable of dissolving the ETFE at a temperature equal to or lower than the melting point of the ETFE.

  The solvent used in the production method of the present invention is not particularly limited as long as it can dissolve ETFE at a temperature not higher than the melting point of ETFE. Specifically, it includes one or more fluorinated aromatic compounds and carbonyl groups. The aliphatic compound having at least one selected from the group consisting of an aliphatic compound and a hydrofluoroalkyl ether is preferable. In addition, it does not specifically limit as a pressure condition at the time of a solvent melt | dissolving ETFE at the said temperature, In addition to melt | dissolution by a normal pressure, the melt | dissolution conditions under pressure are also included.

  Here, many of the solvents cannot dissolve the ETFE at room temperature, but can be dissolved at least at a temperature lower than the melting point of ETFE to give a transparent and uniform ETFE solution. In addition, as said solvent, the solvent which can melt | dissolve 0.1 mass% or more with respect to the whole quantity of the solution which can obtain ETFE at the temperature below the melting | fusing point of ETFE is preferable. Furthermore, the amount by which the solvent can dissolve ETFE is more preferably 5% by mass or more, and most preferably 10% by mass or more with respect to the total amount of the resulting solution.

  The melting point of the fluorinated aromatic compound capable of dissolving ETFE is preferably 100 ° C. or lower, more preferably 80 ° C. or lower, and further preferably 50 ° C. or lower. When the melting point is within this range, the handleability when dissolving ETFE is excellent. Moreover, it is preferable that the boiling point of the said fluorine-containing aromatic compound is more than the temperature which melt | dissolves the said ETFE.

  The fluorine content ((fluorine atom weight × number of fluorine atoms in the molecule) × 100 / molecular weight) of the fluorine-containing aromatic compound used as the solvent is preferably 5 to 75% by mass, more preferably 9 to 75% by mass. 12 to 75% by mass is most preferable. When in this range, the solubility of ETFE is excellent.

  Specific examples of the fluorine-containing aromatic compound include fluorine-containing benzonitrile, fluorine-containing benzoic acid and its ester, fluorine-containing polycyclic aromatic compound, fluorine-containing nitrobenzene, fluorine-containing phenyl alkyl alcohol, fluorine-containing phenol and its ester, Fluoroaromatic ketone, fluorinated aromatic ether, fluorinated aromatic sulfonyl compound, fluorinated pyridine compound, fluorinated aromatic carbonate, perfluoroalkyl-substituted benzene, perfluorobenzene, polyfluoroalkyl ester of benzoic acid, polyfluoro of phthalic acid Examples thereof include alkyl esters and aryl esters of trifluoromethanesulfonic acid. The fluorine-containing aromatic compound used in the present invention is preferably a fluorine-containing aromatic compound having at least two fluorine atoms. A fluorine-containing aromatic compound may be used individually by 1 type, and may use 2 or more types together.

  Among the fluorine-containing aromatic compounds, more preferred examples include pentafluorobenzonitrile, 2,3,4,5-tetrafluorobenzonitrile, 2,3,5,6-tetrafluorobenzonitrile, 2,4,5. -Trifluorobenzonitrile, 2,4,6-trifluorobenzonitrile, 3,4,5-trifluorobenzonitrile, 2,3-difluorobenzonitrile, 2,4-difluorobenzonitrile, 2,5-difluorobenzo Nitrile, 2,6-difluorobenzonitrile, 3,4-difluorobenzonitrile, 3,5-difluorobenzonitrile, 4-fluorobenzonitrile, 3,5-bis (trifluoromethyl) benzonitrile, 2- (trifluoro Methyl) benzonitrile, 3- (trifluoromethyl) benzonitrile, -(Trifluoromethyl) benzonitrile, 2- (trifluoromethoxy) benzonitrile, 3- (trifluoromethoxy) benzonitrile, 4- (trifluoromethoxy) benzonitrile, (3-cyanophenyl) sulfa pentafluoride, (4-Cyanophenyl) sulfa pentafluoride, pentafluorobenzoic acid, ethyl pentafluorobenzoate, methyl 2,4-difluorobenzoate, methyl 3- (trifluoromethyl) benzoate, 4- (trifluoromethyl) benzoic acid Methyl acid, methyl 3,5-bis (trifluoromethyl) benzoate, perfluorobiphenyl, perfluoronaphthalene, pentafluoronitrobenzene, 2,4-difluoronitrobenzene, (3-nitrophenyl) sulfur pentafluoride, pentafur Robenzyl alcohol, 1- (pentafluorophenyl) ethanol, pentafluorophenyl acetate, pentafluorophenyl propanoate, pentafluorophenyl butanoate, pentafluorophenyl pentanoate, perfluorobenzophenone, 2,3,4,5,6-penta Fluorobenzophenone, 2 ′, 3 ′, 4 ′, 5 ′, 6′-pentafluoroacetophenone, 3 ′, 5′-bis (trifluoromethyl) acetophenone, 3 ′-(trifluoromethyl) acetophenone, 2,2, 2-trifluoroacetophenone, pentafluoroanisole, 3,5-bis (trifluoromethyl) anisole, decafluorodiphenyl ether, 4-bromo-2,2 ', 3,3', 4 ', 5,5', 6 6'-nonafluorodiphenyl ether, pen Tafluorophenylsulfonyl chloride, pentafluoropyridine, 3-cyano-2,5,6-trifluoropyridine, bis (pentafluorophenyl) carbonate, benzotrifluoride, 4-chlorobenzotrifluoride, 1,3-bis (tri Fluoromethyl) benzene, hexafluorobenzene, 2,2,2-trifluoroethyl benzoate, 2,2,3,3-tetrafluoropropyl benzoate, 2,2,3,3,3-pentafluoropropyl benzoate Benzoic acid 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl, bis (2,2,2-trifluoroethyl) phthalate, trifluoro Examples include 4-methanephenyl methanesulfonate.

  The melting point of the aliphatic compound having one or more carbonyl groups capable of dissolving ETFE is preferably 100 ° C. or lower, more preferably 50 ° C. or lower, and most preferably 20 ° C. or lower. The boiling point of the aliphatic compound having one or more carbonyl groups is preferably equal to or higher than the temperature at which the ETFE is dissolved.

  However, in the present invention, when the ETFE is dissolved under a naturally occurring pressure, an aliphatic compound having one or more carbonyl groups whose boiling point of the aliphatic compound having one or more carbonyl groups is lower than the dissolution temperature is also included. Applicable. Here, “spontaneously generated pressure” means the pressure that the mixture of the solvent and ETFE naturally exhibits in the closed container. When an aliphatic compound having at least one carbonyl group having a lower boiling point is used, the spontaneously generated pressure increases, so that the boiling point of the aliphatic compound having at least one carbonyl group is considered from the viewpoint of safety and convenience. Is preferably room temperature or higher, more preferably 50 ° C. or higher. The upper limit of the boiling point of the aliphatic compound having one or more carbonyl groups is not particularly limited, but is preferably 220 ° C. or lower from the viewpoint of ease of drying in the spray drying step (B).

  Examples of the aliphatic compound having one or more carbonyl groups include cyclic ketones having 3 to 10 carbon atoms, ketones such as chain ketones, esters such as chain esters and glycol monoesters, and carbonates. What is 1 or more types chosen from a group is preferable. The number of carbonyl groups is preferably 1 or 2.

  The molecular structure of the aliphatic compound having one or more carbonyl groups is not particularly limited. For example, the carbon skeleton may be linear, branched, or cyclic, and carbon constituting the main chain or side chain. -An etheric oxygen atom may be present between the carbon bonds, and a part of the hydrogen atoms bonded to the carbon atom may be substituted with a halogen atom such as a fluorine atom. Among these, cyclic ketones are more preferable as the aliphatic compound having one or more carbonyl groups. These may be used alone or in combination of two or more.

  More preferred specific examples of the aliphatic compound having one or more carbonyl groups in the present invention are as follows.

  Examples of the cyclic ketone include cyclopentanone, cyclohexanone, 2-methylcyclohexanone, 3-methylcyclohexanone, 4-ethylcyclohexanone, 2,6-dimethylcyclohexanone, 3,3,5-trimethylcyclohexanone, 4-tert-butylcyclohexanone, Examples include cycloheptanone and isophorone.

  Examples of the chain ketone include acetone, methyl ethyl ketone, 2-pentanone, methyl isopropyl ketone, 2-hexanone, methyl isobutyl ketone, 2-heptanone, 2-octanone, 2-nonanone, diisobutyl ketone, 2-decanone and the like.

  Examples of the chain esters include ethyl formate, isopentyl formate, methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, isopentyl acetate, hexyl acetate, cyclohexyl acetate, 2-ethylhexyl acetate, ethyl butyrate, butyl butyrate, pentyl butyrate Bis (2,2,2-trifluoroethyl) adipate, methyl cyclohexanecarboxylate, 2,2,2-trifluoroethyl cyclohexanecarboxylic acid, ethyl perfluoropentanoate and the like.

  Monoesters of the glycols include 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butoxyethyl acetate, 1-methoxy-2-acetoxypropane, 1-ethoxy-2-acetoxypropane, and 3-methoxybutyl acetate. And 3-methoxy-3-methylbutyl acetate.

  Examples of the carbonate include bis (2,2,3,3-tetrafluoropropyl) carbonate, bis (2,2,2-trifluoroethyl) carbonate, diethyl carbonate, and propylene carbonate.

  The melting point of the hydrofluoroalkyl ether used in the present invention capable of dissolving ETFE is preferably 100 ° C. or lower, more preferably 80 ° C. or lower, and most preferably 50 ° C. or lower. Moreover, it is preferable that the boiling point of the said hydrofluoroalkyl ether is more than the temperature which melt | dissolves the said ETFE.

  Specific examples of the hydrofluoroalkyl ether used in the present invention capable of dissolving ETFE include 1,1,1,2,3,3-hexafluoro-4- (1,1,2,3,3,3- Hexafluoropropoxy) pentane, 1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4- (trifluoromethyl) pentane and the like. Among these, 1,1,1,2,3,3-hexafluoro-4- (1,1,2,3,3,3-hexafluoropropoxy) pentane is preferable.

  The solvent which can melt | dissolve the said ETFE may be used individually by 1 type, and may use 2 or more types together. When two or more kinds of solvents are used, the speed of phase separation may be controlled.

  In this specification, a solvent that does not dissolve or swell ETFE up to the melting point of ETFE or the boiling point of a liquid is defined as a non-solvent. In the production method of the present invention, a non-solvent may be contained in the ETFE solution as long as the solubility of ETFE is not impaired.

  Specific examples of the ETFE non-solvent include aromatic compounds not containing fluorine atoms, alcohols, and the like. Of these, aromatic compounds containing no fluorine atom, such as acetonitrile, dichlorobenzene, and dimethyl phthalate, are preferably used in the production method of the present invention. In the production method of the present invention, when the ETFE solution contains a non-solvent together with a solvent capable of dissolving ETFE alone, the mixing ratio is as follows: solvent / non-solvent (mass ratio) capable of dissolving ETFE alone. 10/90 to 90/10 are preferable, and 30/70 to 70/30 are more preferable.

  In the production method of the present invention, when the ETFE solution contains a non-solvent in combination with a solvent capable of dissolving ETFE alone, the mixture of the solvent capable of dissolving ETFE alone and the non-solvent is referred to as “solvent”.

The ETFE solution in the present invention is obtained by the step (A) of dissolving ETFE in the solvent. Here, the concentration of the prepared ETFE solution is preferably 0.1 to 80% by mass, more preferably 1 to 70% by mass, and more preferably 3 to 60% as the content of ETFE with respect to the total amount of the ETFE solution. More preferably, it is mass%. If the content of ETFE with respect to the total amount of the ETFE solution is less than 0.1% by mass, the yield of the obtained powder may be low, and if it exceeds 80% by mass, spraying may be difficult.
The concentration of the ETFE solution is preferably adjusted as appropriate so that the type of ETFE, the type of solvent, the spray drying conditions in step (B), the powder yield, and the like have predetermined values.

  The lower limit of the temperature at which ETFE in step (A) is dissolved in the solvent is the phase separation temperature of the solution at a predetermined concentration. As will be described below, a mixture containing at least two compounds, here ETFE and a solvent, is separated into two phases at a temperature below the phase separation temperature, and thus does not form a uniform solution. That is, the solution can be produced only at a temperature higher than the phase separation temperature. The temperature of the ETEF solution obtained is not a problem even if it is higher than the melting point of ETFE, but because of deterioration and volatilization of ETFE and the solvent, it is preferably lower than the melting point of ETFE, and is higher than the phase separation temperature of the ETFE solution.

  The temperature at which ETFE is dissolved in the above solvent, that is, the dissolution temperature varies depending on the type of solvent, the solution composition, etc., the vertical axis indicates the temperature, the horizontal axis indicates the concentration ratio of ETFE and the solvent, and the ETFE and solvent at each temperature. It is preferable to optimize by the phase diagram in which the concentration of the two-phase coexistence with is plotted. If the temperature at which ETFE is dissolved in the solvent is too high in the production method of the present invention, ETFE is thermally deteriorated and the solvent is volatilized, which is not preferable. If the temperature is lower than the phase separation temperature in the ETFE solution, ETFE is not dissolved in the solvent as described above.

  Therefore, in the step (A), the melting temperature is preferably 5 ° C. or more higher than the phase separation temperature of the solution to be produced, and more preferably 10 ° C. or more higher than the phase separation temperature. In addition, the upper limit of the dissolution temperature in the production method of the present invention is not particularly limited, but is preferably equal to or lower than the melting point of ETFE to be dissolved from the viewpoint of ease of making ETFE powder, volatility of the solvent, and the like. .

  Here, the phase separation temperature is also called a cloud point (cloud point), and when a solution of a certain concentration is maintained at a temperature higher than that temperature, the solute (ETFE in the present invention) and the solvent are mixed. It becomes a uniform one-phase solution, but below the cloud point is the temperature at which phase separation occurs. In general, when the ETFE solution is brought to a temperature equal to or lower than the phase separation temperature, it is separated into a phase containing a solvent and containing ETFE in a concentrated phase and a phase containing ETFE and containing a solvent in a concentrated manner. Furthermore, below the crystallization temperature of the ETFE used, ETFE is fixed in a ETFE-rich phase, and a porous precursor is formed. The heat transfer rate in the ETFE solution is 100 times faster than the diffusion rate of the solvent / non-solvent. Therefore, in the following step (B), when the droplet particles of the ETFE solution are set to a temperature equal to or lower than the crystallization temperature of ETFE, the ETFE in the droplet particles is phase-separated and fixed almost instantaneously and becomes porous.

  In step (A) of the present invention, when ETFE is dissolved in the solvent, conditions other than temperature are not particularly limited, and it is usually preferable to carry out the reaction under normal pressure. However, depending on the type of ETFE or solvent used, when the boiling point of the solvent is lower than the dissolution temperature, dissolution may be carried out in a pressure resistant container under pressure, for example, about 0.01 to 1 MPa. The dissolution time is appropriately adjusted depending on the type of ETFE and solvent to be used, the shape of ETFE, the concentration of the ETFE solution to be prepared, and the like.

<Process (B)>
Step (B) in the production method of the present invention is a step of spray drying the ETFE solution prepared in the above step (A).

  As a method for spray drying the ETFE solution, a method similar to the method for producing a fluorine-containing copolymer powder by spray-drying a conventionally known fluorine-containing copolymer solution can be used without any particular limitation. .

  The apparatus used for spray drying of the ETFE solution is not particularly limited as long as it can remove the solvent from the sprayed ETFE solution. Usually, the droplet particles of the sprayed ETFE solution are brought into contact with the heat source gas. A spray drying apparatus that volatilizes the solvent is used. In this case, since the drying is performed by volatilizing the solvent, the spray drying apparatus is preferably explosion-proof.

  When an ETFE solution having a temperature equal to or higher than the phase separation temperature is sprayed in a space equal to or lower than the phase separation temperature, ETFE having low solubility at a low temperature as described above instantaneously causes phase separation from the solvent. That is, ETFE and the solvent are uniformly phase-separated in the sprayed droplet particles. Therefore, ETFE tends to form porous particles, and the solvent exists in the pores of ETFE. And the porous ETFE powder is obtained by volatilizing and drying the solvent in the ETFE particles.

  Here, when spraying with an ETFE solution having a temperature lower than or equal to the phase separation temperature, there may be a problem that the ETFE and the solvent are separated into two phases and the ETFE particles are clogged inside the pipe. In order to maintain the ETFE solution, it is preferable to spray at a temperature equal to or higher than the phase separation temperature. The porous ETFE powder is preferable because it tends to easily form a coating film when heated to form a coating film, and the coating baking temperature may be reduced.

  The temperature at which the ETFE solution is sprayed is preferably equal to or higher than the phase separation temperature of the ETFE solution as described above in order to efficiently spray the ETFE solution, and specifically depends on the type of ETFE and the solvent used. Is preferably 40 ° C. or higher, more preferably 50 ° C. or higher. The upper limit of the temperature in spraying is preferably 350 ° C. or less, more preferably 300 ° C. or less, from the viewpoint that the resin may be deteriorated.

  Moreover, the temperature of drying performed simultaneously with spraying is not particularly limited as long as the solvent can be sufficiently removed by drying. However, it is performed at 40 to 350 ° C. from the viewpoint that phase separation can be performed to produce a porous ETFE powder. Preferably, 50 to 200 ° C is more preferable, and 80 to 200 ° C is most preferable. Here, since spraying and drying in the step (B) are not performed separately and are performed simultaneously, the spray drying temperature in the step (B) is 40 to 350 from the above viewpoint. It is preferable to carry out at 50 degreeC, It is more preferable to carry out at 50-200 degreeC, 80-200 degreeC is the most preferable.

  Note that the spray drying apparatus includes a solvent recovery device from the viewpoint of keeping the vapor content of the solvent in the heat source gas used for drying the droplet particles of the sprayed ETFE solution low. preferable.

  Further, the method of bringing the porous ETFE particles having the solvent in the pores obtained by phase separation into contact with the heat source gas is not particularly limited, and commonly used cocurrent, countercurrent, Any method such as a flow / countercurrent mixing method can be used.

  As for the spraying method of the ETFE solution, any known and conventional ones such as a rotating disk type, a two-fluid nozzle type, and a pressure nozzle type can be used. Factors for controlling the particle size of the droplet solution during spraying include the rotation speed of the disk in the rotating disk type, the discharge speed from the nozzle in the two-fluid nozzle type, and mixing with the raw material solution. There are discharge pressures and the like in the mixing ratio of the compressed gas and the raw material solution used, and the pressure nozzle type, and these values may be appropriately determined according to the target particle diameter. For example, in the rotating disk type, the rotational speed of the disk depends on the ETEF solution to be used and the like, but an ETFE powder having a particle diameter range described later is produced by appropriately adjusting the speed within a range from 8000 to 20000 rpm.

  The supply rate of the ETFE solution and the flow rate of the heat source gas are appropriately determined according to the target particle size, specifically, the particle size described later, depending on the application. When the supply rate of the ETFE solution and the flow rate of the heat source gas change during spray drying, the particle diameter and non-volatile value of the obtained particles, that is, the porosity ratio also changes. Therefore, it is preferable to keep it constant during spray drying. .

  Thus, in the production method of the present invention, the bulk density and particle diameter of the ETFE powder can be easily controlled by controlling the temperature in the spray drying step (B) and blowing conditions. However, it can be produced with almost no whiskers or corners.

  The heat source gas containing the ETFE powder obtained by spray drying in this manner is usually represented by a cyclone in the same manner as in the case of producing a fluorinated copolymer powder by such an operation. The ETFE powder is collected and classified.

  The heat source gas used in the spray drying is preferably an inert gas. Of these, the use of nitrogen gas is preferred from the viewpoint of cost and the like. The temperature of the heat source gas is preferably a high temperature so that the temperature of the ETFE solution is lowered and cannot be sprayed, and is appropriately determined within a temperature range that does not substantially hinder the spraying of the ETFE solution. do it. When the temperature of the heat source gas is low and the ETFE solution is clogged with the nozzle, it is necessary to increase the temperature so that the temperature of the ETFE solution does not decrease. The lower limit of the temperature of the heat source gas is not particularly limited. However, in order to efficiently spray the ETFE solution, it is preferably not less than the phase separation temperature of the ETFE solution as described above, although it depends on the type of ETFE and the solvent used. Specifically, it is preferably 40 ° C. or higher, more preferably 50 ° C. or higher.

  Usually, the temperature of the heat source gas is appropriately determined in the range of 40 to 400 ° C. The flow rate of the heat source gas and the supply rate of the ETFE solution are as follows under the condition that the nonvolatile content of the obtained ETFE powder, that is, the content of ETFE is 99% by mass or more with respect to the total amount of ETFE and the solvent. What is necessary is just to adjust suitably according to the particle diameter to carry out. The pressure in the apparatus is not particularly limited, whether it is normal pressure, reduced pressure or increased pressure.

  Also, the non-volatile content of the ETFE solution at the time of spray drying, that is, the content of ETFE with respect to the total amount of the ETFE solution, is appropriately determined in accordance with the specifications of the spray drying apparatus, the conditions for spray drying, etc. within the above preferred range. That's fine.

  Thus, the ETFE powder of the present invention is obtained by the production method of the present invention. The particle size and particle size distribution of the ETFE powder of the present invention are appropriately selected depending on the application, for example, the size of the substrate to be coated, the coating method, etc. Thus, the conditions in the manufacturing method are adjusted. In general, the average particle size of the ETFE powder is preferably 0.01 to 1000 μm, more preferably 1 to 500 μm. For example, when used in the electrostatic coating method, the average particle diameter is preferably 0.5 to 300 μm, more preferably 1 to 200 μm. When used in the rotational molding method, 1 to 500 μm is preferable, and 5 to 300 μm is more preferable. The average particle diameter may be adjusted by classification using a sieve or the like.

  Here, in this specification, the average particle size and particle size distribution of the ETFE powder are obtained by measuring the particle size distribution by a dry method using a laser diffraction particle size distribution measuring device (manufactured by Sympatec: HELOS & RODOS). Say.

  The ETFE powder of the present invention is useful in powder coating applications as an ETFE powder or as an ETFE powder composition in combination with other components described later. Furthermore, it is also useful as a primer for powder coating of fluororesin powders such as ETFE, TFE / perfluoro (propyl vinyl ether) copolymer, TFE / hexafluoropropylene copolymer, etc. other than the present invention. In particular, when ETFE used for powder production contains a repeating unit based on a monomer having an acid anhydride residue and a polymerizable unsaturated bond, the adhesion between the fluororesin and the substrate is obtained when used as a primer. Is significantly improved.

  Thus, although the ETFE powder of the present invention is useful as a raw material for coating, the coating method can be carried out in the same manner as conventional ETFE powder, synthetic resin powder and powder compositions containing them. . For example, the substrate surface is heat-treated at 200 to 600 ° C. in an oxygen-containing atmosphere, and then the substrate surface is roughened by blasting or the like. A coating film is formed by powder-coating ETFE powder or ETFE powder composition on the surface of the blasted substrate.

  Here, the powder coating material comprising the ETFE powder of the present invention and the ETFE powder composition containing the same has a tendency to easily form a coating film by heating because the ETFE powder is porous. There is a possibility that the film baking temperature can be reduced as compared with a powder coating using ordinary ETFE powder. In addition, the ETFE powder of the present invention is obtained in a state where there are almost no whiskers or corners, and the particle diameter is controlled within a desired range. It is.

  The ETFE powder of the present invention is close in properties to ordinary ETFE powder, and can be applied with primer and powder using the same coating apparatus, so that it is excellent in productivity and economy.

  As thickness of the coating film formed using the ETFE powder in this invention and the ETFE powder composition containing this, 1 micrometer-1 mm are preferable, 5-500 micrometers is more preferable, 10-200 micrometers is the most preferable. In particular, when ETFE used for powder production contains a repeating unit based on a monomer having an acid anhydride residue and a polymerizable unsaturated bond, if it is within this range, sufficient adhesion can be achieved by one coating. Expresses sex. If it is thinner than 1 μm, the adhesiveness is not sufficient, and if it is thicker than 1 mm, it must be painted twice or more, resulting in poor production efficiency.

  Examples of the material of the base material in the present invention include metals such as iron, stainless steel, aluminum, copper, tin, titanium, chromium, nickel, and zinc, and inorganic materials such as glass and ceramics. More preferred.

  Examples of the shape of the substrate in the present invention include pipes, tubes, films, plates, tanks, rolls, vessels, valves, elbows and the like.

  In the present invention, the ETFE powder composition preferably contains the ETFE powder of the present invention and a heat stabilizer. As an ETFE powder composition in combination with ETFE powder and other components, ETFE powder, in particular, ETFE used for powder production is repeatedly based on a monomer having an acid anhydride residue and a polymerizable unsaturated bond. When an ETFE powder composition containing a unit-containing ETFE powder and a heat stabilizer is used, the adhesion between the coating film and the substrate is remarkably excellent. The reason is not necessarily clear, but is estimated as follows. When a heat stabilizer is contained, the thermal stability of ETFE is further improved, so that deterioration and shrinkage of the coating film in the coating process are prevented, and adhesion of the coating film to the substrate is improved. Moreover, since the stability of ETFE at high temperature is improved, a coating film can be formed on the substrate at high temperature, which is considered to further improve the adhesiveness.

The heat stabilizer is preferably one or more selected from the group consisting of copper compounds, tin compounds, iron compounds, lead compounds, titanium compounds and aluminum compounds. Specific examples include copper oxide, copper iodide, alumina, tin sulfate, germanium sulfate, basic lead sulfate, tin sulfite, barium phosphate, tin pyrophosphate and the like, and copper oxide and copper iodide are preferred. The content of the heat stabilizer in the ETFE powder composition is preferably 1 × 10 ^{−8 to} 5 mass%, more preferably 1 × 10 ⁻⁷ to 2 mass%, most preferably 5 × 10 ⁻⁷ to 1 mass%. preferable.

  In the present invention, in addition to the ETFE powder and the heat stabilizer, in addition to the ETFE powder of the present invention, other additives, various additives, fillers, You may mix | blend another synthetic resin powder. The content of the ETFE powder in the composition containing the ETFE powder of the present invention is preferably 20% by mass or more, more preferably 50% by mass or more, and most preferably 80% by mass or more based on the total amount of the composition. The content of the heat stabilizer and other compounding agents is preferably 80% by mass or less, more preferably 50% by mass or less, and most preferably 20% by mass or less.

  In addition, it is preferable to mix a heat stabilizer and another compounding agent with an ETFE powder previously using a mixer before powder coating. Further, it is also preferable to mix a ETFE powder with a mixer to produce a masterbatch powder, and to mix the masterbatch powder with the ETFE powder.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. In the following examples and comparative examples, coating was performed using the following electrostatic coating method.
[Electrostatic coating method]
Using a powder spray gun, the ETFE powder was sprayed onto the surface of the SS400 stainless steel plate at an applied voltage of −60 kV and baked in an oven at a predetermined temperature and time. The coating was repeated until a sufficient film thickness was obtained.

[Measurement of physical properties]
The Q value is measured by using a flow tester (manufactured by Shimadzu Corporation) to measure the extrusion rate of ETFE when extruding into an orifice having a diameter of 2.1 mm and a length of 8 mm under a load of 7 kg and a temperature of 297 ° C. I went there.
The average particle size was measured by measuring the particle size distribution by a dry method using a laser diffraction particle size distribution analyzer (manufactured by Sympatec: HELOS & RODOS).

[Example 1]
ETFE (Repeating unit based on TFE / Repeating unit based on ethylene / Perfluorobutylethylene (CH ₂ ═CH (CF ₂ ) ₄ F) using a composite kneading extruder IMC-1973 (manufactured by Imoto Seisakusho) The repeating unit based on the formula = 58.1 / 38.7 / 3.2 (mol%), melting point: 225 ° C., Q value: 49 mm ³ / sec or less, referred to as “ETFE1”) Mixing was performed at 200 ° C. at 100 rpm for 20 minutes to obtain an ETFE solution.

  An ETFE powder was produced by using a rotary disk type spraying method in an explosion-proof vertical descending co-current type spray drying device equipped with a solvent recovery device. The rotational speed of the disk was 12,000 rpm, nitrogen gas was used as the heat source gas, the ETFE solution obtained above was further diluted 2-fold with isophorone, and then the heat source gas was contacted in a vertical descending cocurrent manner. The gas temperature was set at 200 ° C. The diluted solution preheated to 200 ° C. is sprayed into a spray drying apparatus at a supply rate of 0.8 kg / hr, and the particles of the powder coating material dried in the apparatus are collected by a cyclone, whereby the average particle diameter is 50 μm. Porous ETFE powder was obtained. In the obtained particles, no corners or whiskers were confirmed by microscopic observation, and the shape was almost spherical.

  After blasting the surface of an SS400 stainless steel plate having a length of 50 mm, a width of 100 mm, and a thickness of 2 mm, the blast powder was removed with an air gun, and the stainless steel plate was immersed in ethanol for 30 minutes. Then, the base material 1 was obtained by heat-processing in air at 400 degreeC for 1 hour. An ETFE powder was electrostatically coated on the surface of the substrate 1 and baked at 300 ° C. for 45 minutes to obtain a coated substrate 1. The coating and baking process was repeated three times to obtain a coating film having a film thickness of 220 μm and no pinholes.

[Example 2]
In the same manner as in Example 1, ETFE (repeat unit based on TFE / repeat unit based on ethylene / repeat unit based on perfluorobutylethylene / repeat unit based on IAH = 57.6 / 40.0 / 1.8 / 0 .6 (mol%), melting point 242 ° C., Q value: 38 mm ³ / sec, hereinafter referred to as “ETFE2”)) An ETFE solution was obtained in the same manner as in Example 1 except that it was changed to 50 g. When spray drying was performed, a porous ETFE powder having an average particle size of 80 μm was obtained. In the obtained particles, no corners or whiskers were confirmed by microscopic observation, and the shape was almost spherical. Similarly, electrostatic coating was performed to obtain a coated substrate 2. The coating and baking process was repeated twice, and a coating film having a film thickness of 200 μm and no pinholes was obtained.

Example 3
In the same manner as in Example 1, 300 g of 2,6-difluorobenzonitrile was added to 50 g of ETFE1, and the mixture was mixed at 200 ° C. at 100 rpm for 20 minutes to obtain an ETFE solution.

  An ETFE powder was produced by using a rotary disk type spraying method in an explosion-proof vertical descending co-current type spray drying device equipped with a solvent recovery device. The rotation speed of the disk was 12,000 rpm, nitrogen gas was used as the heat source gas, and the solution obtained by further doubling the ETFE solution obtained above with 2,6-difluorobenzonitrile and the heat source gas in a vertically descending parallel flow Contacted by the formula. The gas temperature was set at 200 ° C. The diluted solution preheated to 200 ° C. is sprayed into a spray drying apparatus at a supply rate of 0.8 kg / hr, and the particles of the powder coating material dried in the apparatus are collected by a cyclone, whereby the average particle diameter is 40 μm. Porous ETFE powder was obtained. In the obtained particles, no corners or whiskers were confirmed by microscopic observation, and the shape was almost spherical. Electrostatic coating was performed in the same manner as in Example 1 to obtain a coated substrate 3. The coating baking process was repeated 3 times, and a coating film having no pinholes at 200 μm was obtained.

[Comparative Example 1]
In C ₄ F ₉ CH ₂ CH ₃ which is a fluorohydrocarbon polymerization medium, copolymerization of TFE, ethylene and perfluorobutylethylene is carried out, followed by drying to remove the polymerization medium, and ETFE [copolymerization] Combined composition: repeating unit based on TFE / repeating unit based on ethylene / repeating unit based on perfluorobutylethylene = 53/46/1 (mol%), melting point: 265 ° C., Q value: 7.5 mm ³ / sec] Fine particles were obtained.

As a heat treatment device, a taper is provided by narrowing the lower part, a hot air inlet is provided on the upper side of a cylindrical container on the upper part, and a powder supply nozzle is provided on the upper part. A device with a body outlet was used. The fine particles were sprayed and melted in an atmosphere of a melting zone maintained at 320 ° C. The residence time in the melting zone is about 1 second. The molten particles were immediately cooled and collected with a cyclone to obtain a powder having an average particle size of 13 μm and an apparent specific gravity of 0.61 g / cc.
When the powder was observed with a microscope, there were many aggregates in which the melted particles were fused.

  This powder was applied to an electrostatic coating machine (GX3300S manufactured by Onoda), coated on an aluminum plate of 150 × 150 × 2 mmt, and baked in an electric furnace at 300 ° C. for 10 minutes. Then, when it cooled and solidified at room temperature, the pinhole was detected by the coating film with the film thickness of 73 micrometers.

[Comparative Example 2]
After the solution polymerization, granulation is performed, and the repeating unit based on TFE / the repeating unit based on ethylene / the repeating unit based on perfluorobutylethylene / the repeating unit based on IAH = 57.6 / 40.0 / 1.8 / 0. An ETFE2 granulated product having a melting point of 242 ° C. and a Q value of 38 mm ³ / sec was obtained (6 mol%). The granulated product was pulverized by a turbo mill to obtain ETFE2 powder having an average particle size of 39.4 μm. The obtained powder was confirmed to have corners and whiskers by microscopic observation.

  According to the production method of the present invention, an ETFE powder having good moldability with suppressed generation of square and beard-like particles can be used regardless of the type of ETFE, for example, flexible ETFE. Also, it can be easily manufactured. Further, the porous ETFE powder obtained by the production method of the present invention is a powder having good moldability. In addition, since the ETFE powder is porous, when it is heated to form a coating film, it tends to form a coating film easily, and the coating film baking temperature may be reduced.

  Such ETFE powder of the present invention is excellent in paintability and can be coated on the surface of a substrate such as metal, ceramics, glass, and synthetic resin. Also used for lining, coating, surface treatment, etc., various containers, pipes, tubes, tanks, piping, fittings, rolls, autoclaves, heat exchangers, distillation towers, jigs, valves, stirring blades, tank trucks, pumps Can be used in blower casings, centrifuges, cooking equipment, etc.

Claims (7)

A fluorine-containing copolymer containing a repeating unit based on ethylene and a repeating unit based on tetrafluoroethylene is dissolved in a solvent capable of dissolving the fluorine-containing copolymer at a temperature below the melting point of the fluorine-containing copolymer. A step (A) of obtaining a fluorine copolymer solution;
(B) spray drying the fluorine-containing copolymer solution;
A process for producing a fluorinated copolymer powder, comprising:   2. The inclusion according to claim 1, wherein the solvent is at least one selected from the group consisting of a fluorine-containing aromatic compound, an aliphatic compound having one or more carbonyl groups, and a hydrofluoroalkyl ether. Method for producing fluorine copolymer powder.   The method for producing a fluorinated copolymer powder according to claim 1 or 2, wherein the step (A) is performed at a temperature not higher than the melting point of the fluorinated copolymer.   The manufacturing method of the fluorine-containing copolymer powder of any one of Claims 1-3 which perform the said process (B) at 40-350 degreeC.   The fluorine-containing copolymer according to any one of claims 1 to 4, wherein the fluorine-containing copolymer contains a repeating unit based on a monomer having an acid anhydride residue and a polymerizable unsaturated bond. Powder manufacturing method.   The fluorine-containing copolymer according to any one of claims 1 to 5, wherein a content of the fluorine-containing copolymer in the fluorine-containing copolymer solution is 0.1 to 80% by mass based on the total amount of the solution. Production method of polymer powder.   A porous fluorine-containing copolymer powder having an average particle diameter of 0.01 to 1000 µm, obtained by the production method according to any one of claims 1 to 6.