JP4894096B2 - Fluoropolymer powder manufacturing method - Google Patents

Description

【００６３】
表１から、本発明の範囲内にない温度で粉砕した比較例１〜２及びドライブレンドによる比較例３〜４では、焼成後の塗膜の全面に発泡が認められ、上述のρ及びＰに関する式
ρ＞０．２３ｌｎＰ−０．４５
を満たさない場合があるのに対し、本発明の範囲内の温度で粉砕した実施例１〜７では、焼成後の塗膜に発泡は認められず、上記式を満たすことがわかった。表１から、また、フッ素系重合体以外のその他の成分を含有する場合について、ドライブレンドによる比較例３〜４と異なり、溶融混練物を粉砕する実施例５〜７では、焼成後の塗膜に発泡が認められないことがわかった。
【００６４】
５．電子顕微鏡による観察
実施例１により得られた粉末及び実施例２により得られた粉末を、走査型電子顕微鏡で観察した。図１及び図２に走査型電子顕微鏡写真（倍率５０倍）を示す。これらの写真から、得られる粉末はヒゲ様の繊維状突出部がなく、比較的滑らかな表面を有することがわかった。
【００６５】
【発明の効果】
本発明のフッ素系重合体粉末製造方法は、上述の構成を有することから、得られるフッ素系重合体粉末は、粒子表面にヒゲ様の繊維状突出部が殆ど発生しないので、高密度で流動性が良好であり、粉体塗料に好適に用いられる。本発明のフッ素系重合体粉末製造方法は、原材料としてペレット、シート、成形物等の形状の如何を問わないので、フッ素系重合体を用いた成形品等のリサイクルに利用することができる。
【図面の簡単な説明】
【図１】実施例１により得られた粉末の走査型電子顕微鏡写真（倍率５０倍）である。
【図２】実施例２により得られた粉末の走査型電子顕微鏡写真（倍率５０倍）である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a fluoropolymer powder that can be used for powder coating.
[0002]
[Prior art]
Fluoropolymers have excellent properties such as chemical resistance and heat resistance, and are therefore used in various applications including corrosion-resistant linings for chemical / medical instruments and semiconductor manufacturing equipment. When using fluorine-based polymers for corrosion-resistant lining, etc. using chemical resistance, etc., it is necessary to apply a sufficient amount to exhibit various characteristics such as chemical resistance according to the various shapes of workpieces. In addition, it is suitably used as a powder coating because it has a small amount of waste during construction and is easy to handle.
[0003]
The fluorine-based powder coating is generally configured to take advantage of the characteristics of the fluorine-based polymer, and further contains other components such as a pigment and a conductivity-imparting material, depending on the application. Properties such as conductivity can be added.
[0004]
Powder coatings mainly composed of fluoropolymers are produced by dry blending, where other components are contained, the particles composed of fluoropolymers and the particles composed of other components are dry-mixed. Is normal. However, in such a dry blend method, the other components do not enter the inside of the particles made of the fluorine-based polymer, but are present outside as separate particles. Even if it is applied by painting, etc., there is a problem that paintability and uniform paintability (unevenness due to different electrostatic adhesion) deteriorate due to the influence of other components, and characteristics such as coloring and conductivity cannot be obtained sufficiently. there were.
[0005]
In order to solve this problem, as a method for producing a powder coating material containing a fluoropolymer as a main component, there is a method in which a fluoropolymer and other components are melt-kneaded and then pulverized and classified. However, in this method, since the glass transition temperature of the fluoropolymer is relatively low, the particles obtained by pulverization will have a beard-like fibrous protrusion on the surface, which is a high-density and fluid powder. It was difficult to get. Therefore, a method of performing pulverization after melt-kneading at a low temperature is conceivable. However, in this case, an extremely low temperature using liquid nitrogen or the like is necessary, which causes a problem in terms of energy efficiency and cost.
[0006]
In Japanese Patent Publication No. 53-11296, for the purpose of providing a powder coating having high density and good fluidity, a dispersion of a tetrafluoroethylene copolymer is agglomerated and then placed in an atmosphere having a melting point or higher. A method of dispersing and condensing by spray is disclosed. However, this technique requires a large amount of equipment and a large equipment cost, and there is a problem that high yield cannot be obtained because particles are fused.
[0007]
In JP-A-63-270740, for the purpose of providing a tetrafluoroethylene copolymer powder that can be used for powder coating or the like, the tetrafluoroethylene copolymer is formed into a sheet with a roll, Next, a method for grinding is disclosed. However, in this technique, other components other than the fluorine-based polymer are not uniformly dispersed, so that there are problems such as being unable to uniformly impart properties such as coloring and conductivity as a powder coating.
[0008]
In recent years, it has been demanded to recycle used products and defective products generated in the molding process from the environmental point of view, such as resource saving and waste reduction, for molded products using fluoropolymers. Therefore, development of a simple and efficient recycling method corresponding to this is desired.
[0009]
[Problems to be solved by the invention]
In view of the above situation, the object of the present invention can be used as a raw material regardless of the shape of pellets, sheets, other molded articles, etc., and has high density and good fluidity, and is suitable for powder coatings. The present invention is to provide a production method capable of obtaining a fluoropolymer powder to be used, which can be applied to recycling of molded articles using the fluoropolymer.
[0010]
[Means for Solving the Problems]
The present invention is a fluoropolymer powder production method for producing a fluoropolymer powder by pulverizing a fluoropolymer-containing material in a certain temperature range, wherein the certain temperature range is the above-mentioned fluoropolymer weight. A method for producing a fluoropolymer powder, characterized in that the temperature is 100 ° C. lower than the melting start temperature of the coal-containing material and not more than the melting point of the fluoropolymer-containing material.
[0011]
The fluoropolymer powder production method further comprises a pulverized product obtained by pulverizing the fluoropolymer-containing material in a certain temperature range to a temperature of 50 ° C. from the melting start temperature of the fluoropolymer-containing material. It is preferable that the heat treatment is performed at a temperature that is lower than the low temperature and lower than the melting point of the fluoropolymer-containing material.
[0012]
The fluorine-containing polymer-containing material is preferably melted.
The pulverization is preferably performed by a method using shearing or cutting.
The fluoropolymer powder has an apparent density ρ (g / ml) and an average particle size P (μm) of the formula
ρ> 0.23lnP−0.45
It is preferable that
[0013]
The fluoropolymer powder preferably has an average particle size of 10 to 1000 μm.
The fluorine-based polymer powder includes particles composed of fine particles composed of a conductivity-imparting material or fine particles composed of a pigment and a matrix composed of a fluorine-based polymer, and the fine particles are contained in the matrix. It is preferable that it exists.
The present invention is also a fluoropolymer powder comprising particles composed of fine particles comprising a conductivity-imparting material or fine particles comprising a pigment and a matrix comprising a fluoropolymer, wherein the fine particles are contained in the matrix. Is a fluorine-based polymer powder.
The fluoropolymer powder has an apparent density ρ (g / ml) and an average particle size P (μm) of the formula
ρ> 0.23lnP−0.45
It is preferable that
Hereinafter, the present invention will be described in detail.
[0014]
The method for producing a fluoropolymer powder of the present invention is to produce a fluoropolymer powder by pulverizing a fluoropolymer-containing material in a certain temperature range.
In the present specification, the fluoropolymer-containing material means a substance containing a fluoropolymer. The fluorine-containing polymer-containing material may be composed only of the fluorine-based polymer itself, or may contain other components other than the fluorine-based polymer as desired.
[0015]
In the present specification, the fluorine polymer powder means a powder containing a fluorine polymer. The fluoropolymer powder may be composed only of the fluoropolymer itself, or may contain other components and / or compounding components other than the fluoropolymer as desired. In the fluoropolymer powder, the other components other than the fluoropolymer and the fluoropolymer are usually derived from the fluoropolymer-containing material as a raw material. The blending component is a component blended as desired separately from the fluoropolymer-containing material in the step of producing the fluoropolymer powder.
[0016]
The fluorine-based polymer powder can be used for various applications according to needs, but can be obtained as a high-density and high-fluidity powder by the fluorine-based polymer powder manufacturing method of the present invention. If necessary, additives and the like can be appropriately mixed and used suitably for powder coatings.
[0017]
The fluoropolymer powder production method of the present invention is carried out by pulverizing a fluoropolymer-containing material, and if necessary, washing, heat treatment, drying, roughening of the fluoropolymer-containing material as a raw material. It may include steps such as pretreatment such as pulverization and particle size adjustment after the pulverization.
[0018]
The fluorine-based polymer is not particularly limited as long as it is a polymer containing a fluorine atom in the molecule, but a thermoplastic one is preferable. Examples of the thermoplastic fluorine-based polymer include, as monomer components, fluorine-containing vinyl-based monomers such as vinylidene fluoride, tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, and perfluoro (alkyl vinyl ether). Body components and, if necessary, those obtained by polymerization using other vinyl-based monomer components such as ethylene and propylene, and the like may be homopolymers or copolymers. There may be.
[0019]
Examples of the thermoplastic fluoropolymer include, for example, polyvinylidene fluoride, ethylene / tetrafluoroethylene copolymer, ethylene / chlorotrifluoroethylene copolymer, tetrafluoroethylene / hexafluoropropylene copolymer, and tetrafluoroethylene. / Fluoro-type melt processable polymer such as perfluoro (alkyl vinyl ether) copolymer. Of these, ethylene / tetrafluoroethylene copolymer, tetrafluoroethylene / hexafluoropropylene copolymer, tetrafluoroethylene / perfluoroethylene copolymer, and the like in terms of corrosion resistance when the obtained fluoropolymer powder is used for powder coatings. Tetrafluoroethylene copolymers such as fluoro (alkyl vinyl ether) copolymers are preferred.
[0020]
Other components other than the fluoropolymer that may be contained in the fluoropolymer-containing material are not particularly limited. For example, for the purpose of imparting properties to the coating film or improving the performance of the coating film, Examples of the commonly used component include fillers (fillers) such as pigments, coating film reinforcing materials, and conductivity imparting materials.
[0021]
The pigment is mainly used for coloring purposes, and examples thereof include titanium dioxide, carbon black, cobalt, and chromium oxide. The coating film reinforcing material is used for the purpose of reinforcing the obtained coating film, and examples thereof include carbon fiber, glass fiber, and glass flake. The said electroconductivity imparting material is used in order to provide electroconductivity to the coating film obtained, for example, electroconductive carbon, a potassium titanate whisker, a tin oxide etc. are mentioned.
[0022]
Although it does not specifically limit as content of other components other than the said fluoropolymer, It is preferable that it is 0 to 60% of the said fluoropolymer on a mass basis. When it exceeds 60%, the resulting fluoropolymer powder has a too low content of the fluoropolymer, and when used in a powder coating, the leveling during film formation deteriorates and cracks in the coating film. Defects such as pinholes occur, which is not preferable as a corrosion-resistant coating film. More preferably, it is 0 to 40%.
[0023]
When the fluoropolymer-containing material is melted, the fluoropolymer powder production method of the present invention can be suitably used. The fluoropolymer-containing material is melted because the other components can be uniformly dispersed inside, particularly when the fluoropolymer-containing material contains other components other than the fluoropolymer. It is preferable. More preferably, the fluoropolymer-containing material is melted and further kneaded. The melting / kneading is usually carried out by mixing the fluoropolymer and, if necessary, the other components in advance with a mixer, and then melting and kneading with a kneader, a melt extruder, or the like.
[0024]
The fluoropolymer-containing material can be used regardless of its shape. Examples of the fluorine-containing polymer-containing material include those obtained by blending the above-mentioned fluorine-based polymer and, if necessary, the above-mentioned other components, into pellets. Examples of the pellets include those obtained by extruding pellets after performing the above-described melt-kneading as desired.
[0025]
Examples of the fluoropolymer-containing material include: molded products; various injection-molded products and extruded products such as sheets, films, and wire coverings; molded products such as pipes and tubes; What was collect | recovered after use may be used. As what was collect | recovered after the said use, what gave water washing, heat processing, drying, etc. as needed after collection | recovery is normally used. The fluorine-containing polymer-containing material may further be a surplus raw material for the molding process, an amount attached to the molding apparatus, or the like. Molded products using such fluoropolymers, surplus raw materials for molding processing, apparatus adhering parts, etc. have not been conventionally recycled properly, but according to the fluoropolymer powder production method of the present invention, Recycling is possible.
[0026]
The pulverization of the fluoropolymer-containing material is performed within a certain temperature range. The certain temperature range is not less than 100 ° C. lower than the melting start temperature of the fluorine-containing polymer-containing material and not more than the melting point of the fluorine-containing polymer-containing material. When the temperature is within the certain temperature range, the strength and elongation of the fluoropolymer are reduced, so that in the pulverization, fibrous protrusions are rarely generated on the particle surface, and deformation of the particle shape can be suppressed. . Conventionally, it has been necessary to cool and pulverize with liquid nitrogen or the like, but according to the fluoropolymer powder production method of the present invention, the pulverization can be performed relatively easily by setting the above-mentioned constant temperature range. Can do.
[0027]
When the lower limit of a certain temperature range for pulverizing the fluoropolymer-containing material is less than 100 ° C. lower than the melting start temperature, fibrous protrusions are formed on the obtained particle surface, resulting in high density and fluidity. If a good powder is not obtained and the upper limit exceeds the melting point, the fluidity of the material to be pulverized increases and pulverization becomes difficult. The certain temperature range is preferably a temperature not less than 50 ° C. lower than the melting start temperature of the fluorine-containing polymer-containing material and not more than the melting point of the fluorine-containing polymer-containing material.
[0028]
In the present specification, the melting start temperature is a temperature at which the melting heat generation starts when the fluorine-containing polymer-containing material is heated at 10 ° C./min using a differential calorimetric tester (DSC). The melting point is the peak point temperature when the temperature is raised in this way.
[0029]
The pulverization is preferably performed by a method using shearing or cutting. The method using shearing is usually a method of crushing by applying pressure to the fluoropolymer and applying shearing force. The method using the above-described cutting is usually a method of pulverizing using cutting with a cutting tool such as a knife.
[0030]
The pulverization can be performed using a pulverizer, and examples of the pulverizer include a turbo cutter, a cross bitter mill, a rotor bitter mill, and a cutting mill. Although there is a method of using impact by centrifugal force as a general pulverization method, in the present invention, a relatively elastic fluoropolymer-containing material is used as a material to be crushed, so that the shape of the resulting particles is deformed. Is not preferable from the viewpoint of large.
[0031]
A pulverized product obtained by pulverizing the fluoropolymer-containing material may be subjected to heat treatment as necessary. Even when the heat treatment is not performed, the fluoropolymer powder can be obtained, but by performing the heat treatment, it is possible to eliminate a small amount of fibrous protrusions that may be generated on the particle surface by pulverization. Thus, a fluorine-based polymer powder with higher density and improved fluidity can be obtained.
[0032]
The heat treatment is performed at a temperature that is 50 ° C. or more lower than the melting start temperature of the fluorine-containing polymer-containing material and not more than the melting point of the fluorine-containing polymer-containing material. When the temperature is less than 50 ° C. lower than the melting start temperature, the shrinkage of the fibrous protrusions becomes insufficient, and the effects of densification and fluidity improvement due to the heat treatment do not appear, and the fluoropolymer When the melting point of the inclusion is exceeded, fusion of particles obtained by pulverization occurs. Preferably, it is carried out at a temperature that is not lower than the melting start temperature of the fluoropolymer-containing material and not higher than the melting point of the fluoropolymer-containing material. The heat treatment is preferably performed for several minutes to several tens of hours.
[0033]
The fluoropolymer powder obtained as described above is subjected to heat treatment as described above, or a pulverized product obtained by pulverizing a fluoropolymer-containing material in a certain temperature range as described above, or the pulverized product as described above. It may be a heat-treated product obtained by the above, and may further contain a blending component if desired. The pulverized product and the heat-treated product are aggregates of particles.
[0034]
When the fluoropolymer powder is obtained using the above-described fluoropolymer-containing material containing other components other than the fluoropolymer, it is usually composed of a fluoropolymer. Including particles composed of a matrix and fine particles composed of other components such as a pigment, a coating film reinforcing material, and a conductivity imparting material, and at least a part of the fine particles is present in the matrix It is.
[0035]
The particles composed of the fine particles and the matrix are particles constituting the above-mentioned pulverized product or heat-treated product. Accordingly, the fine particles comprising the other components and the matrix comprising the fluoropolymer are derived from the fluoropolymer-containing material.
[0036]
The fluoropolymer powder is composed of particles having a structure in which the fine particles are present in the matrix as described above. Therefore, when the powder is applied to a powder coating material by electrostatic coating or the like, the other components described above are used. Is sufficiently applied, and a coating film having expected properties such as coloring, coating film reinforcement, and conductivity imparting can be obtained depending on the application.
[0037]
The blending component optionally contained in the fluoropolymer powder is blended separately from the fluoropolymer-containing material in any stage of the fluoropolymer powder production method of the present invention. It may be blended in combination with the fluoropolymer-containing material at the time of pulverization, or may be blended after the pulverization or after the heat treatment. The compounding component is not particularly limited, and may be, for example, an additive such as a leveling agent ordinarily used in a powder coating, or may be the same component as already described as the other component. Good.
[0038]
The fluoropolymer powder preferably has an apparent density of 0.4 g / ml or more. When it is less than 0.4 g / ml, when the obtained fluoropolymer powder is used for a powder coating, foaming may occur during coating or the number of coating may be increased. According to the fluoropolymer powder production method of the present invention, as described above, the particles are pulverized in a certain temperature range and heat-treated as necessary, so that particles having almost no fibrous protrusions on the surface can be obtained. Therefore, a fluoropolymer powder having a high apparent density in the above range can be easily obtained. In the present specification, the apparent density (g / ml) is a value obtained by measurement based on JIS K 6891.
[0039]
The fluoropolymer powder preferably has an average particle size of 10 to 1000 μm. When it is less than 10 μm, electrostatic repulsion is likely to occur when it is used for powder coatings for lining applications, etc., so it tends to be difficult to increase the film thickness. Leveling properties, etc. deteriorate. The particle size can be adjusted so that the fluoropolymer powder has an average particle diameter within the above range by classification according to the above-mentioned pulverization conditions and if necessary. Preferably, it is 20-500 micrometers. In the present specification, the average particle diameter is a value obtained using a laser diffraction particle size distribution analyzer.
[0040]
When the above-mentioned fluoropolymer powder represents the above apparent density by ρ (g / ml) and the average particle diameter by P (μm), ρ and P are
ρ> 0.23lnP−0.45
It is preferable that When the fluoropolymer powder satisfies the above formula, a preferable powder coating can be easily obtained from the viewpoints of coating workability and thickening. The fluoropolymer powder satisfying the above formula can be obtained mainly by adjusting the above-mentioned pulverization conditions and heat treatment conditions.
[0041]
The said fluoropolymer powder can be used for a powder coating material. When the fluoropolymer powder is used in a powder coating, the powder obtained by the fluoropolymer powder production method can be used as it is as a powder coating, and if necessary, an additive or the like can be mixed as appropriate. Body paints may be prepared. The additive is not particularly limited, and examples thereof include additives usually used in powder coatings, and the same as those already described for other components and blending components other than the above-mentioned fluoropolymers. It may be.
[0042]
The powder coating is usually applied by coating a material to be coated and then forming a film by heating and baking. The material to be coated is not particularly limited. For example, as a corrosion-resistant lining application, tanks, vessels, towers, valves, pumps, joints, other piping materials, etc., for chemical plants, pharmaceuticals, agricultural chemical manufacturing equipment, semiconductor manufacturing equipment, etc. Widely used. The object to be coated may be subjected to cleaning, surface treatment or primer coating as necessary.
[0043]
The method for applying the powder coating is not particularly limited, and examples thereof include an electrostatic coating method and a rolining method. Examples of the temperature for the heating and baking include 250 to 350 ° C.
[0044]
Since the fluoropolymer powder production method of the present invention is performed by pulverizing the fluoropolymer-containing material in a certain temperature range as described above, the particles obtained by pulverization have a beard-like surface. Since almost no fibrous protrusions are produced, it is possible to obtain a fluorinated polymer powder having high density and good fluidity, and such a fluorinated polymer powder is suitably used for powder coatings.
[0045]
The fluoropolymer powder production method of the present invention is such that the fluoropolymer-containing material contains other components other than the fluoropolymer such as a pigment, a coating film reinforcing material, and a conductivity imparting material. Since the fluoropolymer powder thus obtained contains the above-mentioned other components inside the particles, the above-mentioned other components are applied to the surface of the object to be coated by being applied to the powder coating. It is possible to obtain a coating film that is sufficiently coated and has characteristics according to needs such as coloring, coating film reinforcement, and conductivity imparting.
[0046]
Since the fluoropolymer powder production method of the present invention may use not only pellets but also molded products as the fluoropolymer-containing material, the fluoropolymers such as molded products recovered after use, defective products generated during molding processing, etc. It can be used for recycling molded articles using polymers. Molded articles that are desired to be recycled often contain pigments, electrical conductivity-imparting agents, carbon fibers, and other fluoropolymers. According to the manufacturing method, it can be used.
[0047]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.
Example 1
RapidR-1528 type (trade name; manufactured by Kawata Co., Ltd.) using tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer (PFA) pellets (melting start temperature 285 ° C., melting point 305 ° C., Daikin Industries, Ltd.) as a shearing pulverizer ) Was used and pulverized under the conditions of a rotation speed of 1800 rpm, a screen diameter of 3 mmφ, and a temperature of 280 ° C.
[0048]
Comparative Example 1
PFA pellets (melting start temperature 285 ° C., melting point 305 ° C., manufactured by Daikin Industries, Ltd.) were crushed using RapidR-1528 type (trade name; manufactured by Kawata Corp.) under the conditions of a rotation speed of 1800 rpm, a screen diameter of 3 mmφ, and a temperature of 120 ° C. did.
[0049]
Example 2
Tetrafluoroethylene / hexafluoropropylene copolymer (FEP) pellets (melting start temperature 240 ° C., melting point 270 ° C., manufactured by Daikin Industries, Ltd.) using RapidR-1528 type (trade name; manufactured by Kawata Corp.), rotation speed 1500 rpm Then, it was pulverized under the conditions of a screen diameter of 3 mmφ and a temperature of 265 ° C.
[0050]
Comparative Example 2
FEP pellets (melting start temperature 240 ° C., melting point 270 ° C., manufactured by Daikin Industries, Ltd.) were pulverized using a Rapid R-1528 type (manufactured by Kawata Corp.) under the conditions of a rotational speed of 1500 rpm, a screen diameter of 3 mmφ, and a temperature of 120 ° C.
[0051]
Example 3
Ethylene / tetrafluoroethylene copolymer (ETFE) pellets (melting start temperature 240 ° C., melting point 260 ° C., manufactured by Daikin Industries, Ltd.) using RapidR-1528 type (trade name; manufactured by Kawata Corp.), rotation speed 1500 rpm, screen It grind | pulverized on the conditions of diameter 3mmphi and temperature 255 degreeC.
[0052]
Example 4
A used PFA wafer carrier (melting start temperature: 285 ° C., melting point: 305 ° C.) was heat-treated at 150 ° C. for 1 hour, then washed with pure water and dried. Using a Rapid R-1528 type (trade name; manufactured by Kawata Corporation), a pellet-like coarsely pulverized product was obtained under the conditions of a rotational speed of 270 rpm, a screen diameter of 5 mmφ, and a temperature of 280 ° C.
[0053]
Example 5
PFA conductive pellets (melting start temperature 290 ° C., melting point 310 ° C., manufactured by Daikin Industries, Ltd.) obtained by adding 20% by mass of PFA as a conductivity-imparting material and melting and kneading the same are used in the same manner as in Example 1. -1528 type (trade name; manufactured by Kawata Corp.) was used for pulverization under the conditions of 1800 rpm, screen diameter 0.7 mmφ, temperature 280 ° C, and then a box dryer with 10 kg charged in a 70 mm thick tray was used. Then, heat treatment was performed at 300 ° C. for 4 hours. After cooling, it was classified with a vibration sieve (250 μm opening).
[0054]
Comparative Example 3
Carbon black was added to AC-5539 as a PFA powder coating (trade name; melting start temperature 290 ° C., melting point 310 ° C., manufactured by Daikin Industries, Ltd.) so as to be 20% by mass of AC-5539, and a speed kneader as a stirrer. (Made by Showa Engineering Co., Ltd.) was mixed for 20 minutes at 1500 rpm to obtain a conductive powder coating material.
[0055]
Example 6
FEP white color pellets (melting start temperature: 240 ° C., melting point: 270 ° C., manufactured by Daikin Industries, Ltd.) obtained by adding 5% by mass of FEP to titanium oxide as a white pigment and melting and kneading them are the same as in Example 2, RapidR-1528. After pulverizing using a mold (trade name; manufactured by Kawata Co., Ltd.) at a rotation speed of 1500 rpm, a screen diameter of 0.7 mmφ, and a temperature of 260 ° C., it is 250 ° C. using a box dryer with 10 kg charged in a 70 mm thick tray. For 4 hours. After cooling, it was classified with a vibration sieve (250 μm opening).
[0056]
Comparative Example 4
NC1500 (trade name; melting start temperature 240 ° C., melting point 270 ° C., manufactured by Daikin Industries, Ltd.) as FEP powder coating, and Taipei CR93 (trade name; manufactured by Ishihara Sangyo Co., Ltd.) as titanium oxide is 5% by mass of NC 1500. And mixed at 1500 rpm for 30 minutes using a speed kneader (manufactured by Showa Engineering Co., Ltd.) as a stirrer.
[0057]
Example 7
Using a speed kneader (manufactured by Showa Engineering Co., Ltd.) as a stirrer with PFA powder compressed with a roll into a sheet, made into a sheet, pulverized to 90 μm or less with an impact pulverizer, and 40% by mass of carbon black of the PFA powder Mixing at 1500 rpm for 30 minutes, and further supplying PFA pellets (melting start temperature 285 ° C., melting point 305 ° C., manufactured by Daikin Industries, Ltd.) with a quantitative feeder so that the mass ratio with this mixture is 1: 1. Extruded with a melt extruder to be pelletized, and crushed under the conditions of a rotational speed of 1500 rpm, a screen diameter of 0.7 mmφ, and a temperature of 280 ° C. using a Rapid R-1528 type (trade name; manufactured by Kawata) as in Example 1. After that, heat treatment was performed at 300 ° C. for 4 hours using a box-type dryer charged with 10 kg on a tray having a thickness of 70 mm. After cooling, it was classified with a vibration sieve (250 μm opening).
[0058]
(Evaluation methods)
The powder obtained as described above was evaluated by the following method.
1. Measuring method of average particle size
Microtrac X-100 type (trade name; manufactured by Nikkiso Co., Ltd.) was used as a laser diffraction type particle size distribution measuring instrument, and the dispersion was measured with a 1% by weight aqueous solution of Charmy (trade name; manufactured by Lion Corporation) as a dispersant. The results are shown in Table 1.
[0059]
2. Apparent density measurement method
It measured based on JISK6891. The results are shown in Table 1.
[0060]
3. Prime test
A 10 cm × 10 cm rectangular mold placed on a sandblasted iron plate was filled with the powder obtained above as a powder coating so that the film thickness after baking was about 2000 μm. After gently removing the formwork, PFA and FEP were baked in an electric furnace at 350 ° C for 60 minutes and ETFE was 290 ° C for 60 minutes, respectively, and the foamed state of the coating film after baking was visually observed. And evaluated according to the following criteria. The results are shown in Table 1.
(Double-circle): Foaming was not recognized at all.
○: Almost no foaming was observed.
X: Foaming was observed on the entire surface.
[0061]
4). Electrostatic paintability test
After baking the powder obtained above as a powder coating on an aluminum plate (100 mm × 100 mm × 1.5 mm) using GX3300 (trade name; manufactured by Onoda Cement) as an electrostatic coating machine at an applied voltage of 40 kV The film was electrostatically coated so that the film thickness was about 100 μm. After coating, PFA and FEP were baked in an electric furnace under conditions of 350 ° C. for 60 minutes and ETFE at 290 ° C. for 60 minutes. The foamed state of the coating film after firing was visually observed and evaluated according to the following criteria. The results are shown in Table 1.
(Double-circle): Foaming was not recognized at all.
○: Almost no foaming was observed.
X: Foaming was observed on the entire surface.
[0062]
[Table 1]

[0063]
From Table 1, in Comparative Examples 1 and 2 pulverized at a temperature not within the scope of the present invention and Comparative Examples 3 and 4 by dry blending, foaming was observed on the entire surface of the fired coating film, and the above ρ and P were related to each other. formula
ρ> 0.23lnP−0.45
In Examples 1 to 7 pulverized at a temperature within the range of the present invention, foaming was not observed in the fired coating film, and it was found that the above formula was satisfied. From Table 1, also in the case of containing other components other than the fluorine-based polymer, unlike Comparative Examples 3 to 4 by dry blending, in Examples 5 to 7 where the melt-kneaded material is pulverized, the coating film after firing It was found that no foaming was observed.
[0064]
5. Observation by electron microscope
The powder obtained in Example 1 and the powder obtained in Example 2 were observed with a scanning electron microscope. 1 and 2 show scanning electron micrographs (50 times magnification). From these photographs, it was found that the obtained powder had no beard-like fibrous protrusions and had a relatively smooth surface.
[0065]
【Effect of the invention】
Since the fluoropolymer powder production method of the present invention has the above-described configuration, the resulting fluoropolymer powder has almost no whisker-like fibrous protrusions on the particle surface. Is favorable and is suitably used for powder coatings. The fluoropolymer powder production method of the present invention can be used for recycling molded products using a fluoropolymer, since it does not matter if the raw material is in the form of pellets, sheets, molded products or the like.
[Brief description of the drawings]
1 is a scanning electron micrograph (magnification 50 times) of a powder obtained in Example 1. FIG.
2 is a scanning electron micrograph (magnification 50 times) of the powder obtained in Example 2. FIG.

Claims (6)

A fluoropolymer powder production method for producing a fluoropolymer powder by grinding a fluoropolymer-containing material in a certain temperature range,
The certain temperature range is not less than 100 ° C. lower than the melting start temperature of the fluorine-containing polymer-containing material and not more than the melting point of the fluorine-containing polymer-containing material. Method.   Further, the pulverized product obtained by pulverizing the fluorine-containing polymer-containing material in a certain temperature range is at least 50 ° C. lower than the melting start temperature of the fluorine-containing polymer-containing material, 2. The method for producing a fluoropolymer powder according to claim 1, wherein the heat treatment is performed at a temperature which is not higher than the melting point of the coal-containing material.   The method for producing a fluoropolymer powder according to claim 1 or 2, wherein the fluoropolymer-containing material is melted.   The method for producing a fluoropolymer powder according to claim 1, 2 or 3, wherein the pulverization is performed by a method using shearing or cutting. The method for producing a fluoropolymer powder according to claim 1, 2, 3, or 4 , wherein the fluoropolymer powder has an average particle size of 10 to 1000 µm. The fluorine-based polymer powder includes particles composed of fine particles made of a conductivity imparting material or fine particles made of a pigment and a matrix made of a fluorine-based polymer, and the fine particles are present in the matrix. The method for producing a fluoropolymer powder according to claim 3 , 4 or 5 .

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