JPH10316892A - Production of powder coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a powder coating material, capable of homogeneously mixing a surface modifier therewith, slight in the loss for the amount of the surface modifier to be added, and excellent in productivity. SOLUTION: This method for producing a powder coating material comprises as follows: a feedstock 11 is ground by a grinder 1 into resin powder, which, in turn, is fed to a sieving process using a screen 21; wherein, just before feeding the resin powder to the sieving process, a surface modifier 12 at 0.01-10 wt.% based on the resin powder is introduced via a surface modifier inlet 7 and added to the resin powder and the surface modifier 12 is mixed with the resin powder in the cylindrical screen 21, and the resultant mixture is allowed to pass through the screen 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a powder coating, and more particularly, to a method for producing a powder coating mixed with a surface modifier.

[0002]

2. Description of the Related Art Powder coatings do not use organic solvents.
It has been evaluated from the viewpoint of low pollution and has been widely used. In powder coatings, a surface modifier such as finely divided silica is often added for the purpose of preventing powder agglomeration and improving fluidity in order to further improve the appearance of the coating film. .

[0003] As a method for adding such a surface modifier, as disclosed in Japanese Patent Application Laid-Open No. 58-65770, etc., in the step of pulverizing resin pellets as a raw material of powder coating, resin pellets are added. A method of uniformly pulverizing a resin powder and a surface modifier by simultaneously pulverizing a surface modifier such as finely divided silica into a powder coating material has been proposed and implemented.

As another method of adding the surface modifier, as disclosed in Japanese Patent Application Laid-Open No. 63-186776, etc., a resin powder after pulverization and a surface modifier are mixed with a Henschel mixer. There is known a method of dry blending using such methods.

[0005]

However, in the above-mentioned conventional method of simultaneously pulverizing the raw material resin pellets and the surface modifier, the pulverized powder usually provided after the pulverizing step is collected. In such a cyclone, there is a problem that the surface modifier, which is a fine powder, is discharged from the cyclone to the outside, causing a loss in the amount of the surface modifier added. Therefore, it is necessary to add a large amount of the surface modifier in consideration of such a loss of the addition amount, which causes a problem that it is not economically preferable. Furthermore, although the surface modifying agent discharged from the cyclone is collected by the bag filter, a large amount of the surface modifying agent is collected in the bag filter, so that the bag filter is frequently clogged. Was.

Further, in the method of dry-blending the pulverized powder and the surface modifier with a Henschel mixer or the like, since the addition and mixing of the surface modifier is performed in a batch process, the production efficiency is poor and the cost is high. There was a problem. Further, there is also a problem that if a large amount of powder and the surface modifier are to be mixed at once, they cannot be mixed uniformly.

SUMMARY OF THE INVENTION An object of the present invention is to solve such conventional problems, to enable uniform mixing of the surface modifier, to reduce the loss with respect to the amount of the surface modifier added, and to improve productivity. To provide a method for producing a powder coating.

[0008]

SUMMARY OF THE INVENTION The present invention is a method for producing a powder coating in which a surface modifier is added to and mixed with a resin powder. Adding a surface modifier just before supplying the resin powder to the sieving process using a screen, mixing the surface modifier and the resin powder in the sieving process, and passing the mixture through the screen. This is a method for producing a powder coating.

According to the present invention, since the surface modifier is added immediately before supplying the crushed resin powder to the sieving step, the surface modifier is added between the crushing step and the sieving step. There is no loss. Usually, after the pulverization, a cyclone is provided to collect the pulverized powder.However, when the surface modifier is introduced into the cyclone, the surface modifier is generally a fine powder, so the cyclone is discharged from the cyclone to the outside. Exhausted, causing loss of surface modifier. In the present invention, since the surface modifier is added immediately before the sieving step, the loss of the surface modifier in the cyclone does not occur, and the loss with respect to the amount of the surface modifier added can be significantly reduced. . Further, when a bag filter or the like is connected to the cyclone, if the surface modifier is discharged from the cyclone, the bag filter is likely to be clogged. The present invention prevents such bag filter clogging. be able to.

In the present invention, "immediately before supplying the resin powder to the sieving process" means between the sieving process and a process immediately before the sieving process, for example, a powder collection process using a cyclone. If the sieving step is performed in a sieving machine, a surface modifier may be added between the sieving machine and the equipment in the immediately preceding step. That is, the surface modifier may be added to the resin powder before being supplied to the sieving machine. When the sieving process is performed in the sieving machine, a surface modifier may be added to the resin powder supplied to the sieving machine, and then the sieving process using a screen may be performed.

According to the present invention, the surface modifier and the resin powder are mixed in the sieving process, and then pass through the screen. Since the surface modifier and the resin powder are mixed in the sieving process, the surface modifier and the powder can be continuously mixed, and a powder coating can be manufactured with high productivity.

The sieving step using a screen in the present invention may be any sieving step that uses a screen and can mix a surface modifier and resin powder before passing through the screen. A particularly preferred sieving process is
This is a sieving machine having a cylindrical screen and a rotating member provided inside the screen, and is a sieving process using a sieving machine generally called a centrifugal sifter or a rotary sifter. In such a sieving machine, the resin powder and the surface modifier are mixed by a rotating member provided inside the screen, and the resin powder and the surface modifier are applied to the inner surface of the screen by centrifugal force of the rotating member. Pressed through the screen. Therefore, the resin powder and the surface modifier are sufficiently stirred and mixed by the rotating member inside the screen, so that the surface modifier and the powder can be more uniformly mixed. Specific examples of the rotating member include a member provided with a bar, a paddle, a blade, a blade, or the like around a rotation axis. Also,
Usually, a plurality of these bars and the like are provided.

The sieving step in the present invention may be another type of sieving step, for example, a sieving step using a vibrating screen machine that vibrates a screen.

In one preferred embodiment according to the present invention, a surface modifier is added to the resin powder using a feeder having a compressed air inlet, a suction port, and a discharge port. According to this feeder, compressed air is introduced from the compressed air introduction port, the surface modifier is sucked from the suction port by a pressure difference generated by this, and the surface modifier is discharged from the discharge port to modify the surface. An agent can be added to the resin powder.

Hereinafter, the configuration of the present invention will be described in more detail. Resin for Powder Coating In the present invention, the resin powder obtained by pulverizing a raw material with a pulverizer is a powder containing a film-forming resin as a main component. As the film-forming resin, a resin suitable for an electrostatic coating method, that is, a thermosetting resin is generally used.
As the thermosetting resin, those which are solid at room temperature are preferably used, and specifically, epoxy resins, epoxy-polyester resins, polyester resins, acrylic resins, acrylic-polyester resins, fluorine resins, and the like. Can be exemplified. Among these, when it is necessary to form a coating film having good weather resistance with the pulverized paint of the present invention, the acrylic resin is required to form a coating film having good coating physical properties such as impact resistance. In order to form a coating film having good corrosion resistance, an epoxy resin is preferably used.

Here, examples of the acrylic resin include styrene, acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate and iso acrylate.
A polymer obtained by polymerizing monomers such as -butyl, tert-butyl acrylate, glycidyl acrylate, glycidyl methacrylate, and 2-methylglycidyl methacrylate according to a conventional method is used.

Examples of the polyester resin include polyhydric alcohols such as ethylene glycol, propanediol, pentanediol, hexanediol, neopentyl glycol, trimethylolpropane, and pentaerythritol, and maleic acid, terephthalic acid, and isophthalic acid. What polymerized with carboxylic acids, such as phthalic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, and (beta) -oxypropionic acid, according to a conventional method is used.

Further, as the epoxy resin, for example, a compound having two or more oxirane groups in the molecule is preferably used, and specifically, a glycidyl ester resin, a condensation reaction of bisphenol A with epichlorohydrin, and the like. Ether resins such as products and condensation products of bisphenol F and epichlorohydrin, alicyclic epoxy resins, flocculent aliphatic epoxy resins, brominated epoxy resins, phenol novolak epoxy resins, cresol novolac epoxy resins Are used.

When a thermosetting resin is used as the film-forming resin, a curing agent is used in combination. As a curing agent,
Various known compounds can be used depending on the functional group of the thermosetting resin to be used. Specifically, blocked isocyanates, aliphatic polycarboxylic acids such as sebacic acid, aliphatic acid anhydrides, amino acids Plast resin, epoxy resin, triglycidyl isocyanate, polyamide-based curing agent, hydroxyalkylamide (for example, product name “Primid XL552” manufactured by Rohm and Haas), glycouril hardening agent (for example, product name “Powderlink” manufactured by Scitech) 1174 "), amine curing agents, triglycidyl isocyanurate, dicyandiamide, phenolic resins, imidazoles and imidazolines.

As the film-forming resin, if necessary, a thermoplastic resin usually used mainly in a fluidized immersion method may be used. Examples of such a thermoplastic resin include a polyvinyl chloride resin, a polyethylene resin, a polyamide resin, a fluorine resin, and a modified polyolefin resin.

The above-mentioned various film-forming resins may be used in combination of two or more. In addition, in the resin powder of the present invention, in addition to the film-forming resin described above, if necessary, titanium dioxide, red iron oxide, iron oxide, carbon black, phthalocyanine blue, phthalocyanine green, quinacridone pigments, azo pigments and the like Colored pigments, talc, silica,
Extenders such as calcium carbonate and precipitated barium sulfate,
Silicones such as dimethylsilicone and methylsilicone, surface modifiers such as acrylic oligomers, foam inhibitors such as benzoin and benzoins such as benzoin derivatives having 1-3 types of functional groups added to benzoin, and curing accelerators ( Or curing catalyst), plasticizer, antistatic agent, ultraviolet absorber, antioxidant, pigment dispersant, flame retardant,
Various additives such as a fluidity-imparting agent may be included.

Surface Modifier The surface modifier used in the present invention is added to and mixed with the resin powder in order to improve the fluidity, chargeability and the like of the resin powder obtained by pulverizing the raw material. is there. When such a surface modifier is added to and mixed with the resin powder, it generally adheres to the surface of the resin powder and can change the surface properties of the resin powder. As the surface modifier, generally, solid particles are used, and those having a maximum particle size of 20 μm or less are preferably used. As a surface modifier, specifically,
Inorganic fine particles such as finely divided silica and finely divided aluminum oxide, and organic fine particles made of resin such as acrylic resin are used.

Commercial products of such a surface modifier include:
For example, Carplex FPS-1 manufactured by Shionogi & Co., Ltd.
(Maximum particle size of 6 μm or less), Carplex FPS-2
(Maximum particle size 10 μm or less), Carplex FPS-3
(Maximum particle size of 6 μm or less), Aluminum Oxide-C (primary particles 15 nm) manufactured by Nippon Aerosil Co., Ltd., acrylic resin-based organic fine particles (primary particles 10
0 nm).

The addition amount of the surface modifier is preferably 0.01 to 10% by weight based on the powder. That is, the amount of the surface modifier added is preferably 0.01 to 10 parts by weight based on 100 parts by weight of the powder. If the amount of the surface modifier is less than 0.01% by weight, the effect of the addition of the surface modifier is not sufficiently obtained, and the desired effects are obtained in the fluidity and the surface properties of the powder coating. May not be possible. On the other hand, if the amount of the surface modifier exceeds 10% by weight, the physical properties of the resulting coating film, especially the appearance of the coating film, tend to deteriorate. As a more preferable addition amount of the surface modifier,
It is 0.05 to 5% by weight based on the powder.

The sieving machine used in the present invention is, as described above,
There is no particular limitation as long as the surface modifier and the resin powder can be mixed in the sieving process using a screen, but a sieving machine generally called a centrifugal sifter or a rotary sifter is used. Is preferred. The screen is preferably 60 to 166 mesh (diameter of mesh holes: 250 μm to 90 μm). Examples of the dimensions of the cylindrical screen include a length of about 30 cm to 1 m and a diameter of about 10 cm to 50 cm. The rotation speed of the cylindrical screen is generally 50 to 3000 rpm. Generally, 50 kg /
Time to 1 t / hour is appropriate. The material of the screen is not particularly limited, and a screen made of a metal such as iron, stainless steel or brass, or a plastic such as nylon or the like can be generally used.

Commercially available centrifugal sieves include, for example, a cyclone screener manufactured by Azo, a turbo screener manufactured by Turbo Kogyo, a KEK shifter manufactured by Tokuju Kogyo, and a caisson sentry shifter manufactured by Tomoe Kogyo. and so on.

Compressed Air Feeder In one preferred embodiment according to the present invention, as described above, a compressed air inlet, a suction port, and a discharge port are provided when the surface modifier is added to the powder. Using a supply device, compressed air is introduced from a compressed air introduction port, a surface modifier is sucked from a suction port by a pressure difference generated by this, and the surface modifier is discharged and supplied from a discharge port. Such a feeder includes a device generally called an injector or an ejector. These devices are pipe-shaped devices having three inlets and outlets, in which compressed air is introduced from a compressed air inlet, whereby the pressure is reduced on the suction port side and the surface modifier connected to the suction port is discharged. The surface modifier is sucked from the storage part, and the sucked surface modifier is discharged from the other discharge port together with the compressed air. Therefore, by connecting this discharge port to a portion to which the surface modifier is to be supplied, the surface modifier can be supplied. The pressure of the compressed air when using such an injector or an ejector is generally about ² to 5 kg / cm ² . As a commercially available product of such a supply machine, there is, for example, a wonder gun manufactured by Osawa Company.

In the present embodiment, the surface modifier is sucked with a pressure difference by using such a supply device, and is discharged and supplied to the other. When the surface modifier is supplied through such a supply device, the surface modifier is crushed by the stress of air and supplied to the powder in a state where it is easily dispersed. Therefore, the surface modifier can be more uniformly mixed by the subsequent mixing on the screen of the vibrating screen machine.

Pulverizer In the present invention, as a pulverizer for pulverizing the raw material, a pulverizer generally used in pulverization of powder coating materials, such as a pneumatic pulverizer or an impact pulverizer, can be used. Commercial products of such a pulverizer include, for example, a turbo mill manufactured by Turbo Kogyo Co., Ltd., an ACM pulverizer manufactured by Hosokawa Micron Co., Ltd., and an Ec Sample Mill manufactured by Dalton Co., Ltd.

Cyclone The cyclone used in the present invention is for collecting powder after pulverization, and a cyclone generally used in the production of powder coatings and the like can be used.

[0031]

FIG. 1 is a schematic configuration diagram showing an example of a manufacturing apparatus used to carry out the manufacturing method of the present invention.

As shown in FIG. 1, raw material pellets 11 of powder coating material are supplied to a crusher 1 and crushed. The pulverized powder is sent to the powder inlet 2a of the powder paint collection cyclone 2. In the cyclone 2, the pulverized powder settles down due to its weight, and air and fine dust are sent to the bag filter 4 from 2b. A blower 6 is connected to the bag filter 4, and the powder crushed by the crusher 1 is sucked by the blower 6 and sent to the cyclone 2.

In the cyclone 2, the pulverized resin powder is sent to an outlet 2c. A rotary valve 3 is provided below the outlet 2c. Rotary valve 3
A surface modifying agent inlet 7 is provided below the surface modifier, and the surface modifying agent is supplied from the surface modifying agent inlet 7. The surface modifying agent introduction port 7 has an ejection port 1 of the injector 10.
0c is connected. A hopper 9 is connected to a suction port 10 b of the injector 10, and a surface modifier 12 is quantitatively supplied to the hopper 9 from a quantitative supply device 8. A compressor (not shown) is connected to the compressed air inlet 10a of the injector 10, and compressed air is supplied.

FIG. 2 is an enlarged sectional view showing the injector 10. As shown in FIG. 2, inside the injector 10, there are provided portions 10e and 10f whose diameters are reduced in a direction from the suction port 10b to the discharge port 10c. A compressed air ejection port 10d for introducing compressed air into the nozzle is provided at the portion 10e where the diameter is reduced. A total of three compressed air jets are provided, and two are also provided at locations not shown. These compressed air outlets are provided around a portion 10e where the diameter is reduced at equal intervals at 120 degrees pitch. Compressed air inlet 10
The air introduced into the injector 10 from a is branched into three inside the injector 10, is respectively sent to the compressed air ejection port 10d, and is ejected from the compressed air ejection port 10d into the nozzle. When the compressed air ejected from the compressed air ejection port 10d passes through the portion 10f having a small diameter, the velocity further increases, and a pressure difference is generated inside the nozzle. This pressure difference causes the surface modifier to be discharged from the suction port 10b. It is sucked. The surface modifier sucked into the injector 10 is
When passing through the inside of the injector 10, it is crushed under the stress of air and sent to the discharge port 10c. Accordingly, such an injector has a function of supplying the surface modifier and pulverizing the surface modifier therein.

Referring again to FIG. 1, the surface modifier 12 thus supplied by the injector 10 is introduced from the surface modifier inlet 7 and added to the powder collected by the cyclone 2. Is done.

The resin powder and the surface modifier are then sent to a centrifugal sieve 20. FIG. 3 is a partially cutaway sectional view showing the internal structure of the centrifugal screen machine 20. As shown in FIG. 3, the resin powder and the surface modifier are fed from a feed port 24, and are supplied by a feed screw 25 to the cylindrical screen 2.
Sent within 1. A rotating blade 26 as a rotating member is provided inside the cylindrical screen 21. The rotating blade 26 has a rotating shaft 27 rotated by a motor 28.
And rotates inside the cylindrical screen 21 to mix the supplied surface modifier and the resin powder, and the surface modification mixed on the inner surface of the cylindrical screen 21 by the centrifugal force. Press the filler and the resin powder.
The mixture of the surface modifier and the resin powder that has passed through the cylindrical screen 21 is discharged from the discharge port 22. Coarse particles such as foreign matter that do not pass through the cylindrical screen 21 pass through the separation aperture 29 and are discharged from the discharge port 23.

As described above, the surface modifier and the resin powder are uniformly mixed by the rotating blades 16 inside the cylindrical screen 21 in the centrifugal screen machine 20, so that the surface modifier is A powder coating uniformly adhered to the surface of the powder can be obtained.

In the apparatus shown in FIG. 1, an ACM pulperizer ACM-1 manufactured by Hosokawa Micron Co., Ltd.
0 is used. The cyclone 2 for collecting powder paint has a diameter of 350 cm. As the injector 10, a wonder gun mini type NW501 manufactured by Osawa Company is used. As the centrifugal sieve 20, a cyclone screener model E360 manufactured by Azo having a 100-mesh screen is used. In addition, as the quantitative feeder 8, FS-J2-S manufactured by Koken Powtex is used.

Hereinafter, Examples and Comparative Examples in which powder coating materials were manufactured using the apparatus shown in FIG. 1 will be described. Hereinafter, all parts are parts by weight. Example 1 60.0 parts of a polyester resin (trade name "Finedec M-8020" manufactured by Dainippon Ink and Chemicals, Inc.), blocked isocyanate (trade name "Adduct B" manufactured by Fürs Co.)
9.7 parts), 3.0 parts of epoxy resin (trade name “Epicoat 1004”, manufactured by Yuka Shell Co., Ltd.), and a surface conditioner (trade name “YF-3919”, manufactured by Toshiba Silicon Corporation)
0.3 parts and 27.0 parts of titanium oxide (trade name "Titanium R-960" manufactured by DuPont) are dry-mixed with a dry mixer (Henschel mixer manufactured by Mitsui Mining Co., Ltd.) for 2 minutes, and then melted. Kneader (Bus Co., Kneader, PR
After melt-kneading at -46), the mixture was rolled and cooled by a press roller (manufactured by Nippon Steel Conveyor Co.), and then coarsely pulverized to obtain a white pellet having a volume average particle diameter of 5 mm and a thickness of about 1 mm.

The white pellets thus obtained were pulverized using the apparatus shown in FIG. The powder collected by the cyclone 2 was supplied to the centrifugal sieve 20 at a rate of 100 kg / hour by the rotary valve 3. As the surface modifier 12, fine powder silica (manufactured by Shionogi & Co., Ltd., trade name “Carplex FPS-1”) is adjusted by adjusting the fixed-quantity supply machine 8 and the injector 10 so as to be 0.2 kg / hour. The liquid was supplied from the inlet port 7. Note that the discharge pressure from the injector 10 was 3.0 kg / cm ² . As described above, a white polyester resin-based powder coating material having a volume average particle diameter of 35 μm and good fluidity was obtained.

Example 2 35.0 parts of a polyester resin (trade name "Yupika Coat GV-230" manufactured by Yupika Japan Co., Ltd.) and 35.0 parts of an epoxy resin (trade name "Epicoat 1004" manufactured by Yuka Shell Co., Ltd.)
Part, catalyst (manufactured by Shikoku Chemicals Co., Ltd., trade name "Curesol C"
-17Z ") 0.15 part, a surface conditioner (trade name" Acronal 4F ", manufactured by Basff Co.) 0.85 part, titanium oxide (trade name," Titanium R-960 ", manufactured by DuPont)
0 parts were dry-mixed for 2 minutes using the same dry mixer as in Example 1, then melt-kneaded using the same melt-kneader as in Example 1, and then roll-cooled using the same press roller as in Example 1. Then, coarsely pulverized to a volume average particle size of 5 mm and a thickness of 1
A white pellet of about mm was obtained.

The white pellets described above were used as the raw material pellets of the powder coating material, and the supply amount of the fine silica powder as the surface modifier 12 was 0.1 kg / hour, which was half that of the first embodiment. In the same manner as in Example 1, a powder coating was produced. As a result, a white epoxy / polyester resin-based powder coating material having a volume average particle diameter of 35 μm and good fluidity was obtained.

Example 3 Acrylic resin organic fine particles (trade name "FINESPHERE N-3000", manufactured by Nippon Paint Co., Ltd.)
Using an average particle size of 0.1 μm) and a supply amount of resin powder of 100
A powder coating was produced in the same manner as in Example 1 except that the supply amount of the surface modifier was 1.0 kg / hour with respect to kg / hour. As a result, a white polyester resin-based powder coating material having a volume average particle size of 35 μm and good fluidity was obtained.

Comparative Example 1 A powder coating was produced in the same manner as in Example 1 except that the surface modifier was not added through the surface modifier inlet 7.
As a result, a white polyester resin powder coating having a volume average particle size of 35 μm was obtained.

Comparative Example 2 The pellets obtained in Example 1 were used as raw material pellets, and the fine silica used in Example 1 was used as a surface modifier. The powder coating material was manufactured by mixing with the raw material pellets at the time of pulverization and pulverizing at the same time instead of supplying the powder coating material from Step 7. The amount of the fine silica powder was 0.2% by weight based on the powder. As a result, a white polyester resin-based powder coating having a volume average particle size of 35 μm was obtained.

Evaluation of coating film Examples 1 to 3 and Comparative Examples 1 and 2 obtained as described above
Using a powder coating machine GX-508 manufactured by Nippon Parkerizing Co., Ltd., a zinc phosphate treating agent (Nippon Paint Co., Ltd., trade name "Surfdyne Select 1000")
Coated on a steel plate (0.8 × 70 × 150 mm) treated at a temperature of 180 ° C. for 20 to 50 μm.
A test piece was obtained by baking for minutes. The coating film of the obtained test piece was evaluated for coating film appearance, cross cut test, impact resistance, and Erichsen. The evaluation results are shown in Table 1. In addition, each test method is as follows.

Appearance of coating film: Judged visually. Cross-cut test: A cross-cut having a base of 1 mm ² × 100 was made with an NT cutter, peeled off with a self-adhesive tape, and the number of cross-cuts not peeled was counted.

Impact resistance: 6.1 of JIS K 5400
Measured according to 3.3B. Ericssen: Using a testing machine of JIS K 7729,
It measured according to the method of JISK2247.

Evaluation of Powder Properties of Powder Coating Examples 1 to 3 and Comparative Examples 1 and 2 obtained as described above
The angle of repose, storage stability and differential pressure of the dust collector were measured for the powder coating No. 2 and the measurement results are shown in Table 1. Example 1
And about the comparative example 2, the quantity of the fine silica powder which was the surface modifier which adhered was measured from the fluorescent X-ray analysis. Table 1 shows the measurement results. The angle of repose, storage stability and differential pressure of the dust collector were measured as follows.

Angle of repose: Measured using a powder tester manufactured by Hosokawa Micron Corporation. Storage stability: about 20 g of paint in a 50 ml glass bottle
Then, the state of the paint after leaving it in a constant temperature room at 35 ° C. for one week was evaluated. The evaluation was made visually.

Dust collector differential pressure: The degree of clogging in the bag filter in the pulverizing step was determined by differential pressure. Note that the differential pressure is a differential pressure after 2 tons of powder is manufactured, and the differential pressure is 150 to 2
Those having a diameter of 00 mmAq were indicated by a circle and those having a diameter of 200 mmAq or more were indicated by a cross.

[0052]

[Table 1]

As is evident from the results in Table 1, the powder coatings of Examples 1 to 3 according to the present invention are surface-modified by mixing a surface modifier. Comparative Example 1 which is not excellent in storage stability. Further, as is clear from the comparison of the amount of the surface modifier attached to Example 1 and Comparative Example 2, the loss according to the amount of the surface modifier added can be reduced according to the present invention, and the productivity can be reduced. Can be enhanced. In Comparative Example 2, the bag filter was clogged.
It can be seen that in Examples 1 to 3 according to the present invention, clogging of the bag filter hardly occurs.

In the above embodiment, the surface modifier is supplied from the surface modifier inlet 7 provided between the cyclone 2 and the centrifugal sieve 20. For example, the inlet shown in FIG. From 24, a surface modifier may be added and supplied.

[0055]

According to the present invention, the surface modifier can be mixed uniformly, the loss with respect to the amount of the surface modifier added can be reduced, and the powder coating can be manufactured with high production efficiency. .

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an example of a manufacturing apparatus according to a manufacturing method of the present invention.

FIG. 2 is an enlarged cross-sectional view showing an injector used in the manufacturing apparatus shown in FIG.

FIG. 3 is a partially cutaway sectional view showing a centrifugal sieve used in the manufacturing apparatus shown in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Pulverizer 2 ... Cyclone for powder coating material collection 3 ... Rotary valve 4 ... Bag filter 5 ... Pressure gauge 6 ... Blower 7 ... Surface modifier inlet 8 ... Quantitative feeder 9 ... Hopper 10 ... Injector 11: Powder coating material pellets 12: Surface modifier 20: Centrifugal screen 21: Centrifugal screen 22: Centrifugal outlet 23: Centrifugal outlet 24: Inlet 25 supply screw 26 rotating blade 27 rotating shaft 28 motor 29 separation aperture

Claims (7)

[Claims] 1. A method for producing a powder coating in which a surface modifier is added to and mixed with a resin powder, wherein the raw material of the resin powder is pulverized into the resin powder.
Immediately before supplying the resin powder to the sieving process using a screen, the surface modifier is added, and the surface modifier and the resin powder are mixed and passed through the screen in the sieving process. A method for producing a powder coating, comprising: 2. The method according to claim 1, wherein the surface modifier is added by using a feeder having a compressed air inlet, a suction port, and a discharge port. 2. The method for producing a powder coating according to claim 1, wherein the method is carried out by sucking a surface modifier from an opening and discharging and supplying the surface modifier from an outlet. 3. The method according to claim 1, wherein the sieving step using the screen is performed in a sieving machine. 4. The method according to claim 3, wherein the surface modifier is added to the resin powder before being supplied to the sieving machine. 5. The method according to claim 3, wherein the surface modifier is added to the resin powder supplied to the sieving machine. 6. The sieving step using a screen uses a cylindrical screen, and the resin powder and the surface modifier are mixed by a rotating member provided inside the screen, and the rotating is performed. 6. The sieving process in which the resin powder and the surface modifier are pressed against the inner surface of the screen by centrifugal force of a member and pass through the screen. Production method of powder coating. 7. The powder according to claim 1, wherein the amount of the surface modifier added is 0.01 to 10% by weight based on the resin powder. Manufacturing method of body paint.