JPH10231446A - Powder coating material and powder coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a uniform coating film to be formed on an object having a nonplane surface by spraying a powder coating material contg. a specific film-forming resin powder and an antistatic agent to an object having a nonplane surface with a power spray gun. SOLUTION: A film-forming resin comprising a thermosetting resin (e.g. an epoxy resin, an epoxy-polyester resin, or a polyester resin), having a vol. average particle size of 3-30μm, and contg. 5wt.% or lower powder having particle size of 1/5 of the vol. average particle size or lower is subjected to corona discharge treatment to give a powder which has a permittivity of 2.0-6.0 and exhibits, under a voltage of 100V, a vol. resistivity of 1×10<14> Ω.cm and a static charge of -0.5 to -3.0μC/g. This powder is compounded with a curative and 0.03-1.0wt.% antistatic agent to give a power coating material. The coating material is spray applied to an object having a nonplane surface placed 100-300mm apart from the gun tip of a powder spray gun at a delivery rate of 50-300g/min.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a paint and a coating method, and more particularly to a powder paint and a powder coating method.

[0002]

2. Description of the Related Art Powder coatings have been attracting attention as coatings suitable for pollution-free and resource-saving in recent years because they can form coating films without using organic solvents. In addition to the remarkable increase, the application field is also expanding.

[0003] Such a powder coating generally comprises a powder containing a film-forming resin as a main component, and is usually applied to an object to be coated by an electrostatic powder coating method. In the electrostatic powder coating method, a powder coating is charged by a corona charging method or a friction charging method, and the powder coating is sprayed onto a grounded object to be electrostatically attached, and then heated and melted. To form a coating film.

[0004] In the above-mentioned electrostatic powder coating method, it is necessary to uniformly apply a charged powder coating material to the whole object to be coated in order to form a uniform coating film on the object to be coated. However, when the object to be coated has a complicated non-planar part, especially when the object to be coated has a non-planar part such as a concave part or a convex part such as a box-shaped object to be coated or an object having a bent part. In the case of an object, the powder paint hardly enters the non-planar part, and the amount of the powder paint adhering to the non-planar part is often smaller than the amount of the powder paint adhering to other parts. Therefore, in this case, since the film thickness of the coating film formed on the non-planar portion is smaller than the film thickness of the coating film formed on the other portions, the coating film having a uniform thickness over the entire object to be coated. Is difficult to form. In particular, when the powder coating is charged by the corona charging method, the powder coating hardly adheres to the non-planar part due to the Faraday gauge effect, and the film thickness of the coating film formed on the object to be coated is uneven. It is easy to be uniform. On the other hand, when charged by the triboelectric charging method, the coating efficiency and turnability of the powder coating are improved for objects to be coated such as net-shaped or complex-shaped small parts as compared with the case of the corona charging method. However, when the object to be coated is a three-dimensional structure having many flat parts such as a corrugated plate or a box, the powder coating hardly adheres to the non-planar parts, similar to the case of the corona charging method. In addition, the thickness of the coating film tends to be uneven.

An object of the present invention is to form a uniform coating film of a powder coating on an object having a complicated shape having a non-planar portion.

[0006]

The powder coating composition according to the present invention comprises a powder having a volume average particle size of 3 to 30 μm and a film-forming resin as a main component. This powder is
5% by weight of powder having a particle diameter of 1/5 or less of the volume average particle diameter
It is included in the following ratio.

Here, the powder contains, for example, a powder having a particle diameter of three times or more the volume average particle diameter at a ratio of 8% by weight or less. The powder has, for example, a dielectric constant of 2.0-6.
It is set to 0. Further, the powder is, for example, 100
Volume specific resistance value when a voltage of V is applied is 1 × 10 ¹⁴ Ω
・ Cm or more. Further, the powder contains, for example, a charge control material for imparting triboelectricity to the powder.

The powder is, for example, subjected to a corona discharge treatment and has a charge amount of -0.5 to -3.0 μC / g. Alternatively, the powder has, for example, an internally generated current value of 1.
It has been subjected to a triboelectric charging treatment so as to be 0 to 8.0 μA.

Another powder coating according to the present invention is for forming a coating film on an object having a non-planar portion. The powder coating has a volume average particle diameter of 3 to 30 μm and is composed of a powder containing a film-forming resin as a main component. This powder contains powder having a particle diameter of 1/5 or less of the volume average particle diameter at a ratio of 5% by weight or less.

[0010] The powder contains, for example, a powder having a particle diameter three times or more the volume average particle diameter at a ratio of 8% by weight or less.

The powder coating method according to the present invention is a method for forming a coating film on an object having a non-planar portion by using a powder coating gun. In this coating method, the volume average particle diameter is set to 3 to 30 μm, the film-forming resin is a main component, and the content of powder having a particle diameter of 1/5 or less of the volume average particle diameter is 5% by weight or less. The method includes a step of preparing a powder coating composed of a powder, and a step of spraying the powder coating on an object to be coated using a powder coating gun.
Here, the distance between the powder coating gun and the object to be coated is, for example, 1
It is set to 00 to 300 mm.

The powder coating gun is, for example, a corona charging type coating gun capable of performing a corona discharge treatment on a powder coating.
In this case, the charge amount of the powder coating is set to, for example, −0.5 to −3.0 μC / g by corona discharge treatment.

The powder coating gun is, for example, a triboelectric coating gun capable of performing triboelectric treatment on powder coating. In this case, the internally generated current value of the powder coating is set to, for example, 1.0 to 8.0 μA by the triboelectric charging process.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Powder Coating The powder coating of the present invention comprises a powder containing a film-forming resin as a main component. Here, 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. Specifically, epoxy resins, epoxy-
Examples thereof include polyester resins, polyester resins, acrylic resins, acrylic-polyester resins, and fluorine resins. Among these, when it is necessary to form a coating film having good weather resistance with the powder coating of the present invention, the acrylic resin needs to form a coating film having good coating properties such as impact resistance. In this case, a polyester resin is preferably used, and when it is necessary 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. A polymer obtained by polymerizing a carboxylic acid such as phthalic acid, phthalic acid, succinic acid, glutaric acid, adipic acid, sebacic acid and β-oxypropionic acid in a conventional manner 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 above-mentioned film-forming resin, a curing agent is used in combination. As a curing agent,
Various known ones 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, Aminoplast 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 manufactured by Scitech) “powder” Link 1174 ″), amine-based curing agents, triglycidyl isocyanurate, dicyandiamide, phenolic resins, imidazoles, imidazolines, and the like.

As the film-forming resin, a thermoplastic resin which is usually mainly used in a fluid immersion method may be used, if necessary. 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.

The powder constituting the powder coating of the present invention may contain, if necessary, titanium dioxide, red iron oxide, carbon black, phthalocyanine blue, phthalocyanine green, quinacridone pigment, in addition to the above-mentioned film-forming resin.
Color pigments such as azo pigments, extender pigments such as talc, silica, calcium carbonate, and precipitated barium sulfate; silicones such as dimethyl silicone and methyl silicone; surface modifiers such as acrylic oligomers; and 1 to 3 types of benzoin and benzoin Antifoaming agents represented by benzoins such as benzoin derivatives to which functional groups are added, curing accelerators (or curing catalysts), plasticizers, antistatic agents, ultraviolet absorbers, antioxidants, pigment dispersants, flame retardants And various additives such as a fluidity-imparting agent.

Here, as the fluidity-imparting agent, for example,
AEROSIL (trade name) manufactured by Nippon Aerosil Co., Ltd.
130 ”,“ AEROSIL 200 ”,“ AER ”
OSIL 300 ”and“ AEROSIL R-97 ”
2 ”,“ AEROSIL R-812 ”,“ AEROSIL R-812 ”
OSIL R-812S "and" IL "titanium dioxide T-80
5 "," Titanium dioxide P-25 "," Almini "
um Oxide C "and" Carplex FPS-1 "(trade name, manufactured by Shionogi & Co., Ltd.).

When the powder coating of the present invention is applied by being charged by a triboelectric charging method, the powder constituting the powder coating of the present invention contains a charge control material for imparting triboelectric charging. Is preferred. As the charge control material, for example,
Inorganic fine particles such as aluminum oxide or organic fine particles of a nitrogen compound can be used. However, it is preferable to use fine particles of aluminum oxide from the viewpoint that the chargeability and powder fluidity can be more efficiently improved.

The amount of the charge control material to be added is usually
It is preferably set to 0.03 to 1.0% by weight of the powder, and more preferably set to 0.1 to 0.5% by weight. When the amount of the charge control material is less than 0.03% by weight, the powder coating is not sufficiently charged when the powder coating is subjected to a charging treatment by a triboelectric charging method. The coating efficiency of the body paint may decrease. On the other hand, when the addition amount exceeds 1.0% by weight, when the charging treatment is performed on the powder coating by a triboelectric charging method, the powder coating is excessively charged and the charge on the object to be coated is saturated. It is likely to be in a state, and as a result, the coating efficiency of the powder coating may decrease.

The powder constituting the powder coating of the present invention has a volume average particle diameter of 3 to 30 μm, preferably 5 to 25 μm,
More preferably, it is set to 8 to 25 μm. When the volume average particle diameter is less than 3 μm, the production process is often complicated, and the efficiency of applying the powder coating to the object to be coated may be reduced. Conversely, when the volume average particle diameter is 3
When the thickness exceeds 0 μm, the ease of entry of the powder coating material into a non-planar part of the object to be coated, for example, a concave portion (hereinafter referred to as “penetration”) is reduced, and a coating film having a uniform film thickness is applied to the entire object to be coated. In some cases, or the appearance of the coating film may be degraded.

In the above-mentioned powder, the proportion of the powder having a particle diameter of 1/5 or less of the above-mentioned volume average particle diameter is regulated to 5% by weight or less (preferably 3% by weight or less). 5% by weight of powder having a particle diameter of 1/5 or less of the volume average particle diameter
If the ratio exceeds the above range, the penetration of the powder coating material may be reduced, and it may be difficult to apply a coating film having a uniform film thickness to the whole object to be coated.

In the above-mentioned powder, the proportion of the powder having a particle diameter of three times or more of the above-mentioned volume average particle diameter is preferably regulated to 8% by weight or less, more preferably 3% by weight or less. Is more preferable. If this proportion exceeds 8% by weight, the coating efficiency and the appearance of the coating film may be reduced.

The above powder has a dielectric constant of 2.0 to 2.0.
It is preferably set to 6.0, and 2.0 to 5.0
Is more preferably set to. When the dielectric constant is less than 2.0, the coating efficiency of the powder coating may decrease. Conversely, when the dielectric constant exceeds 6.0, the penetrability of the powder coating is reduced, and it may be difficult to provide a coating film having a uniform film thickness on the entire object to be coated.

Here, the permittivity is a value measured as follows. First, 300g of powder coating 1.0g
Pressurize at a pressure of g / cm ² for 1 minute to produce a pellet having a diameter of 2.0 cm. Next, the obtained pellets were heated at a temperature =
Leave for 24 hours in a measurement environment of 25 ° C and 50% humidity,
The permittivity is measured using a permittivity meter.

Further, the above-mentioned powder preferably has a volume resistivity value of 1 × 10 ¹⁴ Ω · cm or more when a voltage of 100 V is applied, and preferably 1 × 10 ¹⁴ to 1 × 10 ¹⁶ Ω · cm.
More preferably, it is in the range of cm. When the volume resistivity is less than 1 × 10 ¹⁴ Ω · cm, the electric charge easily escapes from the particles constituting the powder, and as a result, the powder coating particles easily fall off from the object to be coated. In addition, the charged particles may be discharged before being applied to the object to be coated, and as a result, the application efficiency may be reduced. If the volume resistivity exceeds 1 × 10 ¹⁶ Ω · cm, the penetration may be reduced. In addition, as a result of the charge being easily accumulated in the layer of the powder coating particles attached to the object to be coated, a discharge phenomenon occurs from the layer of the powder coating particles, and a crater-like trace is formed in the layer, and after the baking treatment, The appearance of the resulting coating film may be reduced.

The volume resistivity was determined by preparing a pellet similar to that used in the measurement of the dielectric constant, leaving the pellet in a measuring environment of temperature = 25 ° C. and humidity = 50% for 24 hours. This is a resistance value measured using a resistance measuring instrument.

The above-mentioned dielectric constant and volume resistivity can be determined, for example, by appropriately selecting the type of the above-mentioned film-forming resin and the type of various additives, or by appropriately adjusting the blending ratio thereof. It can be easily set to a desired value.

The powder coating of the present invention can be produced by a method similar to that of a conventional powder coating. Specifically, the above-mentioned film-forming resin and other additives are mixed at a predetermined ratio, melt-kneaded, cooled, and then coarsely pulverized.
After further coarsely pulverizing the obtained coarsely pulverized particles, fine particles and coarse particles are removed using a classifier,
When the volume average particle diameter and the particle size distribution are set in the above-mentioned ranges, it can be produced.

Coating Method The powder coating of the present invention is applied to an object to be coated by an electrostatic powder coating method. Here, as the electrostatic powder coating method, any of a corona charging method and a friction charging method may be adopted. In the case of the corona charging method, any of the external charging method and the internal charging method may be employed.

The object to be coated with the powder coating of the present invention is not particularly limited as long as the conventional powder coating is applied. However, since the powder coating of the present invention has particularly good penetration into non-planar portions such as concave portions and convex portions, even when applied to a three-dimensional structure having such non-planar portions. In addition, a coating film having a uniform film thickness can be applied to the whole object including the non-planar part. In other words, the powder coating of the present invention is particularly effective when used to apply a coating film to an object having a non-planar portion as described above.

Here, the three-dimensional structure having a non-planar portion includes various types having a complicated shape such as a concave portion or a convex portion. Box, bag, rod, cylinder, cylinder, prism, cone, pyramid, plate with uneven pattern, plate with slit, punching hole Plates, nets, spheres, hemispheres, propellers, louvers,
Box-shaped objects having curved surfaces, plate-shaped objects having curved surfaces, perforated block-shaped objects such as engine blocks, sash rails such as windows, hood-shaped objects, motorcycle fuel tanks, automobile wheels, etc. Can be.

The powder coating of the present invention has a depth of 2 to 1
It is about 00 cm and has good penetration into a concave part where the ratio of the width to the depth of the opening is about 1/50 to 50/1. It is particularly useful when applied to

When the powder coating of the present invention is applied by the electrostatic powder coating method, the object to be coated with the powder coating is usually grounded (grounded), and the powder is applied to the object. The powder paint is sprayed using a coating gun, specifically, a corona charging type coating gun or a friction charging type coating gun. In addition, the corona charging type coating gun used here is a type which can be sprayed by performing a corona discharge treatment on the powder coating, and the friction charging type coating gun can be sprayed by performing a friction charging processing on the powder coating. Things.

At this time, the discharge amount of the powder coating from the powder coating gun is preferably set to 50 to 300 g / min.
Further, the distance from the tip of the gun portion of the powder coating gun to the object to be coated is preferably set to 100 to 300 mm from the viewpoint of coating efficiency.

When the powder coating composition of the present invention is applied by discharging the powder coating composition from the corona charging type coating gun, the charging voltage applied to the powder constituting the powder coating composition by corona discharge treatment is -30 to -1.
Set to 50 kv (preferably -50 to -90 kv),
It is preferable to set the charge amount of the powder coating to -0.5 to -3.0 µC / g (preferably -0.5 to -2.0 µC / g). If the charge amount of the powder coating is greater than -0.5 μC / g, the powder coating becomes difficult to adhere to the object to be coated,
Coating efficiency may decrease. Conversely, when the charge amount of the powder coating is smaller than -3.0 μC / g, the average charge amount per particle of the powder coating increases, so that the non-planar part of the object to be coated by the Faraday gauge effect. The penetration of the powder coating particles into (particularly, the concave portion) may be reduced, and it may be difficult to form a uniform coating film on the entire workpiece including the non-planar portion (particularly, the concave portion). There is.

Here, the charge amount is a value that can be obtained as follows. Using a Faraday gauge to collect the powder coating discharged from the corona charging type coating gun,
The charge amount (Q) of the collected powder coating is measured using a digital electrometer. Next, the amount (M) of the powder paint collected by the Faraday gauge is measured. Then, the charge amount (Q) is divided by the powder paint amount (M) (Q / M), and the obtained value is set as the charge amount.

On the other hand, when the powder coating of the present invention is discharged from the triboelectric coating gun to perform coating, a friction charging treatment is performed so that the current generated inside the powder coating is 1.0 to 8.0 μA. Is preferred. When the internally generated current value is less than 1.0 μA, the powder coating becomes difficult to adhere to the object to be coated, and the coating efficiency may decrease. Conversely, if the internally generated current value exceeds 8.0 μA, the particles 1 constituting the powder coating
Since the average charge amount per unit becomes too large, the penetration of the powder coating material into the non-planar portion (particularly, the concave portion) of the object to be coated is reduced due to the Faraday gauge effect, and the object to be coated including the non-planar portion is reduced. It may be difficult to form a uniform coating film as a whole.

Here, the internally generated current value was obtained by reading the internally generated current value when the electrostatic powder coating was performed using a triboelectric coating gun using an ammeter of the triboelectric coating gun. Value.

The powder coating of the present invention discharged from the powder coating gun toward the object to be coated as described above adheres electrostatically to the object to be coated, and forms a powder on the object to be coated. Form a particle layer of paint. At this time, since the volume average particle diameter and the particle size distribution of the powder coating are set as described above, the powder coating easily penetrates into a non-planar part such as a concave part or a convex part of the object to be coated, and It can adhere to parts as well as other planar parts. Therefore, the powder coating of the present invention has poor penetration of the powder coating due to the Faraday gauge effect, and as a result, it is difficult to form a coating film having a uniform film thickness. Even when applied to the entire surface of the object to be coated.

The powder coating of the present invention applied to the object to be coated in this manner can form a coating film while melting and curing when heated. At this time, as described above, the powder coating adheres to the non-planar part of the object to be coated as well as other parts, so that the object to be coated includes a uniform coating as a whole including the non-planar part. A film can be formed.

[0046]

Example 1 (Production of polyester powder coating ) 60 parts by weight of a polyester resin ("FINDIC M8021" manufactured by Dainippon Ink and Chemicals, Inc.), ε-
10 parts by weight of caprolactam-blocked isocyanate ("Adduct B-1530" manufactured by Huls), 5 parts by weight of calcium carbonate, 30 parts by weight of titanium dioxide, and a surface conditioner ("CF-105" manufactured by Toshiba Silicone Co., Ltd.)
6 ") 0.5 part by weight was mixed for about 3 minutes using a" Supermixer "manufactured by Nippon Spindle Co., Ltd., and was further melt-kneaded at about 100 ° C using a" Kneader "manufactured by Buss. The obtained melt-kneaded product was cooled at room temperature, coarsely pulverized, and further pulverized using an “Atomizer” manufactured by Fuji Paudal Co., Ltd. The obtained powder was subjected to an airflow classifier (produced by Nippon Pneumatic Industries, Ltd.). "DS-2" type) to remove fine particles and coarse particles, thereby reducing the proportion of particles having a volume average particle diameter of 24 µm and a particle diameter of 1/5 or less of the volume average particle diameter. A polyester powder coating material in which the ratio of particles having a particle diameter of 1.7% by weight and three times or more the volume average particle diameter was adjusted to 1.1% by weight was obtained.

The volume average particle size and the particle size distribution are as follows:
It is a value measured using a particle size analyzer (trade name “Microtrack HRA X-100” manufactured by Nikkiso Co., Ltd.). At the time of this measurement, Nikkiso Co., Ltd. product name “MICROTRAC DHSS.
X100 Data Handling System S
D-9300PRO-100 ", and" Particle Transparency "as a measurement condition.
Was set to “reflect”. The measurement sample is
50 g of a 0.1% surfactant aqueous solution and 0.5 g of a powder coating to be measured are added to the sample bottle, and the sample bottle is washed with an ultrasonic cleaner (trade name “SILENT” of Sharp Corporation).
The powder coating dispersion water prepared by immersing in water subjected to ultrasonic vibration by SONIC UT-105 ") for 3 minutes was used. The method of measuring such volume average particle diameter and particle size distribution is described in each of the following Examples. The same applies to each comparative example.

Example 2 (Production of Epoxy Powder Coating) As materials, 65 parts by weight of an epoxy resin ("Epicoat 1004" manufactured by Yuka Shell Epoxy Co., Ltd.), 5 parts by weight of dicyandiamide, 20 parts by weight of titanium dioxide, and 5 parts by weight of calcium carbonate The same procedure as in Example 1 was conducted except that 0.5 parts by weight and 0.5 part by weight of a surface conditioner (“CF-1056” manufactured by Toshiba Silicone Co., Ltd.) were used, and the volume average particle diameter was 26 μm.
m, the proportion of particles having a particle diameter of 1/5 or less of the volume average particle diameter was adjusted to 1.2% by weight, and the proportion of particles having a particle diameter of 3 times or more the volume average particle diameter was adjusted to 2.3% by weight. An epoxy powder coating was obtained.

Example 3 (Production of Acrylic Powder Coating) A reactor equipped with a thermometer, a stirrer, a cooling pipe, a nitrogen introduction pipe and a dropping funnel was prepared, and 63 parts by weight of xylene was charged to 130 ° C. Heated. In this reactor, a monomer mixture consisting of 45 parts by weight of glycidyl methacrylate, 20 parts by weight of styrene, 27 parts by weight of methyl methacrylate and 8 parts by weight of isobutyl methacrylate, 6.5 parts of t-butyl peroxy-2-ethylhexanoate were added. An initiator solution consisting of parts by weight and 6 parts by weight of xylene was added dropwise over 3 hours using a dropping funnel. After dropping,
After keeping the temperature for 30 minutes, 0.1 part by weight of t-butylperoxy-2-ethylhexanoate and 7 parts by weight of xylene were added dropwise using a dropping funnel. After dropping, 1 more
After maintaining at 30 ° C. for 1 hour and removing xylene by distillation under reduced pressure, an acrylic resin having a glass transition temperature of 52 ° C. was obtained.

Next, 48 parts by weight of the obtained acrylic resin,
12 parts by weight of decanedicarboxylic acid, 10 parts by weight of titanium dioxide, 5 parts by weight of calcium carbonate, 0.1 part by weight of a surface conditioner (“CF-1056” manufactured by Toshiba Silicone Co., Ltd.)
Benzoin 0.3 parts by weight and bisphenol A type epoxy resin ("YD-012" manufactured by Toto Kasei Co., Ltd.)
2.2 parts by weight were mixed for about 3 minutes using a “Supermixer” manufactured by Nippon Spindle Co., Ltd., and were melt-kneaded at 100 ° C. using a “Coneder” manufactured by Buss. The obtained melt-kneaded material was cooled at room temperature and coarsely pulverized, and further, “Jet Mill ID” manufactured by Nippon Pneumatic Industry Co., Ltd.
After pulverization using an "S-2 type", the particles were classified using an airflow classifier ("DS-2" type manufactured by Nippon Pneumatic Industries, Ltd.), whereby the volume average particle diameter was 9.6 μm,
Acrylic powder in which the proportion of particles having a particle diameter of 1/5 or less of the volume average particle diameter is adjusted to 0.5% by weight, and the proportion of particles having a particle diameter of 3 times or more the volume average particle diameter is adjusted to 0.4% by weight. A body paint was obtained.

Example 4 (Production of Polyester Powder Coating) The same melt-kneaded product obtained in the process of Example 1 was cooled at room temperature, and then pulverized using an “Atomizer” manufactured by Fuji Paudal Co., Ltd. Then, only fine particles were classified using an airflow classifier ("DS-2" type, manufactured by Nippon Pneumatic Industries, Ltd.). Thereby, the volume average particle diameter becomes 29
The ratio of particles having a particle diameter of μm and 1/5 or less of the volume average particle diameter was adjusted to 1.3% by weight, and the ratio of particles having a particle diameter of 3 times or more the volume average particle diameter was adjusted to 7.1% by weight. A polyester powder coating was obtained.

Example 5 (Production of Polyester Powder Coating) The same procedure as in Example 1 was carried out except that a material further added with 2 parts by weight of sodium salt of a secondary alkanesulfonic acid was used. The ratio of particles having a diameter of 25 μm and a particle diameter of 1/5 or less of the volume average particle diameter is adjusted to 1.8% by weight, and the ratio of particles having a particle diameter of 3 times or more the volume average particle diameter is adjusted to 2.1% by weight. The obtained polyester powder coating was obtained.

Example 6 (Preparation of a polyester powder coating) Except that a material further added with 20 parts by weight of calcium carbonate, 5 parts by weight of titanium dioxide and 2 parts by weight of copper phthalocyanine blue was used. 1, the volume average particle diameter was 24 μm, and 1 / of the volume average particle diameter.
2.3% by weight of particles having a particle diameter of 5 or less, and 0.9% by weight of particles having a particle diameter of 3 times or more the volume average particle diameter.
To obtain a polyester powder coating adjusted to.

Example 7 (Production of Acrylic Powder Coating) The same operation as in Example 3 was carried out except that the conditions for pulverization and classification were changed, and the volume average particle diameter was 4.6 μm and 1/1 of the volume average particle diameter. An acrylic powder coating material was obtained in which the ratio of particles having a particle size of 5 or less was adjusted to 2.3% by weight, and the ratio of particles having a particle size three times or more the volume average particle size was adjusted to 1.1% by weight.

Example 8 (Production of Acrylic Powder Coating) As materials, 48 parts by weight of the acrylic resin used in Example 3, 12 parts by weight of decanedicarboxylic acid, and a surface conditioner ("CF-1056" manufactured by Toshiba Silicone Co., Ltd.) ") 0.1 parts by weight, benzoin 0.3 parts by weight, and bisphenol A type epoxy resin (" YD-01 "manufactured by Toto Kasei Co., Ltd.)
2 ″) The same operation as in Example 3 was carried out except that 2.2 parts by weight were used, and the ratio of particles having a volume average particle diameter of 9.7 μm and a particle diameter of 1/5 or less of the volume average particle diameter was 0. 0.5% by weight, the ratio of particles having a particle diameter of three times or more of the volume average particle diameter is 0.7%
An acrylic powder coating adjusted to weight% was obtained.

Comparative Example 1 (Production of Polyester Powder Coating) The same melt-kneaded product obtained in the process of Example 1 was cooled at room temperature, and then pulverized using an “Atomizer” manufactured by Fuji Paudal Co., Ltd. Then, coarse particles were classified using a 150-mesh sieve. As a result, the ratio of particles having a volume average particle diameter of 39 μm, particles having a particle diameter of 1/5 or less of the volume average particle diameter is 4.4% by weight, and the ratio of particles having a particle diameter of 3 times or more the volume average particle diameter is 0%. A polyester powder paint adjusted to 0.4% by weight was obtained.

Comparative Example 2 (Production of Polyester Powder Coating) The same melt-kneaded product obtained in the process of Example 1 was cooled at room temperature and then pulverized using an “Atomizer” manufactured by Fuji Paudal Co., Ltd. Then, only coarse particles were classified using a 150-mesh sieve. As a result, the ratio of particles having a volume average particle diameter of 24 μm, particles having a particle diameter of ５ or less of the volume average particle diameter is 6.7% by weight, and the ratio of particles having a particle diameter of three times or more the volume average particle diameter is 1 A polyester powder paint adjusted to 0.5% by weight was obtained.

Example 9 (Production of Polyester Powder Coating ) 60 parts by weight of a polyester resin (“FINEDIC M8021” manufactured by Dainippon Ink and Chemicals, Inc.), ε-
10 parts by weight of caprolactam-blocked isocyanate ("Adduct B-1530" manufactured by Huls), 5 parts by weight of calcium carbonate, 30 parts by weight of titanium dioxide, and a surface conditioner ("CF-105" manufactured by Toshiba Silicone Co., Ltd.)
6 ") 0.5 part by weight was mixed for about 3 minutes using a" Supermixer "manufactured by Nippon Spindle Co., Ltd., and was further melt-kneaded at about 100 ° C using a" Kneader "manufactured by Buss. The obtained melt-kneaded product was cooled at room temperature, coarsely pulverized, and further pulverized using an “Atomizer” manufactured by Fuji Paudal Co., Ltd. The obtained powder was subjected to an airflow classifier (produced by Nippon Pneumatic Industries, Ltd.). The particles were classified using a “DS-2” type to remove fine particles and coarse particles, and 100 parts by weight of the powder obtained through such a classification step was added to a fine powder of aluminum oxide ( Product name "Aluminium O" manufactured by Nippon Aerosil Co., Ltd.
xide C ") was added and mixed for 1 minute using" Supermixer "manufactured by Nippon Spindle Co., Ltd.

As described above, the volume average particle diameter was 24 μm,
Polyester powder in which the proportion of particles having a particle diameter of 1/5 or less of the volume average particle diameter is adjusted to 2.0% by weight, and the proportion of particles having a particle diameter of 3 times or more the volume average particle diameter is adjusted to 0.9% by weight. A body paint was obtained.

Example 10 (Production of Epoxy Powder Coating) As materials, 65 parts by weight of an epoxy resin (“Epicoat 1004” manufactured by Yuka Shell Epoxy Co., Ltd.), 5 parts by weight of dicyandiamide, 20 parts by weight of titanium dioxide, and 5 parts by weight of calcium carbonate The same procedure as in Example 9 was carried out except that the weight part and 0.5 part by weight of a surface conditioner (“CF-1056” manufactured by Toshiba Silicone Co., Ltd.) were used, the volume average particle diameter was 24 μm.
m, the proportion of particles having a particle diameter of 1/5 or less of the volume average particle diameter was adjusted to 2.2% by weight, and the proportion of particles having a particle diameter of 3 times or more the volume average particle diameter was adjusted to 2.0% by weight. An epoxy powder coating was obtained.

Example 11 (Production of polyester powder paint)
Production) The same melt-kneaded product obtained in the process of Example 9 was cooled at room temperature and then pulverized using an "Atomizer" manufactured by Fuji Paudal Co., Ltd., and further subjected to an air flow classifier (Nippon Nyumatic Industrial Co., Ltd.). Only the fine particles were classified using a company “DS-2” type. With respect to 100 parts by weight of the powder obtained through such a classification step, aluminum oxide fine powder (trade name “A” manufactured by Nippon Aerosil Co., Ltd.) was used as a charge controlling material.
luminum oxide C)) was added and mixed for 1 minute using a “Supermixer” manufactured by Nippon Spindle Co., Ltd., whereby the volume average particle diameter was 28 μm and 1/5 of the volume average particle diameter. A polyester powder coating material was obtained in which the proportion of particles having the following particle diameter was adjusted to 1.1% by weight and the proportion of particles having a particle diameter of three times or more the volume average particle diameter was adjusted to 6.8% by weight.

Example 12 (Production of polyester powder paint)
Manufacture) The same operation as in Example 9 was performed except that a material further added with 2 parts by weight of a sodium salt of a secondary alkanesulfonic acid was used, and the volume average particle diameter was 25 μm and 1/5 of the volume average particle diameter. A polyester powder coating material was prepared in which the proportion of particles having the following particle diameter was adjusted to 1.8% by weight, and the proportion of particles having a particle diameter three times or more the volume average particle diameter was adjusted to 0.8% by weight.

Example 13 (Production of polyester powder paint)
Manufacture) The same operation as in Example 9 was carried out except that a material further added with 20 parts by weight of calcium carbonate, 5 parts by weight of titanium dioxide and 2 parts by weight of copper phthalocyanine blue was used. 24 μm, 1 / of the volume average particle diameter
2.3% by weight of particles having a particle diameter of 5 or less, and 0.9% by weight of particles having a particle diameter of 3 times or more the volume average particle diameter.
To obtain a polyester powder coating adjusted to.

Example 14 (Production of polyester powder coating)
Concrete) except changing 0.7 parts by weight the amount of the aluminum oxide fine powder (Nippon Aerosil Co., Ltd. under the trade name "Aluminum Oxide C") same operation as in Example 9, the volume average particle diameter Is 24 μm, and the proportion of particles having a particle diameter of 1/5 or less of the volume average particle diameter is 2.0% by weight,
The ratio of particles having a particle diameter of three times or more of the volume average particle diameter is 1.
A polyester powder coating adjusted to 4% by weight was obtained.

Example 15 (Production of polyester powder paint)
Manufacture) The same procedure as in Example 9 was carried out except that the addition amount of aluminum oxide fine powder (trade name “Aluminium Oxide C” manufactured by Nippon Aerosil Co., Ltd.) was changed to 0.05 parts by weight, the volume average particle diameter was changed. Is adjusted to be 24 μm, the proportion of particles having a particle diameter of 1/5 or less of the volume average particle diameter is 2.0% by weight, and the proportion of particles having a particle diameter not less than 3 times the volume average particle diameter is adjusted to 1.0% by weight. A polyester powder coating was obtained.

Comparative Example 3 (Production of Polyester Powder Coating) The same melt-kneaded product obtained in the process of Example 9 was cooled at room temperature, and then pulverized using an “Atomizer” manufactured by Fuji Paudal Co., Ltd. Then, coarse particles were classified using a 150-mesh sieve. To 100 parts by weight of the powder obtained through such a classification step, 0.2 parts of aluminum oxide fine powder (trade name “Aluminium Oxide C” manufactured by Nippon Aerosil Co., Ltd.) was added as a charge control material to 0.2 part.
Parts by weight were added and mixed for 1 minute using "Super Mixer" manufactured by Nippon Spindle Co., Ltd. As a result, the ratio of particles having a volume average particle diameter of 36 μm, a particle diameter of 1/5 or less of the volume average particle diameter is 4.5% by weight, and the ratio of particles having a particle diameter of 3 times or more of the volume average particle diameter is 0%. A polyester powder paint adjusted to 0.1% by weight was obtained.

Comparative Example 4 (Production of Polyester Powder Coating) The same melt-kneaded product obtained in the process of Example 9 was cooled at room temperature, and then pulverized using an “Atomizer” manufactured by Fuji Paudal Co., Ltd. Then, only coarse particles were classified using a 150-mesh sieve. To 100 parts by weight of the powder obtained through such a classification step, 0.2 parts by weight of aluminum oxide fine powder (trade name “Aluminium Oxide C” manufactured by Nippon Aerosil Co., Ltd.) was added as a charge control material, The mixture was mixed for 1 minute using "Super Mixer" manufactured by Nippon Spindle Co., Ltd. Thereby, the volume average particle diameter is 23 μm, and 1 /
The ratio of particles having a particle size of 5 or less is 7.3% by weight, and the ratio of particles having a particle size not less than 3 times the volume average particle size is 1.5% by weight.
To obtain a polyester powder coating adjusted to.

[0068] As coated test object to be coated, Fig. 1 (bottom view) and 2 (front view)
As shown in (1), a substrate 1 having a concave portion 2 extending in the width direction at the center portion and having flange portions 3 at both ends was prepared.
This substrate 1 is a phosphoric acid-treated steel sheet having a thickness of 0.8 mm, and the size and angle of each part shown in FIGS. 1 and 2 are as follows.

A = 70 mm b = 40 mm c = 290 mm d = 600 mm θ = 60 °

Next, as shown in FIG. 3, three substrates 1 were suspended from a horizontally movable overhead conveyor (not shown) at intervals of 100 mm. Then, as shown in FIG. 4, when the base material 1 is moved by the horizontally moving overhead conveyor, a spray pattern having a locus as shown by a dashed line in FIG. 3 is drawn in front of the placed base material 1. The powder coating gun G was fixed as described above. At this time, the distance X between the flange 3 of the base material 1 and the tip of the head of the powder coating gun G was set to be 200 mm. Examples of the powder coating gun G include Examples 1 to 8 and Comparative Examples 1 and 2.
, A corona charging type coating gun (trade name “PG-1” manufactured by GEMA) is used. In Examples 9 to 15 and Comparative Examples 3 and 4, a friction charging type coating gun (Matsuo Sangyo Co., Ltd.) Trade name "SFC-TR100D").

Using the coating apparatus set as described above,
The powder coating obtained in each of the examples and the comparative examples was applied to the substrate 1. At this time, the coating conditions were set as follows, and the film thickness was set to be 60 ± 5 μm.

(Examples 1 to 8 and Comparative Examples 1 and 2) Moving speed of overhead conveyor: 1.8 m / min Applied voltage: -80 kv Discharge amount: 100 g / min Discharge pressure: 1.0 kgf / cm ² Air flow rate : 4.5 m ³ / h

(Examples 9 to 15 and Comparative Examples 3 and 4) Moving speed of overhead conveyor: 1.8 m / min Discharge amount: 100 g / min Discharge pressure: 2.0 kgf / cm ² Acceleration pressure: 2.0 kgf / cm ²

Next, the base material 1 coated with the powder coating material (the one arranged at the center of the above three base materials 1) is
It was baked in a hot air drying oven at 0 ° C. for 20 minutes to form a coating film. About the obtained coating film, the coating film appearance, the coating efficiency of the powder coating, and the penetration of the powder coating were examined. In addition, for the powder coatings obtained in each of the examples and comparative examples, the powder coating properties, that is, the dielectric constant and the volume resistivity when a voltage of 100 V was applied, and the discharge from the corona charging type coating gun. (Examples 1 to 8 and Comparative Examples 1 and 2) or an internally generated current value when discharged from a triboelectric coating gun (Examples 9 to 15 and Comparative Examples 3 and 4) ). The survey method is as follows. The results are shown in Tables 1 and 2.

(Appearance of coating film) Ra was measured using a surface roughness shape measuring instrument (“Surfcom 470A” manufactured by Tokyo Seimitsu Co., Ltd.).
The values were measured and evaluated. When the Ra value is 0.6 or less, the appearance of the coating film is good.

(Coating Efficiency) Evaluation was made by obtaining the ratio (%) of the weight of the powder coating applied to the substrate 1 to the total amount of the powder coating discharged from the coating gun. The larger the value, the better the coating efficiency. More specifically,
When a corona charging type coating gun is used, 65% or more is good, and when a friction charging type coating gun is used, 50% or more is good.

(Penetration Property) With respect to the coated base material 1, the thickness of the coating film at each of the portions A, B and C shown in FIG. 2 was measured. Then, the film thickness of each part is substituted into the following equation (1),
Intrusion was sought. The higher the value, the better the penetration. More specifically, when the corona charging type coating gun is used, 0.7 or more is good, and when the friction charging type coating gun is used, 0.55 or more is good.

[0078]

## EQU1 ## Penetration = B / ((A + C) / 2)

(Characteristics of powder paint) Dielectric constant, volume resistivity, charge amount (Examples 1 to 8 and Comparative Examples 1 and 2)
And the internally generated current value (in the case of Examples 9 to 15 and Comparative Examples 3 and 4) was measured according to the method described above. At this time, TYP manufactured by Ando Electric Co., Ltd. was used as a dielectric constant measuring device.
EAG-4311 LCR METER, TR8601 manufactured by Takedariken Co., Ltd. was used as a resistance measuring instrument, and "TR-8652" manufactured by Advantest Co., Ltd. was used as a digital electrometer for measuring a charge amount. In the measurement of the charge amount, the powder coating material discharged from the corona charging type coating gun was collected by a Faraday gauge under the same conditions as the above-mentioned coating method.

[0080]

[Table 1]

[0081]

[Table 2]

From Tables 1 and 2, it can be seen that when the proportion of coarse particles is large (Examples 4 and 11), although the penetration is good, the appearance of the coating film and the coating efficiency are slightly reduced. When the volume resistivity is smaller than the above-mentioned preferable range (Examples 5 and 12), it can be seen that the appearance of the coating film and the coating efficiency are slightly impaired. Further, when the dielectric constant or the charge amount is out of the preferable range described above (Examples 6, 7, and 13), it can be seen that the coating efficiency is impaired. Furthermore, even if the volume specific resistance value is within the above preferable range, if it is larger than the more preferable range,
It can be seen that the appearance and penetration of the coating film are slightly impaired within an acceptable range. Further, when the internally generated current value is larger than the above preferred range (Example 14), the appearance of the coating film is slightly impaired, and when it is smaller than the preferred range (Example 15), the appearance and coating of the coating film are reduced. It can be seen that both efficiency is impaired. However, in any of the above-mentioned examples, since the volume average particle diameter and the fine particle ratio are within the range of the present invention, the penetration is generally good.

[0083]

According to the powder coating of the present invention, the volume average particle diameter and the particle size distribution are set as described above. A coating can be formed.

Since the powder coating method of the present invention uses the above-described powder coating, a uniform coating film can be formed even on a workpiece having a complicated shape having a non-planar portion.

[Brief description of the drawings]

FIG. 1 is a bottom view of a substrate used in a coating test according to an example of the present invention.

FIG. 2 is a front view of the substrate.

FIG. 3 is a view showing an arrangement state of the base material when applying a powder coating material to the base material in an embodiment.

FIG. 4 is a plan view showing an arrangement state of the base materials when a powder coating material is applied to the base materials in the embodiment.

[Explanation of symbols]

 1 base material 2 concave part G powder coating gun

Claims (15)

[Claims] 1. A powder having a volume average particle size of 3 to 30 μm and comprising a film-forming resin as a main component, wherein the powder has a particle size of １ ／ or less of the volume average particle size. A powder coating containing powder in an amount of 5% by weight or less. 2. The powder coating according to claim 1, wherein said powder contains a powder having a particle diameter of three times or more of said volume average particle diameter at a ratio of 8% by weight or less. 3. The powder coating according to claim 1, wherein the powder has a dielectric constant of 2.0 to 6.0. 4. The powder coating according to claim 1, wherein the powder has a volume resistivity of 1 × 10 ¹⁴ Ω · cm or more when a voltage of 100 V is applied. 5. The powder according to claim 1, wherein the powder contains a charge control material for imparting triboelectricity to the powder.
The powder coating according to 2, 3, or 4. 6. The powder coating according to claim 1, wherein the powder is subjected to a corona discharge treatment and has a charge amount of -0.5 to -3.0 μC / g. . 7. The powder has an internally generated current value of 1.0 to 1.0.
The powder coating according to claim 1, which has been subjected to a triboelectric charging treatment so as to have a current of 8.0 μA. 8. A powder coating material for forming a coating film on an object to be coated having a non-planar part, wherein a volume average particle diameter is set to 3 to 30 μm and a film-forming resin is used as a main component. A powder coating, comprising: a powder having a particle diameter of 1/5 or less of the volume average particle diameter at a ratio of 5% by weight or less. 9. The powder coating material according to claim 8, wherein said powder contains a powder having a particle diameter three times or more of said volume average particle diameter at a ratio of 8% by weight or less. 10. A powder coating method for forming a coating film on an object having a non-planar part using a powder coating gun, wherein the volume average particle diameter is set to 3 to 30 μm and A step of preparing a powder coating comprising a powder having a film-forming resin as a main component and a powder having a particle diameter of 1/5 or less of the volume average particle diameter of 5% by weight or less; A step of spraying the powder coating on the object using a powder coating gun. 11. The powder coating method according to claim 10, wherein a distance between the powder coating gun and the object to be coated is set to 100 to 300 mm. 12. The powder coating method according to claim 10, wherein the powder coating gun is a corona charging type coating gun capable of performing a corona discharge treatment on the powder coating. 13. The powder coating method according to claim 12, wherein the charge amount of the powder coating is set to -0.5 to -3.0 μC / g by the corona discharge treatment. 14. The powder coating gun according to claim 1, wherein said powder coating gun is a triboelectric coating gun capable of triboelectrically treating said powder coating.
12. The powder coating method according to 0 or 11. 15. The powder coating method according to claim 14, wherein the internally generated current value of the powder coating is set to 1.0 to 8.0 μA by the triboelectric charging process.