NISSIN Powder

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Preface

By first paying our attention to the possibility of electrostatic powder coating our company successfully put on the market the electrostatic epoxy resin powder coating for the first time in Japan in 1967. Since the first sale as a pioneer in manufacturing the powder coating, satisfying the needs towards higher performance of coating film with "Powder coat S", etc. from the future-oriented point of view, we are contributing to the development of the industry in terms of energy /labor saving, reduction in coating cost, measures to clear the environmental regulations, etc., with the aim of achieving the complete electrostatic powder coating system that allows for making thinner coating film, baking at lower temperatures, etc.

l.	Contents of Powder Coating
	Powder coating consists of fine powders having 100% coating film-forming contents, and capable of forming a coating film on the surface to be coated, by applying the coatings in a powdery form.

[Compounding example]

White type coating	Epoxy-based	Epoxy- polyester- based	Polyester- based	Acrylic-based
Pigment (TiO2)	35%	33%	33%	30%
Synthetic resin	57%	63%	53%	55%
Curing agent	4%	63%	9%	10%
Additive	3%	3%	3%	2%
Others	1%	1%	2%	3%
Total	100%	100%	100%	100%

The powder coating is a powdery coating obtained synthetic resins, pigments, curing agents and other additives as compounding raw materials, followed by mechanical grinding; and has characteristics described below.

Particle size	Diameter: several microns to 100 μ (mean particle diameter: 20 to 50 μ)
Form	Amorphous polyhedron fine powder
Apparent specific gravity	0.4 to 0.8
True specific gravity	1.0 to 1.7
Angle of repose	35 to 45℃

2.	Advantages of Electrostatic Powder Coating

	(A)	Non-solvent
		Powder coating is a coating having a 100% solid content.
	(B)	Decrease in Environmental Problems and Disaster
		Occurrence
		In the powder coating, there is no dangerous property for causing environmental problems and disaster occurrence. In addition, recovery and cleaning are comparatively simple without polluting the working environment by scattering and adhesion of coatings.
	(C)	High Quality Coating Film
		Since it is possible to make the powder coating with a high performance and high molecular weight synthetic resin, making it possible to obtain a high quality coating film having respective characteristics.
	(D)	Easy Thick Coating
		The powder coating allows for a thick coating film from 30 μ to 400 μ by one coating. since there are little hanging, blobbing and pinholes, and Further, the throwing power of electric coloring to edge parts is superior, a relatively high thick coating film can easily be obtained.
	(E)	Little Loss of Coating
		Since a coating over-sprayed can be recovered for recycling in the powder coating, the loss of coating becomes very little.
	(F)	Improvement in Coating Efficiency
		Thick film coating can be easily applied and there is no need for setting area which usually required a baking processing, therefore that will save a plant line and space for equipment at the same time. Furthermore, it is easy for even non trained technician to handle painting since it is effective processing and there is a low probability for defective painting.

3.	Method of Powder Coating

Main methods of powder coating follows below.

	3-1.	Electrostatic Coating
		The principle of electrostatic powder coating is that powder electrostatically charged by a direct current high voltage, which is given by a high voltage electrostatic generator, is adhered onto a grounded article to be coated by an electrostatic attraction force. A continuous coating film is made by heating, kneading, and curing the coating adhered onto the article to be coated. The powder coating over-sprayed is recovered for recycling. There are two kinds of powder coating methods.
	(A)	Electrostatic Spray Method
		The powder coating is fed to a spray gun by air from a coating feeder. Further, the powder coating obtains a negative charge by high voltage (usually -40KV to -90KV) given by a high voltage electrostatic generator. The article to be coated is connected to the earth, and the powder coating sprayed is adhered onto the surface of an article to be coated by an electrostatic attraction force. In accordance with the thick adherence of powder particles, charge is accumulated on a coating film, and the powder particles are hardly adhered thereto any more due to the electrostatic repulsion. Based on these behaviors, a uniform coating film with a pre-fixed thickness can be obtained with a limitation in thickness derived the re from. In addition, a frictional charging-type spray coating which applies a principle of frictional charging is a coating method with such advantages that will not need a high voltage generator, retains good properties of throwing power of electrolytic coloring and a getting-in property, with an electrostatic repulsion hardly generated.
	(B)	Electrostatic Immersion Method
		The bottom plate of an immersion vessel in which the powder coating is filled is made of a porous plate, and electrodes are arranged at a fixed interval. The coating powder retained in the vessel comes to a fluidized condition by the air blown up from the porous bottom plate. A high voltage of -40KV to -90KV is applied by a high voltage electrostatic generator, the ionized powder particles flying in the air are charged and flown in the vessel, and then adhered onto the grounded article to be coated. The particles which were not adhered onto the article to be coated fall down by the gravity become charged again and fly up, followed by repeating this flow of adhering onto the article to be coated.

	3-2.	Fluidized Coating
		Fluidized coating is a method for forming a film, by air-fluidizing the powder in a vessel in which a porous plate is put on the bottom, immersing an article to be coated which is previously heated, in the flowing particles, and melting the powder which adhered onto the surface of the article to be coated by heat. The equipment investment is comparatively low, and a highly thick film of 250 μ to 1000 μ can be easily obtained. However, there are problems that the size and shape of the article to be coated are limited and pre-heating for the article to be coated is required (250℃ to 300℃) as its conditions.

We are always prepared to comply with requests from customers / prospects with our coating design for coating machines as well as coating systems, so that the respectively characteristic coating can be best applied to their advantage. Since there is rarely a case of not fully applicable to customer's requirement with a coating method, please consult our member in charge of coating machine, a coating system and the like. Powder (Tribo Prescription) for exclusive use of a frictional charging gun is prepared for the customers adopting a frictional charging gun.