Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1997-06-29
1999-04-27
Lipman, Bernard
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
428407, 523206, 523207, 523220, 5253266, 5253273, 5253285, 5253291, 5253292, 5253294, 5253297, 5253298, 5253299, 5253301, 5253303, 5253304, 5253305, 5253306, C08F 842
Patent
active
058980431
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a powder coating composition which is capable of forming a coating film superior in gloss, definition property, weatherability and other film properties and which is useful for coating of vehicles, ships, household electric appliances, coated steel plates, etc.; as well as to a process for production of the powder coating composition.
BACKGROUND ART
Organic solvent type coatings, which are obtained by dissolving main components such as resin and the like in an organic solvent and adding thereto auxiliary components such as coloring agent, curing agent and the like, have heretofore been used widely in coating applications. As there were seriously taken up recently the problems of these organic solvent type coatings, such as fire hazard, adverse effect on safety and hydigene, environmental pollution and the like, attention is being paid to coatings which vaporize no organic solvent, particularly aqueous emulsion type coatings and powder coatings.
Aqueous emulsion type coatings, however, have drawbacks. For example, since, in producing such a coating, resin particles and a pigment must be dispersed stably in an aqueous medium and therefore a hydrophilic substance such as emulsifier or the like is used, the film formed with the coating is inevitably inferior in properties such as water resistance, alkali resistance and the like; moreover, the film has low adhesivity to a material to be coated; further, it takes a time to obtain a dried film, as compared with the case of an organic solvent type coating and, in order to complete film drying in a short time, special equipment and a high cost are required.
Meanwhile, powder coatings, which contain no organic solvent, have various excellent advantages. For example, they are free from fire hazard, adverse effect on safety and hygiene, environmental pollution, or the like; they can be stored in an ordinary storehouse; the air amount of ventillation in spray booth can be minimum and the ventiallation air can be recirculated, resulting in high energy efficiency; and the coating film obtained has no foams which are generated by the vaporization of solvent during film drying. Powder coatings have further advantages. For example, they can be used as. they are without the necessity of adjusting the viscosity, solid content, etc.; and they can be easily recovered without staining the operation site and producing any waste. Furthermore, powder coatings can be applied by automated coating and, in view of the total cost including cost of coating materials, pretreatment cost, cost of coating operation, equipment cost, etc., are very economical as compared with organic solvent type coatings and aqueous emulsion type coatings.
In spite of the above-mentioned various advantages, powder coatings are not used popularly. One reason therefor is that when a conventional powder coating is applied and baked, it is difficult to obtain a coating film having luster and smoothness and, when applied in a thin film, the film cannot hide the substrate thereof sufficiently. In applying an organic solvent type coating or an aqueous coating on a material to be coated, the resulting film can flow during the vaporization of solvent and a smooth and continuous film can be obtained easily; meanwhile, in applying a powder coating, it is difficult to obtain a film having luster and smoothness because the powder (which is a solid) causes fusion bonding and thereby a film is formed. In order to obtain a film having luster and smoothness with a powder coating, it was proposed to make smaller the particle diameters of powder coating. However, this approach is not practical because the smaller particle diameters of powder coating result in lower fluidity of particles (i.e. powder coating) and inferior coatability.
In addition, powder coatings essentially have a serious drawback. Generally, coatings are required to not only have a role of protecting a material to be coated, from outside circumstances but also give a fine appearance on the material to be coa
REFERENCES:
patent: 5319001 (1994-06-01), Morgan et al.
Nakazato Yukinori
Serizawa Hiroshi
Tonami Noriyuki
Uemae Masami
Lipman Bernard
Nippon Carbide Kogyo Kabushiki Kaisha
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