Coating processes – Direct application of electrical – magnetic – wave – or... – Polymerization of coating utilizing direct application of...
Patent
1997-08-04
1999-08-03
Cameron, Erma
Coating processes
Direct application of electrical, magnetic, wave, or...
Polymerization of coating utilizing direct application of...
427498, 427512, 427517, 427521, 427386, 427421, B05D 102, B05D 302, B05D 306
Patent
active
059322977
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method for forming a coating film. More particularly, the present invention relates to a method for forming a coating film by using a heat- and active energy beam-curable coating composition, which method can give a coating film of improved fluidity without adversely affecting various properties of the coating film.
BACKGROUND ART
Conventional thermosetting coatings contain a fluidity-controlling agent in order to control the fluidity of coating and give a coating film of smooth surface and also to substantially eliminate the sagging of coating applied on a vertical plane. As the fluidity-controlling agent, various types are known. Generally and widely used are, for example, inorganic additives such as AEROSIL, Bentone and the like; polyamide compounds such as Disparlon (trade name, a product of Kusumoto Chemicals, Ltd.) and the like; diurea compounds obtained by the reaction of a diisocyanate compound and a primary amine; and finely divided gelled polymers.
These fluidity-controlling agents have influences on the rheology and physical properties of coating composition and, as a result, can improve the spraying efficiency of coating, the sagging-preventability of coating film, the pattern controllability of metallic pigment, etc. On the other hand, the fluidity-controlling agents have had problems in that they reduce the finish appearance (e.g. luster) of coating film, the intercoat adhesion when a plurality of coatings are applied in layers, and the water resistance of coating film.
In order to alleviate the above problems when a conventional fluidity-controlling agent is used, coating methods were proposed which comprises ejecting a curable coating composition from a spray gun and spray-coating the ejected composition while applying an active energy beam thereto. In these methods, the curable coating composition has a low viscosity right after injection but has a high viscosity when coated on a material to be coated, whereby sagging of coating from the coated material can be prevented.
For example, in JP-A-6-65523 is disclosed a coating method which comprises, in coating, on a material to be coated, a high-solid coating containing an acrylic resin, a heat-crosslinking agent, a photopolymerizing monomer (which has a double bond in the molecule and can be polymerized by an electromagnetic wave), a photopolymerization initiator and an organic solvent, ejecting the high-solid coating from a spray gun and spray-coating the injected coating while applying a given electromagnetic wave to the coating.
Also, in JP-A-7-70471 is disclosed a coating method which comprises spraying, on a material to be coated, a high-solid coating containing a macromonomer having an ethylenically unsaturated bond at one end and a photopolymerization initiator, while applying an ultraviolet light to the coating particles formed by spraying and flying in the air.
These methods can certainly prevent sagging. They, however, have a problem of no applicability as a top clear for automobiles, for the following reason. In the above methods, since a photo-induced radical polymerization reaction is utilized, the polymerization reaction of double bonds is easily hinderd by the presence of oxygen; consequently, the double bonds remain in the coating film formed, which tends to allow the film to have various defects, for example, reduced weatherability and yellowing.
DISCLOSURE OF THE INVENTION
The present inventors made an extensive study in order to solve the above-mentioned problems. As a result, the present inventors found out that the problems can be solved by using, as a coating composition, a curable coating composition containing an epoxy group-containing resin and a photo-induced cationic polymerization initiator and curing the composition with an active energy beam and a heat. The present invention has been completed based on the above finding.
According to the present invention, there is provided a method for forming a coating film, which comprises ejecting a curable coating com
REFERENCES:
patent: 4246298 (1981-01-01), Guarney et al.
patent: 4868288 (1989-09-01), Meier
patent: 5242715 (1993-09-01), Schoen et al.
patent: 5416173 (1995-05-01), Gagiiani et al.
Hayase Toru
Tatsuno Tadayoshi
Cameron Erma
Kansai Paint Co. Ltd.
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