Stock material or miscellaneous articles – Composite – Of metal
Patent
1998-02-06
2000-12-26
Beck, Shrive
Stock material or miscellaneous articles
Composite
Of metal
4273882, 427409, 4274195, 427380, 428204, B05D 716, B05D 506
Patent
active
061656216
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a novel method for forming a multi-layer metallic coating film.
BACKGROUND ART
A metallic coating film sparkles when there occur reflections from light rays incident on a metallic pigment in the coating film. Metallic coating films have an esthetically attractive appearance of their own with wide variations as in color, and are chiefly applied to metal articles such as automobiles, motor cycles and the like.
A 3-coat 1-bake coating method for forming a metallic coating film is known from Japanese Examined Patent Publication No.25076/1992, the method comprising applying an organic solvent-based thermosetting coating composition comprising a neutralized carboxyl-containing resin having an acid value of 5 to 100 mgKOH/g and an amino resin, adjusting the coating layer to a specific viscosity range, applying an aqueous thermosetting metallic coating composition, applying an organic solvent-based thermosetting clear coating composition, and heating the coatings for curing at the same time.
According to the foregoing conventional coating method, the first layer of organic solvent-based thermosetting coating composition is adjusted to a specific viscosity range while the second layer of aqueous thermosetting metallic coating composition is formed on the viscosity-adjusted first layer, whereby advantageously the amount of the organic solvent can be reduced and the unevenness of metallic effect can be prevented without degrading the esthetic property or surface smoothness of coating film which would occur because of surface roughening and sagging at varied humidities.
However, the foregoing conventional method has drawbacks that the obtained metallic coating film appears flat and deficient in depth feeling, and is not always satisfactory in distinctness-of-image gloss, namely insufficient in esthetic property.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a novel method of forming a multi-layer metallic coating film which retains the above-mentioned advantages of conventional coating methods but is free of their drawbacks.
Another object of the invention is to provide a novel method capable of forming a multi-layer metallic coating film on a metal substrate, the film being enhanced in depth feeling and in distinctness-of-image gloss, consequently improved in esthetic property and surface smoothness.
Other features of the invention are apparent from the following description.
According to the present invention, there is provided a method for forming a multi-layer metallic coating film, the method being characterized by a 3-coat system comprising the steps of applying the following coating compositions (A), (B) and (C) in this order to a metal substrate coated with a cationically electrodepositable coating composition; (A) an organic solvent-based thermosetting metallic first base coating composition which comprises a neutralized carboxyl-containing resin having an acid value of 5 to 100 mgKOH/g, an amino resin and a metallic pigment, the composition having a substrate-hiding power corresponding to not higher than 3% transmittance of light at a wavelength of 400 to 700 nm in a 15 am-thick cured coating film, (B) an aqueous thermosetting second base coating composition which shows a transparency corresponding to 10 to 95% transmittance of light at a wavelength of 400 to 700 nm in a 15-pm thick cured coating film, and (C) an organic solvent-based thermosetting clear coating composition.
The present inventors conducted extensive research to overcome the drawbacks of conventional methods while retaining the above-mentioned prior art advantages, and obtained the following novel findings. first base coating composition having the above-specified hiding power, (B) the second base coating composition having the above-specified transparency and (C) the clear coating composition in this order, there is formed a multi-layer metallic coating film which is improved in depth feeling and distinctness-of-image gloss and therefore s
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Endo Mitsugu
Kasari Akira
Oda Hiroaki
Shimakawa Mikio
Yokoyama Tetsuya
Beck Shrive
Crockford Kirsten A.
Kansai Paint Co. Ltd.
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