Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-07-21
2003-08-05
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C106S436000, C106S439000, C106S456000, C106S459000, C106S482000, C523S210000
Reexamination Certificate
active
06602934
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a multicolor coating composition containing a metal oxide-coated silica flake pigment specially treated for improved heat stability, to a coating film forming method and to an article obtainable by this method. The invention is preferably utilized in the field of coated articles where multicoloredness is required, such as outer panel of automobiles, bicycles and other vehicles, container exterior surfaces, coil coatings and household electrical appliances.
PRIOR ART
A coating composition capable of providing a coating film showing a plurality of different colors when observed from different angles and thus having multicoloredness with large color differences is disclosed in Japanese Kohyo Publication Hei-09-508172.
The interference platelets incorporated in the above coating composition according to Japanese Kohyo Publication Hei-09-508172 as a luster agent for attaining multicoloredness are a very effective material from the standpoint of achieving multicoloredness. However, this agent expresses very dynamic multicoloredness, in other words, the image obtained is too showy with great color differences noticed as the angle of view varies. Such showiness may cause some people to lose their presence of mind in certain instances. Therefore, it is desirable that the color differences be reduced to moderate levels to thereby realize more subdued or calm multicoloredness. Metal oxide-coated silica flake pigments have recently attracted attention as materials for realizing such calm multicoloredness. However, such metal oxide-coated silica flake pigments have a composition similar to hydrophilic silica pigments and the color cannot be said to have sufficient heat stability against moisture absorption and heating.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide a multicolor coating composition capable of forming multicolor coating films with a good heat stability of color development in addition to the calm multicoloredness of those metal oxide-coated silica flake pigments which have so far been utilized.
Intensive investigations made by the present inventors to accomplish the above object have now led to completion of the present invention which comprises:
1. A multicolor coating composition comprising a vehicle and a metal oxide-coated silica flake pigment
wherein a coating film resulting from baking of said coating composition and a coating film resulting from reheating of the former coating film under the same conditions as in said baking, followed by 10 minutes of standing at room temperature, show a color difference of less than 0.5.
2. The multicolor coating composition as mentioned above comprising a luster pigment and/or color pigment other than the metal oxide-coated silica flake pigment.
3. A coating film forming method comprising forming a base coat layer by applying said multicolor coating composition to a substrate and then forming a top coat layer using a clear coating.
4. The coating film forming method as mentioned above,
wherein the clear coating contains a carboxyl-containing polymer and an epoxy-containing polymer.
5. A coated article as obtainable by the above coating film forming method.
DETAILED DESCRIPTION OF THE INVENTION
In the following, the constitution of the present invention is described in detail.
The multicolor coating composition of the present invention capable of providing coating films with good heat stability contains a vehicle and a metal oxide-coated silica flake pigment, wherein a coating film resulting from baking of said coating composition and a coating film resulting from reheating of the former coating film under the same conditions as in said baking, followed by 10 minutes of standing at room temperature show a color difference of less than 0.5. The term “good heat stability” as used herein means that visual inspection does not reveal any substantial color change after the above reheating and 10 minutes of standing based on the color of the coating film before reheating under the coating film baking conditions. Specifically, the color change &Dgr;E is 0 to 0.5. When the value of &Dgr;E is in excess of 0.5, the coated article will take on different hues according to the temperature distribution of the substrate, hence color matching will be confounded in making spot repairs which accompany local heating. Preferably, the color change is 0 to 0.3. The above value &Dgr;E is measured after a period of standing at room temperature, and ten minutes, which is sufficient for the temperature to fall to room temperature following heating, is taken as the standing period.
Vehicle
The vehicle contained in the multicolor coating composition of the present invention is a dispersion medium for a metal oxide-coated silica flake pigment, if necessary together with at least one pigment selected from among other luster pigments and color pigments, and/or the like and is constituted of a coating film-forming resin and, when necessary, a crosslinking agent.
The above coating film-forming resin, which constitutes the vehicle, includes, among others, (a) acrylic resins, (b) polyester resins, (c) alkydresins, (d) fluororesins, (e) epoxy resins, (f) polyurethane resins and (g) polyether resins. These may be used singly or two or more of them may be used combinedly. Particularly preferred are acrylic resins and polyester resins. The above coating film-forming resin may be of the curable type or of the lacquer type. Generally, curable type thermosetting resins are used, however. Curable type ones are generally used in admixture with a crosslinking agent, such as an amino resin, a (blocked) polyisocyanate compound, an amine, a polyamide or a polybasic carboxylic acid, and the curing reaction thereof can be allowed to proceed with heating or at ordinary temperature. It is also possible to combinedly use a noncurable lacquer type coating film-forming resin and a curable type one.
(a) Acrylic Resins
As the above acrylic resins, there may be mentioned copolymers of an acrylic monomer and another ethylenically unsaturated monomer. The acrylic monomer which can be used in this copolymerization include the methyl, ethyl, propyl, n-butyl, isobutyl, tert-butyl, 2-ethylhexyl, lauryl, phenyl, benzyl, 2-hydroxyethyl, 2-hydroxypropyl and like esters of acrylic acid or methacrylic acid, ring-opening adducts of caprolactone to 2-hydroxyethyl acrylate or methacrylate, glycidyl acrylate or methacrylate, acrylamide, methacrylamide and N-methylolacrylamide, among others. The other ethylenically unsaturated monomers copolymerizable with these include styrene, &agr;-methylstyrene, itaconic acid, maleic acid, vinyl acetate and the like.
(b) Polyester Resins
As the above polyester resins, there may be mentioned saturated polyester resins and unsaturated polyester resins, among others, for example condensation products obtained by subjecting a polybasic acid and a polyhydric alcohol to condensation under heating. The polybasic acid includes, for example, saturated polybasic acids, unsaturated polybasic acids. The saturated polybasic acid include, among others, phthalic anhydride, terephthalic acid and succinic acid, while the unsaturated polybasic acids include, among others, maleic acid, maleic anhydride and fumaric acid. The polyhydric alcohol includes, for example, dihydric alcohols, such as ethylene glycol and diethylene glycol, and trihydric alcohols, such as glycerol, trimethylolpropane and the like.
(c) Alkyd Resins
Useful as the above alkyd resins are those alkyd resins produced by reacting together such a polybasic acid as mentioned above and such a polyhydric alcohol as mentioned above and, further, a modifier such as a fat or oil or a fat- or oil-derived fatty acid (e.g. soybean oil, linseed oil, coconut oil, stearic acid) or a natural resin (e.g. rosin, amber).
(d) Fluororesins
The above fluororesins include vinylidene fluoride resins, tetrafluoroethylene resins, mixture of these, and various fluorine-containing copolymer resins resulting from copolymerization of a fluoroolefin(s) and a
Cain Edward J.
Jordan and Hamburg LLP
Nippon Paint Co. Ltd.
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