Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1997-11-25
2001-03-27
Sellers, Robert E. L. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S116000, C525S119000, C525S123000, C525S143000, C525S162000, C525S169000, C525S170000, C525S182000, C525S207000, C525S208000, C525S217000, C525S218000, C525S221000, C525S423000, C525S424000, C525S425000, C525S426000, C525S440030, C525S443000, C525S444000, C525S455000, C525S456000, C525S481000, C525S531000
Reexamination Certificate
active
06207768
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a combination of two or more powder coatings of which each color is different, a powder coating composition comprising two or more powder coatings of which each color is different, a coating method using two or more powder coatings of which each color is different, a coating film or a coated substrate prepared by applying to a substrate two or more powder coatings according to the combination of powder coatings, and a coating film or a coated substrate prepared according to the coating method.
2. Discussion of the Related Art
Conventionally, powder coatings have been prepared by adding numerous color pigments to resins, curing agents, additives, mixing the above components, melt-kneading the mixture, followed by cooling, pulverization, and classification. Therefore, in these powder coatings, the powder coatings have to be prepared for each color needed, so that an enormous number of powder coating products are needed.
By contrast, in order to simplify the toning process, there has been proposed a powder coating prepared by forming a composite of several kinds of colored powders.
However, when the powder coatings of which each color is different are uniformly mixed upon use, in cases where of using the mixed powder coatings with particle sizes exceeding 20 &mgr;m, the particles of the powder coatings of each color can be generally distinguished by gross examination, thereby making it impossible to obtain a coating film having a homogeneous hue.
On the other hand, as disclosed in Japanese Unexamined Patent No. 4-504431, a method of forming a coating film of a desired hue comprising mixing two or more color powders each having an average particle size of 20 &mgr;m or less has been proposed. However, the yield tends to be lowered by down-sizing the particle size to 20 &mgr;m or less, and the particles are likely to be agglomerated when they are in the order of 20 &mgr;m or less, so that the free flowability of the powder coatings becomes poor, thereby giving rise to such problems as lack of handleability.
Also, a method of improving free flowability by granulating powder coatings by adding a granulating agent solution has been proposed. However, such processes require a large number of production steps, undesirably leading to an increase in costs.
One object of the present invention is to provide a combination of two or more powder coatings of which each color is different, to thereby give a coating film having a homogeneous hue.
Another object of the present invention is to provide a powder coating composition comprising two or more powder coatings of which each color is different, to thereby give a coating film having a homogeneous hue.
Another object of the present invention is to provide a coating method using two or more powder coatings of which each color is different, to thereby give a coating film having a homogeneous hue.
Another object of the present invention is to provide a coating film or a coated substrate having a homogeneous hue prepared by applying to a substrate two or more powder coatings, of which each color is different, according to the combination of powder coatings.
Another object of the present invention is to provide a coating film or a coated substrate having a homogeneous hue prepared by applying to a substrate two or more powder coatings, of which each color is different, according to the coating method described above.
These and other objects of the present invention will be apparent from the following description.
SUMMARY OF THE INVENTION
One aspect of the present invention is a combination of powder coatings usable in a coating method comprising mixing two or more powder coatings of which each color is different, wherein each of the powder coatings fuses with each other and is heat-cured, to thereby give a coating film having a homogenous hue.
Another aspect of the present invention is a powder coating composition comprising two or more powder coatings of which each color is different, wherein each of the powder coatings fuses with each other and is heat-cured, to thereby give a coating film having a homogenous hue.
Another aspect of the present invention is a coating method comprising the steps of:
(a) applying to a substrate two or more powder coatings, of which each color is different;
(b) heating to fuse with each other each of the two or more powder coatings applied in step (a); and
(c) curing the resulting fused product in step (b), to give a coating film having a homogeneous hue.
Another aspect of the present invention is a coating film or a coated substrate having a homogeneous hue prepared by applying to a substrate two or more powder coatings, of which each color is different, according to the combination of powder coatings described above.
Another aspect of the present invention is a coating film or a coated substrate having a homogeneous hue prepared by applying to a substrate two or more powder coatings, of which each color is different, according to the coating method as described above.
DETAILED DESCRIPTION OF THE INVENTION
The combination of powder coatings of the present invention is a combination of powder coatings usable in a coating method comprising mixing two or more powder coatings of which each color is different, wherein each of powder coatings fuses with each other and is heat-cured, to thereby give a coating film having a homogenous hue.
Here, in the present specification, a coating film having a “homogeneous” hue means that the hue of the formed coated film is made homogenous to an extent that the colors of the mixed powder coatings cannot be distinguished by gross examination. Also, “each of powder coatings fuses” means that molten products of each of powder coatings are mixed with each other, to have a substantially homogenous state.
Each of the embodiments of the combination of the powder coatings of the present invention will be detailed below.
First Embodiment
The First Embodiment is a combination of two or more powder coatings which have such properties that each of the powder coatings does not have thermosetting properties alone at a temperature of 250° C. or less, and is heat-cured with other powder coatings used in combination at a temperature of 250° C. or less when mixed therewith.
The resins usable in the powder coatings in the First Embodiment include any of conventionally known resins without particular limitation. In the present invention, it is desired to adjust the fusing temperature of each of the usable resins such that the resins are together fused upon stoving. Since the fusing temperature of the usable resins is adjusted, curing reaction takes place after fusing together and homogeneously mixing the resins upon stoving, thereby making it possible to obtain a coating film having a homogeneous hue. The fusing temperature of the resins may be adjusted by such methods, for instance, of adjusting the chemical structure of the resins and of adjusting the molecular weight distribution.
In the First Embodiment, for instance, when two powder coatings are respectively denoted by Powder Coating (i) and Powder Coating (ii), each of which does not have thermosetting properties alone at a temperature of 250° C. or less, powder coatings having properties described above can be obtained by suitably selecting a combination of resins usable for Powder Coating (i) and resins usable for Powder Coating (ii), and preparing each of powder coatings according to each of embodiments detailed below.
In other words, the combinations of two or more powder coatings of the First Embodiment are roughly classified into two embodiments:
(1) An embodiment where each of the resins contained in the respective powder coatings is fused with each other to cause curing reaction by the resins themselves at a temperature of 250° C. or less; and
(2) An embodiment where no curing reactions take place between resins themselves at a temperature of 250° C. or less, but when adding a curing agent with the resin, the curing agent being reactive with the counterpa
Aoki Katsutoshi
Inagaki Yasunori
Maruta Masayuki
Sato Yukiya
Tajima Hisakazu
Birch Stewart Kolasch & Birch, LLP.
Kao Corporation
Sellers Robert E. L.
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