Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-09-04
2004-04-06
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C427S372200, C427S385500, C427S402000, C427S407100, C428S423100, C428S500000, C524S589000, C524S590000, C524S507000, C524S839000, C524S840000, C524S201000
Reexamination Certificate
active
06716909
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a water-borne coating composition to be applied to automotive bodies and the like and a method of forming a multilayer coating film on automotive bodies and the like, more particularly, to a water-borne coating composition and a method of forming a multilayer coating film both giving coating films excellent in smoothness and appearance.
BACKGROUND ART
In the art, coatings used for industrial purposes are so-called solvent-borne coatings and contain an organic solvent as a diluent. Thus, coatings contain an organic solvent or solvents in large amounts. In recent years, however, water-borne coatings in which organic solvent contained is reduced and water is used as a diluent have been developed from the environmental protection viewpoint.
As such water-borne coating, for example, in Japanese Kokai Publication Hei-07-53913, a water-borne coating composition is disclosed which comprises a resin obtained by at least partly neutralizing a polymer containing an amide group-containing ethylenically unsaturated monomer, an acidic group-containing ethylenically unsaturated monomer and a hydroxyl group-containing ethylenically unsaturated monomer and an aqueous dispersion of carboxyl group-containing acrylic resin particles.
Generally, the coating films obtained from the water-borne coating so far known have a problem in that they are poor in smoothness and appearance as compared with the conventional solvent-borne coating. In particular, in the case of the application to automotive bodies requiring excellent appearance, the coating films obtained from water-borne coatings containing a luster color pigment as a color component have a problem in that they are very poor in flip-flop property, smoothness and film appearance as compared with the solvent-borne coatings.
Accordingly, it is the object of the present invention to provide a water-borne coating composition excellent in smoothness and film appearance and, particularly when a luster color pigment is contained as a color component, excellent in flip-flop property.
SUMMARY OF THE INVENTION
The present invention provides a water-borne coating composition comprising
an emulsion resin obtained by emulsion polymerization of an &agr;,&bgr;-ethylenically unsaturated monomer mixture comprising not less than 65% by weight of a (meth)acrylate ester whose ester-forming moiety contains 1 or 2 carbon atoms and having an acid value of 3 to 50
and a urethane compound represented by the general formula (1) or (2):
in formulas, R
1
, R
2
, R
3
, R
4
and R
5
may be the same or different and each represents a hydrocarbon group, R
1
represents a hydrocarbon group which may optionally have a urethane bond, R
3
represents a branched or secondary hydrocarbon group, n is a number not less than 2, j is a number not less than 1 in the general formula (1) or a number not less than 2 in the general formula (2) and k and m each is a number within the range of 1 to 500,
wherein the content of said urethane compound is 0.01 to 20% by weight on the solid basis relative to the resin solid in the coating composition.
The present invention also provides a water-borne coating composition comprising
a water-borne resin resulting from dissolving or dispersing a resin having an acid value of 10 to 100, a hydroxyl value of 30 to 200 and a weight average molecular weight of 4,000 to 2,000,000 in an aqueous medium by means of a neutralizing base
and a urethane compound represented by the general formula (1) or (2):
wherein the content of said urethane compound is 0.01 to 20% by weight on the solid basis relative to the resin solid in the coating composition. Referring to the general formulas (1) and (2), it is preferable that R
2
and R
5
, which may be the same or different, each is an alkylene group containing 2 to 4 carbon atoms or a phenylethylene group and that R
3
is a branched or secondary alkyl group containing 8 to 36 carbon atoms. The composition comprises a color component.
The composition comprises a polyether polyol having not less than 0.02, on average, of a primary hydroxyl group per molecule, a number average molecular weight of 300 to 3,000 and a water tolerance value of not less than 2.0. The polyether polyol preferably has at least one primary hydroxyl group per molecule and a hydroxyl value of 30 to 700. More preferably, it has at least 3 hydroxyl groups per molecule. The composition preferably comprises a polyester resin and/or an alkyd resin.
The present invention also provides a method of forming a multilayer coating film comprising: applying a water-borne base coating to an article to be coated and then applying a clear coating thereonto, followed by curing by heating,
wherein said water-borne base coating is the above-mentioned water-borne coating composition.
The water-borne base coating preferably has an application viscosity (viscosity in the step of application) at 25° C. of 500 to 5,000 mPa·s as determined on a single cylindrical rotational viscometer at 6 rpm.
The present invention also provides a multilayer coating film obtainable by the method mentioned above.
REFERENCES:
patent: 4327008 (1982-04-01), Schimmel et al.
patent: 5064695 (1991-11-01), Hotta et al.
patent: 5204404 (1993-04-01), Werner, Jr. et al.
patent: 5286569 (1994-02-01), Werner, Jr. et al.
patent: 0421609 (1991-04-01), None
patent: 7048537 (1995-02-01), None
patent: 7048538 (1995-02-01), None
patent: 8-209059 (1996-08-01), None
Harakawa Tsuyoshi
Murayama Masaru
Seo Shinnji
Tsuji Naohiro
Connolly Bove & Lodge & Hutz LLP
Niland Patrick D.
Nippon Paint Co. Ltd.
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