Coating processes – Applying superposed diverse coating or coating a coated base – Synthetic resin coating
Patent
1996-01-31
1997-11-25
Dudash, Diana
Coating processes
Applying superposed diverse coating or coating a coated base
Synthetic resin coating
B05D 136
Patent
active
056910029
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a coating method, and an object of the invention is to improve the adhesion between layers of a multi-layer coating film formed from aqueous coating compositions and the chipping resistance of said coating film.
BACKGROUND ART
A technique is known wherein an automotive exterior panel is finished by sequentially applying a cationic electrophoretic coating composition, an aqueous intermediate coating composition and an aqueous top coating composition. In this coating system, thermosetting aqueous coating compositions mainly comprising (A) an amine-neutralized base resin having a hydroxyl group and a carboxyl group and (B) an amino resin are used as the aqueous intermediate coating composition and aqueous top coating composition. However, there is a problem that the coating film formed from such aqueous coating compositions is not satisfactory in adhesion between layers and chipping resistance.
DISCLOSURE OF INVENTION
An object of the invention is to provide a coating method which can improve the adhesion between layers of a multi-layer coating film formed from aqueous coating compositions.
Another object of the invention is to provide a coating method which can improve the chipping resistance of a coating film formed from aqueous coating compositions.
Other characteristics of the present invention will be apparent from the following description.
The coating method of the present invention comprises sequentially applying an amine-neutralized type aqueous intermediate coating composition and an amine-neutralized type aqueous top coating composition, the method being characterized in that a coating composition mainly comprising (A) an amine-neutralized base resin having a hydroxyl value of 30 to 150 KOH mg/g and an acid value of 15 to 50 KOH mg/g, (B) an amino resin and (C) an organic sulfonic acid amine salt is used as the amine-neutralized type aqueous intermediate coating composition.
The amine-neutralized type aqueous intermediate coating composition for use in the invention mainly comprises (A) a resin prepared by neutralizing, with an amine, a base resin having a hydroxyl value of 30 to 150 KOH mg/g and an acid value of 15 to 50 KOH mg/g, (B) an amino resin and (C) an organic sulfonic acid amine salt, and can be readily prepared by mixing components (A), (B) and (C) with water to disperse the components.
The base resin for use in component (A) is a polyester resin, an acrylic resin, an urethane resin, an alkyd resin or the like which contains a hydroxyl group and a carboxyl group and has a hydroxyl value of 30 to 150 KOH mg/g, preferably 60 to 120 KOH mg/g, and an acid value of 15 to 50 KOH mg/g, preferably 20 to 40 KOH mg/g. If the hydroxyl value of the base resin is less than 30 KOH mg/g, the obtained coating film has a reduced curability, whereas if the hydroxyl value is more than 150 KOH mg/g, the obtained coating film is poor in flexibility, chipping resistance and the like. Thus hydroxyl values outside said range are not preferable. Further, if the acid value of the base resin is less than 15 KOH mg/g, the water-dispersion stability of the intermediate coating composition as such is reduced, whereas an acid value more than 50 KOH mg/g results in a coating film which is poor in water resistance, chemical resistance and the like. Thus, acid values outside said range are not preferable.
In the invention, any of conventionally known resins can be used as the base resin insofar as they have the above characteristic values, and formulation of the starting components of the resin and the molecular weight of the resin are not specifically limited. Suitable number average molecular weight of the base resin for use in the invention is usually about 1000 to 50000, more preferably about 5000 to 30000.
Component (A) for use in the invention is an amine-neutralized base resin prepared by neutralizing, with an amine, a part or the whole of the carboxyl groups in the above-mentioned base resin. A wide variety of conventionally known amines can be used herein.
REFERENCES:
patent: 4444960 (1984-04-01), Salee et al.
patent: 4728545 (1988-03-01), Kurauchi et al.
patent: 4889793 (1989-12-01), Taniguch et al.
patent: 4916020 (1990-04-01), Golding et al.
patent: 5266361 (1993-11-01), Schwarte et al.
patent: 5334420 (1994-08-01), Hartung et al.
patent: 5356670 (1994-10-01), Briggs et al.
patent: 5439710 (1995-08-01), Vogt et al.
patent: 5510148 (1996-04-01), Taljan et al.
patent: 5538076 (1996-07-01), Mizuno et al.
patent: 5601880 (1997-02-01), Schwarte et al.
Inoue Hiroshi
Isaka Hisashi
Mitsuji Masaru
Oda Hiroaki
Okumura Yasumasa
Dudash Diana
Kansai Paint Company, Limited.
LandOfFree
Coating method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Coating method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Coating method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2104846