Stock material or miscellaneous articles – Composite – Of polyisocyanurate
Patent
1995-02-21
1996-12-03
Short, Patricia A.
Stock material or miscellaneous articles
Composite
Of polyisocyanurate
4284231, 4284258, 4273882, 4273855, 5253285, 525375, 525440, B23B 2706
Patent
active
055806600
DESCRIPTION:
BRIEF SUMMARY
The invention relates to the use of a binder composition for the preparation of a powder coating for use a top coat in the automotive industry. The invention also concerns top-coated automotive substrates.
The top coat or finish coat is the coating intended to be the last coat applied in a coating system and is usually applied over a primer, a basecoat or surfaces.
The clear top coats which, according to the present state of the art in the automotive industry, are used as a two-component system are solvent-containing paint systems based on acrylate resins cured with isocyanates. In order to meet the requirements regarding the reduction in solvent emissions, so-called high-solids systems are already being used. The only way to reduce solvent emissions still further is to use powder coatings for clear automotive coatings (Lattke, E. "Pulverlack am Auto; Aus der Sicht der Autoindustrie", presented at "Der Pulvertreff '92, 23.01.92, M unchen"; JOT-Veranstaltungen, pages 1-11).
The same requirements will be made of powder coating systems for said application as of the solvent-containing systems. These requirements concern for instance flow, chemical resistance, gloss and outdoor durability (Kinza, W. "Pulverklarlack for die Karosseriebeschichtung", presented at "Die EPS-Praxis 1991, 25.11.91, Bad Neuheim"; Schriftenreihe Praxis-Forum, Fachbrochure Oberflachentechnik 27/91, pages 49-55). The aim is to obtain these properties at a curing temperature of less than 150.degree. C. There are no systems known amongst the present powder resin systems which meet the combination of properties required. There are several properties which can be obtained with systems based on an acid-epoxy curing reaction, but the required combination of good flow, good chemical resistance, high gloss, high scratch resistance, good mechanical properties and good outdoor durability has never yet been obtained with powder coatings. With systems based on polymers containing hydroxyl groups and curing agents containing blocked isocyanate groups, too, several of the above-mentioned properties can be obtained. The usual temperature (above 170.degree. C.) at which these systems must be cured is, however, much too high for application as a (clear) topcoat for automotive applications.
It is the object of the present invention to provide a binder composition which can be cured at relatively low temperatures and which, moreover, gives a combination of the desired properties. The powder coating have to result in a clear top coat on exterior parts in the automotive industry.
The binder composition according to the invention consists of a polyester containing hydroxyl groups having a hydroxyl number of between 20 and 100 mg KOH/g resin and an acid number of less than 10 mg KOH/g resin or a polyacrylate containing hydroxyl groups having a hydroxyl number of between 40 and 150 mg KOH/g resin and an acid number of less than 20 mg KOH/g resin, a with 1,2,4-triazole blocked hexamethylenediisocyanate trimer and usual additives and wherein in the polyester the acid moieties therein are based on 40-100 mol % isophthalic acid and 0-60 mol % terephthalic acid and the polyacrylate is based on
The binder composition according to the invention results in powder coatings with optimum flow, gasoline resistance, flexibility and clarity at a curing temperature of between 130.degree. C. and 170.degree. C.
The weight ratio of the polymer containing hydroxyl groups to the blocked hexamethylenediisocyanate trimer is usually between 90:10 and 50:50. Said ratio is amongst others depending of the hydroxyl number of the polymer.
The binder composition can also comprise mixtures of hydroxyl-functional polyesters and hydroxyl-functional polyacrylates.
To obtain powder coatings the hydroxyl functional polymers are mixed with the blocked crosslinker at a temperature of approximately 100.degree. C. by means of, for example, extrusion, and after being electrostatically sprayed the mixture can be cured at temperatures of between 130.degree. C. and 170.degree. C., preferably at or below
REFERENCES:
patent: 3721645 (1973-03-01), Zemlin
patent: 4324879 (1982-04-01), Bock
patent: 4482721 (1984-11-01), Wegner
patent: 4748242 (1988-05-01), Halpaap
patent: 4782128 (1988-11-01), Gras
patent: 4824909 (1989-04-01), Togo et al.
Kieft Gerrit
Van Den Elshout Wilhelmus H. H. A.
Witte Franciscus M.
DSM N.V.
Short Patricia A.
LandOfFree
Use of a binder composition for the preparation of a powder coat does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Use of a binder composition for the preparation of a powder coat, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Use of a binder composition for the preparation of a powder coat will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-783962