Coating processes – With post-treatment of coating or coating material – Heating or drying
Patent
1999-07-27
2000-11-07
Cameron, Erma
Coating processes
With post-treatment of coating or coating material
Heating or drying
427391, 427393, 4273935, 427408, 427409, 4274121, 528 73, B05D 302
Patent
active
061433675
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a two-component system for a multicomponent coating composition comprising (1) a hydroxy-functional binder or a mixture of hydroxy-functional binders, (2) tris(alkoxycarbonylamino)triazine or a mixture of tris(alkoxycarbonylamino)triazines and (3) free isocyanates or a mixture of free isocyanates. The invention also relates to a process for preparing such a component system and to its use.
By component system is meant a package of different coatings components which are prepared and stored separately and yet are always dealt with in conjunction with one another and which are mixed to form a coating composition by a user wishing to produce a coating from the coating composition, before the coating is produced. Component systems of this kind are common, inter alia, in the preparation of topcoats. The term topcoats here refers to coating materials which are used to produce the topmost coat. This topmost coat can itself comprise one or more coats, especially two coats. Two-coat topcoat finishes consist of a pigmented basecoat film and, applied thereto, a clearcoat film which is pigmented only with transparent pigments if at all. Two-coat finishes are nowadays produced by the wet-on-wet method, in which a pigmented basecoat is applied first and the resulting basecoat film is coated over with a clearcoat, without a baking step, and then basecoat film and clearcoat film are cured together. This method is very advantageous economically but places high demands on the basecoat and the clearcoat. The clearcoat applied to the as yet uncured basecoat must not cause bleeding of the basecoat film or any other disruption, since otherwise finishes of poor appearance are obtained. This applies in particular to finishes for which basecoats comprising special-effect pigments (e.g. metal pigments, especially aluminium flakes, or pearlescent pigments) are employed.
Component systems for clearcoats, which are used predominantly for the finishing of cars, consist usually of hydroxy-functional polyacrylates with free isocyanate trimers of hexamethylene diisocyanate. The resulting clearcoats in the application-ready state have a solids content of from 32 to 45% by weight. Their advantages lie in a low curing temperature of from 20 to 120 degrees C. and high chemical resistance. These clearcoat systems, however, currently have a number of serious disadvantages compared with melamine resin-crosslinked one-component clearcoats: especially following a refinish. economic grounds. reduced flop in the case of metallic basecoats or in changes in shade in the base-coat, especially if an attempt is made to raise the solids content by including acrylate resins of low molecular weight.
One-component clearcoats do not exhibit these problems, or at least not to the same extent, but because of their much poorer chemical resistance cannot be used in place of two-component clearcoats.
The object of the present invention, therefore, is to provide a coating composition which does not feature the abovementioned disadvantages of customary two-component clearcoat systems but which has a resistance to chemicals and to weathering which is comparable with that of customary two-component clearcoat systems.
This object is achieved in accordance with the invention by a component system which is characterized in that a first component (I) is formed at least from the hydroxy-functional binder or from the mixture of hydroxy-functional binders (1) and in that a second component (II) is formed at least from the free isocyanates or from the mixture of free isocyanates (3), the tris(alkoxycarbonylamino)triazine or the mixture of tris(alkoxycarbonylamino)triazines (2) is alternatively a constituent of the first component (I), the second comonent (II) or both components (I) and (II).
Surprisingly, through the use of a crosslinker combination comprising tris(alkoxycarbonylamino)triazine and free isocyanates, the invention achieves considerable advantages over customary two-component clearcoats. These advantages include in particular: im
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Bartol Fritz
Baumgart Hubert
Rockrath Ulrike
BASF Coatings AG
Cameron Erma
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