Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Patent
1995-12-20
1997-09-23
Gorr, Rachel
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
528 81, 528 71, 525123, 4284231, 427402, 524502, C08G 1867
Patent
active
056706006
DESCRIPTION:
BRIEF SUMMARY
The present application was filed under the provisions of 35 U.S.C 371(c) as the U.S. National Phase of PCT application PCT/EP/01991, filed Jul. 18, 1994.
The present invention relates to an aqueous two-component polyurethane coating composition comprising carboxylate groups and has an OH number of from 40 to 200 mg of KOH/g, preferably from 60 to 140 mg of KOH/g, an acid number of from 20 to 100 mg of KOH/g, preferably from 25 to 50 mg of KOH/g, and a glass transition temperature of from -40.degree. C. to +60.degree. C., preferably from -20.degree. C. to +40.degree. C., and
The present invention also relates to a process for the preparation of these aqueous coating compositions and to their use in processes for the production of a multicoat finish, and to coated articles for which at least one coat has been produced using these coating compositions.
For ecological and economic reasons the paint industry is attempting to replace as much as possible of the organic solvents employed in coating materials by water. In motor vehicle finishing in particular there is a great requirement for aqueous coating materials. This applies both to the sector of automotive production-line finishing and to the sector of automotive refinishing. In this context aqueous coating compositions are employed in particular in the area of topcoats. Topcoats in this instance are understood as coating materials which are used to produce the topmost coating layer. This topmost coating layer may comprise one or more coats, in particular two coats. Two-coat topcoat finishes consist of a pigmented basecoat and, applied over the basecoat, a clearcoat which is free of pigment or is pigmented only with transparent pigments.
Two-coat finishes are currently produced by the wet-on-wet method, in which a pigmented basecoat is first applied, the resulting basecoat is coated over with a clearcoat, without a baking step, and subsequently basecoat and clearcoat are cured together. This method is very advantageous in economic terms but places severe demands on the basecoat and the clearcoat. The clearcoat applied to the as yet uncured basecoat must not start to dissolve the basecoat or interfere in any other way, since otherwise the finishes obtained are of poor appearance. This applies in particular to finishes for which the basecoats employed contain special-effect pigments (e.g. metallic pigments, especially aluminum flakes or pearlescent pigments). In addition, it must be possible to apply the topcoat compositions by spraying with the aid of automatic coating units. For this purpose the compositions must have a solids content at spray viscosity which is high enough to ensure that paint films obtained with 1 or 2 spray passes (cross passes) are of sufficient thickness, and they must give baked coating films which exhibit a good appearance (good evenness, high gloss, good topcoat holdout and a high degree of hardness) and good weathering resistance. In the area of automotive refinishing there is the additional requirement for the coating compositions employed to be fully curable at low temperatures (in general .ltoreq.80.degree. C.) and also, on curing at these low temperatures, to lead to films having the good mechanical properties required.
EP-B-358 979 discloses aqueous two-component polyurethane coating compositions which contain a hydroxyl group-containing polyacrylate resin and a polyisocyanate component. These coating materials described in EP-B-358 979, however, show great disadvantages with respect to weathering resistance, in particular with respect to resistance under conditions of constant humidity (40.degree. C., 240 h), and processability (drop in viscosity and deficient pot life).
Furthermore, DE-A-41 32 430 discloses aqueous coating materials and their use in automotive topcoats. These aqueous coating materials contain a water-dilutable polyacrylate resin and, as crosslinking agent, a blocked polyisocyanate. However, the use of blocked polyisocyanates in general necessitates the application of elevated baking temperatures, with the re
REFERENCES:
patent: 3861425 (1975-01-01), Clark
patent: 4079028 (1978-03-01), Emmons et al.
patent: 4981921 (1991-01-01), Blum et al.
patent: 5275847 (1994-01-01), Schwarte
Mayer Bernd
Meisenburg Uwe
Nienhaus Egbert
BASF Lacke & Farben AG
Gorr Rachel
LandOfFree
Aqueous two-component polyurethane coating composition, process does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Aqueous two-component polyurethane coating composition, process , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Aqueous two-component polyurethane coating composition, process will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1938989