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
1990-04-04
1992-12-08
Kight, III, John
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 49, 528 55, 528 65, 525455, 524457, 524507, C08G 1810, C08G 1867
Patent
active
051699222
DESCRIPTION:
BRIEF SUMMARY
The invention relates to coating compositions which are particularly suitable for the preparation of the basecoat for two-coat coatings of the basecoat/clearcoat type, and which comprise organic diluents, at least one resin containing urethane and urea groups, and, where appropriate, other resins, pigments and other conventional additives in common use.
In the field of automotive finishing in particular, but also in other areas there is considerable interest in basecoat compositions for the preparation of multicoat coatings.
In automotive finishing, two-coat coatings of the basecoat/clearcoat type in particular have gained wide acceptance, especially for metallic finishes.
Basecoat/clearcoat coatings are prepared by first applying a pigmented basecoat which, after a brief flush-off period, is overcoated by a clearcoat without a baking stage (wet-on-wet process), the basecoat and clearcoat being subsequently baked together.
The coating compositions for the preparation of these basecoats must be capable of being processed by the expedient wet-on-wet process, in general use today, i.e. they must be capable, after an as short a drying time as possible without a baking stage, of being overcoated with a transparent topcoat, without the appearance of any defects due to solvent action of one coat on the other and of any "strike-in" phenomena.
In addition, other problems must be solved in the development of coating compositions for basecoats for metallic finishes. The metallic effect depends crucially on the orientation of the metallic pigment particles in the paint film. A basecoat for metallic finishes, capable of being processed by the wet-on-wet process, must therefore produce paint films in which the metallic pigments are present after the application in a suitable spatial orientation and in which this orientation becomes rapidly set in such a way that it cannot be disturbed in the course of further painting processes.
EP-A-137,256 discloses coating compositions for the preparation of the basecoat for two-coating coatings of the basecoat/clearcoat type which contain polyurethane elastomers and/or polyurea elastomers as binder components.
From the coating compositions disclosed in EP-A-137,256 it is possible to prepare two-coat coatings, in particular two-coat metallic coatings which possess a good metallic effect, good adhesion and excellent resistance to stone impact.
More recently, automotive manufacturers have gone over to using two-component clearcoats based on polyisocyanates for refinishing. These clearcoats are cured at room temperature or at temperatures not exceeding 80.degree. C.
When the coating compositions disclosed in EP-A-137,256 are used for the preparation of the basecoat, color differences appear between the original finish baked at 140.degree. C. and the refinish carried out using the two-component clearcoats.
The object of the present invention was to make available coating compositions for the preparation of the basecoat for two-coat coatings of the basecoat/clearcoat type which would be free from the shortcomings referred to above.
Surprisingly, this object is achieved by the coating compositions according to the main concept of the principal claim which comprise at least one resin containing urethane and urea groups, which resin is obtainable by reacting groups, with reacting the isocyanate groups of the prepolymer (A), at least in part, with p1 a3) an adduct produced from a (meth)acrylic ester, preferably an acrylic ester, and an aliphatic or cycloaliphatic compound containing at least two aminic hydrogen atoms, the adduct containing at least one active aminic hydrogen atom.
The benefits achieved by the invention consist essentially in the absence of any color differences between the original finish and the refinish when the coating compositions according to the invention are used. A further important benefit is that the resins containing urethane and urea groups, used in the basecoat compositions according to the invention, may be prepared by using an a3) component containing hydroxyl
REFERENCES:
patent: 4097439 (1978-06-01), Darling
patent: 4317894 (1982-03-01), Lewarchik et al.
patent: 5011881 (1991-04-01), Fujii et al.
Dobbelstein Arnold
Grosch Horst
Hille Hans-Dieter
BASF Lacke & Farben AG
Kight III John
Truong Duc
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