Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1988-08-22
1990-04-03
Welsh, Maurice J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
524539, 524542, 524591, 4273855, 4284231, 4284258, C08L 7504
Patent
active
049141481
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a basecoating composition for preparing multilayered, protective and/or decorative coatings on substrate surfaces,
comprising an aqueous dispersion which contains number of from 5 to 70, which has been prepared by preparing from of from 400 to 3,000 groups, one or more of the compounds used as component C having one or more groups capable of anion formation which have preferably been neutralized before the reaction with a tertiary amine, isocyanate groups have subsequently been reacted with groups,
It is known in particular in automotive coating but also in other areas where coatings of pleasing decorative effect and at the same time high corrosion inhibition are desirable to provide substrates with a plurality of superposed coating layers.
Multilayer coatings are preferably applied by the basecoat-clearcoat process, wherein a pigmented basecoat is applied first and, after a short flashoff time, is overpainted wet-on-wet (i.e. without prior baking) with clearcoat. Basecoat and clearcoat are subsequently baked together.
The basecoat-clearcoat process has attained particularly great importance in the application of automotive metallic effect coatings.
Economic and ecological reasons were behind attempts to use waterborne basecoating compositions in the preparation of multilayer coatings.
Coating agents for preparing basecoats for multilayer automotive coatings must be processable by the currently customary efficient wet-on-wet process, i.e. they must be overcoatable after a very short predrying time with a (transparent) topcoat without showing unwanted signs of redissolving.
In the development of coating agents for basecoats of metallic effect coatings, it is additionally necessary to solve other problems. The metallic effect depends crucially on the orientation of the metal pigment particles in the paint film. A metallic effect basecoat which is processable wet-on-wet must accordingly produce paint films in which the metal pigments are present after application in a favorable spatial orientation and in which this orientation is rapidly fixed in such a way that it cannot be disturbed in the course of the rest of the coating process.
In the development of water-dilutable systems which are to meet the requirements described above, difficult problems arise due to the special physical properties of water, and to date there exist only few water-dilutable coating systems which can be used as baecoating compositions in the abovementioned sense.
For instance, U.S. Pat. No. 4,558,090 discloses coating agents for preparing the base layer of multilayer coatings, which comprise an aqueous dispersion of a polyurethane resin having an acid number of 5-70. The aqueous polyurethane dispersion which, in addition to the binder, may also contain pigments and customary additives and if desired further binder components is prepared by reacting groups and a molecular weight of from 400 to 3,000 with groups and one or more groups capable of anion formation, the group capable of anion formation having been neutralized before the reaction with a tertiary amine, the intermediate contained (sic) from (A), (B) and (C) into a predominantly aqueous phase and polyamine having primary and/or secondary amino groups.
The coating agents disclosed in U.S. Pat. No. 4,558,090 are highly suitable for preparing the base layer of multilayer coatings, but they are unsuitable for practical use, in particular in mass production coating processes, since the rapidly drying coating agents are so highly adherent to the application equipment used (for example paint spray guns; automatic, electrostatically aided high-rotation units and the like) that they can only be removed with great difficulty. As a consequence, it is impossible to change the applied coating systems, for example to change the color, with the high speed which is very frequently required in particular in automotive mass production coating.
It is an object of the present invention to develop aqueous dispersions which can be used as basecoating compositions for prepa
REFERENCES:
patent: 3438940 (1969-04-01), Keberle et al.
Drexler Hermann-Josef
Ebner Franz
Hille Hans-Dieter
BASF Lacke & Farben AG
Welsh Maurice J.
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