Aqueous coating product and a process for producing multiple lay

Details Aqueous coating product and a process for producing multiple lay Aqueous coating product and a process for producing multiple lay

1996-09-24

1998-10-20

Michl, Paul R.

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...

524507, C08L 8300

Patent

active

058247335

DESCRIPTION:

BRIEF SUMMARY
The invention relates to water-dilutable coating compositions which are suitable for producing coatings having a particularly bright perceived color which depends on the viewing angle. These coating compositions are, in particular, aqueous basecoats.
On environmental grounds, attempts are being made to replace solvent-containing coating compositions by their aqueous counterparts. This replacement is particularly important in the case of effect basecoats, since such systems, owing to their nature, have a particularly high solvent content. Accordingly, aqueous effect basecoats have been developed. They comprise plateletlike special-effect pigments which bring about a so-called brightness flop and/or color flop. On the basis of pure metal flake pigments for producing a brightness flop, for example those of aluminum, a large number of further plateletlike special-effect pigments have been developed which are suitable for use in aqueous effect basecoats. Examples of further plateletlike special-effect pigments are interference pigments, for example metal pigments coated with metal oxide, an example being aluminum coated with titanium dioxide or with mixed oxide, and coated micas, for instance micas coated with titanium dioxide, and graphite special-effect pigments. Using the known interference pigments, only a relatively weak color flop can be obtained.
EP-A-0 357 844 describes water-dilutable coating compositions which comprise a combination of flop effect pigments and encapsulated, thermochromic, liquid-crystal pigments. Coatings produced therewith change their perceived color reversibly in dependence on the temperature.
The earlier, as yet unpublished German Patent Application P 42 40 743.5 describes pigments whose color depends on the viewing angle, which consist of oriented, three-dimensionally crosslinked substances having a liquid-crystalline structure with a chiral phase.
The object of the invention is to provide environmentally friendly coating compositions, especially basecoats, whose solvent content is as low as possible and which permit the production of coatings with novel color effects, in which context their perceived color is to be independent of the temperature.
It has been found that this object can be achieved by the use of plateletlike pigments whose color depends on the viewing angle, which consist of oriented, three-dimensionally crosslinked substances of liquid-crystalline structure with a chiral phase, in aqueous coating compositions.
One subject of the invention is therefore constituted by an aqueous coating composition comprising which consist of oriented, three-dimensionally crosslinked substances of liquid-crystalline structure with a chiral phase, and also include organic solvents.
The pigments whose color depends on the viewing angle, which consist of oriented, three-dimensionally crosslinked substances of liquid-crystalline structure with a chiral phase, are referred to below as LCP pigments (LCP=liquid crystal polymer). The LCP pigments can be obtained by subjecting one or more three-dimensionally crosslinkable liquid-crystalline substances with a chiral phase to orientation, then to three-dimensional crosslinking and subsequently to comminution to the desired particle size. This can be carried out, for example, by first applying the three-dimensionally crosslinkable liquid-crystalline substances with a chiral phase to a substrate in a thin layer, for example by knife coating, crosslinking the layer on this substrate, then detaching it from the substrate and comminuting it to the desired particle fineness. This produces plateletlike pigments which are transparent and colorless per se. By means of appropriate chemical structure-forming measures in relation to the molecular structure, LCP pigments having different effective interference colors can be produced. The plateletlike LCP pigments preferably have a diameter of from 1 to 100 .mu.m, particularly preferably from 10 to 60 .mu.m, and a thickness of preferably from 3 to 15 .mu.m, particularly preferably from 5 to 10 .mu.m. In ac

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