Powdered pigments with improved rheological properties, processe

Details Powdered pigments with improved rheological properties, processe Powdered pigments with improved rheological properties, processe

1986-08-11

1988-03-22

Lieberman, Paul

Compositions: coating or plastic

Materials or ingredients

106308M, 106309, 528 49, C09D 1700

Patent

active

047326182

DESCRIPTION:

BRIEF SUMMARY
The invention relates to powdered pigments which are coated with 1-20% by weight of the active substance of an additive of the polyurethane series prepared as fully described below and contain at least 5% by weight of unsubstituted quinacridone and have improved rheological properties for pigmenting polymeric materials, in particular the conventional and modern paint systems of the "high solids" type, and to the process for their preparation.
When organic pigments are dispersed in paint systems, the aim must be to achieve optimum stabilization of the pigment particles with the binders of the paint system. In addition to the chemical structure and the physical nature of the pigments, the dispersion method and, in particular, the type of binder and amount of solvent in the paint system is decisive for the degree of this stabilization. Inadequate stabilization leads to gloss, viscosity and flocculation problems, alongside deterioration of the coloristic pattern. A number of measures are known for improving these properties of the pigments, and these all lead to a clear reduction in the problems in conventional paint systems. The following may be mentioned here specifically: preparation with surface-active agents, such as, for example, resin soaps, alkylphenol polyglycol ether-sulfonates (German Patent No. 2,152,485) or quaternary ammonium compounds (Patent Application No. P 33 38 806.7); and, in the case of copper phthalocyanines or quinacridones, the addition of small amounts of sulfonic acids or sulfonic acid derivatives of the pigment on which the system is based. A number of paint additives which are added during paint conditioning to improve the rheological properties are also known and in some cases are commercially available.
As a result of new developments in the paint field with the aim of drastic reduction in the amount of solvent and a marked reduction in the size of the binder molecules, such as, for example, in the direction of "TSA-NAD" (thermosetting acrylic non-aqueous dispersion) and "high solids" (paint systems with a binder content of more than 50% during processing), there are considerable difficulties in achieving perfect stabilization of the pigments in these paint systems. For this reason, special additives have been developed, which either the pigments in solvents and subsequent combination with the paint, or
U.S. Pat. Nos. 4,029,861, 4,032,698, 4,048,207 and 4,070,388 relate to an example of the first said route. Here, the pigment is subjected to predispersion in the paint solvent with the polymeric active substances, which are dissolved in organic solvents, up to 50% by weight of active substance, based on the pigment employed, being used. The pigment dispersion thus obtained is then added to the paint binder system for pigmenting.
The polymeric materials used for dispersion are prepared by linking polymeric structural units of the paint with organic compounds carrying acids, basic or silane end groups via at least bifunctional isocyanates of the aliphatic and aromatic series. Linking can be effected either by urethane or via urea groupings.
A fair number of wetting and dispersing additives for the second said route are known.
In European Published Application No. 0,154,678, addition compounds suitable as dispersing agents are proposed, which are obtained by reacting polyisocyanates having a mean functionality of 2.5 to 6 with monohydroxide compounds, reacting the reaction product obtained with compounds of the formula II having 1 to 4 carbon atoms), n is 2 or 3 and G is an aliphatic, cycloaliphatic and/or aromatic group, and further reaction of the reaction product thus obtained with compounds of the formula III 1 to 4 carbon atoms) or --SH and Z is a group which contains at least one nitrogen-containing basic group.
Both in the case of the technology from U.S. Pat. Nos. 4,029,861, 4,032,698, 4,048,207 and 4,070,388, that is to say, for example, predispersing of the pigments with relatively large quantities of the additive (up to 50%) followed by addition to the paint system, and in

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