Easily dispersible solid pigment preparations

#The present invention relates to solid pigment preparations comprising dispersing additives based on water-soluble polymers comprising sulfonate groups and to the use of said solid pigment preparations for coloring natural and synthetic materials.

#Quality in the production of pigmented coatings is decisively dependent upon achieving a fine and uniform distribution of the particles of solid material in the coating system. If the particles of pigment are not optimally dispersed and stabilized in the application system, flocculation phenomena and sedimenting can occur and can lead to undesirable changes in the viscosity of the application system, to hue changes and losses of color strength, hiding power, luster, homogeneity, brilliance and also poorly reproducible hues and to higher tendency to sag in the case of finishes. To facilitate fine dispersion and stabilization of pigments in paint systems, printing inks and finishes and hence to achieve optimum performance characteristics, wetting and dispersing agents are frequently used. Dispersing organic pigments in an application system is a critical and far from straightforward operation. In general, pigments are incorporated in a liquid phase in combination with dispersing and wetting agents through the use of energy-intensive ball mills, stirred media mills or high-performance bead mills. One way to make the pigmentation of paint systems, printing inks and finishes more efficient and less cost and energy intensive consists in using easily dispersible solid pigment preparations which can be incorporated in the application system with significantly lower energy input and faster color development then conventional pigments, which is of substantial economic advantage.

#WO 2004/046251 describes solid pigment preparations comprising water-soluble anionic additives based on homo- and copolymers of ethylenically unsaturated mono- and/or dicarboxylic acids.

#540 g of water-moist presscake (30% by weight) of Hostaperm® Scharlach GO (Pigment Red 168, C.I. No. 59300) were suspended in 1800 g of water and admixed with 18 g of dispersing additive (copolymer of 12.5 mol % of p-styrenesulfonic acid sodium salt, 62.5 mol % of methyl (meth)acrylate and 25 mol % of VeoVa 9; Mw about 7000 g/mol, dissolved in 200 g of water). The pH was adjusted to 8-8.5 and the mixture was stirred at 80° C. for 1 hour. The surface-coated pigment was then filtered off and washed with water to a conductivity (filtrate) <0.5 mS/cm. The coated pigment was dried in a circulating drying cabinet at 80° C. and subsequently pulverized to obtain 171 g of solid pigment preparation having 94 μmol of sulfonate groups/g of pigment preparation.

#540 g of water-moist presscake (30% by weight) of Hostaperm® Scharlach GO (C.I. No. 59300) were suspended in 1800 g of water and admixed with 9 g of dispersing additive (copolymer of 12.5 mol % of vinylsulfonic acid sodium salt, 50 mol % of vinyl acetate and 37.5 mol % of VeoVa 10®; Mw=8000 g/mol, dissolved in 100 g of water). The pH was adjusted to 8-8.5 and the mixture was stirred at 80° C. for 1 hour. The surface-coated pigment was then filtered off and washed with water to a conductivity (filtrate) <0.5 mS/cm. The coated pigment was dried in a circulating drying cabinet at 80° C. and subsequently pulverized to obtain 162 g of solid pigment preparation having 47 μmol of sulfonate groups/g of pigment preparation.

#543 g of water-moist presscake (29.5% by weight) of Pigment Red 122 (C.I. No. 73915) were suspended in 900 g of water and admixed with 18 g of dispersing additive (copolymer of 11.1 mol % of vinylsulfonic acid sodium salt, 44.5 mol % of vinyl acetate, 33.3 mol % of VeoVa 10® and 11.1 mol % of vinyl alcohol, Mw=7500 g/mol) and 7.5 g of C12/C16-alkyl ethoxylate with 10 EO units, dissolved in 200 g of water. The pH was adjusted to 8-8.5 and 800 g of isobutanol were added thereto. The mixture was subjected to pressure finishing at 125° C. for 3 hours. The isobutanol was then distilled off by steam distillation, the coated pigment was filtered off and washed with water to a conductivity (filtrate) <0.5 mS/cm. The coated pigment was dried in a circulating drying cabinet at 80° C. and subsequently pulverized to obtain 173 g of solid pigment preparation having 87 μmol of sulfonate groups/g of pigment preparation.