Composite pigments and process for their preparation

Abstract

Novel composite pigments containing both organic and inorganic portions have been produced. These pigments consist of an inorganic binary titanium dioxide/aluminum hydrate component, in a percent quantity comprised between 70% and 95% by weight, the remaining organic component amounting to between 5% and 30% by weight, consisting of an organic dye selected from the group consisting of azoic and quinophtalonic compounds, containing in their structure at least one carboxylic and/or sulphonic, substantially salified, acid function. The pigments are obtained according to a co-precipitation process, under substantially alkaline controlled pH conditions, of the acid organic dye together with the aluminum hydroxide (hydrated aluminum), by acidification of a solution and/or an aqueous dispersion of the acid organic dye in sodium aluminate, in the presence of titanium dioxide, at from 40.degree. C. to about 80.degree. C., and by a subsequent lacquering by treatment with an aqueous solution of an alkaline-earth metal salt (Ca, Mg, Ba, Sr) or of a Mn, Zn salt. The above-mentioned pigments are insoluble in water and in common organic solvents. They possess, moreover, a good dyeing power, an excellent stability under heat, a good fastness to light, a good fastness to bases and acids, to migration in plastic materials and stability to over varnishing in the stove, etc. Lastly, they may be obtained with different degrees of covering power. Thus, the pigments find a preferential application in varnishing products, air-drying and stove-baked enamels, in the pigmentation of plastic materials, in inks and in the beprinting of fabrics, etc., by means of conventional applicational methods.