Basf Aktiengesellschaft

Basf Lacke+farben Ag

Basf Farben and Fasern Ag

Fasern Aktiengesellschaft

Basf Farben

Lacke & Farben Aktiengesellschaft

Helmut Knittel

Henning Wienand

Egon Liedek

Norbert Mronga

Werner Ostertag

Wolfgang Habermann

Joachim Kranz

Rolf Schneider

Hansulrich Reisacher

Peter Dimroth

Harald Ochmann

Guenter Etzrodt

Gunter Etzrodt

Karl-Ludwig Hock

Peter Hammes

Harry Distler

Fritz Brunnmueller

Peter Thoma

Christoph Schwidetzky

Roland Bauer

Friedrich Brunnmueller

Hans-Ulrich Reisacher

August Seitz

Dietrich Wolff

Joachim Felger

Ferriferous bismuth vanadate pigments

Bismuth vanadate pigments

An essentially monoclinic bismuth vanadate of the formula Bi[V.sub.1-x P.sub.x)O.sub.4 ] where x is from 0 to 0.1 has a chroma of .gtoreq.85, a lightness of .gtoreq.80, a hue angle of from 89 to 95 and a photochromism with a .DELTA.E value of .ltoreq.2 under the CIELAB system.

Bismuth phosphovanadate pigments

Thermostable bismuth vanadate/molybdate pigments are prepared by precipitating onto a pigment, obtained by calcination, of the formula

Thermostable bismuth vanadate/molybdate pigments

Thermostable rutile mixed phase pigments of the ternary system titanium, antimony and chromium contain from 0.1 to 2.0% by weight of magnesium.

Thermostable rutile mixed phase pigments

Thermally stable lead chromate pigments or pigments containing lead chromate, which have high color strength and are provided with a precipitated coating containing silicon dioxide, are prepared by a process in which an aqueous pigment suspension is mixed once or several times with an aqueous MgSiF.sub.6 solution, the pH being maintained at 4.5-9.5 and the temperature at 50.degree.-95.degree. C., and the pigment is then separated off and worked up, these steps being carried out in a conventional manner.

Preparation of thermally stable lead chromate pigments

Blue iron hexacyanoferrate-III pigments are produced by a process wherein complex iron-II hexacyanoferrate-II (Berlin white) is prepared by electrolysis of an aqueous catholyte solution containing (a) an iron-II salt, (b) an alkali metal salt, an ammonium salt or a mixture of these, and (c) hydrogen cyanide, in an electrolysis cell in which the anode chamber and cathode chamber are separated by an ion exchange membrane, using an electrically conductive aqueous liquid in the anode chamber, and the iron-II hexacyanoferrate-II obtained is then converted to the blue pigment. The process gives Berlin white, which is substantially free from salt, in high yield and high purity. Pollution caused by the process is very low, since only a small amount of salt is produced. Compared with the corresponding blue pigments produced by prior art processes, the pigments obtained give purer colorations with better gloss, and are of higher color strength.

Production of blue iron hexacyanoferrate-III pigments

Blue iron hexacyanoferrate-III pigments (I) are prepared by anodic oxidation of metallic iron in hydrogen cyanide, or a reaction medium containing hydrogen cyanide, at pH&lt;7 and at an anode potential of .ltoreq.0.76 V (measured against a standard hydrogen electrode) to complex iron-II hexacyanoferrate-II compounds (II), which are then oxidized to (I) in a conventional manner. The oxidation of (II) is advantageously carried out with air or oxygen at pH 0-4 and at from 70 to 95.degree. C., but can also be carried out at pH&gt;8. The process gives readily dispersible pigments (I) which are of high color strength and give brilliant, glossy colorations.

Preparation of blue iron hexacyanoferrate-III pigments, and the pigments

Pigment compositions including nickel titanium yellow or chromium titanium yellow as an inorganic component together with an organic pigment component impart better gloss and/or hiding power to organic coatings containing 10% or more of the compositions if the compositions are prepared by subjecting a suspension of the components in a liquid medium to intense shearing stresses and thereafter separating the mixed pigments from the medium.

Process for preparing pigment compositions

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Ludwigsburg, Germany

Helmut Knittel