Process for preparing metalized azo pigments
AssigneeE. I. Du Pont de Nemours and Company
InventorErnest A. Stefancsik
Life of this patent
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Abstract
Preparation of Aqueous-Stable Metalized Azo Pigment from 5-amino or 4-amino-2-chloro-toluene-5-sulfonic Acid and 3-hydroxy-2-naphthoic Acid with Calcium and Strontium Salts by diazotizing one of 2-chloro-5-amino-toluene-4-sulfonic acid and 2-chloro-4-amino-toluene-5-sulfonic acid, contacting the diazo with an inorganic salt of calcium, coupling the diazo with 3-hydroxy-2-naphthoic acid, and contacting the coupled diazo with an inorganic salt of strontium. The resulting metalized azo pigment exhibits high stability in aqueous coating compositions.
Claims3
In a process for preparing metalized azo pigment of the general formula ##STR2## wherein R and R' are selected from CH.sub.3 and Cl and one of R and R' must be CH.sub.3, and where M is selected from at least one of calcium and strontium by the steps of (i) diazotizing one of 2-chloro-5-amino-toluene-4-sulfonic acid and 2-chloro-4-amino-toluene-5-sulfonic acid, (ii) coupling the diazo of Step (i) with 3-hydroxy-2-naphthoic acid to form an azo, and (iii) forming the metalized azo pigment by contacting azo formed in Step (ii) with an inorganic salt of at least one of calcium and strontium,
- the improvement comprising contacting the diazo of Step (i) with an inorganic salt of calcium prior to Step (ii) and contacting the azo formed in Step (ii) with an inorganic salt of strontium to form the metalized azo pigment.
Dependencies are inferred from the claim text.