Use of a colorant solution containing a stable, at least partially neutralized chromium (III) coordination compound for coloring unglazed ceramic

US6352587B1 · kind B1 · utility

Assignee

• BK Giulini Chemie GmbH & Co. OHG · DE

Inventors

• Thomas Staffel · Grünstadt, DE
• Jürgen Straub · Mannheim, DE
• Thomas Klein · Saratoga, US

Key dates

• Filing date: Jun 1, 1999
• Grant date: Mar 5, 2002
• Expiry date: Jun 1, 2019

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C04B41/5033
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

A process for coloring an unglazed ceramic with an aqueous colorant solution containing a chromium (III) coordination compound which is at least partially neutralized and stable, including (a) dissolving a carboxylic acid selected from the group consisting of acetic acid, an organic dicarboxylic acid having a general formula (COOH)—(CH2)n—(COOH), where n ranges from 0 to 10, and an unsaturated, organic dicarboxylic acid in water at a temperature ranging from 40 to 60° C. to provide an aqueous solution of a carboxylic acid; (b) adding a chromium (III) compound to the aqueous solution of a carboxylic acid while stirring for a time and at a temperature effective for reaction to form an aqueous solution containing a chromium (III) coordination compound; (c) filtering the aqueous solution containing the chromium (III) coordination compound to provide a filtered aqueous solution; and (d) adjusting pH of the filtered aqueous solution to a pH ranging from 3 to 6.5 by addition of one of alkali hydroxide or ammonia to provide the aqueous colorant solution containing a chromium (III) coordination compound which is at least partially neutralized, which is stable, and which has …