Bleaching bath

US5238791A · kind A · utility

Assignee

• Agfa-Gevaert NV · BE

Inventors

• Gustav Tappe · Leverkusen, DE
• Ralf Wichmann · Bensberg, DE
• Heinz Meckl · Bensberg, DE

Key dates

• Filing date: Nov 27, 1991
• Grant date: Aug 24, 1993
• Expiry date: Nov 27, 2011

Classification

• Technology area (CPC G): Physics
• CPC primary: G03C7/42
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

A readily biodegradable bleaching bath having an adequate bleaching effect PA0 (1) contains an iron(III) complex salt in which at least 20 mol-% and preferably at least 80 mol-% of the complexing agent corresponds to formula (I) ##STR1## in which R.sub.1 is hydrogen or hydroxy, PA1 n is 1 or 2, PA1 x is 2 or 3 and PA1 y is 0 or 1 PA1 and the sum of x and y is always 3, and PA0 (2) an excess of free complexing agent of 1 to 120 mol-% and preferably 5 to 20 mol-%, based on the iron complex or the iron complex salt, and PA0 (3) is adjusted to a pH value of .ltoreq.4.5.