GB857518A - A method of counteracting the formation of precipitates and discolourations and of sequestering iron in aqueous media - Google Patents

Abstract

Aqueous media containing iron and/or ingredients which cause hardness of water are treated to sequester the iron, and to reduce or prevent the formation of precipitates and discolourations during the use of the media (e.g. in the mercerization, bleaching, washing, dyeing or after-treatment of textiles), by adding triethanolamine and at least one condensed metal phosphate, and then adding alkali until the pH of the mixture is 10 or more. The condensed phosphate may be a metaphosphate, pyrophosphate or polyphosphate. The use of an alkali metal salt of gluconic acid in conjunction with the triethanolamine and the condensed metal phosphate is also mentioned. Oxidizing agents (e.g. sodium periodate) or reducing agents may also be added to the aqueous medium. In an example, triethanolamine and sodium tripolyphosphate are added to a dye bath prepared from hard water, Sirius light green BB and Glauber's salt, and the pH of the bath is then adjusted by the addition of soda. In a further example, cotton fabric is washed with hard water (containing iron) to which has been added sodium dodecylbenzene sulphonate, triethanolamine and sodium tripolyphosphate, followed by sufficient soda to bring the pH of the bath to 10.ALSO:Aqueous media containing iron and/or ingredients which cause hardness of water are treated to sequester the iron, and to reduce or prevent the formation of precipitates and discolorations during the use of the media, by adding triethanolamine and at least one condensed metal phosphate, and then adding alkali until the pH of the mixture is 10 or more. The condensed phosphate may be a metaphosphate, pyrophosphate or polyphosphate. The use of an alkali metal salt of gluconic acid in conjunction with the triethanolamine and the condensed metal phosphate is also mentioned. Oxidizing agents (e.g. sodium periodate) or reducing agents may also be added to the aqueous medium. In examples, triethanolamine and sodium tri- or hepta-polyphosphate are added to hard water, which in some cases also contains iron, and the pH then adjusted with sodium hydroxide or sodium carbonate. In further examples, triethanolamine, sodium gluconate and sodium hexametaphosphate are added to hard water and the pH then adjusted with sodium hydroxide or sodium carbonate.