GB683128A - Improvements in and relating to dyestuff preparations, and the dyeing of cellulosic materials such as paper, therewith - Google Patents

Abstract

A dyestuff composition comprises a dry powdered mixture of a basic dye, a heteropoly acid known to be capable of forming a lake with a basic dye and a dispersing agent. Anionic dispersing agents are preferred and sodium lignin sulphonate and sodium salts of condensation products of naphthalene sulphonic acid with formaldehyde are specified. Preferred heteropoly acids are phosphomolybdic or phosphotungstic acid or a phosphomolybdotungstic acid or such an acid in which all or part of the phosphorus, molybdenum or tungsten is replaced by vanadium or selenium. The so-called reduction products of heteropoly acids cf. Specification 313,209, [Class 2(iii)], are also mentioned. Aqueous dispersions of the composition are preferably made by forming it into paste with cold water, adding to hot water and subsequently boiling. More than one basic dye and more than one acid may be present. The preferred relative proportions are 30-50 parts of dye, 40-60 parts of acid and up to 20 parts of dispersing agent. The products are used in the dyeing of cellulosic materials, e.g. paper and textiles, when other substances such as binding or stiffening agents, e.g. water-soluble gums or starch, may also be present in the dye-bath. They may be used on paper pulps such as bleached sulphite, esparto and rag pulps. Paper may be dyed during its manufacture, e.g. by adding the composition to the pulp, or after manufacture by padding through, or coating with an aqueous dispersion of the composition. In examples, preparations are given of (1) auramine O 150 per cent, (2) Rhodamine B 500 per cent, and (3) mixed auramine O 150 per cent and malachite green, the dispersing agent in each case being a sodium salt of a naphthalene sulphonic acid condensation product with formaldehyde and aqueous dispersions of these preparations together with other ingredients, e.g. starch, alum sulphate, casein and barium chloride are made in (4), (5) and (6) by the above preferred process and used for coating and dyeing paper.