STUDIES ON THE DYEING OF ACRYLONITRILE FIBRE

Abstract

In the scientific investigation, pure dye is required, first of all, to secure accurate results, but the purification fo dyeis a process difficult and troublesome. Concerning acid azo dyes, most attention was directed toward the preparation of separating electrolytes in the dye. Two methods of general application was studied with this intention. One is to salt out the dye from aqueous solution by the addition of sodium acetate, and the other is to employ weak base type ion exchange resin to remove inorganic impurities and intermediates. The standard analytical method to decide, when purification is carried out sufficiently or to estimate the concentration of pure dye in a sample, is the wellknown reduction process using titanous chloride solution. With the object of establishing these methods and searching the relationship between purification and estimation of dyes, experiments were carried out with old and new commercial acid dyes, and those prepared at laborately making their materials from which the following general conclusions are reached.By titanous salt analysis, satisfactory results were obtained for both acid azo dye and nitro dye, but it needs to provide annoying apparatus and tedious procedure. Salting out by sodium acetate is adequate to purify the acid dye, and by repeating this process several times, better result are obtained. Many dyes have some solubility in alcohol, hence loss occures in the process, and there is the disadvantage of giving a poor yield. The method of ash contents, in which acid dye is burned with sulphuric acid to convert it into sodium sulphate, and then weighted, is apt to be overesimated due to the presence of the electrolyte in acid dye. During the calculation of purity from ash contents analytical data, an interesting result was found that molecular weight of impurities-containing salt outed dye is nearly equal to that of sodium acetate.