GB384901A - Manufacture of yellow mordant dyestuffs - Google Patents

Abstract

Naphthalene dyes are derived by reacting a 4- or 3-aminonaphthalene-1 : 8-dicarboxylic acid or a sulphonated derivative thereof (or the corresponding acid anhydride) with an aminosalicylic acid or a homologue or substitution product thereof. The products may be condensed by boiling together in aqueous suspension, but preferably a condensing agent, such as an alkali bisulphite, is present. Since the nitro group of a nitronaphthalene-1 : 8-dicarboxylic acid can be reduced to an amino group by means of bisulphite with simultaneous introduction of a sulpho group, the same products may also be derived by condensing a 3- or 4-nitronaphthalene-1 : 8-dicarboxylic acid, an aminosalicylic acid and a bisulphite together. A sulpho group is preferably present in one or other of the components in order to obtain good solubility. The products are fast yellow mordant dyestuffs which can be used in colour discharge printing processes involving reduction on account of their resistance to reducing agents such as hydrosulphite. In examples: (1) p-aminosalicylic acid is condensed with 4-aminonaphthalene-6-sulpho-1 : 8-dicarboxylic acid (or anhydride) in presence of sodium bisulphite; the product yields green-yellow shades on chrome-printed cotton and can be used in reduction colour discharge printing: (2) p-amino-m-cresotinic acid is condensed with 4-aminonaphthalene - 6 - sulpho - 1 : 8-dicarboxylic acid in presence of bisulphite to give a yellow mordant dye; the p-amino-o-cresotinic acid may be similarly condensed or with a sulphonic acid of 3-aminonaphthalene-1 : 8-dicarboxylic acid, and 2-oxy-3-aminobenzoic acid may likewise be employed: (3) p-amino-o-sulphosalicylic is condensed with 4-aminonaphthalene - 1 : 8 - dicarboxylic acid in presence of bisulphite; the product, when used with chromium mordant in colour discharge printing, yields fast resistant shades; (4) 4-nitronaphthalene - 1 : 8 - dicarboxylic acid is condensed with p-aminosalicylic acid in presence of bisulphite. Specification 299,721, [Class 2 (iii), Dyes &c.], is referred to. 4 - Aminonaphthalene - 6 - sulpho - 1 : 8 - dicarboxylic acid (or anhydride) is prepared by nitrating naphthalic anhydride, reducing the 4-nitro derivative, and sulphonating. p-Amino-o-sulphosalicylic acid is prepared by sulphonating p-nitrosalicylic acid and reducing.