GB694451A - Improvements relating to polyazine dyestuffs - Google Patents

Abstract

Insoluble coloured polyazines are made by reacting hydrazine, its hydrate or a salt thereof with an aromatic p- or m dialdehyde or a tetra-acetate thereof in substantially an aqueous medium the hydrazine, its hydrate or its salt being used in the proportion of at least 1 mol. to 1 mol. of the dialdehyde; 80-90 DEG C. are preferred temperatures. Water-miscible organic solvents, e.g. lower aliphatic alcohols, may be present. The dialdehyde may be substituted and specified dialdehydes are terephthal-, isophthal-, 4-methoxy-, isophthal-, 2,5-dichloroterephthal-, 5-hydroxy-isophthal-, 2,5-dibromoterephthal and 2,5-dimethoxy-terephthal-aldehyde. The pigments are yellow. The tetra-acetates may be made by oxidizing the corresponding dimethyl compound with chromium trioxide and sulphuric acid in the presence of acetic acid and anhydride. In examples: (1) terephthalaldehyde tetra-acetate is reacted in aqueous ethanol with hydrazine sulphate in the presence of sulphuric acid, (5) 4-methoxy-isophthalaldehyde is reacted in aqueous ethanol with hydrazine sulphate, (6) 2,5-dichloro-terephthalaldehyde tetra-acetate is reacted in aqueous ethanol with hydrazine hydrate in the presence of sulphuric acid, (7) 5-acetoxy-isophthalaldehyde tetra-acetate is reacted in aqueous ethanol with hydrazine sulphate and (8) 2,5-dibromo-terephthaldehyde in aqueousethanol is reacted with hydrazine sulphate.ALSO:Insoluble coloured polyazines used in dyeing processes are made by reacting hydrazine, its hydrate or a salt thereof with an aromatic p-or m-dialdehyde or a tetra-acetate thereof in substantially an aqueous medium, the hydrazine, its hydrate or its salt being used in the proportion of at least 1 mol. to 1 mol. of the dialdehyde. 80-90 DEG C. are preferred temperatures. Water-miscible organic solvents, e.g. a lower aliphatic alcohol, may be present. The dialdehyde may be substituted and specified dialdehydes are terephthal-, isophthal-, 4-methoxy-isophthal-, 2,5-dichloro-terephthal-, 5-hydroxy - isophthal-, 2,5 - dibromo - terephthal and 2,5-dimethoxy-terephthal-aldehyde. The pigments are yellow. The tetra-acetates may be made by oxidizing the corresponding dimethyl compound with chromium trioxide and sulphuric acid in the presence of acetic acid and anhydride. In the dyeing of textiles the polyazine may be caused to form on the materials, e.g. by impregnating with a solution of the dialdehyde, and after removal of excess liquid the material is run, with or without drying, through an aqueous solution containing the hydrazine compound, preferably at an elevated temperature, the fabric finally being washed and dried. Alternatively treatment with the hydrazine compound may precede that with dialdehyde. Pattern effects are produced by applying one or both reagents in selected areas only. The polyazine may be caused to form subsequently, e.g. by steaming, tetraacetates being particularly useful in this respect since they require hydrolysis before they react. In examples: (1) terephthalaldehyde tetraacetate is reacted in aqueous ethanol with hydrazine sulphate in the presence of sulphuric acid; (5) 4-methoxy-isophthalaldehyde is reacted in aqueous ethanol with hydrazine sulphate; (6) 2,5-dichloro-terephthalaldehyde tetra-acetate is reacted in aqueous ethanol with hydrazine hydrate in the presence of sulphuric acid; (7) 5-acetoxy-isophthalaldehyde tetraacetate is reacted in aqueous ethanol with hydrazine sulphate and (8) 2,5-dibromo-terephthalaldehyde in aqueous-ethanol is reacted with hydrazine sulphate; in (2) a cotton fabric is impregnated with a 5 per cent aqueous ethanol solution of terephthalaldehyde and run through a 5 per cent aqueous solution of hydrazine sulphate to be dyed a bright lemon yellow; (3) a cotton fabric is impregnated with a solution containing terephthalaldehyde tetraacetate and hydrazine hydrate, dried and the colour developed by passing through steam and formic acid vapour; (4) a cotton fabric is printed with a paste containing terephthalaldehyde tetracetate, hydrazine hydrate and tragacanth thickening, dried and steamed to develop the colour and in (9) a cotton fabric is impregnated with an aqueous alcohol solution of 2,5-dimethoxy terephthalaldehyde, dried and further impregnated with an aqueous solution of hydrazine sulphate, dried and steamed to yield an orange dyeing.