GB300594A - Improvements in and relating to the manufacture of dyestuffs of the pyrone series - Google Patents

Abstract

300,594. Carpmael, K., Carpmael, K. S., and I. G. Farbenindustrie, Akt.- Ges. June 16, 1927. Addition to 247,003. Pyrone dyestuffs, prepared according to the parent Specification, are freed from secondary products, usually of a browner shade by converting the dyestuff acids into salts, and separating the more soluble secondary products. According to an example, the dyestuff acid obtained as described in example 1 of the parent Specification from 2: 6-dichlorbenzaldehyde and 2 : 4-dioxy-3- methylbenzoic acid, is dissolved in aqueous sodium carbonate and the pyrone dyestuff separated as a sodium salt by adding sodium chloride. It dyes wool clear red shades from an acid bath; clear shades are also obtained on chroming. If caustic soda lyes be added, as well as sodium chloride to the normal sodium salt solution, a basic sodium salt of the pyrone dyestuff is obtained. The pyrone dyestuffs obtained from o- and m-chlorbenzaldehyde and from 2- chlorbenzaldehyde-5-sulphonic acid may be freed from secondary products in a similar manner, but in the case of the dye containing a sulpho group a larger quantity of potassium carbonate must be added to salt it out. In the case of other pyrone dyes containing sulpho groups, the calcium, barium or lead salts must be produced in order t° separate them from the secondary dyestuffs. The latter are obtained from the filtrates, by adding mineral acid, after salting out the clear pyrone dyestuffs.