GB478277A - Improvements in or relating to bleaching wild silk - Google Patents

Abstract

Degummed wild silk, e.g. tussah silk, is bleached by subjecting it to the action of an alkaline bleaching liquor, at an elevated temperature, e.g. 40--60 DEG C., and of pH preferably 9,0--10,5, containing hydrogen peroxide and an ammonium or alkali metal persulphate. Such bleaching may be preceded or followed by a supplementary bleach, e.g. a preliminary bleaching may be effected with a reducing agent such as sodium bisulphite or by adding some sodium peroxide to the scouring bath or an after-treatment may be effected with an alkali metal hydrosulphite. In examples: (1) tussah silk, degummed by treatment for 1 hour in an aqueous solution of soda ash and soap, is immersed for 6 hours in a 3 volume aqueous solution at 45 DEG C. of hydrogen peroxide, containing 1 per cent of potassium persulphate, 1 per cent of trisodium phosphate and 1 per cent of sodium silicate, washed, further treated for \ba1/2\be hour in an aqueous solution at 45 DEG C. of sodium hydrosulphite, washed and finished; (2) degummed and scoured tussah silk is treated for 1 hour in an aqueous solution at 90 DEG C. containing sodium carbonate, sodium peroxide and soap, immersed for 5 hours in a peroxide-persulphate solution as in (1), washed and finished; (3) tussah silk, degummed as in (1), is immersed for 6 hours in a 2 volume aqueous solution at 45 DEG C. of hydrogen peroxide containing 0,5 per cent of potassium persulphate, 0,5 per cent of trisodium phosphate and 1 per cent of sodium silicate, washed and finished. Specification 268,325, [Class 15 (i)], is referred to.