METHOD FOR DYEING SYNTHETIC MATERIALS WITH VAT DYESTUFFS

摘要

A method is provide for dyeing a non-cellulosic organic material with a dye, preferably a vat dye, comprising (a) treating the material with a dye in the presence of a reducing agent and an alkali and (b) oxidising the treated material produced in step (a) characterised in that the concentration of reducing agent used in step (a) is increased above that used for conventional vat dyeing such that the resultant dyed material has a lightfastness of 5 or more by BS1006 B01 and B02 (1978) and/or has a washfastness of 5 or more by British Standard Test BS1006 CO6.C2 (1981). Preferably the step (a) is carried out in the presence of an alkali in concentration of greater than 0.1 molar, more preferably a concentration of 0.2 molar or more and most preferably greater than 1 molar. The method provides vat dyed non-cellulosic organic materials having a reflectance of infra-red light of wavelength 400 nm to 680 nm of less than 15%.