Sequential oxidative and reductive bleaching of pigmented and

Abstract

The present invention is drawn to new processes for sequential oxidative and reductive bleaching of pigmented and unpigmented fibers (e.g. natural, synthetic, or blends thereof) e.g. in a single bath, which provide superior bleaching with less physical damage. Said processes including processes comprised of: (1) adsorption of ferrous ions by pigmented and unpigmented fibers; (2) removing a portion of the ferrous ions from the fibers, with at least a portion of the ions remaining on the pigmented fibers; (3) contacting the fibers with hydrogen peroxide to provide oxidative bleaching including bleaching by interaction with the ferrous ions; (4) adding either (a) a material which combines with hydrogen peroxide to form a reductive beaching agent, or (b) an inactivating material to inactivate unspent hydrogen peroxide with subsequent addition of a reductive bleaching agent, and; (5) reductively bleaching the already oxidatively bleached fibers. The aforementioned processes provide the advantages of preventing deposition of ferric species and producing fibers which are essentially free of iron residue. The present invention also encompasses processes employing hydrogen peroxide and at least one persulfate containing compound, rather than the aforementioned iron-mordanting. The instant invention produces fibers having surprising, highly advantageous, and desirable properties, e.g. fibers which are essentially pigment free, have a high degree of whiteness with low degree of damage.