Combined scouring and bleaching

In another process [14,15], the kier circulation is reduced by using emulsified solvent systems (Chapter 4). Emulsified solvent system consists of blends of emulsifier and solvents like chlorinated hydrocarbons, mineral oils etc., which stabilises 

In order to reduce the peroxide consumption, the fabric can be treated with sodium hypochlorite prior to peroxide treatment to increase the initial whiteness 

In an energy saving and trouble free combined scouring and bleaching system 

Ingradients Impregnation liquor (ml/1) Feed liquor (re-inforced 3.5 times) (ml/1) Impregnation liquor (ml/1) Feed liquor (ml/1) 

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The whiteness of the fabric made of acetate may be improved by treatment with hydrogen peroxide (30%), 1-3 g/1 in presence of sodium silicate, 0.3 g/1. During this treatment the alkalinity of the bath and the required temperature should be carefully maintained. The pH of the bleach bath should not be greater than 9 and treatment for 1 h at 45°C gives combined scour and bleaching with the addition of non-ionic detergent. 

A single stage combined scouring and bleaching of polyester/cotton blended fabric can also be done for economy. There are various approaches which include alkali treatment with detergent and peroxide hot bleach alkali treatment with detergent and sodium chlorite bleach sodium chlorite and peroxide bleach and peroxide cold and peroxide hot bleach. 

Aftertreatment with detergent (2-5 g/1) and sodium carbonate (2-5 g/1) often enhances whiteness and may improve fabric absorbency, particularly if the goods have not been scoured before bleaching. Antichlor treatment is unnecessary for white goods but may be required before coloration. A convenient antichlor treatment involves combining the detergent aftertreatment with sodium perborate, percarbonate or thiosulphate [143]. Traditional reductive antichlors such as sodium bisulphite are not recommended, since their residues can be just as troublesome as chlorite residues. 

An electrochemical system combining scouring, mercerising and bleaching has been proposed. It is a non-polluting method based on an electrochemical cell, the cathode of which produces the base to mercerise and bleach, whilst the anode produces an acid to neutralise the base remaining after mercerisation [321]. 

The ICI Markal III process combines bleaching with scouring and desizing by using an emulsion of aqueous H Oj in trichloroethylene-surfactant solution, followed by steaming and washing-off... 

BURCO SCOUR VAR-DF3 is particularly effective for J-Box and Kler bleaching, and for prescouring, of 100% cotton and polyester/cotton blends. It combines the solvents and emulsifiers to penetrate and remove troublesome oils and waxes by holding them in suspension, thus preventing any redeposit on the fabric. 

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