GB1036540A - Bleaching wool - Google Patents

Abstract

Wool, which may be in the form of fibres, tow, yarn or fabric, is bleached by saturating it with a first aqueous solution containing 1-10% by weight of an alkali or alkaline earth metal bisulphite, e.g. sodium, potassium or magnesium bisulphite, or ammonium bisulphite, contacting it for 5 seconds to 10 minutes with a second aqueous solution containing 0.001-10% by weight of an alkali or alkaline earth metal borohydride, e.g. sodium, potassium, lithium or magnesium borohydride, used in an amount to provide in contact with the saturated wool 0.05-7% by weight of the borohydride based on the wool, providing a pH of 1-8 in the immediate environment of the wool in the second aqueous solution, withdrawing the wool from the second aqueous solution within 10 minutes from the time it is contacted therewith and removing the borohydride from the wool. Prior to treatment with the bisulphite solution the wool may be scoured with an aqueous solution containing a nonionic wetting agent, e.g. iso-octylphenyl polyethoxyethanol, containing 9 moles of ethylene oxide per mole of iso-octylphenol. The bisulphite may be formed in the solution from metabisulphites, sulphites or sulphur dioxide in the presence of water and alkali ions at a pH of 1-8. The wool may be immersed in bisulphite solution and all but 50-150% by weight of the solution expressed. The bisulphite solution may have a pH below 8 adjusted with a mineral acid, e.g. sulphuric acid, or a lower aliphatic organic acid or sulphonic acid to provide the pH 1-8 in the environment of the wool since the borohydride solution is normally maintained at a pH above 8 for stability. The borohydride solution may be agitated by moving the wool through it. The borohydride solution may be removed from the wool by washing with water containing a detergent or by mechanically reducing the amount of the second solution it carries and then heating to 110 DEG -180 DEG F. for 10-30 minutes to decompose the borohydride followed by washing with water and drying at 110 DEG -180 DEG F. The process may be carried out at 40 DEG -230 DEG F.