Processing of Wool

A. Sorting : Raw wool brought to the mill is sorted out first as per the requirement. Sorting is a more advanced step requiring more skill and is different from classing or grading, where fleece as a whole is the unit; but in sorting, the fleece is opened up into different subsorts for more specific usage.

B. Opening and Dusting : Raw wool contains natural impurities such as oils and fats secreted by sebaceous glands, and water-soluble salts from dried excretion from the from the skin known as suint. The acquired impurities include sand, dirt, burrs and other form of vegetable matter. The applied impurities consist of tar, pitch and paint used in small quantities for animal identification purposes or chemicals used for treatment. The machinery employed for scouring opens up the clumps of fibres into individual staples and at the same time delivers a uniform quantity of opened stock to the scouring train. This facilitates the proper penetration of the scouring liquor into the wool fibre, rendering the scouring more uniform and thorough. It also reduces costs by saving on soap alkali scouring liquor.

C. Scouring : The removal of the impurities in raw wool is an intricate and important operation. It is accomplished by aqueous scouring process or by solvent-degreasing process. Scouring is accomplished in a series of vats or bowls (3-6) through which the wool is propelled by mechanical rakes with intervening squeezers. The scoured stock is dried through specially constructed driers. For Indian carpet type wools, 3 bowls are sufficient.

Recovery of wax from wool : Wool wax is a greasy substance secreted by fatty glands of the skin. Wool grease is recovered by centrifuging aqueous scouring liquors from the washing of greasy wool with detergents, often called centrifugal woolgrease. Chemically speaking, it is a complex mixture of wax esters of long chain fatty acids and alcohols, the latter including cholesterol, lanosterol and dihydrolanosterol. Centrifugal woolgrease is often considered by buyers to be of the best quality, especially if it is passed through 2 or more centrifuging steps. Industrial uses include fuel, lubricating greases, concrete mould lubricants, rust preventatives. Woolgrease is also an important component in many leather softeners.

Lanolin : In its refined form, wool grease is called “Lanolin”, and is widely used in cosmetics for its emollient properties (virtually all cosmetics and beauty aids, such as lipsticks, mascara, lotions, shampoos, and hair conditioners contain lanolin.), in pharmaceutical products as carrier bases and for various industrial applications (eg, rust preventatives, leather dressings, fur dressings, putty, cutting oils, and insulating tapes). Lanolin is graded based upon its colour and presence of impurities, with the highest grades being white or very pale yellow in colour. It is produced by reducing the level of impurities in wool grease, by neutralising free fatty acids, bleaching and deodourising.

D. Carbonization : All wools contain a larger or smaller amount of burr. If burrs are not removed, they cause considerable difficulty in all the manufacturing processes and may even damage the card clothing and combs. The burrs are removed by mechanical means such as burr crushers or manually by hand scissoring of the heavy burry parts of the fleece. The chemical removal of burr is known as carbonization. It is done using acids such as sulphuric or hydrochloric acid and by salts such as aluminium chloride which produces acid when heated. The acid reduces the vegetable matter to carbon. The carbon is removed by mechanical action during crushing, beating and neutralizing.