Greasy wool contains substantial amounts of contaminants.Before it can be used as a textile fibre these contaminants must be removed bya scouring (washing) process. There are four principal issues associated withwool scouring. These are:
- effective contaminant removal
- minimal fibre entanglement
- product quality
- cost minimization
High levels of residual contaminant on the scoured wool showup as poor colour, dirt/oil accumulation on processing equipment, deleteriousinteractive effects with processing additives, poor drafting performance, poordyeing and dust accumulation in the mill. Fibre entanglement leads to breakagein the subsequent carding and combing operations leading to reduced hauteur, ortop length, and increased wastage as noil.
Mechanism of Scouring
Aqueous scouring involves passing the wool through a seriesof tanks (bowls). The first few bowls contain hot detergent solution and theremaining bowls are used to rinse the wool. Basically scouring is a multi-stagecountercurrent extraction process.
Contaminant removal occurs in a number of stages. First thecontaminants are penetrated by water and detergent followed by rapid swellingof the wool wax and proteinaceous contaminants along with dissolution of someof the water-soluble suint. Second, wax globules are formed within the swollenmass. Third, complexed and uncomplexed contaminants that are not strongly boundto the fibre surface (easy-to-remove contaminants) are swept from the fibresurface. Fourth, harder-to-remove contaminants, such as swollen proteins, oxidised wool wax and less soluble suint residues either complexed or uncomplexed, arepartially removed.
Originallypublished in New Cloth Market; May 2009
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