Prior to wet spinning, a few more production steps take place (Scheme below). After selecting the batches of hackled sliver, a plan is made for mixing, drafting and doubling the slivers (‘mixing plan’). Then, hackled sliver from selected bales are drafted on a drawing frame and reassembled into a new sliver (Figure below). This drafting and doubling process takes place at least 4 times and aims to obtain a more homogeneous sliver with further refined fibres. The sliver is lightly twisted using a roving frame (Figure 33below) into roving that is wound onto a rove bobbin after which the fibre is suitable for further refining and wet spinning (§7.1.5).
If necessary, the wick or rove bobbin can be demineralised, alkaline boiled and/or bleached before wet spinning.
Demineralisation contributes to:
Removal of iron which can lead to holes in the fibre and thus in textiles due to rusting and possible washing out during washes.
Removal of other metals to avoid possible negative effects in subsequent processes (e.g., dyeing).
Higher degree of whiteness after peroxide bleaching.
Lower hardness of the fibres, yarns and ultimately the fabric.
Demineralisation takes place before or after alkaline boiling.
Alkaline boiling contributes to:
Removal of secondary substances (hemicellulose, pectin, lignin, natural fats and waxes).
Spinnability due to smoother fibres as a result of removing lignin and pectin.
Bleaching contributes to:
Removal of natural dyes, or coloured impurities
Increasing hydrophilicity
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