7.1.4 Spinning preparation

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 below) into roving that is wound onto a rove bobbin after which the fibre is suitable for further refining and wet spinning (§7.1.5).

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Process steps from hackled sliver to spinning.

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Drafting and doubling of hackled sliver into sliver. Photos HOGENT.

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