Fibre description of Viscose (CV) / Cupro (CU) / Acetate
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Viscose (CV)
The starting material is the cellulose that is extracted from coniferous timber and supplied to the fibre manufacture in sheets about 1 cm thick. The wood contains about 40-50% cellulose that is useable to make viscose. The cellulose is first allowed to swell in a NaOH solution. The white flakes obtained are then treated with carbon disulphide until the sodium cellulose xantogenate is formed. The xantogenate is soluble in diluted sodium hydroxide and the formed solution (pulp) is already called viscose. The pulp then needs to be spun. Spinning consists in coagulating the xantogenate solution at the outlet of the spinneret in an acid bath containing sulphuric acid, sodium sulphate and zinc sulphate.
Cupro (CU)
Cellulose (wood pulp) can also be dissolved in an aqueous solution of ammonia and copper sulphate. Cupro fibres are produced by wet spinning.
Acetate fibres
The Cellulose molecule contains 3 alcohol groups. When between 2 and 2,5 of the 3 groups are esterified with acetic acid, the polymer is called diacetate. When all the three alcohol groups are esterified, then the polymer is called triacetate. The acetate fibres contain less than 92% of cellulose acetate, but at least 74% of the hydroxilic groups must be acetylated.
Litertaure: BAT for the Textile Industry, July 2003
