| 摘要 |
Fibres or filaments of polyacrylonitrile, or of copolymers containing at least 80% of acrylonitrile, are rendered more resistant to heat and steam discolouration by treating the "neverdried" material with aqueous solutions or suspensions of reducing agents. The process may be carried out by passing a bundle of the wet fibres through a bath containing a 0,1%-10% solution of the reducing agent, optionally at elevated temperature. The treatment may be combined with other treatments such as finishing. Suitable reducing agents are thiourea dioxide, sodium or potassium metabisulphite, formaldehyde, and compounds yielding formaldehyde. The latter group includes paraformaldehyde, sodium formaldehyde bisulphite, and methylol derivatives of amides, for example hydroxymethyl formamide and hydroxymethyl dimethyl hydantoin. Examples, using a copolymer of acrylonitrile, methyl acrylate and itaconic acid, compare "fibre yellowness" when treated and untreated samples are heated in air or in steam under pressure. |
