| 摘要 |
A composition comprises a stable dispersion of viscose and "acrylonitrile polymer," the latter covering not only polymers of acrylonitrile itself but also copolymers of it with one or more monomers, e.g. ethylenically unsaturated monomers with the proviso that acrylonitrile units predominate in the copolymer chain. Small quantities of other materials, monomeric or polymeric, may be added to the acrylonitrile polymer. Preferably, the composition comprises a stable aqueous dispersion containing up to 25 per cent by weight of polyacrylonitrile with viscose containing up to about 7.5 per cent by weight of free caustic alkali. Agglomeration of the disperse phase of the polymer dispersion can be avoided by decationizing, using a cation exchange resin with subsequent adjustment of the pH to 9-10 with ammonium hydroxide. The described compositions may be wet spun to form filaments or films. In an example, viscose containing 2.4 per cent by weight excess caustic alkali, 5 per cent by weight cellulose and having a degree of xanthation of 0.62 is stirred into a polymer dispersion containing 20 per cent by weight polyacrylonitrile. After deaerating the dispersion is extended into an aqueous bath containing sulphuric acid, zinc and sodium sulphates and the filaments formed passed into another bath containing calcium thiocyanate solution. Finally' the filaments are washed and stretched. |
