Abstract
Viscose rayon is at first immersed in water, the imbibition water is displaced either with liquid solvent or vapor, and then acetylated using sulfuric acid (sulfoacetic acid) as a catalyst. The method of displacement has no significant influence on the acetylation rate. As imbition liquid not pure water but salt solution is used, the water is displaced with acetic acid or ethyl acetate vapor and then acetylated, whereby salt, which remains in the fiber reacts, as a catalyst. Kinds of imbibition liquid and salt have much influence on the reaction rate. Salts which have only a small affinity to acetic anhydride such as zinc sulfate, disturb the displacement with the acetylating bath, whereas salts which have great affinity to acetic anhydride such as potassium acetate make the displacement easier. Viscose rayon may be acetylated smoothly with impregnated potassium acetate without imbibition liquid.
