STUDIES ON POLYVINYL ALCOHOL FIBERS

Abstract

The reaction of polyvinyl alcohol in powder form with aldehydes containing basic groups such as aminoacetaldehyde was studied for the purpose of improving the dye affinity of polyvinyl alcohol fibers. The fibers prepared from partially aminoacetalized polyvinyl alcohol, however, were obsurved to discolor during the heat treatment. Aldehydes containing tertiary amino groups such as dimethyl-amino acetaldehyde dimethyl acetal were found to yield fibers that are less susceptible to discoloration than those containing aminoacetaldehyde dimethyl acetal.Higher reaction temperatures and longer reaction periods are required for the system consisting of polyvinyl alcohol and dimethyl-amino acetaldehyde dimethyl acetal because of the slow rate of reaction. The use of sulphuric acid catalyst in this system is found to yield fibers with poor physical properties as the acid reacts with polyvinyl alcohol to form an ester. Hydrochloric acid, however, gave good results as a catalyst. The degree of preheat treatment of the polyvinyl alcohol powder prior to dimethyl-amino acetaldehyde dimethyl acetalization is found to influence the properties of the fibers. If the polyvinyl alcohol powder ls properly heat treated, then the properties of the fibers will be similar to those obtained from resaponified polyvinyl alcohol. This indicates that dimethyl-amino acetaldehyde dimethyl acetal is selectively incorporated into the polyvinyl alcohol molecule without disturbing crystallization of the fiber. The results of X-ray diffraction are found to be in agreement with the properties of the fibers and the degree of swelling of films prepared from partially dimethyl-amino acetalized polyvinyl alcohol.