抄録
In order to improve the brittleness and the fibrillation properties, the influence of small amount of ZnSO4 in the coagulating bath and the conditions of the stretching and regeneration bath upon the structure and characteristics of polynosic fibers was investigated.
The filaments coagulated in a bath of low acid concentration and containing small amounts of ZnSO4 were stretched or passed, after being stretched, in the hot water baths of various H2SO4 concentration. It was found that the knot tenacities and the fibrillation properties of the polynosic fibers were remarkably improved by using the hot bath of very low H2SO4 concentration. With the increase in H2SO4 or the salt concentration of the bath, the above fiber characteristics were deteriorated severely.
The improved polynosic fiber gave a thick outer layer containing no fibrillar portion, while the inner layer showed a well developed fibrillar structure. It was found that the outer layer had higher crystallinity, lower orientation and more porous structure than the inner layer.
The coagulating bath containing ZnSO4 in the concentration 0.2-0.6g/l was most effective in improving the fiber properties, while the bath devoid of the salt gave no such effect.
The mechanism of forming such a double layered structure in the polynosic fiber was inferred as follows: the outer layer of the coagulated filament could be subject to swelling and be relaxed by the diffusion of alkali from the inner layer when the filament was passed through the hot water bath of very low acid and salt concentration.
