STUDIES ON ACETALIZATION OF POLYVINYL ALCOHOL FIBER WITH HIGHER ALDEHYDES

Abstract

Though a benzalized polyvinyl alcohol fiber shows fairly high elastic recovery, it has a drawback of very poor acid resistance. In order to obtain a resilient and acid resistant fiber, heated polyvinyl alcohol fibers were acetalized with some benzaldehyde derivatives obtained by substitution of chloro-, nitro-, or cyano-group into the benzene ring, and aliphatic aldehydes having a benzene ring or an alicyclic ring. And benzaldehyde and formaldehyde were also used for the control. On these acetalized fibers, the acid resistance, elastic recovery, and other properties were examined. Concerning the acid resistance, the formalized fiber is the best, the benzalized fiber and tolualdehy-de-acetalized fiber belong to the lowest class, and the others are generally intermediate between the above two groups. Among three fibers acetalized with o-, m-, or p-chlorobenzaldehyde, the ortho shows the best acid resistance, the meta is the medium, and the para is the lowest. The resistance of 2, 4-dichloro-, m-nitro-, p-nitro-, p-cyano-, or p-chloro-m-nitro-benzaldehyde-acet-alized fiber is almost same as that of the o- chlorobenzalized fiber. The effects of various substitutions into the benzene ring in benzaldehyde on the acid resistance seem to be almost parallel to Hammett's σ-constants. The fibers acetalized with benzaldehyde derivatives substituted by electronegative groups have almost similar wet- and dry-heat resistance, tenacity, breaking elongation, and elastic recovery, and fairly superior acid resistance to the benzalized fiber. In the case of aliphatic aldehydes, such as phenylacetaldehyde, and tetrahydro-, and trimethyltetrahydro benzaldehyde, a better acid resistance is obtained than in the benzalized fiber. The results on the acid resistance of acetalized fibers seem to be explained by the mechanism in the hydrolysis of acetals shown by O'Gorman and Lucas.