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Method of manufacture of discontinuous fibers in polyacrylonitrile and fibers having a narrowing increased potential obtained by this process
Method of manufacture of discontinuous fibers in polyacrylonitrile and fibers having a narrowing increased potential obtained by this process
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机译：制备聚丙烯腈中的不连续纤维的方法以及通过该方法获得的具有增加的变窄电位的纤维
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摘要
Staple polyacrylonitrile fibres of increased potential shrinkage are produced by stretching a bundle of continuous polyacrylonitrile filaments to a degree sufficient to break the filaments without destroying the cohesion of the bundle, while heating the filaments in a zone. The heated zone is preferably much narrower parallel to the length of the filaments than the width of the bundle and is preferably at or near to the feed end of the stretching zone. The bundle may be passed through the nip of a pair of feed rollers to the nip of a second pair of rollers rotating at a higher peripheral speed to stretch the filaments a breaker draft ratio of, for example, 5,0 to 15,0. The heating elements may be a pair of electrical bar heaters one above and one below the tow which is travelling along a horizontal path, each heater may be partially enclosed in an asbestos box and the filaments may be heated in the short heating zone to a temperature of, for example, 101 DEG to 172 DEG F. The filaments are preferably cooled in a second zone after leaving the heating zone, e.g. by a blast of cold air directed on to them. The cohesive top of staple fibres obtained by breaker drafting of the filaments in the above manner may be forwarded directly to a third pair of rollers which forms the nip entrance to a stuffer box for crimping the fibres. "Potential shrinkage" is defined as the ability of the staple fibres to contract in steam or hot aqueous liquids and is increased by the process of the invention, which also produces fibres of improved uniformity of staple length. The fibres may be homopolymers of acrylonitrile or copolymers containing at least 80% of acrylonitrile.
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