MANUFACTURE OF UN-SPUN HIGHLY-ORIENTED ACRYLIC SHORT FIBER

摘要

PURPOSE: To obtain the titled fiber having a large surface area, excellent physical properties and bonding properties and useful as an asbestos-substitutive fiber or the like. by fiber-forming a specified mixture under specific conditions and beating the formed fiber. CONSTITUTION: Acrylonitrile (co-)polymer having 10,000-600,000 viscosity average molecular weight obtained by polymerizing >=70 wt.% acrylonitrile and <=30 wt.% copolymerizable monomer is mixed with 5-100% water to the (co-)polymer. The mixture is heated to its melting temperature or higher under enclosed conditions to form an amorphous melt and then the resultant melt is cooled to the temperature between the melting and solidifying temperatures to obtain a semicrystalline melt phase. The obtained melt phase is extruded into an external atmosphere to obtain extrudates having cross-sectional structures of completely arrayed and laminated planar fibrils or the like, fibrous crystalline structures and >=70% degree of orientation. The extrudates are drawn in the gaseous atmosphere of 100-220 deg.C or passed between compression rollers of the same temperature in a drawn state and beaten after subjected to the drawing and heat treatment to obtain the objective short fibers having 0.1-100μm thickness distribution and 0.1-100 mm length distribution.