Pulp-like short fibres with highly-oriented fibril structure - by melting a mixt. of water and acrylonitrile (co)polymer, cooling below the m.pt., extruding the supercooled melt and breaking up the prod.

摘要

A process is claimed for the prodn. of pulp-like short fibres (I) with a highly-oriented fibrillar structure, thickness distribution 0.1-100 microns and length 0.1-100mm; the process involves heating a mixt. of 5-100 wt.% water and an acrylonitrile (AN) homo- or co-polymer (II) (above 70 wt.% AN and below 30 wt.% other comonomers (III); viscosity average mol.wt. = 10,000-600,000) to above the m.pt. of the mixt. in a closed vessel to produce an amorphous melt, cooling to below the m.pt. to form a supercooled melt, extruding through a die at a temp. between the melting pt. and solidification pt. to give an extrudate with a cross-sectional structure, plate-like fibrils uniformly ordered and laminated by spontaneous loss of water after extrusion, a fibrous crystal structure and degree of orientation of at least 70% (by X-ray diffraction), hot-drawing the extruded strip by passing it through hot gas at 100-220 deg.C or over heated rollers, and then mechanically beating the drawn strip.