Method for making paper-like and related non-woven products from acrylonitrile polymer fibers

Claim 1

IN THE METHOD OF PREPARING PAPER-LIKE AND RELATED NON-WOVEN FIBROUS WEBS FROM GEL FILAMENTS OF A POLYMERIZED ETHYLENICALLY UNSATURATED MONOMERIC MATERIAL CONTAINING AT LEAST ABOUT 80 WEIGHT PERCENT POLYMERIZED ACRYLONITRILE WHEREIN THE GEL FILAMENTS ARE CUT TO STAPLE LENGTHS AND THE CUT LENGTHS ARE THEN FIBRILLATED BY A BEATING ACTION IN AN AQUEOUS SUSPENSION, AFTER WHICH THE FIBRILLATED FIBERS ARE SHEETED OUT INTO A WEB-LIKE STRUCTURE OF PRE-DETERMINED DIMENSIONS FOLLOWED BY IRREVERSIBLY DRYING OF THE WEB-LIKE STRUCTURE, THE IMPROVEMENT COMPRISING, PRIOR TO THE FIBRILLATION OF THE CUT GEL FILAMENTS IN THE AQUEOUS SUSPENSION, (A) SUBJECTING THE GEL FILAMENTS TO A MECHANICAL CRUSHING ACTION SO AS TO AT LEAST PARTIALLY CRUSH DAMAGE THE GEL FILAMENTS INDUCING LONGITUDINAL SPLITTING THEREIN; (B) SUBEJCTING THE CRUSH-DAMAGED GEL FILAMENTS WHILE THEY ARE IN A COMPLETELY RELAXED, UNRESTRAINED, FREE TO SHRINK CONDITION TO A HEATED, AQUEOUS NON-DRYING MEDIUM AT A TEMPERATURE OF BETWEEN ABOUT 180* AND 300*F. FOR A MINIMUM PERIOD OF TIME OF BETWEEN AT LEAST ABOUT 20 MINUTES AND 5 SECONDS, THE MINIMUM TIME VARYING INVERSELY WITH THE TEMPERATURE OF THE AQUEOUS MEDIUM; AND, (C) COOLING THE HEATED GEL FIBRS TO AT LEAST ABOUT 125*F.