To obtain polyvinyl alcohol-based fibers having high strength and high elastic modulus with slight sticking and useful as a reinforcing material of a molded material, etc., by spinning a spinning solution containing boric acid (salt) under specific conditions and drawing.
The objective fibers having ≥8g/d single fiber strength, ≥260g/d initial modulus, ≤1wt.% of boric acid content and skin-core structures are obtained by spinning a spinning solution containing 0.03-0.2wt.% of boric acid and/or borate and 5-30wt.% of a PVA-based polymer into an alkaline coagulation bath containing 0.0025-0.25mol/L of alkali and inorganic salts, neutralizing as-spun yarn in an aqueous solution containing 0.005-0.5mol/L of acid and inorganic salts, dipping into a saturated aqueous solution of inorganic salts and subjecting to wet-heat drawing, drying and dry-heat drawing.
YAMAMOTO YOICHI
HIKASA JUNICHI
NOGUCHI YOSHISHIGE
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