Abstract: A process for producing a high strength and high initial modulus polyvinyl alcohol monofilament yarn. The monofilament yarn is polyvinyl alcohol having a polymerization degree of from 1500 to 7000, a tensile strength of not less than 10 g/d and an initial modulus of not less than 200 g/d, with a fineness of 100 denier or more. The monofilament yarn is made by dry-wet spinning a spinning dope prepared by dissolving polyvinyl alcohol having a polymerization degree of from 1500 to 7000 in a solvent and stretching the resulting unstretched filament, where a plurality of filaments immediately after being spun from a spinning nozzle having a plurality of orifices are closely adhered and united into a substantially single strand in an inert atmosphere and then introduced into a coagulating bath or a cooling bath.

Abstract: A high tenacity, high initial modulus polyvinyl alcohol fiber is produced by:(1) dissolving polyvinyl alcohol with a degree of polymerization of not less than 1,500 in a solvent capable of giving a 5 wt % polyvinyl alcohol solution and the solvent is further characterized in that the nuclear magnetic resonance spectrum measured at 50.degree. C. after storage of the solution at 50.degree. C. for 96 hours following preparation thereof is substantially identical with that measured at 50.degree. C. immediately after preparation thereof, with peaks for the three kinds of hydroxyl groups of polyvinyl alcohol being clearly distinguishable in each nuclear magnetic resonance spectrum,(ii) forming filaments by spinning the spinning solution under conditions which satisfy the requirementsDs.ltoreq.5.0wherein Ds is the spinning stretch ratio defined as the ratio (V.sub.2 /V.sub.1) of the take off speed (V.sub.2) to the first take off roller speed (V.sub.

Abstract: A high strength and high initial modulus polyvinyl alcohol monofilament yarn and a process for producing the same with high productivity are disclosed, the monofilament yarn comprising polyvinyl alcohol having a polymerization degree of from 1500 to 7000, having a tensile strength of not less than 10 g/d and an initial modulus of not less than 200 g/d, and having a fineness of 100 denier or more; and the process comprising dry-wet spinning a spinning dope prepared by dissolving polyvinyl alcohol having a polymerization degree of from 1500 to 7000 in a solvent and stretching the resulting unstretched filament, wherein a plurality of filaments immediately after being spun from a spinning nozzle having a plurality of orifices are closely adhered and united into a substantially single strand in an inert atmosphere and then introduced into a coagulating bath or a cooling bath.

Abstract: A high tenacity, high intitial modulus polyvinyl alcohol fiber showing a high level of crystalline heat of fusion, characterized in that the fiber is made of polyvinyl alcohol having a degree of polymerization of not less than 1,500, has a tenacity of not less than 17 g/d and an initial modulus of elasticity of not less than 400 g/d and shows a crystalline heat of fusion of not less than 29 cal/g, and a method of producing said polyvinyl alcohol fiber comprising:(i) dissolving polyvinyl alcohol with a degree of polymerization of not less than 1,500 in a solvent capable of giving a 5 wt % polyvinyl alcohol solution and the solvent is further characterized in that the nuclear magnetic resonance spectrum measured at 50.degree. C. after storage of the solution at 50.degree. C. for 96 hours following preparation thereof is substantially identical with that measured at 50.degree. C.