Method of preparing high strength and modulus polyvinyl alcohol fibers

A process comprising the steps:

• (a) forming a solution of a linear polyvinyl alcohol having a weight average molecular weight at least 500,000 in a first solvent at a first concentration between about 2 and about 15 weight percent polyvinyl alcohol,
• (b) extruding said solution through an aperture, said solution being at a temperature no less than a first temperature upstream of the aperature and being substantially at the first concentration both upstream and downstream of said aperture,
• (c) cooling the solution adjacent to and downstream of the aperture to a second temperature below the temperature at which a rubbery gel is formed, forming a gel containing first solvent of substantially indefinite length,
• (d) extracting the gel containing first solvent with a second, volatile solvent for a sufficient contact time to form a fibrous structure containing second solvent, which gel is substantially free of first solvent and is of substantially indefinite length;
• (e) drying the fibrous structure containing second solvent to form a xerogel of substantially indefinite length free of first and second solvent;
• and
• (f) stretching at least one of:
• (i) the gel containing the first solvent,
• (ii) the fibrous structure containing the second solvent and,
• (iii) the xerogel,
• at a total stretch ratio sufficient to achieve a tenacity of at least about 10 g/denier and a modulus of at least about 200 g/denier.