Process for the preparation of polyvinyl alcohol fibers

Claim 1

PROCESS FOR THE PREPARATION OF POLYVINYL ALCOHOL FIBERS COMPRISING: I. SPINNING AN AQUEOUS POLYVINYL ALCOHOL SOLUTION COMPRISING 10 TO 30 PERCENT BY WEIGHT OF A POLYVINYL ALCOHOL HAVING A DEGREE OF POLYMERIZATION RANGING FROM 1,200 TO 3,500 AND 1 TO 5 PERCENT BORIC ACID OR A SUBSTANTIALLY WATER SOLUBLE BORATE SALT THEREOF BASED ON THE WEIGHT OF POLYVINYL ALCOHOL; II. COAGULATING THE SPUN POLYVINYL ALCOHOL SOLUTION IN AN AQUEOUS SOLUTION CONTAINING 10 TO 100 GMS/LITER SODIUM OR POTASSIUM HYDROXIDE AND 100 TO 330 GMS/LITER SODIUM SULFATE TO OBTAIN FIBERS; III. ROLLER DRAWING SAID FIBERS; IV. NEUTRALIZING ALKALI ADHERED TO SAID FIBERS WITH ACID; V. WET-HEAT DRAWING SAID FIBERS; VI. RINSING SAID FIBERS WITH WATER TO ADJUST THE AMOUNT OF RESIDUAL BORIC ACID OR BORATE SALT TO 0.2 TO 0.9 PERCENT BY WEIGHT OF POLYVINYL ALCOHOL; VII. DEHYDRATING AND DRYING SAID FIBERS; AND VIII. DRY-HEAT DRAWING SAID FIBERS TO A TOTAL DRAWING RATIO OF AT LEAST 1,300 PERCENT, THEREBY OBTAINING POLYVINYL ALCOHOL FIBERS EXHIBITING THE FOLLOWING HIGH TEMPERATURE PROPERTIES: YARN TENACITY AT 120*C.-AT LEAST 7.5 GMS/DENIER YARN INITAL MODULUS AT 120*C.-AT LEAST 100 GMS/DENIER YARN CREEP AT 135*C.-LESS THAN 2 PERCENT.