Process of improving the heat and water resistance of polyvinyl alcohol fibers with lower aliphatic alcohol vapors or superheated steam and optionally acetalizing said fibers

Claim 1

A PROCESS FOR IMPROVING THE HEAT AND WATER RESISTANCE OF POLYVINYL ALCOHOL FIBERS COMPRISING THE STEPS OF EXTRUDING AN AQUEOUS SOLUTION OF POLYVINYL ALCOHOL INTO AN ACID COAGULATING BATH TO FORM FILAMENTS OF POLYVINYL ALCOHOL, DRYING SAID FILAMENTS IN A CHEMICALLY INERT GAS AT TEMPERATURES BELOW 160* C. TO A WATER CONTENT BELOW ABOUT 5 PERCENT AND HEATING SAID DRIED FILAMENTS, WHILE STILL CONTAINING ADHERED THERETO ACID FROM SAID COAGULATING BATH, IN THE VAPOR OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF SUPERHEATED STEAM AND WATER SOLUBLE LOWER ALIPHATIC WATER SOLUBLE ALCOHOLS AT ABOUT 140 TO 225* C. FOR ABOUT 60 TO 3 MIN., THE LONGER TIMES BEING EMPLOYED AT THE LOWER TEMPERATURES, THE MINIMUM VAPOR PRESSURE OF THE SUPERHEATED STEAM VARYING INVERSELY AS THE TEMPERATURE WITHIN THE RANGE OF ABOUT 1 ATM. FOR ABOUT 225* C. TO ABOUT 4 ATM. AT 140* C., THE MINIMUM VAPOR PRESSURE OF SAID ALCOHOLS VARYING WITHIN THE RANGE OF ABOUT 1 ATM. FOR ABOUT 225* C. TO ABOUT 8 ATM. AT 140* C.