Process of improving the dyeing properties of polyvinyl alcohol fibers

Claim 1

A PROCESS FOR IMPROVING THE DYEING PROPERTIES OF POLYVINYL ALCOHOL FIBERS COMPRISING SPINNING AN AQUEOUS SOLUTION CONTAINING POLYVINYL ALCOHOL INTO A COAGULATING BATH CONTAINING A COAGULATING SALT SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL AND AMMONIUM SULFATES AND CHLORIDES, HEATING THE OBTAINED FILAMENTS TO A TEMPERATURE OF ABOUT 140 TO 225*C. UNTIL SAID FILAMENTS SHRINK LESS THAN 5 PERCENT OF THEIR LENGTH IN WATER OF 80*C., REMOVING THE COAGULATING SALT ADHERED TO THE FILAMENTS FROM THE COAGULATING BATH TO SUCH AN EXTENT THAT THE FILAMENTS CONTAIN NOT MORE THAN 10 PERCENT BY WEIGHT OF SAID SALT, AND TREATING SAID FILAMENTS WITH AN AQUEOUS ACETALIZING SOLUTION CONTAINING BY WEIGHT ABOUT .5 TO 15 PERCENT OF FORMALDEHYDE, ABOUT .5 TO 25 PERCENT OF THE ACID OF SAID COAGULATING SALT, AND SAID COAGULATING SALT IN SUCH AN AMOUNT THAT SAID SALT TOTAL CONCENTRATION IN THE SOLUTION DOES NOT EXCEED 5 PERCENT, FOR A TIME AND AT A TEMPERATURE SUFFICIENT TO ACETALIZE ABOUT 25 TO 50 PERCENT OF THE HYDROXYL GROUPS OF THE POLYVINYL ALCOHOL.