Process for producing uniform polyacrylonitrile fibers by heat relaxing solvent containing undrawn fibers, removing solvent and drawing the fibers

Claim 1

A PROCESS FOR THE PREPARATION OF AN ACRYLONITRILE POLYMER FIBER FROM AN UNDRAWN SPUN POLYMER WHICH CONTAINS AT LEAST 5% BY WEIGHT OF AN INERT SOLVENT FOR SAID POLYMER, AT LEAST 85% OF ACRYLONITRILE WITH A MAXIMUM OF 15% OF COPOLYMERIZABLE MONOMERS IN THE POLYMER MOLECULE AND WHICH IS CAPABLE OF BEING DRAWN AT LEAST ABOUT TWO TIMES ITS ORIGINAL LENGTH, THE SAID PROCESS COMPRISING HEATING SAID SPUN POLYMER, WHILE IT IS IN A RELAXED CONDITION, IN AN INERT NON-AQUEOUS MEDIUM AT A TEMPERATURE OF FROM ABOUT 100*C. TO ABOUT 150*C. FOR A PERIOD OF TIME OF FROM ABOUT 5 SECONDS TO ABOUT 2 HOURS; REMOVING THE INERT SOLVENT FROM SPUN POLYMER UNTIL ITS SOLVENT CONTENT IS NO MORE THAN ABOUT 2.5% BY WEIGHT; AND THEREAFTER DRAWING SAID SPUN POLYMER AT LEAST ABOUT TWO TIMES ITS ORIGINAL LENGTH.