Production of cellulose ester yarns suitable for conversion into staple fiber

Claim 1

PROCESS FOR THE MANUFACTURE OF YARNS HAVING A BASIS OF A LOWER ALIPHATIC ESTER OF CELLULOSE AND SUITABLE FOR CONVERSION INTO STAPLE FIBRE, WHICH COMPRISES FORMING FILAMENTS FROM THE CELLULOSE ESTER BY EXTRUDING AN ACETONE SOLUTION OF THE CELLULOSE ESTER THROUGH A MULTI-HOLE SPINNING JET INTO A COAGULATING BATH, STRETCHING THE FILAMENTS DURING THEIR PASSAGE THROUGH THE COAGULATING BATH, AND THEN SUBJECTING THE FILAMENTS, UNTIL THEY ARE SUBSTANTIALLY FREE FROM ACETONE AND WHILE ALLOWING THEM TO SHRINK FREELY, TO THE ACTION OF A REGULATING BATH, THE COAGULATING AND REGULATING BATHS BOTH BEING AQUEOUS SOLUTIONS SELECTED FROM THE GROUP WHICH CONSISTS OF AQUEOUS SOLUTIONS OF DIETHYLENE GLYCOL DIACETATE AND AQUEOUS SOLUTIONS OF MIXTURES OF DIETHYLENE GLYCOL DIACETATE AND MONOACETATE IN WHICH THE AMOUNT OF DIACETATE BY WEIGHT IS AT LEAST 4 TIMES THAT OF MONOACETATE, THE CONCENTRATION OF THE SOLUTIONS BEING SUCH THAT THEIR CONTENT OF COMBINED ACETIC ACID IS EQUAL TO THAT OF A DIETHYLENE GLYCOL DIACETATE SOLUTION OF CONCENTRATION BELOW 38%, AT LEAST ONE OF THE BATHS CONTAINING BOTH THE DIACETATE AND THE MONOACETATE, REMOVING THE COAGULATING AND REGULATING BATHS FROM THEIR RESPECTIVE ZONE OF OPERATION, REMOVING FROM SAID BATHS BY DISTILLATION SUBSTANTIALLY ALL OF THE ACETONE DERIVED FROM THE SPINNING SOLUTIONS, ADDING TO THE BATHS SUFFICIENT DIETHYLENE GLYCOL DIACETATE TO RESTORE THEIR INITIAL CONCENTRATION OF COMBINED ACETIC ACID WHILE MAINTAINING THE AMOUNT OF DIETHYLENE GLYCOL DIACETATE IN EACH BATH AT LEAST 88% OF THE TOTAL WEIGHT OF DIETHYLENE GLYCOL DIACETATE AND MONOACETATE IN THE BATH, AND RETURNING THE BATHS TO THEIR RESPECTIVE ZONES OF OPERATION.