Spin bath treatment

Claim 1

IN A PROCESS FOR THE PRODUCTION OF REGENERATED CELLULOSE WHEREIN VISCOSE SPINNING SOLUTION IS EXTRUDED INTO A SPIN BATH COMPRISING AN AQUEOUS SOLUTION OF SULFURIC ACID, SODIUM SULFATE AND ZINC SULFATE FOR COAGULATING SAID SPINNING SOLUTION, IN WHICH PROCESS THE SPIN BATH IS CIRCULATED THROUGH AND OUTSIDE THE COAGULATING ZONE THEREBY COMING INTO CONTACT WITH METALLIC LEAD EQUIPMENT, CAUSING SAID SPIN BATH TO BECOME CONTAMINATED WITH LEAD, THE IMPROVEMENT WHICH COMPRISES ADDING AN ALKALINE EARTH METAL COMPOUND, WHICH REACTS WITH SAID SPIN BATH TO PRODUCE AN ALKALINE EARTH METAL SULFATE, TO SAID CIRCULATING SPIN BATH, AT A POINT REMOVED FROM THE COAGULATING ZONE AND UNDER SUCH CONDITIONS AS TO PRODUCE AN ALKALINE EARTH METAL SULFATE IN FINELY DIVIDED FORM WHICH PRECIPITATES AND CASUES THE CO-PRECIPITATION OF THE LEAD SULFATE IN SAID SPIN BATH, AND REMOVING THE PRECIPITATE WHEREBY THE AMOUNT OF LEAD CONTAMINANT IS DIMINISHED AND THE TENDENCY OF THE REGENERATED CELLULOSE TO DISCOLOR IS REDUCED.