Hydrolyzed polyacrylonitrile polymers and process of preparing same

Claim 1

A PROCESS OF PREPARING POLYMERIC DERIVATIVES WHICH COMPRISES TREATING A SUBSTANTIALLY STABLE AQUEOUS DISPERSION COMPRISING AN EMULSIFYING AGENT AND A POLYACRYLONITRILE WITH AN AQUEOUS SOLUTION OF AN ALKALI METAL HYDROXIDE, SAID DISPERSION AND SOLUTION CONTAINING LESS THAN 15% BY WEIGHT OF POLYACRYLONITRILE, HEATING THE RESULTING DISPERSION IN THE PRESENCE OF SUFFICIENT OF SAID HYDROXIDE TO SAPONIFY FROM ABOUT 4 TO 10% OF THE NITRILE GROUPS OF THE POLYACRYLONITRILE, THEN ADDING A FURTHER AMOUNT OF SAID AQUEOUS SOLUTION CONTAINING SUFFICIENT HYDROXIDE TO SAPONIFY FROM 40 TO 80% OF SAID POLYACRYLONITRILE AND HEATING THE RESULTANT DISPERSION UNTIL 40 TO 80% SAPONIFICATION IS ATTAINED, TREATING THE RESULTING SOLUTION WITH AN ACID SELECTED FROM THE GROUP CONSISTING OF STRONG MINERAL AND ORGANIC ACIDS WHICH ARE CAPABLE OF LOWERING THE PH OF THE POLYMER SOLUTION TO AT LEAST 1.5 UNTIL ACIDIFIED POLYMER SEPARATES FROM THE AQUEOUS PHASE, THE TEMPERATURE OF THE ACIDIFIED POLYMER BEING ADJUSTED TO PROVIDE A COHERENT, PLASTIC MASS, AND THEN WASHING THE MASS WITH WATER UNTIL THE MASS IS SUBSTANTIALLY FREE OF SALTS.