Hitco, Inc.

Ian R Rule

Ramon B Fernandez

Gary D Shepherd

Fibrous PAN material in raw or oxidized form is purified of alkali metals, particularly sodium, and alkaline earth metals by treating with an aqueous acid solution such as hydrochloric acid having a concentration of at least 0.5% by weight and preferably at least 3% and a temperature greater than 100.degree. F. and preferably at least 125.degree. F. but not greater than the temperature at which the aqueous acid solution boils, for 5-120 minutes and preferably at least about 15 minutes. An ion exchange occurs between the acid and the PAN material, and alkali and alkaline earth metal salts are formed. The PAN material is then rinsed in solvent such as deionized water which is substantially free of metallic ions at a temperature which is preferably at least about 150.degree. F. but not greater than the temperature at which the solvent boils for 5-30 minutes to remove the formed salts, following which the material is dried and may thereafter be carbonized to produce a carbon product which is very low in alkali and alkaline earth metal content while at the same time relatively low in thermal conductivity. Methods in accordance with the invention are preferably implemented as a continuous process, and have been found to reduce the total alkali and alkaline earth metal content in commercially available oxidized PAN material to less than 13 ppm prior to carbonization in well under an hour of processing.

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Encino, CA, United States of America

Ian R Rule