PREPARATION OF LIGNIN FIBERS FROM SOFTWOOD ACETIC-ACID LIGNIN - RELATIONSHIP BETWEEN FUSIBILITY AND THE CHEMICAL-STRUCTURE OF LIGNIN

Softwood acetic acid lignin (S-AL), obtained by aqueous acetic acid pu lping of todomatsu (Abies sachalinensis Masters), is infusible. In thi s study, a method for conversion of S-AL to a fusible material for the preparation of lignin fibers was developed based on examination of th e relationship between the thermal properties and the chemical structu re of S-AL. S-AL was found to be converted to fusible material by remo val of the high-molecular-mass fraction by solvent extraction with 70% acetic acid, with a yield of 80%. From a comparison of the chemical s tructure of the fusible and infusible fractions, we found that the str uctures of aromatic nuclei in the acetic acid lignin (AL), such as con densed and aryl-ether structures, were related closely to the thermal mobility of AL. The large contents of condensed and aryl-ether structu res in AL seemed likely to hinder thermal motion. Therefore, the cutti ng of aryl-ether bonds by re-cooking with aqueous acetic acid resulted in a fusible lignin, with a yield of approximately 90%. The fusible f raction of S-AL and the re-cooked S-AL were capable of being spun by f usion spinning.