TEMPO 触媒酸化パルプシートの特性解析

抄録

2,2,6,6-Tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized hardwood bleached kraft pulps (TO-HBKP) with various carboxyl contents were prepared under mild aqueous conditions by controlling the addition level of NaClO (0-5 mmol/g-HBKP) under as the primary oxidant. Aqueous slurries of unfibrillated TO-HBKP and mechanically-fibrillated TEMPO-oxidized HBKP (FTO-HBKP) with various degrees of TEMPO-oxidation were subjected to handsheet-making using either tap or de-ionized water. Characteristics of these TO-HBKP and FTO-HBKP handsheets were evaluated from various aspects. All TO-HBKP sheets prepared under various TEMPO-oxidation conditions and the FTO-HBKP sheets prepared by slight oxidation had sheet properties almost similar to those of the reference HBKP sheets. On the other hand, the FTO-HBKP sheets prepared from the TEMPO-oxidized pulp with NaClO of 5 mmol/g-pulp decreased in sheet yield to ca. 80%, i. e. ca. 20% of the FTO-HBKP was lost during the drainage process in handsheet-making. Moreover, opacity of the FTO-HBKP sheet became clearly lower, and the sheet density was in turn higher. Sheet formation analysis revealed that the FTO-HBKP components enhanced flocculation of fibers when tap water was used in sheet-making, resulting in heterogeneous sheet formation. Besides, calcium content in the TO-HBKP and FTO-HBKP sheets increased with increasing the degrees of TEMPO-oxidation or the addition level of NaClO in the TEMPO-oxidation, when tap water was used in sheet-making. Sodium carboxylate groups in the TEMPO-oxidized HKBPs were presumably ion-exchanged to calcium ones in tap water during the sheet-making process. These results indicate that the TO-HBKP and FTO-HBKP sheets have some potential applications for filter paper materials with ion-exchange properties.