2018 年 72 巻 5 号 p. 545-552
Catalytic oxidation using 2,2,6,6-tetramethylpiperidine-1-oxyl（TEMPO）can be used to selectively convert primary hydroxyl groups in accessible regions of cellulose and hemicellulose molecules in pulp fibers into aldehyde and carboxy groups. Clear improvement of the wet tensile strength of handsheets prepared from a TEMPO-oxidized pulp（TOP）was previously demonstrated without the use of any wet strengthening agent. Moreover, the paper chemical contents added at the wet end and retained in the handsheets increased. However, the practical use of TOPs as raw materials in papermaking has not yet been sufficiently studied. In this study, the effects of refining TOPs on the resultant fiber morphologies and properties were investigated. TOPs with carboxy group contents of 0.42 and 0.86 mmol/g were prepared and refined to various levels using a PFI mill. The average fiber lengths of the TOPs decreased and their fines contents increased with increasing number of PFI revolutions; these results were similar to those for the original pulp. However, the freeness remarkably decreased and the water retention value significantly increased with increasing number of PFI revolutions compared with those of the refined original pulp. Moreover, the fibrillation behavior of the TOPs with refinement clearly differed from that of the original pulp in terms of the changes in pulp morphology and the amount of functional groups.
