Comprehensive Study of Preparation of Carboxy Group-Containing Cellulose Fibers from Dry-Lap Kraft Pulps by Catalytic Oxidation with Solid NaOCl
Gaoyuan Hou, Korawit Chitbanyong, Miyuki Takeuchi, Izumi Shibata, Akira Isogai
Abstract
High Resolution Image Download MS PowerPoint Slide Catalytic oxidation of commercial and dry-lap hardwood and softwood bleached kraft pulps (HBKP and SBKP, respectively) with 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) and NaBr has been comprehensively studied using solid NaOCl·5H 2 O as the primary oxidant for the preparation of carboxy group-containing cellulose fibers. When the amount of solid NaOCl added to the pulp suspension at pH 10 was 5 mmol/g pulp, a high initial reaction rate, a short time for complete oxidation, and high carboxy content and viscosity-average degree of polymerization for both the oxidized HBKP and SBKP were achieved. When they were prepared with 15 mmol NaOCl/g pulp, the mass recovery ratios of the water-insoluble oxidized cellulose fibers decreased to 40 and 26% for HBKP and SBKP, respectively, and their viscosity-average degrees of polymerization decreased to 180–230; side reactions always occurred on the pulps during oxidation. Solid-state 13 C NMR and X-ray diffraction showed that the crystallinity and crystal size of cellulose I in the original pulps were preserved for the oxidized cellulose fibers prepared with 2.5 to 15 mmol of NaOCl/g pulp. The obtained carboxy group-rich cellulose fibers can be used as scaffolds for diverse cationic compounds and are suitable to be used as new functional group-containing sheet materials using the conventional papermaking process.