Abstract:

In order to expose the causes of the poor bleachability and brightness stability of the sulfonated chemimachenical pulp（SCMP） from bamboo Bambusa chungii,NMR spectroscopy was used to analyze the structures of lignin samples of SCMP,bleached SCMP（BSCMP） and aged BSCMP.The results show that the SCMP of bamboo Bambusa chungii is of poor bleachability not only because the SCMP lignin has a high content of p-hydroxyl-phenyl unit,the phenolic hydroxyl groups of syringyl unit in the SCMP mainly exist in the form of ether bond,but also because there are 20 condensed units in per 100 aromatic units in the lignin.Moreover,it is found that,during the bleaching and the aging,the total contents of phenolic hydroxyl groups in lignin samples decrease by 30.7% and 38.4%,respectively,while those of carboxylic hydroxyl groups increase respectively by 53.2% and 55.3%,that Alk-O-Arand α-OAlk ether bonds in lignin samples are cleaved,while γ-OAlk ether bond is stable,and that the linkage of the side chain in lignin samples is simultaneously cleaved to form conjugated bonds such as Ar-CHO and Ar-COOH,thus reducing the brightness and the brightness stability of the pulp.

Key words: Bambusa chungii, sulfonated chemimachenical pulp, lignin, nuclear magnetic resonance spectroscopy