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[Oral Session 6] THE ORIGIN AND DISTRIBUTION OF ANIONIC GROUPSIN TMP
Anna Sundberg,Andrey Pranovich,Bjarne Holmbom 한국펄프·종이공학회 1999 한국펄프종이학회 기타 간행물 Vol.- No.-
The distribution of anionic groups in the fibres, the fines, the colloidal fraction and the dissolved fraction, respectively, of thermo mechanical pulp (TMP) suspensions was determined. The influence of extraction, alkaline treatment and peroxide bleaching of spruce TMP were also studied.<br/> Spruce TMP was extracted with hexane, treated with alkali, or bleached with peroxide. Suspensions made at pH 5.5 were fractionated into long fibres, large fines, small fines, a colloidal fraction and a dissolved fraction. The charge of the fractions was determined using polyelectrolyte titration. To determine the origin of the charges, the contents of fatty acids, resin acids and acidic units in hemicelluloses in the different fractions were determined by gas chromatography.<br/> Extraction of TMP with hexane prior to fractionation increased the measured charge of the fibres. The removal of the wood resin probably uncovered some carboxyl groups on the fibre surfaces, or improved the penetration of polybrene into the pores of the fibres. The charge of the fines and the colloidal fraction was lower when the wood resin had been removed.<br/> Alkaline treatment of the TMP increased the charge of the fibres and fines, mainly because of demethylation of pectins. Alkaline treatment increased the charge also of the dissolved fraction. because of the release of pectic acids into the water phase. Alkaline peroxide bleaching further increased the charge of fibres and the dissolved fraction, most likely because of lignin oxidation. The charge of the colloidal fraction, consisting mainly of wood resin, was only slightly affected by alkaline treatment and peroxide bleaching.<br/> The anionic groups in TMP suspensions were mainly free uronic acids in the hemicelluloses. The contribution from the fatty and resin acids was substantial only for the colloidal fraction.