| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing kraft pulp, particularly the kraft pulp is produced through the chlorine-free bleaching method (particularly using broad-leaved tree) as the color-fastness is improved and the strength of the kraft pulp is improved. SOLUTION: In the kraft pulp producing method employing the digestion step, the oxygen delignification step and the chlorine-free bleaching step, the amount of hexeneuronic acid in the pulp component after the oxygen delignification step is controlled to less than 45 mmol/bone dry pulp kg. Further, in order to improve the discoloration of the produced pulp, the amount of hexeneuronic acid is set to less than 5 mmol/bone dry pulp kg. When the method for this process is carried out after the oxygen delignification, the pulp component is preferably acid-treated at the pH of 2.5 to 3.5, at the reaction temperature of 80 to 90°C, the reaction time is set more than 180 minutes or more, preferably from 180 to 480 minutes, more preferably 240 to 420 minutes. COPYRIGHT: (C)2007,JPO&INPIT
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