To provide a kraft cooking method capable of producing unbleached pulp that contains a small amount of residue and is easily bleached, with a high yield by using hardwood as a raw material.
The unbleached pulp that has a Kappa number of 16-25 and contains 50-70 mmol/kg of hexeneuronic acid is obtained by subjecting the hardwood to kraft cooking treatment under a condition of a cooking temperature of 130°C or higher and lower than 150°C and a cooking period of time of 240 min or longer, and preferably 480 min or shorter. Bleached pulp that has high whiteness and contains a reduced amount of hexeneuronic acid is obtained by processing the obtained unbleached pulp with oxygen delignification treatment, acid treatment and further multistage bleaching processing.
KUROSU KAZUHIRO
TAGAMI AYUMI
SATO KANA
TAKAYAMA MASAHITO
| JP2003096680A | 2003-04-03 | |||
| JP2006342462A | 2006-12-21 |
Atsushi Yamada
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