チップのせん断圧縮処理による蒸解促進効果

Abstract

Some eucalyptus species from Western Australia contain high amount of polyphenols to give a lower pulp yield by alkaline cooking. H. G. Higgins has suggested that destruction of chips by passing between two rolls of different peripherical speeds improves pulping.This study has been carried out to improve pulp yields and delignification of chips from above species. Mill chips of E. marginata, mixture of E. calophylla and E. diversicolor and mixture of domestic hardwood species were destructured passing through two rolls of 8″ diameter, of which rotation were 24.8 and 32.2 rpm respectively at clearance of 1.6, 1.3, 1.0 and 0.7 mm. Bulk density of treated chips were increased about 10 to 25%.It was obiously observed that screened yields of sulphate pulps at the same Kappa number were improved by destruction treatment. As far as pulp strengths, over-destructured chips by 0.7 mm clearance of rolls showed some damages due to reduction of fibre length. However, strengths of handsheets seemed not so lowered in case of some moderate roll clearances.Destruction treatments induced fissures in chips, however, the pore or void volume in chips measured by the mercury penetration revealed that chips were significantly densified. Further investigations are to be needed.