Abstract
Spruce wood (Picea glehnii) chips were cooked with cresol-water mixture of various compositions with or without acetic acid at 180-190°C for 90-120 min. And the properties of the pulps were compared with those of kraft pulp. The difference between delignification behaviors of soft-and hardwoods is discussed in terms of chemical properties of lignins. The results obtained are as follows :
1) Addition of 10-50 wt% acetic acid of spruce chips improved selective delignification and strength properties of pulp sheets.
2) Acetic acid addition to the cooking solvent for birch wood (Betula pala palatyphylla var. japonica) gave no effect, in contrast to spruce wood.
3) Preconditioning at 100°C, for 120 min. gave no effect on the cooking of spruce wood, in contrast to birch wood.
4) One of the characteristics of solvolysis pulping with cresol-water is that crude yields and screened pulp yields are almost the same, even if the yields are so high as over 70 per cent.
5) Delignification of spruce wood is more difficult than that of birch wood by the solvolysis. The difference may likely be due to the lignin structures, guaiacyl and syringyl lignins.
