Research and development of solvolysis pulping. Part 3 Cooking conditions and pulp properties.

Cooking conditions of solvolysis pulping with cresol as a model solvent, which is a major phenolic compound produced by degradation of lignin, were investigated and the properties of solvolysis pulps from various woods were characterized.Solvent-water ratio and cooking temperature had significant effects on delignification in this pocess. For instance, high solvent ratio in cooking liquor or low temerature were favorable for the pulp yield and for the pulp properties. It was possible to produce pulps by solvolysis pulping process from all hardwoods and softwoods used in this study.To shorten the cooking time of solvolysis pulping process which was longer than that of kraft pulping process, was achieved by the addition of small amounts of acetic acid in cooking liquor or by the circulation of cooking liquor.At a given kappa number, the yields of solvolysis hardwood pulps were same as those of kraft pulps. In contrast, solvolysis softwood pulps could be produced in high yield. Though the refining of solvolysis pulp needed less energy, the strength properties of solvolysis pulp were somewhat inferior to those of kraft pulp.Finaly, cooking experiments with various phenolic compounds, being expected to be recovered from lignin degradation products, were studied. Cooking abilities of the phenlic compounds depended on their solubility in water. The pulping with mixed phenols, which composition was determined by the data of cooking, washing and recovery experiments, gave almost same results as those of cresol pulping.