Lignin Removal During Kraft Pulping. An Investigation by Thioacidolysis

A series of Pinus radiata kraft pulps with yields between 96% and 47% were prepared and examined by thioacidolysis. The levels of uncondensed β-ether units in the residual pulp lignins dropped almost linearly with the decreasing lignin content of the pulp. The drop in the levels of uncondensed β-ether units in the spent liquor lignins was much less rapid than in the fibre lignin. Enol ether units were formed in the dissolved lignin during the bulk phase of cooking, and also to a small extent in the residual fibre lignin (...)