Abstract
A series of pulps with different lignin content was prepared from a softwood sodium bisulfite high-yield pulp. Sodium chlorite at pH 4 served as the delignification agent. The resulting pulps were subjected to grafting with acrylonitrile using the cellulose xanthate–hydrogen peroxide redox system to initiate the copolymerization reaction. The resulting products were isolated and analyzed for homopolymer content by dimethylformamide extraction. The results indicate that the presence of larger amounts of lignin in pulp may have a favorable effect on grafting. The plots of total conversion as well as of polymer loading show a minimum centered around approximately 15% of lignin. This minimum is observed invariably at five different reaction times and it coincides with the maximum concentration of reductive groups in the pulps as well as with the maximum cation exchange capacity. The parameter of grafting efficiency has a tendency to increase with rising lignin content, reflecting the lower relative yields of homopolymer obtained with high-lignin pulps. This observation is discussed in relation to possible chain transfer reactions by lignin.
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