Research on so-called "Holocellulose pulp" from Hard Woods

Abstract

Applying, as the first stage, the neutral sulphite semi-chemical pulping process to beech tree and other several hard wood species common in this district (Shizuoka Prefecture), we got unbleached pulps containing various amounts of lignin by varying Na₂SO₃ percentage addition from 14 to 20 on the basis of dry chips and digesting time at 170°C from 2 to 3 hours.
By treating, then, these unbleached pulps successively with chlorine solution, sodium hydroxide solution, and chlorite solution activated by the addition of acetic acid under proper conditions in accordance with each pulp quality, we obtained, in all the cases, bleached pulps with about 85 brightness in the yield of about 60 per cent on the basis of dry chips.
But, in the first place, the very low pulp strength and poor quality of the bleached pulps prepared from unbleached pulps having high lignin content which might possibly cause unfavorable effects at refining process, should restrict the pulp digesting conditions to such that would give unbleached pulp having less lignin content than 14 per cent.
Nextly, we found out that the bleached pulps having pentosan contents of about 23 to 24 per cent give the best pulp strength measured in bursting factor or breaking length. This favorable results can be realized by making the pentosan in wood chips remain in the bleached pulp in the yield of about 60 per cent.Thus utilizing the holocellulose in the wood in so high rate that has not been achieved by any other chemical pulping process, the present report process might be named "holocellulose pulp method".