ソルボリシスパルプ化に関する研究開発 第４報 ソルボリシスパルプの漂白

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To establish the optimum bleaching method of solvolysis pulp, cresol pulps produced by the cooking with cresol followed by the washing with methanol, were bleached with various bleaching reagents.The bleaching of cresol pulps was easier than that of kraft pulps in the conventional bleaching sequence with chlorine, but some pretreatments were needed for the removal of cresol in unbleached pulps and for the additional delignification.The oxygen-alkali pretreatment of unbleached cresol pulps, 45 of kappa number, was suitable for producing semibleached pulps at 20 of kappa number, which had high yield and good pulp properties.Though beech cresol pulps bleached in the ODED sequence had the best quality, it was also possible to produce bleached pulps in the OCED, OZED and OZP sequence, which had almost same quality.The yield of bleached cresol pulps from beech was same as that of bleached kraft pulps, but bleached cresol pulps from red pine had 15-20% high yield. Bleached cresol pulps had good brightness stability and high density.Though strength properties of bleached cresol pulps were somewhat inferior to those of kraft bleached pulps, those were enough to utilize the solvolysis pulp as a furnish for printing paper. Remained cresol in bleached pulps was less than 1 ppm.Fainally, mixed phenol pulps were produced by the cooking with phenolic solvents corresponding the mixture produced by hydrogenolysis or pyrolysis of solvolysis lignins and by the washing with hot water. This would be a ultimate (or ideal) solvolysis pulping process. And the differences of bleaching behavior between cresol pulps and mixed phenol pulps were investigated.Bleached mixed phenol pulps had same porperties as bleached cresol pulps except somewhat low pulp yield, which was caused by the washing with hot water.As oxygen-alkali pretreatment could not remove cooking solvents in pulps well enough, chlorinated phenols were present in the bleaching effuluents of OCED sequence in high level. So the ODED sequence was recommended for the bleaching of solvolysis pulp from the economical and environmental viewpoint.