過酢酸気相標白したＢＳＰの強度特性について

Abstract

In order to elucidate the mechanical properties of bleached sulfite pulp, NUSP and LUSP were bleached with peracetic acid (PA) in vapor phase under the following conditions : Chemicals addition on pulp, 10 to 32% ; DAISERU stabilizer addition on pulp, 0.018% ; pulp consistency, 33% ; temperature, 90°C ; pH 4 ; bleaching time, 60 min for NUSP and 30 min for LUSP. Viscosity of BSP thus obtained was 4 to 16 cp, and the brightness was 86 to 94% GE. Comparison between the sheet strengths and pentosan content or viscosity of BSP prepared under above conditions was also carried out. The results are summarized as follows : 1. NUSP and LUSP were more easily bleached than NUKP or LUK1 by PA-bleaching in vapor phase. Brightness of both SP, bleached with PA in vapor phase, was 5 to 8% GE higher than that of multistage-bleached SP at the equal pulp viscosity. 2. The decrease in tensile strengh, burst factor, tear factor and folding end. of linter pulp during PA- or multistage-bleaching was attributed to decrease viscosity of the pulp in a cupri ethylenediamine solution. On the other hand, sheet strengths of PA- or multistage-beached NSP and LSP at the equal freeness increased proportionally with increasing pentosan content in the bleached pulps, except folding end. of multistage-bleached NSP sheet. 3. The ellution pattern of gel filtration of hemicellulose, isolated from NSP with 5% KOH solution, was found to unchange hardly during multistage- or PA-bleaching in vapor phase. Whereas hemicellulose in LSP was partially degraded to lower molecular part during both bleaching. The lower molecular content of hemicellose in the PA-bleached LSP was more than that in the multistage-bleached pulp. 4. Tensile strength and burst factor of PA- or multistage-bleached pulp increased proportionally with increasing sheet density of each bleached pulp at the equal f reeness. The sheet strengths of PA- or multistage bleached KP were stronger than that of BSP at the equal sheet density. From the facts described above, it is assumed that the decrease of DP of polysaccharides in BSP is reduced the sheet strengths of the BP, and also, that the strengths are greater affected by the amounts of pentosan and lower molecular part of hemicellulose in the pulps.