Studies on the Digestion for Bamboo Pulp (1st report)

Abstract

(I) Analyses : Bamboo is the more heterogeneous material chemically as well as structurally and generally inferior cellulose content to wood. Chemically analysing, the more valuable parts of bamboo for paper pulp are internodes than nodes, and outerparts than innerparts of the stems.(II) Cooking of internodes : In the preparation of stock, internodes have been splitted into 4 layers in thickness to the growing direction of stems, cut each layer to 1.51.8 cms and chipped to the size of (1.5 1.8)2× (0.10.2) cms. I have tried the cooking of 4 layers respectively using some chemicals of the same kind and quantities, and researched into the differences from cooking operation, pulp yield and pulp quantities of each layer.a) Ammonium hydroxide and ammonium monosulphite cooking : When the cooking takes place 3 hrs at maximum temperature 170°C respectively, outerlayer consumes smaller percentage of chemicals and outerlayer pulp is more chlorine requirement than innerlayer. In other words, the pulping velocity of cortial part is very slower than others.b) Ammonium monosulphite cooking : The cooking takes place at high temperature as well as alkaline process. But near the end of the cooking that sulphur dioxide content of the liquor is less than 0.5 percent may be subjected to the burning reaction (difference from sodium monosulphite cooking).In this case, both the pulp and the liquor darken and the pulp is somewhat degraded. To avoid this reaction, an excess of sulphur dioxide content and at least 4.04.5 of pH value should be maintained in the cooking liquor. High unbleached brightness and high yield of pulp result from this cooking as well as sulphite cooking.c) Ammonium bisulphite cooking : The cooking operation generally follows to sulphite cooking, and it has taken place at temperature rising time 3 hrs and maximum temperature 145°C at these experiments.d) Ammonium base sulphite cooking : During the first 5 hrs of sulphite cooking temperature has been raised slowly and precautions being taken that the chips are completely impregnated with cooking liquor, and afterwards it has been at 140°C.To summerize, the obtained general results show as follows :i) NH3 consumption (evolved by boiled solution of caustic soda) is very little in sulphite cooking, and a little in bisulphite cooking. But when ammonium monosulphite cooking or ammomium monosulphite and hydroxide cooking takes place, NH3 consumption is increased distinctly.ii) As compared of pulp qualities in each pulping by the same chlorine consumption pulp, sulphite pulp is the highest α-cellulose content and the least β-cellulose content. In order of sulphite, bisulphite, monosulphite and monosulphite and hydroxide cooking, α-cellulose content is gradually increased but β-cellulose content is decreased.iii) In these cookings, nonuniform cooking takes place and pulp qualities resulting from these cooks for each parts of internodes would be varied in chlorine consumption.e) But in kraft process, the cooking takes place uniformly and there is little difference between chlorine consumption pulp of each layer.