Cellulose acetate production from Finnish hardwood and softwood dissolving pulp
Kemian tekniikan korkeakoulu | Master's thesis
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Master's Programme in Chemical, Biochemical and Materials Engineering
64 + 5
AbstractCellulose acetate pulp was produced from viscose-grade, unbleached and bleached hardwood dissolving pulps and bleached softwood dissolving pulp. The raw materials were purified by cold caustic extraction and elemental-chlorine free bleaching. Initially, pulp purification was optimized for all of the pulps. The unbleached hardwood pulp was purified with cold caustic extraction, bleached with D0-EOP-D1-P bleaching sequence and then acetylated. The same acetylation and bleaching conditions were applied for all the samples. The resulting cellulose acetate quality had a complex relation to the quality of raw material and extent of purification. The most cost-effective CCE was obtained with 5% consistency, 30 min reaction time, and 30 °C 70 g/L NaOH. Transmission and yellowness of the cellulose acetate solution for the most successful hardwood sample were 50 % and 0.29 respectively and for the most successful softwood sample 40 % and 0.26. The corresponding values for cellulose acetates prepared from the commercially available acetate-grade pulps were 78 % and 0.27 for hardwood and 73 % and 0.35 for softwood. The produced cellulose acetate quality was mediocre even when the purification was on an excellent level due to several factors affecting the acetylation process; some of the main reasons are probably extensive degradation of the fibers due non-optimal raw material with too low degree of polymerization. The result of the experimental work was the production of a low-quality acetate pulp from hardwood and softwood viscose pulps by cold caustic extraction and, in the case of unbleached pulp, by additional ECF bleaching.
Thesis advisorStåhl, Marina
cellulose acetate, cold caustic extraction, dissolving pulp, ECF bleaching