Production of acetate-grade pulps by organic acid pulping and TCF ...
absorbable cellulose oxidized c.
cellulose acetate an acetylated cellulose used as a hemodialyzer membrane.
oxidized cellulose an absorbable oxidation product of cellulose, used as a local hemostatic.
derivatives such as cellulose acetate acetate /ac·e·tate/ (as´e-tat) any salt of acetic">acetic acetic /ace·tic/ (ah-se´tik) (ah-set´ik) pertaining to vinegar or its acid; sour. acid.ac·e·tate (
s
from Eucalyptus eucalyptus (y
'kəlĭp`təs): see myrtle. globulus or aspen wood via pulping in organic acid media (Milox or Acetosolv technologies) and TCF bleaching bleaching, process of whitening by chemicals or by exposure to sun and air, commonly applied to textiles, paper pulp, wheat flour, petroleum products, oils and fats, straw, hair, feathers, and wood. Chemical methods include oxidation, as by hypochlorites, ozone, and the per-compounds; reduction, as with sulfur dioxide; and adsorption, as by bone charcoal used to decolorize sugar solutions.. This work deals with the production of high-purity pulps from Eucalyptus globulus or aspen wood via pulping in organic acid media (Milox or Acetosolv technologies) and totally chlorine free (TCF) bleaching. The selected delignification technologies cause extended delignification with limited cellulose alteration at comparatively low operating temperatures and pressures. The production of marketable by products (sugars, furfural furfural /fur·fu·ral/ (fur´fu-ral) an aromatic compound from the distillation of bran, sawdust, etc., which irritates mucous membranes and causes photosensitivity and headaches., acetic+acid">acetic acid acetic acid /ace·tic ac·id/ (ah-se´tik) the two-carbon carboxylic acid, the characteristic component of vinegar; used as a solvent, menstruum, and pharmaceutic necessity. Glacial a. a. (anhydrous acetic acid) is used as a solvent, vesicant and caustic, and pharmaceutical necessity., and sulphur-free lignin lignin (lĭg`nĭn), a highly polymerized and complex chemical compound especially common in woody plants. The cellulose walls of the wood become impregnated with lignin, a process called lignification, which greatly increases the strength and hardness of the cell and gives the necessary rigidity to the tree. fragments) and the susceptibility of pulps to TCF bleaching are also favorable characteristics of both pulping technologies.
The experimental work focused on the comparative susceptibility of pulps toward TCF bleaching using an optimized sequence [E(O)Z[C.sub.CP]P, to measure their potential as substrates for cellulose acetate production.
Following an alkaline extraction reinforced with oxygen [E(O)] stage, we subjected the pulp samples to an ozone (Z) stage and pH 2 using medium consistency operation. Cold caustic extraction (CCE stage) reduced the hemicellulose hem·i·cel·lu·lose (h
m
-sl content of pulps. After this stage, Milox-processed Eucalyptus pulp presented the lowest kappa number (0.5); the best brightnesses were obtained for Milox-delignified pulps (85.9% and 85.8% for pulps from Eucalyptus and aspen, respectively). The treatments caused limited viscosity loss (23-31 mL/g). The procedure for TCF-delignification of Milox-and Acetosolv-pulps from Eucalyptus and aspen considered in this work produced high-purity pulps suitable for the manufacture of cellulose derivatives. Among the possibilities examined, Milox-delignified pulps from aspen and Eucalyptus showed the best properties.
Dapia and Parajo are with the Department of Chemical Engineering, University of Vigo (Campus Ourense), Polytechnical Building, Ourense, Spain. Sixta, Borgards, and Harms are with Lenzing A.G. in Lenzing, Austria. Contact Parajo by e-mail at jcparajo@uvigo.es: or by fax at +34988387001.