Monica Ek

Combination of alkaline and enzymatic treatments as a process for upgrading sisal paper-grade pulp to dissolving-grade pulp

A sequence of treatments consisting of an initial xylanase treatment followed by cold alkaline extraction and a final endoglucanase treatment was investigated as a process for upgrading non-wood paper-grade pulps to dissolving-grade pulps for viscose production. Five commercial dried bleached non-wood soda/AQ paper pulps, from flax, hemp, sisal, abaca, and jute, were studied for this purpose. Commercial dried bleached eucalyptus dissolving pulp was used as reference sample. Sisal pulp showed the highest improvement in Focks reactivity, reaching levels nearly as high or even higher than that of eucalyptus dissolving pulp (65%), and a low hemicellulose content (3-4%) when was subjected to this sequence of treatments. The viscosity, however, decreased considerably. A uniform and narrow molecular weight distribution was observed by size exclusion chromatography. (13)C nuclear magnetic resonance spectroscopy and Raman microspectroscopy revealed that the cellulose structure consisted of cellulose I.

Exploring enzymatic treatments for the production of dissolving grade pulp from different wood and non-wood paper grade pulps 10th EWLP, Stockholm, Sweden, August 25–28, 2008

Abstract The feasibility of producing dissolving grade pulps for viscose production from different fiber raw materials, such as paper grade pulps from wood and non-woody plants, was investigated. Commercial dried bleached hardwood kraft pulps from eucalypt, and bleached non-wood soda/AQ pulps from flax, hemp, sisal, abaca, and jute, were subjected to enzymatic and chemical pre-treatments in order to improve the accessibility and reactivity of cellulose and to reduce their hemicellulose content. A commercial monocomponent endoglucanase and a commercial xylanase were employed for biochemical treatment. The chemical treatment consisted of cold alkaline extraction. The effects of these pre-treatments on pulps were studied by reactivity, according to Focks method, and viscosity measurements, determination of hemicellulose content, and recording of molecular weight distributions. The results were compared to those of commercial bleached eucalypt dissolving pulp. Eucalypt and sisal pulps showed high improvement in reactivity, reaching levels near or even higher than that of the eucalypt dissolving pulp (65%–70%), and a low hemicellulose content (2%–4%), when both were submitted to a sequence of treatments consisting of an initial xylanase treatment followed by cold alkaline extraction, and a final endoglucanase treatment. However, the viscosity decreased considerably. A uniform and narrow molecular weight distribution was observed in both eucalypt and sisal pulps after this sequential pre-treatment.

Optimization of treatments for the conversion of eucalyptus kraft pulp to dissolving pulp

Eucalyptus wood is known worldwide for its use in the production of kraft pulps and dissolving pulps. In our previous study, the feasibility of using a eucalyptus kraft pulp as a dissolving pulp was investigated. It was demonstrated that a kraft pulp subjected to a sequence of treatments that included enzymatic treatments using a xylanase and a monocomponent endoglucanase and, an alkali extraction, accomplished the requirements of a commercial dissolving pulp in terms of cellulose reactivity and hemicellulose content. Nevertheless, the low degree of polymerization and the presence of cellulose II showed that the combination of treatments had to be optimized. As a result, the parameters involved in the sequence of treatments were examined as well as their influence in the production of dissolving pulps. Furthermore, new sequences were tested. It was noticed that by decreasing the concentration of alkali in the alkali extraction stage, no cellulose II formed at short reaction times (10 min.) and that the degree of polymerization was increased. On the other hand, the cellulose reactivity and the hemicellulose content were barely affected. Moreover, a high pulp consistency (10%) led to an inhomogeneous mixture and the stirring effect was slightly noticeable.