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A raw material with high cellulose content and low content of hemicelluloses, residual lignin, extractives and minerals is required for many important applications in the pharmaceutical, textile, food and paint industries i.e. cotton and dissolving grade pulp are used. However, the high costs for the production of dissolving grade pulps has triggered interest in upgrading paper-grade pulps into dissolving pulps by selective removal of hemicelluloses and subsequent activation of the pulps. This study reports the feasibility to produce dissolving grade pulps from different wood and non-wood paper-grade pulps employing enzymatic and chemical pre-treatments. The results were compared to those of commercial bleached dissolving pulps., QC 20130523

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 Fock's 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. C-13 nuclear magnetic resonance spectroscopy and Raman microspectroscopy revealed that the cellulose structure consisted of cellulose I., QC 20101201

As a continuation of our work, the viability of converting paper-grade kraft pulps into dissolving-grade pulps, for several raw materials, has been presented. It has been demonstrated that a combination of an enzymatic treatment using a commercial xylanase followed by alkali extraction resulted in an efficient hemicellulose removal. Furthermore, the cellulose reactivity could be enhanced by an additional enzymatic treatment using a commercial monocomponent endoglucanase. As a result, pulps with the characteristics of those of a commercial dissolving pulp, in terms of hemicellulose content and cellulose reactivity, were obtained. The viscosity of the treated pulps, however, was significantly affected by the treatments; they present lower values than those suitable for the production of cellulose derivatives and regenerated cellulose. The pulps, on the other hand, contained mostly cellulose II, which may also affect the process. Therefore, as a continuation of this work, an optimization of the sequences of treatments as well as a study of the parameters involved was performed in order to overcome the low viscosity values and the presence of cellulose II. After the optimization, it was observed that the xylanase treatment could be replaced by an alkali extraction step, the reaction time for the alkali treatment could be shortened, the viscosity could be increased and pulps containing cellulose I could be obtained. ; In addition, the hemicellulose content and cellulose reactivity values remained in the range of those of a commercial dissolving-grade pulp., QC 20101201

QC 20120214

Cellulose is the most abundant biorenewable material, constitutes an important polymer since it is used as raw material for several products, e.g. Paper and board but also cellulose-based products which have many important applications in the pharmaceutical, textile, food and paint industries. A raw material with high cellulose content and low content of hemicelluloses, residual lignin, extractives and minerals is required for the prodn. of these products, e.g. Cotton and dissolving grade pulp are used. However, the high cost prodn. of dissolving grade pulps has aroused the possibility of upgrading paper grade pulps into dissolving pulps by selective removal of hemicelluloses and subsequent activation of the pulps. This study reports the feasibility to produce dissolving grade pulps from different pulps, i.e. Non-wood paper grade pulps and conventional hardwood kraft pulps, employing enzymic and chem. pretreatments. A monocomponent endoglucanase and a xylanase followed by alk. extn. were tested in order to increase the accessibility and reactivity of the cellulose pulp and decrease the hemicellulose content, resp. An optimization of these treatments in terms of enzyme dosage, incubation time and a possible combination of them was investigated. The treatment effects on reactivity according to Fock's method, viscosity, hemicellulose content and mol. wt. distribution, using size exclusion chromatog. (SEC), were analyzed. The characterization of cellulose structure after the enzymic and chem. treatments was investigated by different techniques., QC 20120420

QC 20150624

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 pretreatments 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 Fock's 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., QC 20100525 10th European Workshop on Lignocellulosics and Pulp, Stockholm, SWEDEN, AUG 25-28, 2008

QC 20120427

QC 20190617

In this study, the feasibility of using different kraft pulps as dissolving pulps for the viscose process was investigated. Two different bleached hardwood kraft pulps from eucalypt (Eucalyptus globulus) and birch (Betula pendula) were subjected to several enzymatic and chemical pretreatments in order to improve the accessibility and reactivity of the pulps and to reduce the hemicellulose content. Enzymatic treatments were carried out using a commercial monocomponent endoglucanase and a commercial xylanase. Chemical treatment consisted of an alkali extraction. The effects of these pretreatments on reactivity and viscosity were assayed. In both pulps, the endoglucanase enhanced the cellulose reactivity and reduced the viscosity. The sequential combination of xylanase and endoglucanase enhanced the positive effect of endoglucanase treatment alone for eucalypt but showed no major effect for birch. The addition of an alkali extraction step after the xylanase followed by endoglucanase treatment as a final step significantly reduced the hemicellulose content to 24% while the reactivity reached the value of a commercial dissolving pulp (65-70%). The viscosity, on the other hand, showed a considerably decrease., QC 20100917. Uppdaterad från Manuskript till Artikel (20100917).

For the prodn. of cellulose derivs. raw material contg. high cellulose and low hemicellulose content is required and today's industrial state of the art is to use dissolving pulps produced by sulphite process or prehydrolisis kraft. This work, in contrast, focuses on the study of two different paper-grade kraft pulps from hardwood - birch and eucalyptus -- and the possibility to use it as raw material for the prodn. of cellulose derivs. There have been different studies that focus their investigations mainly on the decrease of the hemicellulose content. The aspects of accessibility and reactivity of cellulose towards solvents and reagents, however, are investigated far less although being key parameters when a homogenous substitution is desired for the prodn. of cellulose derivs. of high quality. In order to accomplish the requirements of a com. dissolving pulp, the kraft pulps were subjected to different enzymic treatments using com. enzymes, xylanase and monocomponent endoglucanase. Reactivity (Fock) was notably improved and the hemicellulose content decreased down to com. typical dissolving pulp values. Further on, the structural characteristics of the pulps will be studied by means of 13C-CP/MAS NMR and size exclusion chromatog. (SEC)., QC 20120302