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Badila M.,Kompetenzzentrum Holz GmbH | Badila M.,University of Strasbourg | Hebraud A.,University of Strasbourg | Brochon C.,CNRS Organic Polymer Chemistry Laboratory | Hadziioannou G.,CNRS Organic Polymer Chemistry Laboratory
ACS Applied Materials and Interfaces | Year: 2011

The preparation of multilayered latex particles with surface functional groups suitable for use as electrophoretic particles in electronic inks has been studied. The particles are formed by dispersion polymerization and have a polystyrene core, slightly cross-linked with divinylbenzene (DVB), and a poly(methyl methacrylate) (PMMA) or a poly(acrylic acid) (PAA) shell. After grafting alkyl chains on their surface, the particles are negatively or positively charged and sterically stabilized against aggregation in nonpolar solvent. The particles were dyed by incorporation of Nigrosin during polymerization or by swelling in supercritical CO 2 in the presence of a dye. Particle size, morphology, incorporated dye content and zeta potential were determined. A dual-particle electronic ink based on a mixture of the colored multilayered particles and white hybrid TiO 2-polymer particles was prepared and electro-optically tested. © 2011 American Chemical Society. Source

Gehmayr V.,Kompetenzzentrum Holz GmbH | Sixta H.,Aalto University | Sixta H.,Lenzing AG
Biomacromolecules | Year: 2012

Endoglucanase treatment of pulp for the adjustment of viscosity and the increase in pulp reactivity is a promising step in the concept for the beneficial production of dissolving pulps from paper grade pulps. To promote the commercial applicability of these enzymes, the influence of pulp properties such as carbohydrate composition, pulp type and cellulose morphology on the enzymatic degradability of a pulp was examined. High contents of hemicelluloses and lignin were shown to impair the accessibility of the cellulose to the enzymes. Due to the elevated swelling capacity of cellulose II, conversion of the cellulose morphology from I to II upon alkaline treatments showed a large increasing effect on the cellulose accessibility, and enzymatic degradability. Reactivity measurements of softwood sulfite pulps after enzymatic degradation and acid-catalyzed hydrolysis, respectively, revealed elevated reactivity for the pulp after acid treatment. This is in contrast to effects of enzyme treatments reported for CCE treated kraft pulps. © 2012 American Chemical Society. Source

Schild G.,Kompetenzzentrum Holz GmbH | Sixta H.,Lenzing AG | Sixta H.,Aalto University
Cellulose | Year: 2011

In this study, the concept of multifunctional alkaline pulping has been approved to produce high-purity and high-yield dissolving pulps. The selective removal of hemicelluloses was achieved by either water autohydrolysis (PH) or alkaline extraction (E) both applied as pre-treatments prior to cooking. Alternatively, hemicelluloses were isolated after oxygen delignification in a process step denoted as cold caustic extraction (CCE). Eucalyptus globulus wood chips were used as the raw material for kraft and soda-AQ pulping. In all process modifications sulfur was successfully replaced by anthraquinone. By these modifications purified dissolving pulps were subjected to TCF bleaching and comprehensive viscose and lyocell application tests. All pulps met the specifications for dissolving pulps. Further more, CCE-pulps showed a significantly higher yield after final bleaching. Morphological changes such as ultrastructure of the preserved outer cell wall layers, specific surface area and lateral fibril aggregate dimension correlated with the reduced reactivity towards regular viscose processing. The residual xylan after alkali purification depicted a lower content of functional groups and a higher molecular weight and was obviously entrapped in the cellulose fibril aggregates which render the hemicelluloses more resistant to steeping in the standard viscose process. Simultaneously, the supramolecular structure of the cellulose is partly converted from cellulose I to cellulose II by the alkaline purification step which did not influence the pulps reactivity significantly. Nevertheless, these differences in pulp parameters did not affect the lyocell process due to the outstanding solubility of the pulps in NMMO. Laboratory spinning revealed good fiber strength for both, regular viscose and lyocell fibers. The high molecular weight xylan of the CCE-treated pulps even took part in fiber forming. © 2011 Springer Science+Business Media B.V. Source

Gehmayr V.,Kompetenzzentrum Holz GmbH | Schild G.,Kompetenzzentrum Holz GmbH | Sixta H.,Aalto University | Sixta H.,Lenzing AG
Cellulose | Year: 2011

The development of efficient process steps to convert paper-grade to dissolving pulps was investigated as part of the work programme to improve the process economics. The challenge of pulp refinement comprises the selective removal of hemicelluloses and the precise adjustment of the pulp viscosity, while maintaining the reactivity of the pulp as required for viscose application. The purpose of this study was to investigate the effects of various enzyme treatments on a commercial oxygen-delignified Eucalyptus globulus paper-grade kraft pulp in the course of a total chlorine free bleaching sequence in combination with refining techniques following the principle of Modified Kraft Cooking (Sixta et al. 2007). The objectives were to assess its applicability as viscose pulp besides the reduction of chemical consumption in alkaline and ozone bleaching steps by means of xylanase pre-treatment and the controlled adjustment of final pulp viscosity utilizing endoglucanase post-treatment. Xylanase pre-treatment combined with cold caustic extraction at reduced alkalinity efficiently removed the hemicelluloses from the pulp and clearly increased the pulp brightness by extensive removal of hexenuronic acid side chains. The xylanase pre-treated pulp showed increased reactivity towards xanthation and high viscose dope quality in terms of particle content. The dependence of cellulose chain scission on the applied endoglucanase concentration was analyzed in detail, and this allowed precise viscosity reduction as well as reactivity increase. The differently treated pulps, with and without xylanase pre-treatment, were of very narrow molecular weight distribution and the quality of the spun fibers were very similar to those viscose fibers from commercial dissolving pulps. © 2010 Springer Science+Business Media B.V. Source

Gutsch J.S.,Kompetenzzentrum Holz GmbH | Sixta H.,Lenzing AG | Sixta H.,Aalto University
Industrial and Engineering Chemistry Research | Year: 2012

Lignin in prehydrolysis-kraft prehydrolyzates leads to incrustations and impedes the utilization of the hemicellulosic fraction as a product. The adsorption of the lignin on activated charcoal directly after prehydrolysis at prehydrolysis temperatures prevents the formation of these incrustations efficiently. However, reutilization of the charcoal is necessary to ensure an economic process. To develop adequate recycling strategies for the spent activated charcoal, solvent extraction and thermal regeneration were investigated with respect to the recycling performance of the regenerated charcoals. Solvent extraction of the spent charcoals showed only limited efficiency, while the adsorption capacity of the activated charcoal was quantitatively restored by a thermal treatment at 950 °C. This was demonstrated by a pore size distribution and a lignin adsorption behavior of the recycled activated charcoal comparable to that of a fresh one which allows the reutilization of the charcoal in the adsorption process. © 2012 American Chemical Society. Source

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