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Chemical changes of cellulose pulps in the processing to viscose dope
Umeå University, Faculty of Science and Technology, Department of Chemistry.
AkzoNobel Functional Chemicals AB, Stenungsund, Sweden.
Umeå University, Faculty of Science and Technology, Department of Chemistry.
DomInnova, Domsjö Fabriker AB, Örnsköldsvik, Sweden.
2012 (English)In: Cellulose Chemistry and Technology, ISSN 0576-9787, Vol. 46, no 9-10, 559-569 p.Article in journal (Refereed) Published
Abstract [en]

A selection of cellulose pulps was investigated for their chemical changes during the required process steps to viscose dope. The selection of the pulps was based on pulping process, original wood type and intrinsic viscosity. In total, five sulfite pulps and four sulfate pulps were chosen, of which all but one sulfate pulp were of dissolving grades. The physical and chemical properties of the pulps were analyzed as well as important qualitative parameters of the cellulose intermediates during mercerization, pre-aging and in the final viscose dope. Pre-aging curves were reported as a measure of each pulp's reactivity with respect to oxidative degradation, where high hemicellulose content and small pore area and pore diameter were found to hamper cellulose degradation. The correlations in pre-aged pulps of intrinsic viscosity to Mz, Mv and Mw were found to be ambiguous and show the need for a description of total molecular weight distribution of the alkali celluloses to better understand the degradation behavior of each pulp, instead of only intrinsic viscosity. It was also shown that R18 and R10 are insufficient analyses to determine pulp, and to predict viscose quality. Further, many pulps, independently of initial hemicellulose content, reached the same level of hemicellulose content after mercerization. The presence of crystalline hemicelluloses could be a possible cause for this level-off behavior, combined with hemicelluloses resistant to caustic lye treatment. The change of both low-molecular-weight celluloses and PD in the process to viscose dope was investigated due to the importance of these variables on dope spinnability and viscose fiber strength. Caustic resistance of cellulose and hemicelluloses and a more rigid fiber structure in some pulps are suggested to contribute to the different degradation behavior.

Place, publisher, year, edition, pages
2012. Vol. 46, no 9-10, 559-569 p.
Keyword [en]
aging, cellulose pulp, hemicelluloses, long fiber, short fiber, sulfate, sulfite, mercerization, molecular weight, reactivity, viscose
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:umu:diva-54007ISI: 000209015600005OAI: oai:DiVA.org:umu-54007DiVA: diva2:514896
Available from: 2012-04-11 Created: 2012-04-11 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Characterization of cellulose pulps and the influence of their properties on the process and production of viscose and cellulose ethers
Open this publication in new window or tab >>Characterization of cellulose pulps and the influence of their properties on the process and production of viscose and cellulose ethers
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Today’s market offers an ever-increasing range of cellulose pulps (derivative pulps) made fromvarious wood types through different delignification processes. Each pulp segment has its uniquecharacteristics, which makes it difficult for the producer of cellulose derivatives to choose the mostsuitable pulp for optimum processability and product quality. The objective of this study was toimprove knowledge of cellulose pulps and to describe how different pulp properties affectprocessability and quality in the production of viscose dope and cellulose ethers.Ten pulp samples were investigated, originating from both sulfite and sulfate processes, with highand low viscosities and with softwood and hardwood as raw material. The pulps were analyzed fortheir properties and then processed to viscose dope and a cellulose ether in two separate pilotfacilities. The intermediates in the viscose process as well as the quality of the viscose dope andcellulose ether were analyzed and the results correlated to pulp properties.Multivariate regression methods were applied to investigate the dominating physical and chemicalproperties of each pulp and pulp segment, and to study the use of spectroscopic analyses inpredicting pulp origin, concentration and composition of hemicelluloses as well as the content ofreducing end groups in cellulose. For the production of viscose dope, the models presented showedthe most important pulp properties for good cellulose reactivity and viscose filterability. In addition,the properties affecting gel formation, flocculation, degree of substitution and clarity in theproduction of cellulose ether were highlighted. The study also emphasized the need to supplementthe use of conventional analyses on pulps and viscose intermediates with other analytical methods,such as molecular weight distribution and carbohydrate analysis, to better predict the quality ofboth viscose dope and viscose fiber.The results of the present study could be useful to predict the origin and properties of new pulps, toreplace or supplement otherwise expensive pulp analyses, and to assess the impact of pulpproperties on the production of cellulose derivatives without extensive pilot-scale trials.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2012. 80 p.
Keyword
cellulose ether, dissolving pulp, ethyl hydroxyethyl cellulose, hardwood, multivariate data analysis, reactivity, softwood, sulfate, sulfite, viscose
National Category
Chemical Engineering
Identifiers
urn:nbn:se:umu:diva-54008 (URN)978-91-7459-406-5 (ISBN)
Public defence
2012-05-11, Naturvetarhuset, N320, Umeå Universitet, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2012-04-20 Created: 2012-04-11 Last updated: 2012-04-20Bibliographically approved

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http://www.cellulosechemtechnol.ro/pdf/CCT46,9-10%282012%29/p.559-569.pdf

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