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Characterization of cellulose pulps and the influence of their properties on the process and production of viscose and cellulose ethers
Umeå University, Faculty of Science and Technology, Department of Chemistry.
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 [en]
cellulose ether, dissolving pulp, ethyl hydroxyethyl cellulose, hardwood, multivariate data analysis, reactivity, softwood, sulfate, sulfite, viscose
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:umu:diva-54008ISBN: 978-91-7459-406-5 (print)OAI: oai:DiVA.org:umu-54008DiVA: diva2:514909
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
List of papers
1. The influence of properties in cellulose pulps on the reactivity in viscose manufacturing
Open this publication in new window or tab >>The influence of properties in cellulose pulps on the reactivity in viscose manufacturing
2011 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 26, no 1, 81-89 p.Article in journal (Refereed) Published
Abstract [en]

This paper describes properties in cellulose pulps to adress the increased quality demands on pulps for viscose production. Several grades of cellulose pulps were selected to investigate their chemical reactivity based on pulping process, original wood type and intrinsic viscosity. In total, six sulfite pulps and four sulfate pulps were chosen, of which all but one sulfate pulp were of dissolving grade. The physical and chemical properties of the pulps were tested. The influence of these properties on xanthation and viscose manufacturing as well as their correlation to each of the three selection criteria was investigated by the use of multivariate data analyses. Two methods to describe cellulose reactivity were used: a laboratory scale viscose test method for cellulose reactivity (Fock) and a filter clogging test for viscose dope. It was shown that all pulps chosen in this investigation formed groups according to all three selection criteria using principal component analysis. The analysis shows that sulfite pulps, from both wood types, are strongly correlated to the variables Fock reactivity, pore size and concentration of extractives. Sulfate pulps, however, are separated into two groups, hardwood and softwood. Hardwood sulfate pulps are strongly described by the variables permeability, content of hemicelluloses and filter clogging value. Softwood sulfate pulps, on the other hand, are described by variables such as alpha cellulose content, R10 and R18. Partial least square regression showed that Fock reactivity is influenced by the following cellulose pulp properties, in order of importance: absorption rate with caustic, pore area, permeability and pore diameter. The main property affecting the filter clogging value of the viscose dope is pulp permeability, followed by pore diameter, content of hemicelluloses, R18 and pore area.

Place, publisher, year, edition, pages
Stockholm: Nordic Pulp & Paper Research Journal, 2011
Keyword
Cellulose pulp, Filter clogging value, Long fiber, Short fiber, Sulfate pulp, Sulfite pulp, Reactivity, Multivariate data analysis, Viscose
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-50770 (URN)10.3183/NPPRJ-2011-26-01-p081-089 (DOI)000293770200008 ()
Available from: 2011-12-21 Created: 2011-12-21 Last updated: 2017-12-08Bibliographically approved
2. Characterization of dissolving pulp by multivariate data analysis of FT-IR and NMR spectra
Open this publication in new window or tab >>Characterization of dissolving pulp by multivariate data analysis of FT-IR and NMR spectra
Show others...
2011 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 26, no 4, 398-409 p.Article in journal (Refereed) Published
Abstract [en]

Several grades of dissolving pulps have been analyzed using FT-IR, solid state13C NMR and two dimensional1H-13C HSQC NMR spectroscopy to obtain an extensive data set for further characterization. The selection of the dissolving pulps with high cellulose purity was based on pulping process, wood type and, intrinsic pulp viscosity. Multivariate data analysis was used to investigate how information derived from the spectroscopic data correlate to each of the selection criterion: wood type, process type and viscosity. The spectroscopic methods were also compared with common dissolving pulp analyses to see to what extent spectroscopy can predict pulp analyses.

Correlations were found between the spectroscopic data and the pulp characteristics process type and wood type, but not for intrinsic viscosity. A reason for a good correlation to wood type appears to be the hemicelluloses composition, expressed as the xylose:mannose ratio by 2D NMR spectroscopy. For process type, 2D NMR showed the most characteristic property to be the amount of reducing ends in the cellulosic samples, which in turn strongly correlates to lower molecular weight for the sulfite samples as determined by molecular weight distribution.

Many common, yet expensive and time consuming, pulp analyses could also be predicted by the achieved models. It can be concluded that investigations of dissolving pulp characteristics, especially concerning different wood and process types, can take advantage of the methods and models presented in this study.

Place, publisher, year, edition, pages
Stockholm: AB Svensk papperstidning, 2011
Keyword
Cellulose, Dissolving pulp, Hemicelluloses, FT-IR spectroscopy, Multivariate data analysis, NMR spectroscopy, Pulp viscosity, Wood type
National Category
Chemical Sciences Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:umu:diva-51978 (URN)000298868000006 ()
Available from: 2012-02-06 Created: 2012-02-06 Last updated: 2017-12-08Bibliographically approved
3. Properties of cellulose pulps and their influence on the production of a cellulose ether
Open this publication in new window or tab >>Properties of cellulose pulps and their influence on the production of a cellulose ether
2012 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, no 1, 24-34 p.Article in journal (Refereed) Published
Abstract [en]

Several grades of cellulose pulps were investigated for their influence on the product quality of a cellulose ether, ethyl hydroxyethyl cellulose (EHEC). 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 grade. The physical and chemical properties of the pulps were analyzed as well as important qualitative parameters of the final product EHEC. The influence of pulp properties on EHEC quality was investigated by multivariate data analyses.Principal component analysis showed that due to the influence of all variables, the pulps aligned in groups in accordance to the selection criteria pulping process and wood type. Partial least square regression revealed that high gel formation in EHEC is explained by the pulp properties high intrinsic viscosity and high Mw in combination with high caustic absorption rate and high total caustic absorption. The amount of hemicelluloses, in particular xylose, also contributed to gel formation. High cloud point for an EHEC solution was explained by a high MSEO and low DSEt of the EHEC molecules, where in turn a high MSEO could be predicted by a high pore area, high PD and a low caustic absorption rate. A low DSEt could on the other hand be predicted by a low hemicellulose content and hence a high R18. In a separate model, the same pulp properties explaining MSEO and DSEt also predicted cloud point directly. Fock reactivity and viscose dope filterability, both test methods originating from the viscose manufacturing, were shown to predict cloud point but have low predictability on other EHEC quality parameters.The models achieved can thus be utilized to predict final EHEC product qualities for new pulps within the design set of the chosen pulps.

Keyword
Cellulose ether, Dissolving pulp, Ethyl-hydroxy-ethyl cellulose, Long fiber, Reactivity, Short fiber, Sulfate, Sulfite, Multivariate data analysis
National Category
Chemical Engineering
Identifiers
urn:nbn:se:umu:diva-54004 (URN)10.3183/NPPRJ-2012-27-01-p024-034 (DOI)000311019900003 ()
Available from: 2012-04-11 Created: 2012-04-11 Last updated: 2017-12-07Bibliographically approved
4. Chemical changes of cellulose pulps in the processing to viscose dope
Open this publication in new window or tab >>Chemical changes of cellulose pulps in the processing to viscose dope
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.

Keyword
aging, cellulose pulp, hemicelluloses, long fiber, short fiber, sulfate, sulfite, mercerization, molecular weight, reactivity, viscose
National Category
Chemical Engineering
Identifiers
urn:nbn:se:umu:diva-54007 (URN)000209015600005 ()
Available from: 2012-04-11 Created: 2012-04-11 Last updated: 2017-12-07Bibliographically approved

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