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The influence of different parameters on the mercerisation of cellulose for viscose production
Umeå University, Faculty of Science and Technology, Department of Chemistry.
Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden .ORCID iD: 0000-0002-5777-9241
Umeå University, Faculty of Science and Technology, Department of Chemistry.
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2016 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 2, p. 1061-1072Article in journal (Refereed) Published
Resource type
Text
Abstract [en]

A quantitative analysis of degree of transformation from a softwood sulphite dissolving pulp to alkalised material and the yield of this transformation as a function of the simultaneous variation of the NaOH concentration, denoted [NaOH], reaction time and temperature was performed. Samples were analysed with Raman spectroscopy in combination with multivariate data analysis and these results were confirmed by X-ray diffraction. Gravimetry was used to measure the yield. The resulting data were related to the processing conditions in a Partial Least Square regression model, which made it possible to explore the relevance of the three studied variables on the responses. The detailed predictions for the interactive effects of the measured parameters made it possible to determine optimal conditions for both yield and degree of transformation in viscose manufacturing. The yield was positively correlated to the temperature from room temperature up to 45 A degrees C, after which the relation was negative. Temperature was found to be important for the degree of transformation and yield. The time to reach a certain degree of transformation (i.e. mercerisation) depended on both temperature and [NaOH]. At low temperatures and high [NaOH], mercerisation was instantaneous. It was concluded that the size of fibre particles (mesh range 0.25-1 mm) had no influence on degree of transformation in viscose processing conditions, apparently due to the quick reaction with the excess of NaOH.

Place, publisher, year, edition, pages
Springer Netherlands, 2016. Vol. 23, no 2, p. 1061-1072
Keywords [en]
Mercerisation, Cellulose I, Cellulose II, Raman spectroscopy, X-ray diffraction patterns, Multivariate data analysis
National Category
Polymer Technologies Polymer Chemistry
Identifiers
URN: urn:nbn:se:umu:diva-119633DOI: 10.1007/s10570-016-0879-0ISI: 000373136400005OAI: oai:DiVA.org:umu-119633DiVA, id: diva2:927131
Projects
bio4EnergyAvailable from: 2016-05-11 Created: 2016-04-25 Last updated: 2019-08-30Bibliographically approved
In thesis
1. Experimental study of alkalinisation of cellulose in industrial relevant conditions
Open this publication in new window or tab >>Experimental study of alkalinisation of cellulose in industrial relevant conditions
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Mercerisation of cellulose pulp with a solution of NaOH is the first step of manufacturing cellulose-based value-added products, e.g. viscose fibres and cellulose ethers. During this process, cellulose transforms into a swollen crystalline structure, alkali cellulose (Na-Cell). This increases the reactivity of the cellulose and makes it more accessible for reagents to penetrate and react with the hydroxyl groups. The mercerisation conditions are known to affect the degree of alkalinisation of cellulose as well as the final products. The main objective of this thesis is to investigate how the alkalinisation of softwood sulphite dissolving cellulose pulp is influenced by the co-variation of process variables in the mercerisation in industrial relevant conditions, for both viscose and cellulose ether production. This objective was achieved by quantitative analysis of the effect of simultaneous variation of a set of key parameters on the degree of alkalinisation (i.e. degree of activation, DoA) of the chosen dissolving pulp. Quantitative measurements were performed using Raman spectroscopy data, evaluated by partial least squares (PLS) regression. For mercerisation at viscose production conditions, the effect of studied variables on mass yield was also considered. In the case of mercerisation at ether processing conditions, formation of alkali cellulose at a fixed temperature was included. The knowledge obtained on mercerisation under ether processing conditions was then applied for preparation of the ionic cellulose ether carboxymethylcellulose (CMC).

The overall results show that temperature has a strong effect on DoA and mass yield for mercerised samples under steeping conditions. Measured DoA decreases as the temperature increases from 20 to 70 °C. Mass yield correlates positively with the temperature up to 45-50 °C in the PLS model, after which the relation is negative. The [NaOH] and reaction time show a complex dependence of other variables. At mercerisation conditions for cellulose ether production, the NaOH/AGU stoichiometric ratio, denoted as (r), shows to be very important for DoA, with a positive correlation. At these mercerisation conditions, temperature shows no effect on DoA. The influence of the [NaOH] (which also refers to the concentration of water) shows a complex dependence on (r). As (r) increases and [NaOH] decreases, the measured DoA increases. Prolonged mercerisation time shows no significance in the modelled DoA. However, a gradual increase of the DoA over time was seen when mercerisation was performed with 30% and 40% [NaOH] at (r) = 0.8, suggesting a slow diffusion of NaOH and Na-Cell formation. 13C CP-MAS NMR measurements of samples produced at room temperature show that formation of the Na-Cell allomorph is mainly determined by the [NaOH]. However, in the transition area between Na-Cell I and Na-Cell II, (r) also seems to be of importance.  An increase of DS in the produced CMC samples also shows to be consistent at such conditions with the increase in the measured DoA and with increased (r) and decreased [NaOH]. However, these conditions also favour the formation of by-products. In the synthesised CMC samples, a DS of up to 0.7 was achieved. Measured solubility was lower than expected for any given DS. This, along with the non-statistical distribution of monomer units in the polymer chains, indicates high heterogeneity in the synthesised samples. The distribution of substituents within the AGU shows attachment to hydroxyl oxygens in the order O3 < O2 ≈ O6. The relative importance of the substitution at O3 indicates an increase at this position when [NaOH] increases.

The models presented in this thesis will hopefully serve as a basis for predicting the effects of the studied variables on the DoA, as well as on the mass yield of cellulose pulp when mercerisation conditions are adjusted. Moreover, it is believed that the presented studies can give a better understanding of mercerisation at cellulose ether conditions, hence enabling further development of this process step.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2018. p. 81
Keywords
Mercerisation, Alkalinisation, Cellulose I, Cellulose II, Alkali cellulose, Viscose, Cellulose ether, Carboxymethylcellulose, Sodium glycolate, Sodium diglycolate, Raman spectroscopy
National Category
Chemical Engineering Polymer Chemistry
Identifiers
urn:nbn:se:umu:diva-153412 (URN)978-91-7601-987-0 (ISBN)
Public defence
2018-12-14, KB.E3.01 (Lilla hörsalen), KBC-huset, Umeå, 10:00 (English)
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Available from: 2018-11-23 Created: 2018-11-19 Last updated: 2019-01-10Bibliographically approved

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Albán Reyes, Diana CarolinaSkoglund, NilsEliasson, BertilSundman, Ola

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