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Carboxymethyl cellulose produced at different mercerization conditions and characterized by NIR FT Raman spectroscopy and chemometric methods
Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
Department of Natural Science III, Institute of Agriculture and Nutritional Science, Martin Luther University, Germany.
Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
2013 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 8, no 2, p. 1918-1932Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2013. Vol. 8, no 2, p. 1918-1932
Keywords [en]
carboxymethyl cellulose, cellulose backbone structure, degree of substitution, extended mercerization, gel formation, multivariate analytical methods, NIR FT Taman spectroscopy
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kau:diva-6420ISI: 000315386400037OAI: oai:DiVA.org:kau-6420DiVA, id: diva2:353670
Available from: 2010-09-28 Created: 2010-09-28 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Extended Mercerization Prior to Carboxymethyl Cellulose Preparation
Open this publication in new window or tab >>Extended Mercerization Prior to Carboxymethyl Cellulose Preparation
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Carboxymethyl cellulose (CMC) is produced commercially in a two-stage process consisting of a mercerization stage, where the pulp is treated with alkali in a water alcohol solution, followed by an etherification stage in which monochloroacetic acid is added to the pulp slurry. In this thesis an extended mercerization stage of a spruce ether pulp was investigated where the parameters studied were the ratio of cellulose I and II, concentration of alkali, temperature and retention time. The influence of the mercerization stage conditions on the etherification stage, were evaluated as the degree of substitution (DS) of the resulting CMC and the filterability of CMC dissolved in water at a concentration of 1%. The DS results suggested that the NaOH concentration in the mercerization stage was the most important of the parameters studied. When the NaOH concentration in the mercerization step was low (9%), a high cellulose II content in the pulp used was found to have no negative impact on the DS of the resulting CMC compared with pulps with only cellulose I. However, when the NaOH concentration was high (27.5%), pulps with high content of cellulose II showed a lower reactivity than those with only cellulose I with respect to the DS of the CMC obtained after a given charge of NaMCA.

The results obtained from the filtration ability study of CMC water solutions suggested that both the amount of cellulose II in the original pulp and the temperature had a negative influence on the filtration ability whereas the NaOH concentration in the mercerization stage had a positive influence. The filtration ability was assumed to be influenced highly by the presence of poorly reacted cellulose segments. A retention time between 1-48 h in the mercerization stage had no effect on either the DS or the filtration ability of the CMC.

Using NIR FT Raman spectroscopy molecular structures of CMC and its gel fraction were analyzed with respect to the conditions used in the extended mercerization stage. Here it was found that the alkaline concentration had a very strong influence on the following etherification reaction. FT Raman spectra of CMC samples and their gel fractions prepared with low NaOH concentrations (9%) in the mercerization stage indicated an incomplete transformation of cellulose to Na-cellulose before carboxymethylation to CMC. Low average DS values of the CMC, i.e. between 0.42 and 0.50, were yielded. Such CMC dissolved in water caused very thick and semi solid gum-like gels, probably due to an uneven distribution of substituting groups along the cellulose backbone. FT Raman spectra of CMC mercerized with alkaline concentrations at 18.25 and 27.5% in the mercerization stage indicated, however, that all of the cellulose molecules were totally transferred to CMC of high DS, i.e. between 0.88 and 1.05. When dissolved in water such CMC caused gels when they were prepared from ether pulp with a high fraction of cellulose II.

Place, publisher, year, edition, pages
Karlstad: Karlstad University, 2010. p. 51
Series
Karlstad University Studies, ISSN 1403-8099 ; 2010:22
Keywords
Carboxymethyl cellulose, Mercerization, DS, FT Raman spectroscopy, Filtration ability
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-5947 (URN)978-91-7063-314-0 (ISBN)
Presentation
2010-10-01, 9C 204 (Rejmersalen), Karlstads universitet, KARLSTAD, 13:15 (Swedish)
Opponent
Supervisors
Available from: 2010-10-11 Created: 2010-06-21 Last updated: 2011-10-04Bibliographically approved
2. Mercerization and Enzymatic Pretreatment of Cellulose in Dissolving Pulps
Open this publication in new window or tab >>Mercerization and Enzymatic Pretreatment of Cellulose in Dissolving Pulps
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with the preparation of chemically and/or enzymatically modified cellulose. This modification can be either irreversible or reversible. Irreversible modification is used to prepare cellulose derivatives as end products, whereas reversible modification is used to enhance solubility in the preparation of regenerated cellulose.

The irreversible modification studied here was the preparation of carboxymethyl cellulose (CMC) using extended mercerization of a spruce dissolving pulp. More specifically the parameters studied were the effect of mercerization at different proportions of cellulose I and II in the dissolving pulp, the concentration of alkali, the temperature and the reaction time. The parameters evaluated were the degree of substitution, the filterability and the amount of gel obtained when the resulting CMC was dissolved in water. Molecular structures of CMC and its gel fractions were analysed by using NIR FT Raman spectroscopy. It was found that the alkali concentration in the mercerization stage had an extensive influence on the subsequent etherification reaction. FT Raman spectra of CMC samples and their gel fractions prepared with low NaOH concentrations (9%) in the mercerization stage indicated an incomplete transformation of cellulose to Na-cellulose before carboxymethylation to CMC. Low average DS values of the CMC, i.e. between 0.42 and 0.50 were obtained. Such CMC dissolved in water resulted in very thick and semi solid gum-like gels, probably due to an uneven distribution of substituents along the cellulose backbone. FT Raman spectra of CMC samples and their gel fractions mercerized at higher alkaline concentration, i.e. 18.25 and 27.5% in the mercerization stage, indicated on the other hand a complete transformation of cellulose to Na-cellulose before carboxymethylation to CMC. Higher average DS values of the CMC, i.e. between 0.88 and 1.05 were therefore obtained. When dissolved in water such CMC caused gel formation especially when prepared from dissolving pulp with a high fraction of cellulose II.

The reversible modification studied was the dissolution of cellulose in NaOH/ZnO. Here the effect of enzyme pretreatment was investigated by using two mono-component enzymes; namely xylanase and endoglucanase, used in consecutive stages. It was found that although the crystallinity and the specific surface area of the dissolving pulp sustained minimal change during the enzymatic treatment; the solubility of pulp increased in a NaOH/ZnO solution from 29% for untreated pulp up to 81% for enzymatic pretreated pulp.

Abstract [en]

Baksidetext

Cellulose can be chemically and/or enzymatically modified. Irreversible modification is used to prepare cellulose derivatives as end products, reversible modification to enhance solubility in the preparation of regenerated cellulose.

The irreversible modification studied here was the preparation of carboxymethyl cellulose (CMC) using extended mercerization of a spruce dissolving pulp. More specifically the parameters studied were the effect of mercerization at different proportions of cellulose I and II in the dissolving pulp, the concentration of alkali, the temperature and the reaction time. It was found that the alkali concentration in the mercerization stage had an extensive influence on the subsequent etherification reaction. The content of cellulose II had little effect on degree of substitution (DS) at low NaOH concentration, but tended to decrease DS at higher NaOH concentration in both cases compared with cellulose I. It was also found that the content of cellulose II correlates with the gel formation obtained when the CMC is dissolved in water.

The reversible modification studied was the dissolution of cellulose in NaOH/ZnO. Here the effect of enzyme pretreatment was investigated by using two mono-component enzymes; namely xylanase and endoglucanase, used in consecutive stages. It was found that the solubility of pulp increased in a NaOH/ZnO solution from 29% for untreated pulp up to 81% for enzymatic pretreated pulp.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2013. p. 69
Series
Karlstad University Studies, ISSN 1403-8099 ; 2013:22
Keywords
alkali, carboxymethyl cellulose, cellulose I, cellulose II, cellulose dissolution, degree of substitution, enzymatic treatment, filterability, gel formation, mercerization, multivariate analytical methods, NIR FT Raman spectroscopy, sodium hydroxide, zink oxide
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-26960 (URN)91-7063-499-4 (ISBN)
Public defence
2013-05-31, Nyquistsalen 9C 203, Karlstads universitet, Karlstad, 09:15 (Swedish)
Opponent
Supervisors
Available from: 2013-05-17 Created: 2013-04-16 Last updated: 2013-05-17Bibliographically approved

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Almlöf, HeléneGermgård, Ulf

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