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  • 1.
    Almlöf Ambjörnsson, Heléne
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Mercerization and Enzymatic Pretreatment of Cellulose in Dissolving Pulps2013Doctoral 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.

  • 2.
    Almlöf Ambjörnsson, Heléne
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Enzyme treatment of dissolving pulps as a way to improve the following dissolution of the fibres2012Conference paper (Other academic)
  • 3.
    Almlöf Ambjörnsson, Heléne
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Extended Mercerization Prior to Carboxymethyl Cellulose Preparation2011Conference paper (Other (popular science, discussion, etc.))
  • 4.
    Almlöf Ambjörnsson, Heléne
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Jardeby, Kristina
    Borregaard Chemcell, Sarpsborg, Norge.
    Kreutz, Björn
    Borregaard Chemcell, Sarpsborg, Norge.
    The influence of mercerization on the degree of substitution in carboxymethyl cellulose2009Conference paper (Other (popular science, discussion, etc.))
  • 5.
    Almlöf Ambjörnsson, Heléne
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Schenzel, Karla
    Marthin-Luther University Halle-Wittenberg.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Characterization of CMC by NIR FT Raman spectroscopy2012Conference paper (Other (popular science, discussion, etc.))
  • 6.
    Almlöf Ambjörnsson, Heléne
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Östberg, Linda
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Schenzel, Karla
    Martin Luther University Halle-Wittenberg, Department of Natural Scinence III, Institute of Agriculture and Nutritional Science.
    Larsson, Per Tomas
    Innventia AB, Fibre and Material Science Business area Biorefining, Stockholm.
    Germgård, Ulf
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Enzyme pretreatment of dissolving pulp as a way to improve the following dissolution in NaOH/ZnO2014In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 68, no 4, p. 385-391Article in journal (Refereed)
  • 7.
    Almlöf, Heléne
    Karlstad University, Faculty of Technology and Science, Avdelningen för kemiteknik.
    Extended Mercerization Prior to Carboxymethyl Cellulose Preparation2010Licentiate 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.

  • 8.
    Almlöf, Heléne
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Basta, Jiri
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Guo, Sanchuan
    Heijnesson-Hulten, Anette
    The Effect of Stock Storage on The Quality of Bamboo Kraft Pulp2010In: O PAPEL, ISSN 0031-1057, Vol. 72, no 6, p. 43-53Article in journal (Refereed)
  • 9.
    Almlöf, Heléne
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Kreutz, Bjørn
    Borregaard Chemcell, Norway.
    Jardeby, Kristina
    Borregaard Chemcell, Norway.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    The influence of extended mercerization on some properties of carboxymethyl cellulose (CMC)2012In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 66, p. 21-27Article in journal (Refereed)
    Abstract [en]

    Carboxymethyl cellulose (CMC) is produced commercially in a two stage process consisting of a mercerization stage in which the pulp is treated with alkali in a water alcohol solution and a second etherification stage whereby monochloro-acetic acid is added to the pulp slurry. In this study, the influence of the conditions of an extended mercerization stage was evaluated on the etherification stage concerning the degree of substitution (DS) and the filterability of the resulting CMC. The parameters studied were: (1) the ratio of cellulose I and cellulose II in the original pulp, (2) the concentration of alkali, (3) the temperature and (4) the retention time in the mercerization stage. The DS results indicate that the NaOH concentration in the mercerization stage is the most important among the parameters studied. When the NaOH concentration in the mercerization stage was high (27.5%), cellulose II showed a lower reactivity than cellulose I with respect to the DS obtained in the resulting CMC. The results from the filtration ability of CMC water solutions are interpreted that the amount of cellulose II in the original pulp and the temperature has a negative influence, while the NaOH concentration in the mercerization stage has a positive influence on the filtration ability. Retention time between 1 h–48 h in the mercerization stage had no effect on the DS or the filtration value. The filtration ability was assumed to be highly influenced by the presence of poorly reacted cellulose segments. The CMC samples with the lowest filtration ability at a given DS can be assumed to have the highest degree of unevenly substituted segments.

  • 10.
    Almlöf, Heléne
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Schenzel, Karla
    Department of Natural Science III, Institute of Agriculture and Nutritional Science, Martin Luther University, Germany.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Carboxymethyl cellulose produced at different mercerization conditions and characterized by NIR FT Raman spectroscopy and chemometric methods2013In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 8, no 2, p. 1918-1932Article in journal (Refereed)
  • 11. Schenzel, Karla
    et al.
    Almlöf Ambjörnsson, Heléne
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Two new methods determining the degree of substitution of carboxymethyl cellulose by utilizing NIR FT Raman and FT IR (ATR) spectroscopy2012Conference paper (Other academic)
  • 12.
    Schenzel, Karla
    et al.
    Department of Natural Science III, Institute of Agriculture and Nutritional Science, Martin Luther University, Germany.
    Almlöf, Heléne
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Quantitative analysis of the transformation process of cellulose I → cellulose II using NIR FT Raman spectroscopy and chemometric methods2009In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 16, p. 407-415Article in journal (Refereed)
    Abstract [en]

    This paper reports a new, successful, utilization of NIR FT Raman spectroscopy for determinining the polymorphic transformation of native cellulose I into the allomorph cellulose II quantitatively. A rapid prediction of the transformation order is made possible by applying multivariate linear regression to the FT Raman spectral data of alkali-treated cellulose pulps. Simultaneously, changes in the crystallinity of cellulose I of these pulps were followed with respect to the lattice conversion process. The application of both multivariate quantification methods to the FT Raman spectra of the alkali-treated pulps yields a corrected polymorphic transformation order and enables the quantitative description to be made of the cellulose lattice conversion process as a system consisting of three participating forms of cellulose: crystalline cellulose I, amorphous cellulose and cellulose II.

1 - 12 of 12
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