The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Kari Rissanen - One of the best experts on this subject based on the ideXlab platform.
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the conversion from cellulose i to cellulose ii in naoh mercerization performed in alcohol water systems an x ray powder diffraction study
Carbohydrate Polymers, 2007Co-Authors: Paavo Mansikkamaki, Manu Lahtinen, Kari RissanenAbstract:Abstract The slurry-mercerization (SM) processes in 2-propanol–water and 2-propanol–ethanol–water and wet-mass-mercerization (WMM) process in ethanol–water solvents are investigated. Based on X-ray diffraction measurements in the earlier reports, we have derived a mathematical method to evaluate more exactly the conversion of cellulose I (CI) to cellulose II (CII) and used it to survey the effects of different alkali treatments on cellulose crystals. This method is very useful when the crystal system changes in a certain set of experiments are compared with each other. The optimal alcohol concentration in SM processes was found to be 80–92 w/w-% in 2-propanol–water solution, 85–90 w/w-% in 2-propanol–ethanol–water solution and 45–55 w/w-% in the WMM process. In the WMM mercerization, the effect of the solvent/cellulose ratio showed that the conversion to CII increased linearly with a decreasing solvent/cellulose ratio. Temperature increase, as well as higher lye concentration, had a positive effect on the conversion of CI to CII. This study confirms also our earlier results that the concentration of soluble lye in the used solvent system is the most important factors in the mercerization of cellulose.
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Structural Changes of Cellulose Crystallites Induced by Mercerisation in Different Solvent Systems; Determined by Powder X-ray Diffraction Method
Cellulose, 2005Co-Authors: Paavo Mansikkamaki, Manu Lahtinen, Kari RissanenAbstract:The completeness of Mercerisation can be evaluated by investigating the changes in the crystalline regions of cellulose from cellulose I (C-I) to cellulose II (C-II) by the X-ray powder diffraction method. Mercerisation experiments in four different solution systems: ethanol/water, acetone, DMSO and xylene, are reported. Also the effect of some additives, external pressure, treatment time and alkalisation temperature were studied. In two-phase solvent systems, structural changes of cellulose crystallites depended primarily on the distribution and solubility of sodium hydroxide in the solvent phases. The sodium hydroxide concentration in the hydrophilic phase must exceed 7–8 w/w-% before complete crystal change from C-I to C-II can occur. The precipitation of sodium hydroxide due to high concentration prevents the successful use of one-phase ethanol/water system in slurry process. On the contrary, the 2-propanol/water/sodium hydroxide system separates into two layers; to the water-rich lower layer and the 2-propanol-rich upper layer, where the sodium hydroxide remains mainly in the water-rich lower layer. This prevents the precipitation of sodium hydroxide and promotes the alkalisation of cellulose. Ammonium chloride and ammonium hydroxide clearly had a positive effect by promoting the crystal changes, however, the urea concentration used in this study was obviously too small. In the advantageous two-phase 2-propanol/water systems, the alkalisation time was only 15 min when the treatment temperature was kept between 0 and 10 °C. Reduced external pressure was found to have a small but still detectable positive effect on cellulose alkalisation while over-pressure prevented crystal changes.
Paavo Mansikkamaki - One of the best experts on this subject based on the ideXlab platform.
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the conversion from cellulose i to cellulose ii in naoh mercerization performed in alcohol water systems an x ray powder diffraction study
Carbohydrate Polymers, 2007Co-Authors: Paavo Mansikkamaki, Manu Lahtinen, Kari RissanenAbstract:Abstract The slurry-mercerization (SM) processes in 2-propanol–water and 2-propanol–ethanol–water and wet-mass-mercerization (WMM) process in ethanol–water solvents are investigated. Based on X-ray diffraction measurements in the earlier reports, we have derived a mathematical method to evaluate more exactly the conversion of cellulose I (CI) to cellulose II (CII) and used it to survey the effects of different alkali treatments on cellulose crystals. This method is very useful when the crystal system changes in a certain set of experiments are compared with each other. The optimal alcohol concentration in SM processes was found to be 80–92 w/w-% in 2-propanol–water solution, 85–90 w/w-% in 2-propanol–ethanol–water solution and 45–55 w/w-% in the WMM process. In the WMM mercerization, the effect of the solvent/cellulose ratio showed that the conversion to CII increased linearly with a decreasing solvent/cellulose ratio. Temperature increase, as well as higher lye concentration, had a positive effect on the conversion of CI to CII. This study confirms also our earlier results that the concentration of soluble lye in the used solvent system is the most important factors in the mercerization of cellulose.
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Structural Changes of Cellulose Crystallites Induced by Mercerisation in Different Solvent Systems; Determined by Powder X-ray Diffraction Method
Cellulose, 2005Co-Authors: Paavo Mansikkamaki, Manu Lahtinen, Kari RissanenAbstract:The completeness of Mercerisation can be evaluated by investigating the changes in the crystalline regions of cellulose from cellulose I (C-I) to cellulose II (C-II) by the X-ray powder diffraction method. Mercerisation experiments in four different solution systems: ethanol/water, acetone, DMSO and xylene, are reported. Also the effect of some additives, external pressure, treatment time and alkalisation temperature were studied. In two-phase solvent systems, structural changes of cellulose crystallites depended primarily on the distribution and solubility of sodium hydroxide in the solvent phases. The sodium hydroxide concentration in the hydrophilic phase must exceed 7–8 w/w-% before complete crystal change from C-I to C-II can occur. The precipitation of sodium hydroxide due to high concentration prevents the successful use of one-phase ethanol/water system in slurry process. On the contrary, the 2-propanol/water/sodium hydroxide system separates into two layers; to the water-rich lower layer and the 2-propanol-rich upper layer, where the sodium hydroxide remains mainly in the water-rich lower layer. This prevents the precipitation of sodium hydroxide and promotes the alkalisation of cellulose. Ammonium chloride and ammonium hydroxide clearly had a positive effect by promoting the crystal changes, however, the urea concentration used in this study was obviously too small. In the advantageous two-phase 2-propanol/water systems, the alkalisation time was only 15 min when the treatment temperature was kept between 0 and 10 °C. Reduced external pressure was found to have a small but still detectable positive effect on cellulose alkalisation while over-pressure prevented crystal changes.
Ulf Germgård - One of the best experts on this subject based on the ideXlab platform.
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The influence of the solvent system used during manufacturing of CMC
Cellulose, 2006Co-Authors: Veronica Stigsson, Göran Kloow, Ulf GermgårdAbstract:The influence of the solvent system used during the CMC manufacturing on the characteristics of CMC in different solutions was studied by producing CMC in ethanol, isopropanol or a mixture thereof. This paper shows that the solvent system used has an impact on the substituent pattern and this is especially the case during the Mercerisation. When isopropanol is used in comparison with ethanol the distribution of the substituents along the cellulose backbone becomes more uneven and the amount of tri-substituted glucose units increases as well as the number the amount of substituents on the C-6 position. This affects the behaviour of CMC when dissolved in different electrolyte solutions.
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The Influence of Cobalt (II) in Carboxymethyl Cellulose Processing
Cellulose, 2005Co-Authors: Veronica Stigsson, Göran Kloow, Ulf Germgård, Niclas AnderssonAbstract:Controlling the reduction in molecular weight of the cellulose chains is essential in the production of carboxymethyl cellulose (CMC). Such a reduction can be achieved by the addition of cobalt during the process of cobalt(II) ions, which act as a catalyst for oxidative cleavage, and the influence thereof has been studied under a variety of conditions. This study has resulted in a model that summarises the effects of the added amount of cobalt, the time for the cobalt reaction, the temperature in the Mercerisation stage of the CMC-manufacturing process and finally the effect of the temperature in the etherification stage. It is shown that it is important for cobalt to be present during the Mercerisation stage in order to achieve the desired viscosity.
Manu Lahtinen - One of the best experts on this subject based on the ideXlab platform.
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the conversion from cellulose i to cellulose ii in naoh mercerization performed in alcohol water systems an x ray powder diffraction study
Carbohydrate Polymers, 2007Co-Authors: Paavo Mansikkamaki, Manu Lahtinen, Kari RissanenAbstract:Abstract The slurry-mercerization (SM) processes in 2-propanol–water and 2-propanol–ethanol–water and wet-mass-mercerization (WMM) process in ethanol–water solvents are investigated. Based on X-ray diffraction measurements in the earlier reports, we have derived a mathematical method to evaluate more exactly the conversion of cellulose I (CI) to cellulose II (CII) and used it to survey the effects of different alkali treatments on cellulose crystals. This method is very useful when the crystal system changes in a certain set of experiments are compared with each other. The optimal alcohol concentration in SM processes was found to be 80–92 w/w-% in 2-propanol–water solution, 85–90 w/w-% in 2-propanol–ethanol–water solution and 45–55 w/w-% in the WMM process. In the WMM mercerization, the effect of the solvent/cellulose ratio showed that the conversion to CII increased linearly with a decreasing solvent/cellulose ratio. Temperature increase, as well as higher lye concentration, had a positive effect on the conversion of CI to CII. This study confirms also our earlier results that the concentration of soluble lye in the used solvent system is the most important factors in the mercerization of cellulose.
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Structural Changes of Cellulose Crystallites Induced by Mercerisation in Different Solvent Systems; Determined by Powder X-ray Diffraction Method
Cellulose, 2005Co-Authors: Paavo Mansikkamaki, Manu Lahtinen, Kari RissanenAbstract:The completeness of Mercerisation can be evaluated by investigating the changes in the crystalline regions of cellulose from cellulose I (C-I) to cellulose II (C-II) by the X-ray powder diffraction method. Mercerisation experiments in four different solution systems: ethanol/water, acetone, DMSO and xylene, are reported. Also the effect of some additives, external pressure, treatment time and alkalisation temperature were studied. In two-phase solvent systems, structural changes of cellulose crystallites depended primarily on the distribution and solubility of sodium hydroxide in the solvent phases. The sodium hydroxide concentration in the hydrophilic phase must exceed 7–8 w/w-% before complete crystal change from C-I to C-II can occur. The precipitation of sodium hydroxide due to high concentration prevents the successful use of one-phase ethanol/water system in slurry process. On the contrary, the 2-propanol/water/sodium hydroxide system separates into two layers; to the water-rich lower layer and the 2-propanol-rich upper layer, where the sodium hydroxide remains mainly in the water-rich lower layer. This prevents the precipitation of sodium hydroxide and promotes the alkalisation of cellulose. Ammonium chloride and ammonium hydroxide clearly had a positive effect by promoting the crystal changes, however, the urea concentration used in this study was obviously too small. In the advantageous two-phase 2-propanol/water systems, the alkalisation time was only 15 min when the treatment temperature was kept between 0 and 10 °C. Reduced external pressure was found to have a small but still detectable positive effect on cellulose alkalisation while over-pressure prevented crystal changes.
Veronica Stigsson - One of the best experts on this subject based on the ideXlab platform.
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The influence of the solvent system used during manufacturing of CMC
Cellulose, 2006Co-Authors: Veronica Stigsson, Göran Kloow, Ulf GermgårdAbstract:The influence of the solvent system used during the CMC manufacturing on the characteristics of CMC in different solutions was studied by producing CMC in ethanol, isopropanol or a mixture thereof. This paper shows that the solvent system used has an impact on the substituent pattern and this is especially the case during the Mercerisation. When isopropanol is used in comparison with ethanol the distribution of the substituents along the cellulose backbone becomes more uneven and the amount of tri-substituted glucose units increases as well as the number the amount of substituents on the C-6 position. This affects the behaviour of CMC when dissolved in different electrolyte solutions.
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The Influence of Cobalt (II) in Carboxymethyl Cellulose Processing
Cellulose, 2005Co-Authors: Veronica Stigsson, Göran Kloow, Ulf Germgård, Niclas AnderssonAbstract:Controlling the reduction in molecular weight of the cellulose chains is essential in the production of carboxymethyl cellulose (CMC). Such a reduction can be achieved by the addition of cobalt during the process of cobalt(II) ions, which act as a catalyst for oxidative cleavage, and the influence thereof has been studied under a variety of conditions. This study has resulted in a model that summarises the effects of the added amount of cobalt, the time for the cobalt reaction, the temperature in the Mercerisation stage of the CMC-manufacturing process and finally the effect of the temperature in the etherification stage. It is shown that it is important for cobalt to be present during the Mercerisation stage in order to achieve the desired viscosity.