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- Engstrand, Per, Professor, 1955-, et al.
(författare)
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Decrease in strengthalong a process line for SC paper
- 2019
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Ingår i: Fundamental Mechanical Pulp Research Seminar, FMPRS2019, Norrköping, SwedenArranged by Mid Sweden University in cooperatrion with Holmen AB, Valmet AB, AF AB and Treesearch..
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Konferensbidrag (refereegranskat)
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| 4. |
- Parkås, Jim, 1974, et al.
(författare)
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Photoyellowing behavior of non-phenolic lignin models representative of end groups and beta-ether structures
- 2004
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Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 19:2, s. 146-154
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Tidskriftsartikel (refereegranskat)abstract
- Lignin model compounds representative of etherified end groups [(E)-3-(3,4-dimethoxyphenyl)-2-propenl-ol (1), (E)-3-(3,4-dimethoxyphenyl) propenal (2)] and βethers, [1-(3,4-dimethoxyphenyl)-3-hydroxy-2-(2-methoxy- phenoxy)-1-propanone (3), erythiro-1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)- 1,3-propanediol (4)] have been applied to filter paper and subjected to accelerated photoaging with UV/VIS-light. The changes in optical properties were monitored. In case of all the models, the brightness decreased and the b*-value increased as a result of irradiation, which shows that they are sensitive to light simulating sunlight behind window-glass. In the case of the end group models, the photo-products identified were veratraldehyde and veratric acid together with the Z-isomers of the starting materials. In the case of the cinnamyl alcohol 1, photo-oxidation to the cinnamaldehyde 2 was observed. The irradiation of the αt-carbonylic βether 3 resulted in the homolytic cleavage of the CβO bond and a recombination that led to a β-5 dimer [1-(3,4-dimethoxyphenyl)-3-hydroxy-2-(2-hydroxy-3-methoxyphenyl)- 1-propanone] and a β-1 dimer [1-(3,4-dimethoxyphenyl)-3-hydroxy-2-(4- hydroxy-3-methoxyphenyl)-l-propanone]. The monomeric products veratraldehyde, vanillin, acetoveratrone, and 1-(3,4-dimethoxyphenyl)-3-hydroxy-l-propanone were also formed. The only photoproduct conclusively identified in experiments with the arylglycerol-β-aryl ether 4 was veratraldehyde and most of the starting material was unaffected by the irradiation. The addition of a photosensitizer (acetoveratrone) to this type of model prior to irradiation resulted in some increase in discoloration.
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| 7. |
- Paulsson, Magnus, 1966
(författare)
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Light-Induced Yellowing of High-Yield Pulps. The Effect of Acetylation
- 1996
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is a contribution to the understanding of the mechanism of photoyellowing of high-yield pulps. It also gives some general information about the reactivity of different functional groups in lignin towards acetic anhydride. The effect of acetylation on both optical and mechanical properties of unbleached and hydrogen-peroxide-bleached high-yield pulps is also discussed. Acetylation was found strongly to improve the long-term photostability of both unbleached and bleached mechanical pulps at a low extent of derivatization. This was achieved with retained or even considerably improved strength properties (e.g., in the wet state) provided that the paper product instead of the pulp is acetylated. The improved stability towards light was closely related to the decrease in the phenolic hydroxyl content of the pulps as a result of the acetylation treatment. The acetylation of model compounds of the .beta.-guaiacyl ether type and model compounds representative of chromophoric and leucochromophoric structures in lignin was studied to obtain a basis for judging how fast and in which order different functional groups in lignin are derivatized. The results showed that phenolic hydroxyl groups and .gamma.-hydroxyl groups (in both .beta.-O-4 and coniferyl alcohol structures) together with ortho-quinonoid units are easily acetylated. The benzylic hydroxyl groups (in .beta.-O-4 structures) are acetylated more slowly and most of these groups are still present at a moderate extent of derivatization. This suggests that reactions involving photooxidation of free phenolic hydroxyl groups and cleavage of 2-aryloxy-1-arylpropanone structures are important for the light-induced discoloration of lignin-containing materials. Cleavage of arylglycerol .beta.-aryl ether structures is a less probable reaction pathway for chromophore formation during irradiation, at least in the initial stage of yellowing. The results of this work also demonstrate that the light-induced brightness reversion of unbleached and hydrogen-peroxide-bleached high-yield pulps proceeds in a rapid initial phase that is followed by a slower and less detrimental phase. Bleaching with hydrogen peroxide generates structures that make the bleached pulp more sensitive towards light exposure than the unbleached pulp.
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| 9. |
- Terashima, N., et al.
(författare)
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2D-NMR (HSQC) difference spectra between specifically C-13-enriched and unenriched protolignin of Ginkgo biloba obtained in the solution state of whole cell wall material
- 2009
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Ingår i: Holzforschung. - 1437-434X .- 0018-3830. ; 63:4, s. 379-384
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Tidskriftsartikel (refereegranskat)abstract
- In the structural analysis of lignins by C-13-NMR, signal overlap limits definitive assignment and accurate intensity measurement. Selective labeling by C-13-enrichment of a specific carbon in lignin enhances its signal intensity in the spectrum. Further enhancement of the specifically labeled carbons can be realized via difference spectra created from the enriched and unenriched samples. Difference 2D C-13-H-1 correlation (HSQC) NMR spectra, derived from the spectra of specifically C-13-enriched lignin model polymers (so-called dehydrogenation polymers) and their unenriched counterparts, take advantage of the enhanced dispersion afforded by both C-13 and H-1 chemical shifts, diminishing the difficulties arising from the signal-overlap problem and aiding in definitive signal assignments. In this research, protolignin in xylem cell walls was specifically C-13-enriched at all of the individual phenylpropanoid side-chain carbons by feeding C-13-enriched coniferins to growing stems of Ginkgo biloba. The whole xylem fractions containing C-13-enriched and unenriched protolignins were dissolved in a mixture of N-methylimidazole and DMSO, and then acetylated. Solution state 2D-NMR (HSQC) spectra of the acetylated whole cell wall were acquired. Difference spectra between the walls containing C-13-enriched and unenriched lignins afforded simplified 2D spectra in which well-separated signals were assigned exclusively to the specifically enriched carbons. This novel NMR technique provides a useful tool for elucidation of entire protolignin in the cell wall of ginkgo xylem.
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| 10. |
- Walter, Karin, 1974-, et al.
(författare)
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Energy efficient refining of Black spruce TMP by using acid hydrogen peroxide : Part 1. A pilot plant study
- 2009
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Ingår i: Nordic Pulp & Paper Research Journal. - Stockholm : SPCI. - 0283-2631 .- 2000-0669. ; 24:3, s. 255-265
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Tidskriftsartikel (refereegranskat)abstract
- The potential of using acid hydrogen peroxide for lowering the electrical energy consumption during production of Black spruce (Picea mariana) thermomechanical pulp (TMP) was investigated. The chemical system, which consisted of ferrous sulphate, hydrogen peroxide and optionally an enhancer [ethylenediaminetetraacetic acid (sodium salt), 3,4-dimethoxybenzyl (veratryl) alcohol or oxalic acid/sodium oxalate], was evaluated as an inter-stage treatment where the primary refiner was used as a mixer. The approach has the advantage of minimising the capital investment needed for implementation, thus being directly applicable in a thermomechanical pulping process consisting of two or more refiners in series. The results obtained in a pilot plant trial revealed that is was possible to significantly reduce the specific energy consumption by approximately 20-and 35% to a freeness value of 100 ml CSF by using 1 and 2% hydrogen peroxide, respectively. The energy reduction could be obtained without any substantial change in fibre length, fractional composition of the pulp or tensile strength of the paper. The tear strength was slightly reduced however, as was the pulp yield. The major drawback with the acid hydrogen peroxide system was a reduction in brightness by at least 6 brightness units. The addition level of ferrous sulphate was too high and the possibility to reducing the discoloration should be considerable when the chemical system is optimized.
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| 11. |
- Walter, Karin, 1974-, et al.
(författare)
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Energy efficient refining of Black spruce TMP by using acid hydrogen peroxide : Part 2. Washing, chelating and bleaching studies
- 2009
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Ingår i: Nordic Pulp & Paper Research Journal. - Stockholm : SPCI. - 0283-2631 .- 2000-0669. ; 24:3, s. 266-272
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Tidskriftsartikel (refereegranskat)abstract
- The acid hydrogen peroxide system has the potential to significantly reduce the specific energy consumption in the production of softwood thermomechanical pulps (TMPs). A drawback of the chemical system is discoloration of the pulp during refining. The work presented in this study evaluates the possibility to regain the lost brightness by washing, chelating and sodium dithionite or hydrogen peroxide bleaching of the treated pulps. A washing or chelating procedure can reduce the metal ion content of the chemically treated TMPs considerably, though brightness can be increased by a maximum of two ISO units. The amount of iron can be further reduced to a level similar to that of untreated pulps by performing a reducing agent-assisted chelating stage (Q(Y)) with dithionite. The discoloration cannot,, however, be completely eliminated. The brightness decrease-of the treated pulps is thus not only caused by higher iron content in the pulp, but is also dependent on the type of iron compound and/or other coloured compounds connected with the acid hydrogen peroxide treatment. Oxidative bleaching with hydrogen peroxide (P) is more effective than reductive bleaching with sodium dithionite in regaining the brightness lost during the energy reductive treatment. By using a Q(Y) P sequence, a hydrogen peroxide charge of 3.8% was needed to reach an ISO brightness of 75% for the chemically treated pulps. The corresponding hydrogen peroxide charge for the untreated TMP reference was 2.5%.
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| 13. |
- Walter, Karin, 1974-, et al.
(författare)
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Energy-efficient refining of Black spruce TMP using acid hydrogen peroxide
- 2009
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Ingår i: Proceedings - 2009 International Mechanical Pulping Conference, IMPC 2009. - Stockholm : SPCI. - 9789186073404 ; , s. 286-291
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Konferensbidrag (refereegranskat)abstract
- By using Fenton chemistry (hydrogen peroxide, ferrous iron, pH<4) as an inter-stage treatment during production of Black spruce thermomechanical pulp, the specific energy consumption can be reduced by at least 20% to a constant tensile strength. The energy reduction can be achieved with preserved fibre length and cross-sectional dimensions. However, the fibre cross-sectional shape is affected, and fibres of the chemically treated pulps had the highest collapse index. A drawback with the acid hydrogen peroxide system is a decrease in pulp yield and a reduction in brightness. Different approaches for lowering the iron content of the chemically treated pulps prior to bleaching are presented. The discoloration is advantageously reduced (but not completely eliminated) by hydrogen peroxide bleaching.
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