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| 2. |
- Määttänen, Marjo, et al.
(författare)
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Pre-treatments of pre-consumer cotton-based textile waste for production of textile fibres in the cold NaOH(aq) and cellulose carbamate processes
- 2021
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 28, s. 3869-3886
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Tidskriftsartikel (refereegranskat)abstract
- Recycling of textiles is of importance due to the large amount of waste generated from the increasing consumption and use worldwide. Cotton-rich pre-consumer textiles are considered as potential raw material for production of man-made regenerated fibres, but demands purification from the blends with synthetic fibres as well as the dyes and finishing chemicals. In this study we explore the use of different pre-treatments of pre-consumer textiles to meet specific parameters for production of fibres in the cold NaOH(aq) or cellulose carbamate process. The pre-treatments consisted of different bleaching sequences and were performed on both uncoloured and coloured pre-consumer textiles. For the uncoloured textile, degree of polymerisation and amount of inorganic content was efficiently reduced making the material suitable for both the cold NaOH(aq) and the cellulose carbamate process. In case of the coloured textile, the pre-treatments were able to remove the dye and decrease the inorganic content as well as reduce the degree of polymerisation but only sufficiently enough for production of fibres in the cellulose carbamate process. The work was able to prove a fibre-to-fibre concept while further optimisation of the regeneration steps is expected to improve the mechanical properties of the produced fibres in future studies.
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| 3. |
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| 4. |
- Sevasyanova, Olena, et al.
(författare)
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Tailoring the Molecular and Thermo-Mechanical Properties of Kraft Lignin by Ultrafiltration
- 2014
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 131:18, s. 9505-9515
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Tidskriftsartikel (refereegranskat)abstract
- This study has shown that ultrafiltration allows the selective extraction from industrial black liquors of lignin fraction with specific thermo-mechanical properties, which can be matched to the intended end uses. Ultrafiltration resulted in the efficient fractionation of kraft lignin according to its molecular weight, with an accumulation of sulfur-containing compounds in the low-molecular weight fractions. The obtained lignin samples had a varying quantities of functional groups, which correlated with their molecular weight with decreased molecular size, the lignin fractions had a higher amount of phenolic hydroxyl groups and fewer aliphatic hydroxyl groups. Depending on the molecular weight, glass-transition temperatures (T-g) between 70 and 170 degrees C were obtained for lignin samples isolated from the same batch of black liquor, a tendency confirmed by two independent methods, DSC, and dynamic rheology (DMA). The Fox-Flory equation adequately described the relationship between the number average molecular masses (M-n) and T-g's-irrespective of the method applied. DMA showed that low-molecular-weight lignin exhibits a good flow behavior as well as high-temperature crosslinking capability. Unfractionated and high molecular weight lignin (M-w > 5 kDa), on the other hand, do not soften sufficiently and may require additional modifications for use in thermal processings where melt-flow is required as the first step.
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| 5. |
- Wedin, Helena, 1981-
(författare)
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Aspects of extended impregnation kraft cooking for high-yield pulping of hardwood
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The long-term trend regarding wood is an increase in price. Because wood contributes to a large part of production costs, the efficient utilisation of wood is greatly desired to reduce production costs for kraft pulp producers. During the 1990s, the development of improved modified kraft cooking began, which led to higher yields. There was also a trend of terminating kraft cooking at a higher kappa number to maximise the overall yield. For hardwood, the defibration point became a critical setback in allowing this termination at a high kappa number. This thesis discusses how this issue has been tackled in the laboratory by using improved modified kraft cooking combined with extended impregnation to enable a decrease in reject content and shift the defibration point towards a higher kappa number for hardwood. This lab concept is referred to as extended impregnation kraft cooking (EIC), and this thesis reveals that EIC cooking efficiently reduces the reject content for both birch and eucalypt. By using EIC cooking, the defibration point was shifted to a kappa number of ca. 30 from ca. 20 using conventional kraft cooking. This study demonstrates the great potential for achieving a higher overall yield for eucalypt by terminating the EIC cooking at a high kappa number, but with the conditions used in this thesis, no improvement in yield was observed for birch. An important issue is that the termination of kraft cooking at high kappa number increases the demand for extended oxygen delignification to reach a similar kappa number into bleaching, i.e., due to cost and environmental reasons. Extended oxygen delignification was shown to be possible for both birch and eucalypt EIC pulps (i.e., from kappa number 27 to 10) with an acceptable pulp viscosity number. The other part of this thesis addresses aspects regarding the limitations in oxygen delignification. It has previously been shown in the literature that a high xylan yield of kraft cooking could negatively affect the efficiency of subsequent oxygen delignification. In this work, the increased xylan content in eucalypt kraft pulp within the range of 8–18% had only a marginally negative impact on the oxygen delignification efficiency after correcting for the HexA contribution to the kappa number. It is also desired to extend the oxygen delignification towards lower kappa number, i.e., below kappa number 10 to decrease the bleaching chemical requirement. In this study, the hypothesis that the reduced efficiency of oxygen delignification at low kappa numbers could partly be due to the formation of oxidisable carbohydrate-related structures (i.e., HexA and/or other non-lignin structures) was also tested. No formation was established. On the other hand, a final oxygen delignification stage in the bleaching could be an attractive alternative for reducing yellowing and enhancing brightness; in fact, this has led to the development of a patent (SE 528066).
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| 6. |
- Wedin, Helena, et al.
(författare)
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Evaluation of dyeing and finishingcomponents in recycling and regeneration ofcoloured textiles prototypes
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The ability to create secondary raw materials with low impurity content is importantfrom a fibre regeneration processing perspective. Cotton textiles contain colourantsand textile finish, which can be considered as impurities in a chemical recyclingprocess. Removal of such impurities in a decolourisation stage would enhance the fibredissolving capacity and stabilise and simplify the fibre regeneration process.Moreover, the removal of impurities from secondary raw materials is also importantfrom an environmental and health perspective. Chemical recycling has the potentialto deal with the risk of retaining or spreading hazardous substances further inre-circulated textile loops. Of specific concern are colourants or additives withcarcinogenic or endocrine disruptive attributes as well as bioaccumulative substancessuch as PFAS (per- and polyfluoroalkyl substances), which are commonly used intextiles for dirt and water repellency.This report describes an experimental evaluation of physical properties of decolourisedcotton regenerated into viscose fibres and an analysis of potentially hazardous textilefinish components throughout a decolourisation approach. The three main researchquestions in this report are:1. Can we obtain viscose fibres from a decolourised black cotton fabric withsimilar physical properties as commercial viscose fibres by using the re:newcelldecolourisation approach?2. Can the impact from a DMeDHEU(1) anti-wrinkle and a fatty acid softener finish onthe physical viscose fibre properties be eliminated using this decolourisation approach?3. Could chemical recycling be a potential solution for recirculation of textiles whichhave a risk of containing hazardous substances of for example PFAS dirt and waterrepellent type?The project has been performed within the Mistra Future Fashion research program byjoint work from re:newcell, MoRe research, Swerea IVF, Swedish School of Textile and RISE,and with support from the companies DyStar®, Lenzing AG, H&M, I:CO, Boob design,Wiges, New Wave Group, Filippa K and Kappahl. The part of the study that concerned thedirt and water repellent was performed in cooperation with the research project SUPFESfunded by the Swedish Research Council for Environment, Agricultural Sciences andSpatial Planning (FORMAS) under grant agreement No. 2012-2148.The study showed that viscose fibres can be produced from decolourised cotton usingthe re:newcell decolourisation approach. However, the desired physical fibre propertieswere not obtained. More optimisation in the decolourisation stage is needed to adapt thecotton substrate for the viscose process.A first indication of the softener to positively affect tenacity of the viscose fibre wasobserved. The anti-wrinkle treated fabric showed a tendency in higher reduced cloggingnumber, but no influence on the physical fibre properties was seen. While caution shouldbe taken in drawing conclusions from the few performed trials, it seems likely that theimpact from the tested types of anti-wrinkle agent and softener on the viscose processcould not be eliminated by the use of the decolourisation approach. This also raisesthe question of how persistent the softener is in a decolourisation process. The resultsfrom the analysis on dirt and water repellent substances (DWR/PFAS) throughout thedecolourisation process showed that one third remained in the pulp. This suggests thatthe DWR binds to the fibres in a way which the decolourisation process is not able toreverse.Taken together, these results are not sufficient to prove the hypothesis of whetherchemical recycling could be a potential solution for recirculation of textiles with risk forcontaining hazardous substances of this sort.The trials lead to the following conclusions: The used decolourisation approach haspotential to remove the type of reactive dye, wrinkle-free agent and softener tested inthis study. Adaption of the decolourisation process for the cotton substrate is neededin further trials. In the specific case of cotton flows with presence of dirt and waterrepellent finish we recommend designing of another decolourisation approach.
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| 7. |
- Wedin, Helena, et al.
(författare)
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Evaluation of post-consumer cellulosic textile waste for chemical recycling based on cellulose degree of polymerization and molar mass distribution
- 2019
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Ingår i: Textile research journal. - : SAGE Publications Ltd. - 0040-5175 .- 1746-7748. ; 89:23-24, s. 5067-5075
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study is to improve the understanding of which end-of-life cellulosic textiles can be used for chemical recycling according to their composition, wear life and laundering—domestic versus service sector. For that purpose, end-of-life textiles were generated through laboratorial laundering of virgin fabrics under domestic and industrial conditions, and the cellulose content and its intrinsic viscosity and molar mass distribution were measured in all samples after two, 10, 20, and 50 laundering cycles. Results presented herein also address the knowledge gap concerning polymer properties of end-of-life man-made cellulosic fabrics—viscose and Lyocell. The results show that post-consumer textiles from the home consumer sector, using domestic laundering, can be assumed to have a similar, or only slightly lower, degree of polymerization than the virgin textiles (−15%). Post-consumer textiles from the service sector, using industrial laundering, can be assumed to have a substantially lower degree of polymerization. An approximate decrease of up to 80% of the original degree of polymerization can be expected when they are worn out. A higher relative decrease for cotton than man-made cellulosic textiles is expected. Furthermore, in these laboratorial laundering trials, no evidence evolved that the cellulose content in blended polyester fabrics would be significantly affected by domestic or industrial laundering. With respect to molar mass distribution, domestic post-consumer cotton waste seems to be the most suitable feedstock for chemical textile recycling using Lyocell-type processes, although a pre-treatment step might be required to remove contaminants and lower the intrinsic viscosity to 400–500 ml/g. © The Author(s) 2019.
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| 8. |
- Wedin, Helena, et al.
(författare)
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Extended impregnation in the kraft cook : an approach to improve the overall yield in eucalypt kraft pulping
- 2010
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 25:1, s. 7-14
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Tidskriftsartikel (refereegranskat)abstract
- A potential way to improve the overall yield is to terminate the kraft cook at higher kappa number. This method was investigated using Extended Impregnation kraft Cook (EIC). As a reference, kraft pulp manufactured by conventional kraft cooking was used. By utilising the EIC concept, the defibration point in the kraft cook is shifted towards higher kappa numbers, resulting in a lower reject content at a given kappa number. This enables a termination of the ETC cook at higher kappa number. The results show that an overall yield gain of 2.6 percentage units could be achieved using ETC with higher cooking kappa number followed by extended oxygen delignification and bleaching with a D*(OP)D sequence to full brightness. However, the EIC concept at higher cooking kappa number resulted in somewhat higher bleaching chemical requirement. Extended oxygen delignification was shown to be possible to reach as low a kappa number as 10, but a high cooking kappa number is clearly a disadvantage if a high limiting viscosity number after oxygen delignification is required.
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| 9. |
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| 10. |
- Wedin, Helena, et al.
(författare)
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Further insights into extended-impregnation kraft cooking of birch
- 2012
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 27:5, s. 890-899
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Tidskriftsartikel (refereegranskat)abstract
- Extended-impregnation kraft cooking (EIC) is a cooking concept that combines prolonged impregnation with modern improved modified kraft cooking. In the current investigation, the EIC cooking of birch was studied in relation to conventional kraft cooking. Specifically, the reject content and carbohydrate yield retention when terminating at a high cooking kappa number were examined. It was demonstrated that EIC cooking reduced the reject content. Unexpectedly, a high cooking kappa number led to no increase in carbohydrate yield, possibly due to the chemical composition of birch wood and the EIC cook lab procedure. A large amount of liquor was withdrawn after the impregnation, resulting in a loss of dissolved xylan that otherwise could have redeposited on the fibres and contributed to the carbohydrate yield. The effects of EIC cooking on extended oxygen delignification, bleaching chemical requirement in a D(OP)DP sequence, and strength properties were also examined. Compared with conventional lab cooking, EIC cooking resulted in a lower bleaching chemical requirement and similar strength properties.
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