| 1. |
|
|
| 2. |
- Lund, Kristoffer, 1983, et al.
(författare)
-
Diepoxide treatment of softwood kraft pulp: influence on absorption properties of fibre networks
- 2011
-
Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 18:5, s. 1365-1375
-
Tidskriftsartikel (refereegranskat)abstract
- Many different approaches to the introduction of intra-fibre cross-links in fibres for use in absorption products are described in the patent literature, but relatively little has been done in terms of academic research. In this study, the long fibre fraction of a Scandinavian softwood kraft pulp has been cross-linked with the diepoxide 1,4-butanediol diglycidyl ether (BDDE). The fibre properties and the performance of the pulp in low density fibre networks were analyzed. In experiments, the cross-linking agent (BDDE) was dissolved in acetone and then mixed with the pulp. It was shown that a prior wash with NaOH (0.1 M) activates the polysaccharides and increases the extent of cross-linking, detected as a decrease in the water retention value. Chemical analysis of modified fibres also gave a clear indication of that cross-linking reactions actually occurred. The pulp properties could furthermore be influenced by varying time, temperature and the amount of BDDE in the reaction. It was also shown that it is possible to use water as a solvent for the cross-linking agent, even though the reactivity of water towards diepoxide must be considered to be high. The cross-linked pulps showed wet bulk under load comparable to that of the mechanical pulps and enhanced properties than unmodified Scandinavian softwood kraft pulp. It was also observed that fibre network test pads of the cross-linked pulp fibres, after being tested in the wet state, regained a substantially large part of their low-density structure when air-dried.
|
|
| 3. |
|
|
| 4. |
- Wernersson Brodin, Fredrik, 1983, et al.
(författare)
-
Reinforced absorbent material: a cellulosic composite of TEMPO-oxidized MFC and CTMP fibres
- 2012
-
Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 19:4, s. 1413-1423
-
Tidskriftsartikel (refereegranskat)abstract
- This research aims to develop new materials based on renewable resources that can fulfill the functions necessary in the absorption core of a disposable diaper. Absorbent foam was recently produced from softwood kraft pulp by TEMPO oxidation, disintegration and freeze drying. In this study, the TEMPO-oxidized MFC was mixed with pulp fibres, thus forming a cellulosic composite, in an attempt to improve the mechanical stability of the freeze-dried absorbent material. The fibres were added in different amounts and the freeze-dried materials were evaluated for their absorption and retention properties. The results of this study suggest that the composite material has a better mechanical stability than the absorbent foam without fibres. It was shown that using spruce CTMP fibres in the composite resulted in better absorption and retention capacities than in a composite with softwood kraft pulp fibres. The higher stiffness of the CTMP fibres is a probable explanation for this difference. For the composite material with CTMP fibres, liquid porosimetry showed that pore size distribution was more or less retained when put under load. Furthermore, it was seen that the retention properties reached a maximum around 85 % CTMP fibres and 15 % TEMPO-oxidized MFC. In the centrifuge retention test, the retention of the TEMPO-oxidized MFC in the composite material reached about the same capacity as conventional superabsorbent polymers.
|
|
| 5. |
- Köhnke, Tobias, 1978, et al.
(författare)
-
Kraft pulp hornification: A closer look at the preventive effect gained by glucuronoxylan adsorption
- 2010
-
Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 81:2, s. 226-233
-
Tidskriftsartikel (refereegranskat)abstract
- Xylan is known to adsorb irreversibly on cellulose and on bleached kraft pulp fibres. This investigation shows that adsorption of birch glucuronoxylan (GX) reduces the degree of drying-induced property changes of bleached softwood kraft pulp fibres. GX was adsorbed at different amounts on never-dried fibres, which provided pulps with xylan contents ranging from 67 to 126 mg/g. By fluorescent labelling of the GX, followed by adsorption and subsequent imaging using confocal laser scanning microscopy, it was concluded that GX adsorbs on fibril surfaces throughout the fibre wall with enrichment on the outer fibre surface. Adsorption of GX before drying preserved a considerable part of the fibre-swelling (water retention value and fibre saturation point), specific fibre surface area, and wet fibre flexibility observed in the never-dried state. It is therefore suggested that GX adsorption reduces the degree of drying-induced fibre wall cross-linking. The use of GX as a hornification inhibitor would provide once-dried pulps with increased tensile strength and beatability.
|
|
| 6. |
- Lund, Kristoffer, 1983, et al.
(författare)
-
1,2,3,4-Butanetetracarboxylic Acid Cross-Linked Softwood Kraft Pulp Fibers for Use in Fluff Pulp Applications
- 2014
-
Ingår i: Journal of Engineered Fibers and Fabrics. - : SAGE Publications. - 1558-9250. ; 9:3, s. 142-150
-
Tidskriftsartikel (refereegranskat)abstract
- Cross-linked fluff pulp fibers for use in, for example, acquisition layers in absorption products can be found in the patent literature. Cross-linking improves properties such as the wet resilience of fluff pulp fiber networks. Among the more commonly seen cross-linkers are polycarboxylic acids, such as 1,2,3,4-butanetetracarboxylic acid (BTCA). These acids form ester bonds with the hydroxyl groups in the fiber wall. In this study, softwood kraft pulp fibers were cross-linked with BTCA. The swelling behavior of the fibers and properties related to acquisition in absorption products were studied. It was found that the water retention value (WRV) decreased as a consequence of the introduced crosslinker. After deprotonization of a large part of the introduced carboxylic acids, the WRV increased, but the cross-linker was still able to limit significant swelling of the fiber wall. The wet bulk under load of fiber networks, composed of cross-linked fibers, generally increased with a decrease in WRV. Furthermore, it was found that the property development obtained after a cross-linking reaction with BTCA may be predicted by introducing a relative reaction intensity, RIrel, that takes into account both time and temperature in the curing step. This shows that the time and temperature in the curing step are interchangeable.
|
|
| 7. |
- Lund, Kristoffer, 1983, et al.
(författare)
-
Alkali Extraction of Kraft Pulp Fibers: Influence on Fiber and Fluff Pulp Properties
- 2012
-
Ingår i: Journal of Engineered Fibers and Fabrics. - : SAGE Publications. - 1558-9250. ; 7:2, s. 30-39
-
Tidskriftsartikel (refereegranskat)abstract
- The importance of hemicelluloses for the papermaking properties of pulp fibers is well documented. In the patent literature, it can be seen that there is also an interest in this type of modification of pulp fibers for use in absorption products. In this study, a Scandinavian softwood kraft pulp and a birch kraft pulp were alkali extracted at 3 different concentrations of NaOH (2%, 4% and 8% NaOH in the suspension). The alkali extraction removed a large part of the hemicelluloses from the pulp fibers and decreased the content of the charged groups. After extraction, the pulps were dried in the form of sheets (approx. 600 g/m(2)). The alkali extracted pulp fibers exhibited a greater decrease in swelling when re-wetted than untreated pulp. A significant increase in the curl index after extraction with 4% and 8% NaOH was also noted. The tensile strength index of the formed sheets increased at the lowest concentration of NaOH and, at the higher concentrations, a decrease was observed. The pulp sheets were dry defibrated at different defibration intensities and the performance of the resulting pulps in fluff pulp applications was studied. The air-laid fiber networks of softwood pulp fibers showed higher network strength than the networks of birch pulps. The birch pulp extracted at the highest alkali level tended to give the highest network strength. The results from the network strength tests also indicated that the increased curl of the fibers from the softwood pulp extracted at the highest alkali level rendered a more flexible fiber network. In water absorption tests, the alkali treated softwood fibers tended to give networks with a somewhat enhanced water holding capacity under pressure.
|
|
| 8. |
- Lund, Kristoffer, 1983, et al.
(författare)
-
Kinetics of Cross-Linking Softwood Kraft Pulp with 1,2,3,4-Butanetetracarboxylic Acid
- 2013
-
Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 52:33, s. 11502-11509
-
Tidskriftsartikel (refereegranskat)abstract
- Cross-linking of polysaccharides has been well studied in both the pulp and textile industries. One of the more investigated cross-linking agents is 1,2,3,4-butanetetracarboxylic acid (BTCA). The intrafiber cross-linking of cotton cellulose with BTCA has attracted great interest. In the case of wood pulp, reaction kinetics has been studied relatively little; instead, investigations have focused on fiber and paper properties. In this study, softwood kraft pulp fibers were cross-linked with BTCA, and the kinetics of the reaction was investigated and modeled. It was found that the reaction follows second-order kinetics, dependent on both the concentration of BTCA and the concentration of accessible hydroxyl groups in the fiber wall. It was further found that the initial concentration of accessible hydroxyl groups was proportional to the initial concentration of BTCA, thus simplifying the model into a second-order rate equation dependent only on the concentration of BTCA. A cross-linking reaction was confirmed by performing conductometric titration.
|
|
| 9. |
- Lund, Kristoffer, 1983
(författare)
-
Modification of fluff pulp fibres: Cross-linking and alkali extraction
- 2011
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fluff pulp has been one of the key components of hygienic products, such as diapers, for many years. Fluff pulp is dry defibrated and air-laid into the absorption core of diapers. The introduction of superabsorbent polymers (SAPs) in the 1980s decreased the dependence on fluff pulp, as the SAPs became the main absorbing material. Nevertheless, in order to decrease reliance on oil-based SAPs, it is important to investigate fluff pulp once again. This thesis investigates possibilities for modifying fluff pulp for use in absorption applications.In the first part of the thesis, softwood kraft pulp fibres were modified with a diepoxide in order to introduce cross-links into the fibre wall. Results show that the wet bulk under load of the low-density fibre networks increased as a result of the modification, most likely due to higher fibre stiffness. When the fibre networks were dried after the compression test, the low-density networks with the more extensively modified fibres also regained much of their bulk.In the second part of the thesis, a softwood kraft pulp and a birch kraft pulp were alkali extracted at 3 different concentrations of NaOH (2%, 4% and 8% NaOH in suspension). The extraction was done in order to remove hemicelluloses from the fibre walls. The pulps were then dried in sheet form. Sheets were also dry defibrated and air-laid to investigate the performance of the pulps in fluff pulp applications. It could be seen that the extent of hornification of the once-dried fibres increased with increasing concentration of NaOH. Further, the tensile strength index of the sheets increased when the fibres were treated with 2% NaOH, and decreased at the two highest concentrations. The birch pulp treated with 8% NaOH had a low amount of knots after defibration. This was related to the low tensile strength index of that pulp, indicating an importance of fibre-fibre bond strength on ease of defibration. The network strength of dry defibrated and air-laid softwood pulp treated with 8% NaOH was lower than the softwood pulps treated with 0%, 2% and 4% NaOH, which was most likely an effect of the high curl index of that pulp. The network strength of the birch pulps was lower than in the softwood pulps. The network strength of the birch pulps also correlated well with the amount of knots in the pulps.
|
|
| 10. |
|
|
