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EP-4735674-A1 - A METHOD FOR FORMING A FILAMENT COMPRISING CROSS-LINKED FIBERS AND A FILAMENT

EP4735674A1EP 4735674 A1EP4735674 A1EP 4735674A1EP-4735674-A1

Abstract

A method for forming a filament comprising cross-linked fibers, the method comprising providing an aqueous suspension comprising at least natural non-modified microfibrillated cellulose (MFC) fibers and a dichlorotriazine-based crosslinker as a cross-linking agent, and drying the aqueous suspension to form at least one filament, wherein the filament comprises at least 50 % wt. preferably at least 70 % wt, MFC.

Inventors

  • KIM, EUNYOUNG
  • VENTO, PIA
  • SETÄLÄ, Harri

Assignees

  • Spinnova Oyj

Dates

Publication Date
20260506
Application Date
20240627

Claims (19)

  1. 1. A method for forming a filament comprising cross-linked fibers, the method comprising - providing an aqueous suspension comprising at least natural nonmodified microfibrillated cellulose (MFC) fibers and a dichlorotriazinebased crosslinker as a cross-linking agent, and - drying the aqueous suspension to form at least one filament, wherein the filament comprises at least 50 % wt. preferably at least 70 % wt, MFC.
  2. 2. The method of any previous claim, comprising adjusting an initial pH of the suspension comprising MFC, before adding said cross-linking agent, using a base until the pH of the suspension is 7-12, such as 8- 11.
  3. 3. The method of any previous claim, wherein the amount of cross-linking agent is 0.1-10 % wt, such as 0.5-7 % wt, or 3-5 % wt of the dried filament.
  4. 4. The method of claim 3, wherein the amount of cross-linking agent is selected based on the MFC-type and associated hemicellulose content of the MFC, such that the amount of crosslinking agent is decreased with increasing amount of hemicellulose content.
  5. 5. The method of claim 4, wherein if the hemicellulose content of the MFC is under 5% wt of the dry weight of the MFC, the amount of crosslinking agent is between 2-8% wt, such as 3-5 % wt of the dried filament, and if the hemicellulose content of the MFC is over 5% wt, such as over 10% wt of the dry weight of the MFC, the amount of crosslinking agent is under 2% wt, such as about 1 % wt of the suspension.
  6. 6. The method of any previous claim, the method comprising providing the aqueous suspension with selected components in a selected adding order.
  7. 7. The method of claim 6, wherein the selected components comprise at least MFC, at least one base, such as NaOH, the at least one crosslinking agent, at least one strength resin, optionally polyamideamine- epichlorohydrin (PAE), anionic polyacrylamide (APAM), and/or glyoxalated polyacrylamide (GPAM), optionally at least one hydrophobic adhesive, such as alkyl ketene dimer (AKD), and optionally at least one dispersion agent, such as carboxymethylcellulose (CMC).
  8. 8. The method of claim 7, wherein the selected adding order is: MFC, the at least one base, the at least one cross-linking agent, the at least one wet-strength resin, optionally hydrophobic adhesive, optionally dispersion agent, and optionally a further wet-strength resin.
  9. 9. The method of claim 7 or claim 8, wherein the selected components and adding order comprises: MFC, NaOH, cross-linking agent, PAE, CMC, and APAM.
  10. 10. The method of any previous claim, wherein the cross-linking agent is 2- sodium hydroxy-4, 6-dichloro-1 ,3,5-triazine.
  11. 11. The method of any previous claim, wherein the filament is formed by extruding the aqueous suspension through a nozzle to form a filament comprising cross-linked fibers.
  12. 12. The method of any previous claim, additionally comprising a curing step, wherein the filament is subjected to a selected temperature for a selected time period to heat the filament after drying.
  13. 13. The method of claim 12, wherein said selected temperature is 70-200 °C, preferably 80-150 °C.
  14. 14. The method of claim 12 or claim 13, wherein said selected time period is 1-60 minutes, preferably 5-30 minutes.
  15. 15. The method of any previous claim, additionally comprising a humidifying step, wherein the filament is subjected to a selected relative humidity for a selected time period after drying.
  16. 16. The method of claim 15, wherein said selected relative humidity is 10- 80%, preferably 50-70%, more preferably 60-65%.
  17. 17. The method of claim 15 or claim 16, wherein said selected time period is at least 10 days, such as at least 1-15 days, or at least 3-6 days, preferably at least 4-5 days.
  18. 18. The method of any previous claim 1-11 , additionally comprising a combined humidifying and curing step, wherein the filament is subjected to a selected temperature and selected relative humidity for a selected time period, optionally wherein the combined humidifying and curing step comprises subjecting the filament to steam, comprising temperature of 80-150 °C, preferably 100-120 °C, relative humidity of 50-70%, preferably 60-65%, and for a time period of 5 minutes to 6 days, preferably 4-5 days.
  19. 19. A filament produced by the method of any previous claim.

Description

A METHOD FOR FORMING A FILAMENT COMPRISING CROSS-LINKED FIBERS AND A FILAMENT TECHNICAL FIELD OF THE INVENTION The invention relates to fiber suspensions and filaments in general. More specifically, the invention relates to a method for forming a filament comprising cross-linked fibers and a filament. BACKGROUND OF THE INVENTION In processes relating to manufacture of e.g. filaments to be utilized in for instance woven fabric production, where the filaments can be made from a fiber suspension, the properties of the formed filaments are important to ensure that the end product has desired properties and/or that the processing of the filaments is manageable or according to appropriate specifications. It is especially advantageous to obtain filaments that have a high tenacity (wet and/or dry) and/or high elongation. These are characteristics that provide strength to the filaments and may make processing them easier and/or may give end products such as fabrics that are resilient to wear and tear. Alkali resistance is another quality that is preferred to be improved, as chemicals utilized in washing products are usually alkalic. In the prior art, fiber suspensions and methods for producing filaments from such exist, where cross-linking chemicals are used to improve some property of the suspension or formed filaments. In these methods, fibers in the cellulose suspensions are cross-linked to each other. Cross-linked cellulose fibers are typically made by reacting cellulose with multifunctional agents that are capable of reacting with the hydroxyl groups of the anhydroglucose repeating units of the cellulose either in the same chain, or in neighboring chains simultaneously. Formaldehyde and urea-formaldehyde products were among the first agents used to cross-link cellulosic fibers. Formaldehyde, however, has many adverse effects on health and is a known human carcinogen. Monomers having multifunctional groups, such as carboxylic acid groups and aldehyde groups, have also been used as cross-linking agents for cellulosic fibers. For example, alkanepolycarboxylic acids are capable of cross-linking cellulose fibers by forming an ester bond with the fiber's hydroxyl groups. One problem associated with the use of alkanepolycarboxylic acid is that the cellulosic fibers cross-linked thereby tend to lose their cross-linking upon storage, and revert to un-cross-linked fibers. Some methods are also known where cross-linking of fibers is carried out not in the fiber suspension but as a post-processing or finishing step on a formed filament. These methods may especially be related to properties of the filament affecting the appearance of e.g. fabric, such as reduction of pilling, by applying chemicals to a formed filament to reduce the pilling or aid in giving an appearance of a cleaner surface by removing split fibrils e.g. via enzymatic treatments. It would be advantageous to discover a cross-linking agent to be used in a fiber suspension, where a formed filament may be provided with selected characteristics, where the cross-linking agent would advantageously provide several different desired characteristics. The use of cross-linking agents that are not harmful for the environment or humans is desirable, while preferably also enabling a method for forming filaments that is easy, effective, and may be carried out in an environmentally friendly manner. SUMMARY OF THE INVENTION The object of the invention is to alleviate at least some of the problems in the prior art. In accordance with one aspect of the present invention, a method is provided for forming a filament comprising cross-linked fibers, the method comprising - providing an aqueous suspension comprising at least natural nonmodified microfibrillated cellulose (MFC) fibers and a dichlorotriazinebased crosslinker as a cross-linking agent, and - drying the aqueous suspension to form at least one filament, wherein the filament comprises at least 50 % wt. preferably at least 70 % wt, MFC. Through embodiments of the invention, filaments may be formed where the fibers are cross-linked to provide one or more selected qualities. The selected qualities may be related to wet and/or dry tenacity and/or elongation (or a combined property, such as workability, which will be considered further below), alkali resistance, and/or dye affinity, for instance. Through the present invention, filaments may have a higher wet tenacity as compared to prior art filaments, while maintaining a dry tenacity that is similar to that of the prior art or does not differ from it at least more than a threshold amount. It is known that many cross-linking agents that increase wet tenacity of a filament will simultaneously decrease the dry tenacity, which may be undesirable. Improved alkali resistance may be provided, which is beneficial as during textile processing, filaments may be subjected to NaOH or alkalic conditions. With the present invention, a formed filament may not dissolve in alkalic conditi