Wash-resistant bioactive cellulose fibre having antibacterial and antiviral properties

Abstract

The invention relates to a cellulosic fibre loaded with a biologically active substance formed by the steps of: a) producing a cellulosic fibre loaded with ion exchanger, b) after-treating the fibre thus produced with an aqueous solution of a metal salt which exhibits antibacterial activity and/or antiviral activity, and c) after-treating the loaded fibre with an aqueous fixing solution to convert the metal salt into a water-insoluble form. The cellulosic fibres thus produced can be used to form textile fabrics, wound dressings, sanitary products, specialty papers, packaging or filter materials.

Claims

1. A method for producing a cellulosic fibre loaded with a biologically active substance, wherein said method comprises of the steps: (a) producing a cellulosic fibre loaded with ion exchanger; (b) after-treating the fibre in step (a) with an aqueous solution of a metal salt which exhibits antibacterial activity and/or antiviral activity; and (c) after-treating the fibre in step (b) with an aqueous fixing solution to convert the metal salt into a water-insoluble form.

2. The method according to claim 1, wherein said metal salt comprises water-soluble silver, copper or zinc salts.

3. The method according to claim 2, wherein said metal salt comprises CuSO.sub.4, AgNO.sub.3 and ZnSO.sub.4.

4. The method according to claim 1, wherein said aqueous fixing solution comprises salts having anions selected from F.sub.−, Cl.sub.−, Br.sup.−, I.sup.−, ClO.sub.3.sup.−, ClO.sub.4.sup.−, CO.sub.3.sup.2−, HCO.sub.3.sup.−, PO.sub.4.sup.3−, HPO.sub.4.sup.2, H.sub.2PO.sub.4.sup.−, S.sup.2−, citrate, and salts of fatty acids.

5. The method according to claim 1, wherein said aqueous fixing solution comprises a base a reducing agent.

6. The method according to claim 5, wherein said base is NaOH or ammonia and said reducing agent is an aldehyde.

7. A cellulosic fibre produced according to the method of claim 1.

8. The cellulosic fibre according to claim 7, further comprising textile fibre, wherein said textile fibre is mixed with said cellulosic fibre to produce textile fabric(s).

9. The cellulosic fibre according to claim 8, wherein said textile fibre comprises polyethylene, polypropylene, polyester, polyamide, polyacrylic or cellulosic fibre.

10. The cellulosic fibre according to claim 7, wherein said cellulosic fibre is used for producing wound dressings, sanitary products, specialty papers, packaging and filter materials.

11. The cellulosic fibre according to claim 7, wherein said cellulosic fibre is used as intrinsic fibre protection for nonwoven filter fabrics and nonwoven geotextile fabrics.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1 shows a spectrum generated by wide-angle X-ray scattering (WAXS) of a fibre loaded with silver ions in which the silver ions were subsequently fixed with sodium chloride (top) and a spectrum of pure silver chloride for comparison (bottom).

[0034] FIG. 2 shows the proportion of copper in an SAP fibre loaded with copper sulfate, with or without fixation by a sodium carbonate solution, according to the number of washes carried out.

[0035] FIG. 3 shows the WAXS spectrum of a fibre which has been loaded with divalent copper ions and then treated with a basic glucose solution (top) and a spectrum of pure copper (I) oxide for comparison (bottom).

EXAMPLES

[0036] The following examples serve to further illustrate the method according to the invention.

[0037] Test methods for determination of element contents and for assessment of antibacterial and antiviral activity of cellulosic fibres:

[0038] The antibacterial effect of the fibres was determined in accordance with test standard DIN EN ISO 20743 “Textiles—Determination of antibacterial activity of textile products” by application of a defined number of bacteria in dilute nutrient solution to the fibres and incubation thereof at 37° C. for 24 h. The bacteria were then detached by means of shaking and the number of surviving bacteria that remained was determined by means of a plating method. From the logarithms of the bacterial cell counts obtained for a sample without an antibacterial finish (control material) and for the antibacterial fibres, the difference was calculated, said difference representing a measure of antibacterial activity, with a log 2 reduction meaning good antibacterial activity and a log 3 reduction meaning very good activity.

[0039] Antiviral activity was determined in accordance with test standard ISO 18184 “Textiles—Determination of antiviral activity of textile products”. To this end, the enveloped bacteriophage phi6 was used as surrogate virus for the human enveloped viruses influenza A or SARS-CoV-2 and applied in a defined number to the fibres and incubated at 25° C. for 2 h. The phages were then detached by means of shaking and the number of surviving phages that remained was determined by means of a plaque titre assay. From the logarithms of the plaque titres obtained for a sample without an antiviral finish (control material) and for the antiviral fibres, the difference was calculated, said difference representing a measure of antiviral activity, with a log 2 reduction meaning low antiviral activity and a log 3 reduction meaning full antiviral activity.

[0040] Copper, silver and. zinc contents were determined by ICP-OES in accordance with DIN EN ISO 11885 after microwave pressure digestion.

[0041] The WAXS measurements were carried out using a BRUKER D8 Advance series instrument equipped with a position-sensitive row detector, in symmetric transmission. Measurement was carried out by using Cu K.sub.α radiation of wavelength λ=0.1542 nm (doublet) with a tube voltage of 40 kV and 40 mA anode current and the K.sub.β portion filtered out. The test specimens prepared were tablets of uniform density and a thickness of 2 mm.

[0042] Chemicals used: [0043] Sodium polyacrylate, cross-linked (CAS: 9033-79-8, PRODUCT T 5066 F, from Evonik) [0044] Copper(II) sulfate pentahydrate (CAS: 7758-99-8, purity ≥98%, from, for example, VWR) [0045] Sodium carbonate (CAS: 497-19-8, purity ≥98%, from, for example, VWR) [0046] Glucose monohydrate (CAS: 14431-43-7, purity ≥98%, from, for example, VWR) [0047] Sodium chloride (CAS number: 7647-14-5, purity ≥98%, from, for example, VWR) [0048] AFILAN® RA (octadecanamide, CAS number: 10220-90-3, from Archroma)

Example 1

[0049] The ion-exchange fibres, produced according to DE19917614 and containing a proportion of 15% sodium polyacrylate, are treated with a copper sulfate solution. To this end, 15 kg of the ion-exchange fibre are washed with deionized water and then loaded with a 0.15 M aqueous copper sulfate solution. After a residence time of 20 min in this solution with intensive stirring, the fibres are spun down and centrifuged. In a second treatment bath, the fibres are finished using a customary softener, for example AFILAN® RA, The fibres have a linear density of 6.7 dtex, an elongation of 10% and a breaking strength of 21 cN/tex. The copper concentration is 28 000 mg/kg copper. After 50 wash cycles, the fibres still contained 200 mg/kg copper. Measurement of the antibacterial effect versus Staphylococcus aureus showed a reduction of log 5.8 and, after 50 wash cycles, log 5.3; versus Klebsiella pneumoniae, there was a reduction of log 5.8 and, after 50 wash cycles, log 5.5. For both bacterial species, this signifies strong antibacterial activity that is still maintained even after 50 wash cycles. Measurement of the antiviral effect against Pseudomonas sp. DSM 21482 revealed a log 3.0 reduction, which corresponds to a strong antiviral effect.

Example 2

[0050] Ion-exchange fibres produced according to Example 1 are, following copper loading, additionally placed in a second immersion bath containing a 10 g/l sodium carbonate solution and stirred therein for 20 minutes. The fibres are then spun down and centrifuged. In a third treatment bath, the fibres are finished according to Example 1. The copper concentration is 26 500 mg/kg copper. After 50 wash cycles, the fibres still contained 10 400 mg/kg copper. Compared to the non-fixed fibre from Example 1, this corresponds to an increase in recovery after 50 washes from approx. 0.7 to approx. 39%.

Example 3

[0051] Ion-exchange fibres produced according to Example 1 are, following copper loading, additionally placed in a second immersion bath containing a solution containing 10 g/l glucose and 5 g/l NaOH and stirred therein for 20 minutes. The fibres are then washed, spun down and centrifuged multiple times until a neutral reaction is achieved. In a third treatment bath, the fibres are finished according to Example 1. The copper concentration is 7890 mg/kg copper, After 50 wash cycles, the fibres still contained 321 mg/kg copper. The antibacterial effect after 50 wash cycles versus Staphylococcus aureus showed a reduction of log 4.7, and versus Klebsiella pneumoniae a reduction of log 4.4, The antiviral effect against Pseudomonas sp. DSM 21482 showed a log 4.5 reduction and, after 50 washes, still a reduction of log 4.1. This corresponds to strong antiviral activity even after 50 washes.

Example 4

[0052] Ion-exchange fibres produced according to Example 1 are processed in a 6% mixture, with pure Lyocell fibres into a needle-punched nonwoven. The antibacterial effect versus Staphylococcus aureus was determined as a log 5.6 reduction; after 20 wash cycles, the reduction was still log 5.3. Versus Klebsiella pneumoniae, there was a log 5.9 reduction and, after 20 wash cycles, a log 4.4 reduction.

Example 5

[0053] Ion-exchange fibres produced according to Example 1, but treated with 0.15 M aqueous silver nitrate solution instead of copper sulfate. The fibres have a linear density of 6.7 dtex, an elongation of 11% and a breaking strength of 23 cN/tex. The silver concentration is 51 200 mg/kg silver. After 50 wash cycles, the fibres still contained 2150 mg/kg silver.

Example 6

[0054] Ion-exchange fibres produced according to Example 5 are, following silver loading, additionally placed in a second immersion bath containing a 10 g/l sodium chloride solution and stirred therein for 20 minutes, The fibres are then spun down, centrifuged and finished according to Example 2. The silver concentration is 48 300 mg/kg silver. After 50 wash cycles, the fibres still contained 14 500 mg/kg silver. Compared to the non-fixed fibre from Example 3, this corresponds to an increase in recovery after 50 washes from approx. 4% to approx. 30%, Measurement of the antibacterial effect versus Staphylococcus aureus showed a reduction of log 6.0 and, after 50 wash cycles, of log 5.8; versus Klebsiella pneumoniae, there was a reduction of log 6.0 and, after 50 wash cycles, of log 5.6. For both bacterial species, this signifies strong antibacterial activity which is still maintained even after 50 wash cycles.