A method of manufacturing an antimicrobial fibrous monofilament, an antimicrobial fibrous monofilament, and a fibrous material comprising the antimicrobial fibrous monofilament

Abstract

A method of manufacturing an antimicrobial fibrous monofilament is provided. The method comprises the following steps: (i) forming an aqueous suspension comprising from 90 to 96 wt.% of water, and from 4 to 10 wt.% of dry matter including microfibrillar cellulose (MFC), dispersing agent, wet strength agent and antimicrobial agent, the dry matter comprising at least 50 wt.% of MFC, (ii) extruding the aqueous suspension into a monofilament, and (iii) drying the monofilament. Further, an antimicrobial fibrous monofilament and a fibrous material comprising the same are provided.

Description

[0001] A method of manufacturing an antimicrobial fibrous monofilament, an antimicrobial fibrous monofilament, and a fibrous material comprising the antimicrobial fibrous monofilament

[0002] Technical field

[0003] This specification relates to a method of manufacturing an antimicrobial fibrous monofilament. The specification also relates to an antimicrobial fibrous monofilament as well as to products comprising the same.

[0004] Background

[0005] Antimicrobial fabrics and textiles find use in a variety of applications ranging from households to commercial, including clothing, air filters, food packaging, health care, hygiene, medical, sportswear, storage, ventilation and water purification systems.

[0006] Conventionally, the antimicrobial effect is obtained through application of specific chemical components during the finishing stage of the fabric / textile or the fiber / yarn utilized for preparing it, thereby requiring an extra process step for providing the antimicrobial effect. Further, very often the antimicrobial effect is achieved by inorganics or organometallic compounds, which can be problematic because of their effects to the environment. Still further, the conventional approaches employing loading of the antimicrobial additives onto the surface of the fabric / textile or the fiber / yarn makes the products susceptible to deterioration after long-term use and / or washing due to leaching of the additives.

[0007] Biobased antimicrobial agents have been studied, but their adherence to the textile / fabric has posed challenges.

[0008] Summary

[0009] A novel method for manufacturing a sustainable antimicrobial fibrous monofilament is disclosed. The presented method is more environmentally friendly one when compared to methods for producing other cellulose-based fibers, such as viscose and Lyocell. Further, the resulting monofilament enables replacing unsustainable cotton in woven, knitted or non-woven materials or in composite materials. The method provides a solution for adding the antimicrobial agent directly into the fibrous monofilament. By this way an extra process step for introducing the antimicrobial agent as part of postprocessing of the monofilament or yarn / fiber or even the fabric / textile may be avoided. The method also enables addition of the antimicrobial agent in a wash-proof manner.

[0010] According to an embodiment, a method of manufacturing an antimicrobial fibrous monofilament is provided. The method comprises the following steps:

[0011] (i) forming an aqueous suspension comprising from 90 to 96 wt.% of water, and from 4 to 10 wt.% of dry matter including microfibrillar cellulose (MFC), dispersing agent, wet strength agent and antimicrobial agent, the dry matter comprising at least 50 wt.% of MFC,

[0012] (ii) extruding the aqueous suspension into a monofilament, and

[0013] (iii) drying the monofilament.

[0014] According to another embodiment, an antimicrobial fibrous monofilament is provided. The antimicrobial fibrous monofilament comprises at least 50 wt.% of microfibrillar cellulose (MFC), a dispersing agent, a wet strength agent, and an antimicrobial agent.

[0015] According to yet another embodiment, a fibrous material comprising the antimicrobial fibrous monofilament as described above is provided.

[0016] Detailed description

[0017] The solution is described in the following in more detail with reference to some embodiments, which shall not be regarded as limiting.

[0018] The features recited in the embodiments of the description and in the claims are mutually freely combinable unless otherwise explicitly stated. Plant materials are built up by a matrix formed by cellulose fibers also containing lignin and hemicelluloses. The cellulosic fibers that form such a matrix are fibril bundles which in turn consist of microfibrils. Through a fibrillation process the cellulose fibers are separated into a three-dimensional network of microfibrils with a large surface area. These entangled fibrils are called microfibrillar cellulose (MFC). The width of entangled fibrils in MFC may be from 50 nanometers to 2 micrometers and length or longitudinal dimension may be from 100 nanometers to 500 micrometers, such as from 100 nanometers to 200 micrometers.

[0019] Within context of this disclosure, the method of manufacturing MFC is not limited. MFC may be produced from cellulose fibers using methods known within the art through high pressure, high temperature and high velocity impact homogenization, for instance. The homogenization process is used to delaminate or disintegrate the cell walls of the fibers and to liberate their sub- structural fibrils and microfibrils. Enzymatic and / or mechanical pre-treatments of wood fibers may also be used.

[0020] In the present disclosure expressions “non-regenerated cellulose” or “natural cellulose” refer to cellulose or cellulose fibrils or fibers that have not undergone chemical or physical modification of their macromolecular structure. Nonregenerated MFC as discussed herein is substantially non-regenerated and consists mainly of crystalline structure of cellulose I. Cellulose I may have structures laand Ip. Man-made cellulosic fibers commonly used in textile applications are regenerated and their crystalline structure is mainly other than cellulose I. Conversion of cellulose I to cellulose II (or other forms, like cellulose III or cellulose IV) is irreversible. Thus, these forms are stable and cannot be converted back to cellulose I.

[0021] Within context of this disclosure, cellulose may originate from any plant-based material. Plant-based raw material may be wood material or non-wood material. The wood material can be based on softwood tree, such as spruce, pine, fir, larch, Douglas-fir or hemlock, or on hardwood tree, such as birch, aspen, poplar, alder, eucalyptus or acacia, or on any mixture of above. The non-wood material may be as cotton, hemp, flax, sisal, jute, kenaf, bamboo, peat, or coconut. Non-wood based natural cellulose fibers may also be derived from agricultural residues, grasses, or other plant substances such as straw, leaves, bark, seeds, hulls, flowers, vegetables, or fruits. Woody plants have a good availability, small environmental burden and the quality of fiber is good. The above applies both to non-regenerated cellulose and also regenerated and processed forms of cellulose.

[0022] The term “fibrous monofilament” as used herein refers to a continuous length of individual fibrils grouped and extending generally along the longitudinal dimension of the cellulose monofilament. The fibrils interact chemically and / or mechanically in order to form a permanent monofilament structure. Disintegration of fibrous monofilament yields only individual fibrils. The fibrous monofilament may comprise continuous length of several meters or kilometers. Individual fibrils of the fibrous monofilament are mainly oriented along length of the fibrous monofilament. Term “monofilament” refers to a single strand filament produced by extruding a polymer suspension. Fibrous monofilament may also be called a monofilament fiber.

[0023] It is an aim of this disclosure to provide a novel method for manufacturing a sustainable antimicrobial fibrous monofilament. The presented method is more environmentally friendly one when compared to methods for producing other cellulose-based fibers, such as viscose and Lyocell. Further, the resulting monofilament enables replacing unsustainable cotton. The disclosed monofilament can be used for producing antimicrobial fibrous materials, such as antimicrobial woven or knitted materials, antimicrobial non-woven materials or antimicrobial composites.

[0024] Term “antimicrobial” refers to anything that is about controlling the spread of infectious microorganisms. General term antimicrobial comprises more specific terms antibacterial, antifungal and antiviral. Any antimicrobial entity within context of this disclosure may also act against bacteria, fungi and viruses simultaneously. Antimicrobial agent is an agent that is capable of killing microorganisms and / or inhibiting their growth.

[0025] A method of manufacturing an antimicrobial fibrous monofilament is provided. The method comprises forming an aqueous suspension, extruding the aqueous suspension into a monofilament and drying the monofilament. The aqueous suspension is extruded onto a solid surface.

[0026] The aqueous suspension comprises or consists of from 90 to 96 wt.% of water (based on the suspension weight) and from 4 to 10 wt.% of dry matter. The dry matter comprises or consists of microfibrillar cellulose (MFC), dispersing agent, wet strength agent and antimicrobial agent.

[0027] The dry matter of the aqueous suspension comprises at least 50 wt.% of MFC. Preferably, the amount of the MFC is from 50 to 95 wt.%. For example, the amount of the MFC in the dry matter of the aqueous suspension may be from 60 to 95 wt.%, from 70 to 95 wt.%, from 80 to 95 wt.%, from 80 to 90 wt.%, or from 80 to 85 wt.%.

[0028] The MFC used may be non-regenerated and / or regenerated. According to an embodiment the MFC is non-regenerated MFC.

[0029] The dispersing agent is needed in the manufacturing process phase to improve separation of the MFC fibrils and to prevent their settling or clumping. The dispersing agent can be any anionic hydrophilic polymer. In an example, the dispersing agent is carboxymethyl cellulose (CMC) and / or anionic polyacrylamide (aPAM). Alternatively, the dispersing agent may be any of the following: hydroxyethyl cellulose (HEC), ethyl hydroxyethyl cellulose (EHEC), methyl cellulose (MC), hydroxypropyl methyl cellulose (HPMC), hydroxyethyl methyl cellulose (HEMC), methyl ethyl hydroxyethyl cellulose (MEHEC), hydroxypropyl cellulose (HPC), ethyl cellulose (EC) and starch, or any combination thereof. Dispersing agent may also have an effect on tensile strength of the fibrous monofilament. aPAM may also function as a rheology modifier.

[0030] According to an embodiment, the dispersing agent is used in an amount of 0.5 to 25 wt.% of the dry matter of the aqueous suspension. For example, the amount of the dispersing agent may be from 5 to 25 wt.%, from 10 to 25 wt.%, from 13 to 20 wt.%, such as about 14 wt.% of the dry matter of the aqueous suspension. The wet strength agent may also be called a crosslinking agent. According to an embodiment, the amount of the wet strength agent is from 1 to 6 wt.%, such as from 2 to 5 wt.% of the dry matter of the aqueous suspension. For example, the amount of the wet strength agent may be about 3 wt.% of the dry matter of the aqueous suspension. In an example, the wet strength agent is a polyamidoamine-epichlorohydrin (PAE) resin. PAE provides improved wet strength properties such as wet tenacity and elongation to the fibrous monofilament. PAE may also prevent shrinkage and improve wet abrasion resistance.

[0031] As already mentioned, the antimicrobial agent is an agent that is capable of killing microorganisms and / or inhibiting their growth. The antimicrobial agent can be biobased or non-biobased. Non-biobased antimicrobial agents include for example metals (such as silver (Ag) and copper (Cu)) and synthetic polymers (such as polyethyleneimines).

[0032] Preferably the antimicrobial agent is biobased. Term “biobased” means that the substance is derived from living (or once-living) organism. This may enhance the biodegradability of the fibrous monofilament produced as well as the materials comprising it. Utilization of biobased and safe antimicrobial agent enables maintaining recyclability of the fibrous monofilament. For example, presence of metals or any other detrimental elements may cause problems in the recycling process.

[0033] According to an embodiment, amount of the antimicrobial agent is from 0.1 to 10 wt.%, such as from 0.1 to 6 wt.% of the dry matter of the aqueous suspension. In an example, the amount of the antimicrobial agent is from 0.5 to 4 wt.%, such as about 2 wt.% of the dry matter of the aqueous suspension.

[0034] The antimicrobial agent may be at least one selected from the following: polyphenol, resin acid, surfactant, polyanionic substance, antimicrobial peptide, fucoidan, lignin, chitosan, natural dye, willow bark extract, coffee extract and cyclodextrin. Polyphenols are naturally occurring organic compounds characterized by multiples of phenol units. They are abundant in plants and structurally diverse. Tannic acid is a representative of polyphenols.

[0035] Tannic acid is a specific form of tannin (plant polyphenol) with a chemical formula of C76H52O46. It is weakly acidic due to the numerous phenol groups in the structure. Tannic acid is a mixture of polygalloyl glucoses or polygalloyl quinic acid esters with the number of galloyl moieties per molecule ranging from 2 up to 12, depending on the plant source used to extract the tannic acid. Commercial tannic acid is typically extracted from any of the following plant parts: Tara pods (Caesalpinia spinosa), gallnuts from Rhus semialata or Quercus infectoria or Sicilian sumac leaves (Rhus coriaria).

[0036] Resin acids are mixtures of several related carboxylic acids found in tree resins. Resin acids may also be called coniferous resin acids. Nearly all resin acids have three fused rings having the empirical formula C19H29COOH as their basic skeleton. Resin acids include abietic-type acids (such as abietic acid, neoabietic acid, dehydroabietic acid, palustric acid and levopimaric acid) and pimaric-type acids (such as pimaric acid and isopimaric acids). Resin acids may be obtained from fraction distillation of crude tall oil. Crude tall oil may derived from Kraft pulping processes of coniferous trees. Thus, resin acids are side stream products of pulping industry, thereby advancing circular economy.

[0037] According to an embodiment, the coniferous resin acid as antimicrobial agent is added as a composition called NordShield BioLayr®.

[0038] Surfactants are compounds that decrease the surface tension or interfacial tension between two liquids, a liquid and a gas, or a liquid and a solid. Surfactant may also be called a surface-active agent. Surfactants may function as emulsifiers, wetting agents, detergents, foaming agents and / or dispersants. Surfactants are divided into four major classes: cationic, anionic, amphoteric and non-ionic surfactants. Antimicrobial activity has been demonstrated in all major surfactant classes and structural differences in a particular surfactant type can have an impact on antimicrobial activity. In an example, the surfactant preferably is a non-ionic surfactant. Polyanionic substances include for example polysulfates and polyphosphate. Antimicrobial agents belonging to this class include for example dextran sulfate, polyvinyl alcohol sulfate and naphthalene sulfonate.

[0039] Antimicrobial peptides are short oligopeptides, generally comprising between 12 and 50 amino acids. These peptides typically include at least two positively charged residues provided by arginine, lysine or, in acidic environments, histidine, and a large proportion (generally more than 50 %) of hydrophobic residues.

[0040] Fucoidans are long chain sulfated polysaccharides found in various species of brown marine algae. The main sugar of the polymer backbone is fucose. Other sugars are often present alongside fucose, including galactose, xylose, arabinose and rhamnose. Relative content of the sugars in fucoidan varies between species of algae and can also be affected by the extraction method. The polymer backbone of fucoidan is negatively charged owing to the presence of sulfate groups.

[0041] Lignin refers to polymer class composed by crosslinking of phenolic precursors, lignols. Lignin is rich in aromatic subunits, thus being hydrophobic. Lignin forms key structural materials in the support tissues of most plants. Particularly, lignins are important in formation of cell walls, especially in wood and bark. Lignin is a side stream product of pulping industry.

[0042] Chitosan is a linear polysaccharide composed of randomly distributed 0- (1 — >4)-linked D-glucosamine (deacetylated unit) and / V-acetyl-D-glucosamine (acetylated unit). Chitosan is produced commercially by deacetylation of chitin, which is a structural element in the exoskeleton of crustaceans and cell walls of fungi. Degree of deacetylation (%DD) in commercial chitosan ranges from 60 to 100 %.

[0043] Cyclodextrins are cyclic oligosaccharides comprising a macrocyclic ring of glucose subunits joined by a-1 ,4 glycosidic bonds. Cyclodextrins are produced from starch by enzymatic conversion. Typical cyclodextrins contain a number of glucose monomers ranging from 6 to 8 units in a ring. Cyclodextrins have a hydrophilic outer surface and a lipophilic central cavity.

[0044] Several natural dyes and biobased extracts, such as willow bark extract and coffee extract have shown to possess antimicrobial activity. Such components can also be used to provide the antimicrobial activity into the fibrous monofilament produced as disclosed herein. Natural dyes are dyes or colorants derived from nature, typically from plant sources or other biological sources, such as fungi or animals.

[0045] Preferably the antimicrobial agent is at least one selected from polyphenol, resin acid, surfactant and lignin.

[0046] Besides the dispersing agent and the wet strength agent the suspension may comprise additional additive(s), such as hydrophobic adhesive. The hydrophobic adhesive may be alkyl ketene dimer (AKD, an alkaline or neutral sizing agent), alkenylsuccinic anhydride (ASA, sizing agent), rosin (acidic sizing agent), natural wax, and modified sunflower-based adhesive (MSOHO) or any mixture thereof. Additional additives may include strength additive(s), rheology modifier(s), pigment(s) and / or other modifier(s). For example, polyethylene oxide (PEO) may be utilized as a rheology modifier. These additives can be used for tailoring properties of the antimicrobial fibrous monofilament and / or the products manufactured thereof as appreciated by the skilled person.

[0047] In an example, the suspension contains AKD as the hydrophobic adhesive. As a hydrophobic adhesive AKD reduces the absorption properties of the fibrous monofilament. AKD may also increase strength of the fibrous monofilament. Amount of AKD, when used, may be from 0.5 to 10 wt.%, such as from 0.5 to 5 wt.% of the dry matter of the aqueous suspension.

[0048] According to an exemplary embodiment, the dry matter of the aqueous suspension for manufacturing the antimicrobial fibrous monofilament comprises from 80 to 85 wt.% of non-regenerated MFC and about 2 wt.% of tannic acid as an antimicrobial agent. Further, dry matter of the aqueous suspension for manufacturing the antimicrobial fibrous monofilament comprises CMC and aPAM as dispersing agents and PAE as wet strength agent. Dry matter of the aqueous suspension for manufacturing the antimicrobial fibrous monofilament may further comprise AKD as hydrophobic adhesive.

[0049] According to another exemplary embodiment, the dry matter of the aqueous suspension for manufacturing the antimicrobial fibrous monofilament comprises from 80 to 85 wt.% of non-regenerated MFC and about 2 wt.% of a composition called NordShield BioLayr® as the antimicrobial agent. Further, dry matter of the aqueous suspension for manufacturing the antimicrobial fibrous monofilament comprises CMC and aPAM as dispersing agents and PAE as wet strength agent. Dry matter of the aqueous suspension for manufacturing the antimicrobial fibrous monofilament may further comprise AKD as hydrophobic adhesive.

[0050] According to yet another exemplary embodiment, the dry matter of the aqueous suspension for manufacturing the antimicrobial fibrous monofilament comprises from 80 to 85 wt.% of non-regenerated MFC and about 2 wt.% of lignin as an antimicrobial agent. Further, dry matter of the aqueous suspension for manufacturing the antimicrobial fibrous monofilament comprises CMC and aPAM as dispersing agents and PAE as wet strength agent. Dry matter of the aqueous suspension for manufacturing the antimicrobial fibrous monofilament may further comprise AKD as hydrophobic adhesive.

[0051] Usual order of adding the components (added to an aqueous solution) to form the aqueous suspension is MFC, wet strength agent, dispersing agent and antimicrobial agent. Further, in an alternative approach the antimicrobial agent is added right after MFC, prior to adding any other components. Preferably, the antimicrobial agent is not added simultaneously or right after addition of the wet strength agent. This enables maintaining the wet strength properties of the fibrous monofilament as desired.

[0052] The aqueous suspension is directed through a small nozzle (extruded) where fibers align (orient) well with the flow. The nozzle feeds the aqueous suspension to a solid surface which is followed by drying to obtain the fibrous monofilament. Initial fibril orientation of the fibrous monofilament may be achieved during the extrusion phase. A nozzle having an outer diameter smaller than or equal to the maximum fibril length of the fibers causes the fibrils to orientate substantially in the longitudinal direction of the suspension exiting the nozzle. Fibril orientation along the longitudinal direction of the fibrous monofilament provides strength to the filament.

[0053] Manufactured antimicrobial fibrous monofilament is continuous but it may be post-processed into shorter lengths by any of suitable methods known in the art. Thickness of the fibrous monofilament may be affected at least in part by adapting manufacturing speed, aqueous suspension concentration and nozzle geometry. Chemical post-treatment, such as dyeing or introduction of a surface finishing agent is possible.

[0054] The manufacturing method disclosed herein is an environmentally friendly one, utilizing mild conditions and not employing any harmful substances. This is a significant benefit when compared to other cellulose-based textile fibers, such as viscose and Lyocell. The method is free of organic solvents. The sole solvent used in the method is water.

[0055] The method provides a solution for adding the antimicrobial agent directly into the fibrous monofilament, as the antimicrobial agent is contained in the suspension for producing the monofilament. This avoids utilization of an extra process step for introducing the antimicrobial agent as part of post-processing of the monofilament or yarn / fiber or even the fabric / textile. Unlike processes for producing other cellulose-based textile fibers, the manufacturing process does not have a water circulation or chemical circulation, and thus 100 % of added antimicrobial agent remains in the fibrous monofilament produced.

[0056] The method also allows addition of the antimicrobial agent and its efficacy in a permanent manner. Durability of the antimicrobial agent efficacy can be studied by wash durability. Wash durability of the fibrous monofilament or the materials prepared therefrom may be studied by conducting washing according to a standard ISO 6330. The wash-proof addition may be achieved via covalent bonding. Wash durability, i.e. the ability of the fibrous monofilament to maintain the antimicrobial efficacy even after washing particularly plays a role for end use in washable textile products. In single-use products utilizing for example non-woven material comprising the antimicrobial fibrous monofilament disclosed herein, the wash durability may not be that important. However, it is to be noted that permanent bonding of the antimicrobial agent may be of importance from the product safety perspective also in case of the non-woven materials. Wash durability also enables further product processing steps that include usage of water, such as hydroentangling.

[0057] However, if needed, it is also possible to include an antimicrobial surface finishing agent in a post-processing step to the monofilament / yarn / fiber / fabric / textile as disclosed herein to provide supplementary antimicrobial effect. The antimicrobial surface finishing agent may be introduced for example by at least one of the following: plasma coating, wet spray coating, dipping, impregnation, immersion and kiss roller coating. In certain cases, the antimicrobial surface finishing agent may be arranged to be attached to the antimicrobial fibrous monofilament via covalent bonding. Covalent bonding may represent a wash-proof manner of attaching the antimicrobial surface finishing agent.

[0058] The antimicrobial fibrous monofilament disclosed herein comprises at least 50 wt.% of microfibrillar cellulose (MFC) of the dry weight of the fibrous monofilament. The antimicrobial fibrous monofilament further comprises a dispersing agent, a wet strength agent, and an antimicrobial agent, as discussed above.

[0059] The antimicrobial fibrous monofilament according to this disclosure may have a density of between 500 and 2000 kg / m3, for example between 1000 and 1700 kg / m3, such as about 1500 kg / m3.

[0060] Tenacity is a customary measure of strength of a fiber or yarn. It is usually defined as the ultimate (breaking) force of the fiber / yarn (in gram-force units) divided by the linear density. Tenacity is often expressed as cN / (d)tex. Linear density is a value expressing the fiber / yarn weight in grams per 1 000 meters of fiber / yarn (tex) or grams per 10 000 meters of fiber / yarn (dtex). The antimicrobial fibrous monofilament according to this disclosure may have a linear density of from 1 to 10 dtex, when measured following standard ASTM 3822 / D3822M-14 at RH 65% (+ / - 2%) and temperature 20 degrees C (+ / - 2 degrees C).

[0061] The antimicrobial fibrous monofilament according to this disclosure may have a tenacity of at least 1 .2 cN / dtex, preferably at least 1 .5 cN / dtex or 1 .7 cN / dtex, or more preferably at least 2 cN / dtex, when measured following standard ASTM 3822 / D3822M-14 at RH 65% (+ / - 2%) and temperature 20 degrees C (+ / - 2 degrees C).

[0062] According to an embodiment, the antimicrobial fibrous monofilament is biobased and / or biodegradable. Biodegradability of a material means that greater than 90 % of the original material is converted into CO2, water and minerals by biological processes within 6 months.

[0063] The antimicrobial fibrous monofilament according to this disclosure finds use in fibrous materials, such as woven, knitted or non-woven materials or as composite materials. The fibrous monofilaments may be utilized for producing fiber or yarn for fibrous materials. The fibrous material comprising the antimicrobial fibrous monofilament may be called antimicrobial fibrous material. Particularly, the fibrous monofilaments disclosed herein are utilizable for producing fiber or yarn for woven or knitted materials. The manufacturing method disclosed herein is such that fibrous monofilaments with properties (e.g., linear density and tenacity) required from monofilaments suitable for producing fiber or yarn for woven or knitted materials are produced.

[0064] The fibrous materials may be manufactured by using any methods known in the art.

[0065] Exemplary uses of the antimicrobial fibrous materials include for example antimicrobial non-woven fabrics. Non-woven fabrics are sheet or web structures formed from fibers bonded together via mechanical, thermal or chemical treatment. The antimicrobial fibrous monofilament disclosed herein may be used for providing antimicrobial non-woven fabric for use e.g. in medical applications, such as protective layers, surgical masks, face masks, wipes and in wound care products.

[0066] Antimicrobial non-woven materials may also find use in thermal insulation materials for example in clothing. Generally, for items employing thermal insulation materials the less they are washed the better their properties remain. Thus, use of the antimicrobial non-woven materials in such items may enable keeping the washing process as rare as possible.

[0067] Further, the antimicrobial fibrous monofilament disclosed herein may be used in any woven or knitted fabric or textile, wherein antimicrobial properties are desired. Examples include for example clothing and sportswear. Clothing and other textiles may be vectors for the culture and transfer of microbial species, and thereby incorporation of antimicrobial properties therein is of particular interest. Antimicrobial woven or knitted materials may find use in medical field, for example in clothing or bedding applications. Further, home textiles and textiles for use in public spaces may also employ antimicrobial fibrous monofilament as disclosed herein.

[0068] Examples

[0069] Exemplary fibrous monofilaments were prepared and their antimicrobial properties studied.

[0070] Suspensions were prepared and treated as discussed above to yield fibrous monofilaments containing from 80 to 85 wt.% of non-regenerated MFC as the main component. The fibrous monofilaments contained about 2 wt.% of tannic acid, about 2 wt.% of NordShield BioLayr® composition, about 2 wt.% of surfactant solution, or about 2 wt.% of silver composition as the antimicrobial agent. The fibrous monofilaments further contained CMC (about 11 wt.%) as dispersing agent, PAE (about 3 wt.%) as wet strength agent, aPAM (about 2.5 wt.%) as rheology modifier and AKD (about 0.5 wt.%) as hydrophobic adhesive. The weight percentages of the fibrous monofilament components are calculated from the dry weight of the fibrous monofilament. Antimicrobial properties of the fibrous monofilaments against bacteria Klebsiella pneumoniae, Escherichia coli, Acinetobacter baumannii and Staphylococcus aureus, as well as OC43 (human coronavirus, HCoV-OC43) and enterovirus CVA9 (coxsackievirus A9) were studied. Antibacterial studies were performed by following standard ISO 20743 and antiviral studies by following standard ISO 18184, both with minor adjustments.

[0071] Samples for antimicrobial studies were prepared by placing the fibrous monofilament on the bottom of a well plate. Sample weight was 20 mg. Three replicates (and three additional replicates in order to test possible direct toxicity for mammalian cells) were prepared. Fibrous monofilament not comprising any antimicrobial agent was used as a reference. 10 pl of viral / bacterial droplet was added on the top of the fibrous monofilament samples and preincubated at 37 degrees C for 1 hour. The samples were rinsed with 1990 pl of aqueous medium. Final virus dilutions were prepared from the rinsing medium (50 000 x dilution for HCoV-OC43).

[0072] For antiviral studies the final dilutions were added onto cultured MRC-5 (15k cells per well) or A549 (12k cells per well) cells on 96-well plate. For coronavirus studies the samples were incubated for 5 days in an incubator at 34 degrees C prior to CPE (cytopathic effect) staining. On the third day of incubation, 25 pl of the coronavirus sample was collected for qPCR (quantitative polymerase chain reaction) measurement of viral RNA. For CPE determination, absorbance at 570 nm (absorbance of viable cells) was measured.

[0073] Results of the antiviral studies against coronavirus OC43 are presented in Tables 1-4. Table 1.

[0074] Table 2. Table3. Table 4.

[0075] Results of the antiviral studies against enterovirus CVA9 are presented in Table 5.

[0076] Table 5.

[0077] The studies show that for the reference sample not comprising any antimicrobial agent the absorbance at 570 nm is low compared to the cell control. This indicates that the reference sample is not capable of showing antiviral effect, but the viral dilutions incubated with the cells contain active viruses and infect the cells, resulting in low absorption caused by the low number of viable cells. For the samples containing tannic acid or NordShield Biolayr® the absorbance at 570 nm is comparable with the cell control, thereby demonstrating the antiviral activity of said samples. This is further proven by the qPCR results. Further, the high antiviral activity of the fibrous monofilaments containing surfactant solution or silver as the antimicrobial component, particularly against coronavirus OC43 is demonstrated. For antibacterial studies, 100 pl of the final dilution was placed on Petri dishes and incubated at 37 degrees C overnight. Bacterial colonies were counted on the following day.

[0078] In antibacterial studies, no significant difference was observed between the reference sample and the fibrous monofilament sample containing tannic acid as the antimicrobial agent. Therefore, the fibrous monofilament containing tannic acid did not show antibacterial effect against Klebsiella pneumoniae, Escherichia coli, Acinetobacter baumannii and Staphylococcus aureus.

[0079] The fibrous monofilament samples containing NordShield BioLayr® composition including coniferous resin acid as the antimicrobial agent showed antibacterial effect against the bacteria studied, i.e. Klebsiella pneumoniae, Escherichia coli, Acinetobacter baumannii and Staphylococcus aureus. Reduction in the colony-forming units (in percentage) when compared to the reference samples was shown to be at least 90 % (Staphylococcus aureus), and at best 99,8 % (Klebsiella pneumoniae) (Table 6). The log differences varied from 1 ,01 to 2,71 , respectively. Log difference of at least 1 can be considered as significant.

[0080] Table 6.

[0081] Antibacterial effect of the fibrous monofilament samples containing surfactant solution or silver as the antimicrobial agent against Escherichia coli and Staphylococcus aureus were studied and the results are shown in Table 7. Reduction in the colony-forming units (in percentage) with the surfactant solution when compared to the reference sample was shown to be 99,78 % (log difference 2,6) with E. coli and 99,9 % (log difference 2,9) with S. aureus. With silver as the antimicrobial agent no colony-forming units were observable, thus demonstrating the high antibacterial effect of monofilaments containing silver.

[0082] Table 7.

[0083] Wash durability, i.e. the ability of the fibrous monofilament to maintain the antimicrobial activity after washing was tested, as well. Wash durability tests were performed for samples containing NordShield BioLayr® composition including coniferous resin acid. Wash durability of the material comprising or consisting of the monofilaments as disclosed herein was tested by following a standard ISO 6330 using a 40 degrees C washing program.

[0084] Exemplary results are presented in Tables 8a and 8b. Table 8a shows the CPE and qPCR results before washing. Results for the same samples after three washing and drying cycles are shown in Table 8b. The studies show that the fibrous monofilaments maintain their antiviral activity after three washing and drying cycles. Also, in general, the antibacterial activity was shown to remain after three washing and drying cycles. Thus, by adding the antimicrobial agent into the suspension for forming the fibrous monofilament, a wash-proof antimicrobial fibrous monofilament can be obtained. Table 8a.

[0085] Table 8b.

Claims

Claims:

1. A method of manufacturing an antimicrobial fibrous monofilament, the method comprising the following steps:(i) forming an aqueous suspension comprising from 90 to 96 wt.% of water, and from 4 to 10 wt.% of dry matter including microfibrillar cellulose (MFC), dispersing agent, wet strength agent and antimicrobial agent, the dry matter comprising at least 50 wt.% of MFC,(ii) extruding the aqueous suspension into a monofilament, and(iii) drying the monofilament.

2. The method according to claim 1 , wherein the antimicrobial agent is biobased.

3. The method according to claim 1 or 2, wherein amount of the antimicrobial agent is from 0.1 to 10 wt.% of the dry matter content.

4. The method according to any of the preceding claims, wherein the antimicrobial agent is at least one selected from the following: polyphenol, resin acid, surfactant, and lignin.

5. The method according to claim 4, wherein the polyphenol is tannic acid.

6. The method according to any of the preceding claims, wherein the antimicrobial agent is added as a composition containing coniferous resin acid.

7. An antimicrobial fibrous monofilament comprising:- at least 50 wt.% of microfibrillar cellulose (MFC),- a dispersing agent,- a wet strength agent, and- an antimicrobial agent.

8. The antimicrobial fibrous monofilament according to claim 7, wherein the antimicrobial agent is biobased.

9. The antimicrobial fibrous monofilament according to claim 7 or 8, wherein amount of the antimicrobial agent is from 0.1 to 10 wt.%.

10. The antimicrobial fibrous monofilament according to any of the claims 7-9, wherein the antimicrobial agent is at least one selected from the following: polyphenol, resin acid, surfactant, and lignin.

11. The antimicrobial fibrous monofilament according to claim 10, wherein the polyphenol is tannic acid.

12. The antimicrobial fibrous monofilament according to claim 10 or 11 , comprising a composition containing coniferous resin acid as the antimicrobial agent.

13. A fibrous material comprising the antimicrobial fibrous monofilament according to any of the claims 7-12.

14. The fibrous material according to claim 13, wherein the fibrous material is a woven material, a knitted material, a non-woven material or a composite material.

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