Method for manufacturing antimicrobial fiber monofilament, antimicrobial fiber monofilament and fiber material comprising said antimicrobial fiber monofilament

Abstract

A method of making an antimicrobial fiber monofilament is provided. The present invention relates to a method for producing a monofilament comprising the steps of: (i) forming an aqueous suspension comprising 90% to 96% by weight of water and 4% to 10% by weight of a dry matter comprising microfibrillar cellulose (MFC), a dispersant, a wet strength agent and an antimicrobial agent, the dry matter comprising at least 50% by weight of MFC, (ii) extruding the aqueous suspension into a monofilament, and (iii) drying the monofilaments. In addition, an antimicrobial fiber monofilament and a fiber material comprising the monofilament are also provided.

Description

TECHNICAL FIELD

[0001] The present specification relates to a method of manufacturing an antimicrobial fibre filament. The present specification also relates to an antimicrobial fibre filament and products comprising the same. BACKGROUND

[0002] Antimicrobial fabrics and textiles can be used for various applications ranging from home to commercial, including clothing, air filters, food packaging, healthcare, hygiene, medical, sportswear, warehousing, ventilation and water purification systems.

[0003] Typically, the antimicrobial effect is achieved by applying specific chemical components in the finishing stage of the fabric / textile or the fibre / yarn used to make it, thus requiring additional process steps to provide the antimicrobial effect. Furthermore, the antimicrobial effect is typically achieved by inorganics or organometallic compounds, which pose problems as they can have an impact on the environment. Moreover, the traditional approach is to load the antimicrobial additives onto the surface of the fabric / textile or the fibre / yarn, which makes the product susceptible to degradation due to leaching of the additives after prolonged use and / or washing.

[0004] Bio-based antimicrobial agents have been researched, but their adhesion on textiles / fabrics poses a challenging. SUMMARY

[0005] A new method for manufacturing a sustainable antimicrobial fibre filament is disclosed. The method of the present invention is more environmentally friendly compared to the methods of producing other cellulose-based fibres such as viscose and Lyocell. Furthermore, the resulting filament is able to replace unsustainable cotton in woven, knitted or non-woven materials or composites. The method provides a solution to add antimicrobial agents directly into the fibre filament. In this way, the use of additional processing steps to introduce antimicrobial agents as part of the post-treatment of the filament or yarn / fibre or even fabric / textile can be avoided. The method is also able to add antimicrobial agents in a wash-resistant manner.

[0006] According to one embodiment, a method of manufacturing an antimicrobial fibre filament is provided. The method comprises the steps of:

[0007] (i) forming an aqueous suspension comprising 90 to 96 wt% water and 4 to 10 wt% dry substance, the dry substance comprising microfibrillar cellulose (MFC), a dispersing agent, a wet strength agent and an antimicrobial agent, the dry substance comprising at least 50 wt% MFC,

[0008] (ii) extruding the aqueous suspension into a filament, and

[0009] (iii) drying the filament.

[0010] According to another embodiment, an antimicrobial fiber filament is provided. The antimicrobial fiber filament comprises at least 50 weight-% of microfibrillar cellulose (MFC), a dispersing agent, a wet strength agent, and an antimicrobial agent.

[0011] According to another embodiment, a fiber material comprising the antimicrobial fiber filament as described above is provided. Particular embodiments

[0012] The solution will be described in more detail below in connection with some embodiments, but these embodiments should not be considered limiting.

[0013] The features recited in the embodiments of the description and the claims can be combined freely unless otherwise explicitly stated.

[0014] Plant material is composed of a matrix of cellulose fibers, which also contain lignin and hemicellulose. The cellulose fibers forming this matrix are primary fiber bundles, which in turn are composed of microfibrils. Through the process of defibrillation, the cellulose fibers are separated into a three-dimensional network of microfibrils with a large surface area. These entangled primary fibers are called microfibrillar cellulose (MFC). The width of the entangled primary fibers in MFC can be 50 nanometers to 2 micrometers, and the length or longitudinal dimension can be 100 nanometers to 500 micrometers, such as 100 nanometers to 200 micrometers.

[0015] In the context of the present disclosure, the method of manufacturing MFC is not limited. MFC can be made from cellulose fibers using methods known in the art, such as by high pressure, high temperature, and high speed impingement homogenization. The homogenization process is used to delaminate or disintegrate the cell walls of the fibers and release their sub-structural primary fibers and microfibrils. Enzymatic and / or mechanical pretreatment of the wood fibers can also be utilized.

[0016] In the present disclosure, the expression "non-regenerated cellulose" or "native cellulose" refers to cellulose or cellulose fibers or fibers whose macromolecular structure has not been chemically or physically modified. The non-regenerated MFC as discussed herein is essentially non-regenerated and consists mainly of crystalline structure of cellulose I. Cellulose I can have structure I α and I β . Artificial cellulose fibers commonly used in textile applications are regenerated, and their crystalline structure is not mainly cellulose I. The transformation of cellulose I to cellulose II (or other forms, such as cellulose III or cellulose IV) is irreversible. Therefore, these forms are stable and cannot be transformed back to cellulose I.

[0017] In the context of the present disclosure, the cellulose can be derived from any plant-based material. The plant-based raw material can be a woody material or a non-woody material. The woody material can be based on a softwood species, such as spruce, pine, fir, larch, Douglas fir or hemlock, or on a hardwood species, such as birch, aspen, poplar, alder, eucalyptus or acacia, or on any mixture of the above. The non-woody material can be cotton, hemp, flax, sisal, jute, kenaf, bamboo, peat or coconut. Non-woody natural cellulose fibers can also be derived from agricultural residues, grasses or other plant matter, such as straw, leaves, bark, seeds, husks, flowers, vegetables or fruits. Woody plants have good availability, low environmental burden and good fiber quality. The above applies to non-regenerated cellulose as well as to cellulose in regenerated and processed form.

[0018] The term "fibre filament" as used herein refers to a continuous length of individual fibrils that are gathered and extended generally along the longitudinal dimension of the cellulose filament. The fibrils form a permanent filament structure by chemical and / or mechanical interaction. The fibre filament yields only individual fibrils upon disintegration. The length of the fibre filament can be up to several meters or several kilometers. The individual fibrils of the fibre filament are mainly oriented along the length of the fibre filament. The term "filament" refers to a single strand of a filament produced by extruding a polymer suspension. The fibre filament can also be referred to as a filament fibre.

[0019] It is an object of the present disclosure to provide a new method for manufacturing sustainable antimicrobial fibre filaments. The method of the present invention is more environmentally friendly compared to methods of producing other cellulose-based fibres, such as viscose and lyocell. Furthermore, the resulting filaments are able to replace unsustainable cotton. The filaments disclosed in the present invention can be used to produce antimicrobial fibre materials, such as antimicrobial woven or knitted materials, antimicrobial nonwoven materials or antimicrobial composite materials.

[0020] The term "antimicrobial" refers to any substance that controls the spread of infectious microorganisms. The general term antimicrobial includes the more specific terms antibacterial, antifungal and antiviral. Any antimicrobial entity in the context of the present disclosure can also combat bacteria, fungi and viruses simultaneously. An antimicrobial agent is an agent that is able to kill microorganisms and / or inhibit their growth.

[0021] The present invention provides a method of manufacturing an antimicrobial fibre filament. The method comprises forming an aqueous suspension, extruding the aqueous suspension into a filament and drying the filament. The aqueous suspension is extruded onto a solid surface.

[0022] The aqueous suspension consists of or consists of 90 to 96 weight-% water (based on the weight of the suspension) and 4 to 10 weight-% dry matter. The dry matter consists of or consists of microfibrillar cellulose (MFC), a dispersant, a wet strength agent, and an antimicrobial agent.

[0023] The dry matter of the aqueous suspension consists of at least 50 weight-% MFC. Preferably, the amount of MFC is 50 to 95 weight-%. For example, the amount of MFC in the dry matter of the aqueous suspension can be 60 to 95 weight-%, 70 to 95 weight-%, 80 to 95 weight-%, 80 to 90 weight-%, or 80 to 85 weight-%.

[0024] The MFC used can be non-regenerated and / or regenerated. According to one embodiment, the MFC is non-regenerated MFC.

[0025] In the manufacturing process phase, a dispersant is needed to improve the separation of the MFC fibrils and to prevent them from settling or caking. The dispersant can be any anionic hydrophilic polymer. In one example, the dispersant is carboxymethyl cellulose (CMC) and / or anionic polyacrylamide (aPAM). Alternatively, the dispersant can be any one 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. The dispersant can also have an effect on the tensile strength of the fiber filaments. aPAM can also be used as a rheology modifier.

[0026] According to one embodiment, the amount of dispersant is 0.5 to 25 weight-% of the dry matter of the aqueous suspension. For example, the amount of dispersant can be 5 to 25 weight-%, 10 to 25 weight-%, 13 to 20 weight-%, for example about 14 weight-% of the dry matter of the aqueous suspension.

[0027] The wet strength agent can also be referred to as a crosslinking agent. According to one embodiment, the amount of wet strength agent is 1 to 6 weight-% of the dry matter of the aqueous suspension, for example 2 to 5 weight-%. For example, the amount of wet strength agent can be about 3 weight-% of the dry matter of the aqueous suspension. In one 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 fiber filaments. PAE can also prevent shrinkage and improve wet abrasion resistance.

[0028] As mentioned above, the antimicrobial agent is an agent capable of killing microorganisms and / or inhibiting their growth. The antimicrobial agent can be bio-based or non-bio-based. Non-bio-based antimicrobial agents include, for example, metals (e.g. silver (Ag) and copper (Cu)) and synthetic polymers (e.g. polyethyleneimine).

[0029] Preferably, the antimicrobial agent is bio-based. The term “bio-based” means that the substance is derived from a living (or once-living) organism. This can enhance the biodegradability of the produced fiber filaments and materials comprising the fiber filaments. The use of bio-based and safe antimicrobial agents can maintain the recyclability of the fiber filaments. For example, the presence of metals or any other harmful elements can cause problems in the recycling process.

[0030] According to one embodiment, the amount of antimicrobial agent is from 0.1 to 10 wt.%, for example from 0.1 to 6 wt.% of the dry matter of the aqueous suspension. In one example, the amount of antimicrobial agent is from 0.5 to 4 wt.%, for example about 2 wt.% of the dry matter of the aqueous suspension.

[0031] The antimicrobial agent can be at least one selected from the group consisting of a polyphenol, a resin acid, a surfactant, a polyanionic substance, an antimicrobial peptide, a fucoidan, a lignin, a chitosan, a natural dye, a willow bark extract, a coffee extract, and a cyclodextrin.

[0032] Polyphenols are naturally occurring organic compounds characterized by containing multiple phenolic units. They are abundant in plants and structurally diverse. Tannic acid is one of the representatives of polyphenols.

[0033] Tannic acid is a special form of tannins (plant polyphenols) with the chemical formula C 76 H 52 O 46 Due to the presence of a large number of phenolic groups in the structure, it is weakly acidic. Tannic acid is a mixture of polygalloyl glucose or polygalloyl quinic acid esters with the number of galloyl groups in each molecule being from 2 to 12, depending on the plant source used to extract the tannic acid. Commercial tannic acid is usually extracted from any of the following plant parts: Caesalpinia spinosa, gall from Rhus semialata or Quercus infectoria, or Rhus coriaria leaves.

[0034] Resin acids are a mixture of several related carboxylic acids found in conifer resins. Resin acids can also be referred to as conifer resin acids. Almost all resin acids have three fused rings (empirical formula C 19 H 29Resin acids include abietane-type acids (e.g., abietic acid, neoabietic acid, dehydroabietic acid, palustric acid, and levopimaric acid) and pimarate-type acids (e.g., pimaric acid and isopimaric acid). Resin acids can be obtained from distillate fractionation of tall oil crude. Tall oil crude can be derived from kraft pulping processes of coniferous trees. Resin acids are thus a byproduct of the pulp industry, thus facilitating a circular economy.

[0035] According to one embodiment, the conifer resin acid as antimicrobial agent is added in the form of a composition named NordShield®.

[0036] Surfactants are compounds that lower the surface or interfacial tension between two liquids (liquid and gas, or liquid and solid). Surfactants can also be referred to as surface-active agents. Surfactants can be used as emulsifiers, wetting agents, detergents, foaming agents, and / or dispersants. Surfactants are classified into four major categories: cationic surfactants, anionic surfactants, amphoteric surfactants, and non-ionic surfactants. Anti-microbial activity has been demonstrated for all major surfactant classes, and structural differences within a particular surfactant type can have an impact on anti-microbial activity. In one example, the surfactant is preferably a non-ionic surfactant.

[0037] Polyanionic substances include, for example, polysulfates and polyphosphates. Anti-microbial agents belonging to this class include, for example, dextran sulfate, polyvinyl alcohol sulfate, and naphthalene sulfonate.

[0038] Anti-microbial peptides are short chain oligopeptides, typically comprising 12 to 50 amino acids. These peptides typically include at least two positively charged residues and a high number (typically more than 50%) of hydrophobic residues, where these residues are provided by arginine, lysine, or histidine in an acidic environment.

[0039] Fucoidan is a long chain sulfated polysaccharide found in various brown algae. The main sugar of the polymer backbone is fucose. In addition to fucose, other sugars are often present, including galactose, xylose, arabinose, and rhamnose. The relative content of sugars in fucoidan varies among algal species and can also be influenced by the extraction method. The polymer backbone of fucoidan is negatively charged due to the presence of sulfate groups.

[0040] ​Lignin refers to a class of polymers composed of cross-linked phenolic precursors (lignols). Lignin is rich in aromatic subunits and is therefore hydrophobic. Lignin is a key structural material in the supporting tissues of most plants. In particular, lignin plays an important role in the formation of cell walls, especially in wood and bark. Lignin is a byproduct of the pulp industry.

[0041] Chitosan is a linear polysaccharide composed of randomly distributed β-(1→4)-linked D-glucosamine (deacetylated units) and N-acetyl-D-glucosamine (acetylated units). Commercial chitosan is produced by deacetylation of chitin, a structural element in the exoskeleton of crustaceans and the cell wall of fungi. Commercial chitosan has a degree of deacetylation (%DD) of 60% to 100%.

[0042] Cyclodextrins are cyclic oligosaccharides comprising a macrocyclic ring of glucose subunits linked by a-1,4 glycosidic bonds. Cyclodextrins are produced from starch through enzymatic conversion. Typical cyclodextrins contain 6 to 8 glucose monomers in the ring. Cyclodextrins have a hydrophilic outer surface and a lipophilic central cavity.

[0043] A variety of natural dyes and bio-based extracts, such as willow bark extract and coffee extract, have shown to have antimicrobial activity. Such components can also be used to provide antimicrobial activity to the fiber filaments 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.

[0044] Preferably, the antimicrobial agent is at least one selected from the group consisting of polyphenols, resin acids, surfactants, and lignin.

[0045] In addition to the dispersant and wet strength agent, the suspension can also include additional additives, such as a hydrophobic binder. The hydrophobic binder can be alkyl ketene dimer (AKD, an alkaline or neutral sizing agent), alkenyl succinic anhydride (ASA, a sizing agent), rosin (an acidic sizing agent), natural waxes, and modified sunflower oil-based binders (MSOHO), or any mixture thereof. Additional additives can include strength additives, rheology modifiers, pigments, and / or other modifiers. For example, polyethylene oxide (PEO) can be used as a rheology modifier. Those skilled in the art will appreciate that these additives can be used to adjust the properties of the antimicrobial fiber filaments and / or articles made therefrom.

[0046] In one example, the suspension contains AKD as the hydrophobic binder. Due to the hydrophobic binder, AKD reduces the absorbency of the fiber filaments. AKD can also increase the strength of the fiber filaments. When used, the amount of AKD can be 0.5% to 10% by weight, such as 0.5% to 5% by weight, of the dry matter of the aqueous suspension.

[0047] According to one exemplary embodiment, the dry matter of the aqueous suspension for manufacturing the antimicrobial fibrous filament comprises 80-85 wt% of non-regenerated MFC and about 2 wt% of tannic acid as antimicrobial agent. Furthermore, the dry matter of the aqueous suspension for manufacturing the antimicrobial fibrous filament comprises CMC and aPAM as dispersing agents and PAE as wet strength agent. The dry matter of the aqueous suspension for manufacturing the antimicrobial fibrous filament can further comprise AKD as hydrophobic binder.

[0048] According to another exemplary embodiment, the dry matter of the aqueous suspension for manufacturing the antimicrobial fibrous filament comprises 80-85 wt% of non-regenerated MFC and about 2 wt% of a composition named NordShield® as antimicrobial agent. Furthermore, the dry matter of the aqueous suspension for manufacturing the antimicrobial fibrous filament comprises CMC and aPAM as dispersing agents and PAE as wet strength agent. The dry matter of the aqueous suspension for manufacturing the antimicrobial fibrous filament can further comprise AKD as hydrophobic binder.

[0049] According to yet another exemplary embodiment, the dry matter of the aqueous suspension for manufacturing the antimicrobial fibrous filament comprises 80-85 wt% of non-regenerated MFC and about 2 wt% of lignin as antimicrobial agent. Furthermore, the dry matter of the aqueous suspension for manufacturing the antimicrobial fibrous filament comprises CMC and aPAM as dispersing agents and PAE as wet strength agent. The dry matter of the aqueous suspension for manufacturing the antimicrobial fibrous filament can further comprise AKD as hydrophobic binder.

[0050] The order of addition of the components typically forming the aqueous suspension (to the aqueous solution) is MFC, wet strength agent, dispersing agent and antimicrobial agent. Furthermore, in another approach, the antimicrobial agent is added immediately after the MFC, before any other components are added. Preferably, the antimicrobial agent is not added at the same time or immediately after the wet strength agent is added. This enables the wet strength properties of the fibrous filament to be maintained as required.

[0051] The aqueous suspension is directed through a small nozzle (extrusion), where the fibres are well aligned (oriented) with the flow. The nozzle feeds the aqueous suspension to a solid surface, which is then dried to obtain the fibrous filament.

[0052] The initial fibril orientation of the fibrous filament can be obtained at the extrusion stage. A nozzle with an outer diameter less than or equal to the maximum fibril length of the fibres enables the fibrils to be essentially oriented in the longitudinal direction of the fibre as the suspension flows out of the nozzle. Fibril orientation along the longitudinal direction of the fibrous filament provides strength to the filament.

[0053] The manufactured antimicrobial fiber filaments are continuous, but it can be post-processed into shorter lengths by any suitable method known in the art. The thickness of the fiber filaments can be influenced at least partially by adjusting the manufacturing speed, the aqueous suspension concentration, and the nozzle geometry. Chemical post-treatments such as dyeing or the introduction of a surface finish can be performed.

[0054] The manufacturing process disclosed herein is an environmentally friendly process, utilizing mild conditions and not using any hazardous substances. This is a significant benefit when compared to other cellulose-based textile fibers such as viscose and lyocell. The process is free of organic solvents. Only water is used as solvent.

[0055] The process provides a solution to incorporate antimicrobial agents directly into the fiber filaments, as the antimicrobial agents are comprised in the suspension used to produce the filaments. This avoids the use of additional process steps to introduce antimicrobial agents as a post-treatment of the filaments or yarns / fibers or even fabrics / textiles. Unlike processes to produce other cellulose-based textile fibers, the production process does not have a water or chemical cycle, so 100% of the added antimicrobial agents remain in the produced fiber filaments.

[0056] The process also allows for the addition of antimicrobial agents and their efficacy in a permanent manner. The durability of the antimicrobial efficacy can be investigated by wash durability. The wash durability of the fiber filaments or materials made therefrom can be investigated by washing according to standard ISO 6330. The wash-resistant addition can be achieved by covalent bonds. The wash durability, i.e. the ability of the fiber filaments to maintain antimicrobial efficacy even after washing, is particularly important for end-uses of washable textiles. In single-use products using for example nonwoven materials comprising the antimicrobial fiber filaments disclosed herein, wash durability can not be important. However, it should be noted that from a product safety perspective, the permanent binding of the antimicrobial agents is important for nonwoven materials. The wash durability also enables further product processing steps using water, such as the hydroentanglement process.

[0057] However, if desired, antimicrobial surface finishes can also be added to the filaments / yarns / fibers / fabrics / textiles as disclosed herein in a post-treatment step to provide a supplementary antimicrobial effect. The antimicrobial surface finishes can be introduced for example by at least one of the following: plasma coating, wet spray coating, dipping, impregnation, immersion, and roll coating. In certain cases, the antimicrobial surface finishes can be arranged to attach to the antimicrobial fiber filaments by covalent bonding. The covalent bonds can represent a wash-resistant way of attaching the antimicrobial surface finishes.

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

[0059] The density of the antimicrobial fiber monofilament according to the present disclosure can be 500 kg / m 3 to 2000 kg / m 3 , for example 1000 kg / m 3 to 1700 kg / m 3 , for example about 1500 kg / m 3 .

[0060] Toughness is a conventional measure of the strength of a fiber or yarn. It is usually defined as the ultimate (breaking) force of the fiber / yarn in gram-force divided by the linear density. Toughness is usually expressed as cN / (d)tex. Linear density is the fiber / yarn gram weight per 1000 meters of fiber / yarn (tex) or per 10000 meters of fiber / yarn (dtex).

[0061] The linear density of the antimicrobial fiber monofilament according to the present disclosure can be 1 dtex to 10 dtex when measured according to standard ASTM 3822 / D3822M-14 at RH 65% (+ / - 2%) and temperature 20°C (+ / - 2°C).

[0062] The toughness of the antimicrobial fiber monofilament according to the present disclosure can be 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 according to standard ASTM 3822 / D3822M-14 at RH 65% (+ / - 2%) and temperature 20°C (+ / - 2°C).

[0063] According to one embodiment, the antimicrobial fiber monofilament is bio-based and / or biodegradable. Biodegradability of a material means that more than 90% of the original material is converted into CO2, water and minerals through biological processes within 6 months.

[0064] The antimicrobial fiber monofilament according to the present disclosure can be used in a fibrous material, such as a woven, knitted or nonwoven material or as a composite material. The fiber monofilament can be used to produce a fiber or a yarn of the fibrous material. The fibrous material comprising the antimicrobial fiber monofilament can be referred to as an antimicrobial fibrous material. In particular, the fiber monofilament disclosed herein can be used to produce a fiber or a yarn of a woven or knitted material. The manufacturing method disclosed herein is such that a fiber monofilament having the properties (such as linear density and strength) required for a monofilament suitable for producing a fiber or a yarn of a woven or knitted material can be produced.

[0065] The fibrous material can be manufactured by using any method known in the art.

[0066] Exemplary uses of the antimicrobial fibrous material include, for example, antimicrobial nonwoven fabrics. Nonwoven fabrics are sheet or web structures formed from fibers that are bonded together by mechanical, thermal, or chemical treatment. The antimicrobial fibrous filaments disclosed herein can be used to provide antimicrobial nonwoven fabrics, for example, for use in medical applications, such as protective layers, medical masks, face masks, wipes, and wound care products.

[0067] Antimicrobial nonwoven materials can also be used in thermal insulation materials, such as clothing. Generally, for items that employ thermal insulation materials, the less washing they undergo, the better their performance is maintained. Thus, the use of antimicrobial nonwoven materials in such items can minimize the washing process as much as possible.

[0068] Further, the antimicrobial fibrous filaments disclosed herein can be used in any woven or knitted fabric or textile where antimicrobial properties are desired. Examples include, for example, clothing and sportswear. Clothing and other textiles can be carriers of microbial species that are cultivated and transferred, and thus it is of particular interest to incorporate antimicrobial properties therein. Antimicrobial woven or knitted materials can be used in the medical field, for example, for clothing or bedding. Further, household textiles and textiles used in public places can also use the antimicrobial fibrous filaments as disclosed herein.

[0069] Example

[0070] Exemplary fibrous filaments were prepared and their antimicrobial properties were investigated.

[0071] The suspension was prepared and treated as described above to produce fibrous filaments containing 80-85 wt% non-regenerated MFC as the main component. The fibrous filaments contained about 2 wt% tannic acid, about 2 wt% NordShield® The composition, about 2 wt% surfactant solution, or about 2 wt% silver composition as the antimicrobial agent. The fibrous filaments also contained CMC (about 11 wt%) as a dispersant, PAE (about 3 wt%) as a wet strength agent, aPAM (about 2.5 wt%) as a rheology modifier, and AKD (about 0.5 wt%) as a hydrophobic binder. The weight percentages of the fibrous filament components were calculated from the dry weight of the fibrous filaments.

[0072] The antimicrobial properties of the fiber filaments against the bacteria Klebsiella pneumoniae, Escherichia coli, Acinetobacter baumannii and Staphylococcus aureus as well as OC43 (human coronavirus, HCoV-OC43) and enterovirus CVA9 (Coxsackie virus A9) were investigated. The antibacterial studies were performed according to standard ISO 20743 and the antiviral studies according to standard ISO 18184 with minor adaptations.

[0073] The samples for the antimicrobial studies were prepared by placing the fiber filaments at the bottom of a well plate. The sample weight was 20 mg. Three replicates were prepared (for testing their potential direct toxicity on mammalian cells, three additional replicates were prepared). Fiber filaments without any antimicrobial agent were used as reference. On top of the fiber filament samples, 10 μΐ droplets of the virus / bacteria solution were added and pre-incubated for 1 hour at 37 °C. The samples were rinsed with 1990 μΐ aqueous medium. From the rinsing medium, the final virus dilution was prepared (HCoV-OC43 dilution 50000x).

[0074] For the antiviral studies, the final dilution was added to MRC-5 (15000 cells per well) or A549 (12000 cells per well) cells cultivated on 96 well plates. For the coronavirus studies, the samples were incubated for 5 days at 34 °C in an incubator and then CPE (cytopathic effect) staining was performed. On the third day of incubation, 25 μΐ of the coronavirus samples were collected for qPCR (quantitative polymerase chain reaction) measurement of viral RNA. For the CPE assay, the absorbance at 570 nm (absorbance of living cells) was measured.

[0075] Table 1-4 lists the results of the antiviral studies against the coronavirus OC43.

[0076] Table 1.

[0077]

[0078] Table 2.

[0079]

[0080] Table 3.

[0081]

[0082] Table 4.

[0083]

[0084] Table 5 lists the results of the antiviral study against enterovirus CVA9.

[0085] Table 5.

[0086]

[0087] The study showed that for the reference sample, which did not contain any antimicrobial agent, the absorbance at 570 nm was lower compared to the cell control. This indicated that the reference sample did not show antiviral effect, but the virus dilution that was incubated with the cells contained active virus and infected the cells, resulting in a low absorbance due to the low number of living cells. For the samples containing tannic acid or NordShield as antimicrobial component, the absorbance at 570 nm was comparable to the cell control, proving the antiviral activity of the samples. This was further proven by the qPCR results. In addition, high antiviral activity of the fibres filaments containing surfactant solution or silver as antimicrobial component was proven, in particular high antiviral activity against coronavirus OC43.

[0088] For the antibacterial study, 100 μΙ of the final dilution was placed on a Petri dish and incubated overnight at 37 °C. The bacterial colonies were counted on the next day.

[0089] In the antibacterial study, no significant difference was observed between the reference sample and the sample of fibres filaments containing tannic acid as antimicrobial agent. Therefore, the fibres filaments containing tannic acid did not show antibacterial effect against Klebsiella pneumoniae, Escherichia coli, Acinetobacter baumannii and Staphylococcus aureus.

[0090] The sample of fibres filaments containing NordShield compositions (including coniferous resin acids) as antimicrobial agent showed antibacterial effect against the bacteria studied, i.e. Klebsiella pneumoniae, Escherichia coli, Acinetobacter baumannii and Staphylococcus aureus. The reduction in colony forming units, expressed as a percentage, when compared to the reference sample showed at least 90% for Staphylococcus aureus and at most 99.8% for Klebsiella pneumoniae (Table 6). The difference in log was between 1.01 and 2.71, respectively. A difference in log of at least 1 can be considered significant.

[0091] Table 6.

[0092] Bacterial species % Reduction in colony forming units Escherichia coli 99,41 Acinetobacter baumannii 96,94 Staphylococcus aureus 90,24 Klebsiella pneumoniae 99,8

[0093] The antibacterial effect of fibre filament samples containing either a surfactant solution or silver as an antimicrobial agent against E. coli and S. aureus was investigated, the results of which are shown in Table 7. The reduction in colony forming units (as a percentage) for the surfactant solution showed a 99.78% reduction in E. coli (log difference 2,6) and a 99.9% reduction in S. aureus (log difference 2,9) when compared to the reference sample. No colony forming units were observed using silver as an antimicrobial agent, demonstrating the high antibacterial effect of the silver containing filaments.

[0094] Table 7.

[0095]

[0096] Wash durability, the ability of the fibre filaments to retain antimicrobial activity after washing, was also tested. The wash durability of samples containing NordShield Samples of the composition, including coniferous resin acids, were tested for wash durability. The wash durability of materials comprising or consisting of filaments as disclosed herein was tested according to standard ISO 6330 using a 40°C wash programme.

[0097] Exemplary results are shown in Tables 8a and 8b. Table 8a shows the CPE and qPCR results before washing. The results for the same samples after three wash and dry cycles are shown in Table 8b. The study shows that the fibre filaments retain their antiviral activity after three wash and dry cycles. Furthermore, in general, the antibacterial activity is retained after three wash and dry cycles. Thus, by adding an antimicrobial agent to the suspension to form the fibre filaments, wash-resistant antimicrobial fibre filaments can be obtained.

[0098] Table 8a.

[0099]

[0100] Table 8b.

[0101]

[0102]

Claims

1. A method for manufacturing antimicrobial fiber monofilaments, the method comprising the following steps: (i) Forming an aqueous suspension comprising 90% to 96% by weight of water and 4% to 10% by weight of dry matter, said dry matter comprising microfibrillated cellulose (MFC), dispersant, wet strength agent and antimicrobial agent, said dry matter comprising at least 50% by weight of MFC. (ii) Extruding the aqueous suspension into monofilaments, and (iii) Dry the monofilament.

2. The method according to claim 1, wherein the antimicrobial agent is bio-based.

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

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

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

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

7. An antimicrobial fiber monofilament, comprising: - At least 50% by weight of microfibrillated cellulose (MFC) - Dispersant, -Wet strength agent, and - Antimicrobial agents.

8. The antimicrobial fiber monofilament according to claim 7, wherein the antimicrobial agent is bio-based.

9. The antimicrobial fiber monofilament according to claim 7 or 8, wherein the amount of said antimicrobial agent is from 0.1% to 10% by weight.

10. The antimicrobial fiber monofilament according to any one of claims 7 to 9, wherein the antimicrobial agent is selected from at least one of the following: polyphenols, resin acids, surfactants, and lignin.

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

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

13. A fiber material comprising antimicrobial fiber monofilaments according to any one of claims 7 to 12.

14. The fiber material according to claim 13, wherein the fiber material is a woven material, a knitted material, a nonwoven material, or a composite material.

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