DESCRIPTION

Background of the invention

With the Covid-19 pandemic, antiviral and disinfecting textiles and fabrics have become ubiquitous, especially as applied in face masks like the Livingard® masks and face masks made from Heiq Viroblock® coated fabric. Common types of such fabrics contain powder or nanoparticles of metals or metal oxides, such as silver nanoparticles or copper oxide. While many metals and metal oxides are known to have disinfecting effects, the efficacy of such materials are limited. Further, the release of metal oxide, metal particle or nano particles can be a potential health and environmental concern, as the substances are toxic to both the organism and the environment (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7177798/).

The disinfecting efficacy of a certain chemical compound depends on its surface of interaction with the viral or microbial matter. E.g. exposing a thick layer of contamination to a flat antiviral surface might only destroy the part of the matter which comes in direct contact with the antiviral surface. For this reason, antiviral compounds are more effective when either spread over a material with a large effective surface area, like highly porous activated carbon (activated carbon) or when in solution, e.g. when released from a textile to drops or mist of water. Normally, one needs then significant amounts of dissolvable or releasable disinfecting compounds (metals, metal oxides, metal particles etc.) on a textile in order to obtain an appreciable disinfecting effect.

Especially, the current standard for antiviral textiles IS018184 measures the remaining activated virus after two hours of interaction between the textile and inoculated virus, from a concentration of about ten to the seventh (1e7) virus per ml. Tests at the Zurich University of Applied Sciences (ZHAW), Wadenswil, Zurich, under the supervision of Prof. Chahan Yeretzian, have shown that state of the art commercial fabrics like Livingard® and Viroblock® show very poor performance in tougher tests using shorter duration and/or higher viral concentrations and tough/robust virus types (MS2 phages).

Obviously, when being exposed to virus or microbial contamination, it would be an advantage that a protective mask works as quickly as possible, keeping the live viral or bacterial concentration in the mask low even in situations of continuous supply of virus.

Meanwhile, activated carbon is a material known for absorbing and trapping chemicals as well as viruses and microbes. Examples of materials include textiles or non-wovens from rayon, polyaniline or kynol carbonized to give high effective surface areas. Alternatively, activated carbon particles, which may have diameters of 10-50 micron, can be immobilized in textiles for fabric, like done by the German company Blucher. One technique includes mixing with a binder like styrene-butadiene rubber or PVDF, applying the coating on a textile by means of e.g. a knife coater, and curing. Such pastes are used e.g. to make electrodes for use in capacitive deionization used for water desalination, e.g. by the company Voltea. Yet other techniques include immobilizing the carbon particles between textile or non-woven or membrane layers. In addition to trapping virus and microbes, the carbon fabrics show a low to moderate efficacy in destroying / inactivating virus and microbes.

Summary of the invention

The present invention builds on the realization that the high surface area of activated carbon can provide the needed surface to spread metals or metal ions thinly, thus obtaining the following advantages:

• Strongly increased disinfection efficacy compared to current state of the art antiviral and antimicrobial fabrics and textiles. • Environmentally and biologically friendliness - without metal oxides, nanoparticles or other particulate or highly dissolvable matter which could be taken up by the environment or organism.

The activated carbon layer also provides the advantage of being able to trap virus and microbes. The present invention therefore offers an effective “trap and inactivate” material. E.g. applied to face masks, mist containing virus would be absorbed by the carbon layer, were the virus will be trapped on the carbon surface and inactivated by the presence of metal or metal ions on the same surface.

The present invention provides a layered disinfecting fabric, as defined in the claims, and articles comprising the fabric. Also provided are methods of inactivating microbes and viruses using the fabric, and methods to make the layered disinfecting fabric.

Therefore, according to the current invention, a second fabric layer is added on one side of the carbon layer (in an alternative embodiment, such layers are added on both sides of the carbon layer), which contains a metal not as a highly soluble coating, but instead as a continuous and strong coating as can be obtained by galvanic techniques as well as by physical or chemical vapor deposition techniques. Silver coated yarns and textiles are for example offered under the brands Statex®, Shieldex® and Xstatic®. Still, as is true for all metal surfaces, there will be a minor release of metal and metal ions, which is important for the current invention. The metal coating thickness can range from 0.5nm to 20 micron, more typically between 50 nm and 2 micron.

The present invention utilizes the ability of activated carbon to provide a surface onto which the very small release of metal or metal ions from solid and coated metal surfaces can be trapped, thus providing a high surface area with both trapping and inactivation of viral and microbial matter. Typical metals include silver and copper. Alternative metals include gold, iron, titanium, molybdenum, cobalt, nickel, tin and other metals. Silver is particularly preferred as the metal.

The terms “fabric” and “textile” are used interchangeably herein.

Details of the invention

In one aspect, provided is a layered disinfecting fabric comprising: a first layer, wherein the first layer is made from activated carbon, and a second layer, wherein the second layer contains a metallic component; wherein the second layer is a porous layer, wherein the second layer is in direct contact with the first layer, and wherein the second layer contains metal as a coating between 0.5 nanometer and 20 micrometer in average thickness.

The fabric of the current invention may comprise or consist of the following layers:

• An activated carbon fabric made from, for example, carbonized polyacrylonitrile fabrics (or alternatively carbonized kynol/novoloid or rayon or other fabrics), with a basis weight which may be between 30 and 400 g/m ² ;

• A silver-coated yarn based textile, where the coating thickness of the silver on the yarn may be 0.5 to 1.5 micrometer, and the basis weight of the finished coated textile may be between about 30 and 250 g/m ² ;

• The layers may be laminated together with a highly porous polyamide web-glue, or sewn together by sewing e.g. a square mesh pattern, where the mesh size may be between 0.5 cm to 10 cm; • Optionally, an additional porous layer or textile could be applied between the carbon and silver-containing layers as long as it does not completely prevent contact between the activated carbon fabric and the silver-coated yarn based textile.

The first layer in the structures of the invention may be an activated carbon cloth (ACC) or activated carbon textile, woven or non-woven. It may be made by the carbonization of precursor textile or non-woven made of rayon, kynol/novoloid, polyacrylonitrile or other fiber. Alternatively, it could be made of activated carbon particles or fibers immobilized in a binder such as polyvinylidene fluoride (PVDF) or styrene-butadiene rubber. Alternatively, the first layer may comprise activated carbon particles immobilized in a textile or non-woven, either between such textile or non-woven layers, or by affixing the activated carbon particles to the non-woven or textile fibers using a glue or binder. The basis weight of the first layer may be between 30 and 400 g/m ²

In the application to face masks, the activated carbon layer and the metal-containing textile layer could be sewn together along a line at or close to the periphery of the mask. The layers might also instead be laminated together along part of or over their entire surfaces.

Yet in another embodiment, a metal coating between 0.5 nanometer and 20 micrometer in average thickness is applied directly to at least one side of the activated carbon layer, instead of it being present in a separate textile layer.

When used e.g. in a face mask, virus or bacteria may arrive in the mask embedded in mist with the air stream. The carbon layer will effectively trap the virus or bacteria, while the metal or metal ions adsorbed on the carbon surface will inactivate them.

In order to provide an initial transfer of metal or metal ions from the metal containing fabric to the activated carbon surface, the layered fabric according to the present invention may be soaked in, or wetted with, water or another solvent and then dried as part of the manufacturing procedure. The procedure may be repeated one or more times during the fabric’s service life in order to maintain its disinfectant properties.

The activated carbon and metal coated fabric layers may be laminated together using hot- melt glue, web glue, reactivated glue or other techniques available in the textile industry. Any lamination should be such that some area(s) of contact between the activated carbon layer and the metal containing layer is/are maintained. Alternatively, the layers may be sewn together.

The metal-containing fabric may be produced from a metal coated yarn (Statex, Xstatic or similar) alone or in combination with a conventional synthetic or natural yarn. Alternatively, the metal coating may be applied as a post- treatment on a conventional textile. In one embodiment, the metal will be coated directly onto the activated carbon layer, thus providing a porous layer on top of the carbon. Metal may be applied to yarn, to the conventional textile layer or on top of the activated carbon layer using sputter coating, physical vapor deposition or chemical vapor deposition or galvanic methods. Alternatively, the fabric could consist of massive metal yarns or a mixture of metal containing yarns and synthetic or natural fiber based yarns. The basis weight of the second layer may be between about 30 and 250 g/m ² .

In one embodiment, the second layer consists of a textile containing yarns which are coated with a metal by means of vapor deposition or galvanic techniques. In another embodiment, the second layer consists of a metal layer deposited directly on the first layer by means of vapor deposition or galvanic techniques.

Brief description of the drawings

Figure 1 is a schematic of an exemplary layered structure. Figure 2 is another exemplary layered structure.

Figure 3 is yet another exemplary layered structure

Figure 1 shows a layered disinfecting structure 1 according to the present invention. The structure 1 comprises first layer 1 that is an activated carbon layer and a layer 2 that is a metal containing layer and a layer 3 that is a porous layer providing binding between layers 1 and 2.

Layer 1 could be an activated carbon cloth (ACC) or activated carbon textile, woven or non- woven. It may be made by the carbonization of precursor textile or non-woven made of rayon, kynol/novoloid, polyacrylonitrile or other fiber. Alternatively, it could be made of activated carbon particles or fibers immobilized in a binder which might be PVDF or styrene- butadiene rubber. In yet another embodiment, the layer 1 comprises activated carbon particles immobilized in a textile or non-woven, either between such textile or non-woven layers, or by affixing the activated carbon particles to the non-woven or textile fibers using a glue or binder.

Layer 2 could be a metallized textile or a textile containing at least in part metal coated fibers, like Shieldex®, Statex® or Xstatic® textiles. Alternatively, it could be a textile made at least in part from massive metal fibers.

Layer 3 may be a porous binder or adhesion layer, such as a hot melt glue, reactive porous glue or a porous web glue, or other binding technique used in the textile and lamination industries.

Figure 2 shows a layered disinfecting structure T according to the present invention. Here, the intermediate layer 3 consists of a seam connecting the layers 1 and 2, which may be applied at the periphery of the layered structure. The cross sectional figure shows five stitches of the seam.

Figure 3 shows a layered disinfecting structure 1” according to the present invention. Here, the metal containing layer 2 consists of a porous metal coating directly onto the activated carbon layer. The coating might be applied by galvanic, sputter, physical vapor deposition or chemical vapor deposition methods, including plasma enhanced chemical vapor deposition (PECVD). The metal containing layer 2 is applied directly on the carbon layer 1.

Additional porous textile or other layers might be put between the activated carbon and metal containing layers.

Potential applications of the disinfecting textile fabric include wound dressings and other medical applications, such as protective clothing, surgical drapes and other surface textiles in operating theaters and health care institutions, for example curtains or bedsheets. A preferred use is in face masks. The disinfecting textile could be used in portable applications, like linings of bags. Further, the disinfecting textile might be applied in furniture and as interior textiles in work places, public building, public transport, rental cars etc.

T est results

The laboratory tests presented in this section were performed and reported by the Zurich University of Applied Sciences (ZHAW), Wadenswil, Switzerland, under supervision of Prof. Dr. Chahan Yeretzian.

Testing methodology

Escherichia virus MS2 was used as a model pathogen: a virus infecting the Bacterium Escherichia Coli and belonging to the same taxonomic kingdom as coronaviruses. Procedure: Pieces of Textile were wetted with double-distilled water using an atomizer. The textile laminate was then inoculated by spotting a fresh MS2 virus suspension on its surface [3][4] Reference tests were conducted using a cotton textile (acc. ISO 105-F02). Each experiment was performed at least in triplicate and for each experiment the concentration of the virus stock (= inoculum) used was verified. The viruses were then recovered by means of a washout procedure by either stomaching or vortexing the textile in a wash-out solution (SCDLP medium acc. ISO 18184). Serial dilutions of the resulting liquid were then mixed with soft agar and E. coli and poured onto an agar plate. After incubation, the phage (virus) plaques were counted, and the inactivation rates calculated.

Uncertainties refer to a 95% confidence interval unless otherwise indicated. The method was less accurate for low activation degrees, partly because a large number of plaques (live viruses) have to be manually counted.

Tests of Antiviral effect of Activated Carbon Textile

A standard commercial activated carbon textile with weight 110g/m ² was tested. The fabric was produced by carbonization of polyacrylonitrile.

A viral deactivation degree of 30% ± 45 % was measured. This is a very poor deactivation. Experimental data are given below.

Table 1

Table 2

Table 3

Tests of Antiviral effect of Silver coated textile

A standard textile containing polyester and silver coated polyamide (Statex) yarn was tested. It was not possible to measure any viral deactivation. The technical results were calculated as -1 ± 213%, which in practice means that no disinfection could be measured.

Table 4 Table 5

Table 6

Tests of Antiviral effect of activated carbon textile laminated to silver textile according to the current invention

A laminate of the activated carbon textiles and silver coated yarn textiles of the tests above were finally tested for its antiviral efficacy. In this case a very high deactivation degree of 98.5 % ± 0.5 % was measured.

Table 7

Table 8

Table 9

Later tests by the same institute reported even higher disinfection degrees, above 99%.

Comparison with disinfecting textiles currently on the market:

ZHAW tested the fabrics used in two common antiviral textile facemasks on the market.

The mean inactivation degrees were 79-87% for Textile A (Livingard mask fabric), 53-77% for Textile B (textile impregnated with Heiq Viroblock) and 99% for the material according to the present invention.

In conclusion, while using non-toxic materials, the present invention provides a very strong enhancement of disinfecting effect over the component materials as well over conventional disinfecting textiles.