The present invention relates to a method of manufacturing a hygiene filtration material and such hygiene air filtration material.

BACKGROUND OF THE INVENTION

The inhalation of air contaminated by harmful virus and/or other micro-organisms is a common route for infection of human beings, particularly health and others caused to work with infected humans or animals. Air exhaled by infected patients is a source of contamination. Masks incorporating a suitable filter material are considered advantageous for use as a barrier to prevent species-to-species transmission of the virus. Air filters believed to remove such virus and/or other micro-organisms are known.

One type of such a filter comprises a fibrous or particulate substrate on which is deposited, upon the surface and/or into the bulk of such fibres or particles, a substance, which captures and/or neutralises virus and/or other micro-organisms of concern.

Accordingly, from WO 2011/026515 there is known a multi-layered filtration material for a face mask. The material comprises i) a filter segment comprising the filtration material adapted to cover the mouth and nostrils of the user, ii) a support segment adapted for dismountable placement around the head of the user, and adapted to align the filter segment over the mouth and nostrils of the user.

This multi-layered filtration material comprises a core layer that is a non-woven material impregnated with sodium chloride, which is incorporated in a liquid vehicle or sprayed onto the non-woven material. On each side of the core layer filtration layers and exterior silver nano-particle-coated non-woven layers are provided in the multi-layered structure. In use, the sodium chloride in core layer permeates the inhaled air with salt which has the effect of dissolving phlegm in the bronchial tubes and killing micro organisms that cause infections. This makes breathing easier, alleviates sneezing, coughing, and shortness of breath.

However, this multi-layered structure is a somewhat complicated structure which is expensive to produce. It appears necessary to provide exterior layers around the sodium chloride, which is deposited in the core layer in order to contain the sodium chloride therein. The sodium chloride is left in the non-woven after evaporation of the water vehicle. This means that the particles are loosely deposited in the non-woven layer and therefore easily falls out of the non-woven, if not during manufacturing of the face masks then when the filtration material is in use as e.g. a face mask. This loss of sodium chloride particles reduces the sanitary/disinfecting effect of the filtration material.

From US 5,307,796 a filtration face mask is known which is moulded into a domed shape as a non-woven web material comprises bi-component fibres and is moulded under the application of heat to form the dome shaped face masks. However, the temperatures in excess of at least 110°C needed prevents any water solutions from being present in the non-woven material as the water will evaporate and leave any matter dissolved therein as loose residues in the web.

A method of manufacturing a fibrous web which can be used for fluid filtration is known from WO 2012/006338. In this disclosure a multi-layered fibrous web is produced which may contain particulates of different kinds in the core layer of the multi-layer. The top and bottom layer must prevent the particulates from being washed out of the multilayer construction, which makes this fibrous web structure unsuitable for many filtration functions.

Other methods for manufacturing non-woven dry-formed mats of bi-component fibres are disclosed in WO 2005/044529 or WO 2014/177497.

OBJECT OF THE INVENTION On this background, it is an object of the present invention to provide a filtration material for hygienic or sanitary use and a manufacturing method therefore alleviates the above mentioned problems of the prior art.

SUMMARY OF THE INVENTION

This object is achieved by a method of manufacturing a filtration material for hygienic use comprising the steps of

- dry-forming of a mat of fibrous material by blowing fibrous material comprising bi-component fibres into a forming box having an open bottom positioned over a forming wire to form a mat of fibres on the forming wire forming a fibrous web, where the bi-component fibres have at least two components comprising different polymeric compositions having dissimilar softening temperatures;

- advancing an air-laid non-woven fibrous web on a moving substrate;

- applying in a dry state a granulate material comprising sodium chloride to the mat of fibres; and then

- heating the advancing web at a heating temperature exceeding a first softening temperature, where said first softening temperature corresponds to the lowermost softening temperature of the components of the bi-component fibres.; and then

- calendaring the heated web to provide the web of filtration material to a predetermined thickness, and forwarding the web for further processing.

In a further aspect of the invention there is provided a filtration material for sanitary use, comprising an air-laid non-woven fibrous mat comprising bi component fibres and a portion of granulate material comprising sodium chloride. Hereby, at least a major portion of the granulate material grains are adhered to the surfaces of the bi-component fibres. This is advantageous as the grains or particulates are mechanically attached to the fibre structure of the fibrous mat and are thereby constrained inside the fibrous mat. In contrast, in the prior art the grains may be dissolved and the granular material will be left as a flake-like material on the surface of the fibrous mat which in turn means the material will fall off the fibrous mat when sued as a filtration mat. By a method according to the invention, a non-woven filtration material is achieved which is suitable for use in a variety of applications. The non-woven material is sufficiently porous so that air can penetrate through the material, which makes the material suitable for e.g. face masks. The method according to the invention is advantageous as the sodium chloride "saturation" of the non- woven fibrous mat can be achieved without a liquid carrier due to the use of bi component fibres that can be heat activated to bind the granular particles inside the non-woven mat.

In use, the sodium chloride on the fibres of the non-woven material permeates the inhaled air with salt which has the effect of dissolving phlegm in the bronchial tubes and killing micro-organisms that cause infections. This makes breathing easier, alleviates sneezing, coughing, and shortness of breath. Thus, as the air passes through the filtration material the contaminants are neutralised, securely trapped and adsorbed by the sodium chloride, and the air thereby cleaned.

In further aspect of the invention, it is found advantageous to use of an air filtration material for a face mask releasing material of the granular material in the airflow through the filter material for cleaning said airflow.

The sodium chloride also provides a disinfecting effect, which may be used for other purposes than protective face masks.

According to the invention, the granulate material grains are adhered to the surfaces of the bi-component fibres. Surplus granular material may be removed depending on the actual application of the filtration material. In other applications, it may be found advantageous to use the filtration material as a vehicle for providing drugs for treatment of a disorder, e.g. by supplementing the portion of granulate material comprising sodium chloride with granular additives, such as antibiotics or the like.

In an embodiment of the filtration material according to the present disclosure, the bi-component fibres are hydrophilic fibres. This is advantageous in applications of the filtration material in relation to moisture absorption, e.g. in relation to packaging in the food industry, or the like. Accordingly, the filtration material may be used for protective wrapping of a food product whereby release of the material of the granular material of any airflow through the wrapping is cleaned and thereby preserves the food product.

Preferably, the fibre length of the bi-component fibres is within the range of 1 to 100 mm. Furthermore, the bi-component fibres may advantageously be biodegradable. This allows for environmentally friendly filtration solutions, such as disposable products, such as face masks.

Furthermore, the granulate material may be in crystalline form. This dry state is suitable for easy adherence to the bi-component fibres. The filtration material according to the invention may contain between 5-95 % bi-component fibres, and the filtration material may contain up to 95 % sodium chloride.

When using the filtration material for face masks, it is desirable that all fibres in the non-woven material are bonded and no lose fibres are left in the mat. This may be achieved by adding a step of suction before the application of the sodium chloride granulate. It may also be of preference that subsequent to the step of calendaring, the web of filtration material is passed over a vacuum box for removing excess granular material before advancing to further processing. Said step of further processing may include winding the web of filtration material into a roll. This facilitates transport to other production sites, for instance where the filtration material is used for producing face masks or other types of products.

In the present disclosure, by the term "bi-component fibre" or "bi-co fibre" is meant a fibre composed of two or more components comprising different polymeric compositions having dissimilar softening temperatures, where said components are arranged in separate and distinct regionals along the length of the fibre such as a core component having a higher softening temperature than the coating component coating the core component.

Advantageously, in the step of heating the advancing web at a heating temperature exceeding a first softening temperature, the first softening temperature corresponds to the lowermost softening temperature of the components of the bi-component fibres. Hereby, the bi-co fibres become sticky on its surfaces whereby the granular particles become attached to the fibre surfaces. This heating temperature is preferably between 110°C and 200°C, more preferably at least approx. 145°C. A suitable type of bi-co fibres could be Fiber Trevira 255 1,3 dtex 3 - 6 -12 - 18 mm.

The granular material may be applied in different manners.

In a first embodiment, the air-laid non-woven fibrous web is advanced on a moving substrate, and the step of applying the granulate material is carried out by passing said fibrous web through an applicator where the granulate material is supplied to the advancing web.

In a second embodiment, the step of applying is carried out by the granulate material is supplied into the forming box, so this granulate material supply is mixed with the fibres supplied through the fibre inlet.

By the invention it is realised that the portion of granulate material comprising sodium chloride may be mixed with granular additives, such as antibiotics or the like. Hereby, oral masks may be provided for treatment of respiratory diseases.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention is described in more detail with reference to the accompanying drawings, in which

Figure 1 is a schematic illustration of the manufacturing of a web of filtration material according to an embodiment of the invention;

Figure 2 is a schematic drawing of the filtration material according to the invention;

Figures 3 and 4 are microscopic photos of a filtration material according to the invention. DETAILED DESCRIPTION With reference to fig. 1, a web 2 of non-woven fibrous material is provided. Not shown in the figure, this web is provided by dry-forming of a mat of fibrous material by blowing fibrous material comprising bi-component fibres 20 into a forming box having an open bottom positioned over a forming wire to form a mat of fibres on the forming wire forming a fibrous web. As an example such dry- formed mat of fibrous material may be produced on the apparatuses and under use of the methods disclosed in WO 2005/044529 or WO 2014/177497, which are both incorporated by reference.

The web 2 is advanced on a moving substrate (not shown) through a series of processing steps.

Firstly, the web 2 is advanced through an applicator station comprising an applicator 4 above the web 2 and a suction box 6 below the web 2. Granulate material 8 comprising sodium chloride is fed into the applicator box 4 and onto the web 2. Due to the porosity of the web 2 and supplemented by the suction box 6, the sodium chloride particles of the granular material 8 are drawn into the web 2 and in between the fibres.

The web 2 - now "dry-saturated" with granular particles 8 - are subjected to heat in a heating station 10. As mentioned above, the web 2 is made of bi-component fibres, and such bi-co fibres 20 have a core component having a higher softening temperature than the coating component coating the core component. The web 2 is here heated to a temperature in between said two softening temperatures. Hereby, the coating component of the bi-co fibres 20 become soft and tacky and thereby adheres the granular particles, i.e. the sodium chloride particles 8.

The heated web is then calendared in a calendaring station 12 to provide the web 2 of filtration material to a predetermined thickness and density, and forwarding the web for further processing 16.

The web 2 of filtration material may be advanced over a suction box 14 to remove surplus granular particles before coming to a winding station 16, where the web 2 is wound up in a roll. The roll of filtration material may subsequent be used in the manufacture of face mask or other types of products utilising the sanitary air filtration capabilities that the filtration material according to this disclosure is provided with.

By the manufacturing method described in relation to fig. 1, the sodium chloride is deposited in the non-woven fibrous mat without the use of any liquid carrier due to the use of bi-component fibres. The outer component of the bi-co fibres is heat activated to bind the granular particles inside the non-woven mat. In fig. 2 a schematic illustration of the non-woven mat is shown.

As explained earlier, the sodium chloride 8 on the fibres 20 of the non-woven material permeates the inhaled air with salt which has the effect of dissolving phlegm in the bronchial tubes and killing micro-organisms 22 that cause infections. Thus, as the air passes through the filtration material the contaminants, such as bacteria or virus, are neutralised, securely trapped and adsorbed by the sodium chloride, and the air thereby cleaned.

The photos in figures 3 and 4 are from a prototype production of a filtration material according to the invention. In the photos, it is apparent that the fibres in the non-woven mat are "saturated" with the sodium chloride particles. It is surprisingly experienced that an extremely high amount of sodium chloride particles can be disposed on the fibres in the non-woven mat structure.

Above, the invention is described with reference to a currently preferred embodiment. However it is realised that variants may be provided depending on the actual use of the filtration material without departing from the accompanying claims.