GB2608599A

GB2608599A - Biodegradable filter

Info

Publication number: GB2608599A
Application number: GB2109557.5A
Authority: GB
Inventors: Nesin Volodymyr; Boedecker Johann
Original assignee: Pentatonic Ltd
Current assignee: Pentatonic Ltd
Priority date: 2021-07-01
Filing date: 2021-07-01
Publication date: 2023-01-11
Also published as: WO2023275547A1; GB202109557D0

Abstract

The filter comprises non-woven nano-fibre filtration membrane 10 between outer layers 5. The outer layers comprise cellulosic, bast, protein based or polyvinyl alcohol (PVA) fibres. The membrane has area density = 0.2-10 (0.2-6) g/m2. The outer layer includes a thermoplastic or a thermoplastic 15 is located between the outer layers 5 and membrane 10. The thermoplastic 15 is preferably fibers or a spray coating. The preferred nanofibres have denier = 50-500 nm. Preferably the membrane 10 is biodegradable polycaprolactone, polyhyroxybutyrate (hydroxyvalerate), polylactic acid, polyglycolic acid, polybutylene adipate terephthalate, polybutylene succinate, polypropylene terephthalate, PVA or starch. The outer layers 5 are preferably viscose, cellulose acetate, lyocell, bamboo, cotton, silk, wool, fur, flax, hemp, jute, ramie or kenaf. The replaceable filter is used in face mask with ear loops and preferably nose clip. The membrane 10 is produced by centrifugal- or electro-spinning, and then bonded to the outer layers by ultrasonic bonding. The outer layers 5 are preferably spun-laid and calendar roll bonded.

Description

BIODEGRADABLE FILTER

FIELD

The present invention relates to a biodegradable filter for a mask, a method of manufacturing the filter, and a mask comprising the filter.

BACKGROUND

The prevention of viral and microbial transmission is a huge societal problem, as illustrated by the Covid-19 pandemic that began in 2020. As such, the global demand for face coverings (such as cloth, surgical, and FFP respirators) as a precautionary measure to suppress transmission has surged.

Single-use surgical masks, which are arguably the most prevalent in society today, are primarily composed of synthetic, woven polymeric materials. This type of mask cannot be recycled, and may even break down into micro or nanoplastics, which are particularly concerning pollutants. As such, single-use disposable masks are now largely contributing to the already substantial plastic waste problem. For instance, according to a survey by TradeWaste.co.uk in November 2020, an average of 53 million disposable masks were sent to landfill every day in the UK. Additionally, not only are single-use surgical masks contributing to the global plastic problem, they also pollute water and can substantially harm wildlife.

Therefore, given that face coverings are currently a legal requirement in the majority of indoor public places around the world, there is a clear need for breathable face masks that not only exhibit a high filtration efficiency, but which do not negatively impact the environment, and which meet the requirements for FFP1, FFP2, FFP3 assigned according to EN 149, or TYPE II or TYPE IIR according to EN 14683.

The disclosed invention is intended to overcome or ameliorate at least some aspects of this problem.

SUMMARY

Accordingly, in a first aspect of the invention, there is provided a biodegradable filter for a mask, the filter comprising: at least two outer layers comprising cellulosic-based fibres, bast fibres, protein-based fibres, and/or polyvinyl alcohol fibres; and a filtration membrane located between the two outer layers, wherein the filtration membrane is a non-woven nanofibre layer having an areal density in the range of from about 0.2 and about 10 g/m2; and wherein the at least two outer layers comprise a thermoplastic additive and/or wherein the filter comprises a thermoplastic layer located between the filtration membrane and each of the at least two outer layers.

The biodegradable filter according to the first aspect of the invention is biodegradable and home or industrially compostable. As such, the filter according to the invention is considerably more environmentally friendly compared to existing filters.

As used herein, the term "cellulosic-based fibres" relates to fibres made of ethers or esters of cellulose. Examples of cellulosic-based fibres include but are not limited to viscose, lyocell, bamboo, cotton, and sisal. The cellulosic fibres may be composites with synthetic or other natural polymers. The fibres may also contain hemicellulose. As used herein, the term "bast fibres" refers to plant fibres from the phloem or bast surrounding the stem of certain dicotyledonous plants. Examples of bast fibres include but are not limited to flax, hemp, jute, ramie, kenaf, or abaca.

As used herein, the term "protein-based fibres" relates to fibres derived from animals or insects. Examples of protein-based fibres include but are not limited to silk, wool or fur. Natural fibres, such as those described above, are beneficial as they deliver natural hydrophilicity to the filter, which allows for efficient absorption of breathing moisture.

As used herein, the term "areal density" relates to the weight of fibre per unit area. The filtration membrane comprises a non-woven nanofibre layer having an areal density in the range of from about 0.2 to about 10 g/m2, optionally in the range of from about 0.2 to about 6 g/m2. Areal densities within this range result in a membrane that has higher filtration capacity, as the fine nature of the fibres are able to effectively trap small particles, often down to the nano or sub-nano size range.

The outer layers serve as protective layers to the filtration membrane and also provide structural integrity to the biodegradable filter. The filter comprises at least two outer layers, but may further comprise additional outer layers depending on the structural properties desired. The areal density of each of the at least two outer layers may be in the range of from about 10 to about 100 g/m2, optionally in the range of from about 15 to about 35 g/m2. This density range in particular provides the optimum balance between structural rigidity, and flexibility and breathability of the filter.

As used herein, the term "thermoplastic additive" relates to a plastic or polymer material that is malleable at an elevated temperature and is then able to solidify upon cooling. Addition of a thermoplastic additive enhances the structural integrity of the product. Moreover, inclusion of a thermoplastic additive within the outer layers allows for connection of the elements of the filter by ultrasonic bonding. As used herein, the term "ultrasonic bonding" relates to standard sonic welding processes which use sound waves and pressure in order to fuse components together.

Optionally, the thermoplastic additive comprises thermoplastic fibres. The thermoplastic additive may comprise thermoplastic fibres present in the range of from about 15 wt. % to about 80 wt. % of the total weight of fibres present in each of the at least two outer layers, optionally in the range of from about 25 wt. % to about 50 wt. % of the total weight of fibres present in each of the at least two outer layers. Use of thermoplastic fibres blended with the fibres present in the at least two outer layers provides for a simplified manufacturing process. Thermoplastic fibres include but are not limited to biodegradable polyamides, a copolymer of polylactic acid /poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PLA/PHBV), biodegradable polypropylene (PP), biodegradable polyethylene terephthalate (PET) or polytrimethylene terephthalate (PTT). As used herein, the terms "biodegradable polypropylene (PP)" and "biodegradable polyethylene terephthalate (PET)" relate to PP and PET comprising a biodegradable plastic additive respectively. As defined herein, a "biodegradable plastic additive" is an additive that is used to increase the biodegradation of the polymer material in question, so that it can be broken down by microorganisms. An example of a biodegradable plastic additive includes but is not limited to BioSphere 201®. The biodegradable plastic additive is typically present in the range of about 1 wt. % to about 4 wt. % to provide optimum biodegradability of polypropylene whilst maintaining a relatively narrow nanofibre diameter distribution and maintaining the physical properties of the polymer.

As used herein, the term "thermoplastic layer" is a quantity or thickness of plastic or polymer material that is malleable at an elevated temperature and is then able to solidify upon cooling. An example of a material used for the thermoplastic layer includes but is not limited to a biodegradable polyamide (such as biodegradable Nylon), poly 3-hydroxybutyrateco-3-hydroxyvalerate (PHBV), polylactic acid (PLA), biodegradable polyester base polymers, polyurethanes, polyfurfuryl alcohol or thermoplastic starch.

Optionally, the thermoplastic layer is provided as a coating on a surface of a respective one of each of the at least two outer layers. As used herein, the term "surface" relates to an inner surface of the outer layer away from the external environment. Optionally, when the thermoplastic layer is a coating, it is in the range of 0.5% to 1% of the total areal density of each of the at least two outer layers. Advantageously, a coating allows for uniform and controlled coverage of the thermoplastic material, which provides for strong adhesion of the outer layers and filtration membrane following ultrasonic bonding. The thermoplastic layer can be mixed with additives, such as plasticisers, which facilitate application as a coating.

Optionally, the filtration membrane is provided as a coating on a surface of at least one of the at least two outer layers. Application of the filtration membrane as a coating minimises the individual components present in the filter, and thereby results in a simpler manufacturing process. Moreover, a coating means that the filtration membrane is securely integrated into at least one of the at least two outer layers.

In the case where the at least two thermoplastic layers are provided as a coating on a surface of the at least two outer layers, and wherein the filtration membrane is provided as a coating on a surface of at least one of the at least two outer layers, typically the filtration membrane will be provided as a coating on the thermoplastic layer. However, it may also be possible to provide the thermoplastic layer as a coating on the filtration membrane.

Optionally, the filtration membrane comprises nanofibres having a diameter in the range of from about 50 to about 500 nm, optionally having a diameter in the range of from about 100 nm to about 400 nm. Nanofibres in this particular range provide a filtration membrane with enhanced porosity, which enhances the breathability of the filter whilst also being electrostatically charged to enhance the performance of the filter. As used herein, the term "porosity" relates to the voids present in between the fibres formed, which are able to hold fluid/particles.

Optionally, the filtration membrane comprises a biodegradable polymer. The biodegradable polymer may be selected from polycaprolactone (PCL), polyhydroxybutyrate (PHB), polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), polyhydroxyalkanoate (PI-IA), polytetramethylene adipatecoterephthalate (PTAT), poly 3-hydroxybutyrateco-3-hydroxyvalerate (PHBV), polybutylene succinate (PBS), polytrimethylene terephthalate (PTT), polyvinyl alcohol (PVA), polyglycolic acid (PGA), or combinations thereof. Biodegradable polymer blends may include but are not limited to PHB/PCL, PCL/PLA, PLA/PHA, PLA/PHB, PLA/PGA, PLA/PHBV, PLA/PBAT, PHBV/PBAT, and PHBV/PBS. With regard to polymer blends comprising two polymers, the ratio of the polymers may be present in the ratio of 5:95, 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, 70:30, 80:20, 90:10, or 95:5. Advantageously, the polymers are biodegradable, resulting in a more environmentally friendly filter. Moreover, PHB, PHA, PCL, PBAT and PLA/PCL in particular are home compostable. In addition, PLA is industrially compostable.

The biodegradable polymer may further comprise thermoplastic starch. Thermoplastic starch may be incorporated such that a composite is formed, for instance, using conventional synthetic thermoplastic processing techniques (for instance re-compounding, polymer coating, extrusion and injection). Incorporation of thermoplastic starch into the biodegradable polymer enhances the structural and mechanical properties of the filtration membrane.

It is often the case that the filtration membrane is entirely formed of a biodegradable material, such as a biodegradable polymer and/or protein-based fibre.

Accordingly, in a second aspect of the invention, there is described a mask comprising: a mask body; and ear loops arranged proximate to opposing sides of the mask body; wherein the mask body comprises a biodegradable filter according to the first aspect of the invention.

As used herein, the term "mask body" relates to the portion of the mask used to cover the nose and mouth region of the face of the user; and the term "ear loop" relates to the portion of the mask that is positioned around the ears to ensure the mask stays in place.

A mask comprising the biodegradable filter according to the first aspect of the invention is considerably more environmentally friendly compared to standard disposable plastic masks currently in circulation. As such, their disposal would have less of a deleterious impact on climate change.

Optionally, the biodegradable filter is replaceable within the mask body. Provision of a replaceable filter allows for easy replacement of the filter once the current filter being used has reached its maximum filtration capacity.

Optionally, the ear loops are connected to the mask body via heat-bonding, stitching and/or via a biodegradable adhesive. Heat-bonding, stitching, and/or biodegradable adhesives allow for strong attachment of the ear loops to the mask body, which reduces the possibility of detachment and therefore results in a more robust and secure mask.

Optionally, each ear loop comprises an elastomeric material, e.g. a biodegradable natural rubber, or a biodegradable fabric, e.g. natural or synthetic fibres, such as biodegradable polyamide fibres (e.g. Nylon). Use of either biodegradable natural rubber, or a biodegradable fabric enhances the biodegradability and compostability of the mask.

Optionally, the mask body further comprises a biodegradable nose clip. The term "nose clip" relates to the part of the mask positioned against the user's nose to help keep the mask in place. A nose clip is beneficial as it helps direct air out the sides of the mask, which is particularly beneficial if the user wears glasses, as this helps prevent build-up of condensation. In addition, a nose clip also aids with the comfort of the mask.

Optionally, the biodegradable nose clip comprises a biodegradable metallic layer located between at least two layers of paper.

Optionally, the biodegradable metallic layer of the nose clip comprises magnesium, iron, zinc, or biodegradable alloys thereof. These metals are readily available, cheap, and their use further enhances the biodegradability and compostability of the mask.

Accordingly, in a third aspect of the invention, there is described a method of manufacturing a filter according to the first aspect of the invention, the method comprising the following steps: i) producing the filtration membrane by centrifugal spinning or electrospinning technology; ii) providing at least two outer layers, and iii) connecting the filtration membrane and the at least two outer layers by ultrasonic bonding; wherein the method comprises providing the at least two outer layers comprising a thermoplastic additive and/or wherein the method further comprises providing a thermoplastic layer between the filtration membrane and each of the at least two outer layers.

As used herein, the term "electrospinning" refers to the process of generating spun nanofibres using high voltage to create an electric field between a droplet of solution at the tip of a needle and a collector plate. As used herein, the term "centrifugal spinning" refers to an alternative process of generating nanofibres using a centrifugal force as opposed to high voltage. Spinning fluid is placed on a rotating head having a nozzle, and when the centrifugal force overcomes the surface tension of the fluid, a liquid jet is ejected from the tip of the nozzle. The jet can then be collected and processed to produce fibres.

It is often the case that the filtration membrane is produced by electrospinning technology.

Optionally, the filtration membrane is coated on a surface of at least one of the at least two outer layers. When used as a coating, the filtration membrane is directly spun onto a surface of at least one of the outer layers, which effectively acts as a substrate. Applying the filtration membrane as a coating streamlines the manufacturing process of the filter.

Where at least two thermoplastic layers are provided, connecting the filtration membrane and the at least two outer layers may take place via melting the at least two thermoplastic layers followed by subsequent cooling. Typically, the at least two thermoplastic layers are heated to a temperature in the range of from about 60°C to about 270°C, more typically in the range of from about 100°C to about 250°C. Typically, the at least two thermoplastic layers are cooled at room temperature to below the melting point of the thermoplastic layer.

Where at least two thermoplastic layers are provided, each thermoplastic layer is spray coated onto the at least two outer layers. Optionally, the two thermoplastic layers are powder coated. Powder coating provides for more accurate application of the thermoplastic layers, allowing for more even coverage and enhanced adhesion of the outer layers to the filtration membrane.

Optionally, in step (ii), the at least two outer layers are produced through a spun-laid process and calendar roll bonded.

As used herein, the term "spun-laid" is the process used to melt polymers that are extruded through many small holes and collected on a belt. The filaments adhere to each other before cooling down. Fabric will have greater strength, but lower flexibility. A spun-laid web is also self-bonded during the web forming process and additionally stabilized by the calendar bonding step, optionally accompanied by hydro-entaglement that uses high-pressure water jet to entangle the fibers.

As used herein, the term "calendar roll bonding" relates to processing of a spun laid web via calendar rollers to generate a layer of material. Calendar roll bonding is a type of thermal bonding, and is particularly advantageous in preparation of nonwovens as it is environmentally friendly. For calendar roll bonding, no harsh chemicals are required; it does not cause water pollution, which is the case with chemical bonding; and it imparts a soft feel on the nonwoven, which enhances comfort for the user. In addition, the roll may be patterned, which can improve abrasion resistance of the material, as well as producing an aesthetically pleasing fabric.

It may be the case that the fibres of the at least two outer layers are produced by treatment of pellets. For instance, it may be the case that pellets are compounded, blended and/or ground; and said processed pellets are extruded into spun-laid fabric, which is then followed by calendar roll bonding to form a web. In yet another embodiment, the at least two outer layers can be produced by compounding, blending and/or grinding pellets of the respective material; extruding said processed pellets into filaments; crimping and cutting fibres from said filaments; and using a spun-laid process followed by calendar roll bonding to form a web. The skilled person will appreciate that carding can be used instead of spun-laid processing. As used herein, the term "carding" is the process used to separate and disentangle fibres to form a continuous web.

Unless otherwise stated, each of the integers described may be used in combination with any other integer as would be understood by the person skilled in the art. Further, although all aspects of the invention preferably "comprise" the features described in relation to that aspect, it is specifically envisaged that they may "consist" or "consist essentially" of those features outlined in the claims. In addition, all terms, unless specifically defined herein, are intended to be given their commonly understood meaning in the art.

Further, in the discussion of the invention, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, is to be construed as an implied statement that each intermediate value of said parameter, lying between the smaller and greater of the alternatives, is itself also disclosed as a possible value for the parameter.

In addition, unless otherwise stated, all numerical values appearing in this application are to be understood as being modified by the term "about".

In order that the invention may be more readily understood, it will be described further with reference to the figures and to the specific examples hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1: A schematic diagram of the construction of a biodegradable filter according to a first aspect of the invention.

Figure 2: A schematic diagram of the nose clip construction of a mask according to a second aspect of the invention.

Figure 3: (a) A scanning electron microscope (SEM) image of an outer layer of the biodegradable filter wherein the outer layer comprises viscose fibres; (b) a SEM image of a thermoplastic layer comprising biodegradable nylon; (c) a SEM image of a filtration membrane comprising electrospun PHB nanofibres.

Figure 4: A SEM image of electrospun PHB fibres at (a) a magnification of 1,000 (b) a magnification of 5,000; and (c) a magnification of 10,000.

Figure 5: (a) A SEM image of an outer layer comprising viscose fibres at a magnification of (i) 400 and (ii) 1,000; and (b) a SEM image of an outer layer comprising viscose fibres coated with a biodegradable nylon coating at a magnification of (i) 400 and (ii) 1,000.

DETAILED DESCRIPTION OF EMBODIMENT(S)

Figure 1 is a schematic diagram of the construction of a biodegradable filter according to an embodiment of the first aspect of the invention. Two outer layers comprising viscose fibres 5 are positioned either side of a filtration membrane 10 comprising PHB fibres. Two thermoplastic layers 15 are located between the filtration membrane and each of the at least two outer layers 5. Thermoplastic layers 15 comprise biodegradable nylon and have been applied as a coating onto a surface of the two outer layers 5. The two outer layers 5, the filtration membrane 10, and the two thermoplastic layers 15 have been bonded together via ultrasonic bonding.

Figure 2 is a schematic diagram of the construction of a nose clip according to an embodiment of the second aspect of the invention. Two layers 35 of undyed paper are positioned either side of iron wire 30.The two layers 35 of undyed paper and the iron wire 30 are connected by use of water as a binder. Upon drying, the two layers 35 of paper and the iron wire 30 form a self-bonded web.

Figure 3 (a) to (c) are scanning electron microscope (SEM) images of an outer layer of the biodegradable filter wherein the outer layer comprises viscose fibres; a thermoplastic layer comprising biodegradable nylon; and a filtration membrane comprising electrospun PHB nanofibres respectively. The images were taken using a SEMOSCOPE (Turkey).

Figure 4 shows a SEM image of electrospun PHB fibres at (a) a magnification of 1,000 (b) a magnification of 5,000; and (c) a magnification of 10,000. The images were taken using a SEMOSCOPE (Turkey). As can be seen from the images, the fibres have a smooth surface, a stable homogeneous morphology without wet branching, and the profiles of the fibres have consistent diameter along their lengths.

Figure 5(a)(i) shows a SEM image of an outer layer comprising viscose fibres at a magnification of 400 and figure 5(a)(ii) is at a magnification of 1,000. Figure 5(b)(i) shows a SEM image of an outer layer comprising viscose fibres coated with a biodegradable nylon coating at a magnification of 400 and figure 5(b)(ii) is at a magnification of 1,000. The images were taken using a SEMOSCOPE (Turkey).

EXAMPLES

Production of PHB fibres using Electrosoinnino Technology PHB fibres were electrospun using a multi-nozzle electrospinning system (Ne300 Laboratory Scale -INOVENSO, Turkey).

A solution comprising 3g PHB from biomer, 77.6g chloroform, 19.4g tetrahydrofuran, and 0.08g of lithium chloride (LiCI) salt was prepared.

PHB was dissolved in chloroform with a heat of 130°C and stirred for two hours. The solution was then stirred for an additional five hours without heat. THE was then added to slow down the evaporation in the process and stirred for an additional two hours. To increase the conductivity, lithium chloride was added, and the mixture was stirred until the lithium chloride salt dissolved completely.

The viscosity of the polymer solution according to ASTM/ISO 2555 at 200 rpm was 36.63 +/-0.85 mPa.s. Viscosity was measured at room temperature (25 °C) using a rotating viscometer (Lamy Rheology Instruments, France) and the rotation speeds were between 0.3 and 250 rpm.

The conductivity of the solution was measured using Ohaus St 3100 (Switzerland) and was 0.3933 +/-0.0047 ps/cm.

The prepared solution was fed into a 10m1 syringe and the syringe was attached to a syringe pump.

(i) Example 1 -Operation Parameters for preparation of an electrospun filtration membrane comprising PHB fibres Flow Rate (ml/h) High Voltage (KVolt) Distance (mm) Needle Diameter (mm) Collector rotating speed (rpm) Temperature (°C) Relative Humidity (%) Areal density (g/m2) 24 250 1.2 100 25-27 35-40 0.8 Typically, electrospun PHB fibres are obtained using solution flow rates of 1.5-7 ml/h controlled by a syringe pump with distance of needle-collector (working distance) of 150-305 mm, a needle with a diameter of 1.2 mm, and voltage of 1590 kV.

(ii) Example 1 -Fibre Diameter Measurement SEM images of the fibres of Example 1 were taken using SEMOSCOPE (Turkey), which can be seen in Figures 6(a)-(c), and the fibre diameter analysis was done using FIBRAQUANT software. Specifically, the scanning electron microscope focuses on a single layer of depth and the software measures diameters across a wide range of fibres within that layer, and the shortest distance from one side to the other of the cross-section of each fibre is measured. The average, standard deviation, and median are then calculated: Average (pm) Standard Deviation (pm) Median (pm) 0.402 0.173 0.383 Filtration Efficiency of a filtration membrane coated on an outer laver Examples 2 to 25 show the filtration efficiency of filtration membranes of varying areal densities coated onto an outer layer. The outer layer comprises viscose fibres, and the filtration membrane comprises polyhydroxybutyrate (PHB) fibres.

(i) Areal density Areal density was calculated using the following equation: Areal density = weight NJ/sample area [m2] (ii) Average Filtration Efficiency The average filtration efficiency was calculated according to EN 149 standard (European standard).

Example Working 1st pump 2nd pump Applied Substrate Areal Average filtration efficiency (a/o) Distance feeding rate feeding rate Voltage Speed Density (mm) (ml/min)' (ml/min)1 (kV) (m/min)2 (g/m2) 2 280 6.75 5 60 0.14 2 98.76 3 280 6.75 5 60 0.17 1.8 95 4 280 6.75 5 60 0.19 1.6 93.66 280 6.75 5 60 0.22 1.4 90.3 6 280 6.75 5 60 0.24 1.2 89.96 7 280 6.5 5 60 0.26 1 83.49 8 280 6.5 5 60 0.32 0.8 77.76 9 290 3.5 2 60 0.2 0.8 99.65 290 4 2 60 0.26 0.6 98.74 11 290 4 2 60 0.39 0.4 95.17 12 290 4 2 60 0.19 1 99.32 13 260 4 2 55 0.26 0.6 94.11 14 260 4 2 56 0.39 0.4 87.7 260 4 2 60 0.2 0.8 99.49 16 300 3.5 1.7 60 0.23 0.6 98.32 17 295 5 3 60 0.24 0.8 95.45 18 295 5 3 60 0.39 0.6 84.03 19 310 2.5 2.3 55 0.24 0.4 94 310 2.5 2.3 55 0.2 0.6 98.5 21 305 2.5 2.3 60 0.15 0.8 99.96 22 305 2.5 2.3 60 0.39 0.2 81.38 23 305 2.5 2.3 60 0.26 0.3 93.15 24 305 2.5 2.3 60 0.16 0.5 99.29 305 2.5 2.3 60 0.2 0.4 92.95 Feeding rates per pump are the total volume supplied on a set of 2 rods, consisting from 27 nozzles each. A peristaltic pump was used.

2 Substrate speed relates to the speed of the substrate passing through the working area (electrospinning area).

Claims

Claims 1. A biodegradable filter for a mask, the filter comprising: at least two outer layers comprising cellulosic-based fibres, bast fibres, protein-based fibres, and/or polyvinyl alcohol fibres; and a filtration membrane located between the two outer layers, wherein the filtration membrane is a non-woven nanofibre layer having an areal density in the range of from 0.2 to 10 g/m2; wherein the at least two outer layers comprise a thermoplastic additive and/or wherein the filter comprises a thermoplastic layer located between the filtration membrane and each of the at least two outer layers.
A biodegradable filter according to claim 1, wherein the thermoplastic additive comprises thermoplastic fibres.
A biodegradable filter according to claim 1 or 2, wherein the thermoplastic additive comprises thermoplastic fibres present in the range of from 25 wt. to 50 wt. % of the total weight of fibres present in each of the at least two outer layers.
A biodegradable filter according to any preceding claim, wherein the thermoplastic layer is provided as a coating on a surface of a respective one of each of the at least two outer layers.
A biodegradable filter according to any preceding claim, wherein the filtration membrane is provided as a coating on a surface of at least one of the at least two outer layers.
A biodegradable filter according to any preceding claim, wherein the nanofibres of the filtration membrane have a diameter in the range of from 50 to 500 nm.
A biodegradable filter according to any preceding claim, wherein the filtration membrane has an areal density in the range of from 0.2 to 6 g/m2.
A biodegradable filter according to any preceding claim, wherein the filtration membrane comprises a biodegradable polymer. 2. 3. 4. 5. 6. 7. 8.
9. A biodegradable filter according to claim 8, wherein the biodegradable polymer is selected from polycaprolactone, polyhydroxybutyrate, polylactic acid, polyglycolic acid, polybutylene adipate terephthalate, polyhydroxyalkanoate, polytetramethylene adipate-coterephthalate, poly 3-hydroxybutyrateco-3-hydroxyvalerate, polybutylene succinate, polytrimethylene terephthalate, polyvinyl alcohol, polyglycolic acid, or combinations thereof.
10.A biodegradable filter according to claims 8 or 9, wherein the biodegradable polymer further comprises thermoplastic starch.
11.A biodegradable filter according to any preceding claim, wherein the cellulosic-based fibres are selected from viscose, cellulose acetate, lyocell, bamboo, or cotton.
12.A biodegradable filter according to any preceding claim, wherein the protein-based fibres are selected from silk, wool, or fur.
13.A biodegradable filter according to any of any preceding claim, wherein the bast fibres are selected from flax, hemp, jute, ramie, or kenaf.
14.A biodegradable filter according to any preceding claim, wherein the areal density of each of the at least two outer layers is in the range of from 10 to 100 g/m2, optionally in the range of from 15 to 35 g/m2.
15.A mask comprising: a mask body; and ear loops arranged proximate to opposing sides of the mask body, wherein the mask body comprises a biodegradable filter according to any one of claims 1 to 14.
16.A mask according to claim 15, wherein the biodegradable filter is replaceable within the mask body.
17.A mask according to claim 15 or claim 16, wherein the ear loops are connected to the mask body via heat-bonding, stitching and/or via a biodegradable adhesive.
18.A mask according to any one of claims 15 to 17, wherein each ear loop comprises an elastomeric material, e.g. a biodegradable natural rubber, or a biodegradable fabric, e.g. natural or synthetic fibres.
19.A mask according to any one of claims 15 to 18, wherein the mask body further comprises a biodegradable nose clip, optionally comprising a biodegradable metallic layer located between at least two layers of paper, optionally wherein the biodegradable metallic layer comprises magnesium, iron, zinc, or biodegradable alloys thereof.
20.A method of manufacturing a biodegradable filter according to any one of claims 1 to 14, the method comprising the following steps: i) producing the filtration membrane by centrifugal spinning or electrospinning; ii) providing at least two outer layers, and Hi) connecting the filtration membrane and the at least two outer layers by ultrasonic bonding, wherein the method comprises providing the at least two outer layers comprising a thermoplastic additive and/or wherein the method comprises providing a thermoplastic layer between the filtration membrane and each of the at least two outer layers.
21.A method according to claim 20, wherein the filtration membrane is coated on a surface of at least one of the at least two outer layers.
22.A method according to claim 20 or 21, wherein where at least two thermoplastic layers are provided, connecting the filtration membrane and the at least two outer layers takes place via melting the at least two thermoplastic layers and then cooling the at least two thermoplastic layers.
23.A method according to any of claims 20 to 22, wherein where at least two thermoplastic layers are provided, each thermoplastic layer is spray coated onto the at least two outer layers.
24.A method according to any of claims 20 to 23, wherein the filtration membrane is produced by electrospinning technology.
25.A method according to any of claims 20 to 24, wherein in step (ii), the at least two outer layers are produced through a spun-laid process followed by calendar roll bonding.