PVDF filtering facepiece respirator and recycling method

Abstract

The present invention relates to a filtering face-piece respirator made of polyvinylidene fluoride and a method for manufacturing the respirator. The present invention also relates to a method for repairing the respirator. The present invention also relates to a method for recycling the filtering face-piece respirator.

Description

Technical Field

[0001] The present invention relates to a respiratory protective mask made of polyvinylidene fluoride and a method for manufacturing the mask. The present invention also relates to a method for repairing the mask. The present invention also relates to a method for recycling this respiratory protective mask.

Background Art

[0002] A dust mask is a respiratory protective device capable of filtering particles and fine dust. Examples of such masks include personal protective equipment such as FFP masks (representing "Filtering Facepiece Particles"). Its protection range is defined by the European standard EN149, which defines the minimum characteristics required for a filtering half-mask used as a respiratory protective device against particles, excluding those for escape purposes. This standard defines three classes of protective equipment, namely FFP1, FFP2, and FFP3, based on three criteria: the maximum penetration rate of the filter material by an aerosol with a mass median diameter of 0.6 μm, the exhalation resistance, and the internal leakage rate.

[0003] An FFP1 dust mask has an aerosol filtration rate of at least 80% and an internal leakage rate of 22% or less.

[0004] An FFP2 mask has an aerosol filtration rate of at least 94% and an internal leakage rate of 8% or less. This mask serves to protect against chemical substances that become powders and also against aerosols carrying virus particles and / or bacteria.

[0005] An FFP3 mask has an aerosol filtration rate of 99% or more and an internal leakage rate of 2% or less. The FFP3 mask protects against very fine particles of asbestos (asbestosis) or silica (silicosis).

[0006] There are also medical masks (surgical masks) developed in accordance with the standard EN14683, which aim to prevent droplets emitted by mask wearers from being released into the surroundings. Such masks also protect the wearer from the release of droplets emitted by the person facing them. On the other hand, such masks do not protect, depending on the situation, from the inhalation of very small particles that float in the air and may carry viruses.

[0007] Respiratory protective masks are generally composed of fibers obtained from polymers of thermoplastic resins such as polyolefins, polyamides, polyvinyls, polyimides, polyacrylates, polymethacrylates, polyurethanes, or fluoropolymers, especially combinations of synthetic fibers obtained from them. The polymer that has been used most widely up to now is polyolefin, especially polypropylene.

[0008] Among many known types of masks, there are those that contain at least one nanofiber layer particularly suitable for ensuring the barrier properties required for FFP-type respiratory protectors. By electrospinning a polymer solution, it is possible to obtain fibers with a sufficiently small diameter for good air permeability and good mechanical and electrostatic filtration efficiency of the air filtration membrane under certain conditions.

[0009] Document EP2517607 describes a mask containing at least one nanofiber layer and the advantages of its production by electrospinning. The mask has a sandwich-type structure because it includes several superimposed layers, for example, a type of three-layer non-woven layer - nanofiber layer - non-woven layer.

[0010] Document US2019 / 0314746 describes obtaining a porous PVDF membrane of non-woven fabric suitable for air filtration by the electrospinning method. The nanofibers are electrospun onto the surface of a drum covered with a non-woven polypropylene (PP) substrate.

[0011] The increasing use of single-use (disposable) respiratory masks has posed significant environmental problems regarding the management of this waste and / or the reuse of the polymeric materials used in the manufacture of such masks. Used masks may contain particles and / or be contaminated with pathogenic microorganisms (bacteria and / or viruses).

[0012] Some types of masks can withstand one or more washings and sterilizations without deterioration of their filtration characteristics. Some methods for washing used masks are known, including washing with detergents at 60 °C or 95 °C, sterilization at 121 °C for 50 minutes, irradiation with gamma or beta rays, exposure to ethylene oxide, dry heat at 70 °C or heating in water, and the use of hydrogen peroxide vapor.

[0013] There is a need to develop a new air filtration mask that is resistant, i.e., can reach temperatures of 80 - 90 °C, especially during high-temperature mechanical washing or heating under pressure in an autoclave, and maintains the quality of breathability and filtration performance in accordance with standards EN149 and EN14683.

[0014] However, even if washing is effective and can remove dust particles and / or microorganisms attached to the mask by washing, the mask can only undergo a limited number of washing cycles, and thereafter, there are issues regarding the treatment of used masks and the desired recovery of all or part of the raw materials used in the manufacture of the masks.

[0015] Therefore, there is a need to develop a method for recycling used masks that can prevent the accumulation of used masks and potential environmental pollution and enable the recovery of the raw materials used in the manufacture of the masks.

[0016] It has now been found that a mask made of a single raw material, namely PVDF, has very good filtration properties, and these filtration properties enable it to meet the standards required for FFP masks compliant with the European standard EN149 and the standards required for surgical masks compliant with the standard EN14683. The PVDF mask according to the present invention can be subjected to a washing process and is thus reusable. In addition, used masks made of PVDF can be fed into a recycling process that enables easy reuse of the single polymer used in their manufacture.

Summary of the Invention

[0017] The present invention proposes to provide a respiratory protection mask that can meet at least one of the above-mentioned needs.

[0018] According to a first aspect, the subject matter of the present invention is made of polyvinylidene fluoride (PVDF) and has the following structure: - An inner layer of non-woven PVDF, - A central layer of PVDF composed of a support layer of PVDF on which PVDF nanofibers are deposited by electrospinning, - An outer layer of non-woven PVDF, - A nose bridge composed of a mixture of PVDF homopolymer and VDF copolymer, and - A retaining strap of PVDF and is a respiratory protection mask.

[0019] According to a second aspect, the present invention is a method for manufacturing the PVDF mask, comprising the following steps: - Providing a first layer of non-woven PVDF for the purpose of forming the outer and inner layers; - Providing a second layer of PVDF selected from a non-woven polymer or a polymer obtained by extrusion spinning for the purpose of forming the support layer of the central layer; - Depositing a layer of PVDF nanofibers on the surface of the support layer using the electrospinning method, - Inserting a nasal bridge composed of a mixture structure of PVDF homopolymer and VDF copolymer into a space created, for example, by folding a non-woven fabric material, and - Providing a retaining strap and attaching the retaining strap to the edge of the mask by welding relates to a method.

[0020] According to a third aspect, the present invention is a method for repairing the PVDF mask, comprising the following: - Treatment with a hydrogen peroxide solution having a concentration of less than 8%; - Treatment with UV-C having an energy of 1 J / cm 2 or more; - Treatment by dry or wet heating (oven, autoclave, microwave) at a temperature of 60 °C or higher relates to a method of implementing a technique selected from the above.

[0021] The present invention also relates to a method for recycling a poly(vinylidene fluoride) respiratory protection mask or a PVDF respiratory protection mask, comprising the following steps: a) Optionally, grinding the mask to obtain flakes or chips as a result; b) Granulating (extruding) the flakes to obtain PVDF granules as a result; c) Using the granules for melt or solvent-based processing of PVDF relates to a method.

[0022] The subject of the present invention is a mask having all the performance qualities of an FFP-type mask or a surgical mask, but made of a single thermoplastic resin raw material and having the advantage of being reusable multiple times by either sterilization or washing. By using non-woven PVDF for the inner layer, it is possible to avoid any phenomenon of skin flushing and sensitization when the mask comes into contact with the face.

Embodiments for Carrying Out the Invention

[0023] The present invention will now be described in more detail and non - limitatively in the following description.

[0024] The present invention uses several techniques to form the polyvinylidene fluoride to be processed into different fiber layers, and by using the assembly, it is possible to manufacture FFP - type respiratory protection masks and even surgical masks. The mask can maintain a high level of air filtration on the one hand and can be washed, reused, and sterilized, and on the other hand, it can be used in a recycling method for recovering the polymer with reuse in mind. This discovery is based on the fact that the fluoropolymer used in the present invention, generally abbreviated as PVDF, is a polymer based on vinylidene difluoride.

[0025] PVDF adopted within the context of the present invention is a polymer of a thermoplastic resin. The term "thermoplastic resin" means a polymer that is not an elastomer. A polymer that is an elastomer is defined as a polymer that can be stretched to twice its original length at room temperature as shown in ASTM Special Technical Publication No. 184 and rapidly returns to within about 10% of its original length after the stress is released.

[0026] According to a first aspect, the subject matter of the present invention is made of polyvinylidene fluoride and has the following structure: - An inner layer of PVDF non - woven fabric, - A central layer of PVDF composed of a support layer of PVDF and an electrospun layer of PVDF nanofibers, - An outer layer of PVDF non - woven fabric, - A nose bridge composed of a mixture of PVDF homopolymer and VDF copolymer, and - A retaining strap of PVDF which is a respiratory protection mask.

[0027] According to various embodiments, the mask includes the following features, and these features are combined as needed.

[0028] According to one embodiment, the respiratory protection mask consists of a main body and a retaining strap. The main body is composed of a plurality of layers including a layer of filter material. The retaining strap is fixed to the mask body without adding material, preferably by welding.

[0029] According to one embodiment, the inner layer of the mask is a PVDF non-woven fabric, and the basis weight of the inner layer is between 20 and 100 g / m 2 and the air permeability of the inner layer measured at a pressure of 100 Pa is between 500 and 1500 l / m 2 / s. This PVDF may be a PVDF homopolymer with a viscosity of 3200 Pa·s at 230 °C and 100 s -1 .

[0030] The central layer of the mask is composed of a PVDF non-woven support with PVDF nanofibers deposited on its surface by electrospinning.

[0031] According to one embodiment, the support layer is a non-woven PVDF, and the basis weight of the support layer is between 20 and 100 g / m 2 and the air permeability of the support layer measured at a pressure of 100 Pa is between 500 and 2500 l / m 2 / s. This PVDF may be a PVDF homopolymer with a viscosity of 3200 Pa·s at 230 °C and 100 s -1 .

[0032] According to another embodiment, the support layer is PVDF produced by extrusion spinning. This PVDF may be a PVDF homopolymer with a melt flow rate (MFR) of 34 g / 10 min under 2.16 kg at 230 °C.

[0033] Deposited on the surface of this support by electrospinning is a layer of PVDF nanofibers, which are as follows: i. PVDF homopolymer; ii. A mixture of two PVDF homopolymers having different viscosities, or different molar masses, or different structures, such as different degrees of branching; iii. A copolymer comprising vinylidene fluoride (VDF) units and one or more units of a comonomer compatible with vinylidene fluoride (hereinafter referred to as "VDF copolymer"); iv. A mixture of a PVDF homopolymer and a VDF copolymer; v. A mixture of two VDF copolymers including, preferably, consisting of these.

[0034] The comonomer compatible with vinylidene fluoride may be halogenated (fluorinated, chlorinated, brominated) or may not be halogenated. As used herein, the term "compatible comonomer" is understood to mean that the comonomer can copolymerize with VDF and as a result form a copolymer.

[0035] Examples of suitable fluorocomonomers are vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, trifluoropropene, especially 3,3,3-trifluoropropene, tetrafluoropropene, especially 2,3,3,3-tetrafluoropropene or 1,3,3,3-tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, especially 1,1,3,3,3-pentafluoropropene or 1,2,3,3,3-pentafluoropropene, perfluoroalkyl vinyl ether, especially the perfluoroalkyl vinyl ether of the general formula Rf-O-CF-CF 2 where Rf is an alkyl group, preferably C 1 ~C 4It is an alkyl group (preferred examples are perfluoropropyl vinyl ether and perfluoromethyl vinyl ether). The fluoromonomer may contain a chlorine atom or a bromine atom. The fluoromonomer can be particularly selected from bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene, and chlorotrifluoropropene. Chlorofluoroethylene can represent either 1-chloro-1-fluoroethylene or 1-chloro-2-fluoroethylene. Isomers of 1-chloro-1-fluoroethylene are preferred. Chlorotrifluoropropene is preferably 1-chloro-3,3,3-trifluoropropene or 2-chloro-3,3,3-trifluoropropene.

[0036] Also, the VDF copolymer may contain a non-halogenated monomer such as ethylene, and / or an acrylic acid copolymer or a methacrylic acid copolymer.

[0037] When the layer of nanofibers is composed of a mixture of two components selected from the above (ii., iv., and v.), the mass ratio between the components is in the range of 1:99 to 99:1.

[0038] All viscosities are measured at 232 °C with a shear rate of 100 s -1 using a capillary rheometer or a parallel plate rheometer in accordance with the standard ASTM D3835.

[0039] The PVDF homopolymer and VDF copolymer used in the present invention can be obtained by known polymerization methods, such as solution polymerization, emulsion polymerization, or suspension polymerization. According to one embodiment, the PVDF homopolymer and VDF copolymer are prepared by an emulsion polymerization method in the absence of a fluorinated surfactant.

[0040] According to some embodiments, the PVDF homopolymer and the VDF copolymer are composed of bio-based VDF. The term "bio-based" means "derived from biomass". This makes it possible to improve the ecological footprint of the membrane. The bio-based VDF has a content of renewable carbon, i.e., naturally derived carbon from bio-based materials or biomass, which is 14 characterized by at least 1 atomic % when determined by the content of C according to the standard NF EN 16640. The term "renewable carbon" means that the carbon is of natural origin and is derived from bio-based materials (or biomass) as shown below. According to some embodiments, the bio-carbon content of VDF may exceed 5%, preferably exceed 10%, preferably exceed 25%, preferably be 33% or more, preferably exceed 50%, preferably be 66% or more, preferably exceed 75%, preferably exceed 90%, preferably exceed 95%, preferably exceed 98%, preferably exceed 99%, and advantageously may be equal to 100%.

[0041] According to one embodiment, the average fiber diameter Dv50 of the PVDF nanofibers is between 30 and 500 nm, preferably between 30 and 300 nm.

[0042] According to one embodiment, the basis weight of the electrospun layer of the PVDF is between 0.03 g / m 2 and 3 g / m 2 .

[0043] Dv50 is the volume median diameter and corresponds to the value of the particle size that exactly divides the investigated particle population into two. Dv50 is measured in accordance with the standard ISO9276 - Parts 1 to 6.

[0044] The average thickness of this layer of PVDF nanofibers is 0.1 μm to 100 μm. The fiber diameter, fiber thickness, and fiber distribution can be estimated by a scanning electron microscope (SEM).

[0045] The solvents used to dissolve PVDF by electrospinning are selected from cyclopentanone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, acetone, ethyl methyl ketone, tetrahydrofuran, γ-butyrolactone, hexafluoroisopropanol, or mixtures thereof in all ratios.

[0046] According to one embodiment, the layer of PVDF deposited by electrospinning is charged by corona treatment in order to improve its filtration characteristics, obtain breathability and filtration performance quality compliant with standards EN149 and EN14683, and a pressure loss much smaller than 70 Pa·s for an intake air flow rate of 95 l / min.

[0047] Also, the mask also includes an outer layer of non-woven PVDF with a basis weight between 10 and 60 g / m 2 .

[0048] The basis weight can be estimated by simply measuring the weight after baking a predetermined area, for example 200 mm×250 mm, preferably to ensure no residual solvent. This PVDF has a viscosity of 3200 Pa·s at 230 °C and 100 s -1 and an air permeability measured at a pressure of 100 Pa between 500 and 2500 l / m 2 / s and may be a PVDF homopolymer.

[0049] The metal filaments that are present in most respiratory protection masks and are adapted to contact the nose are replaced in the mask according to the present invention by PVDF bridges, said bridges comprising a mixture formed from a PVDF homopolymer and a copolymer of a comonomer selected from vinylidene fluoride, and hexafluoropropylene (HFP), tetrafluoroethylene (TFE), and vinylidene trifluoride (TrFE), the ratio of the mass of the homopolymer to the mass of the copolymer being in the range of 10:90 to 90:10, and preferably in the range of 25:75 to 75:25.

[0050] According to one embodiment, the bridge is manufactured from a mixture of a PVDF homopolymer and a P(VDF-HFP) copolymer, the mass content of HFP in the copolymer exceeds 20%, and the mass ratio between the two components is in the range of 30:70 to 70:30, preferably in the range of 40:60 to 60:40.

[0051] According to one embodiment, the bridge is 50% by mass of a PVDF homopolymer and 50% of a P(VDF-HFP) copolymer having a viscosity of 3300 Pa·s at 230 °C and 100 s, exhibits a co-continuous two-phase morphology (percolation of the two phases of the PVDF matrix and the copolymer), and has a yield point elongation of less than 0.5%. -1 The PVDF bridge exhibits permanent deformation while the molding pressure is applied. According to one embodiment, the bridge is inserted into a space created by folding a non-woven material.

[0052] According to one embodiment, the retaining strap of PVDF is an adjustable loop manufactured by injection molding or 3D printing.

[0053] According to one embodiment, the retaining strap of PVDF is an elastic band based on a PVDF textile (non-woven or wound filament). This PVDF may be a PVDF homopolymer having a viscosity of 3200 Pa·s at 230 °C and 100 s that can be wound around itself to obtain the desired elastic effect.

[0054] -1 In a second aspect, the present invention is a method for manufacturing the mask of PVDF, comprising the following steps:

[0055] - providing a first layer of non-woven PVDF for the purpose of forming an outer layer and an inner layer; - providing a second layer of PVDF selected from a non-woven polymer or a polymer obtained by extrusion spinning for the purpose of forming a support layer for the central layer; ​​- A step of depositing a layer of PVDF nanofibers on the surface of the support layer using the electrospinning method; - A step of inserting a nasal bridge composed of a mixture of PVDF homopolymer and VDF copolymer into a space created by folding a non-woven material; - A step of welding the ends of the PVDF retaining straps to the mask body, for example, by ultrasonic waves relates to a method comprising.

[0056] By using a single type of particularly resistant material (polyvinylidene fluoride), the mask according to the present invention can be easily recycled for subsequent use. Therefore, the mask according to the present invention contributes to reducing the environmental impact of this article and is particularly effective in protecting the wearer.

[0057] The mask according to the present invention has the advantage that there is no deterioration of the mask components and it can be sterilized by irradiation with UV-C or UV-B. This is because PVDF is extremely resistant to this type of irradiation, in contrast to other materials of the polypropylene or poly(ethylene terephthalate) type, which are degraded during the sterilization cycle under UV irradiation, particularly under a UV-C (254 nm) lamp.

[0058] Furthermore, the mask according to the present invention can be decontaminated by heating to 70 °C in dry heat or in water.

[0059] According to a third aspect, the present invention is a method for repairing the mask of PVDF, comprising the following: - Treatment with a solution of hydrogen peroxide at a concentration of less than 8%; - Treatment with UV-C having an energy of 1 J / cm 2 or more; - Treatment by dry or wet heating (oven, autoclave, or microwave) at a temperature of 60 °C or higher relates to a method of implementing a technique selected from.

[0060] The present invention also relates to a method for recycling a used poly(vinylidene fluoride) respiratory protection mask or a PVDF respiratory protection mask, the method comprising the following steps: a) Optionally, grinding the mask to obtain flakes; b) Pelletizing the flakes to obtain PVDF pellets; c) Using the pellets for melt or solvent-based processing of PVDF. The invention relates to such a method.

[0061] According to various embodiments, the method includes the following features, which may be combined as required.

[0062] As used herein, the term "used mask" includes masks that have served their purpose (worn out), as well as unused masks that have expired because their warranty period defined by the manufacturer has passed, and further includes waste recovered during mask production, and may correspond to 15-16% of the total used materials.

[0063] When the nose bridge is made of PVDF, the grinding step is optional.

[0064] When the mask to be recycled has a metal nose bridge, grinding is necessary to remove the metal parts. The used mask is passed through a knife mill and processed into fibers several millimeters long. By screening, the fiber pulp can be adjusted to the desired length. The metal parts are removed using a magnet.

[0065] The grinding of the used mask is carried out at a temperature at least 30°C lower than the melting temperature Tm. For PVDF, the temperature generated by shear should not exceed 140°C.

[0066] According to one embodiment, the pelletizing step is carried out continuously.

[0067] The mask according to the present invention may be pre-crushed or shredded and introduced into an extruder, or directly introduced into a BUSS-type or twin-screw extruder at a temperature between 220 and 250 °C, and then granulated. The product granulated in this way can be melt-processed back into PVDF. In fact, due to the very high stability of PVDF, it is possible to recycle PVDF in the melt medium without any change in the viscosity or mechanical properties of PVDF.

[0068] According to one embodiment, granulation is performed by extruding through a die having circular holes in a molten state to produce granules with a diameter of 1 to 5 millimeters, followed by cutting and drying the cooled strands.

[0069] According to another embodiment, melt granulation is performed with a BUSS-type co-kneader, along with underwater cutting and the production of lens-shaped granules.

[0070] The PVDF obtained by the recycling method according to the present invention can then be processed by melt or solvent-based means for the production of articles of any kind, especially articles in the form of films, fibers, cables, or molded parts.

Example

[0071] The following examples illustrate the present invention and do not limit the present invention.

[0072] Example 1: Production of PVDF non-woven fabric by spunbond A VF2 homopolymer with a melt flow rate (MFR) of 32 g / 10 min at 2.16 kg at 230 °C is employed for the extrusion of non-woven fabric by spun-bonding (spunbond) and thermocompression bonding by calendering. Non-woven fabrics with a width of 250 mm and a length of 250 m and several basis weights (g / m 2 ) are produced. In this way, three different masses per unit area are produced using the conditions shown in Table 1. TIFF0007679407000001.tif102170

[0073] Example 2: Production of PVDF Nonwoven Fabric by Melt Blowing A VF2 homopolymer with an MFR exceeding 1200 g / 10 min at 2.16 kg at 230°C is employed for the extrusion of a nonwoven fabric by melt blowing (“melt blown”). In this way, two basis weights (gsm) are produced at a width of 550 mm using the conditions shown in Table 2. TIFF0007679407000002.tif63170

[0074] Example 3: Production of Electrospun Fibers on the Surface of the 30 g / m 2 Spunbond Produced in Example 1 A mixture of a VF2 homopolymer (Kynar® 761A) and a copolymer (Kynar® 2801-00) is dissolved according to the composition shown in Table 3 while stirring at 55°C for 2 hours. TIFF0007679407000003.tif52170

[0075] Thereafter, this solution is fed to the electrospinning process on the surface of the 30 g / m 2 PVDF spunbond support produced in Example 1. In this way, a filter membrane based on electrospun fibers is produced at a width of 250 mm using the conditions shown in Table 4. TIFF0007679407000004.tif87170

[0076] Example 4: Production of Nasal Bridge The nasal support bridge is in the form of a PVDF rod with a diameter of 1.5 mm and a length of 10 cm. This rod is obtained by mixing / extruding a 50 / 50 mass ratio mixture of a Kynar® 705 homopolymer and a Kynar® UltraFlex copolymer, which has a viscosity of 3300 Pa·s at 230°C and 100 s -1 in a single-screw extruder at 230°C. This rod shows a two-phase morphology and has a particularly low yield point elongation, less than 0.5%.

[0077] Example 5: Production of an elastic holding band by winding the non-woven fabrics produced in Examples 1 and 2 A) The elastic band of the mask is produced from the spunbond non-woven fabric of 41 g / m produced in Example 1. A plurality of strips, typically two strips, each 1 cm wide, cut from the spunbond non-woven fabric material 1 are wound around themselves and around each other to obtain the required elasticity. 2

[0078] B) The elastic band of the mask is produced from the meltblown non-woven fabric of 39.2 g / m produced in Example 2. A plurality of strips, typically two strips, each 1 cm wide, cut from the meltblown non-woven fabric material 1 are wound around themselves and around each other to obtain the required elasticity. 2

[0079] Example 6: Assembly of a mask from the components produced in Examples 1 to 5 Using the components obtained in Examples 1 to 5, a mask is produced in the configuration of spunbond 1 - electrospun (Espun) membrane 1 - spunbond 3. The "spunbond 1" non-woven fabric (41 g / m 2 ) forms the outer layer and improves the mechanical strength of the mask body. The "electrospun 1" intermediate layer provides aerosol filtration. Finally, the "spunbond 3" non-woven fabric (21.7 g / m 2 ) placed inside the mask is intended to come into contact with the user's face, provides excellent comfort and also prevents possible degradation of the filter layer.

[0080] The assembly is carried out according to the following steps. - The bonding between the non-woven fabric layers is obtained by laminating. - The nose bridge produced in Example 4 is inserted into the space created by folding the non-woven fabric material at a width of 5 ± 2 mm close to the outer periphery of the mask. The bridge is held by spot welding regularly arranged in the length direction of the folded part. ​​- Fix the elastic bands manufactured in Example 5 on each side of the mask so as to form loops, and fix them by ultrasonic welding without adding materials.

[0081] Example 7: Grinding / granulation and characterization of recycled materials After decontaminating the mask by passing it through an oven at 70 °C for 1 hour, grind it with a knife mill. To produce granules, supply the obtained flakes to a BUSS-type twin-screw extruder at 230 °C.

[0082] Confirm the quality of the recycled product PVDF-R1 thus obtained by thermal analysis and viscosity measurement. The characteristics obtained as a result are, as shown in Table 5, similar to those of most of the major materials used in the production of spunbond nonwovens. TIFF0007679407000005.tif37170

Claims

1. It is made from polyvinylidene fluoride and has the following structure: An inner layer of non-woven PVDF; A central PVDF layer composed of a support layer made of PVDF and an electrospun layer of PVDF nanofibers; A non-woven PVDF outer layer; PVDF nose bridge, and PVDF Retaining Straps A respiratory protective mask comprising:

2. The inner layer is non-woven PVDF, 20 and 100 g / m ２ 10. The mask of claim 1 having a basis weight of between 0.1 and 0.

25.

3. The support layer is a nonwoven PVDF fabric, 20 and 100 g / m ２ 3. The mask of claim 1 or 2, having a basis weight of between 0.1 and 0.

25.

4. 3. The mask of claim 1 or 2, wherein the support layer is PVDF produced by extrusion spinning.

5. 5. The mask of any one of claims 1 to 4, wherein the electrospun layer of PVDF nanofibers comprises a PVDF homopolymer; a mixture of two PVDF homopolymers; a copolymer comprising vinylidene difluoride (VDF) units and one or more units of a comonomer compatible with vinylidene difluoride; a mixture of a PVDF homopolymer and a VDF copolymer; or a mixture of two VDF copolymers.

6. 6. The mask of claim 5, wherein the comonomer compatible with VDF is selected from vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, perfluoroalkyl vinyl ethers of the general formula Rf-O-CF-CF2, where Rf is an alkyl group, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene, and chlorotrifluoropropene.

7. The mask according to any one of claims 1 to 6, wherein the layer of PVDF nanofibers has an average thickness of from 0.1 μm to 100 μm.

8. The mask according to any one of claims 5 to 7, wherein the layer of nanofibers is composed of a mixture of two components, the mass ratio between which ranges from 1:99 to 99:

1.

9. 9. The mask of claim 1, wherein the PVDF nanofibers have an average fiber diameter Dv50 between 30 and 500 nm.

10. The PVDF outer layer of the nonwoven fabric is 10 and 60 g / m ２ 10. The mask of claim 1 having a basis weight of between 0.1 and 0.

5.

11. A method for manufacturing a mask according to any one of claims 1 to 10, comprising the steps of: providing a first layer of nonwoven PVDF intended to define an outer layer and an inner layer; providing a second layer of PVDF, intended to constitute a support layer for the central layer, chosen from nonwoven polymers or polymers obtained by extrusion spinning; depositing a layer of PVDF nanofibers onto a surface of the support layer using electrospinning; inserting a nose bridge comprised of a blend of PVDF homopolymer and VDF copolymer into the space created by folding the nonwoven material; and Welding the ends of the PVDF retention straps to the mask body A method comprising:

12. The method of claim 11, wherein the retention strap is an adjustable loop manufactured by injection molding or 3D printing, or an elastic band based on a PVDF textile.

13. 11. A method for repairing a mask according to any one of claims 1 to 10, comprising the steps of: Treatment with a solution of hydrogen peroxide with a concentration of less than 8%; 1 J / cm ２ Treatment with UV-C having an energy of at least 1000 nm; Treatment by dry or wet heat at temperatures above 60°C The method comprises:

14. A method for recycling used PVDF respirator masks, the masks having a structure according to any one of claims 1 to 10, the method comprising the steps of: Optionally, crushing the mask to result in flakes; granulating the flakes to result in PVDF granules; and Using the granules to convert PVDF via melt or solvent-based routes. A method comprising:

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