TECHNICAL FIELD

[0001] The present application generally relates to face masks, and more particularly to a face mask for removal of environmental pollutants and impurities from breathed air, and method for producing same.

BACKGROUND ART

[0002] Pollutants and impurities, such as dust, viruses, and other tiny pollutants at submicron scale have increased in the environment very quickly, and they threaten human health. These pollutants cannot be filtered by the existing filtration methods, such as ordinary respiratory masks. Thanks to the ever growing field of nanotechnology, and the ability to produce nanofibers with the dimensions of less than 100 nm, new methods can be used to develop protective masks that can remove tiny pollutants and impurities even at nanometric or submicron scales.

[0003] Nanofibers are among the most important types of nanostructures. When the diameters of polymer fiber materials are shrunk from micrometers to nanometers, several characteristics appear, such as very large surface area to volume ratio, flexibility in surface functionalities, and superior mechanical performance compared to any other known form of material. Different materials can be used for nanofiber production, among which, polymers and ceramics are the most important ones. Nanofibers can have several applications in medicine (tissue engineering, wound dressing, drug delivery, artificial organ components, medical textile materials, surgical masks, etc.), filtration (water, air), protective clothing, composites and electronics.

[0004] Over the past few decades, different methods have been introduced in the art for the production of nanofibers. These methods include: drawing, template synthesis, self- assembly, island-in-the-sea, phase separation, electrostatic centrifugation, and electro spinning. Electro spinning seems to be an efficient method, which can address the shortcomings of other methods, such as feasibility or controllability. Electro spinning has been a well-known method for nanofiber production for decades. Most polymer solutions including biodegradable and environmental friendly polymer solutions can be used as the spinning solution.

[0005] Several variants of face masks designed for removal of environmental pollutants or impurities from breathed air, which contain at least one layer of nanofibers have been disclosed in the art. In these face masks, either one filtration layer of nanofibers is arranged between two layers of fabric, or the layer of nanofibers is arranged between two layers of non-woven material. The methods used to manufacture these face masks are complex and technologically demanding.

[0006] There is, therefore, a need in the art for a face mask, which is capable of removing biological and mechanical impurities from breathed air, and a simple and cost-effective method for producing the same. SUMMARY OF THE INVENTION

[0007] The following brief summary is not intended to include all features and aspects of the present invention, nor does it imply that the invention must include all features and aspects discussed in this summary.

[0008] In one general aspect, the present disclosure describes a nano face mask including a middle layer including a nano layer, wherein the nano layer includes a plurality of nanofibers; and two cover layers including nonwoven layers; where, the nano layer is placed between the two cover layers to form a face mask.

[0009] The abovementioned general aspect may include one of the following features. The nano layer can be coated onto a nonwoven layer using a method, such as electro spinning or particularly needleless electro spinning.

[0010] In some implementations a plurality of nano fibers can be placed between the two cover layers, as the nano layer. The nano layer can be coated onto the nonwoven layer by electro spinning a polymer solution. The polymer solution can include polyolefin, polyamide, polyester, cellulose ether and ester, cellulose acetate, polyvinylidene fluoride, poly aery lonitrile, polyvinyl alcohol, polyethersulfone, nylon, polystyrene, poly aery lonitrile, polycarbonate, chitosan, or mixtures thereof.

[0011] In other implementations the two cover layers can include nonwoven layers made of a polymer, such as polypropylene, polyester, polyethylene, polyamide, polyurethane, or mixtures thereof. BRIEF DESCRIPTION OF DRAWINGS

[0012] While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter that is regarded as forming the present invention, it is believed that the invention will be better understood from the following description taken in conjunction with the accompanying DRAWINGS, where like reference numerals designate like structural and other elements, in which:

[0013] FIG. 1 illustrates an exemplar and non-limiting schematic representation of layers of a nano face mask, pursuant to the teachings of the present disclosure.

[0014] FIG. 2 is a scanning electron microscope (SEM) image of a nanofiber mat, produced pursuant to the teachings of the present disclosure.

[0015] FIG. 3 is a field emission scanning electron microscope (FESEM) image of a plurality of nanofibers coated on a nonwoven layer, pursuant to the teachings of the present invention.

[0016] FIG. 4 illustrates an exemplar and non-limiting schematic representation of layers of a nano face mask, pursuant to the teachings of the present disclosure.

DESCRIPTION OF EMBODIMENTS

[0017] In the following detailed description, numerous specific details are set forth by way of examples in order to provide a thorough understanding of the relevant teachings. However, it should be apparent that the present teachings may be practiced without such details. In other instances, well known methods, procedures, components, and/or circuitry have been described at a relatively high-level, without detail, in order to avoid unnecessarily obscuring aspects of the present teachings. [0018] For purposes of explanation, specific nomenclature is set forth to provide a thorough understanding of the present application. However, it will be apparent to one skilled in the art that these specific details are not required to practice the application. Descriptions of specific applications are provided only as representative examples. Various modifications to the preferred implementations will be readily apparent to one skilled in the art, and the general principles defined herein may be applied to other implementations and applications without departing from the scope of the application. The present application is not intended to be limited to the implementations shown, but is to be accorded the widest possible scope consistent with the principles and features disclosed herein.

[0019] Referring to FIG. 1, an exemplar nano face mask 100 according to the teachings of the present application includes a middle layer 101, having a non- woven layer 102, which is coated by a nano-layer 103 having a plurality of nanofibers; and two cover layers 104, which are located on both sides of the middle layer 101. The middle layer 101 is configured to filter nano-sized or sub-micron particles from the air stream. The plurality of nanofibers in the nano-layer 103, which is coated onto the non-woven layer 102, intercept particles in the nanometer size range or sub-micron size range, as they pass through the middle layer 101. Due to the small size of the nanofibers, the filtration efficiency is higher for removing nano- sized or sub-micron particles from the air flowing across the middle layer 101, and consequently across the whole nano face mask 100, whereas there is non-significant increase in pressure drop. These nano-sized or sub-micron particles, can include, for example, viruses, bacteria, dust, or allergic materials.

[0020] FIG. 4 illustrates an exemplar schematic illustration of different layers of the nano face mask 100 and how they could be arranged relative to a user's face. [0021] The cover layers 104 may be prepared in variety of ways. For example, the cover layers 104, which are non-woven polymeric layers, can be produced by a spunbond process. Different Polymers including polypropylene, polyester, polyethylene, polyamide, polyurethane, etc. can be used in the spunbond process.

[0022] According to the spunbond process: first, a polymer is melted by heating and mechanical action when it is conveyed to an extruder. The polymer can be mixed with stabilizers, additives, color master-batch, resin modifiers, or other additives. The polymer mixture is then conveyed through the screw of the extruder, and it is melted through the heated screw; then, the molten polymer or polymer mixture can be conveyed to a filter to remove foreign particles, such as metals, and solid polymer particles. After that, the polymer mixture is conveyed to a metering pump, which ensures a precise volumetric flow rate of the molten polymer; the molten polymer is then conveyed to a die assembly, which consists of a feed distributor and a spinneret; the molten polymer is then emitted through the spinneret holes, and the emitted filaments pass through a quench chamber and the molten filaments are cooled by air and are solidified; after that, the filaments can be led into a tapered conduit by high velocity air, which leads to the stretching of the individual filaments; the filaments are then deposited on a moving belt, on which web formation occurs, and filaments are separated; after that, the filaments are bonded. Many bonding methods can be used to bond the filaments in the spunbond process. For example, hydroentangle bonding, needlepunching bonding, thermal bonding, chemical bonding, etc.; after the filaments are bonded, there can be extra treatment processes, such as embossing, resin treatment, dyeing, or printing.

[0023] In one implementation, polypropylene (PP) can be used for producing the cover layers 104 in a spunbond process. Polypropylene is relatively inexpensive and provides the highest yield, and moreover, it has the lowest specific gravity and the highest versatility for nonwovens. Polyester (PET) can be used in the spunbond process due to its tensile strength, modulus, and heat stability. Polyethylene (PE) with acceptable chemical resistance, and suitable electrical insulation properties can also be used in the spunbond process. Polyamide including nylon 6 and nylon 66 has the properties, which are highly energy intensive compared to polyester (PET) or polypropylene (PP). Therefore, polyamide can also be used to produce the non- woven cover layers 104.

[0024] The plurality of nanofibers in the nano layer 103 may be produced in a variety of ways. For example, nanofibers may be produced by electro spinning a polymer solution. Both hydrophilic and hydrophobic polymers can be used as the polymer solution in producing the nanofibers. Examples of applicable polymers may include polyolefin, polyamide, polyester, cellulose ether and ester, cellulose acetate, polyvinylidene fluoride, polyacrylonitrile, polyvinyl alcohol, polyethersulfone, nylon, polystyrene, polyacrylonitrile, polycarbonate, chitosan, or mixtures thereof.

[0025] In one implementation, the plurality of the nanofibers in the nano layer 103 are produced using a needleless electro spinning method. In needleless electro spinning apparatuses, a high electric field is used to produce ultra-fine polymeric fibers with diameters ranging from a few nanometers to a few micrometers. The mechanism of the electro spinning process is based on a complex electro-physical activity between a polymer solution and an electrostatic force. In the needleless electro spinning process, a high-voltage electric field is set up between a viscoelastic polymer solution (herein after the "spinning solution") and a collector using a high voltage power supply. When the spinning solution is exposed to the electric field, a semispherical droplet of the spinning solution is formed. With increasing voltage, the charged polymer droplet elongates to form a conical shape and the surface charge on the polymer droplet increases with time. Once the surface charge overcomes the surface tension of the polymer droplet, a polymer jet is initiated. The solvent in the polymer jet evaporates during its travel to the collector, increasing the surface charge on the jet. This increase in surface charge induces instability in the polymer jet as it passes through the electric field. To compensate for this instability, the polymer jet divides geometrically, first into two jets, and then into many more as the process repeats itself. The formation of nanofibers and sub-micron fibers results from the action of the spinning force provided by the electrostatic force on the continuously splitting polymer droplets. Nanofibers or sub-micron fibers are deposited layer-by-layer on the collector, forming a non-woven nanofibrous mat. During the needleless electro spinning process, both extrinsic and intrinsic parameters (the electro spinning parameters) are known to affect the structural morphology of the nanofibers or the sub-micron fibers. Specifically, extrinsic parameters, such as environmental humidity and temperature, and intrinsic parameters, including applied voltage, electro spinning distance, and conductivity and viscosity of the polymer solution, need to be optimized to produce uniform nanofibers or sub-micron fibers. The two major structures usually found in the nanofibrous mat are a uniform, continuous fibrous structure and a bead-containing fibrous structure. Variation in the relative abundance of these two structures is determined by the relative contributions of the parameters during the electrospinning process.

[0026] The plurality of nanofibers comprise a nano layer 103, which can be separately placed between the cover layers 104, or it can be coated on a non-woven layer 102 by a method, such as, for example electrospinning or more particularly, needleless electrospinning. The electrospun nanofibers with uniform size distribution possess superior mechanical performance and significantly increase the filtration yield.

[0027] In some implementations, other optional additives, such as scents and natural essences can be added to the spinning solution to improve the quality of the face mask. [0028] In some implementations, the nano layer 103 can be produced using natural polymers, such as chitosan, optional nanoparticles and herbal extracts can also be added to this layer to enhance self -cleansing and antibacterial properties of the nano face mask 100.

[0029] The non-woven layer 102 may be obtained in a variety of ways. For example by a melt-blown process. Examples of applicable polymers may include polymers, such as polyolefin (polypropylene, polyethylene, etc.), polyester, nylon 6, nylon 11, polycarbonate, polystyrene, etc.

[0030] The melt-blown process is a one-step process, in which high-velocity air blows a molten thermoplastic resin from an extruder die tip onto a conveyor or take-up screen to form a fine fibrous and self-bonding web. The melt-blown process is similar to the spunbond process, which converts resins to nonwoven fabrics in a single integrated process.

[0031] Two cover layers 104 and the middle layer 101 are folded and bound together to form the nano face mask 100, pursuant to the teachings of the present invention. An elastic band can be used as an ear loop, which holds the mask in its optimal position on a human' s face.

EXAMPLE

[0032] An electro spinning process according to an implementation of the present disclosure is performed under the following process conditions: Nylon 66 is dissolved in formic acid under continuous stirring at room temperature for 6 hours, in order to prepare a spinning solution having a concentration of 12 wt%. The following electro spinning conditions were set: a high voltage of 50 kV was applied to establish the electrical field between the solution and the collector. The temperature was set at 30 °C and the electro spinner drum rotation speed and the collector rotation speed were set at 6 rpm. The electro spinning distance was set at 12 cm.

[0033] FIG. 2 is a scanning electron microscope (SEM) image of the nanofibers produced pursuant to the teachings of this example. The produced nanofiber mat can be placed between the non- woven cover layers 104 to form the nano face mask 100. Or it can be coated on a non-woven layer using the same electro spinning process, as described hereinabove, to form a middle layer 101, which in turn, is placed between the two cover layers 104 to form a nano face mask 100. FIG. 3 illustrates field emission scanning electron microscope (FESEM) image of the electrospun nylon 66 nanofibers deposited on a layer of melt-blown nonwoven.

[0034] While the foregoing has described what are considered to be the best mode and/or other examples, it is understood that various modifications may be made therein and that the subject matter disclosed herein may be implemented in various forms and examples, and that the teachings may be applied in numerous applications, only some of which have been described herein. It is intended by the following claims to claim any and all applications, modifications and variations that fall within the true scope of the present teachings.

[0035] Unless otherwise stated, all measurements, values, ratings, positions, magnitudes, sizes, and other specifications that are set forth in this specification, including in the claims that follow, are approximate, not exact. They are intended to have a reasonable range that is consistent with the functions to which they relate and with what is customary in the art to which they pertain.

[0036] The scope of protection is limited solely by the claims that now follow. That scope is intended and may be interpreted to be as broad as is consistent with the ordinary meaning of the language that is used in the claims when interpreted in light of this specification and the prosecution history that follows and to encompass all structural and functional equivalents. Notwithstanding, none of the claims are intended to embrace subject matter that fails to satisfy the requirement of Sections 101, 102, or 103 of the Patent Act, should may they be interpreted in such a way. Any unintended embracement of such subject matter is hereby disclaimed.

[0037] Except as stated immediately above, nothing that has been stated or illustrated is intended or should be interpreted to cause a dedication of any component, step, feature, object, benefit, advantage, or equivalent to the public, regardless of whether it is or is not recited in the claims.

[0038] It will be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein. Relational terms such as first and second and the like may be used solely to distinguish one entity or action from another without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "a" or "an" does not, without further constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0039] The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in various embodiments for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separately claimed subject matter.