Patent Publication Number: US-9421707-B2

Title: Nanofiber filtering material for disposable/reusable respirators

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     None. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     REFERENCE TO A MICROFICHE APPENDIX 
     Not applicable. 
     BACKGROUND 
     Personal protection equipment (PPE), specifically disposable masks, may be required to conform to certain regulations during design and manufacture. The user&#39;s ability and ease of breathing while wearing the mask may be considered, as well as the fit and the comfort of the user who may wear the mask. Because of the disposable nature of the mask, a low cost manufacturing process may be desired. Certain regulatory standards may need to be met, such as EN149:2001 for Europe or 42 CFR part 84 for US or ISO 17420. PPE under these regulations are class III products according to PPE directive in Europe or other parts of the world. PPE, such as disposable masks or reusable cartridges, may comprise filtration media, which may be made of melt-blown fibers and/or micro glass material. Filtration by a mask is accomplished when particles in the air are trapped in the matrix of the fibers contained in the filtration media of the mask. 
     SUMMARY 
     Aspects of the disclosure may include embodiments of a method of manufacturing a personal protection equipment mask, comprising: providing a stock of polymer material; creating nanofibers from the stock polymer material to form a nanofiber material; placing the nanofiber material onto a convex mold; cutting the nanofiber material to the shape of a personal protection equipment mask; and attaching retaining straps to the personal protection equipment mask. In an embodiment, creating the nanofibers and placing the nanofiber material may comprise electrospinning the polymer material onto the convex mold. In an embodiment, the convex mold comprises the shape of one or more of: a spherical cap with a spherical base, a spherical cap with an ovoid base, or a human face. In an embodiment, the nanofiber material of the personal protection equipment mask may be functionalized to remove gas, wherein the nanofiber material of the personal protection equipment mask may be functionalized to remove at least some volatile organic chemicals (VOCs) and acid vapors. In an embodiment the nanofiber material of the personal protection equipment mask may be functionalized to remove at least one of: nitrogen monoxide (NO), nitrogen dioxide (NO 2 ), ozone (O 3 ), hydrogen cyanide (HCN), arsine (AsH 3 ), hydrogen fluoride (HF), chlorine dioxide (ClO 2 ), ethylene oxide (C 2 H 4 O), formaldehyde (CH 2 O), methyl bromide (CH 3 Br), and phosphine (PH 3 ). In an embodiment, providing the stock of polymer material may comprise providing the stock of polymer material mixed with functionalizing material. 
     Additional aspects of the disclosure may include embodiments of a method of manufacturing a personal protection equipment mask, comprising: thermoforming outer and inner shells of a personal protection equipment mask; electrospinning a polymer material as nanofibers onto the inner shell; coupling the outer shell to the inner shell having the nanofibers to form the personal protection equipment mask; cutting the personal protection equipment mask to shape; and attaching retaining straps to the personal protection equipment mask. In an embodiment, the method may further comprise electrospinning a polymer material as nanofibers onto the outer shell. In an embodiment the nanofibers may be less than about 1000 nanometers in diameter. In an embodiment, the nanofibers may be functionalized to remove gas, wherein the nanofibers may be functionalized with at least one of a biocide, a virucide, or a bactericide. In an embodiment, the personal protection equipment mask is a flat fold mask. 
     Other aspects of the disclosure may include embodiments of a method of manufacturing a personal protection equipment mask, comprising: electrospinning a material as nanofibers to form at least a portion of a personal protection equipment mask, wherein the nanofibers may be functionalized to remove gas; cutting the personal protection equipment mask to shape; and attaching retaining straps to the personal protection equipment mask. In an embodiment, the material that is electrospun into nanofibers may comprise a polymer and one or more functionalizing materials. In an embodiment the one or more functionalizing materials may be one or more chemicals that capture one or more of volatile organic chemicals (VOCs), acid vapors, or CO 2 . In an embodiment, the one or more functionalizing materials may be one or more of a biocide, a virucide, or a bactericide. In an embodiment, the material may be a homogenous mix of the polymer and the functionalizing materials. In an embodiment, the material may comprise the functionalizing materials emulsified in the polymer. In an embodiment, the material may be electrospun using a co-axial electrospinning process. 
     These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts. 
         FIG. 1  illustrates an embodiment of one way to manufacture nanofibers with an electrospinning process; 
         FIG. 2  illustrates an embodiment of an electrospinning process where the target comprises a molded form; 
         FIG. 3  illustrates exemplary human face shapes that may be used as a molded form; 
         FIG. 4  illustrates a method of manufacturing a PPE mask which incorporates an electrospinning process; 
         FIG. 5  illustrates another method of manufacturing a PPE mask which incorporates an electrospinning process; 
         FIGS. 6A-6B  illustrate methods of manufacturing filter material, such as rolled media and pleated media, which incorporate an electrospinning process; and 
         FIGS. 7A-7D  illustrate embodiments of methods for functionalizing an electrospun material. 
     
    
    
     DETAILED DESCRIPTION 
     It should be understood at the outset that although illustrative implementations of one or more embodiments are illustrated below, the disclosed systems and methods may be implemented using any number of techniques, whether currently known or not yet in existence. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, but may be modified within the scope of the appended claims along with their full scope of equivalents. 
     The following brief definition of terms shall apply throughout the application: 
     The term “comprising” means including but not limited to, and should be interpreted in the manner it is typically used in the patent context; 
     The phrases “in one embodiment,” “according to one embodiment,” and the like generally mean that the particular feature, structure, or characteristic following the phrase may be included in at least one embodiment of the present invention, and may be included in more than one embodiment of the present invention (importantly, such phrases do not necessarily refer to the same embodiment); 
     If the specification describes something as “exemplary” or an “example,” it should be understood that refers to a non-exclusive example; 
     The terms “about” or “approximately” or the like, when used with a number, may mean that specific number, or alternatively, a range in proximity to the specific number, as understood by persons of skill in the art field; and 
     If the specification states a component or feature “may,” “can,” “could,” “should,” “would,” “preferably,” “possibly,” “typically,” “optionally,” “for example,” “often,” or “might” (or other such language) be included or have a characteristic, that particular component or feature is not required to be included or to have the characteristic. Such component or feature may be optionally included in some embodiments, or it may be excluded. 
     Embodiments relate generally to methods for incorporating the use of electrospinning technology to form filtration media made of nanofibers into the manufacture of personal protective equipment (PPE) (for example, disposable/reusable respirators and/or masks). More specifically, the filtration media may be used in Class III PPE, which may, for example, be regulated by standards such as EN149-42 CFR Part 84. Typical disposable and/or reusable filters for respirators may be constructed of melt-blown material, usually melt-blown nanofibers. Additionally, an electrical charge may typically be applied to the fibers to capture smaller particles in the air and provide a higher level of respiratory protection, for example to meet certain EN or US standards. However, the effect of the electrical charge may be time sensitive, causing the filter material to have a limited storage capability or “shelf-life” (i.e. how long the filter media may be stored and still retain necessary filtering capabilities, which may for example be a maximum of 5 years). Applicant has proposed methods for the manufacture of filter material from nanofibers using electrospinning technology that may not require the filter material to be electrically charged, and therefore may eliminate the constraints of a shelf-life for the material. This may be accomplished by relying only on the mechanical properties of the filter media to perform filtration rather than electrical properties. Further, Applicant has developed methods for integrating the production of nanofibers using electrospinning into a manufacturing process for a filter material (for example, a mask or respirator filter). Additionally, Applicant has developed methods of functionalizing nanofibers (to capture specific gases, for example) which may allow for additional applications of a filtration media. Embodiments may also relate to other aspects of a PPE mask, such as fit to the face of a user, air leakage through the filter media, etc. For example, an embodiment of the disclosure may use nanofibers (which may be functionalized) to improve breathing resistance, solid or liquid aerosol penetration, as well as fit and comfort of the respirators. 
     Referring to  FIG. 1 , an exemplary electrospinning process (as would be understood by persons of ordinary skill in the art) may typically involve the use of an electrical charge to draw very fine fibers from a liquid. In an embodiment, a liquid solution  105  may be contained in a syringe  106  which may be controlled by a syringe pump  110 . The syringe pump  110  may drive the solution  105  to an opening in a needle  120 , where the solution  105  may form a liquid droplet  123  at the tip of the needle  120 . In an embodiment, the solution  105  may comprise a polymer material, wherein the polymer material may comprise polylactic acid (PLA) which may be diluted in a water solvent. In an alternative embodiment, the polymer material may comprise polyamide (PA) 6.6 diluted in a solvent which may comprise about ⅓ formic acid and about ⅔ acetic acid. A voltage  130  may be applied between the liquid droplet  123  and a grounded target  140  held at ground, causing the body of the liquid solution  105  to become charged and form a liquid jet  125 . The liquid jet  125  may then be elongated by a whipping process and may typically dry in flight to form solid fibers  126  which may then collect on the grounded target  140 . The fibers  126  that collect on the grounded target  140  may typically comprise nanofibers (i.e. fibers that are less than about 1000 nanometers in diameter). 
     Referring now to  FIG. 2 , in an embodiment, a molded form  250  may be located on the grounded target  240 , where the fibers  226  may collect on the surface of the molded form  250  and may form a layer of filtration media on the molded form  250 . In an embodiment, the molded form  250  may be convex and may be in the shape of a mask, a shell, a plate or any other form operable to receive electrospun nanofibers  226 . In an embodiment, the molded form  250  may comprise a shape of a human face. In an embodiment the convex molded form  250  may comprise the shape of a spherical cap with a spherical or ovoid base. Additionally, the molded form  250  may comprise a plastic material such as polypropylene or polyethylene. 
     As shown in  FIG. 3 , the shape of a human face used as a mold may, for example, comprise one of the five standard shapes listed in the PCA Panel according to anthropometric studies and ISO 17420. These different face shapes may include Small  301 , Medium  302 , Large  303 , Long/Narrow  304 , and Short/Wide  305 , and according to anthropometric studies, these five standard face shapes may encompass the 5 to 95 percentiles of human face shapes. In an embodiment, the nanofibers  226  may be electrospun directly onto the convex mold (which may, for example, be in the shape of a human face) wherein the nanofibers may adhere to (and possibly take the shape of) the contours of the shape of the mold. 
     Methods disclosed herein may comprise integrating electrospinning into an automatic line process for the manufacture of a mask or other filtration media. In the embodiment of  FIG. 4 , a process  400  for manufacturing a molded mask is shown which may comprise manufacturing filtering media  410  using electrospinning. In an alternative embodiment, the filter media may be manufactured using another method of creating nanofibers. An embodiment of the process  400  may comprise feeding a moldable material  405  through ovens  420  (operable to heat the material  405 ) and then through a thermoforming press  430 , which may create a molded form  406 . In an embodiment, the molded form  406  may comprise the shape of a human face (as shown in  FIG. 3 ), and in other embodiments the molded form may comprise another shape, such as that of a respirator mask and/or filter cartridge. The molded form  406  may then be fed through the manufacturing of filtering media  410  where (as shown in  FIG. 2  above) nanofibers may be electrospun onto the molded form  406  to form a filtering media layer on the molded form  406 . In an embodiment, the process may comprise welding  440  the filtering media to the molded form  406 . The filtering media and/or the molded form  406  may then be cut using a cutting press  450  into the shape of a PPE mask. In an embodiment, the process may additionally comprise removing the nanofiber filtering media from the molded form  406 , while in other embodiments, the filtering media may remain attached to the molded form  406 . In an embodiment, the filtering media may be attached to a cover layer, which may provide structural support and protect the filtering media from damage, wherein the cover layer would comprise a part of the finished mask formed by the filtering media. In an embodiment, the molded form  406  described above may be equivalent to the cover layer, wherein the molded form  406  (or cover layer) may comprise a plastic material such as polypropylene or polyethylene. Elastic retaining straps (operable to hold the mask onto the head of a user) may be attached to the body of the PPE mask using stapling and/or welding  460 . The finished PPE mask may be visually inspected using a camera control system  470  to ensure the quality of the PPE masks and possibly to detect defects. 
     As shown in  FIG. 5 , another embodiment of a method of manufacturing a PPE mask may comprise unwinding  515  a lower part  505  (which may also be referred to as an inner shell), wherein the lower part  505  may comprise a moldable material, and may feed through the process  500 . Another step may comprise electrospinning  510  a polymer material in the form of nanofibers onto the surface of the lower part  505  (as shown in the embodiment of  FIG. 2 ). The process  500  may further comprise cutting  520  the lower part  505  to a shape (which may for example be the shape of a PPE mask, such as a flat fold mask) wherein the cutting may allow for folding of the mask, especially at the nose and chin area. 
     In an embodiment, the method may further comprise unwinding  516  an upper part  506  (which may also be referred to as an outer shell), wherein the upper part  506  may comprise a moldable material, and feed through the process  500 . In an embodiment, the upper part  506  may also be known as a cover layer and may comprise a spunbond material. In an embodiment, the process  500  may optionally comprise electrospinning  511  a polymer material (which may be similar or different to the polymer material electrospun at step  510 ) in the form of nanofibers onto a surface of the upper part  506  (which may for example be the inner surface of the upper part). The upper part  506  may be cut  540  to form a shape that may correspond to the shape of the lower part  505 , where, in an embodiment, the upper part  506  may be coupled  550  to the lower part  505  having electrospun nanofibers on its surface, and where, in an embodiment, the nanofiber layer might be located between the upper part  506  and lower part  505 . In an embodiment, the method may further comprise attaching elastic retaining straps  530  (which may be operable to hold a PPE mask against the face of a user) to the shape  507  formed by the coupled upper and lower parts. The coupled upper and lower parts may additionally be welded together  560  at their perimeter. In an embodiment, the product may undergo further processing to complete the manufacture of a flat fold (or molded) mask, wherein additional steps may occur prior to or after any of the steps described above. In an embodiment, an additional step may comprise adding a partial or full face seal to the mask. 
     In the embodiments of  FIGS. 6A-6B , a method may comprise manufacturing a disposable/reusable filter material other than a mask, such as a rolled media or pleated media (which may for example be used to make a cartridge for a respirator or other air purification device). As shown in the embodiment of  FIG. 6A , a manufacturing process  600  may comprise unwinding  615  a material  605  and feeding the material  605  through the process  600 . An embodiment of the process  600  may comprise electrospinning  620  filter media as nanofibers onto the material  605 . In alternative embodiment, nanofibers may be electrospun to form a thin layer of filtration media that may then be attached (possibly by welding) to the material  605  (which may for example form a shell of a mask). The process  600  may further comprise cutting  630  the finished material  635  (where the finished material  635  may comprise the material  605  and electrospun filter media). After cutting, the finished material  635  may be wound  640  onto a roll to form a rolled filter material  650 . In an alternative embodiment shown in  FIG. 6B , a method may comprise the finished material  635  being pleated  670  to form a pleated filter material  680 . In an embodiment, the height of the pleats created in step  670  may be between about 3 mm to about 40 mm depending on the desired use of the pleated material and/or the hazardous environment. In an embodiment, the pleated filter material  680  might also be cut to specified dimensions based on the specific product that is being manufactured. 
     In an embodiment, a method of manufacturing a PPE mask may comprise electrospinning a material as nanofibers to form at least a portion of a PPE mask, wherein the nanofibers may be functionalized to remove one or more gases/vapors. Shown in the embodiments of  FIGS. 7A-7D , nanofibers formed by electrospinning a polymer solution may be functionalized by the addition of another material to the polymer solution. The additional functionalizing material may be operable to remove gases and may comprise one or more chemicals that may capture gases (where the gases might be volatile organic chemicals (VOCs), acid vapors, carbon dioxide (CO 2 ), nitrogen monoxide (NO), nitrogen dioxide (NO 2 ), ozone (O 3 ), hydrogen cyanide (HCN), arsine (AsH 3 ), hydrogen fluoride (HF), chlorine dioxide (ClO 2 ), ethylene oxide (C 2 H 4 O), formaldehyde (CH 2 O), methyl bromide (CH 3 Br), and/or phosphine (PH 3 )). In an embodiment, the functionalized material may comprise one of a biocide (i.e. a chemical substance or microorganism which can deter, render harmless, or exert a controlling effect on any harmful organism by chemical or biological means), a virucide (i.e. a physical or chemical agent that deactivates or destroys viruses) and/or a bactericide (i.e. a substance that kills bacteria, for example disinfectants, antiseptics, or antibiotics). In other embodiments, a functionalized nanofiber may be operable to remove humidity, control temperature, indicate end of service life, indicate clogged material, and/or provide a fresh odor inside the mask. 
     Exemplary embodiments of methods for functionalizing electrospun nanofibers are shown in  FIGS. 7A-7D . In the embodiments, the material that is functionalized and electrospun onto a target may be operable to capture molecules in the air (because of the surface area of the nanofibers) as well as remove gases from the air (such as those captured by the functionalizing material, as listed above). In the embodiment of  FIG. 7A , functionalization of a nanofiber material may be accomplished with surface functionalization, where the material  705  (such as a polymer solution) may have already been electrospun onto a target  720 . The functionalizing material  710  may be introduced and may adhere to the surface of the electrospun material  705 , for example by soaking the electrospun material  705  in and/or by spraying on the functionalizing material  710 . In the embodiment of  FIG. 7B , a functionalizing material  710  may be blended with another material  705  (such as a polymer solution) to form a homogenous mixture prior to electrospinning. Then, the blended mixture containing both the functionalizing material  710  and the polymer solution  705  may be electrospun onto a target  720  (such as in any of the methods disclosed above) forming nanofibers which may comprise both the polymer material and the functionalizing material. In an embodiment, during electrospinning, one material might migrate towards the outer surface of the fiber  730  while the other material may migrate towards the center of the fiber  725 . In another embodiment shown in  FIG. 7C , a functionalizing material  710  may be dispersed in a polymer solution  705  (or vice versa, where the polymer solution may be dispersed in a functionalizing material) to form a heterogeneous emulsion mixture. The emulsion may then be electrospun onto a target  720 , where during electrospinning, one of the emulsified materials may migrate towards the center of the fiber  725  and the other material may migrate towards the outer surface of the fiber  730 . In yet another embodiment shown in  FIG. 7D , a polymer solution  705  and a functionalizing material  710  may be electrospun coaxially onto a target  720 , where the materials may align coaxially as they are electrospun. In the embodiment of  FIG. 7D , one of the materials may form the outer surface  730  of the nanofiber while the other material may form the center  725  of the nanofiber. 
     While various embodiments in accordance with the principles disclosed herein have been shown and described above, modifications thereof may be made by one skilled in the art without departing from the spirit and the teachings of the disclosure. The embodiments described herein are representative only and are not intended to be limiting. Many variations, combinations, and modifications are possible and are within the scope of the disclosure. Alternative embodiments that result from combining, integrating, and/or omitting features of the embodiment(s) are also within the scope of the disclosure. Accordingly, the scope of protection is not limited by the description set out above, but is defined by the claims which follow, that scope including all equivalents of the subject matter of the claims. Each and every claim  1 s incorporated as further disclosure into the specification and the claims are embodiment(s) of the present invention(s). Furthermore, any advantages and features described above may relate to specific embodiments, but shall not limit the application of such issued claims to processes and structures accomplishing any or all of the above advantages or having any or all of the above features. 
     Additionally, the section headings used herein are provided for consistency with the suggestions under 37 C.F.R. 1.77 or to otherwise provide organizational cues. These headings shall not limit or characterize the invention(s) set out in any claims that may issue from this disclosure. Specifically and by way of example, although the headings might refer to a “Field,” the claims should not be limited by the language chosen under this heading to describe the so-called field. Further, a description of a technology in the “Background” is not to be construed as an admission that certain technology is prior art to any invention(s) in this disclosure. Neither is the “Summary” to be considered as a limiting characterization of the invention(s) set forth in issued claims. Furthermore, any reference in this disclosure to “invention” in the singular should not be used to argue that there is only a single point of novelty in this disclosure. Multiple inventions may be set forth according to the limitations of the multiple claims issuing from this disclosure, and such claims accordingly define the invention(s), and their equivalents, that are protected thereby. In all instances, the scope of the claims shall be considered on their own merits in light of this disclosure, but should not be constrained by the headings set forth herein. 
     Use of broader terms such as comprises, includes, and having should be understood to provide support for narrower terms such as consisting of, consisting essentially of, and comprised substantially of. Use of the term “optionally,” “may,” “might,” “possibly,” and the like with respect to any element of an embodiment means that the element is not required, or alternatively, the element is required, both alternatives being within the scope of the embodiment(s). Also, references to examples are merely provided for illustrative purposes, and are not intended to be exclusive. 
     While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods may be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted or not implemented. 
     Also, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, device, or intermediate component, whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the spirit and scope disclosed herein.