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WO2014089458A1 - Appareil et procédé utilisant un champ électrique pour créer des motifs de nanoparticules uniformes sur des matériaux non conducteurs afin d'augmenter la filtration et pour l'incrustation de fibres dans des matériaux pour d'autres applications - Google Patents

Appareil et procédé utilisant un champ électrique pour créer des motifs de nanoparticules uniformes sur des matériaux non conducteurs afin d'augmenter la filtration et pour l'incrustation de fibres dans des matériaux pour d'autres applications Download PDF

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Publication number
WO2014089458A1
WO2014089458A1 PCT/US2013/073620 US2013073620W WO2014089458A1 WO 2014089458 A1 WO2014089458 A1 WO 2014089458A1 US 2013073620 W US2013073620 W US 2013073620W WO 2014089458 A1 WO2014089458 A1 WO 2014089458A1
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WIPO (PCT)
Prior art keywords
nanofibers
filtration
patterned
fibers
materials
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Ceased
Application number
PCT/US2013/073620
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English (en)
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WO2014089458A9 (fr
Inventor
Anthony Clint CLAYTON
Howard Jerome WALLS
Adam Joseph RIETH
David Samuel ENSOR
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RTI International Inc
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RTI International Inc
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Priority to US14/646,165 priority Critical patent/US10188973B2/en
Publication of WO2014089458A1 publication Critical patent/WO2014089458A1/fr
Publication of WO2014089458A9 publication Critical patent/WO2014089458A9/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D39/00—Filtering material for liquid or gaseous fluids
    • B01D39/14—Other self-supporting filtering material ; Other filtering material
    • B01D39/16—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres
    • B01D39/1607—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres the material being fibrous
    • B01D39/1623—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres the material being fibrous of synthetic origin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
    • B01D2239/02—Types of fibres, filaments or particles, self-supporting or supported materials
    • B01D2239/025—Types of fibres, filaments or particles, self-supporting or supported materials comprising nanofibres
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
    • B01D2239/06—Filter cloth, e.g. knitted, woven non-woven; self-supported material
    • B01D2239/065—More than one layer present in the filtering material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
    • B01D2239/06—Filter cloth, e.g. knitted, woven non-woven; self-supported material
    • B01D2239/065—More than one layer present in the filtering material
    • B01D2239/0654—Support layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
    • B01D2239/12—Special parameters characterising the filtering material
    • B01D2239/1233—Fibre diameter
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/54—Particle separators, e.g. dust precipitators, using ultra-fine filter sheets or diaphragms
    • B01D46/546—Particle separators, e.g. dust precipitators, using ultra-fine filter sheets or diaphragms using nano- or microfibres

Definitions

  • the present invention is related to nanofibers, methods and devices for
  • the filtration industry has traditionally manufactured particulate air filters using conventional medium such as glass, cotton or polymer fibers made provided as rolled goods.
  • the fibrous media may be made by non- woven processes such as wet laid paper, melt blown- spinning or woven yarn. The material is then transported to equipment where the media is cut, pleated, supported, glued into filter frames, and tested for leaks.
  • Various measures of the properties of the rolled goods include appropriate weight per unit area, porosity, etc.
  • the porous filter media may be pleated or bonded into bags to increase the area of the media within individual filter units to reduce pressure drop. Often screens and other supports are added to prevent collapse of the media from the force of air flowing through the filter unit as dust is collected.
  • the filter may be tested with an appropriate challenge aerosol at a rated or standard airflow rate for pressure drop and particle collection efficiency, (e. g., ASHRAE 52.2, MIL-STD-282, IEST RP-CC 007.1, NIOSH APRS-STP-0051-00, and NIOSH APRS-0057-00 may be used to test the filters)
  • Electrospinning uses a constant voltage to drive the spinning process defined herein as static field electrospinning.
  • FoM filter quality factor or figure of merit
  • FoM - Log ( ⁇ )/ ⁇ (1)
  • Pt is the fractional penetration of a specific aerosol particle diameter
  • the FoM of a high efficiency particulate air (HEP A) glass fiber media is 12 kPa "1 measured at a face velocity of 5.33 cm/s and 0.3 ⁇ particle diameter. These are the standard conditions for HEP A media tests (i.e., IEST -RP-CC021.1).
  • the FoM of the layered nanofiber conventional porous filter media described above is limited by the relatively large fiber diameters of the coarse substrate which produce a relatively low FoM.
  • the FoM of the layered nanofiber conventional porous filter media composite depends on the relative quantities of layers of nanofibers and conventional media and their respective FoM. In other words, while the individual layers of nanofibers may have a higher FoM than the conventional porous filter media substrate, the composite FoM is closer to the value of the convention porous filter media substrate because of the relative quantities of materials used in the conventional approach. Therefore at the current state-of- the-art, conventional layered nanofiber filter media do not provide filters with significantly greater FoM than conventional fiberglass media.
  • nanoparticles by electrospinning from poly(acrylonitrile-co-acrylic acid)- PdC12 solutions. Relations between preparation conditions, particle size, and catalytic activity.” Macromolecules 37(5): 1787-1792.
  • a filtration device which included a filtration medium having a plurality of nano fibers of diameters less than 1 micron which were formed into a fiber mat in the presence of an abruptly varying electric field.
  • the filtration device in the '282 application included a support attached to the filtration medium which had openings for fluid flow there through.
  • a filtration device including a base filtration material having openings for fluid flow there through and a filtration medium comprising a plurality of patterned nanofibers formed on the base filtration material.
  • the filtration medium has a figure of merit greater than 30 kPa "1 , where the figure of merit is given by -Log ( ⁇ )/ ⁇ , where Pt is the fractional penetration of a specific aerosol particle diameter and ⁇ is a pressure drop across the filtration medium corresponding to a face velocity of 5.3 cm/s and particle size of 0.3 microns.
  • an apparatus for depositing the patterned filtration medium as detailed below.
  • Figure 1 is a graph comparing filtration performance for various filter medias including the nano-fiber filters of the present invention
  • Figure 2 is a depiction of one configuration for the patterned deposition of electrospun nanofibers onto substrates such as insulating nonwovens;
  • Figure 3 is a graph comparing patterned nanofiber media of the present invention to nanofiber media without patterning and to nanofiber media on a metal mesh;
  • Figure 4 is a collection of images of patterned nanofiber filter media;
  • Figure 5 is a collection of images of various patterns that are possible including nested or complex patterns
  • Figure 6 is a depiction of various layered structures according to the present invention.
  • Figure 7 is a depiction of one process embodiment of the present invention
  • Figure 8 is a depiction of a scale up concept for patterned deposition according to one embodiment of the present invention.
  • Insulated drive belt to provide rotation or substrate movement
  • Base or structural support typically composed of insulating materials
  • Substrate or backing material composed of woven, nonwoven, etc
  • the present invention provides a way to form patterned nanofibers structures with exceptionally high figures of merit (FOM).
  • the present invention provides for fabrication of nanofiber mats that could be used, for example, but not limited to filtration applications.
  • the present invention can be applied to a wide range of other areas such as single filaments, yarns, nonwoven materials and membranes. Marked improvements in filter performance, as indicated by FoM, are provided for in various embodiments of the present invention.
  • this invention provides an apparatus and method for
  • electrospinning nanofibers onto woven and nonwoven materials where enhanced filtration efficiency per air flow resistance is realized.
  • Potential applications for this technology include: air and liquid filtration, protective equipment, industrial hygiene, health care, food safety, technical textiles, fabrics, multifunctional materials, and defense.
  • nanofibers for use in air filtration provide only modest improvements in collection efficiency per filter pressure drop (i.e., air flow resistance) compared to conventional materials.
  • the '282 application achieved improved results by depositing sub- 100 nm fibers onto a metal mesh developing nanofiber filter materials that have 2 to 6 times improvement (depends on the polymer used) in filtration efficiency per pressure drop compared to conventional filter materials.
  • the nanofibers were deposited onto the conductive metal mesh forms an integrated metal-mesh fiber structure.
  • the present invention does not require an integrated metal-mesh fiber structure and yet still achieves significant improvement in collection efficiency per pressure drop using flexible substrates (e.g., nonwovens).
  • This advancement broadens the potential use of nanofibers on textiles and should lower the cost and technical difficulty of scaling up an advanced filtration media compared to the M-NF Filter Structure.
  • this technology has industrial applications in the field of technical textiles where fibers, microfibers, and nanofibers are incorporated on/into woven and nonwoven textiles.
  • patterned nanofibers are fibers formed in compliance with a predefined pattern and thereby having an organization and orientation of the fibers on the substrate surface set by the predefined pattern.
  • the patterning as described below can include simple patterns as well as nested or complex patterns following the pattern of the underlying substrate, e.g. a patterned grid or metal mesh. As detailed below, this patterning can include parallel lines with large spacing and a small grid pattern, large and small grid patterns nested, etc. This patterning can be seen as thick and thin areas of nanofibers at the macroscopic scale while resulting in three-dimension orientation of the fibers in/on the substrate at the microscopic scale.
  • Figure 1 is a graph comparing filtration performance for various filter medias including the nano-fiber filters of the present invention. Performance measured with 0.3 ⁇ particles at 5.33 cm/s. Data points represent average values of collected data sets.
  • the literature data are from a range of materials and fabrication processes with the error bars representing the full range of values observed in the published literature. Error bars on all other materials are for a standard deviation of a data set.
  • This plot in Figure 1 is in essence the effectiveness of filtration obtained for the level of filtration protection (efficiency of filtration) provided.
  • a filter media with high efficiency and high FoM is able to provide a high level of protection with minimal burden (e.g., filter is easier to breathe through and/or it can be a smaller size).
  • Data for the integrated metal-mesh fiber structure are compared with conventional nanofiber and fiberglass filter media.
  • Polysulfone (PSu)-based nanofiber media Data from “nylon-based nanofiber media” and “polysulfone (PSu)-based nanofiber media” are given as the average and standard deviation for a large number of samples made by the inventors (more than 20). “Fiberglass” data are average and standard deviation for a variety of commercial samples tested by the inventors. "PSu nanofibers on conductive nonwoven” are samples made by the inventors by deposition onto a nonwoven substrate coated with conductive graphite paint (Aerodag). These materials offer no statistically significant improvement over conventional fiberglass filter media.
  • the "literature nanofiber media” are a wide variety of materials reported in the literature with the error bars representing the full range of values observed rather than a standard deviation of samples made via a single fabrication process. For the plot of Figure 1, the further to the top-right of the plot, the better is the filtration performance of the material.
  • nanofiber electrospinning methods rely on a high positive voltage (+20kV to +40kV or higher) applied to a needle (i.e., spinneret) or other device that holds or manages the liquid solution to be spun into nanofibers.
  • the target area (or substrate) for the spun nanofibers has to be at a ground potential (or significantly lower potential than the spinneret) in order to attract the highly positively charged fibers.
  • These charged fibers land onto the grounded surface and form a layer of fibers (also called a mat).
  • the fibers collect in random orientations forming a nonwoven fibrous mat on top of the substrate.
  • the substrate is usually made of conductive materials (e.g., metal mesh), or materials with a conductive coating such as carbon paint.
  • a thin, minimally- insulating substrate such as a light-weight nonwoven backing, is placed on top of a grounded target and then the fibers are deposited onto the substrate.
  • insulating and conductive nonwovens used as deposition substrates lead to little or no improvement over conventional fiberglass filter media (see Figure 1). Furthermore, a metal mesh (i.e., the integrated metal-mesh fiber structure) was required to achieve significant improvement in filtration performance.
  • a patterned grid mechanism is placed directly underneath the substrate.
  • a non-conductive material can now be used including woven or nonwoven materials and possibly even membranes and other materials that are modest electrical insulators.
  • a negative bias voltage is applied directly to the patterned grid that is underneath the substrate. In some embodiments voltages can range from a few hundred to up to ten thousand volts, or more depending upon the materials and needed processing conditions.
  • the positively charged nanofibers are highly attracted to the negative bias on the grid and began to deposit onto the surface in a rapidly growing pattern. The result is that, during the spinning of the nanofibers, the fibers take the same pattern of the grid or patterned design underneath them. It has also been noted that when viewing the fibers through a microscope it appears that the fibers are at least partly embedded into the substrate, not only on the surface. These fibers now take on filtration properties of filters that used the integrated metal-mesh fiber structure.
  • FIG. 2 is a depiction of this configuration for the patterned deposition of electrospun nanofibers onto substrates such as for example insulating nonwovens.
  • a polymer solution containing PSu polymer in a solvent (using standard formulations) is fed to a 30G needle.
  • C0 2 gas mixed with water vapor and heated to 30C flows over the syringe and syringe needle.
  • Additional relative humidity (RH) controlled C0 2 gas is injected into the electro spinning chamber.
  • a positive power supply is connected to the spinneret and shares a common earth ground with a negative power supply connected to the patterned grid used to drive the patterned deposition of the nanofibers.
  • the nonwoven substrate is mounted on a frame above the patterned grid.
  • the grid can be in contact with or with a small air gap between the substrate and the grid.
  • Auxiliary electrodes can be used that are connected to the negative power supply to aid in broadening the overall electric field to provide for even dispersion of fibers over the substrate.
  • the substrate can be rotated relative to the spinneret to improve fiber dispersion.
  • the RH- and temperature-controlled C0 2 gas flows through the substrate and out the chamber venting system. This flow of gas may help dry the fibers and more generally controls the drying rate.
  • a variety of mechanisms are suitable in the present invention to control the chamber RH such as placing materials that absorb (e.g. calcium sulfate) or emit water moisture (e.g., hydrogels), operating a small humidifier in the chamber, and adding moisture into the process gas streams prior to introduction to the electrospinning chamber.
  • materials that absorb e.g. calcium sulfate
  • water moisture e.g., hydrogels
  • positive results were obtained by bubbling C0 2 through deionized (DI) water and then introducing the humidified C0 2 gas into the chamber.
  • DI deionized
  • two gas streams e.g., one humidified and one dry
  • two gas streams are used to obtain a desired RH for the chamber and/or for the gas jacket flowing over the electrospinning orifice.
  • forming/growing nanofiber mat can be readily measured and can be used to determine the quality of the forming filter and point at which to stop electrospinning. However, this flow of gas though the forming filter media may not be required in certain embodiments of the present invention. Furthermore, although the process described above was used to determine the quality of the forming filter and point at which to stop electrospinning. However, this flow of gas though the forming filter media may not be required in certain embodiments of the present invention. Furthermore, although the process described above was used to
  • Performance was measured with 0.3 ⁇ particles at 5.33 cm/s.
  • Figure 3 compares the results of the patterned deposition of nanofibers onto insulating nonwovens with other fibrous media. Specifically, Figure 3 is a graph comparing patterned nanofiber media of the present invention to nanofiber media without patterning and to nanofiber media on a metal mesh. In Figure 3, the patterned nanofiber media are compared to an integrated metal-mesh fiber structure (M-NF Filter structure) and to nanofibers deposited onto flexible nonwoven substrates without patterning.
  • M-NF Filter structure integrated metal-mesh fiber structure
  • Figure 4 is a collection of images of patterned nanofiber filter media.
  • Figure 4 shows images of patterned nanofiber filter media, specifically PSu nanofibers deposited on lightweight nonwoven using a metal mesh at a negative potential behind the nonwoven during electrospinning.
  • the present invention provides the realization of a collection of patterned nanofibers.
  • This collection can be used in a filtration device or in the other applications as discussed below.
  • This collection (as described below) can be included on or removed from a base material having openings for fluid flow there through.
  • the present invention permits filtration figures of merit to be realized from values of 30 kPa "1 to 60 kPa “1 . Higher values are not precluded.
  • the figures of merit can range from 40 kPa “1 to 60 kPa “1 .
  • the figures of merit can range from 50 kPa "1 to 60 kPa “1 .
  • Figure 5 gives examples of some patterns including a nested pattern with broadly spaced parallel lines and a fine grid inside of the lines. More specifically, Figure 5 is a collection of images of various patterns that are possible including nested or complex patterns. This is done by using two different grids and changing which grid is used for patterning partway through the fiber deposition process.
  • Another configuration of the present invention would utilize a grid placed upon a flat plate and a nonwoven placed on top of the grid, thus not using the flow-through gas configuration of Figure 2.
  • a variety of fabrics, nonwovens, and layers of materials were also tested as substrates in this configuration. While not a preferable as the configuration of Figure 2, this arrangement is still suitable.
  • One issue in this configuration was the observance that the fibers passing completely through the substrate often attached to the underlying patterning grid. These fibers would then break off when the substrate was removed from the patterning grid introducing defects into the filter media.
  • nonstick coatings could be applied, the gap between the grid and substrate could be increased, the thickness and porosity of the substrate could be changed, and the negative potential applied to the underlying grid could be reduced.
  • Figure 6 is a depiction of various layered structures according to the present invention. With the present invention a wide variety of possibilities exist including various layered structures. Some examples are illustrated in Figure 6 which shows examples of various layered structures possible with the present invention.
  • a variety of fiber deposition configurations are possible.
  • the first demonstration of the invention was done using a small piece of nonwoven above a metal screen (grid) with a negative potential applied to the grid as described above.
  • a sheet of a substrate material is passed synchronously over a patterning device with continuous deposition of fibers onto the top of the substrate from one or more spinnerets.
  • this process could deposit patterned nanofibers on large sheets as opposed to the small circular pieces demonstrated above.
  • C0 2 or other gas through or over the substrate during electrospinning could be used or omitted.
  • the integrated metal-mesh fiber structure was used to obtain significant improvements in FoM for high efficiency media.
  • the metal mesh is used to create the pattern in conjunction with the use of a negative electric potential applied to the mesh. Accordingly, the nanofibers can be deposited onto a flexible substrate (for example a thin nonwoven that is not inherently conductive).
  • the substrate is placed on, or directly above with a slight air gap, the metal mesh (or other conductive patterned material).
  • the fibers deposit onto the substrate replicating some version of the pattern of the mesh (or other device) behind the substrate.
  • the electrospinning conditions can be the same or similar to those described in the '282 application for formation of the integrated metal-mesh fiber structure.
  • a mixture of dry and wetted (via bubbling through DI water) C0 2 can be used to obtain an RH in the range of 26 to 38%.
  • a 21 wt% PSu (Udel P3500 LCD by Solvay Advanced Polymers) in DMAC with the 0.2 wt.% TBAC can be used as the polymer solution.
  • This polymer solution can be spun from a 30G (ID- 0.152 mm) stainless steel needle with a flow rate of 0.05 ml/hr, a gap of 25.4 cm, an applied potential of 29.5 kV DC, and a C0 2 gas jacket flow rate of 8 L/min.
  • the nanofibers produced by the present invention include, but are not limited to, acrylonitrile/butadiene copolymer, cellulose, cellulose acetate, chitosan, collagen, DNA, fibrinogen, fibronectin, nylon, poly(acrylic acid), poly(chloro styrene), poly(dimethyl siloxane), poly(ether imide), poly(ether sulfone), poly(ethyl acrylate), poly(ethyl vinyl acetate), poly(ethyl-co-vinyl acetate), poly(ethylene oxide), poly(ethylene terephthalate), poly(lactic acid-co-glycolic acid), poly(methacrylic acid) salt, poly(methyl methacrylate), poly(methyl styrene), poly(styrene sulfonic acid) salt, poly(styrene sulfonyl fluoride), poly(styrene-co-acrylonitrile), poly(styrene-
  • polycaprolactone polycarbonate, poly(dimethylsiloxane-co-polyethyleneoxide),
  • polymer blends can also be produced as long as the two or more polymers are soluble in a common solvent or mixed solvent system.
  • a few examples would be: poly(vinylidene fluoride)-blend-poly(methyl methacrylate), polystyrene-blend- poly(vinylmethylether), poly(methyl methacrylate)-blend-poly(ethyleneoxide),
  • Example polymers include the use of polymers that are pH and/or thermal responsive such that the nanofiber mat can later be modified, respond to a change in environment, or easily dissolved.
  • Example polymers include the commercial pH sensitive polymers know as Eudragit polymers as well as copolymers of N-isopropyl acrylamide (NIP AM) and N-methyacryloy-L-Leucine (MALEU) or (N,N- dimethylamino)ethyl methacrylate (DMAEMA).
  • NIP AM N-isopropyl acrylamide
  • MALEU N-methyacryloy-L-Leucine
  • DMAEMA N,N- dimethylaminoethyl methacrylate
  • a similar approach would be to use polymers that are easily degraded with enzymes such as Chitosan which is degraded by Chitosanase and cellulose which is degraded by cc-cellulase.
  • Combinations of polymer systems could be used to
  • the thickness of the nanofiber mat can vary from about 0.25 ⁇ (250 nm) to 500 ⁇ or beyond if needed, where most filters had an average mat thickness in the range of 2 to 5 microns.
  • the average mat thickness numbers represent the average thickness of the total nanofiber mat in a filter.
  • the mat thickness can be defined as layers of nanofibers with the thickness including from 4 to 4000 layers where 4 to 400, or 5 to 100, or 5 to 15 layers were typical in various embodiments.
  • the substrate with the deposited nanofibers can be readily removed from the metal mesh.
  • the result is a flexible substrate with the patterned nanofibers that can then be used without the metal mesh and nevertheless yield the desired high FoM and efficiency previously only possible when using direct deposition of nanofibers onto the metal mesh.
  • Figure 7 is a depiction of one process embodiment of the present invention. More specifically, Figure 7 illustrates an exploded view of the fabrication process usable by the present invention.
  • the left hand side of Figure 7 is an exploded view (Step 1) of the setup to deposit nanofibers onto a flexible substrate (e.g. insulating nonwoven) in a patterned fashion.
  • the right hand side of Figure 7 is an exploded view of Step 2, where the substrate with the patterned nanofibers is removed from the mesh and removed from the deposition system, thus providing a filter media with superior performance in FoM and efficiency.
  • FIG. 8 is a depiction of a scale up concept for patterned deposition according to one embodiment of the present invention. Accordingly, shown in Figure 8 is one way of scaling up the patterned fiber formation process of the present invention.
  • a substrate sheet or part of a roll
  • Supporting and underneath the substrate is a conveyor belt with a mesh or desired pattern that moves at a matching velocity such that the velocity of the substrate relative to the velocity of the conveyor belt, in the region of fiber deposition, is zero.
  • a regular pattern of nanofibers is deposited upon the substrate.
  • the electric field in the vicinity of where the fibers are being deposited moves at the same speed as the sheet or roll.
  • Another approach is to use a moving electric field synchronized with the moving sheet or roll generated by a structure below the moving sheet, or roll.
  • a conveyor belt or mesh moves with the substrate such that the relative velocity of the substrate to the patterned mesh during fiber deposition is zero. This provides for the establishment of well defined patterns of fibers that provide the needed structure for improved filtration performance.
  • the underlying conveyor belt (with a predefined pattern) contacts the substrate as a roller would.
  • the electric field is impressed on the top surface of the substrate which is directly above the contact point.
  • One immediate use for the invention is to improve the filtration performance of non- conductive or semi-conductive materials by making it possible to apply uniform nanofiber patterns to previous materials that had poor filtration properties.
  • the present invention provides the capability to use flexible nonwoven materials instead of a metal mesh to achieve high collection efficiency at reduced airflow resistance.
  • Other applications that may be possible are: the ability to create patterns within fabrics or onto materials that are unseen until a certain wavelength of light is incident thereon, the ability to create enhanced filtration incorporated into products such as face masks, protective suits, gloves, hats, etc.
  • Other applications include the potential to deposit nanofibers onto paper products such as writing paper, various paper products, posters, etc. More applications include the ability to put patterns onto leggings, pantyhose, and other skin hugging materials such as spandex.
  • Other applications include the ability to create layers of nanofiber spun materials by the pulling of the nanofibers into the materials by the electric field; or by overlaying them after preparation. Another possibility is to spin fibers onto materials on one side, then flip the material over to spin on the back side. Another concept is to spin different nanofiber pattern layers on the material.
  • the electric fields may help conformal deposition of fibers onto contoured surfaces.
  • electroblowing can be used here in the present invention.
  • electroblowing can be used here in the present invention.
  • electroblowing can be used here in the present invention.
  • electroblowing and “electro-blown spinning” are used in the art to refer interchangeably to a process for forming a fibrous web by which a forwarding gas stream is directed generally towards a collector, into which gas stream a polymer stream is injected from a spinning nozzle, thereby forming a fibrous web which is collected on the collector, wherein a voltage differential is maintained between the spinning nozzle and an electrode and the voltage differential is of sufficient strength to impart charge on the polymer as it issues from the spinning nozzle.
  • nanofibers suitable for this invention can be formed by an electroblowing process which issues an electrically charged polymer stream from a spinning nozzle in a spinneret and which passes the polymer stream by an electrode to which a voltage is applied.
  • the spinneret is substantially grounded, such that an electric field is generated between the spinneret and the electrode of sufficient strength to impart electrical charge to the polymer stream as it issues from the spinning nozzle.
  • the nanofibers formed from the charged polymer stream could be deposited on a collector holding for example substrates with inter-digitated electrodes.
  • the nanofibers formed from the charged polymer stream could be deposited on a collector holding for example the substrates without electrodes. In that case, the electrodes would be later added to the deposited fibers to form the sensors of this invention.
  • centrifugal spinning could be combined with an electric field to produce charged fibers that would work with this present invention.
  • any fiber-production process that could produce charged fibers that are subject to the directing of the fiber deposition should work with this invention.
  • the present invention is thus applicable to more than fibers that are nanofibers.
  • novel patterning of fibers described above can additionally incorporate materials for functionality (i.e., smart textiles).
  • Functionalities include the incorporation of materials like phosphorus, conductive particles, reactive particles, etc.
  • Textiles could be made that sense and respond to the localized environment next to a patient's skin and provide patient monitoring.
  • light stimulated materials could be incorporated in to the fibers and the fibers thereafter patterned onto a textile to create a composite with pleasing visual effects (e.g. attractive pattern that lights up under certain lighting conditions).

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  • Chemical Kinetics & Catalysis (AREA)
  • Nonwoven Fabrics (AREA)

Abstract

La présente invention concerne un dispositif de filtration comprenant un matériau de filtration de base présentant des ouvertures pour qu'un fluide le traverse et un milieu de filtration. Le milieu de filtration comprend une pluralité de nanofibres à motifs formées sur le matériau de filtration de base. Le milieu de filtration possède un facteur de mérite supérieur à 30 kPa-1, le facteur de mérite étant donné par -Log (Pt)/ΔP, où Pt est la pénétration fractionnelle d'un diamètre de particule d'aérosol spécifique et ΔΡ est une chute de pression dans le milieu de filtration correspondant à une vitesse frontale de 5,3 cm/s et une taille de particules de 0,3 micromètres.
PCT/US2013/073620 2004-04-08 2013-12-06 Appareil et procédé utilisant un champ électrique pour créer des motifs de nanoparticules uniformes sur des matériaux non conducteurs afin d'augmenter la filtration et pour l'incrustation de fibres dans des matériaux pour d'autres applications Ceased WO2014089458A1 (fr)

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US9446547B2 (en) 2012-10-05 2016-09-20 Honeywell International Inc. Nanofiber filtering material for disposable/reusable respirators
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US10639572B2 (en) 2016-01-07 2020-05-05 Donaldson Company, Inc. Styrene-acrylonitrile fine fibers, filter media, recirculation filters, and methods

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