Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/0007—Electro-spinning
  • D01D5/0015—Electro-spinning characterised by the initial state of the material
  • D01D5/003—Electro-spinning characterised by the initial state of the material the material being a polymer solution or dispersion
  • D01D5/0038—Electro-spinning characterised by the initial state of the material the material being a polymer solution or dispersion the fibre formed by solvent evaporation, i.e. dry electro-spinning
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/0007—Electro-spinning
  • D01D5/0061—Electro-spinning characterised by the electro-spinning apparatus
  • D01D5/0069—Electro-spinning characterised by the electro-spinning apparatus characterised by the spinning section, e.g. capillary tube, protrusion or pin
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/08—Melt spinning methods
  • D01D5/098—Melt spinning methods with simultaneous stretching
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/08—Melt spinning methods
  • D01D5/098—Melt spinning methods with simultaneous stretching
  • D01D5/0985—Melt spinning methods with simultaneous stretching by means of a flowing gas (e.g. melt-blowing)
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/11—Flash-spinning
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y40/00—Manufacture or treatment of nanostructures

Definitions

• This invention relates to a method of forming a polymeric nanofiber web via electro-blown spinning or electro-blowing.
• the nanofiber web of the invention can be incorporated in composite fabrics suited for use in apparel, wipes, hygiene products, filters and surgical gowns and drapes.
• Synthetic polymers have been fashioned into very small diameter fibers using various processes including melt spinning, flash spinning, solution blowing, melt blowing, electrostatic spinning and electro-blowing. Webs made from these very small diameter fibers are useful as liquid barrier materials and filters. Often they are combined with other stronger webs into composites for additional strength to meet the needs of the product end use.
• a first embodiment of the present invention is directed to a method for preparing a nanofiber web comprising feeding a polymer solution, which comprises at least one polymer dissolved in at least one flammable solvent to a spinning nozzle, discharging the polymer solution from the spinning nozzle into a blowing gas or gas mixture that will not support combustion, wherein the blowing gas exits a jet at a lower end of the spinning nozzle, to form polymer nanofibers, and collecting the polymer nanofibers on a collector under the spinning nozzle, wherein an applied high voltage differential is maintained between the spinneret and the collector.
• Figure 1 is a schematic diagram of a prior art electro-blowing apparatus for conducting the process of the present invention.
• This invention is directed towards an improvement to the method for preparing a nanofiber web using electro-blown spinning (or "electro- blowing") as described in International Publication Number WO2003/080905 (U.S. Serial No. 10/822,325), which is hereby incorporated by reference.
• This prior art electro-blowing method comprises feeding a solution of a polymer in a solvent to a spinning nozzle to which a high voltage is applied, while compressed air is directed toward the polymer solution in a blowing gas stream as it exits the nozzle to form nanofibers and collecting the nanofibers into a web on a grounded collector under vacuum.
• the compressed air is replaced with a gas or gas mixture that will not support combustion.
• the presence of molecular oxygen gas in air would support combustion when a flammable solvent is used, a situation which is exacerbated by the presence of a high voltage potential difference between the spinning nozzle and the collector. If any of a variety of process parameters are not adequately controlled, an electrical arc can occur, providing an ignition source. By replacing the blowing air with gases that will not support combustion, the potential for a fire is reduced.
• Nanofibers means fibers having diameters varying from a few tens of nanometers up to several hundred nanometers, but generally less than one micrometer.
• FIG. 1 shows a diagram of a nanofiber web preparing apparatus of the invention for illustrating a nanofiber web preparing process.
• a storage tank 100 prepares a polymer solution from dissolution of one or more polymers in one or more solvents.
• Polymers available for the invention are not restricted to thermoplastic resins, but may utilize most synthetic resins such as thermosetting resins.
• Examples of the available polymers may include polyimide, nylon, polyaramid, polybenzimidazole, polyetherimide, polyacrylonitrile, polyethylene terephthalate), polypropylene, polyaniline, poly(ethylene oxide), poly(ethylene naphthalate), poly(butylene terephthalate), styrene butadiene rubber, polystyrene, polyvinyl chloride), polyvinyl alcohol), poly(vinylidene fluoride), polyvinyl butylene) and copolymer or derivative compounds thereof.
• the polymer solution is prepared by selecting a solvent that will dissolve the polymer. Suitable solvents include but are not limited to flammable solvents such as tetrahydrofuran, N-dimethylformamide, dimethylacetamide, acetone and methyl ethyl ketone. Although dissolving most of the polymers may not require any specific temperature ranges, heating may be needed for assisting the dissolution reaction.
• the polymer solution can be mixed with additives, including any resin compatible with an associated polymer, plasticizer, ultraviolet ray stabilizer, crosslinking agent, curing agent, reaction initiator, etc.
• any known means for forcing the polymer solution from the storage tank 100 can be utilized.
• the polymer solution is discharged from the storage tank 100 via a spinning nozzle 104 of a spinneret 102 which is electrically insulated and applied with a high voltage.
• compressed gas comprising a gas or gas mixture (the "blowing gas") that will not support combustion is injected via gas nozzles 106 disposed in sides of the spinning nozzle 104 wherein the gas contacts the polymer solution after the polymer solution exits the spinneret.
• the polymer solution discharged from the spinning nozzle 104 of the spinneret 102 forms nanofibers that are collected in the form of a web on a collector 110 under the spinning nozzle 104.
• the collector 110 is grounded, and designed to draw gas through a gas collecting vessel 114, so that gas is drawn through a high voltage region between the spinning nozzle 104 and the collector 110, and by suction of a blower 112.
• the spinneret 102 can be grounded and the collector 110 can be applied with a high voltage.
• an electrostatic charge can be applied to the web to pin it to the collector without the need for suction under the collector.
• Gas drawn in by the blower 112 contains solvent and thus a Solvent Recovery System (SRS, not shown) is preferably included to recover solvent while recycling gas through the apparatus.
• the SRS may adopt a well-known construction.
• the blowing gas is selected to be a gas or gas mixture which will not support combustion, such as nitrogen, argon, helium, carbon dioxide, hydrocarbons, halocarbons, halohydrocarbons or mixtures thereof.
• a blowing gas only enough of such gases to reduce the molecular oxygen content in the air surrounding the spinning nozzle/collector system to be below the ambient level of approximately 21 vol. %, such that the LEL of any particular flammable solvent in use is elevated to a point which exceeds the likely concentration of such solvent vapors in the reduced oxygen-containing atmosphere surrounding the spinning nozzle/collector system.
• the blowing gas itself can include low concentrations of molecular oxygen, so long as the mixture cannot support combustion.
• the blowing gas is entirely contained within a sealed spinning vessel.
• the spinning vessel can be effectively purged of molecular oxygen, at least to a level that would be insufficient to support combustion.
• gases that would otherwise present a flammability hazard such as hydrocarbons or even recycled solvent vapors, could be used as the blowing gas.
• Various substrates can be arranged on the collector to collect and combine a nanofiber web spun on the substrate so that the combined fiber web is used as a high-performance filter, wipe and so on.
• the substrate may include various non-woven cloths such as melt-blown non- woven cloth, needle punching and spunlace non-woven cloth, woven cloth, knitted cloth, paper and the like, and can be used without limitations so long as a nanofiber layer can be added on the substrate.
• the invention can be conducted under the following process conditions.
• Voltage applied to the spinneret 102 is preferably in the range of about 1 to 300 kV and more preferably of about 10 to 100 kV.
• the polymer solution can be discharged under a pressure ranging from about 0.01 to 200 kg/cm 2 and in preferably about 0.1 to 20 kg/cm 2 . This allows the polymer solution to be discharged by a large quantity in an adequate manner for mass production.
• the process of the invention can discharge the polymer solution with a high discharge rate of about 0.1 to 5 cc/min- hole as compared with electrostatic spinning methods.
• Compressed gas injected via the gas nozzle 106 has a flow velocity of about 10 to 10,000 m/min and preferably of about 100 to 3,000 m/min.
• Gas temperature is preferably in the range of ambient temperature to about 300 0 C and more preferably to about 100 0 C.
• a polymer solution having a concentration of 20 wt % polyacrylonitrile in N-dimethylformamide solvent is prepared and then is spun with the spinneret as shown in Fig. 1.
• a spinning pressure of 6 kg/cm 2 is applied.
• Nitrogen blowing gas is injected at the lower end of the spinning nozzle at about 1 ,000 m/min and the oxygen concentration in the spinning region is monitored, such that the flow velocity of nitrogen blowing gas is adjusted to reduce oxygen concentration within the spinning region to below the level at which combustion would be supported.
• Voltage is applied at 50 kV DC by charging the spinneret and grounding the collector.
• a web of polyacrylonitrile fibers is collected with an average fiber diameter ⁇ 1 ,000 nm.
• a polymer solution having a concentration of 15 wt % poly(vinylidene fluoride) in acetone solvent is prepared and then is spun with the spinneret as shown in Fig. 1.
• a spinning pressure of 6 kg/cm 2 is applied.
• Argon blowing gas is injected at the lower end of the spinning nozzle at about 1 ,000 m/min and the oxygen concentration in the spinning region is monitored, such that the flow velocity of argon blowing gas is adjusted to reduce oxygen concentration within the spinning region to below the level at which combustion would be supported.
• Voltage is applied at 50 kV DC by charging the spinneret and grounding the collector.
• a web of poly(vinylidene fluoride) fibers is collected with an average fiber diameter ⁇ 1 ,000 nm.
• Example 2 The conditions set forth in Example 2 are reproduced, except that the blowing gas is a mixture of 5 vol.% oxygen/95 vol.% nitrogen.
• the mixed blowing gas is injected at the lower end of the spinning nozzle at 1 ,000 m/min and the oxygen concentration in the spinning region is monitored, such that the flow velocity of mixed blowing gas is adjusted to reduce oxygen concentration within the spinning region to below the level at which combustion would be supported.
• Voltage is applied at 50 kV DC by charging the spinneret and grounding the collector.
• a web of poly(vinylidene fluoride) fibers is collected with an average fiber diameter ⁇ 1 ,000 nm.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Textile Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Dispersion Chemistry (AREA)
• Spinning Methods And Devices For Manufacturing Artificial Fibers (AREA)
• Nonwoven Fabrics (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (7)

Cited By (3)

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Citations (4)

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• 2004
  • 2004-11-05 US US10/982,572 patent/US7846374B2/en active Active
• 2005
  • 2005-11-03 KR KR1020077012558A patent/KR101229607B1/ko not_active Expired - Fee Related
  • 2005-11-03 CN CN200580038226XA patent/CN101068956B/zh not_active Expired - Fee Related
  • 2005-11-03 WO PCT/US2005/040143 patent/WO2006052808A1/en not_active Ceased
  • 2005-11-03 EP EP05817398A patent/EP1834013B1/en not_active Ceased
  • 2005-11-03 BR BRPI0516328-5A patent/BRPI0516328A/pt not_active IP Right Cessation
  • 2005-11-03 JP JP2007539368A patent/JP4842957B2/ja not_active Expired - Fee Related

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