US20180094362A1 - Nanofiber structure - Google Patents

Nanofiber structure Download PDF

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Publication number
US20180094362A1
US20180094362A1 US15/564,043 US201515564043A US2018094362A1 US 20180094362 A1 US20180094362 A1 US 20180094362A1 US 201515564043 A US201515564043 A US 201515564043A US 2018094362 A1 US2018094362 A1 US 2018094362A1
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Prior art keywords
nanofiber structure
nanofiber
polyimide
air permeability
produced
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US15/564,043
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Inventor
Kozo Inoue
Kazuya Nitta
Keizou Tanaka
Yutaka Nagashima
Shunsuke Yamada
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Fuence Co Ltd
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Fuence Co Ltd
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Assigned to FUENCE CO., LTD. reassignment FUENCE CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: INOUE, KOZO, NITTA, KAZUYA, NAGASHIMA, YUTAKA, TANAKA, KEIZOU, YAMADA, SHUNSUKE
Publication of US20180094362A1 publication Critical patent/US20180094362A1/en
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    • 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
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/70—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres
    • D04H1/72—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres the fibres being randomly arranged
    • D04H1/728—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres the fibres being randomly arranged by electro-spinning
    • 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
    • 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
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
    • D01F6/58—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products
    • D01F6/74—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polycondensates of cyclic compounds, e.g. polyimides, polybenzimidazoles
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/04—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres having existing or potential cohesive properties, e.g. natural fibres, prestretched or fibrillated artificial fibres
    • D04H1/32—Synthetic pulp
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
    • D04H1/4326—Condensation or reaction polymers
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H13/00—Pulp or paper, comprising synthetic cellulose or non-cellulose fibres or web-forming material
    • D21H13/10—Organic non-cellulose fibres
    • D21H13/20—Organic non-cellulose fibres from macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
    • D21H13/26—Polyamides; Polyimides
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
    • D21H21/50—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by form
    • D21H21/52—Additives of definite length or shape
    • 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
    • B01D2239/10—Filtering material manufacturing

Definitions

  • the present invention relates to a nanofiber structure, and more particularly to a nanofiber structure of a polyimide resin, which has air permeability, moisture permeability, and water resistance. That is, the present invention relates to a nanofiber structure in which a polyimide resin having physical properties such as high heat resistance is transformed into nanofibers so as to have air permeability, moisture permeability, and water resistance.
  • ePTFE resin expanded polytetrafluoroethylene
  • the ePTFE resin is formed by thinning a PTFE resin with special stretching technology, thereby giving it a porous character, and adding air permeability, moisture permeability, and water resistance thereto.
  • the ePTFE resin is typically used for rain gear which requires both waterproofness and moisture permeability, outdoor products such as clothes, and apparel products, uses thereof are not limited thereto and they are used in a very wide range of industrial fields.
  • the ePTFE resin has the bad balance of air permeability and water resistance (the ePTFE resin has the general character in which if the air permeability thereof is improved, the water resistance thereof becomes very bad), that still higher heat resistance thereof is called for now, and that a price thereof is high as industrial material.
  • a polyimide resin has the highest heat resistance, insulation, and chemical stability among high-performance resins, and is used in many industrial fields because of these characteristics.
  • NON-PATENT LITERATURE 2 “polyimide porous membrane.”
  • the polyimide resin is based on such state-of-the-art technology, no polyimide resin having the air permeability, moisture permeability, and water resistance which is equal to ePTFE resin has been developed.
  • PATENT DOCUMENT 1 Patent Application Publication No. 2013-513932, “Electrochemical cell comprising a separator comprising a nanoweb consisting essentially of nanofibers of fully aromatic polyimide”
  • an ePTFE resin is breakthrough material which has the physical properties of water resistance, and moister permeability and air permeability in addition to high heat resistance, insulation, and chemical stability, as mentioned above, there is a drawback that the balance of air permeability and water resistance is bad.
  • the air permeability of the material, which is the ePTFE resin, and the water resistance thereof have a trade-off relation.
  • the present inventors came up with a technique for forming a polyimide solution, in which a polyimide resin is dissolved in a solvent, into nanofibers by the Electrospray Deposition Method (ESD method). Furthermore, by researches and developments under various conditions, they found out that a polyimide resin, which is formed into nanofibers, has water resistance, moisture permeability, and air permeability with a sufficient balance, and has the characteristics equivalent to or more than those of an ePTFE resin. Furthermore, they found out that it is possible to add adhesion properties to the polyimide resin, which is formed into nanofibers.
  • ESD method Electrospray Deposition Method
  • a nanofiber structure according to the first invention comprises a polyimide resin having the following structure:
  • a nanofiber structure according to the second invention is characterized in that a formation of nanofibers is carried out by the electrospray deposition method.
  • a nanofiber structure according to the third invention is characterized in that any change in a nanofiber structure does not occur even if it is heated at 400° C. for 16 hours.
  • a nanofiber structure according to the fourth invention is characterized in that the air permeability thereof is 4.55 cc/cm2/s or more in the JIS-L1096 air permeability A method (Frazier method), or 1.68 or less s/300 cc in the JIS-L1096 air permeability B method (Gurley method).
  • a nanofiber structure according to the fifth invention is characterized in that a moisture permeation resistance (RET) is 3.0 (m2 ⁇ Pa/W) or less in the ISO11092 method.
  • RET moisture permeation resistance
  • a nanofiber structure according to the sixth invention is characterized in that the water resistance thereof is 0.01 MPa or more in the JIS-L1092 water resistance test B method (High-pressure water method).
  • a nanofiber structure according to the seventh invention is characterized in that the thermal conductivity thereof is within a range of from 0.04-0.05 W/mK.
  • a nanofiber structure according to the eighth invention is characterized in that the nanofiber structure has adhesion properties.
  • nanofiber structure is explained as the means for solving the problem
  • present invention can be also realized as a manufacturing method of a nanofiber structure which is substantially equivalent thereto, so that it should be understood that they are within the scope of the present invention.
  • FIG. 1 is a conceptual diagram showing the fundamental configuration of an electrospray deposition apparatus.
  • FIG. 2 shows SEM photographs of a nanofiber structure produced according to an Example 1, wherein a polyimide resin KPI-MX 300 F (75) powder is used as material.
  • FIG. 3 is graphs showing a pore diameter distribution of the nanofiber structure produced according to the Example 1, wherein the polyimide resin KPI-MX 300 F (75) powder is used as material.
  • FIG. 4 shows SEM photographs of a nanofiber structure produced according to an Example 2, wherein a polyimide resin KPI-MX300 F (100) powder is used as material.
  • FIG. 5 shows graphs showing a pore diameter distribution of the nanofiber structure produced according to the Example 2, wherein the polyimide resin KPI-MX300 F (100) powder was used as material.
  • FIG. 6 is a diagram showing physical properties of the nanofiber structures in the Examples 1 and 2.
  • FIG. 7 is a diagram showing a result of study of a high temperature influence to a nanofiber structure in the Example 2.
  • FIG. 8 is a diagram showing a result of study of a high temperature influence to a nanofiber structure of the Example 2.
  • FIG. 9 is a diagram showing a result of study of a high temperature influence to a nanofiber structure of the Example 2.
  • FIG. 10 is a table of measurement of physical properties of water resistance and air permeability about a nanofiber structure of the Examples 1 and 2.
  • FIG. 11 is a table of measurement of physical properties of water resistance and air permeability of the nanofiber structure of the Example 2, and Comparative Examples 3 and 4;
  • FIG. 12 is a table of measurement of physical properties of air permeability of nanofiber structures in the Examples 1 and 2 and a Comparative example 5.
  • ESD method electrospray deposition method
  • ESD electrostatic spraying apparatus
  • FIG. 1 is a conceptual diagram showing the fundamental configuration of the electrospray deposition apparatus.
  • a container CNT contains a sample solution SL.
  • the sample solution SL is, for example, an organic macromolecular solution or polymer fluid etc.
  • the sample solution is, for example, a polyimide dissolved or dispersed in a solvent, namely, a polyimide solution.
  • the ESD method is a very complicated physical phenomenon, and although the entire process has not been figured out, it is generally considered as a phenomenon set forth below.
  • the sample solution is stored in a nozzle NZL in the shape of a thin capillary, and thousands to tens of thousands volt voltage is applied to a target substrate TS (opposite electrode) that faces this nozzle.
  • a target substrate TS opposite electrode
  • a powerful electric field is generated due to effects of electric field concentration, so that charged microdroplets collect on a liquid surface so that a corn is formed (so-called Taylor Cone).
  • the sample solution breaks the surface tension at the tip, so as to become a jet.
  • the jet is heavily charged and serves as a spray due to repulsion of electrostatic force (coulomb explosion).
  • the droplet formed by the spray is very small, so that the solvent is evaporated and dried in a short time, thereby producing fine nanoparticles or nanofibers.
  • a deposition thereof is also possible in a wet state where it is not evaporated and dried.
  • the fine electrified nanoparticles and nanofibers with small diameters are drawn to the target substrate TS which functions as an opposite electrode due to an electrostatic force.
  • a pattern of deposit can be controlled by an insulator mask or an auxiliary electrode, which is not illustrated.
  • the sample is in a liquid form, it is not limited to a solution and may be dispersion liquid.
  • an extrusion pressure towards the nozzle NZL side is applied to the sample solution in the container CNT by an air pressure syringe pump and a plunger etc. (a discharge means, which is not shown in the figures).
  • the extrusion pressure is given thereto by, for example, a stepping motor and a screw feeding mechanism (not shown).
  • An inside pressure increases within the container CNT, so that the sample solution SL which is subject to the extrusion pressure is discharged from the tip of the nozzle NZL.
  • adjustment mechanism a stepping motor and a screw feeding mechanism
  • the nozzle NZL is made of metal, and positive voltage is supplied through a wire WL made from a conductor from a high-voltage power supply HPS.
  • a minus side of the high-voltage power supply HPS is connected to the target substrate TS (a substrate, which is used as an opposite electrode).
  • a positive voltage is impressed to the sample solution SL through the nozzle NZL by impressing voltage from the high-voltage power supply HPS, whereby the solution is positively charged.
  • the polarity of the voltage applied to the sample solution SL may be negative.
  • nanofiber structure when producing a nanofiber structure, it is suitable to place a nonwoven fabric on the target substrate TS, and deposit the nanofiber structure on the nonwoven fabric. Moreover, various conditions, such as a level of voltage, concentration of the sample solution, kinds of polyimide as a sample, and a kind of solvent, are adjusted, so that a nanofiber structure is produced.
  • the material, with which the spraying is carried out becomes fibers and droplets and is repeatedly divided while flying by repulsion due to electrification, thereby forming nanofibers or nanoparticles. Since the material, with which the spraying is carried out is in nano size so that a surface area thereof is large, the material with which the spray was carried out will be almost dried, when they reaches the substrate.
  • the form and size thereof can be changed according to the spray conditions, so that, for example, when a macromolecular solution is used, thick nanofibers can be formed if a molecular weight thereof is made large and the concentration thereof is made high greatly, and thin nanofibers or nanoparticles can be formed if the molecular weight is made small and the concentration is made low.
  • various conditions such as voltage and the distance between the nozzle and the substrate, ambient temperature, humidity, etc. exert influence thereon.
  • various solvent-soluble polyimide resins were used as samples, and nanofibers were produced under various conditions, and the heat resistance, the conductivity, air permeability and moisture permeability and water resistance etc. were confirmed in a method described as the embodiments.
  • the electrospray deposition apparatus not only the above-mentioned apparatus but a different type of ESD apparatus can be also used therefor. Specifically, a method of using air current, which is disclosed in Re-Publication of PCT International Publication No. 2009/060898 and which was developed by applicants, is suitable for a mass-production purpose.
  • This sample solution in amount of 5 mL was put in the container CNT, which was a syringe made of polypropylene (PSY-30E-M produced by Musashi Engineering Inc.), wherein the metal nozzle NZL (MN-23G-13 manufactured by Iwashita Engineering, Inc.) shown in the FIG.
  • the container CNT was attached to an electrospray deposition apparatus (Esprayer ES-2300 manufactured by Fuence Co., Ltd.).
  • a polyester mesh (T-N0280T manufactured by NBC Meshtec Inc.) whose size was A3, was used as base material on the target substrate TS (collector substrate).
  • the voltage between the nozzle NZL and the collector (target substrate TS) was 26-30 kV
  • the distance between the nozzle and the collector was 15 cm
  • the liquid feed pressure was 0.010-0.015 MPa, under which the entire base material was scanned so as to evenly put the spray thereon from front to back and from side to side, whereby the nanofiber structure of polyimide was obtained.
  • other polyimide nanofiber structures were obtained under the same conditions except for the solution concentration of 17 weight percent.
  • a powder of a transparent solvent-soluble polyimide resin (KPI-MX 300 F (100) produced by Kawamura Sangyo Co., Ltd.) in amount of 10 grams was dissolved in N,N-Dimethylacetamide (purity 97.0%, produced by Wako Pure Chemical Industries, Ltd.) in amount of 90 grams, whereby a sample solution whose concentration was 10 weight % was produced in amount of 100 grams.
  • This sample solution in amount of 5 mL was put in the container CNT, which was a syringe made of polypropylene (PSY-30E-M manufactured by Musashi Engineering Inc.), wherein the metal nozzle NZL (MN-23G-13 manufactured by Iwashita Engineering, Inc.) shown in the FIG.
  • the container CNT was put on the electrospray deposition apparatus (Esprayer ES-2300 manufactured by Fuence Co., Ltd.).
  • a polyester mesh (T-N0280T produced by NBC Meshtec Inc.) whose size was A3, was used as base material on the target substrate TS (collector substrate).
  • the voltage between the nozzle NZL and the collector (target substrate TS) was 26-30 kV
  • the distance between the nozzle and the collector was 15 cm
  • the liquid feed pressure was 0.010-0.015 MPa, under which the entire base material was scanned so as to evenly put the spray thereon from front to back and from side to side, whereby the nanofiber structure of polyimide was obtained.
  • FIG. 2 shows SEM photographs of a nanofiber structure produced according to an Example 1, wherein a polyimide resin KPI-MX 300 F (75) powder was used as material.
  • the upper part of the figure shows a SEM photograph taken at a magnification of 30,000 times wherein a plurality of diameters of nanofibers are shown. The diameters were 169, 147, 168, 180, 134, and 145 or 151 nm, and a distribution thereof can be observed in a range of from 134 to 180 nm in the photographed portion.
  • the lower part of the figure shows a SEM photograph taken at a magnification of 3,000 times.
  • FIG. 3 is graphs showing a pore diameter distribution of the nanofiber structure produced according to the Example 1, wherein the polyimide resin KPI-MX 300 F (75) powder was used as material. The measurement was carried out by a. pore diameter distribution measuring device (Automated Perm Porometer CEP-1100A manufactured by PMI).
  • FIG. 3(A) shows a measurement result of a pore diameter distribution in a nanofiber structure containing a mesh base material
  • FIG. 3(B) shows a measurement result of a pore diameter distribution in a nanofiber structure without a mesh base material.
  • the film thickness of the nanofiber structure of (A), which included the mesh base material, was 73.2 ⁇ m, a base weight thereof was 4.0 g/m 2 , and a void ratio thereof was 75.0%.
  • the void ratio was obtained by the expression set forth below.
  • the film thickness of a nanofiber structure without the mesh base material of (B) was 29.8 ⁇ m.
  • the data of the mesh base material of (A) is set forth below.
  • the polyimide nanofiber structure whose physical properties is controlled as set forth below can be manufactured.
  • FIG. 4 shows SEM photographs of a nanofiber structure which was produced according to the Example 2, wherein a polyimide KPI-MX 300 F (100) powder was used as material.
  • the upper part of the figure shows a SEM photograph taken at a magnification of 30,000 times wherein a plurality of diameters of nanofibers are shown. The diameters were 314, 340, 349, 371, 372, and 379 or 385 nm, and a distribution thereof can be observed in a range of from 314 to 385 nm in the photographed portion.
  • the lower part of the figure shows a SEM photograph taken at a magnification of 3,000 times,
  • FIG. 5 shows graphs showing a pore diameter distribution of a nanofiber structure which was produced according to the Example 2, wherein a polyimide resin KPI-MX300 F (100) powder was used as material. The measurement was carried out by the same apparatus as that shown in FIG. 3 .
  • FIG. 5(A) shows a measurement result of a pore diameter distribution in a nanofiber structure without a mesh base material
  • FIG. 5(B) shows a measurement result of a pore diameter distribution in a nanofiber structure without a mesh base material, which was a separate part.
  • a film thickness of the nanofiber structure of (A) was 37.0 ⁇ m, a base weight thereof is 7.9 g/m 2 and a void ratio thereof is 86.4%.
  • a film thickness of the nanofiber structure of (B) without the mesh base material was 37.5 ⁇ m.
  • the peak value in the graph shown in the figure was a value obtained after a curve fitting was applied, and data obtained before the curve fitting was applied shifted a little therefrom, the peak value of (A) was 1.45 ⁇ m and the peak value of (B) was 0.55 ⁇ m.
  • FIG. 6 is a diagram showing physical properties of the nanofiber structures according to the Examples 1 and 2.
  • the physical properties of a commercial polyimide film are shown therein as Comparative Examples 1 and 2.
  • the physical property values of two kinds of polyimide nanofiber structures according to Examples 1 and 2 were measured, one of which was heat treated at 200° C. and the other of which was at room temperature.
  • a DMAc (dimethylacetamide) residual amount was computed from the weight reduction between 100 and 200° C. using the TGA method.
  • the surface and volume resistivity was measured by a double ring electrode method.
  • the CTE was measured under the condition set forth below by the TMA method. “It was calculated from a change rate in a temperature drop between 80-180° C. after being heated from 40 to 210° C. (5° C./min) and then held for 10 minutes at 210° C.”
  • the DMAc residual amount was in the same range as that of Comparative Examples 1 and 2 even without a heat treatment.
  • the surface and volume resistivity was 15th to 16th power ⁇ even, in 20-30 ⁇ m, and thus shows insulation properties.
  • the coefficient of thermal expansion (CTE) was measured by using lamination. It is found that in both the Examples 1 and 2, values of the coefficient of thermal expansion (CTE) were good, and they had a sufficient heat resistance even at 200° C. or higher.
  • the nanofiber structure of the polyimide resin according to the present Example had a sufficient heat resistance, but as shown in SEM photographs of FIGS. 7, 8 and 9 , further heat-resistant examinations were conducted in severer heat environment (400° C.).
  • FIGS. 7, 8 and 9 are diagrams showing results of study of a high temperature influence to a nanofiber structure of the Example 2.
  • FIG. 7 shows SEM photographs at room temperature
  • FIG. 8 shows SEM photographs of a nanofiber structure which was placed in an electric furnace (Ropet Kobata Electric Industries Ltd., electric furnace post III type) at 400° C. for 8 hours
  • FIG. 9 is SEM photographs of a nanofiber structure placed therein for 16 hours.
  • FIG. 7 shows a photograph of a nanofiber structure at room temperature, wherein the upper part of the figure shows a SEM photograph taken at a magnification of 30,000 times and a plurality of diameters of nanofibers are shown. The diameters were 234, 235, 213, and 212 or 225 nm, and a distribution thereof can be observed in a range of from 212 to 235 nm in the photographed portion. The lower part of the figure shows a SEM photograph taken at a magnification of 1,000 times.
  • FIG. 8 shows a photograph of a nanofiber structure which was heat treated at 400° C. for 8 hours, wherein the SEM photograph shown in the upper part was taken at a magnification of 30,000 times, and a plurality of diameters of nanofibers are shown. The diameters were 189, 220, and 204 or 186 nm, and a distribution thereof can be observed in a range of from 186 to 220 nm in the photographed portion.
  • the lower part of the figure shows a SEM photograph taken at a magnification of 1,000 times. Even after the nanofiber structure in FIG. 8 was heat treated at 400° C. for 8 hours, the nanofiber structure maintains the structure similar to that of FIG. 7 , and thus it was observed that it had a sufficient resistance in severer heat environment namely at 400° C. for 8 hours.
  • FIG. 8 shows a photograph of a nanofiber structure which was heat treated at 400° C. for “16 hours,” wherein the SEM photograph shown in the upper part was taken at a magnification of 30,000 times, and a plurality of diameters of nanofibers were shown. The diameters are 163, 179, 192, and 198 or 208 nm, and a distribution thereof can be observed in a range of from 163 to 208 nm in the photographed portion.
  • the lower part of the figure shows a SEM photograph taken at a magnification of 1,000 times. Even after the nanofiber structure in FIG. 8 was heat treated at 400° C. for “16 hours,” the nanofiber structure maintained a structure similar to that of FIG. 7 (room temperature) and that of FIG, 8 (400° C. for 8 hours), and thus it was observed that it had a sufficient resistance in the severer heat environment, namely at 400° C. for 16 hours).
  • the nanofiber structure according to the present Example greatly excels in heat resistance and has high utility value in a use in which it is placed in severe heat environment for a long time.
  • the nanofiber structure according to the present embodiment is very excellent in water resistance and air permeability, and applications in a very wide range of industrial uses are expected, Specifically, as the ESD apparatus used in the embodiment, there is also a mass-produced type in which many nozzles are provided, so that it is possible to mass-produce polyimide resin nano - fiber structures at very low cost.
  • the measurement was performed in accordance with the JIS-L1092 water resistance test method B (high water pressure method) by a manual waterproofing degree testing machine (No. 169 manufactured by Kabushiki Kaisha Yasuda Seiki Seisakusho).
  • a Frazir value and a Gurley value were measured.
  • FIG. 10 is a table of measurement of physical properties of water resistance and air permeability of the nanofiber structures of the Examples 1 and 2.
  • a film thickness thereof was measured by a Mitutoyo Digimatic standard outside micrometer. (MDC-25M). The film thickness was 50 ⁇ m or less.
  • the water resistance was 0.025-0.045 MPa, and in the Example 2, it was 0.01-0.055 MPa, thus the good numerical values were acquired.
  • the air permeability thereof was 4.55-13.9 (cc/cm2/sec) in the Example 1 and 8.12-35.3 (cc/cm2/sec) in the Example 2 and thus the good numerical values thereof were acquired.
  • in Gurley method it was 0.45-1.68 (sec) in the Example 1 and 0.023-0.6 (sec) in the Example 2 and thus, the good numerical values were acquired.
  • FIG. 11 is a table of measurement of physical properties of water resistance and air permeability of the nanofiber structures according to the Example 2, and those of Comparative Examples 3 and 4.
  • the water resistance and air permeability of two kinds of commercial polyimide films were measured in the same manner thereas.
  • the air permeability thereof was 0.55 second in a Gurley value
  • that of the Comparative Examples 3 was 4 to 11.5 seconds
  • that of the comparative example 4 was 242 to 762 seconds, and thus it turns out that the physical properties of the present invention were notably excellent.
  • FIG. 12 is a table of measurement of physical properties of air permeability and water resistance of the nanofiber structures according to the Examples 1 and 2 and that of a comparative example 5.
  • the physical properties which are excellent in air permeability and water resistance may not be necessarily obtained by forming any polyimide resin, which are dissolved in a solvent, into nanofibers.
  • any polyimide resin which are dissolved in a solvent, into nanofibers.
  • the example thereof will be given below.
  • a sample was produced in the same manner as that of the Examples 1 and 2 by using a NMP solution 6,6-PI-Solpit-A of a soluble polyimide produced by another company (concentration was 10 weight percent). Since the produced nanofiber nonwoven fabric contains much solvent, unless it is produced while drying, holes of the nanofiber are closed due to welding and adhesion. No improvement was achieved although various spray conditions (the solution concentration, voltage between the nozzle and the substrate, the liquid sending speed, the nozzle diameter, the distance between the nozzle and the substrate) were adjusted. Moreover, the waterproof pressure thereof was extremely low although the air permeability thereof, which was almost equivalent to that of the nanofiber structure according to the Example 1, was acquired.
  • the thermal conductivity of the nanofiber structure which was produced in accordance with the Example 2 was measured in a hot wire method (at atmosphere temperature: 22° C. by Model TCi manufactured by C-THERMI), and 0.046 W/mK was obtained as a result of the measurement. That is, it is possible to obtain one with the thermal conductivity of 0.04 to 0.05 W/mK. Although this value is a little larger than that of an urethane foam (0.026 w/mk) etc. which is a high performance foam insulation, it has a big advantage that it is flexible and thin material, compared with a heat insulating foam material, which may not be made thin.
  • the nanofiber structure according to the present invention with the above-mentioned physical properties can be used for various purposes. They are various filters, catalyst support objects, structure materials (especially for high temperature environment), breathable water resistance outdoor/apparel items, flexible and thin heat resistance, heat insulation and insulation material, and medical field, etc.
  • nanofiber structure acquired advanced functionality, such as the air permeability and water resistance
  • a nanofiber structure which has another functionality can be produced, depending on an attribution of polyimide which is raw material/material.
  • polyimide which is raw material/material.
  • a polyimide brand name “Solpit-S” manufactured by Orient Chemical Industries Co., Ltd. has adhesiveness.
  • a polyimide solution containing Solpit-S was formed into nanofibers by using the electrospray deposition method (ESD method) according to the technique of the present invention, thereby producing a nanofiber structure.
  • nanofiber structure can be given any or all of characters set forth below, as well as the above-mentioned Examples.
  • properties are not indispensable:
  • this nanofiber structure maintained the adhesiveness which the Solpit-S had.
  • the nanofiber structure which used a polyimide other than Solpit-S as raw material was formed on base material, if the adhesive tape was tried to be removed after an adhesive tape was brought in contact with the nanofiber structure side, the nanofiber structure easily fell away from the base material, and thus a unity which was formed by the substrate and the nanofiber structure was lost.
  • the nanofiber structure which used the Solpit-S as raw material the nanofiber structure and the base material did not fall away from each other, so that adhesiveness was shown between the substrate and the nanofiber structure. That is, it is possible that this nanofiber structure and other material adhere to each other so as to become unified.
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JP2004308031A (ja) * 2003-04-03 2004-11-04 Teijin Ltd ポリアミド酸不織布、それから得られるポリイミド不織布およびそれらの製造方法
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US8557444B2 (en) * 2009-12-15 2013-10-15 E I Du Pont De Nemours And Company Multi-layer article comprising polyimide nanoweb
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