JP2007217836A - Inorganic extrafine fiber sheet and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide bulky inorganic extrafine fiber sheet having handling strength enough to be applicable to various uses, and to provide a method for producing the fiber sheet. <P>SOLUTION: The inorganic extrafine fiber sheet has an apparent density of 0.1 g/cm<SP>3</SP>or less and a tensile strength per basis weight of 0.5 gf/5mm or higher at least unidirectionally. The method for producing the fiber sheet comprises the following process: Inorganic gel-like extrafine fibers formed by making electric field act on a sol solution are made to fly scatteredly and then irradiated with ions to get rid of their flying power to effect accumulation. The thus accumulated extrafine fibers are dried and then interlaced with water current and subsequently sintered. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inorganic ultrafine fiber sheet and a method for producing the same. More specifically, since it is bulky and excellent in handleability, it can be suitably used as a heat insulating material, a fiber-reinforced plastic substrate, a printed wiring board substrate, or the like, and a method for producing the same About.

  Conventionally, the production of a fiber assembly by an electrostatic spinning method is to supply a spinning solution to a spinning space and simultaneously apply an electric field to volatilize and solidify the solvent in the spinning solution to form fibers, and a drum separated by a certain distance. And was accumulated on an assembly such as a conveyor. The fiber assembly manufactured in this way is collected by a scraping device or the like (for example, see Patent Document 1).

  The fiber assembly manufactured in this manner was attracted and collected by the action of an electric field on the aggregate, and thus was a paper-like one having no bulk. For example, such a fiber assembly is inferior in terms of heat insulating properties because it is not bulky even if it is used as a heat insulating material. Thus, the fiber assembly manufactured by the conventional electrospinning method cannot be applied to uses that require bulkiness.

  Therefore, the applicant of the present application stated that “the step of supplying the spinning polymer solution to the spinning space, the step of irradiating the supplied and formed fibers with ions of the opposite polarity to the fibers, and the recovery of the spun fibers. And a step of supplying a polymer solution to be spun to a spinning space, a step of supplying a first air stream in a direction of supplying the polymer solution, A step of irradiating the formed fibers with ions having a polarity opposite to that of the fibers, and supplying a second air flow in a direction intersecting with the direction of supplying the polymer solution and collecting the spun fibers. And a step of recovering the fiber, a method for producing a fiber assembly by an electrospinning method ”(Patent Document 3).

US Pat. No. 2,048,651 (page 2-3, FIG. 2) Japanese Patent Laying-Open No. 2004-238749 (Claim 1) JP-A-2005-264374 (Claim 1)

  According to the method proposed by the applicant of the present application as described above, a bulky fiber assembly can be produced by the electrostatic spinning method. However, since there is almost no strength, it was difficult to apply to various uses such as a heat insulating material.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide an inorganic ultrafine fiber sheet having bulkiness and handling strength applicable to various uses, and a method for producing the same. And

The invention according to claim 1 of the present invention is an “inorganic ultrafine fiber sheet mainly composed of inorganic ultrafine fibers having an average fiber diameter of 2 μm or less, and the CV value of the inorganic ultrafine fibers being 0.6 or less. The apparent density of the inorganic ultrafine fiber sheet is 0.1 g / cm ³ or less, and the tensile strength per unit basis weight in at least one direction is 0.5 gf / 5 mm width or more, Inorganic ultra-fine fiber sheet. "

  The invention according to claim 2 of the present invention is “the inorganic ultrafine fiber sheet according to claim 1, wherein the inorganic ultrafine fiber sheet comprises only inorganic ultrafine fibers”.

  The invention according to claim 3 of the present invention includes: (1) a step of forming a sol solution mainly composed of inorganic components, (2) a step of supplying the sol solution to a spinning space, and (3) the supplied sol solution. A step of flying the gelled and fiberized inorganic gel-like ultrafine fiber by applying an electric field to (4) the inorganic gel-like ultrafine fiber with respect to the flying inorganic gel-like ultrafine fiber; A step of irradiating ions of opposite polarity, (5) a step of accumulating inorganic gel-like ultrafine fibers that have lost flying power due to the irradiation of ions, and (6) an aggregate of the accumulated inorganic gel-like ultrafine fibers. A step of drying to form an inorganic dry gel-like ultrafine fiber aggregate, (7) a step of ejecting a fluid flow from the inorganic dry gel-like ultrafine fiber aggregate and entangled to form a sheet; (8 ) The entangled inorganic dry gel-like ultrafine fiber sheet The by sintering, step of the inorganic microfibrous sheet, characterized in that it comprises a city, a manufacturing method of inorganic microfibrous sheet. "It is.

The invention according to claim 1 of the present invention is bulky with an apparent density of 0.1 g / cm ³ or less, and has a handling strength of a tensile strength per unit basis weight of at least 0.5 gf / 5 mm width in at least one direction. It is an inorganic ultrafine fiber sheet.

  Since the invention according to claim 2 of the present invention is composed of only inorganic ultrafine fibers, it is excellent in heat resistance, electrical characteristics, and the like.

  In the invention according to claim 3 of the present invention, since the inorganic dry gel-like ultrafine fiber assembly is intertwined by the fluid flow and then sintered, the tensile strength is 0.5 gf / 5 mm width or more. It is easy to produce an inorganic ultrafine fiber sheet having handling strength.

  The inorganic ultrafine fiber sheet of the present invention is mainly composed of inorganic ultrafine fibers having an average fiber diameter of 2 μm or less, and thus has excellent flexibility, and also has various functions (for example, filtration performance, function, etc.) due to its large surface area. The performance performance by chemical substances is excellent. A more preferable average fiber diameter is 1 μm or less, and a further preferable average fiber diameter is 0.5 μm or less. On the other hand, the lower limit of the average fiber diameter of the inorganic ultrafine fibers is not particularly limited, but 0.01 μm is appropriate.

  In addition, the average fiber diameter in this invention means the value which measured the fiber diameter of 100 places based on the electron micrograph in the thickness direction cross section of an inorganic type ultrafine fiber sheet, and arithmetically averaged the fiber diameter. When the cross-sectional shape of the fiber is non-circular, the diameter of a circle having the same area as the cross-sectional area is regarded as the fiber diameter.

  The inorganic ultrafine fiber of the present invention may be a continuous fiber or a discontinuous short fiber, but a continuous fiber is preferable because the fiber is less likely to fall off.

  Since the inorganic ultrafine fibers of the present invention are mainly composed of inorganic components, they are excellent in heat resistance, electrical characteristics, and the like. The phrase “mainly composed of an inorganic component” means that the inorganic component occupies 50 mass% or more, preferably 60 mass% or more, more preferably 75 mass% or more.

  The element constituting this inorganic component is not particularly limited. For example, lithium, beryllium, boron, carbon, sodium, magnesium, aluminum, silicon, phosphorus, sulfur, potassium, calcium, scandium, titanium, vanadium, chromium, Manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, arsenic, selenium, rubidium, strontium, yttrium, zirconium, niobium, molybdenum, cadmium, indium, tin, antimony, tellurium, cesium, barium, lanthanum, hafnium, Tantalum, tungsten, mercury, thallium, lead, bismuth, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium Mention may be made of thulium, ytterbium, lutetium or the like.

The inorganic component, for example, there may be mentioned oxides of the elements, _{specifically, SiO 2, Al 2 O 3} , B 2 O 3, TiO 2, ZrO 2, CeO 2, FeO, Fe 3 O _{4, Fe 2 O 3, VO} 2, V 2 O 5, SnO 2, CdO, LiO 2, WO 3, Nb 2 O 5, Ta 2 O 5, In 2 O 3, GeO 2, PbTi 4 O 9, LiNbO ₃ , BaTiO ₃ , PbZrO ₃ , KTaO ₃ , Li ₂ B ₄ O ₇ , NiFe ₂ O ₄ , SrTiO _{3 and the} like. The inorganic component may be composed of one component oxide or may be composed of two or more component oxides. For _example, it can be composed of two components of SiO 2 _-Al 2 _{O 3.}

  The inorganic ultrafine fiber of the present invention can contain an organic component in addition to the inorganic component as described above. For example, it can contain organic components such as silane coupling agents, organic low molecular compounds such as dyes, and organic high molecular compounds such as polymethyl methacrylate. In addition, inorganic or organic fine particles may be included in the inorganic ultrafine fibers.

  The inorganic ultrafine fiber sheet of the present invention is mainly composed of the inorganic ultrafine fibers as described above. That is, the inorganic ultrafine fiber accounts for 50 mass% or more of the inorganic ultrafine fiber sheet, preferably 60 mass% or more, more preferably 70 mass% or more, still more preferably 80 mass% or more, more preferably 90 mass%. Most preferably, it consists of only 100 mass%, that is, only inorganic extra fine fibers. Examples of fibers that can constitute the inorganic ultrafine fiber sheet in addition to the inorganic ultrafine fibers include organic fibers and inorganic fibers having an average fiber diameter exceeding 2 μm. By mixing such fibers, various properties such as strength and formability of the inorganic ultrafine fiber sheet are improved, and it is easy to apply to a wide range of applications.

  The fiber diameter CV value of the inorganic ultrafine fiber constituting the inorganic ultrafine fiber sheet of the present invention is 0.6 or less, and the fiber diameter of the inorganic ultrafine fiber is uniform. Features such as excellent uniformity. The smaller the CV value, the more uniform the fiber diameters of the inorganic ultrafine fibers, and the better the characteristics described above. Therefore, the CV value is preferably 0.5 or less, and 0.4 or less. Further preferred. If the fiber diameters of the inorganic ultrafine fibers are all the same, the standard deviation is 0, so the ideal CV value is 0.

The CV value is a value obtained by dividing the standard deviation value of the fiber diameter of the inorganic ultrafine fiber by the average fiber diameter of the inorganic ultrafine fiber. The standard deviation value is a standard deviation value of the fiber diameter of 100 inorganic ultrafine fibers, and is a value calculated by the following equation.
Standard deviation = {(nΣX ² − (ΣX) ² ) / n (n−1)} ^1/2
n: Number of measurements (100), X: Fiber diameter (μm) of each inorganic ultrafine fiber

The inorganic ultrafine fiber sheet of the present invention is bulky and has an apparent density of 0.1 g / cm ³ or less so as to be excellent in, for example, heat insulating properties and impregnation properties such as resin. The smaller the apparent density is, the more bulky it can be, so the preferred apparent density is 0.09 g / cm ³ or less, and the more preferred apparent density is 0.085 g / cm ³ or less. On the other hand, if the apparent density is too low, the strength is inferior and the handleability tends to be poor, so 0.05 g / cm ³ or more is preferable. The “apparent density” means a value obtained by dividing the basis weight (g / cm ² ) by the thickness (cm). The basis weight means a weight obtained by converting a weight of 10 cm square to 1 m square, and the thickness is a load of 10 kPa. Time value.

  The inorganic ultrafine fiber sheet of the present invention is excellent in handleability with a tensile strength per unit basis weight of at least 0.5 gf / 5 mm in at least one direction despite the bulkiness of the apparent density as described above. Is. The stronger the tensile strength, the better the handling properties. Therefore, it is preferably 0.9 gf / 5 mm or more, more preferably 1 gf / 5 mm or more, and 1.5 gf / 5 mm or more. Is more preferable. The upper limit of the tensile strength is not particularly limited, but is preferably 5 gf / 5 mm. In addition, although the direction which shows such tensile strength is not specifically limited, In general, since an inorganic type microfiber sheet processes or uses it applying a force to a longitudinal direction, the tension | tensile_strength per unit weight in a longitudinal direction is used. The strength is preferably 0.5 gf / 5 mm or more. In addition, the tensile strength per unit basis weight was determined by using a test piece cut to a width of 5 mm and a length of 40 mm, using a small tensile tester (manufactured by Search Corp., product number: TSM01) at a pulling speed of 1 mm / sec. This is the value obtained by dividing the tensile strength measured in step 1 by the basis weight.

  In addition, it is preferable that the inorganic ultrafine fiber sheet of this invention is maintaining the form only by the entanglement of an inorganic ultrafine fiber, without using an adhesive agent. This is because the absence of an adhesive can suppress the generation of contaminants and has additional effects such as better heat resistance.

In addition, the inorganic ultrafine fiber sheet of the present invention may have any apparent density and tensile strength per unit basis weight as described above, and the basis weight is not particularly limited, but is 5 to 200 g / m ² . Is preferable, and it is more preferable that it is 20-50 g / m < ² >. Furthermore, the thickness of the inorganic ultrafine fiber sheet is not particularly limited, but is preferably 50 to 1000 μm, and more preferably 200 to 500 μm.

  As described above, since the inorganic ultrafine fiber sheet of the present invention is bulky and excellent in handleability, it can be suitably used as a heat insulating material, a fiber-reinforced plastic substrate, a printed wiring board substrate, or the like. .

  Such an inorganic microfiber sheet of the present invention includes, for example, (1) a step of forming a sol solution mainly composed of inorganic components, (2) a step of supplying the sol solution to a spinning space, and (3) the supply A step of flying the gelled and fiberized inorganic gel-like ultrafine fiber by applying an electric field to the sol solution, and (4) the inorganic gel-like ultrafine fiber against the flying inorganic gel-like ultrafine fiber. A step of irradiating ions having a polarity opposite to that of the fiber, (5) a step of accumulating the inorganic gel-like ultrafine fibers that have lost flying power due to the irradiation of the ions, and (6) A step of drying the aggregate to form an inorganic dry gel-like ultrafine fiber aggregate; (7) a step of ejecting a fluid stream to the inorganic dry gel-like ultrafine fiber aggregate to form a sheet (8) The intertwined inorganic dry gel The Jo microfibrous sheet by sintering, it is possible to manufacturing process, by which the inorganic microfibrous sheet.

  First, (1) a step of forming a sol solution mainly composed of inorganic components is performed. This sol solution can be obtained by hydrolyzing and polycondensing a raw material solution containing a compound containing an element constituting the inorganic ultrafine fiber as described above at a temperature of about 100 ° C. or less. Consists of. That is, the inorganic component occupies 50 mass% or more, preferably 60 mass% or more, more preferably 75 mass% or more.

  Examples of the solvent for the raw material solution include organic solvents such as alcohols such as ethanol, dimethylformamide, and water. This raw material solution can contain water for hydrolyzing the compound and a catalyst (for example, hydrochloric acid, nitric acid, etc.) that smoothly proceeds the hydrolysis reaction. In addition, a chelating agent that stabilizes the compound contained in the raw material solution, a silane coupling agent for stabilizing the compound, a compound that can impart various functions such as piezoelectricity, adhesive improvement, flexibility, An organic compound (for example, polymethyl methacrylate) for adjusting hardness (fragility), or an additive such as a dye can be included. Furthermore, the raw material solution may contain inorganic or organic fine particles. These additives and fine particles can be added before hydrolysis, during hydrolysis, or after hydrolysis. The temperature for the hydrolysis may be equal to or lower than the boiling point of the solvent used, but the lower the reaction rate, the slower the reaction rate and the easier to form a spinnable sol solution. Since it is difficult for the reaction to proceed even if it is too low, it is preferably 10 ° C. or higher.

  The element constituting the compound can be exactly the same as the element constituting the aforementioned inorganic component, and the compound can be exactly the same as the oxide of the aforementioned element which is the aforementioned inorganic component. In addition, it may be composed of one component oxide or may be composed of two or more component oxides. The sol solution may be supplied to the spinning space and has a viscosity capable of spinning an inorganic ultrafine fiber having an average fiber diameter of 2 μm or less, and is not particularly limited, but preferably 0.1 to 100 poise, More preferably, it is 0.5-20 poise, Especially preferably, it is 1-10 poise, Most preferably, it is 1-5 poise.

  Next, (2) a step of supplying the sol solution to the spinning space is performed. In order to supply the sol solution to the spinning space, for example, a method of discharging the sol solution from a nozzle, a rotating saw-tooth gear is immersed in a container containing the sol solution, and the sol solution is applied to the tip of the saw-tooth gear. The sol solution can be supplied to the spinning space by a conventionally known method such as an adhesion method. Among these, when the sol solution is discharged from the nozzle, the discharge amount can be made uniform, and it is easy to spin inorganic ultrafine fibers with a uniform fiber diameter, that is, the inorganic fiber having a fiber diameter CV value of 0.6 or less. It is suitable because it is easy to produce an ultrafine fiber sheet. When discharging by this suitable nozzle, it is preferable that the diameter of the nozzle is 0.1 to 3 mm so that inorganic fine fibers having an average fiber diameter of 2 μm or less can be easily produced. If the sol solution is continuously supplied from the nozzle to the spinning space, a continuous inorganic gel-like ultrafine fiber can be formed, and the sol solution is intermittently supplied from the nozzle to the spinning space. Thus, discontinuous, that is, short-fiber inorganic gel-like ultrafine fibers can be formed. The spinning space is a space for gelling and fiberizing the sol solution, and usually means a space made of a gas such as air. As described above, when supplying the sol solution to the spinning space, irradiation of ions described later may cause the sol solution or the inorganic gel-like ultrafine fibers to adhere to the sol solution supply body (for example, a nozzle) and prevent continuous production. It is preferable to supply gas in the same direction as the sol solution supply direction from the sol solution supply body to the spinning space.

  Next, (3) a step of flying the gelled and fiberized inorganic gel-like ultrafine fibers by applying an electric field to the supplied sol solution is performed. That is, by applying an electric field to the sol solution, the solvent in the sol solution volatilizes and gels, and the inorganic gel-like ultrafine fibers that have been electrically pulled to form fibers fly. This electric field varies depending on the average fiber diameter of the inorganic ultrafine fibers, the solvent of the sol solution, the viscosity of the sol solution, etc., and is not particularly limited, but the average fiber diameter is 2 μm without causing air breakdown. It is preferably 0.5 to 5 kV / cm so that the following inorganic gel-like ultrafine fibers can be easily formed. Such an electric field can be applied, for example, by providing a potential difference between a sol solution supply body (for example, a nozzle) and a counter electrode positioned facing the sol solution supply body. As the counter electrode, a corona discharge needle, a corona discharge wire, an AC discharge element (for example, a creeping discharge element), a conductive net, or the like can be used. Alternatively, a sol solution supply similar to the sol solution supply can be used as the counter electrode, that is, the sol solution supply can be used facing each other. In this case, the supply amount of the sol solution to the spinning space can be doubled. When the sol solution supply body is a nozzle, when the nozzle is conductive (for example, metal), the nozzle itself can act as an electrode. When the nozzle is non-conductive, the inside of the nozzle or the sol solution supply An electrode can be placed in the tube to apply an electric field to the sol solution.

  Next, (4) a step of irradiating the flying inorganic gel-like ultrafine fibers with ions having a polarity opposite to that of the inorganic gel-like ultrafine fibers is performed. By this process, the inorganic gel-like ultrafine fibers lose their electric flying power. Examples of means for irradiating ions having a polarity opposite to that of the inorganic gel-like ultrafine fiber include a corona discharge needle, a corona discharge wire, and an AC discharge element (for example, a creeping discharge element). These ion irradiation means also act as a counter electrode as described above. An ionizing radiation source can also be used as a means for irradiating ions. When a creeping discharge element or ionizing radiation source is used as the ion irradiation means, ions can be generated and irradiated independently of the formation of a potential difference between the sol solution supply body and the counter electrode. Easy to control the amount. Further, a sol solution supply similar to the sol solution supply can be used as the ion irradiation means. In this case, the effects as described above are obtained.

  Next, (5) a step of accumulating inorganic gel-like ultrafine fibers that have lost flying power due to the irradiation of the ions is performed. By this process, an aggregate of inorganic gel-like ultrafine fibers can be produced, but inorganic gel-like ultrafine fibers that have lost flying power are accumulated and are not attracted and accumulated by the action of an electric field. Therefore, it can be accumulated in a bulky state. In this step, for example, inorganic gel-like ultrafine fibers are accumulated on an accumulation body disposed between the sol solution supply body and the counter electrode. The aggregate is not particularly limited as long as it can accumulate inorganic gel-like ultrafine fibers, and can be, for example, a container, a conveyor, a drum, or the like. In addition, although the flying power is lost due to the irradiation of ions, inorganic gel-like ultrafine fibers can coast and fly in the direction of the counter electrode. It is preferable that inorganic gel-like ultrafine fibers are accumulated on the aggregate. Moreover, gas can be attracted | sucked with the suction device arrange | positioned downstream from an accumulation body, and an inorganic type gel-like microfiber can also be reliably accumulated on an accumulation body. When using a blower and / or a suction device in this manner, the inorganic gel-like ultrafine fibers are brought into close contact with each other by the action of gas, and air or It is necessary to check the suction conditions. It should be noted that organic fibers, inorganic fibers having an average fiber diameter exceeding 2 μm, and the like can be supplied and mixed with inorganic gel-like ultrafine fibers by the above-described blower or the like.

  Next, (6) a step of drying the aggregated inorganic gel-like ultrafine fibers aggregate to form an inorganic dry gel-like ultrafine fiber aggregate is performed. The drying temperature in this drying process should just be the temperature which does not melt | dissolve an inorganic type gel-like ultrafine fiber by the ejection process of the following fluid flow, and can be set by experimenting suitably. Generally, it is preferable to dry at a temperature of 50 ° C to 300 ° C. This drying can be performed by heating with an oven or a heater, and can also be performed by freeze drying or supercritical drying.

Next, (7) a step of jetting a fluid flow to the inorganic dry gel-like ultrafine fiber aggregate and intertwining it into a sheet is carried out. As described above, in the present invention, since the fluid flow is ejected and entangled at the stage of the inorganic dry gel-like ultrafine fiber that is still flexible before sintering, the inorganic dry gel-like ultrafine fibers are in contact with each other. Can be sufficiently entangled, and as a result, an inorganic ultrafine fiber sheet having a tensile strength per unit basis weight and excellent in handleability can be produced. The fluid flow is not particularly limited, but is preferably a water flow that is easy to handle in production. The fluid flow ejection conditions are not particularly limited as long as the apparent density of the inorganic ultrafine fiber sheet does not become a dense structure exceeding 0.1 g / cm ³ . From a nozzle plate in which nozzles are arranged in one or more rows at a pitch of 0.5 to 0.3 mm and a pitch of 0.2 to 3 mm, a fluid flow having a pressure of 0.1 MPa to 50 MPa is applied to the inorganic dry gel-like ultrafine fiber assembly. And squirt. Such a fluid flow may be ejected one or more times.

  Next, (8) the step of sintering the entangled inorganic dry gel-like ultrafine fiber sheet to form an inorganic ultrafine fiber sheet can be carried out to produce the inorganic ultrafine fiber sheet of the present invention. . As described above, in the present invention, since the inorganic dry gel-like ultrafine fibers are sintered in a sufficiently intertwined state, an inorganic ultrafine fiber sheet having a handling strength is produced in spite of being bulky. can do. Since the sintering temperature in this step varies depending on the inorganic component constituting the inorganic dry gel-like ultrafine fiber, it is not particularly limited, but it is generally preferable to sinter at 500 ° C. or higher. In addition, if the inorganic dry gel-like ultrafine fiber sheet is suddenly sintered at the sintering temperature, the inorganic dry gel-like ultrafine fiber may be suddenly contracted and damaged. Sintering is preferred.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

Example 1
Tetraethoxysilane as a metal compound, ethanol as a solvent, water for hydrolysis, and 1N hydrochloric acid as a catalyst were mixed at a molar ratio of 1: 5: 2: 0.003 at a temperature of 78 ° C. for 15 hours. The solvent was removed by a rotary evaporator and then heated to a temperature of 60 ° C. to form a sol solution having a viscosity of about 2 poise.

  Next, a sol solution is supplied at a rate of 1 mL / hour per nozzle to a nozzle group in which stainless steel nozzles having an inner diameter of 0.4 mm are arranged in a line at intervals of 5 cm, and the sol solution is continuously extruded from each nozzle. The wind speed is 10 cm / sec. In the same direction as the extrusion direction. The air was supplied. At the same time, a voltage (−15 kV) is applied to each nozzle, and an AC voltage with a frequency of 50 Hz and a voltage of 5 kV peak is applied to the creeping discharge element which is a counter electrode and an ion irradiation means, which is located 150 mm away from the nozzle tip By applying an electric field (1 kV / cm) to the extruded sol solution, gelling and fiberizing, and irradiating ions to the flying inorganic gel-like ultrafine fibers, the inorganic gel-like ultrafine fibers Lost flying power. Then, between the nozzle and the creeping discharge element, the wind speed is 10 cm / sec. From the direction perpendicular to the flying direction of the inorganic gel-like ultrafine fibers. Of air, and a wind speed of 10 cm / sec. By a suction box (frontage: 15 cm long, 50 cm wide) located below the creeping discharge element. At the same time, the mesh conveyor arranged on the suction box was moved, and the inorganic gel-like ultrafine fibers were accumulated on the mesh conveyor. As a creeping discharge element, the inner wall surface of a glass tube (outer diameter: 10 mm, inner diameter: 8 mm, length: 700 mm) is subjected to conductive processing, and a stainless steel wire (diameter: 30 μm, length: 650 mm) is used as a discharge electrode. Was used on the outer wall surface of the glass tube along the longitudinal direction of the glass tube, an AC voltage was applied to the inner wall surface, and the discharge electrode on the outer wall surface was grounded. Further, the nozzle group was arranged so that the longitudinal direction of the creeping discharge element and the arrangement direction of the nozzle coincided.

  Next, the aggregate of the inorganic gel-like ultrafine fibers thus collected was dried in an oven set at a temperature of 300 ° C. for 1 hour to produce an inorganic dry gel-like ultrafine fiber aggregate.

  Next, this inorganic dry gel-like ultrafine fiber assembly was placed on an 80-mesh plain weave net, and 5 m / min. A water flow with a pressure of 980 kPa is transferred from a nozzle plate (separated distance from the plain weave net: 20 mm) in which two nozzles having a diameter of 0.13 mm are arranged at a pitch of 0.6 mm while being transported by an inorganic dry gel-like ultrafine fiber assembly. One side was ejected once and entangled.

  Then, the entangled inorganic dry gel-like ultrafine fiber aggregate is heated from room temperature at a heating rate of 200 ° C./hour, sintered at a temperature of 800 ° C. for 2 hours, completely vitrified, and quartz glass ultrafine An inorganic extra-fine fiber sheet consisting only of fibers and maintaining the form only by entanglement was produced. The physical properties of this inorganic ultrafine fiber sheet were as shown in Table 1.

＃：長手方向における単位目付あたりの引張り強さ

#: Tensile strength per unit weight in the longitudinal direction

(Example 2)
Except that the pressure of the water flow was 1.47 MPa, an inorganic ultrafine fiber sheet made only of quartz glass ultrafine fibers and maintained in shape only by entanglement was produced in the same manner as in Example 1. The physical properties of this inorganic ultrafine fiber sheet were as shown in Table 1.

(Example 3)
Except that the water flow pressure was 2.94 MPa, an inorganic ultrafine fiber sheet made only of quartz glass ultrafine fibers and maintained in shape only by entanglement was produced in the same manner as in Example 1. The physical properties of this inorganic ultrafine fiber sheet were as shown in Table 1.

Example 4
Except that the pressure of the water flow was 490 kPa, an inorganic ultrafine fiber sheet made of only quartz glass ultrafine fibers and maintaining the form only by entanglement was produced in the same manner as in Example 1. The physical properties of this inorganic ultrafine fiber sheet were as shown in Table 1.

(Comparative Example 1)
The aggregate of the collected inorganic gel-like ultrafine fibers produced in exactly the same manner as in Example 1 was heated from room temperature at a heating rate of 200 ° C./hour, sintered at a temperature of 800 ° C. for 2 hours, and completely By vitrification, an inorganic ultrafine fiber sheet made only of quartz glass ultrafine fibers was produced. The physical properties of this inorganic ultrafine fiber sheet were as shown in Table 1.

(Comparative Example 2)
A sol solution was formed in exactly the same manner as in Example 1.

  Next, the sol solution was supplied to a stainless steel nozzle (one) having an inner diameter of 0.4 mm at a rate of 1 mL / hour by a pump, and the sol solution was continuously extruded from the nozzle. At the same time, a voltage (−20 kV) is applied to the nozzle, and a stainless steel drum as a counter electrode, which is located 100 mm away from the tip of the nozzle, is grounded, and an electric field (2 kV / cm) is applied to the extruded sol solution. Was made to gel and fiber, the inorganic gel-like ultrafine fibers were allowed to fly toward the stainless steel drum, and the inorganic gel-like ultrafine fibers were accumulated on the stainless steel drum. The nozzle pushed out the sol solution and reciprocated with a width of 20 cm in the same direction as the axial direction of the drum.

  Next, the aggregate of the collected inorganic gel-like ultrafine fibers is heated from room temperature at a heating rate of 200 ° C./hour, sintered at a temperature of 800 ° C. for 2 hours, completely vitrified, and the quartz glass ultrafine fiber is obtained. An inorganic extra-fine fiber sheet consisting only of fibers was produced. The physical properties of this inorganic ultrafine fiber sheet were as shown in Table 1.

As is apparent from Table 1, the inorganic ultrafine fiber sheet of the present invention has a bulk strength of 0.82 gf / 5 mm per unit weight despite the apparent density of 0.084 g / cm ³ or less and bulkiness. It was excellent in handleability beyond the width. Therefore, the inorganic ultrafine fiber sheet of the present invention was suitable as a heat insulating material, a fiber reinforced plastic substrate, and the like.

Claims (3)

An inorganic ultrafine fiber sheet mainly composed of inorganic ultrafine fibers having an average fiber diameter of 2 μm or less, and a CV value of the fiber diameter of the inorganic ultrafine fibers being 0.6 or less, and the appearance of the inorganic ultrafine fiber sheet An inorganic ultrafine fiber sheet having a density of 0.1 g / cm ³ or less and a tensile strength per unit weight in at least one direction of 0.5 gf / 5 mm width or more. The inorganic ultrafine fiber sheet according to claim 1, comprising only inorganic ultrafine fibers. (1) a step of forming a sol solution mainly composed of inorganic components;
(2) supplying the sol solution to a spinning space;
(3) a step of flying inorganic gel-like ultrafine fibers that have been gelled and fiberized by applying an electric field to the supplied sol solution;
(4) A step of irradiating the flying inorganic gel-like ultrafine fibers with ions having a polarity opposite to that of the inorganic gel-like ultrafine fibers,
(5) a step of accumulating inorganic gel-like ultrafine fibers that have lost flying power due to irradiation of the ions;
(6) A step of drying the aggregated inorganic gel-like ultrafine fiber aggregate to obtain an inorganic dry gel-like ultrafine fiber aggregate,
(7) A step of ejecting a fluid flow to the inorganic dry gel-like ultrafine fiber aggregate and intertwining it into a sheet,
(8) Sintering the entangled inorganic dry gel-like ultrafine fiber sheet to form an inorganic ultrafine fiber sheet;
The manufacturing method of an inorganic type ultrafine fiber sheet characterized by including these.