KR20030095524A - An ultrafine alumina fiber, and a process of preparing for the same - Google Patents

Abstract

PURPOSE: A manufacturing method of superfine alumina fiber which is characterized by having under 1000nm of diameter, having at least 5 times of length to the diameter and having high specific surface to volume is provided. The superfine alumina fiber is useful for a catalyst supporter, a reinforcing material and a coating material. CONSTITUTION: The superfine alumina fiber is obtained by the steps of: mixing and reacting alumina type sol or gel with a thermoplastic resin to prepare a reaction solution; electric-spinning the reaction solution under the condition of high voltage to prepare hybrid or conjugate fiber mixed with the thermoplastic resin and the alumina sol or gel; and then carbonizing or eluting the thermoplastic resin in the hybrid or the conjugate fiber.

Description

An ultrafine alumina fiber, and a process of preparing for the same

The present invention relates to an ultrafine alumina fiber and a method for producing the same, which have a specific surface area relative to a volume and are applicable to all industrial fields.

Inorganic particles and inorganic fibers include catalyst support, glass reinforcement, contact lens reinforcement, various coatings, biosensor parts, bulletproof vests, bulletproof helmets, aerospace parts, electronic parts, artificial bones and artificial blood vessels. It can be used in all industries such as medical parts and heat-resistant materials.

U.S. Patent 5,917,279 describes a method of dispersing inorganic particles having a diameter of 1 to 100 nm on a polymer binder and using them as an interlayer material for an electron branching. After obtaining the by-product surrounding it, there is described a method of preparing the nano-phase inorganic particles by removing the by-product.

In addition, US Pat. No. 6,068,880 discloses a method for separating nanoparticles from a liquid precursor solution by placing a substrate on a rotatable sample holder in a reactor, filling the reactor with a liquid precursor, and then irradiating a laser while rotating the sample holder. This is described.

Conventional inorganic particles prepared as described above have a relatively small length with respect to the diameter compared to the ultrafine fibers, that is, the specific surface area is relatively small compared to the volume, the effect was not relatively good when used as a reinforcing material.

On the other hand, the egg described in the European Ceramic Society (Jr, European Ceramic Society, Vol 20, 2543-2549, 2000). In the paper by R. Venkatesh, a mixed solution was prepared by adding SiO ₂ sol and polylactic acid or polyvinyl alcohol to an aluminum oxychloride sol having an alumina content of 30.5% by weight, and then sol spinning the mixed solution. A method of producing alumina fibers having a diameter of 10 μm or more is disclosed by calcining the fibers in a gel form and subsequently calcining the fibers at a temperature of 500 ° C. or higher.

As such, since only microfibers having a diameter of 10 μm or more can be manufactured by a known method, there is a limit in increasing the specific surface area to the volume of the microfibers.

The present invention is to provide a method for producing an ultrafine alumina fiber having a length ratio to diameter of 5 times or more and a diameter of 10 to 1,000nm using an electrospinning method. In addition, the present invention is to provide alumina fibers useful as a reinforcing material and coating material in a variety of industries because the specific surface area to volume is very large.

1 is a schematic view of a process for producing fibers by electrospinning

Figure 2a is an electron micrograph of a web (WEB) consisting of polyvinyl alcohol / alumina-boron composite fibers

FIG. 2B is an enlarged electron micrograph of FIG. 2A

Figure 2c is a diameter distribution diagram of the polyvinyl alcohol / alumina-boron composite fiber constituting the web of Figure 2a

3A is an electron micrograph of a web (WEB) made of ultrafine alumina-boron fibers prepared by sintering the web of FIG. 2A at 1000 ° C. for 2 hours to remove polyvinyl alcohol in the composite fiber.

FIG. 3B is an enlarged electron micrograph of FIG. 3A

FIG. 3C is a diameter distribution diagram of the ultrafine alumina-boron fibers constituting the web of FIG. 3A

4A is an electron micrograph of a web (WEB) made of ultrafine alumina-boron fibers prepared by sintering the web of FIG. 2A at 1200 ° C. for 2 hours to remove polyvinyl alcohol in the composite fiber.

FIG. 4B is an enlarged electron micrograph of FIG. 4A

FIG. 4C is a diameter distribution diagram of the ultrafine alumina-boron fibers constituting the web of FIG. 4A

FIG. 5A is an electron micrograph of a web (WEB) made of ultrafine alumina fibers completely removed from polyvinyl alcohol and boron in a composite fiber by sintering the web of FIG. 2A for 2 hours at 1400 ° C. FIG.

FIG. 5B is an enlarged electron micrograph of FIG. 5A

FIG. 5C is a diameter distribution diagram of the ultrafine alumina fibers constituting the web of FIG. 5A

6 is an x-ray diffraction curve of alumina fiber according to heat treatment temperature

※ Explanation of Codes of Major Parts

1: spinning liquid main tank 2: metering pump 3: nozzle

4 collector 5 voltage transfer rod 6 voltage generator

In order to achieve the above-mentioned problems, the method for preparing ultrafine alumina fibers of the present invention includes preparing a reaction solution by mixing and reacting an alumina-based sol or gel with a thermoplastic resin solution, and then electrospinning the reaction solution under high voltage. To prepare a hybrid (hybrid) or a composite fiber mixed with a thermoplastic resin and an alumina sol or gel, and the thermoplastic resin in the hybrid or composite fiber is carbonized or eluted with a solvent.

In addition, the ultrafine alumina fibers of the present invention are characterized by having a length of 5 to 1,000 times the diameter and a diameter of 10 to 1,000 nm.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

First, the thermoplastic resin is dissolved in distilled water, tetrahydrofuran, N, N-dimethylformamide or a mixed solvent thereof, and then alumina-based sol or gel is added thereto and reacted to prepare a reaction solution.

The alumina-based sol or gel is preferably an aluminum alkoxide-based sol or gel, and (Al ₂ O ₃ ) ₉ (B ₂ O ₃ ) ₂ and the like in sol or gel state are used.

As the thermoplastic resin, polyvinylacetate, polyvinyl alcohol, polylactic acid, polyamide, polyester or polypropylene may be used, and more preferably, polyvinyl alcohol is used.

Next, the reaction solution is electrospun under high voltage to produce hybrid or composite fibers in which a thermoplastic resin and an alumina-based sol or gel are mixed. At this time, the electrospinning is carried out using a conventional electrospinning device.

Specifically, the conventional electrospinning device is a spinning liquid main tank 1 for storing spinning liquid as shown in FIG. 1, a metering pump 2 for quantitative supply of spinning liquid, a plurality of nozzles 3 for discharging spinning liquid, It is composed of a collector (4) for accumulating fibers to be located at the bottom of the nozzle, a voltage generator (6) for generating a voltage, and a mechanism (5) for transferring the generated voltage to the nozzle and the collector. The spinning liquid in the spinning liquid main tank 1 is continuously fed into the plurality of nozzles 3 to which a high voltage is applied through the metering pump 2.

Subsequently, the spinning liquid supplied to the nozzles 3 is spun and concentrated through the nozzles onto the collector 4 under high voltage to form a single fiber web. The voltage during electrospinning is preferably 5 kV or more, and the hybrid or composite fiber produced by the electrospinning has a diameter of 1,000 nm or less.

Next, the ultrafine alumina fibers of the present invention are prepared by completely removing the thermoplastic resin in the hybrid or composite fibers by high temperature heat treatment or solvent treatment of the hybrid or composite fibers prepared as described above.

The thermoplastic resin in the hybrid or composite fibers is carbonized by high temperature heat treatment or eluted and removed by solvent treatment. As such, the thermoplastic resin present in the hybrid or composite fibers is completely removed to prepare pure microfine alumina-based fibers.

The ultrafine alumina fibers of the present invention prepared as described above have a length of 5 to 1,000 times the diameter and a diameter of 10 to 1,000 nm.

As described above, the ultrafine alumina fibers of the present invention are very thin in diameter and have a very large specific surface area to volume, which is more useful as materials in various industrial fields.

The ultrafine alumina fibers of the present invention may be ground to produce alumina particles.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the present invention is not limited only to the following examples.

Example 1

Polyvinyl alcohol parts 10 parts by weight at 80 ℃ in distilled water after dissolved for one hour to drop to room temperature, the alumina sol _{[(Al 2 O 3) 9} (B 2 O 3) 2] slowly to the polyvinyl alcohol solution in a drop The mixture was reacted for 24 hours with vigorous stirring at room temperature to prepare an alumina sol and a polyvinyl alcohol reaction solution. Subsequently, the alumina sol / polyvinyl alcohol reaction solution was electrospun under a voltage of 20 kV to prepare an alumina-boron / polyvinyl alcohol composite fiber having a diameter of 560 nm. Electron micrographs of the composite fiber is shown in Figures 2a and 2b. The average diameter of the fiber was 565 nm.

Example 2

The alumina-boron / polyvinyl alcohol composite fiber prepared in Example 1 was sintered at 1000 ° C. for 2 hours to prepare alumina-boron fiber. Electron micrographs of the prepared alumina-boron fibers are shown in Figures 3a and 3b. Grain appears in the magnified electron micrograph of FIG. 3B. The average diameter of the fibers was 625 nm, and the average diameter of the grains was 43 nm. It can be seen from the x-ray diffraction curve of FIG. 6 that the aluminum component and the boron component coexist.

Example 3

The alumina-boron / polyvinyl alcohol composite fiber prepared in Example 1 was sintered at 1200 ° C. for 2 hours to prepare alumina-boron fiber. Electron micrographs of the prepared alumina-boron fibers are shown in Figures 4a and 4b. Grain appears in the magnified electron micrograph of FIG. 4B. It can be seen that the average diameter of the fiber is 580 nm, which is smaller than that of Example 2, and the grain is also larger than that of Example 2. The average diameter of the grains increased to 85 nm. It can be seen from the x-ray diffraction curve of FIG. 6 that the aluminum component and the boron component coexist. The length / diameter ratio of the fibers was 550.

Example 4

The alumina fiber was prepared by sintering the alumina-boron / polyvinyl alcohol composite fiber prepared in Example 1 at 1400 ° C. for 2 hours. Electron micrographs of the prepared alumina fibers are shown in Figures 5a and 5b. The grain does not appear in the magnified electron micrograph of FIG. 5B. It can be seen from the x-ray diffraction curve of FIG. 6 that only pure α-Al ₂ O ₃ fibers are present. The fiber had an average diameter of 525 nm and a length / diameter ratio of 320.

The ultrafine alumina fiber of the present invention has a diameter of 1,000 nm or less and a very high specific surface area to volume, which is very useful as a catalyst support, reinforcing material or coating material in all industries.

Claims (6)

After mixing and reacting an alumina-based sol or gel and a thermoplastic resin solution to prepare a reaction solution, the reaction solution is electrospun under high voltage to hybrid or composite fiber in which a thermoplastic resin and an alumina sol or gel are mixed. And preparing a carbonized or eluted thermoplastic resin in the hybrid or composite fiber. The method for producing ultrafine alumina fibers according to claim 1, wherein the diameter of the alumina fibers is 10 to 1,000 nm or less. The method for producing an ultrafine alumina fiber according to claim 1, wherein the voltage during electrospinning is 5 kV or more. The method for producing an ultrafine alumina fiber according to claim 1, wherein the thermoplastic resin is polyvinyl acetate, polyvinyl alcohol, polylactic acid, polyamide, polyester or polypropylene. The method for producing ultrafine alumina fibers according to claim 1, wherein the alumina-based sol or gel is an aluminum alkoxide-based sol or gel. An ultrafine alumina fiber characterized by a length of 5 to 1,000 times the diameter and a diameter of 10 to 1,000 nm.