Inorganic nanofiber and method for manufacturing same

Abstract

Disclosed are an inorganic nanofiber characterized in that the average fiber diameter is 2 μm or less, the average fiber length is 200 μm or less, and the CV value of the fiber length is 0.7 or less; and a method of manufacturing the same. In the manufacturing method, an inorganic nanofiber sheet consisting of inorganic nanofibers having an average fiber diameter of 2 μm or less is formed by electrospinning, and then, the inorganic nanofiber sheet is pressed using a press machine and crushed so that the average fiber length becomes 200 μm or less, and the CV value of the fiber length becomes 0.7 or less.

Description

TECHNICAL FIELD[0001]The present invention relates to an inorganic nanofiber, and a method of manufacturing the same. The inorganic nanofiber of the present invention may be suitably used as materials which constitute, for example, a filler, a catalyst carrier, a structural material, an electrode material, a filter material, or the like. According to the manufacturing method of the present invention, an inorganic mixed nanofiber, which may be suitably used as a filler for a transparent resin sheet, can be easily produced, since it is easy to adjust the refractive index.BACKGROUND ART[0002]A filler is added, for example, in order to improve mechanical properties such as strength, or thermal properties of a polymer film. In the recent trend of miniaturization of electrical equipment, there is a thinning trend in the field of polymer films. The thinner a polymer film is, the finer and shorter a filler added to the polymer film must be. This is because if the filler is thicker or longer...

AI Technical Summary

Benefits of technology

[0023]The invention of [1] is an inorganic nanofiber, in which the average fiber diameter is 2 μm or less, which is thin, and despite the fact that the average fiber length is 200 μm or less, which could not be obtained by a conventional cutting machine, the CV value of the fiber length is 0.7 or less, i.e., the fiber length is uniform. Therefore, a composite having thin and uniform properties can be formed. For example, even when the inorganic nanofiber is used as a filler for a thin-film polymer film, since it is unlikely to protrude from the surface of the polymer film, it is easy to produce a polymer film composite which is practically problem-free.

[0024]The invention of [2] is an inorganic nanofiber having a rate of change in fiber length of 30% or less, in which it is not easily deformed by pressure or a shearing force, and the mechanical strength is good. Therefore, a composite having a good mechanical strength and a good form stability against a temperature change can be produced.

[0025]The invention of [3] may be a composite having thin and uniform properties, because the inorganic nanofibers are dispersed as a filler.

[0026]The invention of [4] is a composite having a good thermal conductivity, which is 3 W / m·K or more at a thickness of 0.3 mm.

[0027]According to the invention of [5], an inorganic nanofiber sheet having an average fiber diameter of 2 μm or less, which is thin, and having a small average pore size and a uniform pore size, can be formed by electrospinning. The fact that the average pore size is small and the pore size is uniform means that the distances between the intersections of the inorganic nanofibers are short and uniform. Therefore, when pressure is applied to the inorganic nanofiber sheet in such a state using a press machine so that the orientation of the inorganic nanofibers is not changed, the intersections of the inorganic nanofibers are highly pressed, and the intersections are likely to be broken, because the inorganic nanofiber has a high rigidity and is not easily deformed, and therefore, the inorganic nanofibers in which the fiber length is short and uniform can be produced. That is, the inorganic nanofiber of [1] can be produced.

[0028]In the invention of [6], the inventors found that the first spinnable sol solution, and the second spinnable sol solution or metal salt solution (respectively, as materials of the first inorganic oxide and the second inorganic oxide, of which the refractive index is different), are mixed without being gelled, so that the potential hydrogen is matched with one another in accordance with the refractive index of the first and second inorganic oxides, to prepare a spinnable mixed sol solution, and the inorganic mixed nanofibers having a desired refractive index can be easily produced by electrospinning of the spinnable mixed sol solution.

Problems solved by technology

This is because if the filler is thicker or longer than the thickness of the polymer film, the filler is likely to protrude from the polymer film, and therefore, many practical problems arise.

Although this document exemplifies conventional fiber cutting machines, such as a guillotine-type cutting machine and a rotary cutter-type cutting machine, as a method of manufacturing the inorganic short fiber, even if these conventional fiber cutting machines were used, it was extremely difficult to obtain inorganic short fibers having a short fiber length of 200 μm or less, as described in the Examples of the document, due to the mechanism of the machines, and it was difficult to use the fibers as a filler for thinner polymer films.

In addition, since these cutting machines use a metal blade, there was a problem wherein the metal blade was damaged at the time of cutting, and a piece of metal was mixed in with inorganic short fibers or an inorganic fiber aggregate.

This problem was remarkable in the case of manufacturing short fibers consisting of a hard inorganic material such as alumina, which was also used as an abrasive.

However, even if these crushing devices were used, fibers could not be sufficiently crushed to obtain fine fibers having an average fiber diameter of 2 μm or less, or even if fibers could be crushed, short fibers in which the fiber length were uniform could not be prepared.

However, this filler could not be applied to resins other than polycarbonate resins.

In addition to this problem, it was considered that the adjusting of the refractive index was difficult, because it contained at least four components.

It was examined whether or not the refractive index could be controlled utilizing this technique, but the fine adjustment of the refractive index was difficult, and it was difficult to obtain silica-alumina sintered ultrafine long fibers having a uniform refractive index.

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