Method for producing short fiber containing aluminum hydroxide

Abstract

To provide a technology capable of supply a short fiber containing aluminum hydroxide that has a thickness of at most 0.1 micrometers and an aspect ratio of 100 or more and that is obtained by self-assembling an aluminum hydroxide polymer [Al2(OH)6]m generated from hydrolysis of aluminum chloride hexahydrate.SOLUTION: There is provided a method for producing a short fiber containing aluminum hydroxide. The method is configured in that: an aluminum hydroxide polymer [Al2(OH)6]m is sequentially precipitated on a surface of a growing oligopeptide by self-assembling to produce a short fiber containing aluminum hydroxide; the self-assembling is initiated on a solid surface for obtaining a short fiber with a uniform thickness; and the solid surface is preferably a hydrophilic polymer containing hydroxyl groups in which a solubility parameter at 25°C is 20 (J cm-3)0.5 or more as calculated by a Fedors method.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention does not enable the formation of high aspect ratio fibrous products containing aluminum hydroxide by adding an organic auxiliary agent to a liquid of an organometallic compound containing a metal element to optimize the viscosity and then spinning. Instead, it relates to the discovery that after imparting the necessary raw materials for a hydrophilic polymer such as cellulose in the liquid phase and then performing heat treatment, it can be extremely easily formed on the surface of the polymer.

Background Art

[0002] Fibers containing aluminum hydroxide can be used as a raw material (precursor) for producing alumina fibers. However, the general method for producing a precursor of alumina fibers involves adding an organic polymer to a solution of aluminum salts, etc., to thicken it, and then mechanically fiberizing it (Non-Patent Document 1). In Patent Document 1, spinning is performed by adding PVA (polyvinyl alcohol) to a liquid of an organometallic compound. As shown in Patent Document 1, since the diameter of the nozzles used in ordinary spinning methods is 0.1 - 0.5 mm and the number of nozzles is several hundred holes, in order to perform stable spinning, not only the cleaning of the raw materials but also the cleaning management of the spinning apparatus becomes extremely important and requires a lot of labor. Furthermore, the supply of a precursor for producing alumina fibers with a thickness in the nanometer scale cannot be achieved by conventional spinning apparatuses.

[0003] In Non-Patent Document 2, a special surfactant is used to form liquid cells, and after generating aluminum hydroxide inside the liquid cells, the liquid cells are destroyed, and it has been successfully manufactured fine particles of aluminum hydroxide with a size of several nanometers. However, since the shape of the liquid cells is spherical, it is not possible to supply short fibers with a high aspect ratio containing aluminum hydroxide. In Patent Document 2, a polymer of aluminum hydroxide [Al2(OH)6] generated by hydrolysis of aluminum chloride hexahydrate mBy depositing it on various fiber surfaces, the hydrogen bonding ability or chelate complex forming ability with respect to the proteins on the fiber surface is enhanced, and as a result, the fibers have been successfully coated with protein hydrolysates. However, the polymer of aluminum hydroxide [Al2(OH)6] deposited by this method m has a polymerization degree m of at most about 10, so the aluminum hydroxide polymer deposited on the fiber surface cannot be treated as short fibers.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Non-Patent Documents

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Non-Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the production of short fibers containing aluminum hydroxide, instead of making it possible to produce by adding an organic auxiliary agent to a liquid of an organometallic compound to optimize viscosity and then spinning, a polymer of aluminum hydroxide [Al2(OH)6] generated by hydrolysis of aluminum chloride hexahydrate m is actively self - organized to enable the formation of short fibers containing aluminum hydroxide. At this time, the thickness of the short fibers to be formed is at most 0.1 micrometers, and short fibers with an aspect ratio of 100 or more can be supplied.

Means for Solving the Problems

[0006] To actively self - organize a polymer of aluminum hydroxide [Al2(OH)6] m an auxiliary material (template) that interacts with the polymer to form a stable surface is required. Non - Patent Document 3 shows the interaction between aluminum chloride and sericin protein. Non - Patent Document 4 shows the interaction between aluminum ions and the tyrosine side chain of fibroin protein. From these, proteins containing serine or tyrosine are considered suitable as the auxiliary material. On the other hand, a polymer of aluminum hydroxide [Al2(OH)6] mSince it is produced by the hydrolysis of aluminum chloride hexahydrate, the template material needs to be a water-soluble protein. For example, Non-Patent Document 5 reports the self-assembly of water-soluble oligopeptides derived from feathers. The protein hydrolysate shown there exhibits high water solubility and contains serine and tyrosine, so it can be said to be a suitable template material. That is, if polymers of aluminum hydroxide [Al2(OH)6] m are sequentially deposited on the surface of the oligopeptide that self-assembles and grows, fibers containing aluminum hydroxide will be formed along with the self-assembly of the oligopeptide.

[0007] In order to form fibers containing aluminum hydroxide with a uniform thickness, it is necessary to avoid the joining of fibers sequentially formed by the self-assembly of oligopeptides. That is, it is necessary to perform the self-assembly of oligopeptides while taking up space from each other. Therefore, the self-assembly of oligopeptides needs to be initiated on a suitable solid surface rather than in a flow field. And regarding the interaction between such a solid surface and the protein, considering from the solubility parameter, it is considered important that they have somewhat different values from each other in order to avoid the influx (film formation) of the protein to the solid surface. When calculating the solubility parameter of feather keratin at 25°C by the Fedors method, it was 14.1 (J·cm -3 ) 0.5 . It is necessary to consider a solid surface that is away from this value. However, if it is taken lower, the hydrophobicity increases, so we decided to consider a material with higher hydrophilicity and a larger solubility parameter. The solubility parameter of cellulose at 25°C calculated by the Fedors method is 24.1 (J·cm -3 ) 0.5Therefore, cellulose was used as the solid surface. Similar effects can be expected from, for example, hemicellulose, starch, curdlan, paramylon, glucomannan, etc., which have a backbone in which glucose molecules are glycosidically bonded in the same way as cellulose. In the hydrolysis of aluminum chloride hexahydrate, hydrochloric acid is produced, and since it hydrolyzes the glycosidic bond, neutralization treatment of hydrochloric acid is essential. Also, Non-Patent Document 2 shows that the addition of sodium hydroxide is suitable for the production of aluminum hydroxide. However, since sodium hydroxide may strongly denature oligopeptides, sodium carbonate among strongly basic carbonates was used. Similar effects can be expected from potassium carbonate as well.

[0008] For the formation of short fibers containing aluminum hydroxide with a uniform thickness, control of the reaction environment is important. Generally, an environment involving evaporation of moisture (drying) is preferred to promote the self-organization of oligopeptides. Therefore, it was determined that an environment changing from the liquid phase to the gas phase is suitable for promoting the self-organization of oligopeptides and the formation of short fibers containing aluminum hydroxide with a uniform thickness. As a result of intensive studies, a process consisting of two steps was devised, leading to the present invention. In the first step, the raw materials (oligopeptide, aluminum chloride hexahydrate, strongly basic carbonate) necessary for the formation of fibrous products containing aluminum hydroxide with a high aspect ratio are supplied in the liquid phase to the polymer surface serving as the substrate. In the second step, the polymer treated in the first step is heat-treated. The treatment temperature is desirably set below the temperature at which thermal decomposition of the polymer or oligopeptide starts. As a result of intensive studies, it was found that when cellulose is used as the substrate, a range of 80°C to 160°C is most desirable.

Advantages of the Invention

[0009] The short fibers containing aluminum hydroxide produced by the present invention are extremely thin (about 0.1 micron in thickness), reach a length of 10 microns or more, and can have an aspect ratio increased to 100 or more. Since they contain aluminum hydroxide, if fired, it is possible to provide extremely fine alumina fibers. On the other hand, since the short fibers are produced as a composite in a state fixed to the surface of cellulose or the like, they are extremely easy to transfer and can be physically separated from the cellulose surface and used as needed. Also, in the development of a composite material using cellulose fibers as a reinforcing material, improvement of the interfacial adhesion characteristics can be expected by applying the treatment of the present invention to the cellulose surface. Furthermore, the non-woven fabric to which the short fibers are fixed has an enhanced filter function. Aluminum hydroxide, as an inorganic flame retardant, has characteristics such as halogen-free, low smoke, and non-toxic. Therefore, if the treatment of the present invention is performed on combustible cellulose, an expansion in the use of cellulose products in areas where flame retardancy is required can be expected.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

Examples

[0011] In the first stage, the raw materials (oligopeptide, aluminum chloride hexahydrate, sodium carbonate) necessary to form a fibrous product containing aluminum hydroxide with a high aspect ratio on the surface of the cellulose nonwoven fabric were supplied in a liquid phase. After that, in the second stage, a heat treatment at 130 °C was carried out, and then the treated fabric was washed with hot water and dried. The surface of the treated fabric was observed with a scanning electron microscope. The appearance of a typical fibrous product containing aluminum hydroxide is shown in Fig. 1. Innumerable fibrous products were confirmed.

Example

[0012] In the first stage, the raw materials (oligopeptide, aluminum chloride hexahydrate, sodium carbonate) necessary to form a fibrous product containing aluminum hydroxide with a high aspect ratio on the surface of the cellulose nonwoven fabric were supplied in a liquid phase. After that, the heat treatment temperature in the second stage was set to 140 °C to form a fibrous product containing aluminum hydroxide on the surface of the cellulose nonwoven fabric. Then, the treated fabric was further washed with hot water and dried, and the wide-angle X-ray diffraction of the treated fabric was measured by the transmission method. The obtained diffraction intensity curve is shown in Fig. 2. By comparing the diffraction intensity curves of the treated fabric and the untreated cellulose nonwoven fabric, it was found that the diffraction peaks of aluminum hydroxide corresponding to Bayerite and Nordstrandite were included in the treated fabric.

Example

[0013] In the first stage, the raw materials (oligopeptide, aluminum chloride hexahydrate, sodium carbonate) necessary to form a fibrous product containing aluminum hydroxide with a high aspect ratio on the surface of the cellulose nonwoven fabric were supplied in a liquid phase. After that, the heat treatment temperature in the second stage was set to 100 °C to form a fibrous product containing aluminum hydroxide on the surface of the cellulose nonwoven fabric. Then, the treated fabric was further washed with hot water and dried, and the infrared absorption spectrum of the treated fabric was measured by the total reflection measurement method (ATR method). The measurement results are shown in Fig. 3. By comparing the spectra of the treated fabric and the oligopeptide used in the experiment, the amide I peak at 1638 cm -1 and 1516 cm -1The amide II peaks of each are 1729 cm in the treated fabric -1 and 1649 cm -1 It can be seen that as a result of the strong interaction between the generated aluminum hydroxide and the self-organized oligopeptide, changes occurred in the vibration modes of amide I and amide II of the oligopeptide.

Claims

1. A method for producing short fibers containing aluminum hydroxide with a thickness of at most 0.1 micrometers and an aspect ratio of 100 or more by sequentially depositing a polymer of aluminum hydroxide [Al ２ (OH) ６ ] ｍ on the surface of an oligopeptide derived from self-organizing and growing feather keratin, and short fibers containing aluminum hydroxide produced by the treatment method.

2. A polymer fixed on the surface of the short fibers produced by the method according to Claim 1.

3. The polymer according to Claim 2 is a hydrophilic polymer containing a hydroxyl group with a solubility parameter at 25 °C calculated by the Fedors method of 20 (J·cm －３ ) ０．５ or more.

4. The polymer according to Claim 2 is any one of cellulose, hemicellulose, starch, curdlan, paramylon, and glucanmannan.

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