JP3539249B2 - How to make titania fiber - Google Patents

Description

【００３８】
【発明の効果】
本発明により、ゾル溶液が安定化し、当該溶液の曳糸性を長期間保持できる。詳しくは曳糸性の保持時間を、半年以上とすることが可能となる。このため、本発明の方法は量産性に優れる。
【図面の簡単な説明】
【図１】ファイバー作成装置の一例の概略構成図を示す。
【図２】ゲルファイバー形成装置の一例の概略構成図を示す。
【図３】気体浄化装置の一例の概略構成図を示す。
【図４】液体浄化装置の一例の概略構成図を示す。
【符号の説明】
１１:開口を有する容器、１２:シリンダ、１３:ヒータ装置、１４:ファイバー巻き取り機、２１:微小孔を有する容器、２２:支持棒、２３:モータ、２４:微小孔、２５:チタニアファイバー、３１:チタニアファイバー、３２:粗フィルター、３３:ガラスカラム、３４:気体導入部、３５:気体排出部、３６:紫外光、４１:チタニアファイバー、４２:カラム、４３:液体導入部、４４:液体排出部、４５:紫外光。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing titania fiber using a sol-gel method.
[0002]
[Prior art]
Titanium oxide (TiO ₂ : hereinafter referred to as titania) crystals have three types of crystal phases, of which, at room temperature, two types of rutile type (orthogonal type) and anatase type (tetragonal type) are stably present. When the titania is irradiated with light (ultraviolet light) having an energy equal to or greater than the band gap (rutile 3.0 eV, anatase 3.2 eV), electrons and holes are generated inside the titania. Therefore, it has the effect of decomposing water present on the surface into hydrogen and oxygen or decomposing organic molecules present on the surface, and has been put to practical use as a coating material having an antifogging effect and a pollution preventing effect. Since this photocatalytic reaction occurs on the titania surface (titania-water interface or titania-organic molecular interface), it is advantageous to form titania into a fiber and increase the surface area, thereby promoting the reaction.
[0003]
As a method for producing titania fiber, a sol-gel method is mainly used. When produced by the sol-gel method, the spinnability of the sol as a fiber raw material depends on the degree of progress of the hydrolysis reaction. Therefore, the time during which the sol retains the spinnability is a time during which the state in which the hydrolysis reaction has proceeded appropriately can be maintained, and it is very short, less than several hours. For this reason, there was a problem in terms of mass productivity. Here, the `` sol-gel method '' means that a metal organic or inorganic compound is used as a solution, and the hydrolysis / polymerization reaction of the compound proceeds in the solution to pass through a state of a sol containing fine particles (sol). It means a method of producing a crystal, glass or sintered body of a metal oxide by further heating after passing through a state of a gel containing a liquid or a gas in a gap between solid frames.
[0004]
That is, in the sol-gel method, the metal-oxygen skeleton is usually formed by dissolving and mixing the respective alkoxides of the constituent metal cations in a solvent at a composition ratio and allowing the hydrolysis reaction to proceed. Therefore, the viscosity of the solution increases as the hydrolysis reaction proceeds. Further, a solution having an appropriate viscosity shows spinnability. Therefore, the spinnability is exhibited only in a state where the reaction has progressed appropriately, but if the hydrolysis proceeds excessively, the viscosity increases excessively, gelation occurs, and the spinnability is lost. Therefore, according to the conventional production method by the sol-gel method, there is a problem in mass productivity because the duration of spinning property is as short as several minutes to several hours.
[0005]
Therefore, in the sol-gel method, in order to stabilize the state of the sol and secure a long expression duration of spinnability, β-diketone and a keto ester-based chelating agent are used as a stabilizer in the starting solution. Attempts have been made to add. However, for the production of titania fiber, although stabilization occurs, it has not been possible to synthesize a sol having a spinnability for a long period of time (about several days to several weeks or more) so as to be excellent in mass productivity.
[0006]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and relates to a method for producing titania fiber excellent in mass productivity.
[0007]
[Means for Solving the Problems]
The present invention provides a first step of obtaining a gel-like fiber from a sol obtained by concentrating a solution comprising a titanium alkoxide, an amine-based chelating agent, water and a solvent until the solution shows spinnability. A method for producing titania fiber comprising a second step of crystallizing, wherein the number of moles of water in the solution in the first step is 0.1 to 0.35 times the number of moles of titanium alkoxide. The present invention relates to a method for producing a fiber.
[0008]
In the first step of the method of the present invention, a homogeneous solution is prepared by mixing a titanium alkoxide, an amine-based chelating agent and water with a solvent. Here, the titanium alkoxide as a starting material may be either an organic or inorganic compound as long as it can finally form a polycrystalline or glass-ceramic fiber of titania represented by TiO ₂ . Examples of the titanium alkoxide include tetraethoxytitanium, tetraisopropoxytitanium, tetra-n-propoxytitanium, tetra-n-butoxytitanium, tetraisobutoxytitanium, tetrasec-butoxytitanium and the like, among which tetraisopropoxytitanium, Tetra n-butoxytitanium and the like are preferably used. Two or more titanium alkoxides may be used.
[0009]
Titanium alkoxide has a property of producing a metalloxane bond (Ti-O-Ti) by hydrolysis. The bond between the compounds is a structure necessary for the sol to exhibit spinnability.
[0010]
Furthermore, it is sufficient that these compounds can be synthesized by synthesizing them under predetermined conditions without using titanium alkoxide as a starting material. For example, acetate, acetylacetonate, a simple substance of metal, chloride, nitrate, and the like cannot form a metalloxane bond as it is, but a titanium alkoxide can be synthesized by performing a chemical reaction under predetermined conditions. .
[0011]
In the method of the present invention, an amine chelating agent is used. A chelating agent is a general term for a substance in which a plurality of atoms in a ligand molecule bind to a metal ion to form a metal chelate complex. The amino chelating agent of the present invention has a general formula:
NRR'R ''
(Wherein, R, R ′ and R ″ are each independently hydrogen or a hydroxyalkyl group or an alkyl group having 2 to 6, preferably 2 to 3 carbon atoms, provided that R, R ′ and R ′ 'Is not hydrogen at the same time.) Specific examples include 2-aminoethanol, 2,2′-iminodiethanol, 3-aminopropanol, 4-amino1-butanol, N-aminoethyl ethatoramine and the like. In the present invention, by using such a stabilizer, the sol solution is stabilized, spinnability can be maintained for a long time, and mass productivity is excellent. Specifically, the spinning property holding time can be made longer than half a year.
[0012]
The amount of the amine chelating agent as described above is 1 to 4 moles, preferably 1.5 to 3 moles of the titanium alkoxide used. If the amount is too small, the effect of the present invention cannot be obtained, that is, the sol solution cannot be stabilized, and the spinnability cannot be maintained for a long time. If the amount is too large, carbonization occurs during heat treatment. In order to eliminate carbonization, the heat treatment temperature must be increased more than necessary.
[0013]
As the solvent, any medium can be used as long as it can uniformly dissolve the titanium alkoxide and / or the above-mentioned starting materials. The optimum solvent for the metal compound is selected in consideration of the boiling point, the dissolving power of the titanium raw materials, the stability, and the like. do it. As such a solvent, for example, a single alcohol or a mixture of two or more alcohols, more specifically, 2-methoxyethanol or a mixture of 2-methoxyethanol and ethanol can be used. In addition, solvents such as n-propanol, i-propanol, and butanol can be used.
[0014]
Water to be mixed with the solvent may be water at the time of preparation, but may be introduced from water of crystallization of titanium alkoxide, water in alcohol of the solvent, or water in the atmosphere. Moreover, you may combine them. In order to synthesize the aforementioned metalloxane bond, water is required. If this water is introduced from the water of crystallization of titanium alkoxide, the water in the alcohol of the solvent, the water in the atmosphere, or the like, the process can be simplified without the need to introduce any special water.
[0015]
As described above, a titanium alkoxide, an amine chelating agent, water and a solvent are mixed to prepare a homogeneous solution. In this case, the number of moles of the solvent is 3 to 20 times, preferably 5 to 15 times the number of moles of the titanium alkoxide. Is desirable. If the number of moles of the solvent is too small, the stability of the solution decreases due to the reaction with atmospheric moisture, and the solution is easily hydrolyzed, and precipitation is easily caused.If the amount is too large, a large amount of the solvent is removed during concentration. Must be performed, and productivity will be reduced. In addition, the concentration of water is adjusted so that the number of moles of water is 0.1 to 0.35 times the number of moles of titanium alkoxide for the expression of spinnability of the sol after concentration and the stability of the sol. adjust. When the number of moles of water is too small, the spinning property is not obtained due to insufficient hydrolysis, and when it is too large, the hydrolysis proceeds too much to cause gelation, ie, solidification, and the spinning property does not appear.
[0016]
In the present invention, it is preferable that titanium alkoxide is dissolved in a small amount of solvent in advance, and the remaining predetermined amount of the solvent, amine-based chelating agent and water are mixed with the solution.
[0017]
Next, the obtained solution is concentrated until it exhibits spinnability, thereby obtaining a highly viscous sol. Concentration may be performed by any method or means as long as the solvent can be evaporated.However, from the viewpoints of work efficiency, reactivity related to the spinnability of metal ions in the sol, etc., the concentration around the boiling point of the solvent is It is preferable to concentrate at a temperature until the fiber exhibits spinnability. Further, when the concentration is performed by a rotary evaporator, the solution contains water. If water remains in the solution, the hydrolysis reaction proceeds further and gelation occurs. To prevent this, it is effective to remove water under reduced pressure. Further, from the viewpoint of further improving the working efficiency, it is more preferable to perform the above concentration under reduced pressure. The term “under reduced pressure” refers to a pressure condition for promoting the removal of a solvent at a pressure lower than the atmospheric pressure. Here, the "spinnability" refers to the property that the liquid pulls a thread when a high-viscosity solution such as a polymer solution or a colloid solution is applied, or when a rod is inserted and pulled up quickly. The sol used in the present invention means a solution in which a polymer and a complex ion of submicron or less are uniformly dispersed.
[0018]
In the production of a titanium oxide material by a conventional sol-gel method, a hydrolysis reaction and a polymerization reaction progress with time, even during molding into a fiber shape when forming a fiber, resulting in high viscosity. Since the viscosity of the sol changes every moment, the time for the sol to maintain the desired spinnability is extremely short, and there is a problem in mass productivity. Since the sol used in the present invention contains the above-mentioned amine-based chelating agent, the sol is stabilized and has extremely excellent storage stability. In other words, the high-viscosity sol having spinnability has little change with time with respect to viscosity and spinnability and is stable, so that the spinning life is long. Therefore, mass production is possible, and a gel fiber can be spun from a large amount of a high-viscosity sol in a subsequent step for a long period of time under a constant condition, so that the production process is stable, the yield is good, and the production cost can be reduced.
[0019]
Next, a gel fiber is formed from the concentrated high-viscosity sol having spinnability. As a specific method, a method of molding a high-viscosity sol into a fiber while pulling it up, or a method of extruding and molding the high-viscosity sol from a small opening can be used. It can be formed into a gel fiber from the sol state in the atmosphere. The highly viscous sol of the present invention has excellent spinnability, and can be formed into a fiber having a diameter of about 5 to 200 μm.
[0020]
In the second step, the gel fiber obtained in the first step is heated and crystallized to produce a fiber as a final product. The heat treatment may be performed at a temperature at which titania crystallizes, that is, 400 to 800 ° C., preferably 450 to 550 ° C. In a preferred embodiment, the fibers are produced from the high-viscosity sol by a fiber forming apparatus that continuously performs gel fiber formation and heat treatment.
[0021]
The second method of the present invention is characterized in that the concentration in the first step is performed under a pressure condition lower than the atmospheric pressure. By concentrating under such reduced pressure, excess water can be removed from the solution, and excessive progress of hydrolysis can be prevented. As a device for reducing the pressure, a rotary pump or an aspirator can be used.
[0022]
A specific production example is described below. In this specification, crystallization includes the meanings of polycrystallization and glass ceramics.
FIG. 1 is a schematic configuration diagram of a fiber forming apparatus. The fiber forming apparatus generally includes a container 11 of a high-viscosity sol solution having an opening 11a at the bottom, a cylinder 12 for pressurizing the high-viscosity sol, and heating the gel fiber that is pressurized by the cylinder 12 and extruded from the opening to gel. And a winding device 14 for winding the completed fiber 14. In the fiber forming apparatus, the high-viscosity sol is extruded from the opening 11a by the cylinder 12, and is wound around the winder 14 through the heater. The take-up device 15 is driven to rotate at a constant speed by a motor (not shown), and the fibers are sequentially taken up.
[0023]
In the above configuration, the fiber immediately after being extruded is in a sol state, but as the fiber is extruded, the solvent component gradually evaporates to form a gelled gel fiber. The gel fiber is further crystallized by heating at a temperature at which a crystal phase of titania is precipitated by the heater device 13, whereby a titania fiber can be produced. In this apparatus, the diameter of the fiber can be changed by changing the viscosity of the high-viscosity sol, the winding speed of the winding machine 14, and the size of the opening 11a. In order to produce a fiber having a desired diameter, the viscosity of the high-viscosity sol, the winding speed of the winding machine, and the size of the opening at the bottom of the container may be appropriately adjusted.
[0024]
Further, the heat treatment may be performed after the gel fiber is completely molded without using the fiber forming apparatus as described above. In this case, the gel fiber may be sealed and left in a dry atmosphere, and then heat-treated. The gel fiber forming method in that case is described below.
[0025]
FIG. 2 is a schematic configuration diagram of the gel fiber forming apparatus. A highly viscous sol having spinnability is placed in a container 21 having micropores, and the container 21 is connected to a motor 23 by a support rod 22. With the rotation of the motor 23, the container 21 rotates, and the centrifugal force pushes out the fiber-like gel 25 from the micropores 24. The highly viscous sol becomes gel fiber in air. The gel fiber is collected and subjected to a heat treatment to obtain a fiber. In this method, the diameter of the fiber can be controlled by controlling the diameter of the minute hole and the rotation speed of the motor. The heating temperature after gel fiber formation is the same as above.
[0026]
The titania fiber obtained by the method of the present invention has an excellent purification effect. For example, as shown in FIG. 3, in the purification device 1, the gas to be purified is introduced from the gas introduction unit 34, and the coarse filter 32 removes physical dirt (dust and the like). Thereafter, the gas is introduced into the column 33, and the titania fiber 31 is irradiated with ultraviolet light 36, whereby a photocatalytic reaction occurs on the surface. The organic molecules are decomposed by the reaction, and the purified gas is discharged from the gas discharge unit 35. As shown in FIG. 4, in the purification device 2, the liquid introduced from the liquid introduction unit 43 is distributed to a plurality of columns 42 to increase the efficiency of the reaction, and the liquid is introduced into the titania fibers 41 sealed in each column. It is purified by causing a photocatalytic reaction, and is discharged again from one liquid discharge unit 44.
[0027]
The method of the present invention is not limited to producing pure titania fiber, but is applicable to producing fiber mixed with other types of oxides for the purpose of increasing fiber strength. It is.
[0028]
【Example】
Comparative Example 1
8.131 g of 2-methoxyethanol and 10.123 g of tetraisopropoxytitanium (solution 1), 16.408 g of ethanol and 0.321 g of water (solution 2) were weighed (composition 1 in Table 1). Take and mix for 20 minutes each. Solution 2 is added dropwise to Solution 1 and mixed for 20 minutes. Next, the mixed solution is put into an eggplant-shaped flask and concentrated by heating at 145 to 170 ° C. When the volume of the viscous solution stopped changing, heating was stopped. Gelation occurs near the wall of the flask, and it turns white. The viscosity was too high, and no spinning property was observed.
[0029]
Comparative Example 2
8.164 g of 2-methoxyethanol and 10.164 g of tetraisopropoxytitanium (solution 1), 16.474 g of ethanol and 0.161 g of water (solution 2) were weighed (composition 2 in Table 1). Take and mix for 20 minutes each. Solution 2 is added dropwise to Solution 1 and mixed for 20 minutes. Next, the mixed solution is put into an eggplant-shaped flask and concentrated by heating at 145 to 170 ° C. When the volume of the viscous solution stopped changing, heating was stopped. Gelation occurs near the wall of the flask, and it turns white. The viscosity was too high, and no spinning property was observed.
[0030]
Comparative Example 3
8.656 g of 2-methoxyethanol, 10.776 g of tetraisopropoxytitanium, 3.796 g of acetylacetone (solution 1), 17.466 g of ethanol, and 0.171 g of water (solution 2) were used (Table 1). Composition 3) Weigh and mix for 20 minutes each. Solution 2 is added dropwise to Solution 1 and mixed for 20 minutes. Next, the mixed solution is put into an eggplant-shaped flask and concentrated by heating at 145 to 170 ° C. When the volume of the viscous solution stopped changing, heating was stopped. Gelation occurs near the wall of the flask, and it turns white. The viscosity was too high, and no spinning property was observed.
[0031]
Comparative Example 4
8.656 g of 2-methoxyethanol, 10.776 g of tetraisopropoxytitanium, 7.592 g of acetylacetone (solution 1), 17.466 g of ethanol, and 0.171 g of water (solution 2) were used (Table 1). Composition 4) Weigh and mix for 20 minutes each. Solution 2 is added dropwise to Solution 1 and mixed for 20 minutes. Next, the mixed solution is put into an eggplant-shaped flask and concentrated by heating at 145 to 170 ° C. When the volume of the viscous solution stopped changing, heating was stopped. Gelation occurs near the wall of the flask, and it turns white. The viscosity was too high, and no spinning property was observed.
[0032]
Comparative Example 5
Two types (solution 2) of 9.2 g of 2-methoxyethanol, 11.454 g of tetraisopropoxytitanium and 4.923 g of 2-aminoethanol (solution 1), 18.565 g of ethanol, and 0.279 g of water, respectively (solution 2) In Table 1, composition 5) Weigh and mix for 20 minutes each. Solution 2 is added dropwise to Solution 1 and mixed for 20 minutes. Next, the mixed solution is put in an eggplant-shaped flask and concentrated by heating at 140 ° C. When the volume of the viscous solution stopped changing, heating was stopped. Gelation occurs near the wall of the flask, and it turns white. The viscosity was too high, and no spinning property was observed.
[0033]
Comparative Example 6
9.2 g of 2-methoxyethanol, 11.454 g of tetraisopropoxytitanium and 4.923 g of 2-aminoethanol (solution 1), 18.565 g of ethanol, and 0.181 g of water (solution 2) were used respectively ( In Table 1, composition 5 ') is weighed out and mixed for 20 minutes each. Solution 2 is added dropwise to Solution 1 and mixed for 20 minutes. Next, the mixed solution is put in an eggplant-shaped flask and concentrated by heating at 140 ° C. When the volume of the viscous solution stopped changing, heating was stopped. The area near the wall of the flask is gelled and white. The viscosity was too high, and no spinning property was observed.
[0034]
Example 1
Three types of 2-methoxyethanol, tetraisopropoxytitanium, and 2-aminoethanol (solution 1), and two types of ethanol and water (solution 2) were each adjusted to 50 ml in the composition ratio of composition 5 'in Table 1. Weigh and mix for 20 minutes each. Solution 2 is added dropwise to Solution 1 and mixed for 20 minutes. Next, the mixed solution is placed in an eggplant-shaped flask, and heated and concentrated at 140 ° C. for 40 minutes while slightly reducing the pressure (600 mmHg). Heat concentration was performed until the amount of the viscous solution did not change.
A brown, spinnable liquid was obtained. A gel fiber was prepared from the liquid using the apparatus shown in FIG. 2 and heat-treated at 600 ° C. As a result, a white fiber was obtained, and it was confirmed by an X-ray diffraction method that the fiber was rutile-type crystal titania.
[0035]
Example 2
Two kinds of 2-methoxyethanol, tetraisopropoxytitanium, and two kinds of 2,2-iminodiethanol (solution 1), and two kinds of ethanol and water (solution 2) are respectively 50 ml in total composition ratio of composition 6 in Table 1. And mix for 20 minutes each. Solution 2 is added dropwise to Solution 1 and mixed for 20 minutes. Next, the mixed solution is put in an eggplant flask and concentrated by heating at 140 ° C. under atmospheric pressure (760 mmHg) for 2 hours. Heat concentration was performed until the amount of the viscous solution did not change.
A brown, spinnable liquid was obtained. A gel fiber was prepared from the liquid using the apparatus shown in FIG. 2 and heat-treated at 600 ° C. As a result, a white fiber was obtained, and it was confirmed by an X-ray diffraction method that the fiber was rutile-type crystal titania.
[0036]
In the above, a special grade reagent manufactured by Nacalai Tesque is used as 2-methoxyethanol, a primary reagent manufactured by Wako Pure Chemical is used as tetraisopropoxytitanium, a special grade reagent manufactured by Nacalai Tesque is used as acetylacetone, and a special grade reagent manufactured by Nacalai Tesque is used as 2-aminoethanol. Nacalai Tesque's first-class reagent, 2,2-iminodiethanol is a special grade reagent from Wako Pure Chemical Industries, Ltd., ethanol is Nacalai Tesque's special grade reagent, and water is Nacalai Tesque's distilled water. Was.
[0037]
Table 1 summarizes the above results together with the composition ratio. In addition, the numerical value in a table | surface shows a molar ratio.
[Table 1]

[0038]
【The invention's effect】
According to the present invention, the sol solution is stabilized, and the spinnability of the solution can be maintained for a long time. Specifically, the spinning property holding time can be made longer than half a year. For this reason, the method of the present invention is excellent in mass productivity.
[Brief description of the drawings]
FIG. 1 shows a schematic configuration diagram of an example of a fiber producing apparatus.
FIG. 2 shows a schematic configuration diagram of an example of a gel fiber forming apparatus.
FIG. 3 shows a schematic configuration diagram of an example of a gas purification device.
FIG. 4 shows a schematic configuration diagram of an example of a liquid purification device.
[Explanation of symbols]
11: Container having an opening, 12: Cylinder, 13: Heater device, 14: Fiber take-up machine, 21: Container having micro holes, 22: Support rod, 23: Motor, 24: Micro holes, 25: Titania fiber, 31: titania fiber, 32: coarse filter, 33: glass column, 34: gas inlet, 35: gas outlet, 36: ultraviolet light, 41: titania fiber, 42: column, 43: liquid inlet, 44: liquid Discharge unit, 45: ultraviolet light.

Claims (2)

A first step of obtaining a gel-like fiber from a sol obtained by concentrating a solution comprising a titanium alkoxide, an amine-based chelating agent, water and a solvent until the solution shows spinnability, and crystallizing the obtained gel-like fiber A method for producing a titania fiber comprising two steps, wherein the number of moles of water in the solution in the first step is 0.1 to 0.35 times the number of moles of titanium alkoxide. . The method for producing titania fiber according to claim 1, wherein the concentration in the first step is performed under a pressure condition lower than the atmospheric pressure.

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