JPH10192694A - Production of porous inorganic compound hollow capsule - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control a particle size, the thickness of a wall film and the functionality thereof. SOLUTION: A four-component soln. 7 is prepared from an org. solvent 1, a wall film forming material 2, an oil gelling agent 4 and alcohol 6, and an aq. soln. 9 adjusted its pH is dripped to this four-component soln. 9. A gel film is formed to the peripheries of liquid droplets of the aq. soln. 9 by interfatial gelling reaction and the wall film forming material 2 is hydrolyzed and subjected to polycondensation reaction in the gel film to form a product 11 having a porous wall film. The product 11 is washed to be heat-treated to eliminate the gel film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a porous inorganic compound hollow capsule used as a member for reinforcing the strength of an electrolyte plate in a fuel cell or a member for improving the function of various catalyst carriers.

[0002]

2. Description of the Related Art Electrolyte plates used in molten carbonate fuel cells have been conventionally manufactured by various methods.
As one of the manufacturing methods, ceramic particles of several μm or less, for example, lithium aluminate (LiAlO ₂ )
Forming a matrix having a large number of pores by the powder,
There is a type in which the matrix is impregnated with an electrolyte so that the electrolyte is held in voids of the matrix to form an electrolyte plate.

[0003] The electrolyte plate obtained by such a method is used sandwiched between both cathode and anode electrodes, and completely separates the oxidizing gas supplied to the cathode side and the fuel gas supplied to the anode side. Have to do,
The electrolyte plate is subjected to a large stress caused by repeatedly operating between the room temperature and the operating temperature of the fuel cell (about 650 ° C.) with the operation and shutdown of the fuel cell. When the temperature changes rapidly from the liquid phase to the solid phase, particularly when the temperature suddenly drops at the time of emergency stop of the operation, it occurs remarkably.

[0004] However, when the electrolyte plate changes from a liquid phase to a solid phase, the volume rapidly changes and energy is released, and the energy at this time may cause a crack in the electrolyte plate. If a crack penetrates the electrolyte plate in the front and back direction, the electrolyte plate can no longer maintain the ability to separate the oxidizing gas and the fuel gas, and the oxidizing gas and the fuel gas come into direct contact, and the battery output decreases. Alternatively, there is a problem that a danger of explosion may occur.

[0005] Therefore, the present inventors have proposed that if hollow microcapsules having a porous inorganic wall film impregnated with carbonate can be used as a reinforcing material for an electrolyte plate, the fuel cell can be cooled during cooling. It has been found that when the carbonate becomes a solid, the carbonate in the capsule becomes solid with the inside inside and forms a series with the surrounding carbonate, and a series of gaps are not formed around the capsule.

Conventional techniques for producing microcapsules having an inorganic wall film include a chemical method and a physical / mechanical method.

As an example of the chemical method, an interface reaction method will be described. In the interfacial reaction method, in an inorganic chemical reaction (precipitation forming reaction) that proceeds in a normal aqueous solution, one of the two compounds is treated with an organic solvent (in which a nonionic surfactant is dissolved). After mixing to prepare a W / O type (water-in-oil type) emulsion, the emulsion is gently injected into the aqueous solution of the other compound, whereby the reaction of forming a precipitate proceeds at the interface.

[0008]

However, in the case of the method for producing microcapsules by the above-mentioned interface reaction method, not only the production process is complicated, but also it is difficult to control the particle size and wall thickness. Further, it was not possible to add a function to the wall film as a functional material.

Accordingly, an object of the present invention is to provide a method for producing a porous inorganic compound hollow capsule free from the disadvantages of the method for producing a microcapsule by the interface reaction method.

[0010]

In order to solve the above problems, the present invention provides a gel obtained by adding an oil gelling agent to a solution obtained by mixing an organic solvent and an inorganic compound wall film forming material,
A mixed solution is prepared by adding alcohol to the gel to prepare a mixed solution, and an aqueous solution whose pH has been adjusted is dropped into the mixed solution, and the mixture is allowed to stand for a required time. A gel film is formed, and the wall film forming material is hydrolyzed and polycondensed in the gel film to form a porous wall film. Thereafter, the gel film and the wall film are mixed. A method for producing a porous inorganic compound hollow capsule in which the gel film is eliminated by washing and heating the resulting product to leave only the porous wall film.

The particle size can be controlled by the droplet size of the aqueous solution, the thickness of the wall film can be controlled by the reaction time, and the functionality of the wall film can be controlled by selecting the metal alkoxide.

Further, silica powder is used as a wall film forming material,
A porous inorganic compound hollow capsule having a silica wall film can be obtained by using ammonia water having a pH of 13 as the dropping aqueous solution and setting the reaction time to 10 to 60 minutes.

On the other hand, an alumina powder is used as a wall film forming material, and an aqueous solution obtained by mixing distilled water having a pH of 5.7 and formamide in a ratio of 2: 1 to 1: 2 is used as a dropping aqueous solution.
The reaction time is set to 10 to 15 minutes, or an alumina powder is used as a wall film forming material, and a pH of 5.
The reaction time was 10 to 20 minutes using an aqueous solution obtained by mixing distilled water and formamide in a ratio of 1: 3, or an alumina powder was used as a wall film forming material, and a pH 2 aqueous hydrochloric acid solution was used as a dropping aqueous solution. And a reaction time of 10
By setting the time to 15 minutes, a porous inorganic compound hollow capsule having an alumina wall film is obtained.

Further, by using titanium oxide powder as a wall film forming material and using an aqueous solution in which water and a drying control agent are mixed at a required mixing ratio as a dripping aqueous solution, a porous inorganic compound hollow having a titanium wall film can be obtained. A capsule is obtained.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 (a), (b), (c) and (d) show an embodiment of the present invention. First, as shown in FIG. 1 (a), an organic solvent 1 such as decane and a metal alkoxide are used. After shaking a solution 3 in which a wall film forming material 2 made of silica powder as a mixture is mixed at a predetermined weight ratio, the solution 3 is mixed with LGBA (N
-Lauroyl-L-glutamic acid-.alpha.,. Gamma.-di-n-butylamide) to dissolve the oil gelling agent 4 by heating and then to cool the gel 5
The mixture 5 is further prepared by adding an alcohol 6 such as ethanol or methanol to the gel 5 to prepare a mixed solution 7 which is a four-component solution.

Next, as shown in FIG. 1 (b), a pH adjusted aqueous solution 9 is poured into a reaction vessel 8 using a micro syringe 10.
Is dropped into the four-component solution 7 therein, and allowed to stand at a required temperature for a required time. In this case, since the molecules of the oil gelling agent 4 in the mixed solution 7 before the aqueous solution 9 is dropped are subjected to solvation of the alcohol 6, the intermolecular hydrogen bond of the oil gelling agent 4 which is a main factor of gelation is reduced. When the aqueous solution 9 is dropped into the mixed solution 7 without being formed, as shown in FIG.
Aqueous solution (droplets) 9
As shown in FIG. 2 (b), the molecules of the gelling oil gelling agent 4 are hydrogen-bonded to each other, and the organic solvent 1 near the droplets is gelled to form a gel film 13 as shown in FIG. Become. Furthermore,
As shown in FIG. 2 (c), hydrolysis and polycondensation of silica as the wall film forming material 2 are performed in the gel film 13, and as a result, polymerization due to siloxane bonds ({Si—O—Si}) occurs. Since the formation of coalescence proceeds three-dimensionally, the porous wall film 14 having a network structure is formed. Therefore, the mixed solution 7
By allowing the mixture to stand inside, the product 11 in which the gel film 13 and the porous wall film 14 are mixed is obtained in the mixed solution 7 as shown in FIG.

The product 11 thus obtained is washed with hexane and collected by decantation.
By performing the heat treatment, the porous inorganic compound hollow capsule 12 as shown in FIG. in this case,
When the obtained product 11 is heated, the molecular motion of the solvent is intensified and the hydrogen bond is broken, so that the gel film 13 disappears as shown in FIG. 2D, but the siloxane bond is rather strengthened. Since the state is maintained, the porous wall film 14 remains.

The hollow capsule 12 obtained in the above-described manufacturing process can be used as a reinforcing material for an electrolyte plate constituting a fuel cell. In this case, when the matrix of the electrolyte plate is formed by mixing the hollow capsule 12 and the matrix is impregnated with a molten carbonate as an electrolyte, the molten carbonate enters the pores of the hollow capsule 12 and the fuel cell operates. When the molten carbonate is cooled from the temperature (650 ° C.) to room temperature and solidified, the molten carbonate that has entered the pores can be solidified as it is and can form a series with the molten carbonate around the hollow capsule 12. As a result, a series of gaps are not formed around the hollow capsule 12, and even if cracks generated from both sides of the electrolyte plate reach the hollow capsule, the cracks do not penetrate.

In the above, the particle size of the porous inorganic compound hollow capsule 12 can be controlled, for example, from about 1 mm to about 10 mm by adjusting the droplet size of the aqueous solution 9 with the micro syringe 9. , Wall membrane 14
Can be controlled by the combination of the mixed solution 7 and the reaction time (standing time).

Next, the case where the hollow capsule 12 is made larger than the above-mentioned particle size and the case where it is made smaller are described.

When manufacturing a hollow capsule 12 having a larger particle size, the dropping type as shown in FIG. 1 is difficult to produce a dropping solution having a large diameter, and the vibration in the dropping causes the mixed solution 7 and the surface to fluctuate. Since the necessity of providing an interval before the next drop increases, as shown in FIG. 3, the discharge pipe 22 of the aqueous solution tank 21 is positioned so as to be immersed in the mixed solution 7 in the reaction vessel 8, and the hollow capsule 12 to be obtained is obtained. By releasing the aqueous solution 9 having a volume corresponding to the particle diameter of the mixed solution 7 into the mixed solution 7, a product 11 having a desired diameter can be generated in the reaction vessel 8. In FIG. 3, reference numeral 23 denotes a mixed solution tank, 24 denotes a solid-liquid separation unit, 25 denotes a drying unit, and 26 denotes a mixed solution recovery line.

In the above case, the discharge pipe 2 of the aqueous solution tank 21
2 may be horizontal or vertical, and a fixed volume of aqueous solution 9
The product 11 having a diameter of up to several tens of mm can be produced by releasing
Is obtained.

On the other hand, hollow capsule 1 having a smaller particle diameter
4, the aqueous solution 9 is supplied from the inside of the blade 27 rotating at high speed, and the mixed solution 7 is continuously supplied into the container 28 surrounding the blade 27, as shown in FIG. I do. In addition, in FIG. 4, 29 shows a reaction curing part.

As a result, the product 11 having a diameter of several μm to several mm can be produced.
A hollow capsule 12 of about several mm is obtained. In addition, as the blade 27 that rotates at a high speed, a known device that can control the miniaturization by the liquid / liquid shearing force can be used. That is, a technique for producing a kind of microemulsion can be adopted.

In the control of the particle size of the hollow capsule 12 to be produced as described above, the time required for the reaction is substantially proportional to the volume of the product 11, so the reaction time is based on the cube of the change in the particle size. can do. That is, for example, when it is intended to produce a hollow capsule 12 having the same thickness as the wall film 14 but having a particle diameter of 1/2, the reaction time may be about 20% of the original particle.

In the above embodiment, the wall film forming material 2
Although the case where silica was used as the metal alkoxide as above was shown, alumina and titanium oxide can be used, and the functionality (pore distribution, pore diameter) of the wall film 14 can be controlled by selecting these metal alkoxides. Can be. Therefore, for example, by using a mixture of a plurality of metal alkoxides such as alumina and titanium oxide as the wall film forming material 2, the wall film 14 is formed into a layered shape having alumina on the outside and titanium oxide on the inside. It can be a composition component system, whereby the addition of functions to the wall film 14 can be controlled freely.

Hereinafter, the multi-component system will be specifically described.

First, as a basic shape, a structure gradient type (pattern) in which the void state of the wall film has a distribution between inside and outside, and a composition gradient type (pattern) in which the component composition of the wall film has a distribution between the inside and outside. And a composition-deflecting arrangement type (pattern) in which the formation reaction proceeds with the wall film deviating in its constituent components, and a uniform multiple-composition type (pattern) in which the constituent components of the wall film consist of a uniform multi-component composition. 4 with
There is a pattern.

The above patterns can be further divided into the following four patterns depending on the combination of the air gap states. [Pattern-1] As shown in FIG.
4 a, 14 b, and 14 c, having a dense and dense distribution of voids in the thickness direction, and a hole 15 having a diameter of “small, medium, and large” from the inside (lower side in the figure). In the case of two layers, the same applies to “small and large” from the inside. In this case, the specific substance 16 can be incorporated from the outside to the inside,
Further, the outer specific substance 16 can be selectively bent out at the inner hole. [Pattern-2] As shown in FIG. 6, the distribution of voids is dense and dense in the thickness direction of the wall film 14, and the distribution is of the reverse arrangement type to that of FIG. In this case, the specific substance 17 contained inside can be gradually released to the outside as needed. [Pattern-3] As shown in FIG. 7, the type of arrangement is such that the distribution of voids is dense and dense in the thickness direction of the wall film 14 and the pore diameter is "medium, large and small" from the inside (or outside). In this case, when the movement of the substances 18 and 19 between the inside and the outside occurs,
Within which the selectivity of the material change can be controlled. [Pattern-4] As shown in FIG. 8, this is an arrangement type having a density distribution of voids in the plane direction of the wall film 14. in this case,
The specific substance 20 is taken in from the outside to the inside,
Are inside the other substances 20a, 20b, 2 due to decomposition reaction or the like.
0c, etc., the altered substances 20a, 20b, 20
Among c, for example, the substance 20c can be released to the outside again. Such movement of the substance can be selectively caused by the pore diameter. The same applies when mass transfer is reversed.

Next, there are the following two patterns depending on the arrangement of the constituent elements. [Pattern-1] As shown in FIG. 9, the wall film 14 is of a type composed of wall film layers 14d, 14e and 14f made of different constituent elements. In this case, acid resistance is required on the outside,
It is used when base resistance is required inside, or when oxidation reactivity is required outside and reduction reactivity is required inside. For example, when a disinfecting catalyst function is provided, the outside is made of Ti-based, and the inside is made of Pt or Ru-based. [Pattern-2] As shown in FIG. 10, the distribution of constituent elements (for example, A and B) gradually changes in the thickness direction of the wall film 14. In this case, the inner constituent element B gradually changes to form an outer film. As for the function, the expected function inside and outside the particle is different, as in Pattern-1, but there is no clear difference in the function compared to Pattern-1, and the change over time It is effective against gradually occurring phenomena such as control. For example, holding the Li-rich carbonate in the hollow portion, the wall film inside Li abundance large LiAlO _2, wall membrane outside Li: Al abundance ratio of 1: 1 particles of conditions such as LiAlO ₂ (Capsule ), These particles function as a reservoir in a carbonate such as a molten carbonate fuel cell as follows. That is, (i) in the initial stage, Li in the external molten carbonate is full, so mass transfer hardly occurs, but (ii) with time, the Li component in the external carbonate corrodes and evaporates. When the abundance ratio decreases due to loss, the Li concentration gradient inside and outside the particles increases,
The Li component in the hollow portion starts moving from the inside to the outside through the pores and the wall film of the wall film, (iii) shortly, mass transfer stops at a certain equilibrium state in a concentration gradient, and (iv) further time elapses Then, the state (ii) is reached, and mass transfer starts, and such movement and release of the internal substance are repeated as necessary until mass transfer due to the concentration gradient does not completely occur.

Next, as shown in FIG. 11, the above-mentioned pattern is of a type in which, for example, different constituent element compositions 14g and 14h are arranged differently in the plane direction of the wall film 14.

The pattern is of a type in which the constituent elements of the wall film 14 are uniform.

[0034]

Next, embodiments of the present invention will be described. [Example 1] The present inventors first performed the following experiments in order to obtain a uniform solution when preparing a mixed solution 7 as a four-component solution. That is, using decane as the organic solvent 1,
Tetraethoxysilane (TEOS) as the wall film forming material 2
Using LGBA as the oil gelling agent 4, methanol and ethanol were used as the alcohol 6, respectively. As a result, a homogeneous solution was obtained when methanol was used as the alcohol 6 with decane / TEOS = 7:
3: 4: 6, and when ethanol is used, decane /
It was limited to the case of TEOS = 10: 0 to 4: 6, and a uniform solution could not be obtained with other mixing ratios for both methanol and ethanol. The presence of silica in capsules prepared by dropping the aqueous solution 9 into the uniform mixed solution 7 was observed in the range of decane / TEOS = 7: 3 to 4: 6.

Based on this experimental result, decane / TE
OS = 1: 1, decane / ethanol / ethanol / LGBA = 45: 4 using ethanol as alcohol 6
The mixed solution 7 having a weight ratio of 5: 9.5: 0.5 was used.

In the mixed solution 7 having the above weight ratio, various pH values (2.0, 3.4,
When the aqueous solution 9 of 5.7, 7.2, 11, 13) was added dropwise to obtain the product 11, the amount of silicon in the wall film 14 was large when the aqueous solution 9 of pH 2.0 and 13 was used. It turned out to be. Considering that the hydrolysis of metal alkoxide can promote the reaction by using an acid or a base as a catalyst, the reactivity of TEOS is increased by using water having a high H ⁺ ion concentration or OH ^- ion concentration. However, as a result, it is considered that a polymer was easily generated by the siloxane bond.

Next, when the obtained product 11 was to be washed with hexane, it was destroyed during washing or when it was collected from the solution, and could not be isolated. This is probably because the dissociation degree α of the aqueous sodium hydroxide solution is α ≒ 1. Thus, isolation was achieved using ammonia water having a degree of dissociation α << 1.

When the product 11 produced by dropping the aqueous ammonia was immersed in hexane at 25 ° C. and heated to about 70 ° C., only the product 11 produced using aqueous ammonia having a pH of 13 was converted into a white solid ( Silica) remained in hexane, and the product using ammonia water having a pH of 11 or less disappeared. This is because, when using aqueous ammonia 9 having a pH of 13, that is, an aqueous solution 9 having a high OH ^- ion concentration, the base acts as a catalyst to increase the reactivity of TEOS. It is considered that a film was formed. On the other hand, when the aqueous solution 9 having a pH of 11 or less was used, it is considered that no catalyst was present in the neutral pH range of the aqueous solution 9, so that the reactivity of TEOS became poor and the silica wall was not obtained. . If the pH of the aqueous solution 9 is low, that is, if the H ⁺ ion concentration is high, the acid acts as a catalyst, so that the reactivity of TEOS increases and the amount of silica occupying the wall film increases. Contrary to this, it is probable that, because the siloxane bond proceeds one-dimensionally, the degree of polymerization was insufficient and a silica wall film could not be obtained.

The relationship between the reaction time (standing time) of the product 11 in the mixed solution 7 and the silica wall film was considered.
When the reaction time was set to 10 minutes or less, the reaction was insufficient, and the collapse of the wall film was observed. When the reaction time was 60 minutes or more, the mass was not hollow but solid. Therefore, the result that the reaction time should be 10 to 60 minutes in order to obtain a hollow capsule was obtained.

When the product 11 after washing was heat-treated at 700 ° C. for 6 hours, pores of about 5 μm due to spherical silica particles (secondary particles) not observed before the heat treatment were observed. It is considered that the pores were filled with an organic substance before the heat treatment. Further, when heat treatment was performed at 1050 ° C. for 2 hours, spherical silica particles were not observed. This is 1
It is considered that sintering of the silica particles occurred due to the high temperature of 050 ° C., but it was found that the capsule was porous because of the presence of many pores.

From the above, the amount of silica contained in the wall film 14 depends on the pH of the dropping aqueous solution 9 and the degree of dissociation.
When ammonia water was used, the reaction time was significantly increased, and the film thickness was changed from the reaction time (resting time) between the dropping of ammonia water of pH 13 to the mixed solution (decane / TEOS / LGBA / ethanol) 7 and the collection. ), A hollow product 11 can be formed in 10 to 60 minutes, and furthermore, heat treatment removes organic substances on the surface, strengthens Si—O bonds, and forms a porous inorganic compound having a silica wall film. The result was that the hollow capsule 12 could be manufactured. [Example 2] Next, a case of producing a porous inorganic compound hollow capsule 12 having an alumina wall film will be described.

Fluorobenzene was used as the organic solvent 1, aluminum isopropoxide (AIP) was used as the wall film forming material 2, LGBA was used as the oil gelling agent 4, and ethanol was used as the alcohol 6. The procedure is
Almost in the same manner as in Example 1, first, 2.5 g of a solution obtained by mixing 0.5 g of AIP and 2.0 g of fluorobenzene (9
(0 wt%) in a hot water bath to dissolve the AIP, add 0.014 g (0.5 wt%) of LGBA, prepare a gel 5 by a heat dissolution method, and add 0.24 g of ethanol ( 9.5 wt%) to prepare a mixed solution 7, and a dropping aqueous solution 9 was added to the mixed solution 7 by a micro syringe 1.
Using 0, the solution was dropped (5 μl) and allowed to stand for several tens minutes. The obtained product 11 was washed with hexane heated to 70 to 80 ° C., collected by decantation, and heat-treated to produce a porous alumina hollow capsule.

In the above, the pH of the aqueous solution 9 was adjusted to pH 2
Hydrochloric acid aqueous solution (HClaq), distilled water of pH 5.7, pH 13
The production of capsules was attempted using aqueous sodium hydroxide solution (NaOHaq) and aqueous ammonia, respectively. As a result, regardless of the pH of the solution, the product 11 became a solid mass and did not become hollow. This is considered as follows. Aluminum in aluminum alkoxide (Al (OR) ₃ ) is not in a saturated state and can take three stable coordination numbers, so that it is susceptible to nucleophilic coordination. From the kinetic point of view, aluminum is quite susceptible to nucleophilic reactions, so that the reaction rates of hydrolysis and polycondensation of aluminum alkoxides are usually limited to alkoxysilanes (Si (OR) having only one stable coordination number. ₄ ) Very large compared to ₄ ). For this reason, the hydrolysis and polycondensation reaction of AIP, which is an aluminum alkoxide, proceeds in a short time, and it is considered that the capsules are not hollow but have become a solid mass. Therefore,
Experiments were carried out by varying the standing time (reaction time) and the reaction temperature. However, no hollow capsule was obtained, and the wall membrane collapsed or lumps were formed. Therefore, for aqueous solutions
It was found that it was difficult to control the reaction rate of AIP only by changing the pH.

As described above, it has been found that it is difficult to control the reaction rate of AIP with the aqueous solution 9 in which only the pH is changed. Two points of reduction, control of reaction temperature and reaction time were considered.

First, an attempt was made to control the hydrolysis reaction of AIP by reducing the amount of water in the aqueous solution 9 (decreasing the concentration of water), that is, by reducing the absolute amount of water reacting with AIP. Therefore, formamide, which is a polar solvent that is soluble in water but insoluble in oil and does not react with AIP, is mixed with water of various pHs to form a dropping aqueous solution 9, and the temperature is adjusted to 10 to suppress the reaction rate. C. was performed. Table 1 shows the results obtained at this time.

[0046]

[Table 1] In the case of an aqueous solution in which formamide was mixed with water having a pH of 13 (NaOHaq or aqueous ammonia), no hollow product 11 was observed regardless of the amount of formamide added (indicated by x in Table 1). However, an aqueous solution 9 mixed at a weight ratio of water / formamide = 1: 2 or 1: 3 was used and the standing time (reaction time) was set to 10 to 15 minutes, or water / formamide having a pH of 5.7 was used. = 2: 1 ~
An aqueous solution 9 mixed at a weight ratio of 1: 2 and a standing time of 10 to 15 minutes is used. In the case of an aqueous solution 9 mixed at a ratio of 1: 3, a solution left to stand for 10 to 20 minutes produces a hollow. Thing 1
1 was obtained (indicated by ○ in Table 1).

As a result of the experiment, a hollow capsule was obtained by using an aqueous solution 9 prepared by mixing an acidic aqueous solution of pH 2 or water of neutral pH 5.7 with formamide in the above weight ratio. The reason is considered as follows.

When a hollow silica capsule is produced in Example 1, the polymer obtained as a result of the hydrolysis and polycondensation reaction of TEOS is converted into a three-dimensionally formed basic aqueous solution. It was stated that a hollow capsule with a strong wall film formed could be obtained. However, when producing alumina hollow capsules, unlike the case of silica, it is necessary to form a wall film having the strength that can withstand the hollow capsules at the interface between the droplet and the mixed solution while suppressing the reaction rate of AIP. There is. for that reason,
By making a solution in which formamide which does not react with AIP is mixed into a dropping aqueous solution, the absolute amount of water in the aqueous solution is reduced (the concentration of water is reduced) to suppress the hydrolysis reaction of AIP. The reaction of AIP is further suppressed by mixing a neutral aqueous solution (pH 5.7) that has no catalytic action in the reaction or an acidic aqueous solution (pH 2) that is unsuitable for the formation of the Balta body because the reaction proceeds one-dimensionally. It is considered that a hollow capsule was obtained because of this. When other aqueous solutions are used, A
The capsule obtained because the hydrolysis reaction of IP could not be suppressed was observed to have a phenomenon that the capsule collapsed because the AIP did not react because the mass was full or the amount was too low.

From the above, the reaction temperature was set at 10 ° C.
5.7 distilled water / formamide = 2: 1 to 1: 2 (wt%)
10 to 15 when the aqueous solution mixed with
Minutes, 1: 3 when the standing time was 10 to 20 minutes, and pH 2 aqueous hydrochloric acid / formamide = 1: 3.
A porous inorganic compound hollow capsule 12 having an alumina wall film can be produced when the standing time when using an aqueous solution mixed at 2: 1, 3 (wt%) is 10 to 15 minutes. The result was obtained. Example 3 Next, a case of manufacturing a porous inorganic compound hollow capsule 12 having a titanium wall film will be described.

N-tetradecane is used as the organic solvent 1, titanium tetraisopropoxide (TTIP) is used as the wall film forming material 2, LGBA is used as the oil gelling agent 4, isopropanol is used as the alcohol 6, and a dropping aqueous solution 9 is used. Drying Control Chem
As ical additive (DCCA), ethylene glycol, diethylene glycol, formamide, 1,3-butanediol, and glycerin were used.

1.6 g of n-tetradecane and 0.1 g of TTIP.
To 1.8 g of solution 3 mixed with 2 g,
g of the obtained gel 5 was prepared by a heat dissolution method, and 0.19 g of isopropanol was added to the obtained gel 5 and redissolved to obtain a mixed solution (n-tetradecane: TTIP: LGB).
A: Isopropanol = 80: 10: 0.5: 9.5
(Wt%)) 7 and an aqueous solution 9 to which various amounts of a drying control agent were added in a predetermined amount was added to a microsyringe 10 for 5 μm.
l It was dropped and allowed to stand at 25 ° C. for 10 minutes. The product 11 obtained here was washed with hexane, collected by decantation, and heat-treated to produce a porous titanium oxide hollow capsule.

In the above description, the drying control agent was used in the drying process of the product 11 to remain in the product 11 until after the water and to prevent cracks caused by an increase in surface tension. Therefore, the above five kinds of substances having a higher boiling point than water and having a small surface tension were used as a drying control agent, and each was added to water at a predetermined mixing ratio to form a dropping aqueous solution 9, as shown in Table 2. A hollow capsule was obtained.

[0053]

[Table 2] As a result of the experiment, when the aqueous solution 9 having the mixing ratio of the mark x in Table 2 was used, the particles were tentatively formed, but could not be obtained as particles. On the other hand, when the aqueous solution 9 having the mixing ratio indicated by ○ was used, a hollow capsule was obtained.

From the above, while the formamide in the aluminum system was only for adjusting the concentration of the reaction water, the drying control agent in the titanium system was used to dry the inclusions from the inclusion voids during the formation of the wall film in order to assist in maintaining the shape. It was confirmed that it also had the role of performing the removal step by step.

[0055]

As described above, according to the method for producing a porous inorganic compound hollow capsule of the present invention, an oil gelling agent is added to a solution obtained by mixing an organic solvent and an inorganic compound wall film forming material. A gel is prepared, and a mixed solution is prepared by adding alcohol to the gel to prepare a mixed solution.
While dropping the adjusted aqueous solution and allowing it to stand for the required time,
A gel film is formed around the dropped aqueous solution by an interfacial gelation reaction, and the wall film forming material is hydrolyzed and polycondensed in the gel film to form a porous wall film. After that, after washing the product in which the gel film and the wall film are mixed, the gel film is eliminated by heat treatment so that only the porous wall film is left, so that the manufacturing process is simple, In addition, excellent effects such as easy control of particle size and wall thickness, and addition of a function to a wall film as a functional material are exhibited.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a method for producing a porous inorganic compound hollow capsule according to the present invention, wherein (a), (b), and (c).
(D) is a schematic diagram showing a manufacturing process.

FIGS. 2A and 2B show the principle of manufacturing a capsule, wherein FIG. 2A is a schematic view showing a state in which alcohol moves into a droplet, FIG. 2B is a schematic view showing a state in which a gel film is formed, and FIG. FIG. 4D is a schematic diagram showing a state in which a porous wall film is formed in the film, and FIG. 4D is a schematic diagram showing a state in which only the porous wall film remains.

FIG. 3 is a schematic diagram showing another embodiment of the present invention.

FIG. 4 is a schematic diagram showing still another embodiment of the present invention.

FIG. 5 is a conceptual diagram showing an example of a multi-composition component system of a capsule and showing an example of a structure-graded type.

FIG. 6 is a conceptual diagram showing another example of a structure-graded type, which shows a multi-component system of a capsule.

FIG. 7 is a conceptual diagram showing still another example of a structure-graded type, which shows a multi-component system of a capsule.

FIG. 8 is a conceptual view showing a multi-component system of a capsule and showing still another example of a structure-graded type.

FIG. 9 is a conceptual diagram showing an example of a composition gradient type, which shows a multi-component system of a capsule.

FIG. 10 is a conceptual diagram showing another example of a composition gradient type, showing a multiple component system of a capsule.

FIG. 11 is a conceptual diagram showing a multiple component system of a capsule and showing an example of a composition deflection arrangement type.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 organic solvent 2 wall film forming material 3 solution 4 oil gelling agent 5 gel 6 alcohol 7 mixed solution 9 aqueous solution 11 product 13 gel film 14 wall film

Claims (6)

[Claims] An oil gelling agent is added to a solution obtained by mixing an organic solvent and a wall film forming material made of an inorganic compound to form a gel.
A mixed solution is prepared by adding alcohol to the gel to prepare a mixed solution, and an aqueous solution whose pH has been adjusted is dropped into the mixed solution, and the mixture is allowed to stand for a required time. A gel film is formed, and the wall film forming material is hydrolyzed and polycondensed in the gel film to form a porous wall film. Thereafter, the gel film and the wall film are mixed. A method for producing a hollow capsule made of a porous inorganic compound, characterized in that the gel film is eliminated by heat treatment after washing the washed product, leaving only a porous wall film. 2. The method for producing a hollow capsule of a porous inorganic compound according to claim 1, wherein silica powder is used as a wall film forming material, ammonia water having a pH of 13 is used as a dropping aqueous solution, and the reaction time is 10 to 60 minutes. 3. An alumina powder is used as a wall film forming material,
2. The porous inorganic compound hollow capsule according to claim 1, wherein an aqueous solution obtained by mixing distilled water having a pH of 5.7 and formamide at a ratio of 2: 1 to 1: 2 is used as the dropping aqueous solution, and the reaction time is set to 10 to 15 minutes. Manufacturing method. 4. An alumina powder is used as a wall film forming material,
An aqueous solution obtained by mixing distilled water having a pH of 5.7 and formamide at a ratio of 1: 3 was used as the dropping aqueous solution.
The method for producing a porous inorganic compound hollow capsule according to claim 1, wherein the time is from 0 to 20 minutes. 5. An alumina powder is used as a wall film forming material,
The method for producing a hollow capsule of a porous inorganic compound according to claim 1, wherein a hydrochloric acid aqueous solution having a pH of 2 is used as the dropwise aqueous solution, and the reaction time is set to 10 to 15 minutes. 6. The porous inorganic compound hollow capsule according to claim 1, wherein titanium oxide powder is used as a wall film forming material, and an aqueous solution obtained by mixing water and a drying control agent at a required mixing ratio is used as a dropping aqueous solution. Production method.