JP2002224576A - Method for manufacturing titanium oxide-coated fine hollow glass sphere - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a titanium oxide-coated fine hollow glass sphere having a high strength, an excellent whiteness degree, and a good photocatalytic function, by expanding a volcanic vitreous deposit as a raw material and at the same time, denaturing coated titanium oxide hydrate to titanium oxide during a heat treatment, and controlling the crystal size to 10 nm or less. SOLUTION: After a volcanic vitreous deposit powder is dispersed in an aqueous acid solution containing titanium ions and aluminum ions so that the concentration of the powder is 5-40 mass%, an aqueous solution of hydrogen carbonate is added to the suspension to deposit titanium oxide hydrate and aluminum oxide hydrate on the powder surface. Subsequently, the powder is taken out to be washed and dried, and then heat-treated at 900-1100 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a photocatalyst having high strength, good whiteness, and a crystal size of coated titanium oxide controlled to 10 nm or less, using a volcanic glassy deposit as a raw material. And a method for efficiently producing a titanium oxide-coated fine hollow glass sphere.

[0002]

2. Description of the Related Art Fine hollow glass spheres have a low specific gravity and are excellent in heat resistance, so they are used as lightweight fillers for various metals, ceramics, concrete, plastics and the like. Although it has been used as a filler having a photocatalytic function, such as plastics, a fine hollow glass sphere having titanium oxide supported on its surface has recently attracted attention as a lightweight photocatalyst.

Hitherto, as a method for producing a fine hollow glass sphere from a volcanic vitreous sediment as a raw material, shirasu fine particles are fired at a temperature of 800 to 1200 ° C. for 10 seconds to 10 minutes and then fired in water A method for producing a fine hollow glass sphere by specific gravity separation or air classification is known (Japanese Patent Publication No. 48-17645). On the other hand, as a pretreatment of the raw material, volcanic glassy sediment powder is dispersed in an aqueous solution containing aluminum sulfate, and a precipitant is added dropwise at room temperature, whereby alumina hydrate is added to the particle surface of the powder. After coating, heat and foam, particle size is 20μm
A method for producing the following ultrafine hollow glass spheres is known (Japanese Patent Application Laid-Open No. 9-263425).

[0004] However, in order to produce a titanium oxide-coated fine hollow glass sphere, the fine hollow glass sphere obtained by these methods is coated with titanium oxide and then heat-treated again for fixing. Need to be performed, the efficiency is inevitably reduced. In order to remedy such drawbacks, the present inventors have previously prepared a titanium oxide-coated fine hollow glass sphere having a photocatalytic function of high strength and excellent whiteness using a volcanic glassy deposit as a raw material. A method has been proposed in which the coated titanium oxide hydrate is modified into titanium oxide at the same time as the foaming is performed by a single heat treatment to efficiently produce the titanium oxide (JP-A-2000-86292).

By the way, in order for titanium oxide to effectively act as a photocatalyst, the crystal size of titanium oxide is desirably 10 nm or less. However, in this method, it is difficult to control the crystal size of titanium oxide which is important as a photocatalyst. No titanium oxide with a small crystal size could be obtained.

[0006]

SUMMARY OF THE INVENTION Under such circumstances, the present invention uses a volcanic glassy sediment as a raw material to form a titanium oxide of a coated titanium oxide hydrate simultaneously with foaming by a single heat treatment. And the crystal size is reduced to 10n.
The purpose of the present invention is to provide a method for efficiently producing a titanium oxide-coated fine hollow glass sphere having a high strength, excellent whiteness, and a good photocatalytic function, which is controlled to not more than m.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies on a method for producing a titanium oxide-coated fine hollow glass sphere having a photocatalytic function from a volcanic glassy deposit as a raw material. And after dispersing the volcanic glassy sediment powder in an acid aqueous solution containing aluminum ions, and then precipitating this with a precipitant,
It has been found that a mixed hydrate of titanium oxide hydrate and aluminum oxide hydrate precipitates on the surface of the powder particles, and the present invention has been completed based on this finding.

That is, according to the present invention, a volcanic glassy sediment powder is dispersed in an aqueous acid solution containing titanium ions and aluminum ions so that the concentration thereof becomes 5 to 40% by mass, and then the suspension is prepared. A bicarbonate aqueous solution is added to the liquid to precipitate titanium oxide hydrate and aluminum oxide hydrate on the powder surface, and then the powder is taken out, washed, dried, and then heat-treated at a temperature of 900 to 1100 ° C. Another object of the present invention is to provide a method for producing a titanium oxide-coated fine hollow glass sphere.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the method of the present invention, a volcanic glassy deposit used as a raw material is a mineral that naturally occurs as shirasu, obsidian, perlite, pine stone, etc., which are usually SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , CaO, M
gO, consists Na ₂ O and K ₂ O, it contains 3-10 wt% moisture.

In the method of the present invention, these volcanic glassy deposits are pulverized or crushed, and a fraction having a particle size of usually 50 μm or less is classified and used by dry classification or wet classification.

In the method of the present invention, first, the volcanic glassy sediment powder thus obtained is added to an aqueous acid solution containing titanium ions and aluminum ions so that the powder concentration becomes 5 to 40% by mass. To prepare a suspension. If the powder concentration is outside the above range, the effects of the present invention will not be sufficiently exhibited. The preferred concentration of the powder is in the range of 10 to 30% by mass.

The concentration of titanium ions in the aqueous solution used at this time is not less than 0.01 mol / liter, especially 0.1 mol / l.
The range is preferably from 0.5 to 0.2 mol / liter. Also,
The aluminum ion concentration is preferably at least 0.005 mol / l, and particularly preferably in the range of 0.01 to 0.2 mol / l. On the other hand, the concentration of the aqueous acid solution is preferably at least 0.02 mol / l, particularly preferably in the range of 0.1 to 3 mol / l.

A water-soluble titanium compound is used as a source of titanium ions used for preparing the aqueous solution. Examples of such a compound include titanium chloride, titanium sulfate, and titanium nitrate. Also,
As a supply source of aluminum ions, a water-soluble aluminum compound is used. Examples of such a compound include aluminum chloride, aluminum sulfate, and aluminum nitrate. On the other hand, as the acid aqueous solution, for example, an aqueous solution of a mineral acid such as hydrochloric acid, sulfuric acid, and nitric acid is used.

In the method of the present invention, a preferable combination of a titanium ion supply source and an aluminum ion supply source used for preparing the acid aqueous solution includes, for example, titanium chloride and aluminum chloride or titanium sulfate and aluminum sulfate. When using a combination of chlorides, it is preferable to select hydrochloric acid as the acid, and when using a combination of sulfates, it is preferable to select sulfuric acid as the acid.

In the present invention, while stirring the suspension prepared by dispersing the volcanic glassy sediment powder in the acid aqueous solution containing titanium ion and aluminum ion prepared as described above, this is used as a precipitant. An aqueous solution of bicarbonate is gradually added to precipitate a mixed hydrate composed of titanium oxide hydrate and aluminum oxide hydrate on the particle surfaces of the powder. Examples of the bicarbonate aqueous solution include an aqueous solution containing one or more of sodium bicarbonate, potassium bicarbonate, lithium bicarbonate, ammonium bicarbonate and the like, but are easy to handle and high in yield. And an aqueous solution containing ammonium hydrogen carbonate.

The concentration of the aqueous hydrogen carbonate solution is 3 mol /
Liter or less, and particularly preferably in the range of 0.5 to 2 mol / liter. As the addition amount of the aqueous hydrogencarbonate solution, a stoichiometric amount necessary for neutralizing the aqueous acid solution containing titanium ions and aluminum ions is usually used. In addition, the temperature of the suspension at the time of adding the bicarbonate aqueous solution is usually room temperature, but may be appropriately heated if necessary.

By such a treatment, a mixed hydrate composed of titanium oxide hydrate and aluminum oxide hydrate precipitates on the surface of the volcanic glassy sediment powder and forms a coating, thereby forming water inside the particles. Is secured.

Next, the suspension is subjected to solid-liquid separation, which can be performed by known means such as filtration, centrifugation, decantation and the like. The solid separated in this manner is sufficiently washed by washing with water or the like, and then dried. Next, the dried powder is heat-treated at a temperature in the range of 900 to 1100 ° C. to foam. By this heat treatment, the surface of the foamed particles is covered with titanium oxide and aluminum oxide, so that fusion between the particles is effectively prevented. This heat treatment time varies depending on the processing conditions, but is usually 1 hour.
６０60 seconds.

If the heat treatment temperature is lower than 900 ° C., foaming does not occur sufficiently, and if it exceeds 1100 ° C., fusion between particles occurs. Also, if the heat treatment time is short, it will not foam enough,
If the length is too long, fusion between the particles occurs, so that the length is appropriately adjusted.

The thus heat-foamed is a light-weight hollow body, but a lighter-weight hollow body can be recovered by a specific gravity difference, for example, by classification with water or air.

According to such a method, a titanium oxide-coated fine hollow glass sphere having a photocatalytic function having a particle diameter of 50 μm or less and a particle density of 1 g / cm ³ or less can be obtained. The coated titanium oxide usually has an anatase type having a high photocatalytic function and a crystal size of 10 nm or less.

[0022]

According to the present invention, volcanic glassy sediment fines
Using powder, high strength, excellent whiteness, crystal size of 10
Titanium oxide coated fine hollow glass spheres controlled to below nm
The shape can be efficiently produced. Obtained by the method of the present invention.
The titanium oxide coated fine hollow glass spheres
Ceramics, concrete, plus
It is useful as a lightweight filler such as Chicks.
In addition, you mainly controlled the crystal size to 10 nm or less.
Coated with titanium oxide
NO by sunlight _xDecomposed or floating on water
It can be used effectively to decompose oil, paint and other materials
To be used as a filler to give a photocatalytic function to the filler
Can be. This paint is applied to the wall and has a photocatalytic function.
An environmental purification wall can be formed. Also,
Method and apparatus for purifying a contaminated fluid developed earlier by the present inventors
(Japanese Patent Application No. 11-365264)
It is possible to efficiently purify the contaminated fluid.

[0023]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 A volcanic glassy sediment having a composition shown in Table 1 (from Nakano, Iizaka-cho, Fukushima-shi, Fukushima Prefecture, commonly known as Nakano Shirato) was crushed to prepare a powder raw material.

[0025]

[Table 1]

Sodium hexametaphosphate 0.1% by mass
The above-mentioned powdery raw material was put into an aqueous solution, and classified with a water filter at a separation particle size of 10 μm. Next, classification was performed using tap water at a separation particle size of 30 μm. Particle size 3 contained in classified particles
The ratio of particles exceeding 0 μm and the ratio of particles having a particle size of less than 10 μm were 10% by mass or less in each case.

Next, 38 parts by mass of the classified powder are added to 250 parts by mass of a 0.25 mol / l hydrochloric acid aqueous solution containing 0.10 mol / l of titanium chloride and 0.01 mol / l of aluminum chloride. While stirring at room temperature, an aqueous solution of ammonium hydrogencarbonate having a concentration of 1.05 mol / liter was added dropwise over 2 hours so that titanium chloride, aluminum chloride and hydrochloric acid had an equivalent amount for neutralization. Thereafter, the coated solid was filtered, washed with water, and dried.
The dried powder is supplied to a heating and foaming apparatus having a maximum temperature of 1000 ° C., and is passed through the apparatus in about 3 seconds to foam and then collected. The titanium oxide-coated fine particles having a particle density of 0.65 g / cm ³ are collected. A hollow glass sphere was obtained.

Example 2 38 parts by mass of the powder used in Example 1 was mixed with 0.1 parts of titanium chloride.
0 mol / l and aluminum chloride 0.10 mol /
The mixture was added to 250 parts by mass of a 0.25 mol / liter hydrochloric acid aqueous solution containing 1 liter and stirred at room temperature.
An aqueous solution of ammonium bicarbonate having a concentration of 50 mol / liter was added dropwise over 2 hours such that titanium chloride, aluminum chloride and hydrochloric acid had an equivalent amount for neutralization. Thereafter, the coated solid was filtered, washed with water, and dried. The dried powder is supplied to a heating and foaming apparatus having a maximum temperature of 1000 ° C., and is passed through the apparatus in about 3 seconds to foam and then collected. The titanium oxide-coated fine particles having a particle density of 0.63 g / cm ³ are collected. A hollow glass sphere was obtained.

Comparative Example 1 In Example 1, without adding aluminum chloride,
Performed in the same manner as in Example 1, except that the concentration of the aqueous solution of ammonium hydrogen carbonate was replaced with 1.00 mol / L,
A titanium oxide-coated fine hollow glass sphere having a particle density of 0.71 g / cm ³ was obtained.

Comparative Example 2 The procedure of Example 1 was repeated, except that the aluminum chloride was replaced with iron chloride.
A titanium oxide-coated fine hollow glass sphere of 67 g / cm ³ was obtained.

Comparative Example 3 The procedure of Example 2 was repeated, except that the aluminum chloride was replaced with iron chloride.
A titanium oxide-coated fine hollow glass sphere of 64 g / cm ³ was obtained.

The particle densities of Examples 1 and 2 and Comparative Examples 1 to 3 before heating and foaming were all 2.35 g / cm ³ .

Example 3 38 parts by mass of the same classified volcanic glassy sediment powder as in Example 1 were subjected to a concentration of 0.20 mol / l containing 0.10 mol / l of titanium sulfate and 0.10 mol / l of aluminum sulfate. And a 2 mol / liter aqueous ammonium bicarbonate solution was added dropwise over 2 hours while stirring at room temperature so that titanium sulfate, aluminum sulfate and sulfuric acid would have an equivalent amount to neutralize.
The solid material thus coated is filtered, washed with water,
Dried. The dried powder was supplied to a heating and foaming apparatus having a maximum temperature of 1000 ° C., passed through the apparatus for about 3 seconds, foamed, and then collected to obtain a titanium oxide-coated fine hollow glass spherical body. The particle density and crystal size of this sample,
In all of the NO _x purification abilities, results almost equivalent to those of Example 2 were obtained.

Reference Example 1 The titanium oxide-coated fine hollow glass spheres obtained in Examples 1 and 2 and Comparative Examples 1 to 3 were subjected to powder X-ray diffraction. The result is shown in FIG. This figure shows that the titanium oxide coated in all samples is anatase. In addition, the gentle peak of 20 to 30 ° observed in all the samples is a halo of fine hollow glass spheres.

In FIG. 1, the crystal size calculated from Scherrer's formula based on the peak of the (101) plane of anatase observed near 25.3 ° is 9.4 in Example 1.
nm, Example 2 is 7.3 nm, Comparative Example 1 is 13.3 n
m, Comparative Example 2 is 12.9 nm, Comparative Example 3 is 12.6 nm
Met. From this result, it can be seen that the addition of aluminum controls the crystal size to 10 nm or less. Further, it can be seen that the addition of iron in Comparative Examples 2 and 3 did not contribute to the control of the crystal size.

Reference Example 2 The titanium oxide-coated fine hollow glass spheres obtained in Examples 1 and 2 and Comparative Examples 1 to 3 were obtained by the following method.
The NO _x purification ability was measured. ^On a filter plate having an area of 36 cm ² , 0.2 g of the sample was spread evenly, and the center wavelength was 254 nm.
While irradiating the ultraviolet lamp intensity 0.44 mW / cm ^2, concentration of NO _x after passed a rate of 0.5 liters / min from the bottom of the initial concentration 5ppm pseudo contaminated air adjusted to a concentration of NO _x filtration plate Was measured. After the purified air passed through passed through at the same speed, it was repeated 10 times the task of measuring the concentration of NO _x. The relationship between the number of repetitions and the concentration of NO _x shown graphically in Figure 2.

As shown in FIG. 2, by controlling the crystal size of titanium oxide to 10 nm or less by adding aluminum,
It can be seen that the purification of NO _x has been dramatically improved. Comparative Example 1 in which iron was not added due to the fact that the addition of iron in Comparative Examples 2 and 3 did not contribute to the control of the crystal size, and was colored by the coated iron and impeded the transmission of ultraviolet light.
As a result, purification of NO _x was inferior.

[Brief description of the drawings]

FIG. 1 is a powder X-ray diffraction diagram of titanium oxide-coated fine hollow glass spheres obtained in Examples 1 and 2 and Comparative Examples 1 to 3.

FIG. 2 is a graph showing the NO _x purification ability of titanium oxide-coated fine hollow glass spheres obtained in Examples 1 and 2 and Comparative Examples 1 to 3.

[Procedure amendment]

[Submission date] January 31, 2001 (2001.1.3)
1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

Patent application title: Method for producing fine hollow glass spheres coated with titanium oxide

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) C03C 17/23 B01D 53/36 102D (72) Inventor Yoshitada Nemoto 2-24 Karanori, Higashi-ku, Fukuoka City, Fukuoka Prefecture No. 47 (72) Inventor Shigeru Kanamaru F-term (reference) 4D048 AA06 BA03X BA07X BA10X BA41X BB01 EA01 4G059 AA20 AB01 AB02 AB09 AC22 EA04 EA07 EB05 4G069 A14BA14B14A14B BB08C BB10C BC16C BC50C BD12C CA01 CA13 DA05 EA04X EA04Y EA30 EB18X EC22Y FA03 FB08 FC02 FC07 FC08

Claims (6)

[Claims] A volcanic glassy sediment powder is added to an aqueous acid solution containing titanium ions and aluminum ions.
After dispersing so that the concentration becomes 5 to 40% by mass, an aqueous hydrogen carbonate solution is added to this suspension to precipitate titanium oxide hydrate and aluminum oxide hydrate on the powder surface, Next, the powder is taken out, washed and dried, and then 900
A method for producing a titanium oxide-coated fine hollow glass sphere, wherein the heat treatment is performed at a temperature of from 1 to 1100C. 2. The method according to claim 1, wherein the titanium ions and the aluminum ions are supplied by titanium chloride and aluminum chloride. 3. The method according to claim 1, wherein the titanium ions and the aluminum ions are supplied by titanium sulfate and aluminum sulfate. 4. An aqueous acid solution containing titanium ions and aluminum ions has a titanium ion concentration of 0.0
1 mol / liter or more, aluminum ion concentration 0.0
4. The production method according to claim 1, wherein the acid concentration is at least 05 mol / l and the acid concentration is at least 0.02 mol / l. 5. The method according to claim 1, wherein the aqueous hydrogen carbonate solution is an aqueous ammonium hydrogen carbonate solution. 6. The coated titanium oxide has a crystal size of 10 nm.
The method according to any one of claims 1 to 5, wherein