JPH0261423B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of manufacturing spherical porous glass. Porous glass has a sharp pore size distribution,
As an inorganic functional porous material with a large specific surface area, it can be used as various adsorbents, catalyst carriers, carriers for immobilized enzymes, packing materials for gel permeation chromatography, and materials for separation membranes for produced gases in _C1 chemistry. The field is extremely wide. The method for producing porous glass is described in, for example, a US patent.
2215039, U.S. Patent No. 3843341, and Japanese Patent Application Laid-open No. 140334/1984, etc., the basic steps are 1. Production of basic glass by mixing and melting raw materials, 2. Heat treatment for phase separation of glass structure, 3.B ₂ O for ₃ min or remove Na ₂ O rich water soluble layer or acid soluble layer.
It consists of the following steps: solution treatment with hot water, acid solution, or alkaline solution to leave the SiO2 _- rich layer as a porous skeleton, and 4. water washing and drying treatment. The porous glass obtained by the above method is generally crushed in shape. When crushed porous glass is used, for example, in an adsorption column, it has drawbacks such as large pressure loss and low strength. However, such problems can be solved by using spherical porous glass, which has less pressure loss and higher strength than crushed porous glass. To obtain spherical type porous glass,
For example, a general method for manufacturing spherical glass can be applied. For example, for glass of 1 mm or more, there is a method in which crushed glass is placed in a rotary furnace together with coke, and for glass of 1 mm or less, a method is used in which crushed glass is placed in a combustion flame and collected together with the combustion waste gas. However, this spheroidization must be performed before the base glass is heat-treated in the porous glass manufacturing process, and special equipment must be installed for this purpose. The present invention was achieved as a result of various studies in view of the above-mentioned circumstances, and it is possible to combine the heat treatment and spheroidization by using a special additive in the phase separation process by heat treatment of the base glass. The present invention provides an efficient method for producing spherical porous glass in which the following steps are carried out all at once. That is, in the present invention, a basic glass obtained by mixing and melting raw materials for forming porous glass is heat-treated to phase-separate the structure, and then subjected to solution treatment such as acid solution treatment, hot water treatment, alkaline solution treatment, etc. The gist of the present invention is a method for producing spherical porous glass in which the heat treatment is carried out in the presence of inorganic powder. The present invention will be explained in more detail below. The spherical porous glass obtained by the method of the present invention has a basic composition of raw materials such as Na ₂ O-SiO ₂ system, Na ₂ O-
B ₂ O ₃ −SiO ₂ system, Na ₂ O−B ₂ O ₃ −Al ₂ O ₃ −SiO ₂ system,
Na ₂ O−CaO−B ₂ O ₃ −Al ₂ O ₃ −SiO ₂ system, Na ₂ O−
It consists of _{P2O3 - SiO2} system, _{Na2 - B2O3} - _{CeO2.3Nb2O5 , etc.} Porous glass is a molten mixture obtained by heating raw materials having the above composition in an electric current heating furnace, indirect heating furnace, etc. using electricity, heavy oil, gas, etc. as a heating source. The base glass is crushed into particles and heat treated under conditions such as 650 to 750℃.
The structure of the basic glass is divided into a phase mainly composed of Na ₂ O or B ₂ O ₃ soluble in acid solution or hot water and a phase mainly composed of other systems. Porous glass is created by forming pores within the glass structure by phase-separating the glass and subjecting it to solution treatment using an acid solution or hot water to elute the soluble component phase. . In the method of the present invention, if the base glass becomes semi-molten during the heat treatment of the base glass, and if the finely divided particles exist independently in that state, the surface tension of the finely divided glass particles itself It was discovered that spheroidization easily occurs, and that if inorganic powder is present, the formed spherical particles will come into contact with each other and maintain their shape without causing welding, resulting in a spherical porous glass. This is what we arrived at based on this. Here, the inorganic powder does not decompose or melt at the heat treatment temperature of the base glass, and
It is preferable to use a material that does not chemically react or eutectic with glass. Further, it is preferable that the material has a different specific gravity and particle size from glass so that it can be easily separated from glass in a separation operation using a sieve, elutriation classifier, elutriation classifier, etc. after heat treatment. Typical examples of inorganic powders having such physical properties include finely powdered silica, carbon black, powdered alumina, and titanium oxide. The basic glass subjected to heat treatment is usually coarse granules of about 10 mm or less, but in order to obtain spherical porous glass by the method of the present invention, it must be further finely pulverized to a constant particle size before heat treatment. It is desirable to classify them. It is possible to obtain spherical porous glass with a sharp particle size distribution in high yield by pulverizing the particle size of the basic glass to a certain range and adjusting the classification before heat treatment. This is because. For crushing the basic glass before heat treatment, a crusher used for crushing general glass, ceramics, rocks, etc. can be used. For example, for coarse crushing, a known geocrushing mill, roller mill, etc. A ball mill, a vibrating ball mill, a fluid energy mill, etc. are used for fine grinding. Therefore, it is desirable that the pulverized particle size is 1 mm or less, preferably 100 μ or less. Also,
Since the method of the present invention performs heat treatment by a static method,
Even for fine particles of about 1 to 5 microns, heat treatment and spheroidization can be carried out simultaneously with almost no collection loss, unlike in the case of spheroidization of general glass. Furthermore, in order to classify the ground base glass according to particle size as described above, a known elutriation classifier such as a gold wire sieve, a gravity classifier, a centrifugal classifier, an inertial classifier, or a full-flow classifier can be used. , a surface flow classifier, a classification method using a known elutriation classifier such as a Richard vortex classifier, and a classification method using various other sieving devices. The method of the present invention is characterized in that an inorganic powder is present at the same time when the base glass, which has been finely classified in advance as described above, is heat-treated to phase-separate the glass structure before heat treatment. Here, the inorganic powder is preferably one that does not decompose or melt under the heat treatment conditions of the base glass, and does not chemically react or eutectic with the glass. Furthermore, it is preferable to use a material that can be easily separated from glass by a separation operation using a sieve, elutriation classifier, elutriation classifier, etc. after heat treatment, and has a different specific gravity and particle size from glass. Typical examples of inorganic powders having such physical properties include finely powdered silica, carbon black, powdered alumina, and titanium oxide. Among these, when the specific gravity of the mixture is high, the glass particles become flat due to gravity under the heat treatment phase separation conditions, so a pseudospherical powder with a high bulk specific gravity is preferable. From this,
Suitable examples of inorganic powders include finely powdered silica and carbon black, but carbon black colors the glass surface black and requires reheating to remove the color, which is troublesome. Therefore, fine powder silica is most suitable as the inorganic powder used in the method of the present invention. There are various types of fine powder silica, including those manufactured by the gas phase method such as Aerosil, those manufactured by the precipitation method from a solution such as White Carbon, and those manufactured by crushing silica gel. is also applicable. However, if the glass has a high water content, it releases water during heat treatment and forms an azeotrope with the boric acid in the glass component, so it is desirable to heat-treat and dehydrate it before use. Also
Since finely powdered silicic acid containing many impurities such as Na and K is vitrified during heat treatment, it is desirable to remove impurities by acid treatment in advance. When heat-treating the base glass, the pulverized base glass and the above-mentioned inorganic powder are mixed using a known mixer, for example, a V-type mixer. The mixing ratio of the basic glass and the inorganic powder varies depending on the particle size of the finely ground basic glass, the particle size of the inorganic powder, and physical properties such as bulk specific gravity. If the mixing ratio of the base glass is high, the formed spherical glass particles will come into contact with each other, resulting in connected spherical glass, which is undesirable.On the other hand, if the mixing ratio of the inorganic powder is high, the production rate of spherical glass will decrease. This is also not desirable.
Therefore, it is necessary to determine the optimum mixing ratio in advance through small-scale tests. In addition, the finely ground basic glass becomes spheroidal and changes in particle size through heat treatment.
In order to obtain porous glass with the desired particle size, the relationship between the particle size of the glass after heat treatment and the particle size of the crushed basic glass before heat treatment must be investigated in advance, and based on this result, , it is necessary to select the particle size of the ground base glass.
Heat treatment of the basic glass in the presence of inorganic powder, that is, phase separation of the glass structure and simultaneous spheroidization, is carried out by placing a mixture of the pulverized basic glass and inorganic powder in a furnace, and heating it for example at 600 to 800 The process is completed by holding the temperature at 0.degree. C. for 2 to 48 hours. Therefore, as mentioned above, during the heat treatment of the finely classified basic glass, if the basic glass becomes half molten, and in that state, the finely divided particles exist independently. Due to the surface tension of the pulverized particles themselves, spheroidization easily occurs, and due to the presence of the inorganic powder, the formed spherical particles maintain their individual shapes without coming into contact with each other and causing fusion. , a spherical glass with a phase-separated structure can be obtained. During the heat treatment, it is necessary to separate the inorganic powder that is simultaneously present in the spherical glass whose structure is phase-separated by the heat treatment as described above. As the separation device, the above-mentioned gold sieve, elutriation classifier, water elutriation classifier, etc. are used. The inorganic powder is separated and phase-separated into spherical glass, which is then soluble in acid solution, hot water, etc. in the tissue.
A phase mainly composed of _three components, Na ₂ O and B ₂ O, is eluted into a solution of acid solution, hot water, etc. to form pores in the tissue. In order to remove the colloidal silica that blocks the pores, a solution treatment with an alkaline solution is performed to form spherical porous glass. When carrying out the above solution treatment, it is preferable to surface-treat the spherical glass whose structure has been phase-separated by heat treatment with hydrofluoric acid in advance. The reason for this is that when the spherical glass comes into contact with air during heat treatment, some of the boric acid on the surface evaporates, forming a layer with a high silicic acid content on the surface, which prevents the solution treatment from proceeding smoothly. This is because it is necessary to dissolve silicic acid. Examples of acids used in solution treatment include inorganic acids such as HCl, HNO ₃ and H ₂ SO ₄ and organic acids such as acetic acid, formic acid and oxalic acid. Solution treatment with an acid solution or an alkaline solution is preferably carried out at a temperature of 50° C. or higher, for example. In addition, when the acid solution treatment is performed in batches and the acid solution is replaced several times, less colloidal silica is produced as a by-product and the treatment efficiency is better. The same applies to the treatment with an alkaline solution, and specific operating methods thereof will be explained in Examples below. Examples of the alkali that can be used include NaOH, KOH, lithium hydroxide, and the like. After the liquid treatment, the spherical porous glass is thoroughly washed with water and dried. For drying, heat transfer method, hot air drying, microwave method, etc. are applied, and the drying temperature is 500°C or less, which causes little thermal denaturation of the obtained spherical porous glass and does not change the number of surface hydroxyl groups.
The temperature is preferably 100 to 200°C. As described above, in producing spherical porous glass, the present invention involves the presence of inorganic powder in the step of heat-treating and phase-separating a base glass made of a molten mixture of glass raw materials. This method allows for the mass production of spherical porous glass useful as a column packing material, since it can omit special equipment and operations for spheroidization, and its industrial utility value is It's large. Next, the present invention will be described with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Example 1 CaO-B ₂ O ₃ -SiO ₂ -Al ₂ O _3- based glass with composition ratio of CaO 18%, B ₂ O ₃ 17%, SiO ₂ 50%, Na ₂ O 5.59
%, Al ₂ O ₃ The raw materials lime, boric acid,
Silica sand and alumina were thoroughly mixed, placed in a glass melting crucible, and calcined and melted at 1100°C. The temperature was raised to 1350°C to 1500°C and held for 4 hours to complete melting. Drop it into ice water to cool it quickly, or
It was then cast into a mold and rapidly cooled to obtain basic glass. This was coarsely crushed using a geo crusher mill, then a roll crusher mill, and then a fluidized bed counterjet mill (Alpine model) to obtain an average particle size of
It was finely ground to 37μ. The finely ground basic glass is classified using a known elutriation classifier such as a gravity classifier, centrifugal classifier, or inertial classifier,
The fraction was separated into fractions with particle sizes of 10μ (fraction), 10-20μ (fraction), 20-50μ (fraction), and 50μ or more (fraction). Next, out of the above, 1 kg of fraction is added to Thyroid Grade 244 (Fuji Davison product name:
Fine powder silica (hereinafter referred to as fine powder silica)
Add 800gr and mix evenly with a V-type mixer, then
Place it in a phase separation container (250φ1200mm, made of SUS310),
Heat treated in a soaking electric furnace at 700℃ for 16 hours.
Phase separation and spheroidization of the glass structure were performed at the same time. The spheroidized heat-treated glass is separated from finely powdered silica using an elutriation classifier similar to that described above, and then using a known elutriation classifier such as a full flow classifier, a surface flow classifier, or a Richard vortex classifier. The spherical base glass with a particle size of 20 to 40μ is classified and
Got 850gr. Next, put it in a constant temperature stirring vessel made of Teflon.
After adding 1N HCl8.5 and adjusting the temperature to 50℃, add the spherical base glass while stirring.
After stirring for an hour, let stand, and use 1N HCl by decanting method.
was eliminated. Pour 1N HCl8.5 into the same container again, stir for 8 hours, drain the 1N HCl, and pour again.
Add 1N HCl8.5 to the same container and stir for 14 hours.
The 1H.HCl was discharged and then washed several times with water using the decanting method. Next, add 0.5N to the constant temperature stirring vessel.
After adding NaOH6 and adjusting the temperature to 50℃, the spherical base glass treated with acid solution and washed with water was added with stirring, stirred for 2 hours, left to stand, and 0.5N NaOH was removed by the decanting method. , again 0.5N・
Add NaOH6 to the same container and stir for 10 hours to 0.5N・
After the NaOH was discharged, washing with water was repeated using a decanting method until the washing solution became neutral (PH7). Then, 1N HCl5 was put into the same container again and the temperature was adjusted to 50℃, and the spherical base glass that had been treated with alkaline solution and washed with water was added and stirred for 3 hours. After that, washing was repeated by the decanting method until the washing liquid was neutral. Washed until clean. Next, the washing liquid was separated and dried at 180° C. for 2 hours to obtain 430 gr of spherical porous glass. In addition, add 5% hydrofluoric acid 1 to a constant temperature stirring vessel made of Teflon and adjust the temperature to 20°C.
℃, add 850g of spherical base glass prepared separately before solution treatment with 1N HCl and 0.5N NaOH, stir for 6 hours, let stand, and use the tilting method to The spherical base glass treated with hydrofluoric acid, obtained by removing 5% hydrofluoric acid and washing with water several times, was subjected to solution treatment with 1N HCl and 0.5N NaOH in the same manner as in the previous operation example. By washing with water and drying, 430 gr of spherical porous glass surface-treated with hydrofluoric acid was obtained.
For these spherical porous glasses, the surface area was measured by the nitrogen adsorption method, the pore volume and average pore diameter were measured by a mercury intrusion porosimeter manufactured by Carlo Erba, the average particle diameter was measured by the Coulter counter method, and the electron microscope was used. The shape was observed. The results are shown in Table 1. In addition, in the electron micrographs in Figures 1 to 4, in Figure 1, 2.28cm on the photo corresponds to 100μ, and in Figure 2, 2.28cm on the photo corresponds to 100μ.
1.514cm corresponds to 1μ, and in Figure 3 it is 2.26cm on the photo.
corresponds to 100μ, and in Figure 4, 1.0cm on the photograph corresponds to 1μ.

[Table] Example 2 Of the basic glass obtained in Example 1, the fractions (fraction particle size
(10 μ or less) Finely powdered silica as inorganic powder per 1 kg
Add 700gr and mix evenly with a V-type mixer, then
Place it in a phase separation container (180φ, 1200mm, made of SUS310),
Heat treated at 720℃ for 24 hours in a soaking electric furnace.
Phase separation and spheroidization of the glass structure were performed at the same time. The spheroidized heat-treated glass was subjected to elutriation classification and water elutriation classification similar to those in the examples to separate it from fine powder silica, and further elutriation classification yielded 920 gr of spherical basic glass having a particle size of 3 to 10 μm. Next, put 1N HCl9.2 into a Teflon constant temperature stirring container and adjust the temperature to 50℃.
After adjusting to
1N HCl was excluded. Pour 9.2 of 1N HCl into the same container again and stir for 8 hours to eliminate 1N HCl.
9.2 liters of 1N HCl was added again and stirred for 14 hours, and then washed with water several times by the decanting method. Next, put 0.5N NaOH9.2 into the constant temperature stirring container and adjust the temperature to 50°C, then add the spherical base glass treated with the acid solution and washed with water while stirring, stir for 2 hours, let stand, and tilt. Eliminate 0.5N NaOH by law,
0.5N NaOH9.2 was added again and stirred for 10 hours, and then water washing was repeated by the decanting method until the washing liquid became neutral (PH7). Next, after separating the washing liquid, it was dried at 180° C. for 2 hours to obtain 520 gr of spherical porous glass. In addition, 5% hydrofluoric acid 1 was placed in a Teflon constant-temperature stirring container and the temperature was adjusted to 20°C.
Add separately prepared 1N HCl and
Hydrofluoric acid obtained by adding 920g of spherical basic glass before solution treatment with 0.5N NaOH and stirring for 6 hours, filtering with No5c filter paper at Nutsuchie, and then washing with water several times. The treated spherical base glass was subjected to solution treatment with 1N HCl and 0.5N NaOH in the same manner as in the above operation example, washed with water, and dried to obtain 520g of spherical porous glass surface-treated with hydrofluoric acid. . Physical property tests were conducted on these spherical porous glasses in the same manner as in Example 1. The results are shown in Table 2.

【table】 [Brief explanation of the drawing]

1, 2, 3, and 4 show electron micrographs of the spherical porous glass obtained in Example 1.

Claims (1)

[Claims] 1. After heat treating a basic glass obtained by mixing and melting porous glass forming raw materials to phase-separate the structure,
In producing spherical porous glass by subjecting it to solution treatment such as acid solution treatment, hot water treatment, alkaline solution treatment, etc., the heat treatment is performed in the presence of inorganic powder. Production method. 2. A method for producing spherical porous glass according to claim 1, wherein the base glass is classified into predetermined particle size ranges before heat treatment. 3. Claim 1, wherein the inorganic powder is any one or more of fine powder silica, carbon black, powder alumina, and titanium oxide.
A method for producing spherical porous glass according to item 1 or 2. 4. Producing a spherical porous glass according to any one of claims 1 to 3, in which a base glass whose structure has been phase-separated by heat treatment is previously treated with hydrofluoric acid before solution treatment. how to.