JPH04130026A - Production of sio2 porous glass - Google Patents

Abstract

PURPOSE:To obtain SiO2 porous glass having lots of fine pores and excellent heat resistance and corrosion resistance by adding org. polymers into a silicon alkoxide soln. in the production of SiO2 porous glass by sol-gel method. CONSTITUTION:A silicon alkoxide soln. in which org. polymers such as polyethylene glycol is dissolved is hydrolyzed to obtain a sol. A soln. containing a metal alkoxide except for silicon alkoxide (e.g. zirconium alkoxide) is added to this sol, mixed, and hydrolyzed to obtain a sol. This sol is gelatified and dried to obtain a dry gel containing org. polymers. Then, this gel is converted into glass by heating at 500-800 deg.C and by dehydration condensation reaction while removing the org. polymers, and thus, the SiO2 porous glass is obtained.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for producing SiO This invention relates to a method for producing 5iOz porous glass, which is used as a porous material that is required to have heat resistance and corrosion resistance.

(Prior art) Porous materials such as separation membranes and enzyme carriers must have a large number of fine pores, for example, with a pore radius of 5 to 1 O, and have excellent heat resistance and corrosion resistance. is necessary. On the other hand, 5ins type glass has excellent heat resistance and acid resistance, and among them, 5iOz type glass (ZrO) containing ZrO.
rOt-3iO□ glass) has excellent heat resistance and also excellent alkali resistance. Therefore, if 5i02-based glass (that is, 5if2-based porous glass) having a large number of micropores can be produced stably and practically, it can be suitably used as a porous material for separation membranes, enzyme carriers, and the like.

Conventionally, known methods for manufacturing SiO2-based porous glass include a manufacturing method that utilizes the phase separation phenomenon of glass and a manufacturing method that utilizes the sol-kel method.

The former method involves heat-treating SiO2-based glasses containing various metal oxides at temperatures below their softening point for a long period of time to separate the SiO□ phase, which forms the skeleton, and the soluble metal oxide phase. A 5iOz porous glass is produced by eluting the phase with acid.

The latter production method involves hydrolyzing silicon alkoxide (or silicon alkoxide and alkoxides of metals other than silicon) to form a sol, then gelling it, drying it to form a porous dry gel, and producing the dried gel. SiO2-based porous glass is produced by gradually heating the gel to synthesize glass through evaporation of water in the gel and dehydration condensation reaction.

Note that if the heating temperature of the dry gel is further increased, the glass will become denser due to the sintering reaction and the pores will disappear, making it impossible to obtain porous glass.

(Problem to be solved by the invention) However, among the conventional methods for producing SiO2-based porous glass, the method using the phase separation phenomenon of glass has the following problems:
It is possible to manufacture products with micropores with a pore radius of 20 Å or less, and since phase-separated ZrO2 is eluted with acid, ZrO
Since the content of □ is limited to 5 mo1% or less, there is a problem that the alkali resistance is not sufficient.

In the conventional porous glass manufacturing method using the sol-kel method, the ZrO2 content can be increased, so there is no problem with alkali resistance, or there are micropores with a pore radius of about 210 mm. In order to manufacture products, it is necessary to take measures such as stopping the heating just before the glass produced by heating the dry gel becomes densified, or because the densification of glass occurs rapidly within a narrow temperature range. Difficult to control. For example, if the dry gel is heated at about 300 to 500°C, the resulting glass will not have sufficient strength and corrosion resistance, and if it is heated above 500°C, it will be difficult to control the pore diameter.

In addition, since the micropores change depending on the solization and gelation due to hydrolysis and the heating temperature of the gel, the state of the micropores that are generated is naturally determined by the generation conditions, or the generation conditions are controlled to be constant and precise. Since this is extremely difficult, it is difficult to control the state of the micropores, and this has to be done each time it is manufactured, resulting in a lack of reproducibility. The condition of the micropores mentioned above basically refers to the size (radius) of the micropores, their distribution, number, etc., or in practical terms, the condition of the micropores refers to the radius of the micropores, and the size and number of the micropores. The surface area of micropores per unit weight of glass (hereinafter referred to as specific surface area) is determined by In addition, since it takes time to heat the dry gel, which is an important factor in evaluation,
If an attempt is made to shorten the heating time by rapidly heating to a high temperature, there is a drawback that unreacted organic substances remain and the glass tends to blacken due to pyrolytic carbon. To prevent this, it is recommended to perform a steam treatment in which the temperature is gradually raised in steam before heating the dry gel, and then heat the dry gel.In this case, the steam treatment may take a long time. It takes.

The present invention has been made in view of these circumstances, and its purpose is to solve the above-mentioned problems of the conventional methods and to improve the production of SiO2-based porous glass by the sol-kel method. , it is possible to manufacture glass having micropores with a pore radius of about 5 to 10, and it is also possible to improve the glass strength and corrosion resistance compared to the conventional method using the sol-gel method. Provided is a method for producing SiO2-based porous glass that allows easy control of conditions (micropore radius and specific surface area), excellent reproducibility, and further suppresses blackening of the glass without long-term steam treatment. This is what I am trying to do.

(Means for Solving the Problems) In order to achieve the above object, the method for producing SiO2-based porous glass according to the present invention has the following configuration.

That is, in the method for producing a Si-based porous glass according to claim 1, when producing a SiO□-based porous glass by a sol-gel method, the silicon alkoxide solution containing an organic polymer is prepared using the silicon alkoxide solution. Hydrolyze to form a sol, then add and mix a solution containing an alkoxide of a metal other than Noricon to the sol, hydrolyze the metal alkoxide to form a sol, further form a gel, and then dry this. gel, and dry the gel at 500~8
This is a method for producing 5i02-based porous glass, which is characterized by vitrifying it by heating at a temperature of 00°C and removing organic polymers in the dried gel.

The method for producing SiO□-based porous glass according to claim 2,
2. The method for producing SiO2-based porous glass according to claim 1, wherein the dry gel is subjected to a steam treatment in which the temperature is gradually raised and heated in steam before heating the dry gel.

The method for producing SiO2-based porous glass according to claim 3,
2. The method for producing SiO2-based porous glass according to claim 1, wherein the alkoxide of a metal other than silicon or zirconium alkoxide is used.

(Function) As described above, in the method for producing 5i02-based porous glass according to the present invention, in a silicon alkoxide solution containing an organic polymer, the silicon alkoxide is hydrolyzed to form a sol, and then silicon is added to the sol. Add and mix a solution containing an alkoxide of a metal other than the above (hereinafter referred to as other metal alkoxide), hydrolyze the metal alkoxide to form a sol, further gel it, and then dry it to form a dry gel. As a result, a dry gel containing organic polymers can be obtained.

The reason why the above order is used for sol formation by hydrolysis is that silicon alkoxide has a lower hydrolysis reaction rate than other metal alkoxides, and by hydrolyzing those with a lower rate, the composition can be changed. This is because a homogeneous sol can be obtained, and as a result, a dry gel with a homogeneous composition can be obtained, and the functions of the glass can be further improved. That is, if other metal alkoxides are hydrolyzed first, they will become sol quickly, so when silicon alkoxide is added, it will not be mixed uniformly and it will be difficult to obtain a homogeneous sol, and hydrolysis will start at the same time. Even if this is done, it becomes difficult to obtain a homogeneous sol. As a result, the sol and dry gel according to the present invention have a homogeneous composition.

On the other hand, the organic polymer is an extremely small substance with a length of about 5 to 20 molecules, and can be uniformly dispersed in a silicon alkoxide-containing solution, resulting in a homogeneous composition and uniform dispersion of the organic polymer. A dry gel is obtained.

Next, the dried gel is heated at a temperature of 500 to 800°C to vitrify it by a dehydration condensation reaction, and the organic polymer in the dried gel is removed. or formed.

In other words, the dry gel is porous and contains organic polymers, and since the organic polymers coexist with the pores of the gel itself, the heating described above first removes the organic polymers from those near the pore surface of the gel. The organic polymer is gasified and discharged from the gel, and a gas passage is formed in the gel during the vitrification process, through which the organic polymer is sequentially discharged (removed) from the glass.

By heating and removing the organic polymer, the removed portion itself remains as elongated and extremely small pores, and in addition to forming elongated micropores, the micropores of the dried gel itself remain without becoming porous. However, since more micropores are formed, the pore radius can be about 5 to 10 pores. It should be noted that the reason for the above-mentioned micropore formation/remaining is not well understood, or it may be due to the catalytic action of the organic polymer, or the action of the gas passages, which promotes the formation of micropores in the dried gel itself and causes the micropores to disappear. This is thought to be because it is suppressed.

By forming micropores in this manner, a SiO□-based porous glass having a large number of micropores with a narrow pore radius distribution can be obtained. At this time, if the dried gel has organic polymers uniformly dispersed in it as described above, the micropores of the glass can be uniformly dispersed.

Here, the heating temperature of the dry gel is set at 500 to 800°C because if it is less than 500°C, vitrification will be insufficient and the strength and corrosion resistance will deteriorate, and if it exceeds 800°C, fine particles will be formed after the organic polymer is removed. This is because the pores are blocked and the porosity deteriorates.

Since the dried gel is vitrified by heating at a temperature of 500 to 800°C as described above, the glass strength and corrosion resistance can be improved compared to the conventional porous glass manufacturing method using the sol-kel method.

Since micropores are generated by removing organic polymers by heating a dry gel, the state of micropores is determined by the generation conditions, that is, gel heating conditions and the amount and type of organic polymers, and it is extremely difficult to control these conditions. Therefore, it is easy to control the state of the micropores in the glass (micropore radius, specific surface area, etc.) and has excellent reproducibility. In particular, by changing the amount of organic polymer added, the pore diameter can be kept approximately constant and the number of pores (specific surface area) can be easily adjusted.

When heating the dry gel, pyrolytic carbon is discharged out of the glass through the gas passage formed as the organic polymer gasifies, making it difficult for it to remain, and therefore making it difficult to carry out long steam treatment. Even without it, it becomes possible to suppress blackening.

Therefore, according to the method for producing SiO□-based porous glass according to the present invention, it is possible to produce a glass having micropores with a pore radius of about 5 to 1000 μm, and it is also possible to produce a SiO□-based porous glass using the sol-gel method. Compared to the manufacturing method, the glass strength and corrosion resistance can be improved, and the state of the micropores of the glass (especially the specific surface area) can be improved.
It is easy to control and has excellent reproducibility, and furthermore, it becomes possible to suppress the blackening of the glass without requiring a long steam treatment.

If the dry gel is subjected to a steam treatment in which the temperature is gradually raised and heated in steam before heating the dry gel, the time required for heating the gel becomes longer, or glass blackening can be reliably prevented,
Also, since it becomes possible to increase the specific surface area of micropores,
It is advisable to perform steam treatment if necessary.

When zirconium alkoxide is used as the alkoxide of a metal other than silicon, a SiO□-based porous glass containing a large amount of ZrO2 is obtained, and the alkali resistance can be greatly improved.

As the organic polymer, for example, polypropylene glycol such as polyethylene glycol, polyacrylic acid, polyvinylpyrrolidone, polyvinyl alcohol, etc. may be used, as long as it can be uniformly mixed into the metal alkoxide solution and can be easily removed by heating. , and various other types can be used without limitation.

The silicon alkoxide-containing solution and the other metal alkoxide-containing solution may contain an inorganic salt as necessary. The other metal alkoxide-containing solution is not limited to one kind of other metal, but can contain two or more kinds at the same time. Both solutions contain a solvent for hydrolysis of the alkoxide, which can be alcohol and/or water.

(Example) Example 1 Silicon ethoxide (hereinafter referred to as SE): 20.8 g
r Polyethylene glycol (hereinafter referred to as PEG) with a molecular weight of 600
600): 14.6gr (70wt for SE
%).

Ethanol: An alkoxide-containing solution (al
, water: 1.8gr, ethanol: 4.6gr,
Hydrolysis solvent (b) that becomes 0.37g of hydrochloric acid, solution (C) that becomes 6.6g of zirconium tetra-n-propoxide, water: 3.6g, and ethanol: 4.6g.
r, hydrochloric acid: 0.37gr hydrolysis solvent fdl
Each was adjusted and prepared.

Next, solution (a) was slowly added to the above solvent (bl) without stirring, stirred at room temperature for 1 hour, and then solution (C1
was added and stirred at room temperature for 1 hour, and then the solvent (dl
was added and stirred for 10 minutes. The mixture was air-dried at room temperature while being left in the glass speaker.

After a few weeks, the air-dried product (gel) was heated to 600°C for about 1
It was heated for 0 hours to vitrify and remove PEG600 from the glass.

Regarding the 5jtL-based porous glass containing ZrL thus obtained, the specific surface area was measured by the BET method, and the pore volume and pore size distribution were determined by the Cranston-Inkley method. 42
5 m'/gr, the micropore volume was 0.16 cm'/gr, and the average micropore radius was about 6-9.

Furthermore, the glass strength and corrosion resistance were superior to those obtained by the conventional porous glass manufacturing method using the sol-gel method.

Furthermore, the above-mentioned glass had no blackening and was transparent and homogeneous.

Example 2 Amount of PEG600 (wt%) relative to SH in solution fa)
changed. A SiO□-based porous glass containing ZrO□ was prepared in the same manner as in Example 1 except for this point, and the pore radius distribution and specific surface area were determined. The results are shown in FIG. 1 (al, (bi and (C+), and FIG. 2).

Figure 1 ta+, fbl, (C) to PEG600:30
．． In both cases of 50.70 wt%, the average pore radius is 1
It can be seen that it exhibits a Soyabean pore size distribution of 0 Å or less. Second
From the curve (a) in the figure, it can be seen that although the pore size distribution is almost the same, the specific surface area increases as the amount of PEG600 increases.

Note that the curve (b) in Figure 2 shows the results when water vapor treatment is performed before the gel heating, and the specific surface area is larger than that of curve (a), and the specific surface area is further increased by the water vapor treatment. I know it will increase.

In addition to the above, 5I02 porous glasses were prepared in the same manner as in Example 2 using polyethylene glycols with various molecular weights in place of the PEG600, and the pore radius distribution and specific surface area were determined. Substantially the same results as in Example 2 were obtained.

(Effects of the Invention) According to the method for producing 5in2 porous glass according to the present invention, when producing 5te2 porous glass by the sol-gel method, a material having micropores with a pore radius of about 1 In addition to improving the glass strength and corrosion resistance compared to the conventional method using the sol-gel method, it is also possible to easily control and reproduce the state of the micropores in the glass (micropore radius, specific surface area, etc.). Furthermore, it becomes possible to suppress the blackening of glass without requiring long-term steam treatment.

[Brief explanation of the drawing]

FIG. 1(a), FIG. 1(b), and FIG. 1(C) show the pore radius distribution of the SiO2-based porous glass according to Example 2, and FIG. 1(a) shows the pore radius distribution of the SiO2-based porous glass according to Example 2. PEG600 in glass manufacturing
Pore radius distribution when added amount: 30 wt%, Figure 1 (b
) is the pore radius distribution when the amount of PEG600 added is 50wt%, and Figure 1 (C) is the pore radius distribution when the amount of PEG600 added is near 0wt%.
FIG. 3 is a diagram showing the pore radius distribution in the case of FIG. FIG. 2 is a diagram showing the relationship between the amount of PEG600 added (wt%) and the specific surface area of the obtained glass micropores according to Example 2. In FIG. 2, when heating the gel, the curve (al) shows the gel heated to 600°C using a normal heating method, and the curve (bl) shows the gel heated to 600°C after steam treatment.

Claims (3)

[Claims] (1) When producing SiO_2-based porous glass by the sol-gel method, a silicon alkoxide solution containing an organic polymer is hydrolyzed to form a sol, and then an alkoxide of a metal other than silicon is added to the sol. The metal alkoxide is hydrolyzed to form a sol and then gelled, and this is dried to form a dry gel.
A method for producing SiO_2-based porous glass, characterized by vitrifying it by heating at a temperature of °C and removing organic polymers in the dried gel. (2) Claim 1, wherein the dried gel is subjected to a steam treatment in which the temperature is gradually raised and heated in steam before heating the dried gel.
A method for producing SiO_2-based porous glass as described in . (3) SiO_2 according to claim 1, wherein the alkoxide of metal other than silicon is zirconium alkoxide.
Method for manufacturing porous glass.