JPS60200843A - Manufacture of porous glass - Google Patents

Abstract

PURPOSE:To enable the manufacture of massive and porous glass by acid-treating phase split alkaline borosilicate glass with an aq. strong acid soln. of specified concn. and thereafter acid-treating said glass with an aq. strong acid soln. of specified concn. higher than said strong acid soln. CONSTITUTION:Phase split alkaline borosilicate gas is primarily immersed in an aq. strong acid soln. of 0.1-0.5 N to remove the alkali borate phase. Furthermore, the primarily treated glass is immersed in an aq. strong acid soln. of 2-5 N to manufacture porous glass. Sulfuric acid, nitric acid, hydrochloric acid or mixed acids of these are used as the strong acid and the acid treatment temp. is about 100 deg.C and the treatment time is 24-360hr.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing porous glass, and more particularly to a method for producing porous glass by treating a lump of phase-separated alkali borosilicate glass with an acid.

Conventionally, alkali borosilicate glass is phase-separated into a noric acid phase and an alkali borate phase by heat treatment, and the alkali borate phase is eluted by acid treatment to obtain porous glass, and the heat treatment conditions are adjusted to obtain a phase-separated state. control the
It is well known to obtain porous glass having a desired pore size, and this porous glass is being used as a carrier for catalysts and enzymes, molecular sieves, gas separation, and the like.

However, porous glass is mainly available in the form of fine powder, and therefore its scope of use is extremely limited.

One reason for this is that bulk porous glass requires a significant amount of time in the acid treatment process and is prone to cracking, making it extremely difficult to manufacture due to its sharp edges.

Furthermore, the pore diameter of porous glass is usually measured by electron microscopy, but the actual value of its surface area (referred to as surface area per unit weight (m/y) k) can be predicted from the pore diameter. However, the pore volume (pore volume per unit weight (CC/fl)
9°) The measured values are also significantly lower than the predicted values. This is because the alkali borate phase, which should be leached out by the acid, contains about several tens of silica.
It is impossible for it to remain in the pores in the form of a colloid without being eluted by the acid, and this state is schematically shown in Figure 1. Since this silica colloid is scattered and deposited within the pores, the actual pore diameter differs from one individual to another, which is a serious hindrance in its use as a carrier for enzymes, molecular sieves, and gas separation. There is a trend that the higher the surface area value is, the better it is in terms of adsorption performance, but the actual measured value includes the surface area of the silica colloid mentioned above, so it is not necessarily appropriate, and is rather suitable for the above uses. In this case, it is essential that the pore diameter be uniform.

By the way, if the glass is in the form of fine powder or an extremely thin plate with a thickness of several hundred microns, the p-silica colloid can be dissolved and removed by immersing it in acid and then dipping it in a dilute alkaline aqueous solution, reducing the original pore size. However, when trying to apply this method to lumps, it has become a problem because not only the silica colloid but also the six layers of glue that remain as a skeleton gradually dissolve and disintegrate from the surface layer. Ta.

The present invention improves these conventional techniques and solves their problems, and in particular provides a suitable manufacturing method for bulk porous glass. The method for producing porous glass is characterized in that the method is first treated with an aqueous solution of a 0.1 to 0.5N strong acid, and then subjected to the acid treatment with a water bath solution of a 2 to 5N strong acid. This is a summary.

The lump glass applicable to the present invention includes plate-shaped bodies with a thickness of 1 inch or more, similar rectangular bodies, prismatic bodies, etc., and glass bodies with a diameter of I
A sphere of 1nJn or more, an ellipse similar to this, a cylinder, etc.
and combinations thereof.

In the present invention, phase-separated alkali borosilicate glass is first immersed in an aqueous solution of 0.1 to 0.5 N strong acid to remove the alkali boric acid phase. The alkali borosilicate glass may be of a known composition that can be used normally. The strong enemy is sulfuric acid.
Nitric acid, hydrochloric acid, or a mixed acid thereof may be used; other mineral or organic acids are not preferred because of the high processing cost. The acid concentration is 0. If it is less than IN, the elution of the alkali boric acid phase becomes extremely slow. When the acid concentration exceeds 0.5N, the elution of the alkali boric acid phase is rapid, so the volume of the silica phase that remains and forms the skeleton also changes rapidly.
Stress is generated between the unreacted parts and cracks are likely to occur.

A more important reason lies in the fact that dilute acids are more likely to elute silica. The present inventor investigated the behavior of silica present in a considerable amount in the alkali boric acid phase toward acid, and found that the more dilute the acid, the more the silica gradually dissolves and becomes small droplets (Figure 2). ). Note that the relatively dense silica phase remaining as a skeleton is also slightly dissolved, but to a negligible extent. On the other hand, in the case of thick acids, silica is hardly understood and clumps together. The amount of silica dissolved increases in acids of 0.5 N or less, and is dissolved in balance with the common knowledge of the alkali borate phase, while silica aggregation is remarkable in thick acids, especially in the range of 2N to 5N.

Regarding the relationship between acid concentration and silica dissolution, T, H
liilmer et al. (JOunRl of The Am
erican CeramiC5ociety.

53 (1970)) that nitric acid with a low phlegm content increases the amount of silica dissolved.

It is quite natural from the theory of chemical equilibrium that if the amount of acid is small, the concentration of alkali borate and silica in the acid solution will increase during the elution process, reducing the ability to solve problems.

Therefore, the larger the amount, the better, but from a practical standpoint, the amount of acid (
CO)/gara 1 weight (y) is preferably 200 to 800.

The acid treatment temperature is usually used, and a temperature at which the reaction is active, that is, around 100°C, is appropriate.

The acid treatment time is initially determined by visual observation.

That is, during the elution process, the boundary area between the bathed phase and the undissolved tag can be clearly seen, and the time when this boundary area disappears is the completion time. Hereinafter, if glass lumps of the same shape are treated under the same processing conditions and for the same processing time, reproducible results will be obtained.

Generally, for glass blocks having a thickness of 1 to 10 mm, the heating time ranges from 36 hours to 420 hours.

The primary treated glass thus obtained.

Treat with a 2N to 5N strong acid aqueous solution. In addition, 1
Since most of the alkali boric acid phase is eluted in the next treatment, cracks will not occur in the glass even if the acid concentration is rapidly increased in the second treatment. It can be confirmed that in this secondary treatment, the surface area of the primary treated glass decreases and the pore volume increases. As mentioned above, this is because the colloidal silica remaining in the pores, scattered and deposited is not dissolved in the acid, but aggregates with each other, reducing the surface area (Figure 3), while the surface area is still sufficiently dissolved. The volume of the paper pores increased due to the dissolution of the unexhausted alkali boric acid phase. Note that when a concentrated acid exceeding 5N is used, the pore volume hardly increases, but the reason for this has not been elucidated. Further, if it is less than 2N, aggregation becomes slow.

The amount of acid is such that the acid capacity (C/glass M amount Cy) is 20~
If the number is in the range of 80, even if it exceeds 80, the above-mentioned effect will not be achieved, and if it is less than 20, the effect will be small.

The appropriate temperature for the acid treatment is a temperature that is commonly used and at which one reaction is active, that is, around 100°C.

The acid treatment time is determined based on changes over time in the weight, pore volume, or surface area of the glass. That is, during the treatment process, the weight and surface area of the glass gradually decrease, and the pore volume gradually increases, but eventually these fluctuations become extremely small.

This point in time may be taken as the completion time. Upon completion of this process, the pore volume reached approximately 80 cm compared to the target value, which is the pore volume of the porous body obtained by separately treating finely powdered glass with an acid-alkali process, as described later. Since the pore size is uniform and the pore size is uniform, it can be used as a carrier for enzymes, etc. mentioned above. Typical processing times are from 24 hours to 360 hours for bulk glass having a thickness of 1" 107 nm.

Above, we have described a method for producing porous glass from alkali borosilicate glass, but this production method can be used not only for glass in which a fourth component such as titania, zirconia, phosphoric acid, etc. is added to alkali borosilicate glass, but also for phosphosilicate glass, It can also be applied to aluminophosphate glasses and the like.

Hereinafter, the present invention will be explained in detail using specific examples.

Sin□ 66.1wt%, 81203 1.6w
t%, B2O224,I wt%1, Na2O8,2w
t%, As2O30,3wt%, NaNO30,5wt
After producing soda borosilicate glass consisting of , %, and separating the phases by heat-treating it at 640°C for 48 hours, a large number of lumps with a width of 40 mm, a length of 60 mm, and a thickness of 311,111 mm were manufactured and subjected to acid treatment. provided.

In order to know the pore structure of this glass, the pore diameter, pore volume, and surface area were measured in advance by the known method described above.

That is, a part of this glass is powdered (0.8~1.Otra
nφ) was immersed in an IN sulfuric acid aqueous solution at 100°C for 72 hours to remove the sodium borate phase, and then at room temperature with
The colloidal silica particles in the pores were removed by immersion in a N caustic potassium water bath for 6 hours.

The pore diameter was observed using an electron microscope, and the pore volume was determined by measuring the difference between the weight of the sample powder when saturated with water and the weight when dry.
The surface area was measured using an automatic specific surface area measuring device based on the so-called BET method, and the following target values were obtained.

Pore diameter: average 500X Pore volume; 0.60C/P Surface area; 50m/y The primary and secondary acid treatment conditions were changed as appropriate.

The pore diameter, pore volume, and surface area of the obtained porous glass were measured by the measurement method described above.

The results are shown in Table 1.

In Examples 1 to 4 of the present invention, the pore volume is about 80% and the surface area is about 150 to 160 inches, which are almost satisfactory values, and the pore diameters are uniform. Therefore, it can be used as a carrier for enzymes, molecular sieves, and gas separation.

Comparative Examples 1.2 and 3 were conducted in contrast to Example 1 for dilute acid, concentrated acid, and very concentrated acid, respectively. That is, Comparative Example 1 had the same primary treatment conditions as Example 1. However, only the processing time was the same as the total processing time of Example 1. Comparative Example 2 has the same secondary treatment conditions as Example 1. However, the processing time was set to be the same as the total processing time of Example 1. Comparative Example 3 has a higher acid concentration than Comparative Example 2.

Comparative Example 1 does not change any of the effects of this example, and Comparative Example 2.
In No. 3, the occurrence of cracks was observed.

In Comparative Example 4.5, a primary treatment with a dilute acid and a secondary treatment with a concentrated acid were performed in comparison with Example 1, and in Comparative Example 4, the acid concentration in the secondary treatment was too high. Comparative Example 5 also shows the case where the acid concentration is low.

Comparative Examples 4 and 5 do not have the same effect as the e-window of this example.

As detailed above, the present invention enables the production of bulk porous glass, which has been considered difficult in the past, and has uniform pore diameters, making it suitable for practical use as a phase for enzymes, molecular sieves, gas separation, etc. It is something that can be provided.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view showing the state of pores in a conventional porous glass, and FIG. 2 is a schematic plan view showing the state of pores in porous glass after the primary treatment of the present invention. FIG. 3 is a schematic plan view showing the state of pores in the porous glass of the present invention. 1. Solica skeleton 2. Pores 3. Colloid/Sorica patent applicant Central Glass Co., Ltd.

Claims (1)

[Claims] In the method of producing porous glass by acid-treating phase-separated alkali borosilicate glass, first 0.1 to 0.5N
A method for producing porous glass, characterized in that the acid treatment is carried out with an aqueous solution of a strong acid of 2 to 5N, and then with an aqueous solution of a 2 to 5N strong acid.