JPH0226835A - Method for manufacturing porous glass - Google Patents

Abstract

PURPOSE:To produce porous glass having excellent strength and high formability by heating and foaming a dry gel which is obtained, for example, by dispersing a blowing agent in a sol prepared by a sol-gel method. CONSTITUTION:In the production process of glass by a sol-gel method, a blowing agent (for example, azodicarbonamide) is added and dispersed in the prepared sol and pH of the sol is controlled. Then the sol is injected in a desired die, solidified, dried to give a dry gel. The dry gel is heated at the temp. above the decomposition temp. of the blowing agent to decompose and then sintered.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to porous glass used for gas separation under high pressure and high temperature, as a catalyst for desalination of seawater, and as a carrier for immobilized enzymes and inorganic catalysts. Relating to a manufacturing method.

[Prior Art] A conventional method for manufacturing porous glass is shown in FIG. Na
, O-B10. -3 After adjusting the raw material consisting of 02,
Melts at a high temperature of about 1500℃, and further melts at a temperature of 800℃~11
It is formed into shapes such as tubes and plates at a temperature of 00°C. Since the borosilicate glass obtained at this time is unseparated,
Phase separation treatment was performed in the temperature range of ℃ to 650℃ to remove Na, O-
It is separated into two phases: B, O, phase and 810, phase. When this phase-separated glass is acid-treated with nitric acid or hydrochloric acid, the acid-soluble Na, O-B, and O phases are eluted, and S10,
Only the phase remains. Since the Na, OB, O8 and 810 phases are intricately intertwined within the glass, the remaining S1
0. Glass is a porous glass with countless continuous pores.

Another method for producing foam glass, which is used as building materials, involves mixing glass powder with a foaming agent such as carbon and then treating it at high temperatures.

Further, glass can be manufactured by a sol-gel method.

(Refer to Japanese Unexamined Patent Publication No. 59-92924.) In this case, a method has been considered to make porous glass by controlling the sintering conditions, taking advantage of the fact that pores are easily generated in the glass obtained. [Problems to be Solved by the Invention] However, in the conventional manufacturing method, it is necessary to melt the material and then press it to form the desired shape. There's a problem. Furthermore, the Na, O-B, and O8 phases contain SiO2 components, and during acid treatment, this S10. The components remain without being eluted and precipitate in the form of a gel within the pores, creating a secondary structure. This poses a problem in that the volume of the precipitates significantly changes the pore volume, leading to a decrease in performance in gas separation and the like.

The method for producing foam glass has problems such as the introduction of impurities during the production process, the inability to obtain closed pores, and the production of only simple shapes.

Further, the conventional sol-gel method has problems in that pores with large pore diameters cannot be obtained and that the strength of the sintered body is poor because sintering is stopped midway through. .

The present invention is intended to solve these problems, and its purpose is to provide a method for producing porous glass that has a high degree of freedom in shape and has excellent strength.

[Means for solving departmental labor problems] The method for producing porous glass of the present invention involves adding and dispersing a blowing agent to the prepared sol in the production of glass by the sol-gel method, and then shaping the sol into a desired shape. The gel is poured into a mold, solidified and dried to form a dry gel, heated to a temperature higher than the decomposition temperature of the foaming agent to decompose the foaming agent contained therein, and the mixture is further sintered.

[Example 1] Fig. 1 shows the manufacturing process of the present invention for a typical porous glass.

Ethyl silicate is hydrolyzed under acidic conditions to obtain sto, 711 particles with an average particle size o, os ~0.4 (μ771).
After adding the particles and further adding azodicarbonamide as a foaming material at 1 (wt%), aqueous ammonia is added to adjust the pH to 4.5 to prepare a sol.

This sol is placed in six types of polypropylene containers, and gelation is performed in a sealed state to obtain a wet gel. Thereafter, the wet gel is taken out from the sealed container and dried for two weeks to prepare a dry gel.

This dry gel was placed in a sintering furnace, heated to 200°C at a temperature increase rate of 50°C/hour, and held at the same temperature for 5 hours.
It is preferable to further heat the mixture to 300° C. and hold it at the same temperature for 5 hours to completely decompose the added azodicarbonamide and to perform desorption water treatment.

The blowing agents used are azo type such as azodicarbonamide,
Organic blowing agents represented by hydrazine type such as diphenylsulfone-3,31 disulfohydrazine, N-nitrone type such as N,N'-dinitrosopentamethylenetetramine, general organic resin, carbon, Ga003, etc. Any inorganic material may be used.

The dimensions of the obtained porous glass are shown in Table 1, and its properties are shown in Table 2.

The dry gel is further heated to 1000° C. at a heating rate of 50° C./hour and held at the same temperature for 10 hours to perform sintering and obtain porous glass. Sintering is performed in a nitrogen atmosphere or in a vacuum, but the foaming and degassing steps until the foaming agent is completely decomposed are performed in a vacuum. In order to achieve this, porous glasses were created by varying the amount of carbon added as a blowing agent and the sintering conditions. The shape of the sample in this example is φ
55×5 (m), and other manufacturing conditions are the same as in Example 1.

However, since the decomposition temperature of carbon is high, the foaming temperature is 8.
00'a.

Table 3 shows the manufacturing conditions for each sample, and Table 4 shows the characteristics of the obtained porous glass.

Table 4 In this example, porous glasses with various characteristics can be produced by changing the manufacturing conditions such as the amount of foaming agent added and the sintering temperature, according to the manufacturing method of the present invention. Obtainable. (In experiments, it is possible to create pores on the order of 100 μm from 10×.) Furthermore, since complete sintering is performed, the strength of the resulting porous glass is high, and there are no problems in practical terms.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing the method for producing porous glass of the present invention. FIG. 2 is a process diagram showing a conventional method for manufacturing porous glass. [Effects of the Invention] As described above, according to the present invention, since the sol is injected into a mold of an arbitrary shape and solidified, a complex-shaped porous material that requires secondary processing in conventional manufacturing methods can be produced. Glass can be easily manufactured. Furthermore, by taking advantage of the characteristics of the sol-gel method, it is possible to produce porous glass with uniform pore distribution and high strength without the occurrence of cracks in large products. Furthermore, by adjusting the amount of foaming agent added and the sintering temperature, it is possible to adjust the pore diameter and pore volume.

Claims (1)

[Claims] In the production of glass using the sol-gel method, a blowing agent is added to the created sol and dispersed, then this sol is poured into a mold of the desired shape, solidified and dried to form a dry gel, and this gel is heated to the decomposition temperature of the blowing agent. A method for producing porous glass, which comprises heating to the above temperature to decompose the foaming agent contained therein, and further sintering the mixture.