JP2009011895A - Porous glass-made filter and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous glass-made filter which is highly durable and easily cleaned, has low pressure loss and increased permeation flow rate, and to provide its manufacturing method and a complex filter. <P>SOLUTION: The porous glass-made filter comprises a vitreous foam having communication holes. Alternatively, it can be made of a vitreous foam having a plurality of porous layers of average pore diameters different from each other in the passing direction of a filtration object. The manufacturing method of the porous glass-made filter comprises: bringing a formed body consisting of oxynitride glass into contact with superheated steam to make the formed body porous to form the vitreous foam. The formed body is preferably brought into contact with a gaseous mixture of superheated steam and a given amount of oxygen gas (content particularly preferably 10-30 vol.%). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a porous glass filter and a method for producing the same. More specifically, the present invention relates to a porous glass filter that is highly durable, easy to clean, low in pressure loss, can increase the permeation flow rate, and is useful as a microfiltration membrane and the like, and a method for producing the same. . The present invention also provides a porous glass filter on the surface of a porous glass filter made of a vitreous foam having a plurality of porous layers having different porosity, and a support filter made of a porous ceramic sintered body. The present invention relates to a provided composite filter.

  Porous ceramic filters are easy to clean and have high durability, so they are used in many applications as microfiltration membranes. However, there are problems that the pressure loss is large and the permeation flow rate is small as compared with the polymer membrane. Moreover, if the film thickness is reduced and the porosity is increased, the pressure loss can be reduced and the permeation flow rate can be increased. However, in a normal filter made of a porous ceramic sintered body, if the porosity is increased, the strength is increased. As a result, there is a problem that the erosion characteristic with respect to the fluid is deteriorated.

  Porous ceramic filters are used in many applications, but there are many problems, and in order to solve them, for example, a ceramic filter made of a laminated sintered body having a plurality of ceramic layers made of different materials Is known (for example, see Patent Document 1). In particular, a porous ceramic molded body having pores arranged linearly in one direction and a method for producing the same are known (for example, see Patent Document 2).

  In the technical field of electromagnetic induction heating elements that are completely different from filters, an oxidation-resistant composite material in which a dense glass layer is formed on the surface of a substrate made of a carbon material and a porous glass layer is provided on the surface of the dense glass layer. Is known (for example, see Patent Document 3). This porous glass layer is provided in order to resist thermal shock so that the covering state of the dense glass layer can be maintained. In Patent Document 3, the porous glass layer has communication holes. There is no mention of whether it is a selfish bubble or not.

JP 2004-298874 A JP 2006-327913 A JP 2006-1749 A

  The present invention has been made in view of the above situation, has high durability, is easy to wash, has low pressure loss, can increase the permeation flow rate, and is useful as a microfiltration membrane or the like. It aims at providing a filter made from glass, and its manufacturing method. The present invention also provides a porous glass filter on the surface of a porous glass filter made of a vitreous foam having a plurality of porous layers having different porosity, and a support filter made of a porous ceramic sintered body. It aims at providing the provided composite filter.

Porous ceramic filters are used in many applications, but have many problems, and many improvements and developments have been made to solve them. As a result of studying the present invention to improve the disadvantage while maintaining the advantages of the ceramic filter, the oxynitride glass is oxidized by bringing the oxynitride glass into contact with water vapor, and the gas generated at that time is dissipated. As a result, it was found that the glass foams to form communication holes.
The present invention has been made by applying such knowledge to the technical field of ceramic filters.

The present invention is as follows.
1. A porous glass filter comprising a glassy foam having communication holes.
2. 1. The glassy foam has an average pore diameter of 0.1 to 50 μm and a porosity of 30 to 80%. Porous glass filter as described in 1.
3. The glassy foam is made of glass containing at least one of Y, La and Sc, and each element of Al and Si. Or 2. Porous glass filter as described in 1.
4). A porous glass filter made of a vitreous foam, wherein the vitreous foam comprises a plurality of porous layers having different average pore diameters in the direction in which the material to be filtered flows. Quality glass filter.
5). A support filter made of a porous ceramic sintered body, and the above-mentioned 1. provided on the surface of the support filter. To 3. A composite filter comprising the porous glass filter according to any one of the above.
6). 3. A support filter made of a porous ceramic sintered body, and the above-mentioned 4. provided on the surface of the support filter. A composite filter comprising the porous glass filter described in 1.
7). Above 1. To 3. It is a manufacturing method of the filter made from porous glass of any one of these, Comprising: The molded object which consists of oxynitride glass makes a porous body by making it contact with superheated steam, The product made from porous glass A method for manufacturing a filter.
8). 6. When the molded body is brought into contact with a mixed gas of the superheated steam and oxygen gas, and the mixed gas is 100% by volume, the oxygen gas is 50% by volume or less. The manufacturing method of the filter made from porous glass of description.
9. The temperature of the contact is a temperature range from a temperature that is 2.5% lower than the glass transition point of the oxide glass formed by oxidation of the oxynitride glass by the contact to a temperature that is 2.5% higher than the glass transition point. Above 7. Or 8. The manufacturing method of the filter made from porous glass of description.
10. 6. The contact temperature is lower than a glass transition point of oxide glass formed by oxidation of the oxynitride glass by the contact, and is not less than 2.5% lower than the glass transition point. Or 8. The manufacturing method of the filter made from porous glass of description.
11. The content of N element is 0.1 to 5 atomic% when the total content of the elements of the oxynitride glass is 100 atomic%. To 9. The manufacturing method of the filter made from a porous glass of any one of these.

Since the porous glass filter of the present invention is not a ceramic sintered body but is made of a glassy foam and has pores having a spherical shape, there is little stress concentration when an object to be filtered collides with a pore wall during filtration. As a result, the filter has high durability, is easy to clean, has a low pressure loss, can increase the permeation flow rate, and can be a useful filter as a microfiltration membrane.
Moreover, when the average pore diameter of the vitreous foam is 0.1 to 50 μm and the porosity is 30 to 80%, a porous glass filter having a lower pressure loss and a larger permeation flow rate is obtained. it can.
Further, when the vitreous foam is made of glass containing at least one of Y, La and Sc and each element of Al and Si, the porous foam has sufficient durability and is easy to clean. It can be made from a glass filter.
According to another porous glass filter of the present invention comprising a plurality of porous layers having different porosities in the direction in which the material to be filtered flows, the pressure loss is low, the permeation flow rate is large, and sufficient durability is achieved. It can be set as the filter which has.
According to the composite filter of the present invention comprising a filter made of a glassy foam, and the other composite filter of the present invention comprising a filter having a plurality of porous layers in which the glassy foam has mutually different average pore diameters, pressure loss And a filter having a high permeation flow rate and sufficient durability.
According to the method for producing a porous glass filter of the present invention, a filter can be easily produced by bringing oxynitride glass into contact with superheated steam. A porous glass filter having the following can be manufactured.
Further, when the molded body is brought into contact with a mixed gas of superheated steam and oxygen gas and the mixed gas is set to 100% by volume, when the oxygen gas is 50% by volume or less, the superheated steam and oxygen gas are oxidized. Since it easily penetrates into a molded body made of nitrided glass, it is easy to make porous, and a porous glass filter can be produced efficiently.
Furthermore, when the temperature of the contact is in a temperature range from 2.5% below the glass transition point of the oxide glass produced by oxidation of the oxynitride glass by contact to 2.5% above, it is suitable as a filter It is possible to efficiently produce a porous glass filter having an average pore diameter and a porosity, and the average pore diameter can be easily adjusted by the contact temperature.
In addition, when the contact temperature is lower than the glass transition point of the oxide glass formed by oxidation of the oxynitride glass by the contact and 2.5% or lower than the glass transition point, the contact temperature is the glass transition temperature. Compared to the case of more than the point, a more uniform porous glass filter having a more uniform pore shape and a narrow pore size distribution can be efficiently produced.
Furthermore, when the total content of each element of the oxynitride glass is 100 atomic%, when the content of N element is 0.1 to 5 atomic%, the average pore diameter suitable as a filter and A porous glass filter having a porosity can be efficiently produced, and the porosity can be easily adjusted by the content of N element.

The present invention will be described in detail below.
[1] Porous glass filter The porous glass filter of the present invention comprises a glassy foam.
Another porous glass filter of the present invention comprises a plurality of porous layers made of a glassy foam and having different porosity in the direction in which the material to be filtered flows.
Furthermore, the composite filter of the present invention and other composite filters of the present invention include a support filter made of a porous ceramic sintered body, the porous glass filter of the present invention provided on the surface of the support filter, or the like. The porous glass filter of the present invention.

  The “glassy foam” is formed by foaming glass at a temperature near the glass transition point, unlike a porous body made of a sintered body obtained by firing glass powder. Therefore, unlike the irregular pores in the sintered body formed by fusing part of the adjacent particles, the pores have a shape similar to a sphere, and the stress at the time of collision of the material to be filtered with the pore walls, etc. It is possible to obtain a filter with less concentration and excellent durability.

  The average pore diameter of the vitreous foam is not particularly limited, and is preferably set according to the particle diameter of solids contained in the material to be filtered, the strength of the filter, and the like. The average pore diameter can be 0.1 to 50 μm, preferably 1 to 25 μm, particularly preferably 1 to 10 μm. When the average pore diameter is 0.1 to 50 μm, particularly 1 to 25 μm, a porous glass filter having both excellent filtration performance and durability can be obtained. Further, the pore size distribution is not particularly limited, but it is preferable that 70% or more, particularly 80% or more of the total pores are included in the range of ± 50% of the average pore size. Furthermore, the porosity of the vitreous foam is not particularly limited, and is preferably set according to pressure loss and permeation flow rate, filter durability, and the like. This porosity can be 30 to 80%, preferably 35 to 75%, particularly preferably 40 to 70%. If the porosity is 30 to 80%, a porous glass filter having both excellent filtration performance and durability can be obtained.

  The porosity of the glassy foam can be calculated by individually measuring the area of pores on an image such as an SEM image and dividing the sum of the areas of the pores by the area of the entire image. In addition, the pore size distribution can be obtained based on the pore area measured individually. Further, the average pore diameter is obtained by calculating the average area from the area of individual pores in the same manner as the measurement of the porosity, assuming a circle having an area equal to the average area, and calculating the diameter of the circle. be able to. Such image processing can be performed using image processing software such as, for example, Scion Image (manufactured by Scion Corporation).

  The kind of glass which comprises a glassy foam is not specifically limited. Examples of the glass include glass containing Si and rare earth elements such as Y, La and Sc. This glass may contain Al. Moreover, alkaline-earth metal elements, such as Ca, Mg, and Ba, may be contained. Furthermore, although alkali metal elements such as Na and K may be contained, it is preferable that the amount of the alkali metal element is small. The glass may be glass containing B, glass containing Pb, or the like. As this glass, for example, a glass containing at least one of Y, La, and Sc and each element of Al and Si can be used.

  The porous glass filter may be a single-layer filter that is homogeneous from one surface side to the other surface side, and includes a plurality of porous layers having different average pore sizes in the direction in which the material to be filtered flows. It may be a filter. Thus, the layer configuration of the filter including a plurality of porous layers is not particularly limited, and may be, for example, an inclined structure in which the average pore diameter is sequentially changed from one surface side to the other surface side, or the intermediate portion is It may be a dense layer with a relatively small average pore diameter, a rough layer with a relatively large average pore diameter on both surface sides, or a middle layer with a coarse layer with a relatively large average pore diameter. There may be a dense layer having a relatively small average pore diameter on both surface sides. The total number of porous layers is not particularly limited, but may be 2 to 5 layers, particularly 2 to 3 layers.

  The porous glass filter of the present invention and other porous glass filters of the present invention can be used as they are. That is, it can be used as a self-supporting filter only by vitreous foam. In this case, the thickness of the filter is not particularly limited, and may be 100 to 1000 μm, particularly 200 to 700 μm, although it depends on the porosity and the like. Further, since this filter is formed by making a molded body made of oxynitride glass porous, its shape is not particularly limited, and not only a simple shape such as a sheet shape but also a filter with a specific complicated shape. You can also

[2] Composite filter Although the porous glass filter of the present invention and other porous glass filters of the present invention can be used as they are as described above, these porous glass filters are It can also be used as a composite filter combined with other filters.
Other filters to be combined to form this composite filter are not particularly limited, and examples thereof include a filter made of a porous ceramic sintered body.
That is, the composite filter of the present invention and other composite filters of the present invention include a support filter made of a porous ceramic sintered body, the porous glass filter of the present invention provided on the surface of the support filter, or the like. The porous glass filter of the present invention.

  The ceramic constituting the “porous ceramic sintered body” is not particularly limited, and oxide ceramics, nitride ceramics, glass ceramics and the like can be used. In order to obtain a filter, it is necessary to suppress densification and to make a porous body having voids between particles. However, in such a porous body, when the material to be filtered flows, it collides with the void wall. As a result, particles fall off and the durability tends to decrease. Therefore, by providing a porous glass filter on the surface of this porous ceramic sintered body, a composite filter having excellent filtration performance and sufficient durability can be obtained.

  In the composite filter of the present invention and other composite filters of the present invention, the porous ceramic sintered body can serve as a support filter to provide a filter having sufficient strength. The thickness of the support filter is not particularly limited, but in order to obtain a filter having sufficient strength, it is preferably 5 to 30 mm, particularly 10 to 20 mm. The thickness of the porous glass filter is not particularly limited, but may be a thinner layer than that of the self-standing type, and the thickness may be 50 to 500 μm, particularly 50 to 200 μm.

  Furthermore, the porous glass filter of the present invention and the other porous glass filter of the present invention are formed by making a molded body made of oxynitride glass porous. A molded body is formed on the surface, and then it is made porous to form a composite filter. Therefore, the shape of the support filter is not particularly limited, and a porous glass filter can be easily formed on the surface of the support filter regardless of whether it is a simple shape such as a sheet shape or a more complicated shape. The composite filter can be a simple shape or a more complicated shape.

[3] Method for Producing Porous Glass Filter In the method for producing a porous glass filter of the present invention, a molded body made of oxynitride glass is brought into contact with superheated steam to make it porous to form a glassy foam. It is characterized by that.

(1) Production of Oxynitride Glass Molded Body The above “oxynitride glass” only needs to contain an N element, and its composition is not particularly limited. Examples of the oxynitride glass include glass containing Si and rare earth elements such as Y, La and Sc in addition to the N element. The oxynitride glass may contain an alkaline earth metal element such as Al, Ca, Mg, and Ba, and an alkali metal element such as Na and K, but the alkali metal element is a small amount. Is preferred. Further, the oxynitride glass may be a glass containing B, a glass containing Pb, or the like. As this glass, for example, a glass containing N element and at least one of Y, La, and Sc, and each element of Al and Si can be used. In particular, glass containing Y as a rare earth element. Is preferably used. The glass containing Y is preferable because it has a low equilibrium vapor pressure of hydroxide (gas) and is difficult to volatilize in a high-temperature steam atmosphere.

  The content of the N element in the oxynitride glass is not particularly limited, but can be 0.1 to 5 atomic% when the total content of the elements of the oxynitride glass is 100 atomic%. 0.5 to 3 atomic%, particularly 0.5 to 2 atomic% is preferable. If the content of N element is 0.1 to 5 atomic%, particularly 0.5 to 3 atomic%, it is possible to easily produce a porous glass filter having an average pore diameter and porosity that functions as a filter. it can. Furthermore, the porosity of the vitreous foam can be easily adjusted by changing the content of N element in the oxynitride glass.

The method for producing the oxynitride glass is not particularly limited, but by melting a ceramic mixture containing a ceramic containing N element, and then cooling at a rate of 10 to 100 ° C./min, particularly 15 to 40 ° C./min. Can be produced. In addition to the ceramic containing N element, the ceramic mixture contains compounds of the above-mentioned various elements that constitute oxynitride glass, and oxides of the respective elements are usually used as this compound. For example, in the case of a glass containing N element and at least one of Y, La, and Sc, and each element of Al and Si, the ceramic mixture may be ceramic having N element, Y ₂ O ₃ , La _2. It contains at least one of O ₃ and Sc ₂ O ₃ , Al ₂ O ₃ and SiO ₂ . The mass ratio of these oxides, if the sum of the 100 _mass%, Y ₂ O 3, at least one oxide of _La 2 _{O 3} and _Sc 2 _{O 3} is 20 to 50 wt% Al ₂ O ₃ is preferably 10 to 30% by mass and SiO ₂ is preferably 30 to 60% by mass, and the ceramic containing N element is preferably used in such a range that the content of N element falls within the above range. .

The ceramic containing N element is not particularly limited, and various ceramics can be used. The ceramic containing N element is represented by nitrides such as AlN, Si ₃ N ₄ , Mg ₃ N ₂ , silicon oxynitrides such as Si ₂ N ₂ O and Si ₅ N ₆ O, and Al _{2n + 1} O _3n N. And metal oxynitrides and sialons. These ceramics containing N element may be used alone or in combination of two or more. In many cases, AlN and / or Si ₃ N ₄ is used as the ceramic containing N element.

  The “molded body” can be produced by mixing raw material ceramic powder, putting the mixed powder into a mold, then heating, and then cooling. More specifically, the raw material ceramic powder is dispersed in an aqueous medium such as water and / or ethanol, wet-mixed by a ball mill or the like, then dried, sized as necessary to obtain a mixed powder, and then mixed. The powder can be prepared by putting it in a mold such as a carbon mold, heating it at a predetermined temperature, and then rapidly cooling it.

  The temperature of the wet mixing is not particularly limited, and may be room temperature (for example, 20 to 35 ° C.) and may be heated, but usually does not need to be heated. In addition, drying may be performed under normal pressure or under reduced pressure, but for efficient drying, it is preferable to dry under reduced pressure (the pressure is, for example, 1 to 10 kPa). Although a drying temperature is not specifically limited, In the case of an aqueous medium, it is preferable that it is 50-80 degreeC. The apparatus used for drying is not particularly limited, but it is preferable to use an efficient apparatus such as a vibration fluidized dryer.

The mold used for molding the mixed powder is not particularly limited, but a carbon mold is often used. Also, the molding temperature, pressure and time are not particularly limited, but are preferably set according to the powder composition or the like. For _{example, Y 2 O 3, La 2} O 3 and at least one of _Sc 2 _{O 3,} as well as the case of the mixed powder containing ceramics with _Al 2 _O 3, SiO ₂ and N elements, the molding temperature 1350～ 1650 ° C., in particular 1400 to 1600 ° C., and the molding time can be 5 to 15 hours, in particular 7 to 12 hours.

  The molding atmosphere is not particularly limited, but is preferably an inert atmosphere such as a nitrogen gas atmosphere or an inert gas atmosphere such as argon. Ammonia gas can also be used. Further, when molding is performed in a nitrogen gas and ammonia gas atmosphere, the N element in the atmosphere is dissolved in the molded body, and the amount of N element contained in the molded body is compared with the amount of N element calculated from the composition of the mixed powder. Increase. The increasing ratio varies depending on the composition of the mixed powder, molding conditions, and the like. For example, in the case of a nitrogen gas atmosphere, the ratio is 1 to 20%, particularly about 5 to 15% of the calculated N element amount. The amount of N element contained in the molded body affects the average pore diameter and porosity of the vitreous foam, particularly the porosity. Therefore, based on the estimated amount of N element dissolved in the atmosphere, It is preferable to set the composition of the mixed powder, the molding conditions, and the like so that the total amount of N element contained becomes a predetermined value.

  The oxynitride glass can also be produced using a sol-gel method. In this sol-gel method, a metal alkoxide is used as a raw material to prepare an alkoxide solution, which is then hydrolyzed and polymerized to produce an oxide gel, which is then nitrided by heating in an ammonia gas atmosphere. Thus, an oxynitride glass can be manufactured. In this case, the molded body is produced by a method such as applying a sol to the surface of a glass substrate, a ceramic sintered body filter or the like, then gelling the coating film, and then heating in an ammonia gas atmosphere. be able to.

(2) Foaming of molded body A porous glass filter is manufactured by forming a glassy foam by bringing the molded body made of oxynitride glass prepared in (1) above into contact with superheated steam to make it porous. can do.
When the superheated steam comes into contact with the molded body and penetrates into the molded body, the oxynitride glass is oxidized to generate NOx gas. When the NOx gas is desorbed from the molded body, the molded body foams and vitreous foaming occurs. A body is formed and can be used as a porous glass filter. The molded body may be brought into contact with only superheated steam, or may be brought into contact with a mixed gas of superheated steam and a predetermined amount of oxygen gas, argon gas or the like, but is brought into contact with a mixed gas of superheated steam and oxygen gas. Is preferred. By contacting with a mixed gas containing oxygen gas, the porous glass penetrates more quickly into the inside of the molded body than in the case of only superheated steam or a mixed gas of superheated steam and argon gas. The filter made can be manufactured efficiently.

  When a mixed gas with oxygen gas is used, the content of oxygen gas is not particularly limited, but is preferably equal to or less than that of superheated steam. The oxygen gas can be 50% by volume or less, preferably 40% by volume or less, particularly 10 to 30% by volume, and more preferably 15 to 25% by volume when the mixed gas is 100% by volume. If the oxygen gas content is 50% by volume or less, particularly 40% by volume or less, the mixed gas penetrates more rapidly into the molded body, and the oxynitride glass is sufficiently oxidized, foamed, and porous A glass filter can be easily manufactured.

  The temperature of the “contact” is preferably within a temperature range that is not significantly different from the glass transition point of the oxide glass produced by oxidizing at least part of the oxynitride glass with superheated steam or the like. This temperature range is from the glass transition point [Tg × 0.975 (° C.)] that is 2.5% lower than the glass transition point [Tg (° C.)] of the oxide glass formed by oxidation of the oxynitride glass by contact. It is possible to make the temperature range up to a temperature [Tg × 1.025 (° C.)] exceeding 2.5%. Also, the temperature range from a temperature below Tg by 2.0% to a temperature above 2.0%, particularly the temperature range from a temperature below 1.5% to a temperature above 1.5%, and a temperature below Tg by 1% To a temperature range from 1% to 1% higher. If the contact temperature is in the temperature range from 2.5% below the glass transition point of the oxide glass to 2.5% above the temperature, the oxynitride glass will be in a viscous state suitable for foaming and pores approximating a spherical shape will be formed In addition, the pore diameter distribution is narrow and a more homogeneous glassy foam can be obtained.

The contact temperature can be set to a temperature lower than Tg of the oxide glass and 2.5% lower than Tg. Further, it is less than Tg and not less than 2.0% below Tg, particularly less than Tg and not less than 1.5% less than Tg, more preferably less than Tg and not less than 1% less than Tg. It can also be a temperature range. If the contact temperature is less than Tg and not less than 2.5% below Tg, the pore shape is more uniform and the pore size distribution is narrower and more homogeneous than when the contact temperature is Tg or more. A porous glass filter can be produced efficiently.
This contact temperature is preferably set according to the properties of the material to be filtered, the purpose of filtration, and the like.

  The contact time is not particularly limited as long as a glassy foam that can be used as a filter is obtained. This contact time is preferably set so as to obtain a vitreous foam that is preferable as a filter, in correlation with the contact temperature. For example, when the contact temperature is within a specific range based on Tg as described above, the contact temperature can be 100 to 1500 hours, and preferably 350 to 650 hours.

  The average pore diameter of the glassy foam can be easily adjusted by changing the contact temperature and / or contact time between the molded body and superheated steam or the like. That is, when the contact temperature is increased and / or the contact time is increased, the average pore diameter is increased, and when the temperature is decreased and / or the time is decreased, the average pore diameter is decreased. Accordingly, the molded body and superheated steam are brought into contact with each other at a predetermined temperature for a required time to make a predetermined thickness range porous from one side of the molded body, and then the contact temperature and / or contact time is changed to further increase the predetermined thickness. By making the thickness range porous and repeating this operation as necessary, the above-mentioned other consisting of a vitreous foam comprising a plurality of porous layers having different average pore diameters in the direction in which the material to be filtered flows. The porous glass filter of the present invention can be easily produced.

Hereinafter, the present invention will be specifically described by way of examples.
Example 1
(1) Production of Oxynitride Glass Molded Body Y ₂ O ₃ powder (trade name “NRN”, manufactured by Daiichi Rare Chemicals Co., Ltd.) 33.1% by mass when the total amount of the raw material ceramic powder is 100% by mass , 19% by mass of Al ₂ O ₃ powder (manufactured by Sumitomo Chemical Co., Ltd., trade name “AKP-50”), 46.1% by mass of SiO ₂ powder (manufactured by Nacalai Tesque, special grade of reagent), and AlN powder (Dow Chemical Company) 1.8% by mass (trade name “XUS 35560”) manufactured by the company was charged into a ball mill, and enonol was further charged, followed by wet mixing for 24 hours. Thereafter, the contents were taken out from the ball mill, accommodated in a vibration fluidized dryer, and dried at 65 ° C. under reduced pressure. Next, the dried powder was sized using a 150 mesh sieve to obtain a mixed powder. Thereafter, the mixed powder is put into a carbon mold, heated in a nitrogen atmosphere at 1500 ° C. for 10 hours, and then rapidly cooled at an average cooling rate of 20 ° C./min, and a dense oxynitride glass molded body having a thickness of 10 mm. Was made.

  The content of N element calculated from the composition of the raw ceramic powder when the oxynitride glass molded body produced as described above was charged was 1.0 atomic%. On the other hand, when the content of N element in the actually produced oxynitride glass was dissolved in an inert gas atmosphere and measured by a thermal conductivity method, it was 1.1 atomic%. The increase of 0.1 atomic% (the rate of increase is 10%) is considered to be due to the solid solution from the atmosphere. Moreover, the glass transition point measured by the JISR3103-3 thermal expansion method was 910 degreeC.

(2) Porousization A test piece was cut out from the oxynitride glass molded body produced in the above (1), and this test piece was placed on an alumina frame disposed in the middle in the length direction in the processing furnace. Left to stand. The processing furnace is made of quartz glass, and a mixed gas delivery pipe having a vaporizing heater disposed on the outer surface is attached to one end face, and water generated by condensation of superheated steam is formed on the lower face of the other end. A dew condensation water discharge pipe for discharging oxygen gas was attached, and a heater for heating was disposed on the outer surface of the main body. Using this processing furnace, water is supplied into the mixed gas delivery pipe by a pump, oxygen gas is supplied to the water vapor generated by evaporation of this water to form a mixed gas, and this mixed gas is sent into the main body, In the main body heated to a temperature of 910 ° C. by a heater, a mixed gas of superheated steam and oxygen gas was circulated at a flow rate of 100 ml / min. This mixed gas was discharged in the form of condensed water and oxygen gas from a condensed water discharge pipe attached to the lower surface of the other end of the main body. In this process, the compact and the mixed gas of superheated steam and oxygen gas contacted to make the compact porous.

(3) Evaluation of results The composition of the oxide glass that was made porous in the above (2) and oxidized oxynitride glass was 33:21:46 of Y ₂ O ₃ powder, Al ₂ O ₃ powder, and SiO ₂ powder. The glass transition point measured by the same method as described above was 889 ° C., which was the same as the oxide glass prepared by mixing at a composition ratio of (mass ratio) and melting and solidifying. Therefore, the contact temperature (910 ° C.) is a temperature that exceeds the glass transition point of the oxide glass by 2.36%. Furthermore, the cross section of the glassy foam was observed with a scanning electron microscope, and a photograph was taken. FIG. 1 is an explanatory view of a photograph taken at a magnification of 100 times (the total length connecting 11 points on the lower right side of FIG. 1 is 300 μm). FIG. 2 is a view of the field of view of FIG. It is explanatory drawing by the enlarged photograph which observed a part by 1000-times magnification and was image | photographed (The total length which connected 11 points | pieces of the lower right part of FIG. 2 is 30 micrometers). FIG. 3 is a graph plotting the correlation between the gas flow rate (u) and ΔP (pressure loss) / L (specimen thickness) · μ (gas viscosity) in accordance with the Darcy law. Further, FIG. 4 is a graph showing the correlation between the pore diameter measured by the above method and the pore diameter distribution. The average pore diameter was 15.5 μm, and the porosity was 43%.

1 and 2, it is observed that many of the pores are communication holes, and it is understood that a vitreous foam useful as a filter is formed. In addition, according to FIG. 3, the gas flow rate and pressure loss / specimen thickness / gas viscosity have a linear function correlation. It is confirmed that it is doing. The gas permeability calculated as the reciprocal of the slope of this straight line was 3.0 × 10 ⁻¹⁶ (m ² ).

Example 2
(1) An oxynitride glass molded body was produced in the same manner as (1) of Example 1.
(2) The molded body was made porous in the same manner as (2) of Example 1 except that the atmospheric temperature in the processing furnace was 880 ° C.

(3) Evaluation of results As in (3) of Example 1, the composition of oxide glass obtained by oxidizing oxynitride glass was Y ₂ O ₃ powder, Al ₂ O ₃ powder, and SiO ₂ powder 33:21. The glass transition point measured by the same method as described above was 889 ° C., which was the same as the oxide glass prepared by mixing at a composition ratio of 46 (mass ratio) and melting and solidifying. Accordingly, the contact temperature (880 ° C.) is a temperature that is 1.01% below the glass transition point of the oxide glass. Furthermore, the cross section of the glassy foam was observed with a scanning electron microscope, and a photograph was taken. FIG. 5 is an explanatory view of a photograph taken and observed at a magnification of 100 in the same manner as in Example 1 (the total length connecting 11 points on the lower right side of FIG. 5 is 300 μm). 6 is an explanatory view of a magnified photograph obtained by observing a part of the field of view of FIG. 5 at a magnification of 1000 times (the total length connecting 11 points on the lower right side of FIG. 6 is 30 μm). .) FIG. 7 is a graph showing the correlation between the pore size and the pore size distribution created in the same manner as in Example 1. The average pore diameter was 7.0 μm and the porosity was 65%.

  According to FIGS. 5 and 6, the shape of the pores is finer than that in Example 1, and the homogeneity is improved, and a vitreous foam having communication holes is formed. Inferred to be useful.

  Incidentally, the vitreous foam having the communicating holes constituting the porous glass filter of the present invention is not only used as a filter as described above but also used in the opposite manner to filtration, that is, bubbles are introduced from the communicating holes. It can also be used for applications such as cleaning of various parts in the field of discharging and bubbling, for example, in the field of manufacturing electronic parts. Since the glassy foam has high durability, even in this bubbling application, uniform bubbles can be stably bubbled over a long period of time.

An electron microscope of a cross section of a vitreous foam obtained by bringing an oxynitride glass (glass transition point: 910 ° C.) having a glass transition temperature of 889 ° C. into contact with superheated steam at 910 ° C. as in Example 1. It is explanatory drawing based on observation. It is explanatory drawing which expanded a part of visual field of the electron microscope observation of FIG. It is a graph showing the correlation with the gas flow rate measured using the vitreous foam in Example 1, and pressure loss. 3 is a graph showing the pore size distribution of the vitreous foam in Example 1. FIG. An electron microscope of a cross section of a vitreous foam obtained by bringing an oxynitride glass (glass transition point: 910 ° C.) having a glass transition point of 889 ° C. of the oxide glass into contact with superheated steam at 880 ° C. as in Example 2. It is explanatory drawing based on observation. It is explanatory drawing which expanded a part of visual field of electron microscope observation of FIG. 6 is a graph showing a pore size distribution of pores of a vitreous foam in Example 2.

Claims (11)

  A porous glass filter comprising a glassy foam having communication holes.   The porous glass filter according to claim 1, wherein the glassy foam has an average pore diameter of 0.1 to 50 µm and a porosity of 30 to 80%.   The porous glass filter according to claim 1 or 2, wherein the vitreous foam is made of glass containing at least one of Y, La, and Sc, and Al and Si elements. A porous glass filter made of glassy foam,
The glassy foam includes a plurality of porous layers having average pore sizes different from each other in a direction in which an object to be filtered flows.   A composite comprising: a support filter made of a porous ceramic sintered body; and the porous glass filter according to any one of claims 1 to 3 provided on a surface of the support filter. filter.   A composite filter comprising: a support filter made of a porous ceramic sintered body; and the porous glass filter according to claim 4 provided on a surface of the support filter. A method for producing a porous glass filter according to any one of claims 1 to 3,
A method for producing a porous glass filter, comprising: forming a porous body by bringing a molded body made of oxynitride glass into contact with superheated steam to make the molded body porous.   The porous glass according to claim 7, wherein the molded body is brought into contact with a mixed gas of the superheated steam and oxygen gas, and the oxygen gas is 50% by volume or less when the mixed gas is 100% by volume. Manufacturing method for filter.   The temperature of the contact is a temperature range from a temperature that is 2.5% lower than the glass transition point of the oxide glass formed by oxidation of the oxynitride glass by the contact to a temperature that is 2.5% higher than the glass transition point. The manufacturing method of the filter made from porous glass of Claim 7 or 8.   The temperature of the contact is less than a glass transition point of an oxide glass produced by oxidation of the oxynitride glass by the contact, and is not less than 2.5% lower than the glass transition point. The manufacturing method of the filter made from porous glass of description.   11. The element according to claim 7, wherein the content of the N element is 0.1 to 5 atomic% when the total content of the elements of the oxynitride glass is 100 atomic%. The manufacturing method of the filter made from porous glass of description.