JP4951799B2 - Porous glass having phase-separated glass as precursor and method for producing the same - Google Patents

Description

  The present invention relates to a porous glass having a phase-separated glass as a precursor and a method for producing the same.

  Porous glass produced by utilizing microphase separation of glass has a unique and uniformly controlled porous structure, and the pore diameter can be changed within a certain range. Utilizing the excellent features not found in other porous materials, industrial applications such as adsorbents, microcarrier carriers, highly functional separation membranes with excellent fractionation accuracy, monodisperse emulsifying elements, monodispersed bubble generating elements, etc. Is expected.

  However, it is difficult to produce a porous glass and a molded body thereof that are excellent in water resistance and alkali resistance and can be industrially mass-produced by conventional techniques. That is, in the acid elution step in the production process, insoluble substances are deposited in the pores, and it is difficult to stably produce a large amount of porous glass having uniform pores.

  In addition, when forming a phase-separating basic glass, which is a precursor of porous glass, into a tubular or plate-like shape, the phase-separating basic glass according to the prior art generates crystals at the time of molding. It is difficult to produce a molded body. On the other hand, water resistance and alkali resistance are not sufficient in a porous glass having a glass composition range that can be industrially mass-produced and molded articles thereof.

  Furthermore, in order to mass-produce the porous glass and its molded body and reduce the cost, it has been desired to use an inexpensive raw material such as waste glass.

By the way, it is known that the chemical durability of the porous glass can be improved by adding Al ₂ O ₃ to the phase separation base glass. Na ₂ O—CaO—Al ₂ O ₃ —B ₂ O ₃ —SiO ₂ glass (Patent Document 1) and Na ₂ O—CaO—MgO—Al ₂ O ₃ —B ₂ O as such phase separation basic glass ₃ -SiO ₂ type glass (patent document 2) is mentioned.

However, even when these basic glasses are formed into a shape such as a tube, a plate, or a particle, a crystalline material mainly composed of CaO and SiO ₂ is generated in the glass to produce a porous glass having desired characteristics. Difficult to do.

On the other hand, it is known that the chemical durability of the porous glass can be greatly improved by adding ZrO ₂ to the phase separation base glass. Such phase separation base _{glass, MO-Al 2 O 3 -B} 2 O 3 - there are ZrO ₂ -SiO ₂ glass (Patent Document 3). However, this basic glass has a problem that insoluble substances are deposited in the pores in the acid elution step. If this phenomenon occurs in the through-hole (passage), the insoluble matter may block part of the passage, which not only prevents the uniform pore diameter but also increases the porosity. It becomes difficult.
JP 57-140334 A Japanese Patent No. 1518989 JP-A-62-202839

  A main object of the present invention is to provide a method for producing a porous glass that can be industrially mass-produced. Another object of the present invention is to provide a porous glass excellent in water resistance and alkali resistance.

  As a result of intensive studies in view of the above-mentioned problems of the prior art, the present inventor has found that the above object can be achieved by using a glass having a specific composition, and has completed the present invention.

  That is, this invention relates to the following porous glass and its manufacturing method.

1. SiO _2: 40 to 60 _wt%, ZrO 2: 1 to 10 _{wt%, B} 2 O 3: _{15~40 wt%, Al} 2 O 3: _{6~15 wt%,} Na 2 O: 1 to 20% by weight, The phase-separated basic glass containing K ₂ O: 1 to 10 % by weight and CaO: 10 to 20 % by weight is heat-treated at 600 to 800 ° C., and then contacted with an acid solution to elute and remove acid-soluble components. A method for producing porous glass, which is characterized.

  2. Item 2. The method according to Item 1, wherein the phase-separating basic glass is a molded product obtained by molding under heating.

  3. Item 2. The manufacturing method according to Item 1, wherein the phase-separating basic glass is obtained by laminating a plurality of phase-separating basic glasses having different phase separation speeds.

  4). Item 2. The production method according to Item 1, wherein the phase-separated basic glass is obtained by melting a raw material containing at least one of waste glass and volcanic glass.

  5). Porous glass obtained by the manufacturing method according to any one of Items 1 to 4.

  6). Item 6. The porous glass according to Item 5, wherein the average pore diameter is in the range of 1 nm to 25 µm.

  7). Item 7. The porous glass according to Item 5 or 6, wherein the porous glass is a tubular or plate-like membranous porous body.

  8). Item 8. The porous glass according to any one of Items 5 to 7, which has an asymmetric structure.

  According to the production method of the present invention, since a phase-separated basic glass having a specific composition is used as a precursor, it is possible to prevent precipitation of insoluble matters in the pores in the treatment step using an acid solution. In addition, a porous glass excellent in dimensional accuracy and chemical durability (particularly, water resistance and alkali resistance) can be provided. Thereby, the porous glass which has a desired uniform pore diameter, pore volume (porosity), etc. can be obtained more reliably.

Further, in the production method of the present invention, a specific composition (particularly, a combination of K ₂ O, B ₂ O ₃ and ZrO _{2 in} a specific ratio) is adopted as the composition of the phase separation basic glass. Since crystals are not formed when molding under the above, a porous glass molded body (for example, a film-shaped molded body) can be efficiently produced. In other words, in the production method of the present invention, a molded body obtained by molding under heating can be used as the phase separation base glass. Therefore, the production method of the present invention can also be used for mass production of a molded body of porous glass. Is suitable.

  Further, when inexpensive waste glass and / or volcanic glass is used as the raw material for the phase separation base glass, the production cost can be greatly reduced.

  When a plurality of phase-separating basic glasses having different phase separation speeds are laminated in layers, a film-like porous body of porous glass having an asymmetric structure can also be obtained.

  The porous glass obtained by such a production method can be used as, for example, an adsorbent, a microcarrier carrier, a high-performance separation membrane with excellent fractionation accuracy, a monodisperse emulsifying element, a monodispersed bubble generating element, and the like. is there.

1. Method for producing a porous glass manufacturing process invention of the porous _glass, SiO 2: 40 to 60 wt%, ZrO _2: 1~10 wt%, B ₂ O _3: 15~40 wt%, Al ₂ O ₃ : 6 to 15 wt%, Na ₂ O: 1 to 20 wt%, K ₂ O: 1 to 10 wt% and CaO: after heat treatment the phase separation base glass containing 5 to 30 wt% in 600 to 800 ° C., The acid-soluble component is eluted and removed by contacting with an acid solution.

The method of manufacturing a phase separation base glass the present invention, phase separation basic glass used as _precursors, SiO 2: 40 to 60 wt%, ZrO _2: 1 to 10 wt%, B ₂ O _3: 15~40 wt%, al ₂ O _3: 5 to 30% by weight: 6 to 15 wt%, Na ₂ O: 1 to 20 wt%, K ₂ O: 1 to 10 wt% and CaO.

In the present invention, by adopting the composition as described above, porous glass having excellent characteristics can be produced on an industrial scale. In particular, by containing a predetermined amount of ZrO ₂ and controlling the contents of ZrO ₂ , CaO, and B ₂ O ₃ , 1) effective generation of crystalline substances when forming phase-separated basic glass 2) In the acid elution step carried out after phase separation, it is possible to effectively avoid precipitation of insoluble substances in the pores. Moreover, the said composition can obtain the porous glass excellent in water resistance and alkali resistance. This makes it possible to mass-produce porous glass (or a molded body thereof) that can exhibit characteristics superior to those of conventional products.

SiO ₂ is usually 40 to 60% by weight, and preferably 45 to 55% by weight. ZrO ₂ is usually 1 to 10% by weight, and particularly preferably 2 to 5% by weight. In particular, by setting ZrO ₂ in the above range, it is possible to prevent precipitation of insoluble matter in the pores in the acid elution step when producing porous glass. Thereby, the porous glass which has a highly uniform pore diameter can be obtained more reliably. B ₂ O ₃ is usually 15 to 40% by weight, particularly preferably 17 to 25% by weight. When ZrO ₂ is added to the phase-separating basic glass, the phase separation speed decreases, and a porous glass (film-like porous body) with a small pore diameter tends to be obtained. To this, an appropriate amount of B ₂ O ₃ is added together with K ₂ O. As a result, the phase separation speed increases, and a porous glass having a large pore diameter or a membranous porous body thereof is obtained. Al ₂ O ₃ is usually 6 to 15% by weight, preferably 7 to 10% by weight. Na ₂ O is usually 1 to 20% by weight, and preferably 5 to 10% by weight. K ₂ O is usually 1 to 10% by weight, and preferably 2 to 5% by weight. When an appropriate amount of K ₂ O is added together with B ₂ O ₃ , the phase separation speed is increased, and a porous glass having a large pore diameter or a membranous porous body thereof can be obtained. CaO is usually 5 to 30% by weight, and preferably 10 to 20% by weight.

The phase separation basic glass may be composed of a single phase, or may be composed of a plurality of phases having different phase separation speeds. The phase separation speed can be controlled by changing the composition of the phase separation base glass. For example, Al ₂ O ₃ has a role of decreasing the phase separation speed, and K ₂ O, CaO, B ₂ O _{3 and the} like have an effect of increasing the phase separation speed. By combining these appropriately, a desired phase separation speed can be obtained.

  In addition, when it is composed of a plurality of phases with different phase separation speeds, the plurality of phases may be configured in any form, but in particular, it is in a form laminated in layers (membrane porous body). It is desirable.

  The method for producing the phase separation basic glass can be produced using a known method except that the raw materials are prepared so as to have the above composition. For example, it can be produced by heating and melting a raw material containing a supply source of each component and forming it into a desired form as necessary. The heating temperature in the case of heating and melting may be appropriately set depending on the raw material composition or the like, but is usually preferably in the range of 1350 to 1450 ° C (particularly 1380 to 1430 ° C).

For example, sodium carbonate, potassium carbonate, calcium carbonate, magnesium oxide, aluminum oxide, boric acid, zirconium oxide and silicon dioxide may be uniformly mixed as the raw material and heated and melted at 1350 to 1450 ° C. In this case, any raw material may be used as long as it contains the components Na ₂ O, K ₂ O, CaO, Al ₂ O ₃ , B ₂ O ₃ , ZrO ₂ and SiO ₂ as described above. good. In general, even when an oxide having a weight percentage of less than 1% is mixed, the phase separation of the base glass, the acid treatment of the phase separation glass, and the properties of the porous glass are not affected.

  Moreover, when making porous glass into a predetermined | prescribed shape, after synthesize | combining phase separation basic glass, what is necessary is just to shape | mold into various shapes, such as a tube shape, plate shape, and spherical shape, at the temperature of 1000-1200 degreeC. For example, after the above raw materials are melted to synthesize phase-separating basic glass, a method in which the temperature is lowered from the melting temperature and maintained at 1000 to 1200 ° C. can be suitably employed. In the present invention, as described above, since a predetermined composition is adopted, the generation of a crystalline substance during molding can be effectively suppressed or prevented, and a desired molded body can be obtained more reliably. .

A raw material containing at least one of waste glass and volcanic glass can be suitably used as part or all of the raw material. As a result, the resources can be effectively used and the manufacturing cost can be reduced. Examples of the waste glass include soda-lime glass such as a glass bottle, window glass, and glass cup, and heat-resistant borosilicate glass. Further, as a volcanic glass, shirasu can be suitably used as a supply source of Al ₂ O ₃ , SiO _{2 and the} like.

  When manufacturing what consists of a plurality of phases with different phase separation speeds, for example, two or more types of phase separation basic glasses having different compositions may be laminated in a molten state.

Heat treatment step In the production method of the present invention, the phase separation base glass is heat treated. Thereby, a phase separation basic glass is phase-separated.

In the present invention, the term “phase separation” mainly refers to a state of separation into a Na ₂ O—K ₂ O—CaO—B ₂ O ₃ glass phase and an Al ₂ O ₃ —ZrO ₂ —SiO ₂ glass phase. Say. This phenomenon can be confirmed by visually opacifying the phase-separated glass or measuring the transmittance of the glass (measurement with a spectrophotometer or the like).

  The heat treatment temperature is 600 to 800 ° C, preferably 650 to 750 ° C. Within such a temperature range, the pore diameter of the obtained porous glass can be controlled.

  The heat treatment time can be appropriately set in accordance with the desired pore diameter of the obtained phase-separating basic glass, usually within a range of 20 to 60 hours.

  In addition, the heat treatment atmosphere is not particularly limited, but is usually in the air or in an oxidizing atmosphere.

The acid -soluble component is eluted and removed by bringing the phase separation glass obtained by the heat treatment step into contact with an acid solution.

  The method of contacting with the acid solution is not particularly limited. For example, it may be any of 1) a method of immersing the glass in an acid solution, 2) a method of spraying an acid solution onto the glass, and 3) a method of applying an acid solution to the glass. In particular, in the present invention, a method of immersing in an acid solution is preferable.

  As the acid solution, for example, inorganic acids such as hydrochloric acid and nitric acid can be preferably used.

  The acid solution can be suitably used in the form of an aqueous solution usually using water as a solvent. What is necessary is just to set the density | concentration of an acid solution suitably in the range of 0.2-1 normal normally.

  The temperature in the acid treatment step (the temperature of the acid solution) is not particularly limited, but generally may be in the range of 30 to 75 ° C.

  Although the time of an acid treatment process can be suitably determined according to a composition, a magnitude | size, etc. of object glass, Usually, what is necessary is just about 2 to 10 hours.

2. Porous glass The porous glass of the present invention is obtained by the production method described above.

  The average pore diameter of the porous glass is not particularly limited, but is desirably in the range of 1 nm to 25 μm, particularly in the range of 2 nm to 20 μm.

  The porosity of the porous glass is usually 20 to 80%, preferably 30 to 70%.

  The shape of the porous glass is not particularly limited, and examples thereof include a tubular or plate-like film-like molded body. These shapes can be appropriately selected according to the use of the porous glass.

  Among the porous glasses of the present invention, particularly when a phase-separating basic glass composed of a plurality of phases having different phase separation speeds is used as a precursor, it has different physical properties (porosity, pore diameter, etc.). Porous glass can be obtained. For example, as described above, by controlling the phase separation speed of the phase separation basic glass constituting each layer, a film-like porous body in which phase separation basic glasses having different phase separation speeds are laminated in layers is obtained. This membranous porous body has a pore diameter gradient in the thickness direction of the membrane while each layer maintains uniform pores. For example, in the case of a three-layer membranous porous body, an inclined membranous porous body having an average pore diameter of the first layer of 50 nm, an average pore diameter of the second layer of 100 nm, and an average pore diameter of the third layer of 500 nm is used. It can also be configured. That is, it is possible to produce a membranous porous body having an asymmetric structure in which the average pore diameter increases (or decreases) in the order of lamination. Since the membranous porous body having such an asymmetric structure has the effect of significantly reducing the membrane resistance, it is suitable for applications such as membrane separation and membrane emulsification.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to the examples.

Example 1
Silicon dioxide, boric acid, calcium carbonate, anhydrous sodium carbonate, aluminum oxide, and zirconium oxide were prepared so that the main components of the phase separation glass had the composition shown in Table 1, and the base glass was synthesized by melting at 1350 ° C. . Subsequently, when the temperature of the glass melt is lowered to 1100 ° C., a tubular phase-separating basic glass (molded body) having a diameter of 10 mm, a thickness of 0.5 mm, and a length of 500 mm is obtained by a downdraw type glass tube rolling device. It was.

  Next, after heat-treating the above phase-separating basic glass in a furnace capable of accurately maintaining the temperature at 750 ° C. for 20 hours, it is immersed in 0.5 N hydrochloric acid at 30 ° C. for 8 hours to dissolve the acid-soluble glass phase. Was removed by elution. This was washed with water and dried to obtain the desired tubular porous glass membrane.

  A graph of pore distribution obtained by mercury porosimetry of the obtained porous glass film is shown in FIG. 1, and the observation result by a scanning electron microscope is shown in FIG. From these figures, it is clear that the porous glass film has uniform pores that are entangled three-dimensionally.

Test example 1
The alkali resistance of the porous glass obtained in Example 1 was examined. In the test, the porous glass was immersed in an aqueous sodium hydroxide solution (concentration 1 mol / L, temperature 30 ° C.), and the weight loss was determined. The result is shown in FIG. For comparison, the test results of commercially available porous glass (Porous Vycor Glass) and the prior art (Japanese Patent No. 1518959) are also shown in FIG.

Test example 2
The presence or absence of crystal formation during the molding of the phase-separating basic glass in Example 1 was examined. The test was performed by slowly cooling the glass melt of Example 1 to 1000 ° C. and holding the sample for 20 hours by X-ray diffraction analysis. The result is shown in FIG. For comparison, the test result of the prior art (Japanese Patent No. 1518959) is also shown in FIG.

Comparative Example 1
Porous glass (B) was produced in the same manner as in Example 1 except that the content of ZrO _{2 in} the phase-separated basic glass was 11.3 wt%. The pore distribution of the obtained porous glass was measured. The result is shown in FIG. FIG. 5 also shows the pore distribution of the porous glass (A) of Example 1.

Comparative Example 2
Porous glass (C) was produced in the same manner as in Example 1 except that the content of ZrO _{2 in} the phase separation base glass was 15.2% by weight. The pore distribution of the obtained porous glass was measured. The result is shown in FIG.

2 is a graph of pore distribution of the porous glass membrane obtained in Example 1. FIG. It is a result (image figure) by the scanning electron microscope observation of the tubular porous glass membrane obtained in Example 1. 6 is a graph showing the results of Test Example 1. It is a figure which shows the result of X-ray diffraction analysis, such as a phase separation basic glass in Example 1. FIG. It is a figure which shows the pore distribution of the porous glass obtained in Example 1 and Comparative Examples 1-2.

Claims (8)

SiO _2: 40 to 60 _wt%, ZrO 2: 1 to 10 _{wt%, B} 2 O 3: _{15~40 wt%, Al} 2 O 3: _{6~15 wt%,} Na 2 O: 1 to 20% by weight, The phase-separated basic glass containing K ₂ O: 1 to 10 % by weight and CaO: 10 to 20 % by weight is heat-treated at 600 to 800 ° C., and then contacted with an acid solution to elute and remove acid-soluble components. A method for producing porous glass, which is characterized. The manufacturing method of Claim 1 whose phase-separation basic glass is a molded object obtained by shape | molding under a heating. The manufacturing method according to claim 1, wherein the phase-separating basic glass is obtained by laminating a plurality of phase-separating basic glasses having different phase separation speeds. The manufacturing method of Claim 1 obtained by melt | dissolving the raw material containing at least 1 sort (s) of waste glass and volcanic glass for phase separation basic glass. The porous glass obtained by the manufacturing method in any one of Claims 1-4. The porous glass according to claim 5, wherein the average pore diameter is in the range of 1 nm to 25 μm. The porous glass according to claim 5 or 6, wherein the porous glass is a tubular or plate-like membranous porous body. The porous glass according to any one of claims 5 to 7, which has an asymmetric structure.

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