JP5736609B2 - Ceramic porous membrane - Google Patents

Description

The present invention relates to a ceramic porous membrane.

Ceramic porous membranes are often used in the food processing field because they can effectively remove suspended substances, microorganisms, and the like in a liquid by a simple operation.

  In general, equipment used in the field of food processing is washed with caustic soda for the purpose of removing protein components adhering to the equipment. For example, when the object to be cleaned is an organic film, it is normal to perform cleaning with caustic soda of 0.01 to 0.05% by weight or pH 12 or less. However, the ceramic porous film has a higher corrosion resistance than the organic film. In some cases, it is possible to perform cleaning using caustic soda of about 0.5 to 2% by weight.

  FIG. 2 is a cross-sectional explanatory view of a ceramic porous membrane that is usually used in the food processing field. As shown in FIG. 2, in the ceramic porous membrane 1, the outer peripheral surface 3 of the substrate and the end surface 4 in the fluid flow path direction are hermetically isolated by a sealing material 2 such as an O-ring made of an elastic material. As shown in FIG. With respect to the structure of the end face of the ceramic porous body (with a relatively large average pore diameter) constituting the substrate, a technique for covering the end face with a glass seal 6 is disclosed (Patent Document 1, etc.).

  By covering the end face 4 in the fluid flow path direction with the glass seal 6, the fluid to be treated is always formed on the through cell 7 and the surface of the through cell 7 as shown by the solid line (F) in FIG. 2. It passes through the filtration membrane 11 and flows out to the outer peripheral surface 3 of the base material. According to the structure, as shown by a broken line (F ′) in FIG. 2, the fluid to be treated that has entered the inside of the base material from the end surface side 4 of the base material does not permeate the filtration membrane 11 and the outer periphery of the base material. The phenomenon of flowing out to the surface side can be avoided and the intended filtration can be performed reliably.

  However, in the prior art, when cleaning with high concentration (≧ 2 wt%) and high temperature (≧ 70 ° C.) caustic soda is repeated for a long time, the interface between the glass seal and the substrate tends to be eroded. There was a problem that the corrosion resistance was not sufficient.

JP 2006-263498 A

An object of the present invention is to solve the above-mentioned problems and provide a ceramic porous membrane having high corrosion resistance against membrane cleaning using a high concentration of alkali.

The ceramic porous membrane of the present invention, which has been made to solve the above problems, includes a plurality of penetrating cells formed on a porous alumina substrate and an MF formed on the inner surface of the penetrating cell that serves as a fluid flow path. A ceramic porous membrane having a membrane layer and a glass seal layer formed on an end surface in the fluid flow path of the substrate, wherein the glass seal layer is a silica-zirconia glass having an alkali component content of 10 to 15%. And a surface peeling prevention layer made of silica-barium glass having an alkali component content of 1% or less between the glass seal layer and the substrate.

A ceramic porous membrane according to the present invention includes a plurality of through cells serving as fluid flow paths, a porous alumina base material forming the through cells, an MF membrane layer formed on the inner surface of the through cells, In the ceramic porous membrane having a glass seal layer formed on the end surface in the fluid flow path of the substrate, the glass seal layer is made of silica-zirconia glass having an alkali component content of 10 to 15%. Thus, even when the membrane cleaning using a high concentration alkali is repeated for a long period of time, the elution of the glass seal layer by the alkali is effectively suppressed. In the present invention, the alkali component content means the ratio of Na ₂ O + K ₂ O + Li ₂ O in the glass composition. Heretofore, when the ceramic porous membrane was repeatedly washed with caustic soda of about 0.5 to 2% by weight, a phenomenon that the interface between the glass seal and the base material was gradually eroded was observed. This is because Na ₂ O and K ₂ O contained in nepheline produced by the reaction between the substrate component alumina and the glass component are reactive with caustic soda, and a slight void is generated at the reaction site. caused by. On the other hand, in the present invention, a direct contact between the base material and the glass seal layer is avoided by adopting a structure having a surface peeling prevention layer between the glass seal layer and the base material having the above structure, and the glass seal layer. The formation of nepheline at the interface between the substrate and the base material is suppressed, and the phenomenon that Na ₂ O and K ₂ O contained in the neferin react with the caustic soda to form voids in the base material and the associated peeling of the glass seal layer is prevented. It can be effectively suppressed. That is, according to the configuration of the present invention having the above-described effect, it is possible to effectively suppress the problems of elution and peeling of the glass seal layer due to alkali even by long-term repetition of film cleaning using a high concentration of alkali. it can.

Further, as in the present invention, a glass seal layer is formed by having a surface layer peeling prevention layer made of silica-barium glass having an alkali component content of 1% or less between the glass seal layer and the substrate. And the softening point of the surface peeling prevention layer can be optimally adjusted. That is, according to the said structure, after laminating | stacking two layers of glass glazes on the base-material surface, these two glass layers can be baked simultaneously, and a work process can be simplified. Moreover, according to this structure, since the adhesiveness of a glass seal layer and a base material can be improved, peeling of a glass seal layer can be prevented effectively.

It is a section explanatory view of the ceramic porous membrane of the present invention. It is sectional explanatory drawing (state figure accommodated in the housing) of the ceramic porous membrane conventionally used in the food processing field | area.

  Preferred embodiments of the present invention are shown below.

The ceramic porous membrane of the present invention uses an alumina base material having an MF film layer 8 on the inner surface of a plurality of through-cells 7 serving as a fluid flow path, and the porous base material fluid having the MF film layer 8 A step (hereinafter referred to as a first step) of forming a surface layer peeling prevention layer 9 on the end surface 4 in the flow path direction, and a step of forming a glass seal layer 10 on the surface layer peeling prevention layer 9 (hereinafter referred to as a second step). It is manufactured through.

(First step)
The alumina base material used in the present invention is formed with a through cell 7 serving as a fluid flow path. An MF film layer 8 is provided on the surface of the through cell 7. In the first step, surface peeling prevention layers 9 are formed on the upper and lower ends of the alumina base material. As the surface peeling prevention layer, it is preferable to use silica-barium glass having an alkali component content of 1% or less. Although this glass has a low alkali component content, it has excellent adhesion to an alumina substrate and has a low melting point. If the alkali component content exceeds 1%, the alkali component becomes a factor in nepheline production, which is not preferable.

Thus, by setting it as the structure which has the surface layer peeling prevention layer 9 between a glass seal layer and a base material, the direct contact of a base material and a glass seal layer is avoided, and the interface surface of a glass seal layer and a base material Suppresses the generation of nepheline in the glass, and effectively suppresses the phenomenon in which Na ₂ O and K ₂ O contained in the neferin react with caustic soda to form voids in the base material and the associated peeling of the glass seal layer. Can do.

(Second step)
In the second step, the glass seal layer 10 that covers the surface peeling prevention layer 9 formed in the above step is formed. The glass sealing layer of the present invention is a liquid-impermeable sealing material disposed so as to cover at least the end surface 4 of the base material in the fluid flow path, and is a silica having an alkali component content of 10 to 15%. -It means one made of zirconia glass glaze. This glass seal layer prevents the fluid to be treated from entering the substrate from the end surface of the substrate. This glass is excellent in corrosion resistance and has a low melting point. If the alkali component content exceeds 15%, the corrosion resistance decreases, which is not preferable. Moreover, since melting | fusing point will raise that alkali component content rate is less than 10%, it is preferable that alkali component content rate shall be 10 to 15%.

  The glass seal layer may be formed according to a conventional method, and for example, can be formed by the following method. First, glass raw materials are mixed so as to have a silica-zirconia-based composition with an alkali component content of 10 to 15%, melted and homogenized, and cooled to have an average particle size of about 10 to 20 μm. Prepare a crushed frit. Next, water and an organic binder are added to the frit and mixed to prepare a slurry for forming a glass seal. The glass seal layer can be formed by applying the slurry for glass seal formation to both end faces of the ceramic filter, drying, and firing.

The glass seal layer is composed of a silica-zirconia glass glaze having an alkali component content of 10 to 15%, so that the glass seal layer with alkali can be obtained even by repeated film cleaning using a high concentration of alkali. Can be effectively suppressed.

  The glass seal layer is composed of silica-zirconia glass having an alkali component content of 10 to 15%, and the surface layer peeling prevention layer is composed of silica-barium glass having an alkali component content of 1% or less. Can optimally adjust the softening points of the glass seal layer and the surface peeling preventive layer, so that after the two glass glazes are stacked on the surface of the substrate, the two glass layers can be simultaneously fired. The work process can be simplified. In addition, the physical adhesion between the substrate, the surface peeling prevention layer, and the glass seal layer can be improved.

By adopting a configuration that avoids direct contact between the substrate and the glass seal layer, the present invention avoids direct contact between the substrate and the glass seal layer and suppresses the formation of nepheline at the interface between the glass seal and the substrate. and, because it is an effective can suppress the phenomenon that Na 2 _O and K _{2 O} is a gap substrate reacts with caustic soda occurs contained in nepheline it may be with other embodiments.

  Examples of the present invention are shown below.

A glaze A having a glass composition shown in the left column of Table 1 is formed as a glass seal layer on the end surface side of the alumina base material having a monolith shape and having an MF film on the surface of each through-cell. Comparative Example 1), glaze B having the glass composition shown in the right column of Table 1 was formed as a glass seal layer (Comparative Example 2), and glaze B having the glass composition of Table 1 was applied and dried to flatten the surface. Subsequently, the glaze A having the glass composition shown in Table 1 was applied, dried, and then fired to form the glaze A as a glass seal layer, and a surface peeling prevention layer of the glaze B was formed between the base material and the glass seal layer. Each (Example) was prepared, and a corrosion resistance test for circulating an aqueous NaOH solution was performed under the following conditions.
(Corrosion resistance test conditions)
Use element φ30 (φ3 × 37 hole) -150mm
Chemical solution 2wt% -NaOH 75 ℃
Line speed 1m / sec
Filtration pressure 0.1MPa

When the surface condition and the presence / absence of peeling were verified every 250 hours, 500 hours, 1000 hours and 1500 hours, in Comparative Example 1, gaps were uniformly generated at the interface between the base material and the glass seal layer in 500 hours. In 1000 hours, the glass seal layer was completely peeled off. In Comparative Example 2, peeling of the glass seal layer was not observed until 1000 hours, but the surface of the glass seal layer was eroded (alkali elution amount: 0.004 wt% / h), and roughness was observed. In the examples, even after 1500 hours, no peeling between the base material and the glaze layer occurred, and the surface of the glass seal layer (alkaline elution amount: 0.002 wt% / h) was almost intact. .

By forming a glass seal layer having a silica-zirconia-based glass glaze having an alkali component content of 10 to 15% as a surface layer according to the above example, alkali elution on the surface of the glass seal layer can be effectively suppressed, In addition, it is confirmed that peeling of the glaze layer from the substrate surface can be effectively suppressed by forming a glaze layer that avoids direct contact between the substrate and the glass seal layer between the surface layer and the substrate. It was done.

DESCRIPTION OF SYMBOLS 1 Ceramic porous membrane 2 Sealing material 3 Outer peripheral surface 4 End face 5 of fluid flow paths 5 Housing 6 Glass seal 7 Penetration cell 8 MF membrane layer 9 Surface peeling prevention layer 10 Glass seal layer 11 Filtration membrane

Claims (1)

A plurality of penetrating cells formed on a porous alumina substrate, an MF membrane layer formed on the inner surface of the penetrating cell serving as a fluid flow path, and glass formed on the end surface of the substrate in the fluid flow path direction In the ceramic porous membrane having a seal layer, the glass seal layer is made of silica-zirconia glass having an alkali component content of 10 to 15% , and contains an alkali component between the glass seal layer and the substrate. A ceramic porous film comprising a surface layer anti-peeling layer made of silica-barium glass having a rate of 1% or less .

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