JP2012187492A - Porous ceramic membrane, and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous ceramic membrane excellent in durability, capable of preventing the exposure of its substrate caused by the elution of an alkali present in its glass seal layer disposed on the outer peripheral edge A and inner peripheral edge B thereof, and a method of producing the same.SOLUTION: The porous ceramic membrane including a plurality of through holes formed in a porous alumina substrate, a MF membrane layer formed on the inner surface of the plurality of through holes each functioning as a fluid passage, a glass seal layer formed on the end face disposed on the fluid passage direction of the substrate, a chamfered outer periphery formed by chamfering the outer peripheral edge of the porous alumina substrate whereon the outer peripheral face thereof and the end face on the fluid passage direction thereof are disposed to form an angle, and a chamfered inner periphery formed by chamfering the inner peripheral edge of the porous alumina substrate whereon the end face on the fluid passage direction thereof and the MF membrane layer are disposed to form an angle, is characterized in that the chamfered outer periphery and the chamfered inner periphery are covered with the glass seal layer.

Description

  The present invention relates to a ceramic porous membrane and a method for producing the same.

  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. 6 is a cross-sectional explanatory diagram of a ceramic porous membrane that is usually used in the food processing field. As shown in FIG. 6, the ceramic porous membrane 1 is made of a base material 9 made of a monolithic ceramic porous body (with a relatively large average pore diameter) by a sealing material 2 such as an O-ring made of an elastic material. The outer peripheral surface 3 and the fluid flow path direction end surface 4 are housed and used in the housing 5 so as to be hermetically isolated. With respect to the structure of the ceramic porous membrane 1, a technique for covering the end surface 4 in the fluid flow path direction with a glass seal layer 6 is disclosed (Patent Document 1 and the like).

  By forming the glass seal layer 6 on the end surface 4 in the fluid flow path direction, the fluid to be treated is always formed on the through hole 7 and the surface of the through hole 7 as shown by the solid line (F) in FIG. The permeated membrane layer 8 passes through the outer peripheral surface 3 of the substrate. According to the structure, as shown by a broken line (F ′) in FIG. 6, the fluid to be processed that has entered the base material from the end surface 4 side in the fluid flow path direction does not pass through the filtration membrane layer 8. The phenomenon which flows out from the outer peripheral surface 3 of this can be avoided, and the target filtration can be performed reliably.

  However, conventionally, the base material 9 cuts a monolith-shaped ceramic porous body fired in advance with a fixed size, and an outer peripheral edge portion 10 in which the fluid flow direction end surface 4 and the outer peripheral surface 3 are the cut surfaces. In addition, a material having an inner peripheral edge portion 11 in which the end face 4 in the fluid flow path direction and the through hole 7 form an angle is used, and silica-based glaze is applied to the outer peripheral edge portion 10 and the inner peripheral edge portion 11. When the glass seal layer 6 is formed by baking, as a result of surface tension acting on the applied glaze during the baking process, as shown in FIG. The phenomenon of thinning at the peripheral edge portion 11 inevitably occurred. For this reason, when the alkali cleaning of the ceramic porous membrane is repeated and the glass seal layer 6 starts to be eluted, first, the base material 9 is exposed from the outer peripheral edge portion 10 and the inner peripheral edge portion 11, and the membrane life is shortened. There was a problem of shortening.

JP 2006-263498 A

  The object of the present invention is to solve the above problems, avoid exposure of the substrate due to alkali elution of the glass seal layer at the outer peripheral edge portion A and the inner peripheral edge portion B, and a ceramic porous membrane excellent in durability and its It is to provide a manufacturing method.

  The ceramic porous membrane of the present invention made to solve the above-described problems is provided with a plurality of through holes formed in a porous alumina base material and an MF formed on the inner surface of the through hole serving as a fluid flow path. A ceramic porous membrane having a membrane layer and a glass seal layer formed at an end portion in the fluid flow channel direction, and an outer periphery in which an outer peripheral surface of the porous alumina substrate and an end surface in the fluid flow channel direction form an angle An outer peripheral chamfered portion obtained by chamfering the edge portion, and an inner peripheral chamfered portion obtained by chamfering an inner peripheral edge portion where the MF membrane layer and the end surface in the fluid flow path direction form an angle. The peripheral chamfered portion is covered with the glass seal layer.

  According to a second aspect of the present invention, in the ceramic porous membrane according to the first aspect, the porous alumina substrate is a monolithic ceramic porous body.

  According to a third aspect of the present invention, in the ceramic porous membrane according to the first aspect, the MF film layer has a thickness of 120 to 200 μm.

  Invention of Claim 4 is a manufacturing method of the ceramic porous membrane of Claim 1, Comprising: The outer periphery chamfering part formation process which chamfers an outer peripheral edge part with a rotating grindstone, and chamfers an inner peripheral edge part with a polishing brush It has an inner peripheral chamfered portion forming step to be processed.

  The invention according to claim 5 is the method for producing a ceramic porous membrane according to claim 4, wherein the polishing brush is a diamond yarn having a particle size of # 170 to # 240, a diameter of 0.6 to 1.0 mm, and a length of 15 to 25 mm. The polishing brush is rotated at a rotational speed of 800 to 1200 rpm and an eccentric rotational speed of 24 to 40 rpm.

  The ceramic porous membrane according to the present invention includes a plurality of through holes formed in a porous alumina base material, an MF film layer formed on an inner surface of the through hole serving as a fluid flow path, and the fluid flow path. In a ceramic porous membrane having a glass seal layer formed at an end portion in the direction, an outer peripheral chamfering process by chamfering an outer peripheral edge portion where the outer peripheral surface of the porous alumina substrate and the end surface in the fluid flow channel direction form an angle A chamfered inner peripheral chamfered portion, and an outer peripheral chamfered portion and an inner peripheral chamfered portion of the glass seal. Even if surface tension is applied to the glaze applied to the outer peripheral edge and inner peripheral edge by firing, the glass seal at the outer peripheral edge and inner peripheral edge Ensure the thickness of the layer for chamfering Theft has become possible. As a result, when the alkali cleaning of the conventional ceramic porous membrane is repeated and the glass seal layer begins to elute, first, the base material is exposed from these outer peripheral edge portions and inner peripheral edge portions, and the membrane life is shortened. The problem is solved, and durability can be improved as compared with the conventional case.

It is a cross-sectional explanatory drawing of the ceramic porous membrane in the use condition accommodated in the housing. It is a principal part enlarged view of FIG. It is whole explanatory drawing of the porous alumina base material which has a through-hole and the MF film | membrane layer formed in the inner surface of a through-hole. It is explanatory drawing of the outer peripheral chamfer part formation process which chamfers an outer peripheral edge part with a rotating grindstone. It is explanatory drawing of the internal peripheral chamfer part formation process which chamfers an internal peripheral edge part with a polishing brush. 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.

  FIG. 1 is a cross-sectional explanatory view of a ceramic porous membrane in a use state accommodated in a housing, and FIG. 2 is an enlarged view of a main part of FIG.

  The porous ceramic membrane 1 shown in FIG. 1 uses the porous alumina substrate 9 shown in FIG. 3 (for example, a cylindrical substrate having a diameter of 30 to 180 mmφ and a length of 150 to 2000 mm). An outer peripheral chamfered portion forming step of chamfering an outer peripheral edge portion 10 in which the surface 3 and the end surface 4 in the fluid flow channel direction form an angle, and an inner periphery in which the MF membrane layer 12 and the end surface 4 in the fluid flow channel direction form an angle An inner peripheral chamfered portion forming step for chamfering the edge portion 11 and glass for forming the glass seal layer 6 on the end A in the fluid flow path direction so as to cover the outer peripheral chamfered portion 13 and the inner peripheral chamfered portion 14 It is manufactured through a sealing layer forming step. The porous alumina base material 9 shown in FIG. 3 has a plurality of through holes 7 and an MF membrane layer 12 formed on the inner surface of the through holes 7 that serve as fluid flow paths.

(Outer peripheral chamfer forming step)
FIG. 4 is an explanatory diagram of an outer peripheral chamfered portion forming step in which the outer peripheral edge portion 10 is chamfered with the rotating grindstone 15. The rotating grindstone 15 has a taper-shaped inner peripheral surface, and is held by a metal bond on the outer peripheral surface of a conventionally known one (for example, a disk-shaped (donut-shaped) base metal having a hole in the center. In addition, a wheel having a structure to which a diamond abrasive layer is attached can be used.

  In the outer peripheral chamfered portion forming step, an alumina base material 9 (for example, having a diameter of 30 to 180 mmφ and a length of 150 to 2000 mm) in which the MF film layer 12 is formed on the inner surfaces of the plurality of through holes 7 serving as fluid flow paths. A cylindrical base material) is used, and the taper surface of the rotating grindstone 15 is rotated while being pressed against the end face 4 of the base material 9 in the fluid flow path direction, whereby the outer peripheral edge portion 10 is chamfered, and the outer peripheral chamfering is performed. Part 13 is formed. The chamfer angle is preferably 30 to 60 °, and FIG. 4 shows an example of 45 °.

(Inner chamfer forming process)
FIG. 5 shows an explanatory diagram of an inner peripheral chamfered portion forming step in which the inner peripheral edge portion 11 is chamfered with the polishing brush 16.

  The chamfering of the inner peripheral edge 11 can be performed by sequentially polishing the through holes one by one using a grinder such as a leuter, but a plurality of (for example, 19, 37, 61) In the case of an alumina base material having through holes, this method is laborious and time consuming and lacks practicality. Therefore, in this embodiment, a polishing brush 16 made of diamond yarn having a particle size of # 170 to 240, a diameter of 0.6 to 1.0 mm, and a length of 15 to 25 mm is used, and the polishing brush 16 is rotated at a rotational speed of 800 to 1200 rpm. The inner peripheral chamfered portion 14 is formed by performing chamfering by rotating at an eccentric rotational speed of 24 to 40 rpm.

  In the inner peripheral chamfered portion forming step, it is necessary to chamfer the inner peripheral edge portion 11 in which the MF film layer 12 having a thickness of about 120 μm and the end surface 4 of the base material in the fluid flow path form an angle. If the diamond yarn of the brush 16 has a length of 300 mm or more, the amount of bending of the diamond yarn becomes excessive, and the inner peripheral edge portion 11 cannot be effectively polished, which is not preferable. On the other hand, when the diamond yarn of the polishing brush 16 has a length of 100 mm or less, the amount of bending of the diamond yarn is insufficient, and the end surface 4 of the base material in the fluid flow path direction is also polished, thereby effectively polishing the inner peripheral edge portion 11. It is not preferable because it cannot be carried out automatically. On the other hand, by setting the diamond yarn of the polishing brush to a length of 15 to 25 mm, the tip of the diamond yarn is adjusted so that the tip of the polishing brush 16 has an angle for effectively polishing the inner peripheral edge portion 11. The amount of deflection can be adjusted optimally.

(Glass seal layer forming process)
In the glass seal layer forming step, the glass seal layer 6 that covers the outer peripheral chamfered portion 13 and the inner peripheral chamfered portion 14 formed in the above step is formed. The glass seal layer 6 of the present invention means a liquid-impermeable seal material arranged so as to cover the end face 4 of the base material in the fluid flow path, and is composed of glass glaze. The glass seal layer 6 prevents the fluid to be processed from entering the substrate from the end surface 4 in the fluid flow path direction. This glass is excellent in corrosion resistance and has a low melting point.

  The glass seal layer 6 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 slurry for forming a glass seal is applied to both end faces of the ceramic filter to cover the outer peripheral chamfered portion and the inner peripheral chamfered portion, dried, and fired. The glass sealing layer is composed of a silica-zirconia glass glaze having an alkali component content of 10 to 15%, so that the glass with alkali can be obtained even by repeated film cleaning using a high concentration of alkali. Elution of the seal layer can be effectively suppressed.

  According to each said process, it becomes possible to ensure the part for the chamfering process in this outer periphery edge part 10 or the inner periphery edge part 11, and the thickness of the glass seal layer 6. FIG. Even when the glass sealing layer 6 starts to elute after repeated alkali cleaning of the ceramic porous membrane 1 by securing the thickness of the glass sealing layer 6 at the outer peripheral edge portion 10 and the inner peripheral edge portion 11, The exposure of the base material 9 at the edge portion can be effectively suppressed as compared with the conventional case.

  In addition, the glass seal layer tends to have weak adhesion to the MF film, but by forming the inner peripheral chamfered portion, a large adhesion area between the glass seal layer and the MF film can be secured, and the sealing performance is improved. You can also plan. Here, the sealing property means that the porous body of the ceramic membrane is soaked with water (immersed in water and degassed), and air is pressurized from the primary side or the secondary side, and bubbles are generated from the opposite side. Means the sealing function of the glass sealing layer, and the improvement in sealing performance means the extension of the film life.

DESCRIPTION OF SYMBOLS 1 Ceramic porous membrane 2 Seal material 3 Outer peripheral surface 4 End surface 5 in fluid flow path 5 Housing 6 Glass seal layer 7 Through-hole 8 Filtration membrane layer 9 Base material 10 Outer peripheral edge portion 11 Inner peripheral edge portion 12 MF membrane layer 13 Outer peripheral chamfered portion 14 Inner peripheral chamfer 15 Rotating whetstone 16 Polishing brush

Claims (5)

A plurality of through holes formed in the porous alumina base material, an MF film layer formed on the inner surface of the through hole serving as a fluid flow path, and a glass seal layer formed at an end in the fluid flow path direction In a ceramic porous membrane having
An outer peripheral chamfered portion obtained by chamfering an outer peripheral edge portion where an outer peripheral surface of the porous alumina base material and an end surface in the fluid flow channel direction form an angle, and an end surface in the fluid flow channel direction at the MF membrane layer and the end surface in the fluid flow channel direction. It has an inner peripheral chamfered part that chamfers the inner peripheral edge part that is made,
A porous ceramic membrane characterized in that the outer peripheral chamfered portion and the inner peripheral chamfered portion are covered with the glass seal layer.   2. The porous ceramic membrane according to claim 1, wherein the porous alumina substrate is a monolithic ceramic porous body.   The ceramic porous membrane according to claim 1, wherein the thickness of the MF membrane layer is 120 to 200 µm.   It is a manufacturing method of the ceramic porous membrane of Claim 1, Comprising: The outer periphery chamfer part formation process which chamfers an outer periphery edge part with a rotating grindstone, and the inner peripheral chamfer part formation process which chamfers an inner peripheral edge part with a polishing brush A method for producing a ceramic porous membrane, comprising: The polishing brush is made of diamond thread having a particle size of # 170 to 240, a diameter of 0.6 to 1.0 mm, and a length of 15 to 25 mm, and the polishing brush is rotated at a rotational speed of 800 to 1200 rpm and an eccentric rotational speed of 24 to 40 rpm. The method for producing a ceramic porous membrane according to claim 4.