TW201526980A - Porous alumina membrane filter and method for manufacturing the same - Google Patents

Abstract

The invention provides a porous alumina membrane filter and a method for manufacturing the same, wherein the porous alumina membrane filter does not break easily, could restrain a warpage to be suitably used, and has excellent handling property and flatness property. The porous alumina membrane filter has an aluminum portion including an aluminum substrate and an anodic oxide film portion including an anodic oxide film. The anodic oxide film has a plurality of micropores piercing through a thickness direction. The alumina portion is formed by covering at least an end portion of a main surface of the porous alumina membrane filter, and an area ratio of the alumina portion with respect to all the main surface ranges from 10% to 60%.

Description

Porous alumina membrane filter and method of manufacturing same

The present invention relates to a porous alumina membrane filter and a method of producing the same.

In recent years, the anodized film of aluminum has been attracting attention due to the nanostructure and porosity of its crystal structure, and the production of a film in which holes are regularly arranged is being performed.

One of the uses thereof is a porous alumina membrane filter used in the field of microfiltration (Patent Document 1 and Patent Document 2).

In the membrane filter using an anodized film of aluminum, since aluminum is anodized in an acidic electrolytic solution, pores having a narrow pore diameter distribution and independent pores can be formed at a high density, and a high porosity can be obtained. The filtration flow rate per hour can be increased, and it can be manufactured inexpensively.

[Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2009-074133

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2009-050773

In order to increase the filtration efficiency, such a porous alumina membrane filter has a large number of pores so as to have a reduced thickness and a high porosity. Further, the anodized film has low toughness and is not resistant to impact or the like. Therefore, there is a problem that cracking occurs during operation.

Further, such a porous alumina film filter has a small thickness and is easily warped. Therefore, there is a problem that it cannot be properly attached to the filter device, and a sufficient effect cannot be exhibited.

In view of the above, it is an object of the present invention to provide a porous alumina membrane filter which is not easily broken, and which can be suitably used, which is excellent in workability and flatness, and a method for producing the same.

In order to achieve the above object, the inventors of the present invention have conducted an effort to find that the anodized film has a plurality of micropores penetrating in the thickness direction by having an aluminum portion including an aluminum substrate and an anodized film portion including an anodized film. a micropore, which is formed by covering at least an end portion of a main surface of the porous alumina membrane filter, and has an area ratio of 10% to 60% with respect to the entire main surface, thereby improving operability and flatness. The present invention has been completed.

That is, the present invention provides the following (1) to (5).

(1) A porous alumina membrane filter having anodization a film having an aluminum portion and an anodized film portion including an anodized film having a plurality of micropores penetrating in a thickness direction, the aluminum portion covering at least an end portion of a main surface of the porous alumina film filter Formed and the area ratio with respect to the entire main surface is 10% to 60%.

(2) The porous alumina membrane filter according to (1), wherein the anodized film portion is partitioned into a plurality of regions by the aluminum portion.

(3) The porous alumina membrane filter according to (2), wherein a distance between the anodized film portions separated by the aluminum portion is 2 mm or more.

(4) The porous alumina membrane filter according to (2) or (3), wherein the anodized film portion is partitioned into three or more regions by an aluminum portion.

(5) The porous alumina membrane filter according to any one of (1) to (4), wherein the anodized film portion is a line by using a predetermined straight line passing through the center of the main surface and parallel to the main surface as an axis. Formed in a symmetrical manner.

(6) A method for producing a porous alumina membrane filter, the porous alumina membrane filter according to any one of (1) to (5), and a method for producing the porous alumina membrane filter The method includes: masking a region including at least an end portion of the aluminum substrate and an area ratio of 10% to 60% with respect to the entire main surface; and anodizing the aluminum substrate in the unmasked region to form an anodized film portion A step of.

As described below, according to the present invention, it is possible to provide a porous alumina which is less likely to be broken and which can be suitably used and which is excellent in workability and flatness. Membrane filter and method of manufacturing the same.

10, 40, 42, 44‧‧‧ membrane filters

12‧‧‧Aluminum Department

12a‧‧‧Aluminum substrate

14‧‧‧Anodic Oxide Film Department

14a‧‧‧Anodized film

16‧‧‧Micropores

18‧‧‧Microporous through holes

19‧‧‧ Width of micropores through the holes

Α‧‧‧ center line

Da‧‧‧ Diameter of the anodized film section

Db‧‧‧ OD

Dc‧‧‧Down

ta‧‧‧The shortest distance between the anodized film sections

Fig. 1 is a schematic view showing an example of a preferred embodiment of a porous alumina membrane filter of the present invention.

Fig. 2 is a schematic enlarged view showing the surface of the anodized film portion.

Fig. 3 is a partial enlarged view of a cross section taken along line A-A of Fig. 1;

4(A) and 4(B) are schematic views showing another example of a preferred embodiment of the porous alumina film filter of the present invention.

Fig. 5 is a schematic view showing still another example of a preferred embodiment of the porous alumina membrane filter of the present invention.

Fig. 6 is a partial cross-sectional view for explaining the penetration processing.

Fig. 7 is a partial cross-sectional view for explaining a penetrating process.

Fig. 8 is a partial cross-sectional view for explaining the penetration processing.

Hereinafter, the porous alumina film filter of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

The description of the constituent elements described below may be described based on representative embodiments of the present invention, but the present invention is not limited to the embodiments.

In addition, in this specification, the numerical range represented by "~" is the range which has the numerical value of the before and after the "~" as the lower-limit and upper-limit.

[Porous Alumina Membrane Filter]

The porous alumina thin film filter of the present invention has an aluminum portion including an aluminum substrate and an anodized film portion including an anodized film having a plurality of micropores penetrating in a thickness direction, and the aluminum portion is porous The at least end portion of the main surface of the alumina membrane filter is formed, and the area ratio with respect to the entire main surface is 10% to 60%.

Next, the configuration of the porous alumina membrane filter of the present invention will be described with reference to Figs. 1, 2, and 3.

1 is a schematic plan view showing an example of a preferred embodiment of a porous alumina membrane filter of the present invention, FIG. 2 is an enlarged schematic view showing a surface of an anodized film portion, and FIG. 3 is a cross-sectional view taken along line AA of FIG. Partially enlarged view.

As shown in FIG. 1, a porous alumina membrane filter (hereinafter also referred to as a membrane filter) 10 has a circular flat plate shape, and includes an aluminum portion 12 including an aluminum substrate and an anodized film portion 14 including an anodized film. The anodized film has a plurality of microporous through holes penetrating in the thickness direction.

The anodized film portion 14 is an anodized film including an aluminum substrate, and as shown in FIGS. 2 and 3 , is a portion having a plurality of microporous through holes 18 penetrating in the thickness direction.

In the membrane filter 10 shown in Fig. 1, the anodized film portion 14 is formed in a region divided into three circular shapes. Each region of the anodized film portion 14 is separated by an aluminum portion 12.

In the present invention, the anodized film portion 14 can be produced, for example, by anodizing an aluminum substrate and penetrating micropores generated by anodization.

The method of forming the anodized film portion 14 will be described in detail below.

Further, the area ratio of the anodized film portion to the entire main surface of the membrane filter is 40% to 90%.

The aluminum portion 12 is a part of an aluminum substrate including an anodized film. That is, the aluminum portion 12 is a region where the anodized film portion 14 is not formed.

In the membrane filter 10 shown in Fig. 1, the aluminum portion 12 is formed to cover at least an end portion of the main surface, that is, a peripheral portion of the main surface. Further, the area ratio of the aluminum portion to the entire main surface of the membrane filter is 10% to 60%.

As described above, in the membrane filter using the anodized film of the aluminum substrate, the pores having a narrow pore size distribution and independent pores can be disposed at a high density and a high porosity can be set, so that the filtration flow rate can be increased. However, such a membrane filter has a small thickness and a high porosity, and the anodized film has low toughness and is not resistant to impact, so that there is a problem that cracking occurs during handling.

Further, since the thickness of the membrane filter is small, it is easy to warp, but the flexibility is low. Therefore, there is a problem that it cannot be properly attached to the filter device, and sufficient effect cannot be exhibited.

On the other hand, the aluminum portion of the membrane filter of the present invention is formed to cover at least the end portion of the main surface of the membrane filter, and is formed so as to have an area ratio of 10% to 60% with respect to the entire main surface.

The peripheral portion of the membrane filter is formed of the aluminum portion, and a region having an area ratio of 10% or more is formed from the aluminum portion, whereby the resistance to impact or the like can be improved, and the occurrence of cracking or the like can be prevented, and the operability can be improved. Further, since the peripheral portion of the membrane filter is formed of an aluminum portion, it is easy to handle during handling, and the operability can be improved.

Further, since the peripheral portion is formed of the aluminum portion, warpage of the anodized film portion can be suppressed, and flatness can be improved. Therefore, it can be suitably attached to a filtration apparatus, and a sufficient effect can be exhibited.

Further, in order to secure a sufficient filtration flow rate, the area ratio of the aluminum portion is 60% or less.

Further, in terms of operability, flatness, and ensuring filtration flow rate, the area ratio of the aluminum portion is preferably 25% to 45%.

Here, the membrane filter 10 shown in FIG. 1 has a configuration in which the anodized film portion 14 is formed by dividing into three regions. However, the present invention is not limited thereto, and the anode may be divided into a plurality of regions. The oxide film portion is formed as one region. Alternatively, the anodic oxide film portion may be formed by dividing into two or four or more regions.

For example, as in the membrane filter 40 shown in FIG. 4(A), the anodized film portion 14 may be formed by dividing into seven regions. Alternatively, as in the membrane filter 42 shown in FIG. 4(B), the anodized film portion 14 may be formed by dividing into 10 regions.

Further, in terms of further improving workability and flatness, it is preferable to form the anodized film portion by dividing into a plurality of regions. In particular, it is more preferable to form the anodized film portion by dividing into three or more regions, and it is particularly preferable to form the anodized film portion by dividing into five or more regions.

In the case where the anodic oxide film portion is formed by dividing into a plurality of regions, it is preferable to set the line that is passing through the center of the main surface of the membrane filter and that is parallel to the main surface as a line. The size, shape and configuration of each area.

For example, in the membrane filter 10 shown in Fig. 1, the center line α is used as the axis. Further, each region of the anodized film portion 14 is formed in a line symmetrical manner.

By forming each region of the anodized film portion of the membrane filter in a line symmetrical manner, occurrence of warpage can be more suppressed, and flatness can be further improved.

Further, it is more preferable to form each region of the anodized film portion in a rotationally symmetrical manner.

Further, the distance between the respective regions of the anodized film portion, that is, the width of the thinnest portion of the aluminum portion that partitions the anodized film portion into a plurality of regions is preferably 2 mm or more. Thereby, operability and flatness can be further improved.

Further, in terms of ensuring the filtration flow rate, the thickness of the membrane filter is preferably 300 μm or less, more preferably 200 μm or less, and particularly preferably 150 μm or less. Since the membrane filter of the present invention can improve workability and flatness, the thickness can be made thinner as described above.

Further, in the present invention, the average opening diameter of the microporous through-holes in the anodized film portion is preferably 5 nm or more, more preferably 10 nm or more, and particularly preferably 30 nm or more in terms of ensuring the filtration flow rate.

Further, in terms of strength and ensuring the filtration flow rate, the width between the microporous through-holes in the anodized film portion (the portion indicated by reference numeral 19 in Fig. 2) is preferably 20 nm to 1000 nm, more preferably 30 nm. 800nm, particularly preferably 50nm~500nm.

Further, the pore density of the microporous through-holes in the anodized film portion is preferably 1 / μm ² or more and 15,000 / μm ² or less, more preferably 2 / μm, in terms of strength and ensuring filtration flow rate. ² or more and 1000 / μm ² or less, more preferably 3 / μm ² or more and 300 / μm ² or less.

Here, regarding the hole density, a field emission scanning electron microscope (Field) is used. Emission Scanning Electron Microscope (FE-SEM) photographed a surface photograph (magnification: 20,000 times), calculated the number of micropores present in the field of view of 1 μm × 1 μm, and calculated five densities of 1 μm × 1 μm. The average value of the field of view, the resulting value is the pore density.

In the example shown in FIG. 1, each region of the anodized film portion 14 has a circular shape. However, the present invention is not limited thereto, and various shapes such as a quadrangular shape, a triangular shape, a polygonal shape, and an elliptical shape may be employed.

For example, in the same manner as the membrane filter 44 shown in FIG. 5, an anodized film portion may be formed in a region in which a circular region which is smaller than the outer diameter of the circular membrane filter is divided into three. In other words, each region of the anodized film portion 14 of the membrane filter 44 is formed in a sector shape of the same size, and is disposed such that the three regions are substantially circular.

In the example of the drawings, the aluminum portion and the anodized film portion having the microporous through holes are included. However, the present invention is not limited thereto, and may include a portion including an anodized film that does not penetrate.

Further, the shape of the membrane filter is not limited to a circular shape, and may be various shapes such as a quadrangular shape.

[Method of Manufacturing Membrane Filter]

Next, the method of manufacturing the membrane filter will be described in detail.

The membrane filter of the present invention is produced by using a mask in a region to be the aluminum portion, and then anodizing the unmasked region to form an anodized film having a plurality of micropores. The formed micropores of the anodized film The anodized film portion is formed.

Specifically, the method includes the following steps: a masking step of using a mask for a portion of the aluminum substrate; an anodizing treatment step of anodizing the aluminum substrate in the unmasked region; and a penetrating treatment step for the anodizing treatment After the step, the bottom portion of the aluminum substrate is removed, and a plurality of micropores formed by the anodization are penetrated to form an anodized film portion including an anodized film having a plurality of microporous through holes.

Hereinafter, each processing step performed on the aluminum substrate and the aluminum substrate will be described in detail.

[Aluminum plate]

The aluminum substrate used in the membrane filter of the present invention is not particularly limited, and specific examples thereof include a pure aluminum plate; an alloy plate containing aluminum as a main component and containing a trace amount of different elements; and low-purity aluminum (for example) a substrate obtained by vapor-depositing high-purity aluminum; a substrate obtained by coating high-purity aluminum on a surface of a germanium wafer, quartz, glass, or the like by vapor deposition, sputtering, or the like; and a resin substrate laminated with aluminum Wait.

In the present invention, in the aluminum substrate, the surface of the anodized film is provided by an anodizing treatment step to be described later, and the aluminum purity is preferably 99.5% by mass, more preferably 99.9% by mass or more, and still more preferably 99.99% by mass or more. . When the aluminum purity is in the above range, the regularity of the arrangement of the micropores becomes sufficient.

Further, in the present invention, it is preferable that the surface of the aluminum substrate subjected to the anodizing treatment step to be described later is subjected to heat treatment, degreasing treatment, and mirror addition in advance. Work processing.

Here, the heat treatment, the degreasing treatment, and the mirror polishing treatment can be carried out in the same manner as the respective treatments described in paragraphs [0021] to [0031] of Patent Document 1 (Japanese Patent Laid-Open Publication No. 2009-074133).

[shadowing step]

In the present invention, in the region other than the region where the anodized film portion 14 is formed as the anodized film portion 14, the aluminum portion 12 is formed by using a mask or the like without forming an anodized film and leaving a part of the aluminum substrate. That is, the region to be the aluminum portion 12 is shielded and the aluminum substrate is subjected to an anodizing treatment step.

The method of shielding the aluminum portion 12 is not particularly limited, and may be masked by, for example, a method of attaching an adhesive tape; after forming an image recording layer on the surface of the aluminum substrate, by exposure or heating The image recording layer imparts energy and develops into a predetermined opening pattern.

[Anodizing treatment step]

The anodizing treatment step is a step of forming an anodized film having micropores on the surface of the region of the aluminum substrate which becomes the anodized film portion by anodizing the aluminum substrate using the mask.

In the anodic oxidation treatment in the present invention, a conventionally known method can be used. However, in terms of improving the regularity of the arrangement of the micropores and further surely ensuring the insulation of the conductive portion in the planar direction, it is preferable to use a self-adjusting method. Or constant voltage processing.

Here, the self-adjusting method of the anodizing treatment can be carried out in paragraph [0033] to [0075] of Patent Document 1 (Japanese Patent Laid-Open Publication No. 2009-074133) The same processing as the processing described in [Fig. 1].

[through processing steps]

The penetrating treatment step is performed by removing the bottom side of the aluminum substrate after the anodizing treatment step, and further forming a pore of the micropores formed by the anodizing treatment to form the anodized film portion. step.

The penetrating treatment step includes, for example, a method of dissolving the bottom of the aluminum substrate and further dissolving the bottom portion of the anodized film after the anodizing treatment step; after the anodizing treatment step a method of cutting the bottom portion of the aluminum substrate and the anodized film in the vicinity of the aluminum substrate and removing the method; after the anodizing treatment step, cutting the bottom of the aluminum substrate, dissolving the bottom portion of the anodized film, and removing the method; After the anodizing treatment step, the bottom of the aluminum substrate is dissolved, and the bottom of the anodized film is cut and removed.

An example of the penetration processing will be described using a partial cross-sectional view shown in FIGS. 6 to 8.

FIG. 6 is a view showing a state after the anodizing treatment step, and shows a structure in which an anodized film 14a having a plurality of micropores 16 is formed in a part of the aluminum substrate 12a.

First, the bottom of the aluminum substrate 12a is dissolved and removed from the state shown in Fig. 6, and as shown in Fig. 7, a structure in which the aluminum substrate 12a on the bottom side of the anodized film 14a is removed is produced. At this time, only the aluminum substrate which is the aluminum portion 12 of the membrane filter remains, and the bottom side of the aluminum substrate 12a where the anodized film 14a is not formed is also removed.

Therefore, in the aluminum removal treatment, a treatment liquid in which aluminum is dissolved without dissolving aluminum oxide is used.

In the method of the aluminum removal treatment, for example, the same method as each of the methods described in paragraphs [0077] to [0080] of Patent Document 1 (Japanese Patent Laid-Open Publication No. 2009-074133) can be cited.

Then, from the state in which the bottom aluminum substrate 12a is removed as shown in FIG. 7, the bottom portion of the anodized film 14a is dissolved and removed, and the micropores 16 are penetrated (the micropore through holes 18 are formed). Thereby, the membrane filter of the present invention was produced.

8 is a partial cross-sectional perspective view showing a state after the penetration processing, and shows a structure including the anodized film portion 14 having the microporous through holes 18 and the aluminum portion 12, that is, the membrane filter of the present invention.

In addition, in FIG. 8, all the micropores which exist in the anodic oxide film part 14 become the micropore penetration hole 18, However, all the micropores which exist in an anodic oxide film are not penetrated by penetration process. Among them, it is preferable that 70% or more of the micropores present in the anodized film are penetrated by the penetrating treatment.

As the treatment liquid for dissolving the anodized film, an acidic aqueous solution or an alkaline aqueous solution is used.

In the method of dissolving the anodic oxide film, for example, the same method as each of the methods described in paragraphs [0082] to [0085] of Patent Document 1 (Japanese Patent Laid-Open Publication No. 2009-074133).

Further, the penetration treatment in the present invention is not limited to the method.

For example, the following method is preferably exemplified: using a cutting process using a laser or the like or each The polishing process or the like, the bottom (bottom) of the anodized film 14a shown in FIG. 6 and the bottom (bottom) of the aluminum substrate 12a, that is, the bottom of the aluminum substrate 12a including the portion of the anodized film 14a on the side of the aluminum substrate 12a. The film filter including the anodized film portion 14 having the microporous through holes 18 and the aluminum portion 12 shown in Fig. 8 was removed.

Alternatively, the bottom portion of the aluminum substrate and the bottom portion of the anodized film may be physically removed by the following configuration, and the other may be dissolved and removed.

[other processing] <Protective film formation treatment>

In the present invention, the anodized film portion 14 formed of alumina (anodized film) is preferably immersed in the air to cause a change in pore diameter over time. Film formation treatment.

In the protective film forming process, the same processes as those described in the paragraphs [0096] to [0105] of Patent Document 2 (Japanese Patent Laid-Open Publication No. 2009-050773) can be performed.

<Hydrophilic compound imparting treatment>

In the present invention, it is preferred to provide a compound which increases the hydrophilicity of the anodic oxide film after the penetration treatment step. It is particularly preferable to provide a compound having improved hydrophilicity over the entire surface of the surface of the anodized film including the inside of the microporous through hole 18.

By carrying out the hydrophilic compound imparting treatment, the obtained membrane filter of the present invention is excellent in filtration flow rate in a system using an organic solvent-based filtrate.

Here, the hydrophilic compound-imparting treatment can be carried out in paragraphs [0086] to [0101] of Patent Document 1 (Japanese Patent Laid-Open Publication No. 2009-074133). The same processing is performed for each of the described processes.

[Examples]

The invention is specifically illustrated by the following examples. However, the present invention is not limited to this.

<Example 1> (A) Electrolytic grinding treatment step

A high-purity aluminum substrate (manufactured by Sumitomo Light Metal Co., Ltd., purity: 99.99% by mass, thickness: 0.4 mm) was cut into a circular shape having a diameter (symbol Db in Fig. 1) of 50 mm to prepare a sample, and electrolysis using the following composition was used. The polishing liquid was subjected to electrolytic polishing treatment under the conditions of a voltage of 10 V and a liquid temperature of 65 °C.

A carbon electrode was used for the cathode, and the power source was GP-250-30R (manufactured by Takasago Co., Ltd.).

(composition of electrolytic slurry)

(B) Masking step

The adhesive tape was cut into an outer diameter Db = 50 mm, an inner diameter Dc (refer to Fig. 5) = 47 mm, and an annular masking tape having a width of 1.5 mm was produced. The masking tape was attached to the electrolytically polished sample in such a manner that the outer diameter was uniform, without offset, and without wrinkles.

(C) anodizing treatment step

Then, the masked sample was anodized for 25 minutes under the conditions of a voltage of 40.0 V, a liquid temperature of 15 ° C, and a liquid flow rate of 3.0 m/min using an electrolyte of 0.50 mol/L oxalic acid.

Then, the sample after the anodization treatment was subjected to mold release treatment by using a mixed aqueous solution of 0.5 mol/L phosphoric acid and immersing at 40 ° C for 20 minutes. This treatment was repeated 4 times.

Further, as an anodizing treatment, an anodizing treatment was carried out for 15 hours under the conditions of a voltage of 41.7 V, a liquid temperature of 15 ° C, and a liquid flow rate of 3.0 m/min using an electrolytic solution of 0.5 mol/L oxalic acid.

Then, using a mixed aqueous solution of 0.5 mol/L phosphoric acid, immersing at 40 ° C for 20 minutes, and subjecting the re-anodized sample to mold release treatment, thereby forming micropores on the surface of the aluminum substrate. An anodized film that is tubular and arranged in a honeycomb shape.

Further, regarding the anodizing treatment and the re-anodizing treatment, stainless steel electrodes were used for the cathode, and the power source was GP0110-30R (manufactured by Takasago Manufacturing Co., Ltd.). In addition, a cooling device was used (NeoCool) BD36 (manufactured by Daiwa Scientific Co., Ltd.), and a stirring warming device was used with a pair stirrer PS-100 (manufactured by Tokyo Phytochemical Instruments (EYELA) Co., Ltd.). Further, the flow rate of the electrolytic solution was measured using a vortex flow monitor FLM22-10PCW (manufactured by ASONE Co., Ltd.).

(D) Through processing steps (i) Aluminum removal processing steps

The bottom side of the surface on which the anodized surface of the sample subjected to the anodization treatment is opposite to the anodized surface is polished until the thickness of the sample is 150 μm, and the aluminum substrate on the bottom side of the anodized film is removed and An aluminum substrate on the bottom side of the masked area.

(ii) Anodized film removal processing steps

Then, the sample from which a part of the aluminum substrate was removed was immersed in a 0.1 M potassium chloride solution (KClaq) having a pH buffering effect for 10 minutes to sufficiently saturate the inside of the micropores of the anodized film. Then, only the ground surface was immersed in 0.1 M-KOH (potassium hydroxide) at 25 ° C for 5 minutes, thereby removing the bottom of the anodized film, and a membrane filter having one anodized film portion was produced. .

Further, the average value of the pore diameter of the microporous through-hole of the anodized film portion and the distance between the centers of the through-holes was measured. As a result, the average value of the pore diameter was 40 nm, and the average value of the distance between the centers of the through-holes was 100 nm.

Here, regarding the average value of the distance between the center of the aperture and the through hole, a surface photograph (magnification: 20000 times) was taken by a field emission scanning electron microscope (FE-SEM) to measure the presence of a field of view of 1 μm × 1 μm. The average pore diameter of the micropores and the distance between the centers of the adjacent micropores was calculated, and the average value of the five fields of 1 μm × 1 μm was calculated, and the obtained value was the average value of the distance between the center of the aperture and the through hole.

Further, the area ratio was 12% with respect to the entire main surface of the aluminum portion.

<Example 2>

In the (B) masking step, the inner diameter Dc of the masking tape is set to 43 mm, and an annular masking tape having a width of 3.5 mm is formed to be shielded, and Example 1 was carried out in the same manner to prepare a membrane filter. Further, the area ratio was 26% with respect to the entire main surface of the aluminum portion.

<Example 3>

In the (B) masking step, a film was produced in the same manner as in Example 1 except that the inner diameter Dc of the masking tape was set to 39 mm, and an annular masking tape having a width of 5.5 mm was formed. filter. Further, the area ratio was 42% with respect to the entire main surface of the aluminum portion.

<Example 4>

In the above-described (B) shielding step, film formation was carried out in the same manner as in Example 1 except that the inner diameter Dc of the masking tape was 34 mm, and an annular masking tape having a width of 8 mm was formed. Device. Further, the area ratio was 54% with respect to the entire main surface of the aluminum portion.

<Example 5>

In the above-mentioned (B) masking step, as shown in FIG. 1, the masking tape is formed so as to have a pattern of three circular anodized film portions, and the masking is performed in the same manner as in the first embodiment. Make a membrane filter.

Further, the diameter Da of the anodized film portion was 22 mm, and the shortest distance ta (see FIG. 1) between the anodized film portions was set to 1 mm.

Further, the area ratio was 42% with respect to the entire main surface of the aluminum portion.

<Example 6>

In the (B) masking step, as shown in FIG. 4(A), a masking tape is formed so as to have a pattern of seven circular anodized film portions, and the masking is performed. A membrane filter was produced in the same manner as in Example 1.

Further, the diameter Da of the anodized film portion was set to 14.4 mm, and the shortest distance ta between the anodized film portions was set to 1 mm.

Further, the area ratio was 42% with respect to the entire main surface of the aluminum portion.

<Example 7>

In the (B) masking step, as shown in FIG. 4(B), the masking tape is formed so as to have a pattern of ten circular anodized film portions, and the masking is performed in the same manner as in the first embodiment. The film was produced by making a film.

Further, the diameter Da of the anodized film portion was set to 12 mm, and the shortest distance ta between the anodized film portions was set to 1 mm.

Further, the area ratio was 42% with respect to the entire main surface of the aluminum portion.

<Example 8>

In the above-described (B) masking step, as shown in FIG. 5, a masking tape was formed so as to have a pattern of three sector-shaped anodized film portions, and the same manner as in Example 1 was carried out. Membrane filter.

Further, the inner diameter Dc of the anodized film portion was 40 mm, and the distance ta between the anodized film portions was set to 1 mm.

Further, the area ratio was 42% with respect to the entire main surface of the aluminum portion.

<Example 9>

In the (B) shielding step, a film filter was produced in the same manner as in Example 8 except that the inner diameter Dc of the masking tape was 41 mm and the distance ta between the anodized film portions was 2 mm. .

Further, the area ratio was 42% with respect to the entire main surface of the aluminum portion.

<Example 10>

In the above-mentioned (B) shielding step, film filtration was performed in the same manner as in Example 8 except that the inner diameter Dc of the masking tape was 41.6 mm and the distance ta between the anodized film portions was set to 3 mm. Device.

Further, the area ratio was 42% with respect to the entire main surface of the aluminum portion.

<Comparative Example 1>

A membrane filter was produced in the same manner as in Example 1 except that the (B) masking step was not carried out.

<Comparative Example 2>

A membrane filter was produced in the same manner as in Example 1 except that the following (B2) masking step was performed instead of the (B) masking step.

The area ratio was 41% with respect to the entire main surface of the aluminum portion.

(B2) masking step

The adhesive tape was cut into an outer diameter of 32 mm to form a circular mask. The masking tape was attached to the sample after the electrolytic polishing treatment so that the center was uniform, without offset, and without wrinkles.

<Comparative Example 3>

In the above-described (B) masking step, the inner diameter Dc of the masking tape was set to 48.7 mm, and an annular masking tape having a width of 0.65 mm was formed to be shielded, and the same procedure as in Example 1 was carried out. Membrane filter.

The area ratio is 5% with respect to the entire main surface of the aluminum portion.

<Comparative Example 4>

In the above-described (B) masking step, film formation was carried out in the same manner as in Example 1 except that the inner diameter Dc of the masking tape was set to 30 mm, and an annular masking tape having a width of 10 mm was formed. Device.

The area ratio was 64% with respect to the entire main surface of the aluminum portion.

<evaluation>

Each of the produced membrane filters was subjected to the following evaluations.

(strength)

The test of dropping the produced membrane filter from a height of 30 cm was carried out 10 times. The case of unruptured 10 times was evaluated as AA, the case of rupture at the 7th to 9th time was evaluated as A, and the case of rupture at the 4th to the 6th time was evaluated as B, at the 1st time to the first time The case of cracking at 3 times was evaluated as C.

(warping)

The height of the produced membrane filter was measured using a high-precision shape measuring system (KS-1100, manufactured by KEYENCE Co., Ltd.). The difference between the highest value and the lowest value was set to X, the diameter of the membrane filter was set to Y, and X/Y was calculated as the amount of warpage.

When the amount of warpage is less than 5 μm/mm, it is evaluated as AA, and when it is 5 μm/mm or more and less than 10 μm/mm, it is evaluated as A, and when it is 10 μm/mm or more and less than 30 μm/mm, it is evaluated as B, and 30 μm/mm or more. The evaluation is C.

(filtering traffic)

Cross-flow method using the membrane filter produced The filtration treatment was carried out to evaluate the filtration flow rate.

Specifically, a membrane filter was used on a stirring type Ultra Holder (UHP-43K, manufactured by Toyo Filter Co., Ltd.), and a 100% polystyrene particle 1% aqueous solution (standard particle: 3100 / mL) was used. , manufactured by Tech-Jam Co., Ltd., the filtration flow rate per unit time (L/cm ² Hr) with respect to the membrane area was measured under a suction pressure of 0.5 MPa.

Regarding the filtration flow rate, the case of 55 L/cm ² Hr or more is AA, and the case of 45 L/cm ² Hr or more and less than 55 L/cm ² Hr is A, 35 L/cm ² Hr or more and less than 45 L/cm ² Hr. The case is B, and the case of less than 35 L/cm ² Hr is C.

The evaluation results are shown in Table 1.

According to the results shown in Table 1, it is understood that the first to tenth embodiments of the present invention have high strength and excellent workability, and can suppress warpage, are excellent in flatness, and have high filtration flow rate, and the embodiment of the present invention is described. 1 to 10, an aluminum portion including an aluminum substrate and an anodized film portion including an anodized film having a plurality of micropores penetrating in a thickness direction, and the aluminum portion covering a main surface of the membrane filter The at least one end portion is formed, and the area ratio with respect to the entire main surface is 10% to 60%.

On the other hand, it was found that Comparative Example 1 which does not have an aluminum portion has low strength and poor workability, and has large warpage and poor flatness. Further, in Comparative Example 2 having an aluminum portion at a position where the end portion was not covered, the strength was low and the workability was poor. Further, in Comparative Example 3 in which the area ratio of the aluminum portion was 5%, the warpage was large and the flatness was poor. Further, it was found that the filtration flow rate of Comparative Example 4 in which the area ratio of the aluminum portion was 64% was low.

Further, according to the comparison of Examples 1 to 4, the area ratio of the aluminum portion is preferably 25% to 45%.

Further, according to the comparison between Example 3 and Examples 5 to 10, it is preferable that the anodized film portion is partitioned into a plurality of regions.

Further, according to the comparison of the fifth to seventh embodiments, it is preferable that the anodized film portion is partitioned into five or more regions.

Further, according to the comparison of Examples 8 to 10, the gap between the anodized film portions is preferably 2 mm or more.

The effects according to the above invention are clear.

10‧‧‧Film filter

12‧‧‧Aluminum Department

14‧‧‧Anodic Oxide Film Department

Α‧‧‧ center line

Da‧‧‧ Diameter of the anodized film section

Db‧‧‧ OD

ta‧‧‧The shortest distance between the anodized film sections

Claims (6)

A porous alumina membrane filter comprising a porous alumina membrane filter having an anodized film, comprising: an aluminum portion; and an anodized film portion comprising the anodization having a plurality of micropores penetrating through a thickness direction a film; and the aluminum portion is formed to cover at least an end portion of a main surface of the porous alumina film filter, and an area ratio of the entire main surface is 10% to 60%. The porous alumina membrane filter according to claim 1, wherein the anodized film portion is partitioned into a plurality of regions by the aluminum portion. The porous alumina membrane filter according to claim 2, wherein a distance between the anodized film portions separated by the aluminum portion is 2 mm or more. The porous alumina membrane filter according to claim 2, wherein the anodized film portion is partitioned into three or more regions by the aluminum portion. The porous alumina membrane filter according to any one of claims 1 to 3, wherein the anodized film portion is set to pass through a center of the main surface and is parallel to the main surface The straight line is formed as a line and becomes line symmetrical. A method for producing a porous alumina membrane filter, which is a porous alumina membrane filter according to any one of claims 1 to 5 And the method comprising: masking a region containing at least an end portion of the aluminum substrate and an area ratio of 10% to 60% with respect to the entire main surface; and anodizing the aluminum substrate in the unmasked region The step of forming an anodized film portion.