JPS59213402A - Filter - Google Patents

Abstract

PURPOSE:To improve the precision of filtration and the water permeability by providing micropores, having specified pore diameter and passing through vertically to the film surface, to an anodic aluminum oxide film obtained from aluminum or an aluminum alloy. CONSTITUTION:A substrate of aluminum or an aluminum alloy is anodically treated in an acidic or alkaline electrolyte to form an aluminum oxide film, having micropores which are arranged vertically to the surface part of the substrate. At the same time, after forming an activated layer between the substrate and the aluminum oxide film, the substrate and the activated layer are removed by dissolving chemically. In this way, the filter, consisting of aluminum oxide and having micropores passing through vertically to the film surface, can be obtained. The pore diameter of the micropore is regulated to about 50-1,000Angstrom , and the thickness of the film, for example, to 20-100mum.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a separation membrane used for ultraf filtration, gas separation, etc.

Conventionally, this type of separation membrane has mainly been made of cellulose acetate,
Acrylonitrile, polysulfone.

It is made from synthetic polymers such as polycarbonate. This separation membrane has (1) non-uniform pore diameters; (2
) Poor pressure resistance; (3) Poor solvent resistance.

There is a drawback.

The present inventor has discovered the above-mentioned (1) regarding conventional separation membranes.

From the viewpoint that inorganic materials are optimal for improving the drawbacks of (2) and (3), research has been conducted on sintered fine powders of metals, metal oxides, nickel, stainless steel, silicon oxide, etc. However, the pore diameter was non-uniform and a satisfactory result could not be obtained. As a result of further intensive research, the present inventor discovered that aluminum oxide was the most suitable material and invented the filter of the present invention.

The filter of the present invention has an aluminum oxide film provided with micropores that penetrate perpendicularly to the surface of the film. The aluminum oxide film is obtained from an anodized film of aluminum or an aluminum alloy. This aluminum anodic oxide film has a crystal structure of α-alumina, γ-alumina, amorphous alumina, etc., and may have any crystal structure. The crystal structure may contain water of crystallization so as to be suitable for filtration, and the diameter of the micropores is approximately 5.
0 to l, o o o x, and there is no need for the same pore size to be maintained in each part of the cross section. The fine pores must be arranged perpendicularly or perpendicularly to the surface of the filter, but they may be slightly curved or zigzag-like.

In the present invention, these are collectively referred to as vertical.

The filter of the present invention has the following features.

In other words, the diameter of the micropores is uniform and well arranged.
Since it is placed perpendicular to the surface, J-1 accuracy and water permeability are good. Since aluminum oxide is used in the first and second parts, it has excellent surface pressure and surface solvent properties.

Let me explain in more detail.

Since the filter of the present invention is manufactured by anodizing aluminum or aluminum alloy, micropores can be formed regularly at regular intervals, and the size of the pores can be easily changed by changing the electrolytic treatment conditions. , and the variation in pore diameter is extremely small. for that,
This makes it possible to separate fine particles of different sizes in a liquid with high precision. Because the material is inorganic aluminum oxide, it is hard and mechanically strong.

The pressurization during filtration can be increased, thus increasing the filtration efficiency.
- It has excellent features such as being able to wash various organic solvents, and being able to use organic solvents during cleaning.

The filter of the present invention can be obtained as follows. That is, an aluminum or aluminum alloy base material is anodized in an acidic or alkaline electrolyte to produce an aluminum oxide film on the surface of the base material that has micropores arranged perpendicular to the film surface, and at the same time After forming an active layer between the profiteer and the aluminum oxide film, the base material and the active layer are dissolved and removed by a chemical method.

A filter made of aluminum oxide having fine pores penetrating perpendicularly to the surface of the film is obtained.

Aluminum or aluminum alloy base 2ilS! .

Although it is possible to use a board made of commonly available commercially available materials.

From the viewpoint of pore diameter accuracy, it is preferable to make a good profit from relatively pure IW, and the content of impurities other than aluminum is preferably about 5% or less. The hardness of the base material may be soft or hard, and laminated boards made of materials of different purity may also be used. The diameter of the micropores in the aluminum oxide film can be arbitrarily changed depending on the anodizing treatment conditions, but after the anodizing treatment,
The pore size can be further enlarged by immersion in an acidic or alkaline solution or by a decomposition treatment. However, after anodization, the pore size can be further reduced using steam or heated aqueous solution. The electrolyte used for anodization is an inorganic acid solution such as sulfuric acid, phosphoric acid, or chromic acid, or an alkaline solution such as sodium hydroxide, sodium phosphate, or sulfuric acid.

Organic acids such as oxalic acid and sulfosalicylic acid can be used, and mixed acids of the above acids and mixed acids of alkalis can also be used. The power sources used for anodizing are DC, AC, AC/DC superimposition, incomplete rectification, and PR.

It generates pulses, intermittent waveforms, etc.

The thickness of the anodic oxide film can be arbitrarily determined depending on the type of electrolytic solution, electrolytic conditions, etc., and a thickness of about 200 μm1 can be obtained. The thickness of the membrane should be determined from the viewpoints of membrane strength and water permeability.

In order to obtain the strength of the film, it is safe to have at least 1 O1 lrn, and in order to maintain water permeability, it is better to be as thin as possible, and a preferable film thickness is about 20 to 100/1? n range. The oxide film obtained from the electrolyte is γ-At2o3
Although microcrystalline and amorphous.

A γ-At203 film and a crystalline γ-At203 film can be obtained by further subjecting the film to an anodic electrolytic treatment in a molten salt and a carbonate Notter solution, or a heat treatment using a hot wire or in a furnace. The applied film is useful for improving heat resistance, PH resistance, etc.

Next, an example of manufacturing a filter of the present invention will be shown.

Production example 1 Pure aluminum disk] (manufactured by Sumitomo Light Metal ■; symbol 108
After adsorbing and fixing a rubber suction cup 2 with a diameter of 24 mm on one side of a piece of material (0 material, thickness: 05 mm, outer diameter: 40 mm), 5% Na
Immerse in an OH bath (50c) for 1 minute to degrease, and then soak for 1 minute.
Smut removal treatment was performed by immersing it in a 0% HNO3 bath (room temperature) for 30 seconds.

Then, e-soaked in a 5% C2O, H2 bath (30c).
The anodic oxide film 3 was produced by anodizing for 70 minutes under the conditions of , TeW current voltage of 50 V, and current density of 2 A/dm<2>.

After anodizing, remove the suction cup 2 and wash thoroughly with water.

It was dried at room temperature and immersed in a bromine-methanol (volume ratio 1.9) mixed solution (room temperature) for about 5 hours to dissolve and remove the pure aluminum base book in section 4 which had been resist-treated with suction cup 2. Next, a phosphoric acid-chromic acid mixed solution (5% phosphoric acid, 2% chromic acid).

The active layer 5 of the anodic oxide film 3 on the part 4 from which the pure aluminum base was removed was dissolved and removed by immersion in a liquid temperature of 50C for 15 minutes. The surface was resist-treated to prevent it from coming into contact with the phosphoric acid-chromic acid solution.) As a result, in the aluminum disk 1 with the outermost diameter of 40 groups φ, there are 24+III+Iφ and a thickness of 5
A filter having a structure having micropores 6 penetrating perpendicularly to the surface of a 0/Am aluminum oxide film was obtained (FIG. 1).

Production Example 2 After performing the pretreatment process under the same method and conditions as Production Example 1, it was immersed in a 5-layer C204H2 bath (IOU) and a DC voltage of 80
V, anodization was performed for 50 min at a current density of 3 A/dm20. The subsequent treatment was the same as in Production Example 1, except that the sample was immersed in a phosphoric acid-chromic acid mixed solution for 28 minutes. As a result, an aluminum disk l having an outermost diameter of 40 TMlφ has micropores penetrating perpendicularly to the surface of the aluminum oxide film having a diameter of 24 mm and a thickness of 50/Lm. A filter having the same structure as Production Example 1 was obtained.

Production Example 3 After performing the pretreatment process under the same method and conditions as Production Example 1, an aluminum disk sample was heated to 15'% H2S□.

Immersed in a bath (14C) with a DC voltage of 18V and a current density of 2A.
/dm'' (7) conditions for 100 minutes to produce an anodic oxide film 3.The subsequent treatment method was phosphoric acid-
The same treatment as in Production Example 1 was performed except that the sample was immersed in the chromic acid mixed solution for 5 minutes.

As a result, two
It has micropores penetrating perpendicularly to the surface of the aluminum oxide film having a diameter of 4 mm and a thickness of 50/Am. A filter having the same structure as Production Example 1 was obtained.

Production example 4 Pure aluminum disk 1 (manufactured by Sumitomo Light Metal ■; symbol 108
October, thickness 03mm, outer diameter 70mm), 14 sides of 40mm diameter
Screen printing was performed using ebony/based resin ink 7 so that there were countless dotted islands of 1 m+nφ in the area.

After performing the pretreatment process in the same manner and under the same conditions as in Production Example 1, it was immersed in a 5% C204H2 bath (30 tl),
Anodizing was performed for 70 minutes at 0 V and current density of 2 A/'d m20. After the anodization, the resist ink was immersed in a mixed solution of MEK and butylcelonorb (mixing ratio 7:3) to peel it off, and then soaked in a bromine-methanol mixed solution of approx.
After being immersed for a time, only the portion 4 of the aluminum base material in which countless dots of 1 mm in 40 mm in diameter were exposed was dissolved and removed. Next, in the same manner as in Production Example 1, the active layer 5 of the anodic oxide film in the area where the pure aluminum base material had been removed by the above treatment was dissolved and removed (in this case, the porous anodic oxide film adjacent to the active layer was removed). No resist treatment was applied to the surface of the film to prevent it from coming into contact with the phosphoric acid-chromic acid solution.) the result.

A filter was obtained that had a structure in which inside an aluminum disk with an outermost diameter of 70 mm, micropores with a diameter of 40 mm penetrated perpendicularly to the surface of the aluminum oxide film in the form of countless dots of 1 mm diameter. (Figures 2 and 3).

Next, the performance of the filter of the present invention will be described.

(1) Uniformity of pore size The surfaces of the filters obtained in Production Examples I to 4 were observed with an electron microscope, and it was confirmed that (') The filter has a pore size of approximately 2
00X (distribution width is about 1ooX to about 3ooX). The filters obtained in Production Example 2 and Production Example 3 each have a pore size of about 500X (distribution width is about 400X to about 600X).
X) and about 300K (minutes 5 width is about 50 people to about 2
00λ). Each filter had uniform pore size, regularly arranged pores, and vertical pores. Such a structure cannot be obtained in the feed body with filters manufactured by a sintering method of metals or metal oxides, filters manufactured with polymeric materials, and the like.

(2) Pressure resistance The filters obtained in Production Examples 1 to 4 were
Although K9/Crn2 was pressurized, there was no damage or breakage. The filter of the present invention has almost the same pressure suppression properties as filters manufactured by the sintering method of metals or metal oxides, but the pressure suppression properties of filters made with polymer H material are 70 compared to 7 points 2.
It has superior surface J pressure properties compared to the following.

(3) 111I solvent properties The filters obtained in Production Examples 1 to 4 exhibit excellent solvent resistance to alcohols, hydrocarbons, esters, ketones, ethers, hydrogen-containing solvents, and the like. This solvent resistance is almost the same as that of filters manufactured by the sintering method of metals or metal oxides, and has excellent one-sided solvent resistance compared to filters manufactured with polymeric ion materials, which are attacked by organic solvents. has. It also has anti-corrosion properties against animal oils, vegetable oils, mineral oils, plasticizers, activators, etc.

(4) J Goggleability The water permeation rate of the filter obtained in Production Example 1 (pore size is approximately 200 mm) is approximately 015 at 1 overpressure 05 to 9/L:m2
m/! /mJ-Cm2 and f overpressure 4 Kq/cm2
At that time, it was approximately 1.2 ml7w・α2, which was almost directly proportional to the j5 overpressure. Also, when the filtration pressure is 4 Kg/1yn2, σ
Particles larger than about 300 Å in size in the 4-filter solution did not pass through the filter. As is clear from this, the pore diameter of the filter does not change even under particularly high f overpressure, and the filter maintains excellent one-pass performance.

The filter of the present invention has superior performance compared to conventional organic polymer membranes or filters made of metal or metal oxide membranes manufactured by sintering methods.

It has remarkable effects on ultraviolet filtration and gas separation.

[Brief explanation of drawings]

1 and 2 are partially sectional views schematically showing different embodiments of the filter of the present invention, and FIG. 3 is a reduced plan view of the filter of FIG. 2. l...Pure aluminum disk, 3...Anodized film,
5... Active layer, 6... Micropore.

Claims (1)

[Claims] The diameter of the pores that penetrate perpendicularly to the film surface is approximately 50 to 100 mm.
A filter with oX micropores in the aluminum oxide film.