JPH07106289B2 - Metal filter manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a microporous metal filter having sufficient strength for use in filtration of various oils and gases, and a method for producing the same.

(Prior Art and Problems Thereof) Paper and resin filters have been used for filtering various oils and gases. However, the filter made of paper or resin is not sufficient for filtration under severe conditions such as when particularly fine and precise filtration is required or when pressure or heat is applied,
Further, these filters have drawbacks such as irregular filter holes and adsorption. Metal filters have been used to solve these problems. When the metal filter is used, a wire mesh is used for particles of about 40 μm or more, but the wire mesh has a drawback that the filtration passage is straight and irregularly shaped particles pass through. A wire mesh having an opening of 10 μm or less has a problem that it is difficult to manufacture, and the pressure loss is large, which is not practical.

On the other hand, the sintered filter developed in the 1930s is a filter having a three-dimensional spread and is currently widely used without the above-mentioned drawbacks. The sintered filter is one in which spherical powder is sintered and the gaps between the stacked spherical powders are used as filter eyes. If the spherical powders have the same particle size, a theoretical theoretical opening can be obtained. it can. That is, the theoretical opening is in the range of 15.5 to 41.4% of the powder particle diameter, actually in the range of 16.3 to 20%, and about 18% for industrial use. Since these values are based on the assumption that the spherical powder retains its initial size, a so-called loose sintering method is adopted so that the particle size does not change in the case of ordinary sintered filter production. To be done. What is loose sintering?
In order to prevent the particles from being crushed and to minimize the bonding between particles due to sintering, the spherical powder is not pressed when it is molded with a binder or the like, and the sintering is also performed at a low temperature. It is a method to finish within a short time. However, this method only provides a filter having sufficient filter performance but insufficient mechanical strength. Even if the filter for coarse particles is sufficiently sintered, the change in the opening size can be suppressed within the error range and practically no problem occurs, but in the filter for fine pores, the initial particles themselves are small. Therefore, strong sintering cannot be performed, and the mechanical strength cannot be sufficiently improved. Therefore, practically none can be used. In particular, a filter for fine pores of 1 μm or less has a problem that it cannot be obtained by the conventional method although the demand for semiconductor gas is great.

(Object of the Invention) The present invention has been made to solve the above problems, and an object of the present invention is to provide a sintered metal filter for micropores, which has good workability and high mechanical strength.

(Means for Solving the Problems) In the present invention, a first metal filter layer having a relatively large opening is formed in advance on a base material made of a metal mesh body by sintering a first metal powder, Then, a suspension or paste containing a second metal powder having a finer particle size than the metal powder is applied to the surface and sintered to form a second mesh having a mesh size smaller than that of the first metal filter layer. In the method of manufacturing a metal filter for forming a metal filter layer, loose sintering is used as the sintering, and / or an organic metal salt is used as a binder during the sintering of the first metal powder. And a method for manufacturing a metal filter.

Hereinafter, the present invention will be described in detail.

In the present invention, the metal net-like body has good formability (workability).
Is formed on the first metal filter layer due to the presence of the first metal filter layer, which reduces the pressure loss by the first metal filter layer having an intermediate opening and reduces the pressure loss. It is possible to reduce the thickness of the second metal filter layer having a predetermined fine opening, thereby ensuring a uniform opening and minimizing the amount of expensive fine metal powder used. Of the organic metal salt as a binder for sintering the first metal powder, and / or using the organic metal salt as a binder. High performance metal filters can be manufactured.

For example, in the case of forming a filter having fine pores with openings of 1 μm, particularly 0.1 μm or less, it is difficult to control the openings due to the sintering of the metal powder according to the conventionally used sintering method. However, in the present invention, this problem can be solved by laminating at least two types of metal filter layers having different openings.

The material of the metal filter base material, the first metal filter layer and the second metal filter layer used in the present invention may be any conventionally used metal, but in consideration of corrosion resistance and the like, nickel, nickel-based alloys, Titanium and titanium-based alloys are preferable.

The base material made of a metal mesh body is a fine wire woven,
If the metal filter can be provided with sufficient strength, such as an expanded mesh or a three-dimensionally combined wire rod, it can have any shape having a through hole.

Then, a first metal filter layer having a relatively large opening is formed on the base material by sintering. The metal filter layer can be formed by any method capable of forming a porous layer, for example, a method of adding a foaming agent to a metal-containing slurry to cause it to foam and then making it porous during sintering, or a metal added with a substance that volatilizes during sintering. A method of applying the slurry to a base material and making it porous by sintering can be adopted, but the most preferable method is a conventional sintering filter method, that is, kneading by adding a metal powder and a binder such as methylcellulose and a solvent. This is a method in which the slurry is applied to the surface of a base material that has been degreased and activated as necessary, dried, and then heated and sintered in a furnace adjusted to an atmosphere in which the metal is not oxidized. For example, in the case of nickel or a nickel-based alloy, this sintering is carried out under the condition of holding 5 to 95% hydrogen gas in an inert gas such as nitrogen or argon at 500 to 1100 ° C. for 5 to 60 minutes, and titanium or titanium. Since these are easily oxidized in the titanium-based alloy, if the above-mentioned conditions are used, it can be carried out for a short time, preferably under the condition of sintering in argon or helium gas or in vacuum. The mesh size of the first metal filter layer depends on the particle size of the metal powder used. For example, to form a metal filter having a mesh size of 5 μm, the particle size is 25 μm.
Use ~ 30 μm metal particles.

Although the strength can be obtained to some extent only by this sintering operation, the strength can be further improved by adding an organic metal salt as a binder. As the organic metal salt,
For example, when the metal particles are nickel or copper, respective naphthenates, 2-ethylhensanates, metal alkoxides and the like are preferable, and the size of the openings does not substantially change by the addition of the organic metal salt, By the decomposition of the organic metal salt, the whole space between the particles is coated with a thin metal layer, and the organic metal salt functions as a sintering aid, whereby a metal filter having higher strength can be obtained. Sintering conditions when the organic metal salt is added may be the same as those when it is not added.

It is also possible to form a porous layer by mixing particles that are volatilized by a chemical reaction or physical volatilization under the sintering conditions into a paste and sintering the mixture. In this case, since it is porous and does not cause defects due to sintering, it is possible to perform the sintering under the condition that sufficient sintering proceeds. Such a porous layer-forming substance includes carbon powder and magnesium powder. When carbon powder is used, the carbon powder is mixed with the paste and sintered at 700 to 1200 ° C. If it is less than 700 ° C, the volatilization of carbon is insufficient.

Next, a thin layer of the second metal filter having the target openings is formed on the surface of the first metal filter layer thus produced by sintering. The second layer can also be formed under substantially the same conditions as the first layer, such as loose sintering, but since the mesh size is small, it is necessary to use particles having a small particle size accordingly. For example, the target opening is
If it is about 0.1 μm, 0.4 to 0.7 μm metal powder is used, and if it is about 0.01 μm, 0.04 to 0.07 μm.
Use some metal powder. When sintering is performed, the same sintering temperature as described above may be used if the particle size of the particles used is about 0.1 μm, but it is appropriate to use a sintering temperature of 300 to 700 ° C. for openings of 0.01 μm or less. . This is because if the particle size is small, the sintering temperature is lowered and the degree of sintering under the same conditions is large, and if the temperature is high, the desired opening may not be obtained. When using other metals, it is also necessary to select appropriate conditions according to the metals. This operation is 1
Although it may be performed only once, it is possible to repeat a plurality of times to exactly match a predetermined opening.

By laminating two types of layers having different openings by the above operation, a metal filter having sufficient strength and having a predetermined fine opening can be obtained. Further, since the above-mentioned two kinds of layers can be formed under substantially the same conditions, two kinds of metal powders may be laminated on the base material and both the metal powders may be simultaneously sintered. According to this method, the first metal filter layer material layer is formed on the base material in advance and then dried to form the second metal filter layer material layer on the base material. It is preferable to prevent the filter layers from being mixed and then simultaneously sinter by heating once.

In addition, a plurality of layers of these two kinds of metal filter layers may be laminated, that is, for example, both filter layers may be alternately laminated, or one filter layer may be formed in plural layers and the other filter layer may be formed in plural layers. Good.

(Examples) Hereinafter, the present invention will be described in more detail with reference to examples, but the examples do not limit the present invention.

Example 1 A pure nickel expanded mesh having a thickness of 0.1 mm and an opening of 1 × 1 mm was used as a base material, and the base material was washed with a neutral detergent, degreased with acetone, and pickled with a 20% hydrochloric acid aqueous solution at 60 ° C. Activated the surface.

For the first metal filter layer, 30 g of nickel 255 powder by the carbonyl method was added together with 1.5 g of methyl cellulose in pure water 50
A nickel paste was prepared by kneading the mixture in ml, and applying the paste to both surfaces of the nickel base material so as to have a thickness of 0.5 mm. After keeping it at room temperature for 15 minutes, it was dried at 60 ℃ for 30 minutes, and then stored at 700 ℃ in a gas atmosphere consisting of 80% argon and 20% hydrogen.
It sintered for 0 minutes and formed the 1st metal filter layer.

Next, for the second metal filter layer, nickel ultrafine powder (particle size 200Å) 10g, methylcellulose 0.5g and pure water 50ml
Was prepared, and the paste was applied to the surface of the first metal filter layer. After keeping it at room temperature for 30 minutes, dry it at 60 ℃ for 1 hour, and put it in the same gas atmosphere as above.
After sintering at 0 ° C for 15 minutes, a metal filter with openings of 50Å was obtained.

(Example 2) A sintered filter having a mesh of 40 mm and a mesh of nickel wire having a thickness of 0.2 mm was used as a base material, and the surface of the base material was degreased and pickled with a 10% nitric acid aqueous solution.

When a first metal filter layer) was formed on the substrate in the same manner as in Example 1, the opening was 0.1 to 1 μm. A nickel ultrafine powder paste having a particle size of 200Å prepared in the same manner as in Example 1 was formed on the first metal filter layer to a thickness of 10
Apply to 0 μm and dry at room temperature for 15 minutes, then 80
After drying at 0 ° C for 30 minutes, it was heated for 15 minutes in a furnace at 500 ° C in which a mixed gas of nitrogen: hydrogen = 90:10 (volume) was passed. This operation was repeated twice to obtain a metal filter having a large strength with an opening of 30 to 50Å.

(Example 3) A titanium wire having a diameter of 0.1 mm and a mesh having an opening of 1 mm was used as a base material, and the base material was degreased and then pickled in 30% sulfuric acid at 80 ° C.

30 g of titanium powder with a particle size of 10 μm, 1.5 g of methyl cellulose,
Make a paste by kneading 50 ml of pure water and 1 ml of defoaming agent,
The paste was applied to both sides of the mesh so that the total thickness was 1 mm. Hold at room temperature for 15 minutes, then at 60 ° C
It was dried for 30 minutes. Put it in a vacuum furnace (10 ^-6 mmHg) and 900 ℃
Sintered for 30 minutes. The opening of the filter thus produced was 2 μm.

Apply 15 g of titanium ultrafine powder with a particle size of 1000 Å, 0.7 g of methlycellulose and 50 ml of pure water to this surface, and apply the paste.
After being kept at room temperature for 15 minutes, it was dried at 60 ° C. for 1 hour. Further, it was sintered in argon gas at 450 ° C. for 15 minutes. By this operation, it was possible to obtain a metal filter having a mesh opening of 150 to 200Å.

(Example 4) In the same manner as in Example 1, a nickel paste made of nickel 255 powder by the carbonyl method was applied onto an expanded mesh made of nickel, kept at room temperature for 15 minutes, and then dried at 60 ° C for 30 minutes. A nickel paste containing the nickel ultrafine powder (particle size 200Å) used in Example 1 was applied to this surface, kept at room temperature for 30 minutes, dried at 60 ° C. for 1 hour, and further argon:
It was dried at 650 ° C. for 30 minutes in a mixed gas atmosphere with hydrogen = 1: 1.

This made it possible to obtain a metal filter with an opening of 50Å. Observation of the surface of the metal filter revealed that it consisted of a relatively porous first metal filter layer and a dense and thin second metal filter layer.

(Advantages of the Invention) The present invention forms a first metal filter layer having a relatively large opening by sintering a first metal powder in advance on a base material made of a metal mesh, and then forming the above-mentioned surface on the surface. A second metal filter layer having a mesh size smaller than that of the first metal filter layer is formed by applying and sintering a suspension or paste containing a second metal powder having a finer particle size than the metal powder. In the method for producing a metal filter, the loose sintering is used as the sintering, and / or an organic metal salt is used as a binder during the sintering of the first metal powder. It is a manufacturing method.

Therefore, in the present invention, the metal mesh body provides good formability and mechanical strength, and the first metal filter layer having an intermediate mesh reduces pressure loss and the presence of the first metal filter layer. The thickness of the second metal filter layer having a predetermined fine opening formed on the first metal filter layer can be made thinner to ensure a uniform opening and use of expensive fine metal powder The amount can be minimized. This enables the metal filter of the present invention to have contradictory properties such as mechanical strength and a desired opening, which cannot be obtained at one time in the prior art, and
The thickness of the second metal filter layer having fine openings can be made extremely thin, whereby a metal filter layer having a uniform thickness can be obtained, and the expensive ultra-high cost required for forming the layer can be obtained. It becomes possible to economically manufacture a metal filter with a minimum amount of fine powder used. Loose sintering improves the bonding strength between metal powders, and the use of an organic metal salt causes decomposition of the salt. As a result, the entire space between the particles is covered with a thin metal layer, and the salt functions as a sintering aid to obtain a metal filter having high strength.

Claims (3)

[Claims] 1. A first metal filter layer having a relatively large opening is previously formed by loose sintering of a first metal powder on a base material composed of a metal mesh, and then the metal powder is formed on the surface by the loose sintering. Forming a second metal filter layer having openings smaller than the first metal filter layer by applying a suspension or paste containing a second metal powder having a fine particle size and loose sintering. And a method for manufacturing a metal filter. 2. A first metal filter layer having a relatively large opening is formed on a base material composed of a metal mesh body by using an organic metal salt as a binder in advance and sintering the first metal powder.
Then, a suspension or paste containing a second metal powder having a finer particle size than the metal powder is applied to the surface and sintered to form a second mesh having a mesh size smaller than that of the first metal filter layer. A method of manufacturing a metal filter, which comprises forming a metal filter layer. 3. A first metal filter layer having a relatively large opening is formed on a base material made of a metal mesh body by using an organic metal salt as a binder in advance by loose sintering of the first metal powder, and then, By applying a suspension or paste containing a second metal powder having a finer particle size than the metal powder on the surface and loose sintering, a second mesh having a mesh size smaller than that of the first metal filter layer is formed. A method of manufacturing a metal filter, which comprises forming a metal filter layer.