JPH07106288B2 - Metal filter manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a metal filter used for filtering 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 powders are 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. This approach only yields filters with sufficient mechanical strength and 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, there is nothing practically usable. 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 by sintering a first metal powder, and then a finer than the metal powder is formed on the surface. A second opening 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 particle size.
In the method for producing a metal filter for forming a metal filter layer, the loose sintering is used as the sintering,
And / or an organic metal salt is used as a binder at the time of sintering the first metal powder.

Hereinafter, the present invention will be described in detail.

In the present invention, the first metal filter layer having a large opening provides good formability (workability) and mechanical strength, reduces pressure loss, and has a second opening having a desired opening on the metal filter layer. A metal filter having a predetermined filtration performance can be obtained by forming the metal filter layer of No. 1, and further sintering is performed by loose sintering, and / or an organic metal salt is used as a binder for sintering the first metal powder. Can be used to produce high performance metal filters.

The present invention does not use a base material that constitutes a part of the metal filter, but uses an auxiliary plate such as a biscuit plate in the manufacturing process,
Both filter layers may be formed on the auxiliary plate, and after formation, they may be separated from the auxiliary plate to form a metal filter.

The first metal filter layer having a large opening is formed by sintering spherical metal particles. The forming method is not particularly limited. For example, in order to form a metal filter having an opening of 5 μm, metal particles having a particle size of 25 to 30 μm, a binder and a small amount of water are kneaded to form a paste, and the paste is a biscuit plate or the like. And then the molded body is dried at 50 to 100 ° C. and then sintered. Sintering conditions vary depending on the metal particles used, and a sintering temperature of 300 to 1100 ° C. and a sintering time of 10 minutes to several hours are suitable. For example, when nickel is used as the metal particles, it is suitable to sinter at 600 to 1000 ° C. for 10 to 60 minutes. The sintering atmosphere also differs depending on the metal particles used.In copper or copper alloys, an inert atmosphere such as nitrogen or argon is used; in the case of nickel, an atmosphere in which 10 to 50% hydrogen is added to nitrogen or argon; in titanium, it is helium. Or argon gas or vacuum is preferred.

Although it is possible to obtain a certain degree of strength only by the sintering,
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, each naphthenate, 2-ethylhensanate, metal alkoxide, or the like is preferable, and the size of the mesh is increased by the addition of the organic metal salt. Although it does not change substantially, the decomposition of the organic metal salt results in coating the whole space between the particles with a thin layer of metal, and the organic metal salt functions as a sintering aid, so that the strength of the metal is higher. You can get a filter. 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 the disadvantage of porous sintering does not occur, it is possible to perform the sintering under the condition that sufficient sintering proceeds. Examples of such a porous layer forming substance include 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.

Then, 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. 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, when the target opening is about 0.1 μm, use a metal powder of about 0.4 to 0.7 μm, and
When it is about 01 μm, a metal powder of about 0.04 to 0.07 μm is used. When the particle size of the particles used is 1 μm or less, it is necessary to lower the sintering temperature. This is because if the particle size is small, the sintering temperature is lowered and the degree of sintering under the same conditions is increased, and if the temperature is high, the desired opening may not be obtained.

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 and both metal powders may be simultaneously sintered. In the case of this method, the first and second metal filter layers are mixed by applying the first metal filter layer coating material in advance and then drying and then applying the second metal filter layer coating material thereon. It is preferable not to do so and to heat at the same time by heating once.

Further, a plurality of layers of these two kinds of metal filter layers may be laminated, 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. .

(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 nickel paste was prepared by adding 30 g of nickel powder (type 255) by the carbonyl method together with 3 g of methylcellulose into 50 ml of pure water and kneading. The paste was applied to a biscuit plate having a thickness of 10 mm and a length of 50 mm to a thickness of 1 mm. After drying at room temperature for 30 minutes, it was further dried at 60 ° C. for 1 hour.

A bisque plate coated with this paste is filled with 80% argon and 20% hydrogen.
% Gas for 10 minutes, then heated to 750 ° C. and held for 30 minutes. When taken out after cooling, a nickel porous body (first metal filter layer) having a thickness of about 0.5 mm was obtained.

A paste obtained by kneading nickel ultrafine powder having a particle size of 200 Å with ethyl alcohol was applied to the surface of this porous body. After drying, the second metal filter layer was formed by sintering in the same atmosphere as above at 500 ° C. for 30 minutes. By this operation, a fine metal filter having a surface with metallic luster and an opening of 40 to 60 Å was obtained.

For comparison, an attempt was made to sinter without using the first metal filter layer using only ultrafine powder having a particle size of 200 Å, but the physical strength was weak and it could not be peeled from the biscuit plate.

(Example 2) In the same manner as in Example 1, the carbonyl method nickel powder (type
255) as a raw material to produce a porous nickel filter (first metal filter layer) having a thickness of about 0.5 mm. A nickel ultrafine powder paste having a particle size of 500Å was applied to both sides of the surface of the filter in the same manner as in Example 1, dried at room temperature for 30 minutes and then at 70 ° C. for 1 hour. A carbonyl nickel powder (type 255) paste as a protective layer on both sides of this surface with a thickness of approximately 1 mm
Was applied so that After keeping it at room temperature for 30 minutes,
It was dried at ° C for 1 hour.

In a mixed gas atmosphere consisting of 80% argon and 20% hydrogen.
The temperature was maintained at 300 ° C. for 1 hour, then the temperature was raised to 650 ° C. and the temperature was maintained for 1 hour. As a result, a nickel metal filter having a thickness of about 1 to 1.5 mm and an opening of about 100Å was obtained.

(Example 3) 30 g of titanium powder having a particle size of 10 μm, 1.5 g of methyl cellulose,
50 ml of pure water and 1 ml of a defoaming agent were kneaded to prepare a paste. The paste was applied onto a biscuit plate in the same manner as in Example 1 to a thickness of about 1 mm. After being kept at room temperature for 15 minutes, it was dried at 60 ° C. for 30 minutes. Further, it was placed in a vacuum furnace (10 ⁻⁶ mmHg) and sintered at 900 ° C. for 30 minutes to obtain a titanium metal filter having a thickness of about 0.7 mm. The filter thus obtained had an opening of about 2 μm.

A paste obtained by kneading 15 g of titanium ultra fine powder with a particle size of 1000 Å, 0.7 g of methlycellulose and 50 ml of pure water on this surface to a thickness of about 0.5 m
It was applied so as to be m. Hold at room temperature for 15 minutes, then 60
It was dried at ° C for 1 hour. Further, put it in the vacuum furnace at 600 ° C for 30
Sintered for minutes. By this operation, it was possible to obtain a titanium metal filter having an opening of about 200Å.

(Example 4) A titanium paste was prepared in the same manner as in Example 3. To the paste was added twice the volume of magnesium powder having a particle size of 10 to 30 μm, and this was further coated on a biscuit plate to a thickness of about 2 mm, dried at room temperature for 30 minutes, and then dried at 100 ° C. for 2 hours. . The biscuit plate was placed in a vacuum furnace (10 ⁻⁶ mmHg) and sintered at 400 ° C. for 30 minutes and then at 1100 ° C. for 3 hours. Magnesium was volatilized to form porous titanium having a thickness of about 1.5 mm.

A paste formed by adding titanium powder having a particle diameter of 1 μm, methyl cellulose, pure water and a defoaming agent in the same proportions as in Example 3 was applied to the biscuit plate on which the porous titanium was formed, dried and then in an argon atmosphere. Sintered at 700 ° C for 2 hours. By this operation, a titanium metal filter having an opening of about 0.2 μm could be obtained.

(Effects of the Invention) The present invention provides a first metal filter layer having a relatively large opening by sintering the first metal powder in advance, and then having a finer particle size than the metal powder on the surface. By applying and sintering a suspension or paste containing the second metal powder, the second mesh having a mesh size smaller than that of the first metal filter layer is formed.
In the method for producing a metal filter for forming a metal filter layer, the loose sintering is used as the sintering,
And / or an organic metal salt is used as a binder at the time of sintering the first metal powder.

Therefore, the first metal filter layer provides the metal filter with mechanical strength as a whole, and usually has a desired mesh which is likely to cause a large pressure loss due to the fine mesh, that is, the second metal filter. Since the layer thickness can be reduced, pressure loss can be minimized. Further, although the finer particle metal becomes more expensive as the particle diameter becomes smaller, the amount of the fine particle metal used can be minimized, so that it is possible to obtain a cheaper metal filter made of ultrafine particles. The use of sintering improves the bond strength between metal powders, and the use of an organometallic salt results in the decomposition of the salt to coat the entire interparticles with a thin layer of metal, which also serves as a sintering aid. It is possible to obtain a metal filter that functions and has 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, and then a second metal having a finer particle size than the metal powder is formed on the surface thereof. By applying a suspension or paste containing powder and loose-sintering, the opening of
Forming a second metal filter layer that is smaller than the metal filter layer described in 1. above. 2. A first metal filter layer having a relatively large opening is formed in advance by sintering a first metal powder using an organic metal salt as a binder, and then has a finer grain size than the metal powder on the surface. A metal having a mesh size smaller than that of the first metal filter layer to form a second metal filter layer by applying and sintering a suspension or paste containing the second metal powder having Filter manufacturing method. 3. A first metal filter layer having a relatively large opening is previously formed by loose sintering of the first metal powder using an organic metal salt as a binder, and then fine particles finer than the metal powder are formed on the surface. A second metal filter layer having a mesh opening smaller than the first metal filter layer is formed by applying a suspension or paste containing a second metal powder having a diameter and loose sintering. Method for manufacturing metal filter.