JPH05277312A - Filter member for gas - Google Patents

Abstract

PURPOSE:To obtain an advanced filter member for gas using metal short fiber by sintering metal short fiber having a diameter and an aspect ratio of the specified range of values and making it a sintered body where parallel layers having pores of uniform distribution are provided. CONSTITUTION:The filter member for gas 1 is formed by sintering metal short fiber in the shape of a column having a diameter and an aspect ratio, i.e., length/diameter, in the ranges of 0.5-10mum and 2-20, respectively. And it consists of a sintered body 3 having circular openings through which one filter surface 4 communicates with the other filter surface 6 and, simultaneously, is provided with parallel layers 5, 7 where metal short fiber 2 is arranged with its longitudinal axis parallel to the filter surfaces 4, 6 and in the same direction on the sides of the filter surface 4, 6. Thereby, uniform filter diameters and distribution are given, fine particles are effectively removed by filtration, good mechanical strength and dimensional precision are given, and welding and diffusion joining are made and besides baking treatment is made.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter member for a gas, which is made of a sintered body of metal short fibers and can be suitably used, for example, for filtering a process gas used for manufacturing a semiconductor.

[0002]

2. Description of the Related Art For example, technological advances in the semiconductor industry have been remarkable in recent years, and high density densified integrated devices up to 16 Mbits have been prototyped. The pattern width of such an element has a minute interval of submicron. For this reason, the process gas such as argon, nitrogen, hydrogen, Hcl, and HF used in the production is filtered by using a high-precision filtering filter to obtain 1/1 of the pattern width.
It is indispensable to remove even impure particles having a diameter of 0 or more, for example, particles of about 0.01 μm or more to prevent a short circuit of wiring.

In such a filter, for example, as shown in FIG. 20, a cylindrical filter member C1 having a bottom is attached to a large-diameter body of a housing having an inlet A and an outlet B at both ends. As shown in FIG. 21, it is known that a flat plate-shaped gas filter member C2 is attached to the body of the housing. Further, a so-called membrane filter using a porous thin film of a polymer material such as Teflon as a filter member has been widely used because it is excellent for gas.

However, as described above, due to the demand for ultra-high purification of the process gas, it is necessary to suppress moisture and impure gas such as hydrocarbons from the polymer material itself, and the smooth operation is ensured. Heat resistance is also required to withstand the baking process for raising.

[0005] This baking treatment means the entire system for gas filtration including a filter, for example, at 200 to 400 ° C.
The baking is carried out to remove harmful water existing in the system by heating to a certain degree and adhering to the inside of the system, and such a baking process cannot be performed with a filter member made of a polymer material.

As a result, in the semiconductor industry, there is a demand for a high-precision all-metal filter that can withstand baking processing and does not generate an impure gas, without using a polymer-based filter or packing. It was decided.

Such a metal filter for gas is marketed by Nippon Pole Co., Ltd. under the trade name "Ultramet", and JP-A-64-18423 discloses a filter body for filtering ceramic or metal. , A filter member placed on a thick porous body made of the same material is proposed.

However, the former one is obtained by laminating and sintering long metal fibers, and the filter member is formed into a flat plate as shown in FIG. 21 and has a porosity of 9%.
It is set extremely high at 5% or more. The latter proposal is
It is based on the bottomed cylindrical body of FIG. 20, and this proposal merely shows that a metal is used, and does not disclose any specific specifications such as what kind of metal material is used. ..

On the other hand, the applicant of the present invention has filed Japanese Patent Publication No. 63-6364.
Japanese Unexamined Patent Publication No. 5 discloses a metal short fiber and a method for producing the same, which is characterized in that stainless steel fiber is cut by grain boundary selective corrosion. The proposed short metal fibers have a diameter of 2 to 20.
μm, aspect ratio 1 to 50, the same diameter over the entire length, and a columnar shape without sagging at the end, that is, without a hook-shaped protrusion that intersects with the longitudinal axis.

Further, the applicant of the present invention has filed Japanese Patent Publication No. 63-5443.
No. 63-218, there is also disclosed a sintered body obtained by mixing the metal short fibers and metal fine particles which are metal particles at a ratio of 20 to 80%, molding the mixture using a thermosetting resin, and sintering the mixture.
No. 225 proposes a filter material consisting only of the above-mentioned short metal fibers, and Japanese Patent Publication No. 63-31521 proposes a manufacturing method thereof.

The filter proposed by the applicant of the present invention using these short metal fibers and metal particles was developed for the purpose of filtering a viscous liquid such as a liquid polymer.

On the other hand, in the case of a liquid filter, the target impurities are relatively large, such as gel, of several μm, and these impurities are efficiently captured by a physical method while suppressing pressure loss. While the filtration direction is
For gases, it is necessary to remove extremely minute impurities of around 0.1 μm, most of which are adsorbed on the fiber surface by collision with the filter due to Blanc motion or by Van der Waals attraction, etc. Although both are filtrations of fluids, their collection mechanism is completely different.

Further, regarding the filtration mechanism of such impure particles of gas, "Applied Aerosolology" (Kyokan, March 1984)
Issued monthly, pages 157-159, 182-186, 5th category
Page, hereinafter referred to as literature), 10 μm or less, particularly 0.1 μm.
Regarding the theory of dust collection of air filters aimed at the filtration of impure particles of ~ 0.5 μm, the dust collection performance of air filters depends on the internal structure of the filter medium, and further, the following requirements are satisfied as a desirable filter medium structure. It describes what to do.

To make the fiber diameter as small as possible to eliminate the distribution of fiber diameters. Arranging the fibers at right angles to the gas flow. Fill evenly.

[0015]

However, at the same time, there is no filter satisfying such conditions in the literature, and even the most excellent fine fiber group filter has a large fiber diameter distribution and uneven filling. And is not satisfactory.

The present inventor has made various developments in order to obtain a filter member for gas having a satisfactory performance on the basis of such a technique.

In the course of its development, a filter using long metal fibers was first tested. The filter using the metal long fibers is formed into a plate-shaped sintered body by pressing the entangled body of the long fibers to reduce the thickness and sintering. However, as described in the above-mentioned document, this filter is found to have an unsatisfactory collection efficiency of impure particles, although the fibers are arranged at right angles to the direction of gas flow and therefore parallel to the filtration surface. did. As described above, this filter orients the fibers by pressing and constricting the entangled body of long fibers, but when the entangled body is reduced in thickness, the fibers are formed. The reason is that the space itself, that is, the roughness of the eyes, is not significantly reduced, and therefore the pore diameter is relatively large, and the pore diameter distribution is non-uniform, and only a large porosity can be formed. Inferred. Since this is a compressed body of a tangled body,
Although the long fibers themselves are substantially parallel to the filtration surface, the directions of the central axes of the fibers are not the same and are randomly arranged.

Therefore, the present inventor has conceived to use the above-mentioned short metal fibers according to the above-mentioned proposal of the present applicant as a filter member for gas in order to make the pore diameter fine and to make the pore diameter uniform. .. It has been considered that the short metal fibers can be easily compressed at the time of molding and can achieve a finer pore size and a uniform pore size.

If only metal particles such as atomized powder are used without using metal long fibers and metal short fibers, impurity particles having a size of 0.01 μm or more will be collected from the gas. It is necessary to use, for example, a metal atomized powder having a size of micron order,
Since such particles are also usually spherical, the porosity is extremely small, and the pressure loss is large enough to withstand use.

As described above, as a filter member for gas using short metal fibers, the present inventor firstly prepared a filter material obtained by sintering short metal fibers proposed by the above-mentioned Japanese Patent Laid-Open No. 63-218225. Tested However, it has been found that this product is inferior in particle collection efficiency, and particles of 0.01 μm cannot be sufficiently removed.

As a result of various studies on the cause, even if it can be sufficiently used as a filter member for liquids,
It has been found that the uniformity of the pore size distribution on the entire filtration surface is insufficient for use as a gas filter member, and as a result, the quality is not stable as a gas filter member.

As a result of further studies to improve this, the asbestos ratio was set to a relatively narrow range of 2 to 20, and the fiber diameter was 0.5 to 10 μm. In addition to the above-mentioned JP-A-63-218
In the filter material for liquids sintered using the short metal fibers proposed by No. 225, the porosity is 50% or more,
It has been found that a gas filter member having a smaller porosity is preferable.

As described above, as a gas filter member, it is preferable that the porosity is lower than that of the liquid filter member. Next, a filter material having a small porosity can be obtained by using short metal fibers. When the development was carried out focusing on, the direction of the longitudinal axis of the short metal fibers was made parallel to the filtering surface, and the use of a parallel layer of short metal fibers in which the directions of the respective long axes were aligned reduced voids and the like. It has been found that favorable filtration performance can be obtained.

In this way, the provision of the parallel layer in which the longitudinal axis of the short metal fibers is parallel to at least one filtration surface is described in the above-mentioned document. This is consistent with the description that the angle is right, and it is speculated that the filtration performance can be improved by this. When the longitudinal axes of the short metal fibers are aligned in parallel to each other, it is considered that, when they are bonded to each other by sintering, it is possible to form fine and continuous filtration holes between the short metal fibers in parallel, Also, this parallel layer, compared to the random array,
It helps to make the pore size distribution uniform and stabilizes the quality.

On the other hand, in addition to the mechanical vibration of the once-collected impurity particles, in order to prevent the gas from escaping from the filter wall caused by the pulsation of the gas due to the opening and closing of the valve, etc. It has been found preferable to provide layers.

As a result of various developments and studies, the inventor of the present invention has completed the production of a filter member for gas satisfying such requirements.

As described above, the object of the present invention is to provide a highly accurate gas filter member using short metal fibers.

[0028]

The present invention has a diameter of 0.5.
-10 μm, length / diameter aspect ratio 2-20
With a sintered body having pores communicating from one surface to the other surface formed by sintering a metal short fiber having a columnar shape in the range of, and at least one surface side,
A filter member for gas, wherein the metal short fibers are provided with a parallel layer in which the longitudinal axis thereof is parallel to the surface and arranged in the same direction.

[0029]

In the present invention, short metal fibers having a fine diameter of 0.5 to 10 μm are used. In addition, the short metal fibers having a wire diameter of 0.5 μm or more and smaller than 2 μm have been obtained by the research and development of the present applicant in recent years. The diameter is smaller than that of the proposed Japanese Patent Publication No. 63-63645.

The use of such a small-diameter staple fiber contributes to an increase in the surface area for capturing the impure particles in the gas, increases the chances that the impure particles are adsorbed by the filter, and enables effective filtration treatment. It can be carried out. Moreover, since the aspect ratio, that is, the length / diameter is set to a relatively narrow range of 2 to 20, the pores of the filter are made uniform. This facilitates adjusting the porosity of the filter.

The short metal fibers have a columnar shape with the same diameter over the entire length, but when the short metal fibers according to the above-mentioned Japanese Patent Publication No. 63-63645 are used, the short metal fibers are hook-shaped sagging due to cutting or the like. The columnar shape has almost the same diameter over the entire length. At this time, when kneading, the short metal fibers do not get tangled and a uniform distribution is possible, and the porosity can be adjusted and made uniform, which helps stabilize the quality.

Further, in the present invention, at least one surface side is provided with a parallel layer in which the longitudinal axes of the short metal fibers are arranged in the same direction and are parallel to the surface. In this parallel layer, the short metal fibers are arranged orthogonally to the invading gas, and the surface of the short metal fibers can be used for efficient adsorption and the collection efficiency can be improved. In addition, as a result of the appropriate shape and distribution of the filter pores, the captured impure particles are less likely to fall off, and even if they fall off, they are likely to be re-captured later, which can reduce the loss of impure particles.

In the parallel layer, since the longitudinal axes of the metal short fibers are parallel to the filtering surface and the longitudinal axes themselves are parallel to each other, the collection efficiency is improved, and the parallel layer is also described in claim 2. So that the porosity of the gas filter member is 35
% Or less and less than 45% can be easily set, and the pore distribution can be made dense and uniform.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 to 6, a gas filter member 1 of the present invention comprises a sintered body 3 obtained by sintering metal short fibers 2 ...
And on one surface 4, for example, on the outer surface side through which gas flows,
A parallel layer 5 is provided in which the longitudinal axis K of the metal short fibers 2 is parallel to the surface 4 and the longitudinal axes K ... Are in the same direction.

In the present embodiment, the gas filter member 1 is formed in a cup-like shape having a bottomed cylindrical body and is housed in the housing 10 to reduce the outer diameter and increase the filtration area. Form. Although the bottom has a spherical shape, it can be formed in a flat shape.

The short metal fibers 2 have a diameter of 0.5 to 10
The one in the range of μm is used. More preferably, 0.5
The metal short fibers 2 having a size of not less than μm and smaller than 2 μm are used.
With such a wire diameter, a filter having fine filtration holes can be obtained, and the pore diameter distribution can be made uniform.

When using the stainless steel having the diameter of the metal short fibers 2 in the range of 2 to 10 μm, the short fibers made of stainless steel proposed by the present applicant in the above Japanese Patent Publication No. 63-63645 can be used. Also 0.5-2
The metal short fibers 2 made of stainless steel having a thickness of μm have been put to practical use by the present applicant in recent years.

The diameter of the short metal fibers 2 is an average value of diameters measured at respective positions and in respective directions over the entire length of each short metal fiber, and is measured in respective positions and directions of the short fibers. As for the value, the same diameter can be used over the entire length with a diameter of about 30% from the average value. Similarly, the short metal fibers 2 are allowed to include those having a diameter difference of about 20%.

The aspect ratio is 2 to 20, preferably about 2 to 10, which is smaller than that of the above-mentioned proposal. This makes the pore size distribution uniform and stabilizes the quality and accuracy. In addition, the metal short fibers 2 are in this range,
It contains 75%, preferably 85% of the total number.

The short metal fibers 2 are, in this example, at the ends.
It has a hook-shaped protruding portion that projects outward, that is, a columnar shape without sagging. With this, short metal fibers 2 ...
It is possible to reduce the entanglement and make the distribution uniform, and to form a filter having filter holes of uniform filter diameters.

Further, when stainless steel is used as the short metal fibers 2, SUS316L, SU having good corrosion resistance.
S317L and the like are preferable. Also, if the filtered gas is, for example,
When it is a corrosive gas such as Hcl or HF, high corrosion-resistant Inconel, Monel, nickel, Hastelloy C series, X series (registered trademark of Mitsubishi Metals Co., Ltd.), etc. may be adopted. It has been confirmed by the present applicant that some of these metals can be made into short metal fibers.

Further, in the parallel layer 5, as shown in FIG. 2, the longitudinal axis K of the metallic short fibers 2 is parallel to the surface 4, and as shown in the figure, the longitudinal axis K of each metallic short fiber 2 ... Both are facing in the same direction.

Therefore, the short metal fibers 2 are arranged orthogonally to the invading gas, and the surface of the short metal fibers can be utilized for efficient adsorption, thereby improving the filtration efficiency. .. Furthermore, in addition to the longitudinal axis K of the short metal fibers 2 being parallel to the surface 4, the parallel layer 5 makes the longitudinal axes K themselves parallel to each other. As a result, a filter using the short metal fibers 2 has a porosity of 35% or more and a small porosity of 4 or more.
It becomes easy to set the range to less than 5%, the pore distribution can be made precise, and the pore diameter and the pore shape can be made appropriate, and the collection efficiency can be improved. It also functions to make the distribution of filter holes uniform.

In the present specification, "the longitudinal axis K of the short metal fibers 2 is parallel to the surface 4" means that the longitudinal axis K is the same direction as well as the surface 4 when the longitudinal axis K is different. In the present invention, the longitudinal axes K of the short metal fibers 2 are aligned in the same direction and are parallel to the plane 4 although they may be parallel to each other.

In the present specification, "longitudinal axis K is parallel to surface 4 and arranged in the same direction" means that metal short fibers 2 are arranged such that their longitudinal axes K are exactly in the same direction.
Other than the case where the longitudinal axis K is substantially parallel to the surface 4 and is substantially parallel to the surface 4 when the inclination angle of the longitudinal axis K with respect to the surface 4 is within 30 ° and the longitudinal axes K of the respective metal short fibers 2 intersect with each other within 30 °. It is defined to include a case where the angles are substantially the same. Further, in the present invention, it is specified that the parallel layer 4 may include a certain amount of the short metal fibers 2 which are not substantially parallel to the faces 4 of 30% or less.

Whether or not the longitudinal axes K of the short metal fibers 2 are arranged in the same direction in the parallel layer 4 can be confirmed by the fracture surface of the filter member, which is broken at two planes at right angles.

FIG. 5 and FIG. 6 are enlarged microscope views of an actually manufactured example of the gas filter member 1 according to the present invention taken along the line II and line II-II perpendicular to each other in FIG. It is a photograph. 7 to 11 are enlarged photographs of the areas A1 to A5 in FIG. 5, and FIGS. 12 to 16 are enlarged photographs of the areas B1 to B5 in FIG. 7 to 16 are micrographs magnified 250 times, and FIG. 3 schematically shows the distribution of layers in the cross section taken along the line I-II of this actually manufactured example product.

Therefore, FIG. 7 and FIG. 12, FIG. 8 and FIG. 13, and FIG.
14, FIG. 14, FIG. 10 and FIG. 15, and FIG. 11 and FIG. 16 correspond,
Corresponding A1 to A5 and B1 to B5, respectively, indicate the arrangement of the short metal fibers 2 of the fractured planes orthogonal to each other at substantially the same portion.

As shown in the range A1 in FIG. 7, one surface 4, in this example, the surface 4 is provided on the outer peripheral surface side of the filter member 1.
It can be seen that the parallel layer 5 having the metal short fibers 2 in which the longitudinal axes K are arranged in parallel and in the same direction is formed.

In the range B1 of FIG. 12 showing the fracture surface orthogonal to FIG. 7, it can be seen that the longitudinal axis K of the short metal fiber 2 is orthogonal to the fracture surface, that is, the plane of the photograph.

As can be seen by comparing FIGS. 7 and 12, a relatively thin random layer 9 in which the longitudinal axes K of the short metal fibers 2 are randomly arranged is formed on the outer peripheral surface, and the parallel layer 9 is formed on the inner side thereof. Layer 5 is located.

As described above, in the gas filter member 1 of the present invention, the parallel layer 5 is provided on one surface 4 side through the random layer 9 on the outer peripheral surface.

Further, in this embodiment, the parallel layer 7 is also provided on the other surface 6 side, that is, on the inner peripheral surface side. The parallel layer 7 is formed inside the areas A5 and B5 shown in FIGS. 5, 6 and 11 and 16 via the thin random layer 10 similar to the above along the inner peripheral surface. The parallel layer 7 is longer than the parallel layer 4 on the outer peripheral surface side in the longitudinal axis K of the short metal fibers 2.
11, the longitudinal axis K of the short metal fibers 2 is parallel to the plane of the photograph in one of the fracture surfaces of FIG. 11, as is clear from comparison with FIGS. On the other fracture surface, most of the longitudinal axis K is orthogonal to the plane of the photograph, and although the degree of alignment is inferior to that of the parallel layer 4, such a parallel layer 7 also has the parallel layer concept defined in this specification. included.

Further, in the present embodiment, the layer 12 in which the longitudinal axis K of the short metal fiber 2 is oriented in the same direction is formed also in the middle portion in the thickness direction, that is, in the ranges A3 and B3 shown in FIGS. ing.

In the fracture plane where the parallel layers 5 and 7 show the I-I line cross section, the longitudinal axes K of the short metal fibers 2 are parallel in the same direction, while this layer 12 is orthogonal to this II-. In the II line cross section, the longitudinal axis K of the short metal fibers 2 is in the same direction and parallel to the surface 4, and thus the layer 12 is oriented with respect to the long axis K of the short metal fibers of the parallel layer 5 on the surface 4 side. Different different direction parts Z1 are formed.

In the portion between the parallel layers 4 and 6 and the different direction portion Z1, the orientation of the longitudinal axis K of the short metal fiber 2 is not uniform, as shown in the ranges A2, A4, B2 and B4. Different direction parts Z2 and Z3 formed of random parts are formed.

The parallel layers 5 and 7 are 1/6 to 1 of the thickness t.
It is about 3 times. In the gas filter member 1 of FIG. 1, the length L is 41.5 mm and the outer diameter D is 19 m.
m, the inner diameter d is 15 mm, and the thickness T is 1.
A 5 mm flange is provided. The taper of the body is 2
And the thickness t is 2 mm.

The inner and outer parallel layers 5 and 7 enable the impure particles dropped off in the parallel layer 5 to be recollected in the parallel layer 7, and by using the intermediate different direction portion Z1, the inner and outer surfaces can be separated. By rotating and changing the shape of the filter holes by 90 degrees between them, the collection of various impure particles is ensured. Further, the porosity is reduced and the dense voids are continuous, so that the filter member for gas has a high filtering accuracy. Further, the random different-direction portions Z2 and Z3 change the shape of the filter holes to enhance the collection efficiency and also serve to adjust the porosity.

Further, in the present invention, as described above, the average porosity is set to 35% or more and less than 45%. This is a range that can be achieved even in a filter using short metal fibers by aligning the longitudinal axes of the short metal fibers 2 in the same direction, and as a result, a uniform pore size distribution is obtained over the entire filtration surface. In addition, it helps stabilize the quality and can improve the collection efficiency of impure particles.

The average porosity means the average porosity calculated from the volume and weight of the filter member, and this porosity is defined as the ratio of the void volume per unit volume of the sintered body. To be done.

The metal short fibers 2 whose longitudinal axes are aligned parallel to each other are bonded to each other by sintering through the convex portions on the surface of the metal short fibers 2 ... Forming fine and continuous filtration holes in the depth direction,
It is presumed that this helps uniform the pore size distribution and stabilizes the quality.

Further, since the gas filter member 1 is formed of the sintered body of the short metal fibers 2, ..., Impurity gas and the like are not emitted from the filter itself. .

Further, since the gas filter member 1 is a sintered body of short metal fibers, it can be machined, and as a fixing method to a metal member such as a housing body, as shown in FIG. In addition to directly welding, as shown in FIG. 17, the boss 14 provided in the housing 10
It can also be attached by welding by diffusion bonding after screw connection to, and at this time, oxides generated when fixing by welding or the like can be eliminated.

The product of the embodiment can be obtained, for example, by the slip casting method as an example of the powder metallurgy method.

This method uses a slurry in which predetermined metal short fibers are suspended in a liquid having a certain concentration (for example, water),
This is a method of filling a predetermined mold while applying high pressure. In this case, a porous body having fine pores is used as a mold, each short fiber is oriented along the flow direction during filling, and is held in that state on the mold wall side, that is, the filter member surface side. As a result of the pressure being further increased on the central side, the short fibers are pushed by the filling pressure and change in the direction rotated by 90 °.

At the same time, the suspension is discharged to the outside from the pores of the mold, and evaporated by adding a means such as heating. As a result, only short fibers will remain,
As it is, for example, by heating at about 900 to 1500 ° C. in a vacuum atmosphere, the contact portions and the approaching portions of the short fibers are joined together to form an integral sintered body.

Moreover, the sintered body also has a porosity.
From one side to the other side, forming a complex shape
A porous body with fine passages , Its surface side
For this reason, a parallel layer is formed.

In this case, the extrusion condition is 100 kg / or more, preferably 15 depending on the shape of the filter.
0 kg / or more, more preferably 300 kg / cm2 or more,
It is set in consideration of the metal short fibers 2 to be adopted, the property shape of the molded product, and the like.

The sintering is carried out, for example, in a vacuum furnace, an inert gas atmosphere furnace or a hydrogen furnace, and depending on the material, for example, 90
It is possible by heating at a temperature of 0 to 1500 ° C. and holding for about 5 minutes to 6 hours.

As described above, the short metal fibers 2 are filled into the mold while being constantly applied with pressure, so that they are three-dimensionally compressed, resulting in uniform microscopic voids with uniform quality throughout. Can be formed.

As described above, in this embodiment, since the gas filter member is formed by extrusion molding of short metal fibers, it is difficult to sinter after compression molding using a press machine. It becomes possible to manufacture a complicatedly shaped member.

In the examples shown in FIGS. 1 to 5, the longitudinal axes of the metal short fibers 2 of the parallel layers 5 and 7 are oriented in the longitudinal direction of the gas filter member 1, and the metal of the central different direction portion Z1 is used. It is considered that the longitudinal axis of the short fibers 2 is oriented in the lateral direction because the slurry filling port is located at the center of the spherical portion at the lower end. This is because when the metal short fibers are ejected from the filling port in the longitudinal direction and are inverted, in any case, due to friction with the mold wall surface due to pressure, the metal fibers are locked in the vertical state as they are, while inside the It is presumed that it becomes the highest pressure and has sufficient flow displacement, so it faces laterally and solidifies in that state.

FIG. 18 shows another embodiment of the present invention. In this embodiment, the parallel layer 5 is formed on the outer surface of the base 15 by a two-step molding method. Here, the substrate 15 is
For example, it can be obtained by filling a slurry containing metal short fibers into a mold, forming a porous body having a predetermined characteristic by hot pressing, and then performing sintering and integration in a sintering furnace. The fibers are in a random three-dimensional array.

The parallel layer 5 is for distributing short metal fibers by a well-known liquid immersion method, and further by distributing them with their longitudinal axes substantially aligned by an appropriate vibrating screen, and making them into a sintered sheet state. The both are further attached and sintered and integrated.

Due to the parallel layer 5 on the surface 4 side, the short metal fibers are at right angles to the invading gas, and the surface area of the filter hole wall is increased at the time of admission of the gas, so that the contact area with the gas is increased. Impurity particles are effectively collected by increasing the efficiency of collision between the impure particles and the pore wall. Also the base 1
The open surface of 5 forms the other surface 6, and
Form the different direction portion Z2 in which the metal short fibers are three-dimensionally oriented.

Further, such a filter member for gas can also be formed by placing the substrate 15 as an insert material in a die during extrusion molding and providing a parallel layer on at least one surface thereof.

[0077]

[Example 1] A metal short fiber of 316L stainless steel having a fiber diameter of 6 µm and an average aspect ratio of 8 was supplied to a slurry extruder in which water was suspended, and a pressure of 300 was applied to a mold.
The product was discharged at kg / kg to obtain a preform of the whole mold shape.

Then, this molded product was once heated to 200 ° C. to evaporate the suspension to disappear, and then 1100 ° C. × 30 m
in. Sintering was performed in a vacuum atmosphere under the above conditions. As a result,
The length L shown in FIG. 1 is 41.5 mm, and the outer diameter D is 19 m.
m, the inner diameter d is 15 mm, and the thickness T is 1.
A hemispherical cup-shaped filter member (hereinafter referred to as sample S1) provided with a 5 mm flange was obtained.

The filter member for gas has a beautiful surface, fine pores are uniformly formed inside the filter, and the longitudinal axes of the metallic short fibers are parallel to each other on the inner and outer filtration surfaces. It can be understood that it is formed with layers.
Moreover, the inside is a different direction part which turned to the horizontal direction.

The sintered body can be used as a filter member for gas and has the following characteristics. Average porosity: 4.2 μm Average porosity: 44%

[0081]

Example 2 A short metal fiber made of stainless steel having a fiber diameter of 1.2 μm and an average aspect ratio of 4 was used.
Filter member (hereinafter referred to as sample S2
I got)). The gas filter member had a porosity of 36% and an average pore diameter of 0.9 μm. Moreover, a parallel layer similar to the sample S1 exists inside the cross section.

[0082]

[Example 3] Metallic short fibers of Hastelloy C shortened to a fiber diameter of 4 µm and an average aspect ratio of 10 were made into a slurry similar to the above, and this slurry was discharged at a pressure of 150 kg / cm2 and further dried and sintered to obtain a diameter. A disk-shaped gas filter member (hereinafter referred to as sample S3) having a thickness of 30 mm and a thickness of 1 mm was obtained. Since the discharge was performed from the side surface of the circumference, the parallel layers of the short metal fibers were formed on both filtration surfaces in the same direction along the filtration surfaces. The porosity of this filter is 40
%, And the average void diameter was 3 μm.

[0083]

Comparative Example 1 Using the stainless steel short fibers used in Example 1, Japanese Patent Publication No. 63-31521 proposed by the present applicant.
According to the method disclosed in Japanese Unexamined Patent Application Publication No. 2004-242242, fine powder of polyimide resin was dry mixed with short metal fibers, and a hot press was used to obtain a cylindrical preform. This is 1100 ℃ × 3
A cylindrical sintered body was obtained by sintering for 0 minutes. Further, one end was closed by welding a disk body made of a sintered body formed in the same manner, to obtain a filter member (referred to as squid sample R1) having substantially the same shape as in Example 1.

This filter had a pore size of 4 μm and a porosity of 55%, but the short metal fibers were randomly distributed throughout, and no parallel layer could be confirmed.

[0085]

Comparative Example 2 Atomized powder of stainless steel having an average particle diameter of 8.5 μm was used and molded and sintered in the same manner as in Example 1 to obtain a filter member having the same shape (hereinafter referred to as sample R2). Although the filter had a pore size of 6 μm, it had a porosity of 32% or less, and it was expected that it would not be suitable for use because the pressure loss was too large.

[0086]

Comparative Example 3 A filter material was obtained by forming long fibers of stainless steel having a fiber diameter of 2 μm and an average length of 5 mm into a sheet having a thickness of 2 mm by a known wet method and sintering.
This product had a pore diameter of 5 μm and a porosity of 89%. This was cut into a 30 mm disk shape to obtain a filter member (hereinafter referred to as sample R3).

[Test 1] Filtration Characteristics of Filters The characteristics of four types of filters, that is, the filters of the above-described examples (samples S1 and S2) and the filters of comparative examples (samples R1 and R2) were measured. The results are summarized in Table 1.

[ [0088]

[Table 1]

In Table 1, the pressure loss is a value (mmH 2 O) when air is flowed at 1000 CC per minute.

[Test 2] Next, in order to compare variations in the filter characteristics, three samples of each of the samples S1 and R1 of Example 1 and Comparative Example 1 were measured for bubble point pressure and pressure loss. Table 2 shows intersection bubble points, and Table 3 shows variations in pressure loss.

Here, the bubble point pressure is measured by using isopropyl alcohol defined in JIS standard B8536 "Filtration particle size test", and the initial bubble point pressure Pas is the pressure when bubbles are first generated. Further, the intersection point bubble point pressure Pes means a pressure calculated from a graph showing the relationship between the pressure and the flow rate and obtained at the intersection point of a portion with a large change rate and a portion with a small change rate. Therefore, the closer the Pes / Pas value is to 1, the narrower the pore diameter is, which is excellent as a filter member. The filter members of the present invention were all close to this.

[0092]

[Table 2]

[0093]

[Table 3]

Further, as another short fiber constitution, the fiber diameter is 2
The variation of the characteristics was measured for each of 8 types of filters, each of which was manufactured by selecting from a range of ˜8 μm and an aspect ratio of 2 to 10. As a result, the filter having a parallel layer on the surface side and having a porosity of 35 to 45% has a small variation in bubble point pressure and pressure loss of 35 mmH2 O or less and 12 mmH2 O or less, which is 1/10 to 10 times that of the comparative example. It was about 1/20 and excellent in uniformity.

[Test 3] Gas Filtration Test Next, in order to confirm the particle trapping effect by applying the filter members obtained in the above Examples and Comparative Examples to actual gas, the filters of Samples S1 and S3 were used as Examples. As comparative examples, the filter members of Samples R1 and R3 were used.

The measurement was carried out by incorporating these filters in a housing and using a polydisperse aerosol having a particle size of 0.01 to 0.3 μ at 3 liter / Min. The gas flowing out from the introduction side under the conditions described above and flowing out through the filter was measured by a condensation nucleus measuring instrument (CNC) provided on the exit side, and the number of particles passing through the filter was measured.

The measurement results are shown in FIG. 19. As is clear from the figure, the filter of the comparative example (sample R
1 and R3) each have a poor collection rate and particles can be seen forever, but the filter of the present invention has an extremely high effect of 1/20 or less as compared with the comparative example, and is stable at an early stage. I understand.

[0098]

As described above, since the gas filter member of the present invention is provided with a parallel layer having a uniform filtration diameter and pores having a uniform distribution, extremely fine particles can be efficiently treated. It can be filtered well, has good mechanical strength and dimensional accuracy, and in addition to being capable of welding and diffusion bonding,
Baking processing can also be performed.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing an embodiment of the present invention.

FIG. 2 is a perspective view illustrating a parallel layer.

FIG. 3 is a perspective view illustrating a different direction portion.

FIG. 4 is a cross-sectional view illustrating a filter.

FIG. 5 is an enlarged photograph of line II of FIG. 1 taken with a scanning microscope.

6 is an enlarged photograph of a line II-II in FIG. 1 taken by a scanning microscope.

FIG. 7 is an enlarged photograph of an A1 range in FIG.

FIG. 8 is an enlarged photograph of a range A2 in FIG.

FIG. 9 is an enlarged photograph of an A3 range in FIG.

FIG. 10 is an enlarged photograph of an A4 range in FIG.

11 is an enlarged photograph of an A5 range in FIG.

FIG. 12 is an enlarged photograph of a B1 range in FIG.

FIG. 13 is an enlarged photograph of a B2 range in FIG.

FIG. 14 is an enlarged photograph of a range B3 in FIG.

FIG. 15 is an enlarged photograph of a B4 range in FIG.

16 is an enlarged photograph of a B5 range in FIG.

FIG. 17 is a cross-sectional view showing another example of the filter.

FIG. 18 is a sectional view showing another embodiment of the present invention.

FIG. 19 is a diagram showing filtration characteristics.

FIG. 20 is a cross-sectional view illustrating a filter.

FIG. 21 is a cross-sectional view illustrating a filter.

[Explanation of symbols]

 1 Gas Filter Member 2 Metal Short Fiber 3 Sintered Body 4 One Filtering Surface 5 Parallel Layer 6 The Other Filtering Surface 7 Parallel Layer 9 Different Direction Part 10 Housing 11 Base

Claims (5)

[Claims] 1. A short metal fiber having a columnar shape having a diameter of 0.5 to 10 μm and an aspect ratio of 2 to 20 which is a length / diameter, and is formed by sintering and one surface to the other surface. It consists of a sintered body with pores that communicate with
A filter member for gas comprising a parallel layer in which the short metal fibers are arranged on at least one surface side such that their longitudinal axes are parallel to the surface and arranged in the same direction. 2. The gas filter member according to claim 1, wherein the sintered body has an average porosity of 35% or more and less than 45%. 3. The gas filter member according to claim 1, wherein the sintered body has different-direction portions in which the directions of the longitudinal axes of the parallel layers and the short metal fibers are different. 4. The gas filter member according to claim 1 or 2, wherein the sintered body has different-direction portions of metal short fibers oriented in the longitudinal axis in a random manner. 5. The gas filter member according to claim 1, wherein the sintered body has a cup shape.