JP3569682B2 - High corrosion resistance metal sintered filter - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a highly corrosion-resistant metal sintered filter made of a sintered titanium powder.
[0002]
[Prior art]
One of the filters used in the chemical industry, polymer industry, pharmaceutical industry, and the like is a metal powder sintered filter. As the metal here, brass and stainless steel are generally used, and recently titanium is also used.
[0003]
Titanium-based sintered filters have better corrosion resistance and acid resistance than stainless steel-based filters, but have poor moldability. For this reason, it is a common manufacturing method to mold a hydrodehydrogenated titanium powder with relatively good moldability by a mold press and then sinter it. Japanese Patent Application Laid-Open No. H7-238302 also discloses a production method using a sponge titanium powder having a relatively good quality.
[0004]
[Problems to be solved by the invention]
However, in a titanium sintered filter using titanium hydride dehydrogenated powder or sponge titanium powder, the size and shape of pores are randomly distributed. This type of filter is used for a long time while repeating backwashing. However, if the pores are random in size and shape, even if the backwashing is performed, the captured solids are not sufficiently removed. For this reason, there is a problem that the backwash regenerating property is low.
[0005]
Increasing the pore diameter from the front surface to the back surface of the metal powder sintered filter in order to enhance the backwash regenerating property is described in Japanese Patent No. 2791737 for a stainless steel type filter. Specifically, a slurry in which fine powder is dispersed in a binder resin solution is applied to the surface of the porous body obtained by the preliminary sintering, and then the main sintering is performed. A pore skin is formed.
[0006]
According to this multi-layer structure, almost all solids in the treatment liquid are captured by the skin layer in which the micropores are formed, and solids are not captured in pores inside the base layer. Facilitates removal. However, on the other hand, there are the following problems.
[0007]
Stainless steel has lower corrosion resistance than titanium. Further, the stainless steel powder used here is composed of irregular particles produced by a water atomizing method, and the size and shape of pores including the skin layer are random. In addition, since the skin layer is not subjected to press molding unlike the base layer, the size and shape of the micropores are more random than the base layer. For this reason, solids remain in the skin layer even after backwashing, and the expected backwashing reproducibility cannot be obtained. In addition, since the porosity of the skin layer that is not subjected to press molding is greatly different from the porosity of the base layer that has been subjected to press molding, the flowability of the treatment liquid may be reduced.
[0008]
An object of the present invention is to provide a sintered metal filter having excellent corrosion resistance and backwash regenerating property.
[0009]
[Means for Solving the Problems]
In the conventional titanium powder sintered filter, hydrodehydrogenated titanium powder or sponge titanium powder is used as the titanium powder. This is mainly due to the fact that the particles constituting the powder are indefinite in shape and therefore excellent in press moldability. In the case where the particles are amorphous, the pore diameter varies, so that it is necessary to make the pore diameter uniform by press molding, and the press molding is indispensable.
[0010]
However, as described above, even when press molding is performed, the uniformity of the pore diameter is still insufficient, and in the skin layer not subjected to the press molding, the nonuniformity of the pore diameter becomes remarkable as described above.
[0011]
In order to solve this problem, the present inventors have focused on spherical gas atomized titanium powder. Spherical gas atomized titanium powder is a powder of titanium or a titanium alloy produced by a gas atomization method, and individual particles are formed by solidification of molten droplets of titanium or a titanium alloy during scattering. It has a smooth spherical shape. Further, the particle size can be extremely fine, for example, 100 μm or less on average, and it is easy to classify by particle size by sieving.
[0012]
Such a spherical gas atomized titanium powder is extremely excellent in fluidity and has good contact between particles. Therefore, by filling a sintering container, a uniform and sufficient packing density can be obtained without pressurization. Then, by sintering, a porous body having high mechanical strength is produced without press molding, and the produced porous body has excellent uniformity of pore diameter, and the pore shape is also surrounded by a sphere. It has a smooth shape. Further, by changing the particle size of the powder, that is, by controlling the particle size of the powder used, the pore size can be controlled over a wide range while the porosity is kept constant. The porosity is 35 to 55%, which is suitable for a filter, without pressure.
[0013]
The high corrosion-resistant metal sintered filter of the present invention comprises a porous titanium body formed by filling a spherical gas atomized titanium powder into a sintering container and sintering , and from one surface to the other surface of the porous body. The pore size increases stepwise within a range of 3 to 70 μm , and the porosity is uniform within a range of 35 to 55% from one surface to the other surface of the porous body. In addition, it has excellent backwash regenerating properties and can obtain a uniform porosity despite increasing the pore diameter from one surface to the other surface of the porous body .
[0014]
FIG. 1 is an image diagram showing a difference in structure between a conventional example of a metal sintered filter and an example of the present invention.
[0015]
In the conventional example shown in FIG. 1A, a powder composed of amorphous titanium particles 1 such as a hydrodehydrogenated titanium powder and a sponge titanium powder is used as the titanium powder, and the finer the finer the surface layer is used. Thereby, the pore diameter is reduced in the surface layer. The press formability is relatively good, and the porosity is made uniform by the press forming, but the uniformity is insufficient. Further, since the shape of the pores 2 formed between the titanium particles 1 is not smooth, it is difficult to remove solids. On the other hand, in the example of the present invention shown in FIG. 1 (b), a powder composed of spherical titanium particles 1 produced by a gas atomization method is used as the titanium powder. Although the pore diameter decreases as the surface layer increases, the porosity is constant even when no pressure is applied. Further, since the shape of the pores 2 formed between the titanium particles 1 is formed smoothly by a spherical surface, it is easy to remove solids from the pores 2.
[0016]
As the spherical gas atomized titanium powder, for example, the following three types classified by particle size range are commercially available. That is, there are three types of fine particles of 45 μm or less, coarse particles of 45 to 150 μm, and further coarse particles of 150 μm or more. The average particle size is about 25 μm for fine particles and about 80 μm for coarse particles.
[0017]
The particle size of the spherical gas atomized titanium powder affects the pore size. By gradually increasing the particle size of the powder used from one surface to the other surface of the filter, the pore diameter can be increased stepwise. That is, a laminated structure in which a plurality of porous layers whose pore diameters increase stepwise is obtained. Even when the particle diameter of the spherical powder is changed, the porosity is basically constant if no pressure is applied, so that the pore diameter can be changed without changing the porosity. However, if the sintering temperature is changed, the pore area is controlled and the porosity is controlled by changing the contact area between the particles.
[0018]
The pore diameter is selected within the range of 3 to 70 μm. That is, as a highly corrosion-resistant metal sintered filter, a filter having a pore size of 70 μm or less is desired from the viewpoint of filterability. Must be used, which increases manufacturing costs.
[0019]
As for the porosity, a porosity of 35 to 55% can be obtained without using a commercial product as a spherical gas atomized titanium powder and applying pressure during filling or sintering. According to the investigation by the present inventors, this porosity is a preferable value for a metal powder sintered filter and is within the range of the present invention .
[0020]
The particle size range of the spherical gas atomized titanium powder is not particularly limited, and there is no problem at the level of the above-mentioned commercially available products. However, it is difficult to produce extremely fine particles industrially with good yield even by the gas atomizing method. Further, in the case of coarse particles, when a thin porous body is manufactured, the contact area of the titanium powder with respect to the thickness of the porous body becomes small, so that there is a concern about insufficient strength. Therefore, it is preferable to select the particle size from an average of 10 to 150 μm according to the required pore size.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a schematic sectional view of a metal sintered filter showing one embodiment of the present invention.
[0022]
After filling a spherical gas atomized titanium powder having a predetermined average particle size into a high-density alumina sintering vessel without pressure, the spherical gas atomized titanium powder is vacuum-sintered without pressure to obtain a first gas. The plate-like porous body 11 is manufactured.
[0023]
The second plate-like porous body 12 is similarly manufactured using a spherical gas-atomized titanium powder having an average particle diameter larger than that of the spherical gas-atomized titanium powder used for the first plate-like porous body 11. The sintering temperature is adjusted so that the same porosity as that of the first plate-shaped porous body 11 is obtained.
[0024]
The third plate-like porous body 13 is similarly manufactured using a spherical gas-atomized titanium powder having a larger average particle diameter than the spherical gas-atomized titanium powder used for the second plate-like porous body 12. The sintering temperature is adjusted so that the same porosity as that of the first plate-like porous body 11 and the second plate-like porous body 12 is obtained.
[0025]
The sintered filter 10 having a three-layer structure is manufactured by stacking and sintering the manufactured three plate-shaped porous bodies 11, 12, and 13. In the manufactured sintered filter 10, since the particle diameter of the powder used is different, the pore diameter increases in the order of the plate-like porous bodies 11, 12, and 13. The porosity is almost the same in all cases because of filling under no pressure. The pores of each porous body have a small variation in size and a smooth and uniform shape.
[0026]
The performance of the filter should be such that the processing liquid is passed in the order of the plate-like porous bodies 11, 12, and 13, and most of the solid content in the processing liquid is captured by the plate-like porous body 11 having the smallest pore size. As a result, excellent backwashing reproducibility can be obtained. That is, the solid matter does not disperse in the plate-like porous bodies 12 and 13, and the pores in the plate-like porous body 11 are smooth and uniform, so that the solids captured in the pores are backwashed smoothly. It is removed in the.
[0027]
The sintering temperature in each sintering is preferably selected within the range of 850 to 1200 ° C., which is much lower than the melting point of titanium. When the sintering temperature is lower than 850 ° C., sufficient sintering is not performed. If the temperature exceeds 1200 ° C., even when no pressure is applied, the sintered portion does not remain at the contact portion between the individual particles, but the particles are melted with each other. Therefore, there is a risk that an appropriate porosity and pore diameter cannot be secured. As described above, the porosity and the pore diameter are controlled by changing the sintering temperature within this temperature range.
[0028]
As an example of the present invention, a titanium sintered filter having a three-layer structure was manufactured by the above method. The thickness of each layer is 1 mm (total 3 mm). The average particle diameter of the spherical gas atomized titanium powder used for each layer was 20 μm, 60 μm, and 100 μm, and the maximum pore diameter of each layer was 6 μm, 22 μm, and 37 μm. The porosity of each layer was 45%.
[0029]
As a comparative example, a similar titanium sintered filter was manufactured using a commercially available product of hydrodehydrogenated titanium powder. In the production of three plate-like porous bodies, a press was necessary for forming and making the pore diameter uniform. The porosity varied among the layers, being 55%, 48% and 37%.
[0030]
The reproducibility of the two in the backwash was compared. That is, a solution obtained by mixing in water to the silica beads with an average particle size of 10μm the 10 mg / L, the increase in weight after filtration dried in each filter is constant, then constant at air pressure 5 kgf / cm ² After backwashing and drying for a time, the weight change before and after use was measured to evaluate the backwashing reproducibility. In the example, 97% was removed by backwashing, but in the comparative example, only 83% was removed.
[0031]
In the above embodiment, the porous bodies having different pore diameters were prepared and laminated in advance, but the same laminated structure can be obtained by filling and sintering titanium particles having different particle diameters in a layer. Incidentally, the laminated structure shown in FIG. 1B is based on the latter method.
[0032]
【The invention's effect】
As described above, the highly corrosion-resistant metal sintered filter of the present invention uses titanium powder, and thus has extremely excellent corrosion resistance. Since the pore diameter increases stepwise from one surface to the other surface, and the pore size is uniform and the shape is smooth at each stage, the backwashing reproducibility is excellent. Also, despite the gradual increase in the pore size from one surface to the other surface, the porosity is uniform from one surface to the other surface, which has an adverse effect on liquid permeability. Can be avoided. Since the manufacturing is simple, the manufacturing cost can be suppressed at a low cost.
[Brief description of the drawings]
FIG. 1 is an image diagram showing the difference in structure between a conventional example of a metal sintered filter and an example of the present invention, wherein (a) shows a conventional example and (b) shows an example of the present invention.
FIG. 2 is a schematic sectional view of a metal sintered filter showing one embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Titanium particle 2 Porous 10 Sintered filter 11, 12, 13 Plate-like porous body

Claims (1)

With spherical gas atomized titanium powder is filled in a sintering vessel made of titanium porous body formed by sintering, the pore diameter over from one surface to the other surface of the porous body is increased stepwise The porosity is uniform from one surface to the other surface of the porous body, the pore diameter is in a range of 3 to 70 μm, and the porosity is in a range of 35 to 55%. A highly corrosion resistant metal sintered filter characterized by the following:

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