JPH05146649A - Silica glass filter unit - Google Patents

Abstract

PURPOSE:To provide a silica glass filter unit wherein the joint part of a filter and a housing is improved. CONSTITUTION:A silica glass filter unit is composed of a silica glass filter having a finely porous filtration layer 4 and quartz glass housings 2, 21, 22 wherein the filtration layer is formed and integrally fixed on the surface of a supporting body 3 composed of a sintered body of amorphous silica powder with 99.9% or higher purity and composed of a sintered body of amorphous silica powder with practically the same purity and the housings are to be joined with the silica glass filter 1 and have the same purity as the supporting body 3. Further the unit has a joint part 5 of an amorphous silica with 1000mum or longer length in the joining region of the silica glass filter 1 and the housings 2, 21, 22 wherein the number of fine pores decreases continuously and the joint part reaches a dense layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silica glass filter unit, and more particularly to an improved silica glass filter unit.

[0002]

2. Description of the Related Art Ceramic filter units have recently been used for filtering high-purity gases such as reaction gases used in semiconductor manufacturing and other chemicals.

In this ceramic filter unit, a ceramic filter having a filter layer having fine holes on its surface is joined to a housing. To filter a fluid such as gas or liquid using this, the fluid is press-fitted from a fluid inlet provided at one end of the housing, and the fluid is filtered by passing the fluid through a ceramic filter. It is taken out from the spout provided on the other side of the housing.

Many of these ceramic filters are
Up to now, it was made of an alumina sintered body, but in this filter unit, it was absolutely necessary to firmly and airtightly fix the ceramic filter to the housing.

Conventionally, for joining the ceramic filter and the housing, there has been adopted a method in which a Teflon packing is used, the packing is loaded on both inner ends of the housing, and the ceramic filter is inserted in the middle thereof. The work is very troublesome, and it is difficult to ensure airtightness in such joining, and various problems remain.

For example, in such a conventional filter, the packing is pressed by the increase of the liquid pressure, a flow of the liquid to be filtered is caused between the housing and the filter, and the fine particles collected with great care are collected. There is a problem that the baking temperature for removing water cannot be raised sufficiently because it is mixed in the fluid or the material of the packing is resin.

[0007]

DISCLOSURE OF THE INVENTION According to the present invention, a silica glass filter used as a filter and a quartz glass housing are firmly bonded together at a siliceous bonding portion without the use of packing, so that the fluid A silica glass filter unit that maintains airtightness even if pressure fluctuations occur, eliminates leakage of trapped particles that have already been trapped, further increases the heat resistance of the joint, and enables baking at a sufficient temperature. It's about to get.

[0008]

The present invention has a purity of 99.
Formed on a surface of a support body made of a sintered body of amorphous silica powder of 9% or more, integrally fixed to the support body, and made of a sintered body of amorphous silica powder having substantially the same purity as the support body. Silica glass filter having a fine porous filter layer
And a silica glass housing of the same purity as the support to be bonded to the silica glass filter, and further, fine holes are continuously reduced in the bonding area between the silica glass filter and the silica glass housing. The silica glass filter unit is characterized by having a bonded portion of amorphous silica having a length of 1000 μm or more reaching the dense layer.

[0009]

In the silica glass unit of the present invention, the fluid to be filtered is introduced from the fluid inlet of the quartz glass housing provided at one end of the silica glass unit, and the fluid is filtered by the silica glass filter in the housing to clean it. This fluid is made to flow out from the outflow port provided at the other end of the silica glass unit.

[0010]

【Example】

(Embodiment 1) FIG. 1 shows a longitudinal cross section of a silica glass unit A according to the present invention. The silica glass unit A of FIG. 1 comprises a silica glass filter-1 and quartz glass housings 2, 2 ₁ , 2 ₂ .

In FIG. 1, reference numeral 1 denotes a silica glass filter, which is a support 3 made of a sintered body of amorphous silica having a purity of 99.9% or more, and is integrally formed on the outer surface of the support 3. The filter layer 4 is formed of a sintered body of amorphous silica powder having substantially the same purity as that of the support 3.

Although the filter layer 4 is formed on the outer surface of the support 3 in FIG. 1, it may be formed on the inner surface of the support 3.
Silica glass filter-1 particularly dislikes alkali metals, alkaline earth metals and heavy metals as impurities.
It is preferably 50 ppm or less.

The support 3 is a porous sintered body, for example, having a thickness of 2 mm and a porosity of 30 to 40%, while the filtration layer formed on the outer surface of the support 3 has a thickness of, for example, 50. ~ 100
The pore diameter is 0.2 to 0.4 μm, which is minute.

The outer circumference of the silica glass filter-1 is covered with housings 2, 3 ₁ , 2 ₂ . These housings consist of a central main part 2 and end parts 2 ₁ , 2 ₂ ,
These shall be integrated. This housing also has a purity of 99.9% or more. End pipe 2 _first end of the housing is bonded to the silica glass filter -1 loaded in the main housing portion 2.

In the embodiment of FIG. 1, the silica glass filter-1 has an outer diameter of 15 mm, an inner diameter of 11 mm and a length of 50 mm.
The pore diameter of the filtration layer formed on the outer surface of this silica glass filter-1 was 0.2 μm. The end face of this silica glass filter-1 was used as the joint portion 5, and this was heated to 1900 ° C. with a ring-shaped carbon heater to make the depth from the end face about 2 mm transparent. Next, the outer diameter of this joint 5 is 15 m
A quartz glass end tube 2 ₁ having a diameter of 11 mm, an inner diameter of 11 mm and a length of 50 mm, which is a part of the housing, was welded. Next, on the outer periphery of the silica glass filter-1, the main part 2 of the housing and the end tube 2 are provided.
A silica glass filter unit A is formed by coating a housing made of ₂ .

This filter is cut in the axial direction, and its cross section is centered on the joint 5 in particular, and its cross section is taken by a scanning electron microscope (SE).
M). As a result, no pores were found in the quartz glass tube portion 2 ₁ of the housing portion, but at the joint portion 5, the housing end tube 2 ₁ to the silica glass filter-1.
, The pores began to appear, and the pore diameter and pore area gradually increased.
It was confirmed that the pores were the same as those in No. 3, and it was confirmed that the dense layer continuously changed to a porous layer.

Next, the length of this joint was measured. First, observing with a SEM, a portion having a pore area of 10 μm ² (0.1%) or less in a 100 μm square is a dense layer,
This was used as the base end of the joint. On the other hand, the porosity is filtered.
In the part that is substantially the same (about 32%), the position closest to the base end is below the other end of the joint. The length measured during this period was 3900 μm in the above-mentioned example.

The same experiment as above was carried out, and the heating conditions (heating temperature, time, etc.) were simply changed to obtain several kinds of silica glass filter units having different lengths of the above-mentioned joints.
The strength at break and the break position of this product were determined and are shown in Table 1. As shown in the table, it was confirmed that by setting the length of the joint to 1000 μm or more, a strong joint strength without breakage from the joint was obtained.

Although there is no particular upper limit on the length of the joint,
If the joint is too long, the filtration area will decrease, which is not desirable.
The thickness is preferably less than 15000 μm. The rate of change of pores in the joint is preferably about 30% / mm or less.

[0020]

[Table 1] Further, the relationship between the rate of change of pores in the joint and the joint strength is as follows.

Using the silica glass filter unit obtained in Example 1, an experiment for measuring pressure fluctuation and heat resistant temperature was conducted.

The pressure fluctuations, 1 kgf · cm ^- Pas after the addition of ² of the pressure variation - was determined the Tcl number, 15 / Pieces cm
^-It was ³ . On the other hand, the number of particles in the case of joining by the conventional Teflon packing was 370 / piece cm ⁻³ . Regarding the heat-resistant temperature, in the example, the distribution of pores at the joint did not change even at 600 ° C., but the conventional Teflon packing could not heat at 200 ° C. or higher.

(Embodiment 2) FIG. 2 shows a silica glass filter unit B according to another embodiment of the present invention.

The one shown in the figure has an outer diameter of 40 mm and a thickness of 3 mm.
On one side of the disc-shaped indicator body 6 of No. 2, a silica glass filter 8 having a 0.2 μm fine pore filtration layer 7 integrally fixed thereto is connected to an outer peripheral joint portion 9 with a ring-shaped carbon heater. It was heated to make about 2 mm transparent from the outer periphery. An inner housing 10 made of quartz glass having an outer diameter of 40 mm, an inner diameter of 35 mm and a length of 25 mm was heat-bonded to this outer peripheral portion. Thereafter, the silica glass outer housing 11 is welded to the silica glass inner housing 10 to form a silica glass filter unit B.

This filter unit B was cut in the axial direction, and in particular, the cross section was observed by SEM, centering on the joint portion 9, and at the joint portion 9, from the outer periphery of the inner housing to the center of the silica glass filter 8. It was confirmed that micropores were observed toward the pores and that the pore diameter and pore area were continuously increasing.

[0026]

As described above, according to the present invention, high-purity silica glass is used as a raw material, and further, the joining between the filter and the housing does not require packing as in the conventional case. From the end of − to the pipe end of the housing, the porous layer is changed to the dense layer continuously, so that it has high airtightness and joint strength, and stress concentration does not occur at the joint part. It is possible to obtain a filter unit integrated with the filter.

Therefore, even if the pressure of the fluid fluctuates during use, it is possible to prevent the particles trapped with difficulty from flowing back into the filtered fluid, and the baking temperature can be raised to the required high temperature. It became so.

[Brief description of drawings]

FIG. 1 is a silica glass filter according to an embodiment of the present invention.
The sectional side view of a unit.

FIG. 2 is a side sectional view of a silica glass filter unit according to another embodiment of the present invention.

[Explanation of symbols]

A, B ... Silica glass filter unit 1, 8 ... Silica glass filter, 2, 2 ₁ , 2 ₂ , 1
0, 11 ... Housing, 3, 6 ... Support, 4, 7 ... Filtration membrane, 5, 9 ... Joint

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yu Shinbo 30 Soya, Hadano City, Kanagawa Prefecture Central Research Laboratory, Toshiba Ceramics Co., Ltd.

Claims (1)

[Claims] 1. An amorphous silica having a purity substantially equal to that of the support, which is integrally fixed to the surface of an indicator made of a sintered body of amorphous silica powder having a purity of 99.9% or more. Silica glass filter having fine porous filter layer formed of powdered sintered body, and this silica glass filter
And a silica glass housing having the same purity as that of the support to be bonded to the silica glass filter.
A silica glass filter unit, characterized in that it has a joint portion of amorphous silica having a length of 1000 μm or more, which reaches a dense layer, in a joint region between a quartz glass housing and a quartz glass housing.