JPH0618574Y2 - Cylindrical filter element - Google Patents

Description

[Detailed Description of the Invention] (Industrial application field) The present invention is applied to the semiconductor industry, medical field, microbial research field, etc. to remove fine particles and microbes mixed in a relatively small amount of fluid. Regarding a small cylindrical filter using a porous membrane, in particular, it is possible to prevent the microporous membrane from being broken or changing its performance due to stretching due to a back pressure generated when a fluid flows backward, and the fine porous membrane is used as a filter housing. The present invention relates to a cylindrical filter element having a protective outer cylinder which is in close contact with the flow to prevent the flow from being blocked and which is also in a normal flow state and has a function of a prefilter.

(Prior Art) Generally, in order to reliably remove micron-order or submicron-order fine particles and microorganisms in a fluid,
BACKGROUND ART Microporous thin films made of various synthetic resins, so-called membrane filters, are widely used.

Since these fine porous thin films are extremely thin with a thickness of 10 to 200 μm and are porous made of synthetic resin, they are very fragile in terms of strength, and their handling requires careful attention. For this reason, microporous thin films are commonly used with supports having multiple ribs in a fine pattern. In addition, the filtration pressure applied to the microporous thin film is very small and the flow rate is often small.

As the form of the filter, usually, a disc type microporous thin film sandwiched between two supports is often used, but as the application range of the microporous thin film expands, it can be used at a large flow rate and high pressure. The demand for vessels has also increased. If it is attempted to meet this requirement with the conventional disc type filter, the filter itself will become huge and it will not be practically used. For this reason, many efforts have been made to reduce the size of a filter using a fragile microporous thin film. For large flow rate, a so-called pleated cartridge type in which a fine porous thin film is folded and a laminated type in which disc membranes are stacked in multiple layers are known.

On the other hand, since the area of the fine porous thin film used is too small for a small flow rate, it was technically and costly difficult to apply the pleated cartridge type or the laminated structure. Only, a cylindrical type filter in which a microporous thin film is wound around a cylindrical type membrane support has been known.

(Problems to be solved by the invention) Conventionally, as a small-sized filter using such a microporous thin film, one in which a microporous thin film is wound around a cylindrical membrane support is known, It is used for low pressure and low flow rate such as drip injection in the medical field. However, recently, a long-term drip injection using a pump has been performed, and a use for a high-pressure gas line has been developed. However, this cylindrical filter has a structure in which the membrane is more likely to be damaged by the flow in the opposite direction as compared with the original filter sandwiched by the two disc-shaped supports.
That is, although strong in the direction of contact with the cylindrical support, the film is easily damaged by the flow in the direction in which the film peels from the support, which is inconvenient in the case of backflow of fluid. Becomes

In such a situation, as a matter of course, there is a concern that a reverse flow of fluid due to an erroneous operation and a back pressure due to pulsation of the pump may occur. Should the fragile microporous thin film be damaged by such back pressure, not only the function as a filter will be lost instantaneously, but also a large amount of fine particles and microorganisms trapped in the filter will disappear at once. Outflow to the filter and cause excessive contamination on the secondary side of the filter.

Even if the microporous thin film is not damaged, if repeated backflow phenomenon such as pulsation is observed in the fluid, microvibration occurs in the microporous thin film, and fine particles once trapped on the microporous thin film fall off. It is known to flow out to the downstream side,
In this case, it is also inconvenient.

However, despite such a danger, it is difficult to take measures against it because the membrane support has a cylindrical shape and the provision of a protective outer cylinder for counter pressure is small in scope. However, there was no technical or cost match.

The present invention is technically easy and low-priced, prevents the microporous thin film from being damaged when a back pressure is generated, and prevents the deterioration of the apparent filtration performance due to the fall of trapped fine particles, and the pretreatment of the fine porous thin film. An object of the present invention is to provide a small-sized cylindrical filter using a microporous thin film having a protective outer cylinder that can also function as a filter.

(Means for Solving the Problem) As a result of intensive studies to achieve the above-mentioned object, the present invention found that the peripheral edge of the flat plate-shaped microporous thin film was permanently attached to the curved surface and flat surface of the cylindrical membrane support. In the filter element welded to No. 3, the outer surface exposed portion of the microporous thin film including the welded portion was completely covered with the cylindrical heat-shrinkable porous body.

Specifically, when the target fluid makes a normal flow, the fragile microporous thin film should not be damaged against the filtration pressure, and the microporous thin film should not vibrate as much as possible. In the peripheral edge and the flat surface portion of the cylindrical membrane support having the protrusions formed on the peripheral edge, the peripheral edge portion of the square microporous membrane cut into an appropriate size is permanently welded by a method such as heat pressing, Next, a heat-shrinkable cylindrical net made of monofilament fiber etc. is covered, this is shrunk by heating, and the outer exposed surface of the microporous membrane welded to the cylindrical membrane support including the welded portion is entirely covered. did.

(Operation) Therefore, according to the present invention, as described above, the peripheral portion of the flat type microporous membrane is welded to the cylindrical membrane support, and the exposed portion of the outer surface of the microporous membrane is coated with the cylindrical heat-shrinkable porous body. Therefore, even if the back pressure generated when the fluid flows backward,
The cylindrical heat-shrinkable porous body surely protects the microporous membrane, there is no deterioration in performance due to breakage or stretching of the microporous membrane, and the microporous membrane may adhere to the filter housing and block the flow. Not only is there no
Furthermore, in a normal flow state, it also has a function as a prefilter.

(Embodiment) FIGS. 1 and 2 show an embodiment of a cylindrical filter element according to the present invention.

In the drawings, a filter housing 3 having a filter inlet 1 on one side and a filter outlet 2 on the other side is molded from a fluororesin, a fluororesin copolymer, metal or the like. A cylindrical filter element described later is housed in this filter housing 3.

The cylindrical filter element has a structure in which the peripheral portion of the flat plate type microporous membrane 6 is welded to the cylindrical membrane support 10 and the outer surface exposed portion of the microporous membrane 6 is covered with the cylindrical heat-shrinkable porous body 5. It has been established.

This will be described in detail. Protrusions 7b are formed on both sides of the cylindrical membrane support 10 and in the central portion in the longitudinal direction.
The flat plate type microporous film 6 is wound around b, and its peripheral edge is welded via the welded portion 7a. In addition, the cylindrical membrane support 10
A ridge 8 and an opening 9 are provided on the outer periphery of the cylindrical membrane support 10, and a sealing member 4 such as an O-ring for sealing the inner peripheral surface of the filter housing 3 on one side of the cylindrical membrane support 10.
Is mounted, and the protrusion 10a is formed on the other side.

Flat type microporous membrane 6 heat-welded to a cylindrical membrane support 10
Is entirely covered with the cylindrical heat-shrinkable porous body 5,
The maximum hole diameter of this cylindrical heat-shrinkable porous body 5 is 10 times or more the maximum hole diameter of the flat plate type fine porous membrane 6, and this cylindrical heat-shrinkable porous body 5 uses a seamless tubular mesh. .

In the present example, the flat-plate type microporous membrane 6 described above has a thickness of 10 to 500 microns, a maximum pore diameter of 0.01 to 5 microns, and a porosity of 30% or more.

Furthermore, the flat plate type microporous membrane 6, the cylindrical membrane support 10 and the cylindrical heat-shrinkable porous body 5 are made of a fluororesin or a fluororesin copolymer. This fluororesin or fluororesin copolymer is made of PTFE, PFA, EPE, ETF.
E, ECTFE, PCTFE or PVDF can be used.

Next, the operation of the above embodiment will be described.

The raw fluid flows in through the filter inflow port 1 formed in the filter housing 3, passes through the flat plate type microporous membrane 6 whose peripheral edge is heat-welded to the cylindrical membrane support 10 and is cleaned, and between the ridges 8. It flows into the cylindrical membrane support 10 through the opening 9 and flows out as a cleaning fluid from the filter outlet 2 formed in the filter housing 3.

The filter housing 3 and the cylindrical membrane support 10 prevent the contamination caused by the raw fluid being mixed with the clean fluid that has been cleaned by passing through the flat plate type microporous membrane 6.
Are blocked by a suitable sealing member 4, such as an O-ring.

Further, the whole of the flat plate type microporous membrane 6 heat-welded to the cylindrical membrane support 10 is covered with the cylindrical heat-shrinkable porous body 5, and the fluid due to an accident or pulsation of a liquid feeding means such as a pump is removed. The flat microporous membrane 6 is prevented from being damaged by the backflow, or the trapped fine particles are prevented from falling off due to the vibration of the flat microporous membrane 6.

(Effect of the Invention) In a so-called in-line filter provided in the middle of a pipe such as a pipe or a tube, a fluid may flow in a direction opposite to the original flow due to a driver's erroneous operation or a device failure. When such a back flow occurs, in a filter using a fine porous thin film, the material is extremely fragile, and therefore the fine porous thin film may be stretched, which may cause a change in filtration performance. Furthermore, when a large amount of fluid instantaneously flows back, the microporous thin film may be damaged.

On the other hand, when a liquid feeding means such as a pump is used, a slight amount of backflow due to pulsation is always observed even in the original normal direction flow, and when these pulsations occur, the microporous thin film also vibrates slightly. The fine particles once caused to be trapped in the fine porous thin film fall off and flow out to the downstream to contaminate the cleaning fluid.

In the present invention, in the filter element in which the peripheral portion of the flat plate type microporous membrane is welded to the cylindrical type membrane support,
Since the outer surface exposed portion of the above-mentioned microporous membrane is covered with the cylindrical heat-shrinkable porous material, the above problems can be solved all at once. Specifically, for these large or small amount of backflow, In addition, the performance change range due to breakage of the microporous thin film and deformation of the microporous thin film can surely prevent apparent reduction in filtration efficiency due to falling of trapped fine particles due to microvibration of the microporous thin film.

Further, by using the continuously manufactured cylindrical heat-shrinkable porous body, the mounting can be easily performed and the influence on the cost of the product is small.

Further, by appropriately selecting the openings of the protective outer cylinder made of the cylindrical heat-shrinkable porous material, it becomes possible to function as a prefilter for the fine porous thin film.

[Brief description of drawings]

FIG. 1 is a transverse sectional view showing an embodiment of the cylindrical filter element of the present invention, and FIG. 2 is a longitudinal sectional view of the same. 1 ... Filter inlet, 2 ... Filter outlet, 3
... Filter housing, 4 ... Sealing member, 5
...... Cylindrical heat-shrinkable porous body, 6 …… Flat plate type microporous thin film, 7a ・ ・ ・ Welded portion, 7b …… Projection portion, 10 …… Cylindrical membrane support.

Claims (6)

[Scope of utility model registration request] 1. A filter element in which a peripheral portion of a flat plate type microporous membrane is welded to a cylindrical membrane support, wherein the exposed portion of the outer surface of the microporous membrane is covered with a cylindrical heat-shrinkable porous body. Cylindrical filter element. 2. A flat plate type microporous membrane having a thickness of 10 to 500 μm, a maximum pore diameter of 0.01 to 5 μm, and a porosity of 30%.
The cylindrical filter element according to claim 1 of the above utility model registration claim. 3. The utility model registration claim 1 or 2 wherein the flat plate type microporous membrane, the cylindrical membrane support and the cylindrical heat-shrinkable porous body are fluororesins or fluororesin copolymers. Cylindrical filter element. 4. A fluororesin or fluororesin copolymer is PTF.
E, PFA, EPE, ETFE, ECTFE, PCTF
The cylindrical filter element according to any one of claims 1 to 3, characterized in that it is E or PVDF. 5. The cylindrical filter element according to any one of claims 1 to 4, wherein the maximum pore size of the cylindrical heat-shrinkable porous body is 10 times or more the maximum pore size of the flat plate type microporous membrane. . 6. The cylindrical filter element according to any one of claims 1 to 5, wherein the cylindrical heat-shrinkable porous body is a seamless tubular mesh.