JP3244730B2 - Manufacturing method of filter element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a filter element in a filter for purifying a chemical solution for cleaning or etching electronic equipment parts, and more particularly to a method for manufacturing a filter element made of perfluorinated resin. The present invention relates to a method for manufacturing a filter element using a sealing step.

[0002]

2. Description of the Related Art Chemical solutions for cleaning or etching electronic components such as integrated circuit boards and wafers are extremely reluctant to contaminate with impurities. Therefore, a filter having a microporous filter element is required for purifying a chemical solution. Since such a cleaning liquid and an etching liquid are highly corrosive, it has been proposed that all members are made of an inert fluororesin, and they have been put to practical use. For example,
As shown in FIGS. 1, 2 and 3,
Between a porous inner cylinder 1 and a porous outer cylinder 3 formed of fluororesin, a porous filter membrane 7 made of ethylene tetrafluoride and thermoplastic fluororesin porous supports 9 and 11 attached to both surfaces thereof, Media pleated from a laminated body of chrysanthemum flowers 5
And an accordion pleated filter element in which upper and lower edges are adhesively sealed to annular recesses 17 of end plates 13 and 15 made of thermoplastic resin or not. No. 59-82516, No. 59-
No. 176,614 and Japanese Patent Publication No. 62-9962 have similar descriptions.

However, when the filter film 5 made of a tetrafluoroethylene resin used as a filter film is sealed to the upper and lower end plates, it is heated and melted using a thermoplastic fluororesin as an adhesive and adhered to the end plate. However, since the fluororesin has a high viscosity and the filter membrane is a non-thermoplastic resin having a very low stiffness, the adhesive does not penetrate well between the filter membranes 1 and the sealing of the filter material assembly cannot be secured. There is a point. For this reason, in Japanese Utility Model Application Laid-Open No. 59-31410, notches for providing extra adhesive resin are provided along the outer periphery of the upper and lower ends of the inner cylinder 1 and the inner edges of the upper and lower ends of the outer cylinder 3. However, sufficient penetration of the adhesive between the pleats cannot be achieved.

In Japanese Utility Model Application Laid-Open No. 59-82516, the upper and lower edges of the filter medium 5 are heat-sealed in advance by using highly thermoplastic polypropylene instead of fluororesin as the nets 9 and 11, and then the end plates are closed. The molten polypropylene resin inserted into the annular recess is bonded as an adhesive to prevent leakage.However, although the weakness of the upper and lower edges of the filter medium is improved, the viscosity of the adhesive is large. The permeation of the resin between the pleats is still not enough and sufficient sealing is not performed,
In addition, there is a problem of using a resin other than a fluororesin.

Japanese Unexamined Utility Model Publication No. 59-176614 describes a sealing method utilizing mechanical tightening force, but there is a question about the sealing property.

Japanese Patent Publication No. 62-9962 discloses a technique disclosed in
No.-82516 describes a method similar to that described above. First, a thermoplastic fluororesin is charged into a mold having an annular groove and melted. Then, after cooling, a seal portion is first formed, and further this seal portion is inserted into the annular groove of the end plate, and is bonded air-tight or liquid-tight with a molten adhesive. However, due to the high viscosity of the fluororesin, the resin cannot sufficiently penetrate between the pleats of the filter medium at the time of forming the first seal portion, and therefore it is difficult to form a completely air-tight or liquid-tight seal portion. Therefore, if an incomplete seal is generated in the step of forming the seal portion, it is difficult to completely repair the seal even in the subsequent step of bonding to the end plate. In addition, this method has a problem that a two-stage sealing process is required.

Further, US Pat. No. 3,415,384 discloses that
A thermoplastic edge film made of polypropylene or the like is spirally wound along the upper and lower ends of a filter medium having a porous support on one side of a filter membrane, and the upper and lower ends are made of a thermoplastic resin such as polypropylene. It describes that the upper and lower end portions and the end plate are inserted into an annular groove of the plate, and the upper and lower end portions and the end plate are frictionally slid with each other, melted by frictional heat, and integrally bonded.
However, in this method, bonding occurs only at the upper and lower edges of the filter membrane, and the thermoplastic resin does not sufficiently penetrate between the filter membranes, so that sufficient sealing properties cannot be secured.

[0008]

In any of the above-mentioned methods, a highly viscous fluorine-based thermoplastic resin cannot sufficiently penetrate between the pleats at the upper and lower edges of a weakly stiff tetrafluoroethylene resin filter membrane. There are problems, and the known methods require complicated steps and use of other materials with insufficient corrosion resistance.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a simple filter element manufacturing method capable of forming a reliable liquid-tight seal at the upper and lower edges of the filter membrane.

[0010]

According to the present invention , a non-porous state is provided at the upper and lower edges of a filter membrane made of tetrafluoroethylene resin.
With ethylene tetrafluoride-perfluoroalkyl vinyl ether
-Tel copolymer (PFA), ethylene tetrafluoride-6-fluoro
Propylene copolymer (FEP) and ethylene tetrafluoride
-Perfluoroalkyl vinyl ether copolymer-6
Any heat of fluorinated propylene copolymer (EPE)
Overlapping edge film of plastic fluororesin and press fusion
And a fluororesin 1 on both sides of the filter membrane.
A pair of porous supports was attached, and the filter medium thus obtained was bent into accordion pleats, formed endlessly, sealed on both side edges , and melted in a mold for forming an end plate.
Fluorinated ethylene-perfluoroalkyl vinyl ether
Copolymer (PFA), ethylene tetrafluoride-hexafluoride
Pyrene copolymer (FEP) and ethylene tetrafluoride
-Fluoroalkyl vinyl ether copolymer-hexafluoride
By cooling by dipping at least the edge film of the upper bottom edge in one of thermoplastic fluororesin propylene copolymer (EPE), characterized by completely sealing the filter membrane by the end plate It is a manufacturing method of a filter element .

The principle of the present invention is as follows. First, joining a non-porous thermoplastic fluororesin edge film along with the filter membrane is performed by continuous heat fusion such as applying a heating roller before folding it into pleats. The fluororesin penetrates into the pores of the non-thermoplastic filter membrane and connects them in a liquid-tight or air-tight manner to ensure a sufficient sealing property. That is, leakage along the joint surface between the filter film and the edge film is sufficiently prevented. Next, after the pleating process, the filter medium is cut so as to have a predetermined vertical dimension, but the cut portion is prevented from coming off the edge film. Since the filter membrane made of the tetrafluoroethylene resin has extremely low stiffness, meandering at the time of cutting is inevitable. However, since it is cut at the edge film, it is not necessary to worry about suppression of meandering. Next, the upper and lower edges of the filter medium are immersed one side at a time in a molten thermoplastic fluororesin for an end plate in a mold, but the edge film is easily melted, fused and integrated into the molten end plate, and then cooled. This forms a perfect seal. A significant advantage of the method of the present invention is that it is sufficient that some of the melted resin penetrate between the filter membranes. This is because the edge film is already air-tightly or liquid-tightly connected to the filter membrane, so that if a sufficient fluid-tight seal is formed between the edge of the edge film and the end plate, a sufficient sealing property can be secured. is there. Of course, there is no problem if the upper and lower edges of the filter medium are immersed in the melted end plate to the extent that the upper and lower edges of the filter membrane are sufficiently immersed in the end plate, and the principle of sealing does not change at all.

Further, according to the present invention, not only the sealing property but also the durability is sufficiently ensured. This indicates that even if pressure or vibration of the filtered material is applied for a long time, the sealing portion is not loosened because the connection between the filter film and the edge film and between the edge film and the end plate are sufficient.

It is clear that this sealing principle is different from any conventional method. In the present invention, it is not necessary that the molten fluororesin penetrate into the gap between the pleats at the upper and lower ends of the filter medium. It is done.

[0014] By adding a step of compressing and holding the pleats at an elevated temperature close to the softening temperature of the edge film and forming a fold, following the step of bending the accordion pleats, a filter medium having a weak stiffness can be obtained. The shape is stabilized, thereby facilitating subsequent steps. In such a process, one flat portion of the filter media pleats is supported by a fixed end plate, the bent portion of the filter media is supported by a flat fixed wall, and the press movable portion is engaged with the other flat portion of the filter media. By compressing the filter medium toward the fixed end plate.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 is a perspective view showing a state of various members before assembling a filter element made of a fluororesin according to the present invention, wherein 21 is a lower end plate made of a thermoplastic fluororesin, and 22 is a porous end made of a thermoplastic fluororesin. The outer cylinder 24 was folded into a pleated shape, which was a laminate of a filter film made of tetrafluoroethylene resin and a porous support made of thermoplastic fluororesin or tetrafluoroethylene resin attached to both surfaces of the filter film. Filter media,
Reference numeral 23 denotes a non-perforated edge film made of thermoplastic fluororesin bonded to upper and lower edges thereof, 25 a porous inner cylinder made of thermoplastic fluororesin, 26 an upper end plate made of thermoplastic fluororesin, and 27 an external connection. O-ring adapter. Note is here and thermoplastic fluorine resin, four <br/> tetrafluoride you melted by heating - perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene - hexafluoropropylene copolymer (FEP ), Thermoplastic fluorine selected from ethylene tetrafluoride-perfluoroalkyl vinyl ether copolymer-propylene hexafluoride copolymer (EPE)
Resin.

The structure and manufacturing method of the filter medium 24 are shown in FIGS. 5 to 9 and the following steps 1 to 5, and the assembling steps of the filter element are shown in FIGS. 1. Edge Film Fusing Step First, as shown in FIG. 5, a long filter film 31 made of a tetrafluoroethylene resin and a non-porous edge film 23 made of a thermoplastic fluororesin are continuously supplied, and both sides of the filter film are formed. The edge film is passed over a hot roll heated to a temperature equal to or higher than the melting point of the edge film (for example, about 250 to 350 ° C. in the case of FEP), and the edge film is fused to the filter membrane. At this time, the width of the heat-sealed portion of each edge film needs to be determined so that a sufficient fluid-tight seal can be formed after cutting to a predetermined size in step 5 described later. This step may be performed on each side.

The overlapping relationship between the filter film 31 and the edge film 23 may be as shown in FIG. 5 or the edge film 23 may be projected from both edges of the filter film 31 as shown in FIG. Since it is difficult to avoid meandering during continuous supply because the filter membrane 31 made of tetrafluoroethylene resin is weak, it is difficult to maintain a constant overlapping relationship as shown in FIGS. In some cases, the result is as shown in FIG. Therefore, it is necessary to use an edge film having a width sufficient to cut the inside of the edge film at a predetermined interval even if there is a meandering when the filter medium is cut into the predetermined size.

Since the edge film is pressed against the filter membrane in a molten state, the resin of the edge film penetrates into the pores of the filter membrane and is completely bonded by the anchor effect. This achieves a fluid-tight seal. That is, the filtered liquid or gas will not leak through between the filter membrane and the film edge. In addition, it has been found that the connection between the two is mechanically strong, so that it exhibits a durable pressure resistance. These points will be illustrated later by examples.

2. Pleating process A porous support 32 made of a tetrafluoroethylene resin or preferably made of a thermoplastic fluororesin is provided on both surfaces of the combined body of the filter film 31 and the edge film 23 thus obtained.
(A net, a nonwoven fabric, a porous sheet) and laminated, and the laminate is folded into accordion pleats. At this time, the surface temperature (for example, about 50 to
(150 ° C.) to give a folding habit.

3. Heat setting step The laminate pleated in the previous step is cut into a predetermined number of peaks. Preferably, the folding habit is further provided by using a jig. This facilitates subsequent steps. As shown in FIG. 8, a jig 35 is a fixed end plate 34 capable of supporting one end face of a laminate obtained by bending the laminate into accordion pleats.
And a parallel fixed wall 31 supporting both bent portions;
A press movable section movably provided opposite the fixed end plate 34 and capable of pressing against the other end face of the filter medium; and a press movable section for moving the press movable section toward the fixed end plate to compress the filter medium. Drive 38 (eg piston-cylinder)
And a heating device (not shown) for heating the filter medium. For example, to prepare a jig metal having excellent heat transfer properties,
It is heated in an oven, electric heater or steam. The pleated laminate is housed in a jig 35,
By heating at an elevated temperature of 00 to 250 ° C. for a predetermined time, the wake shape is completely set.

4. Endless seam process The pleated laminate obtained in the processes 1 to 3 is made endless and sealed by fusing both side edges. Preferably, as shown in FIG. 9, a part of the porous support 32 of the endless overlapping portion is cut and removed, and instead, a non-porous thermoplastic fluororesin side edge film 33 is placed so as to be in contact with the filter membrane 31, The temperature is raised to a temperature equal to or higher than the melting point of the side edge film 33 and fusion is performed using a suitable hot press jig (not shown). Thereby, the resin of the side edge film 33 penetrates into the pores of the filter membrane to perform sealing, thereby forming a cylindrical body.

5. Next, the cylindrical body is supported by an appropriate jig, and the cylindrical body is cut to a predetermined dimension between the upper and lower edges to obtain a filter medium 24 of the present invention (see FIG. 4). It is important that the cut portion always passes through the edge film portion, and that the heat-sealed portion having a sufficient width remains after the cut as described in the step 1.

An edge film is fused to the upper and lower edges of the filter membrane produced in steps 1 to 5, laminated on both sides with a porous support, pleated, formed into an endless cylindrical shape, and fused at both edges. The filter media obtained by attaching and cutting at the upper and lower edges,
When this is assembled into a filter element, a filter having extremely high liquid tightness and air tightness and high pressure resistance can be constructed.

6. Potting Step Next, a structure and an assembling method of the filter element using the filter medium will be described with reference to FIG. 4 and FIGS. First, in this example, the closed type end plate 21 and the open type end plate 26 of FIG. 4 are used as the end plates, and the filter medium 24 and the connection to these end plates are sequentially performed. First, the end plate 21 is charged into a mold 38 having a structure shown in FIG.
For example, in the case of PFA, it is heated to about 250 to 350 ° C. and melted. Next, the lower end of each of the inner and outer porous cylinders 22 and 25 and the cylindrical filter medium 24 is held for about 30 to 60 seconds in a state where the lower end is pushed to a predetermined depth inside the mold 38, and then the pressure is released.
Allow to cool for 5-10 minutes. Edge film 23 is end plate 21
And perform sufficient sealing. It is preferred, but not necessary, that some of the molten resin penetrate between the pleats, and it is important that the edge film fuses with the end plate. Because if even fluid Mitsusei the edge film and the end plate is secured, since previously been fused to the edge film and the filter membrane, a fluid leakage path between the edge film and the filter membrane will not be present.

Next, the open end plate 26 of FIG. 4 is charged into the mold 39 shown in FIG. 11 and melted, and the assembly assembled up to the previous step is inverted. Then, the inner and outer porous cylinders 22 and 25 and the filter medium 24 are turned over. Are immersed in the mold 39. Thereby, the edge film 23 melts and fuses with the end plate. Subsequently, by cooling to room temperature, the edge film 23 is integrated with the end plate 26, and sufficient sealing is performed.

Experimental Examples Specific examples will be described below. Filter membrane made of tetrafluoroethylene resin (average thickness 45 μm, average pore diameter 0.1 μm, average bubble point value 2.0 kg / cm 2, width 300 mm)
FEP film (width 2)
(5 mm, thickness 12 μm) was thermally fused by a roll heater heated to 270 ° C. with a width of 10 mm. At this time, the distance between the edge films is 250 mm between the centers of the heat-sealed portions.
I tried to be.

The filter membrane with the edge film is placed on a PFA net (100 mesh, 300 mm width) from above and below.
While forming a laminate by being sandwiched, the peak height (Mountain - dimension between valleys) is folded to 11mm pleats, cut every elevated portions 120. At this time, the laminate was preliminarily fixed by heating the laminate to 100 ° C. from above and below immediately before and after the folding machine.

The pleated laminate having a PFA net support on the upper and lower sides of the number of pleats of 120 obtained above and having FEP edge films fused on both edges is made of stainless steel as shown in FIG. It was inserted into a tool and placed in an oven at 150 ° C. while applying a constant pressure. After a heat treatment for 1.5 hours, it was taken out of the oven and allowed to cool to room temperature. Thereby, the pleat shape was finally fixed.

The two side edges of the pleated laminate are overlapped with each other to be endless, and the net of the opposite portion of the overlapped portion is cut off so that the filter films overlap each other. As shown in FIG. Sandwich
Heat fusion was performed at 320 ° C. using a commercially available hot stamping machine.

By cutting the center portions of the edge films fused to the upper and lower ends of the cylindrical pleated filter medium thus obtained, a cylindrical filter medium of a predetermined length was obtained.

Next, both ends of this cylindrical filter medium can be fitted, and a mold (a closed mold in FIG. 10 and an open mold in FIG. 11) in which the final shape of the filter element is cut into the bottom is inserted into a mold. And a 7 mm thick PFA end plate (two types of closed end plate 21 and open end plate 26 in FIG. 4) are inserted at a temperature of 480 ° C. from the top and 300 ° C. from the bottom. The PFA end plate was melted by heating for 5 minutes.

After setting a PFA porous outer cylinder (protective sleeve) on the outside of the cylindrical filter medium and a PFA porous inner cylinder (substantially sleeve) on the inner side (FIG. 4), use an air cylinder in the molten PFA end plate. It was inserted under pressure, pressurized and kept warm for 2 minutes, allowed to cool to room temperature, and removed from the mold. This process was performed on one side for a closed end plate and on the other side for an open end plate. Finally, an O-ring adapter (27 in FIG. 4) for mounting the housing made of PFA was mounted by heat fusion to complete the filter element.

The obtained filter element was subjected to a bubble point test (airtightness test) and a withstand pressure test.
For comparison, a filter element was manufactured in the same manner as in the example except that the edge film was not used. The test results are shown in Table 1. Here, each test is as follows. a. Bubble Point Test A test sample is sufficiently wetted with a 60% IPA aqueous solution, set in a stainless steel housing for pressurization, air for pressurization is gradually fed, and the pressure at which foaming (bubbles) is observed from the filtrate outlet side is measured. This method is a standard method for measuring the maximum pore size of a filter membrane. b. Endurance withstand pressure test After fully wet with a 60% IPA aqueous solution, replace with pure water, and set in a stainless steel housing for pressurization.
After 100 times of pulse filtration under a positive pressure of ² cm ² , 5.
The diffusion value after performing 3 kg / cm ² back-pressure filtration for 3 minutes is measured. The diffusion value indicates the amount of air permeating by diffusion and is proportional to the total pore area.

[0034]

[Table 1]

[0035]

From the above results, it can be seen that the filter element of the present invention has not only a very good sealing property but also a good durability and pressure resistance. Although the diffusion value of sample 3 is slightly large, it is about 20 (cc / min), which is a practically problematic limit.
There is no problem because it is less, and it is considered that such a value can be sufficiently avoided in industrial production processes by improving control. According to the comparative example, it is understood that a leakage path is easily formed and the durability and pressure resistance are inferior when the film edge is not used. This is because the melt viscosity of the thermoplastic fluororesin, which is the material of the end plate, is so high that if there is no edge film, the fluidity will not be achieved unless the resin penetrates between the pleats completely and completely. Is required.
On the other hand, since the edge film is heat-sealed to the filter element in advance, such penetration of the resin is not always necessary, and the edge film fuses with the end plate to obtain sufficient sealing properties and durability and pressure resistance. It is something that can be done.
The present invention is a method which is extremely excellent in workability, operability, reliability, and economic efficiency as compared with the conventional method such as a conventional double seal.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a filter device incorporating a conventional filter element.

FIG. 2 is a partially cutaway perspective view of the filter device of FIG.

FIG. 3 is a perspective view showing a configuration of a filter medium used for a conventional filter element.

FIG. 4 is a perspective view showing components before assembling a filter element according to an embodiment of the present invention.

FIG. 5 is a perspective view showing a step of fusing a filter membrane and an edge film used in the filter element of the present invention.

FIG. 6 is a perspective view showing a step of fusing a filter film and an edge film used in the filter element of the present invention.

FIG. 7 is a perspective view showing a step of fusing a filter film and an edge film used in the filter element of the present invention.

FIG. 8 is a perspective view showing a jig and a process for forming a fold in a pleated filter medium used in the filter element of the present invention.

FIG. 9 is a cross-sectional view showing a process for fusing both side edges of a pleated filter medium used in the filter element of the present invention.

FIG. 10 is a view showing a mold for joining an end plate used in the present invention to one edge of a filter medium.

11 is a diagram showing a mold for an end plate for use in the present invention is coupled to the other end edge of the filter media.

[Explanation of symbols]

 21, 26-end plate 22-perforated outer cylinder 23-filter medium 25-perforated inner cylinder 27-O-ring adapter 31-filter membrane 32-support 33-side edge film 34-fixed end plate 35-pleated jig 36-fixed Wall 37-Press movable part

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B01D 63/00-63/16

Claims (4)

(57) [Claims] 1. A non- porous , non- porous ethylene tetrafluoroethylene resin film is provided on upper and lower edges of a filter membrane made of tetrafluoroethylene resin.
-Fluoroalkyl vinyl ether copolymer (PF
A), ethylene tetrafluoride-propylene hexafluoride copolymer
(FEP), and ethylene tetrafluoride-perfluoroal
Killed vinyl ether copolymer-propylene hexafluoride copolymer
An edge film of any of the thermoplastic fluororesins of the unified (EPE) is overlapped and pressed and fused, and a pair of porous supports made of a fluororesin are attached to both sides of the filter membrane. , The filter medium thus obtained is bent into accordion pleats, and after forming endlessly, both side edges are sealed,
Ethylene tetrafluoride par melted in a mold for forming end plates
Fluoroalkyl vinyl ether copolymer (PFA),
Ethylene tetrafluoride-propylene hexafluoride copolymer (FE
P), and ethylene tetrafluoride-perfluoroalkylbi
Nyl ether copolymer-propylene hexafluoride copolymer
(EPE) a filter wherein at least the edge films at the upper and lower edges are immersed and cooled in any thermoplastic fluororesin of (EPE) to completely seal the filter membrane with the end plates. Element manufacturing method. 2. The filter element according to claim 1, further comprising a step of compressing and holding the pleats at an elevated temperature equal to or lower than the softening temperature of the edge film to form a folding habit, following the step of bending into accordion pleats. Manufacturing method. 3. The filter according to claim 1, further comprising a step of accommodating the filter medium between porous inner and outer cylinders made of a thermoplastic fluororesin, following the step of sealing both side edges after forming endlessly. Element manufacturing method. 4. A fixed end plate capable of supporting one end face of a filter medium obtained by bending a laminate formed by attaching a pair of porous supports to both sides of a filter membrane into accordion pleats,
A parallel fixed wall for supporting a bent portion of the filter medium, a press movable section movably provided opposite the fixed end plate and capable of pressing against the other end face of the filter medium, and a fixed end plate for the press movable section. And a heating device for heating the filter medium by moving the filter medium toward the target and a heating device for heating the filter medium.