JPS60153902A - Capsule type filter and its preparation - Google Patents

Abstract

PURPOSE:To obtain the titled filter excellent in chemical resistance and having no problem of metal elution and easy to handle, by constituting all of materials of a capsule type filter from a fluorocarbon resin and integrally welding filter elements in a housing. CONSTITUTION:A sandwich like sheet, which is formed by superposing reticulated supports made of a thermoplastic fluorocarbon resin to both surfaces of an ethylene tetrafluoride resin filter film, is folded in a pleated state and both side edge parts thereof are welded in a liquid-tight state to obtain a cylindrical filter material 3. Both end parts of the filter material 3 are heated to a temp. equal to or more than the m.p. of the resin of the reticulated supports to preliminarily weld pleats. Separately, a thermoplastic fluorocarbon resin is melted in a doughnut shaped mold under heating and the preliminarily welded pleats are inserted into the molten resin to allow said resin to penetrate into the filter material to seal the end parts of said filter material. One seal end part 6 is inlaid with a non-perforated fluorocarbon resin cap 8 and the other seal end part 6 with a perforated fluorocarbon resin cap 8'. The perforated cap 8' is welded to a housing 12 made of a fluorocarbon resin 12 to obtain a capsule shaped filter.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a capsule-type filter made entirely of fluororesin and a method for manufacturing the same.

In recent years, ultra-purification technology for air, gas, water, chemicals, etc. based on membrane separation technology has made remarkable progress and is widely used in various fields such as food and semiconductor fields. In particular, chemical cleaning technology required in the field of microfabrication technology in the semiconductor integrated circuit manufacturing process has been attracting particular attention recently, as technological support has been delayed compared to cleaning technology for air, gas, water, etc. has been done. Despite efforts to improve the purity of chemicals in order to improve product yields and quality, both semiconductor integrated circuit manufacturers and chemical supply manufacturers have been slow to respond. One of the main reasons is that the development of filter products with low elution and good chemical resistance has been delayed.Currently, filters made of all-fluorine resin are being used to meet the above requirements. Multi-stage flat membrane filters and single-tubular membrane filters have been developed, but the effective overflow area and p flow rate are small, so there are problems with single flow and mass processing of high viscosity drugs, and the market is limited. We have yet to issue a large number of requests.

On the other hand, pleated filter elements using fluororesin membranes have been developed. This is because it has a large effective 7+1 overarea and has very good chemical resistance, and because it is extremely difficult to bond fluororesin, materials other than fluororesin are used for everything other than the filter membrane. Problems such as chemical resistance and metal elution have caused problems, and satisfactory products have not been obtained.

Furthermore, the filters used in the semiconductor integrated circuit manufacturing process require extremely small pores of 0.1 to 10 microns, and the filter membrane itself has extremely low strength.
Severe conditions cannot be used during filter manufacture, and each member of the filter element cannot be simply bonded together; it must be completely sealed.

The inventors of the present invention have previously developed a filter element that satisfies these requirements, and filed a patent application for this (Japanese Patent Application No. 1983).
167202), the present invention relates to a capsule type filter in which this filter element is integrally fused within a housing.

That is, the present invention utilizes polytetrafluoroethylene resin (hereinafter referred to as PTFE) as shown in FIGS.
A sandwich-like sheet in which a thermoplastic fluororesin net-like support (2) is stacked on both sides of the filter membrane (1) of the filter membrane (1) is folded into a pleat shape, and both side edges are fused in a liquid-tight manner. A cylindrical filter material (3) is embedded in a thermoplastic fluororesin leaving a central opening (5) at both ends (4) of the filter material, and the resin is infiltrated between the folds of the pleated ends. a fluororesin cap (8) comprising an end seal part (6) which is sealed and fused, and one of the end seal parts is non-porous;
The other side is a perforated fluororesin cap (8')! : At least an inlet (13 or 14) and an outlet (1) in which a filter element, which is liquid-tightly fused, is built into a fluororesin housing (12) which is liquid-tightly fused to the filter element.
4 or 13) and a method for producing the same.

The capsule type filter of the present invention is made entirely of fluororesin, so there are no problems such as chemical resistance, metal elution, etc., and the fluororesin, which was previously considered difficult to fuse, is liquid-tight due to its special composition. This all-fluoropolymer capsule-type filter is completely new.

The filter membrane (1) used in the present invention is made of PTFE, which may be laminated with a porous fluororesin reinforcing material, and this membrane itself is known as a filtration membrane. The membrane thickness and pore size may be arbitrarily selected depending on the type of processing liquid and the purpose of filtration, but usually the membrane thickness is 60 to 100μ,
Use one with a pore size of 0.1 to 10 μm. This membrane has low mechanical strength and is easily deformed by filtration pressure.
In order to maintain the pleated shape, fluororesin net-like supports are layered on both sides to form a scissor sandwich shape. As this filter membrane, for example, JP-A-58-14
As described in Publication No. 919, the glass fiber surface is fused with fluoroethylene polymer, but the strength is improved, but it is not possible to obtain a micropore size, and the chemical resistance and eluted metal etc. It cannot be used because it is insufficient in this respect and does not meet the purpose of the present invention.

The PTFE filter membrane is sandwiched between thermoplastic fluororesin net supports (2).

This serves as a spacer for effectively filtrating the entire area of the filter membrane, and at the same time prevents the membrane from deforming due to filtration pressure, and also plays an important role in perfecting the fusion of the side edges of the membrane. PTF, the material for filter membranes
E is extremely difficult to heat-bond, and the strength of the membrane is also extremely weak, making it difficult to weld its ends (4) in a liquid-tight manner. This is thought to be one of the reasons why the element was not provided in the past.

The material of the net support (2) is tetrafluoroethylene-perfluoroalkyl vinyl ether resin (1) FA), tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP)
, ethylene-tetrafluoroethylene copolymer resin (ET
FE), trifluorochloroethylene resin (pcTF
E), ethylene-trifluorochloroethylene copolymer resin (ECTFE), vinylidene fluoride resin (PvdF),
Thermoplastic fluororesins such as polyvinyl fluoride resin (PVF), tetrafluoroethylene-hexafluoropropylene-fluoroalkyl vinyl ethyl copolymer resin (EPE), etc. are used. Particularly preferred are PFA, FEP, and EPE from the viewpoint of chemical resistance.

The net support is plain woven fabric of fluororesin fiber, fused nonwoven fabric,
It is desirable to use porous materials such as molded nets, knitted fabrics, and punched sheets that have enough flexibility to be folded into pleats and enough rigidity to not easily lose their shape under filtration pressure. Thickness 0.1~1
．． A material with a pore area of about 0.1 to 5 tptm is used.

The filter membrane is sandwiched between net supports, folded into pleats, and both side edges are fused in a liquid-tight manner to form a pleated cylinder. The filter membrane and the net support may have a multilayer structure (for example, support-membrane-support-one membrane-support).

The both side edges (9) may be fused together by elongating one side edge of the net support and covering the outside of the other side edge and fusing them together as shown in Figure 2. As shown in Figure 3, apply thermoplastic fluororesin sealing tape (10) between both side edges.
It may be fused by sandwiching it.

Alternatively, as shown in FIG. 4, a seal cover (11) made of thermoplastic fluororesin may be covered and fused. As such seal tapes and seal covers, PFA, FEP, EPE, etc., which have excellent chemical resistance and fusion properties, are preferable. In the embodiments shown in FIGS. 3 and 4, the pressure resistance of the seal is improved.

Both ends (4) of the filter material obtained as described above are sufficiently heated to a temperature higher than the melting point of the resin of the net support to preliminarily fuse the pleats between each fold. This step is important as a pre-step for later infiltrating the fluororesin between the folds at both ends of the pleated filter and sealingly welding it to form an end seal. That is, as will be described later, both ends of the pleated filter are pushed into a mold containing molten fluororesin and fused together; however, if preliminary fusion between the pleats is not performed, the viscosity of the molten fluororesin will be high. The pleats buckle and the resin does not infiltrate between the pleats. In other words, the filter membrane is not embedded in the fluororesin.

Therefore, only an incomplete seal is obtained and the pressure resistance is insufficient.

The preliminary fusion between the folds does not need to be completely adhered to the entire surface.
It is sufficient to carry out the process to the extent that the above-mentioned problems that occur when forming the end seal portion can be avoided.

Both ends (4) of the filter material obtained as described above are embedded and fused in a thermoplastic fluororesin, leaving openings (5) for liquid passage. For fusion, a donut-shaped mold into which the end of the filter material can be inserted is filled with thermoplastic fluororesin for sealing.
The end of the filtration side is pushed into the heated and melted material, and the sealing fluororesin infiltrates between the pleats until at least the surface of the fluororesin at the end of the filtration material melts and the infiltrated resin is fused and integrated. This is done by continuing heating.

Thermoplastic fluororesin for seals is P other than P T F E
FA, FEP, ETFI Otsu, PCTI”E, ECTFE
PVdF, PVF, EPE, etc. can be used, but
PFA, FE 1), l) E in terms of chemical resistance
is preferred. PTFE is not preferable because it has poor fusion properties and high viscosity when melted, making it difficult to insert the filtration end and causing air bubbles to remain between the pleats.

A porous hollow cylindrical core 4 that fits into a perforated cap (8A) and a central opening (5) at both ends of the filtration material as desired.
'A (P liquid extraction channel) is fused.

Various methods such as heat fusion, rotational welding, insert injection, and cylinder injection can be used as the fusion method. In the case of heat fusion, the end seal part is fitted to the fluororesin cap and core material pre-formed into the specified shape, inserted into a mold, and heated above the melting point of the fluororesin in the end seal part. , all sides of the cap and/or the entire bottom are completely fused in a liquid-tight manner.

If the end seals are not formed in advance, the gap and the filter media will not fit together completely, making it impossible to obtain a completely sealed filter element.

The fluororesin used for the gap is the aforementioned fluorine 1ffJ.
Any type of fat can be used, but from the viewpoint of chemical resistance, P T
li'l! :, FEP, 1) FA, El) E are desirable.

Preferably, the same resin used for the end seal is used for its adhesion.

The perforated cap (8') is shaped and sized to be fused with the housing.

Any of the above-mentioned fluororesins can be used for the core material, but PTFE, FEP, PFA, and EP are preferred in terms of chemical resistance and adhesive properties.
E is preferred, and the same resin as the end seal is particularly preferred.

A perforated cap (8') is fused to the housing (12). The welding method may be the same as in the case of the cap.

The housing may be made of fluororesin so that the completed filter capsule has at least two apertures, an inlet and an outlet. FIG. 5 is a schematic cross-sectional view of a typical capsule filter of the present invention in which a filter element is attached to a bell-shaped housing (12). In the figure, (13), (14), (16) and (17) are openings, and the filter element is fused to the opening (14) provided in the housing bottom (18).

In FIG. 5, the liquid to be treated may be introduced from (13) or (14), but typically it is introduced from (13). In this case, the opening (13) is the inlet for the liquid to be treated, and the opening (14) is the outlet for the furnace liquid. In addition to the inlet and outlet, the housing has an air vent (16) and a drain (1).
7). Although the housing does not necessarily have to be bell-shaped, it is preferable in order to reduce energy loss due to flow resistance of the liquid to be treated and to provide pressure resistance. The housing apertures (13) and (14) have suitable connection means (19) for plumbing connections with other equipment. This connecting means may be a simple protrusion, a screw thread, or a fitting method.

The housing has an open bottom as shown in FIG. 6, and a perforated cap may be fused thereto. In this case, the connection means (19) is integrally molded in the perforated portion of the perforated cap.

If desired, the housing is preferably provided with a protrusion (20) as shown in FIG. 7 to prevent the filter element from rattling inside the housing. This protrusion is not necessary when the length of the filter element is 5 inches or less, but it is better to provide it when the length of the filter element exceeds 10 inches. Similarly, Figure 8 shows the filter element cap (8).
) is provided with a protrusion (20'). Both FIGS. 7 and 8 show I-I' in which the device shown in FIG. 5 is provided with a protrusion.
A cross section is schematically shown.

Fluororesins suitable for the housing are PFA, P'rFE,
The filter element may be made of FEP, EPE, etc., and after the bottom part (18) and the filter element are fused together, a λ housing cover may be placed over the bottom part and fused together.

Alternatively, the bottom part (18), the filter element and the housing cover may be simultaneously fused together, and the fusion process is the same as in the case of the cap.

If desired, the filter element may be covered with a protective casing (15) made of fluororesin around the p-particle. The protective sleeve may be made from a panel with a number of holes for passage of the processing liquid and does not necessarily need to be fused together with the filter element. It may be fitted inside the cap or inserted outside.

Such an outer cylinder may be a net when the aperture (13) is used as an inlet.

The filter element is entirely made of fluororesin, has excellent chemical resistance, does not have problems such as metal elution, and has a diameter of 0.1μ~
-1 of processing liquid containing very small particles of 10μ
Therefore, it is particularly useful for purifying drugs and the like used in semiconductor integrated circuit manufacturing processes.

Furthermore, in the case of a filter element that is not integrated with a conventional housing, it is necessary to mount it in the housing during use, and at that time, the contamination of particulates is unavoidable. 1')'JProblems are likely to occur when cleaning the filter element, and in the case of a corrosive chemical, there is a risk that it may adhere to the worker when installing or removing the filter element. there were.

In the capsule type filter of the present invention, since the filter element is installed in the housing in advance, the above problems are solved, and the capsule can be easily replaced, and there is no need for a sealing backing, which was necessary for the element to fit tightly. Easy handling.

In addition, in the case of a single element, a space is required to insert and remove the element when it is attached to and removed from the housing, but the capsule of the present invention does not require such space, making the entire device compact. can do.

The present invention will be explained below with reference to Examples.

Example PTFE filter membrane (thickness 60μ, Tokyu pore size 0.22
μ, area 260 x 220 om/) below E I)
E-net support (average thickness Q, 3 mm, pore area ratio 5
0%, area 260 x 2200 Z Sononol) are stacked in a sandwich-like shape to form pleats with 78 pleats.

Layer both edges of the pleats and place E l) lζ film ([
115 dragons, length 260 pieces, thickness 50μ) were sandwiched between them (Fig. 3), and this was heat-sealed with a commercially available impulse sealer to form a cylindrical pleated shape '/)-i Kaori (inner diameter 36m).
m, outermost diameter 65 mm, length 250 mm) is 14).

This heat-sealed portion is completely liquid-tightly sealed.

Next, both ends (15 mm each) of this cylindrical pleated E-shape were inserted into a heating furnace, heat-treated at 350° C. for 30 minutes, and then taken out and cooled.

Separately, place an EPE sheet (thickness 5 yam
), heat the mold to 320°C, and
Melt the PE sheet. The heat-treated end portion of the pleated p-layer was inserted into this and held at 320° C. for 15 minutes, then the mold was cooled and removed. The resulting end sea/l/
The end of the vp4A can withstand high pressure with the P''rFE membrane completely embedded in the EPE resin.

A porous hollow cylindrical core material made of EPE (outer diameter 35 myt, inner diameter 3 Q 1111,
Insert the E, PE non-porous cap (outer diameter 7011 m, depth 5 mm) and the E IJ E perforated cap (outer diameter 33 mm) into the end. , thickness IQ 11711, depth 5 mm, inner diameter 30 mm), and these were placed in a mold and heated at 320°C for 40 minutes, then cooled and taken out to obtain a filter element.

Core (21) as shown in Figure 9 (a = '30 standard, b
-55 bait) and mold (22) (b-55 bait, C=35
fin, d-90 tomo, e=105 ayu, f-20 tomo), insert EPE resin, the perforated cap and housing of the filter element, and heat at 320°C for 40 minutes.
Heat for a minute and then cool to obtain a capsule-type filter.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the filter element of the present invention (however, the filter material and the cap are shown separately); Figs. 5 and 6 are schematic cross-sectional views of the capsule-type filter of the present invention, and FIGS. 7 and 8 are schematic cross-sectional views of the capsule-type filter provided with protrusions for preventing rattling of the filter element, and FIG. The figure shows a mold used to fuse the filter element and housing. (1)...Filter membrane, (2)...Net support, (3)...Filtering material, (4)...Filtration layer end, (
5)...Central opening at the end of the filter medium, (6)...End seal portion, (7)...Central opening of the cap, (8) and (8')...Cap, ( 9)...Net side edges, (10)...Seal tape, (11)...Seal cover, (12)...Housing, (13), (
14)...Opening hole, (15)...Protection net, (1
6)... Air vent, (17)... Drain drain, (
18)...Housing bottom, (19)...Connection means, (20) and (20')...Protrusion, (21)...
- Core, (22)...Mold Figure 2 Figure 3 Figure 4. r3 -r-q t3 12'' Figure 6 M'S Figure 7 Figure 8

Claims (1)

[Claims] 1. A sandwich-like sheet made of a polytetrafluoroethylene resin filter membrane and a thermoplastic fluororesin net support layered on both sides is folded into pleats, and the image side edge is coated with liquid. A tightly fused filtration phase is embedded in a thermoplastic fluororesin leaving a central opening at both ends of the filtration phase, and the end seal is honey-fused by infiltrating the resin between the pleated end folds. A filter element is built in a fluororesin housing, and one of the end sealing portions is liquid-tightly connected to a fluororesin non-porous cap and the other end is a fluororesin perforated cap. A fully fluorocarbon resin capsule type fin/letter having an outflow port and an inflow port 1-1. 2. Filter) A capsule-type filter as described in item 1, in which the diameter of the micropores is 0.1 to 10μ. 3. The net support is 1) FA, FEP or E l) E
2. The capsule-type filter according to claim 1, which is made of 4. Capsule type filter according to item 1, in which the end sealing resin is made of PFA, FEP, or EPE. 5. The cap is made of PTFE, FEP, PFA, or EP.
Capsule type filter 06 according to item 1, which is E. The capsule type filter according to item 1, wherein the filter element further includes a core for supporting a filter material made of fluororesin. 7. The capsule-type filter according to item 1, wherein the filter element further includes a protective outer cylinder made of fluorine resin. 8. The filter according to item 1, wherein the inlet and the outlet are each provided with means for connecting to piping. 9. The housing also has an air vent and a drain.
1ffj filter according to item 1 above. 10. The filter according to item 1, wherein the housing is bell-shaped. 11. The filter according to item 10, wherein the perforated cap portion of the filter is liquid-tightly fused to the bottom of the bell-shaped housing. 12. The filter according to item 1, wherein a protrusion for fixing the filter element is provided inside the housing or on the outer periphery of the filter element. 13. The filter according to item 1, wherein the housing is made of PTFE, FEPS PFA or E'PE. 14. Layer thermoplastic fluororesin net supports on both sides of a tetrafluoroethylene filter membrane and form it into a pleat shape, make the pleats into a cylindrical shape, and fluid-tightly fuse the adjacent recording parts on both sides. Both ends of the cylindrical pleated filter were heated above the melting point of the net support to preliminarily fuse each pleat, and a thermoplastic fluororesin was separately heated and melted in a doughnut-shaped mold having a central opening. Insert the pre-fused folds into the inside, infiltrate the resin between the folds, fuse the ends of the filter and the molten resin together to seal the ends, and seal one end of the resulting end seal with a non-porous , the other is fitted with a perforated fluororesin cap and, if desired, a fluororesin 7JJ over-material support core material, and the perforated cap is integrally fused to the fluororesin housing. Manufacturing method for all-fluoropolymer capsule-type filters. 15. The manufacturing method according to item 14, wherein the side edges of the pleated filter are fused by inserting a thermoplastic fluorine resin fusion tape between the side edges. 16. The method according to item 14, wherein the net support is PFA, FEP or EPE. 17. The manufacturing method according to item 14, wherein the end fusion resin is PFA, FEP or EPE. 18. Cap is PTFE, FEPlPFA or EP
The manufacturing method according to item 14, which is E.