JPS61149218A - Filter element and preparation thereof - Google Patents

Abstract

PURPOSE:To obtain a filter having no problem in chemical resistance and the elution of a metal and capable of withstanding high pressure, by forming a filter membrane made of a fluorocarbon resin into a cylindrical form while folding the same in a plated state and connecting caps made of a fluorocarbon resin to both end parts of the formed cylinder in a liquid-tight state by fusion bonding. CONSTITUTION:A filter membrane made of a tetrafluoroethylene resin having a thickness of 50-200mum and a pore size of 0.01-10mum is folded in a pleated state, in such a state both side surfaces thereof are held between reticulated supports made of a fluorocarbon resin, to form a cylindrical shape. Each end parts of this filter material 3 is engaged with a cap 7 and gradually inserted in the fluorocarbon resin for the end cap, which is melted under heating at temp. of the m.p. of the end cap or more in an end cap mold, to perform the integral fusion bonding of said end part 4 and the end cap 7. After the filter material 3 is sedimented in the resin up to a depth of 1-10mm, the mold is cooled.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a filter element entirely made 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 now widely used in various fields such as food and semiconductors. . In particular, regarding cleaning technology for chemicals required in the field of microfabrication technology in the semiconductor integrated circuit manufacturing process,
Compared to water purification technology, technical response is delayed,
It has received particular attention recently. Although there is a demand for highly purified chemicals in order to improve product yield and quality, semiconductor integrated circuit manufacturers and drug supply manufacturers have been slow to respond to this demand due to metal leaching. The main reason for this is that the development of filter products with low chemical resistance and good chemical resistance has been delayed. the current,
In order to meet the above requirements, there is a need for filters made of all-fluoropolymer resin, and flat membrane multi-stage and tubular one-type membrane filters have been developed, but the effective filtration area is small and As a result, there are problems in the filtration and human processing of high viscosity drugs, which do not meet market requirements.

On the other hand, pleated filter elements using fluororesin membranes have been developed. This has a large effective filtration area and excellent chemical resistance, but since adhesion of fluororesin is inherently extremely difficult, materials other than fluorine are used except for the filter membrane, and this is due to its chemical resistance. This causes bottlenecks such as metal leaching and metal elution, and it is not possible to obtain a satisfactory product.

%F'Q(-Problem to be solved The filters used in the above semiconductor integrated circuit manufacturing process require extremely small pores of 0.01-10μ, and the filter membrane itself has extremely low strength. Harsh conditions cannot be used when manufacturing filters,
Moreover, the adhesion of each member of the filter element cannot be achieved simply by adhesion, but must be in close contact with each other in a completely sealed state.

The present invention provides a filter element made of all fluororesin and a method for manufacturing the same that satisfies such requirements.

That is, as shown in FIGS. 1 and 2, the present invention involves folding a sandwich-like sheet in which a fluororesin filter membrane (1) is laminated with a thermoplastic fluororesin net-like support (2) on both sides into pleats. A cylindrical pleated filter material (3) is made into a cylindrical shape, and both edges of the filter material are liquid-tightly fused. An all-fluoropolymer filter element equipped with a fluororesin cap (7) having a predetermined shape that is fluid-tightly fused (separately shown in Figure 1 for ease of understanding) and its manufacturing method. provide.

The filter membrane (1) used in the present invention is made of fluororesin,
In particular, it is made of polytetrafluoroethylene resin (PTFE), which may be laminated with a porous fluoropolymer reinforcement, and the membrane itself is known as a Y membrane. The membrane thickness and pore size can be arbitrarily selected depending on the type of processing liquid and the purpose of filtration, but usually the membrane thickness is 50 to 200μ.
, with a pore diameter of 0.01-10μ. Since this membrane has low mechanical strength and is easily deformed by filtration pressure, it is used in the form of a sandwich with fluororesin net-like supports placed on both sides to maintain its pleated shape. As this filter membrane, for example, JP-A-58
-14919, in which fluoroethylene polymer is fused to the surface of glass fibers, improves strength but does not have micropores, and has poor chemical resistance and eluted metals. It cannot be used because it is insufficient in this respect and does not meet the purpose of the present invention. In addition, the filter membrane and the cap are fused together using high insertion pressure. Such an insertion pressure cannot be used if the filter membrane is made of all-fluororesin because the filter membrane will be deformed and a liquid-tight fusion cannot be achieved.

The fluororesin filter membrane is sandwiched between thermoplastic fluororesin net supports (2). this is,
It acts as a spacer for the filter membrane to work effectively over its entire area for filtration, and at the same time prevents the membrane from deforming due to filtration pressure.The net support itself acts as a fusing material, which prevents fusing at the side edges of the membrane. It has an important role to complete. Fluororesin, especially PTF, which is the material for filter membranes
E is very difficult to heat-seal and the strength of the pattern is extremely weak, so it is difficult to liquid-tightly fuse both ends (4) with fluororesin, or a cylindrical shape made of all-fluororesin. This is thought to be the reason why pleated filters (elmmen) were not provided in the past.

The material of the net support (2) is tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA
), tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP), ethylene-tetrafluoroethylene copolymer resin (
ETFE), trifluorochloroethylene resin (PCTFE)
, ethylene-trifluorochloride ethylene copolymer tree 1IiiiT
(ECTFE), polyvinylidene resin (PVdP)
, thermoplastic fluororesins such as vinyl fluoride resin (PVF), tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer resin (EPE), fluorine-containing thermoplastic elastomers, and other fluorine-containing copolymer resins. used. Particularly preferable are PFA, FEPSEPE, ET-FE, and PCT in terms of chemical resistance and heat resistance.
FE, ECTFE, especially PPA, FEP, EPE.

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 are flexible enough to be folded into pleats and rigid enough not to easily lose their shape due to filtration pressure. Thickness 01~1
Use one with a 0H1 hole area of 0.1 to 5 butts.

The filter membrane is sandwiched between net supports, folded into pleats to form a cylindrical shape, and both side edges are liquid-tightly fused using, for example, an ordinary impulse sealer. The filter membrane and the net support may have a multilayer structure (eg support-membrane-support-membrane-support).

The both side edges (8) may be fused together by elongating the lower 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, a thermoplastic fluororesin sealing tape (9) may be sandwiched and fused between both side edges. Alternatively, as shown in FIG. 4, a seal cover (10) made of thermoplastic fluororesin may be covered and fused. For such seal tapes and seal covers, PFASFEP, EPF, and E, which have excellent chemical resistance and fusion properties, are used.
TFE, PCTFESECTTr'E, especially PFA.

FEP, EPE, etc. are preferred. In the embodiments shown in FIGS. 3 and 4, the pressure resistance of the seal is improved.

Both ends (4) of the filter cage obtained as described above are embedded and fused in a cap made of thermoplastic fluororesin, leaving openings (5) for liquid passage. When the ends of the pleated filter are rapidly pushed into a cap mold containing molten fluororesin, the pleats buckle and the resin does not penetrate between the pleat folds. That is, the filter membrane is not embedded in the fluororesin. Therefore, only an incomplete seal is obtained and the pressure resistance is insufficient.

In the present invention, the end portion of the filtration house described in -1- is fitted with a cap and, if desired, a porous hollow cylindrical core material (a flow path for taking out the liquid), which will be described later, and this is placed in a mold for the end cap. The end portion of the filter material is gradually inserted into the melted fluororesin for the end cap while maintaining the temperature and fused together. At that time, the filter material is held loosely in a holder until the end cap is sufficiently melted, and when the end cap is sufficiently melted, a slight load, e.g. The cap is allowed to settle gradually.The time required for pushing the cap varies depending on the melt viscosity of the resin used for the cap, but is preferably at least 30 seconds per 11 II m depth, and more preferably at least 1 minute.

The filter material has a predetermined depth, for example 1 to 10! ! I11. After settling into the resin of the end cap, the mold is cooled.

Alternatively, the end portion of the temporary material may be pushed in at a constant speed.

The pushing speed is 0.1 to 6 mi/min, more preferably 0°2
~2 mm 1 minute. By this method, the end cap resin infiltrates between the folds of the filter membrane at the end of the temporary material and is fused in a liquid-tight manner.

Alternatively, the end cap may be pre-melted in a mold and the end cap may be fused by gradually inserting the end of the filter material therein. At this time, if the temperature of the end cap decreases due to the insertion of the end of the y-over material, wait until the cap reaches the melting temperature again, and then press and insert the end of the y-over material at the above speed, Further, as described above, the end portion of the filter material may be pushed in by applying a certain load. The caps to be fused to both ends may both have a central opening (6), one having a central opening and the other having no central opening; But that's fine.

The thickness of the bottom of the cap is 1.5mm or more, preferably 3~
It is 8rllll+.

As the fluororesin used for the cap, any of the aforementioned fluororesins can be used, but FEPlPFA is preferred in terms of chemical resistance.
, EPElETFESPCTFE or ECTFE, especially FET', PFA, EPE. PTFE is preferable because it has poor fusion properties and high viscosity when melted, and it is difficult to insert the ends of the temporary material.

Although the aforementioned porous hollow cylindrical core material is not essential, it is preferably used to protect the filtration material when filtration pressure is applied from the outside.

Although any of the aforementioned fluororesins can be used for the core material, PTFE and FEP are preferred in terms of chemical resistance and heat resistance.

PFA, EPE, ETFE, PCTPESECTFE,
Particularly preferred are FEP, PPA, and EPE, and particularly preferred is the same resin as used for the end seal.

If desired, the filter element of the present invention may be covered with a cylindrical protective sleeve made of fluororesin around the filter medium. 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.

The protective outer cylinder is made of stainless steel or Hastelloy C1 depending on the application.
Materials such as X-alloy, H-alloy, Dura nickel, etc. may be used, and to make it made of fluororesin, fluororesin, such as PTFE, FEP, EPESPFA, ETT? 4
1PCTFE, ECTFE.

Especially PTr'ES1? EP, El"E, PFA, etc. may be used.

The filter element of the present invention is entirely made of fluororesin, has excellent chemical resistance and heat resistance, does not have problems such as metal elution, and can filter processing liquids containing very small particles of 0.01μ to 10μ. Therefore, it is particularly useful for purifying drugs and the like used in semiconductor integrated circuit manufacturing processes.

Kanrankoi PTFE filter membrane (thickness 100μ, average pore diameter 0.1
42 upper and lower EPE net supports (average thickness 0.4mm, pore area ratio 50%, area 250x2000ii') with a diameter of 250x2000Im") were layered to form a sandwich, and these sheets were corrugated to form a fold with 70 folds. form the pleats.

Make the pleats into a cylinder, overlap the edges on both sides, sandwich an EPE film (width 5cm, length 250cm, thickness 50μ) between them (Fig. 3), heat seal this with a commercially available impulse sealer, and make it into a cylindrical shape. A pleated Y overlay material was obtained. This heat-sealed portion is completely liquid-tightly sealed.

Next, a porous hollow cylindrical core material made of PFA (outer diameter 36IIIri, inner diameter 30mm, length 240M) was inserted into the inner hole of the Y filter material.
R), align one end, and fit these EPEs.
These end caps (bottom thickness: 6 mm) are fitted, and these are placed in a mold and heated. At this time, the filter medium is held loosely by a holder. After heating at 320° C. for 20 minutes, a load of 200 g is placed on the sieve material, and the lower end of the sieve material is slowly immersed into the molten resin of the end cap. After about 10 minutes, when the filter material has dropped 5 cm, the load is removed and the filter is cooled down.

When the molten resin is removed from the mold after it has solidified, the resin from the end cap will seep into the folds of the filter membrane at the end of the overfill material.
It was firmly fused. Repeat the same operation on the other end.

The obtained filter element was in fluid tight contact with the pleat side edges, ends, and cap, had no leaks, and was able to withstand a high pressure of 5 kg/cm'' or more.

Effects of the Invention The filter element of the present invention is made entirely of fluororesin, so there are no problems such as chemical resistance or metal elution, and the fluororesin, which was conventionally considered difficult to fuse, can be melted using a special method. It is tightly fused.

The obtained filter element had pleat side edges, ends, and cap portions that were tightly and liquid-tightly adhered to each other, had no leakage, and was able to withstand high pressure.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the filter element of the present invention (however, the temporary material and the cap are shown separately);
Figures 4 to 4 are schematic diagrams showing the manner in which pleat side edges are fused. (1) Filter membrane, (2) Net support,
(3) - filter material, (4)... end of filter material,
(5)...Central opening at the end of the filter material, (6).Central opening of the cap, (7)...Cap, (8) Side edge of the filter material, (9)...Seal tape , (lO)・Seal cover. /“

Claims (1)

[Claims] 1. A sandwich-like sheet in which a thermoplastic fluororesin net support is layered on both sides of a fluororesin filter membrane is folded into a cylindrical shape by pleating, and the edges on both sides are fused in a liquid-tight manner. An all-fluororesin filter element comprising a cylindrical filter medium and a fluororesin cap liquid-tightly fused to both ends of the filter medium, leaving a central opening at both ends. 2. The first filter membrane is made of tetrafluoroethylene resin
Filter element as described in section. 3. The filter element according to item 10, wherein the diameter of the micropores of the filter membrane is 0.01 to 10μ. 4. Net support is PFA, FEP, EPE, ETFE
, PCTFE or ECTFE. 5. The filter element according to item 1, in which both side edges are fused with sealing tape made of EPE, PFA, or FEP. 6. Cap is FEP, PFA, EPE, ETFE, P
2. The filter element according to claim 1, which is CTFE or ECTFE. 7. The filter element according to item 1, wherein the element further includes a core material for supporting the filter material made of fluororesin. 8. The filter element according to item 1, wherein the element further includes a protective outer cylinder made of fluororesin. 9. Thermoplastic fluororesin net supports are layered on both sides of a fluororesin filter membrane and formed into a pleat shape, the pleats are made into a cylindrical shape, and adjacent both side edges are fused in a liquid-tight manner. If desired, the end of the cylindrical pleated filter is fitted with a core material made of fluororesin for supporting the filtration material, and gradually inserted into a cap made of molten fluororesin kept at a temperature higher than the melting temperature, and then heated and fused. A unique manufacturing method for filter elements made of all-fluorine resin. 10. The method according to item 9, wherein the filter membrane is made of tetrafluoroethylene resin. 11. The manufacturing method according to item 9, wherein when fusing the side edges of the pleated filter, a thermoplastic fluororesin fusing tape is inserted between the side edges. 12. Net support is PFA, FEP, EPE, ETF
E, the method according to item 9, which is PCTFE or ECTFE. 13. The cap is FEP, PFA, EPE, ETFE,
The method according to item 9, which is PCTFE or ECTFE. 14. The manufacturing method according to item 9, wherein at least one of the caps has a central opening. 15. The method according to item 9, wherein the end of the cylindrical pleated filter is pushed into the cap for one minute or more.