JP2007111572A - Functionalized membrane, and filtration material and filter element using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a filter element without heating a porous hydrophobic resin membrane having been subjected to a functionalizing treatment such as conversion to a hydrophilic material; and to provide a structure capable of being degassed with ease. <P>SOLUTION: There are provided: a filtration membrane prepared by subjecting a functionalizing treatment, such as conversion to a hydrophilic material, to a porous hydrophobic resin membrane, except for prescribed both salvage portions in the width direction thereof; a filtration material manufactured by bending a pile of the filtration membrane with a support net for supporting the whole of both surfaces into a pleat form, and sealing the side end portions, to thereby form into an endless cylindrical article; and a filter element manufactured by supporting the filtration material with a porous inside core and a porous outside sleeve, and the resultant article adhering to an end cap with heat. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a microporous membrane for use in filtration and a filter element using the same, and more specifically, a hydrophobic resin membrane such as a PTFE (polytetrafluoroethylene) membrane prior to passing water or an aqueous solution, and the like. The present invention relates to a filter element that has been subjected to a so-called functionalization process such as hydrophilization or ion exchange so that an initial process with an alcohol is unnecessary.

  The porous filtration membranes currently used as filtration membranes are primarily hydrophobic resin membranes (PTFE (polytetrafluoroethylene), PE (polyethylene), PP (polypropylene), etc.). For water, those obtained by subjecting these membrane materials to a hydrophilization treatment, and for ion exchange, those obtained by subjecting these membrane materials to a coating treatment for imparting ion exchange properties are used. However, those subjected to hydrophilization treatment or ion exchange treatment imparting treatment have low heat resistance and cannot be fused at a high temperature, and particularly when fused with PFA, which is a fluorine-based thermoplastic resin, causes discoloration or deterioration due to high temperature. For the reason, it could not be enough. Among these membrane materials, there is a PTFE membrane (heat resistance of 200 ° C. or higher) as a filtration membrane that has excellent chemical resistance and can be used at a high temperature. However, when the PTFE membrane is hydrophilized, the heat resistance decreases, A non-porous edge film made of a fluorine-based (PFA, etc.) resin or an end cap made of a fluorine-based (PFA, etc.) resin to be attached to the edge of the membrane for sealing required when incorporating the PTFE membrane into the filter element Unlike the hydrophobic PTFE membrane, the hydrophilic material used in the hydrophilization process is thermally decomposed and eluted into the filtrate. It becomes like this.

Therefore, there is a conventional method of increasing the hydrophilicity by using a composite membrane or increasing the wettability by constructing a filter element, immersing the PTFE membrane in alcohol prior to use, and then substituting the alcohol with water. It is taken. However, the former has a problem in heat resistance and chemical resistance, and the latter takes a lot of steps and time.
In addition, the method of hydrophilizing the PTFE membrane as described above reduces the heat resistance (generally 120 ° C. or lower) and can withstand welding with a fluorine resin edge film or a fluorine resin end cap. The proper filter element could not be constructed.

Japanese Patent No. 3400052 discloses that in manufacturing a perfluorinated resin filter element equipped with a hydrophilic PTFE filtration membrane, the edge of the hydrophilic PTFE filtration membrane is previously joined with a hydrophobic PTFE membrane, and then the hydrophobic PTFE is used. A process for producing a filter element is described in which the end of the membrane is joined to the seal with the end cap.
However, in the method described in the patent, since the entire filtration membrane is a hydrophilic PTFE filtration membrane, the heat resistance of the membrane is reduced, and because of the heat of fusion when fusing with the hydrophobic PTFE membrane. The properties of the membrane subjected to hydrophilic treatment are deteriorated. Certainly, this method is less affected by heat because the heating time is shorter than when a hydrophilic PTFE membrane that does not have a hydrophobic PTFE membrane bonded to the edge is directly fused to the end cap, but heat resistance is reduced. Since the hydrophobic PTFE membrane is thermally bonded to the hydrophilized PTFE membrane at a temperature of 200 ° C. or higher by a hot roll or the like, the influence of heat fusion still remains.
Japanese Patent No. 3400052

As described above, in the conventional method, a porous hydrophobic resin film (PTFE film or the like) that has been subjected to a functionalization process such as a hydrophilization process is incorporated into the filter element through a process of heat-sealing to a high temperature. There is a problem that it is altered under the influence of the above and cannot exhibit a predetermined characteristic. Until now, it has been difficult to assemble a processed film that is vulnerable to thermal processing. For this reason, there existed a problem that a processing process took time and the target performance was not obtained.
Therefore, the present invention uses a porous hydrophobic resin membrane such as a porous PTFE membrane (filtration membrane) that has been subjected to a functionalization treatment such as a hydrophilic treatment by a method that is not affected by heat at all in the construction of the filter element. Objective.
Another object of the present invention is to provide a filter element useful for venting air such as air present or dissolved in the feed liquid.

That is,
(1) The present invention provides a filtration membrane in which a functional treatment such as a hydrophilization treatment is applied to the resin membrane except for a certain width of both edge portions of the porous hydrophobic resin membrane. Examples of the hydrophobic resin film used include PTFE, UPE, PP, PS, PES, and PVDF.
(2) In the present invention, an overlapping body of the filtration membrane and a support net that supports both sides of the filtration membrane is formed into an endless cylindrical shape by bending the pleated shape and sealing the side edges. A filter medium is provided.
(3) In the present invention, when the filtration membrane of (1) is made of a material having poor fusion properties such as PTFE, a thermoplastic resin is formed along the entire length of both hydrophobic edges of a certain width. A non-porous edge film made of heat is press-bonded, overlapped with a support net that supports both sides of the filtration membrane and the edge film, folded into a pleat shape, and side edges are sealed to form an endless cylindrical shape. A filter medium is provided.
(4) The present invention also provides a filter element in which the filter medium of (2) is supported by an inner core and a porous outer sleeve, and the upper and lower hydrophobic edges of the filter medium are thermally welded to an end cap. To do.
(5) In the present invention, the filter medium of (3) is further supported by a porous inner core and a porous outer sleeve, and an edge film provided on the hydrophobic upper and lower edge portions of the filter medium is a thermoplastic end. A filter element thermally welded to a cap is provided.
(6) The present invention is also a filter in which the hydrophobic upper and lower edge portions of a certain width leave a hydrophobic membrane portion between the fused portion to the end cap and the functionalized processing portion so that degassing is possible. Provide an element.

Preferred embodiments in the above (1) to (6) include the following.
First, porous hydrophobic resins that can be used in the present invention include PTFE (polytetrafluoroethylene) and PVDF (polyvinylidene fluoride) as fluorine-based resins, UPE (ultra high molecular weight polyethylene), PP (polypropylene), and other resins. It can be selected from PS (polysulfone), PES (polyethersulfone) and the like.
When the porous hydrophobic resin film is PTFE and a fluorine-based thermoplastic resin is used for the core, sleeve and end cap, it is preferable to use an edge film, and the material is fluorine-based Thermoplastic resins such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), FEP (tetrafluoroethylene-hexafluoropropylene copolymer) and EPE (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) Polymer-propylene hexafluoride copolymer) and a fluorine resin such as PVDF can be used.
When the porous hydrophobic resin film is PTFE and a thermoplastic resin such as PE or PP is used for the core, sleeve and end cap, the edge film may be a heat such as PE or PP. A plastic resin may be used, or an edge film is unnecessary.
If the porous hydrophobic resin membrane is not PTFE, an edge film is generally unnecessary.
Support net, inner core, outer sleeve and end cap include PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), PVDF and EPE Thermoplastic fluororesins such as (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer-hexafluoropropylene copolymer) and other thermoplastic resins such as PP or PE can be used. There is an appropriate combination between the hydrophobic resin film and these members.
(A) That is, when PTFE is used as the porous hydrophobic resin membrane, a hydrophilic treatment or an ion exchange imparting treatment is performed, and an inner core, an outer sleeve, and an end cap are thermoplastic fluororesins as an edge film. In this case, a fluororesin is used. Even when PTFE is used as the porous hydrophobic resin film, when the inner core, the outer sleeve, and the end cap are not thermoplastic fluororesins but PE, PP, etc., the edge film is PE, PP. Etc. or do not use edge film.
(B) When UPE is used as the porous hydrophobic resin membrane, it is subjected to hydrophilization or ion exchange imparting treatment, and the support net, inner core, outer sleeve, and end cap are either PP or PE thermoplastic. It is desirable to use a resin. Edge film is not necessary.
(C) When PP, PS, PES, and PVDF are used as the porous hydrophobic resin film, an ion exchange property imparting treatment is performed, and any of PP or PE as the support net, inner core, outer sleeve, and end cap is performed. Such thermoplastic resin is used. Edge film is not necessary.
However, as shown in the examples, an appropriate combination is selected according to the purpose of use and workability. In other words, the present invention can be applied to all conventional cartridge manufacturing methods.
The functionalization process includes a hydrophilic process and an ion exchange imparting process. Any method for performing these treatments on the hydrophobic resin film is known.

According to the present invention, since the influence of heat on the functionalized membrane part is completely eliminated, a filtration membrane having excellent filtration characteristics and ion exchange properties can be constructed, and the filter element using this can be treated with alcohol. Can be used directly for water filtration without need.
In addition, air or dissolved gas escapes from the hydrophobic portions on both sides that have not been subjected to a hydrophilic treatment, so that an air venting effect can be obtained. That is, the hydrophobic portion of the original material that has not been subjected to a hydrophilic treatment is a portion that melts for sealing with the end cap, but by appropriately controlling this dimension, a portion that does not consciously melt remains. Thus, air or dissolved gas in the treatment liquid can be extracted through the hydrophobic film portion between the molten portion and the portion subjected to the hydrophilic treatment (air does not permeate through the hydrophilic treatment portion).

In the following examples, a method of hydrophilization treatment will be described. However, since the ion exchange property imparting treatment is different only in the treatment liquid and other treatments or manufacturing steps are the same or similar, only the hydrophilization treatment will be described below. To do.
The hydrophilic treatment method itself has been conventionally known, and a functional product of the entire porous hydrophobic resin membrane is commercially available as, for example, a porous hydrophilic PTFE membrane (polytetrafluoroethylene membrane). In the present invention, such a porous hydrophilic PTFE membrane is not employed.

  In the hydrophilization treatment of the hydrophobic PTFE in the present invention, for example, as shown in FIG. 1, a hydrophobic porous PTFE film 108 having fine pores is fed from a supply roll 109, and a rotating roll 113 and a hydrophilization treatment liquid are supplied. Pass between device 110. The hydrophilization treatment liquid is supplied from the nozzle 112 to the hydrophobic PTFE through the reservoir in the coating apparatus 110 from the supply port 111. The width of the nozzle 112 is such that the treatment liquid is not applied to the integral width portion of both edges of the hydrophobic PTFE membrane. The treatment liquid changes the hydrophobic porous PTFE membrane to hydrophilic. Any other application method can be adopted. The obtained film is composed of a hydrophilic portion 105 and hydrophobic portions 106 on both sides thereof.

Hydrophilic treatment liquids are known and are described, for example, in JP-A-6-228359 and Japanese Patent No. 3340501. Alternatively, the hydrophilic PTFE filter membrane may be a hydrophilic PTFE filter membrane modified to be hydrophilic by excimer laser irradiation, plasma irradiation, electron beam irradiation, or the like. Examples of the latter are described in Patent Document 1 and Japanese Patent Laid-Open No. 10-85528.
In addition to this, as a treatment method that can obtain the same effect, it is conceivable to immerse the hydrophobic membrane itself in a functionalized treatment solution and then mask the part of both sides and apply a predetermined fixing treatment (curing). .

As shown in FIG. 2, the obtained hydrophobic porous PTFE membrane 102 subjected to the hydrophilic treatment is composed of the hydrophilic portion 105 and the hydrophobic portions 106 at both edges, and both the hydrophobic portions left untreated. A thermoplastic non-porous edge film 107 made of a thermoplastic fluororesin is thermocompression-bonded to the edge 106 with a hot roll heated to 200 ° C. or more, and then thermoplasticity that serves as a fluid passage for a supply liquid and a filtrate, respectively. It is sandwiched between support nets 101 and 104 made of fluorine resin. The support net also serves to support a porous PTFE membrane that is very flexible and easy to break.
Here, the thermoplastic fluororesin means a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), a tetrafluoroethylene-hexafluoropropylene copolymer (FEP), a tetrafluoroethylene, which is melted by heating. A thermoplastic fluororesin selected from an ethylene-perfluoroalkyl vinyl ether copolymer-propylene hexafluoride copolymer (EPE).
In the case where PTFE is used as the hydrophobic porous membrane and the fluorine resin member is heat-fitted, it is necessary to use a thermoplastic fluorine resin as the edge film. When a membrane other than PTFE is used as the hydrophobic porous resin membrane, the edge film may not be used.

The laminated body 100 having the structure of FIG. 2 is alternately folded in the opposite direction to form a pleat, and both side edges are overlapped and heat-sealed to make endless, thereby obtaining the filter medium of the present invention. Next, as shown in FIGS. 3 to 4, the filter medium is inserted between a porous inner core 2 made of a thermoplastic fluorine resin having a porous 3 and a porous outer sleeve 5 having a porous 4. The upper and lower edge ends are thermally welded to the upper and lower end caps 6 and 7 made of thermoplastic fluororesin according to a conventional method to complete the filter element 1 shown in FIG. The upper end cap 7 has an outlet 8 for drawing out the filtrate, and the lower end cap 6 closes the lower end of the filter element. The presence or absence of the opening depends on the design.
As shown in FIG. 3, a hydrophobic portion 106 is bonded to the upper and lower ends of the hydrophilic portion 105 of the PTFE membrane, and the hydrophobic portion 106 is integrally fused to the end caps 6 and 7 together with the edge film 107 bonded integrally thereto. It is worn.
When the edge film is not used, the porous hydrophobic portions at both edges of the functionalized membrane are directly heat-sealed with the end cap.

In the filter element 1 of the present invention, the hydrophobic portion at the upper edge is left between the portion fused to the end cap 7 and the hydrophilic portion 105. For example, when the edge film 107 is used, a portion of the upper edge hydrophobic portion near the functionalization processing portion is left so as not to be partially covered by the edge film. When the edge film is not used, the portion near the functionalized portion of the hydrophobic portion is left unfused when fused to the end cap.
FIG. 5 illustrates that the filter element of the present invention is useful for degassing. The filter element 1 constructed as described above is inserted into the housing 116 and the manifold 122 is attached (the mounting portion is not shown). A state in which the ring 114 and the manifold 122 are used for sealing is shown. A liquid inlet 115 is provided on the supply side of the liquid to be filtered, and the central flow path of the core 2 of the filter element is connected to the filtrate outlet 121. The supply liquid flows from the inlet 115 through the passage 119 between the sleeve 4 and the housing 116, and the filtrate that has passed through the filter medium 103 exits through the internal passage of the core 2 to the outlet 121.
As shown by the arrows in FIG. 5, the gas permeates the hydrophobic portion 106 of the membrane (the hydrophilic portion does not permeate) and exits to the top of the core. For this reason, the gas generated in the hydrophilized part rises to the upper part by buoyancy, passes through the hydrophobic part 106, and is quickly drawn out from the outlet 121 on the filtrate side, thereby preventing bubbles from staying and maintaining a large filtration area for the liquid. .

  On the other hand, FIG. 6 shows the case of the conventional filter element 1 ′ using the filter medium 103 ′ having no hydrophobic portion, and a liquid inlet 115 and a gas vent port 117 are provided on the supply side of the liquid to be filtered. A gas vent valve 123 is attached to the vent port 117. Air and other bubbles and dissolved gas rise through the passage 119 by buoyancy and are extracted from the vent port 117 through the gas vent valve 123 to the outside. It will be understood that the gas vent port 117 is not required in the present invention.

  An example of a method for manufacturing a filter element according to the present invention is as follows. In addition, processes other than the hydrophilization process are well-known, For example, the method described in the patent 3244730 is employable.

  1. Production of filtration membrane: Commercially available hydrophilization treatment liquid at the central portion excluding both edges of a long porous hydrophobic PTFE membrane having fine pores suitable for filtration purposes by the method described with reference to FIG. (PVP: polyvinyl pyrrolidone, PVA: polyvinyl alcohol) is applied to make it hydrophilic, and dried to obtain a composite filtration membrane comprising a hydrophilic portion 105 and hydrophobic portions 106 at both edges.

2. Fabrication of filter material: Next, a non-porous edge film 107 made of thermoplastic fluororesin is continuously supplied and superposed on the hydrophobic portions 106 on both edges of the hydrophilic hydrophobic hydrophobic PTFE membrane, and the melting point of the edge film The edge film is fused to the filtration membrane through a roll heater heated to the above temperature (for example, about 250 to 350 ° C. in the case of PFA or FEP).
For example, a hydrophobic PTFE membrane having an average thickness of 45 μm, an average pore diameter of 0.1 μm, and an average bubble point value of 2.0 kg / cm ² is used, and a PFA film (for example, a thickness of 12 μm) is used as an edge film on both edges. For example, by a roll heater heated to a temperature of about 270 ° C.
The softened edge film resin penetrates into the pores of the hydrophobic PTFE membrane filtration membrane, and the two are completely bonded by the anchor effect. Both edges of the edge film are trimmed together with a hydrophobic PTFE membrane with a cutter.
The obtained bonded body is laminated on both sides of support nets 101 and 104 made of thermoplastic fluorine resin (100 mesh net of PFA, non-woven fabric, perforated sheet, etc.), and this laminated body is folded into an accordion pleat shape. The laminated body is cut into a predetermined number of peaks, the laminated body is made into an endless shape, PFA or FEP film pieces are sandwiched between both side edges, and are fused and sealed with, for example, a hot stamp at about 320 ° C. to form a cylindrical pleat A mold filter medium 103 is obtained.
It is clear that substantially no heat is applied to the hydrophilic portion 105 of the porous PTFE membrane in this step.

  3. Potting step: Next, an end cap 6 (or 7) made of a thermoplastic fluororesin (for example, PFA) is inserted into a mold and heated to a temperature higher than its melting point, for example, about 250 to 350 ° C. in the case of PFA. Then melt. A state in which the filter medium 103 is supported between the porous inner core member 2 and the porous outer sleeve 4, the lower end portion is heated to soften the edge of the edge film 107 and the support net, and pushed into a predetermined depth inside the mold. Hold for about a few seconds, turn off the heat source and let cool for 5-10 minutes. The edge film 107 is integrated with the end cap 6 (or 7), and sufficient sealing is performed. Also at this time, it is clear that heat is applied to the edge film 107 and the hydrophobic portion on which it overlaps, but not to the hydrophilic portion.

  The present invention is widely used in the manufacture of semiconductor integrated circuits, the purification of chemicals and the like because the functionalized processing section is not affected by high heat and is excellent in precision filter film chemical resistance.

It is a schematic diagram which shows the process of the hydrophilic treatment of the porous hydrophobic PTFE filtration membrane of this invention. It is a perspective view which shows the structure of the filter medium of this invention. It is a fracture | rupture perspective view of the principal part of the filter element incorporating the filtering material of this invention. It is a perspective view of the filter element of this invention. It is sectional drawing of the filter apparatus incorporating the filter element of this invention. It is a figure which shows the gas vent structure of the conventional filter element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1 'Filter element 2 Inner core 3, 4 hole 5 Outer sleeve 6, 7 End cap 8 Outlet part 100 Laminated body 101, 104 Support net 102 Composite PTFE membrane
103, 103 'Filter medium 105 Hydrophilized part 106 Hydrophobic part 107 Edge film 109 Supply roll 110 Coating device 111 Supply port 112 Nozzle 113 Rotating roll 114 O-ring 115 Supply port 116 Housing 117 Gas vent port 119 Passage 123 Gas vent valve

Claims (10)

  A filtration membrane obtained by subjecting the resin membrane to a functionalization treatment such as a hydrophilization treatment except for a constant width portion at both edge portions of the porous hydrophobic resin membrane.   The filtration membrane according to claim 1, wherein the porous hydrophobic resin membrane is made of PTFE, UPE, PP, PS, PES, or PVDF.   3. Filtration formed into an endless cylindrical shape by folding a superposed body of the filtration membrane according to claim 1 and a support net that supports both sides of the filtration membrane into a pleated shape and sealing side edges. Wood.   The filtration membrane of claim 1 using PTFE as a porous hydrophobic resin membrane, and a non-porous edge film made of a thermoplastic resin thermally bonded along the entire length of both edges of the constant width hydrophobic portion, A filter medium formed into an endless cylindrical shape by folding a superposed body with a support net that supports both sides of the filter membrane and the edge film into a pleated shape and sealing side edges.   A filter element in which the filter medium according to claim 3 is supported by a porous inner core and a porous outer sleeve, and the upper and lower hydrophobic edges of the filter medium are thermally welded to an end cap made of a thermoplastic resin.   6. The filter element according to claim 5, wherein the porous hydrophobic resin film is made of PTFE, UPE, PP, PS, PES, or PVDF, and the porous inner core, the porous outer sleeve, and the end cap are made of PE or PP.   The filter medium according to claim 4 is supported by a porous inner core and a porous outer sleeve, and the edge film bonded to the hydrophobic upper and lower edges of the filter medium is thermally welded to an end cap made of a thermoplastic resin. Filter element.   8. The filter element of claim 7, wherein the edge film is made of PFA, FEP, or EPE, and the porous inner core, the porous outer sleeve, and the end cap are made of PFA, FEP, or EPE.   8. The filter element of claim 7, wherein the edge film is made of PE or PP, and the porous inner core, the porous outer sleeve, and the end cap are made of PE or PP.   The filter element according to any one of claims 5 to 9, wherein the hydrophobic upper and lower edge portions having a constant width leave a hydrophobic membrane portion between the fusion-bonding portion to the end cap and the functionalization processing portion.

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