JPH1057779A - Cartridge filter for precision filter membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a filter readily wettable with water and to easily and precisely measure the perfectness of the filter by holding a hydrophilic precision filter membrane having a specified average pore diameter made of polysulfone between two liq. permeable sheets including one hydrophilic sheet and pleating them. SOLUTION: A precision filter membrane 3 having 0.05-10μm average pare diameter made of polysulfone is held between two liq. permeable sheets 2, 4 including one hydrophilic sheet and they are pleated and wound around a core 5 having many liq. gathering holes. The membrane 3 is protected with an outer guard 1. End plates 6a, 6b are fitted to both ends of the resultant cylinder so as to seal the membrane 3. Each of the end plates 6a, 6b comes into contact with the sealing part of filter housing through a gasket 7. A filtered liq. is gathered from the liq. gathering holes in the core 5 and is discharged from an outlet 8.

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 microfiltration filter used for microfiltration of a liquid. More particularly, the present invention relates to a method of manufacturing a highly reliable cartridge-type polysulfone microfiltration filter.

[0002]

2. Description of the Related Art Microfiltration membranes have been known for a long time, and are disclosed in JP-A-63-139930 and JP-A-60-250049.
And those using polysulfone as a raw material described in Japanese Unexamined Patent Publications (Kokai) No. 1993/1996. Microfiltration membranes are used for filtration and sterilization of washing water for the electronics industry, pharmaceutical water, water for the pharmaceutical manufacturing process, food water, etc., and their use and usage are expanding in recent years. Microfiltration membranes have attracted attention and are widely used. And the polysulfone membrane is
There is known a membrane having a structure having a minimum pore diameter layer inside the membrane as described in No. 76510 or the like.

[0003] Various types of filtration modules and filtration elements have been manufactured and sold in order to increase the filtration flow rate and facilitate handling at the time of filtration using a microfiltration membrane. One of the typical filtration elements is a cartridge type filter which is so-called pleated in which a filtration membrane is folded and housed in a cartridge having a fixed capacity. In this case, when a filtration membrane having a small bending strength is used, it is damaged during pleating and loses its function as a microfiltration membrane. To remedy such inconveniences, both sides of the filtration membrane are reinforced with a non-woven fabric or a woven cloth, in order to reinforce the conventional filtration membrane and also to serve as a spacer that prevents contact between the filtration membrane surfaces,
Scissors with a net formed of a polymer, metal, or the like (for example, see JP-A-60-58208, US Pat.
2) Pleating the obtained sandwich type microfiltration membrane is performed.

In such a microfiltration cartridge filter, an "integrity test" is performed to increase the reliability of the filtration, and it is confirmed that the filter has no defects such as pinholes or breaks. One of the conventional methods for testing the integrity of microfiltration filter cartridges is the "bubble point method".
There is. When a gas pressure is applied to a microfiltration membrane wet with water, the pressure gradually increases from a low pressure to a high pressure. At a certain pressure, the gas suddenly starts to pass through the membrane pore, and the pressure at that time is called a bubble point. The maximum pore size of the microfiltration membrane is inversely related to the bubble point pressure, and if an abnormally large hole such as a pinhole is present in the membrane, a bubble point with a much lower pressure than expected is observed, and therefore, Incompleteness "can be found.

[0005] The "diffusion flow method" is used for integrity testing of a cartridge type microfiltration membrane having a large filtration area.
An inspection method called “pressure holding method” is generally used. In either method, a gas pressure lower than the bubble point of the membrane is applied to the microfiltration membrane that is well wetted with water, and the gas leakage to the secondary side of the membrane is measured. If a defect such as a pinhole is present in the film, a gas flow is generated or the pressure on the primary side fluctuates, so that the integrity of the film can be evaluated.

[0006]

As described above, in any method of measuring the integrity of a filter cartridge, the pores of a microfiltration membrane are filled with a liquid such as water and a gas pressure is applied.
The amount of gas permeation and the pressure at which permeation starts are measured. Therefore, if there is a part of the pores of the membrane that is not filled with the liquid, a large amount of gas permeates therefrom at a low pressure, and correct measurement cannot be performed. In filter cartridges, many membranes are folded or stacked in a certain volume, so even if the microfiltration membrane itself is very hydrophilic and easy to absorb water, bubbles in the pleated bundle will interfere when wetting the membrane. May create a location that is not wet by liquids. In particular, water, which is often used as a liquid, has a large surface tension, so that bubbles are hardly removed. For this reason, JIS K 383
2 "Method for testing bubble point of microfiltration membrane element and module" proposes a method in which the liquid on the primary side of the housing is exhausted while applying a filtration differential pressure of about 30 to 100 kPa to filter and wet the liquid.

However, even if the liquid is filtered under these conditions, it cannot always be completely wetted. The location that is hardly wetted by the liquid is not specified, but the location that is particularly difficult to get wet is where the membrane is liquid-tightly sealed with another member. For pleated filter cartridges,
The pleated membrane is rolled into a cylindrical shape and the fit is sealed, and both ends of the cylinder are then sealed to a plate called an end plate. It is difficult to completely wet the vicinity of such a membrane when sealing. Therefore, the diffusion flow rate becomes larger than the original value, and the bubble point value becomes smaller than the original value, so that the fluctuation is large. For this reason, it is not possible to distinguish between poor wetting and defects such as pinholes or tears in the filter, and it is easy to regard a non-defective product as a defect or mistake a defective product for a non-defective product. In the case of a cartridge filter using a polysulfone microfiltration membrane having a minimum pore size layer inside, the seal between the membrane and the end plate is particularly difficult to wet. on the other hand,
In order to apply a filtration pressure difference of 30 to 100 kPa between the primary side and the secondary side of the membrane, a large amount of water must be permeated. For this reason, there is a problem that a large-capacity pump is prepared, and in the pharmaceutical industry, a large amount of expensive distilled water is consumed and the cost is increased.

Japanese Patent Application Laid-Open No. 6-277466 discloses a method in which polyvinyl alcohol is adhered and applied only to a seal portion of a pleated cartridge filter membrane. However, in this method, polyvinyl alcohol is gradually eluted from the filter during filtration, contaminating the filtrate, and the amount of polyvinyl alcohol in the membrane seal portion is reduced, and eventually returns to the same state as uncoated.

Japanese Patent Publication No. 59-501251 proposes a method of eliminating a membrane hole only in a seal portion with an end plate. Several methods for eliminating holes have been proposed. In the method of crushing the hole at the end of the film with a roller or crushing with a heat sealer, the crushed film is thinned to a thickness of 1/3 or less of the original film, and the durability is significantly impaired, which is not practical. A method of laminating a reinforcing film in a place where the holes are crushed and thinned has also been proposed.However, film lamination is not only for safety where the film is thinner but also for places where the film thickness is thicker with some holes remaining for safety. Must also be done. Therefore, even if it is attempted to wind the film after the film is continuously laminated, a long film cannot be wound because there is a thick portion in the film. Pleating a film laminated with a film is very difficult.
Japanese Unexamined Patent Publication (Kokai) No. 59-501251 proposes a method of forming an integral sheet having only non-porous ends and a micro-porous central portion. Since the contraction rate and contraction force of the film in the film process differ greatly, it is very difficult to form a flat film that can withstand practical use.

[0010]

SUMMARY OF THE INVENTION The problem is that a microfiltration membrane sheet having an average pore size of 0.05 to 10 .mu.m is pleated and rounded, and the seam of the sheet is sealed in a liquid-tight manner. In a pleated cartridge filter formed by sealing both ends of a cylinder liquid-tight with an end plate, at least one hydrophilic microfiltration membrane made of polysulfone is placed between at least two hydrophilic liquid-permeable sheets. The problem was solved by a microfiltration membrane cartridge filter characterized by being sandwiched and crimped.
Hereinafter, the structure of the microfiltration membrane cartridge filter of the present invention and its manufacturing method will be described in detail.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an example of a development view showing the entire structure of a general pleated microfiltration membrane cartridge filter. The microfiltration membrane 3 is composed of two liquid-permeable sheets 2,
4 and folded around a core 5 having a large number of liquid collection ports. An outer guard 1 protects the microfiltration membrane on the outside. End plates 6a, 6b at both ends of the cylinder
Seals the microfiltration membrane. The end plate is in contact with a seal portion of a filter housing (not shown) via a gasket 7. The filtered liquid is collected from the liquid collecting port of the core and discharged from the outlet 8. FIG. 2 is a diagram schematically showing a state in which the membrane is sealed to the end plate. In the figures, 12 and 14 are cross sections of the liquid-permeable sheet, 13 is a cross section of the microfiltration membrane, and 17 is a cross section of the end plate. When the membrane and the end plate are sealed by heat, a part of the liquid-permeable sheet is melted by heat and integrated with the end plate. The liquid cannot easily enter the portion of the membrane inserted into the end plate because there is no escape space for air.

The microfiltration membrane that can be used in the present invention is preferably one using a polysulfone represented by the chemical formula 1 or 2 as a raw material. This shows a general manufacturing method for forming a microfiltration membrane using polysulfone. The polysulfone pellet is mixed with formamide, dimethylformamide, dimethylacetamide, dimethylsulfoxide,
-It is dissolved in a polar organic solvent such as pyrrolidone, N-methyl-2-pyrrolidone, sulfolane and the like. The solvent may be a single solvent or a mixture of plural types of solvents. In order to adjust the dissolving power of the solvent, a small amount of a solvent such as alcohol, such as methanol, ethanol, propanol or butanol, or water, which is called a non-solvent or a poor solvent, is often added. The amount of addition depends on the type of the solvent, but in the case of frequently used water, the amount is from 0.05% by weight to
%.

[0013]

Embedded image

To the above polysulfone solution, at least one kind of an inorganic electrolyte, an organic electrolyte, a polymer or the like, which is usually called a swelling agent or a foaming agent, is added to control the porous structure. Examples of the swelling agent that can be used in the present invention include hydrophilic polymers such as polyethylene glycol and polyvinylpyrrolidone, metal salts of inorganic acids such as salt, sodium nitrate, potassium nitrate, sodium sulfate, zinc chloride and magnesium bromide, sodium acetate, formic acid Organic acid salts such as sodium and potassium butyrate, polymer electrolytes such as sodium polystyrenesulfonate and polyvinylbenzyltrimethylammonium chloride, and ionic surfactants such as sodium dioctylsulfosuccinate and sodium alkylmethyltaurate are used. Some of these swelling agents alone show some effects even when added to the polymer solution, but when these swelling agents are added as an aqueous solution, they may show particularly remarkable effects. The addition amount of the swelling agent is not particularly limited as long as the uniformity of the solution is not lost by the addition, but it is usually 0.5% by weight to 35% by weight of the stock solution for film formation. The concentration of polysulfone as a film forming stock solution is 5 to 35% by weight, preferably 10 to 30% by weight.
When it exceeds 35% by weight, the water permeability of the obtained microporous membrane becomes so small that it has no practical meaning, and when it is less than 5% by weight, a microfiltration membrane having a sufficient separation ability cannot be obtained. .

The membrane-forming stock solution prepared as described above is cast on a support, and the polymer solution membrane together with the support is immersed in the coagulation solution immediately after the casting or after a certain period of time. Water is most commonly used as the coagulation liquid, but an organic solvent that does not dissolve the polymer may be used, or two or more of these non-solvents may be used in combination. As the support, a metal plate such as a copper plate or a stainless steel plate, a plastic sheet such as polyester or polyethylene, and a glass plate can be used. The casting membrane in which the polymer was precipitated in the coagulation liquid to form pores was peeled off the membrane from the support as necessary, followed by washing with water,
Perform hot water washing, solvent washing, etc., and dry. When a non-woven fabric, a woven fabric or paper is used as the support, the membrane is washed and dried as it is without peeling off the support.

A brief description will be given of a method for forming a polysulfone membrane having an inner minimum pore diameter layer, which is characterized in that it is hardly clogged, has a long-term filtration performance, and has a feature that the filtration layer is hidden inside the membrane and is not easily damaged. A temperature of 15-60 ° C. and a relative humidity of 10-80 ° C. are applied to the surface of a liquid film obtained by casting a film forming stock solution on a support.
%, The air speed adjusted in the range of 0.2 to 4 m / sec.
There is an important technique for appropriately adjusting the amount of evaporation of the solvent vapor and the amount of absorption of the non-solvent vapor from the atmosphere (absorption of moisture) by exposure for 40 seconds. For such a preparation, for example, a film forming stock solution is cast on a casting support, and is subjected to 25 ° C. and an absolute humidity of 2 ° C.
The coacervation phase is brought to a depth of 1 μm or more, preferably 1 to 30 μm from the outermost surface layer of the liquid film by applying air of gH ₂ O / kg Air or more to the casting surface at a wind speed of 0.2 m / sec or more. Can be formed. Immediately thereafter, it is immersed in a coagulation liquid to form a porous film. In the film obtained in this manner, the deepest part of the part where coacervation has occurred becomes the minimum pore diameter layer. The pore size on the back surface is 10 to 100 with respect to the pore size on the front surface of such an inner minimum pore size layer film.
About 0 times, and its specific surface area measured by BET method is 8 ~
80 m ² / g are obtained. A preferable specific surface area having both the mechanical strength and the filtration capacity of the membrane is 20 to 60 m ^2.
/ G. When the porosity of the membrane is increased, the permeability of water (liquid) is improved. However, when the porosity is too large, the membrane becomes brittle and cannot be used. Therefore, the preferred porosity is 55 to 87%, and particularly preferably 70 to 87%.
84%. The porosity of the membrane is greatly affected by the polysulfone concentration and the swelling agent concentration in the membrane-forming stock solution. When the polysulfone concentration is low and the swelling agent concentration is high, the porosity increases. It is slightly affected by the amount of water absorbed from the air immediately after film formation and the temperature of the coagulating liquid.

The method of hydrophilizing the surface of polysulfone, which is originally hydrophobic, includes a method of adding a hydrophilizing agent to the film forming stock solution and a method of hydrophilizing the surface of the polysulfone skeleton by chemical treatment after forming the porous film. There is a way to do that. In the former method, polyethylene glycol, polyvinylpyrrolidone, sulfonated polysulfone (Japanese Patent Publication No. 5-705)
4) and a hydrophilic polyurethane prepolymer (U.S. Pat. No. 4,137,200, U.S. Pat. No. 130,82).
No. 6 (described on Dec. 9, 1987) or the like) in an amount of 5 to 65% by weight based on the amount of polysulfone.
Added. Some or most of the added hydrophilic polymer dissolves in the coagulation solution and is lost, or is lost in the subsequent washing process.However, in such a film forming process, the hydrophilic polymer is largely distributed on the surface of the polysulfone skeleton. , Resulting in a hydrophilic polysulfone microfiltration membrane. As disclosed in JP-A-7-51550, a chemical treatment after film formation is performed by coating a monomer comprising hydroxyalkyl acrylate or methacrylate, acrylamide or methacrylamide, polar substituted acrylate or methacrylate, etc. on a hydrophobic microfiltration membrane. For free radical polymerization.

The microfiltration membrane 13 formed in this manner is usually folded by a known method. Liquid permeable sheet 1
Nonwoven fabric, woven fabric, paper, and / or net are used as 2 and 14. The folds of the filter media are cut off using a cutter knife or the like to cut the irregular portions at both ends in order to align both ends, and then rounded into a cylindrical shape. Or a liquid-tight seal using an adhesive.

The liquid-permeable sheet used in the present invention is usually a hydrophilic liquid-permeable sheet. In particular, it is essential that the liquid-permeable sheet used on the primary side of the filtration membrane is hydrophilic. The hydrophilicity of a liquid-permeable sheet means that the liquid-permeable sheet has a greater affinity for water than air, and when the liquid-permeable sheet comes into contact with water, it naturally absorbs water without applying extra force. It refers to releasing air. The measure of hydrophilicity is that, for example, if a water droplet of 0.2 ml is gently placed on a liquid-permeable sheet placed on a desk, the water droplet will sit on the sheet within 2 minutes and lose the round shape of the water droplet. It is highly preferred that the sheet has such a hydrophilic property that water droplets are absorbed by the sheet within 20 seconds. The general role of the liquid permeable sheet is firstly to guide the liquid to be filtered into the interior of the membrane folds so that the entire membrane folded into the cartridge can be used effectively for filtration. The second role of the liquid-permeable sheet is to protect the microfiltration membrane. Therefore, the liquid-permeable sheet is required to have a large number of voids and low liquid-permeation resistance, and an appropriate strength. Furthermore, in the present invention, as a third role, it is necessary to easily release bubbles during filtration to increase the contact area between the microfiltration membrane and the liquid.

Most liquid-permeable sheets used in conventional pleated microfiltration membrane cartridge filters are nonwoven fabrics of hydrophobic polyester or polypropylene. However, such a hydrophobic nonwoven fabric retains and hardly releases bubbles during filtration, and thus the membrane is hardly in contact with the filtered liquid and the membrane is hardly wetted by the liquid. In particular, air bubbles are difficult to escape at the seal portion of the end plate, and the holes of the membrane inserted into the seal portion have no escape route for air, so that they are particularly hard to wet with liquid. However, when a hydrophilic liquid-permeation sheet having a small contact angle with water and easily penetrating water is used, bubbles are easily released from the liquid-permeation sheet gap, and the membrane comes into direct contact with the liquid (water). Becomes very wet with liquids.

The hydrophilic liquid-permeable sheet may be a woven fabric, nonwoven fabric or paper made of hydrophilic cellulose, or a woven fabric obtained by making the surface of a hydrophobic polymer fiber such as polyester or polypropylene hydrophilic by chemical treatment or physical treatment. There are cloths and nonwovens, and glass fiber nonwovens. As the chemical treatment of the surface of the hydrophobic polymer fiber, a method of covering the fiber surface with a thin film of gelatin or polyvinyl alcohol, vinylpyrrolidone, acrylic acid, metal acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, polyethylene glycol mono- or di-glycol is used. There is a method in which a water-soluble monomer such as acrylate and acrylamide is applied to the fiber and polymerized in situ. As the physical treatment, there is a method in which corona discharge or glow discharge is performed on the surface of the fiber to impart a hydrophilic group to the surface. Also, a woven or non-woven fabric having an appropriate hydrophilic property by mixing a hydrophilic rayon fiber and a hydrophobic polyester fiber or polypropylene fiber can be used. In this case, at least 20% by weight or more of rayon fiber is required to impart necessary hydrophilicity, and preferably 35% by weight or more of rayon fiber is required.

The width of the pleat pleats is usually pleated so as to be 5 mm to 25 mm. In the present invention, the diameter is preferably set to 5 mm to 12 mm in order to easily release bubbles. Especially 7
It is preferable to set the distance from mm to 10.5 mm. There are several end sealing processes depending on the end plate material.
All are performed by a conventionally known technique. When using a thermosetting epoxy resin for the end plate,
After the liquid of the prepared epoxy resin adhesive is poured into the potting mold and preliminarily cured to increase the viscosity of the adhesive to an appropriate level, one end face of the cylindrical filter medium is inserted into the epoxy adhesive. After that, it is completely cured by heating. When the material of the end plate is a thermoplastic resin such as polypropylene or polyester, a method of inserting one end surface of a cylindrical filter medium into the resin immediately after pouring the hot-melted resin into a mold is performed. On the other hand, only the sealing surface of the already molded end plate is brought into contact with the hot plate or irradiated with an infrared heater to melt only the plate surface, and one end surface of the cylindrical filter medium is pressed against the molten surface of the plate and welded. The method is also performed. The state of air bleeding also changes depending on the structure of the outer peripheral guard 1 used. Preferably, as shown in FIG. 3, a small window may be provided to allow air to escape when sealing the outer peripheral guard with the end plate.

[0023]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to the contents of the examples.

Example 1 An example of forming a microfiltration membrane using polysulfone as a raw material will be described. Polysulfone (Amoco P-3500) 15
Parts, 70 parts of N-methyl-2-pyrrolidone, 15 parts of polyvinylpyrrolidone, 2 parts of lithium chloride, and 1.3 parts of water are uniformly dissolved to prepare a stock solution for film formation. The product thickness is 18
Cast to 0 μm, temperature 25 ° C, relative humidity 50
%, Air of 1.0 m / sec was applied to the surface of the liquid film cast for 8 seconds, and immediately immersed in a coagulation bath filled with water at 25 ° C. to obtain a microporous film. The bubble point of this membrane due to water is 1
It was 50 kPa.

Example 2 A film made in Example 1 was sandwiched between two rayon nonwoven fabrics having a basis weight of 50 g / m ² and pleated to a pleat width of 10 mm.
Remove the 125 ridges and roll them into a cylinder and seal the joint with epoxy adhesive. Cut off both ends of the cylinder 5mm each, seal the cut surface with epoxy adhesive,
Finished as a cartridge filter. Water was permeated through the cartridge filter at a flow rate of 160 liters / h for 15 minutes, and then the amount of air permeation was measured with an air pressure of 100 kPa applied to the cartridge filter. The permeation amount was 8 ml / min or less. The water wettability of the cartridge filter was good.

Example 3 55% by weight of rayon having a fineness of 2.0 d and 45% by weight of polyester having a fineness of 1.5 d were mixed to produce a nonwoven fabric sheet having a basis weight of 35 g / m ² . The film of Example 1 is sandwiched between the two nonwoven fabrics, pleated to a fold width of 10 mm, folds of 145 ridges are taken out, rounded into a cylinder, and the joint is sealed with an epoxy adhesive. The cylinder was cut off at both ends by 5 mm, and the cut surface was sealed with an epoxy adhesive to complete a cartridge filter. Water was permeated through the cartridge filter at a flow rate of 160 liters / h for 15 minutes, and then the amount of air permeation was measured with an air pressure of 100 kPa applied to the cartridge filter. The permeation amount was 8 ml / min or less. The water wettability of the cartridge filter was good.

Example 4 5 parts of polyethylene glycol diacrylate (NK ester A600 manufactured by Shin-Nakamura Chemical Co., Ltd.), polymerization initiator V-5
0, 0.3 part of 0, 40 parts of diethylene glycol and 55 parts of water were prepared as a coating solution. Polyester nonwoven fabric (Unitika Marix 70500, basis weight 50g /
m ² , thickness 0.23 mm)
Heat polymerization at 120 ° C for 20 minutes in a nitrogen atmosphere, and in hot water at 60 ° C
Wash and dry for 20 minutes. The membrane of Example 1 was sandwiched between the two hydrophilic nonwoven fabrics thus formed, pleated to a pleat width of 10 mm, 155 ridges of the pleat were taken out and rounded into a cylinder, and the joint was formed by an impulse sealer. Then, both ends of the cylinder are welded to an end plate made of polypropylene to complete a cartridge filter. The water wettability of this cartridge filter is such that the air permeation amount is 8 ml /
Minutes or less was good.

Example 5 5 parts of polyethylene glycol diacrylate (NK ester A600 manufactured by Shin-Nakamura Chemical Co., Ltd.), polymerization initiator V-5
0, 0.3 part of 0, 40 parts of diethylene glycol and 55 parts of water were prepared as a coating solution. Polypropylene nonwoven fabric (Mitsui Petrochemical Industry Syntex PS-1
06, a basis weight of 30 g / m ² , a thickness of 0.28 mm, and a fineness of 2.0 d) are immersed in this coating solution, taken out, heated and polymerized in a nitrogen atmosphere at 120 ° C. for 20 minutes, and washed in hot water at 60 ° C. for 20 minutes. And dry.
Example 1 between two hydrophilic nonwoven fabrics thus produced
Pleated to a pleat width of 10.5 mm, sandwiched the pleats of 140 mountains, rolled into a cylinder, welded the joint with an impulse sealer, and welded both ends of the cylinder to a polypropylene end plate. And complete the cartridge filter. The water wettability of the cartridge filter was good when the air permeation amount was 8 ml / min or less.

[0029]

According to the present invention, the polysulfone microfiltration membrane cartridge filter can be very easily wetted with water. As a result, the integrity of the filter can be measured easily and with high accuracy, and thus more reliable filtration can be performed. In particular, the effect is remarkable in anisotropically structured membrane cartridge filters in which the pore diameters on both surfaces of the membrane are at least twice the pore diameter of the smallest pore size layer inside the membrane.

[Brief description of the drawings]

FIG. 1 is a view illustrating a structure of a general pleated cartridge filter.

FIG. 2 is a diagram illustrating a structure near an end seal portion according to the embodiment of the present invention.

FIG. 3 is a diagram in which a small air vent window is installed on an outer guard.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Perimeter guard 2 Liquid permeable sheet 3 Filtration membrane 4 Liquid permeable sheet 5 Core 6a End plate 6b End plate 7 Gasket 8 Outlet 9a Air vent small window 9b Air vent small window 9c Air vent small window 12 Liquid permeable sheet 13 Filtration membrane 14 Pass Liquid sheet 17 End plate

Claims (7)

[Claims] 1. A microfiltration membrane sheet having an average pore size of 0.05 to 10 μm is fold-folded, and the seam of the rounded sheet is sealed in a liquid-tight manner, and both ends of the cylinder are also end plates. In a pleated cartridge filter that can be sealed in a liquid-tight manner, a hydrophilic microfiltration membrane made of polysulfone is folded and folded between at least two liquid-permeable sheets, at least one of which is hydrophilic. A microfiltration membrane cartridge filter characterized by the following. 2. The microfiltration membrane cartridge filter according to claim 1, wherein a microfiltration membrane having an anisotropic structure having a minimum pore size layer in the thickness direction is used. 3. The microfiltration membrane cartridge filter according to claim 1, wherein the liquid-permeable sheet is a nonwoven fabric. 4. The microfiltration membrane cartridge filter according to claim 1, wherein the liquid-permeable sheet is a woven fabric. 5. The microfiltration membrane cartridge filter according to claim 1, wherein the width of the pleated fold is 5 mm or more and 12 mm or less. 6. The microfiltration membrane cartridge filter according to claim 2, wherein the porosity is 55 to 87%. 7. The microfiltration membrane cartridge filter according to claim 2, wherein the specific surface area is 8 to 80 m ² / g.