JPH1099661A - Micro filtration membrane cartridge filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily wet a filter with water, easily and precisely measure the perfectness of the filter, and raise the reliability by adding a cross linking monomer to holes in both end parts of a cylindrical pleated membrane, carrying out polymerization, and losing ventilative property. SOLUTION: A cross linking monomer is added to holes in both end parts of a cylindrical pleated membrane and the monomer is polymerized to lose ventilative property. As the cross-linking monomer material, hydrophilic vinyl monomer, acrylates and methacrylates type monomer are preferably used. A solution produced by adding solely these monomers or their mixtures additionally mixed with multifunctional vinyl monomer and an initiator is applied to both end parts of a membrane and polymerization reaction is carried out to form hydrophilic polymer in the membrane holes. The concentration of the solution to be applied is preferably about 10-50wt.%. On the other hand, the necessary buried amount of the polymer to bury the holes of the membrane and lose the ventilation is at the lowest about 1mg/cm<2> per unit surface area of the membrane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a microfiltration filter used for microfiltration of a liquid. More specifically,
The present invention particularly relates to a highly reliable cartridge type microfiltration filter.

[0002]

2. Description of the Related Art Various types of filtration modules and filtration elements are 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 in which a filtration membrane is pleated 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. A pleated filter cartridge in which both ends are reinforced to reinforce the filtration membrane is described in JP-A-64-34403.

Japanese Patent Application Laid-Open No. 6-277466 discloses a method in which polyvinyl alcohol is adhered and applied only to the seal portion of a pleated cartridge filter membrane.
Japanese Patent Publication No. 59-501251 proposes a method of eliminating a membrane hole only in a seal portion with an end plate. Further, Japanese Patent Publication No. 59-501251 proposes a method of forming an integrated sheet having only a non-porous film at both ends and a micro-porous film at the center. In this case, since the contraction force of the film in the film formation process is greatly different, it is very difficult to form a flat film that can be practically used.

[0004]

As described above, in any of the methods for measuring the integrity of a filter cartridge, the pores of a microfiltration membrane are filled with a liquid, a gas pressure is applied, and the amount of gas permeation and the pressure at which permeation starts are determined. Is 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 the filter cartridge, many membranes are folded or stacked in a certain volume,
When wetting the membrane, air bubbles can interfere and create areas that are 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, in JIS K 3832 “Testing method for bubble point of microfiltration membrane element and module”, it is necessary to discharge air from the primary side of the housing to about 30 to 100 kP.
A method is proposed in which the liquid is filtered and wetted by applying the filtration pressure difference a. However, filtration of the liquid under these conditions does not always ensure perfect wetting. 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 good product as a bad product or mistake a bad product for a good product.
In the case of a cartridge filter using a 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.

[0005]

The above problem can be solved by providing a crosslinkable monomer in advance to the membrane pore only in the vicinity of the seal portion and polymerizing the monomer. Taking the pleated type cartridge filter as an example, the microfiltration membrane sheet is fold-folded, the seam of the rounded sheet is sealed liquid-tight, and both ends of the cylinder are also liquid-tight with end plates. In a pleated cartridge filter formed by sealing, a microfiltration membrane cartridge characterized in that a crosslinkable monomer is applied to the pores at both ends of a cylindrical pleated membrane, and liquid permeability is lost by polymerizing the monomer. Achieved by filters. Hereinafter, the structure of the microfiltration membrane cartridge filter of the present invention and its manufacturing method will be described in detail.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an example of a developed view showing the entire structure of a general pleated microfiltration membrane cartridge filter. The microfiltration membrane 3 is folded in a state sandwiched by two nonwoven fabrics 2 and 4 and wound around a core 5 having many liquid collecting ports. An outer guard 1 protects the microfiltration membrane on the outside.
Microfiltration membranes are sealed at both ends of the cylinder by end plates 6a and 6b. 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 5 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 nonwoven fabric, 13 is a cross section of the microfiltration membrane, and 17 is a cross section of the end plate.

[0007] The microfiltration membrane that can be used in the present invention is not particularly limited in terms of membrane material, pore structure, and the like. The production method of the microfiltration membrane is roughly classified into a solution method and a heat melting method. Here, a general production method by the solution method will be described. In the solution method, known polymers such as vinyl polymers such as polyvinylidene fluoride, polyacrylonitrile and polyvinyl chloride, polysulfones, polyethersulfones, aliphatic polyamides and cellulose esters can be used alone or as a mixture. The production of the microfiltration membrane is performed by dissolving the polymer in a good solvent, a mixed solvent of a good solvent and a non-solvent or a mixture of a plurality of solvents having different degrees of solubility in the polymer to prepare a film forming stock solution. Is cast on a support or directly in a coagulating liquid, and washed and dried. In this case, examples of the solvent for dissolving the polymer include dichloromethane, acetone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, 2-pyrrolidone, N-methyl-2-pyrrolidone, and sulfolane. Examples of the non-solvent to be added to the solvent include water, cellosolves, alcohols such as methanol, ethanol and isopropanol, ketones such as acetone and methyl ethyl ketone, ethers such as tetrahydrofuran and dioxane, and polyols such as glycerin and ethylene glycol. And the like. The ratio of the non-solvent to the good solvent may be any range as long as the mixed solution can maintain a uniform state, but is preferably 5 to 50% by weight.

Further, an inorganic electrolyte, an organic electrolyte, a polymer or the like, which is called a swelling agent, can be added to control the porous structure. Examples of swelling agents 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, polyvinylpyrrolidone and polyvinylbenzyltrimethylammonium chloride, and ionic surfactants such as sodium dioctylsulfosuccinate and sodium alkylmethyltaurate are used. . Although some of these electrolytes show a certain effect even when added alone to the polymer solution, when these electrolytes are added as an aqueous solution, a particularly remarkable effect may be exhibited. The addition amount of the electrolyte aqueous solution is not particularly limited as long as the uniformity of the solution is not lost by the addition, but is usually 0.5% by volume to 10% by volume based on the solvent. The concentration of the aqueous electrolyte solution is not particularly limited, and the higher the concentration, the greater the effect. However, the concentration generally used is 1% by weight to 60% by weight. The polymer concentration as a film forming stock solution is 5 to 35% by weight, preferably 10 to 3% by weight.
0% by weight. When the amount exceeds 35% by weight, the water permeability of the obtained microporous membrane becomes so small as to have no practical meaning. When the amount is less than 5% by weight, a microfiltration membrane having a sufficient separation ability cannot be obtained. .

The 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 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. The support can be arbitrarily selected from those which can be used as a support when a microfiltration membrane is usually produced. However, a non-woven fabric is particularly preferable because the support does not need to be peeled off. The nonwoven fabric that can be used in the present invention is a general one made of polypropylene, polyester, or the like, and is not limited by the material. The cast film in which the polymer is precipitated in the coagulation liquid is then washed with water, washed with warm water, washed with a solvent, etc., and dried.

The average pore size of the microfiltration membrane that can be used in the present invention is preferably 0.05 to 10 μm,
More preferably, it is 0.1 to 5 μm. Further, as the microfiltration membrane, it is preferable to use a microfiltration membrane having an anisotropic structure having a minimum pore size layer in the thickness direction.

The microfiltration membrane 13 formed as described above is usually folded by a known method. Liquid permeable sheet 1
Nonwoven fabric, paper, and / or net are used as 2 and 14. The folds of the filter media are cut off using a cutter knife, etc. to align the ends, and then rounded off into a cylindrical shape, and the folds at the joint are sealed liquid-tight using a heat seal or adhesive. I do.

Although there are several methods for the end sealing step depending on the material of the end plate, all of them are performed by a conventionally known technique. When using a thermosetting epoxy resin for the end plate, pour the liquid of the prepared epoxy resin adhesive into the potting mold, pre-cure it, and make the viscosity of the adhesive moderately high. One end 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,
Immediately after the hot-melt resin is poured into a mold, one end surface of a cylindrical filter medium is inserted into the resin. 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 process of imparting a crosslinkable monomer to the hole at the end of the membrane and polymerizing it is a feature of the present invention. There is a way to do it later. When the treatment is performed before pleating, the treatment liquid is simultaneously applied only to both ends of the film by a known method such as a gravure coater or a bar coater, and is passed through a temperature lowering zone. And then wound up. When a crosslinkable monomer is also applied to the hole near the seam where the cylindrical pleated film is rounded and polymerized, a higher effect may be obtained. In the latter case, the treatment liquid is applied by a known method. As a method for applying the processing liquid, an immersion method in which the end of the cylindrical membrane is immersed in the processing liquid adjusted to an appropriate viscosity, a filter is pressed on a porous flexible carrier that supports the processing liquid, and the processing liquid is impregnated with the processing liquid. `` Pressing method '' to apply, `` Applying method '' to apply the processing liquid to the filter using a brush etc. carrying the processing liquid, `` Spraying method '' to spray the processing liquid in the form of a mist and spray on the end face of the filter "Dispensing method" in which the processing liquid is applied to the end while extruding the processing liquid from a cylinder having a circular or band-shaped tip, but a certain amount of the processing liquid is applied to the end, which adversely affects the processing liquid and the film. Any method can be used as long as it selects a method that does not affect the condition.
Next, if necessary, an excess liquid is removed to carry out a polymerization reaction.

As the crosslinkable monomer material for losing the air permeability of the microfiltration membrane, hydrophilic monomers such as hydrophilic vinyl monomer, poly (oxy) di (meth) acrylate, and polypropylene glycol di (meth) acrylate are preferably used. They are used, among which hydrophilic vinyl monomers are preferred. Specific examples include vinyl alcohol (as a structural unit), hydroxyethyl acrylate, hydroxymethyl methacrylate, vinyl pyrrolidone, acrylamide,
Examples include hydrophilic vinyl monomers such as diethylene glycol diacrylate, polyethylene glycol diacrylate, polyethylene glycol monoacrylate, acrylic acid, vinyl sulfonic acid, p-styrene sulfonic acid, and derivatives thereof, and glycerin (meth) acrylate, methylene bisacrylamide. And pentaerythritol di (meth) acrylate, among which acrylate and / or methacrylate monomers are preferred. A solution obtained by adding a polyfunctional vinyl monomer and a polymerization initiator to these monomers alone or in a mixture is applied to both ends of the membrane, and a polymerization reaction is carried out, whereby a hydrophilic polymer can be formed in the pores of the membrane. Further, it may be copolymerized with a monofunctional monomer. The concentration of the applied solution depends on the monomer group used, but is preferably 10 to 50% by weight, more preferably 15 to 45% by weight.
When the concentration of the monomer group in the solution is less than 10% by weight, the polymerization rate may be remarkably lowered regardless of the type of polymerization initiator used. On the other hand, if it exceeds 50% by weight, polymerization may start before or during the application of the solution, resulting in disadvantageous workability. The amount ratio of the polymerization initiator to the monomer group depends on the type of the monomer group and the polymerization initiator used, but is preferably 0.05 to 0.2 mol per 1 mol of the monomer group. If the amount is less than 0.05 mol, the conversion may decrease, and if it exceeds 0.2 mol, it may be economically disadvantageous.

The conditions for carrying out the polymerization reaction depend on the type of the monomer group and the polymerization initiator to be used.
It is preferable to carry out in. More preferably, from 60 ° C. to 1
20 ° C. When the reaction temperature is lower than 50 ° C., the polymerization reaction may not sufficiently occur, and when a sufficient reaction is performed, it takes a long time and causes high cost. Also,
If the temperature exceeds 150 ° C., the physical properties and chemical properties of the film may be adversely affected. A high effect may be obtained by setting the atmosphere of the polymerization reaction to a low oxygen concentration state. The method of low oxygen concentration state is helium,
Using a chemically inert gas such as neon, argon, nitrogen, or carbon dioxide, and replacing the atmosphere with a high oxygen concentration atmosphere such as air. By maintaining the temperature of the polymerization reaction at an appropriate temperature, a higher effect may be obtained. It is desirable that the oxygen concentration in the low oxygen concentration state be 1% or less, more preferably 0.1% or less.
If the oxygen concentration exceeds 1%, the polymerization reaction may not be sufficiently performed, and the gas permeability may not be sufficiently reduced. Those skilled in the art can easily understand the combination of the hydrophilic monofunctional monomer, the polyfunctional monomer and the polymerization initiator and the ratio of each material by a simple experiment. Examples 1 and 2 show examples of polyethylene glycol dialkylate and polyethylene glycol monoacrylate, which are particularly preferred materials.

After the completion of the reaction, the film is washed with water and dried in order to remove unreacted unnecessary components such as a processing solution from the film. If necessary, wash the membrane with hot water. When washing with hot water, washing is preferably performed at 50 ° C. or higher. More preferably, it is 70 ° C. or higher. When cleaning is performed at a temperature lower than 50 ° C., the effect can be expected sufficiently without performing cleaning with hot water. In addition, depending on the form and properties of the film at the time of cleaning, cleaning with water and / or hot water may not sufficiently remove unnecessary components. In this case, a higher effect may be obtained by impregnating the membrane with an appropriate aqueous solution before washing with water to increase the affinity of the membrane with water.
Components that constitute a suitable aqueous solution are water-soluble organic substances such as ethanol, methanol, isopropanol, glycerin, sucrose, and a surfactant, and water-soluble inorganic substances such as sodium chloride and ammonium sulfate, and water. The concentration of the solute that can be expected to increase the affinity of the membrane for water is preferably from 10% by weight to 45% by weight. More preferably, 25% by weight
To 35% by weight. If less than 10% by weight,
The purpose of increasing the affinity of the membrane for water was not met,
If the content exceeds% by weight, the cost is high and it is not practical.

The amount of the polymer to be buried necessary to fill the pores of the membrane to eliminate air permeability must be at least 1 mg / cm ² per unit area of the membrane. Preferably, if the amount is 2 mg / cm ² or more, the object can be achieved almost certainly. If a large amount of polymer is buried in the pores more than necessary, the membrane becomes hard and brittle, and the sealing performance with the end plate tends to deteriorate,
Care must be taken as it may cause inconvenience. If holes on both surfaces of the membrane are left unfilled and polymer material is embedded only in the holes inside the membrane, a liquid-tight seal can be obtained with most end plate materials. When the polymer material is buried up to the holes on the surface, it is necessary to select a material having good adhesiveness with the polymer material as the end plate material. It is sufficient that the width of the burying treatment of the polymer material is 2 mm or more from the edge of the film. Unnecessary processing width is disadvantageous because the effective membrane area for filtration is reduced.

[0018]

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 1) Production of microfiltration membrane An example of the production of a microfiltration membrane made of polysulfone is shown. 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 average pore size of this membrane was 0.8 μm, and the porosity was 82%. The bubble point of this film due to water was 150 kPa.

2) Production of cartridge filter and evaluation of performance 25 parts of polyethylene glycol diacrylate (manufactured by Shin-Nakamura Chemical Co., NK Ester A600), 1 part of polymerization initiator (manufactured by Wako Pure Chemical Industries, V-50), ethylene glycol A uniform solution composed of 37 parts and 37 parts of water was prepared and used as a coating solution. The film 3m of the above 1) is pleated by sandwiching it between two polypropylene nonwoven fabrics (PS106, manufactured by Mitsui Petrochemical Industries, Ltd.), rolled into a cylindrical shape, and heat-sealed at the joint of the film. Alternately, apply 2 g of a coating solution and heat at 90 ° C. for 30 minutes while replacing with humidified nitrogen. 3
Immersed in 0% by weight ethanol aqueous solution for 10 minutes,
After washing with water for 0 minutes, washing with hot water at 80 ° C. for 30 minutes, and drying, both ends of the cylinder are welded to an end plate made of polypropylene to complete a cartridge filter. The water permeation of this cartridge filter is 8 m
It was good at 1 / min or less. The water wettability of the cartridge filter was measured by passing cold water through the dried cartridge filter at a flow rate of 4 liters per minute for 10 minutes, and then applying an air pressure of 100 kPa gauge to measure the amount of air permeation. .

Example 2 5 parts of polyethylene glycol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., NK ester A600), polyethylene glycol monoacrylate (manufactured by NOF Corporation, AE-350)
20 parts, 1 polymerization initiator (V-50, manufactured by Wako Pure Chemical Industries, Ltd.)
, A homogeneous solution consisting of 37 parts of ethylene glycol and 37 parts of water was prepared as a coating solution. The membrane 3m produced in 1) of Example 1 was pleated by sandwiching it between two polypropylene nonwoven fabrics (PS106, manufactured by Mitsui Petrochemical Industries, Ltd.).
Rolled into a cylindrical shape, heat-sealed the joint of the membrane, and alternately immersed both ends of the formed cylinder in a coating solution having a depth of 3 mm.
Thereafter, heating is performed at 90 ° C. for 30 minutes. After washing with hot water at 80 ° C. for 30 minutes and drying, both ends of the cylinder are welded to an end plate made of polypropylene to complete a cartridge filter. The water wettability of the cartridge filter was good when the air permeation amount was 8 ml / min or less.

Comparative Example 1 The film 3m of Example 1 was pleated by sandwiching it between two polypropylene nonwoven fabrics (PS106, manufactured by Mitsui Petrochemical Industries, Ltd.), rolled into a cylindrical shape, and heat-sealed at the joint of the film.
Both ends of the cylinder are welded to a polypropylene end plate to complete the cartridge filter. The water wettability of this cartridge filter is 100 m
1 / min or more was defective.

[0022]

According to the present invention, the microfiltration membrane cartridge filter can be very easily wetted with water. As a result, the integrity of the filter (meaning that there are no large holes or crevices that may cause a defect in the filter, etc.) can be measured easily and with high accuracy, so that more reliable filtration can be performed.

[Brief description of the drawings]

FIG. 1 shows the structure of a general pleated cartridge filter.

FIG. 2 shows a structure near an end seal portion in the embodiment of the present invention.

[Description of Signs] 1 Peripheral guard 2 Liquid permeable sheet 3 Filtration membrane 4 Liquid permeable sheet 5 Core 6a End plate 6b End plate 7 Gasket 8 Outlet 12 Liquid permeable sheet 13 Filtration membrane 14 Liquid permeable sheet 17 End plate

Claims (7)

[Claims] 1. A microfiltration membrane sheet is pleated and rolled into a cylindrical shape, and the seam of the sheet is sealed in a liquid-tight manner.
Furthermore, in a pleated cartridge filter in which both ends of the cylinder are also liquid-tightly sealed with an end plate, a crosslinkable monomer is applied to the holes at both ends of the cylindrical pleated membrane, and this is polymerized to lose air permeability. A microfiltration membrane cartridge filter characterized by the following: 2. The microfiltration membrane cartridge filter according to claim 1, wherein the crosslinkable monomer imparted to the pore is a hydrophilic monomer. 3. The microfiltration membrane cartridge filter according to claim 1, wherein the crosslinkable monomer imparted to the pores is a hydrophilic vinyl monomer. 4. The microfiltration membrane cartridge filter according to claim 1, wherein the crosslinkable monomer provided to the pores is an acrylate and / or methacrylate monomer. 5. A microfiltration membrane having an anisotropic structure having a minimum pore size layer inside a film thickness direction.
7. The microfiltration membrane cartridge filter according to the above. 6. The microfiltration membrane cartridge filter according to claim 1, wherein only the pores inside the membrane are filled with the crosslinking monomer, and pores remain on both the front and back surfaces of the membrane. 7. The microfiltration membrane sheet having an average pore size of 0.05
The microfiltration membrane cartridge filter according to claim 1, which has a diameter of from 10 to 10 µm.