JPH02280820A - Filter cartridge - Google Patents

Abstract

PURPOSE:To prevent the occurrence of small voids in membrane end bonding areas and thereby enhance the reliability of a cartridge by removing nonwoven fabric from either of the sides of filter membrane end bonding area alone of the whole nonwoven fabric on both sides of the filter membrane at the time of bonding the filter membrane at the ends by heat application into a cylindrical form. CONSTITUTION:A supporting material for imparting filtration pressure resistance to a filter cartridge is formed by a method wherein a nonwoven fabric is placed on a filter membrane and their edges are folded, the folded edges are heated and pressed in place, the resulting double materials are cut out into a pleat like filter membrane and this membrane is bonded at the ends by heat application ao as to be formed into a cylindrical shape. At the time of the bonding, the nonwoven fabric is removed from either of the sides of the filter membrane, so that the nonwoven fabric does not exist on both sides of the bonding areas. This bonding method prevents the occurrence of small voids in the bonding areas, improve the sealability to avoid the passage of microorganisms or fine particles in filtrate and enhance the reliability of the filter cartridge. After the above-mentioned method, the production of the filter cartridge is completed by undergoing the process of fixing a membrane frame and bonding together the end faces of a cylinder.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to the structure of a pleated filter cartridge in which a sheet-like membrane used for fluid filtration is creased in the form of folds.

The filter cartridge referred to here is a device that filters and collects particulates and microorganisms present in a fluid, and is used in semiconductor manufacturing processes, pharmaceutical manufacturing processes, food, drinking water, alcoholic beverage manufacturing processes, etc.

<Prior art> Microporous filtration membranes have been known for a long time (for example, R, K
esting, published by McGraw Hi11, Sy.
nthetic Polymeric Membrane
s) Widely used in filters, etc. Microporous filtration membranes are disclosed in, for example, U.S. Pat. No. 1,421,341, U.S. Pat. As described in No. 4B-39586, Japanese Patent Publication No. 4B-40050, etc., those manufactured using cellulose ester as a raw material 1, U.S. Patent No. 2゜784.89
No. 4, No. 3.408,315, No. 4.340,479
No. 4,340,480, No. 4,450,126, German Patent No. D3,138.525, JP-A-58-3
No. 7842, etc., manufactured from aliphatic polyamide as a raw material, U.S. Patent No. 4,196
．． No. 070, No. 4,340.482, JP-A-5599
No. 934, JP-A-59-86941, JP-A-56-1
As described in No. 2640, etc., those made from polysulfone, German patent (OLS) 3,003,
There are some that use polypropylene as a raw material, as described in No. 400. These microporous membranes are used for filtration and sterilization of electronic industry cleaning water, medical water, water for pharmaceutical manufacturing processes, food water, etc., and their applications and usage have expanded in recent years, especially in terms of particle capture and microbial capture. Microporous filtration membranes are widely used because of their high reliability.

Such filtration membranes are made by casting a polymer solution or polymer melt onto a flat plate, a smooth surface, or a sheet-like support that moves directly onto or along the sides of a cylindrical body to form a flat sheet. Manufactured. Depending on the purpose, it may be punched or cut from a flat sheet into a certain shape and size and used in the form of a flat membrane, or it may be combined with resin or metal parts and used as a filter cartridge.

In particular, from the viewpoint of increasing the filtration flow rate and at the same time making handling easier, pleated filter cartridges in which a flat membrane filtration membrane is folded to have a fixed volume have been widely used. The filtration membranes incorporated into such filter cartridges are often made from hydrophobic polymers, and when the purpose is to filter aqueous liquids, a hydrophilic treatment is performed to impart hydrophilicity to the micropore surface. This hydrophilic treatment is generally carried out because of the simple method of applying a hydrophilic agent to the surface of the micropores.

In general, pleated filter cartridges are formed and manufactured through the following steps.

(1) Pleating process The filtration membrane, which is the raw material, is in the form of a sheet, and in industrial production, it is usually supplied to the assembly process in the form of a roll.

The filtration membrane is folded into pleats at regular intervals in a direction perpendicular to the length of the filtration membrane using a folding machine with two blades. At this time, in order to impart filtration pressure resistance to the filter cartridge, a support material such as a nonwoven fabric is often folded over the filtration membrane. After the pleats are performed, the pleats are fixed by heating if necessary. This process gives the filtration membrane a corrugated shape.

(2) Cutting process The filtration membrane fixed in pleated form is cut in parallel to the fold direction so as to have a constant filtration area.

(3) Membrane end adhesion process Both ends of the cut filtration membrane fixed in a pleat shape are adhered with heat, solvent, adhesive, etc. to form a cylindrical shape. This adhesive surface is required to have sealing properties so that microorganisms, particles, etc. in the filtrate do not pass through.

(4) Membrane frame fixing process A cylindrical member called an inner cylinder having multiple openings on the side is placed inside the cylindrical body of the filtration membrane fixed in a pleated shape, and a cylindrical member called an inner cylinder having multiple openings on the side is placed on the outside. The filtration membrane structure is protected by covering it with a shaped outer cylinder.

(5) Cylindrical end face adhesion process Heat, solvent, or adhesive is applied to the cylindrical filtration membrane structure and both end faces of the inner cylinder and outer cylinder to a disc-shaped member or a disc-shaped annular member having liquid inflow and liquid outlet ports. Adhesive to provide airtightness.

<Problems to be Solved by the Invention> In the membrane end bonding process of such a filter cartridge assembly process, there may be cases where the sealing performance is insufficient and the filter cartridge does not function as a filter cartridge. When the cause of this was analyzed in detail, it was found that minute voids were generated at the bonded portion of the membrane edge. If such voids occur during the filter cartridge assembly process, the filter cartridge cannot fulfill its original purpose of capturing particulates and microorganisms, resulting in a defective product. The purpose of the present invention is to provide a safe filter cartridge with higher reliability of performance without generating the above-mentioned voids in the filtration membrane during the assembly process of a pleated filter cartridge, and to improve workability and yield. Another object of the present invention is to provide a pleated filter cartridge that is inexpensive to manufacture.

As a result of intensive study of the above-mentioned problem, we found that the cause lies in the structure of the filtration membrane structure that makes up the filter cartridge. In other words, we found that the problem lies in the structure of the filtration membrane structure that makes up the filter cartridge. It was found that the overlapping structure causes defects at the membrane edge adhesion part.

The inventors conventionally used a layered material such as nonwoven fabric, filtration membrane, and nonwoven fabric to bond the membrane ends of the filter cartridge, and then used a heat sealer to bond the membrane ends, resulting in a structure of nonwoven fabric, filtration membrane, nonwoven fabric, nonwoven fabric, filtration membrane, and nonwoven fabric. The problem was solved by adopting a structure that does not overlap nonwoven fabric on both sides of the filtration membrane.

The above object of the present invention is achieved by a structure in which nonwoven fabric is not disposed on both sides of a filtration membrane, ie, a structure such as nonwoven fabric - filtration membrane - filtration membrane - nonwoven fabric, or filtration membrane - nonwoven fabric - nonwoven fabric - filtration membrane.

In order to obtain the above structure, the pleating process and the cutting process are carried out as in the conventional technology, and after the cutting process is completed, only the part of the membrane edge that is to be bonded to one of the membranes on both sides of the filtration membrane is removed. This is done by

The material of the filtration membrane applied to the present invention is polyvinylidene fluoride,
Known hydrophobic polymers such as fluororesins such as polytetrafluoroethylene, polysulfone, polyethersulfone, aliphatic polyamide, cellulose ester, polypropylene, and polyamide can be used, but the material is not particularly selected.

Its thickness is from 50 to 300 μm. In addition, the nonwoven fabric applied to the present invention can be made of polypropylene, polyester, fluororesin, etc., but the material is not limited.The thickness of the nonwoven fabric depends on the mechanical strength of the filtration membrane and the flow rate of the permeated liquid required for the filter cartridge. The diameter of the filter cartridge is selected depending on the pressure resistance of the filter cartridge, etc., but in general, one with a diameter of 100 to 300 μm is used. Also, the basis weight is selected from the same viewpoint as the thickness, from 2o to 150
g/rd is used. A heat sealer is usually used to bond the film edges, and its surface temperature is approximately 200 to 270°C.

<Example> A polysulfone membrane with a thickness of 180 μm and an average pore size of 0.2 μm was used as the filtration membrane, and polyester was used as the nonwoven fabric.The nonwoven fabric was stacked on both sides of the filtration membrane and folded using a pleating machine.
It was cut parallel to the folding direction so that the effective membrane area was 0.4 mm. Thirty samples were prepared and divided into three groups of 10 samples each. In the first group, after the cutting process, when adhering the membrane edges, the part of the nonwoven fabric in the area where the membrane edges were bonded, which overlapped on the inside of the two sheets, was removed and the membrane edges were bonded. In the second group, among the nonwoven fabrics in the membrane edge bonding portion, two nonwoven fabrics located at the outermost side when overlapped were removed and membrane edge bonding was performed. The third group performed membrane edge adhesion using a prior art configuration.

The membrane end bonded portion of the filtration membrane thus formed was observed using a microscope for the presence or absence of voids. The results are shown in Table 1.

Table 1 ↓Shimato Bokukai Green Applicant Fuji Photo Film Co., Ltd. Procedural amendment

Claims (1)

[Claims] A pleated filter cartridge having a filtration membrane and a nonwoven fabric, characterized in that the nonwoven fabric is not present on both sides of the filtration membrane at the membrane end heat-sealed portion of the cylindrical filtration membrane structure.