JPH11114383A - Cylindrical filter cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cylindrical pleated filter cartridge having excellent filtration accuracy and stability in chemical resistance, liquid permeability, filtering life and filtering accuracy. SOLUTION: This filter cartridge consists of a laminated body of at least three members of a fluorocarbon resin fine porous film, a multicomponent superfine fiber nonwoven fabric and a long-fiber nonwoven fabric. The structural fibers of the multicomponent superfine fiber nonwoven fabric consist of two or more components of thermoplastic resins with >=15 deg.C max. difference in the melting point among the components, and the structural fibers are heat- bonded and have <=10 μm average fiber diameter. The laminated body is folded into pleats and formed into a cylinder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a filter cartridge for liquid filtration. More specifically, it relates to a pleated tubular filter cartridge that is more resistant to chemicals, has better filtration accuracy, has less filtration deterioration over time, and is more resistant to pressure than conventional filter cartridges. is there.

[0002]

2. Description of the Related Art At present, various filters have been developed and produced for purifying fluids. Above all, filters for precision filtration having a filtration accuracy of about 0.1 μm to 10 μm are used in a wide range of industrial fields such as removal of fungi, removal of suspended particles, and removal of cake flowing out of a cake filtration device.

[0003] There are various types of filters for microfiltration depending on the application. In particular, a filter formed by processing a folded filter material into a tubular shape is called a tubular pleated filter cartridge.This filter has a simple structure, low pressure loss, a long filtration life, and a high-precision filter. It has been used in many applications because it is possible to make it. However, there are some points to be improved in the filter having such a structure.

[0004] One of the problems of the conventional cylindrical pleated filter cartridge is that when the filtration pressure increases, the interval between the pleats changes from the original state, and the pleats are partially clogged. It is mentioned that the filtration life may not be obtained.

As a means for solving this problem, Japanese Patent Laid-Open No.
JP-A-8-7357 discloses a method of fixing a space by inserting a spacer between folds. This method has the advantage that the interval between the folds is firmly fixed, but the processing method of inserting a spacer between the folds is difficult, and the spacer itself has a pressure loss, so that the liquid permeability deteriorates, or the filtering material There is a need for an improvement in that the filter life may be shortened due to the blockage of the filter by a spacer. Further, since the number of folds of the cylindrical filter cartridge is reduced by the space in which the spacer is inserted, and the filtration area is reduced, improvement is desired also in that the amount of liquid flow decreases.

Japanese Unexamined Patent Publication (Kokai) No. 59-39313 discloses a method of increasing the strength of a filter medium itself by corrugating the filter medium with a pleated folded shape. If this method is used, there is no blocking of the filter medium by the spacer as described above, but since such processing is technically difficult, the filter medium may be damaged by corrugation processing and cause a pinhole, When the filter medium does not have appropriate hardness, the corrugation process itself is difficult. In addition, since the apparent thickness of the filter medium is increased by the corrugation processing, the number of folds of the cylindrical filter cartridge is reduced,
A sufficient filtration area cannot be secured.

As a method for increasing the strength of the filter medium,
Japanese Patent Application Laid-Open No. 53-87981 discloses a method in which a polyethylene powder is applied to a filter material and the resultant is thermally fused. Although the strength of the filter medium can be increased by using this method, a new problem arises in that the molten polyethylene powder blocks the pores of the filter medium, so that the liquid permeability and the filter life characteristics deteriorate.

Another point of improvement of the cylindrical pleated filter cartridge is that the filter medium is thin and has no strength, so that the filtration pressure is increased or the pores of the filter medium are closed with use. In this case, a phenomenon called “push out” of particles flowing out to the downstream side occurs. In particular, in the case of a cylindrical pleated filter cartridge using a non-woven fabric as a filtering material, the fibers constituting the pores move when the filtration pressure increases, so that this phenomenon is often noticeable.

In the production of a tubular pleated filter cartridge, the step of pleating the filter medium comprises:
After folding the nonwoven fabric, heat treatment is often performed in a folded state so that the shape of the fold is fixed, and the temperature range is from the glass transition point of the raw material resin of the filtering material to the melting point or less. Often set to temperature.
However, since the processing temperature is often close to the melting point of the raw resin, if the heating temperature and time are insufficient, the shape of the fold may not be fixed, and conversely, if the heating is excessive, In some cases, the constituent fibers of the filter medium are thermally deformed to lower the strength of the filter medium, or pinholes are formed in the filter medium, and the filter performance is sometimes reduced.

[0010] As another method for strengthening the filter medium,
Japanese Patent Application Laid-Open No. 6-201313 discloses a method of using a heat-fusible ultrafine composite fiber nonwoven fabric and a heat-fusible composite monofilament net on a filter medium. By using this method, since the filter medium is made of a heat-fusible composite material, the fibers constituting the filter medium are thermally bonded, and it is possible to obtain a strong filter medium without performing the processing described above. Can be. However, this method uses a melt-blowing method for the production of the ultrafine composite fiber nonwoven fabric, so that the filtration accuracy becomes about several microns, and although it is useful as a pre-filter for air or a cleaning liquid, it is used in the semiconductor field and the drinking water field. When used for collecting microorganisms having a size of 1 micron or less or extremely fine particles as required in the food field, it is necessary to treat the filtrate with a filter having a smaller pore size.

[0011] Further, the cylindrical pleated filter cartridge is often used mainly in fields such as pharmaceuticals, healthcare, and chemicals where the amount of elution from the filter material is extremely low. As a material for such a filter, a material having excellent chemical resistance such as polytetrafluoroethylene is desired. For example, JP-A-60-58208 and JP-A-61-149218 disclose a method of manufacturing a pleated filter cartridge using a fluororesin as a filtering material. However, since the filter material of the filter according to the present invention is merely a laminate of a filter film made of fluororesin and a net-like material,
Although it is excellent in chemical resistance, it does not solve the above-mentioned problems such as insufficient filter material strength and push-out when the pressure rises.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a cylindrical tube which has excellent filtration accuracy, and is excellent in chemical resistance, liquid permeability, filtration life and stability of filtration accuracy. An object of the present invention is to provide a pleated filter cartridge.

[0013]

The present invention has the following arrangement. (1) a multicomponent ultrafine fiber nonwoven fabric having an average fiber diameter of 10 μm or less, in which constituent fibers made of a fluororesin microporous membrane and two or more components of thermoplastic resin and having a maximum melting point difference of 15 ° C or more between the components are thermally bonded to each other; A cylindrical filter cartridge comprising: a filter material formed by overlapping at least three members of a long-fiber nonwoven fabric with each other and bending into a pleat shape to form a cylindrical shape. (2) The tubular filter cartridge according to the above (1), wherein the long-fiber nonwoven fabric is a long-fiber nonwoven fabric made of a two-component thermoplastic resin having a melting point difference of 15 ° C. or more and the constituent fibers are thermally bonded to each other. (3) The cylindrical filter cartridge according to (1) or (2), wherein the multicomponent ultrafine fiber nonwoven fabric and the long fiber nonwoven fabric are thermally bonded. (4) The filter according to any one of the above (1) to (3), wherein the filtering material is made by pleating and bending a net in addition to a fluororesin microporous membrane, a multicomponent ultrafine fiber nonwoven fabric, and a long fiber nonwoven fabric. The cylindrical filter cartridge according to the above. (5) The cylindrical filter cartridge according to any one of the above (1) to (4), wherein the material constituting the filtering material is entirely made of a fluororesin. (6) When the fluororesin is polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, ethylene-tetrafluoroethylene copolymer, polytrifluorochloroethylene, ethylene-trifluorochloroethylene copolymer Polymer, polyvinyl fluoride, tetrafluoroethylene
The cylindrical filter cartridge according to any one of (1) to (5), which is at least one member selected from the group consisting of a hexafluoropropylene-perfluoroalkylvinyl ether copolymer.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

The filter material of the tubular pleated filter cartridge according to the present invention comprises a microporous fluororesin membrane, a long-fiber nonwoven fabric, and a thermoplastic resin of two or more components having a melting point difference of 15 ° C. or more, and the constituent fibers are thermally bonded to each other. It consists of at least three types of multicomponent ultrafine fiber nonwoven fabric having an average fiber diameter of 10 μm or less.

As the multicomponent ultrafine fiber nonwoven fabric used in the present invention, a split fiber nonwoven fabric, a melt blown nonwoven fabric and the like can be used. In particular, it is preferable to use a melt blown nonwoven fabric because it is inexpensive and composed of fine fibers.

The multi-component ultrafine fiber nonwoven fabric is made of two or more thermoplastic resins having different melting points, and the difference in melting point between the resin having the highest melting point and the resin having the lowest melting point must be 15 ° C. or more. As a mixed form of these resins, a method of converting the constituent fibers of the nonwoven fabric into a composite fiber such as a side-by-side composite, a sheath-core composite, an eccentric sheath-core composite, and a fiber composed of two or more resins, For example, a method of mixing by mixing cotton or the like can be used.

The multicomponent ultrafine fiber nonwoven fabric used in the present invention has constituent fibers having an average fiber diameter of 10 μm or less thermally bonded. That is, the melting point difference between at least two components is 1
Since a thermoplastic resin having a temperature of 5 ° C. or more is contained, the low melting point resin is easily melted by thermal processing, and the constituent fibers are thermally bonded. For this reason, in the filter of the present invention, the constituent fibers are heat-bonded to each other, the pores of the filtering material do not expand, and the filtering accuracy hardly decreases with use.
Moreover, as compared with a filter in which a filter medium is reinforced by using a resin binder or the like, the filter of the present invention has a higher porosity and a higher porosity of the nonwoven fabric because there is no blockage by the binder. In addition, since the strength of the filter medium is high, the filter medium has excellent liquid permeability and filtration life, and has very little elution from the filter medium, and has excellent chemical resistance. In addition, since the shape retention after heat processing is excellent, it is easy to fix the folded shape by heating, so that the fold folding workability is superior to a nonwoven fabric made of a single component.

Examples of resins that can be used in the multicomponent ultrafine nonwoven fabric used in the present invention include polypropylene (P
P), linear low density polyethylene, low density polyethylene,
High density polyethylene (HDPE), propylene and other α
-Polyolefins such as copolymers with olefins, or polyesters such as polyethylene terephthalate, copolymerized polyesters, low melting thermoplastic polyesters, polyamides such as nylon 6, nylon 66, or polystyrenes, vinyl chlorides, A thermoplastic resin such as a thermoplastic elastomer and a synthetic resin composed of a mixture thereof can be given. In particular, when used for applications requiring heat resistance and chemical resistance, polytetrafluoroethylene (PTFE), polyvinylidene fluoride, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, tetrafluoroethylene-hexafluoro Propylene copolymer, ethylene-tetrafluoroethylene copolymer, polytrifluorochloroethylene, ethylene-trifluorochloroethylene copolymer, polyvinylidene fluoride, polyvinyl fluoride, tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether It is preferable to use a fluororesin such as a copolymer.

The combination of resins used in the multi-component ultrafine fiber nonwoven fabric is not particularly limited as long as the above requirements are satisfied. Examples of combinations include high density polyethylene / polypropylene, linear low density polyethylene / polypropylene, low density polyethylene / polypropylene,
Copolymer of propylene and other α-olefins / polypropylene, linear low density polyethylene / high density polyethylene, low density polyethylene / high density polyethylene, various polyethylene / thermoplastic polyester, polypropylene / thermoplastic polyester, copolymer polyester / Thermoplastic polyester, various polyethylene / nylon 6, polypropylene / nylon 6, nylon 6 / nylon 6
6, nylon 6 / thermoplastic polyester and the like. In particular, when heat resistance and chemical resistance are imparted, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer / polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer / polytetrafluoroethylene, ethylene −
Tetrafluoroethylene copolymer / polytetrafluoroethylene, polytrifluorochloroethylene / polytetrafluoroethylene, ethylene-trifluorochloroethylene copolymer / polytetrafluoroethylene, polyvinylidene fluoride / polytetrafluoroethylene, polyvinyl fluoride / Polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene-perfluoroalkylvinylether copolymer / polyvinylidene fluoride, tetrafluoroethylene-perfluoroalkylvinylether copolymer / polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer Polymer / Polyvinylidene fluoride, Ethylene-tetrafluoroethylene copolymer / Polyvinylidene fluoride, Polytrifluorochloroethylene Combination of polystyrene / polyvinylidene fluoride, ethylene-trifluorochloroethylene copolymer / polyvinylidene fluoride, polyvinyl fluoride / polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene-perfluoroalkylvinyl ether copolymer / polyvinylidene fluoride Can be mentioned. Among them, a combination of high-density polyethylene / polypropylene, a copolymer of propylene and another α-olefin / polypropylene, a copolymerized polyester / thermoplastic polyester is preferable because of its excellent price, processability, and adhesiveness. . When a fluororesin is used, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer / polytetrafluoroethylene and tetrafluoroethylene-hexafluoropropylene copolymers are used in view of price, processability, adhesiveness, and chemical resistance. Polymer /
Polytetrafluoroethylene, a combination of tetrafluoroethylene-hexafluoropropylene-perfluoroalkylvinyl ether copolymer / polytetrafluoroethylene is preferred.

Next, a method for thermally bonding the constituent fibers of the multicomponent ultrafine fiber nonwoven fabric will be described. As a method of heat bonding, a known method such as an air-through processing method and a far-infrared heater heating method can be used, in addition to bonding by residual heat of heated air during spinning. The processing temperature at that time depends on the method used, but it is desirable that the ambient temperature on the surface of the nonwoven fabric is 1 ° C. or more higher than the melting point of the low melting point resin of the nonwoven fabric and lower than the melting point of the high melting point resin. If the difference between the processing temperature and the melting point of the low melting point resin is less than 1 ° C., it is not preferable because the adhesion of the fibers becomes insufficient. Further, if the processing temperature is higher than the melting point of the high melting point resin, the entire nonwoven fabric is melted and the form is lost, which is not preferable. However, by making the constituent fibers of the nonwoven fabric a structure in which the high-melting point resin such as the sheath-core conjugate fiber does not appear on the fiber surface, the heating time is set to be extremely short enough to melt only the constituent fiber surfaces of the nonwoven fabric. If the high melting point resin of the constituent fibers of the nonwoven fabric is not exposed to a temperature substantially higher than the melting point, there is no problem even if the heating temperature is higher than the melting point of the high melting point resin of the nonwoven fabric.

Further, the multicomponent ultrafine fiber nonwoven fabric used in the present invention may be compacted by a flat calender roll or the like in order to reduce the passing particle size. It is desirable that the degree of the consolidation processing be such that the porosity after the processing is 50% to 90%. If this value is less than 50%, the liquid permeability of the nonwoven fabric becomes extremely poor, and uniform consolidation becomes difficult. On the other hand, if the porosity after processing exceeds 90%, there is no point in performing consolidation processing. If a heating roll is used for the consolidation processing, the constituent fibers of the nonwoven fabric are bonded by the consolidation processing, so that the above-described air-through processing, far-infrared heater heating, and the like can be omitted.

Next, the long-fiber nonwoven fabric used in the present invention will be described. The method for producing the long-fiber nonwoven fabric used in the present invention is not particularly limited, but it is preferable to use a spunbond nonwoven fabric from the viewpoint of low cost and high strength.
Examples of the resin that can be used for the long-fiber nonwoven fabric include a polyolefin resin, a polyester resin, a polyamide resin,
Any of the above-mentioned resins that can be used for the microfiber nonwoven fabric, such as a fluororesin, can be used. In particular, when a filter is used in a field where heat resistance and chemical resistance are required, it is preferable to use a fluororesin.

The long-fiber nonwoven fabric used in the present invention may be composed of a two-component thermoplastic resin having a melting point difference of 15 ° C. or more. As a mixed form of the two components,
Composites such as parallel composite, sheath-core composite, eccentric sheath-core composite,
Alternatively, a mixed fiber, a mixed cotton or the like can be used. In this case, it is preferable that the constituent fibers are bonded to each other by previously processing the long-fiber nonwoven fabric, because the filter medium has strength without impairing the liquid permeability. This long-fiber nonwoven fabric 2
As the combination of the components, any combination of the low-melting resin and the high-melting resin of the resin used for the multicomponent ultrafine fiber nonwoven fabric described above can be used. The thermal processing method of this long-fiber non-woven fabric is the same as the method of thermally bonding the constituent fibers of the multi-component ultrafine fiber non-woven fabric described above, and air-through processing,
A far infrared heater heating method or the like can be used.

Further, in order to further improve the properties such as the pleating property, the strength of the filtering material, and the filtering performance as described above, not only the multi-component ultrafine fiber nonwoven fabric and the long-fiber nonwoven fabric but also heat You may adhere. A calender roll such as an emboss roll or a flat roll may be used as a method of the thermal bonding, or an air through processing method, far infrared heater heating, or the like may be used. In this case, the combination of the resin used for the multi-component ultrafine fiber nonwoven fabric and the long fiber nonwoven fabric is a combination of a polyolefin resin and a combination of polyester resins.
It is preferable to use a combination of resins having high compatibility since the adhesiveness is improved. Further, when the long-fiber nonwoven fabric is a composite long-fiber nonwoven fabric, it can be processed under mild conditions without excessively applying heat during thermal bonding, which is a more preferable embodiment.

Next, the fluororesin microporous membrane used in the present invention will be described. The method for producing the fluororesin porous membrane is not particularly limited, and for example, a phase inversion method, a stretching method,
A track etch method or the like can be used. Especially,
Since the raw material is a fluororesin, it is useful to use a stretching method to uniaxially or biaxially stretch a film made by mixing fine fluororesin powder and a molding aid. The pore size of the fluororesin microporous membrane is 0.01 μm.
It is preferably between m and 5 μm. Pore size 0.0
If it is smaller than 1 μm, the porosity of the membrane becomes low, so that the liquid permeability deteriorates, which is not preferable. Further, those having a pore size larger than 5 μm are not preferred because they are disadvantageous in terms of cost as compared with nonwoven fabrics made by a melt blow method or the like. The thickness of the fluororesin microporous membrane is not particularly limited, but a thickness of 30 µm to 200 µm is easy to use from the viewpoint of strength and workability. This film may be subjected to a hydrophilic treatment.

Next, a description will be given of a combination of filter materials for the cylindrical pleated filter cartridge. The filter material of the present invention is composed of at least three types of fluororesin microporous membrane, multi-component ultrafine fiber nonwoven fabric, and long-fiber nonwoven fabric.
It is preferable to use a microporous fluororesin membrane. In the case of such a combination, the size of the particles that can be collected by each nonwoven fabric or membrane gradually decreases from the upstream side, so that the life of the filter medium is prolonged. Further, in order to further increase the strength of the filter medium, or to secure a space for liquid passage when the number of folds is increased, between the multi-component ultrafine fiber nonwoven fabric and the fluororesin microporous membrane, or the fluororesin microporous membrane A long-fiber nonwoven fabric may be used on the downstream side.

The fluororesin microporous membrane may be simply superposed, but before pleating, the above-mentioned long-fiber nonwoven fabric, multi-component ultrafine-fiber nonwoven fabric or a heat-bonded multifilament nonwoven fabric is previously used using a flat calender roll or the like. It may be pasted together with what has been done. Thereby, the pleating workability of the soft fluororesin porous film can be remarkably improved, and the reinforcing effect is also improved. Furthermore, for the purpose of the same improvement, a long-fiber nonwoven fabric, a multi-component ultrafine-fiber nonwoven fabric, or a perforated sheet such as a nonwoven fabric may be attached separately from those obtained by thermally bonding them. As the perforated sheet to be bonded, the same long-fiber nonwoven fabric and multi-component ultrafine fiber nonwoven fabric as described above may be used, and other nonwoven fabrics, woven fabrics, nets, punched sheets and the like can also be used. The material of the perforated sheet is not particularly limited, but since it is inexpensive and has high strength, it is preferable to use a spunbond nonwoven fabric, and when manufacturing a filter cartridge requiring heat resistance and chemical resistance. Is preferably a perforated sheet using a fluororesin.

Further, as a filtering material for the cylindrical pleated filter cartridge, a net may be further superimposed and used in addition to the perforated sheet. The material of the net is not particularly limited, but a fluororesin is preferable because of its excellent heat resistance and chemical resistance. If a net is used, a space for liquid to enter between the folds can be secured, so that the entire surface of the filter can be used more efficiently. When the nets are superimposed, the nets may be superimposed on either the inner or outer surface of the entire filter medium, or may be superimposed on both surfaces.

Next, a method of forming the combined filtering material into a cylindrical pleated filter cartridge will be described.

First, the filter material, which is a combination of the above-mentioned fluororesin microporous membrane, multi-component ultrafine fiber nonwoven fabric, and long fiber nonwoven fabric, is subjected to a fold-folding process, and heat treatment is performed in a folded state to fix the folded shape. Do. The temperature of the heat treatment may be set between the glass transition point of the resin having the lowest glass transition point and the melting point of some of the resins mixed in the filter medium. In the present invention, since the filter medium is composed of a plurality of components having different melting points, the heat treatment after the fold processing can be performed at a relatively low temperature. Pinholes do not occur.

Next, both ends of the obtained pleated filter material are adhered to each other to form a cylindrical shape. At this time, since the filtration is usually performed from the outside to the inside of the tubular filter cartridge, the filter material is formed so that the upstream side of the filter material is outside the tube, but the purpose is to filter in the opposite direction (from inside to outside). In the case where a filter cartridge is manufactured, the reverse may be performed. When performing molding, it is difficult to bond with a conventional single-component filter medium, particularly a fluororesin filter medium, but the filter medium of the present invention has a maximum melting point difference of 15 ° C. or more between components.
Since it is made of a thermoplastic resin having more than the components, the end portions can be easily bonded by using a heat sealing method such as a heat sealing method or an ultrasonic bonding method. When the adhesive strength is particularly increased, a film of the same resin as the resin used as the lowest low melting point resin of the multi-component ultrafine fiber nonwoven fabric may be interposed between both surfaces of the filter material.

Next, a porous cylindrical core is disposed at the center of the cylindrical filter material, or a porous cylindrical outer tube is disposed outside the filter material, and caps are adhered to both ends thereof. By doing so, the cylindrical filter cartridge of the present invention is obtained. Whether to use a core or an outer cylinder is determined by the direction in which the pressure is applied. In the case of a normal type filter cartridge that performs filtration from the outside to the inside, a type that uses the core and performs filtration in the opposite direction is used. In this case, an outer cylinder may be used. Further, both the core and the outer cylinder may be used in combination in order to enable back washing. The core (or outer cylinder) and cap material used at this time
Any resin can be used among the resins that can be used for the above-mentioned ultrafine fiber non-woven fabric such as a fluororesin. In particular, it is preferable to use a resin having good compatibility with the filter medium in order to improve the adhesiveness with the filter medium. As a method of bonding the cap, the filter medium may be heated to a temperature equal to or higher than the melting point of the low-melting resin to melt the low-melting resin and adhere to the cap. The resin having a low melting point may be melted, poured and adhered. The cap may be bonded by heating and melting the bonding surface.

[0034]

The present invention will be described in more detail with reference to the following examples and comparative examples. In each example, the evaluation of the physical properties, filtration performance, and the like of the filtering material was performed by the methods described below.

(Fiber diameter of non-woven fabric)
The samples were sampled at several locations, photographed with a scanning electron microscope, 20 fibers were randomly selected for each location, their fiber diameters were measured, and the average value was taken as the fiber diameter of the nonwoven fabric.

(Melting Point of Resin) Using a differential thermal analyzer (DSC), the peak temperature of the peak appearing in the melting curve of the resin measured at a heating rate of 10 ° C./min was defined as the melting point of the resin. In the case where no clear peak appears, a small piece of the resin was heated at a heating rate of 10 ° C./min while observing it with an optical microscope, and the temperature at which the shape of the small piece was completely lost was taken as the melting point of the resin. .

(Initial collection efficiency, initial pressure loss, 0.2M
(Pa-time collection efficiency, filtration life) One filter is attached to the housing of the circulation-type filtration performance tester, and the flow rate is adjusted to 10 liters per minute by a pump to circulate water. The pressure loss before and after the filter at this time was defined as the initial pressure loss. Next, fine test dust (abbreviated as ACFTD) for air cleaner is added to the circulating water. Median diameter: 6.6 to 8.6 μm
m) and course test dust for air cleaner (ACC)
Abbreviated as TD. (Medium diameter: 27-31 μm) with a weight ratio of 1: 1
Was added continuously at 4 g / min per minute. After 5 minutes from the start of the addition, the undiluted solution and the filtrate were collected, and the number of particles having a diameter of 0.5 μm contained in each solution was determined by a light scattering type particle detector. And the initial collection efficiency was calculated. Continue to add cake, filter pressure drop 0.2MPa
At the time of reaching, the undiluted solution and the filtrate were collected, and the number of particles having a diameter of 0.5 micron contained in each solution was measured using a light scattering type particle detector to calculate the collection efficiency at 0.2 MPa. . The time required to reach 0.2 MPa was defined as the filtration life.

(Chemical resistance) One filter was attached to the housing of the above-mentioned circulating filtration performance tester, and kerosene was used as a filtrate at a temperature of 20 ° C. and a flow rate of 10 liters per minute for 10 minutes. Circulate. The filter after that was taken out and the dry weight was measured, and the difference from the weight before use was 0.
Those with less than 1% were evaluated as 、, those with 0.1% or more and less than 5% as Δ, those with 5% or more as X. A similar test was performed using toluene as the filtrate.

Example 1 As a microporous fluororesin membrane,
A microporous polytetrafluoroethylene (hereinafter abbreviated as PTFE) having a thickness of 100 μm and a pore diameter of 0.45 μm was used. Further, a melt flow rate (MFR) as a first component was used using a melt-blowing spinneret having a hole diameter of 0.3 mm, in which spinning holes of a high melting point resin and spinning holes of a low melting point resin were alternately arranged in a line at 1 mm intervals. 80g at 230 ° C)
Polypropylene with a melting point of 165 ° C./10 min and propylene (91.7% by weight) · ethylene (3.8% by weight) · butene-1 having a second component MFR of 65 g / 10 minutes and a melting point of 138 ° C. (4.5% by weight) random copolymer was discharged at a single hole discharge rate of 0.25 g / min.
Blowing with 300 ° C heated air, fiber diameter 2μ
Thus, a two-component ultrafine fiber nonwoven fabric having a basis weight of 50 g / m ² was obtained. In this two-component ultrafine fiber nonwoven fabric, the joining points of the constituent fibers were thermally bonded with heated air during spinning. On the other hand, using a spinneret for a spun bond having a hole diameter of 0.35 mm, using polypropylene having an MFR of 35 g / 10 min and a melting point of 165 ° C., discharging a single hole at a discharge rate of 0.8 g / min, The group is introduced into the air soccer, drawn and stretched, and the long fiber group discharged from the air soccer is collected on an endless suction conveyor, which is then subjected to point bond processing consisting of a heated uneven roll and a smooth roll. A long-fiber nonwoven fabric having a basis weight of 30 g / m ² and a fineness of 4 d / f (denier / fiber) was obtained by introducing the mixture between the pressurized rolls of the machine. And a long-fiber nonwoven fabric,
Three sheets of the component ultrafine fiber nonwoven fabric and the microporous fluororesin membrane were laminated in this order, and fold-folded to a folding width of 13 mm, and heated at 90 ° C. to fix the fold. It is cut at 140 folds, and both ends are bonded by a heat sealing machine to form a cylinder. A porous cylindrical core made of polypropylene is arranged at the center of the cylindrical shape, and polypropylene ends are formed at its ends. The inner diameter is 30 mm and the outer diameter is 6
A cylindrical pleated filter cartridge having a length of 6 mm and a length of 250 mm was obtained. Table 2 shows the performance.

(Comparative Example 1) MFR (230 ° C.) is 80 g / 10 min and the melting point is 165 ° C.
A cylindrical pleated filter cartridge was obtained in the same manner as in Example 1, except that the ultrafine fiber nonwoven fabric was made into a single composition by using the polypropylene. Table 2 shows the performance. The filter of Comparative Example 1 had the same initial performance as that of the filter of Example 1, but had a marked decrease in collection efficiency with use, and was therefore inferior to the filter of Example 1. Further, when kerosene is used for the filtrate, the fiber whose fiber intersection is not thermally bonded is used, so that the fibers whose strength has been reduced by kerosene are easily dropped off, and the filter weight is reduced compared to Example 1. It was big.

Example 2 The same microporous fluororesin membrane, ultrafine nonwoven fabric and long-fiber nonwoven fabric as in Example 1 were used. Then, five sheets of a long-fiber nonwoven fabric, a two-component ultrafine-fiber nonwoven fabric, a long-fiber nonwoven fabric, a fluororesin microporous membrane, and a long-fiber nonwoven fabric are stacked in this order, fold-folded to a folding width of 13 mm, and fixed at 90 ° C. to fix the fold. Except that the heated material was used as a filtering material, the inner diameter was 30 mm in the same manner as in Example 1;
A cylindrical pleated filter cartridge having an outer diameter of 66 mm and a length of 250 mm was obtained. Table 2 shows the performance. The filter of Example 2 had a lower initial pressure loss and was superior in liquid permeability as compared with the filter of Example 1.

(Comparative Example 2) MFR (230 ° C.) is 80 g / 10 min and the melting point is 165 ° C.
A cylindrical pleated filter cartridge was obtained in the same manner as in Example 2 except that the ultrafine fiber nonwoven fabric was made into a single composition by using the polypropylene. Table 2 shows the performance. The filter of Comparative Example 2 had the same initial performance as that of the filter of Example 2, but showed a marked decrease in collection efficiency with use, and was therefore inferior to the filter of Example 2. In addition, when kerosene is used for the filtrate, the fibers whose fiber intersections are not thermally bonded are used, so the fibers whose strength has been reduced by kerosene are easily dropped off, and the filter weight is reduced compared to Example 2. It was big.

Example 3 A mixed fiber type spinneret having a hole diameter of 0.4 μm and a hole ratio of 50/50 in which a first component and a second component are alternately discharged was used. (Temperature 230 ° C.) polypropylene having a melting point of 164 ° C. at 60 g / 10 min and a MFR (190 ° C.) of the second component of 22
g / 10 minutes, using a high-density polyethylene having a melting point of 133 ° C., and discharging at a single hole discharge rate of 0.8 g / min. By collecting the long fiber group discharged from the air soccer on the endless suction conveyor and introducing it between the pressurized rolls of a point bond processing machine composed of a heated uneven roll and a smooth roll A long-fiber nonwoven fabric with a basis weight of 30 g / m ² and a fineness of 4 d / f was obtained. This long-fiber nonwoven fabric had a fiber joint point thermally bonded. Example 2 except that this long-fiber nonwoven fabric was used as the long-fiber nonwoven fabric of the filter material of the cylindrical filter cartridge.
A cylindrical pleat filter cartridge was obtained in the same manner as described above. Table 2 shows the performance. The filter of Example 3 has the same initial performance as that of the filter of Example 2, but has a smaller decrease in collection efficiency due to use as compared with Example 2, and is superior to Example 2. Was something.

Example 4 The same microporous fluororesin membrane, microfiber nonwoven fabric and long fiber nonwoven fabric as in Example 3 were used. First, three sheets of a long-fiber nonwoven fabric / ultrafine-fiber nonwoven fabric / long-fiber nonwoven fabric were stacked in this order, and the fiber intersections and the nonwoven fabrics were heated and bonded by a through-air machine at a temperature of 140 ° C. to form a laminated bonded nonwoven fabric. Then, on this laminated bonded nonwoven fabric, three sheets of a fluororesin microporous membrane and a long-fiber nonwoven fabric are further laminated in this order, and folded in a folding width of 13 mm,
Heated at 90 ° C. to fix the fold. Thereafter, a cylindrical pleated filter cartridge was obtained in the same manner as in Example 2. Table 2 shows the performance. The filter of Example 4 showed almost no decrease in collection efficiency with use within the experimental error range.

Comparative Example 3 A tubular pleated filter cartridge was obtained in the same manner as in Example 4 except that the same ultrafine fiber nonwoven fabric and long fiber nonwoven fabric were used as in Comparative Example 2. Table 2 shows the performance. Since the fiber material of Comparative Example 3 was not thermally bonded at the fiber intersection by the through-air machine, the collection efficiency was almost the same as that of the filter of Comparative Example 2, and the initial pressure loss and the filtration life were rather poor. Therefore, the performance was inferior to that of the filter of Example 4.

Example 5 A polypropylene net having a mesh size (fiber spacing) of 1 mm and a fineness of 300 d / f was used as the net. Then, the same fluororesin microporous membrane, ultrafine fiber nonwoven fabric and long fiber nonwoven fabric as in Example 2 were used, and the net, long fiber nonwoven fabric, ultrafine fiber nonwoven fabric, long fiber nonwoven fabric,
Seven sheets of PTFE microporous membrane, long-fiber nonwoven fabric, and net were stacked in this order, and fold-folded to a fold width of 13 mm.
A cylindrical pleated filter cartridge was obtained in the same manner as in Example 2 except that the number was 20. Table 2 shows the performance.
Shown in The filter of Example 5 had a lower initial pressure loss than the filter of Example 2 and was excellent in liquid permeability.

(Example 6) First of multicomponent ultrafine fiber nonwoven fabric
Polytetrafluoroethylene (PTFE) resin is used as a component, and tetrafluoroethylene-
Perfluoroalkyl vinyl ether copolymer (PF
A), a polytetrafluoroethylene resin is used as a material for the long-fiber nonwoven fabric, and the spinning temperature is 400
° C and the temperature of the heated air were changed to 450 ° C, to obtain a fluororesin microfiber nonwoven fabric and a long-fiber nonwoven fabric having the same basis weight, the same fiber diameter and the same fiber joints as those of Example 2, except that the fiber bonding points were thermally bonded. . Then, a long fiber nonwoven fabric, a two-component ultrafine fiber nonwoven fabric, a long fiber nonwoven fabric, the same PTFE microporous membrane as in Example 2,
Five sheets of the long-fiber nonwoven fabric were stacked in order and fold-folded to a folding width of 13 mm, and heated at 200 ° C. to fix the fold. It is cut at 140 folds, and both ends are bonded by a heat sealing machine to form a tube. A porous cylindrical core made of PFA is disposed at the center of the cylindrical shape, and PF is formed at the end thereof.
The cap made of A was bonded by a hot plate welding method to obtain a cylindrical pleated filter cartridge. Table 2 shows the performance. The filtration performance of the filter of Example 6 was almost the same as the filter of Example 2, but the chemical resistance was much better.

(Comparative Example 4) A cylindrical pleated filter cartridge was obtained by using the same filter medium and method as in Example 6 except that a nonwoven fabric made of only polytetrafluoroethylene resin was used as the ultrafine fiber nonwoven fabric. Table 2 shows the performance.
Shown in The filter of Comparative Example 4 had the same initial filtration performance as that of Example 6, but had very low collection efficiency at 0.2 MPa, and was much worse overall than the filter of Example 6. there were.

Summarizing the above, the filters of the examples all adhere to the fiber intersections of the microfiber nonwoven fabric used, so that the collection efficiency is not increased without increasing the initial pressure loss or decreasing the filtration life. Change was very small. In comparison, the filters of Comparative Examples all had significantly lower collection efficiency because the fiber intersections were not adhered. Further, when kerosene is allowed to pass through the filter, since the fiber intersections of the ultrafine fiber non-woven fabric used in all of the filters of the examples are bonded, the constituent fibers do not fall off due to kerosene, and the weight is reduced. There were few. On the other hand, in the filters of Comparative Examples 1 to 3, since the fiber intersections were not adhered, the constituent fibers were relatively easily dropped off by kerosene, so that a decrease in the filter weight after the passage of the liquid was observed.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

As described above, according to the present invention, the constituent fibers composed of a fluororesin microporous membrane and two or more thermoplastic resins having a maximum melting point difference of 15 ° C. or more between the components are used as the filter material. By using a combination of at least three of a heat-bonded ultrafine fiber nonwoven fabric having an average fiber diameter of 10 μm or less and a long-fiber nonwoven fabric, it was possible to prevent a reduction in collection efficiency. Further, by using a fluororesin as the filtering material, it was possible to obtain a filter having extremely excellent chemical resistance and hardly showing a decrease in the collection efficiency as compared with a conventional filter made of a fluororesin.

Claims (6)

[Claims] 1. An average fiber diameter of 10 μm, in which constituent fibers made of a fluororesin microporous membrane and two or more components of a thermoplastic resin and having a maximum melting point difference of 15 ° C. or more between the components are thermally bonded to each other.
m. A cylindrical filter cartridge comprising a filter material formed by laminating at least three members of a multicomponent ultrafine fiber nonwoven fabric having a length of m or less and a long-fiber nonwoven fabric and folding the resultant into a pleat shape to form a cylinder. 2. The tubular filter cartridge according to claim 1, wherein the long-fiber nonwoven fabric is a long-fiber nonwoven fabric made of a two-component thermoplastic resin having a melting point difference of 15 ° C. or more, and the constituent fibers are thermally bonded to each other. 3. The cylindrical filter cartridge according to claim 1, wherein the multi-component ultrafine fiber nonwoven fabric and the long fiber nonwoven fabric are thermally bonded. 4. The filter material according to claim 1, wherein the filter material is formed by pleating a net in addition to a fluororesin microporous membrane, a multicomponent ultrafine fiber nonwoven fabric, and a long fiber nonwoven fabric. Cylindrical filter cartridge. 5. The cylindrical filter cartridge according to claim 1, wherein all of the materials constituting the filter medium are made of fluororesin. 6. The fluororesin is polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-
Perfluoroalkyl vinyl ether copolymer, ethylene-tetrafluoroethylene copolymer, polytrifluorochloroethylene, ethylene-trifluorochloroethylene copolymer, polyvinyl fluoride, tetrafluoroethylene-hexafluoropropylene-perfluoroalkylvinyl ether copolymer The cylindrical filter cartridge according to any one of claims 1 to 5, which is at least one selected from the group of polymers.