JP2001149720A - Filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filter that has low water passing resistance and long filtration life. SOLUTION: In the filter consisting of a thermoplastic fiber, the filter has a fibrous layer I and a fibrous layer II, and the fibrous layer I has a rugged structure and has a surface structure having a disordered shaped fine porous structure by the thermoplastic fiber dispersed in random, and the fibrous layer II is constituted of a nonwoven fabric having a surface structure having a long and thin shaped pore part by the thermoplastic fiber arranged in unidirection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a filter. More particularly, it relates to a filter particularly suitable for liquid filtration.

[0002]

2. Description of the Related Art There are many filters manufactured using fibers as raw materials. For example, a wind filter in which spun yarn is wound around a perforated tube, or a nonwoven fabric formed by a card method, a melt blow method, a spun bond method, or the like, is formed into a tubular shape. Examples include a wound cartridge filter. Further, after laminating the nonwoven fabric or the membrane sheet, a pleated filter obtained by processing the filter material subjected to the fold processing into a cylindrical shape, and a bag filter obtained by processing a filter cloth made of a woven fabric or a nonwoven fabric into a bag shape, and the like. Widely used in industrial fields.

In such a filter, when the fibers constituting the filter have a constant fiber diameter, or when the nonwoven fabric constituting the filter has a constant porosity, the filtration life is short. By making the outer layer part coarser, such as by increasing the fiber diameter of the outer layer part on the upstream side of the filter medium constituting the filter or increasing the porosity, large particles are collected by the outer layer part on the upstream side, and fine particles are narrowed by the inner layer part. Means of extending the filtration life of the filter by collecting in the fiber layer are employed. However, since the outer layer portion of the filter is roughened, the thickness of the inner layer portion that determines the filtration accuracy is reduced, so that the filtration accuracy is reduced. Therefore, in order not to lower the filtration accuracy, measures were taken to cope with the means for forming the inner layer fine fiber part layer from thinner fibers and the means for lowering the porosity, but the water flow resistance of the filter was high. A new problem has arisen. If the water flow resistance of the filter is high, it is necessary to set the water flow pressure of the filtration line high in order to maintain the water flow, which increases the load on the pump and further increases the power consumption. There was a problem. Further, the number of filters can be increased in order to lower the water flow pressure, but this has the problem that a larger housing must be used and the equipment cost increases.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a filter which is made of a non-woven fabric made of a thermoplastic fiber and which has a reduced water flow resistance and which has a further improved filtration life. .

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have obtained the prospect that the intended purpose will be achieved by adopting the following structure.
The present invention has been completed. (1) A filter comprising a thermoplastic fiber, the filter having a fiber layer (I) and a fiber layer (II), wherein the fiber layer (I) has an uneven structure and is randomly dispersed. It has a surface structure having a microporous structure of irregular shape due to thermoplastic fibers, and the fiber layer (II) has a surface structure having an elongated shape opening by thermoplastic fibers arranged in one direction. A filter comprising a nonwoven fabric. (2) The filter according to (1), wherein the fiber layer (I) is formed of a nonwoven fabric having a higher porosity than the fiber layer (II). (3) The nonwoven fabric is moved from the surface of the fiber layer (I) to the fiber layer (I).
The filter according to the above (1) or (2), which is a nonwoven fabric having a fiber diameter gradient over the surface of I). (4) The filter according to the above (1), wherein the thermoplastic fiber is a composite fiber composed of at least two kinds of thermoplastic resins having a melting point difference of 10 ° C. or more. (5) The filter according to the above (1), wherein the thermoplastic fiber is a mixed fiber composed of at least two kinds of thermoplastic resins having a melting point difference of 10 ° C. or more. (6) The filter according to any one of (1) to (3), wherein the nonwoven fabric is a nonwoven fabric obtained by melt blowing. (7) A filter in which the filter according to any one of the above (1) to (6) is laminated on at least one surface of at least one type of article selected from the group consisting of a microporous membrane and a cloth. (8) The filter according to any one of the above (1) to (7), wherein the filter is a cartridge filter formed by winding a nonwoven fabric into a cylindrical shape. (9) The filter according to any one of the above (1) to (7), wherein the filter is a pleated filter obtained by folding a nonwoven fabric.
The filter according to the item. (10) The filter according to any one of the above (1) to (7), wherein the filter is a bag filter formed of a nonwoven fabric in a bag shape.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. In the filter of the present invention, the nonwoven fabric made of thermoplastic fibers constituting the filter has a fiber layer (I) on the side where the filtrate flows in, has an uneven structure, and is irregularly formed by randomly dispersed thermoplastic fibers. By making it a fiber layer with a surface structure having a microporous structure, the surface area is large,
In addition, the porosity can be increased, the flow resistance at the time of inflow of the filtrate is small, and the collection amount of relatively large particles is increased. Also, by making the fiber layer (II) from which the filtrate flows out into a fibrous layer having a surface structure having elongated openings with thermoplastic fibers arranged with directionality in one direction, Even if the shape of the opening is the same as that of a circular opening, the effect of trapping finer particles will be produced. By utilizing this effect, when obtaining approximately the same filtration accuracy, a higher opening ratio (ratio of the opening area to the surface area of the back layer side of the nonwoven fabric) is higher than in the case of an opening having a circular shape. ) Makes it possible to collect particles of the same diameter, the water permeability of the filter can be improved by increasing the porosity of the fiber layer (II), and the synergistic effect with the fiber layer (I) on the inflow side can be improved. As a result, excellent water permeability and a prolonged filtration life can be realized. Further, the filter of the present invention comprises a fiber layer (I) and a fiber layer (I).
The nonwoven fabric having (I) may be used alone, but one or more articles selected from the group consisting of a microporous membrane such as a membrane sheet and a fabric such as a net, a woven fabric, and a nonwoven fabric may be further combined with a fiber layer. It can be used by laminating it on at least one side of a nonwoven fabric having (I) and a fiber layer (II).

[0007] The nonwoven fabric comprising thermoplastic fibers used in the present invention may be obtained directly by spinning to obtain a nonwoven fabric, such as a spunbonding method or a melt-blowing method, or a short fiber as a raw material, a card method or an airlaid method. And those obtained by a nonwoven fabric manufacturing method such as a needle punching method and a water jet method. Further, a nonwoven fabric obtained by laminating and integrating a web or nonwoven fabric made of randomly dispersed fibers having an uneven structure on one surface thereof and a web or nonwoven fabric made of fibers arranged in a directional manner may be used. To laminate and integrate web or nonwoven
It is desirable to include a composite fiber or a mixed fiber made of at least two or more thermoplastic resins having a melting point difference of 10 ° C. or more in each web or nonwoven fabric,
Each web or nonwoven fabric is passed through a through-air dryer in a state of being laminated, and heat treatment is performed so that the nonwoven fabrics are thermally bonded and integrated.

As a method of forming a concavo-convex structure on one side of a nonwoven fabric, a web or nonwoven fabric is pressurized and heated by an embossing device including one having a smooth roll (mirror surface roll) and the other having an embossing roll having a concavo-convex pattern (engraving pattern). Or a method of heating the nonwoven fabric with a through-air dryer and then pressing the nonwoven fabric against the conveyor net with a smooth roll at the exit of the dryer to form an uneven structure on one side of the nonwoven fabric by the uneven pattern of the conveyor net. . Further, as a method for obtaining a nonwoven fabric having thermoplastic fibers arranged in one direction, that is, in one direction, a web obtained by a card method is stretched by a drafter in a nonwoven fabric flow direction (hereinafter referred to as MD direction). A method of arranging fibers can be used, and a spun bond method or a melt blow method in which fibers spun from a spinning machine are deposited on a suction conveyor is preferably used. In the spun bond method, the fibers can be easily positively oriented in the MD direction by, for example, increasing the speed of a suction conveyor belt, and thus can be used for producing the filter of the present invention. . However, since the range of the fiber diameter of the thermoplastic fiber that can be produced by the spunbond method is narrow, it is difficult to produce a filter having various filtration accuracy using only the spunbond nonwoven fabric. For this reason, the melt blow method having a wide range of fiber diameters that can be produced is most preferably used.

However, the fibers obtained by the melt blow method are generally dispersed at random, so that the thermoplastic fibers can be arranged in one direction with a direction by using the following manufacturing method. Hereinafter, a method for producing a nonwoven fabric used in the present invention will be described with reference to the drawings by way of examples. As shown in FIG. 1, between a spinneret 1 and a suction conveyor 3 for collecting thermoplastic fibers (which may be a suction drum), a rotating cylindrical body 2 having a smooth surface (which is a rotating cylinder having a smooth surface). A moving conveyor may be installed), and when a part of all the fibers of the spun thermoplastic fiber 6 is in a semi-solid state, the fiber is directly brought into contact with the inclined surface of the rotating cylindrical body 2 and brought into contact therewith. The nonwoven fabric (B) in which the thermoplastic fibers are arranged in the MD direction by moving and collecting the thermoplastic fibers on the lower suction conveyor 3
Can be formed. On the other hand, the fibers which do not hit the rotary cylinder 2 are directly semi-solidified in the suction conveyor 3.
By being collected on the upper side, a fiber layer (I) 6A having an uneven structure is formed in a form in which the uneven pattern of the net of the suction conveyor is copied. Then, in a state in which the fiber layer (I) 6A and the fiber layer (II) 6B are laminated, the fiber layer (I) is passed through a heat treatment apparatus 5 (preferably a through-air dryer), and has the lowest melting point among the thermoplastic resins constituting the thermoplastic fibers. By heating to a temperature at which the thermoplastic resin melts, the two types of nonwoven fabrics are thermally bonded to form the integrated nonwoven fabric 9. In this manufacturing method, the shape and size of the concavo-convex structure are adjusted by adjusting the pattern of the conveyor net, the type of material and the suction amount of suction, the distance between the spinneret and the suction conveyor, the clearance between the rotating cylinder and the suction conveyor, and the like. It is possible to change. Further, by moving the rotating cylindrical body 2 in the X direction, the proportion of randomly dispersed fibers can be increased, and conversely, by moving the rotating cylinder 2 in the X ′ direction, the proportion of fibers arranged in one direction can be increased. is there. Also,
The porosity of the fiber layer (I) can be made higher than that of the fiber layer (II) of the nonwoven fabric, and the filtration life can be improved. Further, as shown in FIG. 2, the spinneret (B) 1B is located upstream of the basic spinneret (A) 1A, and the spinneret (C) 1B is located downstream.
C and the rotating cylinder 2B can be added. That is, a fiber layer (III) 7 made of only randomly dispersed fibers is produced on the upstream side, and a fiber layer (IV) 8 made of only fibers arranged in one direction by the spinneret (C) 1C on the downstream side is produced. Fiber layer (I) 6A and fiber layer (II) 6B to be made
By integrating and laminating all the layers, it is possible to adjust the thickness of each fiber layer arranged in one direction and the thickness of the randomly dispersed fiber layer having a concavo-convex structure, so that the bulkiness and porosity can be easily adjusted. Become. In other words, the laminated nonwoven fabric 9 obtained in FIG. 2 has a fiber layer (I) / fiber layer (I) having the two-layer structure as an intermediate layer between the fiber layer (IV) and the fiber layer (III).
Since I) is interposed, a multilayer filtration structure having a microporous structure which is bulky and capable of providing a multi-stage porosity gradient is obtained. Further, by changing the fiber diameter in each spinneret, it is possible to impart a fiber diameter gradient to the nonwoven fabric. In other words, the fibers constituting the fiber layer (I) of the filter are thickened,
By making the fibers constituting the fiber layer (II) thin, a fiber diameter gradient can be provided from the fiber layer (I) to the fiber layer (II), and thereby a pore diameter gradient can be provided by the fiber diameter. Improvement of filtration life can be measured.

[0010] The material of the surface on which the thermoplastic fibers in the semi-solidified state are deposited in the rotating cylindrical body or the rotating moving conveyor,
Metals, Teflon, and the like are preferably used because they need to withstand high-temperature hot air jetted from a spinneret during melt-blow spinning and have excellent releasability from fibers. Further, if necessary, an air cooling or water cooling mechanism may be provided on the rotating cylinder or the belt of the rotating moving conveyor to adjust the surface temperature so as not to rise too much. Further, the rotation speed of the rotating cylinder or the rotary moving conveyor is adjusted so as to be synchronized with the peripheral speed of the suction drum or the suction conveyor.

The thermoplastic fiber of the present invention refers to a fiber made of a thermoplastic resin, and a melt-spinnable thermoplastic resin can be used as a raw material. Examples thereof include polyethylene resins such as high-density polyethylene, low-density polyethylene, and linear low-density polyethylene, polypropylene, poly-4-methylpentene, and propylene and other α-olefins.
Polypropylene resin, polyethylene terephthalate, polybutylene terephthalate, and acid components polymerized using a Ziegler-Natta-based catalyst or metallocene-based catalyst such as a ternary or terpolymer, and an acid component were polymerized using isophthalic acid in addition to terephthalic acid. Examples include polyester resins such as low-melting polyesters, polyamide resins such as nylon-6 and nylon-66, and thermoplastic resins such as polycarbonate. These thermoplastic resins may be used alone or as a mixture of two or more. Further, a coloring agent, a light-proofing agent, a flame retardant, an antibacterial agent and the like may be added. Further, from the thermoplastic resin, at least two or more kinds of thermoplastic resins having a difference in melting point of 10 ° C. or more are appropriately selected, and a parallel type, a sheath-core type, an eccentric type or the like, or
Fibers made of at least two kinds of thermoplastic resins having a melting point difference of 10 ° C. or more may be mixed or mixed.
By including the above configuration having a melting point difference, by heating, the low melting point thermoplastic resin is melted, and the fibers are thermally bonded to each other, so that the fibers do not fall off, the filter medium strength is high, and the filtration accuracy is stable. Can be created.

The combination of at least two kinds of thermoplastic resins having a difference in melting point used for the conjugate fiber is as follows:
There is no particular limitation as long as the difference in melting point is 10 ° C. or more, preferably 15 ° C. or more. When there are two types of thermoplastic resins having a melting point difference, when a combination of a low melting thermoplastic resin / a high melting thermoplastic resin is used, a high density polyethylene / polypropylene, a low density polyethylene / polypropylene, a linear low density polyethylene / Polypropylene, binary or terpolymer of propylene and other α-olefins / polypropylene, propylene and other α-olefins
Binary copolymer or terpolymer with olefin / Binary copolymer or terpolymer with propylene and other α-olefin, linear low density polyethylene / high density polyethylene, low density polyethylene / High-density polyethylene, linear low-density polyethylene / polyethylene terephthalate, low-density polyethylene / polyethylene terephthalate, high-density polyethylene / polyethylene terephthalate, polypropylene / polyethylene terephthalate, binary copolymer or ternary copolymer of propylene and other α-olefins Examples thereof include polymer / polyethylene terephthalate, low melting point polyester / polyethylene terephthalate, nylon 6 / nylon 66, and the like. Among these, a combination of a polyethylene resin / polypropylene resin, which is a combination of polyolefin resins, and a combination of a polyethylene resin / polyester resin, which is a combination of a polyolefin resin and a polyester resin, are preferably used. Further, it is preferable that the combination of the thermoplastic resin used as the mixed fiber is the same as the combination used for the conjugate fiber, so that the fibers are appropriately thermally bonded to each other. The ratio of the high melting point thermoplastic resin to the low melting point thermoplastic resin (composite ratio, blend ratio) is preferably in the range of 80:20 to 20:80, but the ratio of the low melting point thermoplastic resin is extremely high. When the number is too small, the number of heat bonding points between the fibers decreases, and the shape retention property decreases. Further, if the ratio of the high melting point thermoplastic resin is extremely small, the fibers are excessively melted during heating, and the shape is likely to be collapsed.
The range is 0:70.

The fiber diameter of the thermoplastic fiber used in the present invention is selected in accordance with the target filtration accuracy of a filter as a final product, and a filter having a high filtration accuracy has a diameter of 1 to 10 μm produced by a melt blow method. A filter having a large fiber diameter is suitably selected from a melt blow method, a spun bond method, and a card method as a coarse precision filter. Further, the shape of the fiber cross section of the thermoplastic fiber used in the present invention may be circular or irregular, and if a modified cross section yarn or split fiber is used, the life of the filtration life can be prolonged due to an increase in the collecting area and the filtration accuracy can be improved. preferable. In addition, the fiber diameter and cross-sectional shape of the thermoplastic fiber composed of the low melting thermoplastic resin and the thermoplastic fiber composed of the high melting thermoplastic resin by blending or blending may be different from each other. It may be a mixture of fibers.

The elongated hole formed by the fibers arranged in one direction in the fiber layer (II) used in the present invention has an average ratio of major axis to minor axis (= major axis length / minor axis length).
Is desirably in the range of 3.5 to 15, and if this value is significantly lower than 3.5, the ability to collect fine particles is reduced, and the effect of reducing the pressure loss is not obtained. On the other hand, when the value exceeds 15, the strength of the nonwoven fabric in the minor diameter direction decreases, and the shape of the opening changes, so that the collected particles can easily escape and the filtration accuracy decreases. Also, in one surface layer, various shapes of holes are generated by randomly dispersed thermoplastic fibers, and the shape of the holes is close to a circular shape, and the average length ratio is 1 to 3. Is desirable. When this value exceeds 3, the bulk decreases,
It becomes difficult to obtain a nonwoven fabric having a high porosity. In this way, by changing the shape of the hole from a circular shape to an elongated shape (slit shape) from one surface layer of the nonwoven fabric to the other surface layer, a large particle size is collected at the circular opening. However, since fine particles are trapped in the elongated opening, a pore diameter gradient having a deep structure is formed from one surface layer to the other surface layer, which has an effect of extending the filtration life.

The porosity of the nonwoven fabric used in the present invention is 6
A range of 0 to 90% is desirable, and more preferably 65 to 8%.
A range of 5% is desirable. When the porosity is less than 60%, the water flow resistance increases remarkably, and when the porosity greatly exceeds 90%, the strength of the nonwoven fabric is reduced, and the nonwoven fabric layer is crushed by the differential pressure at the time of filtration or the shape of the pores is changed. Therefore, there occurs a problem that the collection efficiency of the particles is reduced. Further, by increasing the porosity of the fiber layer (I) in the range of 5 to 15% with respect to the porosity of the fiber layer (II), a space for collecting coarse particles is widened, and the filtration life is further extended. Can be done. If this value is higher than 15%, there is a large difference in the collected particle size between the layers, and the particles are not sufficiently collected in the fiber layer (I), and as a result, the particles are collected only inside the fiber layer (II). And the filtration life is significantly shortened.

[0016] The filter of the present invention can control filtration accuracy,
In order to improve the strength of the filter medium, improve liquid permeability and particle collection, etc.,
One or more types of articles selected from the group consisting of microporous membranes, nets, and woven fabrics are combined with a fiber layer (I) and a fiber layer (II).
May be laminated on at least one surface of a nonwoven fabric having Examples of the microporous membrane include a membrane sheet made of polyethylene, polytetrafluoroethylene, polycarbonate, cellulose acetate, and the like, and a hydrophilized membrane is preferably used for aqueous filtration. Examples of the net include a net formed by knitting monofilaments such as nylon, polyethylene, polypropylene, and polyester, and a net formed by extrusion. Examples of the woven fabric include those obtained by knitting a spun yarn of cotton, nylon, polyethylene, polypropylene, polyester, or the like, and a spun yarn mixed with fibrous activated carbon or the like may be used. Further, an adsorbent such as an organic substance or heavy metal, an antibacterial agent, or the like may be added to these cloths.

An example of a method for producing the filter of the present invention will be described. In the case of a cartridge filter in which a nonwoven fabric is wound in a cylindrical shape, a porous cylinder is used as a core of the nonwoven fabric, and the nonwoven fabric is wound on the porous cylinder with the surface having the uneven structure of the fiber layer (I) facing outside, A method of manufacturing is provided in which the winding ends are bonded by heat sealing, hot melt or the like, and then a gasket or end cap having a shape covering both end surfaces is bonded. In the case of a nonwoven fabric made of a composite fiber or a mixed fiber, the nonwoven fabric is passed through a through-air dryer with the surface of the uneven structure of the fiber layer (I) facing down, and the thermoplastic resin having the lowest melting point among the fibers is used. Is melted at a temperature at which the non-woven fabric is unevenly wound on a metal pipe at the outlet of the dryer to a predetermined outer diameter such that the surface of the uneven structure is on the outside, and after cooling, the filter is formed by removing the metal pipe. A method is also possible.

In the case of a pleated filter obtained by pleating a nonwoven fabric, a spunbonded nonwoven fabric or the like is laminated on the surface layer side of the fiber layer (II) having a surface structure having elongated openings, and then subjected to a pleating process. Then, cutting is performed at a predetermined number of peaks. After making the cylindrical shape so that one surface layer of the nonwoven fabric is on the outside and heat-sealing the ends of the nonwoven fabric, insert the porous cylinder on the inside, fit the outer cylinder on the outside, and attach the end caps to both end surfaces It can be manufactured by Instead of the spunbonded nonwoven fabric or the like, the nonwoven fabric of the present invention may have a structure in which the back layers are laminated so as to be in contact with each other, and the uneven structure of the fiber layer (I) serves as a spacer for maintaining the interval, so that water permeability and filtration life are reduced. It will be excellent. When a more accurate filter is required, a highly accurate pleated filter can be manufactured by laminating a microporous membrane such as a membrane sheet between the fiber layer (I) and the spunbonded nonwoven fabric.

With respect to the bag filter, the nonwoven fabric is formed into a bag shape such that the surface of the uneven structure of the fiber layer (I) is on the inside, and the mating surface of the nonwoven fabric and the bottom of the bag are heat-sealed or ultrasonically welded. Weld. Next, the nonwoven fabric on the opening side is folded inward from the outside to wrap the metal muzzle, and the folded nonwoven fabric tip and the nonwoven fabric on the bag side are welded by a heat sealing machine or an ultrasonic welding machine. The muzzle may be made of resin, or the opening of the nonwoven fabric may be directly welded to the muzzle made of resin. When the strength of the filter material is required, a resin net is laminated on the outside of the non-woven fabric, and the above-described processing is performed to obtain a bag filter having excellent strength. Further, a sewn bag-shaped woven fabric or the like may be arranged on the outside.

[0020]

The present invention will be described in detail with reference to examples and comparative examples, but the present invention is not limited to these examples. The measurement method used in each example is shown below. 〇Average fiber diameter An electron microscope image of the thermoplastic fibers constituting the nonwoven fabric was taken into an image processing apparatus, and the fiber diameter was measured for 100 arbitrary fibers, and the average value was defined as the average fiber diameter. ○ Average long-short diameter ratio The electron microscope image of the thermoplastic fibers constituting the nonwoven fabric is taken into an image processing device, and the maximum diameter in the axial direction orthogonal to the long diameter and the long diameter direction is defined as a short diameter for 100 arbitrary opening portions. The measurement was performed, and the major axis / minor axis was calculated at each opening, and the average value at 100 locations was defined as the average major axis / minor axis ratio. 〇Porosity The thickness of each layer is measured at arbitrary 20 points by taking an optical microscope image of the vertical cross section of the nonwoven fabric composed of the laminated fiber layer (I) and the fiber layer (II) into an image processing device. The porosity was calculated from the average value and the basis weight of each layer.
As for the thickness of the fiber layer (I), the maximum value in the image is obtained for 10 places out of 20 places,
For the remaining 10 points, the minimum value in the image was measured, and the average value was used. ○ Water flow resistance A filter is attached to the housing of the circulating filtration tester,
Water is circulated at a flow rate of 30 liters per minute, and the pressure difference between the inlet and the outlet of the housing is measured. Next, the filter is removed from the housing, and the differential pressure is measured at the same flow rate. The value obtained by subtracting the differential pressure when the filter was removed from the differential pressure when the filter was attached was defined as the water flow resistance. ○ Filtration accuracy A filter is attached to the housing of the circulating filtration tester.
AC fine test dust (ACFTD, median diameter 6.6-8.cm) while circulating water at a flow rate of 30 liters per minute.
6 μm) is added at 0.5 g / min, and after 5 minutes, and when the pressure difference between the inlet and outlet of the housing reaches 0.15 MPa, the stock solution and the solution after passing through the filter are sampled. The particle size distribution of each liquid was measured for filtration accuracy with a light-blocking particle size distribution analyzer, and the particle size at which the collection efficiency was 99.9% or more was defined as the filtration accuracy. ○ Filtration life In the above-mentioned circulation type filtration accuracy tester, a filter was attached to the housing and ACFTD was added at a rate of 0.5 g / min while circulating water at a flow rate of 30 liters per minute, and the inlet and outlet sides of the housing were added. And measure the pressure difference. The time until the differential pressure showed 0.15 MPa was defined as the filtration life.

Example 1 Using a spinneret for a core-core composite spunbond having a pore diameter of 0.4 mm, a high melting point thermoplastic resin having a melting point of 163 ° C. and a melt flow rate of 40 g / 10 min (JISK 721)
0 as a core component and a low melting point thermoplastic resin having a melting point of 125 (value measured under condition 14 in Table 1).
° C, melt flow rate 20g / 10min (JIS K
7210) of the linear low-density polyethylene (measured under condition 4 in Table 1) as the sheath-side component.
And extruded at a composite ratio of 50:50. After sucking at a speed of 2500 m / min by air soccer, the fibers were collected on a suction conveyor to produce a composite spunbond nonwoven fabric. The obtained composite spunbond nonwoven fabric had a basis weight of 30 g / m ² and an average fiber diameter of 18.1 μm. Next, a high melting point thermoplastic resin having a melting point of 163 ° C. and a melt flow rate of 40 g / 10 min (JIS K 721)
0 as a core component and a low melting point thermoplastic resin having a melting point of 125 (value measured under condition 14 in Table 1).
° C, melt flow rate 20g / 10min (JIS K
7210 A sheath-core composite fiber (composite ratio of 5) using a linear low-density polyethylene having a sheath-side component of a value measured under condition 4 in Table 1.
0:50, 13 crimps / 25 mm, fiber diameter 22.
3 μm, cut length 51 mm) using a card machine with a basis weight of 40
g / m ² web. After passing the web between a smoothing roll heated to 125 ° C. and an embossing roll (height: 1 mm, embossing ratio: 20%, embossing shape: 1 mm square), an uneven structure is formed on one side. The composite spunbonded nonwoven fabric was heated to 125 ° C. with an air-through drier in a laminated state, and the laminated surface and the fiber intersections in the nonwoven fabric were thermally bonded. The composite spunbonded nonwoven fabric side of the laminated and integrated nonwoven fabric corresponds to the fiber layer (II), and the card nonwoven fabric side corresponds to the fiber layer (I). The average ratio of major axis to minor axis was 7.2 for the spunbond nonwoven fabric and 2.5 for the card nonwoven fabric. This laminated non-woven fabric was wound around a polypropylene porous tube having an inner diameter of 30 mm, an outer diameter of 34 mm, and a length of 250 mm to produce a cartridge filter having an outer diameter of 68 mm. Table 1 shows the measurement results.
The obtained filter had low water flow resistance and excellent filtration life.

Comparative Example 1 The same polypropylene as in Example 1 was spun at a spinning temperature of 270 ° C. as a thermoplastic resin using a spinneret for regular fiber spunbond having a pore diameter of 0.4 mm. After sucking the fiber in the semi-molten state at a speed of 2500 m / min by air sucker, the fiber was collected on a suction conveyor to produce a spunbond nonwoven fabric. The resulting spunbonded nonwoven fabric was made of regular fibers, and had a basis weight of 40 g / m ² , an average fiber diameter of 19.2 μm, and an average ratio of major axis to minor axis of 6.8. Next, an outer diameter of 68 m was wound around the same porous tube as in Example 1.
m cartridge filters were produced. Table 1 shows the measurement results. The obtained filter had higher water flow resistance and shorter filtration life than the filter of Example 1.

Example 2 A composite melt-blowing spinneret having a hole diameter of 0.3 mm was used.
As a high melting point thermoplastic resin, the melting point is 162 ° C. and the melt flow rate is 68 g / 10 min (JIS K 7210).
The polypropylene having a melting point of 13 as a low-melting thermoplastic resin was used as the core component of the polypropylene (value measured under the condition 14 in Table 1).
0 ° C, melt flow rate 70g / 10min (JIS
K 7210 (measured under condition 14 in Table 1) using a propylene / ethylene / butene-1 terpolymer as a sheath component, at a spinning temperature of 290 ° C., 270 ° C. and a composite ratio of 50:50, respectively, from a spinning machine. Spinning was performed, and heated air at 380 ° C. was blown at a pressure of 0.08 MPa. A portion of the finely divided thermoplastic fiber was deposited on the surface of a stainless steel rotary cylinder having an outer diameter of 120 mm, which was installed under the mouthpiece and parallel to the mouthpiece by the method shown in FIG. 1 and then trapped on the suction conveyor net. The remaining thermoplastic fibers that were not deposited on the surface of the stainless steel rotary cylinder were directly collected on a conveyor net to produce a composite melt-blown nonwoven fabric having a basis weight of 50 g / m ² . The side of the melt-blown non-woven fabric directly collected on the conveyor corresponds to the fiber layer (I), and the side of the non-woven fabric collected on the surface of the stainless steel rotary cylinder and then collected on the suction conveyor net corresponds to the fiber layer (II). . These have an average fiber diameter of 12.6 μm, an average length ratio of the fiber layer (II) of 3.9, and an average length ratio of the fiber layer (I) of 1.8.
Met. This non-woven fabric is dried with an air-through dryer.
After heating to 30 ° C. and melting the low melting point thermoplastic resin, it is wound around a stainless steel pipe having an outer diameter of 30 mm. After cooling, the stainless steel pipe is pulled out and cut to obtain an inner diameter of 30 mm.
A cartridge filter having an outer diameter of 68 mm and a length of 250 mm was manufactured. Table 1 shows the measurement results. The obtained filter had low water flow resistance and excellent filtration life.

Comparative Example 2 A raw material, an apparatus, and spinning conditions similar to those in Example 2 were used.
/ M ² of a composite meltblown nonwoven fabric. However, the rotating cylindrical body made of stainless steel was not used, and all the finely divided thermoplastic fibers were directly collected on the suction conveyor net. All of the obtained nonwoven fabrics were composed of randomly dispersed thermoplastic fibers, and had an average fiber diameter of 13.1 μm and an average ratio of major axis to minor axis of 1.9. This nonwoven fabric was molded in the same manner as in Example 2 to produce a cartridge filter having an inner diameter of 30 mm, an outer diameter of 68 mm, and a length of 250 mm. Table 1 shows the measurement results. The obtained filter had higher water flow resistance and shorter filtration life than the filter of Example 2.

Example 3 Using the same raw materials, equipment, and extrusion conditions as in Example 2, 38
5 ° C. heated air was blown at a pressure of 0.11 MPa.
After depositing a part of the thermoplastic fiber finely divided by the method shown in the above on the surface of a stainless steel rotating cylindrical body having an outer diameter of 120 mm placed in parallel with the base under the base, it is collected on a suction conveyor net. Then, the remaining fibers were directly collected on a conveyor net to produce a melt-blown nonwoven fabric having a basis weight of 50 g / m ² . The obtained melt-blown nonwoven fabric was subjected to a heat treatment at 130 ° C. with a through-air dryer to form a nonwoven fabric in which fiber intersections were thermally bonded. The melt-blown non-woven fabric side directly collected on the conveyor corresponds to the fiber layer (I),
After being deposited on the surface of the stainless steel rotating cylinder, the nonwoven fabric collected on the suction conveyor net has a fiber layer (I
It corresponds to I). This had an average fiber diameter of 5.3 μm, an average length ratio of the fiber layer (II) of 5.1, and an average length ratio of the fiber layer (I) of 1.9. Next, after laminating the two nonwoven fabrics so that the surfaces on which the thermoplastic fibers were arranged in one direction were aligned, pleating with a peak height of 12 mm was performed by a pleating machine. Cut with 120 folds, heat-seal the end to form a cylinder, set a polypropylene porous cylinder inside and outside, and weld an end cap to the end face of the cylinder to obtain an inner diameter of 36 mm and an outer diameter of A pleated filter having a length of 70 mm and a length of 250 mm was manufactured. Table 1 shows the measurement results. The resulting filter is
The water flow resistance was low, and the filtration life was excellent.

Comparative Example 3 The same polypropylene as in Example 2 was spun from a spinning machine at a spinning temperature of 290 ° C. as a thermoplastic resin using a spinning nozzle for melt-blowing regular fibers having a pore diameter of 0.3 mm.
A 90 ° C. heated air was blown at a pressure of 0.11 MPa, and the fine fibers were directly collected on a conveyor net, thereby producing a composite melt-blown nonwoven fabric having a basis weight of 50 g / m ² . All of the obtained nonwoven fabrics were composed of randomly dispersed thermoplastic fibers, and had an average fiber diameter of 5.0 μm and an average ratio of major axis to minor axis of 1.8. This nonwoven fabric was processed in the same manner as in Example 3 by using an inner diameter of 36 mm, an outer diameter of 70 mm, and a length of 25 mm.
A 0 mm pleated filter was manufactured. Table 1 shows the measurement results. The obtained filter had higher water flow resistance and shorter filtration life than the filter of Example 3.

Example 4 385 ° C. under the same raw materials, equipment, and extrusion conditions as in Example 2.
The heated air is blown at a pressure of 0.12 MPa, and a part of the fibers finely divided by the method shown in FIG. 1 is applied to the surface of a stainless steel rotary cylinder having an outer diameter of 120 mm which is installed under the base and parallel to the base. After the accumulation, the melt-blown nonwoven fabric having a basis weight of 40 g / m ² was manufactured by collecting the fibers on a suction conveyor net and collecting the remaining fibers directly on the conveyor net. The obtained melt-blown nonwoven fabric was subjected to a heat treatment at 130 ° C. with a through-air drier to form a nonwoven fabric in which intersections of thermoplastic fibers were thermally bonded. The melt-blown non-woven fabric directly collected on the conveyor corresponds to the fiber layer (I) 6A, and the non-woven fabric collected on the suction conveyor net becomes the fiber layer (II) 6B after being deposited on the surface of the stainless steel rotary cylinder. Equivalent to. These fibers had an average fiber diameter of 3.4 μm, an average length ratio of the fiber layer (II) of 6.7,
The average ratio of major axis to minor axis of the fiber layer (I) was 2.1. next,
After laminating two obtained nonwoven fabrics on and under a polytetrafluoroethylene membrane sheet having an average pore diameter of 0.65 μm so that the surface of the fiber layer (II) fits with the membrane sheet, a pleating machine is used to obtain a peak height. A 12 mm pleating process was performed. Cut with 120 folds, heat-seal the end to form a cylinder, set a polypropylene porous cylinder inside and outside, and weld an end cap to the end face of the cylinder to obtain an inner diameter of 36 mm and an outer diameter of A pleated filter having a length of 70 mm and a length of 250 mm was manufactured. Table 1 shows the measurement results. The resulting filter is
The water flow resistance was low, and the filtration life was excellent.

Comparative Example 4 390 using the same raw materials, equipment and extrusion conditions as in Comparative Example 3.
℃ heated air at a pressure of 0.12MPa, the basis weight 4
A melt-blown nonwoven fabric of 0 g / m ² was produced. All of the obtained nonwoven fabrics were composed of randomly dispersed thermoplastic fibers, the average fiber diameter was 3.2 μm, and the average ratio of major axis to minor axis was 2.0. Next, using a polytetrafluoroethylene membrane sheet having an average pore diameter of 0.65 μm and the obtained nonwoven fabric, an inner diameter of 36 m was obtained by the same processing method as in Example 4.
m, an outer diameter of 70 mm and a length of 250 mm were produced. Table 1 shows the measurement results. The obtained filter had higher water flow resistance and shorter filtration life than the filter of Example 4.

Example 5 A mixed fiber melt-blowing spinneret having a hole diameter of 0.3 mm, which extrudes two kinds of thermoplastic resins alternately from spinning holes, was used as a thermoplastic resin having a high melting point, polyethylene terephthalate having a melting point of 251 ° C., and a low melting point. Melting point of 1 as thermoplastic resin
92 ° C ethylene glycol terephthalate / isophthalate copolymer spinning temperature 330 ° C, 300 ° C
At 0:50, the fiber was spun from the spinning machine, and at the same time, heated air at 420 ° C. was blown at a pressure of 0.08 MPa, and a part of the fine fiber was placed under the base in parallel with the base by the method shown in FIG. After being deposited on the surface of a stainless steel rotary cylinder having an outer diameter of 120 mm, it was collected on a suction conveyor net to produce a mixed melt blown nonwoven fabric having a basis weight of 100 g / m ² . The obtained mixed-melt-blown nonwoven fabric was heat-treated at 192 ° C. with a through-air drier to form a nonwoven fabric in which thermoplastic fiber intersections were thermally bonded. The mixed fiber melt-blown non-woven fabric collected directly on the conveyor is the fiber layer (I).
6A, and the mixed-melt-blown nonwoven fabric side collected on the suction conveyor net after being deposited on the surface of the stainless steel rotary cylinder corresponds to the fiber layer (II) 6B. The average fiber diameter was 14.5 μm, the average length ratio of the fiber layer (II) was 5.6, and the average length ratio of the fiber layer (I) was 1.7. Next, a polyester net having a mesh size of 40 mesh / 25.4 mm and a fiber diameter of 200 μm is superimposed on the fiber layer (II) 6B side of the nonwoven fabric, and formed into a bag shape by ultrasonic welding so that the net is on the outside. A stainless steel ring having a diameter of 180 mm and a thickness of 3 mm was folded into the side, and the folded nonwoven fabric and net were ultrasonically welded to produce a bag filter having a bag diameter of 180 mm and a length of 400 mm. Table 1 shows the measurement results. The obtained filter had low water flow resistance and excellent filtration life.

Comparative Example 5 Using the same spinneret as in Comparative Example 3, the same polyethylene terephthalate as in Example 5 was spun from a spinning machine as a thermoplastic resin at a spinning temperature of 330.degree. Blowed at 08 MPa, the fine fibers are collected directly on the suction conveyor net, and the basis weight is 100 g /
An m ² meltblown nonwoven fabric was produced. The resulting melt blown nonwoven fabric had an average fiber diameter of 11.7 μm and an average ratio of major axis to minor axis of 1.6. Using the same net as in Example 5 and using the same processing method, a bag diameter of 180 mm and a length of 400 m
m were manufactured. Table 1 shows the measurement results. The obtained filter had higher water flow resistance and shorter filtration life than Example 5.

Example 6 Using the same composite melt-blow spinneret as in Example 2, spinning was performed by the method shown in FIG. The thermoplastic resin used for the core side and the sheath side for all three units was the same as in Example 2, and these thermoplastic resins were combined at a composite ratio of 50:50 and a spinning temperature of 290.
At ℃ from the spinning machine. The spinneret 1B blows heated air at 380 ° C. at 0.07 MPa and directly collects fibers on the conveyor net surface to form a composite melt-blown nonwoven fabric (fiber layer (III) 7) having a basis weight of 50 g / m ² . Next, the spinneret 1A heated air at 390 ° C. to 0.08MPa.
a, and a part of the fiber is deposited on the surface of a rotary cylinder 2A made of stainless steel having a diameter of 100 mm, then collected on a suction conveyor net, and a composite melt-blown nonwoven fabric having a basis weight of 25 g / m ² (fiber layer (I) 6A) ) And basis weight 25g
/ M ² composite meltblown nonwoven fabric (fiber layer (II) 6B)
Was manufactured. The spinneret 1C uses heated air at 400 ° C.
After blowing at 09 MPa and depositing all of the fibers on the surface of the rotary cylinder 2B made of stainless steel having a diameter of 100 mm, the fibers are collected on a suction conveyor net and a composite melt-blown nonwoven fabric having a basis weight of 50 g / m ² (fiber layer (IV) 8) Was manufactured. Each obtained composite meltblown nonwoven fabric (fiber layer (II
I) 7), (fiber layer (I) 6A), (fiber layer (II) 6
B) and (fiber layer (IV) 8) were laminated in this order, and a heat treatment at 130 ° C. was performed by a through-air dryer in this state to obtain a nonwoven fabric in which thermoplastic fiber intersections and layers were thermally bonded. The laminated non-woven fabric obtained by heat treatment is
Fiber layer (III) has an average fiber diameter of 16.3 μm, average length ratio of 1.7, fiber layer (I) has an average fiber diameter of 12.5 μm, average length ratio of 2.2, and fiber layer (II) has an average fiber length. Diameter 12.5
μm, the average ratio of major axis to minor axis was 4.2, and the fiber layer (IV) had an average fiber diameter of 10.3 μm and the average ratio of major axis to minor axis of 5.7. Next, 40 mesh / 25.4m on the fiber layer (IV) side of this nonwoven fabric
m, superimposed with a polypropylene net having a fiber diameter of 200 μm, formed into a bag shape by ultrasonic welding so that the net is on the outside, and a stainless steel ring having a diameter of 180 mm and a thickness of 3 mm was folded into the opening side. 180m bag diameter by ultrasonic welding of non-woven fabric and net
m, a bag filter having a length of 400 mm was produced. Table 2 shows the measurement results. The obtained filter had low water flow resistance and excellent filtration life.

Comparative Example 6 The same raw materials, equipment and spinning temperature as in Comparative Example 3 were used.
Heated air at 0 ° C. was blown at a pressure of 0.1 MPa, and the finely divided thermoplastic fibers were directly collected on a suction conveyor net to produce a melt-blown nonwoven fabric having a basis weight of 150 g / m ² . The resulting melt blown nonwoven fabric has an average fiber diameter of 1
0.7 μm, and the average ratio of major axis to minor axis was 1.6. A bag filter having a bag diameter of 180 mm and a length of 400 mm was manufactured using the same net as in Example 6 and by the same processing method. Table 2 shows the measurement results. The resulting filter is
As compared with Example 6, the water flow resistance was higher and the filtration life was shorter.

[0033]

[Table 1]

From the results in Table 1, it can be seen that, in the nonwoven fabric constituting the filter, the fibrous layer (II), that is, the fibrous layer having an average ratio of major axis to minor axis on the filtrate outflow side of 3.5 or more is used to maintain the filtration accuracy. Water flow resistance has been reduced. On the other hand, the surface life of the fiber layer (I) on the filtrate inflow side was made uneven, and the fiber layer was randomly dispersed with an average ratio of major axis to minor axis of 3 or less, so that the filtration life could be improved. Furthermore, it was confirmed that the filtration life was significantly improved by making the porosity of the fiber layer (I) on the filtrate inflow side higher than that of the fiber layer (II) on the filtrate outflow side. Further, a composite fiber composed of at least two or more thermoplastic resins having a melting point difference of 10 ° C. or more,
By using mixed fibers and bonding the intersections of the fibers,
It was confirmed that stable filtration accuracy was maintained even when the flow resistance increased.

[0035]

[Table 2]

Further, from the results shown in Table 2, in the nonwoven fabric obtained by the production method shown in FIG. 2, the fiber layer (I) side is made of thermoplastic fibers dispersed at random like the fiber layer (I). A fiber layer (III) having a higher porosity than the layer (I) or a fiber layer (III) having a larger fiber diameter is laminated, and a fiber having an average ratio of the major axis to the minor axis larger than the fiber layer (II) is provided on the fiber layer (II) side. Layer (I
By laminating V) or a fiber layer (IV) with a small fiber diameter, it becomes possible to increase or smooth the average non-major axis ratio, fiber diameter, and porosity gradient of the laminated nonwoven fabric. This has a great effect on extending the filtration life when a filter is formed. Furthermore, according to the manufacturing method as shown in FIG. 2, the number of spinnerets to be spun and the respective spinning conditions can be adjusted, so that nonwoven fabrics of various combinations can be produced at once, and the productivity is also extremely excellent. It should be noted that the number of bases is not limited to three or more, and a method of feeding the nonwoven fabric from a roll may be combined.

[0037]

The nonwoven fabric used in the filter of the present invention has a fiber layer (I) and a fiber layer (II), and the fiber layer (I)
Has an irregular structure and a surface structure with an irregularly shaped microporous structure made up of randomly dispersed thermoplastic fibers, and the fiber layer (II) is made up of unidirectionally arranged thermoplastic fibers And a non-woven fabric having a surface structure having elongated openings. That is, since the pore structure of the nonwoven fabric is made different between the outflow side and the inflow side, there is an effect that the water flow resistance is reduced and the filtration life is further prolonged as compared with a filter consisting simply of randomly dispersed fibers. In particular, the porosity of the fiber layer (I) on the outer layer side of the filter is changed to the fiber layer (II)
By making it higher, a better effect of extending the filtration life appears. Furthermore, the filtration life can be improved by forming a fiber diameter gradient from the fiber layer (I) on the outer layer side of the filter to the fiber layer (II) on the back side. It becomes more remarkable by increasing or smoothing the gradients of the ratio of major axis to minor axis, fiber diameter, and porosity. Also, a filter medium when the water flow resistance is increased by using a composite fiber or a mixed fiber made of at least two or more kinds of thermoplastic resins having a melting point difference of 10 ° C. or more and bonding the intersections of the fibers. Has the effect of preventing squeezing and reduction of filtration accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic view illustrating an example of a method for producing a nonwoven fabric used in the present invention.

FIG. 2 is a schematic view illustrating an example of a method for producing a nonwoven fabric used in the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 spinneret 1A spinneret (A) 1B spinneret (B) 1C spinneret (C) 2 rotating cylinder having smooth surface 2A rotating cylinder having smooth surface 2B rotating cylinder having smooth surface 3 suction conveyor 4 suction Reference Signs List 5 heat treatment device 6 thermoplastic fiber 6A fiber layer (I) 6B fiber layer (II) 7 fiber layer (III) 8 fiber layer (IV) 9 nonwoven fabric

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01D 29/12 A (72) Inventor Daisuke Masuda 230 Kawadacho, Moriyama-shi, Shiga Prefecture Chisso Polypro Textile Co., Ltd. Textile Development Laboratory F term (reference) 4D019 AA03 BA13 BB02 BB03 BB10 BD01 CA02 CA03 CA04 DA02 DA06

Claims (10)

[Claims] 1. A filter comprising a thermoplastic fiber, said filter having a fiber layer (I) and a fiber layer (II), wherein said fiber layer (I) has an uneven structure and is randomly formed. The fiber layer (II) has a surface structure having an irregularly shaped microporous structure formed by dispersed thermoplastic fibers.
Is a non-woven fabric having a surface structure having elongated openings with thermoplastic fibers arranged in one direction. 2. The filter according to claim 1, wherein the fiber layer (I) is made of a nonwoven fabric having a higher porosity than the fiber layer (II). 3. The filter according to claim 1, wherein the nonwoven fabric has a fiber diameter gradient from the surface of the fiber layer (I) to the surface of the fiber layer (II). 4. The filter according to claim 1, wherein the thermoplastic fiber is a composite fiber composed of at least two types of thermoplastic resins having a difference in melting point of 10 ° C. or more. 5. The filter according to claim 1, wherein the thermoplastic fiber is a mixed fiber comprising at least two kinds of thermoplastic resins having a melting point difference of 10 ° C. or more. 6. The filter according to claim 1, wherein the nonwoven fabric is a nonwoven fabric obtained by a melt blow method. 7. A filter in which the filter according to claim 1 is laminated on at least one surface of at least one article selected from the group consisting of a microporous membrane and a cloth. 8. The filter according to claim 1, wherein the filter is a cartridge filter formed by winding a nonwoven fabric into a cylindrical shape.
The filter according to the item. 9. The filter according to claim 1, wherein the filter is a pleated filter obtained by folding a nonwoven fabric. 10. The filter according to claim 1, wherein the filter is a bag filter in which a nonwoven fabric is formed in a bag shape.