JPH1119435A - Cylindrical filter composed of extra fine conjugate fiber nonwoven fabric and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cylindrical filter excellent in filtration accuracy, the service life of the filter and pressure strength in the cylindrical filter using an extrafine conjugate fiber nonwoven fabric composed of >=2 kinds of the thermoplastic resins. SOLUTION: The cylindrical filter is constituted of the slit spinning melt blow extrafine conjugate fiber nonwoven fabric obtained by spinning >=2 kinds of the thermoplastic resins from the same slit mouth piece and the producing method is composed of a production process of the slit spinning melt blow extrafine conjugate fiber nonwoven fabric by discharging >=2 kinds of the thermoplastic resins from a slit die into a conjugate resin film form and jetting a heating gas to the discharged film like resin to collect the film like conjugate thermoplastic resin while fining into fibrous, a winding process for winding the extrafine conjugate fiber nonwoven fabric on a cylinder and a heat treating process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylindrical filter made of an ultrafine composite fiber nonwoven fabric produced by a slit-spinning melt-blowing method and having excellent pressure resistance and filtration accuracy and a long filtration life.

[0002]

2. Description of the Related Art Ultrafine fibers are processed into nonwoven fabrics and molded articles, and are widely used in disposable diaper surface agents, dustproof clothing, masks, wiping cloths, filters for precision filtration, battery separators and the like. Examples of the filter for microfiltration include applications such as a filter for a cleaning liquid in an electronic device manufacturing process, an air filter, a pre-filter for water for medical products, and a filter for removing microorganisms from food and drinking water.

[0003] In the production of these ultrafine fiber non-woven fabrics, a thermoplastic resin is melt-spun from a plurality of spinnerets, pulled and thinned by a high-speed air stream to form a fiber stream of ultrafine fibers, and then the fiber stream is formed. The melt blow method of collecting and accumulating to produce a nonwoven fabric is mainly used. The conventional filter using the single-component ultrafine fiber component using the melt blown nonwoven fabric method has little adhesion between fibers, so that the filtration accuracy fluctuates due to heat sterilization, high-temperature filtration, vibration, etc. And the pressure resistance is insufficient.

[0004] In recent years, a composite ultrafine fiber nonwoven fabric made of two different polymers, particularly polymers having different melting points, has been proposed as one that solves the above problem not only by entanglement of fibers but also by fusion. This ultrafine fiber mixed nonwoven fabric can be used by laminating two types of low melting point ultrafine fiber webs and high melting point ultrafine fiber webs, or by using a composite melt blow spinning method (for example, JP-A-60-99057 and JP-A-60-9057). No. 99058, U.S. Pat.
No. 0, JP-A-5-263307, etc.), a web is produced in which two types of ultrafine fibers simultaneously or alternately extruded from a die having a plurality of orifices are mixed.

[0005] However, the nonwoven fabric made of ultrafine mixed fiber from two kinds of resins by these methods has a complicated spinneret, is expensive, cannot form a composite blown fiber having a uniform composite ratio, and has a fineness of the obtained fiber. There was a problem that unevenness became large. JP-A-60-2
No. 16818 discloses that microfibers are accumulated on a mandrel and the structure is maintained only by mechanical entanglement of the fibers.
A filter for microfiltration having a constant porosity is disclosed, and Japanese Patent Application Laid-Open No. 1-297113 discloses a filter obtained by winding up a nonwoven fabric, using a nonwoven fabric having a larger fiber diameter and a larger pore diameter as being outside the filter. ,
Japanese Patent Application Laid-Open No. 4-126508 discloses a cartridge filter made of an ultrafine conjugate fiber made by a melt blow method, and Japanese Patent Application Laid-Open No. 5-96110 discloses a fiber diameter made of an ultrafine conjugate fiber made by a melt blow method. Are disclosed, the cartridge filter of which is sequentially changed.
JP-A-82649 discloses a cylindrical filter using a composite meltblown mixed fiber nonwoven fabric comprising a pore melting point ultrafine fiber having a melting point difference of 10 ° C or more and a low melting point ultrafine fiber, but a meltblown filter using a plurality of orifices. It had the disadvantage of using a nonwoven fabric.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a cylindrical filter using an ultrafine composite fiber nonwoven fabric made of two or more kinds of thermoplastic resins, which is excellent in filtration accuracy, filtration life and pressure resistance. Is to provide.

[0007]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that two or more extruders are used so that two or more kinds of thermoplastic resins are in a predetermined ratio. Using a wide slit with a specific lip width instead of a plurality of spinning orifices, the film-shaped molten composite resin is thinned by high-speed gas at a specific flow rate and simultaneously stretched to capture the composite fiber flow. The present inventors have found that a slit-spun meltblown composite fiber nonwoven fabric obtained by collecting is an excellent nonwoven fabric as a filter material, and completed the present invention.

[0008] That is, the present invention is a cylindrical filter made of a slit-spun meltblown ultrafine composite fiber non-woven fabric obtained by spinning two or more kinds of thermoplastic resins from the same slit die. A thermoplastic resin is discharged into a composite resin film from a die having a slit having a lip width of 0.1 to 2.0 mm, and the discharged film-shaped molten composite thermoplastic resin is provided adjacent to both sides of the slit. A slit-spun melt-blown ultrafine composite fiber non-woven fabric that collects in a sheet form on a moving collection surface provided in the downstream direction while thinning the film-like composite thermoplastic resin into fibers by injecting heating gas from the slits provided , A step of winding the ultrafine composite fiber nonwoven fabric on a cylinder, and a heat treatment step.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION
Two or more thermoplastic resins are discharged from a spinning slit having a wide slit, and a high-speed gas is blown from both sides of the slit onto a wide plastic film obtained from the wide slit, and the film is decomposed into ultrafine fibers, stretched, and , A non-woven fabric obtained by collecting these ultra-fine fiber flows, having fine inter-fiber voids composed of ultra-fine fibers, excellent properties of high strength, and ultra-fine of two or more different resins. Due to the three-dimensional network structure fused and fixed due to the difference in the melting point and the like of the fibers, the shape is not easily collapsed. In particular, the ultrafine composite fiber nonwoven fabric by the slit-spinning melt blow method of the present invention, because the ultrafine fibers of two or more thermoplastic resins are uniformly mixed, the filtration accuracy,
A cylindrical filter with improved filtration life and pressure resistance can be manufactured.

The ultrafine composite fiber nonwoven fabric of the present invention is obtained by extruding two or more kinds of thermoplastic resins into a slit die portion from each extruder and joining them together, from a die having a slit having a lip width of 0.1 to 2.0 mm. Discharge into a mixed resin film,
By injecting a heated high-speed gas from the slit provided adjacent to both sides of the resin discharge slit to the discharged film-shaped molten composite thermoplastic polymer, the film-shaped composite thermoplastic polymer is thinned into a fibrous shape, It is manufactured by collecting in a sheet shape on a moving collection surface provided in the downstream direction while stretching.

In the present invention, as the slit die for discharging the mixed resin, a generally used sheet die or a flat die T die or a coat hanger die used for film production can be used. Of these, a coat hanger die is preferred. The lip width of the slit die is 0.1 to 2.0 mm, preferably 0.2 to 2.0 mm.
1.5 mm. When the width is less than 0.1 mm, the resin cannot be discharged smoothly, and when the width is more than 2.0 mm, the fiber of the film cannot be reduced, which is not preferable. The width of the heated high-speed gas slit provided adjacent to the slit for discharging the resin depends on the high-speed gas velocity, but may have the same width as the resin slit.

A feature of the present invention is that the time during which the thermoplastic resin convects into the heated high velocity inert gas stream and becomes delicate is relatively short, and thus the decomposition of the thermoplastic resin at elevated temperatures. Is relatively rare. But in general,
The thermoplastic convects into the heated die head for a longer period of time than in a fast inert gas stream, and is degraded by both the residence time in the die head and the temperature at which the thermoplastic is held. However, the slit die of the present invention is characterized in that the residence time of the polymer in the die head is short and polymer decomposition is unlikely to occur.

The flow rate of the high-speed gas is determined by
Immediately after exiting from the wide slit spinning nozzle, it is necessary to decompose into ultra-fine fibers, and then collect these fibers as a non-woven fabric. For this purpose, it is necessary to spray 0.1 to 5 kg / cm ² from the slit. 0.1 kg / cm ²
If it is less than 5 kg / cm ² , the film cannot be fiberized.
Exceeding this is not preferable because it becomes difficult to collect as a nonwoven fabric. An advantage of the present invention is that these speeds can be increased throughout.

The thermoplastic resin applicable to the tubular filter made of the slit-spun melt-blown nonwoven fabric of the present invention includes:
Any thermoplastic resin can be used. There are various combinations depending on the use of the obtained nonwoven fabric. For example, there is a combination of a resin having an amorphous form and a softening polymer, or a combination of resins having a melting point difference, but as a filter, in order to make the fusion between fibers strong, Melting point difference is 30
A combination of a low-melting thermoplastic resin and a high-melting thermoplastic resin having a temperature of not less than ° C is preferable. Examples of the thermoplastic resin, for example, polyolefin-based resin, polyamide, polyester, polyester elastomer, low-melting copolymer polyester,
Polyester ether copolymer elastomer, polyester lactone copolymer elastomer, polystyrene,
Thermoplastic polyurethane, polyurethane elastomer, and the like. Polyolefin resins include polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-
α-olefin random copolymer, atactic polypropylene, polybutene, etc. are listed, and the α-olefin of the ethylene-α-olefin copolymer has 3 carbon atoms.
Propylene, butene-1, pentene-1, hexene-1,4-methyl-pentene-
Examples thereof include 1,3-methyl-butene-1, heptene-1, octene-1, nonene-1, and decene-1.

Specific combinations of thermoplastic resins preferably used in the present invention and having a difference in melting point of 30 ° C. or more include polypropylene and linear low-density polyethylene, polybutylene terephthalate and polypropylene, polyethylene terephthalate and polypropylene, and polyethylene and polyethylene. There are polypropylene, polyethylene terephthalate and nylon 6, polypropylene and nylon 6, and the like. Further, different materials may be blended to form one component of the composite fiber.

The resin component of each resin in the bicomponent conjugate fiber of the present invention is 10 to 90% by weight, preferably 40 to 6% by weight.
Used at 0% by weight. When the content of the low melting point resin in the ultrafine fiber non-woven fabric is less than 10% by weight, the cylindrical filter obtained by heat-treating the non-woven fabric molded product has a small number of thermal bonding points of fibers and is not preferable because the strength becomes weak. . or,
When the content of the low-melting point resin exceeds 90% by weight, the low-melting-point ultrafine fibers, which have lost the fiber form by the heat treatment, fill the fiber voids, forming a non-woven fabric into a film, lowering the texture,
Or it is not preferable because it causes a decrease in filtration accuracy of the filter.

Further, it is considered that, when two kinds of resins are used as A / B, for example, the finely divided fine fibers become very fine fibers similar to the side-by-side type.
When used as B / A, it is considered to be an ultrafine fiber similar to the core-sheath structure type. Also, by using three or more types of resins, ultrafine fibers similar to a side-by-side type having three or more layers can be easily obtained.

The fiber diameter of the ultrafine composite fiber nonwoven fabric of the present invention is not particularly limited, but ultrafine fibers of 15 μm or less can be used by adopting the slit spinning melt blow method. .1 μm, and more preferably 10 μm to 0.5 μm. The ultrafine fiber nonwoven fabric having a fiber diameter of 15 μm or more can be heat-treated as described below before or after forming into a cylindrical filter, to obtain a filter suitable for microfiltration. The fiber diameter of the ultrafine fiber of the high melting point resin and the fiber diameter of the ultrafine fiber of the low melting point resin do not necessarily have to be the same. The ultrafine conjugate fiber nonwoven fabric used for the cylindrical filter of the present invention mainly uses the above ultrafine conjugate fiber, but a fiber having a fiber diameter of 20 μm or more may be mixed as long as the filtration accuracy is not impaired.

The cylindrical filter of the present invention, which is made of a conjugate fiber having a melting point difference of 30 ° C. or more and made of an ultrafine conjugate fiber spun by a slit spin meltblowing method, is an ultrafine fiber spun by the slit spin meltblowing method. Can be deposited on a rotating air-permeable mandrel, or a method of winding the above ultrafine composite fiber nonwoven fabric on a rotating mandrel while transporting the same on a net conveyor. The basis weight of the extra fine composite fiber non-woven fabric is 3 ~
1000 g / m ^2, preferably from the 4~700g / m ² can be used, it refractory resin by fusion of the low melting point resin microfine fibers of the ultrafine fibers fixed reliably and uniformly achieved by the heat treatment described later, is the basis weight Most preferably, it is 100 g / m ² or less.

In either method, it is necessary to perform a heat treatment at a temperature between the softening point of the low melting point resin and the softening point of the high melting point resin of the ultrafine conjugate fiber before or after the cylindrical filter is formed. For the heat treatment, a method of heating the nonwoven fabric,
Alternatively, there is a method of heating an ultrafine conjugate fiber wound on a mandrel. As a heating method, a known method such as a thermocompression bonding method using a heating embossing roll, a method using heated air, a method using an infrared lamp, or a method of heating under reduced pressure in an autoclave can be used. Among these, the method of heating under reduced pressure in an autoclave has the effect of uniformly heating the entire filter, which is a nonwoven fabric molded article, and increasing the pressure resistance of the filter itself, and has a cylindrical filter with stable quality such as filtration accuracy. Is obtained, which is preferable. In addition, when the ultrafine conjugate fiber spun by the slit spinning meltblowing method is deposited on a rotating air-permeable mandrel without being cooled and wound up, the high melting point ultrafine fiber is fixed by its own heat. Can also.

Since the cylindrical filter thus obtained is made of ultrafine fibers, the filtration accuracy is high, and the tertiary fibers of the high melting point resin are fixed by the fusion of the ultrafine fibers of the low melting point resin. The original mesh structure is formed, the pressure resistance is large, and the filtration accuracy is not changed by heat sterilization, high-temperature filtration, or vibration.

When the ultrafine fiber composite nonwoven fabric is processed into a cylindrical filter, a more excellent cylindrical filter can be obtained by sequentially changing the fiber diameter of the ultrafine composite fiber used. For example, if the fiber diameter of the ultrafine composite fiber nonwoven fabric at the start of winding is small and the fiber diameter is gradually increased as the winding progresses, the size of the interfiber space inside the filter is gradually reduced from the outside to the inside of the filter. Become. Such a filter has a long filtration life because particles having different particle sizes can be separated from coarse particles to fine particles and collected from the surface to the inside of the filter. Further, the fiber diameter at the start of winding of the ultrafine composite fiber nonwoven fabric is large, and once the small fiber diameter is obtained as the winding progresses, and then the large fiber diameter is again obtained. A filter having a feature of high pressure resistance is obtained.

In any case, the greater the change in the fiber diameter, the greater the effect is obtained. If the ratio between the maximum fiber diameter and the minimum fiber diameter is twice or more, the efficiency is remarkable. As means for changing the fiber diameter, a method of changing the extrusion amount of the thermoplastic resin, a method of changing the flow rate of the high-speed gas, and changing the distance between the slit die as the spinneret and the conveyor net as the moving collecting surface There are methods. Further, these means can be used in combination. Of these,
A method of changing the distance between the die and the conveyor net is preferred. In particular, in the slit-spun melt-blown nonwoven fabric manufacturing apparatus, the positional relationship between the die and the conveyor net is, in an apparatus in which the conveyor net is installed below the die,
The method of changing the distance between the die and the conveyor net is preferable from the viewpoint of easy operation.

In the method of changing the distance between the die and the conveyor net, when the distance between the die and the conveyor net is increased, the chances of the fusion of the ultrafine fibers in the fiber stream are increased. Easy, and the apparent fiber diameter increases. As a result, the obtained nonwoven fabric is bulkier and has a high porosity. On the other hand, when the distance between the die and the conveyor net is shortened, the fiber diameter becomes small, and the obtained nonwoven fabric becomes a nonwoven fabric having a small porosity. When the nonwoven fabric is manufactured while separating the conveyor net from the die at a constant speed, the apparent fiber diameter of the obtained nonwoven fabric continuously increases, and the porosity of the nonwoven fabric continuously increases. When this nonwoven fabric is wound with the thinner fiber inside, the above-mentioned cylindrical filter having excellent filtration life and pressure resistance can be obtained.

As another method of obtaining a filter in which the pore size of the filtration layer is sequentially changed along the filtration direction of the filter, there is a method of sequentially changing the pressure applied to the ultrafine fiber composite nonwoven fabric wound on the rotating mandrel. For example, if the pressure at the start of winding of the ultrafine composite nonwoven fabric is large and the pressure is gradually reduced as the winding progresses, the pore size of the filter layer gradually decreases from the outside to the inside of the filter.
The filter obtained in this manner is similar to the filter obtained by changing the fiber diameter from small to large,
The feature is that the filtration life is long.

The filter of the present invention may be an electret filter. As a method of forming an electret filter, a method of treating an ultrafine composite fiber nonwoven fabric or a cylindrical filter produced by winding the same with corona discharge or the like is used, and a surface charge density of about 10 to 45 Coulomb / cm ² is used. Are preferred.

Although the cylindrical filter of the present invention has sufficient pressure resistance without a core, it may have a core. The cross-sectional shape of the core may be circular, elliptical, triangular, quadrangular, or more polygonal. The cylindrical filter referred to in the present invention is a cylindrical filter having a cross-sectional shape of a filter such as a circle or an ellipse, but a filter having a polygonal shape such as a triangle or a rectangle is also included as long as it performs the same function. . The cylindrical filter of the present invention can be widely used as a filter for a cleaning liquid such as a material for an electronic device, an air filter for dust removal, a prefilter for water, food, beverage, alcoholic beverage and the like used for medical supplies.

[0028]

Embodiments of the present invention will be described below in detail. The present invention is not construed as being limited to the following examples. The test method in this example is as follows. (1) Weight: 100 × 100 mm from the sample length direction
Of the test piece was taken, and the weight of the water equilibrium state was measured.
^It was converted to ^two . (2) Thickness: 100 × 100 mm from the sample length direction
Of the test specimen and dial thickness gauge (Co., Ltd.)
It was measured by 7321 manufactured by Mitoyo Seisakusho, 1 mm / 1 rotation). (3) Average fiber diameter: Five photographs were taken of any five points of the test piece with an electron microscope, the diameter of 20 fibers was measured for each photograph, and these were performed for the five photographs.
The average fiber diameter of 100 fibers was determined.

(4) Filtration efficiency: A filter cartridge was loaded into a housing of a filtration device equipped with a 10 liter tank and a circulation pump, and the flow rate was 5 liters per minute.
Circulate 5 liters of purified water. Thereafter, 1 g of 50% weight average 0.5 μm quartz particles made by Tatsumori Co., Ltd. was added to the tank, and 1 minute after the addition of the quartz particles, 100 ml of filtered water was added.
Milliliters were collected and the filtration efficiency was measured using a Poic integrating sphere turbidity meter manufactured by Nippon Seimitsu Kogaku Co., Ltd.

(5) Filtration life: A filter cartridge is loaded in a housing of a filtration device equipped with a 10 liter tank and a circulation pump, and a flow rate of 5 liters per minute and 5 liters of purified water are circulated. Then, the Kanto loam layer particles (J) having an average particle size of 1.6 to 2.3 μm were added to the tank.
(11 kinds of ISZ8901) are added at intervals of 1 minute in 0.1 g portions. Continuing the water circulation while continuing to add the Kanto loam layer particles, the difference in water pressure between the inlet and outlet of the filter is 3 kg
The time (minutes) at which the pressure reached / cm ² was defined as the filtration life.

Example 1 The ratio of the length to the diameter (L / D) of the screw of the extruder was 25.
2 extruders, 3 inches long, resin discharge lip width 0.
As a first component, a melt flow rate (hereinafter, referred to as MFR) of 300 (g / m 2) was measured using a melt-blowing slit spinneret having a diameter of 35 mm and an air discharge slit of 0.20 mm.
(10 minutes, 230 ° C), polypropylene having a melting point of 165 ° C at an extrusion temperature of 300 ° C, and as the second component, the adjusted MF
R = 100 (g / 10 min, 190 ° C.), melting point: 123 ° C.
Each of the linear low-density polyethylenes was extruded at an extrusion temperature of 270 ° C. and melted at a die temperature of 28 from the resin discharge slit.
The mixture was melt-blown at 0 ° C. and sprayed onto a conveyor net with a suction device with a distance of 200 mm between the melt spinning spinneret and the conveyor to obtain a two-component slit composite meltblown nonwoven fabric. At this time, the weight ratio of the first component to the second component is 50:50, and the total discharge amount is 1
00 g / hr / inch. The temperature of the air used for the melt blow was 300 ° C. at the inlet, and the pressure was 3.2.
kg / cm ² .

The obtained polypropylene / polyethylene two-component slit composite meltblown nonwoven fabric has a basis weight of 5%.
The thickness was 5.3 g / m ² , the thickness was 0.41 mm, and the average fiber diameter was 8.0 μm. Next, this non-woven fabric is applied with an outer diameter of 30
It was wound on a polypropylene plastic core having a thickness of 2 mm to form a filter. Atmospheric temperature 1
It was placed in an autoclave at 25 ° C. and left for 1 hour while reducing the pressure. The tubular filter was taken out of the autoclave, left standing at room temperature and cooled, and a polyethylene end cap was attached. The outer diameter was 60 mm, the inner diameter was 30 mm, and the length was 7 mm.
A 6 mm cylindrical filter was obtained. In this cylindrical filter, the fibers were fixed by fusion of a polyethylene resin portion, which is the second component of the conjugate fiber. When this filter was attached to the housing and the filtration performance was measured,
The filtration efficiency was 54.4%, and the filtration life was 40 minutes.

Example 2 Example 2 was the same as Example 1 except that the distance between the melt-blowing slit spinneret and the conveyor net was lowered from 200 mm to 2000 mm at a speed of 39.3 cm / min, and the conveyor net was lowered and widened. The two-component slit composite meltblown nonwoven fabric was wound up by the method described in the above. The resulting propylene / polyethylene two-component slit composite meltblown nonwoven fabric has a distance between the spinneret and the conveyor net of 2
At 00 mm, basis weight 52.4 g / m ² , thickness 0.38 mm
The average fiber diameter was 8.5 μm, and the porosity calculated from the thickness was 84.9%. The distance between the spinneret and the conveyor net is 2000 mm, and the thickness is 1.0 mm.
5 mm, the average fiber diameter was 23.3 μm, and the porosity calculated from the thickness was 94.5%.

The obtained polypropylene / polyethylene two-component slit composite meltblown nonwoven fabric having a sequentially changing fiber diameter was prepared by adjusting the distance between the spinneret and the conveyor net to two.
30m outside diameter so that the one obtained at 00mm is inside
A 6 m portion of which the distance between the spinneret and the conveyor net was obtained up to 2000 mm was wound on a polypropylene plastic core of m to obtain a filter. Thereafter, the filter was placed in an autoclave at an ambient temperature of 125 ° C., and left for 1 hour under reduced pressure. Remove the cylindrical filter from the autoclave, leave it at room temperature, cool it down, attach a polypropylene end cap,
A cylindrical filter having a length of 0 mm, an inner diameter of 30 mm, and a length of 76 mm was obtained. In this cylindrical filter, the fibers were fixed by fusion of a polyethylene resin portion as the second component of the conjugate fiber. When this cylindrical filter was attached to the housing and the filtration performance was measured, the filtration efficiency was 52.
At 1%, the filtration life was 58 minutes.

Example 3 In the apparatus of Example 1, the lip width of the resin discharge port was set to 0.
Extrusion was performed at an extrusion temperature of 300 ° C. using the same polypropylene as the polypropylene used in the examples as the first component of the resin, using the same apparatus as in the example 1 except that the diameter was changed to 3 mm. 84, melting point 224 ° C
Extruded at an extrusion temperature of 290 ° C., melt-blown from the same spinning slit die at a die temperature of 310 ° C., and sprayed on a conveyor net with a suction device, so that the distance between the melt-blowing spinneret and the conveyor was from 200 mm to 2000 mm, The conveyor net was lowered at a speed of 33.7 cm / min, and the two-component slit composite meltblown nonwoven fabric was wound. At this time, the weight ratio of the first component to the second component was 40:60, and the total discharge amount was 100 g / hour / inch. The temperature of the air used for melt blowing was 320 ° C. at the inlet, and the pressure was 3.5 kg / cm ² .

The obtained polypropylene / polybutylene terephthalate two-component slit composite meltblown nonwoven fabric has a distance between the spinneret and the conveyor net of 200 mm.
And a basis weight of 51.0 g / m ² and a thickness of 0.30 mm,
The average fiber diameter was 7.5 μm, and the porosity calculated from the thickness was 85.1%. The distance between the spinneret and the conveyor net was 2000 mm, the thickness was 1.0 mm, the average fiber diameter was 24.8 μm, and the porosity calculated from the thickness was 95.5%.

A two-component slit composite meltblown nonwoven fabric of polypropylene / polybutylene terephthalate in which the obtained fiber diameters are sequentially changed was placed such that the one obtained with a distance between the spinneret and the conveyor net of 200 mm was on the inside. On a polypropylene plastic core having an outer diameter of 30 mm, the distance between the spinneret and the conveyor net is 2,000.
A 7 m portion obtained up to mm was wound and used as a filter. Thereafter, the filter was placed in an autoclave at an ambient temperature of 160 ° C., and left for 1 hour while reducing the pressure. When the tubular filter was removed from the autoclave and left to cool to room temperature, the fibers were fixed by fusion of the polypropylene resin portion, which is the first component of the conjugate fiber, and some wrinkles were generated due to heat shrinkage. However, it was determined that it worked well for filter production. Next, attach an end cap made of polyethylene,
mm, an inner diameter of 30 mm and a length of 76 mm were obtained. When this cylindrical filter was attached to the housing and the filtration performance was measured, the filtration efficiency was 57.0% and the filtration life was 51 minutes.

Comparative Example 1 A total of 95 spinning holes having a hole diameter of 0.4 mm were arranged in a line.
Using the same apparatus as in Example 1 except that the usual spinneret for melt-blowing was used, the polypropylene used in Example 1 was extruded at a temperature of 300 ° C., a die temperature of 280 ° C., and a discharge rate of 1
00g / hr / inch, heated air at 300 ° C, pressure 3.1
A melt blown nonwoven fabric made of polypropylene having a weight of 50 g / m ^{2 and} a kg / cm 2 was obtained. The average fiber diameter of this nonwoven fabric was 7.0 μm, and the thickness was 0.37 mm.

The obtained polypropylene melt-blown nonwoven fabric was wound around a polypropylene plastic core having an outer diameter of 30 mm to form a cylindrical filter. Thereafter, the filter was placed in an autoclave at an atmospheric temperature of 155 ° C., and left under reduced pressure for 1 hour. The cylindrical filter was taken out of the autoclave, left standing at room temperature and cooled, and a polyethylene end cap was attached to obtain a cylindrical filter having an outer diameter of 60 mm, an inner diameter of 30 mm and a length of 76 mm. This cylindrical filter was weakly fixed between fibers, easily deformed when pressed with a finger, and had many wrinkles due to heat shrinkage. When this cylindrical filter was attached to the housing and the filtration performance was measured, the filtration efficiency was 45.0% and the filtration life was 27 minutes.

Comparative Example 2 Using the same apparatus as in Example 1 and the same two kinds of resin components as used in Example 1, the first component polypropylene was extruded at an extrusion temperature of 300 ° C., a die temperature of 280 ° C., and a discharge amount of 100 g. /
Hour / inch, heated air at 300 ° C, pressure 3.1kg / c
m2, linear low-density polyethylene of the second component is extruded at 270 ° C., die temperature is 280 ° C., discharge rate is 100 g / hour / inch, heated air is 290 ° C., pressure is 3.1 kg / cm 2.
, Each melt blown, the basis weight is 25 g / m
² was obtained single component slit spun melt blown nonwoven fabric. The average fiber diameter of each of these nonwoven fabrics is 7.0 μm.
m and 8.5 μm. The resulting single-component slit-spun meltblown nonwoven fabric of polypropylene and polyethylene was laminated to give a total basis weight of 50 g / m ² .

The obtained laminated nonwoven fabric was wound on a polypropylene plastic core having an outer diameter of 30 mm so that the polyethylene layer was on the inside, to obtain a cylindrical filter. Thereafter, the filter was placed in an autoclave at an ambient temperature of 125 ° C., and left for 1 hour under reduced pressure. The cylindrical filter was taken out of the autoclave, left standing at room temperature and cooled, and a polyethylene end cap was attached to obtain a cylindrical filter having an outer diameter of 60 mm, an inner diameter of 30 mm and a length of 76 mm. In this cylindrical filter, the polypropylene layer and the polyethylene layer were more strongly adhered to each other by the polyethylene layer, but the polypropylene layer was weakly fixed between the fibers and easily deformed when pressed with a finger. When this cylindrical filter was attached to the housing and the filtration performance was measured, the filtration efficiency was 48.5% and the filtration life was 22 minutes.

[0042]

The cylindrical filter made of the slit-spun meltblown ultrafine composite fiber nonwoven fabric of the present invention has a high filtration efficiency and a long filtration life. Further, as the filtration proceeds, the difference between the water pressure at the inlet and the outlet of the cylindrical filter gradually increases, but the cylindrical filter of the present invention has two or more thermoplastic resin fibers uniformly mixed with each other, The entanglement is superior to that of the single resin fiber non-woven fabric laminate, and the parts of the low melting point resin are fused by heating, fixing the fibers,
It is solid and has excellent pressure resistance. In addition, the composite ultrafine fiber nonwoven fabric of the present invention has a more uniform resin blend ratio in the fiber length direction than the meltblown nonwoven fabric using a die having a plurality of orifices, maintains strength, and can be easily manufactured.

Claims (3)

[Claims] 1. A cylindrical filter comprising a slit-spun melt-blow ultrafine composite fiber nonwoven fabric obtained by spinning two or more kinds of thermoplastic resins from the same slit die. 2. A method in which two or more kinds of thermoplastic resins are discharged from a die having a slit having a lip width of 0.1 to 2.0 mm into a composite resin film, and the discharged film-like molten composite thermoplastic resin is By injecting a heating gas from slits provided adjacent to both sides of the slit, the film-like composite thermoplastic resin is captured in a sheet shape on a moving collection surface provided in a downstream direction while being thinned into a fibrous shape. A method for producing a cylindrical filter, comprising: a step of producing a slit-spun melt-blown ultrafine composite fiber nonwoven fabric to be collected; a step of winding the ultrafine composite fiber nonwoven fabric into a cylindrical shape; and a step of heat treatment. 3. In a manufacturing process of a slit-spun melt-blow ultrafine composite fiber nonwoven fabric, an ultrafine composite fiber nonwoven fabric having a fiber diameter continuously or stepwise changed by changing a distance between a slit die and a collecting surface. The method for producing a cylindrical filter according to claim 2, characterized in that: