JPH0568823A - Filter medium - Google Patents

Abstract

PURPOSE:To provide a bulky coarse and dense-structure filter medium capable of being extremely easily pleated into a unit and contg. a flame-resistant extra fine fiber. CONSTITUTION:This filter medium is made of a nonwoven fabric consisting of an extra fine fiber having <10mum diameter, 20-80wt.% of a self-welding fiber and 10-50wt.% of an org. flame-resistant fiber having >=25 LOI value. The fibers are adhesively bonded to each other by the self-welding fiber, and the pore size on the upstream side is controlled to 150-250mum and that on the downstream side to 20-80mum. Namely, the filter medium has such a coarse and dense gradient structure, and its bending resistance is adjusted to >=100mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a long-life filter medium which is excellent in dust retention and is mainly used for air treatment.

[0002]

2. Description of the Related Art In addition to the filter characteristics required for air-conditioning filter media, in order to unitize the filter media, the rigidity for folding the filter media in ridges and valleys and the suitability for pleats (suitability for folding such as mountain valley folds) are required.

In the prior art, a method of satisfying the above requirements by dipping a single-layer non-woven fabric made of a relatively thick fiber having a fineness of 2 denier or more into a synthetic flame-retardant resin (JP-A-54-83).
181) and a method of processing a two-layer structure nonwoven fabric by the same method (Japanese Utility Model Publication No. 55-91915), but in these conventional techniques, among the important spaces for holding dust, The resin adhered in the form of a film caused a portion to be blocked, resulting in a short life as a filter medium.

A filter medium using ultrafine fibers is known as a high-performance filter medium. For example, Japanese Patent Application Laid-Open No. 51-134475, Japanese Patent Application Laid-Open No. 62-83017, and Japanese Patent Application Laid-Open No. 2-10 are known as conventional techniques in which ultrafine fibers are used as a part of a filter medium.
4765, JP-A-2-151218, JP-A-2-303509, JP-B-3-28892, and JP-A-2-12415 are known.

Among these, in Japanese Patent Publication No. 28892/1989, a melt blown non-woven fabric is used for ultrafine fibers,
There is shown a coarse-dense structure filter medium obtained by laminating a non-woven fabric support layer processed with a synthetic resin thereon. In this prior art, the support layer is used to give the melt-blown nonwoven fabric improved pleat suitability and flame retardancy, and does not impart rigidity to the melt-blown nonwoven fabric composed of ultrafine fibers.
Further, since the collection efficiency of the coarse-structured filter medium on the upstream side is low, high-density dust reaches the dense melt-blown nonwoven fabric layer as it is, and the pressure loss increases rapidly and the life is short.

Further, Japanese Unexamined Patent Publication No. 2-104765 discloses a method in which self-fusing short fibers are mixed with a melt blown nonwoven fabric to give bulkiness and shape stability. This prior art also aims at bulkiness and morphological stabilization, and does not give the melt blown nonwoven fabric itself rigidity to withstand pleating. Furthermore, JP-A-2-3035
No. 09 discloses a technique in which ultrafine fibers obtained by fibrillation are made into a non-woven fabric by a papermaking method, and self-fusing fibers made into a non-woven fabric by a papermaking method are polymerized to obtain a HEPA filter. Although shown, in this method, it is used in a laminated form, and the purpose of use of the self-bonding fiber is to prevent fuzzing and falling off, and the idea of giving rigidity to the ultrafine fiber filter medium itself has been suggested. There wasn't. Further, since the method of making the nonwoven fabric is a papermaking method, the fiber length was extremely short, about 5 mm. Therefore, even with this conventional technique, the idea of increasing the rigidity of the filter medium made of long and short bulky ultrafine fibers has not been shown.

Further, Japanese Patent Application Laid-Open No. 62-83017 discloses a technique in which a nonwoven fabric layer containing self-bonding fibers is provided with a fiber packing density gradient (roughness gradient) and an electret sheet is laminated on this. There is. However, this conventional technique does not specifically show the numerical range of the fiber packing density, and the technique of basically providing a coarse / dense gradient to the filter medium has been publicly known before this. It was lacking. Further, in the same publication, the flame retardancy of the non-woven fabric layer containing the self-fusing fiber is also mentioned, and a method of kneading the flame retardant into the fiber is shown, which is a flame retardant fiber due to the composition of the polymer. Was not included.

Further, regarding the flame retardance, JP-A-51-1
Japanese Patent No. 34475 discloses a flame-retardant technology for ultrafine fiber filter media, but this method is difficult by resin-processing a non-woven fabric composed of flame-retardant fibers or combustible fibers with a rigid flame-retardant resin. This is a technology to obtain a flame-retardant filter material by laminating a combustible bulky nonwoven fabric and an ultra-fine nonwoven fabric layer (melt-blown nonwoven fabric) that has not been flame-retarded. It was not shown.

Further, although it is not an ultrafine fiber, it is disclosed in Japanese Patent Laid-Open No. 2-1
Japanese Patent No. 51218 discloses a separate nonwoven fabric technology for increasing rigidity by mixing a self-bonding fiber with a very thick fiber, but this one is intended to separate a melt blown filter medium in a separate nonwoven fabric and is actively used. It was not a filter medium for collecting dust. This prior art does not have the idea of increasing rigidity and flame retardance because the layer containing ultrafine fibers is positively used as a filter medium.

As described above, according to the prior art, a bulky layer having a dense and dense structure containing ultrafine fibers is used as a basic structure, and a rigid and flame-retardant material for pleating is obtained to obtain a long-life filter medium. There was no technical idea.

[0011]

DISCLOSURE OF THE INVENTION The present invention is intended to provide a bulky dense-structured filter medium containing ultrafine fibers having very good pleat suitability for unitization and flame retardant properties.

[0012]

The present invention has the following configuration.

That is, the filter medium of the present invention comprises ultrafine fibers having a diameter of less than 10 μm, self-bonding fibers of 20 to 80% by weight, and organic flame-retardant fibers of 10 to 50% by weight and LOI value of 25 or more. Made of a non-woven fabric, the fibers are partially adhered to each other by the self-bonding fibers, and the upstream side having a pore size of 150 to 250 μm on the upstream side and the pore size of 20 to 80 μm on the downstream side is rough and the downstream side is A filter medium having a dense gradient structure and a bending resistance of 100 mm or more.

Alternatively, the filter medium of the present invention is composed of ultrafine fibers having a diameter of less than 10 μm, 20-80% by weight of self-bonding fibers and 10-50% by weight of organic flame-retardant fibers having LOI value of 25 or more. At least one of the ultrafine fibers, self-bonding fibers or organic flame-retardant fibers is an electretized fiber, and the fibers are partially bonded by the self-bonding fibers, and the upstream side Has a pore size in the range of 150 to 300 μm and a downstream side pore size in the range of 20 to 130 μm and has a coarse and dense gradient structure in which the upstream side is coarse and the downstream side is dense, and the bending resistance is 1
It is a filter medium characterized by having a length of at least 00 mm.

[0015]

The present invention mainly relates to a bulky air-conditioning filter medium containing ultrafine fibers suitable for treating various gases, and relates to a long-life filter medium satisfying pleat suitability and flame retardancy.

The filter material of the present invention will be described in detail below.

The fibers used in the filter medium of the present invention are ultrafine fibers, self-bonding fibers and flame-retardant fibers, and melt-blown non-woven fabrics or electretized melt-blown non-woven fabrics are laminated for use.

The ultrafine fibers having a single yarn diameter of less than 10 μm include self-fusing fibers (20 to 80% by weight) used for the purpose of increasing rigidity and organic flame-retardant fibers (10 to 50) having LOI value of 25 or more. (% By weight ratio), which is used by mixing with each other, and the fibers are partially fused and fixed at the contact entanglement points of the fibers by the self-bonding fibers, and the bending resistance is 100 mm.
In the above, the density of the fibers is in the range of 150 to 250 μm in the upstream pore size (representing the average spatial distance between the fibers) and the downstream pore size is in the range of 20 to 80 μm, and the upstream side is coarse and the downstream side is dense and dense structure. It is a filter medium having.

As a means for forming a cloth, a card and a cloth wrapper, a random webber method, an air lay method, or the like, which is a method of web-forming generally short crimped fibers, is used to make a web, and this is directly or needled. After entanglement with a punch, a method in which a nonwoven fabric is continuously passed through a gap between a roll heated to a temperature above the melting point of the low melting point component of the self-bonding fiber and a roll having a temperature lower than this, or the web is heated above the melting point. After that, by a method such as continuously passing the non-woven fabric through the gap between the cold rolls with a lower temperature difference,
The filter material thickness, pore size, and bending resistance are set.

There are typically two methods of web formation for increasing the bending resistance. Firstly, increasing the fiber orientation in the pleating direction of the filter medium, and secondly, using needle punching. By increasing the punch density, the fiber orientation becomes three-dimensional and the effect is obtained.

Explaining the fiber constituents in more detail, ultrafine fibers are advantageous for the purpose of obtaining fibers having a single yarn diameter of less than 10 μm with high collection efficiency with a small basis weight. In particular, fibers having a size of less than 5 μm are suitable materials for the present invention because of the requirements for low basis weight and thinning. This is because when a fiber having a large fiber diameter is used, it has many basis weights to obtain a predetermined collection efficiency, and the thickness of the filter medium becomes too thick, which makes it difficult to form an excellent filter unit. ..

In order to prolong the service life of the filter medium, it is necessary to secure a pore volume, and in order to realize this with a high collection efficiency, a space partitioned by an appropriate pore size is required.
In order to efficiently carry out this with a relatively thin filter medium, fibers having a single yarn diameter of less than 10 μm are suitable.

Suitable materials are staples (short fibers) obtained by spinning and then shortening, or fibers that can be made into ultrafine fibers by spinning and then making them into short fibers, and fibers that can be made into ultrafine fibers by fibrillation. Particularly suitable are short fibers having a fiber length of 20 to 100 mm. Among them, staples are excellent in uniformizing pore size and filter characteristics because they are opened one by one in the web-making process with a card, and since they have crimps, they are bulky and formed into the desired pore size. Easy and suitable material.

Among staples, the fiber diameter is 2 to 8 μm
Polypropylene, acrylic, polyester, polycarbonate, polyamide and the like are materials which are well suited for card passage when the staples are turned into webs. In particular, polypropylene and polycarbonate are preferable materials because they can be easily converted into an electret and a high collection efficiency can be obtained as a filter medium, especially when the electret is used. Further, polyester and polycarbonate are preferable because they are materials that easily become flame retardant.

In the present invention, the total fiber areal weight of 20 to
80% by weight self-bonding fiber, 10-50% by weight LO
Since the organic flame-retardant fiber having an I value of 25 or more is used, the amount of the ultrafine fiber used is less than 70% by weight based on the total fiber areal weight, depending on the fineness of the self-bonding fiber or the organic flame-retardant fiber or the purpose. The amount of ultrafine fibers used may be optimized depending on the collection efficiency.

The self-fusing fiber is used for the purpose of increasing rigidity. Therefore, the material and the usage rate have important meanings. A composite fiber having a core-sheath structure or a bimetal structure having a low melting point component and a high melting point component and having a melting point difference of 30 ° C. or more is suitable as a fiber cross-sectional structure. In particular, a core-sheath structure having a small number of crimps and a heat shrinkage of 15% or less is preferable because the effect of increasing rigidity is high. Therefore, the sheath component is a combination of polyethylene or copolymerized polyethylene and the core component such as polypropylene, or the sheath component is a combination of copolymerized polyester and the core component such as polyethylene terephthalate, or at least a part of the core or sheath component is flame retardant. A composite fiber made of a material containing a sex component is also suitable.
Among them, the sheath component is a copolyester (melting point 80 to 14
At 0 ° C., the combination of polyethylene terephthalate (melting point 258 ° C.) as the core component has a large temperature difference, so that the shrinkage is small and the rigidity of the material is also high, so that the effect of increasing the rigidity is high and excellent. Further, when the electret fiber is used in part, the electret property is deteriorated by heating for fusing, so that a material having a melting point of 60 to 140 ° C. that can be bonded at a low temperature for stabilizing the electret is used. Optimal. The core-sheath structure also includes fibers having a concentric circular structure and an eccentric structure.

The self-fusing fiber having a fineness of less than 30 denier can be used, but if the fineness is too small, the effect of increasing the rigidity is low, and if it is too thick, the number of fibers contained in the filter medium decreases. The number of adhesion points is reduced, and similarly, the effect of increasing rigidity is low. For this reason, those having a denier of less than 1 to 20 are suitable in view of the collection efficiency and the suitability for pleats. The amount of the self-fusing fiber used is 20 to 80% by weight, and the total basis weight of the filter medium, the fineness of the self-fusing fiber,
The usage rate varies depending on the material and the amount of ultrafine fibers used, but the bending resistance (45 degree cantilever) is 100.
The amount of use should be determined so that it is not less than mm, preferably not less than 150 mm. This represents a characteristic range required for preventing the shape of the pleated filter medium from being deformed by wind pressure or the like.

Generally, the greater the number of adhesion points of the self-fusing fiber, the ultrafine fiber and the organic flame-retardant fiber, the higher the strength of the filter medium, but the rigidity is not related only to the adhesion strength, It is also related to the thickness of the filter medium. In addition, the pore size, which is closely related to the use ratio, fineness, material, etc. of the self-fusing fiber, and which changes depending on these constituent elements affects the collection efficiency and the life of the filter medium, so that the pore size in the target range can be obtained. It is important to select the use ratio, fineness, and material of the self-bonding fiber so that the rigidity is also satisfied under the given conditions.

Next, the pore size will be explained. In order to design a filter medium satisfying the building management method by using a filter medium having a basis weight of 30 to 200 g / m ² , the pore size is optimized and the dust holding amount is adjusted. It is important to increase the collection rate and satisfy the collection efficiency at the same time.

Up to now, a filter medium having a coarse and dense structure has been known, but since a filter medium having a large fineness is mainly used, it is necessary to directly and strongly compress it by means of a roll having a temperature gradient as a coarsening and densifying means. Therefore, the fibers in the densified portion are deformed to fill the space, resulting in a large increase in ventilation resistance. For this reason, there are many cases in which the advantage of the coarse and dense structure, that is, the long life cannot be sufficiently achieved.

However, in the case of the filter medium containing the ultrafine fibers and the self-bonding fibers of the present invention, since the ultrafine fibers are used, the pore size can be made smaller than in the initial stage, and even when densifying, extremely weak pressing (fiber Thickness change without deformation)
Thus, it is possible to form a densified portion in which fibers are frequently bonded. For this reason, since densification can be performed with almost no loss of ventilation, it is possible to design a filter medium having a coarse-dense gradient from the upstream side to the downstream side.

Therefore, while the collection efficiency due to the adhesion of dust is accelerated, the dust can be held over the entire layer, so that the holding amount can be increased. That is, it is possible to improve the average collection efficiency and extend the life with less basis weight.

The pore size for obtaining this characteristic is preferably 150 to 250 μm on the upstream side and 20 to 80 μm on the downstream side. More preferably, the upstream side is 150 to 2
00 μm, and the downstream side is in the range of 20 to 60 μm. Such a pore size has a weight average diameter of about 2.1 μm of suspended dust in a general living room, a conference room, etc., and has a pore size structure distribution that efficiently collects the suspended dust in this distribution and is unlikely to be clogged.

If the pore size is larger than 250 μm, the amount of dust that can be collected before reaching a certain pressure loss increases and a long life can be achieved, but it becomes difficult to satisfy the collection efficiency. Further, if the pore size is smaller than 20 μm, the trapping efficiency can be satisfied, but the amount of dust that can be trapped by the time the constant pressure loss is reached is reduced and the life cannot be extended.

However, when the electret fiber is used as a part of the fiber, a high collection efficiency can be obtained by the electrostatic adsorption effect, so that the range of the appropriate pore size described above is expanded, and the findings of the present inventors. According to the
50 to 300 μm and 20 to 130 μm on the downstream side, but a more preferable range is 150 to 250 on the upstream side.
μm, and the downstream side is 20 to 100 μm.

The method for obtaining the pore size is COUNT in UK.
ER ELECTRONICS LIMITED PO
It is evaluated using ROMETER II. The evaluation procedure may be carried out according to the handling material of the device. The specific method is to slice a 10 cm square evaluation sample into halves of thickness and divide it into upstream and downstream samples, and every 5 cm, 5 points x 5 points. Point = total of 25 points, sample evaluation area 0.1
It is evaluated by 96 cm ² , and the average pore size of each individual is obtained, and then the average pore size of the whole is obtained. As a method for preparing each evaluation sample, the evaluation sample is immersed in an aqueous polyvinyl alcohol solution, an appropriate amount of resin is adhered thereto, and then dried to prepare a hard sheet that is not deformed even in the step of slicing. After slicing the center of the filter medium, it is immersed in water to completely remove polyvinyl alcohol and naturally dried to obtain an evaluation sample.

Next, the organic flame-retardant fiber will be described. Limiting oxygen index (LOI), (measurement method JIS K7201)
Is 25 or more flame-retardant fibers.

This is because in the case of inorganic fibers such as glass and asbestos, a large amount is required to make other fibers used together flame-retardant, and the fiber length is short and it is difficult to make them bulky. So it is not suitable. In the case of an organic substance, shrinkage is likely to occur along with combustion, and there is a phenomenon of moving away from the fire source, and it is easy to obtain a flame retardant effect with a small amount. Further, this effect is easily obtained and suitable for a bulky structure having a large pore size in the range of 20 to 300 μm.

Further, those having a high flame retardant effect are produced by materials such as vinyl chloride, vinylidene chloride, polyclar, modacrylic (modacrylic) which generate a fire-extinguishing gas by combustion, and a flame-retarded natural fiber, for example, procane. It is a suitable material such as cotton and wool subjected to Saburo processing, which has a high flame retardancy even in a small amount because the fire-extinguishing gas covers the burning portion. These are 10-5 for the non-woven fabric weight.
The object can be achieved by using 0% by weight (flame retardancy test method; JIS L1091A-1 method). Among them, vinylidene chloride, polyclar, modacrylic fiber fineness 5
Fibers having a LOI of 27 to 56 or less in denier can be flame-retarded with a small amount, which is particularly preferable.

Next, in order to obtain a filter medium having a high collection efficiency, for example, a colorimetric method of 65% or more, the collection efficiency of the meltblown nonwoven fabric or the electretized meltblown nonwoven fabric should be 25% or more on the most downstream side of the air flow. With a thickness of 0.
It is possible to obtain a filter medium satisfying the overall pleats and flame retardancy by a method of laminating 5 mm or less.

In this case, the method of integration may be partial ultrasonic bonding, heat bonding, or self-fusing fibers used in the filter material of the present invention.

[0042]

【Example】

Example 1 20 g / m ² of polyester staple fibers having a total basis weight of 100 g / m ² and ultrafine fibers of 8 μm and self-bonding staple fibers (fineness 4
Denier, core; polyester, sheath; copolyester melting point 85 ° C.) 55 g / m ² , flame-retardant short fibers (modacrylic fiber; LOI value 32, fineness 2.4 denier)
Needle punched non-woven fabric consisting of 25 g / m ² at 130 ° C
The density gradient of the present invention having an upstream pore size of 150 μm and a downstream pore size of 30 μm in which the fibers are fused is passed through a gap (0.5 mm) between the metal roll heated to 60 ° C. and the metal roll heated to 60 ° C. A filter material having the above was prepared.
The bending resistance of this product was 120 mm, which satisfied the rigidity. In addition, flame retardancy (JIS L1091A-1 method)
Also obtained Category 3 which satisfies the target. The collection efficiency of this filter medium was 35 with respect to 0.8 μm polystyrene particles.
%, The pressure loss was 0.9 mmAq (measured wind speed 5 m
/ Min).

Further, the dust holding amount of this filter medium was evaluated according to the evaluation method of Ashure 52-76. Evaluation conditions are: sample area = 120 cm ² (sheet state), measured wind speed = 5 m / min, dust = JIS15, final pressure loss = initial pressure loss + 5 mmAq, dust concentration =
It was 80 mg / m ³ ± 10%.

As a result of the measurement, the dust adhesion amount was 16 g / m ² .

Example 2 25 g / m ² of acrylic short fibers having a total basis weight of 110 g / m ² , ultrafine fibers of 3.4 μm, self-bonding short fibers (fineness: 1.5 denier, core; copolymerized polyethylene, sheath; A needle-punched non-woven fabric comprising polypropylene and a melting point of 98 ° C.) of 55 g / m ² and flame-retardant short fibers (modacrylic fiber, LOI value 36, 2.4 denier) of 30 g / m ²
The density of the present invention having an upstream pore size of 120 μm and a downstream pore size of 25 μm in which fibers were fused by passing through a gap (0.5 mm) between a metal roll heated to 30 ° C. and a metal roll heated to 60 ° C. A filter medium having a gradient was prepared. The bending resistance of this product was 115 mm, which satisfied the rigidity. Flame retardance (JIS L1091A-1
The law) also obtained Category 3 satisfying the target.

The collection efficiency of this filter medium was 38% with respect to 0.8 μm polystyrene particles, and the pressure loss was 1.3 mmAq (measured wind speed 5 m / min).

Further, when the dust retention amount of this filter medium was evaluated by the method of Example 1, the dust attachment amount was 14 g / m ² . This value shows the dust adhesion amount corresponding to 7,000 hours under actual use conditions.

Example 3 20 g / m ² of polypropylene electretized short fibers having a total basis weight of 120 g / m ² and ultrafine fibers of 7 μm, and self-bonding short fibers (fineness 4 denier, core; polyester, sheath;
Copolymerized polyester melting point 85 ° C), and 25 short flame-retardant fibers (polychloral; LOI value 28, 4 denier)
gap between the metal roll nonwoven fabric was heated to 95 ° C. consisting g / m ² and a metal roll heated to 60 ° C. (0.5 m
m) through which fibers were fused to each other to prepare a filter medium having a density gradient of the present invention with an upstream pore size of 220 μm and a downstream pore size of 50 μm. This product has a bending resistance of 1
At 20 mm, the rigidity was satisfied. Flame retardance (JI
S L1091A-1 method) also obtained Category 3 satisfying the target. The collection efficiency of this filter material was 78% with respect to 0.8 μm polystyrene particles, and the pressure loss was 0.8 mmAq, confirming the effect of the electret (measured wind speed 5 m / m.
in). Furthermore, when the dust retention amount of this filter medium was evaluated by the method of Example 1, it was found that the dust attachment amount was 25 g / m ² . Due to the effect of electret and the effect of increasing the pore size.

Example 4 Electretized polypropylene meltblown nonwoven fabric (fiber diameter 1.8 μm, basis weight 20 g /
m ² , thickness 0.2 mm, pore size 18 μm, bending resistance 3
0 mm) was laminated and adhered using self-bonding fibers. The bending resistance of this product was 110 mm, which satisfied the rigidity. Category 3 was obtained in which the flame retardancy (JIS L1091A-1 method) also satisfied the target. The collection efficiency of this filter medium is 0.
95% relative to 8 μm polystyrene particles, pressure loss was 1.
It was 5 mmAq, and the effect of electret was confirmed (measured wind speed 5 m / min). Furthermore, when the dust retention amount of this filter medium was evaluated by the method of Example 1, it was found to be 13 g / m.
^The amount of attached dust was ² . Even with the electret sheet, the amount of dust adhered was large.

Comparative Example 1 A filter medium was prepared in the same manner as in Example 1 except that the following conditions were changed.
15 g / m ² polyester short fibers with an overall basis weight of 100 g / m ² and ultrafine fibers of 8 μm and self-bonding short fibers (fineness 4
Denier, core; polyester, sheath; copolyester melting point 85 ° C.) 15 g / m ² , further flame-retardant short fibers (modacrylic fiber, LOI value 36, 2.4 denier) 70 g /
A filter medium (upstream side pore size 200 μm, downstream side pore size 50 μm) obtained by processing a needle punched nonwoven fabric made of m ^{2 by} the method of Example 1 was prepared. The bending resistance of this product was 35 mm, which did not satisfy the rigidity.

This is because the amount of self-bonding fibers used was too small.

Comparative Example 2 A filter medium was prepared in the same manner as in Example 2 except that the following conditions were changed.
25 g / m ² of acrylic short fibers having a total basis weight of 110 g / m ² , ultrafine fibers of 3.4 μm, self-bonding short fibers (fineness of 1.5 denier, core: copolyethylene, sheath; polypropylene, melting point 98 ° C.) 75 g / m ² and further flame-retardant short fibers (modacrylic fiber, LOI value 36, 2.4 denier) using 10 g / m ² of needle-punched nonwoven fabric,
A filter medium processed under the same conditions as in Example 2, a filter medium having an upstream pore size of 125 μm and a downstream pore size of 30 μm was prepared.

This product had a bending resistance of 140 mm, but its flame retardancy (JIS L1091A-1 method) was Category 1 which did not satisfy the target. This is a result of using too little flame retardant fiber.

Comparative Example 3 A filter medium was prepared by changing the following conditions in the same manner as in Example 2.
25 g / m ² of acrylic short fibers having a total basis weight of 110 g / m ² , ultrafine fibers of 3.4 μm, self-bonding short fibers (fineness of 1.5 denier, core: copolyethylene, sheath; polypropylene, melting point 98 ° C.) Of 55 g / m ² and flame-retardant short fibers (modacrylic fiber, LOI value 36, 2.4 denier) of 30 g / m ² using a needle punched nonwoven fabric,
A filter medium (upstream side pore size 90 μm, downstream side pore size 15 μm) processed under the same conditions (clearance 0.2 mm) as in Example 2 was prepared. This one is 270m
It has a bending resistance of m and is flame retardant (JIS L1091A-1
The law) also obtained Category 3 satisfying the target.

Collection efficiency is 50%, pressure loss is 3 mmA
It was q. Furthermore, as a result of evaluating the dust holding amount of this filter medium under the same conditions as in Example 1, the dust adhering amount of 3.0 g / m ² was an extremely small dust adhering amount. this is,
The result was that the pore size was too small.

Comparative Example 4 Modacrylic short fiber nonwoven fabric (fineness 2.4 denier, LOI
Value 27) 40 g / m ² processed with synthetic flame-retardant resin (vinyl chloride and vinyl acetate)
m ² , thickness 0.6 mm, pore size 284 μm, meltblown nonwoven fabric (fiber diameter 1.8 μm, basis weight 30 g /
m ² , thickness 0.2 mm, pore size 18 μm) were laminated. The collection efficiency of this filter medium was 35% with respect to 0.8 μm polystyrene particles, and the pressure loss was 2.4 mmAq (measured wind speed 5 m / min).

The amount of dust retained by this filter medium was evaluated under the same conditions as in Example 1, with the rough structure side being the upstream side, and the result was 4 g / m.
^The amount of attached dust was ² .

This was because the pore size on the upstream side was too large and the pore size of the meltblown nonwoven fabric was too small.

Comparative Example 5 The amount of dust adhering to a melt-blown non-woven fabric having a denser structure (fiber diameter 1.8 μm, basis weight 30 g / m ² , thickness 0.2 mm, pore size 18 μm, bending resistance 30 mm) was evaluated. The collection efficiency of this product was 30% with respect to 0.8 μm polystyrene particles, and the pressure loss was 1.8 mmA.
It was q (measured wind speed 5 m / min).

When the dust holding amount of this filter medium was evaluated under the same conditions as in Example 1, the dust adhering amount of ² g / m ² was extremely small. This is because the pore size is small.

[0061]

The effect of the present invention is that a long-life filter medium suitable as an air-conditioning filter medium is produced in a coarse-dense gradient structure by the constitution of fibers, that is, the constitution of ultrafine fibers, self-bonding fibers and organic flame-retardant fibers. The point is that we were able to realize many merits from what we obtained.

In the conventional resin processed product, the space for holding the dust is covered with the resin and is lost, so that the amount of dust held is small and the service life is short, and the collection efficiency of the coarse structure filter medium on the upstream side is low, so that it is dense. Since high-concentration dust reaches the melt-blown non-woven fabric layer as it is, the pressure loss rises quickly and the life is short.However, in the present invention, by using ultrafine fibers, high collection efficiency and rigidity By fusing and fixing the fusible fiber, further flame retardancy is configured by separating the function by the flame retardant fiber, and as a result of configuring the upstream side and the downstream side density configuration to have an appropriate pore size, The effect is that flame retardancy and higher collection efficiency than the initial stage are obtained, and the effective pore volume for holding dust is large, so that a long life can be realized.

Therefore, the filter medium having a coarse and dense structure of the present invention has a pleating property / strength resistant to wind pressure and high flame retardancy,
Furthermore, it has low ventilation resistance and long service life, so it can be effectively used in filter units that are pleated or are stored flat as they are, and have high flame retardancy and prevent fire spread. It is highly effective. For this reason, it can be widely used for various building air conditioners, AHU filters, long life filters, precision instrument filters, printer filters, coarse dust filters, medium to high performance filters, automobile filters, and other air filters. ..

As the liquid filter, an oil filter, an aqueous filter, a solvent filter or the like can be used.
It can be suitably used for separating particles of 1 micron or more.

Claims (7)

[Claims] 1. Ultrafine fibers having a diameter of less than 10 μm and 2
A non-woven fabric composed of 0 to 80% by weight of self-bonding fiber and 10 to 50% by weight of organic flame-retardant fiber having LOI value of 25 or more, and the fibers are partially bonded by the self-bonding fiber. , And the pore size on the upstream side is 150 to 250 μm, and the pore size on the downstream side is 20.
A filter medium having a coarse-dense gradient structure in which the upstream side is coarse and the downstream side is dense in the range of ˜80 μm, and the bending resistance is 100 mm or more. 2. Single filament fiber and ultrafine fiber having a diameter of less than 10 μm and 2
A non-woven fabric composed of 0 to 80% by weight of a self-fusing fiber and 10 to 50% by weight of an organic flame-retardant fiber having a LOI value of 25 or more. At least one of them is an electretized fiber, the fibers are partially bonded by the self-bonding fiber, and the pore size on the upstream side is 150.
~ 300 μm, pore size on the downstream side is 20 ~ 13
A filter medium having a coarse and dense gradient structure in which the upstream side is coarse and the downstream side is dense in the range of 0 μm, and the bending resistance is 100 mm or more. 3. The filter medium according to claim 1 or 2, wherein the ultrafine fibers constituting the filter medium are opened short fibers. 4. The structure of the self-bonding fiber constituting the filter medium,
The core-sheath type composite fiber, wherein the difference in melting point between the core and the sheath is 30 ° C. or more, and the material contains a polyester polymer, and the filter medium according to claim 1 or 2. 5. The filter medium according to claim 1 or 2, wherein the organic flame-retardant fiber is one which generates a fire-extinguishing gas upon combustion. 6. The filter medium according to claim 1, wherein the meltblown nonwoven fabric is laminated and adhered. 7. The filter medium according to claim 6, wherein the meltblown nonwoven fabric is an electret.