JP2006289209A - Filter having high collection efficiency and low pressure loss in combination - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filter having a combination of high collection efficiency and low pressure loss. <P>SOLUTION: The filter having a combination of high collection efficiency and low pressure loss is constituted from a fiber of which the fiber diameter is 5,000 to 20,000 and is composed of at least two layers or more of a non-woven fabric (A) layer containing 50 to 80 wt.% of a fiber of which the fiber axial angle to the plane of the non-woven fabric is 40 to 140° and a nano fiber non-woven fabric (B) layer constituted from a fiber of which the fiber diameter is 1 to 500 nm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a filter that is made of a nonwoven fabric and filters solids or liquid mist floating in a gas. More specifically, the filter can be suitably used for an air filter, a mask or the like.

  In general, the filter performance is evaluated by pressure loss, dust collection efficiency, filter life, etc., and a sheet-like fiber structure is used in which the basis weight of the woven fabric and nonwoven fabric, fiber density, fiber diameter, etc. are changed according to the purpose of use. ing.

  The performance of the filter is classified according to the particle size of the collected dust and the collection efficiency. Recently, there is a filter for collecting dust of 0.1 mm or less. This filter has been attempted to achieve its purpose by using fibers with a fiber diameter of micro or nano order, and a method for adhering nanofibers on a filter substrate such as a spun bonded fabric, a nonwoven fabric, or a plastic screen is disclosed. (For example, Patent Document 1).

  However, even if high dust collection efficiency can be achieved by using micro- and nano-order fibers, there is a problem that pressure loss increases depending on the configuration of the filter substrate.

Further, a filter and a non-woven fabric composed of micro and nano-order fibers are combined with other non-woven fabrics, for example, a carding method using short fibers as a raw material, and a non-woven fabric prepared by a spunbond method using continuous fibers as a raw material. As a result, the pressure loss was higher and it was not practical. Therefore, with the conventionally proposed filter, it is difficult to simultaneously achieve high dust collection efficiency and low pressure loss.
JP-T-2004-508169

  An object of the present invention is to solve the above-mentioned problems of the prior art and provide a filter having high collection efficiency and low pressure loss.

  As a result of intensive studies to achieve the above object, the present inventors have found that when a plurality of nonwoven fabrics having different fiber diameters are laminated and the fiber axis arrangement of one nonwoven fabric is controlled, high collection efficiency and low It has been found that a filter having a pressure drop at the same time can be obtained.

  That is, according to the present invention, the layer of the nonwoven fabric (A) containing 50 to 80% by weight of fibers having a fiber diameter of 5000 to 20000 nm and a fiber axis angle with respect to the nonwoven fabric plane axis of 40 to 140 degrees. And a nanofiber nonwoven fabric (B) layer composed of fibers having a fiber diameter of 1 to 500 nm is provided, and a filter having high collection efficiency and low pressure loss is provided. .

  In the filter of the present invention, a non-woven fabric having a specific fiber axis orientation and a non-woven fabric composed of nanofibers are laminated, and with this structure, the pressure loss does not increase while having high collection efficiency. And can be suitably used for applications such as masks.

  The filter of the present invention comprises a nonwoven fabric (A) layer and a nanofiber nonwoven fabric (B) layer.

  In the present invention, natural fibers, synthetic fibers, and the like can be used as the fibers constituting the nonwoven fabric (A). Specifically, polyethylene fibers, polyester fibers, polyamide fibers, aromatic polyamide fibers, acrylic fibers, poly Vinyl chloride fiber, polyolefin fiber, and polyacrylonitrile fiber are preferred.

  On the other hand, as fibers constituting the nanofiber nonwoven fabric (B), synthetic fibers such as inorganic fibers, polyethylene fibers, polyester fibers, polyamide fibers, aromatic polyamide fibers, acrylic fibers, polyvinyl chloride fibers, polyolefin fibers, and the like are used. However, polyacrylonitrile fiber is particularly preferable.

  In the present invention, the nonwoven fabric (A) is composed of fibers having the following fiber diameters and has a fiber axis orientation, the nanofiber nonwoven fabric (B) is composed of fibers having a fiber diameter described below, and It is important that the filter of the present invention is a filter formed by laminating at least two layers of the nonwoven fabric (A) and the nanofiber nonwoven fabric (B).

  That is, the fiber diameter of the fibers constituting the nonwoven fabric (A) needs to be 5000 to 20000 nm, preferably 9000 to 15000 nm. If the fiber diameter is less than 5000 nm, the strength of the nonwoven fabric becomes weak. On the other hand, if it exceeds 20000 nm, the collection efficiency deteriorates, which is not preferable.

  The non-woven fabric (A) is a fiber having an angle of 40 to 140 degrees with respect to the plane axis of the non-woven fabric of the fibers constituting the non-woven fabric (A), based on the weight of the non-woven fabric (A). It is necessary to contain 70% by weight. When the ratio of the fibers having the fiber axis angle is less than 50% by weight, a high pressure loss is exhibited. On the other hand, when the ratio exceeds 80% by weight, the pressure loss tends to be low, but the configuration as a nonwoven fabric can be maintained. It becomes difficult.

  In addition, as shown in FIG. 1, the “fiber axis angle” in the present invention refers to an angle θ between an axis connecting both ends of a fiber with a straight line and a nonwoven fabric plane axis.

In the present invention, the basis weight of the nonwoven fabric (A) is preferably from 10 to 250 g / ^{m 2,} more preferably from 150 to 200 g / ^{m 2.}

  The fiber constituting the nanofiber nonwoven fabric (B) needs to have a single fiber diameter of 1 to 500 nm, preferably 50 to 200 nm. When the fiber diameter is less than 1 nm, the strength of the resulting nanofiber nonwoven fabric is reduced. On the other hand, when the fiber diameter exceeds 500 nm, the superiority of the nanofiber fibers is not expressed and the collection efficiency is deteriorated.

In the present invention, it is preferable that the basis weight of the nanofiber nonwoven fabric (B) is 0.01 to 1.0 g / ^{m 2,} and more preferably 0.05~0.7g / ^{m 2.}
If the basis weight is less than 0.01 g / m ² , it tends to be difficult to uniformly coat the nanofibers on the surface of the nonwoven fabric (A), while if it exceeds 1.0 g / m ² , the pressure loss increases. There is a tendency.

The filter of the present invention described above can be manufactured, for example, as follows.
The layer of the non-woven fabric (A) can be preferably formed by the air-laid non-woven fabric manufacturing method, whereby a non-woven fabric having a fiber axis angle of 40 to 140 degrees of 50 to 80% by weight can be easily formed. . Specifically, dried short fibers having a fiber diameter of 5000 to 20000 nm and a fiber length of 1 to 100 mm are transported on an air flow using, for example, the production described in JP 2000-11027 A, Form the web on the net. This web can be adjusted to an arbitrary fiber axis angle by adjusting the pressure for sucking air from under the net to 0.2 to 0.4 MPa. It is preferable to increase the suction pressure when using a fiber having a thick fiber diameter and to decrease the suction pressure when using a fiber having a short fiber diameter.

  On the other hand, the nanofiber nonwoven fabric (B) is preferably formed by an electrospinning method. In this method, nanofibers are formed by spraying a solution by applying a high voltage to a polymer solution located on a substrate. The fiber diameter of the resulting nonwoven fabric is determined by applying voltage, solution concentration, and spraying. Depending on the scattering distance, the fiber diameter can be adjusted by adjusting these conditions.

  For example, in the case of polyacrylonitrile fiber, a polymer solution prepared by dissolving a powder state mainly composed of polyacrylonitrile and a solvent N, N-dimethylformamide in a weight ratio of 5:95 to 15:85 is prepared, and 5 to 30 kV is prepared. It can be manufactured under a voltage of.

  If the above method is used, not only a planar nonwoven fabric but also a three-dimensional nonwoven fabric having a three-dimensional network structure can be formed.

  The filter of the present invention laminates two or more layers of the nonwoven fabric (A) and the nanofiber nonwoven fabric (B) in order to increase the collection efficiency while maintaining a low pressure loss. 2-5 layers are preferable. The adhesion between the layers may be carried out after only the non-woven fabric (A) is produced, and the nanofiber non-woven fabric (B) may be laminated, or the nanofiber non-woven fabric (B) is laminated on the non-woven fabric (A). Adhesion treatment may be applied after manufacturing, and further, the nonwoven fabric (A) or the nanofiber nonwoven fabric (B) is laminated on the one that has already been subjected to the adhesion treatment between the nonwoven fabric (A) and the nanofiber nonwoven fabric (B). Alternatively, after several layers of the nonwoven fabric (A) or the nanofiber nonwoven fabric (B) are laminated, the adhesion treatment may be performed at once.

  At this time, for example, the bonding treatment may be performed by using a heat-fusible fiber as a fiber constituting the nonwoven fabric (A) and laminating with the nanofiber nonwoven fabric (B), followed by heat-sealing. A method of applying one to a nonwoven fabric and laminating the other nonwoven fabric and then heat-sealing them, or a method of applying a water-soluble binder between the nonwoven fabrics and bonding them are preferably employed.

Hereinafter, the present invention will be described in more detail based on examples. In addition, each physical property in an Example is calculated | required with the following method.
(1) Fiber diameter A section obtained by cutting the nonwoven fabric (A) and the nanofiber nonwoven fabric (B) in the fiber thickness direction is prepared, the nonwoven fabric (A) is scanned using an optical microscope, and the nanofiber nonwoven fabric (B) is scanned. Measurement was performed using an electron microscope. The results are shown in Table 1.
(2) cutting the angle nonwoven (A) of the fiber axis and observe the cross section, the fiber axis angles shown in FIG. 1 was calculated percentage of 1cm ² of fibers chosen arbitrarily is 40 to 140 degrees . The results are shown in Table 1.
(3) Weight per unit area of 21.0 cm × 29.7 cm was measured and converted per 1 m ² .
(4) Filter performance (collection efficiency, pressure loss)
The dust used is 8 kinds of standard dust for JIS test, and the collection efficiency is calculated using the following formula based on the dust concentration that passed through a filter in which at least two layers of nonwoven fabric (A) and nanofiber nonwoven fabric (B) are laminated. Calculated. The higher the numerical value, the better the collection efficiency, and 99.98% or more was considered acceptable.
Collection efficiency = [(dust supply concentration−blown dust concentration) / dust supply concentration] × 100
The pressure loss was determined by measuring the air pressure before and after the filter measured without loading dust. The lower the value, the better, and 70 Pa or less was considered acceptable. The results are shown in Table 1.

[Example 1]
Nonwoven fabric (A) is a polyester-based binder fiber having a fiber diameter of 11800 nm (1.5 dtex) (core: polyethylene terephthalate, sheath: molar ratio of terephthalic acid component: isophthalic acid component = 65: 35, diol component is ethylene glycol, Tg 65 ° C. ) With an airlaid nonwoven fabric manufacturing apparatus described in Japanese Patent Application Laid-Open No. 2004-11027, the suction pressure was set to 0.2 MPa from the lower part of the apparatus, and the web was molded so as to have a basis weight of 200 g / m ² . Further, the web was heat-treated at 170 ° C. with a hot air treatment machine to form a nonwoven fabric (A) having a basis weight of 200 g / m ² .

Next, the nanofiber nonwoven fabric (B) is prepared by preparing a powder state mainly composed of polyacrylonitrile and a polymer solution in which the solvent N, N-dimethylformamide is dissolved at a weight ratio of 11:89, and electrospinning. Under an applied voltage of 25 kV, the polyacrylonitrile nanofiber was molded so as to be laminated directly on the nonwoven fabric (A) under the conditions that the fiber diameter was 50 nm and the basis weight was 0.5 g / m ² .
Next, it heat-processed with a 170 degreeC hot air processing machine, and the nonwoven fabric (A) and the fiber nonwoven fabric (B) were heat-seal | fused, and the filter which consists of two layers was produced. The results are shown in Table 1.

[Example 2]
In preparation of the airlaid nonwoven fabric used as the nonwoven fabric (A), a polyester binder fiber having a fiber diameter of 14300 nm (2.2 dtex) is used, the suction pressure is 0.23 MPa, and the fiber weight is 150 g / m ^2. A filter was prepared in the same manner as in Example 1 except that the web was formed by adjusting The results are shown in Table 1.

[Example 3]
In the preparation of the nanofiber nonwoven fabric (B), the applied voltage in the electrospinning method is 20 kV, the fiber diameter of the polyacrylonitrile nanofibers constituting the nonwoven fabric (B) is 200 nm, and the basis weight of the nonwoven fabric (B) is 0. A filter was prepared in the same manner as in Example 1 except that the amount was 1 g / m ² . The results are shown in Table 1.

[Example 4]
The nonwoven fabric (A) created in Example 1 was further laminated on the nanofiber nonwoven fabric (B) on the nonwoven fabric laminate comprising two layers of the nonwoven fabric (A) and nanofiber nonwoven fabric (B) created in Example 1, A filter comprising three layers of nonwoven fabric (A) / nanofiber nonwoven fabric (B) / nonwoven fabric (A) was prepared. The results are shown in Table 1.

[Comparative Example 1]
Example of production of airlaid nonwoven fabric used as nonwoven fabric (A), except that the suction pressure was 0.4 MPa, the amount of fibers was adjusted so that the nonwoven fabric (A) had a basis weight of 200 g / m ² and the web was molded. A filter was prepared in the same manner as in 1. The results are shown in Table 1.

[Comparative Example 2]
In preparation of the airlaid method nonwoven fabric used as the nonwoven fabric (A), a polyester binder fiber having a fiber diameter of 24800 nm (6.6 dtex) is used, the suction pressure is 0.3 MPa, and the basis weight of the nonwoven fabric (A) is 150 g / m ² . A filter was prepared in the same manner as in Example 1 except that the amount of fibers was adjusted to form a web. The results are shown in Table 1.

[Comparative Example 3]
In the preparation of the nanofiber nonwoven fabric (B), the weight ratio of polyacrylonitrile: N, N-dimethylformamide was 2:98, the fiber diameter of the polyacrylonitrile nanofibers constituting the nonwoven fabric (B) was 550 nm, A filter was prepared in the same manner as in Example 1 except that the basis weight of B) was 0.5 g / m ² . The results are shown in Table 1.

[Comparative Example 4]
Example 1 except that the airlaid nonwoven fabric used as the nonwoven fabric (A) was formed by forming a web by adjusting the amount of fibers so that the suction pressure was 0.05 MPa and the basis weight of the nonwoven fabric (A) was 200 g / m ^2. A filter was created in the same manner as above. The results are shown in Table 1.

  The filter of the present invention is a laminate of a non-woven fabric having a specific fiber axis orientation and a non-woven fabric composed of nanofibers. With such a structure, the pressure loss does not increase while having high collection efficiency. It can be suitably used for applications such as air filters and masks, and its industrial utility value is extremely high.

The schematic diagram for demonstrating the fiber axis angle of the fiber which comprises a nonwoven fabric (A).

Explanation of symbols

a: Fiber axis b: Non-woven fabric plane axis c: Short fiber θ: Fiber axis angle

Claims (5)

  A layer of a nonwoven fabric (A) containing 50 to 80% by weight of fibers having a fiber diameter of 5000 to 20000 nm and a fiber axis angle of 40 to 140 degrees with respect to the nonwoven fabric plane axis, and a fiber diameter of 1 to 500 nm A filter having both high collection efficiency and low pressure loss, in which at least two layers of nanofiber nonwoven fabric (B) composed of these fibers are laminated.   The layer of the non-woven fabric (A) and the layer of the nanofiber non-woven fabric (B) are substantially bonded to each other, and have both high collection efficiency and low pressure loss according to claim 1 or 2. filter. Nonwoven basis weight of (A) is 10 to 250 g / ^{m 2,} the basis weight of the nanofiber nonwoven fabric (B) is 0.01 to 1.0 g / ^{m 2,} a high collection efficiency according to claim 1 or 2 And low pressure loss filter.   The filter having both high collection efficiency and low pressure loss according to any one of claims 1 to 3, wherein the nonwoven fabric (A) is a nonwoven fabric produced by an airlaid method.   The filter which has high collection efficiency and low pressure loss in any one of Claims 1-4 whose nanofiber nonwoven fabric (B) is the nonwoven fabric produced by the electrospinning method.

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