JPH0568822A - Laminated filter medium for streamer type filter - Google Patents

Abstract

PURPOSE:To obtain a laminated filter medium for streamer type filters with low pressure loss and high removal efficiency by making at least one layer on the downstream side of electret nonwoven fabrics with the prescribed METSUKE (unit weight) and letting the measured bending resistance take the limited value. CONSTITUTION:Unwoven fabrics of 10-200g/m<2> METSUKE (unit weight) are used as base material for electret nonwoven fabrics. Nonwoven fabrics of 0.5-18 fineness and 0.03-0.15cc/cc denier fiber density are used for a dust holding layer laminated on the upstream side so that the dust holding layer may have fineness gradually smaller from the upstream to the downstream side and have multilayer structure with a fiber density gradient. Fiber layers are made to adhere to each other by lamination using needle punching treatment, spot deposition treatment, adhesion by heat fusion fiber or binders, etc., and the bending resistance of the laminated filter medium for filters is <=20mm. Fiber packing density is determined by the following formula after measuring METSUKE of fiber layer, W g/m<2> and thickness on putting no-load, T cm. Fiber packing density, cc/cc=WX10<-4>divided by (TXrho), where rho is density of fiber, g/cc. The bending resistance is measured in accordance with JIS L1096, 'Testing Methods for Woven Fabrics, Bending Resistance'.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated filter medium for a windsock type filter in which the filter medium opens like a bag when ventilated to increase the filtration area, and the filter medium can be widely used in air conditioners such as buildings and factories. You can

[0002]

2. Description of the Related Art A blow-off filter has a structure as shown in FIG. 1, for example, and is characterized by a wide filtration area. Since the filter media for blow-away filters that have been used in the past are composed of ultrafine glass fibers, the removal rate of dust is high, but the pressure loss due to the filter media is also extremely high, and most of the dust is on the filter surface. Since it is collected, it has a drawback that clogging occurs early and the amount of dust retained is small. Further, since it is glass fiber, there is a problem that the volume reduction treatment by incineration cannot be performed after use. Therefore, it has been attempted to use organic fibers. However, in order to obtain high removal efficiency, it is necessary to use a non-woven fabric of ultrafine fibers such as a melt blown non-woven fabric, but the non-woven fabric is repeatedly subjected to forces such as pulling, bending and friction due to the flow of wind, so that fluffing and tearing may occur. It had the drawback of being easily damaged.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is a filter medium for a blow-off filter having high removal efficiency, low pressure loss, and a large dust holding amount. Moreover, it aims to provide a product that can be incinerated and is not easily damaged.

[0004]

Means for Solving the Problems The laminated filter medium for a windsock type filter of the present invention which has been able to solve the above problems is at least one layer on the downstream side, and the basis weight is an electretized non-woven fabric of 10 to 200 g / m ² . In addition, the gist is that the bending resistance measured by the measuring method described in the text is 200 mm or less.

[0005]

The present inventors have studied various materials such as glass fiber and ultrafine organic fiber non-woven fabric as a filter medium for a blow-off type filter, and have found that a filter medium using an electretized non-woven fabric is very excellent. Electretization means that even if the external electric field is removed, positive and negative charges remain, and the electretized non-woven fabric can effectively collect particles due to strong electrostatic attraction, so It is possible to obtain a high removal efficiency with a low pressure loss as compared with the glass fiber filter material of No. Also, by stacking the dust holding layer on the upstream side of the electretized nonwoven fabric,
Coarse particles are collected by the dust holding layer, so that the amount of dust added to the electret nonwoven fabric can be reduced, and as a result, a large dust holding amount can be obtained.

A more detailed description will be given below. In the present invention, the basis weight is 10 to 10 as the base material of the electretized nonwoven fabric.
A non-woven fabric of 200 g / m ² is used. If the basis weight is too small, the strength is insufficient and sufficient collection efficiency cannot be obtained, while if it is too large, the collection efficiency increases but the pressure loss increases. Further, since the electretized non-woven fabric has electrostatic attraction, it is possible to improve abrasion resistance by using fibers having a relatively large fineness without lowering collection efficiency. Preferred fineness is 0.5-1
It is 5 denier, more preferably 1 to 10 denier. If the fineness is too small, the strength against pulling, bending, friction, etc. is insufficient, and if too fine, the flexibility of the filter medium is impaired.

The fiber raw material of the electretized nonwoven fabric is not particularly limited, but examples thereof include combustible materials such as polypropylene, polyethylene, polyvinyl chloride, polyvinylidene fluoride, etc., and one or more of them may be used in combination. You can The method of forming an electret is not particularly limited, and various methods such as a thermal electret method, a radio electret method, a magnet electret method, a mechano electret method, and an electro electret method can be adopted. The electretized non-woven fabric is preferably sheeted by subjecting the fibers to entanglement by subjecting it to needle punching treatment, spot welding treatment or the like in order to increase its strength.

As the dust holding layer laminated on the upstream side of the electretized nonwoven fabric, it is preferable to use a nonwoven fabric having a fineness of 0.5 to 18 denier and a fiber density of 0.03 to 0.15 cc / cc. If the fineness is too small, the pressure loss will be large, and if the fineness is too large, the dust retention will be poor. Further, if the fiber packing density is too low, a flexible finish is obtained but the shape retention is poor, and if the fiber packing density is too high, the fibers are compacted, which impairs the flexibility of the filter medium and the surface of the dust retaining layer. Dust collection is prioritized, and the effect due to the multilayer structure cannot be sufficiently obtained. Further, by further reducing the fineness of the dust holding layer from the upstream side to the downstream side to form a multilayer structure having a fiber density gradient, a further larger dust holding amount can be obtained.

The fiber raw material for the dust holding layer is not particularly limited, but examples thereof include polyester, polyamide, polyethylene, polypropylene, rayon, pulp and composite fibers thereof. By using combustible fibers together with the electretized nonwoven fabric, it is possible to obtain a filter medium that can be incinerated. In the present invention, the electret non-woven fabric and the dust holding layer are used in a laminated manner, in which case a needle punching treatment method, a spot welding treatment method, an adhesive method using a heat fusion fiber or a binder, or a fiber between fiber layers The fiber layers are adhered to each other by adopting a pressing method or the like for generating the entanglement.

In addition to the electretized nonwoven fabric and the dust holding layer, a protective layer may be provided further downstream of the electretized nonwoven fabric. By providing the protective layer, damage to the electretized nonwoven fabric can be prevented. The material of the protective layer is not particularly limited, but it is necessary to use a material having low air resistance such as a mesh material, and it is preferable that the material is flammable. The bending resistance of the laminated filter media for filters obtained as described above needs to be 200 mm or less in the following measuring method. If the bending resistance is too high, the filter medium does not swell sufficiently during filtration, and a wide filtration area cannot be obtained. However, in the case where a protective layer is provided, it is evaluated by the bending resistance as a whole including the protective layer.

The present invention will be described in more detail with reference to the following examples, but the following examples do not limit the present invention.
All modifications and implementations are included in the technical scope of the present invention without departing from the spirit of the description below.

[0012]

EXAMPLES Various laminated filter media for filters were prepared and their characteristics were investigated. The fiber packing density shown below is the basis weight W (g / m ² ) of the fiber layer and the thickness T (c
It is a value calculated by the following formula by measuring m) and using the measured value. Fiber packing density (cc / cc) = W × 10 ⁻⁴ ÷ (T × ρ) where ρ is the fiber density (g / cc).

Experimental Example 1 From the upstream side, the first layer: polyester fiber (6 denier, 68 mm long) 5
0% and polypropylene / polyethylene hot melt fiber (6
Denier, 68 mm long) 50% mixed card non-woven fabric layer (8
0 g / m ² ) Second layer: polypropylene spunbonded non-woven fabric (50 g / m ² ) having a fiber diameter of 20 μm was laminated and integrally molded by a heat fusion method, and then DC voltage was 20 kv and the distance between electrodes was 10 mm.
The corona treatment was performed for 0 seconds to obtain an electret-made laminated filter material for a windsock type filter. The fiber packing density of the dust retaining layer of the first layer was 0.07 cc / cc.

A sample having a filtration area of 20 cm ² was prepared using the above-mentioned filter material (Example 1) and a filter material (Comparative Example 1) made of an organic non-woven fabric having a basis weight of 250 g / m ² which was not electretized, and a filtration wind speed of 10 cm / s. The initial pressure loss, initial collection efficiency, and bending resistance were measured by the following methods. Initial pressure loss: The differential pressure was measured with a tilt manometer. Initial collection efficiency: The number of 0.3-0.5 μm particles on the inlet side and the outlet side was measured by the light scattering integration method using NaCl particles. Stiffness: Measured according to JIS L 1096 "General woven fabric test method", Stiffness A method. The results are shown in Table 1.

[0015]

[Table 1]

As shown in Table 1, the electretized Example 1 has excellent dust collecting efficiency.

Experimental Example 2 From the upstream side, the first layer: polyester fiber (6 denier, 68 mm long) 9
5% and heat-meltable polyester fiber (3 denier, 51 mm
Long) 5% mixed card non-woven fabric layer (150 g / m ² ) Second layer: flame-retardant polyester fiber (1.5 denier, 5
1% length) 97% and heat-meltable polyester fiber (3 denier, 51 mm length) 3% mixed card nonwoven fabric layer (100 g /
m ² ) Third layer: Electretized spunbonded non-woven fabric made of polypropylene (50 g / m ² ) having a fiber diameter of 20 μm was laminated and integrally molded by a heat fusion method, and then a DC voltage was 20 kv and a distance between electrodes was 10 mm for 10 seconds. A corona treatment was performed to obtain an electret laminated filter material for a windsock type filter (Example 2). The fiber packing density of the dust holding layer composed of the first layer and the second layer was 0.05 cc / cc.

The filter material (Example 2) and the basis weight of 180 g / m ²
Using the glass fiber (Comparative example 2), the ventilation part is 500 mm ×
A 500 mm sample was prepared, and the initial pressure loss at a wind velocity of 8.7 cm / s, the initial collection efficiency, the amount of dust retained, and the flexibility were measured by the following methods. Further, the filter medium of Example 2 was subjected to a flammability test based on JIS L 1091 "Method for testing flammability of textiles" A-1 method. As a result, it had flame retardancy that passed Category 3. Initial pressure loss: Measured in the same manner as in Experimental Example 1. Initial collection efficiency: Dust concentrations on the inlet side and the outlet side were simultaneously measured by the light scattering integration method using JIS 11 test dust. Dust retention amount: The amount of dust retained on the filter medium was measured until the pressure loss reached 30 mmAq using JIS 15 test dust. Bending: Measured in the same manner as in Experimental Example 1. The results are shown in Table 2.

[0019]

[Table 2]

As shown in Table 2, the filter using the filter medium of Example 2 has a lower pressure loss than that of Comparative Example 2 and is provided with a dust holding layer having a density concentration gradient. There were many.

Experimental Example 3 From the upstream side, the first layer: a card non-woven fabric layer of polypropylene / polyester heat-meltable fiber of 3 denier (80 g / m ² ) The second layer: polypropylene melt-blown non-woven fabric of 0.03 denier (22 g / m ² ) were laminated and integrally molded by a heat fusion method to obtain a laminated filter medium for a blow-through filter. Using the obtained filter medium (Comparative Example 3) and the filter medium of Example 2
JIS L 1096 "General woven fabric test method" Abrasion resistance and hardness were measured based on abrasion strength A-1 method and bending resistance A method.
The results are shown in Table 3.

[0022]

[Table 3]

As shown in Table 3, Example 2 was excellent in abrasion resistance, and the flexibility was also higher than that of Comparative Example 3.

[0024]

The present invention is configured as described above,
It has become possible to provide a filter material for a blow-away filter that has a high removal efficiency despite a low pressure loss and has a large dust holding amount. Further, the filter medium can be reduced in volume by incineration and is not easily damaged.

[Brief description of drawings]

FIG. 1 is a schematic view of a windsock filter.

Claims (1)

[Claims] 1. A basis weight of at least one downstream layer is 10.
A laminated filter material for a windsock type filter, characterized by comprising an electretized non-woven fabric of ˜200 g / m ^{2 and having} a bending resistance of 200 mm or less measured by the measuring method described in the present text.