JP2023137062A - Filter medium for measure against salt damage, and pleat type filter - Google Patents

Abstract

To provide a filter medium that reduces re-entrainment of salt during deliquescence by high salt retention characteristics while securing dust removal efficiency and ventilation resistance.SOLUTION: A filter medium for measures against salt damage according to the present invention comprises a support fiber layer for being arranged on the upstream side of ventilation, and a melt-blown nonwoven fabric layer for being arranged on the downstream side. The support fiber layer has moisture absorbency and fire retardancy. The melt-blown nonwoven fabric layer is subjected to liquid-repellent treatment. The melt-blown nonwoven fabric layer and the support fiber layer are joined together with an adhesive.SELECTED DRAWING: Figure 1

Description

The present invention relates to a filter medium used in filters and filter units used for air conditioning, air conditioners, and the like.

Conventionally, when outside air is taken into a factory, building, etc., a rather fine dust filter unit to which Type 2 of JIS B 9908:2011 is applied is used. Generally, in such applications, a filter is formed by folding a filter medium made of glass fiber into a zigzag shape and inserting it into a frame. With these filter units, when the outside air is relatively dry, the salt particles contained in the outside air become crystalline solid particles, so they can be removed in the same way as the particles normally contained in the outside air. However, when the outside air is humid, the salt particles that were once collected on the surface of the filter medium of the filter unit deliquesce and spread in the form of a film on the surface of the filter medium, causing a sudden increase in pressure loss and eventually passing through the filter medium to the factory. There was a problem with salt entering buildings and causing salt damage. Furthermore, when seawater particles are violently scattered from the interface due to strong winds, the same phenomenon occurs because liquid seawater particles are blown away.

Various types of filter media have been devised that reduce the temporary pressure loss and re-scattering downstream due to salt collection. For example, a filter that does not cause salt deliquescence due to a certain fiber diameter and packing ratio (Patent Document 1), and an intermediate filter medium layer that contains fibers that have a moisture absorption and desorption function between two water-repellent filter medium layers. There are methods in which salt-containing moisture is collected in an intermediate layer (Patent Document 2), and methods in which salt-containing particles are adsorbed and collected by a material with ion exchange ability (Patent Document 3). . However, in Patent Document 1, it is difficult to increase the dust removal efficiency because a certain level of particle collection efficiency requires a certain fiber density, and in Patent Document 2, deliquesced salt is collected in an intermediate layer. However, since the thickness of the filter medium becomes thicker, the ventilation resistance after folding becomes relatively high. Further, in Patent Document 3, since the material used for ion exchange is granular, the geometric surface area necessary for the reaction is small, and there is a problem that the amount of salt captured is unsatisfactory.

In order to solve these problems, a filter medium that combines a highly water-absorbent support layer and a highly water-repellent fine dust collection layer has also been devised (Patent Document 4). However, in Patent Documents 1 to 4, flame retardance, which should be ensured in terms of safety, is not taken into consideration. Therefore, there are filters that are made into sheets by mixing cellulose-based fibers with hot-melt resin containing a phosphate-based flame retardant (Patent Document 5), and filters that are made of halogen-free polyester fibers as a main component. There are sheets bound with isocyanate resin as a binder (Patent Document 6).

Japanese Patent Application Publication No. 5-15716 Japanese Unexamined Patent Publication No. 7-148406 Japanese Patent Application Publication No. 6-182127 Japanese Patent Application Publication No. 2020-189255 Japanese Patent Application Publication No. 11-253717 Japanese Patent Application Publication No. 2001-310106

However, sheets in which flame retardants or binders with flame retardant properties are added to the fibers are unable to absorb deliquescent salt into the sheet, and there are concerns about increased ventilation resistance and re-scattering of the collected salt. .

Therefore, the present invention was made in view of the above problems, and its purpose is to provide a filter medium for preventing salt damage, which can reduce salt re-scattering during deliquescence due to its salt retention properties, and has flame retardancy, while ensuring high dust removal efficiency. That's true.

The present invention was achieved through intensive study by the present inventor. The invention is as follows.
(1) In a salt damage prevention filter medium comprising a support fiber layer disposed on the upstream side of ventilation and a melt-blown nonwoven fabric layer disposed on the downstream side, the support fiber layer has hygroscopicity and flame retardancy, and the support fiber layer has hygroscopicity and flame retardancy; A filter medium for preventing salt damage, characterized in that the melt-blown non-woven fabric layer has water repellency, and the melt-blown non-woven fabric layer and the supporting fiber layer are bonded together with an adhesive.
(2) The filter medium for preventing salt damage according to (1) above, wherein the supporting fiber layer has a water absorption degree of 10 mm or more according to the Pyrex method according to JIS L 1907:2004.
(3) The filter medium for preventing salt damage according to (1) or (2) above, wherein the supporting fiber layer contains a flame retardant material in an amount of 15 to 35% by weight based on the weight of the fiber layer.
(4) The filter medium for preventing salt damage according to any one of (1) to (3) above, wherein the melt-blown nonwoven fabric layer is electrically charged and has a surface tension of 34 mN/m or less.
(5) The filter medium for preventing salt damage according to any one of (1) to (4) above, wherein the melt-blown non-woven fabric layer is formed by adhering a fluorine compound to the surface of a polyolefin-based melt-blown non-woven fabric.
(6) A pleated filter using the salt damage prevention filter medium according to any one of (1) to (5) above.

The present invention provides a filter medium that maintains general filter characteristics such as dust collection efficiency and dust supply amount, has low re-scattering of deliquesced salt to the downstream side as a salt damage prevention filter, and has flame retardant properties. becomes possible. The filter medium of the present invention is suitably used in a filter unit for slightly fine dust to which Type 2 of JIS B 9908:2011 is applied.

FIG. 2 is a cross-sectional view of a salt damage prevention filter medium according to the present invention. It is a schematic diagram of particle collection efficiency evaluation equipment used in the present invention. FIG. 2 is a schematic diagram of salt re-entrainment rate evaluation equipment used in the present invention. 1 is a schematic diagram of flammability test equipment used in the present invention.

The present invention will be explained in detail below, but the present invention is not limited to the following and can be practiced with appropriate modifications within the scope of the spirit of the above and below. All are included within the technical scope of the present invention.

FIG. 1 shows a cross-sectional view of a filter medium 100 for preventing salt damage (hereinafter referred to as a filter medium) having flame retardant properties according to the present invention. The filter medium 100 is applied to a salt damage prevention filter. The filter medium 10 includes at least a support fiber layer 1 disposed on the upstream side of the airflow and a melt-blown nonwoven fabric layer 2 disposed on the downstream side of the airflow. The supporting fiber layer 1 has hygroscopicity and flame retardancy, the melt-blown nonwoven fabric layer has water repellency, and the supporting fiber layer 1 and the melt-blown nonwoven fabric layer 2 are bonded with an adhesive.

The support fiber layer 1 is a sheet-like fiber that has flame retardancy and hygroscopicity, and is a fibrous layer that has appropriate strength, flame retardancy, and hygroscopicity for the purpose of maintaining its shape as a filter medium. Due to this hygroscopicity, it actively absorbs water droplets containing salt that are temporarily collected on the downstream side.

The melt-blown non-woven fabric layer 2 preferably has a water-repellent (liquid-repellent) treatment applied to the melt-blown non-woven fabric to suppress the spread of water droplets on the melt-blown fibers into the fibrous form.

Therefore, due to the synergistic effect of the supporting fiber layer 1 and the melt-blown nonwoven fabric layer 2, water particles containing salt are collected by the melt-blown nonwoven fabric with more water repellency, thereby suppressing deliquescence on the fiber surface. Because of this, it does not spread out, but instead exists as large droplets on the fiber surface, and is quickly absorbed by the upstream support fiber layer 1, which has water absorption properties. This mechanism prevents the collected salt-containing water droplets from scattering downstream again.

The support fiber layer 1 needs to maintain the original shape of the support and maintain water absorption. Of course, since it is a filter medium, it is preferable that the ventilation resistance is low. The water absorbency of the support fiber layer 1 is desirably 10 mm or more, preferably 15 mm or more, as determined by the Pyrex method according to JIS L 1907:2004. If the water absorption is less than 10 mm, sufficient water absorption cannot be expected and the collected droplets cannot be retained, resulting in re-scattering to the downstream side, which is not preferable.

The supporting fiber layer 1 is made of a single material having a hydrophilic group such as polyester, nylon, rayon, or cotton, in order to achieve both water absorption and the original functions of the supporting fiber layer 1, such as strength and ventilation resistance. Alternatively, it can be obtained by appropriately mixing them, forming them into a sheet, and adding a binder that exhibits hydrophilicity using a known method. In particular, it is preferable to use nonwoven fabric as the sheet in terms of breathability, handling, and cost. Specifically, the support fiber layer 1 is made by forming short fibers of the above-mentioned materials into a web, forming it into a sheet by a known method such as needle punching or hydroentangling, impregnating the sheet with an acrylic binder by a dipping method or coating method, and drying it. obtained by letting For example, the supporting fiber layer 1 uses fibers with a fineness of 1.1 to 5.5T, contains 10 to 30% by weight of a binder to obtain appropriate strength, has a basis weight of 30 to 90 g/m ² , and a thickness of 0.3 It is preferably in the range of ~1.0 mm.

Furthermore, a flame retardant (flame retardant substance) is added to the support fiber layer 1 to ensure the flame retardancy of the filter medium 100 itself. The flame retardant needs to be compatible with the support fiber layer and maintain water absorption. In particular, phosphorus-based water-soluble flame retardants, particularly ammonium monohydrogen phosphate, guanidine phosphate, and their analogs are preferably used. By adding a flame-retardant substance to the water-absorbent supporting fiber layer 1, it becomes possible to have flame retardancy without impairing the inherent water-absorbing property. When a flame retardant having a water-repellent function is used, the original water absorption of the support fiber layer is impaired, the amount of water absorption decreases, and the desired salt-trapping performance cannot be maintained.

The addition amount of the flame retardant substance to the total fiber weight of the support fiber layer 1 is preferably 15% to 35% by weight, preferably 20% to 30% in order to obtain flame retardancy and hygroscopicity. If it is less than 15% by weight, sufficient flame retardancy cannot be ensured, and if it exceeds 35%, the amount of deliquescent substances is too large and salt cannot be absorbed, which is not preferable. Addition of a flame retardant substance to the support fiber layer 1 can be carried out by a known method, but in order to maintain flame retardancy while maintaining the original water absorbency of the support fiber layer 1, it is necessary to add a water-soluble substance to the support fiber layer 1. A preferred method is to uniformly apply the flame retardant by a dipping method and then dry it. In addition to completely water-soluble water-soluble flame retardants, emulsion type flame retardants can also be used, but water-insoluble flame retardants cannot be uniformly supported on the fiber layer, so sufficient flame retardancy cannot be expected.

The melt-blown nonwoven fabric layer 2 is composed of fibers made of polyolefin resin, and polypropylene resin is particularly preferably used as the polyolefin resin. In addition, appropriate fiber diameter and fabric weight are selected in order to obtain ventilation resistance and collection efficiency according to the standards. However, in order to obtain water repellency, it is necessary to perform necessary water repellent treatment. In particular, when a fluorine-based compound is attached to the fiber surface, nano-level fine irregularities are formed on the fiber surface, which lowers the surface tension, making it possible to increase water repellency. Appropriate water repellency can be obtained by reducing the surface tension to 34 mN/m or less by adhering the fluorine-based compound to the fiber surface. A method for attaching a fluorine-based compound to the fiber surface is by dispersing a chemical solution containing a fluorine-based compound in water or an organic solvent and using a known method such as a dip method or a spray method. The vapor deposition method described in 2007 can also be used, and the method is not particularly limited. Further, in order to improve the dust removal efficiency and reduce the ventilation resistance, it is possible to perform charging treatment using a known method to make it an electret.

The supporting fiber layer 1 and the melt-blown nonwoven fabric layer 2 are laminated and bonded with an adhesive between the layers to form a filter medium. Lamination and bonding methods include spraying adhesive powder onto at least one layer and heating and compressing it, or spraying molten adhesive from a thin nozzle and finely scattering it over the surface of at least one layer. There are methods such as a method of compressing the material by heating (spray method), a method of laminating sheets of adhesive fibers between layers and compressing with heat, but there are no particular limitations. If stronger flame retardancy is desired, this can be achieved by mixing a flame retardant into the adhesive, or by selecting a material with a high ROI value when using adhesive fibers.

The salt damage prevention filter medium may be used by being laminated with other sheets or processed. Further, pleated filters using filter media for preventing salt damage are also included in the scope of the present invention.

The present invention will be specifically explained below using Examples and Comparative Examples, but the present invention is not limited only to the Examples.

First, methods for measuring physical property values of Examples and Comparative Examples will be explained.
<Flame retardant content>
Flame retardant content (%): The sheet dry weight before and after flame retardant impregnation was measured, and calculated using the following formula (1).
Flame retardant content = (1-weight before impregnation/total weight after flame retardant impregnation) x 100...(1)
<Weight>
The basis weight (g/m ² ) was determined by cutting out a 200 mm square, weighing it, and dividing it by the size.

<Thickness>
The thickness (mm) was measured at a load of 0.7 kPa.
<Pressure loss/particle collection efficiency>
Using the particle collection efficiency evaluation equipment 200 shown in FIG. 2, the sample 12 is set in the duct 4, air is flowed at a linear velocity of 10 cm/sec, and the differential pressure upstream and downstream of the filter material is measured with the differential pressure gauge 7. It was taken as pressure loss. Furthermore, the air on the upstream and downstream sides was sampled, and the number of particles with a particle size of 0.3 to 0.5 μm was counted using a particle counter 8. Particle collection efficiency (E) was calculated using the following formula (2).
Particle collection efficiency E (%) = {1-(number of downstream particles/number of upstream particles)}×100...(2)

<Water absorption>
The water absorption was evaluated by the Pyrex method according to JIS L 1907:2004.

<Water repellency>
Based on JIS K 6768 for surface tension, a droplet of a mixed liquid for wetting tension test was dropped and brought into contact for 30 seconds to check whether or not the droplet had penetrated.

<Flame retardancy>
The test was carried out in accordance with JIS L 1091:1999 A-1 method (45° microburner method) using the flammability test equipment 400 shown in FIG.

<Re-entrainment rate during NaCl deliquescence>
After cutting out the sample so that the effective ventilation area was 82 cm ² (10.2 cmφ), the dry weight was measured and defined as the "initial weight" (W ₀ ). Next, about 0.3 g of NaCl particles, which had been previously dried and pulverized and passed through a 400-mesh (opening 37 μm) sieve, was attached, and the dry weight was measured and the "weight after adhesion of NaCl" (W ₁ ) was determined. did. At this time, the difference between W ₁ and W ₀ was defined as the amount of NaCl attached (W). The sample with NaCl attached was attached to the sample holder 8 in the salt re-entrainment rate evaluation equipment 300 shown in FIG. Ventilation was carried out using a blower 11 while adjusting the flow rate using a flow meter 9 so that the flow rate was 0.84 m ² /hr), and left for 8 hours. Note that the ventilated air was made dust-free using a HEPA filter 13. After standing, the sample was taken out from the test device, and its weight after drying was measured and defined as "weight after re-encrusting NaCl" (W ₂ ). The re-entrainment amount _W3 of NaCl is expressed as the difference between _W1 and _W2 . The re-entrainment rate during NaCl deliquescence is expressed by the following equation (3).
NaCl re-entrainment rate = W ₃ /W × 100... (3)

Next, methods for manufacturing filter media of Examples and Comparative Examples will be explained.
(1) Support fiber layer The production of the support fiber layer disposed on the upstream side will be explained.
Polyester fibers of 2.2 T x 51 mm were formed into a web by passing them through a miniature card, and the fibers were weakly entangled with a small needle punch machine to obtain a nonwoven fabric with a basis weight of 46 g/m ² . This was impregnated with an aqueous solution in which an acrylic binder "DICNAL E-8290N" (manufactured by DIC Corporation) was dispersed, squeezed with a mangle, and dried at 110° C. to obtain a supporting fiber layer. After drying the supporting fiber layer, physical properties were measured and found to be a basis weight of 55 to 60 g/m ² , a thickness of 0.7 mm, a tensile strength of 6 kgf/5 cm, and a water absorption of 35 mm.
(2) Melt-blown non-woven fabric layer For the melt-blown non-woven fabric layer disposed on the downstream side, a commercially available melt-blown non-woven fabric (Mitsui Chemicals MPEA04: basis weight 20 g/m ² , thickness 0.24 mm, air permeability 58 cc/cm ² /sec) was used. It was impregnated with a polytetrafluoroethylene solvent as a water repellent, and after being taken out, volatile components were evaporated to obtain a melt-blown nonwoven fabric layer. In the melt-blown nonwoven fabric layer, the amount of polytetrafluoroethylene added was 2 g/m ² and the surface tension was 30 mN/m.
(3) Method for joining filter media A: Spray method Spray 2±0.5 g/ ^m2 of "Spray Glue 77" (manufactured by 3M Japan Co., Ltd.) onto the support fiber layer to adhere it, and then apply the melt-blown nonwoven fabric layer on top of it. were laminated and pressed lightly with hand to join them.
B: Method using adhesive fiber Place the adhesive fiber (Dynac LNS-0010) on the support fiber layer, place the melt-blown nonwoven fabric layer on top of it, and press the top of the support fiber layer with an iron set at 130°C for 1 minute to join. I let it happen.
(4) Charge treatment Earth side: A silicone sheet with a thickness of 2 mm was laid on an aluminum plate.
Electrode side: needle electrode with needle spacing of 10 mm Electrode-ground distance: 10 mm from needle tip to silicone sheet
Applied voltage: 20kV
Charging time: 30 seconds Charging was carried out by laying the bonded filter medium on the ground side.

(Examples 1 to 3, Comparative Examples 1 and 2)
The support fiber layer obtained above was impregnated with an aqueous solution of a phosphoric acid flame retardant (Apinon 307, manufactured by Sanwa Chemical Industries, Ltd.), dehydrated using a mangle, and then dried at 120° C. for 10 minutes. After drying, the support fiber layer and the melt-blown nonwoven fabric layer obtained above were joined by the above spray method, subjected to the above charging treatment, and a filter medium was obtained.
Table 1 shows the amount of flame retardant impregnated in the support fiber layer, water absorption, basis weight of filter medium, thickness, pressure loss, particle collection efficiency, salt re-entrainment rate, and flame retardant classification.
(Example 5, Comparative Example 5)
The supporting fiber layer obtained above was impregnated with an aqueous solution of a phosphoric acid flame retardant (Furan TTC: manufactured by Yamato Chemical), dehydrated with a mangle, and then dried at 120° C. for 10 minutes. After drying, the support fiber layer and the melt-blown nonwoven fabric layer obtained above were joined by the above-mentioned spray method and subjected to the above-mentioned charging treatment to obtain a filter medium.
Table 1 shows the amount of flame retardant impregnated in the support fiber layer, water absorption, basis weight of filter medium, thickness, pressure loss, particle collection efficiency, salt re-entrainment rate, and flame retardant classification.
(Example 4)
The support fiber layer obtained above was impregnated with an aqueous solution of a phosphoric acid flame retardant (Apinon 307, manufactured by Sanwa Chemical Industries, Ltd.), dehydrated using a mangle, and then dried at 120° C. for 10 minutes. After drying, the support fiber layer and the obtained melt-blown nonwoven fabric were joined by the method using the adhesive fibers, and the charging treatment was performed to obtain a filter medium.
Table 1 shows the amount of flame retardant impregnated in the support fiber layer, water absorption, basis weight of filter medium, thickness, pressure loss, particle collection efficiency, salt re-entrainment rate, and flame retardant classification.
(Comparative example 3)
The supporting fiber layer obtained above was impregnated in a water bath containing a phosphoric acid flame retardant (MPP-B: manufactured by Sanwa Chemical Co., Ltd.) dispersed in water containing a small amount of surfactant (nonionic). After dehydration, it was dried at 120°C for 10 minutes. After drying, the supporting fiber layer and the melt-blown nonwoven fabric obtained above were joined by the above-mentioned spray method, and subjected to the above-mentioned charging treatment to obtain a filter medium.
Table 1 shows the amount of flame retardant impregnated in the support fiber layer, water absorption, basis weight of filter medium, thickness, pressure loss, particle collection efficiency, salt re-entrainment rate, and flame retardant classification.
(Comparative example 4)
The supporting fiber layer obtained above is impregnated in a water bath containing a small amount of surfactant (nonionic) and a phosphoric acid flame retardant (Tyen K: manufactured by Taihei Kagaku) dispersed therein, and then dehydrated using a mangle. , and dried at 120°C for 10 minutes. After drying, the supporting fiber layer and the melt-blown nonwoven fabric obtained above were joined by the above-mentioned spray method and subjected to the above-mentioned charging treatment to obtain a filter medium.
Table 1 shows the amount of flame retardant impregnated in the support fiber layer, water absorption, basis weight of filter medium, thickness, pressure loss, particle collection efficiency, salt re-entrainment rate, and flame retardant classification.

From Table 1, it can be seen that Examples 1 to 5 have lower salt re-entrainment rates and superior flame retardancy than Comparative Examples 1 to 5.

The filter medium obtained according to the present invention has the same thickness as the filter medium for general air conditioning filters, has salt trapping and re-entrainment prevention functions, and has the efficiency and ventilation resistance of the conventional filter medium. Moreover, since it has flame retardant function, safety against fire after the filter is installed is also ensured. Since the pressure loss and efficiency are the same as regular air conditioning equipment filters, we can propose it as a replacement for regular products. It is very effective as a replacement in the field of pleated type air conditioning applications.

1: Support fiber layer (upstream side)
2: Melt-blown nonwoven fabric layer (downstream side)
3: Duct 4: Upstream sampling pipe 5: Downstream sampling pipe 6: Differential pressure gauge 7: Particle counter 8: Flow meter 9: Valve 10: Blower 11: Evaluation sample 12: HEPA filter 13: Test piece 14: Gas burner 100 : Salt damage prevention filter media 200 : Particle collection efficiency evaluation equipment 300 : Salt re-entrainment rate evaluation equipment 400 : Combustibility test equipment

Claims (6)

In a salt damage prevention filter medium comprising a support fiber layer disposed on the upstream side of ventilation and a melt-blown nonwoven fabric layer disposed on the downstream side,
The supporting fiber layer has hygroscopicity and flame retardancy,
The melt-blown nonwoven fabric layer is treated to be water repellent,
A filter medium for preventing salt damage, characterized in that the melt-blown nonwoven fabric layer and the supporting fiber layer are bonded together with an adhesive. The filter medium for preventing salt damage according to claim 1, wherein the support fiber layer has a water absorption of 10 mm or more according to the Pyrex method according to JIS L 1907:2004. The filter medium for preventing salt damage according to claim 1 or 2, wherein the support fiber layer contains a flame retardant substance in an amount of 15 to 35% by weight based on the weight of the fibers. The filter medium for preventing salt damage according to any one of claims 1 to 3, wherein the melt-blown nonwoven fabric layer is electrically charged and has a surface tension of 34 mN/m or less. The filter medium for preventing salt damage according to any one of claims 1 to 4, wherein the melt-blown non-woven fabric layer is formed by adhering a fluorine-based compound to the surface of a polyolefin-based melt-blown non-woven fabric. A pleated filter using the salt damage prevention filter medium according to any one of claims 1 to 5.