JP2005131485A - High performance air filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high performance air filter comprising a filter medium low in pressure loss and having high efficiency comprising a thermoplastic extremely fine fiber nonwoven fabric increased in charge quantity. <P>SOLUTION: This high performance air filter comprises a nonwoven fabric obtained by charging the extremely fine fiber nonwoven fabric, which is formed of a resin composition prepared by compounding 0.05-3 wt.% of a fatty acid amide compound with a thermoplastic resin, preferably polyporopylene, preferably a melt blow polypropylene nonwoven fabric, which is specified in weight basis, average fiber diameter, thickness and air permeability, by electret charging using a water stream charging method. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a high-performance air filter made of a nonwoven fabric of thermoplastic resin, and more particularly to a high-performance air filter of a low pressure loss, high-efficiency filter medium made of a thermoplastic resin ultrafine fiber nonwoven fabric having an increased charge amount.

Conventionally, non-woven fabric made of ultrafine fibers has been used as a filter material that can efficiently collect relatively large dust as well as fine particles in gas. Especially, it is a filter that improves the collection efficiency of fine particles under low pressure loss. As a material, electret nonwoven fabric obtained by imparting electric charge to a nonwoven fabric has been mainly used.
For electretization in these filters, a method of corona charging a non-woven fabric, a method of colliding a water flow, and the like are mainly used. However, in the corona charging method, it is necessary to increase the voltage in order to sufficiently increase the charge amount, and there is a problem that if the voltage is increased too much, sparks occur and pinholes are likely to occur in the nonwoven fabric. Moreover, in the method based on the collision of the water flow, the nonwoven fabric constituting fibers are likely to be entangled by the collision of the high pressure water flow, and as a result, the fiber orientation is changed and openings are easily formed. However, it was difficult to design.

As a method for solving such a problem, there is disclosed a method (for example, refer to Patent Document 1) in which ultrasonic vibration is applied to a structure made of a thermoplastic resin via a polar liquid to make it electretized. In addition, a method is disclosed in which a melt blown nonwoven fabric is subjected to a high-pressure fluid spray treatment and then corona charged (for example, see Patent Document 2). However, these methods all require complicated steps, and the development of simpler methods is required.
JP 2003-205210 A JP 2003-220310 A

An object of the present invention is to solve the above-mentioned problems and to provide a high-performance air filter having a low pressure loss and a high-efficiency filter medium made of a thermoplastic ultra-fine fiber nonwoven fabric having an increased charge amount.

As a result of intensive studies to achieve the above-mentioned object, the present inventors water-treated a nonwoven fabric obtained from a resin composition in which a specific amount of a fatty acid amide compound is blended with a raw material resin of the nonwoven fabric, and then dry the nonwoven fabric. As a result, it was found that a nonwoven fabric for high-performance air filters having excellent particle collection efficiency and low pressure loss can be obtained, thereby completing the present invention.

  That is, according to the first invention of the present invention, it comprises a nonwoven fabric obtained by electretizing an ultrafine fiber nonwoven fabric obtained from a resin composition in which a fatty acid amide compound is blended in a thermoplastic resin in an amount of 0.05 to 3% by weight. A high-performance air filter characterized by the above is provided.

  According to the second invention of the present invention, in the first invention, the thermoplastic resin is at least one resin selected from the group consisting of polyolefin, polyethylene terephthalate, and polybutylene terephthalate. A performance air filter is provided.

According to the third invention of the present invention, in the first or second invention, the nonwoven fabric has a basis weight of 5 to 100 g / m ² , an average fiber diameter of ^{2 to} 30 μm, a thickness of 0.1 to 0.6 mm, and an air permeability. A high-performance air filter characterized by being a polypropylene melt blown nonwoven fabric of ^{20 to} 200 cc / sec / cm ² is provided.

  The filter of the present invention is obtained by electretizing a thermoplastic resin nonwoven fabric containing a fatty acid amide compound by a water flow treatment method, and can be used as a high-performance air filter having excellent particle collection efficiency and low pressure loss.

The present invention is described in detail below.
The thermoplastic resin used in the nonwoven fabric of the present invention includes polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyamides such as nylon 6, nylon 66 and nylon 46, polyvinyl chloride, polyvinylidene chloride, polystyrene, Polycarbonate, polyvinylidene fluoride, polyarylene sulfide and the like can be mentioned. Among these, polyolefins and polyesters are preferable, and in particular, homopolymers and copolymers made of propylene are easy to obtain a thin and uniform fiber structure, and are also preferable from the viewpoint of nonwoven fabric strength. Moreover, these thermoplastic resins can be appropriately blended and used as necessary.

  Moreover, you may use the composite fiber which consists of 2 or more types of combinations of the said thermoplastic resin. For example, a composite fiber made of a resin having an outer layer made of polyethylene and an inner core layer having a melting point higher than that of the outer layer polyethylene by 20 ° C. or more, preferably 30 ° C. or more. In this composite fiber, for example, as the outer layer polyethylene, any of ultrahigh molecular weight polyethylene, high density polyethylene, medium density polyethylene, low density polyethylene, ethylene-vinyl acetate copolymer, etc. can be used. Polyethylene having a low melting point such as an ethylene-vinyl acetate copolymer is preferable.

  As a resin constituting the inner core layer, a resin having a melting point higher than that of polyethylene by 20 ° C. or more, polypropylene, poly-4-methylpentene-1, poly-3-methylbutene-1, polyethylene terephthalate, polybutylene terephthalate, Examples of the resin include polycarbonate, polyamide, polyarylene sulfide, and polyarylene oxide. Particularly preferred is polypropylene.

The thickness of the inner core layer is preferably about 1/5 to 4/5 of the fiber diameter in order to maintain the adhesiveness of the outer layer and the shape retention effect of the inner core layer. The position of the inner core layer is the position of the fiber. It may be centered or eccentric.
It is preferable that the material of the sheath is polyethylene because the processing step of the heat embossing process and the heat calendar process when manufacturing the nonwoven fabric can be performed at a lower temperature. In addition, the polyethylene part is melted at the crystallization temperature of the polypropylene of the melt blown polypropylene nonwoven fabric, which advantageously increases the degree of bonding with polypropylene fibers. Further, even when the sheath polyethylene is melted, the core portion is not melted, the shape as a fiber is maintained, and the strength is also maintained.

  In the present invention, the fatty acid amide compound used by blending with the thermoplastic resin is a compound having a function of improving electret electrification rate by water flow of the melt blown nonwoven fabric fiber of the thermoplastic resin. Examples of the fatty acid amide compound that can be used in the present invention include fatty acids, monoamides of unsaturated fatty acids, and bisamides. For example, stearic acid amide, valmitic acid amide, behenic acid amide, myristic acid amide, erucic acid amide, Oleic acid amide, caprylic acid amide, capric acid amide, linoleic acid amide, linolenic acid amide, ridinol sun amide, palmitoleic acid amide, lauric acid amide, arachidic acid amide, arachidic acid amide, eicosenoic acid amide, bridic acid amide, elaidin Acid amide, N-stearyl erucic acid amide, N- (2-hydroxymethyl) stearic acid amide, N- (2-hydroxyethyl) lauric acid amide, ethylenebisolein Amide, ethylene bis-stearic acid amide, methylene bis-stearic acid amide, may be mentioned hexamethylene bis oleic acid amide, hexamethylene bis erucic acid amide, an octamethylene bis erucic acid amide and the like.

  In this invention, the compounding quantity of the fatty acid amide compound mix | blended with a thermoplastic resin is 0.05 to 3 weight% with respect to a thermoplastic resin, Preferably it is 0.5 to 2 weight%. If the blending amount is less than 0.05% by weight, the effect of maintaining the electric charge of the fiber is small. If the blending amount exceeds 3% by weight, the effect is saturated and the blend is decomposed in the non-woven fabric forming process, resulting in product coloring, odor, and generation of volatile components. It is not preferable because side effects such as

The nonwoven fabric of the present invention is obtained by using a resin composition in which a fatty acid amide compound is blended with the above thermoplastic resin, and manufactured by a melt blow method, a spun bond method, a dry method, a wet method, or the like.
In particular, as a melt blown nonwoven fabric using polyolefin, the basis weight is preferably 5 to 100 g / m ² , more preferably 10 to 40 g / m ² . An average fiber diameter becomes like this. Preferably it is 2-30 micrometers, More preferably, it is 4-25 micrometers. The thickness is preferably 0.1 to 0.6 mm, more preferably 0.2 to 0.4 mm. The air permeability is preferably 20 to 200 cc / sec / cm ² , more preferably 30 to 150 cc / sec / cm ² . A polypropylene melt blown nonwoven fabric having such physical properties is preferable for use as an air filter.
As the spunbonded nonwoven fabric using polyolefin, a weight per unit area is preferably 5 to 100 g / ^{m 2,} more preferably from 10 to 40 g / ^{m 2.} An average fiber diameter becomes like this. Preferably it is 10-30 micrometers, More preferably, it is 10-20 micrometers. The thickness is preferably 0.1 to 0.6 mm, more preferably 0.2 to 0.4 mm. The air permeability is preferably 100 to 400 cc / sec / cm ² , more preferably 150 to 300 cc / sec / cm ² . A polypropylene spunbond nonwoven fabric having such physical properties is preferable for use as an air filter.

The electretization of the nonwoven fabric in the present invention is based on a method in which a jet of water or a droplet of water collides. The method of causing the water jet or water droplet flow to collide is not particularly limited, and the following method is preferable because water can be uniformly infiltrated into the nonwoven fabric.
For example, when a thermoplastic resin is melt-spun from a die having a large number of spinning holes and the spun yarn is collected in a lower net to form a nonwoven fabric, water is sprayed onto the spun yarn from the die to the net or There is a method in which the nonwoven fabric obtained by spraying and collecting the spun yarn is dried to form an electret sheet. When fabricating a nonwoven fabric directly at the same time as melt spinning as described above, water is sprayed or sprayed onto the spun yarn from the base to the collection net, and then a nonwoven fabric is formed on the net. Thus, by drying the nonwoven fabric, a high-quality, high-performance electret sheet can be obtained. In addition, electret sheets can be obtained in one step from spinning, and the production facilities are spinning facilities, water injection or spraying facilities, drying facilities, etc., so that they are less expensive than conventional high voltage generating facilities. In addition, safety maintenance management can be performed at a low cost.

In addition, while running a nonwoven fabric sheet of a thermoplastic resin produced in advance, the sheet is brought into contact with the sheet so as to cross the slit-shaped suction nozzle in the sheet width direction, and the sheet surface opposite to the contact portion is in contact with or immersed in the water surface. And a method of sucking water through the suction nozzle so as to penetrate in the sheet thickness direction so that the water penetrates into the nonwoven fabric sheet, and then drying the nonwoven fabric sheet. While running the nonwoven sheet in this way, the slit-like suction nozzle is brought into contact with the sheet, the sheet surface on the opposite side of the contact portion is brought into contact with or immersed in the water surface, and water is sucked from the suction nozzle, Since the water is moved so as to penetrate in the sheet thickness direction, the water can be permeated throughout the thickness direction inside the sheet. In addition, since the suction nozzle is disposed so as to cross the sheet width direction and suction is performed while the sheet is running, the permeation action of the water in the entire sheet thickness direction is evenly distributed over the entire sheet surface. Therefore, when this sheet is dried, an electret sheet having a uniform and high charge on the entire surface of the sheet can be obtained.
In addition, the above-mentioned osmotic action can be achieved with a small water tank only because the slit-like suction nozzle is in contact with the non-conductive fiber sheet, so it can be achieved with a small water tank, and no large water tank is required. become. Therefore, the manufacturing apparatus can be made as compact as possible, and the conventional high voltage generating facility is unnecessary, so that it can be made safe and low in cost.

  Furthermore, the method of spraying a water jet with the water pressure of 5 GPa or more to the nonwoven fabric sheet of the thermoplastic resin manufactured previously and then drying this nonwoven fabric sheet is mentioned. In this method, water can be penetrated in the thickness direction inside the sheet by the high water pressure, and the water can penetrate into the entire thickness direction inside the sheet. Therefore, when this sheet is dried, an electret sheet having a uniform and high charge on the entire surface of the sheet can be obtained.

  In addition, the filter of the present invention may be used by laminating other non-woven fabrics in order to impart functions such as pleating to the electret non-woven fabric obtained from the resin composition in which the fatty acid amide compound is blended with the thermoplastic resin. . As a nonwoven fabric which can be laminated | stacked, a chemical bond nonwoven fabric, a dry-type nonwoven fabric, a thermal bond dry-type nonwoven fabric, a wet nonwoven fabric etc. can be mentioned.

  In the filter of the present invention, since the nonwoven fabric obtained from the thermoplastic resin blended with the fatty acid amide compound is electretized by a water stream, the charge amount becomes high, and the air cleaning filter, mask, automobile cabin filter, wiper Can be used effectively.

The present invention will be specifically described by the following examples and comparative examples. The physical properties were measured using the following methods.
(1) Average fiber diameter: Take five photographs with an electron microscope at any five points of the test piece, measure the diameter of 20 fibers per photograph, and perform these five photographs. 100 fiber diameters were averaged.
(2) Weight per unit: A test piece of 100 × 100 mm was taken from the sample length direction, the weight in a moisture equilibrium state was measured, and calculated per 1 m ² .
(3) Thickness: A test piece of 100 × 100 mm was taken from the sample length direction and measured with a dial thickness gauge.
(4) Collection efficiency: 0.3 μm NaCl particle test air containing dust is passed at a flow rate of 95 L / min, and the dust concentration after passing before passing is measured by the light scattering light quantity integrating method according to JIS Z 8813. Simultaneously measured continuously, the collection efficiency was determined by the following equation.
Collection efficiency (%) = (Dust concentration after passage (mg / m ² ) −Dust concentration before passage (mg / m ² )) / (Dust concentration before passage (mg / m ² ) × 100
(5) Pressure loss: Using an aneroid pressure gauge in parallel with the collection efficiency test, the pressure before and after the passage of the test dust-containing air of 0.3 μm NaCl particles was measured, and the differential pressure was determined.

(Example 1)
A resin composition containing 2% by weight of ethylenebisstearic acid amide (Sripax-E manufactured by Nippon Kasei Co., Ltd.) is melt plasticized by an extruder with respect to a homopolypropylene (PP) having a melt flow rate of 50 g / 10 min. Through the polymer line, a nozzle piece with a die width of 20 inches, nozzle holes of 300 holes per 10 inches, an air gap of 1.0 mm, and a setback of 1.0 mm, a total resin discharge rate of 7 kg / hr, a die temperature of 300 ° C., and an air temperature of 300 ° C., air flow rate 15 Nm 3 / ^hr, the die - in conveyor length 200 mm, discharged into the atmosphere together with the heated compressed air, which is continuously collected on a rotary screen, appropriately adjusting the moving speed of the screen Thus, a melt blown nonwoven fabric having an average fiber diameter of 4 μm, a basis weight of 40 g / m ² , and a thickness of 0.19 mm was obtained.
Next, water is sprayed on one side of the obtained melt blown nonwoven fabric, suction is performed from the opposite side so that the amount of water passing is about 1 L / m ² , and then drying is performed at a temperature of 80 ° C. Obtained. The collection efficiency and pressure loss of the obtained filter were measured. The results are shown in Table 1.

(Comparative Example 1)
A filter was obtained in the same manner as in Example 1 except that polypropylene containing no ethylenebisstearic acid amide was used and electretized by a corona discharge method. The collection efficiency and pressure loss of the obtained filter were measured. The results are shown in Table 1.

(Comparative Example 2)
A filter was obtained in the same manner as in Example 1 except that polypropylene not containing ethylenebisstearic acid amide was used. The collection efficiency and pressure loss of the obtained filter were measured. The results are shown in Table 1.

(Comparative Example 3)
A filter was obtained in the same manner as in Example 1 except that the electretization was performed by corona discharge treatment. The collection efficiency and pressure loss of the obtained filter were measured. The results are shown in Table 1.

  The filter of the present invention is obtained by electretizing a thermoplastic resin nonwoven fabric containing a fatty acid amide compound by a water flow treatment method, as a high-performance air filter with excellent particle collection efficiency and low pressure loss, Useful for cabin filters and masks.

Claims (3)

  A high-performance air filter comprising a nonwoven fabric obtained by electretizing an ultrafine fiber nonwoven fabric obtained from a resin composition containing 0.05 to 3% by weight of a fatty acid amide compound in a thermoplastic resin.   The high-performance air filter according to claim 1, wherein the thermoplastic resin is at least one resin selected from the group consisting of polyolefin, polyethylene terephthalate, and polybutylene terephthalate. The nonwoven fabric is a polypropylene melt blown nonwoven fabric having a basis weight of 5 to 100 g / m ² , an average fiber diameter of ^{2 to} 30 μm, a thickness of 0.1 to 0.6 mm, and an air permeability of 20 to 200 cc / sec / cm ^2. The high performance air filter according to 1 or 2.