JP2719102B2 - Honeycomb-shaped electret filter and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a honeycomb-type electret filter and a method for producing the same, and more particularly, to a honeycomb-type electret filter excellent in dust collection, low in pressure loss, and excellent in collection performance. It relates to a manufacturing method.

[0002]

2. Description of the Related Art A method for producing an electretized nonwoven fabric by forming a polyolefin, for example, polypropylene, into a nonwoven fabric by a melt blow method and applying a high DC voltage to the obtained nonwoven fabric to form an electret.
JP-A-60-168511, JP-A-2-1971
No. 10 discloses this.

[0003] This electretized nonwoven fabric is, for example,
It is known that the filter can be used as a filter that is formed into a pleated shape, allows an airflow to pass through the inside thereof, and adsorbs and removes fine particles such as dust and dust in the airflow by electrostatic force.

[0004] However, filters using electretized nonwoven fabrics have the problems of (1) high pressure loss and (2) short life due to easy clogging of particles.

In order to solve such a problem, there has been proposed a filter formed by forming the electret nonwoven fabric into a honeycomb shape (JP-B-59-51323, etc.).

[0006]

However, as a result of investigations by the present inventors, even such a honeycomb-shaped electretized filter does not necessarily (1) have a low pressure loss,
It was found that none of the three points of (2) high collection performance and (3) long life could be satisfied. For example, in the case of an air conditioner filter, the pressure loss is 1 mmAq or less,
It is required that the trapping performance is 12% or more and the life of the trapping performance for tobacco particles is 100 or more.

Accordingly, an object of the present invention is to produce a honeycomb-type electret filter for an air conditioner having such a low pressure loss, and having excellent collection performance and a long life of the collection performance over a long period of time, and the honeycomb-type electret filter. It is to provide a method that can be used.

[0008]

According to the present invention, there is provided a honeycomb-type electret filter formed by forming an electret-formed nonwoven laminated sheet into a honeycomb shape, wherein the nonwoven laminated sheet is formed of a film. Electretized nonwoven fabric (A) made of defibrated yarn;
An object of the present invention is to provide a honeycomb-shaped electret filter which is a laminated sheet having an electretized nonwoven fabric (B) made of a meltblown nonwoven fabric.

The present invention also provides a method for producing the above-mentioned honeycomb-shaped electret filter, wherein the thermoplastic resin film is electretized to form an electretized film, and the electretized film is defibrated to form an electretized nonwoven fabric. A step of forming (A); a step of electretizing the meltblown nonwoven fabric made of a thermoplastic resin to form an electretized nonwoven fabric (B); and laminating the electretized nonwoven fabric (A) and the electretized nonwoven fabric (B). The present invention also provides a method for manufacturing a honeycomb-shaped electret filter, which includes a step of forming a laminated sheet by performing the method and a step of forming the laminated sheet into a honeycomb shape.

Hereinafter, the honeycomb-shaped electret filter of the present invention (hereinafter, referred to as “filter of the present invention”) and a method of manufacturing the same will be described in detail.

[0011] The filter of the present invention is formed by forming a laminated sheet having an electret nonwoven fabric (A) made of a defibrated film and an electret nonwoven fabric (B) made of a meltblown nonwoven fabric into a honeycomb shape. . The nonwoven fabrics (A) and (B) are made of a thermoplastic resin. The thermoplastic resin used is not particularly limited, and various thermoplastic resins can be used.
In particular, a polyolefin-based polymer having a polar group or a polyolefin composition containing the polyolefin-based polymer is preferred because it is easily electretized and has excellent durability of charge and collection performance. As the polyolefin polymer or the polyolefin composition having the polar group, (A) a copolymer of a monomer having a polar group and an α-olefin, (B) a side chain of the polyolefin by oxidation or halogenation, A modified polyolefin obtained by introducing a polar group into the main chain; (C) a polyolefin or a modified polyolefin obtained by graft copolymerizing a monomer having a polar group with the polymer (B); (D) an unmodified polyolefin; A composition containing a polymer alone such as a mixture with at least one selected from the above (A), (B) and (C) or a mixture thereof as a main component is exemplified. Here, when the polyolefin composition contains a modified polyolefin and an unmodified polyolefin, the modified polyolefin and the unmodified polyolefin may be composed of the same polyolefin or different polyolefins. You may.

Examples of the polar group contained in the polyolefin polymer or the polyolefin composition containing the polyolefin polymer include a halogen atom such as a chlorine atom, a fluorine atom, a bromine atom and an iodine; a carbonyl group and a nitro group. An atomic group; or the following formula: —COOCH ₃ , —COOC ₂ H ₅ , —OCOCH ₃ ,
_{-OC 2 H 5, -OCH 2 C} 6 H 5, -COOH, -O
_{H, -NH 2, -CONH 2,} -COONH 4,

[0013]

Embedded image

And the like. One or more of these polar groups may be contained in the polyolefin-based polymer or the polyolefin composition. Hereinafter, the polyolefin-based polymer or the polyolefin composition containing the polyolefin-based polymer is generically referred to as "polyolefin-based composition".

As a specific example of the copolymer (A) of a monomer having a polar group and an α-olefin,
pentabromophenyl methacrylate having a group represented by (iii), or 2,2 having a group represented by formula (iv)
Copolymers of 4,6-tribromophenyl methacrylate or trifluoroethyl methacrylate having a group represented by the formula (v) with α-olefins such as ethylene and propylene are exemplified.

Examples of (B) a modified polyolefin obtained by introducing a polar group into a side chain or a main chain of the polyolefin by oxidation or halogenation include polyethylene,
Polypropylene, etc. is reacted with ozone, nitric oxide, etc. to oxidize it, or the surface is oxidized by corona discharge treatment, etc., and carbonyl groups or nitro groups are formed in the molecule, or polyolefin is converted to chlorine. And a compound obtained by introducing a chlorine atom into a molecule.

Further, as a specific example of (C) a modified polyolefin obtained by graft-copolymerizing a monomer having a polar group, the modified polyolefin is modified with at least one modified monomer selected from unsaturated carboxylic acids or derivatives thereof. Modified polyolefin.

The modified polyolefin or the polyolefin which is the main component of the unmodified polyolefin is a homopolymer of α-olefin, a copolymer of two or more α-olefins, or a mixture of two or more selected from these. It is. Examples of the α-olefin include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, isopentene, 4-methyl-1-pentene, 3-
Methyl-1-pentene, 1-octene, 1-decene, 1
-Hexadecene, 1-octadecene, 1-eicosene and the like.

Specific examples of the polyolefin include polyethylene, polypropylene, poly-1-butene, poly-
4-methyl-1-pentene, ethylene / propylene copolymer, ethylene / 1-butene copolymer, ethylene / 4-
Examples thereof include a methyl-1-pentene copolymer, a propylene / 1-butene copolymer, and a 4-methyl-1-pentene / 1-decene copolymer. Among these, strength is high,
Polypropylene, poly-1-butene, and poly-4-methyl-1-pentene are preferred because they can be easily adjusted to an appropriate melt viscosity and are easily molded by a melt blow method. In particular, polypropylene is inexpensive and molded. It is particularly preferable because it can be easily formed and can be easily electretized.

In addition, since the polyolefin exhibits appropriate flow characteristics, it is easy to produce a nonwoven fabric by a melt blow method, and a nonwoven fabric having excellent strength can be obtained.
[Η] is usually 0.5 to 3 dl / g, preferably 0.1 to 3 dl / g.
7 to 1.5 dl / g, particularly preferably 0.8 to 1.3 d
Those in the range of 1 / g are preferred. In the present invention,
[Η] is a value measured in decalin at 135 ° C.

The modified polyolefin (C) is obtained by modifying the above-mentioned polyolefin by graft copolymerization with at least one modified monomer selected from unsaturated carboxylic acids and derivatives thereof. As this modified polyolefin, it is preferable to use a polyolefin having the same or excellent compatibility with the unmodified polyolefin. For example, when a composition containing a modified polyolefin and an unmodified polyolefin is used as a component of the polyolefin-based composition, and when polypropylene is used as the unmodified polyolefin, it is preferable to use polypropylene as a raw polyolefin for the graft-modified polyolefin.

(C) As an unsaturated carboxylic acid or its derivative used as a modifying monomer for graft-modifying a modified polyolefin, for example, unsaturated carboxylic acid, its anhydride, ester, amide, imide, chloride and the like can be used. Can be mentioned.

Specific examples of the unsaturated carboxylic acids or derivatives thereof include acrylic acid, methacrylic acid, vinyl acetic acid, ethyl acryl acetic acid, 2,4-pentadienoic acid, carboxystyrene, maleic acid, fumaric acid, itaconic acid and citraconic acid. Acid, allyl succinic acid, mesaconic acid, glutaconic acid, nadic acid, methyl nadic acid, tetrahydrophthalic acid, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, monomethyl maleate, Dimethyl maleate, monoethyl maleate, diethyl maleate, monomethyl fumarate, dimethyl fumarate, monoethyl fumarate, diethyl fumarate, monomethyl citraconic acid, dimethyl citraconic acid, monoethyl citraconic acid, citraconic acid Ethyl, nadic monomethyl,
Dimethyl nadic acid, monoethyl nadic acid, diethyl nadic acid, glycidyl acrylate, glycidyl methacrylate, maleic anhydride, itaconic anhydride, citraconic anhydride, methyl hexahydrophthalic acid, 3,6-endomethylene phthalic anhydride, methyl anhydride Tetrahydrophthalic acid, acrylamide, methacrylamide, maleic monoamide, maleic diamide, maleic acid-N-monoethylamide, maleic acid-N, N-diethylamide,
Maleic acid-N-monobutylamide, maleic acid-N,
N-diethylamide, fumaric acid monoamide, fumaric acid diamide, fumaric acid-N-monoethylamide, fumaric acid-
N, N-diethylamide, fumaric acid-N-monobutylamide, fumaric acid-N, N-dibutylamide, maleimide, N-butylmaleimide, N-phenylmaleimide,
Sodium acrylate, sodium methacrylate, potassium acrylate, potassium methacrylate and the like,
These can be used alone or in combination of two or more. Of these, maleic anhydride is preferred.

As a method for preparing the modified polyolefin (C) by graft copolymerizing the modified monomer with a polyolefin, various known methods can be employed. For example, the reaction can be carried out by heating a polyolefin and a modified monomer at a high temperature in the presence or absence of a solvent, with or without the addition of a radical polymerization initiator. In this reaction, another vinyl monomer such as styrene may coexist.

The content of the modified monomer in the modified polyolefin (C), that is, the grafting ratio of the modified polyolefin (C) is usually 3 mol% or less, particularly 1.5 mol% or less. Preparation is preferred.
In particular, when the nonwoven fabric (A) and / or the nonwoven fabric (B) are formed by using the modified polyolefin alone as the polyolefin-based composition, the graft ratio is preferably 1 mol% or less.

The intrinsic viscosity (135 ° C., decalin) of the modified polyolefin (C) facilitates uniform mixing with the unmodified polyolefin, has appropriate flow characteristics, and facilitates the production of a melt-blown nonwoven fabric. In general,
0.1-3.0 dl / g, preferably 0.3-2.0 d
l / g, particularly preferably 0.5 to 1.5 dl / g.

In the present invention, when a polyolefin composition containing an unmodified polyolefin and a modified polyolefin is used as a main material of the nonwoven fabric (A) and the nonwoven fabric (B), the modified polyolefin / unmodified polyolefin in the polyolefin composition is used. Is usually about 0.1 / 99.9 to 20/80 by weight, preferably about 1/99 to 5/95.

The polyolefin composition may contain various additives in addition to the modified polyolefin and the unmodified polyolefin as long as the object of the present invention is not impaired. Examples of the additive include an antioxidant, an ultraviolet absorber, a pigment, a dye, a nucleating agent, a filler, a slip agent, an antiblocking agent, a lubricant, a flame retardant, and a plasticizer.

Further, the preparation of the polyolefin composition can be carried out according to various conventional methods. For example, it can be carried out according to a method of mixing the above-mentioned modified polyolefin and / or unmodified polyolefin and, if necessary, various additives, followed by melt-kneading. Examples of the mixer used include a ribbon blender, a V-type blender, a tumbler, and a Henschel mixer. The melt-kneading can be performed using, for example, a single-screw or twin-screw extruder, a Banbury mixer, a kneader, a twin roll, or the like.

The laminated sheet constituting the filter of the present invention has a nonwoven fabric (A) and a nonwoven fabric (B) made of a thermoplastic resin represented by the above-mentioned polyolefin composition, and the nonwoven fabric (A) is a film defibrated. The non-woven fabric (B) is made of a melt-blown non-woven fabric, and the non-woven fabrics forming both layers are electretized. The nonwoven fabric (A) and the nonwoven fabric (B) may be formed of a thermoplastic resin composed of the same component, or may be formed of a thermoplastic resin composed of different components.

The nonwoven fabric (A) is made of defibrated yarn of a film, and its production method is not particularly limited as long as it is produced by defibrating a thermoplastic resin film. For example, a thermoplastic resin represented by the polyolefin composition is melted by an extruder and extruded from an annular die to form a film. This film is cut into a fixed width by a slitter, or the film is stretched to an elongation ratio or more without cutting to produce a defibrated yarn. Next, the defibrated yarn can be manufactured by, for example, uniformly dispersing the defibrated yarn in the width direction of the sheet using a device such as carding, and then preferably press-bonding with an embossing roll or the like.

The nonwoven fabric (A) has an average single fiber diameter of 20 to 60 μm and a basis weight of 10 to 30 g /
The electret nonwoven fabric has a m ² , a bulk density of 0.05 to 0.2 g / cm ³ , and an average surface charge density of 0.1 × 10 ⁻⁹ coulomb / cm ² or more. Here, in the present invention, the average fiber diameter of a single fiber is determined by taking an electron micrograph (500 times) of the surface of a fiber sample, arbitrarily selecting 30 fibers on the obtained photograph, and selecting the fiber of each fiber. It is a value obtained by measuring the diameter using a caliper or the like, and calculating the average value of the measured values of each fiber diameter.

The non-woven fabric (A) may be electret-treated at the time of film formation, or may be formed by electret-forming the non-woven fabric after forming the non-woven fabric. Here, when performing at the time of film forming, since the efficiency of electret formation is excellent, the collection performance is preferable because it is better than when the nonwoven fabric after forming is electretized.

The electretization can be performed by applying a DC voltage to the nonwoven fabric or the film. The applied DC voltage value depends on the shape of the electrodes used, the distance between the electrodes, etc.
In addition, it is appropriately selected according to the charge amount required for the electretized nonwoven fabric, the processing speed, and the like. For example, when the distance between the electrodes is 8 mm, it can be performed by applying a DC voltage of at least -5 kV, preferably -6 to -20 kV, to the nonwoven fabric.

The application of the DC voltage may be performed according to any method, and is not particularly limited. For example, a method in which a nonwoven fabric or a film is passed between a pair of electrodes to which a DC voltage is applied; a method in which a corona discharge or a pulsed high voltage is applied to the surface of the nonwoven fabric; The method may be performed by any method such as a method of applying a high DC voltage to the substrate.

Further, the melt blown nonwoven fabric constituting the nonwoven fabric (B) is prepared by first supplying a thermoplastic resin, preferably the above-mentioned polyolefin composition, to an extruder or the like, heating and melting and kneading the mixture to form a large number of pores. It is extruded as a fine resin flow from the melt blow die. The extruded resin stream is cooled and solidified by contacting it with a high-speed heated gas stream to form discontinuous fibers having a fine fiber diameter, and the fibers can be manufactured by accumulating on a porous support. it can.

The heating temperature during melting and kneading of the polyolefin composition is appropriately adjusted depending on the melting point of the polyolefin which is the main component of the polyolefin composition. The non-woven fabric having good mechanical strength is obtained without degrading the polyolefin and having a low molecular weight, and the melt viscosity of the melted polyolefin composition is moderate and melt molding is easy. About 200-350 ° C, especially 220-
It is preferable to carry out in the range of 300 ° C.

The discharge rate of melt kneading and extrusion of the polyolefin composition is usually about 10 to 130 kg / hr.

The melt blow die used is:
The tip lip has a large number of pores for discharging the molten polyolefin-based composition.
It is from 0 to 2000 mm. Usually, 800 to 3000 such pores are formed in the tip lip portion, and the pore diameter is usually about 0.5 mm.

In the melt blow die, the molten polyolefin composition comes into contact with a high-speed heated gas, is divided, is drafted in a molten state, is elongated in the fiber length direction, and has a smaller fiber diameter. Miniaturization proceeds. Therefore, the meltblowing die introduces a high-speed heated gas flow, inside the die or outside the die,
The apparatus has a device for bringing a molten polyolefin-based composition into contact with a heated gas stream to form fine discontinuous single fibers.
This apparatus may be configured such that an outlet for a heated gas flow is provided inside a melt-blowing die, or heated so as to blow a heated gas flow to a polyolefin composition melted outside a tip lip of the melt-blow die. A gas outlet may be provided.

The heating gas is not particularly limited, and heating air is generally used in terms of cost, but a heated inert gas may be used to prevent deterioration of the polyolefin composition. The temperature of the heated gas stream is typically between 200 and 3
It is preferably 60 ° C, particularly preferably 230-310 ° C, at least about 10 ° C higher than the temperature of the molten polyolefin composition. The flow rate of the heated gas flow is
Usually 100 to 600 m / sec, especially 200 to 400
It is desirable to be about m / sec.

The fine discontinuous single fibers discharged from the melt-blowing die are accumulated on a porous support to obtain a web-like melt-blown nonwoven fabric. As the porous support, for example, a network structure made of stainless steel, polyester, or the like can be used.

The nonwoven fabric (B) is usually about 0.5 to 10 μm in that the average fiber of monofilaments has appropriate air permeability and good dust collecting property for fine dust.
Particularly preferably, it is in the range of 1 to 6 μm, and the fiber length is usually about 50 to 400 mm. Further, the bulk density is 0.
It is about 5 to 0.40 g / cm ³ , and the weight per unit area is usually 5 to 30 in that the nonwoven fabric having a moderate breathability and a high strength is obtained, and the local weight per unit area is small. 10
Was 0 g / m ² approximately, in particular in the range of 10 to 80 g / m ² is preferred.

[0044] Further, the thickness of the nonwoven fabric (B) is determined in accordance with the basis weight and bulk density, generally 0.1 to zero.
It is about 7 mm.

The electret of the nonwoven fabric (B) is
The electreting of the nonwoven fabric (A) can be performed in the same manner.

Further, the average surface charge density of the nonwoven fabric (B) is usually 0.1 × 10 ⁻⁹ coulomb / c since it can exhibit sufficient dust collection performance as an electret.
m ² or more, preferably 0.3 to 5 × 10 ⁻⁹ coulomb / cm ² .

The intrinsic viscosity [η] (135 ° C., decalin) of the thermoplastic resin forming the single fiber which is a constituent material of the electretized nonwoven fabric (B) is 0.3 to 1.5 dl.
/ G, preferably 0.5 to 1.0 dl / g.

The laminated sheet constituting the filter of the present invention has the nonwoven fabric (A) and the nonwoven fabric (B). The layer configuration of the laminated sheet is not limited to the configuration of the nonwoven fabric (A) / nonwoven fabric (B), but also the nonwoven fabric (B) / nonwoven fabric (A) /
The nonwoven fabric (B) and the nonwoven fabric (A) / nonwoven fabric (B) / nonwoven fabric (A) can be configured, but the laminated structure of nonwoven fabric (A) / nonwoven fabric (B) can achieve the object of the present invention. Most preferred.

The preferred thickness of the nonwoven fabric (A) in the laminated sheet is 0.1 to 0.5 mm, and the preferred thickness of the nonwoven fabric (B) is 0.1 to 0.7 mm. Is preferably 0.2 to 1 mm.

In the production of the laminated sheet, the nonwoven fabric (A) and the nonwoven fabric (B) are wound into rolls, respectively.
It is possible to adopt a method in which the nonwoven fabric is unwound from the rolls at the same speed, supplied to an apparatus for laminating and integrating, laminated, and the resulting laminated sheet is wound up. When the nonwoven fabric (A) is molded, a method of simultaneously introducing the nonwoven fabric (B) into a molding device and laminating both can also be adopted.

As an apparatus for laminating and integrating two non-woven fabrics, for example, a hot roll, ultrasonic welding and the like can be mentioned. In the hot roll method, both nonwoven fabric sheets are kept at 110 ° C
It is preferable to perform the lamination process using an embossing roll heated to 140 ° C. Also, in ultrasonic fusion,
Frequency 10-50kHz, Horn pressure 2-4kg / cm
It is preferable to laminate under the condition of ² . Among these lamination methods, the hot emboss fusion method that causes little loss of electric charge is more preferable in that a laminated sheet having good honeycomb formability is obtained because the rigidity of the molded body is high.

The filter of the present invention is obtained by forming the laminated sheet into a honeycomb shape. The method for forming the laminated sheet into a honeycomb shape is not particularly limited, and for example, after slitting the laminated sheet to a fixed width, continuously folding or folding, forming a fold over the entire surface of the nonwoven fabric sheet to obtain a thickness. And a method of forming a structure having a large number of continuous voids, that is, honeycomb-shaped cells. Laminated sheet bonding of each other, it is preferable to fix to each other by fusing the adhesive or laminated sheets together.

As a method for manufacturing this honeycomb-shaped cell,
For example, as shown in FIG.
(B) is continuously folded, and
A first sheet 4 having a number of peaks 2 and valleys 3 in a row is formed.
To make. This first sheet 4 is made of a nonwoven fabric (A) and a nonwoven fabric.
(B) A flat second sheet made of a laminated sheet having
5 and the bottom 6 of the valley 3 is placed on the surface of the second sheet 5.
To form a structural unit 7 as shown in FIG.
To make. Next, a required number of such structural units 7 are manufactured.
After that, as shown in FIG.₁When
Second structural unit 7 _TwoAnd the first structural unit 7₁Mountain
The top 8 of the part 2 is replaced with the second structural unit 7_TwoGlued to the lower surface,
Further, similarly, the second structural unit 7_TwoOn the third configuration unit
Rank 7_ThreeTo form a second structural unit 7_TwoThe top of the mountain
Third constituent unit 7_ThreeAdhere to the lower surface. This stacking and
And bonding process, or the first sheet 4 and the second sheet
A large number of pairs of stacked sheets are formed, and the pair
Are stacked in a required number to form a large number of honeycomb-shaped cells 9.
A method of forming a structure having the same.

The filter of the present invention has a honeycomb thickness of 5 to 20 mm and a honeycomb unit cell shape as shown in FIG. 1. Usually, the cell height is 1 to 5 mm and the bottom of the cell is It is 2 to 10 mm.

[0055]

EXAMPLES Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples unless it exceeds the gist thereof.

Example 1 A density of 0.91 g / cm ³ and an MFR of 800 g / 10 min (ASTM D123)
8) 97 parts by weight of polypropylene (A) and maleic anhydride-modified polypropylene (B) (maleic anhydride graft amount: 2.7% by weight, intrinsic viscosity: 0.3 dl /
g) and 3 parts by weight were mixed with a tumbler blender to prepare a polyolefin composition (composition I). The content of maleic anhydride in this composition I was 3.9 × 10 ^-2 mol%.

Next, the composition I was supplied with a screw diameter of 65 m.
into a single-screw extruder of mφ, melt at 310 ° C., and 20 kg from a melt blow die connected to the tip of the extruder
/ Hr with a discharge rate of 13m /
min to form a melt blown nonwoven fabric. The melt blow die used was a die width of 1.3 m.
2 rows of forming holes (hole diameter: 0.5 mm) over the entire width of the die
(φ, hole interval: 0.8 mm). In this molding, heated air at 320 ° C. was injected into the melt blow die at a flow rate of 500 m ³ / hr.

The thickness of the obtained melt blown nonwoven fabric is
0.49mm, basis weight 30g / m ^Two, Bulk density is 0.0
67g / cm^ThreeMet. In addition, non-woven melt blown
Observe the fibers constituting the fabric with a microscope and measure the average fiber diameter
As a result, it was 4 μm. Further forming this fiber
[Η] of the resulting resin was 0.58 dl / g.

Next, this melt blown nonwoven fabric was applied to a charge application device having needle electrodes arranged in two rows at intervals of 5 mm in the length direction while applying a DC voltage of -18 kV to the charge application device at 20 m / m2. passing continuously at a speed of min,
An electret meltblown nonwoven fabric was manufactured.

When the average surface charge density of the obtained electret meltblown nonwoven fabric was measured, it was found to be 1.2.
× 10 ⁻⁹ coulomb / cm ² . The measurement of the average surface charge density was performed by using a surface charge density measurement device manufactured by RIKEN with an electrode probe having an area of 1 cm ² in contact with the surface of the nonwoven fabric.

Polypropylene (manufactured by Mitsui Petrochemical Industries, Ltd., Hypol B200, MFR: 0.5 g / 10
9000 g), 500 g of polycarbonate (manufactured by General Electric Company, Lexan 101) and 500 g of maleic anhydride-modified polypropylene (maleic anhydride graft-modified amount: 3% by weight) were mixed to prepare a resin composition.

The obtained resin composition was supplied to an inflation film forming machine (manufactured by Toshiba Machine Co., Ltd.),
At 0 ° C., a 30 μm thick film was formed. Next, this film was stretched with a hot plate heated to 135 ° C. in the longitudinal direction at a stretch ratio of 6.6 times to obtain a stretched film.
Next, the stretched film is supplied to a corona discharge electrode having an applied voltage of -9 kV (direct current) and an electrode interval of 8 mm for a residence time of 0.5 seconds to perform a charging treatment, and then is applied to a needle-shaped roll to form a mesh. And the obtained electretized defibrated yarn was wound around a paper tube. This electretized defibrated yarn was cut into 90 mm by a cutter, and opened by a cotton opening machine to obtain electretized raw cotton.

Next, this electretized raw cotton was supplied to a web forming machine and formed into a web.

The web and the electret melt-blown nonwoven fabric were supplied to a hot embossing roll set at 130 ° C. and bonded by bonding.
A laminated sheet of electret nonwoven fabric having a basis weight of 25 g / m ² and a thickness of 0.32 mm was obtained.

Next, this laminated sheet is shown in FIGS.
According to the step shown in (c), a honeycomb-shaped electret filter composed of 30 honeycomb-shaped sheets and having 70 honeycomb cells having a base of 4.2 mm and a height of 2.7 mm was manufactured. This honeycomb-shaped electret filter is cut, and the length is 70 mm, the width is 297 mm, and the thickness is 5 m.
m test filters were prepared.

The collection efficiency of the test filter was measured according to the following method. The measurement results were represented by an average value of five measurement values at each time. Table 1 shows the results.

Measurement of Collection Efficiency The collection efficiency was measured using an apparatus schematically shown in FIG. First, the aerosol generator (Nippon Kagaku Kogyo) 11 to N
aCl particles (particle size: 0.3 μm)
2 was supplied into the chamber 13 into which clean air was introduced. After the concentration of NaCl in the chamber 13 becomes constant (2 to 6 × 10 ⁶ / cm ³ ), the suction device 1
4, suction is performed in the direction of arrow A through the filter sample 15 disposed at the bottom of the chamber 13, and the upstream and downstream of the filter sample 25 when the wind speed passing through the filter becomes constant (v = 10 cm / sec). The NaCl particle concentration Cin and Cout on the 17 side were measured with a particle counter (KC-01B, manufactured by Rion), respectively.
The collection efficiency was determined by the following equation. 19 is a flow meter, 20 is a flow control valve. Collection efficiency E = (1−Cout / Cin) × 100 [%]

Measurement of pressure loss Measurement was performed simultaneously with the measurement of the collection efficiency using a differential pressure gauge (KD146, manufactured by Yamatake Honeywell Co., Ltd.).

[0069] As shown in the measurement Figure 3 filter life, inside commercial air conditioner having an inner volume of 1 m ³ of an acrylic resin box 21 (Matsushita Electrical Industrial Co.,
A device equipped with Aeolia 22 and a stirring fan 23 was prepared. Next, the test filter is set in the air conditioner, and smoke generated by burning tobacco is injected into the box 21. After that, the attenuation of the smoke density in the box 21 is measured with a dust meter (manufactured by Shibata Kagaku Co., Ltd .; -5) was measured. First, with the filter not set in the air conditioner, after injecting smoke generated when one cigarette is burned into the box 21, the air conditioner 22 is operated to obtain a half-life that is half the initial concentration. , Blank value. A predetermined number of cigarettes are burned, the generated smoke is collected by a filter, and the cumulative number of tobacco burned when the half time of the amount of dust in the box reaches half the difference between the blank value and the initial value is calculated. The life of the filter.

(Example 2) In the composition I of Example 1, except that the mixing ratio of polypropylene (A) / (maleic anhydride-grafted polypropylene (B)) was changed to 95/5, In the same manner, an electret nonwoven fabric was manufactured, and a filter was formed. The content of maleic anhydride in the composition used to prepare the filter was 6.5 × 10 ^-2 mol%. The bulk density of the obtained filter is 0.065 g / cm 3, the average surface charge density is 1.4 × 10 ⁻⁹ coulomb / cm ² , the resin forming the fiber has [η] of 0.57 dl / g, and the average fiber diameter. Was 4 μm. In addition, the initial performance of the filter and the tobacco life were measured. Table 1 shows the results.

Example 3 Instead of the filter obtained by the method of Example 1, ultrasonic treatment (processing conditions: horn pressure: 2.6 kg / cm ² , frequency: 20 kHz, processing speed: 25 m / min) A filter was prepared in the same manner as in Example 1 except that the laminated nonwoven fabric sheet obtained by laminating the electretized nonwoven fabric (A) and the electretized nonwoven fabric (B) was used. And the tobacco life was measured. Table 1 shows the results.

Comparative Example 1 A honeycomb electret filter was manufactured in the same manner as in Example 1, except that only the electretized nonwoven fabric obtained from the defibrated yarn was used instead of the filter of Example 1. The bulk density of the obtained filter is 0.092 g / cm ³ , and the basis weight is 25 g / c.
m ² . In addition, the initial performance of the filter and the tobacco life were measured. Table 1 shows the results.

(Comparative Example 2) A honeycomb-shaped electret filter was manufactured in the same manner as in Example 1 except that only the electret nonwoven fabric (B) obtained by the melt blown method was used instead of the electret filter of Example 1. . The bulk density of the obtained filter is 0.06
7 g / cm ³ , the basis weight was 25 g / cm ² , and the average surface charge density was 1.3 × 10 ⁻⁹ coulomb / cm ² . In addition, the initial performance of the filter and the tobacco life were measured. Table 1 shows the results.

[0074]

[0075]

The honeycomb-shaped electret filter of the present invention comprises two or more layers of the non-woven fabric (A) and the non-woven fabric (B), and has a lower pressure loss than a conventional honeycomb-shaped electret filter composed of only a melt-blown non-woven fabric. And excellent collection performance. In addition, the long-term life of the trapping performance is superior to that of a filter composed of a conventional nonwoven fabric made of defibrated yarn.

Therefore, the honeycomb-shaped electret filter of the present invention can be used for air conditioners, air purifiers, vacuum cleaners, fan heaters, general air conditioners, etc.
It can be suitably used as an air filter for a vehicle interior or the like.

Further, when the honeycomb-shaped electret filter of the present invention is used as an air filter, it is useful because not only the initial collection performance is high, but also the collection performance is maintained and the life of the filter is long. .

[Brief description of the drawings]

FIG. 1 is a diagram illustrating main steps of a method for manufacturing a honeycomb-shaped electret filter of the present invention.

FIG. 2 is a schematic diagram illustrating a method for measuring trapping efficiency performed in Examples and Comparative Examples of the present invention.

FIG. 3 is a schematic diagram illustrating a method for measuring the filter life performed in Examples and Comparative Examples of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 laminated sheet 2 peak 3 valley 4 first sheet 5 second sheet 6 bottom of valley 3 7 structural unit 8 top of peak 2 9 honeycomb-shaped cell 11 aerosol generator 12 air filter 13 chamber 14 suction device 15 filter Sample 16 Upstream of Filter Sample 15 17 Downstream of Filter Sample 15 18a, 18b Particle Counter 19 Flowmeter 20 Flow Control Valve 21 Box 22 Air Conditioner 23 Stirring Fan

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hironori Shirai 1-2-2 Waki, Waki-machi, Kuga-gun, Yamaguchi Prefecture Inside Mitsui Petrochemical Industry Co., Ltd. (56) References JP-A-5-68821 (JP) , A) JP-A-63-116714 (JP, A)

Claims (5)

(57) [Claims] 1. A honeycomb-shaped electret filter formed by forming an electretized nonwoven fabric laminated sheet into a honeycomb shape, wherein the nonwoven fabric laminated sheet comprises an electretized nonwoven fabric (A) comprising a defibrated yarn, and a melt blown method. A honeycomb-shaped electret filter, which is a laminated sheet having an electret nonwoven fabric (B) made of a nonwoven fabric. 2. A process for forming an electret film by electretizing a thermoplastic resin film to form an electret film, and then forming the electret film into an electret nonwoven fabric (A). To form an electretized nonwoven fabric (B) by electretizing the same, a process of laminating the electretized nonwoven fabric (A) and the electretized nonwoven fabric (B) to form a nonwoven fabric laminated sheet, Forming a honeycomb-shaped electret filter. 3. The method for manufacturing a honeycomb-shaped electret filter according to claim 2, wherein the lamination is performed by a hot emboss fusion method. 4. The method for manufacturing a honeycomb-shaped electret filter according to claim 2, wherein the lamination is performed by an ultrasonic fusion method. 5. The method for manufacturing a honeycomb-shaped electret filter according to claim 2, wherein the lamination is performed by a needle punch method.