JP2015183327A - Melt-blown nonwoven fabric and composite filter medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite filter medium which is a filter medium including gas-removing particles held therein, and which is free from breakage even when pleated and has high collection efficiency; and to provide a melt-blown nonwoven fabric which is suitably used for an air filter unit made by pleating the filter medium.SOLUTION: A melt-blown nonwoven fabric is a nonwoven fabric including long fibers which are formed of a thermoplastic resin and have average single fiber diameter of 0.1 μm to 8.0 μm. The nonwoven fabric has an average degree of fiber orientation of 40 to 80 degrees and apparent density of 0.1 to 0.5 g/cm, and is electret-processed. The melt-blown nonwoven fabric can be appropriately produced by: making an adjustment so that the center of a collection drum 15 is arranged ahead of a vertical direction below a spinneret 14 in a sheet travel direction; jetting the thermoplastic resin from the spinneret 14 as a melt-blown fiber flow; and adjusting a jetting flow rate so that the melt-blown fiber flow is vertically collected on the collection drum 15.

Description

  The present invention mainly uses a melt-blown nonwoven fabric suitably used for a filter medium and an air filter unit that have both the performance of dust collection and deodorization, which is preferably used as a filter for an air cleaner, and the melt-blown nonwoven fabric. The present invention relates to a composite filter medium and an air filter unit.

  In recent years, air filters used in homes and living rooms, and cabin filters installed in the outside air intake part of automobiles, dust collection filters that collect solid particles such as pollen, ammonia, aldehydes, etc. In general, a deodorizing filter that decomposes gaseous particles by adsorption or scientific reaction is mounted as a set.

Conventionally, a filter that regulates a stress at 2% elongation of a melt blown nonwoven fabric and is difficult to break when sandwiching activated carbon has been proposed (see Patent Document 1). However, in this proposal, the amount of the activated carbon sandwiched is about 120 g / m ² and the deodorizing effect is still insufficient.

  Further, Patent Document 2 proposes a melt-blown nonwoven fabric excellent in flexibility, but if the sheet is too flexible, the problem is that the melt-blowing at the peak of the pleats will be missed and the mesh will open at the time of pleating. There is.

  Further, there has been proposed a melt-blown nonwoven fabric that is excellent in flexibility by subjecting the melt-blown nonwoven fabric to water jet punching (see Patent Document 3). However, in this proposal, a gap is formed in the sheet due to water jet processing, and it cannot be applied as a filter.

  Moreover, although the fiber orientation of a melt blown nonwoven fabric is orientated in the longitudinal direction at the time of manufacture, a filter that improves sheet rigidity and pleatability has been proposed (see Patent Document 4), but the fiber is vertical. When used in a filter that sandwiches gas adsorbent particles by aligning in the direction, if the vertical direction is the pleating direction, the fibers constituting the sheet are molded in a fixed state, so there is no fiber stretchability, There is a problem that tearing occurs.

  Moreover, although there is a proposal for a nonwoven fabric containing a large amount of gas adsorbing particles (see Patent Document 5), when gas adsorbing particles are included inside the nonwoven fabric, extra voids are formed, which makes it easier for dust to pass through. The collection efficiency is not excellent.

  In addition, there is a method of defining the fiber diameter of the nonwoven fabric and sandwiching a large amount of gas adsorbing particles (see Patent Document 6). However, since the fibers are as thick as 10 μm or more, the collection efficiency is not excellent.

  Furthermore, a filter for laminating two layers of melt blow has been proposed (see Patent Document 7). However, because of the lamination, the manufacturing cost increases, and peeling occurs when the layers are laminated or wrinkles occur. There are challenges.

  Moreover, although it has been proposed for a cylindrical filter in which a sheet having a fiber blown nonwoven fabric having a fiber orientation of 30 degrees or less is laminated with a sheet having a degree of 35 to 65 degrees (see Patent Document 8), the sheet is oriented at 35 to 65 degrees. The sheet is rough and cannot be used as a filter monolayer.

  Further, a manufacturing method has been proposed in which a difference is made between the front and back of the sheet and the fiber orientation is set to the longitudinal direction at the time of manufacture (see Patent Document 9). In the case where the activated carbon is sandwiched and used in a method of pleating, there is a problem that tearing occurs.

JP 2011-212636 A JP 2000-8259 A Japanese Patent Laid-Open No. 10-88458 JP-A-8-224212 JP 2001-226860 A Special table 2008-531280 JP 2010-234285 A Republication No. 01/52969 Japanese Patent No. 4110651

  Accordingly, an object of the present invention is to eliminate the above-mentioned disadvantages of the prior art, and to combine a filter medium having high collection efficiency without tearing even if pleating is performed on a filter medium sandwiched with gas removal particles, and the filter medium is pleated. It is providing the melt blown nonwoven fabric used suitably for an air filter unit.

  Another object of the invention is a composite medium using the above melt-blown nonwoven fabric and the filter medium, which has a high collection efficiency and does not break even when pleated, in a filter medium sandwiched with gas removal particles, and the filter medium is pleated. The object is to provide an air filter unit.

The present invention is to solve the above problems, and the melt blown nonwoven fabric of the present invention is a nonwoven fabric composed of long fibers having an average single fiber diameter of 0.1 μm to 8.0 μm composed of a thermoplastic resin. In addition, the nonwoven fabric has an average fiber orientation degree of 40 to 80 degrees, an apparent density of 0.1 to 0.5 g / cm ³ , and is a melt blown nonwoven fabric obtained by electret processing.

  According to a preferred embodiment of the melt blown nonwoven fabric of the present invention, the melt blow nonwoven fabric has a tensile strength warp / width ratio of 0.7 to 1.3, and a stress at 1% elongation during the tape adhesion tensile test is 0.0 N / 5 cm to 12.0 N / 5 cm.

  The composite filter medium of the present invention comprises at least two base layers, of which the melt blown nonwoven fabric is used in at least one layer, and gas removal particles are sandwiched between the at least two base layers. A composite filter medium.

According to a preferred embodiment of the composite filter media of the present invention, a gas scavenging particles comprising sandwiched the base material layers is ^{100g / m 2 ~1000g / m 2} .

  In the air filter unit of the present invention, the composite filter medium is pleated and the periphery thereof is provided with a frame.

  In the air filter unit for air cleaning of the present invention, the composite filter medium is pleated and the periphery thereof is provided with a frame.

  The cabin filter unit for automobiles of the present invention is formed by pleating the composite filter medium and surrounding the periphery thereof with a frame.

  The method for producing the melt blown nonwoven fabric of the present invention is adjusted so that the center of the collecting drum is arranged in front of the sheet traveling direction with respect to the vertical direction below the die, and the thermoplastic resin melted from the die is melt blown. This is a method for producing a melt blown nonwoven fabric, which is jetted as a fiber stream, and the jet flow rate is adjusted so as to collect the melt blown fiber stream perpendicularly to the collecting drum.

  According to the present invention, an electret nonwoven fabric having excellent mechanical strength and high collection efficiency can be obtained.

  According to the present invention, since the electret nonwoven fabric is not torn even if pleated, a thin filter unit having a high fine dust collecting performance and also having a deodorizing effect by the gas removing particles can be obtained. .

FIG. 1 is a side view for explaining the collection efficiency measuring apparatus. FIG. 2 is a side view showing a test sample of the tape adhesion tensile test. FIG. 3 is a side view showing the sandwiched composite filter medium of the present invention. FIG. 4 is a graph showing the SS curve of the tape adhesion tensile test. FIG. 5 is a side view for explaining the steps of the method for producing the melt blown nonwoven fabric of the present invention. FIG. 6 is a side view for explaining the steps of the conventional method for producing a melt blown nonwoven fabric. FIG. 7 is an SEM observation image of the meltblown surface for explaining a method for measuring the average fiber orientation degree.

  The present invention has been achieved as a result of intensive studies on a method for obtaining a filter unit having high collection efficiency by preventing breakage of a nonwoven fabric sheet during pleating processing in a composite filter medium sandwiched with gas removal particles. Hereinafter, the present invention will be discussed in detail.

The melt blown nonwoven fabric of the present invention is a nonwoven fabric made of long fibers having an average single fiber diameter of 0.1 μm to 8.0 μm made of a thermoplastic resin, and the average fiber orientation degree of the nonwoven fabric is 40 to 80 degrees. It is a melt blown nonwoven fabric having a density of 0.1 to 0.5 g / cm ³ and subjected to electret processing.

  The raw material constituting the meltblown nonwoven fabric is a spinnable thermoplastic resin, and a polyolefin resin is preferably used from the viewpoint of spinnability, and polypropylene is particularly suitable.

  The average single fiber diameter of the melt blown nonwoven fabric is preferably 0.1 to 8.0 μm, more preferably 0.5 to 6.0 μm in order to have high collection efficiency and prevent tearing due to gas removal particles. More preferably, it is 1.0-4.0 micrometers. When the average single fiber diameter exceeds 8.0 μm, the pore size of the melt blown nonwoven fabric increases and the collection efficiency decreases. On the contrary, if the average single fiber diameter is less than 0.1 μm, the breaking strength per fiber is remarkably low and breakage during pleating tends to occur.

In the same purpose as the average single fiber diameter of the basis weight of the meltblown nonwoven fabric is preferably 10 to 50 g / ^{m 2,} more preferably from 15 to 40 g / ^{m 2.} If the basis weight is too high, the thickness of the composite filter medium increases and the filter pressure loss tends to increase. Conversely, if the basis weight is too low, the collection efficiency tends to decrease.

  The average fiber orientation degree of the melt blown nonwoven fabric of the present invention is preferably 40 to 80 degrees, more preferably 42 to 65 degrees, and still more preferably 43 to 60 degrees. When the average fiber orientation is less than 40 degrees, the fibers are aligned in the vertical direction, so that when used in a filter that sandwiches the gas adsorbed particles, when the vertical direction is the pleating direction, the fibers constituting the meltblown nonwoven fabric are fixed. Since it is molded with, there is no stretch of fiber, and tearing is likely to occur. Further, when the average fiber orientation degree is larger than 80 degrees, the strength in the vertical direction is remarkably lowered, and tearing may occur during sheet conveyance.

The apparent density of the melt blown nonwoven fabric of the present invention is preferably 0.10 to 0.50 g / cm ³ , more preferably 0.11 to 0.30, and further preferably 0.12 to 0.20. is there. When the apparent density is less than 0.10 g / cm ³ , the fusion of the fibers constituting the meltblown nonwoven fabric is too sweet, and the meltblown nonwoven fabric may be broken during processing. Moreover, when the apparent density is larger than 0.50 g / cm ³ , the melt-blown nonwoven fabric is densified, the air permeability is poor and it cannot be used as a filter, and the melt-blown nonwoven fabric is hard and may break during processing.

  The melt blown nonwoven fabric according to the present invention is preferably a melt blown nonwoven fabric with a charge applied to the surface and inside, that is, a so-called electret process. Examples of a method for imparting electric charge to the melt blown nonwoven fabric include methods such as a corona discharge method, a pure water suction method, and a friction charging method.

  The length / width ratio of the tensile strength in the sheet tensile test of the melt blown nonwoven fabric of the present invention is preferably 0.7 to 1.6, more preferably 0.8 to 1.5, and still more preferably 0.8. 9 to 1.4. When the warp / width ratio of the tensile strength is less than 0.7, the melt blown nonwoven fabric has a low warp strength in the warp direction, resulting in poor process passability. Moreover, when the tensile strength warp / width ratio is larger than 1.6, the fibers are aligned in the warp direction of the melt blown nonwoven fabric, and therefore, there is a problem that when the activated carbon is sandwiched and pleated, the fibers are easily torn.

  Here, the tape adhesion tensile test will be described. Conventionally, a tensile test defined by JIS-L1913 (2010) has been widely used as an index representing the strength of a nonwoven fabric. In this test method, the width of the test piece is stretched while being deformed thinly during elongation. For this reason, the gas adsorbing particles are sandwiched between the fibers constituting the sheet, which is inappropriate as an index indicating the ease of tearing during pleating with a composite filter medium molded in a fixed state.

  Therefore, when the ease of tearing of the nonwoven fabric during the pleating process was examined, as shown in FIG. 2, since the tape butting position 11 was provided on one side of the test piece of the obtained nonwoven fabric 9, only the central portion of the test piece was bonded. It was found that the stress at 1% elongation obtained by bonding the adhesive tape 10 in a state where the tape 10 is not bonded and performing a tensile test is important. The tape butting positions 11 are preferably installed at intervals of 0 to 1 mm. The adhesive tape to be used is preferably JIS-Z0237 (2009) 10.4.1 Method 1: Adhesive strength measured by 180 ° peeling adhesive strength to the test plate is 4.0 N / 10 mm or more. Moreover, when bonding an adhesive tape to a test piece, it bonds together so that a nonwoven fabric may not be torn, and it bonds by applying a load of 2 kg / (5 * 30 cm) to the whole adhesive tape.

  The 1% elongation stress during the tape adhesion tensile test of the melt blown nonwoven fabric of the present invention is preferably 1.0 to 12.0 N / 5 cm, more preferably 2.0 to 10.0 N / 5 cm, Preferably it is 3.0-6.0N / 5cm. When the stress at 1% elongation is less than 1.0 N / 5 cm, the strength of the meltblown nonwoven fabric is too weak, so that tearing may easily occur during pleating. Further, when the stress at 1% elongation is greater than 12 N / 5 cm, the looseness of the meltblown nonwoven fabric is lost, and the pleats in the composite filter medium in which the fibers constituting the meltblown nonwoven fabric are molded in a fixed state During processing, tearing may occur.

  Various additives are added to the thermoplastic resin constituting the melt blown nonwoven fabric of the present invention in order to enhance and improve the charging property, weather resistance, thermal stability, mechanical properties, coloring, surface properties, or other properties. be able to. In particular, when electret processing is performed on the melt-blown nonwoven fabric, it is a preferable aspect that an electret additive is included for the purpose of enhancing the chargeability.

  In particular, the electret additive preferably includes at least one electret additive selected from the group consisting of a hindered amine compound and a triazine compound.

  As the hindered amine compound, poly [(6- (1,1,3,3-tetramethylbutyl) imino-1,3,5-triazine-2,4-diyl) ((2,2,6,6- Tetramethyl-4-piperidyl) imino) hexamethylene ((2,2,6,6-tetramethyl-4-piperidyl) imino)] (manufactured by BASF Japan Ltd., “Kimasorb” (registered trademark) 944LD), succinic acid Dimethyl-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate (manufactured by BASF Japan Ltd., “Tinuvin” (registered trademark) 622LD), and 2- ( 3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonate bis (1,2,2,6,6-pentamethyl-4-piperidyl) (BASF Japan) , "Tinuvin" ® 144), and the like.

  Examples of the triazine compound include the poly [(6- (1,1,3,3-tetramethylbutyl) imino-1,3,5-triazine-2,4-diyl) ((2,2, 6,6-Tetramethyl-4-piperidyl) imino) hexamethylene ((2,2,6,6-tetramethyl-4-piperidyl) imino)] (manufactured by BASF Japan Ltd., “Kimasorb” (registered trademark) 944LD ), And 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-((hexyl) oxy) -phenol (manufactured by BASF Japan Ltd., “Tinuvin” (registered trademark) 1577FF) ) And the like.

  Among these electret additives, hindered amine compounds are particularly preferably used.

  The content of the hindered amine compound and / or triazine compound added to the thermoplastic resin is preferably in the range of 0.1 to 5.0 mass%, more preferably 0, based on the total mass of the meltblown nonwoven fabric. It is the range of 0.5-3 mass%, More preferably, it is the range of 0.8-2.0 mass%. When these hindered amine compounds and triazine compounds are attached to the nonwoven fabric or fiber surface, it is preferable to attach the hindered amine compound or the triazine compound in the range of 0.1 to 5.0 mass% with respect to the total mass of the melt blown nonwoven fabric.

  In addition to the above-mentioned compounds, the meltblown nonwoven fabric of the present invention may be added with usual additives generally used for electret processed nonwoven fabrics, such as heat stabilizers, weathering agents and polymerization inhibitors. .

  FIG. 3 is a side view showing the sandwiched composite filter medium of the present invention. In the composite filter medium of the present invention, as shown in FIG. 3, the gas removal particles 12 are preferably sandwiched between a nonwoven fabric (melt blown nonwoven fabric) 9 and another base material 13. The other substrate 13 can be arbitrarily selected from a nonwoven fabric, a woven fabric, a knit, and the like, but it is preferable to use a nonwoven fabric that has high air permeability and excellent pleated shape retention. As the material, synthetic resin, synthetic fiber, natural fiber, inorganic fiber, metal fiber, and the like can be used.

  The melt blown nonwoven fabric used for the composite filter medium of the present invention is preferably used in one layer. When another base material is bonded to the melt blown nonwoven fabric, it is difficult to break during pleating, but the air permeability as a filter is lost.

  Examples of the gas removal particles used in the composite filter medium of the present invention are particulate substances having a property of adsorbing gas components such as ammonia and aldehydes or removing them by reaction or the like. Examples of the type include activated carbon, porous silica, zeolite, and sepiolite. Among these, activated carbon has a large pore volume and has pores with a wide diameter, and therefore, various gases can be removed and is preferably used.

  The average particle diameter of the gas removal particles used in the present invention is preferably 100 to 300 μm, more preferably 150 to 260 μm. When the average particle diameter exceeds 300 μm, the thickness of the composite filter medium increases, and the interval between adjacent ridges after pleating, that is, the ventilation area becomes narrow, which may cause an increase in pressure loss. On the other hand, when the average particle diameter is less than 100 μm, the possibility of flowing out from the aperture of the base material increases. The average particle size referred to here means a particle size at which the accumulated mass is halved in the particle size distribution measured by sieving the particles.

The amount of the gas adsorption particles used in the present invention is preferably 120 to 1000 g / m ² , more preferably 150 to 800 g / m ² , and still more preferably from the viewpoint of the efficiency and durability of the gas adsorption performance. Is 420 to 600 g / m ² . When the amount used is less than 120 g / m ² , the durability of the adsorption performance is low and the filter life is short. On the other hand, when the amount used exceeds 1000 g / m ² , the composite filter medium becomes extremely thick, and the amount of filter material that can be stored in the filter decreases.

  A chemical can be attached to the gas removal particles used in the present invention for the purpose of increasing the reactivity with the gas component to be removed. Examples of such chemicals include phosphoric acid and hydrochloric acid that generate an oxidation reaction to remove an alkaline gas such as ammonia, and potassium hydroxide and potassium carbonate that generate an alkaline reaction and remove an acid gas such as acetic acid. And sodium hydrogen carbonate, primary to tertiary amine compounds that generate a reaction with aldehydes, such as adipic acid dihydrazide, dodecanedioic acid dihydrazide and succinic acid dihydrazide, p-aminobenzenesulfonic acid, and ethylene Examples include urea condensate drugs. 3-30 mass% is preferable with respect to the mass of a gas removal particle, and, as for the addition amount of a chemical | medical agent, More preferably, it is 5-20 mass%.

  In the composite filter medium of the present invention, as the state where the gas removal particles are sandwiched as shown in FIG. 3, adhesion to the surface of the base material through an adhesive such as polyethylene or polyolefin-based heat-bonding adhesive powder, and A material in which a part of the base material is melted by heat and particles are adhered can be arbitrarily selected. At this time, a method in which the gas removal particles 12 are adhered to the base material 13 on the side different from the nonwoven fabric (melt blown nonwoven fabric) 9 and the melt blown nonwoven fabric sheet is bonded and sandwiched thereafter is preferable.

  The thickness of the meltblown nonwoven fabric in the present invention is preferably 0.1 to 1.0 mm, more preferably 0.2 to 0.8 mm. The thickness of the substrate in the present invention is preferably 0.1 to 1.0 mm, more preferably 0.2 to 0.8 mm. The thickness of the composite filter medium in the present invention is preferably 0.2 to 8.0 mm, more preferably 0.4 to 5.0 mm. If the thickness of the composite filter medium is too large, the ventilation interval after the filter unit processing by pleating becomes narrow, and there is a tendency to cause an undesired increase in pressure loss. On the other hand, if the thickness is too small, the amount of sandwiched gas adsorbent particles tends to be insufficient and the service life tends to be short.

  The composite filter medium in the present invention can be used as an air filter unit, for example, by performing pleating or corrugating, or by storing (ie, setting) in a frame. The obtained air filter unit has the same effect as the above-described composite filter medium. Therefore, the composite filter medium is preferably used in various air cleaners and automobile cabin filters by pleating and joining the periphery with a frame. The air purifier in the present invention is used mainly for the purpose of purifying indoor air in a general house or a hotel. An adhesive or the like can be used for joining with the frame. Further, other members are arranged as necessary. The other members mentioned here are thermoplastic in the direction perpendicular to the direction of the valley with resin in order to prevent the peaks and valleys in the pleated part from being deformed by wind pressure when used as a filter after pleating. This refers to a comb-shaped thermoplastic resin or paper plate molded into the shape of a mountain valley in order to perform bead processing for applying the resin linearly or to insert into a mountain valley portion after pleating. About a frame and other members, the thing of a well-known shape and a raw material can be used.

  FIG. 5 is a side view for explaining the steps of the method for producing the melt blown nonwoven fabric of the present invention.

  As an example of the method for producing a melt blown nonwoven fabric according to the present invention, a thermoplastic synthetic resin is discharged at a discharge amount of 0.2 g / hole / minute or more from a die in which spinning hole groups are arranged at a hole pitch of 1.0 mm or less. As shown in FIG. 4, the center of the cylindrical collecting drum 15 is adjusted to be arranged in front of the sheet traveling direction with respect to the vertical direction below the base 14, and the melt is blown as a melt blown fiber stream. The jet is adjusted so that the flow is vertically collected on the circumference of the collecting drum on the rear side in the traveling direction of the collecting drum 15. A melt blown nonwoven fabric having an average fiber orientation of 40 to 80 ° can be obtained by spraying the melt blown fiber stream perpendicularly to the collecting drum, whereby the fibers are easily dispersed in the horizontal direction with respect to the sheet traveling direction. It is. The melt-blown fiber stream collected by the collection drum 15 is bonded to each other by self-bonding to form a sheet, and is wound by the winder 16.

  Moreover, FIG. 6 is a side view for demonstrating the process of the manufacturing method of the conventional melt blown nonwoven fabric. As shown in FIG. 6, the center of the collecting drum 15 is adjusted so that the center of the collecting drum 15 is arranged at the rear of the sheet traveling direction with respect to the vertical direction below the base 14, and the melt blown fiber stream is jetted. In the case where the fibers are not collected vertically with respect to the collecting drum 15, the fibers are not preferred because the fibers are vertically oriented along the circumference. The melt-blown fiber stream collected by the collection drum 15 is bonded to each other by self-bonding to form a sheet, and is wound by the winder 16. Further, the vertical direction below the base 14 and the center of the collecting drum 15 are adjusted so as to be arranged on the same line, and the melt blown fiber stream is injected perpendicularly to the apex of the collecting drum 15. In this case, the fibers are not preferable because the fibers are blown back and forth to form a vertical orientation. The melt-blown fiber stream collected by the collection drum 15 is bonded to each other by self-bonding to form a sheet, and is wound by the winder 16.

  The air filter unit by this invention is mainly used for the air filter for normalizing the air of a domestic air cleaner air filter. Further, it is preferably used as an air filter for an air conditioner, an air intake / disposal filter for office automation equipment, a building air conditioner, an air filter for individual air conditioner, an air filter for an industrial clean room, and an air filter for a vehicle interior such as an automobile or a railway vehicle.

  Next, the melt blown nonwoven fabric of the present invention, the composite filter medium, and the function and effect thereof will be described more specifically by examples, but the present invention is not limited only to the following examples.

[Measuring method]
(1) Thickness (mm) of melt blown nonwoven fabric
About melt blown nonwoven fabric cut to 20cm x 20cm, measure 10 points at random using a thickness meter ("TECLOCK" (registered trademark) SM-114 manufactured by Teclock Corporation), round off the third decimal place from the average value, thickness It was.

  Moreover, when measuring the thickness of the melt-blown nonwoven fabric of the composite filter material which carried out the lamination | stacking process by inserting gas adsorption particle | grains, it can measure and obtain | require from the cross-sectional observation photograph by SEM. In this case, 10 samples were taken from any location of the meltblown nonwoven fabric, the magnification was adjusted with a scanning electron microscope, and 10 cross-sectional photographs of the collected samples were taken one by one. The magnification was arbitrarily set at 50 to 500 times. Measure the thickness of the meltblown nonwoven fabric in the photo. These values were summed and the third decimal place of the value divided by the number of measurements was rounded off to obtain the thickness.

(2) Weight per unit area of melt blown nonwoven fabric (g / m ² )
The mass of the melt blown nonwoven fabric cut to 25 cm x 25 cm was measured for 4 sheets using a mass meter (FY-300 manufactured by A & D Co., Ltd.), and the average value was converted to the mass per 1 m ² . The 2nd place was rounded to the basis weight. When measuring the thickness of the melt-blown nonwoven fabric of the composite filter medium that has been sandwiched with gas adsorbed particles and then laminated, the composite filter medium is decomposed and its mass is measured.

(3) Apparent density of meltblown nonwoven fabric (g / cm ³ )
The apparent density was calculated by the following formula using the obtained thickness and basis weight, and the third decimal place was rounded off.
Apparent density (g / cm ³ ) = weight per unit area (g / m ² ) / thickness (mm) / 1000
(4) Average single fiber diameter (μm)
Twelve measurement samples of length x width = 3 mm x 3 mm were collected from any location on the meltblown nonwoven fabric, the magnification was adjusted with a scanning electron microscope, and each fiber surface photograph from the collected samples was 12 in total. I took a picture. The magnification was arbitrarily set at 200 to 3000 times. The fiber diameter was measured for all fibers in the photograph where the fiber diameter could be clearly confirmed. Each fiber diameter was measured with a measurement accuracy of an effective number of 0.1 μm. These values were summed, and the value after dividing by the number of fibers measured was rounded off to the second decimal place to obtain the average fiber diameter.

(5) Average fiber orientation (°)
As shown in FIG. 7, the length direction specified from the direction at the time of manufacture of the melt blown nonwoven fabric is set as the vertical direction 17, and a measurement sample of length × width = 3 mm × 3 mm is measured on the front and back sides in the width direction of the melt blown nonwoven fabric. As shown in the figure, three samples are collected, and the vertical direction of the screen and the melt blown nonwoven fabric are aligned with the vertical direction 17 which is the length direction specified from the direction at the time of production. A total of 6 photographs of the fiber surface were taken from each sample. Photographed at a magnification set to 2000 times, the vertical direction of the dispersed fiber screen is 0 degree, and the center line 18 of one fiber and the vertical line 17 of the vertical direction of the screen, that is, the reference line that is 0 degree. The angle 19 was measured in the range of 0 to 90 degrees, 10 points were measured per photograph, the average value was calculated from the obtained values, and the second decimal place was rounded off. The fiber includes a part where the angle is changed in the middle rather than on a straight line. In this case, a part where the angle is the largest is selected and measured. Moreover, as the location of one fiber for measuring the angle, the portion where the length of the center line is a straight line and a straight line more than twice the fiber diameter was measured.

(6) Tensile strength (N / 5cm) and elongation (%) of melt blown nonwoven fabric
For the melt blown nonwoven fabric, the length direction specified from the production direction is the vertical direction, the width direction perpendicular to the length direction is the horizontal direction, and the test piece size is 5 cm wide × 30 cm long. Samples were taken one by one, using a tensile tester to conduct a tensile test with a grip width of 5 cm, a grip interval of 20 cm, and a tensile speed of 10 cm / min. The maximum value was the tensile strength and the elongation at that time was the elongation. The average value was calculated and rounded to the first decimal place. The vertical / horizontal ratio was calculated from the obtained vertical and horizontal tensile strength values by vertical / horizontal, and rounded to the first decimal place.

(7) Stress at 1% elongation during tape adhesion tensile test (N / 5cm)
The length direction specified from the direction at the time of manufacture of the melt blown nonwoven fabric is taken as a vertical direction, and 3 sheets are collected in a horizontal 5 cm × vertical 20 cm, and a horizontal 5 cm × vertical 10 cm tape (Nichiban Co., Ltd. cloth adhesive tape) LS (5cm width, adhesive strength 4.74N / 10mm) is bonded to the whole tape with a load of 2kg / (5x30cm) so that the end of the tape does not overlap at the center of the test piece. The tension test was carried out with a grip width of 5 cm, a grip interval of 10 cm, and a tensile speed of 10 cm / min. The strength at 1% elongation was the stress at 1% elongation at the tape adhesion tensile test, and the average value for each of the three points. And rounded off to the second decimal place.

(8) Collection Efficiency and Pressure Loss Measurement samples of length × width = 15 cm × 15 cm were collected at 5 points in the longitudinal direction of the melt blown nonwoven fabric, and each sample was measured with a collection efficiency measuring device shown in FIG. In this collection efficiency measuring device, a dust storage box 2 is connected to an upstream side of a sample holder 1 for setting a measurement sample M, and a flow meter 3, a flow rate adjusting valve 4 and a blower 5 are connected to a downstream side. In addition, the particle counter 6 is used in the sample holder 1, and the number of dusts on the upstream side and the number of dusts on the downstream side of the measurement sample M can be measured via the switching cock 7. Furthermore, the sample holder 1 includes a pressure gauge 8 and can read a static pressure difference between the upstream and downstream of the measurement sample M.

In measuring the collection efficiency, a 0.309U 10% polystyrene solution (manufacturer: Nacalai Tesque Co., Ltd.) is diluted 200 times with distilled water and filled in the dust storage box 2. Next, the measurement sample M is set in the sample holder 1, the air volume is adjusted by the flow rate adjusting valve 4 so that the filter passing speed is 4.5 m / min, and the dust concentration is 10,000 to 40,000 pieces / 2.83. × 10 ⁻⁴ m ³ (0.01 ft ³ ) is stabilized, and the number of dusts D upstream of the measurement sample M and the number of dusts d downstream are one with a particle counter 6 (manufactured by Lion, KC-01B). Based on JIS K 0901: 1991 “Shape, size and performance test method of dust filter for collecting dust sample in gas”, 0.3 to 0 using the following calculation formula: The collection efficiency (%) of .5 μm particles was determined. The final collection efficiency was obtained by rounding off the second decimal place from the average value of the five measurement samples.
Collection efficiency (%) = [1- (d / D)] × 100
However,
d: Total number of downstream dust measured three times D: Total number of upstream dust measured three times The higher the melt-blown nonwoven fabric with higher collection, the lower the number of downstream dust, and the higher the collection efficiency value.

  Further, the pressure loss was obtained by reading the static pressure difference between the upstream and downstream of the measurement sample M at the time of measuring the collection efficiency with the pressure gauge 8. The final pressure loss was calculated by rounding off the second decimal place from the average value of five measurement samples.

(9) Pleated vertex hole (pieces)
Appearance determination of the perforation of the melt blown nonwoven fabric when the composite filter medium is pleated continuously for 400 piles in the vertical direction of the melt blown nonwoven fabric electret processed with a reciprocating pleating machine so that the peak height is 29.5 to 30.0 mm The average was calculated based on the following definitions. As operating conditions of the reciprocating pleating machine, the hot plate temperature of the heater was 80 ° C. on both the upper and lower surfaces, the hot plate interval was 31.2 mm, and the pressure on the filter medium was 6 kg.
<Definition of perforated>: An electret-processed melt-blown non-woven fabric is torn at a length of 1 mm or more, and the sandwiched gas adsorbing particles (12 in FIG. 3) or other base material (13 in FIG. 3) can be seen.

[Example 1]
As a thermoplastic resin, a polypropylene (PP) resin having an MFR of 860 g / 10 minutes at a temperature of 230 ° C. and a load of 21.18 N and a melting point of 163 ° C. was used. “Kimasorb” (registered trademark) 944 (BASF Japan ( Co., Ltd.) 1% by mass added polypropylene resin composition, extruder and gear pump, melt blow nozzle (hole pitch: 1.0 mm, hole diameter: 0.30 mm, hole depth: 3.0 mm), compressed air generation The melt blown nonwoven fabric was manufactured using the apparatus and the apparatus which consists of an air heater, a collection conveyor, and a winder.

The polypropylene resin composition described above was charged into an extruder, melted by heating, weighed in a certain amount using a gear pump, led to a melt blow nozzle and discharged. As shown in FIG. 5, the center of the collecting drum is adjusted so that the center of the collecting drum is arranged in front of the sheet traveling direction with respect to the vertical direction below the base, and is injected from the melt blow base as a fiber flow together with hot hot air. The meltblown fiber stream was collected perpendicularly to the rear side in the traveling direction of the collecting drum and formed into a sheet. The collecting drum speed was adjusted, the basis weight was 40.9 g / m ² , the average single fiber diameter was 4.8 μm, the thickness was 0.32 mm, the apparent density was 0.13 g / cm ³ , and the average fiber orientation was 47.6. Degree melt blown nonwoven fabric was obtained.

  The obtained melt blown nonwoven fabric was electret processed by a pure water suction method. The pressure loss of this melt blown nonwoven fabric was 7.3 Pa, and the collection efficiency was 94.7%. Further, the stress at 1% elongation during the tape adhesion tensile test was 5.0 N / 5 cm.

Furthermore, in order to create a composite filter medium, as another base material, on a polyester thermal bond nonwoven fabric sheet (47 g / m ² ), granular activated carbon (average particle size 240 μm) 100 g / m ² and phosphoric acid as gas adsorbed particles. 10 wt% impregnated is not activated carbon (average particle size 150 [mu] m) to 25 g / ^{m 2,} the activated carbon was 10 mass% impregnating calcium carbonate 125 g / ^{m 2,} an ethylene - vinyl acetate-based heat-bonding powder to 75 g / ^{m 2} uniformly After spraying, the adhesive powder was melted by heating, and the electret meltblown nonwoven fabric obtained above was laminated on the surface, and then pressed with a nip roll and bonded to obtain a composite filter medium.

  When the obtained composite filter material was pleated in the vertical direction of the electret-processed meltblown nonwoven fabric, there were no holes. The results are shown in Table 1.

[Example 2]
The collection drum speed was adjusted by the same method as in Example 1, the basis weight was 34.8 g / m ² , the average fiber diameter was 3.6 μm, the thickness was 0.25 mm, the apparent density was 0.14 g / cm ³ , and the average A meltblown nonwoven fabric having a fiber orientation of 43.7 degrees was obtained. The obtained melt blown nonwoven fabric was electret processed by a pure water suction method. The pressure loss of this melt blown nonwoven fabric was 32.9 Pa, and the collection efficiency was 99.9%. The stress at 1% elongation during the tape adhesion tensile test was 5.2 N / 5 cm.

  Furthermore, in order to create a composite filter medium, the substrate and gas adsorbed particles were bonded together in the same manner as in Example 1 to obtain a composite filter medium. When the obtained composite filter medium was pleated in the vertical direction of the electret-processed meltblown nonwoven fabric, there were no holes. The results are shown in Table 1.

[Example 3]
The collection drum speed was adjusted by the same method as in Example 1, the basis weight was 30.0 g / m ² , the average fiber diameter was 5.1 μm, the thickness was 0.24 mm, the apparent density was 0.13 g / cm ³ , the average A meltblown nonwoven fabric having a fiber orientation of 45.8 degrees was obtained. The obtained melt blown nonwoven fabric was electret processed by a pure water suction method. The pressure loss of this melt blown nonwoven fabric was 5.9 Pa, and the collection efficiency was 92.7%. Further, the stress at 1% elongation during the tape adhesion tensile test was 5.9 N / 5 cm.

  Further, in the same manner as in Example 1, the base material and the gas adsorbing particles were bonded together to obtain a composite filter medium. When the obtained composite filter medium was pleated in the vertical direction of the electret-processed meltblown nonwoven fabric, there were no holes. The results are shown in Table 1.

[Comparative Example 1]
In the same manner as in Example 1, the above polypropylene resin composition was put into an extruder, heated and melted, weighed in a fixed amount using a gear pump, led to a melt blow cap and discharged. As shown in FIG. 6, the center of the collecting drum is adjusted so that the center of the collecting drum is arranged behind the sheet traveling direction with respect to the vertical direction below the base, and is jetted as a fiber stream from the melt blow base together with high-temperature hot air. The meltblown fiber stream was collected on the circumference of the collecting drum in the traveling direction and formed into a sheet. The collection drum speed was adjusted, the basis weight was 30.0 g / m ² , the average fiber diameter was 5.4 μm, the thickness was 0.25 mm, the apparent density was 0.12 g / cm ³ , and the average fiber orientation was 23.1 degrees. The melt blown nonwoven fabric was obtained. The obtained melt blown nonwoven fabric was electret processed by a pure water suction method. The pressure loss of this melt blown nonwoven fabric was 6.3 Pa, and the collection efficiency was 92.0%. The stress at 1% elongation during the tape adhesion tensile test was 12.5 N / 5 cm.

  Further, in the same manner as in Example 1, the substrate and the gas adsorbing particles were bonded together to obtain a composite filter medium. When the obtained composite filter material was pleated in the vertical direction of the electret meltblown nonwoven fabric, there were 10 holes. The results are shown in Table 1.

  As shown in Table 1, Examples 1 to 3 having an average fiber orientation degree in the range of 40 to 80 ° were not broken during pleating, but the average fiber orientation degree was lower than 40 °. In Comparative Example 1 at 23.1 °, tearing was observed during pleating. This is because the gas adsorbent particles are sandwiched between the fibers of Comparative Example 1 oriented in the vertical direction, and the fibers and the gas adsorbent particles are fixed with an adhesive, so that the fibers do not stretch and are torn during pleating. In contrast, in Examples 1 to 4, since the fibers were oriented in the horizontal direction, the fibers had an allowance for elongation, and no breakage occurred during pleating.

  Furthermore, in FIG. 4, the graph of SS curve of the tape adhesion tension test of said Examples 1-3 and the comparative example 1 is shown. As can be seen from FIG. 4, in Examples 1 to 3, the stress at 1% elongation is low, and the bending followability of the melt blown nonwoven fabric during pleating is good.

  On the other hand, in Comparative Example 1, the stress at the time of 1% elongation was high, and the bending followability of the melt blown nonwoven fabric was poor at the time of pleating, and tearing occurred.

1: Sample holder 2: Dust storage box 3: Flow meter 4: Flow control valve 5: Blower 6: Particle counter 7: Switch cock 8: Pressure gauge M: Measurement sample 9: Non-woven fabric 10: Adhesive tape 11: Tape butt position 12 : Gas adsorption particles 13: Base material 14: Base 15: Collection drum 16: Winding machine 17: Length direction specified from the direction at the time of production of the melt blown nonwoven fabric 18: Center line of one fiber 19: Degree of fiber orientation

Claims (8)

A nonwoven fabric composed of long fibers having an average single fiber diameter of 0.1 μm to 8.0 μm made of a thermoplastic resin, wherein the nonwoven has an average fiber orientation of 40 to 80 degrees and an apparent density of 0.1 to 0.00. A melt-blown nonwoven fabric that is 5 g / cm ³ and is electret processed.   The melt blown nonwoven fabric according to claim 1, wherein the tensile strength warp / width ratio is 0.7 to 1.3, and the stress at 1% elongation during the tape adhesion tensile test is 1.0 N / 5 cm to 12.0 N / 5 cm. .   A composite filter medium comprising at least two base layers, wherein at least one of the melt blown nonwoven fabrics according to claim 1 or 2 is used, and gas removal particles are sandwiched between the at least two base layers. . Composite filter medium of claim 3, wherein the gas scavenging particles is sandwiched ^{100g / m 2 ~1000g / m 2} .   5. An air filter unit, wherein the composite filter medium according to claim 3 or 4 is pleated and a periphery thereof is provided with a frame.   5. An air filter unit for an air purifier, wherein the composite filter medium according to claim 3 or 4 is pleated and the periphery thereof is provided with a frame.   5. A cabin filter unit for automobiles, wherein the composite filter medium according to claim 3 or 4 is pleated and the periphery thereof is provided with a frame.   The center of the collecting drum is adjusted so that the center of the collecting drum is disposed in front of the sheet traveling direction with respect to the vertical direction below the base, and the melted thermoplastic resin is sprayed as a meltblown fiber stream. The method for producing a melt blown nonwoven fabric according to claim 1 or 2, wherein the spray flow rate is adjusted so as to be collected perpendicularly to the collecting drum.