JP2018071018A - Electret fiber sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electret fiber sheet having high oil mist sampling performance and high oil mist resistance.SOLUTION: An oil mist-resistance electret fiber sheet is an electret fiber sheet consisted of nonconductive fiber containing perfluoroalkyl compounds. The appearance number of the perfluoroalkyl compounds for the fiber specific surface area of fiber forming the electret fiber sheet is 3×10to 15×10/m.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electretized fiber sheet, and more specifically, the present invention relates to an electret fiber sheet having high oil mist collection performance and high oil mist resistance.

  Conventionally, an air filter has been used to remove pollen, dust and the like in the gas, and a nonwoven fabric is often used as a filter medium for the air filter. Among them, the melt blow method, which is one of the methods for producing nonwoven fabrics, is widely used in the manufacture of filter media for air filter products, battery separators, and the like. In general, the melt blow method is a method in which a thermoplastic polymer extruded from a spinneret is thinned into a fiber by spraying with hot air and formed into a fiber web by utilizing the self-bonding characteristics of the obtained fiber. Compared to other nonwoven fabric manufacturing methods such as the spunbond method, this melt blow method does not require a complicated process and has the advantage that thin fibers of several tens to several μm can be easily obtained. .

  The performance required for the air filter is high collection efficiency capable of collecting a large amount of micro dust, and low pressure loss with low resistance when gas passes through the air filter. In order to obtain the filter medium having the above high collection efficiency, it is suitable that the single fiber constituting the nonwoven fabric has a fineness. On the other hand, if the single fiber is made finer, the nonwoven fabric tends to be crushed. There is a problem that the pressure loss increases as the fiber density increases.

  In order to obtain a filter medium with low pressure loss, it is suitable that the single fibers constituting the nonwoven fabric have a large fineness. On the other hand, when the single fibers are thickened, the fiber surface area in the nonwoven fabric decreases. Therefore, there is a problem that the collection efficiency is lowered. Thus, having a high collection efficiency and having a low pressure loss are in a conflicting relationship.

  As a method for solving the above-mentioned problems, attempts have been made to simultaneously satisfy high collection efficiency and low pressure loss by electretizing a nonwoven fabric and utilizing an electrostatic action in addition to a physical action.

  For example, a corona discharge method in which a non-contact type application electrode is applied to apply a high voltage while moving the ground electrode and the nonwoven fabric together while the nonwoven fabric is in contact with the ground electrode (Patent Document 1). ) Has been proposed. As another method of charging water by contacting the fiber with the fiber, a jet or water droplet of water is sprayed at a pressure sufficient to allow the water to penetrate into the nonwoven fabric, and electretized. The method of mixing the electric charges uniformly (Patent Document 2) or passing the fiber sheet over a slit-like nozzle and sucking water with the nozzle so that the fiber sheet is infiltrated with water, positive polarity and negative polarity A so-called hydrocharge method has been proposed, such as a method of uniformly mixing charges (Patent Document 3).

  However, the electret filter obtained by the above method has a drawback that the electrostatic attraction is reduced as the particles are collected. Particularly, the oil mist having a small surface tension causes a significant charge loss by covering the fiber surface thinly. General electret filters use resins with excellent charge stability, but they do not exhibit sufficient oil repellency as material characteristics for oil mist represented by tobacco smoke. Has a problem of low dust collection efficiency retention performance (hereinafter referred to as “oil mist resistance”).

  In order to solve such problems, oil repellency is imparted to the fiber sheet constituting the filter, and the loss of electric charge is reduced by suppressing the spread of oil mist on the fiber surface and the absorption and diffusion into the fiber material. There are known methods for improving the performance. Specifically, a method of coating polytetrafluoroethylene on the resin surface (for example, Patent Document 4 and Patent Document 5), a method of mixing an additive having a perfluoroalkyl group in the resin (for example, Patent Document 6), etc. There has been proposed a method of imparting oil repellency to an electret filter and improving oil mist resistance.

JP-A 61-289177 US Pat. No. 6,119,691 JP 2003-3367 A Japanese Patent Laying-Open No. 2015-200058 Japanese Patent Laying-Open No. 2015-85232 JP 2009-6313 A

  Although the electret filter which has high oil repellency has high oil mist resistance like the method of patent documents 3-6, since the collected oil mist flows out outside, an odor and wallpaper There was a problem of deteriorating the external environment such as coloring. Thus, having high oil mist collection performance and having high oil mist resistance are in a conflicting relationship.

  An object of the present invention is to provide an electret fiber sheet that has both high oil mist collection performance and high oil mist resistance in view of the problem of oil mist collection technology.

The present invention is to solve the above-mentioned problems, and the electret fiber sheet of the present invention is an electret fiber sheet composed of non-conductive fibers containing a perfluoroalkyl compound, and the electret fiber sheet is It is an electret fiber sheet characterized in that the apparent number of perfluoroalkyl compounds with respect to the fiber specific surface area of the constituent fibers is 3 × 10 ¹³ to 15 × 10 ¹³ pieces / m ² .
According to the preferable aspect of the electret fiber sheet of this invention, content of the perfluoroalkyl compound contained in the said electret fiber sheet is 0.1 to 5 weight% with respect to the weight of an electret fiber sheet.

  According to a preferred aspect of the electret fiber sheet of the present invention, the nonconductive fiber is a polyolefin resin.

  According to a preferred aspect of the electret fiber sheet of the present invention, the polyolefin resin is polypropylene.

  According to a preferred aspect of the electret fiber sheet of the present invention, the fiber sheet is a melt blown nonwoven fabric.

  The electret fiber sheet of the present invention has both high oil mist collecting performance and high oil mist resistance, and is a dust mask, various air conditioning elements, an air cleaner, a cabin filter, and a filter for various devices. Is preferably used.

FIG. 1 is a schematic side view showing a collection efficiency measuring device.

The electret fiber sheet of the present invention is an electret fiber sheet composed of non-conductive fibers containing a perfluoroalkyl compound, and the apparent number of perfluoroalkyl compounds with respect to the fiber specific surface area of the fibers constituting the electret fiber sheet is It is an electret fiber sheet characterized by being 3 × 10 ¹¹ to 15 × 10 ¹¹ pieces / m ² . Examples of the fiber sheet include synthetic fiber woven fabrics, knitted fabrics, and non-woven fabrics. In particular, in the case of an air filter, a nonwoven fabric made of synthetic fibers is preferable, and further, a melt blown nonwoven fabric is preferable. By using a melt-blown nonwoven fabric, a complicated process is not required, a fine fiber of several μm can be easily obtained, and high collection efficiency for dust can be easily achieved.

In the present invention, non-conductive means that the volume resistivity is 10 ¹² · Ω · cm or more, and preferably 10 ¹⁴ · Ω · cm or more. Volume resistivity was measured according to ASTM D257.

  Examples of the non-conductive fiber material used in the present invention include polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate and polylactic acid, polycarbonate resins, polystyrene Resin, polyphenylene sulfide resin, fluorine resin, polystyrene elastomer, polyolefin elastomer, polyester elastomer, polyamide elastomer and polyurethane elastomer, and copolymers or mixtures thereof.

  Among these, polyolefin resins are preferably used. Since the polyolefin resin has a high volume resistivity and low water absorption, the chargeability and charge retention when fiberized are strong, so that high collection efficiency can be achieved by these effects.

  Examples of the polyolefin resin include homopolymers such as polyethylene, polypropylene, polybutene, and polymethylpentene. Moreover, a copolymer obtained by copolymerizing different components with these homopolymers, or two or more different polymer blends can be used. Among these, polypropylene and polymethylpentene are preferably used from the viewpoint of charge retention. Also, polypropylene is more preferably used from the viewpoint that it can be used at low cost.

  Although the manufacturing method of the electret fiber sheet of this invention is not specifically limited, For example, it can manufacture with the following method.

  First, a non-conductive resin as a raw material is prepared, then the resin is supplied to a resin hopper of a spinning machine, extruded while being melted by an extruder, and supplied to a base part, such as a fiber, a fiber web, or a nonwoven fabric. It is processed into a structure. Next, when the fiber sheet is made of woven fabric or knitted fabric, it can be produced by forming a yarn using the fiber and then weaving or knitting. In addition, when the fiber sheet is made of a nonwoven fabric, the fiber web is formed by a dry method or a wet method using the fibers, and then the fiber web is bonded to produce a nonwoven fabric, or the fiber web is spunbonded. After forming by a melt blow method, a nonwoven fabric can be produced by bonding fiber webs. In addition, a nonwoven fabric mainly composed of nanofibers can be produced by an electrostatic spinning method or a method of eluting sea portions of sea-island fibers. Next, the manufactured fiber sheet is electretized to produce an electret fiber sheet. The electretization treatment may be performed on a fiber sheet single layer or a laminated fiber sheet laminated with another sheet.

  As the electretization method used in the production of the electret fiber sheet of the present invention, a method of electretization by applying water to the non-conductive fiber sheet and drying it is preferably used. As a method for imparting water to the fiber sheet, a method of spraying a water jet or water droplet at a pressure sufficient to allow water to penetrate into the fiber sheet, or after applying or imparting water, A method of allowing water to penetrate into the fiber sheet by sucking from one side, and immersing the fiber sheet in a mixed solution of water and a water-soluble organic solvent such as isopropyl alcohol, ethyl alcohol and acetone so that the water penetrates into the fiber sheet. Methods and the like.

In the present invention, the water used for electretization is preferably water that has been cleaned of dirt with a liquid filter or the like and is as clean as possible. In particular, pure water such as ion-exchanged water, distilled water and filtered water permeated through a reverse osmosis membrane is preferably used. The level of pure water is preferably 10 ³ μS / m or less in electrical conductivity, more preferably 10 ² μS / m or less. The electrical conductivity was measured according to JIS K 0130. Moreover, a water-soluble organic solvent can be mixed with said water in the range which does not affect a collection characteristic.

The perfluoroalkyl compound used in the present invention is a fluorine compound containing a perfluoroalkyl group in the chemical structure, and is not particularly limited as long as it can impart oil repellency to the electret fiber sheet. Since the environmental load of PFOA (PerfluoroOcanoic Acid) is a problem, it is preferable that the perfluoroalkyl group has 6 or less carbon atoms. Examples of such a perfluoroalkyl compound include acrylic acid-based, methacrylic acid-based, fumaric acid-based, carboxylic acid-based, and phosphoric acid-based compounds, and any of aqueous and non-aqueous compounds can be used. Specifically, “Mega Fuck” (registered trademark) F-477, F-562 manufactured by DIC Corporation, “Surflon” (registered trademark) S-242, S-651 manufactured by AGC Seimi Chemical Co., Ltd., etc. Can be used.
In the electret fiber sheet of the present invention, the apparent number of perfluoroalkyl compounds with respect to the fiber specific surface area of the fibers constituting the electret fiber sheet is 3 × 10 ¹³ to 15 × 10 ¹³ pieces / m ² , preferably 4 × 10 ^13. -10 × 10 ¹³ pieces / m ² . By making the apparent number of perfluoroalkyl compounds with respect to the fiber specific surface area of the fibers constituting the electret fiber sheet within this range, both high oil mist collecting performance and high oil mist resistance can be achieved. If the apparent number of perfluoroalkyl compounds with respect to the fiber specific surface area of the fibers constituting the electret fiber sheet is less than 3 × 10 ¹³ / m ² , the density of the perfluoroalkyl compounds on the fiber surface becomes small, and the oil mist spreads. It cannot be suppressed and oil mist resistance is reduced. On the other hand, if the apparent number of perfluoroalkyl compounds with respect to the fiber specific surface area of the fibers constituting the electret fiber sheet exceeds 15 × 10 ¹³ / m ² , the density of the perfluoroalkyl compounds on the fiber surface increases and oil mist adheres. This makes it difficult to collect oil mist.

  The content of the perfluoroalkyl compound in the electret fiber sheet of the present invention is 0.1 to 5% by weight, preferably 0.5 to 2% by weight, based on the weight of the electret fiber sheet. By setting the content within this range, both high oil mist collecting performance and high oil mist resistance can be achieved. When the content is less than 0.1% by weight, the apparent number of perfluoroalkyl compounds with respect to the fiber specific surface area of the fibers constituting the electret fiber sheet becomes small, and the oil mist resistance is lowered. On the other hand, when the content exceeds 5% by weight, the apparent number of perfluoroalkyl compounds with respect to the specific fiber surface area of the fibers constituting the electret fiber sheet is increased, and the oil mist collecting performance is reduced or the spinnability is increased. Causes deterioration and cost increase.

  Examples of the method for adding a perfluoroalkyl compound to the electret fiber sheet in the present invention include a method of adding to a resin material that is a raw material of the fiber sheet, a method of adding after production of the fiber sheet or after electretization.

  Specifically, a resin material and a perfluoroalkyl compound are kneaded in advance with a kneading extruder, a static kneader, or the like to prepare a master chip, and an electret fiber sheet is produced using the master chip. A resin material and a perfluoroalkyl compound are mixed and supplied to a hopper, kneaded in an extruder, and directly supplied to a base part to produce an electret fiber sheet, or after production of a fiber sheet or after electretization treatment There is a method in which a perfluoroalkyl compound is attached to the fiber surface by impregnating or spraying an electret fiber sheet with a solution containing the perfluoroalkyl compound.

  Among these, since the method of adding after electretization of the fiber sheet may cause the disappearance of electric charge, the method of adding before electretization is preferable, and the fiber can be more easily manufactured from the point that the electret fiber sheet can be manufactured more easily. The method of adding to the resin material used as the raw material of the sheet is more preferable.

When a perfluoroalkyl compound is added by a method of adding to the resin material used as the raw material of the fiber sheet, heat treatment such as annealing is performed on the fiber sheet in order to further promote bleeding out of the perfluoroalkyl compound to the fiber surface. May be applied.
The annealing method is not particularly limited as long as bleed-out of the perfluoroalkyl compound to the fiber surface can be promoted. For example, for an electret fiber sheet made of polypropylene, the treatment temperature is 130 ° C. or less, preferably 120 It is good to set it as below ℃. When the processing temperature in annealing exceeds 130 ° C., significant charge disappearance in the electret fiber sheet is caused.

In addition to the perfluoroalkyl compound, additives generally used in electret fiber sheets, such as heat stabilizers, weathering agents, and polymerization inhibitors, can be added to the electret fiber sheet of the present invention.
The electret fiber sheet of the present invention may contain at least one hindered amine-based additive and / or triazine-based additive in the fiber material from the viewpoint of improving weather resistance and improving electret performance. preferable.

  Of the above two types of additives, examples of the hindered amine compound include 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)] (BASF Japan Ltd.) “Kimasorb” (registered trademark) 944LD), dimethyl-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate (BASF Japan) , “Tinuvin” (registered trademark) 622LD), and bis (1,2,2,6,6-6- (3,5-di-tert-butyl-4-hydroxybenzyl) -2-n-butylmalonate). Pentamethyl 4-piperidyl) (BASF Japan Ltd., "TINUVIN" (registered trademark) 144), and the like.

  Examples of the triazine-based additive include 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).

  Among these, it is preferable to use a hindered amine-based additive from the viewpoint of further improving electret performance, and in particular, 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 ]] (BASF Japan K.K., “Kimasorb” (registered trademark) 944LD) is preferably used.

  The total amount of the hindered amine additive and the triazine additive is preferably 0.5 to 5% by weight, more preferably 0.7 to 3% by weight, based on the weight of the electret fiber sheet. is there. By setting the addition amount within this range, it becomes easy to obtain a high collection characteristic for dust that is excellent when electretized.

  It is preferable that the average single fiber diameter of the fiber which comprises the electret fiber sheet of this invention is the range of 0.1-8 micrometers. An electret having excellent air permeability and dust collection performance by making the average single fiber diameter preferably 0.1 to 0.8 μm, more preferably 0.3 to 7 μm, and even more preferably 0.5 to 5 μm. A fiber sheet is easily obtained.

The basis weight of the electret fiber sheet of the present invention is preferably in the range of ^{3 to} 100 g / m2. When the basis weight is preferably 3 to 100 g / m ² , more preferably 5 to 70 g / m ² , and still more preferably 10 to 50 g / m ² , an electret fiber sheet excellent in air permeability and dust collection performance is obtained. It becomes easy to be done.

Hereinafter, the present invention will be described more specifically based on examples. Measuring methods such as physical properties are as follows.
(1) Fabric weight About fabric mass, the mass of the electret fiber sheet of length x width = 10 cm x 10 cm was measured about 1 sample. The obtained value was converted into a value per 1 m ² , and the basis weight (g / m ² ) of the electret fiber sheet was calculated by rounding off the first decimal place.
(2) Thickness For thickness, using a thickness meter ("TECLOCK" (registered trademark) SM-114 manufactured by Teclock Corporation), the thickness of the electret fiber sheet is measured at equal intervals in the width direction, and from the average value The thickness (mm) was calculated by rounding off the third decimal place.
(3) Average single fiber diameter About average single fiber diameter, ten arbitrary positions of an electret fiber sheet were image | photographed by 2000 times using the scanning electron microscope, and fiber diameter (single fiber diameter) was taken from the photographed image. ) Were measured, and the average single fiber diameter (μm) was calculated by rounding off the second decimal place from the average value.
(4) Fiber filling rate The fiber filling rate was calculated from the measured basis weight, thickness and specific gravity of the resin used by the following formula, and rounded off to the first decimal place to obtain the fiber filling rate (%).

Fiber filling rate (%) = (weight per unit area / (thickness × resin specific gravity)) × 100
(5) Fiber specific surface area The fiber surface area (fiber specific surface area) of the fibers constituting the electret fiber sheet per unit volume of the electret fiber sheet was calculated from the calculated average single fiber diameter and fiber filling rate according to the following formula. .

Fiber specific surface area (m ² / m ³ ) = 4 × (fiber filling rate / 100) / average single fiber diameter (6) Apparent number of perfluoroalkyl compound Apparent number of perfluoroalkyl compound with respect to fiber specific surface area of electret fiber sheet Was calculated from the calculated fiber specific surface area by the following equation.

Apparent number of perfluoroalkyl compounds (pieces / m ² )
= (Perfluoroalkyl compound-containing weight in electret fiber sheet /
Perfluoroalkyl compound number average molecular weight × 6.0 × 10 ²³ (Avogadro constant)) / fiber specific surface area (7) Collection efficiency For measurement of length × width = 15 cm × 15 cm at three locations in the length direction of the electret fiber sheet One sample was collected (three samples in total), and the collection efficiency of each sample was measured using the collection efficiency measurement device shown in FIG. In the collection efficiency measuring device of FIG. 1, a dust storage box 2 is connected to the upstream side of the sample holder 1 for setting the measurement sample M, and a flow meter 3, a flow rate adjusting valve 4 and a blower 5 are connected to the downstream side. ing. 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.

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 ), and the number of dusts D upstream of the measurement sample M and the number of dusts d downstream of the measurement sample M are set to 1 with a particle counter 6 (manufactured by Lion, KC-01D) Based on JIS K 0901 (1991) “Shape, size and performance test method of filter material for collecting dust sample in gas”, it was measured three times per measurement sample using the following formula. The collection efficiency (%) of 3-0.5 μm particles was determined. The average value of three measurement samples was calculated, and the final collection efficiency (%) was calculated by rounding off the second decimal place.

Collection efficiency (%) = [1- (d / D)] × 100
(However, d represents the total number of three times of downstream dust, and D represents the total number of three times of upstream dust.)
(8) Oil mist collection performance and oil mist resistance due to tobacco smoke load (cigarette smoke load)
In a 1 m ³ acrylic container, using a cigarette smoke absorber and method compliant with the JEMA standard (JEM1467 method), burn one “Mevius Original” tar 10 mg (manufactured by Nippon Tobacco Co., Ltd.) from Japan Tobacco Co., Ltd. The electret fiber sheet attached to the adapter having an effective ventilation diameter of φ135 mm was vented for 1 hour at an air volume of 1.3 m ³ / min. This was repeated 5 times for the same electret fiber sheet.

(Oil mist collection performance)
The oil mist adhesion weight (mg) was calculated from the electret fiber sheet weight before and after the tobacco smoke was loaded by the above method using the following formula, and the first decimal place was rounded off. It shows that oil mist collection performance is so high that oil mist adhesion weight is large.

Oil mist adhesion weight (mg) = Fiber sheet weight after tobacco smoke load-Fiber sheet weight before tobacco smoke load (oil mist resistance)
The collection efficiency after the tobacco smoke was loaded by the above method was measured by the method (6), and the collection efficiency retention rate was determined by the following equation. The higher the collection efficiency retention rate, the higher the oil mist resistance.

Collection efficiency retention rate (%) = (collection efficiency after tobacco smoke load / collection efficiency before tobacco smoke load) × 100
[Example 1]
1% by weight of “Megafac” (registered trademark) F-477 (manufactured by DIC Corporation)) and 1% by weight of hindered amine compound “Kimasorb” (registered trademark) 944 (manufactured by BASF Japan) Polypropylene having a melt flow rate of 850 g / 10 min was used.

The raw material is put into a raw material hopper of a spinning machine, and a nozzle (hole pitch: 1.6 mm, number of holes: 94 holes, width: 150 mm) in which discharge holes having a diameter of 0.4 mm and 0.6 mm are alternately arranged in a straight line. ) Using a melt-blowing method with a polymer discharge rate of 28.9 g / min, a nozzle temperature of 265 ° C., and an air pressure of 0.15 MPa, and by adjusting the collection conveyor speed, the basis weight is 25 g / m ² A meltblown nonwoven sheet was obtained. Then, while running along the water surface of the water tank to which pure water is supplied, the surface of the fiber sheet is infiltrated by sucking water by bringing a slit-like suction nozzle into contact with the surface, and after draining An electret fiber sheet was obtained by natural drying (hydrocharging).

  The obtained electret fiber sheet was loaded with tobacco smoke using the method (7), the collection efficiency before and after the tobacco smoke load was measured, and the collection efficiency retention rate was calculated. Table 1 shows the measured values and calculated values of the electret fiber sheet.

[Example 2]
An electret fiber sheet was obtained in the same manner as in Example 1 except that “Surflon” (registered trademark) S-651 (manufactured by AGC Seimi Chemical Co., Ltd.) was used as the raw material for the perfluoroalkyl compound.

  Each characteristic value was measured by the method similar to Example 1 about the obtained electret fiber sheet. The obtained results are shown in Table 1.

[Example 3]
The electretization method is the same as that of Example 2 except that the electretization method (corona discharge) is performed by applying a high voltage with a non-contact type application electrode while the fiber sheet is in contact with the ground electrode. An electret fiber sheet was obtained.

About the obtained electret fiber sheet, each characteristic value was measured by the method similar to Example 1. FIG. The obtained results are shown in Table 1.
[Example 4]
As a raw material, polypropylene having a melt flow rate of 850 g / 10 min containing 3% by weight of “Megafac” F-477 and 1% by weight of a hindered amine compound “Kimasorb” (registered trademark) 944 (manufactured by BASF Japan Ltd.) is used. An electret fiber sheet was obtained using the same method as in Example 1 except that it was used.

  Each characteristic value was measured by the method similar to Example 1 about the obtained electret fiber sheet. The obtained results are shown in Table 1.

[Comparative Example 1]
An electret fiber sheet was obtained by the same method as in Example 1 except that “Megafac” F-477 was not added to the polypropylene used in Example 1 as a raw material.

  Each characteristic value was measured by the method similar to Example 1 about the obtained electret fiber sheet. The obtained results are shown in Table 1.

[Comparative Example 2]
An electret fiber sheet was obtained in the same manner as in Example 1 except that “Megafac” (registered trademark) F-562 (manufactured by DIC Corporation) was used as the raw material for the perfluoroalkyl compound.

  Each characteristic value was measured by the method similar to Example 1 about the obtained electret fiber sheet. The obtained results are shown in Table 1.

[Comparative Example 3]
As a raw material, a polypropylene having a melt flow rate of 850 g / 10 min containing 4% by weight of “Megafac” F-477 and 1% by weight of a hindered amine compound “Kimasorb” (registered trademark) 944 (manufactured by BASF Japan Ltd.) is used. An electret fiber sheet was obtained using the same method as in Example 1 except that it was used.

  Each characteristic value was measured by the method similar to Example 1 about the obtained electret fiber sheet. The obtained results are shown in Table 1.

[Comparative Example 4]
An electret fiber sheet was obtained using the same method as in Example 3 except that “Surflon” (registered trademark) S-242 (manufactured by AGC Seimi Chemical Co., Ltd.) was used as the raw material for the perfluoroalkyl compound.

  Each characteristic value was measured by the method similar to Example 1 about the obtained electret fiber sheet. The obtained results are shown in Table 1.

As shown in Examples 1 to 4, the electret fiber sheet in which the apparent number of perfluoroalkyl compounds with respect to the fiber specific surface area of the fibers constituting the electret fiber sheet is 3 × 10 ¹³ to 15 × 10 ¹³ pieces / m ² is oil mist. It can be seen that both the collection performance and the oil mist resistance are excellent.

As shown in Comparative Examples 1 and 2, when the apparent number of perfluoroalkyl compounds with respect to the fiber specific surface area of the fibers constituting the electret fiber sheet is less than 3 × 10 ¹³ / m ² , the oil mist collecting performance is excellent, It turns out that it is inferior to oil mist property.

When the apparent number of perfluoroalkyl compounds with respect to the fiber specific surface area of the fibers constituting the electret fiber sheet exceeds 15 × 10 ¹³ / m ² as shown in Comparative Examples 3 to 4, the oil mist resistance is excellent, but the oil mist It turns out that it is inferior to collection performance.
As described above, the electret fiber sheet in which the apparent number of perfluoroalkyl compounds with respect to the fiber specific surface area of the fibers constituting the electret fiber sheet is 3 × 10 ¹³ to 15 × 10 ¹³ pieces / m ² is excellent in oil mist load. Both oil mist collecting performance and oil mist resistance were exhibited.

According to the present invention, an electret fiber sheet having both excellent oil mist collecting performance and oil mist resistance can be obtained. This electret fiber sheet is a dust mask, an air purifier, a cabin filter, an air conditioning element, etc. As a filter medium for various filters, it can be suitably used in an oil mist load environment such as tobacco smoke.

1: Sample holder 2: Dust storage box 3: Flow meter 4: Flow control valve 5: Blower 6: Particle counter 7: Switching cock M: Measurement sample

Claims (5)

An electret fiber sheet composed of non-conductive fibers containing a perfluoroalkyl compound, wherein the apparent number of perfluoroalkyl compounds with respect to the specific surface area of the fibers constituting the electret fiber sheet is 3 × 10 ¹³ to 15 × 10 An electret fiber sheet, wherein the number is ¹³ / m ² . The electret fiber sheet according to claim 1, wherein the content of the perfluoroalkyl compound contained in the electret fiber sheet is 0.1 to 5% by weight with respect to the weight of the electret fiber sheet. The electret fiber sheet according to any one of claims 1 to 2, wherein the non-conductive fiber constituting the electret fiber sheet is a polyolefin resin. The electret fiber sheet according to claim 3, wherein the polyolefin resin is polypropylene. The electret fiber sheet according to any one of claims 1 to 4, wherein the electret fiber sheet is a melt blown nonwoven fabric.

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