JP2008081894A - Electret fiber sheet and air filter using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fiber sheet low in pressure loss and high in collective performance as well, and in particular suitably usable as an air filter. <P>SOLUTION: The fiber sheet mainly includes electrically non-conductive fibers and includes 0.01-0.5 wt.% of a compound having a structure represented by general formula[1] (wherein, R<SB>1</SB>to R<SB>9</SB>are each H or a 1-3C alkyl). The fiber sheet is such a laminate fiber sheet having two or more fiber sheets laminated together, in which at least one fiber sheet layer is constituted of an electret fiber sheet. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electret fiber sheet. Particularly, the present invention relates to a high-performance electret fiber sheet that exhibits high collection and low pressure loss as an air filter.

  Conventionally, an air filter has been used to remove pollen, dust, and the like in a gas, and a fiber sheet is often used as a filter medium.

  The performance required for the air filter is “high collection” capable of collecting a large amount of micro dust, and “low pressure loss” with low resistance when gas passes through the air filter.

  The collection mechanism of the air filter is mainly due to physical actions such as Brownian diffusion, shielding, and inertial collision. Therefore, in order to obtain a filter medium having high collection performance, the fiber sheet to be configured must be fine. While suitable, on the other hand, the pressure loss is increased by increasing the fiber density in the sheet.

  Moreover, in order to obtain a filter medium with low pressure loss, it is suitable that the fiber sheet to be configured has a large fineness, but on the other hand, the gap between the fibers in the sheet is widened, so that the collection performance is reduced. .

In this way, “high collection” and “low pressure loss” are in a contradictory relationship, and as a method of solving this problem, the fiber sheet is electretized and used for physical action. In addition, attempts have been made to simultaneously satisfy high collection and low pressure loss by utilizing electrostatic action.
For example, Patent Document 1 states that “in a state where the fibrous sheet is in contact with the ground electrode, the ground electrode and the fiber sheet are moved together and a non-contact type application electrode is used to apply a high voltage to continuously electret. The manufacturing method of the electret fibrous sheet | seat characterized by making it into a "disclosed" is disclosed. This is to polarize the fiber sheet by injecting electrons, moving ions, or aligning dipoles, and imparting electric charge to the sheet. According to this method, high collection and low pressure loss can be achieved to some extent, but the electret charge amount is insufficient.

  Therefore, it has been proposed to add an additive to the fibers constituting the fiber sheet to increase the charge amount.

For example, Patent Document 2 states that “a material obtained by blending at least one selected from a hindered amine-based, nitrogen-containing hindered phenol-based, metal salt hindered phenol-based or phenol-based stabilizer into a polymer. And a heat-resistant electret material having a trap charge amount from a thermally stimulated depolarization current at 100 ° C. or higher of 2.0 × 10 ⁻¹⁰ coulomb / cm ² or more is disclosed.

Thus, although the balance of collection performance and pressure loss was improved by electretizing the fiber sheet containing the additive, it was not a sufficient level.
JP-A 61-289177 JP 63-280408 A

  In view of the background of such conventional technology, the present invention provides an electret fiber sheet that has low pressure loss and excellent collection performance, particularly an electret fiber sheet that can be suitably used for an air filter.

  The present invention employs the following means in order to solve such problems. That is, the electret fiber sheet of the present invention is an electret fiber sheet mainly containing non-conductive fibers, and the electret fiber sheet contains a compound having a structure represented by the following general formula [1]. It is a feature.

(Where R _{1 to} R ₉ are hydrogen or an alkyl group having 1 to 3 carbon atoms)
The preferable aspect of this electret fiber sheet is as follows. That is,
(1) When the compound having the structure represented by the general formula [1] is measured by the measurement method defined in the text, it is contained in the electret fiber sheet in an amount of 0.01 to 0.5% by weight. ,
(2) The non-conductive fiber is a polyolefin fiber,
(3) The polyolefin fiber is mainly composed of polypropylene,
(4) The electret fiber sheet is a melt blown nonwoven fabric,
(5) The electret fiber sheet is a nonwoven fabric mainly composed of ultrafine fibers,
(6) The basis weight of the electret fiber sheet is 0.1 to 80 g / m ² ;
(7) The electret fiber sheet is a laminate fiber sheet obtained by laminating two or more fiber sheets, and at least one layer thereof is composed of the electret fiber sheet according to any one of the preceding items;
It is.

  According to the present invention, it is possible to provide an electret fiber sheet that is low pressure loss and at the same time excellent in high collection. If such an electret fiber sheet is used, a high-performance air filter that exhibits high collection and low pressure loss can be provided.

  The present invention, as a result of intensive investigations on the above-described electret fiber sheet that has a low pressure loss and excellent collection performance, particularly an electret fiber sheet that can be suitably used for an air filter, The present inventors have investigated that this problem can be solved at once by adding a specific amount of a compound having a structure.

  The electret fiber sheet of the present invention is an electret fiber sheet mainly comprising non-conductive fibers and containing a compound having a structure represented by the general formula [1].

  If the electret fiber sheet of this invention contains a nonelectroconductive fiber, the kind will not be specifically limited, For example, a woven fabric, a knitted fabric, a nonwoven fabric etc. are mentioned. When used as an air filter, non-woven fabrics are preferred because of their excellent collection performance. Among them, high-performance filters are mainly melt-blown non-woven fabrics and ultrafine fibers because of their excellent physical properties due to their small fiber diameter. It is preferable that it is the nonwoven fabric comprised by this.

  Melt blown nonwoven fabrics are manufactured by the melt blown method, which is one of the nonwoven fabric manufacturing methods. In general, the thermoplastic polymer extruded from the spinneret is thinned into fibers by hot air jetting, and the self-bonding properties of the fibers are used. And forming it as a web. Compared to other nonwoven fabric manufacturing methods such as the spunbond method, a complicated process is not required, and fine fibers of several tens of μm to several μm or less can be easily obtained. Spinning conditions in the melt-blowing method include polymer discharge rate, nozzle temperature, air pressure, and the like. By optimizing these spinning conditions, a nonwoven fabric having a desired fiber diameter can be obtained.

  In addition, the nonwoven fabric mainly composed of ultrafine fibers is not particularly limited in its production method, but is described in, for example, an electrospinning method (for example, US Pat. No. 6,106,913 or JP-A-2002-249966). And a non-woven polymer composed of fibers that form a sea-island structure in which an easily soluble polymer is a sea component and a non-conductive polymer is an island component, and then the easily soluble polymer component of the nonwoven fabric is eluted with a solvent. (For example, the method described in Japanese Patent Application No. 2005-202560) or the like. The ultrafine fiber referred to here is one having an average fiber diameter of 50 to 800 nm. The average fiber diameter of the ultrafine fibers is a value determined by the following method. That is, 30 sample samples of 1 cm × 1 cm were collected from an arbitrary location of a nonwoven fabric mainly composed of ultrafine fibers, and the magnification was adjusted to 80000 times with a scanning electron microscope. Take a total of 30 images, one for each. Measure all fiber diameters in the photograph that can be clearly confirmed, and use the average value as the average fiber diameter. Compared with the melt blow method described above, the productivity is generally inferior and requires a complicated process, but it is possible to obtain ultrafine fibers that cannot be obtained by the usual melt blow method, and as a result, it has a low basis weight and excellent high collection. Fiber sheet can be obtained.

The nonconductive fiber referred to in the present invention is not particularly limited as long as it mainly includes fibers made of a nonconductive polymer. The non-conductivity here has a volume resistivity of preferably 10 ¹² · Ω · cm or more, and more preferably 10 ¹⁴ · Ω · cm or more. The volume resistivity here is measured according to ASTM D257.

  When such a fiber sheet is converted into an electret, a large amount of charge can be retained, and as a result, the collection performance is excellent and the pressure loss can be reduced.

  Examples of such nonconductive materials include polyolefins such as polyethylene and polypropylene, polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyester such as polylactic acid, polycarbonate, polystyrene, polyphenylene sulfide, fluorine-based resin, and These copolymers or mixtures can be mentioned. Among these, those mainly composed of polyolefin are preferable from the viewpoint of exhibiting electret performance, and among polyolefins, polypropylene is more preferable because of its excellent heat resistance. Further, other components may be copolymerized as long as the properties of the polymer are not impaired.

  The electret fiber sheet of the present invention is characterized in that the fiber constituting the sheet is an electret fiber sheet containing a compound having a structure represented by the general formula [1].

(Where R _{1 to} R ₉ are hydrogen or an alkyl group having 1 to 3 carbon atoms)
The filter performance is surprisingly improved by incorporating the compound having the specific structure represented by the general formula [1] into the fiber constituting the fiber sheet before electretization and then electretizing. To do.

Such a compound is not particularly limited as long as it is a compound having the above structure, but among R _{1 to} R ₉ of the general formula [1], R ₁ and R ₈ are methyl groups, R ₂ , R ₆ , A compound having a structure in which R ₇ and R ₉ are ethyl groups and the remaining three are hydrogen is preferable. The compound represented by the general formula [1] may be used alone or as a mixture of plural kinds. By making this compound exist in an electret fiber sheet, the charge imparted by electretization can be stabilized more effectively.

  The content of such a compound is 0.01 to 0.5% by weight of the fiber sheet. In the present invention, the content of the compound having the structure represented by the general formula [1] refers to a value obtained as follows.

After Soxhlet extraction of 2 g of fiber sheet with chloroform, HPLC fractionation is repeated for the extract, and the structure of each fraction is confirmed by ¹ H-NMR measurement. The weights of the fractions containing the compound are totaled to determine the ratio to the entire sheet, and this is the content of the compound having the structure represented by the general formula [1].

  When the content of the compound having the structure represented by the general formula [1] is less than 0.01% by weight, the collection performance is deteriorated. On the other hand, when the content of the compound exceeds 0.5% by weight, the spinnability is increased. Decreases. More preferably, it is 0.02 weight%-0.45 weight%, More preferably, it is 0.05 weight%-0.4 weight%.

  The electret fiber sheet of the present invention contains a conductive polymer containing a compound as described above, but the polymer is usually an antioxidant, a light stabilizer, a heat stabilizer, etc. in addition to the compound as described above. The stabilizer contained in the resin material may be included.

  Furthermore, the electret fiber sheet of the present invention is electretized. If an electret fiber sheet is used, a further low pressure loss and high collection performance can be obtained due to the electrostatic adsorption effect.

In addition, the pressure loss and collection performance in this invention say the value calculated | required with the following method. Samples for measurement of 15 cm × 15 cm were collected at 10 positions in the longitudinal direction of the fiber sheet, and each sample was measured with a collection performance measuring apparatus shown in FIG. In this collection performance measuring apparatus, 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 for 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 the static pressure difference between the upstream and downstream of the sample M. In measuring the collection performance, polystyrene 0.309U 10% solution (manufacturer: Nacalai Tech) is diluted 200 times with distilled water and filled in the dust storage box 2. Next, the sample M is set in the holder 1, and the air volume is adjusted by the flow rate adjusting valve 4 so that the filter passing speed is 1.5 m / min, and the dust concentration is 10,000 to 40,000 pieces / 2.83 × 10 ^{−. 4} m ³ (0.01 ft ³ ) was stabilized, and the number of dusts D upstream of the sample M and the number of dusts d downstream were measured 10 times per sample with a particle counter 6 (manufactured by Lion, KC-01B). Based on JIS K-0901, the collection performance (%) of 0.3 to 0.5 μm particles was determined by the following formula. The average value of 10 samples was taken as the final collection performance.
Collection performance (%) = [1- (d / D)] × 100
However,
d: 10 times measurement total number of downstream dusts D: 10 times measurement total number of upstream dusts.

  Further, the pressure loss was obtained by reading the static pressure difference between the upstream and downstream of the sample M when measuring the collection performance with the pressure gauge 8. The average value of 10 samples was taken as the final pressure loss.

Further, a QF value is known as an index of filtration performance, and is calculated by the following formula using the collection performance and pressure loss. The lower the pressure loss and the higher the collection performance, the higher the QF value, indicating better filtration performance.
QF value (Pa ⁻¹ ) = − [ln (1- [collecting performance (%)] / 100)] / [pressure loss (Pa)]
The electretization method is not particularly limited, but a corona charging method or a method of electretization by applying water to a non-woven fabric sheet and drying it (for example, JP 9-501604 A, JP 2002-249978 A). The method described in Japanese Patent Publication No. Gazette etc. is preferably used. In the case of the corona charging method, an electric field strength of 15 kV / cm or more, preferably 20 kV / cm or more is suitable.

  Moreover, it is preferable that at least 1 type chosen from the group which consists of a hindered amine type compound and a triazine type compound is contained in the fiber sheet of this invention from a viewpoint of improving a weather resistance and improving electret performance.

  Examples of hindered amine compounds include poly [(6- (1,1,3,3-tetramethylbutyl) imino-1,3,5-triazine-2,4-diyl) ((2,2,6,6-6- Tetramethyl-4-piperidyl) imino) hexamethylene ((2,2,6,6-tetramethyl-4-piperidyl) imino)] (manufactured by Ciba Geigy, Chima Soap 944LD), dimethyl-1- (2-hydroxyethyl succinate) ) -4-Hydroxy-2,2,6,6-tetramethylpiperidine polycondensate (manufactured by Ciba Specialty Chemicals, Tinuvin 622LD), 2- (3,5-di-t-butyl-4-hydroxybenzyl) 2-n-butyl malonate bis (1,2,2,6,6-pentamethyl-4-piperidyl) (manufactured by Ciba Specialty Chemicals, Tinuvin 144), etc. And the like.

  As the triazine-based additive, 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 Ciba Specialty Chemicals, Chima Soap 944LD), 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-((hexyl) oxy) -phenol (manufactured by Ciba Specialty Chemicals, Tinuvin 1577FF). Among these, hindered amine compounds are particularly preferable.

  Although content of a hindered amine type compound or a triazine type compound is not specifically limited, It is preferable that it is the range of 0.5-5 weight%, and it is more preferable that it is the range of 0.7-3 weight%. The amount of the hindered amine-based additive or triazine-based additive is not particularly limited, but is preferably in the range of 0.5 to 5% by weight, more preferably in the range of 0.7 to 3% by weight. Good. If the addition amount is less than 0.5% by weight, it is difficult to obtain the desired high level electret performance. Moreover, when it mix | blends so much that it exceeds 5 weight%, it becomes unpreferable since it will worsen the yarn-making property and will also become disadvantageous also in cost.

Moreover, it is preferable that the fabric weight of the electret fiber sheet of this invention is 0.1-80 g / m < ² >. In particular, if the fiber sheet of meltblown nonwoven fabric is preferably 80 g / ^{m 2,} more preferably 1~70g / ^{m 2,} more preferably from 1~60g / ^{m 2.} Moreover, when the fiber sheet is a non-woven fabric mainly composed of ultrafine fibers, a high filter performance can be obtained with a low basis weight, and therefore it is preferably 0.1 to 15 g / m ² . More preferably, it is 0.1-10 g / m < ² >.

  Furthermore, the electret fiber sheet of the present invention may be laminated with other sheets to form a laminate fiber sheet. For example, a fiber sheet and a sheet having higher rigidity may be laminated to improve product strength, or may be used in combination with a sheet having functionalities such as deodorization and antibacterial properties.

  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 compound and a resin material having a structure represented by the general formula [1] as described above are prepared. Next, after kneading the compound and the resin material, the compound is extruded from an extruder and processed into a desired structure such as a fiber, a fiber web, or a nonwoven fabric. As a method of kneading the compound and the resin material, they are mixed and supplied to the extruder hopper of the spinning machine, kneaded in the extruder, and directly fed to the die, or the compound and the resin material are kneaded in advance. There is a method in which a master chip is prepared by kneading with an extruder or a static kneader, and this is melted in the extruder and supplied to the die part.

  Subsequently, a fiber sheet is formed by a conventional method using fibers. For example, when a fiber sheet consists of a woven fabric or a knitted fabric, it can be manufactured by forming a yarn using the fibers 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 ultrafine fibers can be produced by an electrostatic spinning method or a method of eluting sea portions of sea-island fibers.

  Next, the fiber sheet is subjected to electret treatment by a conventional method to obtain 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.

  The electret fiber sheet of the present invention can be used as a filter medium. The filter medium is suitable for high-performance applications such as air filters in general, air-conditioning filters, air cleaner filters, and automobile cabin filters, but the application range is not limited thereto.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated more concretely, it is not limited to these Examples. The characteristic values used in the examples are measured by the following measuring method.

(1) Weight per unit area The weight of a 15 cm × 15 cm sheet was measured, and the obtained value was converted to a value per 1 m ² to obtain a basis weight (g / m ² ).

(2) Average fiber diameter 30 sample samples of 1 cm × 1 cm were collected from any location on the fiber sheet, the magnification was adjusted with a scanning electron microscope, and each fiber surface photograph was taken from the sample collected, A total of 30 pictures were taken. The magnification was 2000 times when the fiber sheet was a melt blown nonwoven fabric and 80000 times when the fiber sheet was an ultrafine fiber nonwoven fabric. All of the photographs in which the fiber diameter was clearly confirmed were measured, and the average value was taken as the average fiber diameter.

(3) Collection performance, pressure loss 15 cm × 15 cm measurement samples were collected at 10 positions in the longitudinal direction of the fiber sheet, and each sample was measured with the collection performance measuring apparatus shown in FIG. In this collection performance measuring apparatus, 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 for 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 the static pressure difference between the upstream and downstream of the sample M. In measuring the collection performance, polystyrene 0.309U 10% solution (manufacturer: Nacalai Tech) is diluted 200 times with distilled water and filled in the dust storage box 2. Next, the sample M is set in the holder 1, and the air volume is adjusted by the flow rate adjusting valve 4 so that the filter passing speed is 1.5 m / min, and the dust concentration is 10,000 to 40,000 pieces / 2.83 × 10 ^{−. 4} m ³ (0.01 ft ³ ) was stabilized, and the number of dusts D upstream of the sample M and the number of dusts d downstream were measured 10 times per sample with a particle counter 6 (manufactured by Lion, KC-01B). Based on JIS K-0901, the collection performance (%) of 0.3 to 0.5 μm particles was determined by the following formula. The average value of 10 samples was taken as the final collection performance.
Collection performance (%) = [1- (d / D)] × 100
However,
d: Total number of 10 times measurement of downstream dust D: Total number of 10 times measurement of upstream dust Further, the pressure loss was obtained by reading the static pressure difference between the upstream and downstream of the sample M at the time of collecting performance measurement with a pressure gauge 8. The average value of 10 samples was taken as the final pressure loss.

(4) QF value The QF value that serves as an index of filtration performance is calculated by the following formula using the collection performance and pressure loss. The lower the pressure loss and the higher the collection performance, the higher the QF value, indicating better filtration performance.
QF value (Pa ⁻¹ ) = − [ln (1- [collecting performance (%)] / 100)] / [pressure loss (Pa)]
(5) Compound content in fiber sheet The content of the compound having the structure represented by the general formula [1] contained in the fiber sheet was determined as follows.

After Soxhlet extraction of 2 g of the fiber sheet sample with chloroform, HPLC fractionation was repeated for the extract, and the structure of each fraction was confirmed by ¹ H-NMR measurement. The weights of the fractions containing the compound were totaled to determine the ratio to the entire sheet, and this was defined as the compound content in the fiber sheet.

Example 1
As a raw material, polypropylene (MFR = 800, Kimasorb 944 (manufactured by Ciba Specialty Chemicals) was added by 1% by weight) was used. Compound A (produced by the method described in JP-T-2003-534347, structural formula Is added to the raw material hopper of the spinning machine by adding 0.2% by weight of the formula [2], and a nozzle having a 0.4 mm diameter discharge hole arranged in a straight line (hole pitch: 1 mm, number of holes) 155 holes, width: 150 mm) using a melt-blowing method, the polymer discharge rate is 40 g / min, the nozzle temperature is 230 ° C., the air pressure is 0.05 MPa, and the basis weight is adjusted by adjusting the collection conveyor speed. A nonwoven sheet of 30 g / m ² was obtained.

  While the obtained non-woven sheet is run along the water surface of the water tank to which the reverse osmosis membrane filtered water is supplied, the slit-like suction nozzle is brought into contact with the surface to suck water and then drains. Later, it was hot-air dried at 80 ° C. for 20 minutes to obtain an electret melt blown nonwoven fabric. The characteristic values of this electret meltblown nonwoven fabric were measured and are shown in Table 1.

Example 2
0.2% by weight of compound A is added to polypropylene (MFR = 50, 1% by weight of Kimasorb 944 (manufactured by Ciba Specialty Chemicals)) and kneaded to prepare a master chip. This chip and polylactic acid (melted) A viscosity of 350 Pa · s / 230 ° C. and a shear rate of 121.6 sec ⁻¹ ) were kneaded at 230 ° C. at a blend ratio of 8/2 by a biaxial extrusion kneader to obtain a polymer alloy chip.

Using this chip, the same die as in Example 1 is used, and the spraying is performed under the conditions of a polymer discharge rate of 40 g / min, a nozzle temperature of 230 ° C., and an air pressure of 0.03 MPa by the melt blow method to adjust the collection conveyor speed. As a result, a nonwoven fabric having a basis weight of 15 g / m ² was obtained.

Next, this non-woven fabric was subjected to alkali treatment to elute the polylactic acid component to obtain a non-woven fabric having a basis weight of 3 g / m ² .

  The obtained nonwoven fabric was subjected to electret treatment with an applied voltage of 25 kV / cm by a corona charging method to obtain an electret nonwoven fabric. The characteristic values of this electret nonwoven were measured and are shown in Table 1.

Comparative Example 1
As the raw material, the same raw material as in Example 1 was used, Compound A was not added thereto, and it was charged into the raw material hopper of the spinning machine. The same nozzle as in Example 1 was used, and the polymer discharge rate was 40 g / min by the melt blow method. A nonwoven fabric sheet having a basis weight of 30 g / m ² was obtained by spraying under conditions of a nozzle temperature of 280 ° C. and an air pressure of 0.06 MPa and adjusting the collection conveyor speed.

  The obtained nonwoven sheet was electret-treated in the same manner as in Example 1, and the characteristic values were measured and shown in Table 1.

Comparative Example 2
A polymer alloy tip was prepared in the same manner as in Example 2 except that Compound A was not used. Using this tip, the same nozzle as in Example 1 was used, and a polymer discharge rate of 40 g / min. A nonwoven fabric having a basis weight of 15 g / m ² was obtained by spraying under conditions of a temperature of 210 ° C. and an air pressure of 0.03 MPa and adjusting the collection conveyor speed.

Next, this non-woven fabric was subjected to alkali treatment to elute the polylactic acid component to obtain a non-woven fabric having a basis weight of 3 g / m ² .
The obtained nonwoven fabric was electret-treated in the same manner as in Example 2, and the characteristic values were measured and shown in Table 1.

  For Example 1 and Comparative Example 1 in which the fiber sheet type is a meltblown nonwoven fabric, in Example 1 containing the compound having the structure represented by the general formula [1] (compound of the formula [2]), the low pressure It showed high collection performance while having a loss, and as a result showed a high QF value. On the other hand, in Comparative Example 1 that does not contain the compound having the structure represented by the general formula [1], the basis weight, average fiber diameter, and pressure loss were the same as those in Example 1, but the collection performance was As a result, the QF value was also low.

  Further, with respect to Example 2 and Comparative Example 2 in which the fiber sheet type is a nonwoven fabric mainly composed of ultrafine fibers, Example 2 containing a compound having a structure represented by the general formula [1] has a low pressure loss. It showed a high collection performance while having a high QF value as a result. On the other hand, in Comparative Example 2 that does not contain the compound having the structure represented by the general formula [1], the basis weight, average fiber diameter, and pressure loss were the same as those in Example 2, but the collection performance was As a result, the QF value was also low.

  As described above, the electret fiber sheet containing the compound having the structure represented by the general formula [1] satisfies both low pressure loss and high collection at the same time.

  According to the present invention, a fiber sheet having a low pressure loss and high collection performance can be obtained. This fiber sheet can be preferably used as an air filter as a filter medium, but its application range is not limited thereto.

It is the schematic which shows the measuring apparatus of collection performance and a pressure loss.

Explanation of symbols

1: Holder 2: Dust storage box 3: Flow meter 4: Flow control valve 5: Blower 6: Particle counter 7: Switching cock 8: Pressure gauge M: Measurement sample

Claims (9)

An electret fiber sheet mainly comprising non-conductive fibers, wherein the electret fiber sheet contains a compound having a structure represented by the following general formula [1].

(Where R _{1 to} R ₉ are hydrogen or an alkyl group having 1 to 3 carbon atoms) The electret fiber sheet according to claim 1, wherein the compound having the structure represented by the general formula [1] is contained in the electret fiber sheet in an amount of 0.01 to 0.5 wt%. . The electret fiber sheet according to claim 1 or 2, wherein the non-conductive fibers are polyolefin fibers. The electret fiber sheet according to claim 3, wherein the polyolefin fiber is mainly composed of polypropylene. It is a melt blown nonwoven fabric, The electret fiber sheet in any one of Claims 1-4 characterized by the above-mentioned. The electret fiber sheet according to any one of claims 1 to 5, wherein the electret fiber sheet is a nonwoven fabric mainly composed of ultrafine fibers. Electret fiber sheet according to claim 1, basis weight is characterized by a 0.1~80g / ^{m 2.} It is a laminated fiber sheet formed by laminating two or more fiber sheets, and at least one layer thereof is composed of the electret fiber sheet according to any one of claims 1 to 7. Sheet. It is comprised with the electret fiber sheet in any one of Claims 1-8, The air filter characterized by the above-mentioned.

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