WO2018062237A1

WO2018062237A1 - Device for manufacturing electret processed article and method for electret conversion of a nonconductive sheet

Info

Publication number: WO2018062237A1
Application number: PCT/JP2017/034889
Authority: WO
Inventors: 実紀河井; 洪林金; 稔千田
Original assignee: タピルス株式会社
Priority date: 2016-09-30
Filing date: 2017-09-27
Publication date: 2018-04-05
Also published as: CN109790670A; KR102389599B1; KR20190053959A; JP6842022B2; CN109790670B; JPWO2018062237A1

Abstract

A device for manufacturing an electret processed article, which is a device that converts a nonconductive sheet into an electret and manufactures an electret processed article, has a mesh-like conveyor (2) for transporting a nonconductive sheet (S), a means (3) for imparting band-shaped water to the sheet (S), and a suction nozzle (4) for sucking the imparted water from the opposite side of the sheet (S). The water imparting means (3) comprises a slide surface (31) for making water flow down in a band shape, a tank (32) provided on the upstream side of the slide surface (31), and a water supply unit for supplying the water to the tank (32), and supplies band-shaped water uniform in the direction of the width of the sheet (s) by making water overflowing from the tank (32) flow down the slide surface (31).

Description

Electret processed product manufacturing apparatus and method for electretizing non-conductive sheet

The present invention relates to an apparatus for producing a high-quality electret processed product by a simple method and a method for electretizing a non-conductive sheet using the apparatus.

Conventionally, electret fiber sheets have been used as air filters and mask filters with low pressure loss and high collection performance. As a method for electretization, a method is known in which a high voltage is applied to a nonconductive fiber sheet and electretization is performed by corona discharge. However, in the method using corona discharge, if the voltage is increased too much in order to increase the amount of charge, there is a problem in that spark discharge occurs between the high voltage electrode and the ground electrode and the sheet is damaged. Further, in this method, charges are accumulated only in the surface layer portion of the sheet, that is, the portion exposed to corona ions. Then, due to the repulsive electric field formed by the accumulated charges, corona ions cannot penetrate into the sheet, and as a result, there is a disadvantage that the sheet is not sufficiently charged.

Another method for electretizing a fiber sheet is a method using frictional charging by a fluid. No. 9-501604 and No. 11-510862 use a water jet device to impinge a jet of water or a drop of water against the web at a pressure sufficient to provide a filtration-enhancing electret charge. Discloses a method for electretizing a web.

However, the method described in JP-A-9-501604 and JP-A-11-510862 for causing water to collide with the web requires additional equipment such as a compressor, which is expensive to install and operate. . In addition, since it is necessary to apply sufficient pressure to electretize the sheet, when applied to a nonwoven fabric with low basis weight and low strength, the texture changes due to the trace of water flow remaining on the nonwoven fabric, and the expected performance There is a problem that it cannot be expressed. Further, in the method of applying water from the nozzle as in the water jet device, periodic cleaning is necessary to avoid clogging of the nozzle, and the maintenance becomes complicated.

Japanese Patent Application Laid-Open No. 2002-249978 applies water discharged from a slit-shaped discharge port in the form of a film on the surface of a traveling non-conductive sheet and sucks the applied water by a suction device disposed on the lower surface side of the non-conductive sheet. Then, after passing through the lower surface side and making the entire front and back surfaces of the non-conductive sheet infiltrated, excess water is removed with a nip roll and dried to produce an electret sheet.

However, in the method described in Japanese Patent Application Laid-Open No. 2002-249978, water is discharged from the slit-shaped discharge port in order to apply water in a film shape to the surface of the conductive sheet. When clogged, water may not spread uniformly in the form of a film, and electretization of the sheet may become uneven. In addition, when electrifying a wider sheet, it is necessary to feed liquid at a high pressure in order to uniformly discharge water from the slit-like discharge port, and the apparatus becomes large. Furthermore, since the suction device arranged on the lower surface side of the non-conductive sheet is in direct contact with the non-conductive sheet, the sheet may be damaged by rubbing the suction device against the non-conductive sheet, and the quality may be deteriorated. In particular, in the case of a weak fiber sheet with a low basis weight or filling rate, it may be damaged.

Therefore, the object of the present invention is to supply a band of water to one surface of the nonconductive sheet by a simple method in the method of electretizing the nonconductive sheet by passing water through the nonconductive sheet. And it is providing the manufacturing apparatus of the electret processed goods which can attract | suck water from the other surface, without reducing the quality of a nonelectroconductive sheet, and the manufacturing method of an electret processed goods using the same.

As a result of diligent research in view of the above object, the present inventors have supplied water to one surface of a non-conductive sheet by means of water applying means having a slide surface for allowing water to flow down in a strip shape, and a non-conductive sheet. By placing a suction nozzle for sucking water on the back surface of the mesh-like conveyor placed on the mesh-like conveyor, a non-conductive sheet can be electreted without causing a deterioration in quality by a simple method. As a result, the present invention was conceived.

That is, the manufacturing apparatus of the present invention
An apparatus for producing an electret processed product by electretizing a non-conductive sheet,
A mesh-like conveyor for placing the non-conductive sheet and conveying it horizontally;
Water application means for applying band-like water to the non-conductive sheet placed on the conveyor;
A suction nozzle disposed on the back side of the conveyor, for sucking the applied water from the opposite side of the non-conductive sheet;
The water applying means comprises a slide surface for allowing water to flow down in a strip shape, a tank provided on the upstream side of the slide surface, and a water supply unit for supplying water to the tank,
Water that has overflowed from the tank is caused to flow down to the slide surface, whereby uniform strip-shaped water is supplied in the width direction of the non-conductive sheet.

It is preferable that the slide surface has an inclination angle of 45 to 75 ° with respect to the non-conductive sheet.

It is preferable that guides for controlling the width of water flowing down are provided at both ends of the slide surface.

The method of the present invention for electretizing a non-conductive sheet is:
While transporting the non-conductive sheet placed on the mesh-shaped conveyor, the water that flows down the slide surface in a strip shape is supplied to the non-conductive sheet, or at the same time as the water is supplied, the surface opposite to the side on which the water is supplied By sucking the supplied water by a suction nozzle disposed in the water, water is passed through the non-conductive sheet, and then the sheet is dried.

The non-conductive sheet preferably contains 0.5 to 5% by weight of a hindered amine additive or a triazine additive.

The non-conductive sheet is preferably a sheet made of synthetic fiber. The synthetic fiber sheet is preferably a melt blown nonwoven fabric.

The non-conductive sheet is preferably composed mainly of polyolefin. The polyolefin is preferably composed mainly of polypropylene.

The water may contain a water-soluble organic solvent. The water-soluble organic solvent preferably has a lower boiling point than water.

The water-soluble organic solvent is preferably composed mainly of alcohols or ketones. The water-soluble organic solvent is preferably at least one of isopropyl alcohol, ethyl alcohol, and acetone.

In the method of electretizing the non-conductive sheet, the non-conductive sheet may be electretized in advance by corona charging.

Since the production apparatus of the present invention enables the production of high-quality and high-performance electret fiber sheets by a simple method, in particular, even fiber sheets such as weak non-woven fabric with a low basis weight and filling rate, Electretization is possible at a low cost without causing quality degradation such as breakage.

It is a front view which shows the manufacturing apparatus of the electret processed goods of this invention. It is a side view which shows the manufacturing apparatus of the electret processed goods of this invention. It is a perspective view which shows the principal part of the manufacturing apparatus of the electret processed goods of this invention. FIG. 3 is a perspective view in which a non-conductive sheet to be conveyed is added to FIG. It is a schematic diagram which expands and shows the water provision means and suction nozzle of the manufacturing apparatus of the electret processed goods of this invention. It is a schematic diagram which shows an example of the water supply part of the manufacturing apparatus of the electret processed goods of this invention. It is a schematic diagram which shows another example of the water supply part of the manufacturing apparatus of the electret processed goods of this invention. It is a schematic diagram which shows another example of the water supply part of the manufacturing apparatus of the electret processed goods of this invention.

[1] Electret processed product manufacturing apparatus The electret processed product manufacturing apparatus of the present invention is an apparatus for producing an electret processed product by electretizing a non-conductive sheet,
A mesh-like conveyor for placing the non-conductive sheet and conveying it horizontally;
Water application means for applying band-like water to the non-conductive sheet placed on the conveyor;
A suction nozzle disposed on the back side of the conveyor, for sucking the applied water from the opposite side of the non-conductive sheet;
The water applying means comprises a slide surface for allowing water to flow down in a strip shape, a tank provided on the upstream side of the slide surface, and a water supply unit for supplying water to the tank,
Water that has overflowed from the tank is caused to flow down to the slide surface, whereby uniform strip-shaped water is supplied in the width direction of the non-conductive sheet.

Fig. 1, Fig. 2 and Fig. 3 show a front view, a side view, and a perspective view of an electret processed product manufacturing apparatus, respectively. Further, FIG. 4 is a perspective view showing a state in which the non-conductive sheet is conveyed to the electret processed product manufacturing apparatus. The electret processed product manufacturing apparatus 1 includes a mesh-like conveyor 2 for placing a non-conductive sheet S and transporting it in a horizontal direction, and a non-conductive sheet S placed on the conveyor 2 with strip-shaped water. Water application means 3 for applying, and a suction nozzle 4 disposed on the back side of the conveyor 2 for sucking the applied water from the opposite side of the non-conductive sheet S.

The conveyor 2 is supported by three support rolls 51, 52, and 53. The support roll 51 is driven by the power of the motor 6, and the conveyor 2 moves from right to left in FIGS. 1 and 2 (FIG. 4). The non-conductive sheet S is conveyed by moving from the upper right to the lower left. The method for supporting and driving the conveyor is not limited to the one described in FIGS. 1 and 2, and can be changed as appropriate.

The water applying means 3 includes a slide surface 31 for allowing water to flow down in a strip shape, a tank 32 provided on the upstream side of the slide surface 31, a water supply unit 33 for supplying water to the tank 32, and a use A drain hole 34 for draining the water of the tank 32 later, and the edge of the upper portion of the slide surface 31 so that the water supplied to the tank 32 overflows from the upper portion of the slide surface 31 and flows down the slide surface 31. 31a is made one step lower than the other edges. The edge 31a is horizontally provided so that water flows uniformly in the width direction of the slide surface 31. The slide surface 31 is provided with

guides

35, 35 on both sides in the flow direction so that the water flowing out from the edge 31a of the tank 32 flows down with a certain width. The water flowing down the slide surface 31 is applied (applied) in a strip shape (film shape) onto the non-conductive sheet S conveyed by the conveyor 2 from the lower portion of the slide surface 31.

As shown in FIG. 5, the tank 32 includes a first tank 32a provided with a water supply unit 33, and a second tank for temporarily storing water overflowed from the first tank 32a and flowing it down to the slide surface 31. And a tank 32b. The second tank 32b is, in order from the first tank 32a side, a first baffle 35a provided in the substantially lower half of the second tank 32b and a first baffle provided in the substantially upper half of the second tank 32b. Second baffle 35b. The water flowing into the second tank 32b from the first tank 32a is rectified by the first baffle 35a and the second baffle 35b provided in the second tank 32b, and overflows from the edge 31a at the upper part of the slide surface 31. Then the slide surface 31 flows down.

If the water in the tank needs to be further rectified, it may be adjusted by increasing the number of baffles or adding a mechanism that can change the height of the baffles. In addition, a wire bar used in a fine adjustment plate, a coating machine, or the like may be installed inside or outside the edge 31a, and adjustment may be made so that water is evenly applied in the width direction.

The water supply unit 33 may be provided by connecting a pipe directly to the side surface of the first tank 32a as shown in FIG.6 (a), or a large number of holes as shown in FIG.6 (b). It may be configured by a provided pipe portion 33a and a supply pipe 33b provided at an end thereof. The position where the supply pipe 33b is provided may be the center of the pipe portion 33a as shown in FIG. 6 (c). In the case of electretizing a wide non-conductive sheet, since there may be unevenness in the supply of water in the width direction, the configuration as shown in FIG. 6 (c) is preferable.

The slide surface 31, the tank 32, and the guide 35 that constitute the water applying means 3 are made of a material that can maintain strength and accuracy. For example, materials such as metal, glass, ceramics, and plastic are preferable. In particular, the slide surface 31 is preferably formed of a material with good wettability in order to allow water to spread uniformly in the width direction and spread on the non-conductive sheet S in a uniform band shape. Examples of materials having good wettability include materials obtained by hydrophilizing the surfaces of metals, glass, ceramics, plastics, and the like, and materials obtained by coating those surfaces with hydrophilic materials. The slide surface 31 preferably has an inclination angle of 45 to 75 °. If the tilt angle is less than 45 °, the water flow is weak and the water volume tends to be uneven in the width direction. Further, since the tank 32 becomes shallow, it is necessary to increase the bottom area of the water application portion in order to maintain a certain amount of water, and the apparatus becomes large. If the inclination angle is greater than 75 °, the supplied water has a strong momentum and may damage the non-conductive sheet. In addition, since the amount of water splash increases and cannot be sufficiently sucked by the slits, moisture remaining on the non-conductive sheet increases, and extra energy is required for drying.

The water (in a film form) applied to the non-conductive sheet S is a surface (upper surface) to which the water of the non-conductive sheet S is applied immediately after the application or after a certain time has elapsed after the application. By being sucked by the suction force of the suction nozzle 4 from the opposite surface (back surface), the non-conductive sheet S passes from the upper surface to the back surface, and in this process, the non-conductive sheet S is electretized. The suction nozzle 4 has a slit 41 that is substantially the same width as the non-conductive sheet S and is provided in a direction perpendicular to the conveying direction of the non-conductive sheet S. Water is sucked by the slit 41. In the figure, one suction nozzle 4 having three

slits

41a, 41b, 41c is arranged, but the number of slits is not particularly limited, and the suction nozzle 4 is set to 2 in the conveyance direction of the non-conductive sheet S. Two or more may be arranged side by side.

The amount of water applied (the amount supplied per unit area of the nonconductive sheet S) can be adjusted by the amount of water supplied by the water applying means 3 and the conveyance speed of the nonconductive sheet S. The time from application to suction is determined by the distance from the position of the slide surface 31 of the water application means 3 to the position of the suction nozzle 4 and the conveyance speed of the non-conductive sheet S. The distance from the position of the slide surface 31 to the position of the suction nozzle can be changed by selecting which slit among the plurality of slits provided in the suction nozzle 4 is used for suction. Further, the distance may be changed by shifting the position of the suction nozzle 4. The amount of water sucked by the suction nozzle 4 is preferably adjusted by measuring the amount of water supplied to the tank 32 with a flow meter and feeding back the value.

By using the water applying means 3 comprising the slide surface 31, the tank 32 and the guide 35 in this way, it is simpler than a method using a conventional water jet device or a method of supplying water from a slit-like discharge port. Since a large amount of water can be supplied uniformly, sufficient water can be passed through the nonconductive sheet without deteriorating the quality of the nonconductive sheet. For this reason, according to the present invention, a high-quality and high-performance electret processed product can be manufactured at low cost.

[2] Method for electretizing a non-conductive sheet The method of the present invention for electretizing a non-conductive sheet includes:
While transporting the non-conductive sheet placed on the mesh-shaped conveyor, the water that flows down the slide surface in a strip shape is supplied to the non-conductive sheet, or at the same time as the water is supplied, the surface opposite to the side on which the water is supplied By sucking the supplied water by a suction nozzle disposed in the water, water is passed through the non-conductive sheet, and then the sheet is dried.

As described above, the electretization of the non-conductive sheet is performed by supplying water to one surface of the non-conductive sheet (hereinafter sometimes simply referred to as “sheet”) and using the water as the other side of the non-conductive sheet. The sheet is then passed through and then the sheet is dried. It is preferable to uniformly supply and pass water through the non-conductive sheet. For that purpose, it is important to apply water so as to form a uniform film surface on the non-conductive sheet. In order to apply water so as to form a uniform film surface in this way, the apparatus for manufacturing an electret processed product according to the present invention is used to supply water that flows in a strip shape on the non-conductive sheet while supplying water. This is possible by conveying the conductive sheet.

(1) Supply of water The supply amount of water is not particularly limited, but is preferably 0.05 g / cm ² or more, and more preferably 0.1 g / cm ² or more. If the amount of water supplied is less than 0.05 g / cm ² , sufficient charging effect may not be obtained. The upper limit of the amount of water supplied is not particularly limited, but is preferably usually 1 g / cm ² or less, more preferably 0.5 g / cm ² or less. If the amount of water supply exceeds 1 g / cm ² , the amount of water remaining on the non-conductive sheet will increase, so it will be necessary to increase the capacity of the suction pump, and the energy load for drying in the subsequent process will increase. End up.

The water supplied to one surface of the non-conductive sheet is linearly formed in the width direction of the non-conductive sheet from the other surface of the non-conductive sheet simultaneously with the supply or after a lapse of a certain time from the supply. Water is passed from one surface of the non-conductive sheet to the other surface by being sucked by the suction nozzle. Since the suction nozzle is disposed so as to suck water from the other surface of the non-conductive sheet via the mesh-shaped conveyor, the suction nozzle does not directly contact the non-conductive sheet. Therefore, there is no possibility that the non-conductive sheet is damaged by rubbing the suction device against the non-conductive sheet, and the quality is not lowered.

The elapsed time from when water is supplied to one surface until suction is set can be set by moving the suction nozzle from the location where the water is supplied in the conveying direction of the non-conductive sheet. For example, when a suction nozzle is disposed directly below the water supply location, the elapsed time from when the water is sucked and sucked simultaneously with the supply is zero. On the other hand, when the suction nozzle is arranged at a distance x (m) away from the water supply location in the transport direction, if the transport speed of the non-conductive sheet is v (m / min), the elapsed time t from the supply to the suction t (Minutes) can be expressed as t = x / v. The elapsed time t may be appropriately set depending on the wettability of the non-conductive sheet, but is preferably 0 to 2 seconds, more preferably 0 to 1 second, and most preferably 0 to 0.5 seconds.

The suction pressure of the suction nozzle is preferably in the range of -0.005 to -0.05 MPa, more preferably in the range of -0.006 to -0.04 MPa, and most preferably in the range of -0.01 to -0.03 MPa. If the suction pressure is less than -0.005 MPa, the suction will be insufficient, and if it exceeds -0.05 MPa, the suction may be too strong and the sheet may be torn.

Any conventionally known method can be used for drying the electret sheet after passing water. For example, methods such as a hot air drying method, a vacuum drying method, and a natural drying method can be applied. Among these, the hot air drying method is preferable because continuous processing is possible. In the case of the hot air drying method, the drying temperature needs to be a temperature that does not deactivate the electret. Preferably it is 120 degrees C or less, More preferably, it is 100 degrees C or less, More preferably, it is 80 degrees C or less. Prior to hot air drying, excess water may be removed as preliminary drying by nip roll, water-absorbing roll, suction suction or the like.

In the present invention, as water supplied to the non-conductive sheet, normal tap water or industrial water filtered with a filter or the like can be used. When using colored or turbid water, it is preferable to remove the turbidity by ion exchange, distillation, permeation through a reverse osmosis membrane, or the like.

In order to further improve the water permeability to the non-conductive sheet, a water-soluble organic solvent may be mixed with water. When the water-soluble organic solvent is mixed, the concentration of the water-soluble organic solvent is preferably 20% by mass or less. As the water-soluble organic solvent mixed with water, those having a boiling point lower than that of water are preferable. A water-soluble organic solvent having a boiling point lower than the boiling point of water improves the permeability of water into the sheet, and at the same time, can be vaporized quickly and dried. The boiling point difference with water is preferably 10 ° C. or more.

The water-soluble organic solvent is not particularly limited as long as the mixed solution has good permeability to the non-conductive sheet. For example, alcohols such as methyl alcohol, ethyl alcohol and isopropyl alcohol, ketones such as acetone and methyl ethyl ketone, esters such as propyl acetate and butyl acetate, other aldehydes and carboxylic acids can be used. In particular, alcohols or ketones are preferable from the viewpoint of permeability, and at least one of acetone, isopropyl alcohol and ethanol is preferably used. Most preferably, isopropyl alcohol is the main component.

(2) Non-conductive sheet The non-conductive sheet used in the present invention is not particularly limited as long as it is a non-conductive material. Examples thereof include fiber sheets such as woven fabrics, knitted fabrics, and nonwoven fabrics of synthetic fibers or natural fibers. Among these, a fiber sheet made of synthetic fibers is preferable. In particular, synthetic fiber nonwoven fabrics are preferable for air filter applications, and melt blown nonwoven fabrics are particularly preferable for high performance filter applications.

The raw material which comprises a nonelectroconductive sheet will not be specifically limited if it is a material which has nonelectroconductivity. Preferably, the material mainly comprises a material having a volume resistivity of 10 ¹² · Ω · cm or more, more preferably 10 ¹⁴ · Ω · cm or more.

Examples of the material constituting the non-conductive sheet include polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polylactic acid, polycarbonate, polystyrene, polyphenylene sulfite, fluororesin, and mixtures thereof. Among these, those mainly composed of polyolefin or polylactic acid are preferable from the viewpoint of electret performance, and those mainly composed of polypropylene are more preferable.

In the electretization method of allowing water to pass through according to the present invention, the nonconductive sheet may be electretized in advance by corona charging or the like.

(3) Additive The non-conductive sheet used in the present invention preferably contains at least one hindered amine-based additive or triazine-based additive. By including this additive in the non-conductive sheet, it is possible to maintain particularly high electret performance.

Hindered amine additives 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, Chimassorb 944LD), dimethyl succinate-1 -(2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate (manufactured by BASF, Tinuvin 622LD), 2- (3,5-di-t-butyl-4- Hydroxybenzyl) -2-n-butylmalonate bis (1,2,2,6,6-pentamethyl-4-piperidyl) (manufactured by BASF, Tinuvin 144) and the like.

Examples of the triazine-based additive include the aforementioned 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, Chimassorb 944LD), 2- ( 4,6-diphenyl-1,3,5-triazin-2-yl) -5-((hexyl) oxy) -phenol (manufactured by BASF, Tinuvin 1577FF), etc. Among these, particularly hindered amines Additives are preferred.

In addition to the above additives, additives that are generally used in non-conductive sheets of electret processed products such as heat stabilizers, weathering agents, polymerization inhibitors, and nucleating agents may be added to the non-conductive sheets. Good.

The addition amount of the hindered amine additive or triazine additive is not particularly limited, but is preferably 0.5 to 5% by mass, more preferably 0.7 to 3% by mass with respect to 100% by mass of the fiber. If the addition amount is less than 0.5% by mass, a sufficient addition effect may not be obtained. If it exceeds 5% by mass, the yarn-forming property and film-forming property are deteriorated, and the cost becomes disadvantageous.

The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

Example 1
Triazine-based additive as an additive (BASF Corp., Chimassorb 944LD) a containing 1 wt%, the polypropylene MFR = 1550 as a starting material, by meltblowing basis weight 30 g / m ^2, thickness 0.2 mm, average fiber diameter 2.5μm of A meltblown nonwoven was produced. The average fiber diameter, basis weight and thickness were measured by the methods described later.

To the resulting melt-blown nonwoven fabric, using the electret processed product manufacturing apparatus shown in FIG. 1, the supply amount 0.2 g / cm ² of water, impregnated with water at time 0.1 seconds until the suction conveying speed 33 cm / sec, the water Finally, it was dried with a drying device to produce an electret meltblown nonwoven fabric. When the collection performance (collection efficiency and pressure loss) of the obtained electret meltblown nonwoven fabric was measured by the method described later, the collection efficiency was 99.99% and the pressure loss was 25 Pa.

Comparative Example 1
The same melt blown nonwoven fabric as in Example 1 was used, and corona charging was performed in the atmosphere at a voltage of 16 kV and a distance between electrodes of 20 mm. When the collection performance of the obtained electret melt blown nonwoven fabric was measured, the collection efficiency was 98% and the pressure loss was 25 Pa.

(1) Measurement of average fiber diameter Photographing 5 arbitrary positions of the test piece with an electron microscope, and measuring the diameter of 20 fibers per sheet for the obtained 5 photographs, a total of 100 fiber diameters Was obtained on average.

(2) Measurement of basis weight A test piece of 100 × 100 mm was collected, the weight in a water equilibrium state was measured, and the mass per 1 m ² was obtained as the basis weight.

(3) Measurement of thickness A 100 × 100 mm test piece was collected and measured with a dial thickness gauge.

(4) Measurement of collection efficiency Air for dust test with 0.3 μm NaCl particles is passed at a flow rate of 31.8 L / min, and the dust concentration before and after passage is simultaneously measured by the light scattering light amount integration method according to JIS Z 8813 Continuously measured, the following formula:
Collection efficiency (%) = [(Dust concentration before passage (mg / m ² ) −Dust concentration after passage (mg / m ² )) / (Dust concentration before passage (mg / m ² ))] × 100
The collection efficiency was determined by

(5) Measurement of pressure loss In parallel with the collection efficiency test, an aneroid pressure gauge was used to measure the pressure before and after passage of the test dust-containing air of 0.3 μm NaCl particles to determine the differential pressure.

Claims

An apparatus for producing an electret processed product by electretizing a non-conductive sheet,
A mesh-like conveyor for placing the non-conductive sheet and conveying it horizontally;
Water application means for applying band-like water to the non-conductive sheet placed on the conveyor;
A suction nozzle disposed on the back side of the conveyor, for sucking the applied water from the opposite side of the non-conductive sheet;
The water applying means comprises a slide surface for allowing water to flow down in a strip shape, a tank provided on the upstream side of the slide surface, and a water supply unit for supplying water to the tank,
An apparatus for producing an electret processed product, characterized in that uniform strip-shaped water is supplied in the width direction of the non-conductive sheet by causing water overflowed from the tank to flow down to the slide surface.
2. The electret processed product manufacturing apparatus according to claim 1, wherein the slide surface has an inclination angle of 45 to 75 ° with respect to the non-conductive sheet.
3. The apparatus for manufacturing an electret processed product according to claim 1 or 2, wherein guides for controlling the width of water flowing down are provided at both ends of the slide surface. .
A method of electretizing a non-conductive sheet,
While transporting the non-conductive sheet placed on the mesh-shaped conveyor, the water that flows down the slide surface in a strip shape is supplied to the non-conductive sheet, or at the same time as the water is supplied, the surface opposite to the side on which the water is supplied The method is characterized in that water is passed through the non-conductive sheet by sucking the supplied water through a suction nozzle disposed in the sheet, and then the sheet is dried.
5. The method of electretizing a non-conductive sheet according to claim 4, wherein the non-conductive sheet contains 0.5 to 5% by weight of a hindered amine-based additive or a triazine-based additive.
6. The method of electretizing a nonconductive sheet according to claim 4 or 5, wherein the nonconductive sheet is a sheet made of synthetic fibers.
7. The method for electretizing a non-conductive sheet according to claim 6, wherein the sheet made of synthetic fibers is a melt blown nonwoven fabric.
8. The method for electretizing a non-conductive sheet according to claim 4, wherein the non-conductive sheet is mainly composed of polyolefin.
9. The method of electretizing the non-conductive sheet according to claim 8, wherein the polyolefin is mainly composed of polypropylene.
10. The method for electretizing the non-conductive sheet according to claim 4, wherein the water contains a water-soluble organic solvent.
11. The method for electretizing a non-conductive sheet according to claim 10, wherein the water-soluble organic solvent has a boiling point lower than that of water.
12. The method for electretizing a non-conductive sheet according to claim 11, wherein the water-soluble organic solvent is mainly composed of alcohols or ketones.
13. The method of electretizing a non-conductive sheet according to claim 11 or 12, wherein the water-soluble organic solvent is at least one of isopropyl alcohol, ethyl alcohol, and acetone.
14. The method of electretizing a nonconductive sheet according to claim 4, wherein the nonconductive sheet is electretized beforehand by corona charging.