JP3780916B2 - Manufacturing method of electret processed product - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing an electret processed product, and more particularly, to a method for manufacturing an electret processed product that enables high-quality electret processed products to be produced at low cost.
[0002]
[Prior art]
Conventionally, as an air filter material having a low pressure loss, an electret processed fiber sheet has been used because of its excellent performance. The electretized fiber sheet can be produced by applying a high voltage to a fiber sheet such as a synthetic fiber nonwoven fabric and electretizing it by corona discharge (see Japanese Patent Application Laid-Open No. 61-102476), A method is known in which a high voltage is applied by an electrode and electretized by corona discharge, and then the film sheet is made into a non-woven fabric by making it into a nonwoven fabric (see Japanese Patent Publication No. 57-14467).
[0003]
However, as shown in FIG. 5 , all the conventional electretization methods place a high-voltage DC high voltage generator 33 on the surface of the polymer material sheet S while placing or moving the polymer material sheet S on the ground electrode 31. A voltage is applied from a needle or wire electrode 32 and electretized by corona discharge. Therefore, there is a problem that unevenness is likely to occur due to gap accuracy between the high voltage application electrode 32 and the ground electrode 31, the electret sheet is unevenly charged, and the sheet is damaged by spark discharge.
[0004]
Furthermore, the high voltage equipment is generally expensive and expensive for safety maintenance, and there is a problem that the cost is increased.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a method of manufacturing an electret processed product that eliminates the above-mentioned problems of the prior art and enables a high-quality, high-performance electret processed product to be produced at low cost.
[0006]
[Means for Solving the Problems]
Manufacturing method of an electret processed product of the present invention to solve the above problems, after imparting water to the non-conductive sheet of non-conductive sheet is immersed in water or water, or a non-conductive sheet water or the water surface The sheet is sucked from one side of the sheet while water is applied to the non-conductive sheet while running to allow the water to penetrate into the non-conductive sheet, and then the non-conductive sheet is dried to form an electret sheet. It is what.
[0007]
In this way, after immersing the non-conductive sheet in water or on the water surface and applying water to the non-conductive sheet, or while running the non-conductive sheet in water or on the water surface while applying water to the non-conductive sheet By sucking from one side of the sheet, water can be uniformly permeated through the entire sheet, so that a high-quality, high-performance electret sheet can be obtained simply by drying the sheet. Moreover, since the manufacturing equipment is a water supply equipment, a suction equipment, a drying equipment, etc., it is cheaper than conventional high voltage generating equipment, and safe maintenance management can be performed at a low cost.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The non-conductive sheet used in the present invention is not particularly limited as long as it is a non-conductive material. For example, fiber sheets such as woven fabrics, knitted fabrics, and nonwoven fabrics of synthetic fibers or natural fibers, plastic film sheets, and the like can be given. Among these, a synthetic fiber sheet is particularly preferable. Further, in the case of an air filter, a synthetic fiber nonwoven fabric is preferable, and in particular, for a high performance filter, it is preferable to use a melt blown nonwoven fabric.
[0009]
The material of the nonconductive sheet is not particularly limited as long as it is a nonconductive material. It is preferable to use a material mainly composed of a material having a volume resistivity of 10 ¹² · Ω · cm or more, more preferably 10 ¹⁴ · Ω · cm or more.
[0010]
Examples thereof include polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polylactic acid, polycarbonates, polystyrenes, polyphenylene sulfites, fluororesins, 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.
[0011]
The non-conductive sheet used in the present invention preferably contains at least one hindered amine additive or triazine additive. It is because it becomes possible to hold | maintain especially high electret performance by containing this additive in a nonelectroconductive sheet.
[0012]
Of the above two types of additives, the hindered amine-based additive may be 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 Geigy, Chimasorp 944LD ), Dimethyl succinate-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate (manufactured by Ciba Geigy, Tinupin 622LD), 2- (3,5-di- t-butyl-4-hydroxybenzyl) -2-n-butylmalonate bis (1,2,2,6,6-pentamethyl-4-piperidyl) (manufactured by Ciba-Geigy, Tinupin 144) It is.
[0013]
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 Ciba Geigy, Chima Soap 944LD), 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-((hexyl) oxy) -phenol (manufactured by Ciba Geigy, Tinupin 1577FF), etc. Among these, particularly hindered amine It is preferable to use system additives.
[0014]
In addition to the above additives, the non-conductive sheet is added with known additives generally used for non-conductive sheets of electret processed products such as heat stabilizers, weathering agents, polymerization inhibitors, etc. Also good.
[0015]
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 is unpreferable since it will worsen a spinning property and film forming property, and will become disadvantageous also in cost.
[0016]
The manufacturing method of the electret processed goods of this invention provides water to the nonelectroconductive sheet mentioned above to make it a sufficient osmosis | permeation state, and dries the sheet | seat of this osmosis | permeation state. It is necessary to make the water permeate the entire non-conductive sheet evenly and sufficiently, so that water on the opposite side can be obtained by applying suction to one side of the sheet after or while applying water to the non-conductive sheet. It is important to pass through to the suction side.
[0017]
Because of the suction action, water penetrates through the non-conductive sheet, and evenly penetrates the entire sheet. After that, simply drying the non-conductive sheet will make the high-quality electret charged uniformly and at a high density. It can be made into a conversion sheet. In particular, when sucking while applying water, the water penetration effect can be made larger than when sucking after applying water. The series of water application, suction, and drying steps may be performed continuously or batchwise.
[0018]
The method for applying water to the non-conductive sheet may be a method of immersing in a water tank as long as it can be immersed in water or on the surface of water .
[0019]
Moreover, as a method of sucking while applying water, a method of sucking while running the sheet in water, a method of sucking from the upper surface of the sheet running on the water surface, and the like can be preferably used. Among these, the method of sucking from the water surface of the sheet traveling on the water surface is particularly preferable.
[0020]
The amount of water sucked is not particularly limited, but is preferably 0.2 g / cm ² or more, and more preferably 0.3 g / cm ² or more. If it is less than 0.2 g / cm ² , a sufficient charging effect cannot be obtained.
[0021]
The non-conductive sheet infiltrated with water by water application and suction may be subjected to a vacuum suction process using a suction nozzle from one side of the non-conductive sheet before drying. By this vacuum suction treatment, the charging performance can be further improved.
[0022]
The vacuum suction pressure is preferably in the range of -0.005 MPa to -0.05 MPa, and more preferably in the range of -0.006 MPa to -0.04 MPa. Most preferably, it is in the range of -0.01 MPa to -0.03 MPa. If the vacuum suction pressure is less than -0.005 MPa, suction may be insufficient, and if it is greater than -0.05 MPa, the suction may become too strong and the sheet may be torn.
[0023]
In addition, any conventionally known method can be used for drying the non-conductive sheet after water has penetrated. For example, methods such as a hot air drying method, a vacuum drying method, and a natural drying method can be applied. Of 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 good to set it as 80 degrees C or less. Further, it is more preferable to remove excess water by nip roll, water absorption roll, suction suction or the like as preliminary drying before hot air drying.
[0024]
In the present invention, it is preferable that the water used for the permeation treatment on the non-conductive sheet is one from which dirt has been removed with a liquid filter or the like and is as clean as possible. In particular, pure water such as ion-exchanged water, distilled water, filtered water permeated through a reverse osmosis membrane is preferable. The level of pure water is preferably 10 ³ μS / m or less, more preferably 10 ² μS / m or less in terms of conductivity.
[0025]
Moreover, the water permeability to the non-conductive sheet can be further improved by mixing the water with a water-soluble organic solvent. In this case, the concentration of the water-soluble organic solvent is usually 20% by weight or less. As the water-soluble organic solvent mixed with water, those having a boiling point lower than that of water are preferable. That is, since the water-soluble organic solvent is for improving the permeability of water into the sheet, once it has permeated the sheet, it is preferable to vaporize and dry it as soon as possible. More preferably, the boiling point difference with water is 10 ° C. or more lower.
[0026]
The kind of 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 it is particularly preferable to use at least one of acetone, isopropyl alcohol, and ethanol. More preferably, the main component is isopropyl alcohol.
[0027]
FIG. 1 illustrates an apparatus for carrying out an electret processed product manufacturing method of the present invention.
[0028]
In the apparatus of FIG. 1, 1 is an immersion tank, 2 is an aspirator, and 3 is a drying apparatus. The tank of the immersion tank 1 is filled with water W. The non-conductive sheet S to be treated is introduced into the immersion tank 1 via the feed roller 4 and the immersion roller 5 and immersed in the water W, and then transferred to the next suction device 2. The non-conductive sheet S coming out of the immersion tank 1 is sucked on the lower surface side while passing over the suction port 2 a of the suction device 2. The aspirator 2 is connected to a negative pressure source (not shown), and when the negative pressure is applied to the lower surface of the non-conductive sheet S, the water on the upper surface side of the sheet permeates to the lower surface side, and the non-conductive sheet S Make the entire front and back of the osmotic state infiltrated. The suction device 2 is not limited to one as shown in the drawing, and a plurality of suction devices may be arranged continuously in the transfer direction of the non-conductive sheet S.
[0029]
The non-conductive sheet S in which water is infiltrated is squeezed out in advance by a pair of nip rollers 6 and 6 and then transferred to the drying device 3. A plurality of guide rollers 7 are provided in the drying device 3 in a zigzag shape, and heated air is supplied from the supply port 3a and discharged from the exhaust port 3b so that the inside is heated. The non-conductive sheet S transferred to the drying device 3 is dried while traveling in a zigzag manner on the guide roller 7, and is carried out as an electret sheet.
[0030]
The electret sheet obtained in this way has water uniformly permeated throughout the sheet by the suction action of the aspirator, so that it becomes a high-quality, high-performance electret processed product in which high charges are uniformly distributed throughout the sheet. .
[0034]
FIG. 2 illustrates another mode for carrying out the method of manufacturing an electret processed product of the present invention.
[0035]
In FIG. 2 , 9 is a water immersion treatment tank, 11 is a suction nozzle, and 12 is a vacuum suction nozzle. The water immersion treatment tank 9 is always supplied with water from the lower surface, and overflows the overflow tank 10 so that the water surface is always kept constant. The non-conductive sheet S of the material to be treated is introduced into the water surface of the water immersion treatment tank 9 through the feed roller 4 and the immersion roller 5 and is then fed by the suction nozzle 11 connected to a negative pressure source (not shown). By sucking from the upper surface, water permeates from the lower surface of the sheet to the upper surface, and the entire front and back surfaces of the non-conductive sheet S are infiltrated. Only one suction nozzle 11 may be provided as in the illustrated example, or a plurality of suction nozzles may be arranged continuously.
[0036]
The non-conductive sheet S in which water is infiltrated is subjected to vacuum suction processing by the vacuum suction nozzle 12 as necessary, and then sent to the drying device 3 as in the case of FIG. 1 to be dried and electretized. To be carried out.
[0037]
FIG. 3 illustrates still another embodiment for carrying out the method of manufacturing an electret processed product of the present invention.
[0038]
The apparatus of FIG. 3 is provided with a water tank 1 instead of the water immersion treatment tank 9 in the apparatus of FIG. 2 , and water is infiltrated into the non-conductive sheet S by the suction nozzle 11 in the water tank 1. . Step after impregnated with water is similar to the device of FIG.
[0039]
Sheets obtained from the apparatus shown in FIGS. 2 and 3 can also be made into high-quality and high-performance electret products.
[0040]
【Example】
The characteristic values used in the examples described below are measured by the following measuring method.
[0041]
[Collection performance]
It measured with the collection performance measuring apparatus shown in FIG . In this collection performance measuring apparatus, a dust storage box 22 is connected to an upstream side of a sample holder 21 for setting a measurement sample M, and a flow meter 23, a flow rate adjusting valve 24, and a blower 25 are connected to a downstream side. In addition, a sample holder 21 is provided with a perk counter 26, and the perk counter 26 is used to measure the number of dusts on the upstream side and the number of dusts on the downstream side of the measurement sample M via the switching cock 27, respectively. Can do.
[0042]
When measuring the collection performance, polystyrene standard latex powder with a diameter of 0.3 μm is filled in the dust storage box 22, the sample M is set in the holder 21, and the air flow is adjusted to 1.5 m / min. Adjusted with the flow rate adjusting valve 24, the dust concentration is stabilized in the range of 10,000 to 40,000 / 2.83 × 10 ⁻⁴ m ³ (0.01 ft ³ ), and the number of dusts D upstream of the sample M and the number of dusts d downstream. Was measured five times with a particle counter 26 (KC-01B, manufactured by Rion Co., Ltd.), and the collection performance (%) was determined by the following formula based on JIS K-0901.
[0043]
Collection performance (%) = [1- (d / D)] × 100
Where d: number of downstream dusts D: number of upstream dusts [average fiber diameter]
The diameter of 100 or more fibers expanded by the SEM photograph was measured, and the average value was obtained.
[0046]
Example 1
A melt blown non-woven fabric having a basis weight of 40 g / m ² and an average fiber diameter of 2.0 μm by a normal melt blow method using a polypropylene of MI = 700 containing 1% of a triazine-based additive (manufactured by Ciba Geigy Co., Ltd., Chima Soap 944) as a weathering agent Was made. Next, the melt blown nonwoven fabric was used to infiltrate water with the apparatus shown in FIG .
[0047]
The collection efficiency of the obtained electret meltblown nonwoven fabric was 99.994% when vacuum suction was not performed, and 99.9995% when vacuum suction was performed.
[0048]
Example 2
The melt blown nonwoven fabric of Example 1 was used to infiltrate water with the apparatus shown in FIG .
[0049]
The collection efficiency of the obtained electret meltblown nonwoven fabric was 99.8% when vacuum suction was not performed and 99.992% when vacuum suction was performed.
[0050]
Comparative Example 1
The same melt blown nonwoven fabric as in Example 1 was used, immersed in pure water for 1 minute, drained, and dried. When the collection performance of the nonwoven fabric after a process was measured, it was as low as 56.3%.
[0051]
Comparative Example 2
When the collection performance of the same melt blown nonwoven fabric as Example 1 was measured, it was as low as 57.5%.
[0052]
【The invention's effect】
According to the production method of the present invention, after the application of water to the nonconductive sheet of non-conductive sheet is immersed in water or water, or a non-conductive sheet is run in water or water surface non conductive While sucking and sucking from one side of the sheet while applying water to the sheet, water can be uniformly permeated throughout the sheet, so that it can be made into a high-quality, high-performance electret sheet simply by drying it. . Moreover, since the manufacturing equipment is a water supply equipment, a suction equipment, a drying equipment, etc., it is cheaper than conventional high voltage generating equipment, and safe maintenance management can be performed at a low cost.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of an apparatus for carrying out an electret processed product manufacturing method of the present invention.
FIG. 2 is a schematic view showing another example of an apparatus for carrying out the electret processed product manufacturing method of the present invention.
FIG. 3 is a schematic view showing still another example of an apparatus for carrying out the method for producing an electret processed product of the present invention.
FIG. 4 is a schematic view showing a collection performance measuring apparatus used in an example of the present invention .
FIG. 5 is a schematic view showing a conventional electretization method by applying a high voltage .
[Explanation of symbols]
1 Immersion tank 2 Suction machine 3 Drying device 4 Feed roller
5 Immersion roller
9 Water immersion treatment tank 10 Overflow tank 11 Suction nozzle 12 Vacuum suction nozzle S Non-conductive sheet W Water

Claims (11)

After the non-conductive sheet in water or by immersion in water to impart water to the non-conductive sheet, or while applying water to the non-conductive sheet of non-conductive sheet is run in water or water surface, the sheet A method for producing an electret processed product, wherein suction is performed from one side to allow the water to penetrate into the non-conductive sheet, and then the non-conductive sheet is dried to form an electret sheet.   The manufacturing method of the electret processed goods of Claim 1 which performs a vacuum suction process from the single side | surface of this nonelectroconductive sheet, before drying the nonelectroconductive sheet after osmosis | permeating the said water.   The method for producing an electret processed product according to claim 1 or 2, wherein the non-conductive sheet contains a hindered amine-based additive or a triazine-based additive in an amount of 0.5 to 5% by weight.   The method of manufacturing an electret processed product according to claim 1, 2 or 3, wherein the non-conductive sheet is a sheet made of a synthetic fiber.   The method for producing an electret processed product according to claim 4, wherein the synthetic fiber sheet is a melt blown nonwoven fabric.   The method for producing an electret processed product according to any one of claims 1 to 5, wherein the non-conductive sheet is mainly composed of polyolefin.   The method for producing an electret processed product according to claim 6, wherein the polyolefin is mainly composed of polypropylene.   The said water is ion-exchange water, distilled water, or filtered water by a reverse osmosis membrane, The manufacturing method of the electret processed goods in any one of Claims 1-7.   The method for producing an electret processed product according to claim 1, wherein the water contains a water-soluble organic solvent having a boiling point lower than that of water.   The method for producing an electret processed product according to claim 9, wherein the water-soluble organic solvent is mainly composed of alcohols or ketones.   The method for producing an electret processed product according to claim 10, wherein the water-soluble organic solvent is at least one of isopropyl alcohol, ethyl alcohol, and acetone.

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