JP2017094250A - Electret filter medium, filter using the same, method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electret filter medium in which a part ranging to the inside of a porous dielectric sheet is sufficiently and highly turned into an electret.SOLUTION: An electret filter medium of the present invention comprises a porous dielectric sheet including a hindered amine-based or triazine-based additive as a principal additive and including a hindered phenolic additive as a sub-additive. The mass ratio of the principal additive to the sub-additive is in the range of 3-30 times.SELECTED DRAWING: None

Description

  The present invention relates to an electret filter medium used for capturing fine particles in a gas, a filter using the same, and a method for producing an electret filter medium.

  A conventional technique for electretizing a porous dielectric sheet includes a water spray charging method.

  For example, Patent Document 1 discloses a method of electretization by causing a jet of water or a water droplet to collide with a porous dielectric sheet. As water to be collided with the porous dielectric sheet, it is preferable to use water with higher purity such as distilled water or ion exchange water.

  For example, Patent Document 2 discloses a method for manufacturing an electret processed product in which a mixed solution of water and a water-soluble organic solvent is applied to a non-conductive sheet, and then the non-conductive sheet is dried. There is a description that in a mixed solution of water and a water-soluble organic solvent, it is preferable to use water having higher purity such as distilled water or ion-exchanged water.

  Furthermore, for example, Patent Document 3 discloses a method for producing an electret filter material in which an aqueous solution exceeding pH 7 is sprayed onto a non-conductive porous dielectric sheet subjected to corona charging treatment, and then dried. There is a description that it is preferable to perform corona charging treatment before water is jetted to accumulate charges on the surface.

Japanese National Patent Publication No. 9-501604 JP 2002-115177 A JP 2004-66027 A

  However, the charging effect due to contact between the high-purity water and the porous dielectric sheet is low, and the porous dielectric sheet cannot be highly electretized. Further, even when a mixed solution of high-purity water and a water-soluble organic solvent is applied to the non-conductive sheet, the charging effect due to contact between the non-conductive sheet and the mixed solution is low. In addition, since a water-soluble organic solvent is mixed for the purpose of increasing the permeability to the non-conductive sheet, the contact angle between the non-conductive sheet and the mixed solution is reduced, and the accumulated charge on the sheet is contained in the mixed solution. It becomes easy to leak. As a result, there is a drawback that the non-conductive sheet cannot be highly electretized. Furthermore, the electric charge given by the corona charging treatment has a drawback that it disappears by jetting the aqueous solution.

  As described above, the present state is that there is no electret filter medium that is sufficiently electretized to the inside and a manufacturing method thereof. In the present specification, “highly electretized” is used to mean electretized so as to increase the charge amount.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide an electret filter medium that is sufficiently electretized to the inside and highly electretized, a filter using the same, and a method for manufacturing the same. is there.

As a result of intensive studies to solve the above problems, the present inventors have finally completed the present invention. That is, the present invention is as follows.
(1) An electret filter medium according to the present invention includes a porous dielectric sheet containing a hindered amine or triazine additive as a main additive and a hindered phenol additive as a secondary additive, The mass ratio to the secondary additive is 3 to 30 times.
(2) Moreover, in addition to the said structure, the electret filter medium which concerns on this invention is 1-3 weight part of the said main additive with respect to 100 weight part of materials of the said porous dielectric sheet, and the said auxiliary additive is You may contain 0.1-0.3 weight part.
(3) Moreover, in addition to the said structure, the said electret filter material which concerns on this invention may contain at least 1 or more types of materials with the volume resistivity of 10 < ¹⁴ > ohm-cm or more.
(4) Moreover, in the electret filter medium which concerns on this invention, in addition to the said structure, a melt blown nonwoven fabric may be sufficient as the said porous dielectric sheet.
(5) The filter according to the present invention is a filter using the electret filter medium described in any one of the above.
(6) The method for producing an electret filter medium according to the present invention includes a hindered amine or triazine additive as a main additive, a hindered phenol additive as a secondary additive, and a mass ratio of the main additive to the secondary additive. Injecting water having a pH of 7 or less and a total organic carbon (TOC) of 0.1 to 20 mgC / L to a porous dielectric sheet containing 3 to 30 times, and drying. Features.

  According to the above configuration, an electret filter medium can be obtained that is sufficiently and highly electretized to the inside of the porous dielectric sheet and has a high particle collection efficiency while maintaining a low pressure loss.

Hereinafter, embodiments of the present invention will be described in detail.
The electret filter medium of this embodiment includes a porous dielectric sheet containing a hindered amine or triazine additive as a main additive and a hindered phenol additive as a sub additive, and the sub addition of the main additive The mass ratio to the agent is 3 to 30 times.

  The porous dielectric sheet of the present embodiment is used as an object to be charged. For example, a fiber sheet (for example, a woven fabric, a knitted fabric, a non-woven fabric, and a composite thereof), a porous film (for example, perforated) Film), foam, or a composite of these, but is not limited thereto. The porous dielectric sheet is preferably an ultrafine fiber nonwoven fabric produced by a melt blow method. This is because the ultrafine fiber nonwoven fabric has a large fiber surface area, so that the particle collection efficiency is improved.

  The porous dielectric sheet may be a single sheet or a structure in which a plurality of sheets are stacked. Further, in order to increase the sheet strength, a reinforcing material such as spunbond may be laminated.

The porous dielectric sheet may be composed of one kind or a plurality of kinds of materials, but preferably contains at least one kind of material having a volume resistivity of 10 ¹⁴ Ωcm or more from the viewpoint of charge retention. If the porous dielectric sheet is composed only of a material having a volume resistivity of less than 10 ¹⁴ Ωcm, it is difficult for charges to accumulate and it cannot be highly electretized. Moreover, the problem that a charge lifetime will become extremely short arises.

  Specific examples of the porous dielectric sheet include polyolefin, polyester, polylactic acid, polycarbonate, polyvinyl chloride, and polyvinylidene chloride. Of these, polyolefin is preferred, and polypropylene is particularly preferred.

When the porous dielectric sheet of this embodiment is a melt blown nonwoven fabric made of polypropylene, the basis weight is preferably 5 to 100 g / m ² , more preferably 10 to 60 g / m ² . An average fiber diameter becomes like this. Preferably it is 1-20 micrometers, More preferably, it is 1-10 micrometers.

  The additive contained in the porous dielectric sheet is a main additive having a higher content and a sub-additive having a lower content.

  The hindered amine-based or triazine-based additive used as the main additive contained in the porous dielectric sheet is not particularly limited, but specifically, 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, Chimassorb (registered trademark) 944LD), dimethyl-1- (2-hydroxyethyl) -4-hydroxy-2,2,6 succinate , 6-tetramethylpiperidine polycondensate (manufactured by Ciba Geigy, Tinuvin (registered trademark) 622LD), 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-buty Bis (1,2,2,6,6-pentamethyl-4-piperidyl) malonate (manufactured by Ciba Geigy, Tinuvin (registered trademark) 144), dibutylamine, 1,3,5-triazine, N, N′-bis ( 2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine / N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine polycondensate (Ciba Geigy, Chimassorb (registered trademark) 2020FDL), 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-((hexyl) oxy) -phenol (manufactured by Ciba Geigy, Tinuvin (registered trademark) 1577FF) ) And the like.

  In this embodiment, the porous dielectric sheet contains a hindered amine or triazine additive as described above as a main additive, and a hindered phenol additive as a secondary additive. By containing these additives, the electret property of the porous dielectric sheet is dramatically improved.

  The hindered phenol-based additive is not particularly limited, but specifically, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] ( Irganox 1010, manufactured by BASF), octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (Irganox 1076, manufactured by BASF), tris- (3,5-di-t-butyl-4) -Hydroxybenzyl) -isocyanurate (Irganox 3114, manufactured by BASF), 3,9-bis- {2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) -propionyloxy] -1 , 1-Dimethylethyl} -2,4,8,10-tetraoxaspiro- [5,5] undecane (Sumirai Over GA-80, include Sumitomo Chemical Co., Ltd.).

  The content of the additive is 1 to 3 parts by weight, preferably 1.3 to 2.5 parts by weight, and most preferably 1. to 100 parts by weight of the porous dielectric sheet. 5 to 2 parts by weight. The amount of the auxiliary additive is 0.1 to 0.3 part by weight, preferably 0.15 to 0.23 part by weight, and most preferably 0.15 to 0.2 part by weight. The content ratio of the main additive to the secondary additive is preferably 3 to 30 times, and most preferably 3.5 to 25 times. If the additive content ratio is low, the electretization effect is not sufficient, and conversely if the additive content ratio is large, the effect is saturated and bleeds out, which is not preferable.

  In the production of the electret filter medium of this embodiment, water (or an aqueous solution) is sprayed onto the porous dielectric sheet containing the additive as described above, and dried to be electret.

  In the electretization, the water sprayed onto the porous dielectric sheet preferably has a pH of 7 or less. When water exceeding pH 7 is used, the porous dielectric sheet cannot be highly electretized. As water of pH 7 or less, high-purity water obtained by subjecting general tap water to two-stage reverse osmosis membrane treatment and then ion-exchange membrane treatment, and hydrogen chloride, sulfuric acid, citric acid, etc. are added to the water. Water having a pH of 7 or less can be obtained.

  In addition, total organic carbon (TOC) is mentioned as a parameter | index of the amount of organic components in water. The organic component in water includes a surfactant and an organic solvent, but TOC may be contained in an amount of 0.1 to 20 mgC / L, preferably about 0.3 to 20 mgC / L. If it is less than that, it is difficult to produce, and if it is more than that, it will significantly inhibit electretization.

In the present embodiment, when the water is sprayed onto the porous dielectric sheet, the sheet is placed on a mesh-like support having an air permeability of 50 to 400 cm ³ / cm ² / second, and water is jetted from above the mesh-like support. It is preferable to set the pressure below the lower part. The air permeability is measured using a frangole type tester described in JIS-L1096.

  Specifically, the net-like support is a porous structure made of metal yarn or plastic yarn, and examples thereof include plain weave, twill weave and satin weave. Examples of the metal material include stainless steel and bronze, and examples of the plastic material include polypropylene, polyester, polyurethane, nylon, and polyphenylene sulfide.

Water is sprayed at a pressure sufficient to allow the water to pass through the nozzle from a nozzle having a large number of orifices along the width direction of the sheet, which is installed several cm above the porous dielectric sheet. The pressure sufficient to pass depends on the basis weight of the porous dielectric sheet. For example, for a sheet having a basis weight of 5 to 20 g / m ² , 0.3 to ² MPa, for a sheet of 20 to 50 g / m ^2, a sheet having a weight of 0.6 to 3 MPa and 50 to 100 g / m ² Is preferably 1 to 4 MPa. If the jetting pressure is too high, pinholes will open in the porous dielectric sheet, resulting in a reduction in filtration performance. If water cannot sufficiently pass through the porous dielectric sheet due to the pressure being too low, the porous dielectric sheet cannot be highly electretized.

  The nozzle preferably has one or more rows of orifices having a diameter of 0.05 to 0.2 mm arranged at a pitch of 0.5 to 3 mm. In addition, for example, it is preferable that the reticulate support can be moved and the injection treatment can be continuously performed by transporting the porous dielectric sheet in the longitudinal direction. Although the conveyance speed is not particularly limited, a preferable range is 1 to 100 m / min. Further, the optimum number of injections and the treatment surface (one side or both sides) are not particularly limited because they depend on the basis weight of the porous dielectric sheet and the average fiber diameter.

  At the same time as the water injection, it is preferable that the lower part of the mesh support is in a reduced pressure state using an exhaust blower or the like. The suction negative pressure is not particularly limited, but 200 to 2000 mmAq is preferable. When the pressure is reduced, water can sufficiently pass through the porous dielectric sheet, and the porous dielectric sheet can be highly electretized.

  Any conventionally known method can be used as the drying method after the water jet treatment on the porous dielectric sheet. For example, methods such as a hot air drying method, a vacuum drying method, and a natural drying method are applicable. 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 cause the electret to disappear. 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. In addition, 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.

  Hereinafter, the effects of the present invention will be described more specifically by way of examples. The following examples are not intended to limit the present invention, and any design changes that fall within the spirit of the preceding and following descriptions are within the technical scope of the present invention.

First, the characteristic value measurement method and processing method performed in the examples are shown below.
(Water pH measurement method)
The pH of water prepared using a low conductivity water / nonaqueous solvent pH electrode (6377-10D, manufactured by HORIBA) as an electrode, under the condition of a water temperature of 25 ° C., according to the pH measurement method described in JIS-Z8802. Was measured.

(Injection process (electret process))
A porous dielectric sheet was placed on a mesh support (96 mesh) having an air permeability of 120 cm ³ / cm ² / sec, and a nozzle having a diameter of 0.1 mmφ and a pitch of 0.6 mm located 3 cm above the porous dielectric sheet, Water was sprayed at a pressure of 2 MPa. The base water is high-purity water obtained by subjecting general tap water to two-stage reverse osmosis membrane treatment and then ion exchange membrane treatment, and polyalphaolefin is added to the water to have a desired TOC. Water (or an aqueous solution) was obtained. The conveyance speed of the mesh support was 4 m / min, and the lower portion of the mesh support just below the nozzle was in a reduced pressure state of 600 mmAq. This treatment was performed 3 times on the surface of the sheet. Thereafter, the porous dielectric sheet was naturally dried. In addition, you may dwell for 1 minute in a 80 degreeC hot-air oven, and may dry.

(Evaluation of filtration characteristics)
The pressure loss (PD) was obtained by installing the electret filter medium sample in the duct, controlling the linear passage speed of the filter medium to 10 cm / second, and reading the static pressure difference between the upstream and downstream of the electret filter medium with a pressure gauge. .

  The particle collection efficiency E (%) was evaluated at 10 cm / second using atmospheric dust particles having a particle diameter of 0.3 μm. The filter medium quality factor QF was calculated from the following equation using the pressure loss PD (mmAq) and the particle collection efficiency E (%). Here, QF is used as one of the determination indexes for electretization. If QF is 1.0 or more, it can be said that it is highly electretized.

  QF = -LN ((100-E) / 100) / PD

(Evaluation of average fiber diameter)
As an evaluation of the average fiber diameter, the fiber diameter was measured for 100 fibers enlarged by SEM photographs, and the average value Dfs [μm] was obtained.

(TOC evaluation)
A small amount of hydrochloric acid was added to the sampled water to make it acidic, and the TOC amount of water was measured with a total organic carbon meter (manufactured by Shimadzu Corporation; TOC-VCSH).

In the following examples and comparative examples, a melt blown nonwoven fabric produced by a conventionally known method was used as the porous dielectric sheet, but the present invention is not limited to this.
Example 1
1 part by weight of Kimasorb 944 as a main additive and 0.1 g of auxiliary additive Irganox 1010 are added to 100 parts by weight of a polypropylene resin (manufactured by Prime Polymer Co., Ltd.) having a melt flow index 700 as a porous dielectric sheet material. 3 parts by weight of a melt blown nonwoven fabric with a basis weight of 30 g / m ² and an average fiber diameter (Dfs) of 2.5 μm was prepared. Thereafter, an injection treatment was performed with water having a TOC of 1.5 mgC / L, followed by natural drying, whereby the electret filter medium of Example 1 was obtained. The characteristics of this filter medium were measured. The characteristics are summarized in Table 1 below.

(Example 2)
3 parts by weight of Kimasorb 944 as a main additive and 0.3 parts by weight of Irganox 1010 as a secondary additive are blended with 100 parts by weight of the polymer used in Example 1, and the basis weight is 30 g / m ² . A melt blown nonwoven fabric having a diameter (Dfs) of 2.5 μm was prepared. Thereafter, a jet treatment was performed with water having a TOC of 1.7 mg C / L, followed by natural drying to obtain an electret filter medium of Example 2. The characteristics of this filter medium were measured. The characteristics are summarized in Table 1 below.

(Example 3)
3 parts by weight of Kimasorb 944 as a main additive and 0.1 part by weight of Irganox 1010 as a secondary additive are blended with 100 parts by weight of the polymer used in Example 1, and the basis weight is 30 g / m ² . A melt blown nonwoven fabric having a diameter (Dfs) of 2.5 μm was prepared. Thereafter, a jet treatment was performed with water having a TOC of 1.8 mg C / L, followed by natural drying to obtain an electret filter medium of Example 3. The characteristics of this filter medium were measured. The characteristics are summarized in Table 1 below.

Example 4
The melt blown nonwoven fabric produced in Example 2 was sprayed with water having a TOC of 6 mg C / L and dried naturally to obtain the electret filter medium of Example 4. The characteristics of this filter medium were measured. The characteristics are summarized in Table 1 below.

(Example 5)
The melt blown nonwoven fabric produced in Example 2 was sprayed with water having a TOC of 15 mg C / L and dried naturally to obtain the electret filter medium of Example 5. The characteristics of this filter medium were measured. The characteristics are summarized in Table 1 below.

(Example 6)
The melt blown nonwoven fabric produced in Example 2 was sprayed with water having a TOC of 0.4 mg C / L and dried naturally to obtain the electret filter medium of Example 6. The characteristics of this filter medium were measured. The characteristics are summarized in Table 1 below.

(Comparative Example 1)
3 parts by weight of Kimasorb 944 was blended with 100 parts by weight of the polymer used in Example 1 to prepare a melt blown nonwoven fabric having a basis weight of 30 g / m ² and an average fiber diameter (Dfs) of 2.5 μm. Thereafter, an injection treatment was performed with water having a TOC of 1.5 mgC / L, followed by natural drying, whereby the electret filter medium of Comparative Example 1 was obtained. The characteristics of this filter medium were measured. The characteristics are summarized in Table 2 below.

(Comparative Example 2)
3 parts by weight of Irganox 1010 was blended with 100 parts by weight of the polymer used in Example 1 to prepare a melt blown nonwoven fabric having a basis weight of 30 g / m ² and an average fiber diameter (Dfs) of 2.5 μm. Thereafter, an injection treatment was performed with water having a TOC of 1.9 mgC / L, followed by natural drying, whereby an electret filter medium of Comparative Example 2 was obtained. The characteristics of this filter medium were measured. The characteristics are summarized in Table 2 below.

(Comparative Example 3)
The melt blown nonwoven fabric produced in Example 2 was subjected to an injection treatment with water having a pH of 5.4 and a TOC of 50 mgC / L, followed by natural drying to obtain an electret filter medium of Comparative Example 3. The characteristics of this filter medium were measured. The characteristics are summarized in Table 2 below.

(Comparative Example 4)
To the meltblown nonwoven fabric used in Example 2, 100 ppm of potassium carbonate (manufactured by Nacalai Tesque) was added to the base water, and the injection treatment was performed with water having a pH of 10.4 and a TOC of 1.5 mgC / L. It dried naturally and the electret filter medium of the comparative example 4 was obtained. The characteristics of this filter medium were measured. The characteristics are summarized in Table 2 below.

(Comparative Example 5)
100 ppm of potassium carbonate (manufactured by Nacalai Tesque) is added to the base water to the melt-blown nonwoven fabric produced in Example 2, spray treatment is performed with water having a pH of 10.4 and a TOC of 3 mg C / L, followed by natural drying. The electret filter medium of Comparative Example 5 was obtained. The characteristics of this filter medium were measured. The characteristics are summarized in Table 2 below.

(Comparative Example 6)
100 ppm of potassium carbonate (manufactured by Nacalai Tesque) is added to the base water for the melt-blown nonwoven fabric produced in Example 2, spray treatment is performed with water having a pH of 10.4 and a TOC of 10 mg C / L, followed by natural drying The electret filter medium of Comparative Example 6 was obtained. The characteristics of this filter medium were measured. The characteristics are summarized in Table 2 below.

(Comparative Example 7)
0.3 parts by weight of Kimasorb 944 was blended with 100 parts by weight of the polymer used in Example 1, to prepare a melt blown nonwoven fabric having a basis weight of 30 g / m ² and an average fiber diameter (Dfs) of 2.5 μm. Thereafter, a jet treatment was performed with water having a pH of 6.5 and a TOC of 1.5 mgC / L, followed by natural drying. Thus, an electret filter medium of Comparative Example 7 was obtained. The characteristics of this filter medium were measured. The characteristics are summarized in Table 2 below.

  As is clear from Table 1, Examples 1, 2, 3, 4, and 5 showed high particle collection efficiency. On the other hand, as can be seen from Table 2, when only the main additive (Comparative Examples 1 and 2), when the TOC is high (Comparative Example 3), and when the pH is high (Comparative Examples 4, 5, and 6) It was confirmed that the particle collection efficiency and QF were lower than those of Examples 1, 2, 3, 4, and 5, and it was not possible to highly electretize.

  The electret filter medium according to the present invention has a high particle collection efficiency with a low pressure loss, can be widely used in various filter applications, and can greatly contribute industrially.

Claims (6)

A porous dielectric sheet containing a hindered amine or triazine additive as a main additive and a hindered phenol additive as a secondary additive,
The electret filter medium, wherein a mass ratio of the main additive to the sub-additive is 3 to 30 times.   The main additive is contained in an amount of 1 to 3 parts by weight and the auxiliary additive is contained in an amount of 0.1 to 0.3 parts by weight with respect to 100 parts by weight of the material of the porous dielectric sheet. Item 10. The electret filter medium according to Item 1. The electret filter medium according to claim 1, wherein the porous dielectric sheet includes at least one material having a volume resistivity of 10 ¹⁴ Ωcm or more.   The electret filter medium according to any one of claims 1 to 3, wherein the porous dielectric sheet is a melt blown nonwoven fabric.   The filter using the electret filter material of any one of Claim 1 to 4.   A porous dielectric sheet containing a hindered amine or triazine additive as a main additive and a hindered phenol additive as a secondary additive in a mass ratio of the main additive to the secondary additive of 3 to 30 times. A method for producing an electret filter medium, characterized in that water having a pH of 7 or less and a total organic carbon (TOC) of 0.1 to 20 mgC / L is sprayed and dried.