JPH02152509A - Filter medium - Google Patents

Abstract

PURPOSE:To achieve high efficiency and performance of the subject filter medium by using a nonionic surfactant having 10-20 HLB value jointly with an org. fiber a part of which is fibrillated into the fiber having <=1mum diameter in the filter medium consisting of >=2 kinds of fibers. CONSTITUTION:The filter medium consists of >=2 kinds of fibers, contains an org. fiber a part of which is fibrillated into the fiber having <=1mum diameter, and is used jointly with a nonionic surfactant having 10-20 HLB value. The content of the fibrillated org. fiber is controlled to >=3% based on the total fiber weight from the standpoint of filtration efficiency. The org. fiber of aromatic polyester, aromatic polyamide, etc., having high crystallinity and orientational property is fibrillated to obtain the fibrillated org. fiber. The amt. of the nonionic surfactant to be added is preferably controlled to 0.1-5.0% based on the total fiber weight. An industrially useful high-performance filter medium is obtained without using glass fiber, and the consumption of the expensive fibrillated org. fiber is reduced by use of a surfactant.

Description

[Detailed Description of the Invention] <A) Industrial Application Field The present invention efficiently removes fine dust contained in gases such as high performance air filters (HEPA) and automobile air filters, resulting in clean air filters. Furnace materials for air filters to obtain gas, and oil filters for automobiles R-materials for liquids for removing fine particles in liquids such as automobile fuel filters, filters for electrical discharge machines, and water treatment filters for ultrapure water recovery. etc. are related to materials.

(B) Prior Art Glass is often used as a high-performance furnace material for removing particulates contained in liquid or gas because it can be produced with a small diameter at a relatively low cost. However, with furnace materials using ultra-fine glass fibers, it is inevitable that the fine glass fibers contained in the R material will fall off during use, and dust generation from the P material itself due to vibrations of the furnace material is unavoidable. Its use in applications that pose health and safety issues, such as high-performance furnace materials and food applications, is restricted, and glass is not resistant to chemicals such as hydrofluoric acid, so it cannot be used in applications where it may be exposed to hydrofluoric acid vapor. There were problems such as restrictions on its use, and there was a limit to its use in nuclear power applications because it could not be reduced in volume by incineration.

For this reason, furnace materials using fibrillated organic fibers have been developed to solve the drawbacks of furnace materials using ultrafine glass fibers (Japanese Patent Application Laid-Open Nos. 59-92011 and 63 -232814 Publication, JP-A-63-2
36512).

However, even when such fibers are used, despite the small diameter of the fibers, characteristics that satisfy both the high collection efficiency and low passage resistance obtained with ultrafine glass fibers cannot be obtained.

In addition, when these fibrillated organic fibers are used in some wet papermaking methods, there are manufacturing problems such as a large amount of flow from the wire and clogging of the wire. is unavoidable.

(C) Problems to be Solved by the Invention The present invention solves the above-mentioned drawbacks and problems, maximizes the trapping ability of fibrillated organic fibers as a constituent element of filter media, does not contain glass fibers, and is easy to manufacture. The purpose of this invention is to provide a filter medium with high efficiency and high performance, which is not problematic in the prior art and could not be achieved without microglass fibers.

(D) Means for solving the problems As a result of various studies as a method to solve these problems, we found that by using a nonionic surfactant with an HLB value in a specific range in combination with fibrillated organic fibers. ,
The present invention was completed by discovering that it is possible to maximize the capture ability of fibrillated organic fibers.

That is, the present invention provides a filter medium made of two or more types of fibers,
It is characterized by being manufactured by a wet papermaking method from an aqueous slurry whose essential components are fibrillated organic fibers with a fiber diameter of 1 μm or less and a nonionic surfactant with an HLEI value of 10 or more and less than 20. It is a filter medium that

The fibrillated organic fiber in which part of the fiber has a fiber diameter of 1 μm or less in the present invention can be obtained by, for example, 1) flowing a synthetic polymer solution into a poor solvent for the polymer while applying a shearing force;
Method for precipitating fibrous fibrils (fibrid method,
(Special Publication No. 3511851).

2) A method in which fibrils are precipitated by shearing synthetic monomers without polymerizing them (new method for polymerization, Japanese Patent Publication No. 47-2
Publication No. 1898).

3) A method in which two or more types of incompatible polymers are mixed, melt-extruded or spun, and then cut and fibrillated into fibers by mechanical means (split method, Japanese Patent Publication No. 35-9651).

4) A method in which two or more types of incompatible polymers are mixed, melt-extruded or spun, and after cutting, immersed in a solvent to dissolve one of the polymers and fibrillate it into a fiber (polymer blend dissolution method, US Patent No. 3,382.305).

5) A method in which the synthetic polymer is explosively ejected from the high-pressure side to the low-pressure side at a temperature higher than the boiling point of the solvent, and then fibrillated into fibers (flash spinning method, Japanese Patent Publication No. 36-16460)
Publication No.).

6) A method in which a polyester polymer is blended with an alkali-soluble component that is incompatible with the polyester, and after molding, it is subjected to a weight loss treatment with an alkali, and then beaten to form fibrils into a fibrous form (alkali weight loss beating method, JP-A-1988-1999). Publication No. 315).

7) After cutting the highly crystalline and highly oriented fibers to an appropriate fiber length,
A method of dispersing in water and fibrillating it using a homogenizer, a beater, a sand mill, etc.
No. 0801, JP-A-59-92011, US
-4761203).

The amount of these fibrillated organic fibers is not particularly limited as it depends on the required characteristics of the r-material, but from the viewpoint of filtration efficiency it is preferably 3% or more of the total fiber weight.

Particularly preferred examples of these fibrillated organic fibers include highly crystalline and highly oriented fibers that are cut into appropriate fiber lengths, dispersed in water, and fibrillated using a homogenizer, beater, sand mill, etc. The following can be mentioned.

The highly crystalline and highly oriented fibers mentioned here include, for example,
Aromatic polyester (Econol manufactured by Sumitomo Chemical Co., Ltd.)
, aromatic polyamide (manufactured by Kevlar DuPont), Technora (manufactured by Ryotaisha), and the like.

A specific example of fibrillated highly crystalline and highly oriented fibers is MFC-400 (manufactured by Daicel Chemical Industries, Ltd.).

In the present invention, the nonionic surfactant having an HLB value of 10 or more and less than 20 refers to an HLB value (Hydrophile Lip
It is a highly hydrophilic nonionic surfactant whose chemical structure is not particularly limited, such as polyoxyethylene alkyl ether surfactant, polyoxyethylene alkyl phenyl ether surfactant, etc. , polyoxyethylene polystyrylphenyl ether surfactant, polyoxyethylene-poliodipropylene glycol surfactant, polyoxyethylene-polyoxypropylene alkyl ether surfactant, polyhydric alcohol fatty acid partial ester surfactant agent, polyoxyethylene polyhydric alcohol fatty acid partial ester surfactant, polyoxyethylene fatty acid ester surfactant, polyglycerin fatty acid ester surfactant, polyoxyethylated castor oil surfactant, fatty acid jetanolamide surfactant, polyoxyethylene alkylamine surfactant,
Nonionic surfactants such as triethanolamine fatty acid partial ester surfactants and trialkylaminoxide surfactants, and specific examples include:
Emulgen 108.109P, 120.123P, 14
7.130K, 210.220.306P, 320P,
408.409P, 420.430.705.707.
709.810.840S, 906.909.910,
PI-20T, 911.913.920.930.93
1.935.950.985, A-60, A-90, A
300, B-66, Rheodor TW-L120, TW-
LiO2, TW-PL20, TW-3L20, TW-9
320, TW-0120, TW-0106, TW-03
20,430,440,460, SEM, Emazol 0
-105R, Emanone 1112.3115.3130
．． 3170.3199.3299.4110 (manufactured by Kao Corporation), Nirasan Nonion L-4, F-2,5,
P-6, S-4, S-6, 5-10, 5-15, 5-1
5,4,5-40,0-3,O-4,O-6,T-15
, K-207, K-211, K-220, K-230,
P-208, P-210, P-213, P-223, P
-240, E-212, E-215, E-220, E-
230, S-207, S-211, S-215, S-2
20,3-230, T-208,5, H8-206, H
S-208, H8-210, MS-215, ) (S-2
20, H8-240, NS-206, NS-208,5
, H5-210, H5-212, H5-215, NS-
220, NS-230, NS-240, NS-240,
NS-270, LT-221, PT-221, 5T-2
21,0T-221, Unigri GL-102, GL-1
06, Uniox Hc-40, HC-50, HC-6
0 (manufactured by NOF Corporation), etc. are exemplified.

) (The amount of nonionic surfactant with an LB value of 10 or more and less than 20 is not particularly limited, but if it is less than 0.1% based on the fiber content, a sufficient effect cannot be expected, and even if it exceeds 5%, the effect remains constant.) Since the above effects cannot be obtained, a range of 0.1% to 5% of the fiber content is preferable.

Further, nonionic surfactants other than those mentioned above, anionic surfactants, cationic surfactants, amphoteric surfactants, etc. can also be used in combination.

Fibers other than the fibrillated organic fibers used in the present invention include natural fibers such as wood bulbs, hemp pulp, esparto, and cotton fibers, polyester fibers, vinylon fibers, acrylic fibers, polyethylene fibers, polypropylene fibers, and polyamide fibers. , synthetic fibers and recycled fibers such as rayon fibers, glass fibers, ceramic fibers, rock wool, alumina fibers, beryllium oxide fibers, boron carbide fibers, silicon carbide fibers, silicon nitride fibers, potassium titanate fibers, graphite, silica, and other inorganic fibers. Fibers are exemplified, 1
One or more types may be appropriately selected and blended depending on the purpose.

The filter medium of the present invention may contain a binder such as an acrylic emulsion, if necessary, to the extent that it does not impede the properties of the furnace material.
Additives such as fluorine-based or silicone-based water repellents, sticky agents, retention improvers, dyes, etc. can be blended.

The filter medium of the present invention is manufactured using a paper machine for manufacturing general paper or wet-laid nonwoven fabric, such as a Fourdrinier paper machine, a cylinder paper machine, or an inclined wire paper machine.

(E) Effect It is not clear why the combination of fibrillated organic fibers and nonionic surfactants is effective in the filter medium of the present invention, but when the nonionic surfactant is not included, fibrillated organic fibers However, even if the filtration resistance is large, high filtration efficiency cannot be obtained even if the filtration resistance is large, and the combination of ultrafine glass fibers or general organic fibers and surfactants does not improve the filtration efficiency as clearly as observed in the present invention. Therefore, it cannot be considered that the improvement in filtration efficiency achieved by the present invention is due solely to the improvement in the dispersibility between fibers, and that the nonionic surfactant causes fine particles due to the surface tension of water during dehydration and drying. It is presumed that this is because it prevents the fibrils from converging, and as a result, each fine fibril functions effectively for filtration.

(F) Examples Hereinafter, the present invention will be explained by examples, but the present invention is not limited to these examples.

% in Examples and Comparative Examples represents % by weight.

In addition, the pressure loss, dust collection efficiency, filtration rate, and in-liquid particle collection efficiency in Examples and Comparative Examples were measured by the following methods.

Pressure loss: The ventilation resistance when air was passed through the furnace material at a flow rate of 4.75 cm/sec was determined using a water column manometer.

Dust collection efficiency: Dioctyl phthalate particles with an average particle size of 0.3μ are generated, air containing these particles is passed through the furnace material at a flow rate of 5.3 cm/sec, and the air sampled before and after the furnace material is The number of particles was measured using a light scattering particle counter (KC-1 1, manufactured by Rion Co., Ltd.), and calculated using the following formula.

Dust collection efficiency (%') = (A-B)/AX100 (A is the number of particles before r-filtration, B is the number of particles after filtration) Filtration speed: 1000
It was calculated from the amount of liquid passed in one minute when water was filtered at a water column pressure of mmAq.

Particle collection efficiency in liquid: Polystyrene standard particle dilution semi-liquid with an average particle size of 0.34μ is filtered through a furnace material, and the number of particles in the liquid before and after filtration is measured using a particle counter in liquid (manufactured by Rion Co., Ltd.). It was calculated using the same formula as the dust collection efficiency above.

Examples 1 to 4 Nonionic surfactant (Emanon 3299, polyoxyethylene fatty acid ester type, HLB value = 18.3, manufactured by Kao Corporation) was added at 0.5% and 1%, respectively, based on the total fiber weight.
Kevlar fine fiber (MFC-400, manufactured by Daicel Chemical Industries, Ltd.) 18%, polyester fiber (manufactured by Asahi Kasei Industries, Ltd.,
0.1 denier x 3 mm, diameter 3 μm) 8%, Y-type vinylon fiber (manufactured by Kuraray Co., Ltd., 2 denier x 6 mm, M
Aqueous slurry was prepared by mixing 74% of t large projected diameter (approximately 20μ), and from this slurry, a standard square hand paper machine was used to make a basis weight of 75g/n? After forming a sheet, it was lightly pressed and dried to obtain filter media sheets of Examples 1 to 4, respectively.

Table 1 shows the physical properties and filter performance of these sheets. Indicated.

Example 5 Kevlar was added to an aqueous solution in which a nonionic surfactant (Emanon 3199, polyoxyethylene fatty acid ester type, HLB value = 19.1, manufactured by Kao Corporation) was dissolved at a concentration of 3.0% based on the total fiber weight. Fine fiber (MFC-400, manufactured by Daicel Chemical Industries, Ltd.) 18%, polyester fiber (manufactured by Asahi Kasei Industries, Ltd., 0.1 denier x 3 m, diameter approximately 3μ), 8%, Y-type vinylon fiber (Kuraray Co., Ltd.) 2 denier x 61, maximum projected diameter approximately 20 μm) 74% was mixed to create an aqueous slurry, and from this slurry a sheet with a basis weight of 75 g/rrr was formed using a standard square hand paper machine. After that, it was lightly pressed and dried, and the resulting sheet was coated with an acrylic latex binder (Blymar H).
A-8, Nippon Acrylic Chemical Co., Ltd.) 0.25% and fluorine water repellent (FP210, Sumitomo Chemical Co., Ltd. >0.15%)
The swamp material sheet of Example 5 was obtained by impregnating the solid material with an aqueous solution containing Ig/r[1' in solid content and drying. The physical properties and filter performance of this sheet are shown in Table 1.
The obtained P material sheet exhibited filter performance without any practical problems as a HEPA filter, and also exhibited good volume reduction properties since it did not contain glass.

Comparative Example 1 A P material sheet of Comparative Example 1 was obtained in exactly the same manner as in Example 1 except that the nonionic surfactant was removed. The physical properties and filter performance of this sheet are shown in Table 1. The obtained P material sheet had lower dust collection efficiency and inferior performance than the sheets of Examples 1 to 4.

Comparative Example 2 The nonionic surfactant of Example 3 (NS-204,5
, polyoxyethylene alkylphenol ether type,
A P material sheet of Comparative Example 2 was obtained in the same manner as in Example 3, except that the HLB value was 9.5 (manufactured by NOF Corporation). The physical properties and filter performance of this sheet are shown in Table 1.
The obtained oak sheets had lower dust collection efficiency and inferior performance than the sheets of Examples 1 to 4.

Example 6 Kevlar was added to an aqueous solution in which a nonionic surfactant (Emanon 3115, polyoxyethylene fatty acid ester type, HLB value = 13.4, manufactured by Kao Corporation) was dissolved at a concentration of 3.0% based on the total fiber weight. @Fine fiber (MFC-400, manufactured by Daicel Chemical Industries, Ltd.) 3%, ultrafine polyester fiber (manufactured by Asahi Kasei Industries, Ltd., 0.1 denier x 3 mm>67%), polyester binder fiber (manufactured by Unitika, #4080.
After mixing 30% of 2 denier x 5 m) to create an aqueous slurry and forming a sheet from this slurry using a standard square hand paper machine to have a basis weight of 40 g/rrl, The P material sheet of Example 6 was obtained by lightly pressing, drying, and further performing heat calender treatment. Table 2 shows the physical properties and filter performance of this sheet.

The obtained furnace material sheet had high particle collection efficiency in liquid, low filtration resistance, and exhibited good filter performance.

Comparative Example 3 A sheet of Comparative Example 3 was obtained in exactly the same manner as in Example 6 except that the nonionic surfactant of Example 6 was removed. The physical properties and filter performance of this sheet are shown in Table 2. The obtained furnace material sheet had lower collection efficiency than the filter material sheet of Example 6 and had poor filter performance.

(G) Effects of the Invention The present invention eliminates the drawbacks of the P material using ultrafine glass fibers, and provides a high-performance filter medium that has hitherto been impossible to achieve with anything other than ultrafine glass fibers. It solves the disadvantages of self-dust generation, mixing of fine glass into the filter body, low volume reduction by incineration, and sensitivity to hydrofluoric acid, which are disadvantages when using The present invention provides a highly useful high-performance oak material. Furthermore, the use of surfactants makes it possible to reduce the amount of expensive fibrillated organic fibers used.

Claims (4)

[Claims] (1) In a filter medium consisting of two or more types of fibers, organic fibers partially fibrillated to a fiber diameter of 1 μm or less and HLB
A filter medium comprising a nonionic surfactant having a value of 10 or more and less than 20. (2) Claim 1, characterized in that the amount of nonionic surfactant added is 0.1 to 5.0% based on the total fiber weight.
The filter media listed. (3) The filter medium according to claim 1 or 2, wherein the fibrillated organic fibers, some of which have a fiber diameter of 1 μm or less, are highly crystalline and highly oriented fibers. (4) The filter medium according to claim 1, 2, or 3, wherein the amount of the organic fibers, some of which are fibrillated and have a fiber diameter of 1 μm or less, is 3% or more of the total fiber weight.