JP2019034269A - Filter medium for filter, and filter medium for laminated filter - Google Patents

Abstract

To provide a filter medium for a liquid filter, and a filter medium for an air filter, which can capture fine particulate matter and processed waste by filtration.SOLUTION: A filter medium for a filter includes non-meltable oriented polyethylene terephthalate fibers, acrylic fibers, fibrillated organic fibers, and hot-melt binder fibers. In a filter medium for a laminated filter, the filter medium for the filter, which serves as a dense layer, is superposed on a coarse layer and integrated with it.SELECTED DRAWING: None

Description

  The present invention relates to a filter material for a filter such as a filter material for a liquid filter for efficiently removing particles contained in the liquid and obtaining a clean liquid, and a filter medium for an air filter for collecting dust in the air. .

  There are roughly two structures of the filter medium for liquid filters. One is an “internal filtration type”, which is a filter medium structured to trap solid particles inside the filter medium. The other is a “surface filtration type”, which is a filter medium having a structure of capturing solid particles on the surface of the filter medium (see, for example, Patent Document 1). These filter media are pleated to increase the surface area of the filter media and then molded into a predetermined shape to produce a liquid filter, which is used in combination with other components in a filter.

  Conventionally, the filter media for liquid filters used in electrical discharge machines and IC production processes, and the filter media for various types of liquids such as automobile engine oils and fuels are made of natural pulp and organic fiber mixed sheets with phenolic resin. Although impregnated sheets, polyester spunbonded nonwoven fabrics, and the like are used, there are disadvantages such as low filtration efficiency and short life. In addition, a porous sheet such as a fluororesin is available as a high-performance filter medium. However, since it is expensive, it is limited to special applications and is not suitable as a filter medium for treating a large amount of liquid.

As one of the filter media for solving these problems, 5 to 40% by mass of organic fibers fibrillated to 1 μm or less, 5 to 60% by mass of ultrafine organic fibers having a fiber diameter of 1 to 5 μm, and organic fibers having a fiber diameter of 5 μm or more. A surface filtration type liquid comprising 20 to 70% by mass and part or all of the organic fiber having a fiber diameter of 5 μm or more is a fibrous organic binder, and the density of the filter medium is 0.25 to 0.8 g / cm ^3. A filter medium for filtration is disclosed (for example, see Patent Document 2). In this filter medium, the fibrillated organic fiber expresses the collection efficiency of solid particles and limits the content with other organic fibers to suppress pressure loss and efficiently process a large amount of liquid in a short time. can do.

  The filter medium of Patent Document 2 has a problem that it cannot be fold-folded because the thickness is very thin and not stiff, so it is thin and has excellent surface filtration performance in order to improve strength and waist (stiffness). In addition, a filter medium for liquid filtration is disclosed in which a filter medium is used as a filter medium layer, and a support layer having good liquid permeability, high strength, and good crease workability is combined (for example, patent document) 3).

  In recent years, the processing precision has been increased, and the refinement of the processing waste has progressed. In order to ensure a clean filtrate, a filter medium with higher filtration precision is required.

JP 2000-70628 A Japanese Patent No. 2633355 Japanese Patent No. 3305372

  The subject of this invention is providing the filter medium for liquid filters and the filter medium for air filters which can capture | acquire fine dust and processed waste by filtration.

As a result of intensive studies to solve the above problems, the present inventor,
(1) a filter medium for a filter comprising non-meltable stretched polyethylene terephthalate fiber, acrylic fiber, fibrillated organic fiber, and heat-meltable binder fiber,
(2) The filter medium for a filter according to the above (1) is a dense layer, and is laminated and integrated with a coarse layer;
I found.

  As a method for increasing the collection efficiency of the filter medium for filters, it is effective to use fibrillated organic fibers having a very thin fiber diameter. However, since the fiber diameter of the fibrillated organic fiber is thin, when the filter medium for the filter is produced by a wet method, the fiber is easily dropped from the papermaking net. Further, the filter medium containing fibrillated organic fibers remaining on the papermaking net without falling off tends to decrease the air permeability and liquid permeability due to excessive increase in density. Then, by using together the acrylic fiber which is easy to fluff, it can suppress that the fibrillated organic fiber and acrylic fiber form a network, and the fibrillated organic fiber falls off from the papermaking net. In addition, by using the stretched polyethylene terephthalate fiber together, the stretched polyethylene terephthalate fiber exists between the fibrillated organic fiber and the acrylic fiber network, thereby forming a three-dimensional network and improving air permeability and liquid permeability. Can be increased. Furthermore, by containing a heat-meltable binder fiber, it is possible to prevent the fibers from dropping from the filter medium and to increase the strength of the filter medium.

  In addition, the filter medium for filter containing non-melting stretched polyethylene terephthalate fiber, acrylic fiber, fibrillated organic fiber, and heat-meltable binder fiber is used as a dense layer and laminated with a coarse layer. The filter medium for multilayer filters has good liquid permeability, high strength, and good pleating processability.

  Hereinafter, the filter medium of the present invention will be described in detail. The filter medium of the present invention is characterized by containing non-melting stretched polyethylene terephthalate (PET) fiber, acrylic fiber, fibrillated organic fiber, and heat-melting binder fiber. Stretched PET fibers and acrylic fibers are non-fibrillated fibers and are short fibers called “staples”. “Heat-melting property” refers to a property of heat-melting by heat treatment (for example, drying treatment, heat calender treatment, etc.) at the time of producing filter media for a filter. The “non-melting property” is a property that does not melt by heat treatment.

  The fiber length of the stretched PET fiber is preferably 2 to 10 mm, more preferably 3 to 7 mm. When the fiber length is less than 2 mm, the stretched PET fiber may fall off from the papermaking net, and when the fiber length exceeds 10 mm, the texture may deteriorate. The fineness of the stretched PET fiber is preferably 0.05 to 1.0 dtex, more preferably 0.1 to 0.8 dtex. When the fineness is less than 0.05 dtex, the paper may be detached from the papermaking net. When the fineness exceeds 1.0 dtex, the voids of the network become large and the collection efficiency may be reduced.

  The content of the stretched PET fiber is preferably 10 to 50% by mass, more preferably 10 to 40% by mass, and 10 to 30% by mass with respect to the total fibers contained in the filter medium for the filter. More preferably. When the content of the stretched PET fiber is less than 10% by mass, there is a possibility that the filter medium for the filter medium lacks the gap and the ventilation resistance is increased. When the content of the stretched PET fiber exceeds 50% by mass, the content of the binder fiber is relatively low, and the strength may be insufficient.

  The fiber length of the acrylic fiber is preferably 2 to 10 mm, more preferably 3 to 7 mm. When the fiber length is less than 2 mm, the acrylic fiber may fall off the papermaking net, and when the fiber length exceeds 10 mm, the texture may deteriorate. The fineness of the acrylic fiber is preferably 0.05 to 1.0 dtex, more preferably 0.1 to 0.8 dtex. When the fineness is less than 0.05 dtex, the paper may be separated from the papermaking net. When the fineness exceeds 1.0 dtex, the voids of the network become large and the collection efficiency may be reduced.

  The acrylic fiber content is preferably 10 to 50% by mass, more preferably 10 to 40% by mass, and 10 to 30% by mass with respect to the total fibers contained in the filter medium. Is more preferable. When the acrylic fiber content is less than 10% by mass, a network with fibrillated organic fibers may not be formed well, and the fibrillated organic fibers may fall off the papermaking net. Moreover, when content of an acrylic fiber exceeds 50 mass%, content of a binder fiber will become comparatively low and there exists a possibility that intensity | strength may become inadequate.

  In the present invention, the fibrillated organic fiber refers to a fiber having a fiber shape having a portion finely divided mainly in a direction parallel to the fiber axis, and at least a part of the fiber diameter being 1 μm or less. . In the present invention, it is preferable that the aspect ratio of the length and width is distributed in the range of 20: 1 to 100,000: 1 and the Canadian standard freeness is in the range of 0 ml to 500 ml. The content of the fibrillated organic fiber is preferably 2 to 50% by mass, more preferably 5 to 40% by mass, and more preferably 5 to 30% by mass with respect to the total fibers contained in the filter medium. More preferably. When the content of the fibrillated organic fiber is less than 2% by mass, the uniformity and the collection efficiency may not be improved. On the other hand, if the content of fibrillated organic fibers exceeds 50% by mass, the filter medium may have insufficient voids and the filter life may be reduced.

  As the fibrillated organic fiber, celluloses such as natural cellulose, regenerated cellulose such as lyocell and rayon are preferable, and lyocell which is regenerated cellulose is particularly preferable. Also, aramid fibers such as wholly aromatic polyamide, polyester fibers such as wholly aromatic polyester, polyimide, polyamideimide, polyether ether ketone, polyphenylene sulfide, polybenzimidazole, poly-p-phenylenebenzobisthiazole, poly-p -Heat-resistant fibers made of phenylene benzobisoxazole, polytetrafluoroethylene, acrylic fibers, etc. are also preferable because they can further improve heat resistance, and among these, aramid fibers such as para-type wholly aromatic polyamides that are particularly easily fibrillated and acrylonitrile An acrylic fiber such as a copolymer of acrylate and acrylate is preferred. These may be used alone or in combination of two or more.

  In the present invention, in order to obtain fibrillated fibers, for example, short fibers are dispersed in water at an appropriate concentration, and this is rotated by a refiner, a beater, a mill, a grinding device, and a high-speed rotary blade to give a shearing force. Blade-type homogenizer, double-cylindrical high-speed homogenizer that generates a shearing force between a cylindrical inner blade that rotates at high speed and a fixed outer blade, ultrasonic crusher that refines by ultrasonic shock, and high-pressure homogenizer It is sufficient to adjust the conditions such as the blade shape, flow rate, number of treatments, treatment speed, treatment concentration, etc.

  In the present invention, in order to express the filter medium uniformity, solid particle capturing ability, pressure loss, etc. in a well-balanced manner, (A) A fibrillated organic material having a fiber diameter of 1 μm or less is separated from the trunk by applying a shearing force. It is preferable that the fiber and (B) a fibrillated organic fiber in which a branching part having a fiber diameter of 1 μm or less is generated from a trunk part having a fiber diameter of 2 μm or more by applying a shearing force is a fibrillated organic fiber. .

  The heat-meltable binder fiber in the filter medium of the present invention is a fiber having a property of being thermally melted by a heat treatment (for example, a drying process, a heat calendar process, etc.) at the time of producing the filter medium for the filter. Examples of the binder fiber include composite fibers such as a core-sheath fiber (core-shell type), a parallel fiber (side-by-side type), and a radial split fiber. Since the composite fiber hardly forms a film, the strength can be improved while maintaining the space of the filter medium for the filter. For example, polypropylene fiber, combination of polypropylene (core) and polyethylene (sheath), combination of polypropylene (core) and ethylene vinyl alcohol (sheath), combination of polypropylene (core) and vinyl acetate alcohol (sheath), polypropylene (core) and A combination of polyethylene (sheath), a combination of high melting point polyester (core) and low melting point polyester (sheath), and the like can be mentioned. From the viewpoint of increasing the strength of the nonwoven fabric, in particular, a core-sheath type polyester binder fiber should be used. Is preferred. In addition, single fibers (fully fused type) composed only of low melting point resins such as polyethylene and hot water soluble binder fibers such as hot water soluble polyvinyl alcohol fibers are easy to form a film in the heating process, Can be used as long as they are not hindered.

  The fiber length of the binder fiber is preferably 1 to 12 mm, and more preferably 3 to 10 mm. Binder fibers having a fiber length of less than 1 mm are more likely to fall off the papermaking net in the papermaking process, resulting in a decrease in adhesion points with other fibers and a reduction in strength. On the other hand, when the fiber length exceeds 12 mm, the water dispersibility is impaired, the texture becomes uneven, and the strength of the nonwoven fabric may be lowered.

  The fiber diameter of the binder fiber is preferably 3 to 20 μm, and more preferably 5 to 18 μm. If the fiber diameter is less than 3 μm, pressure loss may increase. On the other hand, when the fiber diameter exceeds 20 μm, the number of points of adhesion with other fibers decreases, and the strength may decrease.

  In the present invention, the “fiber diameter” refers to a fiber diameter having a value converted to the diameter of a perfect circle having the same cross-sectional area when the cross section of the fiber is an ellipse or a polygon.

  The content of the binder fiber is preferably 10 to 50% by mass, more preferably 15 to 45% by mass, and more preferably 20 to 40% by mass with respect to the total fibers contained in the filter medium. Is more preferable. If the content of the binder fiber is less than 10% by mass, the adhesion between the fibers tends to be insufficient, and the strength may be insufficient. When the content of the binder fiber exceeds 50% by mass, the filtration resistance is increased, which may cause a practical problem.

  The filter medium for a filter of the present invention may contain fibers other than stretched PET fibers, acrylic fibers, fibrillated organic fibers, and binder fibers as necessary. The fibers that may be added are preferably non-heat-meltable fibers. Specifically, examples of the synthetic fiber include polyester-based, polyolefin-based, polyamide-based, polyacrylic-based, vinylon-based, vinylidene, polyvinyl chloride, polyester-based, benzoate, polychlor, and phenol-based fibers. . Natural fiber includes hemp pulp, cotton linter, lint; regenerated fiber is lyocell fiber, rayon, cupra; semi-synthetic fiber is acetate, triacetate, promix; inorganic fiber is alumina fiber, alumina -Fibers such as silica fiber, rock wool, glass fiber, micro glass fiber, zirconia fiber, potassium titanate fiber, alumina whisker, and aluminum borate whisker. In addition to the above-mentioned fibers, wood fibers such as conifer pulp and hardwood pulp, woods such as bamboo pulp, bamboo pulp, kenaf pulp, and herbs can be used as plant fibers. Moreover, as long as the said fiber is a range which does not inhibit liquid permeability and air permeability, it may be fibrillated at all. Furthermore, pulp fibers obtained from waste paper, waste paper, etc. can also be used. Moreover, the fiber which has irregular cross sections, such as T type, Y type, and a triangle, can also be contained.

The basis weight of the filter medium of the present invention is not particularly limited, but is preferably ^{8~70g / m 2, 10~60g / m} 2 is more preferable. If it is less than 8 g / m ² , sufficient collection efficiency may not be obtained. On the other hand, when it exceeds 70 g / m ² , the pressure loss increases and the filter life may be reduced.

Although the filter medium for a filter of the present invention can be used as it is, the filter medium for a filter of the present invention is formed as a dense layer, and is laminated and integrated with a coarse layer having a density lower than that of the dense layer. It can be used preferentially. The coarse layer preferably contains at least one kind of polyolefin-based, polyamide-based, polyester-based, acrylic-based, vinylon-based, and regenerated fiber-based non-binder fibers having a fiber diameter of 20 μm or less. Moreover, it is preferable that the basic weight of a coarse layer is 30-70 g / m < ² >. Furthermore, it is preferable to contain 10 to 80% by mass of at least one binder fiber such as polyester, polyolefin, vinyl chloride-vinyl acetate, and polyvinyl alcohol, and a rough layer having high surface strength can be obtained. This coarse layer can be produced by a wet paper machine, but depending on the application, an electrospinning method comprising a material such as polyester, polyamide, polyolefin, or cellulose, spunbond, melt blow, needle punch A sheet produced by a method such as spunlace can be used.

  The filter material for a multilayer filter of the present invention obtained by laminating and integrating a coarse layer and a dense layer prevents the filter medium from being broken by pressure, has excellent filtration performance, for an electric discharge machine, for engine oil, It can be suitably used as a filter material for liquid filters such as for fuel, oil / water separation, and hydraulic equipment. In this case, the surface layer filtration mechanism can be developed by using the dense layer as the upstream side. Also, depending on the conditions used or the intended effect, the internal filtration mechanism can be developed with the coarse layer upstream.

  The filter medium of the present invention is used for an air filter for liquid crystal, bio, pharmaceutical, food industry clean rooms, clean benches, etc., an air filter for air conditioning, an air filter for an air purifier, a gas turbine or a steam turbine. It can also be suitably used for industrial air filters suitable for collecting particles in air or gas.

In the filter medium for a multilayer filter of the present invention, the density of the dense layer is preferably 0.1 to 0.8 g / cm ³ . When the density is less than 0.1 g / cm ³ , particles are likely to be clogged in the dense layer, and the lifetime may be shortened. Conversely, if it exceeds 0.8 g / cm ³ , the filtration resistance may become too high. The density of the coarse layer is preferably smaller than the dense layer and 0.05 to 0.6 g / cm ³ . When the density of the coarse layer is less than 0.05 g / cm ³ , the strength of the filter medium for the multilayer filter may be insufficient, or the pleatability may be impaired. Conversely, if it exceeds 0.6 g / cm ³ , the filtration resistance may become too high. Further, the density of the entire (laminated) filter medium is preferably 0.1 to 0.6 g / cm ³ . (Multilayer) If the density of the filter medium as a whole is less than 0.1 g / cm ³ , there is a problem in terms of reliability due to pinholes and the like.

  In addition, it is preferable that the filter material for (laminated) filter of the present invention contains a thermoplastic resin because rigidity is improved. Examples of the thermoplastic resin include acrylic, vinyl acetate, epoxy, synthetic rubber, urethane, polyester, vinylidene chloride, polyvinyl alcohol, starch, phenol resin, and the like alone or Can be used in two or more types.

  When the thermoplastic resin is contained in the (laminated) filter medium of the present invention, the content is preferably 0.01 to 10% by mass with respect to the filter medium. If it exceeds 10% by mass, the pressure loss of the (filtered) filter medium may become too large. If it is less than 0.01% by mass, the rigidity may not be changed as compared with a filter material containing no thermoplastic resin (lamination).

  The state in which the thermoplastic resin is contained in the filter medium for the laminated filter may be only the dense layer, both the dense layer and the coarse layer, or only the coarse layer. However, when the dense layer contains a thermoplastic resin, the space of the dense layer is blocked, the solid particle capturing ability is reduced, and the pressure loss is increased, so that it is preferably contained only in the coarse layer.

  The method of incorporating the thermoplastic resin into the (laminated) filter medium is not particularly limited, and examples thereof include a size press method, a tab size press method, a spray method, an internal addition method, and a gravure coating method. In order to make it contain only in a rough layer, it is preferable to use a spray system and a gravure coating system.

  In the filter material for (laminated) filter of the present invention, a cross-linking agent, a water repellent, a dispersant, a yield improver, a paper strength agent, and a dye are added to the filter material for the (laminated) filter as needed. Additives such as can be appropriately blended.

  The filter medium for a filter of the present invention is preferably produced by a wet method. In the wet method, paper machines such as long nets, circular nets, and inclined wires are installed alone, and two or more of the same or different types selected from these paper nets are installed online. Filter media can be manufactured by a composite paper machine. The wet paper (web) manufactured by the papermaking net is dried with a dryer. After drying, a thermoplastic resin may be contained in some cases and dried with a dryer. As the dryer, an air dryer, a Yankee dryer, a cylinder dryer, a suction drum dryer, an infrared dryer, or the like can be used. In addition, when using a coarse layer produced by a dry method, a dense layer produced by a paper machine and a coarse layer produced by a dry method may be laminated by a paper machine, or a separate calender device, thermal calender device, pasting device may be used. You may laminate | stack using processing machines, such as a matching apparatus.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the examples. In the examples, all parts and percentages are by mass unless otherwise specified.

<PET fiber 1>
A drawn PET fiber having a fineness of 0.1 dtex and a fiber length of 3 mm was designated as PET fiber 1.

<PET fiber 2>
The drawn PET fiber having a fineness of 0.4 dtex and a fiber length of 5 mm was designated as PET fiber 2.

<PET fiber 3>
A drawn PET fiber having a fineness of 0.6 dtex and a fiber length of 5 mm was designated as PET fiber 3.

<PET fiber 4>
A drawn PET fiber having a fineness of 1.7 dtex and a fiber length of 5 mm was designated as PET fiber 4.

<Acrylic fiber 1>
The acrylic fiber 1 was an acrylic fiber having a fineness of 0.1 dtex and a fiber length of 3 mm.

<Acrylic fiber 2>
The acrylic fiber 2 was an acrylic fiber having a fineness of 0.4 dtex and a fiber length of 5 mm.

<Acrylic fiber 3>
The acrylic fiber 3 was an acrylic fiber having a fineness of 0.6 dtex and a fiber length of 5 mm.

<Binder fiber>
A polyester core-sheath type heat-sealable fiber having a fiber diameter of 1.7 dtex, a fiber length of 5 mm, a core part of PET (melting point 253 ° C.), and a sheath part of a polyethylene terephthalate-isophthalate copolymer (softening point 75 ° C.) as a binder Made of fiber.

<FB fiber 1>
A fibrillated lyocell fiber obtained by repeatedly treating a non-fibrillated lyocell single fiber (1.7 dtex × 4 mm, manufactured by Coatles Co., Ltd.) 60 times using a double disc refiner was designated as FB fiber 1.

<FB fiber 2>
A fibrillated para-type wholly aromatic polyamide fiber obtained by treating a para-type wholly aromatic polyamide fiber having a fiber diameter of 10 μm and a fiber length of 3 mm with a double disc refiner 60 times was designated as FB fiber 2.

(Examples 1-15 and Comparative Examples 1-4)
Water is added to a 2 m ³ dispersion tank and then blended in the proportions shown in Table 1, dispersed at a dispersion concentration of 0.2% by mass for 5 minutes, and stirred uniformly with an agitator. % Concentration) was prepared. This slurry for paper making is made up by a wet method using a circular paper machine, and binder fibers are bonded by a cylinder dryer at 130 ° C. to develop non-woven fabric strength, and a filter medium for filter having a basis weight of 20 g / m ³ is produced. did.

(Examples 16 and 17)
After pouring water into a 2 m ³ dispersion tank, the dense layer and the coarse layer are mixed separately in the ratios shown in Table 2, dispersed for 5 minutes at a dispersion concentration of 0.2% by mass, and uniform with stirring by an agitator. A papermaking slurry (0.2% concentration) was prepared. Using an inclined / circular mesh paper machine, a web is formed so that the coarse layer has a dry mass of 40 g / m ² on the inclined wire, and the dense layer has a dry mass of 20 g / m ² on the circular wire. After the webs were formed and laminated before drying, the touch roll was dried and integrated with a cylinder dryer having a surface temperature of 130 ° C. at a pressure of 400 N / cm ² , and Example 16 and 17 filter media for multilayer filters were obtained.

(Example 18)
After pouring water into a 2 m ³ dispersion tank, the dense layer is blended at the ratio shown in Table 2, dispersed at a dispersion concentration of 0.2% by mass for 5 minutes, and stirred uniformly with an agitator to make a uniform papermaking slurry ( 0.2% concentration) was prepared. Using a circular paper machine, a web is formed so as to have a dry mass of 20 g / m ² , and a dense layer is formed by pressing the touch roll at a pressure of 400 N / cm ² with a cylinder dryer having a surface temperature of 130 ° C. Obtained. A dense layer and a PET non-woven fabric (fiber diameter 15 μm, basis weight 40 g / m ² ) prepared by a spunbond method as a coarse layer were laminated and integrated by embossing to obtain a laminated filter medium of Example 18.

  The following evaluations were performed on the filter media and the filter media obtained in Examples and Comparative Examples, and the results are shown in Tables 1 and 2.

<Evaluation>
The filter media obtained in Examples and Comparative Examples and the filter media for multilayer filters were subjected to the following evaluation, and the evaluation results of pressure loss, particle collection efficiency, and strength are shown in Tables 1 and 2.

[Pressure loss] (Unit: Pa)
According to JIS B9908, it measured on the conditions of the surface wind speed of 5.3 cm / sec. The pressure loss is preferably as low as possible. “◎” is less than 150 Pa, “◯” is 150 Pa or more and less than 200 Pa, “Δ” is 200 Pa or more and less than 250 Pa, and “X” is 250 Pa or more.

[Collection efficiency] (Unit:%)
According to JIS B9908, it measured on the conditions of the surface wind speed of 5.3 cm / sec. Particles to be measured are measured using air dust and the collection efficiency of particles having a particle diameter of 0.25 to 0.35 μm using a particle counter (trade name “KC-11”, manufactured by Rion Co., Ltd.). From the following formula 1, the collection efficiency was calculated.

η = (1−C2 / C1) × 100 (Equation 1)
η: Collection efficiency (%)
C1: Particle concentration upstream of the filter medium C2: Particle concentration downstream of the filter medium

  The higher the collection efficiency, the better. "◎" if 50% or more, "○" if 40% or more and less than 50%, "△" if 30% or more and less than 40%, if less than 30%. It was set as “x”.

[Strength]
The filter media for filters and the filter media for multilayer filters of Examples and Comparative Examples were cut into a strip shape having a width of 50 mm. The test piece was mounted on a 40 mmφ fixed frame installed on a tabletop material testing machine (trade name: STA-1150, manufactured by Orientec Co., Ltd.), and the tip was rounded (curvature: 1.6) with a diameter of 1.0 mm. The metal needle (manufactured by Orientec Co., Ltd.) was lowered at a constant speed of 50 mm / min. The maximum load (g) at this time was measured and used as the puncture strength. Measure the puncture strength at 5 or more locations for one sample, and the minimum puncture strength among all the measured values is “◎◎” if it is 100 g or more, “◎” if it is 50 g or more and less than 100 g, and 40 g or more and less than 50 g. If it is, it is represented by “◯”, if it is 30 g or more and less than 40 g, “Δ”, if it is less than 30 g, it is represented by “x”.

[Applicability to pleating]
The filter medium for laminated filter is cut into a machine flow direction (MD) 30 cm and a horizontal direction 20 cm, and a mountain fold and a valley fold are repeated every 5 cm so as to cross the flow direction. On the folded filter medium, the diameter is 5 cm and the length is 30 cm. Then, a cylindrical metal roll having a weight of 3 kg is slowly rolled to make a crease and a bellows shape. The crease is clear and has no distortion, and if the crease is not deformed even if it is pushed, it is considered good. The pleatability was evaluated for the filter media for laminated filters obtained in Examples 16-18.

  From the comparison between Examples 1 to 15 and Comparative Examples 1 to 4, the filter media obtained in Examples 1 to 15 were non-melted stretched polyethylene terephthalate fiber, acrylic fiber, fibrillated organic fiber, and hot melt. Since the binder fiber is contained, the results are excellent in uniformity, good balance between collection efficiency and pressure loss, and good strength.

  On the other hand, the filter medium obtained in Comparative Example 1 did not contain fibrillated organic fibers, which resulted in low collection efficiency. Moreover, since the filter medium for filters obtained in Comparative Example 2 did not contain stretched PET fibers, the pressure loss was larger than that of the Examples. Furthermore, since the filter medium for filter obtained in Comparative Example 3 did not contain acrylic fibers, the fibrillated organic fibers were often detached from the papermaking net, resulting in low collection efficiency. Moreover, since the filter material for filters obtained in Comparative Example 4 did not contain hot-melt binder fibers, the results were low in strength.

Example 16 and Example 17 are filter media for laminated filters in which a dense layer and a coarse layer are laminated and integrated, and each dense layer has the same fiber composition as the filter media of Example 1 and Example 7. . The filter media for laminated filters of Examples 16 and 17 were good in pressure loss, collection efficiency, and strength. In addition, since the filter media for the laminated filter of Example 16 and Example 17 are formed by integrating the dense layer and the coarse layer, in the pleating suitability test, the crease is clear and has no distortion, and it does not deform even when the crease is pushed, Excellent suitability for pleating. In Example 18, the dense layer has the same fiber composition as the filter medium of Example 1, and a PET nonwoven fabric (fiber diameter 15 μm, basis weight 40 g / m ² ) prepared by the spunbond method as a rough layer is embossed. It was a filter material for laminated filters laminated and integrated with a dense layer, and had good pressure loss, collection efficiency, strength, and suitability for pleating.

  The filter material for the (laminated) filter of the present invention is used for cutting, polishing, and etching of processing waste contained in the machining fluid of an electric discharge machine used for metal engraving and cutting, and wafers of substrates in IC production. It can be suitably used for a liquid filter for efficiently removing processing waste contained in ultrapure water used in the process, etc., and obtaining a clean liquid, a liquid filter for automobile engine oil, a fuel, etc. . Moreover, it can be used suitably also for the air filter which collects the dust in the air.

Claims (2)

  A filter medium comprising a non-melting drawn polyethylene terephthalate fiber, an acrylic fiber, a fibrillated organic fiber, and a heat-melting binder fiber.   A filter material for a multilayer filter obtained by forming the filter medium according to claim 1 as a dense layer and laminating and integrating with a coarse layer.