JP2014061502A - Nonwoven fabric for filter and filtering medium for filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a nonwoven fabric for a filter that hardly deforms even under high pressure and provide a filtering medium for a filter with a long service life.SOLUTION: There is provided a nonwoven fabric for a filter, containing polyethylene terephthalate fibers whose ratio (I/I) is 3.0 or higher of peak intensities at around 1096 cmand at around 1120 cmin a Raman scattering spectrum, and a filtering medium for the filter comprising the nonwoven fabric for the filter.

Description

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

  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). In addition, the filter medium is subjected to pleating to increase the surface area of the filter medium, and then formed into a predetermined shape to produce a liquid filter, which is used in combination with other components in a filter.

  Conventionally, filter media for liquid filters used in electrical discharge machines and IC production processes, filter media for various types of liquids such as automotive engine oil, fuel, etc., mixed pulp of natural pulp and organic fibers, phenol resin, etc. Sheets impregnated with polyester, polyester nonwoven fabric (spunbond), and the like are used, but have 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 a method 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 20 to 70% by mass of organic fibers having a fiber diameter of 5 μm or more. % 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 0.80 g / cm ^3. Is disclosed (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. To be able to.

  The above filter media has a problem that it is difficult to pleat because the thickness is very thin and not hard. Therefore, the filter media is thin and excellent in surface filtration performance in order to improve strength and waist (stiffness). A filter medium for liquid filtration is disclosed in which a layer and a support layer with good liquid permeability, high strength and good pleatability are combined and integrated (see Patent Document 3). However, in recent years, the pressure applied to the filter medium has been increasing as the processing speed of the processing machine is increased, the size of the processing waste is further reduced, and further, the pressure difference in use limit of the filter medium is increased, which is disclosed in Patent Document 3. When the thickness of the filter medium is reduced, the filter medium may be deformed by the pressure of the liquid, and the pleated ridges may be brought into close contact with each other to shorten the life.

JP 2000-70628 A Japanese Patent Laid-Open No. 3-12208 JP-A-6-126112

  The subject of this invention is providing the filter medium for liquid filters and the filter medium for air filters which implement | achieve the non-woven fabric for filters which cannot be easily deformed even under high pressure, and have a long life.

As a result of intensive studies to solve the above problems, the present inventors have
(1) A nonwoven fabric for a filter comprising a polyethylene terephthalate fiber having a peak intensity ratio (I ₁₀₉₆ / I ₁₁₂₀ ) in the vicinity of ₁₀₉₆ cm ⁻¹ and 1120 cm ^{−1 of the} Raman scattering spectrum of 3.0 or more,
(2) The content of polyethylene terephthalate fiber having a peak intensity ratio (I ₁₀₉₆ / I ₁₁₂₀ ) in the vicinity of ₁₀₉₆ cm ⁻¹ and 1120 cm ^{−1 of the} Raman scattering spectrum of 3.0 or more is 10 to 80% in the nonwoven fabric mass ratio. A non-woven fabric for a filter according to the above (1),
(3) The fineness of the polyethylene terephthalate fiber having a peak intensity ratio (I ₁₀₉₆ / I ₁₁₂₀ ) in the vicinity of ₁₀₉₆ cm ⁻¹ and 1120 cm ^{−1 of the} Raman scattering spectrum of 3.0 or more is 0.3 to 5.0 dtex. (1) or the nonwoven fabric for filters according to (2),
(4) A filter medium for a filter comprising the filter nonwoven fabric according to any one of (1) to (3) above,
(5) A filter medium for a filter obtained by forming the nonwoven fabric for a filter according to any one of the above (1) to (3) as a rough layer and laminating and integrating with a dense layer,
(6) The filter medium according to (5), wherein the dense layer contains fibrillated organic fibers,
(7) The filter medium for a filter according to any one of the above (1) to (5), comprising a thermoplastic resin,
I found.

Polyethylene terephthalate fiber is a fiber that is easy to be made fine, has moderate rigidity, and is excellent in heat resistance and chemical resistance. In the nonwoven fabric for filter (1) of the present invention, by containing polyethylene terephthalate fibers having a peak intensity ratio (I ₁₀₉₆ / I ₁₁₂₀ ) of about ₁₀₉₆ cm ⁻¹ and 1120 cm ^{−1 of the} Raman scattering spectrum of 3.0 or more, A non-woven fabric for a filter that is excellent in rigidity and hardly deforms even under high pressure can be obtained.

In the filter nonwoven fabrics (2) and (3) of the present invention, the inclusion of polyethylene terephthalate fibers having a peak intensity ratio (I ₁₀₉₆ / I ₁₁₂₀ ) in the vicinity of ₁₀₉₆ cm ⁻¹ and 1120 cm ^{−1 of the} Raman scattering spectrum of 3.0 or more. When the amount and the fineness are in an appropriate range, the rigidity is preferably improved.

  The filter medium (4) for a filter of the present invention contains any one of filter nonwoven fabrics (1) to (3) having excellent rigidity. Moreover, in the filter medium (5) for the filter of the present invention, any one of the filter nonwoven fabrics (1) to (3) having excellent rigidity is made into a rough layer, and laminated and integrated with a dense layer, A filter medium for a filter having a long life and excellent filtration performance is preferable. Furthermore, in the filter medium (6) for a filter of the present invention, by containing fibrillated organic fibers in a dense layer, a homogeneous fiber network is obtained, and filtration performance is improved, which is preferable.

  In the filter medium (7) for a filter of the present invention, it is preferable to impregnate with a thermoplastic resin because pleatability is improved.

It is a Raman scattering spectrum of a polyethylene terephthalate fiber.

Hereinafter, the nonwoven fabric for filter and the filter medium for filter of the present invention will be described in detail. Filter nonwoven fabric of the present invention is characterized in that 1096Cm ^-1 and 1,120 cm ^-1 vicinity of the peak intensity ratio of the Raman scattering spectrum _(I 1096 _/ I ₁₁₂₀₎ contains 3.0 or more polyethylene terephthalate fibers. Hereinafter, “(I ₁₀₉₆ / I ₁₁₂₀ )” may be referred to as “(I _t / I _g )”. Polyethylene terephthalate fibers can be improved in crystallinity by adjusting the spinning conditions. For example, it is known that the yarn is produced by a method in which an undrawn yarn having a high degree of molecular orientation is pulled and heat-drawn by increasing the spinning speed, but the present invention is not limited to this. Peak near 1096cm ^-1 and around 1,120 cm ^-1 of the Raman scattering spectra, which respectively show the Trans and Gauche component of ethylene glycol moieties polyethylene terephthalate fibers, Trans components are known to form a crystalline . The peak intensity ratio (I _t / I _g ) of the polyethylene terephthalate fiber according to the present invention need not be particularly limited, but if it is too large, the spinnability may be impaired, so 3.0 to 6.0 is It is preferably 3.5 to 5.0. Hereinafter, unless otherwise indicated, referred to in the present invention, "polyethylene terephthalate fibers", "1096Cm ^-1 and around 1120cm peak intensity ratio in the vicinity of ^-1 of the Raman scattering spectrum _(I t / I _g) is 3.0 or more polyethylene It shall mean “terephthalate fiber”. Since the nonwoven fabric for filters of the present invention contains polyethylene terephthalate fibers having excellent crystallinity, the nonwoven fabric for filters is excellent in preventing structural pressure loss.

  The content of the polyethylene terephthalate fiber is preferably 10 to 80% and more preferably 20 to 60% in terms of the nonwoven fabric mass ratio. If the content is less than 10%, the filter medium may be deformed by the pressure of the liquid, and the effect of preventing the pleated peaks from sticking to each other may be weakened. On the other hand, if it exceeds 80%, the content of the binder fiber is relatively low, sufficient rigidity cannot be obtained, the filter medium may be in close contact and the life may be shortened, and the pleatability may be impaired.

  The fineness of the polyethylene terephthalate fiber is preferably 0.3 to 5.0 dtex, more preferably 0.4 to 4.0 dtex, and still more preferably 0.6 to 3.5 dtex. If the fineness is too small, sufficient rigidity may not be obtained. On the other hand, if the fineness is too large, the rigidity is too high, which may impair the suitability for pleating and may cause poor formation.

  The fiber length of the polyethylene terephthalate fiber is preferably 1 to 10 mm, particularly preferably 3 to 7 mm. If the fiber length is too short, sufficient rigidity may not be obtained, and if the fiber length is too long, there is a risk of formation failure.

  The nonwoven fabric for filter of the present invention preferably contains a binder fiber in addition to the polyethylene terephthalate fiber. The binder fiber is a fiber having a property of being thermally melted by heat treatment (for example, drying treatment, heat calender treatment, etc.) at the time of manufacturing the nonwoven fabric for a filter. Examples of the binder fiber include single fibers, and composite fibers such as core-sheath fibers (core-shell type), parallel fibers (side-by-side type), and radially divided fibers. Since the composite fiber hardly forms a film, the strength can be improved while maintaining the space of the composite filter medium. 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 Examples include a combination of polyethylene (sheath), a combination of high-melting polyester (core) and low-melting polyester (sheath), and the like. 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 content of the binder fiber is preferably 20 to 80% and more preferably 30 to 70% in terms of the nonwoven fabric mass ratio. If the binder fiber is less than 20%, the adhesion between the fibers tends to be insufficient, and the rigidity may be insufficient. If it exceeds 80%, the filtration resistance increases, which may cause problems in practice.

  Although the fiber diameter of a binder fiber is not specifically limited, It is preferable that it is 3-20 micrometers, More preferably, it is 5-18 micrometers. If the fiber diameter is less than 3 μm, the adhesion between the fibers tends to be insufficient, and the mechanical strength may be insufficient. On the other hand, if the fiber diameter exceeds 20 μm, the formation may be impaired.

  The fiber length of the binder fiber is preferably 1 mm to 10 mm, particularly preferably 3 to 7 mm. If the fiber length is less than 1 mm, the adhesiveness between the fibers may be insufficient, and if the fiber length exceeds 10 mm, the formation may be poor.

Filter nonwoven fabric of the present invention may optionally, 1096cm ^-1 and around 1,120 cm ^-1 vicinity of the peak intensity ratio of the Raman scattering spectrum _(I t / I _g) is non-binder fibers other than 3.0 or more polyethylene terephthalate May be added. Specifically, examples of the synthetic fiber include polyester, polyolefin, polyamide, polyacryl, vinylon, vinylidene, polyvinyl chloride, polyester, benzoate, polyclar, and phenol 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 nonwoven fabric for filters of the present invention is not particularly limited, is preferably from 20 to 150 g / ^{m 2,} more preferably 30 to 120 g / ^{m 2,} more preferably 35~100g / ^{m 2.} If it is less than 20 g / m ² , sufficient rigidity may not be obtained. On the other hand, if it exceeds 150 g / m ² , the area of the filter medium that can be incorporated in the filter unit is reduced, and as a result, the life may be shortened.

The filter medium for a filter of the present invention contains the filter nonwoven fabric of the present invention. Although the filter nonwoven fabric of the present invention can be used as a filter medium as it is, the filter nonwoven fabric of the present invention is used as a coarse layer, and is laminated and integrated with a dense layer having a higher density than the coarse layer. Filter media can be used advantageously. The dense 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 to consist of 5-50 g / m < ² > basic weight. Furthermore, it is preferable to contain 5 to 60% by mass of at least one binder fiber such as polyester, polyolefin, vinyl chloride, vinyl acetate or vinylon, and a dense layer with high surface strength can be obtained. This dense 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 “fiber diameter” as used in the present invention refers to the fiber diameter of a value converted into a true circular diameter having the same cross-sectional area when the cross section of the fiber is an ellipse or a polygon, and is referred to in the present invention. The “average fiber diameter” indicates a mass average fiber diameter calculated by ΣDi ² Ni / ΣDiNi when Ni fibers having a fiber diameter Di exist.

  The filter medium of the present invention obtained by laminating and integrating the coarse layer and the dense layer prevents the filter medium from being deformed by pressure and prevents the pleated peaks from adhering to each other. It can be suitably used as a filter material for liquid filters for processing machines, engine oil, fuel, oil-water separation, hydraulic equipment, and the like. In this case, the surface layer filtration mechanism can be developed by using the dense layer as the upstream side. Moreover, depending on the conditions used or the targeted 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.

  The dense layer constituting the filter medium of the present invention preferably contains fibrillated organic fibers, so that the dense fiber network is more uniform and the filtration performance is further improved.

  The fibrillated organic fiber used in the present invention refers to a fiber mainly having a fiber portion that is very finely divided in a direction parallel to the fiber axis, and at least a part of the fiber diameter is 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.

  As the fibrillated organic fiber used in the present invention, 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 resins, etc. are also preferable because they can further improve heat resistance, and among these, aramid fibers such as para-type wholly aromatic polyamides and acrylonitrile that are particularly easily fibrillated 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) two fibrillated organic fibers of a fibrillated organic fiber in which a branch portion 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.

  In addition, the fiber length and fiber length distribution of the fibrillated fiber can be determined by using a deflection characteristic obtained by applying laser light to the fiber, and can be measured using a commercially available fiber length measuring device. In the present invention, JAPAN TAPPI paper pulp test method no. It was measured using Kajaani Fiber Lab V3.5 (manufactured by Metso Automation) according to 52 “Fiber length test method for paper and pulp (automatic optical measurement method)”. “Fiber length”, “average fiber length” and “fiber length distribution” of fibrillated fibers are “length-weighted fiber length”, “length-weighted average fiber length” and “length” measured and calculated according to the above. "Weighted fiber length distribution".

In the filter medium 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 pressure loss may become too large. The density of the coarse layer is preferably 0.05 to 0.6 g / cm ³ . If the density of the rough layer is less than 0.05 g / cm ^3, there is the strength of the filter medium, workability too low, if it exceeds 0.6 g / cm ^3, there is a case where the filtration resistance is too high . Moreover, it is preferable that the density of the whole filter material for filters is 0.1-0.6 g / cm < ³ >. When the density of the filter medium as a whole is less than 0.1 g / cm ^3, the thickness of the filter medium is increased, so that the area of the filter medium that can be incorporated into the unit is reduced. May decrease.

  Moreover, when the filter medium for a filter of the present invention contains a thermoplastic resin, the rigidity is preferably 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. Can be used with more than one type.

  The amount of the thermoplastic resin contained in the filter medium of the present invention is preferably 0.01 to 10% by mass with respect to the filter medium. When it exceeds 10 mass%, the pressure loss of the filter medium for a filter may become too large. Moreover, if less than 0.01 mass%, compared with the filter medium which does not contain a thermoplastic resin, rigidity may not change.

  The state in which the thermoplastic resin is contained in the filter medium may be only the dense layer, both the dense layer and the coarse layer, or only the coarse layer. However, when a thermoplastic resin is contained in the dense layer, the space of the dense layer is blocked, the trapping ability of the solid particles is reduced, and the pressure loss is increased. Therefore, it is preferably contained only in the coarse layer.

  The method of incorporating the thermoplastic resin into the 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 medium of the present invention, additives such as a cross-linking agent, a water repellent, a dispersant, a yield improver, a paper strength agent, and a dye may be appropriately blended as long as the characteristics of the filter medium are not impaired as necessary. Can do.

  The non-woven fabric for filter and the filter medium for filter of the present invention are a paper machine in which a paper net such as a long net, a circular net, or an inclined wire is installed alone, or two or more of the same or different types of these paper nets are online. It can be manufactured by an installed combination paper machine. The wet paper (web) manufactured by the papermaking net is dried with a dryer. After drying, a thermoplastic resin is optionally contained and dried with an air dryer, cylinder dryer, suction drum dryer, infrared dryer or the like. In addition, when using a dense layer produced by a dry method, a rough layer and a dense layer produced by a paper machine may be laminated by a paper machine, or a separate calender device, thermal calender device, laminating device, etc. You may laminate using a machine.

  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.

  The Raman scattering peak intensity ratio in this example was measured by the following method.

  A cross section of a polyethylene terephthalate fiber used as a sample was measured under the conditions of laser wavelength: 780 mm, laser power: 100%, aperture: 100 μpinhole, objective lens: MPlan 100X BD using a NICOLET ALMEGA XR Dispersive Raman manufactured by Thermo Electron Corp. did.

FIG. 1 is a Raman scattering spectrum of polyethylene terephthalate fiber. As a data analysis method, as shown in FIG. 1, after baseline correction, the height of the peak around 1096cm ^-1 _{(I t)} and the peak of 1,120 cm ^-1 height _{(I g)} was measured, the peak intensity The ratio (I _t / I _g ) was calculated. The position of a point X in FIG. 1 is the wavelength of the Raman scattering intensity between the two peaks is the lowest, and the position of point B _t and B _g is the wavelength of the slope of the baseline I _t and I _g is largest did.

<PET fiber 1>
Polyethylene terephthalate fiber having a fineness of 0.1 dtex, a fiber length of 3 mm, and a peak intensity ratio of 5.0 was designated as PET fiber 1.

<PET fiber 2>
A polyethylene terephthalate fiber having a fineness of 0.3 dtex, a fiber length of 5 mm, and a peak intensity ratio of 5.0 was designated as PET fiber 2.

<PET fiber 3>
A polyethylene terephthalate fiber having a fineness of 0.6 dtex, a fiber length of 5 mm, and a peak intensity ratio of 4.5 was designated as PET fiber 3.

<PET fiber 4>
Polyethylene terephthalate fiber having a fineness of 1.7 dtex, a fiber length of 5 mm, and a peak intensity ratio of 4.0 was designated as PET fiber 4.

<PET fiber 5>
A polyethylene terephthalate fiber having a fineness of 3.3 dtex, a fiber length of 5 mm, and a peak intensity ratio of 3.5 was designated as PET fiber 5.

<PET fiber 6>
Polyethylene terephthalate fiber having a fineness of 5.0 dtex, a fiber length of 5 mm, and a peak intensity ratio of 3.0 was designated as PET fiber 6.

<PET fiber 7>
A polyethylene terephthalate fiber having a fineness of 5.5 dtex, a fiber length of 5 mm, and a peak intensity ratio of 3.0 was designated as PET fiber 7.

<PET fiber 8>
Polyethylene terephthalate fiber having a fineness of 0.6 dtex, a fiber length of 5 mm, and a peak intensity ratio of 2.8 was designated as PET fiber 8.

<PET fiber 9>
A polyethylene terephthalate fiber having a fineness of 1.7 dtex, a fiber length of 5 mm, and a peak intensity ratio of 2.7 was designated as PET fiber 9.

<PET fiber 10>
Polyethylene terephthalate fiber having a fineness of 3.3 dtex, a fiber length of 5 mm, and a peak intensity ratio of 2.5 was designated as PET fiber 10.

<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 having an average 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.

<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.

<Binder fiber 1>
A polyester core-sheath type heat-sealable fiber having a fineness of 2.2 dtex, a fiber length of 5 mm, a core part of polyethylene terephthalate (melting point 253 ° C.), and a sheath part of polyethylene terephthalate-isophthalate copolymer (softening point 75 ° C.) Fiber 1 was obtained.

(Examples 1-11 and Comparative Examples 1-3)
After adding water to a 2 m ³ dispersion tank, blended in the ratios shown in Tables 1, 2 and 4, and dispersed for 5 minutes at a dispersion concentration of 0.2% by mass, a fiber dispersion for a coarse layer (nonwoven fabric for filter) and A dense layer fiber dispersion was prepared.

Using a combination paper machine in which a long net and a circular net are installed online, wet paper is formed with a long net paper machine so that the coarse layer has a dry mass of 50 g / m ² , and the dense layer is formed into a circular net paper machine. After forming the web so that the dry mass becomes 20 g / m ² and laminating both webs before drying, while pressing the touch roll with a pressure of 400 N / cm ² with a cylinder dryer having a surface temperature of 130 ° C. , Dried and integrated to obtain filter media 1-11 and filter media 17-19.

(Examples 12 to 15)
Compounded at the ratio shown in Table 3, and obtained a filter medium in the same manner as in Examples 1 to 11 and Comparative Examples 1 to 3, and further coated with an acrylic resin liquid only on the coarse layer by a gravure coating method, It dried with the air dryer and obtained the filter media 12-15 of the thermoplastic resin adhesion amount 1.0g / m < ² >.

(Example 16)
Water was added to a 2 m ³ dispersion tank and then blended at the ratio shown in Table 3 and dispersed at a dispersion concentration of 0.2% by mass for 5 minutes to prepare a coarse-layer fiber dispersion.

Using a long paper machine, a web was formed so as to have a dry mass of 50 g / m ² , and a coarse layer dried while pressing a touch roll with a pressure of 400 N / cm ² with a cylinder dryer having a surface temperature of 130 ° C. A polyethylene terephthalate nonwoven fabric (average fiber diameter of 0.8 μm, basis weight of 20 g / m ² ) produced by a melt blow method as a dense layer was laminated and integrated by embossing to obtain a filter medium 16.

  The following evaluation was performed on the filter media obtained in Examples and Comparative Examples, and the results are shown in Tables 1 to 4.

Test 1 (basis weight)
The basis weight was measured according to JIS P8124.

Test 2 (thickness)
The thickness was measured in accordance with JIS P 8118.

Test 3 (rigidity)
Using a Gurley type flexibility tester (manufactured by Yasuda Seiki Seisakusho Co., Ltd., trade name: No. 311 Gurley type flexibility tester), the measurement was performed by the method shown in JIS L1085.

Test 4 (collection efficiency)
According to JIS B9908, DOP aerosol (dioctyl phthalate, particle size: 0.3 to 0.5 μm) particles are generated, and air containing the particles is aerated at a wind speed of 5.3 cm / second, The particle concentration (unit time, number of particles per unit flow rate) of the air on the downstream side was measured with a particle counter (KC-11, manufactured by Rion Co., Ltd.), and the collection efficiency was calculated from Equation 1 below.

(Equation 1)
η = (1−C2 / C1) × 100
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. 40% or more can be used as a filter medium, and 60% or more is preferable.

Test 4 (suitability for pleating)
The ease of processing when the filter media 1 to 19 were processed into mini-pleats with an interval of 5 cm was evaluated according to the following criteria.

A: Excellent workability and high workability.
○: Can be processed without problems. Good workability.
Δ: Workability is slightly inferior for reasons such as rigidity.
X: Workability is remarkably inferior for reasons such as rigidity.

Test 5 (Life test)
A filter is produced by pleating the filter media 1 to 19, and is set in a filter set portion of an electric discharge machine using a wire having a diameter of 0.32 mm for roughing. When continuously cut, the filter pressure becomes 300 kPa. The time to become was measured.

Filter medium of Example 1 to 15, 1096cm ^-1 and around 1,120 cm ^-1 vicinity of the peak intensity ratio of the Raman scattering spectrum _(I t / I _g) is blended with polyethylene terephthalate fibers of 3.0 above rough layers Therefore, it was a filter medium with high rigidity, excellent pleatability, and a long life time. Moreover, when the filter medium after a life test was visually confirmed, the deformation | transformation of the filter medium and the close_contact | adherence of the peak parts of a pleating process were not confirmed.

Content is less than 10%, or 80% in the nonwoven fabric mass ratio of around 1096cm ^-1 in the Raman scattering spectrum and 1,120 cm ^-1 vicinity of the peak intensity ratio _(I t / I _g) is 3.0 or more polyethylene terephthalate fibers The filter media of Examples 7 to 9 had slightly low rigidity, slightly inferior pleatability, and a slightly shorter life time. In the visual confirmation of the filter medium after the life test, the filter medium was slightly deformed, but adhesion between the pleating processes was not confirmed.

The fineness of the Raman scattering 1096Cm ^-1 and around 1,120 cm ^-1 vicinity of the peak intensity ratio of the spectrum _(I t / I _g) is 3.0 or more polyethylene terephthalate fibers containing the filter medium of Example 10 less than 0.3dtex Has a slightly low rigidity, slightly inferior suitability for pleating, and has a slightly shorter life time. In the visual confirmation of the filter medium after the life test, the filter medium was slightly deformed, but adhesion between the pleating processes was not confirmed. The fineness of the Raman scattering 1096Cm ^-1 and around 1,120 cm ^-1 vicinity of the peak intensity ratio of the spectrum _(I t / I _g) is 3.0 or more polyethylene terephthalate fibers containing the Example 11 is 5.0dtex greater The filter medium was slightly inferior in texture and was slightly inferior in pleatability.

  The filter media of Examples 12 to 14 to which an acrylic resin was adhered as a thermoplastic resin were very excellent in pleatability. In addition, the filter media of Examples 15 and 16 that did not contain fibrillated organic fibers in the filter media layer resulted in a slightly lower collection efficiency.

For Examples 1-16, Comparative Examples 1096Cm ^-1 and around 1,120 cm ^-1 vicinity of the peak intensity ratio of the Raman scattering spectrum _(I t / I _g) does not contain 3.0 or more polyethylene terephthalate fiber 1-3 This filter medium had a low rigidity, poor pleatability, and a short life time. Moreover, when the filter medium after the life test was visually confirmed, the filter medium was greatly deformed, and a number of locations where the pleated ridges were in close contact with each other were confirmed.

  The non-woven fabric for filter of the present invention is a process of cutting, polishing, etching, etc. of processing waste contained in the machining fluid of an electric discharge machine used for metal sculpture, cutting, etc., and substrate wafer in IC production Can be suitably used for various filter materials for liquid filters, such as filter media for liquid filters, automobile engine oil, fuel, etc. for efficiently removing processing waste contained in ultrapure water used in . Moreover, it can be used conveniently also as a filter medium for air filters which collects dust in the air.

Claims (7)

A nonwoven fabric for a filter, comprising a polyethylene terephthalate fiber having a peak intensity ratio (I ₁₀₉₆ / I ₁₁₂₀ ) in the vicinity of ₁₀₉₆ cm ⁻¹ and 1120 cm ^{−1 of a} Raman scattering spectrum of 3.0 or more. The content of polyethylene terephthalate fibers having a peak intensity ratio (I ₁₀₉₆ / I ₁₁₂₀ ) in the vicinity of ₁₀₉₆ cm ⁻¹ and 1120 cm ^{−1 of the} Raman scattering spectrum of 3.0 or more is 10 to 80% in terms of a nonwoven fabric mass ratio. The nonwoven fabric for filters according to 1. The fineness of the polyethylene terephthalate fiber having a peak intensity ratio (I ₁₀₉₆ / I ₁₁₂₀ ) in the vicinity of ₁₀₉₆ cm ⁻¹ and 1120 cm ^{−1 of the} Raman scattering spectrum of 3.0 or more is 0.3 to 5.0 dtex. 2. The nonwoven fabric for filters according to 2.   A filter medium for a filter comprising the filter nonwoven fabric according to any one of claims 1 to 3.   A filter medium for a filter obtained by forming the filter nonwoven fabric according to any one of claims 1 to 3 as a rough layer and laminating and integrating with a dense layer.   The filter medium according to claim 5, wherein the dense layer contains fibrillated organic fibers.   The filter medium for a filter according to any one of claims 1 to 5, comprising a thermoplastic resin.