JP2020131065A - Filter medium - Google Patents

Abstract

To provide a filter medium having alkali resistance, heat resistance and excellent in collection efficiency.SOLUTION: A filter medium is characterized by comprising a nonwoven fabric including as an essential component, a fibrid comprising polyolefin fiber, polyolefin-based heat fusible binder fiber and para-aromatic polyamide whose modified freeness is 300 ml or less (here, modified freeness is a value measured based on JIS P8121-2:2012 except 0.1% of sample concentration using a 80 mesh wire gauze having a wire size of 0.14 mm and sieve opening of 0.18 mm).SELECTED DRAWING: Figure 1

Description

The present invention is a filter medium for efficiently removing solid particles contained in a gas or liquid to obtain a clean gas or liquid.

Filter media for efficiently removing solid particles contained in gases and liquids to obtain clean gases and liquids have alkali resistance, acid resistance, solvent resistance, and heat resistance due to the diversification of gases and liquids to be filtered. Etc. are increasing. As a filter medium having excellent alkali resistance, a filter medium made of a melt-blown non-woven fabric made of an olefin-based material such as polypropylene or polyethylene has been proposed. In addition, PM2.5 has been highlighted due to the problem of air pollution. PM2.5 is a particulate matter with a particle size of 2.5 μm (one-thousandth of 2.5 mm) or less, and is not a single chemical substance, but mainly contains carbon, nitrate, sulfate, and metal. It is a mixture of various substances. Therefore, the filter medium is required to be able to capture these particles.

For example, in Patent Document 1, a first melt-blown non-woven fabric having an average fiber diameter of 5 to 20 μm and a grain size of 10 to 50 g / m ² is laminated and formed by elution of fibers onto the first melt-blow non-woven fabric. A filter medium having a diameter of 40 to 100 μm and a second melt blown non-woven fabric having a grain size of 60 to 120 g / m ² and having high rigidity in the entire filter medium has been proposed.

In Patent Document 2, it is a melt-blown non-woven fabric composed mainly of polyolefin and / or polyester, which has a texture of 80 to 140 g / m ² , a thickness of 0.5 to 1.5 mm, and a rigidity of 3 mN. As described above, and a non-woven fabric for an air filter in which the single layer has a filling rate gradient in the thickness direction has been proposed.

Further, in Patent Document 3, the mixed fiber melt blown nonwoven fabric is a mixed fiber melt blown nonwoven fabric containing at least two kinds of fiber groups, and the first fiber group is composed of a polyolefin resin component A and each fiber diameter is 7. The second fiber group is composed of resin component B and has a fiber diameter of 15 μm to 100 μm, and the tensile strength of the mixed fiber melt-blown non-woven fabric in the length direction is 0.45 (N / 5 cm) per unit. ) / (G / m ² ) or more, and a mixed fiber melt blown nonwoven fabric in which the rate of increase in pressure loss after applying a load of 6 kg / cm ^{2 to} the mixed fiber melt blown nonwoven fabric is 25% or less has been proposed. ..

Further, Patent Document 4 describes at least one heat-resistant organic fiber selected from the group consisting of polyphenylene sulfide fiber, meta-aramid fiber, para-aramid fiber, polyamideimide fiber, polyimide fiber and the like, and olefin-based fiber. At least one low melting point fiber having a melting point range of 100 to 180 ° C. selected from the group consisting of modified nylon fiber, modified polyester fiber, olefin / polyester core sheath fiber, modified nylon / polyester core sheath fiber, or the sheath portion of the fiber. After weighing, mixing, carding, and wrapping, the composite fibers are bulky and the apparent density is in the range of 0.005 to 0.020 g / cm ³ when a load of 20 gf / cm ² is applied. After entwining the fibers, the low melting point fibers are fused and solidified with hot air, and then the polyacrylic acid ester resin, epoxy resin, polyurethane resin, unsaturated polyester resin, melamine resin, and urea resin are maintained in a state of maintaining the bulkiness. , At least one thermocurable resin selected from the group consisting of phenolic resins and the like is spray-processed or impregnated-suction-processed, and heat-resistant organic fibers are fixed and solidified again. A method for producing a filter medium for a heat-resistant filter having both texture and hardness has been proposed.

Since the filter media and the non-woven fabric shown in Patent Documents 1 to 3 are olefin-based materials, they have good chemical resistance. However, heat resistance was not considered. Further, the filter medium for a heat-resistant filter shown in Patent Document 4 has bulkiness, heat resistance, and texture hardness by using fibers having heat resistance, but the filter medium is punched by needle punching. Therefore, the collection efficiency was never satisfactory.

Japanese Unexamined Patent Publication No. 2012-152706 JP-A-2009-106824 Japanese Patent No. 6007899 Japanese Unexamined Patent Publication No. 2011-183236

In view of the above problems, an object of the present invention is to provide a filter medium having alkali resistance and heat resistance and having excellent collection efficiency.

As a result of diligent research to solve the above problems
(1) A filter medium comprising a non-woven fabric containing a fibrid composed of a polyolefin-based fiber, a polyolefin-based heat-sealing binder fiber, and a para-aromatic polyamide having a modified drainage degree of 300 ml or less as an essential component.
Modified degree of drainage: An 80-mesh wire mesh with a wire diameter of 0.14 mm and a mesh size of 0.18 mm was used as a sieve plate, and the measurement was performed in accordance with JIS P8121-2: 2012 except that the sample concentration was 0.1%. value.
(2) The content of the fibrid made of para-aromatic polyamide having a modified water flow rate of 300 ml or less in the filter medium is 1% by mass or more and 20% by mass or less with respect to all the fibers constituting the filter medium. The filter medium according to (1).
I found.

The filter medium (1) of the present invention is made of a non-woven fabric containing a fibrid composed of a polyolefin fiber, a polyolefin-based heat-sealing binder fiber, and a para-based aromatic polyamide as essential components. Furthermore, when the modified drainage degree of the fibrid made of para-aromatic polyamide is 300 ml or less, particles containing PM2.5 (particulate matter having a particle size of 2.5 μm or less), which has been highlighted due to the problem of air pollution. It is possible to efficiently capture particles having a diameter of 1.0 to 5.0 μm.

In addition, since the blending ratio of the fibrid made of para-aromatic polyamide having a modified drainage degree of 300 ml or less is 1% by mass or more and 20% by mass or less with respect to the filter medium, it has both alkali resistance and heat resistance and can be captured. It suppresses pressure loss while maintaining collection efficiency.

A filter medium containing no fibrid made of para-aromatic polyamide having a modified water flow rate of 300 ml or less (left in the photo) and a filter medium containing a fibrid made of para-aromatic polyamide having a modified water drainage degree of 300 ml or less (in the photo). Right) is a photograph of a filter medium after heating in a hot air dryer at 160 ° C. for 30 minutes.

Hereinafter, the filter medium of the present invention will be described in detail.

In the present invention, "a fibrid made of a para-aromatic polyamide having a modified drainage degree of 300 ml or less" may be abbreviated as "fibrid".

In the present invention, a fibril is a thin leaf-like or scaly small piece having fine fibrils, and water molecules or water are present in the crystal structure in a non-crystalline state without the crystal structure of the fiber being firmly formed. Refers to fine heat-resistant fibers. The fibrils can be obtained by introducing a fiber-forming polymer polymer solution into an aqueous coagulation bath, recovering the formed product without drying, and if necessary, fibrillating the fibers by beating or the like. For example, a fibrid produced by mixing a polymer polymer solution with the precipitant in a system in which shearing force exists, or an amorphous substance having molecular orientation formed from a polymer polymer solution exhibiting optical anisotropy. It is a quality water-containing polymer and can be beaten if necessary.

The beating process includes a refiner, beater, mill, grinder, a rotary homogenizer that applies shearing force with a high-speed rotary blade, and a shearing force between the inner and fixed outer blades of a high-speed rotating cylinder. Double-cylindrical high-speed homogenizer that produces By decelerating, it can be obtained by treating the fiber with a high-pressure homogenizer or the like that applies a shearing force or a cutting force to the fiber.

In the present invention, the fibrid contracts greatly when the water existing in the crystal structure is removed by heating or depressurizing, and strengthens the fiber network, thereby improving the strength characteristics of the filter medium and improving the particle collection efficiency. It has the effect of increasing.

The modified drainage degree of fibrid in the present invention is 300 ml or less, more preferably 0 to 300 ml, still more preferably 0 to 200 ml, and particularly preferably 0 to 100 ml. If the modified drainage level exceeds 300 ml, the fiber width of the fibrid becomes thicker, and the collection efficiency may not increase.

The modified drainage degree in the present invention is based on JIS P8121-2: 2012 except that an 80-mesh wire mesh having a wire diameter of 0.14 mm and a mesh size of 0.18 mm is used as a sieving plate and the sample concentration is 0.1%. It is the value measured by

The mass-weighted average fiber length of the fibrid is preferably 0.30 mm or more and 1.00 mm or less. The length-weighted average fiber length of the fibrid is preferably 0.10 mm or more and 0.50 mm or less. If the average fiber length is shorter than the preferred range, the fibrid may fall off from the filter medium. If the average fiber length is longer than the preferable range, the formation of the filter medium may deteriorate and the internal resistance of the filter medium may increase. When the average fiber length is shorter than the preferable range, the entanglement between the polyolefin fiber and the polyolefin-based heat-sealing binder fiber is insufficient, and the fiber may fall off from the papermaking wire. When the average fiber length is longer than the preferable range, The fibers may be twisted to form lumps, which may reduce the uniformity of the filter medium.

In the present invention, the weighted average fiber length and the length weighted average fiber length are measured in the projected fiber length (Proj) mode using KajaniFiberLab V3.5 (manufactured by Metso Automation). w)) and length-weighted average fiber length (L (l)).

The average fiber width of the fibrid made of a para-aromatic polyamide having a modified drainage degree of 300 ml or less is preferably 3 μm or more and 40 μm or less, more preferably 5 μm or more and 35 μm or less, and further preferably 10 μm or more and 30 μm or less. When the average fiber width exceeds 40 μm, the collection efficiency is unlikely to increase. On the other hand, when the average fiber width is less than 3 μm, the entanglement between the polyolefin fiber and the polyolefin-based heat-sealing binder fiber is insufficient, and the fiber may fall off from the papermaking wire.

In the present invention, the average fiber width is the fiber width (Fiber Width) measured using Kajani FiberLab V3.5 (manufactured by Metso Automation).

In the filter medium of the present invention, the blending ratio of the fibrid made of a para-aromatic polyamide having a modified drainage degree of 300 ml or less is preferably 1% by mass or more and 20% by mass or less with respect to all the fibers constituting the filter medium, preferably 3% by mass. % Or more and 15% by mass or less are more preferable, and 5% by mass or more and 15% by mass or less are further preferable. If the blending ratio of the fibrid made of para-aromatic polyamide having a modified drainage degree of 300 ml or less is less than 1% by mass, the uniformity, collection efficiency and heat resistance may not be improved. The photograph on the left of FIG. 1 shows a state after heating a filter medium made of a para-aromatic polyamide having a modified drainage degree of 300 ml or less and containing no fibrid in a dryer at 160 ° C. for 30 minutes. From the photograph, it can be seen that the four corners of the filter medium after heating are warped and deformed. On the other hand, the photograph on the right of FIG. 1 shows a state after heating a filter medium containing 5% by mass of a fibrid made of a para-aromatic polyamide having a modified drainage degree of 300 ml or less under the same conditions. From the photograph, it can be seen that there is no warping, no deformation, and the heat resistance is improved. Further, if the blending ratio of the fibrid made of a para-aromatic polyamide having a modified drainage degree of 300 ml or less exceeds 20% by mass, the pressure loss may be too high.

In the filter medium of the present invention, the blending ratio of the polyolefin fiber is preferably 10 to 50% by mass, more preferably 10 to 40% by mass, still more preferably 20 to 40% by mass, based on the total fibers constituting the filter medium. When the blending ratio of the polyolefin fiber is less than 10% by mass, the liquid passage resistance may be increased. Further, if the blending ratio of the polyolefin fiber exceeds 50% by mass, the strength may be insufficient and opening may occur.

In the present invention, examples of the resin constituting the polyolefin fiber include polymers of olefins such as ethylene, propylene and butylene, and examples thereof include polypropylene and the like. The polyolefin fiber is a fiber that does not melt in a drying process such as a Yankee dryer for wet paper making, and is a fiber that functions as an aggregate of a filter medium.

The polyolefin fiber may be a fiber made of a single resin (single fiber) or a fiber made of two or more kinds of resins (composite fiber). Further, the polyolefin fiber contained in the filter medium of the present invention may be used alone or in combination of two or more having different fiber diameter, fiber length, resin composition and resin composition.

The fiber diameter of the polyolefin fiber is preferably 1 to 20 μm, more preferably 3 to 18 μm, and even more preferably 5 to 15 μm. If the fiber diameter of the polyolefin fiber exceeds 20 μm, the uniformity of the filter medium may not be ensured. Further, when the fiber diameter of the polyolefin fiber is less than 1 μm, the fiber may fall off from the papermaking wire, making stable production difficult.

The fiber length of the polyolefin fiber is preferably 1 mm or more and 15 mm or less, more preferably 1 mm or more and 10 mm or less, and further preferably 2 mm or more and 7 mm or less. If the fiber length exceeds 15 mm, the formation may be poor. On the other hand, if the fiber length is less than 1 mm, the mechanical strength of the filter medium may be low.

The polyolefin-based heat-sealing binder fiber is blended to bond a fibrid made of a polyolefin-based fiber or a para-aromatic polyamide having a modified drainage degree of 300 ml or less by a dot or a line. It has a lower melting point than the fibrid made of para-aromatic polyamide having a modified drainage degree of 300 ml or less. The polyolefin-based heat-sealing binder fiber consists of a core-sheath type consisting of a sheath part with a low melting point and a core part with a high melting point, and a sheath part with a low melting point and a core part with a high melting point of the same material, and the core components are biased. Eccentric type, side-by-side type in which the part with low melting point and the part with high melting point are separated by half a circle, other sea-island type, orange type, multiple bimetal type composite fiber, or drawing process in the manufacturing process of polyolefin fiber Examples thereof include unstretched single fibers that are cut into short fibers in an unstretched state, softened in a drying step after wet paper making, and adhered to other fibers. From the viewpoint of increasing the strength of the filter medium, it is particularly preferable to use a core-sheath type polyolefin-based heat-sealing binder fiber. For example, the resin component of the sheath portion of the fiber surface in the core-sheath type polyolefin-based heat-sealing binder fiber has a melting point of 50 to 150 as measured by differential scanning calorimetry (hereinafter referred to as DSC) specified in JIS K7121: 2012. The temperature is preferably 60 to 140 ° C. If the melting point is less than 50 ° C., the filter medium may soften when exposed to a high temperature, resulting in a decrease in strength. On the other hand, when the melting point exceeds 150 ° C., it is necessary to heat at a high temperature in order to exhibit the heat fusion function, and a large amount of energy may be required. Polyethylene is preferably used for the sheath portion having a low melting point, and polypropylene is preferably used for the core portion having a high melting point.

In the filter medium of the present invention, the blending ratio of the polyolefin-based heat-sealing binder fiber is preferably 20 to 80% by mass, more preferably 30 to 70% by mass, and 30 to 60% by mass with respect to the total fibers constituting the filter medium. % Is more preferable. If the blending ratio of the polyolefin-based heat-sealing binder fiber exceeds 80% by mass, the pressure loss of the filter medium increases, or the fibrid network made of para-aromatic polyamide having a modified water flow rate of 300 ml or less is formed into a film. It may cover the area and reduce the collection efficiency. When the blending ratio of the polyolefin-based heat-sealing binder fiber is less than 20% by mass, the mechanical strength of the filter medium may be low.

The fiber diameter of the polyolefin-based heat-sealing binder fiber is preferably 1 to 20 μm, more preferably 3 to 18 μm, and even more preferably 5 to 15 μm. If the fiber diameter of the polyolefin-based heat-sealing binder fiber exceeds 20 μm, the uniformity of the filter medium may not be ensured. Further, when the fiber diameter of the polyolefin-based heat-sealing binder fiber is less than 1 μm, stable production of the fiber becomes difficult.

The fiber length of the polyolefin-based heat-sealing binder fiber is preferably 1 mm or more and 15 mm or less, more preferably 1 mm or more and 10 mm or less, and further preferably 1 mm or more and 7 mm or less. If the fiber length exceeds 15 mm, the formation may be poor. On the other hand, if the fiber length is less than 1 mm, the mechanical strength of the filter medium may be low.

The filter medium of the present invention is a paper machine for producing general paper and wet non-woven fabric, for example, a paper machine in which a paper machine such as a long net, a circular net, and an inclined wire is independently installed; a long net or an inclined wire paper machine. A paper machine capable of multi-layer papermaking with two or more layers having two or more heads on the same wire; manufactured by a combination paper machine or the like in which two or more machines of the same type or different types of these paper machines are installed online. be able to. The wet paper produced by the paper machine is dried by a dryer such as an air dryer, a yankee dryer, a cylinder dryer, a suction drum type dryer, or an infrared type dryer.

The filter medium of the present invention is suitable as a filter medium for a filter for liquid filtration such as for engine oil, fuel, oil-water separation, and hydraulic equipment. It can also be used as a filter medium for gas. Then, not only the filtration of the alkaline liquid but also the filtration of the alkaline gas is suitable because the strength and performance of the filter medium are less deteriorated. It can also be used for filtration of acidic liquids or gases.

Basis weight of the filter medium of the present invention is not particularly limited but is preferably from 30 to 150 g / ^{m 2,} more preferably 40 to 120 g / ^{m 2,} more preferably 50 to 100 g / ^{m 2.} If it exceeds 150 g / m ² , the pressure loss may become too high or the thickness may become excessive, and if it is less than 30 g / m ² , the strength of the filter medium is weak and the pressure during liquid flow or ventilation may increase. The filter medium may be deformed. The basis weight means the basis weight based on the method specified in JIS P8124: 2011 (Paper and paperboard-measurement method of basis weight).

The thickness of the filter medium of the present invention is not particularly limited, but is preferably 50 to 1000 μm, more preferably 100 to 800 μm, and even more preferably 200 to 600 μm. If it exceeds 1000 μm, the pressure loss may become excessive, and if it is less than 50 μm, the filter medium may be deformed by the pressure at the time of passing liquid or aeration. The thickness means a value measured at a load of 5 N using an outer micrometer defined by JIS B7502: 2016.

In the filter medium of the present invention, the density of the filter medium is preferably 0.05~0.8g / cm ^3, more preferably 0.10~0.6g / cm ^3, 0.15~0.5g / cm ³ is more preferable. If the density is less than 0.05 g / cm ³ , the liquid permeability may increase and the collection efficiency may decrease. On the contrary, if it exceeds 0.8 g / cm ³ , the pressure loss may increase.

If necessary, additives such as a cross-linking agent, a water-repellent agent, a dispersant, a yield improver, a paper strength agent, and a dye can be appropriately added to the filter medium of the present invention as long as the characteristics of the filter medium are not impaired. .. Further, the filter medium may contain a thermoplastic resin in order to impart mechanical strength and water resistance. Examples of the thermoplastic resin include acrylic type, vinyl acetate type, epoxy type, synthetic rubber type, urethane type, polyester type, vinyl chloride type, vinylidene chloride type, polyvinyl alcohol type, starch type, phenol resin and the like. These can be used alone or in combination of two or more.

The appropriate amount of the thermoplastic resin contained in the filter medium is 0.01 to 10% by mass with respect to the filter medium. If it exceeds 10% by mass, the pressure loss of the filter medium becomes large. Further, if it is less than 0.01% by mass, the mechanical strength and water resistance are not improved as compared with the filter medium containing no thermoplastic resin.

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 coating method, and a gravure coating method. After containing the thermoplastic resin, it is dried with an air dryer, a Yankee dryer, a cylinder dryer, a suction drum type dryer, an infrared type dryer, or the like.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the present Examples. Unless otherwise specified, all parts and percentages in the examples are based on mass.

<PP fiber 1>
PP fiber 1 was a polypropylene fiber having a fineness of 0.3 dtex (fiber diameter: 6.5 μm), a fiber length of 3 mm, and a melting point of 160 ° C.

<PP fiber 2>
PP fiber 2 was a polypropylene fiber having a fineness of 0.4 dtex (fiber diameter: 7.5 μm), a fiber length of 5 mm, and a melting point of 160 ° C.

<PP fiber 3>
PP fiber 3 was a polypropylene fiber having a fineness of 2.2 dtex (fiber diameter: 17.6 μm), a fiber length of 5 mm, and a melting point of 160 ° C.

<PET fiber 4>
PET fiber 4 was a drawn polyester fiber having a fineness of 2.2 dtex (fiber diameter: 14.3 μm), a fiber length of 5 mm, and a melting point of 160 ° C.

<Polyolefin-based binder fiber 1>
A core-sheath type binder fiber having a fineness of 0.2 dtex (fiber diameter: 5.3 μm), a fiber length of 3 mm, a core portion of polypropylene, and a sheath portion of polyethylene having a melting point of 130 ° C. was designated as a polyolefin-based heat-sealing binder fiber 1.

<Polyolefin-based binder fiber 2>
A core-sheath type binder fiber having a fineness of 0.8 dtex (fiber diameter: 10.6 μm), a fiber length of 5 mm, a core portion of polypropylene, and a sheath portion of polyethylene having a melting point of 130 ° C. was designated as a polyolefin-based heat-sealing binder fiber 2.

<Polyolefin-based binder fiber 3>
A core-sheath type binder fiber having a fineness of 2.2 dtex (fiber diameter: 17.6 μm), a fiber length of 5 mm, a core portion of polypropylene, and a sheath portion of polyethylene having a melting point of 130 ° C. was designated as a polyolefin-based heat-sealing binder fiber 3.

<Polyester binder fiber 4>
Polyester core sheath with a fineness of 2.2 dtex (fiber diameter: 14.3 μm), a fiber length of 5 mm, a core of PET (melting point 253 ° C), and a sheath of a polyethylene terephthalate-isophthalate copolymer (softening point 75 ° C). The mold heat-sealing fiber was designated as polyester binder fiber 4.

<Fibrid 1 made of para-aromatic polyamide with a modified drainage degree of 300 ml or less>
A fibrid made of a para-aromatic polyamide having a modified drainage degree of 88 ml was obtained as a fibrid 1 made of a para-aromatic polyamide having a modified drainage degree of 300 ml or less by dissociation and beating using a high-speed homogenizer.

<Fibrid 2 made of para-aromatic polyamide with a modified drainage level of more than 300 ml>
A fibrid made of a para-aromatic polyamide having a modified drainage degree of 350 ml was obtained as a fibrid 2 made of a para-aromatic polyamide having a modified drainage degree of more than 300 ml by dissociation and beating using a high-speed homogenizer.

(Examples 1 to 12 and Comparative Examples 1 to 5)
After pouring water into a 2 m ³ dispersion tank, mix in the ratio shown in Table 1, disperse at a dispersion concentration of 0.2% by mass for 5 minutes, and stir with an agitator to make a uniform papermaking slurry (0.2). % Concentration) was prepared. This slurry for papermaking was made by a wet method using a circular net paper machine, and binder fibers were adhered to each other by a cylinder dryer at 130 ° C. to develop the strength of the non-woven fabric, and a filter medium having a grain size of 60 g / m ² was prepared.

<Evaluation>
The filter media obtained in Examples 1 to 12 and Comparative Examples 1 to 5 were evaluated as follows, and the evaluation results of alkali resistance, pressure loss, collection efficiency, pleating workability, and heat resistance are shown in Table 1.

[Alkali resistance]
Five filter media were cut into 25 mm width and 160 mm length with respect to the flow direction (MD) of the machine to prepare a sample for tensile strength of MD, and 5 with 25 mm width and 160 mm length with respect to the lateral direction (CD) of the machine. The sheet was cut into a sample for tensile strength of CD. These cut samples were immersed in an aqueous sodium hydroxide solution (10% concentration) at 25 ° C. for 100 hours, washed with water and air-dried to prepare samples for evaluating alkali resistance. The sample is stretched using a desktop material tester (trade name: STA-1150, manufactured by Orientec Co., Ltd.) under the conditions of a grip interval of 100 mm and a tensile speed of 20 mm / min, and the load value at the time of cutting is used as the tensile strength. , Evaluated according to the following criteria. The tensile strengths of all the samples of 5 MDs and 5 CDs in the filter medium not soaked in the sodium hydroxide aqueous solution in advance were measured, and the average value was set to 100, and the 5 sheets in the separately cut sample for alkali resistance evaluation were measured. If the average tensile strength of all the samples of MD and 5 CDs is 98 or more, it is "◎", if it is 95 or more and less than 98, it is "○", if it is 90 or more and less than 95, it is "△", and it is less than 90. Or, if it cannot be evaluated, it is marked with "x".

[Pressure loss] (Unit: Pa)
The measurement was performed under the condition of a surface wind speed of 5.3 cm / sec according to JIS B9908: 2011. The lower the pressure loss is, the more preferable it is. If it is less than 150 Pa, it is rated as “⊚”, if it is 150 Pa or more and less than 200 Pa, it is rated as “◯”, if it is 200 Pa or more and less than 250 Pa, it is rated as “Δ”, and if it is 250 Pa or more and less than 250 Pa, it is rated as “x”.

[Collection efficiency] (Unit:%)
The measurement was performed under the condition of a surface wind speed of 5.3 cm / sec according to JIS B9908: 2011. As the particles to be measured, atmospheric dust was used, and the collection efficiency of particles having a particle diameter of 1.0 to 5.0 μm was measured using a particle counter (trade name “KC-11”, manufactured by Rion). .. The higher the collection efficiency, the more preferable. If it is 70% or more, it is "◎", if it is 50% or more and less than 70%, it is "○", if it is 30% or more and less than 50%, it is "△", and if it is less than 30%. It was set as "x".

[Pleated workability]
The filter medium is cut in the flow direction (MD) of 30 cm and the lateral direction (CD) of 20 cm of the machine, and mountain folds and valley folds are repeated every 5 cm so as to cross the flow direction, and on the folded filter medium, the diameter is 5 cm and the length is 30 cm. , Slowly roll a cylindrical metal roll weighing 3 kg to make creases and make it bellows. The creases are clear and there is no distortion, and if the creases are not deformed even if they are pressed, it is rated as "○", the ones that are slightly deformed but have no problem in use are marked with "△", and the others are marked with "x". In addition, those that are extremely hard and superior to "○" are designated as "◎".

[Heat-resistant]
The filter medium is cut into squares with a flow direction (MD) of 10 cm and a lateral direction (CD) of 10 cm, and the cut filter medium is set to 160 ° C. in a blower constant temperature dryer (WHO-450ND, manufactured by Tokyo Rika Kikai Co., Ltd.) 30 After heating for a minute, the filter medium was taken out and the filter medium was observed. If the average value of the warp of the four corners of the filter medium is less than 0 to 2 mm, it is evaluated as good "○", and if the average value of the warp of the four corners is less than 2 to 5 mm, it is evaluated as "△". Those having an average value of warpage at the four corners of 5 mm or more were designated as "x".

From the comparison between Examples 1 to 5 and Example 8 and Comparative Example 1, it does not contain a fibrid made of a para-aromatic polyamide having a modified drainage degree of 300 ml or less, and has a polyolefin-based fiber and a polyolefin-based heat-sealing property. The filter medium of Comparative Example 1 containing the binder fiber had a low collection efficiency of less than 30%, was not suitable for the filter medium, and had low heat resistance. On the other hand, it contains a fibrid composed of a polyolefin fiber, a polyolefin-based heat-sealing binder fiber, and a para-aromatic polyamide having a modified drainage degree of 300 ml or less as an essential component, and a para-based fiber having a modified drainage degree of 300 ml or less. The filter medium of Example 1 in which the blending ratio of the fibrid made of aromatic polyamide was 1% and the filter medium of Example 2 in which the blending ratio was 3% had a collection efficiency of 30% or more, which was a level that could be used for the filter medium. .. Contains a polyolefin fiber, a polyolefin-based heat-sealing binder fiber, and a fibrid composed of a para-aromatic polyamide having a modified drainage degree of 300 ml or less as an essential component, and a para-aromatic aromatic having a modified drainage degree of 300 ml or less. The filter medium of Example 3 in which the compounding ratio of the fibrid made of polyamide was 5% and the filter medium of Example 4 in which the blending ratio was 10% had a collection efficiency of 50% or more, which was a good level as a filter medium. Contains a polyolefin fiber, a polyolefin-based heat-sealing binder fiber, and a fibrid composed of a para-aromatic polyamide having a modified drainage degree of 300 ml or less as an essential component, and a para-aromatic aromatic having a modified drainage degree of 300 ml or less. The filter medium of Example 5 in which the compounding ratio of the fibrid made of polyamide was 15% and the filter medium of Example 8 in which the blending ratio was 20% had a collection efficiency of 70% or more, which was a very good level as a filter medium.

Examples 6 and 7 are examples in which the fiber diameters of the polyolefin-based fiber (polypropylene fiber) and the polyolefin-based heat-sealing binder fiber are made larger than those of Example 5. The collection efficiency of the filter medium of Example 6 is 70% or more, which is very good, but the collection efficiency of the thicker filter medium of Example 7 is lower than that of Examples 5 and 6, and less than 70%. However, it was a good level as a filter medium.

From the comparison of Examples 6, 9 and 10, the blending ratio of the polyolefin-based heat-sealing binder fiber is 20% as compared with the filter medium of Example 6 in which the blending ratio of the polyolefin-based heat-sealing binder fiber is 50%. The filter medium of Example 9 was at a usable level although the pleating processability was lowered. Further, the filter medium of Example 10 having a blending ratio of the polyolefin-based heat-sealing binder fiber of 10% has lower pleating workability and alkali resistance than the filter medium of Example 6, but is at a usable level. It was.

From the comparison of Examples 6, 11 and 12, the pressure loss of the filter medium of Example 6 in which the blending ratio of the polyolefin-based heat-sealing binder fiber was 50% was less than 200 Pa, which was good, whereas the polyolefin was good. The pressure loss of the filter medium of Example 11 in which the blending ratio of the heat-bondable binder fiber was 60% was less than 200 Pa, which was good. The pressure loss of the filter medium of Example 12 in which the blending ratio of the polyolefin-based heat-sealing binder fiber was 70% was less than 250 Pa, which was higher than that of the filter medium of Example 6 and Example 11, but was at a usable level. .. Regarding the pleated workability, the filter media of Examples 11 and 12 had a very good level of hardness as compared with the filter media of Example 6.

In the filter medium of Comparative Example 2 which does not contain any polyolefin fiber (polypropylene fiber) and contains a fibrid composed of a polyolefin-based heat-sealing binder fiber and a para-aromatic polyamide having a modified drainage degree of 300 ml or less. The pressure loss was 250 Pa or more, which was a level unsuitable for a filter medium. On the other hand, in the filter medium of Comparative Example 3 in which the polyolefin-based heat-sealing binder fiber was not blended at all and the fibrid made of the polyolefin-based fiber and the para-aromatic polyamide having a modified drainage degree of 300 ml or less was contained, the filter medium was pleated. The workability was very poor and deformation occurred. Further, in the alkali resistance evaluation, the filter medium was torn when it was taken out after being immersed in the sodium hydroxide aqueous solution, and the alkali resistance could not be evaluated. The filter medium of Comparative Example 4 containing a fibrid composed of polyester fiber, polyester binder fiber, and para-aromatic polyamide having a modified drainage degree of 300 ml or less had good pressure loss, collection efficiency, and pleating workability. However, the alkali resistance was very poor.

From the comparison between Example 2 and Comparative Example 5, a fibrid composed of a polyolefin fiber, a polyolefin-based heat-sealing binder fiber, and a para-aromatic polyamide having a modified drainage degree of 300 ml or less is contained as an essential component. The filter medium of Example 2 was at a usable level in all the evaluation items, but the filter medium of Comparative Example 5 in which the modified fluidity of the fibrid made of para-aromatic polyamide was more than 300 ml had a collection efficiency of 30. It was less than%, which was an unsuitable level as a filter medium.

The filter medium of the present invention can be suitably used for a filter medium for an air filter and a filter medium for a liquid filter, and can be particularly preferably used for an alkaline liquid filter.

Claims (2)

A filter medium comprising a non-woven fabric containing a fibrid composed of a polyolefin fiber, a polyolefin-based heat-sealing binder fiber, and a para-aromatic polyamide having a modified drainage degree of 300 ml or less as an essential component.
Modified degree of drainage: An 80-mesh wire mesh with a wire diameter of 0.14 mm and a mesh size of 0.18 mm was used as a sieve plate, and the measurement was performed in accordance with JIS P8121-2: 2012 except that the sample concentration was 0.1%. value. The claim is characterized in that the blending ratio of the fibrid made of a para-aromatic polyamide having a modified water flow rate of 300 ml or less in the filter medium is 1% by mass or more and 20% by mass or less with respect to all the fibers constituting the filter medium. Item 1. The filter medium according to item 1.