JP6571563B2 - Air filter media - Google Patents

Description

  The present invention relates to an air filter medium having a support and a charged nonwoven fabric layer.

  Air filters are widely used in air conditioners and air purifiers used in buildings, factories, automobiles, general households, and the like. The shape of the air filter varies depending on the application and the design of the device. In particular, a pleated shape obtained by folding a filter medium in a wave shape can accommodate a large area of filter medium in a relatively small volume, and is known as one of general filter shapes.

  As a filter medium used for a pleated filter, a laminate in which a plurality of layers having different densities are formed is often used in order to maintain the strength as a filter and to achieve high collection and low pressure loss. As a laminated body, a laminated body including at least a support for maintaining strength as a filter and a dust collection layer for collecting particles is known. In particular, the support is required to have high strength and low pressure loss.

  Patent Document 1 and Patent Document 2 propose a composite filter medium in which a glass fiber sheet is used as an aggregate (support) and a melt blown nonwoven fabric or electret sheet is superimposed on the glass fiber sheet. The filter using this composite filter medium has high strength and can suppress the pressure loss. However, when this composite filter medium is pleated, the glass fiber is easily broken, so the broken glass fiber is scattered and the filter medium is removed. There is a problem that scratches and fluffing from the filter medium are likely to occur.

  In Patent Document 3, it is proposed that the nonwoven fabric is provided on both surfaces of the glass fiber sheet to prevent the glass fiber from scattering and fluffing during pleating. However, since it is necessary to provide a nonwoven fabric on both surfaces of the glass fiber sheet, there is a problem that pressure loss is likely to increase.

JP-A-6-198108 JP-A-6-205915 Japanese Patent Laid-Open No. 2002-18216

  An object of the present invention is to provide a filter medium for an air filter that does not damage the filter medium during pleating and has a high strength and excellent suitability for pleating.

  As a result of intensive studies to solve the above problems, the following invention has been found.

(1) A filter medium for an air filter having a support and a charged nonwoven fabric layer, the support comprising stretched polyester fibers, unstretched polyester fibers as binder fibers, and a copolyester having a glass transition point of 40 to 80 ° C. A filter medium for an air filter comprising a core-sheath type polyester composite fiber as a sheath.

  The filter medium for an air filter of the present invention has a support and a charged nonwoven fabric layer, and the support is a stretched polyester fiber, an unstretched polyester fiber as a binder fiber, and a copolymer having a glass transition point of 40 to 80 ° C. Since the core-sheath polyester composite fiber having polyester as a sheath portion is contained, the filter medium is strong and the air filter excellent in pleat processing suitability can be obtained.

  The filter medium for an air filter of the present invention has a support and a charged nonwoven fabric layer. The support is a stretched polyester fiber, an unstretched polyester fiber as a binder fiber, and a glass transition point of 40 to 80 ° C. It comprises a core-sheath type polyester composite fiber having a polymer polyester as a sheath part.

  In the present invention, as the unstretched polyester fiber used as the binder fiber for the support, a polyester such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and a copolymer mainly composed thereof is spun at a speed of 800 to 1,200 m. An unstretched fiber spun at / min. These unstretched polyester fibers are heat-pressure fused by thermal calendering, whereby a high strength support can be obtained.

  In the present invention, the sheath of the core-sheath polyester composite fiber used as the binder fiber is a copolyester having a glass transition point of 40 to 80 ° C. Copolyester includes a terephthalic acid component and an ethylene glycol component, and an isophthalic acid component, adipic acid component, sebacic acid component, naphthalenedicarboxylic acid component, diethyl glycol component, 1,4-butanediol component and aliphatic Examples thereof include a copolyester containing at least one component selected from the group of lactone components. This copolyester may be amorphous or crystalline.

  When the glass transition point of the copolyester in the sheath part of the core-sheath polyester composite fiber is 40 ° C. or higher, the mechanical strength of the sheath part is increased, so that the glass transition point is lower than 40 ° C. The strength of the origami after pleating is increased. In general, when pleating is performed, heating is performed immediately after folding for the purpose of strongly attaching a crease and maintaining the shape of the fold. When the glass transition temperature is less than 40 ° C., the support members of adjacent folds are thermally bonded to each other at the time of pleating, and the workability of the work of separating the pleats in the subsequent steps and the work of assembling the filter are lowered. Further, when the supports are more firmly bonded, the filter cannot be assembled. Further, when the heat-bonded supports are forcibly peeled off, the strength of the folded mountain is lowered and the filter performance is deteriorated. On the other hand, when the glass transition point is 80 ° C. or lower, a sharp crease is obtained, and a good filter with high strength and low pressure loss is obtained, but when the glass transition point exceeds 80 ° C., the filter medium , The crease is difficult to be formed, sharp folds cannot be obtained, and the filter performance is inferior compared with the case where the glass transition point is 80 ° C. or lower.

  In the present invention, the core of the core-sheath type polyester composite fiber is a polyester whose main repeating unit is alkylene terephthalate, and is preferably polyethylene terephthalate having high heat resistance.

  In the present invention, the cross-sectional shape of the core-sheath polyester composite fiber is not particularly limited, but is preferably circular. Further, the ratio of the core part to the sheath part is preferably in the range of core / sheath = 30/70 to 70/30, more preferably 40/60 to 60/40, in terms of volume ratio.

  In this invention, it is preferable that content of a binder fiber is 30-60 mass%, and it is more preferable that it is 30-50 mass%. When the content of the binder fiber is less than 30% by mass, the adhesive strength between the fibers becomes insufficient, the strength of the filter is lowered, and the filter performance may be inferior. On the other hand, when the content of the binder fiber exceeds 60% by mass, the ratio of the binder fiber exposed on the surface of the support increases, and the adjacent fold mountain supports adhere to each other during pleating, and the pleating and filter preparation are performed. Workability may be reduced in the subsequent processes. In particular, in the case of all-melt type binder fibers, pressure loss may increase due to melting.

  In the present invention, by containing the core-sheath type polyester composite fiber, by including the core-sheath type polyester composite fiber having a core portion that does not heat-melt as a part of the binder fiber, the formation of the binder fiber due to heat melting is suppressed. In addition, it is possible to develop strength while keeping the pressure loss low.

  In this invention, it is preferable that content of a core-sheath-type polyester composite fiber is 20-40 mass%, and 20-35 mass% is more preferable. When the content of the core-sheath polyester composite fiber is less than 20% by mass, the point adhesion ratio increases as the adhesion between the fibers, and the strength may decrease. On the other hand, when the amount exceeds 40% by mass, the ratio of the binder fibers exposed on the surface of the support increases, and the adjacent fold mountain supports adhere to each other at the time of pleating, and workability in the subsequent steps of pleating and filter preparation. May decrease.

  In the present invention, the fiber diameter of the binder fiber is preferably 2 to 25 μm, more preferably 5 to 20 μm, and still more preferably 10 to 20 μm. When a binder fiber having a fiber diameter of less than 2 μm is used, the strength of the support may be insufficient. On the other hand, when a binder fiber having a fiber diameter exceeding 25 μm is used, the adhesive point between the fibers is relatively reduced, and thus the strength of the support may be lowered.

  In the present invention, the support contains stretched polyester fibers as the main fibers. When the support is produced, the support is provided with sufficient strength by raising the temperature until the binder fiber is softened or melted. At that time, the stretched polyester fiber does not soften or melt, and forms a skeleton of the support as the main fiber. Moreover, since it can suppress that thickness becomes thin too much and can maintain the space | gap between fibers, a pressure loss can be kept low. Examples of the stretched polyester fiber include polyesters whose main repeating unit is alkylene terephthalate, but polyethylene terephthalate having high heat resistance is preferable. The cross-sectional shape of the fiber is preferably circular. However, fibers having an irregular cross section such as T-type, Y-type, and triangle can also be used as long as other characteristics are not impaired.

  The fiber diameter of the stretched polyester fiber is preferably 2 to 35 μm, more preferably 5 to 30 μm, and still more preferably 7 to 27 μm. When fibers having a fiber diameter of less than 2 μm are used, the strength of the support may be insufficient or the pressure loss may increase. On the other hand, when fibers having a fiber diameter exceeding 35 μm are used, the number of fibers is relatively reduced, and the gap between the fibers becomes too large, so that the strength of the support may be lowered.

  In this invention, you may add fibers other than the above-mentioned stretched polyester fiber and binder fiber to a support body as needed. Specifically, examples of synthetic fibers include polyolefin fibers, polyamide fibers, polyacrylic resins, vinylon resins, vinylidene, polyvinyl chloride, benzoate, polyclar, and phenol fibers. Natural fiber includes hemp pulp, cotton linter, lint, regenerated fiber, lyocell fiber, rayon, cupra, semi-synthetic fiber, acetate, triacetate, promix, inorganic fiber, 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 said fiber is a range which does not inhibit air permeability, it does not interfere with fibrillation. Furthermore, pulp fibers obtained from waste paper, waste paper, and the like 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 support in the air filter medium of the present invention preferably has a glass transition point derived from the core-sheath polyester composite fiber by differential scanning calorimetry. When the content of the core-sheath polyester composite fiber is low, or when the crystallinity of the core-sheath polyester composite fiber is increased by the heat treatment at the time of forming a sheet, it becomes a support that cannot determine the glass transition point There is. The support for which the glass transition point is required has a tendency that the rigidity of the filter is higher and the pleatability is superior than the support for which the glass transition point is not required.

  In addition, the glass transition point of the sheath part of the core-sheath type polyester composite fiber in the present invention and the support of the filter medium for the air filter is heated using a differential scanning calorimeter (manufactured by Perkin Elmer, apparatus name: DSC8500). Measured at a rate of 10 ° C / min. The glass transition point was defined as the temperature at which the straight line equidistant in the vertical axis direction from the extended straight line of each baseline intersects with the curve of the stepwise change portion of the glass transition.

  In the present invention, the support can be provided with functionality by containing an antibacterial agent, antifungal agent, antiallergen agent, deodorant and the like. These functional materials can be added when the support is made into a sheet, or can be applied by impregnation or coating after the support is made into a sheet.

In the present invention, the basis weight of the support is preferably from 30 to 200 g / ^{m 2,} more preferably 60 to 150 g / ^{m 2,} more preferably 80 to 120 / ^{m 2.} If it is less than 30 g / m ² , the strength of the filter medium may be insufficient. On the other hand, when it exceeds 200 g / m ² , the pressure loss increases, the thickness of the filter medium increases, the required amount of filter medium area cannot be stored, and the size of the filter may increase.

  In the present invention, the thickness of the support is preferably 0.2 to 1.2 mm, more preferably 0.3 to 0.8 μm, and still more preferably 0.4 to 0.6 mm. . If the thickness exceeds 1.2 mm, the filter medium area that can be stored is reduced, and the life of the filter may be shortened. On the other hand, if the thickness is less than 0.2 mm, sufficient strength may not be obtained.

  In the present invention, the method for producing the nonwoven fabric used as the support is arbitrarily selected from known methods such as the card method, airlaid method, air-through method, wet papermaking method, thermal bond method, chemical bond method, and spunbond method. Can do.

  In the filter medium for an air filter of the present invention, an electret-processed spunbond nonwoven fabric, a melt blown nonwoven fabric, or the like is used as the charged nonwoven fabric layer, and a melt blown nonwoven fabric that provides high dust collection performance is preferable. Synthetic polymer materials such as polypropylene, polyethylene, polystyrene, polyolefin resins such as polybutylene terephthalate, polytetrafluoroethylene, aromatic polyester resins such as polyethylene terephthalate, polycarbonate resins, etc. A material having a high electric resistivity such as polypropylene is preferable, and a polypropylene having a low melting point and easy to produce a melt blown nonwoven fabric is more preferable. In addition, various additives are added to the resin used for the charged nonwoven fabric layer in order to enhance and improve the chargeability, weather resistance, thermal stability, mechanical properties, coloring, surface properties, or other properties. Can do. In particular, since electret processing is performed, it is preferable to include an electret additive for the purpose of enhancing the chargeability. The electret additive preferably contains at least one electret additive selected from the group consisting of hindered amine compounds and triazine compounds.

  Examples of the hindered amine compound include poly [(6- (1,1,3,3-tetramethylbutyl) imino-1,3,5-triazine-2,4-diyl) ((2,2,6,6 -Tetramethyl-4-piperidyl) imino) hexamethylene ((2,2,6,6-tetramethyl-4-piperidyl) imino)] (manufactured by BASF Japan Ltd., trade name: Kimasorb (registered trademark) 944LD), Succinic acid dimethyl-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate (manufactured by BASF Japan Ltd., trade name: Tinuvin (registered trademark) 622LD), 2 -(3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonate bis (1,2,2,6,6-pentamethyl-4-piperidyl) (BASF Japan) Company, Ltd., trade name: Tinuvin (registered trademark) 144), and the like.

  Examples of the triazine compound include the poly [(6- (1,1,3,3-tetramethylbutyl) imino-1,3,5-triazine-2,4-diyl) ((2,2 , 6,6-tetramethyl-4-piperidyl) imino) hexamethylene ((2,2,6,6-tetramethyl-4-piperidyl) imino)] (manufactured by BASF Japan Ltd., trade name: Kimasorb (registered trademark) 944LD), 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-((hexyl) oxy) -phenol (manufactured by BASF Japan Ltd., trade name: Tinuvin (registered trademark) ) 1577FF).

  In the present invention, in addition to the above-mentioned compounds, the charged nonwoven fabric layer can be added with usual additives generally used for nonwoven fabrics that are generally electret processed, such as heat stabilizers, weathering agents, and polymerization inhibitors. .

In the present invention, the average single fiber diameter of the fibers contained in the charged nonwoven fabric layer is preferably 0.1 to 8.0 μm, more preferably 0.5 to 6.0 μm, still more preferably 1. It is 0-4.0 micrometers. When the average single fiber diameter exceeds 8.0 μm, the gap between the fibers of the charged nonwoven fabric layer becomes large, and the collection efficiency may be lowered. On the other hand, when the average single fiber diameter is less than 0.1 μm, the gap between the fibers becomes narrow, and the pressure loss may increase.

In the present invention, the basis weight of the charged nonwoven fabric layer is preferably 10 to 50 g / m ² , more preferably 15 to 40 g / m ² . If the basis weight exceeds 50 g / m ² , the pressure loss may increase. Conversely, if the basis weight is less than 10 g / m ² , the collection efficiency may decrease.

In the air filter medium of the present invention, as a method of forming the support and the charged nonwoven fabric layer, the support and the charged nonwoven fabric layer are respectively formed into sheets and then bonded together, or the charged nonwoven fabric layer directly on the support. The method of forming is used. In the present invention, a wide range of selection of the support member and the charging nonwoven layer, it bonded method is preferred. Further, as a method for bonding the support member and the charging nonwoven layer, sintering method of thermally bonded by spraying the powdery adhesive between the support member and the charging nonwoven layer, a spray between the support member and the charging nonwoven layer And a method of spraying and bonding an adhesive in a hot melt state, an ultrasonic method of superimposing a support and a charged nonwoven fabric layer and ultrasonic welding, and the like.

  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.

<Stretched PET fiber>
A stretched polyester fiber made of polyethylene terephthalate and having a fiber diameter of 13 μm and a fiber length of 5 mm was used.

<Unstretched PET fiber>
An unstretched polyester fiber composed of polyethylene terephthalate and isophthalic acid and having a fiber diameter of 11 μm and a fiber length of 5 mm was used.

<Core sheath PET fiber 1>
The core is polyethylene terephthalate, the sheath is an amorphous copolyester composed of polyethylene terephthalate and isophthalic acid (glass transition point: 72 ° C.), fiber diameter 15 μm, fiber length 5 mm, core / sheath volume ratio The 50/50 core-sheath type polyester composite fiber was designated as core-sheath PET fiber 1.

<Core sheath PET fiber 2>
The core is polyethylene terephthalate, the sheath is a crystalline copolymer polyester (glass transition point: 45 ° C.) made of polyethylene terephthalate, 1,4-butanediol and ε-caprolactone, fiber diameter 15 μm, fiber length 5 mm, core The core-sheath polyester composite fiber having a volume ratio of the part / sheath part of 50/50 was designated as the core-sheath PET fiber 2.

<Core sheath PET fiber 3>
The core is polyethylene terephthalate, the sheath is a crystalline copolymerized polyester (glass transition point: 86 ° C.) made of polyethylene terephthalate and 1,4-butanediol, fiber diameter 15 μm, fiber length 5 mm, core / sheath The core-sheath polyester composite fiber having a volume ratio of 50/50 was designated as core-sheath PET fiber 3.

<Core sheath PET fiber 4>
The core is polyethylene terephthalate, the sheath is a crystalline copolymer polyester (glass transition point: 32 ° C.) made of polyethylene terephthalate, 1,4-butanediol and ε-caprolactone, fiber diameter 15 μm, fiber length 5 mm, core The core-sheath polyester composite fiber having a volume ratio of the part / sheath part of 50/50 was designated as the core-sheath PET fiber 4.

  The filter media for air filters of Examples 1 to 9 and Comparative Examples 1 to 4 were produced by obtaining the following steps.

(Production of support)
After water is added to a 2 m ³ dispersion tank, it is blended at the raw material blending ratio (%) shown in Table 1, and is dispersed for 5 minutes at a dispersion concentration of 0.2% by mass, with a basis weight of 100 g / m ² as a target. A wet paper web is formed by a circular paper machine, dried by hot pressure with a Yankee dryer having a surface temperature of 130 ° C., and then subjected to a heat calender treatment with an elastic roll facing a metal roll having a surface temperature of 200 ° C. The support body of the filter material for air filters of 1, 3-9 and Comparative Examples 1-4 was obtained.

  In addition, Example 2 was carried out in the same manner as the support for the air filter medium of Examples 1, 3 to 9 and Comparative Examples 1 to 4 except that the surface temperature of the heat calendered metal roll was 230 ° C. A filter medium support for air filter was obtained.

(Production of charged non-woven fabric layer)
10 ppm of hindered amine based additive (manufactured by BASF Japan Ltd., trade name: Kimasorb (registered trademark) 944) is added to polypropylene (manufactured by Prime Polymer Co., Ltd., trade name: S10AL), and the basis weight obtained by the melt blow method is 15 g / The melt blown nonwoven fabric obtained by applying electret processing to a nonwoven fabric of m ² and an average single fiber diameter of 7.2 μm by the corona discharge method was used for the charged nonwoven fabric layer.

(Lamination of support and charged nonwoven fabric layer)
Between the melt blown nonwoven fabric and the support for the air filter media of Examples 1 to 9 and Comparative Examples 1 to 4, a heat-curing moisture-curing urethane resin was sprayed and adhered, and Examples 1 to 9 and Comparative Examples 1 to 4 were obtained.

  About the glass transition point of the support bodies of Examples 1 to 9 and Comparative Examples 1 to 4 obtained as described above, and the pleat processing suitability of the air filter media of Examples 1 to 9 and Comparative Examples 1 to 4, Measurement and evaluation were performed as follows. The measurement and evaluation results are shown in Table 2.

(Glass transition point of support)
It measured with the temperature increase rate of 10 degree-C / min using the differential scanning calorimeter (The Perkin-Elmer company make, apparatus name: DSC8500). The glass transition point was determined from the temperature at the point where the straight line equidistant in the vertical axis direction from the straight line extended from each baseline intersects with the curve of the stepwise change portion of the glass transition.

(Applicability of air filter media for pleating)
About the filter medium for air filters of Examples 1 to 9 and Comparative Examples 1 to 4, with a reciprocating pleating machine set at a processing temperature of 80 ° C., while slitting to a width of 235 mm at a speed of 50 mountains, Pleating was performed at a thickness of 28 mm. Thereafter, pleats were cut every 50 peaks, and a filter unit was prepared using a nonwoven fabric frame coated with a hot melt adhesive. The situation at the time of pleating and the orderliness of the origami after the filter unit was produced were judged visually to evaluate the suitability for pleating. Regarding the filter unit, "◎", "○" from the standpoints that the tip of the origami has an acute angle, linearity, that the pleats are aligned evenly, and that there are no problems with pleating. , “Δ”, “×”, and “Δ” or higher were accepted, and “×” was a problem in performance or processing.

  From the results of Examples 1 and 2, since the support of the filter material for air filter of Example 2 was prepared by setting the surface temperature of the metal roll to 230 ° C. during the heat calendering process, the crystallinity of the sheath part of the core sheath PET fiber 2 was The glass transition point derived from the core-sheath PET fiber 2 could not be determined by differential scanning calorimetry of the support. For this reason, the air filter medium of Example 1 in which the glass transition point derived from the core-sheath PET fiber 2 was required by differential scanning calorimetry of the support was superior in pleatability.

  From the results of Examples 3 and 4, the support of the filter medium for the air filter of Example 4 has a core-sheath PET fiber 1 content of less than 20% by mass, and the core-sheath PET fiber by differential scanning calorimetry of the support. No glass transition point derived from 1 was found. Therefore, the air filter medium of Example 3 containing 20% by mass of the core-sheath PET fiber and requiring a glass transition point derived from the core-sheath PET fiber 1 by differential scanning calorimetry of the support is more suitable for pleating. It was excellent.

  From the results of Examples 3 and 5, since the support of the air filter medium of Example 5 has a binder fiber content of less than 30% by mass, the strength of the filter medium compared with the air filter medium of Example 3 However, the filter unit made of the air filter medium of Example 3 was superior in pleat processing suitability because of its sharp angle and linearity.

From the results of Examples 6 and 7, the support of the filter medium for air filter of Example 7 had a binder fiber content of more than 60% by mass, and the ratio of binder fibers exposed on the surface of the support increased. At the time of pleating, the adjacent folded mountain supports were bonded to each other so that they could be peeled off by hand. Towards the filter medium for an air filter of Example 6 content of the binder fibers is 60 wt% were excellent pleating suitability, and the workability during pleating.

From the results of Examples 6 and 8, the support of the air filter medium of Example 8 has a core-sheath PET fiber 1 content of more than 40% by mass, and the ratio of binder fibers exposed on the surface of the support is high. Because of the increase, during the pleating process, the adjacent folded mountain supports were adhered to each other so that they could be peeled off by hand. Sheath content of PET fiber 1 is more of the filter medium for an air filter of Example 6 is 40% by mass was excellent pleating suitability, and the workability during pleating.

  From the results of Examples 3 and 9, the glass transition point of the air filter medium support of Example 3 is higher than the glass transition point of the air filter medium support of Example 9, so that Compared with the filter material for air filters, the strength of the filter media was stronger, and the filter unit made of the filter media for air filter of Example 3 had a sharper fold angle and linearity, and was more suitable for pleating.

  From the results of Example 3 and Comparative Examples 1 and 2, the support for the filter medium for the air filter of Comparative Example 1 contains a core-sheath polyester composite fiber having a copolymer polyester having a glass transition point of 40 to 80 ° C. as a sheath. Thus, the glass transition point derived from the core-sheath polyester composite fiber was not determined by differential scanning calorimetry of the support. Moreover, the strength of the filter medium was weak, and the filter unit produced in Comparative Example 1 had no oriyama linearity and was poor in pleatability. Moreover, since the support body of the filter material for air filters of the comparative example 2 does not contain unstretched PET fibers, the strength of the filter media does not increase even when the thermal calendar treatment is performed, and the filter unit produced in the comparative example 2 is There was no oriyama's linearity and the pleatability was poor.

From the results of Example 3 and Comparative Examples 3 and 4, the support for the filter material for the air filter of Comparative Example 3 includes a core-sheath polyester composite fiber having a sheath portion of a copolyester having a glass transition point of more than 80 ° C. The glass transition point derived from the core-sheath polyester composite fiber obtained by differential scanning calorimetry of the support exceeds 80 ° C., so the rigidity of the filter medium is too high, and the fold mountain cannot be folded at an acute angle during pleating. It was. Therefore, the filter unit made of the filter material for air filter of Comparative Example 3 had rounded folds, and some irregularities were observed between the folds, which was inferior in pleatability. Further, the support of the filter material for air filter of Comparative Example 4 includes a core-sheath type polyester composite fiber having a sheath made of a copolyester having a glass transition point of less than 40 ° C., and is obtained by differential scanning thermal analysis of the support. The glass transition point derived from the core-sheath polyester composite fiber is less than 40 ° C., and when the pleating process is set at a processing temperature of 80 ° C., adjacent fold mountain supports can be bonded together to assemble the filter unit. There wasn't.

  The filter material for an air filter of the present invention can be used for an air filter used in an air conditioner or an air cleaner used in buildings, factories, automobiles, general households and the like.

Claims (1)

  A filter medium for an air filter having a support and a charged non-woven fabric layer, the support comprising a stretched polyester fiber, an unstretched polyester fiber as a binder fiber, and a copolymer polyester having a glass transition point of 40 to 80 ° C. A filter medium for an air filter comprising a core-sheath type polyester composite fiber.