JP6579876B2 - Filter medium and filter unit using the same - Google Patents

Description

  The present invention relates to a filter medium for removing dust by attaching it to various air conditioners, and a filter unit using the same.

  Conventionally, an air conditioner has been installed and used in various environments, and a filter medium that collects dust has been widely exchanged as a filter unit designed to be attached to the apparatus. Note that filter units used in office buildings and the like are required to have an average colorimetric efficiency (detailed later) of 65 [%] or more according to a colorimetric method defined by JIS. The present applicant has also proposed various techniques for realizing a highly efficient and low pressure loss filter unit with high reproducibility. For example, in Japanese Patent Application Laid-Open No. 2008-212858 (hereinafter referred to as Patent Document 1). , A manufacturing technique of a filter element (hereinafter, used comprehensively as a filter unit in the present specification) is proposed. This Patent Document 1 discloses a jig for holding a pleat for use in a process until a tape-shaped frame member is fixed to an outer peripheral edge of a filter medium on which a pleat is formed. In this technique, there is a description that non-woven fabrics made of various materials can be used as a filter medium that can be pleated. Regarding the pleat shape, a suitable form in which the peak height of the filter medium is about 5 to 150 [mm] is disclosed, and a separator made of a hot melt resin is linearly applied to the filter medium surface in order to maintain the pleated shape after being produced. The form to do is disclosed.

In addition, as a filter medium used in such a filter unit, for example, Japanese Patent Application Laid-Open No. 2014-208318 (hereinafter referred to as Patent Document 2) has antibacterial properties in addition to general properties such as pressure loss, dust collection efficiency and life. Filter media that can be demonstrated are disclosed. This technology relates to a non-woven filter medium having a single layer structure in which a sheath component is made of polyethylene and a core component is made of polypropylene, and has a bulk density of 0.03 for realizing a balance between dust collection efficiency and ventilation resistance of the filter medium. ~ 0.20 [g / cm ³ ], thickness 1.5 [mm] or less considering the pressure loss of the filter unit after pleating, in order to realize moderate pleating workability, the bending repulsion characteristic in the Gurley method is 100 There is disclosure such as ˜500 [mg], and it is described that the content of the antibacterial agent is a predetermined amount. Further, in this publication technique, the filter medium is electret-treated, a bead resin having a peak height of 50 [mm] and a peak pitch of 6 [mm] is applied, and then pleated to give a 610 [mm] square filter unit. Produced and verified for pressure loss, JIS11 initial collection efficiency and antibacterial properties

As a technique relating to such pleating, Japanese Patent Application Laid-Open No. 2002-95920 (Patent Document 3) relates to a pleated filter medium, by defining the relationship between the pleat height H and the pitch P, A technique for realizing a high filter unit is disclosed. In this publication, when a filter medium having a thickness of 0.4 to 1.2 [mm] is processed into a pleat shape, the relationship between the peak height H and the pitch P is “0.05 ≦ H / P ² ≦ 0.2”. It is described that a filter unit excellent in so-called structural pressure loss can be provided by satisfying the above conditions, and preferably by setting the peak height H to 25 [mm] or more. In the Example column which is a specific form, an electret treatment is performed as a filter medium, a filter unit using a polypropylene net as a reinforcing material for the purpose of shape retention is manufactured, and pressure loss is verified.

  Each of these literature techniques relates to pleating of a filter unit, and proposes to evaluate and select the processing suitability of a filter medium to be used from the viewpoint of bending resistance (bending repulsion), thickness, and the like. Here, two basic characteristics that are originally required for the filter medium are pressure loss and collection efficiency. As an evaluation method that can simultaneously evaluate the improvement of these two basic characteristics, a QF (QUALITY FACTOR) value described later is used. It has been known.

JP 2008-212858 A ([Claims], [0008], [0024], [0028] to [0029], [FIG. 1], [FIG. 2], etc.) JP 2014-208318 A ([Claims], [0012] to [0014], [0020], [Table 1], etc.) JP 2002-95920 A ([Claims], Example column)

  In the background art described above, auxiliary components such as a jig (Patent Document 1), a bead-shaped resin (Patent Document 2), and a net (Patent Document 3) in the manufacturing process are used for the purpose of maintaining a pleated shape. A filter unit has been produced. Considering the suitability for pleating, instead of using these auxiliary components, instead of a material with low rigidity as proposed in Patent Document 2 in order to maintain a self-supporting structure, a material having higher bending resistance is used. It is possible to select. However, although the basis weight and bulk density of the filter medium are required to increase the bending resistance, there has been a problem that a technique that combines both pressure loss and collection efficiency has not been known yet.

  For this reason, the inventor according to the present application did not need the above-described auxiliary member, and as a result of earnestly examining the compatibility of the processing performance of the filter medium with the basic performance such as high efficiency and low pressure loss of the filter medium, The invention has been completed. Accordingly, an object of the present invention is to provide a technique that can maintain the pleated shape substantially without using an auxiliary member and that satisfies both of the excellent basic performance of the filter medium.

In order to achieve this object, according to the configuration of the filter unit according to this application, the filter medium satisfying the following characteristics (A) to (C) is a non-woven fabric made of heat-bonding fibers, and has a pleated shape. The ratio of the pleated peak height divided by the peak spacing is 3.0 or more and 4.0 or less, and this filter unit complies with the performance test (JIS B9908). The average colorimetric efficiency by the colorimetric method is 65% or more, and the QF value is 0.070 or more and 0.079 or less .

(A) Weight per unit area: 120 [g / m ² ] or more (B) Bulk density: 0.071 [g / cm ³ ] or less (C) Gurley bending resistance: 900 [mg] or more This is a value determined according to JIS L1096 (2010 edition) “Fabric and knitted fabric test method”, and “bulk density” is 1.96 [kPa] (corresponding to 20 [g / cm ² ]) at a compressive load. The value calculated from the required thickness and basis weight is shown. In the present specification, “Gurley stiffness” may be simply referred to as stiffness.

  Further, in realizing this filter medium, it is preferable that the above-described filter medium has a QF value of 0.14 or more. The QF value mentioned here represents an actual measurement value obtained from the following equation by measuring the collection efficiency [%] and pressure loss [Pa] of the filter medium under predetermined conditions, as will be described in detail later. Note that “Ln” in the equation represents a logarithmic function with the natural logarithm as the base.

QF value = -Ln (1-collection efficiency / 100) / pressure loss
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By applying the configuration of the present invention, Ri figure optimization of pleating can provide a filter unit with excellent basic performance.

  Hereinafter, preferred embodiments of the present invention will be described. In the following description, in order to facilitate understanding of the present invention, specific shapes, arrangement relationships, etc. will be described as examples. However, the present invention is not limited to these examples, and the object of the present invention Any suitable design and modification can be made within the range of.

  First, the nonwoven fabric composed of the thermobonding fibers constituting the filter medium of the present invention is composed of two or more resins having a melting point difference of at least 15 [° C.] or more, more preferably 20 [° C.] or more, as is well known. A core-sheath type or side-by-side type composite fiber is preferably used. As the combination of resins used, polyethylene terephthalate and polybutylene terephthalate, 6-nylon and 6,6-nylon, polyethylene and polypropylene, etc. can be used, but a filter medium with an excellent balance between pressure loss and collection efficiency can be used. In order to realize, a composite fiber having polyethylene as a sheath and polypropylene as a core that can be easily electret-treated is most preferable. The fineness and the fiber length can be arbitrarily suitably employed, but since the preferred basis weight and bulk density of the filter medium of the present invention are relatively large, the fineness 2.2 to 22 [ dtex] and a fiber length of 33 to 150 [mm] can efficiently prepare a card nonwoven fabric excellent in economic efficiency.

  Further, when heat-bonding the card web composed of such constituent fibers, a dry oven, a calender, or the like can be arbitrarily selected so that the card web can be heated under substantially no pressure. In order to achieve the physical property values defined by No. 1 with high reproducibility, calendar processing with a pair of heating rolls having a predetermined clearance is most preferable. The filter medium obtained in this manner can be subjected to electret processing such as well-known corona charging after heat bonding to ensure low pressure loss and high collection efficiency.

  This filter medium is finished in a pleated shape by being applied to a known pleating machine, and at that time, the shape can be maintained by applying heat only to the creased portion that becomes a mountain or a valley. At this time, the higher the bending resistance, the more the shape can be maintained at a lower temperature, thereby reducing the ineffectiveness of the electret process performed prior to the pleating process described above. Thereafter, as proposed in Patent Document 1, for example, the adhesive surface of the frame material laminated with a hot melt film is heated and melted in advance, and held at both ends of each ridge line of the pleated valleys, whereby the rigidity of the filter medium itself is obtained. Therefore, it is possible to produce a filter unit in which the filter medium has the function of a pair of frames parallel to the ridgeline. Therefore, the filter medium functions as a frame material at both ends parallel to the above-described ridge line. During this time, by holding the pleated shape with a jig or the like, the above-described ratio can be realized with high reproducibility by maintaining the peak height and the peak interval according to the present invention.

Hereinafter, for the examples of the present invention, the specific nonwoven fabric described in the preferred embodiment described above will be exemplified, and when a filter medium that satisfies the conditions specified by the present invention is compared and studied on a flat plate, this plate-shaped filter medium is determined in a predetermined manner. Each result when the pleated filter unit is verified will be described.
(Verification of filter media composition)
First, the nonwoven fabric as an example of the present invention is a polyolefin short fiber “UC fiber HR-LE” (fineness 6.6 [dtex], fiber length having a commercially available core-sheath structure shown in Patent Document 2 described above. 64 [mm]; 3 types of carded nonwoven fabric consisting only of Ube Eximo Co., Ltd. (trade name), and a pair of rolls with a predetermined thickness after heating at 150 [° C.] for 1 minute. Thermal adhesion was performed while adjusting the thickness on a calendar, and then corona charging was performed to obtain four types of filter media. Table 1 shows the basis weight, the thickness, the bulk density, the bending resistance, and the QF value of the non-woven fabric used as the filter medium. In order to calculate the QF value, a filter medium is sandwiched in a duct with a 25 cm square opening at a flow rate of 10 cm / s while atmospheric dust is loaded from the upstream, and the differential pressure (pressure loss) between upstream and downstream and upstream and downstream. A particle counter was installed, the number of particles of 0.3 μm to 0.5 μm contained in the atmospheric dust was counted to calculate the collection efficiency, and the above calculation formula was used.

As can be understood from Table 1, compared to Comparative Examples C and D as filter media, both of the filter media of Example A and Example B had a high QF value due to their low bulk density. This is because the filter medium of Example B has the same basis weight as the filter medium of Comparative Example D, but the bulk density is reduced and the pressure loss is reduced by increasing the thickness. Further, if the fibers are equally charged by corona charging, it is estimated that the filter medium having a larger thickness has a higher contact probability with the particles. Therefore, it is considered that the collection efficiency of Example B is higher than that of Comparative Example D, the electret effect due to corona charging is higher, and the QF value obtained is also higher. Moreover, since the thickness was taken large compared with the increase in the fabric weight, the nonwoven fabric was bent and hardened and the Gurley stiffness was increased as the bulk density decreased. Thus, it can be understood that the two types of filter media according to Example A and Example B can achieve excellent performance. Moreover, in the filter medium according to Comparative Example C, the Gurley bending resistance is the lowest of the four, and it is difficult to maintain the pleated shape. A separator serving as an auxiliary member was formed by linear application in a direction perpendicular to the ridge line, and the evaluation was made for evaluation. Furthermore, the filter medium of Comparative Example D was excluded from unit evaluation because it had the lowest QF value among these filter media.
(Verification of filter unit)
The optimization of the pleat shape as a filter unit was verified using the three types of filter media of Example A, Example B, and Comparative Example C which were bead-formed. As a technique, the peak height was unified to 60 [mm], and the performance was verified by calculating the QF value from the initial pressure loss and the efficiency by the colorimetric method with various peak intervals changed.

The filter unit is finished with a 300 mm square front area, and frame materials are attached to both ends of the pleat ridgeline. JIS B 9908 (2001) "Performance test method for ventilation air filter units and ventilation electric dust collectors" The initial pressure loss, average colorimetric efficiency, and final performance when supplying JIS 11 and JIS 15 dusts are loaded with an apparatus based on type 2 specified in Section 2 and airflow is 7 [m ³ / min]. The amount of dust supplied until the pressure loss reached 70 [Pa] was measured and recorded. In organizing the results, the balance between pressure loss and efficiency was evaluated as the basic performance by obtaining the above-mentioned QF value. As shown in Table 2, both the pressure loss and efficiency were satisfied, and the QF value was excellent. “◯” when two items are good, and “X” when only one item is good. However, even if the average colorimetric efficiency by the colorimetric method does not satisfy 65% is excellent in QF value, it is determined as not satisfying the requirement.

  As can be understood from this table, it can be understood that good results are obtained when the ratio of the peak height to the peak interval is in the range of 3.0 to 4.0. Further, as described above, Reference Example B-2 was excellent in the QF value, but did not satisfy the requirement that the average colorimetric efficiency was 65% or more. This can be understood as a result supporting the usefulness of the ratio described above.

Claims (1)

A non-woven fabric made of heat-bonded fibers, and a filter unit that satisfies the following characteristics (A) to (C) in a pleated shape and is held by a frame material, and the pleated-shaped peak height is divided by a peak interval. The filter unit has an average colorimetric efficiency of 65% or more according to a colorimetric method based on a performance test (JIS B9908), and a QF of 3.0 to 4.0. A filter unit having a value of 0.070 or more and 0.079 or less .
(A) Weight per unit area: 120 (g / m ² ) or more
(B) Bulk density: 0.071 (g / cm ³ ) or less
(C) Gurley bending resistance: 900 (mg) or more