Replaceable pre-filter and air filter unit having the same

Abstract

To solve the problem that joining of a pre-filter and an air filter is performed by holding and fixing the pre-filter between a device body and the air filter, and the pre-filter is broken when it is held.SOLUTION: Provided is a replaceable pre-filter which can be installed on an air filter by electrostatic force without impairing air permeability of an air filter unit even when attached to the air filter.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a replaceable pre-filter that can be installed independently of an air filter, and an air filter unit having the replaceable pre-filter. [Background technology]

[0002] In recent years, there has been a growing need in the air filter market for applications such as air purifiers, air conditioners, and automobiles to impart various functions to air filters, such as antibacterial and antiviral properties.

[0003] As a method for imparting a function to an air filter, a method in which the support layer constituting the air filter is previously imparted with the function, and then the support layer is bonded to a melt-blown nonwoven fabric and pleated to form an air filter can be given.

[0004] Another method of imparting functionality to an air filter unit (prefilter + air filter) is to impart functionality to the prefilter, then attach it to the upstream surface of a pleated air filter, thereby imparting functionality to the prefilter.

[0005] For example, Patent Document 1 describes a filter in which a filter medium and a layered pre-filter are joined together, and the pre-filter has at least one of the following functions: antibacterial, antifungal, antiviral, aromatic, and deodorizing. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-96118 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in Patent Document 1, the prefilter and air filter are joined by sandwiching and fixing the prefilter between the air purifier body and the air filter, and if a prefilter with low strength is used, there is a problem that it may break when sandwiched.

[0008] Furthermore, since the pre-filter attached to the air filter is in the form of a sheet, there is a problem that when a melt-blown nonwoven fabric with a large pressure loss is used as the pre-filter, the breathability of the air filter unit is significantly impaired.

[0009] Furthermore, in the case of an integrated air filter unit in which a pre-filter and an air filter are integrated, the pre-filter cannot be installed during use, so functions cannot be changed or added while the air filter unit is in use, and users must select an air filter unit that has the desired functions pre-installed. [Means for solving the problem]

[0010] In order to solve the above problems, the replaceable pre-filter and the air filter unit having the same of the present invention have the following features. (1) A replaceable prefilter having an electrostatically charged fiber sheet, characterized in that the average fiber diameter of the constituent fibers of the electrostatically charged fiber sheet is 0.1 to 50 μm, and the replaceable prefilter can be installed independently on an air filter. (2) The replaceable prefilter according to (1), characterized in that it has at least one function selected from antibacterial, antiviral, and antifungal properties. (3) An air filter unit comprising the replaceable pre-filter and air filter according to (1) or (2). [Effects of the Invention]

[0011] The replaceable prefilter of the present invention does not impair breathability even when installed in an air filter, and can be installed on the air filter using electrostatic force. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram of a collection efficiency measurement device. DETAILED DESCRIPTION OF THE INVENTION

[0013] The replaceable prefilter of the present invention has an electrically charged fiber sheet, which is imparted with an electret treatment to impart an electric charge to the fiber sheet.

[0014] In the present invention, the electret processing method can be arbitrarily selected from known methods such as corona discharge, fluid contact, and frictional charging. Among the fluid contact methods, the so-called hydrocharging method is particularly preferred, in which the electret is applied by spraying pure water onto the nonwoven fabric or by contacting it with a water stream in a water tank. As the polar solvent used in this case, pure water is preferably used from the viewpoint of productivity, such as wastewater discharge.

[0015] The replaceable prefilter of the present invention has an electrostatically charged fiber sheet. Polyolefin-based resins are preferred as the raw material for the fibers. Examples of polyolefin-based resins include homopolymers such as polyethylene, polypropylene, polybutene, and polymethylpentene. Resins such as copolymers in which different components are copolymerized with these homopolymers, and blends of two or more different polymers can also be used. Among these, polypropylene-based resins and polymethylpentene-based resins are preferred from the viewpoint of charge retention. Polypropylene-based resins are particularly preferred from the viewpoints of low cost and ease of reducing the fiber diameter.

[0016] In the present invention, the term "polyolefin resin composition" refers to a resin composition containing 80 mass % or more of polypropylene homopolymer (or polyethylene homopolymer, etc.) and propylene units (or ethylene units, etc.), among resins such as polypropylene (or polyethylene, etc.) homopolymer, copolymer with other components, and polymer blend with different resins. The same applies to other polyolefin resin compositions.

[0017] The polyolefin resin composition used in the present invention may contain a nucleating agent. By containing a nucleating agent, the temperature-lowering crystallization temperature of the polyolefin resin composition increases, and the solidification of the spun fibers proceeds more quickly, reducing fusion between the fibers and improving the breathability of the electrostatic fiber sheet.

[0018] Examples of the crystal nucleating agent include sorbitol-based nucleating agents, nonitol-based nucleating agents, xylitol-based nucleating agents, phosphoric acid-based nucleating agents, triaminobenzene derivative nucleating agents, and metal carboxylate nucleating agents.

[0019] In addition to the nucleating agent, the polyolefin resin composition used in the present invention may contain at least one hindered amine additive and / or triazine additive, in order to improve the electret performance of the electrostatically charged fiber sheet.

[0020] 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., "Chimassorb" (registered trademark) 944LD), dimethyl succinate-1-(2- hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate (manufactured by BASF Japan Ltd., "TINUVIN" (registered trademark) 622LD), and bis(1,2,2,6,6-pentamethyl-4-piperidyl) 2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butylmalonate (manufactured by BASF Japan Ltd., "TINUVIN" (registered trademark) 144).

[0021] Examples of triazine additives 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., "Chimassorb" (registered trademark) 944LD), and 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-((hexyl)oxy)-phenol (manufactured by BASF Japan Ltd., "Tinuvin" (registered trademark) 1577FF).

[0022] The average fiber diameter of the constituent fibers of the electrostatically charged fiber sheet used in the present invention is 0.1 to 50 μm. By setting the average fiber diameter to preferably 1.0 μm or more, more preferably 2.0 μm or more, and even more preferably 3.0 μm or more, the strength of the electrostatically charged fiber sheet can be improved. On the other hand, by setting the average fiber diameter to preferably 30.0 μm or less, more preferably 10.0 μm or less, and even more preferably 5.0 μm or less, the collection efficiency of the electrostatically charged fiber sheet can be improved. If the average fiber diameter of the constituent fibers of the electrostatically charged fiber sheet is less than 0.1 μm, the strength of the electrostatically charged fiber sheet will be significantly reduced, making it more likely to tear when placed. Conversely, if the average short fiber diameter exceeds 50 μm, the collection efficiency will be significantly reduced.

[0023] To calculate the average fiber diameter of the constituent fibers of the electrostatic fiber sheet, 15 3mm x 3mm measurement samples are taken from 3 points across the width of the electrostatic fiber sheet (2 side edges and 1 center point) and 5 points spaced 5cm apart in the longitudinal direction, for a total of 15 points, and a scanning electron microscope (such as the Keyence Corporation's VHX-D500) is used to adjust the magnification to 3000x, taking 15 photographs of the fiber surface from each of the taken measurement samples.Then, the fiber diameter is measured for all fibers whose fiber diameter (fiber diameter) can be clearly identified in the photographs, and the arithmetic mean value of these measurements, rounded to one decimal place, is used as the average fiber diameter.

[0024] In the electrostatic fiber sheet used in the replaceable prefilter of the present invention, the method for forming the fibers into a sheet is not particularly limited, and known methods can be used. Among them, it is preferable to form the sheet from a nonwoven fabric by the melt-blowing method, which is suitable for producing fibers with a fiber diameter in the above-mentioned range.

[0025] The electrostatic fiber sheet used in the replaceable prefilter of the present invention has a basis weight of 3 g / m 2 More than 100g / m 2 The basis weight of the pre-filter is preferably 3 g / m or less. 2 More than 5g / m 2 More preferably, 10 g / m 2By setting the amount to 100 g / m or more, the collection efficiency of the electrostatic fiber sheet can be improved. 2 or less, more preferably 70 g / m 2 or less, more preferably 50 g / m 2 By setting the thickness as follows, it is possible to alleviate the decrease in the air permeability when the filter is attached to the air filter.

[0026] The basis weight of the electrostatic fiber sheet used in the replaceable prefilter of the present invention is determined by taking five samples of 15 cm x 15 cm length x width from the sheet at random positions, measuring the mass of the samples, and calculating the mass of the samples as a function of the weight per unit area of ​​the sheet. 2 The arithmetic mean value of each sample (g / m 2 ) is rounded to the nearest tenth to obtain the basis weight (g / m 2 ) will be calculated.

[0027] The thickness of the replaceable prefilter of the present invention is preferably 0.05 mm or more, more preferably 0.08 mm or more, and even more preferably 0.12 mm or more, which increases the strength and prevents the electrostatic fiber sheet from tearing when the prefilter is installed in an air filter to form an air filter unit. The thickness is preferably 0.50 mm or less, more preferably 0.40 mm or less, and even more preferably 0.30 mm or less, which allows the replaceable prefilter to have excellent breathability.

[0028] The thickness (mm) of the replaceable prefilter of the present invention is calculated by measuring the thickness of the replaceable prefilter at 10 equally spaced points across the width using a thickness meter (for example, "TECLOCK" (registered trademark) SM-114 manufactured by Teclock Corporation) and rounding the average value to two decimal places.

[0029] The air filter of the present invention is a filter used in combination with the replaceable prefilter of the present invention. The air filter is configured by pleating a sheet-like filter material by repeatedly making mountain and valley folds and setting it in a frame. A known method can be used to obtain the filter material used in the air filter of the present invention. For example, an electret-processed meltblown nonwoven fabric can be bonded to an aggregate sheet to form a laminated sheet. The aggregate sheet is intended to capture relatively large dust particles and to be bonded to the electret meltblown nonwoven fabric to obtain the rigidity required for the filter material. Examples of the aggregate sheet that can be used include nonwoven fabrics, woven and knitted fabrics, etc. made of polyester fiber, polypropylene fiber, rayon fiber, glass fiber, natural pulp, etc.

[0030] In the air filter of the present invention, adjacent pleats may be connected by linear separators to maintain equal pleat pitches. In this case, it is preferable to use a hot melt resin for the separator.

[0031] The number of pleats of the air filter in the present invention is preferably 20 or more, more preferably 40 or more, and even more preferably 50 mm or more, which increases the contact area between the air filter and the replaceable pre-filter and contributes to improving the air filter's self-supporting ability. 2 The ratio of [ to ] is represented as the contact ratio Sn, and Sn is preferably 3.0 or more, more preferably 5.0 or more, and even more preferably 10.0 or more, which increases the contact area between the air filter and the replaceable prefilter, contributing to improved self-supporting properties. Sn=K / S [UN / cm 2 ] In the present invention, the independent installation of a replaceable prefilter refers to electrostatic adhesion, in which adhesion occurs due to the electrostatic force of the replaceable prefilter itself, which has an electrostatic fiber sheet, without the use of an intermediary such as an adhesive when installing the replaceable prefilter on the air filter.

[0032] The replaceable prefilter of the present invention preferably has at least one function selected from antibacterial, antiviral, and antifungal properties. The method for imparting a function to the replaceable prefilter is not particularly limited, and can be selected from a method in which a functional material is kneaded into a resin and then spun into fibers to form a sheet, or a method in which a functional agent is impregnated into a sheet.

[0033] The air filter unit of the present invention comprises the replaceable pre-filter of the present invention and an air filter.As a configuration, the replaceable pre-filter of the present invention is arranged on the air inflow side, and the air filter is arranged downstream.In particular, when the filter material used in the air filter is a bond between an electret nonwoven fabric and an aggregate sheet, by arranging the aggregate sheet on the upstream side and the electret nonwoven fabric on the downstream side, dust particles with large particle sizes can be collected in stages, and a thin filter material can be obtained, so that an air filter unit with a larger filter material use area can be obtained, which is preferable.

[0034] The replaceable prefilter of the present invention and the air filter unit having the same are suitable for use in the air filter field in general, and particularly suitable for use as a prefilter for air conditioner filters, air cleaner filters, and automobile cabin filters. [Example]

[0035] The present invention will be described in more detail below using examples, but the present invention is not necessarily limited to these. The measurement items in the examples were measured by the following methods.

[0036] (average fiber diameter) Twenty sample locations were randomly selected from a 1000mm x 1000mm surface of each layer, and 15 3mm x 3mm measurement samples were taken from three locations across the width of the fiber sheet (two side edges and one center location) and five locations 5cm apart in the longitudinal direction, for a total of 15 locations. A scanning electron microscope (Keyence Corporation, VHX-D500) was used to take a magnification of 3000x, and 15 photographs of the fiber surface were taken of each of the sampled measurement samples, for a total of 15. The fiber diameters of all fibers in the photographs where they could be clearly seen were then measured, and the arithmetic mean value of these measurements, rounded to one decimal place, was used as the average fiber diameter.

[0037] (Metsuke) Calculate the mass of the evaluation sample (nonwoven fabric, anti-static nonwoven fabric, or filter material) and calculate 1 m from its area. 2 The mass was converted to the mass per unit area and calculated as the basis weight of each evaluation sample. The minimum sampling area was 0.01 m 2 That's all.

[0038] (Collection efficiency, pressure loss) To measure the collection efficiency, NaCl solution is filled into the dust collection box 2. Next, the measurement sample M is set in the sample holder 1, and the air flow rate is adjusted with the flow rate control valve 4 so that the filter passing speed becomes 3.2 m / min. The dust concentration is set to 10,000 to 30,000 particles / 2.83 × 10 -4 m 3 (0.01ft 3 ), and the number of dust particles D upstream and d downstream of the measurement sample M were measured three times per measurement sample using a particle counter 6 (Rion Co., Ltd., KC-01D). The collection efficiency (%) of 0.3 μm anti-static NaCl particles was calculated using the following formula based on JIS K 0901 (1991) "Test methods for the shape, dimensions and performance of filter media for collecting dust samples in gas." The average value of the three measurement samples was taken as the final collection efficiency (Ia). Collection efficiency (%) = [1-(d / D)] x 100 (where d represents the total number of downstream dust particles measured three times, and D represents the total number of upstream dust particles measured three times).

[0039] The higher the collection efficiency of the nonwoven fabric, the fewer the downstream dust particles, and therefore the higher the collection efficiency. The pressure loss was determined by reading the static pressure difference between the upstream and downstream of measurement sample M during collection efficiency measurement using a pressure gauge 8. The average value of the five measurement samples was taken as the final pressure loss.

[0040] (Contact ratio Sn) The number of pleats K [UN] of the air filter and the opening area S [cm 2 The ratio of [to] was calculated using the following formula and expressed as the contact ratio Sn. Sn=K / S [UN / cm 2 ] (Independence) To check for self-standing ability, the frame material on the long side of the air filter was placed in contact with a desk, and a pre-filter with the same dimensions as the air filter's opening was placed in contact with the air inlet surface of the air filter, which was perpendicular to the desk.If the pre-filter did not fall off even when the air filter and pre-filter were left stationary without any intervening material such as adhesive, it was determined to be self-standing.

[0041] Example 1 Polyolefin resin fiber with an average fiber diameter of 0.1 μm and a basis weight of 20 g / m 2 The test used a replaceable prefilter made of electret meltblown nonwoven fabric with an initial collection efficiency of 99.97% and an initial pressure drop of 30.0 Pa, and a pleated air filter consisting of two layers of filter media: a chemical-bonded nonwoven fabric support layer and an electret meltblown dust collection layer. The frame material on the long side of this air filter was placed in contact with a desk, and a single replaceable prefilter with the same dimensions as the air filter's opening was placed in contact with the dust collection layer side of the air filter, which was perpendicular to the desk. The test results for the replaceable prefilter's independence from the air filter are shown in Table 1.

[0042] Example 2 Except for changing the contact surface of the replaceable prefilter to the support layer side of the air filter, an experiment was conducted in the same manner as in Example 1. The results of the experiment on the independence of this replaceable prefilter relative to the air filter are shown in Table 1.

[0043] Example 3 An experiment was conducted in the same manner as in Example 1, except that the average fiber diameter constituting the replaceable prefilter was changed to 6.5 μm, the initial collection efficiency was changed to 95.00%, and the initial pressure loss was changed to 15.0 Pa. The results of the experiment on the independence of this replaceable prefilter relative to the air filter are shown in Table 1.

[0044] Example 4 An experiment was conducted in the same manner as in Example 2, except that the average fiber diameter constituting the replaceable prefilter was changed to 6.5 μm, the initial collection efficiency to 95.00%, and the initial pressure loss to 15.0 Pa. The experimental results of the independence of this replaceable prefilter relative to the air filter are shown in Table 1.

[0045] Example 5 An experiment was conducted in the same manner as in Example 1, except that the average fiber diameter constituting the replaceable prefilter was changed to 50.0 μm, the initial collection efficiency to 20.00%, and the initial pressure loss to 5.0 Pa. The results of the experiment on the independence of this replaceable prefilter relative to the air filter are shown in Table 2.

[0046] Example 6 An experiment was conducted in the same manner as in Example 2, except that the average fiber diameter constituting the replaceable prefilter was changed to 50.0 μm, the initial collection efficiency to 20.00%, and the initial pressure loss to 5.0 Pa. The experimental results of the independence of this replaceable prefilter relative to the air filter are shown in Table 2.

[0047] Example 7 An experiment was conducted in the same manner as in Example 5, except that an antibacterial sheet made of polyolefin resin with 1% by mass of zinc oxide-based antibacterial agent mixed in was used for the replaceable prefilter. The results of the experiment on the independence of this replaceable prefilter relative to the air filter are shown in Table 2.

[0048] Example 8 An experiment was conducted in the same manner as in Example 6, except that an antibacterial sheet made of polyolefin resin with 1% by mass of zinc oxide-based antibacterial agent mixed in was used for the replaceable prefilter. The results of the experiment on the independence of this replaceable prefilter relative to the air filter are shown in Table 2.

[0049] (Comparative Example 1) Except for not applying electret processing to the meltblown nonwoven fabric constituting the prefilter, an experiment was carried out in the same manner as in Example 5. Table 3 shows the experimental results of the self-supporting ability of this prefilter relative to the air filter.

[0050] (Comparative Example 2) An experiment was carried out in the same manner as in Example 6, except that the melt-blown nonwoven fabric constituting the prefilter was not subjected to electret processing. The results of the experiment on the self-supporting ability of this prefilter relative to the air filter are shown in Table 3.

[0051] (Comparative Example 3) An experiment was carried out in the same manner as in Example 7, except that the melt-blown nonwoven fabric constituting the prefilter was not subjected to electret processing. The results of the experiment on the self-supporting ability of this prefilter relative to the air filter are shown in Table 3.

[0052] Comparative Example 4 An experiment was carried out in the same manner as in Example 8, except that the melt-blown nonwoven fabric constituting the prefilter was not subjected to electret processing. The results of the experiment on the self-supporting ability of this prefilter relative to the air filter are shown in Table 3.

[0053] (Comparative Example 5) Except for using a chemically bonded nonwoven fabric made of polyester fiber as the prefilter material, the experiment was carried out in the same manner as in Example 5. Table 3 shows the experimental results of the prefilter's self-supporting ability relative to the air filter.

[0054] (Comparative Example 6) The experiment was carried out in the same manner as in Example 6, except that the prefilter material was a chemically bonded nonwoven fabric made of polyester fiber. Table 3 shows the experimental results of the prefilter's ability to stand up to the air filter.

[0055] [Table 1]

[0056] [Table 2]

[0057] [Table 3]

[0058] As is clear from Tables 1 to 3, in Examples 1 to 6 of the present invention, by using electret melt-blown nonwoven fabric as a prefilter, the air filter has self-supporting properties due to electrostatic force on both the dust collection layer side and the support layer side, and the results show that the prefilter has self-supporting properties regardless of the initial collection efficiency, initial pressure loss, and average fiber diameter. In Examples 7 and 8, the prefilter having antibacterial properties has self-supporting properties.

[0059] On the other hand, in Comparative Examples 1 and 2, in which an electret-untreated melt-blown nonwoven fabric was used as a prefilter, self-supporting ability was not confirmed on either the dust collection layer side or the support layer side of the air filter. Similarly, in Comparative Examples 3 and 4, even when antibacterial and antiviral properties were imparted, when an electret-untreated melt-blown nonwoven fabric was used as a prefilter, self-supporting ability was not confirmed on either the dust collection layer side or the support layer side of the air filter.

[0060] Furthermore, in Comparative Examples 5 and 6 in which a chemically bonded nonwoven fabric made of polyester fiber was used as the prefilter, independence on either the dust collecting layer side or the support layer side of the air filter could not be confirmed.

[0061] As described above, the electret-processed melt-blown nonwoven fabric can be installed independently on an air filter, and a replaceable prefilter can be provided that does not impair breathability even when attached to an air filter. [Industrial Applicability]

[0062] The replaceable pre-filter and the air filter unit having the replaceable pre-filter of the present invention are mainly used as air filter materials and air filter units for normalizing the air in air filters of home air cleaners. [Explanation of symbols]

[0063] 1: Sample holder 2: Dust storage box 3:Flow meter 4: Flow control valve 5: Blower 6: Particle Counter 7: Switch cock 8: Pressure gauge 9: Static eliminator M: Measurement sample

Claims

1. A replaceable prefilter having an electrostatically charged fiber sheet, wherein the average fiber diameter of the constituent fibers of the electrostatically charged fiber sheet is 0.1 to 50 μm, and the replaceable prefilter can be installed independently on an air filter.

2. 2. The replaceable prefilter according to claim 1, which has at least one function selected from the group consisting of antibacterial, antiviral, and antifungal properties.

3. 3. An air filter unit comprising a replaceable pre-filter and an air filter according to claim 1.

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