Moisture-permeable film for total heat exchange element and total heat exchange element

Abstract

[Problem] To provide a moisture-permeable film for total heat exchange elements that exhibits an excellent adherence with microporous polyolefin films and has a high moisture permeability, gas barrier performance, and moisture resistance, with regard to a moisture-permeable film for total heat exchange elements, that is a partition plate for constructing total heat exchange elements for a total heat exchanger. [Solution] A moisture-permeable film for total heat exchange elements characterized by providing with a moisture-permeable resin layer on at least one side of a microporous polyolefin film that has an air permeation resistance of at least 100 sec and a moisture permeability of at least 750 g / m2·24 hr.

Description

[Technical Field]

[0001] The present invention relates to a total heat exchange element that simultaneously exchanges sensible heat (temperature) and latent heat (humidity), and to a total heat exchange element used as a partition plate for the total heat exchange element, which is installed in a total heat exchanger that supplies fresh outside air to the room and discharges polluted indoor air in order to maintain a comfortable space in buildings, offices, shops, residences, etc. [Background technology]

[0002] In indoor air conditioning, total heat exchange is a well-known ventilation method that offers excellent heating and cooling efficiency. It involves the simultaneous exchange of both temperature (sensible heat) and humidity (latent heat) between a supply airflow that provides fresh outside air and an exhaust airflow that expels stale indoor air.

[0003] Total heat exchange elements include direct-flow (DC) and counter-flow (OCR) total heat exchange elements, which are manufactured by processing total heat exchange paper or moisture-permeable film for total heat exchange elements to serve as partition plates. Both types of total heat exchange elements are manufactured using specialized machinery, and both consist of a laminate in which an air supply layer through which the air supply flow passes and an exhaust layer through which the exhaust flow passes are alternately stacked with moisture-permeable partition plates in between. Each flow path has a spacing plate to maintain the spacing between the partition plates, which are placed at predetermined intervals. Generally, for direct-flow (DC) total heat exchange elements, corrugated paper spacing plates are used, while for counter-flow (OCR) total heat exchange elements, resin frames manufactured by injection molding or similar methods are used. In the case of direct-flow (DC) total heat exchange elements, the direction in which the air supply flow is guided by the air supply flow path and the direction in which the exhaust flow is guided by the exhaust flow path are perpendicular to each other, while in the case of counter-flow (OCR) total heat exchange elements, they are opposite to each other.

[0004] Conventional heat exchange elements use porous materials for their partition plates, which allows for the passage of polluted gaseous components such as carbon dioxide. This has the drawback of mixing the supply and exhaust airflows within the heat exchange element during heat exchange, reducing ventilation efficiency. This mixing of supply and exhaust airflows is a fatal flaw for a heat exchanger. In a heat exchanger where supply and exhaust airflows mix, the exchanger may be perceived as merely stirring up polluted indoor air rather than recovering and exchanging indoor and outdoor air with energy. When indoor and outdoor air are mixed in this way, the purpose of ventilation cannot be achieved, and the heat exchanger becomes completely ineffective.

[0005] Furthermore, with the widespread adoption of total heat exchangers, they are now being installed in a variety of locations and environments. While there are no problems when the temperature and humidity differences between the supply and exhaust airflows are small, in environments with large temperature and humidity differences between the supply and exhaust airflows, such as cold regions where condensation is likely to occur due to low outside temperatures, or bathrooms with high indoor humidity, the partition plates may be exposed to high humidity conditions during total heat exchange. If these conditions persist, the partition plates may not be able to hold a large amount of moisture, and water may drip from the partition plates, a phenomenon known as "water dripping." If water dripping occurs, depending on the type of desiccant used, rust may form on the metal outer frame used as a reinforcing material. Moreover, if water dripping continues, the total heat exchange element may lose its shape, potentially rendering the total heat exchanger completely inoperable.

[0006] For these reasons, when fabricating a total heat exchange element, there is a need for a partition plate that is difficult for the supply airflow and exhaust airflow to mix (i.e., has excellent gas shielding properties), is less prone to water dripping, has excellent moisture resistance, and has high moisture permeability. In response to these demands, a composite membrane substrate (for example, Patent Document 1) made of a polyolefin microporous membrane has been disclosed for supporting a hydrophilic resin compound in the pores of the microporous membrane. However, with the technology of Patent Document 1, if the substrate is used as is, it does not have shielding properties and sufficient exchange efficiency cannot be obtained. If a hydrophilic resin compound is impregnated into it, some shielding properties can be obtained, but the moisture permeability becomes low and sufficient exchange efficiency cannot be obtained.

[0007] In addition, there is disclosed a film for a total heat exchange element (for example, Patent Document 2) including a synthetic resin film member having a large number of through-holes formed by pulling on both sides, and a hydrophilic polymer compound filled in the through-hole portions of the synthetic resin film member. However, in the technique of Patent Document 2, although shielding properties can be obtained, high moisture permeability cannot be obtained, and sufficient exchange efficiency cannot be achieved.

[0008] Also, there is disclosed a water-permeable and waterproof film (for example, Patent Document 3) made of a polyolefin microporous membrane containing polyethylene and defining water vapor transmission rate and water pressure resistance. However, in the technique of Patent Document 3, there is room for improvement to achieve both shielding properties and moisture permeability.

[0009] In addition, there is disclosed a total heat exchange element (for example, Patent Document 4) in which a partition plate includes a first layer and a third layer having waterproofness, gas permeability, and water-insolubility, and a second layer sandwiched between these layers contains an adhesive having gas permeability and water vapor permeability. However, in the technique of Patent Document 4, sufficient moisture permeability and moisture resistance cannot be obtained, and it is economically disadvantageous in actual production.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0011] An object of the present invention is to provide a moisture permeable film for a total heat exchange element, which is a partition plate for constituting a total heat exchange element for a total heat exchanger, has excellent adhesion to a polyolefin microporous membrane, and has high moisture permeability, gas barrier properties, and moisture resistance.

Means for Solving the Problems

[0012] The problems according to the present invention can be solved by the following means.

[0013] (1) A moisture permeable film for a total heat exchange element, comprising a polyolefin microporous membrane having an air permeability resistance of 100 sec or more and a moisture permeability of 750 g / m 2 ·24 hr or more, and a moisture permeable resin layer provided on at least one surface of the polyolefin microporous membrane. (2) The moisture permeable film for a total heat exchange element according to (1) above, wherein the moisture permeable resin layer contains a cellulose acetate resin having an acetylation degree of 60% or less and a polymerization degree of 165 or more and 185 or less. (3) The moisture permeable film for a total heat exchange element according to (1) above, wherein the moisture permeable resin layer contains a urethane resin. (4) A total heat exchange element containing the moisture permeable film for a total heat exchange element according to any one of (1) to (3) above.

Effects of the Invention

[0014] The moisture permeable film for a total heat exchange element of the present invention is characterized in that a moisture permeable resin layer is provided on at least one surface of a polyolefin microporous membrane having an air permeability resistance of 100 sec or more and a moisture permeability of 750 g / m 2 ·24 hr or more. According to the present invention, it is possible to provide a moisture permeable film for a total heat exchange element that has excellent adhesion to a polyolefin microporous membrane and has high moisture permeability, gas barrier properties, and moisture resistance.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, the moisture permeable film for a total heat exchange element and the total heat exchange element of the present invention will be described in detail.

[0016] In the present invention, the polyolefin microporous membrane is a microporous membrane composed of polyolefin. Here, a microporous membrane means a membrane having a large number of micropores inside, in which these micropores are connected, and which allows gas or liquid to pass from one side to the other. Examples of polyolefins include homopolymers or copolymers of polyethylene, polypropylene, polybutylene, polymethylpentene, etc., and mixtures of one or more of these. Among these, polyethylene or polypropylene is particularly preferred. In the polyolefin microporous membrane, it is preferable that the polyolefin is present in an amount of 90% by mass or more. In addition to polyolefin, the polyolefin microporous membrane may contain additives such as organic fillers, inorganic fillers, and surfactants, to the extent that they do not affect the effects of the present invention.

[0017] In the present invention, there are no particular limitations on the thickness of the polyolefin microporous membrane. The thickness is preferably 5 μm or more and 30 μm or less, and more preferably 10 μm or more and 20 μm or less. If the thickness is less than 5 μm, mechanical strength cannot be obtained, which may cause problems in actual processing. If the thickness is greater than 30 μm, the moisture permeability may decrease.

[0018] In the present invention, there are no particular restrictions on the porosity of the polyolefin microporous membrane. The porosity is preferably 30% to 70%, and more preferably 40% to 60%. If the porosity is lower than 30%, sufficient moisture permeability may not be obtained. If the porosity is higher than 70%, the mechanical strength may decrease.

[0019] In the present invention, there are no particular restrictions on the average pore size of the polyolefin microporous membrane. The average pore size is preferably 10 nm to 500 nm, and more preferably 50 nm to 200 nm. If the average pore size is smaller than 10 nm, sufficient moisture permeability may not be obtained. If the average pore size is larger than 500 nm, the mechanical strength may decrease.

[0020] In this invention, the air permeability resistance of the polyolefin microporous membrane is 100 sec or higher, and the moisture permeability is 750 g / m². 2 • It is 24 hours or longer.

[0021] The air permeability resistance of the polyolefin microporous membrane is 100 sec or more, more preferably 200 sec or more, and even more preferably 300 sec or more, as measured by the Wang-Ren test method according to JIS P 8117:2009. If the air permeability is less than 100 sec, sufficient adhesion with the moisture-permeable resin layer may not be obtained. Furthermore, from the viewpoint of the moisture permeability of the polyolefin microporous membrane itself, it is preferable that the air permeability of the polyolefin microporous membrane is 500 sec or less.

[0022] The moisture permeability of the polyolefin microporous membrane is 750 g / m². 2 • 24 hours or more, more preferably 800 g / m² 2 • 24 hours or more, more preferably 850 g / m² 2 • It is 24 hours or more. Moisture permeability is 750 g / m². 2 If the time interval is less than 24hr, sufficient moisture permeability as a moisture-permeable film may not be obtained. Within the range of air permeability described above, a higher moisture permeability of the polyolefin microporous membrane is preferable, and the higher the better. The moisture permeability of the polyolefin microporous membrane was measured by the method used in the moisture permeability evaluation of the moisture-permeable film for total heat exchange elements or the paper for total heat exchange elements in the examples described later.

[0023] In the present invention, the method for obtaining a polyolefin microporous membrane can be any known method and is not particularly limited. An example of a specific manufacturing method is shown below.

[0024] First, a raw material composition is obtained by stirring and mixing a predetermined amount of polyolefin resin and plasticizer, along with inorganic or organic fillers and various additives as needed, in a mixer. Next, this mixture (raw material composition) is fed into a twin-screw extruder equipped with a T-die at its tip, and extruded into a sheet while being heated, melted, and kneaded to obtain a film. Next, this film is immersed in a suitable extraction solvent to extract and remove the plasticizer and then dried. Finally, the dried film is stretched in at least one axial direction and molded into a film of a predetermined thickness to obtain a polyolefin microporous film in which countless interconnected pores with uniform, fine, and intricately interwoven pathways are formed throughout the film.

[0025] Examples of polyolefin resins include homopolymers, copolymers, or mixtures of polymers selected from the group including polyethylene, polypropylene, polybutylene, and polymethylpentene. Among these, homopolymers, copolymers, or mixtures of polymers selected from the group including polyethylene and polypropylene are particularly preferred. Furthermore, the polyolefin microporous membrane may consist of two or more layers, and the polyolefin resins in each layer may be the same or different.

[0026] As a plasticizer, it is preferable to select a material that can act as a plasticizer for polyolefin resins, and various organic liquids that are compatible with polyolefin resins and can be easily extracted with various solvents can be used. Specifically, mineral oils such as industrial lubricants made of saturated hydrocarbons (paraffins), higher alcohols such as stearyl alcohol, and ester-based plasticizers such as dioctyl phthalate can be used. Among these, mineral oil is preferred as a plasticizer because it is easy to reuse. The plasticizer is preferably blended into the raw material composition in a proportion of 30% by mass or more and 70% by mass or less.

[0027] As the solvent used to extract and remove the plasticizer, saturated hydrocarbon organic solvents such as hexane, heptane, octane, nonane, and decane can be used.

[0028] In addition, the polyolefin microporous membrane may contain, as needed, additives such as surfactants (hydrophilizers), antioxidants, ultraviolet absorbers, weather-resistant agents, lubricants, antibacterial agents, antifungal agents, pigments, dyes, colorants, antifogging agents, and matting agents, to the extent that they do not impair the purpose and effects of the present invention.

[0029] <Method for measuring porosity and average pore diameter> A polyolefin microporous membrane was cut using an ion mill (Hitachi High-Technologies Corporation, model number: IM4000PLUS) in cooling mode, and magnified imaging (50,000x) was performed using an FE-SEM (JEOL Ltd., model number: JSM-6700F). The magnified image was printed, and the unprinted areas (margins) were cut out to obtain the original image paper. The area of ​​the magnified cross-section of the obtained original image paper was calculated, and this area was defined as S0.

[0030] Next, the mass (M0) of the original image paper was measured using an electronic balance (AS ONE, model number: ITX-120). The portions corresponding to the perforations of the original image paper were cut out, and these cut-out papers were designated as perforated image papers. The mass of all perforated image papers was measured using the electronic balance, and the mass of each perforated image paper was designated as M1. From this, the porosity (%) was calculated using [Equation 1].

[0031] [Formula 1] TIFF0007881543000001.tif18150

[0032] Furthermore, the area (S1) of each opening was calculated using [Equation 2].

[0033] [Formula 2] TIFF0007881543000002.tif14150

[0034] The hole diameter (R1) of each opening was calculated using [Equation 3]. Using the calculated R1, the average hole diameter (R ave ) was sought.

[0035] [Formula 3] TIFF0007881543000003.tif17150

[0036] [Formula 4] TIFF0007881543000004.tif12150

[0037] As described above, in the present invention, the polyolefin microporous membrane is a microporous membrane composed of a polyolefin resin and can be used without particular limitation. It is also possible to adjust the thickness, air permeability, moisture permeability, porosity, average pore diameter, etc. of the polyolefin microporous membrane of the present invention. The method for controlling these physical properties is not particularly limited, but for example, the average molecular weight of the polyolefin resin, the concentration of the polyolefin resin in the raw material composition, the mixing ratio of the solvent, the stretching ratio, the heat treatment temperature after stretching, the immersion time in the extraction solvent, and other manufacturing conditions can be adjusted. Various types of polyolefin microporous membranes are already commercially available, and such commercial products can be used in the present invention. Examples of commercial products include the product name: SD220202 manufactured by Shenzhen Lingyan Technology Co., Ltd., SD216E, and the product name: SD21601+ manufactured by Shenzhen Senior Technology Material Co., Ltd.

[0038] The moisture-permeable resin layer is formed on at least one surface of the polyolefin microporous membrane. The moisture-permeable resin layer can also be formed on both surfaces, but from an economic perspective, it is preferably formed on only one of the surfaces. As the coating method of the moisture-permeable resin layer, any general coating method can be used without particular limitation as long as it can coat the polyolefin microporous membrane as uniformly as possible. By methods such as coating (bar coater, gravure coater, microgravure coater, blade coater, air knife, etc.), impregnation (size press, etc.) or spraying, the moisture-permeable resin layer is applied to the polyolefin microporous membrane, and the solvent is removed by methods such as drying to obtain a moisture-permeable film for the total heat exchange element.

[0039] The coating amount (based on the mass after drying) of the moisture-permeable resin layer is not particularly limited, but is 0.1 g / m 2 or more and 5 g / m2 The following range is preferred: 0.5 g / m 2 More than 2g / m 2 The following range is more preferable: the application amount is 0.1 g / m². 2 If the amount is less than 5 g / m², sufficient gas shielding may not be obtained. 2 If the amount is too high, sufficient breathability may not be achieved.

[0040] In the present invention, examples of resins used in the moisture-permeable resin layer include cellulose acetate and urethane resin.

[0041] In the present invention, cellulose acetate is preferably cellulose acetate having a degree of acetic acid of 60% or less and a degree of polymerization of 165 to 185.

[0042] Cellulose acetate is a semi-synthetic polymer obtained by esterifying (acetylating) cellulose, a natural polymer. Cellulose is a polymer with anhydrous glucose as a repeating unit, and each repeating unit has three hydroxyl groups. Different types of cellulose acetate with varying properties can be obtained depending on the degree of esterification (acetylation). This degree of esterification can be expressed by an index called the degree of acetic acidation. In the present invention, the degree of acetic acidation of the cellulose acetate used is preferably 60% or less. Cellulose acetate with a degree of acetic acidation greater than 60% may have low water permeability. Furthermore, cellulose acetate with a degree of acetic acidation greater than 60% also has reduced solubility, which may limit the use of solvents when forming the cellulose acetate resin layer, making it difficult to manufacture a water-permeable film.

[0043] The degree of polymerization of the cellulose acetate in this invention is preferably 165 to 185. If cellulose acetate with a degree of polymerization outside this range is used, the moisture permeability may be reduced. Furthermore, if cellulose acetate with a degree of polymerization outside this range is used, the solubility will also decrease, limiting the use of solvents when forming the cellulose acetate resin layer, which may make it difficult to manufacture a moisture-permeable film.

[0044] Cellulose acetate is already commercially available in various types, and such commercially available products can be used in the present invention. Examples of commercially available products include those manufactured by Daicel Corporation, such as L40 and L50.

[0045] Various types of urethane resins are already commercially available, and such commercially available products can be used in the present invention. Urethane resin is a general term for polymers having urethane bonds, and is usually a compound obtained by reacting a compound having an isocyanate group and a hydroxyl group. The urethane resin used in the present invention is preferably one with excellent moisture permeability, for example, product name: SANPLENE (registered trademark) H-600 manufactured by Sanyo Chemical Industries, Ltd.

[0046] There are no particular restrictions on the spacing plate used in the total heat exchange element of the present invention, and paper, film, nonwoven fabric, metal plate, etc., can be used. From the viewpoint of processability and moisture resistance, film is preferred as the spacing plate. There are no particular restrictions on the main components that make up the film, but polyester, polyamide, polyolefin, etc. are preferably used from the viewpoint of processability and cost. Examples of polyester include polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polylactic acid (PLA), polyethylene naphthalate (PEN), and liquid crystal polyester. Examples of polyamide include nylon 6 (N6), nylon 66 (N66), nylon 11 (N11), and nylon 12 (N12). Examples of polyolefin include polyethylene (PE) and polypropylene (PP). There are no particular restrictions on the basis weight of the film used as such a spacing plate, but 50 g / m² is preferred. 2 More than 100g / m 2 The following ranges are preferred. The thickness of the film is preferably in the range of 50 μm to 100 μm.

[0047] Total heat exchange elements include direct-flow (DC) and counter-flow (OCR) total heat exchange elements, which are manufactured by processing heat exchange paper or moisture-permeable film for heat exchange elements, which serve as partition plates. Both types of total heat exchange elements are manufactured using specialized machinery, and both consist of a laminate in which an air supply layer through which the air supply flow passes and an exhaust layer through which the exhaust flow passes are alternately stacked with moisture-permeable partition plates in between. Each flow path has a spacer plate formed to maintain the spacing between the partition plates, which are placed at predetermined intervals. Generally, for direct-flow (DC) total heat exchange elements, corrugated paper spacer plates are used, while for counter-flow (OCR) total heat exchange elements, resin frames manufactured by injection molding or similar methods are used. In the case of direct-flow (DC) total heat exchange elements, the direction in which the air supply flow is guided by the air supply flow path and the direction in which the exhaust flow is guided by the exhaust flow path are perpendicular to each other, while in the case of counter-flow (OCR) total heat exchange elements, they are opposite to each other.

[0048] There are no particular restrictions on the adhesive used when manufacturing the total heat exchange element of the present invention. Examples of such adhesives include polyvinyl alcohol-based adhesives, polyvinyl acetate-based adhesives, ether-based cellulose-based adhesives, acrylic resin-based adhesives, polyolefin-based adhesives, polyurethane-based adhesives, epoxy resin-based adhesives, styrene-butadiene rubber-based adhesives, and the like. There are no particular restrictions on the amount of adhesive applied (based on mass after drying), but 0.5 g / m² is recommended. 2 More than 4.0g / m 2 The following ranges are preferable. If the amount of adhesive used (applied) is too small, the adhesive strength may be weak. If the amount of adhesive used (applied) is too large, the adhesive strength can be ensured, but the moisture permeability may be impaired. The reference area of ​​the spacer plate for the amount of adhesive applied is the area of ​​the spacer plate used in the fabrication of the total heat exchange element before it was processed into a corrugated shape.

[0049] In the present invention, flame retardants, fungicides, etc., may be added to the partition plates, spacing plates, and adhesives as needed. There are no particular restrictions on the types of flame retardants and fungicides. [Examples]

[0050] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The films obtained in each example and comparative example are referred to as "moisture-permeable films for total heat exchange elements," however, some of the "moisture-permeable films for total heat exchange elements" obtained in the comparative example have insufficient moisture permeability. Furthermore, Examples 3-7 should be read as Reference Examples 3-7.

[0051] (Example 1) A coating solution was prepared by dissolving cellulose acetate (manufactured by Daicel Corporation, product name: L50), with a degree of acetate of 55% and a degree of polymerization of 180, in methyl ethyl ketone (MEK) to a concentration of 5% by mass. This coating solution was then applied to a commercially available polypropylene microporous film (thickness: 16 μm, porosity: 47%, average pore size: 142 nm, air permeability resistance (Wangyan): 165 sec, moisture permeability: 880 g / m²). 2 A predetermined amount was applied to one side (24hr) using a microgravure coater and then dried. As a result, the coating amount (based on the mass after drying) was 0.5 g / m². 2 A moisture-permeable film (partition plate) for a total heat exchange element was obtained, having a cellulose acetate resin layer on one side.

[0052] (Example 2) A moisture-permeable film for a total heat exchange element was obtained by following the same procedure as in Example 1, except that cellulose acetate with a degree of acetic acidity of 55% and a degree of polymerization of 170 (manufactured by Daicel Corporation, product name: L40) was used as the cellulose acetate.

[0053] (Example 3) A moisture-permeable film for a total heat exchange element was obtained by following the same procedure as in Example 1, except that a urethane resin manufactured by Sanyo Chemical Industries, Ltd. (product name: Sunprene H-600) was used instead of cellulose acetate.

[0054] (Comparative Example 1) As a microporous membrane, a commercially available polyethylene microporous membrane (thickness: 9 μm, air permeability resistance (Wangyan): 64 sec, moisture permeability: 972 g / m²) was used. 2 Except for using 24hr, the procedure was the same as in Example 1 to obtain a moisture-permeable film for the total heat exchange element.

[0055] (Comparative Example 2) As a microporous membrane, we used KTF34 manufactured by Mitsubishi Chemical Corporation (thickness: 34 μm, air permeability resistance (Wangyan): 1550 sec, moisture permeability: 593 g / m²). 2 Except for using 24hr, the procedure was the same as in Example 1 to obtain a moisture-permeable film for the total heat exchange element.

[0056] (Comparative Example 3) As a microporous membrane, we used YPBF37 manufactured by Yamato River Polymer Co., Ltd. (thickness: 37 μm, air permeability resistance (Wangyan): 2231 sec, moisture permeability: 512 g / m²). 2 Except for using 24hr, the procedure was the same as in Example 1 to obtain a moisture-permeable film for the total heat exchange element.

[0057] (Comparative Example 4) A moisture-permeable film for a total heat exchange element was obtained in the same manner as in Example 1, except that a methacrylic acid ester polymer resin (non-permeable resin, trade name: HI-PEAL, registered trademark) MA4620 manufactured by Negami Kogyo Co., Ltd. was used instead of cellulose acetate.

[0058] (Comparative Example 5) A moisture-permeable film for a total heat exchange element was obtained by following the same procedure as in Example 1, except that polyamide resin (non-permeable resin, trade name: TOHMIDE (registered trademark) 1320) manufactured by T&KTOKA Corporation was used instead of cellulose acetate.

[0059] (Example 4) A moisture-permeable film for a total heat exchange element was obtained by following the same procedure as in Example 1, except that cellulose acetate with a degree of acetate of 61% and a degree of polymerization of 270 (manufactured by Daicel Corporation, product name: LT35) was used as the cellulose acetate and dissolved in methylene chloride.

[0060] (Example 5) A moisture-permeable film for a total heat exchange element was obtained by following the same procedure as in Example 1, except that cellulose acetate with a degree of acetic acidity of 55% and a degree of polymerization of 160 (manufactured by Daicel Corporation, product name: L30) was used as the cellulose acetate and dissolved in acetone.

[0061] (Example 6) A moisture-permeable film for a total heat exchange element was obtained by following the same procedure as in Example 1, except that cellulose acetate with a degree of acetic acidity of 55% and a degree of polymerization of 150 (manufactured by Daicel Corporation, trade name: L20) was used as the cellulose acetate and dissolved in acetone.

[0062] (Example 7) A moisture-permeable film for a total heat exchange element was obtained in the same manner as in Example 1, except that cellulose acetate with a degree of acetic acidization of 55% and a degree of polymerization of 190 (manufactured by Daicel Corporation, trade name: L70) was used as the cellulose acetate.

[0063] (Comparative Example 6) Base paper (weight: 30g / m²) 2 A total heat exchange element paper was obtained by impregnating a 40 μm thick, air permeability resistance (Wangyan): 2.77 million sec with 4.8 g / m2 of lithium chloride using a nip coater at a speed of 60 m / min and a nip pressure of 343 kPa.

[0064] The moisture-permeable films or heat exchange element papers for total heat exchange elements used in Examples 1-7 and Comparative Examples 1-6 were evaluated using the methods described below, and the evaluation results are shown in Table 1.

[0065] [Moisture permeability: Method for evaluating moisture permeability] The moisture permeability was measured in accordance with JIS Z 0208:1976 "Test method for moisture permeability of moisture-proof packaging materials (cup method)". However, the temperature and humidity conditions were changed to 23°C and relative humidity 50%, 10g of calcium chloride was used, and the measurement time was changed to 1 hour. The mass change obtained from the measurement under these conditions was converted to the mass change over 24 hours. The evaluation criteria are as follows:

[0066] ◎: Moisture permeability is 850g / m 2 • Greater than 24 hours. Excellent. ○: Moisture permeability is 800g / m 2 ·24hr or more, 850g / m 2 Less than 24 hours. Good. △: Moisture permeability is 750g / m 2 ·24hr or more, 800g / m 2 Less than 24 hours. Within acceptable limits. ×: Moisture permeability is 750g / m 2 Less than 24 hours. Outside the acceptable range.

[0067] [Gas Barrier: Evaluation Method of Air Permeability Resistance (Wang Research Institute)] The air permeability resistance (Wangyan) was measured in accordance with JIS P 8117:2009. The evaluation criteria are as follows:

[0068] ◎: Air permeability resistance (Wang Research) is 1.0 × 10 6 sec or longer. Excellent. ○: Air permeability resistance (Wang Research) is 1.0 × 10 5 sec or more, 1.0×10 6 Less than sec. Good. △: Air permeability resistance (Wang Research) is 1.0 × 10 4 sec or more, 1.0×10 5 Less than sec. Within acceptable limits. ×: Air permeability resistance (Wang Research) is 1.0 × 10 4 Less than sec. Outside the acceptable range.

[0069] [Moisture resistance: Method for evaluating moisture resistance] A total heat exchange element with dimensions of 200 mm (length) x 200 mm (width) x 250 mm (height), and a height of 3 mm per layer, was fabricated using a moisture-permeable film for total heat exchange elements and total heat exchange element paper. The spacing plate used at this time was 60 g / m². 2 A polypropylene film was used. A polyvinyl acetate-based adhesive was used as the adhesive. This total heat exchange element was left for 72 hours under conditions of 40°C and 95% relative humidity, and the presence or absence of water dripping and changes in the shape of the total heat exchange element were visually evaluated. The evaluation criteria were as follows:

[0070] ◎: No water dripping or deformation whatsoever. Excellent condition. ○: Minimal water dripping or shape change. Good. △: There is some water dripping or slight deformation. It is within acceptable limits. ×: Water dripping or deformation occurs. Outside acceptable limits.

[0071] [Adhesion: Methods for evaluating adhesion] The degree of peeling of the resin layer was evaluated by pressing the adhesive side of cellophane tape against the resin layer coated surface of a moisture-permeable film for a total heat exchange element. Regardless of the dispersibility of the coating solution, after coating and drying, a 1.8 cm wide x 5 cm long piece of cellophane tape was lightly adhered to the moisture-permeable film for the total heat exchange element and slowly removed. The adhesive surface of the cellophane tape was used as the observation surface, and its adhesion was evaluated visually as follows.

[0072] ◎: No residue is visible on the adhesive surface of the cellophane tape. Excellent condition. ○: Some residue is visible on the adhesive surface of the cellophane tape. Good. △: A resin layer is attached to a portion of the adhesive surface of the cellophane tape. This is within acceptable limits. ×: A resin layer is attached to the entire adhesive surface of the cellophane tape. This is outside the acceptable range.

[0073] [Table 1]

[0074] From a comparison between Example 1 and Comparative Examples 1-3, it was found that the air permeability resistance was 100 sec or higher and the moisture permeability was 750 g / m². 2It can be seen that a moisture-permeable film for a total heat exchange element using a polyolefin microporous membrane with a 24hr or longer lifespan exhibits good adhesion to the polyolefin microporous membrane and is a moisture-permeable film for a total heat exchange element with high moisture permeability, gas shielding, and moisture resistance. From a comparison of Examples 1-7 with Comparative Examples 4 and 5, it can be seen that a moisture-permeable film for a total heat exchange element having a polyolefin microporous membrane and a moisture-permeable resin layer (more preferably a cellulose acetate resin layer and a urethane resin layer with a degree of acetation of 60% or less and a degree of polymerization of 165 to 185) provided on at least one surface of the polyolefin microporous membrane is a moisture-permeable film for a total heat exchange element with high moisture permeability, gas shielding, and moisture resistance. The moisture-permeable film using cellulose acetate with a degree of acetation of 61% in Example 4 had no performance issues, but the cellulose acetate could not be dissolved in MEK and instead dissolved in methylene chloride, which added some burden to the manufacturing process. A comparison of Examples 1-7 and Comparative Example 6 shows that the moisture-permeable film for total heat exchange elements of the present invention has better moisture resistance compared to paper-based total heat exchange element paper. [Industrial applicability]

[0075] The moisture-permeable film for total heat exchange elements of the present invention is used in the total heat exchange element of a total heat exchanger that exchanges humidity (latent heat) along with temperature (sensible heat) when supplying fresh air and discharging polluted indoor air.

Claims

1. The air permeability resistance measured by the Wang Ren test method in accordance with JIS P 8117:2009 is 100 sec or more, and the moisture permeability, converted to a change in mass over 24 hours, is 750 g / m², measured in accordance with JIS Z 0208:1976, with temperature and humidity conditions of 23°C and relative humidity of 50%, using 10 g of calcium chloride, and with the measurement time changed to 1 hour. ２ A moisture-permeable film for a total heat exchange element, comprising a polyolefin microporous membrane with a curing time of 24 hours or more, and a moisture-permeable resin layer provided on at least one surface of the polyolefin microporous membrane, wherein the moisture-permeable resin layer contains a cellulose acetate resin having a degree of acetic acid of 60% or less and a degree of polymerization of 165 to 185.

2. The moisture-permeable film for a total heat exchange element according to Claim 1, wherein the air permeability resistance of the moisture-permeable film for a total heat exchange element measured by the Wang-Ren test method in accordance with JIS P 8117:2009 is 1.0 × 10⁶ sec or more.

3. A total heat exchange element containing a moisture-permeable film for a total heat exchange element as described in claim 1 or claim 2.

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