Gas barrier sheet and total heat exchange element

Abstract

To provide a gas barrier sheet excellent in both gas barrier property and moisture permeability even if a partition member is made thin.SOLUTION: A gas barrier sheet includes a coated layer containing at least one polymer selected from water-soluble polymers and water-dispersible polymers on at least one surface of a hydrophobic porous substrate. The moisture permeability of the coated layer can be controlled by selecting a water-soluble polymer and a water-dispersible polymer. A gas barrier sheet having a high moisture permeability can be used as a partition member for a total heat exchange element.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a gas barrier sheet and a total heat exchange element. [Background technology]

[0002] Conventionally, heat exchange ventilation devices (total heat exchangers) that exchange heat between intake air and exhaust air during ventilation have been proposed as devices that can ventilate without impairing the effectiveness of cooling or heating. These total heat exchangers are widely used, in which multiple partition members (liners) are stacked with spacing members to separate an intake air path that introduces outdoor air into the room and an exhaust air path that exhausts indoor air to the outside, and a total heat exchange element is incorporated to exchange sensible heat (temperature) and latent heat (humidity) at the same time.

[0003] For example, in winter, outdoor air as supply air and indoor air as exhaust air are guided into each flow path separated by a spacing member. At this time, the supply air and exhaust air exchange temperature and humidity through the partition member. The partition member through which heat exchange occurs has moisture permeability, allowing water vapor to pass through but not air. The partition member also has gas barrier properties by isolating the supply air from the exhaust air. As a result, the supply air is heated and humidified before being supplied indoors, and the exhaust air is cooled and dehumidified before being discharged outdoors. The partition member has both moisture permeability and gas barrier properties, thereby achieving ventilation through total heat exchange. Such partition members must have both heat conductivity and moisture permeability, and therefore in many cases, paper containing natural pulp as a main component, such as glassine paper, is used (Patent Document 1).

[0004] Furthermore, in recent years, attempts have been made to apply cellulose nanofibers, which have gas barrier properties, to partition members (Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4252892 [Patent Document 2] Patent Publication No. 2021-155865 Summary of the Invention [Problem to be solved by the invention]

[0006] In the face of growing demands for global warming and energy conservation, total heat exchange elements are attracting attention. In order to further improve the heat exchange efficiency of total heat exchange elements, it is believed that it would be effective to make the partition members thinner than ever before and to increase the number of stacked layers of the total heat exchange element. However, this has been difficult to achieve with the partition members described in Patent Documents 1 and 2.

[0007] Furthermore, if the thickness of the partition member is reduced, it becomes difficult to achieve both gas barrier properties and moisture permeability. Therefore, an object of the present invention is to provide a partition member for a total heat exchange element that achieves both excellent gas barrier properties and moisture permeability even when the thickness of the partition member is reduced. [Means for solving the problem]

[0008] Examples of specific embodiments of the present invention are given below. <1> A gas barrier sheet having a coating layer containing at least one polymer selected from water-soluble polymers and water-dispersible polymers on at least one surface of a hydrophobic porous substrate. <2> The hydrophobic porous substrate has an Oken air permeability of 1000 seconds or less. <1> The gas barrier sheet according to claim 1. <3> The thickness of the hydrophobic porous substrate is 5 μm or more and 30 μm or less. <1> or <2> The gas barrier sheet according to claim 1. <4> The coating layer contains fine fibers of polymeric polysaccharides having a fiber width of 1 to 1000 nm. <1> ~ <3> The gas barrier sheet according to any one of the above. <5> The fine fibers are chemically modified fine cellulose fibers. <4> The gas barrier sheet according to claim 1. <6> The coating weight of the coating layer is 0.03 g / m 2 More than 3g / m 2is <1> ~ <5> The gas barrier sheet according to any one of the above. <7> The gas barrier sheet has an Oken air permeability of 10,000 seconds or more. <1> ~ <6> 1. The gas barrier sheet according to any one of claims 1 to 9. <8> The gas barrier sheet has a moisture permeability of 2500 g / m at a temperature of 20°C and a relative humidity of 65%. 2 24 hours or more <1> ~ <7> 1. The gas barrier sheet according to any one of claims 1 to 9. <9> The gas barrier sheet is for use as a partition member for a total heat exchange element. <1> ~ <8> 1. The gas barrier sheet according to any one of claims 1 to 9.

[0009] <10> <1> ~ <9> a gas barrier sheet according to any one of the preceding items as a partition member for a total heat exchange element; a spacing member disposed between the total heat exchange element partition members to maintain a spacing between the adjacent total heat exchange element partition members; A total heat exchange element in which first air flow paths and second air flow paths are alternately formed with the total heat exchange element partition member interposed therebetween. <11> The gas barrier sheet has an Oken air permeability of 10,000 seconds or more. <10> The total heat exchange element according to claim 1. <12> The gas barrier sheet has a moisture permeability of 2500 g / m at a temperature of 20°C and a relative humidity of 65%. 2 24 hours or more <10> The total heat exchange element according to claim 1. [Effects of the Invention]

[0010] According to the present invention, a gas barrier sheet having both excellent gas barrier properties and moisture permeability is provided, and the gas barrier sheet is useful as a partition member for a total heat exchange element. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram illustrating the structure of a total heat exchange element. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Gas barrier sheet] The gas barrier sheet of the present invention is a gas barrier sheet comprising a coating layer provided on at least one surface of a hydrophobic porous substrate. The Oken air permeability of the gas barrier sheet is 10,000 seconds or more, preferably 50,000 seconds or more, more preferably 80,000 seconds or more, and particularly preferably 99,999 seconds or more. The air permeability of the gas barrier sheet is preferably 150,000 seconds or less. As described above, the gas barrier sheet of the present invention has excellent gas barrier properties, and since a porous substrate is used as the substrate, the coating layer provides excellent moisture permeability. Below, a partition member for a total heat exchange element, which is an expected application of the gas barrier sheet of the present invention, will be described as a representative example, but the present invention is not limited to applications such as a partition member for a total heat exchange element.

[0013] The gas barrier sheet of the present invention is a gas barrier sheet characterized by having a coating layer containing at least one polymer selected from water-soluble polymers and water-dispersible polymers on at least one surface of a hydrophobic porous substrate.

[0014] The Oken air permeability of a gas barrier sheet is a value measured at 20°C and a relative humidity of 65% in accordance with the Oken air permeability method of JAPAN TAPPI Paper and Pulp Testing Method No. 5-2:2000. The higher the Oken air permeability value of a gas barrier sheet, the better the gas barrier properties of the gas barrier sheet can be determined to be.

[0015] The gas barrier sheet of the present invention preferably has an Oken air permeability of 10,000 seconds or more at 20°C and a relative humidity of 65% after undergoing the water immersion test described below, more preferably 20,000 seconds or more, even more preferably 30,000 seconds or more, even more preferably 50,000 seconds or more, and particularly preferably 80,000 seconds or more. Furthermore, the gas barrier sheet preferably has an Oken air permeability of 150,000 seconds or less at 20°C and a relative humidity of 65% after undergoing the water immersion test described below. The Oken air permeability after the water immersion test is a value measured at 20°C and a relative humidity of 65% in accordance with the Oken air permeability method of JAPAN TAPPI Paper and Pulp Testing Method No. 5-2:2000. The Oken air permeability of the gas barrier sheet after the water immersion test can be controlled, for example, by appropriately adjusting the composition and physical properties of the coating layer.

[0016] "Water immersion test" A sample prepared by cutting a gas barrier sheet into A4 size is immersed in 30 liters of tap water, and after 10 minutes, the sample is taken out and air-dried at room temperature until no water droplets remain on the film surface.

[0017] Gas barrier sheets may be exposed to water due to condensation or the like. If the above physical properties are satisfied, the sheet can maintain its function as a partition member for a total heat exchange element even when exposed to water. In this way, the present invention can provide a partition member for a total heat exchange element that is excellent in water resistance. A partition member for a total heat exchange element that is excellent in water resistance can be obtained, for example, by providing a coating layer as described below.

[0018] The gas barrier sheet has a moisture permeability of 2500g / m at a temperature of 20℃ and a relative humidity of 65%. 2 24 hours or more is preferable, 2800 g / m 2 24 hours or more is more preferable, and 3000g / m 2 The gas barrier sheet has a moisture permeability of 3800 g / m at a temperature of 20°C and a relative humidity of 65%. 2Preferably, it is 24 hours or less. The moisture permeability of the gas barrier sheet can be controlled, for example, by appropriately adjusting the composition and physical properties of the coating layer. The moisture permeability of the gas barrier sheet is measured in accordance with JIS Z 0208:1976. A higher moisture permeability value indicates better heat exchange efficiency.

[0019] The basis weight of the gas barrier sheet is 5 g / m 2 It is preferable that the content is 6 g / m or more. 2 More preferably, it is 7 g / m or more. 2 The basis weight of the gas barrier sheet is more preferably 30 g / m or more. 2 Preferably, it is 25 g / m or less. 2 The basis weight of the gas barrier sheet is preferably 1 / 3 m or less. 2 The basis weight is the mass per unit area, and is measured in accordance with JIS P 8124:2011. The basis weight of the gas barrier sheet can be controlled, for example, by using a low-basis-weight hydrophobic porous substrate and a low-coating-weight coating layer.

[0020] The gas barrier sheet of the present invention is lightweight and has a thin basis weight, yet exhibits both excellent gas barrier properties and moisture permeability. Such a gas barrier sheet can be used as a partition member with excellent heat exchange efficiency.

[0021] "Hydrophobic porous substrate" The hydrophobic porous substrate is not particularly limited, but a thickness of 5 μm to 30 μm is preferred, and a thickness of 10 μm to 25 μm is even more preferred. By setting the thickness at or above the lower limit, the strength as a partition member is maintained, while by setting the thickness at or below the upper limit, the heat exchange efficiency of sensible heat (temperature) is improved and weight reduction is possible. The thickness is measured in accordance with JIS P 8118:2014.

[0022] The surface density of the hydrophobic porous substrate is 29 g / m 2 It is preferable that the content is 25 g / m or less, and more preferably 25 g / m 2 More preferably, it is 20 g / m or less. 2The lower limit is not particularly limited, and is 2 g / m or less. 2 It is preferable that the content is at least 5 g / m 2 The areal density of the hydrophobic porous substrate can be calculated by dividing the weight of a film cut to a predetermined area by that area.

[0023] The hydrophobic porous substrate needs to be hydrophobic. By making the substrate hydrophobic, it is possible to reduce the weight. For example, by making the substrate hydrophobic, it is not necessary to apply a large amount of fine fibers of polymeric polysaccharides to improve gas barrier properties, and as a result, it is easy to reduce the weight.

[0024] Furthermore, since the hydrophobic porous substrate is porous with an Oken air permeability of 1000 seconds or less, it allows for heat exchange of latent heat (humidity). The Oken air permeability of the hydrophobic porous substrate is preferably 1000 seconds or less, more preferably 500 seconds or less. There is no particular restriction on the lower limit of the Oken air permeability of the hydrophobic porous substrate, but it is preferably 10 seconds or more, more preferably 30 seconds or more, and even more preferably 50 seconds or more.

[0025] The hydrophobic porous substrate may be, for example, a film or nonwoven fabric made of a thermoplastic resin such as polyolefin or polyester, with an Oken air permeability of 1000 seconds or less, preferably 500 seconds or less. The Oken air permeability is a value measured in accordance with the Oken air permeability method of JAPAN TAPPI Paper and Pulp Testing Method No. 5-2:2000.

[0026] "Coating layer" In order to enhance gas barrier properties, the gas barrier sheet of the present invention has a coating layer containing at least one polymer selected from water-soluble polymers and water-dispersible polymers provided at least in the pore areas of the hydrophobic porous substrate. The gas barrier sheet thus obtained has an Oken air permeability of 10,000 seconds or more, preferably 50,000 seconds or more, more preferably 80,000 seconds or more, and even more preferably 99,999 seconds or more.

[0027] Furthermore, when the gas barrier sheet of the present invention is used as a partition member for a total heat exchange element, the moisture permeability at a temperature of 20°C and a relative humidity of 65% is 2500 g / m 2 The moisture permeability is measured in accordance with JIS Z 0208:1976. A higher moisture permeability value indicates better heat exchange efficiency. The preferred moisture permeability is 2800 g / m 2 24 hours or more, the preferred moisture permeability is 3000g / m 2 24 hours or more. The preferred moisture permeability is 3800 g / m 2 - Less than 24 hours.

[0028] In the present invention, a coating layer containing at least one polymer selected from water-soluble polymers and water-dispersible polymers is provided on at least one surface of a hydrophobic porous substrate so as to satisfy the above physical properties. The amount of the coating layer applied to the hydrophobic porous substrate is not particularly limited, but it is preferably 0.03 g / m. 2 More than 3g / m 2 It is preferable that the content is 0.03 g / m or less, and more preferably 0.03 g / m 2 More than 2g / m 2 By coating, the pores of the substrate can be blocked with a hydrophilic material, and as a result, the decrease in moisture permeability can be suppressed. Note that as the coating amount increases, the gas barrier property improves, but moisture permeability tends to decrease. 2 On the other hand, if the coating amount is too small, the pores will not be sufficiently covered and sufficient gas barrier properties will not be obtained. 2 It is preferable that this is equal to or greater than this.

[0029] "Water-soluble polymer or water-dispersible polymer (binder)" The coating layer contains at least one polymer (binder) selected from water-soluble and water-dispersible polymers. Water-soluble or water-dispersible polymers can be prepared as aqueous coating solutions. Coating layers formed from such solutions have excellent film-forming properties, resulting in enhanced gas barrier properties. Examples of water-soluble polymers include cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxymethyl cellulose (excluding microfine cellulose fibers, as described below); etherified starches such as oxidized starch, cationic starch, urea phosphate esterified starch, and hydroxyethyl etherified starch; starches such as dextrin; proteins such as casein, soy protein, and synthetic protein; polyvinyl alcohols; and polyacrylamides. Examples of water-dispersible polymers include copolymers such as styrene-butadiene copolymers, styrene-acrylic copolymers, ethylene-vinyl acetate copolymers, butadiene-methyl methacrylate copolymers, vinyl acetate-butyl acrylate copolymers, maleic anhydride copolymers, and acrylic acid-methyl methacrylate copolymers. These can be used alone or in combination as needed. Among these, water-soluble polymers are preferred due to their excellent film-forming properties. That is, the coating layer preferably contains a water-soluble polymer as a binder, more preferably a cellulose derivative, even more preferably at least one selected from the group consisting of carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxymethyl cellulose, or at least one selected from their salts, even more preferably at least one selected from carboxymethyl cellulose and its salts, and particularly preferably an ammonium salt of carboxymethyl cellulose. Cellulose derivatives have a structure similar to the fine fibers of polymeric polysaccharides, and after film formation, the coating layer exhibits excellent moisture permeability. Furthermore, a coating layer using at least one selected from carboxymethyl cellulose and its salts is preferred because it can achieve excellent gas barrier properties and high moisture permeability. Note that binders other than cellulose derivatives may be used in combination as long as they do not impair the effects of the present invention.

[0030] "Microfibers of polymeric polysaccharides" The coating layer preferably contains polymeric polysaccharide fine fibers in addition to a water-soluble or water-dispersible polymer. By applying a coating containing polymeric polysaccharide fine fibers to a hydrophobic porous substrate, both higher gas barrier properties and higher moisture permeability can be achieved. Examples include polymeric polysaccharides such as cellulose, chitin, and chitosan. Polymeric polysaccharides have a molecular structure with many hydroxyl groups (-OH), which allows them to absorb moisture, and the coating film they form has gas barrier properties. The coating layer preferably contains polymeric polysaccharide fine fibers with a fiber width of 1 to 1,000 nm. From the perspective of gas barrier properties, a fiber width of 1 to 500 nm is preferred, a fiber width of 1 to 100 nm is more preferred, and a fiber width of 1 to 30 nm is particularly preferred. In particular, the polymeric polysaccharide fine fibers are preferably fine cellulose fibers, which are preferred because they form a dense structure when coated and dried, resulting in excellent gas barrier properties.

[0031] As the fine cellulose fibers, it is preferable to use fine cellulose fibers having a fiber width of 1 to 1,000 nm. Among these, from the viewpoint of gas barrier properties, a fiber width of 1 to 500 nm is preferred, a fiber width of 1 to 100 nm is more preferred, a fiber width of 1 to 30 nm is even more preferred, and a fiber width of 1 to 10 nm is particularly preferred. By making the fiber width of the fine cellulose fibers 1 nm or more, dissolution of the cellulose molecules in water is suppressed, and the effect of improving the air permeability and moisture permeability of the fine cellulose fibers is easily achieved. Furthermore, by making the fiber width of the fine cellulose fibers equal to or less than the above upper limit, the gas barrier properties and moisture permeability can be further improved.

[0032] The fiber width of the fine cellulose fibers is measured using an electron microscope as follows. First, an aqueous suspension of fine cellulose fibers with a concentration of 0.05% by mass to 0.1% by mass is prepared, and this suspension is cast onto a hydrophilized carbon film-coated grid to prepare a sample for TEM observation. If the sample contains wide fibers, it may be cast onto a glass plate and the surface may be observed by SEM. Next, the image is observed using an electron microscope at a magnification of 1,000x, 5,000x, 10,000x, or 50,000x depending on the width of the fiber to be observed. However, the sample, observation conditions, and magnification should be adjusted to meet the following conditions. (1) Draw a line X at any point in the observed image, and 20 or more fibers intersect with the line X. (2) Draw a line Y that intersects the line perpendicularly within the same image, and 20 or more fibers intersect the line Y. For observation images that satisfy the above conditions, the widths of the fibers intersecting with lines X and Y are visually read. In this way, three or more sets of observation images of at least the surface portions that do not overlap each other are obtained. Next, for each image, the widths of the fibers intersecting with lines X and Y are read. In this way, the fiber widths of at least 20 fibers x 2 x 3 = 120 fibers are read. The average fiber width is the average value of the fiber widths of the read fine cellulose fibers.

[0033] The fiber length of the fine cellulose fibers is not particularly limited, but is preferably 0.1 μm or more, and preferably 1,000 μm or less, more preferably 800 μm or less, and even more preferably 600 μm or less. By setting the fiber length of the fine cellulose fibers within the above range, destruction of the crystalline regions of the fine cellulose fibers can be suppressed. In addition, it is possible to set the slurry viscosity of the fine cellulose fibers within an appropriate range, making it easier to form a fiber layer. The fiber length of the fine cellulose fibers can be determined by image analysis using, for example, TEM, SEM, or AFM.

[0034] The axial ratio (fiber length / fiber width) of the fine cellulose fibers is not particularly limited, but is preferably at least 20, more preferably at least 50, and is preferably at most 10,000, more preferably at most 1,000. By setting the axial ratio within the above range, a slurry viscosity suitable for forming a fiber layer can be obtained.

[0035] In the present invention, the fine cellulose fibers are preferably chemically modified fine cellulose fibers. Specifically, it is preferable that at least one type of group selected from ionic groups and nonionic groups is introduced into the fine cellulose fibers. Furthermore, it is preferable that the ionic groups and nonionic groups are hydrophilic groups. From the viewpoint of improving the dispersibility of the fibers in the dispersion medium and increasing the defibration efficiency in the defibration treatment, it is more preferable that the fine cellulose fibers have ionic groups. The ionic groups may include either or both of anionic groups and cationic groups. In the present invention, it is particularly preferable that the ionic groups include anionic groups. The anionic group is preferably at least one selected from a phosphate group, a group derived from a phosphate group, a phosphite group, a group derived from a phosphite group, a carboxy group, a group derived from a carboxy group, a sulfonic acid group, and a group derived from a sulfonic acid group.

[0036] The coating layer of the gas barrier sheet of the present invention preferably contains a water-soluble or water-dispersible polymer and fine fibers of a polymeric polysaccharide having a fiber width of 1 to 1,000 nm. In the coating layer, the water-soluble or water-dispersible polymer acts as a binder, resulting in improved adhesion to a hydrophobic porous substrate compared to a coating layer formed using fine fibers of a polymeric polysaccharide alone. Furthermore, when a cellulose derivative is used as the water-soluble or water-dispersible polymer, the cellulose derivative has a structure similar to that of fine fibers of a polymeric polysaccharide, resulting in a coating layer with excellent moisture permeability after film formation. Furthermore, a coating layer using at least one selected from carboxymethyl cellulose and its salts can achieve both excellent gas barrier properties and high moisture permeability.

[0037] When polymeric polysaccharide fine fibers having a fiber width of 1 to 1000 nm are used in combination with a binder, the blending ratio of the two is not particularly limited, but is preferably 50 to 200 parts by mass, preferably 60 to 180 parts by mass, and more preferably 70 to 160 parts by mass of the binder solid content per 100 parts by mass of the polymeric polysaccharide fine fibers having a fiber width of 1 to 1000 nm.More preferably, the cellulose derivative solid content is 50 to 200 parts by mass, preferably 60 to 180 parts by mass, and more preferably 70 to 160 parts by mass per 100 parts by mass of the polymeric polysaccharide fine fibers having a fiber width of 1 to 1000 nm.

[0038] The gas barrier sheet of the present invention has high air permeability and is therefore suitable for a variety of uses as a gas barrier sheet. Furthermore, gas barrier sheets that have high not only air permeability but also moisture permeability are suitable for use as partition members for total heat exchange elements. Furthermore, because a hydrophobic porous substrate is used, mechanical strength is less likely to decrease even if condensation occurs. Furthermore, because the sheet is lightweight, it is possible to increase the number of stacked layers in a total heat exchange element.

[0039] [Method of manufacturing gas barrier sheet] The present invention relates to a method for producing a gas barrier sheet, which comprises applying a coating liquid containing at least a water-soluble polymer or a water-dispersible polymer (binder) to at least one surface of a hydrophobic porous substrate, followed by drying. The present invention also relates to a method for producing a gas barrier sheet, which comprises applying a coating liquid containing at least a water-soluble polymer or a water-dispersible polymer and fine fibers of a polymeric polysaccharide, followed by drying. The coating liquid preferably contains fine fibers of a polymeric polysaccharide having a fiber width of 1 to 1000 nm, a binder, and water. Details of the hydrophobic porous substrate, the fine fibers of a polymeric polysaccharide, and the binder are as described above.

[0040] Details of the hydrophobic porous substrate, water-soluble or water-dispersible polymer, and polymeric polysaccharide fine fibers are as described above. The polymeric polysaccharide fine fibers and binder are preferably prepared in the form of an aqueous dispersion and an aqueous solution, respectively, and then mixed to form a coating solution. Depending on the environment in which the total heat exchange element is used, condensation or the like may occur, and the coating layer formed may require water resistance. A water-resistant agent may be added to impart water resistance, but water resistance can be more effectively improved by using, for example, a cellulose derivative, more preferably an ammonium salt of carboxymethylcellulose, as the binder. This is thought to be because the ammonium salt of carboxymethylcellulose evaporates as ammonium upon drying, thereby improving the water resistance of the coating layer itself.

[0041] The coating layer can be formed, for example, by applying a coating liquid containing the above components to a hydrophobic porous substrate and drying it. Known coating machines can be used for the coating method, and are not particularly limited. Examples include blade coaters, bar coaters, curtain coaters, die coaters, air knife coaters, and roll coaters. Blade coaters and bar coaters are preferred because the pressing force of the blade or bar during coating allows the coating liquid to penetrate into the pores of the porous substrate. For drying, a dryer attached to the coating machine can be used. The drying temperature is preferably 65°C or higher, more preferably 70°C or higher, even more preferably 75°C or higher, even more preferably 80°C or higher, even more preferably 85°C or higher, and particularly preferably 90°C or higher. The drying temperature is preferably 130°C or lower, more preferably 120°C or lower, and even more preferably 110°C or lower. By setting the drying temperature at or above the lower limit, the water resistance of the coating layer can be more effectively improved. Furthermore, by setting the drying temperature to the above upper limit or less, it is possible to suppress a decrease in strength of the hydrophobic porous substrate due to drying.

[0042] The amount of coating liquid applied to the hydrophobic porous substrate is not particularly limited, but is preferably 0.03 g / m 2 More than 3g / m 2 It is preferable that the content is 0.03 g / m or less, and more preferably 0.03 g / m 2More than 2g / m 2 As the coating weight increases, the gas barrier property improves, but the moisture permeability tends to decrease. 2 On the other hand, if the coating amount is too small, the pores will not be sufficiently covered and sufficient gas barrier properties will not be obtained. 2 The coating amount of the coating liquid is preferably 0.03 g / m or more. 2 More than 3g / m 2 When the thickness is less than 100 μm, a uniform coating film can be formed, and the pores of the substrate can be blocked with the hydrophilic material, thereby suppressing a decrease in moisture permeability. In the present invention, it is preferable to incorporate fine fibers of polymeric polysaccharides into the coating layer, since the fine fibers of polymeric polysaccharides penetrate not only the surface of the hydrophobic porous substrate but also into the interior of the pores, thereby more effectively increasing the moisture permeability.

[0043] When applying a coating liquid to a hydrophobic porous substrate, if the substrate repels the coating liquid, it is recommended to add a surfactant (also known as a wetting agent or leveling agent) to the coating liquid, or to subject the substrate to a surface hydrophilization treatment such as corona discharge treatment in advance, or to use a combination of these. If repelling occurs during coating, it tends to be difficult to obtain a gas barrier sheet with an Oken air permeability of 10,000 seconds or more. It is preferable to use a surfactant with reduced foaming properties.

[0044] Since the partition member of the present invention requires a small amount of coating, heat exchange of latent heat (humidity) occurs even without the application of a moisture absorbent. However, a moisture absorbent may be blended to further increase moisture permeability. Examples of moisture absorbents include inorganic acid salts, organic acid salts, polyhydric alcohols, and ureas. Examples of inorganic acid salts include lithium chloride, calcium chloride, and magnesium chloride. Examples of organic acid salts include sodium lactate, calcium lactate, and sodium pyrrolidone carboxylate. Examples of polyhydric alcohols include glycerin, ethylene glycol, triethylene glycol, and polyglycerin. Examples of ureas include urea and hydroxyethyl urea.

[0045] Furthermore, the coating liquid may contain auxiliary agents such as water-resistant agents, preservatives, mildew-proofing agents, flame retardants, viscosity adjusters, pH adjusters, colorants, storage stability improvers, polymer resins, and antiblocking agents, as long as the effects of the present invention are not impaired.

[0046] When applying the coating solution, the coating amount should be adjusted so that the resulting gas barrier sheet has an Oken air permeability of 10,000 seconds or more. 2 It is preferable to adjust the coating amount so that the coating time is 24 hours or more.

[0047] [Total heat exchange element] The total heat exchange element of the present invention is a total heat exchange element comprising a plurality of the above-mentioned gas barrier sheets as partition members for the total heat exchange element. The total heat exchange element of the present invention comprises a plurality of the above-mentioned gas barrier sheets and a spacing member disposed between the gas barrier sheets to maintain a spacing between adjacent gas barrier sheets, and in which first air flow paths and second air flow paths are formed alternately with the gas barrier sheets sandwiched therebetween.

[0048] The total heat exchange element will be described below with reference to FIG. 1, but the present invention is not limited to the total heat exchange element having the structure of FIG. FIG. 1 is a schematic diagram illustrating the structure of a total heat exchange element 10. As shown in FIG. 1, the total heat exchange element 10 is composed of a plurality of partition members 1 and a plurality of spacing members 2 that form air flow paths between the plurality of partition members 1 and maintain the spacing between the partition members 1. The partition members 1 are flat plates that are shaped like squares, diamonds, or the like, and the spacing members 2 maintain the spacing between the partition members 1 and are, for example, corrugated plates formed into waveforms such as sawtooth waves or sine waves whose projected planar shape matches the shape of the partition members 1. The spacing members 2 are shaped, for example, like the core of cardboard and are formed by corrugating.

[0049] The spacing member 2 is not particularly limited as long as it maintains the distance between the partition members. The spacing member maintains the distance between the partition members, thereby forming air flow paths between the partition members. The spacing member is not limited to a corrugated material such as a paper substrate, film, or nonwoven fabric, but may also be a resin rib. Of these, a paper substrate is preferred. Because a paper substrate has the function of regulating moisture, it can compensate for the reduced moisture-regulating function of partition members using a hydrophobic porous substrate.

[0050] The spacing member 2 has a shape similar to the core of cardboard, for example, and is formed by corrugating. The ridges and valleys of the waveforms of the spacing member 2 are joined to the partition member 1 with an adhesive or the like. The spacing member 2 is joined to the partition member 1 on one side with the partition member 1 in between, with the ridges of the waveforms extending in a first direction (for example, the vertical direction), and on the other side with the ridges of the waveforms extending in a second direction (for example, the horizontal direction). In other words, two spacing members 2 adjacent to each other with the partition member 1 in between are stacked alternately so that the direction of the ridges of the waveforms on one side and the direction of the ridges of the waveforms on the other side are perpendicular to each other.

[0051] Between the spacing member 2, whose ridge lines of the waveforms are oriented in a first direction (for example, the vertical direction), and the partition members 1 on both sides, a plurality of first air flow paths 4 are formed along the first direction. Furthermore, between the spacing member 2, whose ridge lines of the waveforms are oriented in a second direction (for example, the horizontal direction), and the partition members 1 on both sides, a plurality of second air flow paths 5 are formed along the second direction. Note that arrow 6 in FIG. 1 indicates the direction of air flow in the first air flow paths 4, and arrow 7 in FIG. 1 indicates the direction of air flow in the second air flow paths 5.

[0052] Spacing members 2 whose corrugated ridgelines are oriented in a first direction and spacing members 2 whose corrugated ridgelines are oriented in a second direction are alternately stacked with the partition member 1 in between so that the ridge directions are perpendicular to each other, and therefore the first air flow paths 4 and the second air flow paths 5 are also formed so that the extension directions are perpendicular to each other. For example, supply air flows through the first air flow path 4 and exhaust air flows through the second air flow path 5, and heat exchange occurs between the supply air and exhaust air via the partition member 1 and spacing members 2.

[0053] The method for joining the partition member and the spacing member can be a known method such as a method using an adhesive or a thermal bonding method without using an adhesive. Among these, a method using an adhesive is preferable because it can firmly bond the spacing member and the partition member. Known adhesives such as polyvinyl alcohol adhesives and ethylene vinyl acetate adhesives can be used as the adhesive. [Example]

[0054] The features of the present invention will be explained in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0055] <Preparing the substrate> Substrate A: A 20 μm thick polyethylene film (product name: SW320H, manufactured by Shenzhen Senior Technology Material Co., Ltd.) was prepared as a hydrophobic porous substrate. The surface density was 10.0 g / m. 2 It was. Substrate B: A 16 μm thick polypropylene film (product name: SD216301, manufactured by Shenzhen Senior Technology Material Co., Ltd.) was prepared as a hydrophobic porous substrate. The surface density was 9.4 g / m. 2 It was.

[0056] <Production of fine cellulose fibers> (Phosphate group introduction step) The raw pulp used was softwood kraft pulp (solid content 93% by mass, basis weight 210 g / m) manufactured by Oji Paper Co., Ltd. 2 A sheet-like product with a Canadian Standard Freeness (CSF) of 690 ml when disintegrated and measured in accordance with JIS P 8121:2012 was used. This raw pulp was subjected to a phosphorylation treatment as follows. First, a mixed aqueous solution of ammonium dihydrogen phosphate and urea was added to the raw pulp to adjust the ratio of 45 parts by mass of ammonium dihydrogen phosphate, 120 parts by mass of urea, and 150 parts by mass of water per 100 parts by mass (bone dry mass) of raw pulp to obtain a chemical-impregnated pulp. The obtained chemical-impregnated pulp was then heated in a hot air dryer at 165°C for 200 seconds to introduce phosphate groups into the cellulose in the pulp, thereby obtaining a phosphorylated pulp.

[0057] (Cleaning process) The resulting phosphorylated pulp was then subjected to a washing treatment. The washing process was carried out by pouring 10 L of ion-exchanged water over 100 g of phosphorylated pulp (bone dry mass), stirring to uniformly disperse the pulp, and then repeatedly filtering and dehydrating the pulp. The washing was completed when the electrical conductivity of the filtrate reached 100 μS / cm or less.

[0058] (Alkali treatment process) Next, the washed phosphorylated pulp was subjected to an alkali treatment (neutralization treatment) as follows. First, the washed phosphorylated pulp was diluted with 10 L of ion-exchanged water, and then a 1 N aqueous solution of sodium hydroxide was added little by little while stirring to obtain a phosphorylated pulp slurry with a pH of 12 to 13. Next, the phosphorylated pulp slurry was dehydrated to obtain phosphorylated pulp that had been subjected to an alkali treatment (neutralization treatment). Next, the phosphorylated pulp after the alkali treatment was subjected to the above-mentioned washing treatment. The infrared absorption spectrum of the resulting alkali-treated phosphorylated pulp was measured using FT-IR. The absorption peak at 1230 cm-1 was due to phosphate groups, confirming the addition of phosphate groups to the pulp. The amount of phosphate groups (strong acid groups) measured using the aforementioned method was 1.45 mmol / g. In addition, the obtained phosphorylated pulp was analyzed using an X-ray diffractometer, and typical peaks for cellulose type I crystals were confirmed at two positions, around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming the presence of cellulose type I crystals.

[0059] (Defibrillation process) Ion-exchanged water was added to the phosphorylated pulp obtained through the alkali treatment step to prepare a slurry with a solids concentration of 2% by mass. This slurry was treated three times at a pressure of 200 MPa using a wet pulverization device (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a microfibrillated cellulose fiber dispersion containing microfibrillated cellulose fibers. X-ray diffraction confirmed that the microfibrillated cellulose fibers maintained cellulose type I crystals. Furthermore, the fiber width of the microfibrillated cellulose fibers was measured using a transmission electron microscope and found to be 3 to 5 nm. Furthermore, the yield of the microfibrillated cellulose fibers obtained was measured according to the method described above, and was found to be 99.2%.

[0060] Example 1 One side of the substrate A was subjected to a corona discharge treatment, and then a 5% coating solution containing polyvinyl alcohol (trade name: Exeval HR-3010, manufactured by Kuraray Co., Ltd.) and water was applied to the substrate using a Mayer bar to a coating weight of 0.42 g / m after drying. 2 The coating was then dried at 70°C for 10 minutes to obtain a gas barrier sheet.

[0061] Example 2 One side of the substrate A was subjected to a corona discharge treatment, and then a 5% coating solution containing polyvinyl alcohol (trade name: Exeval HR-3010, manufactured by Kuraray Co., Ltd.) and water was applied to the substrate using a Mayer bar to a coating weight of 1.05 g / m after drying. 2 The coating was then dried at 70°C for 10 minutes to obtain a gas barrier sheet.

[0062] Example 3 One surface of the substrate A was subjected to a corona discharge treatment, and then a coating liquid containing 3 parts by mass of carboxymethyl cellulose (trade name: CMC1110, manufactured by Daicel Miraize Co., Ltd.), 1.2 parts by mass of a polyether surfactant (trade name: SN Wet 985, manufactured by San Nopco Co., Ltd., 76% aqueous dispersion), and 95.8 parts by mass of water was applied using a Mayer bar to a coating weight of 1.16 g / m after drying. 2 The coating was then dried at 70°C for 10 minutes to obtain a gas barrier sheet.

[0063] Example 4 One surface of the substrate A was subjected to a corona discharge treatment, and then a coating liquid containing 3 parts by mass of carboxymethyl cellulose (trade name: CMC1110, manufactured by Daicel Miraize Co., Ltd.), 1.2 parts by mass of a polyether surfactant (trade name: SN Wet 985, manufactured by San Nopco Co., Ltd., 76% aqueous dispersion), and 95.8 parts by mass of water was applied using a Mayer bar to a coating weight of 0.64 g / m after drying. 2 The coating was then dried at 70°C for 10 minutes to obtain a gas barrier sheet.

[0064] Example 5 One surface of the substrate A was subjected to a corona discharge treatment, and then a coating liquid containing 3 parts by mass of carboxymethyl cellulose ammonium salt (trade name: DN-10L, manufactured by Daicel Millize Co., Ltd.), 1.2 parts by mass of a polyether surfactant (trade name: SN Wet 985, manufactured by San Nopco Co., Ltd., 76% aqueous dispersion), and 95.8 parts by mass of water was applied using a Mayer bar to a coating weight of 0.50 g / m after drying. 2 The coating was then dried at 70°C for 10 minutes to obtain a gas barrier sheet.

[0065] (Comparative Example 1) Substrate A was used as it was as a gas barrier sheet.

[0066] Example 6 One surface of the substrate B was subjected to a corona discharge treatment, and then a coating liquid containing 0.56 parts by mass of carboxymethyl cellulose ammonium salt (trade name: DN-10L, manufactured by Daicel Miraize Co., Ltd.), 18.3 parts by mass of fine cellulose fiber, 0.64 parts by mass of a nonionic surfactant (trade name: Noigen XL-100, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., solid content 100%), and 80.5 parts by mass of water was applied using a Mayer bar to a coating weight of 0.36 g / m after drying. 2 The coating was then dried at 105°C for 10 minutes to obtain a gas barrier sheet.

[0067] (Comparative Example 2) Substrate B was used as it was as a gas barrier sheet.

[0068] (evaluation) The gas barrier sheets obtained in the examples and comparative examples were measured for moisture permeability and Oken air permeability, and the results are shown in Table 1. "Moisture permeability" Measurements were carried out under conditions of 20°C and 65% RH in accordance with JIS Z0208, with calculations being carried out using the following formula: Moisture permeability=(a+b) / 2 where a = mass increase after 1 hour of measurement b = Mass increase per hour from 1 hour after the start of measurement to 2 hours after the start of measurement

[0069] "Ouken style air permeability" Measurement was performed in accordance with the Oken air permeability method of JAPAN TAPPI Paper and Pulp Test Method No. 5-2:2000.

[0070] "Carbon dioxide gas barrier properties" A measuring device was used, equipped with container A, which contained high-concentration CO2, and container B, which measured the CO2 concentration, as 12cm square partition members. Container A was filled with 20,000 ppm of CO2 under room temperature and pressure conditions, and then left for 15 minutes, after which the CO2 concentration in container B was measured using a CO2 analyzer. The amount of CO2 that passed through the partition member over 15 minutes was calculated as the CO2 concentration in container B. When the CO2 concentration in container B was 10,000 ppm or less, the carbon dioxide gas barrier properties of the partition member were judged to be good and marked with a circle, and when it exceeded 10,000 ppm, it was judged to be poor and marked with an X.

[0071] "Water immersion test" A sample of gas barrier sheet cut to A4 size was immersed in 30 liters of tap water. A 120g weight was attached to the sample to prevent it from floating. After 10 minutes, the sample was removed and air-dried at room temperature until no water droplets remained on the film surface. (peeling) The surface of the dried sample was observed to check whether the coating layer had peeled off. (Ouken style air permeability (after immersion in water)) The Oken air permeability of the dried sample was measured in accordance with the Oken air permeability method of JAPAN TAPPI Paper Pulp Test Method No. 5-2:2000.

[0072] "Basic weight" The basis weight of the gas barrier sheet was calculated from the area and mass of the test piece in accordance with JIS P8124:2011.

[0073] [Table 1]

[0074] The gas barrier sheets obtained in each example had high air permeability and excellent gas barrier properties. The gas barrier sheets using the cellulose derivatives of Examples 3 to 6 had high moisture permeability. In particular, when fine fibers of polymeric polysaccharides with a fiber width of 1 to 1000 nm were used in combination, a gas barrier sheet with high air permeability and high moisture permeability was obtained. Gas barrier sheets with high air permeability and high moisture permeability are suitable for use as partition members for total heat exchange elements. [Explanation of symbols]

[0075] 1 Partition member 2 Spacing members 4 First air flow path 5 Second Air Flow Path 10 Total heat exchange element

Claims

1. A gas barrier sheet comprising a hydrophobic porous substrate and a coating layer on at least one surface thereof, the coating layer containing at least one polymer selected from water-soluble polymers and water-dispersible polymers.

2. 2. The gas barrier sheet according to claim 1, wherein the hydrophobic porous substrate has an Oken air permeability of 1000 seconds or less.

3. 2. The gas barrier sheet according to claim 1, wherein the thickness of the hydrophobic porous substrate is 5 μm or more and 30 μm or less.

4. 2. The gas barrier sheet according to claim 1, wherein the coating layer contains fine fibers of a polymeric polysaccharide having a fiber width of 1 to 1000 nm.

5. The gas barrier sheet according to claim 4 , wherein the fine fibers are chemically modified fine cellulose fibers.

6. The coating amount of the coating layer is 0.03 g / m ２ 3g / m or more ２ 2. The gas barrier sheet according to claim 1, wherein:

7. 2. The gas barrier sheet according to claim 1, wherein the gas barrier sheet has an Oken air permeability of 10,000 seconds or more.

8. The gas barrier sheet has a moisture permeability of 2500 g / m at a temperature of 20°C and a relative humidity of 65%. ２ The gas barrier sheet according to claim 1, wherein the shelf life is 24 hours or more.

9. The gas barrier sheet according to claim 1, which is used as a partition member for a total heat exchange element.

10. A method for manufacturing a heat exchanger comprising the steps of: providing a plurality of gas barrier sheets according to any one of claims 1 to 6 as partition members for a total heat exchange element; a spacing member disposed between the total heat exchange element partition members to maintain a spacing between the adjacent total heat exchange element partition members; A total heat exchange element, in which first air flow paths and second air flow paths are formed alternately with the partition member for the total heat exchange element sandwiched therebetween.

11. The total heat exchange element according to claim 10 , wherein the gas barrier sheet has an Oken air permeability of 10,000 seconds or more.

12. The gas barrier sheet has a moisture permeability of 2500 g / m at a temperature of 20°C and a relative humidity of 65%. ２ The total heat exchange element according to claim 10, wherein the total heat exchange element has a life of 24 hours or more.

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