JP7664138B2 - Condensation prevention sheet - Google Patents

Description

This disclosure relates to a condensation suppression sheet for suppressing condensation on the surfaces of components such as air conditioning ducts.

Air conditioning ducts through which air from an air conditioner flows are arranged inside the instrument panel, console box, etc. of a vehicle. When the temperature of the air flowing through the air conditioning duct is low and there is a temperature difference between the inside and outside of the duct, condensation is likely to occur on the outer surface of the duct. Electrical components such as electronic parts and wire harnesses are often arranged below the air conditioning duct, and if water droplets (condensed water) caused by condensation drip onto these components, there is a risk of these components breaking down. Therefore, measures have been taken to suppress condensation from the viewpoint of making the air conditioning duct a thermally insulated structure. Known methods for improving the thermal insulation of an air conditioning duct include manufacturing part or all of the duct from a highly insulating foamed resin material, or wrapping a urethane insulating sheet around the duct (see, for example, Patent Document 1).

JP 2017-24629 A JP 2008-174730 A International Publication No. 2004/085151

Slab urethane is mainly used as an insulating sheet to be attached to air conditioning ducts. The insulating effect of slab urethane sheets makes it possible to suppress condensation for a relatively short period of time. However, if condensation occurs due to long-term use of the air conditioning system, it is difficult to suppress the dripping of condensation water because the sheet itself has a low water retention capacity. Increasing the thickness of the slab urethane sheet is expected to improve the insulation and water retention capacity to some extent, but due to restrictions on placement space, etc., the insulating sheet must be thin. Therefore, it is not practical to make the slab urethane sheet thicker, and even if it is made thicker, there is a limit to its water retention capacity.

On the other hand, in the field of building materials, humidity-conditioning sheets that adjust the humidity in a space are known. For example, Patent Document 2 describes a humidity-conditioning sheet in which a humidity-conditioning layer, in which humidity-conditioning particles are bonded together with thermoplastic resin powder and has a porosity of 5% or more, is laminated with a base sheet made of a breathable material. Examples of humidity-conditioning particles include silica gel and zeolite, and examples of thermoplastic resin powder include polyurethane powder. Examples of base sheets include nonwoven fabrics, resin films, and metal foils.

Patent Document 3 describes a functional member in which a substrate, a first layer made of a dried mixture containing an inorganic porous material and an organic emulsion, and a second layer in which an inorganic filler is fixed with an organic binder are laminated. Examples of inorganic porous materials include silica gel and sepiolite, and examples of organic emulsions include acrylic emulsion. Examples of substrates include paper, synthetic resin sheets, and nonwoven fabrics.

The humidity-conditioning layer described in Patent Document 2 is formed by scattering humidity-conditioning particles and thermoplastic resin powder on a base sheet, and applying heat and pressure. That is, the humidity-conditioning particles are fixed by thermal fusion of the thermoplastic resin powder. The voids between the humidity-conditioning particles are used as water-retaining spaces. Therefore, as described in paragraph [0015] of Patent Document 2, the thermoplastic resin powder is selected from the viewpoint of forming voids between the humidity-conditioning particles and not excessively covering the surface of the humidity-conditioning particles, in addition to being able to be thermally fused. In the humidity-conditioning layer, the ratio of voids between the humidity-conditioning particles is 5 to 75% (paragraph [0089]), and the entire surface of the humidity-conditioning particles is not covered by the thermoplastic resin, which is the binder, so that the humidity-conditioning particles often fall off (so-called powder fall). The presence or absence of moisture permeability in the thermoplastic resin is also irrelevant. In addition, the base sheet is made of a material having air permeability. As described in paragraph [0092], if the material of the substrate itself has poor breathability, fine holes or slits may be formed, and the "breathability" of the substrate sheet simply means that air can pass through. In Patent Document 2, the gaps between the moisture-conditioning particles are used as moisture-retaining spaces, so there is no idea of giving the substrate sheet moisture-retaining ability.

The functional member described in Patent Document 3 is used in interior materials for buildings and the like, and is intended to achieve antifouling and stain shielding properties in addition to humidity control functions. Patent Document 3 does not mention the suppression of condensation using the functional member. Patent Document 3 describes applying a coating liquid containing an inorganic porous body and an organic emulsion onto a substrate, and drying the coating liquid to form a first layer. However, there is no mention or suggestion of impregnating the substrate with the coating liquid, or the degree of impregnation. Therefore, it is difficult to obtain the desired condensation suppression effect using the functional member described in Patent Document 3.

This disclosure was made in light of these circumstances, and aims to provide a condensation suppression sheet that can suppress condensation even though it is thin.

In order to solve the above problems, the condensation suppression sheet of the present disclosure comprises a fiber substrate, and a humidity-conditioning layer laminated on the substrate and made of a dried liquid composition having an emulsion-based binder containing a polymer having moisture permeability and humidity-conditioning particles. The substrate has a main body and an impregnated layer in which the liquid composition has impregnated the gaps between the fibers and dried. The thickness ratio of the impregnated layer is 0.1 to 0.5 when the thickness of the entire substrate is taken as 1. The content of the humidity-conditioning particles in the liquid composition is 150 to 400 parts by mass per 100 parts by mass of the solid content of the emulsion-based binder. The average particle diameter of the humidity-conditioning particles is 10 μm to 200 μm.

In the condensation suppression sheet of the present disclosure, condensation suppression is realized by focusing on moisture absorption and moisture retention, rather than on the viewpoint of increasing the thermal insulation as has been conventionally done. In the condensation suppression sheet of the present disclosure, the substrate is made of a fiber material and has a main body and an impregnated layer in which the liquid composition forming the humidity control layer is impregnated into the gaps between the fibers and dried. The dried liquid composition constituting the humidity control layer and the impregnated layer has moisture absorption and release properties. Therefore, the impregnated layer has moisture absorption and release properties together with the humidity control layer, and plays a role in fixing and maintaining the humidity control layer to the substrate. The moisture absorption properties of the humidity control layer and the impregnated layer are exerted, so that moisture in the air is absorbed and the occurrence of condensation is suppressed. The thickness ratio of the impregnated layer in the substrate is 0.1 or more and 0.5 or less when the thickness of the entire substrate is 1. By setting the thickness ratio of the impregnated layer to 0.5 or less and leaving the part (main body) not impregnated with the liquid composition, the gaps (voids) between the fibers can be maintained. By doing so, even if the impregnated layer is present, the moisture retention capacity of the substrate can be increased. As a result, even if the condensation state continues for a relatively long time, the moisture migrates to and is retained in the main body of the substrate, so that the condensation water is less likely to drip. In addition, by embedding a part of the layer having moisture absorption and release properties in the substrate as an impregnated layer, the condensation suppression sheet can be made thinner and the effect of reinforcing the humidity control layer can also be obtained. In this way, the condensation suppression sheet of the present disclosure exhibits excellent condensation suppression effect even though it is thin.

In order to increase the moisture absorption and improve the condensation suppression effect, the humidity-conditioning layer contains a relatively large amount of humidity-conditioning particles. For this reason, the humidity-conditioning layer alone is brittle and has problems with strength and ease of attachment to members. In this regard, in the condensation suppression sheet of the present disclosure, the humidity-conditioning layer is supported by a substrate. Since the substrate is made of a fiber material, it is lightweight, easy to fold and bend, and has a large degree of freedom in shape. Therefore, the condensation suppression sheet of the present disclosure is lightweight and has excellent attachment properties to members. In addition, the degree of impregnation in the substrate and the moisture retention can be adjusted by changing the type of fiber and the size of the gaps between the fibers.

In the humidity-conditioning layer, the binder that fixes the humidity-conditioning particles has a polymer with moisture permeability. Therefore, even if the entire surface of the humidity-conditioning particles is covered with the binder polymer, the moisture absorption and desorption properties are not easily hindered. Therefore, by covering the entire surface of the humidity-conditioning particles with a polymer, it is possible to prevent the humidity-conditioning particles from falling off (so-called powder falling). As the binder, an emulsion-based binder is used. For example, if a polymer solution in which a polymer is dissolved in a solvent is used, the polymer solution will penetrate the pores of the humidity-conditioning particles and crush the pores when preparing the liquid composition. In contrast, the particle diameter of the polymer particles contained in the emulsion is often several tens to several hundreds of nm. Therefore, when preparing the liquid composition, the polymer particles will not easily penetrate the pores of the humidity-conditioning particles and will not easily hinder the moisture absorption and desorption properties of the humidity-conditioning particles.

1 is a cross-sectional view in the thickness direction of one embodiment of a condensation suppression sheet according to the present disclosure. FIG. 1 is a schematic diagram of an experimental apparatus used to evaluate condensation resistance.

<Condensation prevention sheet>
An embodiment of the condensation suppression sheet of the present disclosure will be described. In this embodiment, the condensation suppression sheet is attached to an air conditioning duct through which air flows from an air conditioning device mounted on an automobile. First, the configuration of the condensation suppression sheet of this embodiment will be described. FIG. 1 shows a cross-sectional view in the thickness direction of the condensation suppression sheet of this embodiment. For convenience of explanation, in FIG. 1, the thickness of the condensation suppression sheet is exaggerated with respect to the air conditioning duct. As shown in FIG. 1, the condensation suppression sheet 10 is disposed on the lower surface of the air conditioning duct 40. The condensation suppression sheet 10 is attached to the air conditioning duct 40 by an adhesive tape 41. The condensation suppression sheet 10 includes a substrate 20 and a humidity conditioning layer 30.

The substrate 20 is a nonwoven fabric using polyester fibers. The basis weight of the nonwoven fabric is 70 g/ ^m2 . The thickness of the substrate 20 is 0.6 mm. The substrate 20 has a main body 21 and an impregnated layer 22. The thickness of the main body 21 is 0.5 mm, and the thickness of the impregnated layer 22 is 0.1 mm. The thickness ratio of the impregnated layer 22 in the substrate 20 is 0.17 when the thickness of the entire substrate 20 is 1. The impregnated layer 22 is formed by impregnating the gaps between the polyester fibers of the substrate 20 with a liquid composition for forming the humidity-conditioning layer 30 described later and drying it.

The humidity-conditioning layer 30 is laminated on the lower surface (the surface on the impregnated layer 22 side) of the substrate 20. The humidity-conditioning layer 30 is made of a dried liquid composition containing an acrylic emulsion (emulsion-based binder) containing an acrylic resin having moisture permeability and B-type silica gel (humidity-conditioning particles). The silica gel is spherical, with an average pore size of 7 nm and an average particle size of 100 μm. The content of silica gel in the liquid composition is 283 parts by mass per 100 parts by mass of the solid content of the acrylic emulsion. The thickness of the humidity-conditioning layer 30 is 0.4 mm, and the total thickness of the humidity-conditioning layer 30 and the impregnated layer 22 is 0.5 mm.

Next, the effects of the condensation suppression sheet of this embodiment will be described. In the condensation suppression sheet 10, the humidity conditioning layer 30 and the impregnated layer 22 have excellent moisture absorption and release properties due to B-type silica gel. The total thickness of the humidity conditioning layer 30 and the impregnated layer 22 is 0.5 mm. These two layers absorb moisture in the air to suppress the occurrence of condensation. When condensation occurs due to long-term use of the air-conditioning duct 40, the moisture moves to and is retained in the main body 21 of the substrate 20. The thickness ratio of the impregnated layer 22 in the substrate 20 is 0.17, and the thickness ratio of the main body is 0.83. The basis weight of the nonwoven fabric, which is the substrate 20, is 70 g/m ² , and the gaps between the fibers are relatively large. Therefore, the substrate 20 has a large moisture retention capacity, and condensed water is unlikely to drip even if the condensed state continues for a relatively long time. Furthermore, because a part of the layer having moisture absorption and release properties is embedded in the substrate 20 as an impregnated layer, the humidity conditioning layer 30 is reinforced by the substrate 20, and the thickness of the condensation suppression sheet 10 can be reduced. In this manner, the condensation suppression sheet 10 exerts an excellent condensation suppression effect even with a thickness as thin as 1 mm.

The substrate 20 supporting the humidity control layer 30 is a nonwoven fabric made of polyester fibers. Therefore, it is lightweight and can be easily attached to the air conditioning duct 40 using adhesive tape 41. In the humidity control layer 30 and the impregnation layer 22, the surfaces of the silica gel particles are covered with a binder. This prevents the silica gel particles from falling off. The acrylic resin of the binder has high moisture permeability. Therefore, even if the entire surface of the silica gel particles is covered with the binder, the moisture absorption and desorption properties are not easily hindered. As the binder, an acrylic emulsion with an average particle size of polymer particles of about 100 nm is used. Therefore, when preparing the liquid composition, the polymer particles are unlikely to penetrate into the pores of the silica gel particles. Therefore, the high moisture absorption and desorption properties of the silica gel particles can be maintained.

Although one embodiment of the condensation suppression sheet of the present disclosure has been described above, the condensation suppression sheet of the present disclosure is not limited to the above-mentioned form, and can be embodied in various forms with modifications and improvements that can be made by a person skilled in the art without departing from the gist of the present disclosure.

In the above embodiment, the condensation suppression sheet is attached to the air conditioning duct of the air conditioning device of the automobile. However, the member to which the condensation suppression sheet is applied is not particularly limited. For example, the condensation suppression sheet can be applied to various pipes for transporting fluids such as cooling water and refrigerant, and wall materials and floor materials of the luggage compartment of a refrigerated vehicle. The condensation suppression sheet can be attached using adhesive tape, adhesives, etc., or welding by applying heat or ultrasonic waves. In addition, when molding the application member using a method such as in-mold molding or insert molding, the condensation suppression sheet can be placed in a molding die and molded as one piece. In either method, it is sufficient to attach the sheet so that the base material is on the application member side. The condensation suppression sheet can be placed so as to cover the entire application member, or can be placed only on a part where condensation water may drip. The condensation suppression sheet includes a base material and a humidity control layer laminated on the base material. The components of the condensation suppression sheet are described below.

[Substrate]
The substrate may be made of a fiber material, and may be a woven fabric or a nonwoven fabric. Nonwoven fabric is preferred because the fibers are entangled with each other and have many voids inside. Examples of fiber materials include resin fibers such as polyester fibers, polypropylene fibers, and nylon fibers, inorganic fibers such as glass fibers, rock wool, ceramic fibers, alumina fibers, silica fibers, and metal fibers, and carbon fibers. Among them, polyester fiber nonwoven fabric is preferred because it is relatively light and inexpensive and has high water retention. From the viewpoint of reducing the weight of the substrate and increasing its water retention, it is desirable for the substrate to be made of a cloth having a basis weight of 30 g/m ² or more and 100 g/m ² or less. The more preferred basis weight of the cloth is 40 g/m ² or more, 50 g/m ² or more, and 90 g/m ² or less, and 80 g/m ² or less. In this disclosure, the concept including both woven fabric and nonwoven fabric is referred to as "cloth".

The substrate has a main body and an impregnated layer in which a liquid composition for forming a humidity-regulating layer is impregnated into gaps between fibers and dried. The liquid composition will be described later. Here, the thickness ratio of the impregnated layer is 0.1 or more and 0.5 or less, assuming that the thickness of the entire substrate is 1. If the thickness ratio of the impregnated layer in the substrate is less than 0.1, the reinforcing effect of the humidity-regulating layer decreases. A more preferable thickness ratio is 0.15 or more. If the thickness ratio of the impregnated layer is more than 0.5, the thickness of the main body becomes smaller, and the moisture retention ability of the substrate decreases accordingly. A more preferable thickness ratio is 0.4 or less.

From the viewpoint of making the condensation suppression sheet thinner, for example, the thickness of the main body is preferably 0.2 mm or more and 1.0 mm or less. If the thickness of the main body is less than 0.2 mm, the moisture retention of the substrate may decrease. A more preferable thickness is 0.4 mm or more. If the thickness of the main body is more than 1.0 mm, the flexibility of the substrate may decrease, and the conformability to the shape of the application member may decrease. A more preferable thickness is 0.8 mm or less. On the other hand, the thickness of the impregnated layer is preferably 0.05 mm or more and 0.2 mm or less. If the thickness of the impregnated layer is less than 0.05 mm, the reinforcing property of the moisture control layer may decrease. A more preferable thickness is 0.08 mm or more. If the thickness of the impregnated layer is more than 0.2 mm, the thickness of the main body becomes relatively small, and the moisture retention of the substrate may decrease. A more preferable thickness is 0.15 mm or less.

[Humidity control layer]
The humidity-conditioning layer is laminated on the substrate. The humidity-conditioning layer may be disposed on a part of the surface of the substrate, or may be disposed on the entire surface. From the viewpoint of making the condensation-suppressing sheet thin, for example, the total thickness of the humidity-conditioning layer and the impregnated layer of the substrate may be set to 0.3 mm or more and 1.0 mm or less. If the thickness of the humidity-conditioning layer and the impregnated layer is less than 0.3 mm, the moisture absorption and release properties may decrease, and sufficient condensation suppression effect may not be obtained. A more suitable thickness is 0.4 mm or more. If the thickness of the humidity-conditioning layer and the impregnated layer is greater than 1.0 mm, the coating film cohesive force when the liquid composition is applied may decrease, and cracks and powder fall may occur after drying. A more suitable thickness is 0.8 mm or less. By adjusting the thickness of the substrate and the humidity-conditioning layer in consideration of moisture absorption and release properties, moisture retention, and attachment to members, the thickness of the entire condensation-suppressing sheet may be set to 2 mm or less, 1.5 mm or less, or 1 mm or less.

The humidity-regulating layer is made of a dried liquid composition having an emulsion-based binder containing a polymer having moisture permeability and humidity-regulating particles. As the emulsion-based binder, an aqueous emulsion-based binder using water as a solvent is suitable. The aqueous emulsion-based binder is emulsified by introducing a surfactant or a hydrophilic group. With an aqueous emulsion-based binder, the surfactant or hydrophilic group volatilizes during drying, reducing the hydrophilicity and making the binder less soluble in water, so that the liquid composition is less likely to become sticky after drying. The emulsion-based binder may be one type or a mixture of two or more types. When preparing the liquid composition, it is desirable that the average particle size of the polymer particles of the emulsion-based binder is 10 nm or more and 300 nm or less from the viewpoint of preventing the polymer particles from penetrating into the pores of the humidity-regulating particles. In the present disclosure, the average particle size of the polymer particles of the emulsion-based binder is determined from the volume-based particle size distribution measured by a laser diffraction/scattering method. However, for commercially available products, catalog values may be used.

The polymer of the emulsion binder has moisture permeability. In the present disclosure, the presence or absence of moisture permeability is judged as follows. First, the entire polyester fiber nonwoven fabric having a basis weight of 60 g/m ² and a thickness of 0.2 mm is impregnated with an emulsion binder having a polymer to be judged, and dried to prepare a test piece. Next, a test is performed based on the A-1 method (calcium chloride method) of JIS L1099:2021 "Test method for moisture permeability of textile products", and if the obtained moisture permeability value is 50 g/m ² ·h or more, it is judged to have moisture permeability.

Examples of polymers with moisture permeability include acrylic resin, urethane resin, acrylic-urethane composite resin, acrylic-styrene composite resin, and acrylic-silicone composite resin. One type selected from these may be used alone, or two or more types may be mixed together. In the case of "composite resins," the morphology of the polymer particles includes copolymers of multiple resins, as well as core-shell structures, microphase separation structures, and interpenetrating polymer network (IPN) structures.

It is desirable for the moisture-conditioning particles to have both moisture absorption and release properties (moisture absorption and release). Examples of materials that have moisture absorption and release properties include silica gel, zeolite, sepiolite, and a complex of amorphous aluminum silicate and low-crystalline clay. A complex of amorphous aluminum silicate and low-crystalline clay is known as HASClay (registered trademark). As the moisture-conditioning particles, one type selected from these may be used alone, or two or more types may be mixed. Among these, silica gel is preferred because it is inexpensive and has excellent moisture absorption and release properties.

From the viewpoint of enhancing moisture absorption and desorption, it is desirable that the average pore diameter of silica gel is 2 nm or more and 10 nm or less. In this disclosure, the value measured by nitrogen gas adsorption method is used as the average pore diameter of silica gel. However, for commercially available products, the catalog value may be used. There are two types of silica gel, type A and type B, which have different moisture absorption and desorption properties. Type A has a relatively small pore diameter and absorbs moisture at low humidity but does not desorb moisture easily. For this reason, heating is required to desorb moisture. On the other hand, type B has a relatively large pore diameter, absorbs moisture at high humidity, absorbs a large amount of moisture, and desorbs moisture even at room temperature if the humidity decreases. Therefore, type B silica gel, which can absorb and desorb moisture at room temperature, is preferable.

The shape of the moisture-conditioning particles is not particularly limited, but it is desirable that they are spherical in terms of being easy to form a close-packed structure, enabling high packing, and good coating properties of the liquid composition. By adopting spherical moisture-conditioning particles and increasing the content, the moisture absorption and desorption properties can be improved. For example, the content of the moisture-conditioning particles in the liquid composition may be 150 parts by mass or more and 400 parts by mass or less per 100 parts by mass of the solid content of the emulsion binder. If it is less than 150 parts by mass, the amount of the moisture-conditioning particles is small, so the moisture absorption and desorption properties are reduced, and there is a risk that sufficient condensation suppression effect cannot be obtained. A more suitable content is 200 parts by mass or more. If it is more than 400 parts by mass, there is a risk of powder falling due to a shortage of binder. A more suitable content is 350 parts by mass or less. The average particle diameter of the moisture-conditioning particles is desirably 10 μm or more and 200 μm or less, taking into account the thickness of the moisture-conditioning layer, etc. A more suitable average particle diameter is 50 μm or more and 150 μm or less. In this disclosure, the average particle size of the humidity-conditioning particles is determined from the volume-based particle size distribution measured by a laser diffraction/scattering method. However, for commercially available products, the catalog value may be used.

In addition to the emulsion binder and the humidity-regulating particles, the liquid composition may contain other components such as a thickener, a crosslinking agent, and a flame retardant. For example, adding a thickener increases the viscosity of the binder liquid, making it easier to disperse the humidity-regulating particles. This shortens the time required to disperse the humidity-regulating particles, and increases productivity. In addition, flexibility is imparted to the humidity-regulating layer, suppressing the occurrence of cracks and the like. Examples of thickeners include polysaccharides such as carboxylmethylcellulose (CMC), polyethylene oxide (PEO), carboxyethyl cellulose, carboxypropyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, xanthan gum, agarose, and carrageenan, as well as polyvinyl alcohol and glucomannan.

<Method of manufacturing condensation suppression sheet>
The condensation suppression sheet of the present disclosure is manufactured by applying a predetermined liquid composition to the surface of a substrate and drying it. First, an emulsion binder containing a moisture-permeable polymer, moisture-regulating particles, and additives such as a thickener that are blended as necessary are added to water and dispersed to prepare a liquid composition. Dispersion may be performed by blade stirring, or active application of shear force or ultrasonic waves may be applied. Next, the prepared liquid composition is applied to the substrate. To apply the composition, a brush may be applied or a coating machine such as a blade coater, a bar coater, a die coater, a comma coater (registered trademark), or a roll coater may be used. For example, the blade coat method is preferable because it can be applied with a uniform thickness. A part of the applied liquid composition is impregnated into the surface layer of the substrate. Then, the substrate is held at a temperature of about 80 to 150° C. for several minutes to several tens of minutes, and the applied liquid composition is dried and solidified. In this manner, a condensation-suppressing sheet is produced, which includes a humidity-conditioning layer made of a dried liquid composition and a substrate having an impregnated layer impregnated with the liquid composition and dried.

Next, the present disclosure will be explained in more detail with reference to examples. In these examples, four types of condensation suppression sheet samples were prepared and the condensation resistance of each sheet was evaluated.

<Sample Production>
To 600 g of water, 45.7 g of acrylic emulsion (Toyochem Co., Ltd. "Torcryl (registered trademark) BCX-8111", solid content 58%) as an emulsion binder, 2.9 g of carboxyl methyl cellulose (Dai-ichi Kogyo Seiyaku Co., Ltd. "Cellogen (registered trademark) BSH-12") as a thickener, and 75 g of silica gel (Fuji Silysia Chemical Co., Ltd. "Fuji Silica Gel Type B", spherical, average particle diameter 100 μm, average pore diameter 7 nm) as humidity-conditioning particles were added and dispersed by blade stirring to prepare a liquid composition for the humidity-conditioning layer. The content of silica gel in the liquid composition was 283 parts by mass relative to 100 parts by mass of the solid content of the acrylic emulsion.

A nonwoven fabric using polyester fibers (Kurashiki Textile Processing Co., Ltd. "SRI-70G", thickness 0.6 mm, basis weight 70 g/ ^m2 ) was cut to A4 size and used as the substrate. The thickness of the substrate was adjusted with a spacer, and the liquid composition was applied to the surface of the substrate with a blade coater, and then dried at 150°C for 10 minutes. By changing the application conditions during blade coating, three types of condensation-suppressing sheet samples with different coating thicknesses (thickness of the moisture-regulating layer and the impregnated layer) were manufactured. Table 1 shows the configurations of the manufactured samples. Separately from this, a 3 mm thick sheet of slab urethane (expanded 30 times) was prepared (shown as sample No. 4 in Table 1).

<Evaluation of Condensation Resistance>
[Experimental Apparatus and Method]
First, the configuration of the experimental apparatus will be described. FIG. 2 shows a schematic diagram of the experimental apparatus. As shown in FIG. 2, the experimental apparatus 8 includes an insulating box 80, a sample mounting plate 81, a sample 82, and a cooling agent 83. The insulating box 80 is made of a phenol foam insulation material for housing with a thickness of 20 mm, and has a box shape with external dimensions of 300 mm length, 400 mm width, and 300 mm height. An opening 801 for installing a sample is formed in a bottom wall 800 of the insulating box 80. The opening 801 has a square shape with one side of 100 mm. The sample mounting plate 81 is made of polypropylene (PP) and has a square plate shape with one side of 100 mm and a thickness of 2 mm. The sample mounting plate 81 is fitted into the opening 801 to close the opening 801. The sample 82 is a sample of the prepared condensation-suppressing sheet (see Table 1 for the configuration), and is attached to the outer surface (lower surface) of the sample mounting plate 81 with adhesive tape. The sample 82 has a square shape with sides of 100 mm, the same as the sample mounting plate 81. The sample 82 is arranged so that the base material (nonwoven fabric) faces the sample mounting plate 81. The ice pack 83 is placed inside the heat-insulating box 80 so as to cover the opening 801 from above. The ice pack 83 has been frozen at -20°C for 24 hours, and has a mass of 2 kg.

Next, the experimental method will be explained. After placing the ice pack 83 in the insulated box 80, it was immediately sealed and the insulated box 80 was placed in a thermo-hygrostat chamber at 40°C and a relative humidity of 80%. After 1 hour, 2 hours, and 3 hours, the condition of the surface (underside) of the sample 82 was visually observed, and the condensation resistance was evaluated on a three-level scale: no moisture, moisture, and condensation.

[Experimental Results]
The evaluation results of the condensation resistance of the samples of the condensation-suppressing sheet are summarized in Table 1 above. In Table 1, cases without moisture are indicated by a circle, cases with moisture are indicated by a triangle, and cases with condensation are indicated by an x. As shown in Table 1, in sample No. 4 made of a slab urethane sheet, moisture was generated after 1 hour, and condensation occurred after 2 hours. In contrast, in sample No. 1, in which the thickness ratio of the impregnated layer is 0.17, there was no moisture until 2 hours had passed, and after 3 hours there was moisture but no condensation occurred. On the other hand, in sample No. 2, which differs from sample No. 1 only in the thickness of the moisture-conditioning layer, there was no moisture until 1 hour had passed, but moisture was generated after 2 hours, and condensation occurred after 3 hours. In sample No. 2, the thickness of the moisture-conditioning layer is thin, and the total thickness of the moisture-conditioning layer and the impregnated layer is 0.2 mm, so that sample No. It is considered that the moisture absorbing effect of the moisture-conditioning particles (silica gel) was not sufficient compared to sample No. 1. In addition, in sample No. 3, in which the liquid composition was entirely impregnated into the substrate and no moisture-conditioning layer was provided, there was no moisture until 1 hour had passed, but moisture was generated after 2 hours, and condensation occurred after 3 hours. In sample No. 3, it is considered that the thickness of the main body of the substrate was thin, and therefore the ability to retain the generated moisture was insufficient. Thus, it was confirmed that the condensation-suppressing sheet of the present disclosure has a higher condensation-suppressing effect than the conventional slab urethane sheet.

The condensation suppression sheet of the present disclosure is suitable for use in air conditioning ducts for vehicles, cooling water hoses, and wall and floor materials for the luggage compartments of refrigerated vehicles.

10: Condensation suppression sheet, 20: Base material, 21: Main body, 22: Impregnation layer, 30: Moisture control layer, 40: Air conditioning duct, 41: Adhesive tape, 8: Experimental device, 80: Insulation box, 81: Sample mounting plate, 82: Sample (condensation suppression sheet), 83: Ice pack, 800: Bottom wall, 801: Opening.

Claims (10)

A fiber substrate;
a humidity-conditioning layer laminated on the substrate and made of a dried liquid composition having an emulsion binder containing a polymer having moisture permeability and humidity-conditioning particles;
Equipped with
the polymer comprises at least one selected from an acrylic resin, a urethane resin, an acrylic-urethane composite resin, an acrylic-styrene composite resin, and an acrylic-silicone composite resin;
the substrate has a main body and an impregnated layer formed by impregnating gaps between the fibers with the liquid composition and drying the liquid composition, and the thickness ratio of the impregnated layer is 0.1 or more and 0.5 or less when the thickness of the entire substrate is taken as 1;
The content of the humidity-conditioning particles in the liquid composition is 150 parts by mass or more and 400 parts by mass or less per 100 parts by mass of the solid content of the emulsion-based binder, and the average particle diameter of the humidity-conditioning particles is 10 μm or more and 200 μm or less. The condensation suppression sheet according to claim 1 , wherein the substrate is made of a cloth having a basis weight of 30 g/m ² or more and 100 g/m ² or less. The condensation suppression sheet according to claim 1 or claim 2, wherein the substrate is made of nonwoven fabric. The condensation suppression sheet according to any one of claims 1 to 3, wherein the thickness of the main body of the substrate is 0.2 mm or more and 1.0 mm or less. The condensation suppression sheet according to any one of claims 1 to 4, wherein the total thickness of the moisture conditioning layer and the impregnated layer of the base material is 0.3 mm or more and 1.0 mm or less. The condensation suppression sheet according to claim 1 , wherein the moisture-conditioning particles have a spherical shape. 7. The condensation suppression sheet according to claim 1 , wherein the humidity-conditioning particles comprise at least one selected from the group consisting of silica gel, zeolite, sepiolite, and a complex of amorphous aluminum silicate and low-crystalline clay. The condensation suppression sheet according to claim 7 , wherein the silica gel is B type. The condensation suppression sheet according to claim 7 or 8 , wherein an average pore diameter of the silica gel is 2 nm or more and 10 nm or less. The condensation suppression sheet according to any one of claims 1 to 9, which is attached to an air conditioning duct.

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