Thermal insulation layer, method for manufacturing thermal insulation layer, coating liquid for forming thermal insulation layer, and method for manufacturing coating liquid

Abstract

The invention relates to a thermal insulation layer, a method of manufacturing a thermal insulation layer, a coating liquid for forming a thermal insulation layer, and a method of manufacturing a coating liquid. A heat insulating layer (1) according to the present disclosure contains a binder resin (11). The binder resin (11) includes a plurality of aggregates (12). The aggregate has a plurality of primary inorganic nanoparticles (121) with hydrophobic functional groups on the surface thereof and at least one pore (122) formed surrounded by these primary inorganic nanoparticles. A coating liquid (2) for forming a thermal insulation layer according to the present disclosure includes a plurality of aggregates (12) and a plurality of binder resin particles (111) in a solvent (21). The solvent contains water and alcohol. The ratio of alcohol to the total solvent is less than 46 vol%. In a method for producing a thermal insulation layer of the present disclosure, a coating liquid (2) is coated in a layered manner on a substrate (4), and then the coated layer is dried to form a thermal insulation layer (1).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a thermal insulation layer, a method for manufacturing the same, a coating liquid for forming the thermal insulation layer, and a method for manufacturing the same. BACKGROUND

[0002] A thermal insulation layer on the surface of a base material composed of a metal material, a resin, a rubber, or the like is formed by coating using a coating liquid for forming the thermal insulation layer. In this method of forming a thermal insulation layer by coating, a coating liquid in which a filler having a hollow structure or a porous aerogel is added is used to form the thermal insulation layer. This reduces the thermal conductivity of the thermal insulation layer, thereby ensuring effective thermal insulation properties.

[0003] JP 2018-123251 A (Japanese Unexamined Patent Application Publication No. 2018-123251) describes a coating material composition and a coated film having thermal insulation properties formed from the coating material composition. The coating material composition includes hollow particles composed of glass or the like, a median diameter (particle size d50) of the hollow particles is in the range of 10 μm to 35 μm, and a ratio of the hollow particles in a non-volatile content is in the range of 45 vol% to 70 vol%.

[0004] Further, JP 2019-501850 A describes an aerogel as a material having high thermal insulation properties. The aerogel is a highly porous material having a porosity of about 90% to 99.9% and a pore size in the range of 1 nm to 100 nm. JP 2022-055295 A discloses a technology relating to a composition for thermal insulation material having a silica aerogel, an aqueous binder, and a thickening agent, and a thermal insulation material having a cured product of the composition for thermal insulation material. SUMMARY

[0005] In the automotive field, for example, electrification of vehicles is being accelerated in order to achieve carbon neutrality. Therefore, an internal combustion engine, which was a heat source in the past, is no longer mounted on vehicles. Therefore, from the viewpoint of heat management and the like, higher thermal insulation technology is required to control heat loss and improve thermal efficiency.

[0006] However, in a thermal insulation layer having hollow particles, there is a limit to how small a hollow structure can be formed inside the particles. Therefore, it is difficult to further reduce the thermal conductivity.

[0007] Aerogels are highly porous materials. Therefore, a thermal insulation layer using an aerogel can reduce thermal conductivity. However, aerogels have a complicated manufacturing process. In addition, aerogels not only lose their thermal insulation properties due to water permeating into their pores during use, but they also permanently lose these properties due to the destruction of the pore structure caused by shrinkage during evaporation of the permeated water. Therefore, although aerogels exhibit low initial thermal conductivity when used, their thermal insulation properties decrease over time.

[0008] In view of the above, the present disclosure aims to provide a thermal insulation layer that can achieve high thermal insulation properties and suppress a decrease in thermal insulation properties during long-term use, a method for manufacturing the same, a coating liquid for forming a thermal insulation layer, and a method for manufacturing the same.

[0009] The thermal insulation layer 1 according to the first aspect of the present disclosure includes a binder resin 11. The binder resin 11 includes a plurality of aggregates 12. The aggregate has a plurality of primary inorganic nanoparticles 121 with a hydrophobic functional group on a surface thereof and at least one pore 122 formed by the plurality of primary inorganic nanoparticles being surrounded.

[0010] The method for manufacturing a thermal insulation layer 1 according to the second aspect of the present disclosure includes:

[0011] a first step S11 of coating a substrate 4 with a coating liquid 2 for forming a thermal insulation layer in a layered manner to form a coating layer 3; and

[0012] a second step S12 of drying the coating layer formed using the coating liquid to form a thermal insulation layer.

[0013] In the first step, the coating layer is formed using the following coating liquid for forming a thermal insulation layer. The coating liquid for forming a thermal insulation layer includes a plurality of aggregates 12 and a plurality of binder resin particles 111 in a solvent 21. The aggregate has a plurality of primary inorganic nanoparticles 121 with a hydrophobic functional group on a surface thereof and at least one pore 122 formed by the plurality of primary inorganic nanoparticles being surrounded. The solvent includes water and alcohol. The ratio of alcohol with respect to the total solvent is less than 46% by volume.

[0014] The coating liquid 2 for forming a thermal insulation layer according to the third aspect of the present disclosure includes a plurality of aggregates 12 and a plurality of binder resin particles 111 in a solvent 21.

[0015] The aggregate has a plurality of primary inorganic nanoparticles 121 with a hydrophobic functional group on a surface thereof and at least one pore 122 formed by the plurality of primary inorganic nanoparticles being surrounded. The solvent includes water and alcohol. The ratio of alcohol with respect to the total solvent is less than 46% by volume.

[0016] The method for manufacturing a coating liquid for forming a thermal insulation layer according to the fourth aspect of the present disclosure includes:

[0017] The first process S1, preparing a dispersion solution 31 in which a plurality of primary inorganic nanoparticles 121 having a hydrophobic functional group on a surface thereof are dispersed in a dispersion medium 310;

[0018] The second process S2, producing a plurality of aggregates 12 including at least one pore 122 formed of a plurality of primary inorganic nanoparticles by mixing the prepared dispersion solution with an aggregation solution 32 for aggregating the dispersed primary inorganic nanoparticles; and

[0019] The third process S3, mixing an aqueous solution 34 containing a plurality of binder resin particles 111 with the mixed solution 33 containing the plurality of aggregates.

[0020] (EFFECTS OF THE INVENTION)

[0021] The thermal insulation layer of the present disclosure contains a plurality of aggregates having a pore (i.e., a micropore) formed by a plurality of primary inorganic nanoparticles surrounding the pore. According to the composition of the thermal insulation layer of the present disclosure, the initial thermal conductivity can be reduced, thereby achieving high thermal insulation properties. In addition, in the thermal insulation layer, the primary inorganic nanoparticles forming the pore have a hydrophobic functional group on a surface thereof. As a result, penetration of moisture into the pore during use is suppressed, thereby suppressing pore collapse due to the penetration of moisture and pore shrinkage due to evaporation of the penetrated moisture. According to the composition of the thermal insulation layer of the present disclosure, the pore structure can be maintained, thereby suppressing a decrease in thermal insulation properties during long-term use.

[0022] In the method of manufacturing a thermal insulation layer of the present disclosure, a thermal insulation layer is formed by coating a coating liquid for forming a thermal insulation layer on a substrate in a layered manner and drying it. In this method, a coating liquid for forming a thermal insulation layer containing a plurality of aggregates and a plurality of binder resin particles in a solvent is used. Here, each aggregate has a plurality of primary inorganic nanoparticles having a hydrophobic functional group on a surface thereof and at least one pore formed by the primary inorganic nanoparticles surrounding the pore. According to the method of manufacturing a thermal insulation layer of the present disclosure, the use of the above-mentioned coating liquid to form a thermal insulation layer makes it possible to produce a thermal insulation layer that achieves high thermal insulation properties and suppresses a decrease in thermal insulation properties during long-term use.

[0023] The coating liquid for forming a thermal insulation layer of the present disclosure contains a plurality of aggregates and a plurality of binder resin particles in a solvent. Further, each aggregate has a plurality of primary inorganic nanoparticles with a hydrophobic functional group on the surface thereof and at least one hole formed by being surrounded by the primary inorganic nanoparticles. According to the composition of the coating liquid for forming a thermal insulation layer of the present disclosure, by performing a method of manufacturing a thermal insulation layer in which the coating liquid is coated on a substrate in a layered manner and dried, a thermal insulation layer capable of achieving high thermal insulation properties and suppressing a decrease in thermal insulation properties during long-term use can be formed.

[0024] The method of manufacturing a coating liquid for forming a thermal insulation layer of the present disclosure produces a coating liquid for forming a thermal insulation layer containing a plurality of aggregates and a plurality of binder resin particles in a solvent. Here, each aggregate has a plurality of primary inorganic nanoparticles with a hydrophobic functional group on the surface thereof and at least one hole formed by being surrounded by the primary inorganic nanoparticles. According to the method of manufacturing a coating liquid for forming a thermal insulation layer of the present disclosure, a coating liquid for forming a thermal insulation layer capable of achieving high thermal insulation properties and suppressing a decrease in thermal insulation properties during long-term use can be produced.

[0025] In each paragraph of the present specification, elements can be designated by bracketed reference numerals. In this case, the reference numerals indicate one example of a correspondence relationship between the same elements and a specific configuration described in the following embodiments. Therefore, the present disclosure is not limited by the reference numerals. BRIEF DESCRIPTION OF DRAWINGS

[0026] In the drawings:

[0027] Figure 1 A schematic cross-sectional view along the thickness direction of the configuration of a thermal insulation layer is shown according to an embodiment;

[0028] Figure 2A A schematic cross-sectional view along the thickness direction of the configuration of a thermal insulation layer formed on the surface of a substrate is shown according to an embodiment;

[0029] Figure 2B A diagram for illustrating a method of manufacturing a thermal insulation layer according to an embodiment.

[0030] Figure 3 A diagram for schematically showing a coating liquid for forming a thermal insulation layer (corresponding to the coating liquid for forming a thermal insulation layer of the embodiment) used in a method of manufacturing a thermal insulation layer according to an embodiment.

[0031] Figure 4 A diagram for schematically showing Figure 3 A diagram for showing a variant of the coating liquid for forming a thermal insulation layer shown in FIG. 1;

[0032] Figure 5 A diagram illustrating a method for manufacturing a coating liquid for forming an insulating layer according to an embodiment;

[0033] Figure 6 For the purpose of illustrating the implementation scheme Figure 5 A diagram showing a variation of the method for manufacturing a coating liquid used to form an insulating layer;

[0034] Figure 7 A scanning electron microscope (SEM) image of a cross section along the in-plane direction of the insulating layer formed by the coating liquid of sample 1 obtained in the experimental example.

[0035] Figure 8 A diagram illustrating the pore size distribution of the insulation layer formed by the coating liquids of samples 1 and 4 obtained in the experimental example.

[0036] Figure 9 Optical images of the surface of the insulation layer formed by the coating liquid of samples 1 and 8 obtained in the experimental example, and transmission electron microscopy (TEM) images of a cross-section along the thickness direction of the insulation layer; and

[0037] Figure 10 A diagram illustrating the pore size distribution of the insulation layer formed by the coating liquid of samples 1 and 8 as obtained in the experimental example.

[0038] [Explanation of reference numerals in the attached figures]

[0039] 1. Insulation layer

[0040] 11. Adhesive Resin

[0041] 12 aggregates

[0042] 121 Primary Inorganic Nanoparticles

[0043] 122 holes

[0044] 2. Coating liquid used to form the insulation layer

[0045] 21 Solvents

[0046] S1 First Process

[0047] S2 Second Process

[0048] S3 Third Process

[0049] 31 dispersion solution

[0050] 310 Dispersion Medium

[0051] 32 Aggregated solution

[0052] 33 Mixed solutions

[0053] 34 Aqueous resin solution Detailed Implementation

[0054] (Implementation Plan)

[0055] The following description, with reference to the accompanying drawings, illustrates the thermal insulation layer of this disclosure, its manufacturing method, and the coating liquid used to form the thermal insulation layer, as well as its manufacturing method.

[0056] The following embodiments and variations thereof, along with the accompanying drawings, are illustrative or simplified to briefly illustrate the content of this disclosure. In the following embodiments, identical or equivalent elements are designated by the same reference numerals in the drawings. The insulation layer and its manufacturing method, as well as the coating liquid for forming the insulation layer and its manufacturing method, are not limited to the embodiments described below. Furthermore, the configurations of the insulation layer and the coating liquid for forming the insulation layer in the embodiments shown below can be arbitrarily combined as needed. The processes of manufacturing the insulation layer and the coating liquid for forming the insulation layer in the embodiments shown below can be arbitrarily combined as needed. The lower and upper limits of the numerical ranges in the embodiments shown below can be arbitrarily combined as needed.

[0057] (Insulation layer)

[0058] use Figure 1 Figure 2 illustrates the insulation layer of this embodiment.

[0059] The insulation layer 1 can be formed, for example, on the surface of the substrate 4, such as... Figure 2A As shown. The insulation layer 1 may be formed to cover the entire surface of the substrate 4, or it may be formed to cover only a portion of the surface of the substrate 4. The substrate 4 may be, for example, a base material that includes at least a portion of a component or product requiring insulation. Examples of materials used for the substrate 4 include metallic materials (including alloys; described below), resin materials, rubber materials (including elastomer materials, described below), and similar materials. Figure 2A The illustration shows a case where the substrate 4 has a flat surface. The surface of the substrate 4 can have an uneven shape and is not limited to a flat surface.

[0060] The insulation layer 1 comprises an adhesive resin 11. The adhesive resin 11 comprises a plurality of aggregates (i.e., blocky material; hereinafter, sometimes referred to as "many aggregates") 12. Figure 2A Aggregate 12 is not shown. Adhesive resin 11 is part of the matrix phase (base phase) used as the insulation layer 1. Adhesive resin 11 can be selected based on the material of the substrate 4 that forms the insulation layer 1.

[0061] The adhesive resin 11 may preferably contain anionic functional groups because it exhibits favorable dispersibility in a solvent 21 containing water and alcohol. This solvent is part of the coating liquid 2 (as described later) used to form the insulating layer 1.

[0062] The adhesive resin 11 specifically comprises at least one resin selected from the group consisting of epoxy resin, urethane resin, and silicone resin. Epoxy resin has OH groups as anionic functional groups. Urethane resin has both OH and COOH groups as anionic functional groups. Silicone resin has OH groups as anionic functional groups. Therefore, epoxy resin, urethane resin, and silicone resin all have anionic functional groups. In this case, the adhesive resin 11 can achieve the aforementioned effects. When the adhesive resin 11 comprises epoxy resin, in addition to high thermal insulation (high heat resistance), it also provides advantages such as achieving an insulation layer 1 with both chemical resistance and high strength. Similarly, when the adhesive resin 11 comprises urethane resin, an insulation layer 1 with high heat resistance and abrasion resistance can be achieved. When the adhesive resin 11 comprises silicone resin, an insulation layer 1 with high toughness and high heat resistance can be achieved.

[0063] In the insulation layer 1, each aggregate (bulk material) 12 has a plurality of primary inorganic nanoparticles (hereinafter sometimes referred to as "a plurality of primary inorganic nanoparticles") 121 and at least one pore 122 formed by the plurality of primary inorganic nanoparticles 121 surrounding it. Here, primary inorganic nanoparticles 121 refer to primary particles of inorganic material at the nanoscale, which are the smallest units of solid particles and cannot be further divided into smaller blocks. Therefore, the aggregates 12 are formed by the aggregation of primary inorganic nanoparticles 121, that is, they correspond to secondary particles. In this disclosure, nanoscale (nanoscale) refers to a size in the range of 0 nm and 1000 nm or smaller. Whether a primary inorganic nanoparticle 121 is nanoscale can be determined by the value of the average particle diameter of the primary inorganic nanoparticle 121 (hereinafter referred to as "average primary particle diameter"). The average primary particle diameter of the primary inorganic nanoparticles 121 is calculated as the arithmetic mean of the primary particle diameters of 200 randomly selected primary inorganic nanoparticles 121 observed in a transmission electron microscope (TEM) image of a cross section along the thickness direction of the insulation layer 1.

[0064] Examples of primary inorganic nanoparticles 121 may include ceramic particles and similar particles. One or more types of primary inorganic nanoparticles 121 may be used in combination. When the primary inorganic nanoparticles 121 are ceramic particles, it is easy to achieve low thermal conductivity and excellent heat resistance in these nanoparticles 121. Therefore, in this case, it is advantageous to achieve low thermal conductivity and improve durability of the insulation layer 1.

[0065] Examples of ceramics that are the main components of ceramic particles may include silica, glass, bentonite and similar compounds; silica is preferred.

[0066] From the perspective of making the particles easier to handle and process, the average primary particle diameter of the primary inorganic nanoparticles 121 is preferably 5 nm or larger. Adjusting the average primary particle diameter of the primary inorganic nanoparticles 121 can make the pore size of the aggregates 12 smaller. From the perspective of making it easier to obtain an insulating layer 1 with high thermal insulation properties, the average primary particle diameter of the primary inorganic nanoparticles 121 is preferably 100 nm or smaller, more preferably 90 nm or smaller, and even more preferably 80 nm or smaller. The average primary particle diameter of the primary inorganic nanoparticles 121 is preferably 70 nm or smaller, even more preferably 60 nm or smaller, and even more preferably 50 nm or smaller.

[0067] The primary inorganic nanoparticles 121 have hydrophobic functional groups on their surface. This makes the surface of the primary inorganic nanoparticles 121 hydrophobic. The primary inorganic nanoparticles 121 may have one or more types of hydrophobic functional groups on their surface.

[0068] The hydrophobic functional group is preferably at least one of alkyl or alkoxy groups. In this case, the degree of hydrophobicity can be easily adjusted by changing the number of carbon atoms in at least one of the alkyl or alkoxy groups. From the perspective of ease of introduction and reaction efficiency, the hydrophobic functional group is preferably alkyl.

[0069] Examples of hydrophobic functional groups may include alkylsilyl, alkoxysilyl, and similar groups. Examples of alkylsilyl groups may include methylsilyl and similar groups. Alkylsilyl groups may also include, for example, any of trialkylsilyl, dialkylsilyl, and monoalkylsilyl. In this embodiment, from the viewpoint of, such as high hydrophobicity, the alkylsilyl group may preferably have a trimethylsilyl group. Examples of alkoxysilyl groups may include methoxysilyl and similar groups. Alkoxysilyl groups may also include, for example, any of trialkoxysilyl, dialkoxysilyl, and monoalkoxysilyl. In this embodiment, from the viewpoint of, such as high hydrophobicity, the alkoxysilyl group may preferably have a trimethoxysilyl group. One or more types of hydrophobic functional groups may be used in combination.

[0070] In the aggregate 12, a pore 122 is formed by a plurality of primary inorganic nanoparticles 121 with hydrophobic functional groups on their surfaces. In other words, the aggregate 12 is configured such that at least one pore 122 is held inside the aggregate 12 by a plurality of primary inorganic nanoparticles 121 with hydrophobic functional groups on their surfaces attached to each other. Thus, the plurality of primary inorganic nanoparticles 121 with hydrophobic functional groups on their surfaces are arranged around the outer periphery of the pore 122. With this configuration, moisture is prevented from permeating from the outside of the aggregate 12 into the pore 122. An aggregate 12 only needs to have at least one pore 122, and can have multiple pores 122. The insulation layer 1 may also include both aggregates 12 with at least one pore 122 and aggregates without at least one pore 122. In the insulation layer 1, the pore 122 is typically filled with atmospheric air, but may be filled with a gas other than atmospheric air (e.g., hydrocarbon gas or rare gas). Furthermore, as long as it does not impede the technical advantages provided by the insulation layer 1, a portion of the solvent 21 in the coating liquid 2 used to form the insulation layer 1 may remain in some pores 122 for manufacturing reasons.

[0071] The size of each pore 122 can preferably be nanometer-sized to achieve low thermal conductivity, etc.

[0072] From the perspective of achieving low thermal conductivity, the average pore size (average pore diameter) of the pores 122 is preferably 200 nm or smaller, more preferably 100 nm or smaller, and even more preferably 50 nm or smaller. The smaller the size of each pore 122 in the aggregate 12, the better from the perspective of thermal conductivity. Therefore, there is no particular limitation on the lower limit of the average pore size of the pores 122. However, from the perspective of manufacturing, the average pore size of the pores 122 is preferably 20 nm or larger. The average pore size of the pores 122 can be measured by mercury intrusion porosimetry. The measurement conditions for mercury intrusion porosimetry in this embodiment are an initial pressure of 4 kPa, a mercury contact angle of 130°, and a mercury surface tension of 485 dynes / cm. The average pore size of the pores 122 mentioned above specifically refers to the most common value (peak value) in the pore size distribution (also called bubble size distribution) of the insulation layer 1.

[0073] From the perspective of ensuring effective thermal insulation properties, the thickness of the insulation layer 1 is preferably 300 μm or greater, more preferably 500 μm or greater, and even more preferably 700 μm or greater. From the perspective of shortening drying time and improving productivity, the thickness of the insulation layer 1 is preferably 1500 μm or less, more preferably 1200 μm or less, and even more preferably 1000 μm or less. The thickness of the insulation layer 1 refers to the average thickness and is calculated as the arithmetic mean of 10 measurements taken arbitrarily in a cross-section along the thickness direction of the insulation layer 1.

[0074] The insulation layer 1 of this embodiment comprises numerous aggregates 12 having pores (micropores) 122 formed by a plurality of primary inorganic nanoparticles 121 in the binder resin 11. This allows for a reduction in initial thermal conductivity, thereby achieving high insulation properties. The insulation layer 1 of this embodiment also has hydrophobic functional groups on the surface of the primary inorganic nanoparticles 121 forming the pores 122. According to this configuration, moisture penetration into the pores 122 during use is suppressed, thereby suppressing the collapse of the pores 122 due to moisture penetration and the shrinkage of the pores 122 due to the evaporation of the penetrated moisture. Therefore, the insulation layer 1 of this embodiment can maintain its porous structure, thereby suppressing the degradation of insulation properties during long-term use.

[0075] The following descriptions, “(Method for manufacturing an insulation layer and coating liquid for forming an insulation layer)” and “(Method for manufacturing a coating liquid for forming an insulation layer)”, may be referenced as needed by the technology of this disclosure.

[0076] (Methods for manufacturing the insulation layer and coating liquid used to form the insulation layer)

[0077] Next, we will utilize Figure 3 and Figure 4 This embodiment describes a method for manufacturing the insulation layer 1 and a coating liquid 2 for forming the insulation layer 1. In the following description, appropriate reference will be made to the above. Figure 1 and Figure 2A .

[0078] In the method for manufacturing the insulation layer 1 according to this embodiment, the coating liquid 2 for forming the insulation layer 1 according to this embodiment is coated on the substrate 4 in a layered manner, and then the coating layer formed by the coating liquid 2 for forming the insulation layer 1 is dried to form the insulation layer 1.

[0079] Specifically, such as Figure 2B As shown, in the method of manufacturing the insulation layer 1, the coating liquid 2 used to form the insulation layer 1 is coated onto the substrate 4 (see reference 1) by various coating methods. Figure 2A A coating 3 is formed on the surface of the coating liquid 2 used to form the insulation layer 1 (first step S11). Subsequently, in the method for manufacturing the insulation layer 1, the coating 3 formed by the coating liquid 2 used to form the insulation layer 1 is dried (second step S12). As a result, the insulation layer 1 of this embodiment (refer to...) can be formed. Figure 1 and Figure 2A ).

[0080] The coating method of this embodiment may include, for example, spraying, brushing, molding by pouring into a mold, and coating by using a dispenser. Coating may be performed only once or may be performed multiple times under the same or different coating conditions.

[0081] From the perspective of shortening drying time, the drying temperature is preferably 23°C or higher, more preferably 40°C or higher, and even more preferably 60°C or higher. From the perspective of suppressing cracking during drying, the drying temperature is preferably 80°C or lower, more preferably 70°C or lower, and even more preferably 60°C or lower. Drying can be performed only once or can be performed multiple times under the same or different drying conditions.

[0082] like Figure 3 As shown, the coating liquid 2 used to form the insulation layer 1 in this embodiment contains a plurality of aggregates 12 and a plurality of binder resin particles 111 in a solvent 21.

[0083] In the coating liquid 2 used to form the insulating layer 1, the aggregate (bulk material) 12 has a plurality of primary inorganic nanoparticles 121 with hydrophobic functional groups on its surface and at least one pore 122 formed by the plurality of primary inorganic nanoparticles 121 surrounding it. Details of the aggregate 12 have already been described above; therefore, their description is omitted. In the coating liquid 2 used to form the insulating layer 1, the pore 122 may be partially filled with solvent 21. Specifically, due to the method of manufacturing the coating liquid 2 used to form the insulating layer 1, the pore 122 may be filled with alcohols, etc., as part of the solvent 21, as described later. Figure 3 In the diagram, the area filled with dots within the hole 122 indicates that the hole 122 is partially filled with solvent 21.

[0084] In the coating liquid 2 used to form the insulation layer 1, adhesive resin particles 111 constitute the adhesive resin 11 in the aforementioned insulation layer 1. Details of the adhesive resin 11 have already been described above; therefore, its description is omitted. In the coating liquid 2 used to form the insulation layer 1, one or more types of adhesive resin particles 111 may be used in combination.

[0085] In the coating liquid 2 used to form the insulating layer 1, the aggregate 12 preferably has at least a portion of its outer surface covered with a resin layer 112 composed of binder resin particles 111, such as... Figure 4 As shown. In this case, the shape of the aggregate 12 is protected by the resin layer 112 (which is formed by binder resin particles 111) covering the outer surface of the aggregate 12, and the retention of the pores 122 is improved. Therefore, the coating liquid 2 used to form the insulation layer 1 can increase the yield of manufacturing the insulation layer 1 with the above-mentioned effects.

[0086] In the coating liquid 2 used to form the insulation layer 1 in this embodiment, the solvent 21 comprises water and alcohol. Therefore, the coating liquid 2 used to form the insulation layer 1 corresponds to an aqueous coating solution.

[0087] The ratio of alcohol to all solvent 21 (hereinafter referred to as "the ratio of alcohol in solvent 21") is less than 46% by volume.

[0088] When the alcohol content in solvent 21 is 46% by volume or greater, it becomes difficult to generate aggregates 12 having pores 122 formed by a plurality of primary inorganic nanoparticles 121 surrounding them. From the viewpoint of reliably generating aggregates 12 with pores 122, the alcohol content in solvent 21 is preferably 44% by volume or less, more preferably 40% by volume or less, and even more preferably 38% by volume or less. The alcohol content in solvent 21 is preferably 35% by volume or less, and even more preferably 30% by volume or less.

[0089] In the coating liquid 2 used to form the insulating layer 1 in this embodiment, the alcohol constituting the solvent 21 is preferably a lower alcohol with 5 or fewer carbon atoms. In this case, the average pore size of the pores 122 can be smaller. Examples of lower alcohols with 5 or fewer carbon atoms include methanol, ethanol, isopropanol (IPA), butanol, pentanol, and similar alcohols. One or more types of lower alcohols with 5 or fewer carbon atoms can be used in combination.

[0090] Other materials can be added to solvent 21 as long as the solvent 21 can form the insulating layer 1 after addition. Examples of other materials may include metal salts and similar salts. The coating liquid 2 used to form the insulating layer 1 is in a microparticle dispersion state, referred to as an emulsion state. In this case, the charge (e.g., negative charge) on the surface of the binder resin particles 111 in the coating liquid 2 used to form the insulating layer 1 is neutralized by the metal salt. This disrupts the dispersion stability of some of the binder resin particles 111. The binder resin particles 111, which have become unstable in the coating liquid 2 used to form the insulating layer 1, adhere to the outer surface of the aggregate 12. Therefore, when the metal salt is added to solvent 21, it is easy to form a structure in which at least a portion of the outer surface of the aggregate 12 is covered by a resin layer 112 composed of binder resin particles 111. Therefore, in this case, the retention of pores 122 in the aggregate 12 is promoted.

[0091] Examples of metal salts may include calcium chloride, calcium sulfate, sodium chloride, magnesium chloride, magnesium sulfate, and similar salts (ionic compounds). One or more types of metal salts may be used in combination.

[0092] Examples of materials other than metal salts can include pH adjusters, such as acidic and alkaline materials.

[0093] The coating liquid 2 for forming the heat insulation layer 1 described in this embodiment can be prepared, for example, by the following method for manufacturing the coating liquid 2 for forming the heat insulation layer 1.

[0094] In the method for manufacturing the insulation layer 1 according to this embodiment, the insulation layer 1 is formed by coating a coating liquid 2 for forming the insulation layer 1 onto a substrate 4 in a layered manner and then drying it. In this method, the coating liquid 2 for forming the insulation layer 1 is used, comprising a plurality of aggregates 12 and a plurality of binder resin particles 111 contained in a solvent 21. Each aggregate 12 has a plurality of primary inorganic nanoparticles 121 with hydrophobic functional groups on its surface and at least one pore 122 formed by these primary inorganic nanoparticles 121 surrounding it. According to the method for manufacturing the insulation layer 1 according to this embodiment, forming the insulation layer 1 using the aforementioned coating liquid 2 enables the production of an insulation layer 1 that achieves high insulation properties and suppresses the degradation of insulation properties during long-term use.

[0095] The coating liquid 2 for forming the insulation layer 1 in this embodiment comprises a plurality of aggregates 12 and a plurality of binder resin particles 111 in a solvent 21. Furthermore, each aggregate 12 has a plurality of primary inorganic nanoparticles 121 with hydrophobic functional groups on its surface and at least one pore 122 formed by these primary inorganic nanoparticles 121 surrounding it. Based on the composition of the coating liquid 2 for forming the insulation layer 1 in this embodiment, by performing a method for manufacturing the insulation layer 1 in which the coating liquid 2 is coated in a layered manner onto a substrate 4 and dried, an insulation layer 1 capable of achieving high insulation properties and suppressing the degradation of insulation properties during long-term use can be formed.

[0096] The description of “(Insulation Layer)” above and the description of “(Method for Manufacturing Coating Liquid for Forming Insulation Layer)” below may be referenced as needed by the technology of this disclosure.

[0097] (Method for manufacturing a coating liquid for forming an insulating layer)

[0098] Next, we will utilize Figure 5 and Figure 6 This embodiment describes a method for manufacturing a coating liquid 2 used to form an insulating layer 1.

[0099] The method for manufacturing the coating liquid 2 used to form the insulation layer 1 in this embodiment mainly includes three steps (first step S1, second step S2 and third step S3).

[0100] The first step S1 is the process of preparing a dispersion solution 31 in which a plurality of primary inorganic nanoparticles 121 bearing hydrophobic functional groups on their surface are dispersed in a dispersion medium 310, such as... Figure 5 As shown.

[0101] Primary inorganic nanoparticles 121 with hydrophobic functional groups on their surface can be prepared by surface treatment to give the surface of the primary inorganic nanoparticles 121 hydrophobic functional groups. The detailed configuration of the primary inorganic nanoparticles 121 with hydrophobic functional groups on their surface has been described in the above description of "(insulating layer)"; therefore, its description is omitted.

[0102] From the perspective of monodispersing the inorganic nanoparticles 121, alcohols or the like can be suitably used as the dispersion medium 310. The alcohol is preferably a lower alcohol with 5 or fewer carbon atoms. In this case, the average pore size of the pores 122 in the formed aggregates 12 can be made smaller. Examples of lower alcohols with 5 or fewer carbon atoms include methanol, ethanol, isopropanol (IPA), butanol, and pentanol, as well as similar alcohols. One or more types of lower alcohols with 5 or fewer carbon atoms can be used in combination.

[0103] The second step S2 is to mix the dispersion solution 31 with the aggregation solution 32 that aggregates the dispersed primary inorganic nanoparticles 121 to produce a plurality of aggregates 12 including at least one pore 122 formed by a plurality of primary inorganic nanoparticles 121, such as... Figure 5 As shown.

[0104] From the perspective of firmly agglomerating the dispersed primary inorganic nanoparticles 121, water or the like can be appropriately used as the agglomeration solution 32. When an alcohol is used as the dispersion medium 310 and water is used as the agglomeration solution 32, the solvent 21 of the resulting coating liquid 2 used to form the insulation layer 1 is configured to contain both water and alcohol. By mixing the dispersion solution 31 and the agglomeration solution 32, the ratio of alcohol to total solvent 21 in the resulting coating liquid 2 used to form the insulation layer 1 can be adjusted so that the ratio of alcohol to total solvent 21 is less than 46% by volume.

[0105] In the second process S2, such as Figure 5 As shown, primary inorganic nanoparticles 121, already monodispersed in dispersion solution 31, aggregate by mixing with aggregation solution 32. As a result, a plurality of aggregates 12 are produced, each having a pore 122 formed by a plurality of primary inorganic nanoparticles 121 surrounding it. In this case, the aggregates 12 aggregate in dispersion solution 31. Therefore, the formed pores 122 are filled with dispersion medium 310. Figure 5 In the diagram, the area filled with dots within the hole 122 indicates that the hole 122 is filled with the dispersion medium 310.

[0106] The third step S3 is the step of mixing an aqueous solution (hereinafter referred to as "aqueous resin solution") 34 containing binder resin particles 111 with a mixed solution 33 containing a plurality of aggregates 12, as follows: Figure 5 As shown.

[0107] The binder resin particles 111 contained in the aqueous resin solution 34 constitute the binder resin 11 in the insulation layer 1 formed by the coating liquid 2 obtained for forming the insulation layer 1. The details of the binder resin 11 composed of the binder resin particles 111 have been described in the above description of "(Insulation Layer)"; therefore, its description is omitted.

[0108] Various coating methods are used to coat the coating liquid 2, which is produced by performing the first step S1 to the third step S3, for forming the heat insulation layer 1, onto the surface of the substrate 4, such as... Figure 2B As shown. As a result, coating 3 is formed. The formed coating 3 is then dried to form insulation layer 1, as shown. Figure 5 As shown.

[0109] This method of manufacturing the coating liquid 2 used to form the insulation layer 1 may, for example, include a fourth step S4, such as... Figure 6 As shown.

[0110] The fourth step, S4, involves mixing the metal salt 35 with a mixed solution 33 in which an aqueous resin solution 34 is mixed. When the method for manufacturing the coating liquid 2 for forming the insulation layer 1 includes the fourth step, S4, the metal salt 35 enables the binder resin particles 111 dispersed in the mixed solution 33 to adhere to the outer surface of the aggregate 12. The metal salt 35 neutralizes the surface charge (e.g., negative charge) of the binder resin particles 111 in the mixed solution 33 containing the aqueous resin solution 34, which is in an emulsion state. This disrupts the dispersion stability of some of the binder resin particles 111. The binder resin particles 111, which have become unstable in the mixed solution 33, adhere to the outer surface of the aggregate 12. Therefore, when the method for manufacturing the coating liquid 2 for forming the insulation layer includes the fourth step, it is easy to form a structure in which at least a portion of the outer surface of the aggregate 12 is covered by a resin layer 112 composed of binder resin particles 111. Using this manufacturing method, the retention of pores 122 in the aggregate 12 is promoted.

[0111] Examples of metal salts 35 may include calcium chloride, calcium sulfate, sodium chloride, magnesium chloride, magnesium sulfate, and similar compounds. One or more types of metal salts 35 may be used in combination. For example, metal salt 35 may be mixed with mixed solution 33 as an aqueous solution containing the metal salt.

[0112] Various coating methods are used to coat the coating liquid 2, which is used to form the heat insulation layer 1 and is produced by performing the first step S1 to the fourth step S4, onto the surface of the substrate 4, such as... Figure 2B As shown. As a result, coating 3 is formed. The formed coating 3 is then dried to form insulation layer 1, as shown. Figure 6 As shown. Note that in the above...Figure 5 and Figure 6 The illustration corresponding to the aggregate 12 in the insulation layer 1 is omitted.

[0113] As described above, the method of manufacturing the coating liquid 2 for forming the insulation layer 1 according to this embodiment produces a coating liquid 2 for forming the insulation layer 1 containing a plurality of aggregates 12 and a plurality of binder resin particles 111 in a solvent 21. Here, each aggregate 12 has a plurality of primary inorganic nanoparticles 121 with hydrophobic functional groups on its surface and at least one pore 122 formed by these primary inorganic nanoparticles 121 surrounding it. According to the method of manufacturing the coating liquid 2 for forming the insulation layer 1 according to this embodiment, a coating liquid 2 for forming an insulation layer 1 capable of achieving high insulation properties and suppressing the degradation of insulation properties during long-term use can be produced.

[0114] (Experimental Example)

[0115] <Preparation of Sample 1>

[0116] Sample 1 was prepared as follows. First, ethanol was added to nano-silica with an average primary particle diameter of 40 nm (manufactured by AEROSIL Japan, Inc., a registered trademark), whose surface was treated with trimethylsilyl groups. After addition, the ethanol was stirred with a stirrer until the nano-silica was uniformly dispersed. Thus, a dispersion solution was prepared in which a number of primary inorganic nanoparticles (primary nano-silica particles) with trimethylsilyl groups on their surface were dispersed in ethanol.

[0117] Then, over a period exceeding 5 minutes, deionized water (ion-exchanged water) was dropwise added to a dispersion solution (i.e., an aqueous solution containing ethanol) in which the primary inorganic nanoparticles were uniformly dispersed, to achieve an ethanol concentration of 24% by volume (the ratio of alcohol in the solvent). This solution was then stirred for 5 minutes to prepare an aggregated solution. Thus, a first mixed solution consisting of a slurry of water and ethanol was prepared, containing numerous aggregates obtained by agglomerating the dispersed primary inorganic nanoparticles.

[0118] Next, deionized water was added to the urethane resin emulsion (PERMARIN UA-368 manufactured by Sanyo Chemical Industries, Ltd.) to achieve a solid content of 20 parts by weight. The solution was then stirred. This prepared an aqueous resin solution containing binder resin particles. This aqueous resin solution was then added dropwise to the first mixed solution above over a period of more than 5 minutes to achieve a binder resin content of 25 parts by weight for every 100 parts by weight of primary inorganic nanoparticles. The solution was then stirred for 5 minutes. Thus, the aqueous resin solution containing binder resin particles was mixed with the mixed solution containing numerous aggregates to prepare a second mixed solution.

[0119] Next, deionized water was added to calcium chloride, which is a metal salt, and the mixture was stirred. Thus, an aqueous solution containing 10% by mass calcium chloride (hereinafter, for convenience, referred to as "aqueous calcium chloride solution") was prepared. Then, this aqueous calcium chloride solution was added dropwise to the second mixed solution above over a period of more than 5 minutes to achieve a calcium chloride content of 1.2 parts by mass for 100 parts by mass of primary inorganic nanoparticles. The solution was then stirred for 5 minutes. Thus, calcium chloride, as a metal salt, was mixed with the second mixed solution above.

[0120] The coating liquid for forming the insulating layer of sample 1 was prepared as described above.

[0121] Next, the prepared coating solution was poured into a mold, and the mold was placed in an oven with a hot air circulation structure at 80°C for 1 hour to dry. Then the temperature was raised to 100°C, and the mold was dried for another hour. This yielded a 200 μm thick film-like heat insulation layer for sample 1.

[0122] <Preparation of Samples 2 to 4>

[0123] The difference in preparation conditions between samples 2 to 4 and sample 1 lies in the change of the average primary particle diameter of the primary inorganic nanoparticles, as shown in Table 1. Except for the aforementioned points, samples 2 to 4 were prepared under the same conditions as sample 1; thus, the coating liquids and insulation layers of samples 2 to 4 were obtained.

[0124] <Preparation of Sample 5>

[0125] The difference in preparation conditions between Sample 5 and Sample 1 lies in the use of nano-silica with a dimethylsilyl-treated surface (“AEROSIL” (registered trademark) manufactured by AEROSIL Japan, Inc.) instead of nano-silica with a trimethylsilyl-treated surface. Apart from the foregoing points, Sample 5 was prepared under the same conditions as Sample 1; thus, the coating liquid and insulating layer of Sample 5 were obtained.

[0126] <Preparation of Sample 6>

[0127] The difference in preparation conditions between Sample 6 and Sample 1 is that an aqueous isopropanol (IPA) solution was used instead of an aqueous ethanol solution. Apart from the aforementioned points, Sample 6 was prepared under the same conditions as Sample 1; thus, the coating liquid and the insulating layer of Sample 6 were obtained.

[0128] <Preparation of Sample 7>

[0129] The difference in preparation conditions between Sample 7 and Sample 1 is that octanol solution was used instead of ethanol solution. Apart from the aforementioned points, Sample 7 was prepared under the same conditions as Sample 1; thus, the coating solution and insulation layer of Sample 7 were obtained.

[0130] <Preparation of Sample 8>

[0131] The difference in preparation conditions between Sample 8 and Sample 1 is that an aqueous solution containing calcium chloride (a metal salt) was not added to the second mixed solution containing the aqueous resin solution. Apart from the aforementioned point, Sample 8 was prepared under the same conditions as Sample 1; thus, the coating liquid and the insulation layer of Sample 8 were obtained.

[0132] <Preparation of Sample 1C>

[0133] Sample 1C was prepared according to Example 5 described in JP 2022-055295A (Japanese Unexamined Patent Application Publication No. 2022-055295). Specifically, an insulating composition having silica aerogel was prepared and used as a coating liquid for sample 1C. An insulating layer for sample 1C was formed by using the coating liquid of sample 1C.

[0134] <Preparation of Sample 2C>

[0135] The difference in preparation conditions between Sample 2C and Sample 1 lies in the use of nano-silica (manufactured by AEROSIL Japan, Inc., a registered trademark) without hydrophobic functional group treatment on its surface instead of nano-silica with trimethylsilyl treatment on its surface. Apart from the aforementioned points, Sample 2C was prepared under the same conditions as Sample 1; thereby, a coating liquid and a heat insulation layer for Sample 2C were obtained.

[0136] <Preparation of Sample 3C>

[0137] The difference in preparation conditions between Sample 3C and Sample 1 lies in that, for a period exceeding 5 minutes, ion-exchanged water, serving as the aggregation solution, was dropwise added to an ethanol solution (dispersion solution) in which the inorganic nanoparticles were uniformly dispersed once, to achieve an ethanol concentration of 46% by volume. This solution was then stirred for 5 minutes. Apart from the aforementioned points, Sample 3C was prepared under the same conditions as Sample 1; thus, a coating solution and an insulating layer for Sample 3C were obtained.

[0138] <Various Assessments>

[0139] - Pore Formation -

[0140] Transmission electron microscopy (TEM) was used to capture cross-sectional images along the thickness direction of the insulation layer of the sample, and the cross-section was observed in the captured images. This determined the presence or absence (yes / no) of aggregates (bulk materials) with micropores formed by numerous primary inorganic nanoparticles. If aggregates with micropores were found to be present in the insulation layer, it could be inferred that the aggregates contained in the coating liquid used to form the insulation layer also had pores.

[0141] A portion of the insulation layer of the sample was cut and used as a sample for pore size measurement. The pore size distribution of the sample used for measurement was measured by mercury intrusion porosimetry using a pore size distribution measuring device (“Autopore V9620”, manufactured by Micromeritics Instrument Corporation). The measurement conditions for mercury intrusion porosimetry were as follows: initial pressure of 4 kPa, mercury contact angle of 130°, and mercury surface tension of 485 dynes / cm. The most common value (peak) in the pore size distribution (bubble size distribution) of the insulation layer was defined as the average pore size contained in the aggregates of the insulation layer.

[0142] If pores are determined to exist in the aggregate, the evaluation result is designated as "A" when the average pore size is 200 nm or less, and as "B" when the average pore size exceeds 200 nm.

[0143] - Thermal insulation properties -

[0144] The thermal conductivity of the insulation layer of the sample was measured using an HFM436 instrument manufactured by NETZSCH Corporation. The measurement conditions were room temperature (23℃ ± 3℃).

[0145] When the thermal conductivity of the insulation layer is 0.03 W / m•K or less, the evaluation result is designated as "A", indicating excellent insulation properties. When the thermal conductivity of the insulation layer is in the range of 0.1 W / m•K or less than 0.03 W / m•K, the evaluation result is designated as "B", indicating moderate insulation properties. When the thermal conductivity of the insulation layer is greater than 0.1 W / m•K, the evaluation result is designated as "C", indicating poor insulation properties.

[0146] - Durability-

[0147] The insulation layer of the sample was placed in a constant temperature and humidity chamber and exposed to 85°C and 85% RH for 1000 hours. Then, the insulation layer was dried in an oven with a hot air circulation structure at 100°C for 6 hours. This produced the insulation layer obtained after the durability treatment. The thermal conductivity of the insulation layer after the durability treatment was measured in the same manner as the method used to evaluate the insulation properties.

[0148] Compare the thermal conductivity of the insulation layer before and after the durability treatment. When the increase in thermal conductivity is less than 20%, the evaluation result is designated as "A," indicating that the reduction in insulation properties during long-term use has been suppressed. When the increase in thermal conductivity is 20% or greater, the evaluation result is designated as "C," indicating that the reduction in insulation properties during long-term use has not been suppressed. The increase in thermal conductivity is calculated using the following formula: 100 × (|(thermal conductivity of insulation layer after durability treatment - thermal conductivity of insulation layer before durability treatment)| / (thermal conductivity of insulation layer before durability treatment)). In the formula, "||" represents an absolute value.

[0149] Table 1 presents the detailed composition of the coating solution for each sample and various evaluation results. Furthermore, Figures 7-10 Examples of SEM images, optical images, TEM images, pore size distribution, etc., of the insulating layer formed by the coating liquid for each sample are shown. Figure 7 This is a SEM image of a cross-section along the in-plane direction of the insulation layer formed by the coating liquid of sample 1. Figure 8 A diagram showing the pore size distribution of the insulation layer formed by the coating liquids of samples 1 and 4. Figure 9 Optical images of the surface of the insulation layer formed by the coating liquid of samples 1 and 8, and TEM images of the cross section along the thickness direction of the insulation layer. Figure 10 A diagram showing the pore size distribution of the insulation layer formed by the coating liquids of samples 1 and 8.

[0150] [Table 1]

[0151]

[0152]

[0153] As shown in Table 1 andFigures 7-10 As shown, the following can be observed. The insulation layer of sample 1C is formed using a coating solution containing silica aerogel. Silica aerogel is a highly porous material. Therefore, the insulation layer of sample 1C formed using this coating solution has low thermal conductivity. However, the insulation layer of sample 1C exhibits low insulation performance during long-term use (durability assessment result: C). This is because the pore structure of the silica aerogel is disrupted due to pore collapse caused by moisture penetration and pore shrinkage caused by the evaporation of moisture that has penetrated into the pores.

[0154] In sample 2C, the primary inorganic nanoparticles used in the coating solution do not possess hydrophobic functional groups on their surface. The insulation layer of sample 2C formed using this coating solution exhibits low insulation properties during long-term use (durability assessment result: C). This is because the pore structure cannot be maintained due to pore collapse caused by moisture penetration and pore shrinkage caused by the evaporation of moisture that has penetrated into the pores.

[0155] In sample 3C, the ratio of alcohol to total solvent in the coating solution is 46% by volume or greater. The insulating layer of sample 3C formed using this coating solution exhibits high thermal conductivity and low insulation properties (insulation property evaluation result: C). This is because, due to the alcohol-to-solvent ratio of 46% by volume or greater in the coating solution, aggregates (bulk materials) with pores formed through numerous primary inorganic nanoparticles in the coating solution cannot be formed.

[0156] In contrast, in samples 1 to 8, a coating liquid meeting the conditions specified in this disclosure was prepared and used to form an insulation layer. Based on the insulation layers of samples 1 to 8, it has been determined that high insulation properties can be achieved and that the degradation of insulation properties during long-term use can be suppressed (insulation property evaluation result: A or B, durability evaluation result: A).

[0157] Comparing samples 1 to 8, when the average primary particle diameter of the inorganic nanoparticles is 100 nm or less, the pore size in the aggregates (bulk materials) can be reduced. As a result, it is easier to obtain an insulating layer with high thermal insulation properties. Similarly, when using lower alcohols with 5 or fewer carbon atoms as the alcohol in the coating solution, the pore size in the aggregates can be reduced. As a result, it is easier to obtain an insulating layer with high thermal insulation properties.

[0158] The technology disclosed herein is not limited to the above implementation schemes and experimental examples. Various modifications can be made to the technology disclosed herein without departing from its essence. The elements described in the above implementation schemes and experimental examples can be combined with each other, as long as there is no technical contradiction between them.

[0159] The following supplementary notes are provided regarding the technology disclosed herein.

[0160] <Supplementary Notes>

[0161] (Supplementary Note 1)

[0162] An insulating layer 1 is provided, comprising an adhesive resin 11 containing a plurality of aggregates 12, wherein

[0163] The aggregate has a plurality of primary inorganic nanoparticles 121 with hydrophobic functional groups on its surface and at least one pore 122 formed by the plurality of primary inorganic nanoparticles surrounding it.

[0164] (Supplementary Note 2)

[0165] According to Supplementary Explanation 1, the primary inorganic nanoparticles in the insulation layer are ceramic particles.

[0166] (Supplementary Note 3)

[0167] According to Supplementary Note 1 or 2, the insulation layer wherein the average primary particle diameter of the primary inorganic nanoparticles is in the range of 5 nm or greater and 100 nm or less.

[0168] (Supplementary Note 4)

[0169] According to any one of the supplementary descriptions 1 to 3, the insulation layer has pores with nanometer-sized pores.

[0170] (Supplementary Note 5)

[0171] According to any one of Supplementary Notes 1 to 4, the thermal insulation layer wherein the hydrophobic functional group has at least one of alkyl or alkoxy groups.

[0172] (Supplementary Note 6)

[0173] According to any one of Supplementary Notes 1 to 5, the insulation layer contains an adhesive resin comprising at least one resin selected from the group consisting of epoxy resin, urethane resin and silicone resin.

[0174] (Supplementary Note 7)

[0175] A method for manufacturing the insulation layer 1 is provided, including:

[0176] In the first step S11, the coating liquid 2 used to form the heat insulation layer is applied to the substrate 4 in a layered manner to form the coating 3; and

[0177] In the second step S12, the coating formed using the coating liquid is dried to form an insulating layer, wherein...

[0178] In the first step, the following coating liquid for forming an insulating layer is used to form a coating, wherein...

[0179] The coating liquid used to form the insulation layer comprises a plurality of aggregates 12 and a plurality of binder resin particles 111 in solvent 21.

[0180] The aggregate has a plurality of primary inorganic nanoparticles 121 with hydrophobic functional groups on its surface and at least one pore 122 formed by the plurality of primary inorganic nanoparticles surrounding it.

[0181] The solvent contains water and alcohol, as well as

[0182] The ratio of alcohol to total solvent is less than 46 by volume.

[0183] (Supplementary Note 8)

[0184] A coating liquid 2 for forming an insulating layer is provided, comprising a plurality of aggregates 12 and a plurality of binder resin particles 111 in a solvent 21, wherein

[0185] The aggregate has a plurality of primary inorganic nanoparticles 121 with hydrophobic functional groups on its surface and at least one pore 122 formed by the plurality of primary inorganic nanoparticles surrounding it.

[0186] The solvent contains water and alcohol, and

[0187] The ratio of alcohol to total solvent is less than 46 by volume.

[0188] (Supplementary Note 9)

[0189] According to the coating liquid described in Supplementary Note 8, at least a portion of the outer surface of the aggregate is covered by a resin layer 112 composed of binder resin particles.

[0190] (Supplementary Note 10)

[0191] According to Supplementary Note 8 or 9, the coating liquid contains a lower alcohol having 5 or fewer carbon atoms.

[0192] (Supplementary Note 11)

[0193] A method for manufacturing a coating liquid for forming an insulating layer is provided, comprising:

[0194] The first step S1 is to prepare a dispersion solution 31 in which a plurality of primary inorganic nanoparticles 121 with hydrophobic functional groups on their surface are dispersed in a dispersion medium 310.

[0195] The second step S2 involves mixing the prepared dispersion solution with an aggregation solution 32 used to aggregate the dispersed primary inorganic nanoparticles to produce a plurality of aggregates 12 comprising at least one pore 122 formed by a plurality of primary inorganic nanoparticles; and

[0196] In the third step S3, an aqueous solution 34 containing a plurality of binder resin particles 111 is mixed with a mixed solution 33 containing a plurality of aggregates.

[0197] (Supplementary Note 12)

[0198] The method for manufacturing a coating liquid for forming an insulating layer, as described in Supplementary Note 11, further includes a fourth step S4, in which a metal salt 35 is mixed in a mixed solution containing an aqueous resin solution.

Claims

1. An insulating layer (1) comprising a binder resin (11) containing a plurality of aggregates (12), wherein the aggregate has a plurality of primary inorganic nanoparticles (121) with a hydrophobic functional group on a surface thereof and at least one hole (122) formed by the plurality of primary inorganic nanoparticles being surrounded.

2. The insulating layer according to claim 1, wherein the primary inorganic nanoparticles are ceramic particles.

3. The insulating layer according to claim 1 or 2, wherein an average primary particle diameter of the primary inorganic nanoparticles is in a range of 5 nm or more and 100 nm or less.

4. The insulating layer according to claim 1 or 2, wherein a size of the hole is a nanometer size.

5. The insulating layer according to claim 1 or 2, wherein the hydrophobic functional group has at least one of an alkyl group or an alkoxy group.

6. The insulating layer according to claim 1 or 2, wherein the binder resin comprises at least one resin selected from a group including an epoxy resin, an urethane resin, and a silicone resin.

7. A method of manufacturing an insulating layer (1), comprising: a first step (S11) of coating a substrate (4) with a coating liquid (2) for forming the insulating layer in a layered manner to form a coating layer (3); and a second step (S12) of drying the coating layer formed with the coating liquid to form the insulating layer, wherein in the first step, the coating layer is formed using the coating liquid for forming the insulating layer, wherein the coating liquid for forming the insulating layer contains a plurality of aggregates (12) and a plurality of binder resin particles (111) in a solvent (21), the aggregate has a plurality of primary inorganic nanoparticles (121) with a hydrophobic functional group on a surface thereof and at least one hole (122) formed by the plurality of primary inorganic nanoparticles being surrounded, the solvent contains water and an alcohol, and a ratio of the alcohol with respect to the total solvent is less than 46% by volume.

8. A coating liquid (2) for forming an insulating layer, containing a plurality of aggregates (12) and a plurality of binder resin particles (111) in a solvent (21), wherein the aggregate has a plurality of primary inorganic nanoparticles (121) with a hydrophobic functional group on a surface thereof and at least one hole (122) formed by the plurality of primary inorganic nanoparticles being surrounded, the solvent contains water and an alcohol, and a ratio of the alcohol with respect to the total solvent is less than 46% by volume.

9. The coating liquid according to claim 8, wherein at least a part of an outer surface of the aggregate is covered with a resin layer (112) composed of the binder resin particles.

10. The coating liquid according to claim 8 or 9, wherein the alcohol is a lower alcohol having a carbon number of 5 or less.

11. A method of manufacturing a coating liquid for forming an insulating layer, comprising: a first step (S1) of preparing a dispersion solution (31) in which a plurality of primary inorganic nanoparticles (121) with a hydrophobic functional group on a surface thereof are dispersed in a dispersion medium (310). ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ a second step (S2) of producing a plurality of aggregates (12) including at least one hole (122) formed of the plurality of primary inorganic nanoparticles by mixing the prepared dispersion solution with an aggregation solution (32) for aggregating the dispersed primary inorganic nanoparticles; and a third step (S3) of mixing an aqueous solution (34) containing a plurality of binder resin particles (111) with the mixed solution (33) containing the plurality of aggregates.

12. The method of manufacturing a coating liquid for forming an insulating layer according to claim 11, further comprising a fourth step (S4) of mixing a metal salt (35) in the mixed solution in which the aqueous resin solution is mixed.

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