JP7849966B2 - Adhesive sheet - Google Patents

Description

This invention relates to an adhesive sheet.

Leveraging the cushioning properties of foam, laminates of foam and tape are used in a wide range of applications, including automotive interior and exterior materials, building materials, and electrical products. For example, foam tapes with low-density foam are used to reduce the weight of automobiles. Some also offer added functionality, such as impact resistance.

Patent No. 4847324 Japanese Patent Publication No. 2010-95722

The present invention aims to provide a novel adhesive sheet with excellent thermal insulation performance and shape conformability.

The inventors of this invention have found that the above problems can be solved by using an aerogel composite material, in which aerogel is filled inside an open-cell resin foam, as the base material for the adhesive sheet. That is, the present invention relates to an adhesive sheet comprising a base material and an adhesive layer provided on one or both sides of the base material, characterized in that the base material is an aerogel composite material in which aerogel is filled inside an open-cell resin foam.

According to the present invention, it is possible to provide an adhesive sheet with excellent heat insulation performance and excellent shape conformability. Therefore, for example, when assembling it onto a curved object to be insulated, the problem of gaps forming can be avoided or mitigated.

The adhesive sheet according to the present invention comprises a base material and an adhesive layer provided on one or both sides of the base material. Here, the adhesive sheet according to the present invention may consist only of the base material and the adhesive layer, or it may have other components. Furthermore, the term "sheet" as used in this specification and in the claims includes concepts such as "film" and "tape." Each element will be described in detail below.

<<<<Base material>>>>
The substrate according to the present invention comprises an open-cell resin foam and an aerogel filled inside the open-cell resin foam. Each element will be described in detail below. In the following description, foam, resin foam, etc. may be used interchangeably.

The average filling rate (the percentage of volume occupied by the filled aerogel within each individual bubble (cell) in the aerogel foam is not particularly limited, but can be between 50% and 100%, more preferably between 70% and 100%, and even more preferably between 90% and 100%. When the average filling rate of the aerogel falls within this range, it is possible to provide an adhesive sheet with excellent thermal insulation performance and superior shape conformability.

The thickness of the base material may be 0.05 mm or more, 0.10 mm or more, 0.20 mm or more, 0.50 mm or more, 0.75 mm or more, or 1.00 mm or more. It may also be 40.0 mm or less, 30.0 mm or less, 20.0 mm or less, 10.0 mm or less, 5.00 mm or less, 4.00 mm or less, 3.00 mm or less, or 2.00 mm or less. The above are examples illustrating the thickness of the base material (aerogel composite). On the other hand, the thickness of the foam, which is the raw material for the base material, may be any of the above thicknesses.

<<<Aerogel>>>
Aerogels are not particularly limited and include, for example, low-density dry gels, specifically aerogels obtained using supercritical fluid drying, as well as xerogels obtained through conventional drying processes and cryogels obtained through freeze-drying.

<<Aerogel Ingredients>>
Any suitable aerogel component can be used as the aerogel. For example, inorganic aerogels such as silica aerogel and alumina aerogel, organic aerogels such as resorcinol-formaldehyde aerogel (RF aerogel) and cellulose nanofiber aerogel (CNF aerogel), carbon aerogels, and mixtures thereof can be selected. Silica aerogel containing silica ( _SiO₂ ) can be preferably used as the aerogel.

Aerogels are typically formed by filling a sol solution, which is a precursor to aerogel, into an open-cell resin foam, where the solution gels and dries within the foam. The gel fracture strength of the wet gel before drying is preferably 10–100 kPa, more preferably 20–60 kPa, and even more preferably 30–50 kPa. Here, "gel fracture strength" is the value measured when a test specimen with a diameter of 50 mm and a thickness of 10 mm is compressed at a speed of 1 mm/min and its strength at the time of collapse is measured.

<<Structure/Physical Properties/Properties of Aerogel>>
<Pore diameter of aerogel>
The pore size of the aerogel is preferably 70 nm or less, more preferably 60 nm or less, and even more preferably 50 nm or less. Here, "pore size" is the value measured using a pore distribution measuring device (for example, BELSORP MINI manufactured by Microtrac-BEL) in accordance with JIS Z8831-2 "Pore size distribution and pore characteristics of powders (solids) - Part 2: Measurement method for mesopores and macropores by gas adsorption". When the pore size is within this range, it is possible to provide an adhesive sheet with excellent thermal insulation performance and superior shape conformability.

<Hydrophobic specific surface area ratio>
The hydrophobic specific surface area ratio of the aerogel composite material is preferably 1.0 or less, more preferably 0.5 or less, and even more preferably 0.1 or less. The lower limit is not particularly limited and is greater than 0 (e.g., 0.01, 0.001). When within this range, it is possible to provide an adhesive sheet that has excellent thermal insulation performance and particularly excellent shape conformability. Here, the "hydrophobic specific surface area ratio" is calculated from the BET specific surface area values obtained by the adsorption method of water vapor and nitrogen gas, measured using a pore distribution measuring device (e.g., BELSORP MINI II manufactured by Microtrac-BEL) in accordance with JIS Z8831-2 "Pore size distribution and pore characteristics of powders (solids) - Part 2: Measurement method of mesopores and macropores by gas adsorption" (hydrophobic specific surface area ratio = BET specific surface area of water vapor / BET specific surface area of nitrogen).

The hydrophobic specific surface area ratio is an indicator of hydrophobicity; a smaller value indicates higher hydrophobicity. This hydrophobic specific surface area ratio can be adjusted by changing the hydrophobic treatment conditions, such as the type and amount of hydrophobic agent and catalyst, treatment temperature, and treatment time. For example, adding an acid catalyst to the hydrophobic treatment solution can increase the hydrophobicity of the aerogel surface, thereby suppressing the decrease in thermal insulation performance due to aerogel shrinkage. It can also be adjusted by changing the type of raw materials and substrate that constitute the aerogel.

<Weight reduction rate of aerogel>
The aerogel preferably has a weight loss rate of less than 15% at 300°C (heating rate of 10°C per minute, temperature increased from 20°C to 300°C) measured using a differential thermogravimetric analyzer (e.g., STA7200 manufactured by Hitachi High-Tech Science Corporation) in accordance with JIS K-7120, and more preferably 5% or less. By using such an aerogel, it is possible to provide an adhesive sheet with excellent heat insulation performance and superior shape conformability.

Furthermore, the weight loss rate of aerogels can be adjusted by the type and amount of raw materials used, the degree of polymerization of the polymer, etc. For example, in the case of silica aerogels, it can be adjusted by selecting the silica component (monomer or oligomer). More specifically, by using oligomers of tetramers or higher as raw materials and increasing the degree of polymerization of the polymer component, it is possible to suppress the weight loss rate of the aerogel. Additionally, by adjusting the type and ratio of solvents, and the type and amount of catalysts used, the degree of polymerization of the polymer component can also be increased, thereby suppressing the weight loss rate of the aerogel.

<<<Foam>>>
The foam is an open-cell resin foam having an open-cell structure. By using an open-cell resin foam, it is possible to provide an adhesive sheet with excellent heat insulation performance and superior shape conformability.

<<Ingredients of the foam>>
The resin components constituting the foam are not particularly limited and can be known resin components, but it is preferable that it contains one or more resin components selected from the group consisting of polyolefin resins, polystyrene resins, polyester resins, polyether resins, acrylic resins, polyamide resins, polyimide resins, urethane resins, vinyl chloride resins, polycarbonate resins, fluororesins, silicone resins, melamine resins, and rubber. Furthermore, it is more preferable that these resins have a softening temperature of 200°C or less. In other words, it is particularly preferable that the foam is a polyolefin resin foam, polystyrene resin foam, polyester resin foam, polyether resin foam, acrylic resin foam, polyamide resin foam, vinyl chloride resin foam, polycarbonate resin foam, or fluororesin foam, all of which have a softening temperature of 200°C or less.

<<Physical properties/characteristics of foam>>
<Air permeability of foam>
The air permeability of the foam is preferably 0.01 ^cm³ / ^cm² /sec or higher, 0.5 ^cm³ / ^cm² /sec or higher, 10 ^cm³ / ^cm² /sec or higher, or 25 ^cm³ / ^cm² /sec or higher. Furthermore, the upper limit of the air permeability is not particularly limited, as a higher value is always better, but a suitable upper limit for the air permeability of the foam is, for example, 300 ^cm³ / ^cm² /sec.

Such air permeability can be measured by known methods and is not particularly limited. For example, it can be measured using the method described in JIS L1096-7:2010 "Testing methods for woven and knitted fabrics: Method A (Fragile method)". If the measured air permeability (or air permeability) of the resin foam is 0.01 ^cm³ / ^cm² /sec or higher, the resin foam is judged to have a certain degree of air permeability.

In particular, when the vacuum level is 10 ^cm³ / ^cm² /sec or higher, the substrate (aerogel composite) does not require the time-consuming vacuuming process described later in the sol solution filling step, making it possible to manufacture it efficiently.

<Density of foam>
The density of the foam may be 0.020 g/ ^cm³ or more, 0.030 g/ ^cm³ or more, 0.040 g/ ^cm³ or ^more , 0.050 g/cm³ or ^more , 0.075 g/ ^cm³ or more, 0.100 g/ ^cm³ or more, 0.120 g/ ^cm³ or more, or 0.50 g/cm³ ^or less, 0.40 g/ ^cm³ or less, 0.275 g/cm³ ^or less, 0.250 g/cm³ or ^less , 0.240 g/cm³ ^or less, 0.230 g/ ^cm³ or less, 0.220 g/ ^cm³ or less, 0.210 g/cm³ or less, or 0.200 g/ ^cm³ or less. By setting the density of the foam within this range, it is possible to control the amount of aerogel filling to have excellent thermal insulation performance while also creating an aerogel composite material with excellent flexibility. Here, "density" as used herein refers to a value measured in accordance with JIS K 7222:2005 "Foamed plastics and rubber - Method for determining apparent density".

<<Preferred structure of foam (open-cell resin foam with skin)>>
Preferably, the foam is a surfaced open-cell resin foam (hereinafter sometimes simply referred to as "resin foam") having a foam layer with open cells and a surface layer provided on the side facing the adhesive layer. The presence of the surface layer suppresses adhesion inhibition by aerogel particles and allows the foam to be attached to the object to be adhered without gaps, making it possible to provide an adhesive sheet with excellent heat insulation performance and superior shape conformability.

The average cell diameter (RB) of the open-cell structure in a cross-section perpendicular to the surface of the epidermal layer is not particularly limited, but can be, for example, 5 μm to 300 μm, preferably 5 μm to 200 μm, and more preferably 5 μm to 100 μm.

Furthermore, the size of the aerogel contained within the open-cell network is constrained by the average cell diameter of this network, resulting in a correspondingly larger aerogel size. When the average cell diameter falls within this range, it becomes possible to provide an adhesive sheet with excellent thermal insulation performance and superior shape conformability.

The open-cell resin foam with a skin comprises a foam layer having open cells as described above, and a breathable skin layer formed on the side facing the adhesive layer. Furthermore, commercially available open-cell resin foams with a skin can be used.

The surface layer is formed, for example, when a foamed composition is supplied onto a PET sheet or the like and molded into a sheet of the desired thickness using known means such as a doctor knife or doctor roll. The surface of the foam layer in contact with the PET sheet and coating tools such as the doctor knife undergoes a change in quality, thus forming the surface layer.

Furthermore, the surface layer can also be formed by creating a foam layer with open cells and then subjecting that foam layer to heat treatment using a hot press or hot roll machine.

Since the foam layer and the skin layer are integrated, the open-cell bubbles in the foam layer and the open-cell bubbles in the skin layer are in communication, and the foam layer also possesses breathability. In other words, even as an open-cell resin foam with a skin, it is breathable.

When the foam includes a surface layer, the thickness of the aerogel composite material (substrate) is the sum of the thickness of the surface layer and the thickness of the foam layer.

The thickness of the epidermal layer is not particularly limited; for example, it can be 0.01 to 30 μm, preferably 0.01 to 15 μm, and more preferably 0.01 to 10 μm. When the thickness of the epidermal layer falls within this range, the powder shedding prevention properties are enhanced.

Furthermore, the epidermal layer contains open-cell structures, including those that reach the surface of the epidermal layer. Therefore, the epidermal layer can permeate the outside air; in other words, it is breathable.

Furthermore, the open-cell bubbles in the epidermal layer and the open-cell bubbles in the foam layer are connected by through-holes, allowing fluids such as outside air to pass between the open-cell bubbles in the epidermal layer and the open-cell bubbles in the foam layer.

While the air permeability of the epidermal layer alone cannot be measured, the air permeability of the epidermal layer can be determined by measuring the air permeability of the open-cell resin foam with the epidermal layer through its surface.

The porosity of a skinned, open-cell resin foam is calculated by dividing the apparent density of the foamed, open-cell resin foam by the density of the unfoamed raw resin, subtracting this divisor from 1, and obtaining the percentage. The measurement of apparent density conforms to JIS K7222:2005 "Foamed Plastics and Rubber - Method for Determining Apparent Density."

The void ratio is not particularly limited; for example, it can be 50-99%, preferably 65-99%, and more preferably 85-99%. When the void ratio falls within this range, it is possible to provide an adhesive sheet with excellent thermal insulation performance and superior shape conformability. The preferred void ratio here refers to a suitable value for open-cell resin foam (regardless of whether it has a surface or not).

<<
<25% compression load of the base material>
The 25% compressive load of the base material (aerogel composite) is preferably 10 to 1000 kPa, more preferably 100 to 500 kPa, and even more preferably 200 to 400 kPa. By using such an aerogel composite, it is possible to provide an adhesive sheet with less powder shedding, excellent heat insulation performance, and superior shape conformability. Here, the "25% compressive load" of the aerogel composite can be measured in accordance with JIS K6254:2016 "Vulcanized rubber and thermoplastic rubber - Method for determining stress-strain properties".

The 25% compressive load of an aerogel composite can be adjusted by the type of raw materials, degree of polymerization, and solid content ratio of the wet gel. It can also be adjusted by the type and amount of resin components and additives constituting the open-cell resin foam, the foam density, and the average filling density of the aerogel. For example, in the case of silica aerogel, it can be adjusted by the selection of silica components (monomers or oligomers) and the solid content ratio of the wet gel. More specifically, using oligomers of tetramers or more, or bifunctional silicone compounds as raw materials, or setting the solid content ratio between 10% and 50%, makes it easier to achieve a 25% compressive load of 10 to 1000 kPa.

The density of the base material is preferably 0.05 to 0.60 g/ ^cm³ , more preferably 0.10 to 0.45 g/ ^cm³ , and even more preferably 0.15 to 0.35 g/ ^cm³ . When the density is within this range, it is possible to provide an adhesive sheet with excellent heat insulation performance and superior shape conformability.

<Thermal conductivity>
The thermal conductivity of the substrate is preferably 0.026 W/m·K or less, more preferably 0.022 W/m·K or less, and even more preferably 0.018 W/m·K or less. Here, "thermal conductivity" is the value measured using a thermal conductivity measuring device (for example, HC-72 manufactured by Eiko Seiki Co., Ltd.) in accordance with JIS A 1412-2:1999 "Method for measuring thermal resistance and thermal conductivity of thermal insulating materials - Part 2: Heat flow meter method (HFM method)".

<Powder fall rate>
The powder shedding rate of the base material is preferably 15% or less, more preferably 10% or less, and even more preferably 5% or less. Here, the "powder shedding rate" is calculated in accordance with JIS K6254:2016 "Vulcanized rubber and thermoplastic rubber - Method for determining stress-strain properties" by compressing the test piece at a speed of 10 mm/min until it reaches a strain of 25%, repeating this 2000 times, and taking the weight of the test piece before and after the test {Powder shedding rate (%) = (Weight before test (g) - Weight after test (g)) / Weight before test (g) × 100}.

<<
The base material (aerogel composite) can be manufactured as follows. Here, we will explain the case where the foam is the open-cell resin foam with a skin as described above.

The manufacturing method for the substrate (aerogel composite material) includes a sol solution filling step in which a sol solution, which is the raw material for aerogel, is filled into a skinned open-cell resin foam under normal pressure or reduced pressure; a gelling step in which the filled sol solution is gelled; and a drying step in which the wet gel is dried. Each step is described in detail below. Regarding the explanation of aerogel, silica aerogel, a preferred example, will be used as an example. Furthermore, the manufacturing method for the aerogel composite material may include steps other than those described below.

<<<Foam Formation Process>>>
The foam formation process is described in detail below, but commercially available open-cell resin foams with a skin may be used as the open-cell resin foam with a skin if the effects of the present invention are achieved. The foam formation process when polyolefin resin and melamine resin are used as raw materials will be described exemplified below. The urethane foam with a skin and the silicone foam with a skin can be manufactured, for example, by the methods described in Japanese Patent No. 5933114 and Japanese Patent No. 3407267, respectively.

<<Foam formation process when using polyolefin resin as raw material>>
<Raw materials>
The polyolefin resin used as the raw material for the open-cell resin foam with a skin is not particularly limited, and known resins can be used. Furthermore, other additives can be added. An example of a method for producing polyolefin foam is described below.

Polyolefin foam is obtained by impregnating a composition containing (A) (A1) polyolefin (excluding ethylene-propylene rubber), (A2) ethylene-propylene rubber and/or styrene-based thermoplastic elastomer, and (B) a nonionic surfactant with a substance that is a gas at room temperature and pressure under supercritical conditions at high temperature and high pressure, and then releasing the pressure to foam it.

(A1) Examples of polyolefins include polyethylene, polypropylene, polybutene-1, ethylene-propylene copolymer, ethylene-α-olefin copolymer, and polymer blends thereof. Polyethylene may be high-density polyethylene, medium-density polyethylene, linear low-density polyethylene, low-density polyethylene, etc., and polypropylene may be atactic, isotactic, syndiotactic, random, etc. In addition, polypropylene with high extensional viscosity, such as polypropylene with long-chain branching in the main chain skeleton (HMS-PP) or polypropylene with a broad molecular weight distribution containing high molecular weight components, which is considered suitable for foaming, may be used. The copolymer may be a random copolymer or a block copolymer, and may be a thermoplastic resin or a thermoplastic elastomer. Of these, random polypropylene is preferred because it can impart heat resistance to the resulting foam and maintain the flexibility of the resulting foam. Because there is no gas leakage and foaming is easy, the melt flow rate of component (A1) is preferably 0.1 to 5 g/10 min, and more preferably 0.3 to 2 g/10 min, at 230°C and 2.16 kgf (according to JIS K7210:1999). Note that while ethylene-propylene copolymers include ethylene-propylene copolymers (EPR) that harden into a rubbery elastic body, these are included in component (A2) and are therefore excluded from (A1). Thus, (A1) includes resinous ethylene-propylene copolymers. Furthermore, other thermoplastic polymers may be present, as long as they do not impair the properties of the open-cell resin foam of this embodiment.

The ethylene-propylene rubber in (A2) includes EPR (EPM), a copolymer of ethylene and propylene that hardens into a rubbery elastic material; and EPDM, a copolymer of ethylene, propylene, and a small amount of non-conjugated diene. Examples of non-conjugated dienes include ethylidene norbornene, dicyclopentadiene, and 1,4-hexadiene.

Furthermore, the styrene-based thermoplastic elastomer of (A2) may be any block copolymer in which styrene is bonded to one or both ends of a polymer consisting of hydrocarbon chains. Examples include block copolymers of styrene with butadiene, isoprene, isobutylene, etc., or further hydrogenated versions of these block copolymers. Examples include styrene-butadiene styrene block copolymer (SBS), and hydrogenated SBS styrene-ethylene-butylene styrene block copolymer (SEBS), styrene-isoprene styrene block copolymer (SIS), and hydrogenated SIS styrene-ethylene-propylene styrene block copolymer (SEPS), styrene-isoprene-butadiene-isoprene styrene block copolymer, and hydrogenated styrene-ethylene-ethylene-propylene styrene block copolymer (SEEPS), styrene-vinyl-isoprene styrene block copolymer, and their hydrogenated products, styrene-isobutylene styrene block copolymer, styrene-butadiene block copolymer, and their hydrogenated products, styrene-isobutylene block copolymer, and their hydrogenated products, etc. These may be used individually or in combination.

Regarding component (A2) above, a higher average molecular weight is preferable. It may also be used after being spread with process oil or the like. Component (A2) is used as is without crosslinking.

(B) Examples of nonionic surfactants include alkyl polyethers such as polyoxyethylene (polyoxypropylene) alkyl ethers, fatty acid polyether esters such as polyoxyethylene (polyoxypropylene) fatty acid esters, dipolyoxyethylene (dipolyoxypropylene) alkylamines, such as di(dioxyethylene)stearylamine, polyoxyethylene (polyoxypropylene) dialkylamines, polyoxyethylene (polyoxypropylene) alkylalkylenediamines, and other alkyl polyetheramines, polyoxyethylene (polyoxypropylene) sorbitan esters, such as polyoxyethylene (polyoxypropylene) sorbitan alkyl esters, polyoxyethylene (polyoxypropylene) alkyl glyceryl ethers, fatty acid (poly)glyceryls, such as monoglyceryl stearate, polyoxyethylene (polyoxypropylene) fatty acid glyceryl, and other alkyl glyceryl polyethers or esters, alkanolamides such as fatty acid (di)ethanolamide, and mixtures thereof. The number of carbon atoms in the alkyl, fatty acid, and alkylene compounds mentioned above is preferably 10 or more, from the viewpoint of compatibility with the polyolefin polymer composition. Examples include C12 (lauryl or laurylate, etc.), C18 (stearyl or stearate, etc.), and C22 (behenyl or behenylate, etc.). Furthermore, the number of repeating units in oxyalkyl groups such as polyoxyethylene and polyoxypropylene is preferably 1 to 20, and more preferably 10 or less. The number of repeating units in polyglyceryl groups is also preferably 1 to 20, and more preferably 10 or less. Additionally, one or a mixture selected from alkyl polyetheramines, fatty acid glyceryls, and fatty acid (di)ethanolamides can be preferably used, and higher alcohols such as stearyl alcohol may be added.

The component (A) used in this embodiment is a polymer composition comprising (A1) 50 to 95% by weight, preferably 60 to 90% by weight, more preferably 65 to 85% by weight of polyolefin (excluding ethylene-propylene rubber), and (A2) 5 to 50% by weight, preferably 10 to 40% by weight, more preferably 15 to 35% by weight of ethylene-propylene rubber and/or styrene-based thermoplastic elastomer.

The amount of component (B) required is 0.2 to 10 parts by weight per 100 parts by weight of polymer composition (A), preferably 0.3 to 5 parts by weight, and more preferably 0.5 to 3 parts by weight.

In the present invention, for example, component (A1), component (A2), component (B), and optionally other components are mixed using a mixing means suitable for mixing polymer materials to prepare a foaming composition. In this process, depending on the intended use, the following components may be optionally added to the foaming composition to impart appropriate properties to the resulting foam or to facilitate the production and processing of the foam: lubricants such as liquid paraffin, hydrocarbon process oil, higher fatty acid glycerol ester, and higher fatty acid amide; wet silica, dry silica, talc, mica, diatomaceous earth, aluminum oxide, titanium dioxide, zinc oxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, potassium carbonate, calcium carbonate, magnesium carbonate, potassium sulfate, barium sulfate, glass beads, polytetrafluoroethylene, tricalcium phosphate, magnesium pyrophosphate, calcium stearate, zinc stearate, magnesium stearate, bisamide compounds such as ethylenebisstearate and methylenebisstearate, stearamide, 12-hydroxystearate, triglyceride stearate, and monoglyceride stearate. The material may contain nucleating agents such as cerides; flame retardants such as phosphate esters, melamine phosphate or piperazine phosphate, aluminum hydroxide, magnesium hydroxide, antimony oxide, zinc carbonate, chlorinated paraffin, and hexachlorocyclopentadiene; anti-aging agents such as aromatic amines, benzimidazoles, dithiocarbamates, phenolic compounds, and phosphite esters; antioxidants such as 2,6-di-t-butylphenol, 2,6-di-t-butyl-4-ethylphenol, 4,4'-butylidenebis(3-methyl-6-t-butylphenol), and 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane; conductive materials such as conductive carbon black, copper powder, nickel powder, and tin oxide; colorants such as carbon black, organic pigments, dyes, and masterbatches containing them; and fillers such as silica, alumina, titanium dioxide, and those additives listed above that have the function of fillers.

The substance impregnated into the foaming composition under supercritical conditions is a gas at room temperature and atmospheric pressure. Any substance that penetrates the polymer in the foaming composition under supercritical conditions is acceptable. Examples include nitrogen, helium, carbon dioxide, propane, butane, and mixtures thereof. Carbon dioxide and nitrogen are preferred, with carbon dioxide being particularly preferred, due to their ease of handling, high safety, and excellent working environment.

<Foaming Process>
Under the following conditions, a substance that is a gas at room temperature and pressure is impregnated into a polymer in a foaming composition, and then the pressure is released to cause foaming into open cells. By reducing the pressure at a rate of typically 10 to 30 MPa/s, foaming into open cells can be achieved. Since an open-cell resin foam is obtained directly in the foaming process, there is no need for a subsequent process to break closed cells with mechanical stress to create open cells.

The temperature at which a substance that is a gas at room temperature and pressure is impregnated into the foaming composition is, in order to efficiently obtain a functional foam, the temperature at which the substance reaches a supercritical state. Particularly preferred is a temperature 20 to 40°C higher than the crystallization peak temperature of the polymer in the foaming composition, as measured by differential scanning calorimeter. Here, a supercritical state is a state exhibiting properties intermediate between a gaseous state and a liquid state.

Furthermore, the impregnation pressure is preferably 8 to 15 MPa, and more preferably 10 to 15 MPa, in order to ensure complete impregnation and obtain fine cells, thereby bringing the impregnated substance, which is a gas at room temperature and pressure, into a supercritical state. In particular, to minimize gas leakage, this pressure is preferable.

The time required to impregnate a foaming composition with a substance that is a gas at room temperature and pressure varies depending on the required impregnation amount and the impregnation temperature and pressure, but is usually 3 to 30 minutes, preferably 5 to 20 minutes.

When foaming a foaming composition to form open bubbles, it is preferable to have a foaming ratio of 5 times or more. While there is no particular upper limit to the foaming ratio, from the viewpoint of mechanical strength, it should be 100 times or less, preferably 80 times or less, and more preferably 50 times or less.

By foaming the material to a foaming ratio of five times or more as described above, and then molding it by extrusion, a molded body of open-cell resin foam with a skin can be obtained. A single-screw tandem extruder is used as the extruder, and in some cases, it may be used in combination with a twin-screw extruder. Extrusion molding allows for the production of an open-cell resin foam with a skin, where the foam layer and the skin layer are integrated, without the need for bonding or fusion processes. Because bonding or fusion processes are not involved, there is no risk of reduced thermal insulation due to the influence of the thermal conductivity of the sealing material, and work efficiency is not reduced because the number of steps is not increased.

This section describes extrusion molding. An example of an extrusion molding apparatus usable for manufacturing a sheet according to the present invention comprises: an apparatus for melting a molding material containing a thermoplastic resin; an apparatus for mixing a gaseous material in a supercritical state at room temperature and atmospheric pressure with the molten molding material during melting; and an extrusion apparatus for heating, compressing, and extruding the molten molding material, which contains the gaseous material mixed at room temperature and atmospheric pressure, through a die. The mixing apparatus is installed so as to allow the gaseous material in a supercritical state at room temperature and atmospheric pressure to be mixed into a receiving port located in a barrel midway along the longitudinal direction of the extruder.

Specifically, supercritical carbon dioxide is supplied to the polymer material being melt-extruded by a screw from a receiving port and mixed to form a single-phase solution. This single-phase solution is then used as a fluid flow of polymer material, uniformly dispersed. Finally, while suppressing bubble growth, this liquid mixture of polymer material and very small bubbles is passed through a die at a high temperature to perform extrusion foam molding.

<<Foam formation process when using melamine resin as a raw material>>
<Foam material formation process>
The foam material formation process is not particularly limited as long as it is possible to form melamine foam, which is the foam material, and can be carried out based on a general method for manufacturing melamine foam.

<Melamine foam>
Melamine foam can be prepared by mixing melamine, formaldehyde or a pre-condensate thereof, which are the main raw materials, with a foaming agent, a catalyst, an emulsifier, etc., pouring the mixture into a mold, and then heating or irradiating with electromagnetic waves, or other appropriate means, to generate heat in the foaming raw materials, causing foaming and hardening.

The molar ratio of melamine to formaldehyde for forming the precondensate is preferably melamine:formaldehyde = 1:1.5 to 4, particularly 1:2 to 3.5. Furthermore, a precondensate with a number-average molecular weight of 200 to 1000, particularly 200 to 400, is preferred. Formalin, an aqueous solution of formaldehyde, is typically used as the formaldehyde.

In addition to melamine and formaldehyde, various monomers can be used as monomers to produce the precondensate, in amounts of 50 parts or less, and especially 20 parts or less, when these monomers are used in amounts of 100 parts by mass (hereinafter abbreviated as "parts").

Other monomers that can be used in conjunction with melamine include alkyl-substituted melamine, urea, urethane, carboxylic acid amides, dicyandiamide, guanidine, sulfurylamide, sulfonic acid amide, aliphatic amine, phenol and its derivatives, etc. Furthermore, as aldehydes, acetaldehyde, trimethylolacetaldehyde, acrolein, benzaldehyde, furflore, glyoxal, phthalaldehyde, and terephthalaldehyde, etc. can be used.

Furthermore, pentane, trichlorofluoromethane, trichlorotrifluoroethane, etc., can be used as foaming agents.

Formic acid is typically used as a catalyst, and anionic surfactants such as sodium sulfonate can be used as emulsifiers.

The electromagnetic waves irradiated to accelerate the curing reaction of the foaming material should preferably be adjusted so that their power consumption is 500 to 1000 kW, particularly 600 to 800 kW, relative to the foaming material.

The thickness and density of the foam material should be appropriately set according to the conditions of the heat compression process and the desired thickness and density of the foam base material.

In the case of melamine foam, it is also possible to leave unreacted methylol groups in the foam material and react these methylol groups in the thermal compression process described later.

The resulting foam may be processed to a predetermined size.

<<Thermal Compression Process>>
The foamed material obtained in the foamed material formation process is thermally compressed to plastically deform the foamed material, thereby obtaining a foamed substrate having a predetermined density and air permeability.

The thermal compression process can be carried out, for example, by heating and compressing between hot plates of a compression molding machine. In this case, the temperature of the hot plates (press temperature) is preferably 100 to 250°C, more preferably 120 to 200°C, and even more preferably 150 to 180°C. In particular, when impregnating with a curing agent as a restoration prevention method described later, the press temperature should be near the curing temperature of the curing agent, preferably ±10°C of the curing temperature. By setting the press temperature within this range, the foam can be sufficiently plastically deformed while achieving the desired shape of each bubble, and the air permeability of the resulting foamed substrate can be easily set to the desired range. The thermal compression time and load should be adjusted to obtain a foamed substrate of the desired thickness.

Furthermore, it is preferable to perform the heat compression process so that the ratio of the thickness of the foamed substrate to the thickness of the foamed material is 1/2 to 1/15, or 1/3 to 1/10. By keeping the ratio within this range, the cells of the foamed substrate become denser through heat compression molding, suppressing aerogel shedding and allowing for the imparting of flexibility to the aerogel composite material.

Here, when a foam is plastically deformed by thermal compression, if thermal compression alone is used, a restorative force may act on the foam when the compressive load is removed. Therefore, it is preferable to employ an additional method to maintain the thermally compressed state of the foam (a method to prevent restorative deformation).

One method to prevent restoration is to include unreacted methylol groups in the foamed material and react these methylol groups during the thermal compression process, as described above.

Unreacted methylol groups in foamed materials can be identified by measuring the absorption spectrum using a Fourier transform infrared spectrometer (FT-IR). The methylol group content can be estimated from the peak intensity of the absorption spectrum around 1000–1100 cm⁻¹. Furthermore, unreacted methylol groups remain in the foamed substrate obtained by heat-compressing the foamed material, and the methylol group content can be estimated using a similar method.

Furthermore, as a method to prevent restoration, another method involves pre-impregnating the foamed material with a curing agent in a curing agent impregnation step before the heat compression step, and then heat-curing the curing agent during the heat compression step. Multiple types and/or multiple restoration prevention methods may be implemented. In particular, when the foamed material is melamine foam, it is preferable to perform the curing agent impregnation step.

The curing agent used in the curing agent impregnation process is not particularly limited as long as it is activated and hardens when heated. Examples include melamine resin, epoxy resin, and phenolic resin.

In the curing agent impregnation process, the amount of curing agent to impregnate the foamed material is preferably 0.5 to 10.0 parts by mass, and more preferably 1.0 to 5.0 parts by mass, when the foamed material is 100 parts by mass. This range allows for a balance between sufficient flexibility and heat insulation, and shape retention after the heat compression process.

<Cutting>
The resulting open-cell resin foam with a surface can be processed to a predetermined size. The open-cell structure of the foam is exposed at the cut surface. The sol solution is then filled into these exposed cells.

Through the above foam formation process, a continuous-cell resin foam with a continuous-cell surface layer is obtained.

<<Solar Solve Filling Process>>
The following describes in detail a preferred method for producing silica aerogel, but the present invention is not limited to silica aerogel.

<Sol solution>
As the silicone raw material for silica aerogel, silicone alkoxides or their derivatives or alkali metal silicates can be used, and these are mixed with an aqueous solvent to form a sol solution.

The silicone raw material is not particularly limited as long as it achieves the effects of the present invention. Examples of silicone alkoxides and their derivatives include tetramethoxysilane, tetraethoxysilane, tetramethoxysilane oligomer, tetraethoxysilane oligomer, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, hexyltrimethoxysilane, monohexyltriethoxysilane, etc. Examples of alkali metal silicates include potassium silicate and sodium silicate. Multiple silicone raw materials can be used in combination. When using multiple materials, the combination and blending ratio can be selected according to the purpose.

For the hydrolysis of silicone raw materials, it is preferable to use water and a solvent that is compatible with water and dissolves the silicone raw materials. Examples of solvents include alcohols such as methanol, ethanol, isopropanol, and butanol; aliphatic diols such as ethanediol, propanediol, butanediol, diethylene glycol, dipropylene glycol, polyethylene glycol, and polypropylene glycol; aromatic diols or alicyclic diols such as hydrogenated bisphenol A, bisphenol A, and cyclohexanediol; polyhydric alcohols such as glycerin, diglycerin, trimethylolpropane, trishydroxymethylaminopentane, pentaerythritol, dipentaerythritol, and hexamethylolmelamine; hexane, toluene, chloroform, diethyl ether, tetrahydrofuran, ethyl acetate, acetone, and acetonitrile. These solvents may be used individually or in combination of two or more.

To efficiently hydrolyze the silicone raw material, it is preferable to add a catalyst to the reaction system beforehand. The catalyst is not particularly limited; for example, acidic catalysts include formic acid, acetic acid, succinic acid, malic acid, citric acid, hydrochloric acid, nitric acid, boric acid, sulfuric acid, carbonic acid, and phosphoric acid. Basic catalysts include metal oxides and/or hydroxides such as sodium hydroxide and potassium hydroxide, aliphatic and/or aromatic amines such as dimethylamine, triethylamine, N,N-dimethylbenzylamine, aniline, and 1,5-naphthalenediamine, ammonia, divalent metal naphthenic acid, and divalent metal hydroxides. These catalysts may be used individually or in combination of two or more.

<Filling method>
The method for filling the sol solution is not particularly limited, as long as it is carried out under normal pressure or reduced pressure, and known methods can be used. For example, one method is to fill the open-cell resin foam with a skin, obtained by the method described above, by completely impregnating it with the prepared sol solution under reduced pressure. In particular, if the air permeability is 10 ^cm³ / ^cm² /sec or higher, filling under normal pressure is possible.

Specifically, taking a sol solution prepared by mixing tetramethoxysilane (hereinafter referred to as TMOS), methanol, water, and catalyst (ammonia) in a molar ratio of 1:7.2:4:0.01 as an example, a foam can be placed in a separable flask, and the sol solution can be gradually introduced to completely immerse the foam in the sol solution, thereby filling the foam with the sol solution. It is then left to gel for 2-3 hours.

Unreacted reactive functional groups such as hydroxyl groups, carboxyl groups, and amino groups remaining in the open-cell resin foam may react with the hydrophobic treatment agent described later. Since a large amount of reactive functional groups may inhibit the hydrophobic reaction of the wet gel, the reactive functional groups remaining in the open-cell resin foam may be deactivated in a step prior to the sol solution filling process. The method for deactivating the reactive functional groups is not particularly limited, and known methods can be used.

<Gelling>
The sol solution filled into the foam undergoes a sol-gel reaction in which TMOS is hydrolyzed by water and a catalyst, passing through a sol state to form a wet gel. Here, a wet gel refers to a solid state that contains residual liquid from the sol solution after gelation.

A sol-gel reaction caused by the hydrolysis of a silicone alkoxide or its derivative forms a wet gel inside the open-cell foam.

The process may include a step to remove water and unreacted substances from the wet gel after it has formed. Examples of solvents used in this step include alcohols such as methanol, ethanol, isopropanol, and butanol, as well as acetone and acetonitrile. The process is completed by immersing the foam containing the wet gel in the solvent and replacing the solvent several times.

The process may include a step of hydrophobizing the OH groups on the silica aerogel surface using a hydrophobic treatment agent having a functional group that reacts with hydrophilic silanol groups and a hydrophobic group. The hydrophobic treatment agent used has a functional group that reacts with silanol groups and a hydrophobic group. Examples of functional groups that react with silanol groups include halogens, amino groups, imino groups, carboxyl groups, alkoxyl groups, and hydroxyl groups. Examples of hydrophobic groups include alkyl groups, phenyl groups, and their fluorides. The hydrophobic treatment agent may have only one of the above functional groups and hydrophobic groups, or it may have two or more of them. Examples include organic silane compounds such as hexamethyldisilazane, hexamethyldisiloxane, trimethylchlorosilane, trimethylmethoxysilane, trimethylethoxysilane, triethylethoxysilane, triethylmethoxysilane, dimethyldichlorosilane, dimethyldiethoxysilane, methyltrichlorosilane, and ethyltrichlorosilane. Other examples include carboxylic acids such as acetic acid, formic acid, and succinic acid, and organic compounds such as alkyl halides like methyl chloride. One hydrophobic treatment agent may be used, or two or more may be used.

To improve the adhesion between the aerogel and the continuous resin foam and to suppress aerogel detachment, a coupling agent may be added. The coupling agent is not particularly limited as long as it can react with both the silanol groups on the aerogel surface and the reactive functional groups such as hydroxyl groups, carboxyl groups, and amino groups remaining in the continuous resin foam; any suitable coupling agent can be used. Silane coupling agents are preferred, and examples include vinyltrimethoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-isocyanatetopropyltriethoxysilane, and tris-(trimethoxysilylpropyl)isocyanurate.

<Drying process>
The present invention includes a drying step for drying the wet gel. Known drying methods can be used and are not particularly limited. When drying the wet gel, supercritical fluid drying is preferred because the silica aerogel is less likely to break down. An example of supercritical fluid drying is a method in which the entire solvent is removed by replacing it with carbon dioxide, which has a lower critical point than the solvent, under conditions of about 80°C and 20 MPa.

<<
<<<<Ingredients>>>
The adhesive layer according to the present invention is not particularly limited and may be any known adhesive. Examples include thermosetting and UV-curing adhesives. More specifically, adhesives such as rubber-based, acrylic-based, urethane-based, silicone-based, and polyvinyl ether adhesives can be used.

<<<Structure>>>
The adhesive layer according to the present invention is present on at least one surface of the substrate. Here, the adhesive layer may be present on the entire surface or only partially (for example, in the form of dots or stripes). In addition, the thickness of the adhesive layer is not particularly limited, and is, for example, about 1 to 200 μm. Preferably, it is 2 to 100 μm, more preferably 2 to 50 μm, and even more preferably 5 to 35 μm. When the thickness is within this range, it is possible to provide an adhesive sheet that has excellent heat insulation performance and excellent shape conformability.

<<
The adhesive sheet according to the present invention can be manufactured, for example, by a method of applying and drying an adhesive component to a substrate, or by a method of overlapping a substrate and an adhesive sheet. The application method is not particularly limited and can be carried out by known methods, such as a comma coater, die coater, or gravure coater. A die coater is preferred because it allows for temperature control during coating and adjustment of the coating viscosity of the raw material composition.

<<
The adhesive sheet according to the present invention has high thermal insulation properties and is therefore useful as a thermal insulation sheet. In particular, because the adhesive sheet according to the present invention has excellent shape conformability, it is useful for applications where it is attached to curved surfaces to be insulated, such as in pipe insulation, industrial tanks, automotive interior materials, building materials, and electronic equipment.

The present invention will be further described in detail below with reference to examples. However, the present invention is not limited to these examples and can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art.

<<
<<
(Polymer resin)
Random-type polypropylene EPDM (ethylene content 36%, diene content 15%)
(Additives)
Nonionic surfactant (polyoxyethylene stearylamine)
• Nucleating agent (wet silica)
• Phenolic antioxidants

<<Surfaced polyolefin foam 1>>
<Preparation of raw materials for resin foam, foam formation process>
63 parts by weight of random-type polypropylene, 30 parts by weight of EPDM (ethylene content 36%, diene content 15%), 1.5 parts by weight of polyoxyethylene stearylamine, 5 parts by weight of wet silica, and 0.2 parts by weight of a phenolic antioxidant were melt-kneaded together, impregnated with carbon dioxide under supercritical conditions, and then foamed by releasing the pressure. Extrusion molding was then performed to obtain the polyolefin foam with a surface shown in Table 1. The manufacturing conditions were an impregnation temperature of 190°C, an impregnation pressure of 15 MPa, and an impregnation time of 30 minutes.

<<Surfaced polyolefin foam 2>>
<Preparation of raw materials for resin foam, foam formation process>
Except for adjusting the manufacturing conditions such as impregnation pressure and impregnation time so that the density was 0.30 g/ ^cm³ , the surfaced polyolefin foam 2 shown in Table 1 was obtained in the same manner as surfaced polyolefin foam 1.

<<
(Water-dispersible resin dispersion)
Polyether carbonate-based urethane emulsion (stable, dispersed, water-dispersible resin; precipitation rate 0.5%), pH 7.5, solids content 60%
(Anionic surfactant)
• Anionic surfactant 1 (sodium alkyl sulfosuccinate derived from beef tallow)
Dispersion medium: water, pH 9.4, solid content 30%
• Anionic surfactant 2 (ammonium stearate)
Dispersion medium: water, pH 11, solid content 30%
(Hardening agent)
Hydrophobic HDI isocyanurate (3.5 functional groups, trimer)

<Preparation of raw materials for resin foam, foam formation process>
A urethane emulsion of a water-dispersible resin dispersion was used as the main component. 100 parts by mass of the main component was mixed with 1 part by mass of 5 parts by mass of an anionic surfactant, 2 parts by mass of an anionic surfactant, and 8 parts by mass of a curing agent to prepare a resin foam raw material. Air was added to the prepared resin foam raw material to cause foaming, and it was cast onto a release-treated PET film (38 μm thick). A film was formed using a doctor knife. The doctor knife was set so that the thickness of the foam after heating, as described later, was 2 mm. The obtained film-like resin foam was heated in an 80°C oven for 1 hour to completely dry the moisture, and a urethane foam with a surface, as shown in Table 1, was obtained.

<<
(Silicone resin foam raw material)
Silicone resin 1: Polyorganosiloxane containing vinyl groups and platinum catalyst. Silicone resin 2: Polyorganohydrogensiloxane. Foaming agent: Fluoro-modified silicone oil.

<Preparation of raw materials for resin foam, foam formation process>
Silicone resin 1 and silicone resin 2 were mixed in a mass ratio of 100:9 to obtain a silicone resin foam raw material. Air was added to the prepared resin foam raw material to cause foaming, and it was cast onto a release-treated PET film (thickness 38 μm), and a film was formed using a doctor knife. The doctor knife was set so that the thickness of the foam after heating, as described later, would be 2 mm. The obtained raw material was heated at 170°C for 1 hour to complete the curing reaction, and a silicone foam with a surface shown in Table 1 was obtained.

<<
(Foam material)
Melamine foam containing unreacted methylol groups, density 0.014 g/ ^cm³

<Preparation of raw materials for resin foam, foam formation process>
A melamine foam with unreacted methylol groups and a thickness of 10.0 mm was used as the foaming material. The foaming material was thermally compressed between hot plates of a compression molding machine at a press temperature of 160°C to a thickness of 2.0 mm, obtaining the thermoformed melamine foam shown in Table 1.

<<
(Raw material for silica aerogel)
• Silicone raw material: Tetrafunctional ethoxysilane oligomer (average pentamer)
(solvent)
• Ethanol (manufactured by Wako Pure Chemical Industries, Ltd.)
- Ion-exchanged water, electrical resistivity of 1 x ^10¹⁰ Ω·cm or higher (catalyst)
25% ammonia solution (manufactured by Wako Pure Chemical Industries, Ltd.)

<<Aerogel composite material using polyolefin foam with surface layer 1 as the foaming agent>>
<Solu solution preparation and sol solution filling process>
Using a silicone raw material as the main component, a sol solution was prepared by mixing 53 moles of ethanol, 21 moles of deionized water, and 0.01 moles of catalyst with 1 mole of the main component. The polyolefin foam 1 with the skin attached was cut to a size that could be stored in a separable flask, with the skin layer still attached, and placed inside. The prepared sol solution was added until the polyolefin foam 1 with the skin attached was completely immersed, and the mixture was left to stand under normal pressure for 3 hours to obtain polyolefin foam 1 with the skin attached filled with a wet gel, as shown in Table 1.

The resulting wet gel-filled, open-cell resin foam with a surface was immersed in ethanol, and the ethanol was repeatedly replaced while stirring, performing solvent replacement for 24 hours. Next, to hydrophobize the gel surface, it was immersed in an ethanol solution of hexamethyldisilazane (15% by mass) with 0.1 mol% hydrochloric acid aqueous solution added as a catalyst, and the hydrophobization treatment was performed for 24 hours while stirring.

(drying process)
The open-cell resin foam with a hydrophobic gel surface was impregnated in carbon dioxide at 80°C and 20 MPa, and supercritical fluid drying was performed for 12 hours.

As described above, an aerogel composite material was obtained by filling the interior of a polyolefin foam 1 with silica aerogel (see Table 1). The thickness of the aerogel composite material was 2 mm, and the average aerogel filling rate in the aerogel composite material was 95%.

<<Other foamed aerogel composite materials>>
An aerogel composite material was obtained in the same manner as the "aerogel composite material using polyolefin foam 1 as the foam" described above, except that polyolefin foam 2 with a skin, urethane foam with a skin, silicone foam with a skin, or thermoformed melamine foam was used instead of polyolefin foam 1 with a skin (see Table 1).

<<
<<<<Preparation of adhesive tape according to Example 1>>>>
An acrylic adhesive (SK Dyne 1604N, manufactured by Soken Chemical Co., Ltd.) was applied to one side of a polyolefin foam 1 with a surface filled with silica aerogel to a predetermined thickness (50 μm) to obtain the aerogel composite tape (adhesive tape) according to Example 1.

<<<<Preparation of adhesive tapes according to Examples 2-5>>>>
Except for using the open-cell resin foams shown in each table, aerogel composite tapes (adhesive tapes) according to Examples 2 to 5 were obtained in the same manner as in Example 1.

<<<<Preparation of adhesive tapes for Comparative Examples 1 and 2>>>>
Foam tapes according to Comparative Examples 1 and 2 were obtained in the same manner as in Example 1, except that the open-cell resin foams shown in each table were used.

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>
<<<<Evaluation of adhesive tape>>>>
The adhesive tapes of the examples and comparative examples prepared as described above were evaluated according to the method shown below.

<<25% Compression Load>>
The 25% compression load was measured according to the method described below and evaluated according to the evaluation criteria.

<Evaluation Method>
The measurements were taken in accordance with JIS K6254:2016 "Vulcanized rubber and thermoplastic rubber - Method for determining stress-strain properties," and then evaluated according to the evaluation criteria.
<Evaluation Criteria>
"○" indicates that the 25% compression load is greater than 0 kPa and less than or equal to 500 kPa, while "△" indicates that the load is greater than 500 kPa and less than or equal to 1000 kPa.

<<Thermal insulation performance>>
Thermal insulation performance was measured according to the following method and then evaluated according to the evaluation criteria.

<Evaluation Method>
A sample (size: 70 mm x 150 mm) was placed on a heater heated to 80°C for 5 minutes, and the surface temperature of the sample was measured after 5 minutes. The temperature difference per unit thickness was calculated from the sample thickness and surface temperature. The temperature difference per unit thickness (°C) was calculated as (heater temperature 80 (°C) - sample surface temperature (°C)) / sample thickness. Here, the surface temperature of the sample can be measured using a thermal camera, for example (e.g., InfReCTthermoFLEX F50A-BAS / Avionics Japan).

<Evaluation Criteria>
"◎" indicates that the temperature difference per unit thickness is greater than 10°C, "○" indicates that the temperature difference per unit thickness is greater than 5°C but 10°C or less, "△" indicates that the temperature difference per unit thickness is greater than 2°C but 5°C or less, and "×" indicates that the temperature difference per unit thickness is 2°C or less.

＜＜Adhesiveness＞＞
Adhesion was measured according to the method described below and then evaluated according to the evaluation criteria.

<Evaluation Method>
The samples were measured in accordance with JIS Z0237 "Test Methods for Adhesive Tapes and Adhesive Sheets" and evaluated according to the evaluation criteria. Samples cut to a width of 25 mm x length of 300 mm were fixed to a SUS304 plate and subjected to a 180° peel test.

<Evaluation Criteria>
"○" indicates a peel strength greater than 10 N/25 mm, and "△" indicates a peel strength greater than 4 N/25 mm and 10 N/25 mm or less.

Claims (1)

An adhesive sheet comprising a base material and an adhesive layer provided on one or both sides of the base material,
The aforementioned substrate is an aerogel composite material in which aerogel is filled inside an open-cell resin foam.
The open-cell resin foam has a surface layer on the surface on which the adhesive layer is provided.
The open-cell resin foam is a polyolefin foam,
An adhesive sheet characterized in that the surface layer is breathable .