Thermal insulation material

Abstract

The heat-insulating material comprises: a porous structure in which a plurality of particles are connected to constitute a skeleton and which has pores between the skeletons; infrared-shielding particles; and organic hollow particles. The content of the infrared-shielding particles in the heat-insulating material is 10-30% by mass (inclusive) with respect to 100% by mass of the heat-insulating material, and the content of the organic hollow particles is 5-30% by mass (inclusive) with respect to 100% by mass of the heat-insulating material. The heat-insulating material has high heat-insulating properties even at high temperatures, and has excellent flexibility against compression and restorability.

Description

Technical Field

[0001] The present disclosure relates to a heat insulating material using a porous structure body such as an aerogel. Background Art

[0002] In in - vehicle components, building materials for houses, industrial machines, etc., various heat insulating materials have been used for the purpose of controlling heat flow. As materials for heat insulating materials, silica aerogel with a low thermal conductivity is known. For example, in a battery pack mounted on a hybrid motor vehicle, an electric motor vehicle, etc., a heat insulating material is disposed between adjacent battery cells. For such a heat insulating material, it is required to suppress heat conduction and thermal runaway in the case of abnormal heating of a battery cell, especially high heat insulation at high temperatures. In addition, in a battery pack, a battery module formed by stacking a plurality of battery cells is housed in a housing in a state of being fixed from both sides in the stacking direction by fastening members. The battery cells expand and contract with charging and discharging. Therefore, preferably, the heat insulating material disposed between the battery cells can deform following external extrusion, expansion, and contraction of the battery cells and can maintain heat insulation.

[0003] For example, in Patent Document 1, as an aerogel composite having heat insulation and flexibility, an aerogel composite containing an aerogel component and hollow silica particles is described. In Patent Document 2, a product is described that includes nanoporous particles and hollow latex particles, and the hollow latex particles are directly bonded to each other to form a continuous matrix, and the nanoporous particles are dispersed in the continuous matrix of the hollow latex particles.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: International Publication No. 2017 / 038646

[0007] Patent Document 2: Japanese Patent Application Laid - Open No. 2013 - 543036 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] According to the aerogel composite described in Patent Document 1 above, flexibility is improved by adding hollow silica particles to the aerogel component. However, although the hollow silica particles have a hollow structure, they are composed of a hard inorganic material. Therefore, the resulting flexibility is insufficient. In addition, in Patent Document 1, flexibility is imparted only for the purpose of improving the processability of the aerogel. Therefore, even if the aerogel composite can be compressed and deformed by external extrusion, etc., it cannot be said to have resilience to return to its original shape after unloading the load. In addition, in Patent Document 1, heat insulation at high temperatures is not considered.

[0010] On the other hand, the hollow latex particles described in Patent Document 2 are composed of a polymer and function as an adhesive for bonding nanoporous particles to each other. As described in Patent Document 2, the hollow latex particles directly bond to each other to form a continuous mesh structure (matrix), and the nanoporous particles are dispersed in the continuous matrix of the hollow latex particles. Therefore, in the product described in Patent Document 2, the continuous hollow latex particles become a heat conduction path, resulting in a decrease in heat insulation performance. On this basis, if this product is used at high temperatures, there is a risk that the matrix will decompose, deteriorate, etc. and disappear, and the shape cannot be maintained. In addition, in paragraph

[0044] of Patent Document 2, it is described that "the concentration of additional additives such as infrared attenuation agents and reflective particles is 5 wt% or less based on the total weight of the product". Assuming that infrared shielding particles are incorporated as additional additives, the effect of blocking radiant heat is poor with such a small amount of 5% by mass or less of the whole product, and the heat insulation at high temperatures is insufficient.

[0011] The present disclosure has been made in view of the above actual situation, and the problem is to provide a heat insulation material that uses a porous structure body and has high heat insulation even at high temperatures, and is excellent in softness and resilience against compression.

[0012] Means for Solving the Problem

[0013] (1) In order to solve the above problems, the heat insulation material of the present disclosure is a heat insulation material having a porous structure body formed by connecting a plurality of particles to form a skeleton and having pores between the skeletons, infrared shielding particles, and organic hollow particles, characterized in that the content of the infrared shielding particles is 10% by mass or more and 30% by mass or less based on 100% by mass of the mass of the heat insulation material, and the content of the organic hollow particles is 5% by mass or more and 30% by mass or less based on 100% by mass of the mass of the heat insulation material.

[0014] According to the porous structure body, a high heat insulation effect can be obtained by mainly suppressing conduction and convection among the three forms of heat transfer (conduction, convection, and radiation). Here, radiation is a phenomenon in which heat moves due to electromagnetic waves, and the higher the temperature, the greater the radiant energy emitted. Therefore, in a high-temperature atmosphere, radiation becomes the main cause of heat transfer. Therefore, if the temperature becomes high, it is difficult to obtain the desired heat insulation performance only by the porous structure body, and it is effective to use infrared shielding particles that can suppress heat transfer caused by radiation. However, in the case of incorporating a large amount of infrared shielding particles, the infrared shielding particles are connected to each other to form a heat conduction path, so the heat transfer based on conduction becomes large, and there is a risk of reducing the heat insulation performance. According to the heat insulation material of the present disclosure, by determining the content of the infrared shielding particles, it is possible to suppress both radiant and conductive heat transfer, and high heat insulation performance can be achieved not only at normal temperature but also at high temperatures of 500 °C or higher.

[0015] The heat-insulating material of the present disclosure has organic hollow particles on the basis of infrared-shielding particles. The organic hollow particles are particles having voids inside formed of an organic material. By means of the organic hollow particles, flexibility capable of deforming in response to a compressive load and resilience after unloading the load are imparted. The organic hollow particles are disposed between the porous inorganic particles. In the heat-insulating material of the present disclosure, since the content of the organic hollow particles is relatively small, the organic hollow particles are not easily connected to each other, and most of them are disposed discontinuously. Thus, in the heat-insulating material of the present disclosure, the porous structure forms a matrix, and the organic hollow particles are dispersed among the porous structures. Therefore, even though the heat-insulating material of the present disclosure contains the organic hollow particles as an organic component, it is not easy to form a heat conduction path. Therefore, even at a high temperature, the organic hollow particles are not easily disappeared, and high heat insulation can be maintained.

[0016] (2) On the basis of the above configuration, it may also be a configuration in which the average particle size of the porous structure is 1 μm or more and 1000 μm or less. According to this configuration, it is easy to exhibit the effect of improving the heat insulation based on the porous structure, and it is also easy to exhibit the effect of blocking radiant heat based on the infrared-shielding particles.

[0017] (3) On the basis of any of the above configurations, it may also be a configuration in which the average particle size of the infrared-shielding particles is 0.3 μm or more and 22 μm or less. According to this configuration, it is easy to exhibit the effect of blocking radiant heat based on the infrared-shielding particles. In addition, the infrared-shielding particles are filled in the gaps between the porous structures, suppressing the connection between the infrared-shielding particles and other components, so that it is difficult to form a heat conduction path, and thus the heat insulation is not easily reduced.

[0018] (4) On the basis of any of the above configurations, it may also be a configuration in which the average particle size of the organic hollow particles is 1 μm or more and 1000 μm or less. According to this configuration, both the desired heat insulation, flexibility and resilience can be achieved.

[0019] (5) On the basis of any of the above configurations, it may also be a configuration in which the elastic modulus of the organic hollow particles is 1 MPa or more and 30 MPa or less. According to this configuration, the desired flexibility and resilience can be achieved.

[0020] (6) On the basis of any of the above configurations, it may also be that the organic hollow particles are composed of one or more selected from natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, ethylene-propylene-diene rubber, chloroprene rubber, polyurethane rubber, silicone rubber, ethylene-vinyl acetate rubber, epichlorohydrin rubber, acrylic rubber, styrene-based thermoplastic elastomer, vinyl chloride-based thermoplastic elastomer, olefin-based thermoplastic elastomer, polyester, polyacrylonitrile crosslinked body, polymethyl methacrylate crosslinked body, polybutyl methacrylate crosslinked body. According to this configuration, it is easy to manufacture particles having a hollow structure, and it is easy to adjust the elastic modulus of the obtained hollow particles. Thus, the desired softness and resilience can be achieved.

[0021] (7) On the basis of any of the above configurations, it may also be that the infrared-shielding particles have a configuration including at least one of particles selected from silicon carbide, kaolin, montmorillonite, titanium oxide, silicon nitride, mica, alumina (aluminum oxide), aluminum nitride, boron carbide, iron oxide, magnesium oxide, tin oxide, zinc oxide, tantalum oxide, manganese ferrite, manganese oxide, nickel oxide, nickel, silver oxide, silver, bismuth oxide, carbon black, graphite, titanium, iron titanate, zirconium, zirconium oxide, zirconium silicate, barium titanate, manganese dioxide, chromium oxide, titanium carbide, tungsten carbide, tungsten oxide, niobium oxide, indium tin oxide, cerium oxide, and a mixture of two or more selected from these. According to this configuration, the heat capacity of the infrared-shielding particles is relatively large, so the particles themselves are not easily heated. On this basis, the heat resistance of the infrared-shielding particles is also high. Therefore, it is beneficial to improve the heat insulation at high temperatures.

[0022] (8) On the basis of any of the above configurations, it may also be that the porous structure has a configuration of silica aerogel in which a plurality of silica particles are connected to form a framework. The balance between the size of the framework and the size of the pores of the silica aerogel is good, and excellent heat insulation is exhibited.

[0023] (9) On the basis of any of the above configurations, it may also be that the configuration further includes at least one of a processing aid and inorganic fibers. From the viewpoint of easy manufacture of heat insulation materials, etc., the processing aid can be appropriately used according to the manufacturing method. For example, when water is used as a solvent for a composition for manufacturing a heat insulation material, by selecting components having a dispersion function and a thickening function, it is easy to mix powders such as a porous structure with water. When compression molding powders such as a porous structure, the moldability is improved by selecting thermoplastic components. In addition, if inorganic fibers are present, it is effective for improving the mechanical strength of the heat insulation material and suppressing the detachment of the porous structure.

[0024] (10) Based on any of the above configurations, it can also be a configuration in which the organic hollow particles are discontinuously present between the porous structure and the porous structure. In this configuration, a large number of organic hollow particles as organic components are discontinuously scattered. Therefore, it is not easy to form a heat conduction path based on the organic hollow particles, and high heat insulation can be maintained.

[0025] (11) Based on any of the above configurations, it can also be a configuration without an adhesive that bonds the porous structure, the infrared ray shielding particles, and the organic hollow particles. Usually, an organic material is used in the adhesive. Therefore, if an adhesive exists, there is a risk of forming a heat conduction path through the adhesive. In this configuration, since there is no adhesive, high heat insulation at high temperatures can be achieved.

[0026] (12) Based on any of the above configurations, it can also be a configuration in which the organic hollow particles have a single pore type particle with one pore inside. In a single pore type particle, only the outermost shell portion is composed of an organic material, and the rest is composed of pores. Therefore, according to this configuration, it is easy to reduce the density of the heat insulation material and easy to adjust the softness.

[0027] (13) Based on any of the above configurations, it can also be a configuration in which the organic hollow particles have a multi-pore type particle with multiple pores inside. In the case of a multi-pore type particle, the multiple pores are arranged in the particle main body composed of an organic material. That is, in a multi-pore type particle, organic materials exist not only in the outermost layer but also inside the particle. Therefore, according to this configuration, it is easy to adjust the resilience of the heat insulation material.

[0028] Advantages of the Invention

[0029] The heat insulation material according to the present disclosure can achieve high heat insulation not only at normal temperature but also at high temperatures above 500°C. The heat insulation material according to the present disclosure can achieve softness that can deform under a compressive load and resilience after unloading the load. Detailed Embodiments

[0030] Hereinafter, the heat insulation material of the present disclosure will be described in detail. The heat insulation material of the present disclosure is not limited to the following embodiments, and can be implemented in various ways with changes, improvements, etc. that can be made by those skilled in the art without departing from the gist of the present disclosure.

[0031] <Heat Insulation Material>

[0032] The heat insulation material of the present disclosure has a porous structure, infrared ray shielding particles, and organic hollow particles.

[0033] [Porous Structure]

[0034] In the porous structure, multiple particles are connected to form a framework, and pores are present between the frameworks. The diameter of the particles (primary particles) constituting the framework is preferably about 2 to 5 nm, and the size of the pores formed between the frameworks is preferably about 10 to 50 nm. In the case of so-called mesopores where most of the pores have a size of 50 nm or less, the mesopores are smaller than the mean free path of air, so the convection of air is restricted and the transfer of heat is hindered. The shape of the porous structure can be spherical, an irregularly shaped block, etc., without particular limitation, and a chamfered shape or a spherical shape is preferred. In this case, the dispersibility of the porous structure is improved, so it becomes easier to prepare a composition for manufacturing a heat-insulating material (hereinafter referred to as "heat-insulating material composition"). In addition, the gaps between the porous structures can be reduced to increase the filling amount, thereby suppressing the connection of infrared-shielding particles and organic hollow particles, and thus the heat-insulating property can be improved. The porous structure can be used in the state after manufacturing, or it can be further pulverized and used. In the pulverization process, a pulverization device such as a jet mill or a spheroidization treatment device can be used. By performing the pulverization process, the corners of the particles are removed, and the particles become a shape with roundness. As a result, the surface of the heat-insulating material becomes smooth and cracks are less likely to occur.

[0035] The average particle diameter of the porous structure is preferably 1 μm or more and 1000 μm or less. When the average particle diameter of the porous structure is less than 1 μm, the filling property of the porous structure decreases and the gaps between the porous structures increase, so it is difficult to obtain the effect of improving the heat-insulating property. On the other hand, if the particle diameter of the porous structure becomes larger than 1000 μm, the infrared-shielding particles fill the gaps between the porous structures, so there is a risk that the area without infrared-shielding particles becomes larger. In this case, the frequency of infrared rays generated from the heat source colliding with the infrared-shielding particles decreases, and there is a risk that the blocking effect of radiant heat decreases. For example, the average particle diameter of the porous structure is preferably 8 μm or more, more preferably 50 μm or more. In addition, considering the stability of the heat-insulating material composition, ease of coating, etc., it is preferably 500 μm or less, more preferably 300 μm or less. The average particle diameter of the porous structure can be the median diameter (D 50 ) obtained from the volume-based particle size distribution measured by the laser diffraction / scattering method. In addition, when using a commercially available product, the catalog value can also be adopted.

[0036] When the particle sizes of the porous structures are different, the porous structures with smaller particle sizes enter the gaps between the porous structures with larger particle sizes. Therefore, the closest packing is likely to occur, and the filling amount of the porous structures can be increased. In addition, the connection of infrared-blocking particles and organic hollow particles can be hindered by the porous structures with smaller particle sizes. As a result, the effect of improving the heat insulation property becomes greater. From the above viewpoints, as the porous structure, it is preferable to use a porous structure with a wide particle size distribution or to use two or more kinds of porous structures having different average particle sizes in combination. In addition, during the manufacturing process of the heat insulation material, the stirring conditions of the material, etc. can be adjusted so that a part of the particles with larger particle sizes are crushed into particles with smaller particle sizes.

[0037] From the viewpoint of improving the heat insulation property, the content of the porous structure is preferably 40% by mass or more, more preferably 50% by mass or more, based on 100% by mass of the total mass of the heat insulation material. On the other hand, considering the balance among heat insulation property, flexibility, and resilience, and suppression of shedding, etc., the content of the porous structure is preferably 75% by mass or less, more preferably 70% by mass or less, based on 100% by mass of the total mass of the heat insulation material.

[0038] The porous structure preferably has a hydrophobic portion at least on the outer surface and the inner part (pore-forming surface). If it has a hydrophobic portion on the surface, the infiltration of moisture, etc. into the pores can be suppressed, so that the porous structure is maintained and the heat insulation property is not easily damaged. For example, by performing surface treatment with a silane coupling agent, etc., functions such as hydrophobicity can be imparted to the surface of the porous structure. In addition, by using a specific material in the raw material of the porous structure, a porous structure having a hydrophobic portion can be manufactured, or a hydrophobization treatment for imparting a hydrophobic group, etc. can also be carried out during the manufacturing process of the porous structure.

[0039] The type of the porous structure is not particularly limited. As the primary particles, for example, inorganic particles such as silica, alumina, zirconia, and carbon dioxide can be mentioned. Among them, from the reason of excellent chemical stability, a porous structure having silica as the primary particle is preferable. For example, a silica aerogel in which a plurality of silica particles are connected to form a framework is preferable because of the good balance between the size of the framework and the size of the pores. In addition, an aggregated structure in which nanoparticles with a particle size of less than 1 μm are connected to form a framework is also preferable. As the nanoparticles, fumed silica, wet silica, and particles obtained by crushing or dispersing them, and particles generated from nanoparticle sols such as colloidal silica and colloidal alumina can be mentioned.

[0040] The manufacturing method of the aerogel is not particularly limited, and the drying process can be carried out under normal pressure or under supercritical conditions. For example, if the drying is carried out under normal pressure, it can be easily and inexpensively manufactured. Depending on the difference in the drying method when manufacturing the aerogel, sometimes the one dried under normal pressure is called a "xerogel", and the one dried under supercritical conditions is called an "aerogel". However, in this specification, both are collectively referred to as "aerogel".

[0041] [Infrared shielding particles]

[0042] The infrared shielding particles absorb the heat from the heat source and re-emit the heat from the surface on the heat source side, thereby blocking the radiant heat from the heat source, and particularly contributing to improving the heat insulation property at high temperatures. From the viewpoint of fully exerting the inhibitory effect on the heat transfer based on radiation, the content of the infrared shielding particles is set to be 10% by mass or more based on the total mass of the heat insulating material being 100% by mass. If it is set to 15% by mass or more, the blocking effect of the radiant heat becomes higher. On the other hand, from the viewpoint of suppressing the connection between the infrared shielding particles and other components and making it difficult to form a heat conduction path, the content of the infrared shielding particles is set to be 30% by mass or less based on the total mass of the heat insulating material being 100% by mass. It is more preferably set to 20% by mass or less.

[0043] From the viewpoint of filling the gaps between the porous structures and suppressing the connection between the infrared shielding particles and other components to make it difficult to form a heat conduction path, the particle size of the infrared shielding particles is preferably relatively small. However, if the particle size is too small, it is difficult for infrared rays to hit, and furthermore, the scattering of infrared rays becomes insufficient, so it is difficult to exert the blocking effect of the radiant heat. From the above viewpoints, the average particle size of the infrared shielding particles is preferably 0.3 μm or more and 22 μm or less. The shape of the infrared shielding particles can be spherical, flat, etc., and is not particularly limited. Regarding the average particle size of the infrared shielding particles, similar to the case of the porous structure, the median diameter (D 50 ) obtained from the volume-based particle size distribution measured by the laser diffraction / scattering method can be used. In the case of using a commercially available product, the catalog value can also be used.

[0044] As infrared ray shielding particles, examples thereof include particles selected from silicon carbide, kaolin, montmorillonite, titanium oxide, silicon nitride, mica, aluminum oxide, aluminum nitride, boron carbide, iron oxide, magnesium oxide, tin oxide, zinc oxide, tantalum oxide, manganese ferrite, manganese oxide, nickel oxide, nickel, silver oxide, silver, bismuth oxide, carbon black, graphite, titanium, iron titanium oxide, zirconium, zirconium oxide, zirconium silicate, barium titanate, manganese dioxide, chromium oxide, titanium carbide, tungsten carbide, tungsten oxide, niobium oxide, indium tin oxide, cerium oxide, or particles which are a mixture of two or more selected from these. Among these, from the viewpoint of improving the blocking effect of radiant heat, the infrared ray shielding particles preferably have a high emissivity of 0.6 or more in the wavelength region of infrared rays. As the high emissivity particles, examples thereof include silicon carbide, kaolin, silicon nitride, mica, aluminum oxide, zirconium oxide, aluminum nitride, zirconium silicate, cerium oxide, boron carbide, manganese oxide, tin oxide, iron oxide, etc. In addition, from the viewpoint of scattering the incident infrared rays to improve the blocking effect of radiant heat, a method using particles having a high refractive index in the wavelength region of infrared rays is also effective. For example, high refractive index particles having a refractive index of 2.0 or more in the wavelength region of visible light are preferred. As the high refractive index particles, examples thereof include silicon carbide, titanium oxide, zirconium oxide, silicon nitride, aluminum nitride, zinc oxide, tantalum oxide, tungsten oxide, niobium oxide, cerium oxide, manganese oxide, tin oxide, bismuth oxide, iron oxide, barium titanate, etc.

[0045] For example, silicon carbide, titanium oxide, silicon nitride, mica, aluminum oxide, aluminum nitride, boron carbide, iron oxide, magnesium oxide, etc. have a relatively large specific heat, and thus have a large heat capacity, and the particles themselves are not easily heated. In this regard, it also contributes to improving the heat insulation property of the heat insulating material. On top of that, the heat resistance is also high, and thus it also contributes to improving the heat resistance of the heat insulating material. In particular, silicon carbide has little increase in thermal conductivity even in a high temperature atmosphere of about 800°C, and thus is preferred.

[0046] [Organic hollow particles]

[0047] From the viewpoint of imparting flexibility and resilience to the heat insulating material, the content of the organic hollow particles is set to 5% by mass or more based on 100% by mass of the total mass of the heat insulating material. More preferably, it is set to 10% by mass or more, and still more preferably, it is set to 15% by mass or more. On the other hand, from the viewpoint of increasing the content of components contributing to heat insulation to improve heat insulation and suppressing the connection between organic hollow particles and other components to make it difficult to form a heat conduction path, the content of the organic hollow particles is set to 30% by mass or less based on 100% by mass of the total mass of the heat insulating material. More preferably, it is set to 20% by mass or less.

[0048] If the particle size of the organic hollow particles is too small, it is difficult to obtain the improvement effects of flexibility and resilience. Therefore, the average particle size of the organic hollow particles is preferably 1 μm or more. More preferably, it is 10 μm or more. On the other hand, if the particle size is too large, the infrared shielding particles arranged together are separated from each other, and there is a risk of reduced heat insulation at high temperatures. Therefore, the average particle size of the organic hollow particles is preferably 1000 μm or less. More preferably, it is 500 μm or less, 200 μm or less. The shape of the organic hollow particles may be spherical, flat, etc., and is not particularly limited. Regarding the average particle size of the organic hollow particles, the median diameter (D 50 ) obtained from the volume-based particle size distribution measured by the laser diffraction / scattering method can be used in the same manner as in the case of the porous structure body. In the case of using a commercially available product, the catalog value can be used.

[0049] The organic hollow particles are particles having pores inside. The pores may be one or more. The former single-pore type particles are also called balloon structures and have a shell part formed of an organic material and one pore disposed inside thereof. The latter multi-pore type particles have a particle main body formed of an organic material and a plurality of pores disposed therein. The multi-pore type particles are a concept including porous particles. As the organic hollow particles, either single-pore type particles or multi-pore type particles can be used, or both can be used in combination. The organic hollow particles can be produced, for example, by foaming organic particles or pulverizing an organic foam.

[0050] The organic material is not particularly limited. As preferred materials, for example, crosslinked rubbers such as natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, ethylene-propylene-diene rubber, chloroprene rubber, polyurethane rubber, silicone rubber, ethylene-vinyl acetate rubber, epichlorohydrin rubber, acrylic rubber, etc., thermoplastic elastomers such as styrene-based, vinyl chloride-based, and olefin-based, resins such as polyester, polyacrylonitrile crosslinked body, polymethyl methacrylate crosslinked body, polybutyl methacrylate crosslinked body, etc. can be cited. On the surface of the organic hollow particles, surface treatment can be carried out for the purpose of suppressing dust generation and improving processability, improving flame retardancy, etc., or inorganic particles, etc. can be attached to the surface. In addition, in the case of improving flame retardancy, the organic material can contain a flame retardant, etc.

[0051] From the viewpoint of imparting the desired resilience to the heat insulating material, the elastic modulus of the organic hollow particles is preferably 1 MPa or more. More preferably, it is 2.5 MPa or more. On the other hand, from the viewpoint of imparting the desired flexibility against compression to the heat insulating material, the elastic modulus of the organic hollow particles is preferably 30 MPa or less. More preferably, it is 20 MPa or less.

[0052] In this specification, as the elastic modulus of the organic hollow particles, the value calculated from the results of the following compression test is adopted. First, the powder of the organic hollow particles is filled into a SUS cylindrical container with a diameter of 11.3 mm. Next, a SUS cylindrical pressing jig with a diameter of 11.2 mm is inserted into the cylindrical container, and the powder of the organic hollow particles is pressed in by the self-weight of the pressing jig (load 2 N). This operation is repeated until the initial filling height of the powder of the organic hollow particles becomes 14 mm, and it is arranged in the compression test machine in the state where the pressing jig is inserted into the cylindrical container. Then, using the Tensilon universal material testing machine "RTF1350" manufactured by A&D Co., Ltd., a compression test is conducted by repeatedly pressing the upper surface of the filled powder with the pressing jig. The conditions of the compression test are as described below.

[0053] Speed of the pressing jig: 6 mm / min.

[0054] Upper limit of the compressive stress: 3 MPa.

[0055] Number of presses: 10 times.

[0056] After the compression test, based on the obtained data, a stress-compression ratio curve is made with the horizontal axis being the compression ratio and the vertical axis being the compressive stress. The compression ratio on the horizontal axis is the value calculated by the following formula (I).

[0057] Compression ratio (%) = Penetration amount of the pressing jig (mm) / 14 [Initial filling height of the powder of the organic hollow particles] (mm) × 100 ··· (I)

[0058] Then, on the stress-compression ratio curve of the tenth press, the point with a compressive stress of 0 MPa and the point with a compressive stress of 3 MPa are connected by a straight line, and the value obtained by multiplying the slope of the obtained straight line by 100 is used as the elastic modulus of the organic hollow particles.

[0059] The organic hollow particles are arranged between the porous structures. From the viewpoint of not forming a heat conduction path based on the organic hollow particles, a mode in which most of the organic hollow particles are discontinuously arranged, in other words, a scattered mode, is preferred. For example, when the heat insulating material is manufactured in a sheet shape and the thickness direction becomes the heat transfer direction, the organic hollow particles do not form a matrix and are discontinuous in the thickness direction, so it is not easy to hinder the heat insulation property.

[0060] [Other components]

[0061] In addition to the porous structure, infrared shielding particles, and organic hollow particles, the heat-insulating material of the present disclosure may contain other components such as processing aids, inorganic fibers, reinforcing inorganic particles, flame retardants, organic fibers, inorganic hollow particles, and organic binders within a range that does not hinder the effects achieved by the present disclosure. Further, if there is a binder for bonding the constituent materials such as the porous structure, there is a risk of forming a heat conduction path through the binder. Therefore, from the perspective of suppressing the formation of a heat conduction path and achieving high heat insulation at high temperatures, the heat-insulating material preferably does not have a binder.

[0062] (1) Processing aids

[0063] A porous structure having hydrophobic sites on its surface and inside is not easily fused with water. Among them, silica aerogel, fumed silica agglomerated structures, etc. have a small specific gravity and thus tend to float on water. From the viewpoint of making the manufacturing easier, such as improving the water suspension of the porous structure and facilitating the dispersion of the porous structure when preparing a heat-insulating material composition using water as a solvent, it is preferable to incorporate processing aids according to the manufacturing method of the heat-insulating material. Examples of processing aids include surfactants, thickeners, and suspending agents.

[0064] Surfactants include ionic surfactants (cationic surfactants, anionic surfactants, amphoteric surfactants) and non-ionic surfactants. For example, if an ionic surfactant is used, even a small amount can increase the viscosity of the heat-insulating material composition or stabilize the dispersion of materials such as the porous structure in the heat-insulating material composition. Examples of ionic surfactants include sodium carboxymethyl cellulose (CMC-Na), polycarboxylic acid amine salts, polycarboxylic acid ammonium salts, polycarboxylic acid sodium salts, TEMPO-oxidized cellulose nanofibers (CNF-Na), etc. If a non-ionic surfactant is used, materials such as the porous structure are easily incorporated into the solvent when preparing the heat-insulating material composition. In addition, when these materials aggregate and separate in the heat-insulating material composition, they are easily redispersed, or the solvent is easily discharged when drying to form the heat-insulating material. Examples of non-ionic surfactants include polyethylene oxide (PEO), polyvinyl alcohol (PVA), etc. In addition, if a non-ionic surfactant and an ionic surfactant are used in combination, the effects based on the above can be adjusted arbitrarily, so it is preferable. For example, the water retention of PEO is not very high. Therefore, when preparing the heat-insulating material composition, water is difficult to enter the gaps between the porous structures, and it is difficult to generate voids when the water evaporates during drying. As a result, the infrared shielding particles and organic hollow particles are easily filled in the gaps between the porous structures. In addition, the small-diameter porous structures are easily filled in the gaps between the large-diameter porous structures.

[0065] If a processing aid exists on the surface or in the gaps of materials such as a porous structure, there is a risk of forming a heat conduction path through the processing aid. Therefore, from the perspective of suppressing the formation of a heat conduction path, the content of the processing aid is preferably 10% or less, more preferably 7% or less, based on the total mass of the heat insulating material being 100% by mass.

[0066] (2) Inorganic fibers

[0067] The inorganic fibers are physically wound around the porous structure to improve the mechanical strength of the heat insulating material and to suppress the shedding of the porous structure. The type of inorganic fiber is not particularly limited. Considering heat resistance, mechanical strength, etc., ceramic fibers such as glass fibers and alumina fibers are preferred. From the perspective of exerting the reinforcing effect, the content of the inorganic fiber based on the total mass of the heat insulating material being 100% by mass is preferably 5% or more. From the perspective of not forming a heat conduction path, it is preferably 15% or less. The length of the inorganic fiber is preferably 16 mm or less in consideration of both the reinforcing effect and the suppression of the formation of a heat conduction path.

[0068] (3) Reinforcing inorganic particles

[0069] From the perspective of improving the mechanical strength of the heat insulating material, reinforcing inorganic particles can be added to the heat insulating material. The type of reinforcing inorganic particles is not particularly limited. For example, particles with relatively high hardness and specific surface area such as precipitated silica, gel silica, fused silica, wollastonite, potassium titanate, magnesium silicate, glass flakes, calcium carbonate, and barium sulfate can be used.

[0070] (4) Flame retardant

[0071] If a flame retardant is added, the heat insulating material can be given flame retardancy. Known flame retardants such as halogen-based, phosphorus-based, and metal hydroxide-based flame retardants can be used. Considering the environmental load, a phosphorus-based flame retardant is preferably used. Examples of phosphorus-based flame retardants include ammonium polyphosphate, red phosphorus, and phosphate esters. Among them, from the reason that the flame retardant is not likely to flow out even when in contact with moisture during use, a water-insoluble phosphorus-based flame retardant or a phosphorus-based flame retardant coated with a water-resistant resin, etc., is preferred. For example, ammonium polyphosphate and ammonium polyphosphate coated with a resin are preferred.

[0072] <Manufacturing method of heat insulating material>

[0073] The heat insulating material of the present disclosure can be manufactured by pressure molding a material containing a porous structure, infrared shielding particles, organic hollow particles, etc. Alternatively, it can be manufactured by coating a liquid (including slurry) heat insulating material composition on a substrate and drying it, or by pressure molding a clay-like heat insulating material composition.

[0074] The thickness of the heat insulation material can be appropriately determined according to its use. For example, from the perspective of heat insulation performance, it is preferably set to 0.1 mm or more, 0.5 mm or more, and more preferably set to 1 mm or more. If the heat insulation material is too thick, not only will the cost increase, but it will also be difficult to install the heat insulation material in a narrow space. Therefore, for example, it is preferably 10 mm or less, 8 mm or less. In particular, from the perspectives of thinning and improving flexibility, etc., it is preferably set to 5 mm or less, and more preferably set to 3 mm or less. The density of the heat insulation material is preferably set to 0.4 g / cm 3 or less.

[0075] <Usage Mode of Heat Insulation Material>

[0076] The heat insulation material of the present disclosure can be used alone or together with a base material that supports the heat insulation material, an exterior material that houses the heat insulation material, etc. The base material can be disposed only on one side in the thickness direction of the heat insulation material, or can be disposed on both sides to sandwich the heat insulation material. In addition, the heat insulation material can be covered with a single piece of base material, and the base material can be used as the exterior material. A bonding layer can also be interposed between the heat insulation material and the base material. In the bonding layer, in addition to the bonding component, a flame retardant, etc. can also be contained.

[0077] Examples of the material of the base material include cloth, resin, paper, steel plate, etc. Examples of the fibers constituting the cloth include glass fiber, asbestos, ceramic fiber, alumina fiber, silica fiber, carbon fiber, metal fiber, polyimide fiber, aramid fiber, polyphenylene sulfide (PPS) fiber, etc. As the ceramic fiber, refractory ceramic fiber (RCF), polycrystalline alumina fiber (Polycrystalline Wool: PCW), and alkaline earth silicate (AES) fiber are known. Among them, AES fiber has biocompatibility, so it has higher safety. Examples of the resin include polyethylene terephthalate (PET), polyimide, polyamide, PPS, etc. Examples of the paper include pulp, a composite material of pulp and magnesium silicate, etc. Examples of the steel plate include galvanized steel sheet (Galvalume registered trademark), galvanized sheet, stainless steel (SUS) sheet, iron sheet, titanium sheet, etc. The shape of the base material is not particularly limited, and examples include woven fabric, non-woven fabric, film, sheet, etc. The base material can be composed of one layer, or can be a laminate formed by laminating two or more layers of the same material or different materials.

[0078] For example, the thermal conductivity of fabrics (woven fabrics), non-woven fabrics made of inorganic fibers such as glass fibers and metal fibers, and refractory heat-insulating papers made as composites of pulp and magnesium silicate, such as glass cloth, is relatively small, and the shape retention is high even in a high-temperature atmosphere. In addition, if a substrate with high heat resistance is used, it can be applied to applications requiring high heat resistance, so the uses of the heat-insulating material of the present disclosure are broadened. Furthermore, if a substrate with fire resistance is used, the safety is further improved. The substrate with high heat resistance can be made of glass fiber, rock wool, ceramic fiber, polyimide, PPS, etc. Specifically, glass fiber non-woven fabric, glass cloth, aluminum glass cloth, AES rock wool paper, polyimide fiber non-woven fabric, etc. can be cited.

[0079] Examples

[0080] Next, the present disclosure will be described more specifically by listing examples.

[0081] <Manufacture of heat-insulating material specimens>

[0082] Heat-insulating material specimens having the compositions shown in Table 1 below were manufactured. For the specimens of Examples 1 to 3, first, water was weighed in a resin container, a surfactant as a processing aid was added, and the surfactant was dissolved in water by stirring with an air-driven vane mixer at 800 rpm for 60 minutes. After stopping the stirring, silicon carbide (SiC) powder as infrared-shielding particles and powder of organic hollow particles were added, and further stirred at 800 rpm for 15 minutes. While continuing the stirring, silica aerogel powder as a porous structure was added to make it completely wet in the liquid. Then, glass fiber as an inorganic fiber was added and stirred at 800 rpm for 30 minutes. After that, additional stirring was performed at 1000 rpm for 10 minutes to manufacture a clay-like heat-insulating material composition.

[0083] For the specimens of Comparative Examples 1 to 3, except that the powder of organic hollow particles was not added, and instead an organic binder was added to the specimen of Comparative Example 2 and the powder of organic solid particles was added to the specimen of Comparative Example 3, the heat-insulating material compositions were manufactured in the same manner as the specimens of Examples 1 to 3.

[0084] The details of the materials used are as follows.

[0085] Silica aerogel powder: A pulverized product of "Aerogel Particles P200" manufactured by Cabot Corporation, with an average particle size of 100 μm.

[0086] Silicon carbide powder: "FUJI RUNDUM GC#4000" manufactured by Fuji Seisakusho Co., Ltd., with an average particle size of 5 μm.

[0087] Powder of organic hollow particles: Micro balloon made of acrylonitrile copolymer, "Matsumoto Microsphere (registered trademark) MFL-HD60CA" manufactured by Matsumoto Yushi Seiyaku Co., Ltd., with an average particle size of 50 to 70 μm and an elastic modulus of 17 MPa.

[0088] Surfactant: Polyethylene oxide "PEO-8" manufactured by Sumitomo Seika Chemicals Co., Ltd., with an average viscosity molecular weight of 1.7 million to 2.2 million.

[0089] Glass fiber: "ECS03-615" manufactured by Central Glass Fiber Co., Ltd., with a length of 3 mm and a fiber diameter of 9 μm.

[0090] Organic binder: Silicone emulsion, "Siltech E-2152" manufactured by Siltech Corporation.

[0091] Powder of organic solid particles: Powder of acrylic rubber, "XM-TM-1" manufactured by Matsumoto Yushi Seiyaku Co., Ltd., with an average particle size of 30 μm.

[0092] Next, a base of a first partition made of SUS was prepared on a glass fiber paper. The first partition had a thickness of 7 mm and a square injection hole with a side length of 150 mm was formed in the center. The produced heat-insulating material composition was filled into the injection hole of the first partition and formed into a plate shape. Next, the first partition was removed, the glass fiber paper was laminated from above, and then a second partition was disposed above it, and a laminate composed of "glass fiber paper / heat-insulating layer composition / glass fiber paper / second partition" was manufactured. The second partition had a thickness of 6 mm and a square injection hole with a side length of 150 mm was formed in the center in the same manner as the first partition. A pre-formed heat-insulating layer composition was disposed in the injection hole of the second partition. A first aluminum plate with a thickness of 5 mm and a side length of 320 mm and a second aluminum plate with a thickness of 1 mm and a side length of 320 mm were prepared separately. A plurality of groove portions were formed on one surface of the first plate. The plurality of groove portions were each linear with a width of 2.5 mm, a depth of 3 mm, and a length of 200 mm, and were formed in parallel at intervals of 5 mm. In the second plate, through holes with a diameter of 1 mm were formed as a whole at intervals of 2 mm. The second plate was laminated on one surface side of the first plate, and the laminate was disposed above it. Then, the second plate was placed on the laminate, and the first plate was further laminated in such a manner that the surface with the groove portions faced the second plate side. In this state, pressure drying based on hot stamping was performed at a temperature of 165 °C and a load of about 980 kN for 10 minutes. After that, it was cooled to room temperature (20 °C ± 5 °C), and the first plate, the second plate, the second partition, and the upper and lower glass fiber papers were removed, and a plate-shaped heat-insulating material specimen with a thickness of 6 mm was obtained. The density of the obtained heat-insulating material specimen was measured using a water displacement type density hydrometer "DSG-1" manufactured by Toyo Seiki Seisaku-sho, Ltd.

[0093] <Method for evaluating heat insulation property>

[0094] (1) Measurement of thermal conductivity at room temperature

[0095] The thermal conductivity of the manufactured heat-insulating material specimen at room temperature (20 °C ± 5 °C) was measured using a "non-steady state method thermal conductivity tester Quick Lambda HC-10" manufactured by Eihiro Seiki Co., Ltd.

[0096] (2) Measurement of thermal conductivity at high temperature

[0097] Using the "Quick Thermal Conductivity Meter QTM-700" and "High Temperature Compatible Probe PD-31N" manufactured by Kyoto Electronics Industry Co., Ltd., the thermal conductivity of the manufactured heat insulation material sample at 800 °C was measured as follows. First, three heat insulation material samples were overlapped to prepare two laminates with a thickness of 18 mm. One such laminate was placed on each of the upper and lower sides of the probe in a way that clamped the probe, and a weight of approximately 5 kg, which was heavy enough to prevent the upper laminate from collapsing, was placed on top and the setup was placed in an electric furnace. Then, the temperature inside the electric furnace was raised to 800 °C, and after the temperature inside the furnace stabilized, the thermal conductivity was measured.

[0098] (3) Evaluation Criteria

[0099] Regarding the heat insulation performance at room temperature, a case where the thermal conductivity at room temperature is 0.050 W / m·K or less is considered qualified (indicated by an ○ mark in Table 1 described later), and a case where the same thermal conductivity is greater than 0.050 W / m·K is considered unqualified (indicated by an × mark in the same table). Regarding the heat insulation performance at high temperature, a case where the thermal conductivity at 800 °C is less than 0.30 W / m·K is considered qualified (indicated by an ○ mark in the same table), and a case where the same thermal conductivity is 0.30 W / m·K or more is considered unqualified (indicated by an × mark in the same table).

[0100] <Evaluation Method for Flexibility and Resilience>

[0101] Using the tensilon universal material testing machine "RTF1350" manufactured by A&D Co., Ltd., a compression test was conducted on the central part of the manufactured heat insulation material sample (a square plate with a length of 150 mm, a width of 150 mm, and a thickness of 6 mm) by pressing it with a compression terminal with a diameter of 60 mm. The compression test was carried out by reciprocating the compression terminal at a speed of 1 mm / minute with the upper limit of the compression stress being 1.0 MPa, and three cycles were repeated with the interval of the compression stress being 0.02 MPa → 1.0 MPa → 0.02 MPa as one cycle. Based on the data obtained from the compression test, a stress-compression ratio curve was made with the compression ratio on the horizontal axis and the compression stress on the vertical axis. The compression ratio on the horizontal axis is the value calculated by the following formula (II).

[0102] Compression ratio (%) = Penetration amount of the compression terminal (mm) after the compression stress reaches 0.01 MPa during the pressing process of the first cycle / Thickness of the heat insulation material sample (mm) when the compression stress reaches 0.01 MPa during the pressing process of the first cycle × 100 ··· (II)

[0103] [Flexibility]

[0104] On the stress-compression ratio curve of the second cycle, connect the point with a compressive stress of 0.02 MPa at the start of the cycle and the point with a compressive stress of 1.0 MPa with a straight line, and use the value obtained by multiplying the slope of the resulting straight line by 100 as the index value of the flexibility of the thermal insulation material sample. That is, the index value of flexibility is the value calculated by the following formula (III).

[0105] Index value of flexibility = (1.0 - 0.02) / (a - b) × 100 ··· (III)

[0106] [a: Compression ratio (%) when the compressive stress is 1.0 MPa, b: Compression ratio (%) when the compressive stress is 0.02 MPa at the start of the cycle]

[0107] In this embodiment, the case where the index value of flexibility is 4.0 or less is considered qualified (indicated by the ○ symbol in Table 1 described later), and the case where it is greater than 4.0 is considered unqualified (indicated by the × symbol in the same table).

[0108] [Recovery]

[0109] On the stress-compression ratio curve of the second cycle, use the value obtained by subtracting the compression ratio when the compressive stress is 0.02 MPa at the end of the cycle from the compression ratio when the compressive stress is 1.0 MPa as the index value of the recovery of the thermal insulation material sample. In this embodiment, the case where the index value of recovery is 25% or more is considered qualified (indicated by the ○ symbol in Table 1 described later), and the case where it is less than 25% is considered unqualified (indicated by the × symbol in the same table).

[0110] <Evaluation results of heat insulation, flexibility, and recovery>

[0111] Table 1 shows the composition, density, and evaluation results of each property of the thermal insulation material sample.

[0112]

Table 1

[0113]

[0114] As shown in Table 1, it was confirmed that the samples of Examples 1 to 3 containing organic hollow particles in a predetermined proportion had excellent heat insulation both at room temperature and at high temperature. It was confirmed that the samples of Examples 1 to 3 also satisfied both flexibility and recovery. In contrast, the samples of Comparative Examples 1 to 3 that did not contain organic hollow particles resulted in poor flexibility and recovery. In addition, in the sample of Comparative Example 2 containing an organic binder and the sample of Comparative Example 3 that did not contain organic hollow particles but contained organic solid particles, the heat insulation at high temperature decreased.

[0115] Industrial applicability

[0116] The heat insulating material of the present disclosure is suitable for heat insulating materials for vehicles, heat insulating materials for houses, heat insulating materials for electronic devices, heat insulating materials for heat-insulating and cold-insulating containers, etc. Among them, it is suitable for heat insulating materials for battery packs that require heat insulation at high temperatures, heat insulating pads that require cushioning, etc.

Claims

1. A heat insulating material comprising a porous structure having a skeleton formed by a plurality of particles connected together and having pores between the skeletons, infrared shielding particles, and organic hollow particles, characterized in that: The content of the infrared shielding particles is 10% by mass or more and 30% by mass or less, when the mass of the heat insulating material is 100% by mass. The content of the organic hollow particles is 5% by mass or more and 30% by mass or less, based on 100% by mass of the heat insulating material.

2. The thermal insulation material according to claim 1, characterized in that: The porous structure has an average particle size of 1 μm or more and 1000 μm or less.

3. The thermal insulation material according to claim 1, characterized in that: The infrared shielding particles have an average particle size of 0.3 μm or more and 22 μm or less.

4. The thermal insulation material according to claim 1, characterized in that: The average particle diameter of the organic hollow particles is 1 μm or more and 1000 μm or less.

5. The thermal insulation material according to claim 1, characterized in that: The elastic modulus of the organic hollow particles is 1 MPa or more and 30 MPa or less.

6. The thermal insulation material according to claim 1, characterized in that: The organic hollow particles are composed of one or more selected from natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, ethylene-propylene-diene rubber, chloroprene rubber, polyurethane rubber, silicone rubber, ethylene-vinyl acetate rubber, epichlorohydrin rubber, acrylic rubber, styrene-based thermoplastic elastomer, vinyl chloride-based thermoplastic elastomer, olefin-based thermoplastic elastomer, polyester, polyacrylonitrile crosslinked body, polymethyl methacrylate crosslinked body, and polybutyl methacrylate crosslinked body.

7. The thermal insulation material according to claim 1, characterized in that: The infrared shielding particles include at least one particle selected from silicon carbide, kaolin, montmorillonite, titanium oxide, silicon nitride, mica, aluminum oxide, aluminum nitride, boron carbide, iron oxide, magnesium oxide, tin oxide, zinc oxide, tantalum oxide, manganese ferrite, manganese oxide, nickel oxide, nickel, silver oxide, silver, bismuth oxide, carbon black, graphite, titanium, titanium iron oxide, zirconium, zirconium oxide, zirconium silicate, barium titanate, manganese dioxide, chromium oxide, titanium carbide, tungsten carbide, tungsten oxide, niobium oxide, indium tin oxide, cerium oxide, and a mixture of two or more of these.

8. The thermal insulation material according to claim 1, characterized in that: The porous structure includes a silica aerogel in which a plurality of silica particles are linked to form a skeleton.

9. The thermal insulation material according to claim 1, characterized in that: The thermal insulation material further comprises at least one of a processing aid and inorganic fibers.

10. The thermal insulation material according to claim 1, characterized in that: The organic hollow particles are discontinuously present between the porous structures.

11. The thermal insulation material according to claim 1, characterized in that: The heat insulating material does not have a binder for bonding the porous structure, the infrared shielding particles, and the organic hollow particles.

12. The thermal insulation material according to claim 1, characterized in that: The organic hollow particles are single-hole type particles having one hole inside.

13. The thermal insulation material according to claim 1, characterized in that The organic hollow particles are porous particles having a plurality of pores inside.

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