Composition for heat insulating material and heat insulating material

Abstract

This composition for a heat insulating material comprises a silica aerogel, a polymer having a function to disperse the silica aerogel, inorganic particles having a hydroxyl group on the surface thereof, and a liquid. The composition for a heat insulating material satisfies the following condition (I) when the spinnability of a measurement liquid, which is obtained by removing the silica aerogel from the composition, is measured: "(I) The thread length obtained at a pulling speed of 4 mm / s is 40 mm or less." The composition for a heat insulating material can suppress crack formation during drying. The heat insulating material comprises a cured product of the composition for a heat insulating material. The heat insulating material has few cracks in the cured product thereof and exhibits excellent heat insulation properties.

Description

Composition for heat insulating material and heat insulating material

[0001] The present disclosure relates to a composition for a heat insulating material using silica aerogel and a heat insulating material.

[0002] Utilizing the high heat insulation property of silica aerogel, various heat insulating materials have been developed. A heat insulating material using silica aerogel can be manufactured, for example, as described in Patent Document 1, by applying a paint (composition for heat insulating material) in which silica aerogel is dispersed in a binder liquid to a substrate and drying it. As the binder, an organic binder such as a urethane resin is used. In this case, when the heat insulating material is used in a high-temperature atmosphere, the organic components of the binder may decompose and deteriorate, generating gas or causing cracks, and there is a risk that the shape cannot be maintained. Therefore, from the viewpoints of heat resistance and the like, heat insulating materials using inorganic binders such as silica nanoparticles have been developed as described in Patent Documents 2 and 3.

[0003] Japanese Patent Application Laid-Open No. 2020-29528, Japanese Patent Application Laid-Open No. 2021-143733, Japanese Patent Application Laid-Open No. 2022-55295

[0004] When silica nanoparticles are used as the binder, the problems due to the decomposition and deterioration of the binder component are improved, but there is a problem that cracks are likely to occur in the obtained heat insulating layer (cured product) when the composition for heat insulating material is applied to a substrate and dried. In this regard, in the above Patent Document 3, paying attention to the fact that when an inorganic binder is used, the cured product tends to be hard and brittle, it is described that by blending a thickener to impart flexibility to the cured product, the generation of cracks can be suppressed. However, simply blending a thickener may not sufficiently suppress the generation of cracks, and further investigation has been desired.

[0005] The present disclosure has been made in view of such circumstances, and an object thereof is to provide a composition for a heat insulating material in which cracks are unlikely to occur during drying. Another object is to provide a heat insulating material having few cracks and excellent heat insulating properties using the composition for heat insulating material.

[0006] (1) In order to solve the above problems, the thermal insulation composition of the present disclosure is a thermal insulation composition comprising silica aerogel, a polymer having the function of dispersing the silica aerogel, inorganic particles having hydroxyl groups on their surface, and a liquid, characterized in that when the stringability of the measurement liquid obtained by removing the silica aerogel from the thermal insulation composition is measured, the following condition (I) is satisfied: (I) The string length at a pulling speed of 4 mm / s is 40 mm or less.

[0007] The inventors of the present invention have conducted extensive research into the causes of crack formation when a thermal insulation composition (hereinafter sometimes simply referred to as "the composition") is applied to a substrate and dried, and have found that the cohesive force of the particles contained in the composition is related. As described in the above-mentioned Patent Documents 1 to 3, the composition may contain polymers such as carboxymethylcellulose, polyethylene oxide, and polyvinyl alcohol as thickeners to improve the dispersibility of silica aerogel. Also, as mentioned above, polymers such as urethane resin may be included as binders. For example, when these polymer chains are adsorbed onto silica particles by hydrogen bonding, a network is formed through the silica particles, shortening the distance between silica particles and increasing the cohesive force. This is thought to cause the coating film to shrink during drying, resulting in crack formation. The inventors of the present invention focused on this phenomenon and found a correlation between the cohesive force of silica particles and the stringiness (string-like property) of the composition.

[0008] In the thermal insulation composition of this disclosure, based on these findings, the stringiness of the measurement liquid (with silica aerogel removed from the composition) is controlled to satisfy condition (I), thereby reducing the cohesive force of the contained inorganic particles and suppressing crack formation. The reason for measuring stringiness in the measurement liquid rather than the entire composition is that the number of particles becomes too large when silica aerogel is included, making accurate measurement of stringiness impossible. When the measurement liquid is stretched upward, the shorter the string length (the length until the string-like liquid breaks), the easier the polymer chains are to break, meaning there is less interaction between the polymer chains and inorganic particles. In this disclosure, the string length at a pulling speed of 4 mm / s is considered to be the string length when no shear force is applied to the measurement liquid (a state close to a static state). Therefore, when condition (I) is satisfied, the cohesive force of the inorganic particles in the composition is small, which can suppress crack formation during drying. Furthermore, by measuring the stringiness of the measurement liquid, it is possible to predict whether or not cracks will occur. Incidentally, according to the inventor's research, even if the viscosity of the measuring liquid is the same, cracks may or may not occur, so simply adjusting the viscosity of the measuring liquid is not enough to suppress the occurrence of cracks.

[0009] (2) In the above configuration, the stringability of the measuring liquid may further satisfy the following condition (II): (II) The ratio of the string length at a pulling speed of 100 mm / s to the string length at a pulling speed of 4 mm / s (stringability ratio) is 2 or more.

[0010] When a thermal insulation composition is stirred or applied to a substrate using a coating machine, shear forces are applied to the composition. When shear forces are applied to the composition, the entanglement of polymer chains is undone, becoming linear, and they become more likely to form hydrogen bonds with inorganic particles that have hydroxyl groups on their surface. As a result, the network mediated by the inorganic particles expands, and gelation is thought to proceed. Therefore, if a gelled composition is dried as is, the cohesive force of the inorganic particles becomes stronger, and cracks are more likely to occur.

[0011] In this configuration, the length of the drawn thread at a tensile speed of 100 mm / s is considered to be the length of the drawn thread when a shear force is applied to the measurement liquid. The return property (gelation relaxation) after the composition has gelled due to stirring, coating, etc. is determined based on the ratio (drawn thread ratio) of this drawn thread length to the drawn thread length when no shear force is applied. In other words, if the length of the drawn thread when a shear force is applied is 2 or more compared to the length of the drawn thread when no shear force is applied, it is determined that the gelation relaxation is high. If the gelation relaxation is high, even if it has gelled once due to stirring, coating, etc., it is easier to return to the original state, so the cohesive force of inorganic particles is reduced and the occurrence of cracks can be suppressed.

[0012] (3) In any of the above configurations, the inorganic particles may consist of silica particles. Silica particles have good affinity with liquids such as water and excellent bonding and reinforcing properties with other materials. Therefore, they are suitable as fillers for purposes such as inorganic binders and reinforcements.

[0013] (4) In any of the above configurations, the inorganic particles may be configured to have nanoparticles having an average particle diameter of 8 nm or more and 45 nm or less. In this configuration, the nanoparticles act as an inorganic binder. When an inorganic binder is used, the cured product of the thermal insulation composition is less likely to deform even when used in a high-temperature atmosphere of 350°C or higher. Also, the cured product is less likely to be crushed even when compressed. As a result, the occurrence of cracks due to deformation and peeling from the substrate can be suppressed. The thermal insulation composition of this configuration is particularly suitable for applications that require high heat resistance.

[0014] (5) In the configuration of (4) above, the content of the nanoparticles may be 1 part by mass or more and 70 parts by mass or less per 100 parts by mass of the silica aerogel. With this configuration, the number of reaction sites between the polymer and nanoparticles contained in the composition can be reduced while ensuring the binder function. As a result, the cohesive force of the inorganic particles including the nanoparticles can be reduced.

[0015] (6) In any of the above configurations, the liquid may be water and the polymer may be a water-soluble resin. Many silica aerogels have hydrophobic regions on their surface to prevent moisture and other substances from penetrating and clogging the pores. Therefore, it is desirable to use a hydrophilic liquid such as water as the liquid constituting the composition, as it does not easily penetrate the pores of the silica aerogel. On the other hand, silica aerogels do not readily mix with water due to the hydrophobic regions on their surface. In addition, because of their low specific gravity, they tend to float on water. For this reason, it is difficult to disperse the silica aerogel when water is used as the liquid. In this respect, with the present configuration, since a water-soluble resin is used as the polymer that has the function of dispersing silica aerogel, the silica aerogel can be easily dispersed even when water is used.

[0016] (7) In the configuration of (6) above, the water-soluble resin may be configured to have one or more selected from polyoxyalkylene and polyvinyl alcohol.

[0017] (8) In the configuration of (7) above, the polyoxyalkylene may be a configuration comprising polyethylene oxide, polyethylene glycol, polyalkylene glycol, polypropylene glycol, polyoxyethylene, and polytetramethylene glycol.

[0018] (9) The thermal insulation material of this disclosure has a cured product of a thermal insulation composition having any of the above configurations. The thermal insulation composition of this disclosure is less prone to cracking during drying. Therefore, the thermal insulation material of this disclosure has fewer cracks in the cured product and excellent thermal insulation properties.

[0019] (10) In the configuration of (9) above, the cured material may be in the form of a sheet. With this configuration, the cured material can be placed as is, bent, wrapped around a component, or used to enclose a component, making it easy to apply to various uses.

[0020] (11) In the configuration of (9) or (10) above, the configuration may also include the cured material and a substrate that supports the cured material. By combining the cured material and the substrate, the strength of the heat insulating material is improved, and the effect of suppressing the shedding of silica aerogel is also improved.

[0021] The thermal insulation composition of this disclosure reduces the cohesive force of inorganic particles, thereby suppressing the occurrence of cracks during drying. Furthermore, the presence or absence of cracks can be predicted by measuring the stringiness of the measurement liquid. The thermal insulation material of this disclosure has a cured product of the thermal insulation composition of this disclosure, and therefore has fewer cracks and excellent thermal insulation properties.

[0022] This graph shows the relationship between the number of silica nanoparticles contained in the measurement solution and its stringiness.

[0023] The embodiments of the thermal insulation composition and thermal insulation material of this disclosure will be described below. However, the thermal insulation composition and thermal insulation material of this disclosure are not limited to the following embodiments and can be implemented in various forms with modifications and improvements that can be made by those skilled in the art, without departing from the gist of this disclosure.

[0024] <Composition for Thermal Insulation> The thermal insulation composition of the present disclosure comprises a silica aerogel, a polymer having the function of dispersing the silica aerogel, inorganic particles having hydroxyl groups on their surface, and a liquid.

[0025] [Silica Aerogel] The structure, shape, and size of silica aerogel are not particularly limited. For example, the diameter of the silica nanoparticles (primary particles) that form the skeleton of the silica aerogel is preferably about 2 to 5 nm, and the size of the pores formed between the skeletons is preferably about 10 to 50 nm. Most of the pores are so-called mesopores, which are 50 nm or smaller. Since mesopores are smaller than the mean free path of air, air convection is restricted and heat transfer is inhibited. As a result, silica aerogel has high thermal insulation properties.

[0026] Silica aerogels can take various shapes, including spherical and irregularly shaped lumps, but a spherical shape is preferable. Spherical shapes improve dispersibility, making composition preparation easier. Furthermore, they facilitate close packing, allowing for larger packing volumes and thus enhancing thermal insulation. Additionally, the smaller surface area allows for a reduction in the amount of binder with relatively high thermal conductivity, further improving thermal insulation.

[0027] When the maximum length of the silica aerogel is considered as the particle diameter, an average particle diameter of approximately 1 to 200 μm is desirable. The larger the particle diameter of the silica aerogel, the smaller the surface area and the larger the pore (void) volume, thus increasing the effect of improving thermal insulation. For example, an average particle diameter of 10 μm or more is preferable. On the other hand, considering the stability of the composition and ease of coating, an average particle diameter of 100 μm or less is preferable. Furthermore, using two or more types with different particle diameters allows the smaller diameter silica aerogel to fill the gaps between the larger diameter silica aerogels, increasing the filling volume and thus enhancing the thermal insulation effect. The average particle diameter of the silica aerogel is determined from the median diameter (D) obtained from the volume-based particle size distribution measured by laser diffraction / scattering. ５０ ) should be adopted.

[0028] It is desirable that silica aerogels have hydrophobic regions on at least the surface, both on the surface and internally. Having hydrophobic regions on at least the surface helps to suppress the penetration of moisture and other substances, thus maintaining the pore structure and preventing damage to the heat insulating properties. The method for manufacturing silica aerogels is not particularly limited, and the drying process may be carried out at atmospheric pressure or under supercritical conditions. Depending on the drying method used in the production of aerogels, those dried at atmospheric pressure are sometimes called "xerogels," those dried under supercritical conditions are called "aerogels," and those freeze-dried are called "cryogels," but in this specification, these will all be collectively referred to as "aerogels."

[0029] [Polymers] The thermal insulation compositions of this disclosure contain a polymer having the function of dispersing silica aerogel (hereinafter sometimes referred to as "polymer as a dispersant"). In addition to the polymer as a dispersant for silica aerogel, the thermal insulation compositions of this disclosure may also contain a polymer as a binder that binds the constituent components together. Of course, the polymer having the function of dispersing silica aerogel may also have a binder function.

[0030] Polymers used as dispersants improve the dispersibility of silica aerogels when preparing compositions or when pulverizing silica aerogels in the presence of liquid. For example, when the liquid is water, suitable polymers include polysaccharides such as carboxymethylcellulose (CMC), carboxyethylcellulose, carboxypropylcellulose, hydroxyethylcellulose, and hydroxypropylcellulose, as well as water-soluble resins such as polyoxyalkylenes and polyvinyl alcohol (PVA). One or more of these can be used. Examples of polyoxyalkylenes include polyethylene oxide (PEO), polyethylene glycol (PEG), polyalkylene glycol, polypropylene glycol (PPG), polyoxyethylene, and polytetramethylene glycol.

[0031] When using a polymer as a binder, separate from the polymer as a dispersant, it is desirable to use a resin with a glass transition temperature (Tg) of -5°C or lower, and even -20°C or lower, from the viewpoint of high adhesion to silica aerogel and making the cured composition flexible to suppress crack formation. Examples include acrylic resins, urethane resins, silicone resins, mixtures of acrylic resins and urethane resins, and mixtures of acrylic resins and silicone resins.

[0032] [Inorganic Particles] The thermal insulation composition of this disclosure contains inorganic particles having hydroxyl groups on its surface. In addition to inorganic particles having hydroxyl groups on its surface, the thermal insulation composition of this disclosure may also contain inorganic particles that do not have hydroxyl groups on their surface. Examples of inorganic particles having hydroxyl groups on their surface include silica, alumina, titanium oxide, and zinc oxide. Among these, silica particles have good affinity with liquids such as water and excellent bonding and reinforcing properties with other materials. Therefore, they are suitable as inorganic binders, fillers, and the like.

[0033] Among inorganic particles, nanometer-order particles (nanoparticles) are suitable as inorganic binders. Using nanoparticles can reduce the drawbacks of hardness and brittleness in the cured product of a thermal insulation composition caused by the incorporation of inorganic materials. The average particle size of the nanoparticles should be between 1 nm and 100 nm, and more preferably between 8 nm and 45 nm. Examples of binder liquids containing silica nanoparticles include sodium silicate solutions and colloidal silica dispersed in water.

[0034] According to the inventors' research, when nanoparticles have hydroxyl groups on their surface, their particle size and content have a significant effect on the stringiness of the measurement solution. For example, from the viewpoint of reducing stringiness by relatively reducing the number of nanoparticles and thus reducing the number of reaction sites between the polymer and the nanoparticles, when the average particle size of the nanoparticles is 8 nm or more and 45 nm or less, the content should be 1 part by mass or more and 70 parts by mass or less per 100 parts by mass of silica aerogel.

[0035] Among inorganic particles, those with a particle size of 1 μm or larger are suitable as fillers for adjusting texture and reinforcing. As fillers, it is preferable to use particles with relatively high hardness, such as precipitated silica, gel silica, fused silica, wollastonite, potassium titanate, magnesium silicate, glass flakes, calcium carbonate, and barium sulfate.

[0036] [Liquid] The liquid should be selected appropriately depending on the type of silica aerogel. For example, water (including pure water, tap water, etc.) is suitable. In addition, a small amount of organic solvent may be added to the water to improve the dispersibility or drying properties of the silica aerogel.

[0037] [Other Components] In addition to the silica aerogel, polymer, and inorganic particles described above, the thermal insulation composition of this disclosure may also contain infrared shielding particles, inorganic fibers, flame retardants, etc. Infrared shielding particles absorb heat from a heat source and re-emit it from the surface on the heat source side, thereby blocking radiant heat from the heat source and contributing to improved thermal insulation, especially at high temperatures. Examples of particles include silicon carbide, kaolinite, silicon nitride, mica, alumina, zirconia, aluminum nitride, zirconium silicate, cerium oxide, boron carbide, manganese oxide, tin oxide, iron oxide, and titanium oxide. Inorganic fibers, by physically intertwining around the silica aerogel, improve the mechanical strength of the thermal insulation layer and suppress the shedding of the silica aerogel. For example, glass fibers and ceramic fibers such as alumina fibers are preferred. As for flame retardants, already known ones such as halogen-based, phosphorus-based, and metal hydroxide-based ones may be used. Considering the environmental impact, it is desirable to use phosphorus-based flame retardants. Examples of phosphorus-based flame retardants include ammonium polyphosphate, red phosphorus, and phosphate esters.

[0038] [Stringability of the Measurement Solution] The thermal insulation composition of this disclosure satisfies condition (I), that when the stringability of the measurement solution, excluding silica aerogel from the composition, is measured, the length of the string drawn at a pulling speed of 4 mm / s is 40 mm or less. The stringability can be measured by immersing a measuring probe in the measurement solution at room temperature (20°C ± 5°C), stretching the measurement solution by pulling the measuring probe vertically at a constant speed, and measuring the length at which the string breaks. For measuring the stringability, for example, the "Stringability, Tension, and Coagulation Measurement Device NEVA® METER" manufactured by Ishikawa Iron Works Co., Ltd. is to be used. Considering the ease of measurement, it is desirable that the solid content concentration of the measurement solution be 3% by mass or more and 10% by mass or less.

[0039] When considering the gelation of the composition due to stirring, coating, etc., it is desirable that the stringiness of the measured liquid also satisfies condition (II), which is that the stringiness ratio calculated by the following formula (a) is 2 or more. Stringiness ratio = (String length at a pulling speed of 100 mm / s) / (String length at a pulling speed of 4 mm / s) ... (a) When condition (II) is satisfied, the gelation is easily relaxed, so even if gelation occurs due to stirring, coating, etc., it is easy to return to the original state where the cohesive force of inorganic particles is small. Therefore, the occurrence of cracks is suppressed.

[0040] [Method for preparing the composition] The thermal insulation composition of this disclosure may be prepared by stirring silica aerogel, a polymer having the function of dispersing silica aerogel, inorganic particles having hydroxyl groups on their surface, a liquid, and components to be added as needed. Stirring may be done by blade stirring, but shear force may also be actively applied or ultrasonic waves may be applied. A rotating and revolving stirring device, a media-type stirring device, or an intensive mixer may also be used.

[0041] <Thermal insulation material> The thermal insulation material of this disclosure has a cured product of the thermal insulation material composition of this disclosure described above. The cured product includes both a form in which the components of the composition solidify through a chemical reaction, and a form in which the liquid solidifies through evaporation without a chemical reaction. The cured product is manufactured by applying the composition and then drying it for a predetermined time at a temperature of room temperature to about 150°C. From the viewpoint of improving the thermal insulation properties of the cured product, it is desirable that the silica aerogel content in the cured product be 40% by mass or more, when the total mass of the cured product is taken as 100% by mass. It is more preferable that it be 50% by mass or more, or 65% by mass or more. On the other hand, if there is too much silica aerogel, it is prone to falling off, so it is desirable that the silica aerogel content be 75% by mass or less, when the total mass of the cured product is taken as 100% by mass.

[0042] The shape of the cured product is not particularly limited, and for example, it can be formed into a sheet shape. In this case, in addition to arranging the cured product as it is, it can be bent, wound around a member, or wrapped around a member, making it easy to apply to various uses. The heat insulating material of the present disclosure may be composed only of the cured product of the composition for the heat insulating material of the present disclosure, or may be configured by combining the cured product and other members. For example, the heat insulating material of the present disclosure may have a configuration including a cured product and a base material that supports the cured product. In this case, the cured product may be in a form laminated on the base material, or may be in a form in which a part penetrates into the inside of the base material. By combining the cured product and the base material, the strength of the heat insulating material is improved, and the effect of suppressing the dropout of silica aerogel is improved.

[0043] Examples of the material of the base material include cloth such as non-woven fabric and resin. Examples of the fibers constituting the cloth include glass fiber, rock wool, ceramic fiber, alumina fiber, silica fiber, carbon fiber, metal fiber, polyimide fiber, aramid fiber, polyphenylene sulfide (PPS) fiber, etc. Known ceramic fibers include refractory ceramic fiber (RCF), polycrystalline alumina fiber (Polycrystalline Wool: PCW), and alkaline earth silicate (AES) fiber. Among them, AES fiber has higher safety because it has biocompatibility. Examples of the resin include polyethylene terephthalate (PET), polyimide, polyamide, PPS, etc. The shape of the base material is not particularly limited, and examples include woven fabric, non-woven fabric, blanket, film, sheet, molded body, etc. The base material may be composed of a single layer, or may be a laminate in which the same material or different materials are laminated in two or more layers. Examples of the laminate include an aluminum vapor-deposited film, an aluminum glass cloth, etc.

[0044] For example, fabrics (woven fabrics) and non-woven fabrics made of inorganic fibers such as glass fibers and metal fibers, such as glass cloth, have relatively low thermal conductivity and high shape retention even in a high-temperature atmosphere. Further, if a base material with high heat resistance is adopted, it can also be applied to applications that require high heat resistance, so the applications of the heat insulating material of the present disclosure are expanded. Furthermore, if a base material having fire resistance is adopted, it becomes possible to protect the cured product from fire. The base material with high heat resistance may be manufactured from glass fiber, rock wool, ceramic fiber, polyimide, PPS, etc. Specifically, glass fiber non-woven fabric, glass cloth, aluminum glass cloth, AES wool paper, polyimide fiber non-woven fabric, etc. can be mentioned.

[0045] The heat insulating material in the form where the cured product is laminated on the base material or the form where a part of the cured product penetrates into the inside of the base material can be manufactured by applying the composition of the present disclosure to the surface of the base material and drying the coating film. Alternatively, after immersing the base material in the composition of the present disclosure, it may be dried. In either the coating or immersion method, when the base material is made of cloth or a porous material, a part of the composition impregnates into the inside of the base material. As a result, the cured product is arranged not only on the surface but also inside the base material. In this case, the flexibility of the heat insulating material is improved, and it becomes easier to follow deformations such as bending. Therefore, it is also easy to apply to members having a curved surface such as piping. For coating, coating machines such as a bar coater, a die coater, a comma coater (registered trademark), a roll coater, or a spray may be used. Further, in order to improve the adhesion between the base material and the cured product, a pretreatment such as a coupling treatment may be applied to the surface of the base material.

[0046] Next, the present disclosure will be described more specifically with reference to examples.

[0047] (1) Stringiness of the measurement solution <Manufacturing of the measurement solution> First, in the process of manufacturing the thermal insulation composition with the composition shown in Table 1 below (units are parts by mass), a measurement solution was manufactured that did not contain only silica aerogel. Specifically, the following were used to produce the measurement solution: carboxymethylcellulose sodium salt (CMC-Na) ("BSH-12" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), which primarily functions as a dispersant; polyethylene oxide (PEO) ("PEO-8" manufactured by Sumitomo Seika Co., Ltd.); colloidal silica (aqueous dispersion of silica particles; "Snowtex® ST-30" manufactured by Nissan Chemical Corporation) as an inorganic binder; silica powder ("Nipsil® VN3" manufactured by Tosoh Silica Co., Ltd., with an average particle size of 10 μm) as a filler; and water. The mixture was then mixed in a kneader and stirred to produce the measurement solution. CMC-Na and PEO are included in the concept of "polymers having the dispersion function of silica aerogel" in this disclosure. Colloidal silica and silica powder are included in the concept of "inorganic particles having hydroxyl groups on their surface" in this disclosure.

[0048] <Measurement of Tinderability of the Test Solution> The tinderability of the manufactured test solution was measured using the "Tinderability, Tinderability, and Coagulation Measurement Device NEVA® METER IMI0501" manufactured by Ishikawa Iron Works Co., Ltd. The measurement was performed at room temperature, using a flat measuring probe with a diameter of 3 mm. The length of the tinder was measured at two different probe pull-up speeds (pulling speeds): 4 mm / s and 100 mm / s. From the measured length of the tinderability, the tinderability ratio was calculated using the formula (a) above. Table 1 shows the composition of the thermal insulation material composition containing the test solution, the average particle size of the silica nanoparticles, and the measurement results of the tinderability. The average particle size of the silica nanoparticles is a converted value from the specific surface area obtained by the BET adsorption method.

[0049] Furthermore, the number of silica nanoparticles, which act as an inorganic binder in the measurement solution, was calculated assuming a spherical particle shape and a specific gravity of 2.2 g / cm³. ３ The calculation was performed as follows. Table 1 shows the number of silica nanoparticles, and Figure 1 shows a graph of the relationship between the number of silica nanoparticles and the stringability (string length at a tensile speed of 4 mm / s). In Figure 1, the values ​​such as "1.0E+17" and "1.0E+20" on the horizontal axis of the graph are "1.0 × 10 １７ "1.0 x 10２０ This means "and so on." In addition, the measurement solutions in the examples are indicated by black circles (excluding Example 2, which does not contain silica nanoparticles), and the measurement solutions in the comparative examples are indicated by black triangles. As shown in Figure 1, the number of silica nanoparticles is 1 × 10 １９ Beyond a certain number, the filament length increased as the number of nanoparticles increased. In the comparative example's measurement solution, the number of silica nanoparticles was greater and the filament length was longer compared to the example's measurement solution.

[0050] (2) Evaluation of Thermal Insulation Samples <Manufacturing of Thermal Insulation Samples> Silica aerogel (P200, manufactured by Cabot Corporation) was added to each measurement liquid and stirred to produce a thermal insulation composition. The manufactured composition was blade-coated onto the surface of a 1 mm thick glass fiber nonwoven fabric to a thickness of approximately 0.5 mm, and then placed in a hot air oven and held at 80°C for 1 hour to dry. In this way, a sheet-like thermal insulation sample (hereinafter sometimes simply referred to as a sample) was produced in which the cured composition was placed on the surface of the nonwoven fabric. A portion of the cured material was impregnated into the surface layer of the nonwoven fabric. Here, the glass fiber nonwoven fabric is included in the concept of a substrate in this disclosure. In Table 1, the samples of Examples 1 to 8 are included in the concept of thermal insulation in this disclosure.

[0051] <Presence or absence of cracks in cured material> The surface of the cured insulation material sample was visually inspected to check for the presence or absence of cracks. If no cracks were found, it was evaluated as "no cracks" (indicated by a circle in Table 1); if cracks were found, it was evaluated as "cracks present" (indicated by an "x" in the same table).

[0052] As shown in Table 1, in the samples of Examples 1 to 8, which satisfied condition (I) that the string length of the measurement solution was 40 mm or less, no cracks occurred in the cured product. These samples also satisfied condition (II) that the stringability ratio of the measurement solution was 2 or more. In contrast, in the samples of Comparative Examples 1 and 2, where the string length of the measurement solution was longer than 40 mm, cracks occurred in the cured product. The stringability ratio of the measurement solution in these samples was also less than 2. As shown in Figure 1, when the string length is short, the number of silica nanoparticles is relatively small, so it is thought that the particles separate from each other and level easily, and the cohesive force between particles is also small.

[0053] <Heat Resistance of Samples> The insulation material samples were left undisturbed in an oven maintained at 300°C for 24 hours, and their condition after heating was observed visually. If there was almost no change in appearance, it was evaluated as "good heat resistance" (indicated by a circle in Table 1), and if the sheet warped or curled, it was evaluated as "poor heat resistance" (indicated by an X in the same table). As shown in Table 1, only the sample from Example 2, which did not contain silica nanoparticles as an inorganic binder, showed poor heat resistance.

[0054] The thermal insulation material disclosed herein can be applied to various parts and components in the automotive, aerospace, marine, logistics, housing, industrial equipment, information and communication equipment, home appliances, and apparel sectors. In the automotive sector, examples include interior parts such as door trims, ceiling materials, instrument panels, console boxes, and armrests. In the aerospace sector, examples include various types of hoses, and in the marine sector, examples include thermal insulation materials placed in the hulls of ships. In the logistics sector, examples include insulated containers used when transporting food, pharmaceuticals, etc. In the housing sector, examples include building materials, wall materials, attic materials, and window sashes. In the industrial equipment sector, examples include thermal insulation materials used in motor parts, sensor parts, etc. In the information and communication equipment sector, examples include thermal insulation materials used in personal computers and smartphones. In the home appliance sector, examples include thermal insulation materials used in refrigerators, air conditioners, ovens, cameras, etc. In the apparel sector, examples include thermal insulation materials used in jackets, trousers, socks, hats, etc. In addition to these, it is also suitable for thermal insulation materials used in drones, thermal insulation materials for shoes such as insoles, thermal insulation materials for outdoor and leisure goods such as tents and seat mats, and everyday items such as cooler boxes. Furthermore, when equipped with a heat-resistant base material, it is suitable for fire-resistant insulation materials for steel frames in building materials, insulation materials used for roofs and walls of factories and plants, piping and sealing components used in factories and plants, and even various equipment such as presses, cutting machines, and drying ovens.

Claims

1. A thermal insulation composition comprising a silica aerogel, a polymer having the function of dispersing the silica aerogel, inorganic particles having hydroxyl groups on their surface, and a liquid, characterized in that when the stringability of the measurement liquid obtained by removing the silica aerogel from the thermal insulation composition is measured, the following condition (I) is satisfied: (I) The string length at a pulling speed of 4 mm / s is 40 mm or less.

2. The thermal insulation composition according to claim 1, wherein the stringability of the measurement liquid further satisfies the following condition (II): (II) The ratio of the string length at a tensile speed of 100 mm / s to the string length at a tensile speed of 4 mm / s (stringability ratio) is 2 or more.

3. The thermal insulation composition according to claim 1 or claim 2, wherein the inorganic particles are silica particles.

4. The thermal insulation composition according to any one of claims 1 to 3, wherein the inorganic particles are nanoparticles having an average particle diameter of 8 nm or more and 45 nm or less.

5. The composition for thermal insulation according to claim 4, wherein the content of the nanoparticles is 1 part by mass or more and 70 parts by mass or less per 100 parts by mass of the silica aerogel.

6. The thermal insulation composition according to any one of claims 1 to 5, wherein the liquid is water and the polymer is a water-soluble resin.

7. The thermal insulation composition according to claim 6, wherein the water-soluble resin is one or more selected from polyoxyalkylene and polyvinyl alcohol.

8. The thermal insulation composition according to claim 7, wherein the polyoxyalkylene comprises polyethylene oxide, polyethylene glycol, polyalkylene glycol, polypropylene glycol, polyoxyethylene, and polytetramethylene glycol.

9. A thermal insulation material having a cured product of the thermal insulation composition according to any one of claims 1 to 8.

10. The heat insulating material according to claim 9, wherein the cured product is in the form of a sheet.

11. The thermal insulation material according to claim 9 or claim 10, comprising the cured product and a substrate for supporting the cured product.

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