Compositions for thermal insulation and thermal insulation materials

Abstract

The present invention provides a thermal insulation composition that is less prone to cracking during drying. Furthermore, it provides a thermal insulation material with fewer cracks and excellent thermal insulation properties using this thermal insulation composition. [Solution] The thermal insulation composition comprises silica aerogel, a polymer having the function of dispersing the silica aerogel, inorganic particles having hydroxyl groups on their surface, and a liquid. 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. The thermal insulation material has a cured product of the thermal insulation composition.

Description

Technical Field

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

Background Art

[0002] Utilizing the high heat insulating property of silica aerogel, various heat insulating materials have been developed. A heat insulating material using silica aerogel can be produced, for example, as described in Patent Document 1, by applying a paint (composition for a 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 viewpoint 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.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] While using silica nanoparticles as a binder improves problems caused by the decomposition and degradation of the binder components, there was a problem in that cracks tended to occur in the resulting thermal insulation layer (cured product) when the thermal insulation composition was applied to a substrate and dried. In this regard, Patent Document 3 described that, focusing on the fact that the cured product tends to be hard and brittle when using an inorganic binder, crack occurrence can be suppressed by adding a thickening agent to impart flexibility to the cured product. However, simply adding a thickening agent is not always sufficient to suppress crack occurrence, and further investigation was desired.

[0005] This disclosure has been made in view of the above circumstances, and aims to provide a thermal insulation composition that is less prone to cracking during drying. Furthermore, it aims to provide a thermal insulation material with fewer cracks and excellent thermal insulation properties using this thermal insulation composition. [Means for solving the problem]

[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 stringiness 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 length of the line towed at a pulling speed of 4 mm / s is 40 mm or less.

[0007] The inventors of this 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 this 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 stringiness of the measuring liquid may further satisfy the following condition (II). (II) The ratio of the length of the line at a pulling speed of 100 mm / s to the length of the line at a pulling speed of 4 mm / s (line length 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 property) 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 property is high. If the gelation relaxation property 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 consist of 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. Furthermore, 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 requiring 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 the 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, it may be configured to have the cured product and a substrate that supports the cured product. By combining the cured product and the substrate, the strength of the heat insulating material is improved, and the effect of suppressing the detachment of silica aerogel is also improved.

Advantages of the Invention

[0021] According to the composition for a heat insulating material of the present disclosure, the cohesive force of inorganic particles can be reduced, and the generation of cracks during drying can be suppressed. Further, by measuring the drawability of the measurement liquid, the presence or absence of crack generation can be predicted. Since the heat insulating material of the present disclosure has a cured product of the composition for a heat insulating material of the present disclosure, it has few cracks and is excellent in heat insulation.

Brief Description of the Drawings

[0022] [Figure 1] It is a graph showing the relationship between the number of silica nanoparticles contained in the measurement liquid and the drawability.

Modes for Carrying Out the Invention

[0023] Hereinafter, embodiments of the composition for a heat insulating material and the heat insulating material of the present disclosure will be described. Note that the composition for a heat insulating material and the heat insulating material of the present 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 the present disclosure.

[0024] <Composition for Heat Insulating Material> The composition for a heat insulating material of the present disclosure includes silica aerogel, a polymer having a dispersion function for the silica aerogel, inorganic particles having hydroxyl groups on the 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] [polymer] The thermal insulation composition of this disclosure contains a polymer having the dispersing function of silica aerogel (hereinafter sometimes referred to as "polymer as a dispersant"). In addition to the polymer as a dispersant of silica aerogel, the thermal insulation composition of this disclosure may also contain a polymer as a binder that binds the constituent components together. Of course, the polymer having the dispersing function of 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, or 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 the 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 hardness and brittleness issues that arise from incorporating inorganic materials in the cured product of a thermal insulation composition. The average particle size of the nanoparticles should ideally 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 between 8 nm and 45 nm, the content should be between 1 and 70 parts by mass 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 and tap water) 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 ingredients] The thermal insulation composition of this disclosure may contain, in addition to the silica aerogel, polymer, and inorganic particles described above, 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] [Stringiness of the measuring solution] The thermal insulation composition disclosed herein satisfies condition (I), which states that when the stringability of the measurement liquid, with silica aerogel removed from the composition, is measured, the string length 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 liquid at room temperature (20°C ± 5°C), stretching the measurement liquid 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 "NEVA® METER stringability, spindle strength, and coagulation properties measuring device" manufactured by Ishikawa Iron Works Co., Ltd. is suitable. Considering the ease of measurement, it is desirable that the solid content concentration of the measurement liquid 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. Troll ratio = (Troll length at a pulling speed of 100 mm / s) / (Troll 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 easily returns to its original state where the cohesive force of inorganic particles is low. 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 a silica aerogel, a polymer having the function of dispersing silica aerogel, inorganic particles having hydroxyl groups on their surface, a liquid, and additional components as needed. Stirring may be done by blade stirring, but may also be done by actively applying shear force or ultrasonic waves. A rotational stirring device, a media-type stirring device, or an intensive mixer may also be used.

[0041] <Insulation material> The thermal insulation material of this disclosure has a cured product of the thermal insulation 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 or other means 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 becomes 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 material is not particularly limited, but it can be formed into a sheet, for example. In this case, 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. The thermal insulation material of this disclosure may consist only of the cured material of the thermal insulation composition of this disclosure, or it may be composed of the cured material in combination with other components. For example, the thermal insulation material of this disclosure may have a configuration comprising a cured material and a substrate that supports the cured material. In this case, the cured material may be in a form that is laminated on the substrate, or in a form in which a part of it penetrates into the interior of the substrate. By combining the cured material and the substrate, the strength of the thermal insulation material is improved, and the effect of suppressing the shedding of silica aerogel is also improved.

[0043] The base material can be fabric such as nonwoven fabric or resin. Fibers that make up the fabric include glass fiber, rock wool, ceramic fiber, alumina fiber, silica fiber, carbon fiber, metal fiber, polyimide fiber, aramid fiber, and polyphenylene sulfide (PPS) fiber. Examples of ceramic fibers include refractory ceramic fiber (RCF), polycrystalline wool (PCW), and alkali earth silicate (AES) fiber. Among these, AES fiber is considered safer due to its bio-soluble properties. Examples of resins include polyethylene terephthalate (PET), polyimide, polyamide, and PPS. The shape of the base material is not particularly limited and can include woven fabric, nonwoven fabric, blanket, film, sheet, and molded body. The base material may consist of a single layer or be a laminate in which the same or different materials are layered in two or more layers. Examples of laminates include aluminum vapor-deposited film and aluminum glass cloth.

[0044] For example, woven and nonwoven fabrics made from inorganic fibers such as glass fibers and metal fibers, such as glass cloth, have relatively low thermal conductivity and high shape retention even in high-temperature atmospheres. Furthermore, by using a heat-resistant substrate, the thermal insulation material can be applied to applications requiring high heat resistance, thus expanding the range of applications for this disclosure. Moreover, by using a fire-resistant substrate, it becomes possible to protect the cured material from flames. Heat-resistant substrates can be manufactured from glass fibers, rock wool, ceramic fibers, polyimide, PPS, etc. Specifically, examples include glass fiber nonwoven fabrics, glass cloths, aluminum glass cloths, AES wool paper, and polyimide fiber nonwoven fabrics.

[0045] Thermal insulation materials in which the cured material is laminated onto a substrate, or in which a portion of the cured material penetrates into the interior of the substrate, can be manufactured by applying the composition of this disclosure to the surface of the substrate and drying the coating. Alternatively, the substrate may be immersed in the composition of this disclosure and then dried. In either the application or immersion method, if the substrate is made of cloth or a porous material, a portion of the composition will be impregnated into the interior of the substrate. As a result, the cured material is positioned not only on the surface of the substrate but also inside. In this case, the flexibility of the thermal insulation material is improved, making it easier to follow deformations such as bending. Therefore, it is easy to apply to members with curved surfaces such as pipes. For application, coating machines such as bar coaters, die coaters, comma coaters (registered trademark), and roll coaters, or sprays may be used. Furthermore, to improve the adhesion between the substrate and the cured material, the surface of the substrate may be pre-treated, such as a coupling treatment. [Examples]

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

[0047] (1) Stringiness of the measuring solution <Manufacturing of measuring solution> First, in the process of manufacturing a thermal insulation composition with the composition (in parts by mass) shown in Table 1 below, a measurement solution was prepared that did not contain only silica aerogel. Specifically, carboxymethylcellulose sodium salt (CMC-Na) ("BSH-12" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and polyethylene oxide (PEO) ("PEO-8" manufactured by Sumitomo Seika Co., Ltd.), which mainly function as a dispersant, 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., average particle size 10 μm) as a filler, and water were added to 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 stringiness of the test solution> The stringability of the manufactured test solution was measured using the "NEVA(registered trademark) 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 strings drawn was measured at two different probe pulling speeds: 4 mm / s and 100 mm / s. From the measured string lengths, the stringability ratio was calculated using equation (a) above. Table 1 shows the composition of the thermal insulation composition containing the test solution, the average particle size of the silica nanoparticles, and the measurement results of the stringability. The average particle size of the silica nanoparticles is a value converted from the specific surface area obtained by the BET adsorption method. [Table 1]

[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" respectively. 17 "1.0×10 20 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 insulation material samples <Manufacturing of insulation material samples> Silica aerogel (P200, manufactured by Cabot Corporation) was added to each measurement solution and stirred to produce a thermal insulation composition. The produced 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 dried in a hot air oven at 80°C for 1 hour. In this way, a sheet-like thermal insulation sample (hereinafter sometimes simply referred to as "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 crack formation in hardened material> The surface of the cured insulation material samples 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 the sample> 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. Samples with little to no change in appearance were evaluated as having "good heat resistance" (indicated by a circle in Table 1), while samples that warped or curled were evaluated as having "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. [Industrial applicability]

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

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

3. The aforementioned inorganic particles are silica particles, as per claim 1, for the thermal insulation composition.

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

5. The thermal insulation composition 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 aforementioned liquid contains water. The thermal insulation composition according to claim 1, wherein 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 described in claim 1.

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, comprising the cured product and a substrate for supporting the cured product.

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