Thermal insulation material

Abstract

Provided is a thermal insulation material including a thermal insulation layer. The thermal insulation layer contains silica particles, and graphite particles having a property parameter G of 6.0 to 30 inclusive, the property parameter G being expressed by the following formula.　G = (F3-6)2 × HW / D50 (In the formula, F3-6 is a volume frequency [%] of a particle diameter of 3 to 6 μm in a volume-based particle size distribution based on a laser diffraction / scattering method, D50 is a cumulative 50% particle diameter [μm] in the volume-based particle size distribution, and HW is a half-width [°] of a (002) peak in X-ray diffraction.)

Description

insulation

[0001] The present invention relates to a thermal insulation material.

[0002] Non-aqueous electrolyte secondary batteries, such as lithium-ion batteries, are widely used as power sources for electric vehicles (e.g., hybrid vehicles, electric vehicles), portable electronic devices (e.g., mobile terminals, mobile phones, and laptop computers), and wearable devices. For example, in lithium-ion battery modules and packs installed in electric vehicles, multiple cells are stacked. Therefore, adjacent cells are not directly contacted, and insulating material is sometimes placed between the cells to further insulate them. For example, Patent Document 1 describes an insulating sheet for a battery assembly to be interposed between battery cells of an assembled battery. The insulating sheet contains first particles composed of silica nanoparticles and second particles composed of a metal oxide, and the content of the first particles relative to the total mass of the first and second particles is within a predetermined range. Patent Document 2 also describes an insulator containing an inorganic insulating material having a porous structure and a predetermined amount or more of a binder, and cites ceramic nanoparticles such as silica as an example of the inorganic insulating material. This application claims priority based on Japanese Patent Application No. 2024-014440, filed February 1, 2024, the entire contents of which are incorporated herein by reference.

[0003] Japanese Patent Application Publication No. 2021-34278 Japanese Patent Application Publication No. 2020-170707

[0004] Insulating materials used in battery modules of nonaqueous electrolyte secondary batteries are sometimes required to have the function of preventing, for example, abnormal heat generation in some cells from propagating to other cells and causing thermal runaway. To achieve such a function, insulating materials that exhibit good insulating properties even at high temperatures (e.g., approximately 600°C to 800°C) are preferred. However, insulating materials designed to exhibit insulating properties by suppressing solid conduction and gas conduction during normal use of nonaqueous electrolyte secondary batteries tend to exhibit reduced insulating performance at high temperatures. It would be beneficial to provide a technology that effectively suppresses such performance degradation.

[0005] The present invention has been made in view of the above circumstances, and has an object to provide a heat insulating material in which the deterioration of heat insulating performance in a high temperature range is suppressed.

[0006] The inventors focused on graphite as a material for improving the insulating performance of insulating layers containing silica particles in the high temperature range, and after extensive research, discovered a property parameter that can effectively correlate the properties of graphite with thermal conductivity in the high temperature range, and further found a numerical range for the property parameter that can efficiently improve the insulating performance in the high temperature range, thereby completing the present invention.

[0007] This specification provides a thermal insulation material including a thermal insulation layer. The thermal insulation layer includes silica particles and graphite particles having a property parameter G expressed by the following formula of 6.0 or more and 30 or less: G=(F ３－６ ) ２ ×H Ｗ / D50; where F in the formula ３－６ is the volume frequency [%] of particle sizes of 3 to 6 μm in the volume-based particle size distribution based on the laser diffraction / scattering method, D50 is the cumulative 50% particle size [μm] in the volume-based particle size distribution, and H Ｗ is the half-width [°] of the (002) peak in X-ray diffraction. By incorporating graphite particles having a property parameter G value (hereinafter also referred to as "G value") in the range of 6.0 to 30 into a heat insulating layer containing silica particles, the heat insulating performance of the heat insulating layer in the high temperature range can be improved. This makes it possible to suppress a decrease in the heat insulating performance of a heat insulating material including the heat insulating layer.

[0008] In some embodiments, the graphite particles have a cumulative 50% particle diameter D50 of 2.0 μm or more and less than 11 μm. The technology disclosed herein can be suitably implemented using graphite particles having a D50 in the above range.

[0009] In some embodiments, the graphite particles have a volume frequency F of 3 to 6 μm. ３－６ It is preferable that the volume frequency F is 10% or more. Particles with a particle size in the range of 3 to 6 μm have good absorption of electromagnetic waves radiated in high temperature ranges and are suitable for suppressing radiant heat transfer. ３－６A heat insulating layer containing graphite particles in which the SiO 2 content is 10% or more and the G value is within the above range can more suitably improve the heat insulating performance in the high temperature range.

[0010] In some embodiments, the graphite particles have a volume frequency F of 4.625 μm in a volume-based particle size distribution based on a laser diffraction / scattering method. ４．６２５ is preferably 3.0% or more. ４．６２５ A heat insulating layer containing graphite particles in which the SiO 2 content is 3.0% or more and the G value is within the above range can more suitably improve the heat insulating performance in the high temperature range.

[0011] In some embodiments, the graphite particles have a half-width H Ｗ It is preferable that the half width H Ｗ Graphite particles having the above structure can efficiently absorb electromagnetic waves by suppressing reflection on the particle surface, and therefore can effectively improve the heat insulating performance in high temperature ranges.

[0012] In some preferred embodiments, the graphite particles are artificial graphite. The technology disclosed herein can be preferably carried out in an embodiment in which artificial graphite is used as the graphite particles.

[0013] The content of the graphite particles in the heat insulating layer can be, for example, in the range of 2.5% by mass to 30% by mass, which makes it easy to achieve a good balance between good heat insulating properties in the high temperature range due to the effect of the graphite particles and good heat insulating properties in the lower temperature range (for example, room temperature to about 80°C).

[0014] In some embodiments, the silica particles are at least one selected from the group consisting of hydrophilic fumed silica and hydrophobic fumed silica. The technology disclosed herein can be preferably applied to a thermal insulation layer containing such silica particles.

[0015] In some embodiments, the density of the insulating layer is 0.2 g / cm ３ ~0.5g / cm ３ When the density of the heat insulating layer is within the above range, it becomes easier to ensure good heat insulating properties and appropriate compressive deformation properties.

[0016] The insulating material disclosed herein can be preferably used, for example, in a battery module or battery pack including a plurality of arranged cells, in which the insulating material is disposed between adjacent cells of the plurality of cells, taking advantage of its characteristic of being able to exhibit good insulating properties even in high temperature ranges.

[0017] Appropriate combinations of the elements described in this specification may also be included within the scope of the invention for which patent protection is sought by this patent application.

[0018] 1 is a perspective view schematically illustrating an example of a battery module in which a heat insulating material is disposed between cells according to an embodiment of the present invention; FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1; and FIG. 3 is a cross-sectional view schematically illustrating a heat insulating material according to an embodiment of the present invention.

[0019] Preferred embodiments of the present invention are described below. Matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood by those skilled in the art based on the teachings for carrying out the invention described in this specification and the common general technical knowledge at the time of filing. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. Furthermore, in the following drawings, components and parts that perform the same function may be denoted by the same reference numerals, and redundant explanations may be omitted or simplified. Furthermore, the embodiments shown in the drawings are schematic for the purpose of clearly explaining the present invention, and do not necessarily accurately represent the size or scale of the actual product provided.

[0020] In this specification, "weight" and "mass" may be read interchangeably. For example, "wt%" and "mass%" may be read interchangeably, and "parts by weight" and "parts by mass" may be read interchangeably.

[0021] <Thermal Insulation Layer> (Silica Particles) The thermal insulation material disclosed herein has a thermal insulation layer containing silica particles. ２) can be classified into crystalline silica, amorphous silica, etc. based on structural characteristics, and into natural silica, synthetic silica, etc. based on the method of acquisition. Synthetic silica can be classified into dry silica, wet silica, silica aerogel, etc. based on the production method. Dry silica can be classified into silica obtained by a combustion method, silica obtained by an arc method, etc., and wet silica can be classified into silica obtained by a gel method, silica obtained by a precipitation method, etc. The type of silica particles used as a component of the heat insulating layer is not particularly limited and can be any of the above-mentioned types. In some embodiments, dry silica is preferred, and among dry silica, fumed silica is more preferred, and among fumed silica, hydrophilic fumed silica is particularly preferred. Note that hydrophilic fumed silica refers to fumed silica that mainly has hydrophilic silanol groups (Si—OH) on the surface, and generally refers to fumed silica in which the silanol groups have not been replaced with hydrophobic groups by surface treatment or the like.

[0022] Silica particles generally exist as primary particles, as aggregates formed by aggregation of primary particles, or as aggregates formed by further aggregation of the aggregates. The silica particles in the heat insulating layer may be dispersed in the form of primary particles, aggregates, aggregates, or a combination thereof.

[0023] The average primary particle diameter of the silica particles is not particularly limited, and is, for example, about 1 nm to 100 nm, preferably 2 nm or more, more preferably 4 nm or more, and preferably 80 nm or less, more preferably 40 nm or less, even more preferably 30 nm or less, and particularly preferably 20 nm or less. When the silica particles contain fumed silica, the average primary particle diameter of the fumed silica is, for example, about 1 nm to 40 nm, preferably 2 nm or more, more preferably 4 nm or more, and preferably 30 nm or less, more preferably 20 nm or less, and even more preferably 18 nm or less. When the average primary particle diameter of the silica particles is within the above range, good heat insulation properties can be easily ensured. Note that, examples of methods for determining the average primary particle diameter of silica particles include a method using an electron microscope such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Specifically, a method can be used in which silica particles are randomly selected and their particle diameters are measured under an electron microscope, and the average value of the measured values ​​is calculated. The particle size may be the diameter if the particle is spherical, the intermediate value between the minor axis and the major axis if the particle is elliptical when viewed under an electron microscope, or the intermediate value between the minor axis and the major axis if the particle is an irregular particle.

[0024] The average particle size of the secondary aggregates of silica particles (aggregates of primary particles) is not particularly limited and is usually 0.1 μm or more and 100 μm or less, preferably 1 μm or more, more preferably 2 μm or more, and preferably 90 μm or less, more preferably 80 μm or less. Note that, as a method for determining the average particle size of the secondary aggregates of silica particles, a method for measuring using the same method as for the primary particle size can be mentioned.

[0025] The BET specific surface area of ​​the silica particles is not particularly limited, and is, for example, 40 m ２ / g or more 800m ２ / g or less, and ２ / g or more 600m ２ In some embodiments, the BET specific surface area of ​​the silica particles may be about 90 m / g or less. ２ / g or more 380m ２ / g, and preferably less than 130m２ / g or more, more preferably 175m ２ / g or more, more preferably 200m ２ / g or more, and preferably 350m ２ / g or less, more preferably 320m ２ / g or less, more preferably 300m ２ / g or less. When the BET specific surface area of ​​the silica particles is within the above range, good heat insulation properties can be easily ensured even under high temperature and high humidity conditions. The BET specific surface area can be measured by the multipoint nitrogen adsorption method (BET method) in accordance with the International Organization for Standardization ISO 5794 / 1. For example, "AEROSIL 380" manufactured by Aerosil Co., Ltd. has a nominal BET specific surface area of ​​380 m ２ / g, and taking into account the error, it is 350m ２ / g~410m ２ In this case, the nominal value of 380 m ２ / g is considered as the standard.

[0026] The apparent specific gravity of the silica particles is not particularly limited and may be, for example, 30 g / L or more and 130 g / L or less, preferably 40 g / L or more (e.g., 50 g / L or more), and preferably 120 g / L or less (e.g., 100 g / L or less). In some embodiments, the apparent specific gravity of the silica particles may be, for example, 80 g / L or less, or 60 g / L or less. The apparent specific gravity of the silica particles can be determined by filling the silica particles into a container capable of measuring volume, such as a 250 mL measuring cylinder, measuring the filling mass (X g) of the silica particles and the filling volume (Y mL), and dividing the filling mass by the filling volume ([apparent specific gravity (g / L)] = X / Y × 1000). In addition, if a nominal value of the apparent specific gravity is provided by a manufacturer, etc., that nominal value can be used.

[0027] Commercially available silica particles include hydrophilic fumed silica such as AEROSIL 50, 90, 130, 200, 200V, 300, and 380 from the AEROSIL series (manufactured by Nippon Aerosil Co., Ltd.), QS-09, QS-10, QS-102, QS-20, QS-20L, QS-30, Q40, and CP-102 from the Reolosil series (manufactured by Tokuyama Corporation), and HDKV15, N20, T30, and T40 from the HDK series (manufactured by Wacker Asahi Kasei Silicone Co., Ltd.), as well as hydrophobic fumed silica such as AEROSIL R972 and R976S from the AEROSIL series (manufactured by Nippon Aerosil Co., Ltd.), and HDK from the HDK series (manufactured by Wacker Asahi Kasei Silicone Co., Ltd.). Examples of suitable silica aerogels include AIRICA (manufactured by Tokuyama Corporation), which is a silica aerogel, such as H15, H20, and H30. The heat insulating layer may contain one type of silica particles or two or more types of silica particles.

[0028] The content of silica particles in the heat insulating layer is not particularly limited, and can be, for example, within the range of 50% by mass or more and 99.5% by mass or less.In some embodiments, the content is preferably 60% by mass or more, more preferably 70% by mass or more, and may be 75% by mass or more, and also preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less, and may be 80% by mass or less.The heat insulating layer having the content of silica particles within any of the above ranges can easily ensure good heat insulating properties.

[0029] (Graphite Particles) The heat insulating layer disclosed herein contains, in addition to silica particles, graphite particles having a property parameter G (G value) represented by the following formula of 6.0 or more and 30 or less: G=(F ３－６ ) ２ ×H Ｗ / D50 where F in the above formula ３－６ is the volume frequency [%] of particle sizes of 3 to 6 μm in the volume-based particle size distribution based on the laser diffraction / scattering method. D50 in the above formula is the cumulative 50% particle size [μm] in the volume-based particle size distribution. H Ｗ is the half-width [°] of the (002) peak in X-ray diffraction. ３－６ , D50 and HＷ The G value calculated by the above formula is a dimensionless number having no unit, and is a numerical value when the volume frequency of particle sizes of 3 to 6 μm is expressed in units of "%", the 50% cumulative particle size is expressed in units of "μm", and the half-value width is expressed in units of "°".

[0030] Above F ３－６ is obtained by measuring the volumetric particle size distribution of a dispersion of graphite particles to be measured in ion-exchanged water using a particle size distribution measuring device based on a laser diffraction / scattering method, and determining the volume frequency of particle sizes in the range of 3 to 6 μm from the measurement results. More specifically, for example, the volume frequencies at particle sizes x1 = 5.998 μm, x2 = 5.500 μm, x3 = 5.044 μm, x4 = 4.625 μm, x5 = 4.241 μm, x6 = 3.889 μm, x7 = 3.566 μm, x8 = 3.270 μm, and x9 = 2.999 μm are expressed as y ｘｎ [%] (where the total frequency in the particle size distribution measurement is 100%), and x ｎ -x ｎ＋１ xy ｎ The value [%] obtained by integrating the values ​​in the range of n = 1 to 8 was used as the volume frequency (F ３－６ In the examples described later, the F calculated by the above method can be used. ３－６ As an alternative method, the integral value of the volume frequency (total frequency is set to 100%) in the particle size range of 3 to 6 μm was calculated from the volume-based particle size distribution curve based on the results of the particle size distribution measurement, and the obtained value was used as F ３－６ As the particle size distribution measuring device based on the laser diffraction / scattering method, an MT3000-II manufactured by MicrotracBEL Corp. or an equivalent product can be used.

[0031] The D50 can be obtained by measuring the volumetric particle size distribution of a dispersion of the graphite particles to be measured in ion-exchanged water using a particle size distribution analyzer based on a laser diffraction / scattering method, and determining the particle diameter at 50% cumulative from the small diameter side of the particle size distribution (50% cumulative particle diameter). More specifically, the D50 can be determined by the method described in the Examples below.

[0032] The half width H ｗ The half width H can be obtained by performing X-ray diffraction measurement on the graphite particles to be measured, separating the graphite (002) peak from the measurement results, and determining the half width (i.e., the diffraction angle at the diffraction intensity of the maximum diffraction intensity of the peak × 1 / 2) [°]. ｗ More specifically, is determined by the method described in the Examples below.

[0033] The inventors have discovered that the G value expressed by the above formula can effectively correlate graphite properties with thermal conductivity at high temperatures, and that incorporating graphite particles having a G value in the range of 6.0 to 30 into a thermal insulation layer can effectively improve the thermal insulation performance of the thermal insulation layer at high temperatures. The reasons for this are thought to be as follows: The graphite particles in the thermal insulation layer can contribute to suppressing radiative heat transfer within the thermal insulation layer by absorbing electromagnetic waves emitted from objects at high temperatures. Meanwhile, incorporating graphite particles into a thermal insulation layer also increases the number of heat transfer paths (increasing heat transfer by solid conduction). Graphite particles with a particle size in the range of 3 to 6 μm are suitable for absorbing electromagnetic waves because they have a particle size close to the peak wavelength of electromagnetic waves emitted at high temperatures (e.g., 600°C to 800°C). Furthermore, the size of the graphite particles affects the degree of solid conduction. Furthermore, from the viewpoint of suppressing reflection on the particle surface and efficiently absorbing electromagnetic waves, the crystallinity of the graphite particles is not too high (half-value width H Ｗ It is believed that it is advantageous for the temperature [°] to be not too small. The above formula appropriately takes into account the influences of these multiple factors, and is therefore believed to be able to satisfactorily correlate the properties of graphite with thermal conductivity in the high temperature range. However, the above mechanism is the inventors' consideration based on experimental results, and the technology disclosed herein should not be interpreted as being limited to the above mechanism.

[0034] A heat insulating layer having a silica-containing structure containing graphite particles having a G value in the range of 6.0 to 30 can effectively improve heat insulating performance in high temperature ranges compared to a structure containing graphite particles having a G value that is either too large or too small. From the viewpoint of easily achieving a higher effect, in some embodiments, the G value is preferably 8.0 or more, more preferably 10 or more (e.g., 12 or more), and is preferably 28 or less, more preferably 24 or less.

[0035] The volume frequency F of the graphite particles having a particle size of 3 to 6 μm ３－６ In some embodiments, the volume frequency F of the particles having a particle size of 3 to 6 μm can be, for example, 5% or more and 50% or less. ３－６ is suitably 8% or more, preferably 10% or more, and more preferably 15% or more. ３－６ is suitably 30% or less, and preferably 25% or less. ３－６ Graphite particles having a G value in the above range can easily achieve a suitable G value and can easily obtain good effects.

[0036] In some embodiments, the graphite particles have a volume frequency F of 4.625 μm in a volume-based particle size distribution based on a laser diffraction / scattering method. ４．６２５ It is preferable that the content of the fluorine-containing compound is 3.0% or more. Particles with a particle size of about 4.625 μm have good absorption properties for electromagnetic waves radiated in high temperature ranges (for example, about 800° C.), and can effectively suppress radiant heat transfer. From the viewpoint of making it easier to exert a better effect, in some embodiments, the above-mentioned F ４．６２５ is suitably 4.0% or more, preferably 5.0% or more, and more preferably 6.0% or more. ４．６２５ may be, for example, 25% or less, 20% or less, or 15% or less, and in some embodiments is preferably 11% or less, may be 10% or less, may be 9.0% or less, or may be 8.0% or less. ４．６２５Graphite particles having a particle size within the above range are likely to provide good results in improving the heat insulating performance.

[0037] The volume frequency F ４．６２５ is the above-mentioned F ３－６ The particle size distribution on a volume basis is measured in the same manner as in the case of F, and the volume frequency at a particle size of 4.625 μm is calculated from the measurement results (the total frequency in the particle size distribution measurement is taken as 100%). ４．６２５ More specifically, F can be determined by the method described in the Examples below. Alternatively, the volume frequency (the total frequency is set to 100%) corresponding to a particle size of 4.625 μm can be read from the volume-based particle size distribution curve based on the results of the particle size distribution measurement, and the obtained value can be used as F ４．６２５ A method of setting the value as follows is as follows.

[0038] The cumulative 50% particle diameter D50 of the graphite particles may be, for example, in the range of about 1.0 μm or more and 20 μm or less. In some embodiments, the D50 of the graphite particles is suitably 2.0 μm or more, advantageously 3.0 μm or more, and preferably 3.5 μm or more (e.g., 4.0 μm or more). In some embodiments, the D50 of the graphite particles may be, for example, 18 μm or less, suitably less than 11 μm, advantageously 10 μm or less, preferably 8.0 μm or less, more preferably 7.0 μm or less, or may be 6.5 μm or less, 6.0 μm or less, or 5.5 μm or less. Graphite particles having a D50 in the above range are likely to achieve a suitable G value and to result in good thermal insulation performance improvement.

[0039] The half-value width H of the graphite particles Ｗ The half width H Ｗ can be used as a measure of the degree of crystallization of graphite, and Ｗ In some embodiments of the technology disclosed herein, the full width at half maximum H Ｗis suitably 0.17° or more, preferably 0.18° or more, more preferably 0.19° or more, and may be 0.20° or more. Ｗ is suitably 0.30° or less, preferably 0.25° or less, and may be 0.23° or less. Ｗ Graphite particles having a G value in the above range are likely to achieve a suitable G value, and are likely to provide good results in improving the heat insulating performance.

[0040] The type of graphite particles used in the technology disclosed herein is not particularly limited, and both artificial graphite and natural graphite can be used. Examples of natural graphite include flake graphite and what is called scaly graphite. The crystallinity or half-width H ｗ In some embodiments, artificial graphite may be preferably used from the viewpoint of ease of adjustment of the graphite content.

[0041] The content of the graphite particles in the heat insulating layer is not particularly limited and can be appropriately set so as to obtain the desired effect. The content of the graphite particles in the heat insulating layer (by mass) may be, for example, 0.5% by mass or more, 1% by mass or more, or 2% by mass or more. From the viewpoint of easily obtaining a higher usage effect (e.g., the effect of improving heat insulating performance in high temperature ranges), in some embodiments, the content of the graphite particles in the heat insulating layer is suitably 2.5% by mass or more, preferably 3.5% by mass or more, and may be 5% by mass or more, 7% by mass or more, 10% by mass or more, 12% by mass or more, or 15% by mass or more. Furthermore, the content of the graphite particles in the heat insulating layer may be, for example, 40% by mass or less. From the viewpoint of suppressing heat transfer due to solid conduction of the graphite particles, it is advantageous to be 35% by mass or less, preferably 30% by mass or less, more preferably 25% by mass or less, and may be 20% by mass or less, 18% by mass or less, 15% by mass or less, 3% by mass or less, 10% by mass or less, or 8% by mass or less. It is also advantageous from the viewpoint of the compressibility of the heat insulating layer that the content of graphite particles is not too high. With this content, the excellent heat insulating properties of the silica particles can be utilized, while the effect of improving the heat insulating properties at high temperatures by including the graphite particles can be suitably exhibited.

[0042] (Inorganic Fibers) In some preferred embodiments, the insulating layer further contains inorganic fibers in addition to the silica particles and graphite particles described above. The inorganic fibers can be useful for improving the ease of manufacture (e.g., ease of molding) of the insulating layer containing silica particles and graphite particles, improving thickness precision, and improving the strength of the insulating layer. The type of inorganic fiber is not particularly limited. Examples of inorganic fibers that can be preferably used from the standpoint of heat resistance and strength include glass fibers, silica fibers, alumina fibers, silica-alumina fibers, silica-alumina-magnesia fibers, biosoluble inorganic fibers, zirconia fibers, alkaline earth metal silicate (alkaline earth silicate (AES)) fibers, glass wool, rock wool, and basalt fibers. The insulating layer may contain one type of inorganic fiber, or two or more types of inorganic fibers.

[0043] The content of inorganic fibers in the heat insulating layer is not particularly limited and may be, for example, 0.5% by mass or more and 50% by mass or less, preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, and is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less. When the fiber content is within the above range, it is easy to ensure good thermal resistance and to manufacture the heat insulating layer.

[0044] The average fiber length of the inorganic fibers is not particularly limited and may be, for example, 0.05 mm or more and 50 mm or less, preferably 0.5 mm or more, more preferably 1.0 mm or more, even more preferably 2 mm or more, or 4 mm or more or 5 mm or more, and preferably 25 mm or less, more preferably 13 mm or less, even more preferably 10 mm or less, or may be 8 mm or less or 6 mm or less. When the average fiber length of the fibers is within the above range, it is easy to achieve both ease of manufacturing and strength of the heat insulating layer.

[0045] The average fiber diameter of the inorganic fibers is not particularly limited and may be, for example, 0.1 μm or more and 50 μm or less, preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 7 μm or more, and is preferably 25 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less. When the average fiber diameter of the fibers is within the above range, good thermal insulation properties and mechanical strength can be easily ensured.

[0046] In some embodiments, the inorganic fibers preferably contain inorganic fibers having a fiber length of 6 mm or more and less than 35 mm. The proportion of inorganic fibers having a fiber length of 6 mm or more and less than 35 mm to the total number of inorganic fibers contained in the thermal insulation layer is not particularly limited, and may be, for example, 30% or more and 100% or less, preferably 95% or less, preferably 35% or more, more preferably 40% or more, and even more preferably 50% or more. When the content proportion of inorganic fibers having the above fiber length is within the above range, good thermal insulation and mechanical strength can be easily ensured.

[0047] In embodiments in which the heat insulating layer contains inorganic fibers, the mass ratio of the silica particles to the inorganic fibers (silica particles:inorganic fibers) contained in the heat insulating layer is not particularly limited and may be, for example, within the range of 40:60 to 99: 1. From the viewpoint of easily ensuring a good balance between good heat insulating properties and mechanical strength, in some embodiments, the mass ratio (silica particles:inorganic fibers) is, for example, suitably 45:55 or more, preferably 50:50 or more, more preferably 60:40 or more, even more preferably 70:30 or more, or may be 80:20 or more (e.g., 82:18 or more), or may be, for example, suitably 98:2 or less, preferably 95:5 or less, may be 90:10 or less, or may be 88:12 or less.

[0048] (Dispersant) The heat insulating layer may contain a dispersant as an optional component. For example, when preparing a heat insulating layer using a mixed solution containing the constituent materials of the heat insulating layer in a solvent, the dispersant can be useful for improving the ease of preparation of the mixed solution, improving handleability (e.g., improving fluidity), improving dispersion stability (e.g., suppressing viscosity changes over time), and improving moldability when forming a heat insulating layer from the mixed solution. An example of an embodiment in which the use of a dispersant is preferable is an embodiment in which a protic solvent is used as the solvent for the mixed solution. For example, in an embodiment in which hydrophilic fumed silica is used as at least a portion of the inorganic particles, the hydrophilic fumed silica and the protic solvent are bonded by hydrogen bonds, which tends to increase the viscosity of the mixed solution. Furthermore, as the specific surface area of ​​inorganic particles (e.g., silica particles such as hydrophilic fumed silica) increases, the area that interacts with the solvent increases, which tends to increase the viscosity of the mixed solution. If the viscosity of the mixed solution becomes excessively high, mixing itself may become difficult, leading to concerns about reduced productivity and reduced quality stability. A dispersant can be used to prevent such phenomena. In addition, in an embodiment in which the heat insulating layer contains inorganic fibers, it is preferable to prevent the viscosity of the mixed liquid from increasing excessively from the viewpoint of preventing damage to the inorganic fibers during the manufacturing process.

[0049] The dispersant is not particularly limited, and materials that can achieve the desired effects can be appropriately selected and used. Dispersants can be classified into 1) polymeric dispersants, 2) surfactant-type dispersants (low-molecular-weight dispersants), and 3) inorganic dispersants. In some embodiments, non-polymeric dispersants are preferably used from the viewpoint of suppressing a decrease in the consistency of the mixed liquid and suppressing the aggregation of inorganic particles. Here, "non-polymeric" refers to molecules that do not contain polymers (polymers) produced by polymerization reactions within their structure, so-called "low-molecular-weight compounds." Suitable examples of non-polymeric dispersants include surfactants. Surfactants are classified into anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. Surfactants can be used alone or in combination of two or more. In some embodiments, cationic or nonionic surfactants are preferably used. For example, so-called quaternary ammonium salt surfactants, amine salt surfactants, pyridium salt surfactants, and amine surfactants are preferred. Suitable examples of non-polymeric dispersants include compounds having at least one alkyl group with 4 or more carbon atoms (preferably 6 or more, more preferably 8 or more) on a nitrogen atom (e.g., quaternary ammonium salt surfactants such as dodecyltrimethylammonium chloride, octadecyltrimethylammonium chloride, and dodecylbenzyldimethylammonium chloride; amine salt surfactants such as tetradecylamine acetate and octadecylamine acetate; and amine surfactants such as dodecylamine and dimethyloctylamine). The non-polymeric dispersant in the heat insulating layer may exist in the form of a salt, a free compound, or an ion. Examples of such salts include quaternary ammonium salts with counterions such as chloride ions, bromide ions, and ethyl sulfate ions, and amine salts with acetic acid.

[0050] The content of the dispersant (e.g., non-polymeric dispersant) in the heat insulating layer is not particularly limited. The content of the dispersant is typically more than 0 mass %, for example, 1 × 10 －５ % by mass or more, and －５% by mass or more, and may be 1×10 －４ % by mass or more, and －４ Mass% or more, 1×10 －３ Mass% or more, 5 x 10 －３ Mass% or more, 1×10 －２ mass% or more or 5 x 10 －２ The content of the dispersant in the heat insulating layer may be, for example, 7% by mass or less, and from the viewpoint of easily suppressing the influence on other properties, it is appropriate that the content is 5% by mass or less. In some embodiments, the content of the dispersant in the heat insulating layer is preferably 3% by mass or less, more preferably 2% by mass or less, even more preferably 1% by mass or less, particularly preferably 0.5% by mass or less, and may be 0.3% by mass or less, 0.1% by mass or less, 5 x 10 －２ Mass% or less, 1×10 －２ Mass% or less, 5 x 10 －３ Mass% or less, 1×10 －３ mass% or less or 5 x 10 －４ It may be % by mass or less. The content of dispersant in the thermal insulation layer can be determined by extracting the dispersant from the thermal insulation layer using an appropriate solvent (a solvent capable of dissolving the target dispersant) and performing quantitative analysis using a known method. The type of dispersant contained in the thermal insulation layer can be determined by extracting the dispersant from the thermal insulation layer using an appropriate solvent as described above and identifying the dispersant contained in the obtained extract using a known method. The dispersant contained in the thermal insulation layer can be considered to be the remaining amount (residual amount) of dispersant used during the production of the thermal insulation material.

[0051] (Other Components) The heat insulating layer may contain other components in addition to those described above, as necessary. Specific examples of the other components include a binder (binding agent), inorganic particles other than silica particles and graphite particles, and organic fibers.

[0052] The binder can be useful for improving the shape stability and strength of the heat insulating layer. In embodiments in which the heat insulating layer contains a binder, the type of binder is not particularly limited, and may be an organic binder or an inorganic binder. Specific examples of organic binders include thermoplastic resins, thermoplastic elastomers, thermosetting resins, thermosetting elastomers, sugars, water-soluble polymers, etc. Specific examples of inorganic binders include aluminum oxide, zirconium oxide, magnesium oxide, titanium oxide, calcium oxide, etc. From the standpoint of heat resistance and flame resistance, inorganic binders are generally more advantageous than organic binders. The heat insulating layer may contain one type of binder or may contain two or more types of binders. Alternatively, it may be substantially binder-free.

[0053] When the heat insulating layer contains a binder, the content of the binder is not particularly limited and can be appropriately set so as to obtain the desired effect. In some embodiments, the content of the binder in the heat insulating layer may be, for example, 0.01% by mass or more and 10% by mass or less of the heat insulating layer. From the viewpoints of shape stability, ease of molding, etc., it may be 0.05% by mass or more, 0.1% by mass or more, or 0.2% by mass or more. In some embodiments, the content of the binder (especially the organic binder) in the heat insulating layer is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less, from the viewpoints of the mechanical strength of the heat insulating layer in the high temperature range.

[0054] The heat insulating layer may contain one or more types of inorganic particles (other inorganic particles) other than silica particles and graphite particles. The types of the other inorganic particles are not particularly limited. Examples of the other inorganic particles include zinc oxide, aluminum oxide particles, titanium oxide particles, silicon carbide particles, ilmenite particles (ilmenite, FeTiO), zirconium silicate particles, iron (III) oxide particles, iron (II) (wustite (FeO) particles), magnetite particles (Fe ３ O ４ ), hematite particles (Fe ２ O ３)), chromium dioxide particles, zirconium oxide particles, manganese dioxide particles, zirconia sol, titania sol, silica sol, alumina sol, bentonite particles, kaolin particles, etc. In some embodiments, the above descriptions regarding the average particle size and BET specific surface area of ​​silica particles can be similarly applied to the average particle size (average primary particle size, average particle size of secondary aggregates) and BET specific surface area of ​​other inorganic particles.

[0055] In embodiments in which the insulating layer contains other inorganic particles, the content of the other inorganic particles in the insulating layer is typically greater than 0% by mass, and may be 0.5% by mass or more, 1% by mass or more, or 3% by mass or more. In some embodiments, from the viewpoint of easily balancing the performance of the insulating layer containing silica particles and graphite particles, the content of the other inorganic particles in the insulating layer is, for example, suitably 10% by mass or less, preferably 5% by mass or less, and may be 3% by mass or less, 1% by mass or less, 0.5% by mass or less, or 0.1% by mass or less. The insulating layer in the technology disclosed herein may be an insulating layer that is substantially free of other inorganic particles. Here, "substantially free" means that inorganic particles other than silica particles and graphite particles are not, at least intentionally, contained in the insulating layer. For example, inorganic particles other than silica particles and graphite particles may not be unintentionally contained in the insulating layer as impurities or crushed particles of other components.

[0056] In the heat insulating material disclosed herein, the proportion of the total amount of silica particles and graphite particles in the inorganic particles contained in the heat insulating layer is preferably 90 mass% or more, more preferably 95 mass% or more, and may be 97 mass% or more, or even 99 mass% or more. The inorganic particles contained in the heat insulating layer may be inorganic particles consisting essentially of silica particles and graphite particles.

[0057] In some embodiments, the insulating layer may contain organic fibers. Specific examples of organic fibers include felts made of cellulose fiber, polyester, polypropylene, etc. Organic fibers are preferably used in combination with inorganic fibers. The content of organic fibers in the insulating layer can be appropriately set to achieve the desired effect, and may be, for example, 0.01% by mass or more, 0.5% by mass or more, or 3% by mass or more of the insulating layer, or may be, for example, 20% by mass or less, 10% by mass or less, or 5% by mass or less. In some embodiments, from the viewpoint of heat resistance, etc., the content of organic fibers in the insulating layer is preferably less than 3% by mass, more preferably less than 1% by mass, and may be less than 0.1% by mass or less than 0.01% by mass. The insulating layer may be substantially free of organic fibers.

[0058] (Shape, characteristics, etc. of the insulating layer) The thickness of the insulating layer is not particularly limited and may be, for example, approximately 0.3 mm or more and 10 mm or less, preferably 0.5 mm or more, and may be 0.7 mm or more, 0.8 mm or more, or 0.9 mm or more. From the viewpoint of thermal insulation performance and strength, a thicker insulating layer is advantageous. In some embodiments, the thickness of the insulating layer may be, for example, 1.0 mm or more, 1.2 mm or more, 1.5 mm or more, or 2.0 mm or more. In some embodiments, the thickness of the insulating layer may be, for example, 9.0 mm or less, preferably 7.0 mm or less, more preferably 5.0 mm or less, and may be 3.0 mm or less, 2.0 mm or less, 1.5 mm or less, 1.3 mm or less, or 1.0 mm or less. By reducing the thickness of the insulating layer, it is possible to reduce the thickness and weight of the insulating material. The thickness of the insulating layer can be determined by measuring the cross section of the insulating layer at several points (e.g., 10 points) using a thickness measuring device (e.g., Ozaki Seisakusho's digital thickness gauge JAN-257 (measuring probe Φ20 mm)).

[0059] The density of the heat insulating layer is not particularly limited, and is, for example, 0.2 g / cm ３ 0.5g / cm or more ３When the density of the heat insulating layer is within the above range, it is easy to ensure good heat insulating properties and appropriate compressive deformation. In some embodiments, the density of the heat insulating layer is preferably 0.3 g / cm ３ More preferably, 0.35 g / cm ３ More preferably, 0.37 g / cm ３ or more, and preferably 0.45 g / cm ３ The following is the result.

[0060] The shape of the heat insulating layer is not particularly limited. In some embodiments, the shape of the heat insulating layer when viewed from above may be, for example, a polygon such as a quadrangle, a circle, an ellipse, etc. Examples of quadrangles include rectangles (including squares and rectangles).

[0061] The thermal conductivity of the heat insulating layer can be measured by the method described in Japanese Industrial Standards JIS A 1412-2:1999 "Method for measuring thermal resistance and thermal conductivity of thermal insulating materials - Part 2: Heat flow meter method (HFM method)."

[0062] The heat flow meter method (HFM method) is a secondary measurement method or comparative measurement method that measures heat transfer characteristics such as thermal conductivity and thermal resistance by comparing a flat thermal insulation material (heat insulating layer) as a test specimen with a standard plate. The detailed measurement procedure and measurement conditions are explained below.

[0063] The insulation layer is cut to a predetermined size (e.g., 20 mm x 20 mm) to prepare a test specimen, and an alumina composite material ("RS-100", manufactured by ZIRCAR Refractory Composites, Inc., thickness: 5 mm, thermal conductivity: 0.66 W / K m) or the like is prepared as a standard plate. Next, the first thermocouple, titanium plate, insulation layer, titanium plate, second thermocouple, standard plate, and third thermocouple are placed on the lower plate of a pneumatic press in this order from top to bottom, and the test specimen, standard plate, thermocouple, etc. are tightly attached between the upper and lower plates. The upper and lower plates are then heated to their respective predetermined measurement temperatures, and a load is applied to the test specimen, etc. using the pneumatic press to achieve the predetermined measurement pressure.

[0064] The measurement temperatures may be, for example, 80° C. for the upper plate on the first thermocouple side and 30° C. for the lower plate on the third thermocouple side. On the other hand, the measurement temperatures under high temperature conditions may be, for example, 600° C. for the upper plate on the first thermocouple side and 40° C. for the lower plate on the third thermocouple side.

[0065] The measurement pressure can be, for example, 1 MPa (load: 400 N). Measurement is continued under heating and pressure until the detected temperature of each thermocouple stabilizes, and the thermal conductivity k1 of the heat insulating layer can be calculated using the following formula (I) from the detected temperature of each thermocouple after the temperature stabilizes, the thickness of the heat insulating layer when pressurized, the thermal conductivity of the standard plate, and the thickness of the standard plate when pressurized. k1 = k2 x (L1 x ΔT1) / (L2 x ΔT2) ... (I) (In the formula, k1 is the thermal conductivity of the insulating layer [W / (m・K)], k2 is the thermal conductivity of the standard plate [W / (m・K)], L1 is the thickness of the insulating layer when pressed, L2 is the thickness of the standard plate, ΔT1 is the temperature difference between the temperatures of the second thermocouple and the third thermocouple, and ΔT2 is the temperature difference between the temperatures of the first thermocouple and the second thermocouple.) Note that the detected temperature being stable means, for example, that the temperature change after about 10 minutes is within a specified range (for example, within ±0.1°C).

[0066] The thermal resistance of the heat insulating layer can be calculated from the thermal conductivity k1 and the thickness under pressure L1 using the following formula (II): R1 = L1 / k1 (II) (where R1 is the thermal resistance [(m ２ K) / W], k1 is the thermal conductivity of the heat insulating layer [W / (m K)], and L1 is the thickness of the heat insulating layer when pressed.

[0067] The thermal conductivity of the heat insulating layer disclosed herein at 600°C and 1 MPa pressure is suitably 0.3 W / K·m or less, preferably 0.2 W / K·m or less, and more preferably 0.1 W / K·m or less. In some embodiments, the thermal conductivity (600°C, 1 MPa) is preferably 0.070 W / K·m or less, more preferably 0.065 W / K·m or less, and even more preferably 0.060 W / K·m or less (e.g., less than 0.060 W / K·m). It may be 0.059 W / K·m or less, 0.058 W / K·m or less, or 0.057 W / K·m or less. There is no particular lower limit for the thermal conductivity (600°C, 1 MPa) of the heat insulating layer, and a lower value is more advantageous from the viewpoint of improving heat insulation. In some embodiments, taking into account the balance with other properties, the thermal conductivity (600°C, 1 MPa) of the insulating layer may be, for example, 0.010 W / K·m or more, or 0.030 W / K·m or more.

[0068] When the initial thickness of the heat insulating layer is adjusted to 1 mm, the thermal resistance at 600°C and 1 MPa pressure is, for example, 0.010 (K m ２ ) / W or more, preferably 0.014 (K m ２ ) / W or more or 0.015 (K·m ２ ) / W or more. There is no particular upper limit to the thermal resistance (1 mm, 600°C, 1 MPa) of the heat insulating layer, and the lower the upper limit, the more advantageous it is from the viewpoint of improving heat insulating properties. In some embodiments, taking into consideration the balance with other properties and the suitability for thinning, the thermal resistance (1 mm, 600°C, 1 MPa) of the heat insulating layer is, for example, 0.1 (K m ２ ) / W or less, and 0.5 (K m ２ ) / W or less or 0.3 (K·m ２ ) / W or less.

[0069] The thermal conductivity of the insulating layer at 80°C and 1 MPa pressure is usually 0.3 W / K·m or less, preferably 0.1 W / K·m or less, more preferably 0.08 W / K·m or less, 0.06 W / K·m or less, 0.055 W / K·m or less, 0.045 W / K·m or less, or 0.04 W / K·m or less, and may be, for example, 0.010 W / K·m or more.

[0070] In a thermal insulation material including a buffer layer (described later) in addition to a thermal insulation layer, the thermal conductivity of the thermal insulation layer is preferably lower than that of the buffer layer under at least one of the conditions of 80°C and 1 MPa pressure and 600°C and 1 MPa pressure. In some embodiments, the thermal conductivity of the thermal insulation layer may be, for example, 90% or less, 75% or less, or 50% or less of the thermal conductivity of the buffer layer.

[0071] When the thickness (initial thickness) of the heat insulating layer is adjusted to 1 mm without pressure, the heat resistance at 80°C and 1 MPa pressure is, for example, 0.020 (K·m ２ ) / W or more, preferably 0.025 (K m ２ ) / W or more, 0.03 (K・m ２ ) / W or more or 0.035 (K m ２ ) / W or more, and for example, 0.1 (K m ２ ) / W or less.

[0072] The compressive properties of the insulating layer constituting the thermal insulation material disclosed herein are not particularly limited and can be appropriately selected depending on the application and usage mode. In some embodiments, the compressive deformation rate of the insulating layer at a compressive stress of 1.0 MPa (hereinafter also referred to as the 1.0 MPa compressive deformation rate) is typically approximately 5% or more, preferably 8% or more, and more preferably 10% or more (e.g., 12% or more). Furthermore, the 1.0 MPa compressive deformation rate of the insulating layer may be, for example, 50% or less. From the viewpoint of shape stability and mechanical strength, in some embodiments, it is preferably 30% or less, more preferably 25% or less, for example, 20% or less, or even 18% or less or 16% or less. By having the 1.0 MPa compressive deformation rate of the insulating layer within an appropriate range, the insulating material including the insulating layer is more likely to achieve appropriate compressive properties as described below. The 1.0 MPa compressive deformation rate of the insulating layer is measured as the compressive strain [%] when the compressive stress becomes 1.0 MPa in a compression test in which the insulating layer is compressed in the thickness direction, and more specifically, it is measured by the method described in the Examples below.

[0073] The compressive properties of the insulating material are not particularly limited and can be appropriately selected depending on the application and usage mode. In some embodiments, the 1.0 MPa compressive deformation rate of the insulating material is typically within a range of approximately 5% to 70% (e.g., 10% to 60%). By having the 1.0 MPa compressive deformation rate of the insulating material within an appropriate range, for example, in an insulating material disposed between cells of a lithium-ion battery module, cell expansion (e.g., expansion associated with charging) can be appropriately buffered. From the viewpoint of exhibiting better buffering properties, in some embodiments, the 1.0 MPa compressive deformation rate of the insulating material is preferably 15% or more, more preferably 20% or more, and may be 25% or more, or even 30% or more. Furthermore, from the viewpoint of facilitating the thinning of the insulating material, in some embodiments, the 1.0 MPa compressive deformation rate may be, for example, 55% or less, 50% or less, 45% or less, or 40% or less. The 1.0 MPa compressive deformation rate of a thermal insulating material is measured as the compressive strain [%] when the compressive stress reaches 1.0 MPa in a compression test in which the thermal insulating material is compressed in the thickness direction. In a thermal insulating material consisting of a thermal insulating layer, the 1.0 MPa compressive deformation rate of the thermal insulating material coincides with the 1.0 MPa compressive deformation rate of the thermal insulating layer.

[0074] The number of insulating layers contained in the insulating material is one or more, usually one to ten, preferably one to seven, and more preferably one to five (for example, one to three, or one to two).

[0075] The heat insulating layer may be bonded to adjacent layers with an adhesive or pressure-sensitive adhesive, or may not be bonded to adjacent layers. In some embodiments, it is preferable that the heat insulating layer is not bonded with an adhesive or pressure-sensitive adhesive. By not using an adhesive or pressure-sensitive adhesive, that is, by not using an adhesive or pressure-sensitive adhesive, the thermal conductivity can be reduced compared to when an adhesive or pressure-sensitive adhesive is used.

[0076] (Preparation of Heat Insulating Layer) The method for preparing the heat insulating layer disclosed herein is not particularly limited, and the layer can be prepared by appropriately employing known processes. For example, a mixture containing silica particles and graphite particles and further containing other optional components (inorganic fibers, dispersants, etc.) that may be used as needed can be prepared by a known mixing method such as a wet method or a dry method, and the mixture can be used to prepare a heat insulating layer. Examples of methods for preparing a heat insulating layer that include preparing the mixture (typically a slurry-like mixed liquid) by a wet method include methods that include the following steps: Mixing step: A step of mixing silica particles, graphite particles, and other optional components (inorganic fibers, dispersants, etc.) that may be used as needed in a solvent to obtain a mixed liquid. Coating step: A step of applying the mixed liquid to obtain a coated film. Molding step: A step of molding the coated film to obtain a heat insulating layer.

[0077] The mixing in the mixing step can be carried out using, for example, a Disper, a Laboplastomill, a Trimix, a planetary mixer, a kneader, or the like.

[0078] The type of solvent is not particularly limited. For example, a solvent selected from protic solvents such as alcohols (e.g., alcohols having about 1 to 4 carbon atoms, such as methanol, ethanol, isopropyl alcohol, and ethylene glycol), amides, and water, and aprotic solvents such as esters, ketones, nitriles, and ethers can be used. A mixed solvent containing two or more solvents may also be used.

[0079] The surface tension of the solvent is not particularly limited and is, for example, 20 mN / m or more and 73 mN / m or less, preferably 21 mN / m or more, preferably 50 mN / m or less, more preferably 40 mN / m or less, and even more preferably 30 mN / m or less. When the surface tension of the solvent is within the above range, a heat insulating layer exhibiting good heat insulating properties and mechanical strength is easily obtained. The above-mentioned range of surface normal force can also be applied to the surface tension of a mixed solvent. The surface tension of a solvent (which may be a mixed solvent) can be measured by the ring method. Note that the surface tension of a mixed solvent obtained by mixing the protic solvent isopropyl alcohol (surface tension: 21 mN / m) and water (surface tension: 73 mN / m) in a mass ratio of 5:1 is approximately 23 mN / m.

[0080] The amount of the non-polymeric dispersant to be mixed in the mixed solution in the mixing step is not particularly limited, and can be appropriately set in consideration of the balance between the effect of use and the influence on other properties. The amount of the dispersant to be mixed in the mixed solution is, for example, 1 × 10 －４ parts by mass or more, and from the viewpoint of easily obtaining a higher use effect, －４ parts by mass or more, and may be 1×10 －３ parts by mass or more, and －３ Parts by mass or more, 1 x 10 －２ Parts by mass or more, 5 x 10 －２ The amount of the dispersant in the mixed solution may be, for example, 10 parts by mass or less, relative to 100 parts by mass of the silica particles contained in the mixed solution, and from the viewpoint of easily avoiding influence on other properties, it is usually 7 parts by mass or less (for example, 1 × 10 －４ The amount of the non-polymeric dispersant blended is suitably from 1 part to 7 parts by mass, preferably 5 parts by mass or less, and may be 3 parts by mass or less, or may be 2 parts by mass or less. When the blend amount of the non-polymeric dispersant blended is within the above range, the blended liquid is stably dispersed, and the heat insulating property of the heat insulating layer is improved.

[0081] The mixing temperature is not particularly limited, but is usually 20° C. or higher and the boiling point of the solvent or lower, preferably 22° C. or higher, and preferably 50° C. or lower, more preferably 40° C. or lower, and even more preferably 30° C. or lower. When the mixing temperature is within the above range, the solvent (e.g., organic solvent) is less likely to volatilize, and the blending ratio is less likely to change.

[0082] The mixing time is not particularly limited, but is usually from 1 minute to 5 hours, preferably from 5 minutes to 4 hours, more preferably from 2 hours to 1 hour. When the mixing time is within the above range, the heat insulating layer can be produced efficiently.

[0083] The consistency (initial consistency) of the mixed liquid is not particularly limited, but can be, for example, within a range of about 50 to 200. In some embodiments, the initial consistency of the mixed liquid is, for example, 55 or more, 60 or more, or 65 or more, preferably 70 or more, more preferably 75 or more, even more preferably 80 or more, and particularly preferably 85 or more (e.g., 90 or more). For example, in the production of a heat insulating layer containing inorganic fibers, it is preferable that the initial consistency of the mixed liquid is not too low from the viewpoint of reducing fiber breakage of the inorganic fibers during preparation, stirring, feeding, application, etc. of the mixed liquid. In addition, in some embodiments, the initial consistency of the mixed liquid is preferably 180 or less, more preferably 160 or less, and even more preferably 140 or less (e.g., 120 or less or 110 or less). Having an initial consistency of the mixed liquid that is not too high can be advantageous from the viewpoint of moldability when molding the mixed liquid to obtain a heat insulating layer, shape accuracy of the molded product (heat insulating layer), etc.

[0084] The method for measuring the consistency of the mixed solution can be exemplified by the method described in Japanese Industrial Standard JIS K 2220:2013, "Grease - Part 7: Consistency Test Method," and in particular, measurement as "immiscible consistency" can be used. Measuring instruments capable of measuring consistency are commercially available, and a specific example is the PENETRO METER manufactured by Nikka Engineering. The measurement procedure involves preparing a container large enough that a conical weight will not come into contact with the container when lowered, filling it with the mixed solution, and placing it in a measuring device with the weight attached. Next, the position of the weight is adjusted to a position where it comes into contact with the mixed solution, and this position is designated as the zero point. Then, at room temperature (25°C), the weight is lowered for 5 seconds (±0.1 seconds), and the depth (mm) of the weight immersed in the mixed solution x 10 is calculated as the consistency. The conical weight may be a standard cone as specified in the Japanese Industrial Standards, with a total mass of 102.5 g ± 0.05 g and a mass of the weight holder of 47.5 ± 0.05 g.

[0085] The coating method and conditions in the coating step are not particularly limited, and any known method can be appropriately used. For example, coating can be performed using a comma coater, spin coater, die coater, roll coater, calendar roll, dispenser, etc.

[0086] The molding method and molding conditions in the molding step are not particularly limited, and known methods can be appropriately adopted. For example, compression molding can be performed using a heat press or a vacuum press, followed by drying using a floating oven, an IR oven, or the like. The drying temperature is preferably, for example, 60°C to 150°C. The drying time is preferably, for example, 4 minutes to 20 minutes.

[0087] <Coating layer> The heat insulating material disclosed in this specification preferably includes a coating layer. The coating layer is a layer that serves to prevent inorganic particles and the like from falling off the heat insulating layer and to protect the heat insulating layer. For example, a coating layer made of a resin film can be preferably used.

[0088] The type of resin constituting the coating layer is not particularly limited. Specific examples of resins used for the coating layer include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyimide (PI), flame-retardant polycarbonate (PC), breathable porous polyethylene (PE), flame-retardant polyethylene (PE), and biaxially oriented nylon film (Ny). Breathable porous PE preferably has a molecular weight of 1,000,000 to 7,000,000.

[0089] The thickness of the coating layer is not particularly limited, and is, for example, 0.001 mm or more and 0.2 mm or less, preferably 0.005 mm or more, more preferably 0.007 mm or more, even more preferably 0.010 mm or more, and preferably 0.15 mm or less, more preferably 0.10 mm or less, and even more preferably 0.050 mm or less. When the thickness of the coating layer is within the above range, low thermal conductivity and mechanical strength can be achieved at the same time. The thickness of the coating layer can be measured in the same manner as the thickness of the heat insulating layer.

[0090] The number of coating layers is usually 1 or more, preferably 2 or more, and usually 5 or less, preferably 4 or less, and more preferably 3 or less. The two or more coating layers may be two or more resin films, or one resin film may be folded back to form two coating layers. In this case, the number of coating layers is considered to be two.

[0091] When the heat insulating material includes two or more coating layers, the two or more coating layers may sandwich and enclose the heat insulating layer from the thickness direction, and the gap between the coating layers (the space partitioned by the two or more coating layers) may be sealed. The method for sealing the gap between the coating layers is not particularly limited, but for example, a method of providing a seal portion on the outer edge of the coating layer and bonding the seal portions between opposing coating layers to each other may be mentioned. The method for bonding the seal portions is also not particularly limited, and for example, welding using heat welding, ultrasonic welding, etc., or adhesion using an adhesive, pressure sensitive adhesive, etc. may be mentioned. In addition, welding may be performed by directly welding the resin of the coating layer, or by providing a separate resin layer for welding and welding.

[0092] The covering layer may be bonded to an adjacent layer other than the covering layer (e.g., a heat insulating layer, a buffer layer, etc.) with an adhesive or pressure-sensitive adhesive, or may not be bonded with an adhesive or pressure-sensitive adhesive. In some embodiments, it is preferable that the covering layer is not bonded with an adhesive or pressure-sensitive adhesive.

[0093] In the heat insulating material disclosed herein, the heat insulating layer may be covered with two or more coating layers in a breathable manner, and may be sealed within a space partitioned by the coating layers. In some embodiments, the coating layer preferably covers the heat insulating layer in a breathable manner. The method for achieving the breathable coating is not particularly limited. For example, methods such as using a coating layer with through holes as a vent or providing a non-sealed portion that functions as a vent at a portion of the joint between two or more coating layers can be used alone or in appropriate combination. The vent is typically provided so as to communicate the inside of the coating layer (the heat insulating layer side) with the external space. A heat insulating material configured such that the heat insulating layer is covered with a coating layer in a breathable manner has good deformability due to the breathability of the coating layer, and is easily compressively deformed, for example, due to volumetric expansion of the cells.

[0094] The number of ventilation holes in the coating layer is usually 1 or more, preferably 2 or more, and usually 50 or less, preferably 25 or less, and more preferably 10 or less.

[0095] The total opening area of ​​the ventilation holes in the coating layer is usually 7.9 × 10 －５ cm ２ 10cm or more ２ It is appropriate that the ratio is equal to or less than 1×10 －４ cm ２ or more, more preferably 5 × 10 －３ cm ２ More preferably, 1×10 －２ cm ２ and preferably 5 cm ２ Less than 4 cm, more preferably ２ Less than 3 cm, more preferably ２ When the total opening area of ​​the vent holes in the coating layer is within the above range, it is easy to prevent powder from leaking out from the heat insulating layer.

[0096] The ventilation holes in the covering layer may be covered with a ventilation membrane. The ventilation membrane usually has an air permeability of 4 cm ３ / (cm 2 ・s) or more 500cm ３ / (cm 2 s) or less, preferably 7 cm ３ / (cm 2 s) or more, more preferably 10 cm ３ / (cm 2 s) or more, more preferably 21 cm ３ / (cm 2 s) or more, and preferably 250 cm ３ / (cm 2 s) or less, more preferably 200 cm ３ / (cm 2 s) or less, more preferably 100 cm ３ / (cm 2 ・s) or less.

[0097] <Buffer layer> The heat insulating material disclosed herein may include a layer other than the heat insulating layer and coating layer described above. One example of such a layer is a buffer layer. The buffer layer may play a role in compensating for physical properties that are likely to be insufficient when provided by the heat insulating layer alone. The buffer layer will be described in detail below.

[0098] In some embodiments, a buffer layer made of a fiber-containing fibrous molded body (hereinafter sometimes abbreviated as "fiber molded body"), or a buffer layer made of a foam-containing foam-molded body (hereinafter sometimes abbreviated as "foam molded body") may be preferably used.

[0099] (Fiber Molded Product) The type of fiber contained in the fiber molded product is not particularly limited and may be inorganic or organic. Examples of inorganic fibers include glass wool, rock wool, alkaline earth silicate (AES) fibers, silica-alumina fibers, alumina fibers, zirconia fibers, silica fibers, and basalt fibers. Examples of organic fibers include cellulose fibers, polyester, and felts made of polypropylene. In some embodiments, inorganic fibers are preferred, and glass wool is particularly preferred. Glass wool is a cured product containing fibers and a thermosetting resin (e.g., a phenolic binder), and the fibers are bonded together with the thermosetting resin. It also has the effect of increasing compressive stress and providing a buffering function. The fiber molded product may contain one type of fiber or two or more types of fibers. The fiber assembly may be in the form of a nonwoven fabric, woven fabric, knitted fabric, or the like, such as a nonwoven fabric.

[0100] The fiber content in the fiber molding is not particularly limited, but is, for example, 50% by mass or more (typically 50% by mass to 99% by mass), preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more (for example, 82% by mass or more), and is preferably 97% by mass or less, more preferably 95% by mass or less, even more preferably 93% by mass or less. When the fiber content is within the above range, the fiber molding is likely to exhibit cushioning properties.

[0101] The average fiber length of the fibers in the fiber molding is not particularly limited and can be, for example, in the range of 0.1 mm to 200 mm. In some embodiments, the average fiber length is preferably 1 mm or more (e.g., 5 mm or more), more preferably 10 mm or more, and even more preferably 20 mm or more, and is preferably 175 mm or less, more preferably 150 mm or less, and even more preferably 125 mm or less, and may be 100 mm or less, 75 mm or less, or 50 mm or less. When the average fiber length of the fibers is within the above range, appropriate cushioning properties are easily exhibited.

[0102] The average fiber diameter of the fibers of the fiber molding is not particularly limited and may be, for example, in the range of 1 μm to 15 μm. In some embodiments, the average fiber diameter is typically 2 μm or more, for example 2.5 μm or more, and may be 3 μm or more, or 4 μm or more. In some embodiments, the average fiber diameter is typically 10 μm or less, for example 9 μm or less, and may be 8 μm or less, 7 μm or less, 6 μm or less, or 5 μm or less. When the average fiber diameter of the fibers is within the above range, the fiber molding is likely to have both cushioning properties and low thermal conductivity.

[0103] The fibrous molded product preferably contains a binder in addition to the fibers. The type of binder for the fibrous molded product is not particularly limited, but may be an organic binder or an inorganic binder.

[0104] Specific examples of organic binders include thermoplastic resins, thermoplastic elastomers, thermosetting resins, thermosetting elastomers, sugars, and water-soluble polymers. Specific examples of inorganic binders include aluminum oxide, zirconium oxide, magnesium oxide, titanium oxide, and calcium oxide. When the binder is one of those described above, shape stability is improved. The binders can be used alone or in combination of two or more.

[0105] The binder content in the fiber molding is not particularly limited, and is, for example, 1% by mass or more and 50% by mass or less, preferably 2% by mass or more, more preferably 5% by mass or more, even more preferably 7% by mass or more, and may be 10% by mass or more or 12% by mass or more, and is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and may be 18% by mass or less or 16% by mass or less. When the binder content is within the above range, low thermal conductivity and good cushioning properties are achieved.

[0106] In some embodiments, the fiber molded article serving as the buffer layer preferably contains fibers but does not contain hydrophilic fumed silica. The fiber molded article may, for example, contain fibers but not contain inorganic particles. In some embodiments, the fiber molded article serving as the buffer layer preferably contains fibers and a binder but does not contain hydrophilic fumed silica. The fiber molded article may, for example, contain fibers and a binder but not contain inorganic particles. Some fibers used in the fiber molded article are sold with a thermosetting resin dispersed as a binder (adhered to at least a portion of the fibers). These fibers can be cut to the desired shape and then heated and compressed to form a fiber molded article.

[0107] (Foam Molded Article) The foam molded article is a molded article containing a foam. The material of the foam is usually a resin such as a thermoplastic resin or a thermosetting resin. The foam can be molded by appropriately adopting a known molding method and its conditions.

[0108] The type of resin of the foam constituting the foam molded article is not particularly limited. Specific examples include foams formed from resins such as polyolefin resins such as polyethylene and polypropylene, polyethylene terephthalate resin, polyvinyl chloride resin (PVC), styrene resins such as polystyrene, polyurethane resins such as polyurethane resin, resol-type phenolic resins such as phenolic resin (PF), melamine resins such as melamine resin (MF), and epoxy resins such as epoxy resin (EP).

[0109] The cell structure of the foamed molded product may be a closed cell structure, an open cell structure, a mixture of these, or an intermediate cell structure. The cell structure of the foamed molded product can be appropriately selected depending on the desired physical properties, etc.

[0110] (Thickness of Buffer Layer) When the thermal insulating material includes a buffer layer, the thickness of the buffer layer is typically 0.5 mm or more and 10 mm or less, preferably 1 mm or more, more preferably 1.5 mm or more, even more preferably 2 mm or more, and preferably 7 mm or less, more preferably 6 mm or less, and even more preferably 5 mm or less. When the thickness of the buffer layer is within the above range, it can appropriately buffer stress generated by battery expansion (e.g., expansion associated with charging a cell). Note that the thickness of the buffer layer is measured by measuring the cross-sectional thickness of the buffer layer using a thickness gauge (digital thickness gauge JAN-257, probe Φ20 mm, manufactured by Ozaki Manufacturing Co., Ltd.) in the same manner as for the thermal insulating layer, and further, this measurement is performed at any 10 locations, and the average value of the obtained values ​​is used.

[0111] (Compression characteristics of buffer layer) The compressive elastic modulus (yield stress / strain) of the buffer layer is, for example, about 0.5 MPa or more and 20 MPa or less, preferably 0.7 MPa or more, more preferably 0.9 MPa or more, even more preferably 1.1 MPa or more, and preferably 18 MPa or less, more preferably 16 MPa or less, even more preferably 14 MPa or less.

[0112] When the compressive strain of the buffer layer is 25%, the compressive stress is, for example, 0.1 MPa to 4 MPa, preferably 0.2 MPa or more, more preferably 0.3 MPa or more, even more preferably 0.4 MPa or more, and preferably 3.7 MPa or less, more preferably 3.5 MPa or less, and even more preferably 3.3 MPa or less. When the compressive strain of the buffer layer is 50%, the compressive stress is, for example, 0.3 MPa to 7 MPa, preferably 0.5 MPa or more, more preferably 0.6 MPa or more, even more preferably 0.7 MPa or more, and preferably 6.5 MPa or less, more preferably 6.0 MPa or less, and even more preferably 5.5 MPa or less. The compressive stress when the compressive strain of the buffer layer is 70% is, for example, 2 MPa or more and 15 MPa or less, preferably 2.3 MPa or more, more preferably 2.5 MPa or more, even more preferably 2.7 MPa or more, and preferably 14 MPa or less, more preferably 12 MPa or less, even more preferably 10 MPa or less.

[0113] The compressive stress and compressive modulus (yield stress / strain) of the buffer layer can be measured using a precision universal testing machine, autograph, etc. Specifically, the buffer layer is cut to a predetermined size to prepare a test specimen (the cross-sectional area parallel to a plane perpendicular to the compression direction is the cross-sectional area used to calculate the compressive stress), and the test specimen is compressed at a predetermined compression speed (e.g., 0.5 m / min) to measure the compressive stress and displacement, thereby allowing the calculation to be performed.

[0114] (Thermal Properties of Buffer Layer) The thermal conductivity of the buffer layer is not particularly limited. In some embodiments, the thermal conductivity of the buffer layer at 80°C and 1 MPa is, for example, 0.02 W / K·m or more, preferably 0.030 W / K·m or more, more preferably 0.040 W / K·m or more, and even more preferably 0.050 W / K·m or more, and is preferably 0.2 W / K·m or less, more preferably 0.15 W / K·m or less, and even more preferably 0.1 W / K·m or less. The thermal conductivity of the buffer layer at 600°C and 1 MPa is preferably 0.04 W / K·m or more, more preferably 0.05 W / K·m or more, and even more preferably 0.06 W / K·m or more, and is preferably 0.30 W / K·m or less, more preferably 0.25 W / K·m or less, and even more preferably 0.20 W / K·m or less. The thermal conductivity of the buffer layer can be measured using a method similar to that used to measure the thermal conductivity of a thermal insulating layer.

[0115] The thermal resistance of the buffer layer is not particularly limited. In some embodiments, the thermal resistance of the buffer layer under conditions of 80°C and 1 MPa is preferably 0.020 (K·m ２ ) / W or more, more preferably 0.025 (K m ２ ) / W or more, more preferably 0.03 (K m ２ ) / W or more, and preferably 0.07 (K m ２ ) / W or less, more preferably 0.06 (K m ２ ) / W or less, more preferably 0.05 (K·m ２ ) / W or less. The thermal resistance of the buffer layer under conditions of 600°C and 1 MPa is preferably 0.001 (K·m ２ ) / W or more, more preferably 0.003 (K m ２ ) / W or more, more preferably 0.005 (K·m ２ ) / W or more, and preferably 0.1 (K m ２ ) / W or less, more preferably 0.05 (K·m ２ ) / W or less, more preferably 0.01 (K m ２ ) / W or less. The thermal resistance of the buffer layer can be measured by the same method as that for measuring the thermal resistance of the heat insulating layer.

[0116] The thermal resistance of the buffer layer when adjusted to have a thickness of 1 mm without pressure at 80°C and 1 MPa is not particularly limited, but is preferably 0.01 (K·m ２ ) / W or more, more preferably 0.02 (K m ２ ) / W or more, more preferably 0.03 (K m ２ ) / W or more, and preferably 0.10 (K·m ２ ) / W or less, more preferably 0.09 (K m ２ ) / W or less, more preferably 0.08 (K m ２ ) / W or less. The thermal resistance of the buffer layer can be measured by the same method as that for measuring the thermal resistance of the heat insulating layer.

[0117] The number of buffer layers is usually 1 to 10, preferably 1 to 5, more preferably 1 to 3, and may be 2 or 1.

[0118] The buffer layer may be bonded to an adjacent layer with an adhesive or pressure-sensitive adhesive, or may not be bonded to the adjacent layer. In some embodiments, it is preferable that the buffer layer is not bonded to the adjacent layer with an adhesive or pressure-sensitive adhesive. By not using an adhesive or pressure-sensitive adhesive, an increase in thermal conductivity can be suppressed compared to when an adhesive or pressure-sensitive adhesive is used.

[0119] The shape of the buffer layer is not particularly limited. In some embodiments, the shape of the buffer layer when viewed in plan may be, for example, a polygon such as a quadrangle, a circle, an ellipse, etc. Examples of quadrangles include rectangles (including squares and rectangles).

[0120] <Applications> The applications of the thermal insulating material disclosed herein are not particularly limited, and the thermal insulating material can be used appropriately for known applications that thermal insulating materials are used in. The thermal insulating material according to some embodiments is preferably used as a thermal insulating material disposed between cells of a battery module, and more specifically, is particularly preferably used as a thermal insulating material disposed between cells of a lithium-ion battery module.

[0121] Fig. 1 is a perspective view schematically illustrating an example of a battery module in which a thermal insulator according to one embodiment is disposed between cells, and Fig. 2 is a cross-sectional view taken along line II-II of Fig. 1. As shown in Fig. 1, a battery module 50 includes a plurality of battery cells (here, rectangular cells) 51 arranged in the thickness direction, with a thermal insulator 1 disposed between each of the battery cells 51. The plurality of battery cells 51 thus arranged with the thermal insulator 1 sandwiched between them are typically restrained by applying a pressing force (compressive force) in the thickness direction via restraint plates 52a, 52a disposed at both ends, and are housed in a battery case 53 for use.

[0122] 2, the thermal insulation material 1 has a structure in which a thermal insulation layer 10 and a buffer layer 20 are laminated together, and these are sandwiched and wrapped in two resin films (two covering layers) 31A, 31B in the thickness direction. The resin films 31A, 31B are sealed by adhesion (for example, heat welding) at seal portions provided along their outer edges, and together form the covering material 30. By sandwiching the thermal insulation material 1 with this structure between two adjacent battery cells 51, 51, it is possible to achieve thermal insulation between the opposing surfaces 51 a, 51 a of the two battery cells 51, 51.

[0123] Several possible embodiments of the thermal insulation material are described below in more detail. Figure 3 is a cross-sectional view schematically illustrating a thermal insulation material according to one embodiment. The thermal insulation material 1 shown in Figure 3 has a configuration in which a thermal insulation layer 10 is laminated on one surface 20a of a buffer layer 20, and the thermal insulation layer 10 is sandwiched and wrapped in two resin films (two coating layers) 31A, 31B from the thickness direction. The resin films 31A, 31B are sealed by adhesion (e.g., thermal welding) at a seal portion 32 provided along their outer edges, and together form the coating material 30. The resin film 31A is formed into a convex shape that generally covers the end face of the laminate of the thermal insulation layer 10 and the buffer layer 20, and a ventilation hole (through-hole) 33 is formed in the portion covering this end face. A ventilation membrane 34 is disposed at the opening of the ventilation hole 33 to the outside to prevent powder from leaking from the thermal insulation layer.

[0124] While FIG. 3 illustrates a configuration having only one insulation layer 10, the number of insulation layers may be two or more. In a configuration having two or more insulation layers, the insulation layers may be adjacent to each other or may be separate, for example, on both sides of the buffer layer. Similarly, while FIG. 3 illustrates a configuration having only one buffer layer 20, the number of buffer layers may be two or more. In a configuration having two or more buffer layers, the buffer layers may be adjacent to each other or may be separate, for example, on both sides of the insulation layer. Furthermore, a buffer layer may be disposed on the outside of the cladding material, or two or more buffer layers may be disposed on the outside and inside of the cladding material.

[0125] The target cells are not limited to rectangular cells, but may be, for example, laminated cells or cylindrical cells. The shape of the heat insulating material can be appropriately adopted depending on the type of cell.

[0126] In addition, target devices for the battery include electric vehicles (EVs), hybrid vehicles (HVs), plug-in hybrid vehicles (PHVs), portable electronic devices such as mobile terminals, mobile phones and notebook computers, and wearable devices.

[0127] As is clear from the above description and the following examples, the present specification discloses the following: [1] silica particles and a polymer having the following formula: G=(F ３－６ ) ２ ×H Ｗ / D50 (where F in the formula ３－６ is the volume frequency [%] of particle sizes of 3 to 6 μm in the volume-based particle size distribution based on the laser diffraction / scattering method, D50 is the cumulative 50% particle size [μm] in the volume-based particle size distribution, and H Ｗ is the half-width [°] of the (002) peak in X-ray diffraction. ); a heat insulating material comprising graphite particles having a property parameter G represented by the following formula: and a heat insulating layer containing: [2] The heat insulating material according to [1] above, wherein the graphite particles have a cumulative 50% particle diameter D50 of 2.0 μm or more and less than 11 μm. [3] The graphite particles have a volume frequency F of particles with a particle diameter of 3 to 6 μm. ３－６[4] The heat insulating material according to the above [1] or [2], wherein the volume frequency F of the graphite particles having a particle size of 4.625 μm in a volume-based particle size distribution based on a laser diffraction / scattering method is 10% or more. ４．６２５ [5] The heat insulating material according to any one of [1] to [3] above, wherein the half width of the graphite particles is 0.18° or more. [6] The heat insulating material according to any one of [1] to [5] above, wherein the graphite particles are artificial graphite. [7] The heat insulating material according to any one of [1] to [6] above, wherein the content of the graphite particles in the heat insulating layer is 2.5 mass% or more and 30 mass% or less. [8] The heat insulating material according to any one of [1] to [7] above, wherein the silica particles are at least one type selected from the group consisting of hydrophilic fumed silica and hydrophobic fumed silica. [9] The heat insulating material according to any one of [1] to [7] above, wherein the density of the heat insulating layer is 0.2 g / cm ３ ~0.5g / cm ３

[10] The heat insulating material according to any one of [1] to [9] above, which is used by being disposed between adjacent cells of a battery module or battery pack including a plurality of arranged cells.

[0128] Several examples of the present invention will be described below, but it is not intended that the present invention be limited to those shown in these examples. In the following description, "parts" and "%" representing amounts used and contents are based on mass unless otherwise specified.

[0129] <Graphite Used> Table 1 shows the characteristic values ​​of the graphite used in the following experiments and the value of the property parameter G (G value) calculated from them.

[0130]

[0131] Graphite A: Manufactured by Chuetsu Graphite Industries, product number "FBF" Graphite B: Manufactured by Nippon Graphite Industries, product number "PAG3000" Graphite C: Manufactured by Nippon Graphite Industries, product number "PAG3000C" Graphite D: Manufactured by Fuji Graphite Industries, product number "SRN-7J" Graphite E: Manufactured by Fuji Graphite Industries, product number "SRN-5J" Graphite F: Manufactured by Fuji Graphite Industries, product number "CRN-5J" Graphite G: Manufactured by Fuji Graphite Industries, product number "SRN-3J" Graphite H: Manufactured by Ito Graphite Industries, product number "Z-5F"

[0132] The characteristic values ​​shown in Table 1 were measured as follows.

[0133] (Cumulative 50% Particle Diameter (D50)) Graphite particles to be measured were dispersed in ion-exchanged water, and a particle size distribution based on volume was determined under the following measurement conditions using a particle size distribution analyzer (MT3000-II manufactured by MicrotracBEL Corp.) based on the laser diffraction / scattering method. The particle diameter at the cumulative 50% from the small diameter side of this particle size distribution was taken as the cumulative 50% particle diameter (D50) of the measurement sample. [Measurement conditions] Set Zero time: 10 seconds Measurement time: 20 seconds Number of measurements: 3 (Table 1 lists the average value of 3 measurements) Particle conditions Transmittance: Absorption Shape: Aspherical Solvent conditions Solvent refractive index: 1.377 DV (concentration index): See Table 1

[0134] (Volume frequency of particle size 3-6 μm (F ３－６ From the results of the particle size distribution measurement, the volume frequency (F ３－６ Specifically, the volume frequencies at particle sizes x1 = 5.998 μm, x2 = 5.500 μm, x3 = 5.044 μm, x4 = 4.625 μm, x5 = 4.241 μm, x6 = 3.889 μm, x7 = 3.566 μm, x8 = 3.270 μm, and x9 = 2.999 μm were calculated as y ｘｎ [%] (where the total frequency in the particle size distribution measurement is 100%), and x ｎ -x ｎ＋１ xy ｎThe values ​​are integrated for the range of n = 1 to 8 (i.e., (5.998-5.500) × volume frequency at 5.998 μm) + (5.500-5.044) × volume frequency at 5.500 μm ... (3.270-2.999) × volume frequency at 3.270 μm), and the resulting value is taken as the volume frequency (F ３－６ ) [%] are shown in Table 1.

[0135] (Volume frequency of particle size 4.624 μm (F ４．６２５ )) The volume frequency of a particle size of 4.625 μm in the particle size distribution measurement (the total frequency in the particle size distribution measurement is taken as 100%) is defined as the volume frequency (F ４．６２５ ) [%] are shown in Table 1.

[0136] (Half width (H ｗ )) was determined by the following method. 1. A fixed proportion of a standard sample was added to the graphite particles to be measured, and the mixture was mixed uniformly and packed into a glass sample plate. Silica powder (grade name: SatnSil-G03A) manufactured by Osaka Yaken Co., Ltd. was used as the standard sample. 2. X-ray diffraction measurement was carried out under the conditions shown in Table 2 below. 3. The graphite (002) peak was separated, and the half-width (i.e., the diffraction angle at the diffraction intensity of the maximum diffraction intensity of the peak × 1 / 2) [°] was determined.

[0137]

[0138] Above F ３－６ [%], H Ｗ Based on the values ​​of F [°] and D50 [μm], the property parameter G of each graphite particle was calculated using the following formula: G = (F ３－６ ) ２ ×H Ｗ / D50

[0139] Experimental Example 1: Investigation of the type of graphite Production of a heat insulating material (heat insulating layer) Example 1 A mixture of 378 parts by mass of a mixed solvent (mass ratio of IPA:water = 9:1, surface tension: 23 mN / m) of isopropyl alcohol (IPA, surface tension: 21 mN / m) as a protic solvent and water (surface tension: 73 mN / m) was added to a hydrophilic fumed silica ("AEROSIL (registered trademark) 200" manufactured by Nippon Aerosil Co., Ltd., average primary particle diameter: about 12 nm, BET specific surface area: 200 m). ２ 100 parts by mass of a mixture of glass fibers ("CS 6J-888" manufactured by Nitto Boseki Co., Ltd., average fiber length: 6 mm, average fiber diameter: 11 μm), 20 parts by mass of glass fiber ("CS 6J-888" manufactured by Nitto Boseki Co., Ltd., average fiber length: 6 mm, average fiber diameter: 11 μm), 6 parts by mass of graphite B (see Table 1), and 2 parts by mass of "Farmin DM0898" (product name: Kao Corporation) as a dispersant containing a non-polymeric dispersant (active ingredient: dimethyloctylamine, active ingredient content: 98% by mass or more) were added and mixed to a consistency of 70 to 140. The resulting mixture was applied to a thickness of 2 mm to form a coating film, which was then coated to a thickness of 1 mm and had a density of 0.3 to 0.5 g / cm. ３ The insulation material (insulating layer) of this example was produced by compression molding using a heat press to form a sheet of 100°C and then drying at 100°C for 10 minutes. The dimethyloctylamine content of the resulting insulation material (insulating layer) was measured using liquid chromatography mass spectrometry (LC / MS). First, standard solutions of various concentrations containing Farmin DM0898 were prepared, and a calibration curve of dimethyloctylamine concentration and LC / MS area value was created. Next, 0.4 g of insulation material was sampled, added to 10 mL of methanol, and shaken for at least 1 hour to extract the dimethyloctylamine contained in the insulation material. The resulting solution was passed through a membrane filter (0.20 μm) and introduced into the LC / MS, and the dimethyloctylamine content in the solution was measured using the calibration curve. The dimethyloctylamine content of the insulation material was calculated from the dimethyloctylamine content of 0.4 g of insulation material, resulting in a value of 2.9 x 10 －４ It was found to be mass %.

[0140] Examples 2 to 7 A heat insulating material (heat insulating layer) according to each example was produced in the same manner as in Example 1, except that graphite C to H (see Table 1) were used instead of graphite B.

[0141] Comparative Example 1 A heat insulating material (heat insulating layer) according to this example was produced in the same manner as in Example 1, except that graphite B was not used.

[0142] Comparative Example 2 A heat insulating material (heat insulating layer) according to this example was produced in the same manner as in Example 1, except that graphite A (see Table 1) was used instead of graphite B.

[0143] <Measurements and Evaluations> The following measurements and evaluations were carried out on the heat insulating materials (heat insulating layers) according to each example. The results are shown in Table 3. In Table 3, "parts" and "%" indicating the composition are all based on mass.

[0144] (Density) The heat insulating material was cut into a size of 20 mm x 20 mm, and the mass and thickness were measured. The mass was divided by the volume to calculate the density (initial density) [g / cm ３ ] was calculated.

[0145] (Compressive deformation rate (1.0 MPa)) A compression test was conducted using a precision universal testing machine (Autograph AGS-5kNX, manufactured by Shimadzu Corporation) to compress the heat insulating material (heat insulating layer) at a compression rate of 0.5 mm / min, and the compressive strain [%] (compressive displacement amount / initial thickness of test piece) and compressive stress [MPa] were measured. The compressive strain when the compressive stress reached 1.0 MPa was read, and this was adopted as the compressive deformation rate of the heat insulating material.

[0146] (Thermal Conductivity (600°C, 1 MPa)) In accordance with the contents of Japanese Industrial Standard JIS A 1412-2:1999 "Method for measuring thermal resistance and thermal conductivity of thermal insulating materials - Part 2: Heat Flow Meter Method (HFM Method)," thermal conductivity at 600°C and 1 MPa was measured as follows. First, a sample was prepared by cutting the insulating material (insulating layer) into a size of 20 mm x 20 mm. The above sample, a reference sample (alumina composite material ("RS-100," manufactured by ZIRCAR Refractory Composites, Inc., thickness: 5 mm, thermal conductivity: 0.66 W / (m·K))), and a titanium plate (thickness: 0.2 mm) were prepared. On the lower plate surface of a pneumatic press (manufactured by Imoto Machinery Co., Ltd.), from the top, thermocouple 1 (sheathed thermocouple K type (SCHS1-0), φ = 0.15, class JIS1, manufactured by Chino Corporation), titanium plate, insulation material (sample) as a test specimen, titanium plate, thermocouple 2 (sheathed thermocouple K type (SCHS1-0), φ = 0.15, class JIS1, manufactured by Chino Corporation), standard plate, thermocouple 3 (sheathed thermocouple K type (SCHS1-0), φ = 0.15, class JIS1, manufactured by Chino Corporation) were sandwiched in this order, and the insulation material, standard plate, thermocouple, etc. were closely attached. Next, the upper and lower plates were heated and the load of the press was adjusted to 400 N (equivalent to 1 MPa), and then pressurized. In the heated and pressurized state, measurement was continued until the detected temperature of the thermocouple stabilized. The heating temperature was 600 ° C. for the upper plate and 40 ° C. for the lower plate. "The temperature stabilized" was defined as a temperature change within ±0.1°C after 10 minutes of compression. After the temperature stabilized, the thermal conductivity k1 of the insulating material was calculated from the detected temperature of each thermocouple, the thickness of the insulating material when compressed, and the thermal conductivity and thickness of the standard sample using the following formula (I): k1 = k2 × (L1 × ΔT1) / (L2 × ΔT2) ... (I) (where k1 is the thermal conductivity of the insulating material [W / (m K)], k2 is the thermal conductivity of the standard plate [W / (m K)], L1 is the thickness of the insulating material when compressed, L2 is the thickness of the standard plate, ΔT1 is the temperature difference between the temperatures of the second thermocouple and the third thermocouple, and ΔT2 is the temperature difference between the temperatures of the first thermocouple and the second thermocouple.) The thermal resistance of each insulating material was calculated from the thermal conductivity k1 and the thickness when compressed L1 using the following formula (II): R1 = L1 / k1 (II) (where R1 is the thermal resistance of the heat insulating layer [(m ２K) / W], k1 is the thermal conductivity of the heat insulating layer [W / (m K)], and L1 is the thickness of the heat insulating layer when pressed.

[0147]

[0148] As can be seen from Tables 1 and 3, the thermal insulating materials of Examples 1 to 7, which used graphites B to H with shape parameter G values ​​(G values) in the range of 6.0 to 30, exhibited a significant effect of suppressing thermal conductivity (600°C, 1 MPa), compared to the thermal insulating material of Comparative Example 1, which did not contain graphite. On the other hand, the thermal insulating material of Comparative Example 2, which used graphite A with a G value outside the above range, exhibited a clearly lower effect of suppressing thermal conductivity (600°C, 1 MPa) compared to the thermal insulating materials of Examples 1 to 7.

[0149] Experimental Example 2: Investigation of the amount of graphite used Production of heat insulating material (heat insulating layer) Examples 8 to 11 Heat insulating materials (heat insulating layers) according to each example were produced in the same manner as in Example 1, except that the type and amount of graphite used were as shown in Table 4. The amount of the mixed solvent (IPA:water=9:1 (mass ratio)) used was adjusted appropriately so that the solid content of the mixture was similar to that of Example 1.

[0150] <Measurements and Evaluations> The following measurements and evaluations were carried out on the heat insulating materials (heat insulating layers) according to each example. The results are shown in Table 4. In Table 4, "parts" and "%" indicating the composition are all based on mass.

[0151] (Density, Compression Deformation Rate) Measurements were carried out in the same manner as in Experimental Example 1.

[0152] (Backside Temperature at 800°C) The heat insulating material (heat insulating layer) according to each example was cut to a 70 mm square to prepare a measurement sample. A hot plate with a 70 mm square heating surface was placed inside a windshield measuring 300 mm x 300 mm x 550 mm (height). The sample, thermocouple, and metal block (material: aluminum, size: 70 mm x 70 mm x 40 mm thick) were placed on the heating surface in this order. The hot plate was heated from 25°C to 800°C (heating rate: approximately 2°C / sec, reaching 800°C 6 minutes after the start of heating). The thermocouple temperature (corresponding to the backside temperature of the heat insulating material) was measured 30 minutes after the thermocouple temperature rose to 29°C, and the "backside temperature at 800°C" was determined and ranked according to the following three levels. The heat insulating properties at 800°C were ranked in order of C, B, and A. Rank A: 340°C or less Rank B: Over 340°C, 360°C or less Rank C: Over 360°C

[0153]

[0154] As shown in Table 4, the insulating materials (insulating layers) using graphite E or F, which has a G value in the range of 6.0 or more and 30 or less, all showed the effect of reducing the back surface temperature when heated to 800°C (i.e., improving the insulating properties in the high temperature range) compared to the insulating materials of Comparative Examples 1 and 2.

[0155] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

[0156] REFERENCE SIGNS LIST 1 heat insulating material 10 heat insulating layer 20 buffer layer 30 covering material 31A resin film 31B resin film 32 seal portion 33 ventilation hole 34 ventilation membrane 50 battery module 51 battery cell

Claims

1. Silica particles and a polymer having the following formula: G = (F ３－６ ) ２ ×H Ｗ / D50 (where F in the formula ３－６ is the volume frequency [%] of particle sizes of 3 to 6 μm in the volume-based particle size distribution based on the laser diffraction / scattering method, D50 is the cumulative 50% particle size [μm] in the volume-based particle size distribution, and H Ｗ is the half width [°] of the (002) peak in X-ray diffraction; and a heat insulating layer containing:

2. The heat insulating material according to claim 1, wherein the graphite particles have a cumulative 50% particle diameter D50 of 2.0 μm or more and less than 11 μm.

3. The graphite particles have a volume frequency F of 3 to 6 μm. ３－６ The heat insulating material according to claim 1 or 2, wherein the ratio of the porosity ...

4. The graphite particles have a volume frequency F of 4.625 μm in the volume-based particle size distribution based on the laser diffraction / scattering method. ４．６２５ The heat insulating material according to claim 1 or 2, wherein the content of SiO2 is 3.0% or more.

5. The heat insulating material according to claim 1 or 2, wherein the graphite particles have a half-value width of 0.18° or more.

6. The heat insulating material according to claim 1 or 2, wherein the graphite particles are artificial graphite.

7. An insulating material according to claim 1 or 2, wherein the content of the graphite particles in the insulating layer is 2.5% by mass or more and 30% by mass or less.

8. The heat insulating material according to claim 1 or 2, wherein the silica particles are at least one type selected from the group consisting of hydrophilic fumed silica and hydrophobic fumed silica.

9. The density of the heat insulating layer is 0.2 g / cm ３ ~0.5g / cm ３ The heat insulating material according to claim 1 or 2, 10. The heat insulating material according to claim 1 or 2, which is used by being disposed between adjacent cells of a battery module or battery pack including a plurality of arranged cells.

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