Vacuum heat insulating material

Abstract

To provide vacuum heat insulating material having excellent long-term reliability and improved compressive strength of core material.SOLUTION: Vacuum heat insulation material 1 comprises core material 10 and a gas barrier film 12 covering the core material, the core material 10 is vacuum-sealed in an outer bag 12 formed of a gas barrier film, and the core material contains fumed silica, a radiation-suppressing component, and inorganic long fibers, the content of the fumed silica is 50 to 90 mass% of the total amount of the core material, the content of the radiation-suppressing component is 3 to 30 mass% of the total amount of the core material, and the content of the inorganic long fibers is 2 to 30 mass% of the total amount of the core material, the density of the core material 10 vacuum-sealed in the outer bag 12 is 0.2 g / cm3 or less, and a fiber sizing agent is adhered to the inorganic long fibers, and the content of the fiber sizing agent is 0.01 mass% or more and less than 0.50 mass% of the total amount of the core material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vacuum insulation panel. [Background technology]

[0002] Vacuum insulation materials are used in various fields, such as refrigerators and water heaters. For example, Patent Document 1 proposes a vacuum insulation material in which a board-shaped core material containing glass fibers is vacuum-sealed in an outer bag. The board-shaped core material is produced by attaching a binder to glass fibers immediately after they are formed using a fiberizing device, and then heating and compressing the glass fibers to form a mat. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-251304 Summary of the Invention [Problem to be solved by the invention]

[0004] In the vacuum insulation material of Patent Document 1, a binder is used to form a laminated mat of glass fibers into a board-shaped core material. Because a certain amount of binder is required to form the core material, it is difficult to reduce the amount of binder used. However, during use, the binder in the core material may volatilize inside the outer bag, which can cause the internal pressure of the vacuum insulation material to gradually increase. This increase in internal pressure can lead to a gradual decline in the long-term insulation performance, which in turn can be a factor in reducing the long-term reliability of the vacuum insulation material.

[0005] In addition, in the vacuum insulation material of Patent Document 1, a binder is attached to the glass fibers before mat formation, so that the contact points between the glass fibers in the core material after heat molding are entangled and bound by the binder. Therefore, there is room for improvement in the reinforcing effect of the core material by the glass fibers.

[0006] The present invention provides a vacuum insulation panel that has excellent long-term reliability and an improved compressive strength of the core material. [Means for solving the problem]

[0007] [1] A gas barrier film is provided to cover a core material. the core material is vacuum sealed in an outer bag formed of the gas barrier film, the core material contains fumed silica, a radiation suppression component, and inorganic long fibers; The content of the fumed silica is 50 to 90 mass% of the total amount of the core material, the content of the radiation-suppressing component is 3 to 30 mass % of the total amount of the core material, The content of the inorganic long fibers is 2 to 30 mass% of the total amount of the core material, The density of the core material vacuum-sealed in the outer bag is 0.20 g / cm 3 is as follows: A fiber sizing agent is attached to the inorganic long fibers, A vacuum insulation material in which the content of the fiber sizing agent is 0.01 mass % or more and less than 0.50 mass % of the total amount of the core material. [2] The vacuum heat insulating material according to [1], wherein the mass ratio of the total amount of the fiber sizing agent to the total amount of the inorganic long fibers is 1 / 200 to 1 / 30. [3] The vacuum insulation material according to [1] or [2], wherein the fiber sizing agent is at least one selected from the group consisting of vinyl acetate resin, vinyl acetate copolymer resin, urethane resin, acrylic resin, epoxy resin, polyester resin, and silane coupling agent. [4] The vacuum insulation material according to any one of [1] to [3], wherein the inorganic long fibers are at least one selected from the group consisting of alumina long fibers, glass long fibers, silica long fibers, silica-alumina long fibers, and carbon long fibers. [5] The vacuum insulation material according to any one of [1] to [4], wherein the radiation suppressing component is at least one selected from the group consisting of graphite, silicon carbide, titanium oxide, tin oxide, and potassium titanate. [6] At least a part of the inorganic long fibers is glass long fibers, The vacuum heat insulating material according to any one of [1] to [5], wherein the ratio of the combined mass of Na2O and K2O in the long glass fibers to the total mass of the long glass fibers is 11 mass % or less. [7] The fiber length of the inorganic long fiber is 0.1 to 10 mm, and The vacuum heat insulating material according to any one of [1] to [6], wherein the inorganic long fibers have a fiber length distribution Lw / Ln, which is expressed as a ratio of the number average fiber length Ln to the weight average fiber length Lw, of 1.05 or more. [Effects of the Invention]

[0008] According to the present invention, a vacuum insulation material having excellent long-term reliability and improved compressive strength of the core material is provided. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a vacuum heat insulating material. [Figure 2] FIG. 2 is an SEM image of the core material of the vacuum heat insulating material of Example 3. [Figure 3] FIG. 3 is an SEM image of the core material of the vacuum heat insulating material of Example 1. [Figure 4] Figure 4 shows the results of an experiment verifying the relationship between the content of fiber sizing agent and the rate of increase in internal pressure. DETAILED DESCRIPTION OF THE INVENTION

[0010] The meanings of the terms are as follows: The term "core material" refers to a molded body made from a raw material mixture in a vacuum insulation material, which is molded into a desired shape. "Fumed silica" refers to fine silica particles consisting of amorphous, spherical, pore-free primary particles. Fumed silica can be obtained, for example, by vaporizing silicon tetrachloride and carrying out a gas-phase reaction in a high-temperature hydrogen flame. The term "radiation suppression component" refers to particles that suppress radiative heat transfer by reflecting or scattering infrared light, or by absorbing infrared light and then isotropically radiating the amount of temperature increase caused by the absorption, thereby disrupting the directionality of the infrared light.

[0011] The "average aggregate particle diameter D50" is the volume-based cumulative 50% diameter determined by laser diffraction scattering. In the volume-based frequency particle size distribution determined by laser diffraction scattering, a cumulative curve is determined with the total volume of the particle group as 100%, and the particle diameter at the point on the cumulative curve where the cumulative volume is 50% is defined as D50.

[0012] The "specific surface area of ​​fumed silica" is measured by the nitrogen adsorption method (BET method). The "bulk density of fumed silica" is determined by the constant mass measurement method specified in JIS R1628 1997.

[0013] The thermal expansion coefficient of the inorganic long fiber is measured using a thermomechanical analyzer (TMA) in the temperature range of 50 to 400°C at a heating rate of 5°C / min. The Young's modulus of the inorganic long fiber is measured by a tensile test method. The proportions of Na2O and K2O in the long glass fibers are determined from various composition analyses performed on the long glass fibers. The amount of alkali elution from the long glass fiber is measured according to the method described in JIS R3503-1994.

[0014] "Fiber length D10" means the fiber length at the point where the cumulative number is 10% in a cumulative number distribution curve where the total number in the fiber length distribution calculated by number is 100%. "Fiber length D50" means the fiber length at the point where the cumulative number is 50% in a cumulative number distribution curve where the total number in the fiber length distribution calculated by number is 100%. "Fiber length D90" means the fiber length at the point where the cumulative number is 90% in a cumulative number distribution curve where the total number in the fiber length distribution calculated by number is 100%. The fiber length distribution can be determined by measuring the lengths of 50 or more randomly selected fibers in a photograph observed under an optical microscope, and then using the frequency distribution and cumulative number distribution curve.

[0015] "Fiber diameter d10" means the fiber diameter at the point where the cumulative number is 10% in a cumulative number distribution curve where the total number in the fiber diameter distribution calculated on a number basis is 100%. "Fiber diameter d50" means the fiber diameter at the point where the cumulative number is 50% in a cumulative number distribution curve where the total number in the fiber diameter distribution calculated on a number basis is 100%. "Fiber diameter d90" means the fiber diameter at the point where the cumulative number is 90% in a cumulative number distribution curve where the total number in the fiber diameter distribution calculated on a number basis is 100%. The fiber diameter distribution can be determined from the frequency distribution and cumulative number distribution curve obtained by measuring the width of 50 or more single fibers at random in a photograph observed with an optical microscope.

[0016] "Core density" refers to the average density of the entire core. Three 30mm x 150mm samples were cut from any location on the core, and each sample was divided into four equal parts in the thickness direction to create test pieces. The density of each test piece was measured, and the average value was used as the density of the core.

[0017] "Density of the core material sealed under reduced pressure" refers to the average density of the entire core material sealed under reduced pressure in the outer bag, and is a value measured by the following measurement method. Measurement method: The core material is placed inside the outer bag and placed in a vacuum chamber equipped with a heat sealing function. The chamber is reduced in pressure to 5 Pa, and the opening of the outer bag is heat-sealed to seal it. The outside of the outer bag is then returned to atmospheric pressure to obtain the vacuum insulation material. The weight of the core material sealed under reduced pressure is calculated from the weight of the vacuum insulation material and the weight of the outer material. The volume is calculated from the average of the side lengths and thicknesses at five points. The density is calculated from the calculated core weight and volume. This value is the density of the core material sealed under reduced pressure.

[0018] The "thickness of the core material" refers to the average thickness of the entire core material. The thickness is measured at any five points on the core material, and the average value is taken as the thickness of the core material. The "total thickness of the vacuum heat insulating material" refers to the thickness of the part excluding the edge folds (folded-back parts) at the ends of the gas barrier film.

[0019] The "Young's modulus of the core material" is determined by the method described in the examples. The "permanent deformation of the core material" is determined by the method described in the examples.

[0020] The symbol "to" indicating a range of values ​​means that the values ​​before and after the symbol "to" are included as the lower and upper limits. The ranges of values ​​disclosed in this specification can be combined in any way to create new ranges of values.

[0021] Hereinafter, several embodiments will be described with reference to the drawings as appropriate. The following description relates to representative examples of embodiments of the invention, and the present invention is not limited to the following description. Furthermore, the dimensional ratios in each drawing may differ from the actual ones for the sake of convenience of explanation.

[0022] The vacuum insulation material according to the embodiment includes a core material and a gas barrier film covering the core material. The core material is enclosed under reduced pressure in an outer bag formed of the gas barrier film. Figure 1 is a cross-sectional view showing an example of a vacuum insulation material. The vacuum insulation material 1 comprises a core material 10 and an outer bag 12 formed from a gas barrier film. The core material 10 is sealed under reduced pressure within the outer bag 12. For example, the vacuum insulation material 1 is obtained by storing the core material 10 inside the outer bag 12, which is a bag-shaped gas barrier film, and sealing the opening of the outer bag 12 under reduced pressure.

[0023] [Core material] The shape of the core material may be, for example, a flat plate, but is not limited thereto. The shape of the core material as viewed in the thickness direction can also be appropriately designed depending on the application, and examples include square, rectangular, and circular shapes.

[0024] The core material contains fumed silica, a radiation-suppressing component, and inorganic long fibers. In one example, the core material may further contain materials other than the fumed silica, the radiation-suppressing component, and the inorganic long fibers, as long as the effects of the invention are not impaired.

[0025] (fumed silica) The average agglomerated particle diameter D50 of the fumed silica is preferably 5 to 50 μm, more preferably 5 to 30 μm, and even more preferably 5 to 20 μm. When the average agglomerated particle diameter D50 of the fumed silica is equal to or greater than the lower limit of the above-mentioned range, scattering of the core material when it is sealed under reduced pressure is easily suppressed. When the average agglomerated particle diameter D50 of the fumed silica is equal to or less than the upper limit of the above-mentioned range, solid-state heat transfer is easily suppressed. Therefore, excellent heat insulating performance is easily obtained.

[0026] The specific surface area of ​​fumed silica is 50 to 400 m 2 / g is preferred, and 100 to 350m 2 / g is more preferable, and 200 to 300m 2 When the specific surface area of ​​the fumed silica is within the above range, excellent heat insulating performance is likely to be obtained.

[0027] The fumed silica may be a commercially available product. Examples of commercially available fumed silica include Aerosil 200 (specific surface area 200 m 2 / g, manufactured by Nippon Aerosil Co., Ltd.), Aerosil 300 (specific surface area 300 m 2 / g, manufactured by Nippon Aerosil Co., Ltd.), CAB-O-SIL M-5 (specific surface area 200 m 2 / g, manufactured by Cabot Japan Co., Ltd.), CAB-O-SIL H-300 (specific surface area 300 m 2 / g, manufactured by Cabot Japan), Reolosil QS30 (specific surface area 300 m 2 / g, manufactured by Tokuyama Corporation). However, the fumed silica is not limited to those exemplified here. The fumed silica may be used alone or in combination of two or more kinds.

[0028] The bulk density of the fumed silica is not particularly limited, but is, for example, 0.1 g / cm 3 It may be less than 0.05 g / cm 3 It may be 0.04 g / cm or less. 3 When the bulk density of the fumed silica is equal to or less than the upper limit, the core material can be easily formed into a desired shape. The lower limit of the bulk density of the fumed silica is not particularly limited, but may be, for example, 0.01 g / cm. 3 It may be 0.02 g / cm or more. 3 It may be 0.03 g / cm or more. 3 It may be more than that.

[0029] (Radiation suppression component) Examples of radiation-suppressing components include metal particles such as aluminum particles, silver particles, and gold particles, graphite, carbon black, silicon carbide, titanium oxide, tin oxide, and potassium titanate, but the radiation-suppressing component is not limited to the examples given here. The radiation suppression component may be used alone or in combination of two or more.

[0030] From the viewpoints of thermal conductivity and workability, the radiation-suppressing component is preferably one or more selected from the group consisting of graphite, silicon carbide, titanium oxide, tin oxide, and potassium titanate, more preferably one or more selected from the group consisting of graphite and silicon carbide, and even more preferably graphite.

[0031] (Inorganic long fiber) Examples of inorganic long fibers include alumina long fibers, glass long fibers, silica long fibers, silica-alumina long fibers, carbon long fibers, silicon carbide long fibers, Tyranno long fibers, and zirconia long fibers, but the inorganic long fibers are not limited to those exemplified here. The inorganic long fibers may be used alone or in combination of two or more kinds.

[0032] As the inorganic long fibers, glass long fibers and silica-alumina long fibers are preferred, with glass long fibers being more preferred. These inorganic long fibers are preferred because they have low volatilization of gas components under vacuum, making it easy to prevent a decrease in insulation performance due to a decrease in the degree of vacuum, have excellent heat resistance, can increase the strength of the core material, are low-cost, and are easy to handle.

[0033] Inorganic fibers include inorganic long fibers, inorganic short fibers, whiskers, etc., and inorganic long fibers are clearly distinguished from inorganic short fibers and whiskers due to their manufacturing process. In one example, inorganic long fibers can be produced by chopping continuous inorganic fiber bundles. Continuous inorganic fiber bundles are produced by bundling a plurality of aligned continuous inorganic fibers with a fiber sizing agent.

[0034] The fiber length of the continuous inorganic fibers and continuous inorganic fiber bundles immediately after spinning is not particularly limited. Since the long fibers are spun endlessly unless thread breakage occurs, the length may be on the order of several kilometers.

[0035] The manufacturing methods for inorganic long fibers and inorganic short fibers and whiskers are significantly different. Glass short fibers, one example of inorganic short fibers, are produced by blowing molten glass using centrifugal force to create thin fibers that are then turned into cotton, with fiber lengths ranging from several tens of centimeters to one meter at most. In contrast, inorganic long fibers are produced using the melt spinning method or precursor method, and theoretically, endless fibers can be drawn as long as raw materials are continuously fed. The number of fiber bundles can be changed depending on the intended use of inorganic long fibers, and the length can be changed by chopping. Inorganic long fibers are required to have technical requirements such as melting properties that enable endless fiber production, and therefore can be clearly distinguished from inorganic short fibers and whiskers in terms of their composition.

[0036] A fiber sizing agent is attached to the inorganic long fibers in the core material. A fiber sizing agent is a surface treatment agent used to bind the spun continuous inorganic fibers in an aligned state. In contrast, although a binder is a type of surface treatment agent for fibers, it is clearly distinguished from a fiber sizing agent in that it fixes the single fibers together in an entangled state at their contact points.

[0037] Examples of fiber sizing agents include vinyl acetate resins, vinyl acetate copolymer resins, urethane resins, acrylic resins, epoxy resins, polyester resins, and silane coupling agents. In addition, lubricants, softeners, surfactants, antistatic agents, etc. may also be used depending on the application. However, the fiber sizing agents are not limited to those exemplified here. The fiber sizing agent may be used alone or in combination of two or more kinds.

[0038] In one example, the fiber length range of the inorganic long fibers in the core material is preferably 0.1 to 10 mm, and the fiber length distribution Lw / Ln is preferably 1.05 or more. In this case, the fiber length distribution of the inorganic long fibers is broad. By using inorganic long fibers with a broad fiber length distribution, the compressive strength of the core material is increased. Therefore, the core material is less likely to be crushed when vacuum-sealed in an outer bag. As a result, the low density of the core material is maintained after vacuum-sealing, resulting in low thermal conductivity. Therefore, excellent heat insulating performance is easily obtained.

[0039] The reason why the use of inorganic long fibers with a wide fiber length distribution increases the compressive strength of the core material is not entirely clear, but it is thought that the wide fiber length distribution makes it easier for the orientation of the inorganic long fibers to vary, which tends to result in an isotropic increase in compressive strength.

[0040] Here, Ln is the number-average fiber length of the inorganic long fibers, which is calculated from the number-based frequency distribution obtained by measuring the lengths of 50 or more inorganic long fibers randomly selected in a photograph observed with an optical microscope, using the following formula 1: Lw is the weight-average fiber length of the inorganic long fibers. Lw is calculated from the weight-based frequency distribution obtained by measuring the lengths of 50 or more inorganic long fibers randomly selected in a photograph observed with an optical microscope, using the following formula 2:

[0041]

number

[0042] In Equations 1 and 2, Ni is the number of fibers in each histogram of mean length Li.

[0043] The fiber length of the inorganic long fibers may be, for example, 0.1 to 10 mm, 1 to 8 mm, or 2 to 6 mm. When the fiber length of the inorganic long fibers is equal to or greater than the lower limit of the above-mentioned range, a high-strength vacuum insulation material is likely to be obtained. In addition, the compressive strength of the core material is likely to be improved. When the fiber length of the inorganic long fibers is equal to or less than the upper limit of the above-mentioned range, the influence of solid-state thermal conduction of the fibers is likely to be reduced. Therefore, a vacuum insulation material with good thermal conductivity is likely to be obtained.

[0044] Lw / Ln is expressed as the ratio of the number-average fiber length Ln to the weight-average fiber length Lw of the inorganic long fibers. Lw / Ln indicates the fiber length distribution of the inorganic long fibers. Lw / Ln is preferably 1.05 or more, more preferably 1.10 or more, and even more preferably 1.20 or more. The upper limit of Lw / Ln is not particularly limited, but may be, for example, 2.00 or less, 1.80 or less, or 1.60 or less. The larger Lw / Ln means the wider the fiber length distribution of the inorganic long fibers.

[0045] The fiber length distribution index of inorganic long fibers is expressed as (D90-D10) / D50, where D10 is the fiber length of inorganic long fibers, D50 is the fiber length of inorganic long fibers, and D90 is the fiber length of inorganic long fibers. The larger (D90-D10) / D50, the wider the fiber length distribution of inorganic long fibers. The ratio (D90-D10) / D50 is preferably 0.21 or more, more preferably 0.4 or more, and even more preferably 0.6 or more. When the ratio (D90-D10) / D50 is equal to or greater than the lower limit, the compressive strength of the core material tends to be high. Furthermore, a vacuum insulation material with excellent heat insulating performance is easily obtained. The upper limit of the ratio (D90-D10) / D50 is not particularly limited, but may be, for example, 2.0 or less, 1.9 or less, or 1.8 or less.

[0046] The fiber length D10 of the inorganic long fibers may be, for example, 2.4 mm or less, 2.0 mm or less, or 1.8 mm or less. The fiber length D50 of the inorganic long fibers may be, for example, 2.0 to 5.0 mm, 2.1 to 4.8 mm, or 2.15 to 4.6 mm. The fiber length D90 of the inorganic long fibers may be, for example, 4.0 to 7.0 mm, 3.5 to 6.7 mm, or 3.2 to 6.5 mm.

[0047] The fiber diameter spread index of inorganic long fibers is expressed as (d90-d10) / d50, where d10 is the fiber diameter of inorganic long fibers, d50 is the fiber diameter of inorganic long fibers, and d90 is the fiber diameter of inorganic long fibers. The larger the (d90-d10) / d50, the wider the fiber diameter distribution of the inorganic long fibers. (d90-d10) / d50 is preferably 0.5 or greater, more preferably 1.0 or greater, and even more preferably 1.5 or greater. When (d90-d10) / d50 is equal to or greater than the lower limit, the relatively small-diameter inorganic long fibers and the relatively large-diameter inorganic long fibers are more likely to mix with each other and are therefore more likely to be uniformly dispersed in the core material. As a result, the compressive strength of the core material is more likely to be high. In addition, a vacuum insulation panel with excellent thermal insulation performance is more likely to be obtained. The upper limit of (d90-d10) / d50 is not particularly limited, but may be, for example, 2.0 or less, 1.9 or less, or 1.8 or less.

[0048] The fiber diameter d10 of the inorganic long fibers may be, for example, 4 μm or less, 3 μm or less, or 2 μm or less. The fiber diameter d50 of the inorganic long fibers may be, for example, 5 to 15 μm, 7 to 13 μm, or 7.5 to 12 μm. The fiber diameter d90 of the inorganic long fibers may be, for example, 8 to 16 μm, 9 to 15 μm, or 10 to 13 μm.

[0049] In one example, the thermal expansion coefficient of inorganic long fibers is 90×10 -7 / ℃ or less is preferable, and 80 × 10 -7 / ℃ or less is more preferable, and 50×10 -7 / °C or less is even more preferable. If the thermal expansion coefficient of the inorganic long fibers is not more than the above upper limit, the initial thermal conductivity will be low. Therefore, it is easy to obtain a vacuum insulation material with excellent thermal insulation performance. The mechanism behind the low initial thermal conductivity is not necessarily clear, but if the thermal expansion coefficient of the inorganic long fibers is not more than the above upper limit, the inorganic long fibers are less likely to change shape when dried after molding the core material. In addition, voids are less likely to occur around the inorganic long fibers. As a result, it is thought that deterioration of the initial thermal conductivity is suppressed. There is no particular limitation on the lower limit of the thermal expansion coefficient of the inorganic long fibers.

[0050] In one example, the Young's modulus of the inorganic long fiber is preferably 50 GPa or more, more preferably 60 GPa or more, and even more preferably 70 GPa or more. When the Young's modulus of the inorganic long fiber is equal to or greater than the lower limit, the compressive strength of the core material is likely to be improved. The upper limit of the Young's modulus of the inorganic long fiber is not particularly limited, but may be, for example, 95 GPa or less, or 90 GPa or less.

[0051] When the core material contains, as at least a portion of the inorganic long fibers, long glass fibers, the ratio of the total mass of Na2O and K2O in the long glass fibers to the total mass of the long glass fibers (hereinafter also referred to as "ratio A") is preferably 11 mass% or less. When the percentage A is 11% by mass or less, it is easy to prevent the thermal conductivity from gradually increasing due to moisture penetrating into the vacuum insulation material. As a result, long-term reliability is likely to improve. The mechanism by which this effect is achieved is not entirely clear, but it is thought to be as follows.

[0052] In vacuum insulation panels in which a core material is vacuum-sealed within an outer bag, moisture can gradually penetrate through the outer surface and heat-sealed portions of the outer bag. When the proportion A of short glass fibers exceeds 11% by mass, the short glass fibers have a high affinity for water. This makes the core material more likely to retain moisture, which can lead to the formation of silanol groups. For example, the vacuum insulation panel disclosed in JP 2008-215538 A uses alkali-containing glass with a high content of sodium and potassium components in the long glass fibers to enable molding at lower temperatures, which may result in a deterioration in long-term insulation performance.

[0053] In contrast, if long glass fibers with a ratio A of 11% by mass or less are used, the core material will be less likely to retain moisture. As a result, the gradual increase in the thermal conductivity of the core material due to moisture penetrating into the vacuum insulation material is suppressed, which is thought to improve the long-term reliability of the insulation performance of the vacuum insulation material.

[0054] To further improve the long-term reliability of the vacuum insulation material, the proportion A is preferably 11% by mass or less, more preferably 6% by mass or less, and even more preferably 3% by mass or less. Long glass fibers that have been given melting properties by using boric acid or the like instead of an alkali component may also be used. As in this example, alkali-free glass that does not substantially contain Na2O or KO can also be suitably used.

[0055] In one example, when long glass fibers having a ratio A of not more than the upper limit are used as inorganic long fibers, the glass constituting the long glass fibers is not particularly limited, but examples thereof include aluminoborosilicate glass, borosilicate glass, and aluminosilicate glass. The long glass fibers may be made of one type of glass alone or two or more types in combination. Among them, one or more types selected from the group consisting of aluminoborosilicate glass, borosilicate glass, and aluminosilicate glass are preferred. Furthermore, E-glass fiber is particularly preferred as the long glass fiber.

[0056] For example, the alkali elution amount of the long glass fiber is preferably 1.9 mL / g or less, more preferably 1.0 mL / g or less, and even more preferably 0.5 mL / g or less. When the alkali elution amount of the long glass fiber is the above-mentioned upper limit or less, an increase in thermal conductivity due to moisture penetrating into the vacuum insulation material can be easily suppressed.

[0057] (Other materials) Materials other than fumed silica, radiation-suppressing components, and inorganic long fibers may be blended into the core material as long as the effects of the present invention are not impaired. Examples of such materials include wet silica, biomass-derived powder, and binders. The other materials may be used singly or in combination of two or more.

[0058] Examples of the binder include inorganic binders such as sodium silicate, aluminum phosphate, magnesium sulfate, magnesium chloride, etc. However, the binder is not limited to inorganic binders and may be an organic binder.

[0059] (Core composition) The content of fumed silica is 50 to 90 mass% of the total amount of the core material. The content of fumed silica is preferably 60 to 90 mass%, more preferably 65 to 90 mass%, and even more preferably 70 to 90 mass% of the total amount of the core material. When the content of fumed silica is equal to or greater than the lower limit of the above-mentioned numerical range, a core material with high compressive strength is easily obtained. In addition, the core material is easily formed into a desired shape. When the content of fumed silica is equal to or less than the upper limit of the above-mentioned numerical range, the reinforcing effect of the inorganic long fibers and the effect of improving heat insulating performance due to the radiation suppression component are easily obtained.

[0060] The content of the radiation-suppressing component is 3 to 30 mass% of the total amount of the core material. The content of the radiation-suppressing component is preferably 5 to 27 mass%, more preferably 8 to 25 mass%, and even more preferably 10 to 20 mass% of the total amount of the core material. When the content of the radiation-suppressing component is equal to or greater than the lower limit of the above-mentioned numerical range, deterioration of the thermal conductivity of the vacuum insulation material due to radiation within the core material can be suppressed. When the content of the radiation-suppressing component is equal to or less than the upper limit of the above-mentioned numerical range, the effect of the radiation-suppressing component in increasing solid-state heat transfer can be suppressed. Therefore, excellent heat insulating performance can be easily obtained.

[0061] The content of the inorganic long fibers is 2 to 30% by mass of the total amount of the core material. The content of the inorganic long fibers is preferably 2 to 20% by mass, more preferably 2 to 10% by mass, and even more preferably 2 to 8% by mass of the total amount of the core material. When the content of the inorganic long fibers is equal to or greater than the lower limit of the above-mentioned numerical range, a core material with high compressive strength is likely to be obtained. When the content of the inorganic long fibers is equal to or less than the upper limit of the above-mentioned numerical range, an increase in solid-state heat transfer due to the fibers can be suppressed. Therefore, a decrease in heat insulating performance can be easily suppressed.

[0062] The content of the fiber sizing agent is 0.01% by mass or more and less than 0.50% by mass of the total amount of the core material. The content of the fiber sizing agent is preferably 0.02 to 0.40% by mass, more preferably 0.04 to 0.30% by mass, and even more preferably 0.06 to 0.20% by mass, of the total amount of the core material. When the content of the fiber sizing agent is equal to or greater than the lower limit of the above-mentioned numerical range, the compressive strength of the core material is improved. When the content of the fiber sizing agent is equal to or less than the upper limit of the above-mentioned numerical range, the internal pressure of the vacuum insulation material is less likely to increase, making it easier to obtain a vacuum insulation material with excellent long-term reliability.

[0063] In the core material, the mass ratio of the total amount of fiber bundling agent to the total amount of inorganic long fibers (total amount of fiber bundling agent / total amount of inorganic long fibers) is preferably 1 / 200 to 1 / 30, more preferably 1 / 150 to 1 / 40, and even more preferably 1 / 100 to 1 / 50 mass%. When this mass ratio is equal to or greater than the lower limit of the above-mentioned numerical range, the compressive strength of the core material is improved. When this mass ratio is equal to or less than the upper limit of the above-mentioned numerical range, the internal pressure of the vacuum insulation material is less likely to increase, making it easier to obtain a vacuum insulation material with excellent long-term reliability.

[0064] When the core material further contains other materials in addition to fumed silica, a radiation-suppressing component, and inorganic long fibers, the content of the other materials may be 0.5 to 20 mass%, 1.0 to 15 mass%, or 1.5 to 10 mass% of the total amount of the core material. When the content of the other materials is equal to or greater than the lower limit of the above-mentioned range, the properties of the other materials are easily imparted to the core material. When the content of the other materials is equal to or less than the upper limit of the above-mentioned range, the effects of the present invention are less likely to be impaired.

[0065] (Physical properties of core material) The thickness of the core material is preferably 2 mm or more, more preferably 5 mm or more, and even more preferably 8 mm or more. When the thickness of the core material is equal to or greater than the lower limit, heat insulating performance is easily achieved, taking into account the influence of thermal bridges that occur at the ends of the vacuum insulation material. The upper limit of the thickness of the core material is not particularly limited, but may be, for example, 50 mm or less, 40 mm or less, or 30 mm or less.

[0066] The density of the core material is 0.15 to 0.25 g / cm 3 is preferable, and 0.15 to 0.20 g / cm 3 More preferably, 0.15 to 0.18 g / cm 3 is more preferable. When the density of the core material is equal to or greater than the lower limit of the above-mentioned range, the core material is easy to handle. Furthermore, the fumed silica and radiation-suppressing components are less likely to scatter from the core material during vacuum sealing. When the density of the core material is equal to or less than the upper limit of the above-mentioned range, a vacuum insulation material with excellent heat insulating performance is more likely to be obtained.

[0067] The density of the vacuum-sealed core is 0.20 g / cm 3 is less than 0.19 g / cm 3 Preferably less than 0.18 g / cm 3 Less than 0.17 g / cm is more preferable. 3When the density of the core material sealed under reduced pressure is equal to or less than the upper limit, it is easy to obtain a vacuum insulation material with low thermal conductivity and excellent heat insulating performance. In terms of facilitating handling of the core material and preventing the fumed silica and radiation suppressing components from scattering from the core material during sealing under reduced pressure, it is more preferable that the density of the core material sealed under reduced pressure is 0.11 g / cm. 3 More than 0.12 g / cm is preferable. 3 More than 0.13 g / cm is preferable. 3 The above is more preferable. These lower and upper limits can also be combined arbitrarily. For example, the density of the core material sealed under reduced pressure is 0.11 to 0.30 g / cm. 3 is preferably 0.13 to 0.20 g / cm 3 is more preferred.

[0068] From the viewpoint of compressive strength, the Young's modulus of the core material is preferably 1.25 MPa or more, more preferably 1.30 MPa or more, and even more preferably 1.35 MPa or more. The upper limit of the Young's modulus of the core material is not particularly limited, but may be, for example, 3.00 MPa or less.

[0069] From the viewpoint of compressive strength, the permanent set of the core material is preferably 5.0% or less, more preferably 4.5% or less, and even more preferably 4.2% or less. The lower limit of the Young's modulus of the core material is not particularly limited, but may be, for example, 0.5% or more.

[0070] [Outer bag] The size and shape of the outer bag are not particularly limited and can be set according to the size and shape of the desired vacuum insulation material. The gas barrier film used for the outer bag is an airtight film. For example, it may be a laminated film having a sealant layer and a barrier layer. However, the gas barrier film is not limited to this example. In addition to the sealant layer and the barrier layer, the gas barrier film may further have other layers such as an adhesive layer and a protective layer.

[0071] The sealant layer is provided as the innermost layer of the gas barrier film. The material for forming the sealant layer is not particularly limited. Examples include polyolefin resins such as low-density polyethylene, medium-density polyethylene, linear low-density polyethylene (LLDPE), and polypropylene. The sealant layer may be made of one material or two or more materials. The sealant layer may have a single layer structure or a multi-layer structure.

[0072] Examples of the barrier layer include an aluminum vapor deposition layer, an aluminum foil layer, and a metal oxide vapor deposition layer made of alumina, silica, or the like. The aluminum vapor deposition layer and the metal oxide vapor deposition layer can be formed by vapor depositing aluminum or a metal oxide onto a vapor deposition substrate. Examples of the vapor deposition substrate include resin films such as polyethylene terephthalate (PET) film and ethylene-vinyl alcohol copolymer (EVOH) film. However, the resin film is not limited to these examples. The number of barrier layers in the gas barrier film is preferably 2 or more, more preferably 2 to 6, and even more preferably 2 to 4.

[0073] The adhesive for the adhesive layer is preferably an adhesive suitable for dry lamination, such as a two-component curing polyurethane adhesive, an acrylic adhesive, or an epoxy adhesive, and is particularly preferably a two-component curing polyester adhesive.

[0074] The protective layer is preferably provided on the outermost layer, but this is not a limitation. The protective layer may be provided between the barrier layer and the sealant layer, or between two barrier layers. When the gas barrier film has a protective layer, the protective layer may be one layer or two or more layers.

[0075] Examples of materials for the protective layer include polyamide resins such as nylon 6, nylon 66, and copolymers of nylon 66 and nylon 6, and polyester resins such as PET and polyethylene naphthalate, but the material for the protective layer is not limited to these examples.

[0076] The thickness of the gas barrier film is preferably 40 to 65 μm, more preferably 45 to 65 μm, and even more preferably 47 to 62 μm. When the thickness of the gas barrier film is at least the lower limit of the above-mentioned numerical range, the film strength is excellent. When the thickness of the gas barrier film is at most the upper limit of the above-mentioned numerical range, the weight of the vacuum insulation material can be reduced.

[0077] [Properties of vacuum insulation material] The degree of vacuum inside the outer bag of the vacuum insulation material is 1 x 10 3 Pa or less is preferable, and 5×10 2 Pa or less is more preferable, and 3×10 2 It is more preferable that the degree of vacuum inside the outer bag of the vacuum insulation material is 1 Pa or less. When the degree of vacuum inside the outer bag of the vacuum insulation material is equal to or less than the above upper limit, excellent heat insulating performance can be obtained. In addition, the life of the vacuum insulation material is extended. In terms of ease of reducing the pressure inside the outer bag, the degree of vacuum inside the outer bag is preferably 1 Pa or more, and more preferably 10 Pa or more. These lower and upper limits can also be combined as desired.

[0078] The total thickness of the vacuum insulation material may be, for example, 3 mm or more, 5 mm or more, or 10 mm or more. The total thickness of the vacuum insulation material may also be 40 mm or less, or 30 mm or less. These lower and upper limits may also be combined in any desired manner.

[0079] [Vacuum insulation panel manufacturing method] There are no particular limitations on the method for producing a vacuum insulation material according to the embodiment, and examples include a method including press-molding a raw material mixture containing fumed silica, a radiation-suppressing component, and inorganic long fibers within the above-described composition ranges to obtain a core material, and then vacuum-sealing the core material in an outer bag formed of a gas barrier film.

[0080] The method for obtaining the raw material mixture containing fumed silica, a radiation-suppressing component, and inorganic long fibers is not particularly limited, and includes, for example, a method using a V-type mixer, a blender equipped with a stirrer, or the like, but is not limited thereto, and various other methods can be used.

[0081] When inorganic long fibers having a fiber length range of 0.1 to 10 mm and a fiber length distribution Lw / Ln of 1.05 or more are used, the desired inorganic long fibers can be prepared in advance by, for example, the following Method 1, Method 2, or Method 3. Method 1: A method in which a portion of inorganic long fibers with fiber lengths of 1.5 to 10 mm are pulverized using a pulverizer such as a ball mill to widen the fiber length distribution. Method 2: A method in which two or more inorganic long fibers with different fiber lengths in the range of 0.1 to 10 mm are mixed to obtain a fiber mixture with a wide fiber length distribution. Method 3: A part of the fiber mixture is crushed by a crushing device.

[0082] In Methods 1, 2, and 3, inorganic long fibers having the same fiber length may be sequentially added to the grinding device while grinding the inorganic long fibers in the grinding device. When a ball mill is used, the grinding treatment time is preferably 1 to 10 hours, more preferably 2 to 5 hours.

[0083] For example, the insulating board manufacturing apparatus described in paragraphs 0013 to 0028 of Japanese Patent Application Laid-Open No. 2016-102511 can be used to press-molde the raw material mixture. This manufacturing apparatus includes an upper mold having a convex portion with a decompression chamber formed therein, and a lower mold having a concave portion, with multiple exhaust holes formed on the surface of the convex portion facing the concave portion. With the raw material mixture poured into the concave portion of the lower mold, the upper mold is lowered by a cylinder, the convex portion of the upper mold is fitted into the concave portion of the lower mold, and the decompression chamber of the upper mold is reduced in pressure using a vacuum pump, thereby evacuating the air from the raw material mixture and performing press molding. The thickness and density of the core material can be controlled by adjusting the amount of raw material mixture poured into the concave portion of the lower mold and the pressing pressure.

[0084] By using an apparatus with such an exhaust mechanism, it is easy to prevent voids from forming in the core material, even when manufacturing a thick core material at a low press pressure. Furthermore, the density of the resulting core material in the thickness direction tends to be lower in the center than in the outer layers on both sides. This lower-density portion has a lower thermal conductivity, which is advantageous for heat insulation.

[0085] After press molding, the core material is preferably heat-treated and dried, which allows sufficient removal of moisture and further reduces the thermal conductivity of the core material. The method for heat treating the core material is not particularly limited, and for example, it can be heated in a constant temperature dryer, an electric furnace, or the like. The heat treatment temperature is preferably 80 to 400°C, more preferably 100 to 300°C. The heat treatment time is preferably 0.1 to 120 hours, more preferably 0.1 to 60 hours.

[0086] The method for vacuum-sealing the core material in the outer bag is not particularly limited, and the core material can be vacuum-sealed in the outer bag by various methods, such as a method in which the core material is placed in the outer bag, the opening of the outer bag is sealed under vacuum conditions, and then the pressure outside the outer bag is returned to atmospheric pressure.

[0087] In one example, a core material is placed inside an outer bag made by overlapping two gas barrier films and sealing three sides, and the outer bag is then placed inside a vacuum chamber equipped with a heat seal function, and the inside of the vacuum chamber is depressurized. After the inside of the vacuum chamber is depressurized to a predetermined pressure, the remaining open side of the outer bag is heat-sealed to seal the outer bag, and the inside of the vacuum chamber is returned to atmospheric pressure. In another example, after the core material is housed in the outer bag, the air inside the outer bag may be sucked out to reduce the pressure inside the outer bag, and the outer bag may be sealed by heat sealing or the like.

[0088] The core material may be housed in a breathable inner bag, which may then be vacuum sealed in an outer bag. The inner bag may be any material that is breathable and prevents leakage of the raw material when the core material is vacuum sealed in. Examples of the material for the inner bag include paper and nonwoven fabric. However, the material for the inner bag is not limited to those exemplified here.

[0089] [Mechanism of action] In the vacuum insulation material according to some of the embodiments described above, the core material contains inorganic long fibers, and the content of the fiber sizing agent attached to the inorganic long fibers is less than 0.50 mass% of the total amount of the core material. Because the content of the volatile fiber sizing agent is appropriately suppressed, the internal pressure of the vacuum insulation material is less likely to increase. As a result, the long-term reliability of the vacuum insulation material is improved.

[0090] In the vacuum insulation material according to the embodiment, the inorganic long fibers are bound together by the long fiber bundling agent, which increases the reinforcing effect of the core material compared to when the contact points between the inorganic fibers are bound together by a binder, thereby improving the compressive strength of the core material.

[0091] Although several embodiments have been described above, the present invention is not limited to the exemplary embodiments disclosed in this specification and can be appropriately modified and implemented without departing from the spirit of the invention. The embodiments disclosed in this specification can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. [Example]

[0092] The following examples will explain the embodiments in more detail, but the present invention is not limited to the following examples. Examples 1, 2, and 7 are comparative examples, and Examples 3 to 6 are working examples.

[0093] [Measurement method] (bulk density) The bulk density of the fumed silica was measured by the constant mass measurement method of JIS R1628 1997.

[0094] (specific surface area) The specific surface area of ​​the fumed silica was measured by the nitrogen adsorption method (BET method).

[0095] (Volume-based frequency particle size distribution) The volume-based frequency particle size distribution of the fumed silica was measured by the laser diffraction scattering method using a scattering particle size distribution analyzer LA-920V (manufactured by HORIBA). For particle size distribution measurement, 0.4 g of sample was placed in 40 g of dispersion liquid (0.1% by mass of sodium hexametaphosphate) and dispersed by ultrasonic waves for 1 minute. The refractive index condition was 1.46.

[0096] (fiber length D10, D50, D90) In a photograph of inorganic long fibers observed with an optical microscope, the lengths of 50 or more randomly selected fibers were measured, and a cumulative number distribution curve was obtained, with the total number of fibers in the fiber length distribution calculated by number as 100%. The fiber lengths at which the cumulative number was 10%, 50%, and 90% were then defined as D10, D50, and D90, respectively.

[0097] (average fiber length) In a photograph of the inorganic long fibers observed with an optical microscope, the lengths of 50 or more randomly selected fibers were measured, and the average value was taken as the average fiber length.

[0098] (Ln and Lw) In a photograph of inorganic long fibers observed with an optical microscope, the lengths of 50 or more randomly selected fibers were measured, and Ln was calculated from the number-based frequency distribution using Equation 1. Furthermore, Lw was calculated from the weight-based frequency distribution using Equation 2. In Equations 1 and 2, Ni is the number of fibers in each histogram of the average length Li.

[0099]

number

[0100] (fiber diameter d10, d50, d90) In a photograph of inorganic long fibers observed under an optical microscope, the widths of 50 or more randomly selected single fibers were measured as diameters, and a cumulative number distribution curve was obtained, with the total number in the fiber diameter distribution calculated by number as 100%. The fiber diameters at the points where the cumulative number was 10%, 50%, and 90%, were then defined as d10, d50, and d90, respectively.

[0101] (average fiber diameter) In a photograph of the inorganic long fibers observed under an optical microscope, the widths of 50 or more randomly selected single fibers were measured as diameters, and the average value was taken as the average fiber diameter.

[0102] (core density) Three 30mm x 150mm samples were cut from random locations on the core material. Each sample was cut into four equal sections in the thickness direction to obtain test pieces. The density of each test piece was measured, and the average value was used as the density of the core material.

[0103] (density of the core material sealed under reduced pressure) The core material of each example was placed inside an outer bag and placed in a vacuum chamber equipped with a heat sealing function. The pressure inside the vacuum chamber was reduced to 5 Pa, and the opening of the outer bag was heat-sealed to seal it. The outside of the outer bag was then returned to atmospheric pressure to obtain a vacuum insulation material. The weight of the core material sealed under reduced pressure was calculated from the weight of the vacuum insulation material and the weight of the outer packaging material. The volume was calculated from the average value of the side length and thickness at five points. The density was calculated from the calculated core weight and volume. This value was used as the density of the core material sealed under reduced pressure.

[0104] (thermal conductivity) The thermal conductivity of the vacuum insulation material was measured using a thermal conductivity measuring device HFM-436 (NETZSCH). Three samples were prepared and measurements were taken, and the average value was used as the thermal conductivity of the vacuum insulation material. The measurement conditions were a core temperature of 25°C and a temperature difference of 20°C. The thermal conductivity measured for the vacuum insulation material before conducting the long-term reliability test described below was used as the "initial thermal conductivity."

[0105] (Long-term reliability test) In the long-term reliability test, the vacuum insulation panels obtained in each example were left to stand in an environment of 70°C and 90% RH for 7 days to test their reliability. The thermal conductivity of the vacuum insulation panels was measured before and after the test, and the increase in thermal conductivity (Δλ) was calculated.

[0106] (Young's modulus of core material) Compression tests were conducted using Shimadzu's fatigue testing machine "EHF-UG." After setting the load cell to 50 kN, the top surface of the 20 mm thick core material was compressed at 5 mm / min at room temperature (approximately 25°C) until the thickness was reduced to 10 mm. The Young's modulus of the core material was calculated from the displacement (mm) and load (kN) of the testing machine.

[0107] (Permanent deformation of core material) A compression fatigue test was carried out using Shimadzu Corporation's fatigue testing machine "EHF-UG." After setting the load cell to 10 kN, the top surface of a 20 mm thick core material was compressed at room temperature (approximately 25°C). A load of 10 kN, equivalent to atmospheric pressure, was applied and the thickness displacement (mm) was measured 200 times to calculate the permanent set.

[0108] [Core material raw materials] Fumed silica 1 (average agglomerated particle diameter D50: 13.5 μm, bulk density: 0.044 g / cm 3 , specific surface area: 287m 2 / g) Inorganic long fiber 1: 3mm long glass fiber with no fiber sizing agent attached, ground for 10 minutes in a blender with an agitator (fiber length range: 0.5-3mm) Inorganic long fiber 2: 3mm long glass fiber coated with urethane resin as a fiber binder, ground for 10 minutes in a blender with an agitator (fiber length range: 0.5-3mm) Inorganic long fiber 3: 3mm long glass fiber coated with polyester resin as a fiber binder, ground for 10 minutes in a blender with an agitator (fiber length range: 0.5-3mm) Inorganic long fiber 4: Glass long fiber with silane coupling agent attached as a fiber bundling agent Radiation suppression component 1: Graphite

[0109] The proportion A of inorganic long fiber 1 is 4 mass%, the amount of alkali elution is 0.1 mL / g, and the thermal expansion coefficient is 45 × 10 -7 / °C and Young's modulus was 50 GPa. The inorganic long fiber 1 had a fiber length D10 of 1.3 mm, a fiber length D50 of 2.55 mm, a fiber length D90 of 3.0 mm, and (D90-D10) / D50 of 0.67. The average fiber length of the inorganic long fiber 1 was 2.47 mm. The inorganic long fiber 1 had an Ln of 2.35, an Lw of 2.53, and an Lw / Ln of 1.08. The inorganic long fibers 1 had a fiber diameter d10 of 5.9 μm, a fiber diameter d50 of 7.05 μm, a fiber diameter d90 of 7.45 μm, and (d90-d10) / d50 of 0.22. The average fiber diameter of the inorganic long fibers 1 was 6.9 μm.

[0110] The proportion A of inorganic long fiber 2 is 4 mass%, the amount of alkali elution is 0.1 mL / g, and the thermal expansion coefficient is 45 × 10 -7 / °C and Young's modulus was 50 GPa. The inorganic long fiber 2 had a fiber length D10 of 1.3 mm, a fiber length D50 of 2.55 mm, a fiber length D90 of 3.0 mm, and (D90-D10) / D50 of 0.67. The average fiber length of the inorganic long fiber 2 was 2.47 mm. The inorganic long fiber 2 had an Ln of 2.35, an Lw of 2.53, and an Lw / Ln of 1.08. The inorganic long fibers 2 had a fiber diameter d10 of 6.6 μm, a fiber diameter d50 of 7 μm, a fiber diameter d90 of 8.9 μm, and (d90−d10) / d50 of 0.33. The average fiber diameter of the inorganic long fibers 2 was 7.4 μm.

[0111] The proportion A of inorganic long fiber 3 is 4 mass%, the amount of alkali elution is 0.1 mL / g, and the thermal expansion coefficient is 45 × 10 -7 / °C and Young's modulus was 50 GPa. The inorganic long fiber 3 had a fiber length D10 of 1.3 mm, a fiber length D50 of 2.55 mm, a fiber length D90 of 3.0 mm, and (D90-D10) / D50 of 0.67. The average fiber length of the inorganic long fiber 3 was 2.47 mm. The inorganic long fiber 3 had an Ln of 2.35, an Lw of 2.47, and an Lw / Ln of 1.08. The inorganic long fibers 3 had a fiber diameter d10 of 10.5 μm, a fiber diameter d50 of 11.4 μm, a fiber diameter d90 of 12.1 μm, and (d90−d10) / d50 of 0.14. The average fiber diameter of the inorganic long fibers 3 was 11.6 μm.

[0112] The proportion A of inorganic long fiber 4 is 100 mass%, the amount of alkali elution is 0.1 mL / g, and the thermal expansion coefficient is 45 × 10 -7 / °C and Young's modulus was 50 GPa. The inorganic long fibers 4 had a fiber diameter d10 of 3.5 μm, a fiber diameter d50 of 6.1 μm, a fiber diameter d90 of 8 μm, and (d90−d10) / d50 of 0.74. The average fiber diameter of the inorganic long fibers 4 was 6.7 μm.

[0113] [Example 1] A raw material mixture was obtained by mixing 1 part of fumed silica, 1 part of radiation-suppressing component, and 1 part of inorganic long fiber to obtain the core material composition shown in Table 1. The raw material mixture was press-molded and heat-treated at 200°C for 1 hour to produce a flat core material measuring 200 mm long x 200 mm wide x 20 mm thick. Next, three sides of two 300mm x 300mm gas barrier films were heat-sealed to create a three-sided sealed outer bag. After placing the core material inside the outer bag, it was placed in a vacuum chamber equipped with a heat-sealing function. The pressure inside the chamber was then reduced to 5 Pa. In this state, the opening of the outer bag was heat-sealed to seal it. The outside of the outer bag was then returned to atmospheric pressure to obtain a vacuum insulation material.

[0114] [Example 2] A vacuum heat insulating material was obtained under the same conditions as in Example 1, except that the density of the core material sealed under reduced pressure was changed to the value shown in Table 1.

[0115] [Example 3] A vacuum insulation material was obtained under the same conditions as in Example 1, except that inorganic long fiber 2 was used instead of inorganic long fiber 1 and the blending amount was changed so as to obtain the core material composition shown in Table 1.

[0116] [Example 4] A vacuum heat insulating material was obtained under the same conditions as in Example 3, except that the density of the core material sealed under reduced pressure was changed to the value shown in Table 1.

[0117] [Example 5] A vacuum insulation material was obtained under the same conditions as in Example 1, except that inorganic long fiber 3 was used instead of inorganic long fiber 1 and the blending amount was changed so as to obtain the core material composition shown in Table 1.

[0118] [Example 6] A vacuum heat insulating material was obtained under the same conditions as in Example 5, except that the density of the core material sealed under reduced pressure was changed to the value shown in Table 1.

[0119] [Example 7] A vacuum insulation material was obtained under the same conditions as in Example 1, except that a nonwoven fabric (200 mm long x 200 mm wide x 5 mm thick) made of inorganic long fiber 4 was layered as the core material to form a flat core material with a thickness of 20 mm.

[0120] [Table 1]

[0121] The meanings of the terms in Table 1 are as follows: "Fumed silica [mass %]" indicates the content of fumed silica in the total amount of the core material. "Radiation suppressing component [mass %]" indicates the content ratio of the radiation suppressing component in the total amount of the core material. "Inorganic long fiber [mass %]" indicates the content ratio of inorganic long fiber in the total amount of the core material. "Fiber sizing agent [mass %]" indicates the content ratio of the fiber sizing agent in the total amount of the core material. "Fiber sizing agent / inorganic long fibers" indicates the mass ratio of the total amount of fiber sizing agent to the total amount of inorganic long fibers. "Density" refers to the density of the core material sealed under reduced pressure in the outer bag.

[0122] The vacuum insulation materials of Examples 3 to 6 showed a smaller increase in thermal conductivity (Δλ) in the long-term reliability test compared to the vacuum insulation material of Example 7. It is believed that the long-term reliability was improved because the content of the volatile fiber sizing agent was kept appropriately low.

[0123] In each of the vacuum insulation materials of Examples 3 to 6, the Young's modulus of the core material was higher and the permanent set was lower than that of the vacuum insulation material of Example 1. As shown in Figure 2, in the core material of the vacuum insulation material of Example 3, it was possible to observe the inorganic long fibers being bundled by the fiber sizing agent. In contrast, as shown in Figure 3, it was not possible to observe the inorganic long fibers being bundled by the fiber sizing agent in the core material of the vacuum insulation material of Example 1. In Example 3, it is believed that the fiber sizing agent attached to the inorganic long fibers provided a sufficient reinforcing effect, improving the compressive strength of the core material.

[0124] Figure 4 is a diagram in which the horizontal axis represents the content of fiber sizing agent in the total amount of core material, and the vertical axis represents the rate of increase in internal pressure of the vacuum insulation material. When the content of fiber sizing agent in the total amount of core material is less than 0.50 mass%, the rate of increase in internal pressure of the vacuum insulation material is kept low. [Industrial Applicability]

[0125] According to the present invention, a vacuum insulation material having excellent long-term reliability and improved compressive strength of the core material is provided. [Explanation of symbols]

[0126] 1. Vacuum insulation material 10 Core material 12 outer bag

Claims

1. A core material and a gas barrier film covering the core material, the core material is vacuum sealed in an outer bag formed of the gas barrier film, the core material contains fumed silica, a radiation suppression component, and inorganic long fibers; The content of the fumed silica is 50 to 90 mass% of the total amount of the core material, the content of the radiation-suppressing component is 3 to 30 mass % of the total amount of the core material, The content of the inorganic long fibers is 2 to 30% by mass of the total amount of the core material, The density of the core material sealed in the outer bag under reduced pressure is 0.20 g / cm ３ is as follows: A fiber sizing agent is attached to the inorganic long fibers, A vacuum insulation material in which the content of the fiber bundling agent is 0.01 mass% or more and less than 0.50 mass% of the total amount of the core material.

2. The vacuum insulation material according to claim 1, wherein the mass ratio of the total amount of the fiber sizing agent to the total amount of the inorganic long fibers is 1 / 200 to 1 / 30.

3. 2. The vacuum insulation material according to claim 1, wherein the fiber sizing agent is at least one selected from the group consisting of vinyl acetate resin, vinyl acetate copolymer resin, urethane resin, acrylic resin, epoxy resin, polyester resin, and silane coupling agent.

4. 2. The vacuum insulation material according to claim 1, wherein the inorganic long fibers are at least one selected from the group consisting of alumina long fibers, glass long fibers, silica long fibers, silica-alumina long fibers, and carbon long fibers.

5. 2. The vacuum insulation material according to claim 1, wherein the radiation suppressing component is at least one selected from the group consisting of graphite, silicon carbide, titanium oxide, tin oxide, and potassium titanate.

6. At least a part of the inorganic long fibers is glass long fibers, The Na in the long glass fiber ２ O and K ２ The vacuum insulation material according to claim 1 , wherein a ratio of the total mass of O to the total mass of the long glass fibers is 11 mass % or less.

7. The inorganic long fibers have a fiber length of 0.1 to 10 mm, and 2. The vacuum insulation material according to claim 1, wherein a fiber length distribution Lw / Ln, which is expressed as a ratio of the number average fiber length Ln to the weight average fiber length Lw of the inorganic long fibers, is 1.05 or more.

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