Heat-insulating sheet and method for producing same, heat-insulating fiber and method for producing same, and fiber-containing suspension used for producing heat-insulating sheet

Abstract

This heat-insulating sheet comprises base material fibers and heat-insulating fine particles, and is characterized in that the base material fibers form a sheet body by being bonded to each other or woven, and the heat-insulating fine particles are present inside and / or outside the base material fibers. A heat-insulating sheet according to one embodiment of the present invention comprises base material fibers, binder fibers, and a binder, and is characterized in that films in which the base material fibers are melted by the binder fibers are bonded to each other, and heat-insulating fine particles are supported by the binder in gaps between the bonded base material fibers. This heat-insulating fiber is present in a state in which at least a portion of heat-insulating fine particles are embedded inside a base material fiber. The heat-insulating fine particles are fine particles which have, as a starting material, an aerogel having a three-dimensional mesh structure in which bone lattices are constituted by clusters that are aggregates of primary particles, and which have a three-dimensional mesh structure in which bone lattices are constituted by primary particles, and in which 50% or more of the volume of the fine particles are dispersed so as to have a mode value at a particle diameter of 0.1 [mu] m to 1.0 [mu] m, and the base material fibers contain a thermoplastic resin.

Description

Technical Field

[0001] The present invention relates to a thermal insulation sheet and a method for producing the same, a thermal insulation fiber and a method for producing the same, and a fiber-containing suspension used in producing the thermal insulation sheet. Background Art

[0002] As a countermeasure to global warming, attention is being paid to raw materials that exhibit heat insulation and heat resistance. For example, in a battery composed of multiple battery cells, in order to suppress the impact of overheating of a part of the cells on adjacent cells, a structure is adopted in which a heat insulation sheet is sandwiched between adjacent cells. At this time, in order to prevent the overheating of the cells from developing and causing thermal runaway, the sandwiched heat insulation sheet is required to have heat resistance. In addition, flame retardancy and fire resistance are required to cope with fire situations. On the other hand, in order to increase the storage capacity per unit volume of the battery, the heat insulation sheet is required to be as thin as possible. In this way, the heat insulation sheet is required to be as thin as possible to achieve the required heat insulation and flame retardancy.

[0003] Patent Document 1 discloses resin-coated flame-retardant fiber yarns. The flame-retardant fiber yarns are coated with two resin coating layers, the outer layer containing titanium dioxide particles, thereby achieving light transmittance, heat shielding, and flame retardancy. The production method is described below. A resin solution containing a titanium dioxide-free adhesive resin is applied to a glass fiber bundle serving as the flame-retardant fiber yarn. The excess resin solution is then gathered and heated to form an inner resin coating layer. Next, a resin solution containing titanium dioxide is applied to the glass fiber bundle with the inner resin coating layer formed thereon. The excess resin solution is then gathered and heated to form a titanium dioxide-containing resin layer on the outer side of the inner resin coating layer (details are provided in paragraphs 0026 to 0045 of the document). The resin-coated flame-retardant fiber yarns can be woven as warp and weft yarns to produce a fabric (paragraph 0046 of the document).

[0004] Patent Document 2 discloses a lightweight thermal and sound insulating material with excellent thermal and sound insulation properties. The material is composed of an aggregate of silica aerogel particles, each consisting of units surrounded by a network of organic nanofibers with anionic functional groups. A three-dimensional, continuous solid composite of these units, formed by close contact, is formed within a nonwoven fabric or open-cell foam, resulting in a lightweight material with excellent sound insulation.

[0005] Patent Document 3 discloses an aerogel ultrafine particle characterized by comprising microparticles having a three-dimensional mesh structure formed by clusters of primary particles as a raw material, and having a three-dimensional mesh structure formed by the primary particles. Patent Document 3 is an invention completed by the inventors of this application and is industrially known as TIISA (a registered trademark of Thermalytica Co., Ltd.). The aerogel ultrafine particle has a thermal conductivity equivalent to that of high-performance aerogel and a bulk density of 0.01 g / cm 3 This is less than approximately one-tenth the size of conventional aerogel. Therefore, it is a lightweight, high-performance thermal insulation material. Unlike conventional aerogels, which have a skeleton composed of secondary particles, aerogel ultrafine particles have a skeleton centered around the primary particles that constitute these secondary particles. Consequently, they are extremely fine particles, with at least 50% of their volume dispersed with a mode of distribution within particle sizes of 0.1 μm to 1.0 μm.

[0006] Patent Document 4 discloses a fiber-reinforced thermoplastic resin sheet and a glass fiber nonwoven fabric carrying silica fine particles. The fiber-reinforced thermoplastic resin sheet comprises a thermoplastic matrix resin and silica fine particles having an average primary particle size of 1 to 100 nm contained in glass fibers.

[0007] Patent Document 5 discloses a heat insulating material having high strength and excellent heat insulating properties. The heat insulating material comprises a composite bonded body of aerogel particles, an adhesive for bonding the aerogel particles, and a heat-fusible adhesive component coated with a protective film.

[0008] Prior art literature Patent Literature Patent Document 1 International Publication No. WO2013 / 136552 Patent Document 2: Japanese Patent Application Laid-Open No. 2022-41332 Patent Document 3 International Publication WO2022 / 107365 Patent Document 4: Japanese Patent Application Laid-Open No. 2018-95673 Patent Document 5: Japanese Patent Application Laid-Open No. 2015-124779 Summary of the Invention Problems to be solved by the invention The primary object of the present invention is to provide a thermal insulation sheet with high thermal insulation performance. Another object of the present invention is to further impart flame retardancy to the thermal insulation sheet. Yet another object of the present invention is to provide a fiber-containing suspension and thermal insulation fibers suitable for producing the aforementioned thermal insulation sheet.

[0009] Hereinafter, means for solving such problems will be described; however, other problems and novel features will become apparent from the description of this specification and the accompanying drawings.

[0010] Means for solving problems According to the present invention, it is as follows.

[0011] That is, the thermal insulation sheet of the present invention comprises matrix fibers and thermal insulation fine particles. The matrix fibers are bonded or woven together to form a sheet body, and the thermal insulation fine particles are present inside and / or outside the matrix fibers.

[0012] The method for manufacturing a thermal insulation sheet of the present invention includes: a step of dispersing thermal insulation fine particles to prepare a suspension containing thermal insulation fine particles, a step of dissolving a binder to prepare a binder solution, a step of mixing the suspension containing the thermal insulation fine particles, the binder solution, matrix fibers, and adhesive fibers to prepare a fiber-containing suspension, and a step of removing the liquid component from the fiber-containing suspension to form a sheet body (papermaking step).

[0013] Another method for manufacturing the thermal insulation sheet of the present invention includes: a process of mixing a thermoplastic resin with thermal insulating particles to obtain a resin containing particles; a process of containing the above-mentioned resin containing particles in a container having pores arranged in a chamber, heating and rotating the above-mentioned container to spray the above-mentioned resin containing particles from the above-mentioned pores to obtain short fibers; and a process of forming the above-mentioned short fibers into a sheet shape.

[0014] Yet another method for manufacturing a thermal insulation sheet of the present invention includes: a process of melting a thermoplastic resin, mixing the molten thermoplastic resin with thermal insulating microparticles to prepare a resin containing microparticles; a process of extruding the molten microparticle-containing resin from fine pores to obtain fibers, a process of spinning the fibers to obtain yarns; and a process of weaving the yarns.

[0015] The fiber-containing suspension for producing the thermal insulation sheet of the present invention is prepared by mixing a suspension containing thermal insulation fine particles dispersed in a solvent, a binder solution, matrix fibers, and binder fibers.

[0016] The fiber-containing suspension used for manufacturing the other thermal insulation sheet of the present invention is prepared by mixing a suspension containing thermal insulation particles in which thermal insulation particles are dispersed in a solvent, a binder solution, thermal insulation fibers, and adhesive fibers. The thermal insulation fibers have thermal insulation particles for the fibers bonded to the surface of the matrix fibers by the fiber binder. The thermal insulation particles for the fibers are made of aerogel having a three-dimensional mesh structure whose skeleton is composed of clusters of aggregates of primary particles. The particles have a three-dimensional mesh structure whose skeleton is composed of the primary particles, and more than 50% of their volume is dispersed with a mode value in a particle size of not less than 0.1 μm and not more than 1.0 μm. The matrix fibers are silica fibers.

[0017] The thermal insulating fiber of the present invention has thermal insulating fine particles bonded to the surface of a base fiber via a binder. The thermal insulating fine particles are made from aerogel having a three-dimensional mesh structure whose skeleton is composed of clusters of aggregates of primary particles. The fine particles have a three-dimensional mesh structure whose skeleton is composed of the primary particles, and more than 50% of their volume is dispersed with a mode of particle size of not less than 0.1 μm and not more than 1.0 μm. The base fiber is silica fiber.

[0018] Another thermal insulating fiber of the present invention exists in a state where at least a portion of thermal insulating microparticles are embedded within a base fiber. The thermal insulating microparticles are made from an aerogel having a three-dimensional network structure with a skeleton composed of clusters of primary particles. The microparticles have a three-dimensional network structure with a skeleton composed of the primary particles, and at least 50% of their volume is dispersed with a mode of distribution in a particle size of 0.1 μm to 1.0 μm. The base fiber contains a thermoplastic resin.

[0019] Based on the above-mentioned method for manufacturing the thermal insulating fiber of the present invention, the method for manufacturing the thermal insulating fiber of the present invention includes: a process of dispersing the above-mentioned thermal insulating microparticles to prepare a suspension containing the thermal insulating microparticles, a process of dissolving a binder to prepare a binder solution, a process of mixing the above-mentioned suspension containing the thermal insulating microparticles with the above-mentioned binder solution to prepare a slurry, and a process of vapor-depositing the above-mentioned base material fiber using the above-mentioned slurry as an evaporation source.

[0020] Based on the above-mentioned method for manufacturing the thermal insulating fiber of the present invention, another method for manufacturing the thermal insulating fiber of the present invention includes: a process of dissolving a binder to prepare a binder solution, a process of vapor-depositing the matrix fiber using the above-mentioned binder solution as an evaporation source, and a process of mechanically coating the matrix fiber with thermal insulating particles on the surface of which the binder solution is attached by the above-mentioned vapor deposition.

[0021] Furthermore, "dispersing (fine particles)" means placing the fine particles into a liquid and dispersing them in the liquid, not dissolving them. The "papermaking process (sheet forming process)" includes the steps of thinly spreading a suspension containing matrix fibers, removing excess liquid, and then drying to form a sheet. In this specification, "polyvinyl alcohol" may be abbreviated as "PVA," "polyvinyl alcohol fiber" may be abbreviated as "PVA fiber," and "polyvinyl alcohol powder" may be abbreviated as "PVA powder."

[0022] Effects of the Invention The effects obtained by the above-mentioned embodiment will be briefly described as follows.

[0023] That is, it is possible to provide a thermal insulation sheet having high thermal insulation performance, a thermal insulation fiber suitable for further imparting flame retardancy to the thermal insulation sheet, and a fiber-containing suspension suitable for producing the thermal insulation sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic explanatory diagram showing a configuration example of a heat-insulating sheet according to one embodiment of the present invention.

[0025] Figure 2 It is an explanatory diagram showing the relationship between the lengths of base material fibers and binder fibers.

[0026] Figure 3 This is an explanatory diagram showing an example of the configuration of a flame-retardant fiber in which heat-insulating fine particles are bonded to the surface of a base fiber.

[0027] Figure 4 This is a flowchart showing an example of a method for producing a thermal insulation sheet according to one embodiment of the present invention.

[0028] Figure 5 This is a flowchart showing an example of a method for producing a flame-retardant fiber according to one embodiment of the present invention.

[0029] Figure 6 This is a flowchart showing an example of a method for producing a flame-retardant thermal insulation sheet.

[0030] Figure 7 This is an explanatory diagram showing the structure of aerogel ultrafine particles as an example of thermal insulation fine particles.

[0031] Figure 8 This is an explanatory diagram illustrating the particle size distribution of aerogel ultrafine particles as an example of thermal insulation fine particles.

[0032] Figure 9 This is a photograph showing the experimental results of flame-bathing glass wool covered with a flame-retardant layer containing aerogel ultrafine particles.

[0033] Figure 10 This is an optical microscope photograph showing the experimental results obtained by flame baking glass wool covered with a flame retardant layer containing aerogel ultrafine particles.

[0034] Figure 11 This is an explanatory diagram showing an example of a base material fiber composed of a mixture of a thermoplastic resin and heat-insulating fine particles.

[0035] Figure 12 This is a flowchart showing an example of a method for producing a thermal insulation sheet according to the eighth embodiment.

[0036] Figure 13 It is an explanatory diagram showing a configuration example of an apparatus for producing base material fibers for a thermal insulation sheet according to an eighth embodiment.

[0037] Figure 14 This is a flowchart showing an example of a method for producing a thermal insulation sheet according to the ninth embodiment.

[0038] Figure 15 This is a schematic diagram showing an example of a known spinning device.

[0039] Figure 16 is a schematic diagram showing the apparatus used in the examples.

[0040] Figure 17 This is a scanning electron microscope (SEM) photograph showing the experimental results. DETAILED DESCRIPTION

[0041] 1. Overview of implementation methods First, a summary of representative embodiments disclosed in this application will be described. In the summary of representative embodiments, reference numerals in the drawings referenced by parentheses merely illustrate the concepts of the components labeled with the numerals.

[0042] [1] Thermal insulation sheet carrying thermal insulation fine particles ( Figure 1 、 Figure 11 ) The thermal insulation sheet shown in this embodiment includes matrix fibers (6, 300) and thermal insulation particles (1, 14). The thermal insulation sheet (100) is characterized in that the matrix fibers (6, 300) are bonded or woven together to form a sheet body, and the thermal insulation particles (1, 14) are present inside and / or outside the matrix fibers (6, 300).

[0043] This makes it possible to realize a heat insulating sheet having excellent heat insulating properties.

[0044] 〔2〕Carrying aerogel ultrafine particles( Figure 7 、 Figure 8) Based on the thermal insulation sheet of [1], the above-mentioned thermal insulation fine particles are made of aerogel having a three-dimensional mesh structure with a skeleton composed of clusters of aggregates as primary particles, and have a three-dimensional mesh structure with a skeleton composed of the above-mentioned primary particles, and more than 50% of their volume are dispersed with a frequency value in a particle size of not less than 0.1 μm and not more than 1.0 μm.

[0045] This makes it possible to realize a thinner thermal insulation sheet by utilizing the small particle size of the aerogel ultrafine particles.

[0046] [3] A heat-insulating sheet having heat-insulating fine particles carried in the gaps between matrix fibers bonded by a film formed by dissolving binder fibers ( Figure 1 ) Based on the thermal insulation sheet of [1] or [2], the above-mentioned base material fiber is silica fiber, and the thermal insulation sheet (100) contains base material fiber (6), adhesive fiber (7), binder (2, wherein Figure 1 (not shown in the figure), the matrix fibers are bonded to each other by a film formed by dissolving the adhesive fibers, and the thermal insulating particles (1) are carried in the gaps between the bonded matrix fibers by the binder.

[0047] Thereby, a thinner thermal insulation sheet can be realized.

[0048] 〔4〕Addition of flame retardancy( Figure 3 ) In the thermal insulation sheet of [3], the thermal insulation fine particles are bonded to the surface of the matrix fiber via the binder.

[0049] The presence of the thermally insulating fine particles on the surface of the matrix fibers imparts flame retardancy in addition to thermal insulation properties, thereby making the entire thermally insulating sheet flame retardant. In this specification, "improving flame retardancy" means applying certain processing to a specific item, thereby rendering it less flammable than before the processing.

[0050] [5] A heat-insulating sheet formed by weaving a matrix fiber carrying heat-insulating fine particles embedded in a thermoplastic resin ( Figure 11 ) Based on the thermal insulation sheet of [1] or [2], the matrix fiber (300) contains a thermoplastic resin (8), the thermal insulation particles (14) exist in a state of the above-mentioned thermoplastic resin (8) being at least partially embedded in the matrix fiber (300), and the sheet body is formed by weaving yarns obtained by spinning the above-mentioned matrix fiber (300).

[0051] A heat-insulating sheet material, wherein a base material fiber (300) is spun by a known spinning method, and the spun yarn is woven or knitted by a known method, thereby forming a sheet material body.

[0052] This makes it possible to realize a heat insulating sheet having high heat insulating performance without using a binder.

[0053] [6] A heat-insulating sheet formed by bonding a matrix fiber in which heat-insulating fine particles are embedded in a thermoplastic resin with a film formed by melting the thermoplastic resin. Figure 11 ) Based on the thermal insulation sheet of [1] or [2], the matrix fiber (300) contains a thermoplastic resin (8), the thermal insulation particles (14) exist in a state of at least a portion of the thermoplastic resin (8) embedded in the matrix fiber (300), and the sheet body is formed by bonding the matrix fibers to each other through a film formed by dissolving the thermoplastic resin.

[0054] This makes it possible to realize a heat insulating sheet having high heat insulating performance without using a binder.

[0055] 〔7〕Method for manufacturing thermal insulation sheet( Figure 4 ) A representative embodiment of the present invention is a method for producing a thermal insulation sheet, and is configured to include the following steps.

[0056] (S1): A step of dispersing heat-shielding fine particles to prepare a suspension containing the heat-shielding fine particles.

[0057] (S2): A step of dissolving a binder to prepare a binder solution.

[0058] (S3): A step of mixing the suspension containing the heat-insulating fine particles, the binder solution, matrix fibers, and binder fibers to prepare a fiber-containing suspension.

[0059] (Papermaking step, S4): A step of removing the liquid component from the fiber-containing suspension to form a sheet.

[0060] Thus, the method for producing the thermal insulation sheet described in [1] to [6] can be provided.

[0061] 〔8〕Carrying aerogel ultrafine particles in the gaps between silica fibers ( Figure 1 、 Figure 4 ) Based on the manufacturing method of the thermal insulation sheet [7], the above-mentioned base material fiber is silica fiber, and the above-mentioned thermal insulating fine particles are made of aerogel having a three-dimensional mesh structure with a skeleton composed of clusters of aggregates as primary particles, and have a three-dimensional mesh structure with a skeleton composed of the above-mentioned primary particles, and more than 50% of their volume are fine particles dispersed with a frequency value of not less than 0.1μm and not more than 1.0μm.

[0062] Thus, similarly to the above-mentioned [2], a method for producing a thin-film thermal insulation sheet can be provided by utilizing the small particle size of aerogel ultrafine particles.

[0063] [9] Method for producing heat-insulating microparticles when they are hydrophobic In the method for producing a thermal insulation sheet according to [7] or [8], the thermal insulation fine particles are hydrophobic, and the suspension containing the thermal insulation fine particles contains ethanol.

[0064] Thus, even if the heat-insulating fine particles are hydrophobic, a method for producing a heat-insulating sheet having high heat-insulating performance can be provided.

[0065]

[10] Method for manufacturing thermal insulation sheet A method for producing a heat insulating sheet according to another embodiment of the present invention includes the following steps.

[0066] A step of mixing a thermoplastic resin with heat-insulating fine particles to obtain a fine particle-containing resin.

[0067] A step of placing the fine particle-containing resin in a container having fine holes, and rotating the container while heating it to eject the fine particle-containing resin from the fine holes to obtain short fibers.

[0068] A step of forming the short fibers into a sheet shape.

[0069] Thereby, a heat insulating sheet carrying heat insulating fine particles can be obtained without using a binder.

[0070]

[11] Method for manufacturing a heat insulating sheet made of short fibers by weaving The method for producing a heat insulating sheet according to

[10] further includes the steps of spinning the short fibers to obtain yarns and knitting the yarns.

[0071] Thereby, a heat insulating sheet comprising a woven sheet having relatively high strength and carrying heat insulating fine particles can be obtained.

[0072]

[12] Method for producing a heat insulating sheet made of short fibers by molding In the step of forming the short fibers into a sheet in the method for producing a heat insulating sheet according to

[10] , the short fibers are expanded into a film shape and heated to form the sheet.

[0073] Thereby, the heat insulating sheet can be manufactured simply without performing a knitting process.

[0074]

[13] Method for manufacturing a heat-insulating sheet comprising woven yarns by weaving A method for producing a heat insulating sheet according to yet another embodiment of the present invention includes the following steps.

[0075] A step of melting a thermoplastic resin and mixing the molten thermoplastic resin with heat-insulating fine particles to prepare a fine particle-containing resin.

[0076] A step of extruding the molten resin containing the microparticles from fine holes into a coagulation liquid to obtain fibers.

[0077] The process of spinning the above fibers to obtain yarn.

[0078] The process of weaving the above yarn.

[0079] Thereby, a heat insulating sheet comprising a woven sheet having relatively high strength and carrying heat insulating fine particles can be obtained.

[0080] 〔14〕Method for producing a flame-retardant heat-insulating sheet( Figure 6 ) A representative embodiment of the present invention is a method for producing a thermal insulation sheet, and is configured to include the following steps.

[0081] A step of dispersing heat-insulating fine particles (1) to prepare a suspension containing the heat-insulating fine particles.

[0082] A step of dissolving a binder to prepare a binder solution.

[0083] A step of mixing thermal insulation fibers, binder fibers, the suspension containing the thermal insulation fine particles, and the binder solution to prepare a fiber-containing suspension.

[0084] A step of removing the liquid component from the fiber-containing suspension to form a sheet.

[0085] In addition, the thermal insulation fiber is made by bonding thermal insulation fine particles for the fiber to the surface of the base fiber through a fiber binder. The thermally insulating fine particles for the above-mentioned fibers are made of aerogel having a three-dimensional mesh structure whose skeleton is composed of clusters of aggregates serving as primary particles. The fine particles have a three-dimensional mesh structure whose skeleton is composed of the above-mentioned primary particles, and more than 50% of their volume is dispersed with a maximum frequency value in a particle size of not less than 0.1 μm and not more than 1.0 μm. The above-mentioned base fiber is silica fiber.

[0086] Thus, a method for producing a flame-retardant thermal insulation sheet can be provided, in which silica fibers serving as base fibers have higher flame retardancy.

[0087] 〔15〕Ultrasonic evaporation or heating evaporation ( Figure 6 ) In the method for producing a thermal insulation sheet described in

[14] , the vapor deposition is ultrasonic vapor deposition or heating vapor deposition.

[0088] This allows the heat-insulating fine particles (aerogel ultrafine particles) to be more efficiently bonded to the surface of the silica fiber serving as the base fiber.

[0089]

[16] Method for producing heat-insulating microparticles when they are hydrophobic In the method for producing a thermal insulation sheet described in

[14] , the thermal insulation fine particles are hydrophobic, and the suspension containing the thermal insulation fine particles in the first step and the suspension containing the thermal insulation fine particles for the fibers contain ethanol.

[0090] Thus, a method for producing flame-retardant fibers can be provided even when the heat-shielding fine particles are hydrophobic.

[0091] 〔17〕Suspension containing fibers A representative embodiment of the present invention is a fiber-containing suspension for manufacturing an insulating sheet obtained by mixing a suspension containing insulating fine particles obtained by dispersing insulating fine particles in a solvent, a binder solution, matrix fibers, and adhesive fibers, which is used in the above-mentioned method for manufacturing an insulating sheet.

[0092]

[18] Suspension containing fibers with added flame retardancy A representative embodiment of the present invention is a fiber-containing suspension for manufacturing an insulating sheet used in the above-mentioned method for manufacturing an insulating sheet, which is obtained by mixing a suspension containing insulating particles obtained by dispersing insulating particles in a solvent, a binder solution, insulating fibers, and adhesive fibers. The insulating fibers have insulating particles for the fibers bonded to the surface of the matrix fibers by a binder for the fibers. The insulating particles for the fibers are made of aerogel having a three-dimensional mesh structure whose skeleton is composed of clusters of aggregates of primary particles, and have a three-dimensional mesh structure whose skeleton is composed of the above-mentioned primary particles, and more than 50% of their volume is dispersed with a mode of particle size of not less than 0.1 μm and not more than 1.0 μm. The matrix fibers are silica fibers.

[0093] This fiber-containing suspension can be provided as a raw material for the papermaking step ( S4 ) or the like.

[0094]

[19] Flame retardant thermal insulation fiber with aerogel ultrafine particles bonded to the surface ( Figure 3 ) A representative embodiment of the present invention is a heat-insulating fiber (flame-retardant fiber) (200) having flame retardancy added thereto, which is configured as follows. In this specification, flame-retardant fiber refers to a heat-insulating fiber to which flame retardancy is added along with heat insulation properties.

[0095] Heat-insulating fine particles (1) are bonded to the surface of the base material fiber (6) via a binder (2).

[0096] The thermally insulating fine particles are made from aerogel having a three-dimensional network structure composed of clusters of primary particles forming a skeleton. The particles have a three-dimensional network structure composed of the primary particles forming a skeleton, and are dispersed with a mode of distribution of at least 50% by volume within a particle size range of 0.1 μm to 1.0 μm. Furthermore, the matrix fiber is silica fiber.

[0097] This makes it possible to provide a flame-retardant fiber in which the silica fiber serving as the base material fiber has higher flame retardancy.

[0098] 〔20〕Insulation fiber with aerogel ultrafine particles bonded on the surface ( Figure 11 ) A representative embodiment of the present invention is a thermal insulation fiber (300) configured as follows.

[0099] The heat-insulating fine particles (14) are present in a state where at least a portion of the fine particles is embedded in the base material fibers (300). The thermal insulating fine particles (14) are made of aerogel having a three-dimensional mesh structure whose skeleton is composed of clusters of primary particles, and have a three-dimensional mesh structure whose skeleton is composed of the primary particles, and more than 50% of the volume of the fine particles are dispersed with a mode of particle size of 0.1 μm or more and 1.0 μm or less. The above-mentioned base material fiber (300) contains thermoplastic resin (8).

[0100] This makes it possible to provide a thermal insulation fiber in which thermal insulation properties are added to a base material fiber without using a binder.

[0101] 〔21〕A method for producing a flame-retardant fiber having aerogel ultrafine particles bonded to the surface Figure 5 (a) The method for manufacturing the thermal insulation fiber (200) described in

[19] is constructed to include the following steps.

[0102] ( S11 ): A step of dissolving thermal insulating fine particles (aerogel ultrafine particles) to prepare a suspension containing the thermal insulating fine particles.

[0103] ( S12 ): A step of dissolving a binder to prepare a binder solution.

[0104] ( S13 ): A step of mixing the suspension containing the heat-insulating fine particles with the binder solution to prepare a slurry.

[0105] ( S14 ): A step of vapor-depositing the matrix fiber using the slurry as an evaporation source.

[0106] Provided is a production method for imparting higher flame retardancy to a base fiber by vapor-depositing heat-insulating fine particles (aerogel ultrafine particles) contained in a slurry onto the surface of the base fiber.

[0107] 〔22〕Method for producing flame-retardant fiber with aerogel ultrafine particles bonded to the surface ( Figure 5 (b) The method for manufacturing the thermal insulation fiber (200) described in

[19] is constructed to include the following steps.

[0108] ( S15 ): A step of dissolving a binder to prepare a binder solution.

[0109] ( S16 ): A step of vapor-depositing the matrix fiber using the binder solution as an evaporation source.

[0110] ( S17 , powder-attaching step): a step of mechanically applying heat-insulating fine particles to the matrix fibers on the surfaces of which the binder solution is attached by the vapor deposition.

[0111] Thus, another production method for adding flame retardancy to base material fibers is provided.

[0112] 〔23〕Ultrasonic evaporation or heating evaporation ( Figure 5 ) In the method for producing a thermal insulation fiber according to

[21] , the vapor deposition in the fourth step (S14) is ultrasonic vapor deposition or heating vapor deposition.

[0113] This allows the heat-insulating fine particles (aerogel ultrafine particles) to be more efficiently bonded to the surface of the silica fiber serving as the base fiber.

[0114]

[24] Method for producing heat-insulating microparticles when they are hydrophobic In the method for producing a flame-retardant fiber described in

[19] to

[23] , the heat-insulating fine particles are hydrophobic, and the suspension containing the heat-insulating fine particles contains ethanol.

[0115] Thus, a method for producing flame-retardant fibers can be provided even when the heat-shielding fine particles are hydrophobic.

[0116] 2. Details of implementation methods The implementation method is further described in detail.

[0117] [Implementation Method 1] Figure 1 This is a schematic diagram showing an example of the structure of the heat insulating sheet of the present invention. The heat insulating sheet 100 of the present invention comprises a base material fiber 6, an adhesive fiber 7, a binder (2, wherein Figure 1Not shown in the figure), the base material fiber 6 is melted by the adhesive fiber 7 to form a film (in Figure 1 The heat-insulating fine particles 1 are bonded to each other (not shown), and the gaps between the bonded matrix fibers 6 support the heat-insulating fine particles 1. Reference numeral 3 will be described later and will be described in further detail in Embodiments 4 and 5.

[0118] This allows for the provision of a thermal insulation sheet with high thermal insulation performance. By using binder fibers 7 that are significantly shorter than the parent fibers 6, multiple layers of parent fibers 6 are formed at a constant thickness. This creates gaps between the parent fibers 6 forming these layers, allowing a greater amount of thermal insulation particles 1 to be loaded within these gaps, thereby improving the thermal insulation performance of the thermal insulation sheet 1.

[0119] Examples of the binder fibers 7 include polyvinyl alcohol (PVA) fibers, polyester fibers, polyester composite fibers, acrylic fibers, acrylic fibers, nylon, polyurethane fibers, and polycarbonate fibers. Examples of binders include polyvinyl alcohol (PVA) powder, methylcellulose, starch paste, and gumarabic paste.

[0120] The length of the binder fiber 7 is preferably several tens of μm. The parent fiber 6 is, for example, a silica fiber, which is significantly longer than the binder fiber 7 by several tens of mm. Figure 1 In contrast, the binder fibers 7 connect the parent fibers 6 vertically (in the thickness direction of the thermal insulation sheet 100). The membrane formed by the parent fibers 6 being melted by the binder fibers 7 (in the horizontal direction) is formed. Figure 1 (not shown in the figure) are bonded to each other, and gaps are formed in the bonded matrix fibers 6, in which the heat insulating particles 1 are carried. For example, PVA fiber, which is an example of the adhesive fiber 7, is heated to 65°C to 85°C in a state wetted with water, thereby melting and becoming a film. "Melt" here means dissolving in water, not melting caused by heat. Matrix fibers 6 such as silica fibers have mechanical strength, but since heat is conducted along the fibers, heat insulating properties cannot be expected. In the heat insulating sheet 100 of the present invention, the matrix fibers 6 are longer and therefore extend in a direction parallel to the front and back surfaces of the sheet, thereby giving the heat insulating sheet 100 mechanical strength in the surface direction. On the other hand, in the thickness direction, as Figure 1 As illustrated, the thermal insulating fine particles 1 are supported in the gaps between the matrix fibers 6 , thereby imparting thermal insulating performance in the thickness direction to the thermal insulating sheet 100 .

[0121] The appropriate length of the adhesive fiber 7 will be explained. Generally, for thermal insulation sheets, thermal insulation performance in the thickness direction is required rather than thermal insulation performance in the in-plane direction. Therefore, it is not preferred to have adhesive fibers extending from one surface of the thermal insulation sheet to the other surface. This is because the thermal conductivity of the adhesive fiber is higher than that of the silica fiber that is often used as the base fiber. Therefore, if the adhesive fiber extends from one surface to the other surface of the thermal insulation sheet in the thickness direction, heat is conducted through the adhesive fiber, thereby acting in the direction of reducing the thermal insulation performance in the thickness direction. Even considering the bending due to the heat applied during manufacturing, the maximum length of the adhesive fiber is preferably several mm, which is equivalent to the thickness of the thermal insulation sheet.

[0122] On the other hand, the minimum value of the appropriate length of the binder fiber 7 is 10 μm to several tens of μm. Figure 2 This diagram illustrates the relationship between the lengths of matrix fibers 6 and binder fibers 7. In the case (a) where matrix fibers 6 are adjacent and in contact with each other, the binder fibers 7 must have a length approximately equal to or greater than the diameter of the matrix fibers 6 in order to bond the adjacent matrix fibers 6. In the cases (b), (c), and (d) where the matrix fibers 6 are coated in some manner, or where thermally insulating particles or the like are present between the matrix fibers 6 and the matrix fibers 6 are separated from each other, as in the present invention, the minimum required length of the binder fibers 7 is one to several times the distance between the connected matrix fibers 6. Specifically, in the case (b) of connecting two matrix fibers, the minimum required length of the binder fibers 7 is approximately equal to the distance between the connected matrix fibers 6; in the case (c) of connecting three matrix fibers in a straight line, the minimum required length of the binder fibers 7 is approximately twice the distance between the connected matrix fibers 6; and in the case (d) of connecting three matrix fibers by sewing, the minimum required length of the binder fibers 7 is approximately three to four times the distance between the connected matrix fibers 6. The inventors have measured silica fibers, which are often used as base fibers, to have a diameter of 8 to 12 μm. Therefore, the minimum value is set within a multiple of this value. Furthermore, the minimum value mentioned here does not exclude binder fibers with a length shorter than this. Binder fibers with a length shorter than this simply contribute less to the purpose of bonding the base fibers.

[0123] As described above, by appropriately designing the lengths of the matrix fibers 6 and the binder fibers 7 , the strength and the heat insulating performance can be adjusted.

[0124] As the heat-insulating fine particles 1, aerogel ultrafine particles described in Patent Document 3 are preferably used.

[0125] Figure 7 This is an explanatory diagram comparing the structure of conventional aerogel fine powder with that of aerogel ultrafine particles whose skeleton is formed by primary particles. The three-dimensional network structure of conventional aerogel fine powder 13 is composed of secondary particles 12 as clusters of primary particles 11 as units ( Figure 7 (a)), in contrast, the aerogel ultrafine particles 14 form a three-dimensional network structure with the primary particles 11 as the skeleton ( Figure 7 (b)).

[0126] Aerogels that are usually circulated are particles, and have a three-dimensional network structure with secondary particles 12 as units forming a skeleton. Therefore, even if they are crushed into smaller pieces using a crushing device, the skeleton structure does not change. The following are experimental results. Figure 8 This diagram shows, from the bottom up, an example of the frequency distribution of particle sizes for aerogel particles, aerogel powder, aerogel fine powder, and aerogel ultrafine particles, which are microparticles with primary particles forming a skeleton. Aerogel particles are the aerogel particles normally circulated. Aerogel powder is produced by pulverizing aerogel particles at 5000-7000 rpm for 2 minutes using a Spin Mix Homogenizer SX08 manufactured by Mitsui Electric Seiki Co., Ltd. Aerogel fine powder is produced by further reducing the particle size by pulverizing aerogel particles at 21000 rpm for 20 seconds using a STEALTH 885 manufactured by Blendtec. Figure 8 The horizontal axis is particle size, and the vertical axis is the frequency distribution of particle size. The vertical axis on the right represents frequency, and the vertical axis on the left represents cumulative value. Figure 8 This is the result of observation based on a laser diffraction particle size distribution (PSD) measuring device. In this manual, the particle size is described based on the premise of PSD measurement. However, in PSD measurement, not only the diameter of the particle itself but also the aggregation of particles is observed as the particle size, so the actual particle size is likely to be smaller than the measured value. If there is a difference in particle size depending on the measurement method, please convert it for understanding. More specifically, Figure 8 This is the particle size distribution measured using the Shimadzu Corporation's SALD-2300 laser diffraction particle size analyzer. The particle size distribution is an indicator that indicates the proportion (relative particle amount relative to the total particle amount as 100%) of particles of varying sizes (particle diameters) within the sample particle population being measured. The particle amount dimension (grade) is based on volume.

[0127] The average particle size of aerogel particles in general circulation is about 400 μm, and the relative particle amount has only one peak value ( Figure 8Bottom layer). When the aerogel particles are crushed using the aforementioned apparatus, the aerogel powder has an average particle size of approximately 90 μm, and the aerogel fine powder has an average particle size of approximately 50 μm. However, the relative particle weight peaks for each are single (the third and second layers). In contrast, the aerogel ultrafine particles have a first peak with an average particle size of approximately 20 μm and a second peak with an average particle size of approximately 0.3 μm. With respect to the relative particle weight, the first peak with an average particle size of approximately 20 μm accounts for 21.2%, while the second peak with an average particle size of approximately 0.3 μm accounts for 78.8%. This is because the first peak with an average particle size of approximately 20 μm is composed of particles having a three-dimensional network structure with secondary particles 12 as the skeleton, while the second peak with an average particle size of approximately 0.3 μm is composed of particles having a three-dimensional network structure with primary particles forming the skeleton.

[0128] Because the skeleton of a conventional aerogel's three-dimensional network structure is composed of secondary particles, producing microparticles with a diameter of 10 μm or less is difficult, regardless of the optimal grinding conditions. Producing microparticles with a three-dimensional network structure composed of primary particles requires fundamental changes to the production process, including not only the grinding conditions but also the aging conditions, which differ from the conventional aerogel production process.

[0129] In the thermal insulation sheet 100 of the present invention, the thermal insulating particles 1 are preferably aerogel ultrafine particles as described above. Specifically, the thermal insulating particles are made from aerogel having a three-dimensional mesh structure composed of clusters of primary particles 11 forming a skeleton. The aerogel has a three-dimensional mesh structure composed of the primary particles described above, and at least 50% of the volume of the particles are dispersed with a mode of distribution within a particle size range of 0.1 μm to 1.0 μm. Furthermore, the matrix fibers 6 are preferably silica fibers, the binder fibers are preferably PVA fibers, and the binder is preferably PVA. As mentioned above, silica fibers, which are representative matrix fibers 6, have a thickness of approximately 10 μm. Therefore, the size is not such that aerogel particles of several 100 μm can be supported in the interstices between the matrix fibers. Therefore, aerogel ultrafine particles of 1 μm or less are preferably used to achieve a structure that allows them to be supported in the interstices.

[0130] This allows for the provision of a thinner thermal insulation sheet that effectively utilizes the extremely small particle size of aerogel ultrafine particles. In the thermal insulation sheet 100 of this embodiment, even when the thickness is reduced to 3 mm or less, the use of aerogel ultrafine particles as the thermal insulating particles 1 improves thermal conductivity to approximately 40 mW / mK to less than 30 mW / mK. Insulating particles with larger particle sizes have fewer particles aligned in the thickness direction when thinned, and the contribution of the particle shell to thermal conductivity is greater. In contrast, aerogel ultrafine particles have an extremely small particle size, so when thinned, the gaps (voids) between them in the thickness direction are larger than the particles, resulting in less thermal conductivity from the particle shell. Furthermore, the voids hinder air convection, thereby improving thermal insulation performance.

[0131] [Addition of flame retardancy] In the thermal insulation sheet 100, the thermal insulation fine particles 1 may be bonded to the surface of the matrix fibers 6 via the binder 2. This imparts flame retardancy to the matrix fibers 6 along with thermal insulation properties, making the entire thermal insulation sheet 100 flame retardant.

[0132] Figure 3 This is an explanatory diagram showing an example of the structure of a flame-retardant fiber 200 (a flame-retardant thermal insulation fiber) in which thermal insulation fine particles 1 are bonded to the surface of a base fiber 6. It is reliable to form a flame-retardant layer 3 containing thermal insulation fine particles 1 so as to completely cover the surface of the base fiber 6. However, if Figure 3 As shown, even if the flame-retardant layer 3 is formed in an island shape, it is believed that the flame retardancy effect is enhanced. For example, if aerogel ultrafine particles are used as the thermal insulating particles 1, flame retardancy can be enhanced to the extent that the surface of the thermal insulating sheet 100 does not burn even when heated with a flame at a high temperature exceeding 1000°C. This is described in detail in Embodiments 3 to 5 and in the Examples.

[0133] [Implementation Method 2] A method for producing the heat insulating sheet 100 according to the first embodiment will be described.

[0134] Figure 4 1 is a flowchart showing an example of a method for producing a thermal insulation sheet according to an embodiment of the present invention. The method for producing the thermal insulation sheet 100 includes the following steps.

[0135] Step 1 (S1): Dispersing the thermally insulating microparticles 1 to prepare a suspension containing the thermally insulating microparticles. "Dispersing (the microparticles)" here means dispersing the microparticles by placing them in a liquid (medium) and stirring them; it does not mean dissolving them. If the thermally insulating microparticles 1 are hydrophobic, they are dispersed in ethanol; if they are hydrophilic, they are dispersed in water. If the thermally insulating microparticles 1 are aerogel ultraparticles whose surfaces are modified with trimethylsiloxane groups or other hydrophobic groups, they exhibit strong hydrophobicity and have a high affinity for ethanol (e.g., alcohol). Therefore, ethanol can be used as the medium in step 1 (S1). On the other hand, treating hydrophobic aerogel ultraparticles at a high temperature of approximately 450°C eliminates the trimethylsiloxane groups on the surface, exposing the silica and making them hydrophilic. Therefore, the suspension containing the thermally insulating microparticles can be a water-based liquid, eliminating the need for ethanol (e.g., alcohol). It is generally known that the thermal decomposition start temperature of the hydrophobic functional groups of silica aerogel is 390°C. However, due to its heat insulating properties, a high temperature of about 450°C is preferably used to allow for sufficient heating of the center of the sample.

[0136] Second step (S2): Dissolving a binder to prepare a binder solution. The binder is preferably, for example, PVA powder. PVA powder is added to room temperature water, heated to approximately 80°C, stirred, and dissolved, and then returned to room temperature.

[0137] Third step ( S3 ): The suspension containing heat-insulating fine particles prepared in the first step ( S1 ), the binder solution prepared in the second step ( S2 ), the matrix fibers 6 , and the binder fibers 7 are mixed to prepare a fiber-containing suspension.

[0138] The fourth step (S4) is a papermaking step of making paper from the fiber-containing suspension prepared in the third step (S3).

[0139] The fourth step (S4), "papermaking," is similar to papermaking (a process in the Japanese paper manufacturing method). It involves removing the liquid component from the suspension, leaving the solid components in the suspension in a thin film to form a sheet. More specifically, the fiber-containing suspension from the third step (S3) is passed through a liquid-permeable mesh. This allows the liquid (medium) to flow through, leaving matrix fibers 6 and binder fibers 7 on the mesh. The remaining matrix fibers 6 and binder fibers 7 are entangled with each other and wetted with a liquid containing thermally insulating particles 1 and a binder. Matrix fibers 6, being longer than binder fibers 7, extend along the mesh, while binder fibers 7, being shorter, are sandwiched between matrix fibers 6. The matrix fibers 6 and binder fibers 7, entangled, extend on the mesh, retaining the thermally insulating particles 1 and the binder solution in their interstices. When peeled from the mesh, the resulting sheet is formed. The sheet is held in a single sheet or several sheets are stacked and compressed vertically to extract excess liquid. Drying results in a nonwoven fabric, namely, the thermal insulation sheet 100 of Embodiment 1. Heating for drying melts part or all of the surface of the binder fiber 7 into a film-like shape, which then bonds to the contacting matrix fiber 6. If the binder fiber 7 is PVA fiber, drying can also be performed at 65°C to 85°C.

[0140] Since the fiber-containing suspension prepared in the fourth step ( S4 ) contains the binder solution prepared in the second step ( S2 ), the binder functions even after drying, and the heat-shielding fine particles 1 are supported without falling from gaps between the matrix fibers 6 .

[0141] Thus, the method for manufacturing the heat insulating sheet 100 according to the first embodiment can be provided.

[0142] The concentration of the heat-insulating fine particles 1 in the first step ( S1 ) is, for example, 0.1 to 0.5 wt %, the concentration of the polyvinyl alcohol in the second step ( S2 ) is, for example, 0.075 g / dl, and the contents of the matrix fibers 6 and the binder fibers 7 in the fiber-containing suspension are, for example, 0.5 wt % and 0.025 wt %, respectively.

[0143] The content of the insulating particles 1 in the suspension containing the insulating particles can be as high as possible, within a range that allows for uniform dispersion. The upper limit of the insulating particles 1 content is set to a level that prevents aggregation, and an appropriate amount of medium is added to achieve this. If the amount of medium added is too low, the insulating particles 1 in the suspension will aggregate and form clusters, preventing uniform dispersion. On the other hand, if the amount of medium is too high, the content of the insulating particles 1 per unit volume decreases, resulting in a trade-off. Optimization design is achieved through experimentation and other means.

[0144] In the fiber-containing suspension, the sheet strength, such as tensile strength, can be increased by increasing the content of matrix fibers 6. Furthermore, the sheet can be further strengthened by increasing the content of binder fibers 7, but this will sacrifice thermal insulation performance.

[0145] [Implementation Method 3] The flame retardant fiber of one embodiment of the present invention is described. Figure 3 As described above, thermal insulating fine particles 1 can be bonded to the surface of matrix fiber 6 using a binder. Using this flame-retardant fiber as the matrix fiber in Embodiments 1 and 2 can impart flame retardancy to thermal insulating sheet 100. Aerogel ultrafine particles are particularly preferred as thermal insulating fine particles 1 in this case.

[0146] Aerogel ultrafine particles, if silica aerogel with high purity is used as the raw material, will become thermally insulating particles that retain the flame retardancy of silica. If ordinary silica fiber is used as the base material fiber 6, its diameter is about 8μm to 12μm. In contrast, as cited in Figure 8 As explained above, the particle size of conventional aerogel fine powder is several tens to several hundreds of μm, and therefore cannot be adhered to the surface of silica fiber. On the other hand, the particle size of aerogel ultrafine particles is mostly distributed in the range of 0.3 μm to 0.7 μm, and therefore can be adhered to the surface of silica fiber. As explained in the "Addition of Flame Retardancy" of the first embodiment, it is reliable to form the flame retardant layer 3 containing the heat insulating fine particles 1 in a manner that completely covers the surface of the base fiber 6, but even if Figure 3 Forming the flame-retardant layer 3 in an island shape as shown can also improve flame retardancy. As the thermally insulating microparticles 1, aerogel ultrafine particles are preferred, as described above. However, this is not a limitation. Any microparticles having flame retardancy and a particle size sufficiently smaller than the diameter of the parent fiber will suffice.

[0147] [Implementation Method 4] The method for producing the flame-retardant fiber according to the third embodiment will be described. Figure 5 This flowchart shows an example of a method for producing flame-retardant fibers according to one embodiment of the present invention. It illustrates a method (a) for producing by vapor-depositing thermally insulating fine particles 1 on the surface of a base fiber 6, and a method (b) for producing by powdering thermally insulating fine particles 1 on the surface of a base fiber 6.

[0148] (a) The method for producing a flame-retardant fiber in which the heat-shielding fine particles 1 are vapor-deposited on the surface of a base fiber 6 includes the following steps.

[0149] First step ( S11 ): Dispersing the heat-shielding fine particles 1 to prepare a suspension containing the heat-shielding fine particles. As in S1 , if the heat-shielding fine particles 1 are hydrophilic, they are dispersed in water; if they are hydrophobic, they are dispersed in ethanol.

[0150] Second step (S12): Dissolve the binder to prepare a binder solution. As in S2, the binder is preferably, for example, PVA powder. PVA powder is added to room temperature water, heated to approximately 80°C, stirred to dissolve, and then returned to room temperature.

[0151] Third step ( S13 ): The suspension containing the heat-insulating fine particles prepared in the first step ( S11 ) and the binder solution prepared in the second step ( S12 ) are mixed to prepare a slurry.

[0152] Step 4 (S14): The slurry prepared in step 3 (S13) is used as an evaporation source to vapor-deposit the matrix fibers 6. The matrix fibers 6 may be in any form such as sheet, blanket, mat, or flocculent, and may be in a defibrated state.

[0153] Thus, a manufacturing method for adding higher flame retardancy to the base fiber can be provided. The vapor deposition in the fourth step (S14) is preferably ultrasonic vapor deposition or heat vapor deposition. Thus, the heat-insulating fine particles 1 can be more efficiently bonded to the surface of the base fiber 6. Here, "more efficiently" means that a larger amount of heat-insulating fine particles 1 can be bonded with a smaller consumption. In the fourth step (S14), instead of vapor deposition, a process of spraying the slurry prepared in the third step (S13) or immersing the sheet-like or blanket-like base fiber 6 in the slurry prepared in the third step (S13) and then lifting and drying it can be used.

[0154] Thermal insulating microparticles (aerogel ultrafine particles) exhibit strong hydrophobicity when their surfaces are modified with trimethylsiloxane or other hydrophobic groups. Furthermore, they have a high affinity for ethanol (e.g., alcohol), so alcohol is used as the medium in step 1 (S1). In addition to aerogel ultrafine particles, any material exhibiting both heat resistance and hydrophobicity can be used as the microparticles. Generally, hydrophobic microparticles have a high affinity for ethanol and can be uniformly dispersed, so other heat-resistant hydrophobic microparticles and suitable media can be substituted. On the other hand, if the thermal insulating microparticles (aerogel ultrafine particles) are hydrophilic, ethanol (alcohol) is not required; water can be used as the medium in step 1 (S1).

[0155] The mixing ratio of water, ethanol (e.g., alcohol), microparticles, and a binder (e.g., PVA) in the prepared slurry is optimized through experiments, etc., based on the target specifications. For example, increasing the amount of PVA as a binder tends to improve the fixation of microparticles but decrease flame retardancy.

[0156] (b) The method for producing a flame-retardant fiber in which the heat-insulating fine particles 1 are attached to the surface of a base fiber 6 includes the following steps.

[0157] Step 5 ( S15 ): Dissolve the binder to prepare a binder solution. As in S2 and S12 , the binder is preferably, for example, PVA powder. PVA powder is added to room temperature water, heated to approximately 80°C, stirred to dissolve, and then returned to room temperature.

[0158] Sixth step ( S16 ): The binder solution prepared in the fifth step ( S15 ) is used as an evaporation source to vapor-deposit the matrix fibers 6 .

[0159] Step 7 (S17, powder-attaching step): Mechanically apply thermal insulating fine particles 1 to the matrix fiber 6 to which the binder solution adhered in step 6 (S16). Mechanical application involves mixing and stirring the thermal insulating fine particles 1 while the matrix fiber 6's surface is wet (i.e., before the deposited binder solution has dried). This allows the thermal insulating fine particles 1 to adhere to the matrix fiber 6's surface, which is wet with the binder solution.

[0160] Another manufacturing method for adding flame retardancy to a base fiber is provided.

[0161] Flame-retardant fibers can be produced by either method (a) of vapor-depositing thermal insulating fine particles 1 on the surface of base fiber 6 or method (b) of applying thermal insulating fine particles 1 to the surface of base fiber 6. For the reasons described in Embodiment 4, aerogel ultrafine particles are particularly preferred as the thermal insulating fine particles 1 in this case.

[0162] [Implementation method 5] A flame retardant heat insulating sheet 100 according to one embodiment of the present invention will be described. Figure 1 In the heat insulating sheet 100 shown, a flame retardant layer 3 containing heat insulating fine particles 1 is formed on the surface of the base fiber 6. The flame retardant layer 3 containing heat insulating fine particles 1 may be formed so as to completely cover the surface of the base fiber 6. However, even if Figure 3 The flame retardant layer 3 is formed in an island shape, which also has the effect of improving the flame retardancy.

[0163] A method for producing the flame-retardant heat-insulating sheet 100 will be described.

[0164] Figure 6This is a flowchart showing an example of a method for producing a flame-retardant thermal insulation sheet.

[0165] As the base fiber 6, flame-retardant fiber 200 manufactured by the manufacturing method (a) of vapor-depositing thermal insulating microparticles 1 on the surface of the base fiber 6 shown in embodiment 4 or the manufacturing method (b) of attaching thermal insulating microparticles 1 to the surface of the base fiber 6 is used. In order to form the same thermal insulating sheet 100 as the thermal insulating sheet described in embodiments 1 and 2, the following steps are performed in sequence.

[0166] Step 8 (S21): Disperse the thermally insulating fine particles 1 to prepare a suspension containing the thermally insulating fine particles. This suspension can be the same as the one prepared in step 1 (S11), or the content of the thermally insulating fine particles 1 can be optimized in consideration of the papermaking process (step 11, S24).

[0167] Step 9 (S22): Dissolve polyvinyl alcohol powder in water to prepare a second binder solution for the fibers. This can be the binder solution prepared in step 2 (S12), or the binder concentration can be optimized based on the papermaking process (step 11, S24).

[0168] Step 10 (S23): The flame-retardant fiber 200, the adhesive fiber 7, the second suspension containing heat-insulating fine particles for the fiber prepared in step 8 (S21), and the second binder solution for the fiber prepared in step 9 (S22) are mixed to prepare a fiber-containing suspension.

[0169] The 11th step (S24) is a papermaking step of preparing the fiber-containing suspension obtained in the 10th step (S23).

[0170] Thereby, a method for producing a heat-insulating sheet to which flame retardancy is added can be provided.

[0171] In this embodiment, similarly to Embodiments 1 to 4, the heat-insulating fine particles 1 may be aerogel ultrafine particles, the matrix fibers 6 may be silica fibers, and the binder may be polyvinyl alcohol.

[0172] By setting the matrix fiber 6 as silica fiber, the thermal insulation sheet 100 can be constructed as in embodiments 1 and 2. As shown in this embodiment 3, the flame-retardant layer 3 is bonded to the matrix fiber 6, thereby obtaining the flame-retardant fiber 200. In addition, by using the flame-retardant fiber as the matrix fiber 6, flame retardancy can be added to the thermal insulation sheet 100. Thus, a thermal insulation sheet that is not only heat-insulating but also heat-resistant and flame-retardant and can withstand high-temperature flames of more than 1000°C can be realized. Such a thermal insulation sheet can shield adjacent battery cells or battery modules in a battery formed by integrating multiple battery cells, and can be used to prevent thermal runaway.

[0173] [Implementation Method 6] In this embodiment, another embodiment of the heat insulating sheet of the present invention will be described. Figure 1 The insulation sheet 100 shown is different from Figure 11 As shown, at least a portion of the thermal insulating particles 14 are embedded in the matrix fibers 300 that constitute the thermal insulating sheet. Specifically, the matrix fibers 300 are composed of thermoplastic resin 8, but the thermal insulating particles 14 are mixed in this thermoplastic resin 8. If the particle size of the thermal insulating particles 14 is relatively large and / or the amount of thermal insulating particles 14 is relatively large relative to the amount of thermoplastic resin 8, the thermal insulating particles 14 may be present on the surface of the matrix fibers 300, with some of the thermal insulating particles 14 protruding from the thermoplastic resin 8. Alternatively, if the particle size of the thermal insulating particles 14 is sufficiently smaller than the diameter of the matrix fibers 300, or the amount of thermal insulating particles 14 is relatively small relative to the amount of thermoplastic resin 8, the thermal insulating particles 14 may be completely embedded in the thermoplastic resin 8, with no thermal insulating particles 14 present on the surface of the matrix fibers 300.

[0174] Examples of thermoplastic resins include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), aromatic polyesters based on polyalkylene terephthalates, aliphatic polyesters such as polylactic acid, and polyesters such as polylactic acid. Other examples include polyamides, polyurethanes, and polyolefins, which are known thermoplastic resins that can be used as materials for chemical fibers. These thermoplastic resins can be used alone or as a mixture of two or more.

[0175] Furthermore, as the thermoplastic resin, for example, recycled resin obtained by remelting thermoplastic resin molded products such as plastic bottles and molding them into pellets or powders may be used.

[0176] The heat insulating sheet of this embodiment is formed by weaving yarns obtained by spinning the above-mentioned base material fibers 300. The base material fibers 300 can be spun by any known spinning method described below.

[0177] The yarns can be woven using any known method. In this embodiment, "weaving" means knitting the yarns to form a fabric, or weaving the yarns to form a woven structure. Examples of woven fabrics include any known structures such as plain, twill, satin, amunzen, and double weave. Examples of woven structures include any known structures such as plain stitch, interlock, half braid, and double raschel.

[0178] The thermal insulation sheet of this embodiment has yarns mixed with thermal insulation fine particles 14 woven into base fiber 300 . Therefore, the thermal insulation fine particles 14 are not supported by a binder, and a thermal insulation sheet with high thermal insulation properties can be obtained.

[0179] [Implementation Method 7] This embodiment describes another embodiment of a thermal insulation sheet according to the present invention. This embodiment utilizes the same matrix fiber 300 as described in Embodiment 6 above. Specifically, the matrix fiber contains a thermoplastic resin, and the thermally insulating fine particles are at least partially embedded in the thermoplastic resin of the matrix fiber. The sheet is formed by bonding films formed by dissolving the matrix fiber in the thermoplastic resin.

[0180] The matrix fibers of this embodiment contain a thermoplastic resin and are therefore easily melted by heat or the like. Therefore, a sheet can be formed by bonding the matrix fibers together using a film formed by the melted thermoplastic resin, without the use of a binder fiber. Furthermore, as in the sixth embodiment, thermally insulating fine particles are mixed into the matrix fibers, eliminating the need for a binder to support the fine particles, resulting in a highly insulating sheet.

[0181] Alternatively, the matrix fiber of this embodiment can be used in place of the matrix fiber of Embodiment 1, and a thermal insulation sheet can be produced using the manufacturing method of Embodiment 2. Specifically, a matrix fiber comprising at least a portion of thermal insulation fine particles embedded in a thermoplastic resin can be used as the matrix fiber, and the thermal insulation sheet can be produced through a papermaking process using PVA fibers, a binder, and a suspension containing the thermal insulation fine particles. Since the matrix fiber contains thermal insulation fine particles, higher thermal insulation performance can be achieved.

[0182] [Implementation Method 8] In this embodiment, one embodiment of a method for producing another thermal insulation sheet of the present invention will be described.

[0183] The manufacturing method of this embodiment can also be cited as an example of the method for manufacturing the thermal insulation sheet shown in the above-mentioned embodiments 6 and 7. Figure 12As illustrated, the method for producing a heat insulating sheet according to the present embodiment includes the following steps.

[0184] Step 12 ( S25 ): A step of mixing a thermoplastic resin and heat-insulating fine particles to obtain a fine particle-containing resin.

[0185] Thirteenth step ( S26 ): a step of placing the fine particle-containing resin in a container having fine holes, rotating the container while heating it, and ejecting the fine particle-containing resin from the fine holes to obtain short fibers.

[0186] Fourteenth step ( S27 ): a step of forming the short fibers into a sheet shape.

[0187] In step 12, the thermoplastic resin may be heated to melt, the heat-insulating fine particles added thereto, and the mixture stirred and mixed while heating to prepare a resin containing fine particles. This fine particle-containing resin may then be pulverized and placed in the container to be melted again. This allows the heat-insulating fine particles to be relatively uniformly dispersed in the thermoplastic resin.

[0188] Alternatively, the microparticle-containing resin may be obtained by placing the molten thermoplastic resin together with the heat-shielding microparticles in a container, etc. In this case, the microparticle-containing resin is formed in a state where the thermoplastic resin and the heat-shielding microparticles are not completely mixed.

[0189] In the 13th step, if Figure 13 As shown, the microparticle-containing resin 9 obtained in the twelfth step is contained in a container 400 having fine pores disposed in a chamber C. The container 400 is heated and rotated by a motor M. Centrifugal force causes the microparticle-containing resin 9 to be ejected from the fine pores of the container 400 onto the inner wall of the chamber C, thereby producing short fibers. Alternatively, the microparticle-containing resin can be obtained by directly placing molten thermoplastic resin and thermally insulating microparticles into the container having fine pores used in the thirteenth step. In this case, the twelfth and thirteenth steps are performed simultaneously.

[0190] The container is connected to a motor M via a rotating shaft 401 and is configured to rotate about the rotating shaft 401 when driven by the motor M. In addition, a plurality of fine holes are provided on the side walls of the container 400, which communicate with the interior and exterior of the container. The container 400 is heated by a heater H provided below, causing the resin 9 containing microparticles inside to dissolve. In this state, the motor M is driven to rotate. The centrifugal force caused by the rotation acts on the resin 9 containing microparticles inside the container 400, causing the resin 9 containing microparticles to be ejected from the fine holes of the container 400. As a result, the resin 9 containing microparticles is rapidly cooled and becomes fibrous, which is then sprayed onto the inner wall of the chamber C in the form of short fibers. The short fibers sprayed onto the inner wall of the chamber C become fibers (flocculated fibers) 500 formed by entanglement of short fibers.

[0191] In step 14, the obtained staple fibers 500 are formed into a sheet. Since the staple fibers contain a thermoplastic resin, they can be easily deformed by heating. Thus, for example, by heating the flocculent fibers while forming them into a sheet, a sheet can be easily formed. Alternatively, as in embodiment 6, the staple fibers can be spun using a known spinning method and then woven into yarn, thereby also forming a sheet.

[0192] [Implementation Method 9] In this embodiment, one embodiment of a method for producing another thermal insulation sheet of the present invention will be described.

[0193] The manufacturing method of this embodiment can also be cited as an example of the method for manufacturing a heat insulating sheet shown in the above-mentioned embodiment 6. Figure 14 As illustrated, a method for producing a heat insulating sheet according to still another embodiment of the present invention includes the following steps.

[0194] Fifteenth step ( S28 ): a step of melting a thermoplastic resin and mixing the molten thermoplastic resin with heat-insulating fine particles to prepare a fine particle-containing resin.

[0195] Sixteenth step ( S29 ): a step of extruding the molten resin containing fine particles from fine holes to obtain fibers.

[0196] Seventeenth step ( S30 ): a step of spinning the fibers to obtain yarn.

[0197] Step 18 ( S31 ): a step of knitting the yarn.

[0198] The 15th step can be combined with the 12th step ( Figure 12 S25) is implemented similarly.

[0199] The 16th step is to extrude the melted resin containing microparticles from the pores to obtain fibers. In the method of obtaining fibers by extrusion, for example, it can be carried out by the following well-known chemical fiber spinning method: using Figure 15 The spinning device 600 shown extrude a molten resin 601 containing microparticles in a cooling atmosphere (blowing cold air) to form a plurality of fibers, and twists the fibers to perform spinning (melt spinning method); a method of extruding a resin containing microparticles into a coagulation liquid instead of a cooling atmosphere (wet spinning method); a method of extruding a resin containing microparticles into a heated atmosphere instead of a cooling atmosphere (dry spinning method), etc.

[0200] The seventeenth and eighteenth steps can be performed in the same manner as in the sixth embodiment.

[0201] <Example> [Example 1] As described in Embodiments 4 and 5, a flame retardant layer was formed by bonding aerogel ultrafine particles to glass wool as silica fibers, and the flame retardant layer was compared with glass wool without the flame retardant layer.

[0202] Samples of the same thickness were cut out from a glass wool blanket to produce glass wool blanket samples without a flame retardant layer and glass wool blanket samples with a flame retardant layer. Starting from one side, they were baked using a small welding torch 170-9105 manufactured by Coleman with a flame of 1300°C for 60 seconds. The baked side and the back side were observed with the naked eye and an optical microscope.

[0203] Figure 9 This is a photo of the actual product. In the glass wool blanket sample without a flame-retardant layer (left), the flame-heated surface (hot side) is observed to melt, while the back side (cold side) also appears to be thinning in the center due to the heat. Meanwhile, the glass wool blanket sample with a flame-retardant layer (right) exhibits dents on the flame-heated surface (hot side), but the back side (cold side) remains unchanged.

[0204] Figure 10 An optical microscope was used. Melting of fibers was observed in the flame-heated portion of the hot side of the glass wool blanket sample (left) without a flame-retardant layer. However, the flame-retardant blanket sample (right) showed almost no change from before the flame-heating.

[0205] As described above, the flame retardant layer is formed by bonding the aerogel ultrafine particles, thereby imparting flame retardancy to the base material fibers.

[0206] [Example 2] The short fibers used in the method for producing a thermal insulation sheet shown in the eighth embodiment are produced by the following method.

[0207] (Material quantity) Plastic bottle slices Aerogel ultrafine particles (trade name: TIISA, manufactured by Thermalytica Co., Ltd.) (Method for producing resin containing fine particles) Put the plastic bottle slices and aerogel ultrafine particles into a stainless steel cup, heat them with an alcohol lamp while stirring until the plastic bottle slices are completely melted, stop heating, and cool to room temperature to obtain a resin containing fine particles.

[0208] The content of aerogel ultrafine particles in the fine particle-containing resin was adjusted to 1 mass %, 3 mass %, 4 mass %, and a control containing no aerogel ultrafine particles (0 mass %). The cooled fine particle-containing resin was struck with a hammer to break it into pieces.

[0209] (Method for producing short fibers) A fine hole was made on the side of a 350ml aluminum beverage bottle using a drill bit and installed on Figure 16 In the device shown, the pore size is 2 mm.

[0210] Each microparticle-containing resin was placed in a bottle and heated with a Bunsen burner while a motor was driven to rotate the bottle. The rotation speed was 1493 rpm (motor voltage 0.7 V). As the bottle rotated, the microparticle-containing resin within the bottle was ejected from the fine holes, and flocculent short fibers adhering to the inner wall of the box were recovered.

[0211] (Observation of short fibers) The recovered short fibers were observed as follows.

[0212] Multiple fibers were removed from the short fibers and fixed upright in a cylindrical plastic container approximately 20 mm in diameter and 20 mm in height. A mixture of epoxy resin and curing agent was poured into the container and allowed to cure, completely securing the fiber sample. Once the epoxy resin had cured, the fiber sample was thinly cut from the side of each container, and the cross-section was polished. The surface to be observed was coated with platinum to impart conductivity, yielding a sample for SEM observation. The sample was observed using a Schottky field emission scanning electron microscope (JSM-7900F, manufactured by JEOL Ltd.).

[0213] Figure 17 Indicates the results of observation. Figure 17The portion surrounded by white circles in each 200x magnification photograph represents a cross-section of the short fibers. The portion surrounded by black circles in each 1000x magnification photograph represents aerogel ultrafine particles within the short fibers. White lumps were observed in the 1% and 4% mass fractions of fibers in the 1000x magnification photographs, which were not present in the control fibers without aerogel ultrafine particles. These lumps represent aerogel ultrafine particles, indicating that fibers containing aerogel ultrafine particles were obtained.

[0214] As mentioned above, although the invention completed by the present inventors was specifically described based on the embodiment, the present invention is not limited thereto, and it goes without saying that various changes can be made within the scope not departing from the gist of the invention.

[0215] Industrial Application Possibilities The present invention can be suitably utilized for a thermal insulation sheet, a thermal insulation fiber, a method for producing the same, and a fiber-containing suspension used for producing the thermal insulation sheet.

[0216] Explanation of symbols: 1. Thermally insulating particles (e.g., aerogel ultrafine particles) 2 Binder (e.g., PVA) 3 flame retardant layer 4. Bonding material layer 6. Fiber parent material (e.g., silica fiber) 7 Binder fibers (e.g., PVA fibers) 8 Thermoplastic resin 9 Resin containing microparticles 11 Primary particles 12 Secondary particles (aggregates or clusters of primary particles) 13 Aerogel powder (powder with a skeleton formed by secondary particles) 14 Microparticles whose skeleton is formed by primary particles (e.g., aerogel ultrafine particles) 100 thermal insulation sheet 200 flame retardant fiber 300 parent material fiber.

Claims

1. A thermal insulation sheet comprising matrix fibers and thermal insulation fine particles, wherein: The matrix fibers are bonded or woven together to form a sheet. The heat-shielding fine particles are present inside and / or outside the base fiber.

2. The thermal insulation sheet according to claim 1, characterized in that The thermally insulating fine particles are made of aerogel having a three-dimensional mesh structure whose skeleton is composed of clusters of aggregates of primary particles, and are fine particles having a three-dimensional mesh structure whose skeleton is composed of the primary particles, and more than 50% of their volume is dispersed with a frequency value in particle sizes of 0.1 μm to 1.0 μm.

3. The thermal insulation sheet according to claim 1 or 2, characterized in that: The parent fiber is silica fiber, The sheet body comprises the matrix fiber, adhesive fiber, and a binder, The matrix fibers are bonded to each other by a film formed by dissolving the binder fibers, and the heat-insulating fine particles are carried in gaps between the bonded matrix fibers by the binder.

4. The thermal insulation sheet according to claim 3, characterized in that The heat-shielding fine particles are bonded to the surface of the matrix fiber by the binder.

5. The thermal insulation sheet according to claim 1 or 2, characterized in that: The matrix fiber comprises a thermoplastic resin, The heat-insulating fine particles are present in a state where at least a portion of the fine particles is embedded in the thermoplastic resin in the matrix fibers. The sheet body is formed by knitting yarns obtained by spinning the base material fibers.

6. The thermal insulation sheet according to claim 1 or 2, characterized in that: The matrix fiber comprises a thermoplastic resin, The heat-insulating fine particles are present in a state where at least a portion of them is embedded in the thermoplastic resin of the matrix fiber. The sheet body is formed by bonding films formed by melting the matrix fibers in the thermoplastic resin.

7. A method for manufacturing a thermal insulation sheet, characterized in that: Include: A step of dispersing heat-insulating fine particles to prepare a suspension containing heat-insulating fine particles, The step of dissolving the binder to prepare a binder solution, a step of mixing the suspension containing the heat-insulating fine particles, the binder solution, the matrix fibers, and the binder fibers to prepare a suspension containing fibers; and A step of removing liquid components from the fiber-containing suspension to form a sheet.

8. The method for manufacturing a thermal insulation sheet according to claim 7, wherein: The parent fiber is silica fiber, The thermally insulating fine particles are made of aerogel having a three-dimensional mesh structure whose skeleton is composed of clusters of aggregates of primary particles, and are fine particles having a three-dimensional mesh structure whose skeleton is composed of the primary particles, and more than 50% of their volume is dispersed with a frequency value in particle sizes of 0.1 μm to 1.0 μm.

9. The method for manufacturing a thermal insulation sheet according to claim 7 or 8, wherein: The heat-insulating fine particles are hydrophobic, and the suspension containing the heat-insulating fine particles contains ethanol.

10. A method for manufacturing a thermal insulation sheet, characterized in that: Include: a step of mixing a thermoplastic resin with heat-insulating fine particles to obtain a resin containing fine particles; The step of placing the fine particle-containing resin in a container having fine pores, and rotating the container while heating it to eject the fine particle-containing resin from the fine pores to obtain short fibers; and A step of forming the short fibers into a sheet shape.

11. The method for manufacturing a thermal insulation sheet according to claim 10, wherein: Include: a step of spinning the short fibers to obtain yarn, and The process of weaving the yarn.

12. The method for manufacturing a thermal insulation sheet according to claim 10, wherein: In the step of forming the short fibers into a sheet shape, the short fibers are expanded into a film shape and formed into a sheet shape by heating.

13. A method for manufacturing a thermal insulation sheet, characterized in that: Include: a step of melting a thermoplastic resin and mixing the molten thermoplastic resin with heat-insulating fine particles to prepare a fine particle-containing resin; a step of extruding the molten resin containing microparticles from fine holes to obtain fibers; a process of spinning the fibers to obtain yarn; and The process of weaving the yarn.

14. A method for manufacturing a thermal insulation sheet, characterized in that: Include: a step of dispersing heat-insulating fine particles to prepare a suspension containing the heat-insulating fine particles; a step of dissolving the binder to prepare a binder solution; a step of mixing thermal insulation fibers, binder fibers, the suspension containing thermal insulation fine particles, and the binder solution to prepare a fiber-containing suspension; as well as a step of removing liquid components from the fiber-containing suspension to form a sheet; The thermal insulation fiber has thermal insulation particles bonded to the surface of the base fiber by a fiber binder. The heat-insulating fine particles for fibers are made of aerogel having a three-dimensional network structure whose skeleton is formed by clusters of primary particles, and have a three-dimensional network structure whose skeleton is formed by the primary particles, and the fine particles have a particle size of 0.1 μm to 1.0 μm, with a mode of dispersion of at least 50% by volume. The matrix fiber is silica fiber.

15. The method for manufacturing a thermal insulation sheet according to claim 14, wherein: Thermal insulating fine particles for the fibers and a binder for the fibers are deposited on the surface of the matrix fibers by ultrasonic deposition or heating deposition.

16. The method for manufacturing a thermal insulation sheet according to claim 14, wherein: The heat-insulating fine particles are hydrophobic, and the suspension containing the heat-insulating fine particles contains ethanol.

17. A fiber-containing suspension for use in the manufacture of a thermal insulation sheet, characterized in that: The heat shielding fiber is prepared by mixing a suspension containing heat shielding fine particles dispersed in a solvent, a binder solution, matrix fibers, and binder fibers.

18. A fiber-containing suspension for use in the manufacture of a thermal insulation sheet, characterized in that: The heat insulating fine particles are dispersed in a solvent, and a suspension containing the heat insulating fine particles is mixed with a binder solution, heat insulating fibers, and binder fibers. The thermal insulation fiber has thermal insulation particles bonded to the surface of the base fiber by a fiber binder. The heat-insulating fine particles for fibers are made of aerogel having a three-dimensional network structure whose skeleton is formed by clusters of primary particles, and have a three-dimensional network structure whose skeleton is formed by the primary particles, and the fine particles have a particle size of 0.1 μm to 1.0 μm, with a mode of dispersion of at least 50% by volume. The matrix fiber is silica fiber.

19. A thermal insulation fiber, characterized in that: Thermal insulation particles are bonded to the surface of the base fiber by a binder. The thermally insulating fine particles are made of aerogel having a three-dimensional network structure whose skeleton is formed by clusters of primary particles, and have a three-dimensional network structure whose skeleton is formed by the primary particles, and are fine particles with a particle size of 0.1 μm to 1.0 μm, wherein at least 50% of the volume of the fine particles is dispersed with a mode. The matrix fiber is silica fiber.

20. A thermal insulation fiber, characterized in that: The heat-insulating fine particles are at least partially embedded in the base material fibers. The thermally insulating fine particles are made of aerogel having a three-dimensional network structure whose skeleton is formed by clusters of primary particles, and have a three-dimensional network structure whose skeleton is formed by the primary particles, and are fine particles with a particle size of 0.1 μm to 1.0 μm, wherein at least 50% of the volume of the fine particles is dispersed with a mode. The matrix fibers include a thermoplastic resin.

21. The method for producing thermal insulation fiber according to claim 19, wherein: Include: a step of dispersing the heat-shielding fine particles to prepare a suspension containing the heat-shielding fine particles; The step of dissolving the binder to prepare a binder solution, a step of mixing the suspension containing the heat-insulating fine particles with the binder solution to prepare a slurry, and The step of vapor-depositing the matrix fiber using the slurry as an evaporation source.

22. The method for producing thermal insulation fiber according to claim 19, wherein: Include: The step of dissolving the binder to prepare a binder solution, The process of evaporating the matrix fiber using the binder solution as an evaporation source, and A step of mechanically applying heat-insulating fine particles to the matrix fiber on the surface of which the binder solution is attached by the vapor deposition.

23. The method for producing thermal insulation fiber according to claim 21, wherein: The vapor deposition performed in the vapor deposition step is ultrasonic vapor deposition or heating vapor deposition.

24. The method for producing thermal insulation fiber according to claim 21, wherein: The heat-insulating fine particles are hydrophobic, and the suspension containing the heat-insulating fine particles contains ethanol.

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