Composite and method for producing composite

Abstract

To provide a composite and a method for producing a composite that exhibit excellent flame retardancy and can prevent detachment of aerogel particles.SOLUTION: The composite comprises a fibrous base material, an aerogel filled in voids of the fibrous base material, and a coating layer covering at least a part of the fibrous base material, wherein the fibrous base material satisfies a flame retardancy rating of V-0 to V-2 based on the vertical burning test UL94.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a composite and a method for producing the composite. [Background technology]

[0002] Insulating materials are used in automobiles, housing, and other applications to promote energy conservation and make effective use of thermal energy. In recent years, materials that combine aerogel or xerogel, which have excellent insulating properties, with nonwoven fabrics or resin foams, have become suitable for use as insulating materials.

[0003] For example, Patent Document 1 discloses a heat insulating material made of a composite of a foam such as polyurethane foam and aerogel, and Patent Document 2 discloses a heat insulating material containing nonwoven fabric fibers and xerogel. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-47710 [Patent Document 2] International Publication No. WO2018 / 003545 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technology of Patent Document 1 has limited applications as a heat insulating material because foams such as polyurethane foam have poor flame retardancy. In the technology of Patent Document 2, the xerogel particles tend to easily fall off (powder off) from the nonwoven fabric fibers, making it difficult to maintain heat insulating performance over a long period of time.

[0006] Therefore, an object of the present invention is to provide a composite body that has excellent flame retardancy and can prevent aerogel particles from falling off, and a method for producing the composite body. [Means for solving the problem]

[0007] One aspect of the present invention is a composite comprising a fiber substrate, an aerogel filling voids in the fiber substrate, and a coating layer covering at least a portion of the fiber substrate, wherein the fiber substrate satisfies a flame retardancy rating of V-0 to V-2 based on the UL94 vertical flame test.

[0008] In the composite of the above aspect, the fiber base material is preferably made of one or more fibers selected from carbonized fibers, phenolic fibers, and fibers to which a flame retardant has been added.

[0009] In the composite of the above aspect, the coating layer is preferably made of one or more materials selected from thermoplastic resins and energy ray-curable elastomers. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a composite that has excellent flame retardancy and is capable of suppressing the shedding of aerogel particles, and a method for producing the composite. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cutaway view showing a composite of the first embodiment. [Figure 2] FIG. 2 is a schematic cutaway view showing the composite of the present embodiment 2A. [Figure 3] FIG. 2 is a schematic cutaway view showing the composite of the present embodiment 2B. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, the first and second embodiments of the present invention will be described in detail.

[0013] In this specification, the expression "a to b" in the description of a range of values ​​means that the range is from a to b, unless otherwise specified.

[0014] In this specification, when multiple upper limit values ​​and multiple lower limit values ​​are separately described, all numerical ranges that can be set by freely combining these upper limit values ​​and lower limit values ​​are considered to be described in this specification.

[0015] The shape of the composite can be any shape suitable for the intended use.

[0016] In the present invention, the density (apparent density) is the apparent density measured in accordance with JIS K7222:2005 "Foamed plastics and rubber - Determination of apparent density".

[0017] In the present invention, the composite includes a fiber substrate filled with aerogel, but the fiber substrate before being filled with aerogel and the fiber substrate after being filled with aerogel are treated as the same thing, and the description of one of them may be omitted or replaced with the description of the other.

[0018] As used herein, dusting refers to the shedding of aerogel particles from the composite.

[0019] [Embodiment 1] 1. Complex Fig. 1 is a schematic cross-sectional view showing a composite of the present embodiment 1. As shown in Fig. 1, a composite 10 of the present embodiment 1 includes a fiber substrate 11, an aerogel 12 filled in voids in the fiber substrate, and a coating layer 13 that covers at least a portion of the surface of the fiber substrate 11.

[0020] 1, for the sake of simplicity, the boundary between the coating layer 13 and the fiber substrate 11 is shown, but in the present embodiment 1, there may be an area between the coating layer 13 and the fiber substrate 11 where part of the coating layer 13 and part of the fiber substrate 11 coexist. This area is considered to be included in the coating layer 13.

[0021] The average filling rate of the aerogel 12 in the voids of the fiber substrate 11 (the volume ratio of the filled aerogel to the voids) is not particularly limited and can be 50% to 100%, more preferably 70% to 100%, and even more preferably 90% to 100%. When the average filling rate of the aerogel is within this range, it is possible to provide a composite with superior heat insulating properties.

[0022] The thickness of the composite 10 is preferably 0.05 mm or more, 0.10 mm or more, 0.20 mm or more, 0.50 mm or more, 0.75 mm or more, 1.00 mm or more, and is preferably 40.0 mm or less, 30.0 mm or less, 20.0 mm or less, 10.0 mm or less, 5.00 mm or less, 4.00 mm or less, 3.00 mm or less, 2.00 mm or less, etc.

[0023] The thermal conductivity of composite 10 is preferably 0.020 W / m·K or less, 0.019 W / m·K or less, 0.018 W / m·K or less, 0.017 W / m·K or less, 0.016 W / m·K or less, etc. When the thermal conductivity of composite 10 is within the above range, composite 10 can have sufficient heat insulating performance as a heat insulating material.

[0024] The aerogel 12, the fiber substrate 11, and the coating layer 13 that constitute the composite 10 will be described in detail below.

[0025] 1-1.Aerogel The aerogel 12 of the present embodiment 1 is not particularly limited, and examples thereof include low-density dry gels, etc. Specific examples include aerogels obtained using a supercritical fluid drying method, xerogels obtained by a normal drying process, and cryogels obtained by freeze-drying.

[0026] 1-1-1.Ingredients Any suitable aerogel component can be used as the aerogel 12 of the first embodiment. For example, it can be selected from inorganic aerogels such as silica aerogel and alumina aerogel, organic aerogels such as resorcinol-formaldehyde aerogel (RF aerogel) and cellulose nanofiber aerogel (CNF aerogel), carbon aerogels, and mixtures thereof. Among these, silica aerogels containing silica (SiO2) are preferably used.

[0027] 1-1-2.Physical properties / properties (pore diameter) The pore diameter of the aerogel 12 of the first embodiment is preferably 70 nm or less, more preferably 60 nm or less, and even more preferably 50 nm or less. Here, the "pore diameter" is a value measured using a pore distribution measuring device (e.g., BELSORP MINI manufactured by Microtrack-Bell) in accordance with JIS Z8831-2 "Pore size distribution and pore characteristics of powders (solids) - Part 2: Measurement method for mesopores and macropores by gas adsorption." When the pore diameter is within this range, it is possible to provide a composite with superior thermal insulation properties.

[0028] (specific surface area) The specific surface area of ​​the aerogel 12 of the first embodiment is 600 m 2 / g or more, 700m 2 / g or more, 900m 2 The upper limit is not particularly limited, and is preferably 1,000 m 2 / g or less is preferable. The method for measuring the specific surface area is the same as that for measuring the pore diameter described above. By setting the specific surface area of ​​the aerogel 12 in the above range, it is possible to provide a heat insulating material with better heat insulating properties.

[0029] (density) The density of the aerogel 12 in the first embodiment is 0.001 g / cm 3 More than 0.010g / cm 3 More than 0.020g / cm 3 More than 0.030g / cm 3 More than 0.040g / cm 3More than 0.050g / cm 3 More than 0.060g / cm 3 More than 0.275 g / cm 3 Below 0.250g / cm 3 Below, 0.240g / cm 3 Below, 0.230g / cm 3 Below, 0.220g / cm 3 Below, 0.210g / cm 3 Below, 0.200g / cm 3 The following are preferred:

[0030] 1-2. Fiber base material The fiber base material 11 of the present embodiment 1 is usually a fiber sheet made of fibers. When the fiber base material 11 is a fiber sheet, it may be a nonwoven fabric or a woven fabric. The thickness, configuration, physical properties / properties, etc. of the fiber base material 11 of the present embodiment 1 will be described below.

[0031] 1-2-1. Thickness The thickness of the fiber base material 11 of the present embodiment 1 can be 0.03 mm to 50.00 mm. This thickness is preferably 0.05 mm or more, 0.10 mm or more, 0.20 mm or more, 0.50 mm or more, 0.75 mm or more, 1.00 mm or more, and is preferably 40.00 mm or less, 30.00 mm or less, 20.00 mm or less, 10.00 mm or less, 5.00 mm or less, 4.00 mm or less, 3.00 mm or less, 2.00 mm or less, etc.

[0032] 1-2-2.Configuration (Constituent fibers) The fibers constituting the fiber substrate 11 of the first embodiment are not particularly limited, and known fibers can be used. For example, depending on the application, they can be selected from metal fibers, organic fibers, inorganic fibers, and the like. More specifically, they may be selected from metal fibers such as stainless steel fibers, nickel fibers, copper fibers, aluminum fibers, silver fibers, gold fibers, and titanium fibers; organic fibers such as polyolefin resins such as polyparaphenylene benzoxazole, polyethylene terephthalate (PET) resin, polyvinyl alcohol (PVA), polyethylene, and polypropylene, polyvinyl chloride resin, aramid resin, acrylic resin, polyimide resin, polyparaphenylene benzoxazole (PBO) fiber, polyphenylene sulfide (PPS) fiber, cellulose, vinylon, nylon, rayon, aramid, phenolic fiber, fluorine fiber, pulp (fiber), kenaf, hemp, and bamboo fiber; and inorganic fibers such as glass fiber, carbonized fiber, silica fiber, rockwool, slag wool, alumina fiber, and ceramic fiber. Among these, carbonized fibers and phenolic fibers are preferred in consideration of the flame retardancy of the fiber substrate, as described below.

[0033] Carbonized fiber generally refers to fiber made by carbonizing organic fiber in an inert gas, and more specifically, fiber made by carbonizing acrylic fiber or pitch (a by-product of petroleum, coal, coal tar, etc.). Among these, fibers with a relatively high degree of carbonization of 90-98% or more are called carbon fibers.

[0034] (components other than fiber) The fiber base material 11 of the first embodiment may contain, for example, a flame retardant as a component other than the fiber. The component (flame retardant) other than the fiber contained in the fiber base material will be described below.

[0035] In the present embodiment 1, even if the above-mentioned fiber does not satisfy the flame retardancy evaluation described below, as long as the addition of a flame retardant enables the fiber base material 11 to satisfy the flame retardancy evaluation described below, the fiber can be used to manufacture the fiber base material 11 of the present embodiment 1. That is, the fiber base material 11 of the present embodiment 1 is preferably made of a fiber to which a flame retardant has been added.

[0036] When the fiber substrate 11 of the first embodiment contains a flame retardant as a component other than the fibers, the flame retardant is not particularly limited, and any known flame retardant can be used. Examples of the flame retardant include phosphate ester flame retardants such as triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, diethyl phenyl phosphonate, dimethyl phenyl phosphonate, and resorcinol diphenyl phosphate, and inorganic flame retardants such as magnesium hydroxide and aluminum hydroxide.

[0037] 1-2-3.Physical properties / properties (Flame retardant) The fiber base material 11 of the present embodiment 1 preferably has a flame retardancy rating of V-0 to V-2 based on the vertical flame test UL94 in accordance with ASTM D3801. If the flame retardancy rating is V-0 to V-2, a composite with excellent flame retardancy can be obtained.

[0038] (Ventilation rate) The air permeability of the fiber base material 11 of the first embodiment is 0.01 cm 3 / cm 2 / sec or more, 0.5cm 3 / cm 2 / sec or more, 10cm 3 / cm 2 / sec or more or 25cm 3 / cm 2 / sec or more. The upper limit of the air permeability is not particularly limited, as the higher the better. The upper limit of the air permeability of the fiber base material 11 is, for example, 300 cm 3 / cm 2 The measured air permeability of the fiber base material 11 may be 0.01 cm / sec or less. 3 / cm 2 / sec or more, it is determined that the fiber base material 11 has a certain degree of breathability.

[0039] Especially 10cm 3 / cm2 / sec or more, the fiber base material 11 does not require time-consuming evacuation in the sol solution filling step described below, making it possible to produce the fiber base material 11 efficiently.

[0040] Such air permeability can be measured by a known method and is not particularly limited, for example, by the method described in JIS L1096-7:2010 "Testing methods for woven and knitted fabrics: Method A (Fragile method)."

[0041] (density) The density of the fiber base material 11 of the first embodiment is 0.020 g / cm 3 More than 0.030g / cm 3 More than 0.040g / cm 3 More than 0.050g / cm 3 More than 0.075g / cm 3 More than 0.100g / cm 3 More than 0.120g / cm 3 More than 0.375 g / cm 3 Below, 0.3250g / cm 3 Below, 0.340g / cm 3 Below, 0.330g / cm 3 Below, 0.320g / cm 3 Below, 0.3210g / cm 3 Below, 0.300g / cm 3 The following are preferable: By setting the density of the fiber base material 11 within the above range, it is possible to obtain a composite having excellent flexibility while controlling the filling amount of the aerogel so as to achieve excellent heat insulation properties.

[0042] (porosity) The porosity of the fiber base material 11 of the present embodiment 1 is not particularly limited, and may be, for example, 50 to 99%, more preferably 65 to 99%, and even more preferably 85 to 99%. When the porosity is within this range, a composite with superior heat insulating properties can be provided.

[0043] (others) The fiber base material 11 of the present embodiment 1 has an average fiber diameter of 2 to 30 μm, and a basis weight of 5 to 300 g / m 2 or 5 to 200 g / m 2 etc.

[0044] 1-3.Coating layer As described above, the coating layer 13 of the first embodiment covers at least a part of the surface of the fiber substrate 11 whose voids are filled with the aerogel 12. By coating the fiber substrate 11 with the coating layer 13, it is possible to prevent the aerogel particles from falling off.

[0045] In this embodiment 1, the entire surface of the fiber substrate 11 may be coated with the coating layer 13, or only a portion (for example, one side) of the fiber substrate 11 may be coated. FIG. 1 shows an example in which only one side of the fiber substrate 11 is coated with the coating layer 13. Considering that the aerogel particles can be further prevented from falling off, it is preferable to coat the entire surface of the fiber substrate 11 with the coating layer 13.

[0046] 1-3-1. Thickness The thickness of the coating layer 13 in the present embodiment 1 is preferably 200 μm or less. There is no particular lower limit, and the thickness is preferably, for example, 10 μm or more, 20 μm or more, 30 μm or more, etc. By setting the thickness of the coating layer 13 within the above range, it is possible to prevent the aerogel particles from falling off.

[0047] 1-3-2.Material The material of the coating layer 13 in the present embodiment 1 is not particularly limited, and any known material can be used as long as it can cover the surface of the fiber base material 11. The material of the coating layer 13 is preferably one or more selected from the group consisting of thermoplastic resins and energy ray-curable elastomers.

[0048] The thermoplastic resin is not particularly limited, and known materials can be used. Examples include polyethylenes such as ethylene-vinyl acetate copolymer (EVA) resin, ethylene-acrylic acid copolymer (EAA) resin, ethylene-methyl acrylate copolymer (EMA) resin, ethylene-methyl methacrylate copolymer (EMMA) resin, and ethylene-methacrylic acid copolymer (EMAA); polyolefins such as polypropylene and polyethylene; styrene-based synthetic rubbers such as styrene-isoprene block copolymer (SI) rubber, styrene-isoprene-styrene block copolymer (SIS) rubber, and polystyrene-polybutadiene block copolymer resin; polyamide (nylon) resin; polyesters such as polyethylene terephthalate; and polyurethanes such as thermoplastic polyurethane (TPU). These can be used alone or as mixtures, copolymers, and polymer alloys. Among these, thermoplastic resins formed from one or more selected from polyolefins, polyesters, and polyurethanes are preferred.

[0049] The energy ray-curable elastomer is not particularly limited as long as it can be cured using energy rays such as ultraviolet rays (UV), electron beams (EB), sunlight, fluorescent light, LED light, etc. Examples include UV-curable elastomers.

[0050] 1-3-3.Physical properties / properties (softening point) When a thermoplastic resin is used for the coating layer 13, the softening point of the thermoplastic resin is preferably 60°C or higher, 80°C or higher, or 90°C or higher, and is preferably 125°C or lower, 120°C or lower, or 115°C or lower. If the softening point of the thermoplastic resin is within this range, the thermoplastic resin softens when the fiber substrate 11 is coated with the coating layer 13 by heat lamination, thereby further strengthening the adhesion to the fiber substrate 11. Furthermore, by heating to the above temperature, the thermoplastic resin softens, allowing the desired portion of the fiber substrate 11 to be reliably coated with the thermoplastic resin.

[0051] The softening point can be measured by any known method without any particular limitation, for example, a method according to JIS K6863-1994 "Test method for softening point of hot melt adhesives."

[0052] (Tensile elongation at break) The coating layer 13 preferably has a tensile breaking elongation of 200% or more, 300% or more, 400% or more, 500% or more, 600% or more, etc. By setting the tensile breaking elongation of the coating layer 13 within the above range, when a thermal insulating material including the composite 10 is applied to a curved portion, cracks or the like do not occur on the surface, and the thermal insulating material can exhibit better conformability to the curved portion.

[0053] The method for measuring the tensile elongation at break can be any known method and is not particularly limited. For example, the tensile elongation at break can be measured according to JIS K6251:2017 "Vulcanized rubber and thermoplastic rubber - Determination of tensile properties."

[0054] 1-3-4.Other The composite 10 of the first embodiment may contain an adhesive or the like between the components described above or on at least a portion of the surface of the coating layer 13. The adhesive is not particularly limited, and various known adhesives can be used. Examples include heat-curable and ultraviolet-curable adhesives. More specifically, examples of such adhesives include rubber-based, acrylic-based, urethane-based, silicone-based, and polyvinyl ether-based adhesives.

[0055] 2. Manufacturing method of the composite The manufacturing method of the composite 10 of this embodiment 1 includes a coating step of forming a coating layer 13 that covers at least a portion of the fiber substrate 11, a filling step of filling the fiber substrate 11 coated with the coating layer 13 with a sol solution, which is a raw material for aerogel, under normal pressure or reduced pressure, a gelling step of gelling the sol solution filled in the fiber substrate 11, and a drying step of drying the wet gel.

[0056] Each step will be described in detail below. The method for producing the composite 10 of the first embodiment may further include steps other than those described below. While the first embodiment illustrates an example in which the coating step is performed before the filling step, the present invention is not limited to this, and the coating step may be performed after the drying step. The coating step is preferably performed before the filling step. The coating layer 13 formed in the coating step can prevent the aerogel particles from falling off after the filling step, allowing the composite 10 to exhibit higher thermal insulation performance.

[0057] 2-1.Coating process In the coating step, a coating layer 13 is formed to cover at least a portion of the fiber substrate 11 described in "1-2. Fiber substrate." The fiber substrate 11 may be a commercially available product. When a thermoplastic resin is used as the material for the coating layer 13, a heat lamination method is preferred as a method for forming the coating layer 13 on the fiber substrate 11. The heat lamination method is a method in which a heating device such as an iron is heated to a predetermined temperature to press and coat the fiber substrate 11 and a film formed of a thermoplastic resin (e.g., a hot melt film). The heating device is not particularly limited, and in addition to an iron, a heat press, a heat roll, an infrared heater, or the like can be used.

[0058] In the heat lamination method, the heating temperature is preferably the melting point of the hot melt film + 20°C, and can be, for example, in the range of 180°C to 200°C, or in the range of 120°C to 150°C, etc. By heating at a temperature in this range, the hot melt film is appropriately softened and can coat the fiber base material 11.

[0059] An energy ray-curable elastomer can also be used to form the coating layer 13. When a UV-curable elastomer is used as the energy ray-curable elastomer, the coating layer 13 can be formed by applying a raw material of the UV-curable elastomer to the surface of the fiber substrate 11 and curing the coating film by irradiating it with ultraviolet rays.

[0060] 2-2. Filling process In the filling step, the fiber substrate 11 coated with the coating layer 13 is filled with a sol solution, which is a raw material for the aerogel, under normal pressure or reduced pressure. Details will be described below using silica aerogel, which is a suitable example of the aerogel, as an example, but the present embodiment 1 is not limited to only silica aerogel.

[0061] 2-2-1.Sol solution Silicone alkoxide or its derivatives or alkali metal silicate can be used as the silicone raw material for silica aerogel, and is mixed with an aqueous solvent to form a sol solution.

[0062] The silicone raw material is not particularly limited as long as it exhibits the effects of the present invention. Examples of silicone alkoxides and derivatives thereof include tetramethoxysilane, tetraethoxysilane, tetramethoxysilane oligomer, tetraethoxysilane oligomer, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, hexyltrimethoxysilane, and monohexyltriethoxysilane. Examples of alkali metal silicates include potassium silicate and sodium silicate. A combination of multiple silicone raw materials can be used. When multiple materials are used, the combination and blending ratio can be selected according to the purpose.

[0063] For the hydrolysis of the silicone raw material, it is preferable to use water and a solvent that is compatible with water and dissolves the silicone raw material. Examples of the solvent include alcohols such as methanol, ethanol, isopropanol, and butanol; aliphatic diols such as ethanediol, propanediol, butanediol, diethylene glycol, dipropylene glycol, polyethylene glycol, and polypropylene glycol; aromatic diols or alicyclic diols such as hydrogenated bisphenol A, bisphenol A, and cyclohexanediol; polyhydric alcohols such as glycerin, diglycerin, trimethylolpropane, trishydroxymethylaminopentane, pentaerythritol, dipentaerythritol, and hexamethylolmelamine; hexane, toluene, chloroform, diethyl ether, tetrahydrofuran, ethyl acetate, acetone, and acetonitrile. These solvents may be used alone or in combination of two or more.

[0064] In order to efficiently hydrolyze the silicone raw material, it is preferable to add a catalyst to the reaction system in advance. The catalyst is not particularly limited, and examples thereof include acidic catalysts such as formic acid, acetic acid, succinic acid, malic acid, citric acid, hydrochloric acid, nitric acid, boric acid, sulfuric acid, carbonic acid, and phosphoric acid, and basic catalysts such as metal oxides and / or hydroxides such as sodium hydroxide and potassium hydroxide, aliphatic and / or aromatic amines such as dimethylamine, triethylamine, N,N-dimethylbenzylamine, aniline, and 1,5-naphthalenediamine, ammonia, naphthenic acids of divalent metals, and hydroxides of divalent metals. These catalysts may be used alone or in combination of two or more.

[0065] 2-2-2. Filling method The method of filling the sol solution is not particularly limited as long as it is carried out under normal pressure or reduced pressure, and any known method can be used. For example, the fiber substrate 11 obtained by the above-mentioned method can be filled by completely immersing it in the prepared sol solution under reduced pressure. In particular, when the air permeability is 10 cm 3 / cm 2 / sec or more, filling under normal pressure is possible.

[0066] Specifically, taking a sol solution prepared by mixing tetramethoxysilane (hereinafter referred to as TMOS), methanol, water, and catalyst (ammonia) in a molar ratio of 1:7.2:4:0.01 as an example, a fiber substrate 11 coated with a coating layer 13 is placed in a separable flask, and the sol solution is gradually introduced to completely immerse the fiber substrate 11 in the sol solution, thereby filling the fiber substrate 11 with the sol solution. The mixture is left as is for 2 to 3 hours until gelation occurs.

[0067] 2-3.Gelling process In the gelation process, the sol solution filled in the fiber substrate is gelled. In the sol solution filled in the fiber substrate 11, TMOS is hydrolyzed by water and a catalyst through a sol-gel reaction, and the sol state is transformed into a wet gel. Here, the wet gel refers to a solid that still contains liquid, such as the residual liquid of the sol solution after gelation.

[0068] A wet gel is formed inside the voids in the fiber base material 11 by a sol-gel reaction caused by hydrolysis of the silicone alkoxide or its derivative.

[0069] After forming the wet gel, a process for removing water and unreacted materials from the wet gel may be performed. Examples of solvents used in this process include alcohols such as methanol, ethanol, isopropanol, and butanol, as well as acetone and acetonitrile. The process is completed by immersing the fiber substrate 11 filled with the wet gel in the solvent and replacing the solvent with fresh solvent several times.

[0070] The method may include a step of hydrophobizing the OH groups on the silica aerogel surface using a hydrophobizing agent having a functional group reactive with hydrophilic silanol groups and a hydrophobic group. The hydrophobizing agent used has a functional group reactive with silanol groups and a hydrophobic group. Examples of functional groups reactive with silanol groups include halogens, amino groups, imino groups, carboxyl groups, alkoxyl groups, and hydroxyl groups. Examples of hydrophobic groups include alkyl groups, phenyl groups, and fluorides thereof. The hydrophobizing agent may have only one type of functional group and one type of hydrophobic group, or two or more types. Examples of the hydrophobic treatment agent include organic silane compounds such as hexamethyldisilazane, hexamethyldisiloxane, trimethylchlorosilane, trimethylmethoxysilane, trimethylethoxysilane, triethylethoxysilane, triethylmethoxysilane, dimethyldichlorosilane, dimethyldiethoxysilane, methyltrichlorosilane, and ethyltrichlorosilane, and other organic compounds such as carboxylic acids such as acetic acid, formic acid, and succinic acid, and alkyl halides such as methyl chloride. Only one type of hydrophobic treatment agent may be used, or two or more types may be used.

[0071] A coupling agent may be added to increase the adhesion between the aerogel 12 and the fiber substrate 11 and prevent the aerogel from falling off. The coupling agent is not particularly limited as long as it can react with the silanol groups on the aerogel surface, and any suitable coupling agent can be used. Examples of suitable coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, and tris-(trimethoxysilylpropyl)isocyanurate.

[0072] 2-4.Drying process In the drying step, the wet gel is dried. Known drying methods can be used and are not particularly limited. When drying the wet gel, supercritical fluid drying is preferred because the silica aerogel is less likely to break. Examples of supercritical fluid drying include a method in which the entire solvent is removed while being replaced with carbon dioxide, which has a lower critical point than the solvent, under conditions of 80°C and approximately 20 MPa.

[0073] [Embodiment 2] Hereinafter, a description will be given of the second embodiment. The same content as in the first embodiment will not be described. The second embodiment differs from the first embodiment in the coating step for forming a coating layer. More specifically, in the coating step of the first embodiment, a resin is laminated onto a fiber substrate to form a coating layer. In contrast, in the coating step of the second embodiment, the surface of a fiber substrate containing multiple types of fibers and / or fibers and a resin (binder) is heated to form a coating layer with the melted and solidified fibers and / or resin.

[0074] This embodiment 2 includes two forms that differ in the structure of the fiber substrate used. That is, this embodiment 2 includes a case where a fiber substrate containing multiple types of fibers is used (embodiment 2A), and a case where a fiber substrate containing fibers and a resin (binder) is used (embodiment 2B). Hereinafter, as examples of this embodiment 2, embodiment 2A and embodiment 2B will be described separately.

[0075] [Embodiment 2A: When a fiber substrate containing multiple types of fibers is used] 3. Complex Fig. 2 is a schematic cross-sectional view showing a composite of this embodiment 2A. As shown in Fig. 2, a composite 20a of this embodiment 2A includes a fiber base material 21a, an aerogel 22a filled in voids in the fiber base material 21a, and a coating layer 23a covering at least a portion of the surface of the fiber base material 21a.

[0076] In the composite 20a of this embodiment 2A, the average filling rate of the aerogel 22a occupying the voids in the fiber base material 21a, the thickness, and the thermal conductivity are the same as those of the composite 10 of the above-mentioned embodiment 1. The aerogel 22a of this embodiment 2A is also the same as the aerogel 12 of embodiment 1. The fiber base material 21a and the coating layer 23a that constitute the composite 20a will be described in detail below.

[0077] 3-1. Fiber base material The fiber base material 21a of this embodiment 2A is usually a fiber sheet made of fibers. When the fiber base material 21a is a fiber sheet, it may be a nonwoven fabric or a woven fabric. The configuration of the fiber base material 21a of this embodiment 2A will be described below.

[0078] 3-1-1.Configuration The fiber base material 21a of this embodiment 2A is composed of the same fibers as those of embodiment 1. The fiber base material 21a may further contain a type of fiber different from the above-mentioned fibers. That is, the fiber base material 21a may contain multiple types of fibers. When the fiber base material 21a contains multiple types of fibers, it is preferable that the fiber base material 21a contains fibers that melt at a lower temperature than the above-mentioned fibers, i.e., fibers with a low melting point. Low melting point fibers refer to fibers with a melting point of 300°C or less, 200°C or less, 100°C or less, for example.

[0079] It is not necessary for the low-melting-point fibers among the multiple types of fibers to be evenly distributed throughout the fiber base material 21a, but they are preferably contained at least on the surface side of the fiber base material 21a, i.e., on the side where the coating layer 23a is formed.

[0080] The low-melting-point fibers contained in the fiber substrate 21a of this embodiment 2A are not particularly limited, and known fibers can be used. As described above, considering that the coating layer 23a is formed by melting the fibers with heat, fibers made of thermoplastic resin are preferred. Examples of low-melting-point fibers include polyparaphenylene benzoxazole; polyester resins such as polyethylene terephthalate (PET); polyolefin resins such as polyvinyl alcohol (PVA), polyethylene, and polypropylene; polyvinyl chloride resin; aramid resin; acrylic resin; polyimide resin; and organic fibers such as polyparaphenylene benzoxazole (PBO) fiber and polyphenylene sulfide (PPS) fiber. These can be used alone or in combination.

[0081] 3-2.Coating layer The coating layer 23a of this embodiment 2A covers at least a portion of the surface of the fiber base material 21a. As described above, the coating layer 23a is formed by melting and solidifying low-melting-point fibers contained in the fiber base material 21a. Therefore, the coating layer 23a preferably includes the melt-solidified low-melting-point fibers and some of the other fibers that make up the fiber base material 21a. Furthermore, the material of the coating layer 23a is preferably the same as that of the low-melting-point fibers contained in the fiber base material 21a described above.

[0082] 4. Manufacturing method of the composite A method for producing the composite 20a of this embodiment 2A will be described below. The method for producing the composite 20a of this embodiment 2A includes a coating step of heating the surface of a fiber base material 21a containing multiple types of fibers to melt low-melting-point fibers among the multiple types of fibers and forming a coating layer 23a made of the low-melting-point fibers on the surface of the fiber base material 21a, a filling step of filling the fiber base material 21a coated with the coating layer 23a with a sol solution, which is a raw material for aerogel, under normal pressure or reduced pressure, a gelling step of gelling the sol solution filled in the fiber base material 21a, and a drying step of drying the wet gel.

[0083] Each step will be described in detail below. The method for producing the composite 20a of this embodiment 2A may further include steps other than those described below. In this embodiment 2A, the coating step is performed before the filling step, but the present invention is not limited to this, and the coating step may be performed after the drying step. The coating step is preferably performed before the filling step. The coating layer 23a formed in the coating step can prevent the aerogel particles from falling off after the filling step, allowing the composite 20a to exhibit higher thermal insulation performance. The filling step, gelling step, and drying step are the same as those in embodiment 1.

[0084] 4-1.Coating process In the covering step, a fiber base material 21a containing multiple types of fibers is prepared, and the surface of the fiber base material 21a containing multiple types of fibers is heated. The fiber base material 21a containing multiple types of fibers may be commercially available.

[0085] More specifically, the surface of the fiber base material 21a is heated by a heat press at 200°C for 10 seconds to melt some of the low-melting-point fibers among the multiple types of fibers present on the surface of the fiber base material 21a. The low-melting-point fibers melted on the surface of the fiber base material 21a solidify on the surface of the fiber base material 21a, forming the coating layer 23a.

[0086] That is, in the second embodiment, a fiber base material 21a containing low-melting-point fibers is used, and the low-melting-point fibers that are part of the fiber base material 21a are melted and solidified to form the coating layer 23a. Therefore, unlike the first embodiment, it is not necessary to form the coating layer by pressing (laminating) a separate member (see "2. Manufacturing method of the composite" in the first embodiment), and therefore the adhesion between the coating layer 23a and the fiber base material 21a can be further improved.

[0087] [Embodiment 2B: When a fiber substrate containing fiber and resin (binder) is used] 5. Complex Fig. 3 is a schematic cross-sectional view showing a composite of embodiment 2B. As shown in Fig. 3, composite 20b of embodiment 2B includes a fiber base material 21b, aerogel 22b filled in voids in the fiber base material 21b, and a coating layer 23b covering at least a portion of the surface of the fiber base material 21b.

[0088] In the composite 20b of this embodiment 2B, the average filling rate of the aerogel 22b occupying the voids in the fiber base material 21b, the thickness, and the thermal conductivity are the same as those of the composite 10 of the above-mentioned embodiment 1. The aerogel 22b of this embodiment 2B is also the same as the aerogel 12 of embodiment 1. The fiber base material 21b and the coating layer 23b constituting the composite 20b will be described in detail below.

[0089] 5-1. Fiber base material The fiber base material 21b of this embodiment 2B is usually a fiber sheet made of fibers. When the fiber base material 21b is a fiber sheet, it may be a nonwoven fabric or a woven fabric. The configuration of the fiber base material 21b of this embodiment 2B will be described below.

[0090] 5-1-1.Configuration The fiber base material 21b of this embodiment 2B is composed of the same fibers as those of embodiment 1. In addition to the above-mentioned fibers, the fiber base material 21b of this embodiment 2B may contain a resin (binder) such as a thermoplastic resin. The resin (binder) does not need to be contained evenly throughout the fiber base material 21b. It is preferable that the resin (binder) be contained at least on the surface side of the fiber base material 21b, i.e., the side on which the coating layer 23b is formed.

[0091] The resin (binder) contained in the fiber substrate 21b of this embodiment 2B is not particularly limited, and known resins can be used. As described above, considering that the coating layer 23b is formed by melting the resin with heat, a thermoplastic resin is preferred. Examples of thermoplastic resins include polyethylenes such as ethylene-vinyl acetate copolymer (EVA) resin, ethylene-acrylic acid copolymer (EAA) resin, ethylene-methyl acrylate copolymer (EMA) resin, ethylene-methyl methacrylate copolymer (EMMA) resin, and ethylene-methacrylic acid copolymer (EMAA); polyolefins such as polypropylene and polyethylene; styrene-based synthetic rubbers such as styrene-isoprene block copolymer (SI) rubber, styrene-isoprene-styrene block copolymer (SIS) rubber, and polystyrene-polybutadiene block copolymer resin; polyamide (nylon) resin; polyesters such as polyethylene terephthalate; and polyurethanes such as thermoplastic polyurethane (TPU). These resins can be used alone or as mixtures, copolymers, or polymer alloys. Of these, polyester resins are preferred.

[0092] 5-2.Coating layer The coating layer 23b of this embodiment 2B covers at least a portion of the surface of the fiber base material 21b. As described above, the coating layer 23b of this embodiment 2B is formed by melting and solidifying the resin (binder) contained in the fiber base material 21b. Therefore, the coating layer 23b preferably contains the melted and solidified resin (binder) and some of the fibers that make up the fiber base material 21b. Furthermore, the material of the coating layer 23b is preferably the same as the resin contained in the fiber base material 21b described above.

[0093] 6. Manufacturing method of the composite A method for producing the composite 20b of this embodiment 2B is described below. The method for producing the composite 20b of this embodiment 2B includes the following steps: a preparation step of preparing a fiber substrate 21b containing fibers and a resin (binder) (e.g., a thermoplastic resin), a coating step of heating the surface of the fiber substrate 21b containing fibers and a resin to melt the resin and form a resin coating layer 23b on the surface of the fiber substrate 21b, a filling step of filling the fiber substrate 21b coated with the coating layer 23b with a sol solution, which is a raw material for an aerogel, under normal pressure or reduced pressure, a gelation step of gelling the sol solution filled in the fiber substrate 21b, and a drying step of drying the wet gel.

[0094] Each step will be described in detail below. The method for producing the composite 20b of this embodiment 2B may further include steps other than those described below. In this embodiment 2B, the coating step is performed before the filling step, but the present invention is not limited to this, and the coating step may be performed after the drying step. The coating step is preferably performed before the filling step. The coating layer 23b formed in the coating step can prevent the aerogel particles from falling off after the filling step, allowing the composite 20b to exhibit higher thermal insulation performance. The filling step, gelling step, and drying step are the same as those in embodiment 1.

[0095] 6-1. Preparation process In the preparation step, a fiber substrate containing fibers and a thermoplastic resin (binder) is prepared. In the step of preparing the fiber substrate 21b containing fibers and a thermoplastic resin, for example, the fiber substrate 21b is preferably prepared by mixing the fibers constituting the fiber substrate described in "1-2. Fiber substrate" with a thermoplastic resin as a binder. Alternatively, the fiber substrate 21b may be prepared by impregnating at least a portion of the fibers constituting the fiber substrate described in "1-2. Fiber substrate" with a thermoplastic resin.

[0096] The thermoplastic resin does not need to be mixed or impregnated evenly throughout the fiber base material 21b, and considering that the thermoplastic resin contained in the fiber base material 21b is melted to form the coating layer 23b in the coating step described below, it is preferable to mix or impregnate the thermoplastic resin at least near the surface side of the fiber base material 21b. Furthermore, the portion of the surface of the fiber base material 21b where the thermoplastic resin is mixed or impregnated can be appropriately adjusted, taking into account the portion of the surface of the fiber base material 21b that is to be covered with the coating layer 23b.

[0097] 6-2.Coating process In the coating process, the surface of the fiber base material 21b containing fibers and a thermoplastic resin (binder) is heated. The thermoplastic resin is melted and solidified by the heating, and a coating layer 23b made of the thermoplastic resin is formed on the surface of the fiber base material 21b.

[0098] More specifically, the surface of the fiber base material 21b is heat-pressed at 200°C for 10 seconds to melt a portion of the thermoplastic resin present on the surface of the fiber base material 21b. The molten thermoplastic resin solidifies on the surface of the fiber base material 21b to form a coating layer 23b made of thermoplastic resin.

[0099] As described above, in this embodiment 2B, a fiber base material 21b containing a thermoplastic resin is used, and the thermoplastic resin that is part of the fiber base material 21b is melted and solidified to form the coating layer 23b. Therefore, unlike in the embodiment 1, it is not necessary to form the coating layer by pressure bonding (laminating) a separate member (see "2. Manufacturing method of the composite" in the embodiment 1), and therefore the adhesion between the coating layer 23b and the fiber base material 21b can be further improved.

[0100] As described above, in this second embodiment, the case where a fiber substrate containing multiple types of fibers is used (Embodiment 2A) and the case where a fiber substrate containing fibers and a resin (binder) is used (Embodiment 2B) are described, but this embodiment is not limited to these aspects. For example, in addition to the multiple types of fibers and resin described above, the fiber substrate may contain a component (material) that can melt and solidify when heated to form a coating layer. Also, a fiber substrate containing both the multiple types of fibers and resin described above may be used.

[0101] Although the first and second embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations can also be adopted. For example, in the first and second embodiments, an example in which a coating layer is formed on only one side of the fiber substrate has been shown, but it may be formed on both sides. When forming coating layers on both sides, the entire fiber substrate may be coated at once by lamination. Alternatively, the main surface and the other surface may be coated separately. In the first and second embodiments, another layer such as an adhesive (e.g., double-sided tape) may be provided on at least a portion of the coating layer of the obtained composite. [Example]

[0102] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the embodiments of the following examples.

[0103] <<Examples and Comparative Examples>> The composites of each example and comparative example were prepared by coating the surface of the fiber substrate with a coating layer and filling it with aerogel using the method described below. In each example and comparative example, the fibers constituting the fiber substrate and the material (coating material) of the coating layer were as shown in Table 2 below. The density and thickness of the fiber substrate used in each example and comparative example are also shown in Tables 1 and 2 below.

[0104] <Production of the composite> (fiber substrate) The fiber substrates used in each of the examples and comparative examples are shown in Table 1 below. [Table 1] *1: Carbonized fiber 2 is a carbonized fiber containing polyester resin as a binder. *2: The flame retardant in flame retardant-containing polyester fiber is a phosphoric acid-based flame retardant. (raw material for silica aerogel) Silicone raw materials Tetrafunctional ethoxysilane oligomer (average pentamer) (solvent) Ethanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Ion-exchanged water, electrical resistivity 1 x 10 10 Ω cm or more (catalyst) 25% ammonia water (Fujifilm Wako Pure Chemical Industries, Ltd.)

[0105] (Coating process) For each of Examples 1 to 3 and 5 to 7, a hot melt film (polyester, 100 μm, tensile elongation at break 400%, flame retardancy: horizontal flame test UL94 HF-1) was laminated as a covering material on the surface of a fiber substrate (50 mm × 25 mm × 2.0 mm thick) composed of the constituent fibers shown in Table 2 below, and heat lamination was performed by pressing with an iron at a temperature of 200°C for 5 seconds, to cover the entire surface of the fiber substrate with a covering layer. The thickness of the covering layer was 50 μm.

[0106] In Example 4, carbonized fiber 2 (carbonized fiber containing polyester resin as a binder) (50 mm × 25 mm × 1.8 mm in thickness) was used as the fiber substrate, and the surface of the fiber substrate was heat-pressed at 200°C for 10 seconds to melt part of the polyester resin present on the surface of the fiber substrate. The molten resin formed a resin coating layer on the surface of the fiber substrate.

[0107] In Comparative Examples 1 and 2, no coating layer was formed.

[0108] As shown in Table 2 below, the coating layer used in Examples 1 to 3 and 5 to 7 was a hot melt film (polyester-based, 100 μm, tensile breaking elongation 400%, flame retardancy: horizontal burning test UL94 HF-1), while in Example 4 it was a polyester resin, and in Example 5 it was a UV-curable elastomer synthesized by the following method.

[0109] (Synthesis of raw material (urethane prepolymer) for UV-curable elastomers) While nitrogen was flowing through the three-way stopcock, 29.24 parts by weight of polyisocyanate (HMDI) was charged into the flask. Next, while stirring and flowing nitrogen, 55.74 parts by weight of polyol (20% polypropylene glycol EO, weight-average molecular weight: 1000, average functionality: 2) was added dropwise, taking care not to overheat the reaction. After the addition was complete, 0.3 g of a catalyst (dibutyltin dilaurate (DBTDL), 0.3 g) was added while stirring for 30 minutes. After the reaction was allowed to proceed for 2 hours, a sample was taken and the isocyanate group content was confirmed to be the specified NCO%. Next, 14.24 parts by weight of an acrylate compound (2-hydroxyethyl methacrylate (HEMA)) was added dropwise. After 2 hours, a sample was taken and the isocyanate group content was confirmed to be 0.5% or less, marking the reaction complete. The resulting product was a urethane prepolymer, a raw material for UV-curable elastomers. (Tensile elongation at break in thin film state: 200%)

[0110] (Sol solution filling process) A silicone raw material was used as the base material, and 53 moles of ethanol, 21 moles of ion-exchanged water, and 0.01 moles of catalyst were mixed with 1 mole of the base material to prepare a sol solution. The above-mentioned fiber substrate was cut into pieces that could be stored in a separable flask and placed in the flask. The prepared sol solution was added until the fiber substrate was completely immersed, and the mixture was left to stand under normal pressure for 3 hours to obtain a fiber substrate filled with a wet gel.

[0111] The resulting wet gel-filled fiber substrate was immersed in ethanol and repeatedly exchanged with other ethanol while stirring for 24 hours. Next, to hydrophobize the gel surface, the substrate was immersed in an ethanol solution of hexamethyldisilazane (concentration: 15% by mass) containing 0.1 mol% aqueous hydrochloric acid as a catalyst, and hydrophobized for 24 hours while stirring.

[0112] (drying process) The fiber substrate with the hydrophobic gel surface was immersed in carbon dioxide at 80°C and 20 MPa, and then subjected to supercritical fluid drying for 12 hours to prepare composite samples for each of the examples and comparative examples.

[0113] <Testing and Evaluation> The composite samples of each example and comparative example were subjected to the following tests and evaluations. The evaluation results are shown in Table 2 below.

[0114] (thermal conductivity) The thermal conductivity of the composite samples of each example and comparative example was measured using a thermal conductivity measuring device (HC-72 manufactured by Eiko Seiki Co., Ltd.) based on JIS A 1412-2:1999 "Methods for measuring thermal resistance and thermal conductivity of thermal insulating materials - Part 2."

[0115] (Flame retardant) For the composite samples of each example and comparative example, a vertical flame test UL94 (based on ASTM D3801) and a flame test based on JIS K6400-6 "Flexible foam materials - Determination of physical properties - Part 6: Flammability" were carried out. Flame retardancy was evaluated based on the criteria of the vertical flame test UL94 (based on ASTM D3801). (Evaluation criteria) A+:V-0 A:V-1 B:V-2 C: Not classified

[0116] (Dust shedding) For the composite samples of each Example and Comparative Example, the weight loss rate after 1000 repeated 25% compression was calculated in accordance with JIS K6254:2016 "Vulcanized rubber and thermoplastic rubber - Determination of stress-strain characteristics." The weight loss rate was calculated using the following formula. The larger the weight loss rate, the worse the powder shedding properties, and the smaller the weight loss rate, the better the powder shedding properties. weight loss rate = {Weight before test (g) - Weight after test (g)} / {Weight before test (g)} x 100 (Evaluation criteria) A: Weight loss rate is less than 5% B: Weight loss rate is more than 5% and less than 10% C: Weight reduction rate is 10% or more

[0117] [Table 2] [Industrial Applicability]

[0118] The composite of the present invention has excellent flame retardancy and can prevent aerogel particles from falling off, and therefore can be used as a heat insulating material for automobiles, houses, etc. [Explanation of symbols]

[0119] 10 Complex 11 Fiber substrate 12 Aerogel 13 Covering layer

Claims

1. A fiber substrate; an aerogel filled in the voids of the fiber substrate; a coating layer that coats at least a portion of the fiber substrate; Equipped with The fiber substrate is a composite whose flame retardancy rating based on the vertical flame test UL94 satisfies V-0 to V-2.

2. The composite according to claim 1 , wherein the fiber substrate is made of at least one fiber selected from the group consisting of carbonized fiber, phenolic fiber, and fiber containing a flame retardant.

3. 2. The composite according to claim 1, wherein the coating layer is made of at least one material selected from the group consisting of thermoplastic resins and energy ray-curable elastomers.

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