Composite thermal insulation material comprising a layer of superabsorbent polymer

Abstract

The present invention provides a composite thermal insulation material, comprising: two or more felts each including a felt base and aerogels formed on the inside and surface of the felt base; and a superabsorbent polymer layer positioned between the two or more felts and containing superabsorbent polymer particles.

Description

Technical Field

[0001] Cross-reference to related applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2022-0085835, filed on July 12, 2022, the entire contents of which are incorporated herein by reference. Technical Field

[0004] This invention relates to composite insulation materials, and more particularly, to composite insulation materials that have improved insulation properties by including a superabsorbent polymer layer (SAP layer) between the felts used as insulation materials. Background Technology

[0005] Aerogels are highly porous materials with a porosity of about 90% to 99.9% and pore sizes ranging from 1 nm to 100 nm. They are used as high-efficiency insulation materials due to their high porosity and specific surface area, as well as their excellent insulation performance, which exhibits lower thermal conductivity than conventional organic insulation materials such as polystyrene foams.

[0006] Aerogels are produced by impregnating a felt substrate with a catalytic sol and then gelling it. In this case, in the case of aerogels such as silica aerogels, moisture in the air is adsorbed onto the surface of the felt through hydrophilic silanol groups present on the surface and penetrates into the interior, causing the thermal conductivity of the felt to increase due to moisture, and ultimately reducing its thermal insulation performance.

[0007] To address these issues, the hydrophilicity of the aerogel surface was modified to make it hydrophobic. However, even under these conditions, the problem of reduced thermal insulation performance was not resolved when the surface was exposed to moisture for an extended period of time.

[0008] Therefore, there is a need for a method that can minimize the reduction in the insulation performance of the felt even when moisture seeps into it. Summary of the Invention

[0009] Technical issues

[0010] In order to address the problems mentioned in the background art, the object of the present invention is to provide a composite insulation material that has improved insulation properties by positioning a superabsorbent polymer layer between felts where there is a risk of increased thermal conductivity due to moisture.

[0011] Technical solution

[0012] In one general aspect, the composite insulation material comprises: two or more felts, each of the two or more felts comprising a felt substrate and an aerogel formed on the interior and surface of the felt substrate; and a superabsorbent polymer layer positioned between the two or more felts and comprising superabsorbent polymer particles.

[0013] Beneficial effects

[0014] According to the composite insulation material of the present invention, the superabsorbent polymer particles contained in the superabsorbent polymer layer positioned between the felts have the property of absorbing moisture from the air. This property pre-absorbs moisture from the air that has penetrated into the felt, thereby maximizing the insulation effect. Furthermore, even when moisture has already penetrated into the felt, the composite insulation material itself maintains a low thermal conductivity by absorbing moisture.

[0015] Furthermore, because superabsorbent polymer particles swell upon absorbing moisture, they can protect the felt from moisture by absorbing and then swelling. This property acts as a protective film to prevent moisture from penetrating deeper into the composite insulation material. Attached Figure Description

[0016] Figure 1 A cross-sectional view of a composite insulation material according to an exemplary embodiment of the present invention is shown. Detailed Implementation

[0017] The terms and words used in the specification and claims of this invention should not be construed as having a general or dictionary meaning, but should be interpreted as having a meaning and concept that satisfies the technical concept of the invention, based on the principle that the inventor is able to appropriately define the concept of the terms in order to best describe his own invention.

[0018] The invention will be described in more detail below to aid in understanding it.

[0019] A composite insulation material according to an exemplary embodiment of the present invention may include: two or more felts, each of the two or more felts comprising a felt substrate and an aerogel formed on the interior and surface of the felt substrate; and a superabsorbent polymer layer positioned between the two or more felts and comprising superabsorbent polymer particles.

[0020] In two or more felts, the felt substrate included in the felt can be specifically a porous substrate to improve the thermal insulation performance of the felt. When the felt substrate is porous, the catalytic sol readily forms an aerogel on the interior and surface of the felt substrate to penetrate into the surface of the felt substrate and then into the interior of the felt substrate. Therefore, the aerogel can be uniformly formed into the interior of the felt substrate, thereby maximizing the thermal insulation effect of the felt and the composite insulation material including it.

[0021] The substrate for felt can be a film, sheet, web, fibrous matrix, nonwoven fabric, or a laminate of two or more layers thereof. Furthermore, depending on the application, its surface can have a roughness or can be patterned. More specifically, the substrate for felt can be a fibrous matrix whose thermal insulation properties can be further improved by incorporating aerogel through its easily embedded pores.

[0022] Specifically, the felt substrate can be polyamide, polybenzimidazole, polyaramid, acrylic resin, phenolic resin, polyester, polyetheretherketone (PEEK), polyolefin (e.g., polyethylene, polypropylene, or copolymers thereof), cellulose, carbon, cotton, wool, linen, nonwoven fabric, glass fiber, or ceramic wool. More specifically, the felt substrate of the present invention can include glass felt (glass fiber) suitable for thermal insulation materials due to its low thermal conductivity.

[0023] A felt according to an exemplary embodiment of the present invention may include aerogel formed on the interior and surface of a felt substrate. The aerogel may be formed on the felt substrate (i.e., pores formed from glass fibers), the pores being spaces formed due to the three-dimensional matrix structure of the glass fibers. Meanwhile, the aerogel formed on the interior and surface of the felt substrate can refer to aggregates of aerogel bonded to the felt substrate. Specifically, aerogel formed on the surface of the felt substrate means a state in which a portion of the aerogel is exposed on the outer surface of the felt and in contact with air, etc., while aerogel formed on the interior of the felt substrate can refer to aerogel that is not exposed on the outer surface of the felt but exists within the felt.

[0024] Furthermore, felts including aerogels formed on the interior and surface of the felt substrate can be produced by impregnating the felt substrate with a catalytic sol and allowing gelation to proceed.

[0025] First, the catalytic sol may comprise an alkaline catalyst and a sol. The sol is a material that forms a porous gel via a sol-gel reaction and may include inorganic sols, organic sols, or combinations thereof. Specifically, inorganic sols may include zirconium oxide, yttrium oxide, hafnium oxide, aluminum oxide, titanium oxide, cerium dioxide, silicon dioxide, magnesium oxide, calcium oxide, magnesium fluoride, calcium fluoride, and combinations thereof; organic sols may include polyacrylates, polyolefins, polystyrene, polyacrylonitrile, polyurethane, polyimide, polyfurfuryl alcohol, phenolic furfuryl alcohol, melamine-formaldehyde, resorcinol-formaldehyde, cresol-formaldehyde, phenol-formaldehyde, polyvinyl alcohol dialdehyde, polycyanurate, polyacrylamide, and combinations thereof. More specifically, in ensuring excellent adhesion to the felt substrate to ultimately achieve a felt with low thermal conductivity, the sol may include silica sol as an inorganic sol.

[0026] Specifically, silica sol can be prepared by mixing a silica precursor, water, and an organic solvent. The silica precursor may include compounds based on silicon-containing alkoxides. Specifically, the silica precursor may include tetraalkyl esters of silica, such as tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), trimethyl orthosilicate, dimethyl diethyl orthosilicate, tetrapropyl orthosilicate, tetraisopropyl orthosilicate, tetrabutyl orthosilicate, tetrasec-butyl orthosilicate, tetratert-butyl orthosilicate, tetrahexyl orthosilicate, tetracyclohexyl orthosilicate, and tetra-dodecyl orthosilicate; more specifically, it may include tetraethyl orthosilicate (TEOS).

[0027] The silica precursor can be used in an amount from 3% to 30% by weight of silica (SiO2) contained in the silica sol. When the silica content is less than 3% by weight, the amount of aerogel formed inside and on the surface of the felt substrate is too low, causing problems such as the insulation effect not being expected to reach the desired level. When the silica content exceeds 30% by weight, excessive aerogel formation may cause a reduction in the mechanical properties (especially the flexibility) of the felt.

[0028] In addition, the silica sol may contain organic solvents and water, and in terms of compatibility with the silica precursor and water, the organic solvent may be one or more of methanol, ethanol, isopropanol and butanol.

[0029] Meanwhile, the alkaline catalyst contained in the catalytic sol is a material that promotes gelation in the gelation step described below by increasing the pH of the sol. The alkaline catalyst can be an inorganic base (e.g., sodium hydroxide or potassium hydroxide) or an organic base (e.g., ammonium hydroxide). Specifically, the alkaline catalyst can be sodium hydroxide, ammonia, ammonium hydroxide, or a mixture thereof.

[0030] Therefore, a catalytic sol can be used to impregnate the felt substrate. In this case, impregnation can be carried out by adding a fluid catalytic sol to the felt substrate, which allows the catalytic sol to penetrate into the pores formed inside and on the surface of the felt substrate.

[0031] When a felt substrate is impregnated with a catalytic silica sol, gelation occurs, thus obtaining a wet gel fiber composite material. Gelation can be achieved by the formation of a network structure from the catalytic sol. This network structure can be a planar network structure in which certain polygons having one or more types of atomic arrangements are connected, or a structure that forms a three-dimensional skeleton structure by sharing the vertices, edges, and faces of a specific polyhedron.

[0032] Gelation can be achieved by impregnating a felt substrate with a catalytic sol and then allowing the impregnated substrate to stand for 0.5 to 2.0 hours, and can be carried out in a temperature range of 20°C to 50°C (preferably at room temperature).

[0033] Subsequently, the wet gel fiber composite material is allowed to stand at an appropriate temperature to mature, allowing for complete chemical changes. Maturation strengthens the resulting network structure, enhancing the insulation properties of the felt. Maturation can be achieved by allowing the wet gel fiber composite material to stand at a temperature between 30°C and 70°C for 3 to 50 hours.

[0034] In a felt according to an exemplary embodiment of the present invention, an aerogel can be formed on the interior and surface of the felt substrate by impregnating it with a catalytic sol, followed by gelation and curing. As described above, a low thermal conductivity is maintained immediately after the aerogel formed on the interior and surface of the felt substrate is dried. However, the aerogel is susceptible to moisture due to the hydrophilic functional groups present on its surface.

[0035] Hydroxyl functional groups present on the surface of aerogels (e.g., hydrophilic silanol groups (Si-OH) present on the surface of silica in the case of silica aerogels) absorb moisture from the air, thus resulting in a gradual increase in thermal conductivity.

[0036] Since the felt of the present invention is used as a thermal insulation material, the above-mentioned disadvantages may have a fatal impact. Therefore, in order to maintain low thermal conductivity, it is necessary to modify the surface of the aerogel to be hydrophobic and replace the hydrophilic functional groups present on the surface with hydrophobic functional groups.

[0037] To modify the surface of an aerogel to be hydrophobic, a surface modifier comprising a polar solvent and an organosilane compound can be used. The polar solvent can be methanol, ethanol, or isopropanol, and the organosilane compound can be trimethylchlorosilane (TMCS), hexamethyldisilazane (HMDS), methyltrimethoxysilane (MTMS), trimethylethoxysilane (TMES), ethyltriethoxysilane (ETES), or phenyltriethoxysilane (PTES), more specifically, trimethylethoxysilane or hexamethyldisilazane.

[0038] As described above, the aerogel formed by impregnating a felt substrate with a catalytic sol and then gelling it is surface modified and then dried, such that the aerogel may include hydrophobic functional groups formed on its surface. The silica aerogel according to an exemplary embodiment of the invention exhibits excellent thermal insulation properties by replacing the surface with hydrophobic functional groups, and the felt containing the silica aerogel ensures low thermal conductivity.

[0039] However, although the surface of the aerogel is replaced by hydrophobic functional groups, the thermal conductivity of the felt may eventually increase due to long-term exposure to moisture, leading to a decrease in insulation performance. Therefore, as described below, the composite insulation material of the present invention is provided with a superabsorbent polymer layer to prevent degradation due to moisture, i.e., a decrease in the insulation performance of the aerogel.

[0040] Furthermore, according to an exemplary embodiment of the present invention, the thermal conductivity deviation of the felt at a location within a felt can be 3.0 mW / m·K or less, preferably 2.0 mW / m·K or less, or 1.0 mW / m·K or less. In this case, felts with a value of 0 and no thermal conductivity deviation (i.e., felts with the same thermal conductivity within the felt) can also be included within the scope of the present invention.

[0041] In addition, the thickness deviation of the felt can be 1.5 mm or less, 1.2 mm or less, or 0.7 mm or less, preferably 0.5 mm or less.

[0042] Thermal conductivity deviation or thickness deviation are characteristics that may occur in cut felt; specifically, they can be within 0.01m. 2 Up to 10.0m 2 The area, more specifically, 0.36m 2 up to 5.0m 2 The difference between the values ​​measured in the regions where the two ends of the region are 30cm apart.

[0043] For example, for the thermal conductivity and thickness of the felt, multiple samples of a certain size are obtained from the felt at predetermined intervals, and the thermal conductivity of each sample is then measured at room temperature (23°C ± 5°C) using an HFM 436 Lambda instrument available from NETZSCH. The thermal conductivity can be represented by comparing the thermal conductivity values ​​measured in the region 30 cm apart from both ends of the multiple samples.

[0044] In this case, the number of samples in the felt can be varied depending on the length of the felt, and can be, for example, 2 to 20, 3 to 10, or 3 to 5.

[0045] Furthermore, according to an exemplary embodiment of the present invention, the felt may include an aerogel and a felt substrate. Specifically, the aerogel may be formed inside and on the surface of the felt substrate, or a large number of aerogel particles may be uniformly formed inside and on the surface of the felt substrate.

[0046] The felt can have an improved thermal conductivity ranging from 10 mW / m·K to 20 mW / m·K. Within this range, the effect of ensuring the maximum insulation performance of the felt can be achieved. The thermal conductivity is a value measured at room temperature (23°C ± 5°C) using an HFM 436 Lambda instrument available from NETZSCH, according to the heat flow method.

[0047] The felt included in the composite insulation material according to an exemplary embodiment of the present invention may include an aerogel, for example, in the case of silica aerogel, which, as mentioned above, has the disadvantage of gradually increasing thermal conductivity due to the absorption of moisture from the air by the hydrophilic silanol groups (Si-OH) present on the surface. Therefore, in order to maintain low thermal conductivity, the surface of the aerogel is typically modified to be hydrophobic.

[0048] As mentioned above, although the felt includes silica aerogel with a surface modified to be hydrophobic to maintain low thermal conductivity, it may not maximize the insulation effect. This is because while short-term exposure to moisture does not cause significant problems due to the hydrophobic treatment of the aerogel, moisture penetration caused by prolonged exposure eventually leads to a decrease in the insulation performance of the felt. Therefore, hydrophobic treatment may not be a fundamental solution to moisture problems.

[0049] Therefore, in a composite insulation material according to an exemplary embodiment of the present invention, the superabsorbent polymer layer is positioned between the felts such that the superabsorbent polymer particles contained in the superabsorbent polymer layer can absorb moisture from the air and moisture that permeates into the felt. Because the superabsorbent polymer particles have the property of absorbing moisture around them and swelling, the reduction in the insulation performance of the composite insulation material can be minimized.

[0050] Specifically, superabsorbent polymer particles may comprise a crosslinked polymer containing a water-soluble olefinic unsaturated monomer having at least partially neutralized acidic groups and an internal crosslinking agent. In this case, the water-soluble olefinic unsaturated monomer may comprise (meth)acrylic acid or a salt thereof. For example, when acrylic acid and / or its alkali metal salt, such as a sodium salt, are used as the water-soluble olefinic unsaturated monomer, superabsorbent polymer particles with improved absorbency can be obtained.

[0051] In addition, examples of water-soluble olefinically unsaturated monomers include those selected from one or more of the following: anionic monomers, such as maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloyl ethane sulfonic acid, 2-methacryloyl ethane sulfonic acid, 2-(meth)acryloyl propane sulfonic acid, or 2-(meth)acrylamide-2-methylpropane sulfonic acid, and their salts; nonionic hydrophilic monomers, such as (meth)acrylamide, N-substituted (meth)acrylates, 2-hydroxyethyl (meth)acrylates, 2-hydroxypropyl (meth)acrylates, methoxy polyethylene glycol (meth)acrylates, or polyethylene glycol (meth)acrylates; amino-containing unsaturated monomers, such as (N,N)-dimethylaminoethyl (meth)acrylates, or (N,N)-dimethylaminopropyl (meth)acrylamide, and their quaternary compounds.

[0052] Simultaneously, the superabsorbent polymer particles may contain cross-linked polymers cross-linked by an internal cross-linking agent. The internal cross-linking agent can be used to polymerize the aforementioned water-soluble olefinic unsaturated monomers by cross-linking their unsaturated bonds.

[0053] The internal crosslinking agent can be a (meth)acrylate-based compound in which the crosslinking reaction is carried out via free-radical polymerization (FRP). Specifically, the internal crosslinking agent can be one or more compounds selected from: ethylene glycol di(meth)acrylate, polyethylene glycol (meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene glycol (meth)acrylate, butanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate. More specifically, the internal crosslinking agent can be polyethylene glycol di(meth)acrylate.

[0054] The crosslinked polymer of the present invention can be prepared by polymerization of a composition comprising a water-soluble olefinically unsaturated monomer, an internal crosslinking agent, and a polymerization initiator, wherein the amount of the internal crosslinking agent in the composition can be from 0.01 parts by weight to 5 parts by weight relative to 100 parts by weight of the water-soluble olefinically unsaturated monomer. For example, the amount of the internal crosslinking agent relative to 100 parts by weight can be 0.01 parts by weight or more, 0.05 parts by weight or more, 0.1 parts by weight, or 0.2 parts by weight or more, and 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, or 0.5 parts by weight or less. When the content of the internal crosslinking agent is too low, crosslinking does not occur sufficiently, making it difficult to achieve an appropriate level or higher strength; when the content of the internal crosslinking agent is too high, the internal crosslinking density increases, making it difficult to achieve the desired water retention capacity.

[0055] Furthermore, the superabsorbent polymer particles of the present invention may have a surface on which a surface crosslinking layer is formed. In this case, the surface crosslinking layer may be crosslinked by a surface crosslinking agent, which may include a polyepoxide compound, and the polyepoxide compound may be a glycidyl ether compound of a polyol.

[0056] Specifically, the surface crosslinking agent may include one or more polycyclic epoxy compounds selected from the following: ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, triethylene glycol diglycidyl ether, tetraethylene glycol diglycidyl ether, glycerol polyglycidyl ether, and sorbitol polyglycidyl ether.

[0057] The amount of surface crosslinking agent relative to 100 parts by weight of the base polymer described below can be from about 0.001 parts by weight to about 5 parts by weight. Specifically, relative to 100 parts by weight of the base polymer, the amount of surface crosslinking agent can be about 0.005 parts by weight or more, about 0.01 parts by weight or more, or about 0.05 parts by weight or more, and about 4 parts by weight or less, about 2 parts by weight or less, or about 1 part by weight or less. When the content of surface crosslinking agent is too low, the crosslinking density of the surface crosslinking layer is too low, which may cause a decrease in absorption properties such as the absorption rate under pressure. When the content of surface crosslinking agent is too high, excessive surface crosslinking reaction occurs, which may make it difficult to suppress the rewetting phenomenon of superabsorbent polymer particles.

[0058] Meanwhile, the particle diameter (D50) of the superabsorbent polymer particles included in the composite insulation material of the present invention can range from 10 μm to 850 μm. Typically, when the particle diameter is 150 μm or less, the superabsorbent polymer particles can be classified into fine particles; when the particle diameter is greater than 150 μm and 850 μm or less, the superabsorbent polymer particles can be classified into general particles. In this case, general particles are typically commercially available, but because the composite insulation material of the present invention utilizes the property of the superabsorbent polymer particles to independently absorb moisture and swell, the particle diameter is independent of the composite insulation material. Therefore, in addition to general particles, the superabsorbent polymer particles of the present invention may also include fine particles. The particle diameter can be measured using laser diffraction.

[0059] The method for preparing superabsorbent polymer particles will be described step by step below. First, a polymerization reaction of the composition is carried out. As mentioned above, the composition may contain a water-soluble olefinically unsaturated monomer, an internal crosslinking agent, and a polymerization initiator, and may additionally contain additives such as thickeners, plasticizers, storage stabilizers, and antioxidants if necessary.

[0060] The composition can be polymerized to form an aqueous gel polymer. The steps of drying and pulverizing the aqueous gel polymer may include a process of coarsely pulverizing the aqueous gel polymer to improve drying efficiency before drying. The aqueous gel polymer that has undergone the coarse pulverization process as described above, or the aqueous gel polymer immediately following polymerization without undergoing coarse pulverization, may be dried. Thereafter, a step can be performed to prepare the base polymer by pulverizing the dried polymer obtained via the drying step.

[0061] Next, a surface crosslinking reaction step is performed to form a surface crosslinking layer on at least a portion of the surface of the base polymer in the presence of a surface crosslinking agent. Typically, the surface crosslinking agent is applied to the surface of the base polymer. Therefore, a surface crosslinking reaction occurs on the surface of the base polymer, which improves the crosslinkability of the base polymer surface without substantially affecting the interior of the particles. Thus, the surface-crosslinked base polymer has a higher degree of crosslinking near the surface than inside. The surface crosslinking reaction and drying can be carried out simultaneously by heating the base polymer to which the surface crosslinking agent has been added.

[0062] Following surface crosslinking, a step of grading the base polymer on which the surface crosslinking layer has been formed can be performed. The base polymer can be processed into superabsorbent polymer particles through processes such as pulverization and grading. Subsequently, the superabsorbent polymer particles are graded according to particle diameter, and superabsorbent polymer particles with appropriate particle diameters can be commercialized according to their intended use.

[0063] When measured according to EDANA method WSP 241.3, the centrifuge retention capacity (CRC) of superabsorbent polymer particles can be 24 g / g or greater, 25 g / g or greater, or 26 g / g or greater, and 40 g / g or less, 38 g / g or less, or 36 g / g or less.

[0064] Furthermore, when measured at 0.7 psi according to EDANA method WSP 242.3, the absorption under pressure (AUP) of superabsorbent polymer particles can be 18 g / g or greater, 20 g / g or greater, or 22 g / g or greater, and 27 g / g or less, or 25 g / g or less.

[0065] Because the superabsorbent polymer particles contained in the superabsorbent polymer layer essentially have the property of absorbing moisture from the air, moisture from the air that will permeate into the felt can be pre-absorbed. Furthermore, moisture already permeated into the felt is also absorbed by the superabsorbent polymer particles, minimizing the reduction in the thermal insulation performance of the composite insulation material.

[0066] To describe in detail a composite insulation material according to an exemplary embodiment of the present invention, refer to... Figure 1 a and Figure 1 b. The composite insulation material 1 may have a structure in which superabsorbent polymer layers 3 and felt 2 are stacked alternately. Figure 1 a shows a composite insulation material 1 in which one of the superabsorbent polymer layers 3 is stacked between felt 2. Figure 1 Figure b shows a composite insulation material 1 in which two superabsorbent polymer layers 3 are stacked alternately in this order between felt 2. That is, one or more surfaces of the felt 2, which serves as the insulation material in the composite insulation material 1, can be in contact with the superabsorbent polymer layers 3, and the superabsorbent polymer particles contained in the superabsorbent polymer layers 3 have the characteristic of absorbing up to 50 times their own weight in water. Therefore, the superabsorbent polymer particles play an excellent role in minimizing the moisture content in the felt 2, which serves as the insulation material. Furthermore, even when the superabsorbent polymer particles absorb moisture, the thermal conductivity of the composite insulation material 1 does not decrease significantly due to moisture absorption. That is, due to the excellent absorption characteristics of the superabsorbent polymer particles, the increase in the thermal conductivity of the felt 2 due to moisture can be suppressed, and the increase in the thermal conductivity of the absorbed superabsorbent polymer layers 3 is small. Therefore, the increase in thermal conductivity due to moisture in the composite insulation material 1 itself can be prevented, thus maintaining excellent insulation performance.

[0067] Reference Figure 1 a and Figure 1 b. In the composite insulation material 1 of the present invention, the superabsorbent polymer layer 3 may be positioned between two or more felts 2. The superabsorbent polymer layer 3 may be a coating layer formed on the felt 2, or a filling layer obtained by filling a breathable acceptor with superabsorbent polymer particles. Specifically, the superabsorbent polymer layer 3 according to an exemplary embodiment of the present invention may include a breathable acceptor and superabsorbent polymer particles filled in the breathable acceptor.

[0068] The coating layer can be formed by applying a coating solution prepared by stirring and mixing superabsorbent polymer particles with a dispersing solvent and a binder onto the felt 2, and then drying the coating solution.

[0069] The filling layer can be formed by filling individual breathable acceptors with superabsorbent polymer particles, sealing the breathable acceptors, placing the breathable acceptors between two or more felts 2, and then pressing them.

[0070] Specifically, since the superabsorbent polymer particles exist in the form of powder, they are dispersed like dust. Even when the superabsorbent polymer layer 3 is applied as a coating layer together with a binder, the superabsorbent polymer particles may separate and disperse from each other as the adhesive force between some of the superabsorbent polymer particles on the surface of the composite insulation layer weakens. Therefore, it is preferable to apply the superabsorbent polymer layer 3 in the form of a filler layer.

[0071] Therefore, the breathable receiver can have a sieve structure that allows moisture and air to pass through but prevents superabsorbent polymer particles from passing through. In this case, the breathable receiver can include nylon, glass fiber / polyethylene (PE), nonwoven fabric materials, and biodegradable materials (e.g., polylactic acid (PLA)).

[0072] According to an exemplary embodiment of the invention, the breathable receiver may include two or more intersecting sutures and receiving portions separated by the sutures, in which superabsorbent polymer particles may be contained. The sutures are lines that pass through and sew the breathable receiver together, thus forming receiving portions that serve as spaces for containing the superabsorbent polymer particles. When the breathable receiver is viewed in a plan view, the receiving portions may have the shape of a plurality of squares or rectangles.

[0073] When a breathable receiver is filled with superabsorbent polymer particles without sutures and a containment section, the superabsorbent polymer particles may not be uniformly distributed within the breathable receiver. For example, when a sheet-like composite insulation material is placed vertically and used as insulation, the superabsorbent polymer particles tend to concentrate downwards due to gravity, resulting in an uneven distribution. Therefore, by forming compartments with containment sections using two or more intersecting sutures, and filling these compartments with superabsorbent polymer particles, a state in which the superabsorbent polymer particles are uniformly contained within the breathable receiver can be achieved even when the composite insulation material is placed vertically and applied.

[0074] According to an exemplary embodiment of the present invention, the weight per unit area of ​​the superabsorbent polymer layer can be 0.08 g / cm³. 2 Up to 0.31 g / cm 2 More specifically, it can be 0.15 g / cm³. 2 Up to 0.25 g / cm 2 The weight per unit area refers to the ratio of the total mass of the superabsorbent polymer particles contained in the superabsorbent polymer layer to the area of ​​the superabsorbent polymer layer. Therefore, when the superabsorbent polymer particles are contained in the superabsorbent polymer layer at a mass within the range specified above, based on the area of ​​the superabsorbent polymer layer, the absorbency of the superabsorbent polymer layer can be maximized.

[0075] Specifically, when the weight per unit area is 0.08 g / cm³ 2 When the absorbency is greater than or equal to that of the composite insulation material, the superabsorbent polymer layer has the following effect: it appropriately absorbs moisture that has seeped into the felt and moisture from the air that has seeped into the felt, thereby reducing the humidity or moisture content of the composite insulation material itself. This prevents a decrease in the insulation performance of the composite insulation material in a humid atmosphere.

[0076] When the weight per unit area is 0.31 g / cm³ 2 Or even smaller, for example, because the superabsorbent polymer layer is formed with an excessively high specific gravity or thickness, the reduction in the thermal insulation performance of the overall composite insulation material can be prevented.

[0077] Simultaneously, the superabsorbent polymer particles contained in the superabsorbent polymer layer of the present invention swell upon absorbing moisture. That is, the spaced-apart superabsorbent polymer particles can swell upon absorbing surrounding moisture and moisture penetrating into the composite insulation material, thereby forming a protective film. The protective film can prevent moisture from penetrating from the surface of the composite insulation material to deeper interiors. Furthermore, the protective film can also act as a buffer against damage to the composite insulation material from external impacts and can prevent moisture penetration due to damage to the felt. For example, even when the felt is damaged, the protective film can prevent excessive moisture penetration into the felt.

[0078] According to an exemplary embodiment of the present invention, the ratio of the total thickness of the superabsorbent polymer layer to the total thickness of two or more felts can be from 0.025 to 0.1. When the thickness ratio exceeds 0.1, the insulation effect of the composite insulation material may decrease as the superabsorbent polymer layer excessively swells and thickens; more precisely, the thermal conductivity may decrease due to excess moisture in the composite insulation material itself. Furthermore, when the thickness ratio is less than 0.025, the effect of the superabsorbent polymer layer in maintaining the insulation effect of the composite insulation material by absorbing moisture that adversely affects the insulation of the felts may be insignificant due to the slightly thinner superabsorbent polymer layer.

[0079] The ratio of the total thickness of the superabsorbent polymer layer to the total thickness of two or more felts can refer, for example, when a superabsorbent polymer layer is positioned between two felts, the ratio of the thickness of the superabsorbent polymer layer to the sum of the thicknesses of the two felts. In this case, the thickness can be measured using vernier calipers.

[0080] The invention will be described in more detail below by way of examples. However, the following examples are provided to illustrate the invention. It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the scope and spirit of the invention, and the scope of the invention is not limited thereto.

[0081] Example

[0082] Example 1

[0083] (1) Preparation of felt

[0084] A silica sol was prepared by mixing tetraethyl orthosilicate (TEOS) and water in a molar ratio of 1:4 and adding TEOS and ethanol in a weight ratio of 1:5. An alkaline catalyst was then added to the silica sol to prepare a catalytic sol.

[0085] Glass fibers used as a felt substrate are placed in a reactor containing a catalytic sol to impregnate the felt substrate with silica sol. The felt substrate impregnated with silica sol is left to stand at room temperature for 1 hour to allow the silica sol to gel, thereby obtaining a wet gel fiber composite material. The temperature is raised to 60°C, and then the wet gel fiber composite material is left to stand for 24 hours to be cured.

[0086] Subsequently, a solution of trimethylethoxysilane was prepared by diluting it in ethanol (water content: 8 wt%) to 40 vol% as a surface modifier. The surface modifier was placed in a reactor and subjected to hydrophobic treatment at 60°C for 24 hours to form an aerogel with hydrophobic functional groups applied to the interior and surface of the felt substrate.

[0087] Finally, the sheet-like felt was dried in an oven at 150°C and atmospheric pressure for 1 hour to prepare a sheet with a thickness of 10 mm.

[0088] (2) Preparation of superabsorbent polymer particles

[0089] In a 3L glass container equipped with a stirrer and a thermometer, 100g (1.388mol) of acrylic acid, 0.26g of polyethylene glycol diacrylate (PEGDA) as an internal crosslinking agent, 0.008g of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide as a photopolymerization initiator (polymerization initiator), 0.20g of sodium persulfate as a thermal polymerization initiator, and 123.5g of 32% caustic soda solution were mixed with water at room temperature to achieve a solid content of 45.0% by weight, thereby preparing a composition.

[0090] Subsequently, the composition is fed onto a conveyor belt, on which a belt having a width of 10 cm and a length of 2 m rotates at a speed of 10 cm / min. At this time, a polymerization reaction is carried out on the conveyor belt equipped with a light source for 20 minutes, thereby obtaining an aqueous gel polymer with a moisture content of 45% by weight.

[0091] Next, the aqueous gel polymer was pulverized into particles with a diameter ranging from 300 μm to 5,000 μm using a meat grinder. Subsequently, the pulverized product was dried in hot air at 185°C for 30 minutes using an airflow oven. The base polymer was obtained through pulverization, drying, and grading.

[0092] A surface crosslinking solution obtained by mixing water, methanol, and ethylene glycol diglycidyl ether as a surface crosslinking agent was added to 100 g of a base polymer, and then a surface crosslinking reaction was carried out at 198 °C. Furthermore, the resulting product was pulverized and graded to prepare superabsorbent polymer particles with particle diameters ranging from 10 μm to 850 μm.

[0093] (3) Preparation of superabsorbent polymer layer

[0094] The superabsorbent polymer particles prepared using 10g of the superabsorbent polymer particles had a filling area of ​​64cm². 2 A plate-shaped, breathable acceptor (8cm long x 8cm wide) was prepared by leveling a breathable acceptor filled with superabsorbent polymer particles, which were then evenly distributed. The breathable acceptor was then sutured together with one suture along its length and another along its width, such that these sutures intersect each other, creating four receiving portions. A solution with a density of 0.16 g / cm³ was prepared by uniformly containing the superabsorbent polymer particles within the plurality of receiving portions separated by the sutures. 2 The superabsorbent polymer layer has a unit area weight and a thickness of 1 mm.

[0095] (4) Preparation of composite thermal insulation materials

[0096] The superabsorbent polymer layers were stacked during the fabrication of the felt, resulting in a thickness of 10 mm and a length of 144 cm. 2 A sheet of felt with an area of ​​12cm in length × 12cm in width is placed on top. A layer of felt identical to the one described above is stacked on top of a stacked superabsorbent polymer layer, and then the felt and the superabsorbent polymer layer are bonded together by pressing. As described above, it has a thickness of 1mm and a strength of 0.16g / cm³. 2 A superabsorbent polymer layer per unit area weight is positioned between two felts. Therefore, a composite insulation material in which the ratio of the total thickness of the superabsorbent polymer layer to the total thickness of the two felts is prepared is produced.

[0097] Example 2

[0098] The composite thermal insulation material was prepared in the same manner as in Example 1, except that the amount of superabsorbent polymer particles used to fill the superabsorbent polymer layer was 20 g, and the weight per unit area of ​​the superabsorbent polymer layer was 0.31 g / cm³. 2 .

[0099] Example 3

[0100] The composite insulation material was prepared in the same manner as in Example 1, except that the plate-shaped breathable receiver was filled with superabsorbent polymer particles, and then two intersecting sutures were not formed, i.e., no additional receiving portion was separated.

[0101] Example 4

[0102] The composite insulation material was prepared in the same manner as in Example 1, except that the amount of superabsorbent polymer particles used to fill the superabsorbent polymer layer was 3g, and the weight per unit area of ​​the superabsorbent polymer layer was 0.05g / cm². 2 .

[0103] Example 5

[0104] The composite insulation material was prepared in the same manner as in Example 1, except that the amount of superabsorbent polymer particles used to fill the superabsorbent polymer layer was 25 g, and the weight per unit area of ​​the superabsorbent polymer layer was 0.39 g / cm³. 2 .

[0105] Comparative example

[0106] Comparative Example 1

[0107] The composite insulation material was prepared in the same manner as in Example 1, except that a superabsorbent polymer layer was not used, and a single layer of felt with a thickness of 20 mm was used.

[0108] Experimental Example

[0109] The thermal conductivity of the composite insulation materials prepared in Examples 1 to 5 and Comparative Example 1 was measured using the following method. The results are shown in Table 1.

[0110] [Table 1]

[0111]

[0112] Samples of the composite thermal insulation materials prepared in Examples 1 to 5 and Comparative Example 1 were prepared, and the weight of the samples was measured using an AND WBA-6200 high-precision balance (0.01 g to 6200 g). Furthermore, the thermal conductivity of the samples at room temperature (23 °C ± 5 °C) was measured using an HFM 436 Lambda instrument available from NETZSCH.

[0113] Subsequently, samples of the composite insulation material were placed in a constant temperature and humidity chamber to absorb moisture under conditions of 80°C and 95% humidity. The weight and thermal conductivity of the samples in the moisture-absorbing state were measured using the following method.

[0114] As shown in Table 1, the thermal conductivity values ​​of the composite insulation materials in the examples and comparative examples were all the same before moisture absorption. However, it was determined that after exposure to moisture absorption conditions, the thermal conductivity values ​​of Examples 1 to 5 were low, thus maintaining excellent insulation performance. Therefore, it can be determined that the insulation performance of the composite insulation material is maximized due to the presence of the superabsorbent polymer layer. Furthermore, it can be determined that the moisture penetration into the felt in the composite insulation material is minimized through the moisture absorption characteristics of the superabsorbent polymer layer.

[0115] Furthermore, in Experiments 6 and 7, where the composite insulation material without the superabsorbent polymer layer was subjected to moisture absorption under the same conditions in a constant temperature and humidity chamber (Experiment 6), and where the composite insulation material was immersed in a constant temperature chamber at 25°C and fixed by placing weights to prevent it from floating on the water surface (Experiment 7), the results showed that thermal conductivity was measured as the insulation effect in Experiments 6 and 7, in which the composite insulation material prepared in Comparative Example 1 was used. In Experiments 6 and 7, the thermal conductivity values ​​increased by 44% and 196%, respectively, compared to the values ​​before moisture absorption, and it could be determined that the insulation capacity was significantly reduced compared to Experiment 1, in which the superabsorbent polymer layer was present.

Claims

1. A composite thermal insulation material, comprising: Two or more felts, each of the two or more felts comprising a felting substrate and an aerogel formed inside and on the surface of the felting substrate; as well as A superabsorbent polymer layer, positioned between the two or more felts and comprising superabsorbent polymer particles. The superabsorbent polymer layer comprises a breathable acceptor and superabsorbent polymer particles filled within the breathable acceptor. The superabsorbent polymer layer has a unit area weight of 0.08 g / cm³. 2 Up to 0.31 g / cm 2 , The superabsorbent polymer particles comprise a crosslinked polymer having at least partially neutralized acidic groups, a water-soluble olefinic unsaturated monomer, and an internal crosslinking agent. The crosslinked polymer is prepared by polymerization of a composition comprising the water-soluble olefinic unsaturated monomer, the internal crosslinking agent, and a polymerization initiator. The amount of the internal crosslinking agent in the composition is from 0.01 parts by weight to 5 parts by weight relative to 100 parts by weight of the water-soluble olefinic unsaturated monomer.

2. The composite insulation material according to claim 1, wherein the felt and the superabsorbent polymer layer are stacked alternately.

3. The composite insulation material according to claim 1, wherein the breathable receiver comprises two or more intersecting sutures and a receiving portion separated by the sutures, and The superabsorbent polymer particles are contained within the containment portion.

4. The composite insulation material according to claim 1, wherein the ratio of the total thickness of the superabsorbent polymer layer to the total thickness of the two or more felts is 0.025 to 0.

1.

5. The composite thermal insulation material according to claim 1, wherein the aerogel has a surface containing hydrophobic functional groups.

6. The composite thermal insulation material according to claim 1, wherein the water-soluble olefinic unsaturated monomer comprises (meth)acrylic acid or a salt thereof.

7. The composite thermal insulation material according to claim 1, wherein the particle diameter of the superabsorbent polymer particles is from 10 μm to 850 μm.

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