Heat insulation sheet and method of manufacturing same

Abstract

A heat insulation sheet includes: a heat insulation layer formed as a nanofiber web form having a plurality of pores by electrospinning a polymeric material; and an adhesion layer laminated on one or both sides of the heat insulation layer and formed as a nanofiber web form by electrospinning an adhesion material, to thereby be made thin and have a plurality of fine pores, and to thus improve heat insulation performance.

Claims

1. A heat insulation sheet consisting of: a heat insulation layer that is formed in a first nanofiber web composed of first nanofibers and having a plurality of pores by electrospinning a polymer material with low thermal conductivity, wherein the first nanofibers further comprise inorganic particles embedded therein, part of which are exposed on a surface of the first nanofibers; an adhesive layer that is laminated on one surface of the heat insulation layer, wherein the adhesive layer is formed in a second nanofiber web composed of second nanofibers by electrospinning an adhesive material; and a nonwoven fabric interposed between the heat insulation layer and the adhesive layer, wherein the nonwoven fabric is formed of a fiber having a double structure of a core and an outer sheath surrounding the core.

2. The heat insulation sheet of claim 1, wherein the plurality of pores are three-dimensional nano-sized fine pores that are formed by a three-dimensional network structure of the first nanofiber web.

3. The heat insulation sheet of claim 1, wherein the first nanofibers have a diameter of 0.1 m-1.5 m.

4. The heat insulation sheet of claim 1, wherein the inorganic particles includes particles of at least one selected from the group consisting of SiO.sub.2, SiON, Si.sub.3N.sub.4, HfO.sub.2, ZrO.sub.2, Al.sub.2O.sub.3, TiO.sub.2, Ta.sub.2O.sub.5, MgO, Y.sub.2O.sub.3, BaTiO.sub.3, ZrSiO.sub.4, and HfO.sub.2, or particles of at least one selected from the group consisting of glass fiber, graphite, rock wool, and clay.

5. The heat insulation sheet of claim 1, wherein the core is made of a first material and the outer sheath is formed of a second material, and the first material has a melting point higher than that of the second material.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a cross-sectional view of a heat insulation sheet according to a first embodiment of the present invention.

(2) FIG. 2 is an enlarged view of a heat insulation layer according to the first embodiment of the present invention.

(3) FIG. 3 is a cross-sectional view of a heat insulation sheet according to a second embodiment of the present invention.

(4) FIG. 4 is a configuration diagram of an electrospinning device for manufacturing a heat insulation sheet according to the present invention.

(5) FIG. 5 is a cross-sectional view of a heat insulation sheet according to a third embodiment of the present invention.

(6) FIG. 6 is a cross-sectional view of a heat insulation sheet according to a fourth embodiment of the present invention.

(7) FIG. 7 is a cross-sectional view showing a core and an outer sheath of a fiber forming a nonwoven fabric according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(8) Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Here, the size or shape of the components illustrated in the drawings may be shown to be exaggerated for convenience and clarity of illustration. In addition, specifically defined terms may be changed according to the intention or practices of users or operators in consideration of the construction and operation of the present invention. The definition of the terms should be made based on contents throughout the present specification.

(9) FIG. 1 is a cross-sectional view of a heat insulation sheet according to a first embodiment of the present invention, and FIG. 2 is an enlarged view of a heat insulation layer according to the first embodiment of the present invention.

(10) Referring to FIGS. 1 and 2, the heat insulation sheet according to the first embodiment includes: a heat insulation layer 10 that is formed by electrospinning a polymer material so as to have a plurality of pores; and an adhesive layer 20 that is laminated on the heat insulation layer 10 and that is formed by electrospinning an adhesive material.

(11) The heat insulation layer 10 is configured by mixing a polymer material that can be electrospun and having excellent heat resistance and a solvent at a constant mixture rate, to thus create a spinning solution, electrospinning the spinning solution to thus form nanofibers 14, and accumulating the nanofibers 14 to thus form a nanofiber web having a plurality of pores 12.

(12) As the diameters of the nanofibers 14 are smaller, the specific surface areas of the nanofibers 14 are increased, and the heat absorption ability of the nanofiber web having a plurality of fine pores is increased, thereby improving the heat insulation performance. Thus, it is preferable that the diameters of the nanofibers 14 should be in the range of 0.1 m-1.5 m. In the case that the diameters of the nanofibers 14 are not more than 0.1 m, the nanofiber characteristics are lowered, while in the case that the diameters of the nanofibers 14 are not less than 1.5 m, pores are enlarged and thus the heat absorption capability is lowered, to thereby deteriorate a heat insulation property. The heat insulation layer 10 can be designed to have a thickness of 5 m-70 m, and the heat insulation layer 10 is preferably set to have a thickness of 10 m-30 m. Further, porosity of the pores 12 formed in the heat insulation layer 10 is preferably in the range of 50-90%.

(13) Here, the spinning method that is applied to the present invention, can employ any one selected from general electrospinning, air-electrospinning (AES), electrospray, electrobrown spinning, centrifugal electrospinning, and flash-electrospinning.

(14) For the purpose of improvement of heat resistance of the heat insulation layer 10 in the present invention, a nanofiber web that is prepared by electrospinning a polymer having low thermal conductivity and excellent heat resistance alone or a mixed polymer that is obtained by mixing a polymer with low thermal conductivity and a polymer with excellent heat resistance at a predetermined mixture ratio, can be applied as the heat insulation layer 10.

(15) In this case, it is preferable that the polymer that can be used in the present invention should be dissolved in an organic solvent so as to be spun, and should have low thermal conductivity, and also it is more preferable that the polymer that can be used in the present invention should have excellent heat resistance.

(16) A polymeric material used to make the insulation layer 10 may be made of one of for example, oligomer polyurethane (PU), and polymer polyurethane (PU), PS (polystylene), PVA (polyvinylalchol), PMMA (polymethyl methacrylate), PLA (polylactic acid), PEO (polyethyleneoxide), PVAc (polyvinylacetate), PAA (polyacrylic acid), PCL (polycaprolactone), PAN (polyacrylonitrile), PVP (polyvinylpyrrolidone), PVC (polyvinylchloride), nylon, PC (polycarbonate), PEI (polyetherimide), PVdF (polyvinylidene fluoride), PEI (polyetherimide), PES (polyesthersulphone) or a mixture thereof.

(17) The thermal conductivity of the polymer is preferably set to less than 0.1 W/mK.

(18) Since it is known that the polyurethane (PU) of the polymer materials has thermal conductivity of 0.0160.040 W/mK and the polystylene (PS) and the polyvinylchloride (PVC) have thermal conductivity of 0.0330.040 W/mK, the nanofiber webs that are obtained by spinning the polystylene (PS) and the polyvinylchloride (PVC) have also low thermal conductivity.

(19) The solvent is at least one selected from the group consisting of DMA (dimethyl acetamide), DMF (N,N-dimethylformamide), NMP (N-methyl-2-pyrrolidinone), DMSO (dimethyl sulfoxide), THF (tetra-hydrofuran), DMAc (di-methylacetamide), EC (ethylene carbonate), DEC (diethyl carbonate), DMC (dimethyl carbonate), EMC (ethyl methyl carbonate), PC (propylene carbonate), water, acetic acid, and acetone.

(20) The heat insulation layer 10 is prepared by the electrospinning method, and thus thickness of the heat insulation layer 10 is determined according to a spinning dose of a spinning solution. Accordingly, it is easy to have the heat insulation layer 10 made into a desired thickness.

(21) As described above, since the heat insulation layer 10 is formed into a nanofiber web shape in which nanofibers 14 are accumulated by a spinning method, the heat insulation layer 10 can be made of a type having plurality of pores 12 without a separate process. It is also possible to adjust size of the pores according to a spinning dose of a spinning solution. Thus, since the multiple pores 12 can be finely made, heat blocking performance is excellent, to accordingly improve heat insulation performance.

(22) In addition, since the nanofiber web structures of the heat insulation layer 10 are formed so that the electrospun nanofibers are irregularly laminated and arranged in a three-dimensional network structure, three-dimensional nano-sized fine pores that are so irregularly distributed by the nanofibers and thus a heat absorption ability of the nanofiber web is increased, thereby improving the heat insulation performance.

(23) Meanwhile, in the present invention, inorganic particles that are heat insulation fillers for blocking the heat transfer may be contained in the spinning solution for forming the heat insulation layer 10. In this case, the nanofiber web of the heat insulation layer 10 may contain inorganic particles. The inorganic particles are positioned within the spun nanofiber, or some of the inorganic particles are exposed on the surface of nanofibers, thereby blocking the heat transfer. Further, the inorganic particles can improve intensity of the heat insulation layer 10 as the heat insulation filler.

(24) Preferably, the inorganic particles are at least one selected from the group consisting of SiO.sub.2, SiON, Si.sub.3N.sub.4, HfO.sub.2, ZrO.sub.2, Al.sub.2O.sub.3, TiO.sub.2, Ta.sub.2O.sub.5, MgO, Y.sub.2O.sub.3, BaTiO.sub.3, ZrSiO.sub.4, and HfO.sub.2, or at least one selected from the group consisting of glass fiber, graphite, rock wool, and clay, but is not necessarily limited thereto. In other words, one selected from the group consisting of the inorganic particles may be contained in the spinning solution alone or a mixture of two or more selected from the group consisting of the inorganic particles may be contained in the spinning solution in a mixture thereof.

(25) Further, fumed silica may be contained in the spinning solution for forming the heat insulation layer 10.

(26) The adhesive layer 20 is prepared by the same electrospinning method as that of creating the heat insulation layer 10. That is, an adhesive agent having an adhesiveness and a solvent are mixed to thus prepare an adhesive material having a viscosity suitable for electrospinning, and the adhesive material is laminated with a predetermined thickness on one or both surfaces of the heat insulation layer 10 by using the electrospinning method. An acrylic adhesive agent is used as an example of the adhesive agent.

(27) In the present invention, the nanofibers of the adhesive material are spun on the heat insulation layer 10 of the nanofiber web structure, to thus form the adhesive layer 20, in which the adhesive layer 20 may be in the form of non-pores by the adhesive properties of the adhesive material. As such, the adhesive layer 20 that is in the form of non-pores is affixed to places where heat is generated, to thereby block the heat transfer first.

(28) The adhesive layer 20 is spun in the form of ultra-fine fiber strands and adhered on the surface of the heat insulation layer 10, in which the adhesive material is introduced into the pores 12 of the heat insulation layer 10, to thereby increase the adhesive strength between the heat insulation layer 10 and the adhesive layer 20, and reinforce the adhesive force between the heat insulation layer 10 and the adhesive layer 20, and to thus reduce a phenomenon of peeling off the heat insulation layer 10 from the adhesive layer 20, improve reliability of the heat insulation sheet, make the thickness of the adhesive layer 20 thin, and thus make the heat insulation sheet made thin.

(29) Here, in addition to the method of electrospinning the adhesive layer 20 directly on the heat insulation layer 10, the heat insulation layer 10 and the adhesive layer 20 are separately prepared by the electrospinning method, and then, the adhesive layer 20 is laminated on one or both sides of the heat insulation layer 10 in a laminating process, to thereby prepare the heat insulation sheet.

(30) Then, the adhesive layer 20 is formed on a release film, and then the heat insulation layer 10 is formed on the adhesive layer 20, or on the contrary, the heat insulation layer 10 is formed on the release film 10, and then the adhesive layer 20 is formed on the heat insulation layer 10 to thus form the heat insulation sheet.

(31) The thickness of the adhesive layer 20 is determined similarly depending on a dose of spinning the adhesive material. Thus, the thickness of the adhesive layer 20 can be freely made. After the heat insulation sheet has been prepared, the surface of the heat insulation sheet can be hardened to some degrees of hardening the surface by a thermocompression process.

(32) As described above, in the present invention, the heat insulation layer 10 and the adhesive layer 20 are laminated by using the nanofiber web, to thereby implement an ultra-thin heat insulation sheet of the thickness of about several tens of micrometers, and to thus allow the ultra-thin heat insulation sheet to be used while bending or folding the ultra-thin heat insulation sheet by the flexible nanofiber web properties, and to be attached on areas having various shapes requiring heat insulation.

(33) FIG. 3 is a cross-sectional view of a heat insulation sheet according to a second embodiment of the present invention.

(34) Referring to FIG. 3, the heat insulation sheet according to the second embodiment includes a heat insulation layer 10 that is formed in a nanofiber web shape by the electrospinning method, a first adhesive layer 22 that is laminated on one surface of the heat insulation layer 10, and a second adhesive layer 24 that is laminated on the other surface of the heat insulation layer 10.

(35) The heat insulation sheet according to the second embodiment has a structure that the adhesive layers are formed on both sides of the heat insulation layer 10, respectively, and is used when the heat insulation sheet is attached between two components for blocking heat transfer therebetween.

(36) Here, since the heat insulation layer 10, the first adhesive layer 22, and the second adhesive layer 24 are the same as the heat insulation layer 10 and the adhesive layer 20 described in the first embodiment, the detailed description thereof will be omitted.

(37) FIG. 4 is a configuration diagram of an electrospinning device for manufacturing a heat insulation sheet according to the present invention.

(38) The electrospinning device according to the present invention includes: a first mixing tank 70 in which an adhesive material that is formed by a mixture of an adhesive material and a solvent is stored; a second mixing tank 72 in which a mixture of a polymer material that can be electrospun and has excellent resistance and the solvent is stored; a first spinning nozzle unit 74 that is connected to a high voltage generator and that is connected to the first mixing tank 70, for forming an adhesive layer 20; a second spinning nozzle unit 76 that is connected to the high voltage generator and that is connected to the second mixing tank 72, for forming a heat insulation layer 10; and a collector 78 that is disposed below the first spinning nozzle unit 74 and the second spinning nozzle unit 76 and that sequentially laminates the adhesive layer 20 and the heat insulation layer 10.

(39) The first mixing tank 70 is provided with a first agitator 60 that evenly mixes the adhesive material and the solvent and maintains a constant viscosity of the adhesive material, and the second mixing tank 72 is provided with a second agitator 62 that evenly mixes the polymer material and the solvent and maintains a constant viscosity of the polymer material.

(40) In addition, a high voltage electrostatic force of 90 to 120 Kv is applied between the collector 78 and each of the spinning nozzle units 74 and 76, to thereby spin nanofibers 14. Accordingly, the nanofibers 14 are collected on the collector 78, to thereby form the adhesive layer 20 and the heat insulation layer 10 in the form of a nanofiber web.

(41) Here, the first spinning nozzle unit 74 and the second spinning nozzle unit 76 are provided with air spray apparatuses 62 and 64, respectively, to thus prevent the nanofibers 14 spun from the first spinning nozzle unit 74 and the second spinning nozzle unit 76 from fluttering without being collected by the collector 78.

(42) A conveyor that automatically transfers the release film 82 so that the adhesive layer 20 and the heat insulation layer 10 are sequentially laminated on the release film 82 may be used as the collector 78. Otherwise, a table-shaped unit may be used as the collector 78 when the adhesive layer 20 and the heat insulation layer 10 are formed in respectively different chambers.

(43) A release film roll 80 is disposed in front of the collector 78, in which the release film 82 is wound on the release film roll 80, to allow the release film 82 to be supplied on top of the collector 78. In addition, a pressure roller 86 that pressurizes (or performs calendaring) the adhesive layer 20 and the heat insulation layer 10 to have a constant thickness is provided at the rear side of the collector 78. A sheet roll 88 is provided, around which heat insulation sheets pressurized in a predetermined thickness via the pressure roller 86 are wound.

(44) A process for producing the heat insulation sheet by using the electrospinning apparatus constructed as described above will be described as follows.

(45) First, when the collector 78 is driven, the release film 82 wound on the release film roll 80 is released and supplied from the release film roll 80 to the collector 78.

(46) Then, a high voltage electrostatic force is applied between the collector 78 and the first spinning nozzle unit 74, and thus the adhesive material is made into nanofibers 14 by the first spinning nozzle unit 74 to then be spun to the surface of the release film 82. As a result, the nanofibers 14 are accumulated onto the surface of the release film 82 to thus form the adhesive layer 20.

(47) Here, when the first spinning nozzle unit 74 spins the nanofibers 14, an air spray apparatus 62 mounted in the first spinning nozzle unit 74 sprays air to the nanofibers 14, so that the nanofibers 14 can be collected and captured on the surface of the release film 82 without fluttering.

(48) Then, when the adhesive layer 20 is completely manufactured, the adhesive layer 20 is moved to the bottom of the second spinning nozzle unit 76, and when a high voltage electrostatic force is applied between the collector 78 and the second spinning nozzle unit 76, the second spinning nozzle unit 76 spins the spinning solution into the nanofibers 14 and then spins the spun nanofibers 14 on the adhesive layer 20. As a result, the heat insulation layer 10 that is in a nanofiber web form and has a plurality of pores 12 is formed on the surface of the adhesive layer 20.

(49) In this way, the finished heat insulation sheet is pressed to a predetermined thickness while passing through the pressing roller 86 and is wound on the sheet roll 88.

(50) In addition to the above-described manufacturing method, it is possible to employ a method of manufacturing the heat insulation sheet including: separately preparing the heat insulation layer 10 and the adhesive layer 20; disposing the adhesive layer 20 on one or both surfaces of the heat insulation layer 10; and laminating between the heat insulation layer 10 and the adhesive layer 20.

(51) FIG. 5 is a cross-sectional view of a heat insulation sheet according to a third embodiment of the present invention, and FIG. 6 is a cross-sectional view of a heat insulation sheet according to a fourth embodiment of the present invention.

(52) Referring to FIG. 5, the heat insulation sheet according to the third embodiment includes: a heat insulation layer 10 in a nanofiber web form formed by an electrospinning method; a first adhesive layer 20a that is laminated on one surface of the heat insulation layer 10; a nonwoven fabric 50 that is fixed to the other surface of the heat insulation layer 10; and a second adhesive layer 20b that is laminated on the nonwoven fabric 50.

(53) The nonwoven fabric 50 is applied to improve the handling characteristics of the heat insulation sheet, to reinforce the strength of the heat insulation sheet, or to be used as a support, and may employ any one of a PE (Polyethylene) nonwoven fabric, a PP (Polypropylene) nonwoven fabric, and a PET (Polythyleneterephthalate) nonwoven fabric.

(54) The heat insulation layer 10 that is formed by electrospinning a spinning solution may be laminated on the nonwoven fabric 50, or the heat insulation layer 10 can be formed by directly electrospinning a spinning solution on the nonwoven fabric 50. The nonwoven fabric 50 applied for the third embodiment is interposed between the heat insulation layer 10 of the heat insulation sheet and the second adhesive layer 24 of the second embodiment as shown in FIG. 3.

(55) Here, in order to prevent the fiber of the nonwoven fabric 50 from being melted by heat applied during laminating the nonwoven fabric 50 on the heat insulation layer 10 and the pores from being clogged, the fiber of the nonwoven fabric 50 is preferably implemented to have a double structure having a core 51 and an outer sheath 52, as shown in FIG. 7. Preferably, the fiber of the nonwoven fabric 50 has a PP (Polypropylene) core 51 having a melting point of 160 C., and a PE (Polyethylene) outer sheath 52 having a melting point of 130 C. and surrounding the PP core 51. That is, a lamination process is performed at a temperature at which the outer sheath is melted but the core is not melted.

(56) Referring to FIGS. 3 and 6, the heat insulation sheet according to the fourth embodiment is implemented by adhering one surface of a PE foam 70 on a first adhesive layer 22 of the heat insulation sheet according to the second embodiment, in which an adhesive layer is formed on the other surface of the PE foam 70. The PE foam 70 plays a role of blocking heat transfer.

(57) That is, the heat insulation sheet includes: a heat insulation layer 10 in a nanofiber web form formed by an electrospinning method; a first adhesive layer 20a that is laminated on one surface of the heat insulation layer 10; a second adhesive layer 20b that is fixed to the other surface of the heat insulation layer 10; a PE foam 70 whose one surface is adhered on the first adhesive layer 20a; and a third adhesive layer 20c that is laminated on the other surface of the PE foam 70.

(58) Here, a PU foam can be applied in place of the PE foam 70.

(59) The adhesive layers that are applied to the heat insulation sheets according to the third and fourth embodiments employ a double-sided tape.

(60) As described above, the present invention has been described with respect to particularly preferred embodiments. However, the present invention is not limited to the above embodiments, and it is possible for one who has an ordinary skill in the art to make various modifications and variations, without departing off the spirit of the present invention. Thus, the protective scope of the present invention is not defined within the detailed description thereof but is defined by the claims to be described later and the technical spirit of the present invention.

(61) The present invention provides a heat insulation sheet that is manufactured in a nanofiber web form by way of an electrospinning method, to thereby be made thin and have a plurality of fine pores, and to thus improve heat insulation performance.