Sheet-shaped heater

Abstract

The present invention addresses the problem of providing a highly insulative sheet-shaped heater that is capable of reducing the tensile (stretching) stress load when disposed on a curved surface of a body to be heated that has a curved surface, such as a pipe. This problem is solved by a sheet-shaped heater wherein: a high-strength highly insulative sheet obtained by impregnating reinforcing fibers with a fluororesin, a first adhesive layer, a first insulating layer, a second adhesive layer, and a heat-emitting layer are layered in the given order; main surfaces of the high-strength highly insulative sheet and the first adhesive layer, respectively, are closely adhered to each other; main surfaces of the first adhesive layer and the first insulating layer, respectively, are closely adhered to each other; main surfaces of the second adhesive layer and the heat-emitting layer, respectively, are closely adhered to each other; and the ratio (h1 / Htotal) of the thickness (h1) of the first insulating layer with respect to the total thickness (Htotal) of the high-strength highly insulative sheet, the first adhesive layer, and the first insulating layer is 0.10 or greater.

Description

Sheet heater

[0001] The present invention relates to a sheet-like heater.

[0002] 2. Description of the Related Art Conventionally, heaters for heating pipes and the like have been proposed, for example, as described in Patent Documents 1 to 4.

[0003] Patent Document 1 describes a sheet-shaped heating element having a lead wire connected to a terminal portion connected to a conductive heating element, and a sheet-shaped heating element having a thermal expansion coefficient of 8×10 on at least one entire surface of the conductive heating element or on at least one entire surface of the sheet-shaped heating element including the conductive heating element and the terminal portion. -5 The publication describes a planar heater comprising a low-thermal expansion resin layer having a thermal expansion coefficient of 1000 psi or less, sandwiched between heat-sealable fluororesin layers A on both sides, and a thermal diffusion material layer provided on each of the heat-sealable fluororesin layers A, and another heat-sealable fluororesin layer B provided on the surface of the heat diffusion material layer. The planar heater of the present invention includes a thermal diffusion material layer. Even if the conductive heating element is extremely thin, the thermal diffusion material layer suppresses the deformation force caused by the shrinkage of the resin during the heat-sealing process by heating the resin during manufacturing, and the deformation force is not transmitted to the conductive heating element itself. Therefore, the planar heater does not deform or warp, resulting in a precisely flat planar heater. This allows for a stable, consistent shape, and even when immersed in a liquid to be heated, the planar heater can be completely immersed.

[0004] Patent Document 2 describes a planar heating element formed by laminating insulating outer coverings on both sides of a metal resistor forming a heating circuit via a heat-melt adhesive layer, characterized in that the heat-melt adhesive layer uses a heat-melt fluororesin, and the insulating outer covering uses glass cloth impregnated and sintered with polytetrafluoroethylene (hereinafter referred to as "PTFE"). According to this planar heating element, by interposing a PFA film or FEP film as a heat-melt adhesive layer between the PTFE-impregnated glass cloths, sandwiching the metal resistor between them and applying heat and pressure to heat-seal the heat-sealed material, a planar heating element having a heat resistance of 200°C or more for continuous use can be obtained. It is also described that, because the PTFE-impregnated glass cloth is used as the insulating outer covering, deformation such as warping does not occur when the temperature rises or falls, and the mechanical strength is high.

[0005] Patent Document 3 describes a plane heater including a heat-generating layer and first fluororubber layers disposed on both sides of the heat-generating layer, the first fluororubber layers having a durometer type A hardness of 65 or less according to JIS K 6253. It also describes that such a plane heater can provide a plane heater with improved thermal conduction efficiency in a plane heater in which the heat-generating layer is covered with a fluororubber layer.

[0006] Patent Document 4 describes a fluororubber sheet heater comprising a heater element and a fluororubber sheet adhered to the heater element, the fluororubber sheet being characterized by having a glass cloth and a fluororubber layer impregnated into the glass cloth with an adhesive strengthening agent. It also describes that such a fluororubber sheet heater has excellent heat resistance, cold resistance, acid resistance, oil resistance, and solvent resistance, and is also excellent in flexibility and impact resistance due to its rubber elasticity.

[0007] Japanese Patent Application Laid-Open No. 2016-110757 Japanese Utility Model Application Laid-Open No. 4-66087 Japanese Patent Application Laid-Open No. 2015-122212 Japanese Patent Application Laid-Open No. 2007-224208

[0008] When a heated object has a curved surface, such as a pipe, and a sheet heater is placed on the curved surface, a tensile (elongation) stress load is applied to the outer periphery of the sheet heater. The present invention provides a sheet heater that can reduce the tensile (elongation) stress load when placed on the curved surface of a heated object having a curved surface, such as a pipe, and also has high insulation properties.

[0009] The present inventors have conducted extensive research to solve the above problems and have completed the present invention. The present invention comprises the following (1) to (6): (1) a high-strength, high-insulation sheet in which reinforcing fibers are impregnated with a fluororesin, a first adhesive layer, a first insulating layer, a second adhesive layer, and a heat generating layer, which are laminated in this order, the high-strength, high-insulation sheet and the first adhesive layer being in close contact with each other at their main surfaces, the first adhesive layer and the first insulating layer being in close contact with each other at their main surfaces, and the second adhesive layer and the heat generating layer being in close contact with each other at their main surfaces, and the total thickness (H total ) the ratio (h1 / H total) is 0.10 or more. (2) A sheet-like heater according to (1) above, having a total thickness of 200 to 800 μm. (3) A sheet-like heater according to (1) above, having a thickness of 100 to 300 μm, and having a thickness of 5 to 50 μm for the high-strength, high-insulation sheet. (4) A sheet-like heater according to any of (1) to (3) above, wherein the heat-generating layer is made of a metal fiber sheet. (5) A sheet-like heater according to any of (1) to (4) above, wherein the first adhesive layer and / or the second adhesive layer is made of a fluorine-based adhesive having a ratio (percentage: E2 / E1 × 100) of the storage modulus (E2) at 70°C to the storage modulus (E1) at 25°C of 8 to 92%. (6) The sheet-like heater according to any one of (1) to (5) above, wherein the first adhesive layer is made of a fluorine-based adhesive having a solubility of 5 to 30% by mass when subjected to a solvent solubility test in which 1,000 g of tetrahydrofuran (THF) is placed in a 2 L plastic bottle, adjusted to 23° C., and stirred at 600 rpm using a medium-viscosity stirrer using disper blades with a blade diameter of 40 mm as stirring blades, 1 to 50 g of a granular sample having a diameter of 0.5 to 2.0 cm is added, and after 24 hours it is confirmed whether or not the entire amount has dissolved. If the entire amount has dissolved, an additional 1 to 50 g of the sample is added again, and after 24 hours it is confirmed whether or not the entire amount has dissolved. This is repeated to determine the maximum amount that can be dissolved (solubility).

[0010] According to the present invention, when the sheet heater is placed on the curved surface of a heated object having a curved surface, such as a pipe, the tensile (elongation) stress load can be reduced, and in addition, a sheet heater having high insulating properties can be provided.

[0011] 1 is a cross section (schematic cross section) of a preferred embodiment of a heater of the present invention cut in a direction perpendicular to its main surface.

[0012] The present invention will be described. The present invention relates to a heat generating device comprising a high-strength, high-insulation sheet having reinforcing fibers impregnated with a fluororesin, a first adhesive layer, a first insulating layer, a second adhesive layer, and a heat generating layer laminated in this order, the high-strength, high-insulation sheet and the first adhesive layer being in close contact with each other at their main surfaces, the first adhesive layer and the first insulating layer being in close contact with each other at their main surfaces, and the second adhesive layer and the heat generating layer being in close contact with each other at their main surfaces, and a total thickness (H total ) the ratio (h1 / H total ) is 0.10 or more. Such a sheet heater will be hereinafter also referred to as "the heater of the present invention."

[0013] The heater of the present invention will be described using a drawing showing a preferred embodiment thereof. Fig. 1 shows a cross section of a preferred embodiment of the heater of the present invention when cut in a direction perpendicular to its main surface. Since Fig. 1 is a schematic cross section, the dimensions in Fig. 1 may differ from the actual dimensions.

[0014] The heater 1 of the present invention shown in Figure 1 comprises a high-strength, high-insulation sheet 3, a first adhesive layer 5, a first insulating layer 7, a second adhesive layer 9, a heat-generating layer 11, a third adhesive layer 13, and a second insulating layer 15 laminated in this order, with the main surfaces of adjacent layers in close contact with each other. That is, in the heater of the present invention, it is not essential that the main surfaces of the first insulating layer 7 and the second adhesive layer 9 be in close contact with each other, and another layer may be included between these layers. However, in the preferred embodiment shown in Figure 1, the main surfaces of the first insulating layer 7 and the second adhesive layer 9 are in close contact with each other. Similarly, in the heater of the present invention, the main surfaces of the heat-generating layer 11, the third adhesive layer 13, and the second insulating layer 15 do not necessarily have to be in close contact with each other, but in the preferred embodiment shown in Figure 1, these layers are in close contact with each other.

[0015] The heater of the present invention does not have to have the third adhesive layer and the second insulating layer, but it is preferable to have these layers as in the preferred embodiment shown in FIG.

[0016] <High-Strength, High-Insulating Sheet> The high-strength, high-insulating sheet 3 is a sheet in which reinforcing fibers are impregnated with fluororesin, and has high strength and high insulating properties.

[0017] Here, the reinforcing fibers are high-strength fibers and may be conventionally known reinforcing fibers. Examples of materials for the reinforcing fibers include glass, aramid (aromatic polyamide resin), and carbon fiber. The reinforcing fibers preferably have a cross-sectional diameter (equivalent diameter of a circle with an equal area) of approximately 5 to 10 μm. The reinforcing fibers are preferably plain woven into a sheet. In other words, they are preferably in the form of a woven fabric.

[0018] The high-strength, high-insulation sheet 3 is obtained by impregnating the reinforcing fibers with a fluororesin. The fluororesin is not particularly limited, but examples thereof include polytetrafluoroethylene (PTFE), vinylidene fluoride-hexafluoropropylene copolymer, and vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer. A primer may be applied to the reinforcing fibers, and then the fibers may be impregnated with the fluororesin.

[0019] The high-strength, high-insulation sheet 3 is preferably a woven fabric of glass fiber, that is, glass cloth impregnated with PTFE.

[0020] The thickness of the high-strength, high-insulation sheet is not limited, but is preferably 100 to 300 μm, and more preferably 125 to 200 μm.

[0021] The thickness of the high-strength, highly insulating sheet refers to a value obtained by measurement as follows: After obtaining an enlarged photograph (200x magnification) of a cross section of the heater of the present invention in a direction perpendicular to the main surface, as shown in Figure 1, the thickness of the high-strength, highly insulating sheet is measured at 100 randomly selected points on the enlarged photograph, and a simple average value is calculated. The obtained average value is then used as the thickness of that layer. The thicknesses of the other layers described below (first adhesive layer 5, first insulating layer 7, second adhesive layer 9, heating layer 11, third adhesive layer 13, second insulating layer 15, and other layers) also refer to values ​​obtained by measurement in the same manner.

[0022] <First Adhesive Layer, Second Adhesive Layer, Third Adhesive Layer> The first adhesive layer 5, the second adhesive layer 9, and the third adhesive layer 13 will now be described. These may be of the same embodiment or may be of different embodiments.

[0023] The main surface of the first adhesive layer 5 is in close contact with the main surfaces of the high-strength, high-insulation sheet 3 and the first insulating layer 7. The main surface of the second adhesive layer 9 is in close contact with the main surfaces of the first insulating layer 7 and the heat-generating layer 11. The main surface of the third adhesive layer 13 is in close contact with the main surfaces of the heat-generating layer 11 and the second insulating layer 15.

[0024] The first adhesive layer 5, the second adhesive layer 9, and the third adhesive layer 13 are preferably made of an adhesive α. Examples of the adhesive α include a fluorine-based adhesive, a silicone-based rubber, a silicone-based pressure-sensitive adhesive, a polyimide-based adhesive, etc. Examples of the fluorine-based adhesive include fluorine rubber and a fluorine-based elastomer (such as PFA).

[0025] The adhesive α preferably has a fluorine content of 64% by mass or less, and more preferably 57 to 60% by mass. Here, the fluorine content of the adhesive α refers to the value obtained by absorbing fluororesin combustion gas in an absorption liquid and performing quantitative analysis according to JIS K 0102, section 34.1, using a method in accordance with JIS K 7217, which is an analytical method for plastic combustion gases.

[0026] The adhesive α is a fluorine-based adhesive, and the unsaturated bond content is preferably in the range of 0.1 to 20%, more preferably in the range of 0.1 to 10%. Here, the unsaturated bond content in the adhesive α is 1 It is calculated from the ratio of the integrated amount of the peak (4.5 to 6.0 ppm) derived from alkyl chain unsaturated bond hydrogen to the integrated amount of the peak derived from saturated bond hydrogen in the spectrum obtained by H-NMR (solid-state NMR) measurement.

[0027] The adhesive α is a fluorine-based adhesive, and preferably has a storage modulus (E1) of 0.2 to 15 MPa, and more preferably 1 to 10 MPa, at 25° C. Here, the storage modulus (E1) of the adhesive α at 25° C. is the value obtained at 25° C. when an adhesive layer having a thickness of 400 μm is used and measured with a dynamic thermoelasticity measuring device at a measurement frequency of 10 Hz while increasing the temperature from 0° C. to 120° C. at a rate of 3° C. / min.

[0028] The adhesive α is a fluorine-based adhesive, and preferably has a storage modulus (E2) of 0.1 to 10 MPa, and more preferably 0.5 to 8 MPa, at 70° C. Here, the storage modulus (E2) of the adhesive α at 70° C. is measured using a 400 μm thick adhesive layer with a dynamic thermoelasticity measuring device at a measurement frequency of 10 Hz while increasing the temperature from 0° C. to 120° C. at a rate of 3° C. / min, and is the value obtained at 70° C.

[0029] The adhesive α is a fluorine-based adhesive, and the ratio of the storage modulus (E2) at 70°C to the storage modulus (E1) at 25°C (percentage: E2 / E1 × 100) is preferably 8 to 92%, more preferably 20 to 85%.

[0030] The present inventors have found that when at least one adhesive layer selected from the group consisting of the first adhesive layer 5, the second adhesive layer 9, and the third adhesive layer 13 is made of a fluororesin adhesive having a ratio (percentage: E2 / E1 x 100) of the storage modulus (E2) at 70°C to the storage modulus (E1) at 25°C of 8 to 92% (preferably 20 to 85%), the heater of the present invention is prone to curling when placed on the curved surface of a heated object such as a pipe. In the heater of the present invention in which at least one adhesive layer selected from the group consisting of the first adhesive layer 5, the second adhesive layer 9, and the third adhesive layer 13 is made of the above-mentioned fluororesin adhesive, when electricity is applied to the heat-generating layer, the elastic modulus of the fluororesin adhesive decreases due to the heat generated from the heat-generating layer. In this state, when the heater of the present invention is deformed to fit closely to the curved surface of the heated object, the fluororesin adhesive easily follows and deforms accordingly. The inventors have found that when the heater of the present invention is then kept in close contact with the curved surface of the heated body, the power supply to the heating layer is stopped and the heater of the present invention is cooled to approximately room temperature, the heater of the present invention will develop a curling tendency because the elastic modulus of the fluorine-based adhesive is high, and as a result, the heater of the present invention can be easily positioned on the curved surface of a heated body having a curved surface, such as a pipe.

[0031] Furthermore, when placing the heater of the present invention on a curved surface of a heated body such as a pipe, the heater of the present invention can be easily applied to the curved surface of the heated body by previously curving the heater to fit the curved surface. The inventors have found that when at least one selected from the group consisting of the first adhesive layer 5, the second adhesive layer 9, and the third adhesive layer 13 is made of a fluorine-based adhesive having a ratio (percentage: E2 / E1 x 100) of the storage modulus (E2) at 70°C to the storage modulus (E1) at 25°C of 8 to 92% (preferably 20 to 85%), the heater of the present invention can be easily pre-curved to fit the curved surface of the heated body. A method for bending the heater of the present invention before installation includes, for example, placing a cylinder having a curved surface with the same curvature as the object to be heated and the heater of the present invention in an oven and heating them to approximately 110°C, wrapping the heater of the present invention around the outer surface of the cylinder in the oven to bend it, removing the cylinder with the heater of the present invention wrapped around it from the oven and allowing it to cool to approximately room temperature, and then removing the heater of the present invention from the cylinder.

[0032] The adhesive α is preferably a fluorine-based adhesive that has a solubility of 5 to 30 mass%, preferably 10 to 28 mass%, as determined in a solvent solubility test. At least one selected from the group consisting of the first adhesive layer 5, the second adhesive layer 9, and the third adhesive layer 13 is preferably made of such a fluorine-based adhesive. Of these, it is preferable that the first adhesive layer 5 be made of a fluorine-based adhesive that has a solubility of 5 to 30 mass% (preferably 10 to 28 mass%) as determined in a solvent solubility test.

[0033] The solvent solubility test herein refers to a test in which 1,000 g of tetrahydrofuran (THF) is placed in a 2 L plastic bottle, adjusted to 23°C, and stirred at 600 rpm using a medium viscosity stirrer equipped with disper blades with a blade diameter of 40 mm as stirring blades. 1 to 50 g of a granular sample (adhesive α) having a diameter of 0.5 to 2.0 cm is then added into the bottle, and after 24 hours it is confirmed whether or not the entire amount has dissolved. If the entire amount has dissolved, an additional 1 to 50 g of the sample (adhesive α) is added again, and after 24 hours it is confirmed whether or not the entire amount has dissolved, repeating this procedure to determine the maximum amount that can be dissolved (solubility).

[0034] The thickness of the first adhesive layer 5 is not limited, but is preferably 5 to 50 μm, and more preferably 20 to 30 μm.

[0035] The thickness of the second adhesive layer 9 is not limited, but is preferably 5 to 100 μm, and more preferably 20 to 30 μm.

[0036] The thickness of the third adhesive layer 13 is not limited, but is preferably 5 to 100 μm, and more preferably 20 to 30 μm.

[0037] <First Insulating Layer, Second Insulating Layer> The first insulating layer 7 and the second insulating layer 15 will now be described. These may be of the same type or may be of different types.

[0038] The main surface of first insulating layer 7 is in close contact with the main surfaces of first adhesive layer 5 and second adhesive layer 9. First insulating layer 7 serves to electrically insulate heating layer 11 from high-strength, high-insulation sheet 3. The main surface of second insulating layer 15 is in close contact with the main surface of third adhesive layer 13. When second insulating layer 15 has another layer on the main surface opposite to third adhesive layer 13, second insulating layer 15 serves to electrically insulate that layer from heating layer 11.

[0039] It is preferable that the first insulating layer 7 and the second insulating layer 15 have thermal conductivity in addition to insulation.

[0040] The first insulating layer 7 and the second insulating layer 15 are preferably made of, for example, PET (polyethylene terephthalate), PI (polyimide), PP (polypropylene), PE (polyethylene), PEN (polyethylene naphthalate), TAC (triacetyl cellulose), ceramic, etc., because these have high insulating properties. Among these, the first insulating layer 7 and the second insulating layer 15 made of PI (polyimide) are preferred because of their excellent heat resistance and insulating properties.

[0041] The thickness (h1) of the first insulating layer 7 is not limited, but is preferably 25 to 75 μm, and more preferably 40 to 60 μm.

[0042] The thickness of the second insulating layer 15 is not limited, but is preferably 10 to 50 μm, and more preferably 20 to 30 μm.

[0043] There are no particular limitations on the shape or size of the main surfaces of the first insulating layer 7 and the second insulating layer 15. However, since the first insulating layer 7 and the second insulating layer 15 serve to electrically insulate the heat generating layer 11 from other layers, the size of the main surfaces of the first insulating layer 7 and the second insulating layer 15 is usually the same as or larger than the main surface of the heat generating layer 11.

[0044] In the heater of the present invention, the total thickness (H total ) the ratio of the thickness (h1) of the first insulating layer to the thickness (h1) of the first insulating layer (h1 / H total ) is 0.10 or more, preferably 0.15 or more, and more preferably 0.20 or more. In such cases, the present inventors have found that when the heater of the present invention is placed on the curved surface of a heated object having a curved surface, such as a pipe, the tensile (elongation) stress load can be reduced. Conventionally, it has been desired to make sheet heaters as thin as possible from the viewpoints of ease of installation on curved surfaces such as pipes, specifically ease of wrapping around the outer surface of the pipe and ease of heat transfer. However, the present inventors have found that simply making the heater thinner increases the tensile (elongation) stress load, raising concerns that a change in resistance value may occur due to elongation of the heating element. And, even if the overall thickness of the sheet heater is reduced, the thickness (h1) of the first insulating layer is not reduced but rather increased, specifically the total thickness (H total ) the ratio of the thickness (h1) of the first insulating layer to the thickness (h1) of the first insulating layer (h1 / H total The present inventors have found that the tensile (elongation) stress load can be reduced by making the ratio (R) of the tensile strength to the elongation constant (R) equal to or greater than 0.10.

[0045] <Heat generating layer> The heat generating layer 11 will be described. The heat generating layer 11 may be a sheet-like material that generates heat when an electric current is applied. The heat generating layer 11 may be, for example, a metal foil, a metal mesh sheet, a metal fiber sheet, or a carbon sheet.

[0046] The material of the heat generating layer 11 is not particularly limited as long as it generates heat when electricity is passed through it, and although stainless steel is preferable, Cu (copper), Al (aluminum), Ni (nickel), nichrome, or carbon may also be used.

[0047] The thickness of the heat generating layer 11 is preferably 10 to 600 μm, more preferably 20 to 150 μm, and from the viewpoint of flexibility and strength, is preferably about 30 μm.

[0048] The shape and size of the main surface of the heat generating layer 11 can be adjusted appropriately to suit the shape and size of the heated body on which the sheet of the present invention is to be placed.

[0049] The resistance value of the heating layer 11 is preferably 10 to 800 Ω, and more preferably 80 to 200 Ω. If this resistance value is too low, there is a possibility that the temperature will become too high due to excessive output, and conversely, if the resistance value is too high, there is a possibility that the temperature will take a long time to rise due to insufficient output. Here, the resistance of the heating layer is a value determined in accordance with JIS K 7194.

[0050] The heat generating layer 11 is preferably composed primarily of metal fibers, and more preferably solely of metal fibers. Here, "primarily" means 70% by mass or more. That is, the heat generating layer 75 is preferably composed of 70% by mass or more of metal fibers. The proportion of metal fibers contained in the heat generating layer 75 is more preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0051] The proportion of metal fibers contained in heat generating layer 11 is determined by the following method: In an SEM image obtained by magnifying the surface of heat generating layer 11 by 1,000 times using a scanning electron microscope (SEM), the area of ​​metal fibers (excluding voids) within the field of view is determined using an image processing device, and this is converted to a volume ratio by raising it to the power of 2 / 3, and then multiplied by the specific gravity to determine a mass ratio, thereby calculating the metal fiber content.

[0052] The metal fibers are preferably metallic fibers having a cross-sectional equivalent circle diameter of 2 to 100 μm (preferably 5 to 20 μm) and a length of 2 to 20 mm. The heat-generating layer 11 is preferably a sheet-like structure (metal fiber sheet) in which countless such metallic fibers are intricately entangled. The metal fiber sheet may consist solely of metal fibers, but may also contain other materials (e.g., resin fibers that function as binders) as long as they do not impede heat generation. The metal fibers constituting the metal fiber sheet are in contact with each other to the extent that they are electrically conductive. The metal fibers are preferably connected to each other at contact points. For example, the metal fibers are preferably sintered at high temperatures to melt some of them, followed by a history of solidification, so that the metal fibers are fused to each other at their contact points.

[0053] The metal fiber sheet is preferably a SUS fiber sheet because of its high heat resistance and chemical resistance. Examples of the SUS fiber sheet include a stainless fiber sheet (for example, Tommyfirec SS, manufactured by Tomoegawa Paper Co., Ltd.).

[0054] The metal fiber sheet has a basis weight of 25 g / m 2 It is preferable that the weight is 50 g / m or more. 2 It is preferable that the density is 1000 g / m or more. 2 It is preferable that the weight is 200 g / m or less. 2 It is more preferable that the basis weight is equal to or less than 10 ...

[0055] The density of the metal fiber sheet is 1.0 to 10.0 g / cm 3 is preferably 1.4 to 2.0 g / cm 3 More preferably, it is 1.7 g / cm 3 The density of the metal fiber sheet is preferably about 1 / 2 of the density (g / cm 3 ) in accordance with JIS P 8118. 3 )=Basic weight (g / m 2 ) / (thickness (mm)×1000).

[0056] Metal fiber sheets can be manufactured by either a dry nonwoven fabric manufacturing method or a wet papermaking method. When manufactured by the wet papermaking method, numerous metallic fibers having a cross-sectional equivalent circle diameter of 2 to 100 μm and a length of 2 to 20 mm are stirred in a dispersion medium (water, organic solvent, etc.), and then an organic flocculant is added, and the mixture is formed into a sheet using a rectangular hand-made sheeting machine (manufactured by Toyo Seiki Co., Ltd., etc.), and the sheet is dried using a ferrotype dryer to a basis weight of 50 to 1100 g / m. 2 A dried sheet of the above is obtained. Then, the sheet is fired at 400 to 1300° C. to obtain a metal fiber sheet. In principle, it is preferable that no organic flocculant remains in the metal fiber sheet.

[0057] <Thermal diffusion layer> As described above, the heater 1 of the present invention comprises a high-strength, high-insulation sheet 3, a first adhesive layer 5, a first insulating layer 7, a second adhesive layer 9, and a heat-generating layer 11 (preferably further comprising a third adhesive layer 13 and a second insulating layer 15) laminated in this order, with the main surfaces of adjacent layers being in close contact with each other. The high-strength, high-insulation sheet 3 may further comprise a thermal diffusion layer on the main surface thereof opposite to the first adhesive layer 5. The thermal diffusion layer diffuses the heat generated by the heat-generating layer, allowing the heated object to be heated more uniformly.

[0058] There are no particular limitations on the method for adhering the thermal diffusion layer to the main surface of the high-strength, high-insulation sheet 3 that does not have the first adhesive layer 5 attached, but it is preferable to use the adhesive α described above for adhesion.

[0059] The thermal conductivity of the thermal diffusion layer in its in-plane direction is preferably higher than that of the heat-generating layer in its in-plane direction, because this further enhances the thermal diffusion ability. The thermal conductivity of the thermal diffusion layer is measured at room temperature using a known measurement method, such as a laser flash thermal diffusivity measurement (e.g., the LFA series manufactured by NETZSCH) or an optical AC thermal diffusivity measurement (e.g., the LaserPit series manufactured by Advance Riko).

[0060] The thermal diffusion layer is preferably made of a metal such as carbon, aluminum, copper, zinc, lead, gold or silver, or a ceramic such as alumina or aluminum nitride.

[0061] The thermal diffusion layer is preferably made of a carbon film, as this has excellent flexibility and high thermal conductivity in the extending direction.

[0062] The thickness of the thermal diffusion layer is not particularly limited, but is preferably 5 to 300 μm, more preferably 15 to 200 μm, and even more preferably about 100 μm.

[0063] The total thickness of the sheet of the present invention is not limited, but is preferably 200 to 800 μm, more preferably 200 to 500 μm, and even more preferably 300 to 450 μm.

[0064] The present invention will be described with reference to examples, but the present invention is not limited to the embodiments described below.

[0065] [Experiment 1]

[0066] Example 1 A sheet heater of the configuration shown in Figure 1 was prepared. Details of each layer are as follows: High-strength, highly insulating sheet: PTFE cloth (FGF-500-8, manufactured by Chukoh Chemical Industry Co., Ltd.), thickness 170 µm; First adhesive layer: layer made of fluorine-based adhesive, thickness 25 µm; First insulating layer: polyimide coating, thickness 50 µm; Second adhesive layer: same as first adhesive layer (thickness 25 µm); Heat-generating layer: stainless steel paper (Tomy Firec SS, manufactured by Tomoegawa Paper Works), thickness 30 µm; Third adhesive layer: same as first adhesive layer and second adhesive layer (thickness 25 µm); Second insulating layer: same as first insulating layer (thickness 25 µm).

[0067] The thickness of each layer is a value obtained by measuring it using the method described above.

[0068] The fluorine-based adhesive used to form the first adhesive layer, the second adhesive layer, and the third adhesive layer is a fluorine-based adhesive whose solubility in the solvent solubility test described above is in the range of 5 to 30 mass %. In the solvent solubility test, a high-power general-purpose mixer BLH1200 manufactured by Shinto Scientific Co., Ltd. was used as a medium-strength mixer.

[0069] Furthermore, the fluorine content of this fluororesin adhesive was measured using the method described above and was found to be in the range of 57 to 60% by mass. Furthermore, the unsaturated bond content of this fluororesin adhesive was measured using the method described above and was found to be in the range of 0.1 to 10%. Furthermore, the storage modulus (E1) of this fluororesin adhesive at 25°C was measured using the method described above and was found to be 5.58 MPa. Furthermore, the storage modulus (E2) of this fluororesin adhesive at 70°C was measured using the method described above and was found to be 3 MPa.

[0070] The strain (gauge value) of the sheet heater obtained in Example 1 was measured. The strain (gauge value) was measured as follows: A strain gauge of a strain measuring instrument (FLAB-1-11-3LJCT manufactured by Tokyo Sokki Kenkyusho) was fixed with an adhesive to the upper side of the heating element layer so that it was in the same direction as the winding direction, and then the adhesive layer 13 and the third insulating layer 15 were laminated. The strain immediately after lamination was defined as zero, and the strain gauge value was read when the heater was wound around a φ27 mm cylinder.

[0071] The results are shown in Table 1. Table 1 also shows the elongation (%) calculated as 1 / 10,000 of the gauge value.

[0072] Example 2 An experiment was carried out in the same manner as in Example 1, except that the thickness of the first insulating layer was set to 25 μm. The results are shown in Table 1.

[0073] Example 3 An experiment was carried out in the same manner as in Example 1, except that a PTFE cloth (FGF-500-10, manufactured by Chukoh Chemical Industry Co., Ltd.) with a thickness of 250 μm was used as the high-strength, high-insulation sheet. The results are shown in Table 1.

[0074] Example 4 The same experiment as in Example 1 was carried out, except that the thickness of the first adhesive layer was set to 50 μm. The results are shown in Table 1.

[0075] Example 5: A layer of fluorine-based adhesive (25 μm thick) and a polyimide coating (50 μm thick) were added between the first insulating layer and the second adhesive layer in Example 1. That is, the high-strength, highly insulating sheet, the first adhesive layer, the first insulating layer, the layer of fluorine-based adhesive (25 μm thick), the polyimide coating (50 μm thick), the second adhesive layer, the heat-generating layer, the third adhesive layer, and the second insulating layer were laminated in this order. Except for these, the experiment was conducted in the same manner as in Example 1. The results are shown in Table 1.

[0076] Example 6 An experiment was carried out in the same manner as in Example 1, except that a PTFE cloth (FGF-500-2, manufactured by Chukoh Chemical Industry Co., Ltd.) with a thickness of 50 μm was used as the high-strength, high-insulation sheet and the thickness of the first insulating layer was set to 25 μm. The results are shown in Table 1.

[0077] Example 7 An experiment identical to Example 1 was carried out, except that a PTFE cloth (FGF-500-6, manufactured by Chukoh Chemical Industry Co., Ltd.) with a thickness of 125 μm was used as the high-strength, high-insulation sheet.

[0078] Example 8 The same experiment as in Example 1 was carried out, except that the thickness of the first adhesive layer was set to 20 μm. The results are shown in Table 1.

[0079] Example 9 An experiment was carried out in the same manner as in Example 1, except that the thickness of the first insulating layer was set to 75 μm. The results are shown in Table 1.

[0080] Comparative Example 1 An experiment was carried out in the same manner as in Example 1, except that a 250 μm thick PTFE cloth (FGF-500-10, manufactured by Chukoh Chemical Industry Co., Ltd.) was used as the high-strength, high-insulation sheet, and the thickness of the first insulating layer was set to 25 μm. The results are shown in Table 1.

[0081] Comparative Example 2 An experiment identical to that of Example 1 was carried out, except that a 250 μm thick PTFE cloth (FGF-500-10, manufactured by Chukoh Chemical Industry Co., Ltd.) was used as the high-strength, high-insulation sheet, the first adhesive layer was set to a thickness of 50 μm, and the first insulating layer was set to a thickness of 25 μm. The results are shown in Table 1.

[0082] <Comparative Example 3> An aluminum layer having a thickness of 30 μm was attached to the main surface (the main surface not having the first adhesive layer) of the high-strength, high-insulation sheet of the sheet-type heater in Comparative Example 1 using an adhesive. The adhesive used here was the same as that used to form the first adhesive layer, and the adhesive layer X made of the adhesive used to attach this aluminum layer had a thickness of 25 μm. Apart from this, the experiment was conducted in the same manner as in Comparative Example 1. The results are shown in Table 1.

[0083]

[0084] As shown in Table 1, the total thickness (H total ) the ratio of the thickness (h1) of the first insulating layer to the thickness (h1) of the first insulating layer (h1 / H total It was confirmed that when this value was 0.10 or more, the elongation percentage was low, which was preferable. On the other hand, in the cases of Comparative Examples 1 to 3 where this value was less than 0.1, the elongation percentage was high.

[0085] [Experiment 2] <Example 10> The first adhesive layer, second adhesive layer, and third adhesive layer in Example 1 described above were formed using a fluorine-based adhesive in which the ratio (percentage: E2 / E1 x 100) of the storage modulus (E2) at 70°C to the storage modulus (E1) at 25°C was 50%. The thickness was 25 μm, the same as in Example 1. A sheet heater was produced using the same high-strength, highly insulating sheet, first insulating layer, heat-generating layer, and second insulating layer as in Example 1. A test was then conducted in which this sheet heater was wrapped around a stainless steel pipe with an outer diameter of 42.7 mm and an inner diameter of 35.7 mm. Specific details are as follows.

[0086] First, the stainless steel pipe and sheet heater were placed in an oven with the inside temperature adjusted to 110°C and heated for 30 minutes. Next, while the stainless steel pipe and sheet heater were heated in the oven, the sheet heater was wrapped around the stainless steel pipe and held in that state for 10 minutes. Next, the stainless steel pipe with the sheet heater wrapped around it was removed from the oven in that state and allowed to cool to room temperature in the room. Next, the sheet heater was removed from the stainless steel pipe, and the inner diameter of the sheet heater, which formed a cylindrical shape or a partial shape, was measured. Next, the inner diameter was compared with the outer diameter (42.7 mm) of the stainless steel pipe. If the inner diameter of the deformed sheet heater was 10 mm or more larger than the outer diameter of the stainless steel pipe, it was judged that there was no curl (X in Table 2). If it was less than 10 mm larger, it was judged that there was a curl (O in Table 2). The results are shown in Table 2.

[0087] Example 11 In Example 10, the first adhesive layer, the second adhesive layer, and the third adhesive layer were formed using a fluorine-based adhesive in which the ratio (percentage: E2 / E1 x 100) of the storage modulus (E2) at 70°C to the storage modulus (E1) at 25°C was 50%, whereas in Example 11, the first adhesive layer, the second adhesive layer, and the third adhesive layer were formed using a fluorine-based adhesive in which the ratio (percentage: E2 / E1 x 100) of the storage modulus (E2) at 70°C to the storage modulus (E1) at 25°C was 70%. A sheet-shaped heater was produced using the same procedures as in Example 10, and the same tests were performed. The results are shown in Table 2.

[0088] Comparative Example 4 In Example 10, the first adhesive layer, the second adhesive layer, and the third adhesive layer were formed using a fluorine-based adhesive in which the ratio (percentage: E2 / E1 x 100) of the storage modulus (E2) at 70°C to the storage modulus (E1) at 25°C was 50%, whereas in Comparative Example 4, the first adhesive layer, the second adhesive layer, and the third adhesive layer were formed using a paraffin-based adhesive in which the ratio (percentage: E2 / E1 x 100) of the storage modulus (E2) at 70°C to the storage modulus (E1) at 25°C was 5%. A sheet heater was produced using the same procedures as in Example 10, and the same tests were performed. The results are shown in Table 2.

[0089] Comparative Example 5 In Example 10, the first adhesive layer, the second adhesive layer, and the third adhesive layer were formed using a fluorine-based adhesive in which the ratio (percentage: E2 / E1 x 100) of the storage modulus (E2) at 70°C to the storage modulus (E1) at 25°C was 50%, whereas in Comparative Example 4, the first adhesive layer, the second adhesive layer, and the third adhesive layer were formed using a polyimide-based adhesive in which the ratio (percentage: E2 / E1 x 100) of the storage modulus (E2) at 70°C to the storage modulus (E1) at 25°C was 100%. A sheet-shaped heater was produced using the same procedures as in Example 10, and the same tests were performed. The results are shown in Table 2.

[0090]

[0091] The sheet heaters obtained in Examples 10 and 11 were able to form a good curl. In contrast, the sheet heaters obtained in Comparative Examples 4 and 5 were unable to form a good curl.

[0092] This application claims priority based on Japanese Patent Application No. 2022-056330, filed on March 30, 2022, the disclosure of which is incorporated herein in its entirety.

[0093] REFERENCE SIGNS LIST 1 heater of the present invention 3 high-strength, high-insulation sheet 5 first adhesive layer 7 first insulating layer 9 second adhesive layer 11 heat-generating layer 13 third adhesive layer 15 second insulating layer

Claims

1. a high-strength, high-insulation sheet in which reinforcing fibers are impregnated with fluororesin; a first adhesive layer; a first insulating layer; a second adhesive layer; A heating layer; are layered in this order, the high-strength, high-insulation sheet and the first adhesive layer are in close contact with each other at their main surfaces, the first adhesive layer and the first insulating layer are in close contact with each other at their principal surfaces, the second adhesive layer and the heat generating layer are in close contact with each other at their main surfaces, The total thickness (H total ) to the thickness (h 1 ) ratio (h 1 / H total ) is 0.10 or more.

2. 2. The sheet heater according to claim 1, wherein the total thickness is 200 to 800 μm.

3. The high-strength, high-insulation sheet has a thickness of 100 to 300 μm, 3. The sheet heater according to claim 1, wherein the first adhesive layer has a thickness of 5 to 50 μm.

4. 3. The sheet heater according to claim 1, wherein the heat generating layer is made of a metal fiber sheet.

5. The first adhesive layer and / or the second adhesive layer are Storage modulus at 25°C (E 1 ) to the storage modulus at 70 ° C. (E 2 ) ratio (percentage: E 2 / E 1 3. The sheet heater according to claim 1, wherein the adhesive is a fluorine-based adhesive having a coefficient of elasticity (x100) of 8 to 92%.

6. The first adhesive layer is 3. The sheet-like heater according to claim 1 or 2, wherein 1,000 g of tetrahydrofuran (THF) is placed in a 2 L plastic bottle, adjusted to 23°C, and stirred at 600 rpm using a medium-viscosity stirrer equipped with disper blades having a blade diameter of 40 mm as stirring blades. 1 to 50 g of a granular sample having a diameter of 0.5 to 2.0 cm is then charged into the bottle, and after 24 hours it is confirmed whether or not the entire amount has dissolved. If the entire amount has dissolved, an additional 1 to 50 g of the sample is charged again, and after 24 hours it is confirmed whether or not the entire amount has dissolved. This procedure is repeated to determine the maximum amount that can be dissolved (solubility).