Cord-like heater and heater unit

Abstract

To provide a cord-like heater which has sufficient insulation property under hot water environment and is excellent in productivity, and a heater unit using the same.SOLUTION: A cord-like heater 10 has conductor strands 5a, and a coating 7 formed on the outer periphery of the conductor strands, wherein the coating 7 is composed of a polymer material, and contains a phosphinic acid-based flame retardant. In the cord-like heater 10, a D95 particle diameter of the phosphinic acid-based flame retardant is 20 μm or less. In the cord-like heater 10, the coating contains 10 to 22.5 pts.wt. of the phosphinic acid-based flame retardant with respect to 100 pts.wt. of the polymer material. In the cord-like heater 10, the polymer material is any one of low density polyethylene, a polyester-based thermoplastic elastomer, and a polyester-based resin. There is provided a heater unit 31 in which the cord-like heater 10 is arranged in a base material 11.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a cord-shaped heater that can be suitably used in electric blankets, electric carpets, car seat heaters, steering wheel heaters, etc., and a heater unit using the same, and in particular to one that can have high resistance to hot water and sufficient insulation properties. [Background technology]

[0002] Cord heaters used in various heaters are generally known to have a configuration in which a conductor wire acting as a resistor is wound in a spiral shape around a core wire and then covered with an insulating layer. Here, copper wires, nickel-chromium alloy wires, etc. are used as the conductor wires, and are configured by drawing or twisting a plurality of them together. Some of these conductor wires are known to have an insulating coating formed on each conductor wire to insulate them from each other. Some of these conductor wires are also known to have a heat-sealed portion formed on the outer periphery of the conductor wire or the outer periphery of the insulating layer. For example, it is known that a cord heater is arranged on a substrate such as a nonwoven fabric, aluminum foil, or polymer foam, and heated and pressurized, so that the cord heater and the substrate are heat-sealed by the heat-sealed portion to form a heater unit (see, for example, Patent Documents 1 to 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] WO2011 / 001953: Crabbe [Patent Document 2] Patent Publication 2021-190170:TOTOKU DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0004] The cord-shaped heater and heater unit described in the above patent document have the following problems. First, there is a concern that the voltage resistance of the cord-shaped heater will decrease if it is immersed in hot water for a long period of time. Even if there is no purpose in actual use to immerse the cord-shaped heater in hot water for a long period of time, the cord-shaped heater generates heat, so if it remains wet with water, it may be subjected to the same load as if it were immersed in hot water for a long period of time. For this reason, it is preferable for the cord-shaped heater to be resistant to hot water. In addition, there is a possibility that defects in the outer diameter and appearance may occur due to insufficient consideration given to the dispersibility of additives. If the dispersibility of additives is poor, the resin may break during extrusion molding, resulting in defects in the outer diameter and appearance, which leads to a decrease in productivity. In addition, it is preferable that the heater wire has a small diameter. If the heater wire has a small diameter, even if it is wired close to the surface of the heating device, the shape of the heater wire is not easily visible on the surface of the heating device, and there is no discomfort when touching it. Therefore, there is a demand for a heater wire that can be designed to have a small diameter.

[0005] The present invention has been made to solve such problems with the prior art, and its object is to provide a cord-shaped heater that is resistant to hot water, has excellent productivity, can be designed to have a small diameter, and has sufficient insulation, and a heater unit that uses the same. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the cord-shaped heater of the present invention has a conductor wire and a coating formed around the outer periphery of the conductor wire, the coating being made of a polymeric material and containing a phosphinic acid-based flame retardant. In addition, it is considered that the D95 particle size of the phosphinic acid flame retardant is 20 μm or less. It is also considered that the coating contains 10 to 22.5 parts by weight of the phosphinic acid flame retardant per 100 parts by weight of the polymer material. The polymer material may be any one of low-density polyethylene, polyester-based thermoplastic elastomer, and polyester-based resin. A heater unit according to the present invention comprises the above cord-shaped heater disposed on a substrate. Effect of the Invention

[0007] According to the cord-shaped heater of the present invention, the polymer material of the covering contains a phosphinic acid-based flame retardant, so that the insulation resistance does not decrease even in a hot water environment exceeding 80°C, and sufficient insulation performance can be maintained. In addition, compared to the coating thickness of 180 μm, the phosphinic acid flame retardant can have a fine and uniform particle size, which makes it highly dispersible during compounding and prevents the resin from breaking during extrusion molding. This prevents roughness of the outer diameter and appearance, improving productivity. In addition, even with a thin extrusion coating, the resin does not break. This makes it possible to design a thin-diameter heater wire that does not feel strange to the touch. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an embodiment of the present invention, and is a partially cutaway side view showing the configuration of a cord-shaped heater. [Diagram 2] FIG. 2 is a diagram showing an embodiment of the present invention, and is a plan view showing a configuration of a heater unit. [Diagram 3] FIG. 1 is a diagram showing an embodiment of the present invention, illustrating the configuration of a hot press heater manufacturing apparatus. [Figure 4] FIG. 1 is a diagram showing an embodiment of the present invention, and is a partial perspective view showing how cord-shaped heaters are arranged in a predetermined pattern shape. [Diagram 5] FIG. 2 is a side view showing an embodiment of the present invention, with a portion cut away, illustrating the configuration of a conductor wire on which an insulating coating is formed. [Figure 6] FIG. 11 is a diagram showing another embodiment of the present invention, and is a partially cutaway side view showing the configuration of a cord-shaped heater. [Figure 7] FIG. 11 is a diagram showing another embodiment of the present invention, and is a partially cutaway side view showing the configuration of a cord-shaped heater. [Figure 8]FIG. 11 is a diagram showing another embodiment of the present invention, and is a partially cutaway side view showing the configuration of a cord-shaped heater. [Figure 9] 1 is a partially cutaway perspective view showing a heater unit according to the present invention embedded in a vehicle seat; BEST MODE FOR CARRYING OUT THEINVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. These embodiments show examples in which the present invention is applied to a heater unit for a steering heater for a vehicle.

[0010] First, the present embodiment will be described with reference to Figs. 1 to 5. The configuration of the cord-shaped heater 10 in this embodiment will be described. The cord-shaped heater 10 in this embodiment is configured as shown in Fig. 1. First, there is a core wire 3 made of an aromatic polyamide fiber bundle having an outer diameter of about 0.2 mm, and five conductor strands 5a made of hard tin-containing copper alloy wires having a strand diameter of 0.08 mm are wound helically at a pitch of about 1.0 mm around the core wire 3. An insulating coating 5b is formed around the conductor strands 5a. The insulating coating 5b has a configuration as shown in Fig. 5, and is formed of an inner layer 5c made of polyurethane resin and an outer layer 5d made of polyamideimide resin. The inner layer 5c of the insulating coating 5b is formed to a thickness of 4 µm by applying polyurethane varnish around the conductor strands 5a and drying it. Next, the outer layer 5d is formed to a thickness of 4 µm by applying polyamideimide varnish to the outer periphery of the inner layer 5c and drying it. The core wire 3 around which the conductor wire 5a is wound is covered with a coating 7. The coating 7 is extrusion-coated with low-density polyethylene having a melting point of 107°C and a phosphinic acid flame retardant to a thickness of 0.180 mm. At this time, 20 parts by weight of the phosphinic acid flame retardant is mixed with 100 parts by weight of the low-density polyethylene, and the D95 particle size of the phosphinic acid flame retardant is 20 μm or less.

[0011] Alternatively, as shown in Fig. 6, an outer layer coating 9 may be provided on the outer periphery of this coating 7. In this case, the coating 7 is preferably extrusion coated with a polyester thermoplastic elastomer having a melting point of 211°C to a thickness of 0.180 mm, and the outer layer coating 9 is preferably extrusion coated with a low-density polyethylene having a melting point of 107°C and containing a phosphinic acid flame retardant to a thickness of 0.175 mm. When the outer layer coating 9 is provided on the outer periphery of the coating 7, the finished outer diameter is 1.1.

[0012] The cord-shaped heater 10 has such a structure, and preferably, the low-density polyethylene containing the phosphinic acid flame retardant is in the outermost layer as the coating 7 or the outer coating 9. In this embodiment, the coating 7 is low-density polyethylene, and the outer coating 9 is not provided.

[0013] Although the above-mentioned core wire 3 is effective when considering flexibility and tensile strength, it is also possible to align or twist a plurality of conductor wires without using the core wire 3. The median particle size of the phosphinic acid flame retardant to be added is preferably 20 μm or less in terms of D95 particle size, and the phosphinic acid flame retardant is preferably contained in an amount of 10 to 22.5 parts by weight per 100 parts by weight of the polymer material.

[0014] A hot water resistance test was conducted in the form of a pressed sheet for the low density polyethylene containing a phosphinic acid flame retardant used in the coating 7 according to the above embodiment. This test method is based on JIS K 6271-1. The reason for conducting the test in the form of a pressed sheet is also based on JIS K 6271-1. First, a pressed sheet of low density polyethylene containing a phosphinic acid flame retardant, measuring 150 mm x 150 mm x 1 mm, was prepared, and the insulation resistance between the circular electrodes of φ50 was measured. After that, the sheet was immersed in hot water of a specified temperature for 24 hours, and then removed. After wiping off the water droplets, the insulation resistance between the circular electrodes of φ50 was measured again. The results of the hot water resistance test are shown in Table 1. In addition, a similar measurement was conducted on a pressed sheet of low density polyethylene containing a phosphoric acid mixture flame retardant, not containing a phosphinic acid flame retardant, measuring 150 mm x 150 mm x 1 mm, as a comparative form. The results of these measurements are shown in Table 1. [Table 1]

[0015] As shown in Table 1, the cord-shaped heater 10 according to the embodiment had sufficient insulation performance in a hot water environment. On the other hand, the cord-shaped heater 10 according to the comparative embodiment 1 had insulation performance that was not problematic in practical use, but was inferior to the embodiment.

[0016] Next, the structure of the base material 11 (see FIG. 2) to which the cord-shaped heater 10 having the above-mentioned structure is adhered and fixed will be described. The base material 11 in this embodiment is a nonwoven fabric (basis weight 150 g / m2) made of a mixture of 10% heat-fusible fibers having a core-sheath structure with a low melting point polyester as the sheath component and 90% flame-retardant fibers made of flame-retardant polyester fibers. 2 The nonwoven fabric is made of long fibers, which are continuous fibers that do not have a specific fiber length and are also called filaments.

[0017] Next, a configuration for disposing and bonding / fixing the cord-like heater 10 on the substrate 11 in a meandering shape will be described. In this embodiment, the meandering interval is 20 mm. FIG. 3 is a diagram showing the configuration of a hot press heater manufacturing apparatus 13 for bonding and fixing the cord-like heater 10 on the substrate 11. First, there is a hot press jig 15, on which a plurality of locking mechanisms 17 are provided. As shown in FIG. 4, the locking mechanism 17 has a pin 19, which is inserted from below into a hole 21 drilled in the hot press jig 15. A locking member 23 is attached to the upper part of the pin 19 so as to be movable in the axial direction, and is constantly biased upward by a coil spring 25. Then, as shown by the imaginary line in FIG. 4, the cord-like heater 10 is hooked on the locking members 23 of the plurality of locking mechanisms 17 and disposed in a meandering shape.

[0018] Returning to FIG. 3, a press hot plate 27 is arranged above the plurality of locking mechanisms 17 so as to be movable up and down. That is, the cord-shaped heater 10 is arranged in a serpentine shape while being hooked on the locking members 23 of the plurality of locking mechanisms 17, and the substrate 11 is placed on top of the cord-shaped heater 10. In this state, the press hot plate 27 is lowered to apply heat and pressure to the cord-shaped heater 10 and the substrate 11, for example, at 230° C. for 5 seconds. This causes the coating 7 on the cord-shaped heater 10 side and the heat-fusible fiber on the substrate 11 side to fuse together, and as a result, the cord-shaped heater 10 and the substrate 11 are bonded and fixed together. When the press hot plate 27 is lowered to apply heat and pressure, the locking members 23 of the plurality of locking mechanisms 17 move downward against the biasing force of the coil spring 25.

[0019] An adhesive layer may be formed or a double-sided tape may be attached to the surface of the base material 11 on which the cord-shaped heater 10 is not provided, in order to fix the heater unit 31 to the seat when the heater unit 31 is attached to the seat.

[0020] By carrying out the above operations, a heater unit 31 for a vehicle seat heater can be obtained as shown in Fig. 2. A cord is connected to both ends of the cord-like heater 10 in the heater unit 31 and to the temperature control device 39, and the cord-like heater 10, the temperature control device 39, and the connector 35 are connected by the cord. The connector 35 is then used to connect to the vehicle's electrical system (not shown).

[0021] The heater unit 31 having the above-mentioned configuration is embedded and disposed in the vehicle seat 41 in a state as shown in FIG. 9. That is, as described above, the heater unit 31 is attached to the seat cover 43 or the seat pad 45 of the vehicle seat 41. In this case, it is preferable that the surface of the heater unit 31 on which the cord-shaped heater 10 is not disposed faces the seat cover 43. This prevents the cord-shaped heater 10 from rubbing against the seat cover 43 and applying a load to the cord-shaped heater 10. On the other hand, if the surface of the heater unit 31 on which the cord-shaped heater 10 is disposed faces the seat cover 43, there is an advantage that heat can be transferred to the seat occupant more efficiently. Therefore, which surface faces the seat cover 43 is appropriately set according to the required characteristics and the usage environment.

[0022] The present invention is not limited to the above embodiment. First, the cord-shaped heater 10 may be configured, for example, as in the above embodiment, by twisting or aligning a plurality of conductor wires 5a covered with an insulating coating 5b, winding the twisted or aligned conductor wires 5a around a core wire 3, and forming a coating 7 and an outer layer coating 9 on the outer periphery (see FIG. 6). Alternatively, the cord-shaped heater 10 may be configured without using a core wire 3, by twisting a plurality of conductor wires 5a covered with an insulating coating 5b together (see FIG. 7), or by aligning a plurality of conductor wires 5a covered with an insulating coating 5b (see FIG. 8).

[0023] Examples of the core wire 3 include inorganic fibers such as glass fibers, polyester fibers such as polyethylene terephthalate, aliphatic polyamide fibers, aromatic polyamide fibers, fully aromatic polyester fibers, and other organic fibers, such as monofilaments, multifilaments, spans, or these fiber materials, or fibers having a configuration in which the organic polymer material constituting these fiber materials is used as a core material and is covered with a thermoplastic organic polymer material. If the core wire 3 is made to have heat shrinkability and heat meltability, when the conductor wire 5a is broken, the core wire melts and cuts and shrinks due to abnormal heating, and the wound conductor wire 5a also follows the movement of the core wire 3, separating the ends of the broken conductor wire 5a. Therefore, the ends of the broken conductor wire do not come into contact with each other or come into contact with a small contact area such as a point contact, and abnormal heat generation can be prevented. If the conductor wire 5a is insulated by the insulating coating 5b, the insulating material of the core wire 3 does not need to be particular. For example, a stainless steel wire or a titanium alloy wire can be used. However, in consideration of what would happen if the conductor wire 5a were to break, it is better for the core wire 3 to be made of an insulating material.

[0024] The conductor wires 5a may be any known wire, such as copper wire, copper alloy wire, nickel wire, iron wire, aluminum wire, nickel-chromium alloy wire, and iron-chromium alloy wire. Examples of the copper alloy wire include tin-copper alloy wire, copper-nickel alloy wire, and silver-containing copper alloy wire in which copper solid solution and copper-silver eutectic are fibrous. Among these, it is preferable to use copper wire or copper alloy wire in terms of the balance between cost and characteristics. The wire diameter of the conductor wire can be appropriately set according to the resistance value of the intended cord-shaped heater 10. For example, it is possible to use two conductor wires that are hard tin-containing copper alloy wires with a wire diameter of 0.095 mm and three conductor wires that are hard tin-containing copper alloy wires with a wire diameter of 0.085 mm.

[0025] However, when the conductor wire 5a is wound around the core wire 3, among the above-mentioned materials for the conductor wire 5a, those that have a small amount of spring back when wound are preferable, and those with a recovery rate of 200% or less are preferable. For example, a silver-containing copper alloy wire in which copper solid solution and copper-silver eutectic are shaped like fibers has excellent tensile strength and excellent tensile strength and bending strength, but is prone to spring back when wound. Therefore, when winding the conductor wire 5a around the core wire 3, the conductor wire 5a is likely to float or break due to excessive winding tension, and after processing, it is likely to develop a twisting tendency, which is not preferable. In particular, when the conductor wire 5a is covered with an insulating coating 5b, the recovery force of the insulating coating 5b is also added. Therefore, it is important to select a conductor wire 5a with a small recovery rate to cover the recovery force of the insulating coating 5b.

[0026] Here, the measurement of the recovery rate specified in the present invention will be described in detail. First, while applying a constant load to the conductor wire, the conductor wire is wound three or more times around a cylindrical mandrel with a diameter 60 times the diameter of the conductor wire without overlapping. After 10 minutes, the load is removed and the conductor wire is removed from the mandrel. The inner diameter of the shape restored by elasticity is measured, and the rate of springback of the conductor wire is calculated according to the following formula (I) and evaluated as the recovery rate. R = (d 2 / d 1 ) x 100―――(I) Legend: R: Recovery rate (%) d 1 : Mandrel diameter used in winding test (mm) d 2 : Inner diameter (mm) of the conductor wire wound around the mandrel and restored to its original shape after the load is released

[0027] The insulating coating 5b covering the conductor wire 5a may be formed of two layers, an inner layer 5c and an outer layer 5d, as in the above embodiment, or may be formed of three or more layers. The thermal decomposition temperature of the material constituting the inner layer is preferably lower than the lower of the melting point or thermal decomposition temperature of the material constituting the outer layer. Here, the inner layer is a layer formed on the conductor wire 5a. The outer layer may be any layer outside the inner layer, so it is possible to form another outer layer outside the outer layer or to form another intermediate layer between the inner layer and the outer layer. In particular, it is preferable that the material constituting the inner layer is a thermosetting resin and the material constituting the outer layer is a thermosetting resin. Here, the thermosetting resin also includes a crosslinkable material. Considering the heat generation characteristics as a cord-shaped heater and the terminal processability such as soldering, it is preferable that the material constituting the inner layer is a polyurethane resin or a polyester resin, and the material constituting the outer layer is any one of a polyimide resin, a polyamide-imide resin, and a silicone resin. In particular, it is preferable that the material constituting the inner layer is a polyurethane resin and the material constituting the outer layer is a polyamide-imide resin. The polyurethane resin may be one that has been modified or blended in various ways, such as imide-containing polyurethane.

[0028] The inner layer of the insulating coating 5b is thermally decomposed at a temperature below the temperature at which the outer layer melts or decomposes. Therefore, when the end of the conductor wire covered with the insulating coating is heated to a temperature above the thermal decomposition temperature of the inner layer and below the lower of the melting point or thermal decomposition temperature of the outer layer, only the inner layer is thermally decomposed, and a space is formed between the conductor wire and the insulating coating. On the other hand, when the outer layer is formed by the extrusion method or the tape horizontal winding method, it is formed by applying stretching in the length direction. Also, when the outer layer is formed by the coating and curing method, a shrinkage force is generated during curing. That is, the outer layer has a residual stress in the direction compressing it in the length direction. When the inner layer of the conductor wire covered with the insulating coating is thermally decomposed, a space is generated between the insulating coating and the conductor wire. Furthermore, when heat is applied, the outer layer of the insulating coating shrinks. Due to this action, for example, when the end of the conductor wire covered with the insulating coating is heated to a predetermined temperature such as the melting temperature of solder, the insulating coating can be removed to expose the conductor wire. This can improve the ease of terminal processing.

[0029] The thickness of the inner layer 5c is preferably 4.0 μm or more. If the thickness is less than 4.0 μm, the conductor wire 5a may corrode when used in an environment where a corrosive liquid or gas is present, so it is necessary to form an insulating coating or the like on the outer periphery of the insulating coating 5b. In particular, the thickness is preferably 5.0 μm or more. If the thickness of the inner layer 5c is too thin, even if the inner layer 5c is thermally decomposed, there is a risk that a sufficient space is not obtained between the conductor wire 5a and the outer layer 5d, and the outer layer 5d cannot be removed. In addition, the thickness of the inner layer 5c is preferably 7.0 μm or less. If the thickness of the inner layer 5c exceeds 7.0 μm, the amount of gas generated during the thermal decomposition of the inner layer 5c increases. For example, if the generated gas is combustible, it may have a negative effect on the flame retardancy, and the effect of the generated gas cannot be ignored. The thickness of the outer layer 5d is preferably 4.0 μm or more. If the thickness is less than 4.0 μm, the conductor wire 5a may corrode when used in an environment where a corrosive liquid or gas is present, so it is necessary to form an insulating coating or the like on the outer periphery of the insulating coating 5b. In particular, it is preferable that the thickness is 5.0 μm or more. As described above, since the inner layer 5c is thermally decomposed at a relatively low temperature, if the thickness of the outer layer 5d is insufficient, the insulating performance may not be maintained, especially at high temperatures. The thickness of the outer layer 5d is preferably 7.0 μm or less. If the thickness of the outer layer 5d exceeds 7.0 μm, the rigidity of the outer layer 5d may be too strong, and even if the inner layer 5c is thermally decomposed, the outer layer 5d may be difficult to remove. In addition, the thickness of the insulating coating 5b, which is the sum of the thicknesses of the inner layer coating 5c ​​and the outer layer coating 5d, is preferably more than 8.0 μm. If the thickness is 8.0 μm or less, the conductor wire 5a may corrode when used in an environment where a corrosive liquid or gas is present. For example, if the insulating coating 5b is thin, pinholes may be formed in the insulating coating 5b depending on the manufacturing conditions. Furthermore, the insulating coating 5b may be worn away due to friction during use. In this case, the conductor wires 5a inside are exposed, and the conductor wires 5a may corrode from that portion. In order to prevent such corrosion, if the insulating coating 5b is thin, it is necessary to further form an insulating coating or the like around the outer periphery of the insulating coating 5b.

[0030] When the conductor wires 5a are wound around the core material 3 by drawing or twisting them, it is preferable to draw them together rather than twisting them. This is because the diameter of the cord-shaped heater becomes smaller and the surface becomes smoother. In addition to drawing or twisting them together, it is also possible to braid the conductor wires 5a around the core material 3.

[0031] In the cord-like heater according to the present invention, a coating 7 is preferably formed on the outer periphery of the conductor wire 5a. This coating 7 insulates other components from electrical current even if the conductor wire 5a is broken, and also insulates high-temperature heat generation in the event of a spark. The coating 7 may be formed by extrusion molding or the like, or a coating 7 previously formed into a tube shape may be applied, and there is no particular limitation on the method of formation. When the coating 7 is formed by extrusion molding, the position of the conductor wire 5a is fixed, and friction and bending of the conductor wire 5a due to positional deviation can be prevented, which improves bending resistance, and is therefore preferable. The material constituting the coating 7 may be appropriately designed depending on the usage form and environment of the cord-shaped heater, and may be, for example, polyolefin resin, high density polyethylene, low density polyethylene, very low density polyethylene, polyester resin, polyurethane resin, aromatic polyamide resin, aliphatic polyamide resin, vinyl chloride resin, modified Noryl resin (polyphenylene oxide resin), nylon resin, polystyrene resin, fluororesin, synthetic rubber, fluororubber, ethylene-based thermoplastic elastomer, urethane-based thermoplastic elastomer, styrene-based thermoplastic elastomer, polyester-based thermoplastic elastomer, and the like. Also, a polymer material having flame retardancy is preferably used. The polymer material having flame retardancy here refers to a polymer material having an oxygen index of 21 or more in the flammability test of JIS-K7201 (1999). A polymer material having an oxygen index of 26 or more is particularly preferred.

[0032] Examples of materials for the coating 7 that have excellent adhesion to the substrate 11 include low-density polyethylene, polyester thermoplastic elastomer, and polyester resin. Low-density polyethylene is a polymer formed by polymerization of long-chain ethylene polymers, and has a flexible property due to the small amount of crosslinking between molecules. Therefore, the contact area with the substrate 11 is increased, and the coating 7 has excellent adhesion. In addition, the ester bond of polyester thermoplastic elastomer and polyester resin has a molecular structure having oxygen in the molecule. Therefore, the combustion heat is smaller than that of a resin having a molecular structure of only carbon and hydrogen, which results in suppression of combustion. When the cord-shaped heater 10 and the substrate 11 are heat-sealed, the adhesive strength between the cord-shaped heater 10 and the substrate 11 is very important. If this adhesive strength is insufficient, the cord-shaped heater 10 will come off the substrate 11 during use, which will cause the cord-shaped heater 10 to bend unexpectedly, increasing the possibility of the conductor wire 5a breaking. If the conductor wire 5a breaks, not only will it no longer function as a heater, but chattering may result in sparks. For this reason, low-density polyethylene, polyester-based thermoplastic elastomer, and polyester-based resin, which have excellent adhesive properties, are particularly preferred.

[0033] In order to obtain flame retardancy, it is preferable to blend a phosphinic acid flame retardant with a polymeric material. Phosphinic acid flame retardants are non-halogen flame retardants, and do not generate halogen gases during combustion, so they are not corrosive to surrounding equipment or harmful to the human body. In addition, the thermal decomposition temperature of phosphinic acid flame retardants is 300°C or higher, so they can exert their flame retardant effect even in high-temperature environments, compared to phosphate ester flame retardants, which have a thermal decomposition temperature of 290°C. In addition, phosphinic acid flame retardants can be obtained with fine and uniform particle sizes. Examples of phosphinic acid flame retardants include metal phosphinates. Phosphinic acid is an inorganic phosphorus compound represented by the formula H3PO2 and has a phosphoryl group P=O. Examples of the phosphinic acid include diethylphosphinic acid, ethyl-butylphosphinic acid, butyl-butylphosphinic acid, ethyl-hexylphosphinic acid, butyl-hexylphosphinic acid, and / or hexyl-hexylphosphinic acid, and in particular, diethylphosphinic acid or ethyl-butylphosphinic acid is preferred. Examples of the metal salt include metal salts of Mg, Ca, Al, Sb, Sn, Ge, Ti, Fe, Zr, Zn, Ce, Bi, Sr, Mn, Li, Na, and K, and in particular, metal salts of aluminum are preferred.

[0034] In addition to the phosphinic acid-based flame retardants, metal hydrates such as magnesium hydroxide and aluminum hydroxide, antimony oxide, melamine compounds, phosphorus-based compounds, chlorine-based flame retardants, bromine-based flame retardants, etc. may be used as appropriate as the flame retardant. In addition, the flame retardant may be subjected to a surface treatment by a known method.

[0035] The D95 particle size of the phosphinic acid flame retardant is preferably 20 μm or less. The D95 particle size of 20 μm or less is a value where 95% of the powder in the powder population is 20 μm or less. The particle size is measured using a laser analysis method. If the D95 particle size exceeds 20 μm, the dispersibility during blending is deteriorated, so that there is a risk of occurrence of defects in the outer diameter and appearance due to resin breakage during extrusion molding, leading to deterioration of productivity. In addition, the phosphinic acid flame retardant is preferably contained in an amount of 10 to 22.5 parts by weight per 100 parts by weight of the polymer material. If the blending amount of the phosphinic acid flame retardant is less than 10 parts by weight, the effect as a flame retardant is insufficient, and if it exceeds 22.5 parts by weight, there is a possibility of occurrence of defects in appearance, which may lead to deterioration of productivity.

[0036] Further insulation can be ensured by forming a new coating 7 using the configuration of this coating 7 as the outer layer coating 9 (see FIG. 6). In this case, the material constituting the coating 7 preferably has a temperature range in which the outer layer coating 9 becomes fluid but the coating 7 does not flow. This allows the shape of the outer layer coating 9 to be substantially unchanged and sufficient insulation performance to be maintained even when the coating 7 is fused by heating and pressurizing. The material constituting the outer layer coating 9 may be appropriately designed depending on the usage form and usage environment of the cord-shaped heater, and examples of the material that constitutes the outer layer coating 9 include various materials such as polyolefin resin, polyester resin, polyurethane resin, aromatic polyamide resin, aliphatic polyamide resin, vinyl chloride resin, modified noryl resin (polyphenylene oxide resin), nylon resin, polystyrene resin, fluororesin, synthetic rubber, fluororubber, thermoplastic polyethylene elastomer, thermoplastic polyurethane elastomer, thermoplastic polystyrene elastomer, and thermoplastic polyester elastomer. In particular, a polymer composition having flame retardancy is preferable. Among these, polyester thermoplastic elastomer is particularly preferable. It is contemplated that either the coating 7 or the outer coating 9, or both, may contain a phosphinic acid-based flame retardant.

[0037] The melting point of the coating 7 or outer coating 9 located in the outermost layer is preferably 100° C. to 185° C., and the melting point of the coating 7, when the outer coating 9 is provided, is preferably 200° C. to 250° C. Furthermore, when an insulating coating 5b is formed on the conductor wires 5a, the melting point of the coating 7 or outer coating 9 located in the outermost layer is preferably lower than the melting point of the insulating coating 5b.

[0038] The conductor wire 5a may have one layer of only the coating 7 or two layers of the coating 7 and the outer coating 9, or other layers may be formed as appropriate. The coating 7 and the outer coating 9 are not limited to being formed continuously in the length direction, and may be formed in a straight line or spiral line along the length direction of the cord-shaped heater 10, in a dot pattern, or intermittently. However, from the viewpoint of adhesive strength, it is preferable that the coating 7 and the outer coating 9 are formed continuously in the length direction.

[0039] Furthermore, the cord-shaped heater 10 obtained as described above is preferably able to withstand 20,000 or more bends before at least one of the conductor wires breaks in a bending test in which the cord is bent 90 degrees at a radius of curvature six times its own diameter.

[0040] As the substrate 11, in addition to the nonwoven fabric shown in the above embodiment, various materials such as woven fabric, knitted fabric, foamed resin sheet, foamed rubber sheet, stretched porous body, etc. can be used. Among these, nonwoven fabric is preferable for use as a car seat heater, since it has a good texture and is flexible. In addition, even when using nonwoven fabric, in the above embodiment, a fiber having a core-sheath structure with a low melting point polyester as a sheath component is used as the heat-fusible fiber constituting the nonwoven fabric, but other fibers such as a fiber having a core-sheath structure with a low melting point polypropylene as a sheath component or a fiber having a core-sheath structure with a polyethylene as a sheath component can be used. By using such heat-fusible fiber, the sheath part of the heat-fusible fiber and the coating 7 are fused to each other and integrated while surrounding the core part of the heat-fusible fiber, so that the adhesion between the cord-shaped heater 1 and the nonwoven fabric is very strong. In addition, as the flame-retardant fiber, for example, in addition to the above-mentioned flame-retardant polyester, various flame-retardant fibers can be used.

[0041] The mixing ratio of the heat-fusible fiber is preferably 5% or more, and more preferably 20% or less. If the mixing ratio of the heat-fusible fiber is less than 5%, sufficient adhesion cannot be obtained. If the mixing ratio of the heat-fusible fiber is more than 20%, the nonwoven fabric becomes hard, and not only may the seated person complain of discomfort, but also the adhesion to the cord-shaped heater may be reduced. Furthermore, the base material may shrink due to the heat during heat fusion, and the dimensions intended in the design may not be obtained. The mixing ratio of the flame-retardant fiber is 70% or more, and preferably 70% or more and 95% or less. If the mixing ratio of the flame-retardant fiber is less than 70%, sufficient flame retardancy cannot be obtained. If the mixing ratio of the flame-retardant fiber is more than 95%, the mixing ratio of the heat-fusible fiber becomes relatively insufficient, and sufficient adhesion cannot be obtained. The mixing ratio of the heat-fusible fiber and the mixing ratio of the flame-retardant fiber do not need to add up to 100%, and other fibers may be mixed in as appropriate. Even if the heat-fusible fiber is not mixed in, for example, by using the same type of material for the heat-fusible portion and the fiber material constituting the base material, sufficient adhesiveness may be obtained, so it is entirely conceivable that the heat-fusible fiber is not mixed in.

[0042] The size and thickness of the nonwoven fabric may be appropriately changed depending on the intended use, but the thickness (measured when dry) is preferably about 0.6 mm to 1.4 mm, for example. If a nonwoven fabric of this thickness is used, when the cord-like heater and the nonwoven fabric are bonded and fixed together by heat and pressure, the nonwoven fabric will be well bonded to at least 30%, and preferably at least 50%, of the outer periphery of the cord-like heater, thereby making it possible to obtain a strong bonded state.

[0043] With regard to the adhesive layer for fixing the heater unit 31 to the seat, in terms of the elasticity of the base material 11 and maintaining a good texture, it is preferable to form an adhesive layer consisting only of an adhesive on a release sheet or the like, and then transfer the adhesive layer from the release sheet to the surface of the base material 11 to form the adhesive layer.

[0044] Furthermore, when the cord-like heater 10 is disposed on the substrate 11, the cord-like heater 10 may be fixed to the substrate 11 in another manner other than the above-mentioned manner of bonding and fixing by fusion through heating and pressure using a hot press tool. For example, it is possible to melt the coating 7 with a heating roll to form a flat shape and then fix the cord-like heater 10 to the substrate 11. It is also possible to dispose the cord-like heater 10 on the substrate 11 by various methods, such as not only bonding using the coating 7 formed on the heater element, but also sewing, or sandwiching and holding the cord-like heater 10 with the substrate 11 having adhesive properties.

[0045] As the adhesive layer, various types can be used, such as an adhesive layer made of a polymeric acrylic adhesive and not using a tape substrate, or an adhesive layer formed on both sides of a polypropylene film. If the adhesive layer alone has flame retardancy that passes the combustion test of FMVSS No. 302 for automotive interior materials, the flame retardancy of the heater unit 31 is improved, which is preferable. In order not to impair the flexibility of the heater unit 31, an adhesive layer made of only an adhesive is preferable.

[0046] When the heater unit 31 of the present invention is applied as a vehicle seat heater, it is embedded in a vehicle seat 41 as shown in Fig. 9. That is, the heater unit 31 is attached to the seat cover 43 or the seat pad 45 of the vehicle seat 41. [Industrial Applicability]

[0047] As described above in detail, according to the present invention, it is possible to obtain a cord-shaped heater that is resistant to hot water, has excellent productivity, can be designed to have a small diameter, and has sufficient insulation. This cord-shaped heater is arranged in a predetermined shape, such as a meandering shape, on a substrate such as a polymer foam or nonwoven fabric to form a heater unit, and can be suitably used in electric blankets, electric carpets, car seat heaters, steering heaters, heated toilet seats, heaters for anti-fog mirrors, heating cookware, and the like. In addition, as a single cord-shaped heater, it is possible to consider a mode in which it is wrapped around and adhered to a pipe or a tank, or placed inside a pipe. Specific applications include, for example, a heater for preventing freezing of pipes and pipe drains of freezers, a heater for keeping warm in air conditioners and dehumidifiers, a heater for defrosting in refrigerators and freezers, a heater for drying, and a heater for floor heating. Furthermore, for the electric blankets, electric carpets, car seat heaters, steering wheel heaters, heated toilet seats, heaters for anti-fog mirrors, heating cookware, floor heating and the like exemplified as uses of the above heater unit, the cord-shaped heater of the present invention can be directly attached to or wrapped around the object to be heated. [Explanation of symbols]

[0048] 3 Core material 5a Conductor wire 5b Insulation coating 5c Inner layer 5d outer layer 7 Covering 9 Outer layer coating 10 Cord heater 11 Base material 31 Heater unit

Claims

1. The coil has a conductor wire and a coating formed on the outer periphery of the conductor wire, The cord-shaped heater, wherein the coating is made of a polymeric material and contains a phosphinic acid-based flame retardant.

2. 2. The cord heater according to claim 1, A cord-shaped heater, wherein the phosphinic acid-based flame retardant has a D95 particle size of 20 μm or less.

3. 2. The cord heater according to claim 1, A cord-shaped heater, wherein the coating contains 10 to 22.5 parts by weight of the phosphinic acid flame retardant per 100 parts by weight of the polymer material.

4. The cord heater according to any one of claims 1 to 3, The cord-shaped heater is characterized in that the polymer material is any one of low-density polyethylene, polyester-based thermoplastic elastomer, and polyester-based resin.

5. A heater unit comprising the cord heater according to claim 4 disposed on a substrate.

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