JPH05299158A - Heating element - Google Patents

Abstract

PURPOSE:To provide a heating element capable of being uniformly heated and having extreme durability against bending. CONSTITUTION:Benzene is introduced into the atmosphere at the temperature of 1100 deg.C, and carbon fibers having the average diameter of about 0.3mum and the average length of about 1mm are generated while ultra-particulates of iron serve as a growth starting point. Carbon fibers of 40 pts.wt. are mixed to fused polyethylene resin of 100 pts.wt., and a rectangular planar heating section 1 having 100mm in length, 100mm in width, and 1mm in thickness is manufactured. Electrode sections 2 made of a copper tape are fitted to it to form a heating element. Lead wires (not shown in the figure) are fitted to the electrode sections 2 of the heating element. When the voltage of 5V and the voltage of 7V are applied, a self-control function is exerted, and the temperature of the surface is kept in the range of 51 deg.+ or -3 deg. and 79 deg.+ or -3. When surface temperatures at various points shown by 'X' in the figure are measured while the voltage of 5V is applied, the difference between the highest temperature and the lowest temperature is within 3.5 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat generating element, and more particularly to a heat generating element having a heat generating portion made of a synthetic resin in which a conductive filler is dispersed and carried.

[0002]

2. Description of the Related Art Heretofore, it has been known that a heating element of this type has a positive temperature characteristic in a certain temperature range, that is, the resistance value increases as the temperature rises. There is. It is considered that this is because the chain of the conductive filler is broken as a result of the resin expanding with an increase in temperature. It is also known that the rate of increase of the resistance value sharply increases near a certain temperature Ta. Therefore, when the temperature rises above the temperature Ta, the current value suddenly decreases, and as a result, the heat generation amount decreases and the temperature lowers. As a result, the calorific value (current value) is balanced near the temperature Ta, and the heating element exerts its own temperature control action.

Such a heating element has, for example, a planar shape and is considered to be applied to a heating carpet or the like.

[0004]

However, in the conventional heating element, since the conductive filler is considerably large, it is difficult to make the dispersion thereof completely uniform, the resistance value is not uniform, and the unevenness of temperature is caused. There was a problem that it could be. As a result, the object to be heated cannot be heated uniformly.
Further, a portion (hot spot) where the temperature rises more easily than other portions is likely to be formed, which may cause overheating and eventually a fire.

Further, since such a heating element is liable to be damaged not only by synthetic resin but also by individual conductive fillers by bending, durability against bending is low, and repeated bending (for example, futon) or opening and closing. It cannot be used for hinges of doors.

An object of the present invention is to solve the above problems and to provide a heating element which can be heated without temperature unevenness and which is extremely durable against bending.

[0007]

The heating element of the present invention is produced by a gas phase method by thermal decomposition of a hydrocarbon compound, and starts to grow an ultrafine powder of a refractory metal and / or a compound of the metal. A whisker-like carbon fiber (hereinafter referred to as vapor-grown carbon fiber) grown as a portion is provided with a synthetic resin heat-generating portion dispersed and carried as a conductive filler, and an electrode portion for supplying current.

The heating element of the present invention having the above-mentioned structure generates heat while exhibiting the self-temperature control function by supplying an electric current. However, like the conventional heating element exhibiting the self-temperature control function, the heating section is No uneven temperature occurs. It also has strong mechanical strength. In particular, even if the bending is repeated, the bent portion is extremely unlikely to be broken, and the durability against bending is significantly higher than that of the conventional heating element exhibiting the self-temperature control function. It is presumed that such an effect is brought about as follows.

The vapor-grown carbon fiber is a well-known carbon fiber of polyacrylonitrile-based or pitch-based because it is produced by a vapor-phase method with an ultrafine powder of refractory metal and / or its compound as a starting point of growth. It is much shorter than. In addition, since it is generated as a fine diameter close to the diameter of the ultrafine powder, it has an extremely small diameter as compared to known carbon fibers (in comparison with known carbon fibers, the length is generally 1 mm and the diameter is 7 to 10 μm or more. If the vapor grown carbon fiber is small, the length may be 10 μm and the diameter may be about 0.01 μm). Based on this point and the excellent affinity and dispersibility with the synthetic resin as the base material, the vapor grown carbon fiber is uniformly dispersed in the entire synthetic resin. Therefore, it is considered that the resistance value becomes uniform at every part of the heating element, and the unevenness of heat cannot be achieved.

Since the vapor grown carbon fiber has a uniform graphite crystal layer with few lattice defects, it has excellent mechanical properties. Also, since the well-known carbon fiber is long, the individual carbon fibers in the bent part are always affected by the bending force and are easily deteriorated by deformation, while the vapor grown carbon fiber is short, Although it is affected as a group in the department, it is considered to be less likely to deteriorate because it is less affected individually. From these points, it is considered that the heating element of the present invention has high durability, especially against breakage.

The vapor-grown carbon fiber which brings about such advantages can be made of various hydrocarbon compounds as raw materials. Examples thereof include benzene, toluene and xylene. Examples of the refractory metal constituting the ultrafine particles used for producing the vapor grown carbon fiber include, for example, metals that do not vaporize at 950 to 1300 ° C., which is the temperature of thermal decomposition of hydrocarbon compounds, such as Ti and Zr. Periodic Table of Groups IVa, V, N
b, a group Va of Ta, a group VIa of Cr, Mo, etc., Mn
Group VIIa elements such as Fe, Co, Ni, etc. are suitable, and Fe, Co, Ni, V, and
Nb, Ta, Ti and Zr. And, such metal compounds include oxides, nitrides and salts thereof.

The diameter of the ultrafine powder is 0.01 μm to 0.05
μm is preferred. 0.1m in length with such ultrafine powder
Vapor grown carbon fibers having a diameter of m to 5 mm and a diameter of 0.05 μm to 1 μm are produced. As the synthetic resin for carrying the vapor-grown carbon fibers in a dispersed manner, known synthetic resins can be widely used without particular limitation. Examples thereof include polyester resins such as polyethylene terephthalate, polyamide resins such as nylon, polypropylene, polyvinyl resins, ABS resins, polyalkylene resins, vinyl resins, polyoxyalkylene resins, polyether resins, polyurethane resins. Resin, polyimide resin, polysulfone resin,
Examples thereof include silicone resin, synthetic rubber such as chloroprene, natural rubber, and copolymers thereof.

The content of vapor-grown carbon fibers in the synthetic resin cannot be unequivocally determined because the appropriate range varies depending on the type of resin and the like, but it is usually in the range of 10 to 60 parts by weight. When the amount of vapor grown carbon fiber is too small, the resistance is high and the electrical conductivity is lost.

The heat generating portion in the heat generating element of the present invention may be in the form of a plane, a line, or the like by itself or together with the substrate. When the heat generating portion and the base body have a planar form, the material of the heat generating portion can be formed by coating or impregnating the base material. As the base, a lump, a sponge,
Examples include non-woven fabrics, woven fabrics, and blinds.

The electrode portion in the heating element of the present invention can be constituted by a metal piece or a metal tape attached with silver paste or the like, but a part of the heating portion may be used. The heating element of the present invention can be used alone or in combination with other members to form the following articles, for example.

[0016] Heating carpets, duvets, blankets, cushions, heating floor mats for bathrooms, corridors, etc., heating seats for automobiles, trains, indoor / outdoor waiting rooms, toilets, bus stops, heating chairs for platforms, engines, etc. Such as warmers for various machines, incubators for experiments, warmers for grips of car handles, motorcycles, etc., tanks for storing hot water, water heaters, dryers, steamers, toasters, rice cookers, etc. Various heating cookers, pots,
Food warmers, pots, heaters such as kotatsu, irons, heating tiles, belts for transporting drying or heating, jackets with heaters, supporters, ski shoes, slippers, foot warmers,
Cairo, door knob warmer, heater to prevent dew condensation on mirrors, window glass and video, heater to prevent icing of outdoor display boards, heater to prevent freezing of water pipes, floors, walls, ceilings, etc. of buildings Heaters for heating, heaters for hyperthermia, heaters for brooding, raising seedlings, animal sheds, aquariums, greenhouses, etc.

The heating element of the present invention can be applied to and utilized in various things as described above, but by utilizing its strong property against bending, it is particularly useful as a drying / heating / conveying belt hung between rolls, Especially effective when applied to articles that can be repeatedly folded, such as futons and blankets for heating, or as a planar heater that covers parts that are repeatedly opened and closed or folded (such as hinges of doors) Is.

Further, if the heating element of the present invention has a constitution in which a protective sheet is attached to the back surface of the heating element via an adhesive, the protective sheet can be peeled off when necessary and attached to a desired portion. The part or its surroundings can be easily heated.

[0019]

EXAMPLES In order to further clarify the constitution and operation of the present invention described above, preferred examples of the heating element of the present invention will be described below. A heating element according to the present invention provided with a rectangular planar heating portion 1 as shown in FIG. 1 and an electrode portion 2 made of copper tape along two long sides thereof is manufactured as follows,
The uniformity of the exothermic temperature was investigated.

The temperature of the inside of a chamber in which iron having a particle diameter of about 0.02 μm was arranged as ultrafine particles was set to 1100 ° C., and benzene as a raw material hydrocarbon compound was introduced therein. Starting from ultrafine particles, the average diameter is about 0.3 μm and the average length is about 1
A carbon fiber of about mm was generated.

100 parts by weight of polyethylene resin in a molten state is mixed with 40 parts by weight of the above-mentioned carbon fiber, followed by a press molding process and a cooling process, and then 100 mm in length and 100 m in width.
A rectangular heat generating portion 1 having a thickness of m and a thickness of 1 mm was manufactured. A copper tape was attached to the two opposite sides of the heat generating portion 1 to form the electrode portion 2 to form a heat generating body.

When a lead wire (not shown) was attached to the electrode portion 2 of this heating element and a voltage of 5 and 7 volts was applied, a self-controlling action was exerted, and the surface temperature was changed with time. Was also kept in the range of 51 ± 3, 79 ± 3. When the applied voltage was 5 V, the surface temperature at each point indicated by “x” in FIG. 1 was measured, and as a result, the difference between the maximum temperature and the minimum temperature was within 3.5 ° C.

PAN known as carbon fiber for comparison
A heating element similar to the above heating element was manufactured except that a carbon fiber (diameter: about 8 μm, length: about 2 mm) was used, and the temperature unevenness was similarly examined. As a result, the difference between the maximum temperature and the minimum temperature was 5 to 6 ° C. As is clear from the above, the heating elements of the respective examples according to the present invention have little temperature unevenness when generating heat.

The embodiment of the present invention has been described above.
The present invention is not limited to these examples, and it goes without saying that the present invention can be implemented in various modes without departing from the scope of the present invention.

[0025]

As described above in detail, the heating element of the present invention is unlikely to form hot spots when it is heated by the self-temperature control function. That is, temperature unevenness hardly occurs in each part. Therefore, the object to be heated can be heated uniformly and there is no fear of fire. Moreover, the heating element of the present invention is extremely strong against mechanical strength, especially bending.

As a result of the above, the heating element of the present invention is extremely effective when applied to a heating blanket, a futon, or the like where there is a flammable material in the surroundings, and it can be bent well. is there.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing an embodiment of a heating element of the present invention.

[Explanation of symbols]

 1 ... Exothermic part, 2 ... Electrode part

Claims (1)

[Claims] 1. A whisker-like carbon fiber produced by a vapor phase method by thermal decomposition of a hydrocarbon compound and grown with a refractory metal and / or an ultrafine powder of a compound of the metal as a growth initiation portion is electrically conductive. A heating element comprising a heating portion made of synthetic resin dispersed and carried as a filler, and an electrode portion for supplying current.