JPH076104B2 - Method of manufacturing heating element - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for producing a novel heating element in which an electric current is passed through a fiber bundle to effectively generate heat.

(Prior Art) It has been well known that a metal having an appropriate resistance value, for example, a resistor such as a nichrome wire is supplied with an electric current to generate heat. However, since these resistor alloys lack ductility, they could not be made into a fine fibrous shape and were inflexible and stiff. On the other hand, a metal that is excellent in ductility and can be formed into a thin fiber has a low resistance value (copper, aluminum, iron, etc.), and when an electric current is passed through it, an excessive current flows and it is difficult to use as a heating element. For this reason, attempts have been made to make flexible and flexible heating elements such as fibers. For example, in Japanese Utility Model Publication No. 51-99829 and Japanese Utility Model Publication No. 51-115653, a large number of short-cut stainless fibers are arranged in parallel and bundled to form a string, which is stretched while correcting thick and thin unevenness. It is described that the above is used as a heating element.
Short fibers made of synthetic resin such as polyamide and polyester are uniformly mixed together with the stainless fibers at a ratio of about 1: 4, and then they are aligned to form a mixed yarn, and the stainless steel is mixed in the mixed yarn. It is disclosed that the fibers are brought into contact with each other to form a heating element. However, since these heating elements are obtained by uniformly mixing the stainless fiber and the synthetic fiber and then aligning them to form a mixed yarn, it is difficult to obtain a uniform resistance value along the yarn axis direction. It could not be manufactured industrially. That is, it is difficult to mix the stainless fiber and the synthetic fiber evenly because the physical properties of the fibers are remarkably different. In particular, since the surface friction coefficients of the both are different, the friction coefficient when aligned and thinned. Since the high stainless fibers gather to form a lump, the stainless fibers cannot be uniformly arranged along the yarn axis direction. In particular, in order to make the contact points of stainless steel fibers or the number of contacts uniform, it is preferable to use long fiber lengths, but it is completely impossible to obtain a heating element using such long stainless steel fibers. Met.

(Object of the invention) The object of the present invention is to use ordinary metal fibers which are easily fibrillated,
Moreover, by changing these to those having an appropriate resistance value, a method for industrially producing a heating element which is soft and flexible and which can obtain an appropriate heat generation state without flowing a large current is proposed. It is a thing.

(Structure and action of the invention) That is, the present invention, by supplying continuous fibers having conductivity and continuous fibers having no conductivity to the check zone at the same time to check and discontinue the continuous fibers. And a discontinuous fiber having no conductivity and a discontinuous fiber are mixed to form a fiber bundle, and the average number of discontinuous fibers having conductivity is 10 or more in any cross section of the mixed fiber bundle. And then
In addition, there is provided a method for producing a heating element, characterized in that the mixed fiber bundle is treated by using a compressed air nozzle so that the electrically conductive discontinuous fibers are brought into contact with each other.

The present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing an example of preferable steps for carrying out the method of the present invention. That is, 1 in FIG. 1 (G) is a bundle of electrically good conductors such as copper, steel, aluminum, etc., which are formed in a thin fibrous shape, and the electric resistance value is 10 ^-5 to 10 ^-6 Ω as it is.
Because of the low resistance value of -cm order, too much current flows and it cannot be used as a heating element. As shown in FIG. 1 (H), this is a pair of rollers 2 that rotate and several times to several times from this.
When the fibers are forcibly stretched between a pair of rollers 3 that rotate 10 times faster (chopping region), the fibers that make up the bundle of good electrical conductors are torn and shredded, and a collection of fibers that have been chopped (chosen). Becomes Because it is easy to fall apart as it is,
The fibers are bundled together by a compressed air nozzle 4 or the like. In this way, when the conductor is cut into short pieces to form discontinuous fibers, the resistance value does not flow directly even when an electric current is passed through it, but it flows through contact resistance, so the resistance value is several times to several tens of times the original value and heat is generated. It can be changed to a range of a preferable resistance value for the body. Therefore, in this case, in order to generate heat uniformly along the yarn axis, it is desirable that there is not much change in the contact resistance at each place, but this is the law of large numbers because the contact point increases as the number of fibers increases. The contact points at each location are unexpectedly averaged, and variations in temperature almost eliminate practical problems. To expect this, if at least 10 or more can be made in each part of the fiber bundle
It is desirable to have 25 or more constituent fibers in order to average the contact points.

In the present invention, it is necessary to prepare a composite fiber bundle in which the conductive discontinuous fibers and the discontinuous fibers having no conductivity are mixed.

Such a composite fiber bundle can be produced, for example, by the method shown in the process diagram of FIG. That is, conductive material 1
In addition, the electrically insulating continuous long fiber bundles 5 are supplied to the roller 2 so as to be superposed on each other, and both of them are cut into pieces by the principle shown in FIG. By doing so, both fibers are drafted and mixed at the same time to form a well-mixed composite fiber bundle.

Further, a plurality of raw materials 1 and a plurality of electrically insulating continuous fiber bundles 5 are alternately arranged, and the roller 2 of FIG.
It is also possible to supply it to and to perform overlap cutting. The fiber length of the discontinuous fiber can be determined by the distance between the rollers 2 and 3, and can be determined by the distance between the rollers 2 and 3, and the circumference of the rollers 2 and 3 can be determined. The thickness of the composite fiber bundle obtained can be determined by the ratio of the speeds.

By mixing the electrically insulating fibers in this manner, the chances of contact between the conductive fibers can be appropriately increased or decreased, and the preferable contact resistance can be obtained, and a good heating element can be obtained. Further, in the case where the composite fiber bundle is formed, the number of fibers increases, so that the shape of the fiber bundle is kept stable and the resistance value is stable even with a relatively small number of conductive fibers. It goes without saying that features such as coloring with a fiber with good dyeability, and compounding with a soft fiber or a fiber with a good feel to improve the hard feel of metal can also be used according to the purpose. Nor. In order to expect these combined effects, it is particularly effective to mix the insulating fibers in about 70 to 95% of the total, but the present invention is not limited to this. In this way, by mixing with insulating fibers, it is possible to make a heating element having an electric resistance value that is one digit higher.

The electrically conductive discontinuous fibers constituting the composite fiber bundle must all be made into discontinuous fibers of finite length, but if the fiber length becomes too short, the number of contact points per discontinuous fiber will be small. It becomes unstable, so if possible, average 100 mm
The above is better. By increasing the length in this way, contact with a large number of fibers increases and the stability becomes stable. However, if it is too long, the components that flow directly through the fiber will increase, so it is better to keep it on average 800 mm or less even if it is long. Further, in order to keep the fibers in an appropriate contact state, in addition to simply bundling the fibers, they are entangled with a compressed air nozzle or the like as shown in 4 of FIG. 1 or 2 or twisted by an ordinary method. It is desirable to put them in an appropriate conjugation state, such as by taking them.

As the compressed air nozzle, one that generates a swirling flow or one that entangles fibers with each other can be used, and specifically, a known compressed air nozzle can be used.

In the present invention, the conductive fiber used in the composite fiber bundle preferably has an electric resistance value of the order of 10 ⁻⁵ to 10 ⁻⁶ Ω-cm. If the resistance value is higher than this, it becomes difficult to draw it into a fine fibrous shape. As a measure of fineness, a diameter of 60 microns or less, preferably 16 microns or less is preferable because of its flexibility. It is convenient to use a metal such as copper, aluminum or steel as the material, but stainless steel is preferable because it does not oxidize even if it generates heat. In addition, metal-plated fibers or conductive polymers such as polyacetylene and polypyrrole may be used. In the case of combining with an electrically insulating fiber, if an ordinary synthetic fiber, regenerated fiber or natural fiber is used as the insulating fiber, the electric resistance value is much higher than that of the conductive fiber, and the purpose is any one. Although it is possible to reach the desired level, the use of wholly aromatic polyamide has high heat resistance, so that even if the temperature rises and the conductive fiber is heated, preferable results can be obtained without deterioration or ignition. In addition, heat resistant polymers such as polybenzimidazole, polyimide, and polyether ether ketone are also suitable. It is desirable that the apparent resistance value of the heating element produced in this manner be on the order of 10 ^-4 to 10 ^-2 Ω-cm. That is, if it is lower than the order of 10 ⁻⁴ Ω-cm, current will flow too much to cause overheating, or a power supply of a low voltage first current will be required, which makes control difficult. On the other hand, if the resistance becomes higher than 10 ^-2 Ω-cm, the current may be too small to raise the temperature sufficiently, or a high voltage may be applied to force the current to increase the risk.

Also, in the conventional heating element that kneads metal powder or carbon powder into the polymer or coats it on the surface, current does not flow unless the powder particles stick to each other, so unless you increase the mixing ratio considerably, it will not become a heating element. In the case of the present invention, it is a long fibrous shape, and in particular, it is particularly so in the case of a long fiber length such as 100 to 800 mm, but since the number of contact points greatly increases, a great feature that it becomes a heating element even with a small mixing ratio There is. For example, in the case of powder, if 50% or more is not mixed, a current enough to generate heat does not flow, but in the present invention, even if it is 5 to 30%, a current necessary for sufficient heat generation can be flowed extremely stably.

FIG. 3 is a diagram for explaining the action of the heating element obtained by the method of the present invention.

FIG. 3A shows a conventional wire-shaped resistor such as a nichrome wire. These resistors have an appropriate resistance value such that they generate heat appropriately when an electric current is applied. However, in order to soften such a wire, if one attempts to make it thin and further multiplies it, in general, such a resistor alloy is not ductile and there is a limit to how thin it can be drawn. As you can see, I can't make something very thin. On the other hand, metals such as copper, aluminum and iron have good ductility and can be made into thin and multi-fibrous form as shown in (C), but generally, metals with good ductility are good electrical conductors with extremely low resistance. However, if a current is passed through this, an excessive current will flow too much and it will be difficult to use as a heating element.

On the other hand, (D) shows a model of the heating element of the present invention, in which the metal wire is cut into pieces by cutting it into pieces, and there is no continuous wire throughout.
Therefore, in the conventional heating element, the current flows directly through the constituent metals as shown in (E), whereas in the heating element of the present invention, the current is discontinuous, so that the current is always in contact with the contact surface as shown in (F).
It flows through Ro, Ha, Ni, and E. However, contact resistance is generated on the contact surface (because free electrons are transferred), so that the entire heating element has a larger resistance value than that when a current flows directly.

Therefore, even a material of a good electric conductor having a low resistance value has a resistance value like a high resistance alloy, and an appropriate amount of heat is generated without an excessive current flowing through the current. Therefore, since a general metal (copper, iron, aluminum, etc.) having a low resistance value that can be stretched into a thin shape can be used as the heating element, a very flexible and flexible heating element which has never existed before can be obtained.

Furthermore, by mixing the electrically insulating fibers, the chances of contact between the electrically conductive fibers can be appropriately increased or decreased, and the preferable contact resistance can be obtained, and a good heating element can be obtained. Further, since the number of fibers is increased in the case where the composite fiber bundle is formed, the shape of the fiber bundle is kept stable even with a relatively small number of conductive fibers, and a heating element having a stable resistance value can be obtained as described above. That's right.

(Example 1) Polymetaphenylene isophthalamide filaments were obtained by bundling 1500 continuous steel filaments having a volume resistivity of the order of 10 ^-5 Ω-cm and elongated to a diameter of 8 microns. Approximately 2700 (single yarn denier) bundles are stacked and fed from the roller 2 shown in FIG.
The distance between both rollers is set to 1000mm in the check-off area consisting of rollers 2 and 3, and further between both rollers.
The average fiber length is about 310 mm, the polymetaphenylene isophthalamide fiber content is 50%, the average fiber length is about 75, and the average fiber length is about 75.
It was wound up by passing through an air swirling nozzle having a pressure of g / cm ² . The apparent volume resistivity at this time was on the order of 10 ^-4 Ω-cm. Next, this fiber bundle is woven into a plain woven fabric, and the relationship between the voltage (E) when an alternating current is applied from both ends of this woven fabric and the current (I) flowing at that time is shown in FIG. 4 and the surface of the woven fabric at that time. The relationship with temperature (T) is shown in FIG. The resulting heating element is not only flexible, but also has a fluffy feel and bulky feel as if it were a conventional fiber, giving it an unprecedented revolutionary heating element that can be used for general clothing without any problems. Was given.

(Effects of the invention) As the use of such a heating element obtained in the present invention, since it has flexibility, it is difficult to be hard, where it is required to bend when pressed, where it is constantly moving, and when uneven. Suitable for places where you want to follow a certain surface. In addition to the above-mentioned features when using a composite heating element, it is soft and bulky to the touch, can be colored, and can be easily woven or knitted. And interior is also possible. For example, a heater that heats the wall or floor of a room to heat it, a heater that heats a toilet seat, a heating furniture that covers the bed surface or a chair to heat it, and a medical device that is worn on a part of the body and locally heats it. , Its characteristics are exhibited when it is used as a base material for various heating devices such as gloves, socks, belly rolls, vests, outerwear, pants and other clothing.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the method of the present invention, FIG. 2 is a diagram for showing an example of steps for carrying out the method of the present invention, and FIG. 3 is for explaining the action of a heating element obtained by the method of the present invention. FIG. 4 is a diagram showing the relationship between voltage and current of the heating element according to the embodiment of the present invention, and FIG. 5 is a diagram showing the relationship between voltage and surface temperature of the heating element according to the embodiment of the present invention. (D) ... Heating element 1 ... Conductive fiber 5 ... Non-conductive fiber I, B, C, D, E ... Contact surface

Claims (1)

[Claims] 1. A continuous fiber having electroconductivity and a continuous fiber having no electroconductivity are simultaneously supplied to a drafting zone to be chopped to form a discontinuous fiber, whereby the discontinuous fiber having electroconductivity and the electroconductivity. Without a discontinuous fiber mixed with a fiber bundle,
The average number of the discontinuous fibers having electrical conductivity is 10 or more in any cross section of the mixed fiber bundle, and the electrically conductive material is obtained by treating the mixed fiber bundle with a compressed air nozzle. A method for producing a heating element, characterized in that discontinuous fibers are brought into contact with each other.