JPH03146730A - Production of heater - Google Patents

Abstract

PURPOSE:To produce a heater with a material which can be easily formed to a fiber, on an industrial scale at a low cost, by supplying an electrically conductive and non-conductive continuous fibers to a stretch-breaking zone to form a mixed discontinuous fiber bundle, including a specific number of the electrically conductive fibers in said fiber bundle and arranging the conductive fibers in a state contacting with each other. CONSTITUTION:A bundle of electrically conductive continuous fibers 1 having an electrical resistance of the order of e.g. 10<-5>-10<-6>OMEGA/cm and a diameter of <=60mum (preferably stainless steel fibers) and a bundle of non-conductive fibers 5 (e.g. synthetic fibers) are supplied in a superposed state to the stretch-breaking zone of rollers 2, 3 and subjected to stretch-breaking to obtain discontinuous fibers of 100-800mm long. The discontinuous fibers are combined with each other by a compressed air nozzle 4 to obtain a mixed fiber bundle to be used as the objective heater. The average number of the electrically conductive fibers in arbitrary cross section of the fiber bundle is >=10 and the electrically conductive fibers are made to be contacted with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a method for manufacturing a novel heating element that effectively generates heat by passing a current through a !I bundle.

(Prior Art) It has been well known to generate heat by passing a current through a resistor such as a metal having an appropriate resistance value, such as a nichrome wire. However, these low-antibody alloys lack ductility, so they cannot be made into thin fibers, which are inflexible and stiff. On the other hand, metals that have excellent ductility and can be made into thin fibers always have a low resistance value (copper, aluminum, iron, etc.), so when current is passed through them, an excessive current flows, making them difficult to use as heating elements. For this reason! Attempts have been made to create flexible and pliable heating elements.

For example, Utility Model Application Publication No. 51-99829 and Utility Model Application No. 51-1
The 15653 bow publication contains a large number of short stainless steel [
It is described that the stainless steel fibers are used as a heating element by arranging them in a parallel state and converging them into a string shape, stretching them while correcting thick and thin unevenness, and furthermore, together with the stainless steel fibers,
After uniformly mixing short fibers made of synthetic resin such as polyamide and polyester at a ratio of about 1:4, they are pulled together to form a blended yarn, and the stainless steel fibers are brought into contact with each other in the blended yarn. A heating element is disclosed. However, these heating elements are made of stainless steel AM and synthetic IL.
After being uniformly mixed with N, the 1st layer disappears to form a blended yarn, so it is difficult to achieve a uniform resistance value along the yarn axis direction, and it cannot be manufactured industrially. It was something. In other words, stainless steel fibers and synthetic fibers have significantly different fiber properties, making it difficult to mix them uniformly. In particular, since the surface friction coefficients of both fibers are different, it is difficult to mix them uniformly when pulling them together to make them thinner. Since the stainless steel fibers having a high coefficient of friction gather together to form a lump, it was not possible to arrange the stainless steel thread uniformly along the yarn axis direction. In particular, in order to quantify the contact points or the number of contacts between stainless steel fibers, it is preferable to use long fiber lengths, but it is completely impossible to obtain a heating element using such long stainless steel fibers. there were.

(Object of the invention) The object of the present invention is to use a metal t41iift that is easily turned into fibers.
By using these materials and changing them to something with an appropriate resistance value, we can industrially manufacture a heating element that is soft and flexible, and that can provide an appropriate heat generation state without flowing a large current. This paper proposes a method.

<Structure and operation of the invention> That is, the present invention provides continuous fibers that have conductivity and continuous fibers that do not have conductivity! By supplying 1 navy blue simultaneously to the tension-cutting area and tension-cutting it into discontinuous fibers, an iIN bundle is formed in which the conductive discontinuous fibers and the non-conductive discontinuous fibers are mixed. The 11 discontinuities with electric properties in any cross section of the mixed tIN bundle! ! A method for producing a heat generating element characterized in that the discontinuous tilli having conductivity are brought into contact with each other so that the number of discontinuous tilli is on average 10 or more.

The present invention will be explained in detail with reference to the figures.

FIG. 1 is a diagram showing an example of a preferred process for carrying out the method of the present invention. 1 in Figure 1 (G) is a bundle of fine electrical conductors such as copper, steel, and aluminum formed into thin fibers, and as it is, the electrical resistance value is 10-5 to 1.
Due to its low resistance value of 0.010-6O-order, too much current flows through it, making it unusable as a heating element. This is shown in Figure 1 (
As shown in b), between a pair of rotating rollers 2 and a pair of rollers 3 rotating several times to several tens of times faster than this (
If it is forcibly stretched in the tension cutting region, it will form a bundle of electrically good conductors! [was torn to shreds and became a collection of IJ & I that were cut into short pieces. Since they tend to fall apart as they are, they are combined using a compressed air nozzle 4 or the like to form a fiber bundle. When a conductor is cut short and made into discontinuous fibers, even if a current is applied to it, it does not flow directly, but instead flows through contact resistance, so the resistance value increases from several to several tens of times the original value and generates heat. The resistance value can be changed within a range that is preferable for the body. Therefore, in this case, in order to generate heat uniformly along the yarn axis, it is desirable that the contact resistance at various points does not change much, but this is due to the law of large numbers because as the number of fibers increases, the number of contact points increases. The contact points at various locations are unexpectedly averaged out, and temperature variations become virtually no problem in practice. In order to expect this, it is desirable to have at least 10 or more Ifi fibers in each part of the 4ja miscellaneous bundle, preferably 25 or more, in order to average out the contact points.

In the present invention, it is necessary to form a composite fiber bundle in which the conductive discontinuous fibers and non-conductive discontinuous IIN are mixed.

Such a composite fiber bundle can be made, for example, by a method as shown in the process diagram of FIG. That is, conductive material 1
In addition, an electrically insulating string bundle 5 having a continuous length of m is supplied to the roller 2 in an overlapping manner, and both are torn off together according to the principle shown in FIG. By doing this, both fibers are cut and mixed at the same time, resulting in a well-mixed composite! Forms l fibers.

Furthermore, a plurality of raw materials 1 and a plurality of electrically insulating continuous long fiber bundles 5 are arranged alternately, and the roller 2 shown in FIG.
It is also possible to perform overlapping cutting by supplying the same. Further, the fiber length of the discontinuous fiber can be determined by the distance between roller 2 and roller 3, further determined by the distance between roller 2 and O-roller 3, and further determined by the distance between roller 2 and roller 3. The thickness of the composite fiber bundle obtained can be determined by the ratio of the peripheral speeds of .

By mixing the electrically insulating IAG in this manner, the chance of contact between the conductive fibers can be increased or decreased as appropriate, and a preferable contact resistance can be achieved, resulting in a good heating element. Furthermore, in the case of forming a composite fiber bundle, the number of fibers increases, so even if the number of conductive nu is relatively small, the shape of the fiber bundle is kept stable and the resistance value is also stabilized. Of course, it can be combined with fibers that have good dyeability to add color or create flexible i&
Needless to say, it can be used depending on the purpose, such as improving the hard feel of metal by combining it with i-fibers or fibers with a good feel. In order to clearly maintain these combined effects, it is particularly effective to mix 70 to 95% of the total amount of insulating fibers, but the invention is not limited to this.

In this way, by mixing it with insulating fibers, it is possible to create a heating element with an electrical resistance that is an order of magnitude higher.

All of the conductive discontinuous fibers constituting the composite fiber bundle must be made into finite length discontinuous fibers, but eRM
If the length is too short, there will be fewer contact points per discontinuous fiber, resulting in instability, so if possible, the average length is 10.
It is better to have 0ffl1 or more.

By increasing the length in this way, contact with many fibers increases and becomes stable. However, if the length is too long, the amount of components flowing directly through the fibers will increase, so even if it is long, the average
■It is better to do the following. Also, 1! In order to maintain proper contact between the fibers, the fibers should not only be bundled, but also entwined with a compressed air nozzle, etc., as shown in Figure 1 or 4 in Figure 2, or twisted using a normal method. , it is desirable to bring it into a suitable conjugated state.

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 electrical resistance of the conductive fibers used in the composite fiber bundle is preferably on the order of 10 Ω to 10 −6 Ω-am. If the resistance value is higher than this, it will be difficult to draw it into a thin fiber. As a guideline for thinness, a diameter of 60 microns or less, preferably 16 microns or less is preferable because of its flexibility. It is convenient to use metals such as copper, aluminum, and steel as materials, but stainless steel is particularly preferred because it does not oxidize even when it generates heat. In addition, metal-plated fibers or conductive polymers such as polyacetylene and polypyrrole may also be used. Also, when composited with electrically insulating fibers, the insulating VA fibers are the usual synthetic 1! If you use miscellaneous, recycled fibers, or natural fibers, the electrical resistance value will be conductive! It is much higher than that of I-cloth, and any of these can achieve the purpose, but in particular, fully aromatic polyamide has high heat resistance, so it will not deteriorate even if the conductive fibers generate heat and the temperature rises. Favorable results can be obtained without burning or igniting. In addition, heat-resistant polymers such as polybenzimidazole, polyimide, and polyetheretherketone are also suitable.

The apparent resistance value of the heating element made in this way is 10
It is desirable to set it to about -4 to 1O-20-CI order. That is, if it is lower than the order of 10-4 Ω-cra, too much current will flow, causing overheating, or it will become difficult to control the current by requiring a low-voltage current power source. On the contrary, 1
If the resistance becomes high, such as 0-2Ω-0111 or more, the current may be too small to raise the temperature sufficiently, or a high voltage may be applied to force the current to flow, increasing the danger.

In addition, with conventional heating elements in which metal powder or carbon powder is kneaded into polymers or applied to the surface, current will not flow unless the powders stick together, so the heating element will not work unless the mixing ratio is increased considerably. In the case of the present invention, the long 1li
This is especially the case when the fiber length is long, such as 100 to 800 IIIll, and has the great advantage that even a small mixing ratio can become a heating element because the number of contact points increases greatly. For example, in the case of powder, if it is not mixed with 50% or more, the current that generates heat will not flow, but in the present invention, 5 to 3
Even at 0%, it is possible to flow the current necessary for sufficient heat generation extremely stably.

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

Figure 3 (A) shows a conventional wire-like resistor such as a nichrome wire. These low antibodies have an appropriate resistance value that generates a moderate amount of heat when a current is passed through them.

However, in order to make this type of wire flexible, we try to make it thinner and make it more multi-layered. Generally speaking, such low-antibody alloys are not ductile and there is a limit to how thin they can be drawn, so it is difficult to make them thin as shown in (B). I can't do thin ones. On the other hand, metals such as copper, aluminum, and iron have good ductility and can be made into thin, mulched fibers as shown in (C), but metals with good ductility are generally good electrical conductors with extremely low resistance. When a current is passed through it, too much current flows, making it difficult to use as a heating element.

On the other hand, (D) schematically shows the heating element of the present invention, in which the metal wires are all cut into short pieces by tearing them into strips, and none of them are continuous throughout.

Therefore, in the conventional heating element, the current flows directly through the constituent metals as shown in (E), whereas in the case of the heating element of the present invention, the current flows discontinuously, so the current always flows through the contact surface 49 as shown in (F).
mouth.

It flows through Ha, 2, and Ho. However, since contact resistance occurs at the contact surface (due to the transfer of free electrons), the heating element as a whole has a larger resistance value than when current flows directly.

Therefore, even a material that is a good electrical conductor with a low resistance value has a resistance value similar to that of a high resistance alloy, and even when current is passed through it, an appropriate amount of heat is generated without excessive current flowing. Therefore, a heating element can be made of a general metal (copper, iron, aluminum, etc.) with a low resistance value that can be stretched thinly, making it possible to create a heating element that is extremely soft and flexible, which has not been possible until now.

Furthermore, by mixing electrically insulating fibers, the chance of contact between the electrically conductive fibers can be increased or decreased, resulting in a preferable contact resistance and a good heating element. In addition, in the case of forming a composite tlN bundle, 11
As described above, since the number of conductive fibers increases, the shape of the fiber bundle can be kept stable even with a relatively small number of conductive fibers, and a heating element with a stable resistance value can be obtained, as described above.

(Example 1) One continuous steel fiber having a volume resistivity on the order of 10"5 Ω-cm and stretched to a thin diameter of 8 microns was
A bundle of about 2,700 polymetaphenylene isophthalic acid long fibers (single yarn denier 2 de) was superimposed on the bundle of 500 fibers and fed to the tension cutting area from the roller 2 shown in FIG. In the stretch cutting area formed by rollers 2 and 3, the distance between both rollers is set to 1000 mm, and the average fiber length is about 31011110 mm by cutting 20 times between the two rollers. The polymetaphenylene isophthalamide Qilt blending rate is 50%, the average number of steel fibers is approximately 15, and this is further made into a discontinuous TL fiber bundle of 5k (
A pressure of 1/cd was passed through the right air swirl nozzle to bind and wind up. The apparent volume resistivity at this time is 10-4Ω-
It was on the order of cm.

Next, this fiber bundle is woven into a plain woven fabric, and the relationship between the voltage (E) and the current flowing at that time (1) when an alternating current is passed through both ends of the woven fabric is shown in Figure 4, and the surface of the woven fabric at that time is shown. The relationship with temperature (T) is shown in Figure 5. The resulting heating element is not only flexible but also has the same texture as conventional fibers.It has the fluffy feel and bulkiness of conventional fibers, making it an unprecedented, revolutionary heating element that can be used in general clothing without any problems. Obtained.

(Effects of the Invention) Due to its flexibility, the heating element obtained by the present invention can be used in places where it is difficult to be rigid, where it is required to bend when pressed, where it is constantly moving, and where uneven surfaces are required. Suitable for places where you want to follow a certain surface. Moreover, when a composite heating element is used, in addition to the above-mentioned features, it can be provided with one color that is soft and bulky to the touch.

&1 It has features such as being easy to knit, making it possible to create clothing and interiors that are 100% heating elements, which was previously difficult. For example, heating equipment that is used on the walls and floor of a room to generate heat, heating equipment that warms the toilet seat, heating furniture that covers the surface of a bed or chair and generates heat, and medical equipment that is worn on a part of the body and heats it locally. 1. Its characteristics are demonstrated when used as base materials for various heating devices such as gloves, socks, belly wraps, vests, jackets, pants, and other clothing.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the present invention in detail, and FIG. 2 is a diagram showing an example of steps for carrying out the method of the present invention. The third figure is a diagram explaining the action of the heating element obtained by the method of the present invention, and the fourth figure is a diagram illustrating the effect of the present invention! FIG. 5 is a diagram showing the relationship between the voltage and the surface temperature of the heating element in the actual WA embodiment of the present invention. (D)... Heating element 1... Conductive fiber 5... Non-conductive! l Navy blue 9 ro, ha, 2, ho...contact surface

Claims (1)

[Claims] By simultaneously supplying conductive continuous fibers and non-conductive continuous fibers to a tension-cutting area and tension-cutting them into discontinuous fibers, the conductive discontinuous fibers and non-conductive discontinuous fibers are separated. The conductive discontinuous fibers are mixed with each other so that the number of conductive discontinuous fibers in any cross section of the mixed fiber bundle is 10 or more on average. A method for manufacturing a heating element, characterized in that the heating element is brought into contact with the heating element.