JPH1053926A - Production of graphite fiber and heating element using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain graphite fiber having a stable and uniform resistance value and capable of being used as a heating element by using a pitch fiber spun by using pitch as a raw material. SOLUTION: This production of graphite fiber is to obtain a pitch fiber by spinning molten pitch through 10-20μm diameter and predrying, bring the pitch fiber to a tow sliver by treating to carbonize and further bringing to change into graphite, remove slubs contaminated in the tow sliver by treating the tow sliver by an intergill machine, then, draw and twist the sliver by a fine spinning frame to obtain a graphite fiber 1 having a stable resistance value, process to bundle the graphite fiber 1 with an aramid fiber 2 and form a polyvinyl chloride layer 3 and polyurethane layer 4 on the aramid fiber and obtain a heating element A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing graphite fiber having a stable resistance value and a heating element made of the graphite fiber, and the heating element is used to promote the growth of crops in a snow melting heater on a road or an agricultural house. The present invention relates to the use as a heating heater.

[0002]

2. Description of the Related Art In recent years, expectations for carbon fiber as a lightweight and high-strength advanced material have been rapidly increasing. In other words, since carbon fibers exhibit high strength and high elasticity, they are combined with other materials such as thermoplastics, engineering plastics such as nylon 66, polycarbonate, polybutylene terephthalate, polyacetal, and polyphenylene oxide, and ceramics. Composite materials such as plastics and fiber reinforced ceramics are used in aerospace, automobiles, civil engineering, mechanical parts, electrical parts,
Attention has been drawn to a wide range of fields such as sports and leisure goods, and applied research has been actively conducted.

[0003] As carbon fibers, PAN-based carbon fibers made from polyacrylonitrile (PAN) have been put into practical use from the earliest.

[0004] However, the above-mentioned PAN-based carbon fiber has problems such as that the raw material PAN is expensive, the yield of carbon fiber from the PAN is extremely low at 50% or less, and the electric resistance is high. Therefore, improvement of this point is urgently needed.

On the other hand, at present, in addition to the above-mentioned PAN as a raw material, pitch-based carbon fibers obtained from a pitch such as petroleum pitch or tar pitch which can be obtained at a low cost are also manufactured for the production of carbon fibers. In any case, the main method is to use the obtained carbon fiber as a composite material in the form of a reinforcing fiber.

[0006]

Further, since carbon fibers are excellent in electrical conductivity, thermal conductivity, etc., it has been studied to spun them into yarns and use them as heating elements. Since the resistance value varies and it is difficult to obtain a stable and uniform resistance value, it has not been put to practical use.

As a heating element, a non-metallic carbon heater is known, which is formed by mixing carbon powder with a synthetic resin such as an epoxy resin and compacting it into a string, rod, or sheet. Since the applied heating element has a high resistance due to resin mixing and requires a large number of short electrodes, a metal wire heater, for example, a nichrome wire heater has a resistance value of 0.02 to 2 Ω / m. 400-5
There was a problem that the resistance value was too high at 00 Ω / m.

[0008] The reason why the heating element using the conductive carbon fiber exhibits a variation in resistance value is that the carbon fiber or the graphite fiber obtained by carbonizing or further graphitizing the material using pitch as a raw material is used. Therefore, it is considered that the slab is mixed in the fiber.

In view of the above, the present invention provides a graphite fiber using pitch as a raw material, which has a small contact resistance, has no variation in resistance value, and exhibits a stable resistance value as a heating element, particularly a heater. It is intended to do so.

[0010]

In order to achieve the above object, the invention according to the first aspect of the present invention is directed to a pitch fiber obtained by spinning a molten pitch at a diameter of 10 to 20 μm and predrying. Is carbonized and further graphitized to give a fiber length of 1
By making a tous sliver of 0 to 90 cm, and then treating this tous sliver with an intergil machine to remove a slab in the tous sliver to obtain a short fiber of 5 to 20 cm, drawing and twisting with a spinning machine, It is characterized by obtaining a graphite fiber having a stable resistance value.

The invention according to claim 3 is characterized in that the pitch fibers obtained by spinning the melted pitch with a diameter of 10 to 20 μm and predrying are carbonized and then graphitized to obtain a fiber length of 10 to 90 cm. The tous sliver is then treated with an intergil machine to remove slabs in the tous sliver to obtain short fibers of 5 to 20 cm, and then drawn and twisted with a spinning machine to obtain graphite. It is characterized by a heating element formed by bundling the fibers or further applying a resin coating.

[0012] In the first or third aspect, the processing by the interus machine of the tous river is repeated a plurality of times, and the heating element obtained in the third aspect is buried in the soil on the road surface to melt snow. It is used as a heater for cultivation or as a heater for cultivating crops buried in soil in an agricultural house.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the present invention provides a method for producing pitch fibers produced by spinning molten pitch from 800 to 1200.
Carbonization firing at 2000 ° C. and graphitization firing at 2000 to 2500 ° C. and a carbon content of 99% obtained by two-step firing.
Rather than immediately drawing and twisting a tousliver bundle of graphite fibers having a fiber length of 0 cm with a spinning machine and processing it into a yarn, the above bundle is carded with an intergil machine, and at the same time, the bundle is bundled during firing. Remove the slab (a mass of graphite) attached to the fiber and reduce the fiber length to 5 to 20 cm.
It is drawn from a short fiber of a spinning machine and twisted to obtain a graphite yarn having a desired denier thickness,
As a result, a graphite yarn having a stable resistance value can be obtained.

Hereinafter, the present invention will be described in detail. Prior to the description, graphite will be described first. Graphite is one of the allotropes of carbon, has a black color, a hardness of 1 to 2, and a specific gravity of 2.3. As shown in FIG. 1, the six-membered ring structure extends infinitely in a plane to form a crystal lattice, which forms a so-called stratified lattice in which a number of layers overlap. The grids are easy to move and give a smooth feel. Since the graphite structure has a larger and more unidirectionally developed graphite structure due to the high-temperature treatment, it is possible to produce high-performance graphite fibers.

Next, an example of the production of graphite fiber will be described. Molten pitch (petroleum pitch or tar pitch) is sprayed from a number of nozzles of 10 to 20 μm, wound around a rotating drum as a fiber having a length of 10 to 90 cm, and pre-dried at a temperature of about 100 ° C. Solidified while removing volatile substances of the above to form pitch fibers. Next, the pitch fibers are fired at about 1000 ° C. in an atmosphere of an inert gas such as nitrogen gas or argon gas to obtain so-called carbon fibers. Since this carbon fiber is a conductor having a carbon content of about 95% and a high resistance value, if the carbon fiber is refired at a high temperature of 2000 to 2500 ° C. in order to further reduce the resistance value, the carbon content becomes about 99% or more. A graphitized 10-20 g / m tous rivet bundle is obtained.

This bundle is composed of extremely long fibers and short fibers having a fiber length of 10 to 90 cm, and a large number of slabs (lumps of fine fibers and graphite) are formed in the bundle. For this reason, if slabs are interposed when spinning as it is to obtain graphite yarn, even if the required number of slabs are used as a heating element, the slab has low resistance and the current may concentrate there. There is no stable function as a heating element. Therefore, it is important to remove the slabs, short fibers, and miscellaneous substances contained in the bundle by applying the bundle to an intergil machine. It is preferable to repeat the slab a plurality of times (3 to 4 times) because the slab still remains in a large amount only once and the electric resistance varies when the yarn is formed. Very small 5-20m
The fiber length can be adjusted to m, and the slab remaining very slightly is dispersed in the short fiber length, and does not affect the resistance value.

FIG. 2 is a conceptual diagram for explaining the situation of slab removal from the tous sliver condensate by the above-mentioned intergil machine. In the first processing, a considerable amount of slab remains in the convergent slab. (FIG. 2 (a)) By repeating the second and third processes, the remaining slab is gradually reduced as shown in FIGS. 2 (b) and (c), and the slab is obtained by performing the fourth process. 2 is almost completely removed (FIG. 2).
(D)).

Even if this intergil processing step is performed only once, it is possible to remove the slab and increase the short fiber length to 5 to 20 mm by increasing the processing speed. It is difficult to draft to the desired yarn count with the spinning machine in the next process and twist it into a yarn because the bundle becomes powder and the yield decreases and the fiber length becomes uneven. There is a problem that is.

If the slab is removed by the above-mentioned multiple intergil treatments, and the tow sliver bundle is adjusted to have a fiber length of 5 to 20 mm, the bundle is drafted to a required yarn count by the next spinning machine, and a predetermined twist is applied. By performing the number of twists, a graphite yarn is formed.

The graphite yarn spun in this manner was adjusted to 4000 denier, and the electrical resistance was measured. As a result, it was found to be 144 Ω / m, which was 1/3 that of the conventional carbon fiber.
Was found to be a value that could compete with a nichrome wire used as a heater.

The graphite yarn spun to a thickness of 4000 denier is twisted and entangled so that a yarn having a diameter of 12 to 15 μm does not come off, and the number thereof is about 2220. And since these 2220 pieces are entangled with each other, they are less likely to fall off, and the denier is made uniform, so that the resistance value is very stable and almost no contact resistance is generated.

For example, when two 4000 denier graphite yarns are aligned and the resistance is measured, an average of 7 is obtained.
1.95 Ω / m, and 36.
It becomes 05 Ω / m, which is consistent with Ohm's law.

In the present invention, as described above, a graphite yarn having a stable resistance value can be obtained by passing a bundle of tous sliver produced by firing pitch fibers several times through an intergil machine before being sent to a spinning machine. When the electric resistance of the graphite yarn after spinning was examined for the fiber passed through the intergil machine once and the fiber passed four times, the results shown in Table 1 were obtained. However, it was found that a stable resistance value with little variation was obtained.

[0024]

[Table 1]

Although this spun graphite yarn is a conductor, it is easy to fall off and has a low tensile bending strength. Therefore, when it is used as a heater for snow melting or heating and buried in the soil, it has insulation and heat resistance. In order to impart strength, the graphite yarn is tied around with a reinforcing yarn such as a twentieth-twisted aramid fiber (for example, Twaron, manufactured by Nippon Aramid Co., Ltd.), and is further protected from water leakage and leakage. For this reason, it is preferable to coat around the aramid fiber woven with polyurethane, polyvinyl chloride, cross-linked polyethylene resin or the like. An example of the structure of such a heater A is shown in FIG.
It was shown to. In the figure, 1 is a graphite thread, 2 is an aramid fiber bundled on the graphite thread 1, 3 is a polyvinyl chloride layer, and 4 is a polyurethane layer of the exterior.

Such a graphite heater A has a resistance of 8 Ω / m if the required resistance is determined to be 9 Ω / m.
Eight 000-denier graphite yarns (4000-denier two strands) were aligned and configured as shown in FIG. 3 (a), and then connected to the lead wire 12 in the rubber cap 13 as shown in FIG. 3 (b). The electrode 11 is inserted into the graphite thread 1 at both ends of the heater A and the rubber cap 13 is fitted to both ends for use.

When such a graphite heater A is buried in the ground and used as a heater for melting snow or heating, it may be wired in parallel in a ladder shape as shown in FIG. Is very thin and has a large surface area, so there is no need to fix the electrodes by welding, etc., and since the resistance value of the graphite thread is high and the surface area (contact area) is large, a stable current flows just by inserting it into the graphite thread. There is no need to worry about overcurrent.

As described above, the present invention provides
The resistance value of the graphite yarn obtained by spinning the tow sliver bundle having a fiber length of 10 to 90 cm obtained by graphitizing at 500 ° C. by repeatedly processing the slab a plurality of times with an intergil machine to remove the slab. This makes it possible to use the graphite yarn as a heating element such as a heater.

In the case of a carbon heater in which a carbon powder and a resin are mixed to form a string, 400 to 500 Ω / m
The graphite heater of the present invention has a high resistance value of 3 to 50 Ω / m, and the nichrome wire heater used as a metal wire heater has a high resistance value of 0.02 to 2 Ω / m.
Since a suitable resistance is high, there is no problem due to overcurrent, a constant temperature is maintained, and a thread-like electrode is also possible.

A comparison between the nichrome wire heater and the graphite heater of the present invention shows that, in the case of the nichrome wire, the entire wire becomes unusable due to one disconnection.
When the thickness of the nichrome wire is increased, the resistance is reduced and the unit length of one heater is increased to 200 to 300 m. Although there are concerns about problems such as easy disconnection due to impact load and the presence of metal oxidation, the graphite heater according to the present invention is hardly affected by linear expansion because its length is as short as 20 m or less. That one wire break in the heater does not affect the whole,
Because it is non-metallic, it has excellent flexibility, and it does not oxidize unless it is 400 ° C or higher, so its durability is much better than that of nichrome wire, and a wide range of heat generation can be obtained by combining resistance and wiring pitch. The advantage is obtained.

The graphite heater of the present invention having many advantages as described above can be used not only as a snow melting heater described in Examples described later but also as a hot mat,
It can be widely used as a heating heater or the like in the soil in the house when cultivating vegetables and fruit trees in the winter.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. (1) Production of Graphite Yarn A pitch fiber having a diameter of 10 to 20 μm obtained by spinning a molten petroleum pitch is subjected to a carbonization step of firing at 1000 ° C. in a nitrogen atmosphere, and a graphitization step of firing at 2500 ° C. to 10 to 90 cm.
A 10 g / m Tous river bundle having a mixed long and short fiber length was obtained.

Next, this condensed body was put into an intergil machine for 4 hours.
The slab (graphite mass) contained in the bundle after the graphitization step is removed repeatedly to reduce contact resistance and comb the bundle to form short fibers having a fiber length of 5 to 20 cm. The short fiber sliver was drafted to a required yarn count by a spinning machine, and twisted in a predetermined manner to obtain a 12,000 denier graphite yarn. Next, seven 12,000 denier graphite yarns were aligned to obtain 84,000 denier graphite yarns. This graphite yarn is 4.54m in diameter by twisting 44650 short fibers having a diameter of 12.5μm with a spinning machine.
m, and the resistance was 6.85 Ω / m.

(2) Manufacture of Graphite Heater Aramid fibers (Twaron 3000D, manufactured by Nippon Aramid Co., Ltd.) were unevenly braided on the peripheral surface of the 84000 denier, 4.5 mm diameter graphite yarn obtained above as a reinforcing yarn. After that, the surface is heat resistant PV to prevent water leakage and leakage.
C, and coated with a polyurethane resin to obtain a graphite heater having a configuration shown in FIG.

(3) Buried in the ground as a heater for snow melting In a snowfall area, before the snowfall, for example, a gravel layer 3 as shown in FIG.
1. Asphalt concrete layer 32, modified asphalt layer 33, road length 50m, width 6m, area 30
About 0 m ² , the modified asphalt layer 33 was scraped off to a depth of about 5 cm from the road surface, and a groove 34 was formed on the surface. In the groove 34, the graphite heater A obtained above was inserted.
Asphalt pavement 3 after burial and burial
3 'was applied to make a snowmelt test road in which a graphite heater was buried.

Graphite heater A on the above road
For example, as shown in FIG. 5, a road of 300 m ² is divided into three blocks in the length direction, and 14 per block
m, No. No. 16m in 2 blocks. 1 in 3 blocks
Use a 8m long graphite heater,
100mm, 150mm, 200mm for each block
13 grooves were cut and embedded at a pitch of mm. The details are shown in Table 2. Then, although not shown, electrodes were inserted into the ends of the respective heaters, lead wiring was performed as shown in FIG. 4, and the outermost lead wires were connected to the control panel.

[0037]

[Table 2]

(4) Snow Melting Test No. 2 was found after 2.5 cm of snow had fallen on the snow melting test road in which the graphite heater was buried. One block and N
o. A 200-volt current was applied to the three blocks to perform a snow melting test. The results were as shown in No. 1 using a 14 m long graphite heater. One block is shown in Table 3 using No. 18 using a graphite heater of 18 m length. The three blocks are shown in Table 4. In addition, No. 16 in which a 16 m graphite heater was embedded. The block No. 2 is energized before snowfall, and when the road surface temperature falls in snow, the 100 pitch portion is 19 ° C.
The temperature was raised to 11.5 ° C. in the 150 pitch portion and 9.5 ° C. in the 200 pitch portion, and the snow melted at the same time as the snow accretion, so no snow accumulation was observed.

[0039]

[Table 3]

[0040]

[Table 4]

In Table 3, the temperature in parentheses indicates the road surface temperature at the start of energization and after a lapse of time from the energization. In each zone of the pitch, one hour after energization, calories due to heat generation are accumulated on the road surface. It was considered that there was no sign of snow melting, but after one hour, the difference in the pitch of the wired heaters was clearly noticeable in the rise of the road surface temperature, and it was recognized that the degree of snow melting was greatly affected.

In Table 4, the heater was 18 m
As shown in Table 2, the use of the heater as a length resulted in an inferior result in that the calorific value was lower as compared with the use of a heater having a length of 14 m.

In this snow melting test, as a comparative heater, seven 12,000 denier yarns obtained by spinning a bundle of 10 g / m of Tous sliver which had undergone a graphitization step only once through an Intergil machine were used. 8400
The resistance value of a 0 denier yarn is 6.78 to 7.56Ω /
In the same manner as in the present invention, a graphite heater having a diameter of 10 mm was formed by covering a graphite yarn having a variation of m with a string and covering the yarn with a length of 14 m.
Allowed to present buried, tried to snow melting test under the same snow 2.5cm to the aforementioned Example, appear in the variation of the resistance value described above is snow melting results in the area of 5 hours elapsed after about 55m ² from the energization Dotted snow remained.

The above-mentioned energization of the graphite heater may be performed manually in view of the snowfall situation. However, a thermocouple is inserted into a required depth in the ground to form a ground temperature sensor.
These lead wires are connected to an automatic recording thermometer and a control device together with the atmospheric temperature sensor, and when the temperature is detected at an ambient temperature of 3 ° C. or less, for example, at an ambient temperature of 3 ° C. or less, the soil temperature becomes 1 ° C. or less. So that the heater is turned on,
When the atmospheric temperature is 3 ° C. or higher and moisture is detected, the temperature may be turned off when the ground temperature is 1 ° C. or higher to enable automatic operation.

In the above embodiment, a graphite heater having a required length is embedded in a grooved road surface. In addition, a graphite heater is attached to a long nonwoven fabric at a required pitch, and the graphite heater is mounted at a predetermined depth. It may be laid, and according to this method, laying is easy.

[0046]

As described above, according to the present invention, pitch fibers obtained by spinning a molten pitch are carbonized and graphitized to form a tous sliver having a fiber length of 10 to 90 cm. It is characterized by removing the slab in the tous sliver by repeatedly processing multiple times at
After removal of the slab, the graphite fiber drawn and twisted by a spinning machine gives a stable resistance value, so it can be used as a heater of 100% carbon / graphite instead of nichrome wire. The target value is very large.

[Brief description of the drawings]

FIG. 1 is a perspective view of a three-dimensional structure model of graphite.

FIG. 2 is an explanatory view showing a state of slab removal in a plurality of times of processing by the intergil machine.

FIG. 3 (a) is a cross-sectional view of a configuration of a graphite heater according to the present invention, and FIG. 3 (b) is an explanatory view showing an electrode inserted state.

FIG. 4 is an explanatory diagram showing an example of a wiring of a graphite heater.

FIG. 5 is an explanatory view showing an example of construction of a graphite heater.

FIG. 6 is an explanatory diagram showing an example of a snow melting road structure using a graphite heater.

[Explanation of symbols]

 A Graphite heater 1 Graphite thread 2 Aramid fiber 3 Polyvinyl chloride coating layer 4 Polyurethane coating layer 11 Electrode 12 Lead wire 13 Rubber cap

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Isamu Tsuda 1-11-6 Motoyamanakacho, Higashinada-ku, Kobe City, Hyogo Prefecture Inside Ozeki Chemical Industry Co., Ltd. (72) Inventor Setsuo Hoshikawa 5-39 Akasakadai, Sakai-shi, Osaka −5 (72) Inventor Sasa ▲ Taka ▼ Person 3-28 Sakuragaoka, Kamimaki-cho, Kitakatsugi-gun, Nara Prefecture 10

Claims (6)

[Claims] 1. A pitch fiber obtained by spinning a molten pitch having a diameter of 10 to 20 μm, preliminarily drying, and carbonizing and further graphitizing the pitch fiber to obtain a tous sliver having a fiber length of 10 to 90 cm. Treat the sliver with an intergil machine to remove the slab in the tous sliver and
A method for producing a graphite fiber having a stable resistance value, which comprises drawing a short fiber having a length of 20 cm, drawing and twisting with a spinning machine. 2. The method for producing graphite fiber according to claim 1, wherein the treatment by the Tousliver intergill machine is repeated a plurality of times. 3. A pitch fiber obtained by spinning a molten pitch at a diameter of 10 to 20 μm, preliminarily drying, and carbonizing and graphitizing the pitch fiber to obtain a tous sliver having a fiber length of 10 to 90 cm. Treat the sliver with an intergil machine to remove the slab in the tous sliver and
A heating element made of graphite fiber having a stable resistance value, characterized in that a graphite fiber obtained by forming a short fiber of 20 cm, drawing and twisting with a spinning machine is subjected to a bundle processing or further resin coating. 4. The heating element made of graphite fiber according to claim 3, wherein the treatment by the Tousliver intergil machine is repeated a plurality of times. 5. A heating element made of graphite fiber according to claim 3 or 4, which is buried in soil on a road surface and used as a snow melting heater. 6. A heating element comprising graphite fibers according to claim 3 or 4, wherein the heating element is buried in soil in an agricultural house and used as a heater for promoting crop growth.