KR940006375B1 - Process for the preparation of pitch-type hollow carbon fiber by spinning of melt pitch and apparatus thereof - Google Patents

Abstract

melting the petroleum-based pitch or the coal-tar mesophase pitch inside the spinneret; spinning the melted pitch by supplying the nitrogen in the amount of 8.5-15 ml/hour on the surface of the melted pitch under the pressure of 1-5 kgf/cm2, while supplying the nitrogen inside the melted pitch in the amount of 150-300 ml/hour to form the hollow spun fiber, having the diameter of the outside 1.5-2.5 times that of the inside; stabilizing the spun-fiber by air-oxidization; carbonizing the stabilized fiber under the nitrogen atmosphere.

Description

Method and apparatus for manufacturing pitch-based hollow carbon fiber by spinning of melt pitch

1 is a schematic view of a spinning machine for producing a pitch-based hollow carbon fiber according to the present invention and a detailed view of the spinning nozzle.

2 (a) is a stabilization process diagram of petroleum-based spinning fiber.

2 (b) is a stabilization process chart of coal tar-based mesophase spinning fibers.

3 is a carbonization process diagram for carbonizing the fibers stabilized by FIGS. 2 (a) and 2 (b).

Figure 4 (a) is an electron micrograph (SEM) of petroleum chipped hollow carbon fiber.

Figure 4 (b) is an electron micrograph of coal tar-based mesophase pitch-based hollow carbon fiber.

* Explanation of symbols for main parts of the drawings

1: radiator 2: heater

3: temperature controller 4, 5: nitrogen supply pipe

6: Spinning nozzle 7: Winding machine

The present invention relates to a method and apparatus for producing hollow carbon fibers, that is, pitch-based carbon fibers by spinning coal tar pitch and petroleum pitch as raw materials.

Recently, many studies on non-circular carbon fibers using pitch have been made.

In particular, during this trial by Eddy of the United States, a pitch spinner was devised to produce hollow carbon fibers.

However, in such a spinning machine, a general polymer material for producing fibers using a spinning machine for general polymers has a drawing length of 1-10 m or more during spinning, but only about 1-5 cm for pitch. It is difficult to manufacture hollow fibers with the spinning machine, and in particular, it is difficult to control the thickness and size of the hollow carbon fibers.

This is because the viscosity of the pitch changes significantly with temperature.

Hollow carbon fiber is not only applicable to the production of activated carbon fiber, separation of enzyme carriers and materials due to the characteristics of the fiber, but also extends to many fields such as weight reduction of composite materials.

An object of the present invention is to produce a hollow carbon fiber in a more stable condition while solving the above problems.

It is also an object of the present invention to provide a spinning machine for producing hollow carbon fibers that operates in a completely different manner from the conventional spinning machine, and a method of manufacturing hollow carbon fibers using the same.

In the manufacturing method of pitch hollow carbon fiber according to the present invention, the pitch is first injected into a melt spinning machine to melt the pitch, and the hollow spinning is primarily performed by changing the pressure, nitrogen flow and winding speed of the spinning machine according to the outer diameter and the thickness of the desired fiber. Get fiber.

At this time, the temperature of the spinning machine is in the range of 285-310 ℃ in the case of petroleum pitch and 350-365 ℃ in the case of coal tar-based meso phase, since the viscosity of the melt pitch to be spun significantly changes outside the temperature range Not desirable

The spinning pressure suitable for extruding the pitch through the nozzle of the spinner at a winding speed as described below is 1-5 kgf / cm ² . Also, the nitrogen flow rate to provide a pressure at which the melt pitch can spin is 8.5-15 ml / hour, which is provided as the first nitrogen feed pipe of the spinner of the present invention.

The single-hole hollow fiber spinning machine may be extended by spinning to a spinning machine having several holes.

The spinneret according to the present invention is equipped with a second nitrogen supply pipe, and the nitrogen flow rate in this pipe is 150-300 ml per hour.

By supplying nitrogen in the above range, it is possible to produce a hollow carbon fiber having a desired size in the present invention, that is, pitch-based hollow carbon fiber having an outer diameter of 22 to 120 μm and an inner diameter of 10 to 80 μm.

In other words, it is possible to produce a pitch-based hollow carbon fiber having an outer diameter in the range of about 1.5 to 2.5 times the inner diameter.

Hollow spun fiber obtained by the first method as described above requires a stabilization process in order not to melt during the carbonization, in the present invention stabilizes the hollow spun fiber by the air oxidation method performed by increasing the temperature in accordance with the change of time.

In the case of petroleum pitch fibers, the temperature is increased by 2 ° C. per minute to 280 ° C. within 1 hour depending on the thickness of the fiber, and in the case of coal tar mesophase pitch fibers, the temperature is stabilized at 350 ° C. within 1 hour at 2 ° C. per minute.

The stabilized fibers are heated to 10 ° C. per minute in a nitrogen atmosphere, heated to 1000 ° C. for 30 minutes, and then cooled to room temperature to produce final hollow carbon fibers. Spinning pitches to be used in the present invention are coal tar-based mesophase pitch (Korean Patent Publication No. 1244, Publication No. 86-2203) and petroleum crab pitch.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The petroleum pitch is placed in the spinning machine 1 shown in FIG. 1 and heated to 300 ° C.

At this time, the radiator 1 is kept constant at proper heating and temperature by using the heater 2 and the temperature controller 3 in the vicinity thereof.

And nitrogen is supplied to the inside of the radiator 1 using the nitrogen supply pipes (4) and (5). The nitrogen supply pipe 4 supplies nitrogen to the upper surface of the molten pitch existing inside the radiator 1 to provide a pressure at which the molten pitch can be spun, and the nitrogen supply pipe 5 directly inside the molten pitch. Supply to form hollow carbon fibers.

When supplying nitrogen to the nitrogen supply pipes (4) and (5), although not shown in the figure, one nitrogen container may be shared or a separate nitrogen container may be used, provided that the nitrogen supply pipes (4) and (5) It should be possible to control the nitrogen pressure and the flow of nitrogen separately.

In the present invention, the pressure P ₁ of the nitrogen supply pipe 4 is in the range of 1-5 kgf / cm ² and the nitrogen flow rate is adjusted to 8.5-15 ml per hour (V ₁ ).

At this time, when the range of the pressure (P ₁ ) and the nitrogen flow rate (V ₁ ) is out of the above conditions, the inner walls of the hollow yarns are bonded to each other, making it difficult to form hollows or making frequent trimming phenomena.

As such, the melt pitch is radiated from the spinning nozzle 6 by the pressure P ₁ , in which hollow carbon fibers are formed by the nitrogen flow supplied from the pipe 5.

The hollow fiber is adjusted to the pressure P ₁ and the nitrogen pressure P ₂ flowing through the pipe 5 and the winding speed in the winder 7 so that the outer diameter is in the range of 1.5 to 2.5 times the inner diameter.

In this case, when the outer diameter of the hollow fiber is less than 1.5 times the inner diameter, the outer wall of the hollow yarn becomes thin and the strength of the yarn decreases or the outer wall is damaged, thereby deteriorating the physical properties.In addition, when the outer diameter exceeds 2.5 times the inner diameter, the outer wall This thickening is so close that there is a reduction in the characteristics and effectiveness of the hollow fiber furnace.

In general, the nitrogen flow rate (V ₂ ) of the pipe (5) is in the range of 150-300ml per hour.

And the winding speed of the winder (7) is adjusted in the range of 20-600m / min so that the hollow spinning fibers radiated from the spinning machine 1 is not broken or cut off.

At this time, when the nitrogen flow rate (V ₁ ) in the pipe (5) is less than 150ml / hour, the solidification time of the hollow yarn becomes long, so that the hollow shape is not uniformly formed by the sagging phenomenon, and when it exceeds 300ml / hour, the hollow fiber Since the internal pressure becomes too large, there is a risk that the outer wall is expanded, broken or trimmed.

On the other hand, coal tar-based mesophase pitch is heated to about 350 ℃ to operate the spinning machine under the same conditions as the petroleum pitch described above to produce a hollow spun fiber.

In the present invention, of course, it is also possible to install and operate not only one radiation nozzle 6 but also several.

If hollow fiber is manufactured according to the above method, it must go through stabilization process to prevent melting during carbonization.

Therefore, in the present invention, the temperature is raised to 280 ° C. at the rate of 2 ° C./min for petroleum pitch fibers within 1 hour depending on the thickness of the fiber, and 350 ° C. at the rate of 2 ° C. for coal tar mesophase pitch fibers. It is stabilized within 1 hour at ℃. This stabilization process is carried out according to FIGS. 2a and 2b.

After the stabilization process, according to FIG. 3, the temperature is heated to 1000 ° C. under a nitrogen atmosphere at a temperature of 10 ° C./min, and the carbonization process maintains the temperature for 30 minutes and then cooled at room temperature to produce the final hollow carbon fiber. .

The geometric shape of the hollow carbon fiber produced by this method is a perfect hollow.

Hereinafter, the present invention will be described in more detail with reference to the following examples.

EXAMPLE

The pitch used in the embodiment of the present invention is a coal tar-based mesophase pitch produced by a method developed by one of the inventors of the present invention (Lee Bosung) (Korean Patent Publication No. 1244, Publication No. 87-2203). ) And petroleum pitch (Korean Patent Publication No. 061131, Publication No. 92-010266). The spinning temperature of mesophase pitch is 350 ℃ and the spinning temperature of petroleum pitch is 300 ℃, and these were selected as the optimum spinning conditions through preliminary experiments.

For spinning the pitch is placed in the spinning machine 1 shown in FIG. 1 and heated to the optimum spinning temperature as described above. At this time, the heating uses the heater 2, and the temperature is kept constant by using the temperature controller (3). When the temperature is kept constant, the pressure is adjusted to about 5 atmospheres through the nitrogen supply pipe 4, and when the pitch starts flowing through the spinning nozzle 6, the nitrogen gas is transferred through another nitrogen supply pipe (5). Flow by 8.5-15ml / min to make the pitch hollow. Then, the winder 7 is adjusted at a speed of 20-600 m / min so as to adjust the outer diameter of the hollow pitch fiber in the range of 20-120 μm.

The spun hollow pitch fiber can be made into the final pitch-based hollow carbon fiber through the stabilization and carbonization step. Stabilization was carried out by the hot air oxidation method, and as shown in Figs. 2 (a) and 2 (b), when petroleum pitch was used as a raw material, heating was performed at a temperature of 2 ° C. per minute up to 280 ° C. for 1 hour at this temperature. After the stabilization was completed, stabilization was completed by heating the temperature by 2 ° C. per minute to 320 ° C. in the case of mesophase pitch, and maintaining at this temperature for 1 hour. In order to carbonize the stabilized fiber, as shown in FIG. 3, carbonization was completed by raising the temperature to 10 ° C. per minute under nitrogen stream, heating to 1000 ° C., and maintaining it for 30 minutes. Carbonization conditions were selected for both petroleum-based pitches, mesophase pitches, and mesophase pitches.

The size and tensile strength of the petroleum and coal tar mesophase hollow carbon fibers prepared above are measured using an Instron tensile strength meter as shown in the following table, and the torsional stiffness is measured by a torsional pendulm. .

As can be seen from the table, both the petroleum and coal tar mesophase hollow carbon fibers produced by the method of the present invention exhibited mechanical properties according to their inner and outer diameters at the winding speeds shown in the table above. In addition to the physical properties, electron micrographs of petroleum pitch hollow carbon fibers are shown in FIG. 4a, and electron micrographs of coal tar mesophase pitch hollow carbon fibers are shown in FIG. 4b. It can be clearly seen that the geometry is perfectly hollow.

Claims (2)

Melting petroleum pitch or coal tar mesophase pitch inside the spinner; Hollow spun fiber having an outer diameter of 1.5 to 2.5 times the inner diameter inside the molten pitch while spinning the melt pitch by supplying nitrogen at a pressure of 1-5 kgf / cm ² and 8.5-15 ml / hour to the molten pitch surface Supplying a flow rate of nitrogen with pressure at a rate of 150-300 ml / hour so that hollow fiber can be formed; Stabilizing the hollow spun fiber formed by air oxidation; A method of producing a pitch-based hollow carbon fiber comprising the step of carbonizing a stabilized hollow fiber under a nitrogen atmosphere. A spinner 1 on which coal tar-based pitch or petroleum-based pitch is to be melted; A heater 2 mounted on the inner wall of the radiator 1; A thermostat 3 for controlling the temperature of the preheater so that the pitch can be melted in an optimal state; A nitrogen supply pipe 4 for introducing nitrogen to the surface of the molten pitch in the radiator 1 to provide a radiation input; Another nitrogen supply pipe 5 for supplying nitrogen to supply hollow nitrogen to the inside of the melt pitch in the spinner 1 so that hollow spun fiber can be formed; One or more spinning nozzles 6 in which the molten pitch is spun by nitrogen and hollows are formed; And Spinning apparatus for producing a pitch-based hollow carbon fiber composed of a winder (7) for winding the spun hollow fiber.