JPS6183321A - Production of hollow carbon fiber - Google Patents

Abstract

PURPOSE:To produce the titled fiber from inexpensive pitch, using conventional spinning apparatus, at a low cost, by spinning molten pitch having a specific viscosity, and quenching the extruded fiber just below the spinning nozzle with cooling gas. CONSTITUTION:Pitch is spun, infusibilized, and carbonized to obtain a carbon fiber. In the above process, a low-viscosity molten pitch having a viscosity of 10-150 poise is extruded through a nozzle having a diameter (d) of 0.1-0.5mm, nozzle length (L) of 1.0-1.5mm, and an L/D ratio of 2-5 with a back pressure of the extrusion gas of 0.2-1.0kg/cm<2>, and the spun fiber is quenched just below the spinning nozzle with cooling gas. The blasting of the cooling gas is preferably carried out in a manner that the surface viscosity of the spun fiber becomes 3-5 times the viscosity of the molten pitch used as the raw material.

Description

[Detailed description of the invention] Riko B shout use 1 The present invention relates to a new method for producing hollow carbon Il fibers.

Prior art and its problems When producing hollow carbon fibers from cellulose-based, polyacrylonitrile-based, lignin-based, etc., raw materials, hollow IN can be obtained by spinning fibers without hollow parts and then controlling the flame-retardant treatment state. Alternatively, hollow fibers are obtained by carbonizing raw fibers having hollow holes. However, the manufacturing method of hollow carbon fiber using these @
The disadvantage is that the carbonization yield is low and it takes a long time to carbonize the culm.

The method for producing hollow mN using pitch as raw material is to melt optically isotropic or anisotropic pitch, and then adjust the nozzle diameter (d) and its length under appropriate spinning temperature and spinning speed. L)
A method of spinning at a gas pressure of 0.5 to 3 Kl/cd-G using a specific nozzle with a ratio L/d of 101 degrees has been proposed (Japanese Unexamined Patent Publication No. 1982-91826). This method 1
．． i. Since a special nozzle with a nozzle LZd ratio of 10JX or more is used, there is a drawback that the existing spinning machine cannot be used as is.

The present inventor has conducted various studies in view of the above-mentioned problems in the production of hollow carbon 81111, and has found that the viscosity is 1.
When molten pitch is heated to 4 degrees Celsius to 0 to 150 poise and the pitch is spun for 11 seconds, and the spun fibers are rapidly cooled near the exit of the spinning nozzle, hollow carbon fibers can be produced using a normal spinning machine. It has been found that it can be easily produced. 4) In the present invention, when manufacturing carbon fiber by spinning pitch, making it invincible, and firing it, the viscosity is 10 to 10.
The present invention relates to a method for producing hollow carbon IN, which is characterized by spinning 150 poise molten pitch and rapidly cooling the spun fibers with cooling gas directly below the spinning nozzle.

Conventionally, molten pitch heated to a low viscosity of 10 to 150 poise has poor stringability, so it has a diameter of 10 to 150 poise.
It was difficult to spin into fibers as small as ~20 microns. However, according to the method of the present invention, spinning wXH
Since the material is rapidly cooled near the nozzle exit, the pitch viscosity of the spun fiber surface increases, and spinning and hollow structure formation are performed smoothly. In other words, the pitch immediately after coming out of the nozzle hole has a low viscosity, so it is easy for the six-membered carbon ring network molecules to rearrange and move, and as a result, the orientation of the six-membered carbon ring network molecules changes. , J! It changes from a "radial type" that extends circumferentially from the center of the fiber cross section to an "onion type" that extends concentrically around the center of the fiber.

In this state, the area near the surface of the spun fiber rapidly cools, solidifies, and contracts, and the molten part inside is drawn to the outside.
Hollow carbon fibers are formed.

The optically isotropic or anisotropic pitch used as a spinning raw material in the present invention may be either coal-based or petroleum-based. Such pitch can be used to process coal-based or petroleum-based vertical oils in accordance with conventional methods, such as refining by removing solids, removing light components by vacuum distillation, hydrogenation reactions, and polycondensation reactions. Obtained by offering

In the present invention, spinning is carried out under the same conditions as in the conventional method, except that heating is performed so that the viscosity of the molten pitch becomes about 10 to 150 poise. That is, in general, the back pressure of the extrusion gas is about 0.2 to 1,0 ko/cd, the spinning nozzle diameter (d) is about 0.1 to 0.5N, and the nozzle length (L) is about 1.
The conditions of approximately 0 to 1.5 #I and L, / d = approximately 2 to 5 are adopted. Although it varies depending on the type of raw material pitch and the dimensions of the spinning nozzle, the viscosity of molten pitch is between 10 and 10.
It is more preferable to set it to about 50 poise.

The spun fibers are then blown with cooling gas near the exit of the spinning nozzle to be rapidly cooled. As a cold fJl gas,
Either an inert gas or an active gas may be used. The cooling gas is preferably sprayed in consideration of the type and viscosity of the raw material pitch, the diameter of the spun fibers, etc., so that the viscosity of the surface portion of the spun fibers is about 3 to 5 times that of the raw pitch. In this case, in order to appropriately adjust the degree of cooling, the temperature of the cooling gas may be adjusted to a range from room temperature to about 100°C.

The spun fibers having a hollow structure formed by the above cooling operation are usually wound up at a speed of about 300 to 500 m/min.

The infusibility treatment and carbonization treatment of hollow spun #A miscellaneous in the present invention are not substantially different from those of known spun fibers having no hollow. That is, by raising the temperature of the spun fiber obtained as described above from room temperature to 300 to 350 °C at a rate of about 2 to 5 minutes per minute, and then holding it in the reached temperature range for about 1 to 2 hours. Infusible treatment. Next, after holding the temperature at about 600°C for about 5 minutes in an inert gas atmosphere such as nitrogen,
Finish baking by holding at 400℃ for about 5 minutes,
Obtain the desired hollow carbon fiber.

1 Ligohuang 1 (1) Hollow carbon fibers can be manufactured using inexpensive pitch as a raw material and using existing spinning machines, so manufacturing costs are significantly reduced.

(2) The internal circular dimensions and shape of the obtained hollow carbon [1] are stable, resulting in a product with homogeneous physical properties.

(3) By adjusting the viscosity of the molten pitch during spinning, extrusion speed, nozzle L/d, cooling rate, etc.
! The outer diameter and inner diameter of i#11 can be adjusted.

(4) Since the molecular direction of carbon IIH is "onion type", its strength is high.

EXAMPLES Examples will be shown below to further clarify the characteristics of the present invention.

Example 1 Approximately 1/4 times ■ of hydrogen-generated An1 to spiral oil was added to coal tar pitch (QI=O%), and after heating to 430°C at a rate of 15°C/min with stirring, nitrogen was added. 1.5 under gas injection
A mesophase pitch was obtained by holding for a period of time. The properties of the pitch are: softening point (Möller method) -304°C, BI=8
0.7%, QI=19.9%.

The mesophase pitch described in Section 2 was spun under the conditions shown in Table 1 to obtain spun IJAH.

Table 1 The spinning operation is performed using a spinning machine (
1), a nitrogen gas supply path (5) is connected to the melting pitch (3).
), applying pressure with nitrogen gas, spinning from the nozzle (7), and spinning 11J by the winding drum (9).
I wound up AH. At this time, the second nitrogen gas supply path (1
The spinning Il directly below the nozzle (7) is caused by the nitrogen gas from 1).
The cord was rapidly cooled. In FIG. 1, (13) and (13) are heaters for heating the molten pitch, and (15) is a thermocouple for measuring the temperature of the molten pitch.

The thus obtained spun yarn #AM was soaked in air at a rate of 2.5°C/min from room temperature to 300°C, and after being infusible at a temperature of 1.5 hours, it was held at 600°C for 5 minutes in nitrogen gas. 5 which was fired under the conditions of J3 and 1400X for 5 minutes.
FIG. 2 shows an electron micrograph (400 times magnification) of the obtained hollow carbon iMM (self-diameter about 7 μm).

In addition, 15 test pieces were taken from the obtained hollow carbon fibers and subjected to a strength test, and the maximum value was 208 kl]/12,
It exhibited a tensile strength with an average value of 143 ko/ma+2.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an overview of the spinning machine used in the examples of the present invention, and FIG. 2 is an electron micrograph of the carbon fibers obtained in the examples of the present invention. This is a mirror photograph (400x). (1)...Spinner, (3)...Melting pitch, (5)
...Nitrogen gas supply path, (7)...Nozzle, (9).
... Winding drum, (11) ... Nitrogen gas supply path,
3)--Heater, (15)--Thermocouple. (That's all) Knee. Agent Patent Attorney Eiji Saegusa = 9 - Fig.

Claims (1)

[Claims] (1) When manufacturing carbon fiber by spinning pitch, making it infusible, and firing it, it is necessary to spin molten pitch with a viscosity of 10 to 150 poise and rapidly cool the spun fiber with cooling gas directly below the spinning nozzle. Characteristic hollow carbon fiber manufacturing method.