JPS616315A - Production of carbon fiber - Google Patents

Abstract

PURPOSE:To obtain carbon fibers efficiently without causing fiber breakage, etc., by melt spinning raw material pitch, irradiating the resultant pitch fibers with ionizing radiation, and carbonizing the resultant infusible fibers in an inert gas atmosphere under heating. CONSTITUTION:Raw material pitch, e.g. petroleum or coal based pitch, is melted and spun through a spinneret 1 to form filaments 2, which are then collected to give pitch fibers 4. The resultant pitch fibers 4 are irradiated with ionizing radiation 5, infusibilized and then carbonized under heating at 700-1,700 deg.C in an inert gas atmosphere, e.g. nitrogen or helium gas, to afford the aimed carbon fibers. The dose of the ionizing radiation is preferably 0.5-30Mrad.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing carbon fibers, and more specifically, a method for producing carbon fibers, which is characterized in that pitch fibers obtained by spinning pinch are reliably rendered infusible in a short period of time using ionizing radiation. Regarding.

Conventionally, carbon fibers can be roughly divided into two methods: one is to manufacture them from polyacrylonitrile fibers, and the other is to manufacture them from petroleum-based or coal-based pitch. The former method produces products with high strength, but the raw materials are expensive and the carbonization yield during firing is low, so in recent years the latter method using pitch as the raw material has been mainly used. When using pitch as raw material,
Carbon fibers are manufactured by performing spinning, infusibility, and firing processes. The infusibility treatment was performed by heating in an oxidizing atmosphere. However, since the heat infusibility treatment has a slow processing speed, it does not match the spinning speed, causing problems in the manufacturing process.

For this reason, methods have been adopted in which the spun yarn is wound or stored in a can, then pulled out and subjected to an infusible process, but this method has the disadvantage that the solidified pitch fibers are brittle and often break. Ta.

Therefore, the present inventors solved the drawbacks of these conventional methods,
As a result of intensive research to develop a method for producing carbon fibers in a short time, efficiently, and without the occurrence of yarn breakage, the inventors discovered that the objective could be achieved by making the fibers infusible by irradiating them with radiation, and completed the present invention.

That is, the present invention is a method for producing carbon fibers from raw material pitch, and is characterized in that pinched fibers obtained by melt-spinning raw material pinches are irradiated with ionizing radiation to make them infusible, and then heated and carbonized in an inert gas atmosphere. The present invention provides a method for manufacturing carbon fiber.

In the present invention, various pitches such as petroleum-based pitch and coal-based pitch can be used as the raw material pinch, but pitches with an optically anisotropic phase content of 80% or more, preferably substantially 100% are used. is preferably used. The pitch preferably has a softening point of 250 to 380°C.

When melt-spinning such a raw material pinch to obtain pinch fibers, an aggravating agent may be added to the raw material or applied to the pitch fibers, if necessary. This sensitizer plays the role of improving the effect of ionizing radiation that is irradiated later for infusibility. Here, there are various sensitizers, including benzophenone compounds such as benzophenone and 4-chlorobenzophenone; benzoin ether compounds such as benzoin isopropyl ether and benzoin isobutyl ether; and acetophenone compounds. , for example (α,α-dimethoxy)-(α-phenyl)acetophenone, (α,α
-dimethyl)-(α-hydroxy)acetophenone,
(α, α-dimethyl)-(α-hydroxy)-4-isopropylacetophenone, (α5 α-dichlor>(
4-tert-butyl)acetophenone, (α, α-
dichloro)-(4-phenoxy)-acetophenone, etc.; thioxanthone compounds, such as α-chlorothioxanthone, α-methylthioxanthone, etc.; diazonium compounds, such as benzenediazonium chloride, benzenediazonium perbromide, etc.; p-quinonediazide compounds, For example, p-quinonediazide, p-iminoquinonediazide, etc.; 0-quinonediazide type compounds, such as 0-quinonediazide.

Examples include 0-iminoquinone diazide, etc.; dichromic acid compounds, such as potassium dichromate, sodium dichromate, and ammonium dichromate; other azide compounds, organic halides, and the like.

When these sensitizers are used, the amount added is usually about 0.01 to 0.1% by weight based on the raw material pinch.The method of the present invention will be explained with reference to FIG. FIG. 1 is an explanatory diagram showing an example of a flow for implementing the method of the present invention.

First, the raw materials as described above are melted and spun from a spinneret 1 to form filaments 2. The conditions for melt spinning vary depending on the type of pitch used as a raw material, the desired properties of the carbon fiber to be produced, etc., and cannot be unambiguously determined, but they may be the conditions conventionally used. Specifically, the spinning temperature is 250~
400°C, preferably 260-380°C, spinning speed 10
0-1500 m/min, preferably 200-10
00 m/min, filament diameter 5-30 m, CI preferably 5-20 m.

Pinch fibers 4 are obtained by converging the filaments 2 spun under these conditions. Focusing is usually performed by an air sunker 3 as shown. Further, a sizing agent may be added to further improve the sizing property. Examples of the sizing agent include water or an oil agent prepared by emulsifying a compound such as an ethylene oxide adduct of a higher alcohol or an alkyl ester of a higher alcohol phosphoric acid ester@3 higher fatty acid in water. The above-mentioned higher alcohols, higher alcohol phosphates, higher fatty acids, etc. usually have about 12 to 18 carbon atoms. Further, an antistatic agent may be added to the above water or oil agent. This sizing agent may be applied to the filament 2, and the air thunker 3 may be used to apply the sizing agent to the pitch fibers 4 after sizing. You can do it. There are no particular restrictions on the method of application, but a method of spraying onto filaments or fibers is preferred.

Next, the pinched fibers 4 are irradiated with ionizing radiation 5 to make them infusible. The present invention is characterized in that the infusibility treatment is performed reliably in a short time by irradiation with ionizing radiation. Here, ionizing radiation means electron beams, neutron beams, alpha rays, gamma rays, X-rays, ultraviolet rays, and the like. Ionizing radiation is usually irradiated in the air, but other sources include hydrogen gas and methane gas.

It can also be carried out in an atmosphere of helium gas, argon gas, xenon gas, krypton gas, etc., and any conventional method may be used. The irradiation dose of ionizing radiation depends on the type of raw material pitch and the pinch fiber diameter.

Although it varies depending on the presence or absence of a sensitizer and is not uniquely determined, it is usually about 0.05 to 30 megarads, preferably about 0.1 to 20 megarads. Ionizing radiation can be irradiated in various ways without particular restrictions, but
As shown in FIG. 1, a common method is to uniformly irradiate pinched fibers before winding them onto a bobbin 6. In addition, it is also possible to store the pinched fibers in a can or the like or wind them up on a bobbin, and then rotate the fibers to uniformly irradiate the fibers.

Before being infusible, pitch fibers are very brittle and easy to cut.
As shown in FIG. 1, a method performed before winding onto a bobbin is particularly suitable. When the infusibility treatment is carried out using a conventional heating method, it takes a relatively long time for the infusibility treatment, so the bundled bi- and 7-chi fibers are infusible continuously in accordance with the winding speed. However, with the method of the present invention, since the infusibility treatment can be carried out in a short time, continuous treatment is possible, and there is no need to cut the pitch fibers at the stage of storing them in a can or winding them onto a bobbin. Situations can also be prevented.

The Bi-Noti fibers that have been subjected to infusibility treatment and wound onto a bobbin are then subjected to firing treatment. The firing treatment may be performed by a conventional method, and there are no special conditions.

Usually, carbonization is carried out by heating under an inert gas atmosphere. Here, nitrogen gas, helium gas, argon gas, etc. are used as the inert gas. Note that the firing may be performed under vacuum. The heating temperature is usually
The temperature is 700 to 1,700°C, preferably 800 to 1,500°C, but it may be graphitized by heating to 2,500 to 3,000°C if desired. In addition, when a sizing agent is used, it is preferable to remove excess sizing agent before firing.

The carbon fiber thus obtained is stored in a can or wound on a bobbin and used for various purposes.

According to the manufacturing method of the present invention, since the infusibility treatment is performed by irradiation with ionizing radiation, the infusibility treatment can be performed continuously in a short time. Therefore, it is possible to manufacture carbon fibers with excellent tensile strength and the like. Furthermore, since there is no need to pull out the wound yarn during the manufacturing process, it is possible to prevent pinch fibers from being cut, which is extremely useful in the production of carbon fibers, and has high practical industrial value.

Next, the present invention will be explained in detail with reference to examples.

Example 1 Pinch fibers were manufactured according to the flow shown in FIG. In other words, petroleum pitch with 100% optically anisotropic phase (
Average molecular weight 1130. Softening point: 345°C, pyridine insoluble content: 52% by weight) at 360°C, spinning speed: 550°C.
Melt spinning was performed from spinneret 1 at m/min and filament diameter of 10 μm.

Approximately 400 of the obtained filaments 2 were bundled using an air sunker 3 to obtain pitch fibers 4. The pinched fibers were continuously irradiated with cobalt 60 gamma rays of 3' hrac3 in air and wound onto a bobbin 6 at a speed of 550 m/min. The tensile strength of this pitch fiber was 25 m/112. Next, the pitch fiber wound around a bobbin was fired at 1500°C for 10 minutes in an argon gas atmosphere in a firing furnace (not shown) to form a carbon fiber. Obtained.

The obtained carbon fiber had a tensile strength of 280 kg/weight/weight 2° and an elastic modulus of 25 t/Tsuru 2.

Example 2 Pitch fibers were obtained in the same manner as in Example 1, except that water was sprayed onto the filaments 2 spun from the spinneret 1. The tensile strength of this product was 23 kg/Iris 2.

Next, carbon fibers were obtained in the same manner as in Example 1.

This carbon fiber has good cohesiveness and tensile strength of 280 kg/11
22 elastic modulus was 25t/mm2.

Example 3 Petroleum pitch in Example 1 (same as Example 1) 1
Pinch fibers were obtained in the same manner as in Example 1, except that a mixture of 0.00 parts by weight and 0.05 parts by weight of benzophenone was used as the raw material, and the radiation irradiation was performed in argon gas.

The tensile strength of this product was 32 kg/m''.

Next, carbon fibers were obtained in the same manner as in Example 1.

The obtained carbon fiber had a tensile strength of 280 kg/mm'' and an elastic modulus of 25 t/Ryu2.

[Brief explanation of the drawing]

FIG. 1 shows a schematic diagram of an example of an apparatus used for producing pitch fibers in the production method of the present invention. 1. Spinneret, 2. Filament. 3. Air soccer, 4. Pinch fiber. 5... Ionizing radiation 56... Bobbin Figure 1 961

Claims (2)

[Claims] (1) A method for producing carbon fibers from raw material pitch, characterized in that the pitch fibers obtained by melt-spinning raw material pitch are irradiated with ionizing radiation to make them infusible, and then heated and carbonized in an inert gas atmosphere. A method for manufacturing carbon fiber. (2) The manufacturing method according to claim 1, wherein the dose of ionizing radiation is 0.05 to 30 megarads.