JPH0860448A - Production of pitch-based carbon yarn - Google Patents

Abstract

PURPOSE: To produce pitch-based carbon yarn having excellent properties in a continuous filament state by facilitating handleability of fragile yarn and preventing occurrence of adhesion and fusing between mutual yarns and damage on the surface of yarn. CONSTITUTION: In a method for producing pitch-based carbon yarn by subjecting a raw material pitch to melt spinning to give pitch yarn, collecting the pitch yarn, infusibilizing and optionally graphitizing, the pitch yarn during or before the collection is coated with a water emulsion of a silicone oil having 0.1-35wt.% silicone oil concentration as a collecting agent, retained at 50-100 deg.C for 2 minutes to 2 hours in a drying furnace set immediately ahead an infusibilizing furnace or in the first process of the infusibilizing furnace and dried to provide a method for producing pitch-based carbon yarn.

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 carbon fibers from pitches such as coal-based pitch, petroleum-based pitch, and polymer-fired pitch. The present invention relates to a method for obtaining a high-quality carbon fiber without adhesion or fusion between the two.

[0002]

2. Description of the Related Art Pitch-based carbon fibers are usually produced by melt-spinning raw material pitch and subjecting the resulting pitch fibers to infusibilization treatment and carbonization treatment. Pitch-based carbon fibers have the advantage that they can be produced industrially advantageously in high yield compared to polyacrylonitrile-based carbon fibers, but on the other hand, pitch fibers are extremely fragile, so they can be handled by infusibilization treatment or carbonization treatment. Difficult, fiber fluffing in these processes,
Easy to wind around the guide roll or break. Further, there is a problem that the pitch fibers are adhered or fused to each other during the infusibilization treatment or the carbonization treatment, and the surface of the obtained carbon fiber is easily damaged.

These problems are greatly different from the case of polyacrylonitrile-based carbon fiber having different raw materials and different manufacturing methods. That is, in the case of polyacrylonitrile-based carbon fiber, by a wet spinning method in which molten polyacrylonitrile is extruded through a spinning nozzle installed in a spinning bath mainly containing a mixture of dimethylformaldehyde and water or a mixture of dimethylsulfoxide and water. In such a wet spinning method after spinning, each of the spun single fibers is wetted on its surface by the liquid in the spinning bath and then focused in a tow state in the spinning bath. When the tow taken out from the spinning bath is subjected to a flameproofing treatment in an oxidizing atmosphere at 200 to 300 ° C and then a carbonization treatment in an inert atmosphere at 300 to 1400 ° C, an oil agent such as polyethylene glycol is used. It is said that a method of adhering it to the surface of tow (usually a bundle of about 500 to 10,000 filaments) is effective.

[0004]

However, even if an oil agent suitable as a sizing agent for these polyacrylonitrile-based carbon fibers is applied to the pitch fiber, the pitch fiber has a physical property such as heat and force as compared with the polyacrylonitrile fiber. It is weak against force, and it is not chemically polymerized like polyacrylonitrile, so it is much more chemically unstable. Most of it melts a part of the pitch fiber, or both fibers bond or fuse. However, it causes defects such as being rigid.

Therefore, the present inventors have previously proposed the use of silicone oil as a sizing agent as a method for solving such a difficulty in bundling pitch fibers. According to this method, bundling can be performed smoothly, but depending on the operation, silicone oil may adhere excessively in some cases, and in that case, there is no inconvenience in bundling itself, but tow after infusibilization treatment or carbonization treatment It tends to be stiff, and in extreme cases, it may be fused to make it difficult to open the fiber.

[0006]

Therefore, as a result of further studies to solve these problems, the present inventors have found that a method of using a water emulsion of silicone oil as a sizing agent is preferable, and the present invention Was completed. That is, the gist of the present invention is a method for producing pitch-based carbon fibers by bundling pitch fibers obtained by melt-spinning raw material pitch, infusibilizing treatment, and further performing graphitization treatment if necessary. , At the time of focusing or on the pitch fiber before focusing,
The concentration of silicone oil as a sizing agent is 0.1 to 35% by weight.
After applying the water emulsion of silicone oil which is
Further, the present invention resides in a method for producing a pitch-based carbon fiber characterized by holding at 50 to 100 ° C. for 5 minutes to 2 hours and drying in the first step of the drying furnace provided immediately before the infusibilizing furnace.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. Examples of the raw material pitch used in the present invention include coal tar pitch, coal pitch such as coal liquefaction, atmospheric distillation residue of crude oil, and vacuum distillation residual oil. Or a heat-treated product thereof, a petroleum-based pitch such as a heat-treated product of thermal decomposition by-product tar such as naphtha, and a polymer calcined pitch obtained by carbonizing a synthetic resin or a natural resin.

Melt spinning of the raw material pitch can be carried out in the same manner as dry-method melt spinning of ordinary synthetic fibers, and there is no particular limitation, and the melted spinning pitch is extruded from the downward spinneret into the gas phase and solidified by cooling. To adopt. As the spinneret, one having a discharge hole diameter of about 0.1 to 0.5 mm is used. The temperature of the spinneret depends on the type of raw material pitch and is determined by considering the melt viscosity suitable for spinning.
A range of 50 to 350 ° C is suitable. It is effective to stabilize the spinning state by providing a heat insulation tube below the spinneret.

In the present invention, a water emulsion of silicone oil is adhered to the spun pitch fiber as a sizing agent. As a concrete silicone oil, dimethylpolysiloxane is usually used. Those modified by introducing the above group can also be used. Specific examples thereof include methylphenyl polysiloxane and hydrogen polysiloxane, but also one of an epoxy group, an alkyl group such as ethyl and propyl, an amino group, a carboxyl group, an alcohol, a phenyl group, and a polyether group, or Those modified with two or more kinds are used. Moreover, you may use 1 type or a mixture of 2 or more types of these silicone oils.

A water emulsion of silicone oil is prepared by mixing it with water using a well-known mixing device such as a high speed mixer, a colloid mill or a homogenizer so that the silicone oil becomes 0.1 to 35% by weight. In forming an emulsion, if the concentration of silicone oil is too high to maintain a good emulsion state, an emulsifier may be added in an amount of 0.25 to 2% by weight. The emulsifier may be a conventionally known emulsifier, for example, sorbitan fatty acid ester such as sorbitan palmitate, sorbitan stearic acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitan caproic acid ester, polyoxyethylene lauric acid ester, and acetyl. Monoglycerides, non-ionic emulsifiers such as acetylated glyceryl monostearate and polyoxyethylene lanolin derivatives, alkyl sulfates, sodium lauryl sulfate, sodium cetyl sulfate, dialkyl sulfosuccinate,
Examples thereof include anionic emulsifiers such as di-2-ethylhexyl sulfosuccinate (sodium salt), and cationic emulsifiers such as alkylpyridinium chloride. Also,
A small amount of solid fine particles may be added to and mixed with a water emulsion of silicone oil and used as a sizing agent.

The solid fine particles are preferably carbonaceous fine particles, inorganic oxide fine particles, inorganic salt fine particles or a mixture thereof, and specifically, graphite, carbon black, silica, calcium carbonate, titanium oxide, talc. Fine particles of clay, clay, barium sulfate, potassium titanate, molybdenum disulfide, etc. are used. As a method of attaching the sizing agent to the pitch fibers, there are a method of spraying, a method of contacting with a roller and a method of dipping. The amount of adhesion to the fiber is usually in the range of 2 to 14% by weight, particularly preferably 2 to 10% by weight. If the adhered amount is less than 2.0% by weight, the spun fibers will not be maintained in a sufficiently bundled state, and handling of the fiber bundles will be extremely difficult, and the fibers will be damaged. Also, depending on the concentration of the oil agent, if it is 14% by weight or more, the volatilization during the infusibilization treatment becomes insufficient, and it remains on the fiber and inhibits the infusibilization reaction. Since the generated low molecular weight gas cannot be sufficiently scattered, the strength of the carbon fiber is rather lowered.

In the production method of the present invention, the water-based emulsion of silicone oil is adhered and the pitch fibers bundled are further subjected to a drying furnace immediately before the infusible furnace, or 50 to 50 in the first step of the infusible furnace. It is kept at 100 ° C. for 5 minutes to 2 hours and dried so that the amount of pitch fibers adhering to water is 0.1% by weight or less. After that, infusibilization treatment and carbonization treatment are performed according to a known method. For example, the infusibilizing treatment is carried out by heating the fibers to a temperature of 150 to 360 ° C. for 5 minutes to 1 in an oxidizing atmosphere such as oxygen, ozone, air, nitrogen oxides, and halogen sulfite gas.
It is carried out by heating for 0 hours. The carbonization is carried out by treating the fibers under an atmosphere of an inert gas such as nitrogen or argon at 100
It is carried out by heating to a temperature of 0 to 2500 ° C. for 0.5 minutes to 10 hours.

When further graphitizing treatment is carried out, 250
The temperature may be kept at 0 to 3500 ° C. for 1 second to 1 hour. Further, during the infusibilizing, carbonizing or graphitizing treatment, if necessary, a slight load or tension may be applied to the object to be treated for the purpose of preventing shrinkage or deformation.

[0014]

As described in detail above, the present invention facilitates the handling of fragile fibers by the simple operation of adhering a water emulsion of silicone oil, and at the same time, adheres or fuses the fibers together or the fiber surface. Since the occurrence of damage to the pitch-based carbon fibers can be heat-treated under continuous industrially advantageous conditions in the form of continuous filaments of pitch-based carbon fibers, pitch-based carbon fibers having excellent performance are obtained. There is also an advantage that it can be obtained at a low price.

[0015]

EXAMPLES Next, the present invention will be described more specifically by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist. (Examples 1 to 9) Tar-based raw material pitch (mesophase pitch with 100% optical anisotropy) was melt-spun at a spinneret temperature of 330 ° C.
The sizing agent shown in the table was sprayed and adhered for focusing. The bundled fibers (tows) were then dried by holding them in air at 80 ° C. for 30 minutes. Next, the temperature was raised from 150 ° C. to 350 ° C. over 2 hours and 40 minutes, and then the temperature was maintained for 30 minutes for infusibilization treatment. Then, in argon, the temperature was raised from room temperature to 1400 ° C. over 2 hours and 20 minutes, and then the temperature was maintained for 1 hour to carry out carbonization treatment to obtain carbon fibers. In the carbon fiber manufacturing process, the bundled state of the yarn, the property of the infusibilized fiber, and the fused state of the single yarn were observed, and the tensile strength of the carbon fiber was measured. The results are shown in Tables 1 and 2. In addition, a simple explanatory drawing is shown in FIG.
As shown.

(Comparative Examples 1 to 7) Table 1 shows the results obtained in Example 1 in the same manner as in Example 1 without using the sizing agent or by changing the sizing agent impregnation amount, emulsion concentration or sizing agent type. And Table 2 together.

[0017]

[Table 1]

[0018]

[Table 2]

[Brief description of drawings]

FIG. 1 is an explanatory diagram related to the steps after spinning of carbon fiber in the present invention.

Claims (2)

[Claims] 1. A method for producing pitch-based carbon fibers by concentrating pitch fibers obtained by melt-spinning raw material pitch, and then subjecting to infusibilization treatment and, if necessary, graphitization treatment, In the drying furnace provided immediately before the infusibilizing furnace after adhering a water emulsion of silicone oil having a silicone oil concentration of 0.1 to 35% by weight as a sizing agent to the pitch fiber before or before sizing. A method for producing a pitch-based carbon fiber, which is characterized by holding at 50 to 100 ° C. for 5 minutes to 2 hours and drying in the first step of the infusibilizing furnace. 2. The method according to claim 1, wherein the sizing agent is applied in an amount of 2 to 14% by weight based on the fiber.