JPS6321922A - Production of pitch based carbon fiber - Google Patents

Abstract

PURPOSE:To readily carry out doubling operation of filament tows or paralleling of filaments constituting the filament tows, by introducing bundled filament tows into a liquid in a direction perpendicular to the liquid surface, reversing the filament tows to the direction opposite to the introductory direction in the liquid and taking the filament tows out of the liquid. CONSTITUTION:Plural filament tows 1, 1', 1''..., together with a water current from an inlet pipe 3, are introduced from a rotating roll 2 into water 8 in a treating bath 7 containing the water 8 at a given water level in a direction perpendicular to the water surface. The tows introduced into the water 8 are pushed deep into the water and the moving direction is reversed in the water. The filament tows are opened to single filament units and an uniform tension is applied to each filament in pulling up. Thereby the pitch fibers can be paralleled and doubled with small tension.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing carbon fiber from pitches such as coal-based pitch, petroleum-based pitch, and polymer calcined pitch. The present invention relates to a method for obtaining high-quality carbon fibers by easily doubling fiber tows together.

[Prior art]

Pitch-based carbon fiber is usually produced by melt-spinning raw material pitch,
It is manufactured by subjecting the obtained pitch fibers to infusible treatment and carbonization treatment.

Pitch-based carbon fibers have the advantage of being industrially advantageous and can be produced in higher yields than polyacrylonitrile-based carbon fibers, but on the other hand, pitch fibers are extremely fragile and their handling is difficult during the production process of pitch-based carbon fibers. When an external force higher than the fiber strength is applied to pitch fibers, which are fragile fibers, they tend to become fluffy, break, become disordered, become entangled, etc., and require careful attention. By the way, one of the uses of pitch-based carbon fiber as a reinforcing material is 7.
00 to 1000 single fibers are bundled into one tow,
Next, 10 to 100 fiber bundles of this tow are required, and a large-diameter fiber bundle is produced by heating the fiber bundles if necessary. When manufacturing such large diameter fiber bundles, pitch fibers are extremely fragile as described above, so fiber tows are usually combined in the form of carbonized fibers having sufficient fiber strength.

[Problem that the invention seeks to solve]

However, as in the past, the carbonized fibers are doubled,
In order to obtain a fiber bundle with the desired large diameter, a large number of fiber tows made of infusible fibers, which are the precursor fibers, and pitch fibers are required, which increases the scale of the equipment used in the firing process and increases manufacturing costs. There's a problem.

On the other hand, when doubling pitch fibers, since the pitch fibers themselves are extremely fragile, it is difficult to handle them. Therefore, it is necessary to keep the take-up speed, tension, etc. low to minimize the influence of mechanical contact with rollers and guides. However, there was a problem in converting it into a process with good productivity. In addition, even if it is possible to avoid problems such as fuzzing and thread breakage by simply doubling pitch fibers, the fibers will separate into units, causing problems in the bundling of the doubled fiber tows. Was.

[Failure to solve the problem]

As a result of repeated studies to solve these problems, the inventors of the present invention have identified a fiber tow in a liquid that is made by loosely piling one or more fiber tows together without applying tension. We have discovered that these problems can be solved by performing the following operations, and have arrived at the present invention.

That is, an object of the present invention is to provide a method for stably producing pitch-based carbon fibers with high properties by performing the doubling operation of fiber tows or the alignment of fibers constituting the fiber tows by a simple means. It is.

The purpose is to melt-spun the raw pitch in a gas phase, bundle the pitch fibers obtained in the presence of a sizing agent, and then perform infusibility treatment, carbonization treatment, and further graphitization treatment as necessary. In a method for producing pitch-based carbon fibers, a focused fiber tow is introduced into a liquid in a direction substantially perpendicular to the liquid surface, and then in the liquid in a direction substantially opposite to the direction of introduction. This can be easily accomplished by inverting and pulling it out of the liquid.

To explain the present invention in detail below, the raw material pitch used in the present invention includes coal tar pitch, coal-based pitch such as coal liquefied product, atmospheric distillation residue of crude oil, vacuum distillation residue,
Alternatively, heat-treated products thereof, petroleum-based pitches such as heat-treated tar by-products of thermal decomposition of naphtha, and polymer calcined pitches obtained by carbonizing synthetic resins or natural resins.

Melt spinning of raw material pitch can be carried out in the same manner as normal dry melt spinning of synthetic fibers, and there are no particular restrictions, and a method is adopted in which the molten spinning pitch is extruded into the gas phase from a downward spinneret and cooled and solidified. . As a spinneret, the diameter of the discharge hole is 0. /~0. ．． ! ;Use something of the order of ran. The temperature of the spinneret depends on the type of raw material pitch and is determined by considering the melt viscosity suitable for spinning, but it is usually between 2 and 0.
A range of 350°C to 350°C is suitable. Providing a heat insulating cylinder under the spinneret is effective in stabilizing the spinning state.

As a sizing agent for pitch fibers, for example, silicone-based oils, higher alcohol-based oils, higher fatty acid-based oils, mixtures thereof, emulsions thereof, and solid fine particles added thereto are used. Specifically, silicone oils include dimethylpolysiloxane, phenylmethylpolysiloxane, epoxypolysiloxane,
Aminopolysiloxane, stearyl alcohol, oleyl alcohol, isopentacosanyl alcohol as higher alcohols, stearic acid glyceride, polyethylene glycol stearate, polyethylene glycol oleate as higher fatty acids, graphite as solid particles,
Examples include carbon blank, silica, titanium oxide, and the like.

As the emulsifier added during emulsification, nonionic emulsifiers such as polyoxyethylene lauric acid, anionic emulsifiers such as alkyl sulfate, and cationic emulsifiers such as alkylpyridium chloride are used.

As the diluent for diluting the sizing agent during emulsification, it is preferable to use those listed as liquids used in the present invention, which will be described later.

In addition, an antistatic agent may be added to the sizing agent if necessary, such as an anionic antistatic agent such as an alkyl sulfate, a cationic antistatic agent such as a quaternary ammonium salt, or an amphoteric antistatic agent such as betaine.

0.7 to 100 parts by weight of these sizing agents as a sizing agent component excluding the diluent per 700 parts by weight of pitch fibers,
It is preferable to deposit / to /S parts by weight.

The liquid used in the present invention is usually water when a water emulsion is used as a sizing agent, but any liquid that does not dissolve the fiber tow may be used, such as methanol, ethanol, propatool, butanol, and impropatool. , aliphatic alcohols with a carbon number of ~q such as ethylene glycol and cellosolve, cyclopentanol,
Alicyclic alcohols with 3 to 6 carbon atoms such as cyclohexanol, ketones with 3 to 6 carbon atoms such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, water, and other single substances or mixtures of them in arbitrary proportions In addition, examples include a sizing agent used in the sizing process, a mixture of water and a surfactant, and the like. As the surfactant, the emulsifier used in the emulsification described above is used.

In the present invention, fiber tows bundled by a binding agent are introduced into the liquid in a direction substantially perpendicular to the surface of the liquid, and then in a direction substantially opposite to the direction in which they were introduced into the liquid. It is important to invert the fiber tow and pull it out of the liquid.

Below, we will explain the case where water is used as the liquid.
For example, the specific gravity of pitch fibers is 83 to 41, which is heavier than water, but if the fiber tow is simply immersed in water, there will be many fine air bubbles between the single fibers, and since pitch fibers are still hydrophobic, water will It is difficult to get wet and it is very difficult to go into the water.

Therefore, when introducing the fiber tow into water, it is preferable to introduce it along with the water flow in a direction perpendicular to the water surface.

In the present invention, when a fiber tow passes through a liquid, the tensile tension applied when it is transferred in a gas phase is eliminated or relaxed, so that no tensile tension is substantially applied to the single fibers constituting the fiber tow. It is desirable to move in the state.

Seven embodiments of the present invention will be specifically explained using FIG. 1. In FIG. 1, the treatment tank 7 is filled with water at a constant level by supplying water from the conduit 6 so that water constantly overflows from the drain port. Multiple fiber tows/
/', /'... are rotating rollers. The threads are loosely doubled by the rotation of the rollers, and are passed through a ring holder installed in the gas phase outside the processing tank 7 together with the water flow supplied from the conduit 3 to the processing tank. is introduced into the water g from a direction perpendicular to the water surface. The fiber tow introduced into the water is pushed deep into the water and its direction of movement is reversed underwater. During this time, the fiber tow is defibrated into single filament units constituting the fiber tow in water, and passed through a ring 10 provided in the gas phase outside the treatment tank 7 to a rotating roller.
drawn out by At this time, uniform tension is applied to each single yarn, and the yarn bundle is aligned. At this time, if the fiber tow to be drawn out is brought into contact with the water flow supplied from the conduit 9 in a countercurrent, the pulling and doubling of the yarn bundle can be performed even more effectively.

However, when using a liquid other than water that has a low surface tension and easily wets the pitch fibers, specifically the aforementioned alcohols, ketones, or sizing agents, it is practically impossible to introduce the fiber tow into the liquid. It may be introduced from a slightly oblique direction as long as it is perpendicular to the liquid level.

The size of the treatment tank is not particularly limited as long as it provides a liquid space in which the fiber tow can be sufficiently defibrated while reversing its moving direction underwater. The depth of the liquid in the processing tank is 30 tan or more, preferably one capable of storing a liquid of 10 to 1,000 tan.

In the fiber tow pulled out from the treatment tank, each single yarn is neatly aligned. Although the number of fiber tows to be treated in the present invention is not particularly limited, it is preferable to use a plurality of fiber tows and perform the doubling operation. If necessary, the liquid contained in the fiber tow is removed by drying it by a known method, and then the fiber tow is introduced into an infusibility treatment step.

The pitch fibers are subjected to infusibility treatment and carbonization treatment according to well-known methods. For example, infusibilization treatment exposes fibers to oxygen,
Under an oxidizing atmosphere such as ozone, air, nitrogen oxides, halogen, sulfur dioxide gas, etc., at a temperature of / θ ~ 3bO℃ for 5 minutes ~ 70 minutes.
This is done by heating for a period of time. In addition, carbonization treatment is carried out by subjecting the fibers to 100% carbonization under an inert gas atmosphere such as nitrogen or argon.
0 to 2100℃. ! This is done by heating for r minutes to 70 hours.

When further graphitizing treatment is performed, the temperature is 2300~. 3!
; It may be heated and maintained at a temperature of 00°C for /second to /hour. Furthermore, during the infusibility, carbonization, or graphitization treatment, a slight load or tension may be applied to the object to be treated, if necessary, in order to prevent shrinkage, deformation, etc.

Furthermore, during the infusibility treatment, a dryer is installed just before the infusibility furnace, or the pitch fibers are held at SO ~ 100°C for ~2 hours to remove the liquid that adheres to the pitch fibers. It is preferable to keep it dry.

Although it is preferable to use a fiber tow made of pitch fibers as the fiber tow of the present invention, it may be a fiber tow made of infusible fibers.

〔effect〕

As detailed above, in the present invention, the fiber tow is defibrated into single fiber units in the liquid by a simple operation of passing the fiber tow through the liquid using a specific method, and when pulling up the fiber tow, uniform tension is applied to each fiber. By doing so, it is possible to carry out the pulling process of the present invention while aligning the fragile pitch fibers well with a small tension. Furthermore, when the pitch fibers are doubled at the stage, the subsequent infusibility treatment and carbonization treatment can be carried out all at once in the state of the doubled fibers, allowing stable production of pitch-based carbon fibers with high properties in the form of continuous filaments. It can be manufactured in

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Example / Tar-based spinning raw material pitch was melt-spun using a spinneret with 1000 holes at a spinneret temperature of 330°C, resulting in a yarn diameter of 70.
A water emulsion of silicone oil was applied to μ pitch fibers and focused. The bundled fiber tows were drawn and combined using the apparatus shown in FIG. Each fiber tow/, /', /'...
・ are pulled up and brought together using rotating roller λ, and together with a sufficient water flow supplied from conduit 3, g m/f'
The water was introduced vertically into the processing tank 7 filled with water at a speed of J-, and the moving direction was reversed at a position 30 crn below the liquid surface. Next, the fiber tow was pulled up at a speed of gm7J by a rotating roller provided in the gas phase outside the treatment tank while being brought into contact with a water flow running countercurrently to the moving direction of the fiber tow supplied from the conduit D.

The combined fiber tow (1000 single yarns x 10 pieces) is
Next, dry it by holding it in air at 750°C for 30 minutes.
moreover/! After raising the temperature to 300C over 2 hours and 30 minutes, it was maintained at that temperature for 3 minutes to perform the infusibility treatment.Then, in argon, the temperature was lowered from room temperature to 1/1
The temperature was raised to 100″C over a period of 20 minutes, and then maintained at that temperature for 7 hours for carbonization treatment to obtain carbon fibers. It had good alignment and supple properties.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention, 0/pitch fiber tow, 2 rotating roller. 3 Conduit, Dalling, S Drain. 6 conduit, 7 treatment tank, g water. 9 Conduit, 10 Ring, // Rotating roller Applicant: Mitsubishi Chemical Industries, Ltd. Agent: Patent Attorney Cho Kagawa - (7 others)

Claims (7)

[Claims] (1) Pitch fibers obtained by melt-spinning raw pitch in a gas phase are bundled in the presence of a sizing agent, and then subjected to infusibility treatment, carbonization treatment, and further graphitization treatment as necessary. In a method for producing carbon fibers, a focused fiber tow is introduced into a liquid in a direction substantially perpendicular to the liquid level, and then reversed in the liquid in a direction substantially opposite to the direction of introduction. 1. A method for producing pitch-based carbon fiber, which comprises pulling out pitch-based carbon fiber from the liquid. (2) The method according to claim 1, characterized in that the fiber tow is a composite of a plurality of fiber tows. (3) The method according to claim 1 or 2, wherein the fiber tow is a fiber tow made of pitch fibers. (4) The method according to claim 1, characterized in that the fiber tow is pulled out of the liquid while being brought into contact with a liquid flow in a countercurrent direction to the moving direction of the fiber tow. (5) A method according to claim 1, characterized in that the fiber tow is introduced into the liquid along with the liquid stream in a direction substantially perpendicular to the liquid surface. (6) an organic solvent in which the liquid does not substantially dissolve the fiber tow;
2. The method according to claim 1, wherein the method is water, an aqueous solution containing a surfactant, or a mixture thereof. (7) the organic solvent is an aliphatic alcohol having 1 to 4 carbon atoms;
Alicyclic alcohols having 3 to 6 carbon atoms, or 3 to 6 carbon atoms
Claim 6 is characterized in that it is a ketone of
The method described in section.