JP2582848B2 - Method for producing pitch-based carbon fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention facilitates the handling of fibers when 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 producing high-quality carbon fiber without adhesion or fusion between fibers.

(Prior art) Pitch-based carbon fiber is usually melt spun from raw material pitch,
It is manufactured by subjecting the obtained pitch fiber to infusibilization treatment and carbonization treatment.

Pitch-based carbon fiber is polyacrylonitrile (PAN)
Although it has the advantage that it can be produced industrially at a higher yield compared to carbon fibers of a system or the like, pitch fibers are extremely fragile, making it difficult to handle in infusibilizing or carbonizing treatments. Fuzz, winding on guide rollers, thread breakage, etc. Further, there is a problem that adhesion and fusion between the fibers occur during the infusibilizing treatment and the carbonizing treatment, and the obtained carbon fibers are easily damaged.

Accordingly, various studies have been made on a method for solving the problems inherent in the pitch-based carbon fiber and stably producing a high-quality pitch-based carbon fiber, and a method using a silicone oil having specific physical properties as a treating agent (particularly, 60-246819
No.) and a method using a silicone oil water emulsion (Japanese Patent Application Laid-Open No. 61-70017) have already been applied for a patent, but with these treatment agents, the fibers are fluffed in the spinning and bundling step, and the fibers are wound around a guide roller. Problems such as thread breakage could be solved, but about 10
In the infusibilizing treatment performed in a heating zone of about 0 ° C. to about 300 ° C. or in the carbonizing treatment performed at a temperature of at least 400 ° C. or more in an inert atmosphere subsequent to the infusibilizing treatment, the fusion and adhesion between the fibers are sufficiently performed. There was still room for improvement to be resolved.

It has been found that the cause of such a phenomenon of fusion or adhesion is that a part of components contained in the treatment agent is decomposed or tarified during heat treatment such as infusibilization treatment or carbonization treatment. In view of the above, the inventors of the present invention filed in Japanese Patent Application No. 62-177801, filed as a treating agent used in the pitch-based carbon fiber manufacturing process, simply volatilizes during the heat treatment during the infusibilizing treatment or the carbonizing treatment. Instead, it was found that the absence of heat generation during volatilization can avoid the phenomenon of adhesion or fusion between fibers.From these findings, a silicone oil having a viscosity of 2 to 20 cst was used as a treating agent at 300 ° C. A pitch characterized by being emulsified in water with a surfactant having a residual heating amount of 5% or less and having substantially no exothermic peak in a differential heating curve (DTA) at 30 ° C. to 350 ° C. A treatment agent for carbon fiber was proposed. Thereby, fusion or adhesion of the fibers by the treatment agent could be avoided. However, due to undrawing occurring on the carbon fibers in the spinning process, the carbon fibers adhere or fuse together, leaving room for improvement.

(Problems to be Solved by the Invention) A high-quality pitch system is obtained by bonding or fusing between fibers in a heat treatment such as an infusibilization treatment because undrawn yarn generated in a spinning process adheres to carbon fibers. There was a problem that carbon fibers could not be produced industrially stably.

(Means for Solving the Problem) The inventors of the present invention have conducted intensive studies in order to solve the conventional problems, and as a result, have found that the unstretched yarn which is a cause of adhesion or fusion between fibers is removed. By using a specific pitch-based carbon fiber manufacturing treatment agent and washing the undrawn yarn and treatment agent by washing with water or the like before performing the infusibilization treatment, the phenomenon of adhesion or fusion between fibers can be reduced. The present inventors have found that it is possible to completely avoid the problem, and that the yarn after the infusibilization treatment becomes flexible and easy to handle. Thus, the present invention has solved the conventional problems and reached the present invention.

That is, the object of the present invention is not only problems such as fluffing of fibers, winding around rollers, thread breakage, etc., when producing pitch-based carbon fibers, fusion between fibers during heat treatment, adhesion, etc. And a method for stably producing high-quality pitch-based carbon fibers.

The purpose is to melt pitch-spun pitch fibers in the gas phase, bundle the pitch fibers in the presence of a sizing agent to form pitch fiber tow, then infusibilize, carbonize and, if necessary, graphite. In the method for producing pitch-based carbon fibers by performing a styling treatment, as a sizing agent, a silicone oil having a viscosity of 2 to 10,000 cst at 25 ° C. and a general formula (R ¹ is an alkyl group having a carbon coefficient of 8 to 18, n is an average of 1 to 10
Indicates the number of 0. ) Using a treating agent consisting of an aliphatic amine polyethylene glycol condensate represented by the formula (1) and water, and contacting the bundled pitch fiber tow with a cleaning liquid before the infusibilization treatment to clean the surface of the pitch fiber. It is easily achieved by the characteristic method for producing pitch-based carbon fibers.

Hereinafter, the present invention will be described in detail. As the raw material pitch used in the present invention, coal-tar pitch, coal-based pitch such as coal liquefied product, atmospheric distillation residue of crude oil, vacuum distillation residue, or heat-treated product thereof And petroleum pitches such as heat-treated naphtha pyrolysis by-product tar, and polymer fired pitches obtained by dry-distilling synthetic resins and natural resins.

Melt spinning of the raw material pitch can be performed by extruding into the gas phase through a spinneret similarly to melt spinning of polyester and polyamide. Preferably, a method is employed in which the pitch is melted by an extruder or the like, extruded from a downward spinneret into the gas phase, and cooled and solidified. A spinneret having a discharge hole diameter of about 0.1 to 0.3 mm is used. The temperature of the spinneret depends on the type of the raw material pitch and is determined in consideration of the melt viscosity appropriate for spinning.
A range of 50 ° C is appropriate. Providing a heat retaining cylinder below the spinneret is effective for stabilizing the spinning state.

In the present invention, the silicone oil to be used for adhesion to the pitch fiber or the infusibilized fiber obtained by the above method is a treating agent obtained by dispersing in water with a surfactant. 10,000cst (25
C.), preferably 2 to 20 cst (25.degree. C.) dimethylpolysiloxane or various modified polysiloxanes.
Here, since the volatility is high at less than 2 cst (25 ° C.), the treatment agent is volatilized after the treatment agent is attached to the carbon fiber, and the treatment agent is not sufficiently effective.
On the other hand, if it is too large, it is not preferable because the single fibers of the carbon fibers are fused together during infusibilization or carbonization, and the physical properties of the fibers are reduced.

Specific examples of such silicone oil include, for example, methylphenyl polysiloxane and hydrogenene polysiloxane.Other alkyl groups such as epoxy group, ethyl and propyl group, amino group, carboxyl group, alcohol, phenyl group, Those modified with one or more polyether groups are used. These silicone oils may be used alone or as a mixture of two or more.

As the surfactant for emulsifying the silicone oil, a general formula (Wherein R ¹ is an alkyl group having 8 to 18 carbon atoms, and n is an average of 1 to 1)
An aliphatic amine polyethylene glycol condensate represented by the following formula is used, and R ¹ is preferably selected from 12 or 14 carbon atoms.

The use amount of the above surfactant is preferably 1% to 20% with respect to the silicone oil. If it is less than 1%, no emulsion of silicone oil is produced, and if it is more than 20%, the properties of the carbon fiber after heat treatment such as infusibility may be adversely affected.

Further, for example, the heating residual amount at 300 ° C. proposed in Japanese Patent Application No.
A surfactant having substantially no exothermic peak in the differential heating curve (DTA) at a temperature of from 350 ° C. to 350 ° C. can be used at all.

As a method of emulsifying the composition, a homomixer,
Conventionally known methods such as a colloid mill, a valve homogenizer, and ultrasonic waves can be applied.

As a method of attaching the treating agent to the fiber, a method of spraying with a spray, a method of attaching to a roller and contacting it,
There is a method of immersion.

0.02% by weight of oil
It is preferable to make it adhere to 1515% by weight. When the content is 0.02% by weight or less, the sizing property of the fiber is poor, and when the content is 15% by weight or more, the fiber properties after infusibilization are adversely affected.

The pitch fibers to which the treatment agent is attached and bundled are preferably washed with water, an organic solvent that does not substantially dissolve the pitch fibers, or a mixture thereof before the infusibilizing treatment, and then subjected to the infusibilizing treatment and the carbonizing treatment. . For example, the infusibilizing treatment is performed by heating the fiber to a temperature of 150 to 360 ° C. for 5 minutes to 10 hours in an oxidizing atmosphere such as oxygen, ozone, air, nitrogen oxide, halogen, and sulfur dioxide. or,
The treating agent can be used as a process oil in the infusibilized carbon fiber. The carbonization treatment is performed by heating the fiber to a temperature of 400 to 2500 ° C. for 0.5 minutes to 10 hours in an atmosphere of an inert gas such as nitrogen or argon.

Further, in the case of performing the graphitization treatment, it may be heated and held at a temperature of 2500 to 3500 ° C. for about 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.

The carbon fiber or graphite fiber obtained in this way is usually defibrated and then used for each application.

(Examples) Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples unless the gist is exceeded.

Example 1 A tar-based raw material pitch (mesophase pitch having 100% optical anisotropy) was melt-spun into a gas phase at a spinneret temperature of 330 ° C.
In the obtained yarn diameter 10μ, pitch filament of 120 filaments,
The treating agents shown in Table 1 were adhered using an oiling guide and focused. The bundled fibers are then brought to 80 ° C in air for 30 minutes.
Hold for minutes and dry. Next, the bundled fibers were washed in a 45 ° C water bath. After the washed yarn was heated from 150 ° C. to 350 ° C. for 2 hours and 40 minutes, it was kept at that temperature for 30 minutes to perform infusibility treatment. Thereafter, the temperature was raised from room temperature to 1400 ° C. for 2 hours and 20 minutes in argon, and then kept at that temperature for 1 hour to carry out carbonization treatment to obtain carbon fibers. In the carbon fiber production process, the bundled state of the yarn, the properties of the infusible fiber, and the fusion state of the single yarn were observed. The result is
It is described in the table.

Comparative Examples 1 to 7 Table 1 shows the results obtained in the same manner as in Example 1 except that the type of the sizing agent was changed.

The excellent performances of the production method according to the present invention are apparent from the results shown in Table 1.

(Effect of the Invention) According to the present invention, by using a carbon fiber treating agent obtained by dispersing silicone oil in water with a surfactant having a specific structure, handling of fragile fibers can be facilitated by a simple operation. At the same time, the washing effect by washing with water before infusibilization is further enhanced, and adhesion and fusion between the fibers are prevented, so that pitch-based carbon fibers having good properties can be produced in continuous filaments under industrially advantageous conditions.

Claims (2)

(57) [Claims] 1. A pitch fiber obtained by melt-spinning a spun pitch in a gas phase to form a pitch fiber tow by bundling the pitch fibers in the presence of a sizing agent, followed by an infusibilization treatment, a carbonization treatment and, if necessary, graphite. In the method for producing pitch-based carbon fibers by performing a sizing treatment, as a sizing agent, silicone oil having a viscosity of 2 to 10,000 cst at 25 ° C. and a general formula (R ¹ is an alkyl group having 8 to 18 carbon atoms, n is an average of 1 to 100
Indicates the number of ) Using a treating agent consisting of an aliphatic amine polyethylene glycol condensate represented by the formula (1) and water, and contacting the bundled pitch fiber tow with a cleaning liquid before the infusibilization treatment to clean the surface of the pitch fiber. A method for producing a pitch-based carbon fiber. 2. The addition amount of an aliphatic amine polyethylene glycol condensate to silicone oil is 0.1 wt% to 20 wt%.
%. The method for producing pitch-based carbon fiber according to claim 1, wherein