JP2013007136A - Method for treating carbon fiber and method for producing carbon fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating a carbon fiber, which can simply remove a sizing agent deposited on the carbon fiber without requiring large-scale facilities.SOLUTION: The method for treating the carbon fiber comprises treating the carbon fiber having the sizing agent deposited thereon by using heated steam to remove the sizing agent.

Description

  The present invention relates to a method for treating carbon fiber and a method for producing carbon fiber.

  Carbon fiber is a material having high specific strength and specific elastic modulus and excellent heat resistance, and is widely used as a reinforcing fiber for composite materials. On the other hand, carbon fibers are liable to cause yarn damage and surface fluff due to friction and the like. Therefore, a treatment that improves the workability and handleability by improving the convergence and affinity for the matrix resin at the same time as suppressing the deterioration by applying a sizing agent to the carbon fiber surface and protecting the fiber surface. Has been made.

On the other hand, when the carbon fiber is opened, there is a problem that the carbon fiber to which the sizing agent is attached cannot be sufficiently opened. In addition, due to the problem of adhesiveness with a resin for compounding carbon fibers, there has been a demand to remove the sizing agent once adhered and to add another sizing agent suitable for the application.
Therefore, various methods for removing the sizing agent have been proposed as methods for solving the above problems.
Patent Document 1 discloses a method for removing a carbon fiber sizing agent using a supercritical or subcritical fluid as a sizing agent.

JP 2002-180369 A

However, when the sizing agent is removed by the method disclosed in Patent Document 1, a large facility is required to generate a supercritical or subcritical fluid, and the treatment cannot be performed easily.
Therefore, the present invention provides a carbon fiber processing method that does not require a large facility and can easily remove the sizing agent adhering to the carbon fiber.

The present invention provides a method for treating carbon fiber, characterized in that carbon fiber to which a sizing agent is attached is treated with superheated steam to remove the sizing agent.
Moreover, this invention provides the method of manufacturing the carbon fiber from which the sizing agent was removed including the process of processing the carbon fiber to which the sizing agent adhered with superheated steam.

  ADVANTAGE OF THE INVENTION According to this invention, the processing method of the carbon fiber which can remove the sizing agent adhering to carbon fiber simply can be provided.

Hereinafter, the present invention will be described in detail.
[Carbon fiber]
The carbon fiber to be treated in the present invention is obtained by subjecting a precursor called a precursor to flame resistance treatment in an oxidizing atmosphere, and then firing the obtained flame resistant fiber in an inert gas atmosphere at about 800 to 2000 ° C. Accordingly, the carbon fiber is obtained by firing in an inert gas at a higher temperature, and a sizing agent is applied to the surface thereof. The type of carbon fiber is not particularly limited, and any carbon fiber such as polyacrylonitrile (PAN), petroleum / coal pitch, rayon, or lignin can be used. The sizing agent is usually attached to the baked carbon fiber after further surface treatment such as electrolytic oxidation treatment or vapor phase oxidation treatment.

The sizing agent is usually composed of an organic substance such as an epoxy compound or a water-soluble polymer. In the treatment method of the present invention, any type of sizing agent can be effectively removed as long as it is a sizing agent composed of these organic substances. For example, an epoxy sizing agent generally used as a sizing agent for carbon fibers can be used. Excellent removal effect is demonstrated.
The form of the carbon fiber processed by the carbon fiber processing method according to the present invention is not particularly limited, a carbon fiber bundle in which a plurality of fiber filaments are converged, a fiber body formed by weaving the carbon fiber bundle as warps and wefts, A fiber body formed by aligning the carbon fiber bundles in one direction can be a processing target.

[Superheated steam]
Superheated steam refers to steam that has been superheated to a superheated state of 100 ° C. or higher. Superheated steam is considered to be in a state in which water clusters are made finer than normal steam. It is presumed that this refined water cluster penetrates into the interface between the carbon fiber and the sizing agent and effectively removes the sizing agent from the carbon fiber.
The method for generating superheated steam is not particularly limited. For example, induction steam furnace, electric heater, heat exchanger, electric / combustion boiler, dryer, IR heater, spray nozzle heating device is used to heat steam or water. By doing so, superheated steam can be generated.

[Method for treating carbon fiber]
The carbon fiber processing method according to the present invention is characterized in that the carbon fiber to which the sizing agent is attached is treated with superheated steam to remove the sizing agent. The conditions and method of treatment with superheated steam can be arbitrarily set according to the type and amount of sizing agent, the form, thickness, and number of carbon fibers, but can be performed as follows, for example.

First, carbon fiber with a sizing agent attached is introduced into an induction heating furnace, the furnace temperature is preferably 150 to 600 ° C., the furnace pressure is preferably 0.1 to 0.3 MPa, and superheated steam is generated. . Hold in this state for 1 minute to several tens of minutes to treat the carbon fiber in the furnace. In the present invention, the carbon fiber to which the sizing agent is adhered can be continuously processed by passing it through the furnace with a conveyor or the like. Thereby, since carbon fiber can be processed and it can also use for the post process according to a use continuously, the processing method of carbon fiber excellent in productivity can be provided.
The sizing agent on the surface of the carbon fiber is removed by the treatment as described above. The amount of the sizing agent to be removed is not particularly limited, and can be appropriately set depending on the use of the carbon fiber from which the sizing agent obtained by the treatment has been removed.

The treatment method of the present invention can remove the sizing agent even in a relatively low temperature region of 150 ° C to 350 ° C. Also, the pressure can be processed at a lower pressure than a supercritical or subcritical fluid. By removing the sizing agent at low temperature and low pressure, it is possible to suppress deterioration in quality such as damage to the carbon fiber yarn and surface fluffing.
Moreover, the carbon fiber from which the sizing agent was removed can be produced by performing the above-described treatment.

Hereinafter, the present invention will be specifically described with reference to examples.
[Manufacture of carbon fiber with sizing agent]
6.00 kg of carbon fiber was opened and immersed in a size bath to attach an epoxy sizing agent. This was used as a raw yarn. It was 6.11 kg when the weight of the carbon fiber after adhesion of a sizing agent was measured. From this, the adhesion amount of the sizing agent is 1.8% in terms of the weight ratio of the raw yarn.

[Evaluation of sizing agent removal amount]
The weight of the removed sizing agent was determined by measuring the weight of the test piece after the sizing agent removal treatment and determining the difference from the weight of the test piece before the sizing removal treatment.

[Example 1]
Carbon fiber to which an epoxy sizing agent was attached by the above-described method was used as a raw yarn. The raw yarn was cut to a weight of about 1.8 g to obtain a test piece. An induction heating furnace (glass coating carbon heater) was used, the furnace pressure was 0.3 MPa, and the furnace temperature was 600 ° C. A test piece was put into the furnace using a chain conveyor, and the treatment was started at 0 minutes. The test piece was held in the furnace with a waiting time of 1, 2, 3, 5, 10 minutes. After holding time passed, the test piece was taken out with a chain conveyor and cooled to room temperature by natural air cooling. Thereafter, the weight of the test piece was measured, and the weight of the removed sizing agent was determined.

[Example 2]
The carbon fiber was treated in the same manner as in Example 1 except that the furnace temperature was 550 ° C.

[Example 3]
The carbon fiber was treated in the same manner as in Example 1 except that the furnace temperature was 500 ° C.

[Example 4]
The carbon fiber was treated in the same manner as in Example 1 except that the furnace temperature was 450 ° C.

[Example 5]
The carbon fiber was treated in the same manner as in Example 1 except that the furnace temperature was 400 ° C.

[Example 6]
The carbon fiber was treated in the same manner as in Example 1 except that the furnace temperature was 350 ° C.

[Example 7]
The carbon fiber was treated in the same manner as in Example 1 except that the furnace temperature was 300 ° C.

[Example 8]
The carbon fiber was treated in the same manner as in Example 1 except that the furnace temperature was 200 ° C. and the standby time was 3 minutes, 5 minutes, 10 minutes, 20 minutes, and 30 minutes.

[Example 9]
The carbon fiber was treated in the same manner as in Example 8 except that the furnace temperature was 150 ° C.

As shown in Tables 1 and 2, it was confirmed that the sizing agent was removed from the carbon fibers treated by the carbon fiber treatment method of the present invention. In particular, it was confirmed that the sizing agent was removed even in a relatively low temperature range of 150 ° C to 350 ° C.
By performing the carbon fiber processing method according to the present invention, the carbon fiber from which the sizing agent has been removed can be produced.

Claims (2)

  A method for treating carbon fiber, comprising treating a carbon fiber having a sizing agent attached thereto with superheated steam to remove the sizing agent.   A method for producing a carbon fiber from which the sizing agent has been removed, comprising a step of treating the carbon fiber to which the sizing agent is adhered with superheated steam.