JPH01282341A - Insolubilization of pitch fiber - Google Patents

Abstract

PURPOSE:To provide the title insolubilization process in an oxidative gas so designed that a pitch raw material is spun and the resulting precursor fiber is imparted with static electricity prior to the insolubilization treatment to facilitate said treatment, thereby obtaining, a high-performance pitch fiber with little fusing. CONSTITUTION:When a pitch precursor fiber produced by spinning a coal- or petroleum-based pitch raw material is to be put to insolubilization treatment in an oxidative gas, said fiber is imparted, prior to said treatment, with static electricity (pref., washing with a solvent such as water or alcohol followed by imparting the fiber with static electricity through non-contact technique) to effect opening to prevent the pitch yarn from fusing when insolubilized, thereby accomplishing the insolubilization in a short time in high efficiency and obtaining a high-grade pitch fiber of improved physical properties.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for infusible pitch fibers. More specifically, the present invention relates to a method for producing pitch-based carbon fiber obtained from coal-based or petroleum-based pitch as a raw material, which facilitates infusibility treatment and provides high-performance carbon fiber with less fusion.

(Prior art) The technology for obtaining carbon fiber from pitch is, for example,
It is well known from publications such as No. 4550 and Japanese Unexamined Patent Publication No. 49-19127.

Pitch yarn needs to be made infusible before firing, but when making it infusible by heating it with an oxidizing gas, the infusibility reaction rate is extremely slow at low temperatures, so the temperature is usually raised as the infusibility progresses. A method is used in which the reaction is performed while that time,
It is necessary to raise the temperature within a range that does not exceed the increase in the softening point as the infusibility reaction progresses.

The oxidation reaction that makes pitch infusible is an exothermic reaction, so when yarn is made infusible in a bundled state such as a normal multifilament, sheet, or bobbin, local heat accumulation occurs and the infusibility treatment is delayed. Even if temperature control is performed, adhesion and fusion of adjacent fibers is extremely likely to occur. This adhesion and fusing of fibers causes surface defects and greatly reduces the physical properties of the yarn.

In addition, there are light forces, tar, dust, etc. that adhere to the surface of the pitch yarn during spinning, and especially when a sizing agent is used, these chemical and physical effects may cause the adhesion, fusion, etc. The problem is that this problem can easily occur.

Due to the above-mentioned properties, in the pitch infusibility reaction, although the reaction rate is faster at higher temperatures, it is necessary to complete the infusibility through a slow temperature increase rate. Therefore,
It usually took 2 to 8 hours.

That is, pitch yarn has the drawbacks of poor handling, adhesion and fusion during infusibility, and therefore there are upper limits to the yarn speed during infusibility treatment, the manner in which the yarn is handled, and the rate of temperature rise. For this reason, it is necessary to adopt conditions as mild as possible for everything such as processing time, which means that these problems can reduce productivity and
It has a major drawback of lowering economic efficiency, carbon fiber physical properties, etc.

In addition, since the pitch yarn is heated during the infusibility treatment, low-molecular components, tar, etc. come out from the system to the surface, and it is presumed that these promote fusion during firing.

A method of cleaning the infusible yarn (Japanese Patent Application Laid-open No. 167021/1983) has been proposed to remove the above substances, but this method is likely to cause fusion during firing because it is bundled again with a binding agent after cleaning. The problem was inevitable.

Furthermore, when obtaining carbon fibers with high strength and high elastic modulus using optically anisotropic pitch, defects occurring during handling and infusibility are a major factor in deterioration of physical properties.

(Problems to be Solved by the Invention) The present invention aims to prevent pitch yarns from fusing during infusibility, perform infusibility treatment efficiently in a short time, and obtain carbon fibers with high physical properties. .

(Means for Solving the Problems) In order to achieve the above object, the present invention has the following configuration.

Specifically, the present invention is characterized in that when pitch precursor fibers obtained by spinning pitch principles obtained from coal-based or petroleum-based materials are infusible in an oxidizing gas, static electricity is imparted before the infusibility treatment. This invention relates to a method for making pitch fibers infusible.

The present invention will be explained in detail below.

The pitch fibers referred to in the present invention may be made of coal-based, petroleum-based, or synthetic pitch-based materials such as naphthalene or polyvinyl chloride, and may include isotropic, optically anisotropic pitch, and mixtures thereof. , pitch to which additives such as polymeric compounds have been added is melt-spun, or in some cases dry or wet-spun to form a fiber, and then processed to be infusible, carbonized, and graphitized.

The pitch precursor fiber in the present invention is obtained by cooling a fibrous material discharged from a spinning nozzle or passing through a coagulation bath, and winding it after applying a sizing agent if necessary. Alternatively, they are stacked on a tray or net 1 by air or the like.

The oxidizing gas in the present invention is typically air, but also includes high oxygen concentration gas, nitrogen oxide, nitrite gas,
Ozone etc. are used.

The biggest feature of the present invention is that the pitch precursor fiber obtained by spinning is given static electricity before being infusible.
The purpose is to spread the multifilament to reduce the frequency of contact between single filaments during infusibility treatment and to prevent fusion.

As for the method of applying static electricity according to the present invention, a non-contact method is preferably used as much as possible because the pitch fibers are fragile, but the effect is the same even if a contact method is used.

Specifically, the pitch precursor fiber is guided in the form of a multifilament onto a static electricity applying device, and the required amount of static electricity is applied by the static electricity applying device to open the multifilament, and then the fiber is moved to the infusible treatment process. let In this case, the depth of application of static electricity varies depending on the number of multifilaments, the sizing agent, the processing speed, etc., and is preferably adjusted as appropriate. A method of washing the yarn with a solvent such as water or alcohol to remove dust, processing agents, etc. before the electrostatic treatment is also preferably used.

The infusible yarn obtained by this method has less fusion, and the yarn that is subsequently carbonized and graphitized using this infusible yarn also has less fusion.

Hereinafter, the present invention will be explained in more detail using Examples.

In addition, the evaluation of fusion in the examples was carried out using the following dispersion test 1.
It was carried out by.

100ml of 0.01% by weight solution of neutral surfactant Noigun
1 into a 3000C beaker. There is a length of 5mm in it.
Add 1 mCl of the cut thread and stir at 10 Qrpm for 1 minute.

The resulting dispersion is passed through filter paper, and the number of bonded single threads is counted. The degree of bonding is expressed by the number of bonds per 1 mC1.

(Examples) Example 1 Coal-based mesophase pitch was used as a pitch raw material. This pitch has a softening point of 235°C, 33% quinoline soluble content, 89% benzene insoluble content, and anisotropy of 85%.
%.

The above pitch was adjusted to 305 mm using a bent extruder.
After melting and degassing at °C16QC16Q, diameter 0.2
mm, hole length Q, 3mm '1OOH mouthpiece,
After focusing with water, take off at 450m/m1n, diameter 1
1q of 0μ pitch precursor fibers were prepared.

The pitch precursor fibers were unwound and guided onto a non-contact type static electricity applying device, and after applying static electricity of 10 microcoulombs, they were treated to be infusible in air using an infusibility treatment device made of a quartz tube. Processing speed is 4 Q Cm/m!
n, LillfA degree is 150℃, 200'C27
0'C1330'C, and each tube length was 1 m.

After that, the temperature was increased to 1000 at a heating rate of 4°C/min.
It was carbonized in nitrogen to 10'C/min and graphitized in nitrogen to 2500°C at a heating rate of 10'C/min.

Comparative Example 1 Infusible treatment, carbonization treatment, and graphitization treatment were performed in the same steps and under the same conditions as in Example 1 except for applying static electricity.

The obtained physical properties and dispersion test results are shown in Table 1 (Example 1
), as shown in Table 2 (Comparative Example 1).

Table 1 (Example 1) Table 2 (Comparative Example 1) (Effects of the invention) The present invention greatly reduces the fusion of infusible yarn, carbonized yarn, and graphitized yarn, so that the physical properties are improved. It is possible to provide high-quality pitch-based carbon fiber.

Patent applicant: Toshi Co., Ltd.

Claims (1)

[Claims] (1) Pitch characterized by imparting static electricity before the infusibility treatment when infusibilizing pitch precursor fibers obtained by spinning pitch raw materials obtained from coal-based or petroleum-based materials in an oxidizing gas. Fiber infusibility method.