JPH0135091B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing high performance carbon fibers. More specifically, the present invention relates to an improvement in a method for producing high-strength, high-modulus carbon fibers by infusibleizing and firing pitch fiber bundles.

Prior Art Carbon fiber was originally manufactured using rayon as a raw material, but as a result of research and development into various raw materials and manufacturing methods, it is now mostly made of polycarbonate due to its characteristics and economic efficiency. They are dominated by PAN-based carbon fibers made from acrylonitrile and pitch-based carbon fibers made from coal-based or petroleum-based pitches.

However, recently there has been growing interest in the technology to produce high-performance grade carbon fibers using pitch as a raw material. A method for producing high-strength, high-modulus carbon fibers by firing in an active gas atmosphere (JP-A-49-19127, JP-A-53-65425,
JP-A No. 53-119326), (b) A method of performing spinning, infusibility treatment, and firing treatment using a "dormant mesophace pitch" that can be easily converted into mesophace during spinning (Japanese Patent Laid-Open No. 57-100186) ), and (c) a method using "prime meso phase pitch" which converts into meso phase during firing (Japanese Patent Application Laid-open No. 1842-1983) has been proposed.

However, when trying to produce high-performance carbon fibers using the above-mentioned methods, the strength of the precursor fibers obtained by either method is extremely weak, and various defects that occur during the infusibility stage cause problems in the carbon fibers after firing. This is a major cause of strength deterioration. That is,
In order to handle fragile precursor fibers, it is desirable to handle them in a concentrated manner. However, in the infusibility step, the precursor fiber undergoes various reactions in an oxidizing atmosphere at a relatively high temperature close to the melting point or decomposition point of the fiber, thereby eliminating the melting point and converting it into a fiber that can withstand subsequent calcination treatment. However, if the fiber bundle (multifilament yarn) has poor splitting properties, the fibers melt or soften before becoming infusible, causing fusion between the fibers.

This fusion makes the fiber bundle hard and brittle, causing fuzz, yarn breakage, etc. during the firing process, and causes a decrease in overall strength and elongation. Furthermore, even when focusing on single fibers, such fused sites become surface defects, resulting in deterioration of strength, which is a big disadvantage in developing high strength.

An effective and practical method for stably handling such fragile precursor fiber bundles and eliminating the fusion that occurs during the infusibility treatment is not yet known. That is, focusing on fusion, several attempts to solve this problem have been proposed in the past. For example, (a) a method of spraying coal powder onto the filament before infusibility (USSR Patent No. 168848); (b) a method of spraying activated carbon powder impregnated with an oxidizing agent (US Pat. No. 3997645);
(c) A method in which precursor fibers are treated with a solution in which graphite or carbon black is dispersed in water in which a water-soluble oxidation agent and a surfactant are dissolved (Japanese Patent Application Laid-Open No. 128020/1984), etc. can be mentioned.

However, when the present inventors implemented each of the above-mentioned methods, it was found that although carbonaceous fine powder is effective in preventing fusion in the infusibility stage, the strength and elongation of carbon fibers after firing are It was found that there was a clear negative effect on That is,
In each of the above-mentioned methods, although fusion was certainly prevented, there was a phenomenon in which the strength and elongation deteriorated compared to those in which fine powder was not applied and the material was made infusible and fired. Although the reason for this is not clear, it is presumed that some new defects are generated by the carbonaceous fine powder. Furthermore, the handling of fragile precursor fibers is not satisfactory from the viewpoint of preventing the generation of fuzz due to single filament breakage.

In addition, in the production of carbon fibers that do not use pith as a raw material, that is, the production of PAN-based carbon fibers, many proposals have been made regarding raw fiber oils, and amino-modified silicones and the like have been used, but PAN does not inherently melt. It was impossible to apply it to pitch-based precursor fibers created by melt spinning because of the fusion during infusibility.

Purpose of the Invention The main purpose of the present invention is to stably handle fragile precursor fiber bundles and prevent fusion between single fibers that occurs when performing infusibility treatment in the production process of pitch-based carbon fibers, and Strength of fiber after firing treatment,
An object of the present invention is to provide a method for producing pitch-based high-performance carbon fibers with excellent elongation. Another object of the present invention is to provide a high-performance pitch type yarn that is excellent in spreadability and flexibility as a fiber bundle (multifilament yarn), has high strength and elongation, and has little variation in strength, and is particularly suitable as a reinforcing material. An object of the present invention is to provide a method for industrially manufacturing carbon fiber.

Structure of the Invention According to the present invention, the above-mentioned object is to apply a dispersion of specific inorganic fine particles and a solution containing a specific alcohol to a precursor fiber bundle during the production of pitch-based carbon fibers, and then perform infusibility treatment and sintering. This is achieved through processing.

That is, in the production of pitch-based carbon fibers, the present invention provides a precursor fiber bundle containing (A) inorganic fine particles containing at least one selected from oxides or carbides of silicon, aluminum, titanium, and boron, and (B). )boiling point
A high-performance carbon fiber characterized by being coated with at least one type of alcohol selected from dihydric alcohols having a temperature of 120 to 300°C and a melting point of 10°C or less, then subjected to an infusible treatment, and then subjected to a firing treatment. This is a method of manufacturing.

In the method of the present invention, any pitch fiber may be used as the precursor fiber for producing carbon fibers, but in order to produce carbon fibers with higher performance, coal-based or petroleum-based pitch should be heat-treated. It is preferable to use pitch fibers obtained by melt spinning pitch, which contains an optically anisotropic component formed by the above method and has a quinoline insoluble portion of 1 to 60% (by weight). If the quinoline insoluble portion of the spinning pitch is less than this, the physical properties of the resulting carbon fiber will be poor.
Moreover, if the amount is more than this, there is a tendency for physical properties to decrease due to decrease in spinnability.

Although ordinary melt spinning can be used as a method for spinning pitch fibers in the present invention, in order to obtain high-performance carbon fibers, the present inventors have
No. 147038, Patent Application No. 125047, Patent Application No. 1983-
It is preferable to control the structure of pitch fibers using the spinning method proposed in No. 125048 or the like.

The present invention is achieved by sequentially or simultaneously applying the treatment agents of the above two groups (A) and (B) to a precursor fiber bundle, and then subjecting the fibers to an infusible firing treatment. Treatment agents include silicon, aluminum,
Fine particles of titanium, boron oxides or carbides are used, and among these, silicon oxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), titanium oxide (TiO ₂ ), and boron carbide (BC) are particularly suitable. .
These fine particles preferably have an average particle size of 1 micron or less and are as uniform in particle size as possible.

These treatment agents (A) are used as a dispersion liquid (a), but the dispersion medium is preferably one that is chemically inert to the pitch precursor fibers and does not agglomerate the fine particles. Water is an example of a dispersion medium. Furthermore, it is also possible to use an emulsifier in combination for the purpose of aiding the dispersion of fine particles.
However, it is desirable to avoid using emulsifiers containing metals.

The above-mentioned inorganic fine particles may be used as a single component, or two or more types may be used in combination.

The treatment agent of group (B) used in the present invention may be any dihydric alcohol having a boiling point and melting point within a predetermined range, but ethylene glycol, propylene glycol, diethylene glycol, etc. are particularly preferred. It is.

In the present invention, the processing agents may be used alone or in combination of two or more. These are usually used as a solution (b), but the solvent must be chemically inert to pitch, and water is usually preferred. It is also possible to use an emulsifier in combination, but it is still desirable to avoid contamination with metals.

In the present invention, it is necessary to apply both the liquids containing the treatment agents (A) and (B) to the precursor fiber bundle, but the order of application may be such that each of them may be applied sequentially, or Individually prepared solutions may be applied at the same time. Furthermore, a dispersion or solution containing both the treatment agents (A) and (B) may be prepared in advance and applied to the fiber bundle. In this case, it is also possible to use the solution (b) above as a dispersion medium for the inorganic fine particles of group (A).

Examples of methods for applying a dispersion or solution containing these treatment agents to the precursor fiber bundle include (i) using an oiling roller, (ii) applying the treatment liquid fed by a metering pump to ceramics, etc. Methods such as metered oiling applied using a prepared guide, (iii) method using a spray, etc. can be adopted.

Application by the above method may be performed anywhere between spinning and infusibility, but from the standpoint of stably handling the fragile precursor fibers, it is preferable to perform it between the spinneret and the winder. In order to initially apply a treatment agent to the brittle precursor fiber bundle discharged from a spinneret, the means (ii) or (iii) above is preferred.

The amount of the inorganic fine particles (A) attached to the precursor fiber is preferably 0.05% (by weight) or more based on the weight of the fiber. If this amount of adhesion is too small, the effect of preventing fusion of the present invention will be poor. In addition, the amount of the dihydric alcohol (B) attached is 0.05 to 0.05 to the weight of the fiber.
20% (by weight) is preferred. If the amount of adhesion is too small, it becomes difficult to handle the precursor fiber bundle stably, and if it is too large, fusion may occur, which is not preferable.

In this way, the precursor fiber bundle to which two types of specific treatment agents have been attached is dried and opened if necessary, and then heated in an oxygen-containing atmosphere such as pure oxygen or air using a conventional method to cure the fibers. melt. and,
The infusible fibers are then typically treated in an inert atmosphere.
Firing treatment is performed by heating to 1000-1500℃,
It becomes carbon fiber.

In the present invention, the conditions for the infusibility/calcination treatment can be those that are known per se, and special consideration is taken during the infusibility/calcination treatment by applying the specific treatment agent of the present invention. There's no need.

Further, although the present invention exhibits useful effects by the above-mentioned method, at least one selected from dimethyl silicone, amino-modified silicon, and phenyl-modified silicon may be added as a third component, if necessary.
It is also possible to use it in combination with the processing agents (A) and (B).

Moreover, 0.01 to 0.05% by weight of iodine can be contained in the solution (b), and in this case, the time required for the infusibility treatment can be shortened.

Effects of the Invention According to the present invention as described above, handling of fragile precursor fibers in the production of pitch-based carbon fibers is stabilized, and fusion between single fibers during infusibility is almost completely prevented. Therefore, continuous carbon fibers can be easily produced, and the resulting yarn has excellent spreadability and flexibility.

As a result, in addition to high levels of strength and elongation,
As a high-performance carbon fiber with small variations in strength, it can be widely used in a variety of applications, including reinforcing materials for rubber, resin, metal, etc.

EXAMPLES The present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1 Using commercially available coal tar pitch, patent application 1982-
Substantially 100% according to the method described in No. 169199
A spinning pitch with optical anisotropy and a quinoline insoluble portion of 31.4% was prepared. After melting and defoaming, this spinning pitch is extruded from a spinneret with 48 holes via a gear pump and wound at a speed of 800 m ² /min.
A precursor fiber bundle was obtained.

In this operation, a dispersion of treatment agent (A) and a solution of treatment agent (B) are sent between the spinneret and the winder using a metering pump along the running direction of the spun yarn in order to apply it to the yarn. A metering oiling device with two ceramic guides is installed, and silica with an average particle size of 30 mm is applied to the precursor fibers as a treatment agent (A) on the upstream side.
It was applied in the form of a 1.5% by weight, 4% aqueous dispersion (a), and then ethylene glycol was applied as a treatment agent (B) in the form of a 1.0% by weight, 4% aqueous solution (b) to the precursor fibers.

The precursor fibers wound in this manner were stable even after being left for several days, and no fluff was observed, and could be easily unwound and continuously fed to the infusibility furnace.

In addition, the infusible yarn was treated in an infusible furnace set at a maximum temperature of 350°C in an air atmosphere, and the infusible yarn that came out of the furnace was flexible and no fusion was observed between the single yarns. This infusible yarn was then fired at 1300° C. in a nitrogen atmosphere, resulting in carbon fibers with a strength of 415 Kg/mm ² and an elongation of 1.82%.

Comparative Example 1 The same procedure as in Example 1 was performed except that only one measuring oiling device was installed between the spinneret and the winder, and only the treatment agent (B) used in Example 1 was applied. Although it was easy to unravel the precursor fiber bundle, the yarn after the infusibility treatment was hard and the fusion between single yarns was severe. When this infusible yarn was fired under the same conditions as in Example 1, the strength of the obtained carbon fiber was 224
It was Kg/ ^mm2 .

Example 2 As a mixed solution of treatment agents (a) and (b), two doses each of silica and ethylene glycol with an average particle size of 30 millimicrons were used.
The process was carried out in the same manner as in Example 1, except that the aqueous dispersions containing % and 4% were applied using one metering oiling device installed between the spinneret and the winder.

The obtained precursor fiber bundle was easily unwound, and the yarn after infusibility was also flexible, and no fusion between single yarns was observed. When this infusible yarn was fired under the same conditions as in Example 1, the strength of the obtained carbon fiber was
It was 399Kg/ ^mm2 .

Comparative Example 2 The procedure was the same as in Comparative Example 1, except that only one metering oil ring was provided between the spinneret and the winder, and only the treatment agent (A) used in Example 1 was applied. The unwinding property of the obtained precursor fiber bundle was inferior to that of Example 1.

Claims (1)

[Claims] 1. In the production of pitch-based carbon fibers, the precursor pitch fiber bundle contains (A) at least one inorganic fine particle selected from oxides or carbides of silicon, aluminum, titanium, and boron; (B) A dihydric alcohol having a boiling point of 120 to 300°C and a melting point of 10°C or less, which is applied simultaneously or sequentially, and then the fiber bundle is treated to make it infusible and then fired. Carbon fiber manufacturing method. 2. Claim 1, wherein the inorganic fine particles of (A) are at least one type of fine particles with an average particle size of 1 micron or less selected from the group consisting of silicon oxide, aluminum oxide, titanium oxide, and carbon boride. Manufacturing method described in section. 3. The manufacturing method according to claim 1, wherein a dispersion containing both the inorganic fine particles (A) and the dihydric alcohol (B) is applied to the precursor pitch fiber bundle. 4. The inorganic fine particles of (A) as an aqueous dispersion (a) and the alcohol of (B) as an aqueous solution (b) are sequentially applied to the precursor pitch fiber bundle. manufacturing method. 5. The manufacturing method according to claim 1, wherein the amount of the inorganic fine particles (A) applied is 0.05% by weight or more based on the precursor pitch fiber bundle. 6. The manufacturing method according to claim 1, wherein the amount of the alcohol (B) applied is 0.05 to 20% by weight based on the precursor pitch fiber bundle.