JPH01282328A - Infusibilization of pitch-based material - Google Patents

Abstract

PURPOSE:To improve productivity in infusibilization treatment and obtain a carbon fiber at a low cost by setting the temperature at the time when a pitch yarn is charged to a temperature lower than the glass transition point thereof in infusibilizing the yarn in an atmosphere where solid powder is heated and fluidized by an oxidative gas. CONSTITUTION:The temperature at the time when a pitch yarn is charged into an atmosphere where solid powder such as silicon oxide is heated and fluidized by an oxidative gas (preferably air) is set to a temperature lower than the glass transition point of the pitch and the pitch yarn is subjected to infusibilization treatment in the above mentioned treatment. In case of infusibilization treatment by a continuous running of the pitch yarn in the above mentioned atmosphere, the inlet temperature is recommended to be set to a temperature lower than the glass transition temperature of the pitch and in case of a batch treatment, a yarn is recommended to be charged at a temperature lower than the glass transition temperature of the pitch followed by increasing the temperature.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for making pitch yarn infusible.

[Prior art] The technology for obtaining carbon fiber from pitch is, for example, disclosed in Japanese Patent Publication No. 1973-
It is well known from publications such as No. 4550 and Japanese Unexamined Patent Publication No. 49-19127.

Pitch-based carbon fiber is a synthetic pitch based on coal-based, petroleum-based, naphthalene and polyvinyl chloride, and is made of isotropic pitch, optically anisotropic pitch, mixtures thereof, and additives such as polymer compounds. Added pitch etc. are melt-spun,
Depending on the case, it may be obtained by dry or wet spinning to obtain a fiber form, followed by infusibility, pre-carbonization if necessary, carbonization, and further graphitization if necessary.

However, pitch yarns generally have extremely low strength and elongation.
In addition, since it is brittle, it has poor handling properties and is susceptible to surface defects during handling, which causes a decrease in productivity and a decrease in carbon fiber strength and elongation properties after firing.

In general, pitch yarn needs to be infusible before firing,
Like the pitch yarn, the infusible yarn is also extremely fragile and has poor handling properties. Furthermore, when heating with an oxidizing gas to make it infusible, the rate of the infusibility reaction at low temperatures is extremely slow, so a method is usually used in which the reaction is carried out while raising the temperature as the infusibility progresses. . At this time, it is necessary to raise the temperature within a range that does not exceed the increase in the softening point accompanying the progress of the infusibility reaction.

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 significantly reduces the physical properties of the yarn.

In addition, on the surface of the pitch yarn, there are light components, tar, dust, etc. that adhered during spinning, and especially when a sizing agent is used, the chemical and physical effects of these substances may cause the adhesion and fusion. This problem can easily occur.

Due to the above-mentioned properties, the infusibility reaction of pitch starts extremely slowly, even though the reaction rate is faster at higher temperatures, and it is necessary to complete the infusibility through a temperature raising process.

In other words, pitch yarn has disadvantages such as poor handling and easy adhesion/fusion during infusibility treatment, so the processing time is limited due to the upper limit on the yarn speed, yarn handling method, and heating rate during infusibility treatment. It is necessary to adopt conditions as mild as possible for all of these, and in other words, these problems have a major drawback in that they reduce productivity, economic efficiency, carbon fiber physical properties, etc.

Furthermore, when obtaining carbon fibers with high strength and high modulus of elasticity using optically anisotropic pitch, there is a problem in that the defects that occur during handling and infusibility are a major factor in the deterioration of physical properties. .

[Problems to be Solved by the Invention] The purpose of the present invention is to significantly improve pitch infusibility treatment in terms of time reduction and energy efficiency improvement, improve productivity, and produce carbon fiber with low cost. We aim to provide a method for obtaining

[Means for Solving the Problems] The present invention provides a method for infusibility treatment of solid powder by placing pitch yarn in an atmosphere heated and fluidized with an oxidizing gas, so that the temperature at the time of inputting the yarn is below the glass transition temperature. A pitch infusible method is characterized in that:

The fixed powder used in the present invention is one that does not contain liquid or sticky substances, that is, one that can be fluidized with gas. The powder may be inert to the pitch yarn at the infusibility temperature of 100 to 450°C.

The particle size is preferably 50 μm or less, more preferably 20 μm or less in order to achieve uniform fluidization.

Furthermore, the shape of the particles is preferably one with a smooth surface, and it is not preferable that the particles have sharp protrusions that may damage the pitch yarn.

The types of particles include silicon oxide, aluminum oxide, titanium oxide, boron carbide, boron nitride, cobalt bromide, etc.
Any of those that are reactive with carbon at a carbonization temperature of 000° C. or higher, and those that are inactive with carbon at a carbonization temperature such as graphite, carbon powder, activated carbon powder, and carbon black can be used.

However, if materials that react with carbon at carbonization temperatures are fired with particles attached, the carbon fiber surface will become minutely uneven or carbide will be formed on the surface, reducing the physical properties of the carbon fiber. It is preferable to wash and remove it before carbonization treatment.

In addition, particles that are inert to carbon do not have the above problems, but when using 1q carbon fiber for reinforcing fibers, etc., if these particles adhere, it may cause problems such as decreased adhesion between the fiber and matrix resin. It is preferable to remove the powder as it may cause problems. However, from the standpoint of preventing fusion during carbonization and firing, it is more preferable to remove it after firing, and it is more preferable to use carbon and inert carbon-based particles during carbonization.

In addition, since low molecular components, tar, etc. come out from the system to the surface of the pitch yarn during the infusibility treatment, it is particularly preferable to use activated carbon particles that can adsorb and remove these. Activated carbon particles can increase the heating rate and complete the infusibility treatment in a short time, and this is presumed to be because they have the effect of removing the substances that promote melting as described above.

Oxidizing gases used for fluidization include air, oxygen, ozone,
Although sulfur oxide, nitrogen oxide, etc. are used, air is most preferable because it is easy to seal the device.

The above-mentioned gas needs to be supplied in a heated state to infusible the pitch yarn and fluidize the solid powder, but the heating temperature is determined depending on the oxidizing power of the gas used. The conditions with the best heating efficiency should be selected by considering the balance between heat generation due to oxidation and heat removal by fluidized solid particles and gas.

However, the temperature at the time when the pitch yarn is introduced into the fluidized state from outside the system must be below the glass transition temperature of the pitch. If the pitch yarn is suddenly exposed to high temperatures above the glass transition temperature (within the glass transition temperature +50 >'C), the yarn will not melt, but it will become soft and fusion between single yarns will occur frequently, so this must be avoided. Must be.

When infusibility treatment is performed by continuously running the pitch yarn in a fluidized state, the inlet temperature is set to be below the glass transition temperature. In the case of batch processing, the material is put into a fluidized state at a temperature below the glass transition temperature and then heated.

When processing by running the thread, it is preferable to run the thread within 5 Qmm from the surface of the fluidized solid powder because resistance and damage to the thread are small, and it is more preferable to run the thread within 30 mm.

Pitch components include coal-based, petroleum-based, synthetic pitch based on naphthalene and polyvinyl chloride, including isotropic pitch, optically anisotropic pitch, mixtures of these pitches, and pitches containing additives such as polymer compounds. means.

The optically anisotropic pitch can be within a range that provides orientation of the liquid crystal component during spinning. The amount of the optically anisotropic component is preferably 60% or more, more preferably 80% or more, from the viewpoint of the physical properties and spinning properties of the carbon fiber obtained.

As a pitch spinning method, melt spinning is usually used, but depending on the purpose, dry spinning, wet spinning, dry-wetting spinning, and other spinning methods can also be used.

For melt spinning the pitch, ordinary pressure extrusion, centrifugal spinning, flash spinning, etc. can be employed.

In addition, the method of taking the pitch and gathering the yarn is to take it with rollers, air suckers, etc., wind it up, and stack it on a tray or net, as long as it does not apply a load that may cause breakage to the fragile yarn. Ordinary methods such as

In the present invention, the pitch yarn to be treated in a fluid state is used in a bundle in the form of a filament, tow, sheet, bobbin, or the like. The method of the present invention has better thermal efficiency than conventional methods using heated gas, and also has the effect of preventing the solid particles used from penetrating between the single filaments and fusing. It is preferably applied when the fibers are in a large aggregate state.

Carbon fibers can be obtained by carbonizing and graphitizing the infusible yarn obtained in the present invention.

Carbonization treatment includes, for example, heating to 800 to 1700'C in an inert gas atmosphere or vacuum, and graphitization treatment includes, for example, heating to 1700'C in an inert gas atmosphere.
There is a method of heat treatment above 'C.

[Examples] Example 1 Hydrogen gas was blown into coal tar in the presence of a nickel-molybdenum catalyst, and the mixture was reacted at 400'C for 120 minutes. The obtained hydrogenated tar was filtered through a 1μ filter to remove solid matter, and then heated at 350'C to obtain hydrogenated pitch. Then, it was heat-treated at 520'C and 117 mmHg for 7 minutes to obtain mesophase pitch.

1q mesophase pitch has a softening point of 235°C1Q
133%, 8189%, anisotropy 85%, and glass transition temperature 205°C.

The obtained pitch was 30 mm using a bent extruder.
After melting and degassing at 5°C and 160mmHg, diameter Q,
Discharge from a 100H nozzle with a hole length of 2 mm and a hole length of Q of 3 mm.
Take-up at 450 m/min, 1 pitch thread with a diameter of 10 μ
It's q.

The obtained pitch yarn was wound around a stainless steel frame, and placed in a fluidized bath in which graphite powder was fluidized with air at various temperatures, and the temperature was raised to 320'C at a rate of 5.8°C/min. So, 3
It was held at 20'C for 5 minutes to make it infusible.

The obtained infusible yarn was graphitized at 2500'C.

Table 1 summarizes the infusibility conditions and the physical properties of the graphitized yarn.

In the present invention examples of Experiment Nos. 1 to 3, there was no fusion of the infusible thread,
A good carbon fiber was obtained.

In the comparative example of experiment No. 4.5, the infusible thread was fused,
The physical properties of carbon fiber are also poor. No. 5 could not be measured due to severe fusion.

When the same pitch yarn was infusible in air, the shortest infusibility time from 180°C to 320°C, which is the upper limit of the input temperature, was 90 minutes, which was three times that of Experiment No. 3 of the present invention. there were.

Example 2 A tow of 30,000 filaments obtained by doubling the pitch system obtained in Example 1 was run on a roll, and activated carbon fibers were fluidized with air in two continuous fluidized beds with a length of 25 cm. Treated in a fluidized bed. The temperature of the layer is 200℃ on the inlet side and 3 on the outlet side.
The temperature was 00°C. The traveling speed of the tow is 5 cm/min,
The tow was run within 20-30 mm of the flow surface.

The obtained infusible yarn has no fusion, and the graphitized yarn fired at 2500'C has a yield of 280 kq/mm2.50 torrl/m1.
2, showing good physical properties.

[Effects of the Invention] The present invention makes it possible to improve energy efficiency, shorten processing time, and improve productivity by making pitch yarn infusible in a solid powder fluid state.

Claims (1)

[Claims] (1) When solid powder is infusible by placing the pitch yarn in an atmosphere heated and fluidized with oxidizing gas, the temperature at the time of inputting the yarn is set to below the glass transition point. Melting method.