JPS58208385A - Preparation of raw material for pitch-based carbon fiber - Google Patents

Abstract

PURPOSE:To prepare meso phase-containing pitch with a very narrow range of molecular weight distribution and a uniform structure in a short period of time, by adding meso phase spheres to raw material pitch, followed by heat treatment. CONSTITUTION:1-20wt% refined meso phase spheres with a diameter of 10mu or larger is added to raw material pitch for carbon fiber and the pitch is heat treated at 350-450 deg.C for 3-12hr for polycondensation to produce all meso phase pitch which has a melting point of 290-340 deg.C and a number-average molecular weight of 1,000-1,300, is non-thixotropic and shows uniform flow. When fibre spun from the pitch is insolubilized, carbonized, and graphitized, a carbon fiber or graphite fiber with a tensile strength of 270kg/mm.<2> or higher and a tensile modulus of 3X10<4>kg/mm.<2> or higher is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preparing pitch, which is a raw material for carbon fibers.

Carbon fiber is used in automobiles,
It is an important element of composite materials, which are attracting a lot of attention as structural and functional materials for aircraft.

Currently, the mainstream carbon fiber is polyacrylonitrile (PAN), and carbon fibers with high strength and high modulus of elasticity have been put into practical use. However, in recent years, pitch-based fibers, especially mesophase-containing pitch fibers, have attracted attention because they can be manufactured at a low cost and do not involve complicated fabrication, and there is an urgent need to establish a method for making them. There is. However, despite its usefulness, a bamboo production method for high-quality pitch-based carbon carpet has not been established.

Since PAN made from the currently available PAN-based carbon fiber raw materials is expensive, the cost of raw materials accounts for a large proportion of the manufacturing cost, and it is difficult to reduce the price significantly below the current level. In addition, when PAN is used as a starting material, it is necessary to perform infusibility and black ship treatment under tension in order to obtain graphitized carbon fibers and further improve molecular orientation, which is a frequent process of fabrication. be.

On the other hand, in the case of Pidge carbon fiber containing one mesophase,
The fibers are easy to graphitize and have excellent molecular conformation, making it easy to perform infusibility and blackening treatment techniques after the spinning process, and the raw materials are cheaper and more cost-effective than PAN. However, it is difficult to obtain a uniform structure of the heat-reacted pitch used as the spinning dope, and there are large variations in molecular weight and viscosity properties, resulting in various gaps in the spinning rod. Also, it takes a long time to process the pitch reaction.
There was a period of trade and production.

Mesophase-containing pitch-based carbon fibers have molecules highly oriented in the fiber axis direction, and are superior in terms of strength and elastic modulus to pitch-based carbon fibers that do not contain mesophases. It is known to provide strength. Therefore, there have been many reports regarding the heat treatment of raw material pitch of mesophase-containing pitch-based carbon ψ fibers. ).According to this method, the treatment time is relatively long, and as a result, high molecular weight components that have undergone too much polycondensation reaction and low molecular weight components that have not undergone sufficient polycondensation reaction. A large difference in molecular weight between the components occurs, resulting in large variations in melt viscosity at the spinning stage, making pitch spinning difficult.

Furthermore, due to the non-uniformity of the pitch structure, it is difficult to provide carbon fibers with high strength and high intelligence comparable to PAN-based carbon fibers. Although the reaction time can be improved by increasing the degree of heat treatment, the structure of the mesophase tends to take on a mosaic structure or imitative mosaic structure, so that favorable results cannot be obtained. There have also been some reports of reaction treatment of hammer pinch using a catalyst or a magnetic field, but this cannot be considered an advantageous method from an industrial perspective.

Therefore, an object of the present invention is to provide a method for thermal reaction treatment of pitch, which can minimize the molecular weight distribution of mesophase-containing pitch and generate a mesophase having a uniform structure in a short period of time. Dechiru.

That is, in the present invention, pre-purified mesokawa spheres are added to the raw material pitch in an amount of 1% to 20% by weight based on the raw material pitch,
This is heat-treated at 350°C to 450°C to cause polycondensation and convert it into mesophase pitch. According to the present invention, almost 100% conversion to mesophase pitch occurs in a t1 reaction time of 3 to 12 hours. However, if the amount of mesophase spheres added is less than 1%, the addition effect will not appear on the flow rate, and if it exceeds 20%, the molecular weight of the mesophase spheres obtained will be large. If it becomes too much, the spinning deviation becomes high, which is not preferable.

As is well known, meso-aioi 5!2. The mesophase progresses to the continuous phase through the generation of mesophase microspheres, the growth and coalescence of spherulites, or the conventional treatment method includes all of the above-mentioned dsJ#2. On the other hand, according to the present invention, the mesophase spheres added in advance to the raw material pitch serve as the catalyst for mesophase production, and the reaction proceeds from the growth and coalescence of spherulites without linking the generation stage of mesophase microspheres. 1
Reaction time will be shortened. The structure of the added mesophase spheres influences the structure of the loo% mesophase pitch obtained after the reaction treatment. As the mesophase spheres to be added, it is desirable to use large-grown spherulites (spherical diameter of 10 μm or more).

In accordance with the present invention, a 100% meso-containing pitch with a uniform flow structure is obtained. Softening point 1' is 290°C ~ 34
0°CS number average molecular weight of 1,000 to 1,300, non-thixotropic, and after spinning, the material obtained by infusible, carbonized and graphitized has a tensile strength of 270 kg/Ya2 or more,
Tensile modulus of elasticity is 3 x 10' Moan/Module 12 or more.

Hereinafter, practical examples of the present invention will be shown.

Pitch produced by pyrolysis of naphtha was subjected to thermal reaction treatment according to the present invention.

(1) The prepared raw material pitch of Soenoro mesophase sphere was suction-filtered using an α45μ glass 9-fiber filter, the humidity was raised to 400°C to expel the substitute particles, and then the reaction humidity was 400° ± 2°. Heat treatment was performed for 17 hours in a nitrogen atmosphere while stirring and refluxing with C, and the mixture was cooled and solidified. When the obtained bits were observed using polarized light and microscopy, it was found that
Approximately 20% of the mesophase spheres had grown significantly. Furthermore, the pitch was extracted with pyridine to separate it from the non-meso phase fraction, and when it was observed again using a polarizing microscope, it was confirmed that the non-meso phase fraction had been completely removed.

(21 100% mesophase reed reaction phase reaction mixture was mixed in a filter filter, 5% by weight of the mesophase spheres prepared above was added to the raw material pitch, and the reaction mixture was stirred and refluxed in a nitrogen atmosphere. 1) 6 wetness 400'C
+ 2°C1 anti-II: time 9 o'clock darkness, heat treatment 7
y0 The temperature of 380°C% is that the temperature of the decomposed molecular compound is 380°C%.
”% Shit vi W 21/m 1n 0.5 face 1ii
When the mixture was purged, cooled, and solidified, and observed under a polarized light, a 100% mesophase composition with a fine and large flow structure was observed over the entire surface.

The 100% mesophase pitch obtained here is the viewing point of 330°
C1 molecule you have 800-1800 sheath I! It contains more than 95 forms of this type, has a number average molecular weight of 1100, exhibits non-thixotropic properties, and is spun using a spinning comb with a nozzle diameter of Q of 41111. When it is made infusible, carbonized and graphitized by conventional methods, it has a tensile strength of 285 kg. /rntn2, tensile k)
Elastic modulus 3. l By applying the present invention to the pitch, the processing time was shortened, and the suspension was improved in both tensile strength and elastic modulus compared to the case where mesophase spheres were not added to the pitch.

As explained above, the raw material pitch thermal reaction treatment of the present invention is characterized in that the mesophase spheres that have been prepared in advance are added to the raw material pitch before the heat treatment is performed, and the resulting mesophase-containing pitch is Compared to conventional pitches, the molecular weight distribution is wider, so spinning is easier, and the mesophase 4
& has a total structure and has excellent molecular orientation, so it has extremely excellent Akio's tensile strength and lX elastic modulus. Furthermore, according to the present invention, jjl during the reaction is also reduced more than in the conventional method.

Agent: Patent attorney, I Teng Φ

Claims (3)

[Claims] (1) In the heat reaction treatment of m7 raw pitch of pitch-based carbon fiber, mesophase spheres are added to the raw pitch in advance in an amount of 1% to 20% by weight based on the raw pitch. L, heat treated at a reaction temperature of 350°C to 450°C.
A method for preparing a raw material for pitch yarn carbon fiber, characterized by converting id pitch into mesophase pitch. (2) A method for producing a pitch-based carbon fiber as a raw material according to claim 1, in which any one of naphtha pyrolyzed pitch, asphalt pinch, and coal tar pitch is used as the raw material pitch. (3) The method for preparing raw material for pinch type carbon fiber according to claim 1, wherein the heat treatment time is 3 to 12 hours.