JPS61291684A - Production of spinning pitch for carbon fiber - Google Patents

Abstract

PURPOSE:To obtain the titled pitch capable of giving pitch based carbon fibers having a high strength and high elastic modulus, by heat-treating a carbonaceous raw material while blowing an inert gas from a feed pipe having a specific caliber at a specific gas linear velocity thereinto and removing volatile low molecular materials. CONSTITUTION:A carbonaceout raw material is filled ina reactor 1 equipped with an agitator 3, and heat-treated while feeding a pregeated inert gas, e.g. nitrogen, from an inert gas feed pipe 2 having <=15mm caliber at >=30m/sec gas linear velocity thereto to afford the aimed spinning pitch. Preferably, the opening part of the inert gas feed pipe 2 is installed at <=150mm distance from the bottom of the reactor 1 containing the carbonaceous raw material and the inert gas is made to collide with the bottom of the reactor 1 and then blown thereinto.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing a spinning pitch for carbon fibers, and more specifically, a method for producing a spinning pitch for producing pitch-based carbon fibers having high strength and high modulus. This relates to a manufacturing method.

(Prior Art) As is well known, when carbonaceous raw materials such as heavy oil, tar, and pitch are heated to 330 to 200°C, optical differences with particle sizes ranging from several microns to several hundred microns occur in these materials under polarized light. Small spheres exhibiting directionality are generated. Then, when heated further, these small spheres grow and coalesce, and finally the whole becomes in a state exhibiting optical anisotropy. This anisotropic structure is composed of polymeric aromatic hydrocarbons produced by a thermal polycondensation reaction of carbonaceous raw materials, stacked and oriented in layers, and is considered to be a precursor of graphite crystal structure.

This heat-treated product is passed through a spinneret, melt-spun, made infusible, carbonized, and optionally graphitized, and then used as a raw material for pitch-based high-performance carbon fibers, which have characteristics such as high strength and high modulus. Proposed.

Carbon fiber is a material with high specific strength and specific modulus, and is attracting the most attention as a filler fiber for high-performance composite materials. Among them, pitch-based high-performance carbon fiber has a high yield in the carbonization process and has a high elasticity of the fiber. It has various advantages over polyacrylonitrile-based carbon fibers, such as a high carbon fiber ratio.

Conventionally, pitch-based high-performance carbon fibers have been produced by using so-called mesophase-containing pitch as a spinning raw material, spinning fibrous pitch from this mesophase-containing pinch, then making it infusible and firing it (carbonization, graphitization). Manufactured.

In particular, when producing spinning pitch containing a large amount of menphase, JP-A-57-1-DA 292-DA, JP-A-Sho! ;g
It is a widely known technique to produce spinning pitch by heat-treating a carbonaceous raw material while stirring or while blowing gas or the like, as disclosed in Publication No. 7 of -/AtAg.

(Problems to be Solved by the Invention) However, in the conventional methods, only stirring is performed, or even when blowing gas under stirring, the total amount of gas is simply specified, and in such methods, carbon It is difficult to sufficiently remove volatile low-molecular substances generated by heat-treating raw materials, and it is necessary to stably and uniformly create a spinning pitch that yields pitch-based carbon fibers with excellent spinnability and high properties. There were problems in manufacturing it.

(Means for Determining the Problem) Therefore, as a result of intensive studies in order to solve the above problem, the present inventors found that Recognizing that sufficient gas-liquid contact is important in order to sufficiently remove molecular substances, we efficiently and The present invention was completed by discovering that volatile low molecules can be sufficiently removed.

That is, the purpose of the present invention is to stably and uniformly create a spinning pitch that provides pitch-based carbon fibers with high properties by injecting an inert gas into a carbonaceous raw material at a specific speed using an inert gas supply pipe with a specific diameter. The present invention provides a method for manufacturing.

This purpose is to produce carbon fII textile spinning pitch by heat-treating the carbonaceous raw material while blowing an inert gas into the carbonaceous raw material. This is achieved by blowing into the carbonaceous feedstock at a feed rate of 70 m/sec or more.

The present invention will be explained in detail below.

The carbonaceous raw materials for obtaining the spinning pitch in the present invention include:
For example, coal-based coal tar, coal-tar pinch, coal liquefaction, petroleum-based heavy oil, tar, pinch, etc., and the benzene-insoluble content is 60% by weight or less, preferably 50% by weight or less, more preferably 5 to 5% by weight. 75% by weight, quinoline solubility: 10% by weight or less, preferably 73% by weight or less, more preferably 5% by weight or less.

If the benzene-insoluble and quinoline-soluble components of this carbonaceous raw material exceed the above ranges, the resulting spinning pitch will have a high melt viscosity, and therefore, it will be necessary to spin at a high temperature.

Therefore, thermal alteration of the spinning pitch is likely to occur during spinning, which is undesirable.

As a preliminary treatment, the carbonaceous raw material is heated to 35θ~SOO℃.
, normal pressure to lO9/crI-G for about θ, 5 to uO hours so that the optically anisotropic portion is at least 30% or more, preferably 50% or more, particularly preferably 70% or more. A heat-treated product is obtained, and then about 0.7 to 3 parts by weight of the heat-treated product/part by weight has a boiling point or an initial boiling point of 7.
It is brought into contact with an aromatic oil at a temperature of 30°C or higher to obtain its soluble content. Aromatic oils include naphthalene oil, absorption oil,
Creosote oil or anthracene oil is preferred.

The meaning of this pretreatment is not completely clear, but the inventors speculate that it is to remove in advance a relatively high molecular weight portion that cannot be restored to a suitable substance in subsequent treatments. Ru. In addition, as a means to satisfy this meaning, carbonaceous raw materials or the above-mentioned aromatic oil soluble components may be used together with a hydrogen-donating solvent such as tetralin, decalin, tetrahydroquinoline, or hydrogenated aromatic oil, or easily into a hydrogen-donating solvent. A solvent such as quinoline, naphthalene oil, anthracene oil, etc., which can be converted into It is also conceivable that after the addition treatment, the solid content is removed by filtration or the like if necessary, and then the solvent is removed by distillation or the like if necessary to obtain a residue.

In the present invention, the carbonaceous raw material subjected to the above pretreatment is heated to a temperature of 300°C to SOO°C, preferably 3gθ to lI! rθ℃
, reduced pressure ~/OKl/cj ”G % preferably 1
0wtmHg to normal pressure for 10 minutes, preferably 7 hours
A spinning pitch is obtained by heat treatment for about ~6 hours, at which time an inert gas is blown into the carbonaceous raw material at a gas linear velocity of 30 m/sec or more through an inert gas supply pipe with a diameter of 15 mm or less. However, it is important to perform the heat treatment under the conditions described above. Preferably, a supply pipe with a diameter of 7 to 11 m or less, more preferably / = g m or less is used, and the gas linear velocity is JOm/sec or more, preferably SO~! ! It is best to blow inert gas at 00 ml/sec. By this method, an inert gas is introduced into the carbonaceous raw material,
For example / =! It can be dispersed as fine bubbles of about rm.

If the diameter of the supply pipe is smaller than the above range, there is a problem that the supply pipe port will be blocked by minute solid substances contained in the carbonaceous raw material, and if it is too large, it may be difficult to obtain an appropriate gas linear velocity. This is not desirable because it is difficult to get caught.

Although stirring is effective in preventing coking caused by local heating near the wall of the heat treatment equipment for carbonaceous raw materials,
It is not sufficient to remove volatile low molecular weight substances that are generated.
Even if an inert gas is blown into the air, the effect of the inert gas in reducing the size of the bubbles is small.

Therefore, the blowing conditions of the present invention are important in order to effect sufficient gas-liquid contact and remove the volatile low-molecular substances along with the inert gas.

Furthermore, in order to make the inert gas bubbles sufficiently small, the installation position of the inert gas supply pipe is also important.
2! rOm, preferably /! The opening is preferably within rOwr, and the opening is preferably placed opposite the bottom of the reactor so that the inert gas collides with the bottom of the reactor.

Furthermore, in order to more effectively remove volatile low-molecular substances, a plurality of inert gas supply pipes, for example, 200
It is preferable to provide it separately.

Also in the present invention, the carbonaceous raw material may be heat-treated while stirring and simultaneously blowing inert gas.

Next, the inert gas is not particularly limited as long as it does not oxidize and make the carbonaceous raw material heavy during heat treatment, and specific examples include nitrogen, argon,
Examples include carbon dioxide, helium, water vapor, hydrogen, and hydrocarbons having 6 or less carbon atoms, and it is particularly preferable to use nitrogen, argon, hydrogen, and the like.

Moreover, these inert gases may be used alone, or if necessary, one or more types of inert gases may be used in combination.

In the present invention, the optically anisotropic phase is 170% or more, preferably 70-100%, particularly preferably 90-1
00%, and the quinoline soluble content is less than or equal to aO weight %, preferably less than 30 weight %, particularly preferably -5
It is necessary to select the above heat treatment conditions so as to obtain a spinning pitch of less than % by weight.

Incidentally, the content of the optically anisotropic phase in the spinning pitch as used in the present invention is a value determined as the area ratio of a portion exhibiting optical anisotropy in a heat-treated sample under a polarizing microscope at room temperature.

Specifically, for example, a sample piece of a heat-treated product is crushed into several square pieces, embedded into almost the entire surface of a resin with a diameter of approximately 2 cm using a conventional method, and after polishing the surface, the entire surface is thoroughly inspected using a polarizing microscope. (100x magnification) and determine the ratio of the area of the optically anisotropic phase to the total surface area of the sample.

The spinning pitch obtained in this way is processed according to a known method.
The fibrous pitch obtained by melt spinning is infusible and carbonized.
In some cases, by further graphitizing, it is possible to obtain high-performance pitch-based carbon fibers with improved strength and small variations in strength distribution.

(Effects) According to the present invention, volatile low-molecular substances generated can be efficiently and sufficiently removed by heating the carbonaceous raw material while blowing an inert gas under specific conditions. A spinning pitch having homogenized physical properties can be stably obtained, and pitch-based carbon fibers with high properties can be produced using this spinning pitch.

Since the spinning pitch of the present invention is homogenized and does not contain gelled substances, it has excellent spinnability, and the obtained fibers have high properties and the present invention has great industrial utility.

(Examples) Hereinafter, the present invention will be specifically explained using Examples, but the present invention is not limited to the Examples described below unless it exceeds the gist of the present invention.

Example 1 - In an autoclave with a Hiro stirrer, 100 parts of coal tar pitch, 100 parts of creosote oil, 3 parts of iron oxide, and 2.0 parts of sulfur were added.
17 parts of the mixture were continuously fed and the hydrogen pressure t s o
The hydrogenation treatment was carried out at a temperature of 70° C. and an average residence time of 2 hours. The treated product was filtered to remove the iron catalyst and the like, and then the solvent was distilled off under reduced pressure to obtain hydrogenated pitch.

An inert gas supply pipe having a predetermined diameter is connected to a stirrer-equipped reactor l having a volume of 1oot (inner diameter 3jOI + 511 length 1100m) shown in Fig. 1, and the opening of the supply pipe λ is connected to the reactor /
It was installed facing downward at a position 100 wm from the bottom.

The above hydrogenated pitch 60Kf was charged into this reactor, and preheated nitrogen gas was supplied from the inert gas supply pipe under the conditions shown in Table 1 under normal pressure or reduced pressure at λO ℃ for 9 hours. A spinning pitch was obtained by heat treatment.

Each spinning pinch (all optical anisotropy ratios are 90% or more) was processed using a spinning nozzle with a nozzle diameter of 0.3 m, a nozzle length of 0, &tm, and a liquid temperature of 410°C and a discharge speed of 0. □ 49
Melt spinning was carried out in part m, the yarn diameter was varied by changing the winding speed during spinning, and the duration at each yarn diameter was measured to evaluate spinnability. The results are shown in Table 1.

Comparative Example -/- The same procedure as Example 7 was carried out except that the diameter of the inert gas supply pipe and the gas linear velocity were changed. The results are shown in Table 1.

Example-7~! In Comparative Examples 7 and 7, fibers with a diameter of IOμ or less could be stably spun, and a spinning pitch that was industrially useful was obtained. Stable spinning could not be achieved even with yarn Example-5 The position of the opening of the inert gas supply pipe was adjusted from the bottom of the reactor to /l.
It was carried out in the same manner as in Example -/, except that Om was used. The results are shown in Table 1.

Qi - Sweeping

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an example of a manufacturing apparatus for manufacturing the spinning pitch of the present invention. /; Reactor U: Inert gas supply pipe 3; Stirring blade; Inert gas introduction pipe 5; Exhaust pipe Applicant Mitsubishi Chemical Industries, Ltd. Patent attorney Yo Hase - 1 other person Figure 1

Claims (5)

[Claims] (1) When producing spinning pitch for carbon fibers by heat-treating carbonaceous raw materials while blowing inert gas into them, inert gas is supplied from an inert gas supply pipe with a diameter of 15 mm or less at a gas linear velocity of 30 m/sec or more. A method for producing spinning pitch for carbon fibers, which comprises blowing into a carbonaceous raw material at a supply rate of . (2) Claims characterized in that the inert gas is at least one selected from the group consisting of nitrogen, argon, carbon dioxide, helium, water vapor, hydrogen, and hydrocarbons having 6 or less carbon atoms. The method described in paragraph 1. (3) The method according to claim 1, characterized in that the opening of the inert gas supply pipe is installed within 150 mm from the bottom of the reactor containing the carbonaceous raw material. (4) Claims characterized in that the opening of the inert gas supply pipe is installed to face the bottom of the reactor containing the carbonaceous raw material, and the inert gas is blown into the reactor by colliding with the bottom of the reactor. The method described in paragraph 1. (5) The method according to claim 1, characterized in that the inert gas is blown through a plurality of supply pipes.