JPS61258023A - Production of pitch carbon yarn - Google Patents

Abstract

PURPOSE:To obtain pitch carbon yarn suppressing occurrence of wedge-shaped cracks extending in the fiber axis direction, by setting both packed layer parts and space parts right above spinning nozzles, passing spinning pitch through the packed part, the space part and the spinning nozzles in this order and spinning the spinning pitch. CONSTITUTION:Spinning pitch is passed through the packed layer 4, fed through the space parts 5 to the spinning nozzles 2 and spun. A fiber structure not causing cracks is obtained by setting the packed layers 4 in the feed holes 6 of spinnerets, variability of flow rate of pitch based on the difference in each of the feed holes 6 having the packed layer 4 is eliminated by the space parts 5 and the unevenness of fineness is not produced. The size of the space parts 5 is set in a range of 0.05-15sec, preferably 0.1-5sec by measuring retention time of the pitch.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing pitch-based carbon fiber, and more specifically, to a method for producing pitch-based carbon fiber that exhibits improved f'L9 strength. The present invention relates to a method for manufacturing the same.

[Conventional technology]

Carbon fiber is a material with high specific strength and specific modulus.

Pitch-based carbon fibers are attracting the most attention as filler fibers for high-performance composite materials, and among them, pitch-based carbon fibers have an abundance of raw materials, a high yield in the carbonization process, and a high fiber elastic modulus compared to polyacrylonitrile-based carbon fibers. It has various advantages.

Incidentally, various types of spinning pitch, which is a raw material for pitch-based carbon fibers having such advantages, have been studied.

In other words, instead of the isotropic pitch conventionally used as spinning pitch, by heat-treating the carbonaceous raw material and using pitch in which anisotropy develops and molecular species that are easily oriented are formed, Since it was reported that pitch-based carbon fibers with high properties could be obtained (Ir! Kosho Datar No. 63U), various studies have been conducted on the preparation of spinning pitch with good orientation.

As is well known, when carbonaceous raw materials such as heavy oil, tar, and pitch are heated to 00°C, particles with particle sizes ranging from several microns to several hundred microns are optically visible under polarized light. Small spheres exhibiting anisotropy are produced. When the material is further heated, these small spheres grow and coalesce, and finally the entire material exhibits optical anisotropy. This anisotropic structure is composed of layers of planar polymeric aromatic hydrocarbons produced by thermal polycondensation reactions of carbonaceous raw materials and is oriented, and is considered to be a precursor of graphite crystal structure.

A heat-treated product containing such an anisotropic structure is generally called mesophase pitch.

As a method for using such mesophase pitch as a spinning pitch, for example, 1 petroleum-based pitch is heat-treated at about 350 to ≠jO ℃ under stationary conditions to obtain a pitch containing 1 to 0 weight of mesophase. A method of using this as the spinning pitch has been proposed (4I Kaisho Santaichi/P/
core issue).

However, since it takes a long time to mentate an isotropic carbonaceous raw material by such a method, the carbonaceous raw material is treated with a sufficient amount of solvent in advance to obtain its insoluble matter, and then the carbonaceous raw material is treated with a sufficient amount of solvent.
A method has been proposed in which a heating treatment is carried out for a short time of 10 minutes or less at a temperature of 00°C to form a highly oriented -zubitch, and this is used as the spinning pitch (Japanese Patent Application Laid-Open No. 5-1989-IAD Section 2). No. 7 and other spinning pitches with good orientation for producing high-performance carbon fibers include, for example, coal tar pitch pipe hydrogenated in the presence of tetrahydroquinoline, and then approximately v-50°C.
Optically isotropic and too
A pitch that has the property of becoming anisotropic when heated above ℃, the so-called pre-mesophase pitch (1!!!
1983-714121), or a pitch obtained by hydrogenating metsuphase pitch by Birch reduction method etc., which is optically isotropic and exhibits orientation in that direction when external force is applied, so-called , dormant mesophase (q#kaishozy-toottt issue), etc. have been proposed.

Pitch fibers can be obtained by melt spinning such spinning pitch through a nozzle. Next, this pitch fiber is made infusible and carbonized.

Furthermore, pitch-based high-performance carbon fibers can be obtained by using 1JVc, which is optionally graphitized.

[Problem that the invention seeks to solve]

When spinning using a spinning pitch with good orientation as described above by the conventional method, the layered structure of planar polymeric hydrocarbons in the resulting pitch fibers tends to be radially oriented within the fiber cross section, resulting in During the subsequent infusibility treatment and carbonization, tensile stress due to carbonization shrinkage acts in the circumferential direction of the fiber cross section.6.The cross section of the resulting carbon fiber has a wedge-shaped crank extending in the fiber axis direction. There are six or nine drawbacks that occur and impair the commercial value of carbon fiber.

[Means for solving problems]

The present invention has been developed by paying attention to the above-mentioned problems, and through intensive study, it has been discovered that the above-mentioned drawbacks can be overcome by passing through the Igakuman layer, and based on this knowledge, the present invention has been achieved.

That is, an object of the present invention is to perform multi-hole spinning while maintaining a homogeneous fiber diameter from each hole, and to prevent the fiber cross-sectional structure from being substantially radially oriented, but with wedge-shaped cracks extending in the fiber axial direction. The objective is to stably produce six-pitch carbon fibers with suppressed generation.

That is, this purpose is to produce a pitch-based carbon fiber by melt-spinning spinning pitch from a multi-hole spinning nozzle, performing infusibility treatment, first carbonization treatment tL, and further graphitization treatment if necessary. This can be easily achieved by providing a filled layer and a space directly in the spinning nozzle, and passing the spinning pitch through the filled layer, the space, and the spinning nozzle in this order to perform spinning.

Hereinafter, the present invention will be described in detail.1 The spinning pitch of the present invention is not particularly limited as long as it forms a molecular species that is easily oriented and provides an optically anisotropic pitch. A variety of conventional ones can be used, such as.

However, if a high degree of specific strength and specific modulus of elasticity is not required, amorphous pitch can also be used. Examples of carbonaceous raw materials to obtain these spinning pitches include coal-based coal tar, coal tarp, coal R compounds, petroleum-based heavy oil, tar, pitch, and the like. These carbonaceous feedstocks usually contain impurities such as free carbon, undissolved coal, and ash, and these impurities can be removed by well-known methods such as filtration, centrifugation, or static sedimentation using solvents. It is preferable to remove it in advance and put it in two containers.

In addition, the carbonaceous raw material may be pretreated by, for example, heat-treated and then extracted with a specific solvent, followed by a running method, or by hydrogenation treatment in the presence of a hydrogen-donating solvent or hydrogen gas. You may also do this in advance.

In the present invention, the carbon 5R raw material or the pretreated carbonaceous raw material is usually heated at JJO to 200°C, preferably JIO to HirojaC, for 2 minutes or more! O hours, preferably j minutes~! Pitch containing an optically anisotropic structure of 4'OS or more, especially 70% or more, obtained by heat treatment under an inert gas atmosphere such as nitrogen or argon, or while blowing, is suitable as a spinning pitch. Can be used.

The optically anisotropic texture ratio of a spinning pitch as used in the present invention is a value determined as the area ratio of a portion exhibiting optical anisotropy in a spinning pitch sample under a polarizing microscope at room temperature.

Specifically, for example, a pitch sample is ground into several squares, and a sample piece is embedded into almost the entire surface of a resin with a diameter of about 2 cllI according to a conventional method, and after polishing the surface, the entire surface is examined using a polarizing microscope ( It is determined by observing the sample under a magnification of 0 to O and measuring the ratio of the area of the optically anisotropic portion to the total surface area of the sample.

In the present invention, after the spinning pitch passes through the filling I layer, it is supplied to the spinning nozzle through the space to form a WJ yarn.

Supply and spin.

FIGS. 1 to .mu. are enlarged views of the vicinity of the spinning nozzle of a spinning apparatus provided with a packed bed according to the present invention. 1 is a spinneret, C is a spinning nozzle, and 3 is a sixth wire mesh supporting the packed layer *"Fi packed layer 2 and a space, respectively.

As shown in FIG. 1, the filled bed≠ is installed with a space 5 provided between it and the spinning nozzle.

Here, the packed bed is a hole provided in the spinning pitch flow path upstream of the spinning nozzle, and when the molten spinning pitch passes through the layer, the flow pattern of the spinning pitch is increased. During the J subdivision and passing through the layer, the stacking state of the mesophase of the spinning pitch is disturbed, and as a result, the mesophase is substantially saturated! Specifically, the S material is JjO~Hiro00.
Stainless steel that can withstand temperatures around ℃,
Copper, aluminum, etc. [＠materials, materials] fine crushed powder, fine grains, sintered bodies of fine powder of inorganic razors such as ceramic, glass, sand, graphite, or fine fibers of the above materials. A nonwoven fabric or a woven fabric, or a substantially spherical microsphere or the like, is selected to have a shape that can sufficiently disturb the laminated state of the mesophase during the passage of the spinning pitch. For example, If a granular filler is used, it is preferable to use a coral tree (see Figure 5) or a fine granule with sharp protrusions (see Figure 6), such as a coral tree (see Figure 6).Also, use a spherical filler. In this case, it is preferable to use true spherical glass peas, etc. If the particles are powder or spherical, the particle size is such that they pass through a 10 mesh sieve but do not pass through a 3 mesh sieve. Preferably, the particle size used is such that it passes through an SO mesh sieve but does not pass through a 100 mesh sieve.Specific examples of preferred fillers include metal powder shaped like a coral tree called metal powder; Ceramic microparticles with sharp protrusions in the shape of a class.

and stainless steel fine wire mesh with sharp notches,
Examples include glass peas.

The thickness of the filling layer≠ varies depending on the type and shape of the filling material, but the thicker the better.

1+ It is preferable that the particle size is also fine. However, if it is too thick, the flow resistance of the spinning pitch will increase, and if it is made too thin, the desired effect will not be obtained.
1111. It is preferably selected from the range of j to 200 cm.

Providing the space j between the packed bed and the spinning nozzle is important in reducing uneven fineness (distribution of diameters of pitch fibers obtained from each spinning nozzle 2) and preventing yarn breakage. . In other words, the fiber structure can be controlled in a preferable direction without cracks by providing the inlet hole of the spinneret in the packed bed, but in the case of a multi-hole spinneret, the packed layer is located just before the inlet of the spinning nozzle. If so, the difference in the structure of the packed bed for each introduction hole tends to cause fluctuations in the pitch flow rate discharged from each spinning nozzle, resulting in uneven fineness. However, there is a space j between the packed bed≠ and the spinning nozzle λ.
By providing this, the above-mentioned fineness unevenness can be significantly improved.

The size of the space j is calculated by dividing the time required for the spinning pitch to reach the spinning nozzle after passing through the packed bed, that is, the internal volume from the end of the packed bed to the upper end of the inlet of the spinning nozzle 2, by the discharge rate of the spinning pitch. The time is 0.0! It is selected from the range of ~/j seconds, preferably o, i-seconds. In other words, it is necessary to set the structure of the nozzle so that the pitch residence time in the space is O, Oj ~ 15 seconds.

Although the spinning nozzle is not particularly limited, for example, a spinning nozzle having a hole diameter in the range of o, os to OJ and a length in the range of 0.0/Nj is used.

Note that the term "spinning nozzle" refers to a pore portion through which the spinning pitch flows just before spinning and that defines the yarn diameter, and the pore diameter refers to the diameter of the pore through which the spinning pitch is discharged. The spinning nozzle used in the present invention may have any shape, such as a straight tube that satisfies the conditions in the above range, a spinning nozzle with an enlarged middle part, or an enlarged lower part of the spinning nozzle. A spinning nozzle can also be used.

In addition, the spinning pitch is discharged from the spinning nozzle 2 through a packed bed for spinning, but by providing the packed bed, the spinning pitch is usually 25 G or more, preferably 25 G or more! ri・G or more, more preferably 10~・G
Spinning can be performed by applying the above pressure.

[For production]

In the present invention, each time the molten spinning pitch passes through the packed bed, the flow of the spinning pitch is divided into smaller pieces, and the stacked state of the menphase is disturbed by passing through the packed bed.
It is thought that pitch fibers and pitch-based carbon fibers whose fiber cross-sectional structure is not substantially radially oriented can be obtained.

[Effects of the present invention]

Therefore, the fluidity of the spinning pitch is improved by the packed bed≠, and the production of gas or bubbles generated from the spinning bit at the spinning temperature is suppressed by the pressurizing operation in the above range during spinning. Improved spinning stability,
Pitch fibers with improved properties can be stably produced over a long period of time as homogeneous fibers with no uneven fineness between single holes.

By making the pitch fibers thus obtained infusible, carbonizing them, and graphitizing them if necessary, they have a fiber cross-sectional structure with random orientation or onion-like orientation, and high properties without wedge-shaped cracks extending in the fiber axis direction. pitch-based carbon fiber can be obtained.

Here, onion-like orientation is one in which the main part of the fiber cross-sectional area has concentric molecular isotropic gold, and a small percentage
In particular, it also includes those in which the outer peripheral portion is radially oriented to such an extent that no cracks occur during subsequent carbonization or graphitization treatment. Mafc.

These fiber cross-sectional structures were measured using a polarizing microscope.

〔Example〕

The present invention will be specifically explained below with reference to Examples.

Example 1 Coal tar pitch and hydrogenated aromatic oil were continuously filtered at a weight ratio of //I to remove solids in an autoclave maintained at a temperature of 0°C and a hydrogen pressure of ~.G. The removed P liquid was distilled under reduced pressure to obtain residual pitch. This residual pitch was heat-treated at 4430° C. under nitrogen gas bubbling for ≠0 minutes. The anisotropy ratio of the nine mesophase pitches obtained was ioo%.

Next, a spinneret 1 having a structure as shown in FIG.
) A 200-mesh stainless steel wire mesh 3 was placed in each of the introduction holes B at a position where the residence time of the pitch in the space J was 2 seconds.

Furthermore, stainless steel metal powder in the shape of coral A4, which had been sieved to a size of 6o-ioo mesh, was filled on the top to a thickness of about rIm. This nozzle has about 3
The amount of water passing through each spinning nozzle λ was measured by testing the flow of water under a pressure of ~.

Coefficient of variation =, f]ヱ7;75-- x = Individual measured value i = Arithmetic mean value of individual measured values n; Number of samples Then, using this spinneret, the above-mentioned menphase pitch was prepared by 3 times. Melt spinning was carried out in the temperature range of ~3t0°C. In either case, pitch fibers with a yarn diameter of up to 1 Opm could be stably obtained over a long period of time without uneven fineness by keeping the temperature at the optimum temperature and changing the winding speed of the yarn.

Pitch fibers obtained by melt spinning at 336°C are infusible at 310°C in air, and then heated under an argon atmosphere/e.
Specializes in carbon fiber by carbonizing at θθ℃. The physical properties of the obtained carbon fiber were measured. The results are shown below. The coefficient of variation marked with * is the value obtained by measuring the diameter of 1JO single yarns using an optical microscope using the above formula, and the other physical property values are the measured values of 30 single yarns. is the average of

Average fiber diameter ta, θμ Average tensile strength Ill' 306/+! j Average tensile modulus 2 ton/mj* Coefficient of variation of fiber diameter! In the ninth comparative example, metal powder was filled in the same manner as in Example 1, except that the same spinneret used in Example 1 was not covered with a wire mesh. That is, the configuration of the spinneret is as shown in FIG. 1 with the wire mesh 3 removed and the space also filled with metal powder. When this spinneret was subjected to the same water flow experiment as in Example 1, the coefficient of variation of the flow rate was 33.5.

Next, using this spinneret, the same pitch as used in Example 1 was spun under the same conditions as in Example 1, and the holes were further subjected to carbonization treatment. As for spinning nozzles with a small amount of carbon fibers, the spinning properties were poor and a stable tow of fibers could not be obtained.

Average fiber diameter! , 2μ Average tensile strength Kota 7 k17ml Average tensile modulus, 2≠torVWl Coefficient of variation of fiber diameter
3! , 0chi Reference Examples 1 to 3 A spinneret l having the structure shown in FIG.
．． 3! 3 m, length 0.6 wm, number of holes 1 each inlet hole JKλOO mesh stainless steel wire mesh 3t-1 is laid at a position where the residence time of the pitch in the space j is the time shown in Table 1, and on the top thereof , the filler shown in Table 1 is about r■
Filled to a thickness of .

Next, a water flow test similar to that in Example 1 was conducted to determine the coefficient of variation of flow. The obtained results are shown in Table 1.

[Brief explanation of drawings]

FIGS. 1 to 3 are enlarged sectional schematic views of the vicinity of the spinneret in various embodiments of the spinning apparatus used in the present invention. 1 to 7 are enlarged schematic diagrams of an example of the sheared F material used in the present invention. l; Spinneret C; Spinning nozzle 3; Wire mesh ≠; Filled layer j; Space 6: Introductory hole Figure 5 Figure 70 ○○○ ○○ Akira 4ro 1st drawing

Claims (6)

[Claims] (1) A method for producing pitch-based carbon fibers by melt-spinning spinning pitch from a multi-hole spinning nozzle, subjecting it to infusibility treatment, then carbonization treatment, and further graphitization treatment as necessary, comprising: A method for producing pitch-based carbon fibers, which comprises providing a filled layer and a space directly above a nozzle, and spinning the spinning pitch by flowing the spinning pitch through the filled layer, the space, and the spinning nozzle in this order. (2) The method for producing pitch-based carbon fibers according to claim 1, characterized in that the spinning pitch is distributed so that the residence time of the pitch in the space is 0.05 to 15 seconds. (3) The method for producing a pitch-based carbon fiber according to claim 1 or 2, wherein the spinning pitch is a pitch exhibiting optical anisotropy of 40% or more. (4) The filling layer according to any one of claims 1 to 3, characterized in that the filling layer is made of crushed powder, fine particles, fine powder sintered body, nonwoven fabric, or woven fabric of a metal material or an inorganic material. A method for producing pitch-based carbon fiber. (5) The method for producing pitch-based carbon fibers according to any one of claims 1 to 3, wherein the filling layer is made of metal powder having a coral tree-like structure. (6) The method for producing pitch-based carbon fibers according to any one of claims 1 to 3, wherein the filling layer is made of a spherical filler made of a metal material or an inorganic material.