JPS59168125A - Production of carbon fiber - Google Patents

Abstract

PURPOSE:To obtain carbon fibers of a radial structure with cleavage on the surface thereof and further a high elasticity, by melt spinning an optically anisotropic pitch at a specific shear rate in spinneret holes and orientation forming parameter. CONSTITUTION:A pitch containing >=60% optically anisotropic component is melt spun at >=550sec<-1> shear rate in spinneret holes expressed by formula I [Q is the flow rate of the pitch (cm<3>/sec); D is the spinneret hole diameter (cm)] and >=100 orientation forming parameter (f) expressed by formula II [t is the average residence time in the spinneret holes (sec)] to give fibers, which are then infusibilized in the presence of oxygen and carbonized or further graphitized in an atmosphere of an inert gas to afford the aimed carbon fibers.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing high performance carbon fiber from pitch, and more specifically, the optically anisotropic structure in the fiber exhibits a radial 4 structure and The present invention relates to a method for producing a bits-based carbon fiber having a high modulus of elasticity that reduces cleavage.

Carbon fibers made from optically anisotropic bits are PAN
It exhibits better graphitization properties than other carbon fibers, so it has the advantage of producing carbon fibers with a high modulus of elasticity.

Among the conventional methods of using pitch as carbon fiber raw material 1, a method of using optically anisotropic pitch is known in order to form an oriented structure in the carbon fibers obtained and obtain high-performance fibers. There is. When the pitch is melt-spun, the optical orientation component of the pitch is aligned in the fiber axis direction, but in a braid cross-sectional structure perpendicular to the fiber Ivli axis, the radial component is typically aligned radially. There are three known types: onion type, which is arranged concentrically, and random type, which is irregularly arranged.

Among the above three types of pitch-based carbon fiber structures, those with a radial structure have carbon layer surfaces forming a graphite structure oriented radially and regularly within the fiber cross section; It forms a large domain that extends in the direction. Therefore, carbon fiber with a radial structure has a high tl when graphitized, and when graphitized, it has high elasticity, thermal conductivity, and electrical conductivity. In use, R<f is the abrasive material. Carbon fibers with a radial structure have cleavage on the surface and -C
In addition, since the surface Ti4i is large, it is superior to other types having a circular cross section (rantum and onion structures) even in applications where adhesiveness is required.

Conventionally, various methods for melt-spinning optically anisotropic pips have been known, but a method for industrially obtaining only the above-mentioned radial structure yarn is not known.

The present invention aims to industrially produce 1q of high-performance radial structure yarns, and as a result of investigation into the melt-spinning method of optically flexible pitch, we have found that the shear in the spinneret hole and the structure of the resulting carbon fibers have been investigated. In this invention, we found the relationship between ff1lJ
It is something that has been achieved.

The present invention is based on optical anisotropy 1 (producing carbon fiber by melt-spinning pitch containing 60% or more of one component, followed by infusibility treatment and carbonization or rough graphitization treatment). , the shear velocity γ in the mouth hole shown in equation (1) is set to 5
This is a method for producing carbon fibers characterized by performing melt spinning under conditions in which the orientation formation parameter f, which is expressed by the following formula (2), exceeds 5 Q sea' and is 100 or more.3, γ -320,,/πD3...
・・・・・・(1)1゛-ff1・・・・・・・・・・・・
・・・・・・・・・・・・(2) [0: Pidge style F3
(am3./sec) D: [1 Gold hole diameter (cm) [: Average residence time in the mouth hole (sec)] Invention iJ
By adopting such a disintegration process, for the first time, carbon fiber with a radial structure having a high bullet rate of 14% was economically manufactured at an industrial level.

In particular, according to the present invention, the carbon fiber shoulder 1 can be stably spun even at a high speed of 160 m/min or more, and the carbon fiber shoulder 1 obtained is characterized in that it is a continuous filament 1 having a uniform radial structure. It is.

Pitch exhibiting optical anisotropy in the present invention achieves high elastic modulus by forming good black 'tit (M'r) through carbonization and graphitization treatment. Optical anisotropy means: As will be explained later, when pitch is observed under polarized light, for example, if the pitch is embedded in epoxy resin, the surface is polished, and then observed under orthogonal polarized light using a reflective polarizing microscope, the orientated parts will shine. It is something that brings forth children.

Another way to tell is to use a decolorized test plate and observe the change in color.

Several methods are already known for producing such anisotropic bits. For example, JP-A-49-1912
Publication No. 7, JP-A-54-160427, JP-A-5
Although it is manufactured by a method such as that disclosed in Japanese Patent No. 7-168989, any of such known anisotropic pitches can be applied to the present invention.

The component exhibiting such optical anisotropy is selected from the viewpoint of its influence on graphitizability, such that it is contained in the pitch in an amount of 60% or more, preferably 75% or more, and more preferably 90% or more.

In the present invention, the pitch is taken into account in the stationary type metal, and the size of the gap in the die hole is determined by the size of the gap in the die hole. 11) It is an essential requirement that the orientation formation parameters defined by the closing time and the orientation formation parameters defined by the The size of the shear is defined by the shear speed γ shown by the following formula (1).

γ-32Q/πD3・・・・・・・・・・・・(1) [
Q: Pitch flow rate (am3/sec) D: [] Gold alloy hole (
am)] The optical anisotropic pitch creates various orientations due to shear, but in order to achieve the orientation of the radial structure, the above-mentioned scraping speed γ should be set to exceed 550 sec-+, more preferably 650 sec-+.
It is important to set it to SeO-1 or higher. 550s
If the yarn is less than ec-1, a random structure is more likely to be formed than a radial structure, and such a yarn forms carbon fibers that are free from cleavage and have poor jointability, thermal properties, and electrical properties.

The orientation structure of the spun fiber set is defined by the thickness of the gap and the time for receiving the scraping, and is defined by the orientation formation parameter [J1-C1 It is even more strongly influenced by b.

f-7J-t ・・・・・・・・・(2) [1:1] The average residence time t in all holes in the above formula is 33 [-πF)2M/4Q (3) [0:
The length of the mouthpiece hole is cm)'1 In the present invention, the orientation forming parameter f is 10
0 or more - F, favorable j: 140 or more is necessary to stably obtain the orientation of the radial structure.
It is.

In addition, in the case of adopting a bright circular mouth hole for the mouthpiece in the present invention, the diameter of the mouthpiece hole (¥D is the diameter when converted to a circle with the same cross section f^) is applied. The slurry speed is determined by the flow path i at the smallest cross-sectional area of the flow path in the 1-1 gold leaf outlet hole portion, and the average residence time t is the average residence time in the flow path in the discharge hole portion Wtl. In other words, the flow path means the flow path portion beyond the minimum cross-sectional area of 1 mm opening to the outside, which extends the pitch, and does not include the introduction portion that is larger than a5 in a normal cap.

The present invention (J, by simultaneously melt-spinning such a strip A! 1 in a range that satisfactorily covers it, a stable and uniform radial (11
It is possible to industrially produce carbon fibers with a high elasticity ↑4 ratio and a 1-structure orientation.

To explain fibers with radial and random structures as used in the present invention using microscopic photographs, Figures 1 to 1C in Figures 1 and 2 are 11i chicks produced immediately after spinning, after infusibility, and after graphitization, respectively. Figure 1 shows an example of a fiber with a radial structure, in which a rehab-type Maltese cross pattern is observed.

Note that C in the figure shows such a fiber graphitized, and it can be clearly seen that a portion of the fiber has been cleaved and lost. Figure 2 a-G
There is an example of carbon fiber ゛C゛ with lantum (b structure),
In any case, it has been found that this structure dominates the fiber at all stages from spinning to graphitization. All such phenomena can be observed in color. For example, when observing the fibers immediately after spinning in Figure 1a using a polarizing microscope, if a decolorizing test plate is inserted and covered with the vibration direction of the light in which the speed of the test plate is smaller in the 1.3 quadrant, the 1st The 3rd quadrant is observed as blue, and the 2nd and 4th quadrants are observed as yellow. , In addition, in the case of Figure 1a, by rotating the sample, the position of the position detected by r4:)m does not change, indicating that the internal optical anisotropic components are radially oriented. You can check it.

According to the method of the present invention, it is possible to perform spinning at a high speed, which was higher than that achieved conventionally. In other words, as can be understood from the above equation (1), the shedding speed depends on the discharge lift Q per 141 holes of the bitge, so by increasing the spinning speed and increasing the amount of rice, the shearing speed increases. , it becomes easier to form a radial structure yarn. Therefore, according to the method of the present invention, the speed of the ember is 160 m/min or more, further 200 m/min or more, or 300 m/min.
High-speed spinning is possible (m tear 'o1 condition ni J:
It is possible to spin at an ultra-high speed of T4; t1 ooo m/min or more.

In the present invention, increasing the shear energization means increasing the back pressure of the spinneret. Under such a thread '1, continuous filaments having a uniform diameter can be easily produced even during high-speed spinning. It has the advantage that it can be manufactured.

In the present invention, by controlling the spinning conditions, both radial and random structures can be mixed in a desired ratio. It is also possible to form threads that

If the pick-up speed γ is 550 sec-+ or less and the orientation formation parameter f is 90 or less, it is possible to produce 1u carbon fiber in which all parts have a random 1f/I structure. By installing the orifice holes of one type or more in the same metal, or by discharging from multiple nozzles and aligning them, the radial,
A mixed fiber yarn with a random structure can be obtained.

1 of the gaps in the mouthpiece? If the I property is between the two, the yarn will be a mixture of radial and random 4F4 structures, but in that case the ratio of the two will not be constant, and in some cases the fibers of one single braid will move in the Iff +11+ direction. Since the cylindrical structure may appear repeatedly, it is not possible to control the radial random ratio.

Pitch can be extruded under pressure using an inert gas using a mass pump, but extrusion using a liquid pump is preferably applied. It is particularly effective when forming uniform Mardinoiramen 1 through a nozzle having a large number of discharge holes or when discharging O1 through a filtration process.

The shoulder diameter of the spun single fiber obtained by the method of the present invention is suitably 30μ or less, preferably in the range of 5 to 30μ, and more preferably in the range of 7 to 20μ to avoid yarn breakage and strength. However, other diameters are also effective.

The fiber thus obtained is then treated to be infusible, carbonized, and graphitized by a conventional method. The infusibility treatment can be traced back to 250 to 420 in the presence of oxygen, usually in air.
A method of avoiding liquefaction at ℃ can be applied. Further, it is also preferable to use an oxidizing gas such as ozone or NO2 as oxygen from the viewpoint of efficiency of the infusibility treatment. The infusible mIff is then carbonized and graphitized, and any commonly used method can be applied to this process. For such carbonization treatment, there is a method of heating to 800 to 1700'C in vacuum or inert gas atmosphere, and for graphitization treatment, for example, heating to 800 to 1700'C in vacuum or inert gas atmosphere is possible. There is a method of heat treatment at temperatures above 1700°C.

The present invention will be further explained below with reference to examples.

Note that the measurement method in the examples is as shown below.

[Optical properties] After embedding in a boxy-based resin, the sample was polished using a conventional method.
II by anti-polarization method using PLA N Fi microscope
A I guess.

The abundance of the optically anisotropic component was determined from the area ratio of the isotropic portion and the traverse portion when observed under the polarized light described above.

[Quinoline solution] This was carried out by a method combining the pre-centrifugation method and the 't filtration method specified in JIS-2425.

[Glass Transition Temperature] -19- 1] Measured in a nitrogen atmosphere using Erkin-E 1mer manufactured by SC-2. After heating the sample to 290° C., wetting it with V, cooling it, and drying it again, we measured the baseline such as the dehydration peak, excluding the disturbance J-factor.

[Elemental analysis] Using a CI-IN Coder M1-3 manufactured by Yanagimoto Seisakusho, the measurement conditions were a sample decomposition furnace of 900 to 950°C, an oxidation furnace of 850°C, a reduction furnace of 550°C, and a helium flow rate of 180 mα/min. It was measured with

[Strength and elongation measurement] According to the method specified in JIS-R-7601. The fiber diameter was measured using a scanning electron microscope at a portion adjacent to the strength/elongation measuring section. Furthermore, the area of the cleaved Ii fiber was determined from a micrograph of its cross section.

Example 1 - Tartar bitge with a softening point of 80°C was warmed to 410°C for about 1 hour to avoid melting in a nitrogen atmosphere, and then heated to 410°C to avoid melting.
Heat treatment was performed at 410° C. for 12 hours while stirring at 0 rpm. Next, the mixture was heated to 380° C. under nitrogen J + tl pressure and insoluble matter was removed by filtration using 200 mesh glass beads, followed by vacuum treatment at 420° C. and 5 mm 1-1 (] to remove low-boiling components.

The obtained bits were embedded in a boxy resin, polished, and then observed with a reflective polarizing microscope. As a result, approximately 90% or more of the bits were optically anisotropic components. The optically anisotropic structure showed a large flow shape. The characteristics of heat-treated pitch are 63W quinoline solubility.
1%, softening point: 340°C, glass transition humidity: 195°C, elemental analysis results: carbon: 93wt%, hydrogen: 3.7wt%
, nitrogen content was 1.0 wt%.

Using this heat treatment pitch, various types of ferrules with different hole diameters and lengths were used, and the discharge amount per single hole was reduced to 0°080cm3.
/min, spinning humidity 380°C, spinneret surface temperature 355°
Melt-spun at C, taken up with rollers at 600 m/min,
Various threads with an average diameter of 12μ were obtained. The density of this thread is 1
．． 30/Cm3, and the density of the molten pitch is 1.19/Cm3.
It was cm3.

This yarn was placed in a hot air circulation oven and subjected to infusibility treatment in air. Infusible treated yarn f't is first processed from 1 item to 15)
The temperature was raised to 0°C in about 15 minutes, and the temperature was maintained at 150°C for 15 minutes from the start of heating. Then, it was heated to 150 to 310°0 at a humidity rate of 1°C/min, and was kept at 310°C for 30 minutes to complete infusibility.
It was carbonized by heating at 200'Cj for 1 hour at 5°C and 7 mtn, and then roughly graphitized at 2000°C.

(For the q graphitized yarn, the optical inner circumference of the cross section / j1
Table 1 summarizes the structure, strength characteristics, etc.

Experiment No. 1, 2, which is an example of the present invention, has a shear speed γ or 550
sec-' and the orientation formation parameter f is also 10
0 or more, and the cross-sectional structure of the jqed graphitized yarn was a radial structure, and the fiber had yarn cleavage.

In Experiment No. 3, which is a comparative example, the orientation formation parameter f was 1.
00 is the case where there is no vortex, and N004 is the shear velocity γ
is less than 550 sec −1 and the orientation formation parameter f is 1
In both cases, the graphitized yarn obtained had a cross section @I weave with a mixture of radial structure and random structure. J: Comparative example N095 had a shear rate γ of 55 Q 5ec-1 without swirling, an orientation formation parameter f of 90 or less, and was a graphitized yarn with a uniform random structure.

As a result of spinning in the same spinneret using the same spinneret with the same number of balls in the same spinneret and the spinneret holes of No. 1 and N005, all parts had a radial structure and all parts had a random structure. Some mixed graphitized yarn was obtained on January 1st.

[Brief explanation of the drawing]

Figure 1.2 shows the changes in structure from spinning to graphitization of each fiber with a random structure and a random structure, respectively. (This is a true view of a local light microscope. In the figure, a is a cross-sectional view of a fiber called green fiber immediately after melt-spinning, 1) is a cross-sectional view of a fiber after infusibility, and G
Black 1a) A cross-sectional view of the Ili wholesaler in Kasetsu. Patent applicant: Toshi Co., Ltd. Rei 1
8-14

Claims (1)

[Claims] After melt-spinning a bitch having an optically anisotropic component of 60% or more, it is subjected to infusibility treatment, carbonization, or further graphitization treatment11! When producing carbon fibers, the conditions are such that the shear velocity γ in the die hole, expressed by the following formula (1), exceeds 550 sec-+, and the orientation formation parameter f, expressed by the following formula (2), is 100 or more. A method for producing carbon fiber, characterized by melt spinning. γ-32Q/πD3 (1) f-γf
t・・・・・・・・・・・・・・・・・・・・・(2)
[Q: Pitch flow m (am3/sec), 1] Niro gold hole diameter (am) 1: Residence time in the mouth hole (sec)]