JP2665118B2 - Method for producing fine pitch-based carbon fiber and spinning nozzle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing pitch-based carbon fiber, and more particularly to a method for stabilizing a multifilament continuous fiber having a fiber diameter of 4 to 8 .mu.m, which is thinner than a conventional pitch-diameter carbon fiber. Manufacturing method.

[0002]

2. Description of the Related Art Carbon fiber is a material having a high specific strength and a high specific elastic modulus, and has recently attracted attention as a strong and light material in the aerospace field, the automobile industry, and other industrial fields.
In such a field, an inexpensive material having high strength and high elastic modulus is desired.

[0003] Currently, PAN-based carbon fibers made from polyacrylonitrile (PAN) and pitch-based carbon fibers made from pitches are manufactured as carbon fibers, but at present, they have high strength and high elastic modulus. PAN-based carbon fibers are mainly used as high-performance carbon fibers.

However, PAN-based carbon fiber is 600
It is very difficult to obtain a high elastic modulus of GPa or more,
In particular, it is almost impossible to produce carbon fibers having a high elastic modulus of 650 GPa or more.

[0005] In recent years, pitch-based carbon fibers made of mesophase pitch, whose elastic modulus is easily increased, are mainly produced and used as carbon fibers having an elastic modulus exceeding 600 GPa.

[0006] As the fibers become more elastic, the fiber yarns become rigid, which causes problems such as fuzzing or breakage of the fiber yarns during fiber handling.

[0007] For this reason, there is a demand for a thinner carbon fiber which can be easily handled.

On the other hand, when making a composite product or an intermediate product thereof, carbon fibers having a large fineness, that is, a large number of filaments, are required in order to reduce the number of bobbins of the carbon fibers used.

However, it has been difficult to produce multifilament continuous fibers composed of pitch-based carbon fibers having an average fiber diameter of 8 μm or less and having 1000 or more filaments.

In order to produce fine fibers from pitch-based carbon fibers, it is necessary to produce fine pitch fibers. However, pitch fibers are very fragile and difficult to spin, and it is very difficult to perform spinning with a filament number of 1000 or more.

This is because, due to the multi-hole structure, the ambient temperature immediately below the nozzle plate becomes high at the inner periphery due to the effect of the accompanying flow generated at the time of spinning, and the speed of the accompanying air flow becomes extremely large. It is considered that the spinning of fine fibers is not performed stably.

[0012] By reducing the number of filaments,
The spinning of fine pitch fibers is slightly easier, but the obtained pitch fiber yarns are brittle and handling in the next step is difficult.

Japanese Patent Application Laid-Open No. 1-229820 discloses a pitch-based carbon fiber having a filament number of less than 1,000.
A method is disclosed in which a pitch fiber yarn of less than 0 is obtained and a plurality of the yarns are combined.

However, if the number of filaments is 1000
In the case of a thin pitch fiber having a diameter of less than 8 μm and a carbon fiber diameter of 8 μm or less, the strength of the yarn is extremely small,
For this reason, it is difficult to sufficiently apply the necessary tension at the time of yarn joining, and only carbon fibers with insufficient yarn alignment can be obtained.

Even if it is possible to produce high-quality carbon fiber by the twining method,
There has been an unavoidable increase in the price of the carbon fiber obtained through a complicated plying process.

[0016]

SUMMARY OF THE INVENTION The object of the present invention is 100
A pitch fiber spinning nozzle and a thin multi-filament carbon fiber capable of stably spinning a fine pitch fiber for a carbon fiber having a fiber diameter of 4 to 8 μm using a spinning nozzle having a capillary of 0 hole or more. An object of the present invention is to provide a method for producing a fiber.

[0017]

According to the present invention, there are provided (1) a single nozzle plate having: a) a capillary having 1000 holes or more; b) 3-20 rows of capillaries arranged concentrically; c) The arrangement of the capillaries is divided into two or more blocks. D) The center of the nozzle plate is 20
e) a fine pitch carbon fiber spinning nozzle having a columnar projection protruding by at least mm, and e) having a capillary diameter of 50 to 110 µm.

(2) When the pitch for spinning is melted to obtain a pitch fiber using a spinning nozzle, and is infusibilized and carbonized to produce a carbon fiber, spinning is performed using the spinning nozzle according to claim 1; The average fiber diameter is 4 to 8 μm, and the number of fibers is 100
A method for producing a small-diameter pitch-based carbon fiber, comprising producing a multifilament pitch-based carbon fiber composed of 0 to 100000 continuous fibers.

(3) A plurality of spinning nozzles according to claim 1, wherein a plurality of spinning nozzles are arranged when a pitch fiber is melted to obtain pitch fibers using a spinning nozzle, and is infusibilized and carbonized to produce carbon fibers. The pitch fibers extruded from the plurality of nozzles are drawn by a single roll and spun, and the average fiber diameter is 4 to 8 μm.
m, wherein a multifilament pitch-based carbon fiber composed of continuous fibers having 1,000 to 100,000 fibers is produced.

Hereinafter, the melt spinning apparatus of the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a cross-sectional view of a melt-spinning nozzle according to the present invention. A melt-spinning nozzle 12 has a nozzle plate 2 on which a plurality of capillaries 9 are arranged.

The capillaries 9 are arranged in concentric circles in 3 to 20 rows. The outermost radius of the concentric capillary position is preferably 50 to 250 mm.

If the number of rows in which the capillaries are arranged is less than three, it is difficult to arrange 1000 or more capillaries in a single nozzle plate, or the nozzle plate becomes very large.

If the number of rows exceeds 20, the ambient temperature at the center of the rows is higher than the ambient temperature of the outer or inner rows, and stable spinning becomes difficult.

As shown in FIG. 2 and FIGS. 3 to 8, the location of the capillary needs to be divided into two or more blocks.

The distance between the capillaries is preferably 1 to 6 mm, more preferably 2 to 3 mm.

When the block is divided into sectors (FIGS. 3 to 6), it is preferable to leave an interval of 10 to 30 ° in the angle or a distance of 10 mm or more at the narrowest part.

The capillary diameter is 50 μm to 1 μm.
It is 10 μm, preferably 70 μm to 100 μm. If the capillary diameter exceeds 110 μm, spinning of fine pitch fibers becomes unstable, and if it is less than 50 μm, processing of the capillary becomes extremely difficult and maintenance of the nozzle becomes complicated, which is not preferable.

If the location where the capillaries are arranged has a continuous concentric shape without being divided, the introduction of the atmosphere gas into the center of the nozzle becomes insufficient, the temperature in the center of the nozzle becomes high, and it is difficult to continue stable spinning. Becomes

In the present invention, it is important to provide a columnar projection 3 having a height of 20 mm or more, preferably 30 to 150 mm, under the nozzle plate.

The columnar projections 3 play a role in controlling the airflow flowing between the blocks in which the capillaries are arranged and between the blocks. When the projections 3 are not provided, or when the height is less than 20 mm, the blocks are not connected to each other. The airflow flowing in the gap collides at the center of the nozzle, and the airflow is extremely disturbed at the center of the nozzle. Therefore, it is extremely difficult to stabilize spinning near the center of the nozzle (near the capillary disposed near the innermost periphery of the nozzle).

By dividing the arrangement of the columnar projections and capillaries for each block, it is possible to achieve both effects of cooling the inner peripheral portion of the nozzle and controlling spinning by controlling the accompanying flow.

The columnar projection 3 is not limited to a cylinder as shown in FIGS. 9 to 12, and the effect is remarkable even if one end of the cylinder is reduced or the corner is rounded. No difference is observed, and the height H shown in FIGS. 9 to 12 may be 20 mm or more, preferably 30 to 150 mm.

If the above requirements are satisfied, 1000 or more, preferably 1500 to 1000 per nozzle
0 capillary, more preferably 1500 to 5000
Even with a nozzle having a capillary number, which is considered to be completely impossible with a conventional spinning apparatus, a stable spinning can be achieved for the first time.

However, when pitch fibers are melt-spun, the nozzle plate surface is significantly soiled by vapor or decomposition products generated from the pitch during melt spinning.

For this reason, the duration of stable spinning must be limited due to contamination of the nozzle plate.

Then, it was found that by making the accompanying flow generated at the time of spinning close to the vicinity of the nozzle plate, the replacement of the atmosphere immediately below the nozzle plate was improved, and the contamination of the nozzle was significantly reduced.

Specifically, the outer periphery of the capillary arrangement portion,
By providing a circumferential slit at the lower part of the nozzle plate and sucking the atmospheric gas from the slit, the accompanying flow generated by spinning flows immediately below the nozzle plate.

At this time, the slit is at least 20 mm, preferably 50 to 200 mm, from the outermost periphery of the capillary arrangement portion.
And the width of the slit is 5 to 30 mm
Is preferred.

If the outermost radius of the concentric capillary position exceeds 100 mm, it becomes difficult to perform uniform suction over the entire slit at one suction position. By dividing into ~ 8 locations and controlling the suction amount to be uniform, stable spinning is possible.

At this time, as shown in FIG. 1, the starting position of the accompanying flow is drawn entirely toward the nozzle plate 2 by the suction of the suction slit 4 as shown in FIG. 1, and flows immediately below the nozzle plate. .

The air flow passing through the gap between the blocks in which the capillaries are arranged is given a downward flow by the columnar projections 3, so that the air flow can flow stably without being disturbed, thereby enabling stable spinning. Becomes

The raw material of the pitch for spinning used in the present invention is:
Coal-based pitch such as coal tar and coal tar pitch,
Includes various pitches, such as coal liquefied pitch, ethylene tar pitch, petroleum pitch such as decant oil pitch obtained from fluid catalytic cracking residue, or synthetic pitch made from naphthalene etc. using a catalyst. is there.

The mesophase pitch used in the carbon fiber of the present invention is one in which the above-mentioned pitch is generated by a known method.

It is desirable that the mesophase pitch has a high orientation of the pitch fiber when spun, so that the content of the mesophase is at least 40%, more preferably at least 70%, further preferably at least 90%. .

The mesophase pitch used in the present invention has a softening point of 200 to 400 ° C., more preferably 250 to 400 ° C.
The thing of 350 ° C is good.

Prior to spinning, it is necessary to remove foreign matter from the pitch by a filter having an absolute filtration accuracy of 3 μm or less or a filtration method capable of obtaining a filtration accuracy equal to or higher than this filter.

If a solid foreign substance having a size of 3 μm or more is present in the pitch, thread breakage frequently occurs.

The above-mentioned mesophase pitch is applied to the spinning device of the present invention.
The conditions for spinning at a setting are, for example, a viscosity of 200 to 900.
At a temperature showing poise, pressure 10-100 kg / cm^Two About
100-1000m / min while extruding in degrees, preferred
Or at a take-off speed of 300 to 600 m / min
Then, a pitch fiber having a predetermined fiber diameter is obtained.

At this time, pitch fibers may be obtained by using a single spinning nozzle having at least 1,000 capillaries, or two or more spinning nozzles and a plurality of spinning nozzles of the present invention as shown in FIG. In the spinning device,
The pitch fiber extruded from the spinning nozzle may be drawn by a single roll to obtain a multifilament pitch fiber.

The number of spinning nozzles arranged at this time is 10
The number is preferably less than or equal to the number, and if the number is more than this, the adjustment between the nozzles becomes complicated, and the interval between the spinning nozzles is widened and it is difficult to stretch with a single roll, and the multifilament having a uniform yarn is provided. Production of carbon fibers becomes difficult.

With the spinning nozzle of the present invention, pitch fibers using fine carbon fibers having a filament number of 1000 or more can be obtained. However, in order to uniformly react the entire fiber bundle in the infusibilizing step, the upper limit of the filament number is 100,000.
Books, preferably 50,000.

The fiber diameter of the pitch fiber can be determined by making the pitch fiber infusible, carbonized, or graphitized, causing the fiber diameter to shrink. By spinning the fibers to a diameter of 5 to 11 μm, fine carbon fibers having a fiber diameter of 4 to 8 μm can be obtained.

The pitch fiber thus obtained is subjected to infusibilization, carbonization and graphitization by a conventionally known method so that the fiber diameter becomes 4
A thin multifilament pitch-based carbon fiber having 1000 to 100,000 filaments of up to 8 μm is obtained. The average fiber diameter D of the carbon fibers is determined from the following equation.

[0055]

(Equation 1)

W = weight of fiber bundle per unit length N = number of filaments (number of single yarns) ρ = density of fiber

[0057]

【Example】

[0058]

Example 1 As a raw material, coal tar pitch having a softening point of 80 ° C. from which quinoline insolubles had been removed was directly hydrogenated using a catalyst. After the hydrogenated pitch was heat-treated at 480 ° C. under normal pressure, a mesophase pitch was obtained except for a low boiling point component.

This pitch had a softening point of 300 ° C. and a mesophase content of 95%. This pitch was filtered at a temperature of 340 ° C. using a stainless steel filter having a filtration accuracy of 3 μm to remove foreign substances in the pitch, thereby obtaining a purified pitch.

This refined pitch is used as a spinning raw material and has a diameter of 22
Capillary diameter 100 μm on 0 mm nozzle plate,
Capillary length 150μm, number of capillaries 2000
The spinning was performed using the nozzle pack of No. 1.

The arrangement of the capillaries is in the form of FIG.
The position of the capillary located at the outermost circumference is 100 mm in radius,
The innermost circumference has a radius of 75 mm, and a block in which eleven rows of capillaries are arranged concentrically is spaced at an angle of 23 °.
Has been split.

In the center of the nozzle, a height of 50 mm and a diameter of 120
A cylindrical projection having a sectional shape of FIG.

The diameter of the nozzle plate is 30
A slit having a width of 0 mm and a width of 15 mm was provided, and suction was performed by dividing from four directions.

The nozzle plate surface temperature was 316 ° C., the spinning viscosity was 600 poise, and the pitch flow rate per capillary was 0.10.
The spinning speed is 400 m / min at 043 g / min.
Then, the roll was rotated and stretched so that the pitch fibers obtained were taken up by a suction nozzle and stored in a can.

At this time, the yarn was not broken for a long time of 6 hours, the average fiber diameter was 9.8 μm, and the number of filaments was 20.
It was possible to spin 00 pitch fibers.

Next, in a state where the pitch fibers are stored in a can, an oxidizing gas obtained by adding 5% by volume of nitrogen dioxide gas to air is blown from the lower part of the can to 150 ° C. to 300 ° C.
The temperature was raised at a rate of 1 ° C./min to 300 ° C. for 30 minutes to obtain infusible fibers.

The infusible fiber was heated at a rate of 10 ° C./min in a nitrogen gas atmosphere with the infusible fiber stored in a can, heated to 390 ° C., and kept at that temperature for 30 minutes to perform carbonization.

Next, the carbonized yarn was linearly fired in a furnace with an internal temperature of 1100 ° C. and a nitrogen gas atmosphere while paying out the fiber yarn from the can, and wound around a bobbin. Graphitizing at a temperature of 2400 ° C. while rewinding the yarn from the obtained bobbin,
A graphitized fiber was obtained.

The graphitized fiber had an average fiber diameter of 7.0 μm,
It had a tensile strength of 4.2 GPa, a tensile modulus of 620 GPa, and a filament count of 2,000.

[0070]

[Comparative Example 1] Spinning was performed under the same conditions as in Example 1 except that spinning was performed by removing the columnar protrusions. In Example 1, yarn breakage frequently occurred from the capillary portion arranged on the inner periphery of the nozzle. It was impossible to continue spinning.

[0071]

Comparative Example 2 Spinning was performed under exactly the same conditions as in Example 1 except that the capillary diameter was changed to 130 μm using the nozzle used in Example 1. As a result, a stable spinning occurred, in which yarn breakage occurred about once every 5 minutes. Was not possible.

[0072]

Comparative Example 3 The same structure as the nozzle used in Example 1 was used.
Spinning was performed under exactly the same conditions as in Example 1 except that the nozzles of the capillaries were arranged on concentric circles (not divided by blocks). As a result, thread breakage occurred frequently and spinning could not be continued.

[0073]

Example 2 A spinning nozzle having exactly the same structure as the nozzle used in Example 1 except that the capillary diameter was 80 μm and the capillary length was 120 μm, a nozzle plate surface temperature of 323 ° C., a spinning viscosity of 400 poise, Spinning was performed under the condition that the pitch flow rate per capillary was 0.022 g / min and the spinning speed was 400 m / min.

At this time, the yarn was not broken for a long time of 2 hours, the average fiber diameter was 7.0 μm, and the number of filaments was 20.
It was possible to spin 00 pitch fibers.

This pitch fiber was prepared under the same conditions as in Example 1,
Infusibilization and carbonization were performed and graphitization was performed at a temperature of 2500 ° C.

The obtained graphitized fiber had an average fiber diameter of 4.9 μm.
m, tensile strength: 4.7 GPa, elastic modulus: 620 GPa, and number of filaments: 2,000.

[0077]

Example 3 The three spinning nozzles used in Example 1 were arranged in parallel in a straight line, and among these, the pitch fiber extruded from the three nozzles with one roll located under the spinning nozzle arranged in the center. At the same time, it was drawn and spun.

The spinning conditions at this time were as follows: the nozzle plate surface temperature was 316 ° C., the spinning viscosity was 600 poise, the pitch flow rate per capillary was 0.035 g / min, and the roll was rotated and stretched so that the spinning speed was 400 m / min. Then, the obtained pitch fiber was taken out by a suction nozzle and stored in a can.

At this time, the yarn was not broken for a long time of 2 hours, the average fiber diameter was 8.8 μm, and the number of filaments was 6000.
Was obtained.

This pitch fiber was prepared under the same conditions as in Example 1.
The graphitized fiber obtained by infusibilizing, carbonizing and graphitizing has an average fiber diameter of 6.3 μm, a tensile strength of 4.3 GPa and an elastic modulus of 60.
It was a beautiful one with 5 GPa and a filament count of 6000 with good thread alignment.

[0081]

According to the present invention, stable spinning without breakage can be performed for a long time, and a multifilament pitch-based carbon fiber having a small diameter can be efficiently produced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a melt spinning nozzle.

FIG. 2 is a bottom view of a melt spinning nozzle.

FIG. 3 is a diagram showing a capillary arrangement of a nozzle.

FIG. 4 is a layout diagram of a nozzle capillary.

FIG. 5 is a diagram showing a capillary arrangement of a nozzle.

FIG. 6 is a capillary arrangement diagram of a nozzle.

FIG. 7 is a capillary arrangement diagram of a nozzle.

FIG. 8 is a layout diagram of a nozzle capillary.

FIG. 9 is a side view of a columnar projection.

FIG. 10 is a side view of a columnar projection.

FIG. 11 is a side view of a columnar projection.

FIG. 12 is a side view of a columnar projection.

FIG. 13 is a schematic diagram of a melt spinning device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Melt pitch 2 Nozzle plate 3 Cylindrical projection 4 Slit for suction 6 Suction amount adjustment damper 8 Pitch fiber 9 Capillary 10 Nozzle plate retainer 11 Capillary arrangement block 12 Melt spinning device 13 Drawing roll transport roll 14 Pitch fiber transport roll 15 Pitch fiber Bundle suction nozzle 16 pitch fiber storage can

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kunio Miura 1 Fujimachi, Hirohata-ku, Himeji-shi Nippon Steel Corporation Hirohata Works (72) Inventor Hiroyuki Tadokoro 1 Fujimachi, Hirohata-ku, Himeji-shi New Japan Hirohata Works

Claims (3)

(57) [Claims] 1. A single nozzle plate has: a) capillaries of 1000 holes or more; b) 3 to 20 rows of capillaries arranged concentrically; c) two or more blocks of capillaries. D) The center of the nozzle plate is 20
e) a fine pitch carbon fiber spinning nozzle having a columnar projection protruding by at least mm, and e) having a capillary diameter of 50 to 110 µm. 2. When a pitch fiber for spinning is melted to obtain a pitch fiber using a spinning nozzle, and is infusibilized and carbonized to produce a carbon fiber, spinning is performed using the spinning nozzle according to claim 1,
The average fiber diameter is 4 to 8 μm, and the number of fibers is 1000 to
A method for producing a small-diameter pitch-based carbon fiber, comprising producing a multifilament pitch-based carbon fiber composed of 100,000 continuous fibers. 3. A plurality of spinning nozzles according to claim 1, wherein a plurality of spinning nozzles according to claim 1 are arranged when a pitch fiber is melted to obtain pitch fibers using a spinning nozzle, and is infusibilized and carbonized to produce carbon fibers.
Pitch fibers extruded from a plurality of the nozzles are drawn by a single roll and spun, and a multifilament pitch composed of continuous fibers having an average fiber diameter of 4 to 8 μm and a number of fibers of 1,000 to 100,000 is used. A method for producing a small-diameter pitch-based carbon fiber, comprising producing a system-based carbon fiber.