JPH02259116A - Drawing of pitch type carbon fiber - Google Patents

Abstract

PURPOSE: To surely produce a pitch-based carbon fiber having high strength and uniform fine structure at a low cost by melt-spinning a pitch fiber through a spinneret and thinning the fiber by passing through a venturi jet supplied with a gas. CONSTITUTION: A pitch fiber 11 melt-spun through a spinneret 10 is thinned by passing through a venturi jet 15 supplied with a gas of a volume sufficient for thinning the fiber. Successively, the thinned fiber is usually stabilized, precarbonized and carbonized by conventional method to obtain the objective carbon fiber. The gas to be supplied to the venturi jet 15 is preferably air of 175-225 deg.C. The venturi jet 15 preferably has an inlet port widening toward the end, a constricted part 22 and an outlet port 23 widening toward the end.

Description

DETAILED DESCRIPTION OF THE INVENTION A process for melt spinning carbon fibers is improved by using a Venturi jet to advance and attenuate the fibers.

BACKGROUND OF THE INVENTION The present invention relates to an improved method for producing carbon fibers from pitch by employing a venturi-assisted melt spinning process. The invention further relates to collecting the fibers thus produced in batt form. Therefore, the present invention combines the best features of traditional melt-spinning through a spinneret process, which allow precise control of fiber diameter and microstructure resulting in enhanced strength, as well as stabilization and carbonization.
) and the economy of processing into a bat shape through appropriate grating. Such fibers contain continuous fibers or very long staple fibers, and are generally used for matrix reinforcement and/or when graphitized, are enhanced. It is useful for applications where high electrical and thermal conductivity is required.

Generally, there are two methods for producing pinch carbon fibers with improved strength: pitch selection and spinning conditions. Riggs (U.S. Patent No. 4)
, 504, 454), using a preferred ``solvent-processed pitch'' and varying the spinning conditions to produce several recognizable fiber morphologies obtained by such control.
(logies) and the formation of strength. Other references teach improvements in American melt spinning through improved spinneret designs, cooling conditions, and the like.

After all, it is only known that this control is the most effective when producing pitch-based carbon fibers using the American spinning method. However, in this spinning method,
Since the winding speed is used to apply tension during spinning, optimize fiber orientation, and control fiber diameter, it is necessary to wind the fibers on the bobbin immediately after spinning or when they are "green". Become.

The subsequent formation of batts is therefore a complicated process, as additional handling is required in the unwinding of such bobbins.

Additionally, the brittle nature of these fibers prior to carbonization has limited the spinning speeds that can be achieved by mechanical drawing.

On the other hand, bat (rolled cotton) is produced by blow spinning (blow -
spinning) and centrifugal spinning (centrifuga)
It can also be produced directly from pitch by spinning). Blow spinning is done by Schulz.
U.S. Pat. No. 3,960,601 and U.S. Pat. No. 4.0326
No. 07 and Sawran et al.
l) in US Pat. No. 4,671,864. The state of the art for centrifugal spinning of meso7Asp7C is described in U.S. Pat. No. 4,746,470 to Fujimaki et al. Although described, jet advancement and attenuation of the fibers is not taught. Japanese Application No. 62-191517 to Shono et al also discusses centrifugal spinning. Rose 1 - U.S. Patent No. 2,182
．． 918A, European Patent Specification No. 86115993.7
No. 87108452゜1.
It can also be manufactured from t-1ayed fiber). In the last one, at some stage in the process, it is necessary to cut the fiber into staple lengths in order to handle it.

Finally, the batt is made from continuous fibers with multiple forwarding jets.
It can also be formed by handling the fibers and arranging them in a laydown pattern using a jet. U.S. Patent No. 3,477.
No. 103 and No. 3,563,838. Jet processing of polymer fibers is described in European Patent No. 8730
3795.6, Sze et al.
al) corresponding U.S. Patent Application No. 857,289 (4/
30/86), which discloses the use of a Venturi jet to advance freshly spun m-fibers.

SUMMARY OF THE INVENTION In accordance with the present invention, fibers are spun through a spinneret and subjected to a Venturi forward jet.
et) and attenuation provides an improved method for melt spinning uniform carbon fibers from pitch.

The method can be applied to fibers spun from either isotropic or mesophase pitch, and processability advantages are achieved for both fibers. However, improvements in physical properties by drawing and thinning the fibers are evident in fibers spun from mesophase, so this is preferred. The gas of choice for operating the jet is air, although others could be used. The gas must be heated to a temperature of 100°C to 300°C, preferably 175°C to 225°C. The fiber is wound onto a bobbin. You can also
Alternatively, it can be placed on a collection device such as a screen or belt to form a bat. By controlling the gas flow, the fibers can be made continuous but tapered, and by increasing the gas flow, they can also be broken into staple lengths. The fibers have a low areal density.
) batt, e.g. about 15-600 g/m2 and preferably about 75-250 g/m'', such that the individual fibers are substantially continuous or very long stable fibers.
Preferably, it is placed on a moving screen. Fibers from Menfaith Spinosi, attenuated by the method of Wood Invention, have a strength of about 10 or more (Kpsi) after stabilization or carbonization.
/modulus (Mps i ) ratio.

It is surprising that unripened fibers can be handled in this way, despite their known brittleness, and that strength up to the highest conventional fibers can be achieved with subsequent heat treatment. That's true. By effectively separating spinning tension from winding tension, higher throughput is possible and more uniform packaging is wound. Combine additional spinning equipment for effective batt production.
As a group, the products can be combined to increase productivity and/or directionality of the laydown pattern.

DETAILED DESCRIPTION OF THE INVENTION The first figure shows a spinneret (10) from which carbon fibers (
11) is discharged. blanket ivy
+~) 12, an inert gas flows over the surface of the cap to reduce the frequency of cleaning cycles of the cap. Below the planker/turret, there is an anilquenching chamber 13 consisting of a cylindrical baffle l 3 (a) and an inner cylindrical screen 1.3 (b), through which the heating nozzle from the inlet 14 is fed. Supplied.

7=-The Luke quench chamber is fitted with a venturi jet 15, which is shown in detail in FIG. The base lO1 balancer 12, the annealing-quench chamber 13, and the venturi jet 15 are circular in cross section, along which the newly formed filament passes and travels to form a take-up means.
mean) (not shown, screens, conventional winders, etc.). In operation, the molten pitch is extruded from the mouthpiece 15, the resulting filament is cooled with uniformly distributed heated gas introduced through the inlet 14 and passed through the screen 1.3 (b), and the filament is advanced and narrowed by the action of the Venturi jet 15. Surprisingly, the filament does not stick to the mouth of the venturi jet 15 and is not damaged at all by passing therethrough. Moreover, the desirable properties of these filaments are
They are bult-in at the point where they exit the Venturi jet 15, which is essentially controlled by the polymer flow rate from the mouthpiece 10 and the volume and temperature of the quench gas supplied from the inlet 14. be done.

FIG. 2 is a detailed cross-sectional view of a venturi shell 20 useful in the practice of the present invention. The Venturi jet 20 has an inlet 21 that widens toward the end, and a constricted portion 22.
and an outlet 23 that widens toward the end. The heated gas supplied to the jet advances and thins the nascent filament.

The angle of the flared inlet 21 (approximately 18 degrees from vertical) and the angle of the divergent outlet 23 (approximately 1 degree from vertical) are selected experimentally to give optimal performance.

The constriction 22 is slightly rounded so as not to present a sharp surface to the filament. Other considerations regarding the design and application of venturi jets can be found in European Patent Application No. 87303795.6 (Sze et al.
Al, ); Published 4/87).

Immediately after spinning or following the production of baggreen''' mesophase pitch carbon fibers and/or filaments as described above, such fibers and/or filaments are stabilized, precarbonized, carbonized and optionally graphitized by well known means. Ru.

A finish that facilitates handling and protects the fibers may be applied during or immediately after spinning. Processing in bat shape is preferred for economy and ease of handling. The areal density of the batts can be easily varied and is controlled by the spinning speed and/or the speed of the collection device, such as a perforated belt.

The heavier the bat, the lower the stabilization temperature must be. The stabilization of Maisonze carbon pitch in air is
Generally carried out at 250°C to 380°C. Bobbin (for example, U.S. Pat. No. 4,527°754; Flynn (
(see Flynn), the stabilization procedure (protoc
ol) can be according to US Pat. No. 4,576.810 (Redick). After stabilization,
The fiber or batt is heated at 800°C to 100°C under an inert atmosphere.
At a temperature of 0 °C, liquefaction (dev.

1 atilized) or pre-carbonized
rbon i zed).

This step helps remove gas-forming components from the fiber or batt from oxygen (from stabilization reactions) and alkyl side chains, heteroatoms, etc. present in the pitch, thereby allowing subsequent It allows the carbonization reaction to proceed more smoothly and also to minimize the formation of voids that would limit strength. Pre-carbonization is usually 0.1-1
Accomplished within minutes. The carbonization reaction under an inert atmosphere is carried out at a temperature of about 1000°C to 2000°C, preferably 1500°C to
It is carried out at 1900°C for about 0.3-3 minutes.

Once the carbonization reaction is complete, the performance of the fiber, e.g. composite material (c
It may be desirable to apply fiber finishing and/or surface treatments to improve fiber adhesion in composites. If graphitization is desired,
It is usually 2400°C to 3300°C1 preferably 2
Achieved at 600°C to 3000°C for at least about 1 minute. There is no harm in employing longer treatment times during any of the above heating steps.

EXAMPLE The following example illustrates one practical approach to the invention. Tensile properties are according to ASTM 3379, gauge length 1.0 inch (2,54 cm) - Petroleum-based "neomesophase" pitch (see U.S. Pat. No. 4,208.267; Diefendorf et al.) Manufactured in accordance with the general teachings of U.S. Pat. No. 4,277,325 (Greenwood). The pinch pellets thus produced were Werner Pfleiderer 28 mm
remelted in a two-screw extruder at 325°C to 360°C and metered into a conventional spinning pack by a gear pump at a predetermined output rate (see below);
Pass it through a 99-sized spinneret. Each capillary is in the direct line 6
mil, L/D ratio 2. The overall design, including the ridges, follows US Pat. No. 4,576, '811.

The spinneret surface is at a temperature of 250°C, and the flow rate is 0.5ft3/h.
Surrounded and blanketed with nitrogen fed at a rate of r. The radial quench-anneal chamber is sealed to the planner and has an outer diameter of 8.5" and an overall length of 3.5".
The quench chamber has a concentric cylindrical baffle device (4,25'' diameter) and an opening area of about 30% to uniformly guide high-temperature quench-annealing air onto the spun fibers.
There is a 100 mesh diffusion screen (2,88" diameter).

Air heated to 2oo0c is supplied to the annealing quench chamber at the following rate. The Venturi jet is firmly bolted to the face of the annealing quench tool and has the following dimensions (see Figure 2): maximum diameter of flared inlet 21 0.9"; constriction 22 0.5".
7" diameter. Distance from mouth to stenosis is 0.55":
The maximum internal diameter of the exit is 0.78" and the distance from the constriction to the exit is 6.4", the filament exiting the Venturi jet is manually collected on a screen, and the resulting sample vat is held at 265° in air. Stabilized in C180 minutes,
Pre-carbonized at 550°C for 2.5 minutes and carbonized for 5 minutes on a belt conveyor passing through an oven with an inlet temperature of 1000°C and a maximum temperature of 1600°C. The obtained physical properties were measured and were as follows.

The fibers in Experiments A and B are continuous, whereas those in Experiments C and II are long but discontinuous. Each modulus is the same because the carbonization conditions are the same. Experiment C provides the best balance of physical properties, has relatively high elongation, and is also easy to process and handle.Embodiments of the invention include the following.

1. By melt-spinning the pitch through a spinneret, characterized in that the spun fibers are passed through a penturi jet supplied with a volume of gas sufficient to attenuate the fibers. Method for producing basic fibers.

2. The method of item 1, wherein the pitch is a meso 7 ace pinch.

3. The method of item 1, wherein the gas is air.

4. The method of item 2, wherein the gas is air.

5. The method of item 1, wherein the gas is air heated to a temperature of 100°C to 300°C, and the pitch is a mesophase pitch.

6. The method of item 1, wherein the gas is air heated to a temperature of 175°C to 225°C, and the pitch is mesophase pitch.

7-Ml, the method of paragraph 3.5 or 6, wherein the attenuated fibers are continuous and/or wound into pohins.

8. The method of paragraph L 3.5 or 6, wherein the attenuated fibers are continuous and arranged on a surface so as to form rosettes 1-.

9. The method of paragraph 1.3.5 or 6, wherein said sufficient gas is supplied to said Venturi jet such that said fiber is broken into stable fibers.

10. The first, 3.5 or Method of Section 6.

[Brief explanation of drawings]

FIG. 1 is a schematic elevational view, partially cut away, of an apparatus for carrying out the present invention. FIG. 2 is an enlarged partial view of the venturi jet used in the examples. 1. Indication of the case 1999 Patent Application No. 310852 Name of the invention Method for drawing pitch-based carbon fiber 3. Person making the amendment Relationship with the case

Claims (1)

[Claims] 1. A method for producing carbon fibers by melt spinning pitch through a spinneret, characterized in that the spun fibers are passed through a ventilate jet supplied with a volume of gas sufficient to thin the fibers.