JPS58208420A - Continuous production of carbon fiber - Google Patents

Abstract

PURPOSE:A plurality of preoxidized yarns are arranged in parallel so that the joining parts may not be overlapped and made into a bundle, interlaced, then subjected to carbonization to produce carbon fibers of stabilized quality in high operability and productivity. CONSTITUTION:A plurality of preoxidized yarns of less than 5 denier in finess, which are obtained by preoxidation of precursors such as acrylic fibers, are arranged in parallel so that their joining parts may not be overlapped, and interlaced with high-speed fluid for integration.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing continuous carbon fibers that is easy to work with and has excellent productivity.

Raw materials for manufacturing carbon fiber include acrylic, pitch,
Various types of fiber threads such as cellulose-based and polyvinyl alcohol-based fibers are used, and these fiber raw materials, ie, precursors, are usually wound onto bobbins or spools, or folded and stacked in boxes before being supplied. Therefore, in order to continuously fire and convert into carbon fiber, it is necessary to connect the fiber end of the rolled up or folded precursor to the end of another precursor by some means, directly or indirectly. There is.

A common method for this connection is to tie both ends of the precursor together, but the knot formed by this tying is particularly susceptible to flame resistance (oxidation) during firing.
Heat is likely to be accumulated during the process, and this heat accumulation causes a relatively large decrease in the strength of the joint, which often causes thread breakage during the flameproofing process and the subsequent carbonization process.

That is, the flame-resistant yarn that has gone through this flame-resistant process is then continuously carbonized in an inert gas atmosphere at 500°C or higher, but the breaking strength of the connection in the carbonization process pc is lower than that of the yarn under normal production conditions. When the tension decreases below , the fiber breaks at the knot. When a fiber yarn breaks, the operation must be interrupted and the yarn must be rethreaded into the furnace, or the series must be operated with the yarn missing, which poses major problems such as low operability and productivity.

Therefore, as a method to avoid such problems and improve productivity, for example, in Japanese Patent Publication No. 53-23411, there is a method for making flameproof by tying breakers together, cutting off the knots and retying them. A method of carbonizing the material has been proposed. However, this method requires manual labor to re-tie the flame-resistant yarns, and the workability is poor especially when carbonizing a large number of flame-resistant yarns.
If the shape of the thread is irregular, there is a risk of yarn breakage due to carbonization.

The present inventor has conducted extensive research into a method for producing continuous carbon fibers that does not have the above-mentioned problems, and has discovered the present invention.

In other words, the purpose of the present invention is to prevent interruption of operation due to the connection part of the breaker, improve operability and productivity, and in particular to improve the production of a large amount of carbon fiber by connecting (entangling) a large number of flame-resistant yarns. Kazuya's objective is to provide a continuous method for producing carbon fibers that is advantageous in the production of carbon fibers with stable quality.

The object of the present invention is, as stated in the claims, to connect the ends of the precursor fiber threads to make them flame resistant,
Next, during continuous carbonization, the plurality of flame-retardant yarns are aligned and bundled so that the connection parts do not overlap each other, and the bundled yarns including the connection parts are subjected to an entanglement treatment. This can be achieved by a continuous carbon fiber manufacturing method.

The flame-retardant yarn of the present invention is a flame-retardant yarn that uses various types of breaker such as acrylic, cellulose, polyvinyl alcohol, and pitch breaker as starting materials and undergoes a flame-retardant process by a conventional method.

In particular, organic breaker fibers such as acrylic, cellulose, and polyvinyl alcohol fibers accumulate heat during the firing process, especially during the flame-retardant process, resulting in a significant drop in tensile strength and bending resistance at the joints. It is very effective to apply the entanglement treatment of the present invention to produce carbon fibers.

The single filament fineness and number of fibers of the flame-resistant yarn in the present invention may be as long as they can be entangled by high-speed fluid treatment described below, and the fineness of the breaker is 5 denier (d).
or less, preferably 0.1 to 5 d, and the number of fibers is at least 3
00, preferably in the range of 500 to 3.

The entanglement treatment of the present invention involves integrally entangling a plurality of flame resistant yarns by pulling several flame resistant yarns at their edges so that their connection parts do not overlap each other. The above-mentioned connections include connections made before flame-retardant treatment, that is, those formed by entangling and connecting yarn ends with knots and/or fluid at the breaker stage. It is preferable that the connection portion be formed by a fluid bonding process that causes less heat accumulation problems during the flameproofing process. A plurality of flame-retardant yarns including such connection portions are aligned and bundled so that the connection portions do not overlap each other, and the bundled yarns including the respective connection portions are subjected to an entanglement treatment.

This entanglement treatment V (air, water, steam, etc. can be used as the fluid, but it is preferable to use air in terms of workability and economy).

The number of flame-retardant yarns to be entangled is usually 2 to 6 yarns, and if there are more than 6 yarns, the entanglement may be insufficient. VC when splitting yarns other than sections into 10 pieces of the original single yarn unit
Flame-resistant yarn with low splitting properties is usually subjected to continuous entanglement treatment during transition to the carbonization process, or the flame-resistant yarn is once wound up on a bobbin or stored in a container and then supplied to the carbonization process. It may also be applied to the case where flameproofing and carbonization are carried out discontinuously.

In the carbonization process, the flame-resistant yarn is continuously VC carbonized in a tensile manner to improve the mechanical properties of the resulting carbon fiber. In this case, the breaking strength of the flame-retardant yarn having a connection part that has gone through the flame-retardant process is that it may break at less than the operating tension during production, or by applying the present invention, it can be The trouble is resolved and the carbonization process can be carried out smoothly.

As for the range of the entanglement treatment using the high-speed fluid of the present invention, for example, the entire range of approximately 1 m from the front and back may be entangled and treated centering around the joint of the bundled flame-resistant yarns, or the same method may be used. The joint process may be performed intermittently at a plurality of locations, for example, at three or more locations, within a range of approximately 1 m in front and behind the connecting portion. [However, the daughter entangled portion is not particularly limited as long as it is appropriately designed depending on the number of yarns, firing treatment conditions, entangled treatment conditions, etc.

In addition, the method of entangling the flame-retardant threads while running is performed by aligning and converging a plurality of threads as described above, and then using a high-speed fluid ejection nozzle to entangle the fibers.

As such a fluid ejecting nozzle, various known nozzles can be used, for example, Japanese Patent Publication No. 36-10511
Nozzles of various structures are disclosed in Japanese Patent Publication No. 37-1175. One example is shown in FIGS. 1-5.

Figure 1 is a perspective view of the entanglement processing device, Figure 2 is a cross-sectional view, and Figure 5 is a side view. In the figure, 12 is a processing space, 5 is a yarn insertion port, and 4 is an air jet hole. . The flame-resistant yarns to be entangled (for example, 1, 1', 1'' in the case of 3 yarns) are inserted into the insertion port 5.
They are inserted into the processing space 2 and entangled integrally by ejecting high-speed airflow from the air ejection holes 4.

The processing space has a smooth inner surface that does not cause yarn fuzz, and is usually rectangular, or is not limited to a rectangular shape.

Further, the cross section of the air jet port is not circular, and may have a slit-like shape, for example, and a plurality of air jet ports may be provided for one device VC. The direction of air jetting does not have to be perpendicular to the yarn; for example, it can be symmetrically oriented at an angle to the yarn axis from two types of jetting holes. In order to facilitate the insertion of the yarn into the yarn insertion opening, it is effective to round off the corners of the opening slit to make it round.

Next, the appropriate value for the air pressure connected to the air nozzle will vary depending on vC, such as the fineness of the single yarn, the number of yarns, the tension when introducing the flame-resistant yarn into the carbonization process, and the shape of the air treatment nozzle. Gauge pressure of at least 2Kg/cr in
I or more, preferably Fi5-10 Kp/c+! It is best to set the pressure to .

If the air pressure is too low, the fibers will not be entangled enough, which may cause problems such as yarn breakage during the carbonization process and winding around other normal yarns. On the other hand, if the air pressure is too high, the fibers will not entangle properly. Although the entanglement is sufficient, the number of single filament breakages in the ml flame-resistant yarn increases, and as a result, the strength of the entangled portion decreases, resulting in the inability to withstand the operating tension VC of the carbonization process and the risk of breakage.

The thus obtained carbonized yarn according to the method of the present invention can be converted into graphitized fiber by further heating in a humid temperature inert gas atmosphere for tCC according to the known graphitized fiber manufacturing method Vc.

In addition, the above-mentioned method of entangling the flame-retardant yarns involves not only aligning and entangling the connected parts of the flame-retardant yarns so that they do not overlap; It is also possible to overlap the ends of the flame-retardant threads that have been wound up and perform an entanglement treatment, followed by a carbonization process.

According to the present invention, since the entanglement process is performed using a high-speed fluid without manual work, the shape of the entangled portion is stable and the thread passageability in the carbonization process is improved.

In addition, the operability and rC productivity can be significantly improved, and carbon fibers of stable quality can be produced.

Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 Comparative Example 1 The terminal end of an acrylic long fiber yarn with a medium fineness of 1 d/f and the number of filaments of 6000 and the starting end of another yarn manufactured under the same conditions are overlapped by about 1 m, and the space between them is about 2 cm at a time. Kasho V
One connection was made after the C-wire intertwining process was performed.

Separately, as a different connection method, the terminal end and starting end of the yarn were connected by a double true knot.

While applying 10 twists per meter to the yarn pc including these connections, it was placed in a flameproofing furnace in which hot air was circulated.
The oxidation treatment was carried out for 90 minutes while being fed at a speed of 0 m/min and being reversed by a roller group PC. Apply the obtained flame-retardant threads to a VC that handles the entanglement, and bundle the three threads by shifting the joints by about 1 m so that the joints do not overlap. Approximately 1'· was added and one length range was continuously entangled using an air entangling device of the type shown in FIG.

The fibers were introduced into a carbonization furnace whose substantial heating section had a temperature distribution of 500 to 1400°C, carbonization treatment was performed, and the yarn passage rate was measured.

As a comparative example, the same procedure as in Example 1 was carried out except that the flame-retardant yarn was not entangled.

Here, the yarn passage rate in the carbonization process was determined by the following formula.

Yarn passing rate (a)
Deaf-uxlo.

Number of connections introduced The results are shown in Table 1.

(Left below) Table 1 Example 2. Comparative Example 2 The terminal end of an acrylic long fiber yarn with a single yarn fineness of 1 d/f and the number of filaments of 3000 and the starting end of the yarn of Man 1 produced under the same conditions were overlapped for about 1 m, and the space between them was approximately 2 m apart. Air entanglement treatment was connected to 3 locations +2 locations.

The yarn including this connection part was oxidized in the same manner as in Example 1,
A flame-resistant yarn was obtained.

Here e (using the obtained flame-resistant yarn, Table 2 11'C
The yarn numbers were changed to the various numbers shown in Fig. 1V (Fig. Processed.

Next, carbonization treatment was carried out in the same manner as in Example 1 under a carbonization tension of 300y/3000 filament.

As a comparative example, a test was also conducted in which the flame-retardant yarn was not subjected to the entanglement treatment.

The results are shown in Table 2.

Table 2

[Brief explanation of drawings]

The drawings show one example of carrying out the present invention, and FIG. 1 is a perspective view of a thread treatment device, FIG. 2 is a cross-sectional view of the same treatment device, and FIG.
The figure shows a side view of the processing device. 1.1', 1"...Flame resistant yarn 2...Entanglement processing space 3...Flame resistant yarn insertion port 4...Air jet hole

Claims (1)

[Claims] (1) When connecting the ends of the precursor fiber threads to make them flame-resistant and then carbonizing them continuously, the connection parts of the plurality of flame-resistant threads are prevented from overlapping each other. A method for producing continuous carbon fibers, which comprises aligning and bundling the fibers, and subjecting the bundled yarns including the connecting portions to an entanglement treatment. (2. A method for producing continuous carbon fibers according to claim 1, characterized in that the bundled flame-retardant yarn including the connection portion is subjected to an entangling treatment using a high-speed fluid. (3) Claims 2. A method for producing continuous carbon fibers according to item 2, characterized in that the bundled flame-retardant yarns are bonded by a high-speed fluid under running conditions.