JP2619755B2 - Method and apparatus for continuous melt spinning of pitch - 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 and an apparatus for continuous melt spinning of pitch and a method for trapping a low-boiling substance which causes a reduction in the spinnability of pitch.

[0002]

BACKGROUND OF THE INVENTION Generally, pitch fiber sheet is
The activated carbon fiber is used as an activated carbon fiber by the activation treatment, and is used as an adsorbent for a malodorous substance, or the carbonization treatment is used as a reinforcing fiber as a carbon fiber having a high elasticity and a high strength fiber function. It is widely used in industry and its use is increasing even now.

To date, various proposals have been made with respect to the spinning process in each step of the method for producing a pitch fiber aggregate sheet. For example, in a spinning process for converting pitch into a fiber through a raw material preparation process consisting of polycondensation of tar distillate, the main process is (pitch raw material).
There are processes for transporting, storing, melting, fiberizing, arranging and sheeting. (A) The above-mentioned storage method for effectively producing the above pitch fiber aggregate sheet is disclosed in Japanese Utility Model Application No. 1-923.
No. 317, in which a vent pipe for preventing powder classification is provided between storage tanks. (B) As the above-mentioned melting method, Japanese Patent Application Laid-Open No. 62-268822 discloses a method in which a low-boiling substance is removed after melting, and then the base is removed. (C) a method characterized in that the surface of the spinneret is subjected to a superheated steam atmosphere for preventing oxidation as disclosed in JP-A-1-239117; As the method, Japanese Patent Application Laid-Open No. 1-314770 discloses a method characterized in that an opening tube is provided directly below a suction gun.
62 and JP-A-2-160967 disclose various techniques such as a method of installing a plurality of suction guns and traverse cylinders in the sheet direction.

[0004] However, simply combining these different technologies does not enable stable pitch spinning to be performed over a long period of time. Furthermore, in consideration of the entire process including the infusibilization and activation (or carbonization) processes, which are the subsequent steps, in addition to the spinning process, stable long-term implementation is impossible at all. This is because it is very difficult to control not only each process such as spinning / infusibilization / activation or carbonization, but also the entire process according to the target end product. In the case where a fiber-forming raw material prepared from a coal-based or petroleum-based raw material is defined as a pitch), the above control becomes more difficult.

[0005]

SUMMARY OF THE INVENTION The present inventors have found that the problems associated with the above operating conditions when producing pitch fibers from pitch as a raw material are mainly due to the unique properties of pitch and the pitch fiber sheet obtained. It was examined from the viewpoint that it was based on the characteristics required for.

As a result, the pitch is particularly 1) brittle, 2)
The melt viscosity gradient with respect to temperature is large, and 3) a large amount of low-boiling substances (vapors) are generated in the molten state, and the pitch fiber sheet has 4) uniform airflow resistance, and 5).
Focusing on the fact that ventilation resistance must be small, we have conducted extensive research.

According to this, first, regarding the above 1) brittleness of pitch, the pitch shape used for melt spinning is preferably a cylindrical shape, usually about 2 to 10 mm in diameter, and the length is 1 to 5 mm in diameter. It is good to make it about twice. A pitch of such a shape is most suitable for being fed to an extruder.
However, in general, when transported by a bucket or the like, the loading capacity at one time is extremely large, and a storage tank for continuously melting the pitch is provided at the upper position of the extruder, and the pitch charging position in the storage tank is usually a vertical distance. Reaches more than about 10m. Therefore, the pitch itself is transported, and the collision between the pitch and the storage tank wall occurs due to the weight of the pitch and the drop impact when the pitch is charged into the storage tank, and the pitch is crushed and powdered. As a result, slippage between the powdered pitch particles becomes extremely poor, and a “clogging phenomenon (bridge)” occurs at the time of transfer due to its own weight in the storage tank or immediately before the pitch supply port of the extruder, and the melt stability is reduced. Not only lower it,
A serious problem arises in that the pitch supply to the extruder is frequently cut off. In addition, the above-described phenomenon is further promoted because the direction of transfer of the powdered pitch in the pipe immediately above the extruder is opposite to the direction of degassing of the gas generated from the extruder.

Next, the large melt viscosity gradient with respect to the temperature in the above item 2) is due to the brittleness of the pitch described in item 1). That is, the difference in the shape of the pitch, particularly the particle size, causes the unevenness of the thermal conductivity, causing a change in the melting position in the extruder during melting. Such fluctuations cause entrainment of bubbles during melting and uneven distribution of low-boiling substances, resulting in mixing of bubbles in the pitch melt or uneven distribution of a different viscosity melt, abnormal discharge during spinning, yarn breakage. Etc.

[0009] In addition, the mixing of bubbles in the pitch melt is also caused by a sudden pressure change in the degree of pressure reduction when introduced into the extruder. Therefore, it is necessary to perform defoaming at the time of pitch melting. As such a defoaming method, a method of performing defoaming in a degassing chamber in which the melt is depressurized after pitch melting, or a defoaming chamber immediately after melting in a vent type extruder is used. Is known. However, in the former method, there is a problem that the low-boiling substance adheres and accumulates on the wall of the defoaming chamber, and the deposit is separated and mixed into the melt. There is a problem that the exhaust fibers adhere to the inner wall of the exhaust pipe and block the exhaust pipe, and it is difficult or impossible to supply a stable pitch fiber for a long period of time by any method.

[0010] The vapor of the gas generated from the pitch according to the above 3) continues to be generated from immediately after discharge until it is solidified, and adheres and accumulates not only on the peripheral device but also on the yarn bundle suction device and the yarn path device, and the deposit is deposited. If the aggregates adhere to the fibers, they cause mutual fusion between the fibers and burn the sheet during the infusibilization reaction in the subsequent step. In addition, scattering around the vapor is a problem not only in the working environment but also in the surrounding environment. On the other hand, an attempt to remove the vapor requires a large-scale apparatus, which is very disadvantageous in cost.

[0011] Further, as the items 4) and 5), uniform and small airflow resistance of the pitch fiber sheet is an important requirement of the sheet during the infusibilization reaction. This is because if the airflow resistance changes greatly in the sheet width direction or the flow direction, the sheet is torn, not only the basis weight becomes non-uniform, but also the heat burrs and the fusion between the fibers or the fusion part becomes the ignition point, Combustion occurs. Even if it does not burn, it will impair operability or significantly impair the quality of the final product. Also, when the airflow resistance is large, the same trouble as described above occurs. For this reason, in order to avoid these problems, it is necessary to reduce the basis weight at the time of manufacturing or to reduce the processing speed and manufacture, so that the manufacturing cost increases.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-quality pitch fiber stably over a long period of time. It is another object of the present invention to provide a method for effectively removing low boiling substances generated during melt spinning.

In view of the above problems 1) to 3), the present inventors have conducted intensive studies and as a result, loaded a fixed amount of pitch, transported the same to a storage tank, and passed through two or more decompression storage tanks. When introduced into an extruder, melted evenly without mixing of air bubbles, and spun, when opening while performing vapor capture,
The present invention solves the problems caused by the pitch shape and the like, finds that the melt spinning and the post-processing after the spinning can be easily and reliably performed, and as a result, it is possible to stably provide high-quality pitch fibers for a long period of time. Was completed.

That is, according to the present invention, in a pitch melt spinning method, a pitch is loaded on a bucket unit with (i) a loading weight of 1 kg or less, and (ii) the internal pressure is reduced to 200 Torr or less, and the pitch is connected in series via a gate valve. (Iii) Next, the pitch is conveyed to another storage tank at one end of the storage tanks, and (iii) the pitch is uniformly melted by an extruder without introducing bubbles. (V) a continuous melt spinning method for pitch, wherein the pitch is melted, discharged from a spinneret, thinned with a suction gun, spread and deposited in a sheet shape to capture low-boiling substances. It is related.

Hereinafter, the present invention will be described with reference to FIG.

In the present invention, a bucket conveyer (3) is used as a means for transferring the liquid to the storage tank. The pitch is loaded into the bucket unit (4) while being measured by the metering machine (1) by a constant amount from the pitch charging port (2) of the bucket conveyor (3). The bucket unit is charged from the charging valve (6) to the intermediate tank (7) while being continuously transported because it is connected via the bucket unit shaft (5).
In this case, the loading weight on the bucket unit (4) is usually 1 kg, preferably 800 g, more preferably 600 g.
Not to exceed. If the weight exceeds 1 kg, the free fall into the storage tank causes severe crushing of the pitch due to the impact of the drop. As a result, the slippage between the powdered pitch particles becomes extremely poor, and a bridge is formed at the time of transfer due to its own weight in the storage tank or immediately before the pitch supply port of the extruder, making melting unstable. And the supply of pitch to the extruder is interrupted.

Next, the pitch is supplied from the bucket conveyor (3) to an intermediate tank (7), which is a storage tank installed immediately below the charging valve. An intermediate tank, which is one of the storage tanks, is provided in series between the charging valve and the storage tank (9) via a gate valve (8). On the other hand, the storage tank (9), which is the other end in series, is connected to the extruder (12). In this case, the intermediate tank is connected to the pressure reducing device (11) via the on-off valve (10) by a pipe, and the storage tank and the intermediate tank are maintained under reduced pressure. By passing the pitch having the substantially maintained shape through the two storage tanks under reduced pressure, the pressure reduction degree of the storage tank can be kept constant even during the raw material charging, so that a special extruder or the like is not required. Melting can be carried out uniformly without introducing air bubbles, thereby eliminating not only the occurrence of thread breakage but also the discontinuity of the raw material, thereby enabling stable spinning for a long period of time. The inside of the storage tank and intermediate tank is 200
It is maintained under reduced pressure of Torr or less, preferably 100 Torr or less, more preferably 5 Torr or less. The internal pressure is 200 Torr
In the case where the spinning speed exceeds the above, the influence of pitch viscosity, pitch shape, etc. on the melt spinning performance becomes large as described above, so that the spinning condition becomes unstable, and furthermore, yarn breakage and die contamination occur and stable spinning for a long period of time. Is undesirably inhibited. The degree of decompression of the storage tank is better as the degree of vacuum is higher, but the effect of the present invention can be achieved if it is practically set to 1/100 Torr or more from the viewpoint of equipment costs and running costs. In the apparatus of the present invention, two or more reduced-pressure storage tanks (or intermediate tanks) may be provided. Further, if necessary, a raw material receiving tank always kept at normal pressure is installed directly above the storage tank via a gate valve, so that continuous spinning can be performed more smoothly. As the pressure reducing device, a known device such as an oil rotary type or a water ring type can be used as long as a desired degree of pressure reduction can be achieved.When charging the pitch into the intermediate tank, the gate valve and the on-off valve are closed. What is necessary is just to open a charging valve and to make an intermediate tank into normal pressure.

After the pitch is melted and defoamed by an arbitrary amount in an extruder (12), it is sent to a spinning head (13), and spinning is performed according to a conventional method. The spinning head (13) and the spinneret (15) of the molten pitch are made of a conventional spinning head (maximum temperature 400 ° C).
) And a spinneret (hole diameter of about 0.2 to 0.6 mm) can be used for spinning, and the yarn (Y) is drawn to a desired fiber diameter by a suction gun (17). As the suction gun, a general-purpose suction gun can be used. Also, the bulk density of the fiber sheet can be arbitrarily adjusted by connecting the fiber opening tube with an elastic body directly below the suction gun and adjusting the thread diameter ratio or mutual position so that the connection portion can be maintained under reduced pressure. it can. A connecting device (20) is provided between the suction gun and the opening tube in order to prevent air leakage and maintain the flexibility of the opening tube,
An air inlet pipe (19) having an air inlet regulating valve (18) penetrating through the coupling.

The opened pitch fibers are discharged while stalling. At this time, the diameter of the yarn passing portion in the suction gun and the fiber opening tube is related to the consumption of the air fluid. The yarn bundle is pulled and opened by air friction in the suction gun and the opening tube, respectively, and the speed ratio of the air fluid speed passing through the yarn passing section to the yarn is about 10 to 40 times that of the suction gun. In a delicate cylinder
It is better that the diameter of each thread part is small because it is about 1 to 2 times, but in a suction gun, in order to allow a low-boiling substance to accompany the yarn and to effectively perform thinning cooling and immediately after opening. The diameter is usually preferably about 10 to 30 mm. On the other hand, in the opening tube, the diameter of the threading portion of the suction gun is about 2 to 5 times, and the length is about 3 to 10 times the diameter of the threading portion. This is adjusted by setting the opening of the air introduction adjusting valve to 1/10 or less of the amount of air supplied to the suction gun. Also, in the opening tube, the discharge opening of the yarn traverses in the oblique direction with respect to the width or the width direction of the sheet, so that the sheet basis weight is equalized. The traverse angle at this time is usually preferably about 5 degrees or less.

Subsequently, the pitch fibers are deposited on a wire mesh (23) of a sheet forming apparatus (30) installed immediately below the opening tube, and discharged from the opening tube by a decompression chamber (22) below the opening. Air fluid is sucked over the entire traverse area of the opening portion. As a result, the pitch fiber aggregate after the ejection is formed into a sheet while being suction-fixed onto the wire mesh. In this case, 2 to 10 times the amount of air supplied to the opening tube is sucked to fix and deposit the pitch fiber aggregate on the wire mesh. The sheet forming apparatus includes a low boiling point capturing device (24)
Is connected to an intake pipe (25), and the device (24),
The suction air fluid including the vapor is filtered and exhausted through the intake blower (26) and the exhaust pipe (27). In addition, a known device can be used as the sheet forming device,
It is good to install in the position of 1-3 m immediately under the normal opening tube.

The suction air fluid contains a large amount of vapor, and the above-described low boiling point trap is provided to remove the vapor. In general, the properties of vapor vary greatly within a narrow temperature range and slightly vary depending on the softening point of the pitch used, but usually begin to change from a solid to a liquid around 50 ° C and easily vaporize at about 150 ° C or higher. Becomes It also has the property of becoming viscous over time due to a change in temperature even once it has solidified. In this case, if the vapor is captured in a liquid or viscous state, clogging of the filter is likely to occur, and continuous filtration for a long period of time becomes difficult. Therefore, the vapor is captured at 50 ° C. or lower, preferably 40 ° C. or lower. Therefore, the low-boiling-point capturing device is provided at a point where the temperature of the vapor sucked from the decompression chamber becomes 50 ° C. or less at which the vapor solidifies while cooling through the suction pipe. The temperature is not particularly limited as long as it is 50 ° C. or less,
Although low-boiling substances can be effectively captured in any temperature range, it is usually room temperature (18 ° C) in terms of cooling cost and operation.
It is preferable to set it to about the same. Since the vapor cooled to 50 ° C or less is almost completely solidified, it can be easily separated from air by using a cloth filter, and the vapor adhering to the filter can be removed, for example, only by knocking it off, thereby impairing the filter performance. It can be reused without. The above-mentioned cloth filter can be used as it is, but by coating the surface of the filter with an inorganic powder such as calcium carbonate or silicon in advance, the filter performance and life can be improved, thereby capturing about 100% of the vapor. Can be.

As described above, the pitch fibers are opened while the vapor is captured, and are deposited as a pitch fiber sheet.
The pitch fiber sheet is infusibilized in a conventional manner, and then carbonized or activated to obtain a final product. In this case, the pitch fiber sheet obtained by the method of the present invention can be subjected to the above-mentioned post-treatment easily and reliably.

[0023]

According to the continuous melt spinning method of the pitch of the present invention, 1) substantially no pulverization until the shape of the raw material pitch is melted, 2) two or more units kept under reduced pressure Through the storage tank, uniformly melts without introducing bubbles, reduces instability of melt spinning due to pitch shape and the like, and 3) low-boiling substances can be effectively and easily removed, so over a long period of time. High-quality pitch fibers can be stably provided.

[0024]

The following examples and test examples are provided to further clarify the features of the present invention. In Examples and Test Examples, a long-term running test was performed using coal-based pitch having a softening point of 280 ° C. measured by the Mettler method. The pitch used here is cylindrical granular with a particle size of 2 to 10 mm and a length of 4 to
Those having a particle size of 15 mm were used in 81% by weight, and the balance was a granular material having a particle size of 2 mm or less.

The specifications of the equipment used and the method of implementation are as follows.

(A) Material transfer: bucket conveyor (2)
(kg / bucket unit capacity, vertical lift distance 15m) (b) Storage tanks: 2 tanks (spreading amount 0.5 and 0.1t), gate valve installed between both tanks, oil rotary vacuum pump and pressure reducing line Connection (c) Extruder: single screw, diameter 40 mm, L / D = 2
0, set temperature supply unit 250 ° C, measuring unit 330 ° C (d) Spinning head: 2 weights, 105mm diameter, 10 holes, 0.4mm hole diameter, L / D = 2, set temperature 330 ° C, start cooling Position: 5cm just below the base, superheated steam 200 ℃, 1.5kg
/ Hr (e) Suction gun: Inside diameter of suction section 25 mm, supply air amount 35 m
³ / hr (f) Spreading cylinder: inner diameter 120 mm, length 1 m, traverse direction is constant at 3 degrees in the sheet width direction, (g) Sheet forming apparatus: sheet width 1.6 m, suction section is for sheet entire width and flow direction in the wire screen 2m 60 #, sucked by a wire mesh surface wind speed 1.5m / sec (h) low boiling substance capturing device ... thickness 50μm calcium carbonate bag filtration surface of the filtration area 100 m ²
Test Example 1 The relationship between the bucket load during transport and the state of the obtained molten pitch was examined. Operating conditions shown in Table 1 (Test Nos.
In step 4), the pressure in the pitch storage tank was kept constant at 10 Torr, and it was continuously discharged into flowing water at 10 cm below the discharge surface for 48 hours, and the submerged condition of the pitch was observed every 10 minutes. Table 1 shows the results. In the table, ◎ indicates that all settled, は indicates that part of the surface floated, and X indicates that the surface almost floated. For comparison, the results of Comparative Tests 1 and 2 are also shown in Table 1.

[0027]

[Table 1]

From Table 1, it can be seen that Test Nos. 1 to 4 do not contain bubbles in the pitch regardless of the change in the melt discharge amount. In the comparative test 1, since the loading amount of the bucket was large, the pitch was crushed at the time of charging, and the portion floating in the water was a pitch containing bubbles. In Comparative Test 2, the supply to the extruder was interrupted, the discharge was discontinuous, and the particles floated in water. Test Example 2 The relationship between the number of storage tanks and the degree of depressurization of the storage tanks and the state of the obtained molten pitch was examined. The sample was transported to the storage tank under the same conditions as in Test No. 3 of Test Example 1, and the number of storage tanks and the degree of depressurization of the storage tank were changed as shown in Table 2 (Test Nos. 5 to 9). The evaluation of the molten pitch was performed in the same manner as in Test Example 1. Table 2 shows the results. For comparison, the results of comparative tests 3 and 4 are also shown in Table 1.

[0029]

[Table 2]

Table 2 shows that Test Nos. 5 to 9 satisfied the required degree of pressure reduction and the number of storage tanks of the present invention, and thus were in a good discharge state. On the other hand, in Comparative Test 3, the degree of decompression in the storage tank satisfies the requirement, but since the number of storage tanks is one, bubbles were included when charged into the storage tank, and the pitch floated in the water. . In Comparative Test 4, since the pressure was not sufficiently reduced, bubbles were contained as in Comparative Test 3.

Example 1 The operation conditions were the same as in Test No. 6 until melting, a nozzle was attached, melt spinning and fiber opening (opening cylinder air amount 11.7 Nm ^3).
/ H, the air supply amount of the opening cylinder / the air supply amount of the suction section = 1/3)
Then, a sheet is formed, and subsequently, the infusibilizing treatment (15
The activation treatment (furnace temperature: 900 ° C., steam activation: 40 minutes) was continuously performed from 0 ° C. to a final temperature of 400 ° C., and a heating rate of 5 ° C./min, to continuously produce activated carbon fibers for 10 days. At that time, the intake air temperature at the bag filter was set to 45 ° C.
Although the filter clogged with the filter was knocked off every three hours and the cycle operation of regeneration and reuse was possible,
In the case of 5 ° C., the vapor adhering to the filter becomes viscous, and it is difficult to regenerate.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a pitch continuous melt spinning apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Measurement charging device 2 ... Pitch charging port 3 ... Bucket conveyor 4 ... Bucket unit 5 ... Bucket unit shaft 6 ... Charging valve 7 ... Intermediate tank 8 ... Partition valve 9 ... Pitch storage tank 10 ... On-off valve 11 ... Decompression device 12 ... Extrusion Machine 13 ... Spinning head 14 ... Spinner pack 15 ... Spinneret Y ... Thread 16 ... Air supply pipe 17 ... Suction gun 18 ... Air introduction adjustment valve 19 ... Air introduction pipe 20 ... Connector 21 ... Opening tube 22 ... Decompression chamber 23 ... wire netting 24 ... low boiling point capturing device 25 ... intake pipe 26 ... intake blower 27 ... exhaust pipe 28 ... spinning chamber 29 ... air inlet 30 ... sheet forming chamber

Continued on the front page (72) Inventor Megumi Kibe 38 Kisehara Jingumae Sky Heights 38, Mise-cho, Kashihara-shi, Nara Prefecture 224 Ichiya-machi, Ichiya (72) Inventor Kenichi Fujii No. 302, No. 302, Otokuyama, Otokuyama, Yawata-shi, Kyoto (56) References JP-A-2-160965 (JP, A)

Claims (3)

(57) [Claims] In a melt spinning method for a pitch, the pitch is (i) loaded in a bucket unit having a loading weight of 1 kg or less, and (ii) the internal pressure is reduced to 200 Torr or less and connected in series via a gate valve. (Iii) Then, the pitch is conveyed to another storage tank at one end of the storage tank, and (iii) the pitch is sequentially introduced into another storage tank. v) A continuous melt spinning method for pitch, comprising discharging the pitch from a spinneret after melting, making the pitch fine with a suction gun, opening the fiber, and trapping low-boiling substances while depositing in a sheet form. 2. In a pitch melt spinning apparatus, (i) a storage tank immediately below a charging valve provided on a bucket conveyor is used as one end, and (ii) the storage tank is connected in series via a gate valve. (Iii) at least two of the storage tanks are depressurized to an internal pressure of 200 Torr or less, and (iv) an extruder connected to a spinning head at the other end of the two or more storage tanks in series. (V) a low-boiling-point substance capturing device is connected to an intake pipe introduced from a decompression chamber provided immediately below the opening tube installed in the sheet forming chamber adjacent to the spinning chamber; The connection position is
A pitch continuous melt spinning apparatus, wherein the temperature of the low boiling substance is 50 ° C. or less from the decompression chamber. 3. The method according to claim 1, wherein the trapping of the low-boiling substance is carried out by solidifying at a temperature of 50 ° C. or less through a cloth filter and filtering.
A continuous melt spinning method for the pitch described.