JPH0364524A - Production of pitch yarn - Google Patents

Abstract

PURPOSE:To obtain high-quality yarn industrially stably by blending plural pitches having different softening points, specifying hole diameter of delivery hole and distance between the delivery hole and inner wall of cooling column and spinning. CONSTITUTION:Two or more pitches having >=5 deg.C different softening points are blended, stored in a tank 1, melted by an extruder 2, sent to a spinning pack 4 while being metered by a metering pump 3, spun from a spinneret 5 having 0.35-0.50mm pore diameter of delivery holes and cooled by a cooling column 6 which is equipped at the bottom of the spinneret 5 and has >=20mm distance A between the delivery hole and the inner wall to give the objective yarn Y.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is based on 9 fiber-forming pitches made from petroleum-based or coal-based heavy oil (hereinafter, fiber-forming pitch is abbreviated as pitch), The present invention relates to a method for producing pitch fibers on an industrial scale by a melt spinning method.

(Prior Art) Pitch fibers become activated carbon fibers by infusibility and activation treatment, and highly elastic and high strength carbon fibers by infusibility and carbonization treatment. Activated carbon fibers are used in the field of adsorbents for solvents, malodorous substances, etc., and carbon fibers are used in the field of reinforcing materials.

At present, nine typical pitch melt spinning methods include: (1) Centrifugal spinning method in which the molten pitch is spun while rotating the discharge section (Japanese Patent Application Laid-open No. 62-231008); (2) The molten pitch is spun directly below the discharge surface. Method of
However, the present invention relates to the melt spinning method (2) above, in which the pitch is spun in a direction directly below the discharge surface to make it finer.

Usually, in pitch melt spinning, the softening point is 200°C.
Pitch is used that has a softening point ranging from about 300°C to about 300°C. In other words, in pitch melt spinning, fibers cannot be stably obtained unless appropriate melting, heating, and cooling conditions are adopted depending on the softening point of the pitch. It was considered preferable to spin the yarn using a pitch of .

(Problem to be solved by the invention) If pitch with a small softening point range is melt-spun, pitch fibers can be stably obtained, and if this fiber is supplied to the subsequent process after infusibility, a certain level of quality can be achieved. However, the quality required by the market is becoming more and more sophisticated, and there has been a need for a method for manufacturing pitch fiber that meets the quality required by the market.

The technical object of the present invention is to provide a method for producing pitch fibers that can meet the increasingly sophisticated quality requirements of the market.

(Means for Solving the Problems) The present inventors have made the following findings as a result of intensive studies to solve the above problems.

Pitch fibers obtained by using a mixture of two or more pitches with softening points different by 5°C or more develop three-dimensional crimp (hereinafter referred to as crimp) when infusible, so the fiber aggregate The activated carbon fibers and carbon fibers obtained have a low bulk density and improve the permeability of heating fluid between the fibers in each step after infusibility, improving infusibility, carbonization, and activation efficiency.
The strength is superior to that of pitch fibers having a uniform softening point. Moreover, if a specific spinneret is used for spinning, even if a mixture of two or more types of pitches having a large difference in softening point is used, stable spinning is possible.

The present invention has been made based on the above findings.

That is, one aspect of the present invention is to melt-spun fiber-forming pitch,
When producing pitch fiber by pulling it through a cooling cylinder,
A mixture of two or more pitches with softening points different by 5°C or more is used, and the diameter of the discharge hole is 0.35 mm to 0.
50mm, and the shortest distance between the discharge hole and the inner circumference of the cooling cylinder is 2.
The gist of the present invention is a method for producing pitch fibers, which is characterized by spinning from a spinneret having discharge holes of 0 mm or more.

Hereinafter, one aspect of the present invention will be explained in detail.

FIG. 1 is a schematic process diagram showing one embodiment of the present invention. In FIG. 1, first, a mixed pitch of spinning raw materials stored in a pitch tank 1 is supplied to an extruder 2 and melted, and then, while being measured by a metering pump 3, the liquid is sent to a spinning pack 4 having a spinneret 5. .

The pitch yarn Y spun from the discharge hole of the spinneret 5 is passed through the cooling tube 6 installed directly below the spinneret 5.

~ While cooling and solidifying while maintaining the atmospheric temperature at the spinneret 5 at a depth of 150 mm below a temperature 10°C lower than the pitch softening point temperature on the low-temperature side, the yarn take-off device 7 is used to continue forming bows, webs, tows, sheets, etc. form a pitch fiber aggregate.

The pitch used in the present invention may be obtained by polycondensing either petroleum-based or coal-based heavy oil, but it has a softening point of 150°C or higher as measured by the Metcou method (according to JIS-2425). , particularly preferably 200°C to 320°C. If the softening point of the pitch is less than 150°C, draft breakage is likely to occur, and if it exceeds 320°C, the composition range of the volatile low-boiling substances generated will become wider, which will not only stain the spinneret surface but also cause yarn breakage. This is not preferable because it tends to occur more easily.

In addition, in the present invention, the softening point is 5° C. or higher.

It is extremely important to perform melt spinning using a mixture of two or more pitches that preferably differ by 7 to 10 degrees Celsius.If the difference in softening point of the pitches to be mixed is less than 5 degrees Celsius, the resulting pitch fibers will not be processed in the subsequent process. Even when treated with pitch fibers, it is not possible to produce a final product of higher quality than pitch fibers from those with a uniform softening point. on the other hand.

If the difference in softening point of the pitches to be mixed becomes too large.

The softening point difference is preferably 10° C. or less because single filament breakage is likely to occur during spinning, making it difficult to perform stable spinning for a long time.

As mentioned above, by melt-spinning a mixture of two or more pitches with softening points different by 5°C or more, the viscosity and cooling effect change at the single-filament level during melt-spinning, resulting in changes in the composition. Each of the pitch fiber single yarns is easily bent and formed. For example, when a web is formed by randomly arranging fibers following spinning and then supplied to the subsequent process after infusibility, when this web is infusible, shrinkage force unevenly distributed in the longitudinal direction of the fibers is applied to each single yarn. As a result, a zigzag-like three-dimensional crimp is likely to occur, and this crimp becomes more pronounced as the softening point difference of the mixed pitches increases.

In this way, a mixture of two or more pitches with softening points different by 5° C. or more is used for melt spinning.

When the obtained pitch fibers are infusible, a zigzag-like three-dimensional ring appears in each single filament, which reduces the bulk density of the fiber aggregate and increases the volume per unit weight.
The ability of the heating fluid to pass through the fibers in each step after infusibility is improved. For this reason.

It becomes possible to improve infusibility, carbonization, and activation efficiency, and to improve quality such as strength of activated carbon fibers and carbon fibers obtained.

As mentioned above, by using a mixture of two or more types of pitches with softening points different by 5°C or more, it is possible to create a final product of higher quality than pitch fibers made from pitch fibers with uniform softening points. In order to stably produce fibers, it is extremely important to specify the diameter of the discharge hole provided in the spinneret used and the shortest distance A between the discharge hole and the inner periphery of the cooling cylinder.

That is, the diameter of the discharge hole is 0.35 mm to 0.50 mm.
If the diameter is less than 0.35 mm, the discharge hole may become clogged or the life of the spinning pack may be shortened, which is not preferable. Moreover, if it exceeds 0.50 mm, when producing fibers with a diameter of 35 μm or less, which is the usual target, the amount of discharge between the discharge holes will occur, making it impossible to obtain stable spinning properties.

In addition, as shown in Fig. 2, the discharge hole and the cold J21JN
13 The shortest distance A between the inner circumferences, that is, the distance A between the outermost discharge hole 8 of the plurality of discharge holes provided in the spinneret and the inner circumference of the cooling cylinder 6 is 20 mm or more, preferably 30 mm or more.
mm to 60mm, and this distance is 20mm
If it is less than 1, or conversely if it is too large, cooling spots will occur between the single filaments during spinning, and filament adhesion and yarn breakage will easily occur, which is undesirable.

The upper limit of this distance is approximately 1150 mm in practical use.

The pitch fibers obtained by the present invention can be converted into infusible pitch fibers by heat treatment at 200°C to 400°C in an oxidizing gas atmosphere.

Activated carbon fibers can then be obtained by steam activation at 600°C to 1200°C. Also, 600℃~1
It can also be converted into carbon fiber by carbonizing at 500°C. Activated carbon fiber is a material with high industrial value as a high-performance adsorbent, and carbon fiber as a reinforcing fiber for composites.

(Example) Next, one embodiment of the present invention will be specifically explained using examples.

Example 1 Coal-based pitches with different softening points were mixed in a 1:1 weight ratio.
Using mixed pitches with various softening point differences,
Continuous spinning was carried out for 48 hours using a spinning apparatus similar to that shown in FIG. The spinning temperature at that time was the softening point of the pitch with a high softening point + 50°C, and the number of discharge holes in the spinneret (1@) was 13.
0 hole, total discharge amount 100g/min, take-up speed 2.50
Spinning at 0 m/min and continued.

A web was produced by depositing fibers on a conveyor whose speed was adjusted so that the basis weight was constant.

In addition, the diameter of the discharge hole of the spinneret is 0.40 mm (L
/D2) was used, and the cooling cylinder was installed so that the shortest distance between the discharge hole and the inner circumference of the cooling cylinder was 30 mm.

Each of the webs obtained above was made infusible at 400°C,
Subsequently, water vapor was activated at 900℃ to obtain a specific surface area of 1,500.
Activated carbon fibers of ±150 m2/g were obtained.

Table 1 shows the spinnability and the strength of single yarns obtained by producing activated carbon fibers from the pitch fibers under two conditions.

0 Judgment was made by the number of threads.

◎: Not at all, ○: 20 times or less, X: 5Q times or more.

The single filament strength is determined by filament 25 in any part of the activated carbon fiber.
The book was measured and the average value was displayed.

As is clear from Table 1, the single fiber strength of activated carbon fiber is 1
The results from Experiment Nos. 3 to 5, which are examples of the present invention, were larger than those from Experiment No. 1.2, which used a commonly used pitch.

The single fiber strength of activated carbon fibers tended to increase as the pitch softening point difference increased, but when the pitch softening point difference was too large, spinnability tended to decrease somewhat.

In addition, the pitches with softening points of 280°C and 290°C used in Experiment No. 4 were spun at five different mixing ratios from 1:9 to 9:1 by weight, but in each case, there was no effect on spinnability. There were no problems.

Example 2 A pitch obtained by mixing two types of pitches with softening points of 275°C, 280°C, and 285°C at a weight ratio of 1:1 was used, except that the arrangement of the discharge holes of the spinneret and the cooling cylinder were changed. Continuous spinning was carried out for 24 hours under the same spinning conditions as in Example 1. The spinnability at that time was evaluated by the number of occurrences of single yarn breakage, and the results are shown in Table 2.

The symbols in Table 1 represent the following.

DI: Occupied outer peripheral diameter of the discharge hole provided at the outermost periphery of the spinneret (mm) D2: Inner diameter of the cooling cylinder (mm) A: Distance between the discharge hole located at the outermost periphery of the spinneret and the inner periphery of the cooling cylinder Calculated as (D 2 D 1)/2 (mm).

Moreover, spinnability was evaluated based on the following criteria.

◎: No single thread breakage occurred.

Δ: Single yarn breakage occurred within 30 times.

×: Single thread breakage occurred more than 30 times.

As is clear from Table 2, in experiments Nos. 8 and 9, in which the distance A was within the range of the present invention, there was no occurrence of single yarn breakage even though the pitch softening point difference was large, and the spinnability was good. .

On the other hand, in Experiment Nos. 6.7 and 10, in which the distance is outside the scope of the present invention, even if the pitch softening point difference changes.

Spinnability was poor.

(Effects of the Invention) As described above, according to the present invention, pitch fibers can be stably produced even when a mixture of two or more pitches with softening points different by 5° C. or more is used for spinning. becomes possible.

Moreover, when the obtained pitch fibers are treated in each step after infusibility, the infusibility, carbonization, and activation efficiency can be improved, and the strength and other qualities of the obtained activated carbon fibers and carbon fibers can be improved. It is something.

[Brief explanation of drawings]

Figure 1 is a schematic process diagram showing one embodiment of the present invention;
The figure is a plan view showing a spinneret and a cooling cylinder. 2: Extruder 4: Spinneret pack 5: Spinneret 6: Cooling tube 8: Discharge hole

Claims (1)

[Claims] (1) When producing pitch fibers by melt-spinning fiber-forming pitch and taking it through a cooling tube, a mixture of two or more pitches with softening points different by 5°C or more is used, and the discharge holes are A method for producing pitch fiber, characterized by spinning from a spinneret having a hole diameter of 0.35 mm to 0.50 mm and provided with a discharge hole such that the shortest distance between the discharge hole and the inner periphery of the cooling cylinder is 20 mm or more. .