JP2834779B2 - Manufacturing method of pitch fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a fiber-forming pitch 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 when infusibilized and activated, and become highly elastic and high strength carbon fibers when infusibilized and carbonized. Activated carbon fiber is used in the field of adsorbents for solvents and odorous substances, and carbon fiber is used in the field of reinforcing materials.

At present, a typical pitch melt spinning method is a centrifugal spinning method in which spinning is performed while rotating a discharge section of a melt pitch (Japanese Patent Laid-Open No. 62-231008), and a method in which a melt pitch is spun directly below a discharge surface. (Japanese Unexamined Patent Publication No. Sho 62-268822), etc., and the present invention relates to the above-mentioned melt spinning method in which pitch is spun in the direction of making the ejection surface thinner and thinned.

Usually, the softening point is 200 ° C in pitch melt spinning.
From 300 to 300 ° C and a small softening point range. In other words, in the melt spinning of pitch, it is not possible to obtain fibers stably unless appropriate conditions such as melting, heating and cooling are adopted according to the softening point of the pitch. Spinning with a range of pitches has been found to be preferred.

(Problems to be Solved by the Invention) If pitch having a small softening point is melt-spun, pitch fibers can be obtained stably, and if the fibers are supplied to the subsequent process after infusibilization, a certain quality can be obtained. Activated carbon fiber or carbon fiber having the following characteristics can be used, but the quality required in the market is becoming more and more advanced, and a method of producing pitch fibers corresponding to the quality required in the market has been demanded.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing pitch fibers that can meet the quality requirements of an increasingly sophisticated market.

(Means for Solving the Problems) As a result of intensive studies to solve the above problems, the present inventors have found the following.

A pitch fiber obtained by using a mixture of two or more pitches having different softening points by 7 ° C. or more develops a three-dimensional crimp (hereinafter referred to as a crimp) at the time of infusibility.
The bulk density of the fiber aggregate is low, the permeability of the heating fluid between the fibers in each step after infusibility is improved, the infusibilization, carbonization and activation efficiency are improved, and the activated carbon fiber or carbon fiber obtained has a softening point. The strength is superior to that of uniform pitch fibers. Moreover, if spinning is performed using a specific spinneret, stable spinning can be performed even if a mixture of two or more pitches having a large difference in softening point is used.

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

That is, the present invention uses a mixture of two or more pitches having different softening points by 7 ° C. or more when melt-spinning a fiber-forming pitch and drawing it through a cooling cylinder to produce pitch fibers. Discharge hole diameter is 0.35mm ~ 0.50mm
The gist of the present invention is a method for producing pitch fibers, which comprises spinning from a spinneret provided with a discharge hole such that the re-short distance between the discharge hole and the inner circumference of the cooling cylinder is 20 mm or more.

 Hereinafter, the present invention will be described 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 sent to a spinning pack 4 having a spinneret 5 while being measured by a measuring pump 3. .

The pitch yarn Y spun from the discharge hole of the spinneret 5 is fed to the spinneret 5 by a cooling cylinder 6 installed immediately below the spinneret 5.
While cooling and solidifying while maintaining the ambient temperature at 150 mm below the surface at a temperature 10 ° C lower than the pitch softening point temperature on the low temperature side,
The yarn is taken up by the yarn take-up device 7 to form a continuous pitch fiber aggregate such as a web, a tow, and a sheet.

The pitch used in the present invention may be obtained by polycondensing any of petroleum-based and coal-based heavy oils.
The softening point measured by the Mettler method (JIS-K-2425) is 1
Those having a temperature of 50 ° C. or higher, particularly 200 ° C. to 320 ° C., are preferred. If the softening point of the pitch is lower than 150 ° C, draft breakage tends to occur. If the softening point of the pitch exceeds 320 ° C, the composition range of the generated volatile low-boiling substance is widened, which not only stains the spinneret surface but also causes yarn breakage. It is not preferable because it easily occurs.

In the present invention, it is extremely important to melt-spun a mixture of two or more pitches having different softening points of 7 ° C. or more, preferably 7 ° C. to 10 ° C. If the point difference is less than 7 ° C., even if the obtained pitch fiber is treated in a post-process, it cannot be a final product of higher quality than a pitch transition from a material having a uniform softening point. On the other hand, if the difference in softening points of the pitches to be mixed is too large, breakage of single yarns is likely to occur during spinning, making it difficult to stably spin for a long time.
The following is preferred.

As described above, melt spinning using a mixture of two or more pitches having different softening points by 7 ° C. or more results in changes in viscosity and cooling effect at the single yarn level during melt spinning. Each of the pitch fiber single yarns to be formed is easily bent and formed. For example, if the fibers are randomly arranged and formed into a web following spinning, and then supplied to the subsequent process after infusibility, when the web is made infusible, the shrinkage force unevenly distributed in the longitudinal direction of each fiber in each of the single yarns Because of the occurrence, a zigzag three-dimensional crimp is easily developed, and the crimp becomes more remarkable as the difference in softening point of the mixed pitch is larger.

In this way, when a mixture of two or more pitches having different softening points of 7 ° C. or more is melt-spun and the resulting pitch fibers are made infusible, a zigzag three-dimensional shape is applied to each single yarn. Crimp appears and the bulk density of the fiber aggregate decreases,
Since the volume per unit weight is increased, the inter-fiber permeability of the heating fluid in each step after infusibility is improved. For this reason, infusibilization, carbonization and activation efficiency are improved, and
It is possible to improve the quality such as the strength of the obtained activated carbon fiber or carbon fiber.

As described above, using a mixture of two or more pitches having different softening points by 7 ° C. or more, a pitch that can be made into a higher-quality final product than a pitch fiber having a uniform softening point. In order to stably produce the fibers, it is extremely important to specify the diameter of the discharge hole provided with the spinneret to be used and the shortest distance A between the discharge hole and the inner circumference of the cooling cylinder.

That is, it is necessary to use a discharge hole having a diameter of 0.35 mm to 0.50 mm. If the diameter is less than 0.35 mm, clogging of the discharge hole occurs and the life of the spinning pack is shortened, which is not preferable. In addition, if it exceeds 0.50 mm, it is usually set as a target.
In the case of producing fibers having a diameter of μ or less, discharge unevenness occurs between discharge holes, and stable spinnability cannot be obtained.

As shown in FIG. 2, the shortest distance A between the discharge hole and the inner circumference of the cooling cylinder, that is, the outermost discharge hole 8 and the cooling cylinder 6 among the plurality of discharge holes provided in the spinneret. The distance A from the inner circumference of the fiber must be 20 mm or more, preferably 30 mm to 60 mm. If this distance is less than 20 mm or too large, cooling spots occur between the single yarns during spinning, It is not preferable because the adhesion of filaments and thread breakage are likely to occur.
The upper limit of this distance is about 150 mm for 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. Then 600 ℃ ~ 1200 ℃
Activated carbon fibers can be formed by activating steam. It can also be converted to carbon fiber by carbonization at 600 to 1500 ° C. Activated carbon fiber is a material with high industrial value as a high-performance adsorbent, and carbon fiber is a reinforcing fiber for composites.

(Examples) Next, the present invention will be described specifically with reference to examples.

Example 1 Coal-based pitches having different softening points were mixed at a weight ratio of 1 to 1, and a mixed pitch having variously changed softening points was used, and continuous spinning was performed for 48 hours using the same spinning apparatus as in FIG. did. The spinning temperature at that time is the softening point of the pitch having a high softening point + 50 ° C, and the number of discharge holes of the spinneret (1 spindle) is 130.
The web was manufactured by spinning holes at a total discharge rate of 100 g / min and a take-up speed of 2,500 m / min, and subsequently depositing fibers on a carrier whose speed was adjusted to keep the basis weight constant.

The spinneret has a discharge hole diameter of 0.40 mm (L / D =
2) The cooling cylinder was arranged 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 is made infusible at 400 ° C,
Subsequently activated by steam at 900 ° C, the specific surface area was 1,500 ± 150m ² /
g of activated carbon fiber was obtained.

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

In addition, the single yarn strength was measured by measuring 25 filaments in an arbitrary portion of the activated carbon fiber, and the average value was displayed.

As is apparent from Table 1, the single yarn strength of the activated carbon fiber was higher than those of Experiment Nos. 1 and 2 using the commonly used pitches, in Experiment Nos. 3 to 5 of the embodiment of the present invention.
Things from were big.

The single-strength of activated carbon fiber increased orally as the softening point difference of pitch increased, but the spinnability tended to decrease slightly if the softening point difference of pitch was too large.

In addition, the pitch at the softening point of 280 ° C. and 290 ° C. used in Experiment No. 4 was spun at five different mixing ratios from 1 to 9 to 9 to 1 in weight ratio. There was no problem.

Example 2 A pitch obtained by mixing two kinds of pitches having a softening point 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. Example 1
Under the same spinning conditions, continuous spinning was performed for 24 hours each. The spinnability at that time was evaluated by the number of occurrences of single yarn breakage, and the results are shown in Table 2.

As is clear from Table 2, in Experiment Nos. 8 and 9 in which the distance A was within the range of the present invention, single yarn breakage did not occur even if there was a difference in the softening point of the pitch, and the spinnability was good.

On the other hand, in Experiment Nos. 6, 7, and 10 in which the distance A was out of the range of the present invention, the spinnability was poor even if the softening point difference of the pitch was changed.

(Effects of the Invention) As described above, according to the present invention, it is possible to stably produce pitch fibers even when spinning using a mixture of two or more pitches having different softening points by 5 ° C or more. Becomes possible.

In addition, the infusibilization, carbonization and activation efficiency are improved when the pitch fibers are obtained and are treated in each process after infusibilization.
Further, the quality of the obtained activated carbon fiber or carbon fiber, such as the strength, can be improved.

[Brief description of the drawings]

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

──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsumi Fujita 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi, Osaka (72) Koji Shinohara 7-84 Terada Fukaya, Joyo-shi, Kyoto Masanori 55 Ujikageyama, Uji-city, Kyoto 55 (72) Inventor Kenichi Fujii 7-Yoshinori Otoyama, Yawata-shi, Kyoto 10 Building No. 302, Examiner Tadahiro Sanada (56) JP-A-61-201005 (JP, A) JP-A-59-168114 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) D01F 9/14, 9/145 D01D 4/02 , 5/092

Claims (1)

(57) [Claims] 1. A fiber-forming pitch which is melt-spun and drawn through a cooling cylinder to produce pitch fibers, wherein a mixture of two or more pitches having different softening points by 7 ° C. or more is used and discharged. A method of producing a pitch fiber, comprising spinning from a spinneret having a discharge hole such that the hole diameter is 0.35 mm to 0.50 mm and the shortest distance between the discharge hole and the inner circumference of the cooling cylinder is at least 20 mm. .