JPH0559620A - Active carbon fiber having large fiber diameter and its production - Google Patents

Abstract

PURPOSE:To obtain the objective active carbon fiber having prescribed values or above of BET specific surface area and diameter by melt spinning pitch, forming the melt into a pitch fiber sheet having bulkiness within a prescribed range, infusibilizing the pitch fiber sheet and then carrying out activating treatment. CONSTITUTION:Pitch obtained from petroleum-based or coal-based heavy oil as a raw material is melt-spun to provide a pitch fiber sheet having 10-25kg/m<3> bulkiness. The resultant sheet is subsequently infusibilized and then subjected to activating treatment to afford the objective active carbon fiber having >=500m<2>/g BET specific surface area and >=20mu fiber diameter.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an activated carbon fiber having a large fiber diameter and a method for producing the same.

[0002]

2. Description of the Related Art Cellulose fibers, acrylic fibers, special phenol resin fibers, pitch fibers and the like are conventionally known as activated carbon fibers. These activated carbon fibers include a heat treatment step (heat-resistant step or infusibilization step) of heat-treating a raw material precursor in an oxidizing atmosphere to convert it into heat-stabilized fibers, and an activation treatment step of obtaining activated carbon fibers from heat-stabilized fibers. Is manufactured through. The activation treatment step is an important step that is directly related to the development of adsorption / desorption properties of the activated carbon fiber, and this activation treatment results in the formation of micro voids that serve as adsorption conformations on the fiber surface. In order to improve the adsorption efficiency of the activated carbon fiber, it is necessary to improve the adsorption capacity of the adsorbent itself and increase the adsorbent filling amount (filling degree) per unit volume under constant ventilation resistance. That is, it is required to use activated carbon fibers having a diameter as large as possible. On the other hand, when a fiber having a small fiber diameter is used, the filling degree can be increased, but the air permeability is lowered, and as a result, the adsorption amount cannot be improved and it cannot be practically used as an adsorbent.

Further, in the above-mentioned activation treatment, generally, as the specific surface area of the fiber is increased with the passage of time, the fiber weight and the fiber diameter are decreased. For example, the original diameter is 20
When producing activated carbon fibers from pitch fibers of μm, BE
When a T specific surface area of 700 m ² / g is to be obtained, the final product has a fiber diameter of 18 μm, whereas when the specific surface area is 2000 m ² / g, the fiber diameter is significantly reduced to 12 μm. Will end up.

Therefore, in order to produce a large-diameter activated carbon fiber, a pitch fiber having a fiber precursor having a larger fiber diameter is required. In addition, among the various activated carbon fibers, cellulose fibers, acrylic fibers and phenol resin fibers have a large decrease in fiber weight and fiber diameter in the activation treatment step as compared with pitch fibers, so these raw material precursors A particularly large fiber diameter is required.

However, various conventional activated carbon fibers are
Winding after spinning It is manufactured by temporarily making a roll of fiber or sheet, infusible while releasing the roll, and activating it. However, when it is made into a roll, the volume density and curvature at the center part and the outer peripheral part of the roll become large. Because of the large difference, there will be more trouble than expected when there is no fusion. That is, especially in the case of pitch-based fibers,
The larger the fiber diameter, the more brittle it becomes, so it is inevitable that the pitch-based fibers will break or become powdery.
Therefore, when the fibers are infusible, the fibers are burnt, or conversely, infusibilization is insufficient and heat resistance cannot be imparted.

As described above, in the conventional activated carbon fiber, even in the case of the pitch type fiber, when the specific surface area is made relatively large to 500 m ² / g or more, only the fiber diameter of about 18 μm is produced. Therefore, the fiber diameter is 20μ
It is difficult or impossible to produce activated carbon fibers having a large diameter of m or more.

From the above viewpoint, at present, there is a strong demand for the development of activated carbon fibers having a large fiber diameter while maintaining the conventional adsorption capacity of activated carbon.

[0008]

The object of the present invention is to provide an activated carbon fiber having a large fiber diameter while maintaining an excellent adsorption capacity, that is, having a specific surface area of 500 m ² / g or more and a fiber diameter of 20 μm or more. To provide activated carbon fiber.

[0009] As a result of intensive studies conducted by the present inventors in view of the above problems, the adsorbing capacity can be increased from the viewpoint that the larger the fiber diameter is, the higher the filling rate and thus the adsorbing capacity can be increased under constant ventilation resistance. Fiber diameter 20 without loss
As a result of investigating a method for producing activated carbon fibers having a size of μm or more, when activated carbon fibers are produced from a sheet having a specific bulk density obtained after melt spinning of pitch, activated carbon fibers excellent in filling degree under constant ventilation resistance are obtained. The present invention has been completed and the present invention has been completed.

That is, the present invention has a BET specific surface area of 500.
The present invention relates to an activated carbon fiber having a diameter of m ² / g or more and a fiber diameter of 20 μm or more, and a method for producing the same. In this specification, the fiber diameter is 100
The fibers of a book are taken at random, and the average value of the diameter of each single yarn is meant.

It is essential that the activated carbon fiber of the present invention has a BET specific surface area of 500 m ² / g or more and a fiber diameter of 20 μm or more. The specific surface area is 500 m ² / g
If it is above, there is no limit on the upper limit, but the cost is 500.
It is preferably ˜2500 m ² / g. Similarly, the fiber diameter is not particularly limited as long as it is 20 μm or more, but if the diameter is too large, the above-mentioned trouble is likely to occur, so it is preferable to set it to 27 μm or less.

The method for producing the activated carbon fiber of the present invention includes:
Manufactured from pitch made from petroleum-based or coal-based heavy oil. The pitch is then melt spun to a bulk of 10
It is essential to use a fiber sheet of -25 kg / m ³ . If the bulk density of the fiber sheet is less than 10 kg / m ³ , the sheet is likely to be deformed when it is infusible, and inhomogeneity of infusibilization occurs. On the contrary, if the bulk density is more than 25 kg / m ³ , There is a problem that the air permeability becomes poor and fusion between fibers and combustion easily occur. In melt spinning, conventionally known melt spinning conditions can be widely applied. For example, the spinning temperature is preferably about 300 to 380 ° C., and the spinning speed is preferably about 500 to 4000 m / min. The bulk density of the fiber sheet can be adjusted to a desired bulk by changing, for example, the distance between the suction gun and the sheet forming device applied to pulling the yarn during melt spinning.

Next, the fiber sheet obtained above is infusibilized immediately without being wound up, and then activated. The conditions for the infusibilizing treatment and the activating treatment are not particularly limited, and those conventional conditions can be widely adopted.

When the activated carbon fiber obtained in the present invention is used, it can be used in various forms. In particular, when it is used as an adsorbent by filling it in various containers such as a filling cylinder, a certain ventilation resistance is obtained. Excellent effect below.
It is practically preferable to use the above ventilation resistance at about 200 mmAq or less.

[0015]

EFFECTS OF THE INVENTION According to the present invention, activated carbon fibers having a large fiber diameter and an excellent adsorptive capacity, which have been difficult or impossible to produce conventionally, that is, having a specific surface area of 500 m ² / g or more, and An activated carbon fiber having a fiber diameter of 20 μm or more can be provided. This activated carbon fiber has excellent filling properties and can improve the adsorption capacity under a constant ventilation resistance. Also, since the ventilation resistance with a certain adsorption capacity can be reduced,
Equipment noise can be reduced and products can be made compact.

[0016]

EXAMPLES Examples will be shown below to further clarify the characteristics of the present invention.

Each physical property in the present invention was measured by the following methods.

1) Specific surface area ... Cantachrome (QUANTA CH
Using a Quantasorb device manufactured by ROME), a nitrogen gas adsorption isotherm at liquid nitrogen temperature, so-called BET1
The measurement was performed by the point method.

2) Bulk density: The pitch sheet height before infusibilizing treatment was measured at four points in the sheet width (Wcm) direction, and the average value (Hcm), total discharge amount (G g / min) and sheet speed ( S g
/ min) and the value was calculated by the following formula.

Bulk density (kg / m ³ ) = (1000 × G) / (S × W × G) Example 1 A coal-based pitch with a softening point (SP) of 280 ° C. according to the METTLER measurement method is shown in FIG. Using a spinning device (2 spinning spindles), the spinning temperature was 325 ° C., the spinneret discharge hole diameter was 0.4 mm, and the number of holes per spinneret was 130, and the fiber diameter was changed while changing the spinning speed. By changing the distance between the sheet forming device (sheet width 80 cm) and the traction device (0.
5 to 2.5 m) The sheet weight is changed and the sheet areal weight is 62.
Keep the sheet speed constant (40 cm) so that it remains constant at 5 g / m ^2.
/ min), continuously spinning for 24 hours, followed by infusibilizing treatment (treatment from 200 ° C to 400 ° C),
Infusible pitch fiber sheet as shown in Table 1 (Sample No. 1 to
10) got. Regarding the non-melting operability in Table 1, ◯ indicates that no trouble occurred, and X indicates that fusion between fibers in the sheet or ignition occurred and it was impossible to operate continuously for 24 hours.

[0021]

[Table 1]

From the results shown in Table 1, the sample Nos. 1 and 2 having a sheet bulk smaller than the range of the present invention, and the samples No. 9 and 10 having a too large sheet bulk were ignited when they were not melted or the fibers were fused to each other to be continuous. It was impossible to operate.

Next, the sample No. having good non-melting operability
The infusible pitch fiber sheet of 3 to 8 was activated (940 ° C. under steam), and activated carbon fibers having almost the same specific surface area (sample
No. 11 to 16) were obtained respectively. The results are shown in Table 2.
Sample No. 17 in Table 2 was 870 ° C using the above sample No. 7.
The sample was obtained in the same manner as the other samples except that the activation temperature was adjusted in step.

Next, each of the obtained samples was subjected to a moisture content of 4 to 5 wt.
The humidity of the straight pipe is 60mm,
The filling weight and the filling weight ratio were measured when a filling cylinder having a fillable length of 50 mm was filled so as to have a pressure loss of 200 mmAq under a flow rate of 0.7 m / min. The results are shown in Table 2.

[0025]

[Table 2]

As shown in Table 2, the sample Nos. 14 to 17 of the present invention having a fiber diameter of 20 [mu] m and a specific surface area of 500 m < ² > / g, as compared with the samples No. 11 to 13 having a fiber diameter of less than 20 [mu] m.
With the activated carbon fiber of No. 3, the filling weight under the same ventilation resistance can be increased, and as a result, the adsorption amount per unit volume can be increased.

[Brief description of drawings]

FIG. 1 is a drawing showing an outline of a spinning device used in Example 1.

[Explanation of symbols]

 P ... Melting pitch Y ... Thread 1 ... Nozzle mouthpiece 2 ... Cooling device 3 ... Suction gun 4 ... Isolation wall 5 ... Air supply port 6 ... Adjusting valve 7 ... Spinning cooling chamber 8 ... Connection part 9 ... Opening cylinder 10 ... Sheet Holding wire mesh 11 ... Suction container part 12 ... Induction duct S ... Pitch fiber sheet

Claims (2)

[Claims] 1. An activated carbon fiber having a BET specific surface area of 500 m ² / g or more and a fiber diameter of 20 μm or more. 2. A pitch fiber sheet having a bulk of 10 to 25 kg / m ³ is melt-spun from a pitch made from petroleum-based or coal-based heavy oil as a raw material, and the sheet is subsequently infusibilized and then activated. The method for producing activated carbon fiber according to claim 1, wherein