JPH09268436A - Production of carbon fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing carbon fibers, capable of preventing the mixing adjacent precursor fibers due to the decrease in the distance among of the precursor fiber strands on a grooved roller for simultane ously sintering the precursor fibers and thereby capable of improving the process ability of the precursor fibers by blowing a gas toward the outside of the grooved roller for the precursor fibers on the feeding side of the grooved roller. SOLUTION: This method for producing carbon fibers contains guiding a plurality of precursor fiber 4 into the grooves of a grooved roller 3. Therein, just before the fibers 4 reach the roller 3, a gas 1 is blown from a pipe 2 for blowing the gas to the outside of the roller 3 in order to prevent the mutual interference of the adjacent fibers. The gas is preferably blown at a velocity of >=0.5m/sec and at a blowing angle of >=10 degree to the fibers. The tensions of the fibers at the gas-blowing positions are preferably 0.05-0.3g/d, and the gas is preferably blown on the fibers just in front of the fiber-guiding positions on the grooved roller.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a carbon fiber, in particular, by preventing interference of yarns when firing precursor yarns in parallel, the process passability is remarkably improved and the productivity is improved. The present invention relates to a method for producing carbon fiber, which is excellent in quality and can provide carbon fiber having excellent quality.

[0002]

2. Description of the Related Art Carbon fibers are acrylic, rayon,
A precursor yarn obtained by spinning a pitch-based or polyvinyl-based polymer or the like is passed through a flame-proofing process in which it is heat-treated in an oxidizing atmosphere at 200 to 400 ° C. to convert it into oxidized fibers, and then nitrogen, argon, It is obtained by undergoing a carbonization and graphitization step of heating at 300 to 3000 ° C. in an inert atmosphere such as helium, and is widely used for reinforced fibers for composite materials and applications utilizing electrical characteristics. Particularly in recent years, in addition to the conventional sports and aircraft applications, the demand for general industrial applications has increased sharply, so that a significant increase in production capacity is required along with cost reduction.

As a means for increasing the production capacity of carbon fiber,
For example, Japanese Patent Application Laid-Open No. 58-214532 discloses a method in which a plurality of precursor yarns are simultaneously run in parallel and fired. In such methods, grooved rollers are commonly used to prevent interference between adjacent yarns. Further, it is effective for improving the production capacity to make the spacing between yarns (hereinafter referred to as yarn pitch) by the grooved roller as small as possible and increase the yarn density.

However, when the yarn pitch is reduced, the ability to prevent interference between adjacent yarns by the grooved roll is exceeded, and mixed fibers occur at the single fiber level, and the fineness of the final product fluctuates. When the fibers are mixed again with a grooved roller after mixing, there are problems such as fluffing due to single fiber cutting at the roller edge and increased winding of the cut yarn around the roller. In particular, when mixed fibers between adjacent yarns occur in the flameproofing process, yarns with a large fineness are present in the flameproofing furnace, and the flameproofing exothermic reaction due to heat storage facilitates a runaway reaction. Therefore, in terms of disaster prevention, use of grooved rolls exceeding the ability to prevent interference between adjacent yarns was restricted. Further, when the yarn pitch is constant, a precursor yarn having a larger fineness per yarn is more likely to be mixed with an adjacent yarn, so that a thick yarn having a high production capacity and a high fineness In the case of producing a yarn, when changing the type, it is necessary to change to a grooved roller suitable for a thick yarn, and there is also a problem that a time loss is large when changing the type.

As a countermeasure against these problems, for example, Japanese Patent Application Laid-Open No. 58-87321 discloses a method in which a precursor yarn is twisted and fired, and the twist is returned after the firing. Japanese Patent Publication No. 47286 discloses a method of improving the convergence of yarns by subjecting the precursor yarns to air entanglement, but in both cases, the entanglement between the monofilaments constituting the yarns increases. There is a problem that the spreadability of the obtained carbon fiber deteriorates and it is difficult for the carbon fiber bundle to be uniformly impregnated with the matrix resin in the high-order processing step.

Further, as a means for preventing the fiber mixture between the adjacent yarns, a fixed or rotary type fiber separating bar may be arranged immediately before the grooved roller to forcibly prevent the fiber mixture. In the former, there is a problem that fluff occurs in the yarn due to contact and rubbing with the fixed bar, and in the latter, because a small diameter roller of about several millimeters is required, maintenance of the roller separating equipment tends to be complicated, and the separating function is There is a problem that it is difficult to maintain for a long time. Further, both of them have a problem that the removal work is hindered when the winding of the yarn occurs on the grooved roller.

In view of the above points, the present inventor has accomplished the present invention as a result of earnestly investigating a method that can realize stable production with a small yarn pitch, which could not be realized by the prior art.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems, that is, to reduce the yarn pitch when arranging grooved rollers for simultaneous multiple yarn firing in the carbon fiber manufacturing process. Prevents the adjacent yarns from being mixed with each other,
It is an object of the present invention to provide a carbon fiber manufacturing method capable of manufacturing a high-quality carbon fiber at low cost by improving the process passability.

[0009]

The present invention has the following constitution in order to solve the above problems. That is, in the method for producing a carbon fiber in which a plurality of precursor yarns are run in parallel using a grooved roller and fired, the precursor yarns on the grooved roller entry side are gas toward the outside of the grooved roller. Is a method for producing a carbon fiber.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

Generally, in the manufacturing process of carbon fibers, a precursor yarn such as an acrylic type or a pitch type is manufactured at 200 to 300 ° C.
After the oxidation treatment in the flameproofing furnace of No. 1, carbonization treatment in an inert atmosphere at 1000 to 2000 ° C., and if necessary, 2000
Graphitization under an inert atmosphere of ~ 3000 ° C, surface treatment for improving wettability with resin and handling.
It consists of winding after applying a sizing agent.
Then, in order to allow a plurality of precursor yarns to run in parallel and pass through each process, many grooved rollers are often arranged in order to prevent interference between adjacent yarns. Particularly, in the flameproofing process, in order to improve the productivity, it is common to fold and process the yarn in the flameproofing furnace, and the number of grooved rollers used is extremely large.

According to the present invention, when a plurality of yarns are guided into the groove of a grooved roller, gas is blown toward the outside of the roller in order to prevent interference between adjacent yarns before the yarns contact the roller. is there. As a result, it is possible to prevent the fluff contained in the yarn from being entangled with the grooved roller and prevent the fluff from winding around the roller.

The wind velocity of the gas blown is 0.5 m / se at a distance of 10 mm from the point where the yarn contacts the grooved roller.
It should be c or more, preferably 2 m / sec or more. If the wind speed is less than 0.5 m / sec, the effect of preventing the fibers from admixing to adjacent yarns will be reduced. In addition, the upper limit of the wind speed is 10 from the viewpoint of increasing the number of fluffs of the yarn and running cost.
It is desirable to set m / sec or less.

The blowing angle of the blowing gas to the yarn is not less than 10 ° so that it is more effective to direct the monofilament of the yarn which is the starting point of the mixed fiber toward the outside of the grooved roller. Is preferred. More preferably, when the angle is 45 ° or more, the effect is large, and when the angle is 90 ° or more, the effect becomes small because the wind velocity at a distance of 10 mm from the point where the yarn contacts the roller becomes small.

As a place to spray the gas, it is more effective and more efficient to spray the yarn immediately before being guided by the grooved roller.

In the present invention, the tension of the yarn at the gas blowing position maintains the processability and directs the single fiber of the yarn, which is the starting point of the mixed fiber, toward the outside of the grooved roller. From the viewpoint of being effective, 0.05 to 0.
It is good to set it in the range of 3 g / denier.

The type and temperature of the gas used in the present invention are
Although not particularly limited, it is desirable to use normal temperature air from the viewpoint of cost and safety during handling,
It is preferable to spray the pressurized gas by jetting it from a pipe, for example.

In the case of applying the present invention, the form of the yarn is a substantially non-twisted yarn in which the filament has a poorer focusing property than the so-called twisted yarn in which the yarn is twisted, and the single fiber is easily protruded from the groove. The effects of the present invention are more prominent. In particular, using a grooved roller, a plurality of thick non-twisted yarn precursor yarns are run in parallel with a yarn pitch of 10 mm or less, preferably 7 mm or less, and a total yarn fineness of 12,000 denier or more, preferably 18,000 denier or more. It exhibits a remarkable effect in the case of the grooved roller used in the flame-proofing treatment, and particularly in the initial stage of the flame-proofing in which the heat shrinkage in the flame-proofing remains. Although the lower limit of the yarn pitch depends on the fineness of the yarn and the groove shape, it is generally 3 mm or more so that adjacent yarns do not completely overlap each other in the air.

[0019]

EXAMPLES The present invention will be described in more detail below with reference to examples. In the present example, the number of times of fiber mixing is determined by visually observing the treated yarn length of the flame-resistant yarn monofilament to the adjacent yarn 10
The number of mixed fibers per km was examined, and the number of windings around the grooved roller per 10 km of the treated yarn length was examined to be used as a guide for the operation results. As a quality characteristic, in a running yarn from the flame-proofing process arbitrarily selected from the above precursor yarn group, the number of fluffs having a length of 1 cm or more was visually observed for 5 minutes × 10.
The yarn was measured and converted per 1 m.

(Examples 1 to 12) Single fiber fineness 1.0 denier × 24000 filaments of carbon fiber precursor acrylic yarn 200 yarns, groove depth 5 mm, groove opening angle 40
Groove having a groove shape of 6 ° and having a groove pitch of 6 mm are run in parallel with a grooved roller having 200 grooves, and subjected to an oxidation treatment at 250 to 280 ° C in a horizontal flame-proofing furnace of a hot air circulation system, and then heated at a maximum temperature of 1300 ° C in a nitrogen atmosphere. It was carbonized. In the flameproof furnace, a grooved roller for folding the yarn was arranged outside the furnace.
A SUS pipe with a hole diameter of 1 inch in which room temperature air is installed inside the roller and the yarn by changing the wind speed and the gas blowing angle as shown in Table 1 in the yarn entering the roller at the position shown in FIG. It was ejected from the hole. Table 1 shows the operation results and yarn quality characteristics at this time.

(Comparative Example 1) Carbon fibers were produced in the same manner as in Examples 1 to 12 except that gas was not blown.
Table 1 shows the operation results and yarn quality characteristics at this time.

[0022]

[Table 1] (Examples 13 to 20) Single fiber fineness 1.0 denier x 24
000 filament carbon fiber precursor acrylic yarn 2
The groove pitch of a grooved roller having 0 yarns, 20 groove-shaped grooves having a groove depth of 5 mm and a groove opening angle of 40 ° is 5, 7,
After changing to 9 and 11 mm and running in parallel, a horizontal flame-proofing furnace of a hot air circulation system was subjected to an oxidation treatment at 250 to 280 ° C, and then heated at a maximum temperature of 1300 ° C in a nitrogen atmosphere to carbonize. In the flameproof furnace, a grooved roller for folding the yarn was arranged outside the furnace. At the position shown in FIG. 1, on the yarn entering the roller,
The gas spray angle is 45 °, the wind speed is 0.5 m / sec,
The air temperature was changed to 5.0 m / sec, and normal temperature air was ejected from the holes of the SUS pipe with a diameter of 1 inch installed inside the roller and the yarn. Table 2 shows the operation results and yarn quality characteristics at this time.

(Comparative Examples 2 to 5) Carbon fibers were produced in the same manner as in Examples 13 to 16 except that the gas was not blown. Table 2 shows the operation results and yarn quality characteristics at this time.

[0024]

[Table 2]

[0025]

EFFECTS OF THE INVENTION According to the present invention, it is possible to prevent the adjacent yarns from being mixed with each other due to the reduction of the yarn pitch, improve the process passability, and efficiently change the type, while the high-quality carbon fiber Can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing how gas is blown in the present invention.

[Explanation of symbols]

 1: Spraying gas 2: Gas spraying pipe 3: Grooved roller 4: Precursor yarn

Claims (3)

[Claims] 1. A method for producing a carbon fiber in which a plurality of precursor yarns are run in parallel by using a grooved roller and fired,
A method for producing carbon fiber, characterized in that a gas is blown toward the outside of the grooved roller to the precursor yarn on the grooved roller entry side. 2. The method for producing a carbon fiber according to claim 1, wherein the distance between the yarns running in parallel is 10 mm or less. 3. The method for producing carbon fiber according to claim 1 or 2, wherein a blowing angle is 10 ° or more when the gas is blown to the precursor yarn.