WO2019167344A1

WO2019167344A1 - Fiber production method and carbon fiber production method

Info

Publication number: WO2019167344A1
Application number: PCT/JP2018/040807
Authority: WO
Inventors: 長坂拓哉; 石尾桂一; 古川直幸
Original assignee: 東レ株式会社
Priority date: 2018-02-27
Filing date: 2018-11-02
Publication date: 2019-09-06
Also published as: US20200407885A1; CN111684114B; EP3760768A4; EP3760768A1; CN111684114A; JPWO2019167344A1; KR20200123776A; RU2020126570A; JP7234634B2

Abstract

A fiber production method for discharging a spin dope made by dissolving a fiber-forming polymer in a solvent from a spinneret 1 and after first running the fiber through air, guiding the same into the liquid of a coagulation bath 3 and coagulating, wherein the air flow (Af) per unit time of a gas phase section formed vertically downward between the discharge surface of the spinneret 1 and the liquid surface of the coagulation bath 3 with respect to the solvent volume (As) in the spin dope per unit time in the gas phase section volume (Vh) satisfies the relational expression 0.0008 m³ ≤ Af/(As/Vh) ≤ 0.0015 m³ and the average one-hour value for absolute humidity at each of four points on the perimeter of the spinneret in the gas phase section is not more than 20 g/m³. Provided is a fiber production method that, in dry spinning, is capable of limiting the generation of condensation on the spinneret, mitigating quality reduction due to winding onto rollers in subsequent steps and to fuzz and yarn breakage in the stretching step, and significantly increasing overall productivity and quality.

Description

Fiber manufacturing method and carbon fiber manufacturing method

The present invention relates to a method for producing a fiber, which can obtain a fiber by remarkably stabilizing the running property of a yarn without generating condensation or water droplets on the spinneret surface when obtaining the fiber by a dry-wet spinning method. is there.

In order to obtain fibers by spinning a fiber-forming polymer that is difficult to melt, such as polyacrylonitrile, a wet spinning method or a dry-wet spinning method is employed. Among these, the dry and wet spinning method is a method in which a spinning stock solution in which a fiber-forming polymer is dissolved in a solvent is discharged from a spinneret, and once run in a gas, it is immediately introduced into a coagulation bath liquid and solidified. However, compared to the wet spinning method, the draft is relaxed in a gas with no bath resistance, so it can be spun at a high speed or a high draft, and can be used for the production of clothing and industrial fibers. Has been. In addition, since the wet and wet spinning method can make the fibers more dense, it has recently been used for the production of high strength and high modulus carbon fiber precursor fibers. To increase productivity.

In such a dry-wet spinning method, a spinning solution is extruded from a spinneret installed outside a coagulation bath, and therefore a gas phase portion exists between the die surface and the coagulation bath, and high-speed spinning or one spinneret If so-called multi-hole formation is performed to increase the number of holes in the gas, the vapor of the solvent constituting the spinning dope increases in the gas phase, and this vapor stays in the gas phase, and condensation tends to occur on the spinneret surface. Become. Condensed droplets close the discharge hole of the spinneret, close the fibers, unevenness of fineness, single yarn breakage, and further, the droplets come into contact with the coagulation liquid surface, so that they become immersed in the die, and the wrapping of the rollers in the subsequent process and drawing process This leads to fluff and thread breakage, and significantly reduces operability and quality. Such a problem is particularly noticeable by performing high speed spinning or increasing the number of holes in the spinneret to increase productivity.

For the purpose of improving these problems, there has been proposed a method for preventing dew condensation by circulating a gas from one direction between the spinneret surface in dry and wet spinning and the gas phase part of the coagulation bath (Patent Document 1).

Further, even in a multi-hole base having more than 2,000 holes, the solvent vapor is obtained by alternately sucking the gas in the gas phase formed between the discharge surface of the spinneret and the coagulation bath from two directions sandwiching the discharge surface. A method for preventing stagnation is studied (Patent Document 2).

In addition, in order to suppress dew condensation on the base surface by controlling the temperature and humidity around the base, a method of circulating air adjusted in temperature and humidity surrounding the coagulation chamber has been studied (Patent Document 3).
JP-A-5-044104 JP 2007-239170 A JP 2010-236139 A

When the number of holes used in the spinneret is as small as about 300 holes, for example, even the technique proposed in Patent Document 1 may be able to effectively suppress condensation, but with a number of 2,000 holes or more. In addition, the vapor density of the solvent is likely to stay in the gas phase part where the hole density is increased and the height of the gas phase part between the spinneret discharge surface and the coagulating bath liquid level is less than 20 mm vertically in the wet and wet spinning. In terms of conditions, even when the technique proposed in Patent Document 1 is applied, there is a problem in that airflow drifts and vapor stays, and condensation cannot be eliminated.

Further, in Patent Document 2, when the pore density is high, there is a problem that the suction of the gas phase portion is not sufficient and the vapor of the solvent is aggregated, and aggregation is progressed and condensation occurs on the surface that is not exhausted.

Regarding Patent Document 3, controlled air was introduced into the discharge hole of the outer base portion of the base, but the controlled air did not reach the inside of the base, and the effect was insufficient to suppress condensation. Furthermore, since the temperature and humidity control is performed by enclosing the entire coagulation chamber, the increase in equipment and the cost of equipment increase, making it practically difficult.

The object of the present invention is, for example, a high density of holes of 2,000 holes or more, and further, the height of the gas phase formed between the spinneret discharge surface in the dry and wet spinning and the coagulating bath liquid level vertically downward. Even under the condition of less than 20 mm, it suppresses the occurrence of condensation in the spinneret, improves the reduction in quality due to roller wrapping in the subsequent process, fluff in the drawing process, and yarn breakage, and greatly increases productivity and quality as a whole. It is in providing the manufacturing method of the fiber which can be performed.

In order to solve the above problems, the fiber manufacturing method of the present invention has the following configuration. That is,
In a method for producing a fiber in which a spinning stock solution in which a fiber-forming polymer is dissolved in a solvent is discharged from a spinneret, once run in air, and then guided into a coagulation bath liquid to be solidified, the discharge surface of the spinneret The amount of air (Af) per unit time in the gas phase formed between the coagulating bath and the liquid level vertically downward is the amount of solvent (As) in the spinning dope per unit time in the volume (Vh) of the gas phase ^{0.0008m 3 ≦ Af / (As /} Vh) ≦ 0.0015m satisfies the ^third relationship, 1 hour average value of the absolute humidity at the mouthpiece outer periphery four points in the gas phase portion, respectively 20 g / ^{m 3} with respect to It is the manufacturing method of the fiber which is the following.

Moreover, the manufacturing method of the carbon fiber of this invention has the following structure. That is,
A method for producing carbon fiber, comprising producing a fiber by the above-described fiber production method, flameproofing in an oxidizing atmosphere at 200 to 300 ° C., and then heating in an inert atmosphere at 1,000 ° C. or higher.

In the fiber manufacturing method of the present invention, it is preferable that the relative standard deviation of the wind speed at the four points on the outer periphery of the base in the gas phase part is 40% or less.

In the fiber production method of the present invention, the number of holes in the spinneret is preferably 2,000 or more and 50,000 or less.

In the fiber production method of the present invention, the fiber-forming polymer is preferably an acrylonitrile-based polymer.

According to the present invention, for example, even in the dry and wet spinning conditions in which the hole density of 2,000 holes or more is high, and the distance between the spinneret and the coagulation bath liquid is less than 20 mm, the occurrence of condensation in the spinneret is suppressed. Roller winding in the subsequent process, fluff in the stretching process, and quality degradation due to yarn breakage can be improved, and productivity and quality can be greatly improved as a whole. In particular, it is suitable for producing acrylonitrile-based precursor fibers for carbon fibers.

It is an example of the schematic top view and front view of a spinning area | region at the time of installing an air supply nozzle or an exhaust nozzle in this invention.

Hereinafter, the present invention will be described in more detail.

The method of the present invention can be used when producing acrylonitrile fiber for clothing, acrylonitrile fiber for carbon fiber production, aromatic polyamide fiber, etc., but particularly when producing acrylonitrile fiber for carbon fiber production, The effect is most noticeable.

In the present invention, a spinning stock solution in which a fiber-forming polymer is dissolved in a solvent is used. As the fiber-forming polymer, an acrylonitrile-based polymer, an aromatic polyamide, or the like can be used. As the polymerization method for obtaining the polymer, solution polymerization, emulsion suspension polymerization, bulk polymerization and the like are used, and either a batch method or a continuous method may be used.

As the solvent in which the polymer is dissolved, in the case of an acrylonitrile-based polymer, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), an aqueous zinc chloride solution (ZnCl ₂ aq), an aqueous sodium thiocyanate solution ( NaSCNaq) or the like can be used, but in terms of productivity, DMSO, DMF, or DMAc, which has a high solidification rate of the polymer, is preferable in the dry and wet spinning method, and DMSO is particularly preferable because of its particularly high solidification rate.

Such a spinning dope is discharged from a discharge surface of a spinneret placed on a coagulation bath via a gas phase part, and coagulated in a coagulation bath to form fibers.

Regarding the temperature of the spinning dope and the temperature of the coagulation bath, the difference between the atmospheric temperature and the dew point (atmosphere temperature-dew point) of the gas phase formed between the spinneret discharge surface and the coagulation bath liquid surface vertically downward is as much as possible. Conditions that appear large are preferred.

As the temperature of the spinning dope, the lower the temperature, the less the amount of evaporation of the solvent is preferable, and it should be above the freezing point of the solvent used in the spinning dope, above the freezing point, freezing point + 20 ° C. or below, and further freezing point + 5 ° C. or above. The freezing point is preferably 15 ° C. or lower. When the temperature of the spinning dope is within this preferred range, the spinning dope viscosity is maintained moderately, the spinnability is good, and the operability is excellent. As the coagulation bath, an aqueous solution of the same solvent as that used for the stock solution for spinning is usually used. However, since condensation easily occurs particularly in an organic solvent system, when an aqueous solution of DMSO, DMF, or DMAc is used as the coagulation bath. In particular, the effect of the present invention appears remarkably. The upper limit of the temperature of the coagulation bath is preferably 20 ° C. or lower, more preferably 10 ° C. or lower, and further preferably 7 ° C. or lower. When the upper limit of the temperature of the coagulation bath is within this preferred range, the occurrence of condensation can be effectively suppressed. The lower limit of the temperature of the coagulation bath is preferably 0 ° C. or higher, more preferably 1 ° C. or higher. When the lower limit of the temperature of the coagulation bath is within this preferred range, the spinnability is good and the operability is excellent.

The number of holes in the spinneret is preferably 2,000 or more and 50,000 or less, and more preferably 4,000 or more and 20,000 or less. When the number of holes is within this preferred range, productivity is good, while the mass of the die is not excessively large and workability is easily ensured, and an increase in equipment costs can be prevented. It is preferable to use a die occupied area per hole (spinner die area ÷ number of holes) of 5 mm ² or more and 10 mm ² or less. When the area occupied by the die per hole is in this preferred range, productivity is good, but sufficient gaps cannot be secured in the gas phase part between the spinneret and the coagulation bath during dry / wet spinning. However, the occurrence of condensation can be effectively prevented.

In the present invention, the air volume per unit time (Af) of the gas phase portion formed between the discharge surface of the spinneret and the coagulation bath liquid surface is the spinning dope per unit time in the volume (Vh) of the gas phase portion. The relational expression of 0.0008 m ³ ≦ Af / (As / Vh) ≦ 0.0015 m ³ is satisfied with respect to the amount of solvent (As) in the sample, and at four points on the outer periphery of the die in the gas phase (measurement points A to D It is important that the one-hour average values of absolute humidity of 20) are 20 g / m ³ or less.

For that purpose, for example, a dehumidifying air blower is installed at a position away from the spinneret, and a method of blowing a certain amount of air to the gas phase part, or an air supply nozzle or exhaust nozzle is installed around the base to supply and exhaust air simultaneously. And a method of switching the supply / exhaust direction over time.

In the present invention, Af / (As / Vh) is set to 0.0008 m ³ or more and 0.0015 m ³ or less, preferably 0.0009 m ³ or more and 0.0014 m ³ or less, more preferably 0.0010 m ³ or more. 0.0013 m ³ or less. When it exceeds 0.0015 m ³ , the liquid level of the coagulation bath is shaken, the spinnability becomes unstable, and the effect becomes insufficient. Moreover, it is good that the 1 hour average value of the absolute humidity at the base outer peripheral portion 4 points is 20 g / m ³ or less, preferably 15 g / m ³ or less, more preferably 10 g / m ³ or less.

From the viewpoint of scavenging without variation in the wind speed at the four points on the outer periphery of the base, the relative standard deviation of the wind speed at the four points on the outer periphery of the base is preferably 40% or less, more preferably 20% or less, and even more preferably 10% or less. When the relative standard deviation of the wind speed at the four points on the outer periphery of the die is within this preferable range, it is possible to suppress the occurrence of condensation on the spinneret discharge surface regardless of the shape of the die such as a circle or rectangle.

In the present invention, the air volume per unit time (Af) is determined from the wind speed measured at the four points of the outer periphery of the base, which is the measurement point, at one point located upstream of the air flow and the spinning base from the upstream side of the air flow. Calculated from the cross-sectional area at that time. The volume (Vh) of the gas phase part is calculated from the discharge area calculated from the nozzle outermost discharge hole and the height of the gas phase part formed between the discharge surface and the coagulating bath liquid level vertically downward. The solvent amount (As) in the discharge stock solution is the amount of solvent contained in the stock solution discharged from the die per unit time.

In addition, in the present invention, the wind speed and absolute humidity at the four points on the outer periphery of the base, as shown in FIG. Measure at a midpoint and at a position 30 mm away from the outermost discharge hole of the base. Here, in the present invention, for example, when the base shape is circular, any of the four points on the outer peripheral circle that uniformly divides the outer peripheral circle into four can be selected. In the case of a rectangle, four midpoints of each line segment constituting the outer periphery can be selected. The wind speed, temperature, and relative humidity can be measured using Kurimo Master MODEL6501 (Nippon Kanomax Co., Ltd.). The absolute humidity (AH) [g / m ³ ] is calculated from the temperature (T) [° C.] and the relative humidity (RH) [%] measured by the crimomaster using the following calculation formula. (E: saturated vapor pressure [hPa])
e = 6.11 × 10 ^{(7.5 T / (T + 237.3))}
AH = 217 × e / (T + 273.15) × RH / 100
Here, the one-hour average value of absolute humidity at the four points on the outer periphery of the base is obtained by measuring the wind speed, temperature, and relative humidity 12 times at 5-minute intervals as described above, and calculating the absolute humidity using the above formula. It is the average value of each measurement point.

Further, when a gas supply or exhaust nozzle is used for supplying or exhausting gas, the nozzle is oriented so that the nozzle outlet is in the direction of the nozzle and parallel to the coagulation bath liquid surface, as shown in FIG. Specifically, it is preferable that the nozzle installation angle is inclined from 60 ° to 120 °, more preferably from 80 ° to 100 °, from vertically downward (0 °) toward the die. More preferably, the angle is 90 °. FIG. 1 shows a case where the nozzle installation angle is 90 ° as an example. When the installation angle of the nozzle (nozzle angle) is 90 °, the vapor generated from the solvent can be efficiently scavenged, and condensation on the spinneret surface can be extremely effectively suppressed. When the installation angle of the nozzle is within this preferred range, in the case of an air supply nozzle, the airflow is difficult to be turbulent because it hits the base surface, stagnation does not occur, and condensation generation can be effectively prevented. Although the generated vapor is easily sucked while being in contact with the base surface, the growth of the droplets can be effectively prevented. On the other hand, both the supply nozzle and the exhaust nozzle are less likely to cause fluctuations in the coagulation bath liquid level, and effectively suppress phenomena that adversely affect quality and process stability, such as base soaking and contact between single threads where the liquid level touches the base. Can do.

The present invention is particularly effective when an acrylonitrile-based fiber, particularly an acrylonitrile-based fiber that is a carbon fiber precursor, is produced using an acrylonitrile-based polymer. Specific conditions in that case will be described in detail below. .

As the spinning dope for dry / wet spinning, a solution in which acrylonitrile polymer composed of 90% by mass or more of acrylonitrile and a vinyl monomer copolymerizable therewith is used. When the copolymerization ratio of acrylonitrile in the acrylonitrile polymer is within this preferable range, the carbon fiber obtained by firing the acrylonitrile fiber obtained by the method of the present invention has high strength and has excellent mechanical properties. It becomes easy to manufacture. Also, if the polymer concentration in the spinning dope is within this preferred range, the solvent content is adequate, and the solvent vapor amount is too high in the gas phase part between the spinneret and the coagulation bath liquid in dry and wet spinning. Condensation is unlikely to occur, and on the other hand, viscosity increase and gelation can be suppressed when polymerizing acrylonitrile-based polymers, and it is difficult to block the spinneret discharge holes during dry-wet spinning. It can effectively prevent fineness, fineness and single fiber breakage, and can effectively prevent roller wrapping in the subsequent process, fluff and thread breakage in the stretching process, and it is excellent in operability and effectively prevents product quality degradation. be able to.

The present invention can be suitably used when the number of filaments per fiber is usually in the range of 2,000 to 50,000, and the single fiber fineness is usually in the range of 0.5 dtex to 3 dtex. The fiber fiberized in the coagulation bath may be stretched directly in a stretching bath, or may be stretched in the bath after the solvent is washed away with water.

After stretching in the bath, oil is usually applied and dried with a hot roller or the like. If necessary, after that, stretching such as steam stretching is performed to obtain a fiber.

Hereinafter, a method for producing carbon fibers from fibers obtained by a method for producing fibers in which the fiber-forming polymer is an acrylonitrile-based polymer will be described.

The acrylonitrile fiber produced by the above-described method for producing acrylonitrile fiber is flameproofed in an oxidizing atmosphere such as air at 200 to 300 ° C. It is preferable to increase the treatment temperature in multiple steps from low temperature to high temperature in order to obtain flame-resistant fibers, and further, drawing the fibers at a high draw ratio within a range not accompanied by the generation of fluff improves the performance of the carbon fiber. It is preferable for sufficient expression. Next, the obtained flame-resistant fiber is heated to 1,000 ° C. or higher in an inert atmosphere such as nitrogen to produce carbon fiber. Thereafter, by performing anodization in an aqueous electrolyte solution, it is possible to impart a functional group to the surface of the carbon fiber and enhance the adhesion to the resin. Moreover, it is preferable to provide a sizing agent such as an epoxy resin to obtain carbon fibers having excellent scratch resistance.

Hereinafter, the present invention will be described more specifically with reference to examples. Note that the wind speed and absolute humidity at the four points on the outer periphery of the base used in this example are the midpoint of the height from the liquid level to the base surface of the part where the rectangular base outer periphery is equally divided into four as shown in FIG. Measurement was performed at a position 30 mm away from the outermost discharge hole of the die. The wind speed, temperature, and relative humidity were measured using Kurimo Master MODEL6501 (Nippon Kanomax Co., Ltd.). The absolute humidity (AH) [g / m ³ ] was calculated from the temperature (T) [° C.] and the relative humidity (RH) [%] measured by the crimomaster using the following formula (e: saturated vapor pressure [ hPa]).

e = 6.11 × 10 ^{(7.5 T / (T + 237.3))}
AH = 217 × e / (t + 273.15) × RH / 100
Here, the one-hour average value of absolute humidity at the four points on the outer periphery of the base is obtained by measuring the wind speed, temperature, and relative humidity 12 times at 5-minute intervals as described above, and calculating the absolute humidity using the above formula. It was set as the average value of each measurement point.

In addition, the air volume per unit time (Af) is the wind speed measured at four measurement points at one point located on the upstream side of the air flow and the cross-sectional area when the spinneret is viewed from the upstream side of the air flow. Calculated. The volume (Vh) of the gas phase part was calculated by the discharge area calculated from the outermost discharge hole of the die and the height of the gas phase part formed between the discharge surface and the coagulating bath liquid level vertically downward. The solvent amount (As) in the discharged stock solution is the amount of solvent contained in the stock solution discharged from the die per unit time.

The degree of condensation on the base surface, the grade of acrylonitrile fiber, and process stability were determined as follows.

(Degree of condensation on the base)
The degree and number of condensation on the spinneret surface when spinning was continued for one week were measured, and converted into points according to the following criteria.

Condensation diameter to less than 2 mm: 1 point / piece Condensation diameter of 2 mm to less than 5 mm: 5 points / piece Condensation diameter of 5 mm or more: 10 points / piece

(Quality of acrylonitrile fiber)
Before winding up the acrylonitrile fiber, the number of fluff of acrylonitrile fiber for 1,000 m was counted, and the quality was evaluated in five stages. The evaluation criteria are as follows.

1: (Number of fluffs / 1 fiber, 1,000 m) ≦ 1
2: 1 <(number of fluffs / 1 fiber, 1,000 m) ≦ 2
3: 2 <(number of fuzz / 1 fiber / 1,000 m) ≦ 5
4: 5 <(number of fuzz / 1 fiber / 1,000 m) <60
5: 60 ≦ (number of fluffs / 1 fiber · 1,000 m).

(Process stability of acrylonitrile fiber)
The evaluation was made in five stages from the number of yarn breaks during the production of 10t acrylonitrile fiber. The evaluation criteria are as follows.

1: (number of thread breakage / manufacturing acrylonitrile fiber 10t) ≦ 1
2: 1 <(number of yarn breaks / acrylonitrile fiber 10t production) ≦ 2
3: 2 <(number of yarn breaks / production of 10t acrylonitrile fiber) ≦ 3
4: 3 <(number of yarn breaks / production of 10 t acrylonitrile fiber) <5
5: 5 ≦ (number of yarn breaks / production of 10 t acrylonitrile fiber).

<Examples 1 to 4>
A DMSO solution of an acrylonitrile polymer consisting of 99% by mass of acrylonitrile and 1% by mass of itaconic acid was prepared by solution polymerization.

The obtained acrylonitrile-based polymer solution (spinning stock solution) was discharged into the air once from the discharge surface of the spinneret using a base having a total of 6,000 stock solution discharge holes, and then passed through the gas phase part, and then DMSO35. It discharged in the coagulation bath liquid which consists of mass% / water 65 mass%, and obtained the coagulation fiber.

Here, at the time of spinning, an air supply nozzle and an exhaust nozzle having an opening of 5 mm × 200 mm are installed on the front side of the spinneret so as to sandwich the base, and air dehumidified from the air supply nozzle is blown, and the exhaust nozzle By sucking, the solvent vapor generated in the gas phase portion between the discharge surface and the coagulation bath was scavenged. In each example, the nozzle angle of the supply / exhaust nozzle, Af / (As / Vh), and the wind speed relative standard deviation at each of the four measurement points were changed as shown in Table 1. Table 1 shows the degree of condensation on the discharge surface and the quality and process stability of the acrylonitrile fiber in each example.

After the obtained coagulated fiber is washed with water, an oil agent is applied while being stretched in a bath stretching process, and a 6,000 acrylonitrile fiber can be stably produced through a drying and stretching process. did it.

<Example 5>
Acrylonitrile-based precursor fibers were obtained in the same manner as in Examples 1 to 4, except that Af / (As / Vh) was changed as shown in Table 1 and the degree of dehumidification was increased.

<Example 6>
Af / (As / Vh) was changed as shown in Table 1, and acrylonitrile-based precursor fibers were obtained in the same manner as in Examples 1 to 4, except that a 9,000-hole cap was used.

<Example 7>
Acrylonitrile-based precursor fibers were obtained in the same manner as in Examples 1 to 4, except that Af / (As / Vh) was changed as shown in Table 1 and a 2,000-hole cap was used.

<Comparative Example 1>
Acrylonitrile-based precursor fibers were obtained in the same manner as in Examples 1 to 4, except that Af / (As / Vh) was changed as shown in Table 1 and the air supply / exhaust nozzle was not operated.

<Comparative example 2>
Acrylonitrile-based precursor fibers were obtained in the same manner as in Examples 1 to 4, except that Af / (As / Vh) was changed as shown in Table 1.

<Comparative Example 3>
Acrylonitrile-based precursor fibers were obtained in the same manner as in Examples 1 to 4, except that Af / (As / Vh) was changed as shown in Table 1 and the degree of dehumidification was reduced.

<Comparative Example 4>
Acrylonitrile-based precursor fibers were obtained in the same manner as in Examples 1 to 4, except that Af / (As / Vh) was changed as shown in Table 1 and the degree of dehumidification was further reduced.

<Comparative Example 5>
Acrylonitrile-based precursor fibers were obtained in the same manner as in Examples 1 to 4, except that Af / (As / Vh) was changed as shown in Table 1 and the supplied air was not dehumidified.

Table 1 shows the degree of condensation on the ejection surface, the quality of acrylonitrile fiber, and the process stability in each example and comparative example.

As shown in Table 1, it can be seen that the present invention suppresses condensation on the discharge surface of the die and improves the quality and process stability.

The present invention is not limited to suppressing the occurrence of condensation on the die surface in the production of carbon fiber precursor fibers, but can be applied as a productivity improvement measure by suppressing condensation in all dry and wet spinning.

1: Spinneret 2: Air supply or exhaust nozzle 3: Coagulation bath 4: Wind speed / air flow measurement point A
5: Wind speed / airflow measurement point B
6: Wind speed / airflow measurement point C
7: Wind speed / airflow measurement point D

Claims

In a fiber manufacturing method in which a spinning stock solution in which a fiber-forming polymer is dissolved in a solvent is discharged from a spinneret, once run in the air, and then guided into a coagulation bath liquid to be solidified, the discharge surface of the spinneret The amount of air (Af) per unit time in the gas phase formed between the coagulating bath and the liquid surface of the coagulating bath vertically downward is the amount of solvent (As) in the spinning dope per unit time in the gas phase volume (Vh) 0.0008m 3 ≦ Af / (As / Vh) ≦ 0.0015m satisfies the third relationship, 1 hour average value of the absolute humidity at the mouthpiece outer periphery four points in the gas phase portion, respectively 20 g / m 3 with respect to The manufacturing method of the fiber which is the following.
The method for producing a fiber according to claim 1, wherein the relative standard deviation of the wind speed at four points on the outer periphery of the base in the gas phase part is 40% or less.
The method for producing a fiber according to claim 1 or 2, wherein the number of holes in the spinneret is 2,000 or more and 50,000 or less.
The method for producing a fiber according to any one of claims 1 to 3, wherein the fiber-forming polymer is an acrylonitrile-based polymer.
A method for producing carbon fiber, comprising producing a fiber by the method for producing a fiber according to claim 4 and then flame-treating it in an oxidizing atmosphere at 200 to 300 ° C and then heating in an inert atmosphere at 1,000 ° C or higher. .